WorldWideScience

Sample records for hemisphere winter mid-latitude

  1. A very deep ozone minihole in the Northern Hemisphere stratosphere at mid-latitudes during the winter of 2000

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    Semane, N.; Teitelbaum, H.; Basdevant, C.

    2011-01-01

    Ozone miniholes appear on total ozone maps as localized ozone minima with horizontal extentsof a few hundreds of kilometres. They are characterized by a rapid and small-scale appearanceof a columnar ozone decrease with an equally rapid recovery after a few days. They are frequentlyobserved at Northern Hemisphere mid-latitudes in winter. Evolving too rapidly to be the resultof an ozone chemical destruction, miniholes should be the result of meteorological processes.According to some authors, m...

  2. The weakening summer circulation in the Northern Hemisphere mid-latitudes

    NARCIS (Netherlands)

    Coumou, Dim; Lehmann, Jascha; Beckmann, Johanna

    2015-01-01

    Rapid warming in the Arctic could influence mid-latitude circulation by reducing the poleward temperature gradient. The largest changes are generally expected in autumn or winter, but whether significant changes have occurred is debated. Here we report significant weakening of summer circulation

  3. The initial dispersal and radiative forcing of a Northern Hemisphere mid-latitude super volcano: a model study

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    C. Timmreck

    2006-01-01

    Full Text Available The chemistry climate model MAECHAM4/ CHEM with interactive and prognostic volcanic aerosol and ozone was used to study the initial dispersal and radiative forcing of a possible Northern Hemisphere mid-latitude super eruption. Tropospheric climate anomalies are not analysed since sea surface temperatures are kept fixed. Our experiments show that the global dispersal of a super eruption located at Yellowstone, Wy. is strongly dependent on the season of the eruption. In Northern Hemisphere summer the volcanic cloud is transported westward and preferentially southward, while in Northern Hemisphere winter the cloud is transported eastward and more northward compared to the summer case. Aerosol induced heating leads to a more global spreading with a pronounced cross equatorial transport. For a summer eruption aerosol is transported much further to the Southern Hemisphere than for a winter eruption. In contrast to Pinatubo case studies, strong cooling tendencies appear with maximum peak values of less than −1.6 K/day three months after the eruption in the upper tropical stratosphere. This strong cooling effect weakens with decreasing aerosol density over time and initially prevents the aerosol laden air from further active rising. All-sky net radiative flux changes of less than −32 W/m2 at the surface are about a factor of 6 larger than for the Pinatubo eruption. Large positive flux anomalies of more than 16 W/m2 are found in the first months in the tropics and sub tropics. These strong forcings call for a fully coupled ocean/atmosphere/chemistry model to study climate sensitivity to such a super-eruption.

  4. The initial dispersal and radiative forcing of a Northern Hemisphere mid-latitude super volcano: a model study

    OpenAIRE

    Timmreck, C.; H.-F. Graf

    2006-01-01

    The chemistry climate model MAECHAM4/ CHEM with interactive and prognostic volcanic aerosol and ozone was used to study the initial dispersal and radiative forcing of a possible Northern Hemisphere mid-latitude super eruption. Tropospheric climate anomalies are not analysed since sea surface temperatures are kept fixed. Our experiments show that the global dispersal of a super eruption located at Yellowstone, Wy. is strongly dependent on the season of the eruption. In Northern Hemisphere sum...

  5. Balloon-borne radiometer measurements of Northern Hemisphere mid-latitude stratospheric HNO3 profiles spanning 12 years

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    K. A. Walker

    2007-12-01

    Full Text Available Low-resolution atmospheric thermal emission spectra collected by balloon-borne radiometers over the time span of 1990–2002 are used to retrieve vertical profiles of HNO3, CFC-11 and CFC-12 volume mixing ratios between approximately 10 and 35 km altitude. All of the data analyzed have been collected from launches from a Northern Hemisphere mid-latitude site, during late summer, when stratospheric dynamic variability is at a minimum. The retrieval technique incorporates detailed forward modeling of the instrument and the radiative properties of the atmosphere, and obtains a best fit between modeled and measured spectra through a combination of onion-peeling and optimization steps. The retrieved HNO3 profiles are consistent over the 12-year period, and are consistent with recent measurements by the Atmospheric Chemistry Experiment-Fourier transform spectrometer satellite instrument. We therefore find no evidence of long-term changes in the HNO3 summer mid-latitude profile, although the uncertainty of our measurements precludes a conclusive trend analysis.

  6. Synoptic climate change as a driver of late Quaternary glaciations in the mid-latitudes of the Southern Hemisphere

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    H. Rother

    2006-01-01

    Full Text Available The relative timing of late Quaternary glacial advances in mid-latitude (40-55° S mountain belts of the Southern Hemisphere (SH has become a critical focus in the debate on global climate teleconnections. On the basis of glacial data from New Zealand (NZ and southern South America it has been argued that interhemispheric synchrony or asynchrony of Quaternary glacial events is due to Northern Hemisphere (NH forcing of SH climate through either the ocean or atmosphere systems. Here we present a glacial snow-mass balance model that demonstrates that large scale glaciation in the temperate and hyperhumid Southern Alps of New Zealand can be generated with moderate cooling. This is because the rapid conversion of precipitation from rainfall to snowfall drives massive ice accumulation at small thermal changes (1-4°C. Our model is consistent with recent paleo-environmental reconstructions showing that glacial advances in New Zealand during the Last Glacial Maximum (LGM and the Last Glacial Interglacial Transition (LGIT occurred under very moderate cooling. We suggest that such moderate cooling could be generated by changes in synoptic climatology, specifically through enhanced regional flow of moist westerly air masses. Our results imply that NH climate forcing may not have been the exclusive driver of Quaternary glaciations in New Zealand and that synoptic style climate variations are a better explanation for at least some late Quaternary glacial events, in particular during the LGIT (e.g. Younger Dryas and/or Antarctic Cold Reversal.

  7. Interaction of polar and tropical influences in the mid-latitudes of the Southern Hemisphere during the Mi-1 deglaciation

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    Fox, B. R. S.; D'Andrea, W. J.; Wilson, G. S.; Lee, D. E.; Wartho, J.-A.

    2017-08-01

    It is well-known from geologic archives that Pleistocene and Holocene climate is characterised by cyclical variation on a wide range of timescales, and that these cycles of variation interact in complex ways. However, it is rarely possible to reconstruct sub-precessional (analysis (PCA) of sediment bulk density, magnetic susceptibility (MS), and CIELAB L* and b* with a resolution of 10 years indicates two major environmental processes governing the physical properties records, which we interpret as changes in wind strength and changes in precipitation. Spectral analysis of the principal components indicates that both processes are strongly influenced by obliquity (41 kyr). We interpret this 41-kyr cycle in wind strength and precipitation as related to the changing position and strength of the Southern Hemisphere westerly winds. Precipitation is also influenced by an 11-kyr cycle. The 11-kyr periodicity is potentially related to orbital cyclicity, representing the equatorial semi-precessional maximum insolation cycle. This semi-precession cycle has been identified in a number of records from the Pleistocene and Holocene and has recently been suggested to indicate that insolation in low-latitude regions may be an important driver of millennial-scale climate response to orbital forcing (Feretti et al., 2015). This is the first time this cycle has been identified in a mid-latitude Southern Hemisphere climate archive, as well as the first identification in pre-Pleistocene records. The 11-kyr cycle appears at around 23.01 Ma, which coincides with the initiation of a major phase of Antarctic deglaciation, and strengthens during the subsequent period of rapid ice decay. This pattern suggests that the westerly winds may have expanded north of 50°S at the height of Mi-1, excluding tropical influence from the Foulden Maar site, and subsequently contracted polewards in tandem with warming deep-sea temperatures and Antarctic deglaciation, allowing the advection of tropical

  8. Indirect Radiative Warming Effect in the Winter and Spring Arctic Associated with Aerosol Pollution from Mid-latitude Regions

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    Zhao, Chuanfeng; Garrett, Timothy

    2016-04-01

    Different from global cooling effects of aerosols and aerosol-cloud interactions, anthropogenic aerosols from mid-latitude are found to play an increased warming effect in the Arctic in later winter and early spring. Using four-year (2000-2003) observation of aerosol, cloud and radiation at North Slope of Alaska, it is found that the aerosols can increase cloud droplet effective radius 3 um for fixed liquid water path, and increase cloud thermal emissivity about 0.05-0.08. In other words, aerosols are associated with a warming of 1-1.6 degrees (3-5 W/m2) in the Arctic during late winter and early spring solely due to their first indirect effect. Further analysis indicates that total aerosol climate effects are even more significant (8-10 W/m2), with about 50% contribution from aerosol first indirect effect and another 50% contribution from complicated feedbacks. It also shows strong seasonal distribution of the aerosol indirect radiative effects, with warming effects in seasons other than in summer. However, only the significant warming effect in winter and spring passes through the significance test. The strong warming effect due to aerosol indirect effect could be further strengthened through following feedbacks involving the surface albedo (early ice melting).

  9. Comparison of the decomposition VOC profile during winter and summer in a moist, mid-latitude (Cfb) climate.

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    Forbes, Shari L; Perrault, Katelynn A; Stefanuto, Pierre-Hugues; Nizio, Katie D; Focant, Jean-François

    2014-01-01

    The investigation of volatile organic compounds (VOCs) associated with decomposition is an emerging field in forensic taphonomy due to their importance in locating human remains using biological detectors such as insects and canines. A consistent decomposition VOC profile has not yet been elucidated due to the intrinsic impact of the environment on the decomposition process in different climatic zones. The study of decomposition VOCs has typically occurred during the warmer months to enable chemical profiling of all decomposition stages. The present study investigated the decomposition VOC profile in air during both warmer and cooler months in a moist, mid-latitude (Cfb) climate as decomposition occurs year-round in this environment. Pig carcasses (Sus scrofa domesticus L.) were placed on a soil surface to decompose naturally and their VOC profile was monitored during the winter and summer months. Corresponding control sites were also monitored to determine the natural VOC profile of the surrounding soil and vegetation. VOC samples were collected onto sorbent tubes and analyzed using comprehensive two-dimensional gas chromatography--time-of-flight mass spectrometry (GC × GC-TOFMS). The summer months were characterized by higher temperatures and solar radiation, greater rainfall accumulation, and comparable humidity when compared to the winter months. The rate of decomposition was faster and the number and abundance of VOCs was proportionally higher in summer. However, a similar trend was observed in winter and summer demonstrating a rapid increase in VOC abundance during active decay with a second increase in abundance occurring later in the decomposition process. Sulfur-containing compounds, alcohols and ketones represented the most abundant classes of compounds in both seasons, although almost all 10 compound classes identified contributed to discriminating the stages of decomposition throughout both seasons. The advantages of GC × GC-TOFMS were demonstrated

  10. Diagnosing sea ice from the north american multi model ensemble and implications on mid-latitude winter climate

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    Elders, Akiko; Pegion, Kathy

    2017-12-01

    Arctic sea ice plays an important role in the climate system, moderating the exchange of energy and moisture between the ocean and the atmosphere. An emerging area of research investigates how changes, particularly declines, in sea ice extent (SIE) impact climate in regions local to and remote from the Arctic. Therefore, both observations and model estimates of sea ice become important. This study investigates the skill of sea ice predictions from models participating in the North American Multi-Model Ensemble (NMME) project. Three of the models in this project provide sea-ice predictions. The ensemble average of these models is used to determine seasonal climate impacts on surface air temperature (SAT) and sea level pressure (SLP) in remote regions such as the mid-latitudes. It is found that declines in fall SIE are associated with cold temperatures in the mid-latitudes and pressure patterns across the Arctic and mid-latitudes similar to the negative phase of the Arctic Oscillation (AO). These findings are consistent with other studies that have investigated the relationship between declines in SIE and mid-latitude weather and climate. In an attempt to include additional NMME models for sea-ice predictions, a proxy for SIE is used to estimate ice extent in the remaining models, using sea surface temperature (SST). It is found that SST is a reasonable proxy for SIE estimation when compared to model SIE forecasts and observations. The proxy sea-ice estimates also show similar relationships to mid-latitude temperature and pressure as the actual sea-ice predictions.

  11. Shifts of seasons at North-Hemisphere mid-latitudes: Natural fluctuations correlated with the North Atlantic Oscillation

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    Palus, Milan; Novotna, Dagmar

    2010-05-01

    One model based and three complex demodulation techniques (Hilbert transform, singular system analysis and wavelet transform) have been applied by Palus et al. [Geophys. Res. Lett. 32, L12805, 2005] to daily mean near-surface air temperature series from several mid-latitude European stations in order to obtain reliable estimates of instantaneous phases of the annual cycle as an objective measure of timing of seasons. The consistency of the estimates was checked by comparing independent methods, their reliability by comparison with actual annual temperature profiles. The previously reported advancement of spring seasons in 1990's has been confirmed, however, these changes did not depart from the range of natural phase fluctuations observed in the historical temperature records. Significant, geographically dependent correlations of the phase fluctuations with the North Atlantic Oscillation index, as well as weaker, negative correlations with the El Nino Southern Oscillation index have been observed. Here we extend the study using monthly NCEP/NCAR and ERA40 near-surface air temperature series. No statistically significant trends in the phase of the annual cycle have been observed, however, both the reanalysis datasets provide consistent patterns of areas with marked, statistically significant correlations between the phase fluctuations and the North Atlantic Oscillation index. Shifts of seasons are probably caused by a process of natural fluctuations. Underlying mechanisms of this dynamical process, as well as its couplings with global circulation phenomena should be understood. In particular, a level of deterministic dynamics in, or couplings of this process with more predictable phenomena should be established, since potential skills in prediction of onsets of seasons could have significant socioeconomic impacts, while an unpredictable phase in the climate may be a more serious problem to society than changes in the amplitude of the annual cycle or even of the mean

  12. Attribution of recent ozone changes in the Southern Hemisphere mid-latitudes using statistical analysis and chemistry-climate model simulations

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    Zeng, Guang; Morgenstern, Olaf; Shiona, Hisako; Thomas, Alan J.; Querel, Richard R.; Nichol, Sylvia E.

    2017-09-01

    Ozone (O3) trends and variability from a 28-year (1987-2014) ozonesonde record at Lauder, New Zealand, have been analysed and interpreted using a statistical model and a global chemistry-climate model (CCM). Lauder is a clean rural measurement site often representative of the Southern Hemisphere (SH) mid-latitude background atmosphere. O3 trends over this period at this location are characterised by a significant positive trend below 6 km, a significant negative trend in the tropopause region and the lower stratosphere between 9 and 15 km, and no significant trend in the free troposphere (6-9 km) and the stratosphere above 15 km. We find that significant positive trends in lower tropospheric ozone are correlated with increasing temperature and decreasing relative humidity at the surface over this period, whereas significant negative trends in the upper troposphere and the lower stratosphere appear to be strongly linked to an upward trend of the tropopause height. Relative humidity and the tropopause height also dominate O3 variability at Lauder in the lower troposphere and the tropopause region, respectively. We perform an attribution of these trends to anthropogenic forcings including O3 precursors, greenhouse gases (GHGs), and O3-depleting substances (ODSs), using CCM simulations. Results indicate that changes in anthropogenic O3 precursors contribute significantly to stratospheric O3 reduction, changes in ODSs contribute significantly to tropospheric O3 reduction, and increased GHGs contribute significantly to stratospheric O3 increases at Lauder. Methane (CH4) likely contributes positively to O3 trends in both the troposphere and the stratosphere, but the contribution is not significant at the 95 % confidence level over this period. An extended analysis of CCM results covering 1960-2010 (i.e. starting well before the observations) reveals significant contributions from all forcings to O3 trends at Lauder - i.e. increases in GHGs and the increase in CH4 alone

  13. Attribution of recent ozone changes in the Southern Hemisphere mid-latitudes using statistical analysis and chemistry–climate model simulations

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    G. Zeng

    2017-09-01

    Full Text Available Ozone (O3 trends and variability from a 28-year (1987–2014 ozonesonde record at Lauder, New Zealand, have been analysed and interpreted using a statistical model and a global chemistry–climate model (CCM. Lauder is a clean rural measurement site often representative of the Southern Hemisphere (SH mid-latitude background atmosphere. O3 trends over this period at this location are characterised by a significant positive trend below 6 km, a significant negative trend in the tropopause region and the lower stratosphere between 9 and 15 km, and no significant trend in the free troposphere (6–9 km and the stratosphere above 15 km. We find that significant positive trends in lower tropospheric ozone are correlated with increasing temperature and decreasing relative humidity at the surface over this period, whereas significant negative trends in the upper troposphere and the lower stratosphere appear to be strongly linked to an upward trend of the tropopause height. Relative humidity and the tropopause height also dominate O3 variability at Lauder in the lower troposphere and the tropopause region, respectively. We perform an attribution of these trends to anthropogenic forcings including O3 precursors, greenhouse gases (GHGs, and O3-depleting substances (ODSs, using CCM simulations. Results indicate that changes in anthropogenic O3 precursors contribute significantly to stratospheric O3 reduction, changes in ODSs contribute significantly to tropospheric O3 reduction, and increased GHGs contribute significantly to stratospheric O3 increases at Lauder. Methane (CH4 likely contributes positively to O3 trends in both the troposphere and the stratosphere, but the contribution is not significant at the 95 % confidence level over this period. An extended analysis of CCM results covering 1960–2010 (i.e. starting well before the observations reveals significant contributions from all forcings to O3 trends at Lauder – i.e. increases in

  14. The initial dispersal and radiative forcing of a Northern Hemisphere mid latitude super volcano: a Yellowstone case study

    OpenAIRE

    Timmreck, C.; Graf, H.-F.

    2005-01-01

    International audience; The chemistry climate model MAECHAM4/CHEM with interactive and prognostic volcanic aerosol and ozone, was used to study the initial dispersal and radiative forcing of a possible Yellowstone super eruption. Tropospheric climate anomalies are not analysed since sea surface temperatures are kept fix. Our experiments show that the global dispersal of a Yellowstone super eruption is strongly dependent on the season of the eruption. In Northern Hemisphere summer the volcanic...

  15. Measurements of the movement of the jet streams at mid-latitudes, in the Northern and Southern Hemispheres, 1979 to 2010

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    R. D. Hudson

    2012-08-01

    Full Text Available Previous studies have shown that the mean latitude of the sub-tropical jet streams in both hemispheres have shifted toward the poles over the last few decades. This paper presents a study of the movement of both the subtropical and Polar fronts, the location of the respective jet streams, between 1979 and 2010 at mid-latitudes, using total ozone measurements to identify the sharp horizontal boundary that occurs at the position of the fronts. Previous studies have shown that the two fronts are the boundaries of three distinct regimes in the stratosphere, corresponding to the Hadley, Ferrel, and polar meridionally overturning circulation cells in the troposphere. Over the period of study the horizontal area of the Hadley cell has increased at latitudes between 20 and 60 degrees while the area of the Polar cell has decreased. A linear regression analysis was performed to identify the major factors associated with the movement of the subtropical jet streams. These were: (1 changes in the Tropical land plus ocean temperature, (2 direct radiative forcing from greenhouse gases in the troposphere, (3 changes in the temperature of the lower tropical stratosphere, (4 the Quasi-Biennial Oscillation, and (5 volcanic eruptions. The dominant mechanism was the direct radiative forcing from greenhouse gases. Between 1979 and 2010 the poleward movement of the subtropical jet streams was 3.7 ± 0.3 degrees in the Northern Hemisphere and 6.5 ± 0.2 degrees in the Southern Hemisphere. Previous studies have shown that weather systems tend to follow the jet streams. The observed poleward movement in both hemispheres over the past thirty years represents a significant change in the position of the sub-tropical jet streams, which should lead to significant latitudinal shifts in the global weather patterns and the hydrologic cycle.

  16. Atmospheric circulation changes and neoglacial conditions in the Southern Hemisphere mid-latitudes: insights from PMIP2 simulations at 6 kyr

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    Rojas, Maisa [University of Chile, Department of Geophysics, Santiago (Chile); Moreno, Patricio I. [University of Chile, Department of Ecology, Santiago (Chile)

    2011-07-15

    Glacial geologic studies in the Southern Hemisphere (SH) mid-latitudes (40-54 S) indicate renewed glacial activity in southern South America (Patagonia) and New Zealand's (NZ) South Island starting at {proportional_to}7 kyr, the so-called neoglaciation. Available data indicate that neoglacial advances in these regions occurred during a rising trend in atmospheric CO{sub 2} and CH{sub 4} concentrations, lower-than-present but increasing summer insolation and seasonality contrasts. In this paper we examine the climatological context in which neoglaciations occurred through analysis of the complete Paleoclimate Modelling Inter-comparison Project (PMIP2) database of simulations at 6 kyr for the SH. We observe that the amplitude of the annual insolation cycle in the SH did not change significantly at 6 kyr compared to the pre-industrial values, the largest difference occurring in autumn (MAM, negative anomalies) and spring (SON, positive anomalies). The simulated changes in temperatures over the SH respond to the insolation changes, with a 1-2 month delay over the oceans. This results in a reduced amplitude of the annual cycle of temperature and precipitation over most continental regions, except over Patagonia and NZ, that show a slight increase. In contrast, large-scale circulation features, such as the low and upper level winds and the subtropical anticyclones show an amplified annual cycle, as a direct response to the increased/decreased insolation during the transitional seasons SON/MAM. In the annual mean, there is a small but consistent equatorward shift of the latitude of maximum wind speed of 1-3 over the entire SH, which results in a small increase of wind speed over the South Pacific and Atlantic Oceans north of {proportional_to}50 S and a widespread decline south of 50 S. PMIP2 simulations for 6 kyr, indicate that in the annual mean, the SH mid-latitudes were colder, wetter and with stronger winds north of about 50 S. These conditions are consistent

  17. Winter soil CO2 flux from different mid-latitude sites from Middle Taihang Mountain in north China.

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    Huitao Shen

    Full Text Available Winter soil respiration is a very important component of the annual soil carbon flux in some ecosystems. We hypothesized that, with all other factors being equal, shorter winter SR result in reduced contribution to annual soil C flux. In this study, the contribution of winter soil respiration to annual soil respiration was measured for three sites (grassland: dominated by Artemisia sacrorum, Bothriochloa ischaemum and Themeda japonica; shrubland: dominated by Vitex negundo var. heterophylla; plantation: dominated by Populus tomatosa in a mountainous area of north China. Diurnal and intra-annual soil CO2 flux patterns were consistent among different sites, with the maximum soil respiration rates at 12∶00 or 14∶00, and in July or August. The lowest respiration rates were seen in February. Mean soil respiration rates ranged from 0.26 to 0.45 µmol m(-2 s(-1 in the winter (December to February, and between 2.38 to 3.16 µmol m(-2 s(-1 during the growing season (May-September. The winter soil carbon flux was 24.6 to 42.8 g C m(-2, which contributed 4.8 to 7.1% of the annual soil carbon flux. Based on exponential functions, soil temperature explained 73.8 to 91.8% of the within year variability in soil respiration rates. The Q10 values of SR against ST at 10 cm ranged from 3.60 to 4.90 among different sites. In addition, the equation between soil respiration and soil temperature for the growing season was used to calculate the "modeled" annual soil carbon flux based on the actual measured soil temperature. The "measured" annual value was significantly higher than the "modeled" annual value. Our results suggest that winter soil respiration plays a significant role in annual soil carbon balance, and should not be neglected when soil ecosystems are assessed as either sinks or sources of atmospheric CO2.

  18. Stratospheric evolution of temperature and different atmospheric trace gases during winters at the NDACC Alpine mid-latitude station at Bern

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    Navas-Guzmán, Francisco; Moreira, Lorena; Lainer, Martin; Schranz, Franziska; Hocke, Klemens; Kämpfer, Niklaus

    2017-04-01

    The Earth's climate is sensitive to changes in temperature and trace gas concentrations in the stratosphere region. There is a wealth of possible sources of natural variability of these atmospheric properties in the stratosphere. The concentration of species as ozone and water vapour can vary as a result of different factors, some interacting among themselves through their effects on chemistry and transport. For example, phenomena originally tropical such as the quasi-biennial oscillation (QBO) and El Niño-Southern Oscillation (ENSO) can lead to wave structures and wave propagation in mid-latitudes. This can affect the zonal mean meridional transport of trace gases from the tropics to mid-latitudes and polar latitudes in the stratosphere and also produce variations in the strength of the polar winter vortices and stratospheric warming events. Wintertime is specially an interesting period in which the variability in atmospheric parameters and composition is large. Strong changes in temperature and in the concentration of trace gases as ozone or water vapour can be observed in a very short time interval, and therefore measurements with a high temporal resolution are needed. The present study shows the capability of ground-based microwave technique to monitor with a relatively good spatial and temporal resolution the stratospheric composition and temperature during complex phenomena occurring in winter. In this way, the evolution of stratospheric temperature, ozone and water vapour profiles during the last winters over Bern (Switzerland) are analyzed. The measurements were performed by three microwave radiometers (TEMPERA for temperature, GROMOS for ozone and MIAWARA for water vapour) which have been designed and built at the University of Bern. The measurement at a fixed location allows to observe local atmospheric dynamics over a long-time period, which is crucial for climate research. The detection of some singular sudden stratospheric warming (SSW) during the

  19. Winds and tides in the mid-latitude Southern Hemisphere upper mesosphere recorded with the Falkland Islands SuperDARN radar

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    R. E. Hibbins

    2011-11-01

    Full Text Available Meteor wind data from the first year of operation of the Falkland Islands SuperDARN radar (52° S, 59° W are used to characterize the atmospheric tides and background winds in the upper mesosphere above the South Atlantic. Strong (>40 m s−1 semidiurnal tides are observed in the winter time and large amplitude (>60 m s−1 bursts of quasi two-day wave activity are seen in January 2011. Data are in good agreement with those presented from the SAAMER meteor radar (54° S, 68° W. Comparison with SuperDARN meteor wind data from a geographically similar Northern Hemisphere site at Goose Bay (53° N 60° W reveal clear interhemispheric differences especially in the semidiurnal and terdiurnal components of the tides. The winter time amplitudes of the tides are much stronger in the Southern Hemisphere than in the north. Background winds are observed to be significantly more polewards and westwards throughout the year than those predicted by the empirical horizontal wind model HWM07.

  20. Tropical influence on boreal summer mid-latitude stationary waves

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    Douville, Herve [Meteo-France/CNRM-GAME, Toulouse (France); CNRM/GMGEC/VDR, Toulouse (France); Bielli, S.; Deque, M.; Tyteca, S.; Voldoire, A. [Meteo-France/CNRM-GAME, Toulouse (France); Cassou, C. [CNRS-Cerfacs, Toulouse (France); Hall, N.M.J. [CNES/LEGOS, Toulouse (France)

    2011-11-15

    While organized tropical convection is a well-known source of extratropical planetary waves, state-of-the-art climate models still show serious deficiencies in simulating accurately the atmospheric response to tropical sea surface temperature (SST) anomalies and the associated teleconnections. In the present study, the remote influence of the tropical atmospheric circulation is evaluated in ensembles of global boreal summer simulations in which the Arpege-Climat atmospheric General Circulation Model (GCM) is nudged towards 6-h reanalyses. The nudging is applied either in the whole tropical band or in a regional summer monsoon domain. Sensitivity tests to the experimental design are first conducted using prescribed climatological SST. They show that the tropical relaxation does not improve the zonal mean extratropical climatology but does lead to a significantly improved representation of the mid-latitude stationary waves in both hemispheres. Low-pass filtering of the relaxation fields has no major effect on the model response, suggesting that high-frequency tropical variability is not responsible for extratropical biases. Dividing the nudging strength by a factor 10 only decreases the magnitude of the response. Model errors in each monsoon domain contribute to deficiencies in the model's mid-latitude climatology, although an exaggerated large-scale subsidence in the central equatorial Pacific appears as the main source of errors for the representation of stationary waves in the Arpege-Climat model. Case studies are then conducted using either climatological or observed SST. The focus is first on summer 2003 characterized by a strong and persistent anticyclonic anomaly over western Europe. This pattern is more realistic in nudging experiments than in simulations only driven by observed SST, especially when the nudging domain is centred over Central America. Other case studies also show a significant tropical forcing of the summer mid-latitude stationary waves

  1. Climatology of vTEC at midnight over mid-latitude regions using PCA

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    Natali, M. Paula; Meza, Amalia

    2017-04-01

    At night the content of the electron density at mid-latitude is mainly controlled by loss processes, recombination and electron movement, which are related by the continuity equation. The vertical wind plays an important role in these processes. Global vertical Total Electron Content (vTEC) maps produced by the International Global Navigation Satellite System (GNSS) Service, the Horizontal Wind Model 2007 (HWM07) and the International Reference Ionosphere (IRI) 2012 model are used to describe the climatology at midnight over mid-latitude regions during 2000-2002. In particular, four regions were selected. They are approximately centered in zero magnetic declination, two in the northern hemisphere and two in southern hemisphere. They are located near and far from geomagnetic poles respectively. Principal Components Analysis (PCA) technique highlights the spatial-temporal variations to the overall vTEC variability which can be well represented by an orthogonal base. Indeed, we show for the four selected regions the contributions of the first three modes account for more than 95% of its variability. PCA results show that vTEC variability respond to vertical wind variation with decreasing values of about 10% -15% with the action of a vertical wind lasting for two hours. The Mid-latitude Summer Night Anomaly (MSNA), which is directly related with vertical wind, is present in regions far from geomagnetic poles. A remnant effect of the winter anomaly is also observed, in regions near geomagnetic poles. A longitudinal variation for mid-latitude ionospheric vTEC with maximum values in equinoxes, associated with negative and positive magnetic declination in all regions is observed. For the IRI model, PCA results, are quite similar but the mean values are lower than the obtained with the Global vTEC Maps. These data show the MSNA but not the remnant of the winter anomaly. In all regions the longitudinal variation is present with the same seasonal variation as Global vTEC Maps.

  2. Mid-Latitude Snowmelt Onset Detection Via Microwave Remote Sensing

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    Vuyovich, C.; Jacobs, J. M.; Osborne, D.; Hunsaker, A. G.; Tuttle, S. E.

    2016-12-01

    The timing and magnitude of spring snowmelt events are critical for understanding the winter-to-spring transition of the hydrologic cycle and ecosystem processes. Melt timing determination is challenging because snowpack ripening observations are seldom available. Remotely sensed passive microwave observations show promise for determining snowpack wetting and melt onset at global scales. Studies performed in northern latitude regions verify the theoretical concept of microwave snowmelt detection methods under ideal conditions. However, early winter snowmelt events within mid-latitude regions introduce large regional climate differences that add considerable amounts of noise to the microwave observations. Diurnal Amplitude Variation (DAV), Frequency Difference (FD) and Polarization Ratio (PR) are three methods that use remotely sensed passive microwave observations to determine snowpack wetting and melt onset. This study evaluates the performance of these approaches to determine spring melt onset and early winter flood events in mid-latitudes. The suitability of microwave remote sensing techniques to detect snowmelt was found to vary regionally. Physical characteristics including basin latitude, regional air temperatures, snow depth, snow covered area, forest density, and rain intensity were examined to understand how and why the observed microwave signatures associated with snow cover vary over contrasting regions.

  3. Remote impact of the Antarctic atmosphere on the southern mid-latitudes

    Directory of Open Access Journals (Sweden)

    Tido Semmler

    2016-02-01

    Full Text Available Would improved prediction capabilities over the Antarctic lead to improved forecast skill in southern mid-latitudes? Or more generally speaking, how large is the influence of the Antarctic atmosphere on the weather and climate of the southern mid-latitudes? To answer these questions we assess the skill of two sets of 14‑day forecasts with the Integrated Forecast System of the European Centre for Medium-Range Weather Forecasts with and without relaxation towards the Interim reanalysis of the ECMWF over the Antarctic south of 75 ° S. Due to the relaxation both the mean absolute error and the root mean square error decrease by 2 to 5 % averaged over the southern mid-latitudes with the larger values in winter. Over southern South America and the South Atlantic error reductions are slightly larger and amount to around 5 to 6 %. No dependency of the error reductions of the El Niño Southern Oscillation or the Antarctic Oscillation could be found although error reductions averaged over the whole southern mid-latitudes tend to be larger in situations with decreased westerly flow in the mid-latitudes. In weather situations with anomalous meridional flow from Antarctica to southern South America improvements are most pronounced in the latter area which implies that this is the major pathway for Antarctic influence on southern mid-latitude weather and climate.

  4. An introduction to mid-latitude ecotone: sustainability and environmental challenges

    Directory of Open Access Journals (Sweden)

    J. Moon

    2017-12-01

    Full Text Available The mid-latitude zone can be broadly defined as part of the hemisphere between 30°–60° latitude. This zone is home to over 50 % of the world population and encompasses about 36 countries throughout the principal region, which host most of the world’s development and poverty related problems. In reviewing some of the past and current major environmental challenges that parts of mid-latitudes are facing, this study sets the context by limiting the scope of mid-latitude region to that of Northern hemisphere, specifically between 30°–45° latitudes which is related to the warm temperate zone comprising the Mid-Latitude ecotone – a transition belt between the forest zone and southern dry land territories. The ongoing climate change reveals a substantial increase of temperature and simultaneous decrease in the amount of precipitation across vast continental regions in the mid-latitudes. According to climatic predictions, these tendencies will continue during the 21st century, which will likely increase the frequency and severity of droughts and water stress of vegetation. Along with climate change, ongoing land degradation and deforestation are observed in many regions of the mid-latitude region. For example, the Korean peninsula, which is divided into South and North Korea, is characterized by drastically different forest conditions. Deforestation in North Korea has been exacerbating at a noticeable pace due to excessive logging and human intervention. Such problems are not confined to Korean peninsula but are witnessed across vast regions of the mid-latitude region. Within this context – acquiring better understanding in the role of terrestrial ecosystems located at different latitudes is critical – for building resilience against the negative impact of climate change and for maintaining the stability of the environment and landscapes.

  5. Using NWP to assess the influence of the Arctic atmosphere on mid-latitude weather and climate

    OpenAIRE

    Semmler, Tido; Jung, Thomas; Kasper, Marta A.; Serrar, Soumia

    2017-01-01

    The influence of the Arctic atmosphere on Northern Hemisphere mid-latitude tropospheric weather and climate is explored by comparing the skill of two sets of 14-day weather forecast experiments using the ECMWF model with and without relaxation of the Arctic atmosphere towards ERA-Interim reanalysis data during the integration. Two pathways are identified along which the Arctic influences mid-latitude weather: a pronounced one over Asia and Eastern Europe, and a secondary one over North Americ...

  6. A link between high-speed solar wind streams and mid-latitude cyclones

    Science.gov (United States)

    Prikryl, Paul; Iwao, Koki; Tsukijihara, Takumi; Muldrew, Donald B.; Rušin, Vojto; Rybanský, Milan; Bruntz, Robert

    2017-04-01

    Mid-latitude cyclone tracks in the northern and southern hemispheres are obtained from meteorological reanalysis datasets to study occurrence of explosively developing extratropical cyclones in the winter season in relation to arrivals of high-speed solar wind streams (HSS) from coronal holes. The new statistical evidence corroborates the previously published results (Prikryl et al., Ann. Geophys., 27, 1-30, 2009). For the northern and southern winters, this evidence shows that explosive extratropical cyclones tend to occur after arrivals of HSS when large amplitude Alfvén waves couple to the magnetosphere-ionosphere system. Solar wind Alfvén waves modulate Joule heating and/or Lorentz forcing of the high-latitude lower thermosphere generating medium-scale atmospheric gravity waves that propagate energy upward and downward from auroral zone through the atmosphere. It is proposed that these gravity waves, in spite of their small amplitudes but subject to amplification upon reflection in the upper troposphere, can trigger instabilities in the troposphere initiating convection to form cloud/precipitation bands. The release of latent heat is known to provide energy for rapid development and intensification of extratropical cyclones.

  7. Arctic sea ice melt, the Polar vortex, and mid-latitude weather: Are they connected?

    Science.gov (United States)

    Vihma, Timo; Overland, James; Francis, Jennifer; Hall, Richard; Hanna, Edward; Kim, Seong-Joong

    2015-04-01

    The potential of recent Arctic changes to influence broader hemispheric weather is a difficult and controversial topic with considerable skepticism, as time series of potential linkages are short (<10 years) and the signal-to-noise ratio relative to chaotic weather events is small. A way forward is through further understanding of potential atmospheric dynamic mechanisms. Although not definitive of change in a statistical or in a causality sense, the exceptionally warm Arctic winters since 2007 do contain increased variability according to some climate indices, with six negative (and two positive) Arctic Oscillation atmospheric circulation index events that created meridional flow reaching unusually far north and south. High pressure anomalies developed east of the Ural Mountains in Russia in response to sea-ice loss in the Barents/Kara Seas, which initiated eastward-propagating wave trains of high and low pressure that advected cold air over central and eastern Asia. Increased Greenland blocking and greater geopotential thickness related to low-level temperatures increases led to northerly meridional flow into eastern North America, inducing persistent cold periods. Arctic connections in Europe and western North America are less clear. The quantitative impact of potential Arctic change on mid-latitude weather will not be resolved within the foreseeable future, yet new approaches to high-latitude atmospheric dynamics can contribute to improved extended range forecasts as outlined by the WMO/Polar Prediction Program and other international activities.

  8. It Takes Two to Tango: Arctic Influence on Mid-Latitude Weather is State-Dependent

    Science.gov (United States)

    Francis, J. A.; Vavrus, S. J.; Cohen, J. L.

    2016-12-01

    Since the late 1990s the Arctic has been warming two to three times faster than mid-latitude regions, a phenomenon known as Arctic amplification (AA). During the first half of 2016, AA reached a new record high value. This disproportionate warming is expected to influence the large-scale atmospheric circulation of the northern hemisphere, but understanding exactly how, where, when, and under what conditions has been an active and controversial topic of research. Observational studies of the atmospheric response are challenged by the short record of AA in a noisy environment, while modeling efforts have produced mixed results owing in part to deficiencies in both capturing the full signal of AA and simulating highly amplified atmospheric features (such as blocks, cut-off lows, and sharp ridging). Despite these challenges, progress in understanding the effects of AA on mid-latitude weather has been steady. In this presentation, we will discuss a new hypothesis and supporting evidence suggesting that the influence of regional AA depends on the background state of the large-scale circulation. Long-lived sea-surface temperature patterns in mid-latitudes, such as the Pacific Decadal Oscillation, favor particular ridge/trough configurations that affect the magnitude of AA's influence on weather patterns. These relationships vary both regionally and seasonally. As AA continues to strengthen with unabated rising concentrations of greenhouse gases, the mechanisms by which AA affects mid-latitude weather, particularly extreme events, may become clearer. The record-breaking AA of 2016 and associated extreme mid-latitude weather events may be a preview of the "new normal" in a warmer world.

  9. Skill and predictability in multimodel ensemble forecasts for Northern Hemisphere regions with dominant winter precipitation

    Science.gov (United States)

    Ehsan, Muhammad Azhar; Tippett, Michael K.; Almazroui, Mansour; Ismail, Muhammad; Yousef, Ahmed; Kucharski, Fred; Omar, Mohamed; Hussein, Mahmoud; Alkhalaf, Abdulrahman A.

    2017-05-01

    Northern Hemisphere winter precipitation reforecasts from the European Centre for Medium Range Weather Forecast System-4 and six of the models in the North American Multi-Model Ensemble are evaluated, focusing on two regions (Region-A: 20°N-45°N, 10°E-65°E and Region-B: 20°N-55°N, 205°E-255°E) where winter precipitation is a dominant fraction of the annual total and where precipitation from mid-latitude storms is important. Predictability and skill (deterministic and probabilistic) are assessed for 1983-2013 by the multimodel composite (MME) of seven prediction models. The MME climatological mean and variability over the two regions is comparable to observation with some regional differences. The statistically significant decreasing trend observed in Region-B precipitation is captured well by the MME and most of the individual models. El Niño Southern Oscillation is a source of forecast skill, and the correlation coefficient between the Niño3.4 index and precipitation over region A and B is 0.46 and 0.35, statistically significant at the 95 % level. The MME reforecasts weakly reproduce the observed teleconnection. Signal, noise and signal to noise ratio analysis show that the signal variance over two regions is very small as compared to noise variance which tends to reduce the prediction skill. The MME ranked probability skill score is higher than that of individual models, showing the advantage of a multimodel ensemble. Observed Region-A rainfall anomalies are strongly associated with the North Atlantic Oscillation, but none of the models reproduce this relation, which may explain the low skill over Region-A. The superior quality of multimodel ensemble compared with individual models is mainly due to larger ensemble size.

  10. Probabilistic evaluation of decadal prediction skill regarding Northern Hemisphere winter storms

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    Tim Kruschke

    2016-12-01

    Full Text Available Winter wind storms related to intense extra-tropical cyclones are meteorological extreme events, often with major impacts on economy and human life, especially for Europe and the mid-latitudes. Hence, skillful decadal predictions regarding the frequency of their occurrence would be of great socio-economic value. The present paper extends the study of Kruschke et al. (2014 in several aspects. First, this study is situated in a more impact oriented context by analyzing the frequency of potentially damaging wind storm events instead of targeting at cyclones as general meteorological features which was done by Kruschke et al. (2014. Second, this study incorporates more data sets by analyzing five decadal hindcast experiments – 41 annual (1961–2001 initializations integrated for ten years each – set up with different initialization strategies. However, all experiments are based on the Max-Planck-Institute Earth System Model in a low-resolution configuration (MPI-ESM-LR. Differing combinations of these five experiments allow for more robust estimates of predictive skill (due to considerably larger ensemble size and systematic comparisons of the underlying initialization strategies. Third, the hindcast experiments are corrected for model bias and potential drifts over lead time by means of a novel parametric approach, accounting for non-stationary model drifts. We analyze whether skillful probabilistic three-category forecasts (enhanced, normal or decreased can be provided regarding winter (ONDJFM wind storm frequencies over the Northern Hemisphere (NH. Skill is assessed by using climatological probabilities and uninitialized transient simulations as reference forecasts. It is shown that forecasts of average winter wind storm frequencies for winters 2–5 and winters 2–9 are skillful over large parts of the NH. However, most of this skill is associated with external forcing from transient greenhouse gas and aerosol concentrations

  11. Synoptic-scale circulation patterns during summer derived from tree rings in mid-latitude Asia

    Science.gov (United States)

    Seim, Andrea; Schultz, Johannes A.; Leland, Caroline; Davi, Nicole; Byambasuren, Oyunsanaa; Liang, Eryuan; Wang, Xiaochun; Beck, Christoph; Linderholm, Hans W.; Pederson, Neil

    2017-09-01

    Understanding past and recent climate and atmospheric circulation variability is vital for regions that are affected by climate extremes. In mid-latitude Asia, however, the synoptic climatology is complex and not yet fully understood. The aim of this study was to investigate dominant synoptic-scale circulation patterns during the summer season using a multi-species tree-ring width (TRW) network comprising 78 sites from mid-latitude Asia. For each TRW chronology, we calculated an atmospheric circulation tree-ring index (ACTI), based on 1000 hPa geopotential height data, to directly link tree growth to 13 summertime weather types and their associated local climate conditions for the period 1871-1993. Using the ACTI, three groups of similarly responding tree-ring sites can be associated with distinct large-scale atmospheric circulation patterns: 1. growth of drought sensitive trees is positively affected by a cyclone over northern Russia; 2. temperature sensitive trees show positive associations to a cyclone over northwestern Russia and an anticyclone over Mongolia; 3. trees at two high elevation sites show positive relations to a zonal cyclone extending from mid-latitude Eurasia to the West Pacific. The identified synoptic-scale circulation patterns showed spatiotemporal variability in their intensity and position, causing temporally varying climate conditions in mid-latitude Asia. Our results highlight that for regions with less pronounced atmospheric action centers during summer such as the occurrence of large-scale cyclones and anticyclones, synoptic-scale circulation patterns can be extracted and linked to the Northern Hemisphere circulation system. Thus, we provide a new and solid envelope for climate studies covering the past to the future.

  12. Twentieth Century Winter Changes in Southern Hemisphere Synoptic Weather Modes

    OpenAIRE

    Frederiksen, Jorgen S.; Frederiksen, Carsten S.

    2011-01-01

    During the last sixty years, there have been large changes in the southern hemisphere winter circulation and reductions in rainfall particularly in the southern Australian region. Here we examine the corresponding changes in dynamical modes of variability ranging from storm tracks, onset-of-blocking modes, northwest cloud-band disturbances, Antarctic low-frequency modes, intraseasonal oscillations, and African easterly waves. Our study is performed using a global two-level primitive equation ...

  13. Sustainable Arctic observing network for predicting weather extremes in mid-latitudes

    Science.gov (United States)

    Inoue, J.; Sato, K.; Yamazaki, A.

    2016-12-01

    Routine atmospheric observations within and over the Arctic Ocean are very expensive and difficult to conduct because of factors such as logistics and the harsh environment. Nevertheless, the great benefit of such observations is their contribution to an improvement of skills of weather predictions over the Arctic and mid-latitudes. The Year of Polar Prediction (YOPP) from mid-2017 to mid-2019 proposed by the World Weather Research Programme - Polar Prediction Project (WWRP-PPP) would be the best opportunity to address the issues. The combination of observations and data assimilation is an effective way to understand the predictability of weather extremes in mid-latitudes. This talk presents the current activities related to PPP based on international special radiosonde observing network in the Arctic, and challenges toward YOPP. Comparing with summer and winter cases, the additional observations over the Arctic during winter were more effective for improving the predicting skills of weather extremes because the impact of the observations would be carried toward the mid-latitudes by the stronger jet stream and its frequent meanderings. During summer, on the other hand, the impact of extra observations was localized over the Arctic region but still important for precise weather forecasts over the Arctic Ocean, contributing to safe navigation along the Northern Sea Route. To consolidate the sustainable Arctic radiosonde observing network, increasing the frequency of observations at Arctic coastal stations, instead of commissioning special observations from ships and ice camps, would be a feasible way. In fact, several existing stations facing the Arctic Ocean have already increased the frequency of observations during winter and/or summer.

  14. Polar vortex evolution during Northern Hemispheric winter 2004/05

    Directory of Open Access Journals (Sweden)

    T. Chshyolkova

    2007-06-01

    Full Text Available As a part of the project "Atmospheric Wave Influences upon the Winter Polar Vortices (0–100 km" of the CAWSES program, data from meteor and Medium Frequency radars at 12 locations and MetO (UK Meteorological Office global assimilated fields have been analyzed for the first campaign during the Northern Hemispheric winter of 2004/05. The stratospheric state has been described using the conventional zonal mean parameters as well as Q-diagnostic, which allows consideration of the longitudinal variability. The stratosphere was cold during winter of 2004/05, and the polar vortex was relatively strong during most of the winter with relatively weak disturbances occurring at the end of December and the end of January. For this winter the strongest deformation with the splitting of the polar vortex in the lower stratosphere was observed at the end of February. Here the results show strong latitudinal and longitudinal differences that are evident in the stratospheric and mesospheric data sets at different stations. Eastward winds are weaker and oscillations with planetary wave periods have smaller amplitudes at more poleward stations. Accordingly, the occurrence, time and magnitude of the observed reversal of the zonal mesospheric winds associated with stratospheric disturbances depend on the local stratospheric conditions. In general, compared to previous years, the winter of 2004/05 could be characterized by weak planetary wave activity at stratospheric and mesospheric heights.

  15. Greenland Blocking As a Mechanism for Recent Arctic/Mid-Latitude Weather Linkages

    Science.gov (United States)

    Overland, J. E.; Hanna, E.; Wang, M.

    2014-12-01

    High-latitude blocking (HLB) located near and west of Greenland and in northeastern Siberia is a process that links Arctic processes to mid-latitude weather. HLB lies north of the jet stream and tends to bifurcate or divert the jet stream southward, rather than providing a complete block to the westerly flow. It is differentiated from mid-latitude blocking located in the central Atlantic to Europe and the western Pacific along eddy-driven jet streams. It is important to identify and understand an increase in recent HLB in early winter during the last five years relative to time series since 1948, even though this length is too short to robustly distinguish the influence of Arctic forcing from random events. In the last five early winters (December-January 2009-10 through 2013-14), two record and four other negative Arctic Oscillation atmospheric circulation index events have been observed, with positive Greenland Blocking Indices (GBI, greater 500 hPa geopotential heights) and increased geopotential thickness west of Greenland. Cold air penetrated into the southeastern United States in December 2009 and 2010 and January 2014 related to amplification in the long-wave upper-level atmospheric wind pattern. Northward air flow over Davis Strait acts as a positive feedback to maintain the Greenland air temperature anomalies. Extreme negative GBI were observed in December 2011-January 2012. Increased thickness associated with positive GBI can be a response to external (local sea ice loss, Greenland surface warming, or even equatorial teleconnections) or internal (advection and orientation of the long wave patterns) processes. A similar blocking feature is observed in Siberia/eastern Asia. A Bayesian approach to an Arctic/mid-latitude weather linkage emphasizes the nearly irresolvable uncertainty surrounding causation of recent major weather events; yet it drives scientific understanding of linkages and potential impacts on seasonal forecasting.

  16. Daily Evolution of Mid-Latitude Clouds on Titan

    Science.gov (United States)

    Adamkovics, Mate; Barnes, J. W.; Hartung, M.; de Pater, I.

    2008-09-01

    Mid-latitude clouds are observed with the SINFONI integral field spectrograph at the Very Large Telescope (VLT) over four consecutive nights (28 Jan 2007 through 31 Jan 2007 UT) during the Cassini T24 flyby. The initially unresolved clouds occur in the same location on the first two nights, increase dramatically in size on the third night, and are displaced on the final night of observation. Cassini/VIMS observations of the clouds during the flyby indicate that cells within the system of clouds are changing in altitude and spatial extent on hourly timescales. Such mid-latitude cloud activity, occurring over a few hours, was first reported by Griffith et. al, 2005, providing evidence for a convective cloud formation mechanism. If the convectively driven cloud system observed here is indeed associated with precipitation, then the long lifetime and greater than 1000 km spatial extent suggests that it may be similar to mesoscale convective systems on Earth. We discuss this and other speculations related to the formation and daily evolution of Titan's mid-latitude clouds.

  17. Mid-latitude solar eclipses and their influence on ionospheric current systems

    Directory of Open Access Journals (Sweden)

    A. T. Tomás

    2009-12-01

    Full Text Available Using CHAMP magnetic field data we study the behaviour of the geomagnetic field during two mid latitude eclipses on 21 June 2001 and 22 September 2006. The possible influence of the eclipses on different ionospheric current systems, as seen in the magnetic field measured by CHAMP, is discussed. It is expected that the blocking of solar radiation during an eclipse causes a reduction of the ionospheric conductivity and therefore has an effect on the different current systems. We address in particular the effects of the eclipses on the inter-hemispheric field-aligned currents and on the Sq current system. The two events studied occur under different seasonal conditions, e.g. June solstice and September equinox, therefore quite different aspects can be investigated. We find that the eclipses might affect the direction and intensity of the inter-hemispheric currents and possibly influence the direction of zonal winds, therefore changing the direction of the prevailing F-region dynamo currents. The eclipse in the Southern Hemisphere during September equinox caused inter-hemispheric currents similar to those observed in northern summer. Reverse inter-hemispheric currents were recorded after the end of the eclipse. A large variety of atypical currents was observed during the June event. Most of them might be related to a reversed F-region dynamo in the morning sector and an enhanced conductivity difference between the hemispheres. The eclipse in the south seems to enhance the June solstice conditions considerably.

  18. DOAS measurements of tropospheric bromine oxide in mid-latitudes

    Science.gov (United States)

    Hebestreit; Stutz; Rosen; Matveiv; Peleg; Luria; Platt

    1999-01-01

    Episodes of elevated bromine oxide (BrO) concentration are known to occur at high latitudes in the Arctic boundary layer and to lead to catalytic destruction of ozone at those latitudes; these events have not been observed at lower latitudes. With the use of differential optical absorption spectroscopy (DOAS), locally high BrO concentrations were observed at mid-latitudes at the Dead Sea, Israel, during spring 1997. Mixing ratios peaked daily at around 80 parts per trillion around noon and were correlated with low boundary-layer ozone mixing ratios.

  19. Twentieth Century Winter Changes in Southern Hemisphere Synoptic Weather Modes

    Directory of Open Access Journals (Sweden)

    Jorgen S. Frederiksen

    2011-01-01

    Full Text Available During the last sixty years, there have been large changes in the southern hemisphere winter circulation and reductions in rainfall particularly in the southern Australian region. Here we examine the corresponding changes in dynamical modes of variability ranging from storm tracks, onset-of-blocking modes, northwest cloud-band disturbances, Antarctic low-frequency modes, intraseasonal oscillations, and African easterly waves. Our study is performed using a global two-level primitive equation instability-model with reanalyzed observed July three-dimensional basic states for the periods 1949–1968, 1975–1994, and 1997–2006. We relate the reduction in the winter rainfall in the southwest of Western Australia since the mid-1970s and in south-eastern Australia since the mid-1990s to changes in growth rate and structures of leading storm track and blocking modes. We find that cyclogenesis and onset-of-blocking modes growing on the subtropical jet have significantly reduced growth rates in the latter periods. On the other hand there is a significant increase in the growth rate of northwest cloud-band modes and intraseasonal oscillation disturbances that cross Australia and are shown to be related to recent positive trends in winter rainfall over northwest Western Australia and central Australia, in general. The implications of our findings are discussed.

  20. Trends and seasonality of extreme precipitation characteristics related to mid-latitude cyclones in Europe

    Directory of Open Access Journals (Sweden)

    A. Karagiannidis

    2009-03-01

    Full Text Available An attempt is made to study the extreme precipitation characteristics, which are related to the mid-latitude cyclonic systems. Daily pluviometric data, from several stations across the continental Europe and the British Islands, are used. The covered time-period is from 1958 to 2000. Only extreme precipitation events related to mid-latitude cyclonic systems are studied, since thermal thunderstorm episodes are being excluded. To accomplish that, summer months are excluded and a strict criterion for identifying the exact episodes is set, which also defines the episode itself and the extremity of it. A decreasing trend in the cases of extreme precipitation of the European continent was found. It starts in the mid 60's and continues until the mid 70's. After that and until the end of the examined period, no significant trend was found. Seasonality of extreme precipitation cases and episodes is also studied. October and November are the two months that present the higher frequencies of such cases and episodes. In general, autumn months indicate the higher percentages of extreme precipitation, with winter and spring months to follow.

  1. Solar ultraviolet doses and vitamin D in a northern mid-latitude.

    Science.gov (United States)

    Serrano, Maria-Antonia; Cañada, Javier; Moreno, Juan Carlos; Gurrea, Gonzalo

    2017-01-01

    Solar ultraviolet (UV) radiation is one of the most important factors in the development of skin cancer in human, solar erythema and skin aging. Nevertheless, numerous studies have shown the benefits of UV solar radiation in moderate doses, such as the reduction of blood pressure and mental health, treatment of various diseases, and the synthesis of vitamin D in the skin. This paper analyses data from solar ultraviolet erythemal (UVER) irradiance in W/m2 measured in a northern mid-latitude as Valencia (Spain) for the period 2003-2010. To estimate effective solar UV radiation in the production of vitamin D (UVD) we used the relationship proposed by McKenzie et al. (2009). It was obtained for one month for each season the minimum exposure time needed around solar noon and at 9 UTC and 15 UTC (Coordinated Universal Time) to obtain the recommended daily dose of 1000IU. Also, it has been calculated time for erythema induction around solar noon for the same months. The median UVER daily dose during the summer months was 4000J/m2day, and 700J/m2day in winter. With regard to UVD, the median UVD daily dose in summer season was 7700J/m2day, and in winter it was 1000J/m2day. Around noon in January it takes more than two hours of solar exposure to obtain the recommended daily dose of vitamin D, whereas the rest of the year range between 7min on July and 31min on October. For the same months around noon, exposure times to produce erythema were obtained, these being of higher value to the previous. The results show that it is difficult to obtain the recommended vitamin D doses in winter in a northern mid-latitude, as the human body is almost entirely covered in this season. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. The behaviour of stratospheric and upper tropospheric ozone in high and mid latitudes; the role of ozone as a climate gas

    Energy Technology Data Exchange (ETDEWEB)

    Kyroe, M.; Rummukainen, M.; Kivi, R.; Turunen, T.; Karhu, J. [Finnish Meteorological Inst., Sodankylae (Finland); Taalas, P. [Finnish Meteorological Inst., Helsinki (Finland)

    1996-12-31

    During the past few years, the dual role that ozone plays in climate change has been becoming increasingly obvious. First, continuous thinning of the ozone layer has been evident, even in the high and middle latitudes in the northern hemisphere. Secondly, ozone is also a greenhouse gas, affecting radiative transfer. Increases in tropospheric ozone have a positive forcing, whereas decreases in stratospheric ozone cause a negative forcing. During the last six years, measurements on total ozone and the vertical distribution of ozone have been performed at the Sodankylae Observatory. At Jokioinen Observatory, measurements on total ozone have been performed since 1990 and measurements on the vertical distribution of ozone since 1993. The overall project has focused on extending the national data series on total ozone and the vertical distribution of ozone. At the same time, the study has contributed to the study of interannual variability of the ozone layer. This SILMU project took part in the large-scale research activities, in addition to performing national studies. The results confirm that there has been fast chemical ozone destruction in the high latitudes in the northern hemisphere. This was particularly evident in the last two winters, 1994/95 and 1995/96. The new data also allows better trend analyses to be made on ozone in high and mid latitudes

  3. Exposed subsurface ice sheets in the Martian mid-latitudes.

    Science.gov (United States)

    Dundas, Colin M; Bramson, Ali M; Ojha, Lujendra; Wray, James J; Mellon, Michael T; Byrne, Shane; McEwen, Alfred S; Putzig, Nathaniel E; Viola, Donna; Sutton, Sarah; Clark, Erin; Holt, John W

    2018-01-12

    Thick deposits cover broad regions of the Martian mid-latitudes with a smooth mantle; erosion in these regions creates scarps that expose the internal structure of the mantle. We investigated eight of these locations and found that they expose deposits of water ice that can be >100 meters thick, extending downward from depths as shallow as 1 to 2 meters below the surface. The scarps are actively retreating because of sublimation of the exposed water ice. The ice deposits likely originated as snowfall during Mars' high-obliquity periods and have now compacted into massive, fractured, and layered ice. We expect the vertical structure of Martian ice-rich deposits to preserve a record of ice deposition and past climate. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  4. Mid-latitude ozone changes: studies with a 3-D CTM forced by ERA-40 analyses

    Directory of Open Access Journals (Sweden)

    W. Feng

    2007-01-01

    Full Text Available We have used an off-line three-dimensional (3-D chemical transport model (CTM to study long-term changes in stratospheric O3. The model was run from 1977–2004 and forced by ECMWF ERA-40 and operational analyses. Model runs were performed to examine the impact of increasing halogens and additional stratospheric bromine from short-lived source gases. The analyses capture much of the observed interannual variability in column ozone, but there are also unrealistic features. In particular the ERA-40 analyses cause a large positive anomaly in northern hemisphere (NH column O3 in the late 1980s. Also, the change from ERA-40 to operational winds at the start of 2002 introduces abrupt changes in some model fields (e.g. temperature, ozone which affect analysis of trends. The model reproduces the observed column increase in NH mid-latitudes from the mid 1990s. Analysis of a run with fixed halogens shows that this increase is not due to a significant decrease in halogen-induced loss, i.e. is not an indication of recovery. The model predicts only a small decrease in halogen-induced loss after 1999. In the upper stratosphere, despite the modelled turnover of chlorine around 1999, O3 does not increase because of the effects of increasing ECMWF temperatures, decreasing modelled CH4 at this altitude, and abrupt changes in the SH temperatures at the end of the ERA-40 period. The impact of an additional 5 pptv stratospheric bromine from short-lived species decreases mid-latitude column O3 by about 10 DU. However, the impact on the modelled relative O3 anomaly is generally small except during periods of large volcanic loading.

  5. Stratospheric condensation nuclei: A climatology in the mid-latitude and Antarctic regions

    Science.gov (United States)

    Campbell, Patrick C.; Deshler, Terry

    2013-05-01

    Balloon-borne stratospheric condensation nuclei (CN) measurements are presented since 1982 over Laramie, Wyoming (41°N) and since 1986 over McMurdo Station, Antarctica (78°S). In the Antarctic region, the climatology shows the formation of a ubiquitous stratospheric CN layer between 21-27 km around mid August, reaching its maximum extent between September and early October. CN concentrations increase from 10-20 cm-3 to over 100 cm-3. In the northern mid-latitudes, the climatology shows a quasi-annual and smaller CN increase (3-10 cm-3 to over 20 cm-3), which is observed between 25-31 km in late winter and early spring. Major volcanic eruptions appear to enhance CN layers over Laramie and McMurdo. The Arctic Oscillation (AO) generally correlates with the magnitude of the Laramie CN layer, suggesting the importance of meridional transport. Volatility measurements and nucleation modeling support a sulfuric acid and water composition, and binary homogeneous nucleation as the primary CN formation mechanism in both locations. Bi-monthly CN measurements above Laramie support coagulation as the main reason for the dissipation of the CN layer, and suggest that the layer has a global extent. This topic is further investigated using the Whole Atmosphere Community Climate Model (WACCM) coupled with the Community Aerosol and Radiation Model for Atmospheres (CARMA). Air parcel trajectory analyses indicated that Arctic conditions and the associated ambient temperature changes during transport to Laramie, impacts the magnitude of the mid-latitude CN layer. The CN layer over Antarctica may be associated with the decrease in springtime ozone loss above 20 km.

  6. Seasonal ionospheric scintillation analysis during increasing solar activity at mid-latitude

    Science.gov (United States)

    Ahmed, Wasiu Akande; Wu, Falin; Agbaje, Ganiyu Ishola; Ednofri, Ednofri; Marlia, Dessi; Zhao, Yan

    2017-09-01

    Monitoring of ionospheric parameters (such as Total Electron Content and scintillation) is of great importance as it affects and contributes to the errors encountered by radio signals. It thus requires constant measurements to avoid disastrous situation for space agencies, parastatals and departments that employ GNSS applications in their daily operations. The research objective is to have a better understanding of the behaviour of ionospheric scintillation at midlatitude as it threatens the performances of satellite communication, navigation systems and military operations. This paper adopts seasonal ionospheric scintillation scenario. The mid-latitude investigation of ionospheric effect of scintillation was conducted during the increasing solar activity from 2011-2015. Ionospheric scintillation data were obtained from four ionospheric monitoring stations located at mid-latitude (i.e Shenzhen North Station, Beijing Changping North Station Branch, Beijing North Station and Beijing Miyun ground Station). The data was collected from January 2011 to December 2015. There were absence of data due to software problem or system failure at some locations. The scintillation phenomenon was computed using Global Ionospheric Scintillation and TEC Monitoring Model. There are four seasons which existed in China namely: Spring, Summer, Autumn and Winter. The relationship between TEC, amplitude and phase scintillation were observed for each of these seasons. The results indicated that the weak amplitude scintillation was observed as against phase scintillation which was high. Phase scintillation was gradually enhanced from 2011 to 2012 and later declined till 2014. TEC was also at peak around 00:00-10:00 UT (08:00-18:00 LT). The seasonal events temporal density characteristics comply with solar cycle prediction as such it ascended from 2011 to 2013 and then scintillation parameters declined significantly afterwards.

  7. Total ozone patterns over the southern mid-latitudes: spatial correlations, extreme events and dynamical contributions

    Science.gov (United States)

    Rieder, Harald E.; di Rocco, Stefania; Staehelin, Johannes; Maeder, Jörg A.; Ribatet, Mathieu; Peter, Thomas; Davison, Anthony C.

    2010-05-01

    Tools from geostatistics and extreme value theory are applied to analyze spatial correlations in total ozone for the southern mid-latitudes. The dataset used in this study is the NIWA-assimilated total ozone dataset (Bodeker et al., 2001; Müller et al., 2008). Recently new tools from extreme value theory (Coles, 2001; Ribatet, 2007) have been applied to the world's longest total ozone record from Arosa, Switzerland (e.g. Staehelin 1998a,b) and 5 other long-term ground based stations to describe extreme events in low and high total ozone (Rieder et al., 2010a,b,c). Excursions in the frequency of extreme events reveal "fingerprints" of dynamical factors such as ENSO or NAO, and chemical factors, such as cold Arctic vortex ozone losses, as well as major volcanic eruptions of the 20th century (e.g. Gunung Agung, El Chichón, Mt. Pinatubo). Furthermore, atmospheric loading in ozone depleting substances lead to a continuous modification of column ozone in the northern hemisphere also with respect to extreme values (partly again in connection with polar vortex contributions). It is shown that application of extreme value theory allows the identification of many more of such fingerprints than conventional time series analysis on basis of annual and seasonal mean values. Especially, the analysis shows the strong influence of dynamics, revealing that even moderate ENSO and NAO events have a discernible effect on total ozone (Rieder et al., 2010b,c). Within the current study patterns in spatial correlation and frequency distributions of extreme events (e.g. ELOs and EHOs) are studied for the southern mid-latitudes. It is analyzed if "fingerprints"found for features in the northern hemisphere occur also in the southern mid-latitudes. New insights in spatial patterns of total ozone for the southern mid-latitudes are presented. Within this study the influence of changes in atmospheric dynamics (e.g. tropospheric and lower stratospheric pressure systems, ENSO) as well as

  8. Cluster observations of mid-latitude hiss near the plasmapause

    Directory of Open Access Journals (Sweden)

    A. Masson

    2004-07-01

    Full Text Available In the vicinity of the plasmapause, around the geomagnetic equator, the four Cluster satellites often observe banded hiss-like electromagnetic emissions (BHE; below the electron gyrofrequency but above the lower hybrid resonance, from 2kHz to 10kHz. We show that below 4kHz, these waves propagate in the whistler mode. Using the first year of scientific operations of WHISPER, STAFF and WBD wave experiments on Cluster, we have identified the following properties of the BHE waves: (i their location is strongly correlated with the position of the plasmapause, (ii no MLT dependence has been found, (iii their spectral width is generally 1 to 2kHz, and (iv the central frequency of their emission band varies from 2kHz to 10kHz. All these features suggest that BHE are in fact mid-latitude hiss emissions (MLH. Moreover, the central frequency was found to be correlated with the Kp index. This suggests either that these banded emissions are generated in a given f/fce range, or that there is a Kp dependent Doppler shift between the satellites and a possible moving source of the MLH.

  9. Ion transport in the mid-latitude F1-region

    Science.gov (United States)

    Footitt, R. J.; Bailey, G. J.; Moffett, R. J.

    1983-06-01

    Taieb et al. (1975) have analyzed data gathered by the French multistatic incoherent scatter radar facility at St. Santin during the period 1967-1972 in the altitude range from 120 to 200 km. They have found that the electron concentration increases as a function of altitude up to a maximum value at a certain altitude and then decreases to a minimum value at a higher altitude before increasing monotonically towards the normal F2 peak value. It is also found that this 'valley' appears just after sunrise and disappears just before sunset. The 'daytime valley' in the F1 region is present only from March to September. The present investigation is concerned with the importance of plasma motions in the daytime mid-latitude F1-region, taking into account the measurements made at St. Santin. Through simultaneous solutions of the coupled continuity and momentum equations for the O(+), O2(+), NO(+), and N2(+) ions it is demonstrated that an F1-valley in the daytime electron concentration altitude profile can be produced by two mechanisms.

  10. Mid-Latitude Circulation and Extremes in a Changing Climate

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Gang [Cornell Univ., Ithaca, NY (United States)

    2016-08-04

    Mid-latitude extreme weather events are responsible for a large part of climate-related damage. Yet large uncertainties remain in climate model projections of heat waves, droughts, and heavy rain/snow events on regional scales, limiting our ability to effectively use these projections for climate adaptation and mitigation. These uncertainties can be attributed to both the lack of spatial resolution in the models, and to the lack of a dynamical understanding of these extremes. The approach of this project is to relate the fine-scale features to the large scales in current climate simulations, seasonal re-forecasts, and climate change projections in a very wide range of models, including the atmospheric and coupled models of ECMWF over a range of horizontal resolutions (125 to 10 km), aqua-planet configuration of the Model for Prediction Across Scales and High Order Method Modeling Environments (resolutions ranging from 240 km – 7.5 km) with various physics suites, and selected CMIP5 model simulations. The large scale circulation will be quantified both on the basis of the well tested preferred circulation regime approach, and very recently developed measures, the finite amplitude Wave Activity (FAWA) and its spectrum. The fine scale structures related to extremes will be diagnosed following the latest approaches in the literature. The goal is to use the large scale measures as indicators of the probability of occurrence of the finer scale structures, and hence extreme events. These indicators will then be applied to the CMIP5 models and time-slice projections of a future climate.

  11. A numerical study of ionospheric profiles for mid-latitudes

    Directory of Open Access Journals (Sweden)

    S.-R. Zhang

    1995-05-01

    Full Text Available This paper presents a numerical model and results for the mid-latitude ionospheric profile below the peak of the F2-layer. The basis of the model is the solving of equations for four ionic species O+, NO+, O+2 and N+2, as well as the meta-stable O+(2D and O+(2P. Diffusion and wind-induced drifts and 21 photo-chemical reactions are also taken into account. Neutral atmospheric density and temperature are derived from the MSIS86 model and solar extreme ultraviolate irradiance from the EUV91 model. In an effort to obtain a more realistic ionospheric profile, the key point at foF2 and hmF2 is fitted from the simulation to observations. The model also utilizes the vertical drifts derived from ionosonde data with the help of the Servo model. It is shown that the ionospheric height of peak can be reproduced more accurately under the derived vertical drifts from the Servo theory than with the HWM90 model. Results from the simulation are given for Wuchang (30.5°N, 114.4°E and Wakkanai (45.6°N, 141.7°E, showing the profile changes with season and solar activity, and the E-F valley structure (the depth and the width. This simulation also reveals the importance of meta-stable ions and dynamical transport processes on the formation of the F1-ledge and F1-F2 valley.

  12. Seasonal and interannual variability of mesospheric gravity wave activity at high and mid-latitudes

    Science.gov (United States)

    Hoffmann, Peter; Singer, Werner; Becker, Erich; Latteck, Ralph; Keuer, Dieter

    The seasonal variation and interannual variability of the gravity wave activity in the mesosphere/lower thermosphere (MLT) region at high and mid-latitudes is investigated. Variations of the gravity wave activity are examined in relation to the filtering processes due to the changes of the background winds, tides and planetary waves. Our studies are basing on wind measurements from meteor and MF radars at Andenes (69° N, 16° E) and Juliusruh (55° N, 13° E). These measurements are supplemented by mesospheric temperatures derived from meteor decay times. Additionally, turbulent energy dissipation rates have been estimated from spectral width measurements using a 3 MHz Doppler radar near Andenes. Particular attention is directed to the influence of the solar activity on the gravity wave activity during the summer months when the mesospheric winds show the strongest correlation with the solar activity. Possible dependencies between the occurrence rates of polar mesospheric summer echoes (PMSE) and the gravity wave activity are discussed. Furthermore, the activity of gravity waves and their dissipation are investigated in winter in relation with wind changes during sudden stratospheric warming (SSW) events. The summer/ winter behavior of the gravity wave activity will be compared to simulations with the simple general circulation model KMCM (K¨hlungsborn Mechanistic u Circulation Model) that extends up to 100 km. In all cases, the percentage rates of the kinetic energy of defined period ranges in relation to the total variances of the horizontal wind fluctuations are estimated.

  13. Testing the water hypothesis: Quantitative morphological analysis of terrestrial and martian mid-latitude gullies

    Science.gov (United States)

    Hobbs, S. W.; Paull, D. J.; Clarke, J. D. A.

    2017-10-01

    Although Martian gullies resemble terrestrial counterparts, two conflicting hypotheses exist for their formation still invoke fluvial processes on the one hand or lubricated CO2 flows on the other. In this work we compared the quantitative morphology of terrestrial gullies, known to have formed by liquid water, and mid-latitude Martian gullies in the Martian southern hemisphere. We also compared these results with measurements of Martian dry ravines adjacent to the gullies. Our results show a similarity between Martian and terrestrial gully formation, supporting the hypothesis that liquid water was involved in their erosion. Our results show dry ravines differ morphologically from gullies, further suggesting fluidised flows as a likely origin of the latter. Variations in the relationships across various terrestrial and Martian gullies indicate the significance of local environmental and geological conditions. Our work supports the idea that Martian gullies may not have been formed by just one single process but may have evolved through a more complex interaction of processes and environment.

  14. Study of water vapor, carbon dioxide and methane fluxes in mid-latitude prairie wetlands

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This proposal is for a research/management study that will provide urgently needed information on carbon dioxide, methane and energy fluxes from mid-latitude...

  15. Air Flow Through Two Wintertime Mid-Latitude Cyclones Interacting with Mountains

    Science.gov (United States)

    Brugman, M. M.; Macdonald, A.; Mo, R.; Milbrandt, J.; Mctaggart-Cowan, R.; Smith, T.; Goosen, J.; Isaac, G. A.

    2011-12-01

    The conveyor belt and tropospheric folding conceptual models of a mid-latitude storm system were examined to determine their utility for improving analysis and forecasting of wintertime precipitation events over the rugged coastal mountains of British Columbia. A Doppler C-band radar probed the underside of several strong cyclones as they crossed the BC coastal ranges. The radar profiles indicated wind shifts and reflectivity layering. The layering was also evident in the moisture, precipitation (type and amount), temperature and wind patterns data collected by SNOW-V10 during the Vancouver 2010 Olympics. Storms from Feb 13-14 and March 12, 2010 are examined in this paper. Air Quality data from Whistler Mountain (elevation 2182 m asl) showed elevated ozone levels ahead of the warm front. The lower elevation sensors nearby did not show ozone with the same warm front or ahead of Trowal features. The ozone pattern observed for these storms was characteristic of similar storms investigated during 2010-2011 and can be best explained using a combination of tropospheric folding and conveyor belt conceptual models. Diabatic cooling due to melting snowfall and associated down valley winds were observed, but flow speeds were greater than expected from the existing operational forecasting models. Results imply that tropospheric folding (STE), cold conveyor dynamics and stronger low level outflow of dry air contribute to enhanced diabatic cooling. This appears to generate stronger down valley outflow winds that help excite gravity waves beneath the warm moist conveyor belt. A feedback between storm intensification, diabatic cooling and heavy precipitation is suggested by the results. A multi-moment precipitation scheme in the experimental Olympic GEM 2.5 and 1 km models reproduced some but not all diabatic effects. A review of all the major winter storms identified by the SNOW-V10 researchers, the 2010 Olympic forecasters and the Pacific Storm Prediction Centre operational

  16. Understanding Predictive Skill of Arctic Sea Ice and its Linkage with Mid-Latitude Weather and Climate in the NCEP Climate Forecast System

    Science.gov (United States)

    McHugh, Colleen

    Arctic climate is undergoing significant change, particularly rapid decline of sea ice. Arctic sea ice plays an important role in local, regional, and global climate through a variety of physical processes as seen in observational analysis as well as modeling studies. Recent research suggested that decreasing autumn and winter Arctic sea ice extent (SIE) has been shown to have an effect on mid-latitude weather patterns during the winter months. Therefore, accurate forecasts of Arctic sea ice extent and the associated teleconnections with the mid-latitudes are important for accurate seasonal climate prediction. The NCEP Climate Forecast System version 2 (CFSv2) is a fully coupled atmosphere-ocean-sea ice-land surface model that is used for seasonal climate prediction and climate reanalysis. This study will evaluate 1) if the CFSv2 can reproduce the observed variability of Arctic SIE in the CFSv2 reanalysis and reforecasts and 2) to what extent the CFSv2 can reproduce the observed linkages seen in mid-latitude weather patterns in its reanalysis and reforecasts. Results show that the CFSv2 reanalysis captures most of the observed variability of autumn and winter SIE but overestimates SIE in both seasons, whereas CFSv2 reforecasts for three different lead times (1-3 months) underestimate SIE in both seasons and are not good in predicting the observed interannual variability. In terms of the winter atmospheric circulation linked to autumn and winter Arctic SIE variability, the CFSv2 reanalysis is able to capture most observed features, however overestimates the magnitude of the negative pressure anomalies in the mid-latitudes, and surface warming at the high latitudes and mid-latitude cooling. The CFSv2 reforecasts miss several observed key features in the atmospheric circulation regression pattern. There is no significant widespread cooling in Eurasia seen in any reforecast, and while all reforecasts show high-latitude warming, it is overestimated in magnitude and

  17. Empirical orthogonal functions and multiple flow regimes in the Southern Hemisphere winter

    Science.gov (United States)

    Farrara, John D.; Ghil, Michael; Mechoso, Carlos R.; Mo, Kingtse C.

    1989-01-01

    A new empirical orthogonal function (EOF) analysis of winter 500 mb geopotential height anomalies in the Southern Hemisphere is presented. An earlier EOF analysis prefiltered the anomalies to exclude wavenumbers 5 and higher; the present analysis does not. The different preprocessing of data affects the results. All three distinct planetary flow regimes identified in the winter circulation of the Southern Hemisphere by a pattern correlation method are captured by the new set of EOFs; only two of those regimes were captured by the earlier set. The new results, therefore, lend further support to the idea that EOFs point to distinct planetary flow regimes.

  18. Characteristics of mid-latitude planetary waves in the lower atmosphere derived from radiosonde data

    Directory of Open Access Journals (Sweden)

    R. Wang

    2012-10-01

    Full Text Available The activities of mid-latitude planetary waves (PWs in the troposphere and lower stratosphere (TLS are presented by using the radiosonde data from 2000 to 2004 over four American stations (Miramar Nas, 32.9° N, 117.2° W; Santa Teresa, 31.9° N, 106.7° W; Fort Worth, 32.8° N, 97.3° W; and Birmingham, 33.1° N, 86.7° W and one Chinese station (Wuhan, 30.5° N, 114.4° E. Statistically, strong PWs mainly appear around subtropical jet stream in the troposphere and lower stratosphere. In the troposphere, the activities of the mid-latitude PWs are strong around the centre of the subtropical jet stream in winter and become small near the tropopause, which indicates that the subtropical jet stream may strengthen the propagation of PWs or even be one of the PW excitation sources. Among the three disturbance components of temperature, zonal and meridional winds, PWs at Wuhan are stronger in the temperature component, but weaker in the zonal wind component than at the other four American stations. While in the meridional wind component, the strengths of PW spectral amplitudes at the four American stations decrease from west to east, and their amplitudes are all larger than that of Wuhan. However, the PWs are much weaker in the stratosphere and only the lower frequency parts remain. The amplitudes of the PWs in the stratosphere increase with height and are strong in winter with the zonal wind component being the strongest. Using the refractive index, we found that whether the PWs could propagate upward to the stratosphere depends on the thickness of the tropopause reflection layer. In the case study of the 2000/2001 winter, it is observed that the quasi 16-day wave in the troposphere is a quasi standing wave in the vertical direction and propagates upward slowly with vertical wavelength greater than 24 km in the meridional component. It propagates eastward with the zonal numbers between 5 and 8, and the quasi 16-day wave at Wuhan is probably the same

  19. Ionospheric variations during sudden stratospheric warming in the high- and mid-latitude regions

    Science.gov (United States)

    Yasyukevich, Anna; Voeykov, Sergey; Mylnikova, Anna

    2017-04-01

    The ionospheric dynamic in the high- and middle-latitude regions during the periods of sudden stratospheric warmings (SSW) was studied by using the international network of phase dual-frequency GPS/GLONASS receivers and the vertical sounding data. Twelve SSW events that occurred in the Northern Hemisphere 2006 through 2013 were considered. In order to identify the possible response of the ionosphere to SSW events, we carried out the analysis of the total electron (TEC) and the F2-layer maximum electron density (NmF2) deviations from the background level. We have also studied changes of the level of total electron content (TEC) wave-like variations characterized by a special index WTEC. The index reflects the intensity of medium- and large-scale traveling ionospheric disturbances. The dynamics of the high- and middle-latitude ionosphere at the points near the SSW areas was found to differ from the regular. For a large number of events, it is shown that, despite quiet geomagnetic conditions, a noticeable decrease in the NmF2 and TEC values (by 5-10% relative to the background level) is observed during the SSW evolution and maximum stages. On the contrary, for 10-20 days after the SSW maxima, NmF2 and TEC significantly exceed the monthly averaged values. Moreover, these electron density changes are observed for both strong and weak stratospheric warmings, and are recorded mainly during daytime. The observed SSW effects in the polar and mid-latitude ionosphere are assumed to be probably associated with the changes in the neutral composition at the thermospheric heights that affect the F2-layer electron density. The study is supported by the Russian Foundation for Basic Research under Grant No. 16-35-60018, as well as by the RF President Grant of Public Support for RF Leading Scientific Schools (NSh-6894.2016.5).

  20. Remote impact of the Antarctic atmosphere on the southern mid-latitudes

    OpenAIRE

    Tido Semmler; Kasper, Marta A.; Thomas Jung; Soumia Serrar

    2016-01-01

    Would improved prediction capabilities over the Antarctic lead to improved forecast skill in southern mid-latitudes? Or more generally speaking, how large is the influence of the Antarctic atmosphere on the weather and climate of the southern mid-latitudes? To answer these questions we assess the skill of two sets of 14‑day forecasts with the Integrated Forecast System of the European Centre for Medium-Range Weather Forecasts with and without relaxation towards the Interim reanalysis of the E...

  1. A study of quasi-millennial extratropical winter cyclone activity over the Southern Hemisphere

    Science.gov (United States)

    Xia, Lan; von Storch, Hans; Feser, Frauke; Wu, Jian

    2016-10-01

    The winter extratropical cyclone activity in the Southern Hemisphere during the last one thousand years within a global climate simulation was analyzed by tracking cyclones, and then clustering them into ten clusters consecutively for each hundred years. There is very strong year-to-year variability for Southern Hemispheric winter extratropical cyclone numbers and larger variations on centennial time scale, more so than for its Northern Hemispherical counterparts. However, no obvious trend can be found. The mean tracks of clusters over the Southern Indian Ocean and near New Zealand shift poleward from the eleventh to the twentieth century while the clusters in the central Southern Pacific shift equatorward. Storm track clusters with largest deepening rates are found over the Southwestern Indian Ocean. In the twentieth century, rapidly deepening cyclones appear more often while long lifespan cyclones appear less frequently. The winter storm activity in the Southern Hemisphere is closely related to the Antarctic Oscillation. The cyclone frequency over the Indian Ocean and South Pacific Ocean can be associated with the Indian Ocean Dipole and El Nino-Southern Oscillation respectively.

  2. Hydrological indications of aeolian salts in mid-latitude deserts of ...

    Indian Academy of Sciences (India)

    Hydrological indications of aeolian salts in mid-latitude deserts of northwestern China. B Q Zhu. Supplementary data. Figure S1. Photograph views of Quaternary and modern sediments of aeolian and lacustrine/fluvial facies that consisted of clay and sand/silt sand alternations in the Taklamakan and Badanjilin Deserts.

  3. Ice-bearing deposits in the southern mid-latitude regions of Terra Cimmeria, Mars

    Science.gov (United States)

    Adeli, S.; Hauber, E.; Jaumann, R.; Michael, G.; Fawdon, P.

    2017-09-01

    We report here the presence of a newly observed well-preserved glacial-like and ice-bearing deposit, named Valley Fill Deposit (VFD), on the surface of Terra Cimmeria, located in the southern mid-latitude regions of Mars.

  4. The influence of mid-latitude storm tracks on hot, cold, dry and wet extremes

    NARCIS (Netherlands)

    Lehmann, Jascha; Coumou, Dim

    2015-01-01

    Changes in mid-latitude circulation can strongly affect the number and intensity of extreme weather events. In particular, high-amplitude quasi-stationary planetary waves have been linked to prolonged weather extremes at the surface. In contrast, analyses of fast-traveling synoptic-scale waves and

  5. Study of the tidal variations in mesospheric temperature at low and mid latitudes from WINDII and potassium lidar observations

    Directory of Open Access Journals (Sweden)

    M. Shepherd

    2004-04-01

    Full Text Available Zonal mean daytime temperatures from the Wind Imaging Interferometer (WINDII on the Upper Atmosphere Research Satellite (UARS and nightly temperatures from a potassium (K lidar are employed in the study of the tidal variations in mesospheric temperature at low and mid latitudes in the Northern Hemisphere. The analysis is applied to observations at 89km height for winter solstice, December to February (DJF, at 55° N, and for May and November at 28° N. The WINDII results are based on observations from 1991 to 1997. The K-lidar observations for DJF at Kühlungsborn (54° N were from 1996–1999, while those for May and November at Tenerife 28° N were from 1999. To avoid possible effects from year-to-year variability in the temperatures observed, as well as differences due to instrument calibration and observation periods, the mean temperature field is removed from the respective data sets, assuming that only tidal and planetary scale perturbations remain in the temperature residuals. The latter are then binned in 0.5h periods and the individual data sets are fitted in a least-mean square sense to 12-h and 8-h harmonics, to infer semidiurnal and terdiurnal tidal parameters. Both the K-lidar and WINDII independently observed a strong semidiurnal tide in November, with amplitudes of 13K and 7.4K, respectively. Good agreement was also found in the tidal parameters derived from the two data sets for DJF and May. It was recognized that insufficient local time coverage of the two separate data sets could lead to an overestimation of the semidiurnal tidal amplitude. A combined ground-based/satellite data set with full diurnal local time coverage was created which was fitted to 24h+12h+8h harmonics and a novel method applied to account for possible differences between the daytime and nighttime means. The results still yielded a strong semidiurnal tide in November at 28° N with an amplitude of 8.8K which is twice the SD amplitude in May and DJF. The

  6. Scotland's forgotten carbon: a national assessment of mid-latitude fjord sedimentary carbon stocks

    Directory of Open Access Journals (Sweden)

    C. Smeaton

    2017-12-01

    Full Text Available Fjords are recognised as hotspots for the burial and long-term storage of carbon (C and potentially provide a significant climate regulation service over multiple timescales. Understanding the magnitude of marine sedimentary C stores and the processes which govern their development is fundamental to understanding the role of the coastal ocean in the global C cycle. In this study, we use the mid-latitude fjords of Scotland as a natural laboratory to further develop methods to quantify these marine sedimentary C stores on both the individual fjord and national scale. Targeted geophysical and geochemical analysis has allowed the quantification of sedimentary C stocks for a number of mid-latitude fjords and, coupled with upscaling techniques based on fjord classification, has generated the first full national sedimentary C inventory for a fjordic system. The sediments within these mid-latitude fjords hold 640.7 ± 46 Mt of C split between 295.6 ± 52 and 345.1 ± 39 Mt of organic and inorganic C, respectively. When compared, these marine mid-latitude sedimentary C stores are of similar magnitude to their terrestrial equivalents, with the exception of the Scottish peatlands, which hold significantly more C. However, when area-normalised comparisons are made, these mid-latitude fjords are significantly more effective as C stores than their terrestrial counterparts, including Scottish peatlands. The C held within Scotland's coastal marine sediments has been largely overlooked as a significant component of the nation's natural capital; such coastal C stores are likely to be key to understanding and constraining improved global C budgets.

  7. Interaction of mid-latitude air masses with the polar dome area during RACEPAC and NETCARE

    Science.gov (United States)

    Bozem, Heiko; Hoor, Peter; Koellner, Franziska; Kunkel, Daniel; Schneider, Johannes; Schulz, Christiane; Herber, Andreas; Borrmann, Stephan; Wendisch, Manfred; Ehrlich, Andre; Leaitch, Richard; Willis, Megan; Burkart, Julia; Thomas, Jennie; Abbatt, Jon

    2016-04-01

    We present aircraft based trace gas measurements in the Arctic during RACEPAC (2014) and NETCARE (2014 and 2015) with the Polar 6 aircraft of Alfred Wegener Institute (AWI) covering an area from 134°W to 17°W and 68°N to 83°N. We focus on cloud, aerosol and general transport processes of polluted air masses into the high Arctic. Based on CO and CO2 measurements and kinematic 10-day back trajectories as well as Flexpart particle dispersion modeling we analyze the transport regimes of mid-latitude air masses traveling to the high Arctic prevalent during spring (RACEPAC 2014, NETCARE 2015) and summer (NETCARE 2014). In general more northern parts of the high Arctic (Lat > 75°N) were relatively unaffected from mid-latitude air masses. In contrast, regions further south are influenced by air masses from Asia and Russia (eastern part of Canadian Arctic and European Arctic) as well as from North America (central and western parts of Canadian Arctic). The transition between the mostly isolated high Arctic and more southern regions indicated by tracer gradients is remarkably sharp. This allows for a chemical definition of the Polar dome based on the variability of CO and CO2 as a marker. Isentropic surfaces that slope from the surface to higher altitudes in the high Arctic form the polar dome that represents a transport barrier for mid-latitude air masses to enter the lower troposphere in the high Arctic. Synoptic-scale weather systems frequently disturb this transport barrier and foster the exchange between air masses from the mid-latitudes and polar regions. This can finally lead to enhanced pollution levels in the lower polar troposphere. Mid-latitude pollution plumes from biomass burning or flaring entering the polar dome area lead to an enhancement of 30% of the observed CO mixing ratio within the polar dome area.

  8. Instabilities in the relation between European Weather Types and mid-latitude circulation in the Atlantic

    Science.gov (United States)

    Alvarez Castro, Maria del Carmen; Gallego, David; Trigo, Ricardo M.; García-Herrera, Ricardo; Ribera, Pedro

    2015-04-01

    Recently, a new instrumental index (Westerly Index or "WI") measuring the frequency of the westerlies over the English Channel has been developed for the period 1685-1750 (Wheeler et al. 2009) and further extended to the present (Barriopedro et al. 2014). This index holds a climatic signal similar to the North Atlantic Oscillation (NAO) in the temperature and precipitation over large areas of Europe. Nevertheless we are confident that the WI offers two major advantages: first the WI signatures are not restricted to the winter being significant during the entire year and second, the WI does not rely on proxy data and, as such, it is less prone to the uncertainties associated to the calibration process of the NAO reconstructions. During the last decades, regional mid-latitude circulation has also been quantified objectively through the widespread use of so-called Weather Types (WT). WT are used to identify and classify the different patterns of Sea Level Pressure configurations originating particular weather in a given area. In consequence, WT over most Western Europe should be closely related to atmospheric circulation indexes such as the WI. Here we adopted a similar WT classification of the classical WTs developed empirically by Hubert Lamb for the UK and automated by Jones et al. (1993) but centered at the English Channel latitudinal band to be compatible with the window used to define the WI (Wheeler et al., 2009). In this work we compare the long-term (1850-2003) monthly values of WI with the corresponding monthly frequency of directional weather types in the WI area. As expected, we found significant positive (negative) correlation values with WTs dominated by a westerly (easterly) component but interestingly, some quasi periodic intervals of lack of correlation have been found, suggesting an oscillating behaviour on the lack of stationarity between the large-scale north Atlantic circulation and local weather types. Wheeler, D.; García-Herrera, R.; Wilkinson

  9. Modes of variability of the vertical temperature profile of the middle atmosphere at mid-latitude: Similarities with solar forcing

    Science.gov (United States)

    Keckhut, Philippe; Hauchecorne, Alain; Kerzenmacher, Tobias; Angot, Guillaume

    2012-02-01

    A long and continuous temperature data set from ground to mesopause was obtained in merging lidar and radiosonde data at mid-latitude over south of France (44°N). The analyses using Empirical Orthogonal Functions has been applied on vertical temperature profiles to investigate the variability differently than it has been done in previous investigations. This study reveals as the first mode in winter, a strong anti-correlation between upper stratosphere and mesosphere that is most probably link with planetary waves propagation and associated stratospheric warmings. While in summer the variability is located in the mesosphere and associated with mesospheric inversions that are probably generated by gravity waves breaking. This study shows that even if the daily temperature variability appears to be complex, a large part (30%) can be modeled, each season, using the first EOF. These vertical patterns exhibit some similarities with solar-atmospheric responses, suggesting a potential feedback of the dynamic. This is already observed for winter response, but during summer the contribution of gravity waves on the mesospheric solar response suggests future investigations to explore the role of this potential mechanism in solar-atmospheric connections.

  10. Estimation of Aerosol Direct Radiative Effects Over the Mid-Latitude North Atlantic from Satellite and In Situ Measurements

    Science.gov (United States)

    Bergstrom, Robert W.; Russell, P. B.

    2000-01-01

    We estimate solar radiative flux changes due to aerosols over the mid-latitude North Atlantic by combining optical depths from AVHRR measurements with aerosol properties from the recent TARFOX program. Results show that, over the ocean the aerosol decreases the net radiative flux at the tropopause and therefore has a cooling effect. Cloud-free, 24-hour average flux changes range from -9 W/sq m near the eastern US coast in summer to -1 W/sq m in the mid-Atlantic during winter. Cloud-free North Atlantic regional averages range from -5.1 W/sq m in summer to -1.7 W/sq m in winter, with an annual average of -3.5 W/sq m. Cloud effects estimated from ISCCP data, reduce the regional annual average to -0.8 W/sq m. All values are for the moderately absorbing TARFOX aerosol (omega(0.55 microns) = 0.9); values for a nonabsorbing aerosol are approx. 30% more negative. We compare our results to a variety of other calculations of aerosol radiative effects.

  11. An analysis on the mid-latitude scintillation and coherence frequency bandwidth using transionospheric VHF signals

    Energy Technology Data Exchange (ETDEWEB)

    Juang, Zhen [Los Alamos National Laboratory; Roussel-dupre, Robert [Los Alamos National Laboratory

    2008-01-01

    An analysis was perfonned on the mid-latitude scintillation and coherence frequency bandwidth (Fcoh) using transionospheric VHF signal data. The data include 1062 events spanning from November 1997 to June 2002. Each event records FORTE satellite received VHF signals from LAPP located at Los Alamos, New Mexico. Fcohs were derived to study scintillation characteristics on diurnal and seasonal variations, as well as changes due to solar and geomagnetic activities. Comparisons to the VHFIUHF coherence frequency bandwidth studies previously reported at equatorial and mid-latitude regions are made using a 4th power frequency dependence relationship. Furthennore, a wideband ionospheric scintillation model, WBMOD, was used to estimate Fcohs and compared with our VHF Fcoh values. Our analysis indicates mid-latitude scintillation characteristics that are not previously revealed. At the VHF bottom frequency range (3035 MHz), distinguished smaller Fcohs are found in time period from sunset to midnight, in wann season from May to August, and in low solar activity years. The effects of geomagnetic storm activity on Fcoh are characterized by a sudden transition at a Kp index of 50-60. Comparisons with median Fcohs estimated from other studies validated our VHF Fcohs for daytime while an order of magnitude larger Fcohs are found for nighttime, implying a time-dependent issue in applying the 4th order power relationship. Furthermore, comparisons with WBMOD-estimated Fcohs indicated generally matched median scintillation level estimates while differences do exist for those events undergoing high geomagnetic stonn activity which may imply underestimates of scintillation level by the WBMOD in the mid-latitude regions.

  12. Mid-Latitude Mobile Wideband HF- NVIS Channel Analysis: Part 1

    Science.gov (United States)

    2017-09-14

    11 5 Virtual heights and round-trip travel times (delay) at 5.82 MHz estimated from Figure 41 26 6 Index of refraction, modes, and acute-angle...fewer layers. In this report, the mid-latitude region is relatively stable with only one traveling ionospheric disturbance (TID) observed in these...Satellite Communications SBIR Small Business Innovation Research SDR Software-defined Radio SIMO Single Input Multiple Output SISO Single Input Single

  13. Are greenhouse gas signals of Northern Hemisphere winter extra-tropical cyclone activity dependent on the identification and tracking algorithm?

    Energy Technology Data Exchange (ETDEWEB)

    Ulbrich, Uwe; Grieger, Jens [Freie Univ. Berlin (Germany). Inst. of Meteorology; Leckebusch, Gregor C. [Birmingham Univ. (United Kingdom). School of Geography, Earth and Environmental Sciences] [and others

    2013-02-15

    For Northern Hemisphere extra-tropical cyclone activity, the dependency of a potential anthropogenic climate change signal on the identification method applied is analysed. This study investigates the impact of the used algorithm on the changing signal, not the robustness of the climate change signal itself. Using one single transient AOGCM simulation as standard input for eleven state-of-the-art identification methods, the patterns of model simulated present day climatologies are found to be close to those computed from re-analysis, independent of the method applied. Although differences in the total number of cyclones identified exist, the climate change signals (IPCC SRES A1B) in the model run considered are largely similar between methods for all cyclones. Taking into account all tracks, decreasing numbers are found in the Mediterranean, the Arctic in the Barents and Greenland Seas, the mid-latitude Pacific and North America. Changing patterns are even more similar, if only the most severe systems are considered: the methods reveal a coherent statistically significant increase in frequency over the eastern North Atlantic and North Pacific. We found that the differences between the methods considered are largely due to the different role of weaker systems in the specific methods. (orig.)

  14. Mid-latitude Ionospheric Storms Density Gradients, Winds, and Drifts Estimated from GPS TEC Imaging

    Science.gov (United States)

    Datta-Barua, S.; Bust, G. S.

    2012-12-01

    Ionospheric storm processes at mid-latitudes stand in stark contrast to the typical quiescent behavior. Storm enhanced density (SED) on the dayside affects continent-sized regions horizontally and are often associated with a plume that extends poleward and upward into the nightside. One proposed cause of this behavior is the sub-auroral polarization stream (SAPS) acting on the SED, and neutral wind effects. The electric field and its effect connecting mid-latitude and polar regions are just beginning to be understood and modeled. Another possible coupling effect is due to neutral winds, particularly those generated at high latitudes by joule heating effects. Of particular interest are electric fields and winds along the boundaries of the SED and plume, because these may be at least partly a cause of sharp horizontal electron density gradients. Thus, it is important to understand what bearing the drifts and winds, and any spatial variations in them (e.g., shear), have on the structure of the enhancement, particularly at its boundaries. Imaging techniques based on GPS TEC play a significant role in study of mid-latitude storm dynamics, particularly at mid-latitudes, where sampling of the ionosphere with ground-based GPS lines of sight is most dense. Ionospheric Data Assimilation 4-Dimensional (IDA4D) is a plasma density estimation algorithm that has been used in a number of scientific investigations over several years. Recently, efforts to estimate drivers of the mid-latitude ionosphere, focusing on electric-field-induced drifts and neutral winds, based on GPS TEC high-resolution imaging have shown promise. Estimating Ionospheric Parameters from Ionospheric Reverse Engineering (EMPIRE) is a tool developed that addresses this kind of investigation. In this work electron density and driver estimates are presented for an ionospheric storm using IDA4D in conjunction with EMPIRE. The IDA4D estimates resolve F-region electron densities at 1-degree resolution at the region

  15. Variability in winter mass balance of Northern Hemisphere glaciers and relations with atmospheric circulation

    Science.gov (United States)

    McCabe, G.J.; Fountain, A.G.; Dyurgerov, M.

    2000-01-01

    An analysis of variability in the winter mass balance (WMB) of 22 glaciers in the Northern Hemisphere indicates two primary modes of variability that explain 46% of the variability among all glaciers. The first mode of variability characterizes WMB variability in Northern and Central Europe and the second mode primarily represents WMB variability in northwestern North America, but also is related to variability in WMB of one glacier in Europe and one in Central Asia. These two modes of WMB variability are explained by variations in mesoscale atmospheric circulation which are driving forces of variations in surface temperature and precipitation. The first mode is highly correlated with the Arctic Oscillation Index, whereas the second mode is highly correlated with the Southern Oscillation Index. In addition, the second mode of WMB variability is highly correlated with variability in global winter temperatures. This result suggests some connection between global temperature trends and WMB for some glaciers.

  16. Observational evidence of preferred flow regimes in the Northern Hemisphere winter stratosphere

    Science.gov (United States)

    Pierce, R. B.; Fairlie, T. D. A.

    1993-01-01

    Ten years of stratospheric geopotential height data are analyzed in an attempt to determine whether there are preferred flow regimes in the Northern Hemisphere winter stratosphere. The data are taken from Stratospheric Sounding Units on board NOAA satellites. The probability density estimate of the amplitude of the wavenumber 1 10-mb height is found to be bimodal. The density distribution is composed of a dominant large-amplitude mode and a less frequent low-amplitude mode. When the wavenumber 1 10-mb height data are projected onto the phase plane defined by the 10-mb zonal-mean winds and wavenumber 1 100-mb heights, three preferred regimes are evident. The small-amplitude mode separates into a strong zonal wind-weak wave regime and a weak zonal wind-weak wave regime. The large-amplitude mode is an intermediate zonal wind-strong wave regime. Transitions between the large-amplitude regime and the weak zonal wind-weak wave regime are found to be associated with major stratospheric warmings. The clustering of the stratospheric data into the preferred flow regimes is interpreted in light of the bifurcation properties of the Holton and Mass model. The interannual variability of the Northern Hemisphere winter stratosphere is interpreted in terms of the relative frequency of the observed preferred regimes.

  17. Seasonal variations of long period oscillations in the mesosphere at high- and mid-latitudes and their relation to mesospheric summer echoes

    Science.gov (United States)

    Zeller, Olof; Hoffmann, Peter; Bremer, Juergen; Singer, Werner

    Continuous MF and meteor radar observations allow detailed studies of the wind field in the mesosphere and lower thermosphere, which is characterized by a high variability due to the presence of gravity and tidal waves as well as planetary waves. Here the seasonal variation of long period oscillations (periods of few days) is used to indicate the presence of transient planetary waves in the mesosphere at high and mid-latitudes. Our studies are based on wind measurements from meteor and MF radars at Andenes (69° N, 16° E) and Juliusruh (55° N, 13° E). These measurements are supplemented by mesospheric temperatures derived from meteor decay times. For investigations of wind and temperature oscillations wavelet analyses have been performed showing the seasonal varations of their preferred periods and amplitudes. The activity of oscillations with a period in the range 2 - 4 d have their maximum during summer while the long period ones (˜10 d) occur preferably in winter. Oscillations with periods of 4 - 7 d occur in every season. Such periods are not only observed in wind and temperature variations, but also in variations of (polar) mesosphere summer echos (P)MSE observed by VHF radars in Kuehlungsborn (54° N, 12° E) and Andenes. (P)MSE are connected with very cold temperatures where ice particles can exist. Due to an equatorward directed meridional temperature gradient variations of meridional wind and temperature are positively correlated. Generally radar echoes at mid latitudes are strongly affected by meridional wind variations due to a mean temperature around the frost point of water vapour. In contrast there is mostly no significant impact of the meridional wind on radar echoes at polar latitudes. A mean temperature well below the frost point and a weaker meridional temperature gradient than at mid latitudes are reasons for this reduced impact. But because of higher temperatures in 2002 long period temperature and meridional wind variations impact the PMSE

  18. Recent Basal Melting of a Mid-Latitude Glacier on Mars

    Science.gov (United States)

    Butcher, Frances E. G.; Balme, M. R.; Gallagher, C.; Arnold, N. S.; Conway, S. J.; Hagermann, A.; Lewis, S. R.

    2017-12-01

    Evidence for past basal melting of young (late Amazonian-aged), debris-covered glaciers in Mars' mid-latitudes is extremely rare. Thus, it is widely thought that these viscous flow features (VFFs) have been perennially frozen to their beds. We identify an instance of recent, localized wet-based mid-latitude glaciation, evidenced by a candidate esker emerging from a VFF in a tectonic rift in Tempe Terra. Eskers are sedimentary ridges deposited in ice-walled meltwater conduits and are indicative of glacial melting. We compare the candidate esker to terrestrial analogues, present a geomorphic map of landforms in the rift, and develop a landsystem model to explain their formation. We propose that the candidate esker formed during a transient phase of wet-based glaciation. We then consider the similarity between the geologic setting of the new candidate esker and that of the only other candidate esker to be identified in association with an existing mid-latitude VFF; both are within tectonic graben/rifts proximal to volcanic provinces. Finally, we calculate potential basal temperatures for a range of VFF thicknesses, driving stresses, mean annual surface temperatures, and geothermal heat fluxes, which unlike previous studies, include the possible role of internal strain heating. Strain heating can form an important additional heat source, especially in flow convergence zones, or where ice is warmer due to elevated surface temperatures or geothermal heat flux. Elevated geothermal heat flux within rifts, perhaps combined with locally-elevated strain heating, may have permitted wet-based glaciation during the late Amazonian, when cold climates precluded more extensive wet-based glaciation on Mars.

  19. Habitat preferences of baleen whales in a mid-latitude habitat

    Science.gov (United States)

    Prieto, Rui; Tobeña, Marta; Silva, Mónica A.

    2017-07-01

    Understanding the dynamics of baleen whale distribution is essential to predict how environmental changes can affect their ecology and, in turn, ecosystem functioning. Recent work showed that mid-latitude habitats along migratory routes may play an important role on the feeding ecology of baleen whales. This study aimed to investigate the function of a mid-latitude habitat for blue (Balaenoptera musculus), fin (Balaenoptera physalus) and sei (Balaenoptera borealis) whales occurring in sympatry during spring and summer months and to what extent their environmental niches overlap. We addressed those questions by developing environmental niche models (ENM) for each species and then making pairwise comparisons of niche overlap and relative habitat patch importance among the three species. ENMs were created using sightings from the Azorean Fisheries Observer Program from May to November, between 2004 and 2009, and a set of 18 predictor environmental variables. We then assessed monthly (April-July) overlap among ENMs using a modified Hellinger's distance metric (I). Results show that the habitat niches of blue and fin whales are strongly influenced by primary productivity and sea surface temperature and are highly dynamic both spatially and temporally due to the oceanography of the region. Niche overlap analyses show that blue and fin whale environmental niches are similar and that the suitable habitats for the two species have high degree of spatial coincidence. These results in combination suggest that this habitat may function as a mid-latitude feeding ground to both species while conditions are adequate. The sei whale model, on the other hand, did not include variables considered to be proxies for prey distribution and little environmental niche overlap was found between this species and the other two. We argue that these results suggest that the region holds little importance as a foraging habitat for the sei whale.

  20. The influence of mid-latitude cyclones on European background surface ozone

    Science.gov (United States)

    Knowland, K. Emma; Doherty, Ruth M.; Hodges, Kevin I.; Ott, Lesley E.

    2017-10-01

    The relationship between springtime mid-latitude cyclones and background ozone (O3) is explored using a combination of observational and reanalysis data sets. First, the relationship between surface O3 observations at two rural monitoring sites on the west coast of Europe - Mace Head, Ireland, and Monte Velho, Portugal - and cyclone track frequency in the surrounding regions is examined. Second, detailed case study examination of four individual mid-latitude cyclones and the influence of the associated frontal passage on surface O3 is performed. Cyclone tracks have a greater influence on the O3 measurements at the more northern coastal European station, Mace Head, located within the main North Atlantic (NA) storm track. In particular, when cyclones track north of 53° N, there is a significant relationship with high levels of surface O3 (> 75th percentile). The further away a cyclone is from the NA storm track, the more likely it will be associated with both high and low (percentile) levels of O3 at the observation site during the cyclone's life cycle. The results of the four case studies demonstrate (a) the importance of the passage of a cyclone's cold front in relation to surface O3 measurements, (b) the ability of mid-latitude cyclones to bring down high levels of O3 from the stratosphere, and (c) that accompanying surface high-pressure systems and their associated transport pathways play an important role in the temporal variability of surface O3. The main source of high O3 to these two sites in springtime is from the stratosphere, either from direct injection into the cyclone or associated with aged airstreams from decaying downstream cyclones that can become entrained and descend toward the surface within new cyclones over the NA region.

  1. Late Cenozoic fire enhancement response to aridification in mid-latitude Asia: Evidence from microcharcoal records

    Science.gov (United States)

    Miao, Yunfa; Fang, Xiaomin; Song, Chunhui; Yan, Xiaoli; Zhang, Ping; Meng, Qingquan; Li, Fang; Wu, Fuli; Yang, Shengli; Kang, Shuyuan; Wang, Yuanping

    2016-05-01

    Fire provides an important indicator of paleoclimatic change. However, little information relating to late Cenozoic fire history has been gathered in mid-latitude Asia (including Inner Asia and East Asia), a key region for understanding the development of the arid-monsoon climate system as well as the driving forces behind it. Here we first report the records of microcharcoal concentrations (MC) covering the Holocene (10-0 ka) and late Pleistocene (0.8-0 Ma), which we use to analyze the fire activity patterns at an orbital time scale; then we compile the late Cenozoic MC record to investigate the long-term fire history by analyzing four cores from the Yangtze River Delta (YRD) area, East Asia (representing 8-0 Ma) and three sites in Inner Asia (representing 18-2 Ma). The results show that the (i) MC remained higher during the relatively dry late Holocene/glacial stages than that during the humid middle Holocene/interglacial stages at individual sites; (ii) MC increased with time in both Inner Asia and East Asia after 18 and 8 Ma, respectively; and (iii) MC always remained higher in the dry Inner Asia than in the contemporaneous wet East Asia. All these characteristics imply that late Cenozoic fire occurrence in mid-latitude Asia experienced a gradual increasing trend along with the global temperature/ice volume change, and indicates a continuous aridification trend across mid-latitude Asia. The global cooling, rather than the Tibetan Plateau uplift, might have played a key role in this observed trend.

  2. 50 MHz continuous wave interferometer observations of the unstable mid-latitude E-region ionosphere

    Directory of Open Access Journals (Sweden)

    C. Haldoupis

    Full Text Available In this paper we describe the conversion of SESCAT (Sporadic-E SCATter experiment, a bistatic 50 MHz continuous wave (CW Doppler radar located on the island of Crete, Greece, to a single (east-west baseline interferometer. The first results show that SESCAT, which provides high quality Doppler spectra and excellent temporal resolution, has its measurement capabilities enhanced significantly when operated as an interferometer, as it can also study short-term dynamics of localized scattering regions within mid-latitude sporadic E-layers. The interferometric observations reveal that the aspect sensitive area viewed by the radar often contains a few zonally located backscatter regions, presumably blobs or patches of unstable metallic ion plasma, which drift across the radar field-of-view with the neutral wind. On average, these active regions of backscatter have mean zonal scales ranging from a few kilometers to several tens of kilometers and drift with westward speeds from ~ 20 m/s to 100 m/s, and occasionally up to 150 m/s. The cross-spectral analysis shows that mid-latitude type 1 echoes occur much more frequently than has been previously assumed and they originate in single and rather localized areas of elevated electric fields. On the other hand, typical bursts of type 2 echoes are often found to result from two adjacent regions in azimuth undergoing the same bulk motion westwards but producing scatter of opposite Doppler polarity, a fact that contradicts the notion of isotropic turbulence to which type 2 echoes are attributed. Finally, quasi-periodic (QP echoes are observed simply to be due to sequential unstable plasma patches or blobs which traverse across the radar field-of-view, sometimes in a wave-like fashion.

    Key words. Ionosphere (ionospheric irregularities; mid-latitude ionosphere; plasma waves and instabilities

  3. In situ measurements constraining the role of sulphate aerosols in mid-latitude ozone depletion

    Science.gov (United States)

    Fahey, D. W.; Kawa, S. R.; Woodbridge, E. L.; Tin, P.; Wilson, J. C.; Jonsson, H. H.; Dye, J. E.; Baumgardner, D.; Borrmann, S.; Toohey, D. W.

    1993-01-01

    In situ measurements of stratospheric sulphate aerosol, reactive nitrogen and chlorine concentrations at middle latitudes confirm the importance of aerosol surface reactions that convert active nitrogen to a less active, reservoir form. This makes mid-latitude stratospheric ozone less vulnerable to active nitrogen and more vulnerable to chlorine species. The effect of aerosol reactions on active nitrogen depends on gas phase reaction rates, so that increases in aerosol concentration following volcanic eruptions will have only a limited effect on ozone depletion at these latitudes.

  4. Present-day Exposures of Water Ice in the Northern Mid-latitudes of Mars

    Science.gov (United States)

    Allen, Carlton C.; Kanner, Lisa C.

    2007-01-01

    Water ice is exposed in the martian north polar cap, but is rarely exposed beyond the cap boundary. Orbital gamma ray spectrometry data strongly imply the presence of water ice within meters of the surface at latitudes north of approximately 60deg. We have examined mid-latitude areas of the northern plains displaying residual ice-rich layers, and report evidence of present-day surface exposures of water ice. These exposures, if confirmed, could con-strain the latitudinal and temporal stability of surface ice on Mars.

  5. The timing and cause of glacial advances in the southern mid-latitudes during the last glacial cycle based on a synthesis of exposure ages from Patagonia and New Zealand

    Science.gov (United States)

    Darvill, Christopher M.; Bentley, Michael J.; Stokes, Chris R.; Shulmeister, James

    2016-10-01

    Glacier advances in the southern mid-latitudes during the last glacial cycle (ca. 110-10 ka) were controlled by changes in temperature and precipitation linked to several important ocean-climate systems. As such, the timing of glacial advance and retreat can yield important insights into the mechanisms of Southern Hemisphere climate change. This is particularly important given that several recent studies have demonstrated significant glacial advances prior to the global Last Glacial Maximum (gLGM) in Patagonia and New Zealand, the cause of which are uncertain. The recent increase in chronological studies in these regions offers the opportunity to compare regional trends in glacial activity. Here, we compile the first consistent 10Be exposure-dating chronologies for Patagonia and New Zealand to highlight the broad pattern of mid-latitude glacial activity over the last glacial cycle. Our results show that advances or still stands culminated at 26-27 ka, 18-19 ka and 13-14 ka in both Patagonia and New Zealand and were broadly synchronous, but with an offset between regions of up to 900 years that cannot be explained by age calculation or physically plausible erosion differences. Furthermore, there is evidence in both regions for glacial advances culminating from at least 45 ka, during the latter half of Marine Isotope Stage (MIS) 3. Glacial activity prior to the gLGM differed from the large Northern Hemisphere ice sheets, likely due to favourable Southern Hemisphere conditions during late MIS 3: summer insolation reached a minimum, seasonality was reduced, winter duration was increasing, and sea ice had expanded significantly, inducing stratification of the ocean and triggering northward migration of oceanic fronts and the Southern Westerly Winds. Glacial advances in Patagonia and New Zealand during the gLGM were probably primed by underlying orbital parameters. However, the precise timing is likely to have been intrinsically linked to migration of the coupled ocean

  6. Green Sahara impact on mid-latitudes during mid-Holocene

    Science.gov (United States)

    Gaetani, Marco; Messori, Gabriele; Pausata, Francesco S. R.; Zhang, Qiong

    2017-04-01

    In the mid-Holocene (6 kyr before present), North Africa was characterised by a vegetated Sahara and a stronger summer monsoon, resulting in a wetter climate. These conditions, induced by the different Earth's orbital parameters, and maintained by the precipitation-vegetation feedback, were associated with a substantial change of the regional atmospheric dynamics, with influences extending across the global Tropics and beyond. In this study, we explore the mid-latitude response to the vegetated Sahara in the mid-Holocene. We use the EC-Earth climate model to simulate the North African environment during mid-Holocene, i.e. extensive vegetation over the Sahara, and a consequent reduced dust emission. Vegetation and dust reduction are prescribed both in combination and in isolation, to determine the specific responses to the individual forcings. A significant response at mid-latitudes is simulated during boreal summer, when the precipitation-vegetation feedback is maximum in the Sahara. Results show increased precipitation over Mediterranean and Middle East, and warm anomalies across western Europe. This response is associated with the modification of the atmospheric circulation in the Euro-Atlantic sector. Specifically, the intensification of the subtropical jetstream favours precipitation across the Middle East, while a positive anomaly in the North Atlantic Oscillation leads the warming further west. These results suggest important implications for the understanding of future climate scenarios in the region, since a number of simulations project wetter conditions in North Africa.

  7. Type-1 echoes from the mid-latitude E-Region ionosphere

    Directory of Open Access Journals (Sweden)

    C. Haldoupis

    1997-07-01

    Full Text Available This paper presents more data on the properties of type-1 irregularities in the nighttime mid-latitude E-region ionosphere. The measurements were made with a 50-MHz Doppler radar system operating in Crete, Greece. The type-1 echoes last from several seconds to a few minutes and are characterized by narrow Doppler spectra with peaks corresponding to wave phase velocities of 250–350 m/s. The average velocity of 285 m/s is about 20% lower than nominal E-region ion-acoustic speeds, probably because of the presence of heavy metallic ions in the sporadic-E-layers that appear to be associated with the mid-latitude plasma instabilities. Sometimes the type-1 echoes are combined with a broad spectrum of type-2 echoes; at other times they dominate the spectrum or may appear in the absence of any type-2 spectral component. We believe these echoes are due to the modified two-stream plasma instability driven by a polarization electric field that must be larger than 10 mV/m. This field is similar in nature to the equatorial electrojet polarization field and can arise when patchy nighttime sporadic-E-layers have the right geometry.

  8. Ozone Depletion at Mid-Latitudes: Coupling of Volcanic Aerosols and Temperature Variability to Anthropogenic Chlorine

    Science.gov (United States)

    Solomon, S.; Portmann, R. W.; Garcia, R. R.; Randel, W.; Wu, F.; Nagatani, R.; Gleason, J.; Thomason, L.; Poole, L. R.; McCormick, M. P.

    1998-01-01

    Satellite observations of total ozone at 40-60 deg N are presented from a variety of instruments over the time period 1979-1997. These reveal record low values in 1992-3 (after Pinatubo) followed by partial but incomplete recovery. The largest post-Pinatubo reductions and longer-term trends occur in spring, providing a critical test for chemical theories of ozone depletion. The observations are shown to be consistent with current understanding of the chemistry of ozone depletion when changes in reactive chlorine and stratospheric aerosol abundances are considered along with estimates of wave-driven fluctuations in stratospheric temperatures derived from global temperature analyses. Temperature fluctuations are shown to make significant contributions to model calculated northern mid-latitude ozone depletion due to heterogeneous chlorine activation on liquid sulfate aerosols at temperatures near 200-210 K (depending upon water vapor pressure), particularly after major volcanic eruptions. Future mid-latitude ozone recovery will hence depend not only on chlorine recovery but also on temperature trends and/or variability, volcanic activity, and any trends in stratospheric sulfate aerosol.

  9. Characteristics of variations in the ground magnetic field during substorms at mid latitudes

    Directory of Open Access Journals (Sweden)

    K. L. Turnbull

    2009-09-01

    Full Text Available Substorms are known to cause geomagnetically induced currents (GIC in power transmission lines through variations in the ground magnetic field. An improved knowledge and understanding of how the different phases of substorms affect the ground magnetic field will ultimately help to better understand how GIC arise. Although usually associated with high latitude power transmission networks, GIC potentially pose a risk to mid latitude networks such as the UK's National Grid. Using a list of substorm expansion phase onsets derived from auroral observations by the IMAGE-FUV satellite, this study examines 553 individual onsets. In order to cover mid latitudes, ground magnetometer data from the UK Sub-Auroral Magnetometer Network (SAMNET are exploited. These high time resolution (5 s data are used to study the ground magnetic field for an hour after onset, in particular the time derivative of the horizontal magnetic field, H. The data covers the period from 2000 to 2003 (just after solar maximum. Results are compared with a previous study of magnetic field variations at higher latitudes, using data with a much lower (1 min cadence during substorms identified from geomagnetic indices during a period just after solar minimum.

  10. Characteristics of variations in the ground magnetic field during substorms at mid latitudes

    Directory of Open Access Journals (Sweden)

    K. L. Turnbull

    2009-09-01

    Full Text Available Substorms are known to cause geomagnetically induced currents (GIC in power transmission lines through variations in the ground magnetic field. An improved knowledge and understanding of how the different phases of substorms affect the ground magnetic field will ultimately help to better understand how GIC arise. Although usually associated with high latitude power transmission networks, GIC potentially pose a risk to mid latitude networks such as the UK's National Grid. Using a list of substorm expansion phase onsets derived from auroral observations by the IMAGE-FUV satellite, this study examines 553 individual onsets. In order to cover mid latitudes, ground magnetometer data from the UK Sub-Auroral Magnetometer Network (SAMNET are exploited. These high time resolution (5 s data are used to study the ground magnetic field for an hour after onset, in particular the time derivative of the horizontal magnetic field, H. The data covers the period from 2000 to 2003 (just after solar maximum. Results are compared with a previous study of magnetic field variations at higher latitudes, using data with a much lower (1 min cadence during substorms identified from geomagnetic indices during a period just after solar minimum.

  11. Mid-latitude E-region bulk motions inferred from digital ionosonde and HF radar measurements

    Directory of Open Access Journals (Sweden)

    J. Delloue

    2004-11-01

    Full Text Available In the mid-latitude E-region there is now evidence suggesting that neutral winds play a significant role in driving the local plasma instabilities and electrodynamics inside sporadicE layers. Neutral winds can be inferred from coherent radar backscatter measurements of the range-/azimuth-time-intensity (RTI/ATI striations of quasi-periodic (QP echoes, or from radar interferometer/imaging observations. In addition, neutral winds in the E-region can be estimated from angle-of-arrival ionosonde measurements of sporadic-E layers. In the present paper we analyse concurrent ionosonde and HF coherent backscatter observations obtained when a Canadian Advanced Digital Ionosonde (CADI was operated under a portion of the field-of-view of the Valensole high frequency (HF radar. The Valensole radar, a mid-latitude radar located in the south of France with a large azimuthal scanning capability of 82° (24° E to 58° W, was used to deduce zonal bulk motions of QP echoing regions using ATI analysis. The CADI was used to measure angle-of-arrival information in two orthogonal horizontal directions and thus derive the motion of sporadic-E patches drifting with the neutral wind. This paper compares the neutral wind drifts of the unstable sporadic-E patches as determined by the two instruments. The CADI measurements show a predominantly westward aligned motion, but the measured zonal drifts are underestimated relative to those observed with the Valensole radar.

  12. Mid-latitude summer response of the middle atmosphere to short-term solar UV changes

    Directory of Open Access Journals (Sweden)

    P. Keckhut

    1995-06-01

    Full Text Available Temperature and wind data obtained with Rayleigh lidar since 1979 and Russian rockets since 1964 are analyzed to deduce the summer response of the middle atmosphere to short-term solar UV changes. The equivalent width of the 1083 nm He I line is used as a proxy to monitor the short-term UV flux changes. Spectral analyses are performed on 108-day windows to extract the 27-day component from temperature, wind and solar data sets. Linear regressions between these spectral harmonics show some significant correlations around 45 km at mid-latitudes. For large 27-day solar cycles, amplitudes of 2 K and 6 m s-1 are calculated for temperature data series over the south of France (44°N, and on wind data series over Volgograd (49°N, respectively. Cross-spectrum analyses have indicated correlations between these atmospheric parameters and the solar proxy with a phase lag of less than 2 days. These statistically correlative results, which provide good qualitative agreement with numerical simulations, are both obtained at mid-latitude. However, the observed amplitudes are larger than expected, with numerical models suggesting that dynamical processes such as equatorial or gravity waves may be responsible.

  13. Mid-latitude summer response of the middle atmosphere to short-term solar UV changes

    Directory of Open Access Journals (Sweden)

    P. Keckhut

    Full Text Available Temperature and wind data obtained with Rayleigh lidar since 1979 and Russian rockets since 1964 are analyzed to deduce the summer response of the middle atmosphere to short-term solar UV changes. The equivalent width of the 1083 nm He I line is used as a proxy to monitor the short-term UV flux changes. Spectral analyses are performed on 108-day windows to extract the 27-day component from temperature, wind and solar data sets. Linear regressions between these spectral harmonics show some significant correlations around 45 km at mid-latitudes. For large 27-day solar cycles, amplitudes of 2 K and 6 m s-1 are calculated for temperature data series over the south of France (44°N, and on wind data series over Volgograd (49°N, respectively. Cross-spectrum analyses have indicated correlations between these atmospheric parameters and the solar proxy with a phase lag of less than 2 days. These statistically correlative results, which provide good qualitative agreement with numerical simulations, are both obtained at mid-latitude. However, the observed amplitudes are larger than expected, with numerical models suggesting that dynamical processes such as equatorial or gravity waves may be responsible.

  14. Total ozone patterns over the northern mid-latitudes: spatial correlations, extreme events and dynamical contributions

    Science.gov (United States)

    Rieder, H. E.; Staehelin, J.; Maeder, J. A.; Ribatet, M.; Bodeker, G. E.; Davison, A. C.

    2009-04-01

    Tools from geostatistics and extreme value theory are applied to analyze spatial correlations in total ozone for the northern mid-latitudes. The dataset used in this study is the NIWA combined total ozone dataset (Bodeker et al., 2001; Müller et al., 2008). New tools from extreme value theory (Coles, 2001; Ribatet, 2007) have recently been applied to the world's longest total ozone record from Arosa, Switzerland (e.g. Staehelin 1998a,b), in order to describe extreme events in low and high total ozone (Rieder et al., 200x). Within the current study, patterns in spatial correlation and frequency distributions of extreme events (e.g. ELOs and EHOs) are studied for the northern mid-latitudes. New insights in spatial patterns of total ozone for the northern mid-latitudes are presented. Koch et al. (2005) found that the increase in fast isentropic transport of tropical air to northern mid-latitudes contributed significantly to ozone changes between 1980 and 1989. Within this study the influence of changes in atmospheric dynamics (e.g. tropospheric and lower stratospheric pressure systems) on column ozone over the northern mid-latitudes is analyzed for the time period 1979-2007. References: Bodeker, G.E., J.C. Scott, K. Kreher, and R.L. McKenzie, Global ozone trends in potential vorticity coordinates using TOMS and GOME intercompared against the Dobson network: 1978-1998, J. Geophys. Res., 106 (D19), 23029-23042, 2001. Coles, S.: An Introduction to Statistical Modeling of Extreme Values, Springer Series in Statistics, ISBN:1852334592, Springer, Berlin, 2001. Koch, G., H. Wernli, C. Schwierz, J. Staehelin, and T. Peter (2005), A composite study on the structure and formation of ozone miniholes and minihighs over central Europe, Geophys. Res. Lett., 32, L12810, doi:10.1029/2004GL022062. Müller, R., Grooß, J.-U., Lemmen, C., Heinze, D., Dameris, M., and Bodeker, G.: Simple measures of ozone depletion in the polar stratosphere, Atmos. Chem. Phys., 8, 251-264, 2008. Ribatet

  15. Madden-Julian Oscillation Teleconnections and Their Influence on Northern Hemisphere Winter Blocking

    Science.gov (United States)

    Henderson, Stephanie A.

    Winter blocking events are characterized by persistent and quasi-stationary patterns that re-direct precipitation and air masses, leading to long-lasting extreme winter weather. Studies have shown that the teleconnection patterns forced by the primary mode of tropical intraseasonal variability, the Madden-Julian Oscillation (MJO), influence extratropical factors associated with blocking, such as the North Atlantic Oscillation. However, the influence of the MJO on winter blocking is not well understood. Understanding this relationship may improve the mid-range forecasting of winter blocking and the associated weather extremes. The impact of the MJO on Northern Hemisphere winter blocking is examined using a two-dimensional blocking index. Results suggest that all MJO phases demonstrate significant changes in west and central Pacific high-latitude blocking. East Pacific and Atlantic blocking are significantly suppressed following phase 3 of the MJO, characterized by anomalous convection in the tropical East Indian Ocean and suppressed convection in the west Pacific. A significant increase in east Pacific and Atlantic blocking follows the opposite-signed MJO heating during MJO phase 7. Over Europe, blocking is suppressed following MJO phase 4 and significantly increased after MJO phase 6. Results suggest that the European blocking increase may be due to two precursors: 1) a pre-existing anomalous Atlantic anticyclone, and 2) a negative Pacific North American (PNA) pattern triggered by the MJO. The influence of the MJO on winter blocking may be different if a change occurs to the basic state and/or MJO heating, such as during El Nino - Southern Oscillation (ENSO) events. MJO teleconnections during ENSO events are examined using composite analysis and a nonlinear baroclinic model and their influence of winter high-latitude blocking is discussed. Results demonstrate that the ENSO-altered MJO teleconnection patterns significantly influence Pacific and Atlantic blocking and

  16. Sensitivity of US air quality to mid-latitude cyclone frequency and implications of 1980–2006 climate change

    Directory of Open Access Journals (Sweden)

    E. M. Leibensperger

    2008-12-01

    Full Text Available We show that the frequency of summertime mid-latitude cyclones tracking across eastern North America at 40°–50° N (the southern climatological storm track is a strong predictor of stagnation and ozone pollution days in the eastern US. The NCEP/NCAR Reanalysis, going back to 1948, shows a significant long-term decline in the number of summertime mid-latitude cyclones in that track starting in 1980 (−0.15 a−1. The more recent but shorter NCEP/DOE Reanalysis (1979–2006 shows similar interannual variability in cyclone frequency but no significant long-term trend. Analysis of NOAA daily weather maps for 1980–2006 supports the trend detected in the NCEP/NCAR Reanalysis 1. A GISS general circulation model (GCM simulation including historical forcing by greenhouse gases reproduces this decreasing cyclone trend starting in 1980. Such a long-term decrease in mid-latitude cyclone frequency over the 1980–2006 period may have offset by half the ozone air quality gains in the northeastern US from reductions in anthropogenic emissions. We find that if mid-latitude cyclone frequency had not declined, the northeastern US would have been largely compliant with the ozone air quality standard by 2001. Mid-latitude cyclone frequency is expected to decrease further over the coming decades in response to greenhouse warming and this will necessitate deeper emission reductions to achieve a given air quality goal.

  17. An assessment of the atmospheric centers of action in the northern hemisphere winter

    Science.gov (United States)

    Sun, X. J.; Wang, P. X.; Wang, J. X. L.

    2017-02-01

    In the northern hemisphere, there are six permanent or semi-permanent atmospheric activity centers, namely the Icelandic Low, Aleutian Low, India Low, Mongolia High, North Pacific High, and North Atlantic High. The first four are semi-permanent action centers and the last two are permanent circulation systems. The India Low exists only during the summer. By using 160 years (1850-2009) of monthly mean sea level pressure data from the Hadley Centre in the UK, we conduct a comprehensive study of the five boreal winter atmospheric centers of action (ACAs). Based on a unified definition and a method determined in previous studies, we calculate the indices of areal coverage (S), intensity (P), and position of action center ( λ c, φ c) for each of these five ACAs. Through an in-depth analysis of these indices and their relationships with climate variables, we evaluate the indices by describing and explaining areal climate anomalies, particularly precipitation and temperature anomalies in China. We show that (1) ACAs significantly influence the climate anomalies of surrounding areas (2) the influences of oceanic ACAs are larger and the intensity anomalies of ACAs have a greater impact than their location displacement, and (3) ACAs exert more control on temperature than they do on precipitation. For the two ACAs over the north Atlantic, the impacts of their intensities on the anomalies of temperature and precipitation are similar. For the two ACAs over the north Pacific, their influences are almost the opposite. The most influential ACA for climate anomalies in China during the boreal winter is HMO. When HMO is stronger, China has a colder winter and it is wetter in the north. With stronger ACAs in the upstream, i.e., the Icelandic Low and North Atlantic High, northern China has a warmer winter. The ACAs over the north Pacific exert little influence on climate anomalies in China during winter. The analyses presented in this paper provide a set of useful indices for

  18. The influence of mid-latitude cyclones on European background surface ozone

    Directory of Open Access Journals (Sweden)

    K. E. Knowland

    2017-10-01

    Full Text Available The relationship between springtime mid-latitude cyclones and background ozone (O3 is explored using a combination of observational and reanalysis data sets. First, the relationship between surface O3 observations at two rural monitoring sites on the west coast of Europe – Mace Head, Ireland, and Monte Velho, Portugal – and cyclone track frequency in the surrounding regions is examined. Second, detailed case study examination of four individual mid-latitude cyclones and the influence of the associated frontal passage on surface O3 is performed. Cyclone tracks have a greater influence on the O3 measurements at the more northern coastal European station, Mace Head, located within the main North Atlantic (NA storm track. In particular, when cyclones track north of 53° N, there is a significant relationship with high levels of surface O3 (> 75th percentile. The further away a cyclone is from the NA storm track, the more likely it will be associated with both high and low (< 25th percentile levels of O3 at the observation site during the cyclone's life cycle. The results of the four case studies demonstrate (a the importance of the passage of a cyclone's cold front in relation to surface O3 measurements, (b the ability of mid-latitude cyclones to bring down high levels of O3 from the stratosphere, and (c that accompanying surface high-pressure systems and their associated transport pathways play an important role in the temporal variability of surface O3. The main source of high O3 to these two sites in springtime is from the stratosphere, either from direct injection into the cyclone or associated with aged airstreams from decaying downstream cyclones that can become entrained and descend toward the surface within new cyclones over the NA region.

  19. Modelled glacier equilibrium line altitudes during the mid-Holocene in the southern mid-latitudes

    Science.gov (United States)

    Bravo, C.; Rojas, M.; Anderson, B. M.; Mackintosh, A. N.; Sagredo, E.; Moreno, P. I.

    2015-11-01

    Glacier behaviour during the mid-Holocene (MH, 6000 years BP) in the Southern Hemisphere provides observational data to constrain our understanding of the origin and propagation of palaeoclimate signals. In this study we examine the climatic forcing of glacier response in the MH by evaluating modelled glacier equilibrium line altitudes (ELAs) and climatic conditions during the MH compared with pre-industrial time (PI, year 1750). We focus on the middle latitudes of the Southern Hemisphere, specifically Patagonia and the South Island of New Zealand. Climate conditions for the MH were obtained from PMIP2 model simulations, which in turn were used to force a simple glacier mass balance model to simulate changes in ELA. In Patagonia, the models simulate colder conditions during the MH in austral summer (-0.2 °C), autumn (-0.5 °C), and winter (-0.4), and warmer temperatures (0.2 °C) during spring. In the Southern Alps the models show colder MH conditions in autumn (-0.7 °C) and winter (-0.4 °C), warmer conditions in spring (0.3 °C), and no significant change in summer temperature. Precipitation does not show significant changes but exhibits a seasonal shift, with less precipitation from April to September and more precipitation from October to April during the MH in both regions. The mass balance model simulates a climatic ELA that is 15-33 m lower during the MH compared with PI conditions. We suggest that the main causes of this difference are driven mainly by colder temperatures associated with the MH simulation. Differences in temperature have a dual effect on glacier mass balance: (i) less energy is available for ablation during summer and early autumn and (ii) lower temperatures cause more precipitation to fall as snow rather than rain in late autumn and winter, resulting in more accumulation and higher surface albedo. For these reasons, we postulate that the modelled ELA changes, although small, may help to explain larger glacier extents observed by 6000

  20. The Mid-latitude Continental Convective Clouds (MC3E) Experiment Final Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, M [Brookhaven National Laboratory; Giangrande, S [Brookhaven National Laboratory; Kollias, P [Stony Brook University

    2014-04-01

    The Mid-latitude Continental Convective Clouds Experiment (MC3E) took place from April 22 through June 6, 2011, centered at the ARM Southern Great Plains site (http://www.arm.gov/sites/sgp) in northcentral Oklahoma. MC3E was a collaborative effort between the ARM Climate Research Facility and the National Aeronautics and Space Administration’s (NASA’s) Global Precipitation Measurement (GPM) mission Ground Validation (GV) program. The campaign leveraged the largest ground-based observing infrastructure available in the central United States, including recent upgrades through the American Recovery and Reinvestment Act of 2009, combined with an extensive sounding array, remote sensing and in situ aircraft observations, and additional radar and in situ precipitation instrumentation. The overarching goal of the campaign was to provide a three-dimensional characterization of convective clouds and precipitation for the purpose of improving the representation of convective lifecycle in atmospheric models and the reliability of satellite-based retrievals of precipitation.

  1. Modelling of the electron density height profiles in the mid-latitude ionospheric D-region

    Directory of Open Access Journals (Sweden)

    P. Y. Mukhtarov

    1996-06-01

    Full Text Available A new mid-latitude D-region (50-105 km model of the electron density is presented obtained on the basis of a full wave theory and by a trial-and-error inversion method. Daytime (at different solar zenith angles absorption measurements by A3-technique made in Bulgaria yielded data with the aid of which the seasonal and diurnal courses of the Ne(h-profiles were derived. Special attention is drawn to the event diurnal asymmetry, or uneven formation of the ionosphere as a function of insulation. The latter is probably connected with the influence of the diurnal fluctuations in the local temperature on the chemistry involved in the electron loss rate, as well as the diurnal variations of the main ionizing agent (NO in the D-region. That is why the Ne(h-profiles in the midlatitude D-region are modelled separately for morning and afternoon hours.

  2. Wind structure during mid-latitude storms and its application in Wind Energy

    DEFF Research Database (Denmark)

    Larsén, Xiaoli Guo; Du, Jianting; Bolanos, Rodolfo

    2015-01-01

    . The numerical modeling is done through an atmosphere-wave coupled system, where the atmospheric model is the Weather Research and Forecasting (WRF) model and the wave model is the Simulating WAves Nearshore (SWAN) model. Measurements from offshore stations, Horns Rev and the FINO platform, as well as satellite......: the mean wind and turbulence structures, as well as gust. This study aims at improving the understanding and modeling for the challenging wind and wave conditions during storms in the coastal offshore zones where a large number of wind farms are being planned in the near future in Europe, especially...... in Denmark. The extreme wind and wave conditions in the coastal area for wind energy application are important but have rarely been studied in the literature. Our experiments are done to the Danish coasts where the mid-latitude depression systems are causes of the extreme wind and wave conditions...

  3. Characterization of Nightside Mid-latitude Irregularities Observed with the Blackstone SuperDARN Radar

    Science.gov (United States)

    Ruohoniemi, J. M.; Ribeiro, A. J.; Baker, J. B.; Greenwald, R. A.; Newell, P. T.

    2009-12-01

    The new mid-latitude SuperDARN radars at Wallops Island and Blackstone observe strong coherent backscattering on an almost nightly basis from latitudes that appear to be subauroral. One study has demonstrated an excellent correlation with the occurrence of density and temperature gradients within the ionospheric projection of the plasmapause (Greenwald et al., Geophys. Res. Lett. [2006]). We have processed all the data collected with the Blackstone radar since its inception in February 2008 for a characterization of the occurrence and properties of ‘plasmapause’ scatter. We have determined the local time and Kp dependencies of the activity and the relation of the spatial distribution of the irregularities to magnetospheric boundaries and ionospheric density gradients. We establish that the irregularities are a feature of the quiet-time subauroral ionosphere and provide a valuable diagnostic of the electric fields in the inner magnetosphere.

  4. Mid-latitude continental temperatures through the early Eocene in western Europe

    Science.gov (United States)

    Inglis, Gordon N.; Collinson, Margaret E.; Riegel, Walter; Wilde, Volker; Farnsworth, Alexander; Lunt, Daniel J.; Valdes, Paul; Robson, Brittany E.; Scott, Andrew C.; Lenz, Olaf K.; Naafs, B. David A.; Pancost, Richard D.

    2017-02-01

    Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are increasingly used to reconstruct mean annual air temperature (MAAT) during the early Paleogene. However, the application of this proxy in coal deposits is limited and brGDGTs have only been detected in immature coals (i.e. lignites). Using samples recovered from Schöningen, Germany (∼48°N palaeolatitude), we provide the first detailed study into the occurrence and distribution of brGDGTs through a sequence of early Eocene lignites and associated interbeds. BrGDGTs are abundant and present in every sample. In comparison to modern studies, changes in vegetation type do not appear to significantly impact brGDGT distributions; however, there are subtle differences between lignites - representing peat-forming environments - and siliciclastic nearshore marine interbed depositional environments. Using the most recent brGDGT temperature calibration (MATmr) developed for soils, we generate the first continental temperature record from central-western continental Europe through the early Eocene. Lignite-derived MAAT estimates range from 23 to 26 °C while those derived from the nearshore marine interbeds exceed 20 °C. These estimates are consistent with other mid-latitude environments and model simulations, indicating enhanced mid-latitude, early Eocene warmth. In the basal part of the section studied, warming is recorded in both the lignites (∼2 °C) and nearshore marine interbeds (∼2-3 °C). This culminates in a long-term temperature maximum, likely including the Early Eocene Climatic Optimum (EECO). Although this long-term warming trend is relatively well established in the marine realm, it has rarely been shown in terrestrial settings. Using a suite of model simulations we show that the magnitude of warming at Schöningen is broadly consistent with a doubling of CO2, in agreement with late Paleocene and early Eocene pCO2 estimates.

  5. Electric field and ion density anomalies in the mid latitude ionosphere: Possible connection with earthquakes?

    Science.gov (United States)

    Gousheva, M. N.; Glavcheva, R. P.; Danov, D. L.; Hristov, P. L.; Kirov, B. B.; Georgieva, K. Y.

    2008-07-01

    The problem of earthquake prediction has stimulated the search for a correlation between seismic activity and ionospherical anomalies. We found observational evidence of possible earthquake effects in the near-equatorial and low latitude ionosphere; these ionospheric anomalies have been proposed by Gousheva et al. [Gousheva, M., Glavcheva, R., Danov, D., Angelov P., Hristov, P., Influence of earthquakes on the electric field disturbances in the ionosphere on board of the Intercosmos-Bulgaria-1300 satellite. Compt. Rend. Acad. Bulg. Sci. 58 (8) 911-916, 2005a; Gousheva, M., Glavcheva, R., Danov, D., Angelov, P., Hristov, P., Kirov, B., Georgieva, K., Observation from the Intercosmos-Bulgaria-1300 satellite of anomalies associated with seismic activity. In: Poster Proceeding of 2nd International Conference on Recent Advances in Space Technologies: Space in the Service of Society, RAST '2005, June 9-11, Istanbul, Turkey, pp. 119-123, 2005b; Gousheva, M., Glavcheva, R., Danov, D., Angelov, P., Hristov, P., Kirov, B., Georgieva, K., Satellite monitoring of anomalous effects in the ionosphere probably related to strong earthquakes. Adv. Space Res. 37 (4), 660-665, 2006]. This paper presents new results from observations of the quasi-static electric field and ion density on board INTERCOSMOS-BULGARIA-1300 satellite in the mid latitude ionosphere above sources of moderate earthquakes. Data from INTERCOSMOS-BULGARIA-1300 satellite and seismic data (World Data Center, Denver, Colorado, USA) for magnetically quiet and medium quiet days are juxtaposed in time-space domain. For satellite's orbits in the time period 15.09-01.10.1981 an increase in the horizontal and vertical components of the quasi-static electric field and fluctuations of the ion density are observed over zones of forthcoming seismic events. Some similar post effects are observed too. The emphasis of this paper is put on the anomalies which specify the mid latitude ionosphere. The obtained results contain

  6. Mid-latitude Electromagnetic and Ionospheric Phenomena Accompanying and Preceding of Abruzzo Earthquakes on April 2009

    Science.gov (United States)

    Gavrilov, B. G.

    2009-12-01

    The results of the analysis of variations of the geomagnetic field, the ground vertical atmospheric electric current and the total electron content of the ionosphere (TEC) during Italy earthquakes on April 2009 are presented. The data were obtained from the MIKHNEVO geophysical observatory (55.0 N; 37.7 E) of the Institute of Geospheres Dynamics of Russian Academy of Sciences. Observatory is located 80 km to the south from Moscow and in a distance of 2250 km from Abruzzo. The analysis showed that the earthquakes of 6 April (1:32:39 UTC, M6.3) and of 7 April (17:47:37 UTC, M5.3) were accompanied by perturbations of the ground geophysical fields and of the ionosphere in mid-latitude Russia. On April, 6 the perturbation of the geomagnetic field was registered 360 sec before the moment of the earthquake, and about 600 sec before the P-wave arrival to the Obninsk station (75 km from Mikhnevo). At that time the index of the geomagnetic activity (AE-index) was very small, so global geomagnetic perturbations were absent. In about 600 sec after the earthquake the ionosphere perturbation was observed. On April, 7 the geomagnetic field variations character changed approximately 250 seconds before the earthquake. The increase of a signal frequency was observed. The perturbation of ground vertical atmospheric electric current coincides with the moment of the earthquake, but advances the arrival of the P-wave. The ionosphere perturbations (decrease of TEC value) were observed approximately on the same time as atmospheric current alteration. The next, weaker aftershocks were not accompanied by appreciable perturbations of the mid-latitude geophysical fields. A - Seismogram (Obninsk); B- Horizontal component magnetic field Bx (Mikhnevo); C - Bx Wavelet

  7. Sporadic Ca and Ca+ layers at mid-latitudes: Simultaneous observations and implications for their formation

    Directory of Open Access Journals (Sweden)

    M. Gerding

    2001-01-01

    Full Text Available We report on the observations of 188 sporadic layers of either Ca atoms and/or Ca ions that we have observed during 112 nights of lidar soundings of Ca, and 58 nights of Ca+ soundings, at Kühlungsborn, Germany (54° N, 12° E. The Ca+ soundings have been performed simultaneously and in a common volume with the Ca soundings by two separate lidars. Correlations between sporadic neutral and ionized metal layers are demonstrated through four case studies. A systematic study of the variations of occurrence of sporadic Ca and Ca+ layers reveals that neutral and ionized Ca layers are not as closely correlated as expected earlier: (a The altitude distribution shows the simultaneous occurrence of both sporadic Ca and Ca+ layers to be most likely only in the narrow altitude range between 90 and 95 km. Above that region, in the lower thermosphere, the sporadic ion layers are much more frequent than atom layers. Below 90 km only very few sporadic layers have been observed; (b The seasonal variation of sporadic Ca layers exhibits a minimum of occurrence in summer, while sporadic Ca+ layers do not show a significant seasonal variation (only the dense Ca+ layers appear to have a maximum in summer. At mid-latitudes sporadic Ca layers are more frequent than sporadic layers of other atmospheric metals like Na or K. For the explanation of our observations new formation mechanisms are discussed.Key words. Ionosphere (ion chemistry and composition; ionosphere-atmosphere interactions; mid-latitude ionosphere

  8. Redistribution of Lunar Polar Water to Mid-latitudes and Its Role in Forming an OH Veneer

    Science.gov (United States)

    Farrell, William M.; Hurley, D. M.; Hodges, R. R.; Killen, R. M.; Halekas, J. S.; Zimmerman, M. I.; Delory, G. T.

    2013-01-01

    We suggest that energization processes like ion sputtering and impact vaporization can eject/release polar water molecules residing within cold trapped regions with sufficient velocity to allow their redistribution to mid-latitudes. We consider the possibility that these polar-ejected molecules can contribution to the water/OH veneer observed as a 3 micrometer IR absorption feature at mid-latitudes by Chandrayaan-1, Cassini, and EPOXI. We find this source cannot fully account for the observed IR feature, but could be a low intensity additional source.

  9. On the influence of zonal gravity wave distributions on the Southern Hemisphere winter circulation

    Directory of Open Access Journals (Sweden)

    F. Lilienthal

    2017-07-01

    Full Text Available A mechanistic global circulation model is used to simulate the Southern Hemisphere stratospheric, mesospheric, and lower thermospheric circulation during austral winter. The model includes a gravity wave (GW parameterization that is initiated by prescribed 2-D fields of GW parameters in the troposphere. These are based on observations of GW potential energy calculated using GPS radio occultations and show enhanced GW activity east of the Andes and around the Antarctic. In order to detect the influence of an observation-based and thus realistic 2-D GW distribution on the middle atmosphere circulation, we perform model experiments with zonal mean and 2-D GW initialization, and additionally with and without forcing of stationary planetary waves (SPWs at the lower boundary of the model. As a result, we find additional forcing of SPWs in the stratosphere, a weaker zonal wind jet in the mesosphere, cooling of the mesosphere and warming near the mesopause above the jet. SPW wavenumber 1 (SPW1 amplitudes are generally increased by about 10 % when GWs are introduced being longitudinally dependent. However, at the upper part of the zonal wind jet, SPW1 in zonal wind and GW acceleration are out of phase, which reduces the amplitudes there.

  10. Variability in seasonal forecast skill of Northern Hemisphere winters over the twentieth century

    Science.gov (United States)

    O'Reilly, Christopher H.; Heatley, James; MacLeod, Dave; Weisheimer, Antje; Palmer, Tim N.; Schaller, Nathalie; Woollings, Tim

    2017-06-01

    Seasonal hindcast experiments, using prescribed sea surface temperatures (SSTs), are analyzed for Northern Hemisphere winters from 1900 to 2010. Ensemble mean Pacific/North American index (PNA) skill varies dramatically, dropping toward zero during the mid-twentieth century, with similar variability in North Atlantic Oscillation (NAO) hindcast skill. The PNA skill closely follows the correlation between the observed PNA index and tropical Pacific SST anomalies. During the mid-century period the PNA and NAO hindcast errors are closely related. The drop in PNA predictability is due to mid-century negative PNA events, which were not forced in a predictable manner by tropical Pacific SST anomalies. Overall, negative PNA events are less predictable and seem likely to arise more from internal atmospheric variability than positive PNA events. Our results suggest that seasonal forecasting systems assessed over the recent 30 year period may be less skillful in periods, such as the mid-twentieth century, with relatively weak forcing from tropical Pacific SST anomalies.

  11. Large Enhancements in the O/N2 Ratio in the Evening Sector of the Winter Hemisphere During Geomagnetic Storms

    Science.gov (United States)

    Burns, A. G.; Killeen, T. L.; Carignan, G. R.; Roble, R. G.

    1995-01-01

    In this paper, we have looked for enhancements of the O/N2 ratio in data measured by the Dynamics Explorer 2 (DE 2) satellite in the middle latitudes of the winter hemisphere, based on a prediction that was made by the National Center for Atmospheric Research thermosphere/tonosphere general circulation model (NCAR-TIGCM) that such increases occur. The NCAR-TIGCM predicts that these enhancements should be seen throughout the low latitude region and in many middle latitude locations, but that the enhancements in O/N2 are particularly strong in the middle-latitude, evening-to-midnight sector of the winter hemisphere. When this prediction was used to look for these effects in DE 2 NACS (neutral atmosphere composition spectrometer) data, large enhancements in the O/N2 ratio (approx. 50 to 90%) were seen. These enhancements were observed during the main phase of a storm that occurred on November 24, 1982, and were seen in the same region of the winter hemisphere predicted by the NCAR-TIGCM. They are partially the result of the depletion of N2 and, as electron loss is dependent on dissociative recombination at F(sub 2) altitudes, they have implications for electron densities in this area. Parcel trajectories, which have been followed through the NCAR-TIGCM history file for this event, show that large O/N2 enhancements occur in this limited region in the winter hemisphere for two reasons. First, these parcels of air are decelerated by the antisunward edge of the ion convection pattern; individual parcels converge and subsidence occurs. Thus molecular-nitrogen-poor air is brought from higher to lower heights. Because neutral parcels that are found a little poleward of the equatorial edge of the eveningside convection pattern are swept inward toward the center of the auroral oval, the enhancements occur only in a very limited range of latitudes. Second, nitrogen-poor air is transported from regions close to the magnetic pole in the winter hemisphere. During geomagnetic

  12. Preliminary climatology and improved modelling of south Indian Ocean and Southern Ocean mid-latitude cyclones

    Science.gov (United States)

    Buckley, Bruce W.; Leslie, Lance M.

    2004-08-01

    The intense mid-latitude cyclones that traverse the southern waters of the Indian Ocean, between South Africa and southwestern Western Australia, are among the strongest depressions found anywhere in the world, outside tropical waters. Near-surface winds that exceed storm force (i.e. 24 m/s or 48 knots), and central pressures of 960 hPa and lower, are relatively common for these systems. They pose a constant threat to both open ocean and coastal shipping, and regularly generate severe weather over the populated southwestern corner of Australia. Large ocean waves and swell produce extensive coastal inundation and erosion.There were two main aims in this study. The first aim was to develop a preliminary climatology of these intense mid-latitude cyclones, for the region 20-60 °S, 30-130 °E. The climatology, which is the first that we are aware of for this notoriously data-sparse region, is based largely upon satellite observations, particularly scatterometer data, and is supplemented by ship, buoy and all available land observations. The climatology revealed that, historically, the frequency and intensity of the mid-latitude cyclones in this domain have been significantly underestimated. This underestimation has resulted in analyses that have serious flaws, and the resultant operational forecasts provided to the duty forecasters in the regional forecast centre located in Perth, Western Australia, are of highly variable quality. A number of other climatological features of these storms are discussed in this article.The second aim was to identify the factors that can contribute to a significant improvement in model forecasts of these storms. So far, there have been very few studies of explosively developing cyclones over this part of the world. Results are presented here from a series of high-resolution numerical simulations of an intense cool season Southern Ocean cyclone that developed in 2003, using the HIRES numerical weather prediction model developed by L

  13. New evidence for geothermal controls upon recent basal melting of mid-latitude glaciers on Mars

    Science.gov (United States)

    Butcher, Frances; Gallagher, Colman; Arnold, Neil; Balme, Matthew; Conway, Susan; Lewis, Stephen; Hagerman, Axel

    2017-04-01

    Diagnostic evidence for past melting of putative debris-covered glaciers (DCGs) in Mars' mid-latitudes [e.g. 1-2] is extremely rare. As such, it is widely believed that these DCGs have been perennially frozen to their beds in cold-based thermal regimes [e.g. 3] since their formation 40 Ma to 1 Ga [4-8]. Here, we present a geomorphic map and propose a landsystem model that challenges this paradigm. We identify a sinuous ridge emerging from the terminus of a DCG in the broad rift zone NE of the Tharsis volcanic province. We interpret this ridge as an esker formed by deposition of sediment within a subglacial meltwater conduit. This is only the second esker-like ridge to be identified in association with a mid-latitude DCG. Recent work [9] identified a complex of esker-like ridges on the foreland of an extant DCG in Phlegra Montes, for which high-resolution analysis is ongoing [10]. Significantly, both candidate eskers are located within graben. Graben are topographic troughs formed by crustal extension and are commonly associated with elevated geothermal heat flux [e.g. 11]. A paucity of meltwater morphologies associated with DCGs elsewhere in Mars' mid-latitudes implies that atmospheric warming alone was insufficient for widespread basal melting. We argue that, during deglaciation, atmospheric warming supplemented enhanced geothermal heat flux within graben such that the basal temperature threshold for basal melting of DCGs was surpassed in these locations [9]. This has implications for the search for recent life on Mars, as it helps constrain the likely regions of recent meltwater production within protected subglacial environments. As eskers are exposed relicts of subglacial drainage systems, they are accessible to landed missions without the high-risk requirement to drill through remnant decametre-thick debris-mantled ice. FEGB is funded by STFC grant ST/N50421X/1 [1] Head, J.W. et al. (2010), Earth Planet. Sc. Lett. 294, 306-320. [2] Levy, J.S. et al. (2014), J

  14. Redistribution of Lunar Polar Water to Mid-latitudes and its Role in Forming an OH veneer - Revisited

    Science.gov (United States)

    Farrell, W. M.; Killen, R. M.; Hurley, D. M.; Hodges, R. R.; Halekas, J. S.; Delory, G. T.

    2012-01-01

    We suggest that energization processes like ion sputtering and impact vaporization can eject/release polar water molecules residing within lunar cold trapped regions with sufficient velocity to allow their redistribution to mid-latitudes. We consider the possibility that these polar-ejected molecules can be an additional (but not dominant) contribution to the water/OH veneer observed as a 3 micron absorption feature at mid-latitudes by Chandrayaan-I, Cassini, and EPOXI. Taking the conservative case that polar water is ejected only from the floor of polar craters with an 0.1 % icy regolith then overall source rates are near 10(exp 18) H20s/s. This outflow amounts to approx 10(exp -7) kg/s of water to be ejected from each pole and is a water source rate that is 10(exp .5 lower than the overall exospheric source rate for all species. Hence, the out-flowing polar water is a perturbation in the overall exosphere composition & dynamics. This polar water 'fountain' model may not fully account for the relatively high concentrations in the mid-latitude water veneer observed in the IR (approx 10-1000 ppm). However, it may account for some part of the veneer. We note that the polar water fountain source rates scale linearly with ice concentration, and larger mass fractions of polar crater water should provide correspondingly larger fractions of water emission out of the poles which then 'spills' on to mid-latitude surfaces.

  15. The role of MJO and mid-latitude fronts in the South China Sea summer monsoon onset

    Energy Technology Data Exchange (ETDEWEB)

    Tong, H.W.; Chan, Johnny C.L.; Zhou, W. [City University of Hong Kong, Guy Carpenter Asia-Pacific Climate Impact Centre, Hong Kong (China)

    2009-11-15

    Previous studies have suggested that the South China Sea (SCS) summer monsoon onset is concurrent with the arrival of a 30-60-day northward-propagating trough. On the other hand, from a synoptic viewpoint, some studies pointed out that the arrival of a mid-latitude front may be the triggering mechanism of the SCSSM onset. This study attempts to link these two viewpoints and to investigate their relative role in inducing the SCSSM onset. Composites of low-level zonal winds, geopotential heights and temperatures during the 1991-1999 SCSSM onsets based on the European Centre for Medium Range Weather Forecast ERA-40 data indicate that both the Madden and Julian Oscillation (MJO)/Kelvin waves and mid-latitude trough are apparently involved in the onset. The MJO/Kelvin waves play a major role in inducing the large-scale easterly-westerly shift over the central SCS, while the effect of the acceleration of westerlies ahead of the mid-latitude trough is limited to the northern SCS only. Numerical experiments using a regional climate model further demonstrate that the MJO/Kelvin waves control the timing of the onset by changing the background meridional geopotential height gradient over the SCS. When the MJO is at its peak phase over the Maritime continent, it imposes a positive meridional geopotential height gradient over the SCS such that easterly winds are induced, which significantly reduces the strength of a mid-latitude trough. After the equatorial convection has dissipated, a Rossby-wave response is induced, leading to the formation of a northward-moving trough. When this trough moves northward, the meridional geopotential height gradient is reversed and westerly winds are induced. At the same time, if a mid-latitude trough arrives in south China, the westerlies associated with the mid-latitude trough will strengthen because of the background meridional geopotential height gradient, which gives the impression that both the northward-moving trough and mid-latitude

  16. Historical deforestation increased the risk of heat extremes in northern mid-latitudes

    Science.gov (United States)

    Lejeune, Quentin; Davin, Edouard; Gudmundsson, Lukas; Winckler, Johannes; Seneviratne, Sonia

    2017-04-01

    During the industrial period, large areas in the world have experienced a reduction in forest cover and an expansion of agricultural areas. Some modelling studies showed that this has significantly affected the intensity of temperature extremes through changes in biophysical land surface properties (Christidis et al. 2013, Pitman et al. 2012), however they exhibit a low level of agreement about its overall climate impact. Besides, even if they generally point toward an albedo-induced cooling over deforested mid-latitudes, this does not align with recent observational evidence suggesting that deforestation has a local daytime warming effect, especially in summer (Lee et al. 2011). Here, for the first time we intend to constrain CMIP5 models with observations in order to assess the contribution of historical deforestation to changes in the risk of warm extreme events. To do so, we have selected five models from the CMIP5 ensemble that can reproduce the observed local warming effect of deforestation during daytime in summer. Our results indicate that deforestation played a primary role in the evolution of hot extremes since preindustrial time. We quantify that a decrease in tree cover by at least 15% locally increased the intensity of the 99th percentile of daily maximum temperature (corresponding to the 3-4 hottest days of the year) by 0.6°C over northern mid-latitudes, accounting for 30-40% of their total warming. Moreover, it amplified the increase in their frequency due to the greenhouse gas forcing by 30%. Our results imply that land-cover changes need to be considered when studying past and future changes in heat extremes, in particular for regional-scale detection and attribution purposes. References: Christidis, N., P. A. Stott, G. C. Hegerl, and R. A. Betts, The role of land use change in the recent warming of daily extreme temperatures (2013), Geophysical Research Letters, 40, 589-594 Pitman, A. J., et al., Effects of land cover change on temperature and

  17. Modeling Convection of Water Vapor into the Mid-latitude Summer Stratosphere

    Science.gov (United States)

    Clapp, C.; Leroy, S. S.; Anderson, J. G.

    2016-12-01

    Water vapor in the upper troposphere and lower stratosphere (UTLS) from the tropics to the poles is important both radiatively and chemically. Water vapor is the most important greenhouse gas, and increases in water vapor concentrations in the UTLS lead to cooling at these levels and induce warming at the surface [Forster and Shine, 1999; 2002; Solomon et al., 2010]. Water vapor is also integral to stratospheric chemistry. It is the dominant source of OH in the lower stratosphere [Hanisco et al., 2001], and increases in water vapor concentrations promote stratospheric ozone loss by raising the reactivity of several key heterogeneous reactions as well as by promoting the growth of reactive surface area [Anderson et al., 2012; Carslaw et al., 1995; Carslaw et al., 1997; Drdla and Muller , 2012; Kirk-Davidoff et al., 1999; Shi et al., 2001]. However, the processes that control the distribution and phase of water in this region of the atmosphere are not well understood. This is especially true at mid-latitudes where several different dynamical mechanisms are capable of influencing UTLS water vapor concentrations. The contribution by deep convective storm systems that penetrate into the lower stratosphere is the least well understood and the least well represented in global models because of the small spatial scales and short time scales over which convection occurs. To address this issue, we have begun a modeling study to investigate the convective injection of water vapor from the troposphere into the stratosphere in the mid-latitudes. Fine-scale models have been previously used to simulate convection from the troposphere to the stratosphere [e.g., Homeyer et al., 2014]. Here we employ the Advanced Research Weather and Research Forecasting model (ARW) at 3-km resolution to resolve convection over the mid-western United States during August of 2013 including a storm system observed by SEAC4RS. We assess the transport of water vapor into the stratosphere over the model

  18. Comparative investigations of equatorial electrodynamics and low-to-mid latitude coupling of the thermosphere-ionosphere system

    Directory of Open Access Journals (Sweden)

    M. J. Colerico

    2006-03-01

    Full Text Available The thermospheric midnight temperature maximum (MTM is a highly variable, but persistent, large scale neutral temperature enhancement which occurs at low latitudes. Its occurrence can impact many fundamental upper atmospheric parameters such as pressure, density, neutral winds, neutral density, and F-region plasma. Although the MTM has been the focus of several investigations employing various instrumentation including photometers, satellites, and Fabry-Perot interferometers, limited knowledge exists regarding the latitude extent of its influence on the upper atmosphere. This is largely due to observational limitations which confined the collective geographic range to latitudes within ±23°. This paper investigates the MTM's latitudinal extent through all-sky imaging observations of its 6300Å airglow signature referred to by Colerico et al. (1996 as the midnight brightness wave (MBW. The combined field of view of three Southern Hemisphere imaging systems located at Arequipa, Peru, and Tucuman and El Leoncito, Argentina, for the first time extends the contiguous latitudinal range of imager observations to 8° S-39° S in the American sector. Our results highlight the propagation of MBW events through the combined fields of view past 39° S latitude, providing the first evidence that the MTM's effect on the upper atmosphere extends into mid-latitudes. The observations presented here are compared with modeled 6300Å emissions calculated using the NCAR thermosphere-ionosphere-electrodynamic general circulation model (TIEGCM in conjunction with an airglow code. We report that at this time TIEGCM is unable to simulate an MBW event due to the model's inability to reproduce an MTM of the same magnitude and occurrence time as those observed via FPI measurements made from Arequipa. This work also investigates the origins of an additional low latitude airglow feature referred to by Colerico et al. (1996 as the pre-midnight brightness wave (PMBW and

  19. Assessment of atmosphere-ocean general circulation model simulations of winter northern hemisphere atmospheric blocking

    Energy Technology Data Exchange (ETDEWEB)

    Vial, Jessica; Osborn, Tim J. [University of East Anglia, Climatic Research Unit, School of Environmental Sciences, Norwich (United Kingdom)

    2012-07-15

    An assessment of six coupled Atmosphere-Ocean General Circulation Models (AOGCMs) is undertaken in order to evaluate their ability in simulating winter atmospheric blocking highs in the northern hemisphere. The poor representation of atmospheric blocking in climate models is a long-standing problem (e.g. D'Andrea et al. in Clim Dyn 4:385-407, 1998), and despite considerable effort in model development, there is only a moderate improvement in blocking simulation. A modified version of the Tibaldi and Molteni (in Tellus A 42:343-365, 1990) blocking index is applied to daily averaged 500 hPa geopotential fields, from the ERA-40 reanalysis and as simulated by the climate models, during the winter periods from 1957 to 1999. The two preferred regions of blocking development, in the Euro-Atlantic and North Pacific, are relatively well captured by most of the models. However, the prominent error in blocking simulations consists of an underestimation of the total frequency of blocking episodes over both regions. A more detailed analysis revealed that this error was due to an insufficient number of medium spells and long-lasting episodes, and a shift in blocking lifetime distributions towards shorter blocks in the Euro-Atlantic sector. In the Pacific, results are more diverse; the models are equally likely to overestimate or underestimate the frequency at different spell lengths. Blocking spatial signatures are relatively well simulated in the Euro-Atlantic sector, while errors in the intensity and geographical location of the blocks emerge in the Pacific. The impact of models' systematic errors on blocking simulation has also been analysed. The time-mean atmospheric circulation biases affect the frequency of blocking episodes, and the maximum event duration in the Euro-Atlantic region, while they sometimes cause geographical mislocations in the Pacific sector. The analysis of the systematic error in time-variability has revealed a negative relationship between the

  20. Effects of strong IMF Bz southward events on the equatorial and mid-latitude ionosphere

    Directory of Open Access Journals (Sweden)

    E. Astafyeva

    2009-03-01

    Full Text Available Dayside ionospheric response to five intense geomagnetic storms (Dst<−120 nT that occurred in 2001–2005 was investigated by use of simultaneous TEC measurements by the CHAMP, SAC-C, TOPEX/Jason-1 satellites. Since the satellites passed over different longitudinal sectors and measured TEC in different range of altitudes, it was possible to obtain information about altitudinal and longitudinal ionosphere redistribution during these storms. Severe enhancements (up to ~350% of the equatorial and mid-latitude TEC above ~430 km with concurrent traveling of the equatorial anomaly crests for a distance of 10–15° of latitude were observed during two of the five events analyzed here (6 November 2001 and 8 November 2004. This phenomenon, known as the dayside ionosphere uplift, or the "daytime super-fountain effect", occurred after sudden drop in IMF Bz and consequent penetration of the electric fields to the low-latitude ionosphere. However, the same order Bz negative events caused comparatively weak changes in the dayside TEC (up to ~80 TECU during the other three events of 18 June 2003, 11 February 2004 and 24 August 2005. At the main phase of these storms there were mostly observed formation of the "typical" dual peak structure of the equatorial anomaly rather than the reinforcement of the fountain effect and the anomaly itself. Possible reasons and factors responsible for the development of the extreme ionosphere effects are discussed in the paper.

  1. New Ionosonde Observations of Mid Latitude Spread-F at Wallops Island

    Science.gov (United States)

    Bullett, T.

    2008-12-01

    A new generation digital ionosonde, a Vertical Incidence Pulsed Ionospheric Radar (VIPIR) was installed at the NASA Wallops Island Flight Facility in Virginia and saw first operation in 2007. The VIPIR features dramatic improvements in ionosonde and radar system design, including multiple phase-coherent, fully digital receivers, improved antenna designs, and higher data resolution. This produces markedly improved ionograms. From the mid 1980's through today, NASA Wallops hosts a first generation digital ionosonde, a US Air Force Digital Ionospheric Sounding System or Digisonde 256. Phase coherent digital sampling of analog receiver output, digital data storage and automated real time ionogram scaling allowed spread-F quantification and use of the data for launch decisions. In the 1970's and early 1980's an analog ionosonde, at Wallops recorded data on photographic film. Hourly characteristics were later scaled by hand, with spread-F being qualitatively identified. Recently, select periods of film ionograms have been digitized by NOAA/NGDC and are available in electronic format. This presentation compares spread-F observations made with three generations of ionospheric sounding equipment operated at the NASA Wallops Island Flight Facility. Comparison of ionogram data from both VIPIR and Digisonde ionosondes during several different events reveals newly observed mid-latitude spread- F features.

  2. ML-CIRRUS - the HALO mission on mid latitude cirrus clouds

    Science.gov (United States)

    Voigt, Christiane; Minikin, Andreas; Schumann, Ulrich

    2015-04-01

    Clouds are a major source of uncertainty in current climate predictions. In particular, the observation of cirrus cloud variability and the classification of cirrus cloud properties in distinct meteorological regimes are prone to substantial ambiguities. Here we present results of the ML-CIRRUS mission with the German atmospheric science community high altitude long range aircraft HALO. The first in-situ cloud mission with the new research aircraft combined a state-of-the-art clould instrumentation consisting of 9 wing station probes with a novel aerosol, trace gas and radiation instrumentation and a high spectral resolution LIDAR inside the cabin. Further, a newly designed counter flow virtual impactor system allowed for the detection of ice residuals. In addition, models were specifically developed to support flight planning by forecasts of the occurrence and properties of natural cirrus (CLAMS, ECMWF) and frontal cirrus (WCB-ETH), as well as of aircraft induced clouds (CoCiP). In March and April 2014, the HALO research aircraft performed 16 flights (88 flight hours) in mid-latitude cirrus clouds and contrail cirrus at longitudes from 15 deg W to 15 deg E and latitudes from 36 to 58 deg N. Cirrus clouds with an ice water content stream cirrus, lee wave cirrus and convective clouds - with a strong focus on frontal cirrus. Besides natural cirrus, aircraft induced contrail cirrus were probed during 4 flights and an interesting contrail cirrus outbreak situation was encountered over the Atlantic. Here we present an overview and first results of the ML-CIRRUS mission. Major progress in cloud research will be achieved by combining the analysis of cirrus clouds properties measured with in-situ and remote sensing instrumentation on aircraft with satellite retrievals of clouds and cloud modelling.

  3. Sub-Auroral Ion Drifts as a Source of Mid-Latitude Plasma Density Irregularities

    Science.gov (United States)

    Sotnikov, V.; Kim, T.; Mishin, E.; Paraschiv, I.; Rose, D.

    Ionospheric irregularities cause scintillations of electromagnetic signals that can severely affect navigation and transionospheric communication, in particular during space storms. At midlatitudes, such space weather events are caused mainly by subauroral electric field structures (SAID/SAPS) [1, 2]. SAID/SAPS -related shear flows and plasma density troughs point to interchange and Kelvin-Helmholtz type instabilities as a possible source of plasma irregularities. A model of nonlinear development of these instabilities based on the two-fluid hydrodynamic description with inclusion of finite Larmor radius effects will be presented. A numerical code in C language to solve the derived nonlinear equations for analysis of interchange and flow velocity shear instabilities in the ionosphere was developed. This code was used to analyze competition between interchange and Kelvin Helmholtz instabilities in the equatorial region [3]. The high-resolution simulations with continuous density and velocity profiles will be driven by the ambient conditions corresponding to the in situ Defence Military Satellite Program (DMSP) satellite low-resolution data [2] during UHF/GPS L-band subauroral scintillation events. [1] Mishin, E. (2013), Interaction of substorm injections with the subauroral geospace: 1. Multispacecraft observations of SAID, J. Geophys. Res. Space Phys., 118, 5782-5796, doi:10.1002/jgra.50548. [2] Mishin, E., and N. Blaunstein (2008), Irregularities within subauroral polarization stream-related troughs and GPS radio interference at midlatitudes. In: T. Fuller-Rowell et al. (eds), AGU Geophysical Monograph 181, MidLatitude Ionospheric Dynamics and Disturbances, pp. 291-295, doi:10.1029/181GM26, Washington, DC, USA. [3] V. Sotnikov, T. Kim, E. Mishin, T. Genoni, D. Rose, I. Paraschiv, Development of a Flow Velocity Shear Instability in the Presence of Finite Larmor Radius Effects, AGU Fall Meeting, San Francisco, 15 - 19 December, 2014.

  4. Changes of benthic fauna in the Kattegat - An indication of climate change at mid-latitudes?

    Science.gov (United States)

    Göransson, Peter

    2017-07-01

    Several predictions point to changes in the marine benthic macrofauna associated with climate change, but so far only a few and minor changes have been reported. This study relates observed changes in the species composition to climate change by looking on the past decades in the Kattegat between Denmark and Sweden. A reduction of the total number species and a reduction of species with a northern range parallel to an increase of species with a southern range have been observed. The most likely explanation of the changes is the increase in temperature of the bottom water. Increased temperature could change the species distributions but also decrease primary production which impacts recruitment and growth. Hypoxia and bottom trawling could also act synergistic in this process. A sparse occurrence of previously encountered Arctic-Boreal species and critical foundation species, which gives the area its special character, suggests a change in biodiversity and might therefore be designated as early warning signals of a warmer climate. The northern fauna below the halocline with limited capacity of dispersal and low reproduction potential, can be considered as sensitive with low adaptive capacity to climate change. Therefore, not only tropical and high-latitude species, but also benthos on deep bottoms at mid-latitudes, could be vulnerable to warming. As many species live at the edge of their range in the Kattegat, and also are dependent of distant recruitment, large scale changes will probably be detected here at an early stage. It is important to protect relatively undisturbed reference areas in the Kattegat for future studies, but also for preserving a large number of ecosystem services, biotopes, habitats, and fish species.

  5. Tidal variations of O2 Atmospheric and OH(6-2 airglow and temperature at mid-latitudes from SATI observations

    Directory of Open Access Journals (Sweden)

    M. J. López-González

    2005-12-01

    Full Text Available Airglow observations with a Spectral Airglow Temperature Imager (SATI, installed at the Sierra Nevada Observatory (37.06° N, 3.38° W at 2900-m height, have been used to investigate the presence of tidal variations at mid-latitudes in the mesosphere/lower thermosphere region. Diurnal variations of the column emission rate and vertically averaged temperature of the O2 Atmospheric (0-1 band and of the OH Meinel (6-2 band from 5 years (1998-2003 of observations have been analysed. From these observations a clear tidal variation of both emission rates and rotational temperatures is inferred. It is found that the amplitude of the daily variation for both emission rates and temperatures is greater from late autumn to spring than during summer. The amplitude decreases by more than a factor of two during summer and early autumn with respect to the amplitude in the winter-spring months. Although the tidal modulations are preferentially semidiurnal in both rotational temperatures and emission rates during the whole year, during early spring the tidal modulations seem to be more consistent with a diurnal modulation in both rotational temperatures and emission rates. Moreover, the OH emission rate from late autumn to early winter has a pattern suggesting both diurnal and semidiurnal tidal modulations.

  6. LHR band emissions at mid-latitude and their relationship to ionospheric ELF hiss and relativistic electrons

    Directory of Open Access Journals (Sweden)

    A. Morioka

    2005-03-01

    Full Text Available LHR band emissions observed at mid-latitude were investigated using data from the EXOS-C (Ohzora satellite. A typical feature of the LHR band emissions is a continuous banded structure without burst-like and cut-off features whose center frequency decreases as the satellite moves to higher latitudes. A statistical analysis of the occurrence characteristics of the phenomena showed that mid-latitude LHR emissions are distributed inside the plasmapause during magnetically quiet periods, and the poleward boundary of the emission region moves to lower latitudes as the magnetic activity increases. The altitude distribution of the waves suggests that the propagation in the LHR duct formed horizontally in the mid-latitude upper-ionosphere. The emission is closely related to the occurrence of ionospheric ELF hiss. It is also shown that LHR emissions are commonly observed in the slot region of the radiation belt, and they sometimes accompany the enhancement of the ionospheric electron temperature. The generation of the LHR band emissions is discussed based on the observed characteristics.

  7. Mesoscale Analysis of AN Intense Mid-Latitude Squall-Line System

    Science.gov (United States)

    Biggerstaff, Michael Irwin

    The kinematic structure of the mature phase of a mid-latitude squall-line system with a leading-line trailing stratiform-percipitation structure was examined using a unique set of composite data analyses. The broad-scale aspects of the storm system was determined from a composite of high-frequency rawinsonde, profiler, and surface mesonetwork data combined with several dual-Doppler analyses in a common framework attached to the moving storm. A higher-resolution, but spatially more limited, composite was constructed using eleven dual-Doppler analyses which provided detailed wind and precipitation information over the entire breadth of the northern half of the storm. Analysis from these two data sets revealed several aspects of the structure of squall-line systems that have not been documented previously. A deep layer of subsidence consisting of two separate, but vertically aligned, downdrafts driven by different mechanisms was found over the mid-to -low level radar-reflectivity minimum in the transition zone. Based on an analysis of the individual downdrafts observed in the near-instantaneous dual-Doppler syntheses, the upper-level and lower-level transition-zone downdrafts were found be the averaged effect of convective drafts in dissipating convective cells that were moving rearward relative to the front edge of the storm. The structure of the individual upper-level downdrafts suggested that they were a combination of dynamically forced gravity waves excited by the interaction of the penetrative updrafts with the stable ambient flow and other pressure forces associated with the rearward moving dissipating convective cells. Hydrometeor trajectories through the transition zone revealed that the hydrometeors in the reflectivity minimum were likely unaffected by the upper-level transition -zone downdraft. However, the mid-to-low level subsidence was important in the development of the reflectivity minimum through the sublimation of small ice crystals in the transition

  8. Mid-latitude ionospheric perturbation associated with the Spacelab-2 plasma depletion experiment at Millstone Hill

    Directory of Open Access Journals (Sweden)

    J. C. Foster

    Full Text Available Elevation scans across geomagnetic mid latitudes by the incoherent scatter radar at Millstone Hill captured the ionospheric response to the firing of the Space Shuttle Challenger OMS thrusters near the peak of the F layer on July 30, 1985. Details of the excitation of airglow and the formation of an ionospheric hole during this event have been reported in an earlier paper by Mendillo et al.. The depletion (factor ~2 near the 320 km Shuttle orbital altitude persisted for ~35 min and then recovered to near normal levels, while at 265 km the density was reduced by a factor of ~6; this significant reduction in the bottomside F-region density persisted for more than 3 hours. Total electron content in the vicinity of the hole was reduced by more than a factor of 2, and an oscillation of the F-region densities with 40-min period ensued and persisted for several hours. Plasma vertical Doppler velocity varied quasi-periodically with a ~80-min period, while magnetic field variations observed on the field line through the Shuttle-burn position exhibited a similar ~80-min periodicity. An interval of magnetic field variations at hydromagnetic frequencies (~95 s period accompanied the ionospheric perturbations on this field line. Radar observations revealed a downward phase progression of the 40-min period density enhancements of -1.12° km-1, corresponding to a 320-km vertical wavelength. An auroral-latitude geomagnetic disturbance began near the time of the Spacelab-2 experiment and was associated with the imposition of a strong southward IMF Bz across the magnetosphere. This created an additional complication in the interpretation of the active ionospheric experiment. It cannot be determined uniquely whether the ionospheric oscillations, which followed the Spacelab-2 experiment, were related to the active experiment or were the result of a propagating ionospheric disturbance (TID launched by the enhanced auroral

  9. A reassessment of the PRIMO recommendations for adjustments to mid-latitude ionospheric models

    Science.gov (United States)

    David, M.; Sojka, J. J.; Schunk, R. W.

    2012-12-01

    In the late 1990s, in response to the realization that ionospheric physical models tended to underestimate the dayside peak F-region electron density (NmF2) by about a factor of 2, a group of modelers convened to find out why. The project was dubbed PRIMO, standing for Problems Relating to Ionospheric Models and Observations. Five ionospheric models were employed in the original study, including the Utah State University Time Dependent Ionospheric Model (TDIM), which is the focus of the present study. No physics-based explanation was put forward for the models' shortcomings, but there was a recommendation that three adjustments be made within the models: 1) The inclusion of a Burnside factor of 1.7 for the diffusion coefficients; 2) that the branching ratio of O+ be changed from 0.38 to 0.25; and 3) that the dayside ion production rates be scaled upward to account for ionization by secondary photons. The PRIMO recommendations were dutifully included in our TDIM model at Utah State University, though as time went on, and particularly while modeling the ionosphere during the International Polar Year (2007), it became clear that the PRIMO adjustments sometimes caused the model to produce excessively high dayside electron densities. As the original PRIMO study [Anderson et al, 1998] was based upon model/observation comparison over a very limited set of observations from just one station (Millstone Hill, Massachusetts), we have expanded the range of the study, taking advantage of resources that were not available 12 years ago, most notably the NGDC SPIDR Internet data base, and faster computers for running large numbers of simulations with the TDIM model. We look at ionosonde measurements of the peak dayside electron densities at mid-latitudes around the world, across the full range of seasons and solar cycles, as well as levels of geomagnetic activity, in order to determine at which times the PRIMO adjustments should be included in the model, and when it is best not to

  10. Mid-latitude ionospheric perturbation associated with the Spacelab-2 plasma depletion experiment at Millstone Hill

    Directory of Open Access Journals (Sweden)

    J. C. Foster

    2000-01-01

    Full Text Available Elevation scans across geomagnetic mid latitudes by the incoherent scatter radar at Millstone Hill captured the ionospheric response to the firing of the Space Shuttle Challenger OMS thrusters near the peak of the F layer on July 30, 1985. Details of the excitation of airglow and the formation of an ionospheric hole during this event have been reported in an earlier paper by Mendillo et al.. The depletion (factor ~2 near the 320 km Shuttle orbital altitude persisted for ~35 min and then recovered to near normal levels, while at 265 km the density was reduced by a factor of ~6; this significant reduction in the bottomside F-region density persisted for more than 3 hours. Total electron content in the vicinity of the hole was reduced by more than a factor of 2, and an oscillation of the F-region densities with 40-min period ensued and persisted for several hours. Plasma vertical Doppler velocity varied quasi-periodically with a ~80-min period, while magnetic field variations observed on the field line through the Shuttle-burn position exhibited a similar ~80-min periodicity. An interval of magnetic field variations at hydromagnetic frequencies (~95 s period accompanied the ionospheric perturbations on this field line. Radar observations revealed a downward phase progression of the 40-min period density enhancements of -1.12° km-1, corresponding to a 320-km vertical wavelength. An auroral-latitude geomagnetic disturbance began near the time of the Spacelab-2 experiment and was associated with the imposition of a strong southward IMF Bz across the magnetosphere. This created an additional complication in the interpretation of the active ionospheric experiment. It cannot be determined uniquely whether the ionospheric oscillations, which followed the Spacelab-2 experiment, were related to the active experiment or were the result of a propagating ionospheric disturbance (TID launched by the enhanced auroral activity. The most reasonable conclusion is

  11. Impacts of Climate Change on Permafrost in Mid-Latitude Mountain Regions

    Science.gov (United States)

    Frauenfelder, R.; Kaeaeb, A.; Roer, I.; Gruber, S.; Noetzli, J.

    2005-12-01

    Global Climate Models (GCMs) predict significant warming through the 21st Century, with the amplitude of change generally increasing at higher latitudes and higher altitudes. Periglacial permafrost in the European mountains occupies today an area about twice as large as the glacierized area. In order to be able to anticipate and quantify the possible impact of forecast climatic change, it is important to investigate and understand the current conditions and dominant processes in these periglacial areas. In this presentation, we review latest findings about the impact of atmospheric warming in mid-latitude mountain regions, focussing on impacts on creeping debris-ice bodies (i.e. rockglaciers) and on the stability of steep rock faces. In debris covered areas, the reaction to warming temperatures is filtered and occurs through the increase in active layer thickness and melting at the top of the permafrost over periods of years. A warming of the temperature profile within permafrost occurs over the span of decades to centuries. Upward displacement of the base of permafrost to reach a new equilibrium thickness takes centuries to millennia. Spatial modelling of the distribution of permafrost suggest a rise of the lower limit of discontinuous Alpine permafrost of around 100 m during the last 150 years. Borehole measurements show a warming of the permafrost in the upper tens of meters of up to 0.5-0.8°C during recent decades. Rising of the permafrost limit leads to climatic inactivation of creeping bodies presently below the lower limit of permafrost. Warming of the permafrost temperature seems to increase creep rates of active rockglaciers. In comparison with debris-covered slopes, rock faces react quickly to climate change. This is due to the absence of a blocky layer and corresponding direct coupling of surface and sub-surface conditions, combined with a low water content and a small transfer of latent heat during melt. Rising temperatures or the complete thaw of

  12. On the vertical structure of longitudinal differences in electron densities in the mid-latitudes: COSMIC radio occultation observations and GITM simulations

    Science.gov (United States)

    Wang, Hui; Liu, Dingwei; Zhang, Kedeng

    2016-04-01

    By using COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) satellite observations, and GITM (Global Ionosphere and Thermosphere Model) simulations, the altitudinal dependences of the longitudinal differences in electron densities Ne were studied at mid-latitudes for the first time. Distinct altitudinal dependences were revealed: (1) in the northern (southern) hemisphere, there were wave-1 variations mainly in the daytime in the altitudes below 180 km, but wave-2 (wave-1) variations over a whole day above 220 km; (2) a transition (or separation) layer occurred mainly in the daytime within 180 km and 220 km, showing reversed longitudinal variation from that at lower altitudes. Solar illumination was one of the plausible mechanisms for the zonal difference of Ne at lower altitudes. At higher altitudes both neutral winds and solar illumination played important roles. The neutral winds effects accounted for the longitudinal differences in Ne in the European-Asian sector. Neutral composition changes and neutral wind effects both contributed to the formation of the transition layer.

  13. Hemispheric transport and influence of meteorology on global aerosol climatology

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    T. L. Zhao

    2012-08-01

    Full Text Available Based on a 10-yr simulation with the global air quality modeling system GEM-AQ/EC, the northern hemispheric aerosol transport with the inter-annual and seasonal variability as well as the mean climate was investigated. The intercontinental aerosol transport is predominant in the zonal direction from west to east with the ranges of inter-annual variability between 14% and 63%, and is 0.5–2 orders of magnitude weaker in the meridional direction but with larger inter-annual variability. The aerosol transport is found to fluctuate seasonally with a factor of 5–8 between the maximum in late winter and spring and the minimum in late summer and fall. Three meteorological factors controlling the intercontinental aerosol transport and its inter-annual variations are identified from the modeling results: (1 Anomalies in the mid-latitude westerlies in the troposphere. (2 Variations of precipitation over the intercontinental transport pathways and (3 Changes of meteorological conditions within the boundary layer. Changed only by the meteorology, the aerosol column loadings in the free troposphere over the source regions of Europe, North America, South and East Asia vary inter-annually with the highest magnitudes of 30–37% in January and December and the lowest magnitudes of 16–20% in August and September, and the inter-annual aerosol variability within the boundary layer influencing the surface concentrations with the magnitudes from 6% to 20% is more region-dependent. As the strongest climatic signal, the El Niño-Southern Oscillation (ENSO can lead the anomalies in the intercontinental aerosols in El Niño- and La Niña-years respectively with the strong and weak transport of the mid-latitude westerlies and the low latitude easterlies in the Northern Hemisphere (NH.

  14. Analysis of the mid-latitude weather regimes in the 200-year control integration of the SINTEX model

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    A. Navarra

    2003-06-01

    Full Text Available Recent results indicate that climate predictions require models which can simulate accurately natural circulation regimes and their associated variability. The main purpose of this study is to investigate whether (and how a coupled model can simulate the real world weather regimes. A 200-year control integration of a coupled GCM (the «SINTEX model» is considered. The output analysed consists of monthly mean values of Northern Hemisphere extended winter (November to April 500-hPa geopotential heights. An Empirical Orthogonal Function (EOF analysis is first applied in order to define a reduced phase space based on the leading modes of variability. Therefore the principal component PDF in the reduced phase space spanned by two leading EOFs is computed. Based on a PDF analysis in the phase space spanned by the leading EOF1 and REOF2, substantial evidence of the nongaussian regime structure of the SINTEX northern winter circulation is found. The model Probability Density Function (PDF exhibits three maxima. The 500-hPa height geographical patterns of these density maxima are strongly reminiscent of well-documented Northern Hemisphere weather regimes. This result indicates that the SINTEX model can not only simulate the non-gaussian structure of the climatic attractor, but is also able to reproduce the natural modes of variability of the system.

  15. Seasonal and magnetic activity variations of ionospheric electric fields above the southern mid-latitude station, Bundoora, Australia

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    M. L. Parkinson

    Full Text Available We investigate the seasonal, local solar time, and geomagnetic activity variations of the average Doppler velocity measured by an HF digital ionosonde deployed at Bundoora, Australia (145.1° E, 37.7° S, geographic; 49° S magnetic. The Doppler velocities were heavily averaged to suppress the short-term effects (<3 hours of atmospheric gravity waves, and thereby obtain the diurnal variations attributed to the tidally-driven ionospheric dynamo and electric fields generated by magnetic disturbances. The observed seasonal variations in Doppler velocity were probably controlled by variations in the lower thermospheric winds and ionospheric conductivity above Bundoora and in the magnetically conjugate location. The diurnal variations of the meridional (field-perpendicular drifts and their perturbations exhibited a complex structure, and were generally smaller than the variations in the zonal drifts. The latter were basically strongly west-ward during the evening to early morning, and weakly east-ward during the late morning to just past noon. The zonal perturbations were strongly enhanced by increasing geomagnetic activity, and closely resembled the perturbation drifts measured by the incoherent scatter radar (ISR at Millstone Hill (71.5° W, 42.6° N; 57° N. There was also some resemblance between the diurnal variations in the meridional drifts. Overall, the comparisons suggest that with sufficient averaging, Doppler velocities measured with digital ionosondes at mid-latitudes correspond to true ion motions driven by ionospheric electric fields. This is a useful result because apart from the ISRs located in the American-European sector, there are no ground-based instruments capable of measuring electric fields in the mid-latitude ionosphere.

    Key words. Ionosphere (electric fields and currents; ionosphere atmosphere interactions; mid-latitude ionosphere

  16. Atmospheric Blocking in the Northern Hemisphere.

    Science.gov (United States)

    Knox, John Lewis

    Blocking is generally understood as the obstruction on a large scale of the normal west - to - east motion of mid-latitude pressure systems. It is a persistent phenomenon lasting from one to several weeks and the resulting prolonged weather regimes may have serious economic and social consequences. The recent Northern Hemisphere winters, starting with 1976 -77, featured unusually large circulation anomalies, many of which can be directly related to prolonged episodes of large scale blocking. The intent of this study is to investigate the statistics and certain diagnostics of blocking in the Northern Hemisphere. The first of the three primary objectives is to present and interpret the spatial and temporal distribution of blocking during the past 33 years. We develop objective identification criteria, adaptable to machine processing methods, by relating the blocking anticyclone to its associated positive anomaly of 5-day mean 500MB height. Anomalies meeting the criteria are called 'blocking signatures.' We present the seasonal frequency of occurrence of these signatures by longitude and by area. The results are in good agreement with published studies for the oceans, but they also reveal a high frequency of blocking signatures over the Northeastern Canadian Archipelago. This result, dubbed the 'Baffin Island Paradox' is further investigated and rationalized. A catalogue has been prepared which identifies the date, centre location and magnitude of every blocking signature which occurred from January 1, 1946 to December 31, 1978. A supplementary Catalogue identifies sequences of these signatures corresponding to actual blocking episodes. The second objective is to investigate whether regions with high incidence of blocking, in either the developing or the mature stage, features non-Gaussian distributions of 5-day mean geopotential. During winter, fields of significantly low kurtosis are found in certain mid-latitude regions where the genesis and amplification of

  17. Habitat-specific bioaccumulation of methylmercury in invertebrates of small mid-latitude lakes in North America

    Energy Technology Data Exchange (ETDEWEB)

    Chetelat, John, E-mail: john.chetelat@ec.gc.c [Groupe de recherche interuniversitaire en limnologie, Departement de sciences biologiques, Universite de Montreal, Montreal, Quebec H3C 3J7 (Canada); Amyot, Marc; Garcia, Edenise [Groupe de recherche interuniversitaire en limnologie, Departement de sciences biologiques, Universite de Montreal, Montreal, Quebec H3C 3J7 (Canada)

    2011-01-15

    We examined habitat-specific bioaccumulation of methylmercury (MeHg) in aquatic food webs by comparing concentrations in pelagic zooplankton to those in littoral macroinvertebrates from 52 mid-latitude lakes in North America. Invertebrate MeHg concentrations were primarily correlated with water pH, and after controlling for this influence, pelagic zooplankton had significantly higher MeHg concentrations than littoral primary consumers but lower MeHg than littoral secondary consumers. Littoral primary consumers and pelagic zooplankton are two dominant prey for fish, and greater MeHg in zooplankton is likely sufficient to increase bioaccumulation in pelagic feeders. Intensive sampling of 8 lakes indicated that habitat-specific bioaccumulation in invertebrates (of similar trophic level) may result from spatial variation in aqueous MeHg concentration or from more efficient uptake of aqueous MeHg into the pelagic food web. Our findings demonstrate that littoral-pelagic differences in MeHg bioaccumulation are widespread in small mid-latitude lakes. - Methylmercury levels in dominant invertebrate prey for fish differ between littoral and pelagic habitats within a lake.

  18. Multi-layer structure of mid-latitude sporadic-E observed during the SEEK-2 campaign

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    T. Ono

    2005-10-01

    Full Text Available In the mid-latitude ionospheric region, sporadic-E layers (Es layers have often been observed, revealing multiple layers. The Es layers observed during the SEEK-2 rocket campaign showed double electron density peaks; namely, there are stable lower peaks and relatively unstable upper peaks. We examined the effects of wind shear and the electric fields on the generation of the multiple layer structure, in comparison with the electron density profile, the neutral wind, and the DC electric field observed by the S310 rocket experiments. The results showed that the neutral wind shear is mainly responsible for the generation of the lower layer, while the DC electric field makes a significant contribution to the formation of the upper layer. The difference between the lower and upper layers was also explained by the enhanced AC electric field observed at about 103–105 km altitude. The external DC electric field intensity is expected to be ~5 mV/m, which is enough to contribute to generate the Es layers in the ionosphere. Keywords. Ionosphere (Electric fields; Ionospheric irregularities, Mid-latitude ionosphere

  19. E-region mid-latitude decametre irregularities observed at four radar frequencies. Experiment and first results

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    A. Bourdillon

    Full Text Available In this paper an experiment designed for multifrequency azimuthal Doppler-spectrum investigations of decametre-scale plasma irregularities in the mid-latitude E region is introduced and some preliminary results are presented. The observations were made with the high-frequency Valensole radar in the south of France. The radar operated in a multifrequency mode that allowed simultaneous measurements of Doppler spectra at the four frequencies of 9.23, 11.03, 12.71 and 16.09 MHz, which correspond to scatter from field-aligned irregularities with wavelengths of 16.2, 13.6, 11.8 and 9.3 m, respectively. In addition, a digital ionosonde was operating beneath a small part of the radar viewing region. The data show that lower-frequency echoes are stronger, more frequent and more spatially extended than higher-frequency ones, in general agreement with theory and rocket measurements. On the other hand, the preliminary analysis shows no pronounced differences of the Doppler spectrum with radar frequency. Some trends in the spectral moments do exist, however, which can be understood as the result of temporal and/or spatial mixing of backscatter from directly generated (primary plasma waves by the gradient drift instability and secondary low-velocity waves. Finally, a close relation of mid-latitude coherent backscatter with patchy sporadic E-layers is present in the data, but the details of this relation remain unresolved.

  20. A three-dimensional modelling study of the processes leading to mid latitude nitric oxide increases in the lower thermosphere following periods of high geomagnetic activity

    Science.gov (United States)

    Dobbin, A. L.; Aylward, A. D.

    2008-11-01

    The processes leading to enhancements in mid latitude nitric oxide (NO) densities following geomagnetic storms have been investigated using the University College London (UCL) Coupled Middle Atmosphere and Thermosphere (CMAT) general circulation model. A comparison of calculated storm time and quiet time NO densities at 110 km altitude reveals the presence of aurorally produced NO at both high and mid latitudes for several days after subsidence of activity. At 150 km, the NO enhancements are shorter lived and remain for up to approximately 2 days after the storm. By separating the contribution of chemical production and loss, horizontal and vertical advection, and molecular and eddy diffusion in the calculation of NO densities, we show that at 150 km altitude, horizontal transport must be taken into consideration if post-storm mid latitude enhancements are to be reproduced. Chemical production of NO at high latitudes continues for up to 2 days after subsidence of a storm at altitudes of around 150 km. We show that equatorward winds at this altitude are sufficiently strong to transport the aurorally produced NO to mid latitudes. Vertical diffusion transports NO from altitudes of 150 km and above, to lower altitudes where it is longer lived. At 110 km altitude, chemical, diffusive and advective terms must all be included in the calculation of NO density in order to simulate realistic mid latitude enhancements. We propose that it is the combined effects of increased chemical production, downward diffusion from altitudes of 150 km and above, and transport by winds that lead to increases in mid latitude NO density at altitudes of around 110 km. This is the first detailed study of the causes of post-storm mid latitude NO enhancements to use a three-dimensional general circulation model.

  1. Variations of energetics of cyclones in the mid-latitude North America, 1948--2000

    Science.gov (United States)

    Tawaye, Yacoubou

    Variations in energetics of cyclones in the midlatitude North America are examined and changes of the cyclone energetics are found with the climate warming since the late 1970s. Generation, horizontal and vertical transports of energy are found to drastically increase after 1978 indicating that cyclones of both cold and warm seasons are more energetic in the warmer period since 1978 than those in the relative cool period of 1948-78. Excess production of potential energy in the warm climate resulted in large generation of available potential energy in both warm and cold seasons. However, large amount of the resulting available potential energy is not converted into kinetic energy. This indicates changes in the efficiency of the atmospheric engine during cyclone activities, especially in winter. The strengthening of cyclones in the warm season of the recent decades can be attributed to a stronger jet stream centered at a lower elevation in the troposphere, while the enhanced cold season cyclones in the warmer climate are found to be associated with the westerly jet centered at a higher elevation of the troposphere. From mid-troposphere to the jet in winter, increase in temperature and meridional wind caused significant development and strength of eddy motion leading to the observed upward displacement of the winter jet. Associated with this elevated jet stream is the enhanced baroclinicity in the upper troposphere in boreal winter. The variations in the energetics of warm and cold season cyclones in the midlatitude North America found in the present study invite more research on the possible consequences of climate warming. Changes in the characteristics of various atmospheric phenomena in the warming climate are still unknown. Examples among the several unknowns are the transition mechanisms from tropical to extratropical cyclones. This transition occurs when a tropical cyclone moves into the midlatitudes and acquires midlatitude characteristics. Studies of the

  2. Long-term variations of the mesospheric wind field at mid-latitudes

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    D. Keuer

    2007-08-01

    Full Text Available Continuous MF radar observations at the station Juliusruh (54.6° N; 13.4° E have been analysed for the time interval between 1990 and 2005, to obtain information about solar activity-induced variations, as well as long-term trends in the mesospheric wind field. Using monthly median values of the zonal and the meridional prevailing wind components, as well as of the amplitude of the semidiurnal tide, regression analyses have been carried out with a dependence on solar activity and time. The solar activity causes a significant amplification of the zonal winds during summer (increasing easterly winds and winter (increasing westerly winds. The meridional wind component is positively correlated with the solar activity during summer but during winter the correlation is very small and non significant. Also, the solar influence upon the amplitude of the semidiurnal tidal component is relatively small (in dependence on height partly positive and partly negative and mostly non-significant.

    The derived trends in the zonal wind component during summer are below an altitude of about 83 km negative and above this height positive. During the winter months the trends are nearly opposite compared with the trends in summer (transition height near 86 km. The trends in the meridional wind components are below about 85 km positive in summer (significant and near zero (nonsignificant in winter; above this height during both seasons negative trends have been detected. The trends in the semidiurnal tidal amplitude are at all heights positive, but only partly significant.

    The detected trends and solar cycle dependencies are compared with other experimental results and model calculations. There is no full agreement between the different results, probably caused by different measuring techniques and evaluation methods used. Also, different heights and observation periods investigated may contribute to the detected differences.

  3. Impact of sea ice cover changes on the Northern Hemisphere atmospheric winter circulation

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    D. Handorf

    2012-01-01

    Full Text Available The response of the Arctic atmosphere to low and high sea ice concentration phases based on European Center for Medium-Range Weather Forecast (ECMWF Re-Analysis Interim (ERA-Interim atmospheric data and Hadley Centre's sea ice dataset (HadISST1 from 1989 until 2010 has been studied. Time slices of winter atmospheric circulation with high (1990–2000 and low (2001–2010 sea ice concentration in the preceding August/September have been analysed with respect to tropospheric interactions between planetary and baroclinic waves. It is shown that a changed sea ice concentration over the Arctic Ocean impacts differently the development of synoptic and planetary atmospheric circulation systems. During the low ice phase, stronger heat release to the atmosphere over the Arctic Ocean reduces the atmospheric vertical static stability. This leads to an earlier onset of baroclinic instability that further modulates the non-linear interactions between baroclinic wave energy fluxes on time scales of 2.5–6 d and planetary scales of 10–90 d. Our analysis suggests that Arctic sea ice concentration changes exert a remote impact on the large-scale atmospheric circulation during winter, exhibiting a barotropic structure with similar patterns of pressure anomalies at the surface and in the mid-troposphere. These are connected to pronounced planetary wave train changes notably over the North Pacific.

  4. On the relationship between total ozone and atmospheric dynamics and chemistry at mid-latitudes – Part 2: The effects of the El Niño/Southern Oscillation, volcanic eruptions and contributions of atmospheric dynamics and chemistry to long-term total ozone changes

    Directory of Open Access Journals (Sweden)

    H. E. Rieder

    2013-01-01

    Full Text Available We present the first spatial analysis of "fingerprints" of the El Niño/Southern Oscillation (ENSO and atmospheric aerosol load after major volcanic eruptions (El Chichón and Mt. Pinatubo in extreme low and high (termed ELOs and EHOs, respectively and mean values of total ozone for the northern and southern mid-latitudes (defined as the region between 30° and 60° north and south, respectively. Significant influence on ozone extremes was found for the warm ENSO phase in both hemispheres during spring, especially towards low latitudes, indicating the enhanced ozone transport from the tropics to the extra-tropics. Further, the results confirm findings of recent work on the connection between the ENSO phase and the strength and extent of the southern ozone "collar". For the volcanic eruptions the analysis confirms findings of earlier studies for the northern mid-latitudes and gives new insights for the Southern Hemisphere. The results provide evidence that the negative effect of the eruption of El Chichón might be partly compensated by a strong warm ENSO phase in 1982–1983 at southern mid-latitudes. The strong west-east gradient in the coefficient estimates for the Mt. Pinatubo eruption and the analysis of the relationship between the AAO and ENSO phase, the extent and the position of the southern ozone "collar" and the polar vortex structure provide clear evidence for a dynamical "masking" of the volcanic signal at southern mid-latitudes. The paper also analyses the contribution of atmospheric dynamics and chemistry to long-term total ozone changes. Here, quite heterogeneous results have been found on spatial scales. In general the results show that EESC and the 11-yr solar cycle can be identified as major contributors to long-term ozone changes. However, a strong contribution of dynamical features (El Niño/Southern Oscillation (ENSO, North Atlantic Oscillation (NAO, Antarctic Oscillation (AAO, Quasi-Biennial Oscillation (QBO to ozone

  5. Mid-latitude shrub steppe plant communities: climate change consequences for soil water resources.

    Science.gov (United States)

    Palmquist, Kyle A; Schlaepfer, Daniel R; Bradford, John B; Lauenroth, William K

    2016-09-01

    In the coming century, climate change is projected to impact precipitation and temperature regimes worldwide, with especially large effects in drylands. We use big sagebrush ecosystems as a model dryland ecosystem to explore the impacts of altered climate on ecohydrology and the implications of those changes for big sagebrush plant communities using output from 10 Global Circulation Models (GCMs) for two representative concentration pathways (RCPs). We ask: (1) What is the magnitude of variability in future temperature and precipitation regimes among GCMs and RCPs for big sagebrush ecosystems, and (2) How will altered climate and uncertainty in climate forecasts influence key aspects of big sagebrush water balance? We explored these questions across 1980-2010, 2030-2060, and 2070-2100 to determine how changes in water balance might develop through the 21st century. We assessed ecohydrological variables at 898 sagebrush sites across the western US using a process-based soil water model, SOILWAT, to model all components of daily water balance using site-specific vegetation parameters and site-specific soil properties for multiple soil layers. Our modeling approach allowed for changes in vegetation based on climate. Temperature increased across all GCMs and RCPs, whereas changes in precipitation were more variable across GCMs. Winter and spring precipitation was predicted to increase in the future (7% by 2030-2060, 12% by 2070-2100), resulting in slight increases in soil water potential (SWP) in winter. Despite wetter winter soil conditions, SWP decreased in late spring and summer due to increased evapotranspiration (6% by 2030-2060, 10% by 2070-2100) and groundwater recharge (26% and 30% increase by 2030-2060 and 2070-2100). Thus, despite increased precipitation in the cold season, soils may dry out earlier in the year, resulting in potentially longer, drier summer conditions. If winter precipitation cannot offset drier summer conditions in the future, we expect big

  6. The sub-auroral electric field as observed by DMSP and the new SuperDARN mid-latitude radars

    Science.gov (United States)

    Talaat, E. R.; Sotirelis, T.; Hairston, M. R.; Ruohoniemi, J. M.; Greenwald, R. A.; Lester, M.

    2008-12-01

    In this paper we present analyses of the sub-auroral electric field environment as observed from both space and ground. We discuss the dependency of the configuration and strength of the sub-auroral electric field on IMF and geomagnetic activity, longitudinal, seasonal, and solar cycle variability. Primarily, e use ~20 years of electric field measurement dataset derived from the suite of DMSP ion drift meters. A major component of our analysis is correctly specifying the aurora boundary, as the behavior and magnitude of these fields will be drastically different away from the high-conductance auroral oval. As such, we use the coincident particle flux measurements from the DMSP SSJ4 monitors. We also present the solar minimum observations of the sub-auroral flow newly available from the mid-latitude SuperDARN radars at Wallops and Blackstone in Virginia. Preliminary comparisons between these flows and the DMSP climatology are discussed.

  7. Classification of Global Land Development Phases by Forest and GDP Changes for Appropriate Land Management in the Mid-Latitude

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    Cholho Song

    2017-08-01

    Full Text Available To implement appropriate land management strategies, it is essential to identify past and current land cover and land use conditions. In addition, an assessment of land development phases (LDPs in a human-dominated landscape coupled with an analysis of the water-food-ecosystem (WFE nexus can deepen our understanding of sustainable land management. In this study, we proposed the concept of land development phases (LDPs by forest and GDP changes using previously-applied theoretical and empirical approaches. The positive relationship between GDP growth and forest stock changes was used to analyze the timing of forest stock changes as five-year averages, which were aggregated over 20 years to classify LDPs. In addition, forest area changes compared with GDP and GDP per capita changes were analyzed to identify LDPs. Based on two conceptual approaches, we suggested global land into three LDPs: degradation, restoration and sustainability. Using this approach, most of Europe, North America and northeast Asia were classified as sustainability phases, while Africa and Central Asia in the Mid-Latitude region appeared to have degradation or restoration phases. The LDPs described could be improved with further incorporation of solid data analysis and clear standards, but even at this stage, these LDP classifications suggest points for implementing appropriate land management. In addition, indices from comparative analysis of the LDPs with the WFE nexus can be connected with socio-economic global indices, such as the Global Hunger Index, the Food Production Index and the Climate Change Performance Index. The LDPs have the potential to facilitate appropriate land management strategies through integrating WFE nexus and ecosystem services; we propose future research that uses this integration for the Mid-Latitude region and worldwide.

  8. Estimate of Low/Mid-Latitude Conductances, Electric Potential and Neutral Winds using IDA4D and EMPIRE

    Science.gov (United States)

    Bust, G. S.; Makela, J. J.; Harding, B. J.; Heelis, R. A.; Bishop, R. L.

    2015-12-01

    In this talk we will focus on the current ability of the ionosphere-thermosphere data assimilative models, Ionospheric Data Assimilation Four Dimensional (IDA4D) and Estimating Model Parameters from Ionospheric Reverse Engineering (EMPIRE), to estimate low and mid latitude ionosphere-thermosphere (IT) state variables at altitudes of 200 km and less. In particular we focus on the estimation of Pederson and Hall conductances, equatorial electric potential, and neutral winds. We will characterize the current state of IDA4D and EMPIRE in terms of data available to be assimilated and geophysical conditions. We will discuss the accuracy expected for given conditions, current limitations, and to what degree data assimilative models can be used to advance our understanding of the low/mid latitude physics at 200 km and below. We will use three case study events to help elucidate the current capabilities of IDA4D and EMPIRE: The March, 2013 storm, the March 2015 storm, and the March 2014 time period, which was relatively quiet. In additional to the normal data sets ingested by IDA4D and EMPIRE we intend to ingest observation from the C/NOFS satellite including radio occultations, in-situ measurements of plasma density and ion drifts. We will also ingest other measurements related to electric fields from coherent scatter radars and magnetometers when available. Finally, we will ingest neutral wind measurements from FPI's. We will conclude with a discussion of the future of IT data assimilation algorithms, the advantages of coupling to first principle models, and what future satellite missions such as ICON, GOLD and COSMIC 2 will contribute to improved IT data assimilation estimates.

  9. Summertime stratospheric processes at northern mid-latitudes: comparisons between MANTRA balloon measurements and the Canadian Middle Atmosphere Model

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    S. M. L. Melo

    2008-04-01

    Full Text Available In this paper we report on a study conducted using the Middle Atmospheric Nitrogen TRend Assessment (MANTRA balloon measurements of stratospheric constituents and temperature and the Canadian Middle Atmosphere Model (CMAM. Three different kinds of data are used to assess the inter-consistency of the combined dataset: single profiles of long-lived species from MANTRA 1998, sparse climatologies from the ozonesonde measurements during the four MANTRA campaigns and from HALOE satellite measurements, and the CMAM climatology. In doing so, we evaluate the ability of the model to reproduce the measured fields and to thereby test our ability to describe mid-latitude summertime stratospheric processes. The MANTRA campaigns were conducted at Vanscoy, Saskatchewan, Canada (52° N, 107° W in late August and early September of 1998, 2000, 2002 and 2004. During late summer at mid-latitudes, the stratosphere is close to photochemical control, providing an ideal scenario for the study reported here. From this analysis we find that: (1 reducing the value for the vertical diffusion coefficient in CMAM to a more physically reasonable value results in the model better reproducing the measured profiles of long-lived species; (2 the existence of compact correlations among the constituents, as expected from independent measurements in the literature and from models, confirms the self-consistency of the MANTRA measurements; and (3 the 1998 measurements show structures in the chemical species profiles that can be associated with transport, adding to the growing evidence that the summertime stratosphere can be much more disturbed than anticipated. The mechanisms responsible for such disturbances need to be understood in order to assess the representativeness of the measurements and to isolate long-term trends.

  10. Impacts of global warming on Northern Hemisphere winter storm tracks in the CMIP5 model suite

    Science.gov (United States)

    Eichler, Timothy Paul; Gaggini, Natalie; Pan, Zaitao

    2013-05-01

    key question in assessing how global warming may affect climate is how it may impact day-to-day weather. To help answer this question, we evaluate the frequency and intensity of northern hemisphere storm tracks in the National Center for Climate Prediction reanalysis I dataset, and the historical, RCP4.5, and RCP8.5 climate scenarios featured in the CMIP5 simulations. We found that a warmer climate resulted in a general decrease in storm frequency in midlatitudes, especially in RCP8.5. In contrast, frequency trends in the reanalysis data reflected an increase in the North Pacific consistent with a shift towards a positive Pacific Decadal Oscillation and more frequent El Niño events post mid-1970s. An examination of frequency and intensity trends in the active storm track regions of the North Pacific and North Atlantic showed that a significant decrease in storm track frequency was evident for RCP8.5. In contrast, intensity trends were dichotomous, with RCP8.5 exhibiting an increase in intensity in the North Atlantic active storm track region and a decrease in intensity in the North Pacific active storm track region. Poleward of these regions, a significant decrease in storm intensity in the North Atlantic and a significant increase in intensity in the North Pacific in RCP8.5 occurred. We also examined the intensity distribution of storms in the active storm track regions of the North Atlantic and North Pacific and determined that the models produced weaker storms with reduced variability relative to reanalysis data regardless of external climate forcing.

  11. Breaking the routine: individual Cory's shearwaters shift winter destinations between hemispheres and across ocean basins

    Science.gov (United States)

    Dias, Maria P.; Granadeiro, José P.; Phillips, Richard A.; Alonso, Hany; Catry, Paulo

    2011-01-01

    There is growing evidence that migratory species are particularly vulnerable to rapid environmental changes arising from human activity. Species are expected to vary in their capacity to respond to these changes: long-distance migrants and those lacking variability in migratory traits are probably at considerable disadvantage. The few studies that have assessed the degree of plasticity in behaviour of marine animals suggest that fidelity to non-breeding destinations is usually high. In the present study, we evaluated individual flexibility in migration strategy of a highly pelagic seabird, the Cory's shearwater Calonectris diomedea. Geolocation data from 72 different migrations, including 14 birds that were tracked for more than one non-breeding season, showed a remarkable capacity to change winter destinations between years. Although some birds exhibited high site fidelity, others shifted from the South to North Atlantic, from the western to eastern South Atlantic, and from the Atlantic to Indian Ocean. Individuals also showed flexibility in stopover behaviour and migratory schedule. Although their K-selected life-history strategy has the disadvantage that the chances of microevolution are slight if circumstances alter rapidly, these results suggest that Cory's shearwaters may be in a better position than many other long-distance migrants to face the consequences of a changing environment. PMID:21106591

  12. Lidar measurements of gravity waves in the middle atmosphere in southern hemisphere winter above New Zealand

    Science.gov (United States)

    Kaifler, Bernd; Kaifler, Natalie; Dörnbrack, Andreas; Ehard, Benedikt; Rapp, Markus

    2015-04-01

    The international Deep Propagating Gravity Wave Experiment (DEEPWAVE) campaign was carried out in New Zealand during austral winter 2014. Its aim was to extensively study gravity waves from their sources in the troposphere, along their propagation through the atmosphere to the regions of dissipation at high altitudes. New Zealand was chosen due to its proximity to the edge of the polar vortex and its orography where strong flows excite gravity waves, making it one of the world's gravity wave hotspots. During DEEPWAVE, a comprehensive set of instruments was operated to observe gravity waves. The DLR Rayleigh/Raman lidar was set up at NIWA station in Lauder on New Zealand's South Island in June 2014. The instrumented was operated whenever weather permitted. Temperature profiles are retrieved between 22 and 80 km with 10 min temporal and 1 km vertical resolution. In order to study variations in gravity wave propagation associated with the breakdown of the polar vortex, observations were continued beyond the DEEPWAVE campaign. In total 755 operation hours during 99 nights were accumulated between June and November 2014. We present statistics of gravity wave activity and wave parameters which we derived from this extensive dataset using filtering techniques and spectral analysis. In a first step, we characterize gravity wave activity using the gravity wave potential energy density. Then we study spectral properties of the waves using two-dimensional FFT of wave-induced temperature variances. We find that in the stratosphere, low-frequency waves with periods close to the inertial period are very common. Large-amplitude waves with periods of less than two hours occur at times mainly in the mesosphere. The distribution of observed phase speeds suggests that observed waves fall into three groups: one group with mean phase speeds of -3 km/h, one group with phase speeds close to zero, and a broad background. In addition to statistics, we show case studies of selected gravity

  13. Air-snow exchange of nitrogen oxides and ozone at a polluted mid-latitude site

    Science.gov (United States)

    Murphy, Jennifer G.; Hong, Angela C.; Quinn, Patricia K.; Bates, Tim

    2017-04-01

    Vertical gradients of O3, NO, NO2 and NOywere measured within and above the snowpack between January 17 to February 14, 2014 as part of the Uintah Basin Winter Ozone Study. During the first half of the campaign, the snowpack was relatively aged and contained high levels of inorganic ions and dissolved and particulate organics. A snowfall on Jan 31 added 5 cm of fresh snow with lower solute concentrations to the top of the snowpack. Vertical gradients (ΔC = C(25cm) - C(125cm)) in the measured gas phase species were used to investigate the role of the snowpack as a source or sink. Small positive gradients were seen for NO, peaking in the middle of the day, which much larger negative gradients were seen for O3 and NOy. Comparing the fresh to the aged snowpacks, there was a noticeable decrease in the gradient for O3, but not for NOy over the fresh snow, implying a chemical control of O3 deposition to the snow. The ratio of the gradient of NOx to the gradient of NOy was used to determine a snowpack NOy recycling ratio (emission/deposition) of approximately 4 %, consistent with independent estimates of low nitrate photolysis rates inferred from nitrogen isotopes by Zatko et al., (2016). Reference Zatko et al., The magnitude of the snow-sourced reactive nitrogen flux to the boundary layer in the Uintah Basin, Utah, USA, Atmos. Chem. Phys., 16, 13837-13851, 2016.

  14. Local climatological modeling of ionospheric irregularities detected by GPS in the mid-latitude region

    Science.gov (United States)

    Wautelet, G.; Warnant, R.

    2012-11-01

    Global Positioning System, or GPS, plays an important role in everyday life. More particularly, precise positioning applications constitute a continuously growing sector whose surveyors, civil engineers and more recently farmers represent the principal users. Ionospheric irregularities are considered as the main threat for those applications as their occurrence and their effects on positioning are generally unknown or unmodeled. This paper aims at setting up a local climatological model of such irregularities which can be used as a forecasting tool. The model is based upon a time series of GPS-derived ionospheric irregularities in Belgium covering 10 years of data (period 2002-2011). Our climatological model is twofold: its first component describes the daily variability and is derived from a principal component analysis (PCA) which allows us to retrieve the main patterns of the time series. With the use of low order polynomial and harmonic functions, the second component describes the influence of solar cycle and seasons on irregularity occurrence. Moreover, a statistical autoregressive formulation adapts the model to current conditions. Model validation covers both low and active solar activity periods (years 2008 and 2011) and shows that model accuracy varies with solar conditions and season: values are lower during winter and active solar activity periods, where modeling error can reach up to 60% of the observed value. During summer, model performance is clearly improved, with relative errors generally smaller than 20% for periods of low but also active solar activity.

  15. Arctic Warmth Becomes a Mid-Latitude Chill: Using Online Data To Teach Climate Change Science

    Science.gov (United States)

    Eichorn, David N.

    Climate change education is a growing sub-discipline of science education. This research reports on the use of the fundamental principles of atmospheric science to explain the potential impact of regional climate change across global latitudes. Since the Arctic is responding to climate change faster than any other place on earth, it offers us a real-time opportunity to teach the larger scale impacts of abrupt regional scale change. In this research I merged elements of both the atmospheric and climate sciences into an online course. The course uses principles of meteorology to teach climate change science and demonstrate cause and effect relationships within the atmosphere. Students learn how climate change in one part of the world impacts weather elsewhere through the use of animated and descriptive video lectures that explain basic atmospheric thermodynamics processes. This paper includes a lesson plan that shows how climatic warming in the Arctic causes colder US winter weather. Formative and summative evaluations taken from course evaluations and exams suggest using meteorology to teach climate change is an effective way to educate students in high school and undergraduate college level courses about cross latitudinal influences of climate change. Keywords: Climate Change, Global Warming, Arctic, Climate Literacy, Lesson Plan, Arctic Oscillation, Education

  16. Comparison between the Temperature Measurements by TIMED/SABER and Lidar in the Mid-Latitude

    Science.gov (United States)

    Xu, Jiyao; She, C. Y.; Yuan, Wei; Mertens, Chris; Mlynczak, Marty; Russell, James

    2005-01-01

    Comparisons of monthly-mean nighttime temperature profiles observed by the Sodium Lidar at Colorado State University and TIMED/SABER over passes are made. In the altitude range from 85 km to about 100 km, the two observations are in excellent agreement. Though within each other s error bars, important differences occur below 85 km in the entire year and above 100 km in the summer season. Possible reasons for these difference are high photon noise below 85 km in lidar observations, and less than accurate assumptions in the concentration of important chemical species like oxygen (and its quenching rate) in the SABER retrieval above 100 km. However, the two techniques both show the two-level mesopause thermal structure, with the times of change from one level to the other in excellent agreement. Comparison indicates that the high-level (winter) mesopause altitudes are also in excellent agreement between the two observations, though some difference may exist in the low-level (summer) mesopause altitudes between ground-based and satellite-borne data.

  17. Modeling Convective Injection of Water Vapor into the Lower Stratosphere in the Mid-Latitudes over North America

    Science.gov (United States)

    Clapp, C.; Leroy, S. S.; Anderson, J. G.

    2015-12-01

    Water vapor in the upper troposphere and lower stratosphere (UTLS) from the tropics to the poles is important both radiatively and chemically. Water vapor is the most important greenhouse gas, and increases in water vapor concentrations in the UTLS lead to cooling at these levels and induce warming at the surface [Forster and Shine, 1999; 2002;Solomon et al., 2010]. Water vapor is also integral to stratospheric chemistry. It is the dominant source of OH in the lower stratosphere [ Hanisco et al. , 2001], and increases in water vapor concentrations promote stratospheric ozone loss by raising the reactivity of several key heterogeneous reactions as well as by promoting the growth of reactive surface area [Anderson et al., 2012; Carslaw et al., 1995; Carslaw et al., 1997; Drdla and Muller , 2012; Kirk-Davidoff et al., 1999; Shi et al., 2001]. However, the processes that control the distribution and phase of water in this region of the atmosphere are not well understood. This is especially true at mid-latitudes where several different dynamical mechanisms are capable of influencing UTLS water vapor concentrations. The contribution by deep convective storm systems that penetrate into the lower stratosphere is the least well understood and the least well represented in global models because of the small spatial scales and short time scales over which convection occurs. To address this issue, we have begun a modeling study to investigate the convective injection of water vapor from the troposphere into the stratosphere in the mid-latitudes. Fine-scale models have been previously used to simulate convection from the troposphere to the stratosphere [e.g., Homeyer et al., 2014]. Here we employ the Advanced Research Weather and Research Forecasting model (ARW) at 3-km resolution to resolve convection over the eastern United States during August of 2007 and August of 2013. We conduct a comparison of MERRA, the reanalysis used to initialize ARW, and the model output to assess

  18. Multi-model assessment of the impact of soil moisture initialization on mid-latitude summer predictability

    Science.gov (United States)

    Ardilouze, Constantin; Batté, L.; Bunzel, F.; Decremer, D.; Déqué, M.; Doblas-Reyes, F. J.; Douville, H.; Fereday, D.; Guemas, V.; MacLachlan, C.; Müller, W.; Prodhomme, C.

    2017-12-01

    Land surface initial conditions have been recognized as a potential source of predictability in sub-seasonal to seasonal forecast systems, at least for near-surface air temperature prediction over the mid-latitude continents. Yet, few studies have systematically explored such an influence over a sufficient hindcast period and in a multi-model framework to produce a robust quantitative assessment. Here, a dedicated set of twin experiments has been carried out with boreal summer retrospective forecasts over the 1992-2010 period performed by five different global coupled ocean-atmosphere models. The impact of a realistic versus climatological soil moisture initialization is assessed in two regions with high potential previously identified as hotspots of land-atmosphere coupling, namely the North American Great Plains and South-Eastern Europe. Over the latter region, temperature predictions show a significant improvement, especially over the Balkans. Forecast systems better simulate the warmest summers if they follow pronounced dry initial anomalies. It is hypothesized that models manage to capture a positive feedback between high temperature and low soil moisture content prone to dominate over other processes during the warmest summers in this region. Over the Great Plains, however, improving the soil moisture initialization does not lead to any robust gain of forecast quality for near-surface temperature. It is suggested that models biases prevent the forecast systems from making the most of the improved initial conditions.

  19. Climate and smoke: an appraisal of nuclear winter.

    Science.gov (United States)

    Turco, R P; Toon, O B; Ackerman, T P; Pollack, J B; Sagan, C

    1990-01-12

    The latest understanding of nuclear winter is reviewed. Considerable progress has been made in quantifying the production and injection of soot by large-scale fires, the regional and global atmospheric dispersion of the soot, and the resulting physical, environmental, and climatic perturbations. New information has been obtained from laboratory studies, field experiments, and numerical modeling on a variety of scales (plume, mesoscale, and global). For the most likely soot injections from a full-scale nuclear exchange, three-dimensional climate simulations yield midsummer land temperature decreases that average 10 degrees to 20 degrees C in northern mid-latitudes, with local cooling as large as 35 degrees C, and subfreezing summer temperatures in some regions. Anomalous atmospheric circulations caused by solar heating of soot is found to stabilize the upper atmosphere against overturning, thus increasing the soot lifetime, and to accelerate interhemispheric transport, leading to persistent effects in the Southern Hemisphere. Serious new environmental problems associated with soot injection have been identified, including disruption of monsoon precipitation and severe depletion of the stratospheric ozone layer in the Northern Hemisphere. The basic physics of nuclear winter has been reaffirmed through several authoritative international technical assessments and numerous individual scientific investigations. Remaining areas of uncertainty and research priorities are discussed in view of the latest findings.

  20. The effects of springtime mid-latitude storms on trace gas composition determined from the MACC reanalysis

    Science.gov (United States)

    Knowland, K. E.; Doherty, R. M.; Hodges, K. I.

    2015-03-01

    The relationship between springtime air pollution transport of ozone (O3) and carbon monoxide (CO) and mid-latitude cyclones is explored for the first time using the Monitoring Atmospheric Composition and Climate (MACC) reanalysis for the period 2003-2012. In this study, the most intense spring storms (95th percentile) are selected for two regions, the North Pacific (NP) and the North Atlantic (NA). These storms (∼60 storms over each region) often track over the major emission sources of East Asia and eastern North America. By compositing the storms, the distributions of O3 and CO within a "typical" intense storm are examined. We compare the storm-centered composite to background composites of "average conditions" created by sampling the reanalysis data of the previous year to the storm locations. Mid-latitude storms are found to redistribute concentrations of O3 and CO horizontally and vertically throughout the storm. This is clearly shown to occur through two main mechanisms: (1) vertical lifting of CO-rich and O3-poor air isentropically, from near the surface to the mid- to upper-troposphere in the region of the warm conveyor belt; and (2) descent of O3-rich and CO-poor air isentropically in the vicinity of the dry intrusion, from the stratosphere toward the mid-troposphere. This can be seen in the composite storm's life cycle as the storm intensifies, with area-averaged O3 (CO) increasing (decreasing) between 200 and 500 hPa. The influence of the storm dynamics compared to the background environment on the composition within an area around the storm center at the time of maximum intensity is as follows. Area-averaged O3 at 300 hPa is enhanced by 50 and 36% and by 11 and 7.6% at 500 hPa for the NP and NA regions, respectively. In contrast, area-averaged CO at 300 hPa decreases by 12% for NP and 5.5% for NA, and area-averaged CO at 500 hPa decreases by 2.4% for NP while there is little change over the NA region. From the mid-troposphere, O3-rich air is clearly

  1. High- and mid-latitude quasi-2-day waves observed simultaneouslyby four meteor radars during summer 2000

    Directory of Open Access Journals (Sweden)

    E. Merzlyakov

    2004-03-01

    Full Text Available Results from the analysis of MLT wind measurements at Dixon (73.5°N, 80°E, Esrange (68°N, 21°E, Castle Eaton (UK (53°N, 2°W, and Obninsk (55°N, 37°E during summer 2000 are presented in this paper. Using S-transform or wavelet analysis, quasi-two-day waves (QTDWs are shown to appear simultaneously at high- and mid-latitudes and reveal themselves as several bursts of wave activity. At first this activity is preceded by a 51–53h wave with S=3 observed mainly at mid-latitudes. After a short recess (or quiet time interval for about 10 days near day 205, we observe a regular sequence of three bursts, the strongest of them corresponding to a QTDW with a period of 47–48h and S=4 at mid-altitudes. We hypothesize that these three bursts may be the result of constructive and destructive interference between several spectral components: a 47–48h component with S=4; a 60-h component with S=3; and a 80-h component with S=2. The magnitudes of the lower (higher zonal wave-number components increase (decrease with increasing latitude. The S-transform or wavelet analysis indicates when these spectral components create the wave activity bursts and gives a range of zonal wave numbers for observed bursts from about 4 to about 2 for mid- and high-latitudes. The main spectral component at Dixon and Esrange latitudes is the 60-h oscillation with S=3. The zonal wave numbers and frequencies of the observed spectral components hint at the possible occurrence of the nonlinear interaction between the primary QTDWs and other planetary waves. Using a simple 3-D nonlinear numerical model, we attempt to simulate some of the observed features and to explain them as a consequence of the nonlinear interaction between the primary 47–48h and the 9–10day waves, and the resulting linear superposition of primary and secondary waves. In addition to the QTDW bursts, we also infer forcing of the 4-day wave with S=2 and the 6–7day wave with S=1, possibly arising from

  2. Electron density and plasma waves in mid-latitude sporadic-E layer observed during the SEEK-2 campaign

    Directory of Open Access Journals (Sweden)

    H. Mori

    2005-10-01

    Full Text Available The SEEK-2 campaign was carried out over Kyushu Island in Japan on 3 August 2002, by using the two sounding rockets of S310-31 and S310-32. This campaign was planned to elucidate generation mechanisms of Quasi-Periodic Echoes (QPEs associated with mid-latitude sporadic-E (Es layers. Electron number densities were successfully measured in the Es layers by using the impedance probe on board two rockets. The plasma waves in the VLF and ELF ranges were also observed on board the S310-32 rocket. Results of electron density measurement showed that there were one or two major peaks in the Es layers along the rockets' trajectories near the altitude of about 10km. There were some smaller peaks associated with the main Es layers in the altitude range from 90 to 120 km. These density peaks were distributed in a very large extent during the SEEK-2 campaign. The Es layer structure is also measured by using the Fixed Bias Probe (FBP, which has a high spatial resolution of several meters (the impedance probe has an altitude resolution of about 400 m. The comparison with the total electron content (TEC measured by the Dual Band Beacon revealed that the Es layer was also modulated in the horizontal direction with the scale size of 30–40 km. It was shown that the QP echoes observed by the ground-based coherent radar come from the major density peak of the Es layer. The plasma wave instrument detected the enhancement of VLF and ELF plasma waves associated with the operation of the TMA release, and also with the passage of the Es layers. Keywords. Ionosphere (Ionospheric irregularities; Midlatitude ionosphere; Plasma temeperature and density

  3. Temporal variation in methane emissions in a shallow lake at a southern mid latitude during high and low rainfall periods.

    Science.gov (United States)

    Fusé, Victoria S; Priano, M Eugenia; Williams, Karen E; Gere, José I; Guzmán, Sergio A; Gratton, Roberto; Juliarena, M Paula

    2016-10-01

    The global methane (CH4) emission of lakes is estimated at between 6 and 16 % of total natural CH4 emissions. However, these values have a high uncertainty due to the wide variety of lakes with important differences in their morphological, biological, and physicochemical parameters and the relatively scarse data from southern mid-latitude lakes. For these reasons, we studied CH4 fluxes and CH4 dissolved in water in a typical shallow lake in the Pampean Wetland, Argentina, during four periods of consecutive years (April 2011-March 2015) preceded by different rainfall conditions. Other water physicochemical parameters were measured and meteorological data were reported. We identified three different states of the lake throughout the study as the result of the irregular alternation between high and low rainfall periods, with similar water temperature values but with important variations in dissolved oxygen, chemical oxygen demand, water turbidity, electric conductivity, and water level. As a consequence, marked seasonal and interannual variations occurred in CH4 dissolved in water and CH4 fluxes from the lake. These temporal variations were best reflected by water temperature and depth of the Secchi disk, as a water turbidity estimation, which had a significant double correlation with CH4 dissolved in water. The mean CH4 fluxes values were 0.22 and 4.09 mg/m2/h for periods with low and high water turbidity, respectively. This work suggests that water temperature and turbidity measurements could serve as indicator parameters of the state of the lake and, therefore, of its behavior as either a CH4 source or sink.

  4. Discriminating raining from non-raining clouds at mid-latitudes using meteosat second generation daytime data

    Directory of Open Access Journals (Sweden)

    B. Thies

    2008-05-01

    Full Text Available A new method for the delineation of precipitation during daytime using multispectral satellite data is proposed. The approach is not only applicable to the detection of mainly convective precipitation by means of the commonly used relation between infrared cloud top temperature and rainfall probability but enables also the detection of stratiform precipitation (e.g. in connection with mid-latitude frontal systems. The presented scheme is based on the conceptual model that precipitating clouds are characterized by a combination of particles large enough to fall, an adequate vertical extension (both represented by the cloud water path; cwp, and the existence of ice particles in the upper part of the cloud. The technique considers the VIS0.6 and the NIR1.6 channel to gain information about the cloud water path. Additionally, the brightness temperature differences ΔT8.7-10.8 and ΔT10.8-12.1 are considered to supply information about the cloud phase. Rain area delineation is realized by using a minimum threshold of the rainfall confidence. To obtain a statistical transfer function between the rainfall confidence and the four parameters VIS, NIR1.6, Δ T8.7-10.8 and Δ T10.8-12.1, the value combinations of these four variables are compared to ground based radar data. The retrieval is validated against independent radar data not used for deriving the transfer function and shows an encouraging performance as well as clear improvements compared to existing optical retrieval techniques using only IR thresholds for cloud top temperature.

  5. Lightning NOx influence on large-scale NOy and O3 plumes observed over the northern mid-latitudes

    Directory of Open Access Journals (Sweden)

    Alicia Gressent

    2014-11-01

    Full Text Available This paper describes the NOy plumes originating from lightning emissions based on 4 yr (2001–2005 of MOZAIC measurements in the upper troposphere of the northern mid-latitudes, together with ground- and space-based observations of lightning flashes and clouds. This analysis is primarily for the North Atlantic region where the MOZAIC flights are the most frequent and for which the measurements are well representative in space and time. The study investigates the influence of lightning NOx (LNOx emissions on large-scale (300–2000 km plumes (LSPs of NOy. One hundred and twenty seven LSPs (6% of the total MOZAIC NOy dataset have been attributed to LNOx emissions. Most of these LSPs were recorded over North America and the Atlantic mainly in spring and summer during the maximum lightning activity occurrence. The majority of the LSPs (74% is related to warm conveyor belts and extra-tropical cyclones originating from North America and entering the intercontinental transport pathway between North America and Europe, leading to a negative (positive west to east NOy (O3 zonal gradient with −0.4 (+18 ppbv difference during spring and −0.6 (+14 ppbv difference in summer. The NOy zonal gradient can correspond to the mixing of the plume with the background air. On the other hand, the O3 gradient is associated with both mixing of background air and with photochemical production during transport. Such transatlantic LSPs may have a potential impact on the European pollution. The remaining sampled LSPs are related to mesoscale convection over Western Europe and the Mediterranean Sea (18% and to tropical convection (8%.

  6. Validation of Martilli's urban boundary layer scheme with measurements from two mid-latitude European cities

    Directory of Open Access Journals (Sweden)

    R. Hamdi

    2007-08-01

    Full Text Available Martilli's urban parameterization scheme is improved and implemented in a mesoscale model in order to take into account the typical effects of a real city on the air temperature near the ground and on the surface exchange fluxes. The mesoscale model is run on a single column using atmospheric data and radiation recorded above roof level as forcing. Here, the authors validate Martilli's urban boundary layer scheme using measurements from two mid-latitude European cities: Basel, Switzerland and Marseilles, France. For Basel, the model performance is evaluated with observations of canyon temperature, surface radiation, and energy balance fluxes obtained during the Basel urban boundary layer experiment (BUBBLE. The results show that the urban parameterization scheme represents correctly most of the behavior of the fluxes typical of the city center of Basel, including the large heat uptake by the urban fabric and the positive sensible heat flux at night. For Marseilles, the model performance is evaluated with observations of surface temperature, canyon temperature, surface radiation, and energy balance fluxes collected during the field experiments to constrain models of atmospheric pollution and transport of emissions (ESCOMPTE and its urban boundary layer (UBL campaign. At both urban sites, vegetation cover is less than 20%, therefore, particular attention was directed to the ability of Martilli's urban boundary layer scheme to reproduce the observations for the Marseilles city center, where the urban parameters and the synoptic forcing are totally different from Basel. Evaluation of the model with wall, road, and roof surface temperatures gave good results. The model correctly simulates the net radiation, canyon temperature, and the partitioning between the turbulent and storage heat fluxes.

  7. Simulation study of the large-scale modification of the mid-latitude F-layer by HF radio waves with different powers

    Directory of Open Access Journals (Sweden)

    G. I. Mingaleva

    2012-08-01

    Full Text Available A mathematical model of the ionosphere, developed earlier, is applied to investigate the large-scale mid-latitude F-layer modification by HF radio waves with different powers. Simulations are performed for the point with geographic coordinates of the "Sura" heating facility (Nizhny Novgorod, Russia for autumn conditions. The calculations are made for distinct cases, in which the effective absorbed power has different values belonging to the 5–100 MW range, both for nocturnal and daytime conditions. The frequency of powerful HF waves is chosen to be close to the most effective frequency for the large-scale F2-layer modification. The results of modeling indicate that the effective absorbed power can influence considerably the F-layer response to high-power radio waves in the mid-latitude ionosphere.

  8. On contributing factors to the winter record low of the northern hemisphere sea ice extent in 2015

    Science.gov (United States)

    Fuckar, Neven-Stjepan; Massonnet, Francois; Guemas, Virginie; Garcia-Serrano, Javier; Bellprat, Omar; Doblas-Reyes, Francisco; Acosta, Mario

    2017-04-01

    The northern hemisphere (NH) sea ice extent (SIE) has reached the record low in the satellite era (since November 1978) in March 2015. Would the 2014/15 fall-winter atmosphere yield this sea ice extreme if we reversed in time the long-term change in the ocean and sea ice state? We examine the contributions of the atmosphere and the long-term memory of the ocean and sea ice to the March 2015 record low of the NH SIE with a state-of-the-art ocean-sea-ice general circulation model (OGCM: NEMOv3.3). First, we perform a set of 5-month-long retrospective control simulations initialized on 1 November from 1979 to 2014 to assess the model skill in predicting the NH March SIE. We produce ERA-Interim-forced five ensemble members initialized from the five members of the ORAS4 ocean reanalysis and the associated five-member sea ice reconstruction. A climate variable can be decomposed into the sum of the background state represented as a linear fit over the period of interest and an interannual anomaly with respect to this fit: var(t) = [at + b] + var'(t). More specifically, initial conditions (IC) and surface forcing fields contain: (i) linear-fit background state of IC, (ii) interannual anomaly in IC with respect to factor (i), (iii) linear-fit background state of surface forcing fields, and (iv) interannual anomaly in surface forcing fields with respect to factor (iii). Next, we conduct two sets of sensitivity experiments with IC and surface forcing fields modified in such manner so that one set examine the influence of 2014/15 fall-winter atmospheric conditions, while the other focuses on the influence of change in linear-fit background state of the ocean and sea ice cover. Our forced experiments indicate that the most important factor driving the NH SIE to the record low in March 2015 was surface atmospheric conditions on average contributing at least 54% to the change from the past March states to 2015. The 1 November 2014 interannual anomaly of IC, which on average

  9. Four Years of Simultaneous Observations of Noctilucent Clouds and Mesospheric Summer Echoes at a Mid-Latitude Site (Kühlungsborn/Germany, 54°N)

    Science.gov (United States)

    Gerding, M.; Zoellner, J.; Zecha, M.; Luebken, F. J.

    2015-12-01

    Occurrence of ice particles in the polar summer mesopause region is an intriguing phenomenon that can be observed either optically as Noctilucent Clouds (NLC) / Polar Mesospheric Clouds (PMC) or by radar as (Polar) Mesosphere Summer Echoes ((P)MSE). The relation of both phenomena is well understood and allows insights into atmospheric properties like temperature, humidity, winds, turbulence and electron density. Simultaneous observations of NLC and PMSE require sufficient electron density (for the radar observation) and therefore daylight conditions that may hinder optical observations by lidar. Up to now, simultaneous observations of NLC and PMSE are mainly limited to polar latitudes, while data from mid-latitudes are lacking. Since 2010 we operate a new RMR lidar at our site at Kühlungsborn/Germany (54°N, 12°E). From the best of our knowledge this lidar allows for the first time observations of mid-latitude NLC independent of solar elevation, i.e. during night and day. With our new RMR lidar and the co-located OSWIN radar we are for the first time able to compare the occurrence and altitude structure of NLC and MSE at mid-latitudes. It turns out that the lower edges of simultaneously observed NLC/MSE typically agree, as expected from higher latitudes. Though, the top edge of MSE is observed about 500 m above the NLC edge, indicating the presence of particles being too small to be observed by lidar. Nevertheless, height difference is small compared to the typical layer widths and smaller than observed at higher latitudes. This hints at different size distributions and, by this, different growing conditions at mid-latitudes. We will present a statistical overview on the comparison of simultaneously observed NLC and MSE layers and their main characteristics. Simultaneous NLC and MSE are of additional importance if observed during twilight conditions. The onset or disappearance of MSE during morning and evening twilight is directly related with changing electron

  10. Airborne measurements of aerosol optical properties related to early spring transport of mid-latitude sources into the Arctic

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    R. A. de Villiers

    2010-06-01

    Full Text Available Airborne lidar and in-situ measurements of the aerosol properties were conducted between Svalbard Island and Scandinavia in April 2008. Evidence of aerosol transport from Europe and Asia is given. The analysis of the aerosol optical properties based on a multiwavelength lidar (355, 532, 1064 nm including volume depolarization at 355 nm aims at distinguishing the role of the different aerosol sources (Siberian wild fires, Eastern Asia and European anthropogenic emissions. Combining, first aircraft measurements, second FLEXPART simulations with a calculation of the PBL air fraction originating from the three different mid-latitude source regions, and third level-2 CALIPSO data products (i.e. backscatter coefficient 532 nm,volume depolarization and color ratio between 1064 and 532 nm in aerosol layers along the transport pathways, appears a valuable approach to identify the role of the different aerosol sources even after a transport time larger than 4 days. Optical depth of the aerosol layers are always rather small (<4% while transported over the Arctic and ratio of the total attenuated backscatter (i.e. including molecular contribution provide more stable result than conventional aerosol backscatter ratio. Above Asia, CALIPSO data indicate more depolarization (up to 15% and largest color ratio (>0.5 for the northeastern Asia emissions (i.e. an expected mixture of Asian pollution and dust, while low depolarization together with smaller and quasi constant color ratio (≈0.3 are observed for the Siberian biomass burning emissions. A similar difference is visible between two layers observed by the aircraft above Scandinavia. The analysis of the time evolution of the aerosol optical properties revealed by CALIPSO between Asia and Scandinavia shows a gradual decrease of the aerosol backscatter, depolarization ratio and color ratio which suggests the removal of the largest particles in the accumulation mode. A similar study conducted for a European

  11. The contribution of component variation and phytoplankton growth to the distribution variation of chromophoric dissolved organic matter content in a mid-latitude subtropical drinking water source reservoir for two different seasons.

    Science.gov (United States)

    Sun, Qiyuan; Jiang, Juan; Zheng, Yuyi; Wang, Feifeng; Wu, Chunshan; Xie, Rong-Rong

    2017-07-01

    The distribution variation in chromophoric dissolved organic matter (CDOM) content in mid-latitude subtropical drinking water source reservoirs (MDWSRs) has great significance in the security of aquatic environments and human health. CDOM distribution is heavily influenced by biogeochemical processes and anthropogenic activity. However, little is known regarding the impact of component variation and phytoplankton growth on CDOM distribution variation in MDWSR. Therefore, samples were collected from a representative MDWSR (the Shanzai Reservoir) for analysis. CDOM absorption and fluorescence coupling with parallel factor analysis were measured and calculated. The results indicated that only two CDOM components were found in the surface water of Shanzai Reservoir, fulvic acid, and high-excitation tryptophan, originating from terrestrial and autochthonous sources, respectively. The types of components did not change with the season. The average molecular weight of CDOM increased in proportion to its fulvic acid content. The distribution variation in CDOM content mainly resulted from the variation in two CDOM components in summer and from high-excitation tryptophan in winter. Phytoplankton growth strongly influenced the distribution variation of CDOM content in summer; the metabolic processes of Cyanobacteria and Bacillariophyta consumed fulvic acid, while that of Cryptophyta produced high-excitation tryptophan.

  12. Evidence for long-lived polar vortex air in the mid-latitude summer stratosphere from in situ laser diode CH4 and H2O measurements

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    G. Durry

    2005-01-01

    Full Text Available A balloon borne diode laser spectrometer was launched in southern France in June 2000 to yield in situ stratospheric CH4 and H2O measurements. In the altitude region ranging from 20km to 25km, striking large spatial structures were observed in the vertical concentration profiles of both species. We suggest these patterns are due to the presence of long-lived remnants of the wintertime polar vortex in the mid-latitude summer stratosphere. To support this interpretation, a high resolution advection model for potential vorticity is used to investigate the evolution of the Arctic vortex after its breakdown phase in spring 2000.

  13. Changing Temperature Gradients Linked to Holocene Moisture Trends in the Northern Hemisphere

    Science.gov (United States)

    Routson, C.; McKay, N.; Kaufman, D. S.; Ault, T.; Rodysill, J. R.

    2016-12-01

    We hypothesize that latitudinal differences in Northern Hemisphere radiative energy balance led to both enhanced hemispheric monsoon strength and mid-latitude aridity during the early-to-mid-Holocene. The width of the Hadley cell and mean position of the subtropical jet stream are influenced by the temperature gradient between the equator and the pole. Climate change is expected to strengthen Hadley circulation while weakening the equator-to-pole temperature gradient, thus shifting the mean position of the subtropical jet northward and causing the sub-tropics to become drier. We analyzed the evolution of Northern Hemisphere latitudinal temperature gradients with moisture in a new compilation of Holocene-length paleoclimate records spanning from 10°S to 90°N latitude. The primary trends in the paleoclimate records agree with future projections showing that weaker early-to-mid Holocene Northern Hemisphere latitudinal temperature gradients (increased warming of the Arctic relative to the equator) are linked to substantial increases in zonally averaged mid-latitude (30°N-55°N) aridity, and simultaneous increases in Northern Hemisphere monsoon strength. These results are significant for current warming, as northern high latitudes are warming faster than the equator, decreasing the equator-to-pole temperature gradient to values comparable with the early Holocene. Our results support model-based projections of increased drought risk in the Northern Hemisphere mid-latitudes in the coming decades.

  14. Titan's cloud seasonal activity from winter to spring with Cassini/VIMS

    Science.gov (United States)

    Rodriguez, S.; Le, Mouelic S.; Rannou, P.; Sotin, Christophe; Brown, R.H.; Barnes, J.W.; Griffith, C.A.; Burgalat, J.; Baines, K.H.; Buratti, B.J.; Clark, R.N.; Nicholson, P.D.

    2011-01-01

    Since Saturn orbital insertion in July 2004, the Cassini orbiter has been observing Titan throughout most of the northern winter season (October 2002-August 2009) and the beginning of spring, allowing a detailed monitoring of Titan's cloud coverage at high spatial resolution with close flybys on a monthly basis. This study reports on the analysis of all the near-infrared images of Titan's clouds acquired by the Visual and Infrared Mapping Spectrometer (VIMS) during 67 targeted flybys of Titan between July 2004 and April 2010.The VIMS observations show numerous sporadic clouds at southern high and mid-latitudes, rare clouds in the equatorial region, and reveal a long-lived cloud cap above the north pole, ubiquitous poleward of 60??N. These observations allow us to follow the evolution of the cloud coverage during almost a 6-year period including the equinox, and greatly help to further constrain global circulation models (GCMs). After 4. years of regular outbursts observed by Cassini between 2004 and 2008, southern polar cloud activity started declining, and completely ceased 1. year before spring equinox. The extensive cloud system over the north pole, stable between 2004 and 2008, progressively fractionated and vanished as Titan entered into northern spring. At southern mid-latitudes, clouds were continuously observed throughout the VIMS observing period, even after equinox, in a latitude band between 30??S and 60??S. During the whole period of observation, only a dozen clouds were observed closer to the equator, though they were slightly more frequent as equinox approached. We also investigated the distribution of clouds with longitude. We found that southern polar clouds, before disappearing in mid-2008, were systematically concentrated in the leading hemisphere of Titan, in particular above and to the east of Ontario Lacus, the largest reservoir of hydrocarbons in the area. Clouds are also non-homogeneously distributed with longitude at southern mid-latitudes

  15. On the relationship between total ozone and atmospheric dynamics and chemistry at mid-latitudes – Part 1: Statistical models and spatial fingerprints of atmospheric dynamics and chemistry

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    L. Frossard

    2013-01-01

    Full Text Available We use statistical models for mean and extreme values of total column ozone to analyze "fingerprints" of atmospheric dynamics and chemistry on long-term ozone changes at northern and southern mid-latitudes on grid cell basis. At each grid cell, the r-largest order statistics method is used for the analysis of extreme events in low and high total ozone (termed ELOs and EHOs, respectively, and an autoregressive moving average (ARMA model is used for the corresponding mean value analysis. In order to describe the dynamical and chemical state of the atmosphere, the statistical models include important atmospheric covariates: the solar cycle, the Quasi-Biennial Oscillation (QBO, ozone depleting substances (ODS in terms of equivalent effective stratospheric chlorine (EESC, the North Atlantic Oscillation (NAO, the Antarctic Oscillation (AAO, the El Niño/Southern Oscillation (ENSO, and aerosol load after the volcanic eruptions of El Chichón and Mt. Pinatubo. The influence of the individual covariates on mean and extreme levels in total column ozone is derived on a grid cell basis. The results show that "fingerprints", i.e., significant influence, of dynamical and chemical features are captured in both the "bulk" and the tails of the statistical distribution of ozone, respectively described by mean values and EHOs/ELOs. While results for the solar cycle, QBO, and EESC are in good agreement with findings of earlier studies, unprecedented spatial fingerprints are retrieved for the dynamical covariates. Column ozone is enhanced over Labrador/Greenland, the North Atlantic sector and over the Norwegian Sea, but is reduced over Europe, Russia and the Eastern United States during the positive NAO phase, and vice-versa during the negative phase. The NAO's southern counterpart, the AAO, strongly influences column ozone at lower southern mid-latitudes, including the southern parts of South America and the Antarctic Peninsula, and the central southern mid-latitudes

  16. Variations in mid-latitude North Atlantic surface water properties during the mid-Brunhes (MIS 9–14 and their implications for the thermohaline circulation

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    A. H. L. Voelker

    2010-08-01

    Full Text Available Stable isotope and ice-rafted debris records from three core sites in the mid-latitude North Atlantic (IODP Site U1313, MD01-2446, MD03-2699 are combined with records of ODP Sites 1056/1058 and 980 to reconstruct hydrographic conditions during the middle Pleistocene spanning Marine Isotope Stages (MIS 9–14 (300–540 ka. Core MD03-2699 is the first high-resolution mid-Brunhes record from the North Atlantic's eastern boundary upwelling system covering the complete MIS 11c interval and MIS 13. The array of sites reflect western and eastern basin boundary current as well as north to south transect sampling of subpolar and transitional water masses and allow the reconstruction of transport pathways in the upper limb of the North Atlantic's circulation. Hydrographic conditions in the surface and deep ocean during peak interglacial MIS 9 and 11 were similar among all the sites with relative stable conditions and confirm prolonged warmth during MIS 11c also for the mid-latitudes. Sea surface temperature (SST reconstructions further reveal that in the mid-latitude North Atlantic MIS 11c is associated with two plateaus, the younger one of which is slightly warmer. Enhanced subsurface northward heat transport in the eastern boundary current system, especially during early MIS 11c, is denoted by the presence of tropical planktic foraminifer species and raises the question how strongly it impacted the Portuguese upwelling system. Deep water ventilation at the onset of MIS 11c significantly preceded surface water ventilation. Although MIS 13 was generally colder and more variable than the younger interglacials the surface water circulation scheme was the same. The greatest differences between the sites existed during the glacial inceptions and glacials. Then a north – south trending hydrographic front separated the nearshore and offshore waters off Portugal. While offshore waters originated from the North Atlantic Current as indicated by the similarities

  17. The evolution of the high-latitude blocked anticyclone during the 2012 winter in the Northern hemisphere

    Science.gov (United States)

    Sokolikhina, Natalia; Kislov, Alexander; Surkova, Galina; Semenov, Eugeny

    2017-04-01

    At present time on the Department of Meteorology and Climatology of the Faculty of Geography of MSU by Lomonosov, the topic, concerned to the dangerous hydrometeorologic events over the Russia, is investigated. A great deal of attention is given to the study of the extremely strong warming in Arctic. Earlier the processes of the synoptic scale during the 2011-2012 winter, which was the most warmest in Arctic for the whole history of meteorologic observations, were investigated. It was shown, that the reason of such an event was the situation of the westerly wind blocking. At present study the method of the analysis of the vortex as of the united formation was used. And the factors, influencing on its evolution, were obtained. Keywords: dangerous hydrometeorologic events, warming in Arctic, westerly wind blocking, analysis of the vortex as of the united formation

  18. Simultaneous radio and optical observations of the mid-latitude atmospheric response to a major geomagnetic storm of 6-8 April 2000

    Science.gov (United States)

    Afraimovich, E. L.; Ashkaliev, Ya. F.; Aushev, V. M.; Beletsky, A. B.; Vodyannikov, V. V.; Leonovich, L. A.; Lesyuta, O. S.; Lipko, Yu. V.; Mikhalev, A. V.; Yakovets, A. F.

    2002-12-01

    Basic properties of the mid-latitude traveling ionospheric disturbances (TIDs) during the maximum phase of a major magnetic storm of 6-8 April 2000 are shown. Total electron content (TEC) variations were studied by using data from GPS receivers located in Russia and Central Asia. The nightglow response to this storm at mesopause and termospheric altitudes was also measured by optical instruments FENIX located at the observatory of the Institute of Solar-Terrestrial Physics /(51.9°N,103.0°E), and MORTI located at the observatory of the Institute of Ionosphere (43.2°N,77.0°E). Observations of the O (557.7and630.0nm) emissions originating from atmospheric layers centered at altitudes of 90 and 250km were carried out at Irkutsk and of the O2(b1∑g+- X3∑g-) (0-1) emission originating from an atmospheric layer centered at altitude of 94km was carried out at Almaty. Our radio and optical measurement network observed a storm-induced solitary large-scale wave with duration of 1h and a wave front width of no less than 5000km, while it traveled equatorward with a velocity of 200m/s from /62°N to /38°N geographic latitude. The TEC disturbance, basically displaying an electron content depression in the maximum of the F2 region, reveals a good correlation with growing nightglow emission, the temporal shift between the TEC and emission variation maxima being different for different altitudes. A comparison of the auroral oval parameters with dynamic spectra of TEC variations and optical 630nm emissions in the frequency range 0.4-4mHz (250-2500s periods) showed that as the auroral oval expands into mid-latitudes, also does the region with a developed medium-sale and small-scale TEC structure.

  19. Variations of Kelvin waves around the TTL region during the stratospheric sudden warming events in the Northern Hemisphere winter

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    Y. Jia

    2016-03-01

    Full Text Available Spatial and temporal variabilities of Kelvin waves during stratospheric sudden warming (SSW events are investigated by the ERA-Interim reanalysis data, and the results are validated by the COSMIC temperature data. A case study on an exceptionally large SSW event in 2009, and a composite analysis comprising 18 events from 1980 to 2013 are presented. During SSW events, the average temperature increases by 20 K in the polar stratosphere, while the temperature in the tropical stratosphere decreases by about 4 K. Kelvin wave with wave numbers 1 and 2, and periods 10–20 days, clearly appear around the tropical tropopause layer (TTL during SSWs. The Kelvin wave activity shows obvious coupling with the convection localized in the India Ocean and western Pacific (Indo-Pacific region. Detailed analysis suggests that the enhanced meridional circulation driven by the extratropical planetary wave forcing during SSW events leads to tropical upwelling, which further produces temperature decrease in the tropical stratosphere. The tropical upwelling and cooling consequently result in enhancement of convection in the equatorial region, which excites the strong Kelvin wave activity. In addition, we investigated the Kelvin wave acceleration to the eastward zonal wind anomalies in the equatorial stratosphere during SSW events. The composite analysis shows that the proportion of Kelvin wave contribution ranges from 5 to 35 % during SSWs, much larger than in the non-SSW mid-winters (less than 5 % in the stratosphere. However, the Kelvin wave alone is insufficient to drive the equatorial eastward zonal wind anomalies during the SSW events, which suggests that the effects of other types of equatorial waves may not be neglected.

  20. Polar stratospheric cloud observations by MIPAS on ENVISAT: detection method, validation and analysis of the northern hemisphere winter 2002/2003

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    R. Spang

    2005-01-01

    Full Text Available The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS on ENVISAT has made extensive measurements of polar stratospheric clouds (PSCs in the northern hemisphere winter 2002/2003. A PSC detection method based on a ratio of radiances (the cloud index has been implemented for MIPAS and is validated in this study with respect to ground-based lidar and space borne occultation measurements. A very good correspondence in PSC sighting and cloud altitude between MIPAS detections and those of other instruments is found for cloud index values of less than four. Comparisons with data from the Stratospheric Aerosol and Gas Experiment (SAGE III are used to further show that the sensitivity of the MIPAS detection method for this threshold value of cloud index is approximately equivalent to an extinction limit of 10-3km-1 at 1022nm, a wavelength used by solar occultation experiments. The MIPAS cloud index data are subsequently used to examine, for the first time with any technique, the evolution of PSCs throughout the Arctic polar vortex up to a latitude close to 90° north on a near-daily basis. We find that the winter of 2002/2003 is characterised by three phases of very different PSC activity. First, an unusual, extremely cold phase in the first three weeks of December resulted in high PSC occurrence rates. This was followed by a second phase of only moderate PSC activity from 5-13 January, separated from the first phase by a minor warming event. Finally there was a third phase from February to the end of March where only sporadic and mostly weak PSC events took place. The composition of PSCs during the winter period has also been examined, exploiting in particular an infra-red spectral signature which is probably characteristic of NAT. The MIPAS observations show the presence of these particles on a number of occasions in December but very rarely in January. The PSC type differentiation from MIPAS indicates that future comparisons of PSC

  1. Large scale variability, long-term trends and extreme events in total ozone over the northern mid-latitudes based on satellite time series

    Science.gov (United States)

    Rieder, H. E.; Staehelin, J.; Maeder, J. A.; Ribatet, M.; Davison, A. C.

    2009-04-01

    Various generations of satellites (e.g. TOMS, GOME, OMI) made spatial datasets of column ozone available to the scientific community. This study has a special focus on column ozone over the northern mid-latitudes. Tools from geostatistics and extreme value theory are applied to analyze variability, long-term trends and frequency distributions of extreme events in total ozone. In a recent case study (Rieder et al., 2009) new tools from extreme value theory (Coles, 2001; Ribatet, 2007) have been applied to the world's longest total ozone record from Arosa, Switzerland (e.g. Staehelin 1998a,b), in order to describe extreme events in low and high total ozone. Within the current study this analysis is extended to satellite datasets for the northern mid-latitudes. Further special emphasis is given on patterns and spatial correlations and the influence of changes in atmospheric dynamics (e.g. tropospheric and lower stratospheric pressure systems) on column ozone. References: Coles, S.: An Introduction to Statistical Modeling of Extreme Values, Springer Series in Statistics, ISBN:1852334592, Springer, Berlin, 2001. Ribatet, M.: POT: Modelling peaks over a threshold, R News, 7, 34-36, 2007. Rieder, H.E., Staehelin, J., Maeder, J.A., Ribatet, M., Stübi, R., Weihs, P., Holawe, F., Peter, T., and Davison, A.C.: From ozone mini holes and mini highs towards extreme value theory: New insights from extreme events and non stationarity, submitted to J. Geophys. Res., 2009. Staehelin, J., Kegel, R., and Harris, N. R.: Trend analysis of the homogenized total ozone series of Arosa (Switzerland), 1929-1996, J. Geophys. Res., 103(D7), 8389-8400, doi:10.1029/97JD03650, 1998a. Staehelin, J., Renaud, A., Bader, J., McPeters, R., Viatte, P., Hoegger, B., Bugnion, V., Giroud, M., and Schill, H.: Total ozone series at Arosa (Switzerland): Homogenization and data comparison, J. Geophys. Res., 103(D5), 5827-5842, doi:10.1029/97JD02402, 1998b.

  2. Mechanisms associated with post-sunset convective initiation close to mountain ranges in Central ArgentinaMany thunderstorms in mid-latitude

    Science.gov (United States)

    Salio, P. V.; Vidal, L.; Zipser, E. J.; Vila, D. A.

    2016-12-01

    Many thunderstorms in mid-latitude South America stand out in satellite observations as being among the strongest anywhere on Earth in terms of satellite-based convective proxies, such as lightning flash rate per storm, prevalence for extremely tall, wide convective cores and broad stratiform regions. Knowing when and where strong convection is initiated is of great importance because of the close relationship between convective storms, heavy precipitation, and severe weather phenomena. This paper seeks to identify the most salient features associated with mesoscale and synoptic scale that condition the environment in which deep convection develops in mid-latitude South America region close to principal mountain barriers (e.g. the Andes). A specific region of complex terrain in Central Argentina, known as Sierras de Córdoba (SCBA), tend to show active initiation near the end of the afternoon (between 21Z and 00Z) during the warm season. These may become very long-lived systems with lifetimes that can exceed 24 hours and even in extreme cases can reach 60 hours. They have associated cloud shields, with large horizontal extent at the time of maturity (>250,000km2), more than twice the average size of MCSs born outside this particular region. These events are strongly favored by the presence of a mid-level trough with a surface cold front and a westerly jet stream aloft, which along with an intense low-level jet (SALLJ) and local circulations, combine to pre-condition the environment and develop deep moist convection in the region of interest in the afternoon on the east and west side of the topography. MCSs tend to detach from the topography and develop in the valley between the Andes and SCBA, or east away from SCBA, where convergence reaches a maximum in low levels as a consequence of the zonal shift of SALLJ. While the circulation associated with the SALLJ plays an important role in strengthening convergences on the mountain and provides moisture and heat from

  3. Derivation of physical and optical properties of mid-latitude cirrus ice crystals for a size-resolved cloud microphysics model

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    A. M. Fridlind

    2016-06-01

    Full Text Available Single-crystal images collected in mid-latitude cirrus are analyzed to provide internally consistent ice physical and optical properties for a size-resolved cloud microphysics model, including single-particle mass, projected area, fall speed, capacitance, single-scattering albedo, and asymmetry parameter. Using measurements gathered during two flights through a widespread synoptic cirrus shield, bullet rosettes are found to be the dominant identifiable habit among ice crystals with maximum dimension (Dmax greater than 100 µm. Properties are therefore first derived for bullet rosettes based on measurements of arm lengths and widths, then for aggregates of bullet rosettes and for unclassified (irregular crystals. Derived bullet rosette masses are substantially greater than reported in existing literature, whereas measured projected areas are similar or lesser, resulting in factors of 1.5–2 greater fall speeds, and, in the limit of large Dmax, near-infrared single-scattering albedo and asymmetry parameter (g greater by  ∼  0.2 and 0.05, respectively. A model that includes commonly imaged side plane growth on bullet rosettes exhibits relatively little difference in microphysical and optical properties aside from  ∼ 0.05 increase in mid-visible g primarily attributable to plate aspect ratio. In parcel simulations, ice size distribution, and g are sensitive to assumed ice properties.

  4. Swell and Wind-Sea Distributions over the Mid-Latitude and Tropical North Atlantic for the Period 2002–2008

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    Eduardo G. G. de Farias

    2012-01-01

    Full Text Available We present an analysis of wind-sea and swell fields for mid-latitude and tropical Atlantic for the period 2002–2008 using a combination of satellite data (altimeter significant wave height and scatterometer surface winds and model results (spectrum peak wave period and propagation direction. Results show a dominance of swell over wind-sea regimes throughout the year. A small but clear decrease in swell energy and an associated increase in wind-sea potential growth were observed in the NE trade winds zone. A seasonal summertime increase in wind-sea energy in the Amazon River mouth and adjacent shelf region and in African coast was apparent in the results, probably associated to a strengthening of the alongshore trade winds in these regions. Albeit with a significantly smaller energy contribution of wind-seas as compared to swell energy, we could say that a kind of mixed seas is more evident in the trade winds region, with the remaining area being highly dominated by swell energy. An analysis of wave-age shows the absence of young-seas. Only ~2% of all data points was classified as wind-sea, a classification confirmed by a fit to a theoretical relation between wind speed, peak period, and significant wave height for fully developed wind-seas.

  5. Imaging observations of nighttime mid-latitude F-region field-aligned irregularities by an MU radar ultra-multi-channel system

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    S. Saito

    2008-08-01

    Full Text Available Mid-latitude F-region field-aligned irregularities (FAIs were studied by using the middle-and-upper atmosphere (MU radar ultra-multi-channel system with the radar imaging technique. On 12 June 2006, F-region FAI echoes with a period of about one hour were observed intermittently. These echoes were found to be embedded in medium-scale traveling ionospheric disturbances (MSTIDs observed as variations of total electron content (TEC. The echoes drifting away from (toward the radar were observed in the depletion (enhancement phase of the MSTID. The Doppler velocity of the echoes is consistent with the range rates in the the range-time-intensity (RTI maps. Fine scale structures with a spatial scale of 10 km or less were found by the radar imaging analysis. Those structures with positive Doppler velocities (moving away from the radar appeared to drift north- (up- westward, and those with negative Doppler velocities south- (down- eastward approximately along the wavefronts of the MSTID. FAIs with positive Doppler velocities filling TEC depletion regions were observed.

  6. Tropospheric ozone column retrieval at northern mid-latitudes from the Ozone Monitoring Instrument by means of a neural network algorithm

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    P. Sellitto

    2011-11-01

    Full Text Available Monitoring tropospheric ozone from space is of critical importance in order to gain more thorough knowledge on phenomena affecting air quality and the greenhouse effect. Deriving information on tropospheric ozone from UV/VIS nadir satellite spectrometers is difficult owing to the weak sensitivity of the measured radiance spectra to variations of ozone in the troposphere. Here we propose an alternative method of analysis to retrieve tropospheric ozone columns from Ozone Monitoring Instrument radiances by means of a neural network algorithm. An extended set of ozone sonde measurements at northern mid-latitudes for the years 2004–2008 has been considered as the training and test data set. The design of the algorithm is extensively discussed. Our retrievals are compared to both tropospheric ozone residuals and optimal estimation retrievals over a similar independent test data set. Results show that our algorithm has comparable accuracy with respect to both correlative methods and its performance is slightly better over a subset containing only European ozone sonde stations. Possible sources of errors are analyzed. Finally, the capabilities of our algorithm to derive information on boundary layer ozone are studied and the results critically discussed.

  7. Preearthquake anomalous ionospheric signatures observed at low-mid latitude Indian station, Delhi, during the year 2015 to early 2016: Preliminary results

    Science.gov (United States)

    Gupta, Sumedha; Upadhayaya, A. K.

    2017-08-01

    We have analyzed five major earthquake events measuring greater than 6 on Richter scale (M > 6) that occurred during the year 2015 to early 2016, affecting Indian region ionosphere, using F2 layer critical parameters (foF2, hmF2) obtained using Digisonde from a low-mid latitude Indian station, Delhi (28.6°N, 77.2°E, 19.2°N geomagnetic latitude, 42.4°N dip). Normal day-to-day variability occurring in ionosphere is segregated by calculating F2 layer critical frequency and peak height variations (ΔfoF2, ΔhmF2) from the normal quiet time behavior apart from computing interquartile range. We find that the ionospheric F2 region across Delhi by and large shows some significant perturbations 3-4 days prior to these earthquake events, resulting in a large peak electron density variation of 200%. These observed perturbations indicate towards a possibility of seismo-ionospheric coupling as the solar and geomagnetic indices were normally quiet and stable during the period of these events. It was also observed that the precursory effect of earthquake was predominantly seen even outside the earthquake preparation zone, as given by Dobrovolsky et al. (1979). The thermosphere neutral composition (O/N2) as observed by Global Ultraviolet Imager, across Delhi, during these earthquake events does not show any marked variation. Further, the effect of earthquake events on ionospheric peak electron density is compared to the lower atmosphere meteorological phenomenon of 2015 sudden stratospheric warming event.

  8. Statistical study of possible pre-, co- (coeval to) and post- earthquake effects in the near-equatorial, low and mid latitude ionosphere

    Science.gov (United States)

    Gousheva, Mariyana; Danov, Dimitar; Hristov, Plamen; Georgieva, Katya

    This paper presents the quasi-static electric field disturbances in the upper ionosphere observed from the satellite INTERCOSMOS-BULGARIA-1300 over earthquakes' source regions at different latitudes. The earthquake data were obtained from United State Geological Survey (USGS) website. In the present paper, an attempt of a statistical stady of ionospheric effects during seismic activity in August- November 1981 is presented. Present study focuses on four main areas- (i) satellite and seismic data selection, (ii) data processing and observations of some most important experimental results, (iii) comparison of observational new data with the results in our previous studies, (iiii) statistical study of possible pre-, co- (coeval to) and postearthquake effects in the near-equatorial, low and mid latitude ionosphere. After review of observational results we analyze an increase of about 5-10-15 mV/m in the vertical component of the quasi-static electric field observed by INTERCOSMOS-BULGARIA-1300 in the upper ionosphere above earthquakes sources during seismic activity. The obtained results strengthen our previous studies (Gousheva et al., 2005a, b; 2006a, b; 2007a, b).The paper discusses the observed effects. The main goal of this study is to generalize our results of possible connection between anomalous vertical electric fields penetrating from the earthquake zone into the ionosphere, and seismic activity. An additional goal of this study is to evaluate some morphological peculiarities of quasi-static electric field disturbances such as their appearance time before and after the main shock, sensitivity, amplitude and time duration.

  9. Ice and liquid partitioning in mid-latitude and artic mixed-phase clouds: how common is the real mixed-phase state

    Science.gov (United States)

    Meyer, Jessica; Krämer, Martina; Afchine, Armin; Gallagher, Martin; Dorsey, James; Brown, Phil; Woolley, Alan; Bierwirth, Eike; Ehrlich, Andre; Wendisch, Manfred; Gehrmann, Martin

    2013-04-01

    The influence of mixed-phase clouds on the radiation budget of the earth is largely unknown. One of the key parameters to determine mixed-phase cloud radiative properties however is the fraction of ice particles and liquid droplets in these clouds. The separate detection of liquid droplets and ice crystals especially in the small cloud particle size range below 50 µm remains challenging though. Here, we present airborne NIXE-CAPS mixed-phase cloud particle measurements observed in mid-latitude and Arctic low-level mixed-phase clouds during the COALESC field campaign in 2011 and the Arctic field campaign VERDI in 2012. NIXE-CAPS (Novel Ice EXpEriment - Cloud and Aerosol Particle Spectrometer, manufactured by DMT) is a cloud particle spectrometer which measures the cloud particle number, size as well as their phase for each cloud particle in the diameter range 0.6 to 945 µm. The common understanding in mixed-phase cloud research is that liquid droplets and ice crystals in the same cloud volume are rather sparse, but instead either liquid droplets or ice crystals are present. However, recently published model studies (e.g. Korolev, A. & Field, P., The effect of dynamics on mixed-phase clouds: Theoretical considerations. J. Atmos. Sci. 65, 66-86, 2008) indicate that a cloud state containing both liquid droplets and ice crystals can be kept up by turbulence. Indeed, our particle by particle analyses of the observed mixed-phase clouds during COALESC and VERDI indicate that the real mixed-phase state is rather common in the atmosphere. The spatial distribution of the mixed-phase ice fraction and the size of the droplets and ice crystals however vary substantially from case to case. The latter parameters seem to be influenced not only by concentration of ice nuclei but also - to a large degree - by cloud dynamics.

  10. Variation of gravity waves on different time scales and the differences between day and nighttime lidar soundings at mid-latitudes

    Science.gov (United States)

    Baumgarten, Kathrin; Gerding, Michael; Luebken, Franz-Josef

    2017-04-01

    A daylight capable Rayleigh-Mie-Raman (RMR) lidar is in operation since summer 2010 at the mid-latitude station at Kühlungsborn (54° N, 12° E). The RMR lidar system is used for measuring wave structures at day and night to investigate short and long periodic atmospheric waves, like gravity waves (GW) and thermal tides (with diurnal, semidiurnal and terdiurnal components) between 30 and 70 km altitude. An extensive data set with over 7500 measurements hours allows deriving the seasonal variation of, e.g., gravity wave potential energy density (GWPED), while several multi-day observations show the variability of gravity waves and tides on shorter time scales. To separate gravity waves, tides and other long periodic waves a 1-dimensional spectral filtering technique is used. The seasonal variation of the potential energy per unit volume shows a clear summer minimum for inertia gravity waves as well as for tides. Contrary to this, short periodic gravity waves with periods between 4 and 8 h show no clear seasonal variation. Especially for altitudes above 55 km an additional semiannual component with a second summer maximum is observed, which shows the increasing relevance of these waves. Because of the availability of whole day data, we have the possibility to distinguish between day and nighttime data. By using only data between 20 UT and 4 UT ("nighttime") we found a summer minimum in GWPED that is hidden in the whole day data. We relate these differences in the seasonal behavior to a diurnal variation of propagation conditions for the particular gravity waves. Beside the monthly averaged data, we will present a 10-day continuous lidar sounding to show the variability of gravity waves and tides on short time scales.

  11. Statistical analysis of the time and space characteristic scales for large precipitating systems in the equatorial, tropical, sahelian and mid-latitude regions.

    Science.gov (United States)

    Duroure, Christophe; Sy, Abdoulaye; Baray, Jean luc; Van baelen, Joel; Diop, Bouya

    2017-04-01

    Precipitation plays a key role in the management of sustainable water resources and flood risk analyses. Changes in rainfall will be a critical factor determining the overall impact of climate change. We propose to analyse long series (10 years) of daily precipitation at different regions. We present the Fourier densities energy spectra and morphological spectra (i.e. probability repartition functions of the duration and the horizontal scale) of large precipitating systems. Satellite data from the Global precipitation climatology project (GPCP) and local pluviometers long time series in Senegal and France are used and compared in this work. For mid-latitude and Sahelian regions (North of 12°N), the morphological spectra are close to exponential decreasing distribution. This fact allows to define two characteristic scales (duration and space extension) for the precipitating region embedded into the large meso-scale convective system (MCS). For tropical and equatorial regions (South of 12°N) the morphological spectra are close to a Levy-stable distribution (power law decrease) which does not allow to define a characteristic scale (scaling range). When the time and space characteristic scales are defined, a "statistical velocity" of precipitating MCS can be defined, and compared to observed zonal advection. Maps of the characteristic scales and Levy-stable exponent over West Africa and south Europe are presented. The 12° latitude transition between exponential and Levy-stable behaviors of precipitating MCS is compared with the result of ECMWF ERA-Interim reanalysis for the same period. This morphological sharp transition could be used to test the different parameterizations of deep convection in forecast models.

  12. Northern Hemisphere forcing of Southern Hemisphere climate during the last deglaciation.

    Science.gov (United States)

    He, Feng; Shakun, Jeremy D; Clark, Peter U; Carlson, Anders E; Liu, Zhengyu; Otto-Bliesner, Bette L; Kutzbach, John E

    2013-02-07

    According to the Milankovitch theory, changes in summer insolation in the high-latitude Northern Hemisphere caused glacial cycles through their impact on ice-sheet mass balance. Statistical analyses of long climate records supported this theory, but they also posed a substantial challenge by showing that changes in Southern Hemisphere climate were in phase with or led those in the north. Although an orbitally forced Northern Hemisphere signal may have been transmitted to the Southern Hemisphere, insolation forcing can also directly influence local Southern Hemisphere climate, potentially intensified by sea-ice feedback, suggesting that the hemispheres may have responded independently to different aspects of orbital forcing. Signal processing of climate records cannot distinguish between these conditions, however, because the proposed insolation forcings share essentially identical variability. Here we use transient simulations with a coupled atmosphere-ocean general circulation model to identify the impacts of forcing from changes in orbits, atmospheric CO(2) concentration, ice sheets and the Atlantic meridional overturning circulation (AMOC) on hemispheric temperatures during the first half of the last deglaciation (22-14.3 kyr BP). Although based on a single model, our transient simulation with only orbital changes supports the Milankovitch theory in showing that the last deglaciation was initiated by rising insolation during spring and summer in the mid-latitude to high-latitude Northern Hemisphere and by terrestrial snow-albedo feedback. The simulation with all forcings best reproduces the timing and magnitude of surface temperature evolution in the Southern Hemisphere in deglacial proxy records. AMOC changes associated with an orbitally induced retreat of Northern Hemisphere ice sheets is the most plausible explanation for the early Southern Hemisphere deglacial warming and its lead over Northern Hemisphere temperature; the ensuing rise in atmospheric CO(2

  13. First airborne water vapor lidar measurements in the tropical upper troposphere and mid-latitudes lower stratosphere: accuracy evaluation and intercomparisons with other instruments

    Directory of Open Access Journals (Sweden)

    C. Schiller

    2008-09-01

    Full Text Available In the tropics, deep convection is the major source of uncertainty in water vapor transport to the upper troposphere and into the stratosphere. Although accurate measurements in this region would be of first order importance to better understand the processes that govern stratospheric water vapor concentrations and trends in the context of a changing climate, they are sparse because of instrumental shortcomings and observational challenges. Therefore, the Falcon research aircraft of the Deutsches Zentrum für Luft- und Raumfahrt (DLR flew a zenith-viewing water vapor differential absorption lidar (DIAL during the Tropical Convection, Cirrus and Nitrogen Oxides Experiment (TROCCINOX in 2004 and 2005 in Brazil. The measurements were performed alternatively on three water vapor absorption lines of different strength around 940 nm. These are the first aircraft DIAL measurements in the tropical upper troposphere and in the mid-latitudes lower stratosphere. Sensitivity analyses reveal an accuracy of 5% between altitudes of 8 and 16 km. This is confirmed by intercomparisons with the Fast In-situ Stratospheric Hygrometer (FISH and the Fluorescent Advanced Stratospheric Hygrometer (FLASH onboard the Russian M-55 Geophysica research aircraft during five coordinated flights. The average relative differences between FISH and DIAL amount to −3%±8% and between FLASH and DIAL to −8%±14%, negative meaning DIAL is more humid. The average distance between the probed air masses was 129 km. The DIAL is found to have no altitude- or latitude-dependent bias. A comparison with the balloon ascent of a laser absorption spectrometer gives an average difference of 0%±19% at a distance of 75 km. Six tropical DIAL under-flights of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS on board ENVISAT reveal a mean difference of −8%±49% at an average distance of 315 km. While the comparison with MIPAS is somewhat less significant due to poorer

  14. The pulsating nature of large-scale Saharan dust transport as a result of interplays between mid-latitude Rossby waves and the North African Dipole Intensity

    Science.gov (United States)

    Cuevas, E.; Gómez-Peláez, A. J.; Rodríguez, S.; Terradellas, E.; Basart, S.; García, R. D.; García, O. E.; Alonso-Pérez, S.

    2017-10-01

    It was previously shown that during August the export of Saharan dust to the Atlantic was strongly affected by the difference of the 700-hPa geopotential height anomaly between the subtropics and the tropics over North Africa, which was termed the North African Dipole Intensity (NAFDI). In this work a more comprehensive analysis of the NAFDI is performed, focusing on the entire summer dust season (June-September), and examining the interactions between the mid-latitude Rossby waves (MLRWs) and NAFDI. Widespread and notable aerosol optical depth (AOD) monthly anomalies are found for each NAFDI-phase over the dust corridors off the Sahara, indicating that NAFDI presents intra-seasonal variability and drives dust transport over both the Mediterranean basin and the North Atlantic. Those summer months with the same NAFDI-phase show similar AOD-anomaly patterns. Variations in NAFDI-phase also control the displacement of the Saharan Heat Low (SHL) westwards or eastwards through horizontal advection of temperature over Morocco-Western Sahara or eastern Algeria-Western Libya, respectively. The connection between the SHL and the NAFDI is quantified statistically by introducing two new daily indexes that account for their respective phases (NAFDI daily index -NAFDIDI-, and SHL longitudinal shift index -SHLLSI-) and explained physically using the energy equation of the atmospheric dynamics. The Pearson's correlation coefficient between the one-day-lag SHLLSI and the NAFDIDI for an extended summer season (1980-2013) is 0.78. A positive NAFDI is associated with the West-phase of the SHL, dust sources intensification on central Algeria, and positive AOD anomalies over this region and the Subtropical North Atlantic. A negative NAFDI is associated with the East-phase of the SHL, and positive AOD anomalies over central-eastern Sahara and the central-western Mediterranean Sea. The results point out that the phase changes of NAFDI at intra-seasonal time scale are conducted by those

  15. Effects of local microclimates on the surface sensible heat flux on a mid-latitude alpine valley glacier using Large-Eddy Simulations

    Science.gov (United States)

    Sauter, Tobias; Galos, Stephan

    2016-04-01

    While the large-scale climate conditions play an important role in shaping the environment in which glaciers exist, the mass and energy balance of each individual glacier are dictated by local conditions. Given the complex mountain topography around alpine glaciers, it is not trivial to find a direct link between the large-scale atmospheric motions and the local-scale weather conditions at an individual glacier. Non-local dynamic effects due to the surrounding complex topography can significantly modify the spatial variability of exchange processes, either by small scale circulations or episodic entrainment of heat and momentum by burst events. Motivated by the fact that distributed glacier models strongly rely on the quality of high resolution forcing data to adequately represent the glacier wide ablation and accumulation processes, the present study investigates (i) whether non-local topographic effects have a significant impact on the spatial distribution of turbulent sensible heat fluxes (local microclimates) over alpine glaciers, and (ii) how much variability is smoothed out when using linearly interpolated fields together with the commonly used bulk approach. To answer these questions, we perform highly resolved and properly designed case experiments by Large-Eddy Simulations with real topography to determine the impact of topographic flow features on the spatial variability of the surface sensible heat flux and compare the fields with those derived with the bulk approach. The analysis shows that there is a significant spatial variability of the mean fluxes with values ranging from -10 Wm-2 to -120 Wm-2. Since the sensible heat flux can make up to 40% of the total melting on mid-latitude alpine valley glaciers, the heterogeneity of the fluxes can substantially dictate the local melting rates. When estimating the glacier-wide surface heat fluxes on the basis of point-measurements and the bulk approach, a considerable amount of spatial information is lost. All

  16. Ten-year trends of atmospheric mercury in the high Arctic compared to Canadian sub-Arctic and mid-latitude sites

    Directory of Open Access Journals (Sweden)

    A. S. Cole

    2013-02-01

    Full Text Available Global emissions of mercury continue to change at the same time as the Arctic is experiencing ongoing climatic changes. Continuous monitoring of atmospheric mercury provides important information about long-term trends in the balance between transport, chemistry, and deposition of this pollutant in the Arctic atmosphere. Ten-year records of total gaseous mercury (TGM from 2000 to 2009 were analyzed from two high Arctic sites at Alert (Nunavut, Canada and Zeppelin Station (Svalbard, Norway; one sub-Arctic site at Kuujjuarapik (Nunavik, Québec, Canada; and three temperate Canadian sites at St. Anicet (Québec, Kejimkujik (Nova Scotia and Egbert (Ontario. Five of the six sites examined showed a decreasing trend over this time period. Overall trend estimates at high latitude sites were: −0.9% yr−1 (95% confidence limits: −1.4, 0 at Alert and no trend (−0.5, +0.7 at Zeppelin Station. Faster decreases were observed at the remainder of the sites: −2.1% yr−1 (−3.1, −1.1 at Kuujjuarapik, −1.9% yr−1 (−2.1, −1.8 at St. Anicet, −1.6% yr−1 (−2.4, −1.0 at Kejimkujik and −2.2% yr−1 (−2.8, −1.7 at Egbert. Trends at the sub-Arctic and mid-latitude sites agree with reported decreases in background TGM concentration since 1996 at Mace Head, Ireland, and Cape Point, South Africa, but conflict with estimates showing an increase in global anthropogenic emissions over a similar period. Trends in TGM at the two high Arctic sites were not only less negative (or neutral overall but much more variable by season. Possible reasons for differences in seasonal and overall trends at the Arctic sites compared to those at lower latitudes are discussed, as well as implications for the Arctic mercury cycle. The first calculations of multi-year trends in reactive gaseous mercury (RGM and total particulate mercury (TPM at Alert were also performed, indicating increases from 2002 to 2009

  17. Depositional environments and cyclo- and chronostratigraphy of uppermost Carboniferous-Lower Triassic -lacustrine deposits, southern Bogda Mountains, NW China - A terrestrfluvialial paleoclimatic record of mid-latitude NE Pangea

    Science.gov (United States)

    Yang, W.; Feng, Q.; Liu, Yajing; Tabor, N.; Miggins, D.; Crowley, J.L.; Lin, J.; Thomas, S.

    2010-01-01

    Two uppermost Carboniferous–Lower Triassic fluvial–lacustrine sections in the Tarlong–Taodonggou half-graben, southern Bogda Mountains, NW China, comprise a 1834 m-thick, relatively complete sedimentary and paleoclimatic record of the east coast of mid-latitude NE Pangea. Depositional environmental interpretations identified three orders (high, intermediate, and low) of sedimentary cycles. High-order cycles (HCs) have five basic types, including fluvial cycles recording repetitive changes of erosion and deposition and lacustrine cycles recording repetitive environmental changes associated with lake expansion and contraction. HCs are grouped into intermediate-order cycles (ICs) on the basis of systematic changes of thickness, type, and component lithofacies of HCs. Nine low-order cycles (LCs) are demarcated by graben-wide surfaces across which significant long-term environmental changes occurred. A preliminary cyclostratigraphic framework provides a foundation for future studies of terrestrial climate, tectonics, and paleontology in mid-latitude NE Pangea.Climate variabilities at the intra-HC, HC, IC, and LC scales were interpreted from sedimentary and paleosol evidence. Four prominent climatic shifts are present: 1) from the humid–subhumid to highly-variable subhumid–semiarid conditions at the beginning of Sakamarian; 2) from highly-variable subhumid–semiarid to humid–subhumid conditions across the Artinskian-Capitanian unconformity; 3) from humid–subhumid to highly-variable subhumid–semiarid conditions at early Induan; and 4) from the highly-variable subhumid–semiarid to humid–subhumid conditions across the Olenekian-Anisian unconformity. The stable humid–subhumid condition from Lopingian to early Induan implies that paleoclimate change may not have been the cause of the end-Permian terrestrial mass extinction. A close documentation of the pace and timing of the extinction and exploration of other causes are needed. In addition, the

  18. Wavelet analysis of the ionospheric response at Mid-latitudes during the april 2000 storm using magnetograms and vTEC from GPS

    Directory of Open Access Journals (Sweden)

    L. I Fernández

    2012-12-01

    Full Text Available In this work we pursue the idea of computing a parameter that allows us to estimate the local ionospheric response to a geospheric event that triggers an ionospheric storm. For that, wavelet technique has been chosen because of its ability to analyze non-stationary signals. The advantage of the time-frequency analysis method called Wavelet Transform resides in providing information not only about the frequencies of the event but also about its location in the time series. Specifically, we compute the Scale Average Wavelet Power (SAWP of two parameters that describe the local geomagnetic field variation at the Earth surface caused by a geospheric storm and ionospheric response to the storm event. In particular, we propose the time delay between the maximum values of SAWP applied to the vTEC (vertical Total Electron Content and the horizontal component of the geomagnetic field (H variations as parameters to characterize the local behavior of the ionospheric storm. We applied the parameter to the geomagnetic and ionospheric disturbances caused by a coronal mass ejection (CME that took place on April 4, 2000. We used vTEC values computed from GPS observations and H at the surface of the Earth, measured in stations near to each GPS station chosen. The vTEC values used came from the GPS permanent stations belonging to the global IGS (International GNSS Service network. We chose stations located at magnetic mid-latitudes. Moreover, three-longitude bands representing the ionospheric behavior at different local times (LT were studied. Because the April 2000 storm has been extensively studied for many authors, the results are compared with those in the literature and we found a very good agreement as expected.En este trabajo perseguimos la idea de estimar un parámetro que nos permita calcular la respuesta ionosférica local a un evento geosférico desencadenante de una tormenta ionosférica. Para ello, se eligió la aplicación de la técnica ondeleta

  19. Evaluation of the ACCESS – chemistry–climate model for the Southern Hemisphere

    Directory of Open Access Journals (Sweden)

    K. A. Stone

    2016-02-01

    Full Text Available Chemistry–climate models are important tools for addressing interactions of composition and climate in the Earth system. In particular, they are used to assess the combined roles of greenhouse gases and ozone in Southern Hemisphere climate and weather. Here we present an evaluation of the Australian Community Climate and Earth System Simulator – chemistry–climate model (ACCESS-CCM, focusing on the Southern Hemisphere and the Australian region. This model is used for the Australian contribution to the international Chemistry–Climate Model Initiative, which is soliciting hindcast, future projection and sensitivity simulations. The model simulates global total column ozone (TCO distributions accurately, with a slight delay in the onset and recovery of springtime Antarctic ozone depletion, and consistently higher ozone values. However, October-averaged Antarctic TCO from 1960 to 2010 shows a similar amount of depletion compared to observations. Comparison with model precursors shows large improvements in the representation of the Southern Hemisphere stratosphere, especially in TCO concentrations. A significant innovation is seen in the evaluation of simulated vertical profiles of ozone and temperature with ozonesonde data from Australia, New Zealand and Antarctica from 38 to 90° S. Excess ozone concentrations (greater than 26 % at Davis and the South Pole during winter and stratospheric cold biases (up to 10 K at the South Pole during summer and autumn outside the period of perturbed springtime ozone depletion are seen during all seasons compared to ozonesondes. A disparity in the vertical location of ozone depletion is seen: centred around 100 hPa in ozonesonde data compared to above 50 hPa in the model. Analysis of vertical chlorine monoxide profiles indicates that colder Antarctic stratospheric temperatures (possibly due to reduced mid-latitude heat flux are artificially enhancing polar stratospheric cloud formation at high altitudes

  20. The Eurasia-North Pacific Oscillation in atmospheric mass variations independent of both IHO and AO and its possible impacts on winter climate

    Science.gov (United States)

    Zhang, Qian; Guan, Zhaoyong; Li, Minggang

    2017-09-01

    Using NCEP/NCAR reanalysis, we have investigated the features of migrations of atmospheric mass (AM) between land and ocean in Eurasia-North Pacific domain in boreal winter after having both signals of Inter-hemispheric Oscillation and Arctic Oscillation removed from the physical quantities. It is found that there is a Eurasia-North Pacific Oscillation (ENPO) in surface air pressure anomalies. This ENPO pattern characterizes with two oppositely signed anomalous surface pressure centers over Eurasia and North Pacific respectively, indicating strong connections between Siberian high and Aleutian low during period 1979-2012. The maintenance of this ENPO teleconnection is significantly associated with three factors including the anomalous AM flows and zonal circulation cell over Eurasia-North Pacific domain, the Rossby wave energy propagations, and the thermal forcing contrasts near the surface between Eurasia and North Pacific during boreal winter. The variations of both wintertime rainfall and temperature over Eurasia may be strongly affected by ENPO. When the ENPO index is positive (negative), there occurs the AM accumulation (depletion) over Eurasia with simultaneous depletion (accumulation) over mid-latitude North-Pacific. Correspondingly, this anomalous surface pressure pattern along with the related circulation anomalies at different isobaric levels possibly results in winter precipitation decreases (increases) over Siberian Plain and East China, whereas increases (decreases) over southeastern Europe, Xinjiang of China, and the west coast of Sea of Okhotsk. On the other hand, surface air temperature decreases (increases) over large areas of Eurasia. These results are helpful for our better understanding the mechanisms behind circulation and winter climate variations over Eurasia-North Pacific region.

  1. Role of Acclimatization in Weather-Related Human Mortality During the Transition Seasons of Autumn and Spring in a Thermally Extreme Mid-Latitude Continental Climate.

    Science.gov (United States)

    de Freitas, Christopher R; Grigorieva, Elena A

    2015-11-26

    Human mortality is closely related to natural climate-determined levels of thermal environmental stress and the resulting thermophysiological strain. Most climate-mortality research has focused on seasonal extremes during winter and summer when mortality is the highest, while relatively little attention has been paid to mortality during the transitional seasons of autumn and spring. The body acclimatizes to heat in the summer and cold in winter and readjusts through acclimatization during the transitions between the two during which time the body experiences the thermophysiological strain of readjustment. To better understand the influences of weather on mortality through the acclimatization process, the aim here is to examine the periods that link very cold and very warms seasons. The study uses the Acclimatization Thermal Strain Index (ATSI), which is a comparative measure of short-term thermophysiological impact on the body. ATSI centers on heat exchange with the body’s core via the respiratory system, which cannot be protected. The analysis is based on data for a major city in the climatic region of the Russian Far East characterized by very hot summers and extremely cold winters. The results show that although mortality peaks in winter (January) and is at its lowest in summer (August), there is not a smooth rise through autumn nor a smooth decline through spring. A secondary peak occurs in autumn (October) with a smaller jump in May. This suggests the acclimatization from warm-to-cold produces more thermophysiological strain than the transition from cold-to-warm. The study shows that ATSI is a useful metric for quantifying the extent to which biophysical adaptation plays a role in increased strain on the body during re-acclimatization and for this reason is a more appropriate climatic indictor than air temperature alone. The work gives useful bioclimatic information on risks involved in transitional seasons in regions characterized by climatic extremes. This

  2. Role of Acclimatization in Weather-Related Human Mortality During the Transition Seasons of Autumn and Spring in a Thermally Extreme Mid-Latitude Continental Climate

    Directory of Open Access Journals (Sweden)

    Christopher R. de Freitas

    2015-11-01

    Full Text Available Human mortality is closely related to natural climate-determined levels of thermal environmental stress and the resulting thermophysiological strain. Most climate-mortality research has focused on seasonal extremes during winter and summer when mortality is the highest, while relatively little attention has been paid to mortality during the transitional seasons of autumn and spring. The body acclimatizes to heat in the summer and cold in winter and readjusts through acclimatization during the transitions between the two during which time the body experiences the thermophysiological strain of readjustment. To better understand the influences of weather on mortality through the acclimatization process, the aim here is to examine the periods that link very cold and very warms seasons. The study uses the Acclimatization Thermal Strain Index (ATSI, which is a comparative measure of short-term thermophysiological impact on the body. ATSI centers on heat exchange with the body’s core via the respiratory system, which cannot be protected. The analysis is based on data for a major city in the climatic region of the Russian Far East characterized by very hot summers and extremely cold winters. The results show that although mortality peaks in winter (January and is at its lowest in summer (August, there is not a smooth rise through autumn nor a smooth decline through spring. A secondary peak occurs in autumn (October with a smaller jump in May. This suggests the acclimatization from warm-to-cold produces more thermophysiological strain than the transition from cold-to-warm. The study shows that ATSI is a useful metric for quantifying the extent to which biophysical adaptation plays a role in increased strain on the body during re-acclimatization and for this reason is a more appropriate climatic indictor than air temperature alone. The work gives useful bioclimatic information on risks involved in transitional seasons in regions characterized by

  3. A coccolithophore based view on paleoenvironmental changes in the open ocean mid-latitude North Atlantic between 130 and 48ka BP with special emphasis on MIS 5e

    DEFF Research Database (Denmark)

    Schwab, C.; Kinkel, Hanno; Weinelt, M.

    2013-01-01

    , result in a distinct coccolithophore productivity peak. As global temperature during MIS 5e are assumed to be similar to the expected future global climate change, MIS 5e serves as a possible scenario for future changes. Taking MIS 5e as a possible analogue for expected future climate change, our results......As oceanographic changes in the North Atlantic are known to modulate global climate, they are key to the understanding of past and future climate changes. Especially the mid-latitudes of the open ocean North Atlantic may be of interest, regarding the large area covered. We therefore reconstructed...... indicate that an expected decrease in marine primary productivity, due to the expansion of the oligotrophic gyres, may be attenuated by increased coccolithophore productivity....

  4. Origin of aerosol particles in the mid-latitude and subtropical upper troposphere and lowermost stratosphere from cluster analysis of CARIBIC data

    Directory of Open Access Journals (Sweden)

    H. Ziereis

    2009-11-01

    Full Text Available The origin of aerosol particles in the upper troposphere and lowermost stratosphere over the Eurasian continent was investigated by applying cluster analysis methods to in situ measured data. Number concentrations of submicrometer aerosol particles and trace gas mixing ratios derived by the CARIBIC (Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container measurement system on flights between Germany and South-East Asia were used for this analysis. Four cluster analysis methods were applied to a test data set and their capability of separating the data points into scientifically reasonable clusters was assessed. The best method was applied to seasonal data subsets for summer and winter resulting in five cluster or air mass types: stratosphere, tropopause, free troposphere, high clouds, and boundary layer influenced. Other source clusters, like aircraft emissions could not be resolved in the present data set with the used methods. While the cluster separation works satisfactory well for the summer data, in winter interpretation is more difficult, which is attributed to either different vertical transport pathways or different chemical lifetimes in both seasons. The geographical distribution of the clusters together with histograms for nucleation and Aitken mode particles within each cluster are presented. Aitken mode particle number concentrations show a clear vertical gradient with the lowest values in the lowermost stratosphere (750–2820 particles/cm3 STP, minimum of the two 25% – and maximum of the two 75%-percentiles of both seasons and the highest values for the boundary-layer-influenced air (4290–22 760 particles/cm3 STP. Nucleation mode particles are also highest in the boundary-layer-influenced air (1260–29 500 particles/cm3 STP, but are lowest in the free troposphere (0–450 particles/cm3 STP. The given submicrometer particle number concentrations

  5. Semidiurnal tidal activity of the middle atmosphere at mid-latitudes derived from O2 atmospheric and OH(6-2) airglow SATI observations

    Science.gov (United States)

    López-González, M. J.; Rodríguez, E.; García-Comas, M.; López-Puertas, M.; Olivares, I.; Ruiz-Bueno, J. A.; Shepherd, M. G.; Shepherd, G. G.; Sargoytchev, S.

    2017-11-01

    In this paper, we investigate the tidal activity in the mesosphere and lower thermosphere region at 370N using OH Meinel and O2 atmospheric airglow observations from 1998 to 2015. The observations were taken with a Spectral Airglow Temperature Imager (SATI) installed at Sierra Nevada Observatory (SNO) (37.060N, 3.380W) at 2900 m height. From these observations a seasonal dependence of the amplitudes of the semidiurnal tide is inferred. The maximum tidal amplitude occurs in winter and the minimum in summer. The vertically averaged rotational temperatures and vertically integrated volume emission rate (rotational temperatures and intensities here in after), from the O2 atmospheric band measurements and the rotational temperature derived from OH Meinel band measurements reach the maximum amplitude about 1-4 h after midnight during almost all the year except in August-September where the maximum is found 2-4 h earlier. The amplitude of the tide in the OH intensity reaches the minimum near midnight in midwinter, then it is progressively delayed until 4:00 LT in August-September, and from there on it moves again forward towards midnight. The mean Krassovsky numbers for OH and O2 emissions are 5.9 ±1.8 and 5.6 ±1.0, respectively, with negative Krassovsky phases for almost all the year, indicating an upward energy transport. The mean vertical wavelengths for the vertical tidal propagation derived from OH and O2 emissions are 35 ±20 km and 33 ±18 km, respectively. The vertical wavelengths together with the phase shift in the temperature derived from both airglow emissions indicate that these airglow emission layers are separated by 7 ±3 km, on average.

  6. Thermal comfort in Quebec City, Canada: sensitivity analysis of the UTCI and other popular thermal comfort indices in a mid-latitude continental city

    Science.gov (United States)

    Provençal, Simon; Bergeron, Onil; Leduc, Richard; Barrette, Nathalie

    2016-04-01

    The newly developed Universal Thermal Climate Index (UTCI), along with the physiological equivalent temperature (PET), the humidex (HX) and the wind chill index (WC), was calculated in Quebec City, Canada, a city with a strong seasonal climatic variability, over a 1-year period. The objective of this study is twofold: evaluate the operational benefits of implementing the UTCI for a climate monitoring program of public comfort and health awareness as opposed to relying on traditional and simple indices, and determine whether thermal comfort monitoring specific to dense urban neighborhoods is necessary to adequately fulfill the goals of the program. In order to do so, an analysis is performed to evaluate each of these indices' sensitivity to the meteorological variables that regulate them in different environments. Overall, the UTCI was found to be slightly more sensitive to mean radiant temperature, moderately more sensitive to humidity and much more sensitive to wind speed than the PET. This dynamic changed slightly depending on the environment and the season. In hot weather, the PET was found to be more sensitive to mean radiant temperature and therefore reached high values that could potentially be hazardous more frequently than the UTCI and the HX. In turn, the UTCI's stronger sensitivity to wind speed makes it a superior index to identify potentially hazardous weather in winter compared to the PET and the WC. Adopting the UTCI broadly would be an improvement over the traditionally popular HX and WC indices. The urban environment produced favorable conditions to sustain heat stress conditions, where the indices reached high values more frequently there than in suburban locations, which advocates for weather monitoring specific to denser urban areas.

  7. Climate change induced by Southern Hemisphere desertification

    Science.gov (United States)

    Wang, Ye; Yan, Xiaodong

    2017-12-01

    Some 10-20% of global dry-lands are already degraded, and the ongoing desertification threatens the world's poorest populations. Studies on desertification effects are essential for humans to adapt to the environmental challenges posed by desertification. Given the importance of the much larger southern ocean to the global climate and the Southern Hemisphere (SH) climate changes in phase with those in the north, the biogeophysical effects of the SH desertification on climate are assessed using an Earth system model of intermediate complexity, MPM-2. This analysis focuses on differences in climate among the averages of simulations with desert expansion in different latitude bands by year 2000. The localized desertification causes significant global changes in temperature and precipitation as well as surface albedo. On the global scale, cooling dominates the SH desertification effects. However, the biogeophysical effects are most significant in regions with desertification, and the cooling is also prominent in northern mid-latitudes. Desert expansion in 15°-30°S reveals statistically most significant cooling and increased precipitation over the forcing regions during spring. The global and regional scale responses from desertification imply the climate teleconnection and address the importance of the effects from the SH which are contingent on the location of the forcing. Our study indicates that biogeophysical mechanisms of land cover changes in the SH need to be accounted for in the assessment of land management options especially for latitude band over 15°-30°S.

  8. On the ability of chemical transport models to simulate the vertical structure of the N2O, NO2 and HNO3 species in the mid-latitude stratosphere

    Directory of Open Access Journals (Sweden)

    G. Berthet

    2006-01-01

    Full Text Available In this paper we study the impact of the modelling of N2O on the simulation of NO2 and HNO3 by comparing in situ vertical profiles measured at mid-latitudes with the results of the Reprobus 3-D CTM (Three-dimensional Chemical Transport Model computed with the kinetic parameters from the JPL recommendation in 2002. The analysis of the measured in situ profile of N2O shows particular features indicating different air mass origins. The measured N2O, NO2 and HNO3 profiles are not satisfyingly reproduced by the CTM when computed using the current 6-hourly ECMWF operational analysis. Improving the simulation of N2O transport allows us to calculate quantities of NO2 and HNO3 in reasonable agreement with observations. This is achieved using 3-hourly winds obtained from ECMWF forecasts. The best agreement is obtained by constraining a one-dimensional version of the model with the observed N2O. This study shows that the modelling of the NOy partitioning with better accuracy relies at least on a correct simulation of N2O and thus of total NOy.

  9. Observations and analysis of polar stratospheric clouds detected by POAM III and SAGE III during the SOLVE II/VINTERSOL campaign in the 2002/2003 Northern Hemisphere winter

    Directory of Open Access Journals (Sweden)

    J. Alfred

    2007-01-01

    Full Text Available The Polar Ozone and Aerosol Measurement and Stratospheric Aerosol and Gas Experiment instruments both observed high numbers of polar stratospheric clouds (PSCs in the polar region during the second SAGE Ozone Loss and Validation (SOLVE II and Validation of INTERnational Satellites and Study of Ozone Loss (VINTERSOL campaign, conducted during the 2002/2003 Northern Hemisphere winter. Between 15 November 2002 (14 November 2002 and 18 March 2003 (21 March 2003 SAGE (POAM observed 122 (151 aerosol extinction profiles containing PSCs. PSCs were observed on an almost daily basis, from early December through 15 January, in both instruments. No PSCs were observed from either instrument from 15 January until 4 February, and from then only sparingly in three periods in mid- and late February and mid-March. In early December, PSCs were observed in the potential temperature range from roughly 375 K to 750 K. Throughout December the top of this range decreases to near 600 K. In February and March, PSC observations were primarily constrained to potential temperatures below 500 K. The PSC observation frequency as a function of ambient temperature relative to the nitric acid-trihydrate saturation point (using a nitric acid profile prior to denitrification was used to infer irreversible denitrification. By late December 38% denitrification was inferred at both the 400–475 K and 475–550 K potential temperature ranges. By early January extensive levels of denitrification near 80% were inferred at both potential temperature ranges, and the air remained denitrified at least through early March.

  10. Hemispheric dispersion of radioactive plume laced with fission nuclides from the Fukushima nuclear event

    Science.gov (United States)

    Hsu, Shih-Chieh; Huh, Chih-An; Chan, Chuen-Yu; Lin, Shuen-Hsin; Lin, Fei-Jan; Liu, Shaw Chen

    2012-01-01

    Radioactivities of particulate 131I and 137Cs released from the Fukushima nuclear accident were monitored in a regional aerosol network including two high mountain sites (central Taiwan and Tibetan Plateau). The results were integrated with data measured elsewhere around the world, with special focus on the mid-latitudes. The hemispheric transport of the Fukushima radiation clouds (FRCs) by the westerlies took ˜18 days, displaying an exponential-like decrease eastward, with a dilution factor of at least five orders of magnitude following a full circuit around the globe. The initial two waves of FRCs may travel at different atitudes: the first one at ˜3-4 km, whereas the second one up to 5 km or more. 131I and 137Cs were fractionated during transport, with 137Cs concentrated in the shallower layer, susceptible to depositional removal, while 131I moving faster and higher. This accident may be exemplified to identify some atmospheric processes on the hemispheric scale.

  11. Employment and winter construction

    DEFF Research Database (Denmark)

    Hansen, Ernst Jan de Place; Larsen, Jacob Norvig

    2011-01-01

    hemisphere. Can climatic conditions alone explain the sizeable difference in reduction in building activity in the construction sector in European countries in the winter months, or are other factors such as technology, economic cycles and schemes for financial compensation influential as well? What...... of contracts for workers is more likely to explain differences in seasonal activity than climatic or technological factors....

  12. WRF prediction of two winter season Saharan dust events using PM10 concentrations: Boundary versus initial conditions

    Science.gov (United States)

    Jenkins, Gregory S.; Diokhane, Aminita Mbow

    2017-10-01

    During the northern hemisphere winter and spring seasons Saharan dust events overspreading West Africa are frequent and linked to mid-latitude interactions. The dust events have the ability to produce low visibilities, poor air quality and can promote respiratory disease. While a number of case studies have been undertaken, the ability to forecast Saharan dust events is largely unknown. To investigate this matter, we have performed hindcasts using the weather research and forecasting (WRF) model with the Goddard Chemistry Aerosols Radiation Transport (GOCART) module, with 6-h boundary conditions from the NOAA ' National Center for Environmental Prediction (NCEP) final analysis (FNL). We use observed and forecasted PM10 concentrations to evaluate the hindcasts. The hindcasts begin with different conditions 3-8 days before two Saharan dust events where the maximum Particulate matter at 10 microns (PM10) concentrations are observed on 20 January and 7 February 2012 in Dakar, Senegal. The results show that all hindcasts are able to capture the timing of the peak on 20 January but the maximum peak during the second dust event occurs one day prior to the observed peak on 7 February with similar pattern from satellite based aerosol optical depth (AOD) estimates. The hindcasts have positive biases in PM10 concentrations relative to the observations in Dakar Senegal. The hindcasts suggest that WRF model has the potential to effectively forecasts Saharan dust events in real-time forecasts, however, they must be evaluated against additional surface PM10 observations at varying locations, which are currently sparse over West Africa.

  13. Mean characteristics of mesosphere winter echoes at mid- and high-latitudes

    Science.gov (United States)

    Zeller, O.; Zecha, M.; Bremer, J.; Latteck, R.; Singer, W.

    2006-06-01

    VHF radar observations are used to investigate different regions of the Earth's atmosphere. Strong echoes from the mesosphere are mainly observed during summer months at polar latitudes (polar mesosphere summer echoes [PMSE]), and less often at mid-latitudes (mesosphere summer echoes [MSE]). Interestingly, in recent years similar echoes have been observed during winter months ([polar] mesosphere winter echoes (P)MWE). This paper reports on VHF radar measurements between September and April at Andenes (2001 2005) and Kühlungsborn (2003 2005) to determine the mean features of (P)MWE at polar and mid-latitudes. The (P)MWE are a rare phenomenon with mean occurrence rates of about 2.9% in polar and only 0.3% in mid-latitudes, with a maximum occurrence height at 70.5 km for daytime and 77.5 km for nighttime echoes. The diurnal variation is characterised by a maximum near noon and minimum during nighttime. The seasonal variation of (P)MWE is weak with some indication of an increased number of PMWE during mid-winter. The occurrence rate of (P)MWE is positively correlated with the ionisation level of the D region of the ionosphere. Mainly high-energetic proton (and electron) fluxes and enhanced X-ray radiation are important for the existence of (P)MWE. The second factor for the existence of (P)MWE are irregularities of the refraction index of half the radar wavelength (about 3 m for the radars used in this paper). Neutral air turbulence due to breaking gravity waves seems to be an important process. Whether charged aerosol particles or partial reflections of infrasound have additionally to be considered to explain (P)MWE is currently a point of discussion in the literature.

  14. Multi-decadal changes in southern hemisphere subduction rates in a 1/12° ocean model hindcast

    Science.gov (United States)

    Nowatzki, Eva; Patara, Lavinia; Böning, Claus; Karstensen, Johannes

    2017-04-01

    Mode and Intermediate Waters formed in the mid-latitudes of the Southern Ocean represent a major agent for the ventilation of the southern hemisphere lower thermocline, playing a key role in the uptake and intermittent storage of anthropogenic CO2. Long-term hydrographic records as well as modelling studies have provided indications that characteristics of these water masses have been changing over the last decades. Changes in heat, freshwater and momentum fluxes may all contribute to the water mass variability. In this study, we investigate the temporal and spatial variability of Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) formation and its linkages to changing atmospheric conditions with a global ocean - sea-ice model for the time period 1979-2007. The model employs a horizontal resolution of 1/12° for the Southern Ocean and is forced with the CORE-II interannually-varying atmospheric forcing data set. The hindcast simulation is complemented by a second experiment with a repeated 'normal-year' atmospheric forcing in order to separate atmospherically-related changes from stochastic variability and spurious model trends. We find that subduction rates in the density range of SAMW and AAIW are dominated by the lateral induction term and as such are tightly linked to the maximum mixed layer depth (MLD) at the end of winter. The model simulation shows multi-decadal trends in subduction rates, however the trends are not uniform across the density range of SAMW/ AAIW and differ between the Pacific and Indian Ocean sectors. Largest changes in AAIW formation are found in the southeast Pacific, whereas changes in SAMW formation are most pronounced in the Indian Ocean. In the Pacific, the decrease of subduction rates in the AAIW range is contrasted by a positive trend in the SAMW range. The changes in subduction rates are linked to salinity and thus density trends of the winter mixed layer that can be traced to multi-decadal trends in heat and

  15. Millennial-scale northern Hemisphere Atlantic-Pacific climate teleconnections in the earliest Middle Pleistocene.

    Science.gov (United States)

    Hyodo, Masayuki; Bradák, Balázs; Okada, Makoto; Katoh, Shigehiro; Kitaba, Ikuko; Dettman, David L; Hayashi, Hiroki; Kumazawa, Koyo; Hirose, Kotaro; Kazaoka, Osamu; Shikoku, Kizuku; Kitamura, Akihisa

    2017-08-30

    Suborbital-scale climate variations, possibly caused by solar activity, are observed in the Holocene and last-glacial climates. Recently published bicentennial-resolution paleoceanic environmental records reveal millennial-scale high-amplitude oscillations postdating the last geomagnetic reversal in the Marine Isotope Stage (MIS) 19 interglacial. These oscillations, together with decoupling of post-reversal warming from maximum sea-level highstand in mid-latitudes, are key features for understanding the climate system of MIS 19 and the following Middle Pleistocene. It is unclear whether the oscillations are synchronous, or have the same driver as Holocene cycles. Here we present a high resolution record of western North Pacific submarine anoxia and sea surface bioproductivity from the Chiba Section, central Japan. The record reveals many oxic events in MIS 19, coincident with cold intervals, or with combined cold and sea-level fall events. This allows detailed correlations with paleoceanic records from the mid-latitude North Atlantic and Osaka Bay, southwest Japan. We find that the millennial-scale oscillations are synchronous between East and West hemispheres. In addition, during the two warmest intervals, bioproductivity follows the same pattern of change modulated by bicentennial cycles that are possibly related to solar activity.

  16. Quantification of temperature persistence over the Northern Hemisphere land-area

    Science.gov (United States)

    Pfleiderer, Peter; Coumou, Dim

    2017-10-01

    Extreme weather events such as heat waves and floods are damaging to society and their contribution to future climate impacts is expected to be large. Such extremes are often related to persistent local weather conditions. Weather persistence is linked to sea surface temperatures, soil-moisture (especially in summer) and large-scale circulation patterns and these factors can alter under past and future climate change. Though persistence is a key characteristic for extreme weather events, to date the climatology and potential changes in persistence have only been poorly documented. Here, we present a systematic analysis of temperature persistence for the northern hemisphere land area. We define persistence as the length of consecutive warm or cold days and use spatial clustering techniques to create regional persistence distributions. We find that persistence is longest in the Arctic and shortest in the mid-latitudes. Parameterizations of the regional persistence distributions show that they are characterized by an exponential decay with a drop in the decay rate for very persistent events, implying that feedback mechanisms are important in prolonging these events. For the mid-latitudes, we find that persistence in summer has increased over the past 60 years. The changes are particularly pronounced for prolonged events suggesting a lengthening in the duration of heat waves.

  17. Aerosol Optical Depth Distribution in Extratropical Cyclones over the Northern Hemisphere Oceans

    Science.gov (United States)

    Naud, Catherine M.; Posselt, Derek J.; van den Heever, Susan C.

    2016-01-01

    Using Moderate Resolution Imaging Spectroradiometer and an extratropical cyclone database,the climatological distribution of aerosol optical depth (AOD) in extratropical cyclones is explored based solely on observations. Cyclone-centered composites of aerosol optical depth are constructed for the Northern Hemisphere mid-latitude ocean regions, and their seasonal variations are examined. These composites are found to be qualitatively stable when the impact of clouds and surface insolation or brightness is tested. The larger AODs occur in spring and summer and are preferentially found in the warm frontal and in the post-cold frontal regions in all seasons. The fine mode aerosols dominate the cold sector AODs, but the coarse mode aerosols display large AODs in the warm sector. These differences between the aerosol modes are related to the varying source regions of the aerosols and could potentially have different impacts on cloud and precipitation within the cyclones.

  18. Winter Storm Zones on Mars

    Science.gov (United States)

    Hollingsworth, J. L.; Haberle, R. M.; Barnes, J. R.; Bridger, A. F. C.; Cuzzi, Jeffrey N. (Technical Monitor)

    1995-01-01

    Preferred regions of weather activity in Mars' winter middle latitudes-so called 'storm zones' are found in a general circulation model of Mars' atmospheric circulation. During northern winter, these storm zones occur in middle latitudes in the major planitia (low-relief regions) of the western and eastern hemisphere. In contrast, the highlands of the eastern hemisphere are mostly quiescent. Compared to Earth's storm zones where diabatic heating associated with land-sea thermal contrasts is crucial, orography on Mars is fundamental to the regionalization of weather activity. Future spacecraft missions aimed at assessing Mars' climate and its variability need to include such regions in observation strategies.

  19. Links of the significant wave height distribution in the Mediterranean sea with the Northern Hemisphere teleconnection patterns

    Directory of Open Access Journals (Sweden)

    P. Lionello

    2008-06-01

    Full Text Available This study analyzes the link between the SWH (Significant Wave Height distribution in the Mediterranean Sea during the second half of the 20th century and the Northern Hemisphere SLP (Sea Level Pressure teleconnection patterns.

    The SWH distribution is computed using the WAM (WAve Model forced by the surface wind fields provided by the ERA-40 reanalysis for the period 1958–2001. The time series of mid-latitude teleconnection patterns are downloaded from the NOAA web site. This study shows that several mid-latitude patterns are linked to the SWH field in the Mediterranean, especially in its western part during the cold season: East Atlantic Pattern (EA, Scandinavian Pattern (SCA, North Atlantic Oscillation (NAO, East Atlantic/West Russia Pattern (EA/WR and East Pacific/ North Pacific Pattern (EP/NP. Though the East Atlantic pattern exerts the largest influence, it is not sufficient to characterize the dominant variability. NAO, though relevant, has an effect smaller than EA and comparable to other patterns. Some link results from possibly spurious structures. Patterns which have a very different global structure are associated to similar spatial features of the wave variability in the Mediterranean Sea. These two problems are, admittedly, shortcomings of this analysis, which shows the complexity of the response of the Mediterranean SWH to global scale SLP teleconnection patterns.

  20. Winter MVC

    OpenAIRE

    Castellón Gadea, Pasqual

    2013-01-01

    Winter MVC és un framework de presentació basat en Spring MVC que simplifica la metodologia de configuracions. Winter MVC es un framework de presentación basado en Spring MVC que simplifica la metodología de configuraciones. Winter MVC is a presentation framework that simplifies Spring MVC configuration methodology.

  1. Persistent high paleosecular variation activity in southern hemisphere for at least 10 000 years

    Science.gov (United States)

    Constable, Catherine; Korte, Monika; Panovska, Sanja

    2016-11-01

    Direct observations of the geomagnetic field show that secular variation is strong in the Atlantic hemisphere, and comparatively reduced in the Pacific region. The dipole has been decaying since at least 1840 AD, driven by growth and migration of reverse flux patches in the southern hemisphere. We investigate whether anything like this modern pattern of geomagnetic secular variation persists and can be detected in global paleomagnetic field models. Synthesis of results from two new time-varying spherical harmonic models shows that geographically distinct geomagnetic secular variation extends to at least 10 000 BP. The models use the same database but differ in methodology, leading to some regional differences in results. Consistent large-scale surface features include strong average fields in the northern hemisphere and weaker fields with greater overall variability in the south. Longitudinal structure is present, with weaker average fields in the western Pacific than in the east, and prominent negative inclination anomalies extending beneath Indonesia, across Africa and to Brazil, but weaker anomalies in the central Pacific. Marginally positive inclination anomalies occur west of the Americas. Paleosecular variation activity peaks at high southern latitudes, and there is a pattern of reduced activity at equatorial and mid-latitudes beneath the Pacific. Although the dipole has exhibited both growth and decay over the interval 0-10 000 BP, our results show that geomagnetic paleosecular variation is preferentially focused in similar geographic regions to secular variation seen in the modern field.

  2. HF radar polar patch formation revisited: summer and winter variations in dayside plasma structuring

    Directory of Open Access Journals (Sweden)

    S. E. Milan

    Full Text Available Three intervals of polar patch formation, as observed by the CUTLASS Finland HF coherent radar, are presented. Simultaneous observations from a vertical ionosonde located at Longyearbyen on Svalbard, situated in the dayside convection throat region, allow for F-region plasma structuring, leading to polar cap patch formation to be determined. Solar wind and interplanetary magnetic field (IMF precursors of polar patch formation are investigated with MFI and SWE measurements from the Wind spacecraft. We find that in the cases studied polar cap patches are formed in response to changes in the orientation of the IMF, especially in the By component. The resultant changes in the dayside convection pattern alter the source of plasma drifting through the convection throat region into the polar cap. When the convection flow is directed predominantly polewards, high density sub-auroral or mid-latitude plasma enters the polar cap; when flow is directed zonally, low density plasma entrained in the convection return flow replaces it. This mechanism can act to significantly structure the plasma density at sub-auroral or mid-latitudes as well as in the polar cap. In winter months, polar patches appear to be produced by depletions in an otherwise high plasma density tongue of ionisation. In summer months, patches are enhancements of an otherwise low density tongue of ionisation.

    Key words. Ionosphere (ionospheric irregularities; plasma convection; polar ionosphere

  3. Potential causes for the extraordinarily cold and strong Arctic polar vortex in winter 2015/16

    Science.gov (United States)

    Matthias, Vivien; Dörnbrack, Andreas; Stober, Gunter

    2017-04-01

    The Arctic polar vortex was extraordinarily cold and strong at the beginning of the winter 2015/16, strong and displaced in mid-winter and broke down in early March 2016. We investigate the characteristics of the polar vortex using global reanalysis data, satellite observations, and mesospheric radar wind measurements over northern Scandinavia. The results are related to previous winters of the last decades. The focus of this study is on finding the causes for the extraordinary behavior of the Arctic polar vortex in the early and late winter 2015/16. In early winter we found a correlation between the planetary wave (PW) activity and the strength and temperature of the Arctic polar vortex in the stratosphere and mesosphere. In Nov/Dec 2015, a reduced PW generation in the troposphere and a stronger PW filtering in the troposphere and stratosphere, caused by stronger zonal winds in mid-latitudes, resulted in a stronger polar vortex. Another peculiarity of the winter 2015/16 occurred after the unusually early breakdown of the Arctic polar vortex. Typically the zonal mean zonal wind remains easterly until autumn. However, the zonal wind in the mesosphere between 50 and 80 km became westerly again after the "final warming" for over 30 days. During this phenomenon there is no sign of planetary wave activity why other possible causes will be discussed.

  4. Nuclear Winter: Global Consequences of Multiple Nuclear Explosions

    Science.gov (United States)

    Turco, R. P.; Toon, O. B.; Ackerman, T. P.; Pollack, J. B.; Sagan, Carl

    1983-12-01

    The potential global atmospheric and climatic consequences of nuclear war are investigated using models previously developed to study the effects of volcanic eruptions. Although the results are necessarily imprecise, due to a wide range of possible scenarios and uncertainty in physical parameters, the most probable first-order effects are serious. Significant hemispherical attenuation of the solar radiation flux and subfreezing land temperatures may be caused by fine dust raised in high-yield nuclear surface bursts and by smoke from city and forest fires ignited by airbursts of all yields. For many simulated exchanges of several thousand megatons, in which dust and smoke are generated and encircle the earth within 1 to 2 weeks, average light levels can be reduced to a few percent of ambient and land temperatures can reach -15 degrees to -25 degrees C. The yield threshold for major optical and climatic consequences may be very low: only about 100 megatons detonated over major urban centers can create average hemispheric smoke optical depths greater than 2 for weeks and, even in summer, subfreezing land temperatures for months. In a 5000-megaton war, at northern mid-latitude sites remote from targets, radioactive fallout on time scales of days to weeks can lead to chronic mean doses of up to 50 rads from external whole-body gamma-ray exposure, with a likely equal or greater internal dose from biologically active radionuclides. Large horizontal and vertical temperature gradients caused by absorption of sunlight in smoke and dust clouds may greatly accelerate transport of particles and radioactivity from the Northern Hemisphere to the Southern Hemisphere. When combined with the prompt destruction from nuclear blast, fires, and fallout and the later enhancement of solar ultraviolet radiation due to ozone depletion, long-term exposure to cold, dark, and radioactivity could pose a serious threat to human survivors and to other species.

  5. Southern Hemisphere tropospheric aerosol microphysics

    Science.gov (United States)

    Gras, John L.

    1991-01-01

    Aerosol particle-size distribution data have been obtained in the Southern Hemisphere from approximately 4-deg S to 44-deg S and between ground level and 5 km, in the vicinity of eastern Australia. The relative shape of the free-tropospheric size distribution for particles with radii larger than approximately 0.04 micron was found to be remarkably stable with time, altitude, and location for the autumn-winter periods considered. This was despite some large concentration changes, which were found to be typical of the southeastern Australian coastal region. The majority of free-troposphere large particles were found to have sulfuric acid or lightly ammoniated sulfate morphology. Large particles in the boundary layer almost exclusively had a sea-salt morphology.

  6. Quantification of transport across the boundary of the lower stratospheric vortex during Arctic winter 2002/2003

    Directory of Open Access Journals (Sweden)

    G. Günther

    2008-07-01

    Full Text Available Strong perturbations of the Arctic stratosphere during the winter 2002/2003 by planetary waves led to enhanced stretching and folding of the vortex. On two occasions the vortex in the lower stratosphere split into two secondary vortices that re-merged after some days. As a result of these strong disturbances the role of transport in and out of the vortex was stronger than usual. An advection and mixing simulation with the Chemical Lagrangian Model of the Stratosphere (CLaMS utilising a suite of inert tracers tagging the original position of the air masses has been carried out. The results show a variety of synoptic and small scale features in the vicinity of the vortex boundary, especially long filaments peeling off the vortex edge and being slowly mixed into the mid latitude environment. The vortex folding events, followed by re-merging of different parts of the vortex led to strong filamentation of the vortex interior. During January, February, and March 2003 flights of the Russian high-altitude aircraft Geophysica were performed in order to probe the vortex, filaments and in one case the merging zone between the secondary vortices. Comparisons between CLaMS results and observations obtained from the Geophysica flights show in general good agreement.

    Several areas affected by both transport and strong mixing could be identified, allowing explanation of many of the structures observed during the flights. Furthermore, the CLaMS simulations allow for a quantification of the air mass exchange between mid latitudes and the vortex interior. The simulation suggests that after the formation of the vortex was completed, its interior remaind relatively undisturbed. Only during the two re-merging events were substantial amounts of extra-vortex air transported into the polar vortex. When in March the vortex starts weakening additional influence from lower latitudes becomes apparent in the model results.

    In the lower stratosphere export

  7. Some physical drivers of changes in the winter storm tracks over the North Atlantic and Mediterranean during the Holocene.

    Science.gov (United States)

    Brayshaw, David James; Hoskins, Brian; Black, Emily

    2010-11-28

    The winter climate of Europe and the Mediterranean is dominated by the weather systems of the mid-latitude storm tracks. The behaviour of the storm tracks is highly variable, particularly in the eastern North Atlantic, and has a profound impact on the hydroclimate of the Mediterranean region. A deeper understanding of the storm tracks and the factors that drive them is therefore crucial for interpreting past changes in Mediterranean climate and the civilizations it has supported over the last 12 000 years (broadly the Holocene period). This paper presents a discussion of how changes in climate forcing (e.g. orbital variations, greenhouse gases, ice sheet cover) may have impacted on the 'basic ingredients' controlling the mid-latitude storm tracks over the North Atlantic and the Mediterranean on intermillennial time scales. Idealized simulations using the HadAM3 atmospheric general circulation model (GCM) are used to explore the basic processes, while a series of timeslice simulations from a similar atmospheric GCM coupled to a thermodynamic slab ocean (HadSM3) are examined to identify the impact these drivers have on the storm track during the Holocene. The results suggest that the North Atlantic storm track has moved northward and strengthened with time since the Early to Mid-Holocene. In contrast, the Mediterranean storm track may have weakened over the same period. It is, however, emphasized that much remains still to be understood about the evolution of the North Atlantic and Mediterranean storm tracks during the Holocene period.

  8. Southern hemisphere observations

    Science.gov (United States)

    Orchiston, Wayne

    Because of insurmountable problems associated with absolute dating, the non-literate cultures of the Southern Hemisphere can contribute little to Applied Historical Astronomy, although Maori traditions document a possible supernova dating to the period 1000-1770 AD. In contrast, the abundant nineteenth century solar, planetary, cometary and stellar observational data provided by Southern Hemisphere professional and amateur observatories can serve as an invaluable mine of information for present-day astronomers seeking to incorporate historical data in their investigations.

  9. Hemispherical Laue camera

    Science.gov (United States)

    Li, James C. M.; Chu, Sungnee G.

    1980-01-01

    A hemispherical Laue camera comprises a crystal sample mount for positioning a sample to be analyzed at the center of sphere of a hemispherical, X-radiation sensitive film cassette, a collimator, a stationary or rotating sample mount and a set of standard spherical projection spheres. X-radiation generated from an external source is directed through the collimator to impinge onto the single crystal sample on the stationary mount. The diffracted beam is recorded on the hemispherical X-radiation sensitive film mounted inside the hemispherical film cassette in either transmission or back-reflection geometry. The distances travelled by X-radiation diffracted from the crystal to the hemispherical film are the same for all crystal planes which satisfy Bragg's Law. The recorded diffraction spots or Laue spots on the film thereby preserve both the symmetry information of the crystal structure and the relative intensities which are directly related to the relative structure factors of the crystal orientations. The diffraction pattern on the exposed film is compared with the known diffraction pattern on one of the standard spherical projection spheres for a specific crystal structure to determine the orientation of the crystal sample. By replacing the stationary sample support with a rotating sample mount, the hemispherical Laue camera can be used for crystal structure determination in a manner previously provided in conventional Debye-Scherrer cameras.

  10. Volcanic Winter and Cold Tropical Uplands in Late Paleozoic Pangaea: A Thought Experiment

    Science.gov (United States)

    Heavens, N. G.; Soreghan, G. S.

    2014-12-01

    The Late Paleozoic Ice Age (LPIA) was the Earth's most recent icehouse climate prior to the Cenozoic. At present, it is generally accepted that the latitudinal gradient in climate conditions was similar to the present icehouse. High-latitude ice sheets occasionally advanced into the mid-latitudes and retreated once more, but the tropics were warmer or similar in climate to the tropics during the Plio-Pleistocene. Recently, this idea has been challenged by sedimentological evidence of glaciation and dry weathering in upland areas of the tropics as well as geochemical evidence for cold tropical oceans that is consistent with the sedimentological evidence. These observations challenge current qualitative and quantitative models of Late Paleozoic climate, implying tropical climate may have been up to 15 degrees Celsius colder than the present day at some point during the LPIA. Here we consider whether the disparity between evidence for equatorial cold in Pangaea and current models can be explained by explosive volcanic activity associated with events such as the Hercynian orogen or the Kennedy-Connors-Auburn Silicic Large Igneous Province. We find that the necessary radiative forcing for glaciation in low-latitude upland areas could be generated by explosive volcanic activity one to two orders of magnitude greater than the present day, perturbing a baseline climate with mid-latitude glaciation in both hemispheres. Such a forcing would have potentially significant impacts on the carbon cycle and ice sheet dynamics, but these effects are not likely to be unambiguously detectable in the record. Instead, we argue that measurements of mass independent fractionation of S in lacustrine sediments or other deposits sampling meteoric water would be the least ambiguous test of a hypothetical volcanic driver for late Paleozoic cold. This work was supported in part by the National Science Foundation, EAR-1337463.

  11. Unilateral Hemispheric Encephalitis

    Directory of Open Access Journals (Sweden)

    Mohan Leslie Noone

    2014-10-01

    Full Text Available A 10 year old boy presented with history of mild fever and upper respiratory symptoms followed by recurrent seizures and loss of consciousness on the next day. Normal blood counts and abnormal hepatic transaminases were noted. MRI of the brain, done on the fourth day of illness, showed extensive involvement of the cortex in the right hemisphere. Lumbar CSF was normal. The EEG showed bilateral slowing with frontal sharp wave discharges and marked attenuation over the entire right hemisphere. The patient succumbed to the illness on the ninth day. A similar pattern of acute unilateral hemispheric cortical involvement is described in the hemiconvulsion-hemiplegia-epilepsy (HHE syndrome, which is typically described to occur in children below 4 years of age. This case of fulminant acute unilateral encaphilitic illness could represent the acute phase of HHE syndrome.

  12. Shift of subtropical transport barriers explains observed hemispheric asymmetry of decadal trends of age of air

    Directory of Open Access Journals (Sweden)

    G. P. Stiller

    2017-09-01

    Full Text Available In response to global warming, the Brewer–Dobson circulation in the stratosphere is expected to accelerate and the mean transport time of air along this circulation to decrease. This would imply a negative stratospheric age of air trend, i.e. an air parcel would need less time to travel from the tropopause to any point in the stratosphere. Age of air as inferred from tracer observations, however, shows zero to positive trends in the northern mid-latitude stratosphere and zonally asymmetric patterns. Using satellite observations and model calculations we show that the observed latitudinal and vertical patterns of the decadal changes of age of air in the lower to middle stratosphere during the period 2002–2012 are predominantly caused by a southward shift of the circulation pattern by about 5°. After correction for this shift, the observations reveal a hemispherically almost symmetric decrease of age of air in the lower to middle stratosphere up to 800 K of up to −0.25 years over the 2002–2012 period with strongest decrease in the northern tropics. This net change is consistent with long-term trends from model predictions.

  13. Energetics of lower tropospheric planetary waves over mid latitudes ...

    Indian Academy of Sciences (India)

    NCAR reanalysis data,kinetic energy and momentum transport of waves 0 to 10 at 850 hPa level are computed from monthly mean zonal (u) and meridional ... Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, Pune 411 008, India.

  14. Northern and Mid-Latitude Soil Database, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: The U.S. Department of Agriculture, Agriculture and Agri-Food Canada, the Russian Academy of Agricultural Sciences, the University of Copenhagen Institute...

  15. Recent Arctic amplification and extreme mid-latitude weather

    NARCIS (Netherlands)

    Cohen, Judah; Screen, James A.; Furtado, Jason C.; Barlow, Mathew; Whittleston, David; Coumou, Dim; Francis, Jennifer; Dethloff, Klaus; Entekhabi, Dara; Overland, James; Jones, Justin

    2014-01-01

    The Arctic region has warmed more than twice as fast as the global average-a phenomenon known as Arctic amplification. The rapid Arctic warming has contributed to dramatic melting of Arctic sea ice and spring snow cover, at a pace greater than that simulated by climate models. These profound changes

  16. Mid-latitude Ionospheric F2 layer at Sunrise

    Science.gov (United States)

    Zhumabayev, Beibit; Yakovets, Artur; Gordienko, Galina

    2017-04-01

    Ionospheric corrections, calculated from ionospheric models corrected during ground-based or transionospheric sounding, should be applied to up-to-date high-tech wireless devices, including long and superlong base-line radio interferometers and differential GPS navigation systems, in order to improve the accuracy characteristics. The introduced corrections considerably increase at high horizontal gradients of the ionospheric electron density observed at sunrise; therefore, new experimental data on the space-time characteristics of the ionospheric F2 layer, which make it possible to improve the ionosphere description accuracy during this period of the day, are undoubtedly attractive. The F2 layer behavior at sunrise was studied based on the data of vertical-incidence ionospheric sounding in a 5-min regime, performed at the Almaty Institute of the Ionosphere (76°55'E, 43°15'N) in 2000-2010 using a Parus ionosonde. The primary ionogram reduction included reading virtual heights of reflection h'(t) at several fixed working frequencies and critical frequency values (foF2). The further data processing included obtaining N(h) profiles from the ionograms, using the POLAN conversion program. The sequence of N(h) profiles made it possible to obtain the behavior of several layer parameters, including the electron density at fixed altitudes (N(t)) and at the layer maximum (NmF2) and altitudes of the layer maximum (hmF2) and bottom (hbotF2), and the electron density growth rate (N'). The N(t) variations obtained bear features typical of all measurement sessions, namely, (a) the instants of the beginning of a pronounced increase observed later on the lower altitudes; (b) the electron density growth rates (N') differ at different altitudes, and the growth rate is maximal at altitudes below the layer maximum altitude. So, based on vertical-incidence ionospheric sounding data, we indicated that the electron density at altitudes of the ionospheric F2 layer increases rapidly at sunrise and a positive correlation exists between the altitude where the growth rate is maximal (h(N'm)) and the layer maximum altitude (hmF2), on the one hand, and between the electron density growth rate at the h(N'm) layer maximum and the maximal electron density growth rate (N'm), on the other hand. We indicated that the solar zenith angle, corresponding to the instant when the electron density starts increasing pronouncedly, and the corresponding altitude of the blanketing layer upper boundary increase with increasing altitude h where the electron density starts increasing pronouncedly. We established that the slope of the average vertical profile of the zenith angle is identical at a solar activity maximum and minimum and the average χ value at an activity maximum is larger than the corresponding value at an activity minimum by approximately one degree at all altitudes.

  17. Particulate emissions from a mid-latitude prescribed chaparral fire

    Science.gov (United States)

    Cofer, Wesley R., III; Levine, Joel S.; Sebacher, Daniel I.; Winstead, Edward L.; Riggin, Philip J.; Brass, James A.; Ambrosia, Vincent G.

    1988-01-01

    Particulate emission from a 400-acre prescribed chaparral fire in the San Dimas Experimental Forest was investigated by collecting smoke aerosol on Teflon and glass-fiber filters from a helicopter, and using SEM and EDAX to study the features of the particles. Aerosol particles ranged in size from about 0.1 to 100 microns, with carbon, oxygen, magnesium, aluminum, silicon, calcium, and iron as the primary elements. The results of ion chromatographic analysis of aerosol-particle extracts (in water-methanol) revealed the presence of significant levels of NO2(-), NO3(-), SO4(2-), Cl(-), PO4(3-), C2O4(2-), Na(+), NH4(+), and K(+). The soluble ionic portion of the aerosol was estimated to be about 2 percent by weight.

  18. Energetics of lower tropospheric planetary waves over mid latitudes ...

    Indian Academy of Sciences (India)

    The t-statistic also indicates that the difference in the v wind is statistically significant over the area where the trough axis shifts eastwards. The southward wind through this region might affect the temperature distribution over the central Asia and Indian land mass. This can be verified through temperature anomaly field.

  19. Exposed subsurface ice sheets in the Martian mid-latitudes

    Science.gov (United States)

    Dundas, Colin M.; Bramson, Ali M.; Ojha, Lujendra; Wray, James J.; Mellon, Michael T.; Byrne, Shane; McEwen, Alfred S.; Putzig, Nathaniel E.; Viola, Donna; Sutton, Sarah; Clark, Erin; Holt, John W.

    2018-01-01

    Some locations on Mars are known to have water ice just below the surface, but how much has remained unclear. Dundas et al. used data from two orbiting spacecraft to examine eight locations where erosion has occurred. This revealed cliffs composed mostly of water ice, which is slowly sublimating as it is exposed to the atmosphere. The ice sheets extend from just below the surface to a depth of 100 meters or more and appear to contain distinct layers, which could preserve a record of Mars' past climate. They might even be a useful source of water for future human exploration of the red planet.

  20. THE MID-LATITUDE BIODIVERSITY RIDGE IN TERRESTRIAL CAVE FAUNA

    Science.gov (United States)

    The world's obligate cave-dwelling fauna holds considerable promise for biogeographic analysis because it represents a large number of independent evolutionary experiments in isolation in caves and adaptation to subterranean life. We focus on seven north temperate regions of at l...

  1. Stratospheric water vapour as tracer for Vortex filamentation in the Arctic winter 2002/2003

    Directory of Open Access Journals (Sweden)

    M. Müller

    2003-01-01

    Full Text Available Balloon-borne frost point hygrometers measured three high-resolution profiles of stratospheric water vapour above Ny-Ålesund, Spitsbergen during winter 2002/2003. The profiles obtained on 12 December 2002 and on 17 January 2003 provide an insight into the vertical distribution of water vapour in the core of the polar vortex. The water vapour sounding on 11 February 2003 was obtained within the vortex edge region of the lower stratosphere. Here, a significant reduction of water vapour mixing ratio was observed between 16 and 19 km. The stratospheric temperatures indicate that this dehydration was not caused by the presence of polar stratospheric clouds or earlier PSC particle sedimentation. Ozone observations on this day indicate a large scale movement of the polar vortex and show laminae in the same altitude range as the water vapour profile. The link between the observed water vapour reduction and filaments in the vortex edge region is indicated in the results of the semi-lagrangian advection model MIMOSA, which show that adjacent filaments of polar and mid latitude air can be identified above the Spitsbergen region. A vertical cross-section produced by the MIMOSA model reveals that the water vapour sonde flew through polar air in the lowest part of the stratosphere below 425 K, then passed through filaments of mid latitude air with lower water vapour concentrations, before it finally entered the polar vortex above 450 K. These results indicate that on 11 February 2003 the frost point hygrometer measured different water vapour concentrations as the sonde detected air with different origins. Instead of being linked to dehydration due to PSC particle sedimentation, the local reduction in the stratospheric water vapour profile was in this case caused by dynamical processes in the polar stratosphere.

  2. Cassini limb images of hazes in Saturn’s northern hemisphere

    Science.gov (United States)

    Sanchez-Lavega, Agustin M.; Garcia, Daniel; del Rio-Gaztelurrutia, Teresa; Garcia-Muñoz, Antonio; Perez-Hoyos, Santiago; Hueso, Ricardo

    2017-10-01

    We have used high resolution Cassini ISS images of the limb of Saturn to study the vertical distribution, altitude location, thickness and optical properties of the haze layers in the northern hemisphere (1°S to 82°N) in 2013 and 2015. The images cover an ample spectral range from the ultraviolet (UV1 filter, 264 nm) to the near infrared (CB3 filter, 938 nm) including methane absorption bands at 619 nm, 724 nm and 890 nm. Spatial resolution ranges from 1.6 to 13 km/pixel depending on wavelength and latitude. Three latitude bands were selected for the analysis according to the background zonal wind profile measured at cloud level and known dynamical activity: (a) North Polar Region encompassing the Hexagon latitude (74°N) (b) Mid-latitudes (45°N-52°N), and (3) Equator (1°N-3°S). The best defined haze structures and most extended haze layers were found at the latitude of the Hexagon. Up to 6-8 haze layers extending up to 400 km in altitude above clouds (in the pressure range from about 0.7 bar to 0.1 mbar) were detected. The vertical thickness of the layers is in the range 3-15 km compared to the scale height which is about 40 km. The spectral reflectivity is relatively uniform between the layers in the blue and red continuum wavelengths coming from the backward light scattering from the haze particles, while the brightness in the methane bands (relative to red continuum) and in the ultraviolet shows the effects of methane absorption and Rayleigh scattering by the gas, respectively. At mid-latitudes 3-4 haze layers are found spanning up to altitudes 200 km above the clouds. At the Equator 5-6 layers are found extending up to altitudes 250 km above the clouds (up to 2 mbar in pressure level) in a region of great dynamical interest because of the particular structure of the zonal winds and their known oscillations. We comment on the possible nature of the haze layers on the basis of condensing species and photochemistry.

  3. Music, Hemisphere Preference and Imagery.

    Science.gov (United States)

    Stratton, Valerie N.; Zalanowski, Annette H.

    Two experiments were conducted to determine a possible relationship between the right hemisphere, music perception, and mental imagery. The first experiment compared two groups of college students, one of which showed a preference for left hemisphere thinking (n=22) and the other a preference for right hemisphere thinking (n=20), in order to test…

  4. Reconstructing atmospheric circulation over southern New Zealand: Establishment of modern westerly airflow 5500 years ago and implications for Southern Hemisphere Holocene climate change

    Science.gov (United States)

    Turney, C. S. M.; Wilmshurst, J. M.; Jones, R. T.; Wood, J. R.; Palmer, J. G.; Hogg, A. G.; Fenwick, P.; Crowley, S. F.; Privat, K.; Thomas, Z.

    2017-03-01

    Late-twentieth century changes in the intensity and migration of Southern Hemisphere westerly winds have been implicated in spatially complex variability in atmospheric and ocean circulation, and ice-sheet dynamics, across the mid- to high-latitudes. A major uncertainty, however, is whether present day hemispheric-wide symmetrical airflow is representative of past behaviour. Here we report a multi-proxy study from Stewart Island and southern Fiordland, New Zealand (46-47°S) reconstructing Holocene changes at the northern limit of westerly airflow. Increased minerogenic input and a pronounced shift in cool-loving vegetation around 5500 years ago is consistent with the establishment of westerly airflow at this latitude in the southwest Pacific. In marked contrast, stronger winds are reported further south over the subantarctic Auckland (50°S) and Campbell (52°S) Islands from 8000 years ago. Intriguingly, reconstructions from the east Pacific suggest a weakening of core westerly airflow after 8500 years ago, but an expansion along the northern limits sometime after 5500 years ago. Our results suggest similar atmospheric circulation changes have been experienced in the Pacific since 5500 years ago, but indicate an expanded network of sites is needed to comprehensively test the driver(s) and impact(s) of Holocene mid-latitude westerly winds across the Southern Hemisphere.

  5. Changes in meandering of the Northern Hemisphere circulation

    NARCIS (Netherlands)

    Di Capua, Giorgia; Coumou, Dim

    2016-01-01

    Strong waves in the mid-latitude circulation have been linked to extreme surface weather and thus changes in waviness could have serious consequences for society. Several theories have been proposed which could alter waviness, including tropical sea surface temperature anomalies or rapid climate

  6. Glacial/interglacial changes of Southern Hemisphere wind circulation from the geochemistry of South American dust

    Science.gov (United States)

    Gili, Stefania; Gaiero, Diego M.; Goldstein, Steven L.; Chemale, Farid; Jweda, Jason; Kaplan, Michael R.; Becchio, Raúl A.; Koester, Edinei

    2017-07-01

    The latitudinal displacement of the southern westerlies and associated climate systems is a key parameter for understanding the variations of Southern Hemisphere atmospheric circulation during the Late Quaternary Period. To increase understanding of past atmospheric circulation and of the paleo-environmental conditions associated with continental dust sources, we dig deeper into dust provenance in paleo-archives of the Southern Hemisphere. We present here a Sr-Nd isotopic and rare earth element study of surface sediments collected along a ∼4000 km latitudinal band from arid and semi-arid terrains in southern South America. Findings from terrains that served as paleo-dust suppliers are compared with modern dust collected from monitoring stations along the same latitudinal band, which affords a test on how actual present-day aeolian compositions compare to those of the past potential source areas. Moreover, the comparison between past and present-day datasets is useful for understanding present-day atmospheric circulation. Armed with a new comprehensive dataset, we revise previous interpretations of the provenance of dust trapped in the Antarctic ice and sediments deposited in the South Atlantic sector of the Southern Ocean. These comparisons support multiple source regions in southern South America that changed with climates. The findings reveal that, although Patagonia plays an important role in contributing dust to the higher latitudes, central Western Argentina and (to a lesser extent) the southern Puna region also emerge as potentially important dust sources during glacial times. The southern Altiplano appears to be a major contributor during interglacial periods as well. We rely in part on an understanding of modern wind-dust activities to conclude that the possible presence of southern South America source regions - other than Patagonia - in East Antarctic ice is consistent with an overall equatorward displacement during glacial times of both the mid-latitude

  7. European cold winter 2009-2010: How unusual in the instrumental record and how reproducible in the ARPEGE-Climat model?

    Science.gov (United States)

    Ouzeau, G.; Cattiaux, J.; Douville, H.; Ribes, A.; Saint-Martin, D.

    2011-06-01

    Boreal winter 2009-2010 made headlines for cold anomalies in many countries of the northern mid-latitudes. Northern Europe was severely hit by this harsh winter in line with a record persistence of the negative phase of the North Atlantic Oscillation (NAO). In the present study, we first provide a wider perspective on how unusual this winter was by using the recent 20th Century Reanalysis. A weather regime analysis shows that the frequency of the negative NAO was unprecedented since winter 1939-1940, which is then used as a dynamical analog of winter 2009-2010 to demonstrate that the latter might have been much colder without the background global warming observed during the twentieth century. We then use an original nudging technique in ensembles of global atmospheric simulations driven by observed sea surface temperature (SST) and radiative forcings to highlight the relevance of the stratosphere for understanding if not predicting such anomalous winter seasons. Our results demonstrate that an improved representation of the lower stratosphere is necessary to reproduce not only the seasonal mean negative NAO signal, but also its intraseasonal distribution and the corresponding increased probability of cold waves over northern Europe.

  8. WINTER SAECULUM

    Directory of Open Access Journals (Sweden)

    Emil Mihalina

    2017-03-01

    Full Text Available Accumulated imbalances in the economy and on the markets cause specific financial market dynamics that have formed characteristic patterns kept throughout long financial history. In 2008 Authors presented their expectations of key macroeconomic and selected asset class markets developments for period ahead based on Saeculum theory. Use of term Secular describes a specific valuation environment during prolonged period. If valuations as well as selected macro variables are considered as a tool for understanding business cycles then market cycles become much more obvious and easily understandable. Therefore over the long run, certain asset classes do better in terms of risk reward profile than others. Further on, there is no need for frequent portfolio rebalancing and timing of specific investment positions within a particular asset class market. Current stage in cycle development suggests a need for reassessment of trends and prevailing phenomena due to cyclical nture of long lasting Saeculums. Paper reviews developments in recognizable patterns of selected metrics in current Winter Saeculum dominated with prevailing forces of delivering, deflation and decrease in velocity of money.

  9. Speech and the Right Hemisphere

    Directory of Open Access Journals (Sweden)

    E. M. R. Critchley

    1991-01-01

    Full Text Available Two facts are well recognized: the location of the speech centre with respect to handedness and early brain damage, and the involvement of the right hemisphere in certain cognitive functions including verbal humour, metaphor interpretation, spatial reasoning and abstract concepts. The importance of the right hemisphere in speech is suggested by pathological studies, blood flow parameters and analysis of learning strategies. An insult to the right hemisphere following left hemisphere damage can affect residual language abilities and may activate non-propositional inner speech. The prosody of speech comprehension even more so than of speech production—identifying the voice, its affective components, gestural interpretation and monitoring one's own speech—may be an essentially right hemisphere task. Errors of a visuospatial type may occur in the learning process. Ease of learning by actors and when learning foreign languages is achieved by marrying speech with gesture and intonation, thereby adopting a right hemisphere strategy.

  10. A record-breaking low ice cover over the Great Lakes during winter 2011/2012: combined effects of a strong positive NAO and La Niña

    Science.gov (United States)

    Bai, Xuezhi; Wang, Jia; Austin, Jay; Schwab, David J.; Assel, Raymond; Clites, Anne; Bratton, John F.; Colton, Marie; Lenters, John; Lofgren, Brent; Wohlleben, Trudy; Helfrich, Sean; Vanderploeg, Henry; Luo, Lin; Leshkevich, George

    2015-03-01

    A record-breaking low ice cover occurred in the North American Great Lakes during winter 2011/2012, in conjunction with a strong positive Arctic Oscillation/North Atlantic Oscillation (+AO/NAO) and a La Niña event. Large-scale atmosphere circulation in the Pacific/North America (PNA) region reflected a combined signal of La Niña and +NAO. Surface heat flux analysis shows that sensible heat flux contributed most to the net surface heat flux anomaly. Surface air temperature is the dominant factor governing the interannual variability of Great Lakes ice cover. Neither La Niña nor +NAO alone can be responsible for the extreme warmth; the typical mid-latitude response to La Niña events is a negative PNA pattern, which does not have a significant impact on Great Lakes winter climate; the positive phase of NAO is usually associated with moderate warming. When the two occurred simultaneously, the combined effects of La Niña and +NAO resulted in a negative East Pacific pattern with a negative center over Alaska/Western Canada, a positive center in the eastern North Pacific (north of Hawaii), and an enhanced positive center over the eastern and southern United States. The overall pattern prohibited the movement of the Arctic air mass into mid-latitudes and enhanced southerly flow and warm advection from the Gulf of Mexico over the eastern United States and Great Lakes region, leading to the record-breaking low ice cover. It is another climatic pattern that can induce extreme warming in the Great Lakes region in addition to strong El Niño events. A very similar event occurred in the winter of 1999/2000. This extreme warm winter and spring in 2012 had significant impacts on the physical environment, as well as counterintuitive effects on phytoplankton abundance.

  11. Long‐lived Rossby wave trains as precursors to strong winter cyclones over Europe

    National Research Council Canada - National Science Library

    Wirth, V; Eichhorn, J

    2014-01-01

    The statistical connection between strong surface cyclones over Europe and long‐lived upper‐tropospheric Rossby wave trains is examined for the Northern Hemisphere winter season using 45 years of reanalysis data...

  12. One-dimensional simulation of lake and ice dynamics during winter

    Directory of Open Access Journals (Sweden)

    Ali Oveisy

    2014-04-01

    Full Text Available An ice formation model, based on the solution of the heat conduction equation across blue ice, white ice and snow cover, is integrated into the Dynamic Reservoir Simulation Model (DYRESM to allow for one-dimensional (vertical winter simulation of lake dynamics during periods of ice cover. This is an extension of a previous three-layer snow and ice model to include two-way coupling between the ice and the water column. The process-based ice formation is suitable for application to mid-latitude regions and includes: snowmelt due to rain; formation of white ice; and variability in snow density, snow conductivity, and ice and snow albedo. The model was validated against published observations from Harmon lake, British Columbia, and new observations from Eagle lake, Ontario. The ice thickness and water column temperature profile beneath the ice were predicted with Root Mean Square Deviations (RMSD of 1 cm and 0.38°C, respectively, during the winter of 1990-91in Harmon lake. In Eagle lake the 2011-12 year-round water column temperature profile was predicted with an RMSD of 1.8°C. Improved prediction of under-ice lake temperature, relative to published results from simpler models, demonstrates the need for models that accurately capture ice-formation processes, including ice to water column coupling, formation of both blue and white ice layers, and process-based ice and snow parameters (density, conductivity and albedo.

  13. Hemispheric asymmetry in stratospheric NO2 trends

    Science.gov (United States)

    Yela, Margarita; Gil-Ojeda, Manuel; Navarro-Comas, Mónica; Gonzalez-Bartolomé, David; Puentedura, Olga; Funke, Bernd; Iglesias, Javier; Rodríguez, Santiago; García, Omaira; Ochoa, Héctor; Deferrari, Guillermo

    2017-11-01

    Over 20 years of stratospheric NO2 vertical column density (VCD) data from ground-based zenith DOAS spectrometers were used for trend analysis, specifically, via multiple linear regression. Spectrometers from the Network for the Detection of Atmospheric Composition Change (NDACC) cover the subtropical latitudes in the Northern Hemisphere (Izaña, 28° N), the southern Subantarctic (Ushuaia, 55° S) and Antarctica (Marambio, 64° S, and Belgrano, 78° S). The results show that for the period 1993-2014, a mean positive decadal trend of +8.7 % was found in the subtropical Northern Hemisphere stations, and negative decadal trends of -8.7 and -13.8 % were found in the Southern Hemisphere at Ushuaia and Marambio, respectively; all trends are statistically significant at 95 %. Belgrano only shows a significant decadal trend of -11.3 % in the summer/autumn period. Most of the trends result from variations after 2005. The trend in the diurnal build-up per hour (DBU) was used to estimate the change in the rate of N2O5 conversion to NO2 during the day. With minor differences, the results reproduce those obtained for NO2. The trends computed for individual months show large month-to-month variability. At Izaña, the maximum occurs in December (+13.1 %), dropping abruptly to lower values in the first part of the year. In the Southern Hemisphere, the polar vortex dominates the monthly distributions of the trends. At Marambio, the maximum occurs in mid-winter (-21 %), whereas at the same time, the Ushuaia trend is close to its annual minimum (-7 %). The large difference in the trends at these two relatively close stations suggests a vortex shift towards the Atlantic/South American area over the past few years. Finally, the hemispheric asymmetry obtained in this work is discussed in the framework of the results obtained by previous works that considered tracer analysis and Brewer-Dobson circulation. The results obtained here provide evidence that the NO2 produced by N2O

  14. HUBBLE SPOTS NORTHERN HEMISPHERIC CLOUDS ON URANUS

    Science.gov (United States)

    2002-01-01

    Using visible light, astronomers for the first time this century have detected clouds in the northern hemisphere of Uranus. The newest images, taken July 31 and Aug. 1, 1997 with NASA Hubble Space Telescope's Wide Field and Planetary Camera 2, show banded structure and multiple clouds. Using these images, Dr. Heidi Hammel (Massachusetts Institute of Technology) and colleagues Wes Lockwood (Lowell Observatory) and Kathy Rages (NASA Ames Research Center) plan to measure the wind speeds in the northern hemisphere for the first time. Uranus is sometimes called the 'sideways' planet, because its rotation axis is tipped more than 90 degrees from the planet's orbit around the Sun. The 'year' on Uranus lasts 84 Earth years, which creates extremely long seasons - winter in the northern hemisphere has lasted for nearly 20 years. Uranus has also been called bland and boring, because no clouds have been detectable in ground-based images of the planet. Even to the cameras of the Voyager spacecraft in 1986, Uranus presented a nearly uniform blank disk, and discrete clouds were detectable only in the southern hemisphere. Voyager flew over the planet's cloud tops near the dead of northern winter (when the northern hemisphere was completely shrouded in darkness). Spring has finally come to the northern hemisphere of Uranus. The newest images, both the visible-wavelength ones described here and those taken a few days earlier with the Near Infrared and Multi-Object Spectrometer (NICMOS) by Erich Karkoschka (University of Arizona), show a planet with banded structure and detectable clouds. Two images are shown here. The 'aqua' image (on the left) is taken at 5,470 Angstroms, which is near the human eye's peak response to wavelength. Color has been added to the image to show what a person on a spacecraft near Uranus might see. Little structure is evident at this wavelength, though with image-processing techniques, a small cloud can be seen near the planet's northern limb (rightmost

  15. Winter- and summertime continental influences on tropospheric O3 and CO observed by TES over the western North Atlantic Ocean

    Directory of Open Access Journals (Sweden)

    R. Talbot

    2010-04-01

    Full Text Available The distributions of tropospheric ozone (O3 and carbon monoxide (CO, and the synoptic factors regulating these distributions over the western North Atlantic Ocean during winter and summer were investigated using profile retrievals from the Tropospheric Emission Spectrometer (TES for 2004–2006. Seasonal composites of TES retrievals, reprocessed to remove the influence of the a priori on geographical and seasonal structure, exhibited strong seasonal differences. At the 681 hPa level during winter months of December, January and February (DJF the composite O3 mixing ratios were uniformly low (~45 ppbv, but continental export was evident in a channel of enhanced CO (100–110 ppbv flowing eastward from the US coast. In summer months June, July, and August (JJA O3 mixing ratios were variable (45–65 ppbv and generally higher due to increased photochemical production. The summer distribution also featured a channel of enhanced CO (95–105 ppbv flowing northeastward around an anticyclone and exiting the continent over the Canadian Maritimes around 50° N. Offshore O3-CO slopes were generally 0.15–0.20 mol mol−1 in JJA, indicative of photochemical O3 production. Composites for 4 predominant synoptic patterns or map types in DJF suggested that export to the lower free troposphere (681 hPa level was enhanced by the warm conveyor belt airstream of mid-latitude cyclones while stratospheric intrusions increased TES O3 levels at 316 hPa. A major finding in the DJF data was that offshore 681 hPa CO mixing ratios behind cold fronts could be enhanced up to >150 ppbv likely by lofting from the surface via shallow convection resulting from rapid destabilization of cold air flowing over much warmer ocean waters. In JJA composites for 3 map types showed that the general export pattern of the seasonal composites was associated with a synoptic pattern featuring the Bermuda High. However, weak cyclones and frontal troughs could enhance offshore 681 hPa CO

  16. Moon - Western Hemisphere

    Science.gov (United States)

    1990-01-01

    This image of the western hemisphere of the Moon was taken through a green filter by the Galileo spacecraft at 9:35 a.m. PST Dec. 9 at a range of about 350,000 miles. In the center is the Orientale Basin, 600 miles in diameter, formed about 3.8 billion years ago by the impact of an asteroid-size body. Orientale's dark center is a small mare. To the right is the lunar nearside with the great, dark Oceanus Procellarum above and the small, circular, dark Mare Humorum below. Maria are broad plains formed mostly over 3 billion years ago as vast basaltic lava flows. To the left is the lunar far side with fewer maria but, at lower left, the South-Pole-Aitken basin, about 1200 miles in diameter, which resembles Orientale but is much older and more weathered and battered by cratering. The intervening cratered highlands of both sides, as well as the maria, are dotted with bright, young craters. This image was 'reprojected' so as to center the Orientale Basin, and was filtered to enhance the visibility of small features. The digital image processing was done by DLR, the German Aerospace Research Establishment near Munich, an international collaborator in the Galileo mission.

  17. Weakening of the Stratospheric Polar Vortex by Arctic Sea-Ice Loss

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Baek-Min; Son, Seok-Woo; Min, Seung-Ki; Jeong, Jee-Hoon; Kim, Seong-Joong; Zhang, Xiangdong; Shim, Taehyoun; Yoon, Jin-Ho

    2014-09-02

    Successive cold winters of severely low temperatures in recent years have had critical social and economic impacts on the mid-latitude continents in the Northern Hemisphere. Although these cold winters are thought to be partly driven by dramatic losses of Arctic sea ice, the mechanism that links sea ice loss to cold winters remains a subject of debate. Here, by conducting observational analyses and model experiments, we show how Arctic sea ice loss and cold winters in extra-polar regions are dynamically connected through the polar stratosphere. We find that decreased sea ice cover during early winter months (November-December), especially over the Barents-Kara seas, enhance the upward propagation of planetary-scale waves with wavenumbers of 1 and 2, subsequently weakening the stratospheric polar vortex in mid-winter (January- February). The weakened polar vortex preferentially induces a negative phase of Arctic Oscillation at the surface, resulting in low temperatures in mid-latitudes.

  18. Classification of hemispheric monthly mean stratospheric potential vorticity fields

    Directory of Open Access Journals (Sweden)

    R. Huth

    2003-03-01

    Full Text Available Monthly mean NCEP reanalysis potential vorticity fields at the 650 K isentropic level over the Northern and Southern Hemispheres between 1979 and 1997 were studied using multivariate analysis tools. Principal component analysis in the T-mode was applied to demonstrate the validity of such statistical techniques for the study of stratospheric dynamics and climatology. The method, complementarily applied to both the raw and anomaly fields, was useful in determining and classifying the characteristics of winter and summer PV fields on both hemispheres, in particular, the well-known differences in the behaviour and persistence of the polar vortices. It was possible to identify such features as sudden warming events in the Northern Hemisphere and final warming dates in both hemispheres. The stratospheric impact of other atmospheric processes, such as volcanic eruptions, also identified though the results, must be viewed at this stage as tentative. An interesting change in behaviour around 1990 was detected over both hemispheres.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; general circulation; climatology

  19. Classification of hemispheric monthly mean stratospheric potential vorticity fields

    Directory of Open Access Journals (Sweden)

    R. Huth

    Full Text Available Monthly mean NCEP reanalysis potential vorticity fields at the 650 K isentropic level over the Northern and Southern Hemispheres between 1979 and 1997 were studied using multivariate analysis tools. Principal component analysis in the T-mode was applied to demonstrate the validity of such statistical techniques for the study of stratospheric dynamics and climatology. The method, complementarily applied to both the raw and anomaly fields, was useful in determining and classifying the characteristics of winter and summer PV fields on both hemispheres, in particular, the well-known differences in the behaviour and persistence of the polar vortices. It was possible to identify such features as sudden warming events in the Northern Hemisphere and final warming dates in both hemispheres. The stratospheric impact of other atmospheric processes, such as volcanic eruptions, also identified though the results, must be viewed at this stage as tentative. An interesting change in behaviour around 1990 was detected over both hemispheres.

    Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; general circulation; climatology

  20. Les nuages de glace en arctique : mécanismes de formation

    OpenAIRE

    Jouan, Caroline

    2013-01-01

    Arctic ice cloud formation during winter is poorly understood mainly due to the lack of observations and the remoteness of this region. Yet, their influence on Northern Hemisphere weather and climate is of paramount importance, and the modification of their properties, linked to aerosol-cloud interaction processes, needs to be better understood.Large concentration of aerosols in the Arctic during winter is associated to long-range transport of anthropogenic aerosols from the mid-latitudes to ...

  1. Interannual variability of the stratospheric wave driving during northern winter

    Directory of Open Access Journals (Sweden)

    H. M. Kelder

    2007-05-01

    Full Text Available The strength of the stratospheric wave driving during northern winter is often quantified by the January–February mean poleward eddy heat flux at 100 hPa, averaged over 40°–80° N (or a similar area and period. Despite the dynamical and chemical relevance of the wave driving, the causes for its variability are still not well understood. In this study, ERA-40 reanalysis data for the period 1979–2002 are used to examine several factors that significantly affect the interannual variability of the wave driving. The total poleward heat flux at 100 hPa is poorly correlated with that in the troposphere, suggesting a decoupling between 100 hPa and the troposphere. However, the individual zonal wave-1 and wave-2 contributions to the wave driving at 100 hPa do exhibit a significant coupling with the troposphere, predominantly their stationary components. The stationary wave-1 contribution to the total wave driving significantly depends on the latitude of the stationary wave-1 source in the troposphere. The results suggest that this dependence is associated with the varying ability of stationary wave-1 activity to enter the tropospheric waveguide at mid-latitudes. The wave driving anomalies are separated into three parts: one part due to anomalies in the zonal correlation coefficient between the eddy temperature and eddy meridional wind, another part due to anomalies in the zonal eddy temperature amplitude, and a third part due to anomalies in the zonal eddy meridional wind amplitude. It is found that year-to-year variability in the zonal correlation coefficient between the eddy temperature and the eddy meridional wind is the most dominant factor in explaining the year-to-year variability of the poleward eddy heat flux.

  2. Postglacial Records of Southern Hemisphere Westerly Wind Variability From the New Zealand Subantarctic Auckland Islands

    Science.gov (United States)

    Moy, C. M.; Vandergoes, M.; Gilmer, G. J.; Nichols, J. E.; Dagg, B. J.; Wilson, G. S.; Browne, I. M.; Curtin, L. G.; Aebig, C.; McGlone, M.

    2015-12-01

    The strength and latitudinal position of the Southern Hemisphere westerly winds (SHWW) play a fundamental role in influencing mid latitude climate and carbon dioxide exchange between the Southern Ocean and the atmosphere. Despite their importance, our understanding of past changes in the SHWW is limited by few paleoclimate records from the modern wind maximum that are often not in agreement. The New Zealand subantarctic Auckland Islands are located within the core of the modern wind belt (50°S) where the ocean-atmospheric linkages between the Antarctic and middle latitudes are strong. In contrast to other subantarctic islands on the Campbell Plateau, the Auckland Islands have protected fjord sub-basins, deep lakes, and peatlands that are advantageous for the development of high-resolution paleoclimate records. We will present ongoing work towards the establishment of multi-proxy and multi-site reconstructions of past SHWW variability from the Auckland Islands. Modern process and paleoclimate results from two research cruises in 2014 and 2015 suggest that in lacustrine and fjord settings, the degree of water column mixing, the stable isotopic composition of n-alkanes and benthic foraminifera, the influx of terrestrial organic matter are good indicators of wind-induced mixing of the water column or precipitation-driven erosion within catchments. In ombrotrophic peatlands, hydrogen isotope ratios of specific organic molecules allow reconstructions of the hydrogen isotope ratios of precipitation, which is related to precipitation source area and the latitudinal position of the SHWW. Using macrofossil counts paired with abundances of leaf wax biomarkers, we are able to estimate the moisture balance at peatland coring sites. Early results indicate an overall strengthening of the SHWW at the Auckland Islands through the Holocene. We will discuss these results within the context of complimentary records developed from New Zealand and southern South America to ultimately

  3. Observations of Coastal IO Emissions on the Southern Hemisphere and Emission Potential of Different Seaweed Species

    Science.gov (United States)

    Horbanski, Martin; Schmitt, Stefan; Frieß, Udo; Pöhler, Denis; Johnston, Paul; Kreher, Karin; Robinson, Andrew D.; Thomas, Alan; Harris, Neil R. P.; Platt, Ulrich

    2014-05-01

    At coastal sites reactive iodine species emitted by seaweed in the intertidal zone during low tide are known to have an important influence on the atmospheric chemistry. However, many underlying mechanisms are presently not understood. Also coastal studies were focused on a few locations on the northern hemisphere and their predominant seaweed species laminaria digitata and ascophyllum nodosum. Therefore the spatial emission and extent of the areas where halogen chemistry is of importance needs to be much better quantified. Especially in the mid latitudes of the southern hemisphere RHS measurements are very sparse. Here we report the first observations of coastal iodine monoxide (IO) in the southern hemisphere during the HALMA/MAORI campaign which was carried out in February to March 2013 on the east coast of New Zealand's South Island at Shag Point located north of Dunedin. To detect IO we used a mobile Open Light Path Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) instrument and a stationary Long Path (LP)-DOAS Instrument, which was furthermore used to measure BrO, O3 and I2. The measurement path was positioned over the water and mainly measured air masses that only passes over submerged seaweed forests. With the CE-DOAS placed close to exposed seaweed patches (mainly Macrocystis Pyrifera) we were able to observe high IO mixing ratios of up to 50 ppt (2ppt detection limit). However, the LP-DOAS did not detect IO above the detection limit of 0.7 ppt. This is consistent with previous observations which found that seaweed only emits halogens when exposed to air. To further investigate the emission potential of the seaweed species we setup a Teflon chamber around the CE-DOAS and measured the emissions of five different species for several hours. Additionally the air in the chamber was probed by a compact gas chromatograph (μDIRAC) for measurements of halocarbons and a TEI Ozone monitor. We found very high IO mixing ratios of up to 500 ppt for

  4. GLOBAL DECREASES IN TOTAL OZONE DURING THE WINTER MONTHS

    OpenAIRE

    タカオ, トシノリ; Toshinori, TAKAO

    1990-01-01

    Global network of total ozone measurements by Dobson spectrophotometer shows ozone decrease in recent years. At midlatitudes of the Northern Hemisphere, ozone loss was significant during the winter months of 1983 and 1985. In some regions, there is a positive correlation between the annual mean of total ozone amounts and the solar cycle.

  5. Landscape: A Southern Hemisphere perspective

    Science.gov (United States)

    Squires, V. R.

    1988-12-01

    Well into the Mesozoic Era, Africa, South America, India and Australia were joined to Antarctica in one supercontinent—Gondwanaland. The northern continents were also joined to form the supercontinent Laurasia. Southern Hemisphere land masses, especially Australia, have been characterised by a long period of relative geological stability and a short period of glaciation during the Quaternary. These circumstances have led to the development of quite old landscapes, developed on surfaces subjected to the processes of weathering for millions of years. Unlike the Gondwanaland continents, much of the Northern Hemisphere has been tectonically active with orogenic processes producing young uplifted surfaces subjected to active erosion. The Northern Hemisphere has experienced four extensive and intense Pleistocene glaciations. The consequence of these periods of glaciation is that present-day landscapes are substantially the product of climate over the past 10,000 years and commonly have not undergone extensive weathering. The applicability therefore of Northern Hemisphere-derived models to explain things as diverse as landforms, stream patterns and processes, soil genesis and ecological theory in the Southern Hemisphere has increasingly come into question. Because southern landscapes have a physiography and palaeohistory quite different from that of the Northern Hemisphere, it provides an unparalleled opportunity to develop new concepts and theories which may have implications for the whole globe.

  6. The formation and evolution of Titan’s winter polar vortex

    NARCIS (Netherlands)

    Teanby, Nicholas; Bezard, Bruno; Vinatier, Sandrine; Sylvestre, Melody; Nixon, Conor; Irwin, Patrick; de Kok, R.J.; Calcutt, Simon; Flasar, Michael

    2017-01-01

    Saturn’s largest moon Titan has a substantial nitrogen-methane atmosphere, with strong seasonal effects, including formation of winter polar vortices. Following Titan’s 2009 northern spring equinox, peak solar heating moved to the northern hemisphere, initiating south-polar subsidence and winter

  7. Using causal effect networks to analyze different arctic drivers of midlatitude winter circulation

    NARCIS (Netherlands)

    Kretschmer, Marlene; Coumou, Dim; Donges, Jonathan F.; Runge, Jakob

    2016-01-01

    In recent years, the Northern Hemisphere midlatitudes have suffered from severe winters like the extreme 2012/13 winter in the eastern United States. These cold spells were linked to a meandering upper-tropospheric jet stream pattern and a negative Arctic Oscillation index (AO). However, the nature

  8. Projected Influences of Changes in Weather Severity on Autumn-Winter Distributions of Dabbling Ducks in the Mississippi and Atlantic Flyways during the Twenty-First Century.

    Directory of Open Access Journals (Sweden)

    Michael Notaro

    Full Text Available Projected changes in the relative abundance and timing of autumn-winter migration are assessed for seven dabbling duck species across the Mississippi and Atlantic Flyways for the mid- and late 21st century. Species-specific observed relationships are established between cumulative weather severity in autumn-winter and duck population rate of change. Dynamically downscaled projections of weather severity are developed using a high-resolution regional climate model, interactively coupled to a one-dimensional lake model to represent the Great Lakes and associated lake-effect snowfall. Based on the observed relationships and downscaled climate projections of rising air temperatures and reduced snow cover, delayed autumn-winter migration is expected for all species, with the least delays for the Northern Pintail and the greatest delays for the Mallard. Indeed, the Mallard, the most common and widespread duck in North America, may overwinter in the Great Lakes region by the late 21st century. This highlights the importance of protecting and restoring wetlands across the mid-latitudes of North America, including the Great Lakes Basin, because dabbling ducks are likely to spend more time there, which would impact existing wetlands through increased foraging pressure. Furthermore, inconsistency in the timing and intensity of the traditional autumn-winter migration of dabbling ducks in the Mississippi and Atlantic Flyways could have social and economic consequences to communities to the south, where hunting and birdwatching would be affected.

  9. Projected Influences of Changes in Weather Severity on Autumn-Winter Distributions of Dabbling Ducks in the Mississippi and Atlantic Flyways during the Twenty-First Century.

    Science.gov (United States)

    Notaro, Michael; Schummer, Michael; Zhong, Yafang; Vavrus, Stephen; Van Den Elsen, Lena; Coluccy, John; Hoving, Christopher

    2016-01-01

    Projected changes in the relative abundance and timing of autumn-winter migration are assessed for seven dabbling duck species across the Mississippi and Atlantic Flyways for the mid- and late 21st century. Species-specific observed relationships are established between cumulative weather severity in autumn-winter and duck population rate of change. Dynamically downscaled projections of weather severity are developed using a high-resolution regional climate model, interactively coupled to a one-dimensional lake model to represent the Great Lakes and associated lake-effect snowfall. Based on the observed relationships and downscaled climate projections of rising air temperatures and reduced snow cover, delayed autumn-winter migration is expected for all species, with the least delays for the Northern Pintail and the greatest delays for the Mallard. Indeed, the Mallard, the most common and widespread duck in North America, may overwinter in the Great Lakes region by the late 21st century. This highlights the importance of protecting and restoring wetlands across the mid-latitudes of North America, including the Great Lakes Basin, because dabbling ducks are likely to spend more time there, which would impact existing wetlands through increased foraging pressure. Furthermore, inconsistency in the timing and intensity of the traditional autumn-winter migration of dabbling ducks in the Mississippi and Atlantic Flyways could have social and economic consequences to communities to the south, where hunting and birdwatching would be affected.

  10. Winter maintenance performance measure.

    Science.gov (United States)

    2016-01-01

    The Winter Performance Index is a method of quantifying winter storm events and the DOTs response to them. : It is a valuable tool for evaluating the States maintenance practices, performing post-storm analysis, training : maintenance personnel...

  11. Concussion in Winter Sports

    Science.gov (United States)

    ... this? Submit Button Past Emails Concussion in Winter Sports Recommend on Facebook Tweet Share Compartir Get prepared ... to enjoy, practice, and compete in various winter sports. There’s no doubt that these sports are a ...

  12. The separated polar winter stratopause - A gravity wave driven climatological feature

    Science.gov (United States)

    Hitchman, Matthew H.; Gille, John C.; Rodgers, Clive D.; Brasseur, Guy

    1989-01-01

    An examination of satellite-derived temperatures reveals that the winter polar stratopause is usually elevated and warmer than the adjacent midlatitude stratopause. This separated stratopause occurs in both hemispheres, but is more pronounced and persistent in the southern winter. It descends with time towards spring and exhibits week-to-week variability. Observational diagnostics and results from a two-dimensional model suggest that gravity-wave driving can account for this separated polar stratopause by driving a meridional circulation, with downwelling over the winter pole. In the model, the solar heating pattern induces stronger winter westerlies than summer easterlies, which leads to a stronger gravity-wave-driven circulation in the winter hemisphere. Spherical geometry and the high latitude location of the winter westerly jet combine to yield a concentrated region of downwelling. Model results suggest that descent of the temperature maximum with time is probably caused by wave/mean-flow interaction.

  13. Western Hemisphere Knowledge Partnerships

    Science.gov (United States)

    Malone, T. F.

    2001-05-01

    , and application of knowledge concerning the nature of -- and interaction among -- matter, living organisms, energy, information, and human behavior. This strategy calls for innovative partnerships among the physical, biological, health, and social sciences, engineering, and the humanities. New kinds of partnership must also be forged among academia, business and industry, governments, and nongovernmental organizations. Geophysicists can play an important role in these partnerships. A focus for these partnerships is to manage the individual economic productivity that drives both human development and global change. As world population approaches stability during the twenty-first century, individual economic productivity will be the critical link between the human and the natural systems on planet Earth. AGU is among a core group of individuals and institutions proposing Western Hemisphere Knowledge Partnerships (WHKP) to test the hypothesis that knowledge, broadly construed, is an important organizing principle in choosing a path into the future. The WHKP agenda includes: (1) life-long learning, (2) the health and resilience of natural ecosystems, (3) eco-efficiency in economic production and consumption, (4) extension of national income accounts, (5) environmentally benign sources of energy, (6) delivery of health care, (7) intellectual property rights, and (8) networks for action by local communities.Collaboratories and distance education technologies will be major tools. A panel of experts will explore this proposal.

  14. SAGE III aerosol extinction validation in the Arctic winter: comparisons with SAGE II and POAM III

    Directory of Open Access Journals (Sweden)

    L. W. Thomason

    2007-01-01

    Full Text Available The use of SAGE III multiwavelength aerosol extinction coefficient measurements to infer PSC type is contingent on the robustness of both the extinction magnitude and its spectral variation. Past validation with SAGE II and other similar measurements has shown that the SAGE III extinction coefficient measurements are reliable though the comparisons have been greatly weighted toward measurements made at mid-latitudes. Some aerosol comparisons made in the Arctic winter as a part of SOLVE II suggested that SAGE III values, particularly at longer wavelengths, are too small with the implication that both the magnitude and the wavelength dependence are not reliable. Comparisons with POAM III have also suggested a similar discrepancy. Herein, we use SAGE II data as a common standard for comparison of SAGE III and POAM III measurements in the Arctic winters of 2002/2003 through 2004/2005. During the winter, SAGE II measurements are made infrequently at the same latitudes as these instruments. We have mitigated this problem through the use of potential vorticity as a spatial coordinate and thus greatly increased of the number of coincident events. We find that SAGE II and III extinction coefficient measurements show a high degree of compatibility at both 1020 nm and 450 nm except a 10–20% bias at both wavelengths. In addition, the 452 to 1020 nm extinction ratio shows a consistent bias of ~30% throughout the lower stratosphere. We also find that SAGE II and POAM III are on average consistent though the comparisons show a much higher variability and larger bias than SAGE II/III comparisons. In addition, we find that SAGE II and POAM III data sets are not well correlated at and below 18 km. Overall, we find both the extinction values and the spectral dependence from SAGE III are robust and we find no evidence of a significant defect within the Arctic vortex.

  15. Mother Knows Best: Occurrence and Associations of Resighted Humpback Whales Suggest Maternally Derived Fidelity to a Southern Hemisphere Coastal Feeding Ground

    Science.gov (United States)

    Barendse, Jaco; Best, Peter B.; Carvalho, Inês; Pomilla, Cristina

    2013-01-01

    Site fidelity is common among migratory cetaceans, including humpback whales (Megaptera novaeangliae). In the Northern Hemisphere it has been found that fidelity to humpback whale feeding grounds is transferred maternally but this has never been shown for the species in the Southern Hemisphere. We examined this in a unique feeding area off west South Africa using resighting data of 68 individually identified humpback whales by means of photographic (tail flukes and dorsal fins) and/or molecular methods (microsatellite genotyping) over an 18 year span. We found short-term association patterns and recurrent visits typical of other feeding grounds. Males and females had different seasonality of attendance. Significant female-dominated presence corresponded to timing of an expected influx of females on their southward migration from the breeding ground: firstly non-nursing (possibly pregnant) females in mid-spring, and mothers and calves in mid-to late summer. The potential benefit of this mid-latitude feeding area for females is illustrated by a record of a cow with known age of at least 23 years that produced calves in three consecutive years, each of which survived to at least six months of age: the first record of successful post-partum ovulation for this species in the Southern Hemisphere. We recorded association of a weaned calf with its mother, and a recurring association between a non-lactating female and male over more than two years. Moreover, three animals first identified as calves returned to the same area in subsequent years, sometimes on the same day as their mothers. This, together with numerous Parent-Offspring relations detected genetically among and between resighted and non-resighted whales is strongly suggestive of maternally derived site fidelity at a small spatial scale by a small sub-population of humpback whales. PMID:24349047

  16. Mother knows best: occurrence and associations of resighted humpback whales suggest maternally derived fidelity to a Southern Hemisphere coastal feeding ground.

    Science.gov (United States)

    Barendse, Jaco; Best, Peter B; Carvalho, Inês; Pomilla, Cristina

    2013-01-01

    Site fidelity is common among migratory cetaceans, including humpback whales (Megaptera novaeangliae). In the Northern Hemisphere it has been found that fidelity to humpback whale feeding grounds is transferred maternally but this has never been shown for the species in the Southern Hemisphere. We examined this in a unique feeding area off west South Africa using resighting data of 68 individually identified humpback whales by means of photographic (tail flukes and dorsal fins) and/or molecular methods (microsatellite genotyping) over an 18 year span. We found short-term association patterns and recurrent visits typical of other feeding grounds. Males and females had different seasonality of attendance. Significant female-dominated presence corresponded to timing of an expected influx of females on their southward migration from the breeding ground: firstly non-nursing (possibly pregnant) females in mid-spring, and mothers and calves in mid-to late summer. The potential benefit of this mid-latitude feeding area for females is illustrated by a record of a cow with known age of at least 23 years that produced calves in three consecutive years, each of which survived to at least six months of age: the first record of successful post-partum ovulation for this species in the Southern Hemisphere. We recorded association of a weaned calf with its mother, and a recurring association between a non-lactating female and male over more than two years. Moreover, three animals first identified as calves returned to the same area in subsequent years, sometimes on the same day as their mothers. This, together with numerous Parent-Offspring relations detected genetically among and between resighted and non-resighted whales is strongly suggestive of maternally derived site fidelity at a small spatial scale by a small sub-population of humpback whales.

  17. Mother knows best: occurrence and associations of resighted humpback whales suggest maternally derived fidelity to a Southern Hemisphere coastal feeding ground.

    Directory of Open Access Journals (Sweden)

    Jaco Barendse

    Full Text Available Site fidelity is common among migratory cetaceans, including humpback whales (Megaptera novaeangliae. In the Northern Hemisphere it has been found that fidelity to humpback whale feeding grounds is transferred maternally but this has never been shown for the species in the Southern Hemisphere. We examined this in a unique feeding area off west South Africa using resighting data of 68 individually identified humpback whales by means of photographic (tail flukes and dorsal fins and/or molecular methods (microsatellite genotyping over an 18 year span. We found short-term association patterns and recurrent visits typical of other feeding grounds. Males and females had different seasonality of attendance. Significant female-dominated presence corresponded to timing of an expected influx of females on their southward migration from the breeding ground: firstly non-nursing (possibly pregnant females in mid-spring, and mothers and calves in mid-to late summer. The potential benefit of this mid-latitude feeding area for females is illustrated by a record of a cow with known age of at least 23 years that produced calves in three consecutive years, each of which survived to at least six months of age: the first record of successful post-partum ovulation for this species in the Southern Hemisphere. We recorded association of a weaned calf with its mother, and a recurring association between a non-lactating female and male over more than two years. Moreover, three animals first identified as calves returned to the same area in subsequent years, sometimes on the same day as their mothers. This, together with numerous Parent-Offspring relations detected genetically among and between resighted and non-resighted whales is strongly suggestive of maternally derived site fidelity at a small spatial scale by a small sub-population of humpback whales.

  18. Widespread land surface wind decline in the Northern Hemisphere

    Science.gov (United States)

    Vautard, R.; Cattiaux, J.; Yiou, P.; Thépaut, J.-N.; Ciais, P.

    2010-09-01

    The decline of surface wind observed in many regions of the world is a potential source of concern for wind power electricity generation. It is also suggested as the main cause of decreasing pan evaporation. In China, a persistent and significant decrease of monsoon winds was observed in all seasons. Surface wind declines were also evidenced in several regions of the world (U.S., Australia, several European countries). Except over China, no clear explanation was given for the wind decrease in the regions studied. Whether surface winds decrease is due to changes in the global atmospheric circulation or its variability, in surface processes or to observational trends has therefore not been elucidated. The identification of the drivers of such a decline requires a global investigation of available surface and upper-air wind data, which has not been conducted so far. Here we use global datasets of in-situ wind measurements that contain surface weather stations wind data (hourly or three-hourly data acquisition time step) and rawinsonde vertical wind data profiles (monthly time step) prepared by the NCAR. A set of 822 worldwide surface stations with continuous wind records was selected after a careful elimination of stations with obvious breaks and large gaps. This dataset mostly covers the Northern mid latitudes over the period 1979-2008. Using this data set, we found that annual mean wind speeds have declined at 73% of the surface stations over the past 30 years. In the Northern Hemisphere, positive wind trends are found only in a few places. In Europe, Central Asia, Eastern Asia and in North America the annual mean surface wind speed has decreased on average at a rate of -2.9, -5.9, -4.2, and -1.8 %/decade respectively, i.e. a decrease of about 10% in 30 years and up to about 20% in Central Asia. These results are robust to changes in the station selection method and parameters. By contrast, upper-air winds observed from rawinsondes, geostrophic winds deduced from

  19. Dependence of thermospheric zonal winds on solar flux, geomagnetic activity, and hemisphere as measured by CHAMP

    Science.gov (United States)

    Zhang, Xiaofang; Liu, Libo; Liu, Songtao

    2017-08-01

    The thermospheric zonal winds measured by the CHAllenging Minisatellite Payload (CHAMP) satellite are used to statistically determine the climatology under quiet and active geomagnetic conditions. By collectively analyzing the bin-averaged wind trend with F10.7 and the solar-induced difference in wind structures, the solar flux dependence of global thermosphere zonal wind is determined. The increase of solar flux enhances the eastward winds at low latitudes from dusk to midnight. The increased ion drag reduces the nighttime eastward wind in the subauroral latitudes, and the daytime westward winds from 06 to 08 MLT at all latitudes decrease with increasing solar flux. Zonal winds show coupled seasonal/extreme ultraviolet (EUV) dependency. The equatorial zonal winds from 18 to 04 magnetic local time (MLT) indicate weaker eastward winds during the June solstice at high solar flux levels. Quiet time eastward winds at subauroral latitudes from 16 to 20 MLT are further decreased in the winter hemisphere. Influenced by asymmetries in solar illumination and the magnetic field, zonal winds show hemispheric asymmetries. Quiet daytime winds are additionally influenced by solar illumination effects, and the westward winds at the middle and subauroral latitudes are always stronger in the summer. The nighttime eastward winds are higher in the winter hemisphere during the solstices, as in the Southern Hemisphere during equinoxes, with the winter-summer asymmetry lessened or receding at the solar maxima. Storm-induced subauroral westward disturbance winds are higher in the summer hemisphere and in the Northern Hemisphere during equinoxes. At a high level of solar flux, the westward disturbance winds are comparable in the two hemispheres during December solstice. Geomagnetic disturbance wind observations from CHAMP agree well with the empirical geomagnetic disturbance wind model, except for stronger subauroral westward jets. Westward winds during the afternoon may be enhanced in

  20. Winters fuels report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-10-27

    The outlook for distillate fuel oil this winter is for increased demand and a return to normal inventory patterns, assuming a resumption of normal, cooler weather than last winter. With industrial production expected to grow slightly from last winter`s pace, overall consumption is projected to increase 3 percent from last winter, to 3.4 million barrels per day during the heating season (October 1, 1995-March 31, 1996). Much of the supply win come from stock drawdowns and refinery production. Estimates for the winter are from the Energy Information Administration`s (EIA) 4th Quarter 1995 Short-Tenn Energy Outlook (STEO) Mid-World Oil Price Case forecast. Inventories in place on September 30, 1995, of 132 million barrels were 9 percent below the unusually high year-earlier level. Inventories of high-sulfur distillate fuel oil, the principal type used for heating, were 13 percent lower than a year earlier. Supply problems are not anticipated because refinery production and the ready availability of imports should be adequate to meet demand. Residential heating off prices are expected to be somewhat higher than last winter`s, as the effects of lower crude oil prices are offset by lower distillate inventories. Heating oil is forecast to average $0.92 per gallon, the highest price since the winter of 1992-93. Diesel fuel (including tax) is predicted to be slightly higher than last year at $1.13 per gallon. This article focuses on the winter assessment for distillate fuel oil, how well last year`s STEO winter outlook compared to actual events, and expectations for the coming winter. Additional analyses include regional low-sulfur and high-sulfur distillate supply, demand, and prices, and recent trends in distillate fuel oil inventories.

  1. Multi-timescale variation of East Asian winter monsoon intensity and its relation with sea surface temperature during last millennium based on ECHO-G simulation

    Science.gov (United States)

    Xueyuan, Kuang; Jian, Liu; Yaocun, Zhang; Danqing, Huang; Ying, Huang

    2011-11-01

    Based on the simulation results derived from ECHO-G global coupled climate model, several East Asian winter monsoon (EAWM) indices are compared in order to choose the most suitable one for signaling the intensity of winter monsoon in the last millennium. The index I_shi, which is defined with normalized sea level pressure difference between sea and land in mid and low latitudes, is selected to describe the winter monsoon intensity variation owing to its better capability for reflecting the variation of winter monsoon subsystems, such as the continental high pressure, Aleutian low, East Asian major trough, westerly jet stream, and surface air temperature than the other indices examined. Wavelet analysis on index I_shi shows that the EAWM intensity is characterized by multi-timescale variation with inter-annual, decadal, inter-decadal and inter-centennial oscillations on the background of a slight descending trend. Correlation analysis between the EAWM index and sea surface temperature (SST) at various timescales reveals that the SST in mid-latitudes might provide the background of the EAWM strength changes above decadal timescales, and a negative-feedback process lasting for about two years is found between the EAWM intensity and the SST in the eastern equatorial Pacific. According to the correlation, the El Nino occurrence in the second-half of the year leads to weaker EAWM than normal in the following winter and the weakened EAWM corresponds to lower SST in eastern equatorial Pacific after about half a year, which will then strengthen the EAWM intensity in the next winter. It is a stable feedback process and its mechanism is discussed.

  2. Hemispheric ultra-wideband antenna.

    Energy Technology Data Exchange (ETDEWEB)

    Brocato, Robert Wesley

    2006-04-01

    This report begins with a review of reduced size ultra-wideband (UWB) antennas and the peculiar problems that arise when building a UWB antenna. It then gives a description of a new type of UWB antenna that resolves these problems. This antenna, dubbed the hemispheric conical antenna, is similar to a conventional conical antenna in that it uses the same inverted conical conductor over a ground plane, but it also uses a hemispheric dielectric fill in between the conductive cone and the ground plane. The dielectric material creates a fundamentally new antenna which is reduced in size and much more rugged than a standard UWB conical antenna. The creation of finite-difference time domain (FDTD) software tools in spherical coordinates, as described in SAND2004-6577, enabled this technological advance.

  3. Individual Differences in Hemispheric Specialization

    Science.gov (United States)

    1987-11-01

    cerebral dominance, slnlstrallty and psychosis . In: Gruzeller, J. & Flor-Henry, P. (Lds.) Hemisphere Asymmetries of Function In...Chapman, L., Numbers, J. and McFall, R. (1979). Relation of social competence to scores on two scales of psychosis proneness...233-236. ’ Rado, S. (1956). Psychoanalysis of Behavior: Collected Papers. New York: ; \\. *. v .-vvvJ >’..’>’, «< ■V

  4. Brain Hemispheric Functions and the Native American.

    Science.gov (United States)

    Ross, Allen Chuck

    1982-01-01

    Uses brain research conducted by Dr. Roger Sperry to show that traditional Native Americans are more dominant in right hemisphere thinking, setting them apart from a modern left hemisphere-oriented society (especially emphasized in schools). Describes some characteristics of Native American thinking that illustrate a right hemisphere orientation…

  5. Right Hemisphere Dominance in Visual Statistical Learning

    Science.gov (United States)

    Roser, Matthew E.; Fiser, Jozsef; Aslin, Richard N.; Gazzaniga, Michael S.

    2011-01-01

    Several studies report a right hemisphere advantage for visuospatial integration and a left hemisphere advantage for inferring conceptual knowledge from patterns of covariation. The present study examined hemispheric asymmetry in the implicit learning of new visual feature combinations. A split-brain patient and normal control participants viewed…

  6. The message, meteorology and myths of the historic West Coast winter flooding of 1861 - 62

    Science.gov (United States)

    Schick, L. J.

    2012-12-01

    The greatest known recorded flooding, ever to impact the West Coast of the United States, occurred during the winter of 1861-1862. In fact, the extraordinary flood flows on five major rivers, remain the record peaks to this day. The flooding was caused by a series of Pacific mid-latitude cyclones and several strong atmospheric rivers. The extreme rainy pattern initially strikes Oregon. The high water causes the flood of record on the Willamette River, with extensive devastation, wiping out several major towns along the river. Communications, food and supplies were cut off for much of the winter in Oregon.The intense wet weather, then redevelops, moves south and stalls - pummeling Northern California with major flooding. The runoff fills California's Central Valley with a huge inland lake. Sacramento is submerged, turned into what was described as a "frontier Venice". Flood damages eliminate a large part of the state's tax base.Finally the stormy pattern shifts into Southern California, producing major flooding. Most of lowland Los Angeles, Orange and San Diego Counties are flooded under several feet of water for weeks.The author researched limited weather data, historical accounts, maps and ship reports to reconstruct this series of storms and their effects along the West Coast. The extent and evolution of this series of flood events is unprecedented. Myths regarding the causes of this flooding are common, but its sheer magnitude is undisputable. This presentation will also demonstrate the nature and impacts of these consecutive major flood events, while revealing the lessons to be learned in light of advances in modern forecasting techniques.

  7. Stratospheric warming in Southern Hemisphere high latitudes since 1979

    Directory of Open Access Journals (Sweden)

    Y. Hu

    2009-07-01

    Full Text Available In the present study, we show evidence of significant stratospheric warming over Southern Hemisphere high latitudes and large portions of the Antarctic polar region in winter and spring seasons, with a maximum warming of 7–8°C in September and October, using satellite Microwave Sounding Unit observations for 1979–2006. It is found that this warming is associated with increasing wave activity from the troposphere into the stratosphere, suggesting that the warming is caused by enhanced wave-driven adiabatic heating. We show that the stratospheric warming in Southern Hemisphere high latitudes has close correlations with sea surface temperature (SST increases, and that general circulation model simulations forced with observed time-varying SSTs reproduce similar warming trend patterns in the Antarctic stratosphere. The simulated stratospheric warming is closely related to increasing wave activity in the Southern Hemisphere. These findings suggest that the stratospheric warming is likely induced by SST warming. As SST warming continues as a consequence of greenhouse gas increases due to anthropogenic activity, the stratospheric warming would also continue, which has important implications to the recovery of the Antarctic ozone hole.

  8. Mid-winter Waterfowl Survey

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Mid-winter Waterfowl Survey is a nationwide effort to survey waterfowl in areas of major concentration on their wintering grounds and provide winter distribution...

  9. Nuclear Winter: Implications for civil defense

    Energy Technology Data Exchange (ETDEWEB)

    Chester, C.V.; Perry, A.M.; Hobbs, B.F.

    1988-05-01

    ''Nuclear Winter'' is the term given to the cooling hypothesized to occur in the Northern Hemisphere following a nuclear war as the result of the injection of smoke from burning cities into the atmosphere. The voluminous literature on this subject produced since the paper was published in 1983 by Turco, Toon, Ackerman, Pollack, and Sagen (TTAPS) has been reviewed. Three-dimensional global circulation models have resulted in reduced estimates of cooling---15 to 25/degree/C for a summer war and a few degrees for a winter war. More serious may be the possibility of suppression of convective precipitation by the altered temperature profiles in the atmosphere. However, very large uncertainties remain in input parameters, the models, and the results of calculations. We believe the state of knowledge about nuclear winter is sufficiently developed to conclude: Neither cold nor drought is likely to be a direct threat to human survival for populations with the wherewithal to survive normal January temperatures. The principal threat from nuclear winter is to food production, and this could present problems to third parties who are without food reserves. Loss of a crop year is neither a new nor an unexpected threat from nuclear war to the United States and the Soviet Union. Both have at least a year's food reserve at all times. Both face formidable organizational problems in distributing their reserves in a war-damaged environment. The consequences of nuclear winter could be expected to fall more heavily on the Soviet Union than the United States due to its higher latitude and less productive agriculture. This may be especially true if disturbances of rainfall amounts and distribution persist for more than a year.

  10. Impact of declining Arctic sea ice on winter snowfall.

    Science.gov (United States)

    Liu, Jiping; Curry, Judith A; Wang, Huijun; Song, Mirong; Horton, Radley M

    2012-03-13

    While the Arctic region has been warming strongly in recent decades, anomalously large snowfall in recent winters has affected large parts of North America, Europe, and east Asia. Here we demonstrate that the decrease in autumn Arctic sea ice area is linked to changes in the winter Northern Hemisphere atmospheric circulation that have some resemblance to the negative phase of the winter Arctic oscillation. However, the atmospheric circulation change linked to the reduction of sea ice shows much broader meridional meanders in midlatitudes and clearly different interannual variability than the classical Arctic oscillation. This circulation change results in more frequent episodes of blocking patterns that lead to increased cold surges over large parts of northern continents. Moreover, the increase in atmospheric water vapor content in the Arctic region during late autumn and winter driven locally by the reduction of sea ice provides enhanced moisture sources, supporting increased heavy snowfall in Europe during early winter and the northeastern and midwestern United States during winter. We conclude that the recent decline of Arctic sea ice has played a critical role in recent cold and snowy winters.

  11. On the discrepancy between observed and CMIP5 multi-model simulated Barents Sea winter sea ice decline

    OpenAIRE

    Li, Dawei; Zhang, Rong; Knutson, Thomas R.

    2017-01-01

    This study aims to understand the relative roles of external forcing versus internal climate variability in causing the observed Barents Sea winter sea ice extent (SIE) decline since 1979. We identify major discrepancies in the spatial patterns of winter Northern Hemisphere sea ice concentration trends over the satellite period between observations and CMIP5 multi-model mean externally forced response. The CMIP5 externally forced decline in Barents Sea winter SIE is much weaker than that obse...

  12. Winter Bottom Trawl Survey

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The standardized NEFSC Winter Bottom Trawl Survey was initiated in 1992 and covered offshore areas from the Mid-Atlantic to Georges Bank. Inshore strata were covered...

  13. Deer Wintering Areas

    Data.gov (United States)

    Vermont Center for Geographic Information — Deer winter habitat is critical to the long term survival of white-tailed deer (Odocoileus virginianus) in Vermont. Being near the northern extreme of the...

  14. Multiple flow regimes in the Northern Hemisphere winter. I - Methodology and hemispheric regimes. II - Sectorial regimes and preferred transitions

    Science.gov (United States)

    Kimoto, Masahide; Ghil, Michael

    1993-01-01

    Multivariate pdfs in the phase space of large-scale atmospheric motions are examined in order to identify recurrent and persistent flow patterns. The extent to which intraseasonal variablity can be described and understood in terms of multiple flow regimes is clarified. It is shown that the synoptically intriguing and statistically significant inhomogeneities exhibited by the 2D phase plane on the periphery of the distribution are due to the existence of persistent and recurrent anomaly patterns. It is argued that these inhomgeneities are obscured when PDFs are examined in a smaller-dimensional subspace than dynamically desired. A synoptic characterization of onsets and breaks for the flow regimes is given by compositing. In situ evolutions of anomaly patterns, slow westward shifts of high-latitude anomaly centers, and successive downstream increase of anomaly magnitudes are the typical signatures of such events.

  15. Enhanced short-term stratospheric ozone fluctuations observed by the GROMOS microwave radiometer during winter at Bern

    Science.gov (United States)

    Moreira, Lorena; Hocke, Klemens; Kämpfer, Niklaus

    2017-04-01

    The ground-based millimeter wave ozone spectrometer (GROMOS) has been continually measuring stratospheric and lower mesospheric ozone volume mixing ratio (VMR) profiles above Bern, Switzerland (46.95°N, 7.44°E, 577 m) since 1994. The high temporal resolution of GROMOS (30 minutes) allows the analysis of short-term fluctuations. The present study analyses the temporal perturbations, ranging from 1 to 4 hours, observed in stratospheric ozone from June 2011 to May 2012. We observe an increase in mid- and upper stratospheric ozone fluctuations of about 0.05 ppm or 0.9% from December to January. The strongest variations of stratospheric ozone above Bern are due to displacements of the polar vortex to mid-latitudes, related with sudden stratospheric warming (SSW) events and produced by breaking of planetary Rossby waves. The breaking of planetary waves and the disruptions of the polar vortex edge can also generate fluctuations in stratospheric ozone, for instance the so-called stratospheric streamers. The increase of inertia-gravity wave activity at the polar vortex edge during these SSW events can also be related with the short-term fluctuations observed in mid- and upper stratospheric ozone during winter.

  16. Geologic map of Southern Hemisphere

    Energy Technology Data Exchange (ETDEWEB)

    Mills, R.A.

    1982-01-01

    A surface geologic map of the Southern Hemisphere should be useful to geologists and geophysicists studying continental drift and petroleum exploration because it relates Antarctic geology to the other continents. The most dominant feature appears to be the Transantarctic lineament that ties with the South American Andes and, to a lesser degree, with tectonic elements in eastern Australia. From the rocks exposed, it appears that Gondwanaland may have broken up during early Paleozoic time, and then the hemisphere remained stable until the end of Jurassic time when the existence of widespread volcanic rocks suggests that further rifting took place. During early Tertiary time, drifting was renewed and it more or less continued until recent time. Several island arcs and deep trenches indicate that rifting is still active today. There appears to be a significant west-to-east drift of crustal material at the far southern latitudes corresponding to the circum-polar ocean currents. Offshore petroleum prospects are related to the age of the continental margins as determined by continental drift, i.e. the trailing edges of the continents have the most mature basins beginning with coastal plain sequences that are prograded over isostatically sinking margins. Thick sedimentary columns which began to form in the Mesozoic include reef facies and diapirs. There are exceptions to this model, and various offshore petroleum basins are described with emphasis on the exposed coastal plain morphology as providing the dominant indicator for large reserves.

  17. Fluorescence polarization study of lipids and membranes prepared from brain hemispheres of a hibernating mammal.

    Science.gov (United States)

    Montaudon, D; Robert, J; Canguilhem, B

    1984-02-29

    The physical behavior of total lipids, microsomes and microsomal lipids prepared from brain hemispheres of European Hamsters (Cricetus cricetus) was approached by the measure of the fluorescence polarization of the probe 1,6-diphenyl 1,3,5-hexatriene. We compare in this study the results obtained for two critical periods for a hibernator: winter (torpid state) and summer (active state). An increase in fluidity was noticed in the winter lipid and membrane preparations. The difference was however of very low magnitude, suggesting that only the microenvironment of some proteins was involved, rather than the bulk membrane fluidity.

  18. Psychological sexual identity and hemispheric orientation.

    Science.gov (United States)

    Hirschman, E C

    1983-04-01

    The study examines gender and psychological sexual identity as alternative bases for the development of hemispheric orientation. Hypotheses anticipated that females place greater reliance upon right hemisphere functions, such as imagery and emotion, whereas males place more emphasis upon left hemisphere functions, such as logical reasoning. This was extended to an examination of the roles of masculinity and femininity within genders upon hemispheric orientation. With a sample of 219 male and 221 female adults, it was found that the male-left hemisphere orientation/female-right hemisphere orientation dichotomy was supported in part. However, this relationship appears to be moderated by a second dimension: females appear more internally oriented, males more externally oriented.

  19. [Long-term outcome after hemispheric disconnection].

    Science.gov (United States)

    Bulteau, C; Dorfmüller, G; Fohlen, M; Jalin, C; Oliver, M-V; Delalande, O

    2008-05-01

    Hemispheric disconnection has been largely proposed for patients with severe epilepsy associated with a congenital or acquired hemispheric cerebral pathology. The classical procedure of anatomical hemispherectomy was progressively abandoned by neurosurgeons in order to avoid postoperative complications since then hemispherotomy techniques have been developed. Globally, with hemispheric disconnection, the rate of patients becoming seizure-free has been between 50 and 80%. The factors affecting seizure control have not been completely elucidated, but several authors suggested that differences in etiology as well as the hemispheric disconnection technique used may partially explain this variability. The percentage of seizure-free patients is higher with hemispherotomy techniques and in the group of patients with Rasmussen encephalitis, Sturge-Weber syndrome, and vascular insults. Depending on overall long-term progression, there is an improvement compared to preoperative status even if children exhibit heterogenous abilities. The lowest scores are observed for motor skills but communication and socialization are relatively well-preserved and strongly related to the duration of epilepsy: the longer the duration, the lower the scores were. Neuropsychological outcome following hemispheric disconnection makes it possible to study the development of hemispheric specialization during infancy and to provide information on cognitive recovery. Cerebral reorganization has been proved to exist in motor and language recovery. Ipsilateral corticospinal pathways seem to be involved in the movement of hemiplegic limbs. Everyday language can be supported by both hemispheres, but there is an early hemispheric specialization of the left hemisphere according to metaphonologic abilities.

  20. Global distribution of winter lightning: a threat to wind turbines and aircraft

    Science.gov (United States)

    Montanyà, Joan; Fabró, Ferran; van der Velde, Oscar; March, Víctor; Rolfe Williams, Earle; Pineda, Nicolau; Romero, David; Solà, Glòria; Freijo, Modesto

    2016-06-01

    Lightning is one of the major threats to multi-megawatt wind turbines and a concern for modern aircraft due to the use of lightweight composite materials. Both wind turbines and aircraft can initiate lightning, and very favorable conditions for lightning initiation occur in winter thunderstorms. Moreover, winter thunderstorms are characterized by a relatively high production of very energetic lightning. This paper reviews the different types of lightning interactions and summarizes the well-known winter thunderstorm areas. Until now comprehensive maps of global distribution of winter lightning prevalence to be used for risk assessment have been unavailable. In this paper we present the global winter lightning activity for a period of 5 years. Using lightning location data and meteorological re-analysis data, six maps are created: annual winter lightning stroke density, seasonal variation of the winter lightning and the annual number of winter thunderstorm days. In the Northern Hemisphere, the maps confirmed Japan to be one of the most active regions but other areas such as the Mediterranean and the USA are active as well. In the Southern Hemisphere, Uruguay and surrounding area, the southwestern Indian Ocean and the Tasman Sea experience the highest activity. The maps provided here can be used in the development of a risk assessment.

  1. The formation and evolution of Titan's winter polar vortex.

    Science.gov (United States)

    Teanby, Nicholas A; Bézard, Bruno; Vinatier, Sandrine; Sylvestre, Melody; Nixon, Conor A; Irwin, Patrick G J; de Kok, Remco J; Calcutt, Simon B; Flasar, F Michael

    2017-11-21

    Saturn's largest moon Titan has a substantial nitrogen-methane atmosphere, with strong seasonal effects, including formation of winter polar vortices. Following Titan's 2009 northern spring equinox, peak solar heating moved to the northern hemisphere, initiating south-polar subsidence and winter polar vortex formation. Throughout 2010-2011, strengthening subsidence produced a mesospheric hot-spot and caused extreme enrichment of photochemically produced trace gases. However, in 2012 unexpected and rapid mesospheric cooling was observed. Here we show extreme trace gas enrichment within the polar vortex dramatically increases mesospheric long-wave radiative cooling efficiency, causing unusually cold temperatures 2-6 years post-equinox. The long time-frame to reach a stable vortex configuration results from the high infrared opacity of Titan's trace gases and the relatively long atmospheric radiative time constant. Winter polar hot-spots have been observed on other planets, but detection of post-equinox cooling is so far unique to Titan.

  2. Hemispheric asymmetries: The comparative view

    Directory of Open Access Journals (Sweden)

    Sebastian eOcklenburg

    2012-01-01

    Full Text Available Hemispheric asymmetries play an important role in almost all cognitive functions. For more than a century, they were considered to be uniquely human but now an increasing number of findings in all vertebrate classes make it likely that we inherited our asymmetries from common ancestors. Thus, studying animal models could provide unique insights into the mechanisms of lateralization. We outline three such avenues of research by providing an overview of experiments on left-right differences in the connectivity of sensory systems, the embryonic determinants of brain asymmetries, and the genetics of lateralization. All these lines of studies could provide a wealth of insights into our own asymmetries that should and will be exploited by future analyses.

  3. Reconstructing Holocene changes in the Southern Hemisphere westerly winds: Integrating modern processes and paleoclimate data from New Zealand's southern fjords

    Science.gov (United States)

    Hinojosa, J.; Moy, C. M.; Wilson, G. S.; Stirling, C. H.

    2013-12-01

    The Southern Hemisphere westerly winds are an important component of the global carbon cycle due to their influence on Southern Ocean CO2 flux. In addition, the winds influence mid-latitude storm tracks, thereby controlling moisture balance over much of New Zealand's South Island and other Southern Hemisphere regions. Fiordland, New Zealand is an ideal locale to investigate Holocene changes in westerly wind behavior: It sits at the northern margin of the wind field maximum, is sensitive to latitudinal and strength fluctuations of the winds, and is the location of numerous fjord sub-basins with high sedimentation rates (up to 3 mm/yr). Due to the strong positive relationship between wind speed and regional rainfall, reconstructions of past precipitation and fjord circulation can inform us of past westerly wind behavior. These processes can be observed through changes in the rate of organic carbon delivery from land: When precipitation is high, more terrestrial organic carbon is delivered to the fjords, while low precipitation shifts the balance toward accumulation of marine organic carbon. An important first step towards reconstructing past westerly wind variability is to characterize the distribution and cycling of carbon throughout different depositional settings in the fjords to determine the optimal location for the development of paleoclimate records. Here, we present a geochemical characterization of surface sediments and the water column throughout the region and apply this understanding to sediment cores. During three field seasons in 2012 and 2013, we collected surface sediments, particulate organic matter, and piston cores from 10 different fjords spanning 44-46° S. Our results suggest that organic carbon in the fjord basins largely follows a two-end-member mixing model, drawing from marine and terrestrial end-member sources. We see consistent down-fjord trends in carbon and nitrogen concentrations and isotopes measured from surface sediments and

  4. Dynamics of Venus' Southern hemisphere and South Polar Vortex from VIRTIS data obtained during the Venus Expres Mission

    Science.gov (United States)

    Hueso, R.; Garate-Lopez, I.; Sanchez-Lavega, A.

    2011-12-01

    The VIRTIS instrument onboard Venus Express observes Venus in two channels (visible and infrared) obtaining spectra and multi-wavelength images of the planet. The images have been used to trace the motions of the atmosphere at different layers of clouds [1-3]. We review the VIRTIS cloud image data and wind results obtained by different groups [1-3] and we present new results concerning the morphology and evolution of the South Polar Vortex at the upper and lower cloud levels with data covering the first 900 days of the mission. We present wind measurements of the South hemisphere obtained by cloud tracking individual cloud features and higher-resolution wind results of the polar region covering the evolution of the South polar vortex. The later were obtained by an image correlation algorithm run under human supervision to validate the data. We present day-side data of the upper clouds obtained at 380 and 980 nm sensitive to altitudes of 66-70 km, night-side data in the near infrared at 1.74 microns of the lower cloud (45-50 km) and day and night-side data obtained in the thermal infrared (wavelengths of 3.8 and 5.1 microns) which covers the dynamical evolution of Venus South Polar vortex at the cloud tops (66-70 km). We explore the different dynamics associated to the varying morphology of the vortex, its dynamical structure at different altitudes, the variability of the global wind data of the southern hemisphere and the interrelation of the polar vortex dynamics with the wind dynamics at subpolar and mid-latitudes. Acknowledgements: Work funded by Spanish MICIIN AYA2009-10701 with FEDER support and Grupos Gobierno Vasco IT-464-07. References [1] A. Sánchez-Lavega et al., Geophys. Res. Lett. 35, L13204, (2008). [2] D. Luz et al., Science, 332, 577-580 (2011). [3] R. Hueso, et al., Icarus doi:10.1016/j.icarus.2011.04.020 (2011)

  5. Homotopic Language Reorganization in the Right Hemisphere after Early Left Hemisphere Injury

    Science.gov (United States)

    Tivarus, Madalina E.; Starling, Sarah J.; Newport, Elissa L.; Langfitt, John T.

    2012-01-01

    To determine the areas involved in reorganization of language to the right hemisphere after early left hemisphere injury, we compared fMRI activation patterns during four production and comprehension tasks in post-surgical epilepsy patients with either left (LH) or right hemisphere (RH) speech dominance (determined by Wada testing) and healthy…

  6. An overview of reactive chlorine measurements during the WINTER C-130 aircraft campaign

    Science.gov (United States)

    Thornton, J. A.; Lopez-Hilfiker, F.; Lee, B. H.; Jaegle, L.; Haskins, J.; Shah, V.; Brown, S. S.; Fibiger, D. L.; McDuffie, E. E.; Veres, P. R.; Dibb, J. E.; Sparks, T.; Ebben, C. J.; Cohen, R. C.; Sullivan, A.; Guo, H.; Weber, R. J.; Schroder, J. C.; Campuzano-Jost, P.; Day, D. A.; Jimenez, J. L.; Campos, T. L.; Weinheimer, A. J.; Apel, E. C.; Blake, N. J.

    2015-12-01

    As part of the Wintertime Investigation of Transport, Emissions, and Reactivity (WINTER) campaign, the University of Washington Iodide-adduct high resolution time of flight chemical ionization mass spectrometer (HRToF-CIMS) was deployed aboard the NSF/NCAR C-130 aircraft. Calibrated measurements of ClNO2, Cl2, HCl, N2O5, HNO3, HONO, among several other compounds, were made at 2Hz on all 13 research flights. ClNO2 and HCl were often the dominant forms of reactive gas-phase chlorine compounds, with ClNO2 routinely reaching >1.5 ppb in the polluted outflow of the eastern U.S. urban corridor. ClNO2 often becomes a substantial fraction (~30%) of NOz (NOz = NOy - NOx) in these plumes at night. Preliminary analyses suggests that ClNO2 production is most efficient in the polluted marine boundary layer, with yields approaching unity and the evolution of nighttime ClNO2 highly correlated with that of HNO3 and particulate nitrate. However, ClNO2 production was observed throughout the region and a significant source of reactive chlorine from coal-fired power plants was directly confirmed with measurements of HCl strongly correlated with SO2. In addition, there is some evidence that biomass or biofuel combustion is a source of reactive chlorine that can lead to ClNO2 production. Examples of the nocturnal and diel evolution of reactive chlorine species are given, and we show to our knowledge the first measurements of chlorine nitrate (ClONO2) in the polluted mid-latitude marine boundary layer.

  7. Hemispheric Dominance of Native American Indian Students.

    Science.gov (United States)

    Stellern, John; And Others

    1986-01-01

    Examines language and spatial lateralization of 49 elementary American Indian students using a cognitive-manual dual task model and psychoeducational assessment techniques. All students were found to be left-hemisphere dominant for language and some were lateralized to the left hemisphere for spatial function. Contradicts evidence of right-brain…

  8. Personality, Hemispheric Dominance, and Cognitive Style.

    Science.gov (United States)

    Hylton, Jaime; Hartman, Steve E.

    1997-01-01

    Shows that 154 medical students and 526 undergraduates (samples treated separately) who were judged left- or right-hemisphere dominant (by the Hemispheric Mode Indicator) were found to have very different personalities (as measured by the Myers-Briggs Type Indicator). Considers some of the practical ramifications of the psychometric overlap of…

  9. The Cost of Action Miscues: Hemispheric Asymmetries

    Science.gov (United States)

    Shenal, Brian V.; Hinze, Stephan; Heilman, Kenneth M.

    2012-01-01

    Adaptive behaviors require preparation and when necessary inhibition or alteration of actions. The right hemisphere has been posited to be dominant for preparatory motor activation. This experiment was designed to learn if there are hemispheric asymmetries in the control of altered plans of actions. Cues, both valid and invalid, which indicate the…

  10. Interaction of cerebral hemispheres and artistic thinking

    Science.gov (United States)

    Nikolaenko, Nikolay N.

    1998-07-01

    Study of drawings by patients with local lesions of the right or left hemisphere allows to understand how artistic thinking is supported by brain structures. The role of the right hemisphere is significant at the early stage of creative process. The right hemisphere is a generator of nonverbal visuo-spatial thinking. It operates with blurred nonverbal images and arrange them in a visual space. With the help of iconic signs the right hemisphere reflects the world and creates perceptive visual standards which are stored in the long-term right hemisphere memory. The image, which appeared in the `inner' space, should be transferred into a principally different language, i.e. a left hemispheric sign language. This language operates with a number of discrete units, logical succession and learned grammar rules. This process can be explained by activation (information) transfer from the right hemisphere to the left one. Thus, natural and spontaneous creative process, which is finished by a conscious effort, can be understood as an activation impulse transfer from the right hemisphere to the left one and back.

  11. UV Observations of Hemispheric Asymmetry

    Science.gov (United States)

    Schaefer, R. K.; Paxton, L. J.; Wolven, B. C.; Zhang, Y.; Romeo, G.

    2015-12-01

    Asymmetry in the auroral patterns can be an important diagnostic for understanding the dynamics of solar wind interaction with the magnetosphere-ionosphere-thermosphere system (e.g., Newel and Meng, 1998; Fillingrim et al., 2005). Molecular nitrogen emission in the UV Lyman-Birge-Hopfield bands can be used to determine energy flux and electron mean energy (Sotirelis, et al, 2013) and thereby Hall and Pederson integrated conductances (Gjerloev, et al., 2014). UV imagery provided by the 4 SSUSI instruments on the Defense Meteorological Satellite Program (DMSP) F16-F19 spacecraft provide two dimensional maps of this emission at different local times. Often there are near simultaneous observations of both poles by some combination of the satellites. (see figure 1) The SSUSI auroral data products are well suited to this study, as they have the following features.: - dayglow has been subtracted on dayside aurora - electron energy flux and mean energy are pre-calculated - individual arcs have been identified through image processing. In order to intercompare data from multiple satellites, we must first ensure that the instrument calibrations are consistent. In this work we show that the instruments are consistently calibrated, and that results generated from the SSUSI data products can be trusted. Several examples of storm time asymmetries captured by the SSUSI instruments will be discussed. Fillingim, M. O., G. K. Parks, H. U. Frey, T. J. Immel, and S. B. Mende (2005), Hemispheric asymmetry of the afternoon electron aurora, Geophys. Res. Lett., 32, L03113, doi:10.1029/2004GL021635. Gjerloev, J., Schaefer, R., Paxton, L, and Zhang, Y. (2014), A comprehensive empirical model of the ionospheric conductivity derived from SSUSI/GUVI, SuperMAG and SuperDARN data, SM51G-4339, Fall 2014 AGU meeting, San Francisco. Newell, P. T., and C.-I. Meng (1988), Hemispherical asymmetry in cusp precipitation near solstices, J. Geophys. Res., 93(A4), 2643-2648, doi:10.1029/JA093iA04p02643

  12. HEMISPHERIC CENTER FOR ENVIRONMENTAL TECHNOLOGY

    Energy Technology Data Exchange (ETDEWEB)

    M.A. Ebadian

    1999-10-31

    The Deactivation and Decommissioning (D&D) Technology Assessment Program (TAP) was developed to provide detailed, comparable data for environmental technologies and to disseminate this data to D&D professionals in a manner that will facilitate the review and selection of technologies to perform decontamination and decommissioning. The objectives for this project include the following: Determine technology needs through review of the Site Technology Coordination Group (STCG) information and other applicable websites and needs databases; Perform a detailed review of industries that perform similar activities as those required in D&D operations to identify additional technologies; Define the technology assessment program for characterization and waste management problem sets; Define the data management program for characterization, dismantlement, and waste management problem sets; Evaluate baseline and innovative technologies under standard test conditions at Florida International University's Hemispheric Center for Environmental Technology (FIU-HCET) and other locations and collect data in the areas of performance, cost, health and safety, operations and maintenance, and primary and secondary waste generation; Continue to locate, verify, and incorporate technology performance data from other sources into the multimedia information system; and Develop the conceptual design for a dismantlement technology decision analysis tool for dismantlement technologies.

  13. Analysis of extreme summers and prior late winter/spring conditions in central Europe

    Directory of Open Access Journals (Sweden)

    C. Träger-Chatterjee

    2013-05-01

    Full Text Available Drought and heat waves during summer in mid-latitudes are a serious threat to human health and agriculture and have negative impacts on the infrastructure, such as problems in energy supply. The appearance of such extreme events is expected to increase with the progress of global warming. A better understanding of the development of extremely hot and dry summers and the identification of possible precursors could help improve existing seasonal forecasts in this regard, and could possibly lead to the development of early warning methods. The development of extremely hot and dry summer seasons in central Europe is attributed to a combined effect of the dominance of anticyclonic weather regimes and soil moisture–atmosphere interactions. The atmospheric circulation largely determines the amount of solar irradiation and the amount of precipitation in an area. These two variables are themselves major factors controlling the soil moisture. Thus, solar irradiation and precipitation are used as proxies to analyse extreme sunny and dry late winter/spring and summer seasons for the period 1958–2011 in Germany and adjacent areas. For this purpose, solar irradiation data from the European Center for Medium Range Weather Forecast 40-yr and interim re-analysis dataset, as well as remote sensing data are used. Precipitation data are taken from the Global Precipitation Climatology Project. To analyse the atmospheric circulation geopotential data at 850 hPa are also taken from the European Center for Medium Range Weather Forecast 40-yr and interim re-analysis datasets. For the years in which extreme summers in terms of high solar irradiation and low precipitation are identified, the previous late winter/spring conditions of solar irradiation and precipitation in Germany and adjacent areas are analysed. Results show that if the El Niño–Southern Oscillation (ENSO is not very intensely developed, extremely high solar irradiation amounts, together with

  14. Month of birth and offspring count of women: data from the Southern hemisphere

    Science.gov (United States)

    Huber, S.; Didham, R.; Fieder, M.

    2010-01-01

    BACKGROUND Several studies indicate that the month of birth affects later reproductive output of women in the Northern hemisphere. METHODS To investigate whether a comparable but time-shifted effect is also present in the Southern hemisphere where the seasonal variation of the environment is reversed, we analysed the association between birth month and offspring count in post-reproductive New Zealand women. We further examined whether this association differed with the hemisphere of birth as well as the socio-economic background. RESULTS We find that the association between birth month and offspring count of New Zealand women born in the Southern, albeit not Northern, hemisphere is a mirror image of the pattern reported from Austrian women: on average, women born during the Southern hemisphere summer months have fewer children than women born in winter. This association is highly significant within the lowest family income category but insignificant within higher family income categories. CONCLUSIONS This study provides evidence for a causal link between the seasonality of the environment during the pre- and perinatal period and offspring count of women. It further indicates that the main contribution of the birth month effect found in the present study comes from the lowest family income category. PMID:18326861

  15. Variability of the extent of the Hadley circulation in the southern hemisphere: a regional perspective

    Science.gov (United States)

    Nguyen, H.; Hendon, H. H.; Lim, E.-P.; Boschat, G.; Maloney, E.; Timbal, B.

    2017-03-01

    In order to understand the regional impacts of variations in the extent of the Hadley circulation in the Southern Hemisphere, regional Hadley circulations are defined in three sectors centered on the main tropical heat sources over Africa, Asia-Pacific (Maritime Continent) and the Americas. These regional circulations are defined by computing a streamfunction from the divergent component of the meridional wind. A major finding from this study is that year-to-year variability in the extent of the hemispheric Hadley circulation in the Southern Hemisphere is primarily governed by variations of the extent of the Hadley circulation in the Asia-Pacific sector, especially during austral spring and summer when there is little co-variability with the African sector, and the American sector exhibits an out of phase behavior. An expanded Hadley circulation in the Southern Hemisphere (both hemispherically and in the Asia-Pacific sector) is associated with La Niña conditions and a poleward expansion of the tropical wet zone in the Asia-Pacific sector. While La Niña also promotes expansion in the American and African sectors during austral winter, these tropical conditions tend to promote contraction in the two sectors during austral summer as a result of compensating convergence over the Americas and Africa sectors: a process driven by variations in the Walker circulation and Rossby wave trains emanating from the tropical Indian Ocean.

  16. Tracking Snow Variations in the Northern Hemisphere Using Multi-Source Remote Sensing Data (2000–2015

    Directory of Open Access Journals (Sweden)

    Yunlong Wang

    2018-01-01

    Full Text Available Multi-source remote sensing data were used to generate 500-m resolution cloud-free daily snow cover images for the Northern Hemisphere. Simultaneously, the spatial and temporal dynamic variations of snow in the Northern Hemisphere were evaluated from 2000 to 2015. The results indicated that (1 the maximum, minimum, and annual average snow-covered area (SCA in the Northern Hemisphere exhibited a fluctuating downward trend; the variation of snow cover in the Northern Hemisphere had well-defined inter-annual and regional differences; (2 the average SCA in the Northern Hemisphere was the largest in January and the smallest in August; the SCA exhibited a downward trend for the monthly variations from February to April; and the seasonal variation in the SCA exhibited a downward trend in the spring, summer, and fall in the Northern Hemisphere (no pronounced variation trend in the winter was observed during the 2000–2015 period; (3 the spatial distribution of the annual average snow-covered day (SCD was related to the latitudinal zonality, and the areas exhibiting an upward trend were mainly at the mid to low latitudes with unstable SCA variations; and (4 the snow reduction was significant in the perennial SCA in the Northern Hemisphere, including high-latitude and high-elevation mountainous regions (between 35° and 50°N, such as the Tibetan Plateau, the Tianshan Mountains, the Pamir Plateau in Asia, the Alps in Europe, the Caucasus Mountains, and the Cordillera Mountains in North America.

  17. Editorial - The winter Atomiades

    CERN Multimedia

    Staff Association

    2011-01-01

    As we wrote in our previous editorial, the Staff Association gives direct support to sports events, such as the Atomiades, a section of the Association of Sports Communities of European Research Institutes, which brings together sportsmen and women from 38 European research centres in 13 countries (Austria, Belgium, Czech Republic, United Kingdom, Finland, France, Germany, Hungary, Italy, Luxemburg, the Netherlands, Russia, and Switzerland). The summer Atomiades take place between the months of June and September every three years. Thirteen such events have taken place since 1973, the last one in June 2009 in Berlin. As far as the winter Atomiades are concerned, also organized every three years, and alternating with the summer Atomiades, there have been eleven since 1981, the last one at the end of January this year in neighbouring France. The following article tells the wonderful adventure of the CERN staff who took part in this event. A positive outcome for CERN skiers at the winter Atomiades The 11t...

  18. Winter in Bavaria

    Directory of Open Access Journals (Sweden)

    Anthony Stephens

    2004-08-01

    Full Text Available "A Winter In Bavaria" was written on location in Regensburg, Germany, and is the first-hand account of a cataclysm, already predicted by Nostradamus, which changed the direction of Bavarian culture forever. Anything vaguely resembling an allusion to any real person or institution is entirely coincidental, has no foundation in fact and is clearly the product of a mind estranged - except that Bavarian beer is, by and large, still to be highly recommended.

  19. Remote canopy hemispherical image collection system

    Science.gov (United States)

    Wan, Xuefen; Liu, Bingyu; Yang, Yi; Han, Fang; Cui, Jian

    2016-11-01

    Canopies are major part of plant photosynthesis and have distinct architectural elements such as tree crowns, whorls, branches, shoots, etc. By measuring canopy structural parameters, the solar radiation interception, photosynthesis effects and the spatio-temporal distribution of solar radiation under the canopy can be evaluated. Among canopy structure parameters, Leaf Area Index (LAI) is the key one. Leaf area index is a crucial variable in agronomic and environmental studies, because of its importance for estimating the amount of radiation intercepted by the canopy and the crop water requirements. The LAI can be achieved by hemispheric images which are obtained below the canopy with high accuracy and effectiveness. But existing hemispheric images canopy-LAI measurement technique is based on digital SLR camera with a fisheye lens. Users need to collect hemispheric image manually. The SLR camera with fisheye lens is not suit for long-term canopy-LAI outdoor measurement too. And the high cost of SLR limits its capacity. In recent years, with the development of embedded system and image processing technology, low cost remote canopy hemispheric image acquisition technology is becoming possible. In this paper, we present a remote hemispheric canopy image acquisition system with in-field/host configuration. In-field node based on imbed platform, low cost image sensor and fisheye lens is designed to achieve hemispherical image of plant canopy at distance with low cost. Solar radiation and temperature/humidity data, which are important for evaluating image data validation, are obtained for invalid hemispherical image elimination and node maintenance too. Host computer interacts with in-field node by 3G network. The hemispherical image calibration and super resolution are used to improve image quality in host computer. Results show that the remote canopy image collection system can make low cost remote canopy image acquisition for LAI effectively. It will be a potential

  20. Compact Autonomous Hemispheric Vision System

    Science.gov (United States)

    Pingree, Paula J.; Cunningham, Thomas J.; Werne, Thomas A.; Eastwood, Michael L.; Walch, Marc J.; Staehle, Robert L.

    2012-01-01

    Solar System Exploration camera implementations to date have involved either single cameras with wide field-of-view (FOV) and consequently coarser spatial resolution, cameras on a movable mast, or single cameras necessitating rotation of the host vehicle to afford visibility outside a relatively narrow FOV. These cameras require detailed commanding from the ground or separate onboard computers to operate properly, and are incapable of making decisions based on image content that control pointing and downlink strategy. For color, a filter wheel having selectable positions was often added, which added moving parts, size, mass, power, and reduced reliability. A system was developed based on a general-purpose miniature visible-light camera using advanced CMOS (complementary metal oxide semiconductor) imager technology. The baseline camera has a 92 FOV and six cameras are arranged in an angled-up carousel fashion, with FOV overlaps such that the system has a 360 FOV (azimuth). A seventh camera, also with a FOV of 92 , is installed normal to the plane of the other 6 cameras giving the system a > 90 FOV in elevation and completing the hemispheric vision system. A central unit houses the common electronics box (CEB) controlling the system (power conversion, data processing, memory, and control software). Stereo is achieved by adding a second system on a baseline, and color is achieved by stacking two more systems (for a total of three, each system equipped with its own filter.) Two connectors on the bottom of the CEB provide a connection to a carrier (rover, spacecraft, balloon, etc.) for telemetry, commands, and power. This system has no moving parts. The system's onboard software (SW) supports autonomous operations such as pattern recognition and tracking.

  1. The influence of winter and summer atmospheric circulation on the variability of temperature and sea ice around Greenland

    Directory of Open Access Journals (Sweden)

    Masayo Ogi

    2016-10-01

    Greenland is similar to the pattern of the SIEs in the Greenland Sea and Kara-Barents Seas. During summer, the T2m anomalies associated with all GrSTs and SIEs have positive anomalies over mid-latitudes. The two times series of all GrSTs and SIEs fluctuate quickly and display large trends towards warming temperatures and decreasing SIE. The summer SLP associated with all GrSTs and SIEs are characterised by a seesaw pattern between positive anomalies over the Arctic and negative anomalies over mid-latitudes. The summer SLP anomalies are similar to the summer AO pattern, and it is noteworthy that the summer anticyclonic circulation over the Arctic and Greenland has contributed to the variability and trends in both summer GrSTs and SIEs.

  2. Phylogeography of Burkholderia pseudomallei Isolates, Western Hemisphere.

    Science.gov (United States)

    Gee, Jay E; Gulvik, Christopher A; Elrod, Mindy G; Batra, Dhwani; Rowe, Lori A; Sheth, Mili; Hoffmaster, Alex R

    2017-07-01

    The bacterium Burkholderia pseudomallei causes melioidosis, which is mainly associated with tropical areas. We analyzed single-nucleotide polymorphisms (SNPs) among genome sequences from isolates of B. pseudomallei that originated in the Western Hemisphere by comparing them with genome sequences of isolates that originated in the Eastern Hemisphere. Analysis indicated that isolates from the Western Hemisphere form a distinct clade, which supports the hypothesis that these isolates were derived from a constricted seeding event from Africa. Subclades have been resolved that are associated with specific regions within the Western Hemisphere and suggest that isolates might be correlated geographically with cases of melioidosis. One isolate associated with a former World War II prisoner of war was believed to represent illness 62 years after exposure in Southeast Asia. However, analysis suggested the isolate originated in Central or South America.

  3. Tympanic Membrane Temperature and Hemispheric Cognitive Style.

    Science.gov (United States)

    Genovese, Jeremy E C; Sparks, Kenneth E; Little, Kathleen D

    2017-01-01

    The authors tested the hypothesis that there is a correlation between hemispheric cognitive style and ear temperature. A sample of 100 participants completed a measure of hemispheric cognitive style, the Hemispheric Consensus Prediction Profile. Ear temperatures were taken in 2 sessions, 2 times for each ear at each session. Average left ear temperature was subtracted from average right ear temperature as an index of dominant temperature. Only 56 of the participants showed a stable dominant ear temperature. For these 56 participants, there was a statistically significant positive correlation between scores on the Hemispheric Consensus Prediction Profile and tympanic member temperature (Spearman's  ρ =.29, 95% CI [.04,.51]). Individuals with a left hemispheric cognitive style tended to have a warmer left tympanic membrane temperature while those with a right hemispheric cognitive style tended to have a warmer right tympanic membrane temperature. Tympanic membrane temperatures are easily obtained using inexpensive and noninvasive technology. The relationship suggested by these findings may open new opportunities for the study of cerebral asymmetry.

  4. Hemispheric ozone variability indices derived from satellite observations and comparison to a coupled chemistry-climate model

    Directory of Open Access Journals (Sweden)

    T. Erbertseder

    2006-01-01

    Full Text Available Total column ozone is used to trace the dynamics of the lower and middle stratosphere which is governed by planetary waves. In order to analyse the planetary wave activity a Harmonic Analysis is applied to global multi-year total ozone observations from the Total Ozone Monitoring Spectrometer (TOMS. As diagnostic variables we introduce the hemispheric ozone variability indices one and two. They are defined as the hemispheric means of the amplitudes of the zonal waves number one and two, respectively, as traced by the total ozone field. The application of these indices as a simple diagnostic for the evaluation of coupled chemistry-climate models (CCMs is demonstrated by comparing results of the CCM ECHAM4.L39(DLR/CHEM (hereafter: E39/C against satellite observations. It is quantified to what extent a multi-year model simulation of E39/C (representing "2000" climate conditions is able to reproduce the zonal and hemispheric planetary wave activity derived from TOMS data (1996–2004, Version 8. Compared to the reference observations the hemispheric ozone variability indices one and two of E39/C are too high in the Northern Hemisphere and too low in the Southern Hemisphere. In the Northern Hemisphere, where the agreement is generally better, E39/C produces too strong a planetary wave one activity in winter and spring and too high an interannual variability. For the Southern Hemisphere we reveal that the indices from observations and model differ significantly during the ozone hole season. The indices are used to give reasons for the late formation of the Antarctic ozone hole, the insufficient vortex elongation and eventually the delayed final warming in E39/C. In general, the hemispheric ozone variability indices can be regarded as a simple and robust diagnostic to quantify model-observation differences concerning planetary wave activity. It allows a first-guess on how the dynamics is represented in a model simulation before applying costly and more

  5. The role of the QBO in the inter-hemispheric coupling of summer mesospheric temperatures

    Directory of Open Access Journals (Sweden)

    P. J. Espy

    2011-01-01

    Full Text Available Inter-hemispheric coupling between the polar summer mesosphere and planetary-wave activity in the extra-tropical winter stratosphere has recently been inferred using Polar Mesospheric Cloud (PMC properties as a proxy for mesospheric temperature (Karlsson et al., 2007. Here we confirm these results using a ten-year time series of July mesospheric temperatures near 60° N derived from the hydroxyl (OH nightglow. In addition, we show that the time-lagged correlation between these summer mesospheric temperatures and the ECMWF winter stratospheric temperatures displays a strong Quasi-Biennial Oscillation (QBO. The sign and phase of the correlation is consistent with the QBO modulation of the extra-tropical stratospheric dynamics in the Southern Hemisphere via the Holton-Tan mechanism (Holton and Tan, 1980. This lends strength to the identification of synoptic and planetary waves as the driver of the inter-hemispheric coupling, and results in a strong QBO modulation of the polar summer mesospheric temperatures.

  6. Winter School Les Houches

    CERN Document Server

    Lannoo, Michel; Bastard, Gérald; Voos, Michel; Boccara, Nino

    1986-01-01

    The Winter School held in Les Houches on March 12-21, 1985 was devoted to Semiconductor Heterojunctions and Superlattices, a topic which is recognized as being now one of the most interesting and active fields in semiconductor physics. In fact, following the pioneering work of Esaki and Tsu in 1970, the study of these two-dimensional semiconductor heterostructures has developed rapidly, both from the point of view of basic physics and of applications. For instance, modulation-doped heterojunctions are nowadays currently used to investigate the quantum Hall effect and to make very fast transistors. This book contains the lectures presented at this Winter School, showing in particular that many aspects of semiconductor heterojunctions and super­ lattices were treated, extending from the fabrication of these two-dimensional systems to their basic properties and applications in micro-and opto-electron­ ics. Among the subjects which were covered, one can quote as examples: molecular beam epitaxy and metallorgani...

  7. Strong signatures of high-latitude blocks and subtropical ridges in winter PM10 over Europe

    Science.gov (United States)

    Garrido-Perez, Jose M.; Ordóñez, Carlos; García-Herrera, Ricardo

    2017-10-01

    This paper analyses the impact of high-latitude blocks and subtropical ridges on daily PM10 (particulate matter ≤ 10 μm) observations obtained from the European Environment Agency's air quality database (AirBase) for the winter period of 2000-2010. The response of the pollutant concentrations to the location of blocks and ridges with centres in two main longitudinal sectors (Atlantic, ATL, 30°-0° W; European, EUR, 0°-30° E) is examined. In particular, EUR blocking is associated with a collapse of the boundary layer as well as reduced wind speeds and precipitation occurrence, yielding large positive anomalies which average 12 μg m-3 over the whole continent. Conversely, the enhanced zonal flow around 50°-60° N and the increased occurrence of precipitation over northern-central Europe on days with ATL ridges favour the ventilation of the boundary layer and the impact of washout processes, reducing PM10 concentrations on average by around 8 μg m-3. The presence of EUR blocks is also concurrent with an increased probability of exceeding the air quality target (50 μg m-3 for 24-h averaged PM10) and the local 90th percentiles for this pollutant at many sites in central Europe, while the opposite effect is found for ridges. In addition, the effect of synoptic persistence on the PM10 concentrations is stronger for EUR blocks than for ATL ridges. This could benefit the predictability of PM10 extremes over wide areas of the region. Finally, we have found that the combined or isolated effect of both synoptic patterns can partly control the interannual variability of winter mean PM10 at many sites of north-western and central Europe, with coefficients of determination (R2) exceeding 0.80 for southern Germany. These results indicate that the response of the particulate matter (PM) concentrations to large-scale circulation patterns is stronger than previously reported for Europe and other mid-latitude regions.

  8. Large-scale Rossby Normal Modes during Some Recent Northern Hemisphere Winters

    Science.gov (United States)

    2011-01-01

    and E. Barker, 2001. NAVDAS: formulation and diagnostics. Mon . Wea. Rev., 129, 869-883. Day, K.A. and N.J. Mitchell, 2010. The 16-day wave in the...atmospheric prediction system’s spectral forecat model. Mon . Weather Rev., 119, 1786-1815. 32 Hoppel, K.W., N.L. Baker, L. Coy, S.D. Eckermann, J.P. McCormack...Academic Press, Burlington (MA), 627 pp. Wu, D.L., P.B. Hays, and W.R. Skinner , 1994. Observations of the 5-day wave in the mesosphere and lower

  9. The Effect of Zonally Asymmetric Ozone Heating on the Northern Hemisphere Winter Polar Stratosphere

    Science.gov (United States)

    2010-12-09

    solar ultraviolet ir- radiance, stratospheric ozone, and planetary wave activity that have often been cited as possible mechanisms linking solar... photochemistry both contribute to the ZAOH effect, up to ∼0.01 hPa (∼65 km) where the ZAOH effect is controlled by ozone photochemistry . Overall, the... photochemistry parameterization for high-altitude NWP and climate models, Atmos. Chem. Phys., 6, 4943–4972. December 9, 2010, 2:01pm X - 12 MCCORMACK ET

  10. Consequences of Recent Southern Hemisphere Winter Variability on Polar Mesospheric Clouds

    Science.gov (United States)

    2011-01-01

    water vapor and winds to drive the Community Aerosol and Radiation Model for Atmospheres (CARMA) micro- physical model. We calculate ice water content...ranging from the near UV to the mid IR (Gordley et al., 2009). A salient feature of SOFIE is that its observations are confined to a single latitude...that assimilates both conventional operational meteorological data as well as data from the NASA AURA Microwave Limb Sounder (temperature, ozone and H2O

  11. Global Ionospheric TEC Perturbations Monitored by the GPS Global Network During Two Northern Hemisphere Winter Storms

    Science.gov (United States)

    Ho, C. M.; Mannucci, A. J.; Sparks, L.; Pi, X.; Lindqwister, U. J.; Wilson, B. D.; Reyes, M. J.

    1997-01-01

    The global evolution of two major ionospheric storms, occurring on November 4, 1993 and November 26, 1994, respectively, is studied using measurements of total electron content (TEC) obtained from a worldwide network of ground-based GPS receivers.

  12. Reindeer (Rangifer tarandus and climate change: Importance of winter forage

    Directory of Open Access Journals (Sweden)

    Thrine Moen Heggberget

    2002-06-01

    Full Text Available As a consequence of increasing greenhouse gas concentrations, climate change is predicted to be particularly pronounced, although regionally variable, in the vast arctic, sub-arctic and alpine tundra areas of the northern hemisphere. Here, we review winter foraging conditions for reindeer and caribou (Rangifer tarandus living in these areas, and consider diet, forage quality and distribution, accessibility due to snow variation, and effects of snow condition on reindeer and caribou populations. Finally, we hypothesise how global warming may affect wild mountain reindeer herds in South Norway. Energy-rich lichens often dominate reindeer and caribou diets. The animals also prefer lichens, and their productivity has been shown to be higher on lichen-rich than on lichen-poor ranges. Nevertheless, this energy source appears to be neither sufficient as winter diet for reindeer or caribou (at least for pregnant females nor necessary. Some reindeer and caribou populations seem to be better adapted to a non-lichen winter diet, e.g. by a larger alimentary tract. Shrubs appear to be the most common alternative winter forage, while some grasses appear to represent a good, nutritionally-balanced winter diet. Reindeer/caribou make good use of a wide variety of plants in winter, including dead and dry parts that are digested more than expected based on their fibre content. The diversity of winter forage is probably important for the mineral content of the diet. A lichen-dominated winter diet may be deficient in essential dietary elements, e.g. minerals. Sodium in particular may be marginal in inland winter ranges. Our review indicates that most Rangifer populations with lichen-dominated winter diets are either periodically or continuously heavily harvested by humans or predators. However, when population size is mainly limited by food, accessible lichen resources are often depleted. Plant studies simulating climatic change indicate that a warmer, wetter

  13. Measurements for winter road maintenance

    OpenAIRE

    Riehm, Mats

    2012-01-01

    Winter road maintenance activities are crucial for maintaining the accessibility and traffic safety of the road network at northerly latitudes during winter. Common winter road maintenance activities include snow ploughing and the use of anti-icing agents (e.g. road salt, NaCl). Since the local weather is decisive in creating an increased risk of slippery conditions, understanding the link between local weather and conditions at the road surface is critically important. Sensors are commonly i...

  14. Salmonid behaviour under winter conditions

    OpenAIRE

    Watz, Johan

    2015-01-01

    Winter conditions are believed to play an important role in the population dynamics of northern temperate stream fish, challenging the ability of fish to physiologically and behaviourally adapt. Climate change is predicted to increase both mean temperature and temperature fluctuations, especially during winter, leading to dynamic environmental conditions in terms of river ice production and flow. Therefore, knowledge about the winter ecology of stream fish is important for predicting and miti...

  15. Northern and Mid-Latitude Soil Database, Version 1, R1

    Data.gov (United States)

    National Aeronautics and Space Administration — The U.S. Department of Agriculture, Agriculture and Agri-Food Canada, the Russian Academy of Agricultural Sciences, the University of Copenhagen Institute of...

  16. Transition region of TEC enhancement phenomena during geomagnetically disturbed periods at mid-latitudes

    Directory of Open Access Journals (Sweden)

    K. Unnikrishnan

    2005-12-01

    Full Text Available Large-scale TEC perturbations/enhancements observed during the day sectors of major storm periods, 12-13 February 2000, 23 September 1999, 29 October 2003, and 21 November 2003, were studied using a high resolution GPS network over Japan. TEC enhancements described in the present study have large magnitudes (≥25×1016 electrons/m2 compared to the quiet-time values and long periods (≥120 min. The sequential manner of development and the propagation of these perturbations show that they are initiated at the northern region and propagate towards the southern region of Japan, with velocities >350 m/s. On 12 February 2000, remarkably high values of TEC and background content are observed at the southern region, compared to the north, because of the poleward expansion of the equatorial anomaly crest, which is characterized by strong latitudinal gradients near 35° N (26° N geomagnetically. When the TEC enhancements, initiating at the north, propagate through the region 39-34° N (30-25° N geomagnetically, they undergo transitions characterized by a severe decrease in amplitude of TEC enhancements. This may be due to their interaction with the higher background content of the expanded anomaly crest. However, at the low-latitude region, below 34° N, an increase in TEC is manifested as an enhanced ionization pattern (EIP. This could be due to the prompt penetration of the eastward electric field, which is evident from high values of the southward Interplanetary Magnetic Field component (IMF Bz and AE index. The TEC perturbations observed on the other storm days also exhibit similar transitions, characterized by a decreasing magnitude of the perturbation component, at the region around 39-34° N. In addition to this, on the other storm days, at the low-latitude region, below 34° N, an increase in TEC (EIP feature also indicates the repeatability of the above scenario. It is found that, the latitude and time at which the decrease in magnitude of the perturbation component/amplitude of the TEC enhancement are matching with the latitude and time of the appearance of the high background content. In the present study, on 12 February 2000, the F-layer height increases at Wakkanai and Kokubunji, by exhibiting a typical dispersion feature of LSTID, or passage of an equatorward surge, which is matching with the time of occurrence of the propagating TEC perturbation component. Similarly, on 29 October 2003, the increase in F-layer heights by more than 150km at Wakkanai and 90 km at Kokubunji around 18:00 JST, indicates the role of the equatorward neutral wind. On that day, TEC perturbation observed at the northern region, after 18:30 JST, which propagates towards south, could be caused mainly by the equatorward neutral wind, leading to an F-layer height increase. These observations imply the role of the equatorward neutral wind, which increases the F-layer height, by lifting the ionization to the regions of lower loss during daytime, when production is still taking place, which, in turn, increases the TEC values. Large-scale traveling ionospheric disturbances (LSTIDs are considered as ionospheric manifestations of the passage of Atmospheric Gravity Waves (AGWs that are generated at the high latitude by energy input from the magnetosphere to the low-latitude ionosphere. This study shows that large-scale TEC perturbations observed here are produced at the northern region due to the combined effects of the equatorward neutral wind, the subsequent F-layer height increase, and LSTIDs. When these perturbation components propagate through the region, 39-34° N, they undergo transitions characterised by a decrease in magnitude. Also, at the low-latitude region, below 34° N, an increase in the TEC exhibits EIP feature, due to the prompt penetration of the eastward electric field.

  17. Cretaceous paleogeography, paleoclimatology, and amniote biogeography of the low and mid-latitude South Atlantic Ocean

    NARCIS (Netherlands)

    Jacobs, Louis L.; Mateus, Octávio; Polcyn, Michael J.; Schulp, Anne S.; Scotese, Christopher R.; Goswami, Argyha; Ferguson, Kurt M.; Robbins, John A.; Vineyard, Diana P.; Neto, André Buto

    2009-01-01

    The Cretaceous tropical Atlantic Ocean was the setting for an initial tectonically controlled late Aptian shallow water (≤ 300 m) connection between the northern and southern portions of the Atlantic, followed by a deep-water connection by the Turonian. Ocean currents changed with deepening of the

  18. Characteristics and sources of the electron density irregularities in the mid latitude E and Fregions

    Science.gov (United States)

    2017-05-10

    Investigators (PI and Co-PIs): Young-Sil Kwak (PI), Jaeheung Park , Tae-Yong Yang, Young-Sook Lee, Jong-Min Choi, and Woo Kyoung Lee - e-mail address : yskwak...decoded and integrated raw data signal samples are subjected to the process of fast Fourier transform for on-line computation of the Doppler power... Park , J., H. Luehr, G. Kervalishvili, J. Rauberg, C. Stolle, Y.-S. Kwak, and W. K. Lee (2017), Morphology of high-latitude plasma density

  19. Identification of runoff formation with two dyes in a mid-latitude mountain headwater

    Directory of Open Access Journals (Sweden)

    L. Vlček

    2017-06-01

    Full Text Available Subsurface flow in peat bog areas and its role in the hydrologic cycle has garnered increased attention as water scarcity and floods have increased due to a changing climate. In order to further probe the mechanisms in peat bog areas and contextualize them at the catchment scale, this experimental study identifies runoff formation at two opposite hillslopes in a peaty mountain headwater; a slope with organic peat soils and a shallow phreatic zone (0.5 m below surface, and a slope with mineral Podzol soils and no detectable groundwater (> 2 m below surface. Similarities and differences in infiltration, percolation and preferential flow paths between both hillslopes could be identified by sprinkling experiments with Brilliant Blue and Fluorescein sodium. To our knowledge, this is the first time these two dyes have been compared in their ability to stain preferential flow paths in soils. Dye-stained soil profiles within and downstream of the sprinkling areas were excavated parallel (lateral profiles and perpendicular (frontal profiles to the slopes' gradients. That way preferential flow patterns in the soil could be clearly identified. The results show that biomat flow, shallow subsurface flow in the organic topsoil layer, occurred at both hillslopes; however, at the peat bog hillslope it was significantly more prominent. The dye solutions infiltrated into the soil and continued either as lateral subsurface pipe flow in the case of the peat bog, or percolated vertically towards the bedrock in the case of the Podzol. This study provides evidence that subsurface pipe flow, lateral preferential flow along decomposed tree roots or logs in the unsaturated zone, is a major runoff formation process at the peat bog hillslope and in the adjacent riparian zone.

  20. Hydrological indications of aeolian salts in mid-latitude deserts of ...

    Indian Academy of Sciences (India)

    transpiration losses, and solar radiation (Borchert and Muir 1964; Sinha ... Asia and central Australia are in part of product of their isolation from ... control) and the Badanjilin Desert (the monsoon climate control). Both the modern and ancient aeolian sediments were designed to be sampled in the field. For modern aeolian ...

  1. Modeling the Meteoroid Input Function at Mid-Latitude Using Meteor Observations by the MU Radar

    Science.gov (United States)

    Pifko, Steven; Janches, Diego; Close, Sigrid; Sparks, Jonathan; Nakamura, Takuji; Nesvorny, David

    2012-01-01

    The Meteoroid Input Function (MIF) model has been developed with the purpose of understanding the temporal and spatial variability of the meteoroid impact in the atmosphere. This model includes the assessment of potential observational biases, namely through the use of empirical measurements to characterize the minimum detectable radar cross-section (RCS) for the particular High Power Large Aperture (HPLA) radar utilized. This RCS sensitivity threshold allows for the characterization of the radar system s ability to detect particles at a given mass and velocity. The MIF has been shown to accurately predict the meteor detection rate of several HPLA radar systems, including the Arecibo Observatory (AO) and the Poker Flat Incoherent Scatter Radar (PFISR), as well as the seasonal and diurnal variations of the meteor flux at various geographic locations. In this paper, the MIF model is used to predict several properties of the meteors observed by the Middle and Upper atmosphere (MU) radar, including the distributions of meteor areal density, speed, and radiant location. This study offers new insight into the accuracy of the MIF, as it addresses the ability of the model to predict meteor observations at middle geographic latitudes and for a radar operating frequency in the low VHF band. Furthermore, the interferometry capability of the MU radar allows for the assessment of the model s ability to capture information about the fundamental input parameters of meteoroid source and speed. This paper demonstrates that the MIF is applicable to a wide range of HPLA radar instruments and increases the confidence of using the MIF as a global model, and it shows that the model accurately considers the speed and sporadic source distributions for the portion of the meteoroid population observable by MU.

  2. Identification of runoff formation with two dyes in a mid-latitude mountain headwater

    Science.gov (United States)

    Vlček, Lukáš; Falátková, Kristýna; Schneider, Philipp

    2017-06-01

    Subsurface flow in peat bog areas and its role in the hydrologic cycle has garnered increased attention as water scarcity and floods have increased due to a changing climate. In order to further probe the mechanisms in peat bog areas and contextualize them at the catchment scale, this experimental study identifies runoff formation at two opposite hillslopes in a peaty mountain headwater; a slope with organic peat soils and a shallow phreatic zone (0.5 m below surface), and a slope with mineral Podzol soils and no detectable groundwater (> 2 m below surface). Similarities and differences in infiltration, percolation and preferential flow paths between both hillslopes could be identified by sprinkling experiments with Brilliant Blue and Fluorescein sodium. To our knowledge, this is the first time these two dyes have been compared in their ability to stain preferential flow paths in soils. Dye-stained soil profiles within and downstream of the sprinkling areas were excavated parallel (lateral profiles) and perpendicular (frontal profiles) to the slopes' gradients. That way preferential flow patterns in the soil could be clearly identified. The results show that biomat flow, shallow subsurface flow in the organic topsoil layer, occurred at both hillslopes; however, at the peat bog hillslope it was significantly more prominent. The dye solutions infiltrated into the soil and continued either as lateral subsurface pipe flow in the case of the peat bog, or percolated vertically towards the bedrock in the case of the Podzol. This study provides evidence that subsurface pipe flow, lateral preferential flow along decomposed tree roots or logs in the unsaturated zone, is a major runoff formation process at the peat bog hillslope and in the adjacent riparian zone.

  3. Trace gas emissions from a mid-latitude prescribed chaparral fire

    Science.gov (United States)

    Cofer, Wesley R., III; Levine, Joel S.; Sebacher, Daniel I.; Riggan, Philip J.; Winstead, Edward L.; Shaw, Edwin F., Jr.; Brass, James A.; Ambrosia, Vincent G.

    1988-01-01

    Smoke-plume gas samples were collected at altitudes from 35-670 m above the ground over the San Dimas Experimental Forest during a 400-acre prescribed chaparral fire. Mean emission ratios relative to CO2 for CO, H2, CH4, and total nonmethane hydrocarbons were lower than previous values obtained for large biomass-burning field experiments. Comparison of samples from vigorously flaming and mixed stages of combustion revealed little differences in CO2 normalized emission ratios for these gases (except for N2O).

  4. Drought impacts on photosynthesis, isoprene emission and atmospheric formaldehyde in a mid-latitude forest

    Science.gov (United States)

    Zheng, Yiqi; Unger, Nadine; Tadić, Jovan M.; Seco, Roger; Guenther, Alex B.; Barkley, Michael P.; Potosnak, Mark J.; Murray, Lee T.; Michalak, Anna M.; Qiu, Xuemei; Kim, Saewung; Karl, Thomas; Gu, Lianhong; Pallardy, Stephen G.

    2017-10-01

    Isoprene plays a critical role in air quality and climate. Photosynthesis (gross primary productivity, GPP) and formaldehyde (HCHO) are both related to isoprene emission at large spatiotemporal scales, but neither is a perfect proxy. We apply multiple satellite products and site-level measurements to examine the impact of water deficit on the three interlinked variables at the Missouri Ozarks site during a 20-day mild dryness stress in summer 2011 and a 3-month severe drought in summer 2012. Isoprene emission shows opposite responses to the short- and long-term droughts, while GPP was substantially reduced in both cases. In 2012, both remote-sensed solar-induced fluorescence (SIF) and satellite HCHO column qualitatively capture reductions in flux-derived GPP and isoprene emission, respectively, on weekly to monthly time scales, but with muted responses. For instance, as flux-derived GPP approaches zero in late summer 2012, SIF drops by 29-33% (July) and 19-27% (August) relative to year 2011. A possible explanation is that electron transport and photosystem activity are maintained to a certain extent under the drought stress. Similarly, flux tower isoprene emissions in July 2012 are 54% lower than July 2011, while the relative reductions in July for 3 independent satellite-derived HCHO data products are 27%, 12% and 6%, respectively. We attribute the muted HCHO response to a photochemical feedback whereby reduced isoprene emission increases the oxidation capacity available to generate HCHO from other volatile organic compound sources. Satellite SIF offers a potential alternative indirect method to monitor isoprene variability at large spatiotemporal scales from space, although further research is needed under different environmental conditions and regions. Our analysis indicates that fairly moderate reductions in satellite SIF and HCHO column may imply severe drought conditions at the surface.

  5. The Surface Energy Balance and Turbulence Characteristics of a Mid-Latitude Glacier

    Science.gov (United States)

    Fitzpatrick, N.; Radic, V.; Menounos, B.

    2016-12-01

    In the vast majority of glacier surface energy balance (SEB) studies, parameterisation rather than direct measurement is used to estimate one or more of the individual heat fluxes, with others, such as the rain and ground heat fluxes, deemed negligible. Turbulent fluxes of sensible and latent heat (QH and QL) are commonly parameterised using the bulk aerodynamic technique. This method was developed for horizontal, uniform landscapes rather than sloped, inhomogeneous glacier terrain, and contains significant uncertainty regarding the selection of appropriate roughness length (z0) values and atmospheric stability schemes. A customised weather station was installed on Nordic Glacier, Canada over the 2014 melt season, to directly measure all relevant heat fluxes, including the use of eddy covariance sensors to observe QH and QL, and to calculate z0 values. The melt rate and surface conditions of the glacier were also simultaneously recorded. The obtained dataset was used to design a SEB model, and evaluate the most common forms of the bulk method. Melt estimates from the model showed very good agreement with observed rates at seasonal and daily timescales, and moderate performance at 30 minute resolution. Using a bulk method with observed z0 values and excluding a stability scheme (neutral stability assumed) produced mean QH and QL values in close agreement with observed fluxes. z0 values obtained using existing methods from the literature were found to result in overestimated fluxes, in some cases, 300% greater than those observed. The Monin-Obukhov and bulk Richardson stability schemes were found to excessively suppress turbulence during stable conditions, when katabatic winds down the glacier slope were increasing turbulence production through wind shear. Overall, the designed observation system and model provide an effective method of capturing glacier SEB, but questions remain regarding turbulence generation, and its relationship with stability and slope angle.

  6. Ionospheric transients observed at mid-latitudes prior to earthquake activity in Central Italy

    Directory of Open Access Journals (Sweden)

    P. Nenovski

    2010-06-01

    Full Text Available Ionograms from Rome (41.8N, 12.5E and Sofia (42.4N, 23.2E ionospheric stations during earthquake (EQ activity with magnitude (M between 5 and 6 in Central Italy are analyzed. It is found that several ionospheric disturbances occur in the intermediate E-F region before the EQ shock. In fact, besides sporadic E (Es layer development (of type h of short duration (transients, fmin increase, trace gaps near the critical frequencies, and E region trace disappearance are also observed within one to three hours before the EQ shock. Before the EQ shocks we find that the F2 region parameters are practically undisturbed. The only exception is the so-called fork trace that appears mostly near the critical frequency of the F2 region. Acoustic gravity waves (AGW are suggested as one of the possible sources of transients observed in the ionosphere before the EQ shock.

  7. The influence of weather on the flight altitude of nocturnal migrants in mid-latitudes

    NARCIS (Netherlands)

    Kemp, M.U.; Shamoun-Baranes, J.; Dokter, A.M.; van Loon, E.; Bouten, W.

    2013-01-01

    By altering its flight altitude, a bird can change the atmospheric conditions it experiences during migration. Although many factors may influence a bird's choice of altitude, wind is generally accepted as being the most influential. However, the influence of wind is not clearly understood,

  8. Evidence of the mid-latitude impact of Antarctic ozone depletion

    Science.gov (United States)

    Atkinson, Roger J.; Matthews, W. Andrew; Newman, Paul A.; Plumb, R. Alan

    1989-01-01

    Record low ozone values found over Australia and New Zealand during December 1987 following the record low Antarctic values of October 1987 are analyzed. The sudden decline of ozone amounts in midmonth rule out photochemical effects as a cause and permit the underlying processes to be investigated on a case study basis. Using data from ozone sondes, radiosondes, the Nimbus-7 total ozone mapping spectrometer, and meteorological analyses from the National Meteorological Center, it is argued that these low values resulted from transport of ozone-poor air from higher latitudes. Thus, it seems that the chemical destruction of ozone over Antarctica in early spring is having an impact on lower latitudes.

  9. Hydrological indications of aeolian salts in mid-latitude deserts of ...

    Indian Academy of Sciences (India)

    Large sandy deserts in middle latitude of northwestern China were studied on salt variations in modernand ancient aeolian sediments, aiming to explore their hydrological indications at the present and past.Globally, sulphate is rich in arid to semi-arid deserts, including the aeolian loess sediments in China andsoils in ...

  10. Mid-latitude tropospheric ozone columns from the MOZAIC program: climatology and interannual variability

    Directory of Open Access Journals (Sweden)

    R. M. Zbinden

    2006-01-01

    Full Text Available Several thousands of ozone vertical profiles collected in the course of the MOZAIC programme (Measurements of Ozone, Water Vapour, Carbon Monoxide and Nitrogen Oxides by In-Service Airbus Aircraft from August 1994 to February 2002 are investigated to bring out climatological and interannual variability aspects. The study is centred on the most frequently visited MOZAIC airports, i.e. Frankfurt (Germany, Paris (France, New York (USA and the cluster of Tokyo, Nagoya and Osaka (Japan. The analysis focuses on the vertical integration of ozone from the ground to the dynamical tropopause and the vertical integration of stratospheric-origin ozone throughout the troposphere. The characteristics of the MOZAIC profiles: frequency of flights, accuracy, precision, and depth of the troposphere observed, are presented. The climatological analysis shows that the Tropospheric Ozone Column (TOC seasonal cycle ranges from a wintertime minimum at all four stations to a spring-summer maximum in Frankfurt, Paris, and New York. Over Japan, the maximum occurs in spring presumably because of the earlier springtime sun. The incursion of monsoon air masses into the boundary layer and into the mid troposphere then steeply diminishes the summertime value. Boundary layer contributions to the TOC are 10% higher in New York than in Frankfurt and Paris during spring and summer, and are 10% higher in Japan than in New York, Frankfurt and Paris during autumn and early spring. Local and remote anthropogenic emissions, and biomass burning over upstream regions of Asia may be responsible for the larger low- and mid-tropospheric contributions to the tropospheric ozone column over Japan throughout the year except during the summer-monsoon season. A simple Lagrangian analysis has shown that a minimum of 10% of the TOC is of stratospheric-origin throughout the year. Investigation of the short-term trends of the TOC over the period 1995–2001 shows a linear increase 0.7%/year in Frankfurt, 0.8%/year in Japan, 1.1%/year in New York and 1.6%/year in Paris for the reduced 1995–1999 period. Dominant ingredients of these positive short-term trends are the continuous increase of wintertime tropospheric ozone columns from 1996 to 1999 and the positive contributions of the mid troposphere whatever the season.

  11. Differences in mid-latitude stratospheric winds between reanalysis data and versus radiosonde observations at Prague

    Directory of Open Access Journals (Sweden)

    M. Kozubek

    2014-04-01

    Full Text Available Reanalysis data are very useful for studying the stratosphere. They can be used for analysis of long-term trends (temperature, wind speed, humidity, etc. or analysis of global atmospheric dynamics, etc. There are various reanalysis projects that provide outputs which are not identical. In this paper, we mutually compare three of them, ERA-40, ERA-Interim and NCEP/NCAR, and compare them with balloon radiosonde observations from Prague, Port Hardy and Valentia stations. This comparison is done for wind speed and direction at pressure levels 100 and 10 hPa and for various periods between 1957 and 2009. The results show that the differences between reanalysis vary. Wind speed data from all three analyses reasonably agree except for the 10 hPa historical data before 1966 and particularly ERA-40 data at the end of the data series (1998–2001. The quality of the ERA-40 10 hPa stratospheric wind data has been proven to be substantially worse over the last four ERA-40 years of 1998–2001 (2002 compared to previous years, both in wind speed and wind direction. The reanalysis data results are compared with radiosonde observations from Prague, Port Hardy and Valentia stations at 10 hPa for the months of February between 1989 and 2009. The results show that there are sometimes surprisingly large differences, more for ERA-Interim versus Prague measurements. Differences in wind direction greater than 45° (outliers between the reanalysis data and Prague observations in wind direction occur in Februaries predominantly when winds in Prague are in "minor" sectors, such as north, northeast and east (easterlies, whereas "major" sectors, particularly the dominant W (westerlies wind sector, exhibit almost no outliers.

  12. Seasonal variation of geomagnetic field and TEC at mid-latitude region

    Science.gov (United States)

    Meza, Amalia; Natali, María Paula

    2017-04-01

    Our study is focused on the analysis of the geomagnetic variability of the H and Z components for two local times, night and noon (corrected by the night time level), recorded by 22 permanent observatories distributed at midlatitude over Europe and North America during 2000-2003. We used Principal Component Analysis (PCA) in order to identify the spatial and temporal variations of the geomagnetic field components. This technique produces a quite compact representation of the data by defining an orthonormal base derived from correlation within the data set. This helps us to identify possible causes of seasonal variations and anomalies, linking them with already observed currents. More than 90% of the original signal is reconstructed using the first two and three modes for Europe and North America respectively. To improve our conclusion, PCA analysis is also applied on Total electron content parameter (TEC), obtained from observations of Global Navigation Satellite System network and termostheric vertical wind (V) from HWM07 model. Combining the variabilities of geomagnetic field, TEC and thermospheric wind, our study relates the different main currents with the pattern show by each parameter' variation. At nighttime PCA first mode reconfirm the existence of a latitudinal dependence in the geomagnetic components, associated with the ring current, the second mode in Z component shows geomagnetic variation, which is correlated with the second PCA mode on TEC, this variability could be related to gravity-driven current and diamagnetic plasma current. During noon, the first mode represents the dominant component of the Sq current. The second and third modes highlighted the existence of other currents that could be related with the variability of TEC distribution, and then with gravity and diamagnetic ionospheric current systems.

  13. Assessing model uncertainties in climate projections of severe, mid-latitude windstorms using seamless approach

    Science.gov (United States)

    Trzeciak, T. M.; Knippertz, P.; Owen, J. S. R.

    2012-04-01

    Despite the enormous advances made in climate change research, robust projections of the position and the strength of the North Atlantic stormtrack are not yet possible. In particular with respect to damaging windstorms, this incertitude bears enormous risks to European societies and the (re-)insurance industry. Previous studies have addressed the problem of climate model uncertainty through statistical comparisons of simulations of the current climate with (re-)analysis data and found that there is large disagreement between different climate models, different ensemble members of the same model and observed climatologies of intense cyclones. The use of different horizontal and vertical resolutions, as well as different approaches to measure storminess further complicate comparison between the results from different studies. One weakness of such statistical evaluations lies in the difficulty to separate influences of the climate model's basic state, which will be governed by slow processes such as ocean circulations or sea-ice transport, from the influence of fast processes such as energy fluxes from the ocean or latent heating on the development of the most intense storms. The former might generate a bias in storm counts through an incorrect occurrence frequency of storm-prone initial conditions, while the latter could generate a similar bias due to the lack of crucial dynamics of extreme cyclone intensification due to over-simplistic model physics or insufficient horizontal resolution. Compensating effects between the two might conceal errors and suggest higher reliability than there really is. Therefore, separating sources of uncertainty is an important step towards a more reliable interpretation of climate projections and towards targeted improvements of future model generations. A possible way to separate influences of fast and slow processes in climate projections is through a "seamless" approach of hindcasting historical, severe storms with climate models started from predefined initial conditions and run in a numerical weather prediction mode on the time-scale of several days. Such a cost-effective case-study approach, which draws from and expands on the concepts from the Transpose-AMIP initiative, is currently undertaken in a recent project at the University of Leeds funded by the AXA Research Fund. Main aspects of interest are the overall quality of the climate model hindcasts, as compared to operational forecasts and reanalysis data, and the identification of systematic biases, which if known could be potentially used to develop calibration techniques for post-processing climate model output from longer simulations. The general concept of the numerical experiments conducted in this project and some first results will be presented at the conference.

  14. On the Origin of Mid-Latitude Mesospheric Clouds: The July 2009 Cloud Outbreak

    Science.gov (United States)

    2011-09-01

    Kirkwood and Stebel, 2003; Merkel et al., 2003, 2008, 2009;Nielsen et al., 2010; von Savigny et al., 2007). In fact, Nielsen et al. (2010) showed that...in PMCs (von Savigny et al., 2007; Nielsen et al., 2010). To performawavelet analysis, daily averagedMLSdata has been binned in 101 longitude and...C., Rusch, D., von Savigny , C., Singer, W., 2009. The noctilucent cloud (NLC) display during the ECOMA/MASS sounding rocket flights on3August 2007

  15. Ice Core Reconnaissance in Siberian Altai for Mid-Latitudes Paleo-Climatic and Environmental Reconstruction

    Science.gov (United States)

    Aizen, V.; Aizen, E.; Kreutz, K.; Nikitin, S.; Fujita, K.; Cecil, D.

    2001-12-01

    Investigations in Siberian Altai permits to expand our scope from Tibet, Himalayas, Tien Shan and Pamir to the area located at the northeastern edge of the Central Asia Mountain System. Altai forms a natural barrier to the northern and western air masses and therefore affords an opportunity to develop modern paleo-climate records relating to the westerly jet stream, the Siberian High and Pacific monsoon. Moreover, Altai alpine snowice accumulation areas are appropriative for studying air pollution dynamics at the center of Eurasia, eastward from the major Former USSR air pollutants in Kazakhstan, South Siberia and Ural Mountains. During the last century Altai Mountains became extremely contaminated region by heavy metal mining, metallurgy, nuclear test in Semipalatinsk polygon and Baikonur rocket site. Our first field reconnaissance on the West Belukha snow/firn plateau at the Central Altai was carried out in July 2001. Dispute of the large Alatai Mountains glaciation, the West Belukha Plateau (49o48' N, 86o32'E, 4000-4100 m a.s.l.) is only one suitable snow accumulation site in Altai to recover ice-core paleo-climatic and environmental records that is not affected by meltwater percolation. The objective of our first reconnaissance was to find an appropriate deep drilling site by radio-echo sounding survey, to recover shallow ice-core, to identify the annual snow accumulation rate, major ions, heavy metals, radio nuclides and oxygen isotopes level distribution. During 6 days of work on the Plateau, a 22 m shallow firn/ice core has been recovered by PICO hand auger at elevation 4050 m where the results of radio-echo sounding suggests about 150 m ice thickness. In addition to the firn/ice core recovery, five 2.5 meter snow pits were sampled for physical statigraphy, major ions, trace element, and heavy metals analysis to assess spatial variability of the environmental impact in this region. Four automatic snow gauges were installed near proposed deep ice coring site for year around records. The seasonal accumulation at the drilling site was ranged from 250 to 300 ?? with density of 0.34 - 0.40 g cm-3. The ice-core stratigraphy analysis has shown that accumulation area seems to lie in the cold infiltration-recrystallization zone. Geochemical analysis of the shallow ice core, snow pit samples collecting during the 2001 field research will be discussed along with meteorological and synoptic data collected at the nearest to Belukha Plateau Akkem, (2050 m) and Kara -Tyurek (3600 ?) stations. A preliminary result has revealed that variability of elementary synoptic processes over the region impact on the amount of precipitation. North Atlantic Oscillation and West Pacific Oscillation indices have inverse associations with average amount of precipitation in Siberia where Altai is located. >http://www.icess.ucsb.edu/%7eaizen/aizen.html

  16. Transition region of TEC enhancement phenomena during geomagnetically disturbed periods at mid-latitudes

    Directory of Open Access Journals (Sweden)

    K. Unnikrishnan

    2005-12-01

    Full Text Available Large-scale TEC perturbations/enhancements observed during the day sectors of major storm periods, 12-13 February 2000, 23 September 1999, 29 October 2003, and 21 November 2003, were studied using a high resolution GPS network over Japan. TEC enhancements described in the present study have large magnitudes (≥25×1016 electrons/m2 compared to the quiet-time values and long periods (≥120 min. The sequential manner of development and the propagation of these perturbations show that they are initiated at the northern region and propagate towards the southern region of Japan, with velocities >350 m/s. On 12 February 2000, remarkably high values of TEC and background content are observed at the southern region, compared to the north, because of the poleward expansion of the equatorial anomaly crest, which is characterized by strong latitudinal gradients near 35° N (26° N geomagnetically. When the TEC enhancements, initiating at the north, propagate through the region 39-34° N (30-25° N geomagnetically, they undergo transitions characterized by a severe decrease in amplitude of TEC enhancements. This may be due to their interaction with the higher background content of the expanded anomaly crest. However, at the low-latitude region, below 34° N, an increase in TEC is manifested as an enhanced ionization pattern (EIP. This could be due to the prompt penetration of the eastward electric field, which is evident from high values of the southward Interplanetary Magnetic Field component (IMF Bz and AE index. The TEC perturbations observed on the other storm days also exhibit similar transitions, characterized by a decreasing magnitude of the perturbation component, at the region around 39-34° N. In addition to this, on the other storm days, at the low-latitude region, below 34° N, an increase in TEC (EIP feature also indicates the repeatability of the above scenario. It is found that, the latitude and time at which the decrease in magnitude of the perturbation component/amplitude of the TEC enhancement are matching with the latitude and time of the appearance of the high background content. In the present study, on 12 February 2000, the F-layer height increases at Wakkanai and Kokubunji, by exhibiting a typical dispersion feature of LSTID, or passage of an equatorward surge, which is matching with the time of occurrence of the propagating TEC perturbation component. Similarly, on 29 October 2003, the increase in F-layer heights by more than 150km at Wakkanai and 90 km at Kokubunji around 18:00 JST, indicates the role of the equatorward neutral wind. On that day, TEC perturbation observed at the northern region, after 18:30 JST, which propagates towards south, could be caused mainly by the equatorward neutral wind, leading to an F-layer height increase. These observations imply the role of the equatorward neutral wind, which increases the F-layer height, by lifting the ionization to the regions of lower loss during daytime, when production is still taking place, which, in turn, increases the TEC values.

    Large-scale traveling ionospheric disturbances (LSTIDs are considered as ionospheric manifestations of the passage of Atmospheric Gravity Waves (AGWs that are generated at the high latitude by energy input from the magnetosphere to the low-latitude ionosphere. This study shows that large-scale TEC perturbations observed here are produced at the northern region due to the combined effects of the equatorward neutral wind, the subsequent F-layer height increase, and LSTIDs. When these perturbation components propagate through the region, 39-34° N, they undergo transitions characterised by a decrease in magnitude. Also, at the low-latitude region, below 34° N, an increase in the TEC exhibits EIP feature, due to the prompt penetration of the eastward electric field.

  17. Evidence for HBr production due to minor channel branching at mid-latitudes

    Science.gov (United States)

    Chartrand, D. J.; McConnell, J. C.

    Recently, Nolt et al. [1997] have presented HBr measurements over the height range 20-36 km. We have compared model calculations with these measurements and find definitive evidence for non-zero branching ratios for HBr production from either HO2+BrO, k1b, or OH+BrO, k2b. For k1b, best agreement between modelled and observed HBr concentrations is obtained if the branching ratio increases from ˜0.4% at 20 km, to about 2% at 34 km with no additional contribution from the OH+BrO branch. However, a height-independent value of 1% also produces reasonable results. This branching ratio contradicts the study of Mellouki et al. [1994]. For OH+BrO, the best value of k2b appears to be 2-3%, if k1a = 0 which is comparable to the recently determined branching ratio for HCl production from the analogous chlorine reaction, OH+ClO.

  18. Seasonal variability and descent of mid-latitude sporadic E layers at Arecibo

    Directory of Open Access Journals (Sweden)

    N. Christakis

    2009-03-01

    Full Text Available Sporadic E layers (Es follow regular daily patterns in variability and altitude descent, which are determined primarily by the vertical tidal wind shears in the lower thermosphere. In the present study a large set of sporadic E layer incoherent scatter radar (ISR measurements are analyzed. These were made at Arecibo (Geog. Lat. ~18° N; Magnetic Dip ~50° over many years with ISR runs lasting from several hours to several days, covering evenly all seasons. A new methodology is applied, in which both weak and strong layers are clearly traced by using the vertical electron density gradient as a function of altitude and time. Taking a time base equal to the 24-h local day, statistics were obtained on the seasonal behavior of the diurnal and semidiurnal tidal variability and altitude descent patterns of sporadic E at Arecibo. The diurnal tide, most likely the S(1,1 tide with a vertical wavelength around 25 km, controls fully the formation and descent of the metallic Es layers at low altitudes below 110 km. At higher altitudes, there are two prevailing layers formed presumably by vertical wind shears associated mainly with semidiurnal tides. These include: 1 a daytime layer starting at ~130 km around midday and descending down to 105 km by local midnight, and 2 a less frequent and weaker nighttime layer which starts prior to midnight at ~130 km, descending downwards at somewhat faster rate to reach 110 km by sunrise. The diurnal and semidiurnal-like pattern prevails, with some differences, in all seasons. The differences in occurrence, strength and descending speeds between the daytime and nighttime upper layers are not well understood from the present data alone and require further study.

  19. Stamena winter wheat variety

    Directory of Open Access Journals (Sweden)

    Mišić Todor

    2001-01-01

    Full Text Available Stamena is a winter wheat variety developed at the Institute of Field and Vegetable Crops in Novi Sad, Yugoslavia. It was released by the Federal Commission for varietals Approval in 1999. Stamena was developed by crossing genetically divergent and highly productive parents Lasta and Rodna (Breeders: T. Mišić. N. Mladenov, Z. Jerković and R. Jevtić. Spike is white, smooth, awn less, medium compact with 18-21 spike lets. The grain is vitreous and dark red (Triticum aestivum L. ssp. vulgar e var. lutescens. Stamena is a medium early variety, 1 day earlier than Partizanka and 3 days earlier than Jugoslavija (Table 4. It has excellent resistance to winterkilling, as in very winter hardy Partizanka. The average stem height is 78 cm, with a good resistance to lodging. Stamena has field resistance to leaf rust (Pucce, recondita tritict, horizontal resistance, which is the type of resistance that modern wheat breeding is interested in. The resistance to stem rust (Pucce, graminis tritict is good and to powdery mildew (Erysiphegraminis tritici very good. The 1000 grain mass is about 32 g and volume grain mass 81.3 kg/hi. (Table 2. Stamena is classified in the subgroup A-l. It has excellent milling and baking quality and it belong to the 1st technological group (quality enhancer. The quantity of dry gluten is about 9%. The variety Stamena is a very productive, with the genetic potential for grain above 11 t/ha suitable for growing on fertile and less fertile soils. It has started to be grown commercially in 2000.

  20. Relationship between frontal dust storms and transient eddy activity in the northern hemisphere of Mars as observed by Mars Global Surveyor

    OpenAIRE

    Wang, Huiqun; Zurek, Richard W.; Richardson, Mark I.

    2005-01-01

    We have compiled a catalog of frontal dust storms in the northern hemisphere using Mars Orbiter Camera daily global maps spanning ~2.3 Martian years of Mars Global Surveyor (MGS) observations (from 1999 to 2003). The most vigorous frontal storms that flush dust to the low latitudes occur in early-mid fall and mid-late winter, away from the northern winter solstice. While many streaks are observed in the polar hood during the winter solstice period, no frontal dust storms are observed in the v...

  1. Right hemisphere grey matter structure and language outcomes in chronic left hemisphere stroke

    Science.gov (United States)

    Xing, Shihui; Lacey, Elizabeth H.; Skipper-Kallal, Laura M.; Jiang, Xiong; Harris-Love, Michelle L.; Zeng, Jinsheng

    2016-01-01

    The neural mechanisms underlying recovery of language after left hemisphere stroke remain elusive. Although older evidence suggested that right hemisphere language homologues compensate for damage in left hemisphere language areas, the current prevailing theory suggests that right hemisphere engagement is ineffective or even maladaptive. Using a novel combination of support vector regression-based lesion-symptom mapping and voxel-based morphometry, we aimed to determine whether local grey matter volume in the right hemisphere independently contributes to aphasia outcomes after chronic left hemisphere stroke. Thirty-two left hemisphere stroke survivors with aphasia underwent language assessment with the Western Aphasia Battery-Revised and tests of other cognitive domains. High-resolution T1-weighted images were obtained in aphasia patients and 30 demographically matched healthy controls. Support vector regression-based multivariate lesion-symptom mapping was used to identify critical language areas in the left hemisphere and then to quantify each stroke survivor’s lesion burden in these areas. After controlling for these direct effects of the stroke on language, voxel-based morphometry was then used to determine whether local grey matter volumes in the right hemisphere explained additional variance in language outcomes. In brain areas in which grey matter volumes related to language outcomes, we then compared grey matter volumes in patients and healthy controls to assess post-stroke plasticity. Lesion–symptom mapping showed that specific left hemisphere regions related to different language abilities. After controlling for lesion burden in these areas, lesion size, and demographic factors, grey matter volumes in parts of the right temporoparietal cortex positively related to spontaneous speech, naming, and repetition scores. Examining whether domain general cognitive functions might explain these relationships, partial correlations demonstrated that grey matter

  2. Optimal Cross Hedging Winter Canola

    OpenAIRE

    Kim, Seon-Woong; Brorsen, B. Wade; Yoon, Byung-Sam

    2014-01-01

    Winter canola in the southern Great Plains has shown large price fluctuations and there have been questions about which futures market could be used to reduce price risk. Our results indicate that the optimal futures contract to cross hedge winter canola is soybean oil futures.

  3. Widespread land surface wind decline in the Northern Hemisphere partly attributed to land surface changes

    Science.gov (United States)

    Thepaut, J.; Vautard, R.; Cattiaux, J.; Yiou, P.; Ciais, P.

    2010-12-01

    The decline of surface wind observed in many regions of the world is a potential source of concern for wind power electricity generation. It is also suggested as the main cause of decreasing pan evaporation. In China, a persistent and significant decrease of monsoon winds was observed in all seasons. Surface wind declines were also evidenced in several regions of the world (U.S., Australia, several European countries). Except over China, no clear explanation was given for the wind decrease in the regions studied. Whether surface winds decrease is due to changes in the global atmospheric circulation or its variability, in surface processes or to observational trends has therefore not been elucidated. The identification of the drivers of such a decline requires a global investigation of available surface and upper-air wind data, which has not been conducted so far. Here we use global datasets of in-situ wind measurements that contain surface weather stations wind data (hourly or three-hourly data acquisition time step) and rawinsonde vertical wind data profiles (monthly time step) prepared by the NCAR. A set of 822 worldwide surface stations with continuous wind records was selected after a careful elimination of stations with obvious breaks and large gaps. This dataset mostly covers the Northern mid latitudes over the period 1979-2008. Using this data set, we found that annual mean wind speeds have declined at 73% of the surface stations over the past 30 years. In the Northern Hemisphere, positive wind trends are found only in a few places. In Europe, Central Asia, Eastern Asia and in North America the annual mean surface wind speed has decreased on average at a rate of -2.9, -5.9, -4.2, and -1.8 %/decade respectively, i.e. a decrease of about 10% in 30 years and up to about 20% in Central Asia. These results are robust to changes in the station selection method and parameters. By contrast, upper-air winds observed from rawinsondes, geostrophic winds deduced from

  4. Klaus Winter (1930 - 2015)

    CERN Multimedia

    2015-01-01

    We learned with great sadness that Klaus Winter passed away on 9 February 2015, after a long illness.   Klaus was born in 1930 in Hamburg, where he obtained his diploma in physics in 1955. From 1955 to 1958 he held a scholarship at the Collège de France, where he received his doctorate in nuclear physics under the guidance of Francis Perrin. Klaus joined CERN in 1958, where he first participated in experiments on π+ and K0 decay properties at the PS, and later became the spokesperson of the CHOV Collaboration at the ISR. Starting in 1976, his work focused on experiments with the SPS neutrino beam. In 1984 he joined Ugo Amaldi to head the CHARM experiment, designed for detailed studies of the neutral current interactions of high-energy neutrinos, which had been discovered in 1973 using the Gargamelle bubble chamber at the PS. The unique feature of the detector was its target calorimeter, which used large Carrara marble plates as an absorber material. From 1984 to 1991, Klau...

  5. Winter fuels report

    Energy Technology Data Exchange (ETDEWEB)

    1995-01-13

    The Winter Fuels Report is intended to provide concise, timely information to the industry, the press, policymakers, consumers, analysts, and State and local governments on the following topics: distillate fuel oil net production, imports and stocks on a US level and for all Petroleum Administration for Defense Districts (PADD) and product supplied on a US level; propane net production, imports and stocks on a US level and for PADD`s I, II, and III; natural gas supply and disposition and underground storage for the US and consumption for all PADD`s, as well as selected National average prices; residential and wholesale pricing data for heating oil and propane for those States participating in the joint Energy Information Administration (EIA)/State Heating Oil and Propane Program; crude oil and petroleum price comparisons for the US and selected cities; and a 6-10 day, 30-Day, and 90-Day outlook for temperature and precipitation and US total heating degree-days by city.

  6. Hemispheric Learning and the Hispanic Student.

    Science.gov (United States)

    Contreras, Maximiliano

    People of different cultures differ in the cognitive style they use. Research reports that Mexican American children indicate a preference for field-sensitive cognitive strategies that are spatial-holistic, and middle class children a preference for field-independent strategies that are verbal-analytic. Brain research in hemisphericity appears to…

  7. Right Hemisphere Specialization for Color Detection

    Science.gov (United States)

    Sasaki, Hitoshi; Morimoto, Akiko; Nishio, Akira; Matsuura, Sumie

    2007-01-01

    Three experiments were carried out to investigate hemispheric asymmetry in color processing among normal participants. In Experiment 1, it was shown that the reaction times (RTs) of the dominant and non-dominant hands assessed using a visual target presented at the central visual field, were not significantly different. In Experiment 2, RTs of…

  8. An Evaluative Review of Hemispheric Learning Potential

    Science.gov (United States)

    1985-10-01

    abilities of both the hemispheres. Specific learning gains on standardized tests have been reported. Neurolinguistic programing is a technique...transformed into possibilities; problems into creative opportunities (U.K. Training Centre broadsheet). Neurolinguistic programing can even be employed to...also draw on suggestopedia and neurolinguistic programing, together with yoga. Inner Track Learning suggests that Recent research has shown that

  9. Forest carbon sinks in the Northern Hemisphere

    Science.gov (United States)

    Christine L. Goodale; Michael J. Apps; Richard A. Birdsey; Christopher B. Field; Linda S. Heath; Richard A. Houghton; Jennifer C. Jenkins; Gundolf H. Kohlmaier; Werner Kurz; Shirong Liu; Gert-Jan Nabuurs; Sten Nilsson; Anatoly Z. Shvidenko

    2002-01-01

    There is general agreement that terrestrial systems in the Northern Hemisphere provide a significant sink for atmospheric CO2; however, estimates of the magnitude and distribution of this sink vary greatly. National forest inventories provide strong, measurement-based constraints on the magnitude of net forest carbon uptake. We brought together...

  10. Pharyngeal Swallowing Mechanics Secondary to Hemispheric Stroke.

    Science.gov (United States)

    May, Nelson H; Pisegna, Jessica M; Marchina, Sarah; Langmore, Susan E; Kumar, Sandeep; Pearson, William G

    2017-05-01

    Computational analysis of swallowing mechanics (CASM) is a method that utilizes multivariate shape change analysis to uncover covariant elements of pharyngeal swallowing mechanics associated with impairment using videofluoroscopic swallowing studies. The goals of this preliminary study were to (1) characterize swallowing mechanics underlying stroke-related dysphagia, (2) decipher the impact of left and right hemispheric strokes on pharyngeal swallowing mechanics, and (3) determine pharyngeal swallowing mechanics associated with penetration-aspiration status. Videofluoroscopic swallowing studies of 18 dysphagic patients with hemispheric infarcts and age- and gender-matched controls were selected from well-controlled data sets. Patient data including laterality and penetration-aspiration status were collected. Coordinates mapping muscle group action during swallowing were collected from videos. Multivariate morphometric analyses of coordinates associated with stroke, affected hemisphere, and penetration-aspiration status were performed. Pharyngeal swallowing mechanics differed significantly in the following comparisons: stroke versus controls (D = 2.19, P mechanics associated with each comparison were visualized using eigenvectors. Whereas current literature focuses on timing changes in stroke-related dysphagia, these data suggest that mechanical changes are also functionally important. Pharyngeal swallowing mechanics differed by the affected hemisphere and the penetration-aspiration status. CASM can be used to identify patient-specific swallowing impairment associated with stroke injury that could help guide rehabilitation strategies to improve swallowing outcomes. Copyright © 2017 National Stroke Association. Published by Elsevier Inc. All rights reserved.

  11. Predicting weather regime transitions in Northern Hemisphere datasets

    Energy Technology Data Exchange (ETDEWEB)

    Kondrashov, D. [University of California, Department of Atmospheric and Oceanic Sciences and Institute of Geophysics and Planetary Physics, Los Angeles, CA (United States); Shen, J. [UCLA, Department of Statistics, Los Angeles, CA (United States); Berk, R. [UCLA, Department of Statistics, Los Angeles, CA (United States); University of Pennsylvania, Department of Criminology, Philadelphia, PA (United States); D' Andrea, F.; Ghil, M. [Ecole Normale Superieure, Departement Terre-Atmosphere-Ocean and Laboratoire de Meteorologie Dynamique (CNRS and IPSL), Paris Cedex 05 (France)

    2007-10-15

    A statistical learning method called random forests is applied to the prediction of transitions between weather regimes of wintertime Northern Hemisphere (NH) atmospheric low-frequency variability. A dataset composed of 55 winters of NH 700-mb geopotential height anomalies is used in the present study. A mixture model finds that the three Gaussian components that were statistically significant in earlier work are robust; they are the Pacific-North American (PNA) regime, its approximate reverse (the reverse PNA, or RNA), and the blocked phase of the North Atlantic Oscillation (BNAO). The most significant and robust transitions in the Markov chain generated by these regimes are PNA {yields} BNAO, PNA {yields} RNA and BNAO {yields} PNA. The break of a regime and subsequent onset of another one is forecast for these three transitions. Taking the relative costs of false positives and false negatives into account, the random-forests method shows useful forecasting skill. The calculations are carried out in the phase space spanned by a few leading empirical orthogonal functions of dataset variability. Plots of estimated response functions to a given predictor confirm the crucial influence of the exit angle on a preferred transition path. This result points to the dynamic origin of the transitions. (orig.)

  12. Resting state EEG power, intra-hemisphere and inter-hemisphere coherence in bipolar disorder

    Science.gov (United States)

    Handayani, Nita; Khotimah, S. N.; Haryanto, F.; Arif, I.; Taruno, Warsito P.

    2017-02-01

    This paper examines the differences of EEG power and coherence between bipolar disorder patients and healthy subjects in the resting state. Observations are focused on the prefrontal cortex area by calculating intra-hemisphere and inter-hemisphere coherence. EEG data acquisition are conducted by using wireless Emotiv Epoc on AF3, AF4, FC5, FC6, F7 and F8 channels. The power spectral analysis shows that in bipolar disoder there is an increase of power in the delta, theta and beta frequencies, and power decrease in the alpha frequency. The coherence test results show that both intra-hemisphere and inter-hemisphere coherence in bipolar disorder patients are lower than healthy subjects. This shows the lack of brain synchronization in bipolar disorder patients.

  13. Choosing words: left hemisphere, right hemisphere, or both? Perspective on the lateralization of word retrieval

    Science.gov (United States)

    Ries, Stephanie K.; Dronkers, Nina F.; Knight, Robert T.

    2015-01-01

    Language is considered to be one of the most lateralized human brain functions. Left hemisphere dominance for language has been consistently confirmed in clinical and experimental settings and constitutes one of the main axioms of neurology and neuroscience. However, functional neuroimaging studies are finding that the right hemisphere also plays a role in diverse language functions. Critically, the right hemisphere may also compensate for the loss or degradation of language functions following extensive stroke-induced damage to the left hemisphere. Here, we review studies that focus on our ability to choose words as we speak. Although fluidly performed in individuals with intact language, this process is routinely compromised in aphasic patients. We suggest that parceling word retrieval into its sub-processes—lexical activation and lexical selection—and examining which of these can be compensated for after left hemisphere stroke can advance the understanding of the lateralization of word retrieval in speech production. In particular, the domain-general nature of the brain regions associated with each process may be a helpful indicator of the right hemisphere's propensity for compensation. PMID:26766393

  14. Melanopsin-Mediated Acute Light Responses Measured in Winter and in Summer

    OpenAIRE

    Münch, Mirjam; Ladaique, Myriam; Roemer, Ségolène; Hashemi, Kattayoon; Kawasaki, Aki

    2017-01-01

    Seasonal adaptation is a ubiquitous behavior seen in many species on both global hemispheres and is conveyed by changing photoperiods. In humans this seasonal adaptation is less apparent, in part because changes in daylength are masked by the use of electrical lighting at night. On the other hand, cataracts which reduce light transmission, may compound seasonal changes related to the reduced daylength of winter. To better understand the effects of different photoperiod lengths in healthy adul...

  15. The Challenge of Winter Backpacking.

    Science.gov (United States)

    Cavanaugh, Michael; Mapes, Alan

    1981-01-01

    Tips and techniques for safe and enjoyable winter backpacking are offered. Topics covered include cross county skis, snowshoes, clothing, footwear, shelter, sleeping bags, food, hypothermia prevention, as well as general rules and requirements. (CO)

  16. Winter waterfowl survey, southeastern Alaska

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Little is known of the total numbers of wintering waterfowl within the north pacific coastal region. The random stratified plot sampling methods used in 1980, as...

  17. Winter/Summer Monsoon Experiment

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Winter/Summer Monsoon Experiment (MONEX) was conducted during the First Global GARP (Global Atmospheric Research Program) Experiment (FGGE). An international...

  18. Shining Light on "Dark Winter"

    National Research Council Canada - National Science Library

    Tara O'Toole; Michael Mair; Thomas V. Inglesby

    2002-01-01

    ... Security, and the Oklahoma National Memorial Institute for the Prevention of Terrorism, held a senior-level exercise entitled "Dark Winter" that simulated a covert smallpox attack on the United States...

  19. The nature of hemispheric specialization for prosody perception

    NARCIS (Netherlands)

    Witteman, Jurriaan; Goerlich-Dobre, Katharina S.; Martens, Sander; Aleman, Andre; Van Heuven, Vincent J.; Schiller, Niels O.

    Recent evidence suggests a relative right-hemispheric specialization for emotional prosody perception, whereas linguistic prosody perception is under bilateral control. It is still unknown, however, how the hemispheric specialization for prosody perception might arise. Two main hypotheses have been

  20. Behavioral evidence for left-hemisphere specialization of motor planning

    NARCIS (Netherlands)

    Janssen, L.; Meulenbroek, R.G.J.; Steenbergen, B.

    2011-01-01

    Recent studies suggest that the left hemisphere is dominant for the planning of motor actions. This left-hemisphere specialization hypothesis was proposed in various lines of research, including patient studies, motor imagery studies, and studies involving neurophysiological techniques. However,

  1. Global characteristics of extreme winters from a multi-millennial simulation

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, B.G. [CSIRO Marine and Atmospheric Research, PO Box 1, Aspendale (Australia)

    2011-10-15

    Output from a multi-millennial simulation with the CSIRO Mark 2 coupled global climatic model has been analysed to determine the principal characteristics of extreme winters over the globe for ''present conditions''. Thus, this study is not concerned with possible changes in winter conditions associated with anthropogenically induced climatic change. Defining an extreme winter as having a surface temperature anomaly of below -2 standard deviations (sd) revealed a general occurrence rate over the globe of between 100 and 200 over a 6,000-year period of the simulation, with somewhat higher values over northwest North America. For temperature anomalies below -3 sd the corresponding occurrence rate drops to about 10. Spatial correlation studies revealed that extreme winters over regions in Europe, North America or Asia were very limited geographically, with time series of the surface temperature anomalies for these regions having mutual correlation coefficients of about 0.2. The temporal occurrence rates of winters (summers) having sd below -3 (above +3) were very asymmetric and sporadic, suggesting that such events arise from stochastic influences. Multi-year sequences of extreme winters were comparatively rare events. Detailed analysis revealed that the temporal and spatial evolution of the monthly surface temperature anomalies associated with an individual extreme winter were well replicated in the simulation, as were daily time series of such anomalies. Apart from an influence of the North Atlantic Oscillation on extreme winters in Europe, other prominent climatic oscillations were very poorly correlated with such winters. Rather modest winter temperature anomalies were found in the southern hemisphere. (orig.)

  2. ENSO and East Asian winter monsoon relationship modulation associated with the anomalous northwest Pacific anticyclone

    Science.gov (United States)

    Kim, Ji-Won; An, Soon-Il; Jun, Sang-Yoon; Park, Hey-Jin; Yeh, Sang-Wook

    2017-08-01

    Using observational datasets and numerical model experiments, the mechanism on the slowly varying change in the relationship between the El Niño-Southern Oscillation (ENSO) and the East Asian winter monsoon (EAWM) is investigated. The decadal-window (11-, 15-, and 21-year) moving correlations show a significant change in the boreal wintertime ENSO-EAWM relationship between two sub-periods of 1976‒1992 and 1997‒2013. Such recent change in ENSO-EAWM relationship is mainly attributed to the changes in the intensity and zonal location of the anomalous lower-tropospheric northwest Pacific anticyclone (NWP-AC). NWP-AC commonly develops near the region of the Philippine Sea during the ENSO's peak phase and plays an important role of bridging the tropical convection and mid-latitude teleconnection. On one hand, the intensity of the NWP-AC is influenced by the interdecadal variation in a linkage between ENSO and the Indian Ocean sea surface temperature (SST) variability, referring that a strong connection between the Pacific and Indian Oceans results in the strengthening of NWP-AC response to ENSO. On the other hand, the zonal displacement of the NWP-AC is associated with the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). That is, the tropical Pacific mean state (i.e., zonal SST gradient between climatologically warm western Pacific and cold eastern Pacific)—strengthened by either the negative PDO phase or the positive AMO phase—drives the anomalous ENSO-induced convection to be shifted to the west. With this westward shift, the zonal center of the NWP-AC also migrates westward over the Philippine Islands and exerts stronger connection between ENSO and EAWM. In contrast, the relaxed zonal SST contrast associated with either the positive PDO phase or the negative AMO phase tends to exhibit weaker ENSO-EAWM relationship via both of eastward shifted zonal centers of the anomalous ENSO-induced convection and the NWP-AC. Finally, a

  3. A hemispherical imaging and tracking (HIT) system

    Science.gov (United States)

    Gilbert, John A.; Fair, Sara B.; Caldwell, Scott E.; Gronner, Sally J.

    1992-05-01

    A hemispherical imaging and tracking (HIT) system is described which is used for an interceptor designed to acquire, select, home, and hit-to-kill reentry vehicle targets from intercontinental ballistic missiles. The system provides a sizable field of view, over which a target may be tracked and yields a unique and distinctive optical signal when the system is 'on target'. The system has an infinite depth of focus and no moving parts are required for imaging within a hemisphere. Critical alignment of the HIT system is based on the comparison of signals captured through different points on an annular window. Assuming that the perturbations are radially symmetric, errors may be eliminated during the subtraction.

  4. Right hemisphere structures predict poststroke speech fluency.

    Science.gov (United States)

    Pani, Ethan; Zheng, Xin; Wang, Jasmine; Norton, Andrea; Schlaug, Gottfried

    2016-04-26

    We sought to determine via a cross-sectional study the contribution of (1) the right hemisphere's speech-relevant white matter regions and (2) interhemispheric connectivity to speech fluency in the chronic phase of left hemisphere stroke with aphasia. Fractional anisotropy (FA) of white matter regions underlying the right middle temporal gyrus (MTG), precentral gyrus (PreCG), pars opercularis (IFGop) and triangularis (IFGtri) of the inferior frontal gyrus, and the corpus callosum (CC) was correlated with speech fluency measures. A region within the superior parietal lobule (SPL) was examined as a control. FA values of regions that significantly predicted speech measures were compared with FA values from healthy age- and sex-matched controls. FA values for the right MTG, PreCG, and IFGop significantly predicted speech fluency, but FA values of the IFGtri and SPL did not. A multiple regression showed that combining FA of the significant right hemisphere regions with the lesion load of the left arcuate fasciculus-a previously identified biomarker of poststroke speech fluency-provided the best model for predicting speech fluency. FA of CC fibers connecting left and right supplementary motor areas (SMA) was also correlated with speech fluency. FA of the right IFGop and PreCG was significantly higher in patients than controls, while FA of a whole CC region of interest (ROI) and the CC-SMA ROI was significantly lower in patients. Right hemisphere white matter integrity is related to speech fluency measures in patients with chronic aphasia. This may indicate premorbid anatomical variability beneficial for recovery or be the result of poststroke remodeling. © 2016 American Academy of Neurology.

  5. Morphology of Southern Hemisphere Riometer Auroral Absorption

    Science.gov (United States)

    2006-06-01

    Departamento de Geofísica Universidad de Concepción, Concepción CHILE foppiano@udec.cl ABSTRACT A morphology of riometer auroral absorption is...PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Departamento de Geofísica Universidad de...UNCLASSIFIED/UNLIMITED UNCLASSIFIED/UNLIMITED MORPHOLOGY OF SOUTHERN HEMISPHERE RIOMETER AURORAL ABSORPTION Alberto J. Foppiano Departamento de

  6. Visual Hemispheric Specialization: A Computational Theory.

    Science.gov (United States)

    1985-10-31

    been extensively tested and his right hemisphere is capable of comprehending involved verbal instructions and of making simple deductions and...1968). Spatial and verbal components of the act of recall. Canadian Journal of Psychology, 19, 289-299. Butters, N., Barton, M., and Brody, B. A. (1970...1967). The relationship between visuo-spatial impairment and constructional apraxia . Cortex, 3, 327-342. Diamond, R., and Carey, S. (1977

  7. Brain Hemisphere Dominance: Building the Whole-Brain Singer

    Science.gov (United States)

    Boyd, Amanda R.

    2012-01-01

    The concept of brain hemisphere dominance serves as the basis for many educational learning theories. The dominant brain hemisphere guides the learning process, but both hemispheres are necessary for true learning to take place. This treatise outlines and analyzes the dominance factor, a learning theory developed by Dr. Carla Hannaford, which…

  8. The Influence of Context on Hemispheric Recruitment during Metaphor Processing

    Science.gov (United States)

    Diaz, Michele T.; Hogstrom, Larson J.

    2011-01-01

    Although the left hemisphere's prominence in language is well established, less emphasis has been placed on possible roles for the right hemisphere. Behavioral, patient, and neuroimaging research suggests that the right hemisphere may be involved in processing figurative language. Additionally, research has demonstrated that context can modify…

  9. Depression and the hyperactive right-hemisphere.

    Science.gov (United States)

    Hecht, David

    2010-10-01

    Depression is associated with an inter-hemispheric imbalance; a hyperactive right-hemisphere (RH) and a relatively hypoactive left-hemisphere (LH). Nevertheless, the underlying mechanisms which can explain why depression is associated with a RH dominance remain elusive. This article points out the potential links between functional cerebral asymmetries and specific symptoms and features of depression. There is evidence that the RH is selectively involved in processing negative emotions, pessimistic thoughts and unconstructive thinking styles--all which comprise the cognitive phenomenology of depression and in turn contribute to the elevated anxiety, stress and pain associated with the illness. Additionally, the RH mediates vigilance and arousal which may explain the sleep disturbances often reported in depression. The RH had also been linked with self-reflection, accounting for the tendency of depressed individuals to withdraw from their external environments and focus attention inward. Physiologically, RH activation is associated with hyprecortisolemia, which contributes to the deterioration of the immune system functioning and puts depressed patients at a greater risk of developing other illnesses, accounting for depression's high comorbidity with other diseases. Conversely, the LH is specifically involved in processing pleasurable experiences, and its relative attenuation is in line with the symptoms of anhedonia that characterize depression. The LH is also relatively more involved in decision-making processes, accounting for the indecisiveness that is often accompanied with depression. 2010 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

  10. Transpolar arcs observed simultaneously in both hemispheres

    Science.gov (United States)

    Carter, J. A.; Milan, S. E.; Fear, R. C.; Walach, M.-T.; Harrison, Z. A.; Paxton, L. J.; Hubert, B.

    2017-06-01

    Two coexisting transpolar arcs are observed on 31 August 2005. We track the formation and motion of the arcs in both the Northern and Southern Hemispheres, using data from two independent satellites (Imager for Magnetopause to Aurora Global Exploration and a Defence Meteorological Satellite Program satellite). The observations are supported by supplementary ground-based ionospheric convection data from the Super Dual Auroral Radar Network. The two arcs form during a period of northward interplanetary magnetic field. Following a change in the direction of the interplanetary magnetic field BY component from negative to positive, the dawnside arc traverses the polar cap to the duskside in the Northern Hemisphere. Over the same time period and in the Southern Hemisphere, the duskside arc traverses the polar cap to the dawnside. A complex magnetic field line topology resulting in the coexistence of two tongues of closed field lines protruding into the otherwise open polar cap is implied. We discuss these observations in terms of magnetic conjugacy and a model of transpolar arcs formation.

  11. Epidemiology of obesity in the Western Hemisphere.

    Science.gov (United States)

    Ford, Earl S; Mokdad, Ali H

    2008-11-01

    Obesity has emerged as a global public health challenge. The objective of this review was to examine epidemiological aspects of obesity in the Western Hemisphere. Using PubMed, we searched for publications about obesity (prevalence, trends, correlates, economic costs) in countries in North America, Central America, South America, and the Caribbean. To the extent possible, we focused on studies that were primarily population based in design and on four countries in the Western Hemisphere: Brazil, Canada, Mexico, and the United States. Data compiled by the International Obesity Task Force show a substantial level of obesity in all of or selected areas of the Bahamas, Barbados, Canada, Chile, Guyana, Mexico, Panama, Paraguay, Peru, St. Lucia, Trinidad and Tobago, the United States, and Venezuela. Furthermore, countries such as Brazil, Canada, Mexico, and the United States have experienced increases in the prevalence of obesity. In many countries, the prevalence of obesity is higher among women than men and in urban areas than in rural areas. The relationship between socioeconomic status and obesity depends on the stage of economic transition. Early in the transition, the prevalence of obesity is positively related to income whereas at some point during the transition the prevalence becomes inversely related to income. Like other countries in the Western Hemisphere, the four countries that we focused on have experienced a rising tide of obesity. The high and increasing prevalence of obesity and its attendant comorbidities are likely to pose a serious challenge to the public health and medical care systems in these countries.

  12. Casimir effect in hemisphere capped tubes

    CERN Document Server

    de Mello, E R Bezerra

    2014-01-01

    In this paper we investigate the vacuum densities for a massive scalar field with general curvature coupling in background of a (2+1)-dimensional spacetime corresponding to a cylindrical tube with a hemispherical cap. A complete set of mode functions is constructed and the positive-frequency Wightman function is evaluated for both the cylindrical and hemispherical subspaces. On the base of this, the vacuum expectation values of the field squared and energy-momentum tensor are investigated. The mean field squared and the normal stress are finite on the boundary separating two subspaces, whereas the energy density and the parallel stress diverge as the inverse power of the distance from the boundary. For a conformally coupled field, the vacuum energy density is negative on the cylindrical part of the space. On the hemisphere, it is negative near the top and positive close to the boundary. In the case of minimal coupling the energy density on the cup is negative. On the tube it is positive near the boundary and ...

  13. Five-day planetary waves in the middle atmosphere from Odin satellite data and ground-based instruments in Northern Hemisphere summer 2003, 2004, 2005 and 2007

    Directory of Open Access Journals (Sweden)

    A. Belova

    2008-11-01

    Full Text Available A number of studies have shown that 5-day planetary waves modulate noctilucent clouds and the closely related Polar Mesosphere Summer Echoes (PMSE at the summer mesopause. Summer stratospheric winds should inhibit wave propagation through the stratosphere and, although some numerical models (Geisler and Dickinson, 1976 do show a possibility for upward wave propagation, it has also been suggested that the upward propagation may in practice be confined to the winter hemisphere with horizontal propagation of the wave from the winter to the summer hemisphere at mesosphere heights causing the effects observed at the summer mesopause. It has further been proposed (Garcia et al., 2005 that 5-day planetary waves observed in the summer mesosphere could be excited in-situ by baroclinic instability in the upper mesosphere. In this study, we first extract and analyze 5-day planetary wave characteristics on a global scale in the middle atmosphere (up to 54 km in temperature, and up to 68 km in ozone concentration using measurements by the Odin satellite for selected days during northern hemisphere summer from 2003, 2004, 2005 and 2007. Second, we show that 5-day temperature fluctuations consistent with westward-traveling 5-day waves are present at the summer mesopause, using local ground-based meteor-radar observations. Finally we examine whether any of three possible sources of the detected temperature fluctuations at the summer mesopause can be excluded: upward propagation from the stratosphere in the summer-hemisphere, horizontal propagation from the winter-hemisphere or in-situ excitation as a result of the baroclinic instability. We find that in one case, far from solstice, the baroclinic instability is unlikely to be involved. In one further case, close to solstice, upward propagation in the same hemisphere seems to be ruled out. In all other cases, all or any of the three proposed mechanisms are consistent with the observations.

  14. Lesion characteristics driving right-hemispheric language reorganization in congenital left-hemispheric brain damage.

    Science.gov (United States)

    Lidzba, Karen; de Haan, Bianca; Wilke, Marko; Krägeloh-Mann, Ingeborg; Staudt, Martin

    2017-10-01

    Pre- or perinatally acquired ("congenital") left-hemispheric brain lesions can be compensated for by reorganizing language into homotopic brain regions in the right hemisphere. Language comprehension may be hemispherically dissociated from language production. We investigated the lesion characteristics driving inter-hemispheric reorganization of language comprehension and language production in 19 patients (7-32years; eight females) with congenital left-hemispheric brain lesions (periventricular lesions [n=11] and middle cerebral artery infarctions [n=8]) by fMRI. 16/17 patients demonstrated reorganized language production, while 7/19 patients had reorganized language comprehension. Lesions to the insular cortex and the temporo-parietal junction (predominantly supramarginal gyrus) were significantly more common in patients in whom both, language production and comprehension were reorganized. These areas belong to the dorsal stream of the language network, participating in the auditory-motor integration of language. Our data suggest that the integrity of this stream might be crucial for a normal left-lateralized language development. Copyright © 2017. Published by Elsevier Inc.

  15. Polar Vortex Conditions during the 1995-96 Artic Winter: Meteorology and MLS Ozone

    Science.gov (United States)

    Manney, G. L.; Santee, M. L.; Froidevaux, L.; Waters, J. W.; Zurek, R. W.

    1996-01-01

    The 1995-96 northern hemisphere (NH) 205 winter stratosphere was colder than in any of the previous 17 winters, with lower stratospheric temperatures continuously below the type 1 (primarily HN03) polar stratospheric cloud (PSC) threshold for over 2 1/2 months. Upper tropospheric ridges in late Feb and early Mar 1996 led to the lowest observed NH lower stratospheric temperatures, and the latest observed NH temperatures below the type 2 (water ice) PSC threshold. Consistent with the unusual cold and chemical processing on PSCS, Upper Atmosphere Research Satellite (UARS) MLS observed a greater decrease in lower stratospheric ozone (03) in 1995-96 than in any of the previous 4 NH winters. 03 decreased throughout the vortex over an altitude range nearly as large as that typical of the southern hemisphere (SH). The decrease between late Dec 1995 and early Mar 1996 was about 2/3 of that over the equivalent SH period. As in other NH winters, temperatures in 1996 rose above the PSC threshold before the spring equinox, ending chemical processing in the NH vortex much earlier than is usual in the SH. A downward trend in column 03 above 100 hPa during Jan and Feb 1996 appears to be related to the lower stratospheric 03 depletion.

  16. Rat model of focal cerebral ischemia in the dominant hemisphere.

    Science.gov (United States)

    Zhang, Hua; Shen, Yan; Wang, Wei; Gao, Huanmin

    2015-01-01

    In the human brain, the dominant hemisphere is more complex than the non-dominant hemisphere. Hence, cerebral ischemia of the dominant hemisphere often leads to serious consequences. This study aims to establish a rodent model of focal cerebral ischemia in the dominant hemisphere. The quadruped feeding test was used to screen 70 male Sprague Dawley rats. From this test, 48 rats with right paw preference were selected and randomly assigned numbers. Half were assigned to the dominant hemisphere ischemia (DHI) group, and the other half were assigned to the non-dominant hemisphere ischemia (NDHI) group. The middle cerebral artery was occluded 2 h before reperfusion. Neurological functions were tested. TTC and HE staining were performed. The volume of cerebral infarction was calculated. Rats in the DHI group had significantly worse neurological scores than rats in the NDHI group (P dominant hemisphere than in the non-dominant hemisphere. The dominant hippocampus indicated severe neuronal loss and disorderly cellular arrangement. The volume of cerebral infarction was also greater in the DHI group compared to the NDHI group (P dominant hemisphere, MCA occlusion in the dominant hemisphere caused greater impairment in neurological functions. The proposed rodent model is reliable and has high levels of reproducibility. Therefore, his model can be reliably for investigating the mechanism of focal cerebral ischemia in the dominant hemisphere of human brains.

  17. Impacts of four northern-hemisphere teleconnection patterns on atmospheric circulations over Eurasia and the Pacific

    Science.gov (United States)

    Gao, Tao; Yu, Jin-yi; Paek, Houk

    2017-08-01

    The impacts of four teleconnection patterns on atmospheric circulation components over Eurasia and the Pacific region, from low to high latitudes in the Northern Hemisphere (NH), were investigated comprehensively in this study. The patterns, as identified by the Climate Prediction Center (USA), were the East Atlantic (EA), East Atlantic/Western Russia (EAWR), Polar/Eurasia (POLEUR), and Scandinavian (SCAND) teleconnections. Results indicate that the EA pattern is closely related to the intensity of the subtropical high over different sectors of the NH in all seasons, especially boreal winter. The wave train associated with this pattern serves as an atmospheric bridge that transfers Atlantic influence into the low-latitude region of the Pacific. In addition, the amplitudes of the EAWR, SCAND, and POLEUR patterns were found to have considerable control on the "Vangengeim-Girs" circulation that forms over the Atlantic-Eurasian region in winter or spring. The EA and EAWR mainly affect the westerlies in winter and spring and the POLEUR and SCAND, respectively, in summer and winter. Strong westerlies confine the extension of the North Polar vortex, which generally results in a small weak vortex and a shallow East Asian trough located in a position further east than normal. Furthermore, the North Polar vortex presents significant connections with the patterns during winter and summer. Analyses in this work suggest that the teleconnection patterns in summer could be driven, at least partly, by the Atlantic Multidecadal Oscillation, which to some degree might transmit the influence of the Atlantic Ocean to Eurasia and the Pacific region.

  18. Right-hemispheric processing of non-linguistic word features

    DEFF Research Database (Denmark)

    Baumgaertner, Annette; Hartwigsen, Gesa; Roman Siebner, Hartwig

    2013-01-01

    Verbal stimuli often induce right-hemispheric activation in patients with aphasia after left-hemispheric stroke. This right-hemispheric activation is commonly attributed to functional reorganization within the language system. Yet previous evidence suggests that functional activation in right......-hemispheric homologues of classic left-hemispheric language areas may partly be due to processing nonlinguistic perceptual features of verbal stimuli. We used functional MRI (fMRI) to clarify the role of the right hemisphere in the perception of nonlinguistic word features in healthy individuals. Participants made......, in some instances, be driven by a "nonlinguistic perceptual processing" mode that focuses on nonlinguistic word features. This raises the possibility that stronger activation of right inferior frontal areas during language tasks in aphasic patients with left-hemispheric stroke may at least partially...

  19. Impact of ENSO events on the interannual variability of Hadley circulation extents in boreal winter

    Directory of Open Access Journals (Sweden)

    Yi-Peng Guo

    2016-03-01

    Full Text Available The interannual variability of the boreal winter Hadley circulation extents during the period of 1979–2014 and its links to El Niño-Southern Oscillation (ENSO were investigated by using reanalysis datasets. Results showed that the El Niño (La Niña events can induce the shrinking (expansion of Hadley circulation extent in the Southern Hemisphere. For the Northern Hemisphere, El Niño (La Niña mainly leads to shrinking (expansion of the Hadley circulation extent in the middle and lower troposphere and expansion (shrinking of the Hadley circulation extent in the upper troposphere. The ENSO associated meridional temperature gradients have close relationship with the Hadley circulation extents in both Hemispheres. But in the Northern Hemisphere, the ENSO associated eddy momentum flux divergence plays more important role in affecting the Hadley circulation extent than the meridional temperature gradient because of the small local Rossby number. In the Southern Hemisphere, as the ENSO induced eddy momentum flux divergence is small, the meridional temperature gradient dominates the change of the Hadley circulation extent.

  20. Winter: Public Enemy #1 for Accessibility EXPLORING NEW SOLUTIONS

    Directory of Open Access Journals (Sweden)

    Ernesto Morales

    2014-05-01

    Full Text Available Abstract: Winter is expensive. For countries situated in the northern hemisphere, closer to the north pole, such as Canada, Russia and Scandinavia, winter requires the acquisition of special clothing, car tires, and sports equipment, snow removal or plowing from the streets, and is associated with the presence of ice patches, along with accidents and illnesses associated with cold weather. Fall-related injuries due to winter conditions have been estimated to cost the Canadian health care system $ 2.8 billion a year. However, the greatest cost snow entails every year is the social isolation of seniors as well as wheelchair and walker users. This results from the lack of accessibility, as it is difficult to circulate on snow-covered streets even for the able-bodied. Social isolation has been associated with other negative consequences such as depression and even suicide. This exploratory pilot study aimed at finding possible and feasible design solutions for improving the accessibility of sidewalks during winter conditions. For this project we used a Co-Design methodology. Stakeholders (City of Quebec representatives, designers, urban planners, occupational therapists, and adults with motor, visual and aural disabilities were invited to participate in the design process. In order to meet the objectives, two main steps were carried out: 1. Conception of the design solutions (through Co-design sessions in a Focus-group format with seniors, designers and researchers; and 2. Validation of the design solutions (consultation with experts and stakeholders. The results are a wide variety of possible and feasible solutions, including the reorganisation of the snow-removal procedure and the development of heated curb cuts. This project was funded by the City of Quebec in partnership with the Centre interdisciplinaire de recherche en réadaptation et intégration sociale (CIRRIS. Ultimately, the project sought to explore possible solutions to be implemented

  1. Phenological changes in the southern hemisphere.

    Directory of Open Access Journals (Sweden)

    Lynda E Chambers

    Full Text Available Current evidence of phenological responses to recent climate change is substantially biased towards northern hemisphere temperate regions. Given regional differences in climate change, shifts in phenology will not be uniform across the globe, and conclusions drawn from temperate systems in the northern hemisphere might not be applicable to other regions on the planet. We conduct the largest meta-analysis to date of phenological drivers and trends among southern hemisphere species, assessing 1208 long-term datasets from 89 studies on 347 species. Data were mostly from Australasia (Australia and New Zealand, South America and the Antarctic/subantarctic, and focused primarily on plants and birds. This meta-analysis shows an advance in the timing of spring events (with a strong Australian data bias, although substantial differences in trends were apparent among taxonomic groups and regions. When only statistically significant trends were considered, 82% of terrestrial datasets and 42% of marine datasets demonstrated an advance in phenology. Temperature was most frequently identified as the primary driver of phenological changes; however, in many studies it was the only climate variable considered. When precipitation was examined, it often played a key role but, in contrast with temperature, the direction of phenological shifts in response to precipitation variation was difficult to predict a priori. We discuss how phenological information can inform the adaptive capacity of species, their resilience, and constraints on autonomous adaptation. We also highlight serious weaknesses in past and current data collection and analyses at large regional scales (with very few studies in the tropics or from Africa and dramatic taxonomic biases. If accurate predictions regarding the general effects of climate change on the biology of organisms are to be made, data collection policies focussing on targeting data-deficient regions and taxa need to be financially

  2. Phenological Changes in the Southern Hemisphere

    Science.gov (United States)

    Chambers, Lynda E.; Altwegg, Res; Barbraud, Christophe; Barnard, Phoebe; Beaumont, Linda J.; Crawford, Robert J. M.; Durant, Joel M.; Hughes, Lesley; Keatley, Marie R.; Low, Matt; Morellato, Patricia C.; Poloczanska, Elvira S.; Ruoppolo, Valeria; Vanstreels, Ralph E. T.; Woehler, Eric J.; Wolfaardt, Anton C.

    2013-01-01

    Current evidence of phenological responses to recent climate change is substantially biased towards northern hemisphere temperate regions. Given regional differences in climate change, shifts in phenology will not be uniform across the globe, and conclusions drawn from temperate systems in the northern hemisphere might not be applicable to other regions on the planet. We conduct the largest meta-analysis to date of phenological drivers and trends among southern hemisphere species, assessing 1208 long-term datasets from 89 studies on 347 species. Data were mostly from Australasia (Australia and New Zealand), South America and the Antarctic/subantarctic, and focused primarily on plants and birds. This meta-analysis shows an advance in the timing of spring events (with a strong Australian data bias), although substantial differences in trends were apparent among taxonomic groups and regions. When only statistically significant trends were considered, 82% of terrestrial datasets and 42% of marine datasets demonstrated an advance in phenology. Temperature was most frequently identified as the primary driver of phenological changes; however, in many studies it was the only climate variable considered. When precipitation was examined, it often played a key role but, in contrast with temperature, the direction of phenological shifts in response to precipitation variation was difficult to predict a priori. We discuss how phenological information can inform the adaptive capacity of species, their resilience, and constraints on autonomous adaptation. We also highlight serious weaknesses in past and current data collection and analyses at large regional scales (with very few studies in the tropics or from Africa) and dramatic taxonomic biases. If accurate predictions regarding the general effects of climate change on the biology of organisms are to be made, data collection policies focussing on targeting data-deficient regions and taxa need to be financially and logistically

  3. Walter Baade and the Southern Hemisphere

    Science.gov (United States)

    Osterbrock, D. E.

    1993-12-01

    The inception of the European Southern Observatory is generally traced to Walter Baade's discussions with Jan Oort during his visit to Leiden in the spring of 1953. However, these discussions had certainly been underway between them previously, during Oort's visit to Pasadena in early 1952. Furthermore, Baade's great interest in southern-hemisphere astronomy and his strong desire to observe there can be traced far back in his career. In 1927, after his return to Germany from a year in the U.S. under a Rockefeller fellowship, Baade reported that his country had no chance to catch up with American astronomy in the northern hemisphere. He advocated moving the Hamburg 1-meter reflector to the southern hemisphere to get in ahead of the U.S. with an effective telescope there. Baade emphasized the research that could be done on high-luminosity and variable stars in the Magellanic Clouds. Later, after he had joined the Mount Wilson staff, his early attempts to locate the center of our Galaxy and globular clusters near it (in 1937) and his observational study (with Edwin Hubble) of the Sculptor and Fornax dwarf galaxies (in 1939) re-emphasized to him the need for a southern observatory. During and soon after World War II he made many suggestions on a search for ``cluster-type variables'' in the Magellanic Clouds to Enrique Gaviola, director of the new 1.5-meter Bosque Alegre reflector in Argentina. Baade wanted to go there to observe with it himself, but his German citizenship prevented him from leaving the U.S.. Finally, in the last year of his life, he was able to observe NGC 6522 (the globular cluster in ``his'' window), with the Mount Stromlo 1.9-meter reflector.

  4. Hemispheric dominance and cell phone use.

    Science.gov (United States)

    Seidman, Michael D; Siegel, Bianca; Shah, Priyanka; Bowyer, Susan M

    2013-05-01

    A thorough understanding of why we hold a cell phone to a particular ear may be of importance when studying the impact of cell phone safety. To determine if there is an obvious association between sidedness of cell phone use and auditory hemispheric dominance (AHD) or language hemispheric dominance (LHD). It is known that 70% to 95% of the population are right-handed, and of these, 96% have left-brain LHD. We have observed that most people use their cell phones in their right ear. An Internet survey was e-mailed to individuals through surveymonkey.com. The survey used a modified Edinburgh Handedness Inventory protocol. Sample questions surveyed which hand was used to write with, whether the right or left ear was used for phone conversations, as well as whether a brain tumor was present. General community. An Internet survey was randomly e-mailed to 5000 individuals selected from an otology online group, patients undergoing Wada testing and functional magnetic resonance imaging, as well as persons on the university listserv, of which 717 surveys were completed. Determination of hemispheric dominance based on preferred ear for cell phone use. A total of 717 surveys were returned. Ninety percent of the respondents were right handed, and 9% were left handed. Sixty-eight percent of the right-handed people used the cell phone in their right ear, 25% in the left ear, and 7% had no preference. Seventy-two of the left-handed respondents used their left ear, 23% used their right ear, and 5% had no preference. Cell phone use averaged 540 minutes per month over the past 9 years. An association exists between hand dominance laterality of cell phone use (73%) and our ability to predict hemispheric dominance. Most right-handed people have left-brain LHD and use their cell phone in their right ear. Similarly, most left-handed people use their cell phone in their left ear. Our study suggests that AHD may differ from LHD owing to the difference in handedness and cell phone ear use

  5. Hemispheric asymmetries in reading Korean: task matters.

    Science.gov (United States)

    Vaid, J; Park, K

    1997-06-01

    Native Korean readers were studied in a visual half-field paradigm. Subjects were to make speeded judgments on Hangul (syllabic) and Hanzza (logographic) scripts based on phonetic or visual properties of the stimuli. A task by visual field interaction was obtained indicating that, for both scripts, responses on the phonetic task were faster in the right visual field, whereas no visual field differences were found on the visual task. Script type did not interact with visual field. The results support a task-based account of hemispheric differences in verbal processing.

  6. Multimodal agnosia after unilateral left hemisphere lesion.

    Science.gov (United States)

    Feinberg, T E; Rothi, L J; Heilman, K M

    1986-06-01

    Agnosia is an abnormality of recognition that is not explained by sensory or cognitive disorders. We studied a patient who had combined visual-tactile agnosia without prosopagnosia after a left hemisphere infarct. Although he copied figures presented visually and he performed intramodal or crossmodal visual-tactile matches, he could not indicate recognition by either sight or touch. The lesion involved areas of the occipital and temporal lobes that may be important for human performance of tasks that require construction and application of meaning to percepts presented both visually and tactually.

  7. Clusters of interannual sea ice variability in the northern hemisphere

    Science.gov (United States)

    Fučkar, Neven S.; Guemas, Virginie; Johnson, Nathaniel C.; Massonnet, François; Doblas-Reyes, Francisco J.

    2016-09-01

    We determine robust modes of the northern hemisphere (NH) sea ice variability on interannual timescales disentangled from the long-term climate change. This study focuses on sea ice thickness (SIT), reconstructed with an ocean-sea-ice general circulation model, because SIT has a potential to contain most of the interannual memory and predictability of the NH sea ice system. We use the K-means cluster analysis—one of clustering methods that partition data into groups or clusters based on their distances in the physical space without the typical constraints of other unsupervised learning statistical methods such as the widely-used principal component analysis. To adequately filter out climate change signal in the Arctic from 1958 to 2013 we have to approximate it with a 2nd degree polynomial. Using 2nd degree residuals of SIT leads to robust K-means cluster patterns, i.e. invariant to further increase of the polynomial degree. A set of clustering validity indices yields K = 3 as the optimal number of SIT clusters for all considered months and seasons with strong similarities in their cluster patterns. The associated time series of cluster occurrences exhibit predominant interannual persistence with mean timescale of about 2 years. Compositing analysis of the NH surface climate conditions associated with each cluster indicates that wind forcing seem to be the key factor driving the formation of interannual SIT cluster patterns during the winter. Climate memory in SIT with such interannual persistence could lead to increased predictability of the Artic sea ice cover beyond seasonal timescales.

  8. Modes of variability of Southern Hemisphere atmospheric circulation estimated by AGCMs

    Energy Technology Data Exchange (ETDEWEB)

    Grainger, Simon; Frederiksen, Carsten S. [Bureau of Meteorology, Centre for Australian Weather and Climate Research, Melbourne (Australia); Zheng, Xiaogu [National Institute of Water and Atmospheric Research, Wellington (New Zealand); Beijing Normal University, College of Global Change and Earth System, Beijing (China); Fereday, David; Folland, Chris K.; Knight, Jeff R. [Met Office Hadley Centre for Climate Change, Exeter (United Kingdom); Jin, Emilia K.; Kinter, James L. [George Mason University, Department of Atmospheric, Oceanic and Earth Sciences, Fairfax, VA (United States); Center for Ocean-Land-Atmosphere Studies, Calverton, MD (United States); Schubert, Siegfried [NASA Goddard Space Flight Center, Greenbelt, MD (United States); Syktus, Jozef [Queensland Climate Change Centre of Excellence, Brisbane (Australia)

    2011-02-15

    The seasonal mean variability of the atmospheric circulation is affected by processes with time scales from less than seasonal to interannual or longer. Using monthly mean data from an ensemble of Atmospheric General Circulation Model (AGCM) realisations, the interannual variability of the seasonal mean is separated into intraseasonal, and slowly varying components. For the first time, using a recently developed method, the slowly varying component in multiple AGCM ensembles is further separated into internal and externally forced components. This is done for Southern Hemisphere 500 hPa geopotential height from five AGCMs in the CLIVAR International Climate of the Twentieth Century project for the summer and winter seasons. In both seasons, the intraseasonal and slow modes of variability are qualitatively well reproduced by the models when compared with reanalysis data, with a relative metric finding little overall difference between the models. The Southern Annular Mode (SAM) is by far the dominant mode of slowly varying internal atmospheric variability. Two slow-external modes of variability are related to El Nino-Southern Oscillation (ENSO) variability, and a third is the atmospheric response to trends in external forcing. An ENSO-SAM relationship is found in the model slow modes of variability, similar to that found by earlier studies using reanalysis data. There is a greater spread in the representation of model slow-external modes in winter than summer, particularly in the atmospheric response to external forcing trends. This may be attributable to weaker external forcing constraints on SH atmospheric circulation in winter. (orig.)

  9. Hemispheric specialization in dogs for processing different acoustic stimuli.

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    Marcello Siniscalchi

    Full Text Available Considerable experimental evidence shows that functional cerebral asymmetries are widespread in animals. Activity of the right cerebral hemisphere has been associated with responses to novel stimuli and the expression of intense emotions, such as aggression, escape behaviour and fear. The left hemisphere uses learned patterns and responds to familiar stimuli. Although such lateralization has been studied mainly for visual responses, there is evidence in primates that auditory perception is lateralized and that vocal communication depends on differential processing by the hemispheres. The aim of the present work was to investigate whether dogs use different hemispheres to process different acoustic stimuli by presenting them with playbacks of a thunderstorm and their species-typical vocalizations. The results revealed that dogs usually process their species-typical vocalizations using the left hemisphere and the thunderstorm sounds using the right hemisphere. Nevertheless, conspecific vocalizations are not always processed by the left hemisphere, since the right hemisphere is used for processing vocalizations when they elicit intense emotion, including fear. These findings suggest that the specialisation of the left hemisphere for intraspecific communication is more ancient that previously thought, and so is specialisation of the right hemisphere for intense emotions.

  10. Novel hemispheric image formation: concepts and applications

    Science.gov (United States)

    Thibault, Simon; Konen, Pierre; Roulet, Patrice; Villegas, Mathieu

    2008-04-01

    Panoramic and hemispheric lens technologies represent new and exciting opportunities in both imaging and projection systems. Such lenses offer intriguing applications for the transportation/automotive industry, in the protection of civilian and military areas, business. In this paper we describe a new optical design technique that provides a greater degree of freedom in producing a variety of hemispheric spatial light distribution areas. This innovative optical design strategy, of generating and controlling image mapping, has been successful in producing high-resolution imaging and projection systems. This success has subsequently generated increased interest in the high-resolution camera/projector and the concept of absolute measurement with high-resolution wide-angle lenses. The new technique described in this paper uses optimization techniques to improve the performance of a customized wide-angle lens optical system for a specific application. By adding a custom angle-to-pixel ratio at the optical design stage, this customized optical system provides ideal image coverage while reducing and optimizing signal processing. This novel image formation technique requires the development of new algorithms in order to view the panoramic image on a display without any residual distortion.

  11. Eikenprocessierups doorstaat koude winter goed

    NARCIS (Netherlands)

    Mulder, S.

    2010-01-01

    Eikenprocessierupsen zijn niet gedeerd door de langdurige koude van deze winter. Bij het opensnijden van eipakketjes blijken de rupsjes springlevend naar buiten te komen. Het is nog te vroeg om nu al iets te zeggen over de mogelijke overlast later dit jaar. Dat is afhankelijk van de

  12. Elevated Ozone in the Troposphere over the Atlantic and Pacific Oceans in the Northern Hemisphere

    Science.gov (United States)

    Chandra, S.; Ziemke, J. R.; Tie, Xuexi

    2003-01-01

    Tropospheric column ozone (TCO) is derived from differential measurements of total column ozone from Nimus-7 and Earth Probe TOMS, and stratospheric column ozone from the Microwave Limb Sounder instrument on the Upper Atmospheric Research Satellite. It is shown that TCO during summer months over the Atlantic and Pacific Oceans at northern mid-latitudes is about the same (50-60 Dobson Units) as over the continents of North America, Europe and Asia, where surface emissions of nitrogen oxides from industrial sources, biomass and biofuel burning and biogenic emissions are significantly larger. This nearly uniform zonal variation in TCO is modulated by surface topography of the Rocky and Himalayan mountains and Tibetan Plateau where TCO is reduced by 20-30 Dobson Units. The zonal characteristics of TCO derived from satellite measurements are well simulated by a global chemical transport model called MOZART-2 (Model of Ozone and Related Chemical Tracers, version 2). The model results are analyzed to delineate the relative importance of various processes contributing to observed zonal characteristics of TCO, and they are shown that the surface emission of NOx contributes about 50% of the TCO at northern mid-latitudes, especially over the continents of North America, Europe and Asia. The result of TCO derived from TOMS and the analysis from MOZART-2 indicate that TCO is a very useful tool to study tropospheric O3 pollution resulting from surface emissions of pollutants.

  13. The Southern Hemisphere and equatorial region ionization response for a 22 September 1999 severe magnetic storm

    Directory of Open Access Journals (Sweden)

    E. Yizengaw

    2004-09-01

    Full Text Available The ionospheric storm evolution process was monitored during the 22 September 1999 magnetic storm over the Australian eastern region, through measurements of the ionospheric Total Electron Content (TEC from seven Global Positioning Systems (GPS stations. The spatial and temporal variations of the ionosphere were analysed as a time series of TEC maps. Results of our analysis show that the main ionospheric effect of the storm under consideration are: the long lasting negative storm effect during a magnetic storm at mid-latitude regions; the strong, positive disturbances during the storm's main phase at auroral latitude regions; the effects of storm-induced equatorward directed wind causing a positive disturbance at high and mid-latitude stations with appropriate time shift between higher and lower latitudes; daytime poleward movement of depleted plasma that causes temporary suppression of the equatorial anomaly during the start of the storm recovery phase; and prompt penetration of eastward electric fields to ionospheric altitudes and the production of nearly simultaneous TEC enhancement at all latitudes. In general, we found dominant negative disturbance over mid and high latitudes and positive disturbance at low latitudes. A comparison of storm-time behaviour of TEC determined from GPS satellites, and foF2 derived from ionosondes at a range of latitudes, showed reasonable agreement between the two independent measurements.

  14. A dual task priming investigation of right hemisphere inhibition for people with left hemisphere lesions

    Directory of Open Access Journals (Sweden)

    Smith-Conway Erin R

    2012-03-01

    Full Text Available Abstract Background During normal semantic processing, the left hemisphere (LH is suggested to restrict right hemisphere (RH performance via interhemispheric suppression. However, a lesion in the LH or the use of concurrent tasks to overload the LH's attentional resource balance has been reported to result in RH disinhibition with subsequent improvements in RH performance. The current study examines variations in RH semantic processing in the context of unilateral LH lesions and the manipulation of the interhemispheric processing resource balance, in order to explore the relevance of RH disinhibition to hemispheric contributions to semantic processing following a unilateral LH lesion. Methods RH disinhibition was examined for nine participants with a single LH lesion and 13 matched controls using the dual task paradigm. Hemispheric performance on a divided visual field lexical decision semantic priming task was compared over three verbal memory load conditions, of zero-, two- and six-words. Related stimuli consisted of categorically related, associatively related, and categorically and associatively related prime-target pairs. Response time and accuracy data were recorded and analyzed using linear mixed model analysis, and planned contrasts were performed to compare priming effects in both visual fields, for each of the memory load conditions. Results Control participants exhibited significant bilateral visual field priming for all related conditions (p Conclusions The results from the control group are consistent with suggestions of an age related hemispheric asymmetry reduction and indicate that in healthy aging compensatory bilateral activation may reduce the impact of inhibition. In comparison, the results for the LHD group indicate that following a LH lesion RH semantic processing can be manipulated and enhanced by the introduction of a verbal memory task designed to engage LH resources and allow disinhibition of RH processing.

  15. Discourse Impairments Following Right Hemisphere Brain Damage: A Critical Review.

    Science.gov (United States)

    Johns, Clinton L; Tooley, Kristen M; Traxler, Matthew J

    2008-11-01

    Right hemisphere brain damage (RHD) rarely causes aphasias marked by clear and widespread failures of comprehension or extreme difficulty producing fluent speech. Nonetheless, subtle language comprehension deficits can occur following unilateral RHD. In this article, we review the empirical record on discourse function following right hemisphere damage, as well as relevant work on non-brain damaged individuals that focuses on right hemisphere function. The review is divided into four sections that focus on discourse processing, inferencing, humor, and non-literal language. While the exact role that the right hemisphere plays in language processing, and the exact way that the two cerebral hemispheres coordinate their linguistic processes are still open to debate, our review suggests that the right hemisphere plays a critical role in managing inferred or implied information by maintaining relevant information and/or suppressing irrelevant information. Deficits in one or both of these mechanisms may account for discourse deficits following RHD.

  16. Why Are the Right and Left Hemisphere Conceptual Representations Different?

    Directory of Open Access Journals (Sweden)

    Guido Gainotti

    2014-01-01

    Full Text Available The present survey develops a previous position paper, in which I suggested that the multimodal semantic impairment observed in advanced stages of semantic dementia is due to the joint disruption of pictorial and verbal representations, subtended by the right and left anterior temporal lobes, rather than to the loss of a unitary, amodal semantic system. The main goals of the present review are (a to survey a larger set of data, in order to confirm the differences in conceptual representations at the level of the right and left hemispheres, (b to examine if language-mediated information plays a greater role in left hemisphere semantic knowledge than sensory-motor information in right hemisphere conceptual knowledge, and (c to discuss the models that could explain both the differences in conceptual representations at the hemispheric level and the prevalence of the left hemisphere language-mediated semantic knowledge over the right hemisphere perceptually based conceptual representations.

  17. Relationship between variability of the semidiurnal tide in the Northern Hemisphere mesosphere and quasi-stationary planetary waves throughout the global middle atmosphere

    Directory of Open Access Journals (Sweden)

    X. Xu

    2009-11-01

    Full Text Available To investigate possible couplings between planetary waves and the semidiurnal tide (SDT, this work examines the statistical correlations between the SDT amplitudes observed in the Northern Hemisphere (NH mesosphere and stationary planetary wave (SPW with wavenumber S=1 (SPW1 amplitudes throughout the global stratosphere and mesosphere. The latter are derived from the Aura-MLS temperature measurements. During NH summer-fall (July–October, the mesospheric SDT amplitudes observed at Svalbard (78° N and Eureka (80° N usually do not show persistent correlations with the SPW1 amplitudes in the opposite hemisphere. Although the SDT amplitudes observed at lower latitudes (~50–70° N, especially at Saskatoon (52° N, are often shown to be highly and positively correlated with the SPW1 amplitudes in high southern latitudes, these correlations cannot be sufficiently explained as evidence for a direct physical link between the Southern Hemisphere (SH winter-early spring SPW and NH summer-early fall mesospheric SDT. This is because the migrating tide's contribution is usually dominant in the mid-high latitude (~50–70° N NH mesosphere during the local late summer-early fall (July–September. The numerical correlation is dominated by similar low-frequency variability or trends between the amplitudes of the NH SDT and SH SPW1 during the respective equinoctial transitions. In contradistinction, during NH winter (November–February, the mesospheric SDT amplitudes at northern mid-high latitudes (~50–80° N are observed to be significantly and positively correlated with the SPW1 amplitudes in the same hemisphere in most cases. Because both the SPW and migrating SDT are large in the NH during the local winter, a non-linear interaction between SPW and migrating SDT probably occurs, thus providing a global non-migrating SDT. This is consistent with observations of SDT in Antarctica that are large in summer than in winter. It is suggested that

  18. Relationship between variability of the semidiurnal tide in the Northern Hemisphere mesosphere and quasi-stationary planetary waves throughout the global middle atmosphere

    Directory of Open Access Journals (Sweden)

    X. Xu

    2009-11-01

    Full Text Available To investigate possible couplings between planetary waves and the semidiurnal tide (SDT, this work examines the statistical correlations between the SDT amplitudes observed in the Northern Hemisphere (NH mesosphere and stationary planetary wave (SPW with wavenumber S=1 (SPW1 amplitudes throughout the global stratosphere and mesosphere. The latter are derived from the Aura-MLS temperature measurements. During NH summer-fall (July–October, the mesospheric SDT amplitudes observed at Svalbard (78° N and Eureka (80° N usually do not show persistent correlations with the SPW1 amplitudes in the opposite hemisphere. Although the SDT amplitudes observed at lower latitudes (~50–70° N, especially at Saskatoon (52° N, are often shown to be highly and positively correlated with the SPW1 amplitudes in high southern latitudes, these correlations cannot be sufficiently explained as evidence for a direct physical link between the Southern Hemisphere (SH winter-early spring SPW and NH summer-early fall mesospheric SDT. This is because the migrating tide's contribution is usually dominant in the mid-high latitude (~50–70° N NH mesosphere during the local late summer-early fall (July–September. The numerical correlation is dominated by similar low-frequency variability or trends between the amplitudes of the NH SDT and SH SPW1 during the respective equinoctial transitions. In contradistinction, during NH winter (November–February, the mesospheric SDT amplitudes at northern mid-high latitudes (~50–80° N are observed to be significantly and positively correlated with the SPW1 amplitudes in the same hemisphere in most cases. Because both the SPW and migrating SDT are large in the NH during the local winter, a non-linear interaction between SPW and migrating SDT probably occurs, thus providing a global non-migrating SDT. This is consistent with observations of SDT in Antarctica that are large in summer than in winter. It is suggested that

  19. Xanthophyll cycle pigment and antioxidant profiles of winter-red (anthocyanic) and winter-green (acyanic) angiosperm evergreen species.

    Science.gov (United States)

    Hughes, Nicole M; Burkey, Kent O; Cavender-Bares, Jeannine; Smith, William K

    2012-03-01

    Leaves of many angiosperm evergreen species change colour from green to red during winter, corresponding with the synthesis of anthocyanin pigments. The ecophysiological function of winter colour change (if any), and why it occurs in some species and not others, are not yet understood. It was hypothesized that anthocyanins play a compensatory photoprotective role in species with limited capacity for energy dissipation. Seasonal xanthophyll pigment content, chlorophyll fluorescence, leaf nitrogen, and low molecular weight antioxidants (LMWA) of five winter-red and five winter-green angiosperm evergreen species were compared. Our results showed no difference in seasonal xanthophyll pigment content (V+A+Z g(-1) leaf dry mass) or LMWA between winter-red and winter-green species, indicating red-leafed species are not deficient in their capacity for non-photochemical energy dissipation via these mechanisms. Winter-red and winter-green species also did not differ in percentage leaf nitrogen, corroborating previous studies showing no difference in seasonal photosynthesis under saturating irradiance. Consistent with a photoprotective function of anthocyanin, winter-red species had significantly lower xanthophyll content per unit chlorophyll and less sustained photoinhibition than winter-green species (i.e. higher pre-dawn F(v)/F(m) and a lower proportion of de-epoxidized xanthophylls retained overnight). Red-leafed species also maintained a higher maximum quantum yield efficiency of PSII at midday (F'(v)/F'(m)) during winter, and showed characteristics of shade acclimation (positive correlation between anthocyanin and chlorophyll content, and negative correlation with chlorophyll a/b). These results suggest that the capacity for photon energy dissipation (photochemical and non-photochemical) is not limited in red-leafed species, and that anthocyanins more likely function as an alternative photoprotective strategy to increased VAZ/Chl during winter.

  20. Total hemispherical emissivity of Inconel 718

    Energy Technology Data Exchange (ETDEWEB)

    Keller, Benjamin P.; Nelson, Shawn E.; Walton, Kyle L.; Ghosh, Tushar K.; Tompson, Robert V.; Loyalka, Sudarshan K., E-mail: LoyalkaS@missouri.edu

    2015-06-15

    Highlights: • We have measured the total hemispherical emissivity for Inconel 718 from about 600–1250 K. • Oxidation in air at 1073 K resulted in an increase in emissivity. • Sandblasting of Inconel 718 was also observed to increase the emissivity. • Coating of graphite powder onto the ‘as-received’ Inconel 718 showed no increase in the emissivity. • Coating of graphite powder onto the 220 grit sandblasted Inconel 718 did show an increase in emissivity. - Abstract: Total hemispherical emissivity for Inconel 718 was measured in anticipation of its application in Very High Temperature Gas Reactors (VHTRs). A majority of current emissivity data for Inconel 718 is in the form of spectral measurements. The data presented here were obtained with an experimental apparatus based on the standard ASTM C835-06 for total hemispherical emittance. Measurements of Inconel 718 were made for four different surface types including: (i) ‘as-received’ from the manufacturer, (ii) oxidized in air and humidified helium, (iii) sandblasted with aluminum oxide powder, and (iv) with a thin coating of nuclear grade graphite powder (grade NGB-18). The emissivity for the ‘as-received’ sample ranged from 0.21 to 0.28 in the temperature interval from 760 K to 1275 K. Oxidation in air at 1073 K resulted in an increase in emissivity into the range from 0.2 at 650 K to 0.52 at 1200 K. There was no dependence on the oxidation times studied here. Oxidation with humidified helium at 1073 K produced less of an increase in emissivity than the oxidation in air but there was an increase up to the range from 0.2 at 600 K to 0.35 at 1200 K. Sandblasting of Inconel 718 was also observed to increase the emissivity up to the range from 0.43 at 780 K to 0.53 at 1270 K when 60 grit sized powder was used and up to the range from 0.45 at 683 K to 0.57 at 1267 K when 120 and 220 grit sized powders were used. Coating of graphite powder onto the ‘as-received’ Inconel 718 showed no increase

  1. Hemispheric asymmetry and theory of mind: is there an association?

    Science.gov (United States)

    Herzig, Daniela A; Sullivan, Sarah; Evans, Jonathan; Corcoran, Rhiannon; Mohr, Christine

    2012-01-01

    In autism and schizophrenia attenuated/atypical functional hemispheric asymmetry and theory of mind impairments have been reported, suggesting common underlying neuroscientific correlates. We here investigated whether impaired theory of mind performance is associated with attenuated/atypical hemispheric asymmetry. An association may explain the co-occurrence of both dysfunctions in psychiatric populations. Healthy participants (n=129) performed a left hemisphere (lateralised lexical decision task) and right hemisphere (lateralised face decision task) dominant task as well as a visual cartoon task to assess theory of mind performance. Linear regression analyses revealed inconsistent associations between theory of mind performance and functional hemisphere asymmetry: enhanced theory of mind performance was only associated with (1) faster right hemisphere language processing, and (2) reduced right hemisphere dominance for face processing (men only). The majority of non-significant findings suggest that theory of mind and functional hemispheric asymmetry are unrelated. Instead of "overinterpreting" the two significant results, discrepancies in the previous literature relating to the problem of the theory of mind concept, the variety of tasks, and the lack of normative data are discussed. We also suggest how future studies could explore a possible link between hemispheric asymmetry and theory of mind.

  2. The inner core hemispheric boundary near 180 °W

    Science.gov (United States)

    Yu, Wen-che; Su, Jun; Song, Teh-Ru Alex; Huang, Hsin-Hua; Mozziconacci, Laetitia; Huang, Bor-Shouh

    2017-11-01

    The inner core (IC) east-west hemispheric dichotomy is widely recognized, but the reported position of the hemispheric boundary varies among studies due to uneven sampling coverage and the data analyzed. This study investigates the sharpness of the western hemispheric boundary (WHB) near 180 °W by analyzing differential time residuals of PKiKP-PKPdf and PKP(bc-df) for PKPdf phases that sample 155 °E-130 °W in various azimuthal directions. Using PKiKP-PKPdf observations, the WHB is located at 175 °E-180 °W in the southern hemisphere, based mainly on the lateral isotropy-anisotropy transition. However, based on the lateral isotropic velocity contrast and this isotropy-anisotropy transition between the two hemispheres, its location is 170-160 °W in the northern hemisphere. These findings indicate that the WHB is sharp and exhibits a latitudinal dependence with a 10°-20° kink, as well as 1.75% anisotropy in the uppermost IC across the 180-155 °W range of the western hemisphere. As suggested by PKP(bc-df), the WHB could remain at 160 °W at depth. The isotropic velocity contrast near the WHB (160 °W) between the eastern and western hemispheres is lower than previous estimates using PKPdf phases sampling the bulk part of each hemisphere.

  3. Shortwave Array Spectroradiometer–Hemispheric (SASHe) Instrument Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Flynn, Connor J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-04-01

    The Shortwave Array Spectroradiometer–Hemispheric (SASHe) provides measurements of direct solar, hemispheric diffuse, and total hemispheric shortwave irradiance over a continuous spectral range from approximately 300 nm to 1700 nm at a rate of about 30 seconds. The SASHe design connects an optical collector located outdoors to a pair of spectrometers and data collections systems located indoors within a climate-controlled building via an umbilical cable of fiber optic and electrical cables. The light collector uses a small Spectralon button as a hemispheric diffuser with a shadowband to distinguish signal from diffuse sky and direct sun.

  4. Predictive influence of sea surface temperature on teleconnection patterns in North Atlantic. A case study on winter seasonal forecast in NW Iberian Peninsula.

    Science.gov (United States)

    Iglesias, I.; Lorenzo, M. N.; Taboada, J. J.; Gómez-Gesteira, M.; Ramos, A. M.

    2010-05-01

    Seasonal forecast in medium latitudes is a research field not too much developed, but it is likely to improve considerable as the dynamics of atmosphere and ocean as a coupled system are better understood. The aim of this work is to study the relationship between the global sea surface temperature anomalies (SSTA) and the most important teleconnection patterns which affect the North Atlantic area: North Atlantic Oscillation (NAO), East Atlantic pattern (EA), Scandinavia pattern (SCA), East Atlantic/Western Russia pattern (EA/WR) and Europe Polar/Eurasia pattern (POL). The relationship between SSTA and those patterns will be explored in autumn and winter, the seasons with the highest quantity of rainfall in the area under study. These teleconnection patterns have a relationship with climate characteristics in Europe. Therefore, any forecast skill over teleconnection patterns will mean a forecast skill on climate. The SST data was provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA. The teleconnection indices were taken from the Climate Prediction Center of the NOAA between 1950 and 2006. Monthly precipitation and temperature data from 1951-2006 for two locations at NW Iberian Peninsula were obtained from the database of MeteoGalicia, the forecast center of the Regional Government of Galicia. The methodology used in this work is the same one used in Phillips and McGregor, 2002 and Lorenzo el al., 2009. Results show that SST anomalies in certain areas of the world ocean have a great potential to improve seasonal climate forecast in the mid-latitudes. A potential predictability for NAO and EA patterns in winter and for SCA and EA patterns in autumn was obtained. The value of those kind of correlations have been studied for a particular region, located at the NW part of the Iberian Peninsula, highlighting the possibility of perform a climate forecast for autumn and winter. This work could serve like a reference for many other regions in Europe, whose climate is

  5. Mexican Mid-winter Waterfowl Survey

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Mexican Mid-winter Waterfowl Survey is a continuation of the annual winter waterfowl survey which is conducted in the United States and Mexico. Since the...

  6. Essential Outdoor Sun Safety Tips for Winter

    Science.gov (United States)

    ... Weekend Warriors expand/collapse Vitamin D Essential Outdoor Sun Safety Tips for Winter Winter sports enthusiasts are ... skiing! Be Mindful of Time Spent in the Sun, Regardless of the Season If possible, ski early ...

  7. Visual attention capacity after right hemisphere lesions

    DEFF Research Database (Denmark)

    Habekost, Thomas; Rostrup, Egill

    2007-01-01

    Recently there has been a growing interest in visual short-term memory (VSTM) including the neural basis of the function. Processing speed, another main aspect of visual attention capacity, has received less investigation. For both cognitive functions human lesion studies are sparse. We used...... a whole report experiment for estimation of these two parameters in 22 patients with right side stroke. Psychophysical performance was analyzed using Bundesen's [Bundesen, C. (1990). A theory of visual attention. Psychological Review, 97, 523-547] Theory of Visual Attention (TVA) and compared...... for both VSTM capacity and ipsilesional processing speed. The study also showed that lesions in a large region of the right hemisphere, including the putamen, insula, and inferior frontal cortex, do not lead to general deficits in the capacity of visual attention. Udgivelsesdato: 2007-Apr-8...

  8. Visual attention capacity after right hemisphere lesions

    DEFF Research Database (Denmark)

    Habekost, Thomas; Rostrup, Egill

    2007-01-01

    a whole report experiment for estimation of these two parameters in 22 patients with right side stroke. Psychophysical performance was analyzed using Bundesen's [Bundesen, C. (1990). A theory of visual attention. Psychological Review, 97, 523-547] Theory of Visual Attention (TVA) and compared...... to damage in the right middle frontal gyrus or leukoaraiosis. The storage capacity of VSTM was also normal for most patients, but deficits were found after severe leukoaraiosis or large strokes extending deep into white matter. Thus, the study demonstrated the importance of white-matter connectivity...... for both VSTM capacity and ipsilesional processing speed. The study also showed that lesions in a large region of the right hemisphere, including the putamen, insula, and inferior frontal cortex, do not lead to general deficits in the capacity of visual attention. Udgivelsesdato: 2007-Apr-8...

  9. Plutonium in Southern Hemisphere ocean Waters

    DEFF Research Database (Denmark)

    Hirose, K.; Aoyama, M.; Gastaud, J.

    2013-01-01

    Plutonium in seawater collected by the BEAGLE2003 cruise was determined using ICP- SF-MS and alpha spectrometry after Fe co-precipitation and radiochemical purification. Levels and distributions of dissolved plutonium activity concentrations in Southern Hemisphere ocean waters are summarized here......, including historical data. Pu-239 concentrations in surface water----of the central South Pacific (32.5 °S) in 2003 were around 1 mBq/m3. The 239Pu concentrations in the Indian Ocean surface waters (20°S) were similar to that in the South Pacific, whereas the 239Pu concentrations in the South Atlantic...... surface waters (30°S) were markedly lower than those in the South Pacific and Indian Oceans. The 239Pu vertical profile pattern was similar to that in the North Pacific subtropical gyre, although 239Pu concentrations in the deep South Pacific were significantly lower than those in the North Pacific. One...

  10. Hemispheric lateralization in an analysis of speech sounds. Left hemisphere dominance replicated in Japanese subjects.

    Science.gov (United States)

    Koyama, S; Gunji, A; Yabe, H; Oiwa, S; Akahane-Yamada, R; Kakigi, R; Näätänen, R

    2000-09-01

    Evoked magnetic responses to speech sounds [R. Näätänen, A. Lehtokoski, M. Lennes, M. Cheour, M. Huotilainen, A. Iivonen, M. Vainio, P. Alku, R.J. Ilmoniemi, A. Luuk, J. Allik, J. Sinkkonen and K. Alho, Language-specific phoneme representations revealed by electric and magnetic brain responses. Nature, 385 (1997) 432-434.] were recorded from 13 Japanese subjects (right-handed). Infrequently presented vowels ([o]) among repetitive vowels ([e]) elicited the magnetic counterpart of mismatch negativity, MMNm (Bilateral, nine subjects; Left hemisphere alone, three subjects; Right hemisphere alone, one subject). The estimated source of the MMNm was stronger in the left than in the right auditory cortex. The sources were located posteriorly in the left than in the right auditory cortex. These findings are consistent with the results obtained in Finnish [R. Näätänen, A. Lehtokoski, M. Lennes, M. Cheour, M. Huotilainen, A. Iivonen, M.Vainio, P.Alku, R.J. Ilmoniemi, A. Luuk, J. Allik, J. Sinkkonen and K. Alho, Language-specific phoneme representations revealed by electric and magnetic brain responses. Nature, 385 (1997) 432-434.][T. Rinne, K. Alho, P. Alku, M. Holi, J. Sinkkonen, J. Virtanen, O. Bertrand and R. Näätänen, Analysis of speech sounds is left-hemisphere predominant at 100-150 ms after sound onset. Neuroreport, 10 (1999) 1113-1117.] and English [K. Alho, J.F. Connolly, M. Cheour, A. Lehtokoski, M. Huotilainen, J. Virtanen, R. Aulanko and R.J. Ilmoniemi, Hemispheric lateralization in preattentive processing of speech sounds. Neurosci. Lett., 258 (1998) 9-12.] subjects. Instead of the P1m observed in Finnish [M. Tervaniemi, A. Kujala, K. Alho, J. Virtanen, R.J. Ilmoniemi and R. Näätänen, Functional specialization of the human auditory cortex in processing phonetic and musical sounds: A magnetoencephalographic (MEG) study. Neuroimage, 9 (1999) 330-336.] and English [K. Alho, J. F. Connolly, M. Cheour, A. Lehtokoski, M. Huotilainen, J. Virtanen, R. Aulanko

  11. The Right Hemisphere in Aesthetic Perception

    Directory of Open Access Journals (Sweden)

    Bianca eBromberger

    2011-10-01

    Full Text Available Little about the neuropsychology of art perception and evaluation is known. Most neuropsychological approaches to art have focused on art production and have been anecdotal and qualitative. The field is in desperate need of quantitative methods if it is to advance. Here, we combine a quantitative approach to the assessment of art with modern voxel-lesion-symptom-mapping (VLSM methods to determine brain-behavior relationships in art perception. We hypothesized that perception of different attributes of art are likely to be disrupted by damage to different regions of the brain. Twenty participants with right hemisphere damage were given the Assessment of Art Attributes (AAA, which is designed to quantify judgments of descriptive attributes of visual art. Each participant rated 24 paintings on 6 conceptual attributes (depictive accuracy, abstractness, emotion, symbolism, realism, and animacy and 6 perceptual attributes (depth, color temperature, color saturation, balance, stroke, and simplicity and their interest in and preference for these paintings. Deviation scores were obtained for each brain-damaged participant for each attribute based on correlations with group average ratings from 30 age-matched healthy participants. Right hemisphere damage affected participants' judgments of abstractness, accuracy, and stroke quality. Damage to areas within different parts of the frontal parietal and lateral temporal cortices produced deviation in judgments in four of six conceptual attributes (abstractness, symbolism, realism and animacy. Of the formal attributes, only depth was affected by inferior prefrontal damage. No areas of brain damage were associated with deviations in interestingness or preference judgments. The perception of conceptual and formal attributes in artwork may in part dissociate from each other and from evaluative judgments. More generally, this approach demonstrates the feasibility of quantitative approaches to the neuropsychology of

  12. Leadership in American Indian Communities: Winter Lessons

    Science.gov (United States)

    Metoyer, Cheryl A.

    2010-01-01

    Winter lessons, or stories told in the winter, were one of the ways in which tribal elders instructed and directed young men and women in the proper ways to assume leadership responsibilities. Winter lessons stressed the appropriate relationship between the leader and the community. The intent was to remember the power and purpose of that…

  13. Differentiating Hemispheric Contributions to Syntax and Semantics in Patients with Left-Hemisphere Lesions

    Science.gov (United States)

    Wright, Paul; Stamatakis, Emmanuel A.; Tyler, Lorraine K.

    2013-01-01

    Understanding the relationship between brain and cognition critically depends on data from brain-damaged patients since these provide major constraints on identifying the essential components of brain–behavior systems. Here we relate structural and functional fMRI data with behavioral data in 21 human patients with chronic left hemisphere (LH) lesions and a range of language impairments to investigate the controversial issue of the role of the hemispheres in different language functions. We address this issue within a dual neurocognitive model of spoken language comprehension in which core linguistic functions, e.g., syntax, depend critically upon an intact left frontotemporal system, whereas more general communicative abilities, e.g., semantics, are supported by a bilateral frontotemporal system and may recover from LH damage through normal or enhanced activity in the intact right hemisphere. The fMRI study used a word-monitoring task that differentiated syntactic and semantic aspects of sentence comprehension. We distinguished overlapping interactions between structure, neural activity, and performance using joint independent components analysis, identifying two structural–functional networks, each with a distinct relationship with performance. Syntactic performance correlated with tissue integrity and activity in a left frontotemporal network. Semantic performance correlated with activity in right superior/middle temporal gyri regardless of tissue integrity. Right temporal activity did not differ between patients and controls, suggesting that the semantic network is degenerately organized, with regions in both hemispheres able to perform similar computations. Our findings support the dual neurocognitive model of spoken language comprehension and emphasize the importance of linguistic specificity in investigations of language recovery in patients. PMID:22699896

  14. Winter to winter recurrence of atmospheric circulation anomalies over East Asia and its impact on winter surface air temperature anomalies.

    Science.gov (United States)

    Zhao, Xia; Yang, Guang

    2017-01-01

    The persistence of atmospheric circulation anomalies over East Asia shows a winter to winter recurrence (WTWR) phenomenon. Seasonal variations in sea level pressure anomalies and surface wind anomalies display significantly different characteristics between WTWR and non-WTWR years. The WTWR years are characterized by the recurrence of both a strong (weak) anomalous Siberian High and an East Asian winter monsoon over two successive winters without persistence through the intervening summer. However, anomalies during the non-WTWR years have the opposite sign between the current and ensuing winters. The WTWR of circulation anomalies contributes to that of surface air temperature anomalies (SATAs), which is useful information for improving seasonal and interannual climate predictions over East Asia and China. In the positive (negative) WTWR years, SATAs are cooler (warmer) over East Asia in two successive winters, but the signs of the SATAs are opposite in the preceding and subsequent winters during the non-WTWR years.

  15. 33 CFR 100.109 - Winter Harbor Lobster Boat Race, Winter Harbor, ME.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Winter Harbor Lobster Boat Race, Winter Harbor, ME. 100.109 Section 100.109 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Lobster Boat Race, Winter Harbor, ME. (a) Regulated area. The regulated area includes all waters of Winter...

  16. Melanopsin-Mediated Acute Light Responses Measured in Winter and in Summer: Seasonal Variations in Adults with and without Cataracts

    OpenAIRE

    Münch, Mirjam; Ladaique, Myriam; Roemer, Ségolène; Hashemi, Kattayoon; Kawasaki, Aki

    2017-01-01

    Seasonal adaptation is a ubiquitous behavior seen in many species on both global hemispheres and is conveyed by changing photoperiods. In humans this seasonal adaptation is less apparent, in part because changes in daylength are masked by the use of electrical lighting at night. On the other hand, cataracts which reduce light transmission, may compound seasonal changes related to the reduced daylength of winter. To better understand the effects of different photoperiod lengths in healthy adul...

  17. The Hemispheric Sign Rule of Current Helicity during the Rising ...

    Indian Academy of Sciences (India)

    We compute the signs of two different current helicity parameters (i.e., best and ) for 87 active regions during the rise of cycle 23. The results indicate that 59% of the active regions in the northern hemisphere have negative best and 65% in the southern hemisphere have positive. This is consistent with that of the cycle ...

  18. Hemispheric Specialization for Tactile-Spatial Processing in Preschool Children.

    Science.gov (United States)

    Etaugh, Claire; Levy, Rhonda B.

    1981-01-01

    Witelson found that boys but not girls showed right-hemisphere specialization for tactile-spatial processing as early as six years. Witelson's task was administered to 46 normal four- and five-year olds. Both sexes showed right-hemisphere specialization. No sex differences appeared either in specialization or in overall performance. (Author/SJL)

  19. Hemispheric Dominance, Conservation Reasoning and the Dominant Eye.

    Science.gov (United States)

    Lawson, Anton E.; Wollman, Warren T.

    This study was based on the following assumptions: (1) functioning of the brain's left hemisphere, because of its logical, verbal mode, facilitates conservation reasoning; (2) functioning of the brain's right hemisphere, because of its nonverbal, spatial mode, inhibits conservation reasoning; (3) visual input from the left eye will reach the left…

  20. Learning-related brain hemispheric dominance in sleeping songbirds

    NARCIS (Netherlands)

    Moorman, Sanne|info:eu-repo/dai/nl/328213187; Gobes, Sharon M H|info:eu-repo/dai/nl/304832669; van de Kamp, Ferdinand C; Zandbergen, Matthijs A|info:eu-repo/dai/nl/14760902X; Bolhuis, Johan J|info:eu-repo/dai/nl/074069454

    2015-01-01

    There are striking behavioural and neural parallels between the acquisition of speech in humans and song learning in songbirds. In humans, language-related brain activation is mostly lateralised to the left hemisphere. During language acquisition in humans, brain hemispheric lateralisation develops

  1. Mercury in wintering seabirds, an aggravating factor to winter wrecks?

    Science.gov (United States)

    Fort, Jérôme; Lacoue-Labarthe, Thomas; Nguyen, Hanh Linh; Boué, Amélie; Spitz, Jérôme; Bustamante, Paco

    2015-09-15

    Every year, thousands of seabirds are cast ashore and are found dead along the coasts of North America and Western Europe. These massive mortality events called 'winter wrecks' have generally been attributed to harsh climatic conditions and prolonged storms which affect bird energy balance and impact their body condition. Nevertheless, additional stress factors, such as contaminant body burden, could potentially cumulate to energy constraints and actively contribute to winter wrecks. However, the role played by these additional factors in seabird massive winter mortality has received little attention to date. In February/March 2014, an unprecedented seabird wreck occurred along the Atlantic French coasts during which > 43,000 seabirds were found dead. By analyzing mercury (Hg) concentrations in various tissues collected on stranded birds, we tested the hypothesis that Hg played a significant role in this mortality. More specifically, we aimed to (1) describe Hg contamination in wintering seabirds found along the French coasts in 2014, and (2) determine if Hg concentrations measured in some vital organs such as kidney and brain reached toxicity thresholds that could have led to deleterious effects and to an enhanced mortality. We found some of the highest Hg levels ever reported in Atlantic puffins, common guillemots, razorbills and kittiwakes. Measured concentrations ranged from 0.8 to 3.6 μg · g(-1) of dry weight in brain, 1.3 to 7.2 μg · g(-1) in muscle, 2.5 to 13.5 μg · g(-1) in kidney, 2.9 to 18.6 μg · g(-1) in blood and from 3.1 to 19.5 μg · g(-1) in liver. Hg concentrations in liver and brain were generally below the estimated acute toxicity levels. However, kidney concentrations were not different than those measured in the liver, and above levels associated to renal sub-lethal effects, suggesting a potential Hg poisoning. We concluded that although Hg was not directly responsible for the high observed mortality, it has been a major aggravating

  2. Hemispherical Resonator Gyroscope Accuracy Analysis Under Temperature Influence

    Directory of Open Access Journals (Sweden)

    Boran LI

    2014-06-01

    Full Text Available Frequency splitting of hemispherical resonator gyroscope will change as system operating temperature changes. This phenomenon leads to navigation accuracy of hemispherical resonator gyroscope reduces. By researching on hemispherical resonator gyroscope dynamical model and its frequency characteristic, the frequency splitting formula and the precession angle formula of gyroscope vibrating mode based on hemispherical resonator gyroscope dynamic equation parameters are derived. By comparison, gyroscope precession angle deviation caused by frequency splitting can be obtained. Based on analysis of temperature variation against gyroscope resonator, the design of hemispherical resonator gyroscope feedback controller under temperature variation conditions is researched and the maximum theoretical fluctuation of gyroscope dynamical is determined by using a numerical analysis example.

  3. Hemispheric processing of memory is affected by sleep.

    Science.gov (United States)

    Monaghan, Padraic; Shaw, John J; Ashworth-Lord, Anneliese; Newbury, Chloe R

    2017-04-01

    Sleep is known to affect learning and memory, but the extent to which it influences behavioural processing in the left and right hemispheres of the brain is as yet unknown. We tested two hypotheses about lateralised effects of sleep on recognition memory for words: whether sleep reactivated recent experiences of words promoting access to the long-term store in the left hemisphere (LH), and whether sleep enhanced spreading activation differentially in semantic networks in the hemispheres. In Experiment 1, participants viewed lists of semantically related words, then slept or stayed awake for 12h before being tested on seen, unseen but related, or unrelated words presented to the left or the right hemisphere. Sleep was found to promote word recognition in the LH, and to spread activation equally within semantic networks in both hemispheres. Experiment 2 ensured that the results were not due to time of day effects influencing cognitive performance. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. Interannual modes of variability of Southern Hemisphere atmospheric circulation in CMIP3 models

    Energy Technology Data Exchange (ETDEWEB)

    Grainger, S; Frederiksen, C S [Centre for Australian Weather and Climate Research, Bureau of Meteorology, Melbourne (Australia); Zheng, X, E-mail: S.Grainger@bom.gov.a [College of Global Change and Earth System Science, Beijing Normal University, Beijing (China)

    2010-08-15

    The atmospheric circulation acts as a bridge between large-scale sources of climate variability, and climate variability on regional scales. Here a statistical method is applied to monthly mean Southern Hemisphere 500hPa geopotential height to separate the interannual variability of the seasonal mean into intraseasonal and slowly varying (time scales of a season or longer) components. Intraseasonal and slow modes of variability are estimated from realisations of models from the Coupled Model Intercomparison Project Phase 3 (CMIP3) twentieth century coupled climate simulation (20c3m) and are evaluated against those estimated from reanalysis data. The intraseasonal modes of variability are generally well reproduced across all CMIP3 20c3m models for both Southern Hemisphere summer and winter. The slow modes are in general less well reproduced than the intraseasonal modes, and there are larger differences between realisations than for the intraseasonal modes. New diagnostics are proposed to evaluate model variability. It is found that differences between realisations from each model are generally less than inter-model differences. Differences between model-mean diagnostics are found. The results obtained are applicable to assessing the reliability of changes in atmospheric circulation variability in CMIP3 models and for their suitability for further studies of regional climate variability.

  5. Seismic hazard map of the western hemisphere

    Directory of Open Access Journals (Sweden)

    J. G. Tanner

    1999-06-01

    Full Text Available Vulnerability to natural disasters increases with urbanization and development of associated support systems (reservoirs, power plants, etc.. Catastrophic earthquakes account for 60% of worldwide casualties associated with natural disasters. Economic damage from earthquakes is increasing, even in technologically advanced countries with some level of seismic zonation, as shown by the 1989 Loma Prieta, CA ($ 6 billion, 1994 Northridge, CA ($ 25 billion, and 1995 Kobe, Japan (> $ 100 billion earthquakes. The growth of megacities in seismically active regions around the world often includes the construction of seismically unsafe buildings and infrastructures, due to an insufficient knowledge of existing seismic hazard. Minimization of the loss of life, property damage, and social and economic disruption due to earthquakes depends on reliable estimates of seismic hazard. National, state, and local governments, decision makers, engineers, planners, emergency response organizations, builders, universities, and the general public require seismic hazard estimates for land use planning, improved building design and construction (including adoption of building construction codes, emergency response preparedness plans, economic forecasts, housing and employment decisions, and many more types of risk mitigation. The seismic hazard map of the Americas is the concatenation of various national and regional maps, involving a suite of approaches. The combined maps and documentation provide a useful global seismic hazard framework and serve as a resource for any national or regional agency for further detailed studies applicable to their needs. This seismic hazard map depicts Peak Ground Acceleration (PGA with a 10% chance of exceedance in 50 years for the western hemisphere. PGA, a short-period ground motion parameter that is proportional to force, is the most commonly mapped ground motion parameter because current building codes that include seismic provisions

  6. Seismic hazard map of the western hemisphere

    Science.gov (United States)

    Shedlock, K.M.; Tanner, J.G.

    1999-01-01

    Vulnerability to natural disasters increases with urbanization and development of associated support systems (reservoirs, power plants, etc.). Catastrophic earthquakes account for 60% of worldwide casualties associated with natural disasters. Economic damage from earthquakes is increasing, even in technologically advanced countries with some level of seismic zonation, as shown by the 1989 Loma Prieta, CA ($6 billion), 1994 Northridge, CA ($ 25 billion), and 1995 Kobe, Japan (> $ 100 billion) earthquakes. The growth of megacities in seismically active regions around the world often includes the construction of seismically unsafe buildings and infrastructures, due to an insufficient knowledge of existing seismic hazard. Minimization of the loss of life, property damage, and social and economic disruption due to earthquakes depends on reliable estimates of seismic hazard. National, state, and local governments, decision makers, engineers, planners, emergency response organizations, builders, universities, and the general public require seismic hazard estimates for land use planning, improved building design and construction (including adoption of building construction codes), emergency response preparedness plans, economic forecasts, housing and employment decisions, and many more types of risk mitigation. The seismic hazard map of the Americas is the concatenation of various national and regional maps, involving a suite of approaches. The combined maps and documentation provide a useful global seismic hazard framework and serve as a resource for any national or regional agency for further detailed studies applicable to their needs. This seismic hazard map depicts Peak Ground Acceleration (PGA) with a 10% chance of exceedance in 50 years for the western hemisphere. PGA, a short-period ground motion parameter that is proportional to force, is the most commonly mapped ground motion parameter because current building codes that include seismic provisions specify the

  7. Modes of low-frequency circulation variability in the Southern Hemisphere

    Science.gov (United States)

    Huth, Radan

    2015-04-01

    In the Northern Hemisphere (NH), the modes of variability of tropospheric circulation on intra-seasonal timescales (also referred to as teleconnections) were described in detail several decades ago. Somewhat surprisingly, a similar description for the Southern Hemisphere (SH) is lacking, a possible reason for this being that the atmospheric circulation in the SH is more transient and less stationary than in the NH, which may have downplayed the importance of the modes for the description of the SH circulation. The only three exceptions that have been described and discussed in detail, including the temporal changes and effects on surface climate elements, are the Southern Annular Mode and two Pacific-South American modes. In the contribution, we present an overview of all the modes of the low-frequency circulation variabiltiy in the Southern Hemisphere extratropics, in all seasons, detected by rotated principal component analysis of monthly mean values of 500 hPa heights. The modes have different spatial structures: zonally oriented dipoles, annular strctures, wavetrains, and monopoles appear among them. Some of the modes are active throughout the year (e.g., the Southern Annular Mode); some of them are active in parts of year only (e.g., wavenumber-3 pattern in the cold half year and wavenumber-4 pattern in the warm half year); some modes forming circumpolar wavetrains in winter are split into two parts in other seasons. One particular mode, consisting of a bi-annular structure, active in all seasons except summer, carries the response of SH circulation to the climate shift in the late 1970's and/or the introducton of satellites in 1979. We provide evidence of the physical realism of the modes by comparing them with correlation maps.

  8. Extreme thermal episodes analyzed with MODIS products during the boreal winter (2000-2016

    Directory of Open Access Journals (Sweden)

    J. Gomis-Cebolla

    2016-06-01

    Full Text Available The beginning of the XXI century is characterized by the intensification of the existing global warming situation and for a series of drastic global meteorological events. Particularly, during the winter season a series of extreme temperature episodes affecting large areas of the northern hemisphere have been produced. In this paper, these episodes are studied by analyzing the thermal anomalies spatial distribution and temporal evolution in the period 2001-2016 from Land Surface Temperature (LST products obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS sensor. The study regions considered in this investigation are eight of the northern hemisphere. The results obtained for the heating and cooling episodes do not reveal an important discrepancy, however, an increase in the area affected by heating versus cooling is observed.

  9. Communicating Certainty About Nuclear Winter

    Science.gov (United States)

    Robock, A.

    2013-12-01

    I have been spending much of my time in the past several years trying to warn the world about the continuing danger of nuclear weapons, and that the solution is a rapid reduction in the nuclear arsenal. I feel that a scientist who discovers dangers to society has an ethical duty to issue a warning, even if the danger is so scary that it is hard for people to deal with. The debate about nuclear winter in the 1980s helped to end the nuclear arms race, but the planet still has enough nuclear weapons, even after reductions planned for 2017 under the New START treaty, to produce nuclear winter, with temperatures plunging below freezing in the summer in major agricultural regions, threatening the food supply for most of the planet. New research by myself, Brian Toon, Mike Mills, and colleagues over the past six years has found that a nuclear war between any two countries, such as India and Pakistan, using 50 atom bombs each of the size dropped on Hiroshima could produce climate change unprecedented in recorded human history, and a world food crisis because of the agricultural effects. This is much less than 1% of the current global arsenal. Communicating certainty - what we know for sure - has been much more effective than communicating uncertainty. The limited success I have had has come from persistence and serendipity. The first step was to do the science. We have published peer-reviewed articles in major journals, including Science, Nature, Proceedings of the National Academy of Sciences, Journal of Geophysical Research, Atmospheric Chemistry and Physics, Physics Today, and Climatic Change. But policymakers do not read these journals. Through fairly convoluted circumstances, which will be described in this talk, we were able to get papers published in Scientific American and the Bulletin of Atomic Scientists. I have also published several encyclopedia articles on the subject. As a Lead Author of Chapter 8 (Radiative Forcing) of the recently published Fifth Assessment

  10. MR imaging features of hemispherical spondylosclerosis

    Energy Technology Data Exchange (ETDEWEB)

    Vicentini, Joao R.T.; Martinez-Salazar, Edgar L.; Chang, Connie Y.; Bredella, Miriam A.; Rosenthal, Daniel I.; Torriani, Martin [Massachusetts General Hospital and Harvard Medical School, Division of Musculoskeletal Imaging and Intervention, Department of Radiology, Boston, MA (United States)

    2017-10-15

    Hemispherical spondylosclerosis (HS) is a rare degenerative entity characterized by dome-shaped sclerosis of a single vertebral body that may pose a diagnostic dilemma. The goal of this study was to describe the MR imaging features of HS. We identified spine radiographs and CT examinations of subjects with HS who also had MR imaging for correlation. Two musculoskeletal radiologists independently assessed sclerosis characteristics, presence of endplate erosions, marrow signal intensity, and disk degeneration (Pfirrmann scale). We identified 11 subjects (six males, five females, mean 48 ± 10 years) with radiographic/CT findings of HS. The most commonly affected vertebral body was L4 (6/11; 55%). On MR imaging, variable signal intensity was noted, being most commonly low on T1 (8/11, 73%) and high on fat-suppressed T2-weighted (8/11, 73%) images. In two subjects, diffuse post-contrast enhancement was seen in the lesion. Moderate disk degeneration and endplate bone erosions adjacent to sclerosis were present in all subjects. Erosions of the opposite endplate were present in two subjects (2/11, 18%). CT data from nine subjects showed the mean attenuation value of HS was 472 ± 96 HU. HS appearance on MR imaging is variable and may not correlate with the degree of sclerosis seen on radiographs or CT. Disk degenerative changes and asymmetric endplate erosions are consistent markers of HS. (orig.)

  11. Individual differences in hemispheric preference and emotion regulation difficulties

    Directory of Open Access Journals (Sweden)

    Garima Gupta

    2011-01-01

    Full Text Available Background: Hemisphericity or individual difference in the preference to use the left or the right hemispheric mode of information processing has been associated with various emotion-related differences. For example, the right hemisphericity has been linked with inhibition of emotional expression, feeling of tension, greater impulsivity etc. These observations suggest that right hemisphericity may be associated with greater difficulties in regulating emotions. However, direct empirical tests of such theoretical proposition are very thin. Aim: In view of this, the present study aims to investigate how and to what extent individual difference in hemispheric preference relate to emotion regulation. Materials and Methods: Thirty-two right-handed male subjects in the age range 18 to 20 years were assessed on self-report measures of hemispheric preference and emotion regulation difficulties. The correlation between dimensions of hemispheric preference and difficulties in regulating emotions was computed. A series of stepwise multiple regression analyses were also done to explore the relative significance of various dimensions of hemispheric preference in predicting emotion regulation difficulties. Results: The findings revealed that in general a preference for the right hemispheric mode of information processing was associated with greater emotion regulation difficulties. The correlation analysis indicated that while impulse control difficulties and difficulties in engaging goal directed behavior was associated with preference for almost all the right hemispheric mode of information processing, the nonacceptance of emotional responses and limited access to emotion regulation was related to preference for only global/synthetic (a right hemispheric mode of information processing. Similarly, the lack of emotional clarity facet of emotion regulation difficulties correlated significantly with a preference for the emotional mode of information processing

  12. Reorganization of syntactic processing following left-hemisphere brain damage: does right-hemisphere activity preserve function?

    Science.gov (United States)

    Tyler, Lorraine K; Wright, Paul; Randall, Billi; Marslen-Wilson, William D; Stamatakis, Emmanuel A

    2010-11-01

    The extent to which the human brain shows evidence of functional plasticity across the lifespan has been addressed in the context of pathological brain changes and, more recently, of the changes that take place during healthy ageing. Here we examine the potential for plasticity by asking whether a strongly left-lateralized system can successfully reorganize to the right-hemisphere following left-hemisphere brain damage. To do this, we focus on syntax, a key linguistic function considered to be strongly left-lateralized, combining measures of tissue integrity, neural activation and behavioural performance. In a functional neuroimaging study participants heard spoken sentences that differentially loaded on syntactic and semantic information. While healthy controls activated a left-hemisphere network of correlated activity including Brodmann areas 45/47 and posterior middle temporal gyrus during syntactic processing, patients activated Brodmann areas 45/47 bilaterally and right middle temporal gyrus. However, voxel-based morphometry analyses showed that only tissue integrity in left Brodmann areas 45/47 was correlated with activity and performance; poor tissue integrity in left Brodmann area 45 was associated with reduced functional activity and increased syntactic deficits. Activity in the right-hemisphere was not correlated with damage in the left-hemisphere or with performance. Reduced neural integrity in the left-hemisphere through brain damage or healthy ageing results in increased right-hemisphere activation in homologous regions to those left-hemisphere regions typically involved in the young. However, these regions do not support the same linguistic functions as those in the left-hemisphere and only indirectly contribute to preserved syntactic capacity. This establishes the unique role of the left hemisphere in syntax, a core component in human language.

  13. Leaf Area Index (LAI Estimation of Boreal Forest Using Wide Optics Airborne Winter Photos

    Directory of Open Access Journals (Sweden)

    Pauline Stenberg

    2009-12-01

    Full Text Available A new simple airborne method based on wide optics camera is developed for leaf area index (LAI estimation in coniferous forests. The measurements are carried out in winter, when the forest floor is completely snow covered and thus acts as a light background for the hemispherical analysis of the images. The photos are taken automatically and stored on a laptop during the flights. The R2 value of the linear regression of the airborne and ground based LAI measurements was 0.89.

  14. On the wintertime low bias of Northern Hemisphere carbon monoxide in global model studies

    Science.gov (United States)

    Stein, O.; Schultz, M. G.; Bouarar, I.; Clark, H.; Huijnen, V.; Gaudel, A.; George, M.; Clerbaux, C.

    2014-01-01

    The uncertainties in the global budget of carbon monoxide (CO) are assessed to explain causes for the long-standing issue of Northern Hemispheric wintertime underestimation of CO concentrations in global models. With a series of MOZART sensitivity simulations for the year 2008, the impacts from changing a variety of surface sources and sinks were analyzed. The model results were evaluated with monthly averages of surface station observations from the global CO monitoring network as well as with total columns observed from satellites and with vertical profiles from measurements on passenger aircraft. Our basic simulation using MACCity anthropogenic emissions underestimated Northern Hemispheric near-surface CO concentrations on average by more than 20 ppb from December to April with the largest bias over Europe of up to 75 ppb in January. An increase in global biomass burning or biogenic emissions of CO or volatile organic compounds (VOC) is not able to reduce the annual course of the model bias and yields too high concentrations over the Southern Hemisphere. Raising global annual anthropogenic emissions results in overestimations of surface concentrations in most regions all-year-round. Instead, our results indicate that anthropogenic emissions in the MACCity inventory are too low for the industrialized countries during winter and spring. Thus we found it necessary to adjust emissions seasonally with regionally varying scaling factors. Moreover, exchanging the original resistance-type dry deposition scheme with a parameterization for CO uptake by oxidation from soil bacteria and microbes reduced the boreal winter dry deposition fluxes and could partly correct for the model bias. When combining the modified dry deposition scheme with increased wintertime road traffic emissions over Europe and North America (factors up to 4.5 and 2, respectively) we were able to optimize the match to surface observations and to reduce the model bias significantly with respect to the

  15. Strong asymmetry of hemispheric climates during MIS-13 inferred from correlating China loess and Antarctica ice records

    Directory of Open Access Journals (Sweden)

    Z. T. Guo

    2009-02-01

    Full Text Available We correlate the China loess and Antarctica ice records to address the inter-hemispheric climate link over the past 800 ka. The results show a broad coupling between Asian and Antarctic climates at the glacial-interglacial scale. However, a number of decoupled aspects are revealed, among which marine isotope stage (MIS 13 exhibits a strong anomaly compared with the other interglacials. It is characterized by unusually positive benthic oxygen (δ18O and carbon isotope (δ13C values in the world oceans, cooler Antarctic temperature, lower summer sea surface temperature in the South Atlantic, lower CO2 and CH4 concentrations, but by extremely strong Asian, Indian and African summer monsoons, weakest Asian winter monsoon, and lowest Asian dust and iron fluxes. Pervasive warm conditions were also evidenced by the records from northern high-latitude regions. These consistently indicate a warmer Northern Hemisphere and a cooler Southern Hemisphere, and hence a strong asymmetry of hemispheric climates during MIS-13. Similar anomalies of lesser extents also occurred during MIS-11 and MIS-5e. Thus, MIS-13 provides a case that the Northern Hemisphere experienced a substantial warming under relatively low concentrations of greenhouse gases. It suggests that the global climate system possesses a natural variability that is not predictable from the simple response of northern summer insolation and atmospheric CO2 changes. During MIS-13, both hemispheres responded in different ways leading to anomalous continental, marine and atmospheric conditions at the global scale. The correlations also suggest that the marine δ18O record is not always a reliable indicator of the northern ice-volume changes, and that the asymmetry of hemispheric climates is one of the prominent factors controlling the strength of Asian, Indian and African monsoon circulations, most likely through modulating the position of

  16. Winter therapy for the accelerators

    CERN Multimedia

    Corinne Pralavorio

    2016-01-01

    Hundreds of people are hard at work during the year-end technical stop as all the accelerators are undergoing maintenance, renovation and upgrade operations in parallel.   The new beam absorber on its way to Point 2 before being lowered into the LHC tunnel for installation. The accelerator teams didn’t waste any time before starting their annual winter rejuvenation programme over the winter. At the end of November, as the LHC ion run was beginning, work got under way on the PS Booster, where operation had already stopped. On 14 December, once the whole complex had been shut down, the technical teams turned their attention to the other injectors and the LHC. The year-end technical stop (YETS) provides an opportunity to carry out maintenance work on equipment and repair any damage as well as to upgrade the machines for the upcoming runs. Numerous work projects are carried out simultaneously, so good coordination is crucial. Marzia Bernardini's team in the Enginee...

  17. Seasonal variability in Northern Hemisphere atmospheric circulation during the Medieval Climate Anomaly and the Little Ice Age

    Science.gov (United States)

    Edwards, Thomas W. D.; Hammarlund, Dan; Newton, Brandi W.; Sjolte, Jesper; Linderson, Hans; Sturm, Christophe; St. Amour, Natalie A.; Bailey, Joscelyn N.-L.; Nilsson, Anders L.

    2017-06-01

    Here we report new reconstructions of winter temperature and summer moisture during the past millennium in southeastern Sweden, based on stable-isotope data from a composite tree-ring sequence, that further enhances our knowledge and understanding of seasonal climate variability in the Northern Hemisphere over the past millennium. Key features of these new climate proxy records include evidence for distinctive fluctuations in winter temperature in SE Sweden, superimposed upon the general pattern of cooling between the so-called Medieval Climate Anomaly (MCA) of the early millennium and the Little Ice Age (LIA) of the late millennium, as well as evidence for sustained summer wetness during the MCA, followed by drier and less variable conditions during the LIA. We also explore these new records within a circumpolar spatial context by employing self-organizing map analysis of meteorological reanalysis data to identify potential modern analogues of mid-tropospheric synoptic circulation types in the Northern Hemisphere extratropics that can reconcile varying seasonal climate states during the MCA and LIA in SE Sweden with less variable conditions in southwestern Canada, as portrayed by paleoclimate records developed in the same manner in an earlier study.

  18. A hemispherical high-pressure xenon gamma radiation spectrometer

    CERN Document Server

    Kessick, R

    2002-01-01

    A prototype hemispherical high-pressure xenon gamma radiation spectrometer was designed, constructed and tested. The detector consists of a pair of concentric hemispherical electrodes contained inside a thin-walled stainless steel pressure dome. Detector performance parameters such as energy resolution, linearity and vibration sensitivity were determined and compared to previous cylindrical and planar designs. Without a Frisch grid, the hemispherical detector provides a total room temperature energy resolution of 6% at 662 keV and is relatively insensitive to acoustic interference.

  19. Motivation and attention following hemispheric stroke.

    Science.gov (United States)

    Olgiati, E; Russell, C; Soto, D; Malhotra, P

    2016-01-01

    Spatial neglect (SN) is an extremely common disorder of attention; it is most frequently a consequence of stroke, especially to the right cerebral hemisphere. The current view of SN is that it is not a unitary deficit but a multicomponent syndrome. Crucially, it has been repeatedly shown that it has a considerable negative impact on rehabilitation outcome. Although a number of behavioral and pharmacological therapies have been developed, none of these appears to be applicable to all patients with SN or has proved unequivocally successful in clinical trials. One potential avenue for therapeutic intervention in neglect relates to the interaction between motivation and attention. A number of investigators, including ourselves, have observed a possible motivational component to the syndrome and showed that motivational stimulation can temporarily improve attention in patients with SN. In this chapter we review previous work looking at how motivation can modulate attention in healthy individuals and how it may be affected by neurological disease before discussing how motivational impairments may contribute to neglect, and how motivation has been used to modulate neglect. In the final section, we present recent experimental work examining how reward interacts with attentional biases in patients with SN. In this study, we adapted the classic Landmark task to explore the mechanisms behind the effect of reward in SN, and found that centrally located stimuli that were explicitly associated with reward appeared to improve neglect and reduce rightward bias. Our results suggest that positive motivation, in the form of anticipated monetary reward, may influence attentional bias via more general mechanisms, such as alerting and task engagement, rather than directly increasing salience of items in contralesional space. We conclude by discussing how motivation might be practically integrated into the rehabilitation of patients with this debilitating disorder. © 2016 Elsevier B

  20. Temperature decrease in the extratropics of South America in response to a tropical forcing during the austral winter

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, G.V. [Centro de Investigaciones Cientificas y Transferencia de Tecnologia a la Produccion (CICYTTP-CONICET), Diamante, Entre Rios (Argentina)

    2010-07-01

    This paper focuses on the dynamic mechanisms that create favorable conditions for the occurrence of frosts that affect large areas of Argentina and are denominated generalized frosts (GF). The hemispheric teleconnection patterns linked to extreme cold events affecting central and northeastern Argentina during winter are identified. The objective is to determine whether the conditions found in previous studies for the composite of winters with extreme (maximum and minimum) frequency of GF occurrence respond to typical characteristics of the austral winter or they are inherent to those particular winters. Taking the mean winter as basic state in the 1961-1990 period, a series of numerical experiments are run using a primitive equation model in which waves are excited with a thermal forcing. The positions of the thermal forcing are chosen according to observed convection anomalies in a basic state given by the austral winters with extreme frequency of GF occurrence. The wave trains excited by anomalous convection situated in specific regions may propagate across the Pacific Ocean and reach South America with the appropriate phase, creating the local favorable conditions for the occurrence of GF. However, the anomalous convection is, by itself, not sufficient since the response also depends on the basic state configuration. This is proved by placing the forcing over the region of significant anomalous convection for maximum and minimum frequency of GF occurrence and the response was very different in comparison to the mean winter. It is concluded that the conditions for a greater GF frequency of occurrence are inherent to these particular winters, so that such conditions are not present in the average winter. (orig.)

  1. Causes of interannual variability over the southern hemispheric tropospheric ozone maximum

    Science.gov (United States)

    Liu, Junhua; Rodriguez, Jose M.; Steenrod, Stephen D.; Douglass, Anne R.; Logan, Jennifer A.; Olsen, Mark A.; Wargan, Krzysztof; Ziemke, Jerald R.

    2017-03-01

    We examine the relative contribution of processes controlling the interannual variability (IAV) of tropospheric ozone over four sub-regions of the southern hemispheric tropospheric ozone maximum (SHTOM) over a 20-year period. Our study is based on hindcast simulations from the National Aeronautics and Space Administration Global Modeling Initiative chemistry transport model (NASA GMI-CTM) of tropospheric and stratospheric chemistry, driven by assimilated Modern Era Retrospective Analysis for Research and Applications (MERRA) meteorological fields. Our analysis shows that over SHTOM region, the IAV of the stratospheric contribution is the most important factor driving the IAV of upper tropospheric ozone (270 hPa), where ozone has a strong radiative effect. Over the South Atlantic region, the contribution from surface emissions to the IAV of ozone exceeds that from stratospheric input at and below 430 hPa. Over the South Indian Ocean, the IAV of stratospheric ozone makes the largest contribution to the IAV of ozone with little or no influence from surface emissions at 270 and 430 hPa in austral winter. Over the tropical South Atlantic region, the contribution from IAV of stratospheric input dominates in austral winter at 270 hPa and drops to less than half but is still significant at 430 hPa. Emission contributions are not significant at these two levels. The IAV of lightning over this region also contributes to the IAV of ozone in September and December. Over the tropical southeastern Pacific, the contribution of the IAV of stratospheric input is significant at 270 and 430 hPa in austral winter, and emissions have little influence.

  2. Hemispheric Differences in the Response of the Upper Atmosphere to the August 2011 Geomagnetic Storm: A Simulation Study

    CERN Document Server

    Yiğit, Erdal; Moldwin, Mark B; Immel, Thomas J; Ridley, Aaron J

    2015-01-01

    Using a three-dimensional nonhydrostatic general circulation model, we investigate the response of the thermosphere-ionosphere system to the 5-6 August 2011 major geomagnetic storm. The model is driven by measured storm-time input data of the Interplanetary Magnetic Field (IMF), solar activity, and auroral activity. Simulations for quiet steady conditions over the same period are performed as well in order to assess the response of the neutral and plasma parameters to the storm. During the storm, the high-latitude mean ion flows are enhanced by up to 150-180%. Largest ion flows are found in the main phase of the storm. Overall, the global mean neutral temperature increases by up to 15%, while the maximum thermal response is higher in the winter Southern Hemisphere at high-latitudes than the summer Northern Hemisphere: 40% vs. 20%increase in high-latitude mean temperature, respectively. The global mean Joule heating increases by more than a factor of three. There are distinct hemispheric differences in the mag...

  3. A modelling study of the latitudinal variations in the nighttime plasma temperatures of the equatorial topside ionosphere during northern winter at solar maximum

    Directory of Open Access Journals (Sweden)

    G. J. Bailey

    2000-11-01

    Full Text Available Latitudinal variations in the nighttime plasma temperatures of the equatorial topside ionosphere during northern winter at solar maximum have been examined by using values modelled by SUPIM (Sheffield University Plasmasphere Ionosphere Model and observations made by the DMSP F10 satellite at 21.00 LT near 800 km altitude. The modelled values confirm that the crests observed near 15° latitude in the winter hemisphere are due to adiabatic heating and the troughs observed near the magnetic equator are due to adiabatic cooling as plasma is transported along the magnetic field lines from the summer hemisphere to the winter hemisphere. The modelled values also confirm that the interhemispheric plasma transport needed to produce the required adiabatic heating/cooling can be induced by F-region neutral winds. It is shown that the longitudinal variations in the observed troughs and crests arise mainly from the longitudinal variations in the magnetic meridional wind. At longitudes where the magnetic declination angle is positive the eastward geographic zonal wind combines with the northward (summer hemisphere to winter hemisphere geographic meridional wind to enhance the northward magnetic meridional wind. This leads to deeper troughs and enhanced crests. At longitudes where the magnetic declination angle is negative the eastward geographic zonal wind opposes the northward geographic meridional wind and the trough depth and crest values are reduced. The characteristic features of the troughs and crests depend, in a complicated manner, on the field-aligned flow of plasma, thermal conduction, and inter-gas heat transfer. At the latitudes of the troughs/crests, the low/high plasma temperatures lead to increased/decreased plasma concentrations.Key words: Ionosphere (equatorial ionosphere; ionosphere-atmosphere interactions

  4. Hemispheric Asymmetries in Price Estimation: Do Brain Hemispheres Attribute Different Monetary Values?

    Science.gov (United States)

    Giuliani, Felice; D’Anselmo, Anita; Tommasi, Luca; Brancucci, Alfredo; Pietroni, Davide

    2017-01-01

    The Spatial Numerical Association of Response Codes (SNARC) effect has been associated with a wide range of magnitude processing. This effect is due to an implicit relationship between numbers and horizontal space, according to which weaker magnitudes and smaller numbers are represented on the left, whereas stronger magnitudes and larger numbers are represented on the right. However, for some particular type of magnitudes such as price, judgments may be also influenced by perceived quality and thus involving valence attribution biases driven by brain asymmetries. In the present study, a lateralized tachistoscopic presentation was used in a price estimation task, using a weight estimation task as a control, to assess differences in asymmetries between these two attributes. Results show a side bias in the former condition but not in the latter, thus indicating that other non-numerical mechanisms are involved in price estimation. Specifically, prices were estimated lower in the left visual field than in the right visual field. The proposed explanation is that price appraisal might involve a valence attribution mechanism leading to a better perceived quality (related to higher prices) when objects are processed primarily in the left hemisphere, and to a lower perceived quality (related to lower prices) when objects are processed primarily in the right hemisphere.

  5. Comprehension and Hemispheric Processing of Irony in Schizophrenia.

    Science.gov (United States)

    Saban-Bezalel, Ronit; Mashal, Nira

    2017-01-01

    Studies focusing on the comprehension of figurative language among schizophrenia patients (SZ) reveal their difficulties comprehending such language and their tendency to interpret it literally. The present study investigated hemispheric processing and comprehension of irony in 16 SZ patients and 18 typically developing (TD) adults. Two experimental tasks were used: an online divided visual field experiment and an offline irony questionnaire. The results show an atypical reversal of hemispheric processing of irony in SZ patients as compared to TD adults. While the TD group demonstrated a right hemisphere advantage in processing irony, SZ patients demonstrated a left hemisphere advantage. Greater comprehension of irony was associated with decreased negative symptoms. In addition, under conditions that not involving a time restriction, the SZ patients' performance improved. Our findings reinforce those of previous studies suggesting that brain lateralization is atypical in SZ patients.

  6. A Novel Hemispherical and Dynamic Camera for EVAs Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The primary objective of this SBIR project is to develop a novel Hemispherical and Dynamic Camera(HDC), with unprecedented capability of optically unwrapping, thus...

  7. Multisensor Analyzed Sea Ice Extent - Northern Hemisphere (MASIE-NH)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Multisensor Analyzed Sea Ice Extent Northern Hemisphere (MASIE-NH) products provide measurements of daily sea ice extent and sea ice edge boundary for the...

  8. A Novel Hemispherical and Dynamic Camera for EVAs Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR project is to develop a novel Hemispherical and Dynamic Camera(HDC) with ultra-wide field of view and low geometric distortion. The novel technology we...

  9. ISLSCP II Northern Hemisphere Monthly Snow Cover Extent

    Data.gov (United States)

    National Aeronautics and Space Administration — This ISLSCP data set is derived from the National Snow and Ice Data Center (NSIDC) Northern Hemisphere EASE-Grid Weekly Snow Cover and Sea Ice Extent product which...

  10. Impacts of hemispheric solar geoengineering on tropical cyclone frequency.

    Science.gov (United States)

    Jones, Anthony C; Haywood, James M; Dunstone, Nick; Emanuel, Kerry; Hawcroft, Matthew K; Hodges, Kevin I; Jones, Andy

    2017-11-14

    Solar geoengineering refers to a range of proposed methods for counteracting global warming by artificially reducing sunlight at Earth's surface. The most widely known solar geoengineering proposal is stratospheric aerosol injection (SAI), which has impacts analogous to those from volcanic eruptions. Observations following major volcanic eruptions indicate that aerosol enhancements confined to a single hemisphere effectively modulate North Atlantic tropical cyclone (TC) activity in the following years. Here we investigate the effects of both single-hemisphere and global SAI scenarios on North Atlantic TC activity using the HadGEM2-ES general circulation model and various TC identification methods. We show that a robust result from all of the methods is that SAI applied to the southern hemisphere would enhance TC frequency relative to a global SAI application, and vice versa for SAI in the northern hemisphere. Our results reemphasise concerns regarding regional geoengineering and should motivate policymakers to regulate large-scale unilateral geoengineering deployments.

  11. Motivation, affect, and hemispheric asymmetry: power versus affiliation.

    Science.gov (United States)

    Kuhl, Julius; Kazén, Miguel

    2008-08-01

    In 4 experiments, the authors examined to what extent information related to different social needs (i.e., power vs. affiliation) is associated with hemispheric laterality. Response latencies to a lateralized dot-probe task following lateralized pictures or verbal labels that were associated with positive or negative episodes related to power, affiliation, or achievement revealed clear-cut laterality effects. These effects were a function of need content rather than of valence: Power-related stimuli were associated with right visual field (left hemisphere) superiority, whereas affiliation-related stimuli were associated with left visual field (right hemisphere) superiority. Additional results demonstrated that in contrast to power, affiliation primes were associated with better discrimination between coherent word triads (e.g., goat, pass, and green, all related to mountain) and noncoherent triads, a remote associate task known to activate areas of the right hemisphere. (c) 2008 APA, all rights reserved

  12. Prediction Center (CPC) Tropical/ Northern Hemisphere Teleconnection Pattern Index

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Monthly tabulated index of the Tropical/ Northern Hemisphere teleconnection pattern. The data spans the period 1950 to present. The index is derived from a rotated...

  13. Improved forecasts of winter weather extremes over midlatitudes with extra Arctic observations

    Science.gov (United States)

    Sato, Kazutoshi; Inoue, Jun; Yamazaki, Akira; Kim, Joo-Hong; Maturilli, Marion; Dethloff, Klaus; Hudson, Stephen R.; Granskog, Mats A.