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Sample records for northern latitude analiz

  1. Beryllium-10 concentrations in water samples of high northern latitudes

    Energy Technology Data Exchange (ETDEWEB)

    Strobl, C.; Eisenhauer, A.; Schulz, V.; Baumann, S.; Mangini, A. [Heidelberger Akademie der Wissenschaften, Heildelberg (Germany); Kubik, P.W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    {sup 10}Be concentrations in the water column of high northern latitudes were not available so far. We present different {sup 10}Be profiles from the Norwegian-Greenland Sea, the Arctic Ocean, and the Laptev Sea. (author) 3 fig., 3 refs.

  2. Distance to the northern high-latitude HI shells

    CERN Document Server

    Puspitarini, Lucky

    2012-01-01

    A detailed 3D distribution of interstellar matter in the solar neighborhood is increasingly necessary. As part of a 3D mapping program, we aim at assigning a precise distance to the high-latitude HI gas in particular the northern part (b \\geq 55^{circ}) of the shell associated with the conspicuous radio continuum Loop I. This shell is thought to be the expanding boundary of an interstellar bubble inflated and recently reheated by the strong stellar winds of the nearby Scorpius-Centaurus OB. We recorded high-resolution spectra of 30 A-type target stars located at various distances in the direction of the northern part of Loop I. Interstellar NaI 5889-5895 and CaII K-H 3934-3968 {\\AA} are modeled and compared with the HI emission spectra from the LAB Survey. About two-thirds of our stellar spectra possess narrow interstellar lines. Narrow lines are located at the velocity of the main, low-velocity Loop 1 HI shell ([-6,+1] km/s in the LSR). Using Hipparcos distances to the target stars, we show that the closest ...

  3. EDITORIAL: Northern Hemisphere high latitude climate and environmental change

    Science.gov (United States)

    Groisman, Pavel; Soja, Amber

    2007-10-01

    High Northern Hemisphere latitudes are undergoing rapid and significant change associated with climate warming. Climatic change in this region interacts with and affects the rate of the global change through atmospheric circulation, biogeophysical, and biogeochemical feedbacks. Changes in the surface energy balance, hydrologic cycle, and carbon budget feedback to regional and global weather and climate systems. Two-thirds of the Northern Hemisphere high latitude land mass resides in Northern Eurasia (~20% of the global land mass), and this region has undergone sweeping socio-economic change throughout the 20th century. How this carbon-rich, cold region component of the Earth system functions as a regional entity and interacts with and feeds back to the greater global system is to a large extent unknown. To mitigate the deficiencies in understanding these feedbacks, which may in turn hamper our understanding of the global change rates and patterns, an initiative was formed. Three years ago the Northern Eurasia Earth Science Partnership Initiative (NEESPI) was established to address large-scale and long-term manifestations of climate and environmental change in this region. The NEESPI Science Plan and its Executive Summary have been published at the NEESPI web site (neespi.org). Since 2004, NEESPI participants have been able to seed several waves of research proposals to international and national funding agencies and institutions and also contribute to the International Polar Year. Currently, NEESPI is widely recognized and endorsed by several Earth System Science Partnership (ESSP) programmes and projects: the International Geosphere and Biosphere Programme, the World Climate Research Programme through the Global Energy and Water Cycle Experiment and Climate and Cryosphere Projects, the Global Water System Project, Global Carbon Project, Global Land Project, and the Integrated Land Ecosystem—Atmosphere Processes Study. Through NEESPI, more than 100 individually

  4. Vitamin D status and its determinants during autumn in children at northern latitudes

    DEFF Research Database (Denmark)

    Petersen, Rikke Agnete; Damsgaard, Camilla T.; Dalskov, Stine-Mathilde;

    2015-01-01

    Sufficient summer/autumn vitamin D status appears important to mitigate winter nadirs at northern latitudes. We conducted a cross-sectional study to evaluate autumn vitamin D status and its determinants in 782 Danish 8-11-year-old children (55°N) using baseline data from the Optimal well-being, d......Sufficient summer/autumn vitamin D status appears important to mitigate winter nadirs at northern latitudes. We conducted a cross-sectional study to evaluate autumn vitamin D status and its determinants in 782 Danish 8-11-year-old children (55°N) using baseline data from the Optimal well...

  5. On the NH3 absorption depression observable at Northern low latitudes of Jupiter

    Science.gov (United States)

    Tejfel, Victor G.; Vdovichenko, Vladimir D.; Lysenko, Peter G.; Karimov, Alibek M.; Kirienko, Galina A.; Bondarenko, Natalya N.; Kharitonova, Galina

    2016-10-01

    From February to April of 2016, we carried out a special series of spectrophotometric observations of Jupiter to study the current behavior of the ammonia absorption at the low latitudes of the Northern hemisphere, where in 2004 we have found a well-defined depression of the 787 nm NH3 absorption band intensity (V.Tejfel et al., Bull.AAS, 2005, Vol. 37, p.682). In subsequent years, an existence of this depression was annually confirmed by spectral observations, although we were noticing its variable character. During observations of 2016 we obtained more than 2,500 CCD-spectrograms, including the spectra of the central meridian, the GRS, and 12 scans of Jovian disk on different dates (70 zonal spectra in each scan). The 787 nm NH3 absorption band was extracted with using of ratios of the Jovian spectra to the Saturn's disk spectrum that was taken as a reference. The depression of absorption in this band begins almost from the equator, and its maximum occurs at the planetographic latitude of 100N then the absorption increases again approaching to the latitude of 200N. The equivalent bandwidths corresponding to these latitudes are equal to 18.7 ± 1.4 A, 14.4 ± 1.0 A and 17.8 ± 0.8A. The 645 nm NH3 absorption band also shows depletion at the low latitudes of the Northern hemisphere, but it is less pronounced. At the temperate latitudes of the Northern hemisphere this band's absorption is systematically lower than the Southern Hemisphere's ones. We will continue research in this direction, especially because recently a significant depletion of gaseous NH3 has also been found with using of the VLA with high resolution (I. de Pater et al., Science, 2016, Vol. 352, Issue 6290, p.1290-1294) at the low latitudes of the Northern hemisphere in the region of the NEB.

  6. Vitamin D status and its determinants during autumn in children at northern latitudes

    DEFF Research Database (Denmark)

    Petersen, Rikke Agnete; Damsgaard, Camilla T.; Dalskov, Stine-Mathilde

    2015-01-01

    Sufficient summer/autumn vitamin D status appears important to mitigate winter nadirs at northern latitudes. We conducted a cross-sectional study to evaluate autumn vitamin D status and its determinants in 782 Danish 8-11-year-old children (55°N) using baseline data from the Optimal well...

  7. Projecting crop yield in northern high latitude area.

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    Matsumura, Kanichiro

    2014-01-01

    Changing climatic conditions on seasonal and longer time scales influence agricultural production. Improvement of soil and fertilizer is a strong factor in agricultural production, but agricultural production is influenced by climate conditions even in highly developed countries. It is valuable if fewer predictors make it possible to conduct future projections. Monthly temperature and precipitation, wintertime 500hPa geopotential height, and the previous year's yield are used as predictors to forecast spring wheat yield in advance. Canadian small agricultural divisions (SAD) are used for analysis. Each SAD is composed of a collection of Canadian Agricultural Regions (CAR) of similar weather and growing conditions. Spring wheat yields in each CAR are forecast from the following variables: (a) the previous year's yield, (b) earlier stages of the growing season's climate conditions and, (c) the previous year's wintertime northern hemisphere 500hPa geopotential height field. Arctic outflow events in the Okanagan Valley in Canada are associated with episodes of extremely low temperatures during wintertime. Principal component analysis (PCA) is applied for wintertime northern hemisphere 500hPa geopotential height anomalies. The spatial PCA mode1 is defined as Arctic Oscillation and it influences prevailing westerlies. The prevailing westerlies meanders and influences climatic conditions. The spatial similarity between wintertime top 5 Arctic outflow event year's composites of 500hPa geopotential height anomalies and mode 3's spatial pattern is found. Mode 3's spatial pattern looks like the Pacific/North American (PNA) pattern which describes the variation of atmospheric circulation pattern over the Pacific Ocean and North America. Climate conditions from April to June, May to July, mode 3's time coefficients, and previous year's yield are used for forecasting spring wheat yield in each SAD. Cross-validation procedure which generates eight sets of models for the eight

  8. Persistent influence of ice sheet melting on high northern latitude climate during the early Last Interglacial

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    A. Govin

    2011-10-01

    Full Text Available Although the Last Interglacial (LIG is often considered as a possible analogue for future climate in high latitudes, its precise climate evolution and associated causes remain uncertain. Here we compile high-resolution marine sediment records from the North Atlantic, Labrador Sea, Norwegian Sea and the Southern Ocean. We document a delay in the establishment of peak interglacial conditions in the North Atlantic, Labrador and Norwegian Seas as compared to the Southern Ocean. In particular, we observe a persistent iceberg melting at high northern latitudes at the beginning of the LIG. It suggests that the input of meltwater has maintained (1 colder and fresher surface-water conditions in the North Atlantic, Labrador and Norwegian Seas and (2 weaker ventilation of North Atlantic deep waters during the early LIG (129–125.5 ka compared to the late LIG. Results from an ocean-atmosphere coupled model with insolation as a sole forcing for three key periods of the LIG show that insolation variations alone lead to warmer North Atlantic surface waters and stronger Atlantic overturning during the early LIG (126 ka than the late LIG (122 ka. Hence insolation variations alone do not explain the delay in peak interglacial conditions observed at high northern latitudes. When freshwater input is interactively computed at 126 ka in response to the high boreal summer insolation, the model simulates colder, fresher North Atlantic surface waters and weaker Atlantic overturning during the early LIG (126 ka compared to the late LIG (122 ka. This result indicates that both insolation variations and ice sheet melting have to be considered to reproduce the LIG climate evolution and supports our hypothesis that optimal thermal and deep ocean circulation conditions at high northern latitudes develop during the late LIG only, when the freshwater supply has already ceased.

  9. Forbush Decreases of Cosmic Rays and Total Ozone at Northern Higher Middle Latitudes

    Science.gov (United States)

    Lastovicka, J.; Krizan, P.

    Space weather affects the Earth's atmosphere in many ways and through various phenomena. Among them, the variability of the galactic cosmic ray flux belongs to the most important ones as for the lower atmosphere. Here we summarize our previous results on the effects of strong Forbush decreases of galactic cosmic rays on the total ozone at the northern higher middle latitudes including Forbush decreases not accompanied by geomagnetic storms, and complete them with investigations of the effects of geomagnetic storms not accompanied by Forbush decreases. The effects of strong geomagnetic storms and Forbush decreases occur only in the winter part of the year, under the high solar activity and the E-phase of QBO (E-max) conditions. The effect seems to be a redistribution of ozone as a consequence of related changes of circulation. No event contradicts the idea that the Forbush decreases are responsible for the effects of geomagnetic storms on the lower atmosphere (troposphere and lower stratosphere) including total ozone. However, under the E-max conditions in the winter part of the year, only several Forbush decreases without geomagnetic storms and only one geomagnetic storm without the Forbush decrease occurred over more than 20 years. Most of geomagnetic storms without Forbush decreases at middle latitudes were accompanied by Forbush decreases at high latitudes compensated for by rigidity decrease at middle latitudes.

  10. Determinants of vitamin D status in fair-skinned women of childbearing age at northern latitudes.

    Directory of Open Access Journals (Sweden)

    Linnea Hedlund

    Full Text Available BACKGROUND AND OBJECTIVE: Poor vitamin D status during pregnancy has been associated with unfavorable outcomes for mother and child. Thus, adequate vitamin D status in women of childbearing age may be important. The aim of this study is to investigate the determinants of 25-hydroxyvitamin D (25(OHD serum concentrations in women of childbearing age living in Sweden, at latitude 57-58° north. METHOD: Eighty four non-pregnant, non-lactating, healthy, fair-skinned women aged between 25-40 years were included. All subjects provided blood samples, four day food records and answered questionnaires about sun exposure and lifestyle. Total serum 25(OHD was analyzed using Roche Cobas® electrochemoluminiescent immunoassay. RESULTS: Mean 25(OHD was 65.8±19.9 nmol/l and 23% of the subjects had concentrations <50 nmol/l. Only 1% had concentrations <25 nmol/l. Determinants of 25(OHD concentrations were recent sunbed use, recent travel to southern latitude, season, estrogen contraceptive use and use of supplementary vitamin D (R(2 = 0.27. CONCLUSION: Every fifth woman had 25(OHD concentrations <50 nmol/l. About 30% of the variation in vitamin D status was explained by sun exposure, use of vitamin D supplements and use of estrogen contraceptives. Cutaneous vitamin D synthesis seems to be a major contributor to vitamin D status, even at northern latitudes. Thus, recommendations on safe UV-B exposure could be beneficial for vitamin D status.

  11. Persistent influence of ice sheet melting on high northern latitude climate during the early Last Interglacial

    Directory of Open Access Journals (Sweden)

    A. Govin

    2012-03-01

    Full Text Available Although the Last Interglacial (LIG is often considered as a possible analogue for future climate in high latitudes, its precise climate evolution and associated causes remain uncertain. Here we compile high-resolution marine sediment records from the North Atlantic, Labrador Sea, Norwegian Sea and the Southern Ocean. We document a delay in the establishment of peak interglacial conditions in the North Atlantic, Labrador and Norwegian Seas as compared to the Southern Ocean. In particular, we observe a persistent iceberg melting at high northern latitudes at the beginning of the LIG. It is associated with (1 colder and fresher surface-water conditions in the North Atlantic, Labrador and Norwegian Seas, and (2 a weaker ventilation of North Atlantic deep waters during the early LIG (129–125 ka compared to the late LIG. Results from an ocean-atmosphere coupled model with insolation as a sole forcing for three key periods of the LIG show warmer North Atlantic surface waters and stronger Atlantic overturning during the early LIG (126 ka than the late LIG (122 ka. Hence, insolation variations alone do not explain the delay in peak interglacial conditions observed at high northern latitudes. Additionally, we consider an idealized meltwater scenario at 126 ka where the freshwater input is interactively computed in response to the high boreal summer insolation. The model simulates colder, fresher North Atlantic surface waters and weaker Atlantic overturning during the early LIG (126 ka compared to the late LIG (122 ka. This result suggests that both insolation and ice sheet melting have to be considered to reproduce the climatic pattern that we identify during the early LIG. Our model-data comparison also reveals a number of limitations and reinforces the need for further detailed investigations using coupled climate-ice sheet models and transient simulations.

  12. Soil-frost-enabled soil-moisture-precipitation feedback over northern high latitudes

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    Hagemann, Stefan; Blome, Tanja; Ekici, Altug; Beer, Christian

    2016-07-01

    Permafrost or perennially frozen ground is an important part of the terrestrial cryosphere; roughly one quarter of Earth's land surface is underlain by permafrost. The currently observed global warming is most pronounced in the Arctic region and is projected to persist during the coming decades due to anthropogenic CO2 input. This warming will certainly have effects on the ecosystems of the vast permafrost areas of the high northern latitudes. The quantification of such effects, however, is still an open question. This is partly due to the complexity of the system, including several feedback mechanisms between land and atmosphere. In this study we contribute to increasing our understanding of such land-atmosphere interactions using an Earth system model (ESM) which includes a representation of cold-region physical soil processes, especially the effects of freezing and thawing of soil water on thermal and hydrological states and processes. The coupled atmosphere-land models of the ESM of the Max Planck Institute for Meteorology, MPI-ESM, have been driven by prescribed observed SST and sea ice in an AMIP2-type setup with and without newly implemented cold-region soil processes. Results show a large improvement in the simulated discharge. On the one hand this is related to an improved snowmelt peak of runoff due to frozen soil in spring. On the other hand a subsequent reduction in soil moisture enables a positive feedback to precipitation over the high latitudes, which reduces the model's wet biases in precipitation and evapotranspiration during the summer. This is noteworthy as soil-moisture-atmosphere feedbacks have previously not been the focus of research on the high latitudes. These results point out the importance of high-latitude physical processes at the land surface for regional climate.

  13. Ozone trends at northern mid- and high latitudes – a European perspective

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    Y. Orsolini

    2008-05-01

    Full Text Available The EU CANDIDOZ project investigated the chemical and dynamical influences on decadal ozone trends focusing on the Northern Hemisphere. High quality long-term ozone data sets, satellite-based as well as ground-based, and the long-term meteorological reanalyses from ECMWF and NCEP are used together with advanced multiple regression models and atmospheric models to assess the relative roles of chemistry and transport in stratospheric ozone changes. This overall synthesis of the individual analyses in CANDIDOZ shows clearly one common feature in the NH mid latitudes and in the Arctic: an almost monotonic negative trend from the late 1970s to the mid 1990s followed by an increase. In most trend studies, the Equivalent Effective Stratospheric Chlorine (EESC which peaked in 1997 as a consequence of the Montreal Protocol was observed to describe ozone loss better than a simple linear trend. Furthermore, all individual analyses point to changes in dynamical drivers, such as the residual circulation (responsible for the meridional transport of ozone into middle and high latitudes playing a key role in the observed turnaround. The changes in ozone transport are associated with variations in polar chemical ozone loss via heterogeneous ozone chemistry on PSCs (polar stratospheric clouds. Synoptic scale processes as represented by the new equivalent latitude proxy, by conventional tropopause altitude or by 250 hPa geopotential height have also been successfully linked to the recent ozone increases in the lowermost stratosphere. These show significant regional variation with a large impact over Europe and seem to be linked to changes in tropospheric climate patterns such as the North Atlantic Oscillation. Some influence in recent ozone increases was also attributed to the rise in solar cycle number 23. Changes from the late 1970s to the mid 1990s were found in a number of characteristics of the Arctic vortex. However, only one trend was found when more recent

  14. Higher northern latitude normalized difference vegetation index and growing season trends from 1982 to 1999

    Science.gov (United States)

    Tucker, C. J.; Slayback, D. A.; Pinzon, J. E.; Los, S. O.; Myneni, R. B.; Taylor, M. G.

    2001-01-01

    Normalized difference vegetation index data from the polar-orbiting National Oceanic and Atmospheric Administration meteorological satellites from 1982 to 1999 show significant variations in photosynthetic activity and growing season length at latitudes above 35 degrees N. Two distinct periods of increasing plant growth are apparent: 1982-1991 and 1992-1999, separated by a reduction from 1991 to 1992 associated with global cooling resulting from the volcanic eruption of Mt. Pinatubo in June 1991. The average May to September normalized difference vegetation index from 45 degrees N to 75 degrees N increased by 9% from 1982 to 1991, decreased by 5% from 1991 to 1992, and increased by 8% from 1992 to 1999. Variations in the normalized difference vegetation index were associated with variations in the start of the growing season of -5.6, +3.9, and -1.7 days respectively, for the three time periods. Our results support surface temperature increases within the same period at higher northern latitudes where temperature limits plant growth.

  15. Holocene pollen records from the northern mid-latitudes: syntheses, spatial patterns and gradients (Invited)

    Science.gov (United States)

    Brewer, S.; Davis, B.; Marsicek, J.

    2013-12-01

    The northern mid-latitudes represent one of the most data-rich regions of the planet for studies of late-Quaternary paleoclimate and paleoecology. The development of well-integrated databases and the tools to mine, visualize and analyze this data have led to a number of synthetic studies looking at changes over time and space. Pollen records are perhaps the most spatial extensive source of information, and we present here a review of some recent work using these records to look at the spatial patterning of paleoclimate changes across eastern North America and Europe. At millennial scale, the results show remarkable spatial coherency in paleoenivronmental changes throughout the Holocene period, and a temporal consistency reflecting orbital-driven climate change. Comparison with output from transient paleo-GCM simulations shows that simulations capture the magnitude, but not the spatial pattern of these changes, with higher latitudes simulated climates often closer to the observations. Results from individual high time resolution sites show a number of abrupt events embedded within these longer-term changes. Using a subset of high-resolution, well dated sites, we present further results showing the timing and spatial pattern of these events for these two regions. These show the expected wide-spread impact of the major climatic transitions (e.g. Holocene start), however other abrupt events have a more regional expression.

  16. 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/m(2) 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/m(2)day, and 700J/m(2)day in winter. With regard to UVD, the median UVD daily dose in summer season was 7700J/m(2)day, and in winter it was 1000J/m(2)day. 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.

  17. Multi-year lags between forest browning and soil respiration at high northern latitudes.

    Directory of Open Access Journals (Sweden)

    Ben Bond-Lamberty

    Full Text Available High-latitude northern ecosystems are experiencing rapid climate changes, and represent a large potential climate feedback because of their high soil carbon densities and shifting disturbance regimes. A significant carbon flow from these ecosystems is soil respiration (R(S, the flow of carbon dioxide, generated by plant roots and soil fauna, from the soil surface to atmosphere, and any change in the high-latitude carbon cycle might thus be reflected in R(S observed in the field. This study used two variants of a machine-learning algorithm and least squares regression to examine how remotely-sensed canopy greenness (NDVI, climate, and other variables are coupled to annual R(S based on 105 observations from 64 circumpolar sites in a global database. The addition of NDVI roughly doubled model performance, with the best-performing models explaining ∼62% of observed R(S variability. We show that early-summer NDVI from previous years is generally the best single predictor of R(S, and is better than current-year temperature or moisture. This implies significant temporal lags between these variables, with multi-year carbon pools exerting large-scale effects. Areas of decreasing R(S are spatially correlated with browning boreal forests and warmer temperatures, particularly in western North America. We suggest that total circumpolar R(S may have slowed by ∼5% over the last decade, depressed by forest stress and mortality, which in turn decrease R(S. Arctic tundra may exhibit a significantly different response, but few data are available with which to test this. Combining large-scale remote observations and small-scale field measurements, as done here, has the potential to allow inferences about the temporal and spatial complexity of the large-scale response of northern ecosystems to changing climate.

  18. Age-related gestation length adjustment in a large iteroparous mammal at northern latitude.

    Science.gov (United States)

    Mysterud, Atle; Røed, Knut H; Holand, Øystein; Yoccoz, Nigel G; Nieminen, Mauri

    2009-09-01

    1. There is considerable interest in patterns of age-dependent reproductive effort and reproductive timing of large iteroparous mammals living in strongly seasonal environments. Due to lack of data on both timing of mating and birth, there is generally little insight into whether variation in gestation length play a role for life-history patterns observed for large mammals at northern latitudes. 2. Based on data on both timing of mating and birth of 88 female reindeer (and paternity confirmed with DNA fingerprinting), we explore the view that adjustment of gestation length plays a role in the reproductive tactic. 3. Observed gestation lengths of reindeer varied between 211 and 229 days (mean of 221 days). Consistent with a dynamic view of gestation length, variation could be predicted from life-history traits. Gestation length was longer for male than female offspring, which is expected in polygynous species where males benefit more from extra allocation of maternal resources. Gestation length increased with maternal age both due to direct effects and indirect effects linked to earlier mating of older, heavier females. Early mating females increased gestation length. A relatively small effect of female age on birth mass operated through variation in gestation length. 4. Our analysis supports the view that adjustment of gestation length is a part of the reproductive tactic of large mammals in northern environments.

  19. Holocene temperature evolution in the Northern Hemisphere high latitudes - Model-data comparisons

    Science.gov (United States)

    Zhang, Yurui; Renssen, Hans; Seppä, Heikki; Valdes, Paul J.

    2017-10-01

    Heterogeneous Holocene climate evolutions in the Northern Hemisphere high latitudes are primarily determined by orbital-scale insolation variations and melting ice sheets. Previous inter-model comparisons have revealed that multi-simulation consistencies vary spatially. We, therefore, compared multiple model results with proxy-based reconstructions in Fennoscandia, Greenland, north Canada, Alaska and Siberia. Our model-data comparisons reveal that data and models generally agree in Fennoscandia, Greenland and Canada, with the early-Holocene warming and subsequent gradual decrease to 0 ka BP (hereinafter referred as ka). In Fennoscandia, simulations and pollen data suggest a 2 °C warming by 8 ka, but this is less expressed in chironomid data. In Canada, a strong early-Holocene warming is suggested by both the simulations and pollen results. In Greenland, the magnitude of early-Holocene warming ranges from 6 °C in simulations to 8 °C in δ18O-based temperatures. Simulated and reconstructed temperatures are mismatched in Alaska. Pollen data suggest strong early-Holocene warming, while the simulations indicate constant Holocene cooling, and chironomid data show a stable trend. Meanwhile, a high frequency of Alaskan peatland initiation before 9 ka can reflect a either high temperature, high soil moisture or large seasonality. In high-latitude Siberia, although simulations and proxy data depict high Holocene temperatures, these signals are noisy owing to a large spread in the simulations and between pollen and chironomid results. On the whole, the Holocene climate evolutions in most regions (Fennoscandia, Greenland and Canada) are well established and understood, but important questions regarding the Holocene temperature trend and mechanisms remain for Alaska and Siberia.

  20. Distribution of Latitudes and Speeds of Coronal Mass Ejections in the Northern and Southern Hemispheres in Cycle 23

    Indian Academy of Sciences (India)

    P. X. Gao; Q. X. Li; S. H. Zhong

    2007-12-01

    Distribution of latitudes and speeds of Coronal Mass Ejections (CMEs) in the northern and southern hemispheres in cycle 23, from September 1996 to December 2006, have been analyzed. By calculating the actual probability of the hemispheric distribution of the activity of the CME, we find that a southern dominance of the activity of the CME is shown to occur in cycle 23 from September 1996 to December 2006. The CME activity occurs at all latitudes and is most common at low latitudes. This should furnish evidence to support that CMEs are associated with source magnetic structures on a large spatial scale, even with transequatorial source magnetic structures on a large spatial scale. The latitudinal distribution of CMEs in the northern and southern hemispheres are no different from a statistical point of view. The speed distribution in the northern and southern hemispheres are nearly identical and to a good approximation they can be fitted with a single lognormal distribution. This finding implies that, statistically, there is no physical distinction between the CME events in the southern and northern hemispheres and the same mechanism of a nonlinear nature acting in both the CME events in the northern and southern hemispheres. Our conclusions seem to suggest that the northern–southern asymmetry of the CME events is related to the northern–southern asymmetry in solar dynamo theory (Jiang et al. 2007).

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

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    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

  2. Phenomenology of the low-latitude ionosphere during northern winter and association with sudden stratospheric warmings

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    Goncharenko, L. P.; Coster, A. J.; Benkevitch, L. V.; Yudin, V. A.

    2014-12-01

    Large number of recent studies has demonstrated strong anomalies in the low-latitude ionosphere during sudden stratospheric warmings (SSW) that occur primarily during the northern winter period (December-February). Such events occurred with unusually high frequency during the last decade, making it possible to take advantage of increasingly available GPS TEC data to make significant progress in studies of atmosphere-ionosphere coupling. We focus on the American longitudinal sector, where good quality GPS TEC data is available for extended period of time, and examine three wintertime (November - February) periods marked by major sudden stratospheric warmings, 2005/06, 2008/09, and 2012/13. The selected events represent wide variety of stratospheric and geophysical conditions, including a vortex-shift (wave 1) SSW during solar minimum (2005/06), vortex-split (wave 2) SSW during extreme solar minimum (2008/09), and vortex-split (wave 2) SSW during moderate-to-high solar activity. To clearly separate ionospheric anomalies associated with SSW from other types of variations, we also examine the winter of 2006/07, which was characterized by less disturbed middle atmosphere. Comparison of ionospheric disturbances for three SSW cases shows remarkably consistent response to all events, albeit with varying magnitude. This response has primarily a tidal character and lasts for extended period of time. WACCM-X simulations of these events demonstrate amplification in global tidal energy for all major tides (diurnal, semidiurnal, terdiurnal), with strongest enhancement of semidiurnal tide.

  3. Intercomparison of the northern hemisphere winter mid-latitude atmospheric variability of the IPCC models

    CERN Document Server

    Lucarini, V; Dell'Aquila, A; Ruti, P M; Speranza, A; Aquila, Alessandro Dell'; Calmanti, Sandro; Lucarini, Valerio; Ruti, Paolo M.; Speranza, Antonio

    2006-01-01

    We compare, for the overlapping time frame 1962-2000, the estimate of the northern hemisphere (NH) mid-latitude winter atmospheric variability within the XX century simulations of 17 global climate models (GCMs) included in the IPCC-4AR with the NCEP and ECMWF reanalyses. We compute the Hayashi spectra of the 500hPa geopotential height fields and introduce an integral measure of the variability observed in the NH on different spectral sub-domains. Only two high-resolution GCMs have a good agreement with reanalyses. Large biases, in most cases larger than 20%, are found between the wave climatologies of most GCMs and the reanalyses, with a relative span of around 50%. The travelling baroclinic waves are usually overestimated, while the planetary waves are usually underestimated, in agreement with previous studies performed on global weather forecasting models. When comparing the results of various versions of similar GCMs, it is clear that in some cases the vertical resolution of the atmosphere and, somewhat u...

  4. Geomagnetic storms, Forbush decreases of cosmic rays and total ozone at northern higher middle latitudes

    Science.gov (United States)

    Laštovička, Jan; Križan, Peter

    2005-01-01

    Space weather affects the Earth's atmosphere in many ways and through various phenomena. Among them, geomagnetic storms and the variability of the galactic cosmic ray flux belong to the most important ones as for the lower atmosphere. Here, we summarize our previous results on the effects of strong geomagnetic storms and strong Forbush decreases of galactic cosmic rays on the total ozone at the northern higher middle latitudes, and complete them with investigations of effects of geomagnetic storms not accompanied by Forbush decreases. The effects of strong geomagnetic storms and Forbush decreases occur only in the winter part of the year, under the high solar activity and the E-phase of QBO (E-max) conditions. The effects of storms seem to be a redistribution of ozone as a consequence of storm-related changes of circulation. No event contradicts the idea that the Forbush decreases are responsible for effects of geomagnetic storms on the lower atmosphere (troposphere and lower stratosphere) including total ozone. However, under the E-max conditions in the winter part of the year, only several Forbush decreases without geomagnetic storms and only one geomagnetic storm without the Forbush decrease occurred over more than 20 years.

  5. Numerical Simulation of Atmosphere-Ocean-Sea Ice Interaction During Interannual Cycle in High Northern Latitudes

    Institute of Scientific and Technical Information of China (English)

    LIU Xiying; LIU Hailong; LI Wei; ZHANG Xuehong; YU Rucong; YU Yongqiang

    2008-01-01

    The interannual atmosphere-ocean-sea ice interaction (AOSI) in high northern latitudes is studied with a global atmosphere-ocean-sea ice coupled model system, in which the model components of atmosphere and land surface are from China National Climate Center and that of ocean and sea ice are from LASG,Institute of Atmospheric Physics, Chinese Academy of Sciences. A daily flux anomaly correction scheme is employed to couple the atmosphere model and the ocean model with the effect of inhomogenity of sea ice in high latitudes is considered. The coupled model system has been run for 50 yr and the results of the last 30 years are analyzed. After the sea level pressure (SLP), surface air temperature (SAT), sea surface temperature (SST), sea ice concentration (SIC), and sea surface sensible heat flux (SHF) are filtered with adigital filter firstly, their normalized anomalies are used to perform the decomposition of combined complex empirical orthogonal function (CCEOF) and then they are reconstructed with the leading mode. The atmosphere-ocean-sea ice interactions in high northern latitudes during a periodical cycle (approximately4 yr) are analyzed. It is shown that: (1) When the North Atlantic Oscillation (NAO) is in its positive phase, the southerly anomaly appears in the Greenland Sea, SAT increases, the sea loses less SHF, SST increases and SIC decreases accordingly; when the NAO is in its negative phase, the northerly anomaly appears in the Greenland Sea, SAT decreases, the sea loses more SHF, SST decreases and SIC increases accordingly. There are similar features in the Barents Sea, but the phase of evolution in the Barents Sea is different from that in the Greenland Sea. (2) For an average of multi-years, there is a cold center in the inner part of the Arctic Ocean near the North Pole. When there is an anomaly of low pressure, which is closer to the Pacific Ocean, in the inner part of the Arctic Ocean, anomalies of warm advection appear in the region near the

  6. Mean Climatic Characteristics in High Northern Latitudes in an Ocean-Sea Ice-Atmosphere Coupled Model

    Institute of Scientific and Technical Information of China (English)

    刘喜迎; 张学洪; 俞永强; 宇如聪

    2004-01-01

    Emphasizing the model's ability in mean climate reproduction in high northern latitudes, results from an ocean-sea ice-atmosphere coupled model are analyzed. It is shown that the coupled model can simulate the main characteristics of annual mean global sea surface temperature and sea level pressure well, but the extent of ice coverage produced in the Southern Hemisphere is not large enough. The main distribution characteristics of simulated sea level pressure and temperature at 850 hPa in high northern latitudes agree well with their counterparts in the NCEP reanalysis dataset, and the model can reproduce the Arctic Oscillation (AO) mode successfully. The simulated seasonal variation of sea ice in the Northern Hemisphere is rational and its main distribution features in winter agree well with those from observations.But the ice concentration in the sea ice edge area close to the Eurasian continent in the inner Arctic Ocean is much larger than the observation. There are significant interannual variation signals in the simulated sea ice concentration in winter in high northern latitudes and the most significant area lies in the Greenland Sea, followed by the Barents Sea. All of these features agree well with the results from observations.

  7. Past perspectives on Northern High-Latitude sensitivity to a 400ppm+ world (Invited)

    Science.gov (United States)

    Jansen, E.; Risebrobakken, B.; Drange, H.

    2013-12-01

    The Cenozoic record of climate change displays clear relationships between global temperatures as well as the development of glaciation in both hemispheres and past atmospheric CO2-levels. A recent update is provided in IPCC AR5 and will be reviewed here. Extensive periods of the past were characterized by CO2-levels in excess of 400ppmv. Analyses of the relationship between carbon emissions and global temperature in 15 Earth System Models used in the CMIP5 experiments underpinning IPCC AR5, show that carbon emissions of about 1000 Pg produces a global warming of about 2 degrees, regardless of emission scenario, indicating that changes in carbon fluxes of this magnitude produces at least 2oC global warming (probably more due to the adjustment of the slower components of the climate system). CO2-levels at the time of 2oC warming are on the order of 400-500ppmv with regional land temperatures at high Northern Latitudes being twice the global average or more, but without major changes in the style and pattern of North Atlantic meridional overturning circulation. Periods with CO2-levels at 400-500ppmv apparently occurred both in the Oligocene and the Pliocene, indicating that these periods may offer insight and perspective into a future climate in equilibrium with CO2-levels between 400 and 500ppmv. Carbonate preservation data from the Nordic Seas indicate that ocean overturning and ventilation was vigourous in the Nordic Seas in the Oligocene, which stands out a colder period, compared to the Eocene and the early Miocene. Isotope data from Oligocene shelf sediments indicate Nordic seas temperatures similar to modern levels or colder, hence implying the possibility of an existing cryosphere in the surrounding region at the time. The timing of this period inside the Oligocene and comparing to the paleo-CO2 record of the Oligocene is difficult, however, in parts because the paleo pCO2-record of the Olgocene shows a declining values also to below 400ppmv in the later part

  8. Current state and prospects of carbon management in high latitudes of Northern Eurasia

    Science.gov (United States)

    Schepaschenko, Dmitry; Shvidenko, Anatoly

    2010-05-01

    The current state and trajectories of future development of natural landscapes in high latitudes of Northern Eurasia are defined inter alia by (1) current unsatisfactory social and economic situation in boreal Northern Eurasia; (2) the dramatic magnitude of on-going and expected climatic change (warming up to 10-12oC under global warming at 4oC); (3) increasing anthropogenic pressure, particularly in regions of intensive oil and gas exploration and extraction; (4) large areas of sparsely populated and practically unmanaged land; (5) vulnerability of northern ecosystems which historically developed under cold climates and buffering capacity of which is not well known; (6) risk of catastrophic natural disturbances (fire, insect outbreaks) whose frequency and severity have accelerated during recent decades; and (7) high probability of irreversible changes of vegetation cover. These specifics are overlapped with insufficient governance of natural renewable resources (e.g., forests) and destructed practice of industrial development of new territories (oil and gas extraction and exploration, metallurgy etc.). Based on a full carbon account for terrestrial vegetation ecosystems of Northern Eurasia, we analyze the relative impacts of major drivers on magnitude and uncertainty of the Net Ecosystem Carbon Balance (NECB) under current and expected climate and environment. Dynamic trends and interannual variability of NECB are mostly dependent on weather conditions during growth seasons of individual years, regimes of natural disturbances, and anthropogenic impacts on ecosystems. In a short term, disturbances and human impacts cause a theoretically 'manageable' part of the full carbon account, which on average is estimated to be of about 20% of annual net primary production. In a long term, thawing of permafrost and change of hydrological regimes of vast territories may result in a catastrophic decline of the forested area and wide distribution of 'green desertification'. The

  9. Soil water storage, mixing dynamics and resulting travel times through the critical zone in northern latitudes

    Science.gov (United States)

    Sprenger, Matthias; Tetzlaff, Doerthe; Weiler, Markus; Soulsby, Chris

    2017-04-01

    Water partitioning in the unsaturated zone into groundwater recharge, plant transpiration, and evaporation is fundamental for estimating storages and travel times. How water is mixed and routed through the soil is of broad interest to understand plant available water, contamination transport and weathering rates in the critical zone. Earlier work has shown how seasonal changes in hydroclimate influence the time variant character of travel times. A strong seasonality characterizes the northern latitudes which are particularly sensitive to climate and land use changes. It is crucial to understand how variation and change in hydroclimate and vegetation phenology impact time variant storage dynamics and flow path partitioning in the unsaturated zone. To better understand the influence of these ecohydrological processes on travel times of evaporative, transpiration and recharge fluxes in northern latitudes, we characterized soil physical properties, hydrometric conditions and soil water isotopic composition in the upper soil profile in two different land scape units in the long term experimental catchment, Bruntland Burn in the Scottish Highlands. Our two sampling locations are characterized by podzol soils with high organic matter content but they differ with regard to their vegetation cover with either Scots Pine (Pinus sylvestris) or heather (Calluna sp. and Erica Sp). To assess storage and mixing dynamics in the vadose zone, we parameterized a numerical 1-D flow model using the soil textural information along with soil moisture and soil water stable isotopes (δ2H and δ18O). The water flow and transport were simulated based on the Richards and the advection dispersion equation. Differences between water flows of mobile and tightly bound soil waters and the mixing between the two pore spaces were considered. Isotopic fractionation due to evaporation from soil and interception storage was taken into account, while plant water uptake did not alter the isotopic

  10. Fall vortex ozone as a predictor of springtime total ozone at high northern latitudes

    Directory of Open Access Journals (Sweden)

    S. R. Kawa

    2005-01-01

    Full Text Available Understanding the impact of atmospheric dynamical variability on observed changes in stratospheric O3 is a key to understanding how O3 will change with future climate dynamics and trace gas abundances. In this paper we examine the linkage between interannual variability in total column O3 at northern high latitudes in March and lower-to-mid stratospheric vortex O3 in the prior November. We find that these two quantities are significantly correlated in the years available from TOMS, SBUV, and POAM data (1978–2004. Additionally, we find that the apparent decadal shift in March O3 variability from the 1980s to years post-1990 is also seen in the November vortex O3, so that interannual variability in both quantities is largely driven by the later years. The cause of this correlation is not clear, however. Interannual variations in March total O3 are known to correspond closely with variations in winter stratospheric wave driving consistent with the effects of varying residual circulation, temperature, and chemical loss. Variation in November vortex O3 may also depend on dynamical wave activity, however, the dynamics in fall are less variable than in winter and spring. We do not find significant correlations of dynamic indicators for November such as temperature, heat flux, or polar average total O3 with the November vortex O3, nor with dynamical indicators later in winter and spring that might lead to a connection to March. We discuss several potential hypotheses for the observed correlation but do not find strong evidence for any considered mechanism. We present the observations as a phenomenon whose understanding may improve our ability to predict the dependence of O3 on changing dynamics and chemistry.

  11. Fall vortex ozone as a predictor of springtime total ozone at high northern latitudes

    Directory of Open Access Journals (Sweden)

    S. R. Kawa

    2005-01-01

    Full Text Available Understanding the impact of atmospheric dynamical variability on observed changes in stratospheric O3 is a key to understanding how O3 will change with future climate dynamics and trace gas abundances. In this paper we examine the linkage between interannual variability in total column O3 at northern high latitudes in March and lower-to-mid stratospheric vortex O3 in the prior November. We find that these two quantities are significantly correlated in the years available from TOMS, SBUV, and POAM data (1978-2004. Additionally, we find that the increase in March O3 variability from the 1980s to years post-1990 is also seen in the November vortex O3, i.e., interannual variability in both quantities is much larger in the later years. The cause of this correlation is not clear, however. Interannual variations in March total O3 are known to correspond closely with variations in winter stratospheric wave driving consistent with the effects of varying residual circulation, temperature, and chemical loss. Variation in November vortex O3 may also depend on dynamical wave activity, but the dynamics in fall are less variable than in winter and spring. We do not find significant correlations of dynamic indicators for November such as temperature, heat flux, or polar average total O3 with the November vortex O3, nor with dynamical indicators later in winter and spring that might lead to a connection to March. We discuss several potential hypotheses for the observed correlation but do not find strong evidence for any considered mechanism. We present the observations as a phenomenon whose understanding may improve our ability to predict the dependence of O3 on changing dynamics and chemistry.

  12. Remote Sensing of Open Water in Northern High Latitudes for use in Hydrologic Modeling

    Science.gov (United States)

    Podest, E.; McDonald, K. C.; Kimball, J.; Maumenee, N.; Bohn, T.; Lettenmaier, D.; Bowling, L.

    2007-12-01

    In the northern high latitudes open water bodies are common landscape features, having a large influence on hydrologic processes as well as surface-atmosphere carbon exchange and associated impacts on global climate. It is therefore of great importance to assess their spatial extent and temporal character in order to improve hydrologic and ecosystem process modeling. Spaceborne synthetic aperture radar (SAR) is an effective tool for this purpose since it is particularly sensitive to surface water and it can monitor large inaccessible areas on a temporal basis regardless of atmospheric conditions or solar illumination. We employ multi-temporal L-band SAR data from the Japanese Earth Remote Sensing Satellite (JERS-1) and ALOS PALSAR to map open water bodies across Alaska and Eurasia. A supervised decision tree-based classification approach was used to generate open water maps. For Alaska, we assembled regional-scale monthly JERS-1 SAR mosaics from data acquired during 1998. Digital elevation model (DEM) terrain and slope information were also employed in the decision tree classifier. These supplementary data aided significantly in improving classification performance in topographically complex regions where radar shadowing was prevalent. For study regions in Eurasia, PALSAR data was used in conjunction with JERS-1 imagery to map spatial patterns and seasonal variability in open water characteristics over selected study basins. These results were examined in relation to regional topographic and land cover characteristics. Classification results were also evaluated relative to other open water and land cover classification maps derived from Landsat, AVHRR, MODIS and SRTM. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology; at the University of Montana; at the University of Washington; and at Purdue University under contract with the National Aeronautics and Space Administration.

  13. Northern high-latitude climate change between the mid and late Holocene – Part 2: Model-data comparisons

    Directory of Open Access Journals (Sweden)

    J. Nilsson

    2009-06-01

    Full Text Available The solar orbital forcing induced changes in insolation at the mid-Holocene compared to the late Holocene, which causes an amplification of the seasonal cycle in the Northern Hemisphere in the earlier period. The climate response over northern high latitudes, to this change in forcing has been investigated in three types of PMIP (Paleoclimate Modelling Intercomparison Project simulations with different complexity of the climate system. The model results have also been compared with available reconstructions from temperature proxy data. Both the reconstructions and the PMIP2 models show a warm response in annual mean temperature, as well as in summer and winter temperature. The model-model comparisons indicate the importance of including the different physical feedbacks (ocean, sea-ice, vegetation in the climate model. An objective selection method is applied in the model-data comparison to evaluate the capability of the climate model in reproducing the spatial response pattern. The comparisons between the reconstructions and the best-fit selected simulations show that over the northern high latitudes, summer temperature change follows closely to the insolation and shows a common feature with strong warming over land and relatively weak warming over ocean. A pronounced warming centre is found over Barents Sea in winter in model simulations, which is also supported by the nearby northern Eurasian continental reconstructions. The warming over Barents Sea corresponds to a positive North Atlantic Oscillation (NAO. The strengthened sea level pressure gradient may have caused a northward shift of the Atlantic storm track. It results in enhanced westerlies towards the northern Eurasia, which may be responsible for the winter warming over northern Fennoscandia and northern Siberia.

  14. Characteristics of episodes with extremely low ozone values in the northern middle latitudes 1957−2000

    Directory of Open Access Journals (Sweden)

    D. S. Balis

    Full Text Available A number of episodes are observed when the total ozone for 2 to 3 days has fallen below 220 matm-cm in the northern mid- and polar latitudes in autumn. The occurrences of such episodes represent ozone deviations of about one-third from the pre-1976 Oct-Nov-Dec monthly mean! By using primarily quality checked Dobson data, a clear identification was made of more than three dozen short spells with extremely low ozone in the 1957–1978 period. In the following twenty-two years (1979–2000, using mainly TOMS data, one can identify ~ 46 cases with ozone values falling below 220 matm-cm for longer than 1 day, with each time over an area greater than 500,000 km2 . The Ozone Mass Deficiency (O3MD from the pre-1976 average ozone values over the affected area was ~2.8 Mt per day, i.e. four to seven times greater than it would be, assuming only a long-term trend in the Oct-Nov-Dec period. The Extremely Low Ozone (ELO3 events on the day of their appearance over the N. Atlantic/European region contribute to the O3MD by representing 16% of the deficiency due to the Oct-Nov trend in the entire 40–65° N latitudinal belt. The O3MD of the greater pool with low ozone (here taken as <260 matm-cm surrounding the area of the lowest events could contribute on the day of their appearance in Oct-Nov up to 60% and in December, ~30% to the deficiency due to the trend over the entire 40–65° N belt. Analysis of synoptic charts, supported by a backward trajectory on the isentropic surfaces 350 and 380 K, shows that in most of the events, subtropical air masses with low ozone content were transported from the Atlantic toward the UK, Scandinavia, and in many cases, further to the western sub-polar regions of Russia. This transport was sometimes combined with upward motions above a tropospheric anticyclone which lifted low ozone mixing ratios to higher altitudes. The ELO3 events cause a significant deficiency above the tropopause where, in general, the subtropical air is

  15. Carbon dioxide in northern high latitude oceans: Anthropogenic increase and air-sea flux variability

    Energy Technology Data Exchange (ETDEWEB)

    Omar, Abdirahman M.

    2003-07-01

    The aim of this thesis is to further our knowledge of carbon dioxide in the northern high latitude oceans (northern North Atlantic, Barents Sea, and Arctic Ocean) by studying the anthropogenic change in the oceanic CO2, the inter-annual variability of the air-sea CO2 flux, and the relationship between this variability and changes in other oceanic processes. An introductory chapter and four papers are presented. Descriptions of the seawater carbonate system parameters, air-sea exchange of CO2, and related processes are given in the introduction chapter. The anthropogenic increase in partial pressure of CO2 (pCO2) in the surface water of the Barents Sea is evaluated in paper I. The effect of alternations of the Barents Sea climate between cold and warm modes on the annual cycles of seawater fugacity and air-sea flux of CO2 is investigated in paper II. Oceanic uptake of atmospheric CO2 associated with the seasonal formation of sea ice in Storfjorden and the implication for the entire Arctic Ocean is studied in paper III. An assessment of the variations of the air-sea flux of CO2 in the northern North Atlantic for 20 winters (1981-2001) is carried out in paper IV. PCO2 in the surface water of the Barents Sea is shown to have increased parallel with the atmospheric pCO2 between 1967 and 2000-2001 (paper I). This was determined by comparing seawater pCO2 from 1967 with that from 2000-2001. The former was estimated from surface seawater temperature (SST) while the latter was computed from data of total dissolved inorganic carbon and alkalinity. A procedure which accounts for the natural variability was applied and the difference between seawater pC02 of 1967 and that of 2000-2001 is attributed to the uptake of excess CO2. In the Atlantic sector of the Barents Sea, the surface seawater fugacity of CO2 (fCO s''w) is shown to be lower than the atmospheric fCO2 throughout the year, implying that the area is an annual sink of atmospheric CO2 (paper II). Additionally

  16. Effects of substorm electrojet on declination along concurrent geomagnetic latitudes in the northern auroral zone

    Science.gov (United States)

    Edvardsen, Inge; Johnsen, Magnar G.; Løvhaug, Unni P.

    2016-10-01

    The geomagnetic field often experiences large fluctuations, especially at high latitudes in the auroral zones. We have found, using simulations, that there are significant differences in the substorm signature, in certain coordinate systems, as a function of longitude. This is confirmed by the analysis of real, measured data from comparable locations. Large geomagnetic fluctuations pose challenges for companies involved in resource exploitation since the Earth's magnetic field is used as the reference when navigating drilling equipment. It is widely known that geomagnetic activity increases with increasing latitude and that the largest fluctuations are caused by substorms. In the auroral zones, substorms are common phenomena, occurring almost every night. In principle, the magnitude of geomagnetic disturbances from two identical substorms along concurrent geomagnetic latitudes around the globe, at different local times, will be the same. However, the signature of a substorm will change as a function of geomagnetic longitude due to varying declination, dipole declination, and horizontal magnetic field along constant geomagnetic latitudes. To investigate and quantify this, we applied a simple substorm current wedge model in combination with a dipole representation of the Earth's magnetic field to simulate magnetic substorms of different morphologies and local times. The results of these simulations were compared to statistical data from observatories and are discussed in the context of resource exploitation in the Arctic. We also attempt to determine and quantify areas in the auroral zone where there is a potential for increased space weather challenges compared to other areas.

  17. The role of midlatitude mixing barriers in creating the annual variation of total ozone in high northern latitudes

    Science.gov (United States)

    Gille, John; Karol, Svetlana; Kinnison, Douglas; Lamarque, Jean-Francois; Yudin, Valery

    2014-08-01

    Data from the HIgh Resolution Dynamics Limb Sounder (HIRDLS), the Microwave Limb Sounder (MLS), and the Whole Atmosphere Community Climate Model (WACCM) are used to investigate the annual variation of total column ozone in high northern latitudes. Downward transport of ozone-rich air by the residual mean circulation during autumn and winter bends ozone isopleths down and increases the high-latitude ozone amounts, leading to an ozone maximum at the end of the winter. During the summer months eddy mixing acts to restore pre-fall distributions of ozone. In this study the large-scale mixing in the lower stratosphere is analyzed using Nakamura's (1996) equivalent length formulation with observed and simulated ozone. The analysis of ozone mixing is performed in the tracer equivalent latitude-potential temperature coordinate system. Steep latitudinal gradients of ozone isopleths below about 500 K occur during the winter, where there are minima in the equivalent length, indicating barriers to mixing at 30°N-40°N. This transport barrier allows large ozone maxima to develop poleward of it. The barrier disappears over the summer, permitting latitudinal mixing of the high ozone air. Above 500 K mixing is more effective during the winter, so a large winter maximum does not occur. In both midlatitude and high latitude the lower stratospheric layer from 330 to 500 K doubles its ozone content from autumn to spring, compared with much smaller changes in the layer from 500 to 650 K. Our results confirm that the presence of the winter transport barrier in the lower stratosphere controls the seasonal variation of total ozone.

  18. Climate change between the mid and late Holocene in northern high latitudes – Part 2: Model-data comparisons

    Directory of Open Access Journals (Sweden)

    K. Holmgren

    2010-09-01

    Full Text Available The climate response over northern high latitudes to the mid-Holocene orbital forcing has been investigated in three types of PMIP (Paleoclimate Modelling Intercomparison Project simulations with different complexity of the modelled climate system. By first undertaking model-data comparison, an objective selection method has been applied to evaluate the capability of the climate models to reproduce the spatial response pattern seen in proxy data. The possible feedback mechanisms behind the climate response have been explored based on the selected model simulations. Subsequent model-model comparisons indicate the importance of including the different physical feedbacks in the climate models. The comparisons between the proxy-based reconstructions and the best fit selected simulations show that over the northern high latitudes, summer temperature change follows closely the insolation change and shows a common feature with strong warming over land and relatively weak warming over ocean at 6 ka compared to 0 ka. Furthermore, the sea-ice-albedo positive feedback enhances this response. The reconstructions of temperature show a stronger response to enhanced insolation in the annual mean temperature than winter and summer temperature. This is verified in the model simulations and the behaviour is attributed to the larger contribution from the large response in autumn. Despite a smaller insolation during winter at 6 ka, a pronounced warming centre is found over Barents Sea in winter in the simulations, which is also supported by the nearby northern Eurasian continental and Fennoscandian reconstructions. This indicates that in the Arctic region, the response of the ocean and the sea ice to the enhanced summer insolation is more important for the winter temperature than the synchronous decrease of the insolation.

  19. Ozone trends derived from the total column and vertical profiles at a northern mid-latitude station

    Directory of Open Access Journals (Sweden)

    P. J. Nair

    2013-10-01

    Full Text Available The trends and variability of ozone are assessed over a northern mid-latitude station, Haute-Provence Observatory (OHP: 43.93° N, 5.71° E, using total column ozone observations from the Dobson and Système d'Analyse par Observation Zénithale spectrometers, and stratospheric ozone profile measurements from light detection and ranging (lidar, ozonesondes, Stratospheric Aerosol and Gas Experiment (SAGE II, Halogen Occultation Experiment (HALOE and Aura Microwave Limb Sounder (MLS. A multivariate regression model with quasi-biennial oscillation (QBO, solar flux, aerosol optical thickness, heat flux, North Atlantic Oscillation (NAO and a piecewise linear trend (PWLT or equivalent effective stratospheric chlorine (EESC functions is applied to the ozone anomalies. The maximum variability of ozone in winter/spring is explained by QBO and heat flux in the ranges 15–45 km and 15–24 km, respectively. The NAO shows maximum influence in the lower stratosphere during winter, while the solar flux influence is largest in the lower and middle stratosphere in summer. The total column ozone trends estimated from the PWLT and EESC functions are of −1.47 ± 0.27 and −1.40 ± 0.25 DU yr−1, respectively, over the period 1984–1996 and about 0.55 ± 0.30 and 0.42 ± 0.08 DU yr−1, respectively, over the period 1997–2010. The ozone profiles yield similar and significant EESC-based and PWLT trends for 1984–1996, and are about −0.5 and −0.8% yr−1 in the lower and upper stratosphere, respectively. For 1997–2010, the EESC-based and PWLT estimates are of the order of 0.3 and 0.1% yr−1, respectively, in the 18–28 km range, and at 40–45 km, EESC provides significant ozone trends larger than the insignificant PWLT results. Furthermore, very similar vertical trends for the respective time periods are also deduced from another long-term satellite-based data set (GOZCARDS–Global OZone Chemistry And Related trace gas Data records for the

  20. Ozone depletion at northern and southern latitudes derived from January 1979 to December 1991 Total Ozone Mapping Spectrometer data

    Science.gov (United States)

    Herman, J. R.; Mcpeters, R.; Larko, D.

    1993-01-01

    An extended version of the Nimbus 7/TOMS ozone data set from the period January 1, 1979 to December 31, 1991 is presented. It is shown that the ozone-trend data indicate that regions of enhanced ozone depletion rates have formed at middle and high latitudes during recent years. The seasonal dependence and geographical extent of the enhanced ozone-depletion rates for the Northern and Southern hemispheres are examined. The variability of the long-term ozone trend determination is discussed via consideration of the differences among 11-, 12-, and 13-yr trend calculations. The effects of the Mount Pinatubo eruption and other volcanic eruptions on the TOMS equatorial zonal average ozone measurements, and its influence on long-term trend determinations are discussed. On the basis of a determination of the aerosol phase function using TOMS data, the effect of stratospheric aerosols on determination of ozone amounts from TOMS are shown to be less than 1 percent.

  1. Tropospheric ozone from IASI: comparison of different inversion algorithms and validation with ozone sondes in the northern middle latitudes

    Directory of Open Access Journals (Sweden)

    C. Keim

    2009-05-01

    Full Text Available This paper presents a first statistical validation of tropospheric ozone products derived from measurements of the satellite instrument IASI. Since end of 2006, IASI (Infrared Atmospheric Sounding Interferometer aboard the polar orbiter Metop-A measures infrared spectra of the Earth's atmosphere in nadir geometry. This validation covers the northern mid-latitudes and the period from July 2007 to August 2008. The comparison of the ozone products with the vertical ozone concentration profiles from balloon sondes leads to estimates of the systematic and random errors in the IASI ozone products. The intercomparison of the retrieval results from four different sources (including the EUMETSAT ozone products shows systematic differences due to the used methods and algorithms. On average the tropospheric columns have a small bias of less than 2 Dobson Units (DU when compared to the sonde measured columns. The comparison of the still pre-operational EUMETSAT columns shows higher mean differences of about 5 DU.

  2. Geomagnetic Field Variation during Winter Storm at Localized Southern and Northern High Latitude

    Indian Academy of Sciences (India)

    Babita Devi; Smita Dubey; Shailendra Saini; Rajni Devi; Rashmi Wahi; Ajay Dhar; S. K. Vijay; A. K. Gwal

    2008-03-01

    This paper presents the effect of geomagnetic storm on geomagnetic field components at Southern (Maitri) and Northern (Kiruna) Hemispheres. The Indian Antarctic Station Maitri is located at geom. long. 66.03° S; 53.21° E whereas Kiruna is located at geom. long. 67.52° N; 23.38° E. We have studied all the geomagnetic storms that occurred during winter season of the year 2004–2005. We observed that at Southern Hemisphere the variation is large as compared to the Northern Hemisphere. Geomagnetic field components vary when the interplanetary magnetic field is oriented in southward direction. Geomagnetic field components vary in the main phase of the ring current. Due to southward orientation of vertical component of IMF reconnection takes place all across the dayside that transports plasma and magnetic flux which create the geomagnetic field variation.

  3. Impacts of Atlantic multi-decadal oscillation to summer atmospheric circulation in the northern mid-latitude

    Science.gov (United States)

    Lin, Jianshe

    2016-04-01

    Previous studies indicated that Atlantic multi-decadal oscillation (AMO) has significant impacts on regional and global climate. The impacts of the AMO on the summertime atmospheric circulation over the mid latitudes of the Northern Hemisphere and possible mechanisms were investigated througal observational analysis and numerical experiments by AGCMs. The results show that the interdecadal oscillation pattern of land surface temperature in the mid-latitudes are highly associated with the AMO. The eastern Europe, East Asia and the United States were warmer, while central Asia and northwest of the North America were cold during the positive phase of the AMO. Associated geopotential height anomalies is dominated by a barotropic wave train propagating along the jet stream, with zonal wavenumber 4 or 5. Basically, positive (negative) geopotential height anomalies correspond to warm (cold) anomalies of land surface temperature. The wave train pattern is called as interdecadal circumglobal teleconnection pattern Idealized numerical experiment by AGCMs indicates that the AMO-related SST anomalies tend to induce the teleconnection pattern, which was primarily forced by extratropical component of the AMO.

  4. Determining the extent and characterizing coral reef habitats of the northern latitudes of the Florida Reef Tract (Martin County).

    Science.gov (United States)

    Walker, Brian K; Gilliam, David S

    2013-01-01

    Climate change has recently been implicated in poleward shifts of many tropical species including corals; thus attention focused on higher-latitude coral communities is warranted to investigate possible range expansions and ecosystem shifts due to global warming. As the northern extension of the Florida Reef Tract (FRT), the third-largest barrier reef ecosystem in the world, southeast Florida (25-27° N latitude) is a prime region to study such effects. Most of the shallow-water FRT benthic habitats have been mapped, however minimal data and limited knowledge exist about the coral reef communities of its northernmost reaches off Martin County. First benthic habitat mapping was conducted using newly acquired high resolution LIDAR bathymetry and aerial photography where possible to map the spatial extent of coral reef habitats. Quantitative data were collected to characterize benthic cover and stony coral demographics and a comprehensive accuracy assessment was performed. The data were then analyzed in a habitat biogeography context to determine if a new coral reef ecosystem region designation was warranted. Of the 374 km(2) seafloor mapped, 95.2% was Sand, 4.1% was Coral Reef and Colonized Pavement, and 0.7% was Other Delineations. Map accuracy assessment yielded an overall accuracy of 94.9% once adjusted for known map marginal proportions. Cluster analysis of cross-shelf habitat type and widths indicated that the benthic habitats were different than those further south and warranted designation of a new coral reef ecosystem region. Unlike the FRT further south, coral communities were dominated by cold-water tolerant species and LIDAR morphology indicated no evidence of historic reef growth during warmer climates. Present-day hydrographic conditions may be inhibiting poleward expansion of coral communities along Florida. This study provides new information on the benthic community composition of the northern FRT, serving as a baseline for future community shift and

  5. Determining the extent and characterizing coral reef habitats of the northern latitudes of the Florida Reef Tract (Martin County.

    Directory of Open Access Journals (Sweden)

    Brian K Walker

    Full Text Available Climate change has recently been implicated in poleward shifts of many tropical species including corals; thus attention focused on higher-latitude coral communities is warranted to investigate possible range expansions and ecosystem shifts due to global warming. As the northern extension of the Florida Reef Tract (FRT, the third-largest barrier reef ecosystem in the world, southeast Florida (25-27° N latitude is a prime region to study such effects. Most of the shallow-water FRT benthic habitats have been mapped, however minimal data and limited knowledge exist about the coral reef communities of its northernmost reaches off Martin County. First benthic habitat mapping was conducted using newly acquired high resolution LIDAR bathymetry and aerial photography where possible to map the spatial extent of coral reef habitats. Quantitative data were collected to characterize benthic cover and stony coral demographics and a comprehensive accuracy assessment was performed. The data were then analyzed in a habitat biogeography context to determine if a new coral reef ecosystem region designation was warranted. Of the 374 km(2 seafloor mapped, 95.2% was Sand, 4.1% was Coral Reef and Colonized Pavement, and 0.7% was Other Delineations. Map accuracy assessment yielded an overall accuracy of 94.9% once adjusted for known map marginal proportions. Cluster analysis of cross-shelf habitat type and widths indicated that the benthic habitats were different than those further south and warranted designation of a new coral reef ecosystem region. Unlike the FRT further south, coral communities were dominated by cold-water tolerant species and LIDAR morphology indicated no evidence of historic reef growth during warmer climates. Present-day hydrographic conditions may be inhibiting poleward expansion of coral communities along Florida. This study provides new information on the benthic community composition of the northern FRT, serving as a baseline for future

  6. Climate change at northern latitudes: rising atmospheric humidity decreases transpiration, N-uptake and growth rate of hybrid aspen.

    Directory of Open Access Journals (Sweden)

    Arvo Tullus

    Full Text Available At northern latitudes a rise in atmospheric humidity and precipitation is predicted as a consequence of global climate change. We studied several growth and functional traits of hybrid aspen (Populus tremula L.×P. tremuloides Michx. in response to elevated atmospheric humidity (on average 7% over the ambient level in a free air experimental facility during three growing seasons (2008-2010 in Estonia, which represents northern temperate climate (boreo-nemoral zone. Data were collected from three humidified (H and three control (C plots, and analysed using nested linear models. Elevated air humidity significantly reduced height, stem diameter and stem volume increments and transpiration of the trees whereas these effects remained highly significant also after considering the side effects from soil-related confounders within the 2.7 ha study area. Tree leaves were smaller, lighter and had lower leaf mass per area (LMA in H plots. The magnitude and significance of the humidity treatment effect--inhibition of above-ground growth rate--was more pronounced in larger trees. The lower growth rate in the humidified plots can be partly explained by a decrease in transpiration-driven mass flow of NO(3 (- in soil, resulting in a significant reduction in the measured uptake of N to foliage in the H plots. The results suggest that the potential growth improvement of fast-growing trees like aspens, due to increasing temperature and atmospheric CO(2 concentration, might be smaller than expected at high latitudes if a rise in atmospheric humidity simultaneously takes place.

  7. Thermal mapping of the northern equatorial and temperate latitudes of Mars

    Science.gov (United States)

    Zimbelman, J. R.; Kieffer, H. H.

    1979-01-01

    The paper describes the mapping of nighttime temperatures over the northern hemisphere of Mars by using Viking infrared thermal mapping observations. It is shown that large variations of the temperature residual, -45 to +19 K, are related primarily to the thermal inertia of the surface. A general hypothesis is given for the transport of loose material on the Martian surface, which invokes the stability of the smooth, fine-grained surfaces to account for the bimodal thermal behavior observed.

  8. Ecosystem responses to recent oceanographic variability in high-latitude Northern Hemisphere ecosystems

    Science.gov (United States)

    Mueter, Franz J.; Broms, Cecilie; Drinkwater, Kenneth F.; Friedland, Kevin D.; Hare, Jonathan A.; Hunt, George L., Jr.; Melle, Webjørn; Taylor, Maureen

    2009-04-01

    As part of the international MENU collaboration, we compared and contrasted ecosystem responses to climate-forced oceanographic variability across several high latitude regions of the North Pacific (Eastern Bering Sea (EBS) and Gulf of Alaska (GOA)) and North Atlantic Oceans (Gulf of Maine/Georges Bank (GOM/GB) and the Norwegian/Barents Seas (NOR/BAR)). Differences in the nitrate content of deep source waters and incoming solar radiation largely explain differences in average primary productivity among these ecosystems. We compared trends in productivity and abundance at various trophic levels and their relationships with sea-surface temperature. Annual net primary production generally increases with annual mean sea-surface temperature between systems and within the EBS, BAR, and GOM/GB. Zooplankton biomass appears to be controlled by both top-down (predation by fish) and bottom-up forcing (advection, SST) in the BAR and NOR regions. In contrast, zooplankton in the GOM/GB region showed no evidence of top-down forcing but appeared to control production of major fish populations through bottom-up processes that are independent of temperature variability. Recruitment of several fish stocks is significantly and positively correlated with temperature in the EBS and BAR, but cod and pollock recruitment in the EBS has been negatively correlated with temperature since the 1977 shift to generally warmer conditions. In each of the ecosystems, fish species showed a general poleward movement in response to warming. In addition, the distribution of groundfish in the EBS has shown a more complex, non-linear response to warming resulting from internal community dynamics. Responses to recent warming differ across systems and appear to be more direct and more pronounced in the higher latitude systems where food webs and trophic interactions are simpler and where both zooplankton and fish species are often limited by cold temperatures.

  9. Quantifying Black Carbon emissions in high northern latitudes using an Atmospheric Bayesian Inversion

    Science.gov (United States)

    Evangeliou, Nikolaos; Thompson, Rona; Stohl, Andreas; Shevchenko, Vladimir P.

    2016-04-01

    Black carbon (BC) is the main light absorbing aerosol species and it has important impacts on air quality, weather and climate. The major source of BC is incomplete combustion of fossil fuels and the burning of biomass or bio-fuels (soot). Therefore, to understand to what extent BC affects climate change and pollutant dynamics, accurate knowledge of the emissions, distribution and variation of BC is required. Most commonly, BC emission inventory datasets are built by "bottom up" approaches based on activity data and emissions factors, but these methods are considered to have large uncertainty (Cao et al, 2006). In this study, we have used a Bayesian Inversion to estimate spatially resolved BC emissions. Emissions are estimated monthly for 2014 and over the domain from 180°W to 180°E and 50°N to 90°N. Atmospheric transport is modeled using the Lagrangian Particle Dispersion Model, FLEXPART (Stohl et al., 1998; 2005), and the inversion framework, FLEXINVERT, developed by Thompson and Stohl, (2014). The study domain is of particular interest concerning the identification and estimation of BC sources. In contrast to Europe and North America, where BC sources are comparatively well documented as a result of intense monitoring, only one station recording BC concentrations exists in the whole of Siberia. In addition, emissions from gas flaring by the oil industry have been geographically misplaced in most emission inventories and may be an important source of BC at high latitudes since a significant proportion of the total gas flared occurs at these high latitudes (Stohl et al., 2013). Our results show large differences with the existing BC inventories, whereas the estimated fluxes improve modeled BC concentrations with respect to observations. References Cao, G. et al. Atmos. Environ., 40, 6516-6527, 2006. Stohl, A. et al. Atmos. Environ., 32(24), 4245-4264, 1998. Stohl, A. et al. Atmos. Chem. Phys., 5(9), 2461-2474, 2005. Stohl, A. et al. Atmos. Chem. Phys., 13

  10. Winter climate change and sea ice-atmosphere interaction at high northern latitudes in ERA40 dataset

    Institute of Scientific and Technical Information of China (English)

    Liu Xiying

    2006-01-01

    Based on the reanalysis dataset ERA40 of European Center of Medium Range Weather Forcast (ECMWF), winter climate change and characteristics of sea ice-atmosphere interaction at high northern latitudes for recent several tens of years are analyzed. Superposed upon the background of global warming, the amplitude of temperature increase in winter at high northern latitudes is bigger and it exhibits different features in different regions. From the end of 1970 s, the Greenland Sea, the Barents Sea and most part of Euro-Asian continent and North American continent are getting warmer, whereas the Labrador Sea, the Greenland and the area around the Bering Strait are getting colder. Meanwhile, the sea level pressure in the central part of the northern polar region and the place where the climatic Icelandic low exist decreases, but in places farther southward it increases. Since the 1970 s, the sensible heat flux and latent heat flux sent to the atmosphere from the Greenland Sea and the Barents Sea has increased, this is mainly due to the reduction of sea ice concentration and the weakening of insulator and shield effect of the solid ice accordingly caused by the increase of air temperature. In sea ice free area of the Norwegian Sea, the sensible heat flux and latent heat flux sent to the atmosphere has reduced due to decrease of temperature and humidity differences between the air and the sea surface caused by increase of air temperature and humidity. In the Labrador Sea, due to decrease of air temperature and humidity and increase of temperature and humidity differences between the air and the sea surface accordingly, the sea gives more sensible heat flux and latent heat flux to the air. This will lead to the growth of sea ice extent there. The features of linear regression of sea level pressure, sea ice concentration and sum of sensible heat flux and latent heat flux toward time series of the leading mode of EOF expansion of surface air temperature are close to those of

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

    Directory of Open Access Journals (Sweden)

    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.

  12. Phylogeography of the intertidal copepod Tigriopus californicus reveals substantially reduced population differentiation at northern latitudes.

    Science.gov (United States)

    Edmands, S

    2001-07-01

    Previous studies of the intertidal copepod Tigriopus californicus revealed one of the highest levels of mitochondrial DNA differentiation ever reported among conspecific populations. The present study extends the geographical sampling northward, adding populations from northern California to south-east Alaska. The mitochondrial phylogeny for the entire species range, based on cytochrome oxidase I sequences for a total of 49 individuals from 27 populations, again shows extreme differentiation among populations (up to 23%). However, populations from Oregon northwards appear to be derived and have interpopulation divergences five times lower than those between southern populations. Furthermore, although few individuals were sequenced from each locality, populations from Puget Sound northward had significantly reduced levels of within-population variation. These patterns are hypothesized to result from the contraction and expansion of populations driven by recent ice ages.

  13. Persistent spread in seasonal albedo change radiative forcings linked to forest cover changes at northern latitudes

    Science.gov (United States)

    Bright, R. M.; Myhre, G.; Astrup, R. A.; Antón-Fernández, C.; Strømman, A. H.

    2014-12-01

    Large-scale land use and land cover change (LULCC) can significantly affect regional climates from changes in surface biogeophysics, and a substantial part of historical LULCC from forest to crop or pasture occurred in the mid- and high-latitudes of North America and Eurasia where the snow-masking effect of forests often leads to a negative radiative forcing from albedo changes linked to deforestation. Results from several recent historical LULCC modeling studies, however, reveal an order of magnitude spread in climate forcing from the snow-masking effect by forests. This is likely because, in months with snow cover, the interactions between vegetation and snow significantly complicate the relationship between the change in forest cover fraction and albedo, thus accurate characterizations of land surface-albedo dynamics are essential given the importance of albedo feedbacks when ground or canopy surfaces are covered in snow Here, we evaluate snow masking parameterization schemes of seven prominent climate models in greater detail in order to pinpoint major sources of the persistent variability in albedo predictions across models. Using a comprehensive dataset of forest structure, meteorology, and daily MODIS albedo observations spanning three winter-spring seasons in three regions of boreal Norway, we estimate radiative forcings connected to canopy snow masking and compare it to the observed forcings. We develop a physically-based regression model and compare its performance to existing modeling schemes, concluding with a discussion on the utility of purely empirical parameterizations relative to those rooted in radiative transfer theory and/or process-based modeling.

  14. Land Cover Mapping in Northern High Latitude Permafrost Regions with Satellite Data: Achievements and Remaining Challenges

    Directory of Open Access Journals (Sweden)

    Annett Bartsch

    2016-11-01

    resolution around 30 m has been shown to be suitable for a range of applications. This implies that the current Landsat-8, as well as Sentinel-2 missions would be adequate as input data. Recent studies have exemplified the value of Synthetic Aperture Radar (SAR in tundra regions. SAR missions may be therefore of added value for large-scale high latitude land cover mapping.

  15. Plate boundary deformation at the latitude of the Salton Trough - northern Gulf of California (Invited)

    Science.gov (United States)

    Stock, J. M.

    2013-12-01

    Along the Pacific-North America plate boundary zone, the segment including the southern San Andreas fault to Salton Trough and northern Gulf of California basins has been transtensional throughout its evolution, based on Pacific-North America displacement vectors calculated from the global plate circuit (900 × 20 km at N54°W since 20 Ma; 460 × 20 km at N48°W since 11 Ma). Nevertheless, active seismicity and focal mechanisms show a broad zone of plate boundary deformation within which the inferred stress regime varies locally (Yang & Hauksson 2013 GJI), and fault patterns in some regions suggest ongoing tectonic rotation. Similar behavior is inferred to have occurred in this zone over most of its history. Crustal structure in this region is constrained by surface geology, geophysical experiments (e.g., the 2011 Salton Seismic Imaging Project (SSIP), USGS Imperial Valley 1979, PACE), and interdisciplinary marine and onland studies in Mexico (e.g., NARS-Baja, Cortes, and surveys by PEMEX). Magnetic data (e.g., EMAG-2) aids in the recognition of large-scale crustal provinces and fault boundaries in regions lacking detailed geophysical surveys. Consideration of existing constraints on crustal thickness and architecture, and fault and basin evolution suggests that to reconcile geological deformation with plate motion history, the following additional factors need to be taken into account. 1) Plate boundary displacement via interacting systems of rotating blocks, coeval with slip on steep strike slip faults, and possibly related to slip on low angle extensional faults (e.g, Axen & Fletcher 1998 IGR) may be typical prior to the onset of seafloor spreading. This fault style may have accommodated up to 150 km of plate motion in the Mexican Continental Borderland and north of the Vizcaino Peninsula, likely between 12 and 15 Ma, as well as explaining younger rotations adjacent to the Gulf of California and current deformation southwest of the Salton Sea. 2) Geophysical

  16. Climatology of northern polar latitude MLT dynamics: mean winds and tides

    Directory of Open Access Journals (Sweden)

    G. Kishore Kumar

    2010-10-01

    Full Text Available Mean winds and tides in the northern polar Mesosphere and Lower Thermosphere (MLT have been studied using meteor radars located at Resolute Bay (75° N, 95° W and Yellowknife (62.5° N, 114.3° W. The measurements for Resolute Bay span almost 12 years from July 1997 to February 2009 and the Yellowknife data cover 7 years from June 2002 to October 2008. The analysis reveals similar wind flow over both sites with a difference in magnitude. The summer zonal flow is westward at lower heights, eastward at upper heights and the winter zonal flow is eastward at all heights. The winter meridional flow is poleward and sometimes weakly equatorward, while non winter months show equatorward flow, with a strong equatorward jet during mid-summer months. The zonal and meridional winds show strong interannual variation with a dominant annual variation as well as significant latitudinal variation. Year to year variability in both zonal and meridional winds exists, with a possible solar cycle dependence. The diurnal, semidiurnal and terdiurnal tides also show large interannual variability and latitudinal variation. The diurnal amplitudes are dominated by an annual variation. The climatological monthly mean winds are compared with CIRA 86, GEWM and HWM07 and the climatological monthly mean amplitudes and phases of diurnal and semidiurnal tides are compared with GSWM00 predictions. The GEWM shows better agreement with observations than the CIRA 86 and HWM07. The GSWM00 model predictions need to be modified above 90 km. The agreements and disagreements between observations and models are discussed.

  17. Ozone trends derived from the total column and vertical profiles at a northern mid-latitude station

    Directory of Open Access Journals (Sweden)

    P. J. Nair

    2013-03-01

    Full Text Available The trends and variability of ozone are assessed over a northern mid-latitude station, Haute-Provence Observatory (OHP – 43.93° N, 5.71° E, using total column ozone observations from the Dobson and Système d'Analyse par Observation Zénithale spectrometers, and stratospheric ozone profile measurements from Light detection and ranging, ozonesondes, Stratospheric Aerosol and Gas Experiment II, Halogen Occultation Experiment and Aura Microwave Limb Sounder. A multi-variate regression model with quasi biennial oscillation (QBO, solar flux, aerosol optical thickness, heat flux, North Atlantic oscillation (NAO and piecewise linear trend (PWLT or Equivalent Effective Stratospheric Chlorine (EESC functions is applied to the ozone anomalies. The maximum variability of ozone in winter/spring is explained by QBO and heat flux in 15–45 km and in 15–24 km, respectively. The NAO shows maximum influence in the lower stratosphere during winter while the solar flux influence is largest in the lower and middle stratosphere in summer. The total column ozone trends estimated from the PWLT and EESC functions are of −1.39±0.26 and −1.40±0.25 DU yr−1, respectively over 1984–1996 and about 0.65±0.32 and 0.42±0.08 DU yr−1, respectively over 1997–2010. The ozone profiles yield similar and significant EESC-based and PWLT trends in 1984–1996 and are about −0.5 and −0.8 % yr−1 in the lower and upper stratosphere, respectively. In 1997–2010, the EESC-based and PWLT trends are significant and of order 0.3 and 0.1 % yr−1, respectively in the 18–28 km range, and at 40–45 km, EESC provides significant ozone trends larger than the insignificant PWLT results. Therefore, this analysis unveils ozone recovery signals from total column ozone and profile measurements at OHP, and hence in the mid-latitudes.

  18. Investigating the Role of Biogeochemical Processes in the Northern High Latitudes on Global Climate Feedbacks Using an Efficient Scalable Earth System Model

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Atul K. [Univ. of Illinois, Urbana-Champaign, IL (United States)

    2016-09-14

    The overall objectives of this DOE funded project is to combine scientific and computational challenges in climate modeling by expanding our understanding of the biogeophysical-biogeochemical processes and their interactions in the northern high latitudes (NHLs) using an earth system modeling (ESM) approach, and by adopting an adaptive parallel runtime system in an ESM to achieve efficient and scalable climate simulations through improved load balancing algorithms.

  19. Has Anthropogenic Global Warming in the Arctic Contributed to Colder Winter Weather in the Northern Hemisphere Mid-latitudes?

    Science.gov (United States)

    Cohen, J. L.; Furtado, J. C.; Barlow, M. A.; Cherry, J. E.; Alexeev, V. A.

    2012-12-01

    The global climate models predict that temperatures will warm the greatest in winter due to a positive feedback of increased greenhouse gases and a diminished and darker cryosphere. Furthermore, current consensus on global climate change predicts warming trends over the NH continents during boreal winter. However, recent trends in Northern Hemisphere (NH) seasonal surface temperatures diverge from these projections. For the last two decades or so, NH landmasses have experienced significant warming trends for all seasons except winter, when large-scale cooling trends exist instead. We propose a mechanism linking Arctic warming and winter continental cooling. Evidence suggests that summer and autumn Arctic warming trends are concurrent with increases in high-latitude moisture and an increase in autumnal Eurasian snow cover, which dynamically induces large-scale wintertime cooling. Understanding this counterintuitive response to radiative warming of the climate system has the potential to improve climate predictions at seasonal and longer timescales.a) JAS area-averaged (poleward of 60°N) surface temperature anomalies (°C) from NASA MERRA. b) September area-averaged (poleward of 65°N) Arctic Ocean sea ice coverage (fractional area). c) September - October vertically integrated (700-1000 hPa) and area-averaged (poleward of 60°N) specific humidity (kg m-2). d) October mean snow cover areal extent (106 km2) over the Eurasian continent from observations (black) and ensemble-mean from the historical runs of the CMIP5 model output (brown line). e) The DJF average AO index (standardized). Same-coloured dashed lines in a) - e) represent the linear trend in each index. Trends with double asterisk (**) indicate trends are significant at the p < 0.01 level.

  20. Tropospheric ozone from IASI: comparison of different inversion algorithms and validation with ozone sondes in the northern middle latitudes

    Directory of Open Access Journals (Sweden)

    R. Stübi

    2009-12-01

    Full Text Available This paper presents a first statistical validation of tropospheric ozone products derived from measurements of the IASI satellite instrument. Since the end of 2006, IASI (Infrared Atmospheric Sounding Interferometer aboard the polar orbiter Metop-A measures infrared spectra of the Earth's atmosphere in nadir geometry. This validation covers the northern mid-latitudes and the period from July 2007 to August 2008. Retrieval results from four different sources are presented: three are from scientific products (LATMOS, LISA, LPMAA and the fourth one is the pre-operational product distributed by EUMETSAT (version 4.2. The different products are derived from different algorithms with different approaches. The difference and their implications for the retrieved products are discussed. In order to evaluate the quality and the performance of each product, comparisons with the vertical ozone concentration profiles measured by balloon sondes are performed and lead to estimates of the systematic and random errors in the IASI ozone products (profiles and partial columns. A first comparison is performed on the given profiles; a second comparison takes into account the altitude dependent sensitivity of the retrievals. Tropospheric columnar amounts are compared to the sonde for a lower tropospheric column (surface to about 6 km and a "total" tropospheric column (surface to about 11 km. On average both tropospheric columns have small biases for the scientific products, less than 2 Dobson Units (DU for the lower troposphere and less than 1 DU for the total troposphere. The comparison of the still pre-operational EUMETSAT columns shows higher mean differences of about 5 DU.

  1. The rotation of the plasmapause-like boundary at high latitudes in Saturn's magnetosphere and its relation to the eccentric rotation of the northern and southern auroral ovals

    Science.gov (United States)

    Gurnett, D. A.; Persoon, A. M.; Groene, J. B.; Kurth, W. S.; Morooka, M.; Wahlund, J.-E.; Nichols, J. D.

    2011-11-01

    Here we present a study of the rotation of the plasmapause-like density boundary discovered by the Cassini spacecraft at high latitudes in the Saturnian magnetosphere, and compare the results with previously published studies of high-latitude magnetic field perturbations and the eccentric rotation of the auroral ovals. Near the planet the density boundary is located at dipole L values ranging from about 8 to 15, and separates a region of very low densities at high latitudes from a region of higher densities at lower latitudes. We show that the density boundary rotates at different rates in the northern and southern hemispheres, and that the periods are the same as the modulation periods of Saturn kilometric radiation in those hemispheres. We also show that the phase of rotation in a given hemisphere is closely correlated with the phase of the high-latitude magnetic field perturbations observed by Cassini in that hemisphere, and also with the phase of the eccentric rotation of the auroral oval observed by the Hubble Space Telescope.

  2. Paauglių smurtas mokykloje: situacija ir analizė

    OpenAIRE

    Bagdžiūnienė, Žaneta

    2008-01-01

    Paauglių smurtas mokykloje: situacija ir analizė Vilniaus pedagoginio universiteto, Socialinės komunikacijos instituto, neakivaizdinių studijų socialinio darbo antro kurso studentės Žanetos Bagdžiūnienės magistro darbo „Paauglių smurtas mokykloje: situacija ir analizė“ tyrimu siekiama išsiaiškinti paauglių smurto apraiškas bei paplitimą mokykloje, atskleisti priežastis, prevencijos galimybes. Iškelta hipotezė - manoma, jog vis dar aktuali problema mokykloje yra paauglių fizinis smurtas, ne...

  3. Altering Their Ecological Niche: Investigating the Response of Avian Migrants to Changes in Vegetation Phenology at Northern Latitudes

    Science.gov (United States)

    Budde, M. E.; Ward, D. H.; Ely, C. R.; Handel, C. M.; Hupp, J. W.

    2009-12-01

    The impacts of global climate change are expected to be most severe at high northern latitudes. There is now strong evidence to support the hypothesis that such changes have had dramatic effects on the phenology of spring vegetative growth in these areas. One aspect of this change that has not been thoroughly investigated is how these changes vary across habitats and whether sub-Arctic and Arctic avifauna have adapted to shifts in plant phenology by modifying the timing of migration and nesting. A recent study showed that certain bird species have experienced population decline due to the varied timing of seasonal events and points to the fact that the degree of risk facing migratory birds is not well quantified. Plant phenology is especially sensitive to annual variation in temperature and precipitation and is a major determinant of plant species distribution, making it a good indicator of climate change effects. Migratory birds are considered one of the most vulnerable groups to the impacts of climate change because climate affects bird movement and distribution through species-specific physiological tolerances and changes in food and habitat resources. In this study we analyze the evidence for long-term plant phenology changes across different biomes of Alaska using satellite remote sensing techniques. We correlate this variability with ground-based measurements of avian migration and breeding. Specifically, we try to determine if the timing of spring green-up is synchronized across breeding areas or whether the process has become fractured across intervening biomes, potentially disrupting the timing of migration and breeding, putting species at risk. Using satellite-based time series of Normalized Difference Vegetation Index (NDVI) data, we create spatially explicit maps of seasonal vegetation metrics and correlate those with the timing and distribution of avian migrant populations. Preliminary investigation focused on the last 10 year period (2000-2009) and

  4. Amplified Late Pliocene terrestrial warmth in northern high latitudes from greater radiative forcing and closed Arctic Ocean gateways

    Science.gov (United States)

    Feng, Ran; Otto-Bliesner, Bette L.; Fletcher, Tamara L.; Tabor, Clay R.; Ballantyne, Ashley P.; Brady, Esther C.

    2017-05-01

    Proxy reconstructions of the mid-Piacenzian warm period (mPWP, between 3.264 and 3.025 Ma) suggest terrestrial temperatures were much warmer in the northern high latitudes (55°-90°N, referred to as NHL) than present-day. Climate models participating in the Pliocene Model Intercomparison Project Phase 1 (PlioMIP1) tend to underestimate this warmth. For instance, the underestimate is ∼10 °C on average across NHL and up to 17 °C in the Canadian Arctic region in the Community Climate System Model version 4 (CCSM4). Here, we explore potential mPWP climate forcings that might contribute to this mPWP mismatch. We carry out seven experiments to assess terrestrial temperature responses to Pliocene Arctic gateway closure, variations in CO2 level, and orbital forcing at millennial time scale. To better compare the full range of simulated terrestrial temperatures with sparse proxy data, we introduce a pattern recognition technique that simplifies the model surface temperatures to a few representative patterns that can be validate with the limited terrestrial proxy data. The pattern recognition technique reveals two prominent features of simulated Pliocene surface temperature responses. First, distinctive patterns of amplified warming occur in the NHL, which can be explained by lowered surface elevation of Greenland, pattern and amount of Arctic sea ice loss, and changing strength of Atlantic meridional overturning circulation. Second, patterns of surface temperature response are similar among experiments with different forcing mechanisms. This similarity is due to strong feedbacks from responses in surface albedo and troposphere water vapor content to sea ice changes, which overwhelm distinctions in forcings from changes in insolation, CO2 forcing, and Arctic gateway closure. By comparing CCSM4 simulations with proxy records, we demonstrate that both model and proxy records show similar patterns of mPWP NHL terrestrial warmth, but the model underestimates the magnitude

  5. Observations and modeling of northern mid-latitude recurring slope lineae (RSL) suggest recharge by a present-day martian briny aquifer

    Science.gov (United States)

    Stillman, David E.; Michaels, Timothy I.; Grimm, Robert E.; Hanley, Jennifer

    2016-02-01

    Recurring slope lineae (RSL) are narrow (0.5-5 m) dark features on Mars that incrementally lengthen down steep slopes, fade in colder seasons, and recur annually. These features have been identified from the northern to southern mid-latitudes. Here, we describe how observations of northern mid-latitude RSL in northern Chryse Planitia and southwestern Acidalia Planitia (CAP) suggest that brines start flowing before northern spring equinox and continue for more than half a Mars-year (490 ± 40 sols, spanning solar longitude 337° ± 11°-224° ± 20°). All CAP RSL are found on the steep slopes of craters and their source zones are at or below the elevation of the surrounding plains. Spacecraft-derived surface temperature observations cannot resolve individual RSL, so thermal modeling was used to determine that CAP RSL have a freezing temperature of 238-252 K, freeze and melt diurnally, and flow only occurs within the top ∼8 cm of the regolith. Furthermore, we calculate that a typical CAP RSL has a water budget of 1.5-5.6 m3/m of headwall. Therefore, such a large water budget makes annual recharge via atmospheric or subsurface diffusion sources unlikely. Alternatively, we hypothesize that the most plausible RSL source is a briny aquifer with a freezing temperature less than or equal to the mean annual CAP surface temperature (220-225 K). The annual cycle is as follows: in late autumn, the shallowest part of the brine feeding the source zone freezes, forming an ice dam. As spring approaches, temperatures rise and the dam is breached. Brine is discharged and the RSL initially lengthens rapidly (>1.86 m/sol), the lengthening rate then slows considerably, to ∼0.25 m/sol. Eventually, the losses equal the discharge rate and the RSL reaches its equilibrium phase. As brine flows in the RSL some of the water is lost to the atmosphere, therefore the freezing temperature of the brine within the RSL is higher (238-252 K) as the brine transitions to a super-eutectic salt

  6. The impact of Arctic sea ice on the Arctic energy budget and on the climate of the Northern mid-latitudes

    Energy Technology Data Exchange (ETDEWEB)

    Semmler, Tido [Alfred Wegener Institute for Polar and Marine Research, Bremerhaven (Germany); Met Eireann, Glasnevin Hill, Dublin 9 (Ireland); McGrath, Ray [Met Eireann, Glasnevin Hill, Dublin 9 (Ireland); Wang, Shiyu [Swedish Meteorological and Hydrological Institute, Norrkoeping (Sweden); Met Eireann, Glasnevin Hill, Dublin 9 (Ireland)

    2012-12-15

    The atmospheric general circulation model EC-EARTH-IFS has been applied to investigate the influence of both a reduced and a removed Arctic sea ice cover on the Arctic energy budget and on the climate of the Northern mid-latitudes. Three 40-year simulations driven by original and modified ERA-40 sea surface temperatures and sea ice concentrations have been performed at T255L62 resolution, corresponding to 79 km horizontal resolution. Simulated changes between sensitivity and reference experiments are most pronounced over the Arctic itself where the reduced or removed sea ice leads to strongly increased upward heat and longwave radiation fluxes and precipitation in winter. In summer, the most pronounced change is the stronger absorption of shortwave radiation which is enhanced by optically thinner clouds. Averaged over the year and over the area north of 70 N, the negative energy imbalance at the top of the atmosphere decreases by about 10 W/m{sup 2} in both sensitivity experiments. The energy transport across 70 N is reduced. Changes are not restricted to the Arctic. Less extreme cold events and less precipitation are simulated in sub-Arctic and Northern mid-latitude regions in winter. (orig.)

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

    Directory of Open Access Journals (Sweden)

    S. M. L. Melo

    2007-08-01

    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 in order to 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 measurements used here are vertical profiles of ozone, temperature, N2O, CH4, HNO3, and HCl obtained during four campaigns, involving the launch of both ozonesondes and large balloons from Vanscoy, Saskatchewan, Canada (52° N, 107° W. The campaigns were conducted in August and September 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 found 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 ozone measurements show a narrow layer of low ozone centered near 25 km that is consistent with fossil debris from the polar vortex, suggesting that localized springtime ozone anomalies can persist through summer, affecting ozone levels at mid-latitudes.

  8. Variability of the nighttime OH layer and mesospheric ozone at high latitudes during northern winter: influence of meteorology

    OpenAIRE

    Damiani, A.; M. Storini; Santee, M.L.; Wang, S

    2010-01-01

    Analyses of OH zonal means, recorded at boreal high latitudes by the Aura Microwave Limb Sounder (MLS) in winters of 2005–2009, have shown medium- (weeks) and short- (days) term variability of the nighttime OH layer.

    Because of the exceptional descent of air from the mesosphere-lower thermosphere (MLT) region, medium-term variability occurred during February 2006 and February/March 2009. The layer normally situated at about 82 km descended by about 5–7 km, and its density...

  9. Variability of the nighttime OH layer and mesospheric ozone at high latitudes during northern winter: influence of meteorology

    OpenAIRE

    Damiani, A.; M. Storini; Santee, M.L.; Wang, S

    2010-01-01

    Analyses of OH zonal means, recorded at boreal high latitudes by the Aura Microwave Limb Sounder (MLS), have shown medium- (weeks) and short-term (days) variability of the nighttime OH layer.

    Because of the exceptional descent of air from the mesosphere-lower thermosphere region, medium-term variability occurred during February 2006 and February/March 2009. The layer normally situated at about 82 km descended by about 5–7 km, and its density increased to more than twice J...

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

    Directory of Open Access Journals (Sweden)

    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.

  11. The Hamburg/RASS Catalogue of optical identifications. Northern high-galactic latitude ROSAT Bright Source Catalogue X-ray sources

    CERN Document Server

    Zickgraf, F J; Hagen, H J; Reimers, D; Voges, W

    2003-01-01

    We present the Hamburg/RASS Catalogue (HRC) of optical identifications of X-ray sources at high-galactic latitude. The HRC includes all X-ray sources from the ROSAT Bright Source Catalogue (RASS-BSC) with galactic latitude |b| >= 30 degr and declination delta >= 0 degr. In this part of the sky covering ~10 000 deg^2 the RASS-BSC contains 5341 X-ray sources. For the optical identification we used blue Schmidt prism and direct plates taken for the northern hemisphere Hamburg Quasar Survey (HQS) which are now available in digitized form. The limiting magnitudes are 18.5 and 20, respectively. For 82% of the selected RASS-BSC an identification could be given. For the rest either no counterpart was visible in the error circle or a plausible identification was not possible. With ~42% AGN represent the largest group of X-ray emitters, \\~31% have a stellar counterpart, whereas galaxies and cluster of galaxies comprise only ~4% and ~5%, respectively. In ~3% of the RASS-BSC sources no object was visible on our blue dire...

  12. THE ROLE OF ALTITUDE, LATITUDE AND LONGITUDE IN THE DISTRIBUTION OF MEADOW VEGETATION IN THE FLOODPLAINS OF THE NORTHERN UKRAINE

    Directory of Open Access Journals (Sweden)

    A. KUZEMKO

    2011-01-01

    Full Text Available This paper presents a comparison of syntaxa at alliance level from Molinio-Arrhenatheretea, Koelerio-Corynephoretea and Phragmito-Magnocaricetea classes, considering altitude, latitude and longitude. The results show that the syntaxa may be divided into two groups: one geographically specific (with a narrow distribution and propensity for certain climatic zones or regions, e.g. Agrostio stoloniferae-Beckmannion eruciformis and the other non-geographically specific (with a wide distribution and occurring in several climatic zones e.g. typical Festucion pratensis alliance. The role of climate in the differentiation of floodplain meadow vegetation is considerable in spite of the well known azonality of such vegetation. This can be explained by the changes in environmental conditions, especially soil reaction, temperature and continentality.

  13. Assessing multi-site δ18O-climate calibrations of the coralline alga Clathromorphum across the high-latitude Northern Hemisphere

    Science.gov (United States)

    Ng, Jessica Y.; Williams, Branwen; Thompson, Diane M.; Mayne, Chloe; Halfar, Jochen; Edinger, Evan; Johnson, Kathleen

    2016-12-01

    An increased number of climate proxy records and more refined interpretation of proxy data are crucial to improve projections of future climate at high latitudes, where internal feedbacks amplify warming and established high-resolution climate archives are especially sparse. Encrusting coralline algae are being developed as a mid- to high-latitude marine climate archive. These long-lived algae form a solid high-Mg calcite skeleton with annual growth bands similar to those of trees and tropical corals. The oxygen isotope ratio of the algal skeleton (δ18Oalg) records local environmental and climatic factors, notably sea surface temperature and seawater δ18O. Here we assess the δ18Oalg-climate relationship in diverse environments across the algal habitat range utilizing two species of coralline algae from the genus Clathromorphum. Clathromorphum is widely distributed from the cold-temperate North Atlantic and Pacific to the Arctic Ocean and has recently yielded numerous climate reconstructions of up to 650 years in length. In this study, we calibrate δ18Oalg of four specimens to gridded temperature and salinity data, the latter a proxy for seawater δ18O. These specimens were collected from a variety of algal growth environments across the high-latitude Northern Hemisphere: two specimens from the Aleutian Archipelago, one from the Canadian Arctic, and one from the Gulf of Maine. Low winter temperatures and insolation restrict the months when algae record local climate in the δ18O of their skeletons; we therefore determine these response seasons by correlating monthly temperature and salinity anomalies with annual δ18Oalg anomalies at each site. We then average gridded data over months that correlate significantly (95% confidence interval) for regression with δ18Oalg. While the timing and nature of the climate signal vary across sites, we find significant relationships between δ18Oalg and either temperature or salinity averaged over the response season at three

  14. Hayashi Spectra of the Northern Hemisphere Mid-latitude Atmospheric Variability in the NCEP and ERA 40 Reanalyses

    CERN Document Server

    Dell'Aquila, A; Ruti, P; Calmanti, S; Aquila, Alessandro Dell'; Lucarini, Valerio; Ruti, Paolo; Calmanti, Sandro

    2004-01-01

    We compare 45 years of the reanalyses of NCEP-NCAR and ECMWF in terms of their representation of the mid-latitude winter atmospheric variability for the overlapping time frame 1957-2002. We adopt the classical approach of computing the Hayashi spectra of the 500 hPa geopotential height fields. Discrepancies are found especially in the first 15 years of the records in the high-frequency-high wavenumber propagating waves and secondly on low frequency-low wavenumber standing waves. This implies that in the first period the two datasets have a different representation of the baroclinic available energy conversion processes. In the period starting from 1973 a positive impact of the aircraft data on the Euro-Atlantic synoptic waves has been highlighted. Since in the first period the assimilated data are scarcer and of lower quality than later on, they provide a weaker constraint to the model dynamics. Therefore, the resulting discrepancies in the reanalysis products may be mainly attributed to differences in the mo...

  15. A New Snow Index for Improved Predictions of Winter Weather in the Northern Hemisphere Mid-latitudes.

    Science.gov (United States)

    Cohen, J. L.; Jones, J.; Brands, S. F.

    2012-12-01

    Seasonal climate prediction remains a difficult challenge. During Northern Hemisphere (NH) winter the large-scale teleconnection pattern of the Arctic Oscillation (AO) explains the largest fraction of temperature variance of any other known climate mode. However the Arctic Oscillation is considered to be a result of intrinsic atmospheric dynamics or chaotic behavior and therefore is unpredictable. Earlier studies established that fall Eurasian mean snow cover extent is significantly correlated with the winter AO. However we have found that the daily change in snow cover extent is a much better predictor of the winter AO, which we refer to as the Snow Advance Index (SAI). With the development of the SAI we can now explain approximately 75% of the variance of the winter AO. The high correlation between the SAI and the winter AO demonstrates that the AO is mostly predictable, which can be exploited for skillful seasonal climate predictions. An immediate benefit of the development of this new index is improved seasonal climate predictions. The ability to predict the winter AO is considered the single most important advance in achieving successful winter forecasts. We created cross-validated hindcasts of winter land surface temperatures using the SAI as a predictor in the AER seasonal forecast model and compared those hindcasts with hindcasts using the observed winter AO and ENSO. Skill or accuracy of the AER model compares favorably to that of the observed winter AO and ENSO especially for the Eastern US and large portions of Northern Eurasia. And considering that the index is known four months prior to the winter AO, yet matches the skill of the winter AO so closely, demonstrates great potential for improved real-time winter forecasts. If time permits we will also show that snow cover can help explain decadal variations in the AO and subsequently decadal winter temperature trends.lt;img border=0 src="images/C34B-03_B.jpg">

  16. Variability of the nighttime OH layer and mesospheric ozone at high latitudes during northern winter: influence of meteorology

    Directory of Open Access Journals (Sweden)

    A. Damiani

    2010-06-01

    Full Text Available Analyses of OH zonal means, recorded at boreal high latitudes by the Aura Microwave Limb Sounder (MLS, have shown medium- (weeks and short-term (days variability of the nighttime OH layer.

    Because of the exceptional descent of air from the mesosphere-lower thermosphere region, medium-term variability occurred during February 2006 and February/March 2009. The layer normally situated at about 82 km descended by about 5–7 km, and its density increased to more than twice January values. In these periods and location the abundance of the lowered OH layer is comparable with the OH values induced by Solar Energetic Particle (SEP forcing (e.g. SEP events of January 2005 at the same altitudes. In both years, the drop of the OH layer was coupled with increased mesospheric temperatures, elevated carbon monoxide and an almost complete disappearance of ozone at the altitude of the descended layer (which was not observed in other years. Moreover, under these exceptional atmospheric conditions, the third ozone peak is shown descending to lower altitude and increasing its abundance, with maximum values recorded during February 2009.

    Short-term variability occurred during Sudden Stratospheric Warming (SSW events, in particular in January 2006, February 2008 and January 2009, when dynamics led to a smaller abundance of the OH layer at its typical altitude. The upward extension of the OH layer coupled to changes in ozone and carbon monoxide is shown to be strongest during the SSW of January 2009, coincident with the lowest upper mesospheric temperatures recorded at that time of year during 2005–2009. Finally, the series of SSW events that occurred in late January/February 2008 induced noticeable short-term variability in ozone at altitudes of both the ozone minimum and the third ozone peak.

    These phenomena, confined inside the polar vortex, are an additional tool that can be used to investigate mesospheric vortex dynamics.

  17. Variability of the nighttime OH layer and mesospheric ozone at high latitudes during northern winter: influence of meteorology

    Science.gov (United States)

    Damiani, A.; Storini, M.; Santee, M. L.; Wang, S.

    2010-11-01

    Analyses of OH zonal means, recorded at boreal high latitudes by the Aura Microwave Limb Sounder (MLS) in winters of 2005-2009, have shown medium- (weeks) and short- (days) term variability of the nighttime OH layer. Because of the exceptional descent of air from the mesosphere-lower thermosphere (MLT) region, medium-term variability occurred during February 2006 and February/March 2009. The layer normally situated at about 82 km descended by about 5-7 km, and its density increased to more than twice January values. In these periods and location the abundance of the lowered OH layer is comparable to the OH values induced by Solar Energetic Particle (SEP) forcing (e.g., SEP events of January 2005) at the same altitudes. In both years, the descent of the OH layer was coupled with increased mesospheric temperatures, elevated carbon monoxide and an almost complete disappearance of ozone at the altitude of the descended layer (which was not observed in other years). Moreover, under these exceptional atmospheric conditions, the third ozone peak, normally at about 72 km, is shown to descend about 5 km to lower altitude and increase in magnitude, with maximum values recorded during February 2009. Short-term variability occurred during Sudden Stratospheric Warming (SSW) events, in particular in January 2006, February 2008 and January 2009, when dynamics led to a smaller abundance of the OH layer at its typical altitude. During these periods, there was an upward displacement of the OH layer coupled to changes in ozone and carbon monoxide. These perturbations were the strongest during the SSW of January 2009; coincident upper mesospheric temperatures were the lowest recorded over the late winters of 2005-2009. Finally, the series of SSW events that occurred in late January/February 2008 induced noticeable short-term variability in ozone at altitudes of both the ozone minimum and the third ozone peak. These phenomena, confined inside the polar vortex, are an additional tool

  18. Variability of the nighttime OH layer and mesospheric ozone at high latitudes during northern winter: influence of meteorology

    Directory of Open Access Journals (Sweden)

    A. Damiani

    2010-11-01

    Full Text Available Analyses of OH zonal means, recorded at boreal high latitudes by the Aura Microwave Limb Sounder (MLS in winters of 2005–2009, have shown medium- (weeks and short- (days term variability of the nighttime OH layer.

    Because of the exceptional descent of air from the mesosphere-lower thermosphere (MLT region, medium-term variability occurred during February 2006 and February/March 2009. The layer normally situated at about 82 km descended by about 5–7 km, and its density increased to more than twice January values. In these periods and location the abundance of the lowered OH layer is comparable to the OH values induced by Solar Energetic Particle (SEP forcing (e.g., SEP events of January 2005 at the same altitudes. In both years, the descent of the OH layer was coupled with increased mesospheric temperatures, elevated carbon monoxide and an almost complete disappearance of ozone at the altitude of the descended layer (which was not observed in other years. Moreover, under these exceptional atmospheric conditions, the third ozone peak, normally at about 72 km, is shown to descend about 5 km to lower altitude and increase in magnitude, with maximum values recorded during February 2009.

    Short-term variability occurred during Sudden Stratospheric Warming (SSW events, in particular in January 2006, February 2008 and January 2009, when dynamics led to a smaller abundance of the OH layer at its typical altitude. During these periods, there was an upward displacement of the OH layer coupled to changes in ozone and carbon monoxide. These perturbations were the strongest during the SSW of January 2009; coincident upper mesospheric temperatures were the lowest recorded over the late winters of 2005–2009. Finally, the series of SSW events that occurred in late January/February 2008 induced noticeable short-term variability in ozone at altitudes of both the ozone minimum and the third ozone peak.

    These phenomena, confined

  19. Long-term trends in the middle atmosphere dynamics at northern middle latitudes – one regime or two different regimes?

    Directory of Open Access Journals (Sweden)

    J. Lastovicka

    2010-02-01

    Full Text Available Due to increasing atmospheric concentration of greenhouse gases and changing stratospheric ozone concentration, both of anthropogenic origin, various quantities in the middle atmosphere reveal long-term changes and trends. Lastovicka and Krizan (2006 indicated possibility of change of trends in the dynamics in the northern midlatitude middle atmosphere as a whole in the 1990s. To search for such change of trends we use data on winds in the mesopause region, on total columnar ozone, on ozone laminae, on winds in the middle and lower stratosphere, and on peak electron density in the E region of the ionosphere. One group of quantities, the mesopause region wind-like trends, changes their trends around 1990, the other one, the total ozone-like trends, in the mid-1990s. Altogether they create a skeleton of scenario of the change of the middle atmosphere dynamics trends in the 1990s. Drivers of these changes appear to be different for the first group and for the second group. Tropospheric processes seem to play a role in the changes of trends in middle atmospheric dynamics.

  20. Foraminifera isotopic records... with special attention to high northern latitudes and the impact of sea-ice distillation processes

    Energy Technology Data Exchange (ETDEWEB)

    Hillaire-Marcel, Claude, E-mail: hillaire-marcel.claude@uqam.ca [GEOTOP, Universite du Quebec a Montreal, PO Box 8888, succursale ' centre ville' Montreal, Qc, H3C 3P8 (Canada)

    2011-05-15

    Since the reassessment of oxygen isotope paleotemperatures by N. Shackleton in the late 60s, most papers using isotopic records from planktic or benthic foraminifers imply a direct relationship between oxygen isotopes in seawater and the ice/ocean volume, thus some linkage with salinity, sea level, etc. Such assumptions are also made when incorporating 'isotopic modules' in coupled models. Here, we will further examine the linkages between salinity and oxygen isotope ratios of sea-water recorded by foraminifers, and their potential temporal and spatial variability, especially in the northern North Atlantic and the Arctic oceans. If temporal and spatial changes in the isotopic composition of precipitations and ice meltwaters tune the isotopic properties of the fresh water end-member that dilutes the ocean, rates of sea-ice formation and evaporation at the ocean surface play a further role on the salt and oxygen isotope contents of water masses. Thus, the oxygen 18-salinity relationship carries a specific isotopic signature for any given water mass. At the ocean scale, residence time and mixing of these water masses, as well as the time dependent-achievement of proxy-tracer equilibrium, will also result in variable recordings of mass transfers into the hydrosphere, notable between ice-sheets and ocean. Since these records in water mass may vary in both amplitude and time, direct correlations of isotopic records will potentially be misleading. Implications of such issues on the interpretation of oxygen isotope records from the sub-arctic seas will be discussed, as well as the inherent flaws of such records due to sedimentological and or ecological parameters.

  1. Variation of atmospheric CO, δ13C, and δ18O at high northern latitude during 2004-2009: Observations and model simulations

    Science.gov (United States)

    Park, Keyhong; Wang, Zhihui; Emmons, Louisa K.; Mak, John E.

    2015-10-01

    Atmospheric CO mixing ratios and stable isotope ratios (δ13C and δ18O) were measured at a high northern latitude site (Westman Islands, Iceland) from January 2004 to March 2010 in order to investigate recent multiyear trends of the sources of atmospheric carbon monoxide in the extratropical Northern Hemisphere. During this period, we observed a decrease of about 2% per year in CO mixing ratios with little significant interannual variability. The seasonal cycles for δ13C and δ18O in CO are similar to that in the CO mixing ratio, and there is a pronounced interannual variation in their seasonal extremes occurring in summer and fall, which is driven by changes in the relative contribution of different sources. Some of the sources of CO are anthropogenic in character (e.g., fossil fuel and biofuel combustion and agricultural waste burning), and some are primarily natural (e.g., oxidation atmospheric methane and other hydrocarbons and wildfires), and distinction among the various major sources can, more or less, be distinguished by the stable isotopic composition of CO. We compare our observations with simulations from a 3-D global chemical transport model (MOZART-4, Model for Ozone and Related Chemical Tracers, version 4). Our results indicate the observed trend of anthropogenic CO emissions is mostly responsible for the observed variation in δ13C and δ18O of CO during 2004-2009. Especially, the δ18O enriched sources such as fossil fuel and biofuel sources are controlling the variation. The modeling results indicate decreasing trends in the fossil fuel and biofuel source contributions at Iceland of -0.61 ± 0.26 ppbv/yr and -0.38 ± 0.10 ppbv/yr, respectively, during the observation period.

  2. Different climatic controls of soil δ13Corg in three mid-latitude regions of the Northern Hemisphere since the Last Glacial period

    Institute of Scientific and Technical Information of China (English)

    RAO ZhiGuo; ZHU ZhaoYu; ZHANG JiaWu

    2007-01-01

    Paleoecological records of soil δ13Corg from three regions in the middle latitudes of the Northern Hemisphere, including the Chinese Loess Plateau (CLP), the Great Plains and adjacent areas of North America and northwestern Europe, showed different variations since the Last Glacial period. An attempt was made to evaluate the causes for the difference in δ13Corg on the basis of the modern climatic data collected in these regions and of the modern C3 and C4 plant distributions. The analysis indicates that temperature, especially the growing season temperature, has a dominant control on the growth of C4 plants. When the mean annual or growing season temperatures are below the "threshold value", the growth of C4 plants is limited. When the temperature is above the "threshold value", C4 plants can grow under a wide range of precipitation. However, when the precipitation is high enough to favor the growth of trees, the proportions of C4 plants in local biomass will decline. The implicit control factor recovered by sedimentary records is consistent with the control factor on modern C3/C4 distribution. Pure C3 plants have been dominating the local biomass since the Last Glacial period in European loess region, mainly owing to the low local temperature. The increases in C4 plants from the late Pleistocene to the Holocene in the Chinese Loess Plateau, the Great Plains and adjacent areas, mainly reflect the influence of increasing temperature.

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

    Directory of Open Access Journals (Sweden)

    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.

  4. Spatial and Temporal Changes in Vegetation Phenology at Middle and High Latitudes of the Northern Hemisphere over the Past Three Decades

    Directory of Open Access Journals (Sweden)

    Jianjun Zhao

    2015-08-01

    Full Text Available Vegetation phenology is a key biological indicator for monitoring terrestrial ecosystems and global change, and regions with the most obvious phenological changes in vegetation are primarily located at high latitudes and altitudes. Over the past three decades, investigations of obvious phenological changes in vegetation at middle and high latitudes in the Northern Hemisphere have provided significant contributions to understanding global climate change. In this study, phenological parameters were extracted from the Global Inventory Modeling and Mapping Studies (GIMMS Normalized Difference Vegetation Index (NDVI3g to analyze the spatial and temporal characteristics of vegetation phenological changes above 40°N in the Northern Hemisphere from 1982–2013. The results showed that the start of season (SOS was significantly advanced (−2.2 ± 0.6 days·decade−1, p < 0.05 and that the end of season (EOS was slightly delayed (0.78 ± 0.6 days·decade−1, p = 0.21 over the entire study area in the initial 21 years (1982–2002. When the time scale was extended to 2013, the change rate of the SOS and EOS was significantly reduced; in addition, the SOS was delayed (3.2 ± 1.7 days·decade−1, p < 0.05, and the EOS was advanced (4.5 ± 0.9 days·decade−1, p < 0.05 over the entire study area in the last 11 years (2003–2013. The trends of advanced SOS and delayed EOS over the past three decades were slower than those over the initial two decades on a hemispheric scale. The change trends showed obvious variability with different vegetation types and were greater for woody plants than for herbaceous plants. For broad-leaved forest, the SOS was significantly advanced (2 ± 0.5 days·decade−1, p < 0.05 and the EOS was significantly delayed (2.7 ± 0.6 days·decade−1, p < 0.05 from 1982–2013. The trend of delayed EOS was greater than that of advanced SOS for different vegetation types. With respect to the spatial distribution of phenological

  5. Distributions of the C37:4 alkenone in the water column, surface sediments and sediment cores of the northern high latitude oceans: implications for palaeoceanography

    Science.gov (United States)

    Bendle, J. A.; Rosell-Melé, A.; Ziveri, P.

    2003-04-01

    Unlike the di- and tri-unsaturated C37 alkenones, C37:4 is rare outside of polar- sub polar waters and the temperature response is less certain. In the northern latitudes increasing values of %C37:4 are coincident with increasing scatter in the relationship of UK37' to SST, moreover, in some studies %C37:4 measurements have demonstrated a closer correlation with SSS than with SST (Rosell-Melé, 1998; Rosell-Melé et al., In press; Sicre et al., 2002). Therefore it has been suggested that %C37:4 may be used as a guide to the reliable limits of the UK37' index and moreover, that %C37:4 may have potential as a palaeo-salinity proxy. However, other studies have found no discernable relationship of %C37:4 to SST or SSS on a global scale (Sikes &Sicre, 2001). To investigate further the relationship between the C37:4 alkenone and sea surface variables we have conducted analysis of a large number of water and sediment samples from the Nordic and Barents seas. We report the highest values of %C37:4 yet measured in the open ocean (up to 72%). The data shows a strong trend towards higher values of %C37:4 at locations with a greater input of low salinity, cold polar water. This suggests that %C37:4 may have potential as palaeoceanographic indicator for the presence of polar water masses. The source of this polar water C37:4 is intriguing given that Emiliania huxleyi is rare in polar waters and the more common polar coccolithophore, Coccolithus pelagicus is not known to produce alkenones. Therefore, we also report data investigating the relationship of C37:4 to standing stocks of coccolithophores in sea surface filters. ROSELL-MELÉ, A. (1998) Interhemispheric appraisal of the value of alkenone indices as temperature and salinity proxies in high-latitude locations. Paleoceanography, 13(6), 694-703. ROSELL-MELÉ, A., JANSEN, E. &WEINELT, M. (In press) Appraisal of a molecular approach to infer variations in surface ocean freshwater inputs into the North Atlantic during the last

  6. Different responses of northern and southern high latitude ionospheric convection to IMF rotations: a case study based on SuperDARN observations

    Directory of Open Access Journals (Sweden)

    D. Ambrosino

    2009-06-01

    Full Text Available We use SuperDARN data to study high-latitude ionospheric convection over a three hour period (starting at 22:00 UT on 2 January 2003, during which the Interplanetary Magnetic Field (IMF flipped between two states, one with By>>|Bz| and one with Bz>0, both with negative Bx. We find, as expected from previous works, that day side ionospheric convection is controlled by the IMF in both hemispheres. For strongly northward IMF, we observed signatures of two reverse cells, both in the Northern Hemisphere (NH and in the Southern Hemisphere (SH, due to lobe reconnection. On one occasion, we also observed in the NH two viscous cells at the sides of the reverse cell pair. For duskward IMF, we observed in the NH a large dusk clockwise cell, accompanied by a smaller dawn cell, and the signature of a corresponding pattern in the SH. On two occasions, a three cell pattern, composed of a large clockwise cell and two viscous cells, was observed in the NH. As regards the timings of the NH and SH convection reconfigurations, we find that the convection reconfiguration from a positive Bz dominated to a positive By dominated pattern occurred almost simultaneously (i.e. within a few minutes in the two hemispheres. On the contrary, the reconfiguration from a By dominated to a northward IMF pattern started in the NH 8–13 min earlier than in the SH. We suggest that part of such a delay can be due to the following mechanism: as IMF Bx<0, the northward-tailward magnetosheath magnetic field reconnects with the magnetospheric field first tailward of the northern cusp and later on tailward of the southern cusp, due to the IMF draping around the magnetopause.

  7. Using dual temperature difference two source energy balance model and MODIS data to estimate surface energy fluxes at regional scales in northern latitudes

    Science.gov (United States)

    Guzinski, R.; Anderson, M.; Kustas, W.; Nieto, H.; Sandholt, I.

    2012-04-01

    A Two Source Energy Balance (TSEB) thermal-based modeling scheme has previously been used to successfully estimate surface latent and sensible heat fluxes at regional to continental scales with the help of satellite surface radiometric temperature observations. The Dual Temperature Difference (DTD) model introduced a simple methodology to address the sensitivity of the thermal-based energy balance models to the absolute measurement of land surface temperature (LST), which when derived with the help of satellites can have errors of several degrees. The original DTD model formulation required an early morning LST observation (1 hour after local sunrise) when fluxes were minimal followed by another LST observations later in the morning or afternoon and so was limited in use to data provided by geostationary satellites having high temporal resolution. This, however, made it unsuitable for areas at higher latitudes, such as northern Eurasia and northern North America. In this poster we present a number of modifications to the DTD model which allows it to exploit the day and night LST observations by the MODIS sensor aboard the Terra and Aqua polar orbiting satellites. Firstly, we look at whether taking the first LST observation around the time of Aqua's night overpass, when fluxes are small but not insignificant, would greatly affect the accuracy of the model. Secondly, we consider the issues directly related to using the MODIS sensor to measure the LST. This includes different view zenith angles of the day and night LST observations, the two observations possibly coming from the two different satellites and the accuracy of the instrument itself. We also evaluate two approaches for estimating αPT, the Priestley-Taylor parameter used in the TSEB modeling scheme to estimate heat fluxes of the vegetation canopy, to improve the performance of the model in coniferous and deciduous forests. The first approach estimates αPT based on tree height, while the second uses

  8. Climate change between the mid and late Holocene in northern high latitudes – Part 1: Survey of temperature and precipitation proxy data

    Directory of Open Access Journals (Sweden)

    J. Nilsson

    2010-09-01

    Full Text Available We undertake a study in two parts, where the overall aim is to quantitatively compare results from climate proxy data with results from several climate model simulations from the Paleoclimate Modelling Intercomparison Project for the mid-Holocene period and the pre-industrial, conditions for the pan-arctic region, north of 60° N. In this first paper, we survey the available published local temperature and precipitation proxy records. We also discuss and quantifiy some uncertainties in the estimated difference in climate between the two periods as recorded in the available data. The spatial distribution of available published local proxies has a marked geographical bias towards land areas surrounding the North Atlantic sector, especially Fennoscandia. The majority of the reconstructions are terrestrial, and there is a large over-representation towards summer temperature records. The available reconstructions indicate that the northern high latitudes were warmer in both summer, winter and the in annual mean temperature at the mid-Holocene (6000 BP ± 500 yrs compared to the pre-industrial period (1500 AD ± 500 yrs. For usage in the model-data comparisons (in Part 1, we estimate the calibration uncertainty and also the internal variability in the proxy records, to derive a combined minimum uncertainty in the reconstructed temperature change between the two periods. Often, the calibration uncertainty alone, at a certain site, exceeds the actual reconstructed climate change at the site level. In high-density regions, however, neighbouring records can be merged into a composite record to increase the signal-to-noise ratio. The challenge of producing reliable inferred climate reconstructions for the Holocene cannot be underestimated, considering the fact that the estimated temperature and precipitation fluctuations during this period are in magnitude similar to, or lower than, the uncertainties the reconstructions. We advocate a more widespread

  9. Application of Satellite Solar-Induced Chlorophyll Fluorescence to Understanding Large-Scale Variations in Vegetation Phenology and Function Over Northern High Latitude Forests

    Science.gov (United States)

    Jeong, Su-Jong; Schimel, David; Frankenberg, Christian; Drewry, Darren T.; Fisher, Joshua B.; Verma, Manish; Berry, Joseph A.; Lee, Jung-Eun; Joiner, Joanna

    2016-01-01

    This study evaluates the large-scale seasonal phenology and physiology of vegetation over northern high latitude forests (40 deg - 55 deg N) during spring and fall by using remote sensing of solar-induced chlorophyll fluorescence (SIF), normalized difference vegetation index (NDVI) and observation-based estimate of gross primary productivity (GPP) from 2009 to 2011. Based on GPP phenology estimation in GPP, the growing season determined by SIF time-series is shorter in length than the growing season length determined solely using NDVI. This is mainly due to the extended period of high NDVI values, as compared to SIF, by about 46 days (+/-11 days), indicating a large-scale seasonal decoupling of physiological activity and changes in greenness in the fall. In addition to phenological timing, mean seasonal NDVI and SIF have different responses to temperature changes throughout the growing season. We observed that both NDVI and SIF linearly increased with temperature increases throughout the spring. However, in the fall, although NDVI linearly responded to temperature increases, SIF and GPP did not linearly increase with temperature increases, implying a seasonal hysteresis of SIF and GPP in response to temperature changes across boreal ecosystems throughout their growing season. Seasonal hysteresis of vegetation at large-scales is consistent with the known phenomena that light limits boreal forest ecosystem productivity in the fall. Our results suggest that continuing measurements from satellite remote sensing of both SIF and NDVI can help to understand the differences between, and information carried by, seasonal variations vegetation structure and greenness and physiology at large-scales across the critical boreal regions.

  10. Ikimokyklinio ugdymo pedagogų pedagoginio pašaukimo analizė

    OpenAIRE

    Gaučienė, Jolanta

    2009-01-01

    Kauno miesto lopšelių - darželių ,,Girinukas“, ,,Rasytė“, ,,Vėrinėlis“, ,,Giliukas“ pedagogų bei Kauno kolegijos I ir II kurso ikimokyklinio ugdymo specialybės studentų pedagoginis pašaukimas. Literatūros šaltinių analizė; Trianguliacija (J. Hollando profesinės orientacijos tipo testas, anketinė apklausa, rašinio ,,Mano pedagoginė autobiografija (vizija)“ kontent analizė; Kiekybinė duomenų analizė, atlikta kompiuteriniu pagrindu, rezultatai apskaičiuoti statistinės analizės programa ...

  11. Precipitation Mediates the Response of Carbon Cycle to Rising Temperature in the Mid-to-High Latitudes of the Northern Hemisphere.

    Directory of Open Access Journals (Sweden)

    Xin Lin

    Full Text Available Over the past decades, rising air temperature has been accompanied by changes in precipitation. Despite relatively robust literature on the temperature sensitivity of carbon cycle at continental to global scales, less is known about the way this sensitivity is affected by precipitation. In this study we investigate how precipitation mediates the response of the carbon cycle to warming over the mid-to-high latitudes in the Northern Hemisphere (north of 30 °N. Based on atmospheric CO2 observations at Point Barrow (BRW in Alaska, satellite-derived NDVI (a proxy of vegetation productivity, and temperature and precipitation data, we analyzed the responses of carbon cycle to temperature change in wet and dry years (with precipitation above or below the multiyear average. The results suggest that, over the past three decades, the net seasonal atmospheric CO2 changes at BRW were significantly correlated with temperature in spring and autumn, yet only weakly correlated with temperature and precipitation during the growing season. We further found that responses of the net CO2 changes to warming in spring and autumn vary with precipitation levels, with the absolute temperature sensitivity in wet years roughly twice that in dry years. The analyses of NDVI and climate data also identify higher sensitivity of vegetation growth to warming in wet years for the growing season, spring and summer. The different temperature sensitivities in wet versus dry years probably result from differences in soil moisture and/or nutrient availability, which may enhance (inhibit the responsiveness of carbon assimilation and/or decomposition to warming under high (low precipitation levels. The precipitation-mediated response of the terrestrial carbon cycle to warming reported here emphasizes the important role of precipitation in assessing the temporal variations of carbon budgets in the past as well as in the future. More efforts are required to reduce uncertainty in future

  12. Precipitation Mediates the Response of Carbon Cycle to Rising Temperature in the Mid-to-High Latitudes of the Northern Hemisphere.

    Science.gov (United States)

    Lin, Xin; Li, Junsheng; Luo, Jianwu; Wu, Xiaopu; Tian, Yu; Wang, Wei

    2015-01-01

    Over the past decades, rising air temperature has been accompanied by changes in precipitation. Despite relatively robust literature on the temperature sensitivity of carbon cycle at continental to global scales, less is known about the way this sensitivity is affected by precipitation. In this study we investigate how precipitation mediates the response of the carbon cycle to warming over the mid-to-high latitudes in the Northern Hemisphere (north of 30 °N). Based on atmospheric CO2 observations at Point Barrow (BRW) in Alaska, satellite-derived NDVI (a proxy of vegetation productivity), and temperature and precipitation data, we analyzed the responses of carbon cycle to temperature change in wet and dry years (with precipitation above or below the multiyear average). The results suggest that, over the past three decades, the net seasonal atmospheric CO2 changes at BRW were significantly correlated with temperature in spring and autumn, yet only weakly correlated with temperature and precipitation during the growing season. We further found that responses of the net CO2 changes to warming in spring and autumn vary with precipitation levels, with the absolute temperature sensitivity in wet years roughly twice that in dry years. The analyses of NDVI and climate data also identify higher sensitivity of vegetation growth to warming in wet years for the growing season, spring and summer. The different temperature sensitivities in wet versus dry years probably result from differences in soil moisture and/or nutrient availability, which may enhance (inhibit) the responsiveness of carbon assimilation and/or decomposition to warming under high (low) precipitation levels. The precipitation-mediated response of the terrestrial carbon cycle to warming reported here emphasizes the important role of precipitation in assessing the temporal variations of carbon budgets in the past as well as in the future. More efforts are required to reduce uncertainty in future precipitation

  13. Effect of high latitude on tea quality of southern tea cultivated at northern area%南茶高纬度北引对茶叶品质的影响

    Institute of Scientific and Technical Information of China (English)

    汪曙晖; 汪东风; 李晓东; 彭正云; 姜星; 张续周

    2015-01-01

    目的:研究南茶高纬度北引后对茶类适制性及绿茶品质产生的影响。方法通过理化方法,分析同一品种茶树在高纬度北引后对其叶片厚度、鲜叶成分、不同茶类感官品质、绿茶成分及感官品质所产生的变化。结果随着纬度的增加,绿茶品质较好,而红茶品质较差;随着南茶高纬度北引,叶片厚度、氨基酸、水溶性糖、水浸出物和芳香物质(精油)总量等含量随纬度增大而增加;茶多酚含量则相反;对精油中各成分分析显示,北方茶烃类成分较多,醇类成分较少。结论本研究明确了南茶高纬度北引后茶叶品质特点及化学成分基础。%Objective To study the effect of high latitude on suitability for processing different teas and green tea quality of southern tea cultivated at northern area.Methods The tea fresh leaves from the tea plant, which was introduced from southern area and cultivated at high latitude of northern area, were made into black tea (full fermentation tea), oolong tea (semi-fermentation tea) and green tea (no fermentation tea). The main component content and quality of the tea fresh leaves and the teas were analyzed by the methods about physicochemical analysis. Results The sensory quality of green tea was the most one in the three teas with latitude increasing; the leaf thickness, amino acid, soluble sugar, water extract and total aromatic compounds (essential oils) content increased with latitude increasing, but tea polyphenol content showed the opposite. Analysis of each component of the essential oil showed that hydrocarbon constituents were much more and alcohol content was less in northern tea.Conclusion The above changes of tea functional components content are the basis of chemical composition of north tea quality characteristics from south tea cultivated at high north latitude.

  14. Towards understanding of the spatio-temporal composition of Terrestrial Water Storage variations in Northern Latitudes using a model-data fusion approach

    Science.gov (United States)

    Trautmann, Tina; Koirala, Sujan; Carvalhais, Nuno; Niemann, Christoph; Fink, Manfred; Jung, Martin

    2017-04-01

    Understanding variations in the terrestrial water storage (TWS) and its components is essential to gain insights into the dynamics of the hydrological cycle, and to assess temporal and spatial variations of water availability under global changes. We investigated spatio-temporal patterns of TWS variations and their composition in the humid regions of northern mid-to-high latitudes during 2001-2014 by using a simple hydrological model with few effective parameters. Compared to traditional modelling studies, our simple model was informed and constrained by multiple state-of-the-art earth observation products including TWS from Gravity Recovery and Climate Experiment (GRACE) satellites (Wiese 2015), Snow Water Equivalent (SWE) from GlobSnow project (Loujous et al. 2014), evapotranspiration fluxes from eddy covariance measurements (Tramontana et al. 2016), and gridded runoff estimates for Europe (Gudmundsson & Seneviratne 2016). Thorough evaluation of model demonstrates that the model reproduces the observed patterns of hydrological fluxes and states well. The validated model results are then used to assess the contributions of snow pack, soil moisture and groundwater on the integrated TWS across spatial (local grid scale, spatially integrated) and temporal (seasonal, inter-annual) scales. Interestingly, our results show that TWS variations on different scales are dominated by different components. On both, seasonal and inter-annual time scales, the spatially integrated TWS signal mainly originates from dynamics of snow pack. On the local grid scale, mean seasonal TWS variations are driven by snow dynamics as well, whereas inter-annual variations are found to originate from soil moisture availability. Thus, we show that the determinants of TWS variations are scale-dependent, while coincidently underline the potential of model-data fusion techniques to gain insights into the complex hydrological system. References: Gudmundsson, L. and S. I. Seneviratne (2016

  15. Extreme events in total ozone over the northern mid-latitudes: A case study based on long-term data sets from 5 ground-based stations

    Science.gov (United States)

    Rieder, Harald E.; Jancso, Leonhardt M.; Staehelin, Johannes; Maeder, Jörg A.; Ribatet, Mathieu; Peter, Thomas; Davison, Anthony C.

    2010-05-01

    In this study we analyze the frequency distribution of extreme events in low and high total ozone (termed ELOs and EHOs) for 5 long-term stations in the northern mid-latitudes in Europe (Belsk, Poland; Hradec Kralove, Czech Republic; Hohenpeissenberg and Potsdam, Germany; and Uccle, Belgium). Further, the influence of these extreme events on annual and seasonal mean values and trends is analysed. The applied method follows the new "ozone extreme concept", which is based on tools from extreme value theory [Coles, 2001; Ribatet, 2007], recently developed by Rieder et al. [2010a, b]. Mathematically seen the decisive feature within the extreme concept is the Generalized Pareto Distribution (GPD). In this analysis, the long-term trends needed to be removed first, differently to the treatment of Rieder et al. [2010a, b], in which the time series of Arosa was analysed, covering many decades of measurements in the anthropogenically undisturbed stratosphere. In contrast to previous studies only focusing on so called ozone mini-holes and mini-highs the "ozone extreme concept" provides a statistical description of the tails in total ozone distributions (i.e. extreme low and high values). It is shown that this concept is not only an appropriate method to describe the frequency and distribution of extreme events, it also provides new information on time series properties and internal variability. Furthermore it allows detection of fingerprints of physical (e.g. El Niño, NAO) and chemical (e.g. polar vortex ozone loss) features in the Earth's atmosphere as well as major volcanic eruptions (e.g. El Chichón, Mt. Pinatubo). It is shown that mean values and trends in total ozone are strongly influenced by extreme events. Trend calculations (for the period 1970-1990) are performed for the entire as well as the extremes-removed time series. The results after excluding extremes show that annual trends are most reduced at Hradec Kralove (about a factor of 3), followed by Potsdam

  16. The evol ution of coupling of Asian winter monsoon and high latitude climate of Northern Hemisphere——Grain evidence from 8.1 Ma loess-red clay sequence on the Chinese central Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    吕连清; 方小敏; JosephA.Mason; 李吉均; 安芷生

    2001-01-01

    The evolution and driving mechanism of the Asian winter monsoon system are of great importance to understanding the present-day climate. Through high-resolution particle size analysis of the oldest loess-red clay sequence known so far (with a basal age of about 8 Ma) and comparison of the results with oxygen isotope curves from North Atlantic marine sediments, 4 stages of the evolution of the Asian winter monsoon were clearly demonstrated. During the first stage, between about 8.1 and 4.3 Ma, there was no relation between Asian winter monsoon and Northern Hemisphere ice volume and high latitude climate inferred from marine sediments. A weak relation developed during the second stage, about 4.3 to 3.5 Ma. During the third stage (3.5 to 2.6 Ma) an Asian winter monsoon system similar to the present formed, initiating a stronger relation between the winter monsoon and Northern Hemisphere ice volume and high latitude climate. In the final stage (2.6 to 0 Ma) the present Asian winter monsoon system was fortifi

  17. In situ northern mid-latitude observations of ClO, O3, and BrO in the wintertime lower stratosphere

    Science.gov (United States)

    Brune, W. H.; Toohey, D. W.; Anderson, J. G.; Starr, W. L.; Vedder, J. F.; Danielsen, E. F.

    1988-01-01

    In order to test photochemical theories linking chlorofluorocarbon derivatives to O3 depletion at high latitudes in the springtime, several related atmospheric species, including O3, ClO, and BrO were measured in the lower stratosphere. The flight path extended to the center of the polar jet associated with but outside of the Arctic vortex, in which the abundance of O3 was twice its midlatitude value, whereas BrO levels were five parts per trillion (pptv) by volume between 18 and 21 km, and 2.4 pptv below that altitude. The ClO mixing ratio was as much as 65 pptv at 60 N latitude at an altitude of 20 km, and was enhanced over midlatitude values by a factor of three to five at altitudes above 18 km and by as much as a factor of 40 at altitudes below 17 km. Levels of ClO and O3 were highly correlated on all measured distance scales, and both showed an abrupt change in character at 54 N latitude. The ClO abundance north of 54 N was probably caused by low NO2 levels in the flight path.

  18. Lower Prevalence of Celiac Disease and Gluten-Related Disorders in Persons Living in Southern vs Northern Latitudes of the United States.

    Science.gov (United States)

    Unalp-Arida, Aynur; Ruhl, Constance E; Choung, Rok Seon; Brantner, Tricia L; Murray, Joseph A

    2017-06-01

    The association between prevalence of celiac disease and geographic region is incompletely understood, but the occurrence of several autoimmune disorders has been found to vary along a North-South gradient. We examined geographic, demographic, and clinical factors associated with prevalence of celiac disease and gluten-free diet in the United States. In a population-based study, we analyzed data on gluten-related conditions from the National Health and Nutrition Examination Survey, from 2009 through 2014, on 22,277 participants 6 years and older. We identified persons with celiac disease based on results of serum tests for IgA against tissue transglutaminase and endomysium or on both a health care provider diagnosis and adherence to a gluten-free diet. Gluten avoidance without celiac disease was defined as adherence to a gluten-free diet without a diagnosis of celiac disease. We compared mean serum levels of biochemical and nutritional markers based on status of gluten-related conditions. We found 0.7% of participants to have celiac disease and 1.1% of participants to avoid gluten without celiac disease. Celiac disease was more common among individuals who lived at latitudes of 35°-39° North (odds ratio, 3.2; 95% confidence interval, 1.4-7.1) or at latitudes of 40° North or more (odds ratio, 5.4; 95% CI, 2.6-11.3) than individuals who lived at latitudes below 35° North, independent of race or ethnicity, socioeconomic status, and body mass index. Gluten avoidance without celiac disease was more common among individuals who lived at latitudes of 40° North or more, independent of demographic factors and body mass index. Participants with undiagnosed celiac disease (identified by positive results from serologic tests) had lower mean levels of vitamin B-12 and folate (data collected from 2009 through 2012) than persons without celiac disease. Participants with a health care provider diagnosis of celiac disease had a lower mean level of hemoglobin than persons

  19. Relationship of peroxyacetyl nitrate to active and total odd nitrogen at northern high latitudes - Influence of reservoir species on NO(x) and O3

    Science.gov (United States)

    Singh, H. B.; Herlth, D.; O'Hara, D.; Zahnle, K.; Bradshaw, J. D.; Sandholm, S. T.; Talbot, R.; Crutzen, P. J.; Kanakidou, M. A.

    1992-01-01

    The partitioning of relative nitrogen in the Arctic and the sub-Arctic troposphere based on measurements conducted during the 1988 Arctic Boundary Layer Expedition (ABLE 3A) is described. The first set of comprehensive odd nitrogen and O3 measurements from the Arctic/sub-Arctic free troposphere shows that a highly aged air mass that has persisted under very cold conditions is present. A large fraction of the odd nitrogen appears to be present in the form of reservoir species such as PAN. Significant quantities of as yet unknown reactive nitrogen species, such as complex alkyl nitrates and pernitrates, are expected to be present. Together with PAN, these nitrate and pernitrate reservoir species could control the entire NO(x) availability of the high-latitude troposphere and in turn influence the O3 photochemistry of the region. The role of PAN in influencing the O3 reservoir is shown to be important and may be responsible for the increasing O3 temporal trend observed at high latitudes.

  20. A comparative analysis of changes in the phasing of temperature and satellite-derived greenness at northern latitudes%北纬地区温度和卫星监测的植被活动节律变化的比较分析

    Institute of Scientific and Technical Information of China (English)

    MA Ting; ZHOU Chenghu; PEI Tao; XIE Yichun

    2013-01-01

    @@%Plant growth at northern latitudes is highly responsive to the climatic changes that have occurred over recent decades.However,the sensitivity of the phasing of the seasonal cycle of terrestrial ecosystems to a changing environment remains less widely understood.We present an investigation and comparative study of large-scale changes in seasonal cycling of both land surface temperature and plant growth.Our results have shown trends indicating a marked increased towards overall plant productivity by ~3% from 1982 to 2005,reduced trends in seasonal variation at low-mid latitudes by ~2%,increased trends in seasonal variations at mid-high latitudes by ~7%,and an earlier phase in northern terrestrial ecosystems (-1.1 days) in parallel with changes in the phasing of surface temperatures at northern latitudes over the 24 years in this study.These shifts in annual cycles of terrestrial vegetation appear to have a distinct geographical zonality and are dependent upon latitudinal changes in climatic variables.More conspicuous changes in overall vegetation productivity and the seasonal phase of ecosystems have been observed in Eurasia compared to North America,largely because of a more rapid rise in temperature.Our results state that changing climate boosts plant growth at northern latitudes,but also alters the phase and seasonal variations of the annual cycle of terrestrial ecosystems.

  1. Impacts of future climate change on the carbon budget of northern high-latitude terrestrial ecosystems: An analysis using ISI-MIP data

    Science.gov (United States)

    Ito, Akihiko; Nishina, Kazuya; Noda, Hibiki M.

    2016-09-01

    This paper assesses future changes in the carbon budgets of northern terrestrial ecosystems (above 60°N) using data from the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP). By analyzing simulations from seven biome models driven by five climate scenarios under two representative concentration pathways (RCP2.6 and RCP8.5), the range of responses and their uncertainty in the 21st century was evaluated. The biome models consistently simulated a gradual increase in vegetation productivity driven by an elevated atmospheric CO2 concentration and a longer growing period. By the 2090s, most simulations showed average net carbon uptake into the northern terrestrial ecosystems of +27 Pg C for RCP2.6 and +48 Pg C for RCP8.5. These estimates showed a wide range of variability among simulations, especially for soil carbon stocks. Even under low greenhouse gas concentrations (RCP2.6), most simulations indicated that vegetation productivity and biomass would change by more than 10%, implying that it will be difficult to completely prevent climatic impacts in northern regions. Simulated spatial patterns and seasonality in the carbon budget can be used to identify sensitive areas and seasons, allowing for improved monitoring. Further research combining observations and modeling will be required to reduce estimation uncertainty and devise ecosystem management options.

  2. Northern Latitude but Not Season Is Associated with Increased Rates of Hospitalizations Related to Inflammatory Bowel Disease: Results of a Multi-Year Analysis of a National Cohort

    Science.gov (United States)

    Stein, Adam C.; Gaetano, John Nick; Jacobs, Jeffrey; Kunnavakkam, Rangesh; Bissonnette, Marc; Pekow, Joel

    2016-01-01

    Background and Aims There is growing evidence that the incidence and severity of inflammatory bowel disease (IBD) may be geographically and seasonally related. Why these associations are observed remains unclear. We assessed the impact of geographic location, season, and exposure to ultraviolet light on disease severity by measuring national hospital IBD-related discharge rates. Methods Utilizing the Nationwide Inpatient Sample (NIS), we identified all patients with IBD-related discharges from 2001–2007. Patients were included if they were discharged from states above the 40th parallel (north) or at or below the 35th parallel (south); and their discharge fell within the winter (January, February, and March) or summer (July, August, and September). Groups of patients were assessed comparing north to south within each season, and summer to winter within each region. UV index was recorded from the National Weather Service data and compared to monthly discharge rates. Results There was a consistent pattern of increased IBD-related hospitalization rates in northern states compared to southern states for both ulcerative colitis and Crohn’s disease. Differences in IBD-related hospitalization rates by season, however, were not uniform across the years studied. UV index was significantly inversely associated although not proportional to discharge rates for both Crohn’s disease and ulcerative colitis. Conclusions In the US, there is a significant increased rate of IBD-related hospitalizations in the northern compared to southern states, which not fully explained by differences in UV exposure. PMID:27579718

  3. A cold-wet middle-latitude environment on Mars during the Hesperian-Amazonian transition: Evidence from northern Arabia valleys and paleolakes

    Science.gov (United States)

    Wilson, Sharon A.; Howard, Alan D.; Moore, Jeffrey M.; Grant, John A.

    2016-09-01

    The growing inventory of post-Noachian fluvial valleys may represent a late, widespread episode of aqueous activity on Mars, contrary to the paradigm that fluvial activity largely ceased around the Noachian-Hesperian boundary. Fresh shallow valleys (FSVs) are widespread from ~30 to 45° in both hemispheres with a high concentration in northern Arabia Terra. Valleys in northern Arabia Terra characteristically start abruptly on steeper slopes and terminate in topographic depressions at elevations corresponding to model-predicted lake levels. Longer valley systems flowed into and out of chains of paleolakes. Minimum discharges based on the dimensions of the incised channel assuming medium to coarse sand-size grains ranges from tens to hundreds of m3 s-1, respectively, consistent with formation via snowmelt from surface or sub-ice flows. Hydrologic calculations indicate the valleys likely formed in hundreds of years or less, and crater statistics constrain the timing of fluvial activity to between the Hesperian and middle Amazonian. Several craters with channels extending radially outward supports evidence for overflow of interior crater lakes possibly fed by groundwater. Most FSVs occur away from young impact craters which make an association with impact processes improbable. The widespread occurrence of FSVs along with their similar morphology and shared modest state of degradation is consistent with most forming during a global interval of favorable climate, perhaps contemporaneous with alluvial fan formation in equatorial and midlatitudes. Evidence for a snowmelt-based hydrology and considerable depths of water on the landscape in Arabia supports a cold, wet, and possibly habitable environment late in Martian history.

  4. Metabolic balance of a plankton community in a pelagic water of a northern high latitude fjord in response to increased pCO2

    Directory of Open Access Journals (Sweden)

    J.-P. Gattuso

    2012-08-01

    Full Text Available The effect of ocean acidification on the balance between gross community production (GCP and community respiration (CR (i.e. net community production, NCP of plankton communities was investigated in summer 2010 in Kongsfjorden, West of Svalbard. Surface water, which was characterized by low concentrations of dissolved inorganic nutrients and chlorophyll, was enclosed in 9 mesocosms and subjected to 8 pCO2 levels (2 replicated controls and 7 enhanced pCO2 treatments for one month. Nutrients were added to all mesocosms on day 13 of the experiment, and thereafter increase of chlorophyll (index of phytoplankton biomass was provoked in all mesocosms. No clear trend in response to increasing pCO2 was found in the daily values of NCP, CR, and GCP. For further analysis, these parameters were cumulated for the following three periods: phase 1: end of CO2 manipulation until nutrient addition (t4 to t13; phase 2: nutrient addition until the second chlorophyll minimum (t14 to t21; phase 3: the second chlorophyll minimum until the end of this study (t22 to t28. Significant response was detected as a decrease of NCP with increasing pCO2 during phase 3. CR was relatively stable throughout the experiment in all mesocosms. As a result, the cumulative GCP significantly decreased with increasing pCO2 during phase 3. After the nutrient addition, the ratios of cumulative NCP to cumulative consumption of NO3 and PO4 showed significant decrease during phase 3 with increasing pCO2. The results suggest that elevated pCO2 influenced cumulative NCP and stoichiometric C and nutrient coupling of the plankton community in a high latitude fjord only for a limited period. However provided that there were some differences or weak correlations between NCP data based on different methods in the same experiment, this conclusion should be taken with caution.

  5. On the stratospheric aerosol budget at Northern mid-latitudes from 21 years of ground-based lidar and satellite observations

    Science.gov (United States)

    Khaykin, Sergey; Godin-Beekmann, Sophie; Hauchecorne, Alain; Vernier, Jean-Paul; Jumelet, Julien; Keckhut, Philippe

    2016-04-01

    The paper presents a new high-quality 21-year series of continuous stratospheric aerosol observations at Observatoire de Haute-Provence (OHP, 44° N, 6° E) in Southern France using two powerful and well-maintained lidar systems. In contrast to previous studies making use of the observations by aerosol-dedicated lidars operating within the Network for Detection of Atmospheric Composition Change (NDACC), we exploit the backscatter measurements from the off-line 355 nm channel of stratospheric ozone lidar (LiO3S) and low-gain 532 nm channel of stratospheric temperature lidar (LTA). The presented series of stratospheric aerosol backscatter and extinction at 532 nm, spanning from January 1994 through 2016, include on average 10-11 lidar acquisitions per month after careful quality screening. The OHP lidar observations are compared with global space-borne measurements of zonal-mean stratospheric extinction by SAGE II, GOMOS, OSIRIS and CALIOP instruments, altogether covering the time span of OHP lidar data sets. Both ground-based and satellite monthly-mean stratospheric Aerosol Optical Depth between 17 and 30 km altitude (sAOD1730km) series are in good cross-agreement with discrepancies well below the measurement errors, thereby ensuring the quality and coherency of all data sets exploited for our study. The global satellite observations are then used to identify the drivers of stratospheric aerosol variability observed locally by the OHP lidars. The 21-year aerosol series reflect two essential periods in the global volcanic activity over the past two decades. The first one, a long volcanically-quiescent period of low aerosol burden (0.002Vernier et al. (2011), takes place mainly during the southern tropics convective season, which together with the timescale of poleward transport is compatible with the observed seasonality of aerosol in the mid-latitude stratosphere.

  6. Long term low latitude and high elevation cosmogenic 3He production rate inferred from a 107 ka-old lava flow in northern Chile; 22°S-3400 m a.s.l.

    Science.gov (United States)

    Delunel, Romain; Blard, Pierre-Henri; Martin, Léo C. P.; Nomade, Sébastien; Schlunegger, Fritz

    2016-07-01

    Available geological calibration sites used to estimate the rate at which cosmogenic 3He is produced at the Earth's surface are mostly clustered in medium to high latitudes. Moreover, most of them have exposure histories shorter than tens of thousands of years. This lack of sites prevents a qualitative assessment of available production models used to convert cosmogenic 3He concentrations into exposure ages and/or denudation rates. It thus limits our ability to take into account the atmospheric, geomagnetic and solar modulation conditions that might have affected the production of cosmogenic nuclides in the past for longer exposure histories and in low latitude regions. We present the cosmogenic 3He production rate inferred from a new geological calibration site located in northern Chile. Five samples were collected on the surface of the largest and best-preserved lava flow of the San Pedro volcano (21.934°S-68.510°W-3390 m a.s.l.), which displays pristine crease-structure features. 40Ar/39Ar dating yields a reliable plateau age of 107 ± 12 ka for the eruption of this lava flow. Eight pyroxene aliquots separated from the surface samples yield a weighted average cosmogenic 3He concentration of 99.3 ± 1.2 Mat g-1 from which a local cosmogenic 3He production rate of 928 ± 101 at g-1 yr-1 is calculated. The local production rate is then scaled to a sea level high latitude (SLHL) reference position using different combinations of geographic spatialization schemes, atmosphere models and geomagnetic field reconstructions, yielding SLHL production rates between 103 ± 11 and 130 ± 14 at g-1 yr-1 consistent with the most recent estimates available from the literature. Finally, we use the same scaling frameworks to re-evaluate the mean global-scale cosmogenic 3He production rate in olivine and pyroxene minerals at 120 ± 16 at g-1 yr-1 from the compilation of previously published calibration datasets.

  7. Vitamin D status and its determinants during autumn in children at northern latitudes: a cross-sectional analysis from the optimal well-being, development and health for Danish children through a healthy New Nordic Diet (OPUS) School Meal Study.

    Science.gov (United States)

    Petersen, Rikke A; Damsgaard, Camilla T; Dalskov, Stine-Mathilde; Sørensen, Louise B; Hjorth, Mads F; Ritz, Christian; Kjølbæk, Louise; Andersen, Rikke; Tetens, Inge; Krarup, Henrik; Astrup, Arne; Michaelsen, Kim F; Mølgaard, Christian

    2016-01-28

    Sufficient summer/autumn vitamin D status appears important to mitigate winter nadirs at northern latitudes. We conducted a cross-sectional study to evaluate autumn vitamin D status and its determinants in 782 Danish 8-11-year-old children (55°N) using baseline data from the Optimal well-being, development and health for Danish children through a healthy New Nordic Diet (OPUS) School Meal Study, a large randomised controlled trial. Blood samples and demographic and behavioural data, including 7-d dietary recordings, objectively measured physical activity, and time spent outdoors during school hours, were collected during September-November. Mean serum 25-hydroxyvitamin D (25(OH)D) was 60·8 (sd 18·7) nmol/l. Serum 25(OH)D levels ≤50 nmol/l were found in 28·4 % of the children and 2·4 % had concentrations <25 nmol/l. Upon multivariate adjustment, increasing age (per year) (β -2·9; 95 % CI -5·1, -0·7 nmol/l), female sex (β -3·3; 95 % CI -5·9, -0·7 nmol/l), sampling in October (β -5·2; 95 % CI -10·1, -0·4 nmol/l) and November (β -13·3; 95 % CI -17·7, -9·1), and non-white ethnicity (β -5·7; 95 % CI -11·1, -0·3 nmol/l) were negatively associated with 25(OH)D (all P<0·05). Likewise, immigrant/descendant background was negatively associated with 25(OH)D, particularly in females (β -16·3; 95 % CI -21·9, -10·7) (P<0·001) (P interaction=0·003). Moderate-to-vigorous physical activity (MVPA) (min/d) (β 0·06; 95 % CI 0·01, 0·12), outdoor walking during school hours (min/week) (β 0·4; 95 % CI 0·1, 0·6) and intake of vitamin D-containing supplements ≥3 d/week (β 8·7; 95 % CI 6·4, 11·0) were positively associated with 25(OH)D (all P<0·05). The high proportion of children with vitamin D status below the recommended sufficiency level of 50 nmol/l raises concern as levels expectedly drop further during winter months. Frequent intake of vitamin D supplements was strongly associated with status. MVPA and outdoor activity during school

  8. An analysis of fast photochemistry over high northern latitudes during spring and summer using in-situ observations from ARCTAS and TOPSE

    Directory of Open Access Journals (Sweden)

    J. R. Olson

    2012-04-01

    Full Text Available Observations of chemical constituents and meteorological quantities obtained during the two Arctic phases of the airborne campaign ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites are analyzed using an observationally constrained steady state box model. Measurements of OH and HO2 from the Penn State ATHOS instrument are compared to model predictions. Forty percent of OH measurements below 2 km are at the limit of detection during the spring phase (ARCTAS-A. While the median observed-to-calculated ratio is near one, both the scatter of observations and the model uncertainty for OH are at the magnitude of ambient values. During the summer phase (ARCTAS-B, model predictions of OH are biased low relative to observations and demonstrate a high sensitivity to the level of uncertainty in NO observations. Predictions of HO2 using observed CH2O and H2O2 as model constraints are up to a factor of two larger than observed. A temperature-dependent terminal loss rate of HO2 to aerosol recently proposed in the literature is shown to be insufficient to reconcile these differences. A comparison of ARCTAS-A to the high latitude springtime portion of the 2000 TOPSE campaign (Tropospheric Ozone Production about the Spring Equinox shows similar meteorological and chemical environments with the exception of peroxides; observations of H2O2 during ARCTAS-A were 2.5 to 3 times larger than those during TOPSE. The cause of this difference in peroxides remains unresolved and has important implications for the Arctic HOx budget. Unconstrained model predictions for both phases indicate photochemistry alone is unable to simultaneously sustain observed levels of CH2O and H2O2; however when the model is constrained with observed CH2O, H2O2 predictions from a range of

  9. An analysis of fast photochemistry over high northern latitudes during spring and summer using in-situ observations from ARCTAS and TOPSE

    Directory of Open Access Journals (Sweden)

    J. R. Olson

    2012-08-01

    Full Text Available Observations of chemical constituents and meteorological quantities obtained during the two Arctic phases of the airborne campaign ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites are analyzed using an observationally constrained steady state box model. Measurements of OH and HO2 from the Penn State ATHOS instrument are compared to model predictions. Forty percent of OH measurements below 2 km are at the limit of detection during the spring phase (ARCTAS-A. While the median observed-to-calculated ratio is near one, both the scatter of observations and the model uncertainty for OH are at the magnitude of ambient values. During the summer phase (ARCTAS-B, model predictions of OH are biased low relative to observations and demonstrate a high sensitivity to the level of uncertainty in NO observations. Predictions of HO2 using observed CH2O and H2O2 as model constraints are up to a factor of two larger than observed. A temperature-dependent terminal loss rate of HO2 to aerosol recently proposed in the literature is shown to be insufficient to reconcile these differences. A comparison of ARCTAS-A to the high latitude springtime portion of the 2000 TOPSE campaign (Tropospheric Ozone Production about the Spring Equinox shows similar meteorological and chemical environments with the exception of peroxides; observations of H2O2 during ARCTAS-A were 2.5 to 3 times larger than those during TOPSE. The cause of this difference in peroxides remains unresolved and has important implications for the Arctic HOx budget. Unconstrained model predictions for both phases indicate photochemistry alone is unable to simultaneously sustain observed levels of CH2O and H2O2; however when the model is constrained with observed CH2O, H2O2 predictions from a range of

  10. Observations on nivation and its geomorphological effects in mountains at high latitude (with Mt. Njulla Massif in Northern Sweden as example

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    Raczkowska, Zofia

    1990-12-01

    Full Text Available This paper presents the geomorphological role of snow patches In the remodeling of mountain slopes in the periglacial zone based on the results of morphological mapping of Mt. Njulla region, Northern Sweden. Effectiveness of nivation is strongly controlled by geological structure. On the Eastern slope, at the foot of the hillside, nivation processes play a critical role in the creation of numerous transverse nival hollows and cryoplanation terraces. On the western slope, meltwater, originating from snow patches, facilitates weathering and transportation of wastes downslope. Vegetation of the studied region is influenced by nivation. Effects of nivation are limited to reshaping of the relief.

    [es] Este trabajo presenta el papel de las manchas de nieve en la evolución de laderas de montaña de la zona periglaciar, apoyándose en los resultados de cartografía geomorfológica de la región de Mt. Njulla, Norte de Suecia. La eficacia de la nivación está fuertemente controlada por la estructura geológica. En la vertiente oriental, al pie de la ladera, los procesos de nivación juegan un papel crítico en la creación de nichos nivales transversales y de terrazas de crioplanación. En la vertiente occidental, el agua de fusión, que surge de las manchas de nieve, facilita la meteorización y el transporte de materiales ladera abajo. La vegetación de la región estudiada también se halla Influida por la vegetación. Sin embargo, los efectos de la nivación se limitan a retoques en el relieve.
    [fr] Dans cette étude on a discuté le rôle géomorphologique des taches de neige dans la transformation du relief dans la zone périglaciére, à la base de l'analyse de la carte morphologique de la région de Njulla, au nord de la Suède. On a constaté un rapport évident entre les effets des processus de nivation et la structure géologique. Sur le versant est formé sur le front de l'escarpement structural, les processus de nivation

  11. Functional Analysis in Public Sector Funkcinė analizė viešajame sektoriuje

    Directory of Open Access Journals (Sweden)

    Živilė Tunčikienė

    2011-02-01

    š privataus sektoriaus „pasiskolintų“ ir viešajam sektoriui pritaikytų efektyvaus valdymo priemonių yra strateginis planavimas. Rengiant viešojo sektoriaus institucijų strateginius veiklos planus ir jų įgyvendinimo priemones, būtina vadovautis valstybės plėtros prioriteto, rinkos kaip institucijų veiklos reguliatoriaus pagrįstumo ir kitais principais. Siekiant įgyvendinti tokius principus, tikslinga taikyti funkcinės analizės metodą. Tyrimo tikslas – atskleisti funkcinės analizės esmę viešajame sektoriuje. Tokio tikslo pasirinkimą lėmė aktuali viešojo sektoriaus veiklos neefektyvumo problema. Tikslui pasiekti straipsnyje nagrinėjami įvairių mokslininkų bei praktikų pateikti funkcinės analizės tikslai ir uždaviniai, funkcinės analizės technologija, siūloma taikyti viešajam sektoriui. Naudojamas kokybinis tyrimo metodas – mokslinės literatūros analizė, vertinimas ir apibendrinimas.

    Raktiniai žodžiai: viešasis sektorius, viešojo administravimo reforma, viešosios institucijos, funkcinė analizė, efektyvumas.

  12. Ulysses breaks latitude record

    Science.gov (United States)

    1993-06-01

    time of closest approach, and the unexpectedly strong influence of the solar wind deep in the magnetosphere during the outbound passage. With the Jupiter fly-by safely accomplished, the scientific focus is now directed towards phenomena related to the increasing latitute of the spacecraft. Already, there is strong evidence that Ulysses is now in the domain of the southern polar magnetic field. By a fortunate coincidence, just as Ulysses was reaching 32 degrees South, the magnetic field and plasma analyser scientific teams were seeing the first evidence of the effect of increasing latitude on the magnetised solar wind. The two complementary sets of observations reveal the passage of Ulysses into a magnetic unipolar regime corresponding to latitudes above the sunspot belt, having permanently crossed the boundary separating northern and southern magnetic fields. Following the flight over the Sun's southern pole, Ulysses' orbit will bring the spaceprobe swinging back towards the equatorial regions, heading for its second high-latitude excursion in mid-1995, this time above the North polar regions. "By the end of September 1995, Ulysses will have put our knowledge of the Sun and its environment in a completely new perspective", says Dr. Marsden, ESA's Project Scientist for Ulysses. "Only by studying the way the Sun influences the space around it in a global manner can we hope to understand its influence on our local interplanetary environment". An example of this "local" influence is the disturbance experienced by technical systems in Earth orbit and on the ground (e.g., telecommunications systems) at the time of major solar flares. Note to the Editors: Near the Sun's equatorial regions, the interplanetary magnetic field alternately points toward and away from the Sun during a single solar rotation which gives rise to so-called magnetic sectors. The existence of these sectors is interpreted as the effect of a vast current sheet, tilted with respect to the Sun's rotation

  13. Geographic latitude and prevalence of adolescent idiopathic scoliosis.

    Science.gov (United States)

    Grivas, Theodoros B; Vasiliadis, Elias; Savvidou, Olga; Mouzakis, Vasilios; Koufopoulos, Georgios

    2006-01-01

    Adolescent Idiopathic Scoliosis (AIS) prevalence has been reported to be different in various geographic latitudes and demonstrates higher values in northern countries. A study on epidemiological reports from the literature was conducted to record the prevalence of AIS among the general population of boys and girls, aged 10-16 years old, in different geographic latitudes, in order to test the hypothesis that the prevalence of AIS among boys and girls is different in various geographic latitudes and to examine if there is a possible association between them. Seventeen peer-reviewed published papers reporting AIS prevalence in the general population of boys and girls from most geographic areas of the northern hemisphere were retrieved from the literature. The geographic latitude of each centre where a particular study was originated was documented. The statistical analysis included a linear regression forward modeling procedure of the AIS prevalence by latitude, weighted by sample size. According to the modelling of the data, a significant positive association between prevalence of AIS and latitude was found for girls (p<0.001), following a rather curvilinear trend, but not a significant positive association was found for boys (p<0.111). A positive association between prevalence of AIS and geographic latitude is reported only for girls in the present study. Prevalence of AIS in boys is not associated significantly with geographic latitude. This differing significant association implicates the possible role of environmental factors in the pathogenesis of AIS that may act in a different way between boys and girls.

  14. ÖĞRETMEN ADAYLARININ TARIHI GÖRSELLERI ANALIZ DÜZEYLERİ / TEACHER CANDIDATES’ ANALYSIS LEVELS of HISTORICAL IMAGES

    Directory of Open Access Journals (Sweden)

    Turan, I.

    2015-10-01

    Full Text Available Görsel kaynaklar tarih araştırmalarında ve öğretiminde büyük bir öneme sahiptir. Tarih eğitiminde görsel kaynaklar doğası gereği soyut olan tarihi bilgiyi somutlaştırarak onu yeni kuşaklar için daha anlaşılır bir hale getirmekte aynı zamanda öğrencilerin yaratıcı düşünce ve hayal gücünün gelişmesinde yardımcı olmaktadır (Smirnova ve Romanov, 2007: 1. Öğrencilerin görsel analiz becerilerini geliştirmek sadece tarih derslerindeki kavrama ve başarı düzeyleri açısından değil aynı zamanda yaşam boyu öğrenme becerilerinin gelişimi açısından da önemlidir. Çünkü bu alanda iyi olan bir kişi, çevresinde gördüğü eylemlerin, objelerin ve sembollerin farklılığını anlayabilmekte ve onları daha doğru yorumlayabilmektedir (Alpan, 2008: 76-77. Öğrencilerin görsel analiz becerilerinin gelişiminde en önemli unsur tabi öğretmenlerdir. Görsellerin öğretmenler tarafından tarih derslerinde doğru kullanımı öğrencilerin görsel analiz ve görsel okuryazarlık becerilerini olumlu yönde etkileyecektir. Bu araştırmanın amacı tarih ve sosyal bilgiler öğretmen adaylarının görsel analiz düzeylerini tespit etmektir. Çalışmada nitel durum araştırması yöntemi ve iç içe geçmiş tek durum deseni kullanılmıştır. Çalışma grubuna Atatürk Üniversitesi Kazım Karabekir Eğitim Fakültesi Tarih Eğitimi ve Sosyal Bilgiler Eğitimi son sınıf öğrencileri dâhil edilmiştir. Veri toplama aracı olarak araştırmacılar tarafından hazırlanmış “Görsel Analiz Düzeyi” çalışma kâğıdı kullanılmıştır. Araştırma sonucunda öğretmen adaylarının büyük çoğunluğunun tarihsel görselleri analiz ederken tanımlama düzeyindeki görevlerde dahi zorlandıkları, görseller hakkında derinlemesine ve detaylı analizler yapamadıkları, genellikle kısa ifadeler ve açıklamalar kullandıkları, akademik bir tavır sergileyemeyerek kaynağa duygusal bir bak

  15. Warming: mechanism and latitude dependence

    Science.gov (United States)

    Barkin, Yury

    2010-05-01

    flows distribution with respect the Earth's hemispheres in first caused by eccentric position of the Earth core with respect to the mantle (displaced in present geological epoch in direction to Brasil). Of course the asymmetric distribution of heat loss is a long-term phenomenon in the geological history. But in present epoch due to drift of the core to the North we must observe some increasing of the heat flow of the Northern hemisphere and decreasing of the heat flow of the Southern hemisphere. In reality mentioned changes of heat flows are contrast (asymmetrical) and can have general tendency of increasing heat flows in both hemispheres (due to activization of relative oscillations of the core and mantle relatively polar axis). Contrast secular warming of Northern and Southern hemispheres of the Earth in present epoch. Dependence of warming from latitude. And warm flows are asymmetrically, more intensively warm is redistributed in northern hemisphere of the Earth and less intensively in a southern hemisphere. From here it follows, that the phenomenon of more intensive warming up of northern hemisphere, rather than southern in present period should be observed. Data of climatic observations (in first temperature trends for various latitude belts). More detailed analysis shows, that the phenomenon of warming in different form is shown in various latitudinal belts of the Earth. This phenomenon is more clearly shown in latitudinal belts further situated on latitude from South Pole, i.e. in high northern latitudes. Really, the trend of increase of temperature in northern hemisphere is characterized by greater rate, than a trend of temperature in a southern hemisphere. And not only trend components of temperatures increase with increasing of latitudes from southern pole to northern pole, but also amplitudes of decade fluctuations of temperature in high northern breadthes are more bigger than in southern hemisphere. Thus again it is necessary to expect a contrast and

  16. [Molecular-genetic characterization of the Okhotskiy virus (OKHV) and Aniva virus (ANIV) (Orbivirus, Reoviridae) isolated from the ticks Ixodes (Ceratixodes) uriae White, 1852 in high latitudes of the Northern Eurasia].

    Science.gov (United States)

    L'vov, D K; Al'khovskiĭ, S V; Shchelkanov, M Iu; Shchetinin, A M; Deriabin, P G; Gitel'man, A K; Samokhvalov, E I; Botikov, A G

    2014-01-01

    Molecular-genetic characteristics of the Okhotskiy virus (OKHV) and Aniva virus (ANIV) were studied (ID GenBank KF981623-32). These viruses are distributed over the shelf and Island areas in the high latitudes in the Okhotsk, Bering, and Barents seas and linked with nesting colonies of Alcidae seabirds and their obligatory parasites, the Ixodes uriae (Ixodidae) ticks. OKHV and ANIV are observed to be independent species within the limits of the Great Island virus (GIV) group of the Orbivirus genus of the Reoviridae family. The majority of the genes of OKHV and ANIV have high homology (VP1 - 96%, T2 - 99%, VP7 (T13) - 98%, NS1 - 94%, NS2 - 98%, NS3 - 72%, VP6 - 93%). Nevertheless, the envelope proteins containing the main specific antigenic determinants (VP2 and VP5) of OKHV and ANIV are sufficiently different (62% and 68% homology for amino acid sequences, respectively).

  17. A nudged chemistry-climate model simulation of chemical constituent distribution at northern high-latitude stratosphere observed by SMILES and MLS during the 2009/2010 stratospheric sudden warming

    Science.gov (United States)

    Akiyoshi, H.; Nakamura, T.; Miyasaka, T.; Shiotani, M.; Suzuki, M.

    2016-02-01

    Stratospheric sudden warming (SSW) is a dramatic phenomenon of the winter stratosphere in which the distribution of chemical constituents, associated chemical tendency, and transport of chemical constituents differ significantly inside and outside of the polar vortex. In this study, the chemical constituent distributions in the major SSW of 2009/2010 were simulated by the Model for Interdisciplinary Research on Climate 3.2-Chemistry-Climate Model (CCM) nudged toward the European Center for Medium-Range Weather Forecasts-Interim Re-Analysis data. The results were compared with Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) and Microwave Limb Sounder (MLS) observations. In addition, ozone tendency due to ozone transport and chemical ozone loss in the high-latitude lower stratosphere before and after the SSW was analyzed for the period from 1 January 2010 to 11 February 2010. The evolution and distribution of ozone and HCl inside/outside the polar vortex associated with the vortex shift to the midlatitudes in January are quite similar between SMILES and MLS. Those of ClO are also similar, considering the difference in the local time for the measurement. Analyses of the nudged CCM run indicate that inside the polar vortex at 50 hPa, the ozone concentration increased moderately owing to partial cancelation between the large negative ozone tendency due to chemical ozone destruction and large positive ozone tendency due to horizontal ozone influx from outside of the vortex as well as downward advection. In the region of a high ozone concentration with the same area as that of the polar vortex at 50 hPa, the large increase in ozone was primarily due to a downward advection of ozone. SMILES and MLS observations, nudged CCM simulations, and ozone tendency analyses revealed a highly longitudinal dependent ozone tendency at high latitudes during the SSW.

  18. Corotating Interaction Regions at High Latitudes

    Science.gov (United States)

    Kunow, H.; Lee, M. A.; Fisk, L. A.; Forsyth, R. J.; Heber, B.; Horbury, T. S.; Keppler, E.; Kóta, J.; Lou, Y.-Q.; McKibben, R. B.; Paizis, C.; Potgieter, M. S.; Roelof, E. C.; Sanderson, T. R.; Simnett, G. M.; von Steiger, R.; Tsurutani, B. T.; Wimmer-Schweingruber, R. F.; Jokipii, J. R.

    1999-07-01

    Ulysses observed a stable strong CIR from early 1992 through 1994 during its first journey into the southern hemisphere. After the rapid latitude scan in early 1995, Ulysses observed a weaker CIR from early 1996 to mid-1997 in the northern hemisphere as it traveled back to the ecliptic at the orbit of Jupiter. These two CIRs are the observational basis of the investigation into the latitudinal structure of CIRs. The first CIR was caused by an extension of the northern coronal hole into the southern hemisphere during declining solar activity, whereas the second CIR near solar minimum activity was caused by small warps in the streamer belt. The latitudinal structure is described through the presentation of three 26-day periods during the southern CIR. The first at ˜24°S shows the full plasma interaction region including fast and slow wind streams, the compressed shocked flows with embedded stream interface and heliospheric current sheet (HCS), and the forward and reverse shocks with associated accelerated ions and electrons. The second at 40°S exhibits only the reverse shock, accelerated particles, and the 26-day modulation of cosmic rays. The third at 60°S shows only the accelerated particles and modulated cosmic rays. The possible mechanisms for the access of the accelerated particles and the CIR-modulated cosmic rays to high latitudes above the plasma interaction region are presented. They include direct magnetic field connection across latitude due to stochastic field line weaving or to systematic weaving caused by solar differential rotation combined with non-radial expansion of the fast wind. Another possible mechanism is particle diffusion across the average magnetic field, which includes stochastic field line weaving. A constraint on connection to a distant portion of the CIR is energy loss in the solar wind, which is substantial for the relatively slow-moving accelerated ions. Finally, the weaker northern CIR is compared with the southern CIR. It is weak

  19. Vulnerability of high-latitude soil organic carbon in North America to disturbance

    Science.gov (United States)

    Guido Grosse; Jennifer Harden; Merritt Turetsky; A. David McGuire; Philip Camill; Charles Tarnocai; Steve Frolking; Edward Schuur; Torre Jorgenson; Sergei Marchenko; Vladimir Romanovsky; Kimberly P. Wickland; Nancy French; Mark Waldrop; Laura Bourgeau-Chavez; Robert G. Streigl

    2011-01-01

    This synthesis addresses the vulnerability of the North American high-latitude soil organic carbon (SOC) pool to climate change. Disturbances caused by climate warming in arctic, subarctic, and boreal environments can result in significant redistribution of C among major reservoirs with potential global impacts. We divide the current northern high-latitude SOC pools...

  20. Is There a Relationship between Fish Cannibalism and Latitude or Species Richness?

    Science.gov (United States)

    Pereira, Larissa Strictar; Keppeler, Friedrich Wolfgang; Agostinho, Angelo Antonio; Winemiller, Kirk O

    2017-01-01

    Cannibalism has been commonly observed in fish from northern and alpine regions and less frequently reported for subtropical and tropical fish in more diverse communities. Assuming all else being equal, cannibalism should be more common in communities with lower species richness because the probability of encountering conspecific versus heterospecific prey would be higher. A global dataset was compiled to determine if cannibalism occurrence is associated with species richness and latitude. Cannibalism occurrence, local species richness and latitude were recorded for 4,100 populations of 2,314 teleost fish species. Relationships between cannibalism, species richness and latitude were evaluated using generalized linear mixed models. Species richness was an important predictor of cannibalism, with occurrences more frequently reported for assemblages containing fewer species. Cannibalism was positively related with latitude for both marine and freshwater ecosystems in the Northern Hemisphere, but not in the Southern Hemisphere. The regression slope for the relationship was steeper for freshwater than marine fishes. In general, cannibalism is more frequent in communities with lower species richness, and the relationship between cannibalism and latitude is stronger in the Northern Hemisphere. In the Southern Hemisphere, weaker latitudinal gradients of fish species richness may account for the weak relationship between cannibalism and latitude. Cannibalism may be more common in freshwater than marine systems because freshwater habitats tend to be smaller and more closed to dispersal. Cannibalism should have greatest potential to influence fish population dynamics in freshwater systems at high northern latitudes.

  1. ROTATION RATE DIFFERENCES OF POSITIVE AND NEGATIVE SOLAR MAGNETIC FIELDS BETWEEN ±60° LATITUDES

    Energy Technology Data Exchange (ETDEWEB)

    Shi, X. J.; Xie, J. L., E-mail: shixiangjun@ynao.ac.cn [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China)

    2015-04-15

    Based on a cross-correlation analysis of the Carrington synoptic maps of solar photospheric magnetic fields from Carrington Rotations Nos. 1625 to 2135 (from 1975 February to 2013 March), the sidereal rotation rates of the positive and negative magnetic fields in the latitude range of ±60° are obtained, and the rotation rate differences between them are investigated. The time–latitude distribution of the rate differences is shown, which looks like a butterfly diagram at the low and middle latitudes. For comparison, the time–latitude distribution of the longitudinally averaged photospheric magnetic fields is shown. We conclude that the magnetic fields having the same polarity as the leading sunspots at a given hemisphere rotate faster than those exhibiting the opposite polarity at low and middle latitudes. However, at higher latitudes, the magnetic fields having the same polarity as the leading sunspots at a given hemisphere do not always rotate faster than those with the opposite polarity. Furthermore, the relationship between the rotation rate differences and solar magnetic fields is studied through a correlation analysis. Our result shows that the correlation coefficients between them reach maximum values at 13° (14°) latitude in the northern (southern) hemisphere, and change sign at 28° latitude in both hemispheres, then reach their minimum values at 58° (53°) latitude in the northern (southern) hemisphere.

  2. 北半球夏季中高纬度大气阻塞对北极海冰变化的影响%EFFECT OF NORTHERN HEMISPHERE MID-HIGH LATITUDE BLOCKING ON THE VARIATION OF SUMMER ARCTIC SEA ICE

    Institute of Scientific and Technical Information of China (English)

    肖贻青; 黄斌; 刁一娜; 罗德海

    2015-01-01

    The relationship between mid-high latitude blocking in the northern hemisphere and the decline in Arctic sum-mer sea ice was investigated using National Centers for Environmental Prediction /National Center for Atmospheric Research daily 500 hPa geopotential height reanalysis data .Results show that there are high blocking frequencies o-ver the Bering Strait , the Okhotsk Sea , Eurasia , and Greenland , which correlate closely with the areas of reduced Arctic summer sea ice in the past 30 years as observed from satellite data .Differences in surface temperature , me-ridional heat transport and temperature advection in 850 hPa anomaly fields between days with and without blocking were calculated and the results show that mid-high latitude blocking has a significant impact on the reduction in sea ice.An increase in blocking frequency in northern hemisphere mid-high latitudes will increase the surface air tem-perature , poleward heat transport , and temperature advection , further accelerate the melting of Arctic sea ice . Therefore, thermodynamic effects caused by blocking over the Okhotsk Sea and Eurasia could result in a marked re -duction in Arctic sea ice .%利用NCEP/NCAR再分析逐日500 hPa高度场资料,对北半球夏季中高纬度大气阻塞特征进行统计分析,发现大气阻塞活动频率高的地区主要集中在白令海峡区域、鄂霍次克海区域、欧亚大陆区域及格陵兰区域。而通过NSIDC提供的卫星观测资料发现近30年夏季海冰容易减少的区域正好对应阻塞活动北部的高纬度地区。分别通过对以上4个区域有阻塞发生相对没有阻塞发生时的500 hPa位势高度场、地面温度场、850 hPa经向瞬变热通量输送和平流输送等异常变化场进行对比分析,结果发现夏季中高纬度阻塞频率的增加对海冰的减少有显著影响,主要体现在阻塞的发生发展可通过增加高纬度地面温度、对极地的热量输送和暖平流输送来

  3. Canadian Space Launch: Exploiting Northern Latitudes For Efficient Space Launch

    Science.gov (United States)

    2015-04-01

    facility and therefore has some basic infrastructure in place. It housed 4,500 personnel and launched over 3,500 sub-orbital flights.49 While the... Melbourne , FL. http://www.spaceops2012.org/ proceedings/documents/id1295313- Paper-002.pdf (accessed 10 Mar 2015). Winters, Nathan J. “Enabling the

  4. Latitudes: new Indian transnational cinema.

    Science.gov (United States)

    Villarejo, Amy

    2014-01-01

    This article examines films and video art that speak to conditions of exile and displacement, including the work of Mona Hatoum, Sonali Gulati, and Onir. It proposes the term "latitude" to interrogate the aesthetic and formal properties of these artworks, seeking to understand how lesbian and same-sex eroticism and identities are central to their efficacy.

  5. Association between adolescent idiopathic scoliosis prevalence and age at menarche in different geographic latitudes

    OpenAIRE

    Mihas Constantinos; Mouzakis Vasilios; Vasiliadis Elias; Grivas Theodoros B; Koufopoulos Georgios

    2006-01-01

    Abstract Background Age at menarche is considered a reliable prognostic factor for idiopathic scoliosis and varies in different geographic latitudes. Adolescent idiopathic scoliosis prevalence has also been reported to be different in various latitudes and demonstrates higher values in northern countries. A study on epidemiological reports from the literature was conducted to investigate a possible association between prevalence of adolescent idiopathic scoliosis and age at menarche among nor...

  6. A comparison of hip fracture incidence rates among elderly in Sweden by latitude and sunlight exposure.

    Science.gov (United States)

    Nilson, Finn; Moniruzzaman, Syed; Andersson, Ragnar

    2014-03-01

    Research has shown that hip fracture risk increases with latitude; hypothetically due to reduced sunlight exposure and its effect on bone quality. Sweden, with large differences in latitude and UV radiation, is ideal to study in order to analyse the association between latitude and UV radiation on age- and sex-specific hip fracture rates among elderly. Aggregated (2006-2008) age- and sex-specific hip fracture data was obtained for each Swedish municipality as well as the municipality's latitudinal coordinates and aggregated (2006-2008) UV radiation levels. Pearson correlations were calculated between hip fracture incidence rates, latitude and UV radiation. Independent t tests were calculated on tertile-categorized latitudinal data in order to investigate the difference in hip fracture risk between these categories. Statistically significant correlations were seen in all groups between hip fracture incidence rates and latitude as well as UV radiation. The independent t tests showed that this correlation was mainly due to high incidence rates in high latitude municipalities. Statistically significant correlations are seen between hip fracture incidence rates and latitude as well as UV radiation in Sweden and the northern parts of Sweden have an increased risk of hip fractures compared to the middle and southern parts. To our knowledge this is the first study using a national discharge register that shows this relationship and provides a starting point for further research to investigate why populations in northern Sweden have a higher risk of hip fractures compared to other Swedish regions.

  7. Latitude, birth date, and allergy.

    Directory of Open Access Journals (Sweden)

    Matthias Wjst

    2005-10-01

    Full Text Available BACKGROUND: The space and time distribution of risk factors for allergic diseases may provide insights into disease mechanisms. Allergy is believed to vary by month of birth, but multinational studies taking into account latitude have not been conducted. METHODS AND FINDINGS: A questionnaire was distributed in 54 centres to a representative sample of 20- to 44-y-old men and women mainly in Europe but also including regions in North Africa, India, North America, Australia, and New Zealand. Data from 200,682 participants were analyzed. The median prevalence of allergic rhinitis was 22%, with a substantial variation across centres. Overall, allergic rhinitis decreased with geographical latitude, but there were many exceptions. No increase in prevalence during certain winters could be observed. Also, no altered risk by birth month was found, except borderline reduced risks in September and October. Effect estimates obtained by a multivariate analysis of total and specific IgE values in 18,085 individuals also excluded major birth month effects and confirmed the independent effect of language grouping. CONCLUSION: Neither time point of first exposure to certain allergens nor early infections during winter months seems to be a major factor for adult allergy. Although there might be effects of climate or environmental UV exposure by latitude, influences within language groups seem to be more important, reflecting so far unknown genetic or cultural risk factors.

  8. High Latitude Mottling on Jupiter

    Science.gov (United States)

    2000-01-01

    The familiar banded appearance of Jupiter at low and middle latitudes gradually gives way to a more mottled appearance at high latitudes in this striking true color image taken Dec. 13, 2000, by NASA's Cassini spacecraft.The intricate structures seen in the polar region are clouds of different chemical composition, height and thickness. Clouds are organized by winds, and the mottled appearance in the polar regions suggests more vortex-type motion and winds of less vigor at higher latitudes.The cause of this difference is not understood. One possible contributor is that the horizontal component of the Coriolis force, which arises from the planet's rotation and is responsible for curving the trajectories of ocean currents and winds on Earth, has its greatest effect at high latitudes and vanishes at the equator. This tends to create small, intense vortices at high latitudes on Jupiter. Another possibility may lie in that fact that Jupiter overall emits nearly as much of its own heat as it absorbs from the Sun, and this internal heat flux is very likely greater at the poles. This condition could lead to enhanced convection at the poles and more vortex-type structures. Further analysis of Cassini images, including analysis of sequences taken over a span of time, should help us understand the cause of equator-to-pole differences in cloud organization and evolution.By the time this picture was taken, Cassini had reached close enough to Jupiter to allow the spacecraft to return images with more detail than what's possible with the planetary camera on NASA's Earth-orbiting Hubble Space Telescope. The resolution here is 114 kilometers (71 miles) per pixel. This contrast-enhanced, edge-sharpened frame was composited from images take at different wavelengths with Cassini's narrow-angle camera, from a distance of 19 million kilometers (11.8 million miles). The spacecraft was in almost a direct line between the Sun and Jupiter, so the solar illumination on Jupiter is almost full

  9. Relationship between Latitude and Melanoma in Italy.

    Science.gov (United States)

    Crocetti, Emanuele; Buzzoni, Carlotta; Chiarugi, Alessandra; Nardini, Paolo; Pimpinelli, Nicola

    2012-01-01

    Objective. Evaluate the ecological relationship between skin melanoma epidemiology and latitude in Italy. Methods. We used data from the Italian network of cancer registries (Airtum). In a Poisson model, we evaluated the effect on incidence, mortality, and survival of latitude, adjusting for some demographic, social, phenotypic, and behavioural variables. Results. Incidence increased in Italy by 17% for each degree of increase in latitude. The effect of latitude was statistically significantly present also adjusting for other variables (incidence rate ratio = 1.08). The effect of latitude on increasing mortality (mortality rate ratio = 1.27) and improving survival (relative excess risk of death = 0.93) was no longer present in the multivariate model. Conclusion. Melanoma incidence, mortality, and survival vary in Italy according to latitude. After adjustment for several confounders, incidence still grows with growing latitude. Presumably, latitude expresses other variables that might be related to individual susceptibility and/or local care.

  10. Association between adolescent idiopathic scoliosis prevalence and age at menarche in different geographic latitudes

    Directory of Open Access Journals (Sweden)

    Mihas Constantinos

    2006-05-01

    Full Text Available Abstract Background Age at menarche is considered a reliable prognostic factor for idiopathic scoliosis and varies in different geographic latitudes. Adolescent idiopathic scoliosis prevalence has also been reported to be different in various latitudes and demonstrates higher values in northern countries. A study on epidemiological reports from the literature was conducted to investigate a possible association between prevalence of adolescent idiopathic scoliosis and age at menarche among normal girls in various geographic latitudes. An attempt is also made to implicate a possible role of melatonin in the above association. Material-methods 20 peer-reviewed published papers reporting adolescent idiopathic scoliosis prevalence and 33 peer-reviewed papers reporting age at menarche in normal girls from most geographic areas of the northern hemisphere were retrieved from the literature. The geographic latitude of each centre where a particular study was originated was documented. The statistical analysis included regression of the adolescent idiopathic scoliosis prevalence and age at menarche by latitude. Results The regression of prevalence of adolescent idiopathic scoliosis and age at menarche by latitude is statistically significant (p Conclusion Late age at menarche is parallel with higher prevalence of adolescent idiopathic scoliosis. Pubarche appears later in girls that live in northern latitudes and thus prolongs the period of spine vulnerability while other pre-existing or aetiological factors are contributing to the development of adolescent idiopathic scoliosis. A possible role of geography in the pathogenesis of idiopathic scoliosis is discussed, as it appears that latitude which differentiates the sunlight influences melatonin secretion and modifies age at menarche, which is associated to the prevalence of idiopathic scoliosis.

  11. Physiological and behavioral adaptations in bats living at high latitudes.

    Science.gov (United States)

    Boyles, Justin G; McGuire, Liam P; Boyles, Esmarie; Reimer, Jesika P; Brooks, Christopher A C; Rutherford, Robert W; Rutherford, Teresa A; Whitaker, John O; McCracken, Gary F

    2016-10-15

    Widespread animals at the extremes of the species' distribution experience ecological constraints different than individuals in the core of the distribution. For example, small endotherms at very high latitudes face short summers with cool temperatures and a lack of true darkness. In particular, insectivorous bats at high latitudes may experience constraints because of their unique life history traits, and may have different energy requirements than bats at lower latitudes. To evaluate the extent of these differences, we estimated an energy budget and refueling rates for reproductively active female little brown bats (Myotis lucifugus) roosting in buildings in eastern Alaska (~63°N). Physiological parameters (torpor use and metabolic rates) and daily energy expenditures (25.7±5.3kJd(-1)) were similar to, or slightly lower than, conspecifics at lower latitudes. Northern little brown bats foraged for less time than southerly conspecifics, but measurements of plasma β-hydroxybutyrate concentrations suggest that northern bats refuel at a rate considerably higher than those to the south. It appears that high refueling rates (and therefore foraging intensity) involve a dietary shift to orb-weaver spiders, which are abundant and likely offer higher energetic benefit than the small, flying insects consumed by individuals in other parts of the distribution. Environmental factors may limit species' distributions, but our results provide an example of a population at the limit of their geographic range that has compensated for environmental challenges by adopting unique behavioral strategies while the underlying physiology (including daily energy expenditure) remains similar to populations at the core of the species' range. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. Amplified mid-latitude planetary waves favour particular regional weather extremes

    Science.gov (United States)

    Screen, James A.; Simmonds, Ian

    2014-08-01

    There has been an ostensibly large number of extreme weather events in the Northern Hemisphere mid-latitudes during the past decade. An open question that is critically important for scientists and policy makers is whether any such increase in weather extremes is natural or anthropogenic in origin. One mechanism proposed to explain the increased frequency of extreme weather events is the amplification of mid-latitude atmospheric planetary waves. Disproportionately large warming in the northern polar regions compared with mid-latitudes--and associated weakening of the north-south temperature gradient--may favour larger amplitude planetary waves, although observational evidence for this remains inconclusive. A better understanding of the role of planetary waves in causing mid-latitude weather extremes is essential for assessing the potential environmental and socio-economic impacts of future planetary wave changes. Here we show that months of extreme weather over mid-latitudes are commonly accompanied by significantly amplified quasi-stationary mid-tropospheric planetary waves. Conversely, months of near-average weather over mid-latitudes are often accompanied by significantly attenuated waves. Depending on geographical region, certain types of extreme weather (for example, hot, cold, wet, dry) are more strongly related to wave amplitude changes than others. The findings suggest that amplification of quasi-stationary waves preferentially increases the probabilities of heat waves in western North America and central Asia, cold outbreaks in eastern North America, droughts in central North America, Europe and central Asia, and wet spells in western Asia.

  13. Zaman Tanım Alanında Analiz Yöntemi Kullanılarak Binalardaki A3 Düzensizliğinin İncelenmesi

    Directory of Open Access Journals (Sweden)

    Mehmet Emin ÖNCÜ

    2014-02-01

    Full Text Available Depreme dayanıklı yapı tasarımları için farklı yöntemler kullanılmaktadır. En güncel yöntemlerden biri de Zaman Tanım Alanında Doğrusal Olmayan Analizdir. Bu yöntemle sismik analizler yapılırken daha önce meydana gelmiş depremlerin ivme kayıtları kullanılmaktadır. Bu deprem ivme kayıtları değişik kaynaklardan çok farklı yöntemlerle elde edilir. Bunlar: Tasarım ivme spektrumu uyumlu yapay kayıtlar, benzeştirilmiş kayıtlar ve deprem esnasında kaydedilen kayıtlardır (Fajhan, 2008. Bu kayıtlar kullanılırken farklı bölgelerdeki zemin özellikleri de dikkate alınmalıdır. Bu çalışmada, Deprem Bölgelerinde Yapılacak Binalar Hakkındaki Yönetmelikte belirtilen Zaman Tanım Alanında Analiz yöntemi ile doğrusal olmayan analizi yapılan A3 düzensizliğine sahip belli tip yapılar incelenmiştir. Önce üç deprem ivme kaydı alınarak Türk Deprem Yönetmeliğinde ifade edilen elastik tasarım ivme spektrumuna göre ölçeklendirilmiştir. Elde edilen maksimum ivme kaydı, daha sonra A3 düzensizliğine sahip bu tip yapılara uygulanmıştır. Analiz sonuçlarına göre yapıların zemin kat kolonlarındaki kesme kuvvetleri bulunmuştur. Anahtar kelimeler: Zaman Tanım Alanında Analiz, A3 Düzensizliği, Deprem İvme Kaydının Ölçeklendirilmesi

  14. High prevalence and no latitude gradient of multiple sclerosis in Norway.

    Science.gov (United States)

    Berg-Hansen, P; Moen, S M; Harbo, H F; Celius, E G

    2014-11-01

    The prevalence of multiple sclerosis (MS) is increasing, and the presence of a latitude gradient for MS risk is still discussed. We present the first nationwide prevalence estimates for Norway, spanning the latitudes from 58-71 degrees North, in order to identify a possible latitude gradient. Information from the Oslo MS Registry and the Norwegian MS Registry and Biobank was combined with data from the Norwegian Patient Registry, the Norwegian Prescription Database and Statistics Norway. We estimated a crude prevalence of 203/100,000 on 1 January 2012. The prevalence in the Northern and Southern regions were not significantly different. MS prevalence in Norway is among the highest reported worldwide. We found no evidence of a latitude gradient.

  15. Drivers of hemispheric differences in return dates of mid-latitude stratospheric ozone to historical levels

    Directory of Open Access Journals (Sweden)

    H. Garny

    2012-12-01

    Full Text Available Chemistry-climate models (CCMs project an earlier return of northern mid-latitude total column ozone to 1980 values compared to the southern mid-latitudes. The chemical and dynamical drivers of this hemispheric difference are investigated in this study. The hemispheric asymmetry in return dates is a robust result across different CCMs and is qualitatively independent of the method used to estimate return dates. However, the differences in dates of return to 1980 levels between the southern and northern mid-latitudes can vary between 0 and 30 yr across the range of CCM projections analyzed. An attribution analysis performed with two CCMs shows that chemically-induced changes in ozone are the major driver of the earlier return of ozone to 1980 levels in northern mid-latitudes; transport changes are of minor importance. This conclusion is supported by the fact that the spread in the simulated hemispheric difference in return dates across an ensemble of twelve models is only weakly related to the spread in the simulated hemispheric asymmetry of trends in the strength of the Brewer–Dobson circulation. The causes for chemically-induced asymmetric ozone trends relevant for the total column ozone return date differences are found to be (i stronger increases in ozone production due to enhanced NOx concentrations in the Northern Hemisphere lowermost stratosphere and troposphere, (ii stronger decreases in the destruction rates of ozone by the NOx cycle in the Northern Hemisphere lower stratosphere linked to effects of dynamics and temperature on NOx concentrations and (iii an increasing efficiency of heterogeneous ozone destruction by Cly in the Southern Hemisphere mid-latitudes as a result of decreasing temperatures.

  16. Atmospheric river landfall-latitude changes in future climate simulations

    Science.gov (United States)

    Shields, Christine A.; Kiehl, Jeffrey T.

    2016-08-01

    The latitude of landfall for atmospheric rivers (ARs) is examined in the fully coupled half-degree version of the Community Climate System Model, version 4 (CCSM4) for warm future climate simulations. Two regions are examined: U.S. West Coast/North Pacific ARs and United Kingdom/North Atlantic ARs. Changes in AR landfall-latitude reflect changes in the atmospheric steering flow. West Coast U.S. ARs are projected to push equatorward in response to the subtropical jet climate change. UK AR response is dominated by eddy-driven jets and is seasonally dependent. UK simulated AR response is modest in the winter with the largest relative changes occurring in the seasonal transition months. Precipitation associated with ARs is also projected to increase in intensity under global warming. CCSM4 projects a marked shift to higher rainfall rates for Southern California. Small to modest rainfall rates may increase for all UK latitudes, for the Pacific Northwest, and central and northern California.

  17. Naujų automobilių pardavimams įtaką darančių veiksnių analizė

    OpenAIRE

    2016-01-01

    Baigiamojo darbo tema - ,,Naujų automobilių pardavimams įtaką darančių veiksnių analizė“. Bakalauro baigiamajame darbe nagrinėjami naujų automobilių pardavimams įtaką darantys veiksniai. Ši tema aktuali, nes šiandieniniai automobilių rinkos vartotojai susiduria su didele prekių pasiūla, todėl naujų automobilių pardavimams įtakos turi įvairūs veiksniai. Taigi baigiamajame darbe iškeltas tikslas - išanalizuoti naujų automobilių pardavimams įtaką darančius veiksnius. Baigiamajam darbui buvo i...

  18. Energy-Efficient Office Buildings at High Latitudes

    Energy Technology Data Exchange (ETDEWEB)

    Lerum, V.

    1996-12-31

    This doctoral thesis describes a method for energy efficient office building design at high latitudes and cold climates. The method combines daylighting, passive solar heating, solar protection, and ventilative cooling. The thesis focuses on optimal design of an equatorial-facing fenestration system. A spreadsheet framework linking existing simplified methods is used. The daylight analysis uses location specific data on frequency distribution of diffuse daylight on vertical surfaces to estimate energy savings from optimal window and room configurations in combination with a daylight-responsive electric lighting system. The passive solar heating analysis is a generalization of a solar load ratio method adapted to cold climates by combining it with the Norwegian standard NS3031 for winter months when the solar savings fraction is negative. The emphasis is on very high computational efficiency to permit rapid and comprehensive examination of a large number of options early in design. The procedure is illustrated for a location in Trondheim, Norway, testing the relative significance of various design improvement options relative to a base case. The method is also tested for two other locations in Norway, at latitudes 58 and 70 degrees North. The band of latitudes between these limits covers cities in Alaska, Canada, Greenland, Iceland, Scandinavia, Finland, Russia, and Northern Japan. A comprehensive study of the ``whole building approach`` shows the impact of integrated daylighting and low-energy design strategies. In general, consumption of lighting electricity may be reduced by 50-80%, even at extremely high latitudes. The reduced internal heat from electric lights is replaced by passive solar heating. 113 refs., 85 figs., 25 tabs.

  19. Low-latitude ionospheric effects on SBAS

    Science.gov (United States)

    Arenas, J.; Sardón, E.; Sainz, A.; Ochoa, B.; Magdaleno, S.

    2016-06-01

    Satellite-based augmentation systems (SBAS) provide augmentation to Global Navigation Satellite Systems (GNSS) users in three areas: (1) broadcasting accurate corrections to GNSS satellite ephemeris, (2) providing a real-time empirical ionospheric model in the service area, and (3) providing integrity information in the form of estimates of the confidence of the ephemeris corrections and ionospheric delays. Ionospheric effects on SBAS are twofold: (a) the input data used by the SBAS will be affected by ionospheric effects, and (b) the more perturbed the ionosphere is, the more difficult it will be to provide accurate and reliable ionospheric information to the users. The ionosphere at low latitudes presents larger variability and more intense phenomena than at midlatitudes. Therefore, SBAS providing service to low-latitude regions will be more affected than those at other latitudes. From the different low-latitude ionospheric effects, this paper will focus on those having the largest impact on SBAS, which are total electron content temporal and spatial gradients, ionospheric scintillations, and depletions. This paper will present the impact of these effects on EGNOS (European Global Navigation Overlay System), the European SBAS. Although EGNOS can be considered as a midlatitude SBAS, it has to provide coverage down to rather low latitudes, so sometimes low-latitude ionospheric effects are observed in the EGNOS data. It will be shown how EGNOS performs under nominal conditions and how its performance is degraded when low-latitude ionospheric phenomena occur. Real EGNOS data affected by low-latitude ionospheric phenomena will be used.

  20. Plastic ingestion by the northern fulmar (Fulmarus glacialis) in Iceland

    NARCIS (Netherlands)

    Kuehn, S.; Franeker, van J.A.

    2012-01-01

    In 2011, northern fulmars (Fulmarus glacialis) from Iceland were used to test the hypothesis that plastic debris decreases at northern latitudes in the Atlantic when moving away from major human centres of coastal and marine activities. Stomach analyses of Icelandic fulmars confirm that plastic poll

  1. Nonlinear response of mid-latitude weather to the changing Arctic

    Science.gov (United States)

    Overland, James E.; Dethloff, Klaus; Francis, Jennifer A.; Hall, Richard J.; Hanna, Edward; Kim, Seong-Joong; Screen, James A.; Shepherd, Theodore G.; Vihma, Timo

    2016-11-01

    Are continuing changes in the Arctic influencing wind patterns and the occurrence of extreme weather events in northern mid-latitudes? The chaotic nature of atmospheric circulation precludes easy answers. The topic is a major science challenge, as continued Arctic temperature increases are an inevitable aspect of anthropogenic climate change. We propose a perspective that rejects simple cause-and-effect pathways and notes diagnostic challenges in interpreting atmospheric dynamics. We present a way forward based on understanding multiple processes that lead to uncertainties in Arctic and mid-latitude weather and climate linkages. We emphasize community coordination for both scientific progress and communication to a broader public.

  2. Sistemos “Sunkiųjų metalų jonai - geležies (III) oksidas/hidroksidas“ cheminė analizė ir sorbcijos procesų tyrimas

    OpenAIRE

    Zubrytė, Edita

    2016-01-01

    Sistemos “Sunkiųjų metalų jonai - geležies (III) oksidas/hidroksidas“ cheminė analizė ir sorbcijos procesų tyrimas Chemical Analysis of the System „Heavy Metal Ions – an Iron (III) Oxide/Hydroxide and Investigation of the Sorption Processes

  3. Ultraviolet light exposure influences skin cancer in association with latitude.

    Science.gov (United States)

    Rivas, Miguel; Araya, María C; Caba, Fresia; Rojas, Elisa; Calaf, Gloria M

    2011-04-01

    The increase in the amount of solar ultraviolet (UV) light that reaches the earth is considered to be responsible for the worldwide increase in skin cancer. It has been reported that excessive levels of UVA and UVB light have multiple effects, which can be harmful to humans. Experimental measurements were obtained using wide-band solar light YES biometers from 2006 to 2009 in Arica, Chile and from 2003 to 2006 in Valdivia, Chile, both instruments having been calibrated according to the World Health Organization (WHO) criteria and integrated into the Chilean Meteorological Organization network. To explain the possible effect of radiation on skin cancer, revised pathological reports in Arica and Valdivia were analyzed. In Arica, data on men and women were collected between 1997 and 1998-2002, and in Valdivia, between 1997-2000 and 2001-2007. In this study, comparative values of ultraviolet index (UVI) from the above datasets, were analyzed. Arica is a city located in the subtropical zone of northern Chile, 25 meters above sea level, with a latitude of 18˚49'S and a longitude of 70˚19'W. It has a microclimate characterized by stable meteorological conditions throughout the year, including low precipitation (<5 mm per decade), predictable winds, a high percentage of clear sky days and high ground reflectivity due to the presence of light sand. Due to its location near sea level, the population performs a great number of outdoor activities. Valdivia is a city located in the southern part of Chile, 19 meters above sea level with a latitude of 39˚38'S and a longitude of 73˚5'W. The aim of the present study was to determine the relationship between latitude and the risk of skin cancer in two cities with different latitudes. The incidence of skin cancer per 100,000 persons significantly (P<0.05) increased in both genders between the periods 1997-2000 and 2001-2007 in Arica. However, it decreased in men between the periods 1993-1997 and 1998-2002 in Valdivia. The results

  4. Mesopause jumps at Antarctic latitudes

    Science.gov (United States)

    Lübken, Franz-Josef; Höffner, Josef; Becker, Erich; Latteck, Ralph; Murphy, Damian

    2016-04-01

    Recent high resolution temperature measurements by resonance lidar at Davis (69°S) occasionally showed a sudden mesopause altitude increase by ˜5 km and an associated mesopause temperature decrease by ˜10 K. We present further observations which are closely related to this 'mesopause jump', namely the increase of mean height of polar mesospheric summer echoes (PMSE) observed by a VHF radar, very strong westward winds in the upper mesosphere measured by an MF radar, and relatively large eastward winds in the stratosphere taken from reanalysis. We compare to similar observations in the Northern Hemisphere, namely at ALOMAR (69°N) where such mesopause jumps have never been observed. We present a detailed explanation of mesopause jumps. They occur only when stratospheric winds are moderately eastward and mesospheric winds are very large (westward). Under these conditions, gravity waves with comparatively large eastward phase Speeds can pass the stratosphere and propagate to the lower thermosphere because their vertical wavelengths in the mesosphere are rather large which implies reduced dynamical stability. When finally breaking in the lower thermosphere, these waves drive an enhanced residual circulation that causes a cold and high-altitude mesopause. The conditions for a mesopause jump occur only in the Southern Hemisphere (SH) and are associated with the late breakdown of the polar vortex. Mesopause jumps are primarily, but not only, observed prior and close to solstice. We also show that during the onset of PMSE in the SH, stratospheric zonal winds are still eastward (up to 30 m/s), and that the onset is not closely related to the Transition of the stratospheric circulation.

  5. Tidi Observations Relating to High Latitude Aeronomy

    Science.gov (United States)

    Gell, D.; Niciejewski, R.; Killeen, T.; Wu, Q.; Skinner, W.; Solomon, S.; Ortland, D.; Kafkalidis, J.; Gablehouse, D.; Johnson, R.

    2003-12-01

    Unique observations of the horizontal neutral winds at high latitudes in the altitude range 60 to 180 km have been performed by TIDI (Thermosphere Ionosphere Doppler Interferometer) since January 2002. The satellite orbit is such that the TIDI field of view includes latitudes to both the north pole and the south pole. Though high latitude neutral wind measurements have been obtained from space with the DE-2 satellite and the UARS satellite, TIDI is the first instrument to sample the mesosphere and the lower thermosphere up to and including both polar regions on a long-term basis. Ground based studies have previously reported a strong semi-diurnal tide in the mesosphere over Resolute, Canada. This paper will describe the climatology that has been obtained by the TIDI instrument since early 2002 for high latitudes. The precession rate of TIMED supports two month averaging of data sets in order to sample all local solar time.

  6. The SDSS High Latitude Cloud Survey

    Science.gov (United States)

    McGehee, P. M.

    2009-01-01

    The high latitude clouds (|b| > 30) are primarily translucent molecular clouds and diffuse Galactic cirrus with the majority of them seen at high latitude simply due to their proximity to the Sun. The rare exceptions are those, like the Draco and other intermediate or high velocity clouds, found significantly above or below the Galactic plane. To date, star formation has only been verified in MBM 12 and MBM 20, which are two of the densest high latitude molecular clouds. We present results from an ongoing study of high latitude clouds based on the Sloan Digital Sky Survey (SDSS) and the Two Micron All-Sky Survey (2MASS). This study consists of two major efforts, the first (described here) to provide a 3-D mapping of the interstellar dust using a color-excess technique, the second to identify candidate low-mass Classical T Tauri stars in the field.

  7. Low Latitude Aurora: Index of Solar Activity

    Science.gov (United States)

    Bekli, M. R.; Aissani, D.; Chadou, I.

    2010-10-01

    Observations of aurora borealis at low latitudes are rare, and are clearly associated with high solar activity. In this paper, we analyze some details of the solar activity during the years 1769-1792. Moreover, we describe in detail three low latitude auroras. The first event was reported by ash-Shalati and observed in North Africa (1770 AD). The second and third events were reported by l'Abbé Mann and observed in Europe (1770 and 1777 AD).

  8. High-Latitude Molecular Clouds as (Gamma)-ray Sources for GLAST

    Energy Technology Data Exchange (ETDEWEB)

    Torres, D F; Dame, T M; Digel, S W

    2005-01-05

    For about two decades, a population of relative small and nearby molecular clouds has been known to exist at high Galactic latitudes. Lying more than 10{sup o} from the Galactic plane, these clouds have typical distances of {approx}150 pc, angular sizes of {approx}1{sup o}, and masses of order tens of solar masses. These objects are passive sources of high-energy {gamma}-rays through cosmic ray-gas interactions. Using a new wide-angle CO survey of the northern sky, we show that typical high-latitude clouds are not bright enough in {gamma}-rays to have been detected by EGRET, but that of order 100 of them will be detectable by the Large Area Telescope (LAT) on GLAST. Thus, we predict a new steady population of {gamma}-ray sources at high Galactic latitudes, perhaps the most numerous after active galactic nuclei.

  9. Analiz vmesto emotsii / Josef Kats

    Index Scriptorium Estoniae

    Kats, Josef, 1977-

    2007-01-01

    Peaminister Andrus Ansipi ja välisminister Urmas Paeti sõnul on valitsus küsinud Vene-Saksa gaasijuhtme ehitamiseks vajalike teadusuuringute läbiviimiseks nõu enam kui 20 asutuselt, nende alusel tuleb teha kaalutletud otsus

  10. Analiz vmesto emotsii / Josef Kats

    Index Scriptorium Estoniae

    Kats, Josef, 1977-

    2007-01-01

    Peaminister Andrus Ansipi ja välisminister Urmas Paeti sõnul on valitsus küsinud Vene-Saksa gaasijuhtme ehitamiseks vajalike teadusuuringute läbiviimiseks nõu enam kui 20 asutuselt, nende alusel tuleb teha kaalutletud otsus

  11. Solar Transients disturbing the Terrestrial Magnetic Environment at Higher Latitudes

    CERN Document Server

    Khan, Parvaiz A; Troshichev, O A; Waheed, Malik A; M., Aslam A; Gwal, A K

    2013-01-01

    Geomagnetic field variations during five major Solar Energetic Particle (SEP) events of solar cycle 23 have been investigated in the present study. The SEP events of 01 oct 2001, 04 Nov 2001, 21 Apr 2002 and 14 May 2005 have been selected to study the geomagnetic field variations at two high-latitude stations, Thule and Resolute Bay of the northern polar cap. We have used the GOES protn flux in seven different energy channels. All the proton events were associated with geoeffective or Earth directed CMEs that caused intense geomagnetic storms in response to geospace. We have taken high-latitude indices, AE and PC, under consideration and found fairly good correlation of thees with the ground magnetic field records during the five proton events. The departure of H component during the events were calculated from the quietest day of the month for each event. The correspondence of spectral index, inferred from event integrated spectra, with ground magnetic signatures along with Dst and PC indices have been broug...

  12. Ambient temperature effects on photo induced gonadal cycles and hormonal secretion patterns in Great Tits from three different breeding latitudes.

    Science.gov (United States)

    Silverin, Bengt; Wingfield, John; Stokkan, Karl-Arne; Massa, Renato; Järvinen, Antero; Andersson, Nils-Ake; Lambrechts, Marcel; Sorace, Alberto; Blomqvist, Donald

    2008-06-01

    The present study determines how populations of Great Tits (Parus major) breeding in southern, mid and northern European latitudes have adjusted their reproductive endocrinology to differences in the ambient temperature during the gonadal cycle. A study based on long-term breeding data, using the Colwell predictability model, showed that the start of the breeding season has a high predictability ( approximately 0.8-0.9) at all latitudes, and that the environmental information factor (I(e)) progressively decreased from mid Italy (I(e)>4) to northern Finland (I(e)Tits from northern Norway, southern Sweden and northern Italy to sub-maximal photo-stimulatory day lengths (13L:11D) under two different ambient temperature regimes (+4 degrees C and +20 degrees C). Changes in testicular size, plasma levels of LH and testosterone were measured. The main results were: (1) Initial testicular growth rate, as well as LH secretion, was affected by temperature in the Italian, but not in birds from the two Scandinavian populations. (2) Maximum testicular size, maximum LH and testosterone levels were maintained for a progressively shorter period of time with increasing latitude, regardless of whether the birds were kept on a low or a high ambient temperature. (3) In birds from all latitudes, the development of photorefractoriness, as indicated by testicular regression and a decrease in plasma levels of LH and testosterone, started much earlier (with the exception for LH Great Tits from northern Scandinavia) when kept on +20 degrees C than when kept on +4 degrees C. The prolonging effects of a low temperature was more pronounced in Mediterranean birds, than in birds from Scandinavia, and more pronounced in Great Tits from southern Scandinavia than in Great Tits from northern Scandinavia. Ecological implications of the results are discussed, as well as possible impact of global warming on the breeding success of European Great Tits from different breeding latitudes.

  13. Millennial-scale interhemispheric asymmetry of low-latitude precipitation: Speleothem evidence and possible high-latitude forcing

    Science.gov (United States)

    Wang, Xianfeng; Edwards, R. Lawrence; Auler, Augusto S.; Cheng, Hai; Ito, Emi

    During the last glacial period, global climate was characterized by numerous millennial-scale abrupt changes. Mechanisms of these events, however, are not yet resolved. Here, we use phasing information between climate records from different localities to distinguish between mechanisms. We establish a 90,000 year-long oxygen isotopic record of cave calcite, with our previously reported and newly obtained data from Caverna Botuverá, southern Brazil. The record was precisely dated with uranium-series methods. Using independent absolute-dated chronologies, we compare the southern Brazil record with contemporaneous oxygen isotopic records of cave calcite from eastern China and the record of speleothem growth periods from northeastern Brazil. Our record anti-correlates remarkably with the eastern China profile, while it correlates positively with the northeastern Brazil one, on both millennial and orbital scales. Thus, rainfall patterns are antiphased between southern Brazil and eastern China but in-phase between the two Brazilian regions. The in-phase Brazilian relationship argues against a Super El Niño-Southern Oscillation (Super-ENSO) mechanism as modern rainfall at these sites is out of phase during ENSO years. Rather, the relationship among the three records is likely related to displacement in the mean position of the intertropical convergence zone and associated asymmetry in Hadley circulation, which leads to an interhemispheric anti-phasing of rainfall between the southern and northern low latitudes. The abrupt climate events during the last glacial-interglacial cycle are probably triggered by meridional overturning circulation changes initiated in the high latitudes and then amplified through air-sea dynamics, resulting in the observed pattern of low-latitude precipitation.

  14. A FUSE Survey of Interstellar Molecular Hydrogen toward High-Latitude AGN

    CERN Document Server

    Gillmon, K; Tumlinson, J; Danforth, C; Gillmon, Kristen; Tumlinson, Jason; Danforth, Charles

    2006-01-01

    We report results from a FUSE survey of interstellar molecular hydrogen (H2) along 45 sight lines to AGN at high Galactic latitudes (|b| > 20 degrees). Most (39 of 45) of the sight lines show detectable Galactic H2 absorption from Lyman and Werner bands between 1000 and 1126 A, with column densities ranging from N(H2) = 10^(14.17-19.82) cm^-2. In the northern Galactic hemisphere, we identify many regions of low column, N(H2) 54 degrees. These `"H2 holes" provide valuable, uncontaminated sight lines for extragalactic UV spectroscopy, and a few may be related to the "Northern Chimney" (low Na I absorption) and "Lockman Hole" with low N(HI). A comparison of high-latitude H2 with 139 OB-star sight lines surveyed in the Galactic disk suggests that high-latitude and disk H2 clouds may have different rates of heating, cooling, and UV excitation. For rotational states J = 0 and 1, the mean excitation temperature at high latitude, = 124 +/- 8 K, is somewhat above that in the Galactic disk, = 86 +/- 20 K. For J = 2-...

  15. Bat and bird diversity along independent gradients of latitude and tree composition in European forests.

    Science.gov (United States)

    Charbonnier, Yohan M; Barbaro, Luc; Barnagaud, Jean-Yves; Ampoorter, Evy; Nezan, Julien; Verheyen, Kris; Jactel, Hervé

    2016-10-01

    Species assemblages are shaped by local and continental-scale processes that are seldom investigated together, due to the lack of surveys along independent gradients of latitude and habitat types. Our study investigated changes in the effects of forest composition and structure on bat and bird diversity across Europe. We compared the taxonomic and functional diversity of bat and bird assemblages in 209 mature forest plots spread along gradients of forest composition and vertical structure, replicated in 6 regions spanning from the Mediterranean to the boreal biomes. Species richness and functional evenness of both bat and bird communities were affected by the interactions between latitude and forest composition and structure. Bat and bird species richness increased with broadleaved tree cover in temperate and especially in boreal regions but not in the Mediterranean where they increased with conifer abundance. Bat species richness was lower in forests with smaller trees and denser understorey only in northern regions. Bird species richness was not affected by forest structure. Bird functional evenness increased in younger and denser forests. Bat functional evenness was also influenced by interactions between latitude and understorey structure, increasing in temperate forests but decreasing in the Mediterranean. Covariation between bat and bird abundances also shifted across Europe, from negative in southern forests to positive in northern forests. Our results suggest that community assembly processes in bats and birds of European forests are predominantly driven by abundance and accessibility of feeding resources, i.e., insect prey, and their changes across both forest types and latitudes.

  16. Millennial-scale interhemispheric asymmetry of low-latitude precipitation: speleothem evidences and possible high-latitude forcing

    Science.gov (United States)

    Wang, X.; Auler, A.; Edwards, R.; Cheng, H.; Ito, E.

    2006-12-01

    A high resolution oxygen isotopic record of cave calcite, spanning the last 90,000 years, was obtained from Caverna Botuverá, southern Brazil. The record broadly follows local insolation changes and shows significant millennial-scale variation with amplitudes as large as 3 per mil. Tests for equilibrium conditions show that oxygen isotopic variations are a direct reflection of changes in rainwater values and temperatures at this low- latitude location. Established with independent absolute-dated uranium series chronologies, our record anti- correlates remarkably with the contemporaneous oxygen isotopic records of cave calcite from eastern China (anti-phase precipitation changes), but positively correlates with the record of speleothem growth periods from northeastern Brazil (in-phase precipitation changes) on millennial time scales. These observations suggest that a rainfall seesaw may have existed between the southern and northern low latitudes on millennial time scales in the past. This interhemipheric anti-phasing of rainfall is probably caused by feedbacks between North Atlantic thermohaline circulation and the intertropical convergence. The interplays affect not only North Atlantic climate but also result in the displacement of the mean position of the intertropical convergence zone and associated asymmetry of the Hadley cell. The Brazilian speleothem records further indicate that millennial-scale abrupt climate change is largely tied to meridional shifts rather than zonal shifts, and are therefore unlikely to have been triggered by tropical Walker circulation changes.

  17. British politics today: moral grounds as reflected in conceptual metaphor. Britų politikos vertinimas: konceptualiosios moralės metaforos analizė

    Directory of Open Access Journals (Sweden)

    Liudmila Arcimavičienė

    2007-01-01

    Full Text Available Šio straipsnio tikslas – atskleisti, kokia pagrindinė konceptualioji metafora vyrauja šiuolaikiniame britų politiniame diskurse ir kokie jos struktūriniai elementai sudaro bendro moralinio vertinimo pagrindą. Tyrimui buvo pasirinkta trisdešimt analitinių politinių straipsnių iš The Economist elektroninio archyvo. Straipsniai analizuojami remiantis kognityvinės lingvistikos principais bei kokybiniu analizės metodu, kurie leidžia atskleisti kalbiniuose pasakymuose (linguistic expressions glūdinčias konceptualiąsias metaforas. Nustatyta, kad Britų politikos moralinis vertinimas yra grindžiamas konceptualiąja metafora POLITINIS GYVENIMAS KAIP KELIONĖ. Išanalizavus šios metaforos kalbinę raišką, paaiškėjo, kad straipsniuose vyrauja neigiamas britų politikos vertinimas, atsispindintis konceptualiosios metaforos POLITINIS GYVENIMAS YRA KELIONĖelementų kalbinėje raiškoje, kai politikos veikėjai (1 vaizduojami kaip „dėmėtos reputacijos“ klajūnai, (2 keliaujantys be tikslo, (3 peržengiantys nustatytas ribas, (4 nesugebantys apeiti/įveikti kelyje pasitaikančių kliūčių ir t.t. ------ The present study aims at examining the moral grounds of today’s British political life as reflected in conceptual metaphors of political discourse. The method applied to analyze the moral grounds is that of hypothetical deduction combined with the theoretical framework of cognitive linguistics (qualitative analysis. The research findings reveal that the underlying conceptual metaphor of British critical political discourse is that of POLITICS AS JOURNEY. The use of this metaphorshows the moral unacceptability of today’s British political life due to the failed moral obligations of British politicians.

  18. Morality through Metaphor: a Cross-Linguistic Analysis of Political Discourse. Moralės metafora: gretinamoji politinio diskurso analizė

    Directory of Open Access Journals (Sweden)

    Liudmila Arcimavičienė

    2008-01-01

    Full Text Available Šio straipsnio tikslas – nustatyti moralės modelius, analizuojant konceptualiąją metaforą politiniame diskurse anglų ir lietuvių kalbose. Remtasi analitiniais straipsniais politikos temomis. Jie pasitelkti iš Interneto tinklalapių www.politika.lt ir www.economist.com elektroninio archyvo. Straipsniai anali­zuojami remiantis kognityvinės lingvistikos principais bei kokybiniu analizės metodu (Fauconnier & Turner 2002; Kövecses 2005; Lakoff & Johnson 1997, Lakoff 2005; Turner 1994, kurie leidžia atskleisti kalbiniuose pasakymuose (linguistic expressions glūdinčias konceptualiąsias metaforas. Kalbiniai pasakymai buvo skirstomi pagal tris moralinio vertinimo modelius: (1 Huxley, kuris apibrėžia moralę kaip žmonių sąmoningai sukurtą vertinimo skalę, reikalingą kovoje su žmogaus įgimtomis blogybėmis, (2 Kanto požiūris į moralę, kaip į racionalų veiksmą glaudžiai siejamą su pareigomis, bei galiausiai (3 integruotas požiūris, kai moralus elgesys suvokiamas kaip sentimentų ir emocinių reakcijų pasekmė (Black 1995; Boehm 2000; Flack & de Waal 2002. Išanalizavus konceptualiųjų metaforų kalbinę raišką paaiškėjo, kad straipsniuose vyrauja metaforos POLITIKA KAIP JĖGA ir POLITIKA KAIP TARPUSAVIO SANTYKIAI.

  19. Poemele homerice în veșminte românești. O analiză diacronică (I

    Directory of Open Access Journals (Sweden)

    Petre Gheorghe Bârlea

    2015-07-01

    Full Text Available Lucrarea pe care o propunem vizează istoria traducerilor românești ale poemelor homerice, din perspectiva evoluției limbii române literare. Pornim de la premisa că orice asemenea traducere reprezintă o probă de virtuozitate nu numai pentru traducătorul în cauză, ci și pentru limba și cultura modernă respectivă, așa încît este interesant de studiat modul în care dezvoltarea exegezei homerice și a teoriilor traductologice se manifestă în paralel cu etapele evoluției limbilor moderne. Grila de analiză va include, așadar, principii, metode și instrumente de lucru ale domeniilor amintite aici (istoria limbii, traductologie, dar și elemente împrumutate din gramatica constrastiv-tipologică, din filologie, în sensul restrîns al conceptului, din teoria mentalităților, istoria culturală ș.a. Demersul nostru evidențiază faptul că evoluția istorică a actului traducerii este marcată, în mod firesc, de personalitatea traducătorului (opțiuni teoretice, ideologice, pe lîngă competențe lingvistice, har poetic etc., dar și de contextul cultural al epocii și al spațiului respectiv. Pentru cultura română, cel puțin, putem constata că, în ansamblu, versiunea cea mai recentă este și cea mai reușită.

  20. Quiet time enhancements over African latitudes

    Science.gov (United States)

    Orford, Nicola; Katamzi, Zama; Buresova, Dalia

    2016-07-01

    F2 layer disturbances not related to geomagnetic activity are known as quiet time enhancements (QTEs). The phenomenon of QTEs has not yet been studied over African latitudes. We therefore explore the occurrence of QTEs over Africa in order to expand our knowledge on the behaviour of the ionosphere over this region. Several GPS stations in the middle to equatorial latitudes, during the solar minimum (2009) and near solar maximum (2013), are used. This data was examined for possible trends in variation with solar cycle, season and latitude as well as time of commencement of enhancements. Over the southern mid-latitude region of Africa we have observed that the QTEs are more likely to commence during the night in both solar minimum and maximum, however a slightly larger portion of daytime commencements during solar minimum than during solar maximum were observed. The total number of enhancements for the solar minimum period appears greater than during solar maximum. A seasonal trend is seen with the maximum number of enhancements occurring in summer during solar minimum and in winter during solar maximum. We explore further whether these trends are mirrored or different at low latitude/equatorial African regions.

  1. Export of Ozone-Poor Air from the Lower Tropical Stratosphere to Mid-latitudes

    Science.gov (United States)

    Spackman, J. R.; Weinstock, E. M.; Anderson, J. G.

    2002-05-01

    Analysis of ozonesonde profiles shows a decline in ozone of 7 to 9%/decade during the past 20 to 30 years in the northern mid-latitude lower stratosphere [Logan et al., 1999], exposing the large population at these latitudes to increased health risks. Heterogeneous processing leading to halogen-catalyzed ozone loss is not expected to occur in the mid-latitude lower stratosphere because in situ measurements indicate the air is consistently undersaturated and low in ClO in this region [Smith et al., 2001]. Furthermore, in situ measurements acquired aboard the NASA ER-2 aircraft during SOLVE (SAGE III Ozone Loss and Validation Experiment) suggest that equatorward mixing of ozone-depleted air from the Arctic vortex does not contribute significantly to declines in mid-latitude lower stratospheric ozone. Instead, tracer-tracer correlations from SOLVE indicate that rapid isentropic transport from the lower tropical stratosphere coupled with diabatic descent in mid-latitudes delivers very young, ozone-poor air to the lowermost stratosphere (θ Journal of Geophysical Research, 104, 26373-26399, 1999. Smith, J.B., et al., Mechanisms for midlatitude ozone loss: Heterogeneous chemistry in the lowermost stratosphere?, Journal of Geophysical Research, 106, 1297-1309, 2001.

  2. NORTHERN TANZANIA

    African Journals Online (AJOL)

    inertia, water balance, physiological strength, and susceptibility to predation between adults .... Judd PW and Rose FL 1977 Aspects of the thermal biology of the Texas tortoise ... pctrdolis lmheoeki) and their conservation in northern Tanzania.

  3. Dependence of Arctic climate on the latitudinal position of stationary waves and to high-latitudes surface warming

    Science.gov (United States)

    Shin, Yechul; Kang, Sarah M.; Watanabe, Masahiro

    2017-02-01

    Previous studies suggest large uncertainties in the stationary wave response under global warming. Here, we investigate how the Arctic climate responds to changes in the latitudinal position of stationary waves, and to high-latitudes surface warming that mimics the effect of Arctic sea ice loss under global warming. To generate stationary waves in an atmospheric model coupled to slab ocean, a series of experiments is performed where the thermal forcing with a zonal wavenumber-2 (with zero zonal-mean) is prescribed at the surface at different latitude bands in the Northern Hemisphere. When the stationary waves are generated in the subtropics, the cooling response dominates over the warming response in the lower troposphere due to cloud radiative effects. Then, the low-level baroclinicity is reduced in the subtropics, which gives rise to a poleward shift of the eddy driven jet, thereby inducing substantial cooling in the northern high latitudes. As the stationary waves are progressively generated at higher latitudes, the zonal-mean climate state gradually becomes more similar to the integration with no stationary waves. These differences in the mean climate affect the Arctic climate response to high-latitudes surface warming. Additional surface heating over the Arctic is imposed to the reference climates in which the stationary waves are located at different latitude bands. When the stationary waves are positioned at lower latitudes, the eddy driven jet is located at higher latitude, closer to the prescribed Arctic heating. As baroclinicity is more effectively perturbed, the jet shifts more equatorward that accompanies a larger reduction in the poleward eddy transport of heat and momentum. A stronger eddy-induced descending motion creates greater warming over the Arctic. Our study calls for a more accurate simulation of the present-day stationary wave pattern to enhance the predictability of the Arctic warming response in a changing climate.

  4. Asthma prevalence associated with geographical latitude and regional insolation in the United States of America and Australia.

    Science.gov (United States)

    Krstić, Goran

    2011-04-08

    It has been proposed that vitamin D deficiency may be responsible for an increase in the prevalence of allergic diseases and asthma worldwide. Human ability to generate physiologically required quantities of vitamin D through sun exposure is decreasing with increasing geographical latitude. Considering that vitamin D deficiency is usually due to lack of outdoor sun exposure, this study is designed to test the hypothesis that a higher prevalence of asthma should be expected at high relative to low geographical latitudes. Linear regression analyses are performed on asthma prevalence in the U.S. adult population vs. geographical latitude, insolation, air temperature, and air pollution (PM(2.5)) for 97 major metropolitan/micropolitan statistical areas of the continental United States of America and on general population asthma prevalence vs. geographical latitude in eight metropolitan areas of Australia. A 10° change in geographical latitude from southern to northern regions of the Eastern Seaboard is associated with a 2% increase in adult asthma prevalence (pinsolation in winter months is almost as strong as latitude in its ability to explain the observed spatial variation in the prevalence of asthma (r(2) = 0.43; pinsolation and asthma prevalence worldwide. The results of this study suggest that, as a known modulator of the immune response closely linked with the geographical latitude and erythemal UV irradiation, vitamin D may play an important role in the development/exacerbation of asthma.

  5. Analysis of the Methods of Water Systems State Estimation Vandens sistemų būsenos įvertinimo metodų analizė

    Directory of Open Access Journals (Sweden)

    Marius Šileika

    2010-04-01

    be unsuitable for fast determination of the water system state. To estimate the water system state reliably, authors of this paper recommend adapting the method based on the parameters of thermodynamic nature.Vandens sistemų būsenos įvertinimo metodų analizė

  6. Climate Effects on High Latitude Daphnia via Food Quality and Thresholds

    Science.gov (United States)

    Przytulska, Anna; Bartosiewicz, Maciej; Rautio, Milla; Dufresne, France; Vincent, Warwick F.

    2015-01-01

    Climate change is proceeding rapidly at high northern latitudes and may have a variety of direct and indirect effects on aquatic food webs. One predicted effect is the potential shift in phytoplankton community structure towards increased cyanobacterial abundance. Given that cyanobacteria are known to be a nutritionally poor food source, we hypothesized that such a shift would reduce the efficiency of feeding and growth of northern zooplankton. To test this hypothesis, we first isolated a clone of Daphnia pulex from a permafrost thaw pond in subarctic Québec, and confirmed that it was triploid but otherwise genetically similar to a diploid, reference clone of the same species isolated from a freshwater pond in southern Québec. We used a controlled flow-through system to investigate the direct effect of temperature and indirect effect of subarctic picocyanobacteria (Synechococcus) on threshold food concentrations and growth rate of the high latitude clone. We also compared the direct effect of temperature on both Daphnia clones feeding on eukaryotic picoplankton (Nannochloropsis). The high latitude clone had a significantly lower food threshold for growth than the temperate clone at both 18 and 26°C, implying adaptation to lower food availability even under warmer conditions. Polyunsaturated fatty acids were present in the picoeukaryote but not the cyanobacterium, confirming the large difference in food quality. The food threshold for growth of the high latitude Daphnia was 3.7 (18°C) to 4.2 (26°C) times higher when fed Synechococcus versus Nannochloropsis, and there was also a significant negative effect of increased temperature and cyanobacterial food on zooplankton fatty acid content and composition. The combined effect of temperature and food quality on the performance of the high latitude Daphnia was greater than their effects added separately, further indicating the potentially strong indirect effects of climate warming on aquatic food web processes. PMID

  7. Obliquity forcing of low-latitude climate

    NARCIS (Netherlands)

    Bosmans, J.H.C.; Hilgen, F.J.; Tuenter, Erik; Lourens, L.J.

    2015-01-01

    The influence of obliquity, the tilt of the Earth's rotational axis, on incoming solar radiation at low latitudes is small, yet many tropical and subtropical palaeoclimate records reveal a clear obliquity signal. Several mechanisms have been proposed to explain this signal, such as the remote

  8. Obliquity forcing of low-latitude climate

    NARCIS (Netherlands)

    Bosmans, J.H.C.; Hilgen, F.J.; Tuenter, Erik; Lourens, L.J.

    2015-01-01

    The influence of obliquity, the tilt of the Earth's rotational axis, on incoming solar radiation at low latitudes is small, yet many tropical and subtropical palaeoclimate records reveal a clear obliquity signal. Several mechanisms have been proposed to explain this signal, such as the remote influe

  9. Speciation, Ecological Opportunity, and Latitude (American Society of Naturalists Address).

    Science.gov (United States)

    Schluter, Dolph

    2016-01-01

    Evolutionary hypotheses to explain the greater numbers of species in the tropics than the temperate zone include greater age and area, higher temperature and metabolic rates, and greater ecological opportunity. These ideas make contrasting predictions about the relationship between speciation processes and latitude, which I elaborate and evaluate. Available data suggest that per capita speciation rates are currently highest in the temperate zone and that diversification rates (speciation minus extinction) are similar between latitudes. In contrast, clades whose oldest analyzed dates precede the Eocene thermal maximum, when the extent of the tropics was much greater than today, tend to show highest speciation and diversification rates in the tropics. These findings are consistent with age and area, which is alone among hypotheses in predicting a time trend. Higher recent speciation rates in the temperate zone than the tropics suggest an additional response to high ecological opportunity associated with low species diversity. These broad patterns are compelling but provide limited insights into underlying mechanisms, arguing that studies of speciation processes along the latitudinal gradient will be vital. Using threespine stickleback in depauperate northern lakes as an example, I show how high ecological opportunity can lead to rapid speciation. The results support a role for ecological opportunity in speciation, but its importance in the evolution of the latitudinal gradient remains uncertain. I conclude that per capita evolutionary rates are no longer higher in the tropics than the temperate zone. Nevertheless, the vast numbers of species that have already accumulated in the tropics ensure that total rate of species production remains highest there. Thus, tropical evolutionary momentum helps to perpetuate the steep latitudinal biodiversity gradient.

  10. High-Latitude Topside Ionospheric Vertical Electron Density Profile Changes in Response to Large Magnetic Storms

    Science.gov (United States)

    Benson, Robert F.; Fainberg, Joseph; Osherovich, Vladimir A.; Truhlik, Vladimir; Wang, Yongli; Bilitza, Dieter; Fung, Shing F.

    2016-01-01

    Large magnetic-storm-induced changes were detected in high-latitude topside vertical electron density profiles Ne(h) in a database of profiles and digital topside ionograms, from the International Satellites for Ionospheric Studies (ISIS) program, that enabled Ne(h) profiles to be obtained in nearly the same region of space before, during, and after a major magnetic storm (Dst -100nT). Storms where Ne(h) profiles were available in the high-latitude Northern Hemisphere had better coverage of solar wind parameters than storms with available Ne(h) profiles in the high-latitude Southern Hemisphere. Large Ne(h) changes were observed during all storms, with enhancements and depletions sometimes near a factor of 10 and 0.1, respectively, but with substantial differences in the responses in the two hemispheres. Large spatial andor temporal Ne(h) changes were often observed during Dst minimum and during the storm recovery phase. The storm-induced Ne(h) changes were the most pronounced and consistent in the Northern Hemisphere in that large enhancements were observed during winter nighttime and large depletions during winter and spring daytime. The limited available cases suggested that these Northern Hemisphere enhancements increased with increases of the time-shifted solar wind velocity v, magnetic field B, and with more negative values of the B components except for the highest common altitude (1100km) of the profiles. There was also some evidence suggesting that the Northern Hemisphere depletions were related to changes in the solar wind parameters. Southern Hemisphere storm-induced enhancements and depletions were typically considerably less with depletions observed during summer nighttime conditions and enhancements during summer daytime and fall nighttime conditions.

  11. Climatic variability, plant phenology, and northern ungulates

    Energy Technology Data Exchange (ETDEWEB)

    Post, E.; Stenseth, N.C. [Univ. of Oslo (Norway)

    1999-06-01

    Models of climate change predict that global temperatures and precipitation will increase within the next century, with the most pronounced changes occurring in northern latitudes and during winter. A large-scale atmospheric phenomenon, the North Atlantic Oscillation (NAO), is a strong determinant of both interannual variation and decadal trends in temperatures and precipitation during winter in northern latitudes, and its recent persistence in one extreme phase may be a substantial component of increases in global temperatures. Hence, the authors investigated the influences of large-scale climatic variability on plant phenology and ungulate population ecology by incorporating the NAO in statistical analyses of previously published data on: (1) the timing of flowering by plants in Norway, and (2) phenotypic and demographic variation in populations of northern ungulates. The authors analyzed 137 time series on plant phenology for 13 species of plants in Norway spanning up to 50 yr and 39 time series on phenotypic and demographic traits of 7 species of northern ungulates from 16 populations in North America and northern Europe spanning up to 30 yr.

  12. Multiple sclerosis in South America: month of birth in different latitudes does not seem to interfere with the prevalence or progression of the disease

    Directory of Open Access Journals (Sweden)

    Yara Dadalti Fragoso

    2013-09-01

    Full Text Available Objective To assess whether the month of birth in different latitudes of South America might influence the presence or severity of multiple sclerosis (MS later in life. Methods Neurologists in four South American countries working at MS units collected data on their patients' month of birth, gender, age, and disease progression. Results Analysis of data from 1207 MS patients and 1207 control subjects did not show any significant variation in the month of birth regarding the prevalence of MS in four latitude bands (0–10; 11–20; 21–30; and 31–40 degrees. There was no relationship between the month of birth and the severity of disease in each latitude band. Conclusion The results from this study show that MS patients born to mothers who were pregnant at different Southern latitudes do not follow the seasonal pattern observed at high Northern latitudes.

  13. High-latitude oceanic variability associated with the 18.6-year nodal tide

    Science.gov (United States)

    Royer, Thomas C.

    1993-03-01

    Ocean temperatures in the upper 250 m in the northern North Pacific (60°N, 149°W) increased by more than 1°C from 1972 to 1986 but are now decreasing. Subsurface temperature anomalies are well correlated (˜0.58) with the air temperature anomalies at Sitka, Alaska; hence the coastal air temperatures can be used as a proxy data set to extend the ocean temperature time series back to 1828. Up to 30% of the low-frequency variance can be accounted for with the 18.6-year nodal signal. Additionally, spectral analysis of these air temperature variations indicates a significant low-frequency peak in the range of the 18.6-year signal. Similar low-frequency signals have been reported for Hudson Bay air temperatures since 1700, for sea surface temperatures in the North Atlantic from 1876 to 1939, and for sea level in the high-latitude southern hemisphere. The water column temperature variations presented here are the first evidence that the upper ocean is responding to this very long period tidal forcing. An enhanced high-latitude response to the 18.6-year forcing is predicted by equilibrium tide theory, and it should be most evident at latitudes poleward of about 50°. These low-frequency ocean-atmosphere variations must be considered in high-latitude assessments of global climate change, since they are of the same magnitude as many of the predicted global changes.

  14. Spacecraft design project: High latitude communications satellite

    Science.gov (United States)

    Josefson, Carl; Myers, Jack; Cloutier, Mike; Paluszek, Steve; Michael, Gerry; Hunter, Dan; Sakoda, Dan; Walters, Wes; Johnson, Dennis; Bauer, Terry

    1989-01-01

    The spacecraft design project was part of AE-4871, Advanced Spacecraft Design. The project was intended to provide experience in the design of all major components of a satellite. Each member of the class was given primary responsibility for a subsystem or design support function. Support was requested from the Naval Research Laboratory to augment the Naval Postgraduate School faculty. Analysis and design of each subsystem was done to the extent possible within the constraints of an eleven week quarter and the design facilities (hardware and software) available. The project team chose to evaluate the design of a high latitude communications satellite as representative of the design issues and tradeoffs necessary for a wide range of satellites. The High-Latitude Communications Satellite (HILACS) will provide a continuous UHF communications link between stations located north of the region covered by geosynchronous communications satellites, i.e., the area above approximately 60 N latitude. HILACS will also provide a communications link to stations below 60 N via a relay Net Control Station (NCS), which is located with access to both the HILACS and geosynchronous communications satellites. The communications payload will operate only for that portion of the orbit necessary to provide specified coverage.

  15. Environmental harshness, latitude and incipient speciation.

    Science.gov (United States)

    Weir, Jason T

    2014-02-01

    Are rates of evolution and speciation fastest where diversity is greatest - the tropics? A commonly accepted theory links the latitudinal diversity gradient to a speciation pump model whereby the tropics produce species at a faster rate than extra-tropical regions. In this issue of Molecular Ecology, Botero et al. () test the speciation pump model using subspecies richness patterns for more than 9000 species of birds and mammals as a proxy for incipient speciation opportunity. Rather than using latitudinal centroids, the authors investigate the role of various environmental correlates of latitude as drivers of subspecies richness. Their key finding points to environmental harshness as a positive predictor of subspecies richness. The authors link high subspecies richness in environmental harsh areas to increased opportunities for geographic range fragmentation and/or faster rates of trait evolution as drivers of incipient speciation. Because environmental harshness generally increases with latitude, these results suggest that opportunity for incipient speciation is lowest where species richness is highest. The authors interpret this finding as incompatible with the view of the tropics as a cradle of diversity. Their results are consistent with a growing body of evidence that reproductive isolation and speciation occur fastest at high latitudes.

  16. Variations in Extratropical Cyclone Activity in Northern East Asia

    Institute of Scientific and Technical Information of China (English)

    WANG Xinmin; ZHAI Panmao; WANG Cuicui

    2009-01-01

    Based on an improved objective cyclone detection and tracking algorithm, decadal variations in extratropical cyclones in northern East Asia are studied by using the ECMWF 40 Year Reanalysis (ERA-40) sea-level pressure data during 1958-2001. The results reveal that extratropical cyclone activity has displayed clear seasonal, interannual, and decadal variability in northern East Asia. Spring is the season when cyclones occur most frequently. The spatial distribution of extratropical cyclones shows that cyclones occur mainly within the 40°-50°N latitudinal band in northern East Asia, and the most frequent region of occurrence is in Mongolia. Furthermore, this study also reveals the fact that the frequency of extratropical cyclones has significantly decreased in the lower latitude region of northern East Asia during 1958-2001, but dccadal variability has dominated in higher latitude bands, with frequent cyclone genesis. The intensity of extratropical cyclones has decreased on an annual and seasonal basis. Variation of the annual number of cyclones in northern East Asia is associated with the mean intensity of the baroclinic frontal zone, which is influenced by climate warming in the higher latitudes. Moreover, the dipole structure of extratopical cyclone change, with increases in the north and decreases in the southern part of northern East Asia, is related to the northward movement of the baroclinic frontal zone on either side of 110°E.

  17. Šunų ir kačių stomatitų, gingivitų, periodontitų susirgimų analizė Kauno miesto "X" ir "Y" veterinarijos klinikose 2011 - 2013 metais

    OpenAIRE

    Vingytė, Aistė

    2014-01-01

    Darbo pavadinimas: Šunų ir kačių stomatitų, gingivitų ir periodontitų susirgimų analizė Kauno miesto “X” ir “Y” veterinarijos klinikose 2011 – 2013 metais. Lietuvos Sveikatos Mokslų Universitetas, Veterinarijos akademija, Veterinarijos fakultetas. Darbo apimtis 41 lapas. Darbe yra 22 paveikslai. Naudotų literatūros šaltinių kiekis: 34. Darbe buvo ištirti šunys ir katės, sergantys stomatitu, gingivitu ir periodontitu. Pasirinktos „X“ ir „Y“ klinikos Kaune. Darbas buvo at...

  18. Evidence for Amazonian mid-latitude glaciation on Mars from impact crater asymmetry

    Science.gov (United States)

    Conway, Susan J.; Mangold, Nicolas

    2013-07-01

    We find that crater slopes in the mid-latitudes of Mars have a marked north-south asymmetry, with the pole-facing slopes being shallower. We mapped impact craters in two southern hemisphere sites (Terra Cimmeria and Noachis Terra) and one northern hemisphere site (Acidalia Planitia) and used elevation data from the High Resolution Stereo Camera (HRSC) onboard Mars Express to find the maximum slope of impact crater walls in the four cardinal directions. Kreslavsky and Head (Kreslavsky, M.A., Head, J.W. [2003]. Geophys. Res. Lett. 30), using Mars Orbiter Laser Altimeter (MOLA) track data, also found that, in general, conjugate slopes are shallower in the pole-facing direction, but over a narrower (˜10°) and more constrained latitude band. They linked the asymmetry to active-layer formation (thaw) at high obliquity. However, Parsons and Nimmo (Parsons, R.A., Nimmo, F. [2009]. J. Geophys. Res. 114) studied crater asymmetry using MOLA gridded data and found no evidence of a relationship between crater asymmetry and latitude. Our work supports the observations of Kreslavsky and Head (Kreslavsky, M.A., Head, J.W. [2003]. Geophys. Res. Lett. 30), and shows that asymmetry is also found on conjugate crater slopes below the resolution of MOLA, over a wider latitude band than found in their work. We do not systematically find a sudden transition to asymmetric craters with latitude as expected for thaw-related processes, such as solifluction, gelifluction, or gully formation. The formation of gullies should produce the opposite sense of asymmetry to our observations, so cannot explain them despite the mid-latitude location and pole-facing preferences of gullies. We instead link this asymmetry to the deposition of ice-rich crater deposits, where the base of pole-facing slopes receive ten to hundreds of meters of additional net deposition, compared to equator-facing ones over the mid-latitudes. In support of this hypothesis we found that craters in Terra Cimmeria that have

  19. A Study of Steady Magnetospheric Convection Using High Latitude Magnetometers

    Science.gov (United States)

    de Silva, J. T.; Erickson, K. N.; Engebretson, M. J.; Murr, D. L.; Hughes, W. J.

    2001-05-01

    Magnetometer data from the MACCS and CANOPUS arrays in northern North America have been analyzed during two of the intervals of steady magnetospheric convection identified by the GEM community, January 29-30 and February 3-4, 1998. These intervals were characterized by extended periods of southward interplanetary magnetic field (negative IMF Bz), and by the absence of substorms. The patterns of ionospheric current flow on the dayside were found to be in general agreement with the disturbance current system, SD, originally described by Silsbee and Vestine [1942]. This indicates that during extended periods of southward IMF the convection on the dayside is the same whether or not there are substorms. When plasma flow patterns measured by the SuperDARN auroral radar network were available for comparison, these patterns agreed with the patterns inferred from magnetometers. Further study will investigate convection patterns on the nightside, and a similar study of convection for the southern high latitude region will be conducted using data from Antarctic stations.

  20. Latitude, elevational climatic zonation and speciation in New World vertebrates.

    Science.gov (United States)

    Cadena, Carlos Daniel; Kozak, Kenneth H; Gómez, Juan Pablo; Parra, Juan Luis; McCain, Christy M; Bowie, Rauri C K; Carnaval, Ana C; Moritz, Craig; Rahbek, Carsten; Roberts, Trina E; Sanders, Nathan J; Schneider, Christopher J; VanDerWal, Jeremy; Zamudio, Kelly R; Graham, Catherine H

    2012-01-07

    Many biodiversity hotspots are located in montane regions, especially in the tropics. A possible explanation for this pattern is that the narrow thermal tolerances of tropical species and greater climatic stratification of tropical mountains create more opportunities for climate-associated parapatric or allopatric speciation in the tropics relative to the temperate zone. However, it is unclear whether a general relationship exists among latitude, climatic zonation and the ecology of speciation. Recent taxon-specific studies obtained different results regarding the role of climate in speciation in tropical versus temperate areas. Here, we quantify overlap in the climatic distributions of 93 pairs of sister species of mammals, birds, amphibians and reptiles restricted to either the New World tropics or to the Northern temperate zone. We show that elevational ranges of tropical- and temperate-zone species do not differ from one another, yet the temperature range experienced by species in the temperate zone is greater than for those in the tropics. Moreover, tropical sister species tend to exhibit greater similarity in their climatic distributions than temperate sister species. This pattern suggests that evolutionary conservatism in the thermal niches of tropical taxa, coupled with the greater thermal zonation of tropical mountains, may result in increased opportunities for allopatric isolation, speciation and the accumulation of species in tropical montane regions. Our study exemplifies the power of combining phylogenetic and spatial datasets of global climatic variation to explore evolutionary (rather than purely ecological) explanations for the high biodiversity of tropical montane regions.

  1. Local genetic adaptation generates latitude-specific effects of warming on predator-prey interactions.

    Science.gov (United States)

    De Block, Marjan; Pauwels, Kevin; Van Den Broeck, Maarten; De Meester, Luc; Stoks, Robby

    2013-03-01

    Temperature effects on predator-prey interactions are fundamental to better understand the effects of global warming. Previous studies never considered local adaptation of both predators and prey at different latitudes, and ignored the novel population combinations of the same predator-prey species system that may arise because of northward dispersal. We set up a common garden warming experiment to study predator-prey interactions between Ischnura elegans damselfly predators and Daphnia magna zooplankton prey from three source latitudes spanning >1500 km. Damselfly foraging rates showed thermal plasticity and strong latitudinal differences consistent with adaptation to local time constraints. Relative survival was higher at 24 °C than at 20 °C in southern Daphnia and higher at 20 °C than at 24 °C, in northern Daphnia indicating local thermal adaptation of the Daphnia prey. Yet, this thermal advantage disappeared when they were confronted with the damselfly predators of the same latitude, reflecting also a signal of local thermal adaptation in the damselfly predators. Our results further suggest the invasion success of northward moving predators as well as prey to be latitude-specific. We advocate the novel common garden experimental approach using predators and prey obtained from natural temperature gradients spanning the predicted temperature increase in the northern populations as a powerful approach to gain mechanistic insights into how community modules will be affected by global warming. It can be used as a space-for-time substitution to inform how predator-prey interaction may gradually evolve to long-term warming.

  2. 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

    2016-11-01

    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.

  3. The Structure of Galactic Gas at High Latitudes: The Southern Polar Cap

    Science.gov (United States)

    Gosachinskii, I. V.; Il'in, G. N.; Prozorov, V. A.

    2004-04-01

    We analyze the angular structure of the 21-cm interstellar neutral hydrogen emission at six and seven declinations in the northern (published previously) and southern polar caps of the Galaxy (Galactic latitudes from -40 deg to -90 deg), respectively, with an extent of 90 deg in right ascension. The RATAN-600 radio telescope has a beam width averaged over these regions of 2.0' x 30'. One-dimensional power spectra for the angular distribution of interstellar neutral hydrogen emission were computed in each 6.3-km/s-wide spectral channel by using the standard Fast Fourier Transform (FFT) code and were smoothed over 1 hour in right ascension. The Galactic latitude dependence of the mean parameters for the sky distribution of H I line emission at high latitudes was found to correspond to the distribution of gas in the form of a flat layer only in the northern region, while in the southern cap, the gas distribution is much less regular. In addition, the mean H I radial velocities are negative everywhere (-3.7 +/- 3.0 km/s in the north and -6.0+/-2.4 km/s in the south). The power spectra of the angular fluctuations in the range of angular periods from 10' to 6 deg appear as power laws. However, the spectral indices change greatly over the sky: from -3 to -1.2; on average, as the Galactic latitude increases and the H I column density decreases, the fluctuation spectrum of the interstellar gas emission becomes flatter. In the northern polar region, this behavior is much more pronounced, which probably stems from the fact that the gas column density in the south is generally a factor of 2 or 3 higher than that in the north. Therefore, the spectra are, on average, also steeper in the south, but the dependence on Galactic latitude is weaker. Using simulations, we show that the observed power-law spectrum of the H I emission distribution can be obtained in terms of not only a turbulent, but also a cloud model of interstellar gas if we use our previous spectra of the diameters

  4. Shallow food for deep divers: Dynamic foraging behavior of male sperm whales in a high latitude habitat

    DEFF Research Database (Denmark)

    Teloni, Valeria; Johnson, M.P.; Miller, P.J.O.

    2008-01-01

    Groups of female and immature sperm whales live at low latitudes and show a stereotypical diving and foraging behavior with dives lasting about 45 min to depths of between 400 and 1200 m. In comparison, physically mature male sperm whales migrate to high latitudes where little is known about...... their foraging behavior and ecology. Here we use acoustic recording tags to study the diving and acoustic behavior of male sperm whales foraging off northern Norway. Sixty-five hours of tag data provide detailed information about the movements and sound repertoire of four male sperm whales performing 83 dives...... epipelagic prey, is consistent with the hypothesis that male sperm whales may migrate to high latitudes to access a productive, multi-layered foraging habitat....

  5. Effect of Latitude on Vitamin D Levels.

    Science.gov (United States)

    Leary, Patrick F; Zamfirova, Ina; Au, Johnathan; McCracken, Ward H

    2017-07-01

    Vitamin D levels have been linked to bone health and to numerous diseases; however, an element that lacks substantial direct data and limits the evidence basis regarding whom to screen for vitamin D deficiency is the effect of latitude on vitamin D levels. To determine whether latitude influences vitamin D levels and to investigate the influence of other factors that may affect vitamin D levels, including sex, race, skin type, and body mass index. Osteopathic medical students were recruited from campuses in Bradenton, Florida, and Erie, Pennsylvania. Surveys were administered to obtain demographic information, and blood samples were drawn to measure total vitamin D levels. Two-sample t tests, Fisher exact test, and logistic regression was used to assess differences in total vitamin D levels between the 2 locations. A total of 359 medical students (aged 22-57 years) were included in the study, 194 at the Bradenton campus and 214 at the Erie campus. The mean (SD) vitamin D level was 34.5 (11.8) ng/mL among participants in Bradenton and 28.1 (12.4) ng/mL among participants in Erie. Logistic regression models revealed an adjusted OR of 3.3 (95% CI, 1.73-6.4) for deficient total vitamin D among Erie students. Non-white race, male sex, and high body mass index were also statistically significant risk factors for vitamin D deficiency in regression models (P<.05). Latitude was found to be a statistically significant risk factor for vitamin D deficiency. Additionally, the findings suggest that persons with darker skin tone and, to a lesser degree, men and persons who are overweight or obese are also at increased risk for vitamin D deficiency. Physicians should be cognizant of these risk factors when deciding whom to screen.

  6. Saturn Chorus as a Function of Latitude

    Science.gov (United States)

    Menietti, J. D.; Hospodarsky, G. B.; Gurnett, D. A.; Shprits, Y.

    2013-12-01

    Not only the dust but also the spatial scale of Saturn, including the background magnetic field inhomogeneity, make the study of whistler mode plasma wave emissions at Saturn quite different from Earth. The significant decrease in chorus intensity nearest the Saturn magnetic equator along a nearly constant L shell has already been reported. In the current study we analyze all known examples of these data and report the collective functional dependence of chorus intensity and wave normal angle, as well as density and magnetic inhomogeneity versus latitude. These values are important in the modeling of pitch angle scattering and possible electron acceleration at Saturn.

  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. High-latitude regions of Siberia and Northeast Russia in the Paleogene: Stratigraphy, flora, climate, coal accumulation

    Science.gov (United States)

    Akhmetiev, M. A.

    2015-07-01

    The geological structure and development history of superposed depressions on the Arctic coast of East Siberia and Bering Sea region (Chukotka, Koryakiya, northern Kamchatka) in the Early Paleogene are considered with the analysis of their flora and climatic parameters. The paleofloral analysis revealed thermophilic assemblages that reflect phases of maximum warming at the Paleocene-Eocene transition and in the Early Eocene. The appearance of thermophilic plants (Magnoliaceae, Myrtaceae, Lauraceae, Araliaceae, Loranthaceae, and others) in the Siberian segment of the Arctic region is explained by the stable atmospheric heat transfer from the Tethys to higher latitudes and absence of the latitudinal orographic barrier (Alpine-Himalayan belt). The plants migrated to high latitudes also along the meridional seaway that connected the Tethys with the Arctic Ocean via marine basins of the Eastern Paratethys, Turgai Strait, and West Siberia. The migration from the American continent was realized along the southern coast of Beringia under influence of a warm current flowing from low latitudes along the western coast of North America. The palm genus Sabal migrated to northern Kamchatka and Koryakiya precisely in this way via southern Alaska. In the Oligocene, shallow-water marine sediments in high-latitude regions were replaced by terrestrial facies. The Late Oligocene was marked by maximum cooling. Coal accumulation in Northeast Russia through the Paleogene is reviewed.

  9. TIDI observations relating to low latitude aeronomy

    Science.gov (United States)

    Niciejewski, R.; Killeen, T.; Kafkalidis, J.; Wu, Q.; Skinner, W.; Solomon, S.; Ortland, D.; Gell, D.; Gablehouse, D.; Johnson, R.

    2003-04-01

    The TIDI instrument aboard the TIMED satellite has been observing the neutral winds in the upper atmosphere on a routine basis since early January 2002. The instrument simultaneously samples the thin limb of the Earth with four separate telescopes providing two forward views and two rearward views, one of each on either side of the orbital path. At equator crossings, these two side views are separated by about 30 degrees of longitude at the tangent point altitude, or 2 hours of local time. Thus, on any orbit TIDI obtains two horizontal vector winds at the dayside equator crossing and two on the nightside equator crossing as well as for all low latitudes. This is significantly greater than the data output of either the HRDI or the DE-2 satellite observations. This paper will describe the climatology that has been obtained by the TIDI instrument since early 2002 for low latitudes. The precession rate of TIMED supports two month averaging of data sets in order to sample all local solar time. Tidal structure is evident in the resulting zonal and meridional winds for mesosphere and lower thermosphere altitudes.

  10. Magnotospheric imaging of high latitude ion outflows

    Directory of Open Access Journals (Sweden)

    D. E. Garrido

    Full Text Available High latitude ion outflows mostly consist of upward streaming O+ and He+ emanating from the ionosphere. At heights above 1000 km, these flows consist of cold and hot components which resonantly scatter solar extreme ultraviolet (EUV light, however, the ion populations respond differently to Doppler shifting resulting from the large relative velocities between the ions and the Sun. The possibility of optical detection of the Doppler effect on the scattering rate will be discussed for the O+ (83.4 nm ions. We have contrasted the EUV solar resonance images of these outflows by simulations of the 30.4 nm He+ and 83.4 nm O+ emissions for both quiet and disturbed geomagnetic conditions. Input data for the 1000 km level has been obtained from the EICS instrument aboard the Dynamics Explorer satellite. Our results show emission rates of 50 and 56 milli-Rayleighs at 30.4 nm for quiet and disturbed conditions and 65 and 75 milli-Rayleighs at 83.4 nm for quiet and disturbed conditions, respectively, obtained for a polar orbiting satellite and viewing radially outward. We also find that an imager at an equatorial distance of 9 RE or more is in a favourable position for detecting ion outflows, particularly when the plasmapause is depressed in latitude. However, an occultation disk is necessary to obscure the bright plasmaspheric emissions.

  11. The prevalence of seasonal affective disorder (SAD) in Greenland is related to latitude.

    Science.gov (United States)

    Kegel, Mogens; Dam, Henrik; Ali, Fatuma; Bjerregaard, Peter

    2009-01-01

    The aim of this study was to determine the prevalence of seasonal affective disorder (SAD) in Greenlanders and Danes living at four different latitudes in Greenland. A Seasonal Pattern Assessment Questionnaire (SPAQ) was mailed to 6021 men and women between the ages of 18 and 59 years living in four different municipalities in Greenland. The recipients were randomly selected from the National Population Register. Approximately 9% of the respondents met the criteria for SAD, and the incidence of SAD varied between a southern municipality and three northern municipalities. The prevalence of SAD was particularly high in northern municipalities. No significant difference was found in the prevalence of SAD between Greenlanders and Danes. The results are comparable with other population studies that have reported a high prevalence of SAD in arctic areas. The clinical implications of our findings and the possibilities for introducing light therapy should be assessed in future studies.

  12. Meta-analysis application process in nursing: A guide intended for methodologyHemşirelikte meta-analiz uygulama süreci: Metodolojiye yönelik bir rehber

    Directory of Open Access Journals (Sweden)

    Ayşe Deliktaş

    2016-04-01

    provide information on the basic principles of meta-analysis, be guidance on the application process and promote the use of the method in the nursing field.   Özet Son yıllarda sağlık alanında bilimsel gelişmelerin var olması ve iyi bakım uygulamalarına olan ilginin artması gibi nedenlerle kanıta dayalı uygulamaya olan ilgi artmıştır. Kanıta dayalı uygulamalar bakımın kalitesini iyileştirir iken hemşireliğin profesyonelleşmesine de katkı sağlayacaktır. Ancak, bilimselleşme yolunda yapılmış çalışma sonuçlarına bakıldığında; sonuçlar arasında çelişkilerin olduğu, her bir çalışmanın farklı kalitelerde olduğu görülmektedir. Çalışmalar arasındaki çelişkilerin eleştirel değerlendirilmesi ve farklılıkların nedenlerinin istatistiksel olarak analiz edilmesi için meta-analiz yöntemi geliştirilmiştir. Aynı konu ile ilgili birbirinden bağımsız farklı yer ve zamanda yapılan çalışma sonuçlarının istatistiksel analizine meta-analiz denilmektedir. Meta-analiz; bir etkinin varlığını ve büyüklüğünü ortaya koyan, çalışmalar arasında var olan tutarsızlıkları ve nedenlerini inceleyen, araştırma sonuçlarını daha önce incelenmemiş olan yeni parametreler ile inceleyebilen, böylece olası yeni ilişkilileri ortaya çıkartabilen ve daha sonraki yapılacak çalışmalara yeni yaklaşımlar getirebilen bir analiz yöntemidir. Meta-analiz uygulama süreci ise zaman alıcı ve sabır isteyen bir süreçtir. Meta-analiz uygulama basamakları; araştırma konusunun ve sorularının belirlenmesi, literatür araştırmasının yapılması, ölçütlerin belirlenmesi, bulunan makalelerin sınıflanması ve elenmesi, verilerin kodlanması, çalışmaların kalitesinin değerlendirilmesi, istatistiksel analizlerin yapılması ve çalışma sonuçlarının raporlanmasını içermektedir. Birçok yararının olmasına rağmen, uygun çalışmaların belirlenmesinin zor ve zaman alıcı olması, ilgili

  13. Dust transport into Martian polar latitudes

    Science.gov (United States)

    Murphy, J. R.; Pollack, J. B.

    1992-01-01

    The presence of suspended dust in the Martian atmosphere, and its return to the planet's surface, is implicated in the formation of the polar layered terrain and the dichotomy in perennial CO2 polar cap retention in the two hemispheres. A three dimensional model was used to study Martian global dust storms. The model accounts for the interactive feedbacks between the atmospheric thermal and dynamical states and an evolving radiatively active suspended dust load. Results from dust storm experiments, as well as from simulations in which there is interest in identifying the conditions under which surface dust lifting occurs at various locations and times, indicate that dust transport due to atmospheric eddy motions is likely to be important in the arrival of suspended dust at polar latitudes. The layered terrain in both polar regions of Mars is interpreted as the reality of cyclical episodes of volatile (CO2, H2O) and dust deposition.

  14. High latitude electromagnetic plasma wave emissions

    Science.gov (United States)

    Gurnett, D. A.

    1983-01-01

    The principal types of electromagnetic plasma wave emission produced in the high latitude auroral regions are reviewed. Three types of radiation are described: auroral kilometric radiation, auroral hiss, and Z mode radiation. Auroral kilometric radiation is a very intense radio emission generated in the free space R-X mode by electrons associated with the formation of discrete auroral arcs in the local evening. Theories suggest that this radiation is an electron cyclotron resonance instability driven by an enhanced loss cone in the auroral acceleration region at altitudes of about 1 to 2 R sub E. Auroral hiss is a somewhat weaker whistler mode emission generated by low energy (100 eV to 10 keV) auroral electrons. The auroral hiss usually has a V shaped frequency time spectrum caused by a freqency dependent beaming of the whistler mode into a conical beam directed upward or downward along the magnetic field.

  15. Integrating the effects of latitude and altitude on the spatial differentiation of plant community diversity in a mountainous ecosystem in China

    Science.gov (United States)

    Xu, Manhou; Ma, Li; Jia, Yanyan; Liu, Min

    2017-01-01

    Varying patterns of plant community diversity along geographical gradients are a significant topic in biodiversity research. Here, to explore the integrated effects of latitude and altitude on the plant community diversity in a mountainous ecosystem, we set Guancen Mountain in the northern section, Guandi Mountain in the middle section, and Wulu Mountain in the southern section of the Lvliang Mountains as study areas, and the plant community diversity (basal diameter and height of tree and species diversity indices of shrub and herb) was measured horizontally at different latitude gradients and vertically at different altitude gradients in late July 2015. The results showed that (1) the trees were taller and wider at the middle latitude and higher altitude with a stronger spatial heterogeneity in the structures along the latitudinal and altitudinal gradients. The evergreen tree growth preceded that of the deciduous trees in the higher latitude and lower altitude regions, whereas the deciduous tree growth preceded that of the evergreen trees in the middle latitude and higher altitude regions. (2) Shrubs and herbs tended to grow well in the lower latitude and middle-lower altitude regions. The shrubs had a larger species diversity at lower latitude and lower altitude, but the species diversity of the herbs was not sensitive to the influences of the latitudinal and altitudinal gradients. With the latitude and altitude increasing, perennial herbs tended to grow well at higher latitude and higher altitude, while annual herbs tended to thrive at the middle latitude and lower altitude. In conclusion, environmental deviations caused by latitudinal and altitudinal gradients had great influences on the spatial distributions of the plant community diversity in the Lvliang Mountains. PMID:28323909

  16. Electrodynamics of ionospheric weather over low latitudes

    Science.gov (United States)

    Abdu, Mangalathayil Ali

    2016-12-01

    The dynamic state of the ionosphere at low latitudes is largely controlled by electric fields originating from dynamo actions by atmospheric waves propagating from below and the solar wind-magnetosphere interaction from above. These electric fields cause structuring of the ionosphere in wide ranging spatial and temporal scales that impact on space-based communication and navigation systems constituting an important segment of our technology-based day-to-day lives. The largest of the ionosphere structures, the equatorial ionization anomaly, with global maximum of plasma densities can cause propagation delays on the GNSS signals. The sunset electrodynamics is responsible for the generation of plasma bubble wide spectrum irregularities that can cause scintillation or even disruptions of satellite communication/navigation signals. Driven basically by upward propagating tides, these electric fields can suffer significant modulations from perturbation winds due to gravity waves, planetary/Kelvin waves, and non-migrating tides, as recent observational and modeling results have demonstrated. The changing state of the plasma distribution arising from these highly variable electric fields constitutes an important component of the ionospheric weather disturbances. Another, often dominating, component arises from solar disturbances when coronal mass ejection (CME) interaction with the earth's magnetosphere results in energy transport to low latitudes in the form of storm time prompt penetration electric fields and thermospheric disturbance winds. As a result, drastic modifications can occur in the form of layer restructuring (Es-, F3 layers etc.), large total electron content (TEC) enhancements, equatorial ionization anomaly (EIA) latitudinal expansion/contraction, anomalous polarization electric fields/vertical drifts, enhanced growth/suppression of plasma structuring, etc. A brief review of our current understanding of the ionospheric weather variations and the

  17. Tropical rainfall over the last two millennia: evidence for a low-latitude hydrologic seesaw

    Science.gov (United States)

    Lechleitner, Franziska A.; Breitenbach, Sebastian F. M.; Rehfeld, Kira; Ridley, Harriet E.; Asmerom, Yemane; Prufer, Keith M.; Marwan, Norbert; Goswami, Bedartha; Kennett, Douglas J.; Aquino, Valorie V.; Polyak, Victor; Haug, Gerald H.; Eglinton, Timothy I.; Baldini, James U. L.

    2017-01-01

    The presence of a low- to mid-latitude interhemispheric hydrologic seesaw is apparent over orbital and glacial-interglacial timescales, but its existence over the most recent past remains unclear. Here we investigate, based on climate proxy reconstructions from both hemispheres, the inter-hemispherical phasing of the Intertropical Convergence Zone (ITCZ) and the low- to mid-latitude teleconnections in the Northern Hemisphere over the past 2000 years. A clear feature is a persistent southward shift of the ITCZ during the Little Ice Age until the beginning of the 19th Century. Strong covariation between our new composite ITCZ-stack and North Atlantic Oscillation (NAO) records reveals a tight coupling between these two synoptic weather and climate phenomena over decadal-to-centennial timescales. This relationship becomes most apparent when comparing two precisely dated, high-resolution paleorainfall records from Belize and Scotland, indicating that the low- to mid-latitude teleconnection was also active over annual-decadal timescales. It is likely a combination of external forcing, i.e., solar and volcanic, and internal feedbacks, that drives the synchronous ITCZ and NAO shifts via energy flux perturbations in the tropics. PMID:28378755

  18. Bimodal Distribution of Area-Weighted Latitude of Sunspots And Solar North-South Asymmetry

    CERN Document Server

    Chang, Heon-Young

    2011-01-01

    We study the latitudinal distribution of sunspots observed from 1874 to 2009 using the center-of-latitude (COL). We calculate COL by taking the area-weighted mean latitude of sunspots for each calendar month. We then form the latitudinal distribution of COL for the sunspots appearing in the northern and southern hemispheres separately, and in both hemispheres with unsigned and signed latitudes, respectively. We repeat the analysis with subsets which are divided based on the criterion of which hemisphere is dominant for a given solar cycle. Our primary findings are as follows: (1) COL is not monotonically decreasing with time in each cycle. Small humps can be seen (or short plateaus) around every solar maxima. (2) The distribution of COL resulting from each hemisphere is bimodal, which can well be represented by the double Gaussian function. (3) As far as the primary component of the double Gaussian function is concerned, for a given data subset, the distributions due to the sunspots appearing in two different...

  19. Revisiting the question: Does high-latitude solar activity lead low-latitude solar activity in time phase?

    Energy Technology Data Exchange (ETDEWEB)

    Kong, D. F.; Qu, Z. N. [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Guo, Q. L., E-mail: kdf@ynao.ac.cn [College of Mathematics Physics and Information Engineering, Jiaxing University, Jiaxing 314001 (China)

    2014-05-01

    Cross-correlation analysis and wavelet transform methods are used to investigate whether high-latitude solar activity leads low-latitude solar activity in time phase or not, using the data of the Carte Synoptique solar filaments archive from 1919 March to 1989 December. From the cross-correlation analysis, high-latitude solar filaments have a time lead of 12 Carrington solar rotations with respect to low-latitude ones. Both the cross-wavelet transform and wavelet coherence indicate that high-latitude solar filaments lead low-latitude ones in time phase. Furthermore, low-latitude solar activity is better correlated with high-latitude solar activity of the previous cycle than with that of the following cycle, which is statistically significant. Thus, the present study confirms that high-latitude solar activity in the polar regions is indeed better correlated with the low-latitude solar activity of the following cycle than with that of the previous cycle, namely, leading in time phase.

  20. High-latitude plasma convection during Northward IMF as derived from in-situ magnetospheric Cluster EDI measurements

    Directory of Open Access Journals (Sweden)

    M. Förster

    2008-09-01

    Full Text Available In this study, we investigate statistical, systematic variations of the high-latitude convection cell structure during northward IMF. Using 1-min-averages of Cluster/EDI electron drift observations above the Northern and Southern polar cap areas for six and a half years (February 2001 till July 2007, and mapping the spatially distributed measurements to a common reference plane at ionospheric level in a magnetic latitude/MLT grid, we obtained regular drift patterns according to the various IMF conditions. We focus on the particular conditions during northward IMF, where lobe cells at magnetic latitudes >80° with opposite (sunward convection over the central polar cap are a permanent feature in addition to the main convection cells at lower latitudes. They are due to reconnection processes at the magnetopause boundary poleward of the cusp regions. Mapped EDI data have a particular good coverage within the central part of the polar cap, so that these patterns and their dependence on various solar wind conditions are well verified in a statistical sense. On average, 4-cell convection pattern are shown as regular structures during periods of nearly northward IMF with the tendency of a small shift toward negative clock angles. The positions of these high-latitude convection foci are within 79° to 85° magnetic latitude and 09:00–15:00 MLT. The MLT positions are approximately symmetric ±2 h about 11:30 MLT, i.e. slightly offset from midday toward prenoon hours, while the maximum (minimum potential of the high-latitude cells is at higher magnetic latitudes near their maximum potential difference at ≈−10° to −15° clock angle for the North (South Hemisphere. With increasing clock angle distances from ≈IMFBz+, a gradual transition occurs from the 4-cell pattern via a 3-cell to the common 2-cell convection pattern, in the course of which one of the medium-scale high-latitude dayside cells diminishes and disappears while the

  1. Observations of ice-exposing impacts in the Martian mid-latitudes

    Science.gov (United States)

    Dundas, C. M.; Byrne, S.; McEwen, A. S.

    2011-12-01

    The Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX) have observed the sites of hundreds of new impacts on the Martian surface. Impacts in the northern mid-latitudes have excavated ice [1], allowing a new approach to studying the Martian cryosphere via active surface processes. HiRISE has systematically monitored these sites to characterize their morphology and changes over time. We will discuss the morphology, distribution and implications of the icy craters observed in this campaign. At the time of writing, ice has been excavated at thirteen impact sites at middle to high northern latitudes. (Detection of impacts is strongly biased towards dusty areas, where large dark blast zones form during impact; due to this bias, impacts are rarely detected in the southern mid-latitudes.) The crater observations indicate that the latitudinal and depth distribution of ice-exposing impacts is in general agreement with models of ice stability [e.g. 2], with ice visible in most craters above 43° N and absent below. A handful of small craters at high latitude do not show visible ice. While the lower-latitude icy impact sites may be closer to the equator than the current stability boundary [1], this boundary is expected to vary over time and extant ice could be a remnant of previous climatic conditions, particularly in exposures associated with lobate aprons. The ice, initially bright, is observed to fade over time, eventually matching the surrounding regolith over a period of months to years. Ice remains visible over a period of months, while as much as millimeters of sublimation occurs [3,4]; the ice must be clean rather than pore-filling. While some clean ice might be produced by melting and refreezing during impact, little or no melting is expected in the smaller craters [5], suggesting that the ice originally had a low regolith content. Such excess ice was observed by the Phoenix lander [6], and our observations suggest

  2. Cloud cover anomalies at middle latitudes: Links to troposphere dynamics and solar variability

    Science.gov (United States)

    Veretenenko, S.; Ogurtsov, M.

    2016-11-01

    In this work we study links between low cloud anomalies (LCA) at middle latitudes of the Northern and Southern hemispheres and galactic cosmic ray (GCR) variations used as a proxy of solar variability on the decadal time scale. It was shown that these links are not direct, but realized through GCR/solar activity phenomena influence on the development of extratropical baric systems (cyclones and troughs) which form cloud field. The violation of a positive correlation between LCA and GCR intensity which was observed in the 1980s-1990s occurred simultaneously in the Northern and Southern hemispheres in the early 2000s and coincided with the sign reversal of GCR effects on troposphere circulation. It was suggested that a possible reason for the correlation reversal between cyclonic activity at middle latitudes and GCR fluxes is the change of the stratospheric polar vortex intensity which influences significantly the troposphere-stratosphere coupling. The evidences for a noticeable weakening of the polar vortices in the Arctic and Antarctic stratosphere in the early 2000s are provided. The results obtained suggest an important role of the polar vortex evolution as a reason for a temporal variability of solar activity effects on the lower atmosphere.

  3. Evidence linking rapid Arctic warming to mid-latitude weather patterns.

    Science.gov (United States)

    Francis, Jennifer; Skific, Natasa

    2015-07-13

    The effects of rapid Arctic warming and ice loss on weather patterns in the Northern Hemisphere is a topic of active research, lively scientific debate and high societal impact. The emergence of Arctic amplification--the enhanced sensitivity of high-latitude temperature to global warming--in only the last 10-20 years presents a challenge to identifying statistically robust atmospheric responses using observations. Several recent studies have proposed and demonstrated new mechanisms by which the changing Arctic may be affecting weather patterns in mid-latitudes, and these linkages differ fundamentally from tropics/jet-stream interactions through the transfer of wave energy. In this study, new metrics and evidence are presented that suggest disproportionate Arctic warming-and resulting weakening of the poleward temperature gradient-is causing the Northern Hemisphere circulation to assume a more meridional character (i.e. wavier), although not uniformly in space or by season, and that highly amplified jet-stream patterns are occurring more frequently. Further analysis based on self-organizing maps supports this finding. These changes in circulation are expected to lead to persistent weather patterns that are known to cause extreme weather events. As emissions of greenhouse gases continue unabated, therefore, the continued amplification of Arctic warming should favour an increased occurrence of extreme events caused by prolonged weather conditions.

  4. Recurring Slope Lineae in Mid-Latitude and Equatorial Mars

    Science.gov (United States)

    McEwen, A. S.; Dundas, C. M.; Mattson, S.; Toigo, A. D.; Ojha, L.; Wray, J. J.; Chojnacki, M.; Byrne, S.; Murchie, S. L.; Thomas, N.

    2013-12-01

    A key to potential present-day habitability of Mars is the presence of liquid H2O (water). Recurring slope lineae (RSL) could be evidence for the seasonal flow of water on relatively warm slopes. RSL are narrow (250 K to >300 K. In the past year we have monitored active RSL in equatorial (0°-15°S) regions of Mars, especially in the deep canyons of Valles Marineris. They are especially active on north-facing slopes in northern summer and spring and on south-facing slopes in southern spring and summer, following the most normal solar incidence angles on these steep slopes. However, predicted peak temperatures for north-facing slopes are nearly constant throughout the Martian year because orbital periapse occurs near the southern summer solstice. Although warm temperatures and steep low-albedo slopes are required, some additional effect besides temperature may serve to trigger and stop RSL activity. Seasonal variation in the atmospheric column abundance of water does not match the RSL activity. Although seasonal melting of shallow ice could explain the mid-latitude RSL, the equatorial activity requires a different explanation, perhaps migration of briny groundwater. To explain RSL flow lengths, exceeding 1 km in Valles Marineris, the water is likely to be salty. Several RSL attributes are not yet understood: (1) the relation between apparent RSL activity and dustiness of the atmosphere; (2) salt composition and concentration; (3) variability in RSL activity from year to year; (4) seasonal activity on north-facing equatorial slopes in spite of little change in temperature; and (5) temporal changes in the color properties of fans where RSL terminate. Continued orbital monitoring, laboratory experiments, and future orbital and landed exploration with new measurement types are needed. Equatorial water activity, if confirmed, creates new exploration opportunities and challenges. RSL >1 km long near boundary between Eos and Capri Chasmata of Valles Marineris, Mars.

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

    Science.gov (United States)

    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.

  6. Impacts of high-latitude volcanic eruptions on ENSO and AMOC.

    Science.gov (United States)

    Pausata, Francesco S R; Chafik, Leon; Caballero, Rodrigo; Battisti, David S

    2015-11-10

    Large volcanic eruptions can have major impacts on global climate, affecting both atmospheric and ocean circulation through changes in atmospheric chemical composition and optical properties. The residence time of volcanic aerosol from strong eruptions is roughly 2-3 y. Attention has consequently focused on their short-term impacts, whereas the long-term, ocean-mediated response has not been well studied. Most studies have focused on tropical eruptions; high-latitude eruptions have drawn less attention because their impacts are thought to be merely hemispheric rather than global. No study to date has investigated the long-term effects of high-latitude eruptions. Here, we use a climate model to show that large summer high-latitude eruptions in the Northern Hemisphere cause strong hemispheric cooling, which could induce an El Niño-like anomaly, in the equatorial Pacific during the first 8-9 mo after the start of the eruption. The hemispherically asymmetric cooling shifts the Intertropical Convergence Zone southward, triggering a weakening of the trade winds over the western and central equatorial Pacific that favors the development of an El Niño-like anomaly. In the model used here, the specified high-latitude eruption also leads to a strengthening of the Atlantic Meridional Overturning Circulation (AMOC) in the first 25 y after the eruption, followed by a weakening lasting at least 35 y. The long-lived changes in the AMOC strength also alter the variability of the El Niño-Southern Oscillation (ENSO).

  7. Upper mesospheric lunar tides over middle and high latitudes during sudden stratospheric warming events

    Science.gov (United States)

    Chau, J. L.; Hoffmann, P.; Pedatella, N. M.; Matthias, V.; Stober, G.

    2015-04-01

    In recent years there have been a series of reported ground- and satellite-based observations of lunar tide signatures in the equatorial and low latitude ionosphere/thermosphere around sudden stratospheric warming (SSW) events. This lower atmosphere/ionosphere coupling has been suggested to be via the E region dynamo. In this work we present the results of analyzing 6 years of hourly upper mesospheric winds from specular meteor radars over a midlatitude (54°N) station and a high latitude (69°N) station. Instead of correlating our results with typical definitions of SSWs, we use the definition of polar vortex weaking (PVW) used by Zhang and Forbes. This definition provides a better representation of the strength in middle atmospheric dynamics that should be responsible for the waves propagating to the E region. We have performed a wave decomposition on hourly wind data in 21 day segments, shifted by 1 day. In addition to the radar wind data, the analysis has been applied to simulations from Whole Atmosphere Community Climate Model Extended version and the thermosphere-ionosphere-mesosphere electrodynamics general circulation model. Our results indicate that the semidiurnal lunar tide (M2) enhances in northern hemispheric winter months, over both middle and high latitudes. The time and magnitude of M2 are highly correlated with the time and associated zonal wind of PVW. At middle/high latitudes, M2 in the upper mesosphere occurs after/before the PVW. At both latitudes, the maximum amplitude of M2 is directly proportional to the strength of PVW westward wind. We have found that M2 amplitudes could be comparable to semidiurnal solar tide amplitudes, particularly around PVW and equinoxes. Besides these general results, we have also found peculiarities in some events, particularly at high latitudes. These peculiarities point to the need of considering the longitudinal features of the polar stratosphere and the upper mesosphere and lower thermosphere regions. For

  8. Bayesian Image Classification At High Latitudes

    Science.gov (United States)

    Bulgin, Claire E.; Eastwood, Steinar; Merchant, Chris J.

    2013-12-01

    The European Space Agency created the Climate Change Initiative (CCI) to maximize the usefulness of Earth Observations to climate science. Sea Surface Temperature (SST) is an essential climate variable to which satellite observations make a crucial contribution, and is one of the projects within the CCI program. SST retrieval is dependent on successful cloud clearing and identification of clear-sky pixels over ocean. At high latitudes image classification is more difficult due to the presence of sea-ice. Newly formed ice has a temperature close to the freezing point of water and a dark surface making it difficult to distinguish from open ocean using data at visible and infrared wavelengths. Similarly, melt ponds on the sea-ice surface make image classification more difficult. We present here a three- way Bayesian classifier for the AATSR instrument classifying pixels as ‘clear-sky over ocean', ‘clear-sky over ice' or ‘cloud' using the 0.6, 1.6, 11 and 12 micron channels. We demonstrate the ability of the classifier to successfully identify sea-ice and consider the potential for generating an ice surface temperature record from AATSR which could be extended using data from SLSTR.

  9. Assimilative modeling of low latitude ionosphere

    Science.gov (United States)

    Pi, Xiaoqing; Wang, Chunining; Hajj, George A.; Rosen, I. Gary; Wilson, Brian D.; Mannucci, Anthony J.

    2004-01-01

    In this paper we present an observation system simulation experiment for modeling low-latitude ionosphere using a 3-dimensional (3-D) global assimilative ionospheric model (GAIM). The experiment is conducted to test the effectiveness of GAIM with a 4-D variational approach (4DVAR) in estimation of the ExB drift and thermospheric wind in the magnetic meridional planes simultaneously for all longitude or local time sectors. The operational Global Positioning System (GPS) satellites and the ground-based global GPS receiver network of the International GPS Service are used in the experiment as the data assimilation source. 'The optimization of the ionospheric state (electron density) modeling is performed through a nonlinear least-squares minimization process that adjusts the dynamical forces to reduce the difference between the modeled and observed slant total electron content in the entire modeled region. The present experiment for multiple force estimations reinforces our previous assessment made through single driver estimations conducted for the ExB drift only.

  10. CHIRALITY OF HIGH-LATITUDE FILAMENTS OVER SOLAR CYCLE 23

    Energy Technology Data Exchange (ETDEWEB)

    Yeates, A. R. [Department of Mathematical Sciences, Durham University, Durham, DH1 3LE (United Kingdom); Mackay, D. H., E-mail: anthony.yeates@durham.ac.uk, E-mail: duncan@mcs.st-and.ac.uk [School of Mathematics and Statistics, University of St Andrews, St Andrews, KY16 9SS (United Kingdom)

    2012-07-10

    A non-potential quasi-static evolution model coupling the Sun's photospheric and coronal magnetic fields is applied to the problem of filament chirality at high latitudes. For the first time, we run a continuous 15 year simulation, using bipolar active regions determined from US National Solar Observatory, Kitt Peak magnetograms between 1996 and 2011. Using this simulation, we are able to address the outstanding question of whether magnetic helicity transport from active latitudes can overcome the effect of differential rotation at higher latitudes. Acting alone, differential rotation would produce high-latitude filaments with opposite chirality to the majority type in each hemisphere. We find that differential rotation can indeed lead to opposite chirality at high latitudes, but only for around 5 years of the solar cycle following the polar field reversal. At other times, including the rising phase, transport of magnetic helicity from lower latitudes overcomes the effect of in situ differential rotation, producing the majority chirality even on the polar crowns at polar field reversal. These simulation predictions will allow for future testing of the non-potential coronal model. The results indicate the importance of long-term memory and helicity transport from active latitudes when modeling the structure and topology of the coronal magnetic field at higher latitudes.

  11. Wood anatomical variation in relation to latitude anf altitude

    NARCIS (Netherlands)

    Graaff, van der N.A.; Baas, P.

    1974-01-01

    The wood anatomical variation within 17 eurytherm hardwood genera in relation to altitude and latitude has been studied using wood samples from 52 species. With increasing latitude a miniaturization of secondary xylem elements (shorter vessel members, narrower vessels, shorter and sometimes narrower

  12. Enhanced seasonal CO2 exchange caused by amplified plant productivity in northern ecosystems.

    Science.gov (United States)

    Forkel, Matthias; Carvalhais, Nuno; Rödenbeck, Christian; Keeling, Ralph; Heimann, Martin; Thonicke, Kirsten; Zaehle, Sönke; Reichstein, Markus

    2016-02-12

    Atmospheric monitoring of high northern latitudes (above 40°N) has shown an enhanced seasonal cycle of carbon dioxide (CO2) since the 1960s, but the underlying mechanisms are not yet fully understood. The much stronger increase in high latitudes relative to low ones suggests that northern ecosystems are experiencing large changes in vegetation and carbon cycle dynamics. We found that the latitudinal gradient of the increasing CO2 amplitude is mainly driven by positive trends in photosynthetic carbon uptake caused by recent climate change and mediated by changing vegetation cover in northern ecosystems. Our results underscore the importance of climate-vegetation-carbon cycle feedbacks at high latitudes; moreover, they indicate that in recent decades, photosynthetic carbon uptake has reacted much more strongly to warming than have carbon release processes.

  13. Turbulence in high latitude molecular clouds

    Science.gov (United States)

    Shore, S. N.; Larosa, T. N.; Magnani, L.; Chastain, R. J.; Costagliola, F.

    We summarize a continuing investigation of turbulence in high-latitude translucent molecular clouds. These low mass (~ 50 M(solar), nearby (~ 100 pc), non-star forming clouds appear to be condensing out of the atomic cirrus and must be forced by external dynamical processes, since they lack internal sources, for which we can distinguish the injection scale for the turbulence. We have now mapped three clouds -- MBM 3, MBM 16, and MBM 40 -- with high spatial (0.03 pc) and velocity resolution (<0.08 km/s) in 12CO(1-0) 13CO(1-0) (NRAO 12m and FCRAO). All three clouds show evidence for large-shear flows and we propose that the turbulent motions are powered by shear-flow instability. The densest gas is structured into filaments but the velocity profiles do not change in going across a filament indicating that shocks are not compressing the gas. The density field is more likely the result of thermal instability. The velocity-size relationship, a commonly used diagnostic of ISM turbulence, does not hold in these clouds: the linewidth does not increase with region size. The centroid velocity probability distribution function (PDF) is a more precise measure of turbulence. In these clouds the PDFs exhibit broad wings, consistent with a Lorentzian distribution and showing evidence non-Gaussian correlated processes. This is a clear signature of intermittency. We have also begun a mapping survey of CS (1-0), CS (2-1), H2CO, and HCO+ at Arecibo and OSO and willdiscuss results for the Polaris flare and L1512. We will also discusssome implications of these studies for the turbulent dissipation in these systems.

  14. Thermodynamics of greenhouse systems for the northern latitudes: analysis, evaluation and prospects for primary energy saving.

    Science.gov (United States)

    Bronchart, Filip; De Paepe, Michel; Dewulf, Jo; Schrevens, Eddie; Demeyer, Peter

    2013-04-15

    In Flanders and the Netherlands greenhouse production systems produce economically important quantities of vegetables, fruit and ornamentals. Indoor environmental control has resulted in high primary energy use. Until now, the research on saving primary energy in greenhouse systems has been mainly based on analysis of energy balances. However, according to the thermodynamic theory, an analysis based on the concept of exergy (free energy) and energy can result in new insights and primary energy savings. Therefore in this paper, we analyse the exergy and energy of various processes, inputs and outputs of a general greenhouse system. Also a total system analysis is then performed by linking the exergy analysis with a dynamic greenhouse climate growth simulation model. The exergy analysis indicates that some processes ("Sources") lie at the origin of several other processes, both destroying the exergy of primary energy inputs. The exergy destruction of these Sources is caused primarily by heat and vapour loss. Their impact can be compensated by exergy input from heating, solar radiation, or both. If the exergy destruction of these Sources is reduced, the necessary compensation can also be reduced. This can be accomplished through insulating the greenhouse and making the building more airtight. Other necessary Sources, namely transpiration and loss of CO2, have a low exergy destruction compared to the other Sources. They are therefore the best candidate for "pump" technologies ("vapour heat pump" and "CO2 pump") designed to have a low primary energy use. The combination of these proposed technologies results in an exergy efficient greenhouse with the highest primary energy savings. It can be concluded that exergy analyses add additional information compared to only energy analyses and it supports the development of primary energy efficient greenhouse systems.

  15. Terrestrial slopes in northern high latitudes: A paradigm shift regarding sediment origin, composition, and dynamic evolution

    Science.gov (United States)

    Lønne, Ida

    2017-01-01

    High-Arctic terrestrial slopes have received limited systematic research interest, but increased vulnerability related to regional warming has driven the call for better knowledge of the dynamics of these systems. Studies of sediment transport from a plateau area in Adventdalen, Svalbard, and associated slopes extending to sea level demonstrate that glacial processes play a more prominent role than earlier anticipated, - especially the impact of glacial meltwater. Traces of drainage at the plateau and the dissection of the plateau edge and upper slope were clearly initiated during various stages of Late Glacial runoff. Further, there is a close association between the sediment distribution and composition at the plateau and the evolution of various types of slopes. The reconstructed sedimentation history shows that the landscape will undergo four stages with contrasting modes of sediment transport: 1) subglacial processes related to active ice, 2) processes related to the margin of active ice, 3) processes related to the melting of inactive ice, and 4) nonglacial processes. These stages form four successions, referred to as supply regimes A-D, which control the supply of water and sediments to a given slope segment. In this landscape, traces of glacial meltwater occur at most altitudes, in "odd" positions and in slope segments "without" catchments. The associated depocenters (isolated, composite or coalescing into aprons), are often outsized compared to the apparent slope catchment. Reworked glacial sediments form a significant part of the slope-debris but are covered partly or entirely by products of physical weathering. Colluvium, senso stricto, thus masks a distinct system shift related to the local termination of glacial meltwater. Consequently, the weathering part of the slope sediment budget in this region is considerably overestimated.

  16. Cirrus, contrails, and ice supersaturated regions in high pressure systems at northern mid latitudes

    Science.gov (United States)

    Immler, F.; Treffeisen, R.; Engelbart, D.; Krüger, K.; Schrems, O.

    2008-03-01

    During the European heat wave summer 2003 with predominant high pressure conditions we performed a detailed study of upper tropospheric humidity and ice particles which yielded striking results concerning the occurrence of ice supersaturated regions (ISSR), cirrus, and contrails. Our study is based on lidar observations and meteorological data obtained at Lindenberg/Germany (52.2° N, 14.1° E) as well as the analysis of the European centre for medium range weather forecast (ECMWF). Cirrus clouds were detected in 55% of the lidar profiles and a large fraction of them were subvisible (optical depth <0.03). Thin ice clouds were particularly ubiquitous in high pressure systems. The radiosonde data showed that the upper troposphere was very often supersaturated with respect to ice. Relating the radiosonde profiles to concurrent lidar observations reveals that the ISSRs almost always contained ice particles. Persistent contrails observed with a camera were frequently embedded in these thin or subvisible cirrus clouds. The ECMWF cloud parametrisation reproduces the observed cirrus clouds consistently and a close correlation between the ice water path in the model and the measured optical depth of cirrus is demonstrated.

  17. Interconnections between the Asian monsoon, ENSO, and high northern latitude climate during the Holocene

    Institute of Scientific and Technical Information of China (English)

    HONG Bing; LIN Qinghua; HONG Yetang

    2006-01-01

    The article emphatically reviews the research progress in interconnections between the East Asian and Indian Ocean summer monsoons, between the Asian monsoon and the El Nino-Southern Oscillation (ENSO) activity, and between the monsoon, ENSO and the changing of the North Atlantic climate during the Holocene. According to the studies of recent years, it is found that the intensity variations of the East Asian and Indian Ocean summer monsoons show an opposite relationship, which may be closely related to the phenomena of ENSO in the equatorial Pacific Ocean and the variation of the deep-water formation of the North Atlantic Ocean on the interannual to orbital time scales. The 4k and 8k events occurring at around 4200 and 8200 a BP, respectively, might be the two in a series of severe paleo-El Nino events during the Holocene, strongly reflecting the interactions and influences of the monsoons, ENSO and the North Atlantic climate. In order to better understand the relationships between these paleoclimatic phenomena, scientists need to strengthen the research work on the Asian monsoon division and the comparison between monsoon proxy records, and the study on the proxy record of sea surface temperature with high time-resolution in the equatorial Pacific Ocean and the simulation research of paleoclimate condition.

  18. Comparison of OMI UV observations with ground-based measurements at high northern latitudes

    Directory of Open Access Journals (Sweden)

    G. Bernhard

    2015-03-01

    Full Text Available The Dutch-Finnish Ozone Monitoring Instrument (OMI on board NASA's Aura spacecraft provides estimates of erythemal (sunburning ultraviolet (UV dose rates and erythemal daily doses. These data were compared with ground-based measurements at 13 stations located throughout the Arctic and Scandinavia from 60 to 83° N. The study corroborates results from earlier work, but is based on a longer time series (eight vs. two years and considers additional data products, such as the erythemal dose rate at the time of the satellite overpass. Furthermore, systematic errors in satellite UV data resulting from inaccuracies in the surface albedo climatology used in the OMI UV algorithm are systematically assessed. At times when the surface albedo is correctly known, OMI data typically exceed ground-based measurements by 0–11%. When the OMI albedo climatology exceeds the actual albedo, OMI data may be biased high by as much as 55%. In turn, when the OMI albedo climatology is too low, OMI data can be biased low by up to 59%. Such large negative biases may occur when reflections from snow and ice, which increase downwelling UV irradiance, are misinterpreted as reflections from clouds, which decrease the UV flux at the surface. Results suggest that a better OMI albedo climatology would greatly improve the accuracy of OMI UV data products even if year-to-year differences of the actual albedo cannot be accounted for. A pathway for improving the OMI albedo climatology is discussed. Results also demonstrate that ground-based measurements from the center of Greenland, where high, homogenous surface albedo is observed year round, are ideally suited to detect systematic problems or temporal drifts in estimates of surface UV irradiance from space.

  19. Forest management as possible driver in mitigating climate change impacts at northern latitudes

    Science.gov (United States)

    Collalti, Alessio; Trotta, Carlo; Santini, Monia; Matteucci, Giorgio

    2017-04-01

    Climate change is likely to impact the dynamics of carbon and water cycles in forests over the next century. To date, it is still debated how forests will react. Some key variables may help in understanding the extent at which terrestrial ecosystems will be affected. Carbon Use Efficiency (CUE) and Water Use Efficiency (WUE) represent some of these key aspects. CUE represents the capacity of the forests to transfer carbon from the atmosphere to the terrestrial biomass, WUE the carbon gained for the water lost via canopy transpiration. Hence, both are key variables since they intimately represent the effects of several coupled ecophysiological processes affected by climate change. Here, we analyzed how within the 3D-CMCC-CNR FEM, forced by five general circulation model data and the four representative concentration pathways, the modeled CUE and WUE are affected by, from seasonal to over medium- and long-time period, warming, rising atmospheric [CO2] and management, assessing at which extent each component influences model results in an existing boreal forest in Finland. The 3D-CMCC-CNR FEM model results reveal that CUE tends to decrease with warmer scenarios, and management may greatly dampen the effects but only in the short- to medium-time period. WUE can increase consistently owing to the increasing of the CO2 fertilization if coupled with management. These results confirm also, at stand spatial scale resolution, what found globally in other recent studies and suggesting to consider for long-term period alternative forest management practices to enhance these effects in mitigating climate change.

  20. Electrical resistivity surveys to understand vegetation-water interlinkages in a northern latitude headwater catchment

    Science.gov (United States)

    Soulsby, C.; Dick, J.; Tetzlaff, D.; Bradford, J.

    2016-12-01

    The role of vegetation on the partitioning of precipitation, and the subsequent storage and release of water within the landscape is poorly understood. In particular, the relationship between vegetation and soil moisture is complex and reciprocal. The role of soil moisture as the primary source of water to plants may affect vegetation distribution. In turn, the structure of vegetation canopies may regulate water partitioning into interception, throughfall and steam flow. Such spatial differences in the inputs, together with complex patterns of water uptake from highly distributed root networks can create marked heterogeneity in soil moisture dynamics at small scales. Here, we present a study combining 3D and 2D ERT surveys with soil moisture measurements in a 3.2km upland catchment in the Scottish Highlands to understand influences of different vegetation types on spatio-temporal dynamics in soil moisture. The study focussed on one year of fortnightly ERT surveys to investigate plant-soil-water interactions within the root zone in podzolic soils. Locations were selected in both forest stands of 15m high Scots pine (Pinus sylvestris) and non-forest locations dominated by heather (Calluna vulgaris) shrubs (fairly heterogeneous are related to micro-topographic affects, lower interception ( 30% compared with 45%) and a smaller microclimatic effect of the canopy which serves to create greater fluctuations in soil moisture. Our results confirm the value in using geophysics to spatially elucidate subsurface plant-soil-water interactions.

  1. All-sky census of Galactic high-latitude molecular intermediate-velocity clouds

    Science.gov (United States)

    Röhser, T.; Kerp, J.; Lenz, D.; Winkel, B.

    2016-12-01

    Context. The H i halo clouds of the Milky Way, and in particular the intermediate-velocity clouds (IVCs), are thought to be connected to Galactic fountain processes. Observations of fountain clouds are important for understanding the role of matter recycling and accretion onto the Galactic disk and subsequent star formation. Aims: Here, we quantify the amount of molecular gas in the Galactic halo. We focus on the rare class of molecular IVCs (MIVCs) and search for new objects. Methods: The H i-FIR correlation was studied across the entire northern and southern Galactic hemispheres at Galactic latitudes | b | > 20° to determine the amount and distribution of molecular gas in IVCs. We used the most recent large-scale H i and FIR data, the Effelsberg Bonn-H i Survey, the Parkes Galactic All-Sky Survey, and the Planck FIR surveys. Results: We present a catalogue of 239 MIVC candidates on the northern and southern Galactic hemispheres. Among these candidates, all previously known MIVCs are recovered except for one single source. The frequency of candidates differs significantly between the northern and southern Galactic hemispheres and between negative and positive LSR velocities as well. Conclusions: In our approach we analyse the local Galactic environment. Extrapolating our results to the entire Galaxy, the global inflow of atomic and molecular IVC gas onto the Milky Way may account for the major fraction of the gaseous mass that is required to sustain the current Galactic star formation rate.

  2. First observations of simultaneous interhemispheric conjugate high-latitude thermospheric winds

    Science.gov (United States)

    Kosch, M. J.; Anderson, C.; Yiu, H.-C. I.; Kellerman, A. C.; Makarevich, R. A.; Aruliah, A.; Conde, M.; Griffin, E.; Davies, T.; McWhirter, I.; Dyson, P. L.

    2010-09-01

    We report the first observations of simultaneous high-latitude interhemispheric F region neutral wind fields by combining the 630 nm optical measurements from two scanning Doppler imagers (SDIs) and three Fabry-Perot interferometers (FPIs) for a period exceeding 5 h. From the Southern Hemisphere, a SDI at Mawson and a FPI at Davis, both in Antarctica, are geomagnetically mapped onto the Northern Hemisphere. These data are combined in the Northern Hemisphere with a SDI at Longyearbyen, Svalbard, and two FPIs near Kiruna in Sweden and Sodankyla in Finland. Geomagnetic conditions were moderate (Kp = 3--3+) and steady although the interplanetary magnetic field Bz component did change polarity several times. There is good agreement between the conjugate 630 nm optical intensities and wind vectors where the two SDIs' fields of view overlap. All wind field vectors are overlaid onto the northern Super Dual Auroral Radar Network ion convection contours. Qualitatively, the agreement between neutral and ion flow is remarkably good throughout the study interval, even down to mesoscale spatial size.

  3. Atmospheric pressure variations at extratropical latitudes associated with Forbush decreases of galactic cosmic rays

    Science.gov (United States)

    Artamonova, I.; Veretenenko, S.

    2014-12-01

    Changes of troposphere pressure associated with short-time variations of galactic cosmic rays (GCRs) taking place in the Northern hemisphere's cold months (October-March) were analyzed for the period 1980-2006, NCEP/NCAR reanalysis data being used. Noticeable pressure variations during Forbush decreases of GCRs were revealed at extratropical latitudes of both hemispheres. The maxima of pressure increase were observed on the 3rd-4th days after the event onsets over Northern Europe and the European part of Russia in the Northern hemisphere, as well as on the 4th-5th days over the eastern part of the South Atlantic opposite Queen Maud Land and over the d'Urville Sea in the Southern Ocean. According to the weather chart analysis, the observed pressure growth, as a rule, results from the weakening of cyclones and intensification of anticyclone development in these areas. The presented results suggest that cosmic ray variations may influence the evolution of extratropical baric systems and play an important role in solar-terrestrial relationships.

  4. SuperDARN CUTLASS Finland radar observations of high-latitude magnetic reconnections under northward interplanetary magnetic field (IMF) conditions

    Institute of Scientific and Technical Information of China (English)

    ZHANG QingHe; LIU RuiYuan; YANG HuiGen; HU HongQiao; ZHANG BeiChen; DUNLOP Malcolm; LESTER Mark; BOGDANOVA Yulia; WALSH Andrew

    2012-01-01

    A number of backscatter power enhancement events with “equatorward-moving radar auroral forms” in the high-latitude ionosphere were observed by SuperDARN CUTLASS Finland radar when the IMF was northward during 09:00 -10:00 UT on 26 March 2004.These events were also associated with sunward flow enhancements at each location in the Northern Hemisphere which were shown in ionospheric convections measured by the SuperDARN radars.These are typical features of high-latitude (lobe) magnetic reconnections.The durations of the velocity enhancements imply that the evolution time of the lobe reconnections is about 8-16 min from their origin at the reconnection site to their addition to the magnetotail lobe again.In additional,the Double Star TC-1 spacecraft was moving from magnetosheath into magnetosphere,and crossing the magnetopause near the subsolar region during this interval,and observed typical low-latitude magnetic reconnection signatures.This infers that the dayside high- and low-latitude reconnections may occur simultaneously.

  5. High-Latitude Ionospheric Structuring at Kilometer Scales

    Science.gov (United States)

    Bust, G. S.; Datta-Barua, S.; Su, Y.; Deshpande, K.; Hampton, D.

    2014-12-01

    Ionospheric observations in the polar and auroral zones have been made regularly with radar chains and optical imaging at larger spatio-temporal cadence. However, the observation of kilometer scale variations at sub-second cadence has not been practically realizable until recently. Quantifying the irregularities at these sizes and scales is necessary for an understanding of the dynamics leading to fine scale phenomena in the high latitude environment. We present measurements of kilometer-scale plasma variations made at the northern auroral zone using an array of specialized Global Positioning System (GPS) receivers. These 6 CASES receivers (plus 1 from ASTRA, LLC) are sited at the Poker Flat Research Range, Alaska, and have been collecting data since late 2013. The array monitors for ionospheric scintillations, fluctuations in phase and amplitude of the GPS L-band signals received due to ionospheric variations. The array spans 2 km east-west and about 1 km north-south, with a variety of intermediate baseline lengths down to about 200 m. In addition to measuring amplitude and phase scintillation with the S4 and sigma_phi indices at 100-s cadence, these receivers also record 100 Hz raw power and phase measurements from GPS baseband signal processing. These low-rate data are publicly available for download through a web portal at http://apollo.tbc.iit.edu/~spaceweather/ with high rate available upon request. A detailed case study is presented from the December 8, 2013, 0300-0400 UT time period. During this period several interesting scintillation periods were observed. We use array cross-correlation processing methods to first estimate direct ground parameters of the array including a) estimate the 2D drift velocity on the ground; b) estimate a de-correlation (or turbulent) speed; and c) parameters of correlation elliptical coordinates (axial ratio and tilt angle). We then use these results and cross-correlation measurements to derive the ground 2D spatial spectrum of

  6. How Strong is the Case for Proterozoic Low-Latitude Glaciation?

    Science.gov (United States)

    Evans, D. A.

    2004-05-01

    The most recent global compilations of paleomagnetic depositional latitudes for Proterozoic glaciogenic formations indicate a dominant mode near the paleo-equator (Evans 2000 AJS; Evans 2003 Tectonophysics). This result would therefore support either the snowball Earth or the large-obliquity hypotheses for Precambrian ice ages, but would reject the uniformitarian comparison to polar-temperate-restricted Phanerozoic glaciogenic deposits. The most reliable low-latitude results come from the Australian Marinoan succession, but a recent summary of these units has suggested that a glaciogenic origin is not yet demonstrated (Eyles and Januszczak 2004 Earth-Sci Reviews). It becomes useful, then, to review the global evidence for Proterozoic low-latitude glaciation. Eyles and Januszczak (ibid.) identified 13 Neoproterozoic deposits with "demonstrated" glacial influence. Among these, poor age constraints and lack of paleomagnetic data prohibit estimation of depositional paleolatitudes for the Fiq, Sturtian, Vreeland, Taoudeni, East Greenland, Port Askaig, and Zhengmuguan units. Moderate paleolatitudes are reasonably well supported for the South China, Gaskiers, Smalfjord, and Moelv units. Among the three remaining units, the Rapitan Group can be assigned a near-equatorial paleolatitude indirectly through use of the Galeros and Franklin-Natkusiak paleomagnetic results, as long as the Rapitan age lies within 750-720 Ma as generally expected. The Moonlight Valley Formation in northern Australia may be assigned a tropical paleolatitude according to high-quality paleomagnetic results from compellingly correlated Marinoan strata in southern Australia. Those strata, including the famous Elatina Formation, have yielded a robust paleomagnetic signature that is commonly interpreted to imply frigid climate (manifest in part by frost-wedge polygons) at near-equatorial latitudes. Concerns that the Neoproterozoic geomagnetic field was either nonaxial or nondipolar are valid in principle

  7. Quiet geomagnetic field representation for all days and latitudes

    Science.gov (United States)

    Campbell, W.H.; Schiffmacher, E.R.; Arora, B.R.

    1992-01-01

    Describes a technique for obtaining the quiet-time geomagnetic field variation expected for all days of the year and distribution of latitudes from a limited set of selected quiet days within a year at a discrete set of locations. A data set of observatories near 75??E longitude was used as illustration. The method relies upon spatial smoothing of the decomposed spectral components. An evaluation of the fidelity of the resulting model shows correlation coefficients usually above 0.9 at the lower latitudes and near 0.7 at the higher latitudes with variations identified as dependent upon season and field element. -from Authors

  8. Dificultăți de traducere în limba română a Aforismelor lui Arthur Schopenhauer. O analiză contrastiv-diacronică (I

    Directory of Open Access Journals (Sweden)

    Cecilia-Iuliana Vârlan

    2016-02-01

    Full Text Available Lucrarea de față se concentrează asupra unei opere de maturitate a filozofului german Arthur Schopenhauer, Aforisme asupra înțelepciunii în viață, și asupra singurei versiuni românești a acesteia, realizate de Titu Maiorescu la sfîrșitul secolului al XIX-lea. Existența a cinci variante ale versiunii românești, publicate de traducătorul însuși de-a lungul a patru decenii, reprezintă o dovadă clară a faptului că transpunerea în românește a acestui text de filozofie practică a incumbat o serie întreagă de dificultăți de traducere. Urmărind modul în care Titu Maiorescu a încercat să rezolve aceste dificultăți, prin adoptarea anumitor soluții traductologice, am realizat o analiză a acestora, din perspectivă lingvistică, cercetarea urmînd concomitent două direcții: contrastivă (rezultată din supra- punerea textului-sursă și a textului-țintă și diacronică (urmărind intervențiile realizate de același traducător asupra propriului text, la intervale de timp diferite. Demersul de analiză lingvistică a traducerii unui text filozofic ni s-a părut util nu doar studiului nostru, ci și viitorilor eventuali traducători ai Aforismelor, a căror intenție ar putea fi aceea de a adapta discursul versiunii românești a lui Titu Maiorescu la limba română contemporană, ținînd seama de evoluția evidentă a acesteia și, mai ales, a componentei sale de limbaj filozofic.

  9. Quantifying the trade-off between carbon sequestration and albedo in midlatitude and high-latitude North American forests

    Science.gov (United States)

    Mykleby, P. M.; Snyder, P. K.; Twine, T. E.

    2017-03-01

    Afforestation is a viable and widely practiced method of sequestering carbon dioxide from the atmosphere. However, because of a change in surface albedo, placement of less reflective forests can cause an increase in net-absorbed radiation and localized surface warming. This effect is enhanced in northern high latitudes where the presence of snow cover exacerbates the albedo difference. Regions where afforestation could provide a climate benefit are determined by comparing net ecosystem production and net radiation differences from afforestation in midlatitude and high latitude of North America. Using the dynamic vegetation model Integrated Biosphere Simulator, agricultural version (Agro-IBIS), we find a boundary through North America where afforestation results in a positive equivalent carbon balance (cooling) to the south, and a negative equivalent carbon balance (warming) to the north. Including the effects of stand age and fraction cover affect whether a site contributes to mitigating global warming.

  10. Latitud sur y control económico del hogar por la mujer peruana

    Directory of Open Access Journals (Sweden)

    Federico R. León

    2011-12-01

    Full Text Available South latitude and household economic control by Peruvian women Southern women’s greater autonomy versus northern women’s more traditional submission to the husband were hypothesized in 1984 to explain variations in Peruvian women’s fertility desires. An analysis of data from Peru 2004-2008 Continuous Demographic and Family Health Survey supports this hypothesis by showing a significant north-to-south growth of women’s control upon husband’s income and, less consistently, household purchasing decisions. These relationships are not explained by variables also correlated with meridionality, such as aboriginal ethnicity, women’s material/informational power, age difference with the husband’s, or working for cash. Findings suggest new hypotheses, concerning the distribution of assertiveness and warmth in the Peruvian territory.

  11. North-South Asymmetries in Earth's Magnetic Field: Effects on High-Latitude Geospace

    CERN Document Server

    Laundal, K M; Milan, S E; Haaland, S E; Coxon, J; Pedatella, N M; Förster, M; Reistad, J P

    2016-01-01

    The solar-wind magnetosphere interaction primarily occurs at altitudes where the dipole component of Earth's magnetic field is dominating. The disturbances that are created in this interaction propagate along magnetic field lines and interact with the ionosphere-thermosphere system. At ionospheric altitudes, the Earth's field deviates significantly from a dipole. North-South asymmetries in the magnetic field imply that the magnetosphere ionosphere-thermosphere (M-I-T) coupling is different in the two hemispheres. In this paper we review the primary differences in the magnetic field at polar latitudes, and the consequences that these have for the M-I-T coupling. We focus on two interhemispheric differences which are thought to have the strongest effects: 1) A difference in the offset between magnetic and geographic poles in the Northern and Southern Hemispheres, and 2) differences in the magnetic field strength at magnetically conjugate regions. These asymmetries lead to differences in plasma convection, neutr...

  12. Cusp observation at Saturn's high-latitude magnetosphere by the Cassini spacecraft

    Science.gov (United States)

    Jasinski, J. M.; Arridge, C. S.; Lamy, L.; Leisner, J. S.; Thomsen, M. F.; Mitchell, D. G.; Coates, A. J.; Radioti, A.; Jones, G. H.; Roussos, E.; Krupp, N.; Grodent, D.; Dougherty, M. K.; Waite, J. H.

    2014-03-01

    We report on the first analysis of magnetospheric cusp observations at Saturn by multiple in situ instruments onboard the Cassini spacecraft. Using this we infer the process of reconnection was occurring at Saturn's magnetopause. This agrees with remote observations that showed the associated auroral signatures of reconnection. Cassini crossed the northern cusp around noon local time along a poleward trajectory. The spacecraft observed ion energy-latitude dispersions—a characteristic signature of the terrestrial cusp. This ion dispersion is "stepped," which shows that the reconnection is pulsed. The ion energy-pitch angle dispersions suggest that the field-aligned distance from the cusp to the reconnection site varies between ˜27 and 51 RS. An intensification of lower frequencies of the Saturn kilometric radiation emissions suggests the prior arrival of a solar wind shock front, compressing the magnetosphere and providing more favorable conditions for magnetopause reconnection.

  13. Interhemispheric Comparison of Dipole Tilt Angle Effects on Latitude of Mid-Altitude Cusp

    Institute of Scientific and Technical Information of China (English)

    GUO Jian-Guang; SHI Jian-Kui; ZHANG Tie-Long; LIU Zhen-Xing

    2008-01-01

    A statistical study of interhemispheric comparison of dipole tilt angle effect on the latitude of the mid-altitude cusp is preformed by a data set of the Cluster cusp crossings over a 5-year period.The result shows that the dipole tilt angle has a clear control of the cusp latitudinal location.When the dipole tilts sunwards,the cusp is shifted poleward.The northern cusp moves 1° ILAT for every 15.4° increase in the dipole tilt angle,while the southern cusp moves 1° ILAT for every 20.8° increase in the dipole tilt angle. This suggests that an interhemispheric difference appears in the dependence of cusp latitudinal location on the dipole tilt angle.

  14. Cosmology with the WFIRST High Latitude Survey

    Science.gov (United States)

    Dore, Olivier

    Cosmic acceleration is the most surprising cosmological discovery in many decades. Testing and distinguishing among possible explanations requires cosmological measurements of extremely high precision that probe the full history of cosmic expansion and structure growth. The WFIRST-AFTA mission, as described in the Science Definition Team (SDT) reports (Spergel 2013, 2015), has the ability to improve these measurements by 1-2 orders of magnitude compared to the current state of the art, while simultaneously extending their redshift grasp, greatly improving control of systematic effects, and taking a unified approach to multiple probes that provide complementary physical information and cross-checks of cosmological results. We have assembled a team with the expertise and commitment needed to address the stringent challenges of the WFIRST dark energy program through the Project's formulation phase. After careful consideration, we have elected to address investigations A (Galaxy Redshift Survey) and C (Weak Lensing and Cluster Growth) of the WFIRST SIT NRA with a unified team, because the two investigations are tightly linked at both the technical level and the theoretical modeling level. The imaging and spectroscopic elements of the High Latitude Survey (HLS) will be realized as an integrated observing program, and they jointly impose requirements on instrument and telescope performance, operations, and data transfer. The methods for simulating and interpreting weak lensing and galaxy clustering observations largely overlap, and many members of our team have expertise in both areas. The team PI, Olivier Dore, is a cosmologist with a broad expertise in cosmic microwave background and large scale structures. Yun Wang and Chris Hirata will serve as Lead Co-Investigators for topics A and C, respectively. Many members of our team have been involved with the design and requirements of a dark energy space mission for a decade or more, including the Co-Chair and three

  15. High-Latitude Topside Ionospheric Vertical Electron-Density-Profile Changes in Response to Large Magnetic Storms

    Science.gov (United States)

    Benson, Robert F.; Fainberg, Joseph; Osherovich, Vladimir A.; Truhlik, Vladimir; Wang, Yongli; Bilitza, Dieter; Fung, Shing F.

    2015-01-01

    Large magnetic-storm induced changes have been detected in high-latitude topside vertical electron-density profiles Ne(h). The investigation was based on the large database of topside Ne(h) profiles and digital topside ionograms from the International Satellites for Ionospheric Studies (ISIS) program available from the NASA Space Physics Data Facility (SPDF) at http://spdf.gsfc.nasa.gov/isis/isis-status.html. This large database enabled Ne(h) profiles to be obtained when an ISIS satellite passed through nearly the same region of space before, during, and after a major magnetic storm. A major goal was to relate the magnetic-storm induced high-latitude Ne(h) profile changes to solar-wind parameters. Thus an additional data constraint was to consider only storms where solar-wind data were available from the NASA/SPDF OMNIWeb database. Ten large magnetic storms (with Dst less than -100 nT) were identified that satisfied both the Ne(h) profile and the solar-wind data constraints. During five of these storms topside ionospheric Ne(h) profiles were available in the high-latitude northern hemisphere and during the other five storms similar ionospheric data were available in the southern hemisphere. Large Ne(h) changes were observed during each one of these storms. Our concentration in this paper is on the northern hemisphere. The data coverage was best for the northern-hemisphere winter. Here Ne(h) profile enhancements were always observed when the magnetic local time (MLT) was between 00 and 03 and Ne(h) profile depletions were always observed between 08 and 10 MLT. The observed Ne(h) deviations were compared with solar-wind parameters, with appropriate time shifts, for four storms.

  16. [Genetic characterization of viruses from the antigenic complex Tyuleniy (Flaviviridae, Flavivirus): Tyuleniy virus (TYUV) (ID GenBank KF815939) isolated from ectoparasites of colonial seabirds--Ixodes (Ceratixodes) uriae White, 1852, ticks collected in the high latitudes of Northern Eurasia--and Kama virus (KAMV) isolated from the Ixodes lividus Roch, 1844, collected in the digging colonies of the middle part of Russian plane].

    Science.gov (United States)

    L'vov, D K; Al'khovskiĭ, S V; Shchelkanov, M Iu; Shchetinin, A M; Deriabin, P G; Samokhvalov, E I; Gitel'man, A K; Botikov, A G

    2014-01-01

    Genetic research into the Tyuleniy virus (TYUV) (ID GenBank KF815939) isolated in high latitudes from the Ixodes uriae White, 1852, ticks collected in the nesting colonies of the Alcidae (Leach, 1820) birds and Kama virus (KAMV) (ID GenBank KF815940) isolated from the I. lividus ticks collected in the nesting bird colonies in the middle part of the Russian Plane was carried out. Full-genome comparative analysis revealed 70% homology between KAMV and TYUV on the nucleotide level and 74% on the amino acid level. Thus, KAMV is a new member of the TYUV complex belonging to the seabird tick-borne virus group (STBVG) of Flavivirus (Flaviviridae). KAMV is a separate virus and forms separate phylogenetic line together with the TYUV, Meaban virus (MEAV), and Saumarez Reef virus (SREV).

  17. Climate response to imposed solar radiation reductions in high latitudes

    OpenAIRE

    M. C. MacCracken; H.-J. Shin; Caldeira, K; G. A. Ban-Weiss

    2012-01-01

    Increasing concentrations of greenhouse gases are the primary contributor to the 0.8 °C increase in the global average temperature since the late 19th century, shortening cold seasons and lengthening warm seasons. The warming is amplified in polar regions, causing retreat of sea ice, snow cover, permafrost, mountain glaciers, and ice sheets, while also modifying mid-latitude weather, amplifying global sea level rise, and initiating high-latitude carbon feedbacks. Model simulations in which we...

  18. 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).

  19. The association of hydrogen with sulfur on Mars across latitudes, longitudes, and compositional extremes

    Science.gov (United States)

    Karunatillake, Suniti; Wray, James J.; Gasnault, Olivier; McLennan, Scott M.; Deanne Rogers, A.; Squyres, Steven W.; Boynton, William V.; Skok, J. R.; Button, Nicole E.; Ojha, Lujendra

    2016-07-01

    Midlatitudinal hydrated sulfates on Mars may influence brine pH, atmospheric humidity, and collectively water activity. These factors affect the habitability of the planetary subsurface and the preservation of relict biomolecules. Regolith at grain sizes smaller than gravel, constituting the bulk of the Martian subsurface at regional scales, may be a primary repository of chemical alteration, mechanical alteration, and biosignatures. The Mars Odyssey Gamma Ray Spectrometer with hundreds of kilometers of lateral resolution and compositional sensitivity to decimeter depth provides unique insight into this component of the regolith, which we call soil. Advancing the globally compelling association between H2O and S established by our previous work, we characterize latitudinal variations in the association between H and S, as well as in the hydration state of soil. Represented by H2O:S molar ratios, the hydration state of candidate sulfates increases with latitude in the northern hemisphere. In contrast, hydration states generally decrease with latitude in the south. Furthermore, we observe that H2O concentration may affect the degree of sulfate hydration more than S concentration. Limited H2O availability in soil-atmosphere exchange and in subsurface recharge could explain such control exerted by H2O on salt hydration. Differences in soil thickness, ground ice table depths, atmospheric circulation, and insolation may contribute to hemispheric differences in the progression of hydration with latitude. Our observations support chemical association of H2O with S in the southern hemisphere as suggested by Karunatillake et al. (2014), including the possibility of Fe sulfates as a key mineral group.

  20. Influence of high-latitude geomagnetic pulsations on recordings of broadband force-balanced seismic sensors

    Directory of Open Access Journals (Sweden)

    E. Kozlovskaya

    2012-08-01

    Full Text Available Seismic broadband sensors with electromagnetic feedback are sensitive to variations of surrounding magnetic field, including variations of geomagnetic field. Usually, the influence of the geomagnetic field on recordings of such seismometers is ignored. It might be justified for seismic observations at middle and low latitudes. The problem is of high importance, however, for observations in Polar Regions (above 60° geomagnetic latitude, where magnitudes of natural magnetic disturbances may be two or even three orders larger. In our study we investigate the effect of ultra-low frequency (ULF magnetic disturbances, known as geomagnetic pulsations, on the STS-2 seismic broadband sensors. The pulsations have their sources and, respectively, maximal amplitudes in the region of the auroral ovals, which surround the magnetic poles in both hemispheres at geomagnetic latitude (GMLAT between 60° and 80°. To investigate sensitivity of the STS-2 seismometer to geomagnetic pulsations, we compared the recordings of permanent seismic stations in northern Finland to the data of the magnetometers of the IMAGE network located in the same area. Our results show that temporary variations of magnetic field with periods of 40–150 s corresponding to regular Pc4 and irregular Pi2 pulsations are seen very well in recordings of the STS-2 seismometers. Therefore, these pulsations may create a serious problem for interpretation of seismic observations in the vicinity of the auroral oval. Moreover, the shape of Pi2 magnetic disturbances and their periods resemble the waveforms of glacial seismic events reported originally by Ekström (2003. The problem may be treated, however, if combined analysis of recordings of co-located seismic and magnetic instruments is used.

  1. 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.

  2. Response of High Latitude Coralline Algae to pCO2 and Thermal Stress

    Science.gov (United States)

    Garlick-Ott, K.; Williams, B.; Chan, P. T. W.; Westfield, I. T.; Rasher, D.; Ries, J. B.; Adey, W.; Halfar, J.

    2016-12-01

    The impacts of recent and future anthropogenic increases in atmospheric pCO2 causing ocean acidification and temperature on high-latitude oceans, and the marine organisms that inhabit them, are varied and poorly understood. The ecologically important crustose coralline alga Clathromorphum compactum may be particularly vulnerable to ocean acidification due to the relatively high solubility of its high Mg-calcite skeleton . This species of coralline algae is abundant throughout coastal mid-to-high latitude areas of the northern hemisphere, and calcifies annually-banded skeletons with longevities of up to 650 years. Here we used micro-computed tomography (micro-CT) to evaluate the impact of decreasing seawater pH and increasing temperature on skeletal density of algal specimens cultured in a fully crossed pCO2 (280, 400, 700, 2800 µatm) and temperature (6.5, 8.7, 12.4 °C) laboratory experiment. To examine the natural variability in coralline algal skeletal density, additional long-lived wild C. compactum specimens were collected along a latitudinal transect extending from the Gulf of Maine to the Canadian Arctic Archipelago. Density time series generated from the wild specimens spans the past several decades to century, and were used to evaluate other environmental parameters that may influence the skeletal density of coralline algae. This research will evaluate the resiliency of this alga to future environmental change.

  3. 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.

  4. Fungal disease incidence along tree diversity gradients depends on latitude in European forests.

    Science.gov (United States)

    Nguyen, Diem; Castagneyrol, Bastien; Bruelheide, Helge; Bussotti, Filippo; Guyot, Virginie; Jactel, Hervé; Jaroszewicz, Bogdan; Valladares, Fernando; Stenlid, Jan; Boberg, Johanna

    2016-04-01

    European forests host a diversity of tree species that are increasingly threatened by fungal pathogens, which may have cascading consequences for forest ecosystems and their functioning. Previous experimental studies suggest that foliar and root pathogen abundance and disease severity decrease with increasing tree species diversity, but evidences from natural forests are rare. Here, we tested whether foliar fungal disease incidence was negatively affected by tree species diversity in different forest types across Europe. We measured the foliar fungal disease incidence on 16 different tree species in 209 plots in six European countries, representing a forest-type gradient from the Mediterranean to boreal forests. Forest plots of single species (monoculture plots) and those with different combinations of two to five tree species (mixed species plots) were compared. Specifically, we analyzed the influence of tree species richness, functional type (conifer vs. broadleaved) and phylogenetic diversity on overall fungal disease incidence. The effect of tree species richness on disease incidence varied with latitude and functional type. Disease incidence tended to increase with tree diversity, in particular in northern latitudes. Disease incidence decreased with tree species richness in conifers, but not in broadleaved trees. However, for specific damage symptoms, no tree species richness effects were observed. Although the patterns were weak, susceptibility of forests to disease appears to depend on the forest site and tree type.

  5. Geomagnetic secular variations of high-latitude glaciomarine sediments: data from the Kola Peninsula, northwestern Russia

    Science.gov (United States)

    Bakhmutov, V.; Yevzerov, V.; Kolka, V.

    1994-08-01

    Geological, radiocarbon and paleomagnetic investigations of paleobays were carried out in the northwestern part of the Kola Peninsula (the Pechenga and Shuonijoki river valleys). The period from 10.3 to 9.5 kyear ago was characterized by the accumulation of glaciomarine sediments while the period 8.6-9.5 kyear was characterized by marine ones. Ca. 8.6 kyear marks the beginning of the formation of marine sediment transgression series. The clay sequences, accumulated in paleobays during a few hundred years, are an important object for studying the ancient geomagnetic field secular variations at high latitudes. Paleomagnetic signals in three outcrops from Pechenga river valley (69.5°N) record high-latitudinal inclination and declination variations in the time interval 8.5-10.0 kyear ago which correlate well with the secular variations of Early Holocene lacustrine deposits in the northern part of Ladoga Lake (61.5°N). A characteristic feature of the paleosecular variations at high latitudes is the proximity VGP to the observation point. Near to vertical inclination with declination variation amplitudes up to 150 took place ca. 9700-9500 year ago. The geomagnetic pole drifted south or crossed the Kola Peninsula at that time. The inclination and declination variations may be used in correlating the Early Holocene marine and lacustrine deposits in adjacent regions.

  6. Changes in Arctic vegetation amplify high-latitude warming through the greenhouse effect.

    Science.gov (United States)

    Swann, Abigail L; Fung, Inez Y; Levis, Samuel; Bonan, Gordon B; Doney, Scott C

    2010-01-26

    Arctic climate is projected to change dramatically in the next 100 years and increases in temperature will likely lead to changes in the distribution and makeup of the Arctic biosphere. A largely deciduous ecosystem has been suggested as a possible landscape for future Arctic vegetation and is seen in paleo-records of warm times in the past. Here we use a global climate model with an interactive terrestrial biosphere to investigate the effects of adding deciduous trees on bare ground at high northern latitudes. We find that the top-of-atmosphere radiative imbalance from enhanced transpiration (associated with the expanded forest cover) is up to 1.5 times larger than the forcing due to albedo change from the forest. Furthermore, the greenhouse warming by additional water vapor melts sea-ice and triggers a positive feedback through changes in ocean albedo and evaporation. Land surface albedo change is considered to be the dominant mechanism by which trees directly modify climate at high-latitudes, but our findings suggest an additional mechanism through transpiration of water vapor and feedbacks from the ocean and sea-ice.

  7. Case study of ionospheric fluctuation over mid-latitude region during one large magnetic storm

    Institute of Scientific and Technical Information of China (English)

    ZHANG DongHe; MO XiaoHua; A Ercha; HAO YongQiang

    2012-01-01

    From Nov.6 to 10,2004,a large number of solar events occurred,which triggered many solar flares and coronal mass ejections (CMEs).These CMEs caused two large geomagnetic storms and continuous energy proton events.During this period,one large positive ionospheric storm happened over the East-Asian region on Nov.8,2004.On Nov.10,2004,a strong spread-F was observed by the ionosonde located in the mid-latitude region of East China and Japan,and the ionospheric fluctuation over the ionosonde stations derived from GPS observation was also obvious.In this report,the characteristics of the spatial distribution of the ionosphere fluctuation and its temporal evolution are studied using the parameter of the rate of total electron content (ROT) derived from dual-frequency GPS measurement.Strong fluctuating activity of the ionosphere was found over the mid-latitude region in the southern and northern hemispheres between longitudes of 100°E and 180°E during the magnetic storm period on Nov.10,2004,and a regular movement of the disturbing region was observed.In the end,the reason of the ionospheric fluctuation during this magnetic storm is analyzed.

  8. 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.

  9. Northern Oklahoma Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (710 records) were compiled by Professor Ahern. This data base was received in June 1992. Principal gravity parameters include latitude,...

  10. Besinsel Lif Analiz Yöntemleri

    OpenAIRE

    Köksel, Hamit; Özboy, Özen

    1993-01-01

    The protective effects of dietary fiber (DF) against certain diseases which are covered by a large number of scientific publications are well accepted in recent years. This fact brought about questions such as which kinds of foods contain DF and how can the amount of DF be determined. In addition numerous suggestions for analysis methods to determine the amount of DF made the selection of the suitable method and the comparison of the results difficult. In this article in order to help these p...

  11. Sillamjaeskii port : analiz riskov / Jevgeni Ashihmin

    Index Scriptorium Estoniae

    Ashihmin, Jevgeni

    2004-01-01

    Tallinna firma E-Konsult eksperdid hindasid Sillamäe sadama riske, esitati soovitused, millised peaksid olema vedelkütuseid vedavad tankerid, raudteesõlme ja raudteejaama ehitusel kasutatavad raudteerööpad. Sadama võimalikust mõjust keskkonnale

  12. Space weather and myocardial infarction diseases at subauroral latitudes

    Science.gov (United States)

    Samsonov, Sergey; Kleimenova, Natalia; Petrova, Palmira

    The relationship of the number of calls for the emergency medical care in Yakutsk (subauroral latitudes) in connection with myocardial infarction diseases during years near the maximum (1992) and minimum (1998) of the 11-year geomagnetic disturbance cycle to space weather parameters has been studied. It is found that at subauroral latitudes, the increase of geomagnetic activity, namely, the occurrence of night magnetospheric substorms, plays the important role in the exacerbation of myocardial infarctions. Substorms are accompanied by Pi1 irregular geomagnetic pulsations with periods of (0.5-3.0) Hz, coinciding with heart rhythms of a human being, thus, these waves can be a biotropic factor negatively influencing on the occurrence of myocardial infarctions. The comparison of seasonal change of the number of calls for emergency medical care to patients at subauroral latitudes with a simultaneous seasonal change of fatal endings because of an infarction at low latitudes (Bulgaria) has shown their essential difference. Thus, in Bulgaria the maximum of infarctions have been marked in winter, and minimum - in summer, and in Yakutsk a few maxima coinciding with the sharp and considerable increases of the level of the planetary geomagnetic disturbances have been observed. In this case, in Bulgaria the infarctions could be connected with availability of the Pc1 geomagnetic pulsations. Thus, the stable quasi-sinusoidal Pc1 pulsations can be a biotropic factor influencing on the development of myocardial infarctions at middle latitudes and the Pi1 irregular geomagnetic pulsations, which do not propagate to the lower latitudes, could be a biotropic factor at subauroral latitudes.

  13. Climate response to imposed solar radiation reductions in high latitudes

    Directory of Open Access Journals (Sweden)

    M. C. MacCracken

    2012-07-01

    Full Text Available Increasing concentrations of greenhouse gases are the primary contributor to the 0.8 °C increase in the global average temperature since the late 19th century, shortening cold seasons and lengthening warm seasons. The warming is amplified in polar regions, causing retreat of sea ice, snow cover, permafrost, mountain glaciers, and ice sheets, while also modifying mid-latitude weather, amplifying global sea level rise, and initiating high-latitude carbon feedbacks. Model simulations in which we reduced solar insolation over high latitudes not only cooled those regions, but also drew energy from lower latitudes, exerting a cooling influence over much of the hemisphere in which the reduction was imposed. Our simulations, which used the National Center for Atmospheric Research's CAM3.1 atmospheric model coupled to a slab ocean, indicated that, on a normalized basis, high-latitude reductions in absorbed solar radiation have a significantly larger cooling influence than equivalent solar reductions spread evenly over the Earth. This amplified influence occurred because high-latitude surface cooling preferentially increased sea ice fraction and, therefore, surface albedo, leading to a larger deficit in the radiation budget at the top of the atmosphere than from an equivalent global reduction in solar radiation. Reductions in incoming solar radiation in one polar region (either north or south resulted in increased poleward energy transport during that hemisphere's cold season and shifted the Inter-Tropical Convergence Zone (ITCZ away from that pole, whereas equivalent reductions in both polar regions tended to leave the ITCZ approximately in place. Together, these results suggest that, until emissions reductions are sufficient to limit the warming influence of greenhouse gas concentrations, polar reductions in solar radiation, if they can be efficiently and effectively implemented, might, because of fewer undesirable side effects than for global solar

  14. US CLIVAR Working Group: Arctic Change and Possible Influence on Mid-latitude Climate and Weather

    Science.gov (United States)

    Cohen, J. L.; Zhang, X.

    2015-12-01

    The Arctic has warmed more than twice as fast as the global average, a phenomenon known as Arctic amplification (AA). These profound changes to the Arctic system have coincided with a period of ostensibly more frequent events of extreme weather across the Northern Hemisphere mid-latitudes, including extreme heat and rainfall events and recent severe winters. The possible link between Arctic change and mid-latitude weather has spurred a rush of new observational and modeling studies. These studies have argued that heavy precipitation events and heat waves are at least partially attributable to Arctic warming. A growing number of recent studies even argue that recent extreme winter weather is related to AA. In part due to the high impact of extreme weather on our society, some of these studies linking AA to the increased frequency of extreme weather have garnered public and media attention. At the same time, uncertainties from the large intrinsic variability of the system, the short observational record due to the recentness of AA and the shortcomings of global climate models have also resulted in much skepticism in any argued links between AA and severe weather. This in turn has resulted in a number of workshops trying to frame the problem and laying the groundwork to improve our understanding of Arctic-mid-latitude linkages and accurate attribution of extreme weather events. Although these workshops identified existing problems and difficulties, and provided broad recommendations, they did not synthesize the diversified research results to identify where community consensus and gaps exist. Therefore we have assembled many of the leading scientists researching Arctic-mid-latitude linkages as part of a US CLIVAR working group. Through the three-year efforts of this working group, we will use the outcome of the previous workshops and newly planned activities to guide the synthesis efforts, coordinate on-going research to fill out key gaps, and provide specific

  15. Inter-comparison of hydro-climatic regimes across northern catchments: snychronicity, resistance and resilience

    Science.gov (United States)

    Sean K. Carey; Doerthe Tetzlaff; Jan Seibert; Chris Soulsby; Jim Buttle; Hjalmar Laudon; Jeff McDonnell; Kevin McGuire; Daniel Caissie; Jamie Shanley; Mike Kennedy; Kevin Devito; John W. Pomeroy

    2010-01-01

    The higher mid-latitudes of the Northern Hemisphere are particularly sensitive to climate change as small differences in temperature determine frozen ground status, precipitation phase, and the magnitude and timing of snow accumulation and melt. An international inter-catchment comparison program, North-Watch, seeks to improve our understanding of the sensitivity of...

  16. @iGlobigerina pachyderma@@ (Ehrenberg) in the shelf-slope sediments of northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Setty, M.G

    resulting in the occurrence of this species in the northern Indian Ocean sediments, it is proposed that the forms which occur in the low latitudes (upto 25~'N) in the norhern Indian Ocean be referred to henceforth as (1) (a) @iG. pachyderma@@ (Ehrenberg...

  17. AN ABSENCE OF FAST RADIO BURSTS AT INTERMEDIATE GALACTIC LATITUDES

    Energy Technology Data Exchange (ETDEWEB)

    Petroff, E.; Van Straten, W.; Bailes, M.; Barr, E. D.; Coster, P.; Flynn, C.; Keane, E. F. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, VIC 3122 (Australia); Johnston, S. [CSIRO Astronomy and Space Science, Australia Telescope National Facility, P.O. Box 76, Epping, NSW 1710 (Australia); Bates, S. D.; Keith, M. J.; Kramer, M.; Stappers, B. W. [Jodrell Bank Centre for Astrophysics, University of Manchester, Alan Turing Building, Oxford Road, Manchester M13 9PL (United Kingdom); Bhat, N. D. R. [ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), 44 Rosehill Street, Redfern, NSW 2016 (Australia); Burgay, M.; Possenti, A.; Tiburzi, C. [INAF—Osservatorio Astronomico di Cagliari, Via della Scienza, I-09047 Selargius (Italy); Burke-Spolaor, S. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91104 (United States); Champion, D.; Ng, C. [Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Levin, L., E-mail: epetroff@astro.swin.edu.au [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); and others

    2014-07-10

    Fast radio bursts (FRBs) are an emerging class of bright, highly dispersed radio pulses. Recent work by Thornton et al. has revealed a population of FRBs in the High Time Resolution Universe (HTRU) survey at high Galactic latitudes. A variety of progenitors have been proposed, including cataclysmic events at cosmological distances, Galactic flare stars, and terrestrial radio frequency interference. Here we report on a search for FRBs at intermediate Galactic latitudes (–15° latitudes. A revised rate estimate or another strong and heretofore unknown selection effect in Galactic latitude would provide closer agreement between the surveys' detection rates. The dearth of detections at low Galactic latitude disfavors a Galactic origin for these bursts.

  18. Derin Yapı Yüzey Yapı İlişkisi Bağlamında Temel Dil Becerileri Üzerine Bir Analiz Çalışması

    Directory of Open Access Journals (Sweden)

    Bilginer ONAN

    2015-07-01

    Full Text Available Bu çalışmada, derin yapı yüzey yapı ilişkileri bağlamında, ana dili eğitiminde temel dil becerileri olarak kabul edilen dinleme, konuşma, okuma ve yazma kavramları analiz edilmiştir. Birinci bölümde, ilk kez Port Royal Gramer Okulu tarafından ortaya konan ve 1960’larda Noam Chomsky tarafından Üretimci Dönüşümsel Dil Bilgisi kuramıyla tekrar gündeme getirilen derin yapı ve yüzey yapı kavramları hakkında bilgi verilmiştir. Çalışmanın ikinci bölümünde ise derin yapı ve yüzey yapı ilişkileri çerçevesinde dinleme, konuşma, okuma ve yazma becerileri analiz edilmiştir. Çalışmanın amacı, dilin iki temel boyutu olan anlam ve biçim ilişkileri bağlamında, temel dil becerilerinin eğitimi sürecinde belirleyici olan unsurları tespit ederek, sürecin programlanmasına yönelik öneriler geliştirmektir. Çalışma çerçevesinde yapılan analizlerde boğumlama, bürün olguları, beden dili, üretici kelime hazinesi, alıcı kelime hazinesi, akıcılık, metin türü, yazım ve noktalama, bağdaşıklık, tutarlılık, ön bilgi, kelime tanıma, kelime ayırt etme, edinilmiş bilgi, önvarsayım, sezdirim kavramlarının derin yapı yüzey yapı ilişkileri bağlamında temel dil becerilerinin geliştirilmesinde süreci etkileyen unsurlar olduğu tespit edilmiştir. Bu kavramlar arasında boğumlama, bürün olgusu, beden dili, akıcılık, bağdaşıklık, metin türü, kelime tanıma, kelime ayırt etme, yazım ve noktalama, doğrudan yüzey yapıyla ilgilidir. Üretici kelime hazinesi, akıcılık, alıcı kelime hazinesi, tutarlılık, ön bilgi, edinilmiş bilgi, önvarsayım ve sezdirim kavramları ise derin yapıyı ilgilendirmektedir. Akıcılık kavramının bütün dil becerileriyle ilgili olduğu belirlenmiştir.

  19. Extensive wet episodes in Late Glacial Australia resulting from high-latitude forcings

    Science.gov (United States)

    Bayon, Germain; De Deckker, Patrick; Magee, John W.; Germain, Yoan; Bermell, Sylvain; Tachikawa, Kazuyo; Norman, Marc D.

    2017-01-01

    Millennial-scale cooling events termed Heinrich Stadials punctuated Northern Hemisphere climate during the last glacial period. Latitudinal shifts of the intertropical convergence zone (ITCZ) are thought to have rapidly propagated these abrupt climatic signals southward, influencing the evolution of Southern Hemisphere climates and contributing to major reorganisation of the global ocean-atmosphere system. Here, we use neodymium isotopes from a marine sediment core to reconstruct the hydroclimatic evolution of subtropical Australia between 90 to 20 thousand years ago. We find a strong correlation between our sediment provenance proxy data and records for western Pacific tropical precipitations and Australian palaeolakes, which indicates that Northern Hemisphere cooling phases were accompanied by pronounced excursions of the ITCZ and associated rainfall as far south as about 32°S. Comparatively, however, each of these humid periods lasted substantially longer than the mean duration of Heinrich Stadials, overlapping with subsequent warming phases of the southern high-latitudes recorded in Antarctic ice cores. In addition to ITCZ-driven hydroclimate forcing, we infer that changes in Southern Ocean climate also played an important role in regulating late glacial atmospheric patterns of the Southern Hemisphere subtropical regions.

  20. An all-sky census of Galactic high-latitude molecular intermediate-velocity clouds

    CERN Document Server

    Röhser, T; Lenz, D; Winkel, B

    2016-01-01

    The HI halo clouds of the Milky Way and in particular the intermediate-velocity clouds (IVCs) are thought to be connected to Galactic fountain processes. Observations of fountain clouds are important for understanding the role of matter recycling and accretion onto the Galactic disk and subsequent star formation. Here, we quantify the amount of molecular gas in the Galactic halo. We focus on the rare class of molecular IVCs (MIVCs) and search for new objects. The HI-FIR correlation is studied across the entire northern and southern Galactic hemispheres at Galactic latitudes $|b|>20^\\circ$ in order to determine the amount and distribution of molecular gas in IVCs. We use the most recent large-scale HI and FIR data, the Effelsberg Bonn-HI Survey, the Parkes Galactic All-Sky Survey, and the Planck FIR surveys. We present a catalogue of 239 MIVC candidates on the northern and southern Galactic hemispheres. Among these candidates all previously known MIVCs are recovered except for a single one only. The frequency ...

  1. High-latitude controls of thermocline nutrients and low latitude biological productivity.

    Science.gov (United States)

    Sarmiento, J L; Gruber, N; Brzezinski, M A; Dunne, J P

    2004-01-01

    The ocean's biological pump strips nutrients out of the surface waters and exports them into the thermocline and deep waters. If there were no return path of nutrients from deep waters, the biological pump would eventually deplete the surface waters and thermocline of nutrients; surface biological productivity would plummet. Here we make use of the combined distributions of silicic acid and nitrate to trace the main nutrient return path from deep waters by upwelling in the Southern Ocean and subsequent entrainment into subantarctic mode water. We show that the subantarctic mode water, which spreads throughout the entire Southern Hemisphere and North Atlantic Ocean, is the main source of nutrients for the thermocline. We also find that an additional return path exists in the northwest corner of the Pacific Ocean, where enhanced vertical mixing, perhaps driven by tides, brings abyssal nutrients to the surface and supplies them to the thermocline of the North Pacific. Our analysis has important implications for our understanding of large-scale controls on the nature and magnitude of low-latitude biological productivity and its sensitivity to climate change.

  2. Dificultăți de traducere în limba română a Aforismelor lui Arthur Schopenhauer. O analiză contrastiv-diacronică (II

    Directory of Open Access Journals (Sweden)

    Cecilia-Iuliana Vârlan

    2016-08-01

    Full Text Available În acest articol continuăm analiza lingvistică a versiunilor românești ale unei opere de maturitate a filosofului german Arthur Schopenhauer, Aforisme asupra înțelepciunii în viață. Vom păstra cele două direcții de cercetare, cea contrastivă (rezultată din suprapunerea textului-sursă și a textului-țintă și cea diacronică (urmărind intervențiile realizate de același traducător asupra propriului text, la intervale de timp diferite. Vom prezenta, de asemenea, rezultatele cercetării, precum și concluziile rezultate în urma acestui demers, a cărui perspectivă lingvistică ne-a permis să urmărim, într-un mod obiectiv, maniera în care traducătorul (Titu Maiorescu a rezolvat dificultățile de transpunere în românește ale unui text filosofic german, consemnînd atît reușitele, cît și nereușitele sale.Demersul de analiză lingvistică a traducerii unui text filosofic ni s-a părut util nu doar studiului nostru, ci și viitorilor eventuali traducători ai Aforismelor, a căror intenție ar putea fi aceea de a adapta discursul versiunii românești a lui Titu Maiorescu la limba română contemporană, ținînd seama de evoluția evidentă a acesteia și, mai ales, a componentei sale de limbaj filosofic.

  3. Operational high latitude surface irradiance products from polar orbiting satellites

    Science.gov (United States)

    Godøy, Øystein

    2016-12-01

    It remains a challenge to find an adequate approach for operational estimation of surface incoming short- and longwave irradiance at high latitudes using polar orbiting meteorological satellite data. In this presentation validation results at a number of North Atlantic and Arctic Ocean high latitude stations are presented and discussed. The validation results have revealed that although the method works well and normally fulfil the operational requirements, there is room for improvement. A number of issues that can improve the estimates at high latitudes have been identified. These improvements are partly related to improved cloud classification using satellite data and partly related to improved handling of multiple reflections over bright surfaces (snow and sea ice), especially in broken cloud conditions. Furthermore, the availability of validation sites over open ocean and sea ice is a challenge.

  4. Multiflash whistlers in ELF-band observed at low latitude

    Directory of Open Access Journals (Sweden)

    Ashutosh K. Singh

    2011-01-01

    Full Text Available Multiflash whistler-like event in the ELF-band, observed during March 1998 at low latitude station Jammu, is reported. The most prominent feature of these events is the multiflash nature along with the decrease in frequency within a very short span of time resembling similar to terrestrial whistlers. The events have a significantly smaller time duration (0.5–3.5 s than those reported earlier from high, mid and low latitudes and also display a diurnal maximum occurring around 09:30 h (IST. There have been similar reportings from other latitudes, but whistlers in the ELF-band with a multiflash nature along with a precursor emission have never been reported. Lightning seems to be the dominant source for the ELF whistlers reported here.

  5. Letter to the Editor: Geomagnetic storm effects at low latitudes

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

    Full Text Available The geomagnetic horizontal (H field from the chain of nine observatories in India are used to study the storm-time and disturbance daily variations. The peak decrease in storm-time variation in H showed significant enhancements at the equatorial electrojet stations over and above the normally expected decrease due to the ring current effects corrected for geomagnetic latitudes. The disturbance daily variation of H at equatorial stations showed a large decrease around midday hours over and above the usual dawn-maximum and dusk-minimum seen at any mid-latitude stations around the world. These slow and persistent additional decreases of H of disturbance daily variation at equatorial latitudes could be the effect of a westward electric field due to the Disturbance Ionospheric dynamo coupled with abnormally large electrical conductivities in the E region over the equator.Key words. Ionosphere (electric fields and currents · Magnetospheric physics (electric fields; storms and substorms

  6. Simulation studies of high-latitude magnetospheric boundary dynamics

    Institute of Scientific and Technical Information of China (English)

    PU; Zuyin; SHI; Quanqi; XIAO; Chijie; FU; Suiyan; ZHANG; Hu

    2004-01-01

    Magnetic reconnection at the high-latitude magnetopause is studied using 2.5-dimensional Hail-MHD simulation. Concentric flow vortices and magnetic islands appear when both Hall effect and sheared flow are considered. Plasma mixing across the magnetopause occurs in the presence of the flow vortices. Reconnected structure generated in the vicinity of the subsolar point changes its geometry with increasing flow shear while moving to high latitudes. In the presence of flow shear, with the Hail-MHD reconnection a higher reconnection rate than with the traditional MHD is obtained. The out-of-plane components of flow and magnetic field produced by the Hall current are redistributed under the action of the flow shear, which makes the plasma transport across the boundaries more complicated. The simulation results provide some help in understanding the dynamic processes at the high latitude magnetopause.

  7. CORAL REEFS. Genomic determinants of coral heat tolerance across latitudes.

    Science.gov (United States)

    Dixon, Groves B; Davies, Sarah W; Aglyamova, Galina A; Meyer, Eli; Bay, Line K; Matz, Mikhail V

    2015-06-26

    As global warming continues, reef-building corals could avoid local population declines through "genetic rescue" involving exchange of heat-tolerant genotypes across latitudes, but only if latitudinal variation in thermal tolerance is heritable. Here, we show an up-to-10-fold increase in odds of survival of coral larvae under heat stress when their parents come from a warmer lower-latitude location. Elevated thermal tolerance was associated with heritable differences in expression of oxidative, extracellular, transport, and mitochondrial functions that indicated a lack of prior stress. Moreover, two genomic regions strongly responded to selection for thermal tolerance in interlatitudinal crosses. These results demonstrate that variation in coral thermal tolerance across latitudes has a strong genetic basis and could serve as raw material for natural selection. Copyright © 2015, American Association for the Advancement of Science.

  8. Simultaneous in-situ observations of the signatures of dayside reconnection at the high- and low-latitude magnetopause

    Directory of Open Access Journals (Sweden)

    J. A. Wild

    2005-02-01

    Full Text Available We present magnetic field and particle data recorded by the Cluster and Geotail satellites in the vicinity of the high- and low-latitude dayside magnetopause, respectively, on 17 February 2003. A favourable conjunction of these spacecraft culminated in the observation of a series of flux transfer events (FTEs, characterised by bipolar perturbations in the component of the magnetic field normal to the magnetopause, an enhancement in the overall magnetic field strength, and field tilting effects in the plane of the magnetopause whilst the satellites were located on the magnetosheath side of the boundary. Whilst a subset of the FTE signatures observed could be identified as being either normal or reverse polarity, the rapid succession of events observed made it difficult to classify some of the signatures unambiguously. Nevertheless, by considering the source region and motion of flux tubes opened by magnetic reconnection at low latitudes (i.e. between Cluster and Geotail, we demonstrate that the observations are consistent with the motion of northward (southward and tailward moving flux tubes anchored in the Northern (Southern Hemisphere passing in close proximity to the Cluster (Geotail satellites. We are able to demonstrate that a multi-spacecraft approach, coupled with a realistic model of flux tube motion in the magnetosheath, enables us to infer the approximate position of the reconnection site, which in this case was located at near-equatorial latitudes.

  9. Present and Future Carbon Balance of Russia's Northern Ecosystems. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Chapin, F. Stuart III; Zimov, Sergei A.

    2000-08-28

    Recent increases in the seasonal amplitude of atmospheric CO{sub 2} at high latitudes suggest a widespread biospheric response to high-latitude warming. We have shown that the seasonal amplitude of net ecosystem carbon exchange by northern Siberian ecosystems is greater in disturbed than undisturbed sites, due to increased summer influx and increased winter efflux. Net carbon gain in summer and respiration in winter were greater in a cool than in a warm year, especially in disturbed sites and did not differ between high-arctic and treeline sites, suggesting that high-latitude warming, if it occurred, would have little effect or would reduce seasonal amplitude of carbon exchange. We suggest that increased disturbance contributes significantly to the amplified seasonal cycle of atmospheric CO{sub 2} at high latitudes.

  10. Seasonal and Interdecadal Variations of Heat Transport over the Northern Hemisphere

    Institute of Scientific and Technical Information of China (English)

    SUN Jilin; XU Delong; GU Dejun

    2006-01-01

    Using NCEP/NCAR reanalysis data, variations of heat transport in the Northern Hemisphere were studied.It was found that there are interdecadal variations in heat transport from middle latitudes to higher latitudes.The variations of interdecadal heat transport over longitudes around 120°E are out of phase with those over around 90°E and over the Northeastern Pacific.The seasonal variations of heat transport were also discussed.It was found that most heat is transported in the lower layer of the troposphere from middle latitudes to higher latitudes.Over around 120°E and over around 120°W, the seasonal and interannual variations of heat transport across 32.5°N are apparent and in phase.

  11. Responses of arthropod populations to warming depend on latitude

    DEFF Research Database (Denmark)

    Youngsteadt, Elsa; Ernst, Andrew F.; Dunn, Robert Roberdeau

    2017-01-01

    Biological effects of climate change are expected to vary geographically, with a strong signature of latitude. For ectothermic animals, there is systematic latitudinal variation in the relationship between climate and thermal performance curves, which describe the relationship between temperature...... and an organism's fitness. Here we ask whether these documented latitudinal patterns can be generalized to predict arthropod responses to warming across mid and high temperate latitudes, for taxa whose thermal physiology has not been measured. To address this question, we used a novel natural experiment...

  12. Topography of the Northern Hemisphere of Mercury from MESSENGER Laser Altimetry

    Science.gov (United States)

    Zuber,Maria T.; Smith, David E.; Phillips, Roger J.; Solomon, Sean C.; Neumann, Gregory A.; Hauck, Steven A., Jr.; Peale, Stanton J.; Barnouin, Oliver S.; Head, James W.; Johnson, Catherine L.; Lemoine, Frank G.; Mazarico, Erwan; Sun, Xiaoli; Torrence, Mark H.; Freed, Andrew M.; Klimczak, Christian; Margot, Jean-Luc; Oberst, Juergen; Perry, Mark E.; McNutt, Ralph L., Jr.; Balcerski, Jeffrey A.; Michel, Nathalie; Talpe, Matthieu J.; Yang, Di

    2012-01-01

    Laser altimetry by the MESSENGER spacecraft has yielded a topographic model of the northern hemisphere of Mercury. The dynamic range of elevations is considerably smaller than those of Mars or the Moon. The most prominent feature is an extensive lowland at high northern latitudes that hosts the volcanic northern plains. Within this lowland is a broad topographic rise that experienced uplift after plains emplacement. The interior of the 1500-km-diameter Caloris impact basin has been modified so that part of the basin floor now stands higher than the rim. The elevated portion of the floor of Caloris appears to be part of a quasi-linear rise that extends for approximately half the planetary circumference at mid-latitudes. Collectively, these features imply that long-wavelength changes to Mercury s topography occurred after the earliest phases of the planet s geological history.

  13. Molecular substitution rate increases with latitude in butterflies

    DEFF Research Database (Denmark)

    Schär, Sämi; Vila, Roger; Petrović, Andjeljko

    2017-01-01

    of five lycaenid butterfly species with varied ecological adaptations, sampled across a latitudinal gradient in the Holarctic region. We found a positive correlation between latitude and substitution rate of mitochondrial DNA sequences in all species investigated. We propose that this result is the signal...

  14. Multifractal analysis of low-latitude geomagnetic fluctuations

    Directory of Open Access Journals (Sweden)

    M. J. A. Bolzan

    2009-02-01

    Full Text Available The technique of large deviation multifractal spectrum has shown that the high-latitude (77.5° N, 69.2° W geomagnetic fluctuations can be described from direct dissipation process or loading-unloading regimes of the solar wind-magnetosphere coupling. In this paper, we analyze the H-component of low-latitude (22.4° S, 43.6° W geomagnetic field variability observed during the month of July 2000 at the Geomagnetic Observatory, Vassouras, RJ, Brazil. The variability pattern during this period is a mixture of quiet and disturbed days including the Bastille Day intense geomagnetic storm on 15 July. Due to the complexity of this data, we pursue a detailed analysis of the geomagnetic fluctuations in different time scales including a multifractal approach using the singular power spectrum deviations obtained from the wavelet transform modulus maxima (WTMM. The results suggest, as observed from high-latitude data, the occurrence of low-latitude multifractal processes driving the intermittent coupling between the solar wind-magnetosphere and geomagnetic field variations. On finer scales possible physical mechanisms in the context of nonlinear magnetosphere response are discussed.

  15. Insolation-sunshine relation with site elevation and latitude

    Energy Technology Data Exchange (ETDEWEB)

    Raja, I.A. (Univ. of Balochistan, Quetta (Pakistan))

    1994-07-01

    Data from six meteorological stations dispersed widely over Pakistan have been used to produce a correlation between the monthly means of easily measured sunshine duration and the less frequently recorded global solar radiation, taking into account the site elevation above sea level and the latitude. The relation is shown to be valuable for other regions too.

  16. Seasonal affective disorder and latitude : a review of the literature

    NARCIS (Netherlands)

    Mersch, PPA; Middendorp, HM; Bouhuys, AL; Beersma, DGM; van den Hoofdakker, RH; Middendorp, Hermine M.

    1999-01-01

    Background: The aim of the study is to investigate the relationship between the prevalence of SAD and latitude. Methods: An overview of the epidemiological literature on the prevalence of SAD is given and studies relevant for the latitudinal dependency of prevalence will be analyzed and discussed. R

  17. Seasonal affective disorder and latitude : a review of the literature

    NARCIS (Netherlands)

    Mersch, PPA; Middendorp, HM; Bouhuys, AL; Beersma, DGM; van den Hoofdakker, RH; Middendorp, Hermine M.

    Background: The aim of the study is to investigate the relationship between the prevalence of SAD and latitude. Methods: An overview of the epidemiological literature on the prevalence of SAD is given and studies relevant for the latitudinal dependency of prevalence will be analyzed and discussed.

  18. The domination of Saturn's low latitude ionosphere by ring `rain'

    CERN Document Server

    O'Donoghue, J; Melin, H; Jones, G H; Cowley, S W H; Miller, S; Baines, K H; Blake, J S D

    2013-01-01

    Saturn's ionosphere is produced when the otherwise neutral atmosphere is exposed to a flow of energetic charged particles or solar radiation. At low latitudes the latter should result in a weak planet-wide glow in infrared (IR), corresponding to the planet's uniform illumination by the Sun. The observed low-latitude ionospheric electron density is lower and the temperature higher than predicted by models. A planet-ring magnetic connection has been previously suggested in which an influx of water from the rings could explain the lower than expected electron densities in Saturn's atmosphere. Here we report the detection of a pattern of features, extending across a broad latitude band from ~25 to 60 degrees, that is superposed on the lower latitude background glow, with peaks in emission that map along the planet's magnetic field lines to gaps in Saturn's rings. This pattern implies the transfer of charged water products from the ring-plane to the ionosphere, revealing the influx on a global scale, flooding betw...

  19. Star Formation and Molecular Clouds at High Galactic Latitude

    Science.gov (United States)

    McGehee, P. M.

    2008-12-01

    In this chapter we review the young stars and molecular clouds found at high Galactic latitudes (|b| ≥ 30°). These are mostly associated with two large-scale structures on the sky, the Gould Belt and the Taurus star formation region, and a handful of molecular clouds including MBM 12 and MBM 20 which, as a population, consist of the nearest star formation sites to our Sun. There are also a few young stars that are found in apparent isolation far from any molecular cloud. The high latitude clouds are primarily translucent molecular clouds and diffuse Galactic cirrus with the majority of them seen at high latitude simply due to their proximity to the Sun. The rare exceptions are those, like the Draco and other intermediate or high velocity clouds, found significantly above or below the Galactic plane. We review the processes that result in star formation within these low density and extraplanar environments as well as the mechanisms for production of isolated T Tauri stars. We present and discuss the known high-latitude stellar nurseries and young stellar objects.

  20. Fertilization of Northern Hardwoods

    Science.gov (United States)

    R. Lea; D.G. Brockway

    1986-01-01

    Northern hardwoods grow over a considerable range of climatic and edaphic conditions and exhibit a wide range in productivity.Many northern hardwood forests are capable of high production relative to other forest types, but are often slow to reach maximum productivity because of low nutrient availability.Altering the patterns of biomass accumulation so that managers...

  1. ENSO response to high-latitude volcanic eruptions: the role of the initial conditions

    Science.gov (United States)

    Pausata, Francesco S. R.; Caballero, Rodrigo; Battisti, David S.

    2016-04-01

    Large volcanic eruptions can have major impacts on global climate affecting both atmospheric and ocean circulation through changes in atmospheric chemical composition and optical properties. The residence time of volcanic aerosol from strong eruptions is around 2-3 years and attention has consequently focused on their short-term impacts, and in particular on tropical eruptions. The long-term, ocean-mediated response has been less studied and large uncertainties remain. Moreover, studies have largely focused on tropical eruptions; high-latitude eruptions have drawn less attention because their impacts have been thought to be merely hemispheric rather than global and no study has hitherto investigated the long-term effects of such eruptions. Here we use a climate model to show that large summer high-latitude eruptions in the Northern Hemisphere could cause an El Niño-like anomaly in the equatorial Pacific during the first 8-9 months after the start of the eruption owing to a strong hemispheric cooling. The hemispherically asymmetric cooling shifts the Inter-Tropical Convergence Zone southwards, triggering a weakening of the trade winds over the western and central equatorial Pacific that leads to an El Niño-like anomaly. However, the El Niño-like anomaly strongly depends on the initial ENSO state: a 3-time larger response is shown when the climate system is going towards a La Niña compared to when is going towards an El Niño. Finally, the eruption also leads to a strengthening of the Atlantic Meridional Overturning Circulation (AMOC) in the first twenty-five years after the eruption, followed by a weakening lasting at least 35 years. The long-lived changes in the AMOC strength also alter the variability of El Niño-Southern Oscillation.

  2. Consequences of declining snow accumulation for water balance of mid-latitude dry regions

    Science.gov (United States)

    Schlaepfer, Daniel R.; Lauenroth, William K.; Bradford, John B.

    2012-01-01

    Widespread documentation of positive winter temperature anomalies, declining snowpack and earlier snow melt in the Northern Hemisphere have raised concerns about the consequences for regional water resources as well as wildfire. A topic that has not been addressed with respect to declining snowpack is effects on ecosystem water balance. Changes in water balance dynamics will be particularly pronounced at low elevations of mid-latitude dry regions because these areas will be the first to be affected by declining snow as a result of rising temperatures. As a model system, we used simulation experiments to investigate big sagebrush ecosystems that dominate a large fraction of the semiarid western United States. Our results suggest that effects on future ecosystem water balance will increase along a climatic gradient from dry, warm and snow-poor to wet, cold and snow-rich. Beyond a threshold within this climatic gradient, predicted consequences for vegetation switched from no change to increasing transpiration. Responses were sensitive to uncertainties in climatic prediction; particularly, a shift of precipitation to the colder season could reduce impacts of a warmer and snow-poorer future, depending on the degree to which ecosystem phenology tracks precipitation changes. Our results suggest that big sagebrush and other similar semiarid ecosystems could decrease in viability or disappear in dry to medium areas and likely increase only in the snow-richest areas, i.e. higher elevations and higher latitudes. Unlike cold locations at high elevations or in the arctic, ecosystems at low elevations respond in a different and complex way to future conditions because of opposing effects of increasing water-limitation and a longer snow-free season. Outcomes of such nonlinear interactions for future ecosystems will likely include changes in plant composition and productivity, dynamics of water balance, and availability of water resources.

  3. 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.

  4. Isotopic composition of low-latitude paleoprecipitation during the Early Cretaceous

    Science.gov (United States)

    Suarez, M.B.; Gonzalez, Luis A.; Ludvigson, Greg A.; Vega, F.J.; Alvarado-Ortega, J.

    2009-01-01

    likely underestimated tropical to subtropical precipitation and evaporation fluxes. The limited latitudinal constraints for earlier isotope mass balance modeling of the Albian hydrologic cycle of the Northern Hemisphere Americas resulted in extrapolated low-latitude precipitation ??18O values that were much heavier (up to 3???) than the values observed in this study. The lighter values identified in this study indicate a more pronounced rainout effect for tropical regions and quite possibly a more vigorous evaporation effect. These and additional low-latitude data are required to better constrain changes in the hydrologic cycle during the Cretaceous greenhouse period, and to reduce the uncertainties resulting from limited geographic coverage of proxy data. ?? 2009 Geological Society of America.

  5. High-latitude electromagnetic and particle energy flux during an event with sustained strongly northward IMF

    Directory of Open Access Journals (Sweden)

    H. Korth

    2005-06-01

    Full Text Available We present a case study of a prolonged interval of strongly northward orientation of the interplanetary magnetic field on 16 July 2000, 16:00-19:00 UT to characterize the energy exchange between the magnetosphere and ionosphere for conditions associated with minimum solar wind-magnetosphere coupling. With reconnection occurring tailward of the cusp under northward IMF conditions, the reconnection dynamo should be separated from the viscous dynamo, presumably driven by the Kelvin-Helmholtz (KH instability. Thus, these conditions are also ideal for evaluating the contribution of a viscous interaction to the coupling process. We derive the two-dimensional distribution of the Poynting vector radial component in the northern sunlit polar ionosphere from magnetic field observations by the constellation of Iridium satellites together with drift meter and magnetometer observations from the Defense Meteorological Satellite Program (DMSP F13 and F15 satellites. The electromagnetic energy flux is then compared with the particle energy flux obtained from auroral images taken by the far-ultraviolet (FUV instrument on the Imager for Magnetopause to Aurora Global Exploration (IMAGE spacecraft. The electromagnetic energy input to the ionosphere of 51 GW calculated from the Iridium/DMSP observations is eight times larger than the 6 GW due to particle precipitation all poleward of 78° MLAT. This result indicates that the energy transport is significant, particularly as it is concentrated in a small region near the magnetic pole, even under conditions traditionally considered to be quiet and is dominated by the electromagnetic flux. We estimate the contributions of the high and mid-latitude dynamos to both the Birkeland currents and electric potentials finding that high-latitude reconnection accounts for 0.8 MA and 45kV while we attribute <0.2MA and ~5kV to an interaction at lower latitudes having the sense of a viscous interaction. Given that these

  6. High-latitude plasma convection from Cluster EDI: variances and solar wind correlations

    Directory of Open Access Journals (Sweden)

    M. Förster

    2007-07-01

    Full Text Available Based on drift velocity measurements of the EDI instruments on Cluster during the years 2001–2006, we have constructed a database of high-latitude ionospheric convection velocities and associated solar wind and magnetospheric activity parameters. In an earlier paper (Haaland et al., 2007, we have described the method, consisting of an improved technique for calculating the propagation delay between the chosen solar wind monitor (ACE and Earth's magnetosphere, filtering the data for periods of sufficiently stable IMF orientations, and mapping the EDI measurements from their high-altitude positions to ionospheric altitudes. The present paper extends this study, by looking at the spatial pattern of the variances of the convection velocities as a function of IMF orientation, and by performing sortings of the data according to the IMF magnitude in the GSM y-z plane, |ByzIMF|, the estimated reconnection electric field, Er,sw, the solar wind dynamic pressure, Pdyn, the season, and indices characterizing the ring current (Dst and tail activity (ASYM-H. The variability of the high-latitude convection shows characteristic spatial patterns, which are mirror symmetric between the Northern and Southern Hemispheres with respect to the IMF By component. The latitude range of the highest variability zone varies with IMF Bz similar to the auroral oval extent. The magnitude of convection standard deviations is of the same order as, or even larger than, the convection magnitude itself. Positive correlations of polar cap activity are found with |ByzIMF| and with Er,sw, in particular. The strict linear increase for small magnitudes of Er,sw starts to deviate toward a flattened increase above about 2 mV/m. There is also a weak positive correlation with Pdyn. At

  7. 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

  8. Determination and analysis of local seasonal terms of latitude variations

    Science.gov (United States)

    Soloducha, Barbara

    1991-03-01

    Local seasonal terms of latitude variations were determined on the basis of phi data of 17 BIH/IMPS stations and x, y, z data of the BIH global solution during the years 1967-1978. Some models for local corrections R to the latitude introduced by the BIH are created. The corrections R obtained from the least squares adjustment from one year data appear to be the best. The present study shows that it is necessary to determine these more frequently than once a year or to compute them for all stations simultaneously with the ERP. This will be particularly important in view of the future re-reduction of past astrometric data.

  9. High-Latitude Ionospheric Dynamics During Conditions of Northward IMF

    Science.gov (United States)

    Sharber, J. R.

    1996-01-01

    In order to better understand the physical processes operating during conditions of northward interplanetary magnetic field (IMF), in situ measurements from the Dynamics Explorer-2 (low altitude) polar satellite and simultaneous observations from the auroral imager on the Dynamics Explorer-1 (high altitude) satellite were used to investigate the relationships between optical emissions, particle precipitation, and convective flows in the high-latitude ionosphere. Field aligned current and convective flow patterns during IMF north include polar cap arcs, the theta aurora or transpolar arc, and the 'horse-collar' aurora. The initial part of the study concentrated on the electrodynamics of auroral features in the horse-collar aurora, a contracted but thickened emission region in which the dawn and dusk portions can spread to very high latitudes, while the latter part focused on the evolution of one type of IMF north auroral pattern to another, specifically the quiet-time horse-collar pattern to a theta aurora.

  10. Assessment of Plasma Transport and Convection at High Latitudes

    Science.gov (United States)

    1984-01-01

    The high-latitude ionosphere is strongly coupled to the thermosphere and magnetosphere. The magnetospheric coupling occurs via electric fields, field-aligned currents, and particle precipitation. Owing to the interaction of the shocked solar wind with the geomagnetic field, an electric potential difference is generated across the tail of the magnetosphere, with the resulting electric field pointing from dawn to dusk. Energetic particle precipitation from the magnetosphere in the auroral region leads to the creation of ionization and to electron, ion, and neutral gas heating. In order to assess the current understanding of plasma transport and convection at high latitudes, it is necessary to take account of the strong coupling between the ionosphere, thermosphere, and magnetosphere.

  11. An absence of fast radio bursts at intermediate galactic latitudes

    CERN Document Server

    Petroff, E; Johnston, S; Bailes, M; Barr, E D; Bates, S D; Bhat, N D R; Burgay, M; Burke-Spolaor, S; Champion, D; Coster, P; Flynn, C; Keane, E F; Keith, M J; Kramer, M; Levin, L; Ng, C; Possenti, A; Stappers, B W; Tiburzi, C; Thornton, D

    2014-01-01

    Fast radio bursts (FRBs) are an emerging class of bright, highly dispersed radio pulses. Recent work by Thornton et al. (2013) has revealed a population of FRBs in the High Time Resolution Universe (HTRU) survey at high Galactic latitudes. A variety of progenitors have been proposed including cataclysmic events at cosmological distances, Galactic flare stars, and terrestrial radio frequency interference. Here we report on a search for FRBs at intermediate Galactic latitudes ($-15^{\\circ}$ $< b <$ 15$^{\\circ}$) in data taken as part of the HTRU survey. No FRBs were discovered in this region. Several effects such as dispersion, scattering, sky temperature and scintillation decrease the sensitivity by more than 3$\\sigma$ in $\\sim$20\\% of survey pointings. Including all of these effects, we exclude the hypothesis that FRBs are uniformly distributed on the sky with 99\\% confidence. This low probability implies that additional factors -- not accounted for by standard Galactic models -- must be included to eas...

  12. A latitude-dependent wind model for Mira's cometary head

    CERN Document Server

    Raga, A C; De Colle, F; Esquivel, A; Kajdic, P; Rodríguez-González, A; Velázquez, P F

    2008-01-01

    We present a 3D numerical simulation of the recently discovered cometary structure produced as Mira travels through the galactic ISM. In our simulation, we consider that Mira ejects a steady, latitude-dependent wind, which interacts with a homogeneous, streaming environment. The axisymmetry of the problem is broken by the lack of alignment between the direction of the relative motion of the environment and the polar axis of the latitude-dependent wind. With this model, we are able to produce a cometary head with a ``double bow shock'' which agrees well with the structure of the head of Mira's comet. We therefore conclude that a time-dependence in the ejected wind is not required for reproducing the observed double bow shock.

  13. Orbital control of low-latitude seasonality during the Eemian

    Science.gov (United States)

    Winter, A.; Paul, A.; Nyberg, J.; Oba, T.; Lundberg, J.; Schrag, D.; Taggart, B.

    2003-01-01

    We used Sr/Ca and stable isotope data from well dated and preserved corals from the northeastern Caribbean to determine the seasonal environmental conditions for four continuous years during the Eemian, the last time the Earth was in a prolonged warm phase. We determined that the seasonal range in SST during the Eemian was 25??-30?? C. This is ???1-2?? larger than at present and caused primarily by winter cooling and, only to a small degree, by summer warming. As climate modeling studies indicate, the bias towards colder winters can be explained by changes in low latitude insolation induced by altered orbital parameters, modulated by atmospheric CO2 levels that were lower than today. Milankovitch forcing at higher latitudes was probably less important.

  14. Cutoff latitude variation during solar proton events: Causes and consequences

    CERN Document Server

    Tyssøy, H Nesse

    2016-01-01

    To accurately quantify the effect of solar proton events (SPEs) on the atmosphere requires a good estimate of the particle energy deposition in the middle atmosphere (60- 100 km) and how the energy is distributed globally. Protons in the energy range 1-20MeV, depositing their energy in the middle atmosphere, are subject to more complex dynamics with strong day-night asymmetries compared to higher-energy particles. Our study targets six SPEs from 2003 to 2012. By using measurements from the Medium Energy Proton and Electron Detector on all available Polar Orbit Environment Satellites (POES), we show that in the main phase of geomagnetic storms the dayside cutoff latitudes are pushed poleward, while the nightside cutoff latitudes have the opposite response, resulting in strong day-night asymmetries in the energy deposition. These features cannot bemeasured by the frequently used Geostationary Operational Environmental Satellites (GOES). Assuming that the protons impact the polar atmosphere homogeneously above a...

  15. Specialization of mutualistic interaction networks decreases toward tropical latitudes

    DEFF Research Database (Denmark)

    Schleuning, M.; Fründ, J.; Klein, A.-M.

    2012-01-01

    ] or differences in plant diversity [10, 11]. Thus, the direction of the latitudinal specialization gradient remains contentious. With an unprecedented global data set, we investigated how biotic specialization between plants and animal pollinators or seed dispersers is associated with latitude, past...... to low plant diversity. This could explain why the latitudinal specialization gradient is reversed relative to the latitudinal diversity gradient. Low mutualistic network specialization in the tropics suggests higher tolerance against extinctions in tropical than in temperate communities....

  16. Summertime total ozone variations over middle and polar latitudes

    OpenAIRE

    Fioletov, Vitali E.; Shepherd, Theodore G.

    2005-01-01

    The statistical relationship between springtime and summertime ozone over middle and polar latitudes is analyzed using zonally averaged total ozone data. Shortterm variations in springtime midlatitude ozone demonstrate only a modest correlation with springtime polar ozone variations. However by early summer, ozone variations throughout the extratropics are highly correlated. Analysis of correlation functions indicates that springtime midlatitude ozone, not polar ozone, is the best predictor f...

  17. Specialization of mutualistic interaction networks decreases toward tropical latitudes

    DEFF Research Database (Denmark)

    Schleuning, Matthias; Fründ, Jochen; Klein, Alexandra-Maria

    2012-01-01

    ] or differences in plant diversity [10, 11]. Thus, the direction of the latitudinal specialization gradient remains contentious. With an unprecedented global data set, we investigated how biotic specialization between plants and animal pollinators or seed dispersers is associated with latitude, past...... that current conditions have a stronger effect on biotic specialization than historical community stability. Biotic specialization decreased with increasing local and regional plant diversity. This suggests that high specialization of mutualistic interactions is a response of pollinators and seed dispersers...

  18. The High Latitude D Region During Electron Precipitation Events

    Science.gov (United States)

    Hargreaves, J. K.; Collis, P. N.; Korth, A.

    1984-01-01

    The fluxes of energetic electrons entering the high-latitude atmosphere during auroral radio absorption events and their effect on the electron density in the auroral D region are discussed. An attempt was made to calculate the radio absorption during precipitation events from the fluxes of energetic electrons measured at geosynchronous orbit, and then to consider the use of absorption measurements to indicate the magnetospheric particle fluxes, the production rates, and electron densities in the D region.

  19. High latitude D region during electron precipitation events

    Energy Technology Data Exchange (ETDEWEB)

    Hargreaves, J.K.; Collis, P.N.; Korth, A.

    1984-05-01

    The fluxes of energetic electrons entering the high-latitude atmosphere during auroral radio absorption events and their effect on the electron density in the auroral D region are discussed. An attempt was made to calculate the radio absorption during precipitation events from the fluxes of energetic electrons measured at geosynchronous orbit, and then to consider the use of absorption measurements to indicate the magnetospheric particle fluxes, the production rates, and electron densities in the D region.

  20. Boundary Current and Mixing Processes in The High Latitude Oceans

    Science.gov (United States)

    2016-06-07

    Boundary Current and Mixing Processes in The High Latitude Oceans Robin D. Muench Earth & Space Research 1910 Fairview Ave E., Ste 210 Seattle...Thorpe and Ozmidov length scales. Journal of Geophysical Research , 87, 9601-9613. Galbraith, P.S., and D.E. Kelley, 1996: Identifying overturns in...and near Marguerite Bay during winter 2003: A SO GLOBEC study. Deep-Sea Research 2, 54. Padman, L., S.L. Howard, and R.D. Muench, 2006a: Internal

  1. Impacts of climate warming on terrestrial ectotherms across latitude.

    Science.gov (United States)

    Deutsch, Curtis A; Tewksbury, Joshua J; Huey, Raymond B; Sheldon, Kimberly S; Ghalambor, Cameron K; Haak, David C; Martin, Paul R

    2008-05-06

    The impact of anthropogenic climate change on terrestrial organisms is often predicted to increase with latitude, in parallel with the rate of warming. Yet the biological impact of rising temperatures also depends on the physiological sensitivity of organisms to temperature change. We integrate empirical fitness curves describing the thermal tolerance of terrestrial insects from around the world with the projected geographic distribution of climate change for the next century to estimate the direct impact of warming on insect fitness across latitude. The results show that warming in the tropics, although relatively small in magnitude, is likely to have the most deleterious consequences because tropical insects are relatively sensitive to temperature change and are currently living very close to their optimal temperature. In contrast, species at higher latitudes have broader thermal tolerance and are living in climates that are currently cooler than their physiological optima, so that warming may even enhance their fitness. Available thermal tolerance data for several vertebrate taxa exhibit similar patterns, suggesting that these results are general for terrestrial ectotherms. Our analyses imply that, in the absence of ameliorating factors such as migration and adaptation, the greatest extinction risks from global warming may be in the tropics, where biological diversity is also greatest.

  2. Mountain biodiversity patterns at low and high latitudes.

    Science.gov (United States)

    Molau, Ulf

    2004-11-01

    This paper presents an overview of mountain biodiversity at a multitude of scales in space, time, and function. Even though species richness is usually the focal component in nature conservation, genetic diversity within species is equally important. The small-scale distribution of species in the tropical Andes, as exemplified by the plant genera Calceolaria and Bartsia, contrasts against the situation in high-latitude mountains, e.g., the Scandes, where species have wide ranges and many are circumpolar. Recent studies on alpine plants based on molecular methods show that the intraspecific genetic diversity tends to increase with latitude, a situation brought about by the glaciation history with repeated contraction-expansion episodes of species' distributions. In tropical mountains, species distributions are geographically much narrower, often as a result of relatively recent, local speciation. Thus, whereas species richness in mountains decreases from the Equator towards the poles, genetic diversity shows the opposite trend. Finally, a comparison of ecosystem diversity in low- and high-latitude mountain ranges (tropical Andes vs. Scandes) shows that the landscapes differ profoundly with regard to timberline ecotones, snow distribution, and climate variables, and are subject to widely different impacts of global change

  3. Ionosphere Scintillation at Low and High Latitudes (Modelling vs Measurement)

    Science.gov (United States)

    Béniguel, Yannick

    2016-04-01

    This paper will address the problem of scintillations characteristics, focusing on the parameters of interest for a navigation system. Those parameters are the probabilities of occurrence of simultaneous fading, the bubbles surface at IPP level, the cycle slips and the fades duration statistics. The scintillation characteristics obtained at low and high latitudes will be compared. These results correspond to the data analysis performed after the ESA Monitor ionosphere measurement campaign [1], [2]. A second aspect of the presentation will be the modelling aspect. It has been observed that the phase scintillation dominates at high latitudes while the intensity scintillation dominates at low latitudes. The way it can be reproduced and implemented in a propagation model (e.g. GISM model [3]) will be presented. Comparisons of measurements with results obtained by modelling will be presented on some typical scenarios. References [1] R. Prieto Cerdeira, Y. Beniguel, "The MONITOR project: architecture, data and products", Ionospheric Effects Symposium, Alexandria (Va), May 2011 [2] Y. Béniguel, R Orus-Perez , R. Prieto-Cerdeira , S. Schlueter , S. Scortan, A. Grosu "MONITOR 2: ionospheric monitoring network in support to SBAS and other GNSS and scientific purposes", IES Conference, Alexandria (Va), May 2015-05-22 [3] Y. Béniguel, P. Hamel, "A Global Ionosphere Scintillation Propagation Model for Equatorial Regions", Journal of Space Weather Space Climate, 1, (2011), doi: 10.1051/swsc/2011004

  4. Star Formation and Molecular Clouds at High Galactic Latitude

    CERN Document Server

    McGehee, Peregrine M

    2008-01-01

    In this chapter we review the young stars and molecular clouds found at high Galactic latitudes $(|b| \\ge 30^\\circ)$. These are mostly associated with two large-scale structures on the sky, the Gould Belt and the Taurus star formation region, and a handful of molecular clouds including MBM 12 and MBM 20 which, as a population, consist of the nearest star formation sites to our Sun. There are also a few young stars that are found in apparent isolation far from any molecular cloud. The high latitude clouds are primarily translucent molecular clouds and diffuse Galactic cirrus with the majority of them seen at high latitude simply due to their proximity to the Sun. The rare exceptions are those, like the Draco and other intermediate or high velocity clouds, found significantly above or below the Galactic plane. We review the processes that result in star formation within these low density and extraplanar environments as well as the mechanisms for production of isolated T Tauri stars. We present and discuss the k...

  5. Northern Dimension: Participant Strategies

    Directory of Open Access Journals (Sweden)

    Busygina Irina

    2009-03-01

    Full Text Available This article is devoted to the “Northern Dimension” initiative of the EU which also includes North-West Russia, Norway and Iceland. It is noted that the “Northern Dimension” in the theoretical perspective can be considered as part of strategic multi-level interactions between member-states of the EU and Russia. On this basis, the authors analyze implications and effects of the strategic interdependence of all the EU-Russia relation levels.

  6. Microphysical Ice Crystal Properties in Mid-Latitude Frontal Cirrus

    Science.gov (United States)

    Schlage, Romy; Jurkat, Tina; Voigt, Christiane; Minikin, Andreas; Weigel, Ralf; Molleker, Sergej; Klingebiel, Marcus; Borrmann, Stephan; Luebke, Anna; Krämer, Martina; Kaufmann, Stefan; Schäfler, Andreas

    2015-04-01

    Cirrus clouds modulate the climate by reflection of shortwave solar radiation and trapping of longwave terrestrial radiation. Their net radiative effect can be positive or negative depending on atmospheric and cloud parameters including ice crystal number density, size and shape. Latter microphysical ice crystal properties have been measured during the mid-latitude cirrus mission ML-CIRRUS with a set of cloud instruments on the new research aircraft HALO. The mission took place in March/April 2014 with 16 flights in cirrus formed above Europe and the Atlantic. The ice clouds were encountered at altitudes from 7 to 14 km in the typical mid-latitude temperature range. A focus of the mission was the detection of frontal cirrus linked to warm conveyor belts (WCBs). Within WCBs, water vapor is transported in the warm sector of an extra-tropical cyclone from the humid boundary layer to the upper troposphere. Cirrus cloud formation can be triggered in the WCB outflow region at moderate updraft velocities and additionally at low updrafts within the high pressure system linked to the WCB. Due to their frequent occurrence, WCBs represent a major source for regions of ice supersaturation and cirrus formation in the mid-latitudes. Here, we use data from the Cloud and Aerosol Spectrometer with detection for POLarization (CAS-POL) and the Cloud Combination Probe (CCP), combining a Cloud Droplet Probe (CDP) and a greyscale Cloud Imaging Probe (CIPgs) to investigate the ice crystal distribution in the size range from 0.5 µm to 1 mm. We derive microphysical cirrus properties in mid-latitude warm front cirrus. Further, we investigate their variability and their dependence on temperature and relative humidity. Finally, we compare the microphysical properties of these frontal cirrus to cirrus clouds that formed at low updrafts within high pressure systems or at high updraft velocities in lee waves. We quantify statistically significant differences in cirrus properties formed in these

  7. Use of radio occultation to probe the high latitude ionosphere

    Directory of Open Access Journals (Sweden)

    A. J. Mannucci

    2015-02-01

    Full Text Available We have explored the use of COSMIC data to provide valuable scientific information on the ionospheric impacts of energetic particle precipitation during geomagnetic storms. Ionospheric electron density in the E region, and hence ionospheric conductivity, is significantly altered by precipitating particles from the magnetosphere. This has global impacts on the thermosphere-ionosphere because of the important role of conductivity on high latitude Joule heating. Two high-speed stream (HSS and two coronal mass ejection (CME storms are examined with the COSMIC data. We find clear correlation between geomagnetic activity and electron density retrievals from COSMIC. At nighttime local times, the number of profiles with maximum electron densities in the E layer (below 200 km altitude is well correlated with geomagnetic activity. We interpret this to mean that electron density increases due to precipitation are captured by the COSMIC profiles. These "E layer dominant ionosphere" (ELDI profiles have geomagnetic latitudes that are consistent with climatological models of the auroral location. For the two HSS storms, that occurred in May of 2011 and 2012, a strong hemispheric asymmetry is observed, with nearly all the ELDI profiles found in the southern, less sunlit, hemisphere. Stronger aurora and precipitation have been observed before in winter hemispheres, but the degree of asymmetry deserves further study. For the two CME storms, occurring in July and November of 2012, large increases in the number of ELDI profiles are found starting in the storm's main phase but continuing for several days into the recovery phase. Analysis of the COSMIC profiles was extended to all local times for the July 2012 CME storm by relaxing the ELDI criterion and instead visually inspecting all profiles above 50° magnetic latitude for signatures of precipitation in the E region. For nine days during the July 2012 period, we find a signature of precipitation occurs nearly

  8. Mountain birch – potentially large source of sesquiterpenes into high latitude atmosphere

    Directory of Open Access Journals (Sweden)

    S. Haapanala

    2009-06-01

    Full Text Available Emissions of volatile organic compounds (VOCs from mountain birches were measured in Abisko, northern Sweden. Mountain birches make up majority of the tree biomass in Scandinavian high latitudes, area subject to significant climate warming. The measurements were carried out in two growing seasons. The emissions of a branch from four individual trees were measured in June–August 2006 and one of them again in July 2007. The measurements were conducted using a dynamic flow through chamber covered with Teflon film. The studied mountain birches were found to emit substantial amounts of linalool, monoterpenes and sesquiterpenes. The monoterpene emission was dominated by sabinene. The magnitude and composition of sesquiterpene emission changed dramatically between the years. For example, the average α-farnesene emission in 2006 was almost 2000 ng gdw−1 h−1 while in 2007 the emission of α-farnesene was negligible. Also the emissions of other sesquiterpenes decreased in 2007 to a fraction of that in 2006. One possible explanation for the change in emissions is the herbivory damage that occurred in the area in 2004. Herbivory is known to enhance the emissions of sesquiterpenes, especially those of α-farnesene, and the effect may last several years.

  9. Mountain birch – potentially large source of sesquiterpenes into high latitude atmosphere

    Directory of Open Access Journals (Sweden)

    A. Arneth

    2009-11-01

    Full Text Available Emissions of volatile organic compounds (VOCs from mountain birches were measured in Abisko, northern Sweden. Mountain birches make up the majority of the tree biomass in Scandinavian high latitudes, a region subject to significant climate warming. The measurements were carried out in two growing seasons. The emissions of four branches, each from a different individual tree, were measured in June–August 2006 and one of them again in July 2007. The measurements were conducted using a dynamic flow through chamber covered with Teflon film. The studied mountain birches were found to emit substantial amounts of linalool, monoterpenes and sesquiterpenes. The monoterpene emission was dominated by sabinene. The magnitude and composition of the sesquiterpene emission changed dramatically between the years. For example, the average α-farnesene emission potential in 2006 was almost 2600 ng gdw−1 h−1 (3.5 pmol gdw−1 s−1 while in 2007 α-farnesene was not detected at all. Also the emissions of other sesquiterpenes decreased in 2007 to a fraction of that in 2006. One possible explanation for the change in emissions is the herbivory damage that occurred in the area in 2004. Herbivory is known to enhance the emissions of sesquiterpenes, especially those of α-farnesene, and the effect may last for several years.

  10. Cusp observation at Saturn's high-latitude magnetosphere by the Cassini spacecraft.

    Science.gov (United States)

    Jasinski, J M; Arridge, C S; Lamy, L; Leisner, J S; Thomsen, M F; Mitchell, D G; Coates, A J; Radioti, A; Jones, G H; Roussos, E; Krupp, N; Grodent, D; Dougherty, M K; Waite, J H

    2014-03-16

    We report on the first analysis of magnetospheric cusp observations at Saturn by multiple in situ instruments onboard the Cassini spacecraft. Using this we infer the process of reconnection was occurring at Saturn's magnetopause. This agrees with remote observations that showed the associated auroral signatures of reconnection. Cassini crossed the northern cusp around noon local time along a poleward trajectory. The spacecraft observed ion energy-latitude dispersions-a characteristic signature of the terrestrial cusp. This ion dispersion is "stepped," which shows that the reconnection is pulsed. The ion energy-pitch angle dispersions suggest that the field-aligned distance from the cusp to the reconnection site varies between ∼27 and 51 RS . An intensification of lower frequencies of the Saturn kilometric radiation emissions suggests the prior arrival of a solar wind shock front, compressing the magnetosphere and providing more favorable conditions for magnetopause reconnection. We observe evidence for reconnection in the cusp plasma at SaturnWe present evidence that the reconnection process can be pulsed at SaturnSaturn's cusp shows similar characteristics to the terrestrial cusp.

  11. 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.

  12. High latitude temperature evolution across the Last Interglacial: a model-data comparison

    Science.gov (United States)

    Capron, Emilie; Stone, Emma; Govin, Aline; Loutre, Marie-France; Masson-Delmotte, Valerie; Mulitza, Stefan; Otto-Bliesner, Betty; Sime, Louise; Waelbroeck, Claire; Wolff, Eric W.

    2014-05-01

    The Last Interglacial (LIG, 129-116 thousand of years, ka) represents an interesting test bed for climate model feedbacks for warmer-than-present high latitudes. However, mainly because synchronising different paleoclimatic archives from different parts of the world is not trivial, a global picture of LIG temperature changes is difficult to obtain. In the framework of the UK iGlass consortium and the European Past4Future project, we have selected 49 polar ice core and sub-polar marine sediment records and developed a strategy to synchronise them onto the recent AICC2012 ice core chronology. This new synthesis enables us to describe the spatial and temporal climatic patterns over polar ice sheets (surface air temperature) and around the ice margins (sea surface temperatures) at a pluri-centennial to millennial-scale. Major features highlighted are (i) non synchronous maximum temperature change between the two hemispheres with the Southern Ocean and Antarctica records showing an early warming compared to North Atlantic records and (ii) Southern hemisphere records exhibiting warm conditions for a longer time period compared to records from the Northern Hemisphere and smaller temperature amplitude changes. Our compiled records are compared with recent snapshot and transient model experiments performed with three state of the art General Circulation Models (HADCM3, CCSM3, FAMOUS) and an Earth Model of Intermediary Complexity (LOVECLIM). Such an exercise enables us to investigate the climate feedbacks which causes the most apparent model-data differences.

  13. Atmospheric teleconnections between the tropics and high southern latitudes during millennial climate change

    Science.gov (United States)

    Markle, Bradley; Steig, Eric; Schoenemann, Spruce; Buizert, Christo; Pedro, Joel; Bitz, Cecilia; Ding, Qinghua; Jones, Tyler; Fudge, Tyler

    2015-04-01

    Rapid climate changes, known as Dansgaard-Oeschger (DO) events, are ubiquitous over the last glacial period. DO climate anomalies are propagated globally through climatic teleconnections that are incompletely understood and insufficiently constrained by paleoclimatic data. Here we use a high-resolution deuterium excess record from West Antarctica to show that changes in the moisture sources for Antarctic precipitation occurred in-phase with the DO shifts in Northern Hemisphere (NH) climate and tropical hydrology. These results support the hypothesis that the Southern Hemisphere (SH) storm tracks migrate northwards during NH warm periods, in parallel with the well-established northward migration of the intertropical convergence zone. Variability in the deuterium excess record also suggests that Southern Ocean sea surface temperatures (SST) followed the pattern of Antarctic surface temperatures -- out of phase with NH climate, as expected from conceptual and numerical models of the ocean bipolar "seesaw" mechanism. Furthermore, using a physically-based definition of the deuterium excess parameter, we show East Antarctic records are highly coherent with the WAIS Divide record, indicating that the SST changes are zonally uniform. Our data demonstrate that both atmospheric and oceanic teleconnections couple climate variations between the NH and SH high latitudes, and constrain the timescales on which they operate.

  14. Trends in motor neuron disease: association with latitude and air lead levels in Spain.

    Science.gov (United States)

    Santurtún, Ana; Villar, Alejandro; Delgado-Alvarado, Manuel; Riancho, Javier

    2016-08-01

    Motor neuron diseases (MND) are a group of disorders characterized by motor neuron degeneration. Among them, amyotrophic lateral sclerosis (ALS) is by far the most common in adulthood. This paper assesses the trend and geographical pattern in MND incidence in Spain and the possible air lead levels effect on this pathology. To confirm this concept, we performed a retrospective analysis of the deaths due to MND in Spain during 2000 and 2013, determined the geographical differences, and explored the relationship between MND and the air levels of lead. Overall, between 2000 and 2013, 11,355 people died in Spain because of MND. Disease mortality significantly increased in recent years (2007-2013) when compared with the first time of the period. Spearman's rank correlation coefficient also showed a statistically significant positive trend (CC = 0.824, p = 0.0002). Among people over 65 years, mortality rates were higher in Northern provinces. Moreover, we found a significant association of MND mortality with higher air lead levels (CC = 0.457, p = 0.01). Our study confirms that MND mortality is increasing in Spain, with a significant latitude gradient, which suggests an important role of environmental exposures. This ecological study suggests that air lead levels may be implicated in ALS pathogenesis.

  15. The high latitude convection response to an interval of substorm activity

    Directory of Open Access Journals (Sweden)

    T. K. Yeoman

    Full Text Available On 17 March 1991, five clear substorm onsets/intensifications took place within a three hour interval. During this interval ground-based data from the EISCAT incoherent scatter radar, a digital CCD all sky camera, and an extensive array of magnetometers were available, in addition to data from the CRRES and DMSP spacecraft, whose footprints passed over Scandinavia very close to most of the ground-based instrumentation. This interval of substorm activity has been interpreted as being in support of a near-Earth current disruption model of substorm onset. In the present study the ionospheric convection response, observed some four hours to the west in MLT by the Halley HF radar in Antarctica, is related to the growth, expansion and recovery phases of two of the substorm onsets/expansions observed in the Northern Hemisphere. Bursts of ionospheric flow and motion of the convection reversal boundary (CRB are observed at Halley in response to the substorm activity and changes in the IMF. The delay between the substorm expansion phase onset and the response in the CRB location is dependent on the local time separation from, and latitude of, the initial substorm onset region. These results are interpreted in terms of a synthesis of the very near-Earth current disruption model and the near-Earth neutral line model of substorm onset.

  16. High northern geomagnetic field behavior and new constraints on the Gilsá event: Paleomagnetic and 40Ar/39Ar results of ∼0.5–3.1 Ma basalts from Jökuldalur, Iceland

    DEFF Research Database (Denmark)

    Døssing Andreasen, Arne; Muxworthy, Adrian R.; Supakulopas, Radchagrit

    2016-01-01

    Recent paleomagnetic results of extrusive rocks from high southern latitudes (>60°S) and high northern latitudes (>60°N) have been suggested to reflect a hemispheric asymmetry of the geomagnetic field on time-scales of 105 to 106 yrs, with higher and more stable fields in the north. This interpre...

  17. Non-native and native organisms moving into high elevation and high latitude ecosystems in an era of climate change

    DEFF Research Database (Denmark)

    Pauchard, Aníbal; Milbau, Ann; Albihn, Ann;

    2016-01-01

    Cold environments at high elevation and high latitude are often viewed as resistant to biological invasions. However, climate warming, land use change and associated increased connectivity all increase the risk of biological invasions in these environments. Here we present a summary of the key...... discussions of the workshop ‘Biosecurity in Mountains and Northern Ecosystems: Current Status and Future Challenges’ (Flen, Sweden, 1–3 June 2015). The aims of the workshop were to (1) increase awareness about the growing importance of species expansion—both non-native and native—at high elevation and high......, especially if it is coupled with prioritisation schemes for targeting invaders likely to have greatest impact. Communication and co-operation between cold environment regions will facilitate rapid response, and maximise the use of limited research and management resources....

  18. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian

    Science.gov (United States)

    Baker, David M. H.; Head, James W.; Marchant, David R.

    2010-05-01

    A variety of Late Amazonian landforms on Mars have been attributed to the dynamics of ice-related processes. Evidence for large-scale, mid-latitude glacial episodes existing within the last 100 million to 1 billion years on Mars has been presented from analyses of lobate debris aprons (LDA) and lineated valley fill (LVF) in the northern and southern mid-latitudes. We test the glacial hypothesis for LDA and LVF along the dichotomy boundary in the northern mid-latitudes by examining the morphological characteristics of LDA and LVF surrounding two large plateaus, proximal massifs, and the dichotomy boundary escarpment north of Ismeniae Fossae (centered at 45.3°N and 39.2°E). Lineations and flow directions within LDA and LVF were mapped using images from the Context (CTX) camera, the Thermal Emission Imaging Spectrometer (THEMIS), and the High Resolution Stereo Camera (HRSC). Flow directions were then compared to topographic contours derived from the Mars Orbiter Laser Altimeter (MOLA) to determine the down-gradient components of LDA and LVF flow. Observations indicate that flow patterns emerge from numerous alcoves within the plateau walls, are integrated over distances of up to tens of kilometers, and have down-gradient flow directions. Smaller lobes confined within alcoves and superposed on the main LDA and LVF represent a later, less extensive glacial phase. Crater size-frequency distributions of LDA and LVF suggest a minimum (youngest) age of 100 Ma. The presence of ring-mold crater morphologies is suggestive that LDA and LVF are formed of near-surface ice-rich bodies. From these observations, we interpret LDA and LVF within our study region to result from formerly active debris-covered glacial flow, consistent with similar observations in the northern mid-latitudes of Mars. Glacial flow was likely initiated from the accumulation and compaction of snow and ice on plateaus and in alcoves within the plateau walls as volatiles were mobilized to the mid-latitudes

  19. The First in situ Observation of Kelvin-Helmholtz Waves at High-Latitude Magnetopause during Strongly Dawnward Interplanetary Magnetic Field Conditions

    Science.gov (United States)

    Hwang, K.-J.; Goldstein, M. L.; Kuznetsova, M. M.; Wang, Y.; Vinas, A. F.; Sibeck, D. G.

    2012-01-01

    We report the first in situ observation of high-latitude magnetopause (near the northern duskward cusp) Kelvin-Helmholtz waves (KHW) by Cluster on January 12, 2003, under strongly dawnward interplanetary magnetic field (IMF) conditions. The fluctuations unstable to Kelvin-Helmholtz instability (KHI) are found to propagate mostly tailward, i.e., along the direction almost 90 deg. to both the magnetosheath and geomagnetic fields, which lowers the threshold of the KHI. The magnetic configuration across the boundary layer near the northern duskward cusp region during dawnward IMF is similar to that in the low-latitude boundary layer under northward IMF, in that (1) both magnetosheath and magnetospheric fields across the local boundary layer constitute the lowest magnetic shear and (2) the tailward propagation of the KHW is perpendicular to both fields. Approximately 3-hour-long periods of the KHW during dawnward IMF are followed by the rapid expansion of the dayside magnetosphere associated with the passage of an IMF discontinuity that characterizes an abrupt change in IMF cone angle, Phi = acos (B(sub x) / absolute value of Beta), from approx. 90 to approx. 10. Cluster, which was on its outbound trajectory, continued observing the boundary waves at the northern evening-side magnetopause during sunward IMF conditions following the passage of the IMF discontinuity. By comparing the signatures of boundary fluctuations before and after the IMF discontinuity, we report that the frequencies of the most unstable KH modes increased after the discontinuity passed. This result demonstrates that differences in IMF orientations (especially in f) are associated with the properties of KHW at the high-latitude magnetopause due to variations in thickness of the boundary layer, and/or width of the KH-unstable band on the surface of the dayside magnetopause.

  20. Case study on total electron content enhancements at low latitudes during low geomagnetic activities before the storms

    Directory of Open Access Journals (Sweden)

    Libo Liu

    2008-05-01

    Full Text Available Sometimes the ionospheric total electron content (TEC is significantly enhanced during low geomagnetic activities before storms. In this article, we investigate the characteristics of those interesting TEC enhancements using regional and global TEC data. We analyzed the low-latitude TEC enhancement events that occurred around longitude 120° E on 10 February 2004, 21 January 2004, and 4 March 2001, respectively. The TEC data are derived from regional Global Positioning System (GPS observations in the Asia/Australia sector as well as global ionospheric maps (GIMs produced by Jet Propulsion Laboratory (JPL. Strong enhancements under low geomagnetic activity before the storms are simultaneously presented at low latitudes in the Asia/Australia sector in regional TEC and JPL GIMs. These TEC enhancements are shown to be regional events with longitudinal and latitudinal extent. The regions of TEC enhancements during these events are confined at narrow longitude ranges around longitude 120° E. The latitudinal belts of maxima of enhancements locate around the northern and southern equatorial ionization anomaly (EIA crests, which are consistent with those low-latitude events presented by Liu et al. (2008. During the 4 March 2001 event, the total plasma density Ni observed by the Defense Meteorological Satellite Program (DMSP spacecraft F13 at 840 km altitude are of considerably higher values on 4 March than on the previous day in the TEC enhanced regions. Some TEC enhancement events are possibly due to contributions from auroral/magnetospheric origins; while there are also quasi-periodic enhancement events not related to geomagnetic activity and associated probably with planetary wave type oscillations (e.g. the 6 January 1998 event. Further investigation is warrented to identify/separate contributions from possible sources.

  1. Magnetospheric effects in atmospheric electricity at high latitudes

    Science.gov (United States)

    Shumilov, O. I.; Kasatkina, E. A.; Frank-Kamenetsky, A. V.; Raspopov, O. M.; Vasiljev, A. N.; Struev, A. G.

    2003-04-01

    Measurements of the vertical atmospheric electric field (Ez) made at auroral station Apatity (geomagnetic latitude: 63.8) and polar cap station Vostok, Antarctica (geomagnetic latitude: -89.3) in 2001-2002 have been analyzed. The measurements were made by a high-latitude computer-aided complex installed at Apatity in 2001. It consists of three spatially placed microbarographs for measurements of atmospheric waves, a device for air conductivity measurement and a device for measurement of vertical component of the atmospheric electric field. The computer-aided system permits to get information with a frequency of five times per second. The ground level atmospheric electric field was found to have systematic local diurnal and seasonal variations. Diurnal variations of atmospheric potential gradient were found to have a departure from the Carnegie curve. A distinct difference in the diurnal variation of atmospheric electric field has been observed also between disturbed (Kp>30) and extremely quiet (Kplatitude electric field variations appear to be the result of solar wind-magnetosphere-ionosphere coupling. Besides, we have found the similarity between the diurnal course of the atmospheric electric field under the quiet geomagnetic conditions and the diurnal variation of galactic cosmic rays. These results have been explained in terms of calculated effective Bz component of the interpalnetary magnetic field arising due to variation of the geomagnetic dipole axis inclination during the Earth's rotation. The results of analysis of the influence of extreme weather conditions (rain, snow, snowstorm, stormclouds, thunderstorms, lightning) on atmospheric electricity (electric field and conductivity) are also discussed. This work was supported by EC (grant INTAS 97-31008) and RFBR (grant 01-05-64850).

  2. Distinct responses of the low-latitude ionosphere to CME and HSSWS: The role of the IMF Bz oscillation frequency

    Science.gov (United States)

    Rodríguez-Zuluaga, J.; Radicella, S. M.; Nava, B.; Amory-Mazaudier, C.; Mora-Páez, H.; Alazo-Cuartas, K.

    2016-11-01

    In this work an attempt to identify the role of the interplanetary magnetic field (IMF) in the response of the ionosphere to different solar phenomena is presented. For this purpose, the day-to-day variability of the equatorial ionospheric anomaly (EIA) and the main ionospheric disturbances are analyzed during one coronal mass ejection (CME) and two high-speed solar wind streams (HSSWSs). The EIA parameters considered are the zonal electric field and both the strength and position of its northern crest. The disturbances being the prompt penetration of magnetospheric electric field (PPMEF) and disturbance dynamo electric field (DDEF) are studied using the magnetic response of their equivalent current systems. In accordance, ground-based Global Navigation Satellite Systems receivers and magnetometers at geomagnetic low latitudes in the American sector are used. During both phenomena, patterns of PPMEF related to fluctuations of the IMF are observed. Diurnal and semidiurnal magnetic oscillations are found to be likely related to DDEF. Comparisons among the EIA parameters and the DDEF magnetic response exhibit poor relation during the CME in contrast to good relation during the HSSWSs. It is concluded that the response of the low-latitude ionosphere to solar phenomena is largely determined through the oscillation frequency of the IMF Bz by affecting the generation of the PPMEF and DDEF differently. This is seen as an effect of how the energy from the solar wind is transferred into the magnetosphere-ionosphere system.

  3. Dawn-dusk asymmetries and sub-Alfvénic flow in the high and low latitude magnetosheath

    Directory of Open Access Journals (Sweden)

    M. Longmore

    2005-11-01

    Full Text Available We present the results of a statistical survey of the magnetosheath using four years of Cluster orbital coverage. Moments of the plasma distribution obtained from the electron and ion instruments together with magnetic field data are used to characterise the flow and density in the magnetosheath. We note two important differences between our survey and the gasdynamic model predictions: a deceleration of the flow at higher latitudes close to the magnetopause, resulting in sub-Alfvénic flow near the cusp, and a dawn-dusk asymmetry with higher velocity magnitudes and lower densities measured on the dusk side of the magnetosheath in the Northern Hemisphere. The latter observation is in agreement with studies carried out by Paularena et al. (2001, Němeček et al. (2000, and Šafránková et al. (2004. In equations of hydrodynamics for a single-component additon to this we observe a reverse of this asymmetry for the Southern Hemisphere. High-latitude sub-Alfvénic flow is thought to be a necessary condition for steady state reconnection pole-ward of the cusp.

  4. Gamma-ray Source Stacking Analysis at Low Galactic Latitude

    Energy Technology Data Exchange (ETDEWEB)

    Cillis, Analia N.; /NASA, Goddard; Reimer, Olaf; /Stanford U., HEPL; Torres, Diego F.; /ICREA, Barcelona /Barcelona, IEEC

    2007-04-25

    We studied the problematic of uncertainties in the diffuse gamma radiation apparent in stacking analysis of EGRET data at low Galactic latitudes. Subsequently, we co-added maps of counts, exposure and diffuse background, and residuals, in varying numbers for different sub-categories of putatively and known source populations (like PSRs). Finally we tested for gamma-ray excess emission in those maps and attempt to quantify the systematic biases in such approach. Such kind of an analysis will help the classification processes of sources and source populations in the GLAST era.

  5. Earth's magnetosphere formed by the low-latitude boundary layer

    CERN Document Server

    Heikkila, W J

    2011-01-01

    The author argues that, after five decades of debate about the interactive of solar wind with the magnetosphere, it is time to get back to basics. Starting with Newton's law, this book also examines Maxwell's equations and subsidiary equations such as continuity, constitutive relations and the Lorentz transformation; Helmholtz' theorem, and Poynting's theorem, among other methods for understanding this interaction. Includes chapters on prompt particle acceleration to high energies, plasma transfer event, and the low latitude boundary layer More than 200 figures illustrate the text Includes a color insert.

  6. Production of secondary Deuterium in the atmosphere at various latitudes

    Energy Technology Data Exchange (ETDEWEB)

    Papini, P. [Florence Univ. (Italy)]|[INFN, Florence (Italy); Grimani, C. [Perugia Univ. (Italy)]|[INFN, Perugia (Italy); Stephens, S.A. [Tata Institute of Fundamental Research, Bombay (International Commission on Radiation Units and Measurements)

    1995-09-01

    Secondary deuterium in the atmosphere are produced in interactions by primary cosmic rays. The shape of their energy spectrum depends on the primary cosmic ray spectrum incident at the top of the atmosphere. At high energies, the spectral shape depends on the primary spectrum of helium and heavy nuclei. However, at very low energies, specially below the geomagnetic cut-off, the spectral shape depends on the evaporation and recoil processes and hence almost independent of the spectral shape of the primary radiation. It is undertaken a calculation of the secondary deuterium spectrum at small atmospheric depths at various latitudes and the results will be presented.

  7. Latitude distribution of nonradial pulsations in rapidly rotating B stars

    Science.gov (United States)

    Jankov, S.; Mathias, P.; Domiciano de Souza, A., Jr.; Uytterhoeven, K.; Aerts, C.

    2004-05-01

    We present a method for the analysis of latitude distribution associated with temperature and/or velocity perturbations of the stellar surface due to non-radial pulsation (NRP) modes in rapidly rotating B stars. The technique is applied together with Fourier Doppler Imaging (FDI) to high resolution and high signal-to-noise ratio spectroscopic observations of ɛ Per. The main advantage of this approach is that it decomposed complex multi-periodic line profile variations into single components, allowing the detailed analysis of each mode seperately. We study the 10.6-d-1 frequency that is particularly important for modal analysis of non-radial pulsations in the star.

  8. How Altitude and Latitude Control Dune Morphometry on Titan

    Science.gov (United States)

    Le Gall, A.; Hayes, A.; Ewing, R.; Janssen, M. A.; Radebaugh, J.; Savage, C.; Encrenaz, P.

    2011-01-01

    Dune fields are one of the dominant landforms and represent the largest known organic reservoir on Titan. SAR-derived topography show that Titan's dune terrains tend to occupy the lowest altitude areas in equatorial regions occurring at mean elevations between approx.-400 and 0 m. In elevated dune terrains, there is a definite trend towards a smaller dune to interdune ratio, interpreted as due to limited sediment availability. A similar linear correlation is observed with latitude, suggesting that the quantity of windblown sand in the dune fields tends to decrease as one moves farther north. These findings place important constraints on Titan's geology and climate.

  9. Occurrence climatology of F region field-aligned irregularities in middle latitudes as observed by a 40.8 MHz coherent scatter radar in Daejeon, South Korea

    Science.gov (United States)

    Yang, Tae-Yong; Kwak, Young-Sil; Kil, Hyosub; Lee, Young-Sook; Lee, Woo Kyoung; Lee, Jae-jin

    2015-11-01

    A new 40.8 MHz coherent scatter radar was built in Daejeon, South Korea (36.18°N, 127.14°E, dip latitude: 26.7°N) on 29 December 2009 and has since been monitoring the occurrence of field-aligned irregularities (FAIs) in the northern middle latitudes. We report on the occurrence climatology of the F region FAIs as observed by the Daejeon radar between 2010 and 2014. The F region FAIs preferentially occur around 250-350 km at 18:00-21:00 local time (postsunset FAI), around 350-450 km near midnight (nighttime FAI), around 250-350 km before sunrise (presunrise FAI), and around 160-300 km after 05:00 local time (postsunrise FAI). The occurrence rates of nighttime and presunrise FAIs are maximal during summer, though the occurrence rates of postsunset and postsunrise FAIs are maximal during the equinoxes. FAIs rarely occur during local winter. The occurrence rate of F region FAIs increases in concert with increases in solar activity. Medium-scale traveling ionospheric disturbances (MSTIDs) are known as an important source of the F region FAIs in middle latitudes. The high occurrence rate of the nighttime FAIs in local summer is consistent with the high occurrence rate of MSTIDs in that season. However, the dependence of the FAI activity on the solar cycle is inconsistent with the MSTID activity. The source of the F region FAIs in middle latitudes is an open question. Our report of different types of FAIs and their occurrence climatology may provide a useful reference for the identification of the source of the middle latitude FAIs.

  10. Evidence That Loss-of-Function Filaggrin Gene Mutations Evolved in Northern Europeans to Favor Intracutaneous Vitamin D3 Production

    DEFF Research Database (Denmark)

    Thyssen, Jacob P; Bikle, Daniel D; Elias, Peter M

    2014-01-01

    Skin pigmentation lightened progressively to a variable extent, as modern humans emigrated out of Africa, but extreme lightening occurred only in northern Europeans. Yet, loss of pigmentation alone cannot suffice to sustain cutaneous vitamin D3 (VD3) formation at the high latitudes of northern...... Europe. We hypothesized that loss-of-function mutations in the epidermal structural protein, filaggrin (FLG), could have evolved to sustain adequate VD3 status. Loss of FLG results in reduced generation of trans-urocanic acid, the principal endogenous ultraviolet-B (UV-B) filter in lightly...... UV-B penetration and intracutaneous VD3 formation, the latitude-dependent gradient in FLG mutations, likely together with other concurrent mutations in VD3 metabolic pathways, provide a non-pigment-based mechanism that sustains higher levels of circulating VD3 in northern Europeans. At the time...

  11. Response of thermosphere density to high-latitude forcing

    Science.gov (United States)

    Yamazaki, Y.; Kosch, M. J.; Vickers, H.; Sutton, E. K.; Ogawa, Y.

    2014-12-01

    Solar wind-magnetospheric disturbances cause enhancements in the energy input to the high-latitude upper atmosphere through particle precipitation and Joule heating. As the upper atmosphere is heated and expanded during geomagnetically disturbed periods, the neutral density in the thermosphere increases at a fixed altitude. Conversely, the thermosphere contracts during the recovery phase of the disturbance, resulting in a decrease of the density. The main objectives of this study are (1) to determine the morphology of the global thermospheric density response to high-latitude forcing, and (2) to determine the recovery speed of the thermosphere density after geomagnetic disturbances. For (1), we use thermospheric density data measured by the Challenging Minisatellite Payload (CHAMP) satellite during 2000-2010. It is demonstrated that the density enhancement during disturbed periods occurs first in the dayside cusp region, and the density at other regions slowly follows it. The reverse process is observed when geomagnetic activity ceases; the density enhancement in the cusp region fades away first, then the global density slowly goes back to the quiet level. For (2), we analyze EISCAT Svalbard radar and Tromso UHF radar data to estimate thermospheric densities during the recovery phase of geomagnetic disturbances. We attempt to determine the time constant for the density recovery both inside and outside the cusp region.

  12. Statistical characteristics of low-latitude ionospheric scintillation over China

    Science.gov (United States)

    Liu, Kangkang; Li, Guozhu; Ning, Baiqi; Hu, Lianhuan; Li, Hongke

    2015-03-01

    The Global Positioning System (GPS) L-band ionospheric scintillation produced by electron density irregularities in the ionospheric E- and F-regions, is mainly a low- and high-latitude phenomenon. In this study, the statistical behavior of GPS ionospheric scintillation over a Chinese low-latitude station Sanya (18.3°N, 109.6°E; dip lat: 12.8°N) has been investigated. A detailed study on the seasonal and solar activity dependence of scintillation occurrence during July 2004-December 2012 show that the amplitude scintillation pattern, with a maximum occurrence during equinox of solar maximum, agrees with plasma bubble observations by in situ satellites in this longitude. A few daytime periodic scintillation events are found during June solstice months of solar minimum. Interestingly, a significant equinoctial asymmetry of scintillation onset time is found in 2011-2012. The initiation of scintillation during September-October is on average earlier than that of March-April about 25 min. Meanwhile, the zonal drifts of irregularities estimated using two spatially separated GPS receivers over Sanya show a similar behavior during the two equinoxes, slowly decreasing from 150 m/s at post-sunset to 50 m/s near midnight. The possible mechanisms responsible for the occurrence characteristics of GPS scintillation over Sanya, and relevant aspects of the zonal drifts of the irregularities are discussed.

  13. Postmidnight ionospheric troughs in summer at high latitudes

    Science.gov (United States)

    Voiculescu, M.; Nygrén, T.; Aikio, A. T.; Vanhamäki, H.; Pierrard, V.

    2016-12-01

    In this article we identify possible mechanisms for the formation of postmidnight ionospheric troughs during summer, in sunlit plasma. Four events were identified in measurements of European Incoherent Scatter and ESR radars during CP3 experiments, when the ionosphere was scanned in a meridional plan. The spatial and temporal variation of plasma density, ion, and electron temperatures were analyzed for each of the four events. Super Dual Auroral Radar Network plasma velocity measurements were added, when these were available. For all high-latitude troughs the ion temperatures are high at density minima (within the trough), at places where the convection plasma velocity is eastward and high. There is no significant change in electron temperature inside the trough, regardless of its temporal evolution. We find that troughs in sunlit plasma form in two steps: the trough starts to form when energetic electron precipitation leads to faster recombination in the F region, and it deepens when entering a region with high eastward flow, producing frictional heating and further depleting the plasma. The high-latitude plasma convection plays an important role in formation and evolution of troughs in the postmidnight sector in sunlit plasma. During one event a second trough is identified at midlatitudes, with different characteristics, which is most likely produced by a rapid subauroral ion drift in the premidnight sector.

  14. Small-scale characteristics of extremely high latitude aurora

    Directory of Open Access Journals (Sweden)

    J. A. Cumnock

    2009-09-01

    Full Text Available We examine 14 cases of an interesting type of extremely high latitude aurora as identified in the precipitating particles measured by the DMSP F13 satellite. In particular we investigate structures within large-scale arcs for which the particle signatures are made up of a group of multiple distinct thin arcs. These cases are chosen without regard to IMF orientation and are part of a group of 87 events where DMSP F13 SSJ/4 measures emissions which occur near the noon-midnight meridian and are spatially separated from both the dawnside and duskside auroral ovals by wide regions with precipitating particles typical of the polar cap. For 73 of these events the high-latitude aurora consists of a continuous region of precipitating particles. We focus on the remaining 14 of these events where the particle signatures show multiple distinct thin arcs. These events occur during northward or weakly southward IMF conditions and follow a change in IMF By. Correlations are seen between the field-aligned currents and plasma flows associated with the arcs, implying local closure of the FACs. Strong correlations are seen only in the sunlit hemisphere. The convection associated with the multiple thin arcs is localized and has little influence on the large-scale convection. This also implies that the sunward flow along the arcs is unrelated to the overall ionospheric convection.

  15. Geomagnetic response to IMF and solar wind over different latitudes

    Science.gov (United States)

    Aslam, A. M.; Tripathi, Sharad Chandra; Mansoori, Azad Ahmad; Waheed, Malik Abdul

    2016-07-01

    In this paper a study on the response of geomagnetic field characteristics to the solar wind variation during three solar cycles (SC 21, SC 22, SC 23) have been conducted in a long term scale. The difference in the response of two different latitudinal characteristic indices has been investigated. For the purpose we have considered the high latitude index AE and the mid-latitude aa index and both gives the knowledge about the perturbations in the geomagnetic field conditions. Eventually we can infer the idea about the ionospheric current system changes in response to the solar wind conditions. The variation found in the AE and aa indices have been found to follow a 11 year cycle as similar to the sunspot variation. Also the correlation between the annual means of the solar wind parameters velocity V, magnetic filed B and the composite parameters BV and BV ^{2 } have been calculated . A difference was found between the correlations obtained for the AE and aa indices. We could also see that the difference in correlation follows a cyclic pattern i.e. the large difference is found during the solar maxima while a small difference is observed during the minima.

  16. Magnetic field draping at the low-latitude magnetopause

    Science.gov (United States)

    Richard, R. L.; Lotko, W.

    1991-01-01

    Magnetohydrodynamic simulations are used to investigate the structure of the low-latitude magnetopause for interplanetary magnetic field conditions with a dominant southward component. The structure is self-consistently calculated as an initial-value problem in which the system is allowed to evolve into a quasi-steady state. All components of the 3D velocity and magnetic field as well as compressibility, resistivity, and viscosity are included in the 2D calculation. The simulation model shows that magnetic field draping can occur at the magnetopause boundary when magnetic merging takes place in the presence of a tangential shear flow. For 'normal' (positive Bx) draping, the higher-latitude portion of the field lines are curved toward the sun on the magnetospheric side of the magnetopause and away from the sun on the magnetosheath side. The thickness of the normal draping structure scales with the viscosity. The field-aligned current system that accompanies normal magnetic draping is consistent with the sense of the region 1 currents that flow into the dayside ionosphere.

  17. Application of Astronomic Time-latitude Residuals in Earthquake Prediction

    Science.gov (United States)

    Yanben, Han; Lihua, Ma; Hui, Hu; Rui, Wang; Youjin, Su

    2007-04-01

    After the earthquake (Ms = 6.1) occurred in Luquan county of Yunnan province on April 18, 1985, the relationship between major earthquakes and astronomical time-latitude residuals (ATLR) of a photoelectric astrolabe in Yunnan Observatory was analyzed. ATLR are the rest after deducting the effects of Earth’s whole motion from the observations of time and latitude. It was found that there appeared the anomalies of the ATLR before earthquakes which happened in and around Yunnan, a seismic active region. The reason of the anomalies is possibly from change of the plumb line due to the motion of the groundmass before earthquakes. Afterwards, using studies of the anomalous characters and laws of ATLR, we tried to provide the warning information prior to the occurrence of a few major earthquakes in the region. The significant synchronous anomalies of ATLR of the observatory appeared before the earthquake of magnitude 6.2 in Dayao county of Yunnan province, on July 21, 2003. It has been again verified that the anomalies possibly provide the prediction information for strong earthquakes around the observatory.

  18. Silicon-carbon interactions in high latitude watersheds

    Science.gov (United States)

    Humborg, C.; Morth, C.; Struyf, E.; Conley, D. J.

    2008-12-01

    Changes in climate and hydrology in high latitude regions could liberate large amounts of previously inactive organic carbon (OC) during a prolonging thawing period, and new studies have shown that a great deal of this organic C is remineralized as CO2 during its transport to the sea. However, OC (with its origin in atmospheric carbon) and dissolved silicate (DSi) concentrations in taiga and tundra rivers are intimately linked, and higher concentrations of weathering products are found in taiga and tundra rivers with a higher percentage of peat in their watersheds. It appears that the weathering regime of taiga and tundra watersheds is tightly linked to carbon-silicon interactions, in which carbon acts both as a weathering agent (soil CO2 from degradation of OC) and as a weathering product (DSi and bicarbonate). Whereas respiration of OC can be regarded as a positive feedback to global warming, weathering can be regarded as a negative feedback to global warming since atmospheric CO2 is converted to bicarbonate and thereby locked into the aquatic phase for geological time scales. Thus, bicarbonate export may compensate for significant amounts of exported OC thereby reducing the positive feedback to atmospheric CO2. However, the silicon-carbon interactions are not straight forward as suggested by classical inverse modelling,using the stochiometry of rock forming minerals as base, since high latitude wetlands contain a massive stock of amorphous silica (diatoms and phytoliths) buffering the actual DSi export, suggesting that the Si cycle is to a large extent biologically controlled.

  19. A polarized fast radio burst at low Galactic latitude

    Science.gov (United States)

    Petroff, E.; Burke-Spolaor, S.; Keane, E. F.; McLaughlin, M. A.; Miller, R.; Andreoni, I.; Bailes, M.; Barr, E. D.; Bernard, S. R.; Bhandari, S.; Bhat, N. D. R.; Burgay, M.; Caleb, M.; Champion, D.; Chandra, P.; Cooke, J.; Dhillon, V. S.; Farnes, J. S.; Hardy, L. K.; Jaroenjittichai, P.; Johnston, S.; Kasliwal, M.; Kramer, M.; Littlefair, S. P.; Macquart, J. P.; Mickaliger, M.; Possenti, A.; Pritchard, T.; Ravi, V.; Rest, A.; Rowlinson, A.; Sawangwit, U.; Stappers, B.; Sullivan, M.; Tiburzi, C.; van Straten, W.; ANTARES Collaboration; Albert, A.; André, M.; Anghinolfi, M.; Anton, G.; Ardid, M.; Aubert, J.-J.; Avgitas, T.; Baret, B.; Barrios-Martí, J.; Basa, S.; Bertin, V.; Biagi, S.; Bormuth, R.; Bourret, S.; Bouwhuis, M. C.; Bruijn, R.; Brunner, J.; Busto, J.; Capone, A.; Caramete, L.; Carr, J.; Celli, S.; Chiarusi, T.; Circella, M.; Coelho, J. A. B.; Coleiro, A.; Coniglione, R.; Costantini, H.; Coyle, P.; Creusot, A.; Deschamps, A.; de Bonis, G.; Distefano, C.; di Palma, I.; Donzaud, C.; Dornic, D.; Drouhin, D.; Eberl, T.; El Bojaddaini, I.; Elsässer, D.; Enzenhöfer, A.; Felis, I.; Fusco, L. A.; Galatà, S.; Gay, P.; Geißelsöder, S.; Geyer, K.; Giordano, V.; Gleixner, A.; Glotin, H.; Grégoire, T.; Gracia-Ruiz, R.; Graf, K.; Hallmann, S.; van Haren, H.; Heijboer, A. J.; Hello, Y.; Hernández-Rey, J. J.; Hößl, J.; Hofestädt, J.; Hugon, C.; Illuminati, G.; James, C. W.; de Jong, M.; Jongen, M.; Kadler, M.; Kalekin, O.; Katz, U.; Kießling, D.; Kouchner, A.; Kreter, M.; Kreykenbohm, I.; Kulikovskiy, V.; Lachaud, C.; Lahmann, R.; Lefèvre, D.; Leonora, E.; Lotze, M.; Loucatos, S.; Marcelin, M.; Margiotta, A.; Marinelli, A.; Martínez-Mora, J. A.; Mathieu, A.; Mele, R.; Melis, K.; Michael, T.; Migliozzi, P.; Moussa, A.; Mueller, C.; Nezri, E.; Pǎvǎlaş, G. E.; Pellegrino, C.; Perrina, C.; Piattelli, P.; Popa, V.; Pradier, T.; Quinn, L.; Racca, C.; Riccobene, G.; Roensch, K.; Sánchez-Losa, A.; Saldaña, M.; Salvadori, I.; Samtleben, D. F. E.; Sanguineti, M.; Sapienza, P.; Schnabel, J.; Seitz, T.; Sieger, C.; Spurio, M.; Stolarczyk, Th.; Taiuti, M.; Tayalati, Y.; Trovato, A.; Tselengidou, M.; Turpin, D.; Tönnis, C.; Vallage, B.; Vallée, C.; van Elewyck, V.; Vivolo, D.; Vizzoca, A.; Wagner, S.; Wilms, J.; Zornoza, J. D.; Zúñiga, J.; H.E.S.S. Collaboration; Abdalla, H.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Andersson, T.; Angüner, E. O.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Tjus, J. Becker; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Bulik, T.; Capasso, M.; Casanova, S.; Cerruti, M.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Condon, B.; Conrad, J.; Cui, Y.; Davids, I. D.; Decock, J.; Degrange, B.; Deil, C.; Devin, J.; Dewilt, P.; Dirson, L.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O'c.; Dubus, G.; Dutson, K.; Dyks, J.; Edwards, T.; Egberts, K.; Eger, P.; Ernenwein, J.-P.; Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Funk, S.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goyal, A.; Grondin, M.-H.; Hadasch, D.; Hahn, J.; Haupt, M.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holler, M.; Horns, D.; Ivascenko, A.; Jacholkowska, A.; Jamrozy, M.; Janiak, M.; Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jogler, T.; Jouvin, L.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Kerszberg, D.; Khélifi, B.; Kieffer, M.; King, J.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lees, J.-P.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; López-Coto, R.; Lypova, I.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Morâ, K.; Moulin, E.; Murach, T.; de Naurois, M.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Öttl, S.; Ohm, S.; Ostrowski, M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Pekeur, N. W.; Pelletier, G.; Perennes, C.; Petrucci, P.-O.; Peyaud, B.; Piel, Q.; Pita, S.; Poon, H.; Prokhorov, D.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Reimer, A.; Reimer, O.; Renaud, M.; Reyes, R. De Los; Rieger, F.; Romoli, C.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schulz, A.; Schüssler, F.; Schwanke, U.; Schwemmer, S.; Settimo, M.; Seyffert, A. S.; Shafi, N.; Shilon, I.; Simoni, R.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tibaldo, L.; Tiziani, D.; Tluczykont, M.; Trichard, C.; Tuffs, R.; Uchiyama, Y.; Walt, D. J. Van Der; van Eldik, C.; van Rensburg, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zanin, R.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Żywucka, N.

    2017-08-01

    We report on the discovery of a new fast radio burst (FRB), FRB 150215, with the Parkes radio telescope on 2015 February 15. The burst was detected in real time with a dispersion measure (DM) of 1105.6 ± 0.8 pc cm-3, a pulse duration of 2.8^{+1.2}_{-0.5} ms, and a measured peak flux density assuming that the burst was at beam centre of 0.7^{+0.2}_{-0.1} Jy. The FRB originated at a Galactic longitude and latitude of 24.66°, 5.28° and 25° away from the Galactic Center. The burst was found to be 43 ± 5 per cent linearly polarized with a rotation measure (RM) in the range -9 magnetic field reversals along the line of sight, a decreased total electron column density from the Milky Way, or some combination of these effects. A lower Galactic DM contribution might explain why this burst was detectable whereas previous searches at low latitude have had lower detection rates than those out of the plane.

  20. Current Patterns of Macroalgal Diversity and Biomass in Northern Hemisphere Rocky Shores

    Science.gov (United States)

    Konar, Brenda; Iken, Katrin; Cruz-Motta, Juan José; Benedetti-Cecchi, Lisandro; Knowlton, Ann; Pohle, Gerhard; Miloslavich, Patricia; Edwards, Matt; Trott, Thomas; Kimani, Edward; Riosmena-Rodriguez, Rafael; Wong, Melisa; Jenkins, Stuart; Silva, Angelica; Pinto, Isabel Sousa; Shirayama, Yoshihisa

    2010-01-01

    Latitudinal gradients in species abundance and diversity have been postulated for nearshore taxa but few analyses have been done over sufficiently broad geographic scales incorporating various nearshore depth strata to empirically test these gradients. Typically, gradients are based on literature reviews and species lists and have focused on alpha diversity across the entire nearshore zone. No studies have used a standardized protocol in the field to examine species density among sites across a large spatial scale while also focusing on particular depth strata. The present research used field collected samples in the northern hemisphere to explore the relationships between macroalgal species density and biomass along intertidal heights and subtidal depths and latitude. Results indicated no overall correlations between either estimates of species density or biomass with latitude, although the highest numbers of both were found at mid-latitudes. However, when strata were examined separately, significant positive correlations were found for both species numbers and biomass at particular strata, namely the intertidal ones. While the data presented in this paper have some limitations, we show that latitudinal macroalgal trends in species density and biomass do exist for some strata in the northern hemisphere with more taxa and biomass at higher latitudes. PMID:20949030

  1. Does Weak Turbulence Impact PMSEs' Strengths Closer To The Northern Pole?

    Science.gov (United States)

    Swarnalingam, N.; Hocking, W. K.; Janches, D.; Nicolls, M. J.

    2015-12-01

    Existing 51.0 MHz VHF radar at Eureka (80N, 86W) in northern Canada is located closer to both the northern magnetic and geomagnetic poles. A recent calibrated study of Polar Mesosphere Summer Echoes (PMSE) using this radar supports the previous results by other radars that the absolute signal strength of PMSE in this region is relatively weak compared with the radar observations located at high latitudes. Although very cold temperature and existence of charged ice particles are the most important ingredient required for PMSE to appear, several other factors could potentially influence the absolute signal strengths of these echoes. One of them is neutral air turbulence. Previous studies indicate that upper mesospheric turbulence's strength decreases with latitudes, especially in the very high latitudes [Becker, 2004; Lubken et. al., 2009]. In this study, we investigate long-term mesospheric turbulence strengths at Eureka and study how they could be associated with the weak PMSE signal strengths compared with other high latitude conditions, where PMSE are strong.

  2. insurgents in Northern Uganda

    African Journals Online (AJOL)

    and the rebel movements in northern Uganda, see Human Rights Watch 2003, and ... of Uganda enacted an Amnesty Act in 2000, and to date more than ten thousand ..... Amnesty Certificate, and then in theory, a package.20 In the case of former .... [H]uman rights obligations are contracted on an international level.

  3. Northern blotting analysis

    DEFF Research Database (Denmark)

    Josefsen, Knud; Nielsen, Henrik

    2011-01-01

    Northern blotting analysis is a classical method for analysis of the size and steady-state level of a specific RNA in a complex sample. In short, the RNA is size-fractionated by gel electrophoresis and transferred by blotting onto a membrane to which the RNA is covalently bound. Then, the membran...

  4. Northern blotting analysis

    DEFF Research Database (Denmark)

    Josefsen, Knud; Nielsen, Henrik

    2011-01-01

    is analysed by hybridization to one or more specific probes that are labelled for subsequent detection. Northern blotting is relatively simple to perform, inexpensive, and not plagued by artefacts. Recent developments of hybridization membranes and buffers have resulted in increased sensitivity closing...

  5. 1990 Northern, Iran Images

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A magnitude 7.7 earthquake occurred in the Gilan Province between the towns of Rudbar and Manjil in northern Iran on Thursday, June 21, 1990 (June 20 at 21:00 GMT)....

  6. What-ifs for a Northern ozone hole

    Energy Technology Data Exchange (ETDEWEB)

    Newman, A.

    1993-08-01

    Based on papers presented at a recent American Geophysical Union meeting in Baltimore, this article discusses various processes that could lead to further significant stratospheric ozone losses over northern latitudes. In southern high latitudes, ClO, formed when Cl atoms react with O[sub 3], persists into the spring and enters a photocatalytic cycle that regenerates ozone-destroying Cl atoms. Type II polar stratospheric clouds (PSCs) are believed to act as catalysts in this cycle. Although type II PSCs rarely form in the warmer Arctic stratosphere, it is possible that type I PSCs and sulfuric acid droplets may act as catalytic surfaces in this region. The arctic however, currently lacks a pronounced ozone hole, unlike Antartica. This is because in the Northern Hemisphere, large-scale tropospheric weather disturbances leak a portion of their energy to the less dense stratosphere. This indirectly leads to the descent of air over the Arctic region which produces compression heating of the polar cap and keeps the Arctic winter stratosphere warm enough to evade the cold temperatures that would produce widespread PSCs, and the associated significant ozone destruction. However, the greenhouse effect could lead to a cooler stratosphere containing more water and weaker tropospheric large-scale disturbances meaning colder Arctic winters. All these factors would contribute to greater PSC formation and the associated ozone destruction.

  7. The Caledonian mountains. Northern Europe, and their changing ecosystems

    Directory of Open Access Journals (Sweden)

    Sonesson, M.

    1998-12-01

    Full Text Available With the exception of solar conditions, the climate of the Caledonian Mountains, Northern Europe, is influenced more by the nearness to the Atlantic Ocean and the Gulf Stream than by altitude and latitude. The length of the photoperiod during the growing season increases with latitude, although the total solar influx decreases. Heaths composed of species with a boreal distribution are particularly characteristic at low altitudes and latitudes, whereas species with an arctic and arctic-alpine distribution dominate at high altitudes and latitudes. Periodic events in the population dynamics of certain plant and animal species distinguish the ecosystems at high latitudes from those at low latitude. The effects of global change are likely to become most pronounced in the north since the rate at which the ultraviolet-B (UV-B absorbing ozone layer is being reduced and the increase in concentration of «greenhouse gases» in the atmosphere are both higher in the arctic than in regions further south. Changes in the ecosystems due to increased direct human impacts are also likely to occur in some areas.

    [fr] À l'exception des conditions solaires, le climat des montagnes dites «Caledonian», au Nord de l'Europe, est beaucoup plus influencé par la proximité de l'Océan Atlantique et le Goulf Stream que par l'altitude ou la latitude. La durée de la photopériode pendant la saison de végétation augmente avec la latitude, tandis que la radiation solaire total s'abaisse. À des altitudes et latitudes basses, les landes riches en espèces à distribution boréale deviennent caractéristiques, tandis que les espèces arctiques et artico-alpines dominent dans les hautes altitudes ou latitudes. Des événements périodiques dans la dynamique de la population de certains animaux ou plantes peuvent distinguer les écosystèmes des hautes latitudes de ceux de basse latitude. Les effets du changement climatique global seraient bien sûr plus prononcés au

  8. Interacting effects of latitude, mass, age, and sex on winter survival of Surf Scoters (Melanitta perspicillata): Implications for differential migration

    Science.gov (United States)

    Uher-Koch, Brian D.; Esler, Daniel N.; Iverson, Samuel A.; Ward, David; Boyd, Sean; Kirk, Molly; Lewis, Tyler L.; VanStratt, Corey S.; Brodhead, Katherine M.; Hupp, Jerry; Schmutz, Joel A.

    2016-01-01

    We quantified variation in winter survival of Surf Scoters (Melanitta perspicillata (L., 1758)) across nearly 30° of latitude on the Pacific coast of North America to evaluate potential effects on winter distributions, including observed differential distributions of age and sex classes. We monitored fates of 297 radio-marked Surf Scoters at three study sites: (1) near the northern periphery of their wintering range in southeast Alaska, USA, (2) the range core in British Columbia, Canada, and (3) the southern periphery in Baja California, Mexico. We detected 34 mortalities and determined that survival averaged lower at the range peripheries than in the range core, was lower during mid-winter than during late winter at all sites, and was positively correlated with body mass within locations. Although neither age nor sex class had direct effects, mass effects led to differential survival patterns among classes. When simultaneously incorporating these interacting influences, adult males of mean mass for their location had highest survival at the northern range periphery in Alaska, whereas adult females and juveniles had higher survival at the range core and the southern periphery. Our observations help to explain patterns of differential migration and distribution reported for this species and highlight seasonal periods (mid-winter) and locations (range peripheries) of elevated levels of mortality for demographically important age–sex classes (adult females).

  9. Equatorwards Expansion of Unperturbed, High-Latitude Fast Solar Wind

    CERN Document Server

    Dorrian, Gareth; Fallows, Richard; Bisi, Mario

    2012-01-01

    We use dual-site radio observations of interplanetary scintillation (IPS) with extremely long baselines (ELB) to examine meridional flow characteristics of the ambient fast solar wind at plane-of-sky heliocentric distances of 24-85 solar radii (R\\odot). Our results demonstrate an equatorwards deviation of 3-4{\\deg} in the bulk fast solar wind flow direction over both northern and southern solar hemispheres during different times in the declining phase of Solar Cycle 23.

  10. Northern ragweed ecotypes flower earlier and longer in response to elevated CO2: what are you sneezing at?

    Science.gov (United States)

    Stinson, Kristina A; Albertine, Jennifer M; Hancock, Laura M S; Seidler, Tristram G; Rogers, Christine A

    2016-10-01

    Significant changes in plant phenology and flower production are predicted over the next century, but we know relatively little about geographic patterns of this response in many species, even those that potentially impact human wellbeing. We tested for variation in flowering responses of the allergenic plant, Ambrosia artemisiifolia (common ragweed). We grew plants originating from three latitudes in the Northeastern USA at experimental levels of CO2 (400, 600, and 800 µL L(-1)). We hypothesized that northern ecotypes adapted to shorter growing seasons would flower earlier than their southern counterparts, and thus disproportionately allocate carbon gains from CO2 to reproduction. As predicted, latitude of origin and carbon dioxide level significantly influenced the timing and magnitude of flowering. Reproductive onset occurred earlier with increasing latitude, with concurrent increases in the number of flowers produced. Elevated carbon dioxide resulted in earlier reproductive onset in all ecotypes, which was significantly more pronounced in the northern populations. We interpret our findings as evidence for ecotypic variation in ragweed flowering time, as well in responses to CO2. Thus, the ecological and human health implications of common ragweed's response to global change are likely to depend on latitude. We conclude that increased flower production, duration, and possibly pollen output, can be expected in Northeastern United States with rising levels of CO2. The effects are likely, however, to be most significant in northern parts of the region.

  11. Altitude and latitude dependence of the equatorial electrojet

    Science.gov (United States)

    Singh, A.; Cole, K. D.

    1988-07-01

    A self-consistent and high-resolution dynamo model is used to investigate the effects of day-to-day or seasonal variation of altitude and latitude profiles of the E-plasma density in the equatorial ionosphere on equatorial electrojet (EEJ) structure. Variations in the E-layer peak altitude and amplitude are shown to significantly affect EEJ structure. The results indicate that, for any shape, the EEJ peak appears at or below the E-layer peak altitude. Distinct double peaks occur in the EEJ structure if the E-layer peak is above 105 km or if the gradient is large. The effect of the latitudinal variation of the integrated conductivities of ionospheric field lines upon the amplitude and altitude of the EEJ peak is discussed.

  12. High-latitude geomagnetic studies (22-23 millihertz)

    Energy Technology Data Exchange (ETDEWEB)

    Wolfe, A. (AT T Bell Laboratories, Murray Hill, NJ (USA) City Univ. of New York, Brooklyn (USA)); Lanzerotti, L.J.; Maclennan, C.C.; Medford, L.V. (AT T Bell Laboratories, Murray Hill, NJ (USA))

    1988-01-01

    Geomagnetic field measurements were initiated at Iqaluit (formerly Frobisher Bay) in the Northwest Territories of Canada during July 1985 (Wolfe et al. 1986). This site was selected because it was calculated to be in the conjugate area to the Amundsen-Scott South Pole Station where extensive geomagnetic research has been conducted. The principal scientific objectives are to study the conjugacy of high-latitude magnetic fluctuations observed at Iqaluit and South Pole (L{approximately}13). In this report, the authors extend the previous report of Wolfe et al. (1987) and comment upon the conjugacy of the stations for magnetic field fluctuations in the Pc3 (22-33 millihertz) hydromagnetic regime and upon the penetration of hydromagnetic energy deeper into the magnetosphere on the local dayside.

  13. DHIGLS: DRAO H I Intermediate Galactic Latitude Survey

    CERN Document Server

    Blagrave, K; Joncas, G; Kothes, R; Stil, J; Miville-Deschenes, M -A; Lockman, Felix J; Taylor, A R

    2016-01-01

    Observations of Galactic H I gas for seven intermediate Galactic latitude fields are presented at 1' angular resolution using data from the DRAO Synthesis Telescope (ST) and the Green Bank Telescope (GBT). The DHIGLS data are the most extensive arcminute resolution measurements of the diffuse atomic interstellar medium beyond those in the Galactic plane. The acquisition, reduction, calibration, and mosaicking of the DRAO ST data and the cross calibration and incorporation of the short-spacing information from the GBT are described. The high quality of the DHIGLS data enables a variety of new studies in directions of low Galactic column density. We find evidence for dramatic changes in the structures in channel maps over even small changes in velocity. This narrow line emission has counterparts in absorption spectra against bright background radio sources, quantifying that the gas is cold and dense and can be identified as the cold neutral medium phase. We analyze the angular power spectra of maps of the integ...

  14. The CH fraction of Carbon stars at high Galactic latitudes

    CERN Document Server

    Goswami, Aruna; Shantikumar, N S

    2009-01-01

    CH stars form a distinct class of objects with characteristic properties like iron deficiency, enrichment of carbon and overabundance in heavy elements. These properties can provide strong observational constraints for theoretical computation of nucleosynthesis at low-metallicity. An important question is the relative surface density of CH stars which can provide valuable inputs to our understanding on the role of low to intermediate-mass stars in the early Galactic chemical evolution. Spectroscopic characterization provides an effective way of identifying CH stars. The present analysis is aimed at a quantitative assessment of the fraction of CH stars in a sample of stars using a set of spectral classification criteria. The sample consists of 92 objects selected from a collection of candidate Faint High Latitude Carbon stars from the Hamburg/ESO survey. Medium resolution (R ~ 1300) spectra for these objects were obtained using OMR at VBO, Kavalur and HFOSC at HCT, IAO, Hanle, during 2007 - 2009 spanning a wav...

  15. Computing rare transitions between zonal mid-latitude jets

    Science.gov (United States)

    Simonnet, Eric; Bouchet, Freddy

    2016-04-01

    Zonal jets are known to naturally emerge from beta-plane turbulence due to the arrest of inverse energy cascade by Rossby waves.Transitions between jets of different wavenumber are indeed observed in particular regimes showing a striking example of bimodality in the context of 2-D turbulence. As the Rayleigh dissipation and stochastic forcing are decreased these transitions become more and more rare. The aim of this talk is to show that it is possible to compute large ensembles of reactive trajectories connecting the different metastable states even at very low probability regimes when direct numerical simulations are not possible. We use an adaptive version of multilevel splitting algorithms on a barotropic quasi geostrophic model of mid-latitude atmosphere. We are able to obtain a detailed statistical description of the high-dimensional phase space as well as the typical transitions. A large-deviation result is also obtained.

  16. The structure of convective rain cells at mid-latitudes

    Directory of Open Access Journals (Sweden)

    N. Rebora

    2006-01-01

    Full Text Available Rain cells are structures which represent an important component of convective precipitation and a study of their properties represents a necessary step both towards improved stochastic models of small-scale precipitation and for the verification of deterministic high resolution local-area models. The case of intense convective precipitation in the tropics has been analysed in a recent study (von Hardenberg et al., 2003. Here we extend the analysis to mid-latitudes and we present results on the structure of convective rain cells observed by radar measurements in Italy. In particular we consider the average shape of precipitation cells and its dependence on radar resolution and the distributions of ellipticities.

  17. Turbulent oceanic western-boundary layers at low latitude

    Science.gov (United States)

    Quam Cyrille Akuetevi, Cataria; Wirth, Achim

    2013-04-01

    Low latitude oceanic western-boundary layers range within the most turbulent regions in the worlds ocean. The Somali current system with the Great Whirl and the Brazilian current system with its eddy shedding are the most prominent examples. Results from analytical calculations and integration of a one layer reduced-gravity fine resolution shallow water model is used to entangle this turbulent dynamics. Two types of wind-forcing are applied: a remote Trade wind forcing with maximum shear along the equator and a local Monsoon wind forcing with maximum shear in the vicinity of the boundary. For high values of the viscosity (> 1000m2s-1) the stationary solutions compare well to analytical predictions using Munk and inertial layer theory. When lowering the friction parameter time dependence results. The onset of instability is strongly influenced by inertial effects. The unstable boundary current proceeds as a succession of anti-cyclonic coherent eddies performing a chaotic dynamics in a turbulent flow. The dynamics is governed by the turbulent fluxes of mass and momentum. We determine these fluxes by analyzing the (potential) vorticity dynamics. We demonstrate that the boundary-layer can be separated in four sub-layers, which are (starting from the boundary): (1) the viscous sub-layer (2) the turbulent buffer-layer (3) the layer containing the coherent structures and (4) the extended boundary layer. The characteristics of each sub-layer and the corresponding turbulent fluxes are determined, as are the dependence on latitude and the type of forcing. A new pragmatic method of determining the eddy viscosity, based on Munk-layer theory, is proposed. Results are compared to observations and solutions of the multi-level primitive equation model (DRAKKAR).

  18. Comparing High-latitude Ionospheric and Thermospheric Lagrangian Coherent Structures

    Science.gov (United States)

    Wang, N.; Ramirez, U.; Flores, F.; Okic, D.; Datta-Barua, S.

    2015-12-01

    Lagrangian Coherent Structures (LCSs) are invisible boundaries in time varying flow fields that may be subject to mixing and turbulence. The LCS is defined by the local maxima of the finite time Lyapunov exponent (FTLE), a scalar field quantifying the degree of stretching of fluid elements over the flow domain. Although the thermosphere is dominated by neutral wind processes and the ionosphere is governed by plasma electrodynamics, we can compare the LCS in the two modeled flow fields to yield insight into transport and interaction processes in the high-latitude IT system. For obtaining thermospheric LCS, we use the Horizontal Wind Model 2014 (HWM14) [1] at a single altitude to generate the two-dimensional velocity field. The FTLE computation is applied to study the flow field of the neutral wind, and to visualize the forward-time Lagrangian Coherent Structures in the flow domain. The time-varying structures indicate a possible thermospheric LCS ridge in the auroral oval area. The results of a two-day run during a geomagnetically quiet period show that the structures are diurnally quasi-periodic, thus that solar radiation influences the neutral wind flow field. To find the LCS in the high-latitude ionospheric drifts, the Weimer 2001 [2] polar electric potential model and the International Geomagnetic Reference Field 11 [3] are used to compute the ExB drift flow field in ionosphere. As with the neutral winds, the Lagrangian Coherent Structures are obtained by applying the FTLE computation. The relationship between the thermospheric and ionospheric LCS is analyzed by comparing overlapping FTLE maps. Both a publicly available FTLE solver [4] and a custom-built FTLE computation are used and compared for validation [5]. Comparing the modeled IT LCSs on a quiet day with the modeled IT LCSs on a storm day indicates important factors on the structure and time evolution of the LCS.

  19. Daylighting in linear atrium buildings at high latitudes

    Energy Technology Data Exchange (ETDEWEB)

    Matusiak, Barbara

    1998-12-31

    This thesis proposes new criteria for visual comfort based on knowledge of visual perception and a method for estimating the modelling ability of light by using inter-reflection calculations. Simplified calculations are presented for the daylight factor in linear building structures, using the projected solid angle principle, for uniform sky and for CIE overcast sky conditions. The calculations are compared with experimental results. Simple diagrams are created based on calculations of the mean daylight factor in rooms adjacent to a narrow street. These diagrams and presented formulas and tables can be used as a simple design tool. Daylighting strategies for linear atrium buildings at high latitudes are developed and examined. These strategies are divided into three groups: (1) the atrium space and facades as light conductor/reflector, (2) the glass roof as a light conductor, and (3) light reflectors on the neighbouring roof. The atrium space and facade strategies are subdivided into passive and active. The strategies connected to the glazed roof includes different configurations of glazing: horizontal, single pitched, double pitched, and the use of laser cut panels and prismatic panels in the glazed roof. The shapes of reflectors on the neighbouring roof are a flat reflector, a parabolic reflector and a parabolic concentrator. Strategies from all three groups are examined on a physical model of scale 1:20 in the artificial sky of mirror box type. Simulations with artificial sun have also been done. The results from model studies are compared with computer simulations. All the active daylighting systems designed for use in the atrium space or on the atrium facades have a huge potential for use in atrium buildings. From the strategies connected with the glazed roof the negatively sloped glass is found to be the best alternative for glazed roofs at high latitudes. Among the roof reflectors, the flat one performs best. 82 refs., 122 figs., 27 tabs.

  20. Clumped isotope thermometry of modern and early Cretaceous molluscan carbonate from high-latitude seas (Invited)

    Science.gov (United States)

    Henkes, G. A.; Price, G. D.; Ambrose, W. G.; Carroll, M. L.; Passey, B. H.

    2010-12-01

    The carbonate clumped isotope thermometer is based on the temperature sensitivity of the relative abundance of carbonate ion groups containing 13C-18O bonds. One application of clumped isotope thermometry is to determine the temperature of ancient seawater from the skeletal material of calcium carbonate-secreting marine organisms. The relationship between Δ47, a parameter describing isotopic clumping, and the temperature of carbonate biomineralization has been well-defined for fish otoliths, corals, foraminifera, and coccolithophore tests, but few data have been published for brachiopods and bivalve mollusks. A comprehensive evaluation of the Δ47-temperature relationship for mollusks is required for paleotemperature interpretations from the marine fossil record. Here we present a more comprehensive calibration for modern mollusks, including bivalves, cephalopods, and gastropods. Further, we focus on a subset of cold water, high-latitude species collected in the northern Barents Sea. The observed Δ47-temperature relationship is similar to the theoretical relationship presented by Guo et al. (2009) but deviates at low temperatures from the original Ghosh et al. (2007) calibration curve. This divergence could be related to methodological differences or unaccounted differences in the biomineralization of mollusks versus that of other carbonate-secreting organisms at low temperature. One advantage of clumped isotope thermometry over traditional oxygen isotope thermometry is that it does not require assumptions about the isotopic composition of the water in which the carbonate formed. This may be particularly useful in Mesozoic paleoceanography where the oxygen isotope value of seawater is uncertain. Using clumped isotope thermometry applied to early Cretaceous (Valangian) belemnite carbonate from the Yatria River, sub-polar Urals, Siberia, we find shell growth temperatures of 20-26°C at a paleolatitude of ~60-65°N. Our data imply average seawater δ18O values of 0

  1. Interactions Between Vestige Atlantic Tropical Cyclones and Mid-Latitude Storms Over Mediterranean Basin

    Science.gov (United States)

    Smith, Eric A.; Mehta, Amita; Mugnai, Alberto; Tripoli, Gregory J.

    2007-01-01

    One of the more interesting tropical-mid-latitude interactions is one that has important effects on precipitation within the Mediterranean basin. This interaction consists of an Atlantic tropical cyclone vestige whose original disturbance travels eastward and northward across Atlantic basin, eventually intermingling with a mid-latitude cyclone entering southern Europe and/or the \\bestern Mediterranean Sea. The period for these interactions is from mid-September through November. If the tropical cyclone and its vestige is able to make the eastward Atlantic transit within the low to mid-levels, or if an upper level potential vorticity perturbation Cjet streak) emitted by a Hurricane in its latter stages within the central Atlantic is able to propagate into and along the longwave pattern affecting the western Mediterranean Sea (MED), then there is the prospect for the tropical cyclone remnant to produce a major modification of the mid-latitude storm system preparing to affect the MED region. For such an occurrence to take place, it is necessary for an amplifying baroclinic perturbation to be already situated to the rear of a longwave trough, or to be excited by the emitted jet streak to the rear of a longwave trough -- in either case, preparing to affect the western MED. The Algiers City flood of 9-10 November 2001, which killed some 700 people, was produced by a Mediterranean cyclone that had been influenced by two vestige Atlantic tropical cyclones, 1,orenzo and Noel. A published modeling study involving various of this study's authors has already described the dynamical development of the Algiers storm as it amplified from a developing baroclinic disturbance in the Rossby wave train, into a northern Africa hazardous flood system, then lingered in the western MED as a semi-intense warm core cyclone. In our new modeling experiments, we investigate the impact of what might have happened in the eventual precipitation field. had the main features of the tropical

  2. Summertime distribution of PAN and other reactive nitrogen species in the northern high-latitude atmosphere of eastern Canada

    Science.gov (United States)

    Singh, H. B.; Herlth, D.; O'Hara, D.; Zahnle, K.; Bradshaw, J. D.; Sandholm, S. T.; Talbot, R.; Gregory, G. L.; Sachse, G. W.; Blake, D. R.

    1994-01-01

    Aircraft measurements of key reactive nitrogen species (NO, NO2, HNO3, PAN, PPN, NO3(-), NO(y)), C1 to C6 hydrocarbons, acetone, O3, chemical tracers (C2Cl4, CO), and important meteorological parameters were performed over eastern Canada during July to August 1990 at altitudes between 0 and 6 km as part of an Arctic Boundary Layer Expedition (ABLE3B). In the free troposphere, PAN was found to be the single most abundant reactive nitrogen species constituting a major fraction of NO(y) and was significantly more abundant than NO(x) and HNO3. PAN and O3 were well correlated both in their fine and gross structures. Compared to data previously collected in the Arctic/subarctic atmosphere over Alaska (ABLE3A), the lower troposphere (0-4 km) over eastern Canada was found to contain larger reactive nitrogen and anthropogenic tracer concentrations. At higher altitudes (4-6 km) the atmospheric composition was in many ways similar to what was seen over Alaska and supports the view that a large-scale reservoir of PAN (and NO(y)) is present in the upper troposphere over the entire Arctic/subarctic region. The reactive nitrogen budget based on missions conducted from the North Bay site (missions 2-10) showed a small shortfall, whereas the budget for data collected from the Goose Bay operation (missions 11-19) showed essential balance. It is calculated that 15-20 ppt of the observed NO(x) may find its source from the available PAN reservoir. Meteorological considerations as well as relationships between reactive nitrogen and tracer species suggest that the atmosphere over eastern Canada during summer is greatly influenced by forest fires and transported industrial pollution.

  3. Savanna ant species richness is maintained along a bioclimatic gradient of increasing latitude and decreasing rainfall in northern Australia

    DEFF Research Database (Denmark)

    Andersen, Alan N.; Del Toro, Israel; Parr, Catherine L.

    2015-01-01

    of other important faunal groups such as termites and lizards is also exceptionally high in arid Australia and is likewise not closely linked to rainfall in Australian savannas. We predict that these taxa are far more sensitive to increasing aridity in savannas elsewhere in the world, and especially...

  4. Common genetic variants are associated with lower serum 25-hydroxyvitamin D concentrations across the year among children at northern latitudes

    DEFF Research Database (Denmark)

    Petersen, Rikke A.; Larsen, Lesli Hingstrup; Damsgaard, Camilla T.

    2017-01-01

    In a longitudinal study including 642 healthy 8-11-year-old Danish children, we investigated associations between vitamin D dependent SNP and serum 25-hydroxyvitamin D (25(OH)D) concentrations across a school year (August-June). Serum 25(OH)D was measured three times for every child, which...... reductase/nicotinamide adenine dinucleotide synthetase-1(DHCR7/NADSYN1); group-specific complement (GC); and vitamin D receptor were genotyped. We found minor alleles of CYP2R1 rs10500804, and of GC rs4588 and rs7041 to be associated with lower serum 25(OH)D concentrations across the three seasons (all P...

  5. Satellite observations of high northern latitude vegetation productivity changes between 1982 and 2008: ecological variability and regional differences

    Science.gov (United States)

    Beck, Pieter S. A.; Goetz, Scott J.

    2011-12-01

    In the first paragraph of the section '2. Data sets and methods', the Normalized Difference Vegetation Index (NDVI) data set used was incorrectly referred to as GIMMS-NDVI version 3G with a 0.084° spatial resolution. This should be corrected to GIMMS-NDVI version G with a 0.07° spatial resolution. Accordingly, the acknowledgement should state 'We would like to thank ... Jim Tucker and Jorge Pinzon for providing the GIMMS version G data', instead of 'We would like to thank ... Jorge Pinzon for providing the GIMMS 3G data'.

  6. Late Miocene increase in precipitation in the Western Cordillera of the Andes between 18-19°S latitudes inferred from shifts in sedimentation patterns

    Science.gov (United States)

    Schlunegger, Fritz; Norton, Kevin P.; Delunel, Romain; Ehlers, Todd A.; Madella, Andrea

    2017-03-01

    Modern climate in the Andes is characterized by strong N-S decreasing trends in precipitation rates. Here we use stratigraphic records to show that this pattern has been established since as early as 12-11 Ma, at least on the western Andean margin of Northern Chile. The stratigraphic architecture on the western Andean margin documents a transition between 19°-20°S latitude where matrix-supported debris flow deposits shift to fluvial conglomerates between 12-11 Ma. The deposition of fluvial sediments has been maintained to the present north of 19°-20°S, while the occurrence of post 11 Ma aeolian sand, matrix-supported breccias with conglomerate interbeds south of these latitudes implies ongoing sedimentation with less water and thus under drier conditions. We relate these changes to the tectonic development of the Andes. Existing palaeoclimate models suggest that an elevated plateau deflects the Andean jet towards the south, thereby focusing moisture from the equatorial Atlantic to the northeastern flanks of the Altiplano. In addition, the formation of the eastern Andean foothills most likely intercepted moisture transport, and shifted it farther to the east, thereby keeping the western Andean margin dry south of 19°-20°S latitudes. The sedimentological data support a strong linkage between orographic precipitation and stratigraphy whereby central Andean deformation controls the distribution of available moisture on the western flank through a combination of orographic precipitation and deflection of air masses.

  7. Recurrent partial mortality events in winter shape the dynamics of the zooxanthellate coral Oculina patagonica at high latitude in the Mediterranean

    Science.gov (United States)

    Serrano, Eduard; Ribes, Marta; Coma, Rafel

    2017-03-01

    Global warming has many biological effects on corals and plays a central role in the regression of tropical coral reefs; therefore, there is an urgent need to understand how some coral species have adapted to environmental conditions at higher latitudes. We examined the effects of temperature and light on the growth of the zooxanthellate coral Oculina patagonica (Scleractinia, Oculinidae) at the northern limit of its distribution in the eastern Iberian Peninsula (western Mediterranean) by transplanting colonies onto plates and excluding them from space competition over a 4-yr period. Each year, most of the colonies ( 70%) exhibited denuded skeletons with isolated polyps persisting on approximately half of the coral surface area. These recurrent episodes of partial coral mortality occurred in winter, and their severity appeared to be related to colony exposure to cold but not to light. Although O. patagonica exhibited high resistance to stress, coral linear extension did not resume until the coenosarc regenerated. The resumption of linear extension was related to the dissociation of the polyps from the coenosarc and the outstanding regenerative capacity of this species (10.3 mm2 d-1). These biological characteristics allow the species to survive at high latitudes. However, the recurrent and severe pattern of denuded skeletons greatly affects the dynamics of the species and may constrain population growth at high latitudes in the Mediterranean.

  8. 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

  9. A Simple Proxy System Model of High-Latitude Encrusting Algal Oxygen Isotope Composition (δ18O)

    Science.gov (United States)

    Williams, B.; Thompson, D. M.; Crowley, M.; Moulton, M.; Ng, J.; Halfar, J.

    2016-12-01

    The calcitic skeletons of marine crustose coralline algae yield important reconstructions of oceanic change spanning the past several centuries. The alga Clathromorphum spp. is abundant in coastal regions throughout the mid-to-high latitude northern hemisphere, forms an annually layered structure, and may grow for 850 years or more. In this alga, the stable oxygen isotopic composition (δ18O) of the skeleton reflects seawater temperature and/or δ18O composition of the seawater during the time of calcification. Here, we build and assess a simple, empirical proxy system model (PSM) of algal δ18O to better evaluate incorporation of the environmental parameters into the skeleton of the algae for future paleoclimate reconstructions. To develop the coralline algal PSM, we first determine the response season (in which the alga incorporates the ambient environmental signals) for four specimens spanning the algal growth range in the northern hemisphere. We find that the alga significantly records ambient seawater temperatures during summer months, but shows no relationship with salinity. This yields a simple, univariate proxy system model of pseodoalgal-δ18O = αSST + error, where α is the slope of the algal-δ18O to SST relationship determined by regressing temperature during the response season with algal-δ18O across the habitat range. We find the coefficients vary within a narrow range from -0.135 to -0.17, depending on the algal location and gridded dataset used, supporting a coherent relationship between seawater temperature and algal-δ18O. Using the average coefficient and associated uncertainty range, we create pseudoalgae records for four locations within the Clathromorphum spp. northern hemisphere range to compare with the observed algal records and assess variability and secular trends over the past century.

  10. Tropical Warm Semi-Arid Regions Expanding Over Temperate Latitudes In The Projected 21st Century

    Science.gov (United States)

    Rajaud, A.; de Noblet, N. I.

    2015-12-01

    Two billion people today live in drylands, where extreme climatic conditions prevail, and natural resources are limited. Drylands are expected to expand under several scenarios of climatic change. However, relevant adaptation strategies need to account for the aridity level: it conditions the equilibrium tree-cover density, ranging from deserts (hyper-arid) to dense savannas (sub-humid). Here we focus on the evolution of climatically defined warm semi-arid areas, where low-tree density covers can be maintained. We study the global repartition of these regions in the future and the bioclimatic shifts involved. We adopted a bioclimatological approach based on the Köppen climate classification. The warm semi-arid class is characterized by mean annual temperatures over 18°C and a rainfall-limitation criterion. A multi-model ensemble of CMIP5 projections for three representative concentration pathways was selected to analyze future conditions. The classification was first applied to the start, middle and end of the 20th and 21st centuries, in order to localize past and future warm semi-arid regions. Then, time-series for the classification were built to characterize trends and variability in the evolution of those regions. According to the CRU datasets, global expansion of the warm semi-arid area has already started (~+13%), following the global warming trend since the 1900s. This will continue according to all projections, most significantly so outside the tropical belt. Under the "business as usual" scenario, the global warm semi-arid area will increase by 30% and expand 12° poleward in the Northern Hemisphere, according to the multi-model mean. Drying drives the conversion from equatorial sub-humid conditions. Beyond 30° of latitude, cold semi-arid conditions become warm semi-arid through warming, and temperate conditions through combined warming and drying processes. Those various transitions may have drastic but also very distinct ecological and sociological

  11. The hydrography of the mid-latitude northeast Atlantic Ocean. I: The deep water masses

    Science.gov (United States)

    van Aken, Hendrik M.

    2000-05-01

    The circulation of the deep water masses in the mid-latitude northeast Atlantic Ocean was studied by analysis of the distributions of potential temperature, salinity, dissolved oxygen, phosphate, nitrate, and silicate. Pre-formed nutrients were used to allow a quantitative description of the deep water masses, especially the Northeast Atlantic Deep Water, in terms of four local source water types: Iceland-Scotland Overflow Water, Lower Deep Water, Labrador Sea Water, and Mediterranean Sea Water. Over the Porcupine Abyssal Plain between 2500 and 2900 dbar Northeast Atlantic Deep Water appears to be a mixture of mainly Iceland-Scotland Overflow Water and Labrador Sea Water (˜80%), with minor contributions of Lower Deep Water and Mediterranean Sea Water. When the Northeast Atlantic Deep Water re-circulates in the north-eastern Atlantic and flows southwards towards the Madeira Abyssal Plain, contributions of the former two water types of northern origin diminish to about 50% due to diapycnal mixing with the overlying and underlying water masses. The observed meridional and zonal trends of dissolved oxygen and nutrients in the Northeast Atlantic Deep Water appear to be caused both by diapycnal mixing with the underlying Lower Deep Water and by mineralization of organic matter. The eastward decrease of oxygen and increase of nutrients especially require considerable mineralization of organic matter near the European continental margin. At deeper levels (˜4100 dbar), where the nutrient rich Lower Deep Water is found near the bottom, the meridional gradients of oxygen and nutrients are opposite to those found between 2500 and 2900 dbar. Diapycnal mixing cannot explain this change in gradients, which is therefore considered to be a qualitative indication of ageing of the Lower Deep Water when it flows northwards. A considerable part of the Iceland-Scotland Overflow Water and the Lower Deep Water that enter the northeast Atlantic may be removed by deep upwelling in the Bay

  12. Northern peatlands in global climatic change

    Energy Technology Data Exchange (ETDEWEB)

    Laiho, R.; Laine, J.; Vasander, H. [eds.] [Helsinki Univ. (Finland). Dept. of Forest Ecology

    1996-12-31

    Northern peatlands are important in regulating the global climate. While sequestering carbon dioxide, these peatlands release ca. 24-39 Tg methane annually to the atmosphere. This is 5-20 % of the annual anthropogenic methane emissions to the atmosphere. The greenhouse gas balance of peatlands may change as a consequence of water level draw-down after land-use change, or if summers become warmer and drier, as has been predicted for high latitudes after climatic warming. Subsequent emissions of methane would decrease, whereas emissions of carbon dioxide and nitrous oxide would increase. Within the Finnish Research Programme on Climate Change (SILMU), the research project `Carbon Balance of Peatlands and Climate Change` (SUOSILMU) has been under progress since 1990. It is a co-operative research project, with research groups from the Universities of Helsinki and Joensuu, the Finnish Forest Research Institute, the National Public Health Institute and the Finnish Environment Agency. The research consortium of this project organised a workshop entitled `Northern Peatlands in Global Climatic Change - Hyytiaelae Revisited` October 8-12, 1995. The main objective of the workshop was to review the state of the art of the carbon cycling research in natural and managed peatlands. The role of peatlands in the greenhouse effect, their response and feedback to the predicted climate change, and the consequences of land-use changes were assessed, and the future research needs were evaluated. The latest information on the role of peatlands in the atmospheric change was given in 50 posters and 4 key lectures. Results of SUOSILMU projects were demonstrated during a 1-day field excursion to one of the intensive study sites, Lakkasuo near Hyytiaelae

  13. Spring Hydrology Determines Summer Net Carbon Uptake in Northern Ecosystems

    Science.gov (United States)

    Yi, Yonghong; Kimball, John; Reichle, Rolf H.

    2014-01-01

    Increased photosynthetic activity and enhanced seasonal CO2 exchange of northern ecosystems have been observed from a variety of sources including satellite vegetation indices (such as the Normalized Difference Vegetation Index; NDVI) and atmospheric CO2 measurements. Most of these changes have been attributed to strong warming trends in the northern high latitudes (greater than or equal to 50N). Here we analyze the interannual variation of summer net carbon uptake derived from atmospheric CO2 measurements and satellite NDVI in relation to surface meteorology from regional observational records. We find that increases in spring precipitation and snow pack promote summer net carbon uptake of northern ecosystems independent of air temperature effects. However, satellite NDVI measurements still show an overall benefit of summer photosynthetic activity from regional warming and limited impact of spring precipitation. This discrepancy is attributed to a similar response of photosynthesis and respiration to warming and thus reduced sensitivity of net ecosystem carbon uptake to temperature. Further analysis of boreal tower eddy covariance CO2 flux measurements indicates that summer net carbon uptake is positively correlated with early growing-season surface soil moisture, which is also strongly affected by spring precipitation and snow pack based on analysis of satellite soil moisture retrievals. This is attributed to strong regulation of spring hydrology on soil respiration in relatively wet boreal and arctic ecosystems. These results document the important role of spring hydrology in determining summer net carbon uptake and contrast with prevailing assumptions of dominant cold temperature limitations to high-latitude ecosystems. Our results indicate potentially stronger coupling of boreal/arctic water and carbon cycles with continued regional warming trends.

  14. Spring hydrology determines summer net carbon uptake in northern ecosystems

    Science.gov (United States)

    Yi, Yonghong; Kimball, John S.; Reichle, Rolf H.

    2014-05-01

    Increased photosynthetic activity and enhanced seasonal CO2 exchange of northern ecosystems have been observed from a variety of sources including satellite vegetation indices (such as the normalized difference vegetation index; NDVI) and atmospheric CO2 measurements. Most of these changes have been attributed to strong warming trends in the northern high latitudes (⩾50° N). Here we analyze the interannual variation of summer net carbon uptake derived from atmospheric CO2 measurements and satellite NDVI in relation to surface meteorology from regional observational records. We find that increases in spring precipitation and snow pack promote summer net carbon uptake of northern ecosystems independent of air temperature effects. However, satellite NDVI measurements still show an overall benefit of summer photosynthetic activity from regional warming and limited impact of spring precipitation. This discrepancy is attributed to a similar response of photosynthesis and respiration to warming and thus reduced sensitivity of net ecosystem carbon uptake to temperature. Further analysis of boreal tower eddy covariance CO2 flux measurements indicates that summer net carbon uptake is positively correlated with early growing-season surface soil moisture, which is also strongly affected by spring precipitation and snow pack based on analysis of satellite soil moisture retrievals. This is attributed to strong regulation of spring hydrology on soil respiration in relatively wet boreal and arctic ecosystems. These results document the important role of spring hydrology in determining summer net carbon uptake and contrast with prevailing assumptions of dominant cold temperature limitations to high-latitude ecosystems. Our results indicate potentially stronger coupling of boreal/arctic water and carbon cycles with continued regional warming trends.

  15. Thickness of the subducting Nazca lithosphere in northern Chile as seen by S receiver functions

    Science.gov (United States)

    Sodoudi, Forough; Asch, Günter; Kind, Rainer; Oncken, Onno; Vilotte, Jean-Pierre; Barrientos, Sergio; Salazar Reinoso, Pablo

    2010-05-01

    Installation of observatories in northern Chile started in 2006 in a close cooperation of the Universidad de Chile (Santiago), the Universidad Catolica del Norte (Antofagasta), the IPGP (Paris), and the GFZ Potsdam. Currently we operate 15 modern seismological stations equipped with STS-2 broadband seismometers. One GEOFON station operated since 2001 completes our dataset in northern Chile. We combined here two methods (P and S receiver function) to have the best vertical as well as horizontal coverage of the area and map the geometry of the subducting Nazca plate. Our high resolution results image the penetration of the Moho of the subducting Nazca plate at depths ranging from 35 km beneath the Coastal Cordillera to an average depth of 80 km beneath the Longitudinal Valley and about 100 km beneath the Precordillera. We found a significant variation in the dip of the subducting Nazca plate obtained from stations located in the northern part (over latitude of 21 deg. South) compared to those located below this latitude. The shape of the Nazca plate shows a shallow dip beneath the southern part and becomes steeper and deeper beneath the northern part of the area, which is coherent with the intermediate seismicity. On the basis of our P and S receiver functions, the lithosphere-asthenosphere boundary of the subducting Nazca plate is at 80 km depth beneath the Coastal Cordillera and dips to a depth of about 120 km beneath the Longitudinal Valley. It becomes 150 km underneath the Precordillera.

  16. Emissions of methane from northern peatlands: a review of management impacts and future implications

    Science.gov (United States)

    Abdalla, Mohamed; Hastings, Astley; Mander, Ulo; Smith, Pete; Nilsson, Mats

    2016-04-01

    Northern peatlands constitute a significant source of atmospheric methane (CH4). However, management of undisturbed peatlands, as well as restoration of disturbed peatlands, will alter the exchange of methane with the atmosphere. The aim of this literature review and meta-analysis was to collate and analyse recent literature to improve our understanding of the impacts of management on CH4 emissions from northern peatlands i.e. latitude 40 to 70o N. Results show that CH4 emissions from natural northern peatlands range from 0 to 154 g C m-2 yr-1 and the overall annual average (mean ± standard deviation) is 11.7 ± 21 g C m-2 yr-1 with the highest emissions from fen ecosystems. Drainage significantly (pMethane emissions are mainly controlled by water table (WT) depth, plant community composition and soil pH. Although temperature is not a good predictor of CH4 emissions by itself, the interaction between temperatures, plant community cover, WT depth and soil pH is important. According to short-term forecasts of climate change, these complex interactions will be the main determinant of increased CH4 emissions from northern peatlands. However, to fully evaluate the net effect of management practice on high latitude peatlands both net ecosystem exchange (NEE) and carbon exports needs to be considered.

  17. Autonomous, continuously recording broadband seismic stations at high-latitude

    Science.gov (United States)

    Beaudoin, B.; Parker, T.; Bonnett, B.; Tytgat, G.; Anderson, K.; Fowler, J.

    2009-04-01

    IRIS PASSCAL is in the third year of an NSF funded development and acquisition effort to establish a pool of cold-hardened seismic stations specifically for high-latitude broadband deployments. We have two complete years of field trials and have successfully recorded continuous seismic data during both years with data recovery rates of ~90%. Our design is premised on a 2W autonomous system recording to local media, capable of lasting two years without service. The system is composed of four new design elements: a heavily insulated station enclosure; a state-of-health (SOH) Iridium modem; a light weight, easily deployed solar panel mount; and a power system that includes power switching between primary (Lithium Thionyl Chloride) and secondary batteries. The station enclosures have proved most critical in keeping our data acquisition systems operating within manufacturer specifications and primary batteries within a 50-70% efficiency range. Enclosures with 2.5cm-thick vacuum panels and 5cm of foam insulation have kept interior enclosure temperatures 25-30°C above background (typically below -50°C). This austral summer we are deploying version three of our enclosures. Significant changes in the design include thicker vacuum panels (5cm), more robust construction, and simplified cable routing. An important aspect of our station design is easy installation and minimal weight. To simplify installation our station enclosures are packed with datalogger, SOH communications and batteries in the lab or base camp, so that access to the internal components is not necessary at the remote site. Bulkhead connectors allow a user to fully interact with the system without ever having to open the enclosure. Solar panel mounts are also fully constructed prior to deployment. Once on site, digging two large holes (one for the enclosure and one for the broadband seismometer) and constructing the site takes roughly 2 hours. A station designed to record continuously for 12-14 months is

  18. The spectral nature of Titan's mid-latitude region

    Science.gov (United States)

    Solomonidou, Anezina; Coustenis, Athena; Lopes, Rosaly; Malaska, Michael; Rodriguez, Sebastien; Drossart, Pierre; Schmitt, Bernard; Philippe, Sylvain; Janssen, Michael; Le Gall, Alice; Lawrence, Kenneth; Hirtzig, Mathieu; Sohl, Frank; Stephan, Katrin; Jaumann, Ralf; Brown, Robert; Villanueva, Edward; Bratsolis, Emmanuel; Matsoukas, Christos; Schoenfeld, Ashley

    2017-04-01

    We infer surface properties, such as surface albedo and atmospheric contributions in the form of haze content, of the mid-latitude region of Titan. In previous studies [1;2] we reported results on two areas presenting indications for possible changes in surface albedo with time [2]. We also investigate the endogenic or exogenic processes linked to the formation of the various mid-latitude geomorphological units. These could be aeolian, fluvial, sedimentary, cryovolcanic, lacustrine, and more. Furthermore, deposition of organics through the atmosphere seems to be predominantly present [1]. We now focus on constraining the chemical composition of the various geomorphological units [5;6] by investigating the lower atmosphere of Titan from Visual and Infrared Mapping Spectrometer (VIMS) spectro-imaging data by use of a recently updated radiative transfer code in the near-IR range. For the distinction of geomorphological units we use RADAR/SAR data [4]. We study the units of interest identified in [1;3] and [4]: mountains, plains, labyrinths, dune fields, and possible cryovolcanic and/or evaporitic features (the latter two are albedo features, [4;5]). Our findings indicate that many of the regions from the same geomorphological unit show compositional variations depending on location, while units of significant geomorphological differences seem to consist of very similar material mixtures. Preliminary results on the chemical composition of the regions that have shown temporal changes (i.e. Tui Regio and Sotra Patera; [6]) are also presented. The albedo differences and similarities among the various geomorphological terrains set constraints on the possible geological processes that govern Titan's surface. References: [1] Lopes, R.M.C., et al.: Icarus, 270, 162-182, 2016; [2] Solomonidou, A., et al.: Icarus, 270, 85-99, 2016; [3] Lopes, R.M.C., et al.: Icarus, 205, 540-558, 2010; [4] Malaska, M., et al.: Icarus, 270, 130-161, 2016; [4] Barnes, J., et al.: Pl. Scie., 2

  19. Arctic East Siberia had a lower latitude in the Pleistocene

    CERN Document Server

    Wölfli, W

    2006-01-01

    In Arctic East Siberia many remains of mammoths have been found. In this region there is not sufficient sunlight over the year to allow for the growth of the plants on which these animals feed. Consequently the latitude of these regions must have been lower before the end of the Pleistocene than at present. It is a challenge to reconstruct this geographic shift of the poles in a manner compa- tible with known facts. A possible sequence of events is described here. It as- sumes an additional planet, which must since have disappeared. This is possible, if it moved in an extremely eccentric orbit and was hot as a result of tidal work and solar radiation. During a few million years evaporation of this planet led to a disk-shaped cloud of ions moving around the Sun. This cloud partially shielded the Earth from the solar radiation, producing the alteration of cold and warm periods characterizing the Pleistocene. The degree of shielding is sensitive to the inclination of Earth's orbit, which has a period of 100000 y...

  20. Sun position calculator (SPC) for Landsat imagery with geodetic latitudes

    Science.gov (United States)

    Seong, Jeong C.

    2015-12-01

    Landsat imagery comes with sun position information such as azimuth and sun elevation, but they are available only at the center of a scene. To aid in the use of Landsat imagery for various solar radiation applications such as topographic correction, solar power, urban heat island, agriculture, climate and vegetation, it is necessary to calculate the sun position information at every pixel. This research developed a PC application that creates sun position data layers in ArcGIS at every pixel in a Landsat scene. The SPC program is composed of two major routines - converting universal transverse Mercator (UTM) projection coordinates to geographic longitudes and latitudes, and calculating sun position information based on the Meeus' routine. For the latter, an innovative method was also implemented to account for the Earth's flattening on an ellipsoid. The Meeus routine implemented in this research showed about 0.2‧ of mean absolute difference from the National Renewable Energy Laboratory (NREL) Solar Position Algorithm (SPA) routine when solar zenith and azimuth angles were tested with every 30 min data at four city locations (Fairbanks, Atlanta, Sydney and Rio Grande) on June 30, 2014. The Meeus routine was about ten times faster than the SPA routine. Professionals who need the Sun's position information for Landsat imagery will benefit from the SPC application.

  1. Analysis of the atmospheric upward radiation in low latitude area

    Science.gov (United States)

    Li, Haiying; Wu, Zhensen; Lin, Leke; Lu, Changsheng

    2016-10-01

    Remote sensing using THz wave has irreplaceable advantage comparing to the microwave and the infrared waves, and study on the THz remote sensing become more and more popular in recent years. The major applications of the remote sensing in THz wavelengths are the retrieval of the atmospheric parameters and the microphysical information of the ice cloud. The remote sensing of the atmosphere is based on the radiation of THz wave along the earth-space path of which the most significant part is the upward radiation of the atmosphere. The upward radiation of the atmosphere in sunny day in the low latitude area is computed and analyzed in this paper. The absorption of THz wave by the atmosphere is calculated using the formulations illustrated in the Recommendation ITU-R P.676 to save machine hour, the frequency range is then restricted below 1THz. The frequencies used for the retrieval of atmospheric parameters such as temperature and water content are usually a few hundred GHz, at the lower end of THz wavelengths, so this frequency range is sufficient. The radiation contribution of every atmospheric layer for typical frequencies such as absorption window frequencies and peak frequencies are analyzed. Results show that at frequencies which absorption is severe, information about lower atmosphere cannot reach the receiver onboard a satellite or other high platforms due to the strong absorption along the path.

  2. 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.

  3. Discovery of an Apparent High Latitude Galactic Supernova Remnant

    CERN Document Server

    Fesen, Robert; Black, Christine; Koeppel, Ari

    2015-01-01

    Deep H$\\alpha$ images of a faint emission complex 4.0 x 5.5 degrees in angular extent and located far off the Galactic plane at l = 70.0 degrees, b=-21.5 degrees reveal numerous thin filaments suggestive of a supernova remnant's shock emission. Low dispersion optical spectra covering the wavelength range 4500 - 7500 A show only Balmer line emissions for one filament while three others show a Balmer dominated spectrum along with weak [N I] 5198, 5200 A, [O I] 6300, 6364 A, [N II] 6583 A, [S II] 6716, 6731 A and in one case [O III] 5007 A line emission. Many of the brighter H$\\alpha$ filaments are visible in near UV GALEX images presumably due to C III] 1909 A line emission. ROSAT All Sky Survey images of this region show a faint crescent shaped X-ray emission nebula coincident with the portion of the H$\\alpha$ nebulosity closest to the Galactic plane. The presence of long, thin Balmer dominated emission filaments with associated UV emission and coincident X-ray emission suggests this nebula is a high latitude ...

  4. A review of recent MLT studies at low latitudes

    Directory of Open Access Journals (Sweden)

    B. R. Clemesha

    2004-09-01

    Full Text Available Recent years have shown a continuing interest in studies of the mesosphere-lower thermosphere region at low latitudes, with more than 50 papers dealing specifically with this area published over the past 5 years. Experimental ground-based work has been carried out mainly in South America and the Caribbean, India and the Pacific areas. Subjects of interest include gravity waves, tides and planetary waves, the temperature structure of the mesopause region, with special reference to temperature inversions and the two-level mesopause, sporadic neutral layers and their relationship with ionized layers, the possible effects of the micrometeoroid influx, and long-term trends in the MLT region. Experimental techniques in use include MF, MST and meteor radar, lidar, airglow (including satellite-borne limb-scanning measurements and rocket-borne instruments. Airglow imaging has shown itself to be a particularly useful technique, mainly for studying gravity wave propagation in the MLT region. This paper will present highlights of recent work and will discuss some of the problems which remain to be resolved.

  5. A polarised fast radio burst at low Galactic latitude

    Science.gov (United States)

    Petroff, Emily; SUPERB Collaboration; HESS Collaboration; ANTARES Collaboration

    2017-01-01

    Fast radio bursts (FRBs) are a growing population of transients detected with radio telescopes which are thought to originate outside the Milky Way. Fewer than 20 sources exist in the literature and the majority of bursts have been found away from the plane of the Galaxy or where the Galactic contribution to the total electron column density is low. Here we report on the discovery of a new burst, FRB 150215, discovered with the Parkes radio telescope in real-time in February 2015. The burst was found to be 43±5% linearly polarised with an imprecisely determined rotation measure (RM) consistent with zero. The burst was followed-up with 9 telescopes to search for radio, optical, X-ray, γ-ray and neutrino emission from the location of the burst. No transient or variable emission was found to be associated with the burst and no repeat pulses have been observed in nine hours of Parkes observations. Radio images of the field were obtained following the FRB but would not have been sensitive enough to pick up a signal like the one emanating from WISE J071634.59-190039.2 following FRB150418 if it had been present. The sightline to the burst is close to the Galactic plane and the Galactic RM foreground may approach a null along this sightline, corresponding to a decreased total electron column density from the Milky Way. This might explain why this burst was detectable at low latitude whereas previous searches have been relatively unsuccessful.

  6. Surface changes in mid-latitude regions on Titan

    Science.gov (United States)

    Solomonidou, A.; Coustenis, A.; Lopes, R. M. C.; Hirtzig, M.; Rodriguez, S.; Stephan, K.; Sotin, C.; Drossart, P.; Lawrence, K.; Le Mouélic, S.; Bratsolis, E.; Jaumann, R.; Brown, R. H.; Malaska, M.

    2014-04-01

    We present a study focused on the mid-latitude and close to the equator surface regions on Titan that present an interest on their spectral behavior and/or morphology. These are regions where spectroscopic anomalies have been reported in the evolution of the brightness and several interpretations have been proposed (cryovolcanic candidates, evaporates, lacustrine, etc [1;2;5]). Also in our work here we have included analysis of some undifferentiated plains (also referred to as 'blandlands'), which are vast expanses of terrains that appear bland in the radar data [3]. By applying a Radiative transfer code [4;2] we have analyzed these regions to look for evolution with time through their spectral behavior. We use as reference point and calibration tool the surface albedo retrieval of the Huygens Landing site (Titan's ground truth) and we also check the variability of the surface albedo of these regions against areas that are not expected to change with time (e.g. dune fields), by retrieving their albedo differences at all wavelengths [2]. We report here surface albedo changes with time for some of these regions of interest that imply connection to exogenic and/or endogenic processes.

  7. Preface: The International Reference Ionosphere (IRI) at equatorial latitudes

    Science.gov (United States)

    Reinisch, Bodo; Bilitza, Dieter

    2017-07-01

    This issue of Advances in Space Research includes papers that report and discuss improvements of the International Reference Ionosphere (IRI). IRI is the international standard for the representation of the plasma in Earth's ionosphere and recognized as such by the Committee on Space Research (COSPAR), the International Union of Radio Science (URSI), the International Telecommunication Union (ITU), and the International Standardization Organization (ISO). As requested, particularly by COSPAR and URSI, IRI is an empirical model relying on most of the available and reliable ground and space observations of the ionosphere. As new data become available and as older data sources are fully exploited the IRI model undergoes improvement cycles to stay as close to the existing data record as possible. The latest episode of this process is documented in the papers included in this issue using data from the worldwide network of ionosondes, from a few of the incoherent scatter radars, from the Alouette and ISIS topside sounders, and from the Global Navigation Satellite Systems (GNSS). The focus of this issue is on the equatorial and low latitude region that is of special importance for ionospheric physics because it includes the largest densities and steep density gradients in the double hump latitudinal structure, the Equatorial Ionization Anomaly (EIA), which is characteristic for this region.

  8. Cosmic rays linked to rapid mid-latitude cloud changes

    Directory of Open Access Journals (Sweden)

    B. A. Laken

    2010-08-01

    Full Text Available The effect of the Galactic Cosmic Ray (GCR flux on Earth's climate is highly uncertain. Using a novel sampling approach based around observing periods of significant cloud changes, a statistically robust relationship is identified between the rate of GCR flux and the most rapid mid-latitude (60°–30° N/S cloud decreases operating over daily timescales; this signal is verified in surface level air temperature (SLAT reanalysis data. A General Circulation Model experiment is used to test the causal relationship of the observed cloud changes to the detected SLAT anomalies. Results indicate that the cloud anomalies were responsible for producing the observed SLAT changes, implying a link between significant decreases in the rate of GCR flux (~0.79%/day (relative to the peak-to-peak amplitude of 11-yr solar cycle, decreases in cloud cover (~1.9%/day and increases in SLAT (~0.05 K/day. The influence of GCRs is clearly distinguishable from changes in solar irradiance and the interplanetary magnetic field. These results provide the most compelling evidence presented thus far of a GCR-climate relationship. From this analysis we conclude: (i a GCR-climate relationship is governed by both the rate of GCR flux and internal precursor conditions; and (ii it is likely that this natural forcing has not contributed significantly to recent anthropogenic temperature rises.

  9. The single event upset environment for avionics at high latitude

    Energy Technology Data Exchange (ETDEWEB)

    Sims, A.J.; Dyer, C.S.; Peerless, C.L. (Defence Research Agency, Farnborough (United Kingdom). Space and Communications Dept.); Johansson, K.; Pettersson, H. (SAAB Military Aircraft, Linkoeping (Sweden)); Farren, J. (AEA Technology, Oxfordshire (United Kingdom). Harwell Lab.)

    1994-12-01

    Modern avionic systems for civil and military applications are becoming increasingly reliant upon embedded microprocessors and associated memory devices. The phenomenon of single event upset (SEU) is well known in space systems and designers have generally been careful to use SEU tolerant devices or to implement error detection and correction (EDAC) techniques where appropriate. In the past, avionics designers have had no reason to consider SEU effects but is clear that the more prevalent use of memory devices combined with increasing levels of IC integration will make SEU mitigation an important design consideration for future avionic systems. To this end, it is necessary to work towards producing models of the avionics SEU environment which will permit system designers to choose components and EDAC techniques which are based on predictions of SEU rates correct to much better than an order of magnitude. Measurements of the high latitude SEU environment at avionics altitude have been made on board a commercial airliner. Results are compared with models of primary and secondary cosmic rays and atmospheric neutrons. Ground based SEU tests of static RAMs are used to predict rates in flight.

  10. Birkeland current effects on high-latitude groundmagnetic field perturbations

    CERN Document Server

    Laundal, K M; Lehtinen, N; Gjerloev, J W; Østgaard, N; Tenfjord, P; Reistad, J P; Snekvik, K; Milan, S E; Ohtani, S; Anderson, B J

    2016-01-01

    Magnetic perturbations on ground at high latitudes are directly associated only with the divergence-free component of the height-integrated horizontal ionospheric current, $\\textbf{J}_{\\perp,df}$. Here we show how $\\textbf{J}_{\\perp,df}$ can be expressed as the total horizontal current $\\textbf{J}_\\perp$ minus its curl-free component, the latter being completely determined by the global Birkeland current pattern. Thus in regions where $\\textbf{J}_\\perp = 0$, the global Birkeland current distribution alone determines the local magnetic perturbation. We show with observations from ground and space that in the polar cap, the ground magnetic field perturbations tend to align with the Birkeland current contribution in darkness but not in sunlight. We also show that in sunlight, the magnetic perturbations are typically such that the equivalent overhead current is anti-parallel to the convection, indicating that the Hall current system dominates. Thus the ground magnetic field in the polar cap relates to different c...

  11. UBVR polarimetry of high-galactic latitude carbon stars

    Directory of Open Access Journals (Sweden)

    J. M. López

    2011-01-01

    Full Text Available Presentamos polarimetría y fotometría en las bandas UBVR, en el periodo de un año, de ocho estrellas de carbón de alta latitud galáctica: V Hya, CZ Hya, R For, R Lep, Y Cvn, T Dra, RV Aqr y RT Cap. La polarización observada alcanza su máximo valor en la banda U y es muy variable en el tiempo. Similarmente, la polarización en la banda B es muy variable pero sus valores son siempre inferiores a los obtenidos en la banda U. El origen y la variabilidad de la polarización en estas bandas puede explicarse como el resultado de la dispersión de la radiación de la estrella central en las regiones interiores de la envolvente circunestelar donde los granos de polvo y las moléculas son creados, destruidos y mezclados por ondas de choque.

  12. MBM 12: young protoplanetary discs at high galactic latitude

    CERN Document Server

    Meeus, G; Henning, T; Bouwman, J; Chen, C; Lawson, W; Apai, D; Pascucci, I; Sicilia-Aguilar, A

    2009-01-01

    (abridged) We present Spitzer infrared observations to constrain disc and dust evolution in young T Tauri stars in MBM 12, a star-forming cloud at high latitude with an age of 2 Myr and a distance of 275 pc. The region contains 12 T Tauri systems, with primary spectral types between K3 and M6; 5 are weak-line and the rest classical T Tauri stars. We first use MIPS and literature photometry to compile spectral energy distributions for each of the 12 members in MBM 12, and derive their IR excesses. The IRS spectra are analysed with the newly developed two-layer temperature distribution (TLTD) spectral decomposition method. For the 7 T Tauri stars with a detected IR excess, we analyse their solid-state features to derive dust properties such as mass-averaged grain size, composition and crystallinity. We find a spatial gradient in the forsterite to enstatite range, with more enstatite present in the warmer regions. The fact that we see a radial dependence of the dust properties indicates that radial mixing is not...

  13. Molecular cores of the high-latitude cloud MBM 40

    Science.gov (United States)

    Chol Minh, Y. C. Young; Kim, Hyun-Goo; Lee, Youngung; Park, Hyeran; Kim, Kwang-Tae; Park, Yong-Sun; Joon Kim, Sang

    2003-11-01

    Towards the high-latitude cloud MBM 40, we identify 3 dense molecular cores of M˜0.2-0.5 M ⊙, and sizes of ˜0.2 pc in diameter embedded in the H I cloud of ˜8 M ⊙ which is observed to be extended along the northeast-southwest direction. The molecular cloud is located almost perpendicularly to the H I emission. We confirm the previous result of Magnani et al. that MBM 40 is not a site for new star formations. We found a very poor correlation between the H I and the IRAS 100 μm emissions, but the CO (1-0) and 100 μm emissions show a better correlation of WCO/ I100=1±0.2 K km s -1 (MJy sr -1) -1. This ratio is larger by a factor of ≥5 than in dense dark clouds, which may indicate that the CO is less depleted in MBM 40 than in dense dark clouds.

  14. Peatmoss (Sphagnum) diversification associated with Miocene Northern Hemisphere climatic cooling?

    Science.gov (United States)

    Shaw, A Jonathan; Devos, Nicolas; Cox, Cymon J; Boles, Sandra B; Shaw, Blanka; Buchanan, Alex M; Cave, Lynette; Seppelt, Rodney

    2010-06-01

    Global climate changes sometimes spark biological radiations that can feed back to effect significant ecological impacts. Northern Hemisphere peatlands dominated by living and dead peatmosses (Sphagnum) harbor almost 30% of the global soil carbon pool and have functioned as a net carbon sink throughout the Holocene, and probably since the late Tertiary. Before that time, northern latitudes were dominated by tropical and temperate plant groups and ecosystems. Phylogenetic analyses of mosses (phylum Bryophyta) based on nucleotide sequences from the plastid, mitochondrial, and nuclear genomes indicate that most species of Sphagnum are of recent origin (ca. <20 Ma). Sphagnum species are not only well-adapted to boreal peatlands, they create the conditions that promote development of peatlands. The recent radiation that gave rise to extant diversity of peatmosses is temporally associated with Miocene climatic cooling in the Northern Hemisphere. The evolution of Sphagnum has had profound influences on global biogeochemistry because of the unique biochemical, physiological, and morphological features of these plants, both while alive and after death.

  15. Seismicity in Northern Germany

    Science.gov (United States)

    Bischoff, Monika; Gestermann, Nicolai; Plenefisch, Thomas; Bönnemann, Christian

    2013-04-01

    Northern Germany is a region of low tectonic activity, where only few and low-magnitude earthquakes occur. The driving tectonic processes are not well-understood up to now. In addition, seismic events during the last decade concentrated at the borders of the natural gas fields. The source depths of these events are shallow and in the depth range of the gas reservoirs. Based on these observations a causal relationship between seismicity near gas fields and the gas production is likely. The strongest of these earthquake had a magnitude of 4.5 and occurred near Rotenburg in 2004. Also smaller seismic events were considerably felt by the public and stimulated the discussion on the underlying processes. The latest seismic event occurred near Langwedel on 22nd November 2012 and had a magnitude of 2.8. Understanding the causes of the seismicity in Northern Germany is crucial for a thorough evaluation. Therefore the Seismological Service of Lower Saxony (NED) was established at the State Office for Mining, Energy and Geology (LBEG) of Lower Saxony in January 2013. Its main task is the monitoring and evaluation of the seismicity in Lower Saxony and adjacent areas. Scientific and technical questions are addressed in close cooperation with the Seismological Central Observatory (SZO) at the Federal Institute for Geosciences and Natural Resources (BGR). The seismological situation of Northern Germany will be presented. Possible causes of seismicity are introduced. Rare seismic events at greater depths are distributed over the whole region and probably are purely tectonic whereas events in the vicinity of natural gas fields are probably related to gas production. Improving the detection threshold of seismic events in Northern Germany is necessary for providing a better statistical basis for further analyses answering these questions. As a first step the existing seismic network will be densified over the next few years. The first borehole station was installed near Rethem by BGR

  16. Comparison of Mid-latitude Cyclones in Sea Level Pressure, Gepotential Height and Vorticity Fields

    Science.gov (United States)

    Raible, Christoph C.; Blender, Richard; Fraedrich, Klaus

    2013-04-01

    The mid-latitudes are dominated by diurnal variability, which is related to traveling high- and low-pressure systems. The lows or cyclones are a major source of natural hazards. This has led to growing interest in the scientific community to develop Eulerian and Lagrangian measures and to analyze the atmospheric high-frequency variability. One important issue is that there is no straight forward definition of cyclones resulting in a large variety of so-called cyclone detection and tracking methods. Each of these methods relies on different input fields which are related to specific features of a cyclone, e.g., sea level pressure (SLP), which specifically focuses on the mass aspect of the velocity field. Recently, the available methods have been compared with respect to climatology and life cycles using the ERA interim data set (Neu et al. 2013). Based on this study we investigate different fields as input for one specific method. We focus on the three mostly used input data, sea level pressure (SLP), 1000-hPa gepotential height (Z1000) and 850-hPa vorticity (850VOR). The cyclone detection and tracking method developed by Blender et al. (1997) is used and we apply it to ERA interim data in the 1.5 x 1.5 resolution. The method was mainly applied for Z1000 and the Northern Hemisphere (e.g., Blender et al. 1997; Raible et al. 2008). To compare the tracks and cyclone characteristics obtained from the different input data we need to adapt critical parameters of the method in such a way that comparable numbers of cyclone centers are identified in either field. The target is set to the number of cyclone centers in northern hemispheric winter. This enables us to assess the seasonal and hemispheric dependence. Preliminary results show that the agreement between cyclones based on SLP and Z1000 varies between roughly 70 to 80% depending on the season and the hemisphere. Spatially, most of the differences are found around orographic features like Greenland. An interesting

  17. Early Tertiary marine fossils from northern Alaska: implications for Arctic Ocean paleogeography and faunal evolution.

    Science.gov (United States)

    Marincovich, L.; Brouwers, E.M.; Carter, L.D.

    1985-01-01

    Marine mollusks and ostracodes indicate a post-Danian Paleocene to early Eocene (Thanetian to Ypresian) age for a fauna from the Prince Creek Formation at Ocean Point, northern Alaska, that also contains genera characteristic of the Cretaceous and Neogene-Quaternary. The life-assocation of heterochronous taxa at Ocean Point resulted from an unusual paleogeographic setting, the nearly complete isolation of the Arctic Ocean from about the end of the Cretaceous until sometime in the Eocene, in which relict Cretaceous taxa survived into Tertiary time while endemic taxa evolved in situ; these later migrated to the northern mid- latitudes. Paleobiogeographic affinities of the Ocean Point assocation with mild temperate faunas of the London Basin (England), Denmark, and northern Germany indicate that a shallow, intermittent Paleocene seaway extended through the Norwegian-Greenland Sea to the North Sea Basin. Early Tertiary Arctic Ocean paleogeography deduced from faunal evidence agrees with that inferred from plate-tectonic reconstructions.-Authors

  18. The missing Northern European winter cooling response to Arctic sea ice loss

    Science.gov (United States)

    Screen, James A.

    2017-03-01

    Reductions in Arctic sea ice may promote the negative phase of the North Atlantic Oscillation (NAO-). It has been argued that NAO-related variability can be used an as analogue to predict the effects of Arctic sea ice loss on mid-latitude weather. As NAO- events are associated with colder winters over Northern Europe, a negatively shifted NAO has been proposed as a dynamical pathway for Arctic sea ice loss to cause Northern European cooling. This study uses large-ensemble atmospheric simulations with prescribed ocean surface conditions to examine how seasonal-scale NAO- events are affected by Arctic sea ice loss. Despite an intensification of NAO- events, reflected by more prevalent easterly flow, sea ice loss does not lead to Northern European winter cooling and daily cold extremes actually decrease. The dynamical cooling from the changed NAO is `missing', because it is offset (or exceeded) by a thermodynamical effect owing to advection of warmer air masses.

  19. Arctic climate and its interaction with lower latitudes under different levels of anthropogenic warming in a global coupled climate model

    Science.gov (United States)

    Koenigk, Torben; Brodeau, Laurent

    2017-07-01

    Three quasi-equilibrium simulations using constant greenhouse gas forcing corresponding to years 2000, 2015 and 2030 have been performed with the global coupled model EC-Earth in order to analyze the Arctic climate and interactions with lower latitudes under different levels of anthropogenic warming. The model simulations indicate an accelerated warming and ice extent reduction in the Arctic between the year-2030 and year-2015 simulations compared to the change between the year-2015 and year-2000 simulations. Both Arctic warming and sea ice reduction are closely linked to the increase of ocean heat transport into the Arctic, particularly through the Barents Sea Opening. Decadal variations of Arctic sea ice extent and ice volume are of the same order of magnitude as the observed ice extent reductions in the last 30 years and are dominated by the variability of the ocean heat transports through the Barents Sea Opening and the Bering Strait. Despite a general warming of mid and high northern latitudes, a substantial cooling is found in the subpolar gyre of the North Atlantic under year-2015 and year-2030 conditions. This cooling is related to a strong reduction in the AMOC, itself due to reduced deep water formation in the Labrador Sea. The observed trend towards a more negative phase of the North Atlantic Oscillation (NAO) and the observed linkage between autumn Arctic ice variations and NAO are reproduced in our model simulations for selected 30-year periods but are not robust over longer time periods. This indicates that the observed linkages between ice and NAO might not be robust in reality either, and that the observational time period is still too short to reliably separate the trend from the natural variability.

  20. Divergent El Niño responses to volcanic eruptions at different latitudes over the past millennium

    Science.gov (United States)

    Liu, Fei; Li, Jinbao; Wang, Bin; Liu, Jian; Li, Tim; Huang, Gang; Wang, Zhiyuan

    2017-08-01

    Detection and attribution of El Niño-Southern Oscillation (ENSO) responses to radiative forcing perturbation are critical for predicting the future change of ENSO under global warming. One of such forcing perturbation is the volcanic eruption. Our understanding of the responses of ENSO system to explosive tropical volcanic eruptions remains controversial, and we know little about the responses to high-latitude eruptions. Here, we synthesize proxy-based ENSO reconstructions, to show that there exist an El Niño-like response to the Northern Hemisphere (NH) and tropical eruptions and a La Niña-like response to the Southern Hemisphere (SH) eruptions over the past millennium. Our climate model simulation results show good agreement with the proxy records. The simulation reveals that due to different meridional thermal contrasts, the westerly wind anomalies can be excited over the tropical Pacific to the south of, at, or to the north of the equator in the first boreal winter after the NH, tropical, or SH eruptions, respectively. Thus, the eastern-Pacific El Niño can develop and peak in the second winter after the NH and tropical eruptions via the Bjerknes feedback. The model simulation only shows a central-Pacific El Niño-like response to the SH eruptions. The reason is that the anticyclonic wind anomaly associated with the SH eruption-induced southeast Pacific cooling will excite westward current anomalies and prevent the development of eastern-Pacific El Niño-like anomaly. These divergent responses to eruptions at different latitudes and in different hemispheres underline the sensitivity of the ENSO system to the spatial structure of radiative disturbances in the atmosphere.

  1. Performance evaluation of linear time-series ionospheric Total Electron Content model over low latitude Indian GPS stations

    Science.gov (United States)

    Dabbakuti, J. R. K. Kumar; Venkata Ratnam, D.

    2017-10-01

    Precise modeling of the ionospheric Total Electron Content (TEC) is a critical aspect of Positioning, Navigation, and Timing (PNT) services intended for the Global Navigation Satellite Systems (GNSS) applications as well as Earth Observation System (EOS), satellite communication, and space weather forecasting applications. In this paper, linear time series modeling has been carried out on ionospheric TEC at two different locations at Koneru Lakshmaiah University (KLU), Guntur (geographic 16.44° N, 80.62° E; geomagnetic 7.55° N) and Bangalore (geographic 12.97° N, 77.59° E; geomagnetic 4.53° N) at the northern low-latitude region, for the year 2013 in the 24th solar cycle. The impact of the solar and geomagnetic activity on periodic oscillations of TEC has been investigated. Results confirm that the correlation coefficient of the estimated TEC from the linear model TEC and the observed GPS-TEC is around 93%. Solar activity is the key component that influences ionospheric daily averaged TEC while periodic component reveals the seasonal dependency of TEC. Furthermore, it is observed that the influence of geomagnetic activity component on TEC is different at both the latitudes. The accuracy of the model has been assessed by comparing the International Reference Ionosphere (IRI) 2012 model TEC and TEC measurements. Moreover, the absence of winter anomaly is remarkable, as determined by the Root Mean Square Error (RMSE) between the linear model TEC and GPS-TEC. On the contrary, the IRI2012 model TEC evidently failed to predict the absence of winter anomaly in the Equatorial Ionization Anomaly (EIA) crest region. The outcome of this work will be useful for improving the ionospheric now-casting models under various geophysical conditions.

  2. Arctic climate and its interaction with lower latitudes under different levels of anthropogenic warming in a global coupled climate model

    Science.gov (United States)

    Koenigk, Torben; Brodeau, Laurent

    2016-09-01

    Three quasi-equilibrium simulations using constant greenhouse gas forcing corresponding to years 2000, 2015 and 2030 have been performed with the global coupled model EC-Earth in order to analyze the Arctic climate and interactions with lower latitudes under different levels of anthropogenic warming. The model simulations indicate an accelerated warming and ice extent reduction in the Arctic between the year-2030 and year-2015 simulations compared to the change between the year-2015 and year-2000 simulations. Both Arctic warming and sea ice reduction are closely linked to the increase of ocean heat transport into the Arctic, particularly through the Barents Sea Opening. Decadal variations of Arctic sea ice extent and ice volume are of the same order of magnitude as the observed ice extent reductions in the last 30 years and are dominated by the variability of the ocean heat transports through the Barents Sea Opening and the Bering Strait. Despite a general warming of mid and high northern latitudes, a substantial cooling is found in the subpolar gyre of the North Atlantic under year-2015 and year-2030 conditions. This cooling is related to a strong reduction in the AMOC, itself due to reduced deep water formation in the Labrador Sea. The observed trend towards a more negative phase of the North Atlantic Oscillation (NAO) and the observed linkage between autumn Arctic ice variations and NAO are reproduced in our model simulations for selected 30-year periods but are not robust over longer time periods. This indicates that the observed linkages between ice and NAO might not be robust in reality either, and that the observational time period is still too short to reliably separate the trend from the natural variability.

  3. Stability of the unlinked Latitude total elbow prosthesis: A biomechanical in vitro analysis

    NARCIS (Netherlands)

    Wagener, Marc L.; Vos, de Maarten J.; Hendriks, Jan C.M.; Eygendaal, Denise; Verdonschot, Nico

    2013-01-01

    Background The purpose of this study is to assess the valgus and varus laxity of the unlinked version of the Latitude total elbow prosthesis and the effects of radial head preservation or replacement. Methods Biomechanical analysis of the valgus and varus laxity of the unlinked Latitude was perform

  4. Stability of the unlinked Latitude total elbow prosthesis: A biomechanical in vitro analysis.

    NARCIS (Netherlands)

    Wagener, M.L.; Vos, M.J. de; Hendriks, J.C.M.; Eygendaal, D.; Verdonschot, N.J.J.

    2013-01-01

    BACKGROUND: The purpose of this study is to assess the valgus and varus laxity of the unlinked version of the Latitude total elbow prosthesis and the effects of radial head preservation or replacement. METHODS: Biomechanical analysis of the valgus and varus laxity of the unlinked Latitude was perfor

  5. Circadian Rhythms of Locomotor Activity in Captive Birds and Mammals : Their Variations with Season and Latitude

    NARCIS (Netherlands)

    Daan, Serge; Aschoff, Jürgen

    1975-01-01

    1. The seasonal variations in time of daily onset and end of locomotor activity are described for 3 species of mammals and 5 species of birds kept in captivity at the arctic circle and at lower latitude. These variations are most pronounced at high latitude. 2. The duration of daily activity plotted

  6. Abrupt climate change and high to low latitude teleconnections as simulated in climate models

    DEFF Research Database (Denmark)

    Cvijanovic, Ivana

    High to low latitude atmospheric teleconnections have been a topic of increasing scientific interest since it was shown that high latitude extratropical forcing can induce tropical precipitation shifts through atmosphere-surface ocean interactions. In this thesis, several aspects of high to low l...

  7. Schizophrenia and vitamin D related genes could have been subject to latitude-driven adaptation

    Directory of Open Access Journals (Sweden)

    Monticelli Antonella

    2010-11-01

    Full Text Available Abstract Background Many natural phenomena are directly or indirectly related to latitude. Living at different latitudes, indeed, has its consequences with being exposed to different climates, diets, light/dark cycles, etc. In humans, one of the best known examples of genetic traits following a latitudinal gradient is skin pigmentation. Nevertheless, also several diseases show latitudinal clinals such as hypertension, cancer, dismetabolic conditions, schizophrenia, Parkinson's disease and many more. Results We investigated, for the first time on a wide genomic scale, the latitude-driven adaptation phenomena. In particular, we selected a set of genes showing signs of latitude-dependent population differentiation. The biological characterization of these genes showed enrichment for neural-related processes. In light of this, we investigated whether genes associated to neuropsychiatric diseases were enriched by Latitude-Related Genes (LRGs. We found a strong enrichment of LRGs in the set of genes associated to schizophrenia. In an attempt to try to explain this possible link between latitude and schizophrenia, we investigated their associations with vitamin D. We found in a set of vitamin D related genes a significant enrichment of both LRGs and of genes involved in schizophrenia. Conclusions Our results suggest a latitude-driven adaptation for both schizophrenia and vitamin D related genes. In addition we confirm, at a molecular level, the link between schizophrenia and vitamin D. Finally, we discuss a model in which schizophrenia is, at least partly, a maladaptive by-product of latitude dependent adaptive changes in vitamin D metabolism.

  8. Investigation of High-Latitude Phenomena Using Polar Data and Global Simulations

    Science.gov (United States)

    Russell, Christopher T.; Hoffman, Robert (Technical Monitor)

    2001-01-01

    The goal of this one-year project was to use data from the Polar satellite in conjunction with global simulations of Earth's magnetosphere to investigate phenomena in the high-latitude magnetosphere. Specifically, we addressed reconnection at the cusp during periods of northward interplanetary magnetic field (IMF), and the effects of substorms on the high-latitude magnetosphere.

  9. Northern Pintail Telemetry [ds231

    Data.gov (United States)

    California Department of Resources — Using radio-telemetry, female northern pintail (Anas acuta) survival, distribution, and movements during late August-March in Central California were determined...

  10. On the cause of IMF By related mid- and low latitude magnetic disturbances

    DEFF Research Database (Denmark)

    Vennerstrøm, Susanne; Christiansen, Freddy; Olsen, Nils

    2007-01-01

    An analysis of the effect of the IMF By on near-Earth low and mid-latitude magnetic disturbances is presented. In particular the contribution from field-aligned currents ( FACs) connected to the polar regions is investigated. Based on statistically determined high-latitude FAC patterns for various...... Interplanetary Magnetic Field ( IMF) directions, we estimate the FAC contribution to the mid-and low latitude magnetic disturbance and its dependence on the IMF. The estimated perturbations are compared with observations from the ground and from the low-altitude polar orbiting satellite Oersted. It is found...... that the long-distance effect of the high-latitude FACs constitute the major source to IMF By and B-z related magnetic east-west disturbances at mid-and low latitudes....

  11. Regional responses of surface ozone in Europe to the location of high-latitude blocks and subtropical ridges

    Science.gov (United States)

    Ordóñez, Carlos; Barriopedro, David; García-Herrera, Ricardo; Sousa, Pedro M.; Schnell, Jordan L.

    2017-02-01

    This paper analyses for the first time the impact of high-latitude blocks and subtropical ridges on near-surface ozone (O3) in Europe during a 15-year period. For this purpose, a catalogue of blocks and ridges over the Euro-Atlantic region is used together with a gridded dataset of maximum daily 8 h running average ozone (MDA8 O3) covering the period 1998-2012. The response of ozone to the location of blocks and ridges with centres in three longitudinal sectors (Atlantic, ATL, 30-0° W; European, EUR, 0-30° E; Russian, RUS, 30-60° E) is examined. The impact of blocks on ozone is regionally and seasonally dependent. In particular, blocks within the EUR sector yield positive ozone anomalies of ˜ 5-10 ppb over large parts of central Europe in spring and northern Europe in summer. Over 20 and 30 % of the days with blocks in that sector register exceedances of the 90th percentile of the seasonal ozone distribution at many European locations during spring and summer, respectively. The impacts of ridges during those seasons are subtle and more sensitive to their specific location, although they can trigger ozone anomalies above 10 ppb in northern Italy and the surrounding countries in summer, eventually exceeding European air quality (AQ) targets. During winter, surface ozone in the north-west of Europe presents completely opposite responses to blocks and ridges. The anticyclonic circulation associated with winter EUR blocking, and to a lesser extent with ATL blocking, yields negative ozone anomalies between -5 and -10 ppb over the UK, northern France and the Benelux. Conversely, the enhanced zonal flow around 50-60° N during the occurrence of ATL ridges favours the arrival of background air masses from the Atlantic and the ventilation of the boundary layer, producing positive ozone anomalies of ˜ 5 ppb in an area spanning from the British Isles to the northern half of Germany. We also show that multiple linear models on the seasonal frequency of occurrence of these

  12. Magnetospheric period oscillations at Saturn: Comparison of equatorial and high-latitude magnetic field periods with north and south Saturn kilometric radiation periods

    Science.gov (United States)

    Andrews, D. J.; Coates, A. J.; Cowley, S. W. H.; Dougherty, M. K.; Lamy, L.; Provan, G.; Zarka, P.

    2010-12-01

    It has recently been shown using Cassini radio data that Saturn kilometric radiation (SKR) emissions from the Northern and Southern hemispheres of Saturn are modulated at distinctly different periods, ˜10.6 h in the north and ˜10.8 h in the south, during the southern summer conditions that prevailed during the interval from 2004 to near-equinox in mid-2009. Here we examine Cassini magnetospheric magnetic field data over the same interval and show that two corresponding systems of magnetic field oscillations that have the same overall periods, as the corresponding SKR modulations, to within ˜0.01% are also present. Specifically, we show that the rotating quasi-dipolar field perturbations on southern open field lines and the rotating quasi-uniform field in the inner region of closed field lines have the same period as the southern SKR modulations, although with some intervals of slow long-term phase drift of unknown origin, while the rotating quasi-dipolar field perturbations on northern open field lines have the same period as the northern SKR modulations. We also show that while the equatorial quasi-uniform field and effective southern transverse dipole are directed down tail and toward dawn at southern SKR maxima, as found in previous studies, the corresponding northern transverse dipole is directed approximately opposite, pointing sunward and also slightly toward dawn at northern SKR maxima. We discuss these findings in terms of the presence of two independent high-latitude field-aligned current systems that rotate with different periods in the two hemispheres.

  13. Tertiary tectonics of the Patagonian Andes retro-arc area between 38°15' and 40°S latitude

    Science.gov (United States)

    Morabito, Ezequiel García; Götze, Hans-Jürgen; Ramos, Víctor A.

    2011-03-01

    these latitudes, between 11 and 5.67 Ma for the northern segment, between 10 and 6.2 Ma for the central segment and between 13 to 8 and 4.3 Ma for the southern segment. After this short-lived compressional stage, deformation migrated to the west associated with the onset of the Liquiñe-Ofqui strike-slip fault zone along the intra-arc zone.

  14. Mid-latitude mesospheric clouds and their environment from SOFIE observations

    Science.gov (United States)

    Hervig, Mark E.; Gerding, Michael; Stevens, Michael H.; Stockwell, Robert; Bailey, Scott M.; Russell, James M.; Stober, Gunter

    2016-11-01

    Observations from the Solar Occultation For Ice Experiment (SOFIE) on the Aeronomy of Ice in the Mesosphere (AIM) satellite are used to examine noctilucent clouds (NLC) and their environment at middle latitudes ( 56°N and 52°S). Because SOFIE is uniquely capable of measuring NLC, water vapor, and temperature simultaneously, the local cloud environment can be specified to examine what controls their formation at mid-latitudes. Compared to higher latitudes, mid-latitude NLCs are less frequent and have lower ice mass density, by roughly a factor of five. Compared to higher latitudes at NLC heights, mid-latitude water vapor is only 12% lower while temperatures are more than 10 K higher. As a result the reduced NLC mass and frequency at mid-latitudes can be attributed primarily to temperature. Middle and high latitude NLCs contain a similar amount of meteoric smoke, which was not anticipated because smoke abundance increases towards the equator in summer. SOFIE indicates that mid-latitude NLCs may or may not be associated with supersaturation with respect to ice. It is speculated that this situation is due in part to SOFIE uncertainties related to the limb measurement geometry combined with the non-uniform nature of NLCs. SOFIE is compared with concurrent NLC, temperature, and wind observations from Kühlungsborn, Germany (54°N) during the 2015 summer. The results indicate good agreement in temperature and NLC occurrence frequency, backscatter, and height. SOFIE indicates that NLCs were less frequent over Europe during 2015 compared to other longitudes, in contrast to previous years at higher latitudes that showed no clear longitude dependence. Comparisons of SOFIE and the Solar Backscatter Ultraviolet (SBUV) indicate good agreement in average ice water column (IWC), although differences in occurrence frequency were often large.

  15. Ionosphere-Thermosphere Coupling in Jupiter's Low Latitudes

    Science.gov (United States)

    Stallard, T.; Melin, H.; Johnson, R.; O'Donoghue, J.; Moore, L.; Miller, S.; Tao, C.; Achilleos, N. A.; Smith, C.; Ray, L. C.; Yates, J. N.

    2015-12-01

    One of the leading problems in our understanding of Jupiter's atmosphere, known colloquially as the 'energy crisis', is that the upper atmosphere has global temperatures far in excess of that predicted by solar heating. Unlike the Earth, solar heating has only a small effect on the thermosphere, varying little in temperature with local time, and with equatorial neutrals co-rotating with the planet due to meridional advection. Within the auroral region, ionosphere-thermosphere coupling produces strong flows and results in huge Joule Heating from auroral currents. In this region, the temperature excess can be explained, but Jupiter's fast rotation means that Coriolis forces prevent energy in the poles from transferring equatorward, so there remains no explanation of why low latitudes are overheated by a factor of 3-5 over that predicted by solar heating alone.Despite this anomaly, although the past twenty years has seen a wealth of new data and results in Jupiter's auroral region, studies of the equatorial region have been somewhat limited. This lack of investigation comes partly from the apparent uniform nature of the equatorial region, and partly from the difficulty in observing this region. It is only in the past three years that observers begun to re-examine this region, revealing evidence of complex interactions between the thermosphere and ionosphere, including what appears to be thermospheric weather patterns at a fixed planetary longitudes, stable over two decades; perhaps caused by continuous flows from the auroral region. Here, we introduce our recent research, in order to compare and contrast what has been observed at Jupiter with the more well understood interactions between Earth's ionosphere and thermosphere. We hope that this will open a discussion between the communities that will improve our understanding of the underlying physical processes, as they occur at both planets.

  16. 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.

  17. Two dimensional hydrodynamic modeling of a high latitude braided river

    Science.gov (United States)

    Humphries, E.; Pavelsky, T.; Bates, P. D.

    2014-12-01

    Rivers are a fundamental resource to physical, ecologic and human systems, yet quantification of river flow in high-latitude environments remains limited due to the prevalence of complex morphologies, remote locations and sparse in situ monitoring equipment. Advances in hydrodynamic modeling and remote sensing technology allow us to address questions such as: How well can two-dimensional models simulate a flood wave in a highly 3-dimensional braided river environment, and how does the structure of such a flood wave differ from flow down a similar-sized single-channel river? Here, we use the raster-based hydrodynamic model LISFLOOD-FP to simulate flood waves, discharge, water surface height, and velocity measurements over a ~70 km reach of the Tanana River in Alaska. In order to use LISFLOOD-FP a digital elevation model (DEM) fused with detailed bathymetric data is required. During summer 2013, we surveyed 220,000 bathymetric points along the study reach using an echo sounder system connected to a high-precision GPS unit. The measurements are interpolated to a smooth bathymetric surface, using Topo to Raster interpolation, and combined with an existing five meter DEM (Alaska IfSAR) to create a seamless river terrain model. Flood waves are simulated using varying complexities in model solvers, then compared to gauge records and water logger data to assess major sources of model uncertainty. Velocity and flow direction maps are also assessed and quantified for detailed analysis of braided channel flow. The most accurate model output occurs with using the full two-dimensional model structure, and major inaccuracies appear to be related to DEM quality and roughness values. Future work will intercompare model outputs with extensive ground measurements and new data from AirSWOT, an airborne analog for the Surface Water and Ocean Topography (SWOT) mission, which aims to provide high-resolution measurements of terrestrial and ocean water surface elevations globally.

  18. Impact of interactive radiation on idealized mid-latitude storms

    Science.gov (United States)

    Schäfer, Sophia; Voigt, Aiko

    2017-04-01

    The evolution of mid-latitude storms is controlled by the interacting impacts of large-scale advection, vertical motion and diabatic processes. It is widely accepted that understanding and accurately representing the diabatic impact of latent heating is crucial for capturing storm dynamics and their response to climate change. By contrast, little, if any, work has been done to study how radiative heating might impact storms. Here, we address this question by comparing idealized baroclinic lifecycles in the state-of-the-art global atmosphere model ICON in full spherical geometry when radiation is included and when radiative effects are neglected. Following previous work, the level of initial moisture is varied to study possible interactions between latent and radiative impacts. We find that in contrast to latent heating, radiation slows the evolution of the storm and leads to an overall weaker storm. Specifically, including radiation leads to a 10 hPa higher storm central pressure and a 30% to 50% weaker domain-averaged eddy-kinetic energy. The overall weakening impact of radiation is independent of the initial moisture content. However, there is some indication that radiation changes the qualitative evolution of the storm when initial moisture is high. For example, with radiation the low-level eddy-kinetic energy and the storm central pressure are non-monotonic functions in time and show a double peak at day 5 and day 7. This does not occur when radiation is neglected, or when the initial moisture is set to zero. Further simulations will be presented to disentangle the radiative impact of clouds, and to investigate the impact of low-level vs. high-level clouds. Moreover, an analysis of the surface pressure tendency equation will be applied to analyze and compare the impact of adiabatic processes, latent heating and radiative heating. Overall, our results show that radiation, while so far neglected, can play a first-order role for the evolution of individual storms.

  19. Under-Ice Operations with AUVS in High Latitudes

    Science.gov (United States)

    Ferguson, J.; Kaminski, C. D.

    2012-12-01

    In 2010 and 2011, ISE Explorer Autonomous Underwater Vehicles (AUV), built for Natural Resources Canada (NRCan), were deployed to Canada's high Arctic. The mission was to undertake under-ice bathymetric surveys supporting Canada's submission under the United Nations Convention on the Law of the Sea (UNCLOS). During these deployments several under-ice records were broken and several new technologies were demonstrated. The NRCan AUV is a 5000 meter depth rated vehicle, with several innovative additions to make it suitable for arctic survey work. Most notable are a depth rated variable ballast system, a 1300 Hz long-range homing system, and under-ice charging and data transfer capabilities. The Explorer's range was extended to approximately 450 km by adding a hull section to accommodate extra batteries. The scientific payload onboard included a Seabird SBE49 Conductivity-Temperature-Depth (CTD) sensor, Knudsen singlebeam echosounder, and a Kongsberg Simrad EM2000 multibeam echosounder. In 2010, operations were conducted from an ice camp near Borden Island (78°14'N, 112°39'W) operating through an ice hole. Following several test missions, the AUV spent 10 days surveying under ice before being successfully recovered. In total, close to 1100 km of under-ice survey was undertaken at depths to 3160 meters. A further set of operations was carried out in August and September 2011 from the Canadian Icebreaker CCGS Louis St. Laurent operating with the American Icebreaker USCGS Healy. Here the operations were much further north to latitudes of 88°30' N and to depths of 3500 meters. In this paper, the 2010 ice camp and the 2011 icebreaker missions are described, with an outline of technology developments that were undertaken, the preparations that were necessary for the success of the missions and finally, the outcome of the missions themselves.

  20. Kinematics and chemistry of faint high latitude dwarf carbon stars

    Science.gov (United States)

    Yoon, Jinmi; Beers, Timothy C.; Dietz, Sarah; Lee, Young Sun; Placco, Vinicius M.

    2017-01-01

    The diffuse halo system of the Milky Way is complex, and has been shown to comprise at least two main components: a near-zero net rotation inner-halo and a more rapidly rotating outer-halo component. Studies of the ancient, very metal-poor stars in the Galactic halo system are crucial for understanding its early formation history. The so-called carbon-enhanced metal-poor (CEMP) stars are an important subset of the stars in the halo system, which exhibit distinctive kinematic and chemical signatures that can be used to constrain the star-formation histories and assembly of the various Galactic components.We have examined the sample of main-sequence dwarf and other faint high Galactic latitude carbon-enhanced stars from the Sloan Digital Sky Survey studied by Green (2013). As noted by Green, many of these starsexhibit high proper motions, which have been later claimed to be related to possible binary ejection models Plant et al. (2016). By use of the CEMP sub-classification approach of Yoon et al. (2016), we investigate whether the kinematics of these stars might instead result from their membership in the inner/outer halo populations of the Galaxy.ReferencesGreen, P. 2013, ApJ, 765, 12Plant, K. et al. 2016, AAS 227.34115Yoon, J. et al. 2016, ApJ, in pressAcknowledgementThis work was supported in part by the National Science Foundation under Grant No. PHY-1430152 (JINA Center for the Evolution of the Elements).

  1. Thermospheric zonal temperature gradients observed at low latitudes

    Directory of Open Access Journals (Sweden)

    P. R. Fagundes

    Full Text Available Fabry-Perot interferometer (FPI measurements of thermospheric temperatures from the Doppler widths of the OI 630 nm nightglow emission line have been carried out at Cachoeira Paulista (23° S, 45° W, 16° S dip latitude, Brazil. The east-west components of the thermospheric temperatures obtained on 73 nights during the period from 1988 to 1992, primarily under quiet geomagnetic conditions, were analyzed and are presented in this paper. It was observed that on 67% of these nights, the temperatures in both the east and west sectors presented similar values and nocturnal variations. However, during 33% of the nights, the observed temperatures in the west sector were usually higher than those observed in the east sector, with zonal temperature gradients in the range of 100 K to 600 K, over about an 800 km horizontal distance. Also, in some cases, the observed temperatures in the east and west sectors show different nocturnal variations. One of the possible sources considered for the observed zonal temperature gradients is the influence of gravity wave dissipation effects due to waves that propagate from lower altitudes to thermospheric heights. The observed zonal temperature gradients could also be produced by orographic gravity waves originated away, over the Andes Cordillera in the Pacific Sector, or by dissipation of orographic gravity waves generated over the Mantiqueira Mountains in the Atlantic sector by tropospheric disturbances (fronts and/or subtropical jet streams.

    Key words. Atmospheric composition and structure (air-glow and aurora; thermosphere - composition and chemistry Ionosphere (equatorial ionosphere

  2. Sponge bioerosion accelerated by ocean acidification across species and latitudes?

    Science.gov (United States)

    Wisshak, M.; Schönberg, C. H. L.; Form, A.; Freiwald, A.

    2014-06-01

    In many marine biogeographic realms, bioeroding sponges dominate the internal bioerosion of calcareous substrates such as mollusc beds and coral reef framework. They biochemically dissolve part of the carbonate and liberate so-called sponge chips, a process that is expected to be facilitated and accelerated in a more acidic environment inherent to the present global change. The bioerosion capacity of the demosponge Cliona celata Grant, 1826 in subfossil oyster shells was assessed via alkalinity anomaly technique based on 4 days of experimental exposure to three different levels of carbon dioxide partial pressure ( pCO2) at ambient temperature in the cold-temperate waters of Helgoland Island, North Sea. The rate of chemical bioerosion at present-day pCO2 was quantified with 0.08-0.1 kg m-2 year-1. Chemical bioerosion was positively correlated with increasing pCO2, with rates more than doubling at carbon dioxide levels predicted for the end of the twenty-first century, clearly confirming that C. celata bioerosion can be expected to be enhanced with progressing ocean acidification (OA). Together with previously published experimental evidence, the present results suggest that OA accelerates sponge bioerosion (1) across latitudes and biogeographic areas, (2) independent of sponge growth form, and (3) for species with or without photosymbionts alike. A general increase in sponge bioerosion with advancing OA can be expected to have a significant impact on global carbonate (re)cycling and may result in widespread negative effects, e.g. on the stability of wild and farmed shellfish populations, as well as calcareous framework builders in tropical and cold-water coral reef ecosystems.

  3. DHIGLS: DRAO H i Intermediate Galactic Latitude Survey

    Science.gov (United States)

    Blagrave, K.; Martin, P. G.; Joncas, G.; Kothes, R.; Stil, J. M.; Miville-Deschênes, M. A.; Lockman, Felix J.; Taylor, A. R.

    2017-01-01

    Observations of Galactic H i gas for seven targeted regions at intermediate Galactic latitude are presented at 1\\prime angular resolution using data from the DRAO Synthesis Telescope (ST) and the Green Bank Telescope (GBT). The DHIGLS data are the most extensive arcminute-resolution measurements of the diffuse atomic interstellar medium beyond those in the Galactic plane. The acquisition, reduction, calibration, and mosaicking of the DRAO ST data and the cross calibration and incorporation of the short-spacing information from the GBT are described. The high quality of the resulting DHIGLS products enables a variety of new studies in directions of low Galactic column density. We analyze the angular power spectra of maps of the integrated H i emission (column density) from the data cubes for several distinct velocity ranges. In fitting power-spectrum models based on a power law, but including the effects of the synthesized beam and noise at high spatial frequencies, we find exponents ranging from ‑2.5 to ‑3.0. Power spectra of maps of the centroid velocity for these components give similar results. These exponents are interpreted as being representative of the three-dimensional density and velocity fields of the atomic gas, respectively. We find evidence for dramatic changes in the H i structures in channel maps over even small changes in velocity. This narrow line emission has counterparts in absorption spectra against bright background radio sources, quantifying that the gas is cold and dense and can be identified as the cold neutral medium phase. Fully reduced DHIGLS H i data cubes and other data products are available at www.cita.utoronto.ca/DHIGLS.

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

    Directory of Open Access Journals (Sweden)

    S.-R. Zhang

    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.

  5. Occurrence of polar mesosphere summer echoes at very high latitudes

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    M. Zecha

    2009-03-01

    Full Text Available Observations of polar mesosphere summer echoes (PMSE have been carried out during the summer periodes 1999–2001 and 2003–2004 at the very high latitude of 78° N using the SOUSY Svalbard Radar (53.5 MHz at Longyearbyen. Although the measurements could not be done continuously in these seasons, PMSE have been detected over more than 6600 h of 9300 h of observation time overall. Using this data base, particular PMSE occurrence characteristics have been determined. PMSE at Svalbard appear from the middle of May to the end of August with an almost permanent total occurrence in June and July. Diurnal variations are observable in the height-depend occurrence rates and in PMSE thickness, they show a maximum around 09:00–10:00 UTC and a minimum around 21:00–22:00 UTC. PMSE occur nearly exclusively between a height of 80 km and 92 km with a maximum near 85 km. However, PMSE appear not simultaneously over the entire height range, the mean vertical PMSE extension is around 4–6 km in June and July. Furthermore, typically PMSE are separated into several layers, and only 30% of all PMSE are single layers. The probability of multiple layers is greater in June and July than at the beginning and the end of the PMSE season and shows a marked 5-day-variation. The same variation is noticeable in the seasonal dependence of the PMSE occurrence and the PMSE thickness. We finally discuss potential geophysical processes to explain our observational results.

  6. Application of a land surface model for simulating river streamflow in high latitudes

    Science.gov (United States)

    Gusev, Yeugeniy; Nasonova, Olga; Dzhogan, Larissa

    2010-05-01

    Nowadays modelling runoff from the pan-Arctic river basins, which represents nearly 50% of water flow to the Arctic Ocean, is of great interest among hydrological modelling community because these regions are very sensitive to natural and anthropogenic impacts. This motivates the necessity of increase of the accuracy of hydrological estimations, runoff predictions, and water resources assessments in high latitudes. However, in these regions, observations required for model simulations (to specify model parameters and forcing inputs) are very scarce or even absent (especially this concerns land surface parameters). At the same time river discharge measurements are usually available that makes it possible to estimate model parameters by their calibration against measured discharge. Such a situation is typical of most of the northern basins of Russia. The major goal of the work is to reveal whether a physically-based land surface model (LSM) Soil Water - Atmosphere - Plants (SWAP) is able to reproduce snowmelt and rain driven daily streamflow in high latitudes (using poor input information) with the accuracy acceptable for hydrologic applications. Three river basins, located on the north of the European part of Russia, were chosen for investigation. They are the Mezen River basin (area: area: 78 000 km2), the Pechora River basin (area: 312 000 km2) and the Severnaya Dvina River basin (area: 348 000 km2). For modeling purposes the basins were presented, respectively, by 10, 57 and 62 one-degree computational grid boxes connected by river network. A priori estimation of the land surface parameters for each grid box was based on the global one-degree datasets prepared within the framework of the International Satellite Land-Surface Climatology Project Initiative II (ISLSCP) / the Second Global Soil Wetness Project (GSWP-2). Three versions of atmospheric forcing data prepared for the basins were based on: (1) NCEP/DOE reanalysis dataset; (2) NCEP/DOE reanalysis product

  7. Fertilization in northern forests

    DEFF Research Database (Denmark)

    Hedwall, Per Ola; Gong, Peichen; Ingerslev, Morten

    2014-01-01

    resources into food, health and industrial products and energy. Fertilization in Sweden and Finland is currently practiced by extensive fertilization regimens where nitrogen fertilizers are applied once, or up to three times, during a rotation period, mainly in mature forest. This type of fertilization......Forests of northern ecosystems respond slowly to management activities and the possibilities to increase the growth in a short-term perspective and meet swift increases in society's demand for biomass are small. An exception among the silvicultural measures is fertilization which can be applied...... in combination with present management systems and, almost instantly, enhances forest productivity. There may, however, be both economic and environmental constraints to large-scale applications of fertilizers in forest. Here we review the literature concerning biomass production of forests under different...

  8. Glyphosate in northern ecosystems.

    Science.gov (United States)

    Helander, Marjo; Saloniemi, Irma; Saikkonen, Kari

    2012-10-01

    Glyphosate is the main nonselective, systemic herbicide used against a wide range of weeds. Its worldwide use has expanded because of extensive use of certain agricultural practices such as no-till cropping, and widespread application of glyphosate-resistant genetically modified crops. Glyphosate has a reputation of being nontoxic to animals and rapidly inactivated in soils. However, recent evidence has cast doubts on its safety. Glyphosate may be retained and transported in soils, and there may be cascading effects on nontarget organisms. These processes may be especially detrimental in northern ecosystems because they are characterized by long biologically inactive winters and short growing seasons. In this opinion article, we discuss the potential ecological, environmental and agricultural risks of intensive glyphosate use in boreal regions.

  9. Does greater thermal plasticity facilitate range expansion of an invasive terrestrial anuran into higher latitudes?

    Science.gov (United States)

    Winwood-Smith, Hugh S; Alton, Lesley A; Franklin, Craig E; White, Craig R

    2015-01-01

    Temperature has pervasive effects on physiological processes and is critical in setting species distribution limits. Since invading Australia, cane toads have spread rapidly across low latitudes, but slowly into higher latitudes. Low temperature is the likely factor limiting high-latitude advancement. Several previous attempts have been made to predict future cane toad distributions in Australia, but understanding the potential contribution of phenotypic plasticity and adaptation to future range expansion remains challenging. Previous research demonstrates the considerable thermal metabolic plasticity of the cane toad, but suggests limited thermal plasticity of locomotor performance. Additionally, the oxygen-limited thermal tolerance hypothesis predicts that reduced aerobic scope sets thermal limits for ectotherm performance. Metabolic plasticity, locomotor performance and aerobic scope are therefore predicted targets of natural selection as cane toads invade colder regions. We measured these traits at temperatures of 10, 15, 22.5 and 30°C in low- and high-latitude toads acclimated to 15 and 30°C, to test the hypothesis that cane toads have adapted to cooler temperatures. High-latitude toads show increased metabolic plasticity and higher resting metabolic rates at lower temperatures. Burst locomotor performance was worse for high-latitude toads. Other traits showed no regional differences. We conclude that increased metabolic plasticity may facilitate invasion into higher latitudes by maintaining critical physiological functions at lower temperatures.

  10. Dense gas in high-latitude molecular clouds

    Energy Technology Data Exchange (ETDEWEB)

    Reach, W.R.; Pound, M.W.; Wilner, D.J. (Univ. of California, Berkeley (United States)); Lee, Y.

    1992-01-01

    The authors have surveyed high-latitude molecular clouds (MBM 12, 7, 55, 40) in spectral lines that are believed to be dense-gas' tracers due to the high H[sub 2] volume density required for collisional excitation. An extensive CS (2-1) line map of MBM 12 revealed emission that is not confined to clumps. Less than 20% of the integrated line emission from the cloud originates in clearly identified clumps with size between 0.2 pc and 0.02 pc in the integrated line map. The bulk of the emission originates from a relatively smooth horseshoe' structure about 0.1 pc wide and 1 pc long. The CS (2-1) map correlates with the published Bell Labs [sup 13] CO map, with significant [sup 13] CO emission even where the CS emission is undetectable. Within the central core, the C[sup 18]O(1-0) and CS(2-1) lines are positively correlated with significant scatter. There is some indication of higher CS/[sup 13]CO in the cores than the horseshoe'. The observed correlations suggest that both the diffuse CS and [sup 13]CO originate from either numerous, unresolved clumps, or the diffuse parts of the cloud. High-spatial-resolution observations of HCO[sup +] from MBM 12 obtained with the BIMA Hat Creek array demonstrated that the main core emission is primarily on spatial scales greater than 0.004 pc. It appears that the authors have resolved most of the spatial structure of the dense-gas' tracers and have found that the emission is primarily diffuse. To understand the excitation mechanism of the CS rotational levels, a multitransitional study of the 1-0, 2-1, and 3-2 lines is being performed. The CS excitation may be governed by electron collisions in regions with H[sub 2] column densities an order of magnitude lower than the critical density' of [approx gt] 2 [times] 10[sup 4] cm[sup -3]. If electron collisions are populating the CS levels, then the CS and [sup 13]CO lines can both be produced in the outer parts of the cloud, explaining their positive correlation

  11. On multifractality of high-latitude geomagnetic fluctuations

    Directory of Open Access Journals (Sweden)

    Z. Vörös

    Full Text Available In order to contribute to the understanding of solar wind-magnetosphere interactions the multifractal scaling properties of high-latitude geomagnetic fluctuations observed at the Thule observatory have been studied. Using the local observatory data and the present experimental knowledge only it seems hard to characterize directly the, presumably intermittent, mesoscale energy accumulation and dissipation processes taking place at the magnetotail, auroral region, etc. Instead a positive probability measure, describing the accumulated local geomagnetic signal energy content at the given time scales has been introduced and its scaling properties have been studied. There is evidence for the multifractal nature of the so defined intermittent field ε, a result obtained by using the recently introduced technique of large deviation multifractal spectra. This technique allows us to describe the geomagnetic fluctuations locally in time by means of singularity exponents α, which represent a generalization of the local degree of differentiability and characterize the power-law scaling dependence of the introduced measure on resolution. A global description of the geomagnetic fluctuations is insured by the spectrum of exponents f(α which represents a rate function quantifying the deviations of the observed singularities α from the expected value. The results show that there exists a multifractal counterpart of the previously reported spectral break and different types of f(α spectra describe the fluctuations in direct dissipation or loading-unloading regimes of the solar wind-magnetosphere interaction. On the time scale of substorms and storms the multi-fractal structure of the loading-unloading mode fluctuations seems to be analogous to the simple multiplicative P-model, while the f(α spectra in direct dissipation regime are close but not equal to the features of a uniform distribution. Larger deviations from the multiplicative

  12. Exchange across the shelf break at high southern latitudes

    Directory of Open Access Journals (Sweden)

    J. M. Klinck

    2010-01-01

    Full Text Available Exchange of water across the Antarctic shelf break has considerable scientific and societal importance due to its effects on circulation and biology of the region, conversion of water masses as part of the global overturning circulation and basal melt of glacial ice and the consequent effect on sea level rise. The focus in this paper is the onshore transport of warm, oceanic Circumpolar Deep Water (CDW; export of dense water from these shelves is equally important, but has been the focus of other recent papers and will not be considered here. A variety of physical mechanisms are described which could play a role in this onshore flux. The relative importance of some processes are evaluated by simple calculations. A numerical model for the Ross Sea continental shelf is used as an example of a more comprehensive evaluation of the details of cross-shelf break exchange. In order for an ocean circulation model simulate these processes at high southern latitudes, it needs to have high spatial resolution, realistic geometry and bathymetry. Grid spacing smaller than the first baroclinic radius deformation (a few km is required to adequately represent the circulation. Because of flow-topography interactions, bathymetry needs to be represented at these same small scales. Atmospheric conditions used to force these circulation models also need to be known at a similar small spatial resolution (a few km in order to represent orographically controlled winds (coastal jets and katabatic winds. Significantly, time variability of surface winds strongly influences the structure of the mixed layer. Daily, if not more frequent, surface fluxes must be imposed for a realistic surface mixed layer. Sea ice and ice shelves are important components of the coastal circulation. Ice isolates the ocean from exchange with the atmosphere, especially in the winter. Melting and freezing of both sea ice and glacial ice influence salinity and thereby the character of shelf water

  13. Exchange across the shelf break at high southern latitudes

    Directory of Open Access Journals (Sweden)

    J. M. Klinck

    2010-05-01

    Full Text Available Exchange of water across the Antarctic shelf break has considerable scientific and societal importance due to its effects on circulation and biology of the region, conversion of water masses as part of the global overturning circulation and basal melt of glacial ice and the consequent effect on sea level rise. The focus in this paper is the onshore transport of warm, oceanic Circumpolar Deep Water (CDW; export of dense water from these shelves is equally important, but has been the focus of other recent papers and will not be considered here. A variety of physical mechanisms are described which could play a role in this onshore flux. The relative importance of some processes are evaluated by simple calculations. A numerical model for the Ross Sea continental shelf is used as an example of a more comprehensive evaluation of the details of cross-shelf break exchange. In order for an ocean circulation model to simulate these processes at high southern latitudes, it needs to have high spatial resolution, realistic geometry and bathymetry. Grid spacing smaller than the first baroclinic radius of deformation (a few km is required to adequately represent the circulation. Because of flow-topography interactions, bathymetry needs to be represented at these same small scales. Atmospheric conditions used to force these circulation models also need to be known at a similar small spatial resolution (a few km in order to represent orographically controlled winds (coastal jets and katabatic winds. Significantly, time variability of surface winds strongly influences the structure of the mixed layer. Daily, if not more frequent, surface fluxes must be imposed for a realistic surface mixed layer. Sea ice and ice shelves are important components of the coastal circulation. Ice isolates the ocean from exchange with the atmosphere, especially in the winter. Melting and freezing of both sea ice and glacial ice influence salinity and thereby the character of shelf

  14. A Mid-Latitude Skywave Propagation Experiment: Overview and Results

    Science.gov (United States)

    Munton, D. C.; Calfas, R. S.; Gaussiran, T., II; Rainwater, D.; Flesichmann, A. M.; Schofield, J. R.

    2016-12-01

    We will describe a mid-latitude HF skywave propagation experiment conducted during 19-27 January, 2014. There were two primary goals to the experiment. First, we wanted to build an understanding of the impact that medium scale traveling ionospheric disturbances have on the angles of arrival of the HF signals. The second goal was to provide a diverse data set that could serve as a baseline for propagation model development and evaluation. We structured individual tests during the experiment to increase the knowledge of temporal and spatial length scales of various ionospheric features. The experiment was conducted during both day and night periods and spanned a wide range of ionospheric states. We conducted the experiment at White Sands Missile Range, New Mexico and in the surrounding area. As part of the experiment, we deployed a number of active HF transmitters, and an array of dipole antennas to provide angle of arrival measurements. We also deployed a smaller array of more novel compact electro-magnetic vector sensors (EMVSs). Other instrumentation specific to the remote sensing of the ionosphere included digisondes, GNSS receivers, beacon satellite receivers, and optical instruments. We will provide a complete description of the experiment configuration and the data products.Finally, we will provide a discussion of experimental results, focusing on ionospheric conditions during the angle-of-arrival determinations, and the impact ionospheric disturbances can have on these measurements. We use the angle-of-arrival determinations to estimate TID properties, including velocity and direction.This research is based upon work supported in part by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA), via US Navy Contract N00024-07-D-6200. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements

  15. Persistence of biological nitrogen fixation in high latitude grass-clover grasslands under different management practices

    Science.gov (United States)

    Tzanakakis, Vasileios; Sturite, Ievina; Dörsch, Peter

    2016-04-01

    Biological nitrogen fixation (BNF) can substantially contribute to N supply in permanent grasslands, improving N yield and forage quality, while reducing inorganic N inputs. Among the factors critical to the performance of BNF in grass-legume mixtures are selected grass and legume species, proportion of legumes, the soil-climatic conditions, in particular winter conditions, and management practices (e.g. fertilization and compaction). In high latitude grasslands, low temperatures can reduce the performance of BNF by hampering the legumés growth and by suppressing N2 fixation. Estimation of BNF in field experiments is not straightforward. Different methods have been developed providing different results. In the present study, we evaluated the performance of BNF, in a newly established field experiment in North Norway over four years. The grassland consisted of white clover (Trifolium repens L.) and red clover (Trifolium pretense L.) sawn in three proportions (0, 15 and 30% in total) together with timothy (Pheum pretense L.) and meadow fescue (Festuca pratensis L.). Three levels of compaction were applied each year (no tractor, light tractor, heavy tractor) together with two different N rates (110 kg N/ha as cattle slurry or 170 kg N/ha as cattle slurry and inorganic N fertilizer). We applied two different methods, the 15N natural abundance and the difference method, to estimate BNF in the first harvest of each year. Overall, the difference method overestimated BNF relative to the 15N natural abundance method. BNF in the first harvest was compared to winter survival of red and white clover plants, which decreased with increasing age of the grassland. However, winter conditions did not seem to affect the grassland's ability to fix N in spring. The fraction of N derived from the atmosphere (NdfA) in white and red clover was close to 100% in each spring, indicating no suppression of BNF. BNF increased the total N yield of the grasslands by up to 75%, mainly due to high

  16. Low-latitude equinoctial spread-F occurrence at different longitude sectors under low solar activity

    Science.gov (United States)

    Pezzopane, M.; Zuccheretti, E.; Abadi, P.; de Abreu, A. J.; de Jesus, R.; Fagundes, P. R.; Supnithi, P.; Rungraengwajiake, S.; Nagatsuma, T.; Tsugawa, T.; Cabrera, M. A.; Ezquer, R. G.

    2013-02-01

    We present the results of a comparative study of spread-F signatures over five low-latitude sites: Chiangmai (CGM; 18.8° N, 98.9° E, mag. Lat. 8.8° N), Thailand; Tanjungsari (TNJ; 6.9° S, 107.6° E, mag. Lat. 16.9° S), Indonesia; Palmas (PAL; 10.2° S, 311.8° E, mag. Lat. 0.9° S) and São José Dos Campos (SJC; 23.2° S, 314.1° E, mag. Lat. 14.0° S), Brazil; and Tucumán (TUC; 26.9° S, 294.6° E, mag. Lat. 16.8° S), Argentina. The investigation was based on simultaneous ionograms recorded by an FMCW (frequency-modulated continuous-wave) at CGM, an IPS-71 (digital ionosonde from KEL aerospace) at TNJ, a CADI (Canadian Advanced Digital Ionosonde) at PAL and SJC, and an AIS-INGV (Advanced Ionospheric Sounder - Istituto Nazionale di Geofisica e Vulcanologia) at TUC, during the equinoctial periods March-April (R12 = 2.0 and R12 = 2.2) and September-October (R12 = 6.1 and R12 = 7.0) 2009, for very low solar activity. Spread-F signatures were categorized into two types: the range spread-F (RSF) and the frequency spread-F (FSF). The study confirms that the dynamics and the physical processes responsible for these phenomena are actually complicated. In fact, the features that arise from the investigation are different, depending on both the longitude sector and on the hemisphere. For instance, TUC, under the southern crest of the ionospheric equatorial ionization anomaly (EIA), shows a predominance of RSF signatures, while both SJC, under the southern crest of EIA but in a different longitude sector, and CGM, under the northern crest of EIA, show a predominance of FSF signatures. Moreover, the spread-F occurrence over the longitude sector that includes CGM and TNJ is significantly lower than the spread-F occurrence over the longitude sector of PAL, SJC, and TUC.

  17. Absorption properties of high-latitude Norwegian coastal water: The impact of CDOM and particulate matter

    Science.gov (United States)

    Nima, Ciren; Frette, Øyvind; Hamre, Børge; Erga, Svein Rune; Chen, Yi-Chun; Zhao, Lu; Sørensen, Kai; Norli, Marit; Stamnes, Knut; Stamnes, Jakob J.

    2016-09-01

    We present data from measurements and analyses of the spectral absorption due to colored dissolved organic matter (CDOM), total suspended matter (TSM), phytoplankton, and non-algal particles (NAP) in high-latitude northern Norwegian coastal water based on samples taken in spring, summer, and autumn. The Chlorophyll-a (Chl-a) concentration was found to vary significantly with season, whereas regardless of season CDOM was found to be the dominant absorber for wavelengths shorter than 600 nm. The absorption spectral slope S350-500 for CDOM varied between 0.011 and 0.022 nm-1 with mean value and standard deviation given by (0.015 ± 0.002) nm-1. The absorption spectral slope was found to be strongly dependent on the wavelength interval used for fitting. On average, S280-500 was found to be 43% higher than S350-500. A linear relationship was found between the base 10 logarithm of the absorption coefficient at 440 nm [log(ag(440))] and S350-500. Regardless of season, phytoplankton were the dominant component of the TSM absorption indicating little influence from land drainage. The mean values of the Chl-a specific absorption coefficient of phytoplankton aph*(λ) at 440 nm and 676 nm were 0.052 m2 mg-1 and 0.023 m2 mg-1, respectively, and aph*(λ) was found to vary with season, being higher in summer and autumn than in spring. The absorption spectral slope SNAP, which is the spectral slope of absorption spectrum for non-algal particles, was lower than that for European coastal water in general. It varied between 0.0048 and 0.022 nm-1 with mean value and standard deviation given by (0.0083-1 ± 0.003) nm-1. Comparisons of absorption coefficients measured in situ using an ac-9 instrument with those measured in the laboratory from water samples show a good agreement.

  18. Latitude and pH driven trends in the molecular composition of DOM across a north south transect along the Yenisei River

    Science.gov (United States)

    Roth, Vanessa-Nina; Dittmar, Thorsten; Gaupp, Reinhard; Gleixner, Gerd

    2013-12-01

    We used electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS) to identify the molecular composition of dissolved organic matter (DOM) collected from different ecosystems along a transect crossing Siberia’s northern and middle Taiga. This information is urgently needed to help elucidate global carbon cycling and export through Russian rivers. In total, we analyzed DOM samples from eleven Yenisei tributaries and seven bogs. Freeze-dried and re-dissolved DOM was desalted via solid phase extraction (SPE) and eluted in methanol for ESI-FT-ICR-MS measurements. We recorded 15209 different masses and identified 7382 molecular formulae in the mass range between m/z = 150 and 800. We utilized the relative FT-ICR-MS signal intensities of 3384 molecular formulae above a conservatively set limit of detection and summarized the molecular characteristics for each measurement using ten magnitude-weighted parameters ((O/C)w, (H/C)w, (N/C)w, (DBE)w, (DBE/C)w, (DBE/O)w, (DBE-O)w, (C#)w, (MW)w and (AI)w) for redundancy analysis. Consequently, we revealed that the molecular composition of DOM depends mainly on pH and geographical latitude. After applying variation partitioning to the peak data, we isolated molecular formulae that were strongly positive or negatively correlated with latitude and pH. We used the chemical information from 13 parameters (C#, H#, N#, O#, O/C, H/C, DBE, DBE/C, DBE/O, AI, N/C, DBE-O and MW) to characterize the extracted molecular formulae. Using latitude along the gradient representing climatic variation, we found a higher abundance of smaller molecules, nitrogen-containing compounds and unsaturated Cdbnd C functionalities at higher latitudes. As possible reasons for the different molecular characteristics occurring along this gradient, we suggested that the decomposition was temperature dependent resulting to a higher abundance of non-degraded lignin-derived phenolic substances. We demonstrated that bog samples

  19. Seasonal variabilities of low-latitude mesospheric winds

    Directory of Open Access Journals (Sweden)

    R. Rajaram

    Full Text Available Observations of mesospheric winds over a period of four years with the partial reflection radar at Tirunelveli (8.7°N, 77.8°E, India, are presented in this study. The emphasis is on describing seasonal variabilities in mean zonal and meridional winds in the altitude region 70–98 km. The meridional winds exhibit overall transequatorial flow associated with differential heating in the Northern and Southern Hemispheres. At lower altitudes (70–80 km the mean zonal winds reveal easterly flow during summer and westerly flow during winter, as expected from a circulation driven by solar forcing. In the higher altitude regime (80–98 km and at all altitudes during equinox periods, the mean zonal flow is subjected to the semi-annual oscillation (SAO. The interannual variability detected in the occurrence of SAO over Tirunelveli has also been observed in the data sets obtained from the recent UARS satellite mission. Harmonic analysis results over a period of two years indicate the presence of long-period oscillations in the mean zonal wind at specific harmonic periods near 240, 150 and 120 days. Results presented in this study are discussed in the context of current understanding of equatorial wave propagation.

    Key words. Meteorological and atmospheric dynamics · General circulation · Middle atmosphere dynamics · waves and tides.

  20. 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.

  1. Tropical and High-latitude Surface Ocean Circulation Across The Mid-Pleistocene Transition: Teleconnections And Impacts For Ice-sheet Growth And Environmental Change Onshore

    Science.gov (United States)

    McClymont, E. L.; Rosell-Mele, A.; Lloyd, J. M.

    2006-12-01

    The Mid-Pleistocene Transition (MPT) is a major event in the Quaternary record, marking the shift to a dominant glacial/interglacial period of 100-kyr and the development of larger northern hemisphere ice-sheets at ca. 0.9 Ma. The significance of the MPT lies in the change of the global climate system response to external insolation forcing, which cannot account for the strength of the 100-kyr cycles. Existing hypotheses link the MPT to falling atmospheric CO2 concentrations, cooler deep-water temperatures, changes in sea-ice distribution and to the basal conditions of the northern hemisphere ice-sheets. We present alkenone-derived records of sea-surface temperature from the tropical Pacific and the south-east Atlantic spanning 1.5-0.5 Ma, coupled with evidence of arctic/polar water mass distributions in the high northern latitudes of the Atlantic and Pacific Oceans. Interaction between the tropics and high-latitudes across the MPT is suggested by the results presented here. At all sites we find evidence for cooling beginning from 1.15 Ma, supporting the hypotheses invoking cooling of both the atmosphere and deep-waters as a driver of the MPT. Sea-ice expansion from 1.15 Ma is suggested by the equatorward migration of arctic/polar water masses in both the Atlantic and Pacific, which reached their maximum extent at 1.0 Ma. The negative impact of more expansive sea-ice cover to the transport of moisture to the ice-sheet source regions may have been critical to the later development of larger northern hemisphere ice-sheets from 0.9 Ma. Significantly, we find that the MPT was not simply a high-latitude phenomenon, but was accompanied by (and perhaps driven by) significant changes to circulation in the tropical Pacific. Between 1.15 0.9 Ma a secular decrease in mean sea-surface temperatures of c.1.5*C in the eastern tropical Pacific marks an intensification of Walker Circulation and a shift towards a `La Niña'-like circulation state. The associated Trade Wind

  2. The High-latitude Electric Potential Disparity and Hemispheric Differences in the Upper Thermospheric Neutral Wind Circulation

    Science.gov (United States)

    Foerster, M.; Haaland, S.; Cnossen, I.

    2014-12-01

    We present statistical studies of both the high-latitude ionospheric potential pattern deduced from long-term observations of the Cluster Electron Drift Instrument (EDI) and upper thermospheric neutral wind circulation patterns in the Northern (NH) and Southern Hemisphere (SH) obtained from accelerometers on board of low-Earth orbiting satellites like CHAMP during about the same time interval. The cross-polar cap potential difference during southward IMF conditions appears to be on average slightly (~7%) larger in the SH compared with the NH, while the neutral wind magnitude and vorticity amplitude are mostly larger in the NH than in the SH, especially during high solar activity conditions. We attribute such behaviour to peculiarities of the hemispheres due to the non-dipolar portions of Earth's main magnetic field that constitute substantial differences between the geomagnetic field configurations of both hemispheres. They cause in particular different magnetic field flux densities in the opposite polar regions and different offsets of the invariant poles with respect to the rotation axis of the Earth. The pole is presently displaced almost twice the distance in the SH compared to the NH, which has substantial implications for the coupled magnetosphere-ionosphere-thermosphere system under the influence of external drivers. To analyse this behaviour, we have run several numerical simulations using the first-principle Coupled Magnetosphere-Ionosphere-Thermosphere (CMIT) model under various seasonal conditions. The survey of both the numerical simulation results and the observations confirm prominent asymmetries between the two hemispheres for these parameters.

  3. The function of male sperm whale slow clicks in a high latitude habitat: communication, echolocation, or prey debilitation?

    Science.gov (United States)

    Oliveira, Cláudia; Wahlberg, Magnus; Johnson, Mark; Miller, Patrick J O; Madsen, Peter T

    2013-05-01

    Sperm whales produce different click types for echolocation and communication. Usual clicks and buzzes appear to be used primarily in foraging while codas are thought to function in social communication. The function of slow clicks is less clear, but they appear to be produced by males at higher latitudes, where they primarily forage solitarily, and on the breeding grounds, where they roam between groups of females. Here the behavioral context in which these vocalizations are produced and the function they may serve was investigated. Ninety-nine hours of acoustic and diving data were analyzed from sound recording tags on six male sperm whales in Northern Norway. The 755 slow clicks detected were produced by tagged animals at the surface (52%), ascending from a dive (37%), and during the bottom phase (11%), but never during the descent. Slow clicks were not associated with the production of buzzes, other echolocation clicks, or fast maneuvering that would indicate foraging. Some slow clicks were emitted in seemingly repetitive temporal patterns supporting the hypothesis that the function for slow clicks on the feeding grounds is long range communication between males, possibly relaying information about individual identity or behavioral states.

  4. Propagation of short-period gravity waves at high-latitudes during the MaCWAVE winter campaign

    Directory of Open Access Journals (Sweden)

    K. Nielsen

    2006-07-01

    Full Text Available As part of the MaCWAVE (Mountain and Convective Waves Ascending Vertically winter campaign an all-sky monochromatic CCD imager has been used to investigate the properties of short-period mesospheric gravity waves at high northern latitudes. Sequential measurements of several nightglow emissions were made from Esrange, Sweden, during a limited period from 27–31 January 2003. Coincident wind measurements over the altitude range (~80–100 km using two meteor radar systems located at Esrange and Andenes have been used to perform a novel investigation of the intrinsic properties of five distinct wave events observed during this period. Additional lidar and MSIS model temperature data have been used to investigate their nature (i.e. freely propagating or ducted. Four of these extensive wave events were found to be freely propagating with potential source regions to the north of Scandinavia. No evidence was found for strong orographic forcing by short-period waves in the airglow emission layers. The fifth event was most unusual exhibiting an extensive, but much smaller and variable wavelength pattern that appeared to be embedded in the background wind field. Coincident wind measurements indicated the presence of a strong shear suggesting this event was probably due to a large-scale Kelvin-Helmholtz instability.

  5. Interhemispheric differences and solar cycle effects of the high-latitude ionospheric convection patterns deduced from Cluster EDI observations

    Science.gov (United States)

    Förster, Matthias; Haaland, Stein

    2015-04-01

    Here, we present a study of ionospheric convection at high latitudes that is based on satellite measurements of the Electron Drift Instrument (EDI) on-board the Cluster satellites, which were obtained over a full solar cycle (2001-2013). The mapped drift measurements are covering both hemispheres and a variety of different solar wind and interplanetary magnetic field (IMF) conditions. The large amount of data allows us to perform more detailed statistical studies. We show that flow patterns and polar cap potentials can differ between the two hemispheres on statistical average for a given IMF orientation. In particular, during southward directed IMF conditions, and thus enhanced energy input from the solar wind, we find that the southern polar cap has a higher cross polar cap potential. We also find persistent north-south asymmetries which cannot be explained by external drivers alone. Much of these asymmetries can probably be explained by significant differences in the strength and configuration of the geomagnetic field between the Northern and Southern Hemisphere. Since the ionosphere is magnetically connected to the magnetosphere, this difference will also be reflected in the magnetosphere in the form of different feedback from the two hemispheres. Consequently, local ionospheric conditions and the geomagnetic field configuration are important for north-south asymmetries in large regions of geospace. The average convection is higher during periods with high solar activity. Although local ionospheric conditions may play a role, we mainly attribute this to higher geomagnetic activity due to enhanced solar wind - magnetosphere interactions.

  6. Keeping It Local: Dispersal Limitations of Coral Larvae to the High Latitude Coral Reefs of the Houtman Abrolhos Islands.

    Directory of Open Access Journals (Sweden)

    Kathryn L Markey

    Full Text Available In 2011 the first recorded bleaching event for the high latitude Houtman Abrolhos Islands (HAI coral communities was documented. This bleaching event highlighted the question of whether a supply of 'heat tolerant' coral recruits from the tropical north would be sufficient to provide a level of resistance for these reefs to future warming events. Using Lagrangian modelling we showed that due to its regional isolation, large-scale larval input from potential tropical northern source populations to the HAI is unlikely, despite the southward flowing Leeuwin current. Successful recruitment to artificial substrates was recorded following the bleaching event. However, this was negligible (0.4 ± 0.1 recruits per tile compared to 2013 post impact recruitment (128.8 ± 15.8 recruits per tile. Our data therefore provides preliminary evidence suggesting that the connectivity of the HAI with coral communities in the north is limited, and population maintenance and recovery is likely driven primarily by self-recruitment. Given the low thermal tolerance of the HAI coral communities, the dominance of Acropora, and the apparent reliance on self-recruitment, an increased frequency of thermally anomalous conditions at the HAI (such as experienced in 2011 has the potential to reduce the long-term stability of the HAI coral populations and species that depend upon them.

  7. ELUSIVE ETHYLENE DETECTED IN SATURN'S NORTHERN STORM REGION

    Energy Technology Data Exchange (ETDEWEB)

    Hesman, B. E.; Achterberg, R. K.; Nixon, C. A. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Bjoraker, G. L.; Romani, P. N. [NASA/GSFC Code 693, Greenbelt, MD 20771 (United States); Sada, P. V. [Departamento de Fisica y Matematicas, Universidad de Monterrey, Garza Garcia, NL 66238 (Mexico); Jennings, D. E. [NASA/GSFC Code 693 and Code 500, Greenbelt, MD 20771 (United States); Lunsford, A. W. [Department of Physics, Catholic University of America, Washington, DC 20064 (United States); Fletcher, L. N.; Irwin, P. G. J. [Atmospheric, Oceanic and Planetary Physics, Clarendon Laboratory, Parks Road, Oxford OX1 3PU (United Kingdom); Boyle, R. J. [Department of Physics and Astronomy, Dickinson College, Carlisle, PA 17013 (United States); Simon-Miller, A. A., E-mail: brigette.e.hesman@nasa.gov [NASA/GSFC Code 690, Greenbelt, MD 20771 (United States)

    2012-11-20

    The massive eruption at 40 Degree-Sign N (planetographic latitude) on Saturn in 2010 December has produced significant and lasting effects in the northern hemisphere on temperature and species abundances. The northern storm region was observed on many occasions in 2011 by Cassini's Composite Infrared Spectrometer (CIRS). In 2011 May, temperatures in the stratosphere greater than 200 K were derived from CIRS spectra in the regions referred to as 'beacons' (warm regions in the stratosphere). Ethylene has been detected in the beacon region in Saturn's northern storm region using CIRS. Ground-based observations using the high-resolution spectrometer Celeste on the McMath-Pierce Telescope on 2011 May 15 were used to confirm the detection and improve the altitude resolution in the retrieved profile. The derived ethylene profile from the CIRS data gives a C{sub 2}H{sub 4} mole fraction of 5.9 {+-} 4.5 Multiplication-Sign 10{sup -7} at 0.5 mbar, and from Celeste data it gives 2.7 {+-} 0.45 Multiplication-Sign 10{sup -6} at 0.1 mbar. This is two orders of magnitude higher than the amount measured in the ultraviolet at other latitudes prior to the storm. It is also much higher than predicted by photochemical models, indicating that perhaps another production mechanism is required or a loss mechanism is being inhibited.

  8. Vitamin D deficiency among northern Native Peoples: a real or apparent problem?

    Directory of Open Access Journals (Sweden)

    Peter Frost

    2012-03-01

    Full Text Available Vitamin D deficiency seems to be common among northern Native peoples, notably Inuit and Amerindians. It has usually been attributed to: (1 higher latitudes that prevent vitamin D synthesis most of the year; (2 darker skin that blocks solar UVB; and (3 fewer dietary sources of vitamin D. Although vitamin D levels are clearly lower among northern Natives, it is less clear that these lower levels indicate a deficiency. The above factors predate European contact, yet pre-Columbian skeletons show few signs of rickets—the most visible sign of vitamin D deficiency. Furthermore, because northern Natives have long inhabited high latitudes, natural selection should have progressively reduced their vitamin D requirements. There is in fact evidence that the Inuit have compensated for decreased production of vitamin D through increased conversion to its most active form and through receptors that bind more effectively. Thus, when diagnosing vitamin D deficiency in these populations, we should not use norms that were originally developed for European-descended populations who produce this vitamin more easily and have adapted accordingly.

  9. Simulated impacts of historical land cover changes on global climate in northern winter

    Energy Technology Data Exchange (ETDEWEB)

    Chase, T.N.; Pielke Sr., R.A. [Colorado State Univ., Fort Collins, CO (United States). Dept. of Atmospheric Science; Kittel, T.G.F. [Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, CO 80307 (United States); Nemani, R.R.; Running, S.W. [School of Forestry, University of Montana, Missoula, MT 59812 (United States)

    2000-02-01

    This ten-year general circulation model experiment compared a simulation where land surface boundary conditions were represented by observed, present day land cover to a simulation where the surface was represented by natural, potential land cover conditions. As a result of these estimated changes in historical land cover, significant temperature and hydrology changes affected tropical land surfaces, where some of the largest historical disruptions in total vegetation biomass have occurred. Also of considerable interest because of their broad scope and magnitude were changes in high-latitude Northern Hemisphere winter climate which resulted from changes in tropical convection, upper-level tropical outflow, and the generation of low-frequency tropical waves which propagated to the extratropics. These effects combined to move the Northern Hemisphere zonally averaged westerly jet to higher latitudes, broaden it, and reduce its maximum intensity. Low-level easterlies were also reduced over much of the tropical Pacific basin while positive anomalies in convective precipitation occurred in the central Pacific. Globally averaged changes were small. Comparisons of recent, observed trends in tropical and Northern Hemisphere, midlatitude climate with these simulations suggests an interaction between the climatic effects of historical land cover changes and other modes of climate variability. (orig.)

  10. Survey of TES high albedo events in Mars' northern polar craters

    Science.gov (United States)

    Armstrong, J.C.; Nielson, S.K.; Titus, T.N.

    2007-01-01

    Following the work exploring Korolev Crater (Armstrong et al., 2005) for evidence of crater interior ice deposits, we have conducted a survey of Thermal Emission Spectroscopy (TES) temperature and albedo measurements for Mars' northern polar craters larger than 10 km. Specifically, we identify a class of craters that exhibits brightening in their interiors during a solar longitude, Ls, of 60 to 120 degrees, roughly depending on latitude. These craters vary in size, latitude, and morphology, but appear to have a specific regional association on the surface that correlates with the distribution of subsurface hydrogen (interpreted as water ice) previously observed on Mars. We suggest that these craters, like Korolev, exhibit seasonal high albedo frost events that indicate subsurface water ice within the craters. A detailed study of these craters may provide insight in the geographical distribution of the ice and context for future polar missions. Copyright 2007 by the American Geophysical Union.

  11. Does the recent warming hiatus exist over northern Asia for winter wind chill temperature?

    Science.gov (United States)

    Ma, Ying

    2017-04-01

    Wind chill temperature (WCT) describes the joint effect of wind velocity and air temperature on exposed body skin and could support policy makers in designing plans to reduce the risks of notably cold and windy weather. This study examined winter WCT over northern Asia during 1973-2013 by analyzing in situ station data. The winter WCT warming rate over the Tibetan Plateau slowed during 1999-2013 (-0.04 °C/decade) compared with that during 1973-1998 (0.67 °C/decade). The winter WCT warming hiatus has also been observed in the remainder of Northern Asia with trends of 1.11 °C/decade during 1973-1998 but -1.02 °C/decade during 1999-2013, except for the Far East of Russia (FE), where the winter WCT has continued to heat up during both the earlier period of 1973-1998 (0.54 °C/decade) and the recent period of 1999-2013 (0.75 °C/decade). The results indicate that the influence of temperature on winter WCT is greater than that of wind speed over northern Asia. Atmospheric circulation changes associated with air temperature and wind speed were analyzed to identify the causes for the warming hiatus of winter WCT over northern Asia. The distributions of sea level pressure and 500 hPa height anomalies during 1999-2013 transported cold air from the high latitudes to middle latitudes, resulting in low air temperature over Northern Asia except for the Far East of Russia. Over the Tibetan Plateau, the increase in wind speed offset the increase in air temperature during 1999-2013. For the Far East, the southerly wind from the Western Pacific drove the temperature up during the 1999-2013 period via warm advection.

  12. BVOC ecosystem flux measurements at a high latitude wetland site

    Directory of Open Access Journals (Sweden)

    T. Holst

    2008-12-01

    Full Text Available In this study, we present summertime concentrations and fluxes of biogenic volatile organic compounds (BVOCs measured at a sub-arctic wetland in northern Sweden using a disjunct eddy-covariance (DEC technique based on a proton transfer reaction mass spectrometer (PTR-MS. The vegetation at the site was dominated by Sphagnum, Carex and Eriophorum spp. The performance of the DEC system was assessed by comparing H3O+-ion cluster formed with water molecules (H3O+(H2O at m37 with water vapour concentration measurements made using an adjacent humidity sensor, and from a comparison of sensible heat fluxes for high frequency and DEC data obtained from the sonic anemometer. These analyses showed no significant PTR-MS sensor drift over a period of several weeks and only a small flux-loss due to high-frequency spectrum omissions. This loss was within the range expected from other studies and the theoretical considerations.

    Standardised (20°C and 1000 μmol m−2 s−1 PAR summer isoprene emission rates of 323 μg C m−2 (ground area h−1 were comparable with findings from more southern boreal forests, and fen-like ecosystems. On a diel scale, measured fluxes indicated a stronger temperature dependence when compared with emissions from temperate or (subtropical ecosystems. For the first time, to our knowledge, we report ecosystem methanol fluxes from a sub-arctic ecosystem. Maximum daytime emission fluxes were around 270 μg m−2 h−1 (ca. 100 μg C m−2 h-1 and measurements indicated some nocturnal deposition.

    The measurements reported here covered a period of 50 days (1 August to 19 September 2006, approximately one half of the growing season at the site, and allowed to investigate the effect of vegetation senescence on daily BVOC fluxes and on their temperature and light

  13. Possible latitude effects of Chern-Simons gravity on quantum interference

    CERN Document Server

    Okawara, Hiroki; Asada, Hideki

    2013-01-01

    It has been recently suggested that possible effects of Chern-Simons gravity on a quantum interferometer are dependent on the latitude and direction of the interferometer on Earth in orbital motion around Sun. Continuing work initiated in the earlier publication [Okawara, Yamada and Asada, Phys. Rev. Lett. 109, 231101 (2012)], we perform numerical calculations of time variation in the induced phase shifts for nonequatorial cases. We show that the maximum phase shift at any latitude might occur at 6, 0 (and 12), and 18 hours (in local time) of each day, when the normal vector to the interferometer is vertical, eastbound and northbound, respectively. If two identical interferometers were located at different latitudes, the difference between two phase shifts that are measured at the same local time would be $O(\\sin \\delta\\varphi)$ for a small latitude difference $\\delta\\varphi$. It might thus become maximally $\\sim 20$ percents for $\\delta\\varphi \\sim 10$ degrees, for instance.

  14. Lean production tools and decision latitude enable conditions for innovative learning in organizations: a multilevel analysis.

    Science.gov (United States)

    Fagerlind Ståhl, Anna-Carin; Gustavsson, Maria; Karlsson, Nadine; Johansson, Gun; Ekberg, Kerstin

    2015-03-01

    The effect of lean production on conditions for learning is debated. This study aimed to investigate how tools inspired by lean production (standardization, resource reduction, visual monitoring, housekeeping, value flow analysis) were associated with an innovative learning climate and with collective dispersion of ideas in organizations, and whether decision latitude contributed to these associations. A questionnaire was sent out to employees in public, private, production and service organizations (n = 4442). Multilevel linear regression analyses were used. Use of lean tools and decision latitude were positively associated with an innovative learning climate and collective dispersion of ideas. A low degree of decision latitude was a modifier in the association to collective dispersion of ideas. Lean tools can enable shared understanding and collective spreading of ideas, needed for the development of work processes, especially when decision latitude is low. Value flow analysis played a pivotal role in the associations.

  15. 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...

  16. Ocean acidification at high latitudes: potential effects on functioning of the Antarctic bivalve Laternula elliptica

    National Research Council Canada - National Science Library

    Cummings, Vonda; Hewitt, Judi; Van Rooyen, Anthony; Currie, Kim; Beard, Samuel; Thrush, Simon; Norkko, Joanna; Barr, Neill; Heath, Philip; Halliday, N Jane; Sedcole, Richard; Gomez, Antony; McGraw, Christina; Metcalf, Victoria

    2011-01-01

    Ocean acidification is a well recognised threat to marine ecosystems. High latitude regions are predicted to be particularly affected due to cold waters and naturally low carbonate saturation levels...

  17. Paleoseismology at high latitudes: Seismic disturbance of upper Quaternary deposits along the Castle Mountain fault near Houston, Alaska

    Science.gov (United States)

    Haeussler, P.J.; Best, T.C.; Waythomas, C.F.

    2002-01-01

    Most paleoseismic studies are at low to moderate latitudes. Here we present results from a high-latitude (61??30??? N) trenching study of the Castle Mountain fault in south-central Alaska. This fault is the only one known in the greater Anchorage, Alaska, area with historical seismicity and a Holocene fault scarp. It strikes eastnortheast and cuts glacial and postglacial sediments in an area of boreal spruce-birch forest, shrub tundra, and sphagnum bog. The fault has a prominent vegetation lineament on the upthrown, north side of the fault. Nine trenches were logged across the fault in glacial and postglacial deposits, seven along the main trace, and two along a splay. In addition to thrust and strike-slip faulting, important controls on observed relationships in the trenches are the season in which faulting occurred, the physical properties of the sediments, liquefaction, a shallow water table, soil-forming processes, the strength of the modern root mat, and freeze-thaw processes. Some of these processes and physical properties are unique to northern-latitude areas and result in seismic disturbance effects not observed at lower latitudes. The two trenches across the Castle Mountain fault splay exposed a thrust fault and few liquefaction features. Radiocarbon ages of soil organic matter and charcoal within and overlying the fault indicate movement on the fault at ca. 2735 cal. (calendar) yr B.P. and no subsequent movement. In the remaining seven trenches, surface faulting was accompanied by extensive liquefaction and a zone of disruption 3 m or more wide. The presence of numerous liquefaction features at depths of soil, but did not penetrate the interlocking spruce-birch root mat. The strength of the root mat prohibited development of a nonvegetated scarp face and colluvial wedge. In only one trench did we observe a discrete fault plane with measurable offset. It lay beneath a 2-m-thick carapace of liquefied sand and silt and displayed a total of 0.9-1.85 m of

  18. A circum-earth shear zone at low-latitudes and episodic large earthquakes in it and the circum-Pacific seismic zone

    Institute of Scientific and Technical Information of China (English)

    MA; Zongjin; DU; Pinren; REN; Jinwei; GAO; Xianglin

    2006-01-01

    Because of the differential motions between the Northern and Southern Hemispheres of the Earth, there exists a motion discordant zone between them. On the surface this zone consists of 13 large faults dominant with strike-slip. We call it a global shear zone at low-latitudes (E system). By statistical analysis of temporal distribution of earthquakes Mw≥7.5 in the E system and the circum-Pacific (P system) during 1900-2003, we find that there exist quasi-episodic and alternative activities in and between these two systems. This phenomenon is likely associated with the half-sphere oscillation in dilation and contraction and the change of the Earth's rotation rate.

  19. 批评的宽度%Critical Latitude

    Institute of Scientific and Technical Information of China (English)

    托马斯·帕威尔

    2016-01-01

    From his educational background both in France and America,Professor Pavel not only expresses his endorsement,understanding and judgment of the concept of "imposed interpretation," but also his opinion and further academic expectations.The article has three parts.First,he confirms the existence of the specific problems of "imposed interpretation,""subjective assumption prior to interpretation," and "reversed route of cognition." Second,he points out that the phenomen on of imposed interpretation is not unique in contemporary times and has existed in Western literary research since the beginning of the 19th century-firom the Zeitgeist of the age of Hegel,the social environment of positivism,the narratology of structuralism,and to contemporary literary critique,all of which have the feature of using concepts to cover the multiformity of literary works.Pavel finally points out that the contemporary phenomen on of"imposed interpretation" embodies the features of American culture and exposes the problem of American education.He hopes that scholars can keep critical latitude and vitality while rectifying the errors in literary research.%帕威尔教授从他兼具法国和美国的学术教育背景出发,一方面给出了他对“强制阐释”概念的赞同、理解和判定,另一方面也提出他的补充意见与进一步的学科期待.本文分三部分内容,首先是确认“强制阐释”核心概念下的场外征用、主观预设和反序认知等具体问题的存在;然后指出强制阐释现象并非当代独有,而是历史性地存在于19世纪初以来的西方文学研究里——从黑格尔时代的“时代精神”到实证主义的“社会环境”,再到结构主义的“叙事学”和当代的文化批评,都有以概念掩盖作品的多样性事实的特点;最后,帕威尔指出,当代的强制阐释现象体现了强烈的美国文化的特点,也暴露了美国文学教育的问题,但他希望文学研究在纠偏的同时,能

  20. MBM 12: young protoplanetary discs at high galactic latitude

    Science.gov (United States)

    Meeus, G.; Juhász, A.; Henning, Th.; Bouwman, J.; Chen, C.; Lawson, W.; Apai, D.; Pascucci, I.; Sicilia-Aguilar, A.

    2009-04-01

    We present Spitzer infrared observations to constrain disc and dust evolution in young T Tauri stars in MBM 12, a star-forming cloud at high latitude with an age of 2 Myr and a distance of 275 pc. The region contains 12 T Tauri systems, with primary spectral types between K3 and M6; 5 are weak-line and the rest classical T Tauri stars. We first use MIPS and literature photometry to compile spectral energy distributions for each of the 12 members in MBM 12, and derive their IR excesses. Of the 8 stars that are detected with MIPS (spectral types between K3 and M5), only 1 lacks an IR excess - the other 7 all have an IR excess that can be attributed to a disc. This means that in MBM 12, for the detected spectral types K3-M5, we have a very high disc fraction rate, about 90%. Furthermore, 3 of those 7 excess sources are candidate transitional discs. The four lowest-mass systems in the cloud, with spectral types of M5-M6, were undetected by Spitzer. Their upper limits indicate that they either have a transitional disc, or no disc at all. The IRS spectra are analysed with the newly developed two-layer temperature distribution (TLTD) spectral decomposition method. For the 7 T Tauri stars with a detected IR excess, we analyse their solid-state features to derive dust properties such as mass-averaged grain size, composition and crystallinity. The mass-averaged grain size we determine from the 10 micron feature has a wide range, between 0.4 and 6 μm. This grain size is much smaller in the longer-wavelength region: between 0.1 and 1.5 μm. We find that later-type objects have larger grain sizes, as was already shown by earlier studies. Furthermore, we find a wide range in mass fraction of the crystalline grains, between 3 and (at least) 30%, with no relation to the spectral type nor grain size. We do find a spatial gradient in the forsterite to enstatite range, with more enstatite present in the warmer regions. The fact that we see a radial dependence of the dust properties

  1. High Altitude Bird Migration at Temperate Latitudes: A Synoptic Perspective on Wind Assistance

    OpenAIRE

    2013-01-01

    At temperate latitudes the synoptic patterns of bird migration are strongly structured by the presence of cyclones and anticyclones, both in the horizontal and altitudinal dimensions. In certain synoptic conditions, birds may efficiently cross regions with opposing surface wind by choosing a higher flight altitude with more favourable wind. We observed migratory passerines at mid-latitudes that selected high altitude wind optima on particular nights, leading to the formation of structured mig...

  2. A Simple Method for Calculating a Planet's Mean Annual Insolation by Latitude

    CERN Document Server

    Nadeau, Alice

    2015-01-01

    Common methods for calculating a planet's annual insolation by latitude have relied on computationally heavy or complex computer algorithms. In this paper, we show that mean annual insolation by latitude of a planet with obliquity angle $\\beta$ can be found by taking the definite integral of a function of longitude. This leads to faster computations and more accurate results. We discuss differences between our method and selected computational results for insolation found in the literature.

  3. A statistical approach to latitude measurements: Ptolemy's and Riccioli's geographical works as case studies

    Science.gov (United States)

    Santoro, Luca

    2017-08-01

    The aim of this work is to analyze latitude measurements typically used in historical geographical works through a statistical approach. We use two sets of different age as case studies: Ptolemy's Geography and Riccioli's work on geography. A statistical approach to historical latitude and longitude databases can reveal systematic errors in geographical georeferencing processes. On the other hand, once exploiting the right statistical analysis, this approach can also lead to new information about ancient city locations.

  4. CO J = 3 -> 2 observations of translucent and high-latitude molecular clouds

    NARCIS (Netherlands)

    Dishoeck, van E.F.; Phillips, T.G.; Black, J.H.; Gredel, R.

    1991-01-01

    Measurements were carried out on the CO J = 3-2 emission line at 345 GHz from a number of translucent and high-latitude molecular clouds, as well as on the J = 2-1 and J = 1-0 lines of both the (C-12)O and (C-13)O. It is shown that the physical conditions in the high-latitude clouds are very similar

  5. MITHRAS: A Program of Simultaneous Radar Observations of the High-Latitude Auroral Zone.

    Science.gov (United States)

    1982-11-01

    CHATANIKA AND MILL - STONE HILL. The vertical arrow indicates local midnight. 29 electron densities. The nighttime minima are not as well reproduced by the... Nuit de Haute Latitude," Proceedings of GRECO Conference, Grenoble, France (September 1982). Senior, C., P. Bauer, C. Taieb, and Michel Petit, "Le R61e...Alignis, Precipitations Diffuses et Electrojets dans le Secteur Nuit de Haute Latitude," C. Senior, Proceedings of GRECO Conference, Grenoble, 1982. 0"On

  6. Sunspot latitudes during the Maunder Minimum: a machine-readable catalogue from previous studies

    OpenAIRE

    J. M. Vaquero; Nogales, J. M.; Sánchez-Bajo, F.

    2015-01-01

    The Maunder Minimum (1645-1715 approximately) was a period of very low solar activity and a strong hemispheric asymmetry, with most of sunspots in the southern hemisphere. In this paper, two data sets of sunspot latitudes during the Maunder minimum have been recovered for the international scientific community. The first data set is constituted by latitudes of sunspots appearing in the catalogue published by Gustav Sp\\"orer nearly 130 years ago. The second data set is based on the sunspot lat...

  7. Metabolism correlates with variation in post-natal growth rate among songbirds at three latitudes

    Science.gov (United States)

    Ton, Riccardo; Martin, Thomas E.

    2016-01-01

    1. Variation in post-natal growth rates is substantial among organisms and especially strong among latitudes because tropical and south temperate species typically have slower growth than north temperate relatives. Metabolic rate is thought to be a critical mechanism underlying growth rates after accounting for allometric effects of body mass. However, comparative tests on a large spatial scale are lacking, and the importance of metabolism for growth rates remains unclear both within and particularly across latitudes.

  8. No association found between cardiovascular mortality, and job demands and decision latitude: experience from the Västerbotten Intervention Programme in Sweden.

    Science.gov (United States)

    Padyab, Mojgan; Blomstedt, Yulia; Norberg, Margareta

    2014-09-01

    The current prospective study with the longest follow-up period in Northern Sweden aims to investigate the association between job demands and decision latitude and cardiovascular disease (CVD) mortality. Further, we aim to assess the effect of conventional risk factors (i.e., body mass index, alcohol consumption, physical activity, marital status, education and smoking) on the association between job demands and decision latitude and CVD mortality. The data originated from the Linnaeus database, available at the Center for Population Studies, Umeå University, Sweden. A cohort of men and women aged 40, 50 and 60 years were recruited from the Västerbotten Intervention Programme. Deaths due to stroke and myocardial infarction at the end of the follow up are considered the outcome. Baseline job characteristics were defined by the Swedish version of the Karasek demand/control model. Statistical methods include proportional Cox hazard modeling and Relative Excess Risk due to Interaction (RERI) to assess interactions. The findings from this study did not support the association between job demands and decision latitude and CVD mortality. Instead, conventional risk factors were found stronger predictors, most evidently education differentials were associated with CVD mortality. We know from previous research that the greater the attenuation of the gradient after adjustment for a given risk factor, the greater the potential to reduce educational inequality via interventions that target this factor. Based on the present findings of the experience in Västerbotten, further research is needed to identify other risk factors besides job strain and its components that would reduce the socioeconomic gradient in CVD mortality.

  9. Northern Hemisphere forcing of climatic cycles in Antarctica over the past 360,000 years.

    Science.gov (United States)

    Kawamura, Kenji; Parrenin, Frédéric; Lisiecki, Lorraine; Uemura, Ryu; Vimeux, Françoise; Severinghaus, Jeffrey P; Hutterli, Manuel A; Nakazawa, Takakiyo; Aoki, Shuji; Jouzel, Jean; Raymo, Maureen E; Matsumoto, Koji; Nakata, Hisakazu; Motoyama, Hideaki; Fujita, Shuji; Goto-Azuma, Kumiko; Fujii, Yoshiyuki; Watanabe, Okitsugu

    2007-08-23

    The Milankovitch theory of climate change proposes that glacial-interglacial cycles are driven by changes in summer insolation at high northern latitudes. The timing of climate change in the Southern Hemisphere at glacial-interglacial transitions (which are known as terminations) relative to variations in summer insolation in the Northern Hemisphere is an important test of this hypothesis. So far, it has only been possible to apply this test to the most recent termination, because the dating uncertainty associated with older terminations is too large to allow phase relationships to be determined. Here we present a new chronology of Antarctic climate change over the past 360,000 years that is based on the ratio of oxygen to nitrogen molecules in air trapped in the Dome Fuji and Vostok ice cores. This ratio is a proxy for local summer insolation, and thus allows the chronology to be constructed by orbital tuning without the need to assume a lag between a climate record and an orbital parameter. The accuracy of the chronology allows us to examine the phase relationships between climate records from the ice cores and changes in insolation. Our results indicate that orbital-scale Antarctic climate change lags Northern Hemisphere insolation by a few millennia, and that the increases in Antarctic temperature and atmospheric carbon dioxid