Inter-Hemispheric Coupling During Recent North Polar Summer Periods as Predicted by MaCWAVE/MIDAS Rocket Data and Traced by TIMED/SABER Measurements

Science.gov (United States)

Goldberg, Richard A.; Feofilov, Artem G.; Kutepov, Alexander A.; Pesnell W. Dean; Schmidlin, Francis J.

2011-01-01

In July, 2002, the MaCWAVE-MIDAS Rocket Program was launched from Andoya Rocket Range (ARR) in Norway. Data from these flights demonstrated that the polar summer mesosphere during this period was unusual, at least above ARR. Theoretical studies have since been published that imply that the abnormal characteristics of this polar summer were generated by dynamical processes occurring in the southern polar winter hemisphere. We have used data from the SABER instrument aboard the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) Satellite to study these characteristics and compare them with the features observed in the ensuing eight years. For background, the TIMED Satellite was launched on December 7,2001 to study the dynamics and energy of the mesosphere and lower thermosphere. The SABER instrument is a limb scanning infrared radiometer designed to measure temperature of the region as well as a large number of minor constituents. In this study, we review the MaCWAVE rocket results. Next, we investigate the temperature characteristics of the polar mesosphere as a function of spatial and temporal considerations. We have used the most recent SABER dataset (1.07). Weekly averages are used to make comparisons between the winter and summer hemispheres. Furthermore, the data analysis agrees with recent theoretical studies showing that this behavior is a result of anomalous dynamical events in the southern hemisphere. The findings discussed here clearly show the value of scientific rocket flights used in a discovery mode.

Plutonium in Southern Hemisphere Ocean Waters

Energy Technology Data Exchange (ETDEWEB)

Hirose, K. [Sophia University, Tokyo (Japan); Aoyama, M. [Meteorological Research Institute, Tsukuba (Japan); Gastaud, J.; Levy, I. [Marine Environment Laboratories, International Atomic Energy Agency (Monaco); Fukasawa, M. [Japan Agency for Marine-Earth Science and Technology Yokosuka (Japan); Kim, C. -S. [Environment Laboratories, International Atomic Energy Agency, Seibersdorf (Austria); Povinec, P. P. [Comenius University, Bratislava (Slovakia); Roos, P. [Riso National Laboratory, Roskilde (Denmark); Sanchez-Cabeza, J. A. [Universitat Autonoma de Barcelona, Bellaterra (Spain); Yim, S. A. [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

2013-07-15

Plutonium in seawater collected by the BEAGLE2003 cruise was determined using ICP-SF-MS and alpha spectrometry after Fe co-precipitation and radiochemical purification. Levels and distributions of dissolved plutonium activity concentrations in Southern Hemisphere ocean waters are summarized here, including historical data. Pu-239 concentrations in surface water of the central South Pacific (32.5{sup o}S) in 2003 were around 1 mBq/m{sup 3}. The {sup 239}Pu concentrations in the Indian Ocean surface waters (20{sup o}S) were similar to that in the South Pacific, whereas the {sup 239}Pu concentrations in the South Atlantic surface waters (30{sup o}S) were markedly lower than those in the South Pacific and Indian Oceans. The {sup 239}Pu vertical profile pattern was similar to that in the North Pacific subtropical gyre, although {sup 239}Pu concentrations in the deep South Pacific were significantly lower than those in the North Pacific. One of the dominant factors controlling plutonium distributions in the Southern Hemisphere oceans is biogeochemical processes including particle scavenging. (author)

Effect of Gravity Waves from Small Islands in the Southern Ocean on the Southern Hemisphere Atmospheric Circulation

Science.gov (United States)

Garfinkel, C. I.; Oman, L. D.

2018-01-01

The effect of small islands in the Southern Ocean on the atmospheric circulation in the Southern Hemisphere is considered with a series of simulations using the NASA Goddard Earth Observing System Chemistry-Climate Model in which the gravity wave stress generated by these islands is increased to resemble observed values. The enhanced gravity wave drag leads to a 2 K warming of the springtime polar stratosphere, partially ameliorating biases in this region. Resolved wave drag declines in the stratospheric region in which the added orographic gravity waves deposit their momentum, such that changes in gravity waves are partially compensated by changes in resolved waves, though resolved wave drag increases further poleward. The orographic drag from these islands has impacts for surface climate, as biases in tropospheric jet position are also partially ameliorated. These results suggest that these small islands are likely contributing to the missing drag near 60 degrees S in the upper stratosphere evident in many data assimilation products.

Marine anthropogenic radiotracers in the Southern Hemisphere: New sampling and analytical strategies

DEFF Research Database (Denmark)

Levy, I.; Povinec, P.P.; Aoyama, M.

2011-01-01

The Japan Agency for Marine Earth Science and Technology conducted in 2003–2004 the Blue Earth Global Expedition (BEAGLE2003) around the Southern Hemisphere Oceans, which was a rare opportunity to collect many seawater samples for anthropogenic radionuclide studies. We describe here sampling...... showed a reasonable agreement between the participating laboratories. The obtained data on the distribution of 137Cs and plutonium isotopes in seawater represent the most comprehensive results available for the Southern Hemisphere Oceans....

Decadal variability and metastability in the Southern Hemisphere

Science.gov (United States)

O'Kane, Terence; Risbey, James; Franzke, Christian; Horenko, Illia; Monselesan, Didier

2014-05-01

An examination of systematic changes in the metastability of the southern hemisphere 500hPa circulation is performed using both cluster analysis techniques and split flow blocking indices. The cluster methodology is a purely data-driven approach for parametrisation whereby a multi-scale approximation to non-stationary dynamical processes is achieved through optimal sequences of locally stationary fast Vector Auto-Regressive Factor (VARX) processes and some slow (or persistent) hidden process switching between them. Comparison is made with blocking indices commonly used in weather forecasting and climate analysis to identify dynamically relevant metastable regimes in the 500hPa circulation in both reanalysis and AMIP model data sets. Our analysis characterises the metastable regime in both reanalysis and model data sets prior to 1978 as positive and negative phases of a hemispheric mid-latitude blocking state with the Southern Annular Mode (SAM) associated with a transition state. Post 1978, SAM emerges as a true metastable state replacing the negative phase of the hemispheric blocking pattern. The hidden state frequency of occurrences exhibits strong trends. The blocking pattern dominates in the early 1980s then gradually decreases. There is a corresponding increase in the SAM frequency of occurrence. This trend is largely evident in the reanalysis summer and spring but was not evident in the AMIP data set. Non-stationary cluster analysis was then further used to identify the Southern Oceans response to the systematic changes in the mid-latitude atmospheric circulation and identify dynamical regimes associated with subsurface thermocline anomalies which were found to teleconnect the Pacific and Atlantic regions of the Antarctic Circumpolar Current (ACC).

The Signature of Southern Hemisphere Atmospheric Circulation Patterns in Antarctic Precipitation.

Science.gov (United States)

Marshall, Gareth J; Thompson, David W J; van den Broeke, Michiel R

2017-11-28

We provide the first comprehensive analysis of the relationships between large-scale patterns of Southern Hemisphere climate variability and the detailed structure of Antarctic precipitation. We examine linkages between the high spatial resolution precipitation from a regional atmospheric model and four patterns of large-scale Southern Hemisphere climate variability: the southern baroclinic annular mode, the southern annular mode, and the two Pacific-South American teleconnection patterns. Variations in all four patterns influence the spatial configuration of precipitation over Antarctica, consistent with their signatures in high-latitude meridional moisture fluxes. They impact not only the mean but also the incidence of extreme precipitation events. Current coupled-climate models are able to reproduce all four patterns of atmospheric variability but struggle to correctly replicate their regional impacts on Antarctic climate. Thus, linking these patterns directly to Antarctic precipitation variability may allow a better estimate of future changes in precipitation than using model output alone.

Southern hemisphere ocean CO2 uptake: reconciling atmospheric and oceanic estimates

International Nuclear Information System (INIS)

Roy, T.; Matear, R.; Rayner, P.; Francey, R.

2003-01-01

Using an atmospheric inversion model we investigate the southern hemisphere ocean CO 2 uptake. From sensitivity studies that varied both the initial ocean flux distribution and the atmospheric data used in the inversion, our inversion predicted a total (ocean and land) uptake of 1.65-1.90 Gt C/yr. We assess the consistency between the mean southern hemisphere ocean uptake predicted by an atmospheric inversion model for the 1991-1997 period and the T99 ocean flux estimate based on observed pCO 2 in Takahashi et al. (2002; Deep-Sea Res II, 49, 1601-1622). The inversion can not match the large 1.8 Gt C/yr southern extratropical (20-90 deg S) uptake of the T99 ocean flux estimate without producing either unreasonable land fluxes in the southern mid-latitudes or by increasing the mismatches between observed and simulated atmospheric CO 2 data. The southern extratropical uptake is redistributed between the mid and high latitudes. Our results suggest that the T99 estimate of the Southern Ocean uptake south of 50 deg S is too large, and that the discrepancy reflects the inadequate representation of wintertime conditions in the T99 estimate

Humpback whale "super-groups" - A novel low-latitude feeding behaviour of Southern Hemisphere humpback whales (Megaptera novaeangliae) in the Benguela Upwelling System.

Science.gov (United States)

Findlay, Ken P; Seakamela, S Mduduzi; Meÿer, Michael A; Kirkman, Stephen P; Barendse, Jaco; Cade, David E; Hurwitz, David; Kennedy, Amy S; Kotze, Pieter G H; McCue, Steven A; Thornton, Meredith; Vargas-Fonseca, O Alejandra; Wilke, Christopher G

2017-01-01

Southern Hemisphere humpback whales (Megaptera novaeangliae) generally undertake annual migrations from polar summer feeding grounds to winter calving and nursery grounds in subtropical and tropical coastal waters. Evidence for such migrations arises from seasonality of historic whaling catches by latitude, Discovery and natural mark returns, and results of satellite tagging studies. Feeding is generally believed to be limited to the southern polar region, where Antarctic krill (Euphausia superba) has been identified as the primary prey item. Non-migrations and / or suspended migrations to the polar feeding grounds have previously been reported from a summer presence of whales in the Benguela System, where feeding on euphausiids (E. lucens), hyperiid amphipods (Themisto gaudichaudii), mantis shrimp (Pterygosquilla armata capensis) and clupeid fish has been described. Three recent research cruises (in October/November 2011, October/November 2014 and October/November 2015) identified large tightly-spaced groups (20 to 200 individuals) of feeding humpback whales aggregated over at least a one-month period across a 220 nautical mile region of the southern Benguela System. Feeding behaviour was identified by lunges, strong milling and repetitive and consecutive diving behaviours, associated bird and seal feeding, defecations and the pungent "fishy" smell of whale blows. Although no dedicated prey sampling could be carried out within the tightly spaced feeding aggregations, observations of E. lucens in the region of groups and the full stomach contents of mantis shrimp from both a co-occurring predatory fish species (Thyrsites atun) and one entangled humpback whale mortality suggest these may be the primary prey items of at least some of the feeding aggregations. Reasons for this recent novel behaviour pattern remain speculative, but may relate to increasing summer humpback whale abundance in the region. These novel, predictable, inter-annual, low latitude feeding events

Photometry of Southern Hemisphere red dwarf stars

Science.gov (United States)

Weistrop, D.

1980-01-01

Results are presented for a photometric investigation of a spectroscopically selected sample of red dwarf stars in the Southern Hemisphere. Absolute magnitudes and distances for the stars are estimated from broadband red colors. Three stars which may be subluminous are identified, as are several stars which may be within 25 pc. The tangential velocity and velocity dispersion of the sample are similar to values found in other studies of nearby late-type stars.

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

Directory of Open Access Journals (Sweden)

K. A. Stone

2016-02-01

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

Quiet ionospheric currents of the southern hemisphere derived from geomagnetic records

International Nuclear Information System (INIS)

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

1988-01-01

This work describes the month-by-month behavior of the equivalent ionospheric current systems derived from spherical harmonic analyses of the quiet time geomagnetic field daily variations in 1965 at selected observatories representing the three southern global half-sector regions separately encompassing South America, Africa, and Australia. These external Sq current patterns were vortices having mid-latitude foci with midday summertime amplitudes reaching 16.2 x 10 4 A above the midnight level. The wintertime amplitudes were about 10 x 10 4 A smaller. At low latitudes there was a large intrusion of the opposite hemisphere external Sq current system into the wintertime hemisphere at prenoon hours, displacing the primary current vortex to later postnoon hours. The behavior of the southern hemisphere external currents were found to be seasonally similar to those of the northern hemisphere for the same year. The quiet year behavior was compared to the results for the 1958 active year determined earlier by Matsushita. The winter-to-summertime increase in focus current was found to be similar in amplitude for the 2 years. The active year summertime and equinoctial current focus amplitudes were about 2.3 times the amplitudes of corresponding months in the quiet year

A time-calibrated phylogeny of southern hemisphere stoneflies: Testing for Gondwanan origins.

Science.gov (United States)

McCulloch, Graham A; Wallis, Graham P; Waters, Jonathan M

2016-03-01

For more than two centuries biogeographers have attempted to explain why terrestrial or freshwater lineages have geographic distributions broken by oceans, with these disjunct distributions either attributed to vicariance associated with Gondwanan fragmentation or trans-oceanic dispersal. Stoneflies (order: Plecoptera) are a widespread order of freshwater insects whose poor dispersal ability and intolerance for salt water make them ideal candidates for Gondwanan relicts - taxa whose distribution can be explained by vicariant isolation driven by the breakup of Gondwana. Here we reconstruct the phylogenetic relationships among southern hemisphere stoneflies (5 families; 86 genera) using 2864bp of mitochondrial (COI) and nuclear (18S, H3) DNA, with a calibrated relaxed molecular clock used to estimate the chronology of diversification. Our analysis suggests that largely antitropical stonefly sub-orders, Arctoperlaria (northern hemisphere) and Antarctoperlaria (southern hemisphere), were formed approximately 121Ma (95% prior probability distribution 107-143Ma), which may reflect the vicariant rifting of the supercontinent Pangaea. Subsequently, we infer that a single Arctoperlaria lineage has dispersed into southern hemisphere 76Ma (95% range 65-98Ma). The majority of divergences between South American and Australian stonefly lineages appear to coincide with the opening of Drake Passage around 40Ma, suggesting vicariant isolation of these landmasses may be responsible for these biogeographic disjunctions. In contrast, divergences between New Zealand lineages and their sister taxa appear to post-date vicariant timeframes, implying more recent dispersal events. Copyright © 2015 Elsevier Inc. All rights reserved.

Polar cap index as a proxy for hemispheric Joule heating

DEFF Research Database (Denmark)

Chun, F.K.; Knipp, D.J.; McHarg, M.G.

1999-01-01

The polar cap (PC) index measures the level of geomagnetic activity in the polar cap based on magnetic perturbations from overhead ionospheric currents and distant field-aligned currents on the poleward edge of the nightside auroral oval. Because PC essentially measures the main sources of energy...... input into the polar cap, we propose to use PC as a proxy for the hemispheric Joule heat production rate (JH). In this study, JH is estimated from the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure. We fit hourly PC values to hourly averages of JH. Using a data base approximately...

Humpback whale "super-groups" - A novel low-latitude feeding behaviour of Southern Hemisphere humpback whales (Megaptera novaeangliae in the Benguela Upwelling System.

Directory of Open Access Journals (Sweden)

Ken P Findlay

Full Text Available Southern Hemisphere humpback whales (Megaptera novaeangliae generally undertake annual migrations from polar summer feeding grounds to winter calving and nursery grounds in subtropical and tropical coastal waters. Evidence for such migrations arises from seasonality of historic whaling catches by latitude, Discovery and natural mark returns, and results of satellite tagging studies. Feeding is generally believed to be limited to the southern polar region, where Antarctic krill (Euphausia superba has been identified as the primary prey item. Non-migrations and / or suspended migrations to the polar feeding grounds have previously been reported from a summer presence of whales in the Benguela System, where feeding on euphausiids (E. lucens, hyperiid amphipods (Themisto gaudichaudii, mantis shrimp (Pterygosquilla armata capensis and clupeid fish has been described. Three recent research cruises (in October/November 2011, October/November 2014 and October/November 2015 identified large tightly-spaced groups (20 to 200 individuals of feeding humpback whales aggregated over at least a one-month period across a 220 nautical mile region of the southern Benguela System. Feeding behaviour was identified by lunges, strong milling and repetitive and consecutive diving behaviours, associated bird and seal feeding, defecations and the pungent "fishy" smell of whale blows. Although no dedicated prey sampling could be carried out within the tightly spaced feeding aggregations, observations of E. lucens in the region of groups and the full stomach contents of mantis shrimp from both a co-occurring predatory fish species (Thyrsites atun and one entangled humpback whale mortality suggest these may be the primary prey items of at least some of the feeding aggregations. Reasons for this recent novel behaviour pattern remain speculative, but may relate to increasing summer humpback whale abundance in the region. These novel, predictable, inter-annual, low latitude

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.

Antarctic lakes suggest millennial reorganizations of Southern Hemisphere atmospheric and oceanic circulation.

Science.gov (United States)

Hall, Brenda L; Denton, George H; Fountain, Andrew G; Hendy, Chris H; Henderson, Gideon M

2010-12-14

The phasing of millennial-scale oscillations in Antarctica relative to those elsewhere in the world is important for discriminating among models for abrupt climate change, particularly those involving the Southern Ocean. However, records of millennial-scale variability from Antarctica dating to the last glacial maximum are rare and rely heavily on data from widely spaced ice cores, some of which show little variability through that time. Here, we present new data from closed-basin lakes in the Dry Valleys region of East Antarctica that show high-magnitude, high-frequency oscillations in surface level during the late Pleistocene synchronous with climate fluctuations elsewhere in the Southern Hemisphere. These data suggest a coherent Southern Hemisphere pattern of climate change on millennial time scales, at least in the Pacific sector, and indicate that any hypothesis concerning the origin of these events must account for synchronous changes in both high and temperate latitudes.

Marine anthropogenic radiotracers in the Southern Hemisphere: New sampling and analytical strategies

Science.gov (United States)

Levy, I.; Povinec, P. P.; Aoyama, M.; Hirose, K.; Sanchez-Cabeza, J. A.; Comanducci, J.-F.; Gastaud, J.; Eriksson, M.; Hamajima, Y.; Kim, C. S.; Komura, K.; Osvath, I.; Roos, P.; Yim, S. A.

2011-04-01

The Japan Agency for Marine Earth Science and Technology conducted in 2003-2004 the Blue Earth Global Expedition (BEAGLE2003) around the Southern Hemisphere Oceans, which was a rare opportunity to collect many seawater samples for anthropogenic radionuclide studies. We describe here sampling and analytical methodologies based on radiochemical separations of Cs and Pu from seawater, as well as radiometric and mass spectrometry measurements. Several laboratories took part in radionuclide analyses using different techniques. The intercomparison exercises and analyses of certified reference materials showed a reasonable agreement between the participating laboratories. The obtained data on the distribution of 137Cs and plutonium isotopes in seawater represent the most comprehensive results available for the Southern Hemisphere Oceans.

Long-period polar rain variations, solar wind and hemispherically symmetric polar rain

International Nuclear Information System (INIS)

Makita, K.; Meng, C.

1987-01-01

On the basic of electron data obtained by the Defense Meteorological Satellite Program (DMSP) F2 satellite the long-period variations of the polar rain flux are examined for four consecutive solar rotations. It is clearly demonstrated that the asymmetric enhancement of the polar rain flux is strongly controlled by the sector structure of the interplanetary magnetic field (IMF). However, the orbit-to-orbit and day-to-day variations of the polar rain flux are detected even during a very stable sector period, and the polar rain flux does not have any clear relationship to the magnitude of the IMF B/sub x/ or B/sub y/. Thus the polarity of B/sub x/ controls only the accessibility of a polar region. It is also noticed that the intensity of polar rain fluxes does not show any relationship to the density of the solar wind, suggesting that the origin of the polar rain electrons is different from the commonly observed part of the solar wind electron distribution function. In addition to the asymmetric polar rain distribution, increasing polar rain fluxes of similar high intensity are sometimes detected over both polar caps. An examination of more than 1 year's data from the DMSP F2 and F4 satellites shows that simultaneous intense uniform precipitations (>10 7 electrons/cm 2 s sr) over both polar caps are not coincidental; it also shows that the spectra are similar. The occurrence of hemispherically symmetric events is not common. They generally are observed after an IMF sector transition period, during unstable periods in the sector structure, and while the solar wind density is high. copyright American Geophysical Union 1987

Late Cretaceous paleosols as paleoclimate proxies of high-latitude Southern Hemisphere: Mata Amarilla Formation, Patagonia, Argentina

Science.gov (United States)

Varela, Augusto N.; Raigemborn, M. Sol; Richiano, Sebastián; White, Tim; Poiré, Daniel G.; Lizzoli, Sabrina

2018-01-01

Although there is general consensus that a global greenhouse climate characterized the mid-Cretaceous, details of the climate state of the mid-Cretaceous Southern Hemisphere are less clearly understood. In particular, continental paleoclimate reconstructions are scarce and exclusively derived from paleontological records. Using paleosol-derived climofunction studies of the mid- to Upper Cretaceous Mata Amarilla Formation, southern Patagonia, Argentina, we present a reconstruction of the mid-Cretaceous climate of southern South America. Our results indicate that at 60° south paleolatitude during the Cenomanian-Santonian stages, the climate was subtropical temperate-warm (12 °C ± 2.1 °C) and humid (1404 ± 108 mm/yr) with marked rainfall seasonality. These results are consistent with both previous estimations from the fossil floras of the Mata Amarilla Formation and other units of the Southern Hemisphere, and with the previous observations of the displacement of tropical and subtropical floras towards the poles in both hemispheres. The data presented here show a more marked seasonality and slightly lower mean annual precipitation and mean annual temperature values than those recorded at the same paleolatitudes in the Northern Hemisphere.

The Southern Oscillation and northern hemisphere temperature variability

International Nuclear Information System (INIS)

Ropelewski, C.F.; Halpert, M.S.

1990-01-01

The Southern Oscillation (SO) is the best defined and understood mode of interannual climate variability. The extreme phases of the SO have been identified with global-scale variations in the atmosphere/ocean circulation system and with the modulation of monsoon precipitation on the global scale. While SO-related precipitation has been the subject of several studies, the magnitude of the SO-related temperature variability on the global scale has not been well documented. In this paper the authors provide an estimate of the SO-related temperature variability in the context of monitoring global warming related to the increase in greenhouse gases. This analysis suggested that traditional time series of hemispheric and global temperature anomalies for the calendar year may confuse interannual temperature variability associated with the SO and perceived climate trend. Analyses based on calendar-year data are likely to split the effects of the SO-related temperature variability over two years. The Northern Hemisphere cold season (october through March) time series may be more appropriate to separate the SO-related effects on the hemispheric temperature from other modes of variability. mean interannual temperature anomaly differences associated with the extremes of the So are estimated to be 0.2 C for the October-to-March season in the Northern Hemisphere. In areas directly linked to the SO, the mean interannual differences amount to over 0.5 C. The So cannot account for all the variability in the hemispheric times series of surface temperature estimates, but the SO signal must be properly accounted for if these time series are to be understood

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

Science.gov (United States)

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

2018-01-01

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

Southern hemisphere coal characteristics and their impact on plant performance

Energy Technology Data Exchange (ETDEWEB)

Chiou, Y Y; Dickson, A J; Lowe, A; Pearson, J M; Pitman, B L; Semark, P M [Taiwan Power Company (Taiwan)

1992-09-01

The paper reports performance information of specific utilities fired by coal mined in the Southern Hemisphere. It includes information from Pacific Power Services, Australia, the China Light and Power Company, Hong Kong, the Taiwan Power Company, Taiwan, and the South Africa Electricity Power Company, South Africa. 12 refs., 3 figs., 12 tabs.

Response of the polar cap boundary and the current system to changes in IMF observed from the MAGSAT satellite in the southern hemisphere during summer

International Nuclear Information System (INIS)

Bhatnagar, V.P.; Burrows, J.R.

1987-01-01

The magnetic field vector residuals observed from the Magsat satellite have been used to obtain the dependence of the polar cap boundary and the current system on IMF for quiet and mildly disturbed conditions. The study has been carried out for the summer months in the Southern Hemisphere. ''Shear reversals'' (SRs) in vector residuals indicative of the infinite current sheet approximation of the field-aligned currents (FACs) indicate roughly the polar cap boundary or the poleward boundary of the plasma sheet. This is also the poleward edge of the region 1 FACs. The SR is defined to occur at the latitude where the vector goes to minimum and changes direction by approximately 180 0 . It is found that SRs mainly occur when the interplanetary magnetic field (IMF) has a southward-directed Bsub(z) component and in the latitude range of about 70 0 -80 0 . SRs in the dusk sector occur predominantly when the azimuthal component Bsub(y) is positive and in the dawn sector when Bsub(y) is negative, irrespective of the sign of Bsub(z). These results agree with the known merging process of IMF with magnetopause field lines. When SRs occur on both dawn and dusk sectors, the residuals over the entire polar cap are nearly uniform in direction and magnitude, indicating negligible polar currents. Similar behaviour is observed during highly disturbed conditions usually associated with large negative values of Bsub(z). Forty-one Magsat orbits with such SRs are quantitatively modelled for preliminary case studies of the resulting current distribution. It is found that SRs, in the plane perpendicular to the geomagnetic field, for the current vectors and the magnetic vector residuals (perturbations relative to the unperturbed field) occur at almost the same latitudes. The electrojet intensities range from 1.2 x 10 4 to 6.5 x 10 5 A (amperes). A preliminary classification of polar cap boundary crossings characterized by vector rotations rather than SRs also shows that they tend to

The optical and physical properties of atmospheric aerosols over the Indian Antarctic stations during southern hemispheric summer of the International Polar Year 2007-2008

Energy Technology Data Exchange (ETDEWEB)

Chaubey, Jai Prakash; Moorthy, K. Krishna; Babu, S. Suresh; Nair, Vijayakumar S. [Vikram Sarabhai Space Centre, Thiruvananthapuram (India). Space Physics Lab.

2011-07-01

The properties of background aerosols and their dependence on meteorological, geographical and human influence are examined using measured spectral aerosol optical depth (AOD), total mass concentration (MT) and derived number size distribution (NSD) over two distinct coastal locations of Antarctica; Maitri (70 S, 12 E, 123 m m.s.l.) and Larsemann Hills (LH; 69 S, 77 E, 48 m m.s.l.) during southern hemispheric summer of 2007-2008 as a part of the 27th Indian Scientific Expedition to Antarctica (ISEA) during International Polar Year (IPY). Our investigations showed comparable values for the mean columnar AOD at 500 nm over Maitri (0.034{+-}0.005) and LH (0.032{+-}0.006) indicating good spatial homogeneity in the columnar aerosol properties over the coastal Antarctica. Estimation of Angstrom exponent {alpha} showed accumulation mode dominance at Maitri ({alpha}{proportional_to}1.2{+-}0.3) and coarse mode dominance at LH (0.7{+-}0.2). On the other hand, mass concentration (MT) of ambient aerosols showed relatively high values ({approx}8.25{+-}2.87 {mu}g m{sup -3}) at Maitri in comparison to LH (6.03{+-}1.33 {mu}g m{sup -3}). (orig.)

Atmospheric mercury in the Southern Hemisphere tropics: seasonal and diurnal variations and influence of inter-hemispheric transport

Science.gov (United States)

Howard, Dean; Nelson, Peter F.; Edwards, Grant C.; Morrison, Anthony L.; Fisher, Jenny A.; Ward, Jason; Harnwell, James; van der Schoot, Marcel; Atkinson, Brad; Chambers, Scott D.; Griffiths, Alan D.; Werczynski, Sylvester; Williams, Alastair G.

2017-09-01

Mercury is a toxic element of serious concern for human and environmental health. Understanding its natural cycling in the environment is an important goal towards assessing its impacts and the effectiveness of mitigation strategies. Due to the unique chemical and physical properties of mercury, the atmosphere is the dominant transport pathway for this heavy metal, with the consequence that regions far removed from sources can be impacted. However, there exists a dearth of long-term monitoring of atmospheric mercury, particularly in the tropics and Southern Hemisphere. This paper presents the first 2 years of gaseous elemental mercury (GEM) measurements taken at the Australian Tropical Atmospheric Research Station (ATARS) in northern Australia, as part of the Global Mercury Observation System (GMOS). Annual mean GEM concentrations determined at ATARS (0.95 ± 0.12 ng m-3) are consistent with recent observations at other sites in the Southern Hemisphere. Comparison with GEM data from other Australian monitoring sites suggests a concentration gradient that decreases with increasing latitude. Seasonal analysis shows that GEM concentrations at ATARS are significantly lower in the distinct wet monsoon season than in the dry season. This result provides insight into alterations of natural mercury cycling processes as a result of changes in atmospheric humidity, oceanic/terrestrial fetch, and convective mixing, and invites future investigation using wet mercury deposition measurements. Due to its location relative to the atmospheric equator, ATARS intermittently samples air originating from the Northern Hemisphere, allowing an opportunity to gain greater understanding of inter-hemispheric transport of mercury and other atmospheric species. Diurnal cycles of GEM at ATARS show distinct nocturnal depletion events that are attributed to dry deposition under stable boundary layer conditions. These cycles provide strong further evidence supportive of a multi-hop model of GEM

Phenological Changes in the Southern Hemisphere

Science.gov (United States)

Chambers, Lynda E.; Altwegg, Res; Barbraud, Christophe; Barnard, Phoebe; Beaumont, Linda J.; Crawford, Robert J. M.; Durant, Joel M.; Hughes, Lesley; Keatley, Marie R.; Low, Matt; Morellato, Patricia C.; Poloczanska, Elvira S.; Ruoppolo, Valeria; Vanstreels, Ralph E. T.; Woehler, Eric J.; Wolfaardt, Anton C.

2013-01-01

Current evidence of phenological responses to recent climate change is substantially biased towards northern hemisphere temperate regions. Given regional differences in climate change, shifts in phenology will not be uniform across the globe, and conclusions drawn from temperate systems in the northern hemisphere might not be applicable to other regions on the planet. We conduct the largest meta-analysis to date of phenological drivers and trends among southern hemisphere species, assessing 1208 long-term datasets from 89 studies on 347 species. Data were mostly from Australasia (Australia and New Zealand), South America and the Antarctic/subantarctic, and focused primarily on plants and birds. This meta-analysis shows an advance in the timing of spring events (with a strong Australian data bias), although substantial differences in trends were apparent among taxonomic groups and regions. When only statistically significant trends were considered, 82% of terrestrial datasets and 42% of marine datasets demonstrated an advance in phenology. Temperature was most frequently identified as the primary driver of phenological changes; however, in many studies it was the only climate variable considered. When precipitation was examined, it often played a key role but, in contrast with temperature, the direction of phenological shifts in response to precipitation variation was difficult to predict a priori. We discuss how phenological information can inform the adaptive capacity of species, their resilience, and constraints on autonomous adaptation. We also highlight serious weaknesses in past and current data collection and analyses at large regional scales (with very few studies in the tropics or from Africa) and dramatic taxonomic biases. If accurate predictions regarding the general effects of climate change on the biology of organisms are to be made, data collection policies focussing on targeting data-deficient regions and taxa need to be financially and logistically

Phenological changes in the southern hemisphere.

Directory of Open Access Journals (Sweden)

Lynda E Chambers

Full Text Available Current evidence of phenological responses to recent climate change is substantially biased towards northern hemisphere temperate regions. Given regional differences in climate change, shifts in phenology will not be uniform across the globe, and conclusions drawn from temperate systems in the northern hemisphere might not be applicable to other regions on the planet. We conduct the largest meta-analysis to date of phenological drivers and trends among southern hemisphere species, assessing 1208 long-term datasets from 89 studies on 347 species. Data were mostly from Australasia (Australia and New Zealand, South America and the Antarctic/subantarctic, and focused primarily on plants and birds. This meta-analysis shows an advance in the timing of spring events (with a strong Australian data bias, although substantial differences in trends were apparent among taxonomic groups and regions. When only statistically significant trends were considered, 82% of terrestrial datasets and 42% of marine datasets demonstrated an advance in phenology. Temperature was most frequently identified as the primary driver of phenological changes; however, in many studies it was the only climate variable considered. When precipitation was examined, it often played a key role but, in contrast with temperature, the direction of phenological shifts in response to precipitation variation was difficult to predict a priori. We discuss how phenological information can inform the adaptive capacity of species, their resilience, and constraints on autonomous adaptation. We also highlight serious weaknesses in past and current data collection and analyses at large regional scales (with very few studies in the tropics or from Africa and dramatic taxonomic biases. If accurate predictions regarding the general effects of climate change on the biology of organisms are to be made, data collection policies focussing on targeting data-deficient regions and taxa need to be financially

Reaching Across the Hemispheres with Science, Language, Arts and Technology

Science.gov (United States)

Sparrow, E. B.; Zicus, S.; Miller, A.; Baird, A.; Page, G.

2009-12-01

Twelve Alaskan elementary and middle school classes (grades 3-8) partnered with twelve Australian middle school classes, with each pair using web-based strategies to develop a collaborative ice-mystery fictional book incorporating authentic polar science. Three professional development workshops were held, bringing together educators and polar scientists in two IPY education outreach projects. The Alaska workshop provided an opportunity to bring together the North American teachers for lessons on arctic and antarctic science and an earth system science program Seasons and Biomes measurement protocols, as well as methods in collaborative e-writing and art in Ice e-Mysteries: Global Student Polar e-books project. Teachers worked with University of Alaska Fairbanks (UAF) and Australian scientists to become familiar with Arctic science research, science artifacts and resources available at UAF and the University of Alaska Museum of the North. In Australia, teachers received a similar project training through the Tasmania Museum and Art Gallery (TMAG) Center for Learning and Discovery on Antarctic science and the University of Tasmania. The long-distance collaboration was accomplished through Skype, emails and a TMAG supported website. A year later, Northern Hemisphere and Southern Hemisphere teacher partners met in a joint workshop in Tasmania, to share their experiences, do project assessments and propose activities for future collaborations. The Australian teachers received training on Seasons and Biomes scientific measurements and the Alaskan teachers, on Tasmanian vegetation, fauna and indigenous culture, Antarctic and Southern ocean studies. This innovative project produced twelve e-polar books written and illustrated by students; heightened scientific literacy about the polar regions and the earth system; increased awareness of the environment and indigenous cultures; stronger connections to the scientific community; and lasting friendships. It also resulted in

NOAA JPSS Visible Infrared Imaging Radiometer Suite (VIIRS) Polar Winds from NDE

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains the Level 3 Polar Winds Northern and Southern Hemisphere datasets. The Level 3 Polar Winds data from VIIRS for the Arctic and Antarctic from 65...

HEMISPHERIC ASYMMETRIES IN THE POLAR SOLAR WIND OBSERVED BY ULYSSES NEAR THE MINIMA OF SOLAR CYCLES 22 AND 23

Energy Technology Data Exchange (ETDEWEB)

Ebert, R. W.; Dayeh, M. A.; Desai, M. I.; McComas, D. J. [Southwest Research Institute, P.O. Drawer 28510, San Antonio, TX 78228 (United States); Pogorelov, N. V. [Physics Department, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)

2013-05-10

We examined solar wind plasma and interplanetary magnetic field (IMF) observations from Ulysses' first and third orbits to study hemispheric differences in the properties of the solar wind and IMF originating from the Sun's large polar coronal holes (PCHs) during the declining and minimum phase of solar cycles 22 and 23. We identified hemispheric asymmetries in several parameters, most notably {approx}15%-30% south-to-north differences in averages for the solar wind density, mass flux, dynamic pressure, and energy flux and the radial and total IMF magnitudes. These differences were driven by relatively larger, more variable solar wind density and radial IMF between {approx}36 Degree-Sign S-60 Degree-Sign S during the declining phase of solar cycles 22 and 23. These observations indicate either a hemispheric asymmetry in the PCH output during the declining and minimum phase of solar cycles 22 and 23 with the southern hemisphere being more active than its northern counterpart, or a solar cycle effect where the PCH output in both hemispheres is enhanced during periods of higher solar activity. We also report a strong linear correlation between these solar wind and IMF parameters, including the periods of enhanced PCH output, that highlight the connection between the solar wind mass and energy output and the Sun's magnetic field. That these enhancements were not matched by similar sized variations in solar wind speed points to the mass and energy responsible for these increases being added to the solar wind while its flow was subsonic.

HEMISPHERIC ASYMMETRIES IN THE POLAR SOLAR WIND OBSERVED BY ULYSSES NEAR THE MINIMA OF SOLAR CYCLES 22 AND 23

International Nuclear Information System (INIS)

Ebert, R. W.; Dayeh, M. A.; Desai, M. I.; McComas, D. J.; Pogorelov, N. V.

2013-01-01

We examined solar wind plasma and interplanetary magnetic field (IMF) observations from Ulysses' first and third orbits to study hemispheric differences in the properties of the solar wind and IMF originating from the Sun's large polar coronal holes (PCHs) during the declining and minimum phase of solar cycles 22 and 23. We identified hemispheric asymmetries in several parameters, most notably ∼15%-30% south-to-north differences in averages for the solar wind density, mass flux, dynamic pressure, and energy flux and the radial and total IMF magnitudes. These differences were driven by relatively larger, more variable solar wind density and radial IMF between ∼36°S-60°S during the declining phase of solar cycles 22 and 23. These observations indicate either a hemispheric asymmetry in the PCH output during the declining and minimum phase of solar cycles 22 and 23 with the southern hemisphere being more active than its northern counterpart, or a solar cycle effect where the PCH output in both hemispheres is enhanced during periods of higher solar activity. We also report a strong linear correlation between these solar wind and IMF parameters, including the periods of enhanced PCH output, that highlight the connection between the solar wind mass and energy output and the Sun's magnetic field. That these enhancements were not matched by similar sized variations in solar wind speed points to the mass and energy responsible for these increases being added to the solar wind while its flow was subsonic.

First record of Rhizoscyphus ericae in Southern Hemisphere´s Ericaceae

Czech Academy of Sciences Publication Activity Database

Bruzone, M. C.; Fehrer, Judith; Fontenla, S. B.; Vohník, Martin

2017-01-01

Roč. 27, č. 2 (2017), s. 147-163 ISSN 0940-6360 R&D Projects: GA MŠk(CZ) 7AMB14AR003; GA MŠk 7AMB12AR014 Institutional support: RVO:67985939 Keywords : ericoid mycorrhiza * Rhizoscipus Ericae * Southern Hemisphere Subject RIV: EH - Ecology, Behaviour OBOR OECD: Ecology Impact factor: 3.047, year: 2016

SIMULATION STUDY OF HEMISPHERIC PHASE-ASYMMETRY IN THE SOLAR CYCLE

Energy Technology Data Exchange (ETDEWEB)

Shukuya, D.; Kusano, K., E-mail: kusano@nagoya-u.jp [Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 4648601 (Japan)

2017-01-20

Observations of the Sun suggest that solar activities systematically create north–south hemispheric asymmetries. For instance, the hemisphere in which sunspot activity is more active tends to switch after the early half of each solar cycle. Svalgaard and Kamide recently pointed out that the time gaps of polar field reversal between the northern and southern hemispheres are simply consequences of the asymmetry of sunspot activity. However, the mechanism underlying the asymmetric feature in solar cycle activity is not yet well understood. In this paper, in order to explain the cause of the asymmetry from the theoretical point of view, we investigate the relationship between the dipole- and quadrupole-type components of the magnetic field in the solar cycle using the mean-field theory based on the flux transport dynamo model. As a result, we found that there are two different attractors of the solar cycle, in which either the north or the south polar field is first reversed, and that the flux transport dynamo model explains well the phase-asymmetry of sunspot activity and the polar field reversal without any ad hoc source of asymmetry.

In Situ Atmospheric Pressure Measurements in the Martian Southern Polar Region: Mars Volatiles and Climate Surveyor Meteorology Package on the Mars Polar Lander

Science.gov (United States)

Harri, A.-M.; Polkko, J.; Siili, T.; Crisp, D.

1998-01-01

Pressure observations are crucial for the success of the Mars Volatiles and Climate Surveyor (MVACS) Meteorology (MET) package onboard the Mars Polar Lander (MPL), due for launch early next year. The spacecraft is expected to land in December 1999 (L(sub s) = 256 degrees) at a high southern latitude (74 degrees - 78 degrees S). The nominal period of operation is 90 sols but may last up to 210 sols. The MVACS/MET experiment will provide the first in situ observations of atmospheric pressure, temperature, wind, and humidity in the southern hemisphere of Mars and in the polar regions. The martian atmosphere goes through a large-scale atmospheric pressure cycle due to the annual condensation/sublimation of the atmospheric CO2. Pressure also exhibits short period variations associated with dust storms, tides, and other atmospheric events. A series of pressure measurements can hence provide us with information on the large-scale state and dynamics of the atmosphere, including the CO2 and dust cycles as well as local weather phenomena. The measurements can also shed light on the shorter time scale phenomena (e.g., passage of dust devils) and hence be important in contributing to our understanding of mixing and transport of heat, dust, and water vapor.

S-N secular ocean tide: explanation of observably coastal velocities of increase of a global mean sea level and mean sea levels in northern and southern hemispheres and prediction of erroneous altimetry velocities

Science.gov (United States)

Barkin, Yury

2010-05-01

The phenomenon of contrast secular changes of sea levels in the southern and northern hemispheres, predicted on the basis of geodynamic model about the forced relative oscillations and displacements of the Earth shells, has obtained a theoretical explanation. In northern hemisphere the mean sea level of ocean increases with velocity about 2.45±0.32 mm/yr, and in a southern hemisphere the mean sea level increases with velocity about 0.67±0.30 mm/yr. Theoretical values of velocity of increase of global mean sea level of ocean has been estimated in 1.61±0.36 mm/yr. 1 Introduction. The secular drift of the centre of mass of the Earth in the direction of North Pole with velocity about 12-20 mm/yr has been predicted by author in 1995 [1], [2], and now has confirmed with methods of space geodesy. For example the DORIS data in period 1999-2008 let us to estimate velocity of polar drift in 5.24±0.29 mm/yr [3]. To explain this fundamental planetary phenomenon it is possible only, having admitted, that similar northern drift tests the centre of mass of the liquid core relatively to the centre of mass of viscous-elastic and thermodynamically changeable mantle with velocity about 2-3 cm/yr in present [4]. The polar drift of the Earth core with huge superfluous mass results in slow increase of a gravity in northern hemisphere with a mean velocity about 1.4 ?Gal and to its decrease approximately with the same mean velocity in southern hemisphere [5]. This conclusion-prediction has obtained already a number of confirmations in precision gravimetric observations fulfilled in last decade around the world [6]. Naturally, a drift of the core is accompanied by the global changes (deformations) of all layers of the mantle and the core, by inversion changes of their tension states when in one hemisphere the tension increases and opposite on the contrary - decreases. Also it is possible that thermodynamical mechanism actively works with inversion properties of molting and

The impact of the pandemic influenza A(H1N1) 2009 virus on seasonal influenza A viruses in the southern hemisphere, 2009.

Science.gov (United States)

Blyth, C C; Kelso, A; McPhie, K A; Ratnamohan, V M; Catton, M; Druce, J D; Smith, D W; Williams, S H; Huang, Q S; Lopez, L; Schoub, B D; Venter, M; Dwyer, D E

2010-08-05

Data collected over winter 2009 by five World Health Organisation National Influenza Centres in the southern hemisphere were used to examine the circulation of pandemic and seasonal influenza A strains during the first pandemic wave in the southern hemisphere.There is compelling evidence that the pandemic influenza A(H1N1) 2009 virus significantly displaced seasonal influenza A(H1N1) and, to a lesser extent, A(H3N2) viruses circulating in the southern hemisphere. Complete replacement of seasonal influenza A strains, however, was not observed during the first pandemic wave.

Plutonium in Southern Hemisphere ocean Waters

DEFF Research Database (Denmark)

Hirose, K.; Aoyama, M.; Gastaud, J.

2013-01-01

Plutonium in seawater collected by the BEAGLE2003 cruise was determined using ICP- SF-MS and alpha spectrometry after Fe co-precipitation and radiochemical purification. Levels and distributions of dissolved plutonium activity concentrations in Southern Hemisphere ocean waters are summarized here......, including historical data. Pu-239 concentrations in surface water----of the central South Pacific (32.5 °S) in 2003 were around 1 mBq/m3. The 239Pu concentrations in the Indian Ocean surface waters (20°S) were similar to that in the South Pacific, whereas the 239Pu concentrations in the South Atlantic...... surface waters (30°S) were markedly lower than those in the South Pacific and Indian Oceans. The 239Pu vertical profile pattern was similar to that in the North Pacific subtropical gyre, although 239Pu concentrations in the deep South Pacific were significantly lower than those in the North Pacific. One...

Evaluation of the tropospheric flows to a major Southern Hemisphere stratospheric warming event using NCEP/NCAR Reanalysis data with a PSU/NCAR nudging MM5V3 model

Science.gov (United States)

Wang, K.

2008-04-01

Previous studies of the exceptional 2002 Southern Hemisphere (SH) stratospheric warming event lead to some uncertainty, namely the question of whether excessive heat fluxes in the upper troposphere and lower stratosphere are a symptom or cause of the 2002 SH warming event. In this work, we use a hemispheric version of the MM5 model with nudging capability and we devised a novel approach to separately test the significance of the stratosphere and troposphere for this year. We paired the flow conditions from 2002 in the stratosphere and troposphere, respectively, against the conditions in 1998 (a year with displaced polar vortex) and in 1948 (a year with strong polar vortex that coincided with the geographical South Pole). Our experiments show that the flow conditions from below determine the stratospheric flow features over the polar region. Regardless of the initial stratospheric conditions in 1998 or 1948, when we simulated these past stratospheres with the troposphere/lower stratosphere conditions constrained to 2002 levels, the simulated middle stratospheres resemble those observed in 2002 stratosphere over the polar region. On the other hand, when the 2002 stratosphere was integrated with the troposphere/lower stratosphere conductions constrained to 1948 and 1998, respectively, the simulated middle stratospheric conditions over the polar region shift toward those of 1948 and 1998. Thus, our experiments further support the wave-forcing theory as the cause of the 2002 SH warming event.

Ecological change drives a decline in mercury concentrations in southern Beaufort Sea polar bears

Science.gov (United States)

McKinney, Melissa A.; Atwood, Todd C.; Pedro, Sara; Peacock, Elizabeth

2017-01-01

We evaluated total mercury (THg) concentrations and trends in polar bears from the southern Beaufort Sea subpopulation from 2004 to 2011. Hair THg concentrations ranged widely among individuals from 0.6 to 13.3 μg g–1 dry weight (mean: 3.5 ± 0.2 μg g–1). Concentrations differed among sex and age classes: solitary adult females ≈ adult females with cubs ≈ subadults > adult males ≈ yearlings > cubs-of-the-year ≈ 2 year old dependent cubs. No variation was observed between spring and fall samples. For spring-sampled adults, THg concentrations declined by 13% per year, contrasting recent trends observed for other Western Hemispheric Arctic biota. Concentrations also declined by 15% per year considering adult males only, while a slower, nonsignificant decrease of 4.4% per year was found for adult females. Lower THg concentrations were associated with higher body mass index (BMI) and higher proportions of lower trophic position food resources consumed. Because BMI and diet were related, and the relationship to THg was strongest for BMI, trends were re-evaluated adjusting for BMI as the covariate. The adjusted annual decline was not significant. These findings indicate that changes in foraging ecology, not declining environmental concentrations of mercury, are driving short-term declines in THg concentrations in southern Beaufort Sea polar bears.

Southern Hemisphere extratropical circulation: Recent trends and natural variability

Science.gov (United States)

Thomas, Jordan L.; Waugh, Darryn W.; Gnanadesikan, Anand

2015-07-01

Changes in the Southern Annular Mode (SAM), Southern Hemisphere (SH) westerly jet location, and magnitude are linked with changes in ocean circulation along with ocean heat and carbon uptake. Recent trends have been observed in these fields but not much is known about the natural variability. Here we aim to quantify the natural variability of the SH extratropical circulation by using Coupled Model Intercomparison Project Phase 5 (CMIP5) preindustrial control model runs and compare with the observed trends in SAM, jet magnitude, and jet location. We show that trends in SAM are due partly to external forcing but are not outside the natural variability as described by these models. Trends in jet location and magnitude, however, lie outside the unforced natural variability but can be explained by a combination of natural variability and the ensemble mean forced trend. These results indicate that trends in these three diagnostics cannot be used interchangeably.

IceVeto: Extended PeV neutrino astronomy in the Southern Hemisphere with IceCube

Energy Technology Data Exchange (ETDEWEB)

Auffenberg, Jan [Physikalisches Institut IIIB RWTH Aachen D-52056, Aachen (Germany); Collaboration: IceCube Collaboration

2014-11-18

IceCube, the world's largest high-energy neutrino observatory, built at the South Pole, recently reported evidence of an astrophysical neutrino flux extending to PeV energies in the Southern Hemisphere. This observation raises the question of how the sensitivity in this energy range could be further increased. In the down-going sector, in IceCube's case the Southern Hemisphere, backgrounds from atmospheric muons and neutrinos pose a challenge to the identification of an astrophysical neutrino flux. The IceCube analysis, that led to the evidence for astrophysical neutrinos, is based on an in-ice veto strategy for background rejection. One possibility available to IceCube is the concept of an extended surface detector, IceVeto, which could allow the rejection of a large fraction of atmospheric backgrounds, primarily for muons from cosmic ray (CR) air showers as well as from neutrinos in the same air showers. Building on the experience of IceTop/IceCube, possibly the most cost-effective and sensitive way to build IceVeto is as an extension of the IceTop detector, with simple photomultiplier based detector modules for CR air shower detection. Initial simulations and estimates indicate that such a veto detector will significantly increase the sensitivity to an astrophysical flux of ν{sub μ} induced muon tracks in the Southern Hemisphere compared to current analyses. Here we present the motivation and capabilities based on initial simulations. Conceptual ideas for a simplified surface array will be discussed briefly.

Topics in extragalactic astronomy with special reference to the southern hemisphere

International Nuclear Information System (INIS)

Vaucouleurs, G. De

1977-01-01

The following topics are covered: classification of galaxies; photometry, colorimetry, spectrophotometry of galaxies; type I supernovae as checks of cosmological models; diameters of galaxies; extragalactic distance indicators; Local Group and nearby group of galaxies; structure of the Local Supercluster of galaxies; anisotropy of the redshifts and kinematics of the Local Supercluster; large scale distribution of galaxies and clusters of galaxies; galaxy counts and probes in depth; problems in the southern hemisphere. (U.K.)

The storm tracks and the energy cycle of the Southern Hemisphere: sensitivity to sea-ice boundary conditions

Directory of Open Access Journals (Sweden)

C. G. Menéndez

1999-11-01

Full Text Available The effect of sea-ice on various aspects of the Southern Hemisphere (SH extratropical climate is examined. Two simulations using the LMD GCM are performed: a control run with the observed sea-ice distribution and an anomaly run in which all SH sea-ice is replaced by open ocean. When sea-ice is removed, the mean sea level pressure displays anomalies predominantly negatives near the Antarctic coast. In general, the meridional temperature gradient is reduced over most of the Southern Ocean, the polar jet is weaker and the sea level pressure rises equatorward of the control ice edge. The high frequency filtered standard deviation of both the sea level pressure and the 300-hPa geopotential height decreases over the southern Pacific and southwestern Atlantic oceans, especially to the north of the ice edge (as prescribed in the control. In contrast, over the Indian Ocean the perturbed simulation exhibits less variability equatorward of about 50°S and increased variability to the south. The zonal averages of the zonal and eddy potential and kinetic energies were evaluated. The effect of removing sea-ice is to diminish the available potential energy of the mean zonal flow, the available potential energy of the perturbations, the kinetic energy of the growing disturbances and the kinetic energy of the mean zonal flow over most of the Southern Ocean. The zonally averaged intensity of the subpolar trough and the rate of the baroclinic energy conversions are also weaker.Key words. Air-sea interactions · Meteorology and atmospheric dynamics (climatology; ocean · atmosphere interactions

The storm tracks and the energy cycle of the Southern Hemisphere: sensitivity to sea-ice boundary conditions

Directory of Open Access Journals (Sweden)

C. G. Menéndez

Full Text Available The effect of sea-ice on various aspects of the Southern Hemisphere (SH extratropical climate is examined. Two simulations using the LMD GCM are performed: a control run with the observed sea-ice distribution and an anomaly run in which all SH sea-ice is replaced by open ocean. When sea-ice is removed, the mean sea level pressure displays anomalies predominantly negatives near the Antarctic coast. In general, the meridional temperature gradient is reduced over most of the Southern Ocean, the polar jet is weaker and the sea level pressure rises equatorward of the control ice edge. The high frequency filtered standard deviation of both the sea level pressure and the 300-hPa geopotential height decreases over the southern Pacific and southwestern Atlantic oceans, especially to the north of the ice edge (as prescribed in the control. In contrast, over the Indian Ocean the perturbed simulation exhibits less variability equatorward of about 50°S and increased variability to the south. The zonal averages of the zonal and eddy potential and kinetic energies were evaluated. The effect of removing sea-ice is to diminish the available potential energy of the mean zonal flow, the available potential energy of the perturbations, the kinetic energy of the growing disturbances and the kinetic energy of the mean zonal flow over most of the Southern Ocean. The zonally averaged intensity of the subpolar trough and the rate of the baroclinic energy conversions are also weaker.

Key words. Air-sea interactions · Meteorology and atmospheric dynamics (climatology; ocean · atmosphere interactions

Classification of hemispheric monthly mean stratospheric potential vorticity fields

Directory of Open Access Journals (Sweden)

R. Huth

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

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

Radiocarbon as a Novel Tracer of Extra-Antarctic Feeding in Southern Hemisphere Humpback Whales.

Science.gov (United States)

Eisenmann, Pascale; Fry, Brian; Mazumder, Debashish; Jacobsen, Geraldine; Holyoake, Carlysle Sian; Coughran, Douglas; Bengtson Nash, Susan

2017-06-29

Bulk stable isotope analysis provides information regarding food web interactions, and has been applied to several cetacean species for the study of migration ecology. One limitation in bulk stable isotope analysis arises when a species, such as Southern hemisphere humpback whales, utilises geographically distinct food webs with differing isotopic baselines. Migrations to areas with different baselines can result in isotopic changes that mimic changes in feeding relations, leading to ambiguous food web interpretations. Here, we demonstrate the novel application of radiocarbon measurement for the resolution of such ambiguities. Radiocarbon was measured in baleen plates from humpback whales stranded in Australia between 2007 and 2013, and in skin samples collected in Australia and Antarctica from stranded and free-ranging animals. Radiocarbon measurements showed lower values for Southern Ocean feeding than for extra-Antarctic feeding in Australian waters. While the whales mostly relied on Antarctic-derived energy stores during their annual migration, there was some evidence of feeding within temperate zone waters in some individuals. This work, to our knowledge, provides the first definitive biochemical evidence for supplementary feeding by southern hemisphere humpback whales within temperate waters during migration. Further, the work contributes a powerful new tool (radiocarbon) for tracing source regions and geographical feeding.

Evidence for long-range transport of carbon monoxide in the Southern Hemisphere from SCIAMACHY observations

NARCIS (Netherlands)

Gloudemans, A.M.S.; Krol, M.C.; Meirink, J.F.; de Laat, A.T.J.; van der Werf, G.R.; Schrijver, H.; van den Broek, M.M.P.; Aben, I.

2006-01-01

The SCIAMACHY satellite instrument shows enhanced carbon monoxide (CO) columns in the Southern Hemisphere during the local Spring. Chemistry-transport model simulations using the new GFEDv2 biomass-burning emission database show a similar temporal and spatial CO distribution, indicating that the

Plastic ingestion by fish in the Southern Hemisphere: A baseline study and review of methods.

Science.gov (United States)

Cannon, Seon M E; Lavers, Jennifer L; Figueiredo, Bianca

2016-06-15

Plastic ingestion is well documented among marine birds and sea turtles but fewer studies have investigated ingestion in fish, particularly in the Southern Hemisphere. We investigated the frequency of plastic ingestion in 21 species of fish and one species of cephalopod. The overall occurrence of plastic ingestion was 0.3%. Two micro-plastic items were recovered from the gastrointestinal tract of a single Antarctic toothfish (Dissostichus mawsoni). Ingestion rates were similar to other studies of fish conducted in both the Northern and Southern Hemispheres, however comparisons across species and locations are challenging due to the lack of consistency in the identification and classification of plastic debris. In response, we propose a standardised sampling protocol based on the available literature to provide a stronger basis for comparisons among existing and future studies of plastic ingestion in fish. Copyright © 2016 Elsevier Ltd. All rights reserved.

Darwin as a plant scientist: a Southern Hemisphere perspective.

Science.gov (United States)

Hopper, Stephen D; Lambers, Hans

2009-08-01

Events around the world this year celebrate the bicentenary of the birth of Charles Darwin (1809-1882) and the sesquicentenary of publication of his most important work, The Origin of Species (Darwin 1859). The associated plethora of books and papers now appearing to commemorate Darwin's work continue the traditional emphasis on his zoological and geological contributions. There has been some recent attention directed towards Darwin's relatively unsung but significant accomplishments as a botanist. Here, we bring together a review of Darwin's botanical discoveries and experiments and relevant aspects of his geological investigations, with a focus on the Southern Hemisphere. This is a relatively unexplored aspect of Darwin's contributions that yields some new insights meriting future research.

Polar vortex evolution during Northern Hemispheric winter 2004/05

Directory of Open Access Journals (Sweden)

T. Chshyolkova

2007-06-01

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

A Southern Hemisphere origin for campanulid angiosperms, with traces of the break-up of Gondwana.

Science.gov (United States)

Beaulieu, Jeremy M; Tank, David C; Donoghue, Michael J

2013-04-08

New powerful biogeographic methods have focused attention on long-standing hypotheses regarding the influence of the break-up of Gondwana on the biogeography of Southern Hemisphere plant groups. Studies to date have often concluded that these groups are too young to have been influenced by these ancient continental movements. Here we examine a much larger and older angiosperm clade, the Campanulidae, and infer its biogeographic history by combining Bayesian divergence time information with a likelihood-based biogeographic model focused on the Gondwanan landmasses. Our analyses imply that campanulids likely originated in the middle Albian (~105 Ma), and that a substantial portion of the early evolutionary history of campanulids took place in the Southern Hemisphere, despite their greater species richness in the Northern Hemisphere today. We also discovered several disjunctions that show biogeographic and temporal correspondence with the break-up of Gondwana. While it is possible to discern traces of the break-up of Gondwana in clades that are old enough, it will generally be difficult to be confident in continental movement as the prime cause of geographic disjunctions. This follows from the need for the geographic disjunction, the inferred biogeographic scenario, and the dating of the lineage splitting events to be consistent with the causal hypothesis.

Hemispheric Asymmetry of Global Warming Explained by a Conceptual Model

Science.gov (United States)

Funke, C. S.; Alexeev, V. A.

2017-12-01

Polar Amplification, the process of amplified warming at high latitudes, manifests itself differently in the Arctic and Antarctic. Not only is the temperature increase in the Arctic more pronounced than in the Antarctic but the dramatic sea ice decline in the Arctic over the last few decades also contrasts sharply with trendless to weak positive trend of Antarctic sea ice throughout the same period. This asymmetric behavior is often partly attributed to the differences in configuration of continents in the Arctic and Antarctic: the Arctic Ocean is surrounded by land while the Southern Ocean has a continent in the middle. A simple conceptual energy balance model of Budyko-Sellers type, accounting for differences between the Northern and Southern hemispheres, is applied to study the mechanisms of climate sensitivity to a variety of forcings. Asymmetry in major modes of variability is explained using an eigenmode analysis of the linearized model. Negative forcings over Antarctica such as from ozone depletion were found to have an amplified effect on southern hemisphere climate and may be an important cause of the muted warming and slightly positive Antarctic sea ice trend.

Climate change induced by Southern Hemisphere desertification

Science.gov (United States)

Wang, Ye; Yan, Xiaodong

2017-12-01

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

Simultaneous observation of traveling ionospheric disturbances in the Northern and Southern Hemispheres

Directory of Open Access Journals (Sweden)

C. E. Valladares

2009-04-01

Full Text Available Measurements of total electron content (TEC using 263 GPS receivers located in the North and South America continents are presented to demonstrate the simultaneous existence of traveling ionospheric disturbances (TID at high, mid, and low latitudes, and in both Northern and Southern Hemispheres. The TID observations pertain to the magnetically disturbed period of 29–30 October 2003 also known as the Halloween storm. The excellent quality of the TEC measurements makes it possible to calculate and remove the diurnal variability of TEC and then estimate the amplitude, wavelength, spectral characteristics of the perturbations, and the approximate velocity of the AGW. On 29 October 2003 between 17:00 and 19:00 UT, there existed a sequence of TEC perturbations (TECP, which were associated with the transit of atmospheric gravity waves (AGW propagating from both auroral regions toward the geographic equator. A marked difference was found between the northern and southern perturbations. In the Northern Hemisphere, the preferred horizontal wavelength varies between 1500 and 1800 km; the propagation velocity is near 700 m/s and the perturbation amplitude about 1 TEC unit (TECu. South of the geographic equator the wavelength of the TECP is as large as 2700 km, the velocity is about 550 m/s, and the TECP amplitude is 3 TECu. Concurrently with our observations, the Jicamarca digisonde observed virtual height traces that exhibited typical features that are associated with TIDs. Here, it is suggested that differences in the local conductivity between northern and southern auroral ovals create a different Joule heating energy term. The quality of these observations illustrates the merits of GPS receivers to probe the ionosphere and thermosphere.

Southern Hemisphere circulation signals in connection with winter rainfall forecasting in central Chile

International Nuclear Information System (INIS)

Rutlant, J.; Aceituno, P.

1991-05-01

The possibility of detecting easterly propagating low frequency signals in the Southern Hemispheric circulation is explored in connection with the assessment of a possible seasonal rainfall forecast in central Chile. The analysis has focused on the seasonal variability associated with the biennial component of the Southern Oscillation (SO) and on the one resulting from superimposed intraseasonal oscillations, in relation with winter precipitation and individual rainfall events, respectively. Based on a previous work, relating wet winters to frequent blocks to the SW of South America during warm events of the SO, time-longitude cross sections of a 5-day average blocking index (BI) calculated from ECMWF 200 hPa daily hemispheric analyses for the period 1980-1987 are presented. A general eastward displacement of western and central Pacific positive BI areas seems to characterize the developing phase of warm SO events and vice versa, while intraseasonal variability patterns appear to be related to single rainstorms, either when the positive BI phase of the wave amplifies while crossing the western Pacific or when it reaches the far southeastern Pacific, frequently with a double block structure. It is concluded that the behaviour of both sources of variability is consistent with previously described teleconnection patterns for ENSO events in the southern winter, and that a primary prospect for winter precipitation and for the occurrence of relatively large individual rainstorms in central Chile could be obtained following the filtered BI and 500 hPa height anomalies in both time scales during the fall season. (author). 28 refs, 12 figs

Interannual modes of variability of Southern Hemisphere atmospheric circulation in CMIP3 models

International Nuclear Information System (INIS)

Grainger, S; Frederiksen, C S; Zheng, X

2010-01-01

The atmospheric circulation acts as a bridge between large-scale sources of climate variability, and climate variability on regional scales. Here a statistical method is applied to monthly mean Southern Hemisphere 500hPa geopotential height to separate the interannual variability of the seasonal mean into intraseasonal and slowly varying (time scales of a season or longer) components. Intraseasonal and slow modes of variability are estimated from realisations of models from the Coupled Model Intercomparison Project Phase 3 (CMIP3) twentieth century coupled climate simulation (20c3m) and are evaluated against those estimated from reanalysis data. The intraseasonal modes of variability are generally well reproduced across all CMIP3 20c3m models for both Southern Hemisphere summer and winter. The slow modes are in general less well reproduced than the intraseasonal modes, and there are larger differences between realisations than for the intraseasonal modes. New diagnostics are proposed to evaluate model variability. It is found that differences between realisations from each model are generally less than inter-model differences. Differences between model-mean diagnostics are found. The results obtained are applicable to assessing the reliability of changes in atmospheric circulation variability in CMIP3 models and for their suitability for further studies of regional climate variability.

Five-year records of mercury wet deposition flux at GMOS sites in the Northern and Southern hemispheres

CSIR Research Space (South Africa)

Sprovieri, F

2017-02-01

Full Text Available samples were collected for approximately 5 years at 17 selected GMOS monitoring sites located in the Northern and Southern hemispheres in the framework of the Global Mercury Observation System (GMOS) project. Total mercury (THg) exhibited annual...

Latitudinal variation of the polar cusp during a geomagnetic storm

International Nuclear Information System (INIS)

Meng, C.

1982-01-01

Large amplitude latitudinal variation of the polar cusp position was observed during the intense geomagnetic storm of 15--16 February 1980. The observation of the polar cusp, identified as the region of intense but extremely soft electron precipitation, was made by two nearly noon-midnight orbit DMSP satellites over both northern and southern hemispheres. The latitudinal shift of the polar cusp is observed to be related to the intensity variation of the ring current indicated by the hourly Dst values. The polar cusp region moved from its normal location at approx.76 0 gm lat down to approx.62 0 gm lat at the peak of this storm. This movement took about 5 hours and was detected over both hemispheres. A drastic variation in the width of the cusp region was also observed; it is very narrow (approx.1 0 ) during the equatorial shift and expands to > or approx. =5 0 during the poleward recovery. Variation of the polar cusp latitude with that of the Dst index was also seen during the period before the intense storm

What is happening in the International Polar Year? Latest news about the climate changes

International Nuclear Information System (INIS)

Orheim, Olav

2008-01-01

The International Polar (IPY) Year 2007-2008 is a large scientific programme focused on the Arctic and the Antarctic. Scientists from over 60 nations participates. The IPY have two primary objectives: to improve weather forecasts especially regarding extreme weather and to improve climatic models for better understanding of possible instabilities, especially regarding ocean currents. The presentation includes data on natural climate change, temperature anomaly, the ice in the Arctic Ocean and Northern and Southern Hemisphere sea ice area, current in Southern and Northern hemisphere sea ice area and variations of the surface temperature ice arctic regions antarctic regions. The presentation was held at the MNT-Forum, 29. January 2008

Navy Tactical Applications Guide. Volume 7. Southern Hemisphere Weather Analysis and Forecast Applications

Science.gov (United States)

1989-10-01

stationary states in the Southern limited use of persistence forecasting on a day-to-day Hemisphere. Mon, Wea. Rev., 114, 808-823. I I 729 I- 768 0I L! I I II...southwesterly Republic of South Africa Weather Bureau ( RSA ) surface flowing Agulhas Current. A ship observation at chart (not shown) had disclosed...20 ft. The potential for abnormally steep and high waves is significant in casesThe RSA daily weather bulletin (Fig. 3C- 18a) on the like this one

Ecological drivers of soil microbial diversity and soil biological networks in the Southern Hemisphere.

Science.gov (United States)

Delgado-Baquerizo, Manuel; Reith, Frank; Dennis, Paul G; Hamonts, Kelly; Powell, Jeff R; Young, Andrew; Singh, Brajesh K; Bissett, Andrew

2018-03-01

The ecological drivers of soil biodiversity in the Southern Hemisphere remain underexplored. Here, in a continental survey comprising 647 sites, across 58 degrees of latitude between tropical Australia and Antarctica, we evaluated the major ecological patterns in soil biodiversity and relative abundance of ecological clusters within a co-occurrence network of soil bacteria, archaea and eukaryotes. Six major ecological clusters (modules) of co-occurring soil taxa were identified. These clusters exhibited strong shifts in their relative abundances with increasing distance from the equator. Temperature was the major environmental driver of the relative abundance of ecological clusters when Australia and Antarctica are analyzed together. Temperature, aridity, soil properties and vegetation types were the major drivers of the relative abundance of different ecological clusters within Australia. Our data supports significant reductions in the diversity of bacteria, archaea and eukaryotes in Antarctica vs. Australia linked to strong reductions in temperature. However, we only detected small latitudinal variations in soil biodiversity within Australia. Different environmental drivers regulate the diversity of soil archaea (temperature and soil carbon), bacteria (aridity, vegetation attributes and pH) and eukaryotes (vegetation type and soil carbon) across Australia. Together, our findings provide new insights into the mechanisms driving soil biodiversity in the Southern Hemisphere. © 2018 by the Ecological Society of America.

Five-year records of mercury wet deposition flux at GMOS sites in the Northern and Southern hemispheres

Science.gov (United States)

Sprovieri, Francesca; Pirrone, Nicola; Bencardino, Mariantonia; D'Amore, Francesco; Angot, Helene; Barbante, Carlo; Brunke, Ernst-Günther; Arcega-Cabrera, Flor; Cairns, Warren; Comero, Sara; Diéguez, María del Carmen; Dommergue, Aurélien; Ebinghaus, Ralf; Feng, Xin Bin; Fu, Xuewu; Garcia, Patricia Elizabeth; Gawlik, Bernd Manfred; Hageström, Ulla; Hansson, Katarina; Horvat, Milena; Kotnik, Jože; Labuschagne, Casper; Magand, Olivier; Martin, Lynwill; Mashyanov, Nikolay; Mkololo, Thumeka; Munthe, John; Obolkin, Vladimir; Ramirez Islas, Martha; Sena, Fabrizio; Somerset, Vernon; Spandow, Pia; Vardè, Massimiliano; Walters, Chavon; Wängberg, Ingvar; Weigelt, Andreas; Yang, Xu; Zhang, Hui

2017-02-01

The atmospheric deposition of mercury (Hg) occurs via several mechanisms, including dry and wet scavenging by precipitation events. In an effort to understand the atmospheric cycling and seasonal depositional characteristics of Hg, wet deposition samples were collected for approximately 5 years at 17 selected GMOS monitoring sites located in the Northern and Southern hemispheres in the framework of the Global Mercury Observation System (GMOS) project. Total mercury (THg) exhibited annual and seasonal patterns in Hg wet deposition samples. Interannual differences in total wet deposition are mostly linked with precipitation volume, with the greatest deposition flux occurring in the wettest years. This data set provides a new insight into baseline concentrations of THg concentrations in precipitation worldwide, particularly in regions such as the Southern Hemisphere and tropical areas where wet deposition as well as atmospheric Hg species were not investigated before, opening the way for future and additional simultaneous measurements across the GMOS network as well as new findings in future modeling studies.

Polarization observations of four southern pulsars at 1560 MHz

Science.gov (United States)

Wu, Xin-Ji; Manchester, R. N.; Lyne, A. G.

1991-12-01

Some interesting results from the mean pulse polarization observations of four southern pulsars made at the Australian National Radio Astronomy Observatory, Parkes, using the 64-m telescope in June and July, 1988, are presented. The 2 x 16 x 5 MHz filter system from Jodrell Bank has proved excellent in dedispersing the pulse signals and measuring their polarization properties. Data for the four pulsars are given in some detail, and their spectral behavior is discussed.

Long-term analysis of ionospheric polar patches based on CHAMP TEC data

DEFF Research Database (Denmark)

Noja, M.; Stolle, Claudia; Park, J.

2013-01-01

Total electron content (TEC) from LEO satellites offers great possibility to sound the upper ionosphere and plasmasphere. This paper describes a method to derive absolute TEC observations aboard CHAMP considering multipath effects and receiver differential code bias. The long-term data set of 9...... years GPS observations is used to investigate the climatological behavior of high-latitude plasma patches in both hemispheres. The occurrence of polar patches has a clear correlation with the solar cycle, which is less pronounced in the Southern Hemisphere (SH). Summed over all years, we observed...... a higher number of patches in the SH. The maximum occurrence rate of patches has been found at the dayside polar cusp during 12:00-18:00 MLT (magnetic local time) supporting the mechanisms for patch creation by local particle precipitation and by intrusion of subauroral plasma into the polar cap through...

Cryptic Eimeria genotypes are common across the southern but not northern hemisphere.

Science.gov (United States)

Clark, Emily L; Macdonald, Sarah E; Thenmozhi, V; Kundu, Krishnendu; Garg, Rajat; Kumar, Saroj; Ayoade, Simeon; Fornace, Kimberly M; Jatau, Isa Danladi; Moftah, Abdalgader; Nolan, Matthew J; Sudhakar, N R; Adebambo, A O; Lawal, I A; Álvarez Zapata, Ramón; Awuni, Joseph A; Chapman, H David; Karimuribo, Esron; Mugasa, Claire M; Namangala, Boniface; Rushton, Jonathan; Suo, Xun; Thangaraj, Kumarasamy; Srinivasa Rao, Arni S R; Tewari, Anup K; Banerjee, Partha S; Dhinakar Raj, G; Raman, M; Tomley, Fiona M; Blake, Damer P

2016-08-01

The phylum Apicomplexa includes parasites of medical, zoonotic and veterinary significance. Understanding the global distribution and genetic diversity of these protozoa is of fundamental importance for efficient, robust and long-lasting methods of control. Eimeria spp. cause intestinal coccidiosis in all major livestock animals and are the most important parasites of domestic chickens in terms of both economic impact and animal welfare. Despite having significant negative impacts on the efficiency of food production, many fundamental questions relating to the global distribution and genetic variation of Eimeria spp. remain largely unanswered. Here, we provide the broadest map yet of Eimeria occurrence for domestic chickens, confirming that all the known species (Eimeria acervulina, Eimeria brunetti, Eimeria maxima, Eimeria mitis, Eimeria necatrix, Eimeria praecox, Eimeria tenella) are present in all six continents where chickens are found (including 21 countries). Analysis of 248 internal transcribed spacer sequences derived from 17 countries provided evidence of possible allopatric diversity for species such as E. tenella (FST values ⩽0.34) but not E. acervulina and E. mitis, and highlighted a trend towards widespread genetic variance. We found that three genetic variants described previously only in Australia and southern Africa (operational taxonomic units x, y and z) have a wide distribution across the southern, but not the northern hemisphere. While the drivers for such a polarised distribution of these operational taxonomic unit genotypes remains unclear, the occurrence of genetically variant Eimeria may pose a risk to food security and animal welfare in Europe and North America should these parasites spread to the northern hemisphere. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Estimating carbonate parameters from hydrographic data for the intermediate and deep waters of the Southern Hemisphere oceans

Science.gov (United States)

Bostock, H. C.; Mikaloff Fletcher, S. E.; Williams, M. J. M.

2013-10-01

Using ocean carbon data from global datasets, we have developed several multiple linear regression (MLR) algorithms to estimate alkalinity and dissolved inorganic carbon (DIC) in the intermediate and deep waters of the Southern Hemisphere (south of 25° S) from only hydrographic data (temperature, salinity and dissolved oxygen). A Monte Carlo experiment was used to identify a potential density (σθ) of 27.5 as an optimal break point between the two regimes with different MLR algorithms. The algorithms provide a good estimate of DIC (R2=0.98) and alkalinity (R2=0.91), and excellent agreement for aragonite and calcite saturation states (R2=0.99). Combining the algorithms with the CSIRO Atlas of Regional Seas (CARS), we have mapped the calcite saturation horizon (CSH) and aragonite saturation horizon (ASH) for the Southern Ocean at a spatial resolution of 0.5°. These maps are more detailed and more consistent with the oceanography than the previously gridded GLODAP data. The high-resolution ASH map reveals a dramatic circumpolar shoaling at the polar front. North of 40° S the CSH is deepest in the Atlantic (~ 4000 m) and shallower in the Pacific Ocean (~ 2750 m), while the CSH sits between 3200 and 3400 m in the Indian Ocean. The uptake of anthropogenic carbon by the ocean will alter the relationships between DIC and hydrographic data in the intermediate and deep waters over time. Thus continued sampling will be required, and the MLR algorithms will need to be adjusted in the future to account for these changes.

Estimating carbonate parameters from hydrographic data for the intermediate and deep waters of the Southern Hemisphere oceans

Directory of Open Access Journals (Sweden)

H. C. Bostock

2013-10-01

Full Text Available Using ocean carbon data from global datasets, we have developed several multiple linear regression (MLR algorithms to estimate alkalinity and dissolved inorganic carbon (DIC in the intermediate and deep waters of the Southern Hemisphere (south of 25° S from only hydrographic data (temperature, salinity and dissolved oxygen. A Monte Carlo experiment was used to identify a potential density (σθ of 27.5 as an optimal break point between the two regimes with different MLR algorithms. The algorithms provide a good estimate of DIC (R2=0.98 and alkalinity (R2=0.91, and excellent agreement for aragonite and calcite saturation states (R2=0.99. Combining the algorithms with the CSIRO Atlas of Regional Seas (CARS, we have mapped the calcite saturation horizon (CSH and aragonite saturation horizon (ASH for the Southern Ocean at a spatial resolution of 0.5°. These maps are more detailed and more consistent with the oceanography than the previously gridded GLODAP data. The high-resolution ASH map reveals a dramatic circumpolar shoaling at the polar front. North of 40° S the CSH is deepest in the Atlantic (~ 4000 m and shallower in the Pacific Ocean (~ 2750 m, while the CSH sits between 3200 and 3400 m in the Indian Ocean. The uptake of anthropogenic carbon by the ocean will alter the relationships between DIC and hydrographic data in the intermediate and deep waters over time. Thus continued sampling will be required, and the MLR algorithms will need to be adjusted in the future to account for these changes.

Unexpected Southern Hemisphere ionospheric response to geomagnetic storm of 15 August 2015

Science.gov (United States)

Edemskiy, Ilya; Lastovicka, Jan; Buresova, Dalia; Bosco Habarulema, John; Nepomnyashchikh, Ivan

2018-01-01

Geomagnetic storms are the most pronounced phenomenon of space weather. When studying ionospheric response to a storm of 15 August 2015, an unexpected phenomenon was observed at higher middle latitudes of the Southern Hemisphere. This phenomenon was a localized total electron content (TEC) enhancement (LTE) in the form of two separated plumes, which peaked southward of South Africa. The plumes were first observed at 05:00 UT near the southwestern coast of Australia. The southern plume was associated with local time slightly after noontime (1-2 h after local noon). The plumes moved with the Sun. They peaked near 13:00 UT southward of South Africa. The southern plume kept constant geomagnetic latitude (63-64° S); it persisted for about 10 h, whereas the northern plume persisted for about 2 h more. Both plumes disappeared over the South Atlantic Ocean. No similar LTE event was observed during the prolonged solar activity minimum period of 2006-2009. In 2012-2016 we detected altogether 26 LTEs and all of them were associated with the southward excursion of Bz. The negative Bz excursion is a necessary but not sufficient condition for the LTE occurrence as during some geomagnetic storms associated with negative Bz excursions the LTE events did not appear.

A Southern Hemisphere origin for campanulid angiosperms, with traces of the break-up of Gondwana

OpenAIRE

Beaulieu, Jeremy M; Tank, David C; Donoghue, Michael J

2013-01-01

Background New powerful biogeographic methods have focused attention on long-standing hypotheses regarding the influence of the break-up of Gondwana on the biogeography of Southern Hemisphere plant groups. Studies to date have often concluded that these groups are too young to have been influenced by these ancient continental movements. Here we examine a much larger and older angiosperm clade, the Campanulidae, and infer its biogeographic history by combining Bayesian divergence time informat...

Climate model diversity in the Northern Hemisphere Polar vortex response to climate change.

Science.gov (United States)

Simpson, I.; Seager, R.; Hitchcock, P.; Cohen, N.

2017-12-01

Global climate models vary widely in their predictions of the future of the Northern Hemisphere stratospheric polar vortex, with some showing a significant strengthening of the vortex, some showing a significant weakening and others displaying a response that is not outside of the range expected from internal variability alone. This inter-model spread in stratospheric predictions may account for some inter-model spread in tropospheric predictions with important implications for the storm tracks and regional climate change, particularly for the North Atlantic sector. Here, our current state of understanding of this model spread and its tropospheric impacts will be reviewed. Previous studies have proposed relationships between a models polar vortex response to climate change and its present day vortex climatology while others have demonstrated links between a models polar vortex response and changing wave activity coming up from the troposphere below under a warming climate. The extent to which these mechanisms can account for the spread in polar vortex changes exhibited by the Coupled Model Intercomparison Project, phase 5 models will be assessed. In addition, preliminary results from a series of idealized experiments with the Community Atmosphere Model will be presented. In these experiments, nudging of the stratospheric zonal mean state has been imposed to mimic the inter-model spread in the polar vortex response to climate change so that the downward influence of the spread in zonal mean stratospheric responses on the tropospheric circulation can be assessed within one model.

A Chronologic Dual-Hemisphere Approach to the Last Glacial Termination from the Southern Alps of New Zealand and the Altai Mountains of Western Mongolia

Science.gov (United States)

Strand, P.; Putnam, A. E.; Schaefer, J. M.; Denton, G.; Barrell, D.; Putnam, D.; Schwartz, R.; Sambuu, O.; Radue, M. J.; Lindsay, B. J.; Stevens, J.

2017-12-01

Understanding the processes that drove the last glacial termination in the tropics and mid-latitudes is a major unresolved problem in paleoclimate. The most recent glacial to interglacial transition represents the last great global warming and the last time CO2 rose by a substantial amount before the industrial period. Determining the speed of this warming will help refine the global climate system sensitivity to CO2 and will place ongoing global warming into a paleoclimatic context. Here, we test possible drivers of the last glacial termination by comparing chronologies of mountain glaciers, which are highly sensitive to changes in atmospheric temperature, in the middle latitudes of both polar hemispheres. The dating of glacier landforms, such as moraine ridges constructed along glacier margins, affords quantitative insight into past climate conditions. We present 10Be surface-exposure chronologies and glacial geomorphologic maps of mountain glacier recession since the Last Glacial Maximum in the Southern Alps of New Zealand (44°S, 170°E) and in the Altai Mountains of western Mongolia (49°N, 88°E). On the basis of these chronologies from opposing hemispheres, we evaluate the relative roles of rising atmospheric CO2, local insolation forcing, and ocean-atmosphere reorganizations in driving the global warming that ended the last ice age.

HIGH-RESOLUTION TOPOGRAPHY OF MERCURY FROM MESSENGER ORBITAL STEREO IMAGING – THE SOUTHERN HEMISPHERE QUADRANGLES

Directory of Open Access Journals (Sweden)

F. Preusker

2018-04-01

Full Text Available We produce high-resolution (222 m/grid element Digital Terrain Models (DTMs for Mercury using stereo images from the MESSENGER orbital mission. We have developed a scheme to process large numbers, typically more than 6000, images by photogrammetric techniques, which include, multiple image matching, pyramid strategy, and bundle block adjustments. In this paper, we present models for map quadrangles of the southern hemisphere H11, H12, H13, and H14.

Water. Unresolved emergency of the Southern hemisphere; Acqua. Istanza irrisolta del Sud del mondo

Energy Technology Data Exchange (ETDEWEB)

Lotti, C. [Associazione Idrotecnica Italiana, Padua (Italy)

2001-10-01

Among the serious dramas in the Southern hemisphere, the most serious relates to health, and the most serious health problem is dysentery among the rural population, caused by the lack of unpolluted water. Bad management frustrates much of the aid sent to this part of the world, including projects to help the water crisis. In view of the success, it would appear that a concrete solution could be found within a decade, at a cost that can easily be sustained by the rich world, so long as funds are managed honestly. Much more ambitious and, at least for the moment, beyond all concrete possibility, is the project to provide a barrel of water per head to each person in the southern hemisphere. Providing unpolluted water and facilitating farming development through minor irrigation and family cattle-raising schemes is an idea that appears entirely Utopian. The conclusion provides a critical analysis of the major hydraulic works essential for true development, but effective only if the human environment is ready to receive them, whereas minor works are useful in any case - at village level - to resolve the thirst of the southern hemisphere. [Italian] Fra i gravi drammi del Sud del Mondo certamente il piu' grave e' quello sanitario; ed in quello sanitario la dissenteria causata dalla mancanza di acque non inquinate a gran parte della popolazione rurale. I molti aiuti destinati a questa parte del mondo sono stati vanificati dalla loro cattiva gestione: fra di essi gli interventi a favore dell'acqua. Da alcuni interventi ad esito positivo si puo' pervenire ad una soluzione concreta nel giro di un decennio. Molto piu' ambizioso ed -almeno per ora- fuori da ogni ipotesi concreta e' quello di rifornire di un barile di acqua pro capite ogni individuo del Sud del Mondo: per dare acqua non inquinata e favorire lo sviluppo alimentare attraverso piccole irrigazioni e familiari allevamenti di bestiame: cio' appare, comunque relegato allo scenario

Isotopic Evidence of a Wide Spectrum of Feeding Strategies in Southern Hemisphere Humpback Whale Baleen Records.

Science.gov (United States)

Eisenmann, Pascale; Fry, Brian; Holyoake, Carly; Coughran, Douglas; Nicol, Steve; Bengtson Nash, Susan

2016-01-01

Our current understanding of Southern hemisphere humpback whale (Megaptera novaeangliae) ecology assumes high-fidelity feeding on Antarctic krill in Antarctic waters during summer, followed by fasting during their annual migration to and from equatorial breeding grounds. An increase in the number of reported departures from this feeding/fasting model suggests that the current model may be oversimplified or, alternatively, undergoing contemporary change. Information about the feeding and fasting cycles of the two Australian breeding populations of humpback whales were obtained through stable isotope analysis of baleen plates from stranded adult individuals. Comparison of isotope profiles showed that individuals from the West Australian breeding population strongly adhered to the classical feeding model. By contrast, East Australian population individuals demonstrated greater heterogeneity in their feeding. On a spectrum from exclusive Antarctic feeding to exclusive feeding in temperate waters, three different strategies were assigned and discussed: classical feeders, supplemental feeders, and temperate zone feeders. Diversity in the inter-annual feeding strategies of humpback whales demonstrates the feeding plasticity of the species, but could also be indicative of changing dynamics within the Antarctic sea-ice ecosystem. This study presents the first investigation of trophodynamics in Southern hemisphere humpback whales derived from baleen plates, and further provides the first estimates of baleen plate elongation rates in the species.

Extended period of polar cap auroral display: auroral dynamics and relation to the IMF and the ionospheric convection

Directory of Open Access Journals (Sweden)

V. G. Vorobjev

1995-08-01

Full Text Available An unusually extended period (5 h of polar cap auroral display on 3 August 1986 is examined. Auroras have been investigated using ground-based data as well as measurements from the IMP-8 spacecraft in interplanetary space and simultaneous observations from the polar-orbiting satellites Viking and DE-1 in the northern and southern hemispheres, respectively. It is found that visible Sun-aligned arcs are located inside the transpolar band of the θ-aurora observed from the satellite in ultraviolet wavelengths. The transpolar band can contain several Sun-aligned arcs that move inside the band toward the morning or evening side of the auroral oval independent of the direction of the band movement. Intensifications of polar cap auroras with durations of up to about 30 min are observed. No change has been found in either IMF parameters or substorm activity that can be related to these intensifications. The θ-aurora occurred during a 2-h period when the B z-component of the IMF was negative. A tendency is noted for dawnward (duskward displacement of the transpolar band when By>0 (By<0 in the southern hemisphere. Simultaneous observations of auroral ovals during interplanetary Bz<0, By<0 and Bx>0 in both hemispheres and convection patterns for Bz<0 and By<0 have been displayed using satellite and ground-based measurements. It was found that the transpolar band of the -aurora in the sunlit hemisphere was situated in the region of large-scale downward Birkeland currents.

Unusual Polar Conditions in Solar Cycle 24 and Their Implications for Cycle 25

Science.gov (United States)

Gopalswamy, Nat; Yashiro, Seiji; Akiyama, Sachiko

2016-01-01

We report on the prolonged solar-maximum conditions until late 2015 at the north-polar region of the Sun indicated by the occurrence of high-latitude prominence eruptions (PEs) and microwave brightness temperature close to the quiet-Sun level. These two aspects of solar activity indicate that the polarity reversal was completed by mid-2014 in the south and late 2015 in the north. The microwave brightness in the south-polar region has increased to a level exceeding the level of the Cycle 23/24 minimum, but just started to increase in the north. The northsouth asymmetry in the polarity reversal has switched from that in Cycle 23. These observations lead us to the hypothesis that the onset of Cycle 25 in the northern hemisphere is likely to be delayed with respect to that in the southern hemisphere. We find that the unusual condition in the north is a direct consequence of the arrival of poleward surges of opposite polarity from the active region belt. We also find that multiple rush-to-the-pole episodes were indicated by the PE locations that lined up at the boundary between opposite-polarity surges. The high-latitude PEs occurred in the boundary between the incumbent polar flux and the insurgent flux of opposite polarity.

First search for a dark matter annual modulation signal with NaI(Tl) in the Southern Hemisphere by DM-Ice17

Energy Technology Data Exchange (ETDEWEB)

Barbosa de Souza, E.; Cherwinka, J.; Cole, A.; Ezeribe, A. C.; Grant, D.; Halzen, F.; Heeger, K. M.; Hsu, L.; Hubbard, A. J. F.; Jo, J. H.; Karle, A.; Kauer, M.; Kudryavtsev, V. A.; Lim, K. E.; Macdonald, C.; Maruyama, R. H.; Mouton, F.; Paling, S. M.; Pettus, W.; Pierpoint, Z. P.; Reilly, B. N.; Robinson, M.; Rogers, F. R.; Sandstrom, P.; Scarff, A.; Spooner, N. J. C.; Telfer, S.; Yang, L.

2017-02-28

The first search for a dark matter annual modulation signal with NaI(Tl) target material in the Southern Hemisphere conducted with the DM-Ice17 experiment is presented. DM-Ice17 consists of 17 kg of NaI(Tl) scintillating crystal under 2200 m.w.e. overburden of Antarctic glacial ice. The analysis presented here utilizes a 60.8 kg yr exposure. While unable to exclude the signal reported by DAMA/LIBRA, the DM-Ice17 data are consistent with no modulation in the energy range of 4-20 keV, providing the strongest limits on WIMP candidates from a direct detection experiment located in the Southern Hemisphere. Additionally, the successful deployment and stable operation of 17 kg of NaI(Tl) crystal over 3.5 years establishes the South Pole ice as a viable location for future underground, low-background experiments.

Annually resolved southern hemisphere volcanic history from two Antarctic ice cores

Science.gov (United States)

Cole-Dai, Jihong; Mosley-Thompson, Ellen; Thompson, Lonnie G.

1997-07-01

The continuous sulfate analysis of two Antarctic ice cores, one from the Antarctic Peninsula region and one from West Antarctica, provides an annually resolved proxy history of southern semisphere volcanism since early in the 15th century. The dating is accurate within ±3 years due to the high rate of snow accumulation at both core sites and the small sample sizes used for analysis. The two sulfate records are consistent with each other. A systematic and objective method of separating outstanding sulfate events from the background sulfate flux is proposed and used to identify all volcanic signals. The resulting volcanic chronology covering 1417-1989 A.D. resolves temporal ambiguities about several recently discovered events. A number of previously unknown, moderate eruptions during late 1600s are uncovered in this chronology. The eruption of Tambora (1815) and the recently discovered eruption of Kuwae (1453) in the tropical South Pacific injected the greatest amount of sulfur dioxide into the southern hemisphere stratosphere during the last half millennium. A technique for comparing the magnitude of volcanic events preserved within different ice cores is developed using normalized sulfate flux. For the same eruptions the variability of the volcanic sulfate flux between the cores is within ±20% of the sulfate flux from the Tambora eruption.

The interaction of a magnetic cloud with the Earth - Ionospheric convection in the Northern and Southern Hemispheres for a wide range of quasi-steady interplanetary magnetic field conditions

Science.gov (United States)

Freeman, M. P.; Farrugia, C. J.; Burlaga, L. F.; Hairston, M. R.; Greenspan, M. E.; Ruohoniemi, J. M.; Lepping, R. P.

1993-01-01

Observations are presented of the ionospheric convection in cross sections of the polar cap and auroral zone as part of the study of the interaction of the Earth's magnetosphere with the magnetic cloud of January 13-15, 1988. For strongly northward IMF, the convection in the Southern Hemisphere is characterized by a two-cell convection pattern comfined to high latitudes with sunward flow over the pole. The strength of the flows is comparable to that later seen under southward IMF. Superimposed on this convection pattern there are clear dawn-dusk asymmetries associated with a one-cell convection component whose sense depends on the polarity of the magnetic cloud's large east-west magnetic field component. When the cloud's magnetic field turns southward, the convection is characterized by a two-cell pattern extending to lower latitude with antisunward flow over the pole. There is no evident interhemispheric difference in the structure and strength of the convection. Superimposed dawn-dusk asymmetries in the flow patterns are observed which are only in part attributable to the east-west component of the magnetic field.

Isotopic Evidence of a Wide Spectrum of Feeding Strategies in Southern Hemisphere Humpback Whale Baleen Records.

Directory of Open Access Journals (Sweden)

Pascale Eisenmann

Full Text Available Our current understanding of Southern hemisphere humpback whale (Megaptera novaeangliae ecology assumes high-fidelity feeding on Antarctic krill in Antarctic waters during summer, followed by fasting during their annual migration to and from equatorial breeding grounds. An increase in the number of reported departures from this feeding/fasting model suggests that the current model may be oversimplified or, alternatively, undergoing contemporary change. Information about the feeding and fasting cycles of the two Australian breeding populations of humpback whales were obtained through stable isotope analysis of baleen plates from stranded adult individuals. Comparison of isotope profiles showed that individuals from the West Australian breeding population strongly adhered to the classical feeding model. By contrast, East Australian population individuals demonstrated greater heterogeneity in their feeding. On a spectrum from exclusive Antarctic feeding to exclusive feeding in temperate waters, three different strategies were assigned and discussed: classical feeders, supplemental feeders, and temperate zone feeders. Diversity in the inter-annual feeding strategies of humpback whales demonstrates the feeding plasticity of the species, but could also be indicative of changing dynamics within the Antarctic sea-ice ecosystem. This study presents the first investigation of trophodynamics in Southern hemisphere humpback whales derived from baleen plates, and further provides the first estimates of baleen plate elongation rates in the species.

Large-Scale Traveling Weather Systems in Mars’ Southern Extratropics

Science.gov (United States)

Hollingsworth, Jeffery L.; Kahre, Melinda A.

2017-10-01

Between late fall and early spring, Mars’ middle- and high-latitude atmosphere supports strong mean equator-to-pole temperature contrasts and an accompanying mean westerly polar vortex. Observations from both the MGS Thermal Emission Spectrometer (TES) and the MRO Mars Climate Sounder (MCS) indicate that a mean baroclinicity-barotropicity supports intense, large-scale eastward traveling weather systems (i.e., transient synoptic-period waves). Such extratropical weather disturbances are critical components of the global circulation as they serve as agents in the transport of heat and momentum, and generalized scalar/tracer quantities (e.g., atmospheric dust, water-vapor and ice clouds). The character of such traveling extratropical synoptic disturbances in Mars' southern hemisphere during late winter through early spring is investigated using a moderately high-resolution Mars global climate model (Mars GCM). This Mars GCM imposes interactively-lifted and radiatively-active dust based on a threshold value of the surface stress. The model exhibits a reasonable "dust cycle" (i.e., globally averaged, a dustier atmosphere during southern spring and summer occurs). Compared to the northern-hemisphere counterparts, the southern synoptic-period weather disturbances and accompanying frontal waves have smaller meridional and zonal scales, and are far less intense. Influences of the zonally asymmetric (i.e., east-west varying) topography on southern large-scale weather are investigated, in addition to large-scale up-slope/down-slope flows and the diurnal cycle. A southern storm zone in late winter and early spring presents in the western hemisphere via orographic influences from the Tharsis highlands, and the Argyre and Hellas impact basins. Geographically localized transient-wave activity diagnostics are constructed that illuminate dynamical differences amongst the simulations and these are presented.

Large-Scale Traveling Weather Systems in Mars Southern Extratropics

Science.gov (United States)

Hollingsworth, Jeffery L.; Kahre, Melinda A.

2017-01-01

Between late fall and early spring, Mars' middle- and high-latitude atmosphere supports strong mean equator-to-pole temperature contrasts and an accompanying mean westerly polar vortex. Observations from both the MGS Thermal Emission Spectrometer (TES) and the MRO Mars Climate Sounder (MCS) indicate that a mean baroclinicity-barotropicity supports intense, large-scale eastward traveling weather systems (i.e., transient synoptic-period waves). Such extratropical weather disturbances are critical components of the global circulation as they serve as agents in the transport of heat and momentum, and generalized scalar/tracer quantities (e.g., atmospheric dust, water-vapor and ice clouds). The character of such traveling extratropical synoptic disturbances in Mars' southern hemisphere during late winter through early spring is investigated using a moderately high-resolution Mars global climate model (Mars GCM). This Mars GCM imposes interactively-lifted and radiatively-active dust based on a threshold value of the surface stress. The model exhibits a reasonable "dust cycle" (i.e., globally averaged, a dustier atmosphere during southern spring and summer occurs). Compared to the northern-hemisphere counterparts, the southern synoptic-period weather disturbances and accompanying frontal waves have smaller meridional and zonal scales, and are far less intense. Influences of the zonally asymmetric (i.e., east-west varying) topography on southern large-scale weather are investigated, in addition to large-scale up-slope/down-slope flows and the diurnal cycle. A southern storm zone in late winter and early spring presents in the western hemisphere via orographic influences from the Tharsis highlands, and the Argyre and Hellas impact basins. Geographically localized transient-wave activity diagnostics are constructed that illuminate dynamical differences amongst the simulations and these are presented.

Historical biogeography and diversification of truffles in the Tuberaceae and their newly identified southern hemisphere sister lineage.

Science.gov (United States)

Bonito, Gregory; Smith, Matthew E; Nowak, Michael; Healy, Rosanne A; Guevara, Gonzalo; Cázares, Efren; Kinoshita, Akihiko; Nouhra, Eduardo R; Domínguez, Laura S; Tedersoo, Leho; Murat, Claude; Wang, Yun; Moreno, Baldomero Arroyo; Pfister, Donald H; Nara, Kazuhide; Zambonelli, Alessandra; Trappe, James M; Vilgalys, Rytas

2013-01-01

Truffles have evolved from epigeous (aboveground) ancestors in nearly every major lineage of fleshy fungi. Because accelerated rates of morphological evolution accompany the transition to the truffle form, closely related epigeous ancestors remain unknown for most truffle lineages. This is the case for the quintessential truffle genus Tuber, which includes species with socio-economic importance and esteemed culinary attributes. Ecologically, Tuber spp. form obligate mycorrhizal symbioses with diverse species of plant hosts including pines, oaks, poplars, orchids, and commercially important trees such as hazelnut and pecan. Unfortunately, limited geographic sampling and inconclusive phylogenetic relationships have obscured our understanding of their origin, biogeography, and diversification. To address this problem, we present a global sampling of Tuberaceae based on DNA sequence data from four loci for phylogenetic inference and molecular dating. Our well-resolved Tuberaceae phylogeny shows high levels of regional and continental endemism. We also identify a previously unknown epigeous member of the Tuberaceae--the South American cup-fungus Nothojafnea thaxteri (E.K. Cash) Gamundí. Phylogenetic resolution was further improved through the inclusion of a previously unrecognized Southern hemisphere sister group of the Tuberaceae. This morphologically diverse assemblage of species includes truffle (e.g. Gymnohydnotrya spp.) and non-truffle forms that are endemic to Australia and South America. Southern hemisphere taxa appear to have diverged more recently than the Northern hemisphere lineages. Our analysis of the Tuberaceae suggests that Tuber evolved from an epigeous ancestor. Molecular dating estimates Tuberaceae divergence in the late Jurassic (~156 million years ago), with subsequent radiations in the Cretaceous and Paleogene. Intra-continental diversification, limited long-distance dispersal, and ecological adaptations help to explain patterns of truffle

Historical biogeography and diversification of truffles in the Tuberaceae and their newly identified southern hemisphere sister lineage.

Directory of Open Access Journals (Sweden)

Gregory Bonito

Full Text Available Truffles have evolved from epigeous (aboveground ancestors in nearly every major lineage of fleshy fungi. Because accelerated rates of morphological evolution accompany the transition to the truffle form, closely related epigeous ancestors remain unknown for most truffle lineages. This is the case for the quintessential truffle genus Tuber, which includes species with socio-economic importance and esteemed culinary attributes. Ecologically, Tuber spp. form obligate mycorrhizal symbioses with diverse species of plant hosts including pines, oaks, poplars, orchids, and commercially important trees such as hazelnut and pecan. Unfortunately, limited geographic sampling and inconclusive phylogenetic relationships have obscured our understanding of their origin, biogeography, and diversification. To address this problem, we present a global sampling of Tuberaceae based on DNA sequence data from four loci for phylogenetic inference and molecular dating. Our well-resolved Tuberaceae phylogeny shows high levels of regional and continental endemism. We also identify a previously unknown epigeous member of the Tuberaceae--the South American cup-fungus Nothojafnea thaxteri (E.K. Cash Gamundí. Phylogenetic resolution was further improved through the inclusion of a previously unrecognized Southern hemisphere sister group of the Tuberaceae. This morphologically diverse assemblage of species includes truffle (e.g. Gymnohydnotrya spp. and non-truffle forms that are endemic to Australia and South America. Southern hemisphere taxa appear to have diverged more recently than the Northern hemisphere lineages. Our analysis of the Tuberaceae suggests that Tuber evolved from an epigeous ancestor. Molecular dating estimates Tuberaceae divergence in the late Jurassic (~156 million years ago, with subsequent radiations in the Cretaceous and Paleogene. Intra-continental diversification, limited long-distance dispersal, and ecological adaptations help to explain patterns of

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

Science.gov (United States)

Rother, H.; Shulmeister, J.

2006-05-01

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

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

Directory of Open Access Journals (Sweden)

H. Rother

2006-01-01

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

The MEarth Project: Status Update and the Commissioning of a Brand New Telescope Array in the Southern Hemisphere

Science.gov (United States)

Berta-Thompson, Zachory K.; Irwin, Jonathan; Charbonneau, David; Newton, Elisabeth R.; Dittmann, Jason

2014-06-01

The MEarth Project is an ongoing all-sky survey for Earth-like planets transiting the closest, smallest M dwarfs. MEarth aims to find good targets for atmospheric characterization with JWST and the next generation of enormous ground-based telescopes. MEarth's yearly data releases, containing precise light curves of nearby mid-to-late M dwarfs, provide a unique window into the photometric variability of the stars that will forever be among the most interesting targets in the search for potentially habitable exoplanets. We present a status update on the MEarth Project, including a detailed map of the progress we’ve made so far with 8 telescopes in the Northern hemisphere and promising early results from our new installation of 8 more telescopes in the Southern hemisphere.

Possible slow periglacial mass wasting at the Southern Hemisphere on Mars.

Science.gov (United States)

Johnsson, Andreas; Reiss, Dennis; Hauber, Ernst; Hiesinger, Harald

2014-05-01

Small-scale lobate landforms which are strikingly similar to terrestrial solifluction lobes are cataloged at the Southern Hemisphere on Mars. Terrestrial periglacial solifluction lobes are formed by frost creep, a combination of repeated frost heave and thaw consolidation, and gelifluction (visco-plastic deformation of near saturated soil) in the active layer on top of the permafrost table (e.g., Matsuoka, 2001). All publically available HiRISE images between latitudes 40°S and 80°S on Mars are being used in this study. Compared to previous studies of small-scale lobes in the northern mid and high latitudes (e.g., Gallagher et al., 2011; Johnsson et al., 2012; Barrett et al., 2013), these landforms also occur, in most cases, in close spatial proximity to fluvial gullies and polygonal terrain. This study aims to investigate whether the southern small-scale lobes differ from the northern counterparts in terms of morphology and distribution. Furthermore, spatio-temporal relationships to landforms with ground-ice affinity, such as gullies and polygonal terrain, are investigated. Solifluction-like small-scale lobes have been studied in detail at the northern hemisphere on Mars (Gallagher et al., 2011), where they are widely distributed at high latitudes between 59°N and 80°N (Johnsson et al., 2012). Small-scale lobes are proposed to represent freeze-thaw activity late in Martian climate history (Gallagher et al., 2011; Balme and Gallagher, 2011; Johnsson et al, 2012; Balme et al., 2013). Small-scale lobes differ from permafrost creep (i.e. rock glaciers) in having low fronts, decimeters to less than impact crater slopes fewer lobes have been observed so far in this study. The project is on-going and more work is required to firmly establish their distribution and their association to gullies and polygonal terrain. Though landforms indicative of freeze-thaw activity may be rare on flat terrain on Mars, there is growing evidence that freeze-thaw conditions may have

Centennial-Scale Relationship Between the Southern Hemisphere Westerly Winds and Temperature

Science.gov (United States)

Hodgson, D. A.; Perren, B.; Roberts, S. J.; Sime, L. C.; Verleyen, E.; Van Nieuwenhuyze, W.; Vyverman, W.

2017-12-01

Recent changes in the intensity and position of the Southern Hemisphere Westerly Winds (SHW) have been implicated in a number of important physical changes in the Southern High Latitudes. These include changes in the efficiency of the Southern Ocean CO2 sink through alterations in ocean circulation, the loss of Antarctic ice shelves through enhanced basal melting, changes in Antarctic sea ice extent, and warming of the Antarctic Peninsula. Many of these changes have far-reaching implications for global climate and sea level rise. Despite the importance of the SHW in global climate, our current understanding of the past and future behaviour of the westerly winds is limited by relatively few reconstructions and measurements of the SHW in their core belt over the Antarctic Circumpolar Current; the region most relevant to Southern Ocean air-sea gas exchange. The aim of this study was to reconstruct changes in the relative strength of the SHW at Marion Island, one of a small number of sub-Antarctic islands that lie in the core of the SHWs. We applied independent diatom- and geochemistry- based methods to track past changes in relative wind intensity. This mutiproxy approach provides a validation that the proxies are responding to the external forcing (the SHW) rather than local (e.g. precipitation ) or internal dynamics. Results show that that the strength of the SHW are intrinsically linked to extratropical temperatures over centennial timescales, with warmer temperatures driving stronger winds. Our findings also suggest that large variations in the path and intensity of the westerly winds are driven by relatively small variations in temperature over these timescales. This means that with continued climate warming, even in the absence of anthropogenic ozone-depletion, we should anticipate large shifts in the SHW, causing stronger, more poleward-intensified winds in the decades and centuries to come, with attendant impacts on ocean circulation, ice shelf stability, and

Carbonate-platform response to the Toarcian Oceanic Anoxic Event in the southern hemisphere: Implications for climatic change and biotic platform demise

Science.gov (United States)

Han, Zhong; Hu, Xiumian; Kemp, David B.; Li, Juan

2018-05-01

The Toarcian Oceanic Anoxic Event (T-OAE, ∼183 Ma) was a profound short-term environmental perturbation associated with the large-scale release of 13C-depleted carbon into the global ocean-atmosphere system, which resulted in a significant negative carbon-isotope excursion (CIE). The general lack of characteristic T-OAE records outside of the northern hemisphere means that the precise environmental effects and significance of this event are uncertain. Many biotic carbonate platforms of the northern hemisphere western Tethys drowned or shifted to non-skeletal platforms during the early Toarcian. However, southern hemisphere records of Toarcian carbonate platforms are rare, and thus the extent and significance of biotic platform demise during the T-OAE is unclear. Here we present high-resolution geochemical and sedimentological data across two Pliensbachian-Toarcian shallow-water carbonate-platform sections exposed in the Tibetan Himalaya. These sections were located paleogeographically on the open southeastern tropical Tethyan margin in the southern hemisphere. The T-OAE in the Tibetan Himalaya is marked by a negative CIE in organic matter. Our sedimentological analysis of the two sections reveals an abundance of storm deposits within the T-OAE interval, which emphasizes a close link between warming and tropical storms during the T-OAE event, in line with evidence recently provided from western Tethyan sections of the northern hemisphere. In addition, our analysis also reveals extensive biotic carbonate-platform demise by drowning or changing to non-skeletal carbonates coincident with the onset of the CIE. Taken together, our results suggest that rapid and pervasive seawater warming in response to carbon release likely played a significant role in sudden biotic carbonate platform demise, and suppression/postponement of biotic platform re-development along the whole tropical/subtropical Tethyan margin.

Long-term hemispheric variation of the flare index

International Nuclear Information System (INIS)

Feng Song; Deng Lin-Hua; Xu Shi-Chun

2013-01-01

The long-term hemispheric variation of the flare index is investigated. It is found that, (1) the phase difference of the flare index between the northern and southern hemispheres is about 6–7 months, which is near the time delay between flare activity and sunspot activity; (2) both the dominant and phase-leading hemisphere of the flare index is the northern hemisphere in the considered time interval, implying that the hemispheric asynchrony of solar activity has a close connection with the N-S asymmetry of solar activity. (research papers)

Developing novel peat isotope proxies from vascular plant-dominated peatlands of New Zealand to reconstruct Southern Hemisphere climate dynamics

Science.gov (United States)

Roland, T.; Amesbury, M. J.; Charman, D.; Newnham, R.; Royles, J.; Griffiths, H.; Ratcliffe, J.; Rees, A.; Campbell, D.; Baisden, T.; Keller, E. D.

2017-12-01

The Southern Annular Mode (SAM) is a key control on the strength and position of the southern westerly winds (SWW), which are a major influence on Southern Hemisphere (SH) mid- to high-latitude climate. A shift towards a more positive SAM has occurred since the 1950s, driven by ozone layer thinning and enhanced by greenhouse gas driven warming. Although these recent changes are thought to be unprecedented over the last 1000 years, the longer-term behaviour of the SAM is poorly understood. We are developing stable isotope proxies from plant cellulose in vascular plant-dominated (Empodisma spp.) peatlands in New Zealand that we hypothesise are related to changes in past temperature (δ13C) and precipitation moisture source (δ18O). The moisture source signal is driven by the balance between Southern Ocean sources (depleted δ18O) and sub-tropical sources (enriched δ18O), reflecting the relative states of SAM and the El Niño-Southern Oscillation. We aim to provide palaeoclimatic context for the recent positive trend in the SAM, and explore the long-term relationship between the SAM and ENSO, testing the contention that tropical Pacific variability is a key influence on past and future SAM variability. Terrestrial palaeoclimate records in the Southern Hemisphere are often spatially isolated and temporally fragmented. However, New Zealand is ideally placed to test such hypotheses as it registers strong correlations between SAM, temperature and precipitation, and it straddles the zone of interaction between the SWW and sub-tropical moisture sources, reflected in a strong precipitation δ18O gradient. We report data from surface samples across New Zealand and explore the spatial and temporal patterns in stable isotopes in cellulose and water that we will use to interpret the palaeoenvironmental data. Preliminary downcore data will be used to demonstrate the efficacy of this approach to reconstructing moisture sources and temperature linked to moisture source variability.

Transmission characteristics of the 2009 H1N1 influenza pandemic: comparison of 8 Southern hemisphere countries.

Directory of Open Access Journals (Sweden)

Lulla Opatowski

2011-09-01

Full Text Available While in Northern hemisphere countries, the pandemic H1N1 virus (H1N1pdm was introduced outside of the typical influenza season, Southern hemisphere countries experienced a single wave of transmission during their 2009 winter season. This provides a unique opportunity to compare the spread of a single virus in different countries and study the factors influencing its transmission. Here, we estimate and compare transmission characteristics of H1N1pdm for eight Southern hemisphere countries/states: Argentina, Australia, Bolivia, Brazil, Chile, New Zealand, South Africa and Victoria (Australia. Weekly incidence of cases and age-distribution of cumulative cases were extracted from public reports of countries' surveillance systems. Estimates of the reproduction numbers, R(0, empirically derived from the country-epidemics' early exponential phase, were positively associated with the proportion of children in the populations (p = 0.004. To explore the role of demography in explaining differences in transmission intensity, we then fitted a dynamic age-structured model of influenza transmission to available incidence data for each country independently, and for all the countries simultaneously. Posterior median estimates of R₀ ranged 1.2-1.8 for the country-specific fits, and 1.29-1.47 for the global fits. Corresponding estimates for overall attack-rate were in the range 20-50%. All model fits indicated a significant decrease in susceptibility to infection with age. These results confirm the transmissibility of the 2009 H1N1 pandemic virus was relatively low compared with past pandemics. The pattern of age-dependent susceptibility found confirms that older populations had substantial--though partial--pre-existing immunity, presumably due to exposure to heterologous influenza strains. Our analysis indicates that between-country-differences in transmission were at least partly due to differences in population demography.

Radioiodine (131I) in animal thyroids during nuclear tests in both hemispheres

International Nuclear Information System (INIS)

Van Middlesworth, L.

1975-01-01

In mid-1974 a small increase of 131 I was observed in animal thyroids following a nuclear test in China. In late 1974 there was no public announcement of an atmospheric nuclear test in the Northern Hemisphere, but 131 I was readily measured in animal thyroids. This latter increase occurred while animals in the Southern Hemisphere accumulated 131 I from nuclear tests in the Southern Hemisphere. It is suggested that in late 1974 the Northern Hemisphere was contaminated by either late fallout from tests in June or by interhemispheric mixing or by a combination of these sources. (author)

Circulation of the polar thermosphere during geomagnetically quiet and active times as observed by Dynamics Explorer 2

International Nuclear Information System (INIS)

McCormac, F.G.; Killeen, T.L.; Thayer, J.P.; Hernandez, G.; Tschan, C.R.; Ponthieu, J.J.; Spencer, N.W.

1987-01-01

Neutral wind measurements obtained by instruments on board the Dynamics Explorer 2 (DE 2) spacecraft have been used to study the effects of geomagnetic activity on the circulation of the high-latitude neutral thermosphere for solar maximum conditions during the periods of November 1981 through January 1982 and November 1982 through January 1983. The data have been sorted and ordered according to the two geophysical indices Kp and (auroral electrojet) AE. Simple expressions have been derived which describe (1) the maximum antisunward wind speed in the geomagnetic polar cap, (2) the maximum sunward wind speeds in the dawn and dusk sectors of the auroral oval, and (3) the latitudinal extent of the polar cap antisunward neutral wind as functions of Kp and AE. The results show a positive correlation between the geomagnetic indices and the three characteristic features of the neutral circulation described above. Averaged vector wind fields in geomagnetic coordinates for Kp ≤ 2 and Kp ≥ 4 in both northern and southern hemispheres for the 6 months have been derived from the data. In doing this, a first-order invariance of the neutral wind circulation in geomagnetic coordinates as a function of universal time (UT) was assumed. The results show a two-cell circulation pattern in the northern winter hemisphere for both quiet and active geomagnetic periods. The cell sizes increase with increasing geomagnetic activity. The dusk cell is always dominant. The southern summer hemisphere averages show only the dusk circulation cell for both quiet and active geomagnetic periods. The cell sizes increase with increasing geomagnetic activity. The dusk cell is always dominant. The southern summer hemisphere averages show only the dusk circulation cell for both quiet and active geomagnetic periods. A diminution of this cell occurs for reduced levels of geomagnetic activity

Polar ocean stratification in a cold climate.

Science.gov (United States)

Sigman, Daniel M; Jaccard, Samuel L; Haug, Gerald H

2004-03-04

The low-latitude ocean is strongly stratified by the warmth of its surface water. As a result, the great volume of the deep ocean has easiest access to the atmosphere through the polar surface ocean. In the modern polar ocean during the winter, the vertical distribution of temperature promotes overturning, with colder water over warmer, while the salinity distribution typically promotes stratification, with fresher water over saltier. However, the sensitivity of seawater density to temperature is reduced as temperature approaches the freezing point, with potential consequences for global ocean circulation under cold climates. Here we present deep-sea records of biogenic opal accumulation and sedimentary nitrogen isotopic composition from the Subarctic North Pacific Ocean and the Southern Ocean. These records indicate that vertical stratification increased in both northern and southern high latitudes 2.7 million years ago, when Northern Hemisphere glaciation intensified in association with global cooling during the late Pliocene epoch. We propose that the cooling caused this increased stratification by weakening the role of temperature in polar ocean density structure so as to reduce its opposition to the stratifying effect of the vertical salinity distribution. The shift towards stratification in the polar ocean 2.7 million years ago may have increased the quantity of carbon dioxide trapped in the abyss, amplifying the global cooling.

Measurement of the neutron and gamma doses accumulated during commercial jet flights from Sydney to several major destinations in the northern and southern hemisphere

International Nuclear Information System (INIS)

Mukherjee, B.; Cross, P.; Alsop, R.

2002-01-01

As recommended by the ICRP, the European Union (EU) agreed to abide by mandatory monitoring of radiation doses to crew during civil aviation flights operated by the airlines of the EU member states. A large number of measured and theoretically predicted values for the in-flights radiation doses of northern hemisphere flight routes are available. On the other hand very few data have been published for the southern hemisphere. This paper will present the results of Australian domestic and international return flight routes originating from Sydney. The paper also presents results of trans-hemisphere air traffic routes. Neutron and gamma doses were measured using superheated bubble dosemeters and semiconductor detectors respectively. Based on our measurements a method is suggested whereby aircrew may share their personal radiation burden by flight crew hemisphere exchange. (author)

Southern Hemisphere origins for interannual variations of Tibetan Plateau snow cover in boreal summer

Science.gov (United States)

Wu, Z.

2017-12-01

The climate response to the Tibetan Plateau (TP) snow cover (TPSC) has been receiving extensive concern. However, relatively few studies have devoted to revealing the potential factors that can contribute to the TPSC variability on the interannual time scale. Especially during the boreal summer, snow cover can persist over the TP at high elevations, which exerts profound influences on the local and remote climate change. The present study finds that May Southern Hemisphere (SH) annular mode (SAM), the dominating mode of atmospheric circulation variability in the SH extratropics, exhibits a significant positive relationship with the boreal summer TPSC interannual variability. Observational analysis and numerical experiments manifest that the signal of May SAM can be "prolonged" by a meridional Indian Ocean tripole (IOT) sea surface temperature anomaly (SSTA) via atmosphere-ocean interaction. The IOT SSTA pattern persists into the following summer and excites anomalous local-scale zonal vertical circulation. Subsequently, a positive (or negative) tropical dipole rainfall (TDR) mode is induced with deficient (or sufficient) precipitation in tropical western Indian Ocean and sufficient (or deficient) precipitation in eastern Indian Ocean-Maritime continent. Rossby wave source diagnosis reveals that the wave energies, generated by the latent heat release of the TDR mode, propagate northward into western TP. As a response, abnormal cyclonic circulation and upward movement are triggered and prevail over western TP, providing favorable dynamical conditions for more TPSC, and vice versa. Hence, the IOT SSTA plays an "ocean bridge" role and the TDR mode acts as an "atmosphere bridge" role in the process of May SAM impacting the following summer TPSC variability. The results of our work may provide new insight about the cross-equatorial propagation of the SAM influence. Keywords Southern Hemisphere annular mode; Tibetan Plateau snow cover; Rossby wave source

Extended period of polar cap auroral display: auroral dynamics and relation to the IMF and the ionospheric convection

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V. G. Vorobjev

Full Text Available An unusually extended period (5 h of polar cap auroral display on 3 August 1986 is examined. Auroras have been investigated using ground-based data as well as measurements from the IMP-8 spacecraft in interplanetary space and simultaneous observations from the polar-orbiting satellites Viking and DE-1 in the northern and southern hemispheres, respectively. It is found that visible Sun-aligned arcs are located inside the transpolar band of the θ-aurora observed from the satellite in ultraviolet wavelengths. The transpolar band can contain several Sun-aligned arcs that move inside the band toward the morning or evening side of the auroral oval independent of the direction of the band movement. Intensifications of polar cap auroras with durations of up to about 30 min are observed. No change has been found in either IMF parameters or substorm activity that can be related to these intensifications. The θ-aurora occurred during a 2-h period when the B _z-component of the IMF was negative. A tendency is noted for dawnward (duskward displacement of the transpolar band when B_y>0 (B_y<0 in the southern hemisphere. Simultaneous observations of auroral ovals during interplanetary B_z<0, B_y<0 and B_x>0 in both hemispheres and convection patterns for B_z<0 and B_y<0 have been displayed using satellite and ground-based measurements. It was found that the transpolar band of the -aurora in the sunlit hemisphere was situated in the region of large-scale downward Birkeland currents.

Unexpected Southern Hemisphere ionospheric response to geomagnetic storm of 15 August 2015

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I. Edemskiy

2018-01-01

Full Text Available Geomagnetic storms are the most pronounced phenomenon of space weather. When studying ionospheric response to a storm of 15 August 2015, an unexpected phenomenon was observed at higher middle latitudes of the Southern Hemisphere. This phenomenon was a localized total electron content (TEC enhancement (LTE in the form of two separated plumes, which peaked southward of South Africa. The plumes were first observed at 05:00 UT near the southwestern coast of Australia. The southern plume was associated with local time slightly after noontime (1–2 h after local noon. The plumes moved with the Sun. They peaked near 13:00 UT southward of South Africa. The southern plume kept constant geomagnetic latitude (63–64° S; it persisted for about 10 h, whereas the northern plume persisted for about 2 h more. Both plumes disappeared over the South Atlantic Ocean. No similar LTE event was observed during the prolonged solar activity minimum period of 2006–2009. In 2012–2016 we detected altogether 26 LTEs and all of them were associated with the southward excursion of Bz. The negative Bz excursion is a necessary but not sufficient condition for the LTE occurrence as during some geomagnetic storms associated with negative Bz excursions the LTE events did not appear.

The effect of sea-ice on the transient atmospheric eddies of the Southern Hemisphere

Energy Technology Data Exchange (ETDEWEB)

Menendez, C.G. [Centro de Investigaciones del Mar y la Atmosfera/CONICET-UBA, Buenos Aires (Argentina); Serafini, V.; Le Treut, H. [Laboratoire de Meteorologie Dynamique/CNRS, Universite P. et M. Curie, Tour 15-25, 4 place Jussieu, 75252 Paris Cedex 05 (France)

1999-09-01

Two 10 y simulations with a full seasonal cycle and 96 x 72 x 19 resolution were carried out with a version of the LMD GCM to diagnose the role of sea-ice on the extratropical climatology of the Southern Hemisphere. The control integration used the usual observed sea-ice distribution, while the anomaly simulation imposed a scenario in which all sea-ice was entirely replaced by open ocean. The simulated control climate was compared with available observational-based analyses. Relevant diagnostics of the time mean and indicators of the transient eddy activity have been evaluated for both integrations. The impact was shown throughout the troposphere and was larger and more organised in winter. We found reduced westerly flow and both falls and rises in sea level pressure in the region from which sea-ice was removed. The removal of ice in the Southern Ocean affects the baroclinic structure of the atmosphere. Changes in baroclinicity and eddy activity are consistent with changes in the mean climate. In general, the meridional wind variance, the poleward transient temperature flux and the eddy flux convergence of westerly momentum were weaker over the Southern Ocean. However, a strengthening of the variance downstream of the subtropical jet was found. The position of the main storm track tends to be slightly displaced equatorward in the anomaly case. (orig.) With 15 figs., 53 refs.

Cluster analysis of tropical cyclone tracks in the Southern Hemisphere

Energy Technology Data Exchange (ETDEWEB)

Ramsay, Hamish A. [Monash University, Monash Weather and Climate, School of Mathematical Sciences, Clayton, VIC (Australia); Camargo, Suzana J.; Kim, Daehyun [Columbia University, Lamont-Doherty Earth Observatory, Palisades, NY (United States)

2012-08-15

A probabilistic clustering method is used to describe various aspects of tropical cyclone (TC) tracks in the Southern Hemisphere, for the period 1969-2008. A total of 7 clusters are examined: three in the South Indian Ocean, three in the Australian Region, and one in the South Pacific Ocean. Large-scale environmental variables related to TC genesis in each cluster are explored, including sea surface temperature, low-level relative vorticity, deep-layer vertical wind shear, outgoing longwave radiation, El Nino-Southern Oscillation (ENSO) and the Madden-Julian Oscillation (MJO). Composite maps, constructed 2 days prior to genesis, show some of these to be significant precursors to TC formation - most prominently, westerly wind anomalies equatorward of the main development regions. Clusters are also evaluated with respect to their genesis location, seasonality, mean peak intensity, track duration, landfall location, and intensity at landfall. ENSO is found to play a significant role in modulating annual frequency and mean genesis location in three of the seven clusters (two in the South Indian Ocean and one in the Pacific). The ENSO-modulating effect on genesis frequency is caused primarily by changes in low-level zonal flow between the equator and 10 S, and associated relative vorticity changes in the main development regions. ENSO also has a significant effect on mean genesis location in three clusters, with TCs forming further equatorward (poleward) during El Nino (La Nina) in addition to large shifts in mean longitude. The MJO has a strong influence on TC genesis in all clusters, though the amount modulation is found to be sensitive to the definition of the MJO. (orig.)

A Southern Hemisphere atmospheric history of carbon monoxide from South Pole firn air

Science.gov (United States)

Verhulst, K. R.; Aydin, M.; Novelli, P. C.; Holmes, C. D.; Prather, M. J.; Saltzman, E. S.

2013-12-01

Carbon monoxide (CO) is a reactive trace gas and is important to tropospheric photochemistry as a major sink of hydroxyl radicals (OH). Major sources of CO are fossil fuel combustion, linked mostly to automotive emissions, biomass burning, and oxidation of atmospheric methane. Understanding changes in carbon monoxide over the past century will improve our understanding of man's influence on the reactivity of the atmosphere. Little observational information is available about CO levels and emissions prior to the 1990s, particularly for the Southern Hemisphere. The NOAA global flask network provides the most complete instrumental record of CO, extending back to 1988. Annually averaged surface flask measurements suggest atmospheric CO levels at South Pole were relatively stable from 2004-2009 at about 51 nmol mol-1 [Novelli and Masarie, 2013]. In this study, a 20th century atmospheric history of CO is reconstructed from South Pole firn air measurements, using a 1-D firn air diffusion model. Firn air samples were collected in glass flasks from two adjacent holes drilled from the surface to 118 m at South Pole, Antarctica during the 2008/2009 field season and CO analysis was carried out by NOAA/CCG. Carbon monoxide levels increase from about 45 nmol mol-1 in the deepest firn sample at 116 m to 52 nmol mol-1 at 107 m, and remain constant at about 51-52 nmol mol-1 at shallower depths. Atmospheric histories based on the firn air reconstructions suggest that CO levels over Antarctica increased by roughly 40% (from about 36 to 50 nmol mol-1) between 1930-1990, at a rate of about 0.18 nmol mol-1 yr-1. Firn air and surface air results suggest the rate of CO increase at South Pole slowed considerably after 1990. The firn air-based atmospheric history is used to infer changes in Southern Hemisphere CO emissions over the 20th century.

Does the bipolar seesaw extend to the terrestrial southern mid-latitudes?

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Newnham, Rewi M.; Vandergoes, Marcus J.; Sikes, Elisabeth; Carter, Lionel; Wilmshurst, Janet M.; Lowe, David J.; McGlone, Matt S.; Sandiford, Anna

2012-03-01

High precision comparison of Greenland and Antarctic ice cores, suggesting a pervasive antiphased temperature relationship between the polar hemispheres during the last glaciation, lends strong support to the bipolar seesaw model (EPICA, 2006). The extent to which reorganisation of ocean-heat transport during abrupt climate change events affected the southern mid-latitudes remains unclear, however, owing to a paucity of well-dated records with robust climate proxies, variability between some records, and varying interpretations of their significance. Here we present temperature reconstructions for three key pollen records recognised by the NZ-INTIMATE (NZ-I) group which, along with the preliminary NZ-I climate event stratigraphy (Alloway et al., 2007) and published marine records, are compared with polar ice core records for the interval 30-10 cal. ka. We focus on key events within the context of Dansgard Oeschger cycles 4-1 and The Antarctic Cold Reversal/Younger Dryas intervals. The New Zealand records are broadly consistent with an extended bipolar seesaw whereby the oceanic southern mid-latitudes are warmed at times of MOC weakening or cessation in the North Atlantic, and vice versa. Variability between records indicate that other factors must be involved, however, and nor do these records refute alternative models that predict an antiphased inter-hemispheric pattern. Nevertheless an extended bipolar model may explain an early onset of LGM conditions in New Zealand and elsewhere in the Southern Hemisphere at a time when interstadials GI3 and GI4 kept Greenland warm. Similar inter-hemispheric dynamics have been invoked to explain an earlier termination of the LGM in Antarctica than in Greenland (Wolff et al., 2009) which is also evident in the New Zealand records. A prominent mid-LGM interstadial complex observed in several New Zealand records, connected by tephrochronology may represent another antiphased event although stronger chronological control is needed

Survival and breeding of polar bears in the southern Beaufort Sea in relation to sea ice.

Science.gov (United States)

Regehr, Eric V; Hunter, Christine M; Caswell, Hal; Amstrup, Steven C; Stirling, Ian

2010-01-01

1. Observed and predicted declines in Arctic sea ice have raised concerns about marine mammals. In May 2008, the US Fish and Wildlife Service listed polar bears (Ursus maritimus) - one of the most ice-dependent marine mammals - as threatened under the US Endangered Species Act. 2. We evaluated the effects of sea ice conditions on vital rates (survival and breeding probabilities) for polar bears in the southern Beaufort Sea. Although sea ice declines in this and other regions of the polar basin have been among the greatest in the Arctic, to date population-level effects of sea ice loss on polar bears have only been identified in western Hudson Bay, near the southern limit of the species' range. 3. We estimated vital rates using multistate capture-recapture models that classified individuals by sex, age and reproductive category. We used multimodel inference to evaluate a range of statistical models, all of which were structurally based on the polar bear life cycle. We estimated parameters by model averaging, and developed a parametric bootstrap procedure to quantify parameter uncertainty. 4. In the most supported models, polar bear survival declined with an increasing number of days per year that waters over the continental shelf were ice free. In 2001-2003, the ice-free period was relatively short (mean 101 days) and adult female survival was high (0.96-0.99, depending on reproductive state). In 2004 and 2005, the ice-free period was longer (mean 135 days) and adult female survival was low (0.73-0.79, depending on reproductive state). Breeding rates and cub litter survival also declined with increasing duration of the ice-free period. Confidence intervals on vital rate estimates were wide. 5. The effects of sea ice loss on polar bears in the southern Beaufort Sea may apply to polar bear populations in other portions of the polar basin that have similar sea ice dynamics and have experienced similar, or more severe, sea ice declines. Our findings therefore are

Biogeography in Cellana (Patellogastropoda, Nacellidae with Special Emphasis on the Relationships of Southern Hemisphere Oceanic Island Species.

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Claudio A González-Wevar

Full Text Available Oceanic islands lacking connections to other land are extremely isolated from sources of potential colonists and have acquired their biota mainly through dispersal from geographically distant areas. Hence, isolated island biota constitutes interesting models to infer biogeographical mechanisms of dispersal, colonization, differentiation, and speciation. Limpets of the genus Cellana (Nacellidae: Patellogastropoda show limited dispersal capacity but are broadly distributed across the Indo-Pacific including many endemic species in isolated oceanic islands. Here, we examined main distributional patterns and geographic boundaries among Cellana lineages with special emphasis in the relationships of Southern Hemisphere oceanic islands species. Phylogenetic reconstructions based on mtDNA (COI recognized three main clades in Cellana including taxa from different provinces of the Indo-Pacific. Clear genetic discontinuities characterize the biogeography of Cellana and several lineages are associated to particular areas of the Indo-Pacific supporting the low dispersal capacity of the genus across recognized biogeographical barriers in the region. However, evolutionary relationships within Cellana suggest that long-distance dispersal processes have been common in the history of the genus and probably associated to the origin of the species in Hawaii and Juan Fernández Archipelago. Therefore, the presence of Cellana species in geographically distant Southern Hemisphere oceanic islands, such as the Juan Fernández Archipelago, suggests that long-distance dispersal mediated by rafting may have played an important role in the biogeography of the genus.

Biogeography in Cellana (Patellogastropoda, Nacellidae) with Special Emphasis on the Relationships of Southern Hemisphere Oceanic Island Species

Science.gov (United States)

Nakano, Tomoyuki; Palma, Alvaro; Poulin, Elie

2017-01-01

Oceanic islands lacking connections to other land are extremely isolated from sources of potential colonists and have acquired their biota mainly through dispersal from geographically distant areas. Hence, isolated island biota constitutes interesting models to infer biogeographical mechanisms of dispersal, colonization, differentiation, and speciation. Limpets of the genus Cellana (Nacellidae: Patellogastropoda) show limited dispersal capacity but are broadly distributed across the Indo-Pacific including many endemic species in isolated oceanic islands. Here, we examined main distributional patterns and geographic boundaries among Cellana lineages with special emphasis in the relationships of Southern Hemisphere oceanic islands species. Phylogenetic reconstructions based on mtDNA (COI) recognized three main clades in Cellana including taxa from different provinces of the Indo-Pacific. Clear genetic discontinuities characterize the biogeography of Cellana and several lineages are associated to particular areas of the Indo-Pacific supporting the low dispersal capacity of the genus across recognized biogeographical barriers in the region. However, evolutionary relationships within Cellana suggest that long-distance dispersal processes have been common in the history of the genus and probably associated to the origin of the species in Hawaii and Juan Fernández Archipelago. Therefore, the presence of Cellana species in geographically distant Southern Hemisphere oceanic islands, such as the Juan Fernández Archipelago, suggests that long-distance dispersal mediated by rafting may have played an important role in the biogeography of the genus. PMID:28099466

Long-range transport of stratospheric aerosols in the Southern Hemisphere following the 2015 Calbuco eruption

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N. Bègue

2017-12-01

Full Text Available After 43 years of inactivity, the Calbuco volcano, which is located in the southern part of Chile, erupted on 22 April 2015. The space–time evolutions (distribution and transport of its aerosol plume are investigated by combining satellite (CALIOP, IASI, OMPS, in situ aerosol counting (LOAC OPC and lidar observations, and the MIMOSA advection model. The Calbuco aerosol plume reached the Indian Ocean 1 week after the eruption. Over the Reunion Island site (21° S, 55.5° E, the aerosol signal was unambiguously enhanced in comparison with background conditions, with a volcanic aerosol layer extending from 18 to 21 km during the May–July period. All the data reveal an increase by a factor of  ∼  2 in the SAOD (stratospheric aerosol optical depth with respect to values observed before the eruption. The aerosol mass e-folding time is approximately 90 days, which is rather close to the value ( ∼  80 days reported for the Sarychev eruption. Microphysical measurements obtained before, during, and after the eruption reflecting the impact of the Calbuco eruption on the lower stratospheric aerosol content have been analyzed over the Reunion Island site. During the passage of the plume, the volcanic aerosol was characterized by an effective radius of 0.16 ± 0.02 µm with a unimodal size distribution for particles above 0.2 µm in diameter. Particle concentrations for sizes larger than 1 µm are too low to be properly detected by the LOAC OPC. The aerosol number concentration was  ∼  20 times higher that observed before and 1 year after the eruption. According to OMPS and lidar observations, a tendency toward conditions before the eruption was observed by April 2016. The volcanic aerosol plume is advected eastward in the Southern Hemisphere and its latitudinal extent is clearly bounded by the subtropical barrier and the polar vortex. The transient behavior of the aerosol layers observed above Reunion Island

Tropical Tropospheric Ozone from SHADOZ (Southern Hemisphere ADditional Ozonesondes) Network: A Project for Satellite Research, Process Studies, Education

Science.gov (United States)

Thompson, Anne M.; Witte, Jacquelyn C.; Oltmans, Samuel J.; Schmidlin, Francis J.; Coetzee, G. J. R.; Hoegger, Bruno; Kirchhoff, V. W. J. H.; Ogawa, Toshihiro; Kawakami, Shuji; Posny, Francoise

2002-01-01

The first climatological overview of total, stratospheric and tropospheric ozone in the southern hemisphere tropical and subtropics is based on ozone sounding data from 10 sites comprising the Southern Hemisphere Additional OZonesondes (SHADOZ) network. The period covered is 1998-2000. Observations were made over: Ascension Island; Nairobi, Kenya; Irene, South Africa; Reunion Island; Watukosek, Java; Fiji; Tahiti; American Samoa; San Cristobal, Galapagos; Natal, Brazil. Campaign data were collected on a trans-Atlantic oceanographic cruise and during SAFARI-2000 in Zambia. The ozone data, with simultaneous temperature profiles to approx. 7 hPa and relative humidity to approx. 200 hPa, reside at: . SHADOZ ozone time-series and profiles give a perspective on tropical total, stratospheric and tropospheric ozone. Prominent features are highly variable tropospheric ozone and a zonal wave-one pattern in total (and tropospheric) column ozone. Total, stratospheric and tropospheric column ozone amounts peak between August and November and are lowest between March and May. Tropospheric ozone variability over the Indian and Pacific Ocean displays influences of the Indian Ocean Dipole and convective mixing. Pollution transport from Africa and South America is a seasonal feature. Tropospheric ozone seasonality over the Atlantic Basin shows effects of regional subsidence and recirculation as well as biomass burning. Dynamical and chemical influences appear to be of comparable magnitude though model studies are needed to quantify this.

SOUTH POL: Revealing the Polarized Southern Sky

Science.gov (United States)

Magalhaes, Antonio Mario Mario; Ramírez, Edgar; Ribeiro, Nadili; Seriacopi, Daiane; Rubinho, Marcelo; Ferrari, Tiberio; Rodrigues, Claudia; Schoenell, William; Herpich, Fabio; Pereyra, Antonio

2018-01-01

SOUTH POL will be a survey of the Southern sky in optical polarized light. It will use a newly built polarimeter for T80-S, an 84 cm robotic telescope installed at Cerro Tololo (CTIO), Chile. It will initially cover the sky South of declination -15 deg with a polarimetric accuracy Solar System.The polarimeter has just been commissioned in mid-November, 2017. The data reduction pipeline has already been built. We will describe the instrument and the data reduction, as well as a few of the science cases. The survey is expected to begin midway through the 1st semester of 2018. Both catalog data and raw images will be made available.

Detection of Northern Hemisphere transient eddies at Gale Crater Mars

Science.gov (United States)

Haberle, Robert M.; Juárez, Manuel de la Torre; Kahre, Melinda A.; Kass, David M.; Barnes, Jeffrey R.; Hollingsworth, Jeffery L.; Harri, Ari-Matti; Kahanpää, Henrik

2018-06-01

The Rover Environmental Monitoring Station (REMS) on the Curiosity Rover is operating in the Southern Hemisphere of Mars and is detecting synoptic period oscillations in the pressure data that we attribute to Northern Hemisphere transient eddies. We base this interpretation on the similarity in the periods of the eddies and their seasonal variations with those observed in northern midlatitudes by Viking Lander 2 (VL-2) 18 Mars years earlier. Further support for this interpretation comes from global circulation modeling which shows similar behavior in the transient eddies at the grid points closest to Curiosity and VL-2. These observations provide the first in situ evidence that the frontal systems often associated with "Flushing Dust Storms" do cross the equator and extend into the Southern Hemisphere.

MIPAS measurements of upper tropospheric C2H6 and O3 during the southern hemispheric biomass burning season in 2003

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T. Steck

2007-11-01

Full Text Available Under cloud free conditions, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS provides measurements of spectrally resolved limb radiances down to the upper troposphere. These are used to infer global distributions of mixing ratios of atmospheric constituents in the upper troposphere and the stratosphere. From 21 October to 12 November 2003, MIPAS observed enhanced amounts of upper tropospheric C2H6 (up to about 400 pptv and ozone (up to about 80 ppbv. The absolute values of C2H6, however, may be systematically low by about 30% due to uncertainties of the spectroscopic data used. By means of trajectory calculations, the enhancements observed in the southern hemisphere are, at least partly, attributed to a biomass burning plume, which covers wide parts of the Southern hemisphere, from South America, the Atlantic Ocean, Africa, the Indian Ocean to Australia. The chemical composition of the part of the plume-like pollution belt associated with South American fires, where rainforest burning is predominant appears different from the part of the plume associated with southern African savanna burning. In particular, African savanna fires lead to a larger ozone enhancement than equatorial American fires. In this analysis, MIPAS observations of high ozone were disregarded where low CFC-11 (below 245 pptv was observed, because this hints at a stratospheric component in the measured signal. Different type of vegetation burning (flaming versus smouldering combustion has been identified as a candidate explanation for the different plume compositions.

Survival and breeding of polar bears in the southern Beaufort Sea in relation to sea ice

Science.gov (United States)

Regehr, E.V.; Hunter, C.M.; Caswell, H.; Amstrup, Steven C.; Stirling, I.

2010-01-01

1. Observed and predicted declines in Arctic sea ice have raised concerns about marine mammals. In May 2008, the US Fish and Wildlife Service listed polar bears (Ursus maritimus) - one of the most ice-dependent marine mammals - as threatened under the US Endangered Species Act. 2. We evaluated the effects of sea ice conditions on vital rates (survival and breeding probabilities) for polar bears in the southern Beaufort Sea. Although sea ice declines in this and other regions of the polar basin have been among the greatest in the Arctic, to date population-level effects of sea ice loss on polar bears have only been identified in western Hudson Bay, near the southern limit of the species' range. 3. We estimated vital rates using multistate capture-recapture models that classified individuals by sex, age and reproductive category. We used multimodel inference to evaluate a range of statistical models, all of which were structurally based on the polar bear life cycle. We estimated parameters by model averaging, and developed a parametric bootstrap procedure to quantify parameter uncertainty. 4. In the most supported models, polar bear survival declined with an increasing number of days per year that waters over the continental shelf were ice free. In 2001-2003, the ice-free period was relatively short (mean 101 days) and adult female survival was high (0 ∙ 96-0 ∙ 99, depending on reproductive state). In 2004 and 2005, the ice-free period was longer (mean 135 days) and adult female survival was low (0 ∙ 73-0 ∙ 79, depending on reproductive state). Breeding rates and cub litter survival also declined with increasing duration of the ice-free period. Confidence intervals on vital rate estimates were wide. 5. The effects of sea ice loss on polar bears in the southern Beaufort Sea may apply to polar bear populations in other portions of the polar basin that have similar sea ice dynamics and have experienced similar, or more severe, sea ice declines. Our findings

Response of the meridional overturning circulation to variable buoyancy forcing in a double hemisphere basin

Energy Technology Data Exchange (ETDEWEB)

Lucas, Marc A. [National Oceanography Centre, University of Southampton, School of Ocean and Earth Science, Southampton (United Kingdom); Collecte Localisation Satellite, Ramonville Saint Agne (France); Hirschi, J.J.M. [National Oceanography Centre, University of Southampton, School of Ocean and Earth Science, Southampton (United Kingdom); Marotzke, J. [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany)

2010-04-15

We consider how a highly idealized double-hemisphere basin responds to a zonally constant restoring surface temperature profile that oscillates in time, with periods ranging from 0.5 to 32,000 years. In both hemispheres, the forcing is similar but can be either in phase or out of phase. The set-up is such that the Northern Hemisphere always produces the densest waters. The model's meridional overturning circulation (MOC) exhibits a strong response in both hemispheres on decadal to multi-millennial timescales. The amplitude of the oscillations reaches up to 140% of the steady-state maximum MOC and exhibits resonance-like behaviour, with a maximum at centennial to millennial forcing periods. When the forcing is in phase between the Northern and Southern Hemispheres, there is a marked decrease in the amplitude of the MOC response as the forcing period is increased beyond the resonance period. In this case the resonance-like behaviour is identical to the one we found earlier in a single-hemisphere model and occurs for the same reasons. When the forcing is out of phase between the Northern and Southern Hemispheres, the amplitude of the MOC response is substantially greater for long forcing periods (millennial and longer), particularly in the Southern Hemisphere. This increased MOC amplitude occurs because for an out of phase forcing, either the northern or the southern deep water source is always active, leading to generally colder bottom waters and thus greater stratification in the opposite hemisphere. This increased stratification in turn stabilises the water column and thus reduces the strength of the weaker overturning cell. The interaction of the two hemispheres leads to response timescales of the deep ocean at half the forcing period. Our results suggest a possible explanation for the half-precessional time scale observed in the deep Atlantic Ocean palaeo-temperature record. (orig.)

CO2 Fluxes and Concentrations in a Residential Area in the Southern Hemisphere

Science.gov (United States)

Weissert, L. F.; Salmond, J. A.; Turnbull, J. C.; Schwendenmann, L.

2014-12-01

While cities are generally major sources of anthropogenic carbon dioxide (CO2) emissions, recent research has shown that parts of urban areas may also act as CO2 sinks due to CO2 uptake by vegetation. However, currently available results are related to a large degree of uncertainty due to the limitations of the applied methods and the limited number of studies available from urban areas, particularly from the southern hemisphere. In this study, we explore the potential of eddy covariance and tracer measurements (13C and 14C isotopes of CO2) to quantify and partition CO2 fluxes and concentrations in a residential urban area in Auckland, New Zealand. Based on preliminary results from autumn and winter (March to July 2014) the residential area is a small source of CO2 (0.11 mol CO2 m-2 day-1). CO2 fluxes and concentrations follow a distinct diurnal cycle with a morning peak between 7:00 and 9:00 (max: 0.25 mol CO2 m-2 day-1/412 ppm) and midday low with negative CO2 fluxes (min: -0.17 mol CO2 m-2 day-1/392 ppm) between 10:00 and 15:00 local time, likely due to photosynthetic CO2 uptake by local vegetation. Soil CO2 efflux may explain that CO2 concentrations increase and remain high (401 ppm) throughout the night. Mean diurnal winter δ13C values are in anti-phase with CO2 concentrations and vary between -9.0 - -9.7‰. The depletion of δ13C compared to clean atmospheric air (-8.2‰) is likely a result of local CO2 sources dominated by gasoline combustion (appr. 60%) during daytime. A sector analysis (based on prevailing wind) of CO2 fluxes and concentrations indicates lower CO2 fluxes and concentrations from the vegetation-dominated sector, further demonstrating the influence of vegetation on local CO2 concentrations. These results provide an insight into the temporal and spatial variability CO2 fluxes/concentrations and potential CO2 sinks and sources from a city in the southern hemisphere and add valuable information to the global database of urban CO2 fluxes.

Natural radioactivity balance in the atmosphere of the southern hemisphere

International Nuclear Information System (INIS)

Lambert, G.; Ardouin, B.; Polian, G.; Sanak, J.

1972-01-01

It is well known that radon-222 is a radioactive rare gas, continuously produced in the soil by the disintegration of radium-226. Radon can diffuse in the soil and is outgassed into the atmosphere from the surface of the continents at the rate of about 0.7 atoms/ (cm 2 -second). Whenever the soil is covered by snow or even an iceshelf, the flux of radon becomes negligible. Surficial sea water also contains radium-226 and the oceans could release into the atmosphere a part of the produced radon. Therefore a small flux of 10 -2 atoms/(cm 2 -second) can be expected from the surface of the oceans. The radon-222 half-life of 3.8 days is long enough so that the measured radon is usually of continental origin even in the middle of any main ocean. However, below 50 0 South, it is difficult to attribute the radon to either a continental or oceanic origin. Data are presented on seasonal and altitudinal variations in radon-220, lead-210, polonium-210, and radon-222 concentrations in air samples from various locations in the Southern Hemisphere. The relation of air mass circulation in the Antartic to radioactivity in air is discussed. (U.S.)

Transport and scavenging of Pu in surface waters of the Southern Hemisphere Oceans

DEFF Research Database (Denmark)

Gastaud, J.; Povinec, P.P.; Aoyama, M.

2011-01-01

The distribution of 239Pu in Atlantic and Indian Ocean waters about four decades after their main injection from atmospheric nuclear weapons tests is discussed. Recent data obtained in the framework of the SHOTS (Southern Hemisphere Ocean Tracer Studies) projects are evaluated and compared...... with previous investigations. Seawater samples were collected during the round the globe BEAGLE2003 (Blue Ocean Global Expedition) along the 30°S transect in the Atlantic and the 20°S transect in the Indian Ocean. The results indicate transport of surface waters labelled with 239Pu from the western North...... Pacific via the Indonesian Seas to the South Indian Ocean and then to the South Atlantic Ocean. Along the whole BEAGLE2003 sampling route, the Atlantic Ocean has the lowest 239Pu content due to its particle scavenging on the long way from the western North Pacific. On the other hand, concentrations...

Hematology of southern Beaufort Sea polar bears (2005-2007): biomarker for an Arctic ecosystem health sentinel.

Science.gov (United States)

Kirk, Cassandra M; Amstrup, Steven; Swor, Rhonda; Holcomb, Darce; O'Hara, Todd M

2010-09-01

Declines in sea-ice habitats have resulted in declining stature, productivity, and survival of polar bears in some regions. With continuing sea-ice declines, negative population effects are projected to expand throughout the polar bear's range. Precise causes of diminished polar bear life history performance are unknown, however, climate and sea-ice condition change are expected to adversely impact polar bear (Ursus maritimus) health and population dynamics. As apex predators in the Arctic, polar bears integrate the status of lower trophic levels and are therefore sentinels of ecosystem health. Arctic residents feed at the apex of the ecosystem, thus polar bears can serve as indicators of human health in the Arctic. Despite their value as indicators of ecosystem welfare, population-level health data for U.S. polar bears are lacking. We present hematological reference ranges for southern Beaufort Sea polar bears. Hematological parameters in southern Beaufort Sea polar bears varied by age, geographic location, and reproductive status. Total leukocytes, lymphocytes, monocytes, eosinophils, and serum immunoglobulin G were significantly greater in males than females. These measures were greater in nonlactating females ages ≥5, than lactating adult females ages ≥5, suggesting that females encumbered by young may be less resilient to new immune system challenges that may accompany ongoing climate change. Hematological values established here provide a necessary baseline for anticipated changes in health as arctic temperatures warm and sea-ice declines accelerate. Data suggest that females with dependent young may be most vulnerable to these changes and should therefore be a targeted cohort for monitoring in this sentinel.

Inter-hemispheric gradient of atmospheric trace gases in the Pacific

International Nuclear Information System (INIS)

Lowe, D.; Manning, M.; Brailsford, G.; Bromley, T.; Moss, R.; Ferretti, D.

1997-01-01

Measurements of atmospheric trace gases show that the concentrations and isotopic compositions of these species can change dramatically across the intertropical convergence zone (ITCZ) separating the two hemispheres. Because the anthropogenic sources of virtually all trace gases are greater in the northern than in the southern hemisphere, concentrations of the species are lower in the southern hemisphere. Typically the concentration gradient is inversely proportional to the lifetime of the trace gas in the atmosphere. Hence understanding the transport across the ITCZ is crucial to determining the variation of important trace gases in the New Zealand region. Container ships are being used to collect large clean air samples on voyages across the Pacific on great circle routes between Auckland (New Zealand), Honolulu (Hawaii) and Los Angeles and Seattle on the US West coast. Measurements on these samples are being used to supplement extensive carbon isotope measurements of atmospheric methane made at fixed sites in the southern hemisphere: Baring Head (New Zealand), Suva (Fiji) and Scott Base (Antarctica) to provide information on the global methane cycle. The authors present the first results of high precision measurements of the stable isotopes of atmospheric carbon monoxide and methane in transects across the equator. These have been obtained using a Finnigan MAT 252 high precision isotope ratio mass spectrometer with a modified miniature inlet system and a stringent calibration protocol. Overall precision for δ 13 C in ambient methane and carbon monoxide in clean air approaches 0.02 per thousand which helps provide information on several subtle processes controlling the abundance of the trace gases in the atmosphere. The 13 C in methane and carbon dioxide data show remarkable seasonal variations across the intertropical convergence zone (ITCZ) and may be used to infer aspects of transport of gases to extra tropical regions in the southern hemisphere

Variations and Regularities in the Hemispheric Distributions in Sunspot Groups of Various Classes

Science.gov (United States)

Gao, Peng-Xin

2018-05-01

The present study investigates the variations and regularities in the distributions in sunspot groups (SGs) of various classes in the northern and southern hemispheres from Solar Cycles (SCs) 12 to 23. Here, we use the separation scheme that was introduced by Gao, Li, and Li ( Solar Phys. 292, 124, 2017), which is based on A/U ( A is the corrected area of the SG, and U is the corrected umbral area of the SG), in order to separate SGs into simple SGs (A/U ≤ 4.5) and complex SGs (A/U > 6.2). The time series of Greenwich photoheliographic results from 1875 to 1976 (corresponding to complete SCs 12 - 20) and Debrecen photoheliographic data during the period 1974 - 2015 (corresponding to complete SCs 21 - 23) are used to show the distributions of simple and complex SGs in the northern and southern hemispheres. The main results we obtain are reported as follows: i) the larger of the maximum annual simple SG numbers in the two hemispheres and the larger of the maximum annual complex SG numbers in the two hemispheres occur in different hemispheres during SCs 12, 14, 18, and 19; ii) the relative changing trends of two curves - cumulative SG numbers in the northern and southern hemispheres - for simple SGs are different from those for complex SGs during SCs 12, 14, 18, and 21; and iii) there are discrepancies between the dominant hemispheres of simple and complex SGs for SCs 12, 14, 18, and 21.

The Science benefits and preliminary design of the southern hemisphere gravitational wave detector AIGO

Energy Technology Data Exchange (ETDEWEB)

Blair, D G; Barriga, P; Coward, D; Dumas, J-C; Fan, Y; Gras, S; Howell, E; Ju, L; Miao, H [School of Physics, University of Western Australia, Perth, WA 6009 (Australia); Brooks, A F; Hosken, D J; Munch, J; Veitch, P J [Department of Physics, The University of Adelaide, Adelaide, SA, 5005 Australia (Australia); Charlton, P [School of Computing and Mathematics, Charles Sturt University, NSW 2678 (Australia); Galloway, D [School of Mathematical Sciences, Monash University, Vic 3800 (Australia); Hughes, S [Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139-4307 (United States); McClelland, D E; Scott, S M; Slagmolen, B J J [Department of Physics, Australian National University, Canberra, ACT 0200 (Australia); Melatos, A [School of Physics University of Melbourne, Parkville Vic 3010 Australia (Australia)], E-mail: dgb@physics.uwa.edu.au (and others)

2008-07-15

The proposed southern hemisphere gravitational wave detector AIGO increases the projected average baseline of the global array of ground based gravitational wave detectors by a factor {approx}4. This allows the world array to be substantially improved. The orientation of AIGO allows much better resolution of both wave polarisations. This enables better distance estimates for inspiral events, allowing unambiguous optical identification of host galaxies for about 25% of neutron star binary inspiral events. This can allow Hubble Law estimation without optical identification of an outburst, and can also allow deep exposure imaging with electromagnetic telescopes to search for weak afterglows. This allows independent estimates of cosmological acceleration and dark energy as well as improved understanding of the physics of neutron star and black hole coalescences. This paper reviews and summarises the science benefits of AIGO and presents a preliminary conceptual design.

The Science benefits and preliminary design of the southern hemisphere gravitational wave detector AIGO

International Nuclear Information System (INIS)

Blair, D G; Barriga, P; Coward, D; Dumas, J-C; Fan, Y; Gras, S; Howell, E; Ju, L; Miao, H; Brooks, A F; Hosken, D J; Munch, J; Veitch, P J; Charlton, P; Galloway, D; Hughes, S; McClelland, D E; Scott, S M; Slagmolen, B J J; Melatos, A

2008-01-01

The proposed southern hemisphere gravitational wave detector AIGO increases the projected average baseline of the global array of ground based gravitational wave detectors by a factor ∼4. This allows the world array to be substantially improved. The orientation of AIGO allows much better resolution of both wave polarisations. This enables better distance estimates for inspiral events, allowing unambiguous optical identification of host galaxies for about 25% of neutron star binary inspiral events. This can allow Hubble Law estimation without optical identification of an outburst, and can also allow deep exposure imaging with electromagnetic telescopes to search for weak afterglows. This allows independent estimates of cosmological acceleration and dark energy as well as improved understanding of the physics of neutron star and black hole coalescences. This paper reviews and summarises the science benefits of AIGO and presents a preliminary conceptual design

SABRE: Dark matter annual modulation detection in the northern and southern hemispheres

Energy Technology Data Exchange (ETDEWEB)

Tomei, C.

2017-02-11

SABRE (Sodium-iodide with Active Background REjection) is a new NaI(Tl) experiment designed to search for galactic Dark Matter through the annual modulation signature. SABRE will consist of highly pure NaI(Tl) crystals operated in an active liquid scintillator veto. The SABRE experiment will follow a two-phase approach. In the first phase, one high-purity NaI(Tl) crystal will be operated at LNGS in an active liquid scintillator veto with the goal of demonstrating backgrounds low enough for a sensitive test of the DAMA/LIBRA result. An unprecedented radio-purity for both the NaI powder and the crystal growth will be needed to achieve this goal. The second phase will consist in building two high-purity NaI(Tl) detector arrays, with a total mass of about 50 kg each, located at LNGS and in the Stawell Gold Mine in Australia. The operation of twin full-scale experiments in both the northern and the southern hemispheres will strengthen the reliability of the result against any possible seasonal systematic effect.

SABRE: Dark matter annual modulation detection in the northern and southern hemispheres

International Nuclear Information System (INIS)

Tomei, C.

2017-01-01

SABRE (Sodium-iodide with Active Background REjection) is a new NaI(Tl) experiment designed to search for galactic Dark Matter through the annual modulation signature. SABRE will consist of highly pure NaI(Tl) crystals operated in an active liquid scintillator veto. The SABRE experiment will follow a two-phase approach. In the first phase, one high-purity NaI(Tl) crystal will be operated at LNGS in an active liquid scintillator veto with the goal of demonstrating backgrounds low enough for a sensitive test of the DAMA/LIBRA result. An unprecedented radio-purity for both the NaI powder and the crystal growth will be needed to achieve this goal. The second phase will consist in building two high-purity NaI(Tl) detector arrays, with a total mass of about 50 kg each, located at LNGS and in the Stawell Gold Mine in Australia. The operation of twin full-scale experiments in both the northern and the southern hemispheres will strengthen the reliability of the result against any possible seasonal systematic effect.

Hematology of southern Beaufort Sea polar bears (2005-2007): Biomarker for an arctic ecosystem health sentinel

Science.gov (United States)

Kirk, Cassandra M.; Amstrup, Steven C.; Swor, Rhonda; Holcomb, Darce; O'Hara, T. M.

2010-01-01

Declines in sea-ice habitats have resulted in declining stature, productivity, and survival of polar bears in some regions. With continuing sea-ice declines, negative population effects are projected to expand throughout the polar bear's range. Precise causes of diminished polar bear life history performance are unknown, however, climate and sea-ice condition change are expected to adversely impact polar bear (Ursus maritimus) health and population dynamics. As apex predators in the Arctic, polar bears integrate the status of lower trophic levels and are therefore sentinels of ecosystem health. Arctic residents feed at the apex of the ecosystem, thus polar bears can serve as indicators of human health in the Arctic. Despite their value as indicators of ecosystem welfare, population-level health data for U.S. polar bears are lacking. We present hematological reference ranges for southern Beaufort Sea polar bears. Hematological parameters in southern Beaufort Sea polar bears varied by age, geographic location, and reproductive status. Total leukocytes, lymphocytes, monocytes, eosinophils, and serum immunoglobulin G were significantly greater in males than females. These measures were greater in nonlactating females ages ???5, than lactating adult females ages ???5, suggesting that females encumbered by young may be less resilient to new immune system challenges that may accompany ongoing climate change. Hematological values established here provide a necessary baseline for anticipated changes in health as arctic temperatures warm and sea-ice declines accelerate. Data suggest that females with dependent young may be most vulnerable to these changes and should therefore be a targeted cohort for monitoring in this sentinel. ?? 2010 International Association for Ecology and Health.

Quaternary paleoecology of aquatic Diptera in tropical and Southern Hemisphere regions, with special reference to the Chironomidae

Science.gov (United States)

Verschuren, Dirk; Eggermont, Hilde

2006-08-01

Chironomid paleoecology in north-temperate regions has made tremendous progress over the past decade, but studies in tropical and Southern Hemisphere regions remain relatively scarce. Reasons for this imbalance are (1) incomplete taxonomic knowledge of chironomid faunas outside Europe and North America, (2) a scarcity of ecological data on local species and genera that might confer bio-indicator value to them, and (3) logistic difficulties hampering the lake surveying necessary to develop paleoenvironmental calibration data sets. Thus far, most chironomid paleoecology in tropical and Southern Hemisphere regions has relied on an indicator-species approach, combining autecological information on local species of which larval morphology is known with the traditional ecological typology of chironomid genera transferred from the Holarctic region. This paper reviews work accomplished to date in tropical and temperate South America, Australia, Africa, and New Zealand, including studies on various families of non-chironomid Diptera with diagnostic fossils. Research has focused mostly on late-Glacial and Holocene climate reconstruction, less on tracing past human disturbance of aquatic ecosystems and their drainage basins. Quantitative chironomid-based paleoenvironmental reconstruction has so far been done only in Australia and Africa. These studies compensated for the lack of traditional surface-sediment calibration data sets, nowadays often the main source of quantitative information on species ecological optima and tolerances, by maximally exploiting archival species-distribution data based on live collections of adult and/or larval midges. This stimulated efforts to achieve trustworthy species-level identification of fossil chironomid remains, and, as a result, the taxonomic resolution of paleoecological studies in Australia and Africa is higher on average than that achieved in European and North American studies.

Tropical cyclone genesis in the Southern Hemisphere and its relationship with the ENSO

Energy Technology Data Exchange (ETDEWEB)

Kuleshov, Y.; Qi, L. [Australian Bureau of Meteorology, Melbourne, VIC (Australia). National Climate Centre; Chane Ming, F.; Chouaibou, I.; Hoareau, C. [UMR CNRS-Meteo-France-Univ. de la Reunion, La Reunion (France). Lab. de l' Atmosphere et des Cyclones; Roux, F. [Paul Sabatier Univ., CNRS, Toulouse (France). Lab. d' Aerologie

2009-07-01

Tropical cyclogenesis climatology over the South Indian and South Pacific Oceans has been developed using a new tropical cyclone (TC) archive for the Southern Hemisphere, and changes in geographical distribution of areas favourable for TC genesis related to changes in the El Nino-Southern Oscillation (ENSO) phases have been investigated. To explain these changes, large-scale environmental variables which influence TC genesis and development such as sea surface temperatures (SSTs), relative humidity in mid-troposphere, vertical wind shear and lower tropospheric vorticity have been examined. In the South Indian Ocean, reduction of TC genesis in the western part of the basin and its increase in the eastern part as well as displacement of the area favourable for TC genesis further away from the equator during La Nina events compared to El Nino events can be explained by changes in geographical distribution of relative humidity and vorticity across the basin as primary contributors; positive anomalies of SSTs observed during La Nina seasons in the eastern part of the basin additionally contribute to enhanced cyclogenesis near the Western Australia. In the South Pacific Ocean, changes in geographical distribution of relative humidity and vorticity appear to be the key large-scale environmental factors responsible for enhanced TC genesis in the eastern (western) part of the basin as well as for the northeast (southwest) shift of points of cyclogenesis during El Nino (La Nina) events, with vertical wind shear and SSTs as additional contributing large-scale environmental variables. (orig.)

Polar night vortex breakdown and large-scale stirring in the southern stratosphere

Energy Technology Data Exchange (ETDEWEB)

Camara, Alvaro de la [Universidad Complutense de Madrid, Departamento de Geofisica y Meteorologia, Madrid (Spain); University of California, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA (United States); Mechoso, C.R. [University of California, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA (United States); Ide, K. [University of California, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA (United States); University of Maryland, Department of Atmospheric and Oceanic Science, Collage Park, MD (United States); Walterscheid, R. [The Aerospace Corporation, Space Sciences Department, Los Angeles, CA (United States); Schubert, G. [University of California, Department of Earth and Space Sciences, Institute of Geophysics and Planetary Physics, Los Angeles, CA (United States)

2010-11-15

The present paper examines the vortex breakdown and large-scale stirring during the final warming of the Southern Hemisphere stratosphere during the spring of 2005. A unique set of in situ observations collected by 27 superpressure balloons (SPBs) is used. The balloons, which were launched from McMurdo, Antarctica, by the Strateole/VORCORE project, drifted for several weeks on two different isopycnic levels in the lower stratosphere. We describe balloon trajectories and compare them with simulations obtained on the basis of the velocity field from the GEOS-5 and NCEP/NCAR reanalyses performed with and without VORCORE data. To gain insight on the mechanisms responsible for the horizontal transport of air inside and outside the well-isolated vortex we examine the balloon trajectories in the framework of the Lagrangian properties of the stratospheric flow. Coherent structures of the flow are visualized by computing finite-time Lyapunov exponents (FTLE). A combination of isentropic analysis and FTLE distributions reveals that air is stripped away from the vortex's interior as stable manifolds eventually cross the vortex's edge. It is shown that two SPBs escaped from the vortex within high potential vorticity tongues that developed in association with wave breaking at locations along the vortex's edge where forward and backward FTLE maxima approximately intersect. The trajectories of three SPBs flying as a group at the same isopycnic level are examined and their behavior is interpreted in reference to the FTLE field. These results support the concept of stable and unstable manifolds governing transport of air masses across the periphery of the stratospheric polar vortex. (orig.)

Electrical signature in polar night cloud base variations

International Nuclear Information System (INIS)

Harrison, R Giles; Ambaum, Maarten H P

2013-01-01

Layer clouds are globally extensive. Their lower edges are charged negatively by the fair weather atmospheric electricity current flowing vertically through them. Using polar winter surface meteorological data from Sodankylä (Finland) and Halley (Antarctica), we find that when meteorological diurnal variations are weak, an appreciable diurnal cycle, on average, persists in the cloud base heights, detected using a laser ceilometer. The diurnal cloud base heights from both sites correlate more closely with the Carnegie curve of global atmospheric electricity than with local meteorological measurements. The cloud base sensitivities are indistinguishable between the northern and southern hemispheres, averaging a (4.0 ± 0.5) m rise for a 1% change in the fair weather electric current density. This suggests that the global fair weather current, which is affected by space weather, cosmic rays and the El Niño Southern Oscillation, is linked with layer cloud properties. (letter)

Polar Bear Population Status in the Southern Beaufort Sea

Science.gov (United States)

Regehr, Eric V.; Amstrup, Steven C.; Stirling, Ian

2006-01-01

Polar bears depend entirely on sea ice for survival. In recent years, a warming climate has caused major changes in the Arctic sea ice environment, leading to concerns regarding the status of polar bear populations. Here we present findings from long-term studies of polar bears in the southern Beaufort Sea (SBS) region of the U.S. and Canada, which are relevant to these concerns. We applied open population capture-recapture models to data collected from 2001 to 2006, and estimated there were 1,526 (95% CI = 1,211; 1,841) polar bears in the SBS region in 2006. The number of polar bears in this region was previously estimated to be approximately 1,800. Because precision of earlier estimates was low, our current estimate of population size and the earlier ones cannot be statistically differentiated. For the 2001-06 period, the best fitting capture-recapture model provided estimates of total apparent survival of 0.43 for cubs of the year (COYs), and 0.92 for all polar bears older than COYs. Because the survival rates for older polar bears included multiple sex and age strata, they could not be compared to previous estimates. Survival rates for COYs, however, were significantly lower than estimates derived in earlier studies (P = 0.03). The lower survival of COYs was corroborated by a comparison of the number of COYs per adult female for periods before (1967-89) and after (1990-2006) the winter of 1989-90, when warming temperatures and altered atmospheric circulation caused an abrupt change in sea ice conditions in the Arctic basin. In the latter period, there were significantly more COYs per adult female in the spring (P = 0.02), and significantly fewer COYs per adult female in the autumn (P adult males captured from 1990 to 2006 were smaller than those captured before 1990. The smaller stature of males was especially notable because it corresponded with a higher mean age of adult males. Male polar bears continue to grow into their teens, and if adequately nourished

Contribution to the caryological study of the African grass Aristida rhiniochloa Hochst., based on specimens from the Southern Hemisphere

Directory of Open Access Journals (Sweden)

Pierre Bourreil

1972-11-01

Full Text Available The chromosome number established for Aristida rhiniochloa Hochst. by the study of material from three localities in the Southern Hemisphere confirms the results obtained on material from North Africa. The haploid complement (n = 11 and the diploid number (2n = 22 of this species conform to the basic number x = 11 typical for the Aristideae. It is shown that the caryotype of this species is sub-symmetrical. Preliminary studies o f material from two localities show that the meiotic behaviour conforms to that found in the diploid species with n bivalents.

Dated historical biogeography of the temperate Loliinae (Poaceae, Pooideae) grasses in the northern and southern hemispheres.

Science.gov (United States)

Inda, Luis A; Segarra-Moragues, José Gabriel; Müller, Jochen; Peterson, Paul M; Catalán, Pilar

2008-03-01

Divergence times and biogeographical analyses have been conducted within the Loliinae, one of the largest subtribes of temperate grasses. New sequence data from representatives of the almost unexplored New World, New Zealand, and Eastern Asian centres were added to those of the panMediterranean region and used to reconstruct the phylogeny of the group and to calculate the times of lineage-splitting using Bayesian approaches. The traditional separation between broad-leaved and fine-leaved Festuca species was still maintained, though several new broad-leaved lineages fell within the fine-leaved clade or were placed in an unsupported intermediate position. A strong biogeographical signal was detected for several Asian-American, American, Neozeylandic, and Macaronesian clades with different affinities to both the broad and the fine-leaved Festuca. Bayesian estimates of divergence and dispersal-vicariance analyses indicate that the broad-leaved and fine-leaved Loliinae likely originated in the Miocene (13My) in the panMediterranean-SW Asian region and then expanded towards C and E Asia from where they colonized the New World. Further expansions in America (10-3.8My) showed a predominant migratory route from North to South (N Americathe AndesPatagonia). This late Tertiary scenario of successive colonizations and secondary polyploid radiations in the southern hemisphere from the northern hemisphere was accompanied by occasional transcontinental long-distance dispersal events between South America and New Zealand. Multiple Pliocene dispersal events (3.6-2.5My) from the near SW European and NW African continents gave rise to the Macaronesian Loliinae flora, while a more recent Pleistocene origin (2-1My) is hypothesized for the high polyploid lineages that successfully colonized newly deglaciated areas in both hemispheres.

Southern Hemisphere Carbon Monoxide Inferannual Variability Observed by Terra/Measurement of Pollution in the Troposphere (MOPITT)

Science.gov (United States)

Edwards, D. P.; Petron, G.; Novelli, P. C.; Emmons, L. K.; Gille, J. C.; Drummond, J. R.

2010-01-01

Biomass burning is an annual occurrence in the tropical southern hemisphere (SH) and represents a major source of regional pollution. Vegetation fires emit carbon monoxide (CO), which due to its medium lifetime is an excellent tracer of tropospheric transport. CO is also one of the few tropospheric trace gases currently observed from satellite and this provides long-term global measurements. In this paper, we use the 5 year CO data record from the Measurement Of Pollution In The Troposphere (MOPITT) instrument to examine the inter-annual variability of the SH CO loading and show how this relates to climate conditions which determine the intensity of fire sources. The MOPITT observations show an annual austral springtime peak in the SH zonal CO loading each year with dry-season biomass burning emissions in S. America, southern Africa, the Maritime Continent, and northwestern Australia. Although fires in southern Africa and S. America typically produce the greatest amount of CO, the most significant inter-annual variation is due to varying fire activity and emissions from the Maritime Continent and northern Australia. We find that this variation in turn correlates well with the El Nino Southern Oscillation precipitation index. Between 2000 and 2005, emissions were greatest in late 2002 and an inverse modeling of the MOPITT data using the MOZART chemical transport model estimates the southeast Asia regional fire source for the year August 2002 to September 2003 to be 52 Tg CO. Comparison of the MOPITT retrievals and NOAA surface network measurements indicate that the latter do not fully capture the inter-annual variability or the seasonal range of the CO zonal average concentration due to biases associated with atmospheric and geographic sampling.

Hemispheric differences in electrical and hemodynamic responses during hemifield visual stimulation with graded contrasts.

Science.gov (United States)

Si, Juanning; Zhang, Xin; Zhang, Yujin; Jiang, Tianzi

2017-04-01

A multimodal neuroimaging technique based on electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) was used with horizontal hemifield visual stimuli with graded contrasts to investigate the retinotopic mapping more fully as well as to explore hemispheric differences in neuronal activity, the hemodynamic response, and the neurovascular coupling relationship in the visual cortex. The fNIRS results showed the expected activation over the contralateral hemisphere for both the left and right hemifield visual stimulations. However, the EEG results presented a paradoxical lateralization, with the maximal response located over the ipsilateral hemisphere but with the polarity inversed components located over the contralateral hemisphere. Our results suggest that the polarity inversion as well as the latency advantage over the contralateral hemisphere cause the amplitude of the VEP over the contralateral hemisphere to be smaller than that over the ipsilateral hemisphere. Both the neuronal and hemodynamic responses changed logarithmically with the level of contrast in the hemifield visual stimulations. Moreover, the amplitudes and latencies of the visual evoked potentials (VEPs) were linearly correlated with the hemodynamic responses despite differences in the slopes.

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

Directory of Open Access Journals (Sweden)

Jaco Barendse

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

A brief report on the statistical study of net electric current in solar active regions with longitudinal fields of opposite polarity

International Nuclear Information System (INIS)

Gao Yu

2013-01-01

Dynamic processes occurring in solar active regions are dominated by the solar magnetic field. As of now, observations using a solar magnetograph have supplied us with the vector components of a solar photospheric magnetic field. The two transverse components of a photospheric magnetic field allow us to compute the amount of electric current. We found that the electric current in areas with positive (negative) polarity due to the longitudinal magnetic field have both positive and negative signs in an active region, however, the net current is found to be an order-of-magnitude less than the mean absolute magnitude and has a preferred sign. In particular, we have statistically found that there is a systematic net electric current from areas with negative (positive) polarity to areas with positive (negative) polarity in solar active regions in the northern (southern) hemisphere, but during the solar minimum this tendency is reversed over time at some latitudes. The result indicates that there is weak net electric current in areas of solar active regions with opposite polarity, thus providing further details about the hemispheric helicity rule found in a series of previous studies.

An evaluation of gravity waves and gravity wave sources in the Southern Hemisphere in a 7 km global climate simulation.

Science.gov (United States)

Holt, L A; Alexander, M J; Coy, L; Liu, C; Molod, A; Putman, W; Pawson, S

2017-07-01

In this study, gravity waves (GWs) in the high-resolution GEOS-5 Nature Run are first evaluated with respect to satellite and other model results. Southern Hemisphere winter sources of non-orographic GWs in the model are then investigated by linking measures of tropospheric non-orographic gravity wave generation tied to precipitation and frontogenesis with absolute gravity wave momentum flux in the lower stratosphere. Finally, non-orographic GW momentum flux is compared to orographic gravity wave momentum flux and compared to previous estimates. The results show that the global patterns in GW amplitude, horizontal wavelength, and propagation direction are realistic compared to observations. However, as in other global models, the amplitudes are weaker and horizontal wavelengths longer than observed. The global patterns in absolute GW momentum flux also agree well with previous model and observational estimates. The evaluation of model non-orographic GW sources in the Southern Hemisphere winter shows that strong intermittent precipitation (greater than 10 mm h -1 ) is associated with GW momentum flux over the South Pacific, whereas frontogenesis and less intermittent, lower precipitation rates (less than 10 mm h -1 ) are associated with GW momentum flux near 60°S. In the model, orographic GWs contribute almost exclusively to a peak in zonal mean momentum flux between 70 and 75°S, while non-orographic waves dominate at 60°S, and non-orographic GWs contribute a third to a peak in zonal mean momentum flux between 25 and 30°S.

Ambient Aerosols in the Southern Hemisphere on Ascension Island during the LASIC Campaign: Biomass Burning Season versus Near Pristine Background Conditions

Science.gov (United States)

Aiken, A. C.; Springston, S. R.; Watson, T. B.; Sedlacek, A. J., III; Zuidema, P.; Adebiyi, A. A.; Uin, J.; Kuang, C.; Flynn, C. J.

2017-12-01

Ascension Island is located 8 degrees South of the Equator and 15 degrees West Longitude in the middle of the South Atlantic Ocean, at least 1000 miles from any major shoreline and closest to the continent of Africa. While low Southern Hemisphere background aerosol and trace gas measurements are observed most of the year, that picture changes during the South African Biomass Burning (BB) season. BB emissions are a large source of carbon to the atmosphere via particles and gas phase species and with a potential rise in drought and extreme events in the future, these numbers are expected to increase. From approximately June-October every year, the plume of South African BB emissions, the largest BB source in the world, are advected West and are known to impact both the boundary layer and free troposphere at Ascension Island (Zuidema et al., 2016). During the U.S. DOE ARM field campaign, Layered Atlantic Smoke Interactions with Clouds (LASIC), aerosol and trace gas measurements were collected continuously from June 2016 through October 2017 over a 1.5 year period. Two BB seasons are contrasted with the near pristine background conditions during the campaign from the ARM Aerosol Mobile Facility 1 (AMF1) and Mobile Aerosol Observing System (MAOS). Numerous direct in situ aerosol and trace gas measurements are presented, e.g. black carbon (BC), carbon monoxide (CO), PM1 and PM10 aerosol absorption and scattering, submicron non-refractory chemical composition (Organics, Sulfate, Nitrate, Ammonium, Chloride), etc. Aerosol and trace gas signatures are investigated along with backtrajectories to identify sources. Carbonaceous aerosols emitted with gas-phase CO are used to determine particulate emission ratios along with intrinsic and extrinsic aerosol properties. BC mass concentrations reach 1 µg m-3 during multiday plumes and exceed 25% of the total aerosol submicron mass concentration. Organic Aerosol (OA) to BC Ratios of 2.4 in the plume are much higher than previously

Tropical cyclone genesis in the Southern Hemisphere and its relationship with the ENSO

Directory of Open Access Journals (Sweden)

Y. Kuleshov

2009-06-01

Full Text Available Tropical cyclogenesis climatology over the South Indian and South Pacific Oceans has been developed using a new tropical cyclone (TC archive for the Southern Hemisphere, and changes in geographical distribution of areas favourable for TC genesis related to changes in the El Niño-Southern Oscillation (ENSO phases have been investigated. To explain these changes, large-scale environmental variables which influence TC genesis and development such as sea surface temperatures (SSTs, relative humidity in mid-troposphere, vertical wind shear and lower tropospheric vorticity have been examined. In the South Indian Ocean, reduction of TC genesis in the western part of the basin and its increase in the eastern part as well as displacement of the area favourable for TC genesis further away from the equator during La Niña events compared to El Niño events can be explained by changes in geographical distribution of relative humidity and vorticity across the basin as primary contributors; positive anomalies of SSTs observed during La Niña seasons in the eastern part of the basin additionally contribute to enhanced cyclogenesis near the Western Australia. In the South Pacific Ocean, changes in geographical distribution of relative humidity and vorticity appear to be the key large-scale environmental factors responsible for enhanced TC genesis in the eastern (western part of the basin as well as for the northeast (southwest shift of points of cyclogenesis during El Niño (La Niña events, with vertical wind shear and SSTs as additional contributing large-scale environmental variables.

Litmus Test for Cosmic Hemispherical Asymmetry in the Cosmic Microwave Background B-Mode Polarization.

Science.gov (United States)

Mukherjee, Suvodip; Souradeep, Tarun

2016-06-03

Recent measurements of the temperature field of the cosmic microwave background (CMB) provide tantalizing evidence for violation of statistical isotropy (SI) that constitutes a fundamental tenet of contemporary cosmology. CMB space based missions, WMAP, and Planck have observed a 7% departure in the SI temperature field at large angular scales. However, due to higher cosmic variance at low multipoles, the significance of this measurement is not expected to improve from any future CMB temperature measurements. We demonstrate that weak lensing of the CMB due to scalar perturbations produces a corresponding SI violation in B modes of CMB polarization at smaller angular scales. The measurability of this phenomenon depends upon the scales (l range) over which power asymmetry is present. Power asymmetry, which is restricted only to l<64 in the temperature field, cannot lead to any significant observable effect from this new window. However, this effect can put an independent bound on the spatial range of scales of hemispherical asymmetry present in the scalar sector.

SOLAR CYCLE VARIATIONS OF THE RADIO BRIGHTNESS OF THE SOLAR POLAR REGIONS AS OBSERVED BY THE NOBEYAMA RADIOHELIOGRAPH

Energy Technology Data Exchange (ETDEWEB)

Nitta, Nariaki V.; DeRosa, Marc L. [Lockheed Martin Advanced Technology Center, Dept/A021S, B/252, 3251 Hanover Street, Palo Alto, CA 94304 (United States); Sun, Xudong; Hoeksema, J. Todd [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States)

2014-01-10

We have analyzed daily microwave images of the Sun at 17 GHz obtained with the Nobeyama Radioheliograph (NoRH) in order to study the solar cycle variations of the enhanced brightness in the polar regions. Unlike in previous works, the averaged brightness of the polar regions is obtained from individual images rather than from synoptic maps. We confirm that the brightness is anti-correlated with the solar cycle and that it has generally declined since solar cycle 22. Including images up to 2013 October, we find that the 17 GHz brightness temperature of the south polar region has decreased noticeably since 2012. This coincides with a significant decrease in the average magnetic field strength around the south pole, signaling the arrival of solar maximum conditions in the southern hemisphere more than a year after the northern hemisphere. We do not attribute the enhanced brightness of the polar regions at 17 GHz to the bright compact sources that occasionally appear in synthesized NoRH images. This is because they have no correspondence with small-scale bright regions in images from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory with a broad temperature coverage. Higher-quality radio images are needed to understand the relationship between microwave brightness and magnetic field strength in the polar regions.

Multi-Decadal to Millennial Scale Holocene Hydrologic Variation in the Southern Hemisphere Tropics of South America

Science.gov (United States)

Ekdahl, E. J.; Fritz, S. C.; Baker, P. A.; Burns, S. J.; Coley, K.; Rigsby, C. A.

2005-12-01

Numerous sites in the Northern Hemisphere show multi-decadal to millennial scale climate variation during the Holocene, many of which have been correlated with changes in atmospheric radiocarbon production or with changes in North Atlantic oceanic circulation. The manifestation of such climate variability in the hydrology of the Southern Hemisphere tropics of South America is unclear, because of the limited number of records at suitably high resolution. In the Lake Titicaca drainage basin of Bolivia and Peru, high-resolution lacustrine records reveal the overall pattern of Holocene lake-level change, the influence of precessional forcing of the South American Summer Monsoon, and the effects of high-frequency climate variability in records of lake productivity and lake ecology. Precessional forcing of regional precipitation is evident in the Lake Titicaca basin as a massive (ca. 85 m) mid-Holocene decline in lake level beginning about 7800 cal yr BP and a subsequent rise in lake level after 4000 cal yr BP. Here we show that multi-decadal to millennial-scale climate variability, superimposed upon the envelope of change at orbital time scales, is similar in timing and pattern to the ice-rafted debris record of Holocene Bond events in the North Atlantic. A high-resolution carbon isotopic record from Lake Titicaca that spans the entire Holocene suggests that cold intervals of Holocene Bond events are periods of increased precipitation, thus indicating an anti-phasing of precipitation variation on the Altiplano relative to the Northern Hemisphere tropics. A similar pattern of variation is also evident in high-resolution (2-30 yr spacing) diatom and geochemical records that span the last 7000 yr from two smaller lakes, Lagos Umayo and Lagunillas, in the Lake Titicaca drainage basin.

Southern Hemisphere Ice Limits, 1973-1978

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Weekly Southern Ocean ice limits, have been digitized from U.S. Navy Fleet Weather Facility ice charts, at the Max-Planck Institut fur Meteorologie, Hamburg....

SHADOZ (Southern Hemisphere ADditional OZonesondes): An Ozonesonde Network and Resource for Remote Sensing Research and Education

Science.gov (United States)

Thompson, Anne M.; Witte, Jacquelyn C.

2000-01-01

Balloon-borne ozone instrumentation (ozonesondes), launched at fixed sites, is used to study local patterns in stratospheric and tropospheric ozone and to provide validation for satellite ozone products and model calculations of ozone. A paucity of coordinated ozonesonde data in the southern hemisphere tropics is being remedied in a 3-year project of coordinated ozonesondes launches at 10 sites. The data are available to the scientific community at the SHADOZ website at NASA/Goddard. Stations and their operational characteristics, with examples of ozone observations, are given. One expectation of SHADOZ is that wide dissemination of data and interaction with users and field projects will leverage local funding to maintain infrastructure and operations. SHADOZ data are well-suited for educational projects in which students learn about regional ozone patterns.

Diurnal and seasonal occurrence of polar patches

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A. S. Rodger

1996-05-01

Full Text Available Analysis of the diurnal and seasonal variation of polar patches, as identified in two years of HF-radar data from Halley, Antarctica during a period near sunspot maximum, shows that there is a broad maximum in occurrence centred about magnetic noon, not local noon. There are minima in occurrence near midsummer and midwinter, with maxima in occurrence between equinox and winter. There are no significant correlations between the occurrence of polar patches and the corresponding hourly averages of the solar wind and IMF parameters, except that patches usually occur when the interplanetary magnetic field has a southward component. The results can be understood in terms of UT and seasonal differences in the plasma concentration being convected from the dayside ionosphere into the polar cap. In summer and winter the electron concentrations in the polar cap are high and low, respectively, but relatively unstructured. About equinox, a tongue of enhanced ionisation is convected into the polar cap; this tongue is then structured by the effects of the interplanetary magnetic field, but these Halley data cannot be used to separate the various competing mechanisms for patch formation. The observed diurnal and seasonal variation in the occurrence of polar patches are largely consistent with predictions of Sojka et al. (1994 when their results are translated into the southern hemisphere. However, the ionospheric effects of flux transfer events are still considered essential in their formation, a feature not yet included in the Sojka et al. model.

Southern Hemisphere Extratropical Cyclones and their Relationship with ENSO in springtime

Science.gov (United States)

Reboita, M. S.; Ambrizzi, T.; Da Rocha, R.

2013-05-01

Extratropical cyclones occurrence is associated with the teleconnection mechanisms that produce climate variability. Among these mechanisms we have El Niño-Southern Oscillation (ENSO). Some works have indicated that during the ENSO positive phase there are more cyclogenetic conditions in some parts of the globe as the southwest of South Atlantic Ocean. Therefore, the purpose of this study is to verify if the extratropical cyclones number and location are altered in the different ENSO phases in the austral spring over the Southern Hemisphere (SH). The Melbourne University automatic tracking scheme was used to determine the cyclone climatology from 1980 to 2012. All cyclones that appear with lifetime higher or equal to 24 hours in the sea level pressure data from National Centers for Environment Prediction reanalysis I were included in the climatology. El Niño (EN), La Niña (LN) and Neutral (N) years were identified through the Oceanic Niño Index (ONI) from Climate Prediction Center/NOAA. The average number of cyclones in the spring over the SH is similar in the EN (200), N (184) and LN (197) episodes. By latitude bands, during EN episodes the cyclones occurrence reduces in 16% between 70-60 degrees and increases in ~15% between 80-70 and 50-40 degrees. On the other hand, during the LN episodes, the cyclones are 17% more frequent in 50-60 degrees and 22% less frequent in 30-20 degrees. One more detailed analysis of the cyclones trajectory density (that is a statistic product of the tracking algorithm) shows that in the South Atlantic Ocean, near the southeast of South America, the number of cyclones in EN years is higher than in the neutral period and lower than in the LN years. In the Indian Ocean, the EN year is characterized by a cyclones reduction in the west and east sector, near the continents. In the Pacific Ocean, the region southward the New Zealand presents more cyclones occurrence in EN years.

Changes in Southern Hemisphere circulation variability in climate change modelling experiments

International Nuclear Information System (INIS)

Grainger, Simon; Frederiksen, Carsten; Zheng, Xiaogu

2007-01-01

Full text: The seasonal mean of a climate variable can be considered as a statistical random variable, consisting of a signal and noise components (Madden 1976). The noise component consists of internal intraseasonal variability, and is not predictable on time-scales of a season or more ahead. The signal consists of slowly varying external and internal variability, and is potentially predictable on seasonal time-scales. The method of Zheng and Frederiksen (2004) has been applied to monthly time series of 500hPa Geopotential height from models submitted to the Coupled Model Intercomparison Project (CMIP3) experiment to obtain covariance matrices of the intraseasonal and slow components of covariability for summer and winter. The Empirical Orthogonal Functions (EOFs) of the intraseasonal and slow covariance matrices for the second half of the 20th century are compared with those observed by Frederiksen and Zheng (2007). The leading EOF in summer and winter for both the intraseasonal and slow components of covariability is the Southern Annular Mode (see, e.g. Kiladis and Mo 1998). This is generally reproduced by the CMIP3 models, although with different variance amounts. The observed secondary intraseasonal covariability modes of wave 4 patterns in summer and wave 3 or blocking in winter are also generally seen in the models, although the actual spatial pattern is different. For the slow covariabilty, the models are less successful in reproducing the two observed ENSO modes, with generally only one of them being represented among the leading EOFs. However, most models reproduce the observed South Pacific wave pattern. The intraseasonal and slow covariances matrices of 500hPa geopotential height under three climate change scenarios are also analysed and compared with those found for the second half of the 20th century. Through aggregating the results from a number of CMIP3 models, a consensus estimate of the changes in Southern Hemisphere variability, and their

Investigating the auroral electrojets with low altitude polar orbiting satellites

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T. Moretto

2002-07-01

Full Text Available Three geomagnetic satellite missions currently provide high precision magnetic field measurements from low altitude polar orbiting spacecraft. We demonstrate how these data can be used to determine the intensity and location of the horizontal currents that flow in the ionosphere, predominantly in the auroral electrojets. First, we examine the results during a recent geomagnetic storm. The currents derived from two satellites at different altitudes are in very good agreement, which verifies good stability of the method. Further, a very high degree of correlation (correlation coefficients of 0.8–0.9 is observed between the amplitudes of the derived currents and the commonly used auroral electrojet indices based on magnetic measurements at ground. This points to the potential of defining an auroral activity index based on the satellite observations, which could be useful for space weather monitoring. A specific advantage of the satellite observations over the ground-based magnetic measurements is their coverage of the Southern Hemisphere, as well as the Northern. We utilize this in an investigation of the ionospheric currents observed in both polar regions during a period of unusually steady interplanetary magnetic field with a large negative Y-component. A pronounced asymmetry is found between the currents in the two hemispheres, which indicates real inter-hemispheric differences beyond the mirror-asymmetry between hemispheres that earlier studies have revealed. The method is also applied to another event for which the combined measurements of the three satellites provide a comprehensive view of the current systems. The analysis hereof reveals some surprising results concerning the connection between solar wind driver and the resulting ionospheric currents. Specifically, preconditioning of the magnetosphere (history of the interplanetary magnetic field is seen to play an important role, and in the winther hemisphere, it seems to be harder to

A hemispherical photoelectron spectrometer with 2-dimensional delay-line detector and integrated spin-polarization analysis

International Nuclear Information System (INIS)

Plucinski, L.; Oelsner, A.; Matthes, F.; Schneider, C.M.

2010-01-01

Photoelectron spectrometers usually allow detection of either spin-resolved energy-distribution curves (EDCs) at single emission angle, or 2D angle-vs.-energy images without spin-resolution. We have combined the two detection schemes into one spectrometer system which permits simultaneous detection of a 1D spin-resolved EDC and a 2D angular map. A state-of-the-art hemispherical analyzer is used as an energy filter. Its original scintillator detector has been replaced by a delay-line-detector (DLD), and part of the electron beam is allowed to pass through to reach the spin-polarized low energy electron diffraction (SPLEED) spin-detector mounted subsequently. The electron-optics between DLD and SPLEED contains a 90 o deflector to feature simultaneous detection of in-plane and out-of-plane spin components. These electron-optics have been optimized for high transmission to reduce acquisition times in the spin-resolved mode.

Revisiting Southern Hemisphere polar stratospheric temperature trends in WACCM: The role of dynamical forcing

Science.gov (United States)

Calvo, N.; Garcia, R. R.; Kinnison, D. E.

2017-04-01

The latest version of the Whole Atmosphere Community Climate Model (WACCM), which includes a new chemistry scheme and an updated parameterization of orographic gravity waves, produces temperature trends in the Antarctic lower stratosphere in excellent agreement with radiosonde observations for 1969-1998 as regards magnitude, location, timing, and persistence. The maximum trend, reached in November at 100 hPa, is -4.4 ± 2.8 K decade-1, which is a third smaller than the largest trend in the previous version of WACCM. Comparison with a simulation without the updated orographic gravity wave parameterization, together with analysis of the model's thermodynamic budget, reveals that the reduced trend is due to the effects of a stronger Brewer-Dobson circulation in the new simulations, which warms the polar cap. The effects are both direct (a trend in adiabatic warming in late spring) and indirect (a smaller trend in ozone, hence a smaller reduction in shortwave heating, due to the warmer environment).

Average thermospheric wind patterns over the polar regions, as observed by CHAMP

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H. Lühr

2007-06-01

Full Text Available Measurements of the CHAMP accelerometer are utilized to investigate the average thermospheric wind distribution in the polar regions at altitudes around 400 km. This study puts special emphasis on the seasonal differences in the wind patterns. For this purpose 131 days centered on the June solstice of 2003 are considered. Within that period CHAMP's orbit is precessing once through all local times. The cross-track wind estimates of all 2030 passes are used to construct mean wind vectors for 918 equal-area cells. These bin averages are presented in corrected geomagnetic coordinates. Both hemispheres are considered simultaneously providing summer and winter responses for the same prevailing geophysical conditions. The period under study is characterized by high magnetic activity (Kp=4− but moderate solar flux level (F10.7=124. Our analysis reveals clear wind features in the summer (Northern Hemisphere. Over the polar cap there is a fast day-to-night flow with mean speeds surpassing 600 m/s in the dawn sector. At auroral latitudes we find strong westward zonal winds on the dawn side. On the dusk side, however, an anti-cyclonic vortex is forming. The dawn/dusk asymmetry is attributed to the combined action of Coriolis and centrifugal forces. Along the auroral oval the sunward streaming plasma causes a stagnation of the day-to-night wind. This effect is particularly clear on the dusk side. On the dawn side it is evident only from midnight to 06:00 MLT. The winter (Southern Hemisphere reveals similar wind features, but they are less well ordered. The mean day-to-night wind over the polar cap is weaker by about 35%. Otherwise, the seasonal differences are mainly confined to the dayside (06:00–18:00 MLT. In addition, the larger offset between geographic and geomagnetic pole in the south also causes hemispheric differences of the thermospheric wind distribution.

Average thermospheric wind patterns over the polar regions, as observed by CHAMP

Directory of Open Access Journals (Sweden)

H. Lühr

2007-06-01

Full Text Available Measurements of the CHAMP accelerometer are utilized to investigate the average thermospheric wind distribution in the polar regions at altitudes around 400 km. This study puts special emphasis on the seasonal differences in the wind patterns. For this purpose 131 days centered on the June solstice of 2003 are considered. Within that period CHAMP's orbit is precessing once through all local times. The cross-track wind estimates of all 2030 passes are used to construct mean wind vectors for 918 equal-area cells. These bin averages are presented in corrected geomagnetic coordinates. Both hemispheres are considered simultaneously providing summer and winter responses for the same prevailing geophysical conditions. The period under study is characterized by high magnetic activity (K_p=4− but moderate solar flux level (F10.7=124. Our analysis reveals clear wind features in the summer (Northern Hemisphere. Over the polar cap there is a fast day-to-night flow with mean speeds surpassing 600 m/s in the dawn sector. At auroral latitudes we find strong westward zonal winds on the dawn side. On the dusk side, however, an anti-cyclonic vortex is forming. The dawn/dusk asymmetry is attributed to the combined action of Coriolis and centrifugal forces. Along the auroral oval the sunward streaming plasma causes a stagnation of the day-to-night wind. This effect is particularly clear on the dusk side. On the dawn side it is evident only from midnight to 06:00 MLT. The winter (Southern Hemisphere reveals similar wind features, but they are less well ordered. The mean day-to-night wind over the polar cap is weaker by about 35%. Otherwise, the seasonal differences are mainly confined to the dayside (06:00–18:00 MLT. In addition, the larger offset between geographic and geomagnetic pole in the south also causes hemispheric differences of the thermospheric wind distribution.

Stratospheric ozone intrusion events and their impacts on tropospheric ozone in the Southern Hemisphere

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J. W. Greenslade

2017-09-01

Full Text Available Stratosphere-to-troposphere transport (STT provides an important natural source of ozone to the upper troposphere, but the characteristics of STT events in the Southern Hemisphere extratropics and their contribution to the regional tropospheric ozone budget remain poorly constrained. Here, we develop a quantitative method to identify STT events from ozonesonde profiles. Using this method we estimate the seasonality of STT events and quantify the ozone transported across the tropopause over Davis (69° S, 2006–2013, Macquarie Island (54° S, 2004–2013, and Melbourne (38° S, 2004–2013. STT seasonality is determined by two distinct methods: a Fourier bandpass filter of the vertical ozone profile and an analysis of the Brunt–Väisälä frequency. Using a bandpass filter on 7–9 years of ozone profiles from each site provides clear detection of STT events, with maximum occurrences during summer and minimum during winter for all three sites. The majority of tropospheric ozone enhancements owing to STT events occur within 2.5 and 3 km of the tropopause at Davis and Macquarie Island respectively. Events are more spread out at Melbourne, occurring frequently up to 6 km from the tropopause. The mean fraction of total tropospheric ozone attributed to STT during STT events is  ∼ 1. 0–3. 5 % at each site; however, during individual events, over 10 % of tropospheric ozone may be directly transported from the stratosphere. The cause of STTs is determined to be largely due to synoptic low-pressure frontal systems, determined using coincident ERA-Interim reanalysis meteorological data. Ozone enhancements can also be caused by biomass burning plumes transported from Africa and South America, which are apparent during austral winter and spring and are determined using satellite measurements of CO. To provide regional context for the ozonesonde observations, we use the GEOS-Chem chemical transport model, which is too coarsely

Penetration of geomagnetic pulsations from one polar cao cap to the other one

International Nuclear Information System (INIS)

Mal'tsev, Yu.P.; Lyatskij, V.B.

1982-01-01

A theoretical study is made of penetration of geomagnetic pulsations, excited in one polar cap in the region of open field lines, into the other one. The geomagnetic pulsations excited in a polar cap in the region of open field lines are also observed in the opposite polar cap. This is connected with the flow of ionospheric perturbation currents from one hemisphere to another over the boundary of the region with closed magnetic lines. In case of long-period oscillations under symmetrical conditions, both in the north and south polar caps, the ionospheric effect of the opposite hemisphere results in the fact that the electrical currents flowing from a source to the polar cap boundary grow 1.5 times as high. In case of short-period oscillations a portion of longitudinal current flowing between the hemispheres is branched away for polarization currents. As a result, the electrical field and currents in the ionosphere of the opposite hemisphere can substantially decrease as compared to the long-period oscillations

Effect of Southern Hemisphere Sudden Stratospheric Warmings on Antarctica Mesospheric Tides: First Observational Study

Science.gov (United States)

Eswaraiah, S.; Kim, Yong Ha; Lee, Jaewook; Ratnam, M. Vankat; Rao, S. V. B.

2018-03-01

We analyzed the structure and variability of observed winds and tides in the Antarctica mesosphere and lower thermosphere (MLT) during the 2002 major sudden stratospheric warming (SSW) and the 2010 minor SSWs. We noted the effect of SSW on the variability of MLT tides for the first time in the Southern Hemisphere, although it has been well recognized in the Northern Hemisphere. We utilized the winds measured by Rothera (68°S, 68°W) medium frequency radar and King Sejong Station (62.22°S, 58.78°W) meteor radar for estimating the tidal components (diurnal, semi-diurnal, and ter-diurnal) in the MLT region. The unusual behavior of diurnal tide (DT) and semidiurnal tide (SDT) was observed in 2002. Zonal SDT amplitudes were enhanced up to 27 m/s after 18 days from the associated SSW day. However, the meridional tidal amplitudes of both DT and SDT suddenly decreased during the peak SSW, and SDT amplitudes slightly increased to 18 m/s afterward. In the normal years, SDT amplitude stays below 15 m/s. During the 2010 SSW, SDT zonal amplitudes increased up to 40 m/s and 50 m/s at altitudes of 80 km and 90 km, respectively, 30 days after the associated SSW. Similar but weaker effect is noticed in the meridional components. The ter-diurnal tide does not show any significant variation during the SSW. The two SSWs offered a challenging issue to answer: why tidal amplitudes are enhanced with a delay after the SSW. The reasons for the delay are discussed in accordance with theoretical predictions.

Areas of Polar Coronal Holes from 1996 Through 2010

Science.gov (United States)

Webber, Hess S. A.; Karna, N.; Pesnell, W. D.; Kirk, M. S.

2014-01-01

Polar coronal holes (PCHs) trace the magnetic variability of the Sun throughout the solar cycle. Their size and evolution have been studied as proxies for the global magnetic field. We present measurements of the PCH areas from 1996 through 2010, derived from an updated perimeter-tracing method and two synoptic-map methods. The perimeter tracing method detects PCH boundaries along the solar limb, using full-disk images from the SOlar and Heliospheric Observatory/Extreme ultraviolet Imaging Telescope (SOHO/EIT). One synoptic-map method uses the line-of-sight magnetic field from the SOHO/Michelson Doppler Imager (MDI) to determine the unipolarity boundaries near the poles. The other method applies thresholding techniques to synoptic maps created from EUV image data from EIT. The results from all three methods suggest that the solar maxima and minima of the two hemispheres are out of phase. The maximum PCH area, averaged over the methods in each hemisphere, is approximately 6 % during both solar minima spanned by the data (between Solar Cycles 22/23 and 23/24). The northern PCH area began a declining trend in 2010, suggesting a downturn toward the maximum of Solar Cycle 24 in that hemisphere, while the southern hole remained large throughout 2010.

Stratospheric warmings - The quasi-biennial oscillation Ozone Hole in the Antarctic but not the Arctic - Correlations between the Solar Cycle, Polar Temperatures, and an Equatorial Oscillation

Energy Technology Data Exchange (ETDEWEB)

Hoppe, Ulf-Peter

2010-05-15

This report is a tutorial and overview over some of the complex dynamic phenomena in the polar and equatorial stratosphere, and the unexpected correlation that exists between these and the solar cycle. Sudden stratospheric warmings (stratwarms) occur in the polar stratosphere in winter, but not equally distributed between the two hemispheres. As a result, the ozone hole in the springtime polar stratosphere is much more severe in the Southern Hemisphere than in the Northern Hemisphere. The Quasi-Biennial Oscillation (QBO) is a dynamic phenomenon of the equatorial stratosphere. Through processes not fully understood, the phase of the QBO (easterly or westerly) influences the onset of stratwarms. In addition, a correlation between the stratospheric winter temperature over the poles and the solar cycle has been found, but only if the datapoints are ordered by the phase of the QBO. - The best explanations and figures from four recent textbooks are selected, and abstracts of most relevant publications from the six last years are collected, with the most relevant portions for these subjects highlighted. - In addition to being basic science, the understanding of these phenomena is important in the context of the ozone hole, the greenhouse effect, as well as anthropogenic and natural climate change. (author)

Polar vortices on Earth and Mars: A comparative study of the climatology and variability from reanalyses.

Science.gov (United States)

Mitchell, D M; Montabone, L; Thomson, S; Read, P L

2015-01-01

Polar vortices on Mars provide case-studies to aid understanding of geophysical vortex dynamics and may help to resolve long-standing issues regarding polar vortices on Earth. Due to the recent development of the first publicly available Martian reanalysis dataset (MACDA), for the first time we are able to characterise thoroughly the structure and evolution of the Martian polar vortices, and hence perform a systematic comparison with the polar vortices on Earth. The winter atmospheric circulations of the two planets are compared, with a specific focus on the structure and evolution of the polar vortices. The Martian residual meridional overturning circulation is found to be very similar to the stratospheric residual circulation on Earth during winter. While on Earth this residual circulation is very different from the Eulerian circulation, on Mars it is found to be very similar. Unlike on Earth, it is found that the Martian polar vortices are annular, and that the Northern Hemisphere vortex is far stronger than its southern counterpart. While winter hemisphere differences in vortex strength are also reported on Earth, the contrast is not as large. Distinctions between the two planets are also apparent in terms of the climatological vertical structure of the vortices, in that the Martian polar vortices are observed to decrease in size at higher altitudes, whereas on Earth the opposite is observed. Finally, it is found that the Martian vortices are less variable through the winter than on Earth, especially in terms of the vortex geometry. During one particular major regional dust storm on Mars (Martian year 26), an equatorward displacement of the vortex is observed, sharing some qualitative characteristics of sudden stratospheric warmings on Earth.

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

Science.gov (United States)

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

2015-12-01

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

Quantum confined Stark effects of single dopant in polarized hemispherical quantum dot: Two-dimensional finite difference approach and Ritz-Hassé variation method

Science.gov (United States)

El Harouny, El Hassan; Nakra Mohajer, Soukaina; Ibral, Asmaa; El Khamkhami, Jamal; Assaid, El Mahdi

2018-05-01

Eigenvalues equation of hydrogen-like off-center single donor impurity confined in polarized homogeneous hemispherical quantum dot deposited on a wetting layer, capped by insulated matrix and submitted to external uniform electric field is solved in the framework of the effective mass approximation. An infinitely deep potential is used to describe effects of quantum confinement due to conduction band offsets at surfaces where quantum dot and surrounding materials meet. Single donor ground state total and binding energies in presence of electric field are determined via two-dimensional finite difference approach and Ritz-Hassé variation principle. For the latter method, attractive coulomb correlation between electron and ionized single donor is taken into account in the expression of trial wave function. It appears that off-center single dopant binding energy, spatial extension and radial probability density are strongly dependent on hemisphere radius and single dopant position inside quantum dot. Influence of a uniform electric field is also investigated. It shows that Stark effect appears even for very small size dots and that single dopant energy shift is more significant when the single donor is near hemispherical surface.

Evidence for Dynamical Coupling of Stratosphere-MLT during recent minor Stratospheric Warmings in Southern Hemisphere

Science.gov (United States)

Kim, Yongha; Sunkara, Eswaraiah; Hong, Junseok; Ratnam, Venkat; Chandran, Amal; Rao, Svb; Riggin, Dennis

2015-04-01

The mesosphere-lower thermosphere (MLT) response to extremely rare minor sudden stratospheric warming (SSW) events was observed for the first time in the southern hemisphere (SH) during 2010 and is investigated using the meteor radar located at King Sejong Station (62.22°S, 58.78°W), Antarctica. Three episodic SSWs were noticed from early August to late October 2010. The mesospheric wind field was found to significantly differ from normal years due to enhanced planetary wave (PW) activity before the SSWs and secondary PWs in the MLT afterwards. The zonal winds in the mesosphere reversed approximately a week before the SSW occurrence in the stratosphere as has been observed 2002 major SSW, suggesting the downward propagation of disturbance during minor SSWs as well. Signatures of mesospheric cooling (MC) in association with SSWs are found in the Microwave Limb Sounder (MLS) measurements. SD-WACCM simulations are able to produce these observed features.

Faunal evidence for reduced productivity and uncoordinated recovery in Southern Hemisphere Cretaceous-Paleogene boundary sections

Science.gov (United States)

Aberhan, Martin; Weidemeyer, Sven; Kiessling, Wolfgang; Scasso, Roberto A.; Medina, Francisco A.

2007-03-01

The mass extinction at the Cretaceous-Paleogene boundary is generally explained by a severe crisis in primary productivity, following a catastrophic bolide impact. Consistent with this scenario, Danian mollusk-dominated benthic shelf ecosystems of southern middle paleolatitudes (Neuquén Basin, Argentina) are characterized by (1) a stratigraphically limited low in macrofossil abundances; (2) an increase in starvation-resistant, nonplanktotrophic deposit feeders and chemosymbionts; (3) a reduction in the average body size of individuals; and (4) individuals with inactive lifestyles being more common than in the late Maastrichtian. Return to pre-extinction conditions of the various synecological attributes occurred over unequal time spans, indicating that recovery was uncoordinated with respect to ecological traits. Global comparison of ecological patterns suggests that reduced food supply (1) was a controlling factor in both hemispheres; (2) affected macrobenthic marine faunas at various distances from the Chicxulub impact site; and (3) was more effective in siliciclastic environments as compared to oligotrophic carbonate settings.

Phylogenomic analyses of Crassiclitellata support major Northern and Southern Hemisphere clades and a Pangaean origin for earthworms.

Science.gov (United States)

Anderson, Frank E; Williams, Bronwyn W; Horn, Kevin M; Erséus, Christer; Halanych, Kenneth M; Santos, Scott R; James, Samuel W

2017-05-30

Earthworms (Crassiclitellata) are a diverse group of annelids of substantial ecological and economic importance. Earthworms are primarily terrestrial infaunal animals, and as such are probably rather poor natural dispersers. Therefore, the near global distribution of earthworms reflects an old and likely complex evolutionary history. Despite a long-standing interest in Crassiclitellata, relationships among and within major clades remain unresolved. In this study, we evaluate crassiclitellate phylogenetic relationships using 38 new transcriptomes in combination with publicly available transcriptome data. Our data include representatives of nearly all extant earthworm families and a representative of Moniligastridae, another terrestrial annelid group thought to be closely related to Crassiclitellata. We use a series of differentially filtered data matrices and analyses to examine the effects of data partitioning, missing data, compositional and branch-length heterogeneity, and outgroup inclusion. We recover a consistent, strongly supported ingroup topology irrespective of differences in methodology. The topology supports two major earthworm clades, each of which consists of a Northern Hemisphere subclade and a Southern Hemisphere subclade. Divergence time analysis results are concordant with the hypothesis that these north-south splits are the result of the breakup of the supercontinent Pangaea. These results support several recently proposed revisions to the classical understanding of earthworm phylogeny, reveal two major clades that seem to reflect Pangaean distributions, and raise new questions about earthworm evolutionary relationships.

The Role of Sea Ice in 2 x CO2 Climate Model Sensitivity. Part 2; Hemispheric Dependencies

Science.gov (United States)

Rind, D.; Healy, R.; Parkinson, C.; Martinson, D.

1997-01-01

How sensitive are doubled CO2 simulations to GCM control-run sea ice thickness and extent? This issue is examined in a series of 10 control-run simulations with different sea ice and corresponding doubled CO2 simulations. Results show that with increased control-run sea ice coverage in the Southern Hemisphere, temperature sensitivity with climate change is enhanced, while there is little effect on temperature sensitivity of (reasonable) variations in control-run sea ice thickness. In the Northern Hemisphere the situation is reversed: sea ice thickness is the key parameter, while (reasonable) variations in control-run sea ice coverage are of less importance. In both cases, the quantity of sea ice that can be removed in the warmer climate is the determining factor. Overall, the Southern Hemisphere sea ice coverage change had a larger impact on global temperature, because Northern Hemisphere sea ice was sufficiently thick to limit its response to doubled CO2, and sea ice changes generally occurred at higher latitudes, reducing the sea ice-albedo feedback. In both these experiments and earlier ones in which sea ice was not allowed to change, the model displayed a sensitivity of -0.02 C global warming per percent change in Southern Hemisphere sea ice coverage.

Tracking Oxidation During Transport of Trace Gases in Air from the Northern to Southern Hemisphere

Science.gov (United States)

Montzka, S. A.; Moore, F. L.; Atlas, E. L.; Parrish, D. D.; Miller, B. R.; Sweeney, C.; McKain, K.; Hall, B. D.; Siso, C.; Crotwell, M.; Hintsa, E. J.; Elkins, J. W.; Blake, D. R.; Barletta, B.; Meinardi, S.; Claxton, T.; Hossaini, R.

2017-12-01

Trace gas mole fractions contain the imprint of recent influences on an air mass such as sources, transport, and oxidation. Covariations among the many gases measured from flasks during ATom and HIPPO, and from the ongoing NOAA cooperative air sampling program enable recent influences to be identified from a wide range of sources including industrial activity, biomass burning, emissions from wetlands, and uptake by terrestrial ecosystems. In this work we explore the evolution of trace gas concentrations owing to atmospheric oxidation as air masses pass through the tropics, the atmospheric region with the highest concentrations of the hydroxyl radical. Variations in C2-C5 hydrocarbon concentrations downwind of source regions provide a measure of photochemical ageing in an air mass since emission, but they become less useful when tracking photochemical ageing as air is transported from the NH into the SH owing to their low mixing ratios, lifetimes that are very short relative to transport times, non-industrial sources in the tropics (e.g., biomass burning), and southern hemispheric sources. Instead, we consider a range of trace gases and trace gas pairs that provide a measure of photochemical processing as air transits the tropics. To be useful in this analysis, these trace gases would have lifetimes comparable to interhemispheric transport times, emissions arising from only the NH at constant relative magnitudes, and concentrations sufficient to allow precise and accurate measurements in both hemispheres. Some anthropogenically-emitted chlorinated hydrocarbons meet these requirements and have been measured during ATom, HIPPO, and from NOAA's ongoing surface sampling efforts. Consideration of these results and their implications for tracking photochemical processing in air as it is transported across the tropics will be presented.

Mio-Pliocene aridity in the south-central Andes associated with Southern Hemisphere cold periods.

Science.gov (United States)

Amidon, William H; Fisher, G Burch; Burbank, Douglas W; Ciccioli, Patricia L; Alonso, Ricardo N; Gorin, Andrew L; Silverhart, Perri H; Kylander-Clark, Andrew R C; Christoffersen, Michael S

2017-06-20

Although Earth's climate history is best known through marine records, the corresponding continental climatic conditions drive the evolution of terrestrial life. Continental conditions during the latest Miocene are of particular interest because global faunal turnover is roughly synchronous with a period of global glaciation from ∼6.2-5.5 Ma and with the Messinian Salinity Crisis from ∼6.0-5.3 Ma. Despite the climatic and ecological significance of this period, the continental climatic conditions associated with it remain unclear. We address this question using erosion rates of ancient watersheds to constrain Mio-Pliocene climatic conditions in the south-central Andes near 30° S. Our results show two slowdowns in erosion rate, one from ∼6.1-5.2 Ma and another from 3.6 to 3.3 Ma, which we attribute to periods of continental aridity. This view is supported by synchrony with other regional proxies for aridity and with the timing of glacial ‟cold" periods as recorded by marine proxies, such as the M2 isotope excursion. We thus conclude that aridity in the south-central Andes is associated with cold periods at high southern latitudes, perhaps due to a northward migration of the Southern Hemisphere westerlies, which disrupted the South American Low Level Jet that delivers moisture to southeastern South America. Colder glacial periods, and possibly associated reductions in atmospheric CO 2 , thus seem to be an important driver of Mio-Pliocene ecological transitions in the central Andes. Finally, this study demonstrates that paleo-erosion rates can be a powerful proxy for ancient continental climates that lie beyond the reach of most lacustrine and glacial archives.

Polar bear population dynamics in the southern Beaufort Sea during a period of sea ice decline.

Science.gov (United States)

Bromaghin, Jeffrey F; Mcdonald, Trent L; Stirling, Ian; Derocher, Andrew E; Richardson, Evan S; Regehr, Eric V; Douglas, David C; Durner, George M; Atwood, Todd; Amstrup, Steven C

2015-04-01

In the southern Beaufort Sea of the United States and Canada, prior investigations have linked declines in summer sea ice to reduced physical condition, growth, and survival of polar bears (Ursus maritimus). Combined with projections of population decline due to continued climate warming and the ensuing loss of sea ice habitat, those findings contributed to the 2008 decision to list the species as threatened under the U.S. Endangered Species Act. Here, we used mark-recapture models to investigate the population dynamics of polar bears in the southern Beaufort Sea from 2001 to 2010, years during which the spatial and temporal extent of summer sea ice generally declined. Low survival from 2004 through 2006 led to a 25-50% decline in abundance. We hypothesize that low survival during this period resulted from (1) unfavorable ice conditions that limited access to prey during multiple seasons; and possibly, (2) low prey abundance. For reasons that are not clear, survival of adults and cubs began to improve in 2007 and abundance was comparatively stable from 2008 to 2010, with ~900 bears in 2010 (90% CI 606-1212). However, survival of subadult bears declined throughout the entire period. Reduced spatial and temporal availability of sea ice is expected to increasingly force population dynamics of polar bears as the climate continues to warm. However, in the short term, our findings suggest that factors other than sea ice can influence survival. A refined understanding of the ecological mechanisms underlying polar bear population dynamics is necessary to improve projections of their future status and facilitate development of management strategies.

Recent observations of intraspecific predation and cannibalism among polar bears in the southern Beaufort Sea

Science.gov (United States)

Amstrup, Steven C.; Stirling, I.; Smith, T.S.; Perham, C.; Thiemann, G.W.

2006-01-01

Intraspecific killing has been reported among polar bears (Ursus maritimus), brown bears (U. arctos), and black bears (U. americanus). Although cannibalism is one motivation for such killings, the ecological factors mediating such events are poorly understood. Between 24 January and 10 April 2004, we confirmed three instances of intraspecific predation and cannibalism in the Beaufort Sea. One of these, the first of this type ever reported for polar bears, was a parturient female killed at her maternal den. The predating bear was hunting in a known maternal denning area and apparently discovered the den by scent. A second predation event involved an adult female and cub recently emerged from their den, and the third involved a yearling male. During 24 years of research on polar bears in the southern Beaufort Sea region of northern Alaska and 34 years in northwestern Canada, we have not seen other incidents of polar bears stalking, killing, and eating other polar bears. We hypothesize that nutritional stresses related to the longer ice-free seasons that have occurred in the Beaufort Sea in recent years may have led to the cannibalism incidents we observed in 2004. ?? Springer-Verlag 2006.

Investment in the Western Hemisphere energy market

International Nuclear Information System (INIS)

Gillam, P.J.

1991-01-01

This paper reports that the main characteristics of Western Hemisphere energy markets are well known to those in the energy industry. The United States sits in the northern half of the hemisphere, importing more and more oil from the rest of the world. Brazil, with a market one-tenth of the size of the United Sates, sits in the southern half of the hemisphere, importing less and less oil from the rest of the world. Venezuela sits in the center with an eye to the future as a long-term player in the world petroleum industry. Venezuela has 6 or 7 percent of the world's known conventional petroleum reserves, plus an uncountable bitumen resource which is now being commercialized as Orimulsion, a low-emission substitute for coal. The United States is circled by major producing countries with smaller exports, such as Mexico and Canada, and there are smaller producing or consuming countries of which Colombia is the largest exporter and Argentian the largest importer. The United States dominates the numbers. Half of British Petroleum's (BP) investments have been in the energy industry of the Western Hemisphere. We are maintaining that proportion, but opportunities are becoming more difficult to find

The impact of volcanic aerosol on the Northern Hemisphere stratospheric polar vortex: mechanisms and sensitivity to forcing structure

Science.gov (United States)

Toohey, M.; Krüger, K.; Bittner, M.; Timmreck, C.; Schmidt, H.

2014-12-01

Observations and simple theoretical arguments suggest that the Northern Hemisphere (NH) stratospheric polar vortex is stronger in winters following major volcanic eruptions. However, recent studies show that climate models forced by prescribed volcanic aerosol fields fail to reproduce this effect. We investigate the impact of volcanic aerosol forcing on stratospheric dynamics, including the strength of the NH polar vortex, in ensemble simulations with the Max Planck Institute Earth System Model. The model is forced by four different prescribed forcing sets representing the radiative properties of stratospheric aerosol following the 1991 eruption of Mt. Pinatubo: two forcing sets are based on observations, and are commonly used in climate model simulations, and two forcing sets are constructed based on coupled aerosol-climate model simulations. For all forcings, we find that simulated temperature and zonal wind anomalies in the NH high latitudes are not directly impacted by anomalous volcanic aerosol heating. Instead, high-latitude effects result from enhancements in stratospheric residual circulation, which in turn result, at least in part, from enhanced stratospheric wave activity. High-latitude effects are therefore much less robust than would be expected if they were the direct result of aerosol heating. Both observation-based forcing sets result in insignificant changes in vortex strength. For the model-based forcing sets, the vortex response is found to be sensitive to the structure of the forcing, with one forcing set leading to significant strengthening of the polar vortex in rough agreement with observation-based expectations. Differences in the dynamical response to the forcing sets imply that reproducing the polar vortex responses to past eruptions, or predicting the response to future eruptions, depends on accurate representation of the space-time structure of the volcanic aerosol forcing.

Matuyama/Brunhes Polarity Transition in Owens Lake, CA, Sediment

Science.gov (United States)

Liddicoat, Joseph; Kravchinsky, Vadim

2014-05-01

The complexity of the Matuyama/Brunhes (M/B) polarity transition is becoming better understood from investigations of volcanic rocks (Coe et al., 2004), loess (Jin et al., 2012; Evans et al., 2011; Kravchinsky, 2013), and marine (Clement and Opdyke, 1982; Hartl and Tauxe, 1996; Macri et al., 2010) and lacustrine (Valet et al., 1988; Sagnotti et al., 2013) sediments. The transition appears to include a brief interval of normal polarity prior to the entry into the Brunhes Normal Chron (Coe et al., 2004; Jin et al., 2012; Evans et al., 2011), and the transition has Virtual Geomagnetic Poles rapidly moving from the Southern Hemisphere to the Northern Hemisphere (Coe et al., 2004; Jin et al., 2012; Evans et al., 2011; Sagnotti et al., 2013). The M/B polarity transition is recorded in exposed Pleistocene lake sediments near Bishop, CA, where the brief interval of normal polarity noted above is present and the change from full reverse to full normal polarity occurs rapidly. The brief interval of normal polarity is recorded at two sites separated laterally by about 150 m and is in single hand samples measured at vertical spacing of 2.0-2.5 cm using six samples per measured level and alternating field demagnetization at 20 mT (Liddicoat, 1993, Table 1 and Fig. 8). The siltstone is unweathered glacial flour from the Sierra Nevada that borders the western side of Owens Valley where the sediments were deposited in Owens Lake. In the siltstone, the majority of the samples have a percentage of about 60 percent where the grain diameter is less than 63 micrometres, and in those samples there is about a five percent fraction when the diameter is two micrometres or less. The Total Inorganic Carbon in most samples is about 0.25 percent (Bergeron, 2013), and magnetite is the dominant carrier of the magnetization (Liddicoat, 1993). The palaeomagnetic directions recording the terminus of the full M/B transition, which occurs before the field intensity is completely recovered, spans no

Daily variation characteristics at polar geomagnetic observatories

Science.gov (United States)

Lepidi, S.; Cafarella, L.; Pietrolungo, M.; Di Mauro, D.

2011-08-01

This paper is based on the statistical analysis of the diurnal variation as observed at six polar geomagnetic observatories, three in the Northern and three in the Southern hemisphere. Data are for 2006, a year of low geomagnetic activity. We compared the Italian observatory Mario Zucchelli Station (TNB; corrected geomagnetic latitude: 80.0°S), the French-Italian observatory Dome C (DMC; 88.9°S), the French observatory Dumont D'Urville (DRV; 80.4°S) and the three Canadian observatories, Resolute Bay (RES; 83.0°N), Cambridge Bay (CBB; 77.0°N) and Alert (ALE, 87.2°N). The aim of this work was to highlight analogies and differences in daily variation as observed at the different observatories during low geomagnetic activity year, also considering Interplanetary Magnetic Field conditions and geomagnetic indices.

Solaris: a global network of autonomous observatories in the southern hemisphere

Science.gov (United States)

Kozłowski, S. K.; Sybilski, P.; Konacki, Maciej; Pawłaszek, R. K.; Ratajczak, Milena; Helminiak, K. G.

2014-07-01

We present Project Solaris, a network of four autonomous observatories in the Southern Hemisphere. The Project's primary goal is to detect and characterize circumbinary planets using the eclipse timing approach. This method requires high-cadence and long time-span photometric coverage of the binaries' eclipses, hence the observatories are located at sites having similar separation in longitude and nearly identical latitudes: South African Astronómical Observatory, Republic of South Africa (Solaris-1 and -2), Siding Spring Observatory, Australia (Solaris-3) and Complejo Astronomico El Leoncito, Argentina (Solaris-4). The headquarters coordinating and monitoring the network is based in Toruń, Poland. All four sites are operational as of December 2013. The instrument and hardware configurations are nearly identical. Each site is equipped with a 0.5-m Ritchey-Chrétien or Schmidt-Cassegrain optical tube assembly mounted on a direct-drive modified German equatorial mount along with a set of instruments. Computer, power and networking components are installed in rack cabinets. Everything is housed in sandwiched fiberglass clamshell 3.5-m diameter robotized domes. The Argentinian site is additionally equipped with a 20-ft office container. We discuss the design requirements of robotic observatories aimed to operate autonomously as a global network with concentration on efficiency, robustness and modularity. We also present a newly introduced spectroscopic mode of operation commissioned on the Solaris-1 telescope. Using a compact échelle spectrograph (20 000 resolution) mounted directly on the imaging train of the telescope, we are able to remotely acquire spectra. A fully robotic spectroscopic mode is planned for 2015.

Interhemispheric Asymmetry of the Sunward Plasma Flows for Strongly Dominant IMF BZ > 0

Science.gov (United States)

Yakymenko, K. N.; Koustov, A. V.; Fiori, R. A. D.

2018-01-01

Super Dual Auroral Radar Network (SuperDARN) convection maps obtained simultaneously in both hemispheres are averaged to infer polar cap ionospheric flow patterns under strongly dominant positive interplanetary magnetic field (IMF) Bz component. The data set consisted of winter observations in the Northern Hemisphere simultaneously with summer observations in the Southern Hemisphere. Long-lasting high-latitude dayside reverse convection cells are shown to have faster sunward flows at near-magnetic noon hours in the summer/Southern Hemisphere. Sunward flows typically deviate from the midnight-noon meridian toward 10-11 h of magnetic local time in the summer/Southern Hemisphere and are more aligned with the midnight-noon meridian in the winter/Northern Hemisphere. Flow deviations in the winter/Northern Hemisphere can be both toward prenoon and postnoon hours, and there is no clear relationship between flow deviation and the IMF By component. No strong preference for the sunward flow occurrence depending on the IMF Bx polarity was found. In addition, the rate of the sunward flow speed increase in response to an increase in driving conditions was found to be comparable for the IMF Bx > 0 and Bx < 0.

ON THE STRENGTH OF THE HEMISPHERIC RULE AND THE ORIGIN OF ACTIVE-REGION HELICITY

International Nuclear Information System (INIS)

Wang, Y.-M.

2013-01-01

Vector magnetograph and morphological observations have shown that the solar magnetic field tends to have negative (positive) helicity in the northern (southern) hemisphere, although only ∼60%-70% of active regions appear to obey this 'hemispheric rule'. In contrast, at least ∼80% of quiescent filaments and filament channels that form during the decay of active regions follow the rule. We attribute this discrepancy to the difficulty in determining the helicity sign of newly emerged active regions, which are dominated by their current-free component; as the transverse field is canceled at the polarity inversion lines, however, the axial component becomes dominant there, allowing a more reliable determination of the original active-region chirality. We thus deduce that the hemispheric rule is far stronger than generally assumed, and cannot be explained by stochastic processes. Earlier studies have shown that the twist associated with the axial tilt of active regions is too small to account for the observed helicity; here, both tilt and twist are induced by the Coriolis force acting on the diverging flow in the emerging flux tube. However, in addition to this east-west expansion about the apex of the loop, each of its legs must expand continually in cross section during its rise through the convection zone, thereby acquiring a further twist through the Coriolis force. Since this transverse pressure effect is not limited by drag or tension forces, the final twist depends mainly on the rise time, and may be large enough to explain the observed active-region helicity

Ross Ice Shelf airstream driven by polar vortex cyclone

Science.gov (United States)

Schultz, Colin

2012-07-01

The powerful air and ocean currents that flow in and above the Southern Ocean, circling in the Southern Hemisphere's high latitudes, form a barrier to mixing between Antarctica and the rest of the planet. Particularly during the austral winter, strong westerly winds isolate the Antarctic continent from heat, energy, and mass exchange, bolstering the scale of the annual polar ozone depletion and driving the continent's record-breaking low temperatures. Pushing through this wall of high winds, the Ross Ice Shelf airstream (RAS) is responsible for a sizable amount of mass and energy exchange from the Antarctic inland areas to lower latitudes. Sitting due south of New Zealand, the roughly 470,000-square-kilometer Ross Ice Shelf is the continent's largest ice shelf and a hub of activity for Antarctic research. A highly variable lower atmospheric air current, RAS draws air from the inland Antarctic Plateau over the Ross Ice Shelf and past the Ross Sea. Drawing on modeled wind patterns for 2001-2005, Seefeldt and Cassano identify the primary drivers of RAS.

Actinobacterial community structure in the Polar Frontal waters of the Southern Ocean of the Antarctica using Geographic Information System (GIS: A novel approach to study Ocean Microbiome

Directory of Open Access Journals (Sweden)

P. Sivasankar

2018-04-01

Full Text Available Integration of microbiological data and geographical locations is necessary to understand the spatiotemporal patterns of the microbial diversity of an ecosystem. The Geographic Information System (GIS to map and catalogue the data on the actinobacterial diversity of the Southern Ocean waters was completed through sampling and analysis. Water samples collected at two sampling stations viz. Polar Front 1 (Station 1 and Polar Front 2 (Station 2 during 7th Indian Scientific Expedition to the Indian Ocean Sector of the Southern Ocean (SOE-2012-13 were used for analysis. At the outset, two different genera of Actinobacteria were recorded at both sampling stations. Streptomyces was the dominanted with the high score (> 60%, followed by Nocardiopsis (< 30% at both the sampling stations-Polar Front 1 and Polar Front 2-along with other invasive genera such as Agrococcus, Arthrobacter, Cryobacterium, Curtobacterium, Microbacterium, Marisediminicola, Rhodococcus and Kocuria. This data will help to discriminate the diversity and distribution pattern of the Actinobacteria in the Polar Frontal Region of the Southern Ocean waters. It is a novel approach useful for geospatial cataloguing of microbial diversity from extreme niches and in various environmental gradations. Furthermore, this research work will act as the milestone for bioprospecting of microbial communities and their products having potential applications in healthcare, agriculture and beneficial to mankind. Hence, this research work would have significance in creating a database on microbial communities of the Antarctic ecosystem. Keywords: Antarctica, Marine actinobacteria, Southern ocean, GIS, Polar Frontal waters, Microbiome

The Primordial Inflation Polarization Explorer (PIPER)

Science.gov (United States)

Lazear, Justin Scott; Ade, Peter A.; Benford, Dominic J.; Bennett, Charles L.; Chuss, David T.; Dotson, Jessie L.; Eimer, Joseph R.; Fixsen, Dale J.; Halpern, Mark; Hinderks, James;

PHASE RELATIONSHIPS OF SOLAR HEMISPHERIC TOROIDAL AND POLOIDAL CYCLES

Energy Technology Data Exchange (ETDEWEB)

Muraközy, J., E-mail: murakozy.judit@csfk.mta.hu [Debrecen Heliophysical Observatory (DHO), Konkoly Observatory, Research Centre for Astronomy and Earth Sciences H-4010 Debrecen P.O.B. 30, H-4010 (Hungary)

2016-08-01

The solar northern and southern hemispheres exhibit differences in their intensities and time profiles of the activity cycles. The time variation of these properties was studied in a previous article covering the data from Cycles 12–23. The hemispheric phase lags exhibited a characteristic variation: the leading role was exchanged between hemispheres every four cycles. The present work extends the investigation of this variation using the data of Staudacher and Schwabe in Cycles 1–4 and 7–10 as well as Spörer’s data in Cycle 11. The previously observed variation cannot be clearly recognized using the data of Staudacher, Schwabe, and Spörer. However, it is more interesting that the phase lags of the reversals of the magnetic fields at the poles follow the same variations as those of the hemispheric cycles in Cycles 12–23, i.e., one of the hemispheres leads in four cyles and the leading role jumps to the opposite hemisphere in the next four cycles. This means that this variation is a long-term property of the entire solar dynamo mechanism, for both the toroidal and poloidal fields, which hints at an unidentified component of the process responsible for the long-term memory.

Polar bear population dynamics in the southern Beaufort Sea during a period of sea ice decline

Science.gov (United States)

Bromaghin, Jeffrey F.; McDonald, Trent L.; Stirling, Ian; Derocher, Andrew E.; Richardson, Evan S.; Regehr, Eric V.; Douglas, David C.; Durner, George M.; Atwood, Todd C.; Amstrup, Steven C.

2015-01-01

In the southern Beaufort Sea of the United States and Canada, prior investigations have linked declines in summer sea ice to reduced physical condition, growth, and survival of polar bears (Ursus maritimus). Combined with projections of population decline due to continued climate warming and the ensuing loss of sea ice habitat, those findings contributed to the 2008 decision to list the species as threatened under the U.S. Endangered Species Act. Here, we used mark–recapture models to investigate the population dynamics of polar bears in the southern Beaufort Sea from 2001 to 2010, years during which the spatial and temporal extent of summer sea ice generally declined. Low survival from 2004 through 2006 led to a 25–50% decline in abundance. We hypothesize that low survival during this period resulted from (1) unfavorable ice conditions that limited access to prey during multiple seasons; and possibly, (2) low prey abundance. For reasons that are not clear, survival of adults and cubs began to improve in 2007 and abundance was comparatively stable from 2008 to 2010, with ~900 bears in 2010 (90% CI 606–1212). However, survival of subadult bears declined throughout the entire period. Reduced spatial and temporal availability of sea ice is expected to increasingly force population dynamics of polar bears as the climate continues to warm. However, in the short term, our findings suggest that factors other than sea ice can influence survival. A refined understanding of the ecological mechanisms underlying polar bear population dynamics is necessary to improve projections of their future status and facilitate development of management strategies.

Population genetics of Southern Hemisphere tope shark (Galeorhinus galeus: Intercontinental divergence and constrained gene flow at different geographical scales.

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Aletta E Bester-van der Merwe

Full Text Available The tope shark (Galeorhinus galeus Linnaeus, 1758 is a temperate, coastal hound shark found in the Atlantic and Indo-Pacific oceans. In this study, the population structure of Galeorhinus galeus was determined across the entire Southern Hemisphere, where the species is heavily targeted by commercial fisheries, as well as locally, along the South African coastline. Analysis was conducted on a total of 185 samples using 19 microsatellite markers and a 671 bp fragment of the NADH dehydrogenase subunit 2 (ND2 gene. Across the Southern Hemisphere, three geographically distinct clades were recovered, including one from South America (Argentina, Chile, one from Africa (all the South African collections and an Australia-New Zealand clade. Nuclear data revealed significant population subdivisions (FST = 0.192 to 0.376, p<0.05 indicating limited gene flow for tope sharks across ocean basins. Marked population connectivity was however evident across the Indian Ocean based on Bayesian clustering analysis. More locally in South Africa, F-statistics and multivariate analysis supported moderate to high gene flow across the Atlantic/Indian Ocean boundary (FST = 0.035 to 0.044, p<0.05, with exception of samples from Struisbaai and Port Elizabeth which differed significantly from the rest. Discriminant and Bayesian clustering analysis indicated admixture in all sampling populations, decreasing from west to east, corroborating possible restriction to gene flow across regional oceanographic barriers. Mitochondrial sequence data recovered seven haplotypes (h = 0.216, π = 0.001 for South Africa, with one major haplotype shared by 87% of the individuals and at least one private haplotype for each sampling location except Port Elizabeth. As with many other coastal shark species with cosmopolitan distribution, this study confirms the lack of both historical dispersal and inter-oceanic gene flow while also implicating contemporary factors such as oceanic currents and

Seasonal variability of surface and column carbon monoxide over the megacity Paris, high-altitude Jungfraujoch and Southern Hemispheric Wollongong stations

Science.gov (United States)

Té, Yao; Jeseck, Pascal; Franco, Bruno; Mahieu, Emmanuel; Jones, Nicholas; Paton-Walsh, Clare; Griffith, David W. T.; Buchholz, Rebecca R.; Hadji-Lazaro, Juliette; Hurtmans, Daniel; Janssen, Christof

2016-09-01

This paper studies the seasonal variation of surface and column CO at three different sites (Paris, Jungfraujoch and Wollongong), with an emphasis on establishing a link between the CO vertical distribution and the nature of CO emission sources. We find the first evidence of a time lag between surface and free tropospheric CO seasonal variations in the Northern Hemisphere. The CO seasonal variability obtained from the total columns and free tropospheric partial columns shows a maximum around March-April and a minimum around September-October in the Northern Hemisphere (Paris and Jungfraujoch). In the Southern Hemisphere (Wollongong) this seasonal variability is shifted by about 6 months. Satellite observations by the IASI-MetOp (Infrared Atmospheric Sounding Interferometer) and MOPITT (Measurements Of Pollution In The Troposphere) instruments confirm this seasonality. Ground-based FTIR (Fourier transform infrared) measurements provide useful complementary information due to good sensitivity in the boundary layer. In situ surface measurements of CO volume mixing ratios at the Paris and Jungfraujoch sites reveal a time lag of the near-surface seasonal variability of about 2 months with respect to the total column variability at the same sites. The chemical transport model GEOS-Chem (Goddard Earth Observing System chemical transport model) is employed to interpret our observations. GEOS-Chem sensitivity runs identify the emission sources influencing the seasonal variation of CO. At both Paris and Jungfraujoch, the surface seasonality is mainly driven by anthropogenic emissions, while the total column seasonality is also controlled by air masses transported from distant sources. At Wollongong, where the CO seasonality is mainly affected by biomass burning, no time shift is observed between surface measurements and total column data.

ASYMMETRIC SUNSPOT ACTIVITY AND THE SOUTHWARD DISPLACEMENT OF THE HELIOSPHERIC CURRENT SHEET

International Nuclear Information System (INIS)

Wang, Y.-M.; Robbrecht, E.

2011-01-01

Observations of the interplanetary magnetic field (IMF) have suggested a statistical tendency for the heliospheric current sheet (HCS) to be shifted a few degrees southward of the heliographic equator during the period 1965-2010, particularly in the years near sunspot minimum. Using potential-field source-surface extrapolations and photospheric flux-transport simulations, we demonstrate that this southward displacement follows from Joy's law and the observed hemispheric asymmetry in the sunspot numbers, with activity being stronger in the southern (northern) hemisphere during the declining (rising) phase of cycles 20-23. The hemispheric asymmetry gives rise to an axisymmetric quadrupole field, whose equatorial zone has the sign of the leading-polarity flux in the dominant hemisphere; during the last four cycles, the polarity of the IMF around the equator thus tended to match that of the north polar field both before and after polar field reversal. However, large fluctuations are introduced by the nonaxisymmetric field components, which depend on the longitudinal distribution of sunspot activity in either hemisphere. Consistent with this model, the HCS showed an average northward displacement during cycle 19, when the 'usual' alternation was reversed and the northern hemisphere became far more active than the southern hemisphere during the declining phase of the cycle. We propose a new method for determining the north-south displacement of the HCS from coronal streamer observations.

Postglacial Records of Southern Hemisphere Climate and Oceanographic Change From the New Zealand Subantarctic Auckland Islands

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

2017-12-01

The strength and latitudinal position of the Southern Hemisphere westerly winds (SHWW) play a fundamental role in influencing mid-latitude climate and CO2 exchange between the Southern Ocean and the atmosphere along seasonal to glaicial-interglacial timescales. Despite their importance, our understanding of past SHWW change is limited by the small number of paleoclimate records from the modern wind maximum, which are often not in agreement. The New Zealand subantarctic Auckland Islands are located within the core of the modern wind belt (50°S), a key latitude where ocean-atmospheric linkages between the Antarctic and mid-latitudes are strong. In contrast to other subantarctic islands on the Campbell Plateau, the Auckland Islands have multiple protected fjord sub-basins, deep lakes, and peatlands that are advantageous for the development of high-resolution paleoclimate records. We will present ongoing work towards the establishment of multi-proxy and multi-site reconstructions of past SHWW variability from the Auckland Islands. Modern process and paleoclimate studies suggest that in lacustrine and fjord settings, the degree of water column mixing, the stable isotopic composition of n-alkanes and benthic foraminifera, and the influx of terrestrial organic matter are good indicators of wind-induced mixing of the water column or precipitation-driven erosion within catchments. During the Late Glacial and early Holocene (15 to 9 ka), elevated long-chain n-alkane δD values from ombrotrophic peatlands and an increase in the concentration of redox-sensitive elements in fjord sediment cores, signal weakening of the SHWW that appears to be coincident with periods of rapid deglacial warming of West Antarctica. Since 5.5 ka, we interpret declining n-alkane δD values to indicate enhanced westerly flow. These interpretations are in broad agreement with terrestrial paleoclimate records developed from southern South America and argue for a symmetrical response of the SHWW during

A comprehensive assessment of mercury exposure in penguin populations throughout the Southern Hemisphere: Using trophic calculations to identify sources of population-level variation.

Science.gov (United States)

Brasso, Rebecka L; Chiaradia, André; Polito, Michael J; Raya Rey, Andrea; Emslie, Steven D

2015-08-15

The wide geographic distribution of penguins (Order Sphenisciformes) throughout the Southern Hemisphere provided a unique opportunity to use a single taxonomic group as biomonitors of mercury among geographically distinct marine ecosystems. Mercury concentrations were compared among ten species of penguins representing 26 geographically distinct breeding populations. Mercury concentrations were relatively low (⩽2.00ppm) in feathers from 18/26 populations considered. Population-level differences in trophic level explained variation in mercury concentrations among Little, King, and Gentoo penguin populations. However, Southern Rockhopper and Magellanic penguins breeding on Staten Island, Tierra del Fuego, had the highest mercury concentrations relative to their conspecifics despite foraging at a lower trophic level. The concurrent use of stable isotope and mercury data allowed us to document penguin populations at the greatest risk of exposure to harmful concentrations of mercury as a result of foraging at a high trophic level or in geographic 'hot spots' of mercury availability. Copyright © 2015 Elsevier Ltd. All rights reserved.

A simple kinematic model for the Lagrangian description of relevant nonlinear processes in the stratospheric polar vortex

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V. J. García-Garrido

2017-06-01

Full Text Available In this work, we study the Lagrangian footprint of the planetary waves present in the Southern Hemisphere stratosphere during the exceptional sudden Stratospheric warming event that took place during September 2002. Our focus is on constructing a simple kinematic model that retains the fundamental mechanisms responsible for complex fluid parcel evolution, during the polar vortex breakdown and its previous stages. The construction of the kinematic model is guided by the Fourier decomposition of the geopotential field. The study of Lagrangian transport phenomena in the ERA-Interim reanalysis data highlights hyperbolic trajectories, and these trajectories are Lagrangian objects that are the kinematic mechanism for the observed filamentation phenomena. Our analysis shows that the breaking and splitting of the polar vortex is justified in our model by the sudden growth of a planetary wave and the decay of the axisymmetric flow.

Southern Annular Mode drives multicentury wildfire activity in southern South America.

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Holz, Andrés; Paritsis, Juan; Mundo, Ignacio A; Veblen, Thomas T; Kitzberger, Thomas; Williamson, Grant J; Aráoz, Ezequiel; Bustos-Schindler, Carlos; González, Mauro E; Grau, H Ricardo; Quezada, Juan M

2017-09-05

The Southern Annular Mode (SAM) is the main driver of climate variability at mid to high latitudes in the Southern Hemisphere, affecting wildfire activity, which in turn pollutes the air and contributes to human health problems and mortality, and potentially provides strong feedback to the climate system through emissions and land cover changes. Here we report the largest Southern Hemisphere network of annually resolved tree ring fire histories, consisting of 1,767 fire-scarred trees from 97 sites (from 22 °S to 54 °S) in southern South America (SAS), to quantify the coupling of SAM and regional wildfire variability using recently created multicentury proxy indices of SAM for the years 1531-2010 AD. We show that at interannual time scales, as well as at multidecadal time scales across 37-54 °S, latitudinal gradient elevated wildfire activity is synchronous with positive phases of the SAM over the years 1665-1995. Positive phases of the SAM are associated primarily with warm conditions in these biomass-rich forests, in which widespread fire activity depends on fuel desiccation. Climate modeling studies indicate that greenhouse gases will force SAM into its positive phase even if stratospheric ozone returns to normal levels, so that climate conditions conducive to widespread fire activity in SAS will continue throughout the 21st century.

Radiation and repeated transoceanic dispersal of Schoeneae (Cyperaceae) through the southern hemisphere.

Science.gov (United States)

Viljoen, Jan-Adriaan; Muasya, A Muthama; Barrett, Russell L; Bruhl, Jeremy J; Gibbs, Adele K; Slingsby, Jasper A; Wilson, Karen L; Verboom, G Anthony

2013-12-01

The broad austral distribution of Schoeneae is almost certainly a product of long-distance dispersal. Owing to the inadequacies of existing phylogenetic data and a lack of rigorous biogeographic analysis, relationships within the tribe remain poorly resolved and its pattern of radiation and dispersal uncertain. We employed an expanded sampling of taxa and markers and a rigorous analytic approach to address these limitations. We evaluated the roles of geography and ecology in stimulating the initial radiation of the group and its subsequent dispersal across the southern hemisphere. A dated tree was reconstructed using reversible-jump Markov chain Monte Carlo (MCMC) with a polytomy prior and molecular dating, applied to data from two nuclear and three cpDNA regions. Ancestral areas and habitats were inferred using dispersal-extinction-cladogenesis models. Schoeneae originated in Australia in the Paleocene. The existence of a "hard" polytomy at the base of the clade reflects the rapid divergence of six principal lineages ca. 50 Ma, within Australia. From this ancestral area, Schoeneae have traversed the austral oceans with remarkable frequency, a total of 29 distinct dispersal events being reported here. Dispersal rates between landmasses are not explicable in terms of the geographical distances separating them. Transoceanic dispersal generally involved habitat stasis. Although the role of dispersal in explaining global distribution patterns is now widely accepted, the apparent ease with which such dispersal may occur has perhaps been under-appreciated. In Schoeneae, transoceanic dispersal has been remarkably frequent, with ecological opportunity, rather than geography, being most important in dictating dispersal patterns.

Retinal amino acid neurochemistry of the southern hemisphere lamprey, Geotria australis.

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Lisa Nivison-Smith

Full Text Available Lampreys are one of the two surviving groups of the agnathan (jawless stages in vertebrate evolution and are thus ideal candidates for elucidating the evolution of visual systems. This study investigated the retinal amino acid neurochemistry of the southern hemisphere lamprey Geotria australis during the downstream migration of the young, recently-metamorphosed juveniles to the sea and during the upstream migration of the fully-grown and sexually-maturing adults to their spawning areas. Glutamate and taurine were distributed throughout the retina, whilst GABA and glycine were confined to neurons of the inner retina matching patterns seen in most other vertebrates. Glutamine and aspartate immunoreactivity was closely matched to Müller cell morphology. Between the migratory phases, few differences were observed in the distribution of major neurotransmitters i.e. glutamate, GABA and glycine, but changes in amino acids associated with retinal metabolism i.e. glutamine and aspartate, were evident. Taurine immunoreactivity was mostly conserved between migrant stages, consistent with its role in primary cell functions such as osmoregulation. Further investigation of glutamate signalling using the probe agmatine (AGB to map cation channel permeability revealed entry of AGB into photoreceptors and horizontal cells followed by accumulation in inner retinal neurons. Similarities in AGB profiles between upstream and downstream migrant of G. australis confirmed the conservation of glutamate neurotransmission. Finally, calcium binding proteins, calbindin and calretinin were localized to the inner retina whilst recoverin was localized to photoreceptors. Overall, conservation of major amino acid neurotransmitters and calcium-associated proteins in the lamprey retina confirms these elements as essential features of the vertebrate visual system. On the other hand, metabolic elements of the retina such as neurotransmitter precursor amino acids and Müller cells

Effects of capturing and collaring on polar bears: findings from long-term research on the southern Beaufort Sea population

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Rode, Karyn D.; Pagano, Anthony M.; Bromaghin, Jeffrey F.; Atwood, Todd C.; Durner, George M.; Simac, Kristin S.; Amstrup, Steven C.

2014-01-01

Context: The potential for research methods to affect wildlife is an increasing concern among both scientists and the public. This topic has a particular urgency for polar bears because additional research is needed to monitor and understand population responses to rapid loss of sea ice habitat.Aims: This study used data collected from polar bears sampled in the Alaska portion of the southern Beaufort Sea to investigate the potential for capture to adversely affect behaviour and vital rates. We evaluated the extent to which capture, collaring and handling may influence activity and movement days to weeks post-capture, and body mass, body condition, reproduction and survival over 6 months or more.Methods: We compared post-capture activity and movement rates, and relationships between prior capture history and body mass, body condition and reproductive success. We also summarised data on capture-related mortality.Key results: Individual-based estimates of activity and movement rates reached near-normal levels within 2–3 days and fully normal levels within 5 days post-capture. Models of activity and movement rates among all bears had poor fit, but suggested potential for prolonged, lower-level rate reductions. Repeated captures was not related to negative effects on body condition, reproduction or cub growth or survival. Capture-related mortality was substantially reduced after 1986, when immobilisation drugs were changed, with only 3 mortalities in 2517 captures from 1987–2013.Conclusions: Polar bears in the southern Beaufort Sea exhibited the greatest reductions in activity and movement rates 3.5 days post-capture. These shorter-term, post-capture effects do not appear to have translated into any long-term effects on body condition, reproduction, or cub survival. Additionally, collaring had no effect on polar bear recovery rates, body condition, reproduction or cub survival.Implications: This study provides empirical evidence that current capture

First measurements of (236)U concentrations and (236)U/(239)Pu isotopic ratios in a Southern Hemisphere soil far from nuclear test or reactor sites.

Science.gov (United States)

Srncik, M; Tims, S G; De Cesare, M; Fifield, L K

2014-06-01

The variation of the (236)U and (239)Pu concentrations as a function of depth has been studied in a soil profile at a site in the Southern Hemisphere well removed from nuclear weapon test sites. Total inventories of (236)U and (239)Pu as well as the (236)U/(239)Pu isotopic ratio were derived. For this investigation a soil core from an undisturbed forest area in the Herbert River catchment (17°30' - 19°S) which is located in north-eastern Queensland (Australia) was chosen. The chemical separation of U and Pu was carried out with a double column which has the advantage of the extraction of both elements from a relatively large soil sample (∼20 g) within a day. The samples were measured by Accelerator Mass Spectrometry using the 14UD pelletron accelerator at the Australian National University. The highest atom concentrations of both (236)U and (239)Pu were found at a depth of 2-3 cm. The (236)U/(239)Pu isotopic ratio in fallout at this site, as deduced from the ratio of the (236)U and (239)Pu inventories, is 0.085 ± 0.003 which is clearly lower than the Northern Hemisphere value of ∼0.2. The (236)U inventory of (8.4 ± 0.3) × 10(11) at/m(2) was more than an order of magnitude lower than values reported for the Northern Hemisphere. The (239)Pu activity concentrations are in excellent agreement with a previous study and the (239+240)Pu inventory was (13.85 ± 0.29) Bq/m(2). The weighted mean (240)Pu/(239)Pu isotopic ratio of 0.142 ± 0.005 is slightly lower than the value for global fallout, but our results are consistent with the average ratio of 0.173 ± 0.027 for the southern equatorial region (0-30°S). Copyright © 2014 Elsevier Ltd. All rights reserved.

Protists in the polar regions: comparing occurrence in the Arctic and Southern oceans using pyrosequencing

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Christian Wolf

2015-05-01

Full Text Available In the ongoing discussion of the distribution of protists, whether they are globally distributed or endemic to one or both of the polar regions is the subject of heated debate. In this study, we compared next-generation sequencing data from the Arctic and the Southern oceans to reveal the extent of similarities and dissimilarities between the protist communities in the polar regions. We found a total overlap of operational taxonomic units (OTUs between the two regions of 11.2%. On closer inspection of different taxonomic groups, the overlap ranged between 5.5% (haptophytes and 14.5% (alveolates. Within the different groups, the proportion of OTUs occurring in both regions greatly differed between the polar regions. On the one hand, the overlap between these two regions is remarkable, given the geographical distance between them. On the other hand, one could expect a greater overlap of OTUs between these regions on account of the similar environmental conditions. The overlap suggests a connection between the polar regions for at least certain species or that the evolutionary divergence has been slow, relative to the timescales of isolation. The different proportions of common OTUs among the groups or regions may be a result of different life cycle strategies or environmental adaptations.

The dynamic relation between activities in the Northern and Southern solar hemispheres

Science.gov (United States)

Volobuev, D. M.; Makarenko, N. G.

2016-12-01

The north-south (N/S) asymmetry of solar activity is the most pronounced phenomenon during 11-year cycle minimums. The goal of this work is to try to interpret the asymmetry as a result of the generalized synchronization of two dynamic systems. It is assumed that these systems are localized in two solar hemispheres. The evolution of these systems is considered in the topological embeddings of a sunspot area time series obtained with the use of the Takens algorithm. We determine the coupling measure and estimate it on the time series of daily sunspot areas. The measurement made it possible to interpret the asymmetry as an exchangeable dynamic equation, in which the roles of the driver-slave components change in time for two hemispheres.

Theropod Fauna from Southern Australia Indicates High Polar Diversity and Climate-Driven Dinosaur Provinciality

Science.gov (United States)

Benson, Roger B. J.; Rich, Thomas H.; Vickers-Rich, Patricia; Hall, Mike

2012-01-01

The Early Cretaceous fauna of Victoria, Australia, provides unique data on the composition of high latitude southern hemisphere dinosaurs. We describe and review theropod dinosaur postcranial remains from the Aptian–Albian Otway and Strzelecki groups, based on at least 37 isolated bones, and more than 90 teeth from the Flat Rocks locality. Several specimens of medium- and large-bodied individuals (estimated up to ∼8.5 metres long) represent allosauroids. Tyrannosauroids are represented by elements indicating medium body sizes (∼3 metres long), likely including the holotype femur of Timimus hermani, and a single cervical vertebra represents a juvenile spinosaurid. Single specimens representing medium- and small-bodied theropods may be referrable to Ceratosauria, Ornithomimosauria, a basal coelurosaur, and at least three taxa within Maniraptora. Thus, nine theropod taxa may have been present. Alternatively, four distinct dorsal vertebrae indicate a minimum of four taxa. However, because most taxa are known from single bones, it is likely that small-bodied theropod diversity remains underestimated. The high abundance of allosauroids and basal coelurosaurs (including tyrannosauroids and possibly ornithomimosaurs), and the relative rarity of ceratosaurs, is strikingly dissimilar to penecontemporaneous dinosaur faunas of Africa and South America, which represent an arid, lower-latitude biome. Similarities between dinosaur faunas of Victoria and the northern continents concern the proportional representatation of higher clades, and may result from the prevailing temperate–polar climate of Australia, especially at high latitudes in Victoria, which is similar to the predominant warm–temperate climate of Laurasia, but distinct from the arid climate zone that covered extensive areas of Gondwana. Most dinosaur groups probably attained a near-cosmopolitan distribution in the Jurassic, prior to fragmentation of the Pangaean supercontinent, and some aspects of the

Molecular evidence for the Southern Hemisphere origin and deep-sea diversification of spiny lobsters (Crustacea: Decapoda: Palinuridae).

Science.gov (United States)

Tsang, L M; Chan, T-Y; Cheung, M K; Chu, K H

2009-05-01

Spiny lobsters (family Palinuridae) are economically important marine animals that have been the subject of a considerable amount of research. However, the phylogeny of this group remains disputed. Morphological analyses have not been able to resolve the relationships of the various members of the group, and no agreement has yet been reached on its phylogeny as indicated by the different gene trees reported to date. In the present study, we attempt to reconstruct the phylogeny of Palinuridae and its allies using sequences from three nuclear protein-coding genes (phosphoenolpyruvate carboxykinase, sodium-potassium ATPase alpha-subunit and histone 3). The inferred topology receives strong nodal support for most of the branches. The family Palinuridae is found to be paraphyletic with the polyphyletic Synaxidae nested within it. Stridentes forms a monophyletic assemblage, indicating that the stridulating sound producing organ evolved only once in the spiny lobsters. By contrast, Silentes is paraphyletic, as Palinurellus is more closely related to Stridentes than to other Silentes genera. The three genera restricted to the southern high latitudes (Jasus, Projasus and Sagmariasus) constitute the basal lineages in the spiny lobsters, suggesting a Southern Hemisphere origin for the group. Subsequent diversification appears to have been driven by the closure of the Tethys Sea and the formation of the Antarctic circumpolar current, which isolated the northern and southern taxa. Contrary to an earlier hypothesis that postulated evolution from a deep-sea ancestral stock, the shallow-water genus Panulirus is the basal taxon in Stridentes, while the deep-sea genera Puerulus and Linuparus are found to be derived. This indicates that the spiny lobsters invaded deep-sea habitats from the shallower water rocky reefs and then radiated. Our results suggest that Synaxidae is not a valid family, and should be considered to be synonymous with Palinuridae. We also found that the

Use of multi-frequency, multi-polarization, multi-angle airborne radars for class discrimination in a southern temperature forest

Science.gov (United States)

Mehta, N. C.

1984-01-01

The utility of radar scatterometers for discrimination and characterization of natural vegetation was investigated. Backscatter measurements were acquired with airborne multi-frequency, multi-polarization, multi-angle radar scatterometers over a test site in a southern temperate forest. Separability between ground cover classes was studied using a two-class separability measure. Very good separability is achieved between most classes. Longer wavelength is useful in separating trees from non-tree classes, while shorter wavelength and cross polarization are helpful for discrimination among tree classes. Using the maximum likelihood classifier, 50% overall classification accuracy is achieved using a single, short-wavelength scatterometer channel. Addition of multiple incidence angles and another radar band improves classification accuracy by 20% and 50%, respectively, over the single channel accuracy. Incorporation of a third radar band seems redundant for vegetation classification. Vertical transmit polarization is critically important for all classes.

Southern hemisphere searches for short period pulsars

International Nuclear Information System (INIS)

Manchester, R.N.

1984-01-01

Two searches of the southern sky for short period pulsars are briefly described. The first, made using the 64-m telescope at Parkes, is sensitive to pulsars with periods greater than about 10 ms and the second, made using the Molonglo radio telescope, has sensitivity down to periods of about 1.5 ms. Four pulsars were found in the Parkes survey and none in the Molonglo survey, although analysis of the latter is as yet incomplete. 10 references, 1 figure, 2 tables

Atmospheric circulation in northern hemisphere and north atlantic oscillation

Directory of Open Access Journals (Sweden)

Александр Вадимович Холопцев

2015-08-01

Full Text Available Conditions under which statistical connections of interannual changes of repitition duration periods in Northern hemisphere of elementary circulation mechanisms associated to meridional northern and meridional southern groups with variations of North Atlantic oscillation are significant were revealed. It is shown, that the characteristics changes of these connections taking place in modern period can be caused by distribution changes of distribution of sea surface temperatures

Simulated warm polar currents during the middle Permian

Energy Technology Data Exchange (ETDEWEB)

Winguth, A M.E.; Kutzbach, J E [Wisconsin Univ., Madison, WI (USA). Center for Climatic Research; Heinze, C; Maier-Reimer, E; Mikolajewicz, U [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany); Rowley, D; Rees, A; Ziegler, A M [Chicago Univ., IL (United States). Dept. of Geophysical Sciences

2001-05-01

During Permian Stage 6 (Wordian, Kazanian) the Pangaean supercontinent was surrounded by a superocean - Panthalassa. An ocean general circulation model has been coupled to an atmospheric energy balance model to simulate the sensitivity of the Wordian climate ({proportional_to}265 million years ago) to changes in greenhouse gas concentrations, high latitude geography, and Earth orbital configurations. The model shows a high sensitivity of the ocean circulation to changes in the greenhouse gas forcing, ranging from a forceful southern circulation at low CO{sub 2} concentration (present level) to a more symmetric circulation cell with deep water formation in both hemispheres at high CO{sub 2} concentration (8 x present level). The simulated climate with 4 x present level CO{sub 2} concentration agrees generally well with climate-sensitive sediments and phytogeographic patterns. In this experiment, the model simulates strong subtropical gyres with similarities to the modern South Pacific circulation and moderate surface temperatures on the southern continent Gondwana, resulting from a strong poleward heat transport in the ocean. An even more moderate climate can be generated if high latitude land is removed so that ocean currents can penetrate into the polar regions or if orbital configurations favor high summer insolation over Gondwana. (orig.)

The Hemispheric Asymmetry of Polar Faculae LH Deng1,2,∗ , ZQ

Indian Academy of Sciences (India)

high-latitude solar activity; (3) the N–S asymmetry of the polar faculae at. TLs depends on ... dinal bands are more elaborately divided, it is necessary to study the N–S asymmetry of the polar .... attention to the solar activity at the polar zone.

Southern Forests: a Journal of Forest Science

African Journals Online (AJOL)

Southern Hemisphere Forestry Journal. ... The journal particularly encourages contributions from South America, Africa and tropical/subtropical ... Alternative eucalypts for commercial pulpwood production at moderately dry sites in the warm ...

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.

Anthropogenic radiative forcing of southern African and Southern Hemisphere climate variability and change

CSIR Research Space (South Africa)

Engelbrecht, FA

2014-10-01

Full Text Available of stratospheric ozone, greenhouse gasses, aerosols and sulphur dioxide, can improve the model's skill to simulate inter-annual variability over southern Africa. The paper secondly explores the role of different radiative forcings of future climate change over...

A polar stratospheric cloud parameterization for the global modeling initiative three-dimensional model and its response to stratospheric aircraft

International Nuclear Information System (INIS)

Considine, D. B.; Douglass, A. R.; Connell, P. S.; Kinnison, D. E.; Rotman, D. A.

2000-01-01

We describe a new parameterization of polar stratospheric clouds (PSCs) which was written for and incorporated into the three-dimensional (3-D) chemistry and transport model (CTM) developed for NASA's Atmospheric Effects of Aviation Project (AEAP) by the Global Modeling Initiative (GMI). The parameterization was designed to respond to changes in NO y and H 2 O produced by high-speed civilian transport (HSCT) emissions. The parameterization predicts surface area densities (SADs) of both Type 1 and Type 2 PSCs for use in heterogeneous chemistry calculations. Type 1 PSCs are assumed to have a supercooled ternary sulfate (STS) composition, and Type 2 PSCs are treated as water ice with a coexisting nitric acid trihydrate (NAT) phase. Sedimentation is treated by assuming that the PSC particles obey lognormal size distributions, resulting in a realistic mass flux of condensed phase H 2 O and HNO 3 . We examine a simulation of the Southern Hemisphere high-latitude lower stratosphere winter and spring seasons driven by temperature and wind fields from a modified version of the National Center for Atmospheric Research (NCAR) Middle Atmosphere Community Climate Model Version 2 (MACCM2). Predicted PSC SADs and median radii for both Type 1 and Type 2 PSCs are consistent with observations. Gas phase HNO 3 and H 2 O concentrations in the high-latitude lower stratosphere qualitatively agree with Cryogenic Limb Array Etalon Spectrometer (CLAES) HNO 3 and Microwave Limb Sounder (MLS) H 2 O observations. The residual denitrification and dehydration of the model polar vortex after polar winter compares well with atmospheric trace molecule spectroscopy (ATMOS) observations taken during November 1994. When the NO x and H 2 O emissions of a standard 500-aircraft HSCT fleet with a NO x emission index of 5 are added, NO x and H 2 O concentrations in the Southern Hemisphere polar vortex before winter increase by up to 3%. This results in earlier onset of PSC formation, denitrification, and

DMSP optical and electron measurements in the vicinity of polar cap arcs

International Nuclear Information System (INIS)

Hardy, D.A.; Burke, W.J.; Gussenhoven, M.S.

1982-01-01

We have completed an extensive analysis of the electron and optical data from the DMSP satellites for an external period of polar cap arc occurrences on December 12, 1977. The polar cap arcs are observed in three distinct intervals in a period of quieting after a time of intense substorm activity. The observation of polar cap arcs is associated with the admittance of large and variable fluxes of low-energy electrons into a major portion of both the northern and southern hemisphere polar caps. These fluxes fall into the following categories: First, nearly Maxwellian distributions of electrons with temperatures between 50 eV and 200 eV and number densities varying from 0.03/cm 3 to 4/cm 3 . The highest densities are found at the poleward boundary of the diffuse aurorae and near the visible polar cap arcs. The lowest densities are associated with the polar rain. Second, distributions of electrons peaked between 50 eV and 200 eV. These distributions result from accelertion of the cold Maxwellian distribution through a potential of 50 to 200 V without any heating of the electrons. Third, distributions of electrons displaying two populations; an intense low-energy component with a temperature of approx.20 eV and a much weaker high-energy component with a temperature of 180 eV. We interpret such distributions as evidence of direct admittance of magnetosheath electrons into the polar cap. Fourth,, distributions of electrons peaked at approx.1 keV. These distributions produce the visible arcs. They result from the acceleration of a two-component electron population with temperatures of 100 and 350 eV through a potential drop of approx.750 V

78 FR 65300 - Western Hemisphere Institute for Security Cooperation Board of Visitors; Meeting

Science.gov (United States)

2013-10-31

... DEPARTMENT OF DEFENSE Department of the Army Western Hemisphere Institute for Security Cooperation Board of Visitors; Meeting AGENCY: Department of the Army, DoD. ACTION: Notice of open meeting. SUMMARY... from the WHINSEC Commandant; Department of State; US Northern Command and US Southern Command; the...

Immunogenicity and safety of Southern Hemisphere inactivated quadrivalent influenza vaccine: a Phase III, open-label study of adults in Brazil.

Science.gov (United States)

Zerbini, Cristiano A F; Ribeiro Dos Santos, Rodrigo; Jose Nunes, Maria; Soni, Jyoti; Li, Ping; Jain, Varsha K; Ofori-Anyinam, Opokua

The World Health Organization influenza forecast now includes an influenza B strain from each of the influenza B lineages (B/Yamagata and B/Victoria) for inclusion in seasonal influenza vaccines. Traditional trivalent influenza vaccines include an influenza B strain from one lineage, but because two influenza B lineages frequently co-circulate, the effectiveness of trivalent vaccines may be reduced in seasons of influenza B vaccine-mismatch. Thus, quadrivalent vaccines may potentially reduce the burden of influenza compared with trivalent vaccines. In this Phase III, open-label study, we assessed the immunogenicity and safety of Southern Hemisphere inactivated quadrivalent influenza vaccine (Fluarix™ Tetra) in Brazilian adults (NCT02369341). The primary objective was to assess hemagglutination-inhibition antibody responses against each vaccine strain 21 days after vaccination in adults (aged ≥18-60 years) and older adults (aged >60 years). Solicited adverse events for four days post-vaccination, and unsolicited adverse events and serious adverse events for 21 days post-vaccination were also assessed. A total of 63 adults and 57 older adults received one dose of inactivated quadrivalent influenza vaccine at the beginning of the 2015 Southern Hemisphere influenza season. After vaccination, in adults and older adults, the hemagglutination-inhibition titers fulfilled the European licensure criteria for immunogenicity. In adults, the seroprotection rates with HI titer ≥1:40 were 100% (A/H1N1), 98.4% (A/H3N2), 100% (B/Yamagata), and 100% (B/Victoria); in older adults were 94.7% (A/H1N1), 96.5% (A/H3N2), 100% (B/Yamagata), and 100% (B/Victoria). Pain was the most common solicited local adverse events in adults (27/62) and in older adults (13/57), and the most common solicited general adverse events in adults was myalgia (9/62), and in older adults were myalgia and arthralgia (both 2/57). Unsolicited adverse events were reported by 11/63 adults and 10/57 older adults

Hemispherically in-phase precipitation variability over the last 1700 years in a Madagascar speleothem record

Science.gov (United States)

Scroxton, Nick; Burns, Stephen J.; McGee, David; Hardt, Ben; Godfrey, Laurie R.; Ranivoharimanana, Lovasoa; Faina, Peterson

2017-05-01

Paleoclimate studies of tropical rainfall have led to a recognition of a predominant pattern of anti-phase behavior between the Northern and Southern hemispheres at both orbital and millennial timescales. Less certain is how regional tropical rainfall patterns have changed in the late Holocene, under boundary conditions and on timescales which are most relevant to the tropics' response to a warming world. Several high-resolution southern hemisphere rainfall records are at odds with meridional movement of the mean Inter-Tropical Convergence Zone location as the major driver of Holocene tropical rainfall variability, with regional precipitation patterns resembling modern day El-Niño Southern Oscillation end members. To test emerging ideas on sub-millennial tropical rainfall variability, additional records from the southern hemisphere are required. We present a new speleothem δ18O record from Anjohibe Cave, northwestern Madagascar, which provides a quasi-annual record of monsoonal strength and precipitation amount for the last 1700 years. The majority of δ18O variability in the record is at the decadal scale, and shows little to no correlation with major climate indices or cyclical climate drivers. At lower frequencies, changes in mean speleothem δ18O show good correlation with other regional precipitation records both north and south of the equator. The regional coherency of tropical rainfall across the west Indian Ocean resembles expansion and contraction of the tropical rain belt and positive-Indian Ocean Dipole-like conditions at different timescales. The cause of this coherency could be related to symmetrical changes in continental sensible heating, or to a low frequency sea surface temperature climate mode.

Reduced connection between the East Asian Summer Monsoon and Southern Hemisphere Circulation on interannual timescales under intense global warming

Science.gov (United States)

Yu, Tianlei; Guo, Pinwen; Cheng, Jun; Hu, Aixue; Lin, Pengfei; Yu, Yongqiang

2018-03-01

Previous studies show a close relationship between the East Asian Summer Monsoon (EASM) and Southern Hemisphere (SH) circulation on interannual timescales. In this study, we investigate whether this close relationship will change under intensive greenhouse-gas effect by analyzing simulations under two different climate background states: preindustrial era and Representative Concentration Pathway (RCP) 8.5 stabilization from the Community Climate System Model Version 4 (CCSM4). Results show a significantly reduced relationship under stabilized RCP8.5 climate state, such a less correlated EASM with the sea level pressure in the southern Indian Ocean and the SH branch of local Hadley Cell. Further analysis suggests that the collapse of the Atlantic Meridional Overturning Circulation (AMOC) due to this warming leads to a less vigorous northward meridional heat transport, a decreased intertropical temperature contrast in boreal summer, which produces a weaker cross-equatorial Hadley Cell in the monsoonal region and a reduced Interhemispheric Mass Exchange (IME). Since the monsoonal IME acts as a bridge connecting EASM and SH circulation, the reduced IME weakens this connection. By performing freshwater hosing experiment using the Flexible Global Ocean—Atmosphere—Land System model, Grid-point Version 2 (FGOALS-g2), we show a weakened relationship between the EASM and SH circulation as in CCSM4 when AMOC collapses. Our results suggest that a substantially weakened AMOC is the main driver leading to the EASM, which is less affected by SH circulation in the future warmer climate.

77 FR 20369 - Western Hemisphere Institute for Security Cooperation Board of Visitors; Meeting

Science.gov (United States)

2012-04-04

... Defense (Policy); Department of State; US Northern Command and US Southern Command as well as receive... DEPARTMENT OF DEFENSE Department of the Army Western Hemisphere Institute for Security Cooperation Board of Visitors; Meeting AGENCY: Department of the Army, DoD. ACTION: Notice of open meeting. SUMMARY...

76 FR 39076 - Western Hemisphere Institute for Security Cooperation Board of Visitors; Meeting

Science.gov (United States)

2011-07-05

... Defense (Policy); Department of State; US Northern Command and US Southern Command meeting on December 3rd... DEPARTMENT OF DEFENSE Department of the Army Western Hemisphere Institute for Security Cooperation Board of Visitors; Meeting AGENCY: Department of the Army, DoD. ACTION: Notice of open meeting. SUMMARY...

Fronts and precipitation in CMIP5 models for the austral winter of the Southern Hemisphere

Science.gov (United States)

Blázquez, Josefina; Solman, Silvina A.

2018-04-01

Wintertime fronts climatology and the relationship between fronts and precipitation as depicted by a group of CMIP5 models are evaluated over the Southern Hemisphere (SH). The frontal activity is represented by an index that takes into account the vorticity, the gradient of temperature and the specific humidity at the 850 hPa level. ERA-Interim reanalysis and GPCP datasets are used to assess the performance of the models in the present climate. Overall, it is found that the models can reproduce adequately the main features of frontal activity and front frequency over the SH. The total precipitation is overestimated in most of the models, especially the maximum values over the mid latitudes. This overestimation could be related to the high values of precipitation frequency that are identified in some of the models evaluated. The relationship between fronts and precipitation has also been evaluated in terms of both frequency of frontal precipitation and percentage of precipitation due to fronts. In general terms, the models overestimate the proportion between frontal and total precipitation. In contrast with frequency of total precipitation, the frequency of frontal precipitation is well reproduced by the models, with the higher values located at the mid latitudes. The results suggest that models represent very well the dynamic forcing (fronts) and the frequency of frontal precipitation, though the amount of precipitation due to fronts is overestimated.

A Model of the Effect of Ozone Depletion on Lower-Stratospheric Structure

Science.gov (United States)

Olsen, Mark A.; Stolarski, Richard S.; Gupta, Mohan L.; Nielsen, J. Eric; Pawson, Steven

2005-01-01

We have run two twenty-year integrations of a global circulation model using 1978-1980 and 1998-2000 monthly mean ozone climatologies. The ozone climatology is used solely in the radiation scheme of the model. Several key differences between the model runs will be presented. The temperature and potential vorticity (PV) structure of the lower stratosphere, particularly in the Southern Hemisphere, is significantly changed using the 1998-2000 ozone climatology. In the Southern Hemisphere summer, the lapse rate and PV-defined polar tropopauses are both at altitudes on the order of several hundred meters greater than the 1978-1980 climatological run. The 380 K potential temperature surf= is likewise at a greater altitude. The mass of the extratropical lowermost stratosphere (between the tropopause and 380 K surface) remains unchanged. The altitude differences are not observed in the Northern Hemisphere. The different ozone fields do not produce a significant change in the annual extratropical stratosphere-troposphere exchange of mass although slight variations in the spatial distribution of the exchange exist. We are also investigating a delay in the breakup of the Southern Hemisphere polar vortex due to the differing ozone climatologies.

Role of Atmospheric Cloud Radiative Effects in the Intermodal Spread in the Shift of Southern Hemispheric Eddy-driven Jet in Responses to Global Warming

Science.gov (United States)

Li, Y.; Thompson, D. W. J.; Bony, S.

2017-12-01

Observations and most climate models suggest storm track and extratropical eddy driven jet shifts poleward in a warmer climate, particularly in the Southern Hemisphere. However, the magnitude of such shifts remains uncertain. Even for a prescribed uniform SST changes, models produce large inter-model spread in the magnitude of jet shift, suggesting that a substantial part of these uncertainties are caused by the impact of cloud radiative effects on the atmospheric heating rate per se. In this study we will investigate 1) how much do clouds contribute to the spread of the circulation response in the absence of SST coupling? 2) how much do clouds contribute to the spread of the direct CO2 and SST-only response?

A study of the geomagnetic indices asymmetry based on the interplanetary magnetic field polarities

Science.gov (United States)

El-Borie, M. A.; El-Taher, A. M.; Aly, N. E.; Bishara, A. A.

2018-05-01

Data of geomagnetic indices ( aa, Kp, Ap, and Dst) recorded near 1 AU over the period 1967-2016, have been studied based on the asymmetry between the interplanetary magnetic field (IMF) directions above and below of the heliospheric current sheet (HCS). Our results led to the following conclusions: (i) Throughout the considered period, 31 random years (62%) showed apparent asymmetries between Toward (T) and Away (A) polarity days and 19 years (38%) exhibited nearly a symmetrical behavior. The days of A polarity predominated over the T polarity days by 4.3% during the positive magnetic polarity epoch (1991-1999). While the days of T polarity exceeded the days of A polarity by 5.8% during the negative magnetic polarity epoch (2001-2012). (ii) Considerable yearly North-South (N-S) asymmetries of geomagnetic indices observed throughout the considered period. (iii) The largest toward dominant peaks for aa and Ap indices occurred in 1995 near to minimum of solar activity. Moreover, the most substantial away dominant peaks for aa and Ap indices occurred in 2003 (during the descending phase of the solar cycle 23) and in 1991 (near the maximum of solar activity cycle) respectively. (iv) The N-S asymmetry of Kp index indicated a most significant away dominant peak occurred in 2003. (v) Four of the away dominant peaks of Dst index occurred at the maxima of solar activity in the years 1980, 1990, 2000, and 2013. The largest toward dominant peak occurred in 1991 (at the reversal of IMF polarity). (vi) The geomagnetic indices ( aa, Ap, and Kp) all have northern dominance during positive magnetic polarity epoch (1971-1979), while the asymmetries shifts to the southern solar hemisphere during negative magnetic polarity epoch (2001-2012).

The effect of dual-hemisphere breeding on stallion fertility.

Science.gov (United States)

Walbornn, S R; Love, C C; Blanchard, T L; Brinsko, S P; Varner, D D

2017-05-01

Breeding records were analyzed from 24 Thoroughbred stallions that were subjected to dual-hemisphere breeding (DH), including novice (first-year; NOV; n = 11) and experienced (EXP; n = 13) stallions. Fertility variables included seasonal pregnancy rate, pregnancy rate per cycle, and first-cycle pregnancy rate. In addition, values for book size, total number of covers, distribution of mare type (maiden, foaling, and barren) within a stallion's book, cycles per mare, and mare age were examined. Some data were also categorized by mare type (maiden-M, foaling-F, and barren-B). Five separate analyses of the data were performed. For Analyses 1-3, the effects of hemisphere (northern hemisphere [NH] vs. southern hemisphere [SH]) and breeding order (refers to the first [O1] or second [O2] season within the first year of dual-hemisphere breeding) were examined for all stallions (combined group [CG]), NOV stallions only, and EXP stallions only, respectively. Fertility values were generally higher in the SH than the NH (P fertility of O1 was generally similar to O2 (P > 0.05). For Analysis 4, fertility of DH breeding seasons was compared to single hemisphere (SIN) breeding seasons within the same 16 stallions and was found to be similar between the two groups (P > 0.05). For Analysis 5, the effect of the number of consecutive DH breeding seasons on fertility was examined and was found to remain unchanged (P > 0.05). In summary, no adverse effects of DH breeding on fertility were detected. Fertility was higher when stallions were bred in the SH, as compared to the NH. Potential reasons for higher fertility achieved in the SH were smaller book sizes and better mare reproductive quality. Copyright © 2017. Published by Elsevier Inc.

Periodicity in changes of Jupiter's hemispheres activity factor is continues to recover in 2018

Science.gov (United States)

Vidmachenko, A. P.

2018-05-01

From the mid-1990s to 2013 that there was a maximum mismatch between the time of Jupiter's passage at orbit at perihelion and aphelion, and the moments of minima and maxima of Solar activity. In 1963-1995 the correlation between the changes in factor AJ, Solar activity and the moments of passage of perihelion and aphelion of the orbit - was high, and the nature of the changes was synchronized. After 1995, inconsistency in the supply of Solar energy to northern and southern hemispheres of Jupiter and its movement in orbit - has become significant. But after 2014, the periodicity in the change of photometric characteristics of the northern and southern hemispheres of Jupiter, again becomes coordinated. And the data for 2017 and 2018 confirm the improvement of the matching of the course of the Aj(T) dependence, SA index and the regime irradiation by the Sun of Jupiter at it moves along the orbit.

Extracting gravity wave parameters during the September 2002 Southern Hemisphere major sudden stratospheric warming using a SANAE imaging riometer

Energy Technology Data Exchange (ETDEWEB)

Mbatha, N. [South African National Space Agency, Hermanus (South Africa). Space Science; KwaZulu-Natal Univ., Durban (South Africa). School of Chemistry and Physics; Sivakumar, V. [KwaZulu-Natal Univ., Durban (South Africa). School of Chemistry and Physics; Bencherif, H. [La Reunion Univ. UMR 8105 CNRS, Saint-Denis (France). Lab. de l' Atmosphere et des Cyclones; Malinga, S. [South African National Space Agency, Hermanus (South Africa). Space Science

2013-11-01

Using absorption data measured by imaging riometer for ionospheric studies (IRIS) located at the South Africa National Antarctic Expedition (SANAE), Antarctica (72 S, 3 W), we extracted the parameters of gravity waves (GW) of periods between 40 and 50 min during late winter/ spring of the year 2002, a period of the unprecedented major sudden stratospheric warming (SSW) in the Southern Hemisphere middle atmosphere. During this period, an unprecedented substantial increase of temperature by about 25-30K throughout the stratosphere was observed. During the period of the occurrence of the major stratospheric warming, there was a reduction of both the GW horizontal phase speeds and the horizontal wavelengths at 90 km. The GW phase speeds and horizontal wavelengths were observed to reach minimum values of about 7ms{sup -1} and 19 km, respectively, while during the quiet period the average value of the phase speed and horizontal wavelength was approximately 23ms{sup -1} and 62 km, respectively. The observed event is discussed in terms of momentum flux and also a potential interaction of gravity waves, planetary waves and mean circulation.

Planetary period oscillations in Saturn's magnetosphere: New results from the F-ring and proximal orbits

Science.gov (United States)

Provan, G.; Cowley, S. W. H.; Bunce, E. J.; Hunt, G. J.; Dougherty, M. K.

2017-12-01

We investigate planetary period oscillations (PPOs) in Saturn's magnetosphere using Cassini magnetic field data during the high cadence ( 7 days) F-ring and proximal orbits. Previous results have shown that there are two PPO systems, one in each hemisphere. Both PPO periods show seasonal dependence, and since mid-2014 the Northern PPO period has been 10.8 h and the Southern PPO period 10.7 h. The beat period of the two oscillations is 45 days. Previous results demonstrated that in the Northern (Southern) polar region only pure Northern (Southern) oscillations can be observed, whilst in the equatorial region both oscillations are present and constructively and destructively interfere over the beat-cycle of the two oscillations. The PPOs are believed to be driven by twin-cell convection patterns in the polar ionosphere/thermosphere regions, with two systems of field-aligned currents transmitting the PPO flows to the magnetospheric plasma.The F-ring and proximal orbits uniquely observe the PPOs over 6 orbits during each PPO beat cycle. This high-cadence data demonstrates that over a beat cycle both the periods and amplitudes of the PPO observed within the each polar region are modulated by the PPO system from the opposite hemisphere. When the two oscillations are in phase (anti-phase) the `drag' of one system on the other acts to decrease (increase) the amplitude of the oscillations and the two PPO periods diverge (converge). We present a theoretical model showing that this coupling is due to the PPO flows from one hemisphere not just being communicated to the magnetosphere as previously assumed, but also to the opposite hemisphere. The result is inter-hemispheric coupling of the PPO flow systems within the ionosphere/thermosphere system, so that the northern PPO system drives a northern twin-cell convection pattern in the southern hemisphere, and vice versa, thus leading to the observed polar modulations of the PPOs.We will also present PPO phase models determined

Hemispherically asymmetric trade wind changes as signatures of past ITCZ shifts

Science.gov (United States)

McGee, David; Moreno-Chamarro, Eduardo; Green, Brian; Marshall, John; Galbraith, Eric; Bradtmiller, Louisa

2018-01-01

The atmospheric Hadley cells, which meet at the Intertropical Convergence Zone (ITCZ), play critical roles in transporting heat, driving ocean circulation and supplying precipitation to the most heavily populated regions of the globe. Paleo-reconstructions can provide concrete evidence of how these major features of the atmospheric circulation can change in response to climate perturbations. While most such reconstructions have focused on ITCZ-related rainfall, here we show that trade wind proxies can document dynamical aspects of meridional ITCZ shifts. Theoretical expectations based on angular momentum constraints and results from freshwater hosing simulations with two different climate models predict that ITCZ shifts due to anomalous cooling of one hemisphere would be accompanied by a strengthening of the Hadley cell and trade winds in the colder hemisphere, with an opposite response in the warmer hemisphere. This expectation of hemispherically asymmetric trade wind changes is confirmed by proxy data of coastal upwelling and windblown dust from the Atlantic basin during Heinrich stadials, showing trade wind strengthening in the Northern Hemisphere and weakening in the Southern Hemisphere subtropics in concert with southward ITCZ shifts. Data from other basins show broadly similar patterns, though improved constraints on past trade wind changes are needed outside the Atlantic Basin. The asymmetric trade wind changes identified here suggest that ITCZ shifts are also marked by intensification of the ocean's wind-driven subtropical cells in the cooler hemisphere and a weakening in the warmer hemisphere, which induces cross-equatorial oceanic heat transport into the colder hemisphere. This response would be expected to prevent extreme meridional ITCZ shifts in response to asymmetric heating or cooling. Understanding trade wind changes and their coupling to cross-equatorial ocean cells is key to better constraining ITCZ shifts and ocean and atmosphere dynamical

Diatom community response to climate variability over the past 37,000 years in the sub-tropics of the Southern Hemisphere

Energy Technology Data Exchange (ETDEWEB)

Hembrow, Sarah C., E-mail: sarah.hembrow@scu.edu.au [School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW 2480 (Australia); Taffs, Kathryn H. [School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW 2480 (Australia); Atahan, Pia [Institute for Environmental Research, Australian Nuclear Science and Technology Organisation, Kirrawee, NSW 2232 (Australia); Parr, Jeff [School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW 2480 (Australia); Zawadzki, Atun; Heijnis, Henk [Institute for Environmental Research, Australian Nuclear Science and Technology Organisation, Kirrawee, NSW 2232 (Australia)

2014-01-01

Climate change is impacting global surface water resources, increasing the need for a deeper understanding of the interaction between climate and biological diversity. This is particularly the case in the Southern Hemisphere sub-tropics, where little information exists on the aquatic biota response to climate variations. Palaeolimnological techniques, in particular the use of diatoms, are well established and can significantly contribute to the understanding of climatic variability and the impacts that change in climate have on aquatic ecosystems. A sediment core from Lake McKenzie, Fraser Island (Australia), was used to investigate interactions between climate influences and aquatic ecosystems. This study utilises a combination of proxies including biological (diatom), geochemical and chronological techniques to investigate long-term aquatic changes within the perched-dune lake. A combination of {sup 210}Pb and AMS {sup 14}C dates showed that the retrieved sediment represented a history of ca. 37,000 cal. yBP. The sedimentation rate in Lake McKenzie is very low, ranging on average from 0.11 mm to 0.26 mm per year. A sediment hiatus was observed between ca. 18,300 and 14,000 cal. yBP suggesting a period of dry conditions at the site. The diatom record shows little variability over the period of record, with benthic, freshwater acidic tolerant species dominating. Relative abundance of planktonic species and geochemical results indicates a period of increased water depth and lake productivity in the early Holocene and a gradual decrease in effective precipitation throughout the Holocene. Results from this study not only support earlier work conducted on Fraser Island using pollen reconstructions but also demonstrate that diatom community diversity has been relatively consistent throughout the Holocene and late Pleistocene with only minor cyclical fluctuation evident. This record is consistent with the few other aquatic palaeoecological records from the Southern

Diatom community response to climate variability over the past 37,000 years in the sub-tropics of the Southern Hemisphere

International Nuclear Information System (INIS)

Hembrow, Sarah C.; Taffs, Kathryn H.; Atahan, Pia; Parr, Jeff; Zawadzki, Atun; Heijnis, Henk

2014-01-01

Climate change is impacting global surface water resources, increasing the need for a deeper understanding of the interaction between climate and biological diversity. This is particularly the case in the Southern Hemisphere sub-tropics, where little information exists on the aquatic biota response to climate variations. Palaeolimnological techniques, in particular the use of diatoms, are well established and can significantly contribute to the understanding of climatic variability and the impacts that change in climate have on aquatic ecosystems. A sediment core from Lake McKenzie, Fraser Island (Australia), was used to investigate interactions between climate influences and aquatic ecosystems. This study utilises a combination of proxies including biological (diatom), geochemical and chronological techniques to investigate long-term aquatic changes within the perched-dune lake. A combination of 210 Pb and AMS 14 C dates showed that the retrieved sediment represented a history of ca. 37,000 cal. yBP. The sedimentation rate in Lake McKenzie is very low, ranging on average from 0.11 mm to 0.26 mm per year. A sediment hiatus was observed between ca. 18,300 and 14,000 cal. yBP suggesting a period of dry conditions at the site. The diatom record shows little variability over the period of record, with benthic, freshwater acidic tolerant species dominating. Relative abundance of planktonic species and geochemical results indicates a period of increased water depth and lake productivity in the early Holocene and a gradual decrease in effective precipitation throughout the Holocene. Results from this study not only support earlier work conducted on Fraser Island using pollen reconstructions but also demonstrate that diatom community diversity has been relatively consistent throughout the Holocene and late Pleistocene with only minor cyclical fluctuation evident. This record is consistent with the few other aquatic palaeoecological records from the Southern Hemisphere sub

Temperature Trends in the Polar Mesosphere between 2002-2007 using TIMED/SABER Data

Science.gov (United States)

Goldberg, Richard A.; Kutepov, Alexander A.; Pesnell, William Dean; Latteck, Ralph; Russell, James M.

2008-01-01

The TIMED Satellite was launched on December 7, 2001 to study the dynamics and energy of the mesosphere and lower thermosphere. The TIMED/SABER instrument is a limb scanning infrared radiometer designed to measure a large number of minor constituents as well as the temperature of the region. In this study, we have concentrated on the polar mesosphere, to investigate the temperature characteristics as a function of spatial and temporal considerations. We used the recently revised SABER dataset (1.07) that contains improved temperature retrievals in the Earth polar summer regions. Weekly averages are used to make comparisons between the winter and summer, as well as to study the variability in different quadrants of each hemisphere. For each year studied, the duration of polar summer based on temperature measurements compares favorably with the PMSE (Polar Mesospheric Summer Echoes) season measured by radar at the ALOMAR Observatory in Norway (69 N). The PMSE period should also define the summer period suitable for the occurrence of polar mesospheric clouds. The unusual short and relatively warm polar summer in the northern hemisphere

Anthropogenic effects on the subtropical jet in the Southern Hemisphere: aerosols versus long-lived greenhouse gases

International Nuclear Information System (INIS)

Rotstayn, L D; Collier, M A; Jeffrey, S J; Syktus, J I; Wong, K K; Kidston, J

2013-01-01

We use single-forcing historical simulations with a coupled atmosphere–ocean global climate model to compare the effects of anthropogenic aerosols (AAs) and increasing long-lived greenhouse gases (LLGHGs) on simulated winter circulation in the Southern Hemisphere (SH). Our primary focus is on the subtropical jet, which is an important source of baroclinic instability, especially in the Australasian region, where the speed of the jet is largest. For the period 1950 to 2005, our simulations suggest that AAs weaken the jet, whereas increasing LLGHGs strengthen the jet. The different responses are explained in terms of thermal wind balance: increasing LLGHGs preferentially warm the tropical mid-troposphere and upper troposphere, whereas AAs have a similar effect of opposite sign. In the mid-troposphere, the warming (cooling) effect of LLGHGs (AAs) is maximal between 20S and 30S; this coincides with the descending branch of the Hadley circulation, which may advect temperature changes from the tropical upper troposphere to the subtropics of the SH. It follows that LLGHGs (AAs) increase (decrease) the mid-tropospheric temperature gradient between low latitudes and the SH mid-latitudes. The strongest effects are seen at longitudes where the southward branches of the Hadley cell in the upper troposphere are strongest, notably at those that correspond to Asia and the western Pacific warm pool. (letter)

Impacts of informal trails on vegetation and soils in the highest protected area in the Southern Hemisphere.

Science.gov (United States)

Barros, Agustina; Gonnet, Jorge; Pickering, Catherine

2013-09-30

There is limited recreation ecology research in South America, especially studies looking at informal trails. Impacts of informal trails formed by hikers and pack animals on vegetation and soils were assessed for the highest protected area in the Southern Hemisphere, Aconcagua Provincial Park. The number of braided trails, their width and depth were surveyed at 30 sites along the main access route to Mt Aconcagua (6962 m a.s.l.). Species composition, richness and cover were also measured on control and trail transects. A total of 3.3 ha of alpine meadows and 13.4 ha of alpine steppe were disturbed by trails. Trails through meadows resulted in greater soil loss, more exposed soil and rock and less vegetation than trails through steppe vegetation. Trampling also affected the composition of meadow and steppe vegetation with declines in sedges, herbs, grasses and shrubs on trails. These results highlight how visitor use can result in substantial cumulative damage to areas of high conservation value in the Andes. With unregulated use of trails and increasing visitation, park agencies need to limit the further spread of informal trails and improve the conservation of plant communities in Aconcagua Provincial Park and other popular parks in the region. Copyright © 2013 Elsevier Ltd. All rights reserved.

A comprehensive assessment of mercury exposure in penguin populations throughout the Southern Hemisphere: Using trophic calculations to identify sources of population-level variation

International Nuclear Information System (INIS)

Brasso, Rebecka L.; Chiaradia, André; Polito, Michael J.; Raya Rey, Andrea; Emslie, Steven D.

2015-01-01

Highlights: • Mercury concentrations documented for 10 species of penguins (26 breeding populations). • Mercury concentrations ⩽2.00 ppm in feathers from 18/26 penguin populations. • Trophic level calculations revealed source of population-level variation in mercury. • First documentation of geographic mercury ‘hotspots’ for penguin populations. - Abstract: The wide geographic distribution of penguins (Order Sphenisciformes) throughout the Southern Hemisphere provided a unique opportunity to use a single taxonomic group as biomonitors of mercury among geographically distinct marine ecosystems. Mercury concentrations were compared among ten species of penguins representing 26 geographically distinct breeding populations. Mercury concentrations were relatively low (⩽2.00 ppm) in feathers from 18/26 populations considered. Population-level differences in trophic level explained variation in mercury concentrations among Little, King, and Gentoo penguin populations. However, Southern Rockhopper and Magellanic penguins breeding on Staten Island, Tierra del Fuego, had the highest mercury concentrations relative to their conspecifics despite foraging at a lower trophic level. The concurrent use of stable isotope and mercury data allowed us to document penguin populations at the greatest risk of exposure to harmful concentrations of mercury as a result of foraging at a high trophic level or in geographic ‘hot spots’ of mercury availability

Satellite Global and Hemispheric Lower Tropospheric Temperature Annual Temperature Cycle

Directory of Open Access Journals (Sweden)

Michael A. Brunke

2010-11-01

Full Text Available Previous analyses of the Earth’s annual cycle and its trends have utilized surface temperature data sets. Here we introduce a new analysis of the global and hemispheric annual cycle using a satellite remote sensing derived data set during the period 1979–2009, as determined from the lower tropospheric (LT channel of the MSU satellite. While the surface annual cycle is tied directly to the heating and cooling of the land areas, the tropospheric annual cycle involves additionally the gain or loss of heat between the surface and atmosphere. The peak in the global tropospheric temperature in the 30 year period occurs on 10 July and the minimum on 9 February in response to the larger land mass in the Northern Hemisphere. The actual dates of the hemispheric maxima and minima are a complex function of many variables which can change from year to year thereby altering these dates.Here we examine the time of occurrence of the global and hemispheric maxima and minima lower tropospheric temperatures, the values of the annual maxima and minima, and the slopes and significance of the changes in these metrics.  The statistically significant trends are all relatively small. The values of the global annual maximum and minimum showed a small, but significant trend. Northern and Southern Hemisphere maxima and minima show a slight trend toward occurring later in the year. Most recent analyses of trends in the global annual cycle using observed surface data have indicated a trend toward earlier maxima and minima.

Probing the Local Bubble with diffuse interstellar bands. I. Project overview and southern hemisphere survey

Science.gov (United States)

Bailey, Mandy; van Loon, Jacco Th.; Farhang, Amin; Javadi, Atefeh; Khosroshahi, Habib G.; Sarre, Peter J.; Smith, Keith T.

2016-01-01

Context. The Sun traverses a low-density, hot entity called the Local Bubble. Despite its relevance to life on Earth, the conditions in the Local Bubble and its exact configuration are not very well known. Besides that, there is some unknown interstellar substance that causes a host of absorption bands across the optical spectrum, called diffuse interstellar bands (DIBs). Aims: We have started a project to chart the Local Bubble in a novel way and learn more about the carriers of the DIBs, by using DIBs as tracers of diffuse gas and environmental conditions. Methods: We conducted a high signal-to-noise spectroscopic survey of 670 nearby early-type stars to map DIB absorption in and around the Local Bubble. The project started with a southern hemisphere survey conducted at the European Southern Observatory's New Technology Telescope and has since been extended to an all-sky survey using the Isaac Newton Telescope. Results: In this first paper in the series, we introduce the overall project and present the results from the southern heiphere survey. We make aviable a catalogue of equivalent-width measurements of the DIBs at 5780, 5797, 5850, 6196, 6203, 6270, 6283, and 6614 Å, of the interstellar Na I D lines at 5890 and 5896 Å, and of the stellar He I line at 5876 Å. We find that the 5780 Å DIB is relatively strong throughout, as compared to the 5797 Å DIB, but especially within the Local Bubble and at the interface iwth a more neutral medium. The 6203 Å DIB shows similar behaviour with respect to the 6196 Å DIB. Some nearby stars show surprisingly strong DIBs, whereas some distant stars show very weak DIBs, indicating small-scale structure within, as well as outside, the Local Bubble. The sight lines with non-detections trace the extent of the Local Bubble especially clearly and show it opening out into the halo. Conclusions: The Local Bubble has a wall that is in contact with hot gas and/or a harsh interstellar radiation field. That wall is perforated

The modulation of oceanic moisture transport by the hemispheric annular modes

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Raquel eNieto

2014-07-01

Full Text Available Leaving aside the contribution made by recycling, it is the main oceanic moisture sources that are responsible for most of the precipitation that falls on the continents. The transport of moisture from these sources can be affected by large-scale variability according to the hemispheric annular modes. The influence of the two dominant modes of extratropical winter climate: the Northern and the Southern Annular Modes (NAM and SAM are herein investigated to assess how they affect the transport of moisture from the major oceanic moisture sources. A Lagrangian model was used, together with ERA-Interim reanalysis data (1979-2012, and differences between the composites of the six strongest higher and lower events observed for both phases of the two modes for the period were analysed. The method is able to reproduce the general pattern of known variations for both annular patterns. Lower values of the NAM Index are associated with the displacement of the storm track towards tropical latitudes. Thus, moisture transport is enhanced from the Northern Pacific towards the northeastern basin and from the Northern Atlantic and Mediterranean towards southern Europe. On the other hand, during higher values of NAM, moisture transport is favoured from the Northern Pacific towards eastern Asia, and moisture transport is enhanced from the Northern Atlantic towards the Caribbean Sea. In the Southern Hemisphere, during higher values of SAM more moisture is transported from the Atlantic and Indian oceanic sources southwards and eastwards than during the opposite phase. In this SAM phase it is also noted by an enhancement of moisture transport from the Coral Sea and Southern Pacific sources towards the Indian Ocean/West Pacific Warm Pool. Southeastern South America received more moisture from the Pacific and Atlantic sources during years with a lower SAM, episodes which also favoured the influx of moisture from the Southern Atlantic towards Africa, causing monsoon

Treasures of the Southern Sky

CERN Document Server

Gendler, Robert; Malin, David

2011-01-01

In these pages, the reader can follow the engaging saga of astronomical exploration in the southern hemisphere, in a modern merger of aesthetics, science, and a story of human endeavor. This book is truly a celebration of southern skies.  Jerry Bonnell, Editor - Astronomy Picture of the Day The southern sky became accessible to scientific scrutiny only a few centuries ago, after the first European explorers ventured south of the equator. Modern observing and imaging techniques have since revealed what seems like a new Universe, previously hidden below the horizon, a fresh astronomical bounty of beauty and knowledge uniquely different from the northern sky. The authors have crafted a book that brings this hidden Universe to all, regardless of location or latitude. Treasures of the Southern Sky celebrates the remarkable beauty and richness of the southern sky in words and with world-class imagery. In part, a photographic anthology of deep sky wonders south of the celestial equator, this book also celebrates th...

Interhemispheric differences in ionospheric convection: Cluster EDI observations revisited

Science.gov (United States)

Förster, M.; Haaland, S.

2015-07-01

The interaction between the interplanetary magnetic field and the geomagnetic field sets up a large-scale circulation in the magnetosphere. This circulation is also reflected in the magnetically connected ionosphere. In this paper, we present a study of ionospheric convection based on Cluster Electron Drift Instrument (EDI) satellite measurements covering both hemispheres and obtained over a full solar cycle. The results from this study show that average flow patterns and polar cap potentials for a given orientation of the interplanetary magnetic field can be very different in the two hemispheres. In particular during southward directed interplanetary magnetic field conditions, and thus enhanced energy input from the solar wind, the measurements show that the southern polar cap has a higher cross polar cap potential. There are persistent north-south asymmetries, which cannot easily be explained by the influence of external drivers. These persistent asymmetries are primarily a result of the significant differences in the strength and configuration of the geomagnetic field between the Northern and Southern Hemispheres. 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.

Coronal Polarization of Pseudostreamers and the Solar Polar Field Reversal

Science.gov (United States)

Rachmeler, L. A.; Guennou, C.; Seaton, D. B.; Gibson, S. E.; Auchere, F.

2016-01-01

The reversal of the solar polar magnetic field is notoriously hard to pin down due to the extreme viewing angle of the pole. In Cycle 24, the southern polar field reversal can be pinpointed with high accuracy due to a large-scale pseudostreamer that formed over the pole and persisted for approximately a year. We tracked the size and shape of this structure with multiple observations and analysis techniques including PROBA2/SWAP EUV images, AIA EUV images, CoMP polarization data, and 3D tomographic reconstructions. We find that the heliospheric field reversed polarity in February 2014, whereas in the photosphere, the last vestiges of the previous polar field polarity remained until March 2015. We present here the evolution of the structure and describe its identification in the Fe XII 1074nm coronal emission line, sensitive to the Hanle effect in the corona.

Southern Hemisphere bog persists as a strong carbon sink during droughts

Science.gov (United States)

Goodrich, Jordan P.; Campbell, David I.; Schipper, Louis A.

2017-10-01

Peatland ecosystems have been important global carbon sinks throughout the Holocene. Most of the research on peatland carbon budgets and effects of variable weather conditions has been done in Northern Hemisphere Sphagnum-dominated systems. Given their importance in other geographic and climatic regions, a better understanding of peatland carbon dynamics is needed across the spectrum of global peatland types. In New Zealand, much of the historic peatland area has been drained for agriculture but little is known about rates of carbon exchange and storage in unaltered peatland remnants that are dominated by the jointed wire rush, Empodisma robustum. We used eddy covariance to measure ecosystem-scale CO2 and CH4 fluxes and a water balance approach to estimate the sub-surface flux of dissolved organic carbon from the largest remaining raised peat bog in New Zealand, Kopuatai bog. The net ecosystem carbon balance (NECB) was estimated over four years, which included two drought summers, a relatively wet summer, and a meteorologically average summer. In all measurement years, the bog was a substantial sink for carbon, ranging from 134.7 to 216.9 gC m-2 yr-1, owing to the large annual net ecosystem production (161.8 to 244.9 gCO2-C m-2 yr-1). Annual methane fluxes were large relative to most Northern Hemisphere peatlands (14.2 to 21.9 gCH4-C m-2 yr-1), although summer and autumn emissions were highly sensitive to dry conditions, leading to very predictable seasonality according to water table position. The annual flux of dissolved organic carbon was similar in magnitude to methane emissions but less variable, ranging from 11.7 to 12.8 gC m-2 yr-1. Dry conditions experienced during late summer droughts led to significant reductions in annual carbon storage, which resulted nearly equally from enhanced ecosystem respiration due to lowered water tables and increased temperatures, and from reduced gross primary production due to vapor pressure deficit-related stresses to the

A possible cause of the AO polarity reversal from winter to summer in 2010 and its relation to hemispheric extreme hot summer

Science.gov (United States)

Tachibana, Yoshihiro; Otomi, Yuriko; Nakamura, Tetsu

2013-04-01

In 2010, the Northern Hemisphere, in particular Russia and Japan, experienced an abnormally hot summer characterized by record-breaking warm temperatures and associated with a strongly positive Arctic Oscillation (AO), that is, low pressure in the Arctic and high pressure in the midlatitudes. In contrast, the AO index the previous winter and spring (2009/2010) was record-breaking negative. The AO polarity reversal that began in summer 2010 can explain the abnormally hot summer. The winter sea surface temperatures (SST) in the North Atlantic Ocean showed a tripolar anomaly pattern—warm SST anomalies over the tropics and high latitudes and cold SST anomalies over the midlatitudes—under the influence of the negative AO. The warm SST anomalies continued into summer 2010 because of the large oceanic heat capacity. A model simulation strongly suggested that the AO-related summertime North Atlantic oceanic warm temperature anomalies remotely caused blocking highs to form over Europe, which amplified the positive summertime AO. Thus, a possible cause of the AO polarity reversal might be the "memory" of the negative winter AO in the North Atlantic Ocean, suggesting an interseasonal linkage of the AO in which the oceanic memory of a wintertime negative AO induces a positive AO in the following summer. Understanding of this interseasonal linkage may aid in the long-term prediction of such abnormal summer events.

A possible cause of the AO polarity reversal from winter to summer in 2010 and its relation to hemispheric extreme summer weather

Science.gov (United States)

Otomi, Yuriko; Tachibana, Yoshihiro; Nakamura, Tetsu

2013-04-01

In 2010, the Northern Hemisphere, in particular Russia and Japan, experienced an abnormally hot summer characterized by record-breaking warm temperatures and associated with a strongly positive Arctic Oscillation (AO), that is, low pressure in the Arctic and high pressure in the midlatitudes. In contrast, the AO index the previous winter and spring (2009/2010) was record-breaking negative. The AO polarity reversal that began in summer 2010 can explain the abnormally hot summer. The winter sea surface temperatures (SST) in the North Atlantic Ocean showed a tripolar anomaly pattern—warm SST anomalies over the tropics and high latitudes and cold SST anomalies over the midlatitudes—under the influence of the negative AO. The warm SST anomalies continued into summer 2010 because of the large oceanic heat capacity. A model simulation strongly suggested that the AO-related summertime North Atlantic oceanic warm temperature anomalies remotely caused blocking highs to form over Europe, which amplified the positive summertime AO. Thus, a possible cause of the AO polarity reversal might be the "memory" of the negative winter AO in the North Atlantic Ocean, suggesting an interseasonal linkage of the AO in which the oceanic memory of a wintertime negative AO induces a positive AO in the following summer. Understanding of this interseasonal linkage may aid in the long-term prediction of such abnormal summer events.

A Climatology of Polar Stratospheric Cloud Types by MIPAS-Envisat

Science.gov (United States)

Spang, Reinhold; Hoffmann, Lars; Griessbach, Sabine; Orr, Andrew; Höpfner, Michael; Müller, Rolf

2015-04-01

uncertainties and the sensitivity to a priori information of the approach. The processing of the complete MIPAS data set of almost 10 years of PSC observations with a first version of the new classification approach is completed. Results for various northern and southern hemisphere winters will be presented. The temporal evolution of the PSC types with respect to the temporal development of the meteorological conditions of the polar vortex as well as comparison with space and ground based lidar measurements will be investigated.

Temporal complexity of southern Beaufort Sea polar bear diets during a period of increasing land use

Science.gov (United States)

McKinney, Melissa A.; Atwood, Todd C.; Iverson, Sara J.; Peacock, Elizabeth

2017-01-01

From 2000 to 2013, use of land as a seasonal habitat by polar bears (Ursus maritimus) of the southern Beaufort Sea (SB) subpopulation substantially increased. This onshore use has been linked to reduced spatial and temporal availability of sea ice, as well as to the availability of subsistence‐harvested bowhead whale (Balaena mysticetus) bone piles. Here, we evaluated the role of climate conditions on consumption of traditional ice‐associated prey relative to onshore bowhead whale bone piles. We determined seasonal and interannual trends in the diets of SB polar bears using fatty acid‐based analysis during this period of increasing land use. Diet estimates of 569 SB polar bears from 2004 to 2012 showed high seasonal fluctuations in the proportions of prey consumed. Higher proportions of bowhead whale, as well as ringed seal (Pusa hispida) and beluga whale (Delphinapterus leucas), were estimated to occur in the winter–spring diet, while higher proportions of bearded seal (Erignathus barbatus) were estimated for summer–fall diets. Trends in the annual mean proportions of individual prey items were not found in either period, except for significant declines in the proportion of beluga in spring‐sampled bears. Nonetheless, in years following a high winter Arctic oscillation index, proportions of ice‐associated ringed seal were lower in the winter–spring diets of adult females and juveniles. Proportions of bowhead increased in the winter–spring diets of adult males with the number of ice‐free days over the continental shelf. In one or both seasons, polar bears that were in better condition were estimated to have consumed less ringed seal and/or more bowhead whale than those in worse condition. Therefore, climate variation over this recent period appeared to influence the extent of onshore vs. on‐ice food use, which in turn, appeared to be linked to fluctuating condition of SB polar bears.

Discovery of a blue whale feeding and nursing ground in southern Chile.

Science.gov (United States)

Hucke-Gaete, Rodrigo; Osman, Layla P; Moreno, Carlos A; Findlay, Ken P; Ljungblad, Don K

2004-05-07

After the extensive exploitation that reduced the Southern Hemisphere blue whale (Balaenoptera musculus) populations to less than 3% of its original numbers, studies on its recovery have been compounded by the inaccessibility of most populations and the extensive migrations between low and high latitudes, thus ensuring that knowledge about blue whale ecology and status remains limited. We report the recent discovery of, arguably, the most important blue whale feeding and nursing ground known to date in the Southern Hemisphere, which is located near the fjords off southern Chile. Through aerial and marine surveys (n = 7) 47 groups, comprising 153 blue whales including at least 11 mother-calf pairs, were sighted during the austral summer and early autumn of 2003. The implications of this discovery on the biological understanding and conservation of this endangered species are discussed.

Magnetic field and electric currents in the vicinity of polar cusps as inferred from Polar and Cluster data

Directory of Open Access Journals (Sweden)

N. A. Tsyganenko

2009-04-01

Full Text Available A detailed statistical study of the magnetic structure of the dayside polar cusps is presented, based on multi-year sets of magnetometer data of Polar and Cluster spacecraft, taken in 1996–2006 and 2001–2007, respectively. Thanks to the dense data coverage in both Northern and Southern Hemispheres, the analysis spanned nearly the entire length of the cusps, from low altitudes to the cusp "throat" and the magnetosheath. Subsets of data falling inside the polar cusp "funnels" were selected with the help of TS05 and IGRF magnetic field models, taking into account the dipole tilt and the solar wind/IMF conditions. The selection funnels were shifted within ±10° of SM latitude around the model cusp location, and linear regression parameters were calculated for each sliding subset, further divided into 10 bins of distance in the range 2≤R≤12 RE, with the following results. (1 Diamagnetic depression, caused by the penetrated magnetosheath plasma, becomes first visible at R~4–5 RE, rapidly deepens with growing R, peaks at R~6–9 RE, and then partially subsides and widens in latitude at the cusp's outer end. (2 The depression peak is systematically shifted poleward (by ~2° of the footpoint latitude with respect to the model cusp field line, passing through the min{|B|} point at the magnetopause. (3 At all radial distances, clear and distinct peaks of the correlation between the local By and By(IMF and of the corresponding proportionality coefficient are observed. A remarkably regular variation of that coefficient with R quantitatively confirms the field-aligned geometry of the cusp currents associated with the IMF By, found in earlier observations.

High Frequency Backscatter from the Polar and Auroral E-Region Ionosphere

Science.gov (United States)

Forsythe, Victoriya V.

The Earth's ionosphere contains collisional and partially-ionized plasma. The electric field, produced by the interaction between the Earth's magnetosphere and the solar wind, drives the plasma bulk motion, also known as convection, in the F-region of the ionosphere. It can also destabilize the plasma in the E-region, producing irregularities or waves. Intermediate-scale waves with wavelengths of hundreds of meters can cause scintillation and fading of the Global Navigation Satellite System (GNSS) signals, whereas the small-scale waves (lambda Network (SuperDARN). The theoretical part of this work focuses on symmetry properties of the general dispersion relation that describes wave propagation in the collisional plasma in the two-stream and gradient-drift instability regimes. The instability growth rate and phase velocity are examined under the presence of a background parallel electric field, whose influence is demonstrated to break the spatial symmetry of the wave propagation patterns. In the observational part of this thesis, a novel dual radar setup is used to examine E-region irregularities in the magnetic polar cap by probing the E-region along the same line from opposite directions. The phase velocity analysis together with raytracing simulations demonstrated that, in the polar cap, the radar backscatter is primarily controlled by the plasma density conditions. In particular, when the E-region layer is strong and stratified, the radar backscatter properties are controlled by the convection velocity, whereas for a tilted E-layer, the height and aspect angle conditions are more important. Finally, the fundamental dependence of the E-region irregularity phase velocity on the component of the plasma convection is investigated using two new SuperDARN radars at high southern latitudes where plasma convection estimates are accurately deduced from all SuperDARN radars in the southern hemisphere. Statistical analysis is presented showing that the predominance of the

An overview of Fukushima radionuclides measured in the northern hemisphere

International Nuclear Information System (INIS)

Thakur, P.; Ballard, S.; Nelson, R.

2013-01-01

The Great East Japan Earthquake and tsunami on March 11, 2011 resulted in the tragic accident at the Fukushima Nuclear Power Plant (NPP) and subsequently uncontrolled release of radioactive contaminants into the atmosphere. This review article attempts to compile and interpret data collected by various national and international monitoring networks in response to the Fukushima releases across the northern hemisphere. The majority of the releases occurred during the period March 12–22 with a maximum release phase from March 14–17, 2011. The radioactivity released was dominated by volatile fission products including isotopes of the noble gases (xenon and krypton), iodine, cesium, and tellurium. The radioactive gases and particles released in the accident were dispersed over the middle latitudes of the entire northern hemisphere and for the first time also measured in the southern Hemisphere. Isotopes of iodine and cesium were detected in air, water, milk and food samples collected across the entire northern hemisphere. Elevated levels of fission products were detected from March to May 2011 at many locations over the northern hemisphere. This article focuses on the most prevalent cesium and iodine isotopes, but other secondary isotopes are also discussed. Spatial and temporal patterns and differences are contrasted. The activity ratios of 131 I/ 137 Cs and 134 Cs/ 137 Cs measured at several locations are evaluated to gain an insight into the fuel burn-up, the inventory of radionuclides in the reactor and the isotopic signature of the accident. It is important to note that all of the radiation levels detected outside of Japan have been very low and are well below any level of public and environmental hazard. - Graphical abstract: The trace levels of radioactivity in air, water, and milk samples collected across the northern hemisphere between March–May, 2011 from the damaged Fukushima Daiichi nuclear power plant, Japan are discussed. Highlights: • We report

An overview of Fukushima radionuclides measured in the northern hemisphere

Energy Technology Data Exchange (ETDEWEB)

Thakur, P., E-mail: pthakur@cemrc.org [Carlsbad Environmental Monitoring and Research Center, 1400 University Drive, Carlsbad, NM 88220 (United States); Ballard, S. [Carlsbad Environmental Monitoring and Research Center, 1400 University Drive, Carlsbad, NM 88220 (United States); Nelson, R. [Department of Energy, Carlsbad Field Office, 4021, National Parks Hwy, Carlsbad, NM 88220 (United States)

2013-08-01

The Great East Japan Earthquake and tsunami on March 11, 2011 resulted in the tragic accident at the Fukushima Nuclear Power Plant (NPP) and subsequently uncontrolled release of radioactive contaminants into the atmosphere. This review article attempts to compile and interpret data collected by various national and international monitoring networks in response to the Fukushima releases across the northern hemisphere. The majority of the releases occurred during the period March 12–22 with a maximum release phase from March 14–17, 2011. The radioactivity released was dominated by volatile fission products including isotopes of the noble gases (xenon and krypton), iodine, cesium, and tellurium. The radioactive gases and particles released in the accident were dispersed over the middle latitudes of the entire northern hemisphere and for the first time also measured in the southern Hemisphere. Isotopes of iodine and cesium were detected in air, water, milk and food samples collected across the entire northern hemisphere. Elevated levels of fission products were detected from March to May 2011 at many locations over the northern hemisphere. This article focuses on the most prevalent cesium and iodine isotopes, but other secondary isotopes are also discussed. Spatial and temporal patterns and differences are contrasted. The activity ratios of {sup 131}I/{sup 137}Cs and {sup 134}Cs/{sup 137}Cs measured at several locations are evaluated to gain an insight into the fuel burn-up, the inventory of radionuclides in the reactor and the isotopic signature of the accident. It is important to note that all of the radiation levels detected outside of Japan have been very low and are well below any level of public and environmental hazard. - Graphical abstract: The trace levels of radioactivity in air, water, and milk samples collected across the northern hemisphere between March–May, 2011 from the damaged Fukushima Daiichi nuclear power plant, Japan are discussed. Highlights

Long-distance swimming by polar bears (Ursus maritimus) of the southern Beaufort Sea during years of extensive open water

Science.gov (United States)

2014-01-01

Polar bears (Ursus maritimus Phipps, 1774) depend on sea ice for catching marine mammal prey. Recent sea-ice declines have been linked to reductions in body condition, survival, and population size. Reduced foraging opportunity is hypothesized to be the primary cause of sea-ice-linked declines, but the costs of travel through a deteriorated sea-ice environment also may be a factor. We used movement data from 52 adult female polar bears wearing Global Positioning System (GPS) collars, including some with dependent young, to document long-distance swimming (>50 km) by polar bears in the southern Beaufort and Chukchi seas. During 6 years (2004-2009), we identified 50 long-distance swims by 20 bears. Swim duration and distance ranged from 0.7 to 9.7 days (mean = 3.4 days) and 53.7 to 687.1 km (mean = 154.2 km), respectively. Frequency of swimming appeared to increase over the course of the study. We show that adult female polar bears and their cubs are capable of swimming long distances during periods when extensive areas of open water are present. However, long-distance swimming appears to have higher energetic demands than moving over sea ice. Our observations suggest long-distance swimming is a behavioral response to declining summer sea-ice conditions.

Continuous Planetary Polar Observation from Hybrid Pole-Sitters at Venus, Earth, and Mars

NARCIS (Netherlands)

Heiligers, M.J.; van den Oever (student TUDelft), Tom; Ceriotti, M.; Mulligan, P.; McInnes, CR

2017-01-01

A pole-sitter is a satellite that is stationed along the polar axis of the Earth, or any other planet, to generate a continuous, hemispherical view of the planet’s polar regions. In order to maintain such a vantage point, a low-thrust propulsion system is required to counterbalance the gravitational

Seasonal and interplanetary magnetic field dependence of the field-aligned currents for both Northern and Southern Hemispheres

Directory of Open Access Journals (Sweden)

D. L. Green

2009-04-01

Full Text Available The configuration of the Earth's magnetosphere under various Interplanetary Magnetic Field (IMF and solar wind conditions alters the global distribution of Field-Aligned Currents (FACs at the high latitude ionospheres. We use magnetic field data obtained from the Iridium constellation to extend recent studies that infer the dependence of the global FAC configuration on IMF direction and magnitude, hemisphere and season. New results are a reduced IMF By influence on the FAC configuration for the winter hemisphere and a redistribution of FAC to the nightside for winter relative to the summer hemisphere. These effects are linked to the winter ionosphere conductance distribution being dominated by localised nightside enhancement associated with ionisation from energetic particle precipitation. A comparison of an estimated open-closed field line boundary (OCFLB with the Region 1 FAC locations shows reasonable agreement for summer FAC configurations. However, the OCFLB location is decoupled from the Region 1 FACs in winter, especially for IMF Bz>0.

Glacier History of the Northern Antarctic Peninsula Region Since the End of the Last Ice Age and Implications for Southern Hemisphere Westerly-Climate Changes

Science.gov (United States)

Kaplan, M. R.; Schaefer, J. M.; Strelin, J. A.; Peltier, C.; Southon, J. R.; Lepper, K. E.; Winckler, G.

2017-12-01

For the area around James Ross Island, we present new cosmogenic 10Be exposure ages on glacial deposits, and 14C ages on associated fossil materials. These data allow us to reconstruct in detail when and how the Antarctic Peninsula Ice Sheet retreated around the Island as the last Ice Age ended, and afterward when local land-based glaciers fluctuated. Similar to other studies, we found widespread deglaciation during the earliest Holocene, with fjords and bays becoming ice free between about 11,000 and 8,000 years ago. After 7,000 years ago, neoglacial type advances initiated. Then, both expansions and ice free periods occurred from the middle to late Holocene. We compare the new glacier record to those in southern Patagonia, which is on the other side of the Drake Passage, and published Southern Ocean marine records, in order to infer past middle to high latitude changes in the Southern Hemisphere Westerlies. Widespread warmth in the earliest Holocene, to the north and south of the Drake Passage, led to small glacier systems in Patagonia and wide-ranging glacier recession around the northern Antarctic Peninsula. We infer that this early Holocene period of overall glacier recession - from Patagonia to the northern Peninsula - was caused by a persistent far-southerly setting of the westerlies and accompanying warm climates. Subsequently, during the middle Holocene renewed glacier expansions occurred on both sides of the Drake Passage, which reflects that the Westerlies and associated colder climate systems were generally more equatorward. From the middle to late Holocene, glacier expansions and ice free periods (and likely related ice shelf behavior) document how the Westerlies and associated higher-latitude climate systems varied.

Traveling Weather Disturbances in Mars Southern Extratropics: Sway of the Great Impact Basins

Science.gov (United States)

Hollingsworth, Jeffery L.

2016-01-01

As on Earth, between late autumn and early spring on Mars middle and high latitudes within its atmosphere support strong mean thermal contrasts between the equator and poles (i.e. "baroclinicity"). Data collected during the Viking era and observations from both the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) indicate that this strong baroclinicity supports vigorous, large-scale eastward traveling weather systems (i.e. transient synoptic-period waves). Within a rapidly rotating, differentially heated, shallow atmosphere such as on Earth and Mars, such large-scale, extratropical weather disturbances are critical components of the global circulation. These wave-like disturbances act as agents in the transport of heat and momentum, and moreover generalized tracer quantities (e.g., atmospheric dust, water vapor and water-ice clouds) between low and high latitudes of the planet. The character of large-scale, traveling extratropical synoptic-period disturbances in Mars' southern hemisphere during late winter through early spring is investigated using a high-resolution Mars global climate model (Mars GCM). This global circulation model imposes interactively lifted (and radiatively active) dust based on a threshold value of the instantaneous surface stress. Compared to observations, the model exhibits a reasonable "dust cycle" (i.e. globally averaged, a more dusty atmosphere during southern spring and summer occurs). In contrast to their northern-hemisphere counterparts, southern synoptic-period weather disturbances and accompanying frontal waves have smaller meridional and zonal scales, and are far less intense synoptically. Influences of the zonally asymmetric (i.e. east-west varying) topography on southern large-scale weather disturbances are examined. Simulations that adapt Mars' full topography compared to simulations that utilize synthetic topographies emulating essential large-scale features of the southern middle latitudes indicate that Mars

Genetic variation, relatedness, and effective population size of polar bears (Ursus maritimus) in the southern Beaufort Sea, Alaska

Science.gov (United States)

Cronin, Matthew A.; Amstrup, Steven C.; Talbot, Sandra L.; Sage, George K.; Amstrup, Kristin S.

2009-01-01

Polar bears (Ursus maritimus) are unique among bears in that they are adapted to the Arctic sea ice environment. Genetic data are useful for understanding their evolution and can contribute to management. We assessed parentage and relatedness of polar bears in the southern Beaufort Sea, Alaska, with genetic data and field observations of age, sex, and mother–offspring and sibling relationships. Genotypes at 14 microsatellite DNA loci for 226 bears indicate that genetic variation is comparable to other populations of polar bears with mean number of alleles per locus of 7.9 and observed and expected heterozygosity of 0.71. The genetic data verified 60 field-identified mother–offspring pairs and identified 10 additional mother–cub pairs and 48 father–offspring pairs. The entire sample of related and unrelated bears had a mean pairwise relatedness index (rxy) of approximately zero, parent–offspring and siblings had rxy of approximately 0.5, and 5.2% of the samples had rxy values within the range expected for parent-offspring. Effective population size (Ne= 277) and the ratio of Ne to total population size (Ne/N = 0.182) were estimated from the numbers of reproducing males and females. Ne estimates with genetic methods gave variable results. Our results verify and expand field data on reproduction by females and provide new data on reproduction by males and estimates of relatedness and Ne in a polar bear population.

Genetic variation, relatedness, and effective population size of polar bears (Ursus maritimus) in the southern Beaufort Sea, Alaska.

Science.gov (United States)

Cronin, Matthew A; Amstrup, Steven C; Talbot, Sandra L; Sage, George K; Amstrup, Kristin S

2009-01-01

Polar bears (Ursus maritimus) are unique among bears in that they are adapted to the Arctic sea ice environment. Genetic data are useful for understanding their evolution and can contribute to management. We assessed parentage and relatedness of polar bears in the southern Beaufort Sea, Alaska, with genetic data and field observations of age, sex, and mother-offspring and sibling relationships. Genotypes at 14 microsatellite DNA loci for 226 bears indicate that genetic variation is comparable to other populations of polar bears with mean number of alleles per locus of 7.9 and observed and expected heterozygosity of 0.71. The genetic data verified 60 field-identified mother-offspring pairs and identified 10 additional mother-cub pairs and 48 father-offspring pairs. The entire sample of related and unrelated bears had a mean pairwise relatedness index (r(xy)) of approximately zero, parent-offspring and siblings had r(xy) of approximately 0.5, and 5.2% of the samples had r(xy) values within the range expected for parent-offspring. Effective population size (N(e) = 277) and the ratio of N(e) to total population size (N(e)/N = 0.182) were estimated from the numbers of reproducing males and females. N(e) estimates with genetic methods gave variable results. Our results verify and expand field data on reproduction by females and provide new data on reproduction by males and estimates of relatedness and N(e) in a polar bear population.

The Transit-Time Distribution from the Northern Hemisphere Midlatitude Surface

Science.gov (United States)

Orbe, Clara; Waugh, Darryn W.; Newman, Paul A.; Strahan, Susan; Steenrod, Stephen

2015-01-01

The distribution of transit times from the Northern Hemisphere (NH) midlatitude surface is a fundamental property of tropospheric transport. Here we present an analysis of the transit time distribution (TTD) since air last contacted the northern midlatitude surface layer, as simulated by the NASA Global Modeling Initiative Chemistry Transport Model. We find that throughout the troposphere the TTD is characterized by long flat tails that reflect the recirculation of old air from the Southern Hemisphere and results in mean ages that are significantly larger than the modal age. Key aspects of the TTD -- its mode, mean and spectral width -- are interpreted in terms of tropospheric dynamics, including seasonal shifts in the location and strength of tropical convection and variations in quasi-isentropic transport out of the northern midlatitude surface layer. Our results indicate that current diagnostics of tropospheric transport are insufficient for comparing model transport and that the full distribution of transit times is a more appropriate constraint.

Constraints on the formation of the Martian crustal dichotomy from remnant crustal magnetism

Science.gov (United States)

Citron, Robert I.; Zhong, Shijie

2012-12-01

The Martian crustal dichotomy characterizing the topographic difference between the northern and southern hemispheres is one of the most important features on Mars. However, the formation mechanism for the dichotomy remains controversial with two competing proposals: exogenic (e.g., a giant impact) and endogenic (e.g., degree-1 mantle convection) mechanisms. Another important observation is the Martian crustal remnant magnetism, which shows a much stronger field in the southern hemisphere than in the northern hemisphere and also magnetic lineations. In this study, we examine how exogenic and endogenic mechanisms for the crustal dichotomy are constrained by the crustal remnant magnetism. Assuming that the dichotomy is caused by a giant impact in the northern hemisphere, we estimate that the average thickness of ejecta in the southern hemisphere is 20-25 km. While such a giant impact may cause crustal demagnetization in the northern hemisphere, we suggest that the impact could also demagnetize the southern hemisphere via ejecta thermal blanketing, impact demagnetization, and heat transfer from the hot layer of ejecta, thus posing a challenge for the giant impact model. We explore how the pattern of magnetic lineations relates to endogenic theories of dichotomy formation, specifically crustal production via degree-1 mantle convection. We observe that the pattern of lineations roughly corresponds to concentric circles about a single pole, and determine the pole for the concentric circles at 76.5° E and 84.5° S, which nearly overlaps with the centroid of the thickened crust in the southern hemisphere. We suggest that the crustal magnetization pattern, magnetic lineations, and crustal dichotomy (i.e., thickened crust in the highlands) can be explained by a simple endogenic process; one-plume convection causes melting and crustal production above the plume in the southern hemisphere, and strong crustal magnetization and magnetic lineations are formed in the southern

Double-layer structure in polar mesospheric clouds observed from SOFIE/AIM

Directory of Open Access Journals (Sweden)

H. Gao

2017-02-01

Full Text Available Double-layer structures in polar mesospheric clouds (PMCs are observed by using Solar Occultation for Ice Experiment (SOFIE data between 2007 and 2014. We find 816 and 301 events of double-layer structure with percentages of 10.32 and 7.25 % compared to total PMC events, and the mean distances between two peaks are 3.06 and 2.73 km for the Northern Hemisphere (NH and Southern Hemisphere (SH respectively. Double-layer PMCs almost always have less mean ice water content (IWC than daily IWC during the core of the season, but they are close to each other at the beginning and the end. The result by averaging over all events shows that the particle concentration has obvious double peaks, while the particle radius exhibits an unexpected monotonic increase with decreasing altitude. By further analysis of the background temperature and water vapour residual profiles, we conclude that the lower layer is a reproduced one formed at the bottom of the upper layer. 56.00 and 47.51 % of all double-layer events for the NH and SH respectively have temperature enhancements larger than 2 K locating between their double peaks. The longitudinal anti-correlation between the gravity waves' (GWs' potential energies and occurrence frequencies of double-layer PMCs suggests that the double-layer PMCs tend to form in an environment where the GWs have weaker intensities.

The Temperature of the Arctic and Antarctic Lower Stratosphere

Science.gov (United States)

Newman, Paul A.; Nash, Eric R.; Bhartia, P. K. (Technical Monitor)

2002-01-01

The temperature of the polar lower stratosphere during spring is the key factor in changing the magnitude of ozone loss in the polar vortices. In this talk, we will review the results of Newman et al. [2000] that quantitatively demonstrate that the polar lower stratospheric temperature is primarily controlled by planetary-scale waves. In particular, the tropospheric eddy heat flux in middle to late winter (January--February) is highly correlated with the mean polar stratospheric temperature during March. Strong midwinter planetary wave forcing leads to a warmer spring Arctic lower stratosphere in early spring, while weak midwinter forcing leads to cooler spring Arctic temperatures. In addition, this planetary wave driving also has a strong impact on the strength of the polar vortex. These results from the Northern Hemisphere will be contrasted with the Southern Hemisphere.

President's message on the first issue of the Southern Hemisphere ...

African Journals Online (AJOL)

It was certainly with great sadness and nostalgia that the SAIF Council, and I am sure most members, saw the passing of the former Southern African Forestry Journal. This publication stood us in good stead for many years and it carried the thoughts and ideas of a great many pioneers to a forestry industry that has been ...

Land-sea coupling of early Pleistocene glacial cycles in the southern North Sea exhibit dominant Northern Hemisphere forcing

Science.gov (United States)

Donders, Timme H.; van Helmond, Niels A. G. M.; Verreussel, Roel; Munsterman, Dirk; ten Veen, Johan; Speijer, Robert P.; Weijers, Johan W. H.; Sangiorgi, Francesca; Peterse, Francien; Reichart, Gert-Jan; Sinninghe Damsté, Jaap S.; Lourens, Lucas; Kuhlmann, Gesa; Brinkhuis, Henk

2018-03-01

We assess the disputed phase relations between forcing and climatic response in the early Pleistocene with a spliced Gelasian (˜ 2.6-1.8 Ma) multi-proxy record from the southern North Sea basin. The cored sections couple climate evolution on both land and sea during the intensification of Northern Hemisphere glaciation (NHG) in NW Europe, providing the first well-constrained stratigraphic sequence of the classic terrestrial Praetiglian stage. Terrestrial signals were derived from the Eridanos paleoriver, a major fluvial system that contributed a large amount of freshwater to the northeast Atlantic. Due to its latitudinal position, the Eridanos catchment was likely affected by early Pleistocene NHG, leading to intermittent shutdown and reactivation of river flow and sediment transport. Here we apply organic geochemistry, palynology, carbonate isotope geochemistry, and seismostratigraphy to document both vegetation changes in the Eridanos catchment and regional surface water conditions and relate them to early Pleistocene glacial-interglacial cycles and relative sea level changes. Paleomagnetic and palynological data provide a solid integrated timeframe that ties the obliquity cycles, expressed in the borehole geophysical logs, to Marine Isotope Stages (MIS) 103 to 92, independently confirmed by a local benthic oxygen isotope record. Marine and terrestrial palynological and organic geochemical records provide high-resolution reconstructions of relative terrestrial and sea surface temperature (TT and SST), vegetation, relative sea level, and coastal influence.During the prominent cold stages MIS 98 and 96, as well as 94, the record indicates increased non-arboreal vegetation, low SST and TT, and low relative sea level. During the warm stages MIS 99, 97, and 95 we infer increased stratification of the water column together with a higher percentage of arboreal vegetation, high SST, and relative sea level maxima. The early Pleistocene distinct warm-cold alterations are

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

Science.gov (United States)

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

2012-01-01

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

An Initial Meteoroid Stream Survey in the Southern Hemisphere Using the Southern Argentina Agile Meteor Radar (SAAMER)

Science.gov (United States)

Janches, D.; Hormaechea, J. L.; Brunini, C.; Hocking, W.; Fritts, D. C.

2013-01-01

We present in this manuscript a 4 year survey of meteor shower radiants utilizing the Southern Argentina Agile Meteor Radar (SAAMER). SAAMER, which operates at the southern most region of South America, is a new generation SKiYMET system designed with significant differences from typical meteor radars including high transmitted power and an 8-antenna transmitting array enabling large detected rates at low zenith angles. We applied the statistical methodology developed by Jones and Jones (Jones, J., Jones, W. [2006]. Month. Not. R. Astron. Soc. 367, 1050-1056) to the data collected each day and compiled the results into 1 composite representative year at 1 resolution in Solar Longitude. We then search for enhancements in the activity which last for at least 3 days and evolve temporally as is expected from a meteor shower. Using this methodology, we have identified in our data 32 shower radiants, two of which were not part of the IAU commission 22 meteor shower working list. Recently, SAAMER's capabilities were enhanced by adding two remote stations to receive meteor forward scatter signals from meteor trails and thus enable the determination of meteoroid orbital parameters. SAAMER started recording orbits in January 2012 and future surveys will focus on the search for unknown meteor streams, in particular in the southern ecliptic sky.

Reconstructing Southern Greenland Ice Sheet History During the Plio-Pleistocene Intensification of Northern Hemisphere Glaciation: Insights from IODP Site U1307

Science.gov (United States)

Blake-Mizen, K. R.; Hatfield, R. G.; Carlson, A. E.; Walczak, M. H.; Stoner, J. S.; Xuan, C.; Lawrence, K. T.; Bailey, I.

2017-12-01

Should it melt entirely, the Greenland Ice Sheet (GrIS) has the potential to raise global sea-level by 7 metres. With the Arctic continuing to warm at a remarkable rate, to better understand how the GrIS will respond to future anthropogenically-induced climate change we must constrain its natural variability in the geological past. In this regard, much uncertainty exists surrounding its pre-Quaternary history; particularly during the mid-Piacenzian warm period (mPWP; 3.3-3.0 Ma) - widely considered an analogue for near-future equilibrium climate with modern atmospheric CO2 levels and elevated temperatures relative to today - and the late Pliocene/early Pleistocene onset of widespread Northern Hemisphere glaciation (NHG, 2.7 Ma). GrIS reconstructions for these intervals have been largely hampered by a lack of well-dated, high-resolution records from suitable sites. To address this, we present new high-resolution, multi-proxy records from IODP Site U1307, a North Atlantic marine sediment core recovered from the Eirik Drift just south of Greenland. Generation of a new high-resolution relative palaeointensity (RPI)-based age-model - representing the first of its kind for high-latitude sediments deposited during NHG - has enabled strong orbital age control. Our ice-rafted debris (IRD) record confirms a 2.72 Ma initiation of major southern GrIS marine-terminating glaciations, which appear to persist even through interglacial periods up to at least 2.24 Ma. XRF-scanning and IRD evidence suggests, however, that an ephemeral ice-cap of likely considerable size persisted on southern Greenland prior to the mPWP. These data, together with the analysed provenance of individual IRD, indicate marine-based GrIS margins extended southward over the NHG interval and only occurred on Greenland's southern tip from 2.7 Ma. Despite a large increase in the deposition of GrIS-derived IRD from this time, bulk sedimentation rates and magnetic grain-size dropped significantly, implying that

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

Science.gov (United States)

Rojas, Maisa; Moreno, Patricio I.

2011-07-01

Glacial geologic studies in the Southern Hemisphere (SH) mid-latitudes (40-54°S) indicate renewed glacial activity in southern South America (Patagonia) and New Zealand's (NZ) South Island starting at ˜7 kyr, the so-called neoglaciation. Available data indicate that neoglacial advances in these regions occurred during a rising trend in atmospheric CO2 and CH4 concentrations, lower-than-present but increasing summer insolation and seasonality contrasts. In this paper we examine the climatological context in which neoglaciations occurred through analysis of the complete Paleoclimate Modelling Inter-comparison Project (PMIP2) database of simulations at 6 kyr for the SH. We observe that the amplitude of the annual insolation cycle in the SH did not change significantly at 6 kyr compared to the pre-industrial values, the largest difference occurring in autumn (MAM, negative anomalies) and spring (SON, positive anomalies). The simulated changes in temperatures over the SH respond to the insolation changes, with a 1-2 month delay over the oceans. This results in a reduced amplitude of the annual cycle of temperature and precipitation over most continental regions, except over Patagonia and NZ, that show a slight increase. In contrast, large-scale circulation features, such as the low and upper level winds and the subtropical anticyclones show an amplified annual cycle, as a direct response to the increased/decreased insolation during the transitional seasons SON/MAM. In the annual mean, there is a small but consistent equatorward shift of the latitude of maximum wind speed of 1-3° over the entire SH, which results in a small increase of wind speed over the South Pacific and Atlantic Oceans north of ˜50°S and a widespread decline south of 50°S. PMIP2 simulations for 6 kyr, indicate that in the annual mean, the SH mid-latitudes were colder, wetter and with stronger winds north of about 50°S. These conditions are consistent with the observed neoglacial advances in the

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

Energy Technology Data Exchange (ETDEWEB)

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

2011-07-15

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

Onsite-effects of dual-hemisphere versus conventional single-hemisphere transcranial direct current stimulation

Science.gov (United States)

Kwon, Yong Hyun; Jang, Sung Ho

2012-01-01

We performed functional MRI examinations in six right-handed healthy subjects. During functional MRI scanning, transcranial direct current stimulation was delivered with the anode over the right primary sensorimotor cortex and the cathode over the left primary sensorimotor cortex using dual-hemispheric transcranial direct current stimulation. This was compared to a cathode over the left supraorbital area using conventional single-hemispheric transcranial direct current stimulation. Voxel counts and blood oxygenation level-dependent signal intensities in the right primary sensorimotor cortex regions were estimated and compared between the two transcranial direct current stimulation conditions. Our results showed that dual-hemispheric transcranial direct current stimulation induced greater cortical activities than single-hemispheric transcranial direct current stimulation. These findings suggest that dual-hemispheric transcranial direct current stimulation may provide more effective cortical stimulation than single-hemispheric transcranial direct current stimulation. PMID:25624815

SOUTH POLE TELESCOPE DETECTIONS OF THE PREVIOUSLY UNCONFIRMED PLANCK EARLY SUNYAEV-ZEL'DOVICH CLUSTERS IN THE SOUTHERN HEMISPHERE

International Nuclear Information System (INIS)

Story, K.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M.; Crites, A. T.; Aird, K. A.; Andersson, K.; Bazin, G.; Armstrong, R.; Desai, S.; Bonamente, M.; Brodwin, M.; Foley, R. J.; Clocchiatti, A.; De Haan, T.; Dobbs, M. A.; Dudley, J. P.; George, E. M.

2011-01-01

We present South Pole Telescope (SPT) observations of the five galaxy cluster candidates in the southern hemisphere which were reported as unconfirmed in the Planck Early Sunyaev-Zel'dovich (ESZ) sample. One cluster candidate, PLCKESZ G255.62-46.16, is located in the 2500 deg 2 SPT SZ survey region and was reported previously as SPT-CL J0411-4819. For the remaining four candidates, which are located outside of the SPT SZ survey region, we performed short, dedicated SPT observations. Each of these four candidates was strongly detected in maps made from these observations, with signal-to-noise ratios ranging from 6.3 to 13.8. We have observed these four candidates on the Magellan-Baade telescope and used these data to estimate cluster redshifts from the red sequence. Resulting redshifts range from 0.24 to 0.46. We report measurements of Y 0.'75 , the integrated Comptonization within a 0.'75 radius, for all five candidates. We also report X-ray luminosities calculated from ROSAT All-Sky Survey catalog counts, as well as optical and improved SZ coordinates for each candidate. The combination of SPT SZ measurements, optical red-sequence measurements, and X-ray luminosity estimates demonstrates that these five Planck ESZ cluster candidates do indeed correspond to real galaxy clusters with redshifts and observable properties consistent with the rest of the ESZ sample.

Right hemisphere grey matter structure and language outcomes in chronic left hemisphere stroke

Science.gov (United States)

Xing, Shihui; Lacey, Elizabeth H.; Skipper-Kallal, Laura M.; Jiang, Xiong; Harris-Love, Michelle L.; Zeng, Jinsheng

2016-01-01

The neural mechanisms underlying recovery of language after left hemisphere stroke remain elusive. Although older evidence suggested that right hemisphere language homologues compensate for damage in left hemisphere language areas, the current prevailing theory suggests that right hemisphere engagement is ineffective or even maladaptive. Using a novel combination of support vector regression-based lesion-symptom mapping and voxel-based morphometry, we aimed to determine whether local grey matter volume in the right hemisphere independently contributes to aphasia outcomes after chronic left hemisphere stroke. Thirty-two left hemisphere stroke survivors with aphasia underwent language assessment with the Western Aphasia Battery-Revised and tests of other cognitive domains. High-resolution T1-weighted images were obtained in aphasia patients and 30 demographically matched healthy controls. Support vector regression-based multivariate lesion-symptom mapping was used to identify critical language areas in the left hemisphere and then to quantify each stroke survivor’s lesion burden in these areas. After controlling for these direct effects of the stroke on language, voxel-based morphometry was then used to determine whether local grey matter volumes in the right hemisphere explained additional variance in language outcomes. In brain areas in which grey matter volumes related to language outcomes, we then compared grey matter volumes in patients and healthy controls to assess post-stroke plasticity. Lesion–symptom mapping showed that specific left hemisphere regions related to different language abilities. After controlling for lesion burden in these areas, lesion size, and demographic factors, grey matter volumes in parts of the right temporoparietal cortex positively related to spontaneous speech, naming, and repetition scores. Examining whether domain general cognitive functions might explain these relationships, partial correlations demonstrated that grey matter

Analysis and application of impedance polar diagram and zstrike rose diagram of magnetotellurics data in southern part of the Wayang Windu geothermal field

Science.gov (United States)

Rohayat, O. R.; Wicaksono, R. A.; Daud, Y.

2018-03-01

In this study, we determined the main direction of geoelectric strike in the southern part of the Wayang Windu geothermal field using magnetotellurics (MT) data. The strike direction was obtained by analyzing data using impedance polar and Zstrike rose diagram. We investigated 51 MT data at different sites of the southern part of the Wayang Windu geothermal field. Determination of geoelectric strike direction is important since the strike is the rotation references in MT data processing. Our findings had pointed out that the geoelectric strike direction in this study area is in accordance with the direction of geological structure and has a good correlation with structures delineated from 3D MT inversion model.

Near-Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Sea Ice Concentrations

Data.gov (United States)

National Aeronautics and Space Administration — This data set provides a near-real-time (NRT) map of sea ice concentrations for both the Northern and Southern Hemispheres. The near-real-time passive microwave...

Distribution of convection potential around the polar cap boundary as a function of the interplanetary magnetic field

International Nuclear Information System (INIS)

Lu, G.; Reiff, P.H.; Karty, J.L.; Hairston, M.R.; Heelis, R.A.

1989-01-01

Plasma flow data from the AE-C, AE-D and DE 2 satellites have been used to systematically study the distribution of the convection potential around the polar cap boundary under a variety of different interplanetary magnetic field (IMF) conditions. For either a garden hose (B x B y x B y >0) orientation of the IMF, the potential distribution is mainly affected by the sign of B y . In the northern hemisphere, the zero potential line (which separates the dusk convection cell from the dawn cell) on the dayside shifts duskward as B y changes from positive to negative. But in the southern hemisphere, a dawnward shift has been found, although the uncertainties are large. The typical range of displacement is about ±1.5 hours MLT. Note that this shift is in the opposite direction from most simple schematic models of ionospheric flow; this reflects the fact that the polar cap boundary is typically more poleward than the flow reversal associated with the region 1 current system, which shifts in the opposite direction. Thus the enhanced flow region typically crosses noon. In most cases a sine wave is an adequate representation of the distribution of potential around the boundary. However, in a few cases the data favors (at the 80% confidence level) a steeper gradient near noon, more indicative of a throat. The potential drop at the duskside boundary is almost greater than at the dawnside boundary. A slight duskward shift of the patterns observed as the IMF changes from garden hose to ortho-garden hose conditions. Analytic equipotential contours, given the potential function as a boundary condition, are constructed for several IMF conditions

Patagonian and southern South Atlantic view of Holocene climate

Science.gov (United States)

Kaplan, M. R.; Schaefer, J. M.; Strelin, J. A.; Denton, G. H.; Anderson, R. F.; Vandergoes, M. J.; Finkel, R. C.; Schwartz, R.; Travis, S. G.; Garcia, J. L.; Martini, M. A.; Nielsen, S. H. H.

2016-06-01

We present a comprehensive 10Be chronology for Holocene moraines in the Lago Argentino basin, on the east side of the South Patagonian Icefield. We focus on three different areas, where prior studies show ample glacier moraine records exist because they were formed by outlet glaciers sensitive to climate change. The 10Be dated records are from the Lago Pearson, Herminita Península-Brazo Upsala, and Lago Frías areas, which span a distance of almost 100 km adjacent to the modern Icefield. New 10Be ages show that expanded glaciers and moraine building events occurred at least at 6120 ± 390 (n = 13), 4450 ± 220 (n = 7), 1450 or 1410 ± 110 (n = 18), 360 ± 30 (n = 5), and 240 ± 20 (n = 8) years ago. Furthermore, other less well-dated glacier expansions of the Upsala Glacier occurred between 1400 and ∼1000 and ∼2300 and ∼2000 years ago. The most extensive glaciers occurred over the interval from ∼6100 to ∼4500 years ago, and their margins over the last ∼600 years were well within and lower than those in the middle Holocene. The 10Be ages agree with 14C-limiting data for the glacier histories in this area. We then link southern South American, adjacent South Atlantic, and other Southern Hemisphere records to elucidate broader regional patterns of climate and their possible causes. In the early Holocene, a far southward position of the westerly winds fostered warmth, small Patagonian glaciers, and reduced sea ice coverage over the South Atlantic. Although we infer a pronounced southward displacement of the westerlies during the early Holocene, these conditions did not occur throughout the southern mid-high latitudes, an important exception being over the southwest Pacific sector. Subsequently, a northward locus and/or expansion of the winds over the Patagonia-South Atlantic sector promoted the largest glaciers between ∼6100 and ∼4500 years ago and greatest sea ice coverage. Over the last few millennia, the South Patagonian Icefield has experienced

Right hemisphere grey matter structure and language outcomes in chronic left hemisphere stroke.

Science.gov (United States)

Xing, Shihui; Lacey, Elizabeth H; Skipper-Kallal, Laura M; Jiang, Xiong; Harris-Love, Michelle L; Zeng, Jinsheng; Turkeltaub, Peter E

2016-01-01

The neural mechanisms underlying recovery of language after left hemisphere stroke remain elusive. Although older evidence suggested that right hemisphere language homologues compensate for damage in left hemisphere language areas, the current prevailing theory suggests that right hemisphere engagement is ineffective or even maladaptive. Using a novel combination of support vector regression-based lesion-symptom mapping and voxel-based morphometry, we aimed to determine whether local grey matter volume in the right hemisphere independently contributes to aphasia outcomes after chronic left hemisphere stroke. Thirty-two left hemisphere stroke survivors with aphasia underwent language assessment with the Western Aphasia Battery-Revised and tests of other cognitive domains. High-resolution T1-weighted images were obtained in aphasia patients and 30 demographically matched healthy controls. Support vector regression-based multivariate lesion-symptom mapping was used to identify critical language areas in the left hemisphere and then to quantify each stroke survivor's lesion burden in these areas. After controlling for these direct effects of the stroke on language, voxel-based morphometry was then used to determine whether local grey matter volumes in the right hemisphere explained additional variance in language outcomes. In brain areas in which grey matter volumes related to language outcomes, we then compared grey matter volumes in patients and healthy controls to assess post-stroke plasticity. Lesion-symptom mapping showed that specific left hemisphere regions related to different language abilities. After controlling for lesion burden in these areas, lesion size, and demographic factors, grey matter volumes in parts of the right temporoparietal cortex positively related to spontaneous speech, naming, and repetition scores. Examining whether domain general cognitive functions might explain these relationships, partial correlations demonstrated that grey matter

Coronal and heliospheric magnetic flux circulation and its relation to open solar flux evolution

Science.gov (United States)

Lockwood, Mike; Owens, Mathew J.; Imber, Suzanne M.; James, Matthew K.; Bunce, Emma J.; Yeoman, Timothy K.

2017-06-01

Solar cycle 24 is notable for three features that can be found in previous cycles but which have been unusually prominent: (1) sunspot activity was considerably greater in the northern/southern hemisphere during the rising/declining phase; (2) accumulation of open solar flux (OSF) during the rising phase was modest, but rapid in the early declining phase; (3) the heliospheric current sheet (HCS) tilt showed large fluctuations. We show that these features had a major influence on the progression of the cycle. All flux emergence causes a rise then a fall in OSF, but only OSF with foot points in opposing hemispheres progresses the solar cycle via the evolution of the polar fields. Emergence in one hemisphere, or symmetric emergence without some form of foot point exchange across the heliographic equator, causes poleward migrating fields of both polarities in one or both (respectively) hemispheres which temporarily enhance OSF but do not advance the polar field cycle. The heliospheric field observed near Mercury and Earth reflects the asymmetries in emergence. Using magnetograms, we find evidence that the poleward magnetic flux transport (of both polarities) is modulated by the HCS tilt, revealing an effect on OSF loss rate. The declining phase rise in OSF was caused by strong emergence in the southern hemisphere with an anomalously low HCS tilt. This implies the recent fall in the southern polar field will be sustained and that the peak OSF has limited implications for the polar field at the next sunspot minimum and hence for the amplitude of cycle 25.type="synopsis">type="main">Plain Language SummaryThere is growing interest in being able to predict the evolution in solar conditions on a better basis than past experience, which is necessarily limited. Two of the key features of the solar magnetic cycle are that the polar fields reverse just after the peak of each sunspot cycle and that the polar field that has accumulated by the time of each sunspot minimum is a good

Field-aligned currents and convection patterns in the Southern Polar Cap during stable northward, southward, and azimuthal IMF

International Nuclear Information System (INIS)

Papitashvili, V.O.; Belov, B.A.; Gromova, L.I.

1989-01-01

Equivalent ionospheric current patterns are derived from ground-based geomagnetic observations for events on 11-12 November 1979 (B/sub z/ >> 0), 24 November 1981 (B/sub z/ > 0) (B/sub y/ >> 0), and 25-26 November 1979 (B/sub y/ 0 . Due to stable external conditions, it is possible to calculate the field-aligned current (FAC) density within cells formed by two adjacent stations by taking into account the uniform conductivity of the summer polar ionosphere. These results completely correspond to regressional analysis of interplanetary magnetic fields (IMF) and ground-based geomagnetic data, and also to satellite observations of the NBZ current system. During stable southward IMF a new result was obtained, a reversal of antisunward convection flow is identified, and an NBZ-like FAC system is restored in the central part of the southern polar cap. The authors conclude that there may be an additional NBZ-like FAC system poleward of -85 0 , which is independent of the IMF and is generated by the quasi-viscous interaction between solar-wind plasma and high-latitude lobes of the magnetospheric tail

THE EFFECTS OF SPATIAL SMOOTHING ON SOLAR MAGNETIC HELICITY PARAMETERS AND THE HEMISPHERIC HELICITY SIGN RULE

Energy Technology Data Exchange (ETDEWEB)

Ocker, Stella Koch [Department of Physics, Oberlin College, Oberlin, OH 44074 (United States); Petrie, Gordon, E-mail: socker@oberlin.edu, E-mail: gpetrie@nso.edu [National Solar Observatory, Boulder, CO 80303 (United States)

2016-12-01

The hemispheric preference for negative/positive helicity to occur in the northern/southern solar hemisphere provides clues to the causes of twisted, flaring magnetic fields. Previous studies on the hemisphere rule may have been affected by seeing from atmospheric turbulence. Using Hinode /SOT-SP data spanning 2006–2013, we studied the effects of two spatial smoothing tests that imitate atmospheric seeing: noise reduction by ignoring pixel values weaker than the estimated noise threshold, and Gaussian spatial smoothing. We studied in detail the effects of atmospheric seeing on the helicity distributions across various field strengths for active regions (ARs) NOAA 11158 and NOAA 11243, in addition to studying the average helicities of 179 ARs with and without smoothing. We found that, rather than changing trends in the helicity distributions, spatial smoothing modified existing trends by reducing random noise and by regressing outliers toward the mean, or removing them altogether. Furthermore, the average helicity parameter values of the 179 ARs did not conform to the hemisphere rule: independent of smoothing, the weak-vertical-field values tended to be negative in both hemispheres, and the strong-vertical-field values tended to be positive, especially in the south. We conclude that spatial smoothing does not significantly affect the overall statistics for space-based data, and thus seeing from atmospheric turbulence seems not to have significantly affected previous studies’ ground-based results on the hemisphere rule.

Right hemispheric reversible cerebral vasoconstriction syndrome in a patient with left hemispheric partial seizures.

Science.gov (United States)

Perez, Gina S; McCaslin, Justin; Shamim, Sadat

2017-04-01

We report a right-handed 19-year-old girl who developed reversible cerebral vasoconstriction syndrome (RCVS) lateralized to the right hemisphere with simultaneous new-onset left hemispheric seizures. RCVS, typically more diffuse, was lateralized to one of the cerebral hemispheres.

Millennial-scale precipitation variability over Easter Island (South Pacific) during MIS 3: inter-hemispheric teleconnections with North Atlantic abrupt cold events

Science.gov (United States)

Margalef, O.; Cacho, I.; Pla-Rabes, S.; Cañellas-Boltà, N.; Pueyo, J. J.; Sáez, A.; Pena, L. D.; Valero-Garcés, B. L.; Rull, V.; Giralt, S.

2015-04-01

Marine Isotope Stage 3 (MIS 3, 59.4-27.8 kyr BP) is characterized by the occurrence of rapid millennial-scale climate oscillations known as Dansgaard-Oeschger cycles (DO) and by abrupt cooling events in the North Atlantic known as Heinrich events. Although both the timing and dynamics of these events have been broadly explored in North Atlantic records, the response of the tropical and subtropical latitudes to these rapid climatic excursions, particularly in the Southern Hemisphere, still remains unclear. The Rano Aroi peat record (Easter Island, 27° S) provides a unique opportunity to understand atmospheric and oceanic changes in the South Pacific during these DO cycles because of its singular location, which is influenced by the South Pacific Anticyclone (SPA), the Southern Westerlies (SW), and the Intertropical Convergence Zone (ITCZ) linked to the South Pacific Convergence Zone (SPCZ). The Rano Aroi sequence records 6 major events of enhanced precipitation between 38 and 65 kyr BP. These events are compared with other hydrological records from the tropical and subtropical band supporting a coherent regional picture, with the dominance of humid conditions in Southern Hemisphere tropical band during Heinrich Stadials (HS) 5, 5a and 6 and other Stadials while dry conditions prevailed in the Northern tropics. This antiphased hydrological pattern between hemispheres has been attributed to ITCZ migration, which in turn might be associated with an eastward expansion of the SPCZ storm track, leading to an increased intensity of cyclogenic storms reaching Easter Island. Low Pacific Sea Surface Temperature (SST) gradients across the Equator were coincident with the here-defined Rano Aroi humid events and consistent with a reorganization of Southern Pacific atmospheric and oceanic circulation also at higher latitudes during Heinrich and Dansgaard-Oeschger stadials.

Saturnian north polar region: a triangle inside the hexagon?

Science.gov (United States)

Kochemasov, Gennady G.

2010-05-01

The famous and "mysterious" stable hexagon structure around the North Pole of Saturn was earlier interpreted as projections of faces of a structural tetrahedron [1]. This "hidden" simplest Plato's polyhedron is a result of an interference of four fundamental (wave 1) warping waves having in any rotating celestial body four directions: orthogonal and diagonal. Origin of the warping waves in any celestial body is due to their movements in elliptical keplerian orbits with periodically changing accelerations. The structural tetrahedron is an intrinsic geometric feature marking the celestial bodies ubiquitous tectonic dichotomy as in a tetrahedron always there is an opposition of a face (expansion) and a vertex (contraction). In the saturnian case the tetrahedron shows a face at the north and a vertex at the south. Morphologically this is manifested by the hexagon and opposing it in the south a vertex. Blue and pink hues of the northern and southern hemispheres also underline the tectonic dichotomy. These geometric expressions are enforced by a subtle dark equilateral triangle appearing in the image PIA11682 also around the north pole and inside the hexagon (the triangle side is about 15000 km long). One angle of the triangle is clearly visible, another one just shows itself and the third one is barely distinguished. The sides of the triangle are not strait lines but slightly broken amidst lines what makes the triangle appear a bit hexagonal (spherical) and the angle is a bit bigger than 60 degrees of a classical equilateral triangle (~70 degrees). The central part of the triangle is not imaged (a black hole in the PIA11682). This image also confirms that the wide northern polar region is also densely "peppered" with bright cloudy more or less isometric spots on average 400 to 800 km across as in other latitudinal belts of Saturn [2, 3, 4]. Earlier they were observed in IR wavelengths, now they show themselves in visible wavelengths. Their origin and size were

Estimating the abundance of the Southern Hudson Bay polar bear subpopulation with aerial surveys

Science.gov (United States)

Obbard, Martyn E.; Stapleton, Seth P.; Middel, Kevin R.; Thibault, Isabelle; Brodeur, Vincent; Jutras, Charles

2015-01-01

The Southern Hudson Bay (SH) polar bear subpopulation occurs at the southern extent of the species’ range. Although capture–recapture studies indicate abundance was likely unchanged between 1986 and 2005, declines in body condition and survival occurred during the period, possibly foreshadowing a future decrease in abundance. To obtain a current estimate of abundance, we conducted a comprehensive line transect aerial survey of SH during 2011–2012. We stratified the study site by anticipated densities and flew coastal contour transects and systematically spaced inland transects in Ontario and on Akimiski Island and large offshore islands in 2011. Data were collected with double-observer and distance sampling protocols. We surveyed small islands in James Bay and eastern Hudson Bay and flew a comprehensive transect along the Québec coastline in 2012. We observed 667 bears in Ontario and on Akimiski Island and nearby islands in 2011, and we sighted 80 bears on offshore islands during 2012. Mark–recapture distance sampling and sight–resight models yielded an estimate of 860 (SE = 174) for the 2011 study area. Our estimate of abundance for the entire SH subpopulation (943; SE = 174) suggests that abundance is unlikely to have changed significantly since 1986. However, this result should be interpreted cautiously because of the methodological differences between historical studies (physical capture–recapture) and this survey. A conservative management approach is warranted given previous increases in duration of the ice-free season, which are predicted to continue in the future, and previously documented declines in body condition and vital rates.

Land–sea coupling of early Pleistocene glacial cycles in the southern North Sea exhibit dominant Northern Hemisphere forcing

Directory of Open Access Journals (Sweden)

T. H. Donders

2018-03-01

Full Text Available We assess the disputed phase relations between forcing and climatic response in the early Pleistocene with a spliced Gelasian (∼ 2.6–1.8 Ma multi-proxy record from the southern North Sea basin. The cored sections couple climate evolution on both land and sea during the intensification of Northern Hemisphere glaciation (NHG in NW Europe, providing the first well-constrained stratigraphic sequence of the classic terrestrial Praetiglian stage. Terrestrial signals were derived from the Eridanos paleoriver, a major fluvial system that contributed a large amount of freshwater to the northeast Atlantic. Due to its latitudinal position, the Eridanos catchment was likely affected by early Pleistocene NHG, leading to intermittent shutdown and reactivation of river flow and sediment transport. Here we apply organic geochemistry, palynology, carbonate isotope geochemistry, and seismostratigraphy to document both vegetation changes in the Eridanos catchment and regional surface water conditions and relate them to early Pleistocene glacial–interglacial cycles and relative sea level changes. Paleomagnetic and palynological data provide a solid integrated timeframe that ties the obliquity cycles, expressed in the borehole geophysical logs, to Marine Isotope Stages (MIS 103 to 92, independently confirmed by a local benthic oxygen isotope record. Marine and terrestrial palynological and organic geochemical records provide high-resolution reconstructions of relative terrestrial and sea surface temperature (TT and SST, vegetation, relative sea level, and coastal influence.During the prominent cold stages MIS 98 and 96, as well as 94, the record indicates increased non-arboreal vegetation, low SST and TT, and low relative sea level. During the warm stages MIS 99, 97, and 95 we infer increased stratification of the water column together with a higher percentage of arboreal vegetation, high SST, and relative sea level maxima. The early Pleistocene distinct

Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE in the Ross Sea and Southern Oceans from 05 February 1992 to 28 February 1992 (NODC Accession 0000888)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the POLAR DUKE. Data were collected from 05...

Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE in the Ross Sea and Southern Oceans from 08 October 1996 to 06 November 1996 (NODC Accession 0000894)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from POLAR DUKE. Data were collected from 08 October...

Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE in the Ross Sea and Southern Oceans from 06 September 1996 to 12 September 1996 (NODC Accession 0000890)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from POLAR DUKE. Data were collected from 06 September...

Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE in the Ross Sea and Southern Oceans from 13 November 1996 to 26 November 1996 (NODC Accession 0000895)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the POLAR DUKE. Data were collected from 13...

Clostridium difficile infection seasonality: patterns across hemispheres and continents - a systematic review.

Science.gov (United States)

Furuya-Kanamori, Luis; McKenzie, Samantha J; Yakob, Laith; Clark, Justin; Paterson, David L; Riley, Thomas V; Clements, Archie C

2015-01-01

Studies have demonstrated seasonal variability in rates of Clostridium difficile infection (CDI). Synthesising all available information on seasonality is a necessary step in identifying large-scale epidemiological patterns and elucidating underlying causes. Three medical and life sciences publication databases were searched from inception to October 2014 for longitudinal epidemiological studies written in English, Spanish or Portuguese that reported the incidence of CDI. The monthly frequency of CDI were extracted, standardized and weighted according to the number of follow-up months. Cross correlation coefficients (XCORR) were calculated to examine the correlation and lag between the year-month frequencies of reported CDI across hemispheres and continents. The search identified 13, 5 and 2 studies from North America, Europe, and Oceania, respectively that met the inclusion criteria. CDI had a similar seasonal pattern in the Northern and Southern Hemisphere characterized by a peak in spring and lower frequencies of CDI in summer/autumn with a lag of 8 months (XCORR = 0.60) between hemispheres. There was no difference between the seasonal patterns across European and North American countries. CDI demonstrates a distinct seasonal pattern that is consistent across North America, Europe and Oceania. Further studies are required to identify the driving factors of the observed seasonality.

Atmospheric Modeling of the Martian Polar Regions: CRISM EPF Coverage During the South Polar Spring Recession

Science.gov (United States)

Brown, A. J.; McGuire, P.; Wolff, M. J.

2008-03-01

We describe efforts to model dust and ice aerosols content and soils and icy surface reflectance in the Martian southern polar region during spring recession (Ls = 152-320) using CRISM emission phase function (EPF) observations.

Reorganization of syntactic processing following left-hemisphere brain damage: does right-hemisphere activity preserve function?

Science.gov (United States)

Tyler, Lorraine K; Wright, Paul; Randall, Billi; Marslen-Wilson, William D; Stamatakis, Emmanuel A

2010-11-01

The extent to which the human brain shows evidence of functional plasticity across the lifespan has been addressed in the context of pathological brain changes and, more recently, of the changes that take place during healthy ageing. Here we examine the potential for plasticity by asking whether a strongly left-lateralized system can successfully reorganize to the right-hemisphere following left-hemisphere brain damage. To do this, we focus on syntax, a key linguistic function considered to be strongly left-lateralized, combining measures of tissue integrity, neural activation and behavioural performance. In a functional neuroimaging study participants heard spoken sentences that differentially loaded on syntactic and semantic information. While healthy controls activated a left-hemisphere network of correlated activity including Brodmann areas 45/47 and posterior middle temporal gyrus during syntactic processing, patients activated Brodmann areas 45/47 bilaterally and right middle temporal gyrus. However, voxel-based morphometry analyses showed that only tissue integrity in left Brodmann areas 45/47 was correlated with activity and performance; poor tissue integrity in left Brodmann area 45 was associated with reduced functional activity and increased syntactic deficits. Activity in the right-hemisphere was not correlated with damage in the left-hemisphere or with performance. Reduced neural integrity in the left-hemisphere through brain damage or healthy ageing results in increased right-hemisphere activation in homologous regions to those left-hemisphere regions typically involved in the young. However, these regions do not support the same linguistic functions as those in the left-hemisphere and only indirectly contribute to preserved syntactic capacity. This establishes the unique role of the left hemisphere in syntax, a core component in human language.

Evaluation of Inter-Hemispheric Characteristics of the Tropopause-Stratopause-Mesopause Over Sub-Tropical Regions

Science.gov (United States)

Sharma, Som; Kumar, Prashant; Vaishnav, Rajesh; Jethva, Chintan; Bencherif, Hassan

2018-03-01

The transition regions in thermal structure viz. Tropopause, stratopause and mesopause play a vital role in the vertical coupling of the Earth's atmosphere. For the first time, inter-hemispheric characteristics of the transition regions over two subtropical regions are studied using temperature observations from the SABER onboard TIMED satellite and the ERA Interim reanalysis during year 2002 to 2015. Results show that tropopause height is higher over Reunion Island (21.11°S, 55.53°E) in the Southern Hemisphere (SH) as compared to Mt. Abu region (24.59°N, 72.70°E) in the Northern Hemisphere (NH). Temporal variation of tropopause temperature reveals a decreasing ( 4 K) trend from year 2002 to 2008 and beyond this, an increasing ( 1.5 K) trend is found in tropopause temperature. These features are reinforcing for Mesopause as compared to tropopause temperature. The SH shows stronger variations in Mesopause temperature ( 7 K) compared to NH during year 2002 to 2008. The occurrence frequency of mesopause and stratopause height shows that the maximum occurrence frequency ( 60%) of mesopause at 100 km in NH, while frequency is found to be 55% in the SH. Results show that stratopause (mesopause) is cooler (warmer) in NH as compared SH. Moreover, Lomb Scargle Periodogram and wavelet transform techniques are used to investigate the periodicity of mesopause, stratopause and tropopause temperatures and heights. Investigations revealed prominent annual oscillations in the tropopause and stratopause temperatures in both hemispheres. These findings will be of immense use for the vertical and inter-hemispheric atmospheric coupling studies.

Lesion characteristics driving right-hemispheric language reorganization in congenital left-hemispheric brain damage.

Science.gov (United States)

Lidzba, Karen; de Haan, Bianca; Wilke, Marko; Krägeloh-Mann, Ingeborg; Staudt, Martin

2017-10-01

Pre- or perinatally acquired ("congenital") left-hemispheric brain lesions can be compensated for by reorganizing language into homotopic brain regions in the right hemisphere. Language comprehension may be hemispherically dissociated from language production. We investigated the lesion characteristics driving inter-hemispheric reorganization of language comprehension and language production in 19 patients (7-32years; eight females) with congenital left-hemispheric brain lesions (periventricular lesions [n=11] and middle cerebral artery infarctions [n=8]) by fMRI. 16/17 patients demonstrated reorganized language production, while 7/19 patients had reorganized language comprehension. Lesions to the insular cortex and the temporo-parietal junction (predominantly supramarginal gyrus) were significantly more common in patients in whom both, language production and comprehension were reorganized. These areas belong to the dorsal stream of the language network, participating in the auditory-motor integration of language. Our data suggest that the integrity of this stream might be crucial for a normal left-lateralized language development. Copyright © 2017. Published by Elsevier Inc.

Validation of cosmogenic nuclide production rate scaling factors through direct measurement. Part 2, Production of 7Be and 10Be in water targets deployed in the Southern Hemisphere, 1997-2001

International Nuclear Information System (INIS)

Graham, I.J.; Barry, B.J.; Ditchburn, R.G.; Zondervan, A.

2005-01-01

Sealed containers of de-ionised water were exposed to cosmic-rays at seven sites in Australia, New Zealand and Antarctica, covering a range of altitudes and geomagnetic latitudes, over time periods of six months to three years (1997-2001). After isotopic analysis by gamma counting (for 7 Be) and accelerator mass spectrometry (for 10 Be), the data obtained were corrected to obtain relative production factors (i.e., 'k' values). This report presents a full description of the target design, isotope extraction, and measurement procedures employed. It thus provides the raw data from which cosmogenic nuclide production rates for the Southern Hemisphere can be calculated, and scaling factors used in surface exposure dating can be independently validated. (author). 35 refs., 7 figs., 5 tabs

Southern hemisphere low level wind circulation statistics from the Seasat scatterometer

Science.gov (United States)

Levy, Gad

1994-01-01

Analyses of remotely sensed low-level wind vector data over the Southern Ocean are performed. Five-day averages and monthly means are created and the month-to-month variability during the winter (July-September) of 1978 is investigated. The remotely sensed winds are compared to the Australian Bureau of Meteorology (ABM) and the National Meteorological Center (NMC) surface analyses. In southern latitudes the remotely sensed winds are stronger than what the weather services' analyses suggest, indicating under-estimation by ABM and NMC in these regions. The evolution of the low-level jet and the major stormtracks during the season are studied and different flow regimes are identified. The large-scale variability of the meridional flow is studied with the aid of empirical orthogonal function (EOF) analysis. The dominance of quasi-stationary wave numbers 3,4, and 5 in the winter flows is evident in both the EOF analysis and the mean flow. The signature of an exceptionally strong blocking situation is evident in July and the special conditions leading to it are discussed. A very large intraseasonal variability with different flow regimes at different months is documented.

Satellite Remote Sensing of Atmospheric Pollution: the Far-Reaching Impact of Burning in Southern Africa

Science.gov (United States)

Fishman, Jack; Al-Saadi, Jassim A.; Neil, Doreen O.; Creilson, John K.; Severance, Kurt; Thomason, Larry W.; Edwards, David R.

2008-01-01

When the first observations of a tropospheric trace gas were obtained in the 1980s, carbon monoxide enhancements from tropical biomass burning dominated the observed features. In 2005, an active remote-sensing system to provide detailed information on the vertical distribution of aerosols and clouds was launched, and again, one of the most imposing features observed was the presence of emissions from tropical biomass burning. This paper presents a brief overview of space-borne observations of the distribution of trace gases and aerosols and how tropical biomass burning, primarily in the Southern Hemisphere, has provided an initially surprising picture of the distribution of these species and how they have evolved from prevailing transport patterns in that hemisphere. We also show how interpretation of these observations has improved significantly as a result of the improved capability of trajectory modeling in recent years and how information from this capability has provided additional insight into previous measurements form satellites. Key words: pollution; biomass burning; aerosols; tropical trace gas emissions; Southern Hemisphere; carbon monoxide.

Recent changes in the ventilation of the southern oceans.

Science.gov (United States)

Waugh, Darryn W; Primeau, Francois; Devries, Tim; Holzer, Mark

2013-02-01

Surface westerly winds in the Southern Hemisphere have intensified over the past few decades, primarily in response to the formation of the Antarctic ozone hole, and there is intense debate on the impact of this on the ocean's circulation and uptake and redistribution of atmospheric gases. We used measurements of chlorofluorocarbon-12 (CFC-12) made in the southern oceans in the early 1990s and mid- to late 2000s to examine changes in ocean ventilation. Our analysis of the CFC-12 data reveals a decrease in the age of subtropical subantarctic mode waters and an increase in the age of circumpolar deep waters, suggesting that the formation of the Antarctic ozone hole has caused large-scale coherent changes in the ventilation of the southern oceans.

Interannual Similarity in the Martian Atmosphere During the Dust Storm Season

Science.gov (United States)

Kass, D. M.; Kleinboehl, A.; McCleese, D. J.; Schofield, J. T.; Smith, M. D.

2016-01-01

We find that during the dusty season on Mars (southern spring and summer) of years without a global dust storm there are three large regional-scale dust storms. The storms are labeled A, B, and C in seasonal order. This classification is based on examining the zonal mean 50 Pa (approximately 25 km) daytime temperature retrievals from TES/MGS and MCS/MRO over 6 Mars Years. Regional-scale storms are defined as events where the temperature exceeds 200 K. Examining the MCS dust field at 50 Pa indicates that warming in the Southern Hemisphere is dominated by direct heating, while northern high latitude warming is a dynamical response. A storms are springtime planet encircling Southern Hemisphere events. B storms are southern polar events that begin near perihelion and last through the solstice. C storms are southern summertime events starting well after the end of the B storm. C storms show the most interannual variability.

A glacial record of the last termination in the southern tropical Andes

Science.gov (United States)

Bromley, G. R.; Schaefer, J. M.; Winckler, G.; Hall, B. L.; Todd, C. E.; Rademaker, K.

2012-12-01

The last glacial termination represents the highest-magnitude climate change of the last hundred thousand years. Accurate resolution of events during the termination is vital to our understanding of how - and why - the global climate system transitions from a full glacial to interglacial state, as well as the causes of abrupt climate change during the late-glacial period. Palaeoclimate data from low latitudes, though relatively sparse, are particularly valuable, since the tropical ocean and atmosphere likely play a crucial role in Quaternary climate variability on all timescales. We present a detailed glacier record from the Andes of southern Peru (15°S), resolved with 3He surface-exposure dating and spanning the last glacial maximum and termination. Our dataset reveals that glaciers in this part of the Southern Hemisphere maintained their Late Pleistocene maxima for several millennia and that the onset of the termination may have occurred relatively late. Deglaciation was punctuated by two major advances during the late-glacial period. Following the glacial-interglacial transition, our preliminary chronologic and morphologic data suggest that, in contrast to the Northern Hemisphere, glaciers in the southern tropical Andes have experienced overall shrinkage during the Holocene.

Hemispheric processing asymmetries: implications for memory.

Science.gov (United States)

Funnell, M G; Corballis, P M; Gazzaniga, M S

2001-01-01

Recent research has demonstrated that memory for words elicits left hemisphere activation, faces right hemisphere activation, and nameable objects bilateral activation. This pattern of results was attributed to dual coding of information, with the left hemisphere employing a verbal code and the right a nonverbal code. Nameable objects can be encoded either verbally or nonverbally and this accounts for their bilateral activation. We investigated this hypothesis in a callosotomy patient. Consistent with dual coding, the left hemisphere was superior to the right in memory for words, whereas the right was superior for faces. Contrary to prediction, performance on nameable pictures was not equivalent in the two hemispheres, but rather resulted in a right hemisphere superiority. In addition, memory for pictures was significantly better than for either words or faces. These findings suggest that the dual code hypothesis is an oversimplification of the processing capabilities of the two hemispheres.

Clostridium difficile Infection Seasonality: Patterns across Hemispheres and Continents – A Systematic Review

Science.gov (United States)

Furuya-Kanamori, Luis; McKenzie, Samantha J.; Yakob, Laith; Clark, Justin; Paterson, David L.; Riley, Thomas V.; Clements, Archie C.

2015-01-01

Background Studies have demonstrated seasonal variability in rates of Clostridium difficile infection (CDI). Synthesising all available information on seasonality is a necessary step in identifying large-scale epidemiological patterns and elucidating underlying causes. Methods Three medical and life sciences publication databases were searched from inception to October 2014 for longitudinal epidemiological studies written in English, Spanish or Portuguese that reported the incidence of CDI. The monthly frequency of CDI were extracted, standardized and weighted according to the number of follow-up months. Cross correlation coefficients (XCORR) were calculated to examine the correlation and lag between the year-month frequencies of reported CDI across hemispheres and continents. Results The search identified 13, 5 and 2 studies from North America, Europe, and Oceania, respectively that met the inclusion criteria. CDI had a similar seasonal pattern in the Northern and Southern Hemisphere characterized by a peak in spring and lower frequencies of CDI in summer/autumn with a lag of 8 months (XCORR = 0.60) between hemispheres. There was no difference between the seasonal patterns across European and North American countries. Conclusion CDI demonstrates a distinct seasonal pattern that is consistent across North America, Europe and Oceania. Further studies are required to identify the driving factors of the observed seasonality. PMID:25775463

Detection and mapping of polar stratospheric clouds using limb scattering observations

Directory of Open Access Journals (Sweden)

C. von Savigny

2005-01-01

Full Text Available Satellite-based measurements of Visible/NIR limb-scattered solar radiation are well suited for the detection and mapping of polar stratospheric clouds (PSCs. This publication describes a method to detect PCSs from limb scattering observations with the Scanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIAMACHY on the European Space Agency's Envisat spacecraft. The method is based on a color-index approach and requires a priori knowledge of the stratospheric background aerosol loading in order to avoid false PSC identifications by stratospheric background aerosol. The method is applied to a sample data set including the 2003 PSC season in the Southern Hemisphere. The PSCs are correlated with coincident UKMO model temperature data, and with very few exceptions, the detected PSCs occur at temperatures below 195–198 K. Monthly averaged PSC descent rates are about 1.5 km/month for the −50° S to −75° S latitude range and assume a maximum between August and September with a value of about 2.5 km/month. The main cause of the PSC descent is the slow descent of the lower stratospheric temperature minimum.

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.

The effects of the Indo-Pacific warm pool on the stratosphere

Science.gov (United States)

Zhou, Xin; Li, Jianping; Xie, Fei; Ding, Ruiqiang; Li, Yanjie; Zhao, Sen; Zhang, Jiankai; Li, Yang

2017-03-01

Sea surface temperature (SST) in the Indo-Pacific warm pool (IPWP) plays a key role in influencing East Asian climate, and even affects global-scale climate change. This study defines IPWP Niño and IPWP Niña events to represent the warm and cold phases of IPWP SST anomalies, respectively, and investigates the effects of these events on stratospheric circulation and temperature. Results from simulations forced by observed SST anomalies during IPWP Niño and Niña events show that the tropical lower stratosphere tends to cool during IPWP Niño events and warm during IPWP Niña events. The responses of the northern and southern polar vortices to IPWP Niño events are fairly symmetric, as both vortices are significantly warmed and weakened. However, the responses of the two polar vortices to IPWP Niña events are of opposite sign: the northern polar vortex is warmed and weakened, but the southern polar vortex is cooled and strengthened. These features are further confirmed by composite analysis using reanalysis data. A possible dynamical mechanism connecting IPWP SST to the stratosphere is suggested, in which IPWP Niño and Niña events excite teleconnections, one similar to the Pacific-North America pattern in the Northern Hemisphere and a Rossby wave train in the Southern Hemisphere, which project onto the climatological wave in the mid-high latitudes, intensifying the upward propagation of planetary waves into the stratosphere and, in turn, affecting the polar vortex.

A novel autonomous real-time position method based on polarized light and geomagnetic field

OpenAIRE

Wang, Yinlong; Chu, Jinkui; Zhang, Ran; Wang, Lu; Wang, Zhiwen

2015-01-01

Many animals exploit polarized light in order to calibrate their magnetic compasses for navigation. For example, some birds are equipped with biological magnetic and celestial compasses enabling them to migrate between the Western and Eastern Hemispheres. The Vikings' ability to derive true direction from polarized light is also widely accepted. However, their amazing navigational capabilities are still not completely clear. Inspired by birds' and Vikings' ancient navigational skills. Here we...

Choosing words: left hemisphere, right hemisphere, or both? Perspective on the lateralization of word retrieval

Science.gov (United States)

Ries, Stephanie K.; Dronkers, Nina F.; Knight, Robert T.

2015-01-01

Language is considered to be one of the most lateralized human brain functions. Left hemisphere dominance for language has been consistently confirmed in clinical and experimental settings and constitutes one of the main axioms of neurology and neuroscience. However, functional neuroimaging studies are finding that the right hemisphere also plays a role in diverse language functions. Critically, the right hemisphere may also compensate for the loss or degradation of language functions following extensive stroke-induced damage to the left hemisphere. Here, we review studies that focus on our ability to choose words as we speak. Although fluidly performed in individuals with intact language, this process is routinely compromised in aphasic patients. We suggest that parceling word retrieval into its sub-processes—lexical activation and lexical selection—and examining which of these can be compensated for after left hemisphere stroke can advance the understanding of the lateralization of word retrieval in speech production. In particular, the domain-general nature of the brain regions associated with each process may be a helpful indicator of the right hemisphere's propensity for compensation. PMID:26766393

Modulating transcallosal and intra-hemispheric brain connectivity with tDCS: Implications for interventions in Aphasia.

Science.gov (United States)

Zheng, Xin; Dai, Weiying; Alsop, David C; Schlaug, Gottfried

2016-07-25

Transcranial direct current stimulation (tDCS) can enhance or diminish cortical excitability levels depending on the polarity of the stimulation. One application of non-invasive brain-stimulation has been to modulate a possible inter-hemispheric disinhibition after a stroke. This disinhibition model has been developed mainly for the upper extremity motor system, but it is not known whether the language/speech-motor system shows a similar inter-hemispheric interaction. We aimed to examine physiological evidence of inter- and intra-hemispheric connectivity changes induced by tDCS of the right inferior frontal gyrus (IFG) using arterial-spin labeling (ASL) MRI. Using an MR-compatible DC-Stimulator, we applied anodal stimulation to the right IFG region of nine healthy adults while undergoing non-invasive cerebral blood flow imaging with arterial-spin labeling (ASL) before, during, and after the stimulation. All ASL images were then normalized and timecourses were extracted in regions of interest (ROIs), which were the left and right IFG regions, and the right supramarginal gyrus (SMG) in the inferior parietal lobule. Two additional ROIs (the right occipital lobe and the left fronto-orbital region) were taken as control regions. Using regional correlation coefficients as a surrogate marker of connectivity, we could show that inter-hemispheric connectivity (right IFG with left IFG) decreased significantly (p < 0.05; r-scores from 0.67 to 0.53) between baseline and post-stimulation, while the intra-hemispheric connectivity (right IFG with right SMG) increased significantly (p < 0.05;r-scores from 0.74 to 0.81). A 2 × 2 ANOVA found a significant main effect of HEMISPHERE (F(8) = 6.83, p < 0.01) and a significant HEMISPHERE-by-TIME interaction (F(8) = 4.24, p < 0.05) in connectivity changes. The correlation scores did not change significantly in the control region pairs (right IFG with right occipital and right IFG with left fronto-orbital) over

Four-parameter model for polarization-resolved rough-surface BRDF.

Science.gov (United States)

Renhorn, Ingmar G E; Hallberg, Tomas; Bergström, David; Boreman, Glenn D

2011-01-17

A modeling procedure is demonstrated, which allows representation of polarization-resolved BRDF data using only four parameters: the real and imaginary parts of an effective refractive index with an added parameter taking grazing incidence absorption into account and an angular-scattering parameter determined from the BRDF measurement of a chosen angle of incidence, preferably close to normal incidence. These parameters allow accurate predictions of s- and p-polarized BRDF for a painted rough surface, over three decades of variation in BRDF magnitude. To characterize any particular surface of interest, the measurements required to determine these four parameters are the directional hemispherical reflectance (DHR) for s- and p-polarized input radiation and the BRDF at a selected angle of incidence. The DHR data describes the angular and polarization dependence, as well as providing the overall normalization constraint. The resulting model conserves energy and fulfills the reciprocity criteria.

Pliocene warmth, polar amplification, and stepped Pleistocene cooling recorded in NE Arctic Russia.

Science.gov (United States)

Brigham-Grette, Julie; Melles, Martin; Minyuk, Pavel; Andreev, Andrei; Tarasov, Pavel; DeConto, Robert; Koenig, Sebastian; Nowaczyk, Norbert; Wennrich, Volker; Rosén, Peter; Haltia, Eeva; Cook, Tim; Gebhardt, Catalina; Meyer-Jacob, Carsten; Snyder, Jeff; Herzschuh, Ulrike

2013-06-21

Understanding the evolution of Arctic polar climate from the protracted warmth of the middle Pliocene into the earliest glacial cycles in the Northern Hemisphere has been hindered by the lack of continuous, highly resolved Arctic time series. Evidence from Lake El'gygytgyn, in northeast (NE) Arctic Russia, shows that 3.6 to 3.4 million years ago, summer temperatures were ~8°C warmer than today, when the partial pressure of CO2 was ~400 parts per million. Multiproxy evidence suggests extreme warmth and polar amplification during the middle Pliocene, sudden stepped cooling events during the Pliocene-Pleistocene transition, and warmer than present Arctic summers until ~2.2 million years ago, after the onset of Northern Hemispheric glaciation. Our data are consistent with sea-level records and other proxies indicating that Arctic cooling was insufficient to support large-scale ice sheets until the early Pleistocene.

Unilateral Hemispheric Encephalitis

Directory of Open Access Journals (Sweden)

Mohan Leslie Noone

2014-10-01

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

Onsite-effects of dual-hemisphere versus conventional single-hemisphere transcranial direct current stimulation: A functional MRI study.

Science.gov (United States)

Kwon, Yong Hyun; Jang, Sung Ho

2012-08-25

We performed functional MRI examinations in six right-handed healthy subjects. During functional MRI scanning, transcranial direct current stimulation was delivered with the anode over the right primary sensorimotor cortex and the cathode over the left primary sensorimotor cortex using dual-hemispheric transcranial direct current stimulation. This was compared to a cathode over the left supraorbital area using conventional single-hemispheric transcranial direct current stimulation. Voxel counts and blood oxygenation level-dependent signal intensities in the right primary sensorimotor cortex regions were estimated and compared between the two transcranial direct current stimulation conditions. Our results showed that dual-hemispheric transcranial direct current stimulation induced greater cortical activities than single-hemispheric transcranial direct current stimulation. These findings suggest that dual-hemispheric transcranial direct current stimulation may provide more effective cortical stimulation than single-hemispheric transcranial direct current stimulation.

First Reprocessing of Southern Hemisphere ADditional OZonesondes Profile Records: 3. Uncertainty in Ozone Profile and Total Column

Science.gov (United States)

Witte, Jacquelyn C.; Thompson, Anne M.; Smit, Herman G. J.; Vömel, Holger; Posny, Françoise; Stübi, Rene

2018-03-01

Reprocessed ozonesonde data from eight SHADOZ (Southern Hemisphere ADditional OZonesondes) sites have been used to derive the first analysis of uncertainty estimates for both profile and total column ozone (TCO). The ozone uncertainty is a composite of the uncertainties of the individual terms in the ozone partial pressure (PO3) equation, those being the ozone sensor current, background current, internal pump temperature, pump efficiency factors, conversion efficiency, and flow rate. Overall, PO3 uncertainties (ΔPO3) are within 15% and peak around the tropopause (15 ± 3 km) where ozone is a minimum and ΔPO3 approaches the measured signal. The uncertainty in the background and sensor currents dominates the overall ΔPO3 in the troposphere including the tropopause region, while the uncertainties in the conversion efficiency and flow rate dominate in the stratosphere. Seasonally, ΔPO3 is generally a maximum in the March-May, with the exception of SHADOZ sites in Asia, for which the highest ΔPO3 occurs in September-February. As a first approach, we calculate sonde TCO uncertainty (ΔTCO) by integrating the profile ΔPO3 and adding the ozone residual uncertainty, derived from the McPeters and Labow (2012, doi:10.1029/2011JD017006) 1σ ozone mixing ratios. Overall, ΔTCO are within ±15 Dobson units (DU), representing 5-6% of the TCO. Total Ozone Mapping Spectrometer and Ozone Monitoring Instrument (TOMS and OMI) satellite overpasses are generally within the sonde ΔTCO. However, there is a discontinuity between TOMS v8.6 (1998 to September 2004) and OMI (October 2004-2016) TCO on the order of 10 DU that accounts for the significant 16 DU overall difference observed between sonde and TOMS. By comparison, the sonde-OMI absolute difference for the eight stations is only 4 DU.

Atmospheric radiocarbon as a Southern Ocean wind proxy over the last 1000 years

Science.gov (United States)

Rodgers, K. B.; Mikaloff Fletcher, S.; Galbraith, E.; Sarmiento, J. L.; Gnanadesikan, A.; Slater, R. D.; Naegler, T.

2009-04-01

Measurements of radiocarbon in tree rings over the last 1000 years indicate that there was a pre-industrial latitudinal gradient of atmospheric radiocarbon of 3.9-4.5 per mail and that this gradient had temporal variability of order 6 per mil. Here we test the idea that the mean gradient as well as variability in he gradient is dominated by the strength of the winds over the Southern Ocean. This is done using an ocean model and an atmospheric transport model. The ocean model is used to derive fluxes of 12CO2 and 14CO2 at the sea surface, and these fluxes are used as a lower boundary condition for the transport model. For the mean state, strong winds in the Southern Ocean drive significant upwelling of radiocarbon-depleted Circumpolar Deep Water (CDW), leading to a net flux of 14CO2 relative to 12CO2 into the ocean. This serves to maintain a hemispheric gradient in pre-anthropogenic atmospheric delta-c14. For perturbations, increased/decreased Southern Ocean winds drive increased/decreased uptake of 14CO2 relative to 12CO2, thus increasing/decreasing the hemispheric gradient in atmospheric delta-c14. The tree ring data is interpreted to reveal a decrease in the strength of the Southern Ocean winds at the transition between the Little Ice Age and the Medieval Warm Period.

Zonally asymmetric response of the Southern Ocean mixed-layer depth to the Southern Annular Mode

Science.gov (United States)

Sallée, J. B.; Speer, K. G.; Rintoul, S. R.

2010-04-01

Interactions between the atmosphere and ocean are mediated by the mixed layer at the ocean surface. The depth of this layer is determined by wind forcing and heating from the atmosphere. Variations in mixed-layer depth affect the rate of exchange between the atmosphere and deeper ocean, the capacity of the ocean to store heat and carbon and the availability of light and nutrients to support the growth of phytoplankton. However, the response of the Southern Ocean mixed layer to changes in the atmosphere is not well known. Here we analyse temperature and salinity data from Argo profiling floats to show that the Southern Annular Mode (SAM), the dominant mode of atmospheric variability in the Southern Hemisphere, leads to large-scale anomalies in mixed-layer depth that are zonally asymmetric. From a simple heat budget of the mixed layer we conclude that meridional winds associated with departures of the SAM from zonal symmetry cause anomalies in heat flux that can, in turn, explain the observed changes of mixed-layer depth and sea surface temperature. Our results suggest that changes in the SAM, including recent and projected trends attributed to human activity, drive variations in Southern Ocean mixed-layer depth, with consequences for air-sea exchange, ocean sequestration of heat and carbon, and biological productivity.

South Polar Polygons

Science.gov (United States)

2005-01-01

4 July 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a polgyon-cracked surface, into which deep, somewhat kidney-bean-shaped pits have formed. These are landscapes of the martian south polar residual cap. This view was captured during May 2005. Location near: 86.9oS, 5.1oW Image width: 1.5 km (0.9 mi) Illumination from: upper left Season Southern Spring

Do minor sudden stratospheric warmings in the Southern Hemisphere (SH) impact coupling between stratosphere and mesosphere-lower thermosphere (MLT) like major warmings?

Science.gov (United States)

Eswaraiah, S.; Kim, Yong Ha; Liu, Huixin; Ratnam, M. Venkat; Lee, Jaewook

2017-08-01

We have investigated the coupling between the stratosphere and mesosphere-lower thermosphere (MLT) in the Southern Hemisphere (SH) during 2010 minor sudden stratospheric warmings (SSWs). Three episodic SSWs were noticed in 2010. Mesospheric zonal winds between 82 and 92 km obtained from King Sejong Station (62.22°S, 58.78°W) meteor radar showed the significant difference from usual trend. The zonal wind reversal in the mesosphere is noticed a week before the associated SSW similar to 2002 major SSW. The mesosphere wind reversal is also noticed in "Specified Dynamics" version of Whole Atmosphere Community Climate Model (SD-WACCM) and Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA) simulations. The similar zonal wind weakening/reversal in the lower thermosphere between 100 and 140 km is simulated by GAIA. Further, we observed the mesospheric cooling in consistency with SSWs using Microwave Limb Sounder data. However, the GAIA simulations showed warming between 130 and 140 km after few days of SSW. Thus, the observation and model simulation indicate for the first time that the 2010 minor SSW also affects dynamics of the MLT region over SH in a manner similar to 2002 major SSW.[Figure not available: see fulltext.

Polar Polygons

Science.gov (United States)

2005-01-01

18 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark-outlined polygons on a frost-covered surface in the south polar region of Mars. In summer, this surface would not be bright and the polygons would not have dark outlines--these are a product of the presence of seasonal frost. Location near: 77.2oS, 204.8oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

An orbital meteoroid stream survey using the Southern Argentina Agile MEteor Radar (SAAMER) based on a wavelet approach

Science.gov (United States)

Pokorný, P.; Janches, D.; Brown, P. G.; Hormaechea, J. L.

2017-07-01

Over a million individually measured meteoroid orbits were collected with the Southern Argentina Agile MEteor Radar (SAAMER) between 2012-2015. This provides a robust statistical database to perform an initial orbital survey of meteor showers in the Southern Hemisphere via the application of a 3D wavelet transform. The method results in a composite year from all 4 years of data, enabling us to obtain an undisturbed year of meteor activity with more than one thousand meteors per day. Our automated meteor shower search methodology identified 58 showers. Of these showers, 24 were associated with previously reported showers from the IAU catalogue while 34 showers are new and not listed in the catalogue. Our searching method combined with our large data sample provides unprecedented accuracy in measuring meteor shower activity and description of shower characteristics in the Southern Hemisphere. Using simple modeling and clustering methods we also propose potential parent bodies for the newly discovered showers.

Hemispheric Laterality in Music and Math

Science.gov (United States)

Szirony, Gary Michael; Burgin, John S.; Pearson, L. Carolyn

2008-01-01

Hemispheric laterality may be a useful concept in teaching, learning, training, and in understanding more about human development. To address this issue, a measure of hemispheric laterality was compared to musical and mathematical ability. The Human Information Processing Survey (HIPS) instrument, designed to measure hemispheric laterality, was…

Interhemispheric gradient of atmospheric radiocarbon reveals natural variability of Southern Ocean winds

Science.gov (United States)

Rodgers, K. B.; Mikaloff-Fletcher, S. E.; Bianchi, D.; Beaulieu, C.; Galbraith, E. D.; Gnanadesikan, A.; Hogg, A. G.; Iudicone, D.; Lintner, B. R.; Naegler, T.; Reimer, P. J.; Sarmiento, J. L.; Slater, R. D.

2011-10-01

Tree ring Δ14C data (Reimer et al., 2004; McCormac et al., 2004) indicate that atmospheric Δ14C varied on multi-decadal to centennial timescales, in both hemispheres, over the period between AD 950 and 1830. The Northern and Southern Hemispheric Δ14C records display similar variability, but from the data alone is it not clear whether these variations are driven by the production of 14C in the stratosphere (Stuiver and Quay, 1980) or by perturbations to exchanges between carbon reservoirs (Siegenthaler et al., 1980). As the sea-air flux of 14CO2 has a clear maximum in the open ocean regions of the Southern Ocean, relatively modest perturbations to the winds over this region drive significant perturbations to the interhemispheric gradient. In this study, model simulations are used to show that Southern Ocean winds are likely a main driver of the observed variability in the interhemispheric gradient over AD 950-1830, and further, that this variability may be larger than the Southern Ocean wind trends that have been reported for recent decades (notably 1980-2004). This interpretation also implies that there may have been a significant weakening of the winds over the Southern Ocean within a few decades of AD 1375, associated with the transition between the Medieval Climate Anomaly and the Little Ice Age. The driving forces that could have produced such a shift in the winds at the Medieval Climate Anomaly to Little Ice Age transition remain unknown. Our process-focused suite of perturbation experiments with models raises the possibility that the current generation of coupled climate and earth system models may underestimate the natural background multi-decadal- to centennial-timescale variations in the winds over the Southern Ocean.

Interhemispheric gradient of atmospheric radiocarbon reveals natural variability of Southern Ocean winds

Directory of Open Access Journals (Sweden)

K. B. Rodgers

2011-10-01

Full Text Available Tree ring Δ¹⁴C data (Reimer et al., 2004; McCormac et al., 2004 indicate that atmospheric Δ¹⁴C varied on multi-decadal to centennial timescales, in both hemispheres, over the period between AD 950 and 1830. The Northern and Southern Hemispheric Δ¹⁴C records display similar variability, but from the data alone is it not clear whether these variations are driven by the production of ¹⁴C in the stratosphere (Stuiver and Quay, 1980 or by perturbations to exchanges between carbon reservoirs (Siegenthaler et al., 1980. As the sea-air flux of ¹⁴CO₂ has a clear maximum in the open ocean regions of the Southern Ocean, relatively modest perturbations to the winds over this region drive significant perturbations to the interhemispheric gradient. In this study, model simulations are used to show that Southern Ocean winds are likely a main driver of the observed variability in the interhemispheric gradient over AD 950–1830, and further, that this variability may be larger than the Southern Ocean wind trends that have been reported for recent decades (notably 1980–2004. This interpretation also implies that there may have been a significant weakening of the winds over the Southern Ocean within a few decades of AD 1375, associated with the transition between the Medieval Climate Anomaly and the Little Ice Age. The driving forces that could have produced such a shift in the winds at the Medieval Climate Anomaly to Little Ice Age transition remain unknown. Our process-focused suite of perturbation experiments with models raises the possibility that the current generation of coupled climate and earth system models may underestimate the natural background multi-decadal- to centennial-timescale variations in the winds over the Southern Ocean.

Model of climate evolution based on continental drift and polar wandering

Science.gov (United States)

Donn, W. L.; Shaw, D. M.

1977-01-01

The thermodynamic meteorologic model of Adem is used to trace the evolution of climate from Triassic to present time by applying it to changing geography as described by continental drift and polar wandering. Results show that the gross changes of climate in the Northern Hemisphere can be fully explained by the strong cooling in high latitudes as continents moved poleward. High-latitude mean temperatures in the Northern Hemisphere dropped below the freezing point 10 to 15 m.y. ago, thereby accounting for the late Cenozoic glacial age. Computed meridional temperature gradients for the Northern Hemisphere steepened from 20 to 40 C over the 200-m.y. period, an effect caused primarily by the high-latitude temperature decrease. The primary result of the work is that the cooling that has occurred since the warm Mesozoic period and has culminated in glaciation is explainable wholly by terrestrial processes.

Evidence that polar cap arcs occur on open field lines

International Nuclear Information System (INIS)

Gussenhoven, M.S.; Hardy, D.A.; Rich, F.J.; Mullen, E.G.; Redus, R.H.

1990-01-01

The characteristics of polar cap arc occurrence are reviewed to show that the assumption of a closed magnetospheric magnetic field topology at very high latitudes when the IMF B z is strongly northward is difficult to reconcile with a wide variety of observational and theoretical considerations. In particular, we consider the implications of observations of particle entry for high and low energy electrons, magnetic flux conservation between the near and far tail, the time sequencing in polar cap arcs events, and the hemispherical differences in polar cap arc observations. These points can be explained either by excluding the need for a major topological magnetic field change from explanations of polar cap arc dynamics, or by assuming a long-tailed magnetosphere for all IMF orientations in which magnetic field lines eventually merge with solar wind field lines in either a smooth or a patchy fashion. (author)

Interaction of cerebral hemispheres and artistic thinking

Science.gov (United States)

Nikolaenko, Nikolay N.

1998-07-01

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

Astronomy of the milky way the observer’s guide to the southern sky

CERN Document Server

Inglis, Mike

2018-01-01

This second edition of Mike Inglis's classic guide to observing the Milky Way in the Southern Hemisphere updates all of the science about the target objects with new findings from the astrophysics field. In addition, the book boasts a larger format with entirely re-drawn maps. Newly laid out for ease of use with an increased number of images in color, it updates and improves the first edition to remain the most comprehensive text on the subject. One of the wonders of the universe we live in is the Milky Way, and this book provides a wonderful tour of its highlights for amateur astronomers observing below the equator. In its pages, Southern Hemisphere observers interested in viewing our own galaxy's finest features will find every constellation that the Milky Way passes through with detailed descriptions of the many objects that can be found therein, including stars, double and multiple stars, emission nebulae, planetary nebulae, dark nebulae and supernovae remnants, open and galactic clusters, and galaxies. T...

Gamma-ray background induced in a double Ge (Li) spectrometer at ballon altitudes in the hemisphere

International Nuclear Information System (INIS)

Bui-Van, N.A.; Braga, J.; Jardim, J.O.D.; Vedrenne, G.

1986-02-01

A double coaxil Ge(li) spetrometer has been flown for the first time in December, from the Southern Hemisphere and the induced background at ceiling in the diodes was studied. During the flight, different anti-coincidence modes were operated to estimate the gamma-ray lines. The results of 511 Kev line show that the fluxes detected by the upper diode are in good agreement with previous measurements, and indicate a probable contamination of the lower diode. (Author) [pt

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

Directory of Open Access Journals (Sweden)

R. Spang

2005-01-01

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

Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE and NATHANIEL B. PALMER in the Ross Sea and Southern Oceans from 08 April 1997 to 05 May 1997 (NODC Accession 0000897)

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National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the POLAR DUKE and NATHANIEL B. PALMER. Data were...

Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE and NATHANIEL B. PALMER in the Ross Sea and Southern Oceans from 10 November 1997 to 12 December 1997 (NODC Accession 0000898)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the POLAR DUKE and NATHANIEL B. PALMER. Data were...

Surface temperatures in the polar regions from Nimbus 7 temperature humidity infrared radiometer

Science.gov (United States)

Comiso, Josefino C.

1994-01-01

Monthly surface temperatures in the Arctic and Antarctic regions have been derived from the 11.5 micrometer thermal infrared channel of the Nimbus 7 temperature humidity infrared radiometer (THIR) for a whole year in 1979 and for a winter and a summer month from 1980 through 1985. The data set shows interannual variability and provides spatial details that allow identification of temperature patterns over sea ice and ice sheet surfaces. For example, the coldest spot in the southern hemisphere is observed to be consistently in the Antarctic plateau in the southern hemisphere, while that in the northern hemisphere is usually located in Greenland, or one of three other general areas: Siberia, the central Arctic, or the Canadian Archipelago. Also, in the southern hemisphere, the amplitude of the seasonal fluctuation of ice sheet temperatures is about 3 times that of sea ice, while in the northern hemisphere, the corresponding fluctuations for the two surfaces are about the same. The main sources of error in the retrieval are cloud and other atmospheric effects. These were minimized by first choosing the highest radiance value from the set of measurements during the day taken within a 30 km by 30 km grid of each daily map. Then the difference of daily maps was taken and where the difference is greater than a certain threshold (which in this case is 12 C), the data element is deleted. Overall, the monthly maps derived from the resulting daily maps are spatially and temporally consistent, are coherent with the topograph y of the Antarctic continent and the location of the sea ice edge, and are in qualitative agreement with climatological data. Quantitatively, THIR data are in good agreement with Antarctic ice sheet surface air temperature station data with a correlation coefficient of 0.997 and a standard deviation of 2.0 C. The absolute values are not as good over the sea ice edges, but a comparison with Russian 2-m drift station temperatures shows very high correlation

Estimating abundance of the Southern Hudson Bay polar bear subpopulation using aerial surveys, 2011 and 2012

Science.gov (United States)

Obbard, Martyn E.; Middel, Kevin R.; Stapleton, Seth P.; Thibault, Isabelle; Brodeur, Vincent; Jutras, Charles

2013-01-01

The Southern Hudson Bay (SH) polar bear subpopulation occurs at the southern extent of the species’ range. Although capture-recapture studies indicate that abundance remained stable between 1986 and 2005, declines in body condition and survival were documented during the period, possibly foreshadowing a future decrease in abundance. To obtain a current estimate of abundance, we conducted a comprehensive line transect aerial survey of SH during 2011–2012. We stratified the study site by anticipated densities and flew coastal contour transects and systematically spaced inland transects in Ontario and on Akimiski Island and large offshore islands in 2011. Data were collected with double observer and distance sampling protocols. We also surveyed small islands in Hudson Bay and James Bay and flew a comprehensive transect along the Québec coastline in 2012. We observed 667 bears in Ontario and on Akimiski Island and nearby islands in 2011, and we sighted 80 bears on offshore islands during 2012. Mark-recapture distance sampling and sightresight models yielded a model-averaged estimate of 868 (SE: 177) for the 2011 study area. Our estimate of abundance for the entire SH subpopulation (951; SE: 177) suggests that abundance has remained unchanged. However, this result should be interpreted cautiously because of the methodological differences between historical studies (physical capture) and this survey. A conservative management approach is warranted given the previous increases in the duration of the ice-free season, which are predicted to continue in the future, and previously documented declines in body condition and vital rates.

The Mysterious Southern Torque

Science.gov (United States)

McDowell, M. S.

2004-05-01

Something weird happened to twist the southern hemisphere out of alignment with the northern, as evidenced by the positions of the mountain ranges of North and South America, the Atlantic MAR, and the closure of West Africa to North America - all smooth were the torque reversed. What happened, and when, and why? We identify a number of global "cracks" of almost exactly the same length and direction, with some, even more peculiarly, turning the same angle, and proceeding an equal distance in the new direction. The Emperor-Hawaiian chain, the Louisville chain and the west coast of North America, as examples, are essentially parallel. Their northerly legs follow the angle of the axis of orbital ellipse. But then they all make equal 45 degree easterly bends, to 17.5 NW, and continue on, still parallel, for very similar distances. It is the same at the north coast of South America, and the mid-section of the MAR from 46W to 12W. It is the distance from the Cameroons to Kenya, from the south end of the Red Sea to the SE Indian Ridge at the Nema Fracture zone, from west to east of the Nazca plate.What is all this? Coincidence? Seeing things? Researchers have attributed plate motion or hot spot motion or both or absolutely none, to all of the above. Geophysicists have dated the surfaces from Archean to Pleistocene by all possible scientific means, certainly no possible correlation can be made. Yet we postulate the physical reality can be demonstrated. It is so global a phenomenon that it is well beyond what a hot spot or a plate could do. Even a really tremendous impact would have trouble making such precise geometric arrangements. So what is it - perhaps the angle of rotation, or the inertia of northern hemisphere mass above the geoid? And if so, then, what changed it? It would seem that some huge imbalance occurred. Suppose the whole bottom blew out of the southern hemisphere, and the center of mass drastically altered. Suppose some unknown universal force changed our

Dust from southern Africa: rates of emission and biogeochemical properties

Science.gov (United States)

Bhattachan, A.; D'Odorico, P.; Zobeck, T. M.; Okin, G. S.; Dintwe, K.

2012-12-01

The stabilized linear dunefields in the southern Kalahari show signs of reactivation due to reduced vegetation cover owing to drought and/or overgrazing. It has been demonstrated with a laboratory dust generator that the southern Kalahari soils are good emitters of dust and that large-scale dune reactivation can potentially make the region an important dust source in the relatively low-dust Southern Hemisphere. We show that emergence of the southern Kalahari as a new dust source may affect ocean biogeochemistry as the soils are rich in soluble iron and the dust from the southern Kalahari commonly reaches the Southern Ocean. We investigate the biogeochemical properties of the fine fraction of soil from the Kalahari dunes and compare them to those of currently active dust sources such as the Makgadikgadi and the Etosha pans as well as other smaller pans in the region. Using field measurements of sediment fluxes and satellite images, we calculate the rates of dust emission from the southern Kalahari under different land cover scenarios. To assess the reversibility of dune reactivation in the southern Kalahari, we investigate the resilience of dunefield vegetation by looking at changes in soil nutrients, fine soil fractions, and seed bank in areas affected by intense denudation.

Increased Ocean Heat Convergence Into the High Latitudes With CO ₂ Doubling Enhances Polar-Amplified Warming: OCEAN HEAT AND POLAR WARMING

Energy Technology Data Exchange (ETDEWEB)

Singh, H. A. [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, U.S. DOE Office of Science, Richland WA USA; Rasch, P. J. [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, U.S. DOE Office of Science, Richland WA USA; Rose, B. E. J. [Department of Atmospheric and Environmental Sciences, State University of New York at Albany, Albany NY USA

2017-10-18

We isolate the role of the ocean in polar climate change by directly evaluating how changes in ocean dynamics with quasi-equilibrium CO2-doubling impact high-latitude climate. With CO2-doubling, the ocean heat flux convergence (OHFC) shifts poleward in winter in both hemispheres. Imposing this pattern of perturbed OHFC in a global climate model results in a poleward shift in ocean-to-atmosphere turbulent heat fluxes (both sensible and latent) and sea ice retreat; the high-latitudes warm while the midlatitudes cool, thereby amplifying polar warming. Furthermore, midlatitude cooling is propagated to the polar mid-troposphere on isentropic surfaces, augmenting the (positive) lapse rate feedback at high latitudes. These results highlight the key role played by the partitioning of meridional energy transport changes between the atmosphere and ocean in high-latitude climate change.

Hypothalamic digoxin, hemispheric chemical dominance, and eating behavior.

Science.gov (United States)

Kurup, Ravi Kumar; Kurup, Parameswara Achutha

2003-08-01

The isoprenoid pathway produces an endogenous membrane Na+-K+ ATPase inhibitor, digoxin, which can regulate neurotransmitter and amino acid transport. Digoxin synthesis and neurotransmitter patterns were assessed in eating disorders. The patterns were compared in those with right hemispheric and left hemispheric dominance. The serum HMG CoA reductase activity, RBC membrane Na+-K+ ATPase activity, serum digoxin, magnesium, tryptophan catabolites (serotonin, quinolinic acid, strychnine, and nicotine), and tyrosine catabolites (morphine, dopamine, and noradrenaline) were measured in anorexia nervosa, bulimia nervosa, right hemispheric dominant, left hemispheric dominant, and bihemispheric dominant individuals. Digoxin synthesis was increased with upregulated tryptophan catabolism and downregulated tyrosine catabolism in those with anorexia nervosa and right hemispheric chemical dominance. Digoxin synthesis was reduced with downregulated tryptophan catabolism and upregulated tyrosine catabolism in those with bulimia nervosa and left hemispheric chemical dominance. The membrane Na+-K+ ATPase activity and serum magnesium were decreased in anorexia nervosa and right hemispheric chemical dominance while they were increased in bulimia nervosa and left hemispheric chemical dominance. Hypothalamic digoxin and hemispheric chemical dominance play a central role in the regulation of eating behavior. Anorexia nervosa represents the right hemispheric chemically dominant/hyperdigoxinemic state and bulimia nervosa the left hemispheric chemically dominant/hypodigoxinemic state.

Main Ionospheric Trough and Equatorial Ionization Anomaly During Substorms With the Different UT Onset Moments

Science.gov (United States)

Klimenko, M. V.; Klimenko, V. V.; Bryukhanov, V. V.

2007-05-01

In the given work the numerical calculation results of ionospheric effects of four modeling substorms which have begun in 00, 06, 12 and 18 UT are presented. Calculations are executed on the basis of Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP), developed in WD IZMIRAN, added by the new block of calculation of electric fields in the ionosphere of the Earth for vernal equinox conditions in the minimum of solar activity. In calculations we considered superposition of magnetospheric convection electric field (at set potential differences through polar caps and field aligned currents of the second zone with taking into account of particle precipitation) and dynamo field generated by thermospheric winds without taking into account the tides. It is shown, that in the given statement of problem the substorms cause strong positive disturbances in F-region of ionosphere in night sector. Negative disturbances are much less and arise, mainly, at night in the middle and low latitudes. During substorms longitudinal extent of main ionospheric trough increases. The substorm beginning in 18 UT, causes negative disturbances in high latitudes except for a southern polar cap. Besides there is "stratification" of the main ionospheric trough. As a result in southern hemisphere the additional high-latitude trough which is absent in quiet conditions is formed. "Stratification" of the main ionospheric trough occurs in northern hemisphere at 6 hours after the beginning of the substorm. These "stratifications" are consequence non-stationary magnetospheric convection. Distinction between these events consists that "stratification" in a southern hemisphere occurs in active phase of substorm, and in northern hemisphere in recovery phase. During a substorm beginning in 00 UT, foF2 increases in all northern polar cap. Positive disturbances of foF2 in the equatorial anomaly region cause all presented substorms, except for a substorm beginning in 18 UT

Enhanced motor learning with bilateral transcranial direct current stimulation: Impact of polarity or current flow direction?

Science.gov (United States)

Naros, Georgios; Geyer, Marc; Koch, Susanne; Mayr, Lena; Ellinger, Tabea; Grimm, Florian; Gharabaghi, Alireza

2016-04-01

Bilateral transcranial direct current stimulation (TDCS) is superior to unilateral TDCS when targeting motor learning. This effect could be related to either the current flow direction or additive polarity-specific effects on each hemisphere. This sham-controlled randomized study included fifty right-handed healthy subjects in a parallel-group design who performed an exoskeleton-based motor task of the proximal left arm on three consecutive days. Prior to training, we applied either sham, right anodal (a-TDCS), left cathodal (c-TDCS), concurrent a-TDCS and c-TDCS with two independent current sources and return electrodes (double source (ds)-TDCS) or classical bilateral stimulation (bi-TDCS). Motor performance improved over time for both unilateral (a-TDCS, c-TDCS) and bilateral (bi-TDCS, ds-TDCS) TDCS montages. However, only the two bilateral paradigms led to an improvement of the final motor performance at the end of the training period as compared to the sham condition. There was no difference between the two bilateral stimulation conditions (bi-TDCS, ds-TDCS). Bilateral TDCS is more effective than unilateral stimulation due to its polarity-specific effects on each hemisphere rather than due to its current flow direction. This study is the first systematic evaluation of stimulation polarity and current flow direction of bi-hemispheric motor cortex TDCS on motor learning of proximal upper limb muscles. Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Relationship between variability of the semidiurnal tide in the Northern Hemisphere mesosphere and quasi-stationary planetary waves throughout the global middle atmosphere

Directory of Open Access Journals (Sweden)

X. Xu

2009-11-01

Full Text Available To investigate possible couplings between planetary waves and the semidiurnal tide (SDT, this work examines the statistical correlations between the SDT amplitudes observed in the Northern Hemisphere (NH mesosphere and stationary planetary wave (SPW with wavenumber S=1 (SPW1 amplitudes throughout the global stratosphere and mesosphere. The latter are derived from the Aura-MLS temperature measurements. During NH summer-fall (July–October, the mesospheric SDT amplitudes observed at Svalbard (78° N and Eureka (80° N usually do not show persistent correlations with the SPW1 amplitudes in the opposite hemisphere. Although the SDT amplitudes observed at lower latitudes (~50–70° N, especially at Saskatoon (52° N, are often shown to be highly and positively correlated with the SPW1 amplitudes in high southern latitudes, these correlations cannot be sufficiently explained as evidence for a direct physical link between the Southern Hemisphere (SH winter-early spring SPW and NH summer-early fall mesospheric SDT. This is because the migrating tide's contribution is usually dominant in the mid-high latitude (~50–70° N NH mesosphere during the local late summer-early fall (July–September. The numerical correlation is dominated by similar low-frequency variability or trends between the amplitudes of the NH SDT and SH SPW1 during the respective equinoctial transitions. In contradistinction, during NH winter (November–February, the mesospheric SDT amplitudes at northern mid-high latitudes (~50–80° N are observed to be significantly and positively correlated with the SPW1 amplitudes in the same hemisphere in most cases. Because both the SPW and migrating SDT are large in the NH during the local winter, a non-linear interaction between SPW and migrating SDT probably occurs, thus providing a global non-migrating SDT. This is consistent with observations of SDT in Antarctica that are large in summer than in winter. It is suggested that

Rapid increase in cosmogenic 14C in AD 775 measured in New Zealand kauri trees indicates short-lived increase in 14C production spanning both hemispheres

Science.gov (United States)

Güttler, D.; Adolphi, F.; Beer, J.; Bleicher, N.; Boswijk, G.; Christl, M.; Hogg, A.; Palmer, J.; Vockenhuber, C.; Wacker, L.; Wunder, J.

2015-02-01

In 2012, Miyake et al. reported a sudden and strong increase of the atmospheric radiocarbon (14C) content in Japanese cedar trees of 1.2% between AD 774 and 775. While their findings were quickly confirmed by a German oak chronology for the Northern Hemisphere (NH), the question remained if the effect was seen in both hemispheres. Here we present the first annually resolved Southern Hemisphere (SH) 14C record spanning the interval AD 760-787, using New Zealand kauri (Agathis australis) chronology wood. An almost identical distinct increase compared to Northern Hemisphere data was observed, suggesting a cosmic event with globally uniform impact as a potential cause for the increase. Deploying a carbon cycle box model a worldwide averaged net 14C production of 2.2 ×108 14C atoms cm-2 was estimated, which is 3.7 times higher than the average annual 14C production. The immediate appearance of the event in tree rings on both hemispheres suggests a short duration event of significantly less than 1 yr.

IMF By associated interhemispheric asymmetries in ionospheric convection and field-aligned currents

Science.gov (United States)

Kunduri, B.; Baker, J.; Ruohoniemi, J. M.; Clausen, L.; Ribeiro, A.

2012-12-01

The solar wind-magnetosphere interaction plays an important role in controlling the dynamics of ionospheric convection. It is widely known that the By component of IMF generates asymmetries in ionospheric convection between the northern and southern polar caps. Some studies show that IMF By-generated electric field penetrates into the closed magnetosphere producing differences in the high latitude ionospheric convection between hemispheres. The differences in convection were attributed to field-aligned potential drop between hemispheres resulting in flow of interhemispheric field aligned currents. In the current paper we present interhemispheric observations of high latitude ionospheric convection on closed field lines in the noon-dusk sector. The observations reveal that the convection is stronger in the northern (southern) hemisphere when IMF By is positive (negative) irrespective of season. The inter-hemispheric differences can be attributed to the flow of interhemispheric field aligned currents which support the existence of oppositely-directed zonal plasma flows in the closed field line regions, suppressing the convection in one hemisphere and aiding it in the other. We estimate the strength of these currents, analyze their characteristics and identify the various factors such as magnetic local time, magnetic latitude and ionospheric conductivity that impact them.

Prevalence and spatio-temporal variation of an alopecia syndrome in polar bears (Ursus maritimus) of the southern Beaufort Sea

Science.gov (United States)

Atwood, Todd C.; Peacock, Elizabeth; Burek, K.A.; Shearn-Bochsler, Valerie I.; Bodenstein, Barbara L.; Beckmen, Kimberlee B.; Durner, George M.

2015-01-01

Alopecia (hair loss) has been observed in several marine mammal species and has potential energetic consequences for sustaining a normal core body temperature, especially for Arctic marine mammals routinely exposed to harsh environmental conditions. Polar bears (Ursus maritimus) rely on a thick layer of adipose tissue and a dense pelage to ameliorate convective heat loss while moving between sea ice and open water. From 1998 to 2012, we observed an alopecia syndrome in polar bears from the southern Beaufort Sea of Alaska that presented as bilaterally asymmetrical loss of guard hairs and thinning of the undercoat around the head, neck, and shoulders, which, in severe cases, was accompanied by exudation and crusted skin lesions. Alopecia was observed in 49 (3.45%) of the bears sampled during 1,421 captures, and the apparent prevalence varied by years with peaks occurring in 1999 (16%) and 2012 (28%). The probability that a bear had alopecia was greatest for subadults and for bears captured in the Prudhoe Bay region, and alopecic individuals had a lower body condition score than unaffected individuals. The cause of the syndrome remains unknown and future work should focus on identifying the causative agent and potential effects on population vital rates.

Prevalence and spatio-temporal variation of an alopecia syndrome in polar bears (Ursus maritimus) of the southern Beaufort Sea.

Science.gov (United States)

Atwood, Todd; Peacock, Elizabeth; Burek-Huntington, Kathy; Shearn-Bochsler, Valerie; Bodenstein, Barbara; Beckmen, Kimberlee; Durner, George

2015-01-01

Alopecia (hair loss) has been observed in several marine mammal species and has potential energetic consequences for sustaining a normal core body temperature, especially for Arctic marine mammals routinely exposed to harsh environmental conditions. Polar bears (Ursus maritimus) rely on a thick layer of adipose tissue and a dense pelage to ameliorate convective heat loss while moving between sea ice and open water. From 1998 to 2012, we observed an alopecia syndrome in polar bears from the southern Beaufort Sea of Alaska that presented as bilaterally asymmetrical loss of guard hairs and thinning of the undercoat around the head, neck, and shoulders, which, in severe cases, was accompanied by exudation and crusted skin lesions. Alopecia was observed in 49 (3.45%) of the bears sampled during 1,421 captures, and the apparent prevalence varied by years with peaks occurring in 1999 (16%) and 2012 (28%). The probability that a bear had alopecia was greatest for subadults and for bears captured in the Prudhoe Bay region, and alopecic individuals had a lower body condition score than unaffected individuals. The cause of the syndrome remains unknown and future work should focus on identifying the causative agent and potential effects on population vital rates.

Testing the Language of German Cerebral Palsy Patients with Right Hemispheric Language Organization after Early Left Hemispheric Damage

Science.gov (United States)

Schwilling, Eleonore; Krageloh-Mann, Ingeborg; Konietzko, Andreas; Winkler, Susanne; Lidzba, Karen

2012-01-01

Language functions are generally represented in the left cerebral hemisphere. After early (prenatally acquired or perinatally acquired) left hemispheric brain damage language functions may be salvaged by reorganization into the right hemisphere. This is different from brain lesions acquired in adulthood which normally lead to aphasia. Right…

Hemispheric Asymmetry in Transition from Equatorial Plasma Bubble to Blob as Deduced from 630.0 nm Airglow Observations at Low Latitudes

Science.gov (United States)

Park, Jaeheung; Martinis, Carlos R.; Luehr, Hermann; Pfaff, Robert F.; Kwak, Young-Sil

2016-01-01

Transitions from depletions to enhancements of 630.0 nm nighttime airglow have been observed at Arecibo. Numerical simulations by Krall et al. (2009) predicted that they should occur only in one hemisphere, which has not yet been confirmed observationally. In this study we investigate the hemispheric conjugacy of the depletion-to-enhancement transition using multiple instruments. We focus on one event observed in the American longitude sector on 22 December 2014: 630.0 nm airglow depletions evolved into enhancements in the Northern Hemisphere while the evolution did not occur in the conjugate location in the Southern Hemisphere. Concurrent plasma density measured by low Earth orbit (LEO) satellites and 777.4 nm airglow images support that the depletions and enhancements of 630.0 nm night time airglow reflect plasma density decreases and increases (blobs), respectively. Characteristics of the airglow depletions, in the context of the LEO satellite data, further suggest that the plasma density depletion deduced from the airglow data represents equatorial plasma bubbles (EPBs) rather than medium-scale traveling ionospheric disturbances from midlatitudes. Hence, the event in this study can be interpreted as EPB-to-blob transition.

Strong asymmetry of hemispheric climates during MIS-13 inferred from correlating China loess and Antarctica ice records

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Z. T. Guo

2009-02-01

Full Text Available We correlate the China loess and Antarctica ice records to address the inter-hemispheric climate link over the past 800 ka. The results show a broad coupling between Asian and Antarctic climates at the glacial-interglacial scale. However, a number of decoupled aspects are revealed, among which marine isotope stage (MIS 13 exhibits a strong anomaly compared with the other interglacials. It is characterized by unusually positive benthic oxygen (δ¹⁸O and carbon isotope (δ¹³C values in the world oceans, cooler Antarctic temperature, lower summer sea surface temperature in the South Atlantic, lower CO₂ and CH₄ concentrations, but by extremely strong Asian, Indian and African summer monsoons, weakest Asian winter monsoon, and lowest Asian dust and iron fluxes. Pervasive warm conditions were also evidenced by the records from northern high-latitude regions. These consistently indicate a warmer Northern Hemisphere and a cooler Southern Hemisphere, and hence a strong asymmetry of hemispheric climates during MIS-13. Similar anomalies of lesser extents also occurred during MIS-11 and MIS-5e. Thus, MIS-13 provides a case that the Northern Hemisphere experienced a substantial warming under relatively low concentrations of greenhouse gases. It suggests that the global climate system possesses a natural variability that is not predictable from the simple response of northern summer insolation and atmospheric CO₂ changes. During MIS-13, both hemispheres responded in different ways leading to anomalous continental, marine and atmospheric conditions at the global scale. The correlations also suggest that the marine δ¹⁸O record is not always a reliable indicator of the northern ice-volume changes, and that the asymmetry of hemispheric climates is one of the prominent factors controlling the strength of Asian, Indian and African monsoon circulations, most likely through modulating the position of

Atypical hemispheric dominance for attention: functional MRI topography.

Science.gov (United States)

Flöel, Agnes; Jansen, Andreas; Deppe, Michael; Kanowski, Martin; Konrad, Carsten; Sommer, Jens; Knecht, Stefan

2005-09-01

The right hemisphere is predominantly involved in tasks associated with spatial attention. However, left hemispheric dominance for spatial attention can be found in healthy individuals, and both spatial attention and language can be lateralized to the same hemisphere. Little is known about the underlying regional distribution of neural activation in these 'atypical' individuals. Previously a large number of healthy subjects were screened for hemispheric dominance of visuospatial attention and language, using functional Doppler ultrasonography. From this group, subjects were chosen who were 'atypical' for hemispheric dominance of visuospatial attention and language, and their pattern of brain activation was studied with functional magnetic resonance imaging during a task probing spatial attention. Right-handed subjects with the 'typical' pattern of brain organization served as control subjects. It was found that subjects with an inverted lateralization of language and spatial attention (language right, attention left) recruited left-hemispheric areas in the attention task, homotopic to those recruited by control subjects in the right hemisphere. Subjects with lateralization of both language and attention to the right hemisphere activated an attentional network in the right hemisphere that was comparable to control subjects. The present findings suggest that not the hemispheric side, but the intrahemispheric pattern of activation is the distinct feature for the neural processes underlying language and attention.

Simulations of the general circulation of the Martian atmosphere. I - Polar processes

Science.gov (United States)

Pollack, James B.; Haberle, Robert M.; Schaeffer, James; Lee, Hilda

1990-01-01

Numerical simulations of the Martian atmosphere general circulation are carried out for 50 simulated days, using a three-dimensional model, based on the primitive equations of meteorology, which incorporated the radiative effects of atmospheric dust on solar and thermal radiation. A large number of numerical experiments were conducted for alternative choices of seasonal date and dust optical depth. It was found that, as the dust content of the winter polar region increased, the rate of atmospheric CO2 condensation increased sharply. It is shown that the strong seasonal variation in the atmospheric dust content observed might cause a number of hemispheric asymmetries. These asymmetries include the greater prevalence of polar hoods in the northern polar region during winter, the lower albedo of the northern polar cap during spring, and the total dissipation of the northern CO2 ice cap during the warmer seasons.

The Martian polar caps: Stability and water transport at low obliquities

Science.gov (United States)

Henderson, B. G.; Jakosky, B. M.

1992-01-01

The seasonal cycle of water on Mars is regulated by the two polar caps. In the winter hemisphere, the seasonal CO2 deposits at a temperature near 150 K acts as a cold trap to remove water vapor from the atmosphere. When summer returns, water is pumped back into the atmosphere by a number of mechanisms, including release from the receding CO2 frost, diffusion from the polar regolith, and sublimation from a water-ice residual cap. These processes drive an exchange of water vapor between the polar caps that helps shape the Martian climate. Thus, understanding the behavior of the polar caps is important for interpreting the Martian climate both now and at other epochs. Mars' obliquity undergoes large variations over large time scales. As the obliquity decreases, the poles receive less solar energy so that more CO2 condenses from the atmosphere onto the poles. It has been suggested that permanent CO2 condenses from the atmosphere onto the poles. It has been suggested that permanent CO2 caps might form at the poles in response to a feedback mechanism existing between the polar cap albedo, the CO2 pressure, and the dust storm frequency. The year-round presence of the CO2 deposits would effectively dry out the atmosphere, while diffusion of water from the regolith would be the only source of water vapor to the atmosphere. We have reviewed the CO2 balance at low obliquity taking into account the asymmetries which make the north and south hemispheres different. Our analysis linked with a numerical model of the polar caps leads us to believe that one summertime cap will always lose its CO2 cover during a Martian year, although we cannot predict which cap this will be. We conclude that significant amounts of water vapor will sublime from the exposed cap during summer, and the Martian atmosphere will support an active water cycle even at low obliquity.

Hypothalamic digoxin, hemispheric chemical dominance and sarcoidosis.

Science.gov (United States)

Ravi Kumar, A; Kurup, Parameswara Achutha

2004-06-01

The isoprenoid pathway produces three key metabolites: endogenous digoxin (membrane sodium-potassium ATPase inhibitor, immunomodulator and regulator of neurotransmitter/amino acid transport), dolichol (regulates N-glycosylation of proteins) and ubiquinone (free radical scavenger). The role of the isoprenoid pathway in the pathogenesis of sarcoidosis in relation to hemispheric dominance was studied. The isoprenoid pathway-related cascade was assessed in patients with systemic sarcoidosis with pulmonary involvement. The pathway was also assessed in patients with right hemispheric, left hemispheric and bihemispheric dominance for comparison to find out the role of hemispheric dominance in the pathogenesis of sarcoidosis. In patients with sarcoidosis there was elevated digoxin synthesis, increased dolichol and glycoconjugate levels and low ubiquinone and elevated free radical levels. There was also an increase in tryptophan catabolites and a reduction in tyrosine catabolites. There was an increase in the cholesterol:phospholipid ratio and a reduction in the glycoconjugate level of red blood cell (RBC) membrane in this group of patients. The same biochemical patterns were obtained in individuals with right hemispheric dominance. In individuals with left hemispheric dominance the patterns were reversed. Endogenous digoxin, by activating the calcineurin signal transduction pathway of T cells, can contribute to immune activation in sarcoidosis. An altered glycoconjugate metabolism can lead to the generation of endogenous self-glycoprotein antigens in the lung as well as other tissues. Increased free radical generation can also lead to immune activation. The role of a dysfunctional isoprenoid pathway and endogenous digoxin in the pathogenesis of sarcoidosis in relation to right hemispheric chemical dominance is discussed. All the patients with sarcoidosis were right-handed/left hemispheric dominant according to the dichotic listening test, but their biochemical patterns

Onsite-effects of dual-hemisphere versus conventional single-hemisphere transcranial direct current stimulation

OpenAIRE

Kwon, Yong Hyun; Jang, Sung Ho

2012-01-01

We performed functional MRI examinations in six right-handed healthy subjects. During functional MRI scanning, transcranial direct current stimulation was delivered with the anode over the right primary sensorimotor cortex and the cathode over the left primary sensorimotor cortex using dual-hemispheric transcranial direct current stimulation. This was compared to a cathode over the left supraorbital area using conventional single-hemispheric transcranial direct current stimulation. Voxel coun...

Distribution of planktonic biogenic carbonate organisms in the Southern Ocean south of Australia: a baseline for ocean acidification impact assessment

Science.gov (United States)

Trull, Thomas W.; Passmore, Abraham; Davies, Diana M.; Smit, Tim; Berry, Kate; Tilbrook, Bronte

2018-01-01

The Southern Ocean provides a vital service by absorbing about one-sixth of humankind's annual emissions of CO2. This comes with a cost - an increase in ocean acidity that is expected to have negative impacts on ocean ecosystems. The reduced ability of phytoplankton and zooplankton to precipitate carbonate shells is a clearly identified risk. The impact depends on the significance of these organisms in Southern Ocean ecosystems, but there is very little information on their abundance or distribution. To quantify their presence, we used coulometric measurement of particulate inorganic carbonate (PIC) on particles filtered from surface seawater into two size fractions: 50-1000 µm to capture foraminifera (the most important biogenic carbonate-forming zooplankton) and 1-50 µm to capture coccolithophores (the most important biogenic carbonate-forming phytoplankton). Ancillary measurements of biogenic silica (BSi) and particulate organic carbon (POC) provided context, as estimates of the biomass of diatoms (the highest biomass phytoplankton in polar waters) and total microbial biomass, respectively. Results for nine transects from Australia to Antarctica in 2008-2015 showed low levels of PIC compared to Northern Hemisphere polar waters. Coccolithophores slightly exceeded the biomass of diatoms in subantarctic waters, but their abundance decreased more than 30-fold poleward, while diatom abundances increased, so that on a molar basis PIC was only 1 % of BSi in Antarctic waters. This limited importance of coccolithophores in the Southern Ocean is further emphasized in terms of their associated POC, representing less than 1 % of total POC in Antarctic waters and less than 10 % in subantarctic waters. NASA satellite ocean-colour-based PIC estimates were in reasonable agreement with the shipboard results in subantarctic waters but greatly overestimated PIC in Antarctic waters. Contrastingly, the NASA Ocean Biogeochemical Model (NOBM) shows coccolithophores as overly

Distribution of planktonic biogenic carbonate organisms in the Southern Ocean south of Australia: a baseline for ocean acidification impact assessment

Directory of Open Access Journals (Sweden)

T. W. Trull

2018-01-01

Full Text Available The Southern Ocean provides a vital service by absorbing about one-sixth of humankind's annual emissions of CO2. This comes with a cost – an increase in ocean acidity that is expected to have negative impacts on ocean ecosystems. The reduced ability of phytoplankton and zooplankton to precipitate carbonate shells is a clearly identified risk. The impact depends on the significance of these organisms in Southern Ocean ecosystems, but there is very little information on their abundance or distribution. To quantify their presence, we used coulometric measurement of particulate inorganic carbonate (PIC on particles filtered from surface seawater into two size fractions: 50–1000 µm to capture foraminifera (the most important biogenic carbonate-forming zooplankton and 1–50 µm to capture coccolithophores (the most important biogenic carbonate-forming phytoplankton. Ancillary measurements of biogenic silica (BSi and particulate organic carbon (POC provided context, as estimates of the biomass of diatoms (the highest biomass phytoplankton in polar waters and total microbial biomass, respectively. Results for nine transects from Australia to Antarctica in 2008–2015 showed low levels of PIC compared to Northern Hemisphere polar waters. Coccolithophores slightly exceeded the biomass of diatoms in subantarctic waters, but their abundance decreased more than 30-fold poleward, while diatom abundances increased, so that on a molar basis PIC was only 1 % of BSi in Antarctic waters. This limited importance of coccolithophores in the Southern Ocean is further emphasized in terms of their associated POC, representing less than 1 % of total POC in Antarctic waters and less than 10 % in subantarctic waters. NASA satellite ocean-colour-based PIC estimates were in reasonable agreement with the shipboard results in subantarctic waters but greatly overestimated PIC in Antarctic waters. Contrastingly, the NASA Ocean Biogeochemical Model (NOBM shows

Sirenophila ovis-atra a new species of maritime Teloschistaceae from the Southern Hemisphere

DEFF Research Database (Denmark)

Søchting, Ulrik; Søgaard, Majbrit Zeuthen; Sancho, Leopoldo G.

2016-01-01

A new species, Sirenophila ovis-atra is described from maritime rocks of southern Patagonia, the Falkland Islands and Macquarie Island, where it grows in the upper part of the black ‘Verrucaria-zone’, most often on members of the genus Hydropunctaria. It is so far the only known species of Sireno......A new species, Sirenophila ovis-atra is described from maritime rocks of southern Patagonia, the Falkland Islands and Macquarie Island, where it grows in the upper part of the black ‘Verrucaria-zone’, most often on members of the genus Hydropunctaria. It is so far the only known species...

Northern Hemisphere moisture variability during the Last Glacial period

Science.gov (United States)

Asmerom, Y.; Polyak, V. J.; Lachniet, M. S.

2013-12-01

It was previously shown that large oxygen isotope variability related to changing moisture sources in the southwestern United States (SW) match the Greenland ice core temperature record. The variations were attributed to changes in the ratio of winter to summer precipitation delivered to the SW, with lighter winter δ18O values compared to summer monsoon rainfall, due to meridonial shifts in the position of the polar jet stream, which directs winter storm tracks. Cold stadial δ18O excursions are associated with strongly negative values, while interstadials have higher than average δ18O values. Although these data documented moisture source variability to the SW, the question of effective moisture variability remains unanswered. Here we present new high-resolution δ18O and δ13C isotopic data from a precisely dated speleothem, FS-AH1, from Fort Stanton Cave, New Mexico USA. The sample grew continuously between 47.6 and 11.1 kyr. The new chronology is more precise than previous work due to high sample growth rate, new gains in efficiency provided by our upgraded Neptune MC-ICPMS and new more precise determinations of the half-lives of 230Th and 234U. The FS-AH1 δ18O and the Greenland δ18O data (on the GICC05 time scale) show a remarkable match, both with respect to stadials/interstadial amplitudes and variability, and in the overall long-term trend. Our interpretation of the δ18O data remains the same, an indicator of moisture source variability. The δ18O and δ13C isotopic data show no correlation (R2 effective moisture in the soil zone overlying the cave, with low δ13C attributed to high soil productivity, high effective moisture, and wet conditions. The stadial and interstadial events are expressed mutely, if at all, in the δ13C data, while the secular variation follows the change in Northern Hemisphere summer insolation (insolation), similar to other Northern Hemisphere data, such as the strength of the East Asian summer monsoon as recorded in the Hulu

Right Hemisphere Dominance in Visual Statistical Learning

Science.gov (United States)

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

2011-01-01

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

The Southern Westerlies during the last glacial maximum in PMIP2 simulations

Energy Technology Data Exchange (ETDEWEB)

Rojas, Maisa [University of Chile Blanco Encalada, Department of Geophysics, Santiago (Chile); Institute of Ecology and Biodiversity, Santiago (Chile); Moreno, Patricio [Institute of Ecology and Biodiversity, Santiago (Chile); University of Chile, Department of Ecological Sciences, Santiago (Chile); Kageyama, Masa [UMR CEA-CNRS-UVSQ 1572, CE Saclay, LSCE/IPSL, Gif-sur-Yvette Cedex (France); Crucifix, Michel [Universite Catholique de Louvain, Institut d' Astronomie et de Geophysique G. Lemaitre, Louvain-la-Neuve (Belgium); Hewitt, Chris [Met Office, Exeter, Devon (United Kingdom); Abe-Ouchi, Ayako [The University of Tokyo, Center for Climate System Research, Kashiwa (Japan); Ohgaito, Rumi [Japan Agency for Marine-Earth Science and Technology, Frontier Research Center for Global Change, Yokohama, Kanagawa (Japan); Brady, Esther C. [Climate Change Research National Center for Atmospheric Research, 1850 Table Mesa Drive, P.O. Box 3000, Boulder, CO (United States); Hope, Pandora [Bureau of Meteorology Research Centre, GPO Box 1289, Melbourne, VIC (Australia)

2009-03-15

The Southern Hemisphere westerly winds are an important component of the climate system at hemispheric and global scales. Variations in their intensity and latitudinal position through an ice-age cycle have been proposed as important drivers of global climate change due to their influence on deep-ocean circulation and changes in atmospheric CO{sub 2}. The position, intensity, and associated climatology of the southern westerlies during the last glacial maximum (LGM), however, is still poorly understood from empirical and modelling standpoints. Here we analyse the behaviour of the southern westerlies during the LGM using four coupled ocean-atmosphere simulations carried out by the Palaeoclimate Modelling Intercomparison Project Phase 2 (PMIP2). We analysed the atmospheric circulation by direct inspection of the winds and by using a cyclone tracking software to indicate storm tracks. The models suggest that changes were most significant during winter and over the Pacific ocean. For this season and region, three out four models indicate decreased wind intensities at the near surface as well as in the upper troposphere. Although the LGM atmosphere is colder and the equator to pole surface temperature gradient generally increases, the tropospheric temperature gradients actually decrease, explaining the weaker circulation. We evaluated the atmospheric influence on the Southern Ocean by examining the effect of wind stress on the Ekman pumping. Again, three of the models indicate decreased upwelling in a latitudinal band over the Southern Ocean. All models indicate a drier LGM than at present with a clear decrease in precipitation south of 40 S over the oceans. We identify important differences in precipitation anomalies over the land masses at regional scale, including a drier climate over New Zealand and wetter over NW Patagonia. (orig.)

Polar Frontal Migration in the Warm Late Pliocene: Diatom Evidence from The Wilkes Land Margin, East Antarctic

Science.gov (United States)

Riesselman, C. R.; Taylor-Silva, B.; Patterson, M. O.

2017-12-01

The Late Pliocene is the most recent interval in Earth's history to sustain global temperatures within the range of warming predicted for the 21st century. Published global reconstructions and climate models find an average +2° C summer SST anomaly relative to modern during the 3.3-3.0 Ma PRISM interval, when atmospheric CO2 concentrations last reached 400 ppm. Here, we present a new diatom-based reconstruction of Pliocene interglacial sea surface conditions from IODP Site U1361, on the East Antarctic continental rise. U1361 biogenic silica concentrations document the alternation of diatom-rich and diatom-poor lithologies; we interpret 8 diatom-rich mudstones within this sequence to record interglacial periods between 3.8 and 2.8 Ma. We find that open-ocean conditions in the mid-Pliocene became increasingly influenced by sea ice from 3.6-3.2 Ma, prior to the onset of Northern Hemisphere glaciation. This cooling trend was interrupted by a temporary southward migration of the Antarctic Polar Front, bathing U1361 in warmer subantarctic waters during a single interglacial, marine isotope stage KM3 (3.17-3.15 Ma), that corresponds to a maximum in summer insolation at 65°S. Following this interval of transient warmth, interglacial periods became progressively cooler starting at 3 Ma, coinciding with a transition from obliquity to precession as the dominant orbital driver of Antarctic ice sheet fluctuations. Building on the identification of a single outlier interglacial within the PRISM interval, we have revisited older reconstructions to explore the response of the Southern Ocean/cryosphere system to peak late Pliocene warmth. By applying a modern chronostratigraphic framework to those low-resolution "mean interglacial" records, we identify the same frontal migration in 4 other cores in the Pacific sector of the Southern Ocean, documenting a major migration of the polar front during a key interval of warm climate. These new results suggest that increased summer

Late Pliocene Northern Hemisphere glaciations: The continental and marine responses in the central Mediterranean

Science.gov (United States)

Nebout, Nathalie Combourieu; Grazzini, Colette Vergnaud

Detailed pollen analyses and oxygen isotope records of three foraminiferal species, Globigerina bulloides, Uvigerina peregrina and Cibicides pachyderma, from the Semaforo and Vrica composite sections (Crotone, southern Italy) have been compared to the global climatic changes depicted by late Pliocene-early Pleistocene foraminiferal δ 18O records of Site 607 in the North Atlantic, and Hole 653A in the Tyrrhenian basin, West Mediterranean. Major overturns in the mid-altitude vegetation are shown near isotopic stages 82, 60, 58 and 50, at about 2.03 Ma, 1.6 Ma and 1.37 Ma according to the Raymo et al. (1989) and Ruddiman et al. (1989) timescales. At the same dates, glacial 18O maxima either became higher or display step increases in the western Mediterranean or in the open ocean as well. This suggests that size increases of Northern Hemisphere ice sheets were the driving factor for regional or local marine and continental environmental changes within the Mediterranean basin. Near isotopic stages 62-60, close to the conventional Plio-Pleistocene boundary, the climatic conditions severed enough within the Mediterranean basin to modify the continental environment, as depicted by a sudden increase of Artemisia percentages, while the first significant southward migration of the North Polar Front may have been recorded by an influx of left coiling Neogloboquadrina pachyderma in the central Mediterranean. It also appears that 'Boreal Guests' entered the Mediterranean during phases of 18O enrichment of foraminiferal calcite. There does not seem to be any discrepancy between the climatic concept of the Pliocene-Pleistocene boundary and its chronostratigraphic definition.

The Southern Ocean's role in ocean circulation and climate transients

Science.gov (United States)

Thompson, A. F.; Stewart, A.; Hines, S.; Adkins, J. F.

2017-12-01

The ventilation of deep and intermediate density classes at the surface of the Southern Ocean impacts water mass modification and the air-sea exchange of heat and trace gases, which in turn influences the global overturning circulation and Earth's climate. Zonal variability occurs along the Antarctic Circumpolar Current and the Antarctic margins related to flow-topography interactions, variations in surface boundary conditions, and exchange with northern basins. Information about these zonal variations, and their impact on mass and tracer transport, are suppressed when the overturning is depicted as a two-dimensional (depth-latitude) streamfunction. Here we present an idealized, multi-basin, time-dependent circulation model that applies residual circulation theory in the Southern Ocean and allows for zonal water mass transfer between different ocean basins. This model efficiently determines the temporal evolution of the ocean's stratification, ventilation and overturning strength in response to perturbations in the external forcing. With this model we explore the dynamics that lead to transitions in the circulation structure between multiple, isolated cells and a three-dimensional, "figure-of-eight," circulation in which traditional upper and lower cells are interleaved. The transient model is also used to support a mechanistic explanation of the hemispheric asymmetry and phase lag associated with Dansgaard-Oeschger (DO) events during the last glacial period. In particular, the 200 year lag in southern hemisphere temperatures, following a perturbation in North Atlantic deep water formation, depends critically on the migration of Southern Ocean isopycnal outcropping in response to low-latitude stratification changes. Our results provide a self-consistent dynamical framework to explain various ocean overturning transitions that have occurred over the Earth's last 100,000 years, and motivate an exploration of these mechanisms in more sophisticated climate models.

Factors Influencing Right Hemisphere Engagement During Metaphor Comprehension

Science.gov (United States)

Diaz, Michele T.; Eppes, Anna

2018-01-01

Although the left hemisphere is critical for language, clinical, behavioral, and neuroimaging research suggest that the right hemisphere also contributes to language comprehension. In particular, research has suggested that figurative language may be one type of language that preferentially engages right hemisphere regions. However, there is disagreement about whether these regions within the right hemisphere are sensitive to figurative language per se or to other factors that co-vary with figurativeness. In this article, we will review the neuroimaging literature on figurative language processing, focusing on metaphors, within the context of several theoretical perspectives that have been proposed about hemispheric function in language. Then we will examine three factors that may influence right hemisphere engagement: novelty, task difficulty, and context. We propose that factors that increase integration demands drive right hemisphere involvement in language processing, and that such recruitment is not limited to figurative language. PMID:29643825

Hypothalamic digoxin, hemispheric chemical dominance, and sleep.

Science.gov (United States)

Kurup, Ravi Kumar; Kurup, Parameswara Achutha

2003-04-01

The isoprenoid path way produces endogenous digoxin, a substance that can regulate neurotransmitter and amino acid transport. Digoxin synthesis and neurotransmitter patterns were assessed in individuals with chronic insomnia. The patterns were compared in those with right hemispheric and left hemispheric dominance. The activity of HMG GoA reductase and serum levels of digoxin, magnesium, tryptophan catabolites, and tyrosine catabolites were measured in individuals with chronic insomnia and in individuals with differing hemispheric dominance. Digoxin synthesis was increased with upregulated tryptophan catabolism (increased levels of serotonin, strychnine, and nicotine), and downregulated tyrosine catabolism (decreased levels of dopamine, noradrenaline, and morphine) in those with chronic insomnia and right hemispheric chemical dominance. Digoxin synthesis was reduced with downregulated tryptophan catabolism (decreased levels of serotonin, strychnine, and nicotine) and upregulated tyrosine catabolism (increased levels of dopamine, noradrenaline, and morphine) in those with normal sleep patterns and left hemispheric chemical dominance. Hypothalamic digoxin plays a central role in the regulation of sleep behavior. Hemispheric chemical dominance in relation to digoxin status is also crucial.

Hypothalamic digoxin, hemispheric chemical dominance, and spirituality.

Science.gov (United States)

Kurup, Ravi Kumar; Kurup, Parameswara Achutha

2003-03-01

The isoprenoid pathway was assessed in atheistic and spiritually inclined individuals. The pathway was also assessed in individuals with differing hemispheric dominance to assess whether hemispheric dominance has a correlation with spiritual and atheistic tendency. HMG CoA reductase activity, serum digoxin, RBC membrane Na(+)-K+ ATPase activity, serum magnesium, and tyrosine/tryptophan catabolic patterns were assessed in spiritual/atheistic individuals and in those differing hemispheric dominance. In spiritually-inclined individuals, there was increased digoxin synthesis, decreased membrane Na(+)-K+ ATPase activity, increased tryptophan catabolites (serotonin, quinolinic acid, and nicotine), and decreased tyrosine catabolites (dopamine, noradrenaline, and morphine). The pattern in spiritually-inclined individuals correlated with right hemispheric chemical dominance. In atheistic individuals there was decreased digoxin synthesis, increased membrane Na(+)-K+ ATPase activity, decreased tryptophan catabolities (serotonin, quinolinic acid, and nicotine), and increased tyrosine catabolites (dopamine, noradrenaline, and morphine). This pattern in atheistic individuals correlated with that obtained in left hemispheric chemical dominance. Hemispheric chemical dominance and hypothalamic digoxin could regulate the predisposition to spirituality or atheism.

Polar cap electric field structures with a northward interplanetary magnetic field

International Nuclear Information System (INIS)

Burke, W.J.; Kelley, M.C.; Sagalyn, R.C.; Smiddy, M.; Lai, S.T.

1979-01-01

Polar cap electric fields patterns are presented from times when the S3-2 Satellite was near the dawn-dusk meridian and IMF data were available. With B/sub z/> or =0.7γ, two characteristic types of electric field patterns were measured in the polar cap. In the sunlit polar cap the convection pattern usually consisted of four cells. Two of the cells were confined to the polar cap with sunward convection in the central portion of the cap. The other pair of cells were marked by anti-sunward flow along the flanks of the polar cap and by sunward flow in the auroral oval. These observations are interpreted in terms of a model for magnetic merging at the poleward wall of the dayside polar cusp. The sunward flow in the auroral zone is not predicted by the magnetic model and may be due to a viscous interaction between the solar wind and and magnetosphere. The second type, which was observed in some of the summer hemisphere passes and all of the winter ones, was characterized by an electric field pattern which was very turbulent, and may be related to inhomogeneous merging

Hemispheric specialization in dogs for processing different acoustic stimuli.

Directory of Open Access Journals (Sweden)

Marcello Siniscalchi

Full Text Available Considerable experimental evidence shows that functional cerebral asymmetries are widespread in animals. Activity of the right cerebral hemisphere has been associated with responses to novel stimuli and the expression of intense emotions, such as aggression, escape behaviour and fear. The left hemisphere uses learned patterns and responds to familiar stimuli. Although such lateralization has been studied mainly for visual responses, there is evidence in primates that auditory perception is lateralized and that vocal communication depends on differential processing by the hemispheres. The aim of the present work was to investigate whether dogs use different hemispheres to process different acoustic stimuli by presenting them with playbacks of a thunderstorm and their species-typical vocalizations. The results revealed that dogs usually process their species-typical vocalizations using the left hemisphere and the thunderstorm sounds using the right hemisphere. Nevertheless, conspecific vocalizations are not always processed by the left hemisphere, since the right hemisphere is used for processing vocalizations when they elicit intense emotion, including fear. These findings suggest that the specialisation of the left hemisphere for intraspecific communication is more ancient that previously thought, and so is specialisation of the right hemisphere for intense emotions.

A novel apparatus for testing binocular function using the 'CyberDome' three-dimensional hemispherical visual display system.

Science.gov (United States)

Handa, T; Ishikawa, H; Shimizu, K; Kawamura, R; Nakayama, H; Sawada, K

2009-11-01

Virtual reality has recently been highlighted as a promising medium for visual presentation and entertainment. A novel apparatus for testing binocular visual function using a hemispherical visual display system, 'CyberDome', has been developed and tested. Subjects comprised 40 volunteers (mean age, 21.63 years) with corrected visual acuity of -0.08 (LogMAR) or better, and stereoacuity better than 100 s of arc on the Titmus stereo test. Subjects were able to experience visual perception like being surrounded by visual images, a feature of the 'CyberDome' hemispherical visual display system. Visual images to the right and left eyes were projected and superimposed on the dome screen, allowing test images to be seen independently by each eye using polarizing glasses. The hemispherical visual display was 1.4 m in diameter. Three test parameters were evaluated: simultaneous perception (subjective angle of strabismus), motor fusion amplitude (convergence and divergence), and stereopsis (binocular disparity at 1260, 840, and 420 s of arc). Testing was performed in volunteer subjects with normal binocular vision, and results were compared with those using a major amblyoscope. Subjective angle of strabismus and motor fusion amplitude showed a significant correlation between our test and the major amblyoscope. All subjects could perceive the stereoscopic target with a binocular disparity of 480 s of arc. Our novel apparatus using the CyberDome, a hemispherical visual display system, was able to quantitatively evaluate binocular function. This apparatus offers clinical promise in the evaluation of binocular function.

Statistical Study of the Magnetic Field Orientation in Solar Filaments

Science.gov (United States)

Hanaoka, Yoichiro; Sakurai, Takashi

2017-12-01

We have carried out a statistical study of the average orientation of the magnetic field in solar filaments with respect to their axes for more than 400 samples, based on data taken with daily full-Sun, full-Stokes spectropolarimetric observations using the He I 1083.0 nm line. The major part of the samples are the filaments in the quiet areas, but those in the active areas are included as well. The average orientation of the magnetic field in filaments shows a systematic property depending on the hemisphere; the direction of the magnetic field in filaments in the northern (southern) hemisphere mostly deviates clockwise (counterclockwise) from their axes, which run along the magnetic polarity inversion line. The deviation angles of the magnetic field from the axes are concentrated between 10° and 30°. This hemispheric pattern is consistent with that revealed for chirality of filament barbs, filament channels, and for other solar features found to possess chirality. For some filaments, it was confirmed that their magnetic field direction is locally parallel to their structure seen in Hα images. Our results for the first time confirmed this hemispheric pattern with the direct observation of the magnetic field in filaments. Interestingly, the filaments which show the opposite magnetic field deviation to the hemispheric pattern, are in many cases found above the polarity inversion line whose ambient photospheric magnetic field has the polarity alignment being opposite to that of active regions following the Hale–Nicholson law.

The effects of dune slopes and material heterogeneity on the thermal behavior of dune fields in Mars' Southern Hemisphere

Science.gov (United States)

O'Shea, P. M.; Putzig, N. E.; Van Kooten, S.; Fenton, L. K.

2015-12-01

We analyzed the effects of slopes on the thermal properties of three dune fields in Mars' southern hemisphere. Although slope has important thermal effects, it is not the main driver of observed apparent thermal inertia (ATI) for these dunes. Comparing the ATI seasonal behavior as derived from Thermal Emission Spectrometer (TES) data with that modeled for compositional heterogeneities, we found that TES results correlate best with models of duricrust overlying and/or horizontally mixing with fines. We measured slopes and aspects in digital terrain models created from High Resolution Imaging Science Experiment (HiRISE) images of dunes within Proctor, Kaiser, and Wirtz craters. Using the MARSTHERM web toolset, we incorporated the slopes and aspects together with TES albedo, TES thermal inertia, surface pressure, and TES dust opacity, into models of seasonal ATI. Models that incorporate sub-pixel slopes show seasonal day and night ATI values that differ from the TES results by 0-300 J m-2 K-1 s-½. In addition, the models' day-night differences are opposite in sign from those of the TES results, indicating that factors other than slope are involved. We therefore compared the TES data to model results for a broad range of horizontally mixed and two-layered surfaces to seek other possible controls on the observed data, finding that a surface layer of higher thermal inertia is a likely contributor. However, it is clear from this study that the overall composition and morphology of the dune fields are more complex than currently available models allow. Future work will combine slopes with other model parameters such as multi-layered surfaces and lateral changes in layer thickness. Coupling these improvements with broader seasonal coverage from the Thermal Emission Imaging System (THEMIS) at more thermally favorable times of day would allow more accurate characterization of dune thermal behavior.

Ionosphere dynamics over the Southern Hemisphere during the 31 March 2001 severe magnetic storm using multi-instrument measurement data

Directory of Open Access Journals (Sweden)

E. Yizengaw

2005-03-01

Full Text Available The effects of the 31 March 2001 severe magnetic storm on the Southern Hemisphere ionosphere have been studied using ground-based and satellite measurements. The prime goal of this comprehensive study is to track the ionospheric response from high-to-low latitude to obtain a clear understanding of storm-time ionospheric change. The study uses a combination of ionospheric Total Electron Content (TEC obtained from GPS signal group delay and phase advance measurements, ionosonde data, and data from satellite in-situ measurements, such as the Defense Metrological Satellite Program (DMSP, TOPographic EXplorer (TOPEX, and solar wind data from the Advanced Composition Explorer (ACE. A chain of Global Positioning System (GPS stations near the 150° E meridian has been used to give comprehensive latitude coverage extending from the cusp to the equatorial region. A tomographic inversion algorithm has been applied to the GPS TEC measurements to obtain maps of the latitudinal structure of the ionospheric during this severe magnetic storm period, enabling both the spatial and temporal response of the ionosphere to be studied. Analysis of data from several of the instruments indicates that a strong density enhancement occurred at mid-latitudes at 11:00 UT on 31 March 2001 and was followed by equatorward propagating large-scale Travelling Ionospheric Disturbances (TIDs. The tomographic reconstruction revealed important features in ionospheric structure, such as quasi-wave formations extending finger-like to higher altitudes. The most pronounced ionospheric effects of the storm occurred at high- and mid-latitudes, where strong positive disturbances occurred during the storm main phase, followed by a long lasting negative storm effect during the recovery phase. Relatively minor storm effects occurred in the equatorial region.

Viking orbiter imaging observations of dust in the Martian atmosphere

International Nuclear Information System (INIS)

Briggs, G.A.; Baum, W.A.; Barnes, J.

1979-01-01

More than 20 local Martian dust clouds and two global dust storms were observed with the Viking orbiter camera. Sixteen of the local clouds were imaged in two colors or were observed with other instruments confirming their identification as dust clouds. These Viking results are compared with earth-based observations of Martian dust storms and with Mariner 9 data. Most of the dust activity seen by Viking occurred during southern hemisphere spring and early summer, when Mars was near perihelion and isolation was near maximum. About half the local clouds occurred near the edge of the southern polar cap, where winds are presumably enhanced by a strong regional temperature gradient. The other half occurred mainly in the southern hemisphere near regions where circulation models incorporating topography predict positive vertical velocities. Although dust clouds observed from earth show a similar partial correlation with models, some ambiguity exists concerning interpretation of regions near Hellespontus that have spawned the most spectacular Martian dust storms on record

Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from USCGC POLAR SEA in the South Pacific Ocean and Southern Oceans from 1994-02-04 to 1994-02-10 (NODC Accession 0116062)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0116062 includes chemical, discrete sample, physical and profile data collected from USCGC POLAR SEA in the South Pacific Ocean and Southern Oceans...

First Reprocessing of Southern Hemisphere Additional Ozonesondes (SHADOZ) Ozone Profiles (1998-2016): 2. Comparisons With Satellites and Ground-Based Instruments

Science.gov (United States)

Thompson, Anne M.; Witte, Jacquelyn C.; Sterling, Chance; Jordan, Allen; Johnson, Bryan J.; Oltmans, Samuel J.; Fujiwara, Masatomo; Vömel, Holger; Allaart, Marc; Piters, Ankie; Coetzee, Gert J. R.; Posny, Françoise; Corrales, Ernesto; Diaz, Jorge Andres; Félix, Christian; Komala, Ninong; Lai, Nga; Ahn Nguyen, H. T.; Maata, Matakite; Mani, Francis; Zainal, Zamuna; Ogino, Shin-ya; Paredes, Francisco; Penha, Tercio Luiz Bezerra; da Silva, Francisco Raimundo; Sallons-Mitro, Sukarni; Selkirk, Henry B.; Schmidlin, F. J.; Stübi, Rene; Thiongo, Kennedy

2017-12-01

The Southern Hemisphere ADditional OZonesonde (SHADOZ) network was assembled to validate a new generation of ozone-monitoring satellites and to better characterize the vertical structure of tropical ozone in the troposphere and stratosphere. Beginning with nine stations in 1998, more than 7,000 ozone and P-T-U profiles are available from 14 SHADOZ sites that have operated continuously for at least a decade. We analyze ozone profiles from the recently reprocessed SHADOZ data set that is based on adjustments for inconsistencies caused by varying ozonesonde instruments and operating techniques. First, sonde-derived total ozone column amounts are compared to the overpasses from the Earth Probe/Total Ozone Mapping Spectrometer, Ozone Monitoring Instrument, and Ozone Mapping and Profiler Suite satellites that cover 1998-2016. Second, characteristics of the stratospheric and tropospheric columns are examined along with ozone structure in the tropical tropopause layer (TTL). We find that (1) relative to our earlier evaluations of SHADOZ data, in 2003, 2007, and 2012, sonde-satellite total ozone column offsets at 12 stations are 2% or less, a significant improvement; (2) as in prior studies, the 10 tropical SHADOZ stations, defined as within ±19° latitude, display statistically uniform stratospheric column ozone, 229 ± 3.9 DU (Dobson units), and a tropospheric zonal wave-one pattern with a 14 DU mean amplitude; (3) the TTL ozone column, which is also zonally uniform, masks complex vertical structure, and this argues against using satellites for lower stratospheric ozone trends; and (4) reprocessing has led to more uniform stratospheric column amounts across sites and reduced bias in stratospheric profiles. As a consequence, the uncertainty in total column ozone now averages 5%.

Polar marine ecosystems: major threats and future change

Energy Technology Data Exchange (ETDEWEB)

Clarke, A. [British Antarctic Survey, Cambridge (United Kingdom); Harris, C.M. [Environmental Research and Assessment, Grantchester (United Kingdom)

2003-07-01

This review of polar marine ecosystems covers both the Arctic and Antarctic, identifying the major threats and, where possible, predicting their possible state(s) in 2025. Although the two polar regions are similar in their extreme photoperiod, low temperatures, and in being heavily influenced by snow and ice, in almost all other respects they are very different. The Arctic Ocean is a basin surrounded by continental landmasses close to, and influenced by, large populations and industrial activities. In contrast, the Southern Ocean is contiguous with all the other great oceans and surrounds a single land mass; Antarctica is remote from major centres of population and sources of pollution. Marine environments in both Polar Regions have been highly disturbed by fishing activity, but, in terms of pollution, some areas remain among the most pristine in the world. There are, however, both local and global pressures. Over the 2025 time horizon, the greatest concern for the Arctic is probably the ecological implications of climate change, particularly insofar as sea ice extent and duration are likely to be affected. Such changes are not expected to be as pronounced in the Southern Ocean over this time period, and concerns are related more to direct threats from harvesting of marine living resources, and the ability to manage these fisheries sustainably. In both Polar Regions, the capacity of marine ecosystems to withstand the cumulative impact of a number of pressures, including climate change, pollution and overexploitation, acting synergistically is of greatest concern. (author)

Observations of the interplanetary sector structure up to heliographic latitudes of 160: Pioneer 11

International Nuclear Information System (INIS)

Smith, E.J.; Tsurutani, B.T.; Rosenberg, R.L.

1978-01-01

A study of the interplanetary sector structure at heliographic latitudes up to 16 0 N is reported. The study is based on magnetic field measurements made on board Pioneer 11 as the spacecraft traveled along the post-Jupiter-encounter trajectory. Preliminary measurements are used to determine the dominant polarity of the interplanetary magnetic field during 43 successive solar rotations including Pioneer's ascent to its maximum latitude and motion inward from 5 to 3.7 AU. As the latitude of Pioneer increased, the dominant polarity became continually more positive, corresponding to an outward-directed solar interplanetary field. When the spacecraft reached the highest latitude, the usual sector structure had essentially disappeared. A histogram of the field longitude angle, based on data acquired during 1 month at 16 0 latitude, shows an almost total absence of inward-directed fields. A comparison with interplanetary field polarities in the ecliptic, as inferred from geomagnetic field variations, rules out the possibility that a time variation rather than a latitude dependence is responsible. The Pioneer 11 observations imply that the boundary between adjacent sectors corresponds physically to a current sheet surrounding the sun and lying near parallel to the solar equatorial plane. Above this current sheet, in the northern hemisphere, the field polarity at this phase of the solar cycle is outward, and below the current sheet, in the southern hemisphere, it is inward. The Pioneer observations confirm earlier theoretical suggestions regarding the existence and equatorial orientation of this current sheet. The properties of the current sheet and some major implications and questions associated with it are discussed. It is shown that the radial component of the sheet current is compensated by the distributed currents in the northern and southern hemispheres associated with the spiraled interplanetary field

The temporal and geographical mercury patterns in polar bears and birds of prey

DEFF Research Database (Denmark)

Dietz, R.; Riget, F.; Olsen, M.T.

2004-01-01

Mercury compounds are bio-accumulated. As a consequence the highest levels of mercury are measured in top predators like seals, toothed whales, polar bears, and also humans. The main mercury source for humans is the diet but the processes that links emission with effects through the transport chain...... and seals. The coupling between transport pathways of carbon and mercury is weak at lower trophic levels. A substantial decrease of Hg concentrations in teeth and hair of polar bears since 1960 was found. Hg concentrations in hair of polar bears sampled in East Greenland during 1999-2001 was 8.3 times...... a new parameterisation of the removal of atmospheric mercury for Danish Eulerian Hemispheric Model (DEHM) and to validate the model. As a first estimate about 200 tons/year is deposited to the surface north of polar circle. In undisturbed sediment cores the mercury concentration and the mercury...

Global-Scale Consequences of Magnetic-Helicity Injection and Condensation on the Sun

Science.gov (United States)

Mackay, Duncan H.; DeVore, C. Richard; Antiochos, Spiro K.

2013-01-01

In the recent paper of Antiochos, a new concept for the injection of magnetic helicity into the solar corona by small-scale convective motions and its condensation onto polarity inversion lines (PILs) has been developed. We investigate this concept through global simulations of the Sun's photospheric and coronal magnetic fields and compare the results with the hemispheric pattern of solar filaments. Assuming that the vorticity of the cells is predominately counter-clockwise/clockwise in the northern/southern hemisphere, the convective motions inject negative/positive helicity into each hemisphere. The simulations show that: (i) On a north-south orientated PIL, both differential rotation and convective motions inject the same sign of helicity which matches that required to reproduce the hemispheric pattern of filaments. (ii) On a high latitude east-west orientated polar crown or sub-polar crown PIL, the vorticity of the cells has to be approximately 2-3 times greater than the local differential rotation gradient in order to overcome the incorrect sign of helicity injection from differential rotation. (iii) In the declining phase of the cycle, as a bipole interacts with the polar field, in some cases helicity condensation can reverse the effect of differential rotation along the East-West lead arm, but not in all cases. The results show that this newly developed concept of magnetic helicity injection and condensation is a viable method to explain the hemispheric pattern of filaments in conjunction with the mechanisms used in Yeates et al. (2008). Future observational studies should focus on determining the vorticity component within convective motions to determine, both its magnitude and latitudinal variation relative to the differential rotation gradient on the Sun.

Hemispherical Resonator Gyroscope Accuracy Analysis Under Temperature Influence

Directory of Open Access Journals (Sweden)

Boran LI

2014-06-01

Full Text Available Frequency splitting of hemispherical resonator gyroscope will change as system operating temperature changes. This phenomenon leads to navigation accuracy of hemispherical resonator gyroscope reduces. By researching on hemispherical resonator gyroscope dynamical model and its frequency characteristic, the frequency splitting formula and the precession angle formula of gyroscope vibrating mode based on hemispherical resonator gyroscope dynamic equation parameters are derived. By comparison, gyroscope precession angle deviation caused by frequency splitting can be obtained. Based on analysis of temperature variation against gyroscope resonator, the design of hemispherical resonator gyroscope feedback controller under temperature variation conditions is researched and the maximum theoretical fluctuation of gyroscope dynamical is determined by using a numerical analysis example.

Stratospheric Impact of Varying Sea Surface Temperatures

Science.gov (United States)

Newman, Paul A.; Nash, Eric R.; Nielsen, Jon E.; Waugh, Darryn; Pawson, Steven

2004-01-01

The Finite-Volume General Circulation Model (FVGCM) has been run in 50 year simulations with the: 1) 1949-1999 Hadley Centre sea surface temperatures (SST), and 2) a fixed annual cycle of SSTs. In this presentation we first show that the 1949-1999 FVGCM simulation produces a very credible stratosphere in comparison to an NCEP/NCAR reanalysis climatology. In particular, the northern hemisphere has numerous major and minor stratospheric warming, while the southern hemisphere has only a few over the 50-year simulation. During the northern hemisphere winter, temperatures are both warmer in the lower stratosphere and the polar vortex is weaker than is found in the mid-winter southern hemisphere. Mean temperature differences in the lower stratosphere are shown to be small (less than 2 K), and planetary wave forcing is found to be very consistent with the climatology. We then will show the differences between our varying SST simulation and the fixed SST simulation in both the dynamics and in two parameterized trace gases (ozone and methane). In general, differences are found to be small, with subtle changes in planetary wave forcing that lead to reduced temperatures in the SH and increased temperatures in the NH.

Impact of strong geomagnetic storms on total ozone at southern higher middle latitudes

Czech Academy of Sciences Publication Activity Database

Laštovička, Jan; Križan, Peter

2009-01-01

Roč. 53, č. 1 (2009), s. 151-156 ISSN 0039-3169 R&D Projects: GA MŠk 1P05OC030 Grant - others:European Commission(XE) COST 724 Institutional research plan: CEZ:AV0Z30420517 Keywords : ozone * Southern Hemisphere * geomagnetic storms * Forbush decreases of cosmic rays Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.000, year: 2009

Hemispheric asymmetry of electroencephalography-based functional brain networks.

Science.gov (United States)

Jalili, Mahdi

2014-11-12

Electroencephalography (EEG)-based functional brain networks have been investigated frequently in health and disease. It has been shown that a number of graph theory metrics are disrupted in brain disorders. EEG-based brain networks are often studied in the whole-brain framework, where all the nodes are grouped into a single network. In this study, we studied the brain networks in two hemispheres and assessed whether there are any hemispheric-specific patterns in the properties of the networks. To this end, resting state closed-eyes EEGs from 44 healthy individuals were processed and the network structures were extracted separately for each hemisphere. We examined neurophysiologically meaningful graph theory metrics: global and local efficiency measures. The global efficiency did not show any hemispheric asymmetry, whereas the local connectivity showed rightward asymmetry for a range of intermediate density values for the constructed networks. Furthermore, the age of the participants showed significant direct correlations with the global efficiency of the left hemisphere, but only in the right hemisphere, with local connectivity. These results suggest that only local connectivity of EEG-based functional networks is associated with brain hemispheres.

The Formation and Maintenance of the Dominant Southern Polar Crown Cavity of Cycle 24

Energy Technology Data Exchange (ETDEWEB)

Karna, N.; Pesnell, W. D. [NASA Goddard Space Flight Center, Greenbelt, MD (United States); Zhang, J. [George Mason University, Fairfax, VA (United States)

2017-02-01

In this article, we report a study of the longest-lived polar crown cavity of Solar Cycle 24, using an observation from 2013, and propose a physical mechanism to explain its sustained existence. We used high temporal and spatial resolution observations from the Atmospheric Imaging Assembly (AIA) and the Helioseismic Magnetic Imager (HMI) instruments on board the Solar Dynamics Observatory ( SDO ) to explore the structure and evolution of the cavity. Although it existed for more than a year, we examined the circumpolar cavity in great detail from 2013 March 21 to 2013 October 31. Our study reinforces the existing theory of formation of polar crown filaments that involves two basic processes to form any polar crown cavity as well as the long-lived cavity that we studied here. First, the underlying polarity inversion line (PIL) of the circumpolar cavity is formed between (1) the trailing part of dozens of decayed active regions distributed in different longitudes and (2) the unipolar magnetic field in the polar coronal hole. Second, the long life of the cavity is sustained by the continuing flux cancellation along the PIL. The flux is persistently transported toward the polar region through surface meridional flow and diffusion. The continuing flux cancellation leads to the shrinking of the polar coronal hole.

Coherence among the Northern Hemisphere land, cryosphere, and ocean responses to natural variability and anthropogenic forcing during the satellite era

Science.gov (United States)

Gonsamo, Alemu; Chen, Jing M.; Shindell, Drew T.; Asner, Gregory P.

2016-08-01

A lack of long-term measurements across Earth's biological and physical systems has made observation-based detection and attribution of climate change impacts to anthropogenic forcing and natural variability difficult. Here we explore coherence among land, cryosphere and ocean responses to recent climate change using 3 decades (1980-2012) of observational satellite and field data throughout the Northern Hemisphere. Our results show coherent interannual variability among snow cover, spring phenology, solar radiation, Scandinavian Pattern, and North Atlantic Oscillation. The interannual variability of the atmospheric peak-to-trough CO2 amplitude is mostly impacted by temperature-mediated effects of El Niño/Southern Oscillation (ENSO) and Pacific/North American Pattern (PNA), whereas CO2 concentration is affected by Polar Pattern control on sea ice extent dynamics. This is assuming the trend in anthropogenic CO2 emission remains constant, or the interannual changes in the trends are negligible. Our analysis suggests that sea ice decline-related CO2 release may outweigh increased CO2 uptake through longer growing seasons and higher temperatures. The direct effects of variation in solar radiation and leading teleconnections, at least in part via their impacts on temperature, dominate the interannual variability of land, cryosphere and ocean indicators. Our results reveal a coherent long-term changes in multiple physical and biological systems that are consistent with anthropogenic forcing of Earth's climate and inconsistent with natural drivers.

Deployment and Performance of an X-Band Dual-Polarization Radar during the Southern China Monsoon Rainfall Experiment

Directory of Open Access Journals (Sweden)

Zhao Shi

2017-12-01

Full Text Available An X-band dual-polarization radar (XPRAD was deployed in Guangdong province as part of the Southern China Monsoon Rainfall Experiment (SCMREX during the storm season in 2016. This paper presents a comprehensive assessment of XPRAD observations during SCMREX with emphasis on data processing and rainfall products. The differential phase-based attenuation correction and radar calibration using self-consistency of dual-polarization observables are presented. It is found that the standard deviation of the Z d r bias is less than 0.2 dB based on ‘light rain at low angle’ and ‘dry aggregate snow’ observations. Cross-comparison with two standard S-band China New Generation Weather Radars (CINRAD shows that the bias of Z h has a mean value less than 1.5 dBZ and a standard deviation less than 0.5 dBZ. In addition, fifteen rainfall events that occurred during the intensive observing period (IOP are analyzed to demonstrate the rainfall estimation performance of XPRAD. In particular, rainfall accumulations at 1-, 2- and 3-h scales derived using R( K d p and R( Z h , Z d r relations are evaluated using national level rain gauge data and CINRAD-based rainfall estimation. The results show that both R( K d p - and R( Z h , Z d r -based products agree well with the rain gauge observations and CINRAD estimation. The difference between R ( K d p and R ( Z h , Z d r is not significant, although R ( K d p shows slightly better performance than R ( Z h , Z d r .

Tolerance of polar phytoplankton communities to metals

International Nuclear Information System (INIS)

Echeveste, P.; Tovar-Sánchez, A.; Agustí, S.

2014-01-01

Large amounts of pollutants reach polar regions, particularly the Arctic, impacting their communities. In this study we analyzed the toxic levels of Hg, Cd and Pb to natural phytoplankton communities of the Arctic and Southern Oceans, and compared their sensitivities with those observed on phytoplankton natural communities from temperate areas. Mercury was the most toxic metal for both Arctic and Antarctic communities, while both Cd and Pb were toxic only for the Antarctic phytoplankton. Total cell abundance of the populations forming the Arctic community increased under high Cd and Pb concentrations, probably due to a decrease of the grazing pressure or the increase of the most resistant species, although analysis of individual cells indicated that cell death was already induced at the highest levels. These results suggest that phytoplankton may have acquired adapting mechanisms to face high levels of Pb and Cd in the Arctic Ocean. Highlights: • First study analyzing the toxicity of Hg, Cd or Pb to natural polar phytoplankton. • Arctic Ocean communities highly resistant to Cd and Pb, but not to Hg. • Southern Ocean communities sensitive to Cd, Pb and Hg. • Both communities incorporated Pb at a similar level. • Arctic phytoplankton may have acquired adapting mechanisms against Cd and Pb. -- Polar phytoplankton communities are tolerant to Cd and Pb, specially the Arctic ones, suggesting the acquisition of adapting mechanisms to face metals' toxicity

Hemispheric resource limitations in comprehending ambiguous pictures.

Science.gov (United States)

White, H; Minor, S W

1990-03-01

Ambiguous pictures (Roschach inkblots) were lateralized for 100 msec vs. 200 msec to the right and left hemispheres (RH and LH) of 32 normal right-handed males who determined which of two previously presented words (an accurate or inaccurate one) better described the inkblot. Over the first 32 trials, subjects receiving each stimulus exposure duration were less accurate when the hemisphere receiving the stimulus also controlled the hand used to register a keypress response (RH-left hand and LH-right hand trials) than when hemispheric resources were shared, i.e., when one hemisphere controlled stimulus processing and the other controlled response programming. These differences were eliminated when the 32 trials were repeated.

Hemispheric lateralization of topological organization in structural brain networks.

Science.gov (United States)

Caeyenberghs, Karen; Leemans, Alexander

2014-09-01

The study on structural brain asymmetries in healthy individuals plays an important role in our understanding of the factors that modulate cognitive specialization in the brain. Here, we used fiber tractography to reconstruct the left and right hemispheric networks of a large cohort of 346 healthy participants (20-86 years) and performed a graph theoretical analysis to investigate this brain laterality from a network perspective. Findings revealed that the left hemisphere is significantly more "efficient" than the right hemisphere, whereas the right hemisphere showed higher values of "betweenness centrality" and "small-worldness." In particular, left-hemispheric networks displayed increased nodal efficiency in brain regions related to language and motor actions, whereas the right hemisphere showed an increase in nodal efficiency in brain regions involved in memory and visuospatial attention. In addition, we found that hemispheric networks decrease in efficiency with age. Finally, we observed significant gender differences in measures of global connectivity. By analyzing the structural hemispheric brain networks, we have provided new insights into understanding the neuroanatomical basis of lateralized brain functions. Copyright © 2014 Wiley Periodicals, Inc.

Seasonal prediction skill of ECMWF System 4 and NCEP CFSv2 retrospective forecast for the Northern Hemisphere Winter

International Nuclear Information System (INIS)

Kim, Hye-Mi; Webster, Peter J.; Curry, Judith A.

2012-01-01

The seasonal prediction skill for the Northern Hemisphere winter is assessed using retrospective predictions (1982-2010) from the ECMWF System 4 (Sys4) and National Center for Environmental Prediction (NCEP) CFS version 2 (CFSv2) coupled atmosphere-ocean seasonal climate prediction systems. Sys4 shows a cold bias in the equatorial Pacific but a warm bias is found in the North Pacific and part of the North Atlantic. The CFSv2 has strong warm bias from the cold tongue region of the eastern Pacific to the equatorial central Pacific and cold bias in broad areas over the North Pacific and the North Atlantic. A cold bias in the Southern Hemisphere is common in both reforecasts. In addition, excessive precipitation is found in the equatorial Pacific, the equatorial Indian Ocean and the western Pacific in Sys4, and in the South Pacific, the southern Indian Ocean and the western Pacific in CFSv2. A dry bias is found for both modeling systems over South America and northern Australia. The mean prediction skill of 2 meter temperature (2mT) and precipitation anomalies are greater over the tropics than the extra-tropics and also greater over ocean than land. The prediction skill of tropical 2mT and precipitation is greater in strong El Nino Southern Oscillation (ENSO) winters than in weak ENSO winters. Both models predict the year-to-year ENSO variation quite accurately, although sea surface temperature trend bias in CFSv2 over the tropical Pacific results in lower prediction skill for the CFSv2 relative to the Sys4. Both models capture the main ENSO teleconnection pattern of strong anomalies over the tropics, the North Pacific and the North America. However, both models have difficulty in forecasting the year-to-year winter temperature variability over the US and northern Europe. (orig.)

Seasonal prediction skill of ECMWF System 4 and NCEP CFSv2 retrospective forecast for the Northern Hemisphere Winter

Energy Technology Data Exchange (ETDEWEB)

Kim, Hye-Mi; Webster, Peter J.; Curry, Judith A. [Georgia Institute of Technology, School of Earth and Atmospheric Science, Atlanta, GA (United States)

2012-12-15

The seasonal prediction skill for the Northern Hemisphere winter is assessed using retrospective predictions (1982-2010) from the ECMWF System 4 (Sys4) and National Center for Environmental Prediction (NCEP) CFS version 2 (CFSv2) coupled atmosphere-ocean seasonal climate prediction systems. Sys4 shows a cold bias in the equatorial Pacific but a warm bias is found in the North Pacific and part of the North Atlantic. The CFSv2 has strong warm bias from the cold tongue region of the eastern Pacific to the equatorial central Pacific and cold bias in broad areas over the North Pacific and the North Atlantic. A cold bias in the Southern Hemisphere is common in both reforecasts. In addition, excessive precipitation is found in the equatorial Pacific, the equatorial Indian Ocean and the western Pacific in Sys4, and in the South Pacific, the southern Indian Ocean and the western Pacific in CFSv2. A dry bias is found for both modeling systems over South America and northern Australia. The mean prediction skill of 2 meter temperature (2mT) and precipitation anomalies are greater over the tropics than the extra-tropics and also greater over ocean than land. The prediction skill of tropical 2mT and precipitation is greater in strong El Nino Southern Oscillation (ENSO) winters than in weak ENSO winters. Both models predict the year-to-year ENSO variation quite accurately, although sea surface temperature trend bias in CFSv2 over the tropical Pacific results in lower prediction skill for the CFSv2 relative to the Sys4. Both models capture the main ENSO teleconnection pattern of strong anomalies over the tropics, the North Pacific and the North America. However, both models have difficulty in forecasting the year-to-year winter temperature variability over the US and northern Europe. (orig.)

A New Orbit for Comet C/1865 B1 (Great Southern Comet of 1865)

Science.gov (United States)

Branham, Richard L., Jr.

2018-04-01

Comet C/1865 B1 (Great southern comet of 1865), observed only in the southern hemisphere, is one of a large number of comets with parabolic orbits. Given that there are 202 observations in right ascension and 165 in declination it proves possible to calculate a better orbit than that Körber published in 1887, the orbit used in various catalogs and data bases. C/1865 B1's orbit is hyperbolic and statistically distinguishable from a parabola. This object, therefore, cannot be considered an NEO. The comet has a small perihelion distance of 0.026 AU.

Trans-pacific glacial response to the Antarctic Cold Reversal in the southern mid-latitudes

Science.gov (United States)

Sagredo, Esteban A.; Kaplan, Michael R.; Araya, Paola S.; Lowell, Thomas V.; Aravena, Juan C.; Moreno, Patricio I.; Kelly, Meredith A.; Schaefer, Joerg M.

2018-05-01

Elucidating the timing and regional extent of abrupt climate events during the last glacial-interglacial transition (∼18-11.5 ka) is critical for identifying spatial patterns and mechanisms responsible for large-magnitude climate events. The record of climate change in the Southern Hemisphere during this time period, however, remains scarce and unevenly distributed. We present new geomorphic, chronological, and equilibrium line altitude (ELA) data from a climatically sensitive mountain glacier at Monte San Lorenzo (47°S), Central Patagonia. Twenty-four new cosmogenic 10Be exposure ages from moraines provide a comprehensive glacial record in the mid-latitudes of South America, which constrain the timing, spatial extent and magnitude of glacial fluctuations during the Antarctic Cold Reversal (ACR, ∼14.5-12.9 ka). Río Tranquilo glacier advanced and reached a maximum extent at 13.9 ± 0.7 ka. Three additional inboard moraines afford statistically similar ages, indicating repeated glacier expansions or marginal fluctuations over the ACR. Our record represents the northernmost robust evidence of glacial fluctuations during the ACR in southern South America, documenting not only the timing of the ACR maximum, but also the sequence of glacier changes within this climate event. Based on ELA reconstructions, we estimate a cooling of >1.6-1.8 °C at the peak of the ACR. The Río Tranquilo record along with existing glacial reconstructions from New Zealand (43°S) and paleovegetation records from northwestern (41°S) and central-west (45°S) Patagonia, suggest an uniform trans-Pacific glacier-climate response to an ACR trigger across the southern mid-latitudes. We posit that the equatorial migration of the southern westerly winds provides an adequate mechanism to propagate a common ACR signal across the Southern Hemisphere.

The glacial record of New Zealand's Southern Alps

Science.gov (United States)

Schaefer, J. M.; Denton, G.; Lowell, T.; Anderson, B.; Rinterknecht, V.; Schlosser, P.; Ivy-Ochs, S.; Kubik, P.; Schluechter, C.; Chinn, T.; Barrell, D.; Lifton, N.; Jull, T.

2004-12-01

We present detailed mapping and surface exposure dating using in-situ Be-10 and C-14 of the moraine set of Lake Pukaki, New Zealand's Southern Alps, spanning from the penultimate glaciation, over several Last Glacial Maximum (LGM) moraines, the late glacial event to Holocene glacial advances. New Zealand, a mountain ridge in the middle of the Southern Ocean, has one of the best preserved moraine records world-wide, offering the opportunity to reconstruct amplitude and timing of climate changes from Southern mid-latitudes, an area where paleoclimate data is scarce. The extensive mapping effort by G. Denton and colleagues (http://wyvern.gns.cri.nz/website/csigg/) provides a unique background for sample selection for Surface Exposure Dating. Our extensive data set (>40 samples analyzed so far) indicate that (i) the LGM in New Zealand terminated clearly prior to the Boelling/Alleroed warming, (ii) the late glacial advance is within uncertainties consistent with the timing of the Younger Dryas cold reversal; (iii) there occurred an early Holocene glacial event of the same amplitude than the Little Ice Age. This latter event is the first Holocene glacial event from the Southern Hemisphere dated by in-situ Be-10 and C-14.

Right-hemispheric processing of non-linguistic word features

DEFF Research Database (Denmark)

Baumgaertner, Annette; Hartwigsen, Gesa; Roman Siebner, Hartwig

2013-01-01

-hemispheric homologues of classic left-hemispheric language areas may partly be due to processing nonlinguistic perceptual features of verbal stimuli. We used functional MRI (fMRI) to clarify the role of the right hemisphere in the perception of nonlinguistic word features in healthy individuals. Participants made...... perceptual, semantic, or phonological decisions on the same set of auditorily and visually presented word stimuli. Perceptual decisions required judgements about stimulus-inherent changes in font size (visual modality) or fundamental frequency contour (auditory modality). The semantic judgement required......, the right inferior frontal gyrus (IFG), an area previously suggested to support language recovery after left-hemispheric stroke, displayed modality-independent activation during perceptual processing of word stimuli. Our findings indicate that activation of the right hemisphere during language tasks may...

Dynamics of longitudinal-latitudinal asymmetry of solar activity at various solar cycle phases

International Nuclear Information System (INIS)

Baranov, D.G.; Vernova, E.S.; Grigoryan, M.S.; Tyasto, M.I.

1995-01-01

Solar activity longitudinal asymmetry in 1943-1984 was studied by means of the polar diagram technique. Longitudinal changes of the activity distribution for northern and southern hemispheres were considered separately. Heliolongitudinal asymmetry was compared with the first harmonic of the 27-days cosmic ray intensity variation and with phases of the Quasi-Biennial Oscillation. There is certain correspondence between the dominance of the asymmetry in one of the solar hemispheres and the phase of the Quasi-Biennial Oscillation. Correlation exists between the amplitude of the 27-days galactic cosmic ray variation and the phase of the Quasi-Biennial Oscillation. 8 refs.; 3 figs

Olive Cultivation in the Southern Hemisphere: Flowering, Water Requirements and Oil Quality Responses to New Crop Environments

Science.gov (United States)

Torres, Mariela; Pierantozzi, Pierluigi; Searles, Peter; Rousseaux, M. Cecilia; García-Inza, Georgina; Miserere, Andrea; Bodoira, Romina; Contreras, Cibeles; Maestri, Damián

2017-01-01

Olive (Olea europaea L.) is a crop well adapted to the environmental conditions prevailing in the Mediterranean Basin. Nevertheless, the increasing international demand for olive oil and table olives in the last two decades has led to expansion of olive cultivation in some countries of the southern hemisphere, notably in Argentina, Chile, Perú and Australia. While the percentage of world production represented by these countries is still low, many of the new production regions do not have typical Mediterranean climates, and some are located at subtropical latitudes where there is relatively little information about crop function. Thus, the primary objective of this review was to assess recently published scientific literature on olive cultivation in these new crop environments. The review focuses on three main aspects: (a) chilling requirements for flowering, (b) water requirements and irrigation management, and (c) environmental effects on fruit oil concentration and quality. In many arid and semiarid regions of South America, temperatures are high and rainfall is low in the winter and early spring months compared to conditions in much of the Mediterranean Basin. High temperatures have often been found to have detrimental effects on olive flowering in many olive cultivars that have been introduced to South America, and a better understanding of chilling requirements is needed. Lack of rainfall in the winter and spring also has resulted in an urgent need to evaluate water requirements from the flower differentiation period in the winter to early fruit bearing. Additionally, in some olive growing areas of South America and Australia, high early season temperatures affect the timing of phenological events such that the onset of oil synthesis occurs sooner than in the Mediterranean Basin with most oil accumulation taking place in the summer when temperatures are very high. Increasing mean daily temperatures have been demonstrated to decrease fruit oil concentration

Interannual and Decadal Variations of Planetary Wave Activity, Stratospheric Cooling, and Northern Hemisphere Annular Mode.

Science.gov (United States)

Hu, Yongyun; Kit Tung, Ka

2002-07-01

Using NCEP-NCAR 51-yr reanalysis data, the interannual and decadal variations of planetary wave activity and its relationship to stratospheric cooling, and the Northern Hemisphere Annular mode (NAM), are studied. It is found that winter stratospheric polar temperature is highly correlated on a year-to-year basis with the Eliassen-Palm (E-P) wave flux from the troposphere, implying a dynamical control of the former by the latter, as often suggested. Greater (lower) wave activity from the troposphere implies larger (smaller) poleward heat flux into the polar region, which leads to warmer (colder) polar temperature. A similar highly correlated antiphase relationship holds for E-P flux divergence and the strength of the polar vortex in the stratosphere. It is tempting to extrapolate these relationships found for interannual timescales to explain the recent stratospheric polar cooling trend in the past few decades as caused by decreased wave activity in the polar region. This speculation is not supported by the data. On timescales of decades the cooling trend is not correlated with the trend in planetary wave activity. In fact, it is found that planetary wave amplitude, E-P flux, and E-P flux convergence all show little statistical evidence of decrease in the past 51 yr, while the stratosphere is experiencing a cooling trend and the NAM index has a positive trend during the past 30 yr. This suggests that the trends in the winter polar temperature and the NAM index can reasonably be attributed to the radiative cooling of the stratosphere, due possibly to increasing greenhouse gases and ozone depletion. It is further shown that the positive trend of the NAM index in the past few decades is not through the inhibition of upward planetary wave propagation from the troposphere to the stratosphere, as previously suggested.

Effect of the interplanetary magnetic field on the distribution of electric fields in the polar ionosphere

Science.gov (United States)

Uvarov, V. M.; Barashkov, P. D.

1985-08-01

Heppner (1972), in an analysis of satellite data, observed 12 types of electric-field distributions in the polar ionosphere along the morning-evening meridian. In the present paper it is shown that these distribution types can be described by the analytical model of Uvarov and Barashkov (1984). In this model the excitation of the electric fields is investigated by solving the set of continuity equations for current in three regions (the north and south polar caps and a region outside the caps) with allowance for the magnetic conjugacy of the ionosphere in the two hemispheres.

Monstrous Ice Cloud System in Titan's Present South Polar Stratosphere

Science.gov (United States)

Anderson, Carrie; Samuelson, Robert; McLain, Jason; Achterberg, Richard; Flasar, F. Michael; Milam, Stefanie

2015-11-01

During southern autumn when sunlight was still available, Cassini's Imaging Science Subsystem discovered a cloud around 300 km near Titan's south pole (West, R. A. et al., AAS/DPS Abstracts, 45, #305.03, 2013); the cloud was later determined by Cassini's Visible and InfraRed Mapping Spectrometer to contain HCN ice (de Kok et al., Nature, 514, pp 65-67, 2014). This cloud has proven to be only the tip of an extensive ice cloud system contained in Titan's south polar stratosphere, as seen through the night-vision goggles of Cassini's Composite InfraRed Spectrometer (CIRS). As the sun sets and the gloom of southern winter approaches, evidence is beginning to accumulate from CIRS far-IR spectra that a massive system of nitrile ice clouds is developing in Titan's south polar stratosphere. Even during the depths of northern winter, nothing like the strength of this southern system was evident in corresponding north polar regions.From the long slant paths that are available from limb-viewing CIRS far-IR spectra, we have the first definitive detection of the ν6 band of cyanoacetylene (HC3N) ice in Titan’s south polar stratosphere. In addition, we also see a strong blend of nitrile ice lattice vibration features around 160 cm-1. From these data we are able to derive ice abundances. The most prominent (and still chemically unidentified) ice emission feature, the Haystack, (at 220 cm-1) is also observed. We establish the vertical distributions of the ice cloud systems associated with both the 160 cm-1 feature and the Haystack. The ultimate aim is to refine the physical and possibly the chemical relationships between the two. Transmittance thin film spectra of nitrile ice mixtures obtained in our Spectroscopy for Planetary ICes Environments (SPICE) laboratory are used to support these analyses.

Hypothalamic digoxin, hemispheric chemical dominance, and creativity.

Science.gov (United States)

Kurup, Ravi Kumar; Kurup, Parameswara Achutha

2003-04-01

The human hypothalamus produces an endogenous membrane Na(+)-K+ ATPase inhibitor, digoxin, which regulates neuronal transmission. The digoxin status and neurotransmitter patterns were studied in creative and non-creative individuals, as well as in individuals with differing hemispheric dominance, in order to find out the role of cerebral dominance in this respect. The activity of HMG CoA reductase and serum levels of digoxin, magnesium, tryptophan catabolites, and tyrosine catabolites were measured in creative/non-creative individuals, and in individuals with differing hemispheric dominance. In creative individuals there was increased digoxin synthesis, decreased membrane Na(+)-K+ ATPase activity, increased tryptophan catabolites (serotonin, quinolinic acid, and nicotine), and decreased tyrosine catabolites (dopamine, noradrenaline, and morphine). The pattern in creative individuals correlated with right hemispheric dominance. In non-creative individuals there was decreased digoxin synthesis, increased membrane Na(+)-K+ ATPase activity, decreased tryptophan catabolites (serotonin, quinolinic acid, and nicotine), and increased tyrosine catabolites (dopamine, noradrenaline, and morphine). This pattern in non-creative individuals correlated with that obtained in left hemispheric chemical dominance. Hemispheric chemical dominance and hypothalamic digoxin could regulate the predisposition to creative tendency.

Personality, Hemispheric Dominance, and Cognitive Style.

Science.gov (United States)

Hylton, Jaime; Hartman, Steve E.

1997-01-01

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

Influence of boundary conditions on the Southern Hemisphere atmospheric circulation during the last glacial maximum Influência das condições de fronteira na circulação atmosférica do Hemisfério Sul durante o último máximo glacial

Directory of Open Access Journals (Sweden)

F. Justino

2008-12-01

Full Text Available Based upon coupled climate simulations driven by present day and glacial boundary conditions, we demonstrate that although the ice sheet topography modifications during the glacial period are primarily placed in the Northern Hemisphere (NH, a climate simulation that employs the ICE-5G glacial topography delivers significantly enhanced climate anomalies in the Southern Hemisphere (SH as well. These conditions, in association with climate anomalies produced by the modification of the atmospheric CO² concentration characteristic of the Last Glacial Maximum (LGM interval, are shown to be the primary forcing of the SH climate during this epoch. Climate anomalies up to -6°C over the Antarctic region and -4°C over South America are predicted to occur in respect to present day conditions. Accompanying the SH cooling in the LGM simulation there exists a remarkable reduction in the specific humidity, which in turn enforces the overall Southern Hemisphere cooling due to the weaker greenhouse capacity of the dry atmosphere.Com base em simulações numéricas conduzidas com condições de fronteiras características dos períodos glaciais e atual, demonstra-se que embora as maiores anomalias da topografia da Terra no período glacial estejam no Hemisfério Norte, esta inclusão dos blocos de gelo leva a substanciais mudanças na circulação atmosférica austral para aquela época, indicando uma forte teleconexão inter-hemisférica. Em associação com a redução nos níveis de carbono atmosférico para 200 ppm, anomalias de temperatura de -6°C em torno da região antártica, e -4°C no continente sul-americano são simuladas para o último máximo glacial (UMG em relação a condições atuais. Concomitantemente, o UMG é caracterizado por uma drástica redução na umidade específica, que por sua vez intensifica o esfriamento inicial devido à mais fraca capacidade de estufa da atmosfera mais seca.

Enhanced activation of the left hemisphere promotes normative decision making.

Science.gov (United States)

Corser, Ryan; Jasper, John D

2014-01-01

Previous studies have reported that enhanced activation of the left cerebral hemisphere reduces risky-choice, attribute, and goal-framing effects relative to enhanced activation of the right cerebral hemisphere. The present study sought to extend these findings and show that enhanced activation of the left hemisphere also reduces violations of other normative principles, besides the invariance principle. Participants completed ratio bias (Experiment 1, N = 296) and base rate neglect problems (Experiment 2, N = 145) under normal (control) viewing or with the right or left hemisphere primarily activated by imposing a unidirectional gaze. In Experiment 1 we found that enhanced left hemispheric activation reduced the ratio bias relative to normal viewing and a group experiencing enhanced right hemispheric activation. In Experiment 2 enhanced left hemispheric activation resulted in using base rates more than normal viewing, but not significantly more than enhanced right hemispheric activation. Results suggest that hemispheric asymmetries can affect higher-order cognitive processes, such as decision-making biases. Possible theoretical accounts are discussed as well as implications for dual-process theories.

Three-dimensional polarization states of monochromatic light fields.

Science.gov (United States)

Azzam, R M A

2011-11-01

The 3×1 generalized Jones vectors (GJVs) [E(x) E(y) E(z)](t) (t indicates the transpose) that describe the linear, circular, and elliptical polarization states of an arbitrary three-dimensional (3-D) monochromatic light field are determined in terms of the geometrical parameters of the 3-D vibration of the time-harmonic electric field. In three dimensions, there are as many distinct linear polarization states as there are points on the surface of a hemisphere, and the number of distinct 3-D circular polarization states equals that of all two-dimensional (2-D) polarization states on the Poincaré sphere, of which only two are circular states. The subset of 3-D polarization states that results from the superposition of three mutually orthogonal x, y, and z field components of equal amplitude is considered as a function of their relative phases. Interesting contours of equal ellipticity and equal inclination of the normal to the polarization ellipse with respect to the x axis are obtained in 2-D phase space. Finally, the 3×3 generalized Jones calculus, in which elastic scattering (e.g., by a nano-object in the near field) is characterized by the 3-D linear transformation E(s)=T E(i), is briefly introduced. In such a matrix transformation, E(i) and E(s) are the 3×1 GJVs of the incident and scattered waves and T is the 3×3 generalized Jones matrix of the scatterer at a given frequency and for given directions of incidence and scattering.

The prevention of geographical proliferation of nuclear weapons: Nuclear-weapon-free zones and zones of peace in the Southern hemisphere

International Nuclear Information System (INIS)

Fujita, E.

1989-01-01

It is understandable that many Non-Nuclear Weapons States (NNWS) worry about the dangers of further geographical or spatial proliferation of nuclear weapons, as well as the extension to their regions of rivalries that are foreign to them. In this regard, there has been since the 1950's a number of proposals and initiatives to turn specific regions into nuclear-weapons-free zones and zones of peace in order to prevent or reduce the above mentioned threats. Although differences exits between the concepts of nuclear-weapon-free-zones and zones of peace as well as among the various NWFZ and ZP, inter se, they do share a common feature insofar as they represent a regional approach to the question of curbing the arms race, especially the nuclear one. This study will address some of these initiatives, examine their specific characteristics and assess their role in the prevention of the geographical proliferation of nuclear weapons. Among the relevant existing initiatives, those situated in the Southern Hemisphere offer an interesting focus of attention, in view of the fact that, together, they form a sort of a contiguous geographical area encompassing virtually half of the globe. The regions covered are the Antarctic, Latin American, South Pacific, South Atlantic and Indian Oceans. The first three have been established as nuclear-weapons-free-zones and the last two are in the process of being turned into zones of peace. The aim of this study is to compare similarities and differences among them and to identify the factors that condition their efficiency. By understanding their usefulness and their weaknesses, one many eventually construct useful paradigms for further regional initiatives to curb the arms race, specially the nuclear one

North-South asymmetry of interplanetary plasma and solar parameters

International Nuclear Information System (INIS)

El-Borie, M. A.

2001-01-01

Data of interplanetary plasma (field magnitude, solar wind speed, ion plasma density and temperature) and solar parameters (sunspot number, solar radio flux, and geomagnetic index) over the period 1965-1991, have been used to examine the asymmetry between the solar field north and south of the heliospheric current sheet (HCS). The dependence of N-S asymmetry of field magnitude (B) upon the interplanetary solar polarities is statistically insignificant. There is no clear indication for the presence of N-S asymmetry in the grand-average field magnitude over the solar cycles. During the period 1981-89 (qA<0; negative solar polarity state), the solar plasma was more dense and cooler south of the HCS than north of it. The solar flux component of toward field vector is larger in magnitude than those of away field vector during the qA<0 epoch, and no asymmetry observed in the qA<0 epoch. Furthermore, the sign of the N-S asymmetry in the solar activity depends positively upon the solar polarity state. In addition, it was studied the N-S asymmetry of solar parameters near the HCS, throughout the periods of northern and southern hemispheres were more active than the other. Some asymmetries (with respect to the HCS) in plasma parameters existed during the periods of southern hemisphere predominance

Ionospheric F-region response to the 26 September 2011 geomagnetic storm in the Antarctica American and Australian sectors

Directory of Open Access Journals (Sweden)

E. Correia

2017-10-01

Full Text Available The ionospheric response at middle and high latitudes in the Antarctica American and Australian sectors to the 26–27 September 2011 moderately intense geomagnetic storm was investigated using instruments including an ionosonde, riometer, and GNSS receivers. The multi-instrument observations permitted us to characterize the ionospheric storm-enhanced density (SED and tongues of ionization (TOIs as a function of storm time and location, considering the effect of prompt penetration electric fields (PPEFs. During the main phase of the geomagnetic storm, dayside SEDs were observed at middle latitudes, and in the nightside only density depletions were observed from middle to high latitudes. Both the increase and decrease in ionospheric density at middle latitudes can be attributed to a combination of processes, including the PPEF effect just after the storm onset, dominated by disturbance dynamo processes during the evolution of the main phase. Two SEDs–TOIs were identified in the Southern Hemisphere, but only the first episode had a counterpart in the Northern Hemisphere. This difference can be explained by the interhemispheric asymmetry caused by the high-latitude coupling between solar wind and the magnetosphere, which drives the dawn-to-dusk component of the interplanetary magnetic field. The formation of polar TOI is a function of the SED plume location that might be near the dayside cusp from which it can enter the polar cap, which was the case in the Southern Hemisphere. Strong GNSS scintillations were observed at stations collocated with SED plumes at middle latitudes and cusp on the dayside and at polar cap TOIs on the nightside.

Beyond Hemispheric Dominance: Brain Regions Underlying the Joint Lateralization of Language and Arithmetic to the Left Hemisphere

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Pinel, Philippe; Dehaene, Stanislas

2010-01-01

Language and arithmetic are both lateralized to the left hemisphere in the majority of right-handed adults. Yet, does this similar lateralization reflect a single overall constraint of brain organization, such an overall "dominance" of the left hemisphere for all linguistic and symbolic operations? Is it related to the lateralization of specific…

Delusions and the Right Hemisphere: A Review of the Case for the Right Hemisphere as a Mediator of Reality-Based Belief.

Science.gov (United States)

Gurin, Lindsey; Blum, Sonja

2017-01-01

Delusions are beliefs that remain fixed despite evidence that they are incorrect. Although the precise neural mechanism of delusional belief remains to be elucidated, there is a predominance of right-hemisphere lesions among patients with delusional syndromes accompanied by structural pathology, suggesting that right-hemisphere lesions, or networks with key nodes in the right hemisphere, may be playing a role. The authors discuss the potential theoretical basis and empiric support for a specific right-hemisphere role in delusion production, drawing on its roles in pragmatic communication; perceptual integration; attentional surveillance and anomaly/novelty detection; and belief updating.

Southward shift of the global wind energy resource under high carbon dioxide emissions

Science.gov (United States)

Karnauskas, Kristopher B.; Lundquist, Julie K.; Zhang, Lei

2018-01-01

The use of wind energy resource is an integral part of many nations' strategies towards realizing the carbon emissions reduction targets set forth in the Paris Agreement, and global installed wind power cumulative capacity has grown on average by 22% per year since 2006. However, assessments of wind energy resource are usually based on today's climate, rather than taking into account that anthropogenic greenhouse gas emissions continue to modify the global atmospheric circulation. Here, we apply an industry wind turbine power curve to simulations of high and low future emissions scenarios in an ensemble of ten fully coupled global climate models to investigate large-scale changes in wind power across the globe. Our calculations reveal decreases in wind power across the Northern Hemisphere mid-latitudes and increases across the tropics and Southern Hemisphere, with substantial regional variations. The changes across the northern mid-latitudes are robust responses over time in both emissions scenarios, whereas the Southern Hemisphere changes appear critically sensitive to each individual emissions scenario. In addition, we find that established features of climate change can explain these patterns: polar amplification is implicated in the northern mid-latitude decrease in wind power, and enhanced land-sea thermal gradients account for the tropical and southern subtropical increases.

Hemispheric asymmetry and theory of mind: is there an association?

Science.gov (United States)

Herzig, Daniela A; Sullivan, Sarah; Evans, Jonathan; Corcoran, Rhiannon; Mohr, Christine

2012-01-01

In autism and schizophrenia attenuated/atypical functional hemispheric asymmetry and theory of mind impairments have been reported, suggesting common underlying neuroscientific correlates. We here investigated whether impaired theory of mind performance is associated with attenuated/atypical hemispheric asymmetry. An association may explain the co-occurrence of both dysfunctions in psychiatric populations. Healthy participants (n=129) performed a left hemisphere (lateralised lexical decision task) and right hemisphere (lateralised face decision task) dominant task as well as a visual cartoon task to assess theory of mind performance. Linear regression analyses revealed inconsistent associations between theory of mind performance and functional hemisphere asymmetry: enhanced theory of mind performance was only associated with (1) faster right hemisphere language processing, and (2) reduced right hemisphere dominance for face processing (men only). The majority of non-significant findings suggest that theory of mind and functional hemispheric asymmetry are unrelated. Instead of "overinterpreting" the two significant results, discrepancies in the previous literature relating to the problem of the theory of mind concept, the variety of tasks, and the lack of normative data are discussed. We also suggest how future studies could explore a possible link between hemispheric asymmetry and theory of mind.

Warm mid-Cretaceous high-latitude sea-surface temperatures from the southern Tethys Ocean and cool high-latitude sea-surface temperatures from the Arctic Ocean: asymmetric worldwide distribution of dinoflagellates

Science.gov (United States)

Masure, Edwige; Desmares, Delphine; Vrielynck, Bruno

2014-05-01

Dealing with 87 articles and using a Geographical Information System, Masure and Vrielynck (2009) have mapped worldwide biogeography of 38 Late Albian dinoflagellate cysts and have demonstrated Cretaceous oceanic bioclimatic belts. For comparison 30 Aptian species derived from 49 studies (Masure et al., 2013) and 49 Cenomanian species recorded from 33 articles have been encountered. Tropical, Subtropical, Boreal, Austral, bipolar and cosmopolitan species have been identified and Cretaceous dinoflagellate biomes are introduced. Asymmetric distribution of Aptian and Late Albian/Cenomanian subtropical Tethyan species, from 40°N to 70°S, demonstrates asymmetric Aptian and Late Albian/Cenomanian Sea Surface Temperature (SST) gradients with warm water masses in high latitudes of Southern Ocean. The SST gradients were stronger in the Northern Hemisphere than in the Southern Hemisphere. We note that Aptian and Late Albian/Cenomanian dinoflagellates restricted to subtropical and subpolar latitudes met and mixed at 35-40°N, while they mixed from 30°S to 70°S and from 50°S to 70°S respectively in the Southern Hemisphere. Mixing belts extend on 5° in the Northern Hemisphere and along 40° (Aptian) and 20° (Late Albian/Cenomanian) in the Southern one. The board southern mixing belt of Tethyan and Austral dinoflagellates suggest co-occurrence of warm and cold currents. We record climatic changes such as the Early Aptian cooler period and Late Aptian and Albian warming through the poleward migration of species constrained to cool water masses. These species sensitive to temperature migrated from 35°N to 55°N through the shallow Greenland-Norwergian Seaway connecting the Central Atlantic and the Arctic Ocean. While Tethyan species did not migrate staying at 40°N. We suggest that the Greenland-Norwergian Seaway might has been a barrier until Late Albian/Cenomanian for oceanic Tethyan dinoflagellates stopped either by the shallow water column or temperature and salinity

Hemispheric lateralization in an analysis of speech sounds. Left hemisphere dominance replicated in Japanese subjects.

Science.gov (United States)

Koyama, S; Gunji, A; Yabe, H; Oiwa, S; Akahane-Yamada, R; Kakigi, R; Näätänen, R

2000-09-01

Evoked magnetic responses to speech sounds [R. Näätänen, A. Lehtokoski, M. Lennes, M. Cheour, M. Huotilainen, A. Iivonen, M. Vainio, P. Alku, R.J. Ilmoniemi, A. Luuk, J. Allik, J. Sinkkonen and K. Alho, Language-specific phoneme representations revealed by electric and magnetic brain responses. Nature, 385 (1997) 432-434.] were recorded from 13 Japanese subjects (right-handed). Infrequently presented vowels ([o]) among repetitive vowels ([e]) elicited the magnetic counterpart of mismatch negativity, MMNm (Bilateral, nine subjects; Left hemisphere alone, three subjects; Right hemisphere alone, one subject). The estimated source of the MMNm was stronger in the left than in the right auditory cortex. The sources were located posteriorly in the left than in the right auditory cortex. These findings are consistent with the results obtained in Finnish [R. Näätänen, A. Lehtokoski, M. Lennes, M. Cheour, M. Huotilainen, A. Iivonen, M.Vainio, P.Alku, R.J. Ilmoniemi, A. Luuk, J. Allik, J. Sinkkonen and K. Alho, Language-specific phoneme representations revealed by electric and magnetic brain responses. Nature, 385 (1997) 432-434.][T. Rinne, K. Alho, P. Alku, M. Holi, J. Sinkkonen, J. Virtanen, O. Bertrand and R. Näätänen, Analysis of speech sounds is left-hemisphere predominant at 100-150 ms after sound onset. Neuroreport, 10 (1999) 1113-1117.] and English [K. Alho, J.F. Connolly, M. Cheour, A. Lehtokoski, M. Huotilainen, J. Virtanen, R. Aulanko and R.J. Ilmoniemi, Hemispheric lateralization in preattentive processing of speech sounds. Neurosci. Lett., 258 (1998) 9-12.] subjects. Instead of the P1m observed in Finnish [M. Tervaniemi, A. Kujala, K. Alho, J. Virtanen, R.J. Ilmoniemi and R. Näätänen, Functional specialization of the human auditory cortex in processing phonetic and musical sounds: A magnetoencephalographic (MEG) study. Neuroimage, 9 (1999) 330-336.] and English [K. Alho, J. F. Connolly, M. Cheour, A. Lehtokoski, M. Huotilainen, J. Virtanen, R. Aulanko

On the Topological Changes of Local Hurst Exponent in Polar Regions

Science.gov (United States)

Consolini, G.; De Michelis, P.

2014-12-01

Geomagnetic activity during magnetic substorms and storms is related to the dinamical and topological changes of the current systems flowing in the Earth's magnetosphere-ionosphere. This is particularly true in the case of polar regions where the enhancement of auroral electrojet current system is responsible for the observed geomagnetic perturbations. Here, using the DMA-technique we evaluate the local Hurst exponent (H"older exponent) for a set of 46 geomagnetic observatories, widely distributed in the northern hemisphere, during one of the most famous and strong geomagnetic storm, the Bastille event, and reconstruct a sequence of polar maps showing the dinamical changes of the topology of the local Hurst exponent with the geomagnetic activity level. The topological evolution of local Hurst exponent maps is discussed in relation to the dinamical changes of the current systems flowing in the polar ionosphere. G. Consolini has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under Grant agreement no. 313038/STORM for this research.

Post-Stroke Longitudinal Alterations of Inter-Hemispheric Correlation and Hemispheric Dominance in Mouse Pre-Motor Cortex.

Science.gov (United States)

Vallone, Fabio; Lai, Stefano; Spalletti, Cristina; Panarese, Alessandro; Alia, Claudia; Micera, Silvestro; Caleo, Matteo; Di Garbo, Angelo

2016-01-01

Limited restoration of function is known to occur spontaneously after an ischemic injury to the primary motor cortex. Evidence suggests that Pre-Motor Areas (PMAs) may "take over" control of the disrupted functions. However, little is known about functional reorganizations in PMAs. Forelimb movements in mice can be driven by two cortical regions, Caudal and Rostral Forelimb Areas (CFA and RFA), generally accepted as primary motor and pre-motor cortex, respectively. Here, we examined longitudinal changes in functional coupling between the two RFAs following unilateral photothrombotic stroke in CFA (mm from Bregma: +0.5 anterior, +1.25 lateral). Local field potentials (LFPs) were recorded from the RFAs of both hemispheres in freely moving injured and naïve mice. Neural signals were acquired at 9, 16 and 23 days after surgery (sub-acute period in stroke animals) through one bipolar electrode per hemisphere placed in the center of RFA, with a ground screw over the occipital bone. LFPs were pre-processed through an efficient method of artifact removal and analysed through: spectral,cross-correlation, mutual information and Granger causality analysis. Spectral analysis demonstrated an early decrease (day 9) in the alpha band power in both the RFAs. In the late sub-acute period (days 16 and 23), inter-hemispheric functional coupling was reduced in ischemic animals, as shown by a decrease in the cross-correlation and mutual information measures. Within the gamma and delta bands, correlation measures were already reduced at day 9. Granger analysis, used as a measure of the symmetry of the inter-hemispheric causal connectivity, showed a less balanced activity in the two RFAs after stroke, with more frequent oscillations of hemispheric dominance. These results indicate robust electrophysiological changes in PMAs after stroke. Specifically, we found alterations in transcallosal connectivity, with reduced inter-hemispheric functional coupling and a fluctuating dominance

Post-Stroke Longitudinal Alterations of Inter-Hemispheric Correlation and Hemispheric Dominance in Mouse Pre-Motor Cortex.

Directory of Open Access Journals (Sweden)

Fabio Vallone

Full Text Available Limited restoration of function is known to occur spontaneously after an ischemic injury to the primary motor cortex. Evidence suggests that Pre-Motor Areas (PMAs may "take over" control of the disrupted functions. However, little is known about functional reorganizations in PMAs. Forelimb movements in mice can be driven by two cortical regions, Caudal and Rostral Forelimb Areas (CFA and RFA, generally accepted as primary motor and pre-motor cortex, respectively. Here, we examined longitudinal changes in functional coupling between the two RFAs following unilateral photothrombotic stroke in CFA (mm from Bregma: +0.5 anterior, +1.25 lateral.Local field potentials (LFPs were recorded from the RFAs of both hemispheres in freely moving injured and naïve mice. Neural signals were acquired at 9, 16 and 23 days after surgery (sub-acute period in stroke animals through one bipolar electrode per hemisphere placed in the center of RFA, with a ground screw over the occipital bone. LFPs were pre-processed through an efficient method of artifact removal and analysed through: spectral,cross-correlation, mutual information and Granger causality analysis.Spectral analysis demonstrated an early decrease (day 9 in the alpha band power in both the RFAs. In the late sub-acute period (days 16 and 23, inter-hemispheric functional coupling was reduced in ischemic animals, as shown by a decrease in the cross-correlation and mutual information measures. Within the gamma and delta bands, correlation measures were already reduced at day 9. Granger analysis, used as a measure of the symmetry of the inter-hemispheric causal connectivity, showed a less balanced activity in the two RFAs after stroke, with more frequent oscillations of hemispheric dominance.These results indicate robust electrophysiological changes in PMAs after stroke. Specifically, we found alterations in transcallosal connectivity, with reduced inter-hemispheric functional coupling and a fluctuating

Shearwater foraging in the Southern Ocean: the roles of prey availability and winds.

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Ben Raymond

Full Text Available BACKGROUND: Sooty (Puffinus griseus and short-tailed (P. tenuirostris shearwaters are abundant seabirds that range widely across global oceans. Understanding the foraging ecology of these species in the Southern Ocean is important for monitoring and ecosystem conservation and management. METHODOLOGY/PRINCIPAL FINDINGS: Tracking data from sooty and short-tailed shearwaters from three regions of New Zealand and Australia were combined with at-sea observations of shearwaters in the Southern Ocean, physical oceanography, near-surface copepod distributions, pelagic trawl data, and synoptic near-surface winds. Shearwaters from all three regions foraged in the Polar Front zone, and showed particular overlap in the region around 140 degrees E. Short-tailed shearwaters from South Australia also foraged in Antarctic waters south of the Polar Front. The spatial distribution of shearwater foraging effort in the Polar Front zone was matched by patterns in large-scale upwelling, primary production, and abundances of copepods and myctophid fish. Oceanic winds were found to be broad determinants of foraging distribution, and of the flight paths taken by the birds on long foraging trips to Antarctic waters. CONCLUSIONS/SIGNIFICANCE: The shearwaters displayed foraging site fidelity and overlap of foraging habitat between species and populations that may enhance their utility as indicators of Southern Ocean ecosystems. The results highlight the importance of upwellings due to interactions of the Antarctic Circumpolar Current with large-scale bottom topography, and the corresponding localised increases in the productivity of the Polar Front ecosystem.

Reorganization of syntactic processing following left-hemisphere brain damage: does right-hemisphere activity preserve function?

OpenAIRE

Tyler, Lorraine K.; Wright, Paul; Randall, Billi; Marslen-Wilson, William D.; Stamatakis, Emmanuel A.

2010-01-01

The extent to which the human brain shows evidence of functional plasticity across the lifespan has been addressed in the context of pathological brain changes and, more recently, of the changes that take place during healthy ageing. Here we examine the potential for plasticity by asking whether a strongly left-lateralized system can successfully reorganize to the right-hemisphere following left-hemisphere brain damage. To do this, we focus on syntax, a key linguistic function considered to b...

A dual task priming investigation of right hemisphere inhibition for people with left hemisphere lesions

Directory of Open Access Journals (Sweden)

Smith-Conway Erin R

2012-03-01

Full Text Available Abstract Background During normal semantic processing, the left hemisphere (LH is suggested to restrict right hemisphere (RH performance via interhemispheric suppression. However, a lesion in the LH or the use of concurrent tasks to overload the LH's attentional resource balance has been reported to result in RH disinhibition with subsequent improvements in RH performance. The current study examines variations in RH semantic processing in the context of unilateral LH lesions and the manipulation of the interhemispheric processing resource balance, in order to explore the relevance of RH disinhibition to hemispheric contributions to semantic processing following a unilateral LH lesion. Methods RH disinhibition was examined for nine participants with a single LH lesion and 13 matched controls using the dual task paradigm. Hemispheric performance on a divided visual field lexical decision semantic priming task was compared over three verbal memory load conditions, of zero-, two- and six-words. Related stimuli consisted of categorically related, associatively related, and categorically and associatively related prime-target pairs. Response time and accuracy data were recorded and analyzed using linear mixed model analysis, and planned contrasts were performed to compare priming effects in both visual fields, for each of the memory load conditions. Results Control participants exhibited significant bilateral visual field priming for all related conditions (p Conclusions The results from the control group are consistent with suggestions of an age related hemispheric asymmetry reduction and indicate that in healthy aging compensatory bilateral activation may reduce the impact of inhibition. In comparison, the results for the LHD group indicate that following a LH lesion RH semantic processing can be manipulated and enhanced by the introduction of a verbal memory task designed to engage LH resources and allow disinhibition of RH processing.

Interindividual variability in the hemispheric organization for speech.

Science.gov (United States)

Tzourio-Mazoyer, N; Josse, G; Crivello, F; Mazoyer, B

2004-01-01

A PET activation study was designed to investigate hemispheric specialization during speech comprehension and production in right- and left-handed subjects. Normalized regional cerebral blood flow (NrCBF) was repeatedly monitored while subjects either listened to factual stories (Story) or covertly generated verbs semantically related to heard nouns (Gener), using silent resting (Rest) as a common control condition. NrCBF variations in each task, as compared to Rest, as well as functional asymmetry indices (FAI = right minus left NrCBF variations), were computed in anatomical regions of interest (AROIs) defined on the single-subject MNI template. FAIs were predominantly leftward in all regions during both tasks, although larger FAIs were observed during Gener. Subjects were declared "typical" for language hemispheric specialization based on the presence of significant leftward asymmetries (FAI Gener, and in the middle and inferior temporal AROIs during Story. Six subjects (including five LH) showed an atypical language representation. Among them, one presented a right hemisphere specialization during both tasks, another a shift in hemispheric specialization from production to comprehension (left during Gener, right during Story). The group of 14 typical subjects showed significant positive correlation between homologous left and right AROIs NrCBF variations in temporal areas during Story, and in temporal and inferior frontal areas during Gener, almost all regions presenting a leftward FAI. Such correlations were also present in deactivated areas with strong leftward asymmetry (supramarginalis gyrus, inferior parietal region). These results suggest that entry into a language task translates into a hemispheric reconfiguration of lateral cortical areas with global NrCBF increase in the dominant hemisphere and decrease in the minor hemisphere. This can be considered as the setting up of a "language mode", under the control of a mechanism that operates at a perisylvian

Polarization measurements of auroral kilometric radiation by Dynamics Explorer-1

International Nuclear Information System (INIS)

Shawhan, S.D.; Gurnett, D.A.

1982-01-01

The plasma wave instrument (PWI) on the Dynamics Explorer-1 has been used to measure polarization of auroral kilometric radiation (AKR) at frequencies of 50 to 400 kHz in both the northern and the southern nightside auroral regions at altitudes of 1 to 3 R/sub E/ above the AKR source regions. The AKR polarization sense is found to be the same as the right hand polarized auroral hiss found in the frequency range of 0.8 to 6.4 kHz. Consequently, these unambiguous direct polarization measurements of AKR lead to the conclusion that AKR escapes the magnetosphere in the R-X mode. Since DE-1 is close to the source region, it can be inferred that AKR is generated predominately in the R-X mode

A THEORETICAL STUDY OF THE BUILD-UP OF THE SUN’S POLAR MAGNETIC FIELD BY USING A 3D KINEMATIC DYNAMO MODEL

Energy Technology Data Exchange (ETDEWEB)

Hazra, Gopal; Choudhuri, Arnab Rai [Department of Physics, Indian Institute of Science, Bangalore, 560012 (India); Miesch, Mark S., E-mail: ghazra@physics.iisc.ernet.in, E-mail: arnab@physics.iisc.ernet.in, E-mail: miesch@ucar.edu [High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO 80301 (United States)

2017-01-20

We develop a three-dimensional kinematic self-sustaining model of the solar dynamo in which the poloidal field generation is from tilted bipolar sunspot pairs placed on the solar surface above regions of strong toroidal field by using the SpotMaker algorithm, and then the transport of this poloidal field to the tachocline is primarily caused by turbulent diffusion. We obtain a dipolar solution within a certain range of parameters. We use this model to study the build-up of the polar magnetic field and show that some insights obtained from surface flux transport models have to be revised. We present results obtained by putting a single bipolar sunspot pair in a hemisphere and two symmetrical sunspot pairs in two hemispheres. We find that the polar fields produced by them disappear due to the upward advection of poloidal flux at low latitudes, which emerges as oppositely signed radial flux and which is then advected poleward by the meridional flow. We also study the effect that a large sunspot pair, violating Hale’s polarity law, would have on the polar field. We find that there would be some effect—especially if the anti-Hale pair appears at high latitudes in the mid-phase of the cycle—though the effect is not very dramatic.

Timing of the Little Ice Age in southern Greenland

DEFF Research Database (Denmark)

Kjær, Kurt H.; Kjeldsen, Kristian K.; Bjørk, Anders A.

2013-01-01

as a signal for ice-free terrain being overridden by LIA glacier advances, and data from threshold lakes showing the onset of glacier-fed lakes, thus revealing the advance-maximum phase initiating the LIA. Finally, we have compiled lichenometry results indicating the onset of bedrock vegetation succeeding ice......Northern hemisphere temperatures reached their Holocene minimum and most glaciers reached their maximum during The Little Ice Age (LIA), but the timing of specific cold intervals is site-specific. In southern Greenland, we have compiled data from organic matter incorporated in LIA sediments, used...

The Little Ice Age climate of New Zealand reconstructed from Southern Alps cirque glaciers: a synoptic type approach

Science.gov (United States)

Lorrey, Andrew; Fauchereau, Nicolas; Stanton, Craig; Chappell, Petra; Phipps, Steven; Mackintosh, Andrew; Renwick, James; Goodwin, Ian; Fowler, Anthony

2014-06-01

Little Ice Age (LIA) austral summer temperature anomalies were derived from palaeoequilibrium line altitudes at 22 cirque glacier sites across the Southern Alps of New Zealand. Modern analog seasons with temperature anomalies akin to the LIA reconstructions were selected, and then applied in a sampling of high-resolution gridded New Zealand climate data and global reanalysis data to generate LIA climate composites at local, regional and hemispheric scales. The composite anomaly patterns assist in improving our understanding of atmospheric circulation contributions to the LIA climate state, allow an interrogation of synoptic type frequency changes for the LIA relative to present, and provide a hemispheric context of the past conditions in New Zealand. An LIA summer temperature anomaly of -0.56 °C (±0.29 °C) for the Southern Alps based on palaeo-equilibrium lines compares well with local tree-ring reconstructions of austral summer temperature. Reconstructed geopotential height at 1,000 hPa (z1000) suggests enhanced southwesterly flow across New Zealand occurred during the LIA to generate the terrestrial temperature anomalies. The mean atmospheric circulation pattern for summer resulted from a crucial reduction of the `HSE'-blocking synoptic type (highs over and to the west of NZ; largely settled conditions) and increases in both the `T'- and `SW'-trough synoptic types (lows passing over NZ; enhanced southerly and southwesterly flow) relative to normal. Associated land-based temperature and precipitation anomalies suggest both colder- and wetter-than-normal conditions were a pervasive component of the base climate state across New Zealand during the LIA, as were colder-than-normal Tasman Sea surface temperatures. Proxy temperature and circulation evidence were used to corroborate the spatially heterogeneous Southern Hemisphere composite z1000 and sea surface temperature patterns generated in this study. A comparison of the composites to climate mode archetypes

The response of Antarctica MLT region for the recent Sudden Stratospheric Warming (SSW) over Southern Hemisphere (SH): An overview

Science.gov (United States)

Eswaraiah, S.; Kim, Y.; Lee, J.; Kim, J. H.; Venkat Ratnam, M.; Riggin, D. M.; Vijaya Bhaskara Rao, S.

2017-12-01

A minor Sudden Stratospheric Warming (SSW) was noticed in the southern hemisphere (SH) during the September (day 259) 2010 along with two episodic warmings in early August (day 212) and late October (day 300) 2010. The signature of the mesosphere and lower thermosphere (MLT) response was detected using the ground based and space borne observations along with the model predictions. The changes in the mesosphere wind field were studied from the observations of both meteor radar and MF radar located at King Sejong Station (62.22°S, 58.78°W) and Rothera (68oS, 68oW), Antarctica, respectively. The zonal winds in the mesosphere reversed approximately a week before the September SSW occurrence. We have also analyzed the MLT tides using both the radars and noticed strong enhancement of semi-diurnal tide (SDT) a few days later the cessation of 2010 SSW. We note the similar enhancement during the 2002 major SSW. Specifically, the SDT amplitude enhancement is greater for the 2010 SSW than 2002 SSW. We found that strong 14-16 day PWs prevailed prior to the 2010 minor SSW and disappeared suddenly after the SSW in the mesosphere by generating the quasi-secondary waves of periodicity 3-9 days. The mesosphere wind reversal is also noticed in "Specified Dynamics" version of Whole Atmosphere Community Climate Model (SD-WACCM) and Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA) simulations. The similar zonal wind weakening/reversal in the lower thermosphere between 100 and 140 km are simulated by GAIA. Further, we observed the mesospheric cooling in consistency with SSWs using Microwave Limb Sounder (MLS) data. However, the GAIA simulations showed warming between 130 and 140 km after few days of SSW. Thus, the observation and model simulation indicate for the first time that the 2010 minor SSW also affects dynamics of the MLT region over SH in a manner similar to the 2002 major SSW.

Empirical high-latitude electric field models

International Nuclear Information System (INIS)

Heppner, J.P.; Maynard, N.C.

1987-01-01

Electric field measurements from the Dynamics Explorer 2 satellite have been analyzed to extend the empirical models previously developed from dawn-dusk OGO 6 measurements (J.P. Heppner, 1977). The analysis embraces large quantities of data from polar crossings entering and exiting the high latitudes in all magnetic local time zones. Paralleling the previous analysis, the modeling is based on the distinctly different polar cap and dayside convective patterns that occur as a function of the sign of the Y component of the interplanetary magnetic field. The objective, which is to represent the typical distributions of convective electric fields with a minimum number of characteristic patterns, is met by deriving one pattern (model BC) for the northern hemisphere with a +Y interplanetary magnetic field (IMF) and southern hemisphere with a -Y IMF and two patterns (models A and DE) for the northern hemisphere with a -Y IMF and southern hemisphere with a +Y IMF. The most significant large-scale revisions of the OGO 6 models are (1) on the dayside where the latitudinal overlap of morning and evening convection cells reverses with the sign of the IMF Y component, (2) on the nightside where a westward flow region poleward from the Harang discontinuity appears under model BC conditions, and (3) magnetic local time shifts in the positions of the convection cell foci. The modeling above was followed by a detailed examination of cases where the IMF Z component was clearly positive (northward). Neglecting the seasonally dependent cases where irregularities obscure pattern recognition, the observations range from reasonable agreement with the new BC and DE models, to cases where different characteristics appeared primarily at dayside high latitudes

A Multiproxy Reconstruction of Holocene Southern Westerlies from the Auckland Islands

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Nichols, J. E.; Moy, C. M.; Peteet, D. M.; Weiss, A.; Curtin, L. G.

2015-12-01

The strength and position of the Southern Hemisphere Westerly Wind belt plays an important role in our understanding of the global carbon cycle and glacial-interglacial climate change. We present a paleoclimate record that is primarily influenced by the strength and latitudinal position of the Southern Hemisphere Westerly Winds from a late Holocene lake sediment core and a peat core that spans the last 13,000 years, both obtained from New Zealand's subantarctic Auckland Islands (50°S, 166°E). Several proxy indicators contribute to our reconstruction. Hydrogen isotope ratios of specific organic molecules allow us to reconstruct the hydrogen isotope ratios of precipitation. Using macrofossil counts and the abundances of leaf wax biomarkers, we are able to estimate the moisture balance at our sites. Model simulations of the Westerlies and the rate and isotope ratios of precipitation allow us to interpret our proxy data as changes in the strength and position of the Westerly Winds. In our lacustrine sediment, we found that the Westerlies have been shifting southward since the Little Ice Age, consistent with modern observations of a southward shift. In the peatland sediment, we found a multi-millennial northward shift in the Westerlies during the middle Holocene. We will present further ongoing work that strengthens the chronology of Auckland Islands environmental change and integrates these results with vegetation shifts identified in pollen and macrofossil data.

Hypothalamic digoxin, hemispheric chemical dominance, and mesenteric artery occlusion.

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Kurup, Ravi Kumar; Kurup, Paramesware Achutha

2003-12-01

The role of the isoprenoid pathway in vascular thrombosis, especially mesenteric artery occlusion and its relation to hemispheric dominance, was assessed in this study. The following parameters were measured in patients with mesenteric artery occlusion and individuals with right hemispheric, left hemispheric, and bihemispheric dominance: (1) plasma HMG CoA reductase, digoxin, dolichol, ubiquinone, and magnesium levels; (2) tryptophan/tyrosine catabolic patterns; (3) free radical metabolism; (4) glycoconjugate metabolism; and (5) membrane composition. In patients with mesenteric artery occlusion there was elevated digoxin synthesis, increased dolichol and glycoconjugate levels, low ubiquinone, and elevated free radical levels. The RBC membrane Na(+)-K+ ATPase activity and serum magnesium were decreased. There was also an increase in tryptophan catabolites and reduction in tyrosine catabolites in the serum. There was an increase in cholesterol:phospholipid ratio and a reduction in glycoconjugate level of RBC membrane in these patients. The biochemical patterns obtained in mesenteric artery occlusion is similar to those obtained in left-handed/right hemispheric dominant individuals by the dichotic listening test. But all the patients with mesenteric artery occlusion were right-handed/left hemispheric dominant by the dichotic listening test. Hemispheric chemical dominance has no correlation with handedness or the dichotic listening test. Mesenteric artery occlusion occurs in right hemispheric chemically dominant individuals and is a reflection of altered brain function. Hemispheric chemical dominance may thus control the risk for developing vascular thrombosis in individuals.

Hypothalamic digoxin, hemispheric chemical dominance, and the tridosha theory.

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Kurup, Ravi Kumar; Kurup, Parameswara Achutha

2003-05-01

Ayurveda, the traditional Indian System of Medicine, deals with the theory of the three tridosha states (both physical and psychological): Vata, Pitta, and Kapha. They are the three major human constitutional types that both depend on psychological and physical characteristics. The Pitta state is described as a critical, discriminative, and rational psychological state of mind, while the Kapha state is described as being dominant for emotional stimuli. The Vata state is an intermediate unstable shifting state. The Pitta types are of average height and built with well developed musculature. The Vata types are thin individuals with low body mass index. The Kapha types are short stocky individuals that tend toward obesity, and who are sedentary. The study assessed the biochemical differences between right hemispheric dominant, bihemispheric dominant, and left hemispheric dominant individuals, and then compared this with the patterns obtained in the Vata, Pitta, and Kapha states. The isoprenoid metabolites (digoxin, dolichol, and ubiquinone), glycoconjugate metabolism, free radical metabolism, and the RBC membrane composition were studied. The hemispheric chemical dominance in various systemic diseases and psychological states was also investigated. The results showed that right hemispheric chemically dominant/Kapha state had elevated digoxin levels, increased free radical production and reduced scavenging, increased tryptophan catabolites and reduced tyrosine catabolites, increased glycoconjugate levels and increased cholesterol: phospholipid ratio of RBC membranes. Left hemispheric chemically dominant/Pitta states had the opposite biochemical patterns. The patterns were normal or intermediate in the bihemispheric chemically dominant/Vata state. This pattern could be correlated with various systemic and neuropsychiatric diseases and personality traits. Right hemispheric chemical dominance/Kapha state represents a hyperdigoxinemic state with membrane sodium

Hypothalamic digoxin, hemispheric chemical dominance, and chronic bronchitis emphysema.

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Kurup, Ravi Kumar; Kurup, Parameswara Achutha

2003-09-01

The isoprenoid pathway produces three key metabolites--endogenous digoxin (membrane sodium-potassium ATPase inhibitor, immunomodulator, and regulator of neurotransmitter/amino acid transport), dolichol (regulates N-glycosylation of proteins), and ubiquinone (free radical scavenger). This was assessed in patients with chronic bronchitis emphysema. The pathway was also assessed in patients with right hemispheric, left hemispheric, and bihemispheric dominance to find the role of hemispheric dominance in the pathogenesis of chronic bronchitis emphysema. All the 15 patients with chronic bronchitis emphysema were right-handed/left hemispheric dominant by the dichotic listening test. In patients with chronic bronchitis emphysema there was elevated digoxin synthesis, increased dolichol, and glycoconjugate levels, and low ubiquinone and elevated free radical levels. There was also an increase in tryptophan catabolites and a reduction in tyrosine catabolites. There was an increase in cholesterol:phospholipid ratio and a reduction in glycoconjugate levels of RBC membrane in patients with chronic bronchitis emphysema. The same biochemical patterns were obtained in individuals with right hemispheric dominance. Endogenous digoxin by activating the calcineurin signal transduction pathway of T-cell can contribute to immune activation in chronic bronchitis emphysema. Increased free radical generation can also lead to immune activation. Endogenous synthesis of nicotine can contribute to the pathogenesis of the disease. Altered glycoconjugate metabolism and membranogenesis can lead to defective lysosomal stability contributing to the disease process by increased release of lysosomal proteases. The role of an endogenous digoxin and hemispheric dominance in the pathogenesis of chronic bronchitis emphysema and in the regulation of lung structure/function is discussed. The biochemical patterns obtained in chronic bronchitis emphysema is similar to those obtained in left

The "Creative Right Brain" Revisited: Individual Creativity and Associative Priming in the Right Hemisphere Relate to Hemispheric Asymmetries in Reward Brain Function.

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Aberg, Kristoffer Carl; Doell, Kimberly C; Schwartz, Sophie

2017-10-01

The idea that creativity resides in the right cerebral hemisphere is persistent in popular science, but has been widely frowned upon by the scientific community due to little empirical support. Yet, creativity is believed to rely on the ability to combine remote concepts into novel and useful ideas, an ability which would depend on associative processing in the right hemisphere. Moreover, associative processing is modulated by dopamine, and asymmetries in dopamine functionality between hemispheres may imbalance the expression of their implemented cognitive functions. Here, by uniting these largely disconnected concepts, we hypothesize that relatively less dopamine function in the right hemisphere boosts creativity by releasing constraining effects of dopamine on remote associations. Indeed, participants with reduced neural responses in the dopaminergic system of the right hemisphere (estimated by functional MRI in a reward task with positive and negative feedback), displayed higher creativity (estimated by convergent and divergent tasks), and increased associative processing in the right hemisphere (estimated by a lateralized lexical decision task). Our findings offer unprecedented empirical support for a crucial and specific contribution of the right hemisphere to creativity. More importantly our study provides a comprehensive view on potential determinants of human creativity, namely dopamine-related activity and associative processing. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

The Effectiveness of 1 Hz rTMS Over the Primary Motor Area of the Unaffected Hemisphere to Improve Hand Function After Stroke Depends on Hemispheric Dominance.

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Lüdemann-Podubecká, Jitka; Bösl, Kathrin; Theilig, Steven; Wiederer, Ralf; Nowak, Dennis Alexander

2015-01-01

Inhibition of motor cortex excitability of the contralesional hemisphere may improve dexterity of the affected hand after stroke. 40 patients (17 dominant hemispheric stroke, 23 non-dominant hemispheric stroke) with a mild to moderate upper limb motor impairment were enrolled in a double-blind, randomized, placebo-controlled trial with two parallel-groups. Both groups received 15 daily sessions of motor training preceded by either 1 Hz rTMS or sham rTMS. Behavioral and neurophysiological evaluations were performed at baseline, after the first week and after the third week of treatment, and after a 6 months follow-up. In both groups motor function of the affected hand improved significantly. Patients with stroke of the non-dominant hemisphere made a similar improvement, regardless of whether the motor training was preceded by sham or 1 Hz rTMS. Patients with stroke of the dominant hemisphere had a less favorable improvement than those with stroke of the non-dominant hemisphere after motor training preceded by sham rTMS. However, when 1 Hz rTMS preceded the motor training, patients with stroke of the dominant hemisphere made a similar improvement as those with stroke of the non-dominant hemisphere. Motor recovery of the affected upper limb after stroke is determined by dominance of the affected hemisphere. Stroke of the dominant hemisphere is associated with per se poorer improvement of the affected hand. 1 Hz rTMS over the contralesional M1 significantly improves dexterity of the affected hand in patients with stroke of the dominant hemisphere, but not in those with stroke of the non-dominant hemisphere. Copyright © 2015 Elsevier Inc. All rights reserved.

A new dipolar potential for numerical simulations of polar fluids on the 4D hypersphere

International Nuclear Information System (INIS)

Caillol, Jean-Michel; Trulsson, Martin

2014-01-01

We present a new method for Monte Carlo or Molecular Dynamics numerical simulations of three-dimensional polar fluids. The simulation cell is defined to be the surface of the northern hemisphere of a four-dimensional (hyper)sphere. The point dipoles are constrained to remain tangent to the sphere and their interactions are derived from the basic laws of electrostatics in this geometry. The dipole-dipole potential has two singularities which correspond to the following boundary conditions: when a dipole leaves the northern hemisphere at some point of the equator, it reappears at the antipodal point bearing the same dipole moment. We derive all the formal expressions needed to obtain the thermodynamic and structural properties of a polar liquid at thermal equilibrium in actual numerical simulation. We notably establish the expression of the static dielectric constant of the fluid as well as the behavior of the pair correlation at large distances. We report and discuss the results of extensive numerical Monte Carlo simulations for two reference states of a fluid of dipolar hard spheres and compare these results with previous methods with a special emphasis on finite size effects

Northern Hemisphere Winter Climate Response to Greenhouse Gas, Ozone, Solar and Volcanic Forcing

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Shindell, Drew T.; Schmidt, Gavin A.; Miller, Ron L.; Rind, David; Hansen, James E. (Technical Monitor)

2001-01-01

The Goddard Institute for Space Studies (GISS) climate/middle atmosphere model has been used to study the impacts of increasing greenhouse gases, polar ozone depletion, volcanic eruptions, and solar cycle variability. We focus on the projection of the induced responses onto Northern Hemisphere winter surface climate. Changes in the model's surface climate take place largely through enhancement of existing variability patterns, with greenhouse gases, polar ozone depletion and volcanic eruptions primarily affecting the Arctic Oscillation (AO) pattern. Perturbations descend from the stratosphere to the surface in the model by altering the propagation of planetary waves coming up from the surface, in accord with observational evidence. Models lacking realistic stratospheric dynamics fail to capture these wave flux changes. The results support the conclusion that the stratosphere plays a crucial role in recent AO trends. We show that in our climate model, while ozone depletion has a significant effect, greenhouse gas forcing is the only one capable of causing the large, sustained increase in the AO observed over recent decades. This suggests that the AO trend, and a concurrent strengthening of the stratospheric vortex over the Arctic, are very likely anthropogenic in origin.

Western Hemisphere Zuphiini: descriptions of Coarazuphium whiteheadi, new species, and Zuphioides, new genus, and classification of the genera (Coleoptera, Carabidae

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George Ball

2013-07-01

Full Text Available Based on small samples (exemplars analyzed with morphological methods, including detailed descriptions and illustrations, this study treats primarily the Zuphium genus-group in the Western Hemisphere, which comprises two precinctive genera: Coarazuphium Gnaspini, Vanin & Godoy, 1998 (type species Parazuphium tessai Godoy & Vanin, 1990 and Zuphioides gen. n. (type species Zuphium mexicanum Chaudoir, 1863. The genus Coarazuphium includes six troglobitic species from Brazilian caves, and one probably hypogaeic (troglophilic species from the mountains of Oaxaca, in Mexico (C. whiteheadi, sp. n., type locality, ridge top, in western Oaxaca, Mexico, at 2164 m, 35 km north of San Pedro Juchatengo, 16.462N, 97.010W. The epigaeic genus Zuphioides includes 23 species, with its geographical range extended from Neotropical temperate Argentina in southern South America, northward through the tropics to north temperate southeastern Canada, in the Nearctic Region. Keys are provided to the species of Coarazuphium and to the genera of Western Hemisphere Zuphiini.

Significance of Hemispheric Security for Mexico

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2003-04-07

La Seguridad Internacional, la Nueva Geopolitica Continental y Mexico ,” Seminario Internacional sobre Misiones de Paz, Seguridad y Defensa, Rio de...USAWC STRATEGY RESEARCH PROJECT SIGNIFICANCE OF HEMISPHERIC SECURITY FOR MEXICO by LTC Enrique Garcia Jaramillo Cavalry, Mexican Army COL Joseph R...xx-xx-2002 to xx-xx-2003 4. TITLE AND SUBTITLE Significance of Hemispheric Security for Mexico Unclassified 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c

Methods of dichotic listening as a research methodology for hemispheric interaction.

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Kovyazina M.S.

2014-07-01

Full Text Available Experimental data was obtained from a dichotic listening test by patients with unilateral brain lesions and corpus callosum pathology (agenesis, cysts, degenerative changes, etc. Efficiency index analysis shows that interhemispheric interaction in the audioverbal sphere depends to a greater extent on the right hemisphere state. The dichotic listening technique is not an informative means of studying hemispheric interaction, since it does not allow a clear distinction between hemispheric symptoms and symptoms of pathology of the corpus callosum. Thus, violations of hemispheric relations caused by disorders of the corpus callosum and cerebral hemispheres change worth more right hemisphere activity.