the late paleozoic el imperial formation western argentina glacial to post glacial transition and stratigraphic correlations with arc related basins in southwestern gondwana abstract the el imperial formation of the san rafael basin records a succession of depositional environments during the latest mississippian to earliest permian that span before during and after the glaciation of west central argentina at the base of the formation a restricted marine environment is recorded in mudstone containing marl and rippled and deformed sandstone beds this unit or sequence 1 is incised by a deltaic facies association composed of cross bedded sandstone and conglomerate that form at least 5 stacked gilbert deltas the deltaic facies association grades upward into the glacially influenced facies association made up of stratified diamictite mudstone with dropstones and massive deformed sandstone indicating deposition by wet based tidewater glaciers that calved icebergs into the basin with contributions from mass movement processes the glacially influenced facies association is overlain by mudstone and horizontally laminated and cross bedded sandstone of the post glacial open marine facies association recording post glacial transgression followed by relative sea level fall the deltaic glacially influenced and post glacial open marine facies associations comprise sequence 2 sequence 2 is incised by conglomerate of the upper fluvial member or sequence 3 the strata of the el imperial formation are correlated to those of the other arc related basins of western argentina rio blanco calingasta uspallata and tepuel a bashkirian transgression and fluvial incision in the el imperial formation correlate with events in the rio blanco and calingasta uspallata basins to the north whereas glaciation continues to the south in the tepuel basin through the early permian the deviating stratigraphic record of the tepuel basin may be the result of its higher latitudinal position during the pennsylvanian early permian and higher altitude due to either tectonic convergence of the patagonian microplate or convergence along the panthalassan margin of southwestern gondwana

a climatology of cyclogenesis for the southern hemisphere abstract this study surveys life cycle characteristics of cyclones in the southern hemisphere sh an objective technique for locating instances of cyclone formation intensification maturation and decay is applied to a 7 year dataset of sh cyclone positions obtained from an automated finding and tracking scheme based on twice daily ecmwf analyses during 1980 86 geostrophic vorticity g at 1000 hpa is used to locate cyclones and determine their intensity cyclones form and develop within middle latitudes and migrate eastward and poleward during their lives preferred genesis and cyclogenesis regions include eastern coasts of australia and south america in winter and leeward of the andes and near the baroclinic zones associated with the principal upper tropospheric jet streams year round over open water winter cyclones tend to form and intensify near zones of strongest sst gradient rapid cyclogenesis is most frequent east of south america southeast of africa south of australia and near new zeal

a new perspective on southern hemisphere storm tracks abstract a detailed view of southern hemisphere storm tracks is obtained based on the application of filtered variance and modern feature tracking techniques to a wide range of 45 yr european centre for medium range weather forecasts ecmwf re analysis era 40 data it has been checked that the conclusions drawn in this study are valid even if data from only the satellite era are used the emphasis of the paper is on the winter season but results for the four seasons are also discussed both upper and lower tropospheric fields are used the tracking analysis focuses on systems that last longer than 2 days and are mobile move more than 1000 km many of the results support previous ideas about the storm tracks but some new insights are also obtained in the summer there is a rather circular strong deep high latitude storm track in winter the high latitude storm track is more asymmetric with a spiral from the atlantic and indian oceans in toward antarctica and a subtropical jet related lower latitu

storm tracks in the southern hemisphere abstract from 1979 to 1989 global european centre for medium range weather forecasts ecmwf analyses of many meteorological variables important in baroclinic storms have been bandpass filtered to highlight fluctuations on 2 to 8 day time scales in order to illuminate the relationships among the variables in baroclinic storm track regions because of the greater zonal symmetry in the southern hemisphere sh versus the northern hemisphere nh it is possible to examine these relationships over a zonal sector without being dominated by local effects associated with jet stream entrance and exit regions of the storm tracks the bandpassed variance of geopotential height is used to define the storm track and its meridional profile has a pronounced midlatitude maximum in the sh the locations of the jet stream and the variance maxima of meridional and zonal velocity components vorticity vertical motion specific humidity and temperature all bear a distinctive relationship to the storm track but the lat

an objective cyclone climatology for the southern hemisphere abstract an objective method is developed and used to derive a climatology of centers of cyclonic vorticity for the southern hemisphere based on twice daily european centre for medium range weather forecasts ecmwf 1000 hpa analyses during 1980 86 these centers were computed as local minima of geostrophic relative vorticity g extending previous studies based on pressure minima this use of g avoids a bias favoring slower and or deeper cyclones that occurs when pressure is used and includes a large number of additional mobile vorticity centers in the 45 55 s band that are missed where a local pressure minimum cannot be found an automated tracking algorithm similar to that of murray and simmonds is used to match predicted location pressure and g from previous track history with available centers large numbers of g centers were found south of 60 s and near the midlatitude continents as in previous studies these were a mixture of migratory centers and other fixed topographic features the maxi

facies control on sandstone composition and influence of statistical methods on interpretations in the john henry member straight cliffs formation southern utah usa abstract the upper cretaceous john henry member of the straight cliffs formation preserves regressive shoreface and channel facies and transgressive lagoonal tidal inlet facies that suggest distinct modal sandstone compositions detrital modes from six sandstone facies upper shoreface lower shoreface deflected mouth bars fluvial channels tidal inlets and washover fans and their spatial and temporal variations provide additional data regarding the depositional environments and setting of the john henry member three statistical methods were utilized univariate standard deviation and confidence interval and multivariate logratio transformations to assess the compositional difference between facies using estimation of means both univariate statistical methods have some inherent problems standard deviation does not account for sample size while the confidence interval method incorporates a t test to account for only some of the uncertainty of small sample size the results of the univariate methods differ slightly and both indicate statistically distinct sandstone compositions based on facies multivariate statistics are much more robust and suggest similar trends yet display different compositional means and have inconclusive confidence fields as they incorporate all of the uncertainty associated with small sampling sizes in general sandstone compositions become more quartz rich and compositionally mature as sediment is transported from proximal fluvial environments to distal upper shoreface environments this trend reflects the degree of preferential reworking or winnowing of unstable grains prior to lithification more complicated relationships are observed as facies distributions shift through space and time sandstone compositions support a deflected wave dominated deltaic interpretation for the john henry member in this area sandstone compositions become more lithic rich from north to south corresponding to the facies distribution of upper shoreface and deflected mouth bars respectively mouth bars occur at the intersection of the fluvial channel and the coastline where sand is deflected via longshore drift to the southern portion of the field area upper shoreface facies located further away from mouth bar facies are heavily reworked by wave processes and contain more mature quartz rich modal compositions additionally high feldspathic and lithic concentrations in tidal inlet facies suggest that this facies was sourced closer to mouth bars rather than updrift upper shoreface sediments a shift in sandstone composition occurs at the end of the second transgressive regressive cycle of the john henry member throughout the rogers canyon area this compositional change is concurrent with a relatively large basinward shift in facies which suggests that it reflects the transition from regressive to transgressive facies associated with the relative sea level fall rather than a change in the main sediment source area

seasonal variations in the southern hemisphere storm tracks and jet streams as revealed in a reanalysis dataset abstract regional characteristics of the climatological seasonal variations in southern hemisphere sh storm tracks are examined based on a reanalysis dataset when differences in vertical structure between the subpolar and subtropical jet streams spj and stj respectively are considered the regional characteristics can be interpreted reasonably well from a potential vorticity perspective of baroclinic eddy growth and downstream development of a baroclinic wave packet eddy activity in the upper and lower tropospheres is strongest in the core region of the spj over the eastern south atlantic and indian ocean throughout the year even in austral winter when the intense stj forms over the indian ocean and south pacific showing its eddy driven nature the spj accompanies the strong surface westerlies along a well defined baroclinic zone above an intense oceanic frontal zone in this core region of the storm track low level eddy activity is strongly correlated with the local near surface baroclinicity

southern hemisphere strong polar mesoscale cyclones in high resolution datasets mesoscale cyclones are small low pressure systems usually 500 km in radius that often appear embedded in synoptic structures these events can be weak and short lived or vigorous and destructive here we use an automatic tracking scheme to investigate two subsets of southern hemisphere mesoscale cyclones that are strong and have the potential to cause damage namely polar lows i e strong and short lived and explosive cyclones i e rapid intensification but not necessarily short lived a short climatology 2009 2012 is obtained by using high resolution 0 5 antarctic mesoscale prediction system amps mean sea level pressure the results show a significant improvement of spatial detail compared to the 0 75 resolution era interim dataset with a total count approximately 46 higher in amps the subset of mesoscale cyclones that are explosive is small with a total genesis number of about 13 that of polar lows in addition only about 1 of the polar lows are explosive suggesting that cyclones that undergo rapid intensification tend to become larger longer lived and hence are no longer regarded as polar lows mesoscale cyclones are more frequent in winter with a maximum concentration around the antarctic but also occurring as far north as tasmania and new zealand analysis of sensible heat flux and sea ice extent anomalies during the genesis days shows that there is a large spread of genesis points over both positive and negative flux anomalies in winter with a somewhat random pattern in the other seasons

synoptic activity in the seas around antarctica abstract the recent ncep department of energy doe reanalysis 2 update of the original ncep ncar dataset provides what is arguably the highest quality analyses spanning two decades available for the high southern latitudes it therefore offers an excellent starting point from which to assemble a modern comprehensive and reliable picture of synoptic activity in the subantarctic region this set covering the modern satellite era from january 1979 to february 2000 is used herein in addition the exploration in this study has been conducted with sophisticated feature tracking and trajectory analysis software it is shown that the high southern latitude cyclone system density is greatest in the indian ocean and to the south of australia near or to the south of 60 s the numbers in winter exceed those in summer except over a few but important regions such as the bellingshausen sea the antarctic coastal region is confirmed as one of high cyclonicity as is that in the northern part of the antarctic

d h ratios of methoxyl groups of the sedimentary organic matter of lake holzmaar eifel germany a potential palaeoclimate hydrology proxy stable hydrogen isotope ratios dd values of methoxyl groups in lignin and pectin from a variety of plant types from different locations have been shown to mirror dd values of precipitation with a mean uniform isotopic fractionation since dd in precipitation is mainly influenced by climatic conditions including temperature evaporation and precipitation amount methoxyl groups of organic matter have been proposed as a potential palaeoclimate proxy here we measured the dd values of the methoxyl groups of sedimentary organic matter derived from sediment core segments of lake holzmaar eifel germany the sediment core covers the entire holocene and part of the late glacial until 13 650 years bp since the sedimentary organic matter was indicated by organic source proxies of predominantly phytoplanktonic origin we considered the dd values of the methoxyl groups as a proxy for the dd value of the lake water presently and probably during most of the holocene the dd value of precipitation was primarily controlled by temperature 2 4 5 c as well as in isotopic equilibrium with the dd value of the lake water we used these modern temperature sensitivities of the eifel region together with the measured dd values of the methoxyl groups of the sedimentary organic matter to evaluate temperature changes recorded for the holocene the resulting mean temperature variance was found to be consistently less than 1 8 4 c and is broadly in line with that reported from the ngrip ice core for the same period the transition from the holocene to the late glacial period was accompanied with more negative dd values of the methoxyl groups 13 for the younger dryas besides the association with temperature we assumed a higher susceptibility of the dd value of lake holzmaar to evaporative enrichment during the younger dryas which could serve as an explanation for discrepancies reported for existing palaeoclimate hydrology records of the eifel region our findings indicate that the dd values of methoxyl groups have great potential for assisting with palaeoclimate and palaeohydrology particularly when the organic matter is well characterized and of uniform origin 2014 elsevier ltd all rights reserved

baroclinic instability in an environment of small stability to slantwise moist convection part i two dimensional models abstract in the semigeostrophic system the growth rate of baroclinic waves varies with the inverse square root of the potential vorticity which acts as the effective static stability recent observations in the ascent regions of middle latitude cyclones show that the effective potential vorticity for saturated air is very near zero in this paper we examine the structure and rate of growth of baroclinic cyclones when the effective potential vorticity is small for upward saturated displacements but large in regions of descent analytic solutions for two dimensional disturbances in a two layer semigeostrophic model and numerical simulations using a multilevel semigeostrophic model show that when the effective potential vorticity is small in regions of upward motion growth rates are modestly increased and the region of ascent intensifies and collapses onto a thin ascending sheet in the limit of zero moist potential vorticity the fastest growing wave has a finite growth rate which is about 2 5 times the

surface cyclones in the era 40 dataset 1958 2001 part i novel identification method and global climatology abstract a novel method is introduced to generate climatological frequency distributions of meteorological features from gridded datasets the method is used here to derive a climatology of extratropical cyclones from sea level pressure slp fields a simple and classical conception of cyclones is adopted where a cyclone is identified as the finite area that surrounds a local slp minimum and is enclosed by the outermost closed slp contour this cyclone identification procedure can be applied to individual time instants and climatologies of cyclone frequency fc are obtained by simple time averaging therefore unlike most other climatologies the method is not based on the application of a tracking algorithm and considers the size of cyclones in combination with a conventional cyclone center tracking algorithm that allows the determination of cyclone life times and the location of cyclogenesis and cyclolysis additional frequency fields can be obtained for special categories of cyclones that are gener

characteristics of the southern hemisphere winter storm track with filtered and unfiltered data abstract the structure and evolution of the fluctuations in synoptic scales in the southern hemisphere sh during winter are discussed using six years of european centre for medium range weather forecasts analyses it is shown that patterns from unfiltered meridional wind series in the sh display all the features needed to represent the synoptic scale waves typical periods and wavelengths are similar to those observed in the northern hemisphere 4 days 4000 km although over the pacific ocean they can be as high as 7 8 days and 4700 km respectively as in the northern hemisphere tilts are not geographically fixed but change with the stage of the evolution of the wave the phase speed of the waves agrees with the low level winds in extensive areas of the middle latitudes and ranges from 12 m s 1 in the indian ocean to 6 m s 1 in the pacific ocean the estimated group velocities achieve maximum values of about 38 m s 1 also in the indian ocean and agree with the upper level maximum winds in accor

explosive cyclone development in the southern hemisphere and a comparison with northern hemisphere events abstract a compilation of southern hemisphere sh explosively developing cyclones or bombs has been assembled based on the national centers for environmental prediction department of energy reanalysis 2 data over the 21 yr period from 1979 to 1999 the identification of these features was undertaken with an objective automated cyclone finding and tracking scheme the procedure allows for the confounding influence of spatial variations of climatological mean pressure on the pressure deepening of explosive cyclones a perspective of particular importance in the sh on average 26 explosive cyclones occur per year in the sh they are more prevalent in winter although their seasonality is more modest than that seen in the northern hemisphere nh the distribution of sh explosive cyclones has a close association with that of strong baroclinicity although the relationship is not one to one it is found that many of these cyclones occurring south of 50 s show equatorward movement in contrast with the pol

reassessment of mid carboniferous glacial extent in southwestern gondwana rio blanco basin argentina inferred from paleo mass transport of diamictites abstract late paleozoic glacial diamictites occur in many localities in western argentina indicating that the region was strongly affected by glaciation during the mid carboniferous late serpukhovian early bashkirian in most instances these diamictites are found in steeply walled paleovalley settings in the andean precordillera this study presents new data from a locality north of the precordillera that suggests an additional distinct volume of ice existed in the region during the carboniferous the glacigenic diamictites in the rio blanco basin were ultimately emplaced as gravity flows precluding inferences of paleo ice volume fold nose orientation and soft sediment groove orientations within the diamictites indicate that the deposits were emplaced from north to south suggesting that glacial ice was most likely not sourced from the proto precordillera at this locality requiring the need for another ice center to the north of the basin diamictite facies indicates that the sediment was initially supplied to the study area by a warm based glacier

synoptic scale perturbations in agcm simulations of the present and last glacial maximum climates the conditions of development of mid latitude depressions synoptic eddies in the winter northern hemisphere mid latitudes at the last glacial maximum lgm 21 000 years ago are very different from the present ones this period is characterised by a general cooling of the extra tropics with massive ice sheets over the northern hemisphere continents and sea ice extending very far south over the north atlantic the present work uses regression analysis to study the characteristics of the synoptic eddies in present day and lgm climate simulations by the atmospheric general circulation model agcm of the uk universities global atmospheric programme ugamp in the lgm experiment the structure of the pacific eddies is similar to the present day pd situation but they are weaker on the other hand the atlantic eddies show an increased zonal wavelength and a much shallower structure in the temperature and vertical wind perturbations to understand the changes of these characteristics from present day to lgm we compare them to those computed for the most unstable modes of the corresponding mean flows determined using a dry primitive equation model a normal mode stability analysis is carried both on zonally symmetric and asymmetric flows for each of the northern hemisphere storm tracks the changes in the most unstable normal modes found by both these analyses give a good account of changes in the structure of the perturbations as retrieved from the agcm suggesting that changes in the mean state especially the temperature gradient is the main driver of these changes however in the case of the present day atlantic storm track the growth rate of these modes is found to be very low compared to the other cases a complementary analysis evaluates the importance of non modal growth in the form of downstream development of perturbations for each of the storm tracks this type of growth is found to be especially important in the case of the present day atlantic storm track

midwinter suppression of baroclinic wave activity in the pacific abstract seasonal variations in baroclinic wave activity and jet stream structure in the northern hemisphere are investigated based upon over 20 years of daily data baroclinic wave activity at each grid point is represented for each day by an envelope function the lowpass filtered time series of the squared highpass filtered geopotential height baroclinic wave activity over the atlantic exhibits a single maximum in january whereas in the pacific it exhibits peaks in late autumn and in early spring and a significant weakening in midwinter which is more evident at the tropopause level than near the surface this suppression occurs despite the fact that the low level baroclinity and the intensity of the jet stream are strongest in midwinter based on the analysis of 31 day running mean fields for individual winters it is shown that over both the oceans baroclinic wave activity is positively correlated with the strength of the upper tropospheric jet for wind speeds up to 45 m s 1 when the strength of t

the three dimensional distribution of clouds around southern hemisphere extratropical cyclones 1 the organization and for the first time the three dimensional structure of clouds associated with the southern hemisphere cyclones are studied using active observations from the cloudsat and calipso satellites first a composite cyclone is constructed from more than 800 individual cases in the years 2007 and 2008 using the cyclone centre as the composite reference point it is shown that the three dimensional cloud distribution around the composite cyclone agrees well with conceptual models of extratropical cyclones composite mean fields of sea level pressure vertical motion potential temperature and relative humidity are superposed on the three dimensional cloud structure to better define the relationship between the clouds and dynamical properties of extratropical cyclones the methodology used here reveals the relationship between dynamical and cloud processes in three dimensions around cyclones and provides the foundation for in depth evaluations of the ability of climate models to simulate the cloud and dynamical structures of southern hemisphere extratropical cyclones

provenance environmental and paleogeographic controls on sandstone composition in an incised valley system the eocene la meseta formation seymour island antarctica abstract the eocene la meseta formation is the youngest exposed unit of the back arc james ross basin antarctic peninsula cropping out in seymour marambio island the formation comprises 720 m of clastic sedimentary rocks of deltaic estuarine and shallow marine origin it was subdivided into six unconformity based units valle de las focas acantilados campamento cucullaea i cucullaea ii and submeseta allomembers grouped into three main facies associations facies association i represents valley confined deposition in a progradational aggradational tide dominated and wave influenced delta front delta plain environment facies association ii includes tidal channels mixed tidal flats tidal inlets and deltas washover and beach environments facies association iii represents nonconfined tide and storm influenced nearshore environments la meseta formation sandstones are quartzofeldspathic with some hybrid arenites glauconite and carbonate bioclasts rich sandstone detrital modes are subdivided into two distinctive petrofacies the low quartz petrofacies petrofacies i q 12 interpreted to retain the original provenance signal and the high quartz petrofacies petrofacies ii q 55 and l 1 4 is clearly dominated by volcanic derived clasts it developed at times of high sea level and or during later stages of the valley fill when an energy fence at the shoreline prevented delivery of sediment from the antarctic peninsula thus enhancing the relative participation of local volcanic sources

southern hemisphere winter extratropical cyclone characteristics and vertical organization observed with the era 40 data in 1979 2001 abstract the mean characteristics and trends of southern hemisphere sh winter extratropical cyclones occurring at six levels of the troposphere over the period 1979 2001 have been investigated using the 40 yr ecmwf re analysis era 40 data cyclonic systems were identified with the melbourne university cyclone finding and tracking scheme this study shows that mean sea level pressure mslp cyclones are more numerous more intense smaller deeper and slower moving than higher level cyclones the novel vertical tracing scheme devised for this research revealed that about 52 of sh winter mslp cyclones have a vertically well organized structure extending through to the 500 hpa level about 80 of these vertically coherent sh cyclones keep their westward tilt until the surface cyclones reach their maximum depths and the mean distance is 300 km between the surface and the 500 hpa level cyclone centers when the surface cyclones obtain their maturity according to the authors definition of vertical orga

insights from petrography mineralogy and u pb zircon geochronology into the provenance and reservoir potential of cenozoic siliciclastic depositional systems supplying the northern margin of the eastern black sea the eastern black sea is one of the few remaining underexplored hydrocarbon basins in europe reservoir quality is a key risk factor in the basin the analysis of up dip portions of oligocene to pliocene depositional systems exposed around its northern and eastern margins enable the composition and provenance of sandstones within the basin to be predicted two major sources of quartz rich sandstone are present the russian western greater caucasus which became a subaerial sediment source in the oligocene and the east european craton scythian platform these are predicted to form better quality reservoirs at shallow and moderate burial depths than their rock fragment rich counterparts due to lesser amounts of compactional porosity loss oligo miocene sandstones from the russian western greater caucasus were deposited as turbidites in the tuapse trough sandstones from the east european craton scythian platform were largely trapped within the indolo kuban basin north of the greater caucasus they only entered the eastern black sea in large volumes from latest miocene or pliocene time in the region of the kerch taman shelf at the western tip of the greater caucasus however it is possible that a precursor to this system supplied the oligocene to early miocene reservoir sandstones within the subbotina field the dziruli massif in western georgia also generated quartz rich sandstones but these are not thought to have entered the black sea

origin and age of rift related fluorite and manganese deposits from the san rafael massif argentina abstract the san rafael massif is characterized by widespread fluorite and manganese epithermal ore deposits whose origin has been under debate to the present isotopic sm nd and k ar and geochemical trace elements and ree data of fluorite and manganese ore allowed to establish the age and genesis of the deposits and to propose a regional genetic model the fluorite deposits were formed during the upper triassic lower jurassic as a result of the triassic rifting that launched a hydrothermal activity at regional scale the hydrothermal fluids had low t and high fo2 with fluorine probably derived from a mantle source and ree scavenged from the volcanics of the gondwanan choiyoi magmatic cycle upper section the manganese deposits were formed by oxidizing hydrothermal fluids that collected mn from deep sources and also leached ree from the upper section of the choiyoi magmatic cycle during two mineralization episodes one episode was linked to the rift tectonic setting that remained active up to the upper cretaceous and the other was related to an early miocene back arc extensional geodynamic setting both manganese and fluorite deposits were formed in extensional tectonic settings within an epithermal environment near the surface and can be ascribed to the general model of detachment related deposits

vb cyclones synchronized with the arctic north atlantic oscillation vb cyclones typically emerge in the western mediterranean and propagate to the northeast into central europe this paper explores the temporal characteristics of vb cyclone occurrence based on cyclone tracks identified at the atmospheric levels of z700 and sea level pressure using jra 55 reanalysis data for the period 1959 2015 the risk of vb occurrence was significantly high in the 1960s and has remained at a lower level since then vb cyclones do not occur fully randomly according to a poisson point process eleven well separated and distinct clusters as well as 11 hiatus periods are identified with average occurrence rates of 21 5 and 5 2 yrea 1 respectively during the event of vb the large scale atmospheric circulation is changed into a state favoring the development of successive vb cyclones clustering is very prominent in the case of genoan vb cyclones in summer as well as those vb cyclones developing over the iberian peninsula or the north african coast in winter superposition of the polar and the subtropical jet stream over the western mediterranean is identified as a main feature at the onset of vb cyclones vb cyclone occurrence appears to be synchronized with the northern atlantic oscillation nao at z500 and arctic oscillation ao at z1000 clusters have occurred when both nao and ao were negative this relation applies to western mediterranean cyclones not following a vb track as well however to a much weaker extent in contrast vb cyclone frequency was particularly low from 1988 to 1997 during a sustained positive phase of both nao and ao

a climatology of southern hemisphere extratropical cyclones a climatology of extratropical cyclones determined by an objective automatic scheme applied to 15 years 1975 89 of once daily australian bureau of meteorology hemispheric analyses is presented contour maps of the positions of formation cyclogenesis dissipation cyclolysis together with other cyclone statistics are presented the distribution of cyclones through the hemisphere was found to be dominated by a permanent high latitude core coincident with the circumpolar trough during the winter and intermediate seasons two mid latitude branches are evident in the cyclone density originating in the tasman sea and south american sectors both spiraling poleward and merging with the circumpolar core in the southern oceans systems were observed to move in an castsouth east direction away from their location of formation exhibiting peak speeds of migration in the mid latitudes little seasonality was evident in the densitiy distribution of cyclones through the southern oceans but a considerable amount was found in their central pressure

the zonal asymmetry of the southern hemisphere winter storm track atmospheric general circulation model experiments have been performed to investigate how the significant zonal asymmetry in the southern hemisphere sh winter storm track is forced by sea surface temperature sst and orography an experiment with zonally symmetric tropical ssts expands the sh upper tropospheric storm track poleward and eastward and destroys its spiral structure diagnosis suggests that these aspects of the observed storm track result from rossby wave propagation from a wave source in the indian ocean region associated with the monsoon there the lower tropospheric storm track is not sensitive to this forcing however an experiment with zonally symmetric midlatitude ssts exhibits a marked reduction in the magnitude of the maximum intensity of the lower tropospheric storm track associated with reduced sst gradients in the western indian ocean experiments without the elevation of the south african plateau or the andes show reductions in the intensity of the major storm track downstream of them due to reduced cyclogenesis associated with the topography these results suggest that the zonal asymmetry of the sh winter storm track is mainly established by stationary waves excited by zonal asymmetry in tropical sst in the upper troposphere and by local sst gradients in the lower troposphere and that it is modified through cyclogenesis associated with the topography of south africa and south america

explosive cyclogenesis in the west central north atlantic ocean 1981 84 part i composite structure and mean behavior abstract tracks and central values of surface low pressure centre and 500 mb absolute vorticity maxima were gathered from operational analysis for 48 casts of expressive cyclogenesis in the west central north atlantic the cases were stratified into relatively strong moderate and weak categories tracking was done from 36 h before to 24 h after the time of most rapid surface deepening the surface center often first appeared only 12 to 24 h before maximum deepening but the upper vorticity maximum was present 36 h or more in advance often many days mean motion of the surface low was rapidly northeastward from the southeastern states or just offshore to newfoundland intense deepening occurred in a period of no more than 24 36 h strong cyclones moved most rapidly and most meridionally traveled farther over warm water and deepened dramatically in a single 12 h period while crossing the closely spaced isotherms of sea surface temperature north of the gulf stream the upper vorticity center moved rapid

source versus depositional controls on sandstone composition in a foreland basin the el imperial formation mid carboniferous lower permian san rafael basin western argentina abstract the el imperial formation mid carboniferous lower permian constitutes a progradational sandstone rich succession deposited in the san rafael foreland basin of western argentina four facies associations have been identified a basal glacial marine association a shallow marine association a deltaic association and an uppermost fluvial association sand prone deposits in the deltaic association are represented by prodelta and delta front shales and subordinate fine sandstones facies a deltaic platform wave reworked channel mouth bar sandstones facies b and fluvial dominated distributary channel sandstones facies c analysis of framework grains of sandstone samples from facies b and c shows two distinct mineral assemblages or petrofacies the quartzose petrofacies is characterized by high contents of quartz and low percentages of feldspar and lithic grains the quartzolithic petrofacies shows an increase in labile components in particular lithic fragments and a concomitant decrease in quartz the quartzolithic petrofacies shows a source signature average detrital modes of sandstones from this petrofacies are similar to those from overlying fluvial sandstones all wave reworked channel mouth bar sandstones facies b correspond compositionally to the quartzose petrofacies whereas detrital modes from the distributary channel sandstones facies c fall into the quartzolithic petrofacies this correspondence between depositional environment and petrofacies suggests a strong depositional influence on composition depositional signature abrasion mechanical breakdown by wave action in shallow marine environments accounts for the quartz rich nature and paucity of labile grains in the quartzose petrofacies

the sedimentary record of carboniferous rivers continuing influence of land plant evolution on alluvial processes and palaeozoic ecosystems abstract evidence from modern rivers and the deep time geological record attests to the fundamental importance of plant life for the construction of physical habitats within fluvial environments data from an extensive literature review and original fieldwork demonstrates that many landforms and geomorphic features of modern river systems appear in the palaeozoic stratigraphic record once terrestrial vegetation had adopted certain evolutionary advances for example stable point bars are associated with the onset of rooted plants in the siluro devonian and avulsive and anabranching fluvial systems become common at the same time as extensive arborescent vegetation in the carboniferous in this paper we demonstrate a correlation between the diversification of physical fluvial environments and the expansion of terrestrial fauna and flora with an emphasis on the culmination of these trends within carboniferous alluvial systems many extrinsic factors have been considered as possible controls on the evolutionary timelines of terrestrialization for organisms however a fundamental prerequisite for achieving terrestrial biodiversity was the variety of physical habitats especially riparian systems available for newly evolved organisms in association with abundant lowland meandering systems the widespread appearance across carboniferous alluvial plains of fixed channel and anabranching reaches created further physical landforms for colonization and would have promoted increasingly complex hyporheic flow regimes furthermore the associated increase in arborescent vegetation and supply of large woody debris to inland and coastal rivers would have created a wealth of microhabitats for continental organisms we argue that the expanding extent and diversity of physical alluvial niches during the palaeozoic is an underappreciated driver of the terrestrialization of early continental life the study of the deep time fossil and stratigraphic record also illustrates that vegetation is a fundamental prerequisite for the creation of biogeomorphic alluvial landforms and physical habitats and microhabitats

an analysis of low level jets in the greater ross ice shelf region based on numerical simulations abstract an analysis of the presence and location of low level jets lljs across the ross ice shelf region in antarctica is presented based on the analysis of archived output from the real time antarctic mesoscale prediction system amps the method of self organizing maps soms is used to objectively identify different patterns in column averaged wind speed over the approximately lowest 1200 m of the atmosphere as an identifier to the location of lljs the results indicate three primary lljs in the region the largest and most dominant llj is along the transantarctic mountains by the siple coast and the southern end of the ross ice shelf the second llj extends from the base of byrd glacier and curves to the north passing by the eastern extremes of ross island the third llj extends from the base of reeves glacier and curves to the north across the western ross sea a strong seasonality is observed in the frequency and intensity of the lljs with the highest values for wind speed and the size of the

a cyclone phase space derived from thermal wind and thermal asymmetry abstract an objectively defined three dimensional cyclone phase space is proposed and explored cyclone phase is described using the parameters of storm motion relative thickness asymmetry symmetric nonfrontal versus asymmetric frontal and vertical derivative of horizontal height gradient cold versus warm core structure via the thermal wind relationship a cyclone s life cycle can be analyzed within this phase space providing substantial insight into the cyclone structural evolution an objective classification of cyclone phase is possible unifying the basic structural description of tropical extratropical and hybrid cyclones into a continuum stereotypical symmetric warm core tropical cyclone and asymmetric cold core extratropical cyclone life cycles are illustrated using 1 navy operational global atmospheric prediction system nogaps operational analyses and 2 5 ncep ncar reanalyses the transitions between cyclone phases are clearly illustrated within the phase space including extratro

reverse osmosis contributing to metal zoning in porphyry type deposits a case study abstract representing the main source of copper in the world porphyry copper deposits have been widely studied different models have tried to explain the observed metal zoning but they did not completely explain it a permian cu mo porphyry deposit in the san rafael massif in argentina shows a similar metal zoning pattern to those described elsewhere however some particular features depart from the conventional cooling model based on data from this deposit and on theoretical background we present and discuss reverse osmosis as a complementary process which could have contributed to porphyry metal zoning during the phyllic stage the existence of potential energy gradients and the different relative rejection values for distinct ions make reverse osmosis a natural mineral concentration process at temperatures corresponding to those of porphyry phyllic halo formation and in presence of a phyllic clay membrane cu ag zn and pb would show a strong osmotic differentiation that could have led to the observed metal zoning

large scale features and energetics of the hybrid subtropical low duck over the tasman sea new aspects of the genesis and partial tropical transition of a rare hybrid subtropical cyclone on the eastern australian coast are presented the duck march 2001 attracted more recent attention due to its underlying genesis mechanisms being remarkably similar to the first south atlantic hurricane march 2004 here we put this cyclone in climate perspective showing that it belongs to a class within the 1 lowest frequency percentile in the southern hemisphere as a function of its thermal evolution a large scale analysis reveals a combined influence from an existing tropical cyclone and a persistent mid latitude block a lagrangian tracer showed that the upper level air parcels arriving at the cyclone s center had been modified by the blocking lorenz energetics is used to identify connections with both tropical and extratropical processes and reveal how these create the large scale environment conducive to the development of the vortex the results reveal that the blocking exerted the most important influence with a strong peak in barotropic generation of kinetic energy over a large area traversed by the air parcels just before genesis a secondary peak also coincided with the first time the cyclone developed an upper level warm core but with insufficient amplitude to allow for a full tropical transition the applications of this technique are numerous and promising particularly on the use of global climate models to infer changes in environmental parameters associated with severe storms

sandstone petrofacies expressions of multiphase basinal tectonics and arc magmatism permian triassic north bowen basin australia abstract modal analyses of 209 sandstone samples from the permian triassic succession of the northern bowen basin eastern australia identify two stratigraphically and compositionally distinct petrofacies the lower to mid upper permian back creek group is characterised by petrofacies a which is quartz rich q82f8l10 it was sourced primarily from cratonic basement terranes to the west where relief was subdued and the quartz content of the sandstones may also reflect some reworking in the marine realm with a consequent loss of labile grains petrofacies b is volcanolithic and characterises alluvial sediments of the upper permian blackwater and lower triassic rewan groups it was sourced from an undissected to transitional magmatic arc provenance located in the contemporary new england orogen to the east which supplied abundant pyroclastic debris to the depositional complex petrofacies b of the northern bowen basin was derived primarily from felsic volcanics compared to an intermediate association recorded for the southern basinal sector indicating significant along arc variation in volcanic style as a consequence its framework grain population is enriched in quartz and is not readily accommodated in the schemes of provenance interpretation currently in use the consistency of framework detrital modes for sandstones distributed throughout the blackwater group q24f10l66 allows the recognition of subpetrofacies b1 and shows that the volcanism associated with the magmatic arc system was remarkably uniform in character and activity during deposition of the entire group the magmatic arc delivered almost identical sedimentary debris over a period of some 9 my in the late permian relative enrichment of quartz within the early triassic rewan group q49f6l45 relative to the blackwater group discriminates subpetrofacies b2 and is attributed to a climatic change and shift in palaeotemperature at the permian triassic boundary the contact between the marine back creek group petrofacies a and the coal bearing blackwater group petrofacies b represents an abrupt switch in provenance with little or no evidence of source mixing the boundary marks the onset of volcanism and associated tectonic uplift in the northern part of the new england orogen to the east sediment from the new source prograded rapidly westwards across the basin coincident with regression direct evidence of contemporaneous volcanism is widespread in the blackwater group as shown by tuffs and tonsteins which are distributed throughout the entire late permian succession

variability of southern hemisphere cyclone and anticyclone behavior further analysis abstract this paper presents some additional results on the use of an automatic scheme for tracking surface cyclones and anticyclones the southern hemisphere sh total amount of synoptic tracks every 12 h was analyzed for the 1973 96 period using sea level pressure from the national centers for environmental prediction national center for atmospheric research ncep ncar reanalysis composites for seven el nino en and la nina ln years were constructed in order to analyze the association between the hemispheric cyclone and anticyclone propagation and the phase of the el nino southern oscillation enso phenomenon a climatological view of cyclone and anticyclone tracks and orphan centers superposed on the same map is presented and analyzed a large area with overlapped cyclone and anticyclone tracks is seen between 30 and 60 s which is approximately the climatological position of the sh transient activity to the north of 30 s the subtropical south atlantic high is embedded in a region with just

a radius depth model for midlatitude cyclones in reanalysis data and simulations geometric properties of winter djf and summer jja midlatitude cyclones are analysed in reanalysis data present day and global warming simulations cyclone centres are identified by the minima of the 1000 hpa geopotential height fitting an azimuthally symmetric gaussian function to the surrounding height field provides cyclone depth difference between the cyclone centre and the synoptic environment radius standard deviation geostrophic wind and vorticity analysing era 40 reanalysis data of different resolutions and intergovernmental panel on climate change ipcc scenario simulations by the coupled atmosphere ocean general circulation model echam5 mpi om yields mean radii of 300 500 km in winter and 300 400 km in summer depth maxima occur in the storm tracks determined by the bandpass filtered variance of the geopotential height and the smallest radii characterize oceanic cyclogenesis regions the geostrophic vorticity derived from the fitted gaussian model agrees reasonably well with the observed relative vorticity future warmer climate scenarios exhibit smaller radii and weaker depths during winter and summer an intense growth of the depth is found during the 2 10 day cyclone life cycles while the radii reveal negligible growth compositing depths with respect to normalized total lifetime leads to rescaled depth life cycles which collapse to a simple universal function a 1 a for relative cyclone age a copyright 2010 royal meteorological society

suppression of baroclinic instability in horizontally sheared flows abstract baroclinic instability in the presence of a meridionally sheared barotropic component to the basic flow is studied using a two level model the inclusion of a linear shear results in merldionally confined normal modes with growth rates much reduced compared to the unsheared case similar results hold for more complicated situations such as a baroclinic jet with barotropic shear the results are applied to life cycle calculations in which it is shown that the nonlinear decay phase of a baroclinic disturbance sets up barotropic shears whichtend to suppress further baroclinic developments an example of the southern hemisphere winter mean flow is found to be strongly stabilized by virtue of a strong sheared barotropic part of the zonal flow