tectono sedimentary evolution of the bowland basin n england during the dinantian the bowland basin is a ne sw trending sedimentary basin lying between the askrigg bowland high to the n and nw and the central pennine high to the se the basin was initiated in late devonian tournaisian times sediment thickness and facies variations within the dinantian succession show marked asymmetry on both a basin wide and intra basin scale as a result of approximate nw se to n s extension across normal faults thickening of the sedimentary sequence from ne to sw over much of the basin resulted from fault controlled extension along the se margin of the basin with downthrow to the nw giving the basin a half graben character extension occurred in two distinct episodes marked by basin wide debris flow and sedimentary slide slump deposits during the late chadian early arundian the simple half graben became modified by a series of ne sw trending antithetic and nw se trending transfer faults associated with local unconformities and marked lateral thickness and facies variations this interval marks the transition from carbonate ramp to slope sedimentation and a temporary halt in carbonate supply to the basin the second episode of extension the late asbian early brigantian marks the break up of the northern basin margin ending major carbonate deposition within the basin reactivation of these structures at the end of the carboniferous created the ribblesdale fold belt as a result of nw se to n s compression transpression application of this research to areas surrounding the bowland basin has led to the recognition of additional shelf basins the orientation of which suggests control by normal and transfer fault systems discussion and

the properties and genesis environments of south atlantic cyclones a new climatology of south atlantic cyclones is produced to provide new insights into the conditions leading to genesis in different regions of the domain cyclones are identified and tracked based on the relative vorticity at 850 hpa computed from the ncep cfsr winds the characteristics of the cyclones are obtained by diagnostic variables sampled within a radial distance from the cyclone centers to produce the spatial distribution of cyclone properties at the time of genesis also cyclone centered composites are used to analyze the cyclone structure and evolution during their genesis there are four main cyclogenesis regions in the south atlantic ocean the southern brazilian coast se br 30 circ text s over the continent near the la plata river discharge region la plata 35 circ text s the southeastern coast of argentina arg 40 circ text s 55 circ text s and the southeastern atlantic se sao centered at 45 circ text s and 10 circ text w we found that cyclogenesis northward of 35 circ text s occurs mainly due to low level forcing associated with moisture transport in the summer and is associated with upper level forcing in the winter due to a strong baroclinic environment southward of 35 circ text s cyclones develop in a high baroclinic environment throughout the year with only a small influence from moist processes the cyclone composites reveal that se br and se sao cyclones are associated with secondary development the la plata cyclones development is influenced by an orographic low in their early stages and arg cyclones are influenced by thermal advection as an essential mechanism in the reduction of static stability

the southern westerlies during the last glacial maximum in pmip2 simulations 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 co2 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

rear flank outflow dynamics and thermodynamics in the 10 june 2010 last chance colorado supercell abstracton 10 june 2010 the second verification of the origins of tornadoes experiment vortex2 armada observed a supercell thunderstorm near last chance colorado tempest unmanned aircraft system uas data collected in the rear flank outflow revealed what appeared to be an elevated outflow head turbulent wake and a cold rear flank internal surge rfis surface thermodynamic and kinematic data collected by the sticknet and mobile mesonet indicated that the outflow wake may have extended to or very near the surface perhaps modifying or outright replacing the leading edge of the outflow at times single doppler data collected by the noaa x pol mobile polarimetric doppler radar noxp were supportive of the possibility of a downdraft in the outflow wake associated with low level divergence a conceptual model of the hypothesized rear flank outflow structure in the nontornadic phase of the last chance supercell is presented the observed turbulent wake is consistent with mixing associated with the rel

carboniferous stratigraphy sedimentation and correlation of well 48 3 3 in the southern north sea basin integrated use of palynology natural gamma sonic logs and carbon sulphur geochemistry a methodology for the correlation of offshore silesian upper carboniferous sequences is developed using an integrative approach based upon biostratigraphy downhole logging and geochemistry we develop the combined use of miospore zonation gamma ray spectrometry formation velocities and carbon sulphur ratios to determine the location of marine horizons and other lithofacies in a thick 1 km largely uncored silesian sequence in the southern north sea gas basin at least nine major marine horizons are recognized within a basin fill sequence of marsdenian yeadonian and langsettian ages namurian b c and westphalian a in the well these horizons help to provide a detailed subdivision of the offshore sequence although the correlations must remain tentative until further deep wells are drilled in the area the implications of the correlations for offshore palaeogeography are that the area of northern quadrant 48 was a deep periodically anoxic basin until infill by successive submarine fan lobes in late marsdenian times yeadonian delta front and coastal plain deposits pass upwards into fluvio deltaic wetland facies of the langsettian

new insights on subsurface energy resources in the southern north sea barrin area the southern north sea basin area stretching from the uk to the netherlands has a rich hydrocarbon exploration and production history the past present and expected future hydrocarbon and geothermal exploration trends in this area are discussed for eight key lithostratigraphic intervals ranging from the lower carboniferous to cenozoic in the period between 2007 and 2017 a total of 95 new hydrocarbon fields were discovered particularly in upper carboniferous rotliegend and triassic reservoirs nineteen geothermal systems were discovered in the netherlands onshore mainly targeting aquifers in the rotliegend and upper jurassic lower cretaceous formations although the southern north sea basin area is mature in terms of hydrocarbon exploration it is shown that with existing and new geological insights additional energy resources are still being proven in new plays such as the basal upper rotliegend ruby discovery for natural gas and a new chalk play for oil it is predicted that hydrocarbon exploration in the southern north sea basin area will probably experience a slight growth in the coming decade before slowing down as the energy transition further matures geothermal exploration is expected to continue growing in the netherlands onshore as well as gain more momentum in the uk

exploring a multiresolution approach using amip simulations abstractthis study presents a diagnosis of a multiresolution approach using the model for prediction across scales atmosphere mpas a for simulating regional climate four atmospheric model intercomparison project amip experiments were conducted for 1999 2009 in the first two experiments mpas a was configured using global quasi uniform grids at 120 and 30 km grid spacing in the other two experiments mpas a was configured using variable resolution vr mesh with local refinement at 30 km over north america and south america and embedded in a quasi uniform domain at 120 km elsewhere precipitation and related fields in the four simulations are examined to determine how well the vrs reproduce the features simulated by the globally high resolution model in the refined domain in previous analyses of idealized aquaplanet simulations characteristics of the global high resolution simulation in moist processes developed only near the boundary of the refined region in contrast amip simulations with vr g

atmospheric response to zonal variations in midlatitude sst transient and stationary eddies and their feedback midwinter storm track response to zonal variations in midlatitude sea surface temperatures ssts has been investigated using an atmospheric general circulation model under aquaplanet and perpetual january conditions zonal wavenumber 1 sst variations with a meridionally confined structure are placed at various latitudes having these sst variations centered at 308n leads to a zonally localized storm track while the storm track becomes nearly zonally uniform when the same sst forcing is moved farther north at 408 and 508n large small baroclinic energy conversion north of the warm cold sst anomaly near the axis of the storm track near 408n is responsible for the large small storm growth the equatorward transfer of eddy kinetic energy by the ageostrophic motion and the mechanical damping are important to diminish the storm track activity in the zonal direction significant stationary eddies form in the upper troposphere with a ridge trough northeast of the warm cold sst anomaly at 308n heat and vorticity budget analyses indicate that zonally localized condensational heating in the storm track is the major cause for these stationary eddies which in turn exert a positive feedback to maintain the localized storm track by strengthening the vertical shear near the surface these results indicate an active role of synoptic eddies in inducing deep tropospheric scale response to midlatitude sst variations finally the application of the model results to the real atmosphere is discussed

the cause of internal outflow surges in a high resolution simulation of the 8 may 2003 oklahoma city tornadic supercell abstracta high resolution simulation of the 8 may 2003 oklahoma tornadic supercell is analyzed to determine the origin of internal outflow surges within the low level cold pool the analyzed simulation has 50 m horizontal grid spacing and is quadruply nested within larger lower resolution domains that were initialized via three dimensional variational data assimilation 3dvar of radar and other observations the high resolution simulation produces two tornadoes that track in close proximity to the observed tornado on 8 may 2003 the authors previous study determined that an internal outflow surge instigated tornadogenesis for the first tornado in this simulation but the cause of this internal outflow surge was unclear in this study the vertical momentum equation is analyzed along backward trajectories that are initialized within the tornado triggering internal outflow surge the analysis reveals that the internal outflow surge is forced by the dynamic part of the vertical pressure gradient further ex

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

storm track dynamics this paper reviews the current state of observational theoretical and modeling knowledge of the midlatitude storm tracks of the northern hemisphere cool season observed storm track structures and variations form the first part of the review the climatological storm track structure is described and the seasonal interannual and interdecadal storm track variations are discussed in particular the observation that the pacific storm track exhibits a marked minimum during midwinter when the background baroclinicity is strongest and a new finding that storm tracks exhibit notable variations in their intensity on decadal timescales are highlighted as challenges that any comprehensive storm track theory or model has to be able to address physical processes important to storm track dynamics make up the second part of the review the roles played by baroclinic processes linear instability downstream development barotropic modulation and diabatic heating are discussed understanding of these processes forms the core of our current theoretical knowledge of storm track dynamics and provides a context within which both observational and modeling results can be interpreted the eddy energy budget is presented to show that all of these processes are important in the maintenance of the storm tracks the final part of the review deals with the ability to model storm tracks the success as well as remaining problems in idealized storm track modeling which is based on a linearized dynamical system are discussed perhaps on a more pragmatic side it is pointed out that while the current generation of atmospheric general circulation models faithfully reproduce the climatological storm track structure and to a certain extent the seasonal and enso related interannual variations of storm tracks in depth comparisons between observed and modeled storm track variations are still lacking

ocean and atmosphere storm tracks the role of eddy vorticity forcing abstract signatures of eddy variability and vorticity forcing are diagnosed in the atmosphere and ocean from weather center reanalysis and altimetric data broadly covering the same period 1992 2002 in the atmosphere there are localized regions of eddy variability referred to as storm tracks at the entrance of the storm track the eddies grow providing a downgradient heat flux and accelerating the mean flow eastward at the exit and downstream of the storm track the eddies decay and instead provide a westward acceleration in the ocean there are similar regions of enhanced eddy variability along the extension of midlatitude boundary currents and the antarctic circumpolar current within these regions of high eddy kinetic energy there are more localized signals of high eady growth rate and downgradient eddy heat fluxes as in the atmosphere there are localized regions in the southern ocean where ocean eddies provide statistically significant vorticity forcing which acts to accelerate the mean flow

the linearity of the el nino teleconnection to the amundsen sea region el nino southern oscillation enso drives interannual variability in west antarctic climate through altering atmospheric circulation in the amundsen sea region asr the el nino asr teleconnection is known to be strongest in austral winter and spring but its variation with el nino amplitude is underexplored this study uses experiments from the hadgem3 a climate model to investigate the el nino asr teleconnection for a range of imposed sst perturbations spanning weak 0 75 k to strong 3 k amplitudes in austral winter the el nino asr teleconnection behaves linearly for el nino amplitudes up to 2 25 k but is found to weaken for stronger forcing 3 k the anomalous rossby wave source in the subtropical south pacific increases monotonically with el nino amplitude however a rossby wave reflection surface originally located in the western south pacific sector extends progressively eastward with increasing el nino amplitude reducing wave propagation into the asr the wave reflection surface is associated with curvature in the upper tropospheric zonal winds which intensifies as the subtropical jet strengthens under el nino forcing in contrast the el nino asr teleconnection in austral summer which more closely resembles the southern annular mode is found to increase linearly for el nino amplitudes up to 3 k the results explicitly demonstrate that a linear approximation of the el nino teleconnection to the asr is reasonable based on the range of el nino amplitudes observed in recent history

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

southern hemisphere circulation features associated with el nino southern oscillation events abstract composite seasonal mean and anomaly fields prepared from operational numerical analyses have been used to describe the southern hemisphere sh circulation features associated with el nino southern oscillation enso events the period of analyses available 1972 83 has limited the composites to include only three enso events the reliability and stability of the composites has been tested using multiple permutation methods and by comparison with the results obtained using a longer period 1950 79 of sh rawinsonde station data in the sh winter a weak equivalent barotropic wavetrain pattern of anomalies extends over australia and the south pacific ocean to south america this wavetrain pattern is quite variable in amplitude and location between enso events although it is more stable over the subtropical pacific in the sh summer the circulation anomalies are more zonally symmetric with increased height at low and high latitudes and decreased height in middle latitudes the circulation anoma

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

the influence of the andes cordillera on transient disturbances abstract the influence of the andes cordillera on transient disturbances is investigated in this study using a lag correlation analysis this analysis shows that the unfiltered geopotential height data have a wavelike pattern moving to the east while tilting to the west in the vertical when the wave approaches the andes cordillera it exhibits orographic effects such as anticyclonic turning of a low level disturbance trajectory a zonal trajectory in the upper levels distortions of the isolines of correlation and an elongation of maximum correlation on the lee side of the andes the anticyclonic turning of the trajectory in the low attitude levels and a zonal trajectory in upper levels implies a decrease in the vertical tilt of the system on the windward side and an increase in the tilt on the lee side the increase of baroclinicity on the lee side results in baroclinic development as predicted from a linearly obtained normal mode solution in the presence of mountains a cross correlation analysis of t

significance of a midlatitude sst frontal zone in the formation of a storm track and an eddy driven westerly jet abstract in a set of idealized aquaplanet experiments with an atmospheric general circulation model to which zonally uniform sea surface temperature sst is prescribed globally as the lower boundary condition an assessment is made of the potential influence of the frontal sst gradient upon the formation of a storm track and an eddy driven midlatitude polar front jet pfj and on its robustness against changes in the intensity of a subtropical jet stj in experiments with the frontal midlatitude sst gradient as that observed in the southwestern indian ocean transient eddy activity in each of the winter and summer hemispheres is organized into a deep storm track along the sst front with an enhanced low level baroclinic growth of eddies in the winter hemisphere another storm track forms just below the intense stj core but it is confined to the upper troposphere with no significant baroclinic eddy growth underneath the near surface westerlies are strongest near the midlatitude sst front as observe

vortex lines within low level mesocyclones obtained from pseudo dual doppler radar observations abstract vortex lines passing through the low level mesocyclone regions of six supercell thunderstorms three nontornadic three tornadic are computed from pseudo dual doppler airborne radar observations obtained during the verification of the origins of rotation in tornadoes experiment vortex in every case at least some of the vortex lines emanating from the low level mesocyclones form arches that is they extend vertically from the cyclonic vorticity maximum then turn horizontally usually toward the south or southwest and descend into a broad region of anticyclonic vertical vorticity this region of anticyclonic vorticity is the same one that has been observed almost invariably to accompany the cyclonic vorticity maximum associated with the low level mesocyclone the vorticity couplet straddles the hook echo of the supercell thunderstorm the arching of the vortex lines and the orientation of the vorticity vector along the vortex line arches compared to the orientation of the ambient barotrop

seasonal variations in lower stratospheric gravity wave energy above the falkland islands 1 the gravity wavefield in the lower stratosphere between 15 km and 22 km altitude above mount pleasant airport 51 49 s 58 26 w on the falkland islands is studied using over 2100 high resolution radiosonde soundings from 2002 to 2010 the seasonal variation in vertical direction of propagation shows a small decrease in numbers of upward propagating waves that is related to critical level filtering however there is a very large increase in numbers of downward propagating waves between july and september this is attributed to the proximity of the edge of the polar vortex there is a seasonal variation in gravity wave energy density with a large peak during the austral autumn equinox this is markedly different to results in the literature both from rothera on the antarctic peninsula and stations on the main antarctic continent this seasonal pattern has been shown to be linked to variations in the sources of upward propagating gravity waves the seasonal variation in gravity wave characteristics above mount pleasant airport seen in our results suggests that the gravity wavefield in this region is determined by a combination of different gravity wave sources located above and below the lower stratosphere

impact of tropical sst on stratospheric planetary waves in the southern hemisphere abstractthe impact of tropical sea surface temperature sst on stratospheric planetary waves in the southern hemisphere sh is investigated in austral spring using observed sst and reanalysis data for the past three decades maximum covariance analysis indicates that the tropical sst and the sh stratospheric planetary wave activity are primarily coupled through two modes the leading two modes show the la nina like and the central pacific el nino like sst anomalies in their positive polarities respectively which each are related to enhanced stratospheric planetary wave activity these two modes also introduce phase shifts to the stratospheric stationary planetary waves a westward shift is seen for la nina and an eastward shift for warm sst anomalies is seen in the central pacific the eliassen palm fluxes associated with the two modes indicate that the anomalous stratospheric wave activity originates in the troposphere and propagates upward over the mid high latitudes so that the linkages between tr

structure and evolution of baroclinic waves as inferred from regression analysis abstract the structure of transient disturbances with periods shorter than a week is documented an the basis of one point regression maps and longitude height sections derived from the national meteorological center nmc operational analyses for nine winter seasons the reference time series for the regression coefficients is highpass filtered normalized 500 mb height at a grid point in the pacific stormtrack the field variables that were regreesed on the reference time series were not filtered the regression statistics yield quantitative estimates of the amplitudes of the high frequency fluctuations in the geopotential height temperature wind ageostrophic wind vorticity divergence vertical velocity and outgoing longwave radiation fields the observed high frequency fluctuations exhibit a vertical and meridional structure suggestive of baroclinic waves evolving through the mature phase of their life cycle most of the results are in qualitative agreement with previous studies but the ageostrop

the metamorphic history of the concealed caledonides of eastern england and their foreland white mica illite crystallinity data derived mostly from borehole samples have been used to generate a contoured metamorphic map of the concealed caledonide fold belt of eastern england and the foreland formed by the midlands microcraton the northern subcrop of the fold belt is characterized by epizonal phyllites and quartzites of possible cambrian age whereas anchizonal grades characterize silurian to lower devonian strata of the anglian basin in the southern subcrop of the fold belt regional metamorphism in the anglian basin resulted from deep burial and acadian deformation beneath a possible overburden of 7 km assuming a metamorphic field gradient of 36 c km 1 late proterozoic volcaniclastic rocks forming the basement of the microcraton show anchizonal to epizonal grades that probably developed during late avalonian metamorphism cambrian to tremadoc strata showing late diagenetic alteration rest on the basement with varying degrees of metamorphic discordance during early palaeozoic times much of the microcraton was a region of slow subsidence with overburden thicknesses of 3 3 5 5 km however concealed tremadoc strata in the northeast of the microcraton reach anchizonal grades and may have been buried to depths of 7 km beneath an overburden of uncertain age

enso related variability of the southern hemisphere winter storm track over the eastern pacific atlantic sector abstract the interannual variability associated with the enso of winter storm tracks over the region extending from the eastern south pacific ocean across south america to the south atlantic ocean is described using 39 yr of data from the ncep reanalysis data base tropical sea surface temperature anomalies associated with enso induce large scale atmospheric circulation anomalies over large areas of the southern hemisphere in particular positive height anomalies dominate the bellingshausen sea during warm events and consistently a weakening of the eddy activity at low levels is found to the west of the antarctic peninsula during el nino en the storm track evidences an equatorward shift over the subtropical pacific ocean and a slight strengthening in the central atlantic ocean time lagged correlation analysis applied to anomalies of the 300 hpa meridional wind at selected base points was used to study the structure and propagation characteristics of the waves during en waves emanating from the at

finescale vertical structure of a cold front as revealed by an airborne doppler radar abstract in the afternoon of 24 may 2002 a well defined and frontogenetic cold front moved through the texas panhandle detailed observations from a series of platforms were collected near the triple point between this cold front and a dryline boundary this paper primarily uses reflectivity and doppler velocity data from an airborne 95 ghz radar as well as flight level thermodynamic data to describe the vertical structure of the cold front as it intersected with the dryline the prefrontal convective boundary layer was weakly capped weakly sheared and about 2 5 times deeper than the cold frontal density current the radar data depict the cold front as a fine example of an atmospheric density current at unprecedented detail 40 m the echo structure and dual doppler inferred airflow in the vertical plane reveal typical features such as a nose a head a rear inflow current and a broad current of rising prefrontal air that feeds the accelerating front to rear current over the head the 2d cross fro

sub greenschist facies metamorphism from the variscides of sw ireland an early syn extensional peak thermal event illite crystallinity studies on metaclastics from the variscides of sw ireland range in value from 0 18 to 0 25 2 indicating a metamorphic grade in the upper anchizone lower epizone c 275 325 c chlorite geothermometry yields a similar metamorphic temperature range 280 315 c combining these data with known overburden estimates for the area c 5km implies late palaeozoic geothermal gradients in excess of 60 ckm 1 fluid inclusion studies on quartz veins in these metaclastics reveal two vein types characterized by fluid densities of 0 7 0 93 g cm 3 group 1 and 0 9 1 0gcm 3 group 2 respectively this variation in fluid density is thought to be dominantly controlled by temperature with group 1 veins linked to late palaeozoic extension and high geothermal gradients and group 2 veins associated with subsequent variscan deformation and lower temperature conditions

the bowdle south dakota cyclic tornadic supercell of 22 may 2010 surface analysis of rear flank downdraft evolution and multiple internal surges abstractmobile mesonet sampling in the hook echo rear flank downdraft rfd region of a tornadic supercell near bowdle south dakota provided the opportunity to examine rfd thermodynamic and kinematic attributes and evolution focused analysis of the fifth low level mesocyclone cycle that produced two significant tornadoes including a violent tornado revealed four rfd internal surge rfdis events rfdiss appeared to influence tornado development intensity and demise by altering the thermodynamic and kinematic character of the rfd region bounding the pretornadic and tornadic circulations significant tornadoes developed and matured when the rfd modulated by internal surges was kinematically strong only weakly negatively buoyant and very potentially buoyant in contrast the demise of the bowdle tornado was concurrent with a much cooler rfdis that replaced more buoyant and far more potentially buoyant rfd air near the tornado this surge also likely contributed to a displacement of the tornado from

the dinantian stratigraphy of the east midlands a seismostratigraphic approach six tectonically controlled seismic sequences have been identified in the dinantian succession of the widmerpool gulf east midlands and they have also been recognized in outcrop sections in derbyshire and the bowland basin these correlations are made possible by integrating and calibrating sequence boundaries with the biostratigraphical evidence from foraminifers conodonts and palynomorphs and relating these to the tectonostratigraphical evolution of the basin it is suggested that the current chronostratigraphical stages of the dinantian do not always reflect major regional stratigraphical events and that the seismic sequence stratigraphy erected herein may provide a more applicable chronostratigraphical subdivision of the dinantian of the east midlands and northern england

atmosphere ocean thermal coupling in the north atlantic a positive feedback in this article it is examined whether a positive atmosphere ocean feedback is found over the north atlantic through a series of general circulation model gcm experiments a 60 year integration of an atmospheric gcm agcm coupled with a 50 m deep motionless ocean was conducted the coupled run was compared with two uncoupled runs one with prescribed mid latitude climato logical sea surface temperatures ssts and the other with daily ssts derived from the coupled experiment the uncoupled atmosphere forces the slab ocean to obtain sst responses in these runs consistent with previous studies the coupled atmosphere ocean fields show interannual variances larger than those in the uncoupled runs due to reduction in the local thermal damping patterns of maximum atmosphere ocean covariability show the north atlantic oscillation nao and tripole sst anomalies both in the coupled and uncoupled fields indicating a dominant role of the atmosphere in generating the sst anomalies on the other hand analyses of the temporal variability in the three runs suggest an active role of sst anomalies in determining the polarity of the air sea coupled variability longer than the interannual time scale a combined analysis of forcing sst upper air height and the response sst anomalies in the uncoupled run identified that a patch of positive sst anomalies in the mid latitude band around 40 n effectively excite the positive phase of the nao which in turn reinforces the tripole sst anomalies this relationship was further confirmed by a nine member ensemble agcm experiment forced by the relevant sst anomalies since the forcing and response sst anomaly patterns bear some resemblance these results manifest positive feedback at work in the coupled atmosphere ocean patterns the processes responsible for this positive feedback were elaborated by a series of linear model experiments the local thermal adjustment of the atmosphere to the sst anomalies results in increased precipitation over the gulf stream region associated diabatic heating applied to a linear baroclinic model yields a positive height response to the east which highly influences the southern part of the nao this stationary response in turn induces a northward deflection in the storm track activity leading to an eddy vorticity feedback that tends to force the positive phase of the nao

palaeozoic terranes and their lithospheric boundaries within the trans european suture zone tesz a review the trans european suture zone tesz is a broad and complex zone of terrane accretion separating ancient lithosphere of the baltic shield and east european craton eec from the younger lithosphere of western and southern europe there is debate about the number of terranes involved and their origins the most significant terrane boundaries originally oceanic sutures are poorly exposed and are defined using faunal provinciality prominent geophysical lineaments may represent sub terrane boundaries within composite terranes the avalonia composite terrane was amalgamated to baltica in latest ician time the provenance of the malopolska and moravo silesian terranes whose neoproterozoic basement is suspect with respect to baltica but with which they nonetheless share faunal affinities is still debated the extent of the variscide rhenohercynian zone defines the southern limit of the early palaeozoic accreted terranes terranes within the bohemian massif exhibit hp metamorphism recording subduction driven collision prior to incorporation in the tesz collage itself associated with a hp event in romania the saxothuringian zone and rheic suture are directly juxtaposed with the eec and the crustal structure of the tesz has been much modified by post palaeozoic tectonism deep seismic reflection data where available show that the oceanic sutures are frequently associated with inclined reflectivity zones irz in the lithospheric mantle here inferred to mark relict subduction zones interpreting the age of subduction is complicated by offset of originally coplanar mantle and crustal segments of the irz resulting from early orogenic lithospheric delamination at the moho interface and or post orogenic reordering processes the mantle irz appear to indicate a n directed polarity for early palaeozoic subduction apparently incompatible with the geological evidence which indicates subduction of the tornquist sea beneath avalonia and a large amount of underthrusting of avalonia by baltica possible explanations for these apparently incompatible observations are evaluated

burial dolomitization and porosity development in a mixed carbonate clastic sequence an example from the bowland basin northern england widespread dolomitization and leaching occur in the asbian to brigantian dinantian sequence of the bowland basin within this mudrock dominated succession dolomite is developed in calcarenites and limestone breccia conglomerates deposited in a carbonate slope environment pendleside limestone and also within graded quartz wackes deposited by density currents in a generally starved basin environment pendleside sandstone the dolomitized intervals range in thickness from less than one metre to several tens of metres and have a stratabound nature all stages of calcite cement pre date dolomitization and calcite veins are dolomitized dolomite crystals replace neomorphic spar and may also contain insoluble residues that were concentrated along stylolites thus dolomitization was a late stage process within the carbonate diagenetic sequence a late stage diagenetic origin is also indicated within the sandstones with dolomite post dating the development of quartz overgrowths six main textural styles of dolomite are observed 1 scattered 2 mosaic 3 subhedral to euhedral rhombic 4 microcrystalline 5 single crystal and 6 saddle the style of dolomite developed is dependent on the host rock mineralogy on whether it is space filling or replacive and also on temperature chemically the dolomite varies from near stoichiometric compositions to ankeritic varieties containing up to 20 mole feco3 generally the dolomites have isotopic compositions depleted in 18o compared to the host limestone with similar or lighter 13c values initial dolomite was of the scattered type but with progressive replacement of the host a mosaic dolostone with a sucrosic texture was produced there was a general increase in the fe and mn content and reduction in 18o ratio of the crystals during dolomitization leaching is restricted to partly dolomitized horizons where calcite feldspars micas clays and to some extent dolomite have been leached this has produced biomouldic and vuggy secondary porosity within the carbonates whereas in the sandstones honeycombed corroded and floating grains associated with oversized pores occur porosity within both carbonates and sandstones is reduced by ferroan dolomite ankerite cements field petrographic and chemical characteristics indicate that dolomitizing solutions were predominantly derived from the enclosing mudrocks bowland shales during intermediate deep burial fluid migration out of the mudrocks would have been sided by dehydration reactions and overpressure the fluids migrating along the most permeable horizons the coarse grained carbonates and sandstones that are now dolomitized and contain secondary porosity

the diagenesis of the late dinantian derbyshire east midland carbonate shelf central england carbonate cements in late dinantian asbian and brigantian limestones of the derbyshire carbonate platform record a diagenetic history starting with early vadose meteoric cementation and finishing with burial and localized mineral and oil emplacement the sequence is documented using cement petrography cathodoluminescence trace element geochemistry and c and o isotopes the earliest cements pre zone 1 are locally developed non luminescent brown sparry calcite below intrastratal palaeokarsts and calcretes they contain negligible fe mn and sr but up to 1000 ppm mg their isotopic compositions centre around 18o 8 5 13c 5 0 calcretes contain less 13c subsequent cements are widespread as inclusion free low mg low fe crinoid overgrowths and are described as having a dead bright dull cathodoluminescence the dead cements zone 1 are mostly non luminescent but contain dissolution hiatuses overlain by finely detailed bright subzones that correlate over several kilometres across dead bright subzones there is a clear trend in mg 500 900 ppm mn 100 450 ppm and fe 80 230 ppm zone 1 cements have isotopic compositions centred around 18o 8 0 and 13c 2 5 zone 2 cement is bright thin and complexly subzoned it is geochemically similar to bright subzones of zone 1 cements dull zone 3 cement pre dates pressure dissolution and fills 70 or more of the pore space it generally contains little mn fe and sr but can have more than 1000 ppm mg increasing stratigraphically upwards the 18o compositions range from 5 5 to 15 and the 13c range is 1 to 3 20 00 zone 4 fills veins and stylolite seams in addition to pores it is synchronous with pb ba f ore mineralization and oil migration zone 4 is ferroan with around 500 ppm fe up to 2500 ppm mg and up to 1500 ppm mn isotopic compositions range widely 15o 2 7 to 9 and 13c 3 8 to 2 50 unaltered marine brachiopods suggest a dinantian seawater composition around 15o 0 smow but vital isotopic effects probably mask the original 13c pdb value pre zone 1 calcites are meteoric vadose cements with light soil derived 13c and light meteoric 18o an unusually fractionated pluvial 15o smow value of around 6 is indicated for local dinantian meteoric water calcrete 18o values are heavier through evaporation zone 1 textures and geochemistry indicate a meteoric phreatic environment fe and mn trends in the bright subzones indicate stagnation and precipitation occurred in increments from widespread cyclically developed shallow meteoric water bodies meteoric alteration of the rock body was pervasive by the end of zone 1 with a general resetting of isotopic values zone 3 is volumetrically important and external sources of water and carbonate are required emplacement was during the namurian early westphalian by meteoric water sourced at a karst landscape on the uplifted eastern edge of the derbyshire east midland shelf the light 18o values mainly reflect burial temperatures and an unusually high local heat flow but an input of highly fractionated hinterland derived meteoric water at the unconformity is also likely relatively heavy 13c values reflect the less altered state of the source carbonate and aquifer zone 4 is partly vein fed and spans burial down to 2000 m and the onset of tectonism light organic matter derived 13c and heavy 18o values suggest basin derived formation water combined with textural evidence of geopressures this relates to local high temperature ore mineralization and oil migration low water to rock ratios with host rock buffering probably affected the final isotopic compositions of zone 4 masking extremes both of temperature and organic matter derived co2

single and dual doppler analysis of a tornadic vortex and surrounding storm scale flow in the crowell texas supercell of 30 april 2000 abstract fine resolution single and dual doppler data were collected in the tornadic region of a supercell storm intercepted by two doppler on wheels radars on 30 april 2000 near crowell texas eleven dual doppler analyses characterize the 2d and 3d near surface wind fields associated with a tornado during a 13 min period an interesting evolution of the low level rotation is observed initially concentric tornado 500 m wide and tornado cyclone 2 km wide radar velocity couplets make a transition into a solitary intermediate sized 750 m wide circulation that widens and makes a further transition into a two celled multiple vortex structure with an asymmetric distribution of vertical vorticity the asymmetry and eventual disruption of the multiple vortex structure may have been partially controlled by locally strong outflow winds that affect the convergence fields in its vicinity a smaller 500 m wide tornado embedded in a broad area of rotation is subsequently observed the dual doppler wi

south pacific split jet itcz shifts and atmospheric north south linkages during abrupt climate changes of the last glacial period abstract a number of key paleoclimate records in the southern hemisphere midlatitudes exhibit climate changes synchronous with abrupt climate changes in the north atlantic we advance a hypothesis argued from consideration of model evidence observational climate diagnostics and atmospheric dynamics that attributes said climate changes in the southern hemisphere to a modulation in the strength of the south pacific split jet a pronounced zonally asymmetric feature of the wintertime southern hemisphere westerlies north atlantic cooling is associated with a weaker split jet characterized by weaker south pacific subtropical and subpolar jets and a strengthened midlatitude jet it leads to climate impacts over the south pacific sector that coincides with regions with observed paleoclimate changes timed to the north atlantic these circulation changes are envisioned to operate in addition to the climate impacts resulting from the oceanic bipolar seesaw a proposed global atmospheric teleconnection links north atlantic cooling to the weakening of the split jet north atlantic cooling induces a southward shift of the marine intertropical convergence zone and weakening of the asian monsoon the resulting hadley circulation change weakens the wintertime south pacific subtropical jet and which in turn leads to a weaker south pacific split jet a weaker split jet leads to a southward shift of the zero wind stress curl line implying a shift in the same sense for the south pacific subtropical front over land it leads to winter warming over new zealand winter cooling over subtropical south america drying over western patagonia and winter warming and wetting of southernmost patagonia our hypothesis also predicts reduced storminess over west antarctica similar changes but of opposite sign occur in the northern hemisphere where a stronger wintertime north pacific subtropical jet increases precipitation over the western united states

processes driving thunderstorms over the agulhas current 1 lightning occurs predominantly over land and is not common over the open ocean we study here one oceanic region in which thunderstorms are frequently found namely the warm agulhas current off the southeast coast of south africa the seasonal and interannual lightning variability is derived from satellite and terrestrial data sets favorable climatic conditions for lightning are investigated using both era interim and ncep ncar reanalysis data we find peak lightning in austral autumn over the agulhas current but with low seasonality i e there is considerable lightning throughout the year while the climatological wind direction varies strongly with latitude and season the wind direction is predominantly northerly throughout the region during thunderstorms a composite of sea level pressure during thunderstorm days indicates that thunderstorms are related to eastward propagating synoptic scale wave trains passing through the agulhas current region the strong convective activity during thunderstorms occur in the warm sector of a cyclone and is associated with horizontal convergence and lifting of warm moist surface air originating over the warm agulhas current

recurrence of extreme floods in southern sakhalin island as evidence of paleo typhoon variability in the northwestern pacific since 6 6 ka abstract history of variability of tropical cyclones tc in the north western pacific is critical for understanding impacts of future climatic changes natural archives of paleo typhoon variability can be used to assess how changes in the planetary climatic system during the holocene could influence tc frequency and intensity in this part of pacific extreme typhoon related rains are the main cause of catastrophic floods on sakhalin island and deposits of these floods are evidence of paleo typhoon the paleo typhoons that triggered extreme floods on southern sakhalin during the last 6 6 kyr are recorded in the sequence on the interfluvial surface in the northern susunay lowland naiba river basin the sequence includes peat bog with numerous loam interlayers deposited during extreme floods inundating the bog we reconstructed paleo environmental conditions including humidity and flood activity based on analysis of diatoms we found biological indicators that point to the past floods the mineral content in the peat being one criteria indicative of the high frequency of floods the peat bog developed in place of a lagoon that existed at the maximum phase of the holocene transgression peat accumulation began in the freshened lagoon coast 6010 cal yr b p when sea level dropped the lagoon turned into a coastal lake 5710 5040 cal yr b p a swamp formed in place of the lake under varying moisture conditions we identified and dated 25 extreme floods and assessed the paleoclimatic background of the events a recent catastrophic flood from typhoon phyllis 1981 ce is considered as an analogue of the paleo events the frequency of extreme typhoons increased both during warm wet and dry phases and in cold dry phases of the climate fluctuations we identified three periods of a high typhoon activity 4640 4360 4030 3580 1860 1380 cal yr b p when super typhoons came onto the island once every 30 90 years a comparison between the extreme typhoons in the south of sakhalin and in the sea of japan region show both synchronism and metachronism of the periods of typhoon activity instrumental measurements during 20th 21st centuries revealed considerable changes in super typhoon tracks a similar variability may be safely supposed in typhoon tracks in the past to predict future tropical cyclone activity and the risk of floods under modern climatic instability it is necessary to understand factors influencing variability in the occurrence of strong typhoons and associated extreme floods events on a paleo scale this is especially important for areas with rapidly developing coastal economies and intensive use of gas and oil resources such as sakhalin island

relations between annular modes and the mean state southern hemisphere winter in a zonally symmetric climatology with a single eddy driven jet such as prevails in the southern hemisphere summer the midlatitude variability is dominated by fluctuations of the jet around its mean position as described by the southern hemisphere annular mode sam to study whether this result holds for a zonally asymmetric climatology the observed variability of the southern hemisphere winter is analyzed the mean state in this case is characterized by relatively weak stationary waves yet there exist significant zonal variations in the mean strength and meridional structure of the subtropical jet stream as in summer the winter sam signature is annular in shape and the corresponding wind anomalies are dipolar but it is associated with two different behaviors of the eddy driven jet in different longitudinal ranges over the indian ocean the sam is associated primarily with a latitudinal shift of the jet around its mean position over the pacific sector it is instead characterized by a seesaw in the wind speed between two distinct latitudes corresponding to the positions of the midlatitude and subtropical jets composites of eddy forcing and baroclinicity over both sectors appear consistent with the two different behaviors as in the zonal mean case high frequency eddies both force and maintain the low frequency wind anomalies associated with the sam the positive feedback by eddies is however not local changes in the eddy forcing are influenced most strongly by zonal wind anomalies located upstream

air sea heat exchanges characteristic of a prominent midlatitude oceanic front in the south indian ocean as simulated in a high resolution coupled gcm abstract an integration of a high resolution coupled general circulation model whose ocean component is eddy permitting and thus able to reproduce a sharp gradient in sea surface temperature sst is analyzed to investigate air sea heat exchanges characteristic of the midlatitude oceanic frontal zone the focus of this paper is placed on a prominent sst front in the south indian ocean which is collocated with the core of the southern hemisphere storm track time mean distribution of sensible heat flux is characterized by a distinct cross frontal contrast it is upward and downward on the warmer and cooler flanks respectively of the sst front acting to maintain the sharp gradient of surface air temperature sat that is important for preconditioning the environment for the recurrent development of storms and thereby anchoring the storm track induced by cross frontal advection of cold warm air associated with migratory atmospheric disturbances the surface flux is highly variable with intermittent en

ocean frontal effects on the vertical development of clouds over the western north pacific in situ and satellite observations abstract a suite of shipboard and satellite observations are analyzed and synthesized to investigate the three dimensional structure of clouds and influences from sea surface temperature fronts over the western north pacific sharp transitions are observed across the kuroshio extension ke front in the marine atmospheric boundary layer mabl and its clouds the ocean s influence appears to extend beyond the mabl with higher cloud tops in altitude along the ke front than the surroundings in winter intense turbulent heat release from the ocean takes place on the southern flank of the ke front where the cloud top penetrates above the mabl and reaches the midtroposphere in this band of high cloud tops frequent lightning activity is observed the results of this study suggest a sea level pressure mechanism for which the temperature gradient in the mabl induces strong surface wind convergence on the southern flank of the ke front deepening the clouds there in early summer sea fog frequently occurs on

an objective study of 500 hpa moving troughs in the southern hemisphere abstract the location and movement of 500 hpa troughs using an automated method are studied with data from a 24 yr period with the objective of determining the trough formation and dissipation regions in the southern hemisphere to identify the 500 hpa mobile troughs an objective method that uses the eulerian centripetal acceleration eca is developed on average 868 troughs per year were identified by the method with an increase in trend during the period studied the troughs have an average lifetime of 4 3 days being longer shorter in subtropical high latitudes the average calculated phase velocity was 13 6 m s 1 being higher lower in middle high latitudes the troughs are normally found in the 60 40 s latitudinal band with maximum occurrence at 50 s the longitudinal distribution of trough genesis has three maximum regions over the drake strait and the south atlantic ocean over the indian ocean around 50 s and over the southwestern pacific ocean between 150 e and 150 w the trough d

sst induced surface wind variations over the brazil malvinas confluence satellite and in situ observations abstract the confluence of the brazil malvinas currents maintains strong sea surface temperature sst fronts in the midlatitude southwestern atlantic year round sst effects on near surface stability and surface wind variations are examined in this region using satellite and in situ datasets satellite observations show strong weak surface wind speeds over the warm brazil cold malvinas current a novel feature of this study is the construction of a high resolution surface meteorological dataset that is based on historical ship observations analysis of this new in situ dataset reveals an increased reduced sea air temperature difference over the brazil malvinas current indicating destabilization stabilization in the atmospheric boundary layer these results are consistent with the sst induced vertical mixing mechanism for wind adjustment the sst effect on the near surface atmosphere is observed both in the climatology and on interannual time scales in the brazil malvinas confluence along a zo

structural evolution timing and tectonic style of the sole pit inversion abstract the nw se oriented sole pit high located in the western half of the southern north sea basin is the result of three different structural processes initiated during the late palaeozoic basin subsidence probably related to late hercynian pull apart movements led to continuous sedimentation from the permian to the middle jurassic mid jurassic doming of its eastern flank followed by erosion transtensional movements and differential subsidence until the early cretaceous reflect the mid and late kimmerian crustal distension and fragmentation of the north sea rift basinwide inversion occurred between the turonian and the campanian and was repeated in the oligocene resulting in a total uplift of some 1500 m the present structural style is represented by a complex network of transpressional and transtensional faults at permian rotliegend levels which are thought to represent the upward termination of a series of wrench induced flower structures with a right lateral sense of displacement these faults are detached by zechstein and triassic salt from more orderly transtensional faults systems at shallower levels in areas where salt is absent late kimmerian normal faults became reactivated in a reverse sense during inversion however the relationship of these shallow mappable tectonic components to the deeper pre permian structure of the sole pit high and to the underlying crustal configuration remains speculative

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

seismic interpretation of dinantian carbonate platforms in the netherlands implications for the palaeogeographical and structural development of the northwest european carboniferous basin the northwest european carboniferous basin is characterized by a series of carbonate platforms and intervening shale dominated troughs during the dinantian sub period these structures have been mainly found along the margins of the basin here we present the results of an investigation of high quality 3d seismic surveys which has allowed the construction of a palaeogeographical and structural framework of the dinantian sub period in the centre of the northwest european carboniferous basin analysis of these data has revealed a series of structures characterized by flat tops well developed slopes and onlap by overlying strata these geometrical features suggest that the structures represent dinantian carbonate platforms an interpretation that is supported by recently published well data these findings suggest the following sequential depositional and structural model for the area 1 during the tournaisian stage carbonate sedimentation took place in basinal areas 2 continued subsidence probably induced by rifting resulted in the gradual onlap of carbonate deposition onto topographically higher areas 3 during the late visean stage rimmed shelf deposition took place by analogy with observations from the uk and belgium the seismically mapped structures represent these rimmed shelf carbonate platforms 2010 geological society of london

a scale interaction study on east asian cyclogenesis using a general circulation model coupled with an interactively nested regional model this study newly developed the interactively nested climate model incl using a general circulation model gcm interactively nested with a regional atmospheric model ram one interactive experiment with finer ram topography and another with coarser topography as well as offline versions of each experiment were performed to investigate the effects of subsynoptic scale eddies and subsynoptic scale mountains in northeast asia on the larger scale climate using the gcm with t42 atmosphere and the ram with 40 km mesh size in the incl system the subsynoptic scale eddy effect restrictively increased synoptic scale eddy activity within the ram domain in contrast subsynoptic scale mountains had the effect of robust anticyclonic circulation around the sea of japan and effectively forced larger scale circulation the effect was positively fed back to the mean field and amplified the anticyclonic circulation accompanied by suppressed storm activity in northeast asia the results suggest that subsynoptic scale mountains affect not only subsynoptic scale eddies but also the global climate

relation between annular modes and the mean state southern hemisphere summer abstract the annular modes emerge as the leading mode of extratropical month to month climate variability in both hemispheres here the influence of the background state on the structure and dynamics of the southern hemisphere annular mode sam during the austral summer when the climatology is characterized by a single well defined eddy driven jet is studied subsets of the climatology are constructed for early and late summer and for contrasting polarities of the enso cycle the analysis is based both on observations and on perpetual state gcm experiments the main differences between the subsets involve variations of the latitude of the mean jet it is found that in all the cases the sam is characterized by latitudinal shifts of the jet about its mean position reinforced by a positive momentum flux feedback from baroclinic waves this result is consistent with previous studies of the dynamics of the zonally averaged circulation but is found here to hold over all longitudes and for different positi

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

precession modulation of the south pacific westerly wind belt over the past million years the southern westerly wind belt sww interacts with the antarctic circumpolar current and strongly impacts the southern ocean carbon budget and antarctic ice sheet dynamics across glacial interglacial cycles we investigated precipitation driven sediment input changes to the southeast pacific off the southern margin of the atacama desert over the past one million years revealing strong precession 19 23 ka cycles our simulations with 2 ocean atmosphere general circulation models suggest that observed cyclic rainfall changes are linked to meridional shifts in water vapor transport from the tropical pacific toward the southern atacama desert these changes reflect a precessional modulation of the split in the austral winter south pacific jet stream for precession maxima we infer significantly enhanced rainfall in the southern atacama desert due to a stronger south pacific split jet with enhanced subtropical subpolar jets and a weaker midlatitude jet conversely we derive dry conditions in northern chile related to reduced subtropical subpolar jets and an enhanced midlatitude jet for precession minima the presence of precessional cycles in the pacific sww and lack thereof in other basins indicate that orbital scale changes of the sww were not zonally homogeneous across the southern hemisphere in contrast to the hemispherewide shifts of the sww suggested for glacial terminations the strengthening of the jet is unique to the south pacific realm and might have affected winter controlled changes in the mixed layer depth the formation of intermediate water and the buildup of sea ice around antarctica with implications for the global overturning circulation and the oceanic storage of atmospheric co2

kelvin helmholtz instability around the tropical tropopause observed with the equatorial atmosphere radar 1 in november 2001 the equatorial atmosphere radar 0 20 s 100 32 e observed a continuous strong eastward wind shear 10 50 m s 1 km 1 westward wind 2 27 m s 1 and the radar echo layer tilted downward to the west in the region 0 1 km above the tropopause during the same period the richardson number calculated with hourly averaged horizontal wind and radiosonde temperature data was almost continuously 0 5 and sometimes 0 25 which seems to indicate that the kelvin helmholtz instability khi frequently occurs in that region the existence of the tilted radar echo layer can be explained by khi billows a spurious updraft caused by the khi induced tilted echo layer and by the strong westward wind was also observed in the region

the response of the pacific storm track and atmospheric circulation to kuroshio extension variability an index of the kuroshio extension front strength is produced using a maximum covariance analysis between sea surface temperature sst and sea surface height ssh gradient observations and composites of the atmospheric state are presented during its positive and negative phases using reanalysis data 1992 2011 it is found that when the kuroshio extension is less more meandering with a stronger weaker sst front the atmospheric heat transport by transient eddies is increased in the western eastern pacific region consistent with an increase decrease in low level baroclinicity analysis of the eddy mean flow interaction shows that this zonal shift in heat transport forces anomalous barotropic flow in the eastern pacific where blocking frequency is strongly influenced the above relationships cannot be reconciled with the known response of the north pacific storm track to remote forcing from the tropical pacific nor can they be explained by the response of the ocean to atmospheric forcing via surface heat fluxes or winds rather the zonal shift in the storm track highlighted here and the associated changes in the large scale circulation are interpreted as a response to the interannual variability of the kuroshio extension front

heat flow heat production and thermo tectonic setting in mainland uk new heat flow data for the united kingdom together with additional heat flow and heat production determinations for caledonian age granites have led to a revision of the uk heat flow map and a re examination of the relationship between heat flow q 0 and heat production a 0 for granites and basement rocks previously recognized broad belts of above average heat flow are now resolved into separate zones which reflect to a greater extent the geological structure and tectonic history of the uk the zones of highest heat flow are spatially associated with voluminous high heat production granitoid batholiths in sw england northern england and the eastern highlands of scotland a single linear correlation between q 0 and a 0 is no longer tenable and an analysis in terms of broad heat flow provinces each with a characteristic upper crustal heat production distribution and deep heat flow contribution is also considered to be an oversimplification on the q 0 a 0 plot the data form four separate clusters three corresponding to the granite batholiths in sw england northern england and the eastern highlands of scotland and the fourth to the basement rocks of central england and wales an explanation of the q 0 a 0 data is proposed in terms of the crustal structure and thermo tectonic setting of each area in the case of the granite batholiths the data reflect the contrasting depth extent and radioelement depth functions of the intrusions these parameters in turn are related to the magmatic evolution and emplacement history of each batholith and the nature of the crust into which they were emplaced

variability patterns of rossby wave source rossby waves rw propagation due to a local forcing is one of the mechanisms responsible for wave trains configurations known as teleconnections the term teleconnection refers to anomalies patterns that are correlated in several regions of the world causing large scale changes in atmospheric waves patterns and temperature and precipitation regimes the aim of teleconnections studies is to provide a better understanding of atmospheric variability and their mechanisms of action in order to identify patterns that can be tracked and predicted the purpose of this study was to characterize seasonal and spatial variability of atmospheric rw sources the rw source at 200 hpa was calculated for the four seasons with reanalysis data of zonal and meridional wind in the northern hemisphere nh the rw sources were located on east asia north america north atlantic and pacific the main rw sources in the southern hemisphere sh were located over intertropical south pacific south atlantic and south indian convergence zones extratropical regions were also identified mainly to the south of australia the vortex stretching term s1 and the advection of absolute vorticity by the divergent wind s2 were analyzed to discuss the physical mechanisms for rw generation in the nh the source at east asia in djf changed to a sink in jja related to the dominance of s1 term in djf and s2 term in jja in the sh the vortex stretching term had the dominant contribution for rw source located to the south of australia the main forcing for rw sources at east of australia was the advection of absolute vorticity by divergent flow over south america both terms contributed to the source in djf the main modes of rw source variability were discussed by using empirical orthogonal functions analysis rw variability was characterized by wave trains configurations in both hemispheres over regions of jet streams and storm tracks associated with favorable and unfavorable areas for rw generation

storm track response to ocean fronts in a global high resolution climate model synoptic atmospheric eddies are affected by lower tropospheric air temperature gradients and by turbulent heat fluxes from the surface in this study we examine how ocean fronts affect these quantities and hence the storm tracks we focus on two midlatitude regions where ocean fronts lie close to the storm tracks the north west atlantic and the southern ocean an atmospheric climate model of reasonably high resolution 50 km is applied in a climate length 60 year simulation in order to obtain stable statistics simulations with frontal structure in the sea surface temperature sst in one of the regions are compared against simulations with globally smoothed sst we show that in both regions the ocean fronts have a strong influence on the transient eddy heat and moisture fluxes not just in the boundary layer but also in the free troposphere local differences in these quantities between the simulations reach 20 40 of the maximum values in the simulation with smoothed sst averaged over the entire region of the storm track over the ocean the corresponding differences are 10 20 the effect on the transient eddy meridional wind variance is strong in the boundary layer but relatively weak above that the potential mechanisms by which the ocean fronts influence the storm tracks are discussed and our results are compared against previous studies with regional models aquaplanet models and coarse resolution coupled models

numerical experiments of the storm track sensitivity to oceanic frontal strength within the kuroshio oyashio extensions the sensitivity of the north pacific storm track to midlatitude oceanic frontal strength within the kuroshio oyashio extensions is investigated by applying artificially changed meridional sea surface temperature sst gradients in the weather research forecasting model version 3 4 the result of sensitivity experiments further confirms the close relationship between the storm track activity and meridional sst gradient i e the storm track activity can be intensified as a response to increases in the oceanic frontal strength in order to better understand the mechanism for the storm track intensification due to increased sst gradient velocity temperature correlation and local energetics are analyzed the result indicates that the enhancement of the meridional sst gradient leads to amplitude magnification of eddy meridional velocity and temperature and their phase consistency suggesting that synoptic scale eddies tend to approach the optimum structure for the baroclinic energy conversion which is mainly responsible for the sst front induced enhancement of storm track activity in order to estimate the impact of the oceanic front on the maintenance of the near surface baroclinicity further investigation is made by the composite analysis with the increase in oceanic frontal strength the near surface baroclinicity experiences a slow but strong restoration the increase in the meridional sst gradient results in the intensification in the cross frontal differential sensible heat flux which can more effectively offset the relaxing effect of the transient eddy poleward heat transport

the generation of global rotational flow by steady idealized tropical divergence abstract tropical convective heating is balanced on the large scale by the adiabatic cooling of ascent the horizontal divergence of the wind above this heating may be viewed as driving the upper tropospheric rotational wind field a vorticity equation model is used to diagnose this relationship it is shown that because of the advection of vorticity by the divergent component of the flow the rossby wave source can be very different from the simple fd source often used in particular an equatorial region of divergence situated in easterly winds can lead to a rossby wave source in the subtropical westerlies where it is extremely effective this part of the source can be relatively insensitive to the longitudinal position of the equatorial divergence a divergence field which is asymmetric about the equator can lead to a quite symmetric rossby wave source for a steady frictionless flow the rossby wave source averaged over regions within closed streamfunction or absolute vorticity contours is under cert

quasi stationary waves in the southern hemisphere part ii generation mechanisms abstract in this part ii the authors investigate the role that antarctic elevations the rest of the world orography thermal forcing from lower latitudes and the transient eddy component of the flow play on the generation of the quasi stationary wave field in the southern hemisphere an approach based on the ucla gcm is followed results from a control simulation with full orography and from experiments without the antarctic elevations and without the rest of the world orography suggest that the quasi stationary wave with zonal wavenumber 1 qs wave 1 around antarctica is primarily generated by mechanisms other than the antarctic elevations comparison of a three dimensional eliassen palm flux vector in the control simulation and those where the antarctic elevation and the rest of the world orography are removed suggests that wave activity propagates both from the subtropics and from polar latitudes although in qualitative agreement with results of part i the horizontal and vertical structure of t

the shape propagation and mean flow interaction of large scale weather systems abstract for a zonal average operator the eliassen palm flux provides a diagnostic of both eddy behavior and the feedback of the eddies onto the mean flow this paper addresses the diagnosis problem for other averaging operators and in particular for time averaging which has proved in recent years such a powerful means of viewing the three dimensional tropospheric flow the horizontal velocity correlation tensor gives a measure of the characteristic horizontal eddy shape at a point it also implies the direction of the group velocity relative to the mean flow in cases where such a concept is valid however the major emphasis here is on the mean flow feedback of eddies in this respect the eddy vorticity flux is determined by derivatives of the components of the anisotropic part of the tensor making a reasonable approximation allows the eddy vorticity flux convergence to be written in terms of e v 2 u 2 u v a simple interpretation of the mean flow feedback of eddies is then possible a sligh

on the existence of storm tracks abstract given that middle latitude weather systems transport heat in a manner such as to weaken the baroclinicity that is thought to be crucial to their growth it is perhaps surprising that concentrated regions of such eddy activity i e storm tracks are found in the northern hemisphere winter the existence and possible self maintenance of storm tracks is investigated using a linear stationary wave model with storm track region forcings taken from data averaged over a number of winters it is found that the direct thermal effect of the eddies does indeed act against the existence of the storm track their vorticity fluxes lead to some reduction of this effect it is argued that the mean diabatic heating in the storm track region is an indirect eddy effect this heating is found to maintain the mean maximum in baroclinicity in the region further the mean low level flow induced by the eddy effects is such as to enhance the warm western oceanic boundary currents that are crucial to the existence of t

the influence of environmental low level shear and cold pools on tornadogenesis insights from idealized simulations abstractidealized dry simulations are used to investigate the roles of environmental vertical wind shear and baroclinic vorticity generation in the development of near surface vortices in supercell like pseudostorms a cyclonically rotating updraft is produced by a stationary cylindrical heat source imposed within a horizontally homogeneous environment containing streamwise vorticity once a nearly steady state is achieved a heat sink which emulates the effects of latent cooling associated with precipitation is activated on the northeastern flank of the updraft at low levels cool outflow emanating from the heat sink spreads beneath the updraft and leads to the development of near surface vertical vorticity via the baroclinic mechanism as has been diagnosed or inferred in actual supercells that have been simulated and observed an intense cyclonic vortex forms in the simulations in which the environmental low level wind shear is strong and the heat sink is of intermediate strength relative to the

characteristics of wave packets in the upper troposphere part ii seasonal and hemispheric variations abstract gridded 300 hpa meridional wind data produced by the ecmwf reanalysis project were analyzed to document the seasonal and hemispheric variations in the properties of upper tropospheric wave packets the properties of the wave packets are mainly illustrated using time lagged one point correlation maps performed on based on indices that show the coherence of wave propagation as well as examination of correlation maps schematic waveguides were constructed for the summer and winter seasons of both hemispheres along which waves preferentially propagate with greatest coherence in the summers the waveguides basically follow the position of the midlatitude jets in the northern hemisphere winter the primary waveguide follows the subtropical jet over southern asia into the pacific but there is a secondary branch running across russia joining the primary waveguide near the entrance to the pacific storm track over the atlantic the waveguide passes east southeastward toward north africa then bac

interannual to decadal variability in the oyashio and its influence on temperature in the subarctic frontal zone an eddy resolving ogcm simulation abstract output of an eddy resolving ogcm simulation is used to investigate mechanisms for interannual to decadal variability in the oyashio and its influence on the subarctic frontal zone in the western north pacific lag correlation analysis reveals that positive anomalies both in basin scale wind stress curl and in local ekman pumping can intensify the southward oyashio almost simultaneously via barotropic and baroclinic rossby wave propagations respectively the oyashio strength can also be influenced by anomalous ekman pumping that is exerted in the western portion of the basin through the baroclinic wave propagation with the lag of 3 yr which appears to arise from a periodicity in the wind field the intensification of the oyashio is accompanied by negative anomalies both in the sea surface temperature and height off of hokkaido island of japan and is followed by their eastward development along the southern branch of the oyashio extension and associated subarctic frontal zone in association with

recent advances in coalification studies and their application to geology abstract recent advances in coalification studies since 1970 are reported concerning microscopic methods causes of coalification the coalification process as such and application to geology the degree of coalification rank is mostly determined on the basis of vitrinite reflectance measured on finely dispersed material in rocks for rocks bare of vitrinite other microscopic methods are used such as fluorescence properties of liptinites and graptolite reflectance under incident light or coloration of microfossils like palynomorphs and conodonts in transmitted light the validity of the various methods is discussed maximum rock temperature and its duration are the main causes of chemical coalification reactions heating rates during subsidence influence the attainment of rank equilibrium contact metamorphic coals and natural cokes formed from bituminous coals are characterized by a relatively high reflectance and anisotropy strong frictional heat may cause local increase of rank adjacent to thrust planes graphitization is thermodynamically not possible in nature without pressure and shearing confining pressure retards the chemical coalification reactions tectonic stress especially shearing promotes the increase of maximum reflectance and of anisotropy it commonly leads to bi axial optical properties instead of the more typical uni axial negative geometry of vitrinite in undisturbed coal seams bi axial optical properties are common for vitrinite inclusions in clastic rocks on the basis of combined fluorescence microscopical and geochemical studies bituminization has been recognized as the characteristic part of coalification in the range between sub bituminous and bituminous coal it is characterized by the generation of petroleum like substances which enable the coal to soften and to agglomerate during carbonization hydrogenation properties are favoured by the bituminization process the different liptinite macerals behave differently during coalification and pass coalification jumps at different rank stages a considerable part of total inertinites is formed during early coalification brown coal to sub bituminous coal stage as rank inertinite this new knowledge appears to become important in relation to hydrocarbon exploration diagenetic methane some examples for the application of coalification studies to geology refer to vitrinite reflectance as an indicator of rock diagenesis and metamorphism palaeogeographical and structural history palaeogeothermics and hydrocarbon exploration large scale areal coalification studies in foredeeps and backdeeps of ancient and recent orogens suggest estimations of crustal thicknesses and relations to plate tectonics