links between southwestern tropical indian ocean sst and precipitation over southeastern africa over the last 17 kyr abstract time series of mg ca ba ca and 18o analyzed in tests of surface dwelling planktonic foraminifer globigerinoides ruber from two marine sediment cores recovered in the mozambique channel off the zambezi river southwestern tropical indian ocean reveal climate variability over the last 17 kyr analysis of samples collected from the water column of the mozambique channel validates that mg ca in g ruber reflects calcification temperatures at 0 30 m water depth and that the surface water of the southwestern indian ocean is very sensitive to dissolved ba input from adjacent rivers foraminiferal ba ca and mg ca time series are used to reconstruct hydrological and thermal changes over southeastern african and southwestern tropical oceans the mg ca based sea surface temperature sst estimates indicate that the thermal evolution of the tropical southwestern indian ocean followed within age model uncertainties climate changes over antarctica the trend of the sst record is marked by a gradual warming from 24 7 0 6 c at 17 0 0 2 kyr bp to 26 4 0 3 c at 10 11 kyr bp interrupted by two prominent coolings of 1 5 0 2 c and 1 c centered at 15 0 1 kyr bp and 13 4 0 2 kyr bp respectively declining ssts in the early holocene reach their minimum 25 c at 8 7 0 2 kyr bp and give way to stable thermal conditions over the middle and late holocene the ba ca record indicates that the zambezi basin experienced relatively wet conditions during the early phase of the last deglaciation bolling allerod and the early holocene these wet phases coincide with an increase of sst in the mozambique channel in contrast relatively dry conditions throughout the middle and late holocene epoch are accompanied by relatively cold mozambique channel surface water these shifts likely reflect a response to meridional shifts of the austral westerlies and subtropical front these hypothesized shifts would have modulated the advection of cold southern ocean water into the mozambique channel changes in sst in the mozambique channel and possible resultant changes in the zonal gradient in the tropical indian ocean in turn had a strong impact on the precipitation over southeastern africa

seismic expression of structural style in norphlet formation offshore alabama during the past several years the jurassic norphlet formation in offshore alabama has been the focus of active exploration and development operations since the 1979 discovery of deep gas greater than 6096 m 20 000 ft in norphlet sandstones which contain estimated reserves of several trillion cubic feet six norphlet fields have been established in alabama state waters and an additional six fields have been established in federal outer continental shelf ocs waters in offshore alabama we describe using seismic data the structural style associated with the norphlet formation in offshore alabama more than 563 line kilometers 350 line miles of multifold common depth point cdp seismic reflection data in mobile bay and offshore alabama have been analyzed interpreted and mapped the lower mobile bay mary ann natural gas field provides an excellent seismic case study for the structural style in the deep norphlet play the field may be used as a geophysical exploration model for other jurassic structures in offshore alabama and the central and eastern gulf of mexico interpretation of the seismic data and maps indicates that norphlet structures in offshore alabama are predominantly east west trending low relief broad elongate anticlines the lower mobile bay fault trend associated with the anticlines consists of pull apart listric normal faults characteristic of salt detachment structures many of these faults exhibit small scale growth salt thickness ostensibly increases from mobile bay to offshore alabama and is exemplified by the development of a sequence of various structures typically associated with basinward increase of salt offshore alabama structures may be classified as early horizontal phase or pillow stage features strata above the haynesville seismic marker appear to be relatively flat indicating early salt movement in the area small downbends associated with salt withdrawal exhibit thickening in the haynesville smackover section and are further complicated by normal faulting the preponderance of the data suggests that the structures containing the large gas accumulations in the norphlet formation in offshore alabama are the result of salt tectonism

subtropical dipole mode in the southern hemisphere a global view a global wavenumber 3 dipole sst mode is showed to exist in the southern hemisphere subtropical climate variability in austral summer a positive negative phase of the mode is characterized by cool warm sst anomalies in the east and warm cool sst anomalies in the southwest of the south indian pacific and atlantic oceans respectively this coherent dipole structure is largely a response of ocean mixed layer to the atmospheric forcing characterized by migration and modulation of the subtropical high pressures in which the latent heat flux play a leading role through wind induced evaporation although ocean dynamics may also be crucial in forming sst anomalies attached to the continents exploratory analyses suggest that this mode is strongly damped by the negative heat flux feedback with a persistence time about three months and no spectral peak at interannual to decadal time scales as the subtropical dipole mode is linearly independent of enso and sam whether it represents an additional source of climate predictability should be further studied citation wang f 2010 subtropical dipole mode in the southern hemisphere a global view geophys res lett 37 l10702 doi 10 1029 2010gl042750

late quaternary vegetation dynamics and hydro climate in the drakensberg south africa abstract a multi proxy study of a sediment sequence from braamhoek wetland covering the last c 16 000 years reveals a record of regional climate and vegetation dynamics in the drakensberg region south africa including signals from both the organic sediment fraction fossil pollen charcoal n alkane abundance n alkane 13c toc and the inorganic fraction mineral magnetic properties the reconstruction supported by a robust chronology indicates two major periods of increased regional wetness during the late pleistocene to early holocene phase c 13 800 12 600 cal yr bp c 10 200 8500 cal yr bp and one during the late holocene c 2000 cal yr bp to present drier conditions are recorded during the younger dryas c 12 600 11 300 cal yr bp and mid holocene c 7000 2000 cal yr bp a major decline in fynbos vegetation during the early holocene suggests a shift towards warmer temperatures and possibly towards less pronounced winter rains in eastern south africa from c 8500 cal yr bp comparison with records from interior of south africa show relatively high inter site variability however the braamhoek moisture proxies do co vary with the speleothem isotope records from makapansgat suggesting a similar hydro climate evolution in eastern and interior parts of the summer rainfall region during the studied period on multi millennial time scales an inverse hydro climatological pattern is evident between these two south african records and reconstructions from tropical locations in southeast africa such a rainfall dipole between eastern tropical and southern africa has previously been identified on shorter time scales i e on inter annual to millennial scales the braamhoek study suggests that a similar dipole pattern is acting also on a multi millennial perspective these long term precipitation anomalies are tentatively coupled to teleconnections from multi millennial changes in the dynamics of the indian ocean dipole iod and el nino southern oscillation enso

heat balance and regime shifts of the mixed layer in the kuroshio extension abstract we investigated the seasonal variations of the mixed layer depth and temperature in the kuroshio extension region 145 180 e 30 36 n and studied the causes of the mixed layer depth and temperature regime shifts which occurred in the late 1980s using upper ocean thermal and heat flux datasets incorporated with a bulk mixed layer model the mixed layer from fall to winter is cooled by the net surface heat flux the ekman transport and the entrainment and warmed by the horizontal heat convergence resulting from the kuroshio heat advection the mixed layer depth is controlled by the entrainment and the horizontal transport divergence convergence which act to slow the mixed layer deepening from fall to early winter and then in winter deepen the mixed layer the entrainment velocity is significantly influenced by the temperature difference between the mixed layer and the layer below the mixed layer shift from its deep to shallow phase occurred in 1985 this shift is preceded the sst shift in 1988 by three years and was caused by the horizontal transport divergence anomaly the horizontal heat convergence of the kuroshio extension caused the sst shift in 1988 whereas its anomaly had been already positive since 1983 the delay from 1983 to 1987 can be attributed to the effects of the negative fall sst anomaly stronger surface heat flux and ekman cooling and the shoaling of the mixed layer depth it is suggested that the kuroshio current system plays a major role in forcing the sst shift and thus the subsequent climate regime shift

direct observation and analysis of a trapped coh fluid growth medium in metamorphic diamond the mechanism by which diamonds grow in earth s mantle has been a subject of discussion for many years arguments have been advanced for growth from a melt from a coh fluid and in the solid state the discovery of microdiamonds within ultra high pressure terranes of continental collision settings re energized this debate because of their very different but well defined continental crust environment we report here the discovery of filled nanometric fluid bubbles in diamonds from marble of the kokchetav massif kazakhstan and the serendipitous measurement of their contents due to bursting of a bubble very shortly after a measurement of chemical composition in the transmission electron microscope thereby allowing immediate re analysis with exactly the same settings of all parameters of the microscope the chemical composition of the fluid is c h o cl s ca fe and k the direct observation and composition of a low viscosity trapped fluid in microdiamond unambiguously establish their fluid growth medium

role of tropical sst variability on the formation of subtropical dipoles abstractinterannual variations of sea surface temperature sst in the midlatitudes of the southern hemisphere play an important role in the rainfall variability over the surrounding countries by modulating synoptic scale atmospheric disturbances these are frequently associated with a northeast southwest oriented dipole of positive and negative sst anomalies in each oceanic basin referred to as a subtropical dipole this study investigates the role of tropical sst variability on the generation of subtropical dipoles by conducting sst nudging experiments using a coupled general circulation model in the experiments where the simulated sst in each tropical basin is nudged to the climatology of the observed sst the subtropical dipoles tend to occur as frequently as the case in which the simulated sst is allowed to freely interact with the atmosphere it is found that without the tropical sst variability the zonally elongated atmospheric mode in the mid to high latitudes called the antarctic oscillation

evidence for the influence of the agulhas current on regional atmospheric circulation patterns abstract the agulhas current is much the strongest western boundary current in the southern hemisphere transporting about 65 sv of warm water along the southeast coast of africa south of africa it retroflects back into the south indian ocean and flows east as the agulhas return current large amounts of heat are lost to the atmosphere from the warm waters of the southern agulhas current its retroflection and the return current particularly during winter and the transition seasons it is thought that this large exchange of heat may have a significant influence on the regional atmospheric circulation the tracks and intensity of transient weather disturbances such as extratropical cyclones and on rainfall received over large parts of neighboring southern africa in an attempt to investigate the potential influence of the agulhas current on the regional atmosphere two ensembles of year long integrations of an atmospheric general circulation model are analyzed in the first ensemble the sea surface tem

a theory for the tropical tropospheric biennial oscillation the key questions of how the tropospheric biennial oscillation tbo maintains the same phase from northern summer in south asia to southern summer in australia and how the reversed phase can last through three locally inactive seasons to the next monsoon are studied by a simple tropical atmosphere ocean land model the model has five boxes representing the south asian and australian monsoon regions and the equatorial indian and western and eastern pacific oceans the five regions interact with each other through the sst monsoon evaporation wind monsoon walker circulation and wind stress ocean thermocline feedbacks a biennial oscillation emerges in a reasonable parameter regime with model sst and wind variations resembling many aspects of the observed tbo warm sst anomalies ssta in july in the equatorial indian ocean cause an increase of surface moisture convergence into south asia leading to a stronger monsoon the monsoon heating on one hand induces a westerly wind anomaly in the indian ocean and on the other hand intensifies a planetary scale east west circulation leading to anomalous easterlies over the western and central pacific the westerly anomaly over the indian ocean decreases the local sst primarily by evaporation wind feedback the easterly anomaly in the central pacific causes a deepening of the ocean thermocline in the western pacific therefore increasing the subsurface and surface temperatures in addition a modest easterly anomaly in the western pacific opposes the seasonal mean westerlies so evaporation is reduced these effects overwhelm those of the cold zonal advection and anomalous upwelling the net result is warm ssta persisting in the western pacific through northern fall leading to a stronger australian monsoon meanwhile the warming in the western pacific also induces a stronger local walker cell and thus a surface westerly anomaly over the indian ocean this westerly anomaly helps the cold ssta to persist through the succeeding seasons leading to a weaker asian monsoon in the following summer during northern winter the westerly anomaly associated with the stronger australian monsoon through anomalous ocean downwelling and reduction of evaporation when the seasonal mean wind is easterly reinvigorates the warm ssta in the western pacific which has been weakened by the slow cold advection from the eastern pacific this further intensifies the eastern walker cell and helps to keep the eastern pacific cold the authors theory indicates that the tbo is an inherent result of the interactions between northern summer and winter monsoon and the tropical indian and pacific oceans thus it is an important component of the

role of indian ocean warming in the development of philippine sea anticyclone during enso 1 the anomalous low level anticyclone near the philippines and suppressed convection over the western pacific associated with the mature warm phase of el nino southern oscillation enso have been suggested as important elements in the interaction between enso and the east asian monsoon we examined the causes of these anomalies in the circulation and convection using a newly developed linear baroclinic model that includes interactive moist processes of the cumulus convection and surface heat fluxes a conventional version of the linear model forced by prescribed heating indicates that the diabatic cooling due to suppressed convection over the maritime continent generates the philippine sea anticyclone from a series of the moist linear model experiments we found that the modest warming of the indian ocean in addition to the strong warming in the central eastern pacific and weak cooling in the western pacific is significant to suppress the convection over the maritime continent observed data also show a coincidence of the development between the philippine sea anticyclone indian ocean warming and the ascending motion over the indian ocean supporting the model results the above results indicate that the atmosphere ocean system in the indian ocean may be one of important factors to improve predictability of the east asian climate during enso

mechanisms for enso phase change in a coupled gcm the mechanisms leading to el nino onset and termination in the echam4 opa coupled gcm are assessed and compared to observations and existing enso paradigms at the equator as well as off equator the patterns and timing of modeled el nino composites are in good agreement with those observed heat content of the west pacific is confirmed as a precursor to enso phase change and the present work emphasizes the role of its northern off equator part west north pacific wnp region 58 158n 1208 1708e the associated heat content changes appear to be dominated by a local ekman pumping or forced rossby waves rather than the accumulation of remotely generated free rossby waves as proposed by many theories the heat content decrease in the wnp region which triggers el nino termination is due to the negative feedback of the atmospheric gill s response to the increased equatorial sst in the east pacific in agreement with most paradigms delayed recharged west pacific oscillators the present study introduces the advection of the off equator signal to the equatorial waveguide by the mean currents of the western pacific as an additional process a similar feedback with opposite sign also seems to drive the modeled el nino onset favoring a too strong and regular biennial enso in the model this is due to the stronger than observed walker circulation that isolates the wnp region from other remote influences like monsoons the model also exhibits aborted enso events where the warming peaks in late spring instead of late autumn and is quickly terminated by the gill s negative feedback the abort event occurs too frequently in the coupled model due to too strong and too zonal a convergence zone south of the equator double itcz it bears some resemblance to the spring 1993 warming when the southern tropics were also warm the results of this paper provide additional insight into the el nino seasonal phase lock mechanisms

an index for tropical temperate troughs over southern africa strong cases of the tropical temperate troughs ttt that are responsible for the most of the summer rainfall over subtropical southern africa are analyzed an index for identifying the ttt is introduced for the first time using anomalies of outgoing longwave radiation olr and the wind the ttt is associated with a ridge trough ridge wave like structure in the lower troposphere over southern africa and the adjoining indian ocean therefore the index considers physical processes that occur over southern africa adjoining the atlantic and indian oceans to depict the variability of the ttt events unusually strong ttt events are identified when the standard deviations of the ttt indices defined by the olr and wind anomalies in the selected regions are above 1 5 and 0 5 respectively after applying this criterion and filtering out consecutive events 55 ttt events are identified during the study period of december january february seasons from 1980 1981 to 2009 2010 from the composite analyses of those 55 events it is found that the ttts evolve with suppressed enhanced convection over the southwest indian ocean adjacent to madagascar southern africa the suppressed convection is in turn found to be associated with the enhanced convection around sumatra in the southeast tropical indian ocean this may explain why more ttt events occur in la nina years as compared to el nino years time evolution of the canonical ttt event shows that it starts 3 days prior to the mature phase of the event suggesting possible predictability after reaching a matured state the system moves east toward the indian ocean and decays within the subsequent couple of days in addition the intertropical convergence zone itcz structure changes over southern africa madagascar during the ttt event and remains similar to climatology over other regions the results indicate that the continental part of the itcz intensifies prior to the ttt event and then spreads southward following the mid latitude influence during and after the event

on the likelihood of tropical extratropical cloud bands in the south indian convergence zone during enso events abstractthe southern hemisphere subtropical convergence zones are important regions of rainfall in the subtropics the south indian ocean convergence zone sicz has the strongest seasonality and exhibits substantial interannual variability in strength and position during austral summer on synoptic time scales the sicz is a preferred region for the formation of tropical extratropical te cloud bands with local maxima over the southern african mainland and madagascar this study investigates how the seasonality in satellite observed cloud band frequency emerges from the interplay between the asynchronous seasonal cycles in convective instability and upper level flow as represented by reanalysis data these atmospheric mean states are diagnosed with a gross convective instability metric and a method to distinguish between subtropical and eddy driven jet axes month by month analysis of these diagnostics elucidates how mean state perturbations during enso events modify cloud band likelihood typically 1

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

importance of the indian ocean for simulating rainfall anomalies over eastern and southern africa the relative contributions of the indian ocean and pacific ocean sea surface temperatures ssts to the rainfall variability over eastern central and southern africa during the austral spring summer are examined the variability of african rainfall is statistically related to both oceans but the variability in the two oceans is also related to separate the effects of the indian and pacific oceans a suite of numerical model simulations is presented goga the atmosphere is forced by observed ssts globally ioga the atmosphere is forced by observed ssts only in the indian ocean basin and poga the atmosphere is forced by observed ssts only in the tropical pacific basin while the sst variability of the tropical pacific exerts some influence over the african region it is the atmospheric response to the indian ocean variability that is essential for simulating the correct rainfall response over eastern central and southern africa analyses of the dynamical response s seen in the numerical experiments and in the observations indicate that the pacific and indian oceans have a competing influence over the indian ocean african region this competition is related to the influence of the two oceans on the walker circulation and the consequences of that variability on low level fluxes of moisture over central and southern africa finally given the high correlation found between sst variability in the indian and pacific oceans with the pacific leading by 3 months we speculate on an approach to long lead dynamical climate prediction over central east and southern africa

space time structure of monsoon interannual variability the analysis of corrected ship reports sea level pressure slp sea surface temperature sst air temperature at and corrected land data slp at rainfall in the indian sector reveals the existence of two low frequency modes of monsoon variability during the 1900 1970 period a definite biennial b mode exists on the slp fields this b oscillation is unambiguously linked with a southwest northeast slp anomaly gradient during the summer monsoon the b slp pattern can be interpreted as an expansion contraction of the monsoon activity since this mode is strongly coupled with rainfall variations over peninsular india a strong low frequency lf mode with period spanning 4 6 years is also seen on slp fields over the indian ocean and subcontinent the variance associated with this band is typically more important than the one observed for the b mode and its spatial mark is also strikingly different since it is linked with a global pattern of variation this mode has also a strong influence on the indian summer rainfall fluctuations particularly on the ghats and in the indo gangetic plains the amplitude of these oscillations varies widely during the 1900 1970 period the lf mode is well defined during 1900 1923 and 1947 1970 there is a tendency for the energy associated with the b mode to decrease on the land while it increases over the indian ocean during the whole 1900 1970 interval although these two timescales exist also on sst fields cross spectral analysis shows that ocean atmosphere interactions are much stronger at the b timescale this result stresses the b nature of the monsoon system the existence of these interannual signals in the indian areas where the annual cycle is so strong raises difficult problems how can climatic anomalies persist for several years in spite of strong seasonality or still more intriguing how can be explained the persistence of climatic anomalies during one year and the appearance of opposite sign climatic anomalies in the following year for the b mode a composite analysis has suggested an explanation for this last problem sst anomalies produced by exceptional summer monsoons can indeed persist during the whole winter and exert an influence on the next summer monsoon

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

south atlantic response to el nino southern oscillation induced climate variability in an ocean general circulation model 1 the response of the south atlantic ocean to el nino southern oscillation enso is investigated by means of an ocean general circulation model orca2 forced with national centers for environmental prediction ncep reanalyses for the 1948 1999 period seasonal enso composites suggest that the enso induced wind anomalies play a major role in driving upper ocean temperatures by altering the net surface heat fluxes the meridional ekman heat transport and ekman pumping model diagnostics indicate that the ekman heat transport changes are in better agreement with the upper ocean temperature anomalies during the first half of the enso event whereas in the latter half the surface heat flux anomalies agree better in general the atmospheric forcing tends to lead to a coherent ocean response with a time lag of about one season subsurface temperatures evolve more slowly in response to enso forcing than the upper ocean they receive time filtered enso signals from mainly ekman pumping suction and variations in thermocline depth that result in the poleward and equatorward margins of the subtropical gyre exhibiting temperature anomalies of the same sign but opposite to those in the central regions of the gyre

improvement of enso prediction using a linear regression model with a southern indian ocean sea surface temperature predictor 1 this study presents a detailed comparison between three enso precursors which can predict across the spring persistence barrier the anomalous equatorial pacific upper ocean heat content the zonal equatorial wind stress anomaly in the far western pacific and sst anomalies in the south east indian ocean seio during the late boreal winter a new correlation analysis confirms that el nino la nina onsets are preceded by significant cold warm sst anomalies in the seio during the late boreal winter after the 1976 77 climate regime shift thus the objective is to examine the respective potential of these three enso precursors to predict enso events across the boreal spring barrier during recent decades surprisingly in this focus cross validated hindcasts of the linear regression models based on the lagged relationship between nino3 4 sst and the predictors suggest that seio sst anomalies during the late boreal winter is the more robust enso predictor

role of ocean mesoscale structures in shaping the angola low pressure system and the southern africa rainfall southern african climate is under the influence of both tropical and subtropical systems which result in a complex region where important interactions co exist over a large spectrum of spatiotemporal scales the angola low al situated on boundary between tropical and subtropical southern africa has been diagnosed as a key driver of moisture distribution in the region on daily to seasonal time scales it has been demonstrated that the al pressure system is sensitive to the dynamics of the neighbouring oceans but to date no study has considered the model resolution of air sea interactions required to simulate this sensitivity using sensitivity experiments with a regional atmospheric model which differ only in the mesoscale sea surface temperature sst forcing characteristics either the full spectrum of sst variability or only its large scale components are included we first quantify the importance of sst gradients on the al strength and variability the results suggest that the mesoscale sst variability of the angola benguela frontal zone abfz plays a key role in al activity particularly during the late summer synoptic scale tropical lows which form the al are automatically detected and the results suggest more extreme events occur when the model is forced by mesoscale ssts everywhere and in the abfz area only the rainfall resulting from those events suggests that tropical low episodes are associated with nearly 15 of the total rain in angola and namibia the link between al dynamics and wet spells is also discussed with the former showing a different spatial pattern as well as frequency when the ocean is fully resolved

frontogenesis in the agulhas return current region simulated by a high resolution cgcm abstractdetailed mechanisms for frontogenesis frontolysis of the sea surface temperature sst front in the agulhas return current arc region are investigated using outputs from a high resolution coupled general circulation model the sst front is maintained throughout the year through an approximate balance between frontolysis by surface heat flux and frontogenesis by horizontal advection although a southward northward cross isotherm flow on the northern southern side of the front is weaker than a strong eastward along isotherm current in the frontal region this cross isotherm confluent flow advects warmer cooler temperature toward the sst front north south of the front and acts as the dominant frontogenesis mechanism in addition stronger weaker frontogenesis in austral summer winter is attributed to the stronger weaker cross isotherm confluence which may be linked to seasonal variations of the agulhas current arc and antarctic circumpolar current on the other hand the contributi

on the emergence of the atlantic multidecadal sst signal a key role of the mixed layer depth variability driven by north atlantic oscillation abstractdespite its wide ranging potential impacts the exact cause of the atlantic multidecadal oscillation variability amo amv is far from settled while the emergence of the amo sea surface te

austral summer teleconnections of indo pacific variability their nonlinearity and impacts on australian climate abstractin austral summer el nino southern oscillation enso covaries with the indian ocean basin mode iobm and with the southern annular mode sam the present study addresses how the iobm and the sam modulate the impact of enso on australia the authors show that the modulating effect of the sam is limited in particular the sam does not modify the enso teleconnection pattern however the iobm extends enso induced convection anomalies westward over northern australia and over the eastern indian ocean whereby extending the enso tropical teleconnection to the northwest of australia the iobm also generates an equivalent barotropic rossby wave train through convection anomalies over northern australia the wave train shares an anomaly center over the tasman sea latitudes with the pacific south american psa pattern shifting the anomaly center of the psa pattern to within a closer proximity to australia there is a strong asymmetry in the iobm modulating effect during an iobm negative phase whic

upper jurassic reefs of smackover formation united states gulf coast the occurrence of reefs in the smackover formation an upper jurassic oxfordian sequence that has been recognized in the subsurface of the united states gulf coast requires a revision of existing depositional models that have been based exclusively on subsurface data gathered from nonskeletal carbonate reservoirs these reefal buildups are 10 to 130 ft 3 to 40 m thick commonly elongate and several square kilometers in plan they developed seaward of oolite shoals on paleostructures of three types that created subtle topographic highs on an otherwise ramplike sea floor 1 basement ridges 2 faulted basement highs and 3 upthrown salt cored fault blocks reef rubble zones have reservoir quality porosity throughout the smackover trend but reef framework is a ta get only where diagenesis has been favorable although only a few reefs have produced commercial hydrocarbons attractive porosities and permeabilities mean phgr of 15 mean k of 20 md result from freshwater leaching dolomitization or fracturing the biota forming smackover reefs is similar to that described for sponge and algal buildups and patch reefs from the late jurassic of europe reef framework is constructed by digitate and branching stromatolitic blue green algae tubiphytes sp and marine cements the biota varies through the smackover trend reefs in southern arkansas and northern louisiana are more diverse in these reefs encrusters and binders produce constructional microframework cavities on and between corals primarily actinastrea skeletal algae parachaetetes sp and cayeuxia sp lithistid and hexactinellid sponges bryozoans and hydrozoans the cavities are commonly filled with marine cements and geopetal sediments a vertical biotic zonation in cores of the reef interval suggests that the reef commu ity of organisms evolved through time the reefs are commonly underlain and overlain by subtidal peloidal lime packstones containing oncolites and scattered fossils and they can develop in close proximity to subtidal quartz sands

modulation of the southern africa precipitation response to the el nino southern oscillation by the subtropical indian ocean dipole the climate of southern africa defined as the land area bound by the region 15 s 35 s 12 5 e 42 5 e during the december march rainy season is driven by indo pacific sea surface temperature sst anomalies associated with the el nino southern oscillation enso and the subtropical indian ocean dipole siod the observed december march 1979 2014 southern africa precipitation during the four enso and siod phase combinations suggests that the phase of the siod can disrupt or enhance the southern africa precipitation response to enso here we use a large ensemble of model simulations driven by global sst and enso only sst to test whether the siod modifies the relationship between southern africa precipitation and enso since enso based precipitation forecasts are used extensively over southern africa an improved understanding of how other modes of sst variability modulate the regional response to enso is important enso in the absence of the siod forces an equivalent barotropic rossby wave over southern africa that modifies the regional mid tropospheric vertical motions and precipitation anomalies el nino la nina is related with high low pressure over southern africa that produces anomalous mid tropospheric descent ascent and decreases increases in precipitation relative to average when the siod and enso are in opposite phases the siod compliments the enso related atmospheric response over southern africa by strengthening the regional equivalent barotropic rossby wave anomalous mid tropospheric vertical motions and anomalous precipitation by contrast when the siod and enso are in the same phase the siod disrupts the enso related atmospheric response over southern africa by weakening the regional equivalent barotropic rossby wave anomalous mid tropospheric vertical motions and anomalous precipitation

mesoscale convective complexes over southern africa abstractthe maximum spatial correlation technique mascotte is an objective and automated method developed to simultaneously determine both the structural properties and evolution tracking of cloud shields of convective systems originally designed to monitor systems over the amazon region this method has now been adapted for subtropical southern africa in this paper a detailed climatology of 70 mesoscale convective complexes mccs that occurred during the austral summer months over southern africa during the 1998 2006 period are presented most mccs are clustered along the eastern regions of southern africa adjacent to the warm waters of the mozambique channel and agulhas current a few infrequent systems are found to be developing in namibia and botswana the systems are found to predominantly occur during the months of november february with maximum activity occurring in november and december the transition from a more midlatitude dominated circulation to a tropical circulation over the regio

the impact of enso on the south atlantic subtropical dipole mode abstractthe impact of el nino southern oscillation enso on the south atlantic subtropical dipole mode sasd is investigated using both observations and model simulations the sasd is the dominant mode of coupled ocean atmosphere variability in the south atlantic this study focuses on austral summer when both enso and sasd peak it is shown that negative sasd events are associated with central pacific el nino events by triggering the pacific south american wave train psa the latter resembles the third leading mode of atmospheric variability in the southern hemisphere psa2 and causes a weakening and meridional shift of the south atlantic subtropical high which then generates the negative sasd events on the other hand a strengthening of the south atlantic subtropical high related to central la nina teleconnections causes positive sasd events the results herein show that the psa2 triggered by central pacific enso events connects the tropical pacific to the atlantic this connection is absent f

impact of southeast indian ocean sea surface temperature anomalies on monsoon enso dipole variability in a coupled ocean atmosphere model recent studies show that southeast indian ocean seio ssts are a highly significant precursor of transitions of the whole monsoon el nino southern oscillation enso system during recent decades however the reasons for this specific interannual variability have not yet been identified unequivocally from the observations among these the possibility of seio sst driven variability in the monsoon enso system is investigated here by inserting positive negative seio temperature anomalies in the february s restart files of a state of the art coupled general circulation model gcm for 49 years of a control simulation for each year of the control simulation the model was then integrated for a 1 year period in fully coupled mode these experiments show that indian summer monsoon ism and tropical indian ocean dipole mode iodm events are significantly influenced by the seio temperature perturbations inserted in the mixed layer of the coupled gcm several months before a warm seio perturbation inserted in late boreal winter slowly propagates northward during the following seasons implies enhanced ism rainfall and finally triggers a negative iodm pattern during boreal fall in agreement with observations a reversed evolution is simulated for a cold seio perturbation it is shown that the life cycle of the simulated seio signal is driven by the positive wind evaporation sst coastal upwelling and wind thermocline sst feedbacks further diagnosis of the sensitivity experiments suggests that stronger ism and iodm variabilities are generated by excluding the el nino years of the control simulation or when the initial background state in the seio is warmer this finding confirms that iodm events may be triggered by multiple factors other than enso including subtropical seio sst anomalies however the enso mode does not react significantly to the seio temperature perturbation in the perturbed runs even though the simulated pacific pattern agrees with the observations during boreal fall these discrepancies with the observations may be linked to model biases in the pacific and to the too strong enso simulated by this coupled gcm these modeling evidences confirm that subtropical indian ocean sst anomalies generated by mascarene high pulses during austral summer are a significant precursor of both ism and iodm events occuring several months later

south pacific origin of the decadal enso like variation as simulated by a coupled gcm 1 the hypothesis of the south pacific origin of the decadal 7 35 years enso like variation is investigated based on 200 year outputs of the echam4 opa oasis coupled gcm associated with the decadal warm cold sst anomalies in the tropical pacific an anomalous cyclonic anticyclonic circulation which is tilted in a southeast northwest direction appears in the south pacific this results in anomalous upward downward ekman pumping along the northeastern edge of the anomalous circulation and hence shallowing deepening the oceanic thermocline there such an external source of heat content tends to slowly discharge recharge the tropical ocean on the decadal timescale the above result is consistent with the observational study of luo and yamagata 2001 besides the model reproduces amazingly a high lagged correlation between the global land surface temperature and the decadal nino3 sst despite the model biases this suggests a potential prediction skill of the global warming based on the enso like decadal variation

generation mechanism of the south pacific subtropical dipole abstractdistinct pattern of interannual variability in sea surface temperature sst in the south pacific i e the south pacific subtropical dipole spsd is examined using outputs from a coupled general circulation model the spsd appears as the second empirical orthogonal function eof mode of the sst anomalies in the south pacific and is associated with a northeast southwest oriented dipole of positive and negative sst anomalies in the central basin the positive and negative sst anomaly poles start to develop during austral spring reach their peak during austral summer and gradually decay afterward close examination of mixed layer heat balance yields that the sst anomaly poles develop mainly because warming of the mixed layer by shortwave radiation is modulated by the anomalous mixed layer thickness over the positive negative pole the mixed layer becomes thinner thicker than normal and acts to enhance reduce the warming of the mixed layer by climatological shortwave radiation this thin

multiple generations of extensional detachments in the rhodope mountains northern greece evidence of episodic exhumation of high pressure rocks abstract an integrated structural and petrological study shows that exhumation of high rocks of the rhodope occurred in several pulses the structurally uppermost kimi complex recording an early cretaceous high p metamorphism was exhumed between about 65 and 42 ma the sidironero kardamos and kechros complexes that record early tertiary high metamorphism at least 19 kbar at 700 c were exhumed at 42 30 ma exhumation occurred with isothermal decompression strain episodes depict thrusting of medium high grade above lower grade high p rocks syn thrusting extension and post thrusting extension polyphase extension created several generations of detachment zones which in sum excise about 20 km of material within the crustal profile this reduction in crustal thickness is consistent with a reduction of the present crustal thickness from more than 40 km to less than 30 km in the eastern rhodope we mapped the post thrusting xanthi low angle detachment system over 100km from its break up zone above the sidironero complex central rhodope into the eastern rhodope this detachment shows an overall ese dip with a ramp and flat geometry cutting across the earlier thrust structures the kimi complex is the hanging wall of all synand post thrusting extensional systems on top of the kimi complex marine basins were formed from the lutetian c 48 43 ma through the oligocene during extension successively at c 26 to 8 ma the thasos pangeon metamorphic core complexes were exhumed in these times representing the early stages of aegean back arc extension the strymon and thasos detachment systems caused crustal thinning in the western rhodope renewed heating of the lithosphere associated with magmatism and exhumation of hot middle crust from beneath the sidironero complex occurred we focusoxn the geometry timing and kinematics of extension and contraction structures related to the 42 30 ma interval and how these exhumed high p rocks we interpret high rocks exhumed in this interval as a window of the apulian plate beneath the earlier in the cretaceous accreted kimi complex

indian ocean sea surface temperature and el nino southern oscillation a new perspective abstract here the 1976 77 climate regime shift that was accompanied by a remarkable change in the lead lag relationships between indian ocean sea surface temperature sst and el nino evolution is shown after the 1976 77 regime shift a correlation analysis suggests that southern indian ocean ssts observed during late boreal winter are a key precursor in predicting el nino evolution as the traditional oceanic heat content anomalies in the equatorial pacific or zonal wind anomalies over the equatorial western pacific the possible physical mechanisms underlying this highly significant statistical relationship are discussed after the 1976 77 regime shift southern indian ocean sst anomalies produced by mascarene high pulses during boreal winter trigger coupled air sea processes in the tropical eastern indian ocean during the following seasons this produces a persistent remote forcing on the pacific climate system promoting wind anomalies over the western equatorial pacific and modulating the regional ha

structure and mechanisms of the southern hemisphere summertime subtropical anticyclones abstract the three dimensional structure and dynamics of the climatological mean summertime subtropical anticyclones in the southern hemisphere sh are investigated as in the northern hemisphere nh each of the surface subtropical anticyclones over the south pacific south atlantic and south indian oceans is accompanied by a meridional vorticity dipole aloft exhibiting barotropic and baroclinic structures in its poleward and equatorward portions respectively in a manner that is dynamically consistent with the observed midtropospheric subsidence their dynamics are also similar to their nh counterpart it is demonstrated through the numerical experiments presented here that each of the sh surface anticyclones observed over the relatively cool eastern oceans can be reproduced as a response to a local near surface cooling heating couplet the cooling is mainly due to radiative cooling associated with low level maritime clouds and the heating to the east is due to sensible heat flux over the dry hea

el nino southern oscillation diversity and southern africa teleconnections during austral summer a wide range of sea surface temperature sst expressions have been observed during the el nino southern oscillation events of 1950 2010 which have occurred simultaneously with different global atmospheric circulations this study examines the atmospheric circulation and precipitation during december march 1950 2010 over the african continent south of 15 circ s a region hereafter known as southern africa associated with eight tropical pacific sst expressions characteristic of el nino and la nina events the self organizing map method along with a statistical distinguishability test was used to isolate the sst expressions of el nino and la nina the seasonal precipitation forcing over southern africa associated with the eight sst expressions was investigated in terms of the horizontal winds moisture budget and vertical motion el nino events with warm sst across the east and central pacific ocean and warmer than average sst over the indian ocean are associated with precipitation reductions over southern africa the regional precipitation reductions are forced primarily by large scale mid tropospheric subsidence associated with anticyclonic circulation in the upper troposphere el nino events with cooler than average sst over the indian ocean are associated with precipitation increases over southern africa associated with lower tropospheric cyclonic circulation and mid tropospheric ascent la nina events with cool sst anomalies over the central pacific and warm sst over the west pacific and indian ocean are associated with precipitation increases over southern africa the regional precipitation increases are forced primarily by lower tropospheric cyclonic circulation resulting in mid tropospheric ascent and an increased flux of moisture into the region

southern hemisphere extra tropical forcing a new paradigm for el nino southern oscillation the main goal of this paper is to shed additional light on the reciprocal dynamical linkages between mid latitude southern hemisphere climate and the el nino southern oscillation enso signal while our analysis confirms that enso is a dominant source of interannual variability in the southern hemisphere it is also suggested here that subtropical dipole variability in both the southern indian and atlantic oceans triggered by southern hemisphere mid latitude variability may also provide a controlling influence on enso in the equatorial pacific this subtropical forcing operates through various coupled air sea feedbacks involving the propagation of subtropical sea surface temperature sst anomalies into the deep tropics of the atlantic and indian oceans from boreal winter to boreal spring and a subsequent dynamical atmospheric response to these sst anomalies linking the three tropical basins at the beginning of the boreal spring this atmospheric response is characterized by a significant weakening of the equatorial atlantic and indian inter tropical convergence zone itcz this weakened itcz forces an equatorial cold kelvin wave response in the middle to upper troposphere that extends eastward from the heat sink regions into the western pacific by modulating the vertical temperature gradient and the stability of the atmosphere over the equatorial western pacific ocean this kelvin wave response promotes persistent zonal wind and convective anomalies over the western equatorial pacific which may trigger el nino onset at the end of the boreal winter these different processes explain why south atlantic and indian subtropical dipole time series indices are highly significant precursors of the nino34 sst index several months in advance before the el nino onset in the equatorial pacific this study illustrates that the atmospheric internal variability in the mid latitudes of the southern hemisphere may significantly influence enso variability however this surprising relationship is observed only during recent decades after the so called 1976 1977 climate regime shift suggesting a possible linkage with global warming or decadal fluctuations of the climate system

summer precipitation anomalies in the low latitude highlands of china coupled with the subtropical indian ocean dipole like sea surface temperature the relationship between the subtropical indian ocean dipole siod like sea surface temperature sst and summer precipitation in the low latitude highlands llh of china is investigated in a suite of numerical simulations using an atmospheric general circulation model agcm and a coupled ocean atmosphere model the agcm experiments driven by siod like sst anomalies are inconsistent with the observations however the coupled ocean atmosphere experiments show a good agreement with the observational results the modeling results indicate that the air sea interaction rather than a simple atmospheric forcing response relationship is a crucial mechanism explaining the connection among the anomalous summer precipitation in the llh the anomalous divergence circulations across the indian ocean and the siod like sst anomalies the effect of the enhanced interhemispheric vertical circulation variability associated with the siod like sst anomalies facilitates zonal wind anomalies in the northern bay of bengal and further induces anomalous water vapor convergence and precipitation anomalies in the llh the sst wind evaporation feedback mechanism could account for maintenance of the siod like pattern in the coupled ocean atmosphere experiments these results could help to improve prediction accuracy of summer rainfall variations over the llh of china

subtropical dipole modes simulated in a coupled general circulation model the growth and decay mechanisms of subtropical dipole modes in the southern indian and south atlantic oceans and their impacts on southern african rainfall are investigated using results from a coupled general circulationmodeloriginallydevelopedforpredictingtropicalclimatevariations thesecond most dominant mode of interannual sea surface temperature sst variations in the southern indian south atlantic ocean represents a northeast southwest oriented dipole now called subtropical dipole mode the positive negative sst interannualanomalypole startsto grow in australspring and reachesits peakin february in austral late spring the suppressed enhanced latent heat flux loss associated with the variations in the subtropical high causes a thinner thicker than normal mixed layer thickness that in turn enhances reduces the warming of the mixed layer by the climatological shortwave radiation the positive negative pole gradually decays in austral fall because the mixed layercooling by the entrainmentis enhanced reduced mostlyowing to the larger smaller temperature difference between the mixed layer and the entrained water the increased decreased latent heat loss due to the warmer colder sst also contributes to the decay of the positive negative pole although furtherverification using longerobservational data is required the present coupled model suggests that the south atlantic subtropical dipole may play a more important role in rainfall variations over the southern african region than the indian ocean subtropical dipole

subtropical sst dipole events in the southern indian ocean sea surface temperature sst anomalies in the subtropical southern indian ocean show interannual dipole events that are seasonally phase locked to the austral summer a positive phase of the event is characterized by cold sst anomalies in the eastern part i e off australia and warm sst anomalies in the southwestern part south of madagascar such an event is found to produce above normal rainfall over many regions in south central africa the cooling of sst in the eastern part is mainly caused by the enhanced evaporation this is associated with stronger winds along the eastern edge of the subtropical high which is strengthened and shifted slightly to the south during the event on the other hand relative decrease in the seasonal latent heat loss due to reduced evaporation dominates the warming in the southwestern part evolution of such subtropical dipole events shows quite a contrast to that of the tropical dipole events discovered recently in the indian ocean

regional jurassic geologic framework of alabama coastal waters area and adjacent federal waters area abstract to date numerous jurassic hydrocarbon fields and pools have been discovered in the cotton valley group haynesville formation smackover formation and norphlet formation in the tri state area of mississippi alabama and florida and in alabama state coastal waters and adjacent federal waters area petroleum traps are basement highs salt anticlines faulted salt anticlines and extensional faults associated with salt movement reservoirs include continental and marine sandstones limestones and dolostones hydrocarbon types are oil condensate and natural gas the onshore stratigraphic and structural information can be used to establish a regional geologic framework for the jurassic for the state coastal waters and adjacent federal waters areas evaluation of the geologic information along with the hydrocarbon data from the tri state area indicates that at least three jurassic hydrocarbon trends oil oil and gas condensate and deep natural gas can be identified onshore these onshore hydrocarbon trends can be projected into the mobile area in the central gulf of mexico and into the pensacola destin dome and apalachicola areas in the eastern gulf of mexico substantial reserves of natural gas are expected to be present in alabama state waters and the northern portion of the mobile area significant accumulations of oil and gas condensate may be encountered in the pensacola destin dome and apalachicola areas

atmosphere ocean coupled variability in the south atlantic abstract the climate variability of the south atlantic region is determined from 40 yr 1953 92 of comprehensive ocean atmosphere data set monthly sea surface temperature sst and sea level pressure slp data using the empirical orthogonal function eof and the singular value decomposition svd analysis methods the eof method is applied to each field separately whereas the svd method is applied to both fields simultaneously the significance of the atmosphere ocean interaction is revealed by a strong resemblance between individual eof and coupled svd modes of sst and slp the three leading modes of coupled variability on interannual and interdecadal timescales are discussed in some detail the first coupled mode which accounts for 63 of the total square covariance represents a 14 16 yr period oscillation in the strength of the subtropical anticyclone accompanied by fluctuations of a north south dipole structure in the sst the atmosphere ocean coupling is strongest during the southern summe

characterisation of igneous terranes by zircon dating implications for uhp occurrences and suture identification in the central rhodope northern greece the occurrence of ultra high pressure uhp and high pressure hp relicts associated with oceanic material suggests the presence of a suture zone within the rhodope massif characterisation of the accreted igneous terranes and their relationship with the uhp eclogite occurrences provide new constraints on the location of this suture single zircon evaporation and sensitive high resolution ion microprobe dating of orthogneiss protoliths define two groups of intrusion ages permo carboniferous and late jurassic early cretaceous structurally the late jurassic gneissic complex overthrust a unit with permo carboniferous orthogneisses a melange zone marked by mylonites eclogites amphibolites and uhp micaschists separates these two units we interpret these observations in terms of two distinct igneous terranes the thracia permo carboniferous and rhodope late jurassic terranes separated by the nestos suture and assembled during the closure of an oceanic basin of the tethys geochemically the late jurassic rocks are akin to subduction magmatism possibly the same subduction that caused the uhp metamorphism of metasediments within the melange zone observed uhp hp relicts are restricted to the tectonic contact zone suggesting that a single subduction collison event can explain the occurrences of uhp relicts and eclogites in the central rhodope and that subducted rocks are exhumed only within the nestos suture

change in the relationship between the southern subtropical dipole modes and the southern annular mode in the mid 1980s abstractthe southern subtropical dipole modes ssdms and southern annular mode sam are important climate modes which are dominant in the southern middle and high latitudes respectively with considerable regional climatic impacts however the relationship between the two modes remains unclear a close inspection reveals that the sam was significantly correlated with the ssdms during the austral summer before the mid 1980s however the correlations have degraded since then this decadal shift in the relationship between these two southern dominant modes is due to a weakened connection between the sam and the subtropical highs that control the ssdms this decadal change could be traced back to a poleward shift in the southern westerly belt el nino southern oscillation enso typically plays a moderate role in influencing the precipitation in australia and a minor role in influencing the precipitation in africa and south america nevertheless the two southern modes could still affect the austral sum

western indian ocean marine and terrestrial records of climate variability a review and new concepts on land ocean interactions since ad 1660 we examine the relationship between three tropical and two subtropical western indian ocean coral oxygen isotope time series to surface air temperatures sat and rainfall over india tropical east africa and southeast africa we review established relationships provide new concepts with regard to distinct rainfall seasons and mean annual temperatures tropical corals are coherent with sat over western india and east africa at interannual and multidecadal periodicities the subtropical corals correlate with southeast african sat at periodicities of 16 30 years the relationship between the coral records and land rainfall is more complex running correlations suggest varying strength of interannual teleconnections between the tropical coral oxygen isotope records and rainfall over equatorial east africa the relationship with rainfall over india changed in the 1970s the subtropical oxygen isotope records are coherent with south african rainfall at interdecadal periodicities paleoclimatological reconstructions of land rainfall and sat reveal that the inferred relationships generally hold during the last 350 years thus the indian ocean corals prove invaluable for investigating land ocean interactions during past centuries

reply to comment on diamond former coesite and supersilicic garnet in metasedimentary rocks from the greek rhodope a new ultrahigh pressure metamorphic province established by o beyssac and c chopin

variability of upper ocean characteristics and tropical cyclones in the south west indian ocean track and intensity are key aspects of tropical cyclone behavior intensity may be impacted by the upper ocean heat content relevant for tc intensification known as tdy and barrier layer thickness blt here the variability of tdy and blt in the south west indian ocean and their relationships with tropical cyclones are investigated it is shown that rapid cyclone intensification is influenced by large tdy values thick barrier layers and the presence of anticyclonic eddies for tc generation in the south west indian ocean the parameter tdy was found to be important large blt values overlay with large tdy values during summer both fields are modulated by the westward propagation of rossby waves which are often associated with enso for example the 1997 1998 el nino shows a strong signal in tdy sst and blt over the south west indian ocean after this event an increasing trend in tdy occurred over most of the basin which may be associated with changes in atmospheric circulation increasing sst power dissipation index and frequency of category 5 tropical cyclones also occurred from 1980 to 2010 to further examine the links between tropical cyclones tdy and blt the ocean response to category 5 tropical cyclone bansi that developed near madagascar during january 2015 was analyzed its unusual track was found to be linked with the strengthening of the monsoonal north westerlies while its rapid intensification from category 2 to category 4 was linked to a high tdy region associated with a warm core eddy and large blt

decadal change of the south atlantic ocean angola benguela frontal zone since 1980 high resolution simulations with a regional atmospheric model coupled to an intermediate level mixed layer ocean model along with multiple atmospheric and oceanic reanalyses are analyzed to understand how and why the angola benguela frontal zone abfz has changed since 1980 a southward shift of 0 05 0 55 latitude decade 1 in the annual mean abfz position accompanied by an intensification of 0 05 to 0 13 k 100 km decade 1 has occurred as ocean mixed layer temperatures have warmed cooled equatorward poleward of the front over the 1980 2014 period these changes are captured in a 35 year model integration the oceanic warming north of the abfz is associated with a weakening of vertical entrainment reduced cooling associated with vertical diffusion and a deepening of the mixed layer along the angola coast these changes coincide with a steady weakening of the onshore atmospheric flow as the zonal pressure gradient between the eastern equatorial atlantic and the congo basin weakens oceanic cooling poleward of the abfz is primarily due to enhanced advection of cooler water from the south and east increased cooling by vertical diffusion and shoaling of the mixed layer depth in the atmosphere these changes are related to an intensification and poleward shift of the south atlantic sub tropical anticyclone as surface winds hence the westward mixed layer ocean currents intensify in the benguela upwelling region along the namibian coast with a few caveats these findings demonstrate that air sea interactions play a prominent role in influencing the observed decadal variability of the abfz over the southeastern atlantic since 1980

remote influence of interdecadal pacific oscillation on the south atlantic meridional overturning circulation variability this study explores potential factors that may influence decadal variability of the south atlantic meridional overturning circulation samoc by using observational data as well as surface forced ocean model runs and a fully coupled climate model run here we show that samoc is strongly correlated with the leading mode of sea surface height ssh variability in the south atlantic ocean which displays a meridional dipole between north and south of 20 s a significant portion 45 of the south atlantic ssh dipole variability is remotely modulated by the interdecadal pacific oscillation ipo further analysis shows that anomalous tropical pacific convection associated with the ipo forces robust stationary rossby wave patterns modulating the wind stress curl over the south atlantic ocean a positive negative phase ipo increases decreases the westerlies over the south atlantic which increases decreases the strength of the subtropical gyre in the south atlantic and thus the samoc

on the relationship between indian ocean sea surface temperature and the transition from el nino to la nina the relationship between indian ocean sea surface temperature and the transition of el nino events into either la nina or el nino southern oscillation neutral conditions is examined in both observations and the retrospective ensemble hindcasts of the national center for environmental prediction climate forecast system the southern indian ocean is shown to demonstrate a particularly robust and consistent relationship with the evolution of these transitions these associations are described and a physical mechanism involving air sea interaction in the indian and western pacific oceans is proposed observations suggest that easterly surface wind anomalies in the western pacific ocean are associated with the emergence of la nina during boreal summer and fall here it is shown that these winds are significantly correlated to southern indian ocean sea surface temperature in the preceding spring that is characterized by a large scale zonal dipole of cool and warm anomalies in the southwestern and southeastern indian oceans respectively these associations are particularly pronounced for strong el nino conditions during the dissipation of which a pronounced wavetrain like atmospheric pattern accompanies sea surface temperature anomalies in the southern indian ocean together the circulation and sea surface temperature anomalies increase the meridional cross equatorial temperature gradient in the western indian ocean and mute intraseasonal variability while strengthening surface equatorial easterly winds in the indo pacific warm pool collectively these anomalies favor subsequent la nina development on the basis of these observed associations a predictive model that demonstrates skill in anticipating the nature of el nino transitions involving the southern indian ocean asian monsoon and el nino southern oscillation is proposed in the national center for environmental prediction climate forecast system the relationships described above are simulated both consistently and realistically despite model weaknesses further bolstering a key role of southern indian ocean and predictive relationship comparison of fully coupled and sea surface temperature forced simulations suggests a key role for air sea interaction in the observed associations moreover it is demonstrated that coupled simulations of el nino southern oscillation may benefit substantially from improved representation of indian ocean variability and indo pacific interaction

modification of the southern african rainfall variability enso relationship since the late 1960s analysis of 149 raingauge series 1946 1988 shows a weak positive correlation between late summer rainfalls january march in tropical southern africa and the southern oscillation index soi the correlation coefficients have been unstable since world war ii they were close to zero before 1970 and significant thereafter before 1970 southern african late summer rainfalls were more specifically correlated with regional patterns of sea surface temperature sst mainly over the southwestern indian ocean after 1970 teleconnections with near global sst anomaly patterns i e over the central pacific and indian oceans dominate the regional connections the increase in the sensitivity of the southern african rainfall to the global so related circulation anomalies is simultaneous with the correlation between soi and more extensive sst anomalies particularly over the southern indian ocean this feature is part of longer term decadal global sst variability as inferred from statistical analyses numerical experiments using the meteo france general circulation model arpege climat are performed to test the impact of the observed sst warming in the southern indian and extratropical oceans during el nino southern oscillation enso events on southern african rainfall simulated results show that enso events which occurred in the relatively cold background of the pre 1970 period in the southern oceans had a little effect on southern africa climatic conditions and atmospheric circulation by contrast more recent enso events with warmer sst over the southern oceans lead to a climatic bipolar pattern between continental southern african and the western indian ocean which is characterized by reduced enhanced deep convection and rainfall over the subcontinent the western indian ocean a weaker subtropical high pressure belt in the southwestern indian ocean is also simulated along with a reduced penetration of the moist southern indian ocean trade winds over the southern african plateau these results are consistent with the strong droughts observed over all southern africa during enso events since 1970

constraining the prograde and retrograde p t t path of eocene hp rocks by shrimp dating of different zircon domains inferred rates of heating burial cooling and exhumation for central rhodope northern greece ion microprobe shrimp dating was carried out on different zircon domains from metamorphic rocks of the hp ht terrane of central rhodope northern greece to constrain the timing of prograde and retrograde stages within a single tectono metamorphic cycle a well determined p t t relative path for the metamorphic rocks of this terrane was used as a petrological basis for the geochronological investigations ion microprobe work was assisted by cathodoluminescence cl images of the zircon crystals the geochronological results revealed that hercynian continental crust was subducted during the eocene several stages of the eocene tectono metamorphic cycle including both the prograde and retrograde parts of the p t path above ca 300 c 0 3 gpa were dated using zircons from the following rock types 1 a deformed quartz vein probably formed at ca 300 c 0 3 gpa zircons in this vein precipitated from a hydrothermal fluid they yielded an age of 45 3 0 9 ma which corresponds to the time of a low t prograde stage of metamorphism 2 in kyanite eclogites zircons were entirely reset during eclogite facies metamorphism resetting was very probably enhanced by the presence of fluids derived by h2o liberating reactions close to the p peak they yielded an age of 42 2 0 9 ma 3 orthogneisses surrounding the kyanite eclogites contained zircons with magmatic oscillatory zoned cores which yielded hercynian ages of 294 8 ma age of granitic protolith formation whereas cl bright metamorphic rims yielded like the eclogite zircons ages of 42 0 1 1 ma therefore both the eclogites and orthogneisses are interpreted to have approached maximum depth at around 42 ma 4 in a leucosome of a migmatized orthogneiss oscillatory zoned zircons yielded an age of 40 0 1 0 ma at this time the rocks reached maximum temperatures during early decompression 5 a late pegmatite crosscutting the schistosity of amphibolites contained oscillatory zoned zircons that yielded a crystallization age of 36 1 1 2 ma thus the whole tectono metamorphic cycle above ca 300 c 0 3 gpa lasted from 45 3 0 9 ma to 36 1 1 2 ma that is 9 2 ma with an extreme error value of 2 1 ma based on combined shrimp and petrological data the average rates of heating and burial during subduction above ca 300 c 0 3 gpa are 94 c ma and 15 mm a respectively rates of cooling and exhumation also above 300 c 0 3 gpa are calculated to be 128 c ma and 7 7 mm a the eocene age of metamorphism in central rhodope implies that the terrane of at least central rhodope and the cyclades very probably was part of the same continental crust

the indian ocean subtropical dipole mode simulated in the cmip3 models using observation data and outputs from the twentieth century climate in coupled models 20c3m control runs of coupled general circulation models submitted to the coupled model intercomparison project phase 3 cmip3 the ability of cmip3 models to simulate the indian ocean subtropical dipole iosd and its influence on the rainfall anomaly over the southern african region is investigated many models simulate the iosd but the location and shape of the sea surface temperature anomaly vary among models this model bias is closely linked to the bias in simulating the anomalous strengthening and southward shift of the subtropical high almost all models fail to simulate the rainfall anomaly associated with the iosd owing to the inaccurate simulation of the location of sea surface temperature and sea level pressure anomalies

moisture transport between the south atlantic ocean and southern africa relationships with summer rainfall and associated dynamics moisture exchange between the south atlantic and southern africa is examined in this study through zonal moisture transport along the west coast of southern africa a multivariate analysis of the zonal flow of moisture computed from ncep doe amip ii re analyses reveals a primary mode of variability typical of variations in intensity and of the latitudinal migration of the circulation associated with the midlatitude westerlies and the south atlantic anticyclone in austral summer january february this mode referred to as the south atlantic midlatitude mode is found to be well correlated with rainfall over southern africa i e to the south of the upper lands surrounding the congo basin its positive negative phases are found to correspond with surface pressures changes over the south atlantic region in austral summer when the south atlantic anticyclone is shifted northward southward respectively such changes are accompanied by dipole like sst anomalies in the midlatitude south atlantic ocean while simultaneous sst anomalies with a similar structure are also found over south indian ocean regions in january february positive negative events linked to the south atlantic midlatitude mode are marked by meridional shifts northward southward and weakening strengthening of the itcz over the southern tropics together with modulations in intensity weakened sustained of the angola low which could act as a tropical source of moisture for tropical temperate troughs ttts in association with a strengthened weakened zonal component of the southern extension of the african easterly jet aej this could modulate the meridional transfer of moisture south of 15 s to the advantage detriment of angolan coastal regions where above below rainfall are expected variations in the latitudinal position northward southward of the south atlantic anticyclone and thus of the midlatitude westerlies are also found to reduce favour moisture advection towards southern africa subtropics allowing the southern indian trades to penetrate less more over the subcontinent south of 25 s this would create a situation where convection processes are inhibited supported within the sicz ttts region resulting in drier wetter conditions locally for positive negative events respectively

metamorphic evolution and geochemistry of kyanite eclogites in central rhodope northern greece in central rhodope of northern greece kyanite eclogites were discovered in the area of thermes they are strongly overprinted and exhibit a multi stage development of minerals and mineral assemblages formed during successive stages of the exhumation the initial high pressure assemblage was garnet omphacite kyanite zoisite phengite rutile quartz corundum fe mg spinel sapphirine and hogbomite occur as products of a first high temperature overprint still at high pressures whereas various symplectites corundum plagioclase pl spinel pl sapphirine pl clinopyroxene pl biotite pl amphibole pl grew during subsequent stages of the exhumation diablastic amphibole plagioclase formed as end products of the amphibolitization according to geochemical data the protoliths of the kyanite eclogites were basalts to basaltic andesites with volcanic arc affinities for the high pressure stage of metamorphism minimum pt conditions were around 19 kbar 700 c while for the initial stages of the overprint high pressure granulite facies conditions prevailed t 800 c at p 15 kbar the pt conditions of the amphibolite facies were 8 11 kbar 580 690 c the kyanite eclogites of thermes record the highest temperatures of metamorphism within the whole of rhodope

isopycnal mixing in ocean circulation models abstract a subgrid scale form for mesoscale eddy mixing on isopycnal surfaces is proposed for use in non eddy resolving ocean circulation models the mixing is applied in isopycnal coordinates to isopycnal layer thickness or inverse density gradient as well as to passive scalars temperature and salinity the transformation of these mixing forms to physical coordinates is also presented

thermodynamic coupled modes in the tropical atmosphere ocean an analytical solution the present study provides a consistent and unified solution for the two types of thermodynamical coupled modes in the atmosphere ocean climate system the tropical meridional mode and the subtropical dipole mode the solution is derived analytically from a linear model that couples a simple atmosphere to a slab ocean via the wind evaporation sst wes feedback for a mean zonal wind the results show that the wind hence latent heat flux anomaly and the sst anomaly differ in phase such that the tropical mode propagates downwind and the subtropical modes propagate upwind with both modes being damped by the sst driven component of latent heat flux despite the existence of positive wes feedback the large scale subtropical modes are always stable while the tropical mode can become unstable only when the air sea coupling is strong and the mean wind is easterly furthermore the mean meridional winds break the equatorial symmetry and enable the coupled modes to intensify in the southern northern hemisphere for a southerly northerly component for realistic parameter values these thermodynamical coupled modes have periods and damping time scales in years hence they may play important roles in the tropical interannual to decadal climate variability

frontolysis by surface heat flux in the agulhas return current region with a focus on mixed layer processes observation and a high resolution cgcm detailed mechanisms for frontogenesis frontolysis of the agulhas return current arc front defined as the maximum of the meridional sea surface temperature sst gradient at each longitude within the arc region 40 50 e 55 35 s are investigated using observational datasets due to larger smaller latent heat release to the atmosphere on the northern southern side of the front the meridional gradient of surface net heat flux nhf is found throughout the year in austral summer surface warming is weaker stronger on the northern southern side and thus the nhf tends to relax the sst front the weaker stronger surface warming at the same time leads to the deeper shallower mixed layer on the northern southern side this enhances the frontolysis because deeper shallower mixed layer is less more sensitive to surface warming in austral winter stronger weaker surface cooling on the northern southern side contributes to the frontolysis however deeper shallower mixed layer is induced by stronger weaker surface cooling on the northern southern side and suppresses the frontolysis because the deeper shallower mixed layer is less more sensitive to surface cooling therefore the frontolysis by the nhf becomes stronger weaker through the mixed layer processes in austral summer winter the cause of the meridional gradient of mixed layer depth is estimated using diagnostic entrainment velocity and the monin obukhov depth furthermore the above mechanisms obtained from the observation are confirmed using outputs from a high resolution coupled general circulation model causes of model biases are also discussed

modelling the precipitation response over southern africa to the 2009 2010 el nino using a stretched grid global atmospheric model the 2009 2010 el nino event was a moderately strong central pacific type enso and as such expected to lead to a substantial drought over southern africa during austral summer however many parts of the region experienced average to well above average rainfall during this season given that seasonal forecasting skill tends only to be good during enso seasons and many parts of the sub continent rely on rain fed agriculture understanding why the rainfall was so anomalous during this el nino event is important to this end a global stretched grid atmospheric general circulation model with relatively high horizontal resolution of 0 5 0 5 is applied over the region with observed and idealised sst forcing in the latter experiments ssts are kept as observed over one ocean basin e g pacific and as climatology over the other two basins e g atlantic indian or as climatology over one basin and as observed over the other two basins in order to help understand which of these three basins may have contributed most to the observed rainfall anomalies in summer 2009 2010 it is found that pacific ocean forcing contributed to the summer rainfall anomalies over most regions of southern africa with the atlantic acting to oppose the effects of the pacific however over mozambique and to some extent zimbabwe the indian ocean was more important with the atlantic again acting in opposition the increased rainfall over most of southern africa appears mainly due to a stronger angola low circulation system and to anomalously strong moisture flux from the tropical western indian ocean and to lesser extent the tropical south east atlantic ocean

the south indian convergence zone and interannual rainfall variability over southern africa abstract the south indian convergence zone sicz is identified in this paper as a region of enhanced precipitation extending off the southeast coast of southern africa during austral summer unlike the south pacific convergence zone the sicz is a land based convergence zone lbcz with position and intensity at least partially determined by surface conditions over southern africa an idealized gcm simulation is used to explore the basic dynamics of lbczs in the tropics and subtropics output from a realistic gcm simulation and the national centers for environmental prediction national center for atmospheric research 40 year reanalysis are analyzed to apply this basic dynamical framework to the case of the sicz in contrast to the intertropical convergence zone where column moisture convergence is primarily due to meridional wind convergence in the moist environment precipitation within the sicz and the lbczs in general is also supported by zonal wind convergence moisture convergence by transient eddy

reply to j berger s comment on the article discovery of metamorphic microdiamonds from the parautochthonous units of the variscan french massif by thiery v et al 2015 gondwana research 28 954 960

subtropical indian ocean sst dipole events and southern african rainfall an atmospheric general circulation model agcm is used to examine how the regional atmospheric circulation and rainfall over southern africa respond to a recently observed dipole in subtropical sea surface temperature sst over the south indian ocean observations suggest that when sst is warm to the south of madagascar and cool off western australia increased summer rains occur over large areas of southeastern africa the model results suggest that this sst pattern leads to increased rainfall via enhanced convergence of moister than average air over the region increased evaporation occurs over the warm pole in the south west indian ocean and this moist air is advected towards mozambique and eastern south africa as a result of the low pressure anomaly generated over this pole which strengthens the onshore flow

summer rainfall variability in low latitude highlands of china and subtropical indian ocean dipole abstractbased on reanalysis and observational datasets this study proposes a reasonable mechanism for summer rainfall variations over the low latitude highlands llh of china in which a subtropical indian ocean dipole siod like pattern is the key external thermal forcing in summers with a positive siod like pattern sea surface temperature sst anomalies may lead to lower tropospheric divergence over the tropical indian ocean and convergence over the subtropical southwestern indian ocean and arabian sea the convergence over the arabian sea can induce easterly anomalies of the divergent wind component off the eastern coast of the bay of bengal bob while the divergence over the tropical indian ocean can change the interhemispheric vertical circulation and produce a descending motion over the same area and cyclonic anomalies in the rotational wind component over the indian peninsula the combined effect of the divergent and rotational wind anomalies and enhanced interhemispheric vertical circulati

norphlet formation upper jurassic of southwestern and offshore alabama environments of deposition and petroleum geology upper jurassic norphlet sediments in southwestern and offshore alabama accumulated under arid climatic conditions the appalachian mountains of the eastern united states extended into southwestern alabama to provide a barrier for air and water circulation during the deposition of the norphlet formation these mountains produced topographic conditions that contributed to the arid climate and they affected sedimentation norphlet paleogeography in southwestern alabama was dominated by a broad desert plain rimmed to the north and east by the appalachians and to the south by a developing shallow sea the desert plain extended westward into eastern and central mississippi norphlet sedimentation initiated as a result of basin subsidence accompanied by erosion of the southern appalachians norphlet conglomerates were deposited in coalescing alluvial fans in proximity to an appalachian source the conglomeratic sandstones grade downdip into red beds that accumulated in distal portions of alluvial fan and wadi systems quartz rich sandstones were deposited as dune and interdune sediments on a broad desert plain the principal source of the sand was updip alluvial fan and plain and wadi deposits wadi and playa lake sediments also accumulated in the interdune areas a marine transgression was initiated during the late phase of deposition of the norphlet formation resulting in the reworking of previously deposited norphlet sediments norphlet hydrocarbon potential in southwestern and offshore alabama is excellent six oil and gas fields already have been established petroleum traps discovered to date are primarily structural traps involving salt anticlines faulted salt anticlines and extensional fault traps associated with salt movement reservoir rocks consist primarily of quartz rich sandstones that are eolian wadi and marine in origin porosity is principally secondary dissolution with some intergranular porosity smackover algal carbonate mudstones were probably the source for the norphlet hydrocarbons jurassic oil generation and migration probably were initiated in the early cretaceous

aeolian stratification and facies association in desert sediments arran basin permian scotland abstract permian aeolian sediments on the island of arran are divisible into dune including draa and interdune deposits both types display a distinctive and unusually wide variation in grain size the dominant features of the dune deposits are grainfall lamination sandflow lamination and inverse graded lamination associated with ripple form lamination and normal graded lamination the flat lying aeolian interdune deposits are characterised by granule and sand ripples horizontal lamination in coarse sand and granules plane bed lamination and inverse graded lamination associated structures include ripple form lamination and deflation lags three types of trace fossil associated with completely bioturbated horizons occur in some low angle dune and interdune deposits the aeolian facies interfinger with alluvial fan deposits giving rise to three recognizable facies belts marginal aeolian deposits are associated with fluvial conglomerates and are dominated by interdune deposits and occasionally very thin barchan deposits set height 3 37 cm intermediate aeolian deposits are characterized by interbedded crescentic dune small draa dune set height 5 cm 4 5 m and interdune deposits and rare fluvial and lake sediments basinal aeolian deposits are dominated by draa deposits dune set height 0 2 28 m associated with rare interdune sediments transverse dunes and draas were moved by north eastern palaeowinds towards the foot of the alluvial fans the aeolian sediments were deposited in a fault bounded desert basin

distinct patterns of sea surface temperature anomaly in the south indian ocean during austral autumn a neural network based cluster technique called self organizing map som determines 12 distinguishable patterns derived from the sea surface temperature sst anomaly fields in the south indian ocean for 1901 2010 in austral autumn march may two out of twelve patterns patterns 1 and 12 are characterized by a dipole pattern with opposite sst anomalies in the southwest indian ocean and to its northeastern side which is similar to the so called indian ocean subtropical dipole iosd and they are named as traditional iosd t iosd in the present work patterns 2 and 11 show a similar dipole pattern of a northeast southwest orientation which can be significantly distinguished from t iosd due to their distinct location of action centers amplitudes and evolution processes these two patterns were called new iosd n iosd for both positive and negative positive phase of t iosd the anomalous dipole pattern is first observed near madagascar in previous spring and it migrates eastward and forms the typical pattern of t iosd in early summer differently for positive phase of n iosd significant sst anomalies appear to the west of australia continent at first in late spring and a well organized dipole pattern could not be observed until late summer approximately one or two months later than the formation time of t iosd the major asymmetry of n iosd characterizes one month later of the formation time for the negative phase of n iosd compared with its positive phase the possible mechanisms responsible for different evolution process of t iosd and n iosd events were examined the results show that latent heat flux not surprisingly plays an essential role in the formation of both t iosd and n iosd however the contribution of meridional advection by anomalous oceanic current to the n iosd event is much more important than that to the t iosd

diagenetic controls on reservoir development and quality smackover formation of southwest alabama abstract abstract smackover reservoirs in southwest alabama are much more complex than those encountered in the central and western portions of the gulf coast basin this heterogeneity is a product of a complex history of diagenetic modification the diagenetic history can be divided into five separate stages 1 marine stage extensive grain micritization and precipitation of minor amounts of fibrous cement 2 meteoric vadose stage extensive dissolution of aragonitic grains 3 meteoric phreatic stage precipitation of granular and blocky cements 4 brine reflux stage extensive dolomitization and sulfate emplacement associated with refluxing of buckner brines and 5 burial stage grain to grain compaction of lithologies not stabilized by early cements stylolitization precipitation of poikilotopic calcite and dolomite cements minor dissolution of calcite associated with the introduction into the formation of undersaturated fluids hydrocarbon migration and sulfate replacement and cementation the diagenetic sequence varies dramatically over short distances in southwest alabama reflecting variation in paleotopography the products of this complex diagenetic history are heterogeneous reservoirs which consist of one or some combination of primary interparticulate moldic dolomitic intercrystalline and vuggy porosity primary interparticulate porosity is less common in southwest alabama than in the central and western portions of the gulf coast basin largely because of extensive compaction or early cementation where present however interparticulate reservoirs are characterized by moderate to high porosity and good permeability moldic porosity is produced by early fabric selective dissolution of aragonitic allochems and is associated with areas of subaerial exposure moldic reservoirs commonly have high porosity but low permeability and are generally productive only when permeability is enhanced by other pore types dolomitic intercrystalline porosity is common in the smackover of southwest alabama intercrystalline porosity alone however is seldom of reservoir quality and hydrocarbon production from dolomitized lithologies is generally dependent upon the coexistence of moldic or vuggy porosity vuggy porosity is the product of late non fabric selective dissolution of calcite vuggy pores are produced by solution enlargement of earlier formed interparticulate moldic or intercrystalline pores vuggy reservoirs are by nature composite and are characterized by moderate to high porosity and good permeability

remote effects of el nino and modoki events on the austral summer precipitation of southern africa abstractremote effects modulating the austral summer precipitation over southern africa during el nino el nino modoki events are investigated by analyzing the observed events during december february of the years from 1982 83 to 2010 11 based on the composite analyses it is found that southern africa experiences significantly below normal precipitation during el nino events compared to el nino modoki events during these latter events precipitation anomalies are not so significant although southern africa as a whole receives below normal precipitations the differences in the spatial distribution of precipitation over southern africa are seen to be related to the sea surface temperature sst anomalies of the equatorial pacific through atmospheric teleconnections the low level 850 hpa matsuno gill response to anomalously high precipitation over the pacific during el nino events results in an anomalous anticyclone extending from the equatorial to the subtropical south indian ocean these anomalous ant

a comprehensive mass flux scheme for cumulus parameterization in large scale models abstract observational studies indicate that a mass flux approach may provide a realistic framework for cumulus parameterization in large scale models but this approach through the introduction of a spectral cloud ensemble leads normally to rather complex schemes in this paper the question is addressed whether much simpler schemes can already provide realistic values of the thermal forcing by convection under various synoptic conditions this is done through verifying such a scheme first on data from field experiments for periods of tropical penetrative convection gate marshall islands tradewind cumuli atex bomex and extratropical organized convection sesame 79 and then in a nwp model the scheme considers a population of clouds where the cloud ensemble is described by a one dimensional bulk model as earlier applied by yanai et al in a diagnostic study of tropical convection cumulus scale downdrafts are included various types of convection are represented i e penetrative convection in c

enso related sst anomalies and relation with surface heat fluxes over south pacific and atlantic the role of surface heat fluxes in southern pacific and atlantic ocean sst anomalies associated with el nino southern oscillation enso is studied using observation and ocean reanalysis products a prominent dipole structure in sst anomaly is found with a positive negative anomaly center over south pacific 65s 45s 120w 70w and negative positive one over south atlantic 50s 30s 30w 0e during austral summer djf of el nino lanina during late austral spring early summer ond of el nino lanina anomalous northerly southerly meridional moisture transport and a positive negative sea level pressure anomaly induces a suppressed enhanced latent heat flux from the ocean surface over south pacific this in turn results in a shallower than normal mixed layer depth which further helps in development of the sst anomaly mixed layer thins further due to anomalous shortwave radiation during summer and a well developed sst anomaly evolves the south atlantic pole exhibits exactly opposite characteristics at the same time the contribution from the surface heat fluxes to mixed layer temperature change is found to be dominant over the advective processes over both the basins net surface heat fluxes anomaly is also found to be maximum during late austral spring early summer period with latent heat flux having a major contribution to it the anomalous latent heat fluxes between atmosphere and ocean surface play important role in the growth of observed summertime sst anomaly sea surface height also shows similar out of phase signatures over the two basins and are well correlated with the enso related sst anomalies it is also observed that the magnitude of enso related anomalies over the southern ocean are weaker in lanina years than in el nino years suggesting an intensified tropics high latitude tele connection during warm phases of enso

recurrent daily olr patterns in the southern africa southwest indian ocean region implications for south african rainfall and teleconnections a cluster analysis of daily outgoing longwave radiation olr anomalies from 1979 to 2002 over the southern africa southwest indian ocean swio region for the november to february season reveals seven robust and statistically well separated recurrent patterns of large scale organized convection among them are three regimes indicative of well defined tropical temperate interactions linking the hinterland parts of southern africa to the mid latitudes of the swio preferred transitions show a tendency for an eastward propagation of these systems analysis of daily rainfall records for south africa shows that six of the olr regimes are associated with spatially coherent and significant patterns of enhanced or reduced daily rainfall over the country atmospheric anomalies from the ncep doe ii reanalysis dataset show that the olr regimes are associated with either regional or near global adjustments of the atmospheric circulation the three regimes representative of tropical temperate interactions being in particular related to a well defined wave structure encompassing the subtropical and temperate latitudes featuring strong vertical anomalies and strong poleward export of momentum in the lee of the location of the cloud band the time series of olr regimes seasonal frequency are correlated to distinctive anomaly patterns in the global sea surface temperature field among which are shown to be those corresponding to el nino and la nina conditions the spatial signature of el nino southern oscillation s enso influence is related to the combination of an increased decreased frequency of these regimes it is shown in particular that the well known dipole in convection anomalies contrasting southern africa and the swio during enso events arises as an effect of seasonal averaging and is therefore not valid at the synoptic scale this study also provides a framework to better understand the observed non linearities between enso and the seasonal convection and rainfall anomalies over the region

zonal movement of the mascarene high in austral summer temporal variations in the mascarene high mh defined by the sea level pressure slp maximum within the region of 40 120 e 50 10 s in austral summer november january were investigated using atmospheric reanalysis datasets the mh longitudinal position has a dominant timescale at about 6 years which appears to be independent of the mh intensity variation the mh longitudinal movement is caused by a combination of slp variations in the eastern south indian ocean esio and in the western south indian ocean wsio as follows 1 pressure variations in the esio region are confined to the lower atmosphere up to the mid troposphere and are associated with the el nino southern oscillation events 2 pressure variations in the wsio region characterized by a quasi barotropic structure throughout the troposphere are related to the meridional movement of storm track sea surface temperature anomalies associated with the longitudinal movement of the mh show a southwest northeast dipole structure but this is shifted 10 westward in longitude compared with that associated with the mh intensity