differences in el nino response over the southern hemisphere southern hemisphere sh circulation conditions during austral springs of enso events are examined based on previous knowledge that sst variations over the subtropical south central pacific sscp region are linked to differences among el nino en events a stratification of the springs associated with en events was performed according to sst conditions over the el nino 3 4 sector and over the sscp region the en events associated with cold conditions in the sscp wc exhibit enhanced convection not only in the intertropical convergence zone over the central equatorial pacific but also in the south pacific convergence zone spcz extended south eastward into the subtropical regions the resulting heating forcing intensifies a localized overturning cell which is associated with an anomalous rossby wave source in the central south pacific extratropical region neither the rossby wave source nor the associated wave pattern is evident during en events associated with warm conditions in the sscp and inactive spcz ww the basic features that characterize the differences in the en response over the south pacific can also be identified through the analysis of the spcz activity over the central south pacific the fact that variations in spcz activity lead sst anomaly changes in the sscp would indicate that the differences in the en response over the sh might be mainly driven by atmospheric changes which induces extratropical sst anomalies the differences in the circulation anomalies that characterize both types of en response over the sh were further explored through the analysis of the activity of the three leading modes of circulation variability the combined effect of the three leading patterns describes in some extent the intensification weakening of the cyclonic circulation anomaly observed over the southeastern pacific in wc ww associated with an active inactive spcz in particular the interdecadal variability observed in the pacific by many previous studies influences the circulation response to enso over the sh mainly through changes in the activity of the sh annular mode

impact of india asia collision on se asia the record in borneo abstract borneo occupies a central position in the sundaland promontory of se asia it has a complex cenozoic geological history of sedimentation and deformation which began at about the same time that india is commonly suggested to have started to collide with asia some tectonic reconstructions of east and se asia interpret a large se asian block with borneo at its centre which has been rotated clockwise and displaced southwards along major strike slip faults during the cenozoic due to the indentation of asia by india however the geological history of borneo is not consistent with the island simply forming part of a large block extruded from asia the large clockwise rotations and displacements predicted by the indentor model for borneo are incompatible with palaeomagnetic evidence and there is no evidence that the major strike slip faults of the asian mainland reach borneo seismic tomography shows there is a deep high velocity anomaly in the lower mantle beneath se asia interpreted as subducted lithosphere but it can be explained just as well by alternative tectonic models as by the indentor model very great thicknesses of cenozoic sediments are present in borneo and circum borneo basins and large amounts of sediment were transported to the crocker turbidite fan of north borneo from the eocene to the early miocene but all evidence indicates that these sediments were derived from local sources and not from distant sources in asia elevated by india asia collision the cenozoic geological history of borneo records subduction of the proto south china sea and miocene collision after this ocean lithosphere was eliminated and a variety of effects resulting from long term subduction beneath se asia there is little to indicate that india asia collision has influenced the cenozoic geological record in borneo

atmosphere ocean mechanisms of climate anomalies in the angola tropical atlantic sector abstract interannual variations in the large scale atmospheric and oceanic fields over the tropical atlantic are studied in relation to rainfall anomalies on the angola coast departure patterns are constructed by stratification with respect to extremely dry and wet years and by correlation with rainfall in angola which is concentrated in march april the analysis suggests a causality chain of atmospheric oceanic anomalies variations of westward wind stress on the western equatorial atlantic constitute an early link in this chain the annual cycle is characterized by a relaxation of the wind stress from september november to february march anomalous seasonal relaxation of easterly wind stress over the western equatorial atlantic remotely forces the sea surface temperature sst departures in the eastern south atlantic a large relaxation being followed by positive sst departures sea surface temperature modulates the rainfall over downstream angola by controlling the atmospheric moisture and stability

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

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

imprint of the el nino modoki on decadal sea level changes 1 decadal variation in sea level is shown to manifest as higher than normal sea level in the central pacific flanked by lower than normal sea level on either side of the basin during the early 21st century this abnormal condition is evidently aided by frequent occurrences of el nino modoki events and associated wind convergence to the dateline during 2000 2004 the sea level rise in central pacific succeeded a phase of lower than normal sea level associated with la nina modoki events toward the end of 20th century a correlation analysis confirms the dominant influence of el nino la nina modoki on the sea level rise in the central pacific as compared to that of the el nino la nina this influence can even be seen in remote regions such as the coasts of california and mauritius through atmospheric teleconnections

first elaphrosaurine theropod dinosaur ceratosauria noasauridae from australia a cervical vertebra from the early cretaceous of victoria abstract elaphrosaurinae is an enigmatic clade of gracile ceratosaurian theropod dinosaurs known from the late jurassic of africa elaphrosaurus bambergi and asia e g limusaurus inextricabilis and the early late cretaceous of argentina huinculsaurus montesi elaphrosaurinae is often placed within noasauridae as the sister taxon to noasaurinae a clade of small bodied theropods that lived in south america africa madagascar and india throughout much of the cretaceous herein we report the first evidence of elaphrosaurinae from australia a nearly complete middle cervical vertebra from the upper lower cretaceous lower albian eumeralla formation of cape otway victoria australia the fact that this site would have been situated at 76 s towards the end of the early cretaceous 110 107 ma implies that elaphrosaurines were capable of tolerating near polar palaeoenvironments whereas its age indicates that elaphrosaurines persisted in australia until at least the late early cretaceous the new australian elaphrosaurine in tandem with the recently described huinculsaurus montesi from the cenomanian turonian of argentina implies that the spatiotemporal distribution of elaphrosaurinae has heretofore been greatly underestimated historic confusion of elaphrosaurines with coelurosaurs especially ornithomimosaurs coupled with our generally poor understanding of noasaurid evolution might explain the apparent dearth of fossils of this theropod clade worldwide

dinosaurs and other fossil vertebrates from fluvial deposits in the lower cretaceous of southern tunisia remains of dinosaurs and other vertebrates sharks bony fishes coelacanths turtles crocodilians pterosaurs are reported from the chenini formation of the tataouine region in southern tunisia the formation is part of the continental intercalaire a succession of continental deposits of early to late cretaceous age distributed over the whole of north africa and the sahara it consists of bar and channel deposits of broad rivers that flowed nnw from the mid sahara region towards the southern shore of tethys dinosaur bearing units in the continental intercalaire have been dated to the hauterivian to cenomanian and the chenini formation is possibly albian in age dinosaur fossils include abundant teeth of the theropods carcharodontosaurus and spinosaurus as well as postcranial elements of theropods and a medium sized sauropod a tooth of an ornithocheirid is the first report of a pterosaur from the region the dinosaur bones and teeth were transported some distance and deposited in a channel lag associated with less damaged locally derived material such as fern fronds coprolites fish teeth and scales and crocodilian scutes

mesozoic and cainozoic rocks dredged from the south china sea reed bank area and sulu sea and their significance for plate tectonic reconstructions abstract outcrops of pre quaternary rocks were sampled by dredging and coring during two cruises of rv sonne in the south china sea and sulu sea 1982 1983 late triassic deltaic sandstones wih plant remains are the oldest sediments recovered late jurassic early cretaceous regional metamorphism is indicated by gneiss and garnet mica schists exposed in the northwestern flanks of reed bank these rocks and occurrences of gabbro diorite dacite rhyolite and siliceous shale prove that the dangerous grounds and reed bank are underlain by a continental fragment during the period of seafloor spreading in the south china see a late oligocene to early miocene carbonate platform developed on this southwards drifting continental fragment which subsided in the middle miocene middle miocene andesite and early to middle miocene reefal carbonates were recovered from the cagayan ridge in the sulu sea the new data are in accord with the plate tectonic history developed by taylor and hayes 1980 1983 and holloway 1981

relationships between cut off lows and the semiannual and southern oscillations the characteristics of southern cut off lows cols are studied for the period 1979 2008 the systematic identification of cols is realized by applying an original automated scheme using mean daily geopotential height and air temperature at 500 hpa ncep doe ii reanalysis data from closed lows trajectories established from the equator to the polar jet stream extratropical lows are analyzed and the stage of cut off is defined as a secluded low presenting a cold core from 4 843 cases the general col features are presented and confirm several previous results such as the geographic distribution which shows that they are more frequent in the latitudinal band contained between 20 s and 45 s and in close proximity to the continents on a seasonal time scale cols are more numerous from late summer to autumn with a maximum of frequency in march april in winter june july august they are fewer but deeper than during the rest of the year in the median domain 32 5 s the annual cycle of the frequency is bimodal and present two peaks during transitional seasons in this zone the seasonal cycle varies in accordance with the semiannual oscillation thereby when the meridional gradient of temperature pressure is reinforced between mid and high latitudes cols are more frequent in the median domain over the period 1979 2008 the annual cols frequency exhibits a positive trend of about 25 this increase is associated with a widening of the latitudinal domain of occurrence equatorward as well as poleward the trend is linked with an abrupt positive shift in the number of cols generation between 1998 and 1999 the geographical distribution of cols frequency varies significantly in accordance with el nino southern oscillation with more col s at lower higher latitudes during la nina el nino events principally in the southern pacific

the angola low relationship with southern african rainfall and enso the main states of the angola low al are identified using clustering analysis applied to daily anomalous patterns of 700 hpa wind vorticity over angola and adjacent countries from november to march for the 1980 81 2014 15 period at the daily timescale we examine the extent to which the main states of the al modulate daily rainfall over southern africa at the interannual timescale we assess both the relationship between the occurrence of these al states and el nino southern oscillation enso and the role of the al in explaining enso s failure in driving southern african rainfall at times three reanalyses are considered to account for uncertainties induced by the scarcity of data available for assimilation over southern africa three preferential states of the angola low are identified al state close to its seasonal climatology with slight zonal displacements anomalously weak al state and anomalously strong al state with meridional displacements these different states all significantly modulate daily southern african rainfall near climatological al state promotes wet rainfall anomalies over eastern subtropical southern africa and dry rainfall anomalies over its western part a slight westward shift in the near climatological position of the al leads to reversed zonal gradient in rainfall the remaining regimes significantly modulate the meridional gradient in southern african rainfall anomalously weak and anomalously northward al states promote wet rainfall anomalies over tropical southern africa and dry rainfall anomalies over subtropical southern africa the reverse prevails for anomalously southward al at the interannual timescale enso significantly modulates the seasonal occurrence of most al states in the three reanalyses anomalously weak and southward al states are more strongly correlated with regional rainfall than enso in all reanalyses suggesting that accounting for al variability may improve seasonal forecasts case study analysis of the major 1982 83 and 1997 98 el nino events suggests that the weak rainfall anomalies and strong seasonal al in 1997 98 may result from counteracting effects between enso and indian ocean coupled modes of variability

climate of the supercontinent pangea numerous climate models predict that the geography of the supercontinent pangea was conducive to the establishment of a megamonsoonal circulation in general geologic evidence supports the hypothesis of a megamonsoon that reached maximum strength in the triassic pangea in the late carboniferous had widespread peat formation in what is now central and eastern north america and europe and relatively dry conditions on the colorado plateau the equatorial region of the continent became drier through the end of the carboniferous by the permian the equatorial region of pangea was dry and indicators of aridity and rainfall seasonality became more widespread wind directions from colorado plateau eolian sandstones are consistent with an increasing influence of monsoonal circulation at this time in the triassic climate in the colorado plateau region became relatively wet though still seasonal and the few eolian sandstones indicate a major shift in wind direction at that time in addition sedimentation

late jurassic paleoclimate of central africa abstract paleopedology and geochemical analysis of upper jurassic deposits in the stanleyville group of central africa indicate harsh late jurassic paleoclimates in the interior of gondwana subsurface samples collected from the samba borehole near the center of the congo basin show only weak morphological evidence of pedogenesis but are characterized by an abundance of shrink swell vertic features and rare calcium carbonate nodules indicating seasonal variations in moisture availability and net soil moisture deficiency respectively x ray diffraction analysis of paleosol matrix material reveals the presence of analcime and the clay mineral palygorskite strong indicators of hot arid climatic conditions the 18 o and d values of clay minerals from paleosol profiles range from 22 3 to 25 4 and 44 4 to 39 6 smow respectively and correspond to crystallization temperatures between 25 c and 40 c these crystallization temperatures compare favorably with austral summer surface temperature estimates for central africa that result from late jurassic global circulation models calculations of soil co 2 production using the 13 c values of pedogenic carbonates and plant derived organic matter produce lower co 2 production estimates for the stanleyville group relative to the roughly contemporary morrison formation of the western u s these low soil co 2 production estimates provide further support for arid late jurassic climate conditions in the congo basin the paleoclimatic conditions inferred here from the stanleyville group are similar to those reconstructed from other upper jurassic african continental localities between 5 s and 20 s paleolatitude however penecontemporaneous terrestrial coastal sites within this latitudinal belt of gondwana retain evidence of generally wetter conditions suggesting that those regions may have received more rainfall than the continental interior the paleoclimatic setting reconstructed here from geologic indicators and geochemical proxies suggests that general circulation models accurately predict unique paleoenvironmental conditions that lack modern analogs

water vapour transport from the tropical atlantic and summer rainfall in tropical southern africa an empirical orthogonal functions analysis of the onshore flow of moisture along the west coast of southern africa using ncep doe amip ii re analyses suggests two dominant modes of variability that are linked to a variations in the circulation linked with the south atlantic anticyclone b the intensity of the flow that penetrates from the tropical atlantic the second mode referred as the equatorial westerly mode contributes the most to moisture input from the atlantic onto the subcontinent at tropical latitudes substantial correlations in austral summer between the atlantic moisture flux in the tropics and rainfall over the upper lands surrounding the congo basin suggest the potential role played by this zonal mode of water vapour transport composites for austral summer months when this equatorial westerly mode had a particularly strong expression show an enhanced moisture input at tropical latitudes that feeds into the deep convection occurring over the congo basin sustained meridional energy fluxes result in above normal rainfall east and south of the congo belt during years of reduced equatorial westerly moisture flux a deficit of available humidity occurs in the southern tropics a concomitant eastward shift of deep convection to the southwest indian ocean and southeastern africa leads to below normal rainfall over the uplands surrounding the congo basin

a southern hemisphere wave response to enso with implications for southern africa precipitation ensemble gcm simulations with an imposed idealized warming of the eastern pacific ocean reveal two wave anomalies in the southern hemisphere one in the eastern and one in the western hemisphere both are statistically significant at the 99 confidence level application of a steady state linear model and a rossby wave source analysis is used to diagnose the causes of the waves the western hemisphere wave is forced by the advection and stretching of planetary vorticity by the divergent flow from the southern hemisphere component of the central pacific twin anticyclones that straddle the equator during warm events the eastern hemisphere wave is a result of the northeastward shift of the south indian convergence zone sicz that in turn is forced from the upper troposphere by convergence to the north an upper level convergence maximum over the equatorial indian ocean induces divergence to the south encouraging vertical motion and precipitation to the northeast of the sicz s normal position the resulting anomalous upper level convergence in the climatological position of the sicz as well as the anomalous vorticity flux convergence by the transients associated with an equatorward shift of the storm track behind the sicz force the eastern hemisphere rossby wave since a shift of the sicz is a fairly robust observed consequence of enso events these results suggest the mechanism by which drought conditions develop over southern africa at the height of many warm events seasonal prediction capabilities in this region can be improved by monitoring and understanding the details and consequences of the adjustment of the walker circulation near the equator outside of the pacific ocean basin

circulation anomalies associated with tropical temperate troughs in southern africa and the south west indian ocean daily rainfall variability over southern africa sa and the southwest indian ocean swio during the austral summer months has recently been described objectively for the first time using newly derived satellite products the principle mode of variability in all months is a dipole structure with bands of rainfall orientated northwest to southeast across the region these represent the location of cloud bands associated with tropical temperate troughs ttt this study objectively identifies major ttt events during november to february and on the basis of composites off ncep reanalysis data describes the associated atmospheric structure the two phases of the rainfall dipole are associated with markedly contrasting circulation patterns there are also pronounced intra seasonal variations in early summer the position of the temperate trough and ttt cloud band alternates between the swio and southwest atlantic in late summer the major ttt axis lies preferentially over the swio associated with an eastward displacement in the indian ocean high in all months positive events in which the ttt cloud band lies primarily over the swio are associated with large scale moisture flux anomalies in which convergent fluxes form a pronounced poleward flux along the cloud band this suggests that ttt events are a major mechanism of poleward transfer of energy and momentum moisture transport occurs along three principle paths 1 the northern or central indian ocean where anomalous fluxes extend eastward to the maritime continent 2 south equatorial africa and the equatorial atlantic 3 from the south within a cyclonic flow around the tropical temperate trough the relative importance of 2 is greatest in late summer thus synoptic scale ttt events over sa swio often result from large scale planetary circulation patterns hovmoeller plots show that ttt development coincides with enhanced tropical convection between 10 30 e itself exhibiting periodicity of around 5 days and often with convergence of eastward and westward propagating convection around 40 e harmonic analysis of 200 hpa geopotential anomalies show that ttt features are forced by a specific zonally asymmetric wave pattern with wave 5 dominant or significant in all months except february when quasi stationary waves 1 2 and 3 dominate these findings illustrate the importance of tropical and extratropical dynamics in understanding ttt events finally it is suggested that in november januar ttt rainfall over sa swio may be in phase with similar rainfall dipole structures observed in the south pacific and south atlantic convergence zones

considerations on the age of the tiouaren formation iullemmeden basin niger africa implications for gondwanan mesozoic terrestrial vertebrate faunas abstract pre aptian mid mesozoic terrestrial vertebrates from the african continent are still very poorly known in niger the tiouaren formation in the iullemmeden basin has yielded dinosaur and other vertebrate remains and this unit has been dated as early cretaceous most probably pre aptian on the basis of its fish fauna and geological relations to other units in the basin a review of the fish fauna and invertebrates from this formation does not provide any evidence for such an age and the geological relations only help to constrain the upper limit for the age of the formation aptian in contrast the described dinosaur taxa are phylogenetically nested with late middle jurassic to early late jurassic taxa from other localities and thus indicate a pre kimmeridgian probably late middle jurassic age for the tiouaren formation under the assumption of such an age the dinosaur fauna of this formation provides new insights into dinosaur faunal provincialism during the latest middle jurassic northern gondwanan faunas of that time seem to have been different from southern gondwanan faunas and show closer affinities to eurasian faunas than to the latter a possible explanation for this might be a climatically controlled geographic barrier due to pronounced arid conditions and thus desert environments in central gondwana during this time

a decadal prediction case study late twentieth century north atlantic ocean heat content an ensemble of initialized decadal prediction dp experiments using the community climate system model version 4 ccsm4 shows considerable skill at forecasting changes in north atlantic upper ocean heat content and surface temperature up to a decade in advance coupled model ensembles were integrated forward from each of 10 different start dates spanning from 1961 to 2006 with ocean and sea ice initial conditions obtained from a forced historical experiment a coordinated ocean ice reference experiment with interannual forcing core ia which exhibits good correspondence with late twentieth century ocean observations from the north atlantic subpolar gyre spg region north atlantic heat content anomalies from the dp ensemble correlate highly with those from the core ia simulation after correcting for a drift bias in particular theobservedlarge rapid rise in spgheatcontentin themid 1990sis successfullypredicted in the ensemble initialized in january of 1991 a budget of spg heat content from the core ia experiment sheds light on the origins of the 1990s regime shift and it demonstrates the extent to which low frequency changes in ocean heat advection related to the atlantic meridional overturning circulation dominate temperature tendencies in this region similar budgets from the dp ensembles reveal varying degrees of predictive skill in the individual heat budget terms with large advective heat flux anomalies from the south exhibiting the highest correlation with core ia the skill of the dp in this region is thus tied to correct initialization of ocean circulation anomalies while external forcing is found to contribute negligibly and for incorrect reasons to predictive skill in this region over this time period

on the three dimensional propagation of stationary waves abstract a locally applicable nonzonally averaged conservation relation is derived for quasi geostrophic stationary waves on a zonal flow a generalization of the eliassen palm relation the flux which appears in this relation constitutes it is argued a useful diagnostic of the three dimensional propagation of stationary wave activity this is illustrated by application to a simple theoretical model of a forced rossby wave train and to a northern hemisphere winter climatology results of the latter procedure suggest that the major forcing of the stationary wave field derives from the orographic effects of the tibetan plateau and from nonorographic effects diabatic heating and or interaction with transient eddies in the western north atlantic and north pacific oceans and siberia no evidence is found in the data for wave trains of tropical origin forcing by the orographic effects of the rocky mountains seems to be of secondary importance

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

two types of el nino events cold tongue el nino and warm pool el nino abstract in this study two types of el nino events are classified based on spatial patterns of the sea surface temperature sst anomaly one is the cold tongue ct el nino which can be regarded as the conventional el nino and the other the warm pool wp el nino the ct el nino is characterized by relatively large sst anomalies in the nino 3 region 5 s 5 n 150 90 w while the wp el nino is associated with sst anomalies mostly confined to the nino 4 region 5 s 5 n 160 e 150 w in addition spatial patterns of many atmospheric and oceanic variables are also distinctively different for the two types of el nino events furthermore the difference in the transition mechanism between the two types of el nino is clearly identified that is the discharge process of the equatorial heat content associated with the wp el nino is not efficient owing to the spatial structure of sst anomaly as a result it cannot trigger a cold event it is also demonstrated that zonal advective feedback i e zonal adve

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

the impact of enso on southern african rainfall in cmip5 ocean atmosphere coupled climate models we study the ability of 24 ocean atmosphere global coupled models from the coupled model intercomparison project 5 cmip5 to reproduce the teleconnections between el nino southern oscillation enso and southern african rainfall in austral summer using historical forced simulations with a focus on the atmospheric dynamic associated with el nino overestimations of summer rainfall occur over southern africa in all cmip5 models abnormal westward extensions of enso patterns are a common feature of all cmip5 models while the warming of the indian ocean that happens during el nino is not correctly reproduced this could impact the teleconnection between enso and southern african rainfall which is represented with mixed success in cmip5 models large scale anomalies of suppressed deep convection over the tropical maritime continent and enhanced convection from the central to eastern pacific are correctly simulated however regional biases occur above africa and the indian ocean particularly in the position of the deep convection anomalies associated with el nino which can lead to the wrong sign in rainfall anomalies in the northwest part of south africa from the near surface to mid troposphere cmip5 models underestimate the observed anomalous pattern of pressure occurring over southern africa that leads to dry conditions during el nino years

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

a stability analysis of tropical ocean atmosphere interactions bridging measurements and theory for el nino abstract interactions between the tropical oceans and atmosphere permit a spectrum of natural modes of oscillation whose properties period intensity spatial structure and direction of propagation depend on the background climatic state i e the mean state this mean state can be described by parameters that include the following the time averaged intensity of the pacific trade winds the mean depth h of the thermocline and the temperature difference across the thermocline t a stability analysis by means of a simple coupled ocean atmosphere model indicates two distinct families of unstable modes one has long periods of several years involves sea surface temperature variations determined by vertical movements of the thermocline that are part of the adjustment of the ocean basin to the fluctuating winds requires a relatively deep thermocline and corresponds to the delayed oscillator the other family requires a shallow thermocline has short periods of a year or two has sea surface tempe

post cranial remains of coelurosaurs dinosauria theropoda from the late jurassic of tanzania small theropod post cranial material from tendaguru tanzania the only known late jurassic theropod locality in the southern hemisphere is reviewed material originally described as coelurosaurs includes at least one taxon of basal tetanuran and one taxon of small abelisauroid together with the abelisauroid elaphrosaurus and the presence of a larger ceratosaur in tendaguru this material indicates that ceratosaurs were an important faunal element of late jurassic east african theropod faunas one bone furthermore shares derived characters with the holotype of the poorly known middle jurassic australian theropod ozraptor and allows the identification of the latter as the oldest known abelisauroid thus indicating an early divergence of ceratosaurids and abelisauroids within ceratosaurs abelisauroids might have originated in gondwana and represent important faunal elements of cretaceous gondwanan theropod faunas in general

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

a giant sauropod dinosaur from an upper cretaceous mangrove deposit in egypt we describe a giant titanosaurid sauropod dinosaur discovered in coastal deposits in the upper cretaceous bahariya formation of egypt a unit that has produced three tyrannosaurus sized theropods and numerous other vertebrate taxa paralititan stromeri is the first tetrapod reported from bahariya since 1935 its 1 69 meter long humerus is longer than that of any known cretaceous sauropod the autochthonous scavenged skeleton was preserved in mangrove deposits raising the possibility that titanosaurids and their predators habitually entered such environments

anomalous winter climate conditions in the pacific rim during recent el nino modoki and el nino events present work compares impacts of el nino modoki and el nino on anomalous climate in the pacific rim during boreal winters of 1979 2005 el nino modoki el nino is associated with tripole dipole patterns in anomalies of sea surface temperature precipitation and upper level divergent wind in the tropical pacific which are related to multiple boomerangs of ocean atmosphere conditions in the pacific zonal and meridional extents of those boomerangs reflect their independent influences which are seen from lower latitudes in the west to higher latitudes in the east in the central pacific more moisture is transported from the tropics to higher latitudes during el nino modoki owing to displacement of the wet boomerang arms more poleward toward east discontinuities at outer boomerang arms manifest intense interactions between tropical and subtropical extratropical systems the pacific north american pattern and related climate anomalies in north america found in earlier studies are modified in very different ways by the two phenomena the seesaw with the dry north and the wet south in the western usa is more likely to occur during el nino modoki while much of the western usa is wet during el nino the moisture to the southwestern usa is transported from the northward shifted itcz during el nino modoki while it is carried by the storms traveling along the southerly shifted polar front jet during el nino the east asian winter monsoon related anticyclone is over the south china sea during el nino modoki as compared to its position over the philippine sea during el nino causing opposite precipitation anomalies in the southern east asia between the two phenomena

an early cretaceous vertebrate assemblage from the cabao formation of nw libya fossil vertebrates from the cabao formation discovered in the area of nalut in northwestern libya include the hybodont shark priohybodus the crocodilian sarcosuchus an abelisaurid a baryonichine spinosaurid and a large sauropod with spatulate teeth the cabao formation may be hauterivian to barremian in age although an earlier berriasian to valanginian age cannot be excluded its dinosaur assemblage is reminiscent of that of the el rhaz and tiouraren formations of niger and strongly differs from both the cenomanian assemblages of morocco and egypt and the late aptian to albian fauna of tunisia fossil vertebrates may be an important tool to establish the stratigraphical framework of the poorly dated early cretaceous continental deposits of africa

interactions between synoptic intraseasonal and interannual convective variability over southern africa after removing the annual cycle a principal component analysis is applied to the daily outgoing longwave radiation anomaly field used here as a proxy for atmospheric convection the analysis is carried out over the southern african region 7 5 e 70 e 10 s 40 s for austral summer november through february for the period 1979 1980 to 2006 2007 the first five principal components pc are retained the first two pcs describe spatial patterns oriented north west to south east from tropical southern africa sa to the mid latitudes they are interpreted to be different possible locations for synoptic scale tropical temperate troughs ttt one dominant rainfall producing synoptic system in the region the phase relationship between these two pcs describes a tendency for these ttt to propagate eastwards from sa to the mozambique channel and southern madagascar the next three pcs describe convective fluctuations respectively located over the north west the south and the centre of sa their time series are significantly associated with madden julian oscillation mjo activity in the tropics however we find that ttt systems are statistically independent of the mjo i e they are equally liable to occur during any phase of the mjo three pcs out of five also show a significant association with el nino southern oscillation confirming that el nino years mostly coincide with suppressed convection at the intraseasonal time scales a result consistent with its impact on seasonal averages diagnosed in previous studies

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

tropical extratropical interactions over southern africa three cases of heavy summer season rainfall abstract the synoptic evolution of three tropical extratropical te interactions each responsible for extreme rainfall events over southern africa is discussed in detail along with the consideration of previously studied events common features of these heavy rainfall producing tropical temperate troughs ttts over southern africa are discussed it is found that 2 days prior to an event northeasterly moisture transports across botswana set up by the angola low are diverted farther south into the semiarid region of subtropical southern africa the ttts reach full maturity as a te cloud band rooted in the central subcontinent which is triggered by upper level divergence along the leading edge of an upper tropospheric westerly wave trough convection and rainfall within the cloud band is supported by poleward moisture transports with subtropical air rising as it leaves the continent and joins the midlatitude westerly flow it is shown that these systems fit within a theoretical framework describing

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

african monsoon teleconnections with tropical ssts validation and evolution in a set of ipcc4 simulations a set of 12 state of the art coupled ocean atmosphere general circulation models oagcms is explored to assess their ability to simulate the main teleconnections between the west african monsoon wam and the tropical sea surface temperatures ssts at the interannual to multi decadal time scales such teleconnections are indeed responsible for the main modes of precipitation variability observed over west africa and represent an interesting benchmark for the models that have contributed to the fourth assessment report of the intergovernmental panel on climate change ipcc4 the evaluation is based on a maximum covariance analysis mca applied on tropical ssts and wam rainfall to distinguish between interannual and multi decadal variability all datasets are partitioned into low frequency lf and high frequency hf components prior to analysis first applied to hf observations the mca reveals two major teleconnections the first mode highlights the strong influence of the el nino southern oscillation enso the second mode reveals a relationship between the sst in the gulf of guinea and the northward migration of the monsoon rainbelt over the west african continent when applied to hf outputs of the twentieth century ipcc4 simulations the mca provides heterogeneous results most simulations show a single dominant pacific teleconnection which is however of the wrong sign for half of the models only one model shows a significant second mode emphasizing the oagcms difficulty in simulating the response of the african rainbelt to atlantic sst anomalies that are not synchronous with pacific anomalies the lf modulation of these hf teleconnections is then explored through running correlations between expansion coefficients ecs for ssts and precipitation the observed time series indicate that both pacific and atlantic teleconnections get stronger during the twentieth century the ipcc4 simulations of the twentieth and twenty first centuries do not show any significant change in the pattern of the teleconnections but the dominant enso teleconnection also exhibits a significant strengthening thereby suggesting that the observed trend could be partly a response to the anthropogenic forcing finally the mca is also applied to the lf data the first observed mode reveals a well known inter hemispheric sst pattern that is strongly related to the multi decadal variability of the wam rainfall dominated by the severe drying trend from the 1950s to the 1980s whereas recent studies suggest that this drying could be partly caused by anthropogenic forcings only 5 among the 12 ipcc4 models capture some features of this lf coupled mode this result suggests the need for a more detailed validation of the wam variability including a dynamical interpretation of the sst rainfall relationships