climatology and dynamics of the link between dry intrusions and cold fronts during winter part i global climatology cold fronts are a primary feature of the day to day variability of weather in the midlatitudes and feature in conceptual extratropical cyclone models alongside the dry intrusion airstream here the climatological frequency and spatial distribution of the co occurrence of these two features are quantified and the differences in cold front characteristics intensity size and precipitation when a dry intrusion is present or not are calculated fronts are objectively identified in the ecmwf era interim dataset for the winter seasons in each hemisphere and split into three sub types central fronts within a cyclone area trailing fronts outwith the cyclone area but connected to a central front and isolated fronts not connected to a cyclone these are then associated with dry intrusions identified using lagrangian trajectory analysis trailing fronts are most likely to be associated with a di in both hemispheres and this occurs more frequently in the western parts of the major storm track regions isolated fronts are linked to dis more frequently on the eastern ends of the storm tracks and in the subtropics all front types when co occurring with a di are stronger in terms of their temperature gradient are much larger in area and typically have higher average precipitation therefore climatologically the link with dis increases the impact of cold fronts there are some differences in the statistics of the precipitation for trailing and isolated fronts that are further investigated in part ii of this study from the front centred perspective

decadal variability in the kuroshio oyashio extension simulated in an eddy resolving ogcm abstract through analysis of a hindcast integration of an eddy resolving quasi global ocean general circulation model decadal variability in the kuroshio oyashio extension region is investigated with particular emphasis on that of the subarctic oyashio and the kuroshio extension ke fronts the ke front is deep and is accompanied by a sharp sea surface height ssh gradient with modest sea surface temperature sst gradient in contrast the subarctic front is shallow and is recognized as a zone of tight gradient in sst but not ssh as a decadal scale change from a warm period around 1970 to a cool period in the mid 1980s those fronts in the model migrate southward as observed and the associated pronounced cooling is confined mainly to those frontal zones reflecting the distinctive vertical structure of the fronts the mixed layer cooling is the strongest along the subarctic front whereas the subsurface cooling and the associated salinity changes are most pronounced along the ke front concomitan

interstadial records of the last glacial period at pantai remis malaysia two eustatic high sea stands during the last glacial period are recognised at pantai remis these highstands lower than present day sea level are tropical manifestations of the ameliorating interstadial climate during the weichselian devensian wisconsin glaciation in the northern hemisphere the earlier highstand corresponds to a sea level of 14 6 m below mean sea level msl it is interpreted as synchronous with oyxgen isotope stage 5a and is correlated with other known sea level curves in other parts of the world the younger high sea stand dated 55810 1140 to 53870 1400 yr bp indicates sea level of 4 3 m below msl it represents an interstadial equivalent that lasted for at least 2000 yr whereas the earlier interstadial period indicates a minimum duration of twice this amount or very likely even longer as reflected from the thickness of the accumulated deposits the palynological records indicate that during interstadial times climatic stability in the tropics is attained and was sufficiently long for vegetation to thrive and develop the palynofloral constituents of the earlier interstadial phase at pantai remis showed the establishment of vegetation in a coastal setting initiated by pandanus swamp forests simultaneously mangrove swamp flourished in the lower lying parts of the area hence the presence of direct tidal influence is evident both the pandanus and mangrove swamps were succeeded by mixed freshwater swamp forests of a campnosperma calophyllum assemblage subsequently a slightly open and somewhat drier mixed swamp forest prevailed marked by the increase in fern spore representation the later interstadial phase showed shorter vegetation successions which commenced on the landward edge of a mangrove swamp forest the mangrove was successively replaced by strand forest as indicated by domination of casuarina equisetifolia the palynological assemblages in both the interstadial periods indicate similarity to the present day coastal vegetation this implies that during the interstadials the climate in the lowlands of peninsular malaysia and presumably throughout the equatorial region was as that prevailing today 1997 john wiley sons ltd

theoretical derivation of artificially cemented granular soil strength abstractthis paper provides a theoretical derivation for the unconfined compression strength of artificially cemented granular soils the proposed developments are based on the concept of superposi

the changing geomorphology of the humid tropics abstract it is debatable whether tropical geomorphology is intrinsically different from the geomorphology of other places the traditional geomorphology of the humid tropics had certain expectations with regard to landforms and processes a number of case studies over the last three decades however using new concepts and field and laboratory techniques have changed such expectations this paper primarily examines the research themes of the last ten years or so identifies the major trends and attempts to predict areas where interest is expected to concentrate in near future the following topics among the current research trends are highlighted geochemical erosion movement on tropical slopes rivers in the tropics tropical landforms hydrology and sedimentation in the rainforest denudation efficiency in the humid tropics the quaternary evolution and changes and the applied side of tropical geomorphology clearly the landforms and geomorphological processes in the tropics are dependent only partially on climate but to greater extent on neotectonism lithology episodic and catastrophic events such as tropical cyclones and above all on anthropogenic alterations of the landscape a wide variety of landforms and processes are found in the humid tropics and generalisations are extremely difficult in the next century geomorphological studies in the tropics are likely to develop along certain lines environmental investigations will form a major component along with the study of postulated sea level rise current major research trends will undoubtedly continue but increasingly through a multidisciplinary and multipeople approach large scale investigations involving pantropic correlation of past events such as synchronised large floods will grow use of new research tools such as satellite imagery various dating facilities etc will become common and expected it seems likely that the arrival of so much information will modify mainstream geomorphological and sedimentological theories or will provide these with a tropical version

the old alluvium of singapore and the extinct drainage system to the south china sea in both sand quarry faces and boreholes the old alluvium of singapore is a matrix supported pebbly sand with minor beds of better sorted sands and clays the beds can be grouped into four textural classes pebbles coarse sand with fine pebbles medium to coarse sand clay and silt each with characteristic sedimentary structures the deposit appears to be the proximal facies of an ancient braided river alluvium of possible pleistocene age this widespread but scattered alluvium is found both on land and offshore on the sunda shelf in southeast asia it is believed to have been deposited during low sea levels in singapore the mineralogy of the grains forming the old alluvium suggests a mixed provenance of granitic and low grade metamorphic origin the volume and freshness of the deposited material indicate an environment of considerable relief seasonal rainfall and extremely active erosional processes conditions considerably different from the current ones the old alluvium was probably deposited by seasonal rivers which experienced periodic large floods such regional conditions could have prevailed over much of southeast asia at the time of deposition of the old alluvium

cemented sands under static loading cemented sands are found in many areas of the world one of their distinguishing characteristics is their ability to stand in steep natural slopes large deposits are located along the california coast and in a number of areas intense urban development has occurred near the crest of high steep slopes because of the hazards posed by slope failures in the cemented sands a test program was undertaken to define the nature of the cementation and its effect on behavior of the soils a total of 137 laboratory compression and tension load tests were performed on undisturbed samples of naturally cemented sands and artificially prepared cemented sands the materials exhibited friction angles similar to uncemented sands but had a cementation strength intercept and a tensile strength the primary cementing agents of the sands tested were silicates and iron oxides the strength of the cemented sands were found to be a function of density amount of cementing agent grain shape and grain arrangement

three dimensional to two dimensional cross strata transition in the lower pleistocene catanzaro tidal strait transgressive succession southern italy sandstone tidal cross strata are the predominant sedimentary feature of strait fill stratigraphic successions however although widely described in numerous studies tidal strait fill two dimensional and three dimensional cross strata have rarely been reported to occur in discrete intervals which are laterally adjacent or vertically stacked and the meaning of this stratigraphic architecture has not yet been fully investigated understanding of the processes responsible for changes in the internal features of modern and ancient tidal bedforms is essential in order to predict lateral and vertical heterogeneities in analogous reservoir strata this facies based study aims to interpret the three dimensional to two dimensional cross strata transition observed in the lower pleistocene mixed siliciclastic bioclastic sandstone filling the catanzaro strait in southern italy during a continuous phase of tectonically driven marine transgression tidal cross strata disappear in the uppermost interval of the studied succession where mudstone strata prevail this stratigraphic trend is interpreted as the evidence of an important change in the tidal strait hydrodynamics due to a phase of relative sea level rise at the beginning of the transgression three dimensional tidal dunes migrated throughout the ca 3 to 4 km wide and ca 30 km long wnw ese oriented catanzaro strait due to strong tidal currents amplified through the seaway and flowing in semi diurnal phase opposition as the intermediate phase of transgression enlarged the seaway width the tidal current strength decreased as tidal water exchange occurred over a larger cross sectional area the progressive reduction of the bed shear stress modified three dimensional tidal dunes into an extensive two dimensional bedform field at the end of the transgression the further widening of the catanzaro strait into a ca 10 to 12 km wide marine passageway changed the tidally dominated strait into a non tidal open shelf the results of this research suggest the presence of a critical cross sectional area in the narrowest strait centre zone which controls the activation and deactivation of tidal current amplification along a marine seaway

sea level pressure minimum along the kuroshio and its extension abstractatmospheric effects of sea surface temperature sst fronts along the kuroshio and kuroshio extension k ke are investigated by examining spatial characteristics of the climatological sea level pressure slp surface winds and surface heat flux q fields based on an in situ observation dataset a hydrostatic effect of the sst front is observed during the northwesterly monsoon characterized by a westward extending low slp wedge trough slightly south of the peak in q along the k ke ageostrophic surface westerlies crossing slp isobars toward a trough center are found north of the low slp wedge apparently because of the eastward acceleration by the vertical mixing effect this feature of the ageostrophic winds is less pronounced south of it a north south asymmetry arising as vertical mixing accelerates decelerates eastward ageostrophic winds north south of it while the slp trough near the sst front is found nearly year round except for summer its meridional location seasonally migrates pr

barriers and bridges early human dispersals in equatorial se asia past environments of equatorial se asia must have played a critical role in determining the timing and trajectory of early human dispersal into and through the region however very few reliable terrestrial records are available with which to contextualize human dispersal events this circumstance coupled with a sparse archaeological record and the likelihood that much of the archaeological record is now submerged means we have an incomplete understanding of the role that geography climate and environment played in shaping human pre history in this region from a review of the literature we conclude that there must have been a substantial environmental barrier resulting in a genetic separation between east and west sundaland that persisted even though a terrestrial connection was present for most of the pleistocene this barrier is likely to be a north south corridor of open non forest vegetation and its existence may have encouraged the rapid dispersal of early humans through the interior of sundaland and on to sahul we conclude that more reliable terrestrial palaeoenvironmental records are required to better understand the links between past environments and dispersal events we highlight avenues of particular research value such as focusing on eastern sumatra western southern borneo and the islands in the java sea where the purported savanna corridor most probably existed and including edaphic factors in palaeovegetation modelling

the influence of sea surface temperature on surface wind in the eastern equatorial pacific weekly to monthly variability abstract temporal correlations between near equatorial surface wind and sea surface temperatures sst at 11 w in the eastern pacific ocean are investigated using data from an array of moored sensors between 5 n and 5 s the signature of tropical instability waves with periods of 20 30 days is apparent in time series of sst and both the meridional and zonal wind components results indicate the existence of a band of pronounced horizontal divergence in the surface wind field associated with the large meridional sst gradient equatorial front normally located just north of the equator perturbations of the equatorial front by the instability waves induce fluctuations in the overlying winds evidence of the air sea coupling is stronger in time series of the meridional gradients of wind and sst than between time series of the variables themselves the meridional differencing serves as a high pass filter in the space domain which removes planetary scale wind fluctuations that are unrelated to the local sst

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

on the observed relationships between wintertime variability in kuroshio oyashio extension sea surface temperatures and the atmospheric circulation over the north pacific abstractobservational analyses reveal that wintertime variations in sea surface temperatures sst in the kuroshio oyashio extension koe region of the north pacific are associated with two distinct and robust patterns of atmospheric variability 1 a pattern that peaks in amplitude approximately 2 3 weeks prior to large koe sst anomalies and is consistent with atmospheric forcing of the sst field and 2 a very different pattern that lags sst anomalies in the koe region by approximately a month the latter pattern is dominated by low sea level pressure anomalies and turbulent heat fluxes directed into the atmosphere over warm sst anomalies and is interpreted as the transient atmospheric response to sst anomalies over the koe region the results contribute to a growing body of evidence that suggests variations in ssts in the midlatitude oceans are capable of significantly influencing the large scale atmospheric circulation especially near western boundary currents

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

long term variations of the kuroshio extension path in winter meridional movement and path state change abstractas an indicator of the kuroshio extension ke path the ke northern boundary kenb was detected based on the position of the strong winter sea surface temperature sst gradient between 142 and 155 e using high spatial resolution satellite derived sst for the 30 winters january to march from 1982 to 2011 the ke path showed meridional movement with a period of 10 15 yr and an amplitude of about 2 latitude the changes in latitudinal position of the ke path were initiated by a north south shift of the aleutian low al negative wind stress curl anomalies around 35 n in the eastern north pacific associated with a northward shift of the al induced a deepening of the main thermocline depth and then this deepening signal propagated westward reaching the ke region after about 3 yr where it caused the ke path to move northward the path state of the ke straight path convoluted path modulated on a time scale of 8 12 yr but this was not significantly correlated with the meridional movement of

satellite measurements reveal persistent small scale features in ocean winds four year averages of 25 kilometer resolution measurements of near surface wind speed and direction over the global ocean from the quikscat satellite radar scatterometer reveal the existence of surprisingly persistent small scale features in the dynamically and thermodynamically important curl and divergence of the wind stress air sea interaction over sea surface temperature fronts throughout the world ocean is evident in both the curl and divergence fields as are the influences of islands and coastal mountains ocean currents such as the gulf stream generate distinctive patterns in the curl field these previously unresolved features have important implications for oceanographic and air sea interaction research

paleogeographic setting and depositional architecture of a sand dominated shelf depositional system miocene utsira formation north sea basin abstract the middle late miocene utsira sandstone of the north sea basin contains a fully preserved regional marine sand deposit that records a stable paleogeographic setting of shelf sand transport and accumulation within an epeiric shelf sea which persisted for ca 8 myr the sediment dispersal system was defined by 1 sediment input through a prograding strandplain platform coast to shelf bypass and regional basin centered transport and deposition within an elongate seaway 2 a high energy marine regime 3 very low rates of sediment supply and accumulation in the accommodation dominated seaway 4 high sediment reworking ratio and consequent abundance of autochthonous sediment 5 regional along strike sediment transport and 6 local to subregional landward sediment transport shelf systems were primarily nourished by sediment reworked from the shetland strandplain which prograded eastward into the central viking trough the viking strait lay between the constructional platform and the nondepositional horda platform southward longshore transport on the high energy shoreface and shallow shelf platform constructed the mounded south viking shelf shoal southward building sandy banner banks that formed along the recurved arc of the platform margin nourished the shoal system low angle sigmoid clinoforms with downstepping aggradational tops are distinctive architectures of the strike fed sand bodies the combination of strong marine currents and slow but continual sand supply from the shetland strandplain created regional sandy shelf depositional systems that individually covered 3500 to 6000 sq km of basin floor defining elements of the shelf shoal systems include their location within the basin axis mounded morphology stratal architecture and construction by amalgamated marine sand facies

on the coupling of wind stress and sea surface temperature a simple quasi equilibrium analytical model is used to explore hypotheses related to observed spatial correlations between sea surface temperatures and wind stress on horizontal scales of 50 500 km it is argued that a plausible contributor to the observed correlations is the approximate linear relationship between the surface wind stress and stress boundary layer depth under conditions in which the stress boundary layer has come into approximate equilibrium with steady free atmospheric forcing warmer sea surface temperature is associated with deeper boundary layers and stronger wind stress while colder temperature is associated with shallower boundary layers and weaker wind stress two interpretations of a previous hypothesis involving the downward mixing of horizontal momentum are discussed and it is argued that neither is appropriate for the warm to cold transition or quasi equilibrium conditions while one may be appropriate for the cold to warm transition solutions of a turbulent large eddy simulation numerical model illustrate some of the processes represented in the analytical model a dimensionless ratio a is introduced to measure the relative influence of lateral momentum advection and local surface stress on the boundary layer wind profile it is argued that when a 1 and under conditions in which the thermodynamically induced lateral pressure gradients are small the boundary layer depth effect will dominate lateral advection and control the surface stress

decadal changes in the north pacific oceanic frontal zones as revealed in ship and satellite observations 1 influence of decadal climate changes upon the north pacific subarctic and subtropical oceanic frontal zones np safz and np stfz respectively is documented both satellite and ship measured sea surface temperature sst data reveal the strong confinement of wintertime decadal sst anomalies to those frontal zones the satellite data indicate that the wintertime np safz tended to be narrow and shift northward under the weakened surface westerlies during a warm event in the early 1990s the opposite was the case under the enhanced westerlies during a cool event in the mid 1980s decadal scale modulations in the frontal intensity are also evident in the satellite data a diagnosis based on a simple linearized mixed layer model suggests that the observed anomalous frontal intensity was contributed by the sign reversal of anomalous wind stress curl through the ekman processes and by an anomaly dipole of the net heat flux around the safz these decadal scale modulations in the np safz and their relationships with decadal fluctuations in the local surface westerlies are confirmed in the ship measured data over the 4 recent decades it is found that the safz happens to be a region where the decadal variability in the surface westerlies are unlikely to be masked by the higher frequency fluctuations as it almost coincides with the ridge trough line of the remote atmospheric response to the el nino southern oscillation

role of the gulf stream and kuroshio oyashio systems in large scale atmosphere ocean interaction a review abstract ocean atmosphere interaction over the northern hemisphere western boundary current wbc regions i e the gulf stream kuroshio oyashio and their extensions is reviewed with an emphasis on their role in basin scale climate variability sst anomalies exhibit considerable variance on interannual to decadal time scales in these regions low frequency sst variability is primarily driven by basin scale wind stress curl variability via the oceanic rossby wave adjustment of the gyre scale circulation that modulates the latitude and strength of the wbc related oceanic fronts rectification of the variability by mesoscale eddies reemergence of the anomalies from the preceding winter and tropical remote forcing also play important roles in driving and maintaining the low frequency variability in these regions in the gulf stream region interaction with the deep western boundary current also likely influences the low frequency variability surface heat fluxes damp the low frequency sst anomalies ove

processes shaping the frontal scale time mean surface wind convergence patterns around the kuroshio extension in winter abstracthigh resolution satellite observations and numerical simulations have revealed that climatological mean surface wind convergence and precipitation are enhanced locally around the midlatitud

western boundary currents and frontal air sea interaction gulf stream and kuroshio extension abstract in the northern hemisphere midlatitude western boundary current wbc systems there is a complex interaction between dynamics and thermodynamics and between atmosphere and ocean their potential contribution to the climate system motivated major parallel field programs in both the north pacific kuroshio extension system study kess and the north atlantic climate variability and predictability clivar mode water dynamics experiment climode and preliminary observations and analyses from these programs highlight that complexity the gulf stream gs in the north atlantic and the kuroshio extension ke in the north pacific have broad similarities as subtropical gyre wbcs but they also have significant differences which affect the regional air sea exchange processes and their larger scale interactions the 15 yr satellite altimeter data record which provides a rich source of information is combined here with the longer historical record from in situ data to describe and compare the curr

interannual modulations of oceanic imprints on the wintertime atmospheric boundary layer under the changing dynamical regimes of the kuroshio extension abstractthe kuroshio extension ke fluctuates between its different dynamic regimes on quasi decadal time scales in its stable unstable regime the ke jet is strengthened weakened and less more meandering the present study investigates wintertime mesoscale atmospheric structures modulated under the changing ke regimes as revealed in high resolution satellite data and data from a particular atmospheric reanalysis era interim in the unstable ke regime a positive anomaly in sea surface temperature sst to the north of the climatological ke jet accompanies positive anomalies in upward heat fluxes from the ocean surface wind convergence and cloudiness as revealed in the atmospheric reanalysis these positive anomalies coincide with local lowering of sea level pressure weaker vertical wind shear warming and thickening of the marine atmospheric boundary layer mabl anomalous ascent and convective precipitation in the stable ke regime by contrast the corresponding imprints of sharp sst

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

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

separation of climatological imprints of the kuroshio extension and oyashio fronts on the wintertime atmospheric boundary layer their sensitivity to sst resolution prescribed for atmospheric reanalysis abstractmesoscale structures of the wintertime marine atmospheric boundary layer mabl as climatological imprints of oceanic fronts within the kuroshio oyashio extension koe region east of japan are investigated by taking advantage of high horizontal resolution of the era interim global atmospheric reanalysis data for which the resolution of sea surface temperature sst data has been improved these imprints including locally enhanced sensible and latent heat fluxes and local maxima in cloudiness and precipitation in association with locally strengthened surface wind convergence in the vicinities of sst fronts along the warm kuroshio extension and cool oyashio to its north are also identified in high resolution satellite data in addition to these mesoscale mabl features meridionally confined near surface baroclinic zones and zonally oriented sea level pressure slp minima associated with the dual sst fronts are represented in era interim only in the period of high resolution sst but those impri

influence of the meridional shifts of the kuroshio and the oyashio extensions on the atmospheric circulation abstract the meridional shifts of the oyashio extension oe and of the kuroshio extension ke as derived from high resolution monthly sea surface temperature sst anomalies in 1982 2008 and historical temperature profiles in 1979 2007 respectively are shown based on lagged regression analysis to significantly influence the large scale atmospheric circulation the signals are independent from the enso teleconnections which were removed by seasonally varying asymmetric regression onto the first three principal components of the tropical pacific sst anomalies the response to the meridional shifts of the oe front is equivalent barotropic and broadly resembles the north pacific oscillation western pacific pattern in a positive phase for a northward frontal displacement the response may reach 35 m at 250 hpa for a typical oe shift a strong sensitivity since the associated sst anomaly is 0 5 k however the amplitude but not the pattern or statistical significance strongly depends on the lag and an

the mechanics of cemented carbonate sands the behaviour of artificially cemented carbonate sand was investigated in triaxial tests at confining pressures of up to 9 mpa the results show that an important effect of cementing is a reduction in specific volume resulting from the increase in fines content this influences both the stress strain behaviour and the peak strength at strains beyond those required to fracture the cement bonding comparisons between the behaviour of cemented and uncemented soils should therefore be carried out on samples with the same gradings for cemented samples it is possible to identify a yield curve outside the state boundary surface of the uncemented soil a framework for the behaviour has been defined which depends on the relative magnitudes of the confining pressure and cement bond strength the behaviour of a natural cal carenite agreed well with this framework which is also likely to be applicable to other cemented soils le comportement d un sable carbonate artificiellement cimente a ete etudie a l aide d essa

on the role of sea surface temperature gradients in forcing low level winds and convergence in the tropics abstract we examine the importance of pressure gradients due to surface temperature gradients to low level p 700 mb flow and convergence in the tropics over time scales 1 month the latter plays a crucial role in determining the distribution of cumulonimbus convection and rainfall our approach is to consider a simple one layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically consistent with ecmwf analyzed data the top of the layer is taken at 700 mb the influence from higher levels is intentionally suppressed by setting horizontal pressure gradients and frictional stresses to zero at the top of the layer horizontal convergence within the layer is taken up by cumulonimbus mass flux however the development of the cumulonimbus mass flux is associated with a short relaxation time o hr roughly the development time for such convection during this short time horizontal convergence acts to redistribute mass so as to reduce horizontal pressur

radiocarbon and thermoluminescence dating of the old alluvium from a coastal site in perak malaysia abstract exposures of the old alluvium in pantai mine and sinar manjung mine in perak peninsular malaysia reveal woody peat layers interbedded with angular sands and gravels eight samples from peat within the pantai mine were dated using accelerator mass spectrometry ams radiocarbon dating together with a near surface shell sample five samples of quartz sand from the pantai mine and three samples of similar sand from sinar manjung mine were dated by thermoluminescence tl dating while for several samples both dating techniques were at the limits of their detection results from the upper strata of the northwestern face of the pantai mine indicate agreement between the two independent dating techniques the age of the old alluvium known as the simpang formation in perak is confirmed as late pleistocene at this site the measured ages range from 28 000 years b p to 67 000 years b p but the lower units are older than this and appear at this site to be beyond the range of both dating techniques

the influence of sea surface temperature on surface wind in the eastern equatorial pacific seasonal and interannual variability abstract the climate of the eastern pacific exhibits a pronounced equatorial asymmetry boundary layer air originating in the southern hemisphere trades crosses the equator and flows into the intertropical convergence zone itcz whose southern limit is nearly always located at least 4 to the north of the equator the sea surface temperature sst distribution is characterized by a prominent cold tongue centered 1 s a strong frontal zone centered 2 n and a warm eastward current centered near 5 n the surface wind field exhibits a pronounced horizontal divergence as the air flows northward across the oceanic frontal zone these features vary in strength in response to the annual cycle and the el nino southern oscillation phenomenon the northward cross equatorial surface winds the cold tongue and the frontal zone all tend to be strongest during the cold season july through november during the cold season of the coldest years when the cold tongue is most prominent the cross equatorial flow t

did panthera pardus linnaeus 1758 become extinct in sumatra because of competition for prey modeling interspecific competition within the late pleistocene carnivore guild of the padang highlands sumatra abstract on the island of sumatra the leopard panthera pardus became extinct during the late pleistocene several theories exist about the reasons why leopards could not subsist in sumatra while today national parks still bear tigers panthera tigris and asiatic wild dogs cuon alpinus one often debated theory is that the competition for prey was the reason for the extinction of leopards in sumatra the aim of our study is to model the impacts of competition for prey in the carnivore guild of the padang highlands in sumatra to test if competition pressure was sufficient to force the leopard to extinction in the first step we reconstructed the carnivore guild of the padang highlands based on fossils collected by dubois in the three cave sites of sibrambang djamboe and lida ajer in the second step we developed and applied an agent based model based on population density prey spectrum and daily meat intake and simulated different scenarios of competition among the sumatran predators we simulated the reconstructed guild and further tested scenarios with the absence of guild members to see under which circumstances leopards could have survived in sumatra simulation of the reconstructed carnivore guild revealed that in fact the leopard could have been driven to extinction by competition from other carnivores excluding one of the competing medium sized cats or the asiatic wild dog leads to the survival of the leopard in our simulations interestingly our model demonstrates that humans and tigers were not the strongest competitors for leopards because their exclusion from the scenarios does not conclude with the survival of leopards in our simulations according to our results the presence of two medium sized cats and the asiatic wild dog in combination with the small litter size of the leopard were the main reasons why the leopard could not tolerate the competition for prey in the padang highlands in sumatra and thus became extinct in sumatra

structure of the cold front observed in sesame ave iii and its comparison with the hoskins bretherton frontogenesis model abstract a cold front which passed through the dense network of the sesame ave severe environmental storms and mesoscale experiment atmospheric variability experiment on 25 26 april 1979 was investigated rawinsonde data collected from 23 special stations and 19 national weather service stations at three hour intervals for a 24 hour period were used along with hourly surface data radar summary charts and goes east satellite images severe storms formed along the surface front during this period the analysis focused on the vertical circulation across the frontal surface at low levels the major features of the cold frontal system that emerged from an analysis of this unique data set include a familiar direct vertical circulation with moist warm air ascending just above the surface front however the upgliding motion was intercepted by a secondary circulation at middle levels the analysis result was compared with model predictions of hoskins and bretherton 1972 as calculated by blumen 1980 sever

submarine landslides along the malacca strait mergui basin shelf margin insights from sequence stratigraphic analysis the enormously destructive tsunami of december 2004 caused by sudden motion of the sunda megathrust beneath the indian ocean raised concerns about tectonically induced tsunami worldwide submarine landslides may also trigger dangerous tsunami however the potential and repeat time for such events is in most places poorly known due to inadequate exploration of the sea floor and age constraints the high sediment flux and tectonic subsidence rate of the malacca strait mergui basin shelf margin ne of northernmost sumatra provide a favorable environment to generate and preserve submarine landslides from ten seismic reflection profiles acquired in 2006 we identify three sediment packages that exhibit sliding characteristics such as headscarps distorted beds and debris toe structures we assign lowstand marine isotope stages to the paleo shoreline indicators observed in the profiles we then determine the ages of these submarine landslides as 20 30 ka 342 364 ka and 435 480 ka by the paleo shoreline indicators that bound the top and bottom of the slide bodies this sequence stratigraphic approach shows that these events occurred near times of sea level lowstands which implies that a large amount of direct sediment influx during glacial periods is an essential precondition for basin margin submarine landsliding spatiotemporal variations of sediment input due to lobe switching or asian monsoon intensity changes also control basin margin instability because we are currently at a highstand stage and sediment flux to the continental margin is relatively small so the chance of having a repeat submarine landslide and landslide tsunami along this basin margin is low

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

spatial patterns and intensity of the surface storm tracks in cmip5 models abstractto improve the understanding of storm tracks and western boundary current wbc interactions surface storm tracks in 12 cmip5 models are examined against era interim all models capture an equatorward displacement toward the wbcs in the locations of the surface storm tracks maxima relative to those at 850 hpa an estimated storm track metric is developed to analyze the location of the surface storm track it shows that the equatorward shift is influenced by both the lower tropospheric instability and the baroclinicity basin scale spatial correlations between models and era interim for the storm tracks near surface stability sst gradient and baroclinicity are calculated to test the ability of the gcms match reanalysis an intermodel comparison of the spatial correlations suggests that differences relative to era interim in the position of the storm track aloft have the strongest influence on differences in the surface storm track position however in the north atlantic biases in the surf

a submerged late pleistocene delta and other features related to sea level changes in the malacca strait abstract bathymetry sea floor echo characteristics and shallow subbottom reflectors in the malacca strait and the slope of the mergui north sumatra basin of the southern andaman sea show a varied and locally complex character which we interpret as a pleistocene lowered sea level alluvial delta fan system sediment waves and elongate banks in the narrow and shoal southern part of the strait indicate strong bottom currents and a rugged subbottom topography demonstrates erosion during low sea level of the late quaternary shallow subbottom reflectors at the northwest approaches to the strait show progradation and cut and fill valleys and the presence of a compound late pleistocene delta of the confluent sumatran and malayan rivers the younger prograding layers are probably of mid wisconsin wurm age ca 40 20 10 3 yr b p and the deeper foresets may be early illinoian glacial stage riss ca 150 10 3 yr b p farther seaward a small fan progrades from the slope a short distance into the shallow northeastern part of the mergui north sumatra basin

late holocene depositional environments and coastal evolution of the mekong river delta southern vietnam abstract the mekong river delta in southern vietnam is a tide dominated delta and has been formed by the mekong river system the sediments are dominantly fine grained and were deposited in the receiving basin with slight inclination of pre existing deposits in the south china sea and gulf of thailand around 6000 to 5000 yr bp maximum holocene transgression occurred and seawaves surrounded uplands of the late pleistocene terrace basement rock and weathered land in the northern parts of the delta double notches were undercut by seawaves on the limestone hill in hatien at about 4 5 and 2 5 m above present sea level marine deposits prevailed throughout the delta during the highstand and regressions of relative sea level over the last 4550 yr bp delta progradation has produced a great flat plain of 62 520 km 2 this extremely fast progradation could be due to a very high sediment supply depositing in the slight inclination of the receiving basin b neotectonic movements and relative sea level changes c widespread mangrove forests playing an important role to enhance sediment accumulation former mangrove marshy deposits were significantly developed in the plain of reeds and longxuyen quadrangle mangrove marshes have also been developing well in the camau peninsula and present coastlines moreover regressions over the last 4550 yr bp have produced many distinct sets of relict beach ridges which are useful in distinguishing the former coastlines and evolutionary history of the delta

global analysis of the pressure adjustment mechanism over sea surface temperature fronts using airs aqua data 1 we investigate the signatures of atmospheric pressure adjustment mechanism for surface wind convergence divergence over major sea surface temperature sst frontal regions using global observations of satellite sounding and scatterometer lower tropospheric air thickness which includes a sea level pressure component modified by air temperature in the marine atmospheric boundary layer is analyzed and the relation between the laplacian of the thickness and wind convergence are examined among four sst frontal regions in mid latitudes correlation between the thickness laplacian and wind convergence is the largest over the gulf stream followed by those for the agulhas return current and for the brazil malvinas current and relatively small but still significant over the kuroshio oyashio extension these correlations strongly suggest that the pressure adjustment mechanism ubiquitously plays an important role in air sea interaction over the global sst frontal regions furthermore air temperatures in the first two regions exhibit sst relating signatures even in the mid troposphere

atmospheric boundary layer response to mesoscale sst anomalies in the kuroshio extension abstract the atmospheric boundary layer abl response to mesoscale eddies in sea surface temperature sst in the kuroshio extension was investigated using a high resolution t213l30 atmospheric general circulation model a control run was performed first by integrating the model for 40 days driven by the satellite derived eddy resolving sst during january 2006 the spatial pattern of surface wind anomalies that is a deviation from large scale winds reveals a positive correlation with the spatial pattern of mesoscale sst anomalies the momentum budget analysis of the anomalous zonal wind was performed to investigate the formation of the abl response the most dominant term was the pressure gradient force the advection term was comparable but in the opposite sense vertical mixing acts to weaken the anomalous zonal wind near the surface however the downward upward vertical turbulent flux anomalies were dominant near the abl top over the warm cold sst anomalies suggesting that the vertical mixi

seasonal evolutions of atmospheric response to decadal sst anomalies in the north pacific subarctic frontal zone observations and a coupled model simulation abstractpotential impacts of pronounced decadal scale variations in the north pacific sea surface temperature sst that tend to be confined to the subarctic frontal zone safz upon seasonally varying atmospheric states are investigated by using 48 yr observational data and a 120 yr simulation with an ocean atmosphere coupled general circulation model cgcm sst fields based on in situ observations and the ocean component of the cgcm have horizontal resolutions of 2 0 and 0 5 respectively which can reasonably resolve frontal sst gradient across the safz both the observations and cgcm simulation provide a consistent picture between sst anomalies in the safz yielded by its decadal scale meridional displacement and their association with atmospheric anomalies correlated with sst anomalies persistent in the safz from fall to winter a coherent decadal scale signal in the wintertime atmospheric circulation over the north pacific starts emerging in november and develops into an equivalent barotropic an

on the importance of midlatitude oceanic frontal zones for the mean state and dominant variability in the tropospheric circulation 1 observations indicate that midlatitude weather systems are organized into storm tracks near oceanic frontal zones with pronounced sea surface temperature sst gradients a pair of atmospheric general circulation model experiments with zonally uniform sst profiles prescribed show that their observed collocation is not fortuitous in one experiment a storm track is anchored around a midlatitude sst front that maintains near surface thermal gradients and energizes eddies westerly momentum transport by eddies produces a well defined polar front jet along the front even in winter when a subtropical jet stream intensifies in the other experiment removal of the sst front leads to a substantial weakening in eddy activity and the pfj especially in winter it also leads to a weakening of the annular mode the dominant mode of westerly jet variability and its notable structural distortion in winter though idealized our experiments suggest the importance of midlatitude oceanic fronts for the tropospheric circulation and its variability