dynamical mechanisms for the south china sea seasonal circulation and thermohaline variabilities abstract the seasonal ocean circulation and the seasonal thermal structure in the south china sea scs were studied numerically using the princeton ocean model pom with 20 km horizontal resolution and 23 sigma levels conforming to a realistic bottom topography a 16 month control run was performed using climatological monthly mean wind stresses restoring type surface salt and heat and observational oceanic inflow outflow at the open boundaries the seasonally averaged effects of isolated forcing terms are presented and analyzed from the following experiments 1 nonlinear dynamic effects removed 2 wind effects removed and 3 open boundary inflow outflow set to zero this procedure allowed analysis of the contribution of individual parameters to the general hydrology and specific features of the scs for example coastal jets mesoscale topographic gyres and countercurrents the results show that the pom model has the capability of simulating seasonal variations of the scs circulation and thermoha

current observations on the development of the yellow sea warm current historically the climatological mean northward flow in the yellow sea trough has been referred to as the yellow sea warm current yswc since it was thought to originate as a branch of the tsushima current which transports warm kuroshio waters however the tsushima current does not penetrate into the yellow sea interior during winter the onset of what is referred to as the yswc during winter is directly observed using measurements of current profiles pressure and temperature and a wind climatology for the time period july 1995 through january 1996 the yswc is a result of weak southerly winds during summer during fall transition and winter monsoon periods strong northerly wind bursts drive a north to south rise in pressure extending from the trough over to the korean coast and force a northward flow in the yellow sea trough the rise in pressure and corresponding north wind forced yswc begin at the end of october for this measurement period and are observed into january these measurements show that the yswc has different seasonal forcing mechanisms direct current measurements are also presented which suggest a current flow north of cheju sometimes referred to as the cheju warm current

a 10 15 yr modulation cycle of enso intensity abstract this study examines the slow modulation of el nino southern oscillation enso intensity and its underlying mechanism a 10 15 yr enso intensity modulation cycle is identified from historical and paleoclimate data by calculating the envelope function of boreal winter nino 3 4 and nino 3 sea surface temperature sst indices composite analyses reveal interesting spatial asymmetries between el nino and la nina events within the modulation cycle in the enhanced intensity periods of the cycle el nino is located in the eastern tropical pacific and la nina in the central tropical pacific the asymmetry is reversed in the weakened intensity periods el nino centers in the central pacific and la nina in the eastern pacific el nino and la nina centered in the eastern pacific are accompanied with basin scale surface wind and thermocline anomalies whereas those centered in the central pacific are accompanied with local wind and thermocline anomalies the el nino la nina asymmetries provide a possible m

wind driven effects on the yellow sea warm current the yellow sea is a shallow basin writh an average depth of 44 m located between china and the korean peninsula one of the dominant ocean circulation features of the yellow sea is a warm wrater intrusion known as the yellow sea warm current this feature is present throughout the year but reaches its farthest northward extension in winter the circulation of the yellow east china and bohai seas was modeled using the princeton ocean model to better understand the dynamics of the yellow sea warm current the horizontal resolution of the model varies from 8 km in the yellow sea to 25 km in the east china sea twenty four sigma levels are used to define the vertical structure the model uses daily atmospheric forcing from the navy operational global atmospheric prediction system for 1993 open boundary conditions are applied at the taiwan strait the tsushima korea strait an area south of taiwan and the tokara strait with a closed boundary south of the ryukyu islands the model results are examined to determine the effect of the wind on the northward extension of the warm water intrusion using both water mass characteristics and northward velocity components sensitivity tests and spectrum analyses performed to study the influence of the wind on the yellow sea warm current show that winds modify the pathway and extent of the yellow sea warm current the current s origin however appears to be due to external forcing from the current systems developed in the east china sea

occurrence of large temperature inversion in the thermohaline frontal zone at the yellow sea entrance in winter and its relation to advection temperature inversion higher temperature at a deeper depth in winter and its relation to advection were investigated by analyzing both conductivity temperature depth data in the southern yellow sea ys and northwestern east china sea during the winter of 2002 2003 and time series data of temperature salinity and currents at a buoy station at the ys entrance significant temperature inversions occur predominantly along the thermohaline front at the ys entrance where the cheju warm current water cwcw and the cold coastal waters meet in february 2003 on the northern frontal zone along 34 n where isotherms and isohalines declined downward to the north particularly large inversions with temperature differences of larger than 2 0 c were observed to occur more in troughs than in the crests of the wave like frontal meander where the cold korean coastal water kcw advances farther southward the inversion persisted until mid april at the buoy station in the frontal zone and both temperature and salinity showed simultaneous variations in the same manner during episodic occurrences of large inversions temperature and salinity decreased sharply in the upper layer but increased concurrently in the lower layer these episodic inversions were found to be closely related to the westward advection of the kcw in the upper layer and the northward advection of the cwcw in the lower layer it is considered that these advections may play an important role in maintaining baroclinicity in the northern frontal zone which is responsible for driving the westward transversal flow across the ys entrance

interdecadal change of the structure of the enso mode and its impact on the enso frequency in the late 1970s the enso cycle exhibited frequency change the oscillation period increased from 2 4 yr high frequency during 1962 75 to 4 6 yr low frequency during 1980 93 observations suggest that this frequency change was accompanied by a significant change in the structure of the coupled enso mode in comparison with the high frequency regime the structure of the coupled mode in the low frequency regime shows three distinctive features during the warm phase of enso the eastward shift of the westerly anomalies the meridional expansion of the westerly anomalies and the weaker intensity of the easterly anomalies in the eastern pacific to test the robustness of the relationship between the oscillation period and the structure of the coupled mode the authors designed empirical atmospheric models based on observations and coupled them with the ocean model of zebiak and cane numerical experiments demonstrate that the enso period is sensitive to changes in the wind anomaly pattern in a way much like the observed enso frequency structure relation the increase of the enso period after 1980 is mainly due to the eastward shift of the zonal wind stress with respect to the sst anomalies physical explanations of the dependence of enso frequency on the structure of the coupled mode are provided by diagnosing the relative contributions of the thermocline feedback and zonal advection feedback on enso evolution

does vertical temperature gradient of the atmosphere matter for el nino development in this work we examine the connection of vertical temperature gradient of the tropospheric atmosphere along the equator with el nino southern oscillation enso and the possible impact of the long term change of the gradient it is suggested that when the temperature anomalies in the lower troposphere are relatively warmer cooler than in the upper troposphere the atmosphere is less more stable and favors an el nino a la nina event to develop enso evolutions in 1997 1998 and 2014 2015 events are good examples of this relationship they started from similar ocean anomaly states in the springs of 1997 and 2014 but developed into an extreme el nino in 1997 1998 and a borderline el nino in 2014 2015 that may be partially due to differences in the evolutions of the vertical temperature anomaly gradient in troposphere thus in addition to the significant atmospheric response to enso the preconditioning of vertical gradient of the tropospheric temperature due to internal atmospheric processes to some extent may play an active role in affecting enso evolution the long term trend with more pronounced warming in the upper troposphere than in the lower troposphere causes a reduction in the vertical temperature gradient in the troposphere moreover unlike almost homogenous warm anomalies in the upper troposphere the lower troposphere shows remarkable regional features along the equator during 1979 2014 with cold anomaly trends over the central and eastern pacific ocean associated with the so called hiatus and some warm anomalies on its two sides in the east and west this vertical and zonal distribution of the air temperature trends in the troposphere over the pacific ocean is consistent with the convection suppression over the central pacific since 2000 implying a weakening of atmosphere and ocean coupling

west florida shelf mean circulation observed with long term moorings 1 the mean circulation on the west florida continental shelf is described using long term current measurements bounded by the florida peninsula to the east and the gulf of mexico to the west the west florida continental shelf mean flow is oriented approximately along isobath and southward the mean velocity vectors veer systematically with depth shoreward over shallow water and seaward over deeper water this polarization change implies that the mean flow is upwelling over shallow water and downwelling seaward from the inner shelf such a well organized three dimensional coastal ocean circulation pattern revealed by an unprecedented set of observations and explained on the basis of wind forcing and density field adjustment has important implications for both fisheries and red tide occurrences

a new paradigm for the predominance of standing central pacific warming after the late 1990s canonical el nino has a warming center in the eastern pacific ep but in recent decades el nino warming center tends to occur more frequently in the central pacific cp the definitions and names of this new type of el nino however have been notoriously diverse which makes it difficult to understand why the warming center shifts here we show that the new type of el nino events is characterized by 1 the maximum warming standing and persisting in the cp and 2 the warming extending to the ep only briefly during its peak phase for this reason we refer to it as standing cp warming cpw global warming has been blamed for the westward shift of maximum warming as well as more frequent occurrence of cpw however we find that since the late 1990s the standing cpw becomes a dominant mode in the pacific meanwhile the epochal mean trade winds have strengthened and the equatorial thermocline slope has increased contrary to the global warming induced weakening trades and flattening thermocline we propose that the recent predominance of standing cpw arises from a dramatic decadal change characterized by a grand la nina like background pattern and strong divergence in the cp atmospheric boundary layer after the late 1990s the anomalous mean cp wind divergence tends to weaken the anomalous convection and shift it westward from the underlying sst warming due to the suppressed low level convergence feedback this leads to a westward shift of anomalous westerly response and thus a zonally in phase sst tendency preventing eastward propagation of the sst anomaly we anticipate more cpw events will occur in the coming decade provided the grand la nina like background state persists

lakes as paleoseismic records in a seismically active low relief area rieti basin central italy abstract small lakes in low relief areas are atypical candidates for studies on paleoseismicity but their sediments can contain seismically induced event layers seismites generated through strong ground shaking sediment transport hydrological reorganization and or changes in groundwater chemistry and flow lakes lungo and ripasottile are shallow lakes

a parametric model for the yellow sea thermal variability a thermal parametric model has been developed for analyzing observed regional sea temperature profiles based on a layered structure of temperature fields mixed layer thermocline and deep layers it contains three major components 1 a first guess parametric model 2 high resolution profiles interpolated from observed profiles and 3 fitting of high resolution profiles to the parametric model the output of this parametric model is a set of major characteristics of each profile sea surface temperature mixed layer depth thermocline depth thermocline temperature gradient and deep layer stratification analyzing nearly 15 000 yellow sea historical 1950 1988 temperature profiles conductivity temperature depth station 4825 expendable bathythermograph 3213 bathythermograph 6965 from the naval oceanographic office s master oceanographic observation data set by this parametric model the yellow sea thermal field reveals dual structure one layer vertically uniform during winter and multilayer mixed layer thermocline sublayer during summer strong seasonal variations were also found in mixed layer depth thermocline depth and thermocline strength

observations of warm water volume changes in the equatorial pacific and their relationship to el nino and la nina abstract this paper describes observed changes in surface winds sea surface temperature sst and the volume of water warmer than 20 c wwv in the equatorial pacific ocean for the period 1980 99 the purpose is to test recent hypotheses about the relationship between variations in wwv and the el nino southern oscillation enso cycle the results confirm inferences based on theory models and previous empirical analyses using proxy data namely sea level that enso involves a recharge and discharge of wwv along the equator and that the cyclic nature of enso results from a disequilibrium between zonal winds and zonal mean thermocline depth the authors also find that the magnitude of enso sst anomalies is directly related to the magnitude of zonal mean wwv anomalies furthermore for a given change in equatorial wwv the corresponding warm el nino sst anomalies are larger than the corresponding cold la nina anomalies this asymmetry between the warm and cold phases of the enso cycle implies differences

seasonal thermocline in the china seas and northwestern pacific ocean climatological seasonal variations of the thermocline in the china seas and northwestern pacific ocean were studied using historical data from 1930 through 2001 707 624 profiles the quantitative roles of surface thermal buoyancy b q haline buoyancy flux b p and total buoyancy flux b against the wind induced mixing tau in different seasons and regions were also explored using the buoyancy ratio r b q b p and the monin obukhov depth ratio delta respectively the thermocline has obvious seasonal variations in the study area north of 20 degrees n there is no thermocline along the west coast of the bohai sea bs yellow sea ys and northern east china sea from december to march resulting from surface cooling and wind mixing the significantly different variation of the thermocline strength on and off the chinese shelf is mainly caused by the fact that the thermal stratification is enhanced by bottom tidal mixing on the shelf the delta indicates that the thermocline depth on the chinese shelf is mainly dominated by b in summer while it is dominated by tau in winter it reveals an opposite feature in the kuroshio region the dominating factor is b in winter associated with the large heat buoyancy loss there south of 20 degrees n the dominating factor is similar to that on the shelf with the more obvious b dominant characteristic during the monsoon transition periods the r demonstrates that b is mainly controlled by b q all year round with some sporadically b p dominated regions in the tropical area in winter and in the bs and eastern ys in september

asymmetry in zonal phase propagation of enso sea surface temperature anomalies 1 it is often emphasized in the literature that the phase propagation of el nino sea surface temperature sst anomalies along the equator changed from westward to eastward after a mid to late 1970s climate regime shift in the pacific theories have been developed to explain this change of phase propagation in terms of changes in background state on which el nino events develop those theories also suggest that the direction of la nina anomaly phase propagation should have changed from westward to eastward as well however the direction of la nina sst anomaly phase propagation did not change after the mid to late 1970s instead la nina ssts continued to exhibit westward phase propagation along the equator a feature overlooked in both observational analyses and theories this paper highlights the asymmetry in zonal phase propagation between el nino and la nina sea surface temperature anomalies since 1980 and discusses the implications of that asymmetry for understanding el nino southern oscillation enso dynamics

the influence of the interdecadal pacific oscillation on temperature and precipitation over the globe the interdecadal pacific oscillation ipo is a 40 60 year quasi oscillation seen mostly in the pacific basin but its impacts on surface temperature t and precipitation p have been found over australia the southwest u s and other regions here a global analysis of ipo s impacts on t and p and its modulation of enso s influence on t and p over the globe is performed using observational and reanalysis data and model simulations since 1920 there are two warm 1924 1944 and 1977 1998 and two cold 1945 1976 and 1999 present ipo phases whose change is associated with abrupt shifts in north pacific sea level pressure slp and contrasting anomaly patterns in t and p and atmospheric circulation over the eastern and western pacific the ipo explains more than half of the interdecadal variations in t and p over many regions such as northeastern australia western canada and northern india significant correlations between the ipo and local p are observed over eastern australia southern africa and the southwest u s the ipo also modulates enso s influence on local t and p over most of these regions t over northern india is positively correlated with nino3 4 enso index during cold ipo phases but the correlation turns negative or insignificant during ipo warm phases over northeastern australia the t versus enso and p versus enso correlations are stronger during the ipo cold phases than during the warm phases the p versus enso correlation over southern africa tends to be negative during ipo warm phases but becomes weaker or insignificant during ipo cold phases the ipo induced p anomalies can be explained by the associated anomaly circulation which is characterized by a high slp center and anti cyclonic flows over the north pacific and negative slp anomalies and increased wind convergence over the indonesia and western pacific region during ipo cold phases these observed influences of the ipo on regional t and p are generally reproduced by an atmospheric model forced by observed sea surface temperatures

twentieth century walker circulation change data analysis and model experiments recent studies indicate a weakening of the walker circulation during the twentieth century here we present evidence from an atmospheric general circulation model agcm forced by the history of observed sea surface temperature sst that the walker circulation may have intensified rather than weakened observed equatorial indo pacific sector sst since 1870 exhibited a zonally asymmetric evolution while the eastern part of the equatorial pacific showed only a weak warming or even cooling in one sst dataset the western part and the equatorial indian ocean exhibited a rather strong warming this has resulted in an increase of the sst gradient between the maritime continent and the eastern part of the equatorial pacific one driving force of the walker circulation the ensemble experiments with the agcm with and without time varying external forcing suggest that the enhancement of the sst gradient drove an anomalous atmospheric circulation with an enhancement of both walker and hadley circulation anomalously strong precipitation is simulated over the indian ocean and anomalously weak precipitation over the western pacific with corresponding changes in the surface wind pattern some sensitivity to the forcing sst however is noticed the analysis of twentieth century integrations with global climate models driven with observed radiative forcing obtained from the coupled model intercomparison project cmip database support the link between the sst gradient and walker circulation strength furthermore control integrations with the cmip models indicate the existence of strong internal variability on centennial timescales the results suggest that a radiatively forced signal in the walker circulation during the twentieth century may have been too weak to be detectable

modeling temperature inversion in southeastern yellow sea during winter 2016 a significant temperature inversion with temperature differences larger than 3 c was observed in the southeastern yellow sea ys during february 2016 by analyzing in situ hydrographic profiles and results from a regional ocean model for the ys this study examines the spatiotemporal evolution of the temperature inversion and its connection with wind induced currents in winter observations reveal that in winter when the northwesterly wind prevails over the ys the temperature inversion occurs largely at the frontal zone southwest of korea where warm saline water of a kuroshio origin meets cold fresh coastal water our model successfully captures the temperature inversion observed in the winter of 2016 and suggests a close relation between northwesterly wind bursts and the occurrence of the large inversion in this respect the strong northwesterly wind drove cold coastal water southward in the upper layer via ekman transport which pushed the water mass southward and increased the sea level slope in the frontal zone in southeastern ys the intensified sea level slope propagated northward away from the frontal zone as a shelf wave causing a northward upwind flow response along the ys trough in the lower layer thereby resulting in the large temperature inversion diagnostic analysis of the momentum balance shows that the westward pressure gradient which developed with shelf wave propagation along the ys trough was balanced with the coriolis force in accordance with the northward upwind current in and around the inversion area

frontal circulation and westward transversal current at the yellow sea entrance in winter 1 during the wintertime monsoon a tongue shaped thermohaline front is established at the yellow sea ys entrance where the cheju warm current cwc water originating in the kuroshio and the ys cold water meet the frontal circulation as well as the frontal structure has been investigated by analyzing comprehensive conductivity temperature density data float tracks current data and wind data the front develops by the westward advance of the cwc water but it is bounded by the shallow changjiang banks cb that acts like a stopper in the deep part of the ys entrance the northern part of the tongue shaped front displays a wave like motion of 20 km in amplitude and 80 km in wavelength and isotherms isohalines and isopycnals are declined downward toward the north the geostrophic current field indicates formation of a cyclonic circulation along the front which consists of a westward transversal current tc along 34 n and a southeastward outflow along the 50 m isobath of the cb the westward trajectories of floats along the northern front support existence of the tc and a superposition of float tracks evidences cyclonic frontal circulation the new observational findings of the tc and the cyclonic circulation do not match the classical paradigm of a northerly wind driven circulation which consists of the northward inflow through the central trough and the southward outflow on the coastal sides the cyclonic turning of the cold water around the warm tongue stands in contrast with the anticyclonic rounding of the warm cwc water around jeju do

enso like interdecadal variability 1900 93 a number of recent studies have reported an enso like eof mode in the global sea surface temperature sst field whose time variability is marked by an abrupt change toward a warmer tropical eastern pacific and a colder extratropical central north pacific in 1976 77 the present study compares this pattern with the structure of the interannual variability associated with the enso cycle and documents its time history back to 1900 the analysis is primarily based on the leading eofs of the sst anomaly and anomaly deviation fields in various domains and the associated expansion coefficient or principal component time series which are used to construct global regression maps of sst sea level pressure slp and a number of related variables the use of anomaly deviations i e departures of local sst anomalies from the concurrent global mean sst anomaly reduces the influence of global mean sst trends upon the structure of the eofs and their expansion coefficient time series an important auxiliary time series used in this study is a southern oscillation index based on marine surface observations by means of several different analysis techniques the time variability of the leading eof of the global sst field is separated into two components one identified with the enso cycle related variability on the interannual timescale and the other a linearly independent residual comprising all the interdecadal variability in the record the two components exhibit rather similar spatial signatures in the global sst slp and wind stress fields the sst signature in the residual variability is less equatorially confined in the eastern pacific and it is relatively more prominent over the extratropical north pacific the corresponding slp signature is also stronger over the extratropical north pacific and its counterpart in the cold season 500 mb height field more closely resembles the pna pattern the amplitude time series of the enso like pattern in the residual variability reflects the above mentioned shift in 1976 77 as well as a number of other prominent features including a shift of opposite polarity during the 1940s

assessing the twenty first century shift in enso variability in terms of the bjerknes stability index abstracta decadal change in the character of enso was observed around year 2000 toward weaker amplitude higher frequency events with an increased occurrence of central pacific el ninos here these changes are assessed in terms of the bjerknes stability index bj index which is a measure of the growth rate of enso related sst anomalies the individual terms of the index are calculated from ocean reanalysis products separately for the time periods 1980 99 and 2000 10 the spread between the products is large but they show a robust weakening of the thermocline feedback due to a reduced thermocline slope response to anomalous zonal wind stress as well as a weakened wind stress response to eastern equatorial pacific sst anomalies these changes are consistent with changes in the background state of the tropical pacific cooler mean sst in the eastern and central equatorial pacific results in reduced convection there together with a westward shift in the ascending branch of the walker circulation this shif

factors that affect the amplitude of el nino in global coupled climate models historically el nino like events simulated in global coupled climate models have had reduced amplitude compared to observations here el nino like phenomena are compared in ten sensitivity experiments using two recent global coupled models these models have various combinations of horizontal and vertical ocean resolution ocean physics and atmospheric model resolution it is demonstrated that the lower the value of the ocean background vertical diffusivity the greater the amplitude of el nino variability which is related primarily to a sharper equatorial thermocline among models with low background vertical diffusivity stronger equatorial zonal wind stress is associated with relatively higher amplitude el nino variability along with more realistic east west sea surface temperature sst gradient along the equator the sst seasonal cycle in the eastern tropical pacific has too much of a semiannual component with a double intertropical convergence zone itcz in all experiments and thus does not affect nor is it affected by the amplitude of el nino variability systematic errors affecting the spatial variability of el nino in the experiments are characterized by the eastern equatorial pacific cold tongue regime extending too far westward into the warm pool the time scales of interannual variability as represented by time series of nino3 ssts show significant power in the 3 4 year enso band and 2 2 5 year tropospheric biennial oscillation tbo band in the model experiments the tbo periods in the models agree well with the observations while the enso periods are near the short end of the range of 3 6 years observed during the period 1950 94 the close association between interannual variability of equatorial eastern pacific ssts and large scale sst patterns is represented by significant correlations between nino3 time series and the pc time series of the first eofs of near global ssts in the models and observations

a mechanism for decadal changes of enso behavior roles of background wind changes this study explains why a number of el nino properties period amplitude structure and propagation have changed in a coherent manner since the late 1970s and why these changes had almost concurred with the pacific decadal climate shift evidence is presented to show that from the pre shift 1961 1975 to the post shift 1981 1995 epoch significant changes in the tropical pacific are found in the surface winds and temperature whereas changes in the thermocline are uncertain numerical experiments with the cane and zebiak model demonstrate that the decadal changes in the surface winds qualitatively reproduce the observed coherent changes in el nino properties the fundamental factor that altered the model s el nino is the decadal changes of the background equatorial winds and associated upwelling the annual cycle is also necessary for the mean state to modulate el nino from the pre to post shift epoch the changes in the background winds and upwelling modify the structure of the coupled mode eastward displacement of the equatorial westerly anomalies by reallocating anomalous atmospheric heating and sst gradient along the equator this structural change amplifies the enso cycle and prolongs the oscillation period by enhancing the coupled instability and delaying transitions from a warm to a cold state or vice versa the changes in the mean currents and upwelling reduce the effect of the zonal temperature advection while enhance that of the vertical advection thus the prevailing westward propagation is replaced by eastward propagation or standing oscillation our results suggest a critical role of the atmospheric bridge that rapidly conveys the influences of extratropical decadal variations to the tropics and the possibility that the pacific climate shift might have affected el nino properties in the late 1970s by changing the background tropical winds and the associated equatorial upwelling

weakened interannual variability in the tropical pacific ocean since 2000 abstractan interdecadal shift in the variability and mean state of the tropical pacific ocean is investigated within the context of changes in el nino southern oscillation enso compared with 1979 99 the interannual variability in the tropical pacific was significantly weaker in 2000 11 and this shift can be seen by coherent changes in both the tropical atmosphere and ocean for example the equatorial thermocline tilt became steeper during 2000 11 which was consistent with positive negative sea surface temperature anomalies increased decreased precipitation and enhanced suppressed convection in the western central and eastern tropical pacific which reflected an intensification of the walker circulation the combination of a steeper thermocline slope with stronger surface trade winds is proposed to have hampered the eastward migration of the warm water along the equatorial pacific as a consequence the variability of the warm water volume was reduced and thus enso amplitude also decreased

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

indices of el nino evolution abstract to characterize the nature of el nino southern oscillation enso sea surface temperature sst anomalies in different regions of the pacific have been used an optimal characterization of both the distinct character and the evolution of each el nino or la nina event is suggested that requires at least two indices i sst anomalies in the nino 3 4 region referred to as n3 4 and ii a new index termed here the trans nino index tni which is given by the difference in normalized anomalies of sst between nino 1 2 and nino 4 regions the first index can be thought of as the mean sst throughout the equatorial pacific east of the date line and the second index is the gradient in sst across the same region consequently they are approximately orthogonal tni leads n3 4 by 3 to 12 months prior to the climate shift in 1976 77 and also follows n3 4 but with opposite sign 3 to 12 months later however after 1976 77 the sign of the tni leads and lags are reversed

seasonal variations of the yellow river plume in the bohai sea a model study 1 we investigated the behavior of the yellow river plume in the bohai sea through a year and its controlling mechanisms using a numerical model driven by monthly averaged wind stress heat flux and river discharge the model produced a clear seasonal behavior of the yellow river plume in summer the yellow river plume extends northeastward into the central bohai sea in autumn it turns southward and flows into laizhou bay along the coast in winter most of the diluted water is found around southeastern corner of laizhou bay and in spring a low salinity area appears in southwest laizhou bay with the same model several well designed numerical experiments were performed to investigate the effect on the behavior of the yellow river plume of tidal current river discharge wind stress and thermal stratification the tidal currents promote the offshore spread of diluted water while the tide induced residual currents prevent the plume from extending further downstream in the direction of kelvin wave propagation wind stresses lead to pronounced changes in the path and shape of the plume in autumn and winter northwesterly or northerly winds drive the buoyant water into laizhou bay along the coast in summer the combination of southeasterly winds and thermal stratification drives the plume extend northeastward into the central bohai sea by changing only the magnitude of wind stress or river discharge in the experiments we examined the sensitivity of summertime plume to the magnitude of wind stress and river discharge

temperature inversion in china seas temperature inversion was reported as a common phenomenon in the areas near the southeastern chinese coast region a west and south of the korean peninsula region b and north and east of the shandong peninsula region c during october may in the present study based on hydrographic data archived from 1930 through 2001 319 029 profiles the inversion was found to be remarkable with obvious temporal and spatial variabilities in both magnitude and coverage with higher probabilities in region a up to about 60 and region c 40 50 than in region b 15 20 the analysis shows that seasonal variation of the net air sea heat flux is closely related to the occurrence time of the inversion in the three areas while the yangtze and yellow river freshwater plumes in the surface layer and ocean origin saline water in the subsurface layer maintain stable stratification it seems that the evaporation excessive precipitation flux makes little contribution to maintaining the stable inversion advection of surface fresh water by the wind driven coastal currents results in the expansion of inversion in regions a and c the inversion lasts for the longest period in region a october may sustained by the taiwan warm current carrying the subsurface saline water while evolution of the inversion in region b is mainly controlled by the yellow sea warm current