low frequency currents from deep moorings in the southern bay of bengal abstracthigh resolution currents and hydrographic fields were measured at six deep water moorings in the southern bay of bengal bob by the naval research laboratory as part of an international effort focused on the dynamics of the indian ocean currents temperature and salinity were sampled over the upper 500 m for 20 months between december 2013 and august 2015 one of the major goals is to understand the space time scales of the currents and physical processes that contribute to the exchange of water between the bob and the arabian sea the observations captured southwest and northeast monsoon currents seasonally varying large eddies including a cyclonic eddy the sri lanka dome sld and an anticyclonic eddy southeast of the sld the observations further showed intraseasonal oscillations with periods of 30 70 days near inertial currents and tides monthly averaged velocities commonly exceeded 50 cm s 1 near the surface and extreme velocities exceeded 150 cm s 1 during the southwest monsoon ti

variability of intraseasonal kelvin waves in the equatorial pacific ocean abstract previous observational work has demonstrated that the phase speed of oceanic equatorial kelvin waves forced by the madden julian oscillation mjo appears to vary substantially processes that are responsible for systematic changes in the phase speed of these waves are examined using an ocean general circulation model the model was integrated for 26 yr with daily wind stress derived from the ncep ncar reanalysis the model is able to reproduce observed systematic changes of kelvin wave phase speed reasonably well providing a tool for the analysis of their dynamics the relative importance of the upper ocean background state and atmospheric forcing for phase speed changes is determined based on a series of model experiments with various surface forcings systematic changes in phase speed are evident in all model experiments that have different slowly varying basic states showing that variations of the upper ocean background state are not the primary cause of the changes the model experiments t

origins and dynamics of the 90 day and 30 60 day variations in the equatorial indian ocean abstract sea level observations in the equatorial indian ocean show a dominant spectral peak at 90 days and secondary peaks at 30 60 days over an intraseasonal period 20 90 days a detailed investigation of the origins and dynamics of these variations is carried out using an ocean general circulation model namely the hybrid coordinate ocean model hycom two parallel experiments are performed in the tropical indian ocean basin for the period 1988 2001 one is forced by ncep 3 day mean forcing fields together with the climate prediction center cpc merged analysis of precipitation cmap pentad precipitation and the other is forced by monthly mean fields to help to understand the role played by the wind driven equatorial wave dynamics a linear continuously stratified ocean model is also used both the observed and modeled 90 day sea level anomaly fields and hycom surface current clearly show equatorial kelvin and first meridional mode rossby wave structures that are forced by the 90 day winds the

origins of wind driven intraseasonal sea level variations in the north indian ocean coastal waveguide 1 in this paper we show that a linear continuously stratified ocean model reproduces observed wind driven intraseasonal sea level variability in the coastal waveguide of the northern indian ocean nio sensitivity experiments with intraseasonal wind forcing selectively applied in the equatorial region bay of bengal and arabian sea show that a large part of the basin scale sea level variations are driven by zonal wind fluctuations along the equator within the nio coastal waveguide the contribution of remote equatorial forcing decreases from 80 90 in the andaman sea to 50 northeast of sri lanka and then increases to 60 70 along the west coast of india during the southwest monsoon intraseasonal wind variations become stronger over the nio resulting in a larger contribution of local wind forcing to sea level variability along the west up to 60 and east up to 40 coasts of india

intraseasonal variability in the upper layer currents observed in the eastern equatorial indian ocean 1 direct observations of the upper ocean velocity in the eastern equatorial indian ocean by an acoustic doppler current profiler from november 2000 to october 2001 on the equator at 90 e demonstrate that the dominant periods of variability in the upper layer zonal and meridional currents are in intraseasonal frequency bands with periods of 30 to 50 days and 10 to 20 days respectively the strong intraseasonal variability in the zonal current obscures the semiannual wyrtki jets which can be seen clearly in the monthly averaged field in addition a zone of strong vertical shear of the zonal current and a distinct equatorial undercurrent with semiannual period are observed the results provide us with a new perspective on importance of the energetic intraseasonal variability in the eastern equatorial indian ocean which indicates strong correlation with the wind variability near the mooring location

intraseasonal to semiannual variability of sea surface height in the astern equatorial indian ocean and southern bay of bengal intraseasonal to semiannual variability of sea surface height ssh in the eastern equatorial indian ocean eeio and southern bay of bengal bob is investigated using altimetric data and solutions to 1 layer first baroclinic mode and linear continuously stratified lcs multi baroclinic mode models the amplitude and dominant period of ssh variability differ regionally large amplitude variability is found along the west coast of sumatra in a zonal band across the bob centered along 5 n east of sri lanka and in the northwestern bob respectively along the sumatran west coast ssh variability peaks at 30 60 days 90 days and 180 days along 5 n and east of sri lanka the 30 60 day variability is dominant sensitivity experiments using a nonlinear version of the 1 layer model forced by realistic winds reproduce the observed patterns of intraseasonal variability in the southern bob at 30 60 days the solutions show that eddies nonlinear rossby waves propagating from the east rather than local wind forcing account for most of the variance east of sri lanka furthermore they demonstrate that the variance is significantly enhanced by the nonlinear transfer of 90 120 day energy into the intraseasonal band of 30 60 days the lcs solutions show that the first two baroclinic modes explain most of the ssh variance at 90 180 days the second baroclinic mode dominates the ssh variance at 180 days a consequence of basin resonance and strong wind forcing

oceanic precondition and evolution of the 2006 indian ocean dipole 1 details of subsurface ocean conditions associated with the indian ocean dipole event iod were observed for the first time by mooring buoys in the eastern equatorial indian ocean large scale sea surface signals in the tropical indian ocean associated with the positive iod started in august 2006 and the anomalous conditions continued until december 2006 data from the mooring buoys however captured the first appearance of the negative temperature anomaly at the thermocline depth with strong westward current anomalies in may 2006 about three months earlier than the development of the surface signatures these subsurface evolutions within the ocean would be a key factor for better understanding of iod mechanisms and its predictability and are providing a fundamental dataset for validation of modeling outputs

erosion by tectonic carving in the concordia subglacial fault zone east antarctica abstract in this work we present the analysis of the footwall morphology of the concordia subglacial extensional fault in the east antarctic craton the concordia fault is a regional fault zone that extends for almost 200 km the displacement up to 1800 m and the listric geometry were recognized by numerical modeling of the resulting hangingwall bedrock morphology and is responsible for the marked asymmetry that characterizes the corresponding scarp in the concordia subglacial trench the portion of the footwall in the proximity of the master fault exhibits an excavated morphology about 500 m deep and up to 5 km wide showing strong correlation with the master fault displacement we excluded a predominant glacial and fluvial origin of this morphology considering i the sharp topography of the concordia fault suggesting that the fault activity started after the onset of the ice sheet ii the ice sheet bedrock contact is characterized by a general negligible erosion deposition rates still allowing clast removal iii the lack of significant deposits in the concordia trench we hence explored the possibility that this morphology may result from the combined action of fault induced fracturing and passive clast removal and scattering by flow and plastic deformation within the ice sheet we introduced the term tectonic carving for this process our modeling shows that tectonic carving relates to the relative fracture intensity in the concordia fracture zone that corresponds to the envelope of master and secondary fault damage zones fracture intensity depends on the frequency and the displacement of secondary faulting and can be approximated by a normal distribution using a monte carlo modeling approach we selected the set of parameters that best fits the data set with the carving theoretical curve the final results of the monte carlo analysis show a root mean square of about 50 meters comparable with the data resolution this analysis demonstrates a method to unravel the presence of fracture zones in similar weak erosional environments

subsurface equatorial zonal current in the eastern indian ocean 1 variations of subsurface zonal current in the eastern equatorial indian ocean are investigated by examining 6 year data december 2000 november 2006 from acoustic doppler current profiler adcp mooring at 0 s 90 e the analysis indicates the presence of an eastward equatorial subsurface current between 90 and 170 m depths during both boreal winter and summer during boreal winter the generation of eastward pressure gradient which drives an eastward flow in the thermocline is caused primarily by upwelling equatorial kelvin waves excited by prevailing easterly winds on the other hand the downwelling rossby waves generated by the reflection of the spring downwelling kelvin waves in the eastern boundary as well as the upwelling equatorial kelvin waves triggered by easterlies create an oceanic state that favors the generation of the eastward pressure gradient during boreal summer the subsurface current reveals a distinct seasonal asymmetry the maximum eastward speed of 63 cm s 1 is observed in april and secondary maximum of 49 cm s 1 is seen in october the zonal transport per unit width within depth of the subsurface current exhibits similar variations reaching maximum eastward transport of 35 m2 s 1 in april and secondary maximum of 29 m2 s 1 in october moreover the subsurface current during boreal summer undergoes significant interannual variations it was absent in 2003 but it was anomalously strong during 2006

the subglacial geology of wilkes land east antarctica wilkes land is a key region for studying the configuration of gondwana and for appreciating the role of tectonic boundary conditions on east antarctic ice sheet eais behavior despite this importance it remains one of the largest regions on earth where we lack a basic knowledge of geology new magnetic gravity and subglacial topography data allow the region s first comprehensive geological interpretation we map lithospheric domains and their bounding faults including the suture between indo antarctica and australo antarctica furthermore we image subglacial sedimentary basins including the aurora and knox subglacial basins and the previously unknown sabrina subglacial basin commonality of structure in magnetic gravity and topography data suggest that pre eais tectonic features are a primary control on subglacial topography the preservation of this relationship after glaciation suggests that these tectonic features provide topographic and basal boundary conditions that have strongly influenced the structure and evolution of the eais

impact of atmospheric intraseasonal oscillations on the indian ocean dipole during the 1990s abstract effects of atmospheric intraseasonal oscillations isos on the indian ocean zonal dipole mode iozdm are investigated by analyzing available observations and a suite of solutions to an ocean general circulation model namely the hybrid coordinate ocean model hycom data and model solutions for the period 1991 2000 are analyzed a period that includes two strong iozdm events during 1994 and 1997 and a weak one in 1991 both the data analysis and model results suggest that atmospheric isos play a significant role in causing irregularity of the two strong iozdm events and the premature termination of the weak one of particular interest is a basinwide wind driven oceanic resonance with a period near 90 days involving the propagation of equatorial kelvin and first meridional mode rossby waves across the basin before the onset of the strong 1997 dipole wind variability had significant power near 90 days and the resonance was strongly excited associated with the resonance was a deepened t

geomechanical studies on slow slope movements in parma apennine abstract the apennine mountains of the parma province italy are characterized by a young geological structure subjected to continuous morphological modification in many areas as a consequence several active landslides can be identified in this region among others slow movements occurring over large areas are the typical type of instability in this zone the slow but constant deformation process can induce major damage when interacting with major civil infrastructures such as bridges roads and railways but has a less severe effect on agricultural practice and smaller structures four different slope instability phenomena are analyzed in this paper all the slopes are characterized by similar geological and hydrogeological features and by similar deformation rates all slopes have been studied by means of experimental tests and numerical modelling in order to understand the failure mechanism and the evolution of slope movement the deformation of each slope was monitored using superficial topographic control points and inclinometers while its water level regime is controlled by means of discontinuous piezometric readings the monitoring results together with in situ and laboratory testing allowed a more detailed understanding of processes such as deformation under a constant active stress the development of a numerical model was necessary to predict creep rates special attention has been given to the mineralogical components of the material involved in the unstable areas in order to identify the material structure characterizing these types of landslides this work is aimed to be a methodological study of a type of complex phenomena that are recurrent in a zone of the apennines these phenomena can be partly considered as mudslides acting in undrained loading condition along localized shear zones but creep gives a fundamental contribution to mass deformation that must also be considered in the phenomenon modelling to be able to obtain measured displacement rates for this purpose creep tests have been performed in undrained conditions and modeled by a finite difference code for the calibration of relevant material mechanical parameters the paper reports the description of the problems encountered to sample and to make experimentation on this kind of complex materials along with the obtained results and at the end gives some operative suggestions on how to overcome such difficulties

volume transports of the wyrtki jets and their relationship to the indian ocean dipole the equatorial indian ocean is characterized by strong eastward flows in the upper 80 100 m during boreal spring and fall referred to as the wyrtki jets these jets are driven by westerly winds during the transition seasons between the southwest and northeast monsoons and represent a major conduit for mass and heat transfer between the eastern and western sides of the basin since their discovery over 40 years ago there have been very few estimates from direct observations of the volume transports associated with these currents in this paper we describe seasonal to interannual time scale variations in volume transports based on 5 years of unique measurements from an array of acoustic doppler current profilers in the central equatorial indian ocean the array was centered at 0 80 5 e and spanned latitudes between 2 5 n and 4 s from august 2008 to december 2013 analysis of these data indicates that the spring jet peaks in may at 14 9 2 9 sv and the fall jet peaks in november at 19 7 2 4 sv around which there are year to year transport variations of 5 10 sv the relationship of the interannual transport variations to zonal wind stress forcing sea surface temperature sea surface height and surface current variations associated with the indian ocean dipole iod are further highlighted we also illustrate the role of wind forced equatorial waves in affecting transport variations of the fall wyrtki jet during the peak season of the iod

response of equatorial oceans to periodic forcing oscillating wind with a period p induce variability with the following characteristics in the upper few hundred meters of the equatorial zone 5 sup 0 n to 5 sup 0 s of the ocean 1 p 10 days these winds fluctuate too rapidly to generate strong currents and excite primarily waves 2 10 days 150 days the amplitude of variability is almost independent of frequency an equilibrium response which is in phase with the forcing and which corresponds to a succession of steady states is approached asymptotically these time scales are for a basin 5000 km wide if the width of the basis exceeds 5000 km then the 150 daytime scale increases in the deep ocean below the thermocline motion corresponds to propagating waves generated by the divergence of the nonlinear currents in the upper ocean

wind driven response of the upper ocean along the u s west coast to tropical mjo convection in this study time lagged composites of oscar upper ocean currents from february to may of 1993 2016 were binned by active phase of the leading atmospheric mode of intraseasonal variability the madden julian oscillation mjo seven days after the convectively active phase of the mjo is present in the tropical indian ocean anomalously strong south southeastward upper ocean currents are seen along nearly the entire u s west coast seven days after the convectively active phase is present in the tropical western pacific ocean upper ocean current anomalies reverse along the u s west coast with weaker southward flow a physical pathway to the ocean was found for both of these phases a tropical mjo convection modulates upper tropospheric heights and circulation over the pacific ocean b those anomalous atmospheric heights adjust the strength and position of the aleutian low and hawaiian high c surface winds change in response to the adjusted atmospheric pressure patterns and d those surface winds project onto upper ocean currents

observed relationships between oceanic kelvin waves and atmospheric forcing abstract the madden julian oscillation mjo has been implicated as a major source of the wind stress variability that generates basin scale kelvin waves in the equatorial pacific one source of debate concerning this relationship is the apparent difference in the frequencies of the two processes this work utilizes data from the tropical atmosphere ocean tao array of moored buoys along with outgoing longwave radiation data to show by means of a multiple linear regression model and case studies that the frequency discrepancy is due to a systematic decrease in the phase speeds of the kelvin waves and an increase in the period of the waves toward the east as conditions adjust toward el nino among the potential contributing factors to this phase speed decrease is an apparent air sea interaction that enhances the wind forcing of some of the kelvin waves allowing them to continue to amplify because the propagating wind stress anomaly decelerates to the speed of the developing kelvin wave instead of the sig

abrupt termination of indian ocean dipole events in response to intraseasonal disturbances 1 we have investigated the role of atmospheric intraseasonal disturbances on termination of the indian ocean dipole iod using multiple datasets we observed significant 30 60 day atmospheric disturbances associated with equatorial westerly zonal winds prior to termination of all iod events except for the 1982 and 1997 events the westerlies excite anomalous downwelling kelvin waves that terminate the basin wide coupled processes by warming the eastern indian ocean the 1982 and 1997 iod events coincide with the strongest el nino events during those years the intraseasonal disturbances are weak

the dynamics of zonal current variations in the central equatorial indian ocean 1 this paper examines the depth integrated zonal momentum balance in the central equatorial indian ocean 0 80 5 e for two periods in 1993 1994 and 2004 2006 using a combination of in situ and satellite observations one to two year record length mean balances are approximately linear and steady state monthly to seasonal time scale variations are also governed by linear dynamics with imbalances between the pressure gradient force and surface wind stress leading to zonal mass transport variations along the equator interannual variations in zonal transports along the equator associated with indian ocean dipole events in 1994 and 2006 are likewise consistent with linear dynamics these results provide a valuable benchmark for evaluating models of equatorial indian ocean circulation on seasonal time scales

dynamics of wind forced intraseasonal zonal current variations in the equatorial indian ocean 1 this study examines the structure and dynamics of wind forced intraseasonal zonal current variability in the equatorial indian ocean we take advantage of a variety of satellite and in situ data sets including unprecedented 4 8 year long velocity time series records from the research moored array for african asian australian monsoon analysis and prediction rama program spectral analysis reveals prominent intraseasonal zonal currents variations along the equator with periods of 30 70 days these oscillations are vertically in phase above the thermocline and propagate eastward with the local zonal winds in the thermocline intraseasonal zonal velocity variations also propagate eastward across a broad range of phase speeds expected for low baroclinic equatorial kelvin waves amplitudes decrease with depth with deeper levels leading those near surface collectively these results suggest that the near surface layer responds directly to intraseasonal zonal wind stress forcing and that subsequently energy radiates downward and eastward in the thermocline in the form of wind forced equatorial kelvin waves in addition intraseasonal zonal current variability on the equator is coherent with off equatorial sea surface height fluctuations in the eastern and central of the basin this coherence is primarily due to the fact that equatorial zonal wind variations are associated with off equatorial wind stress curls that can generate local ekman pumping and westward propagating rossby waves

development characteristics and dynamic structure of tropical intraseasonal convection anomalies abstract the development and dynamical structure of intraseasonal low frequency convection anomalies in the equatorial region are investigated using 10 years 1975 85 of outgoing longwave radiation olr and 7 years 1979 85 of 200 and 850 mb wind data the composite olr anomalies for 36 cases show a four stage development process initiation over equatorial africa rapid intensification when passing through the indian ocean mature evolution characterized by a weakening in the maritime continent and redevelopment over the western pacific and dissipation near the date line in moderate events or emanation from the equator toward north america and southeastern pacific in strong events a noticeable feature in vertical structure is that the 850 mb convergence leads convection and midtropospheric upward motion by about 30 degrees longitude in both developing and mature phases equatorial upper lower level easterly westerly anomalies and associated twin anomalous anticyclonic cyclonic circulation an

yanai waves in the western equatorial indian ocean 1 observations and models have shown the presence of intraseasonal fluctuations in 20 30 day and 10 20 day bands in the equatorial indian ocean west of 60 e weio their spatial and temporal structures characterize them as yanai waves which we label low frequency lfyw and high frequency hfyw yanai waves respectively we explore the dynamics of these intraseasonal signals using an ocean general circulation model modular ocean model and a linear continuously stratified model yanai waves are forced by the meridional wind y everywhere in the weio most strongly during the monsoon seasons they are forced both directly in the interior ocean and by reflection of the interior response from the western boundary interference between the interior and boundary responses results in a complex surface pattern that propagates eastward and has nodes yanai waves are also forced by instabilities primarily during june july in a region offshore from the western boundary 52 55 e at that time eddies generated by barotropic instability of the southern gyre are advected southward to the equator there they generate a westward propagating cross equatorial flow field veq with a wave number frequency spectrum that fits the dispersion relation of a number of yanai waves and these waves are efficiently excited typically yanai waves associated with several baroclinic modes are excited by both wind and eddy forcing and typically they superpose to create beams that carry energy vertically and eastward along ray paths the same processes generate lfyws and hfyws and hence their responses are similar differences are traceable to the property that hfyws have longer wavelengths than lfyws for each baroclinic mode

origins of eddy kinetic energy in the bay of bengal by analyzing satellite observational data and ocean general circulation model experiments this study investigates the key processes that determine the spatial distribution and seasonality of intraseasonal eddy kinetic energy eke within the bay of bengal bob it is revealed that a complicated mechanism involving both local and remote wind forcing and ocean internal instability is responsible for the generation and modulation of eke in this region high level eke mainly resides in four regions east of sri lanka region 1 the western bob region 2 northwest of sumatra region 3 and the coastal rim of the bob region 4 the high eke levels in regions 1 and 2 are predominantly produced by ocean internal instability which contributes 90 and 79 respectively prominent seasonality is also observed in these two regions with higher eke levels in boreal spring and fall due to enhanced instability of the east indian coast current and the southwest monsoon current respectively in contrast ocean internal instability contributes 49 and 52 of the total eke in regions 3 and 4 respectively whereas the atmospheric forcing of intraseasonal oscillations isos also plays an important role isos produce eke mainly through wind stress involving both the remote effect of equatorial winds and the local effect of monsoonal winds equatorial origin wave signals significantly enhance the eke levels in regions 3 and 4 in the form of reflected rossby waves and coastal kelvin waves respectively the local wind forcing effect through ekman pumping also has a significant contribution in regions 3 and 4 24 and 22 respectively

oceanic impetus for convective onset of the madden julian oscillation in the western indian ocean abstracta theory for intraseasonal atmosphere ocean atmosphere feedback is supported whereby oceanic equatorial rossby waves are partly forced in the eastern indian ocean by the madden julian oscillation mjo reemerge in the western indian ocean 70 days later and force large scale convergence in the atmospheric boundary layer that precedes mjo deep convection downwelling equatorial rossby waves permit high sea surface temperature sst and enhance meridional and zonal sst gradients that generate convergent circulations in the atmospheric boundary layer the magnitude of the sst and sst gradient increases are 0 25 c and 1 5 c mm 1 1 megameter is equal to 1000 km respectively the atmospheric circulations driven by the sst gradient are estimated to be responsible for up to 45 of the intraseasonal boundary layer convergence observed in the western indian ocean the sst induced boundary layer convergence maximizes 3 4 days prior to the convective maximum and is hypothesized to serve as a trigger for

southern bay of bengal currents and salinity intrusions during the northeast monsoon shipboard velocity and hydrographic profiles collected in december 2013 along with drifter observations satellite altimetry global ocean nowcast forecast products and coupled model simulations were used to examine the circulation in the southern bay of bengal as part of ongoing international research efforts in the region the observations captured the southward flowing east india coastal current eicc off southeast india and east of sri lanka the eicc was approximately 100 km wide with speeds exceeding 1 m s 1 in the upper 75 m east of the eicc a subsurface intensified 300 km wide northward current was observed with maximum speeds as high as 1 m s 1 between 50 m and 75 m the eicc moved low salinity water out of the bay and the subsurface northward flow carried high salinity water into the bay during typical northeast monsoon conditions during a time period when the central equatorial indian ocean was experiencing a westerly wind burst related to the madden julian oscillation mjo event while the northward subsurface high salinity flow has previously been observed during the southwest monsoon it was observed during the northeast monsoon the observations are consistent with northward high salinity subsurface flow in numerical model solutions the analysis suggests that direct forcing along the equator may play a significant role for high salinity intrusions east of sri lanka

creep behavior of slip zone soil of the majiagou landslide in the three gorges area the creep properties of slip zone soil are critical to deformation prediction and slope stability analysis a series of triaxial drained creep tests were conducted on the slip band soil from a creeping landslide the results indicate that soil creep occurs in two stages with confining and deviatoric stresses being critical factors the long term strength of the soil was estimated to be 60 75 of the conventional strength according to the isochronous curves the soil creep characteristics were used to predict the creep strain using both the burgers and the singh mitchell model and large discrepancies were found between the predicted strain and test results accordingly a new empirical model based on the morgan mercer flodin growth model has been developed to describe the creep behavior of gravely clay in the slip zone four parameters of this model are estimated by nonlinear regression the deformations predicted by this model are in reasonable agreement with experimental data

origin of intraseasonal variability of circulation in the tropical central indian ocean observed upper ocean currents south of sri lanka exhibit large irregular fluctuations with periods of days to weeks an ocean model driven by daily surface winds is able to reproduce the observed fluctuations we find from model experiments that low frequency 30 50 day intraseasonal variability isv arises when rossby waves radiated from the eastern boundary are amplified by hydrodynamic instability in the eastern and central indian ocean high frequency 10 15 day isv is forced directly by isv of the wind field in the eastern indian ocean in spite of the contribution from instability the ocean circulation south of sri lanka is a deterministic response to wind forcing

variability of zonal currents in the eastern equatorial indian ocean on seasonal to interannual time scales this study examines equatorial zonal current variations in the upper layers of eastern indian ocean in relation to variations in the indian ocean dipole iod the analysis utilizes data from the research moored array for african asian australian monsoon analysis and prediction rama and the european centre for medium range weather forecasts ocean reanalysis system 4 ecmwf oras4 surface currents are characterized by semiannual eastward flowing wyrtki jets along the equator in boreal spring and fall forced by westerly monsoon transition winds the fall jet intensifies during negative iod niod events when westerlies are anomalously strong but significantly weakens during positive iod piod events when westerlies are anomalously weak as zonal wind stress weakens during piod events sea surface height becomes unusually low in the eastern basin and high in the west setting up an anomalous pressure force that drives increased eastward transport in the thermocline opposite tendencies are evident during niod events in response to intensified equatorial westerlies current transport adjustments to anomalous zonal wind forcing during iod events extend into the following year consistent with the cycling of equatorial wave energy around the basin a surface layer mass budget calculation for the eastern sea surface temperature sst pole of the iod indicates upwelling of 2 9 0 7 sv during normal periods increasing by 40 50 during piod events and reducing effectively to zero during niod events iod related variations in wyrtki jet and thermocline transports are major influences on these upwelling rates and associated water mass transformations which vary consistently with sst changes

creep and failure of slopes in clays the accumulated experience on slope stability is reviewed with due consideration to the time dependent behaviour of natural clays prior to failure a consistent picture of the behaviour of both man

strong intraseasonal variability of meridional currents near 5 n in the eastern indian ocean characteristics and causes abstractthis paper reports on strong intraseasonal upper ocean meridional currents observed in the indian ocean between the bay of bengal bob and the equator and elucidates the underlying physical processes responsible for them in situ measurements from a subsurface mooring at 5 n 90 5 e reveal strong intraseasonal variability of the meridional current with an amplitude of 0 4 m s 1 and a typical period of 30 50 days in the upper 150 m which by far exceeds the magnitudes of the mean flow and seasonal cycle such prominent intraseasonal variability is however not seen in zonal current at the same location further analysis suggests that the observed intraseasonal flows are closely associated with westward propagating eddylike sea surface height anomalies sshas along 5 n the eddylike sshas are largely manifestations of symmetric rossby waves which result primarily from intraseasonal wind stress forcing in the equatorial waveguide and reflection of the equatorial kelvin waves at the eastern bou

slow variability in the equatorial west central pacific in relation to enso abstract six years of upper ocean velocity temperature and surface wind data collected in the west central pacific at 0 170 w reveal a slow ocean dynamical mode associated with the el nino southern oscillation enso latent and sensible heat flux calculations using the basin wide tropical atmosphere ocean tao array data show a coincident slow ocean atmosphere thermodynamical mode beginning with the la nina conditions in 1988 through the peak el nino conditions in 1992 the equatorial undercurrent euc speed decreased along with the surface zonal wind stress and the zonal pressure gradient simultaneous with these were increasing trends in the richardson number above the euc core and in sea surface temperature sst after peak warming was achieved the variations in all of these quantities reversed in a movement toward their previous la nina conditions as this evolved within the ocean the sensible and latent heat fluxes increased with large values emanating eastward from the western pacific the