westward propagation of latitudinal asymmetry in a coupled ocean atmosphere model abstract hemispheric asymmetries of continental geometry have long been speculated to be the cause of the northern hemisphere position of the intertropical convergence zone over the central and eastern pacific it is unknown however how the effects of continental asymmetries are transmitted to and felt by the central pacific thousands of kilometers away this paper proposes a transmitter mechanism by investigating the response of a coupled ocean atmospheric model to a symmetry breaking force by the american continents the model treats land forcing implicitly as an eastern boundary condition in the absence of oceanic feedback the model response to the eastern boundary forcing is tightly trapped and confined to a small longitudinal extent off the coast whereas the climate over the interior ocean is symmetric about the equator ocean atmosphere coupling greatly enhances the transmissibility of the effects of the land forcing establishing large latitudinal asymmetry over a great zonal extent a westwar

metallogeny of the northern norrbotten ore province northern fennoscandian shield with emphasis on iocg and apatite iron ore deposits the northern norrbotten ore province in northernmost sweden includes the type localities for kiruna type apatite iron deposits and has been the focus for intense exploration and research related to

the annual cycle in equatorial convection and sea surface temperature abstract the coupled atmosphere ocean system in the equatorial eastern pacific and atlantic exhibits a distinct annual cycle that is reflected in contrasting conditions at the times of the two equinoxes the contrasts are so strong that they dominate the annual march of zonally averaged outgoing longwave radiation for the equatorial belt the march equinox corresponds to the warm season when the equatorial cold tongues in the eastern pacific and atlantic are absent with the onset of summer monsoon convection over colombia central america and west africa in may june northward surface winds strengthen over the eastern pacific and atlantic the equatorial cold tongues reappear and the marine convection shifts from the equatorial belt to the intertropical convergence zones itczs along 8 n as the northern summer program the itczs remain strong and shift northward to new 10 n while sea surface temperature sst continues to drop over the cold tongues and the southern tropics perhaps in response to the

modulation of equatorial turbulence by a tropical instability wave 1 strong modulation of turbulent mixing by a westward propagating tropical instability wave tiw was observed in the stratified shear layer between the equatorial undercurrent euc and the surface mixed layer during october and november 2008 at 0 n 140 w the unique deep diurnal cycle mixing in the stratified layer beneath the equatorial cold tongue was observed where nighttime turbulent mixing was a factor of 10 greater than during daytime the turbulent kinetic energy dissipation rate e was 10 6 w kg 1 and the turbulent heat flux was 500 w m 2 at least 5 10 times greater than observed previously in the central equatorial pacific turbulence mixing varied significantly during the four distinct phases of the meridional flow associated with the tiw observations during the northward to southward transition recorded the largest values of reduced shear squared the thickest nighttime surface mixed layer the deepest penetration of the deep cycle turbulence and the largest turbulent heat flux and largest integrated e in the deep cycle layer dcl during steady southward flow the depth of the bases of the nighttime surface mixed layer and of the dcl were the shallowest a 50 m thick layer of strong turbulence was observed immediately above the euc core during the northward to southward and steady southward phases here the average e exceeded 10 6 w kg 1 the eddy diffusivity exceeded 10 3 m2 s 1 and the turbulent heat flux was 500 w m 2 to parameterize mixing in the central equatorial pacific accurately numerical models must simulate the enhancement of mixing associated with tiws and also the variability of mixing in different tiw phases

geochemical evidence for the geotectonic setting of early proterozoic metavolcanic sequences in lapland systematic geochemical study of early proterozoic metavolcanic rocks from the northern part of the baltic shield supports the concept that a complex mosaic of continental masses volcanic arcs and marginal basins were welded into one cratonic massif during the svecokarelian orogeny 1900 1750 ma in the north in finnmark and northern norrbotten tholeiitic metabasalts together with thick shallow water clastic metasediments form the main part of the karelian supracrustal sequences which in turn overlie archaean basement the trace element signatures of these metabasalts are comparable to those of post palaeozoic continental tholeiites which erupted in zones of lithosphere attenuation and which suffered contamination by sialic crust it is not however possible to determine by geochemistry alone whether the continental rift basin in question lay in an intraplate or back arc setting metabasalts with a volcanic arc geochemical signature become an increasingly important component of supracrustal sequences as the diffuse southern margin of the karelian continent is approached in the skellefte field an ensialic volcanic arc developed and fed considerable quantities of immature clastic sediment into the deep water norrland geosyncline which may have been fully oceanic in character subduction magmatism continued during the svecokarelian orogeny giving rise to synorogenic metavolcanic suites such as the kiruna porphyries the evidence for marked spatial variation of magmatic activity in the early proterozoic is in contrast to the rather monotonous pattern of greenstone belt development reported from the archaean we believe that this spatial variability is a consequence of geotectonic processes similar to those of modern day plate tectonics and present a plate tectonic model for the early proterozoic development of the baltic shield

attribution and impacts of upper ocean biases in ccsm3 the largest and potentially most important ocean near surface biases are examined in the community climate system model coupled simulation of present day conditions they are attributed to problems in the component models of the ocean or atmosphere or both tropical biases in sea surface salinity sss are associated with precipitation errors with the most striking being a band of excess rainfall across the south pacific at about 8 s cooler than observed equatorial pacific sea surface temperature sst is necessary to control a potentially catastrophic positive feedback involving precipitation along the equator the strength of the wind driven gyres and interbasin exchange is in reasonable agreement with observations despite the generally too strong near surface winds however the winds drive far too much transport through drake passage 190 sv 1 sv 10 6 m 3 s 1 but with little effect on sst and sss problems with the width separation and location of western boundary currents and their extensions create large correlated sst and sss biases in midlatitudes ocean model deficiencies are suspected because similar signals are seen in uncoupled ocean solutions but there is no evidence of serious remote impacts the seasonal cycles of sst and winds in the equatorial pacific are not well represented and numerical experiments suggest that these problems are initiated by the coupling of either or both wind components the largest mean sst biases develop along the eastern boundaries of subtropical gyres and the overall coupled model response is found to be linear in the south atlantic surface currents advect these biases across much of the tropical basin significant precipitation responses are found both in the northwest indian ocean and locally where the net result is the loss of an identifiable atlantic intertropical convergence zone which can be regained by controlling the coastal temperatures and salinities biases off south america and baja california are shown to significantly degrade precipitation across the pacific subsurface ocean properties on both sides of the equator and the seasonal cycle of equatorial sst in the eastern pacific these signals extend beyond the reach of surface currents so connections via the atmosphere and subsurface ocean are implicated other experimental results indicate that the local atmospheric forcing is only part of the problem along eastern boundaries with the representation of ocean upwelling another likely contributor

why the itcz is mostly north of the equator abstract although the distribution of sunshine is symmetrical about the equator the earth s climate is not climatic asymmetries are prominent in the eastern tropical pacific and atlantic oceans where the regions of maximum sea surface temperature convective cloud cover and rainfall are north of the equator this is the result of two sets of factors interactions between the ocean and atmosphere that are capable of converting symmetry into asymmetry and the geometries of the continents that determine in which longitudes the interactions are effective and in which hemisphere the warmest waters and the intertropical convergence zone are located the ocean atmosphere interactions are most effective where the thermocline is shallow because the winds can readily affect sea surface temperatures in such regions the thermocline happens to shoal in the eastern equatorial pacific and atlantic but not in the eastern indian ocean because easterly trade winds prevail over the tropical atlantic and pacific wher

persistent nature of secondary diurnal modes of precipitation over oceanic and continental regimes abstract this investigation seeks a better understanding of the assorted mechanisms controlling the global distribution of diurnal precipitation variability based on the use of the tropical rainfall measuring mission trmm microwave radiometer and radar data the horizontal distributions of precipitation s diurnal cycle are derived from 8 yr of trmm microwave imager tmi and precipitation radar pr measurements involving three trmm standard rain retrieval algorithms the resultant distributions are analyzed at various spatiotemporal scales the results reveal both the prominent and expected late evening le to early morning em precipitation maxima over oceans and the counterpart prominent and expected mid to late afternoon mla maxima over continents moreover and not generally recognized the results reveal a widespread distribution of secondary maxima which generally mirror their counterpart regime s behavior occurring over both oceans and continents that is many ocean regions exhibit clear

the tropical precipitation response to andes topography and ocean heat fluxes in an aquaplanet model this aquaplanet modeling study using the geophysical fluid dynamics laboratory atmospheric model version 2 1 gfdl am2 1 examines how ocean energy transport and topography influence the location of tropical precipitation addingrealistic andes topographyregionally displaces tropical rainfallfromthe equator into the northern hemisphere even when the wind evaporation feedback is disabled the relative importance of the andes compared to the asymmetric hemispheric heating of the atmosphere by ocean transport is examined by including idealized and realistic zonally averaged surface heat fluxes also known as q fluxes in the slab ocean a hemispherically asymmetric q flux displaces the tropical rainfall toward the hemisphere receiving the greatest heating by the ocean the zonal mean displacement of rainfall is greater in simulations with a realistic q flux than with a realistic andes topography simulations that add both a q flux and topography displace rainfallfarthertothenorthintheregion1208tothewestoftheandesthaninsimulationsthatonlyhaveaqflux cloud and clear sky radiative feedbacks in the tropics and subtropics of this model both act to amplify the energy flux and the precipitation response to a given hemispheric asymmetry in oceanic forcing

processes in the pacific la nina onset triggered by the atlantic nino previous observational and model studies have shown that a warm cold event in the equatorial atlantic during the boreal summer are related to the development of a pacific la nina el nino event that is fully developed in the following winter although the connection takes place via atmospheric bridge the processes at work have not been clarified for such a remote and lagged relationship the present paper uses a partially coupled atmosphere ocean model to infer a mechanism by which a pacific el nino event can be developed in this way enhanced equatorial convection in the equatorial atlantic during a warm event results in enhanced subsidence and surface wind divergence over the equatorial pacific around the dateline this wind anomaly contributes to pile up water in the western equatorial pacific triggering a perturbation in the depth of the oceanic thermocline which propagates eastward as an equatorial kelvin wave from autumn to winter the thermocline shallowing as the wave propagates allows for cooling of the oceanic mixed layer through anomalous temperature advection by anomalous zonal currents and by mean vertical entrainment velocity zonal advective and thermocline feedbacks reinforce the surface winds anomalies over the central eastern equatorial pacific setting up the conditions for the development of a cold event in this ocean the sequence during an atlantic cold event is similar with the appropriate change in signs these findings are relevant to enso predictability at seasonal timescales

manifestation of remote response over the equatorial pacific in a climate model 1 in this paper we examine the simulations over the tropical pacific ocean from long term simulations of two different versions of the center for ocean land atmosphere studies cola coupled climate model that have a different global distribution of the inversion clouds we find that subtle changes made to the numerics of an empirical parameterization of the inversion clouds can result in a significant change in the coupled climate of the equatorial pacific ocean in one coupled simulation of this study we enforce a simple linear spatial filtering of the diagnostic inversion clouds to ameliorate its spatial incoherency as a result of the gibbs effect while in the other we conduct no such filtering it is found from the comparison of these two simulations that changing the distribution of the shallow inversion clouds prevalent in the subsidence region of the subtropical high over the eastern oceans in this manner has a direct bearing on the surface wind stress through surface pressure modifications the sst in the warm pool region responds to this modulation of the wind stress thus affecting the convective activity over the warm pool region and also the large scale walker and hadley circulation the interannual variability of sst in the eastern equatorial pacific ocean is also modulated by this change to the inversion clouds consequently this sensitivity has a bearing on the midlatitude height response the same set of two experiments were conducted with the respective versions of the atmosphere general circulation model uncoupled to the ocean general circulation model but forced with observed sst to demonstrate that this sensitivity of the mean climate of the equatorial pacific ocean is unique to the coupled climate model where atmosphere ocean and land interact therefore a strong case is made for adopting coupled ocean land atmosphere framework to develop climate models as against the usual practice of developing component models independent of each other

a geochemical model of mid ocean ridge magma chambers abstract a computer model of mid ocean ridge basalt generation using trace element geochemistry has been developed the model simulates a periodically replenished continually cooled and fractionated magma chamber with periodic lava extrusion primitive basalts from the ocean floor are used to generate likely evolution paths for the magma chamber the steady state variant of this model has led to the isolation of several variables which critically affect the basalt composition although the fraction of cumulates is an important parameter other variables such as the volume of incoming magma batches their frequency and the volume of the mixing cell play a critical part especially on slow spreading ridges the growing magma chamber model uses random number generators to simulate the initiation and growth of a chamber this model predicts a rapid increase in incompatible element concentrations immediately after chamber initiation on a fast spreading ridge this would occur in situations such as propagating rifts and may help in the understanding of ferrobasalt generation

influences of continental monsoons and air sea coupling on the climate of the equatorial pacific abstract an air sea land coupled model of intermediate complexity was used to reveal the important roles of air sea coupling and adjacent continental monsoons i e american monsoons and asian australian monsoons on the annual cycle and mean state of the equatorial pacific excluding the effects of adjacent continental monsoons the simulated mean sst in the western pacific displays a warm bias the sst seasonal cycle exhibits an erroneous dominant annual component in the western pacific and insufficient strength and a 2 month phase delay in the equatorial eastern pacific the air sea coupling alone cannot sustain the full strength of the annual marches of the itcz cold tongue complex this is because the diabatic heating associated with the itcz rainfall generates both a southerly and a westerly component to its equatorward side while the southerly cools the cold tongue establishing a positive feedback to enhance the itcz and the equatorial westerly favors cold tongue warming inducing a negative fe

observations of annual and el nino thermal and flow variations at 0 110 w and 0 95 w during 1980 1985 moored measurements of the surface wind and of the current and temperature fields within the uppermost 250 m were recorded from march 1980 to september 1985 at 0 110 w and from july 1981 to november 1983 at 0 95 w at these sites the annual mean thicknesses of the equatorial undercurrent euc and of the surface portion of the south equatorial current sec were about 200 m and 20 m respectively the annual mean euc core speed was 0 9 m s 1 annual cycles of temperature and zonal current at 110 w were most distinctive near the surface at nominal depths of 15 m and 47 5 m the average annual amplitudes were 1 5 c and 0 5 m s 1 at about 100 m the annual amplitudes were about 0 5 c and 0 10 m s 1 at 15 m the annual mean zonal current was 0 05 m s 1 which was not representative of the monthly mean zonal current in april the monthly mean direction was eastward and in october it was westward with speeds of about 0 5 m s 1 in both months warmer water occurred in april and colder water in october the direction of the zonal wind component was westward throughout the year and the annual amplitude of the zonal wind was only about 2 5 times larger than that of the zonal current the average amplitude of the annual cycle of the meridional current component was less than 0 05 m s 1 and not distinguishable from year to year monthly mean variations monthly mean anomalous or el nino currents at 110 w were defined as the difference between the observations and the annual cycle during the august december 1982 onset phase of el nino the strength of the normally westward flowing near surface sec was greatly reduced to near zero speed by an el nino eastward flowing zonal current of about 0 3 m s 1 the largest vertically averaged 15 250 m zonal current anomaly 0 5 m s 1 occurred in january and february 1983 and represented a substantial decrease in the eastward transport of the euc causing a disappearance of the undercurrent the duration of the euc disappearance was longer at 95 w than at 110 w a surface intensified eastward jet with a maximum daily speed of 1 75 m s 1 at 15 m occurred in may 1983 at 110 w but not at 95 w a massive redistribution of heat throughout the mixed layer and thermocline was associated with the 1982 1983 el nino beginning in august 1982 the thermocline at 110 w and 95 w sank 100 m reaching its maximum depth in december 1982 temperatures at 100 m and 150 m which normally were about 15 c and 14 c reached 27 5 c and 22 5 c the time rate of change of the 15 to 200 m heat content was 500 w m 2 during the august december 1982 warming phase and 460 w m 2 during the january february 1983 subsurface cooling phase the euc disappeared during the subsurface cooling phase a second less intensive mixed layer deepening occurred in may 1983 at 95 w but not at 110 w

meridional structure of the seasonally varying mixed layer temperature balance in the eastern tropical pacific abstract the eastern tropical pacific ocean is important climatically because of its influence on the el nino southern oscillation enso cycle and the american monsoon accurate prediction of these phenomena requires a better understanding of the background climatological conditions on which seasonal to interannual time scale anomalies develop in the region this study addresses the processes responsible for the seasonal cycle of sea surface temperature sst in the eastern tropical pacific using 3 yr april 2000 march 2003 of moored buoy and satellite data between 8 s and 12 n along 95 w results indicate that at all latitudes surface heat fluxes are important in the mixed layer temperature balance at 8 s in a region of relatively deep mean thermocline and mixed layer local storage of heat crossing the air sea interface accounts for much of the seasonal cycle in sst in the equatorial cold tongue and the intertropical convergence zone where mean upwelling leads to relatively thin mixed layers ver

equatorial atlantic variability and its relation to mean state biases in cmip5 coupled general circulation model gcm simulations participating in the coupled model intercomparison project phase 5 cmip5 are analyzed with respect to their performance in the equatorial atlantic in terms of the mean state 29 out of 33 models examined continue to suffer from serious biases including an annual mean zonal equatorial sst gradient whose sign is opposite to observations westerly surface wind biases in boreal spring play an important role in the reversed sst gradient by deepening the thermocline in the eastern equatorial atlantic and thus reducing upwelling efficiency and sst cooling in the following months both magnitude and seasonal evolution of the biases are very similar to what was found previously for cmip3 models indicating that improvements have only been modest the weaker than observed equatorial easterlies are also simulated by atmospheric gcms forced with observed sst they are related to both continental convection and the latitudinal position of the intertropical convergence zone itcz particularly the latter has a strong influence on equatorial zonal winds in both the seasonal cycle and interannual variability the dependence of equatorial easterlies on itcz latitude shows a marked asymmetry from the equator to 15 n the equatorial easterlies intensify approximately linearly with itcz latitude when the itcz is south of the equator on the other hand the equatorial easterlies are uniformly weak despite serious mean state biases several models are able to capture some aspects of the equatorial mode of interannual sst variability including amplitude pattern phase locking to boreal summer and duration of events the latitudinal position of the boreal spring itcz through its influence on equatorial surface winds appears to play an important role in initiating warm events

interhemispheric influence of the atlantic warm pool on the southeastern pacific abstract the atlantic warm pool awp is a large body of warm water comprising the gulf of mexico caribbean sea and western tropical north atlantic the awp can vary on seasonal interannual and multidecadal time scales the maximum awp size is in the boreal late summer and early fall with the largest extent in the year being about 3 times the smallest one the awp alternates with the amazon basin in south america as the seasonal heating source for circulations of the hadley and walker type in the western hemisphere during the boreal summer fall a strong hadley type circulation is established with ascending motion over the awp and subsidence over the southeastern tropical pacific this is accompanied by equatorward flow in the lower troposphere over the southeastern tropical pacific as dynamically required by the sverdrup vorticity balance it is shown by analyses of observational data and ncar community atmospheric model simulations that an anomalously large small awp during the boreal summer f

geochemistry and tectonic setting of lewisian clastic metasediments from the early proterozoic loch maree group of gairloch nw scotland abstract the early proterozoic 2 0 ga loch maree group lmg of the lewisian complex consists of a supracrustal sequence of metasedimentary schists and associated tholeiitic metavolcanic amphibolites within the archaean basement the metasediments comprise three main mapped units the flowerdale schists kerrysdale schists and charlestown schists together with numerous narrower bands the dominant clastic metasediments within the schist units semipelites and psammites are chemically distinguished as a series of greywackes and lithic sandstones with variable lil and transition element abundances fractionated ree patterns and overall compositions similar to paas three chemical groups are recognized whose range of composition largely reflects the mixing between two main source components lewisian gneissose basement with an intermediate acid continental crust composition and local rift related amphibolites with a primitive tholeiitic composition which also incorporates components not preserved within the lmg the geochemistry of the clastic metasediments confirms a previous tectonic model for the lmg as an intracontinental extensional rift receiving clastic detritus from the adjacent uplifted basement as well as from internal volcanogenic sources

formation and variability of a northerly itcz in a hybrid coupled agcm continental forcing and oceanic atmospheric feedback abstract despite the equatorial symmetry of the annual mean insolation the intertropical convergence zone itcz and the collocated band of high sea surface temperature sst assume perennial northern latitudes over the eastern pacific and atlantic an atmospheric general circulation model is coupled with an intermediate ocean model to study continental forcing and oceanic atmospheric interaction that act to break the equatorial symmetry the model reaches a statistically symmetric mean state under perfectly symmetric conditions with the continental coasts running along meridians when a bulge of landmass is added to the eastern continent north of the equator it initiates a coupled ocean atmosphere wave front that propagates westward across the ocean basin cooling the ocean surface and suppressing deep convection on and south of the equator as a result the itcz shifts into the northern hemisphere in contrast to this basinwide response little latitudinal asymmetry develops in the coupled model when

the south atlantic anticyclone as a key player for the representation of the tropical atlantic climate in coupled climate models the key role of the south atlantic anticyclone saa on the seasonal cycle of the tropical atlantic is investigated with a regionally coupled atmosphere ocean model for two different coupled domains both domains include the equatorial atlantic and a large portion of the northern tropical atlantic but one extends southward and the other northwestward the saa is simulated as internal model variability in the former and is prescribed as external forcing in the latter in the first case the model shows significant warm biases in sea surface temperature sst in the angola benguela front zone if the saa is externally prescribed these biases are substantially reduced the biases are both of oceanic and atmospheric origin and are influenced by ocean atmosphere interactions in coupled runs the strong sst austral summer biases are associated with a weaker saa which weakens the winds over the southeastern tropical atlantic deepens the thermocline and prevents the local coastal upwelling of colder water the biases in the basins interior in this season could be related to the advection and eddy transport of the coastal warm anomalies in winter the deeper thermocline and atmospheric fluxes are probably the main biases sources biases in incoming solar radiation and thus cloudiness seem to be a secondary effect only observed in austral winter we conclude that the external prescription of the saa south of 20 s improves the simulation of the seasonal cycle over the tropical atlantic revealing the fundamental role of this anticyclone in shaping the climate over this region

processes leading to double intertropical convergence zone bias in cesm1 cam5 abstractthe double intertropical convergence zone itcz bias in the eastern pacific in the community earth system model version 1 with community atmosphere model version 5 cesm1 cam5 is diagnosed in cam5 standalone the northern itcz is associated with inertial instability and the southern itcz is thermally forced after air sea coupling the processes on both hemispheres are switched because the spatial pattern of sea surface temperature sst is changed biases occur during boreal spring in both cam5 and the ocean model in cam5 alone weaker than observed equatorial easterly in the tropical eastern south pacific leads to weaker evaporation and an increase in local sst the shallow meridional circulation overly converges in the same region in the cam5 standalone simulation the planetary boundary layer and middle troposphere are too humid and the large scale subsidence is too weak at the middle levels these biases may result from excessive shallow convection behavior in cam5 the extra moisture wou

toward mitigating the double itcz problem in ncar ccsm3 1 the appearance of a spurious inter tropical convergence zone south of the equator in the eastern and central equatorial pacific in addition to the observed one north of the equator is a common problem in coupled global climate models the present study investigates this double itcz problem in the ncar ccsm3 it shows that use of a modified zhang mcfarlane convection scheme significantly mitigates the double itcz problem in boreal summer this has a profound impact on the simulated sea surface temperature through cloud radiative forcing feedback both the warm bias in the southern itcz region and the cold bias in the cold tongue over the equator are reduced examination of the time series of precipitation sst and surface energy fluxes shows that depending on the convection parameterization used double or single itcz emerges quickly within the first few months after the model start

fast sst error growth in the southeast pacific ocean comparison between high and low resolution ccsm4 retrospective forecasts sea surface temperature errors that develop after 1 week are investigated as a function of resolution using retrospective forecasts from the community climate system model one version resolves the ocean and atmosphere to approximately 1 while the second version resolves the ocean to 0 1 and the atmosphere to 0 5 the forecasts are initialized on january 1 from 1982 to 2003 the spatial pattern of the pacific basin sea surface temperatures errors after 1 week is mostly similar at both resolutions with the exception of the coast of south america the coastal ocean surface cools within the higher resolution simulations but warms within the lower resolution simulations the difference in the ocean surface temperature is instead attributed to differing changes in the upwelling coastal upwelling increases within the higher resolution simulation increasing the lower tropospheric stability and encouraging the cloud cover in contrast the upwelling decreases within the lower resolution simulations at 27 s allowing the ocean surface to warm in spite of cooling from the atmosphere in both simulations the northward winds and surface currents weaken because the south pacific sea level pressure high moves westward the increased oceanic upwelling in the high resolution simulation is instead attributed to an increase in the westward zonal currents the high resolution model resolves the narrow humboldt current while the low resolution model does not this study demonstrates that the processes responsible for sst errors in eastern upwelling boundary current regions change when the oceanic grid spacing becomes fine enough to allow resolution of the oceanic boundary currents

impact of mountains on tropical circulation in two earth system models abstracttwo state of the art earth system models esms were used in an idealized experiment to explore the role of mountains in shaping earth s climate system similar to previous studies removing mountains from both esms results in the winds becoming more zonal and weaker indian and asian monsoon circulations however there are also broad changes to the walker circulation and el nino southern oscillation enso without orography convection moves across the entire equatorial indo pacific basin on interannual time scales enso has a stronger amplitude lower frequency and increased regularity a wider equatorial wind zone and changes to equatorial wind stress curl result in a colder cold tongue and a steeper equatorial thermocline across the pacific basin during la nina years anomalies associated with enso warm events are larger without mountains and have greater impact on the mean tropical climate than when mountains are present without mountains the centennial mean pacific walker circulation wea

variations of zonal currents in the central tropical pacific during 1970 to 1987 sea level and dynamic height measurements the annual and interannual variations of the major zonal currents of the central tropical pacific for the period 1970 1987 are described by analyzing two data sets sea level data from a few selected island stations and ship of opportunity expendable bathythermograph xbt observations the annual cycles of geostrophic surface current indices dynamic height or sea level difference between the ridge and the trough defining the current in the north equatorial current nec and north equatorial countercurrent necc are found to be in phase maxima in november to be strong and to explain about 50 of the total variance the annual cycle of volume transport relative to 400 dbar in the necc is also strong but nec volume transport has a weak annual cycle the discrepancy between the nec surface current and the transport is due to the variation of the surface current being larger than that of the deep currents the annual cycle of the transport of the south equatorial current sec is 6 months out of phase with that of the nec and necc phases of the annual cycles of the sea level and dynamic height indices of flow agree well in general but there are significant differences between the annual amplitudes of the two types of measurements these differences arise from a variety of sources dynamic height reference level assumptions longitudinal spacing of sea level gauges meridional resolution of sea level array and different signal to noise ratios for the two sets of indices the necc shows marked flow maxima during the peaks of the strong ninos of 1972 and 1982 which were followed by near disappearance of the current the following year these fluctuations are clearly present in both the surface current indices and the volume transport in 1976 and 1986 1987 moderate ninos the same pattern is not marked the el nino signal in nec transport is weak there was a strong rise of equatorial sea level during the early phases of the 1972 and 1982 ninos followed by a fall the next year this resulted in a decrease of the transport of the sec in the first year followed by an increase to a maximum during the second year the maximum coincides with a minimum in necc transport

mixed layer modeling in the east pacific warm pool during 2002 two vertical mixing models the modified dynamic instability model of price et al pwp and k profile parameterizaton kpp are used to analyze intraseasonal sea surface temperature sst variability in the northeast tropical pacific near the costa rica dome during boreal summer of 2002 anomalies in surface latent heat flux and shortwave radiation are the root cause of the three intraseasonal sst oscillations of order 1 c amplitude that occur during this time although surface stress variations have a significant impact on the third event a slab ocean model that uses observed monthly varying mixed layer depths and accounts for penetrating shortwave radiation appears to well simulate the first two sst oscillations but not the third the third oscillation is associated with small mixed layer depths 5 m forced by and acting with weak surface stresses and a stabilizing heat flux that cause a transient spike in sst of 2 c intraseasonal variations in freshwater flux due to precipitation and diurnal flux variability do not significantly impact these intraseasonal oscillations these results suggest that a slab ocean coupled to an atmospheric general circulation model as used in previous studies of east pacific intraseasonal variability may not be entirely adequate to realistically simulate sst variations further while most of the results from the pwp and kpp models are similar some important differences that emerge are discussed

palaeovolcanology and tectonic setting of a proterozoic metatholeiitic sequence near the baltic shield margin northern norway abstract the kvenvik greenstone formation 1500 m thick is a very well preserved 2 0 1 8 ga old sequence of morb type tholeiitic metabasaltic lavas and volcaniclastic rocks they were deposited as cyclically repeated couplets in a continental shallow water to terrestrial environment near the margin of the baltic shield the effusive facies comprise massive and amygdaloidal lava pillow lava pillow breccia and hyaloclastite volcaniclastic facies are ash and accretionary lapilli tuff lapilli tuff and tuffaceous sedimentary rocks lithofacies associations and primary structures in the tuffs indicate air fall base surge and pyroclastic flow deposits with little input of epiclastic material the prevalence of shallow water to subaerial emplacement throughout the kvenvik greenstone formation and correlative sequences to the south indicates deposition in a spasmodically subsiding basin almost certainly formed by taphrogenic tectonism the rifting may have been incidental to coeval plate convergence tectonism evidenced by calc alkalic magmatism in the repparfjord komagfjord area 50 100 km northeast of the kvenvik area

a satellite derived climatology of the itcz abstract this paper presents fundamental climatological characteristics of the intertropical convergence zone itcz in a simple concise manner using the highly reflective cloud hrc dataset this satellite derived dataset uses both visible and infrared observations to measure the frequency of occurrence of large scale convective systems over the global tropics at a 1 spatial resolution these dataset characteristics make the hrc particularly well suited for climatological analysis of the itcz because the dataset is based on estimates of organized deep convective cloud systems rather than observations of clouds as a whole and it provides the spatial resolution needed to identify thew large wale convective structures furthermore the dataset covers a time period extending nearly two decades which provides for a fairly robust climatology and the opportunity to examine seasonal and interannual variability of both the convection and the latitude of the itcz

the seasonal cycle over the tropical pacific in coupled ocean atmosphere general circulation models abstract the seasonal cycle over the tropical pacific simulated by 11 coupled ocean atmosphere general circulation models gcms is examined each model consists of a high resolution ocean gcm of either the tropical pacific or near global means coupled to a moderate or high resolution atmospheric gcm without the use of flux correction the seasonal behavior of sea surface temperature sst and eastern pacific rainfall is presented for each model the results show that current state of the art coupled gcms share important successes and troublesome systematic errors all 11 models are able to simulate the mean zonal gradient in sst at the equator over the central pacific the simulated equatorial cold tongue generally tends to be too strong too narrow and extend too far west ssts are generally too warm in a broad region west of peru and in a band near 10 s this is accompanied in some models by a double intertropical convergence zone itcz straddling the equator over the eastern pacific and in others

ocean atmosphere interaction and the tropical climatology part i the dangers of flux correction abstract this sequence of papers examines the role of dynamical feedbacks between the ocean and the atmosphere in determining features of the tropical climatology a stripped down intermediate coupled ocean atmosphere model is used to provide a prototype problem for the pacific basin here the authors contrast the fully coupled case with the case where flux correction is used to construct the climatology in the fully coupled case the climatology is determined largely by feedback mechanisms within the ocean basin winds driven by gradients of sea surface temperature sst within the basin interact with the ocean circulation to maintain sst gradients for all realistic cases these lead to a unique steady solution for the tropical climatology in the flux corrected case the artificially constructed climatology becomes unstable at sufficiently large coupling leading to multiple steady states as found in a number of coupled models using continuation methods we show that there is a topological change i

the dynamics of idealized convection schemes and their effect on the zonally averaged tropical circulation in this paper the effect of a simple convection scheme on the zonally averaged tropical general circulation is examined within an idealized moist gcm to obtain broad classifications of the influence of convection on the tropics this is accomplished with a simplified convection scheme in the style of betts and miller the scheme is utilized in a moist gcm with simplified physical parameterizations gray radiation with zonally symmetric slab mixed layer ocean boundary conditions comparisons are made with simulations without a convection scheme i e with large scale condensation lsc only with the moist convective adjustment mca parameterization and with various formulations and parameter sets with a simplified betts miller sbm scheme with the control run using the sbm scheme the tropics become quieter and less dependent on horizontal resolution as compared with the lsc or mca simulations the hadley circulation mass transport is significantly reduced with the sbm scheme as is the itcz precipitation an important factor determining this behavior is the parameterization of shallow convection without shallow convection the convection scheme is largely ineffective at preventing convection from occurring at the grid scale the sensitivities to convection scheme parameters are also examined the simulations are remarkably insensitive to the convective relaxation time and only mildly sensitive to the relative humidity of the reference profile provided significant large scale condensation is not allowed to occur the changes in the zonally averaged tropical circulation that occur in all the simulations are understood based on the convective criteria of the schemes and the gross moist stability of the atmosphere

an improved design method for the riprap of earthfill dams of large reservoirs since impounding of the various reservoirs of the la grande complex in northern quebec the riprap of several dams and dykes suffered some damage during the fifteen year period which followed a mandate was given to the societe d energie de la baie james sebj in january 1992 to review the riprap design and evaluate the necessary repairs the paper focuses on this work an improved design method for the riprap of earthfill dams of large reservoirs is proposed based on four years of intensive studies and fifteen years of field data large scale model tests with irregular waves completed the studies

rayleigh fractionation with continuous removal of liquid abstract in its simple form the rayleigh surface equilibrium fractionation equation is only valid for a closed system in which solid separates from liquid and no liquid is lost many natural systems particularly magma chambers lose liquid continuously as they fractionate here it is shown that evolution in such a system can if loss of liquid proceeds in a constant ratio to precipitation of solid be modelled by a modified rayleigh equation where the solid liquid distribution coefficient d is replaced by d q d 1 q 1 where q is the ratio of solid precipitated to liquid extracted this can be visualised as treating the liquid removed as an additional phase extracted during fractionation for which d 1 the effect of this is particularly important for incompatible elements where as d 0 d 1 q 1 so that when q 1 the most incompatible element gives d 0 5

spatial and temporal diversity of early proterozoic volcanic sequences comparisons between the baltic and laurentian shields abstract early proterozoic volcanic supracrustal sequences in the baltic shield exhibit considerable diversity in their geochemical composition sedimentary and metallogenetic associations the earliest volcanic sequences are calc alkaline associations whose age and mode of origin is poorly understood at present tholeiitic metabasalts erupted at about 2 2 2 0 ga form a significant component of lapponian and jatulian supracrustal sequences in the northern part of the shield these lavas were erupted in marine basins and rifts within archaean cratonic lithosphere ultramafic lavas are present but appear to be spatially restricted to certain supracrustal belts marginal to possible crustal suture zones e g the karasjok belt tholeiitic metabasalts of slightly younger age 1 96 ga form part of an ophiolitic association at jormua in north central finland other kalevian suites of similar age at outokumpu and in northern finland may have formed in marginal basins adjacent to a proterozoic ocean the svecofennian domain of central sweden and southern finland locally contains primitive oceanic arc like terranes representing a juvenile addition to the proterozoic crust most of the svecofennian complex is however composed of turbiditic sediments felsic calc alkaline volcanics dated at 1 92 1 87 ga and plutonic suites which reflect sedimentary and igneous reprocessing of the juvenile arc terranes the porphyry volcanics of norrbotten were subaerially erupted between 1 9 and 1 87 ga they reflect maturation of the svecofennian arc system to an andinotype continental margin terrestrial calc alkaline volcanism continued until 1 6 ga in the transscandinavian granite porphyry belt all the volcanic components of the classic wilson cycle have now been recognised in the baltic shield the early proterozoic history of which is thus readily explicable in terms of plate tectonic concepts in the laurentian shield tholeiitic metabasalts are associated with ultramafic lavas in the cape smith belt and elsewhere along the northern margin of the superior craton the ophiolitic association has recently been described from the cape smith belt the trans hudson and svecofennian belts are complex accretional orogens with comparable magmatic and tectonic histories pre grenville reconstructions suggest that the continuation of the transscandinavian granite porphyry belt is to be found in labrador and possibly in the southern part of the concealed mid continent region in the usa the numerous similarities between the two shields suggest they underwent a parallel and possible juxtaposed evolution in early proterozoic time

an early proterozoic ophiolite the jormua mafic ultramafic complex northeastern finland abstract the 1 96 ga old jormua complex comprises a fault bounded unit 2 5 20 km in the centre of the kainuu schist belt at the eastern margin of the early proterozoic svecokarelides the complex was dismembered and metamorphosed to lower amphibolite facies during the svecokarelian orogeny in the intact complex the basal unit was formed by serpentinites the middle unit of mafic dykes and the uppermost extrusive unit of basaltic pillow lavas gabbroic rocks are present as intrusive bodies in the serpentinites and narrow interdyke screens within the dyke unit trondhjemitic rocks occur as minor segregations in the gabbroic rocks or as cross cutting narrow dykes in the mafic dyke unit the dyke unit is locally composed exclusively of subparallel metabasalt and metadolerite dykes in places interdyke metagabbro and serpentinite screens are abundant well preserved chilled margins are common and many dykes are split and intruded by younger dykes the chemical composition of the serpentinites indicates derivation from harzburgitic dunitic mantle peridotites the gabbroic rocks which represent obvious tholeiitic cumulates show extreme differentiation similar to gabbros of the high ti ophiolites and gabbros dredged from present midocean ridges in chemistry the trondhjemitic rocks are close to granitic rocks from mid ocean ridges and high ti ophiolites the similar chemical composition of the dykes and lavas of the complex indicates that they are cogenetic both being tholeiitic metabasalts with chondrite normalized ree patterns ranging from slightly lree depleted to slightly lree enriched ones compared with modern rocks the jormua metabasalts most closely resemble transitional midocean ridge basalts it is suggested that the jormua complex and related mafic ultramafic bodies in eastern finland originated as divergent margin ophiolites concomitantly with the break up of the archaean craton in the extensional stage of the svecokarelian orogeny which culminated in the opening of a major ocean after 1 97 ga the tectonic emplacement of these ophiolites into their present locations occurred in connection with thrusting during the compressional stage of the orogeny about 1 9 ga ago

direct measurements of upper ocean currents and water properties across the tropical pacific during the 1990s abstract meridional sections of upper ocean zonal currents potential temperature and salinity are estimated at ten longitudes from 143 e to 95 w using conductivity temperature depth and acoustic doppler current profiler data from 172 synoptic sections taken in the tropical pacific between 138 e and 86 w mostly in the 1990s data reduction is carried out in a potential isopycnal and mixed layer framework to preserve a sharp pycnocline a mixed layer water property extrema and velocity extrema mean zonal currents potential temperatures and salinities are produced at each longitude the seasonal cycles of these fields are also estimated as well as a simple el nino southern oscillation enso cycle zonal sections along the equator are also presented properties of the near equatorial zonal currents including transports temperatures and salinities are estimated separately from the synoptic sections the seasonal cycles of these quantities and their correlations with the southern oscillation index are investigated the work is distinguished from most existing literature in that direct estimates of zonal velocity are combined with contemporaneous temperature and salinity data allowing trans pacific estimates of near equatorial current transports and properties including those of the northern branch of the south equatorial current the new guinea coastal undercurrent and the equatorial undercurrent

model study of reservoir riprap stability a series of large scale 1 15 experiments have been undertaken to assist the societe d energie de la baie james sebj in the development of new design guidelines for riprap the stability of revetments resting on 1 1 8 and 1 2 25 v h slopes is considered in an attempt to quantify the relative roles of stone size gradation and armour layer thickness these tests were undertaken with stone gradations varying from mmax mmin ranging from 1 to 10 and with armour layers both 2 2dn50 and 2 7dn50 thick

wind stress variations and interannual sea surface temperature anomalies in the eastern equatorial pacific abstract vertical advection of temperature is the primary mechanism by which el nino southern oscillation enso time scale sea surface temperature sst anomalies are generated in the eastern equatorial pacific variations in vertical advection are mediated primarily by remote wind forced thermocline displacements which control the temperature of water upwelled to the surface however during some enso events large wind stress variations occur in the eastern pacific that in principle should affect local upwelling rates the depth of the thermocline and sst in this study the impact of these wind stress variations on the eastern equatorial pacific is addressed using multiple linear regression analysis and a linear equatorial wave model the regression analysis indicates that a zonal wind stress anomaly of 0 01 n m 2 leads to approximately a 1 c sst anomaly over the nino 3 region 5 n 5 s 90 150 w due to changes in local upwelling rates wind stress variations of this magnitude occurred in the easte

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

seasonal variability in the equatorial pacific abstract five to nine years of observations from the tropical atmosphere ocean array in the tropical pacific are used to document the seasonal cycle of surface winds zonal currents sst thermocline depth and dynamic height along the equator the normally westward surface zonal current reverses direction in late boreal spring and early summer this seasonal variation in the zonal surface current propagates westward as do seasonal variations in the equatorial undercurrent and zonal surface winds at the equator at 5 n and 5 s the seasonal variations in the 20 c isotherm and dynamic height also propagate westward conversely at the equator in the eastern and central pacific the variations in 20 c isotherm depth and dynamic height propagate eastward these seasonal variations are interpreted by means of a simple dynamical model based on linear equatorial wave theory model results indicate that seasonal variability between 5 n and 5 s is dominated by wind forced equatorial kelvin waves and first meridi

simulation of enso with a global atmospheric gcm coupled to a high resolution tropical pacific ocean gcm abstract a global atmospheric general circulation model gcm coupled to an oceanic gcm that is dynamically active only in the tropical pacific simulates variability over a broad spectrum of frequencies even though the forcing the annual mean incoming solar radiation is steady of special interest is the simulation of a realistically irregular southern oscillation between warm el nino and cold la nina states its time scale is on the order of 5 years the spatial structure is strikingly different in the eastern and western halves of the ocean basin sea surface temperature changes have their largest amplitude in the central and eastern tropical pacific but the low frequency zonal wind fluctuations are displaced westward and are large over the western half of the basin these zonal wind anomalies are essentially confined to the band of latitudes 10 to 10 s so that they form a jet and have considerable latitudinal shear during el nino the associated curl contributes to a pair of pronounced minima in th

on the annual cycle of the eastern equatorial pacific abstract although the sun crosses the equator twice a year the eastern equatorial pacific has a pronounced annual cycle in sea surface temperature and in both components of the surface winds for example this is in contrast to the indian ocean and western pacific where a semiannual oscillation of the zonal wind is the dominant signal on the equator calculations with a relatively simple coupled ocean atmosphere model indicate that the principal reason for this phenomenon is the marked asymmetry relative to the equator of the time averaged climatic conditions in the eastern tropical pacific the important asymmetries are in surface winds oceanic currents and sea surface temperature the time averaged winds and currents have northward components at the equator and the warmest waters are north of the equator because of those asymmetries seasonally varying solar radiation that is strictly antisymmetric relative to the equator can force a response that has a symmetric component the amplitude of th

the maintenance of an equatorially asymmetric state in a hybrid coupled gcm abstract an ocean general circulation model is coupled with a simple atmosphere model to investigate the formation mechanism of the intertropical convergence zone in the eastern pacific which is observed in the northern hemisphere the coupled model develops an asymmetric state under conditions symmetric about the equator the zonal variation in equatorial upwelling leads to pronounced differences between the western and other parts of the ocean in the western warm water pool region where the cooling effect of the equatorial upwelling is suppressed both atmospheric and oceanic surface conditions are symmetric about the equator on the other hand in the central region where the upwelling cools the equatorial ocean a single itcz forms off the equator in the northern or southern hemisphere depending on the initial condition a strong contrast exists in the sea surface temperature sst between the hemispheres sst is much higher at the latitude of the itcz than that on the other side of the equator thi

volcanic and geochemical stratigraphy of the nussir group of arctic norway an early proterozoic greenstone suite the nussir group of west finnmark is a suite of metabasaltic lavas and tuffs about 1 8 km thick associated with continental and shallow marine sediments this assemblage is typical of karelian early proterozoic supracrustal sequences throughout northern norway and northernmost sweden primary textures are well preserved and permit the establishment of a volcanic stratigraphy for the nussir group the krokvatn formation is dominated by mafic aquagene tuffs while the overlying svartfjell formation is composed mainly of submarine pillow basalt petrographic evidence for the petrogenesis of the metabasalts is poor because of greenschist facies metamorphism during the svecokarelian orogeny c 1840 ma the earliest lavas have the most primitive compositions but subsequent flows exhibit strong enrichment in fe ti and incompatible elements as a consequence of extensive crystal fractionation the tholeiitic nature of the suite is confirmed by the trace element data the later lavas are more uniform and less evolved and are considered to represent steady state compositions produced by a periodically replenished tapped open system magma chamber the field relationships lithological and geochemical evidence suggest that the nussir group lavas were erupted in a submarine rift basin within continental crust they form part of an extensive tholeiitic magmatic province which occupied much of northern norway sweden and finland in the early proterozoic the tectonic environment of this province is poorly constrained by the geochemical data continental plateau basalt provinces such as the columbia river and karoo provide the closest phanerozoic geochemical analogues

on the genesis of the equatorial annual cycle abstract a linear theory is proposed that can explain both the period and the westward propagation of the equatorial annual cycles in the sst and zonal wind a coupled model linearized about a mean state of the air sea system is used this model allows the surface winds to directly change the sst through surface evaporation and vertical mixing in contrast to the formulation of the conventional air sea coupling models that emphasize the effects of winds on ocean dynamics it is demonstrated that the characteristics of the equatorial seasonal cycle including its period phase and amplitude are determined to a large extent by the mean state of the air sea coupling system the meridional wind which is specified here is the most important forcing for the annual cycle in sst suggesting that the equatorial annual cycle is the response to an annual solar forcing in the off equatorial regions

petrochemistry and tectonic significance of the highland border suite mafic rocks the metamorphosed mafic rocks of the ophiolitic highland border suite on arran and bute are of 2 types greenschist facies pillow lavas and epidote amphibolite facies hornblende schists respectively both types have been affected by post magmatic alteration processes including spilitization i e na enrichment coupled with ca depletion on the basis of 9immobile element9 chemistry and other criteria the mafic rocks are split into 2 magmatic groups a tholeiitic one which shows the effects of extensive low pressure fractionation e g fe and ti enrichment and a less fractionated alkaline group that contains relict al and ti rich clinopyroxenes the tholeiitic rocks are similar to modem ocean floor or marginal basin basalts and the alkaline rocks show affinities with 9within plate9 basalts this 9magma type9 and 9tectonic setting9 dichotomy is found at other highland border localities and is present in both the pillow lavas and hornblende schists the highland border suite mafic rocks may have formed as tholeiitic ocean basin crust upon which alkaline ocean island lavas had been erupted or alternatively as is suggested in this paper they may have formed during the early stages of development of a pre grampian marginal basin of cambrian or cambro ordovician age

epic 95 w observations of the eastern pacific atmospheric boundary layer from the cold tongue to the itcz abstract the atmospheric boundary layer abl along 95 w in the eastern equatorial pacific during boreal autumn is described using data from the east pacific investigation of climate epic 2001 with an emphasis on the evolution of the thermodynamic abl properties from the cold tongue to the cold advection region north of the sea surface temperature sst front surface sensible and latent heat fluxes and wind stresses between 1 s and 12 n are calculated from data from eight ncar c 130 research aircraft flights and from tropical atmosphere ocean tao buoys reduced surface wind speed and a 10 m s 1 jet at a height of 500 m are found over the equatorial cold tongue demonstrating the dependence of the surface wind speed on surface stability the abl exhibits a maximum in cloud cover on the north downwind side of the warm sst front at 1 3 n turbulent mixing driven by both surface buoyancy flux and radiative cooling at the cloud tops plays a significant role in maintaining the depth and structure of t

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

observations of 20 day period meridional current oscillations in the upper ocean along the pacific equator abstract prominent oscillations of the meridional current with a mean period of approximately 20 days have been observed in the upper ocean over several years from may 1979 to october 1985 using moored current measurements along the pacific equator at 95 110 124 140 w and 152 w as well as off but near the equator at 110 and 140 w the fluctuations are relatively narrowband 0 005 cpd in frequency a 95 statistically significant peak in power spectra of meridional current occurred at 110 124 and 140 w but not at 95 and 152 w where the spectral peaks were smaller the dominant wave period decreased by about 4 from 110 to 140 w maximum amplitude was measured at 124 w the amplitude above 80 m was maximum at the equator and decreased poleward from the equator at 15 m the annual averaged root mean square amplitude was about 20 5 cm s 1 and individual peak to trough values reached 150 cm s 1 the wave amplitude decreased with depth and the wave was essentially confined to the upper 80 m

monthly period oscillations in the pacific north equatorial countercurrent monthly period oscillations in temperature and velocity in the vicinity of the north equatorial countercurrent along 140 w are examined using moored time series data collected during 1988 1989 these oscillations which presumably derive their energy from instability of the large scale shear of the zonal equatorial current system are found to be energetic across a broad band of periods of about 15 50 days along 7 n wavelike motions at these periods propagate westward with a phase speed of about 30 40 cm s 1 and a zonal wavelength of 750 1150 km the oscillations are approximately in geostrophic balance with the thermal field with the velocity vector rotating anticyclonically around westward propagating high sea level centers zonal volume transport variations associated with these waves between 5 and 9 n at 20 180 m depth have a standard deviation of about 4 1 sv with peak to peak changes in some instances approaching 20 sv maximum temperature variance along 140 w occurs between 5 and 7 n at 100 150 m depth in a region of strong mean vertical and meridional temperature gradient associated with a thermocline sloping upward to the north at the surface maximum temperature variability occurs from 2 to 5 n in the vicinity of the strong sea surface temperature front north of the equator analysis of the upper ocean temperature balance at 7 n 140 w reveals that meridional advection is important both in the surface layer and in the thermocline vertical advection estimated using vertical velocity calculated from a simplified linear vorticity balance is also important in the thermocline where it contributes a variance comparable to that of meridional advection zonal advection is likely to be significant in the upper 80 m below which it is probably of secondary importance compared to meridional and vertical advection one consequence of advection in the temperature balance is that variance is shifted toward lower frequencies in temperature vis a vis velocity spectra this red shift may account for the apparent difference between periods for instability waves inferred from near equatorial meridional velocity spectra and slightly longer periods reported for oscillations of the sea surface temperature front north of the equator based on satellite imagery

coupled atmosphere ocean model simulations of el nino southern oscillation with and without an active indian ocean an atmospheric general circulation model gcm was coupled with an ocean gcm covering the pacific this coupled model pac was integrated over a 30 year period the pac model stimulates well the mean seasonally varying atmospheric and ocean fields and reproduces interannual variations corresponding to enso el nino southern oscillation the same atmospheric gcm was coupled with an ocean gcm covering the indian ocean and the tropical pacific this coupled model ipc was integrated over a 35 year period the model climate in ipc is fairly reasonable and its pacific part is very similar to the pacific climate of the pac model enso is the major interannual variability in the ipc model the dynamics of enso in ipc are essentially the same as that in pac in the pacific the subsurface ocean heat content anomalies are formed by wind anomalies and show westward propagation centered off the equator after they reach the western pacific they show eastward propagation along the equator they produce changes in the thermocline structure in the eastern equatorial pacific resulting in anomalies in ssts the sst anomalies provide wind anomalies the sign of which is opposite to that of the wind anomalies in the first stage so that thismore chain will continue enso in the pac and ipc models can be regarded as the open quotes delayed oscillator close quotes operating in the pacific although the major interannual variability in the indian ocean is linked to enso in the pacific the indian ocean does not play any active role in the enso cycle in the ipc model interannual variability of monsoon activity in the ipc model is more reasonable than that in the pac model however any definite mechanism for the relationship between monsoon activity and enso does not emerge in the present study 31 refs 14 figs less

observations of coupling between surface wind stress and sea surface temperature in the eastern tropical pacific satellite measurements of surface wind stress from the quikscat scatterometer and sea surface temperature sst from the tropical rainfall measuring mission microwave imager are analyzed for the three month period 21 july 20 october 1999 to investigate ocean atmosphere coupling in the eastern tropical pacific oceanic tropical instability waves tiws with periods of 20 40 days and wavelengths of 1000 2000 km perturb the sst fronts that bracket both sides of the equatorial cold tongue which is centered near 1 8s to the east of 1308w these perturbations are characterized by cusp shaped features that propagate systematically westward on both sides of the equator the space time structures of these sst perturbations are reproduced with remarkable detail in the surface wind stress field the wind stress divergence is shown to be linearly related to the downwind component of the sst gradient with a response on the south side of the cold tongue that is about twice that on the north side the wind stress curl is linearly related to the crosswind component of the sst gradient with a response that is approximately half that of the wind stress divergence response to the downwind sst gradient the perturbed sst and wind stress fields propagate synchronously westward with the tiws this close coupling between sst and wind stress supports the wallace et al hypothesis that surface winds vary in response to sst modification of atmospheric boundary layer stability