parameterization of the vertical transport of momentum by cumulus clouds part i theory abstract a scheme is developed to parameterize the vertical transport of momentum by cumulus clouds in which the effect of a cloud induced pressure field is included in addition a new form for momentum exchange between clouds and their environment is used the scheme incorporates a simple cloud model which includes both updraft and downdraft and specifies the cloud dynamic fields to enable us to determine the mean pressure gradient force across the clouds it is shown that in a typical environment with vertical wind shear the pressure gradient force is along the direction of the wind shear the equation governing cloud mean momentum together with the diagnostic equation for cloud induced pressure field is solved by iteration to evaluate quantitatively the horizontal pressure gradient force across the cloud and determine the cloud mean momentum application of the parameterization scheme to gate convective events will be presented in part ii of this paper

extended eliassen palm fluxes associated with the madden julian oscillation in the stratosphere 1 links are sought between madden julian oscillation mjo related variations in the troposphere and stratospheric circulation tropospheric variations of equatorial mjo filtered 200 hpa zonal winds define indices of mjo activity for two equatorial regions in the indian and western pacific oceans these indices are used to define composite means of mjo filtered extended eliassen palm e p fluxes for eight height levels from the upper troposphere well into the stratosphere evidence is presented for significant and coherent mjo departures throughout the lower stratosphere significant departures of the vertical component of e p flux flow into the lower stratosphere both in the tropics and at higher latitudes especially over canada these are accompanied by horizontal flux departures in the upper troposphere and lower stratosphere from the central tropical pacific into northern canada in this region there is a divergence of extended e p flux piling up wave energy leading to the observed increased cyclonic motion evidence supports the hypothesis that these high latitude circulation variations in the stratosphere are due to a combination of two quite distinct mechanisms in the first poleward propagation occurs in the upper troposphere with vertical propagation at higher latitudes in the second upward propagation occurs in low latitudes into the lower stratosphere this is followed by poleward propagation into higher latitudes and then farther upward propagation

unexpected peak near 15 c in cloudsat echo top climatology 1 we examine a radar derived climatology of earth s cloudiness focusing on the vertical distribution echo tops between the two main peaks at 2 km and 14 km associated with low and high clouds respectively lie two distinct midlevel peaks in the tropics one is in the 5 6 km layer the other between 7 and 8 km both are seen day and night over land and sea over each tropical ocean basin and in published ground radar climatology in the extratropics the vertical echo top distribution by temperature reveals a strikingly sharp peak in the 15 to 20 c layer corresponding to the 7 8 km peak in the tropics again the signal is robust night day land sea summer winter we consider interpretations of the 15 c peak ranging from data artifacts unlikely to mere radar brightening to possible true microphysical or dynamical cloudiness enhancement mechanisms

convective momentum transport associated with the madden julian oscillation based on a reanalysis dataset abstracta better understanding of multiscale interactions within the madden julian oscillation mjo including momentum exchanges is critical for improved mjo prediction skill in this study convective momentum transport cmt associated with the mjo is analyzed based on the noaa climate forecast system reanalysis cfsr a three layer vertical structure associated with the mjo as previously suggested in the mesoscale momentum tendency profile based on global cloud resolving model simulations is evident in the subgrid scale momentum tendency from the cfsr positive negative subgrid scale momentum tendency anomalies are found near the surface negative positive anomalies are found in the low to midtroposphere and positive negative anomalies in the upper troposphere are found within and to the west east of the mjo convection this tends to damp the mjo circulation in the free atmosphere while enhancing mjo winds near the surface in addition it could also reduce the mjo eastward propagation

zonal and vertical structure of the madden julian oscillation abstract a statistical study of the three dimensional structure of the madden julian oscillation mjo is carried out by projecting dynamical fields from reanalysis and radiosonde data onto space time filtered outgoing longwave radiation olr data mjo convection is generally preceded by low level convergence and upward motion in the lower troposphere while subsidence cooling and drying prevail aloft this leads to moistening of the boundary layer and the development of shallow convection followed by a gradual and then more rapid lofting of moisture into the middle troposphere at the onset of deep convection after the passage of the heaviest rainfall a westerly wind burst region is accompanied by stratiform precipitation where lower tropospheric subsidence and drying coincide with continuing upper tropospheric upward motion the evolution of the heating field leads to a temperature structure that favors the growth of the mjo the analysis also reveals distinct differences in the vertical structure

a further study of the tropical western hemisphere warm pool abstract variability of the tropical western hemisphere warm pool whwp of water warmer than 28 5 c which extends seasonally over parts of the eastern north pacific the gulf of mexico the caribbean and the western tropical north atlantic tna was previously studied by wang and enfield using the da silva data from 1945 93 using additional datasets of the ncep ncar reanalysis field and the ncep sst from 1950 99 and the levitus climatological subsurface temperature the present paper confirms and extends the previous study of wang and enfield the whwp alternates with northern south america as the seasonal heating source for the walker and hadley circulations in the western hemisphere during the boreal winter a strong hadley cell emanates northward from the amazon heat source with subsidence over the subtropical north atlantic north of 20 n sustaining a strong north atlantic anticyclone and associated northeast ne trade winds over its southern limb in the tna this circulation including the ne

mjo signals in latent heating results from trmm retrievals abstract four tropical rainfall measuring mission trmm datasets of latent heating were diagnosed for signals in the madden julian oscillation mjo in all four datasets vertical structures of latent heating are dominated by two components one deep with its peak above the melting level and one shallow with its peak below profiles of the two components are nearly ubiquitous in longitude allowing a separation of the vertical and zonal temporal variations when the latitudinal dependence is not considered all four datasets exhibit robust mjo spectral signals in the deep component as eastward propagating spectral peaks centered at a period of 50 days and zonal wavenumber 1 well distinguished from lower and higher frequency power and much stronger than the corresponding westward power the shallow component shows similar but slightly less robust mjo spectral peaks mjo signals were further extracted from a combination of bandpass 30 90 day filtered deep and shallow components largest amplitudes of bo

radiative dynamical consequences of dry tongues in the tropical troposphere abstract dry layers are frequently observed in atmospheric soundings from the climatologically humid western pacific warm pool region some 2400 soundings from the toga coare field program were objectively examined for humidity drops layers in which relative humidity decreases rapidly with height indicative of the bases of dry layers these occur throughout the lower and middle troposphere with frequency peaks near 550 the 0 c level 800 and 950 mb a composite constructed from these sounding data indicates the following almost all dry layers are too dry and not warm enough to be interpreted as conservative vertical displacements rather they apparently consist of filaments or tongues of low moist static energy air advected into the column often from the subtropics dry tongues are anomalously virtually warm near their bases with a slight cool layer below that is they sit atop sharp stable layers or inversions the authors hypothesize that radiation is responsible for the thermal structure o

sea level variations in the tropical pacific ocean and the madden julian oscillation abstract satellite observations of sea level and surface wind from the tropical pacific ocean and their relationship to the madden julian oscillation mjo are analyzed using a combination of statistical techniques and a simple physically based model wavenumber frequency analysis reveals that sea level variations at the equator contain prominent eastward propagating signals as the intraseasonal kelvin waves the component of sea level variation that is coherent with the mjo mjo is concentrated in a narrow strip along the equator between 150 e and 110 w to explain the physical forcing of mjo the component of zonal wind stress that is coherent with the mjo is also calculated it is shown that is strongest in the western pacific but the mjo accounts for a higher percentage of the wind variance in the central equatorial pacific a simple linear model of the kelvin waves based on a first order wave equation forced by and with a linear damping term included successfully reproduces mjo it is also

on the maintenance and initiation of the intraseasonal oscillation in the ncep ncar reanalysis and in the gla and ukmo amip simulations in this study satellite derived outgoing longwave radiation olr and the reanalysis from the national centers for environmental prediction national center for atmospheric research are used as verification data in a study of intraseasonal variability in the goddard laboratory for atmospheres gla and the united kingdom meteorological office ukmo atmospheric general circulation models these models simulated the most realistic intraseasonal oscillations io of the 15 atmospheric model intercomparison project models previously analyzed during the active phase of the intraseasonal oscillation convection is observed to migrate from the indian ocean to the western central pacific ocean and into the south pacific convergence zone spcz the simulated convection particularly in the gla model is most realistic over the western central pacific ocean and the spcz in the reanalysis the baroclinic structure of the io is evident in the eddy stream function and eastward migration of the anticyclone cyclone pairs occurs in conjunction with the eastward development of convection both the gla and ukmo models exhibit a baroclinic structure on intraseasonal time scales the gla model is more realistic than the ukmo model at simulating the eastward migration of the anticyclone cyclone pairs when the convection is active over the western central pacific in the ukmo model the main heating is located off the equator which contributes to the irregular structures seen in this model on intraseasonal time scales the maintenance and initiation of the intraseasonal oscillation has also been investigated analysis of the latent heat flux indicates that evaporative wind feedback is not the dominant mechanism for promoting the eastward propagation of the intraseasonal oscillation since evaporation to the west of the convection dominants the data suggest a wave cisk conditional instability of the secondkind type mechanism although the contribution by frictional convergence is not apparent in the gla model enhanced evaporation tends to develop in place over the west pacific warm pool while in the ukmo simulation westward propagation of enhanced evaporation is evident it is suggested that lack of an interactive ocean may be associated with the models systematic failure to simulate the eastward transition of convection from the indian ocean into the western pacific ocean this hypothesis is based upon the examination of observed sea surface temperature sst and its relationship to the active phase of the intraseasonal oscillation which indicates that the io may evolve as a coupled ocean atmosphere mode the eastward propagation of convection appears to be related to the gradient of sst with above normal sst to the east of the convection maintaining the eastward evolution and decreasing sst near the western portion of the convective envelope being associated with the cessation of convection

impact of a modified convective scheme on the madden julian oscillation and el nino southern oscillation in a coupled climate model 1 the connection between the intraseasonal madden julian oscillation mjo and interannual el nino southern oscillation enso has been proposed and investigated for the last two decades however many fully coupled atmosphere ocean general circulation models gcms are still unable to simulate many important characteristics of these two phenomena partly due to the great uncertainty in the representation of subgrid scale cloud systems we report herein the simulation of an el nino in a fully coupled gcm with a modified convection scheme which captures many of the observed features of the 1997 1998 el nino event the representation of convection in the coupled model plays a major role in modeling both interannual enso and intraseasonal mjo variability in closer accord with observations and in reproducing the evolution of 1997 1998 el nino type events

impact of air sea coupling on the madden julian oscillation in a general circulation model abstract the impact of air sea coupling on the dynamics of the tropical madden julian oscillation mjo is investigated with an atmospheric general circulation model gcm coupled to an ocean mixed layer model in the uncoupled gcm where climatological sea surface temperature sst is specified realistic space time spectra of near equatorial zonal wind and precipitation are produced with power concentrated at eastward wavenumbers 1 3 with periods of 35 90 days however the simulated mjo is roughly 50 stronger than observed largely resulting from enormous activity during northern summer furthermore during southern summer when the observed mjo is most dominant across the indian and western pacific oceans intraseasonal variance in the uncoupled model is overly concentrated to the north and east of australia with little activity extending into the equatorial indian ocean contrary to other recent modeling studies coupling did not alleviate either of these problems nor did it have any other apprecia

interannual variability in a tropical atmosphere ocean model influence of the basic state ocean geometry and nonlinearity abstract the behavior of a tropical coupled atmosphere ocean model is analyzed for a range of different background states and ocean geometries the model is essentially that of cane and zebiak for the tropical pacific except only temporally constant background states are considered here for realistic background states and ocean geometry the model solutions feature oscillations of period of 3 5 yr by comparing the full model solution with a linearized version of the model it is shown that the basic mechanism of the oscillation is contained within linear theory a simple linear analog model is derived that describes the nature of the interannual variability in the coupled tropical atmosphere ocean system the analog model highlights the properties that produce coupled atmosphere ocean instability in the eastern ocean basin and the equatorial wave dynamics in the western ocean basin that are responsible for a delayed negative feedback into this instability growth the growth rate of the local instabil

optimal multiparameter analysis of source water distributions in the southern drake passage in order to evaluate the effects of horizontal advection on iron supply in the vicinity of the shackleton transverse ridge str in the southern drake passage the water composition in the region is estimated along the isopycnal containing the subsurface iron peak optimal multiparameter omp analysis of temperature salinity oxygen and nutrient data is used to estimate the water composition at ctd stations sampled in summer 2004 and winter 2006 the highest iron concentrations in the ona basin are found below the mixed layer both in summer and in winter the water composition derived from the omp analysis is consistent with a scenario in which iron rich shelf waters from the south shetland islands and the antarctic peninsula are advected northward on the eastern side of the str where they interact with the low iron waters of the antarctic circumpolar current acc in the ona basin the shelf waters and the acc waters appear to interact through a stirring process without fully mixing resulting in a filamented distribution that has also been inferred from the satellite data to the west of the str the shelf waters are primarily confined to the continental shelf and do not extend northwards this source of water distribution is consistent with the idea that iron enters the ona basin from the continental shelf through advection along an isopycnal resulting in an iron concentration peak occurring below the winter mixed layer in the ona basin

oxygen isotope records of the australian flat oyster ostrea angasi as a potential temperature archive abstract the response of the oxygen isotope ratio 18o in shells of the australian native flat oyster ostrea angasi to changes in water temperature has been assessed using growth experiments conducted for one year at two locations on the east coast of australia the analysed 18o of the oyster shells 18oshell closely follows the predicted oyster shell 18o constructed from measured 18o in the water 18owater and water temperature influxes of freshwater that occur in the estuarine habitats of o angasi can modify the 18owater and consequently 18oshell salinity fluctuations can also cause interruptions to shell growth in this species this can cause overestimated temperatures in o angasi 18oshell temperature reconstructions a 18oshell temperature calibration was established for o angasi yielding the relationship t c 13 97 3 57 18oshell 18owater 0 17 18oshell 18owater 2 n 79 r2 0 79 which within the experimental uncertainties of the data is similar to other published biogenic carbonate paleotemperature equations

where and how long ago was water in the western north atlantic ventilated maximum entropy inversions of bottle data from woce line a20 1 a maximum entropy me method is used to deconvolve tracer data for the joint distribution of locations and times since last ventilation the deconvolutions utilize world ocean circulation experiment line a20 repeat hydrography for cfc 11 potential temperature salinity oxygen and phosphate as well as global ocean data analysis project glodap radiocarbon data combined with surface boundary conditions derived from the atmospheric history of cfc 11 and the world ocean atlas 2005 and glodap databases because of the limited number of available tracers the deconvolutions are highly underdetermined leading to large entropic uncertainties which are quantified using the information entropy of relative to a prior distribution additional uncertainties resulting from data sparsity are estimated using a monte carlo approach and found to be of secondary importance the me deconvolutions objectively identify key water mass formation regions and quantify the local fraction of water of age or older last ventilated in each region ideal mean age and radiocarbon age are also estimated but found to have large entropic uncertainties that can be attributed to uncertainties in the partitioning of a given water parcel according to where it was last ventilated labrador irminger seawater l water is determined to be mostly less than 40 a old in the vicinity of the deep western boundary current dwbc at the northern end of a20 but several decades older where the dwbc recrosses the section further south pointing to the importance of mixing via a multitude of eddy diffusive paths overflow water lies primarily below l water with young waters 40 a at middepth in the northern part of a20 and waters as old as 600 a below 3500 m

water mass distributions in the southern ocean derived from a parametric analysis of mixing water masses 1 an empirical method to reconstruct distributions of mixing water masses is developed and applied to two southern ocean australian sector data sets the method is a parametric extension of the well known optimum multiparameter omp analysis therefore called pomp parametric omp the main development consists of parameterizing the mixing fractions as a function of position e g latitude and depth and estimating the parameters of the resulting function instead of estimating the mixing fractions for every sampling point individually because this enables to reduce the total number of unknowns to be estimated the proposed adjustments result in more robust estimates of the mixing fractions as illustrated on the southern ocean clivar sr3 data set early spring 2001 an additional consequence of the new working scheme is that the mixing distributions are smoothed it is emphasized that the degree of smoothing should be chosen with care in order not to neglect any significant features statistical rules to do this are applied application of the pomp method to the second southern ocean data set saz 98 summer 1998 revealed the importance of a careful selection of the mixing source water types this study was limited to the subantarctic region and upper 1000 m where variations in water mass characteristics and distributions are most important indeed it seems necessary to redefine the source water characteristics for each data set the direction of these changes suggests that interannual variability or long term changes of water masses overwhelm the seasonal variability

seasonal temperature salinity changes and thermocline development in the mid atlantic bight as recorded by the isotopic composition of bivalves stable isotope records across annual growth increments in specimens of the surf clam spisula solidissima from the mid atlantic bight shelf from 10 m and 45 m depths reflect the changes in temperature and nutrient concentrations on the shelf over the year the 18 o and 13 c records from clams at the two depths record well mixed conditions in the water column during the winter months and the development of a thermocline during the summer spring high productivity and a transient salinity excursion in surface waters are also recorded reconstructing the paleoceanography of late cenozoic temperate continental shelves may be possible using stable isotope records from fossil spisula solidissima and other bivalves

a composite study of onset of the australian summer monsoon abstract onset of the australian summer monsoon is identified each year 1957 87 using the wind and rainfall record at darwin onset is defined as the first occurrence of wet 850 mb westerly winds composites of atmospheric fields at stations in and about the australian tropics are constructed relative to the onset date at darwin the composite onset is accompanied by the development of a convectively driven baroclinic circulation over northern australia upper tropospheric easterlies expand about the equator and the subtropical jet shifts poleward at onset this behavior is interpreted as a transient southerly shift of the local hadley circulation concurrent with the development of an upper level anticyclone over northern australia the composite onset coincides with the arrival of an eastward propagating convective anomaly the anomaly originates in the southern indian ocean propagates eastward at 5 m s 1 and is detectable as far east as the date line an eastward propagating zonal wind anomaly also

madden julian oscillation induced suppression of northeast pacific convection increases u s tornadogenesis abstractthis study investigates the impact of the madden julian oscillation mjo on u s tornadogenesis using atmospheric reanalysis and model experiments our analysis shows that the impact of mj

optimum multiparameter analysis of mixing in the thermocline of the eastern indian ocean a method of water mass analysis is developed which optimizes the use of all information contained in a hydrographic data set by solving an overdetermined linear set of mixing equations it requires representation of water masses by a finite number of water types and observations from at least as many oceanographic parameters as water types the procedure to establish the water types find the correct weights for the parameters and solve the mixing equations through minimization of the residuals is described in detail the method is applied to a data set from the eastern indian ocean where indian central water and australasian mediterranean water meet to produce a strong front in the thermocline it is shown that although most of the water from the indonesian archipelago is carried westward north of 11 s contributions from the australasian mediterranean water are found as far south as 25 s particularly along the australian shelf as a result of advection with the leeuwin current

seasonality of the structure and propagation characteristics of the mjo the seasonality of the madden julian oscillation mjo is documented in observational data and a nonlinear shallow water model is used to help interpret some of the contrasts in mjo structure between the boreal winter season november march ndjfm and the asian summer monsoon period june september jjas at upper tropospheric levels the flanking rossby waves remain centered around 28 degrees n s year round but they tend to be stronger in the winter hemisphere where the climatological mean jet stream is stronger rendering the subtropical circulation more sensitive to forcing by a near equatorial heat source amplitudes of the mjo related deep convection and lower tropospheric zonal wind are stronger in the summer hemisphere where the column integrated water vapor is larger during ndjfm the equatorial asymmetry is subtle as in the annual mean moisture convergence into swallowtail shaped regions of enhanced deep convection is an integral part of the equatorial rossby wave signature and the eastward propagation is due to moistening of the air to the east of the enhanced convection by poleward moisture advection during the asian summer monsoon in jjas the convection assumes the form of northward propagating west northwest east southeast oriented rainbands embedded within cyclonic shear lines these features are maintained by frictional convergence of moisture and their northward propagation is mainly due to the presence of features in the climatological mean fields that is the west east moisture gradient over india and the arabian sea and the southwesterly low level monsoon flow over the northwest pacific

an air sea coupled skeleton model for the madden julian oscillation this work is an extension and improvement of the minimal madden julian oscillation mjo skeleton model developed by majda and stechmann which can capture some important features of the mjo slow eastward propagation quadrupole vortex structure and independence of frequency on wavelength but is unable to produce unstable growth and selection of eastward propagating planetary waves with the addition of planetary boundary layer frictional moisture convergence these deficiencies can be remedied the frictional boundary layer selects the planetary scale eastward propagation as the most unstable mode but the dynamics remains confined to atmospheric processes only here the authors study the role of air sea interaction by implementing an oceanic mixed layer ml model of wang and xie into the mjo skeleton model in this new air sea coupled skeleton model the features of the original skeleton model remain additionally the air sea interaction under mean westerly winds is shown to produce a strong instability that selectively destabilizes the eastward propagating planetary scale waves although the cloud shortwave radiation seasurfacetemperature crs feedbackdestabilizesbotheastwardand westward modes theair sea feedback associated with the evaporation and oceanic entrainment favors planetary scale eastward modes over the western hemisphere where easterly background winds prevail the evaporation and entrainment feedbacks yield damped modes indicating that longitudinal variation of the mean surface winds plays an important role in regulation of the mjo intensity in addition to the longitudinal variation of the mean sea surface temperature or mean moist static stability this theoretical analysis suggests that accurate simulation of the climatological mean state is critical for capturing the realistic air sea interaction and thus the mjo

physical mechanisms for the maintenance of gcm simulated madden julian oscillation over the indian ocean and pacific abstractthe kinetic energy budget is conducted to analyze the physical processes responsible for the improved madden julian oscillation mjo simulated by the iowa state university general circulation models isugcms the modified deep convection scheme that includes the revised convection closure convection trigger condition and convective momentum transport cmt enhances the equatorial 10 s 10 n mjo related perturbation kinetic energy pke in the upper troposphere and leads to a more robust and coherent eastward propagating mjo signal in the mjo source region the indian ocean 45 120 e the upper tropospheric mjo pke is maintained by the vertical convergence of wave energy flux and the barotropic conversion through the horizontal shear of mean flow in the convectively active region the western pacific 120 e 180 the upper tropospheric mjo pke is supported by the convergence of horizontal and vertical wave energy fluxes over the central eastern pacific 180 120 w where convection is s

simulation of the madden julian oscillation in a coupled general circulation model part ii the role of the basic state abstract in part i of this study it was shown that air sea coupling had a positive impact on some aspects of the simulation of the madden julian oscillation mjo by a gcm however errors in the basic state climate of that gcm appeared to be preventing the mjo related convection from propagating into the west pacific in this paper the actual impact of these errors will be addressed an integration of a flux adjusted version of the coupled model has been performed which has reduced basic state errors in the west pacific in this version of the coupled gcm the mjo does propagate into the west pacific the simulation of the mjo by a coupled model with the same atmospheric component but a different ocean gcm is also analyzed this coupled gcm has similar systematic errors in low level zonal wind and precipitation to the model studied in part i but with warmer ssts results from this experiment together with the other available evidence suggest that it is the errors in the low level zonal wind component

seasonality in the madden julian oscillation abstract this study using observational data and global reanalysis products synthesizes existing knowledge on the seasonality in the madden julian oscillation mjo and discusses its possible dependence on the mean background state the seasonality in the mjo is documented in terms of its components in low level zonal wind and precipitation a single peak season boreal winter exists near the equator in the indian and western pacific oceans for the broad tropical region however the seasonality in the mjo is featured by a latitudinal migration across the equator between two peak seasons the primary peak season is in boreal winter december march during which mjo signals are mainly confined to the indian and western pacific ocean and reach their maxima in the south pacific convergence zone the secondary peak season is boreal summer june september during which the strongest mjo occurs north of the equator from the bay of bengal to the south china sea and another separated region of strong mjo

and ratios in skeletal calcite of mytilus trossulus covariation with metabolic rate salinity and carbon isotopic composition of seawater minor element and isotopic compositions of marine bivalve calcite are frequently used as proxy records of seawater temperature and salinity although molluscan calcite is secreted at or near oxygen isotope equilibrium the influence of metabolic activity i e vital effects on skeletal srca ratios and 13c values is not well known we present measurements of skeletal chemistry from a consecutive samples milled in chronological order from the organism s final year of growth and b adjacent samples within three separate growth bands of the marine mussel mytilus trossulus to investigate chemical disequilibrium effects among different parts of the shell seawater temperature and salinity were monitored for one year at squirrel cove british columbia at the end of the year a young rapidly growing mussel mussel a and an old slowly growing mussel mussel b were harvested from this site growth bands within the shells were sampled to provide a chronological record of shell carbonate chemistry results from consecutive samples show 1 a significantly higher average srca ratio in mussel a than that in mussel b and 2 13c values that correlate well with salinity in mussel a but not in mussel b results from time equivalent adjacent samples show 1 higher srca and 13c values near the ventral margin than at time equivalent regions on lateral margins of the shell and 2 little or no variation in 18o values these observations suggest that skeletal chemistry srca and 13c is primarily controlled by rate of mantle metabolic activity and secondarily modified by variation in seawater salinity because metabolic activity in the mantle at the site of carbonate precipitation varies with shell curvature the composition of calcite secreted along lateral margins is influenced to a greater extent by metabolic activity than calcite secreted coevally at the central margin of the shell hence the chemistry of calcite secreted at the ventral margin is precipitated in near equilibrium with seawater and allows accurate estimation of seawater srca ratios and carbon isotopic composition in contrast shell precipitation along lateral margins is dominantly controlled by metabolic activity and calcite chemistry is not in equilibrium with ambient seawater in this context we present a biomineralization model where variations in skeletal srca and 13c values are explained in the context of mantle metabolic activity and seawater salinity

the global monsoon as seen through the divergent atmospheric circulation a comprehensive description is given of the global monsoon as seen through the large scale overturning in the atmosphere that changes with the seasons and it provides a basis for delimiting the monsoon regions of the world the analysis focuses on the mean annual cycle of the divergent winds and associated vertical motions as given by the monthly mean fields for 1979 93 reanalyses from the national centers for environmental prediction national center for atmospheric research ncep ncar and european centre for medium range weather forecasts ecmwf which are able to reproduce the dominant modes a complex empirical orthogonal function analysis of the divergent circulation brings out two dominant modes with essentially the same vertical structures in all months of the year the first mode which depicts the global monsoon has a simple vertical structure with a maximum in vertical motion at about 400 mb divergence in the upper troposphere that is strongest at 150 mb and decays to zero amplitude above 70 mb and convergence in the lower troposphere with a maximum at 925 mb ecmwf or 850 mb ncep however this mode has a rich three dimensional spatial structure that evolves with the seasons it accounts for 60 of the annual cycle variance of the divergent mass circulation and dominates the hadley circulation as well as three overturning transverse cells these include the pacific walker circulation an americas atlantic walker circulation both of which comprise rising motion in the west and sinking in the east and a transverse cell over asia the middle east north africa and the indian ocean that has rising motion in the east and sinking toward the west these exist year round but migrate and evolve considerably with the seasons and have about a third to half of the mass flux of the peak hadley cell the annual cycle of the two hadley cells reveals peak strength in early february and early august in both reanalyses a second monsoon mode which accounts for 20 of the variance features relatively shallow but vigorous overturning with the maximum vertical velocities near 800 mb outflow from 750 to 350 mb and inflow peaking at 925 mb it is especially strong over africa where the shallow mostly meridional overturning migrates back and forth across the equator with the seasons it influences the middle east has a signature over australia and is also an important component of the overturning in the tropical eastern pacific and atlantic and thus of the convergence zones in these regions the relationship of the global monsoon to the regional monsoons is described over six zonal sectors africa australia asia north america south america and the pacific and atlantic oceans only the two ocean areas do not undergo a seasonal reversal required for monsoons although they have direct overturning cells and they nevertheless participate in the global monsoon through the changes in large scale overturning the regional meridional cross sections highlight the importance of the shallow overturning cell in lower troposphere monsoon activity the steadiness of the overturning circulation is determined by comparing the signal of the seasonal mean vertical motions at 500 mb with the standard deviation of the transient daily variations locations where this signal exceeds 60 of the daily noise correspond closely with the regional centers of the monsoon

mixing and remineralization in waters detrained from the surface into subantarctic mode water and antarctic intermediate water in the southeastern pacific a hydrographic data set collected in the region and season of subantarctic mode water and antarctic intermediate water samw and aaiw formation in the southeastern pacific allows us to estimate the preformed properties of surface water detrained into these water masses from deep mixed layers north of the subantarctic front and antarctic surface water south of the front using 10 measured seawater properties we estimate the fractions of samw aaiw that originate as surface source waters as well as fractions that mix into these water masses from subtropical thermocline water above and upper circumpolar deep water below the subducted samw aaiw ages associated with the detrained surface water and remineralization and dissolution rates and ratios the mixing patterns imply that cabbeling can account for 0 005 0 03 kg m 3 of additional density in aaiw and 0 0 02 kg m 3 in samw we estimate a shallow depth 300 700 m above the aragonite saturation horizon calcium carbonate dissolution rate of 0 4 0 2 mol caco3 kg 1 yr 1 a phosphate remineralization rate of 0 031 0 009 mol p kg 1 yr 1 and remineralization ratios of p n o2 corg of 1 15 5 0 6 143 10 104 22 for samw aaiw our shallow depth calcium carbonate dissolution rate is comparable to previous estimates for our region our o2 p ratio is smaller than many global averages our model suggests neglecting diapycnal mixing of preformed phosphate has likely biased previous estimates of o2 p and corg p high but that the corg p ratio bias may have been counteracted by a second bias in previous studies from neglecting anthropogenic carbon gradients

interdecadal water mass changes in the southern ocean between 30 e and 160 e interdecadal water mass changes in the indian western pacific sectors of the southern ocean were investigated using the japanese antarctic research expeditions and historical hydrographic observations from the 1950s to 1990s freshening and cooling occurred on the neutral density surfaces of 27 0 kgm3 equatorward of sub antarctic front results for the area south of the polar front show warm and saline anomalies and oxygen decreases on the surfaces around 27 9 kgm3 which correspond to the upper circumpolar deep water these latter anomalies are most simply explained by the mixing of these shallow waters with warmer and fresher surface waters steric sea level has also increased with an average change of 1mmyr1 from the 1970s to 1990s the changes are larger north of the sub antarctic front implying a strengthening of the antarctic circumpolar current it appears that the observed changes are consistent with the results from coupled climate model results for a similar period

mjo related sst variations over the tropical eastern pacific during northern hemisphere summer abstract the madden julian oscillation mjo significantly modulates eastern tropical pacific sea surface temperatures ssts during northern hemisphere summer typical sst variations during an mjo life cycle are 0 4 0 5 c considerably higher variations occur with the strongest events 1 2 c the magnitudes of these variations are comparable to those associated with west pacific mjo variability during nh winter sst anomalies to the north of 4 n where the strongest modulation of east pacific convection by the mjo occurs are 180 out of phase with equatorial anomalies these sst variations are responsible for variations in surface saturation equivalent potential temperatures of greater than 3 c the highest ssts lead maximum convection by about 10 days and ssts begin to cool with the onset of enhanced convection off equatorial sst anomalies are most likely due to variations in surface latent heat flux although shortwave flux anomalies are important in the heart of the mjo convective region decrea

life history of the pliocene scallop fortipecten based on oxygen and carbon isotope profiles abstract oxygen and carbon isotope profiles from the outer calcite layer of two well preserved specimens of the pliocene scallop fortipecten takahashii exhibit distinct attenuation in their annual ranges throughout the complete growth history of approximately 10 years the segments of oxygen isotope profiles corresponding to winter or summer extremes were compressed suggesting growth retardation during extreme water temperatures these profile compressions correspond well with the positions of growth rings on the outer shell surface one scallop shell which evidently grew in warmer environments based on mean oxygen isotope values developed growth rings in summer while a second shell with colder mean temperature values exhibits winter growth rings a drastic reduction in isotope fluctuation occurred at a shell age of approximately 3 years and possibly is related to the onset of the reproductive phase which may have suppressed shell growth in favor of building up reproductive tissue sexual maturity brought a change in life habit from a swimming to a reclining mode which is clearly shown by the change in shell architecture although scallop shells during the juvenile stage may record a complete seasonal cycle isotopic profiles in the adult stage contain repeated growth breaks as a result using isotope signals as paleoenvironmental proxies must be done carefully at least with scallop shells

shallow meridional circulation in the tropical eastern pacific abstract based on four independent datasets this study presents observational evidence of a shallow meridional circulation cell in the eastern tropical pacific in this shallow meridional circulation cell the northerly cross equatorial return flow from the itcz into the southern hemisphere is found immediately above the atmospheric boundary layer in contrast to the classic concept of the hadley type deep meridional circulation whose northerly return flow resides in the upper troposphere the strength and depth of this shallow meridional circulation undergo a distinct annual cycle possible causes and climatic implications of this shallow meridional circulation are discussed

least squares multiple tracer analysis of water mass composition we present an inverse method that uses measurements of the concentration of several tracer variables to find the mixture of source water types that best describes in a weighted least squares sense the composition of the water sample the solution includes two physically realistic constraints first that all sources together must sum to 100 and second that no source is present in negative amounts these constraints improve the statistical stability of the solution the method is particularly valuable in regions involving strong mixing among a relatively large number of source water types in contrast to conventional ts analysis more water types can be considered the assumption of mixing along isopycnals is unnecessary and sensitivity to errors in individual tracer measurements is reduced by averaging the influence of a larger number of tracers we demonstrate the method using data from two oceanographic regions analysis of summer data from the continental margin off vancouver island british columbia canada confirms and quantifies the importance of deep upwelling of california undercurrent water onto the continental shelf it also identifies localized outer shelf filaments of low salinity water originating from the vancouver island coastal current finally we reanalyze the north african data of tomczak and confirm his interpretation of diapycnal mixing at the frontal boundary between north atlantic central water and south atlantic central water masses

el nino southern oscillation sensitivity to cumulus entrainment in a coupled general circulation model received 6 july 2011 revised 26 august 2011 accepted 14 september 2011 published 22 november 2011 1 a series of 200 year long integrations is performed using the geophysical fluid dynamics laboratory cm2 1 by varying the tokioka parameter a minimum entrainment rate threshold in the cumulus parameterization changing the threshold alters both the tropical pacific mean state and the el nino southern oscillation enso variability increasing the tokioka parameter causes a basin wide cooling in the tropical pacific with the reduction of high clouds the degree of cooling in the western part of the basin is bigger than that in the east as a result the east west asymmetry in the tropical pacific sea surface temperature sst decreases with increasing the tokioka parameter accompanied with the reduced east west sst asymmetry are the increase of mean precipitation over the eastern pacific and the eastward shift of the atmospheric responses to the enso related sst forcing the eastward shifted wind stress anomaly associated with enso leads to the stronger enso variability in this way the magnitude of enso simulated in this model increases with the tokioka parameter implication of our results on the relationship between the tropical pacific mean state and enso is discussed

a high resolution transect of dissolved barium in the southern ocean 1 the dissolved barium bad distribution in the whole water column was examined along the woce sr3 line in the southern ocean australian sector late winter spring 2001 the high sampling resolution offered an excellent opportunity to relate the bad distribution to frontal structures and the water masses such a high resolution was not achieved in previous southern ocean studies and showed the tight overprinting of the frontal zones by bad gradients hydrodynamic control on bad is evident in the case of antarctic bottom water formation westward flow of tasman sea waters and return flow of an eddy of the subantarctic front however biogeochemical processes are also acting as witnessed by enhanced bad contents in deep waters of the subantarctic front zone and by a local mesopelagic minimum in the inter polar front zone these features are respectively ascribed to the dissolution of ba rich phases and ba transfer from solution to particles

convectively coupled kelvin waves in cmip5 coupled climate models this study provided a quantitative evaluation of convectively coupled kelvin waves cckws over the indian ocean and the pacific ocean simulated by 20 coupled climate models that participated in coupled model intercomparison project phase 5 the two leading empirical orthogonal function eof modes of filtered daily precipitation anomalies are used to represent the eastward propagating cckws in both observations and simulations the eigenvectors and eigenvalues of the eof modes represent the spatial patterns and intensity of cckws respectively and the lead lag relationship between the two eof principle components describe the phase propagation of cckws a non dimensional metric was designed in consideration of all the three factors i e pattern amplitude and phase propagation for evaluation the relative rankings of the models based on the skill scores calculated by the metric are conducted for the indian ocean and the pacific ocean respectively two models noresm1 m and mpi esm lr are ranked among the best 20 for both the regions three models inmcm4 mri cgcm3 and hadgem2 es are ranked among the worst 20 for both the regions while the observed cckw amplitude is greater north of the equator in the pacific some models overestimate the cckw ampliutde in the southern hemisphere this bias is related to the mean state precipitation bias along the south pacific convergence zone

the role of shallow cloud moistening in mjo and non mjo convective events over the arm manus site abstractobservations from the atmospheric radiation measurement program arm site at manus island in the western pacific and re analysis products are used to investigate moistening by shallow cumulus clouds and by the circulation in large scale convective events large scale convective events are defined as rainfall anomalies larger than one standard deviation for a minimum of three consecutive days over a 10 10 domain centered at manus these events are categorized into two groups madden julian oscillation mjo events with eastward propagation and non mjo events without propagation shallow cumulus clouds are identified as continuous time height echoes from 1 min cloud radar observations with their tops below the freezing level and their bases within the boundary layer daily moistening tendencies of shallow clouds estimated from differences between their mean liquid water content and precipitation over their presumed life spans and those of physical processes and advection from re analysis

tropical pacific variability in the ncar climate system model a 300 yr simulation with the ncar climate system model csm version 1 captured only 60 of the observed enso signal and exaggerated the interannual variability of sst in the western tropical pacific here a simulation with a new version of the csm which significantly improves the spatial and temporal patterns of tropical pacific variability is described maximum sst variability is shifted to the central and eastern pacific a better simulation of the equatorial pacific thermocline structure results in nino 3 and nino 4 statistics com parable to the observed estimates for the last century the evolution of sst and subsurface temperature anomalies is in excellent agreement with observed events the majority of events evolve as a standing mode with weak sst anomalies occurring in the northern spring in the eastern tropical pacific and maximum anomalies covering the eastern tropical pacific ocean to the date line by the following northern winter at the same time subsurface temperature anomalies spread eastward and upward along the tropical thermocline the delayed oscillator and wyrtki s buildup hypothesis are consistent with aspects of the csm simulation on the equator a westerly wind stress anomaly in the central pacific forces off equatorial upwelling anomalies which propagate westward reaching the western boundary about one half year later this upwelling signal then propagates eastward along the equator arriving 2 months before cooling in the eastern pacific basin the tropical pacific atmospheric response to warm oceanic events also agrees with observational analyses with a negative southern oscillation pattern in sea level pressure wind stress anomalies and low level convergence to the west of the maximum sst anomalies and enhanced deep convection and precipitation in the central and eastern tropical pacific

ventilation of the deep ocean constrained with tracer observations and implications for radiocarbon estimates of ideal mean age abstract ocean ventilation is the process that transports water and climatically important trace gases such as carbon dioxide from the surface mixed layer into the ocean interior quantifying the dominant source regions and time scales remains a major challenge in oceanography a mathematically rigorous approach that accounts for the multiplicity of transport pathways and transit times characteristic of an eddy diffusive flow such as the ocean is to quantify ventilation in terms of a probability distribution that partitions fluid parcels according to the time and location of their last surface contact here we use globally gridded radiocarbon data in combination with other transient cfcs and hydrographic temperature salinity phosphate and oxygen tracer data to estimate the joint distribution of age and surface origin of deep ocean waters our results show that 40 and 26 of the global ocean was last in contact with the southern ocean and north atlantic respectively some 80 of the global deep ocean below 1500 m is ventilated from these high latitude regions however contrary to the classical description of the deep ocean as a roughly equal mixture of northern and southern source waters we find a significantly higher contribution from the southern ocean relative to the north atlantic we estimate the mean transit time from the surface to the deep north pacific at 1360 350 y intermediate between two widely used radiocarbon based estimates to reconcile our estimate of the ideal mean age with ventilation age estimates based on radiocarbon we apply the estimated distribution function to construct a 3 dimensional distribution of the water mass fraction weighted surface initial radiocarbon concentration that can serve as an accurate reservoir age radiocarbon ages corrected for this initial reservoir age are found to be in good agreement within 5 with our ideal age estimate demonstrating that it is essential to take into account the spatially variable surface radiocarbon field when computing ventilation ages using radiocarbon a wide spectrum of ages contributes to the mean age providing evidence for the fundamentally eddy diffusive nature of the large scale general circulation of the ocean

two leading enso modes and el nino types in the zebiak cane model abstractmodern instrumental records reveal that el nino events differ in their spatial patterns and temporal evolutions attempts have been made to categorize them roughly into two main types eastern pacific ep or cold tongue and central pacific cp or warm pool el nino events in this study we use a modified version of zebiak cane mzc coupled model to examine the dynamics of these two types of el nino events we conducted linear eigen analysis of the model to show that there are two leading enso el nino southern oscillation modes with their sst patterns resembling those of two types of el nino thus we refer them as the ep and cp enso modes these two modes sensitively depend on the changes in the mean states the heat budget analyses demonstrate that the ep cp mode is dominated by thermocline zonal advective feedback therefore weak strong mean wind stress and deep shallow mean thermocline prefers the ep cp enso mode because of the relatively dominance of thermocline zonal advect

characteristics associated with the madden julian oscillation at manus island abstractground based high temporal and vertical resolution datasets from observations during 2002 07 at the atmospheric radiation measurement arm tropical western pacific twp site on manus island are used to examine the characteristics of clouds and rainfall associated with the active phase of the madden julian oscillation mjo passing over manus a composite mjo event at manus is developed based on the noaa mjo index 4 and precipitation using 13 events the cloud characteristics associated with the active phase of the mjo at manus show a two phase structure as the wave passes over manus during the development phase congestus plays an important role and the enhanced convection is located between surface westerly and easterly wind anomalies type i structure during the mature phase deep convection is the dominant cloud type and the enhanced convection is collocated with the westerly wind anomalies type ii structure consistent with this two phase structure the heavy rainfall frequency also s

the role of interactions between multiscale circulations on the observed zonally averaged zonal wind variability associated with the madden julian oscillation abstractthe mechanisms driving the upper tropospheric zonal mean intraseasonal zonal wind associated with the madden julian oscillation are examined through budget analysis during boreal winter to diagnose the role of nonlinear and cross scale interactions the wind fields are decomposed into three temporal bands including the intraseasonal time scale 30 100 days and periods shorter and longer than the intraseasonal time scales the intraseasonal zonal mean circulation and its driving mechanisms are first examined based on the leading eofs of the intraseasonal zonal wind consistent with previous studies of intraseasonal atmospheric angular momentum the upper troposphere zonal mean intraseasonal zonal wind anomaly begins in the tropics and propagates poleward results show that interaction between the background state and intraseasonal time scale zonally symmetric and asymmetric circulation helps drive changes in the tropical intraseasonal zonal wind and its poleward propagation the intraseasonal a

spondylus gaederopus a new mediterranean climate archive based on high resolution oxygen and carbon isotope analyses abstract the presented study evaluates the potential of the mediterranean bivalve spondylus gaederopus linne 1758 as a palaeoclimatic archive its fixosessil life in water depths 18 o and carbon 13 c isotope data obtained from high resolution sampling of a modern s gaederopus from rhodes greece collected alive in 4 m water depth in spring 2002 suggest that the outer calcitic shell layer as well as the inner aragonitic shell layer is precipitated in equilibrium with seawater due to the complexity of the outer calcitic shell layer with its spines and prickles a chronological sampling of this part of the shell is not possible in contrast the inner aragonitic shell layer with its well developed growth bands allows a fast chronologic sampling 18 aragonite growth bands were sampled from the inner shell layer of the studied specimen corresponding to 9 years of growth with 9 10 samples per year carbon stable isotopes 13 c ar yield mean values of 0 70 0 6 and show a remarkable negative shift of about 1 8 from about 1 6 to about 0 2 through time this ontogenetic depletion in 13 c might be related to physiological developments like sexual maturity as it is the case in other bivalves seasonal variations with an average amplitude of 0 85 are superimposed on the observed secular trend these cycles show an increase in amplitude that has not been described before and cannot be explained so far oxygen isotopes 18 o ar exhibit mean values of 1 11 0 5 clearly pronounced seasonal cycles with an average amplitude of 1 45 show the same wavelength as the carbon cycles but run out of phase the 18 o ar correlates well with sea surface temperature and correlation fits best during summer periods deviations between measured and predicted 18 o ar input data sea surface temperature seawater 18 o show that maximal discrepancies occur during winter periods these discrepancies can be best explained by a decrease in local seawater 18 o due to increased freshwater influx on rhodes maxima in precipitation hence river runoff occur during winter months

convective momentum transport and perturbation pressure field from a cloud resolving model simulation this study uses a 2d cloud resolving model to investigate the vertical transport of horizontal momentum and to understand the role of a convection generated perturbation pressure field in the momentum transport by convective systems during part of the tropical ocean and global atmosphere coupled ocean atmosphere response experiment toga coare intensive observation period it shows that convective updrafts transport a significant amount of momentum vertically this transport is downgradient in the easterly wind regime but upgradient during a westerly wind burst the differences in convective momentum transport between easterly and westerly wind regimes are examined the perturbation pressure gradient accounts for an important part of the apparent momentum source in general it is opposite in sign to the product of cloud mass flux and the vertical wind shear with smaller magnitude examination of the dynamic forcing to the pressure field demonstrates that the linear forcing representing the interaction between the convective updrafts and the large scale wind shear is the dominant term while the nonlinear forcing is of secondary importance thus parameterization schemes taking into account the linear interaction between the convective updrafts and the large scale wind shear can capture the essential features of the perturbation pressure field the parameterization scheme for momentum transport by zhang and cho is evaluated using the model simulation data the parameterized pressure gradient force using the scheme is in excellent agreement with the simulated one the parameterized apparent momentum source is also in good agreement with the model simulation other parameterization methods for the pressure gradient are also discussed

the role of inertial instability in determining the location and strength of near equatorial convection there are two major organized cloud configurations in the vicinity of the equator where there is a small cross equatorial surface pressure gradient convection is close to the equator and is generally tied to the location of the lowest sea level pressure slp and warmest sea surface temperature sst in agreement with arguments based upon simple thermodynamical considerations however when there is a substantial cross equatorial pressure gradient such as occurs in the monsoon regions organized convection appears off the equator in the summer hemisphere equatorward of the slp minimum and not necessarily collocated with the warmest ssts thus in this instance simple thermodynamical considerations alone cannot explain 2he location of the convection in this situation the zero absolute vorticity contour 0 also lies in the summer hemisphere therefore between the equator and the 0 contour is a region of locally anticyclonic absolute vorticity and an inertially unstable regime it is argued that the convection results from the low level divergence convergence doublet centred about the 0 contour which is the mitigating response to the inertial instability the associated latitude height secondary circulation should provide subsidence suppressed convection over the equator and rising motion enhanced convection to the north of the zero absolute vorticity contour signatures of the inertial instability predicted by theory are found in observations supporting the hypothesis wherever a strong cross equatorial pressure gradient exists the 0 contour bisects a maximum in the divergent wind field divergence is found equatorward of the zero contour and convergence on the poleward side latitude height cross sections show strong local meridional circulations with maximum rising motion on the poleward side of 0 as the regions where the rising motions occur are conditionally unstable there is deep convection and the vertical circulations extend throughout the troposphere it is noted that the intensity of the off equator convection is deeper and probably stronger than convection located at the equator this is probably because the convection associated with the inertial instability is more efficient necessary conditions for the location of near equatorial convection are listed arguments are presented whereby inertial instability is established as the cause rather than an effect of off equatorial convection these include an outline of the sequence of processes leading up to the convection the factors that limit the encroachment of the 0 contour into the summer hemisphere are discussed and an explanation for the existence of the low level westerly monsoon wind maximum is suggested the possible role played by the instability mechanism or the lack of it in coupled model simulations that produce seasonally migrating and or double itczs in the eastern pacific ocean is discussed finally it is proposed that the instability mechanism is important in the initiation of westward moving disturbances found in the eastern pacific and in determining active and break periods in the summer indian monsoon

stable isotope profiles of last interglacial pelukian transgression mollusks and paleoclimate implications in the bering strait region abstract the marine paleoclimate during the last interglaciation in the bering strait region is inferred from the stable oxygen and carbon isotope profiles of fossil bivalve mollusks specimens were collected from the marine highstand deposits of the pelukian transgression from the arctic alaskan coastal plain the nome coastal plain st lawrence island and the val katlen suite on the chukotka peninsula as a calibration modern mollusks were obtained from the major water masses in the bering chukchi seas system and from coastal environments near the fossil localities the 18 o composition of the modern mollusks accurately reflects the seawater 18 o differences among the water masses and the ambient temperature range at each site seasonal paleotemperature ranges are estimated from the 18 o profiles of the fossils by comparison with those of the modern specimens a simple model is developed to correct the paleotemperature ranges for the influence of differences in seawater 18 o between water masses and seasonal variations caused by freshwater discharge paleotemperatures calculated for the skull cliff site alaskan arctic coastal plain are close to but slightly cooler than those of modern specimens from peard bay and icy cape the isotopic composition of a pelukian specimen collected near wainwright shows the obvious influence of locally reduced salinities with a correction for lower seawater 18 o this profile yields a summer temperature of 13 c which is 3 c warmer than that from the modern icy cape specimen the isotope records of two specimens from the nome coastal plain suggest salinities that were 3 5 psu lower than the modern eastern bering shelf the paleotemperature range of 0 15 c is consistent with modern conditions in norton sound the character of the isotope profiles of the pelukian specimens from st lawrence island is very different than that of modern specimens near the island but matches the 18 o values of shells from deeper sites in anadyr water this suggests that the fossil mollusks were living in anadyr strait and were transported by a glacial advance from the chukotka peninsula the last interglacial specimens from the val katlen suite have isotope profiles with large seasonal 18 o ranges and the clear influence of a reduced salinity coastal water mass calculated paleotemperatures from the val katlen specimens range from 0 to 13 c differences in the 13 c of shell carbonate between sites appears to reflect the regional distribution of the 13 c of sedimentary organic matter som which is a mixture between terrestrial organic matter mean 13 c of 24 and marine phytoplankton 21 partitioning of 13 c between shallow and deep waters by phytoplankton productivity and remineralization may also affect the regional distribution differences in shell 13 c between taxa may relate to feeding mode and the type and isotopic composition of ingested particles the filter feeders mya and astarte typically have 13 c values 1 2 more positive than the deposit feeders macoma and serripes this effect is attributed to a 13 c difference between marine phytoplankton and som with a component of terrestrial organic carbon

subsurface structure of interannual temperature anomalies in the australian sector of the southern ocean 1 a 7 year time series of austral summer expendable bathythermograph xbt sections between tasmania and antarctica is used to describe the subsurface structure of southern ocean interannual temperature anomalies comparison of the discontinuous xbt record with a continuous weekly average satellite based sst data set confirms that the xbt sampling is adequate to resolve interannual variability significant correlations are found between changes in surface and subsurface temperature along much of the section in the subantarctic zone surface and subsurface changes are coherent because deep convection in winter homogenizes the upper 600 m and the summer mixed layer temperature reflects the preconditioning of the previous winter at other latitudes the regions of high correlation generally extend well beyond the depth of direct atmospheric influence i e the depth of the winter mixed layer negative positive temperature anomalies at interannual timescales are coherent with poleward equatorward displacements of fronts the simplest explanation for the correspondence between deep vertically coherent temperature anomalies and the location of acc fronts is that the observed features reflect meridional shifts of temperature gradients associated with the fronts the link between temperature anomalies and front displacements suggests southern ocean sea surface temperature sst anomalies primarily reflect a dynamical response of the ocean to wind or other forcing rather than surface trapped features produced by anomalous air sea heat flux the xbt record contains both interannual and longer unresolved period signals which cannot be isolated in the short discontinuous xbt time series spectral analysis of the 17 year sst data set reveals roughly equal variability in 2 7 year and 7 year bands

barrier effect of the indo pacific maritime continent on the mjo perspectives from tracking mjo precipitation abstractexplanations for the barrier effect of the indo pacific maritime continent mc on the mjo should satisfy two criteria first they should include specific features of the mc namely its intricate land sea distributions and elevated terrains second they should include mechanisms for both the barrier effect and its overcoming by some mjo events guided by these two criteria a precipitation tracking method is applied to identify mjo events that propagate across the mc mjo c and those that are blocked by the mc mjo b about a half of mjo events that form over the indian ocean propagate through the mc most of them 75 become weakened over the mc the barrier effect cannot be explained in terms of the strength horizontal scale or spatial distribution of mjo convection when it approaches the mc from the west a distinction between mjo b and mjo c is their precipitation over the sea versus land in the mc region mjo c events rain much more over the sea than over land whereas rainfall over

seasonal migration of itcz precipitation across the equator why can t gcms simulate it 1 the secondary meridional circulation induced by convective momentum transport cmt within the ascending branch of the hadley circulation is a missing dynamical mechanism that can cause common failure of general circulation models gcms in simulating seasonal migration of the intertropical convergence zone itcz precipitation maximum across the equator this failure is manifested by the model bias that the precipitation peak remains north of the equator during november march the cmt induced secondary circulation characterized by strong downward motion along the equatorial belt and upward motion south and north of the belt tends to modify the meridional distribution of precipitation with the strongest impacts during boreal winter and spring a 20 year gcm simulation with the cmt parameterization successfully reproduces the observed seasonal migration of the itcz precipitation across the equator with the peaks near 8 n during boreal summer and near 8 s during boreal winter

untangling biogeochemical processes from the impact of ocean circulation first insight on the mediterranean dissolved barium dynamics based on an unprecedented dissolved barium d ba data set collected in the mediterranean sea during a zonal transect between the lebanon coast and gibraltar m84 3 cruise april 2011 we decompose the d ba distribution to isolate the contribution of biogeochemical processes from the impact of the oceanic circulation we have built a simple parametric water mass analysis parametric optimum multi parameter pomp analysis to reconstruct the contribution of the different mediterranean water masses to the thermohaline structure these water mass fractions have then been used to successfully reconstruct the background vertical gradient of d ba reflecting the balance between the large scale oceanic circulation and the biological activity over long time scales superimposed on the background field several d ba anomalies have been identified positive anomalies are associated with topographic obstacles and may be explained by the dissolution of particulate biogenic barium p ba barite of material resuspended by the local currents the derived dissolution rates range from 0 06 to 0 21 mol m 2 d 1 negative anomalies are present in the mesopelagic region of the western and eastern basins except in the easternmost levantine basin as well as in the abyssal western basin this represents the first quantification of the non conservative component of the d ba signal these mesopelagic anomalies could reflect the subtraction of d ba during p ba barite formation occurring during organic carbon remineralisation the deep anomalies may potentially reflect the transport of material towards the deep sea during winter deep convection and the subsequent remineralisation the d ba subtraction fluxes range from 0 07 to 1 28 mol m 2 d 1 d ba derived fluxes of p ba barite up to 0 21 mol m 2 d 1 and organic carbon 13 to 29 mmol c m 2 d 1 are in good agreement with other independent measurements suggesting that d ba can help constraining remineralisation horizons this study highlights the importance of quantifying the impact of the large scale oceanic circulation in order to better understand the biogeochemical cycling of elements and to build reliable geochemical proxies

ecological and paleoenvironmental information using stable isotope profiles from living and fossil molluscs stable oxygen and carbon isotopic profiles from recent specimens of spisula solidissima and placopecten magellanicus collected off the virginia coast are used to calibrate annual temperature controlled cycles in the 18o profile and shell growth characteristics the amplitude of the annual 18o cycles decreases with increasing water depth and may be used as a relative depth indicator the isotopic of profiles of two fossil specimens of pleistocene spisula are very similar in amplitude and character to modern analogues and verify the formation of annual growth increments in these fossil specimens offsets between the 18o profiles of the fossil and modern specimens are related to known temperature and ice volume effects during the late pleistocene and support the utility of mollusc isotope records as a stratigraphic tool carbon isotopic profiles from all specimens show light values in the spring and or fall associated with seasonal phytoplankton productivity offsets in the carbon isotopic composition between infaunal and epifaunal species may be related to sediment porewater geochemistry and oxidation of organic matter trends toward lighter 13c values through ontogeny suggest the effects of metabolic changes from a fast growing juvenile into a slower growing sexually mature adult anomalies in both the oxygen and carbon isotopic profiles identify the formation of minor shell growth increments as corresponding to hydrographic perturbations and to winter cold temperatures

a combined wave number frequency and time extended eof approach for tracking the progress of modes of large scale organized tropical convection an algorithm combining filtering in the wave number frequency domain with time extended empirical orthogonal function eeof analysis is developed and applied to diagnose and track signals associated with modes of organized moist deep convection in the tropics the wave number frequency spectrum of outgoing long wave radiation olr is broken down into five broad filter bands in order to concentrate signals associated with the madden julian oscillation convectively coupled equatorial rossby kelvin and mixed rossby gravity waves easterly waves and low frequency variations such as the el nino southern oscillation enso the eeof patterns are obtained from analysis of the filtered data and principal component pc time series are generated by projection of temporally smoothed but otherwise unfiltered data onto the eeof patterns filtered data are reconstructed by taking the product of the eeof patterns and the corresponding pcs these reconstructed data compare well with unfiltered olr anomalies and with olr anomalies filtered in the wave number frequency domain for the same modes the method is easily applied in real time since results are not influenced by the proximity to the end of the dataset copyright 2009 royal meteorological society

global deepwater circulation between 2 4 and 1 7 ma and its connection to the onset of northern hemisphere glaciation we have generated an early pleistocene benthic isotopic record for the ocean drilling program odp site 807 2804 m from the western equatorial pacific between 2 4 and 1 7 ma the benthic 13c of this site and a few other deep pacific sites was consistently higher than the southern ocean site mv0502 4jc 4286 m pointing to a reversal relative to the current gradient and hence implying a different circulation regime we reconstructed the deep water mass distribution of this interval using a collection of benthic isotope records from 15 pacific and 10 atlantic sites and a 13c 18o mixing model a two end member mixing regime between the north atlantic deep water nadw and the antarctic bottom water aabw with properties very different from today was identified the southern ocean showed strong signs of stratification and aabw with low benthic 13c but high 18o values reached out to other basins only below 4000 m in contrast nadw ventilated most of the ocean interior contributing 70 to the pacific deep water pdw volumetrically our model results also reveal a strong remineralization effect at the bottom sites of the pacific and the atlantic suggesting significant accumulation of respired carbon in the bottom water between 2 4 and 1 7 ma we propose that such a circulation pattern was initiated by the reversal of salinity gradient between aabw and nadw from 3 0 to 2 4 ma possibly linked to antarctic sea ice expansion and reduced southward heat transport during the onset of northern hemisphere glaciation nhg

mixing and water mass formation in the australian subantarctic abstract a cruise south of eastern australia confirmed the formation of a subantarctic mode water type in late winter on the equatorward side of the subantarctic front this water type mixed with the winter surface waters farther north would form the t s relation observed in the tasman sea intermediate waters a subsurface formation of antarctic intermediate water is supported by data collected in the polar frontal zone a matrix method for analyzing mixing indicates that the antarctic intermediate water is formed from a mixture of circumpolar deep water and antarctic surface water with effectively no input from the subantarctic mode water the nutrient data were found to add very little information on the mixing once the temperatures and salinities are known

cloud resolving modeling of tropical cloud systems during phase iii of gate part i two dimensional experiments abstract a formal framework is established for the way in which cloud resolving numerical models are used to investigate the role of precipitating cloud systems in climate and weather forecasting models emphasis is on models with periodic lateral boundary conditions that eliminate unrealistic numerically generated circulations caused by open boundary conditions in long term simulations defined in this formalism is the concept of large scale forcing and the cloud environment interactions that are consistent with the periodic boundary conditions two dimensional numerical simulations of the evolution of cloud systems during 1 7 september 1974 in phase iii of the global atmospheric research program atlantic tropical experiment gate are conducted based on the above formalism a simple technique is used to force an anelastic cloud resolving model with evolving large scale horizontal wind field and large scale forcing for the temperature and moisture obtained from the gate data the 7 day period selected i

frictional moisture convergence in a composite life cycle of the madden julian oscillation abstract a composite life cycle of the madden julian oscillation mjo is constructed using an index based on the first two eofs of the bandpass filtered 20 80 days 850 mb zonal wind averaged from 5 n to 5 s every 2 5 around the equator precipitation 1000 mb convergence 850 mb wind and 200 mb wind are composited for the period 1979 95 water vapor integrated from the surface to 300 mb is composited for the period 1988 92 frictional moisture convergence at the equator is shown to play an important role in the life cycle of the madden julian oscillation mjo regions of boundary layer convergence foster growth of positive water vapor anomalies to the east of convection this convergence coincides with 850 mb easterly wind anomalies as is consistent with kelvin wave dynamics drying of the atmosphere occurs rapidly after the passage of convection with the onset of 850 mb westerly perturbations possible mechanisms for this drying include boundary layer divergence and subsidence or horizontal advect

polar climate instability and climate teleconnections from the arctic to the midlatitudes and tropics abstract it is generally accepted that the ocean thermohaline circulation plays a key role in polar climate stability and rapid climate change recently reported analyses of the impact of anomalous freshwater outflows from the north american continent onto either the north atlantic or arctic oceans demonstrate that in either case a clear reduction in the atlantic meridional overturning circulation accompanied by an increase in sea ice extent is predicted the results also reconcile proxy inferred younger dryas greenland temperature variations the aim of the present work is to provide a detailed investigation of the pathways along which the signal associated with overturning circulation anomalies propagates into both the midlatitudes and the tropics and the effect such teleconnections have on the tropical ocean atmosphere system the authors consider both the impact of substantial slowing of the overturning circulation due to freshwater forcing of the north atlantic as well as its recovery after the a

cirrus observations in the tropical tropopause layer over the western pacific 1 a polarization lidar was continuously operated aboard the research vessel mirai in the tropical western pacific over three northern winters at 2 0 n 138 0 e during november and december 2001 at 2 0 n 138 5 e during november and december 2002 and at 7 5 n 134 0 e during december 2004 and january 2005 intensive radiosonde soundings were made from the vessel at 3 h intervals during all three campaigns the mechanisms that underlie the observed variations in cirrus in the tropical tropopause layer ttl are discussed from the viewpoint of large scale dynamics and transport during the 2001 campaign the tropopause region was cold but the ttl was often clear with only some subvisual cirrus potential vorticity data and trajectories show that the ttl during this period was strongly affected by dry air transport from the northern midlatitude lower stratosphere during the 2002 campaign a packet of large amplitude equatorial kelvin waves was the primary control on the generation and disappearance of cirrus in the ttl during the 2004 2005 campaign a cold phase of large scale waves resulted in cirrus generation in the ttl in late december of 2004 similar to that observed during the 2002 campaign outflow from the south pacific convergence zone spcz caused optically thick cirrus in the ttl particularly during early january 2005 when we also observed regular diurnal variations in cirrus development within the ttl that is apparent sedimentation during the nighttime we investigated two possible controlling processes namely horizontal advection together with diurnal variations in convective activity within the spcz and diurnal variations in local temperature due to tides and gravity waves in the equatorial western pacific equatorial kelvin waves are the important dynamical process that controls cirrus variations in the ttl dry air horizontal transport from the midlatitude lower stratosphere and wet air vertical transport near the tropical convergence regions should also be considered in fully explaining the cirrus observations in the ttl

the boreal summer intraseasonal oscillation relationship between northward and eastward movement of convection the summertime intraseasonal oscillation iso is an important component of the south asian monsoon lagged regressions of intraseasonally filtered 25 80 days outgoing longwave radiation olr reveal that centers of convection move both northward and eastward from the central equatorial indian ocean subsequent to the initiation of an iso eastward movement of convection is also seen at indian subcontinent latitudes 10 8 208n based on the regression results the summertime iso convection signal appears as a band tilting northwestward with latitude and stretching from the equator to about 208n viewed along any meridian convection appears to propagate northward while equatorial convection propagates to the east to examine the robustness of the connection between eastward and northward movement individual isos are categorized and composited relative to the strength of the large scale eastward component of convection in the central equatorial indian ocean it is found that the majority of isos that exhibit northward movement onto the indian subcontinent 42 out of 54 isos or 78 also exhibit eastward movement into the western pacific ocean it is also found that when convection in the central indian ocean is not followed within 10 20 days by convection in the western pacific ocean 12 out of 54 isos or 22 the independent northward movement of convection in the indian ocean region is somewhat stunted the link between the eastward and northward movement of convection is consistent with an interpretation of the summertime iso in terms of propagating equatorial modes the northward moving portion of convection is forced by surface frictional convergence into the low pressure center of the rossby cell that is excited by equatorial iso convection a similar convergence pattern is seen for the northern winter iso but it does not generate poleward movement due to relatively cool ssts underlying the surface convergence

anthropogenic co2 in the southern ocean distribution and inventory at the indian atlantic boundary world ocean circulation experiment line i6 1 the southern ocean where various water masses are formed mode intermediate deep and bottom waters has a high potential to absorb anthropogenic co2 cant however most data based and model estimates indicate low cant inventories south of 50 s in order to investigate this paradox the distribution of cant is estimated between south africa and antarctica world ocean circulation experiment woce line i6 based on a back calculation technique previously used in the north atlantic kortzinger et al 1998 and adapted here for application in the southern ocean at midlatitudes 30 50 s formation and spreading of mode and intermediate waters results in a deep penetration of cant down to 2000 m south of 50 s significant concentrations of cant were estimated in circumpolar deep water 10 mol kg and antarctic bottom water aabw 20 25 mol kg higher concentrations are detected along the continental slope in aabw presumably formed in prydz bay compared to aabw of weddell sea origin the distribution of cant obtained north of 50 s compares well with previous data based and model estimates but large disagreements are found in the south however although transient tracers are not used in the back calculation technique employed here the distribution of cant is remarkably well correlated with cfcs we reevaluated the column inventories of cant for the southern ocean and found higher values at high latitudes 70 90 mol m2 compared to the subtropical subantarctic region 40 80 mol m2 these results support the idea that deep and bottom water formation in the southern ocean is a key process in the natural sequestration of anthropogenic co2

mineralization of biogenic materials in the water masses of the south atlantic ocean i assessment and results of an optimum multiparameter analysis abstract this is the first of two manuscripts dealing with the circulation mixing ventilation and organic matter mineralization of the south atlantic ocean sao the present work quantifies the complex mixing of water masses in the sao using a constrained least squares regression optimum multiparameter omp analysis the omp based on temperature salinity silicate and the conservative parameter no was applied on two world ocean circulation woce lines a17 and a14 in the western and eastern sao respectively the constrained omp sensitivity to sources of error in the end member characteristics measured parameters equation weights and oxygen to nitrogen mineralization ratio rn was carefully assessed using perturbation tests perturbation of rn was the only test that changed significantly the mixing proportions although by less than 5 the constrained omp method allowed defining the realm and identifying the core of flow of each water mass to study its circulation the evolution of its chemical composition and eventually to separate the contribution of physical and biogeochemical processes relevant specific outputs of this first manuscript are 1 north of the south equatorial current the silicate maximum is primarily composed of antarctic intermediate water aaiw rather than circumpolar deep water cdw 2 the two degree discontinuity tdd experiences a dramatic meridional change of water masses composition being dominated by north atlantic deep water nadw north of the vema channel and by cdw southwards 3 the 50 proportion horizon of weddell sea deep water wdsw with a of 0 3 c at the entry of the sao defines the upper limit of the wsdw realm more properly than the classical isopycnals of 46 04 or 46 06 4 where the proportion of wsdw is around 75

total matrix intercomparison a method for determining the geometry of water mass pathways abstract ocean tracer distributions have long been used to decompose the deep ocean into constituent water masses but previous inverse methods have generally been limited to just a few water masses that have been defined by a subjective choice of static property combinations through air sea interaction and upper ocean processes all surface locations are potential sources of distinct tracer properties and thus it is natural to define a distinct water type for each surface site here a new box inversion method is developed to explore the contributions of all surface locations to the ocean interior as well as the degree to which the observed tracer fields can be explained by a steady state circulation with unchanging surface boundary conditions the total matrix intercomparison tmi method is a novel way to invert observations to solve for the pathways connecting every surface point to every interior point in the limiting case that the circulation is steady and that five conservative tracers are perf

effects of convective processes on gcm simulations of the madden julian oscillation abstract weak temporal variability in tropical climates such as the madden julian oscillation mjo is one of major deficiencies in general circulation models gcms the uncertainties in the representation of convection and cloud processes are responsible for these deficiencies with the improvement made to the convection scheme the iowa state university isu gcm which is based on a version of the ncar community climate model is able to simulate many features of mjo as revealed by observations in this study four 10 yr 1979 88 isu gcm simulations with observed sea surface temperatures are analyzed and compared to examine the effects of the revised convection closure convection trigger condition and convective momentum transport cmt on the mjo simulations the modifications made in the convection scheme improve the simulations of amplitude spatial distribution eastward propagation and horizontal and vertical structures especially for the coherent feature of eastward propagating convection a

intraseasonal behavior of clouds temperature and motion in the tropics abstract the spectral character of tropical convection is investigated in an 11 yr record of outgoing longwave radiation from the advanced very high resolution radiometer to identify interaction with the tropical circulation along the equator in the eastern hemisphere the space time spectrum of convection possesses a broad peak at wave numbers 1 3 and eastward periods of 35 95 days significantly broader than the dynamical signal of the madden julian oscillation mjo this quasi discrete convective signal is associated with a large scale anomaly that propagates across and modulates time mean or climatological convection over the equatorial indian ocean and western pacific outside that region the convective signal is small even though under amplified conditions coherence can be found east of the date line and in the subtropics having a zonal scale of approximately wavenumber 2 anomalous convection propagates eastward at some 5 m s 1 and suppresses as well as reinforces climatological convection

propagating and standing components of the intraseasonal oscillation in tropical convection abstract two questions related to the intraseasonal variability of tropical convection and circulation remain controversial 1 to what degree is the convective component of the madden julian oscillation mjo a standing oscillation 2 is the eastward propagating circulation anomaly of the mjo coherent with a standing oscillation in convection in an attempt to settle these issues the authors undertake a series of statistical analyses of gridded outgoing longwave radiation and winds to quantify the magnitudes of the propagating and standing components of convection and their coherence with the propagating component of the circulation they demonstrate that no dominant standing oscillation in convection can be identified instead intraseasonal variability of convection is dominated by an eastward propagating mode which the authors interpret as the convective signal of the mjo this propagating component accounts for almost all of the convective variance that is coherent with the eastward propagating di

the boreal summer madden julian oscillation and moist convective morphology over the maritime continent abstractwhile the boreal summer madden julian oscillation mjo is commonly defined as a planetary scale disturbance the convective elements that constitute its cloud dipole exhibit pronounced var

coupling of convective momentum transport with convective heating in global climate simulations abstract the effects of convective momentum transport cmt on global climate simulations are examined in this study comparison between two sets of 20 yr 1979 98 integration using the ncar community climate model version 3 ccm3 illustrates that the inclusion of cmt in the convection scheme systematically modifies the climate mean state over the equatorial region the convective momentum tendencies slow down the equatorward flow at higher latitudes near the surface and weaken the equatorial convergence and convection this reduces the convective heating and drying around the equator and produces an improved meridional distribution within the upward branch of the hadley circulation the major heating peak during the boreal winter is moved to south of the equator at about 10 s which is closer to the heat budget residuals of the ecmwf reanalysis data the responses of meridional wind to the reduced heating result in the secondary meridional circulation within the intertropical convergence zone

asymmetric modulation of western north pacific cyclogenesis by the madden julian oscillation under enso conditions abstractthe present study investigates the modulation by the madden julian oscillation mjo and the impact of the el nino southern oscillation enso on tropical cyclone tc genesis in the western north pacific wnp during the period 1975 2010 results reveal a stronger modulation of cyclogenesis by the mjo during el nino years while the modulations in neutral and la nina years are comparable to each other the asymmetric background modification by enso is found to greatly affect the extent of mjo modulation under different enso conditions first mjo activity is intensified and extends farther eastward during el nino years instead of being confined west of 150 e as in neutral and la nina periods thus the influence of mjo is stronger and more zonally widespread in el nino years causing significant differences in cyclogenesis parameters in most parts of the wnp in el nino years cyclogenesis is further enhanced in the active phase due to synchronization of mjo signals with favorable background enso

barrier effect of the indo pacific maritime continent on mjo propagation in observations and cmip5 models abstractthis study explores possible mechanisms for the barrier effect of the indo pacific maritime continent mc on mjo propagation in particular this study examines whether similar mechanisms

a model for interpreting continental shelf hydrographic processes from the stable isotope and cadmium calcium profiles of scallop shells abstract stable oxygen and carbon isotope and cadmium calcium profiles from the shells of scallops collected from the outer continental shelf of the south atlantic bight and the virginia bight appear to trace the hydrographic processes of the two regions a model is developed to distinguish two principal modes of nutrient and trace metal input to the outer shelf from the biogeochemical profiles of the shell the oxygen isotope profiles record bottom water temperature changes caused by seasonal temperature cycles and water mass movements nutrient input and subsequent phytoplankton blooms are recorded in the carbon isotope and cd ca profiles the shell profiles from the south atlantic bight record the dominant effect of upwelling caused by gulf stream meandering the shell profiles from the virginia bight show the influence of spring river runoff and summer water column stratification biogeochemical profiles in mollusk shells are potentially important tools for studying the dynamics of both modern and ancient continental shelf upwelling systems

the tropospheric response to tropical and subtropical zonally asymmetric torques analytical and idealized numerical model results abstractthe tropospheric response to prescribed tropical and subtropical zonally asymmetric torques which can be considered as idealizations of vertical momentum transfers by orographic gravity waves or convection is investigated the linear analytical gill model response to westward upper tropospheric torques is compared to the response to a midtropospheric heating which is a familiar point of reference the response to an equatorial torque projects onto a kelvin wave response to the east that is of opposite sign to the response to the east of the heating at upper levels in contrast the torque and heating both produce rossby gyres of the same sign to the west of the forcing and the zonal mean streamfunction responses are identical when the forcings are shifted into the northern hemisphere the streamfunction responses have opposite signs there is upwelling in the southern northern hemisphere in response to the torque heating the nonlinear response to westward torques was explored in idealized