the effects of wind stress curl on the japan east sea circulation abstract the wind driven ocean circulation of the japan east sea jes is studied using a primitive equation two layer model forced by monthly mean climatological wind of ecmwf the modeled circulation in the upper layer is characterized by a large basin wide cyclonic circulation generated by the positive wind stress curl occupying most of the jes in winter and four small gyres inside of the large circulation one of the four small gyres is cyclonic and located along the primorskii coast two other small gyres located off vladivostok form a dipole with a cylonic gyre to the east and anti cyclonic gyre to the west the remaining small gyre is cyclonic and located around the east korean bay ekb the gyre dipole off vladivostok is generated by the dipole of wind stress curl off vladivostok the cyclonic gyre of the dipole does not change its strength so much seasonally and plays an important role in separating the low salinity coastal water from the coast and advecting it eastward along the subpolar front as subsurface low salinity core which spreads into the subsurface of the tsushima warm current region as the japan east sea intermediate water the anti cyclonic gyre west of the cyclonic gyre of the dipole off vladivostok generated in winter decreases much in amplitude or disappears until summer depending on parameters interfacial friction vertical stability and topographic constraint the coastal current reversal from southwestward to northeastward along the north korean coast suggested by the argos buoy deployed in summer in 1994 during the creams cruise appears to be closely related with the development of this anti cyclonic gyre the cyclonic gyre in the ekb is generated by a dipole of wind stress curl off the ekb and might be important for the separation of the east korean warm current the cyclonic gyre along the primorskii coast is generated by the positive wind stress curl northwest of hokkaido and persists to exist throughout a year with a volume transport more than 1 0 sv and may explain the track of the argos buoy deployed in summer in 1994 during the creams cruise it is concluded that the wind driven surface circulation account for an important part of the circulation of the northern jes since the modeled surface circulation seems to capture many characteristic features of the circulation in the northern jes and the amount of volume transport of modeled circulations and gyres is comparable to the inflow transport at the tsushima straits

the behavior of winter stationary planetary waves forced by topography and diabatic heating abstract a primitive equation linear wave model is developed to examine the effects of mean zonal wind structure on the vertical propagation of stationary planetary waves and to identify the characteristics of the winter stationary waves forced by realistic topography and diabatic heating an analytic mean zonal wind model is used to facilitate changing the wind structure parameters for comparative experiments a more realistic mean wind profile is used to simulate the observed behavior of stationary waves more closely the experiments confirm the sensitivity of vertical wave propagation to the mean wind structure especially to the latitudinal curvature of the mean wind the role of the polar night jet in channeling the planetary waves as they propagate vertically is emphasized at is found that the latitudinal location of the polar night jet also has a significant influence upon the wave propagation a mechanism is proposed to explain the possible connections between the change in the location of the po

observations inferences and mechanisms of the atlantic meridional overturning circulation a review this is a review about the atlantic meridional overturning circulation amoc its mean structure temporal variability controlling mechanisms and role in the coupled climate system the amoc plays a central role in climate through its heat and freshwater transports northward ocean heat transport achieved by the amoc is responsible for the relative warmth of the northern hemisphere compared to the southern hemisphere and is thought to play a role in setting the mean position of the intertropical convergence zone north of the equator the amoc is a key means by which heat anomalies are sequestered into the ocean s interior and thus modulates the trajectory of climate change fluctuations in the amoc have been linked to low frequency variability of atlantic sea surface temperatures with a host of implications for climate variability over surrounding landmasses on intra annual timescales variability in amoc is large and primarily reflects the response to local wind forcing meridional coherence of anomalies is limited to that of the wind field on interannual to decadal timescales amoc changes are primarily geostrophic and related to buoyancy anomalies on the western boundary a pacemaker region for decadal amoc changes is located in a western transition zone along the boundary between the subtropical and subpolar gyres decadal amoc anomalies are communicated meridionally from this region amoc observations as well as the expanded ocean observational network provided by the argo array and satellite altimetry are inspiring efforts to develop decadal predictability systems using coupled atmosphere ocean models initialized by ocean data

the basic ingredients of the north atlantic storm track part ii sea surface temperatures abstractthe impact of north atlantic sst patterns on the storm track is investigated using a hierarchy of gcm simulations using idealized aquaplanet and semirealistic boundary conditions in the atmospheric component hadam3 of the third climate configuration of the met office unified model hadcm3 this framework enables the mechanisms determining the tropospheric response to north atlantic sst patterns to be examined both in isolation and in combination with continental scale landmasses and orography in isolation a gulf stream sst pattern acts to strengthen the downstream storm track while a north atlantic drift sst pattern weakens it these changes are consistent with changes in the extratropical sst gradient and near surface baroclinicity and each storm track response is associated with a consistent change in the tropospheric jet structure locally enhanced near surface horizontal wind convergence is found over the warm side of strengthened sst gradients associated with ascending air and i

on the nature and causes of large scale thermal variability in the central north pacific ocean abstract long range naval aircraft using axbt s obtained meridional temperature sections from the central pacific ocean along 158 and 170 w between 30 and 50 n at approximately monthly intervals between november 1974 and april 1977 29 months analyses of these sections show that the seasonal cycle in the central ocean is confined largely to the upper 100 m the phase of the seasonal cycle increases with depth so that at 100 m it lags the surface by three months exceptions to the above statements occur in two narrow bands centered on latitudes 42 and 36 n where the seasonal cycle apparently penetrates in phase to the limit of observations 300 m except in the interval 100 150 m which lags the surface by 1 2 months approximately 90 95 of the variance in the seasonal change of heat storage in the study region can be accounted for by air sea heat exchange and some type of vertical mixing horizontal and vertical advection were of limited and little use respectively in reproducing the seasonal cycle va

the principal nonseasonal modes of variation of global sea surface temperature abstract thirty five million ship reports for the period 1949 79 have been used to construct global monthly mean sea surface temperature fields for 5 5 latitude longitude regions the monthly means have been subjected to eigenvector analysis to bring out the nonseasonal modes of variation the el nino mode is the most important and its eigenvector time series is identical to that found previously by weare et al for the pacific alone addition of data from the other oceans adds unexplained variance so that the percentage of the variance explained by the el nino mode is smaller in the global case than for the pacific alone the second most important eigenvector pattern shows evidence of a cooling trend for the north pacific and north atlantic in the 1964 79 period this is in agreement with previous work an zonal mean sea surface temperature by the authors with recent work on the north pacific by douglas et al and with a polar cap cooling in the lower troposphere for the same period reported by boer

influence of the north atlantic sst on the atmospheric circulation using the monthly coads dataset and nmc ncar archives we show that significant anomalies of the atmospheric circulation are related to previous sst anomalies in the north atlantic a signal over the northwest labrador sea in late spring is associated with the dominant mode of sst variability during the preceeding winter it is more clearly seen in the mid troposhere than at sea level and appears to be related to the anomalous surface heat exchanges that slowly damp the sst anomalies in addition a nao like signal in early winter is associated with sst anomalies east of newfoundland and in the eastern subtropical north atlantic during the preceeding summer

descriptive oceanography during the frontal air sea interaction experiment medium to large scale variability medium and large scale oceanographic variability in the sargasso sea is examined during the frontal air sea interaction experiment fasinex focusing primarily on processes that influence the formation of subtropical fronts from fall to spring the mean meridional gradient of meridional ekman transport in the subtropical convergence zone stcz enhances the meridional sea surface temperature ts gradients between 26 o and 32on in the presence of this enhanced mean gradient baroclinic eddies with zonal wavelengths of 800 km and periods of 200 days exert the dominant influence on the formation of subtropical fronts at medium and large scales these eddies generate westward propagating ts anomaly features with the same dominant wavelengths and periods they are confined between 26 o and 32on and have amplitudes that occasionally exceed ioc ts fronts tend to be found within bands 200 km wide that roughly follow the periphery of these anomaly features deformation in the horizontal eddy current field is primarily responsible for the existence of these frontal bands the migration of the strong front originally bracketed by the fasinex moored array was related to the westward propagation of the larger scale eddy anomaly frontal band pattern the moored array was located within a warm anomaly feature during most of the experiment which produced exceptionally warm conditions in the upper ocean these anomalies are confined between 26 o and 32on not only because the relatively large seasonal mean tsy there allows horizontal eddy currents to force strong anomalies but also because the baroclinic eddies with wavelengths of 800 km and periods of 200 days are confined to the stcz large meridional variability exists in many properties of the eddy field much of which can be traced to the influence of the sargasso sea mean current field on eddy variability

variability of the atlantic meridional mode during the atlantic hurricane season abstract an observational and modeling study is conducted to investigate the structure of the atlantic meridional mode amm during the atlantic hurricane season and the relationship between amm related sst anomalies and environmental conditions that influence seasonal tropical cyclone activity the observational analysis shows that during the atlantic hurricane season the amm exhibits a similar sst and low level wind structure as during boreal spring when the amm is most active observed amm sst variations are accompanied by air temperature and moisture anomalies that are limited to the boundary layer and an anomalous baroclinic circulation structure in the northern subtropical atlantic with an anomalous lower level cyclonic circulation residing under an anomalous upper level anticyclone during a warm phase this baroclinic structure contributes to a reduction in vertical wind shear over the tropical atlantic that is dominated by changes in the upper level flow two sets of model experiments were cond

large scale vertical eddy diffusion in the main pycnocline of the central north pacific abstract indirect procedures are used to estimate the latitudinal distribution of the large scale vertical eddy diffusivity coefficient in the main pycnocline from the interannual change in t structure of the water column in the central midlatitude north pacific from 35 44 n 150 170 w using t s data from two identical hydrographic surveys one made in june 1976 and the other in may 1977 the interannual change in potential temperature is recorded on three potential density surfaces i e 26 6 27 0 and 27 2 that lie in the upper middle and lower part of the main pycnocline respectively by relating these interannual changes to the vertical gradients of the average potential temperature on each surface i e through the heat conservation equation the large scale vertical eddy diffusivity coefficient and its vertical gradient were determined by least squares estimate procedures the vertical eddy diffusivity coefficient k is found to have been positive over the entire region with magnit

state dependence of atmospheric response to extratropical north pacific sst anomalies by performing two sets of high resolution atmospheric general circulation model agcm experiments we find that the atmospheric response to a sea surface temperature sst anomaly in the extratropical north pacific is sensitive to decadal variations of the background sst on which the sst anomaly is superimposed the response in the first set of experiments in which the sst anomaly is superimposed on the observed daily sst of 1981 1990 strongly differs from the response in the second experiment in which the same sst anomaly is superimposed on the observed daily sst of 1991 2000 the atmospheric response over the north pacific during 1981 1990 is eddy mediated equivalent barotropic and concentrated in the east in contrast the atmospheric response during 1991 2000 is weaker and strongest in the west the results are discussed in terms of rossby wave dynamics with the proposed primary wave source switching from baroclinic eddy vorticity forcing over the eastern north pacific in 1981 1990 to mean flow divergence over the western north pacific in 1991 2000 the wave source changes are linked to the decadal reduction of daily sst variability over the eastern north pacific and strengthening of the oyashio extension front over the western north pacific thus both daily and frontal aspects of the background sst variability in determining the atmospheric response to extratropical north pacific sst anomalies are emphasized by our agcm experiments

low frequency temperature fluctuations off bermuda twenty four years of hydrographic stations made by the r v panulirus southeast of bermuda at approximately semi monthly intervals have been used to construct temperature time series at 10 depths ranging from the surface to 2000 m the data contain no significant seasonal signal at depth 250 m subsurface temperature spectra have a broad peak in the eddy containing band at periods 0 100 days and drop rapidly at high frequencies at very low frequencies the spectra indicate some redness down to the largest resolvable time scales most of the energy in the temperature fluctuations is concentrated into two vertical modes which resemble the first two baroclinic normal modes and explain 60 and 23 of the variance respectively the observed spectrum of sea surface temperature sst anomalies has substantially more variance at periods of a year and less than sst anomaly spectra estimated from ship reports on 5 5 grid it is suggested that the excess variance is due to the advection of the sea surface temperature pattern by the underlying field of smaller scale eddies consistently with the observed coherences between surface and deeper temperature records

sea surface temperature anomalies planetary waves and air sea feedback in the middle latitudes the mechanisms that contribute to the generation and damping of large scale mid latitude sea surface temperature sst anomalies are discussed the sst anomalies reflect primarily the response of the upper ocean to the changes in air sea fluxes that are associated with daily weather fluctuations heat flux forcing is dominant in the lower middle latitudes while wind driven entrainment may be most effective in the high latitudes advection by anomalous ekman current is generally less important and ekman pumping is negligible the sst anomalies decay in part because of entrainment effects associated with mixed layer deepening and oceanic mixing and in part because of heat exchanges with the atmosphere the three approaches commonly used to model the evolution of sst anomalies are reviewed case studies based on monthly or seasonal anomaly maps of the large scale sst and atmospheric anomalies numerical simulations with one dimensional mixed layer models and stochastic forcing models we stress the similarities in the different approaches and discuss their main advantages and limitations the response of the atmosphere to mid latitude sst anomalies is considered first we discuss the poorly known relationship between sst anomalies and diabatic heating using a crude assumption for the air sea coupling we consider a two layer quasi geostrophic channel model and discuss the stationary wave response to sst anomaly forcing and the resulting air sea feedback it is found that the back interaction of the sst anomalies onto the atmosphere causes a weak sst anomaly damping at large scales and a strong one at small scales the air sea coupling should also act as an eastward propagator for the sst anomalies the response of more realistic linear wave models to prescribed diabatic heating is then reviewed and it is suggested that realistic mid latitude sst anomalies have a weak influence on the atmospheric circulation corresponding to changes in the geopotential height of 10 30 m at most this order of magnitude is consistent with the results of general circulation model experiments and with the limited climate predictability associated with mid latitude sst anomalies

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

seasonality in the local and remote atmospheric response to sea surface temperature anomalies abstract two apparently contradictory situations are provided by observations of the atmospheric response to sea surface temperature anomalies these are i the extratropical regions of the winter hemisphere appear to possess strong teleconnections with equatorial forcing but weak or non existent connections with local extratropical heating anomalies ii the extratropical regions of the summer hemisphere are quite sensitive to local thermal forcing but apparently unaffected by the remote forcing from equatorial regions an attempt is made to provide a consistent physical picture which simultaneously embraces these two situations with the aid of a simple linear model it is shown that the summer hemisphere is more sensitive to local forcing than the winter hemisphere because it is closer to the diabatic limit of webster 1981 thus allowing an efficient energy generation the winter hemisphere is much closer to the adjective limit the sensitivity of the midlatitudes to remote equatorial forcing

simulation of the response of the north pacific ocean to the anomalous atmospheric circulation associated with el nino during el nino events when positive sea surface temperature sst anomalies form in the equatorial pacific sst anomalies also tend to develop in the north pacific this study attempts to model and explain the large scale features of the observed sst anomaly field in the north pacific during the fall and winter of the el nino year the experiment design consists of a mixed layer ocean model of the north pacific which is forced by atmospheric surface fields from two sets of community climate model ccm integrations the el nino set with prescribed positive sst anomalies in the tropical pacific and the control set which is obtained from an extended ccm integration with prescribed climatological ssts the response of the midlatitude ocean to atmospheric surface fields associated with el nino is obtained by compositing each set of model integrations el nino and control and then taking the difference between the composites the ocean model is able to reproduce the general features of the observed midlatitude sst anomaly pattern warm water in the northeast pacific and an elliptically shaped cold pool in the central pacific in these regions a large fraction of the temperature anomalies are significant at the 95 level as indicated by a two tailed t test the ocean temperature anomalies simulated by the model are primarily caused by changes in the sensible and latent heat flux and to a lesser extent the longwave radiation flux entrainment of cold water from below the mixed layer also influences ocean temperatures however the entrainment anomaly pattern has a complex spatial structure which does not always coincide with the simulated mixed layer temperature anomalies

horizontal structure of 500 mb height fluctuations with long intermediate and short time scales abstract maps of standard deviations and one point correlation maps based on twice daily data subjected to a variety of temporal filters are presented in order to document the horizontal structure of 500 mb height fluctuations with different time scales the filters have been chosen to isolate fluctuations with long time scales periods much longer than 30 days intermediate time scales 10 30 day periods and short time scales 2 5 6 day periods the one point correlation maps for long time scales resemble the teleconnection patterns described by wallace and cutzler these patterns are strongly regionally dependent with meridionally oriented dipole structures in the jet exit regions over the oceans indicative of strong fluctuations in the zonal wind for intermediate time scales the dominant patterns consist of more zonally oriented wave trains which originate in the jet entrance regions and cross the jet streams as they curve southeastward into the tropics another important distinction between th

possible impacts of mega el nino southern oscillation and atlantic multidecadal oscillation on eurasian heatwave frequency variability identifying predictability sources of heatwave variations is a scientific challenge and of practical importance this study investigates the summertime heatwave frequency hwf over eurasia for 1950 2014 the eurasian hwf is dominated by two distinct modes the interdecadal id mode featured by an increasing pattern overall centred around eastern europe central asia and mongolia southwestern china and the interannual ia mode resembling a tripole anomaly pattern with three centres over western northern europe northeastern asia and east asia the id mode is found to be influenced by mega el nino southern oscillation mega enso and the atlantic multidecadal oscillation amo and the latter has far more effect whereas the ia mode is connected with mega enso further analysis suggests that mega enso variations can incite a gill type response spreading to eurasia while the amo changes cause eastward propagating rossby wave trains toward eurasia these two teleconnection patterns together contribute to the large scale circulation anomalies of the id mode and those related to the ia mode arise from the teleconnection pattern excited by mega enso a strong mega enso triggers subsidence with high pressure anomalies warms the surface and increases the hwf significantly over northeastern asia particularly likewise the warm amo induced circulation anomalies engender surface radiative heating and hwf growth in most of the eurasian continent except some localized siberian and asian regions the situation is opposite for a weak mega enso and amo those models from phase 5 of the coupled model intercomparison project cmip5 which realistically capture the features of the id mode can reproduce the amo like sea surface temperature anomalies sstas while signals resembling mega enso are found in those with favourable capability of simulating the ia mode on the contrary these relevant sstas linked to the respective modes vanish in the models with little skills thus mega enso and the amo might provide two critical predictability sources for heat waves over eurasia

atmosphere ocean coupled variability in the south atlantic abstract the climate variability of the south atlantic region is determined from 40 yr 1953 92 of comprehensive ocean atmosphere data set monthly sea surface temperature sst and sea level pressure slp data using the empirical orthogonal function eof and the singular value decomposition svd analysis methods the eof method is applied to each field separately whereas the svd method is applied to both fields simultaneously the significance of the atmosphere ocean interaction is revealed by a strong resemblance between individual eof and coupled svd modes of sst and slp the three leading modes of coupled variability on interannual and interdecadal timescales are discussed in some detail the first coupled mode which accounts for 63 of the total square covariance represents a 14 16 yr period oscillation in the strength of the subtropical anticyclone accompanied by fluctuations of a north south dipole structure in the sst the atmosphere ocean coupling is strongest during the southern summe

decadal changes in the southern hemisphere sea surface temperature in association with el nino southern oscillation and southern annular mode the spatial structure of el nino southern oscillation enso and the southern annular mode sam which are the two most important climate modes affecting sea surface temperature sst variability in the southern hemisphere sh appear to have changed since 1999 the characteristic features of the enso and sam related atmospheric and oceanic variability in the sh are compared between two sub periods 1979 1998 and 1999 2012 using cyclostationary empirical orthogonal function analysis during the earlier period of 1979 1998 the enso is characterized by conventional eastern pacific type in which the signals in the sh constitute the pacific south america teleconnection pattern in contrast due to a shift of the active center of enso to the central pacific in the later period 1999 2012 atmospheric circulation and sst variability over the sh significantly vary moreover the sam related sst variability also shows remarkable differences before and after 1998 1999 this difference is primarily attributed to differences in the non annular spatial component of the sam between the two periods due to the changes in the spatial structure of the sam as well as those of the enso sst variability in the sh displays a marked change between the two periods detailed descriptions of the decadal changes of the sh sst in terms of interaction in the oceanic and atmospheric variability are presented along with the possible implications of this change

barotropic wave propagation and instability and atmospheric teleconnection patterns abstract a global barotropic model linearized about the 300 mb climatological mean january flow is perturbed by applying a series of localized forcings distributed throughout the tropics and subtropics structures which resemble the observed pacific north american and east atlantic teleconnection patterns noted by wallace and gutzler 1981 tend to recur in the responses similar patterns are found to result from the dispersion of isolated initial perturbations placed at a variety of locations in the tropics and midlatitudes it is shown that these structures are related to the most rapidly growing mode associated with barotropic instability of the zonally varying climatological basic state in the absence of damping this mode has an e folding time of about a week and a period close to 50 days in localized regions the instantaneous growth rates can be competitive with those of baroclinic instability these episodes of rapid local barotropic growth are interspersed with intervals in which the local

a statistical study of large scale long period variability in north pacific sea surface temperature anomalies abstract frequency domain principal components analysis a technique which involves extracting the eigenvalues and eigenvectors of the cross spectrum of a multivariate time series is used to analyze the development and movement of sea surface temperature sst anomalies in the north pacific a prominent feature of the low frequency sst field is an oscillatory pattern with a return period of about four to seven years it involves the slow migration of an anomaly northward into the western north pacific where the anomaly undergoes rapid expansion and intensification and then begins to deteriorate as it moves eastward it is suggested that the rapid expansion in midlatitudes is caused by a positive feedback between the sst anomalies the atmospheric long waves and cyclonic short waves

extratropical large scale air sea interaction in a coupled and uncoupled ocean atmosphere model spatial patterns of mid latitude large scale ocean atmosphere interaction on monthly to seasonal time scales have been observed to exhibit a similar structure in both the north pacific and north atlantic basins these patterns have been interpreted as a generic oceanic response to surface wind anomalies whereby the anomalous winds give rise to corresponding anomalous regions of surface heat flux and consequent oceanic cooling this mechanistic concept is investigated in this study using numerical models of a global atmosphere and a mid latitude ocean basin nominally the atlantic the models were run in both coupled and uncoupled mode model output was used to generate multi year time series of monthly mean fields empirical orthogonal function eof and singular value decomposition svd analyses were then used to obtain the principal patterns of variability in heat flux air temperature wind speed and sea surface temperature sst and to determine the relationships among these variables svd analysis indicates that the turbulent heat flux from the ocean to the atmosphere is primarily controlled by the surface scalar wind speed and to a lesser extent by air temperature and sst the principal patterns of air sea interaction are closely analogous to those found in observational data in the atmosphere the pattern consists of a simultaneous strengthening or weakening of the mid latitude westerlies and the easterly trades in the ocean there is cooling warming under the anomalously strong weak westerlies and trade winds with a weaker warming cooling in the region separating the westerly and easterly wind regimes these patterns occur in both coupled and uncoupled models and the primary influence of the coupling is in localizing the interaction patterns the oceanic patterns can be explained by the principal patterns of surface heat flux and the attendant warming or cooling of the ocean mixed layer

sensitivity of the position and variability of the eddy driven jet to different sst profiles in an aquaplanet general circulation model abstractthe response of the storm track and eddy driven jet to various steady sea surface temperature sst forcings is analyzed using the aquaplanet configuration of the atmospheric general circulation model action de recherche petite echelle grande echelle climat arpege climat the sst profiles are zonally homogeneous and piecewise linear functions of the latitude it allows for modifying the tropical component that controls the intensity of the subtropical jet without changing the midlatitude sst front and vice versa sensitivities to the position width and intensity of the midlatitude sst front as well as to the tropical ssts are investigated the baroclinicity and the storm track eddy activity both intensify for a stronger a wider or a more equatorward sst front the eddy driven jet always lies on the poleward side of the sst front and its relative distance to the front is interpreted in terms of upper tropospheric rossby wave breakings a focus is then made on the eddy driven jet variability t

an extratropical air sea interaction over the north pacific in association with a preceding el nino episode in early summer abstract using data for the month of june from 1951 through 2000 this study examined the air sea interactions over the north pacific after el nino matured during the preceding fall season the principal findings of this work are the following 1 a coherent region near the international date line idl in the extratropical north pacific revealed an area of significant negative correlations sncs between the preceding november sea surface temperature sst in the nino 3 region and the june sst in the north pacific also two indexes of the june okhotsk high show a significant positive correlation with the november sst in the nino 3 region during the 1963 2000 period 2 the strong southeastward wave flux from the upstream area of the okhotsk sea over much of the north pacific in the midlatitudes is associated with a strong preceding el nino event the development of the okhotsk high and a negative 500 hpa geopotential height sst anomaly around the coherent region the stationary wave propagation plays a

transient atmospheric response to interactive sst anomalies abstract the transient atmospheric response to interactive sst anomalies in the midlatitudes is investigated using a three layer qg model coupled in perpetual winter conditions to a slab oceanic mixed layer in the north atlantic the sst anomalies are diagnosed from a coupled run and prescribed as initial conditions but are free to evolve the initial evolution of the atmospheric response is similar to that obtained with a prescribed sst anomaly starting as a quasi linear baroclinic and then quickly evolving into a growing equivalent barotropic one because of the heat flux damping the sst anomaly amplitude slowly decreases albeit with little change in pattern correspondingly the atmospheric response only increases until it reaches a maximum amplitude after about 1 3 5 months depending on the sst anomaly considered the response is similar to that at equilibrium in the fixed sst case but it is 1 5 2 times smaller and then slowly decays away

time variation of 500 mb height fluctuations with long intermediate and short time scales as deduced from lag correlation statistics abstract the time variation of northern hemisphere wintertime 500 mb height fluctuations with short intermediate and long time scales is investigated using lag correlation patterns derived from time filtered data fluctuations with short 2 5 6 day periods time scales propagate eastward at a rate consistent with the notion of a steering level around 700 mb which supports an interpretation in terms of baroclinic waves the mobile teleconnection patterns associated with the intermediate 10 30 day periods time scales exhibit a pattern of time variation suggestive a rossby wave dispersion with a predominance of southward dispersion from middle latitudes into the tropics the geographically fixed teleconnection patterns characteristic of the longer time scales do not show a well defined pattern of time variation but their horizontal structure resembles that of the fastest growing normal mode associated with barotropic instability of the climatological mean wintertime flow

coherent interannual and decadal variations in the atmosphere ocean system 1 we investigate the source of poleward propagating atmospheric zonal wind anomalies originating at the equator and penetrating to high latitudes in both hemispheres in conjunction with enso dickey et al 1992 and report the discovery of similar variability on decadal and longer timescales since atmospheric dissipation times are generally on the order of a month or less we examine the ocean as a memory source for these globally coherent anomalies this hypothesis is substantiated by the observation of complementary oscillation in the sea surface temperature sst field further we detect a robust decadal variability 10 12 yrs in both the sst and contemporaneous atmospheric angular momentum aam series analyzing gisst sst data beginning in 1902 we confirm this decadal mode and find signatures of longer multidecadal sst variability centered in the equatorial and north pacific

the seasonal variation of the surface mixed layer response to the vertical motions of linear rossby waves abstract a kraus turner 1967 seasonal mixed layer model with constant background dissipation is used to study the mixed layer response to the vertical motions of linear rossby waves that are not driven by direct local atmospheric forcing the model equations are solved using analytical and simple numerical techniques a strong seasonal variation in the response to rossby waves is found the mixed layer buoyancy or sea surface temperature response is a maximum toward the end of the heating season or beginning of the cooling season early fall the mixed layer depth response is largest at the end of the cooling season the sea surface temperature sst pattern in response to the two baroclinic rossby waves that mcwilliams and flierl 1976 fit to the mode data is very different from the temperature pattern at a fixed depth below the mixed layer while the shape of the eddies as modeled by the two rossby waves stays fixed the shape of the sst response changes with time in addition the sst response p

results of the mars pathfinder atmospheric structure investigation we report on a thorough analysis of the mars pathfinder atmospheric structure investigation asi accelerometer data spanning the altitude range 161 8 9 km entry descent and landing occurred within 850 km of the viking 1 lander and somewhat later in northern summer the early morning entry 0300 hours provided the first opportunity to study mars nighttime atmospheric structure the close proximity to the viking 1 site has permitted a search for changes in atmospheric structure during the 21 years between the landings our results confirm and refine the major features of the atmospheric structure discovered in the initial analysis of the asi results reported by schofield et al 1997 the current analysis has yielded a much better definition of the temperature structure above 90 km altitude pathfinder measured a thermospheric peak temperature of 153 k at 134 km which is 30 k colder than the value found by viking 1 between 110 and 88 km pathfinder found a broad nearly isothermal plateau at 127 k which correlates very well with a similar structure evident in viking 1 data at the same pressures although the pathfinder layer is 25 k colder at levels above 88 km wavelike oscillations with a wavelength 5 km and amplitudes of 2 3 k are evident possibly reflecting gravity or planetary wave activity between 90 and 60 km the average temperature is 20 30 k cooler than viking 1 values large amplitude 10 20 k long wavelength 20 40 km oscillations which show a remarkable correspondence to equivalent structures found in the viking 1 profile at the same pressures occur in this region and are likely due to a diurnal tidal mode between 85 and 77 km a minimum of one oscillation results in temperatures up to 7 k below the saturation temperature of co2 well outside the uncertainties in the measurements and the vapor pressure curve and comparable to observed supersaturations of water in earth s mesosphere between 55 and 16 km temperatures are close to or warmer than viking 1 values superposed long wavelength oscillations correspond well with similar structures observed by viking 1 between 16 and 9 9 km the temperature profile shows an unexpected strong thermal inversion which may reflect radiative cooling due to a water cloud at the base of the inversion temperatures begin to increase abruptly until the last measurement at 8 9 km the viking like temperatures in the lower atmosphere are consistent with the viking like dust optical depths observed by the mars pathfinder imager the cool temperatures in the middle and upper atmosphere may be indicative of significant nighttime cooling at these levels although other interpretations are possible

assessing the importance of prominent warm sst anomalies over the midlatitude north pacific in forcing large scale atmospheric anomalies during 2011 summer and autumn abstractsets of atmospheric general circulation model agcm experiments are conducted to assess the importance of prominent positive anomalies in sea surface temperature sst observed over the midlatitude north pacific in forcing a persistent basin scale anticyclonic circulation anomaly and its downstream influence in 2011 summer and autumn the anticyclonic anomaly observed in october is well reproduced as a robust response of an agcm forced only with the warm sst anomaly associated with the poleward shifted oceanic frontal zone in the midlatitude pacific the equivalent barotropic anticyclonic anomaly over the north pacific is maintained under strong transient eddy feedback forcing associated with the poleward deflected storm track as the downstream influence of the anomaly abnormal warmth and dryness observed over the northern united states and southern canada in october are also reproduced to some extent the corresponding agcm response over the north pacific to the tropical sst anomalies is simil

testing a dynamical model for mid latitude sea surface temperature anomalies abstract a slab model of the oceanic mixed layer is used to predict the statistical characteristics of the sea surface temperature anomalies that are forced by day to day changes in air sea fluxes in the presence of a mean current because of the short time scale of the atmospheric fields the model validity can be tested without quantitative information on the atmospheric forcing a procedure is developed for the case where the mean current is given it is applied to sea surface temperature sst anomaly data from the north pacific using ship drift data as estimates of the mean ocean currants at the 95 level of significance the model is consistent with the data over more than 85 of the investigated region the results indicate that the atmospheric forcing acts as a white noise forcing in regions of large currents advection effects are important at low frequencies however sst anomaly autospectra are equally well represented by a local model where advection is neglected the available meteorological

numerical simulation of a response of an oceanic front to an atmospheric frontal passage the influence of middle latitude cyclones and their associated cold fronts on open ocean fronts is studied with an embedded mixed layer ocean circulation model similar to that of adamec et al 1981 finite differences with horizontal resolution of 5 km in a staggered grid are used to solve the model equations within a domain of total meridional extension of 300 km and 500 m depth three numerical experiments were performed to investigate the response of an oceanic front similar to the south atlantic subtropical convergence zone to an atmospheric frontal passage under the effect of the cold air outbreak the thermal and dynamic structures of the upper layers are substantially modified with a higher sinking cooling rate of the mixed layer the sinking cooling rate depends strongly on the magnitude of the thermal gradient at the top of the thermocline and on the mixed layer depth due to the differences in sinking cooling rates a single storm can move the oceanic front up to 20 km from its initial position for low intensity winds a change in the wind direction does not affect the thermal structure of the upper layer ocean even in the frontal region the mixed layer oscillations are entirely a function of the daily scale of the solar heating for a sudden change in the wind direction the response of the current velocity field in the mixed layer is almost instantaneous

linear and nonlinear aspects of snow albedo feedbacks in atmospheric models namias hypothesis that anomalous snowcover on the eastern side of the north american continent can generate an anomalous east coast low pressure system and an anomalous inland high pressure system is consistent with the time averaged anomalous response from a nonlinear primitive equation channel model with an idealized flat land sea arrangement an attempt to understand and describe this anomalous response in the nonlinear model as a linear response to anomalous diabatic heating was largely unsuccessful primarily because the anomalous eddy fluxes were also important this unsuccessful attempt to describe the nonlinear model s time averages by linear theory then motivated several comparisons between linear and nonlinear severely truncated quasi geostrophic models it was also found in these models that the eddy fluxes were extremely important for forcing or dissipating the stationary eddies