a cold path for the gulf stream troposphere connection abstractthe mechanism by which the gulf stream sea surface temperature sst front anchors a band of precipitation on its warm edge is still a matter of debate and little is known about how synoptic activity contributes to the mean state in the present study the influence of the sst front on precipitation is investigated during the course of a single extratropical cyclone using a regional configuration of the met office unified model the comparison of a control run with a simulation in which sst gradients were smoothed brought the following conclusions a band of precipitation is reproduced for a single extratropical cyclone and the response to the sst gradient is dominated by a change of convective precipitation in the cold sector of the storm several climatological features described by previous studies such as surface wind convergence on the warm edge or a meridional circulation cell across the sst front are also reproduced at synoptic time scales in the cold sector based on these results a s

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

air sea interaction at the southern brazilian continental shelf in situ observations the influence of the cross shelf oceanographic front occurring between the brazil current bc and the brazilian coastal current bcc on the local marine atmospheric boundary layer mabl is investigated here this front is typical of wintertime in the southern brazilian continental shelf sbcs and this is the first time that its effects are investigated over the above mabl here we analyze variability vertical structure and stability of mabl as well as heat fluxes at air sea interface across five oceanographic transects in the sbcs made during a winter 2012 cruise local thermal gradients associated with mixing between distinct water masses play an essential role on mabl modulation and stability although weaker when compared with other frontal regions the cross shelf thermal gradients reproduce exactly what is expected for open ocean regions stronger weaker winds lower higher sea level pressure and a more unstable stable mabl are found over the warm cold side of the oceanographic front between the bc warm and coastal cold waters our findings strongly support the coexistence of both known mabl modulation mechanisms the static and hydrostatic mabl stability this is the first time that these modulation mechanisms are documented for this region turbulent fluxes were found to be markedly dependent on the cross shelf sst gradients resulting in differences of up to 100 w m 2 especially in the southernmost region where the gradients were more intense

sea level pressure minimum along the kuroshio and its extension abstractatmospheric effects of sea surface temperature sst fronts along the kuroshio and kuroshio extension k ke are investigated by examining spatial characteristics of the climatological sea level pressure slp surface winds and surface heat flux q fields based on an in situ observation dataset a hydrostatic effect of the sst front is observed during the northwesterly monsoon characterized by a westward extending low slp wedge trough slightly south of the peak in q along the k ke ageostrophic surface westerlies crossing slp isobars toward a trough center are found north of the low slp wedge apparently because of the eastward acceleration by the vertical mixing effect this feature of the ageostrophic winds is less pronounced south of it a north south asymmetry arising as vertical mixing accelerates decelerates eastward ageostrophic winds north south of it while the slp trough near the sst front is found nearly year round except for summer its meridional location seasonally migrates pr

the influence of sea surface temperature on surface wind in the eastern equatorial pacific weekly to monthly variability abstract temporal correlations between near equatorial surface wind and sea surface temperatures sst at 11 w in the eastern pacific ocean are investigated using data from an array of moored sensors between 5 n and 5 s the signature of tropical instability waves with periods of 20 30 days is apparent in time series of sst and both the meridional and zonal wind components results indicate the existence of a band of pronounced horizontal divergence in the surface wind field associated with the large meridional sst gradient equatorial front normally located just north of the equator perturbations of the equatorial front by the instability waves induce fluctuations in the overlying winds evidence of the air sea coupling is stronger in time series of the meridional gradients of wind and sst than between time series of the variables themselves the meridional differencing serves as a high pass filter in the space domain which removes planetary scale wind fluctuations that are unrelated to the local sst

an objective cyclone climatology for the southern hemisphere abstract an objective method is developed and used to derive a climatology of centers of cyclonic vorticity for the southern hemisphere based on twice daily european centre for medium range weather forecasts ecmwf 1000 hpa analyses during 1980 86 these centers were computed as local minima of geostrophic relative vorticity g extending previous studies based on pressure minima this use of g avoids a bias favoring slower and or deeper cyclones that occurs when pressure is used and includes a large number of additional mobile vorticity centers in the 45 55 s band that are missed where a local pressure minimum cannot be found an automated tracking algorithm similar to that of murray and simmonds is used to match predicted location pressure and g from previous track history with available centers large numbers of g centers were found south of 60 s and near the midlatitude continents as in previous studies these were a mixture of migratory centers and other fixed topographic features the maxi

seasonal variations in the southern hemisphere storm tracks and jet streams as revealed in a reanalysis dataset abstract regional characteristics of the climatological seasonal variations in southern hemisphere sh storm tracks are examined based on a reanalysis dataset when differences in vertical structure between the subpolar and subtropical jet streams spj and stj respectively are considered the regional characteristics can be interpreted reasonably well from a potential vorticity perspective of baroclinic eddy growth and downstream development of a baroclinic wave packet eddy activity in the upper and lower tropospheres is strongest in the core region of the spj over the eastern south atlantic and indian ocean throughout the year even in austral winter when the intense stj forms over the indian ocean and south pacific showing its eddy driven nature the spj accompanies the strong surface westerlies along a well defined baroclinic zone above an intense oceanic frontal zone in this core region of the storm track low level eddy activity is strongly correlated with the local near surface baroclinicity

evidence for sst forced anomalous winds revealed from simultaneous radiosonde launches from three ships across the kuroshio extension front abstractsimultaneous launches of radiosondes were conducted from three research vessels aligned meridionally across a sea surface temperature sst front on the flank of the kuroshio extension the soundings carried out every 2 h over 5 days in early july 2012 provided a unique opportunity in capturing unambiguous data on anomalous easterly winds derived from a pronounced meridional sst gradient the data indicate that a meridional contrast in surface heat fluxes from the underlying ocean enhanced the air temperature anomaly across the sst front which was observed from the surface up to 300 m altitude correspondingly high and low pressure anomalies that reached 800 m altitude formed on the north and south sides of the sst front respectively these temperature and pressure anomalies were maintained even during the passage of synoptic scale disturbances although the free tropospheric winds are overall westerly winds below the 1000 m level were easterly due to geostrophic anomalies driven by the northw

air sea interaction effects in the lower troposphere across the north wall of the gulf stream abstract significant atmospheric and oceanographic differences have often been observed in the regions lying on either side of the north wall of the gulf stream satellite visible range sensors have revealed changes in reflectivity across the gulf stream believed to be due to changes in sea state that are related to these atmospheric and oceanic differences in addition lines of low level cloud paralleling the edge of the gulf stream have been observed to persist in satellite imagery for several days at a time anomalous radar propagation also has been noted to occur in these same regions in an attempt to document the interrelation of these phenomena the lower atmosphere over the north wall of the gulf stream was studied on two separate occasions sea state photography and measurements of sea surface temperature air temperature dew point temperature and atmospheric pressure were made by an instrumented rp 3a aircraft flying at various altitudes from the gulf stream across the north wall and onto

atmospheric responses to kuroshio sst front in the east china sea under different prevailing winds in winter and spring abstractatmospheric responses to the kuroshio sst front in the east china sea under different prevailing winds are examined using high resolution observations and numerical modeling satellite data reveal a significant in phase relationship between sst and surface wind speed indicative of ocean to atmosphere influence the atmospheric response varies according to the relative surface wind direction with respect to the sst front orientation under the alongfront condition low high slp anomalies are found on the warmer colder flank of the front accompanied by surface wind convergence divergence enhanced precipitation and frequent cumulus convection appear over the warm kuroshio suggesting an atmospheric response extending into the free troposphere under the cross front condition when the air blows from cold to warm warm to cold sst divergence convergence is located directly over the sst front and its magnitude is proportional to the downwind sst gradient under such prevailing winds the

atmospheric circulations induced by a midlatitude sst front a gcm study the atmospheric effects of sea surface temperature sst anomalies over and near western boundary currents are a matter of renewed interest the general circulation model gcm of the laboratoire de meteorologie dynamique lmd z has a zooming capability that allows a regionally increased resolution this gcm is used to analyze the impact of a sharp sst front in the north atlantic ocean two simulations are compared one with climatological ssts and the other with an enhanced gulf stream front the results corroborate the theory developed previously by the present team to explain the impact of oceanic fronts in this theory the vertical velocity at the top of the atmospheric boundary layer has two components mechanical and thermal it is the latter that is dominant in the tropics while in midlatitudes both play a role in determining the wind convergence above the boundary layer the strengthened sst front does generate the previously predicted stronger ascent above the warmer water south of the front and stronger descent above the colder waters to the north in the gcm simulations the ascent over the warm anomalies is deeper and more intense than the descent

multiyear measurements of the oceanic and atmospheric boundary layers at the brazil malvinas confluence region 1 this study analyzes and discusses data taken from oceanic and atmospheric measurements performed simultaneously at the brazil malvinas confluence bmc region in the southwestern atlantic ocean this area is one of the most dynamical frontal regions of the world ocean data were collected during four research cruises in the region once a year in consecutive years between 2004 and 2007 very few studies have addressed the importance of studying the air sea coupling at the bmc region lateral temperature gradients at the study region were as high as 0 3 c km 1 at the surface and subsurface in the oceanic boundary layer the vertical temperature gradient reached 0 08 c m 1 at 500 m depth our results show that the marine atmospheric boundary layer mabl at the bmc region is modulated by the strong sea surface temperature sst gradients present at the sea surface the mean mabl structure is thicker over the warmside of the bmc where brazil current bc waters predominate the opposite occurs over the coldside of the confluence where waters from the malvinas falkland current mc are found the warmside of the confluence presented systematically higher mabl top height compared to the coldside this type of modulation at the synoptic scale is consistent to what happens in other frontal regions of the world ocean where the mabl adjusts itself to modifications along the sst gradients over warm waters at the bmc region the mabl static instability and turbulence were increased while winds at the lower portion of the mabl were strong over the coldside of the bc mc front an opposite behavior is found the mabl is thinner and more stable our results suggest that the sea level pressure slp was also modulated locally together with static stability vertical mixing mechanism by the surface condition during all cruises sst gradients at the bmc region modulate the synoptic atmospheric pressure gradient postfrontal and prefrontal conditions produce opposite thermal advections in the mabl that lead to different pressure intensification patterns across the confluence

direct observations of atmospheric boundary layer response to sst variations associated with tropical instability waves over the eastern equatorial pacific tropical instability waves tiws with a typical wavelength of 1000 km and period of 30 days cause the equatorial front to meander and result in sst variations on the order of 18 28c vertical soundings of temperature humidity and wind velocity were obtained on board a japanese research vessel which sailed through three fully developed sst waves from 1408 to 1108w along 28n during 21 28 september 1999 a strong temperature inversion is observed throughout the cruise along 28n capping the planetary boundary layer pbl that is 1 1 5 km deep temperature response to tiw induced sst changes penetrates the whole depth of the pbl in response to an sst increase air temperature rises in the lowest kilometer and shows a strong cooling at the mean inversion height as a result this temperature dipole is associated with little tiw signal in the observed sea level pressure slp the cruise mean vertical profiles show a speed maximum at 400 500 m for both zonal and meridional velocities sst based composite profiles of zonal wind velocity show weakened intensified vertical shear within the pbl that is consistent with enhanced reduced vertical mixing causing surface wind to accelerate decelerate over warm cold ssts taken together the temperature and wind soundings indicate the dominance of the vertical mixing over the slp driving mechanism based on the authors measurements a physical interpretation of the widely used pbl model proposed by lindzen and nigam is presented

frontogenesis in the agulhas return current region simulated by a high resolution cgcm abstractdetailed mechanisms for frontogenesis frontolysis of the sea surface temperature sst front in the agulhas return current arc region are investigated using outputs from a high resolution coupled general circulation model the sst front is maintained throughout the year through an approximate balance between frontolysis by surface heat flux and frontogenesis by horizontal advection although a southward northward cross isotherm flow on the northern southern side of the front is weaker than a strong eastward along isotherm current in the frontal region this cross isotherm confluent flow advects warmer cooler temperature toward the sst front north south of the front and acts as the dominant frontogenesis mechanism in addition stronger weaker frontogenesis in austral summer winter is attributed to the stronger weaker cross isotherm confluence which may be linked to seasonal variations of the agulhas current arc and antarctic circumpolar current on the other hand the contributi

teleconnections in the geopotential height field during the northern hemisphere winter abstract contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on earth referred to as teleconnections in this paper are studied in an attempt to identify and document recurrent spatial patterns which might be indicative of standing oscillations in the planetary waves during the northern hemisphere winter with time scales on the order of a month or longer a review of existing literature on the subject reveals the existence of at least four such patterns the north atlantic and north pacific oscillations identified by walker and bliss 1932 a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes first noted by lorenz 1951 and what we will refer to as the pacific north american pattern which has been known to operational long range forecasters in this country since the 1950 s a data set consisting of nmc monthly mean sea level pressure and 500 mb height analyses for a 15 year period is used as a basis fo

satellite measurements reveal persistent small scale features in ocean winds four year averages of 25 kilometer resolution measurements of near surface wind speed and direction over the global ocean from the quikscat satellite radar scatterometer reveal the existence of surprisingly persistent small scale features in the dynamically and thermodynamically important curl and divergence of the wind stress air sea interaction over sea surface temperature fronts throughout the world ocean is evident in both the curl and divergence fields as are the influences of islands and coastal mountains ocean currents such as the gulf stream generate distinctive patterns in the curl field these previously unresolved features have important implications for oceanographic and air sea interaction research

ocean atmosphere covariability in the western arabian sea abstract the western arabian sea exhibits strong spatial variability in sea surface temperature sst during the southwest monsoon with changes in sst that can exceed 5 c over 200 km exploration of satellite based and in situ data shows a strong connection between mesoscale sst features and changes in the atmospheric boundary layer the fundamental relationship is that of weak strong wind velocities overlying cold warm sst features there are also coherent changes in other near surface meteorological parameters such as the air sea temperature difference and relative humidity indicating changes in the stability of the planetary boundary layer over the mesoscale sst features these relationships are similar to those recently reported over the equatorial pacific tropical instability wave region this observed covariability of atmospheric boundary layer structure and sst results in variations of the surface heat and moisture fluxes latent heat flux is modified by changes in relative humidity principa

coupled ocean atmospheric waves on the equatorial front striking 20 30 day sea surface temperature waves observed along the equatorial front in the later half of the year are generally believed to be of an oceanic origin here we report the detection of atmospheric waves that are unambiguously tied to these oceanic waves using new satellite measurements of surface winds a general circulation model simulation reveals that these atmospheric waves have a shallow vertical structure trapped in the planetary boundary layer pbl unlike el nino southern oscillation where changes in deep convection are the cause of anomalous winds vertical wave motion penetrates well above the pbl and is likely to impact the distribution and transport of climatically important gas species such as ozone and dimethyl sulfide

atmospheric boundary layer adjustment to the synoptic cycle at the brazil malvinas confluence south atlantic ocean 1 this study analyzes and discusses atmospheric boundary layer vertical profiles of potential temperature specific humidity and wind speed at each of the sides of the brazil malvinas confluence in the southwestern atlantic ocean such confluence is characterized by the meeting of water masses with very different characteristics the southern waters of the malvinas current can be several degrees colder and appreciably less salty than the northern brazil current waters at the same time a synoptic cycle can be identified at the region marked by the successive passages of frontal systems and extratropical cyclones the different phases of the synoptic cycle lead to different thermal advections at the confluence causing respective different patterns of atmospheric boundary layer adjustment to the surface heterogeneity induced by the confluence in the present study this adjustment along the synoptic cycle is analyzed using data from five experiments performed across the confluence from 2003 to 2008 in each of the campaigns a number of soundings were launched from a ship at both sides of the confluence a climatological analysis with respect to the closest frontal passage is presented and it suggests that the observations collected at each of the years analyzed are referent to a different day of the synoptic cycle the average profiles at each side of the confluence are in agreement with previous modeling studies of warm and cold thermal advection patterns over an oceanic front furthermore our study shows that peculiar transitional characteristics are also observed between the conditions of well established warm and cold advection at many phases of the synoptic cycle a strongly stratified boundary layer occurs at one or both sides of the confluence some of the observed characteristics such as a large moisture accumulation near the surface suggest that existing sensible and latent heat fluxes parameterizations fail under very strong stratifications and the consequences of this deficiency are analyzed

deep atmospheric response to the spring kuroshio over the east china sea abstractthe atmospheric response to the spring kuroshio front over the east china sea is investigated using a suite of high resolution satellite data and a regional atmospheric model the atmospheric response appears to extend beyond the marine atmospheric boundary layer with frequent occurrence of cumulus convection in spring quick scatterometer quikscat wind speed shows a clear effect of sea surface temperature sst with high low wind speed observed over the warm cold tongue this in phase relationship between sst and surface wind speed is indicative of sst influence on the atmosphere wind convergence is found on the warmer flank of the kuroshio front accompanied by a narrow rainband the analysis of satellite borne radar measurements indicates that deep convection appears over the kuroshio warm tongue in the spring season with enhanced convective precipitation frequent occurrence of cumulus convection and increased precipitation cloud tops in altitude these deep convective activities

local and remote atmospheric response to tropical instability waves a global view from space a la nina took place in the equatorial pacific in 1999 and strong tropical instability waves tiws developed causing large meanders of a sea surface temperature sst front between the equator and 3 n high resolution satellite measurements are used to describe the variability of sst surface wind velocity column integrated water vapor cloud liquid water and precipitation associated with these strong tiws in 1999 coherent ocean atmosphere patterns emerge in both the pacific and atlantic revealing rich regional characteristics in the far eastern pacific southeasterly trades strengthen weaken over positive negative sst anomalies apparently due to enhanced reduced mixing with high speed winds aloft in the central pacific we find evidence that sst induced sea level pressure changes also contribute substantially to wind fluctuations similar sst wind covariability also exists in the southern hemisphere along 2 s but the wind variability induced by unit sst anomaly is much larger than that north of the equator in the central pacific where the equatorial front is broad the northern sst pattern has a large meridional scale and reaches as far north as 6 n further to the north in the intertropical convergence zone itcz where local sst anomalies are small significant variability is found in clouds and precipitation which is further correlated with surface wind convergence in the atlantic tiw signals in sst are strongly trapped near the equator but they induce significant remote response in the itcz which takes a more southern position than its pacific counterpart and thus more susceptible to tiw influence

bathymetric effect on the winter sea surface temperature and climate of the yellow and east china seas 1 whether and how the atmosphere reacts to changes in extratropical sea surface temperature sst is under intense debate and this lack of understanding has been a major obstacle in the study of non el nino climate variability using new satellite measurements we detect clear ocean to atmospheric feedback in the yellow and east china yec seas that is triggered by the submerged ocean bottom topography under intense surface cooling in winter water properties are well mixed up to 100 m deep ocean depth thus has a strong influence on sst of the continental shelf leading to a remarkable collocation of warm tongues and deep channels high winds and increased cloudiness are found over these warm tongues one such band of ocean atmospheric co variation meanders through the basin following a deep channel for an amazing distance of 1000 km in addition to these climatic effects the kuroshio front where the warm current meets the much colder shelf water strengthens the growth of storms

carbon dioxide speciation in silicate melts a restart abstract using infrared spectroscopy we investigated the speciation of carbon dioxide in albitic and synthetic iron free dacitic glasses after annealing the glasses below the glass transition temperature in the temperature range 673 973 k at 0 5 gpa samples were rapidly quenched under constant pressure the experiments show that the ratio of the integrated intensities of the 2350 cm 1 band due to molecular co 2 to that of the band doublet at 1700 1375 cm 1 due to co 3 2 increases with higher annealing temperatures for both glass compositions our study demonstrates that in contrast to recent suggestions the equilibrium of the co 2 species reaction co 2 o 2 co 3 2 in silicate glasses melts shifts towards molecular co 2 with increasing temperature the co 2 species concentrations and an ideal solution model were used to determine equilibrium constants for the homogeneous species reaction we derived preliminary values for the enthalpy h 0 and entropy s 0 of this reaction assuming that the species concentrations reflect those at experimental temperatures h 0 12 2 kj mol 1 and s 0 23 3 j mol 1 k 1 for albitic composition h 0 29 2 kj mol 1 and s 0 32 3 j mol 1 k 1 for dacitic composition

barometric pressure variations associated with eastern pacific tropical instability waves abstract barometric pressure surface temperature and wind time series in the eastern equatorial pacific are analyzed to determine if oceanic tropical instability wave tiw sea surface temperature variations cause barometric pressure gradients large enough to influence the atmospheric boundary layer during the study period from april 2001 to september 2002 11 tiws propagated westward past 110 w causing a spectral peak at 20 30 days in the sea surface temperature sst meridional difference between 2 n 110 w and 0 110 w likewise the meridional pressure difference also had a spectral peak in the 20 30 day tiw band cross spectral analysis shows that within the tiw band sst induced pressure variations were roughly 0 1 hpa c 1 in magnitude the resulting pressure gradient force is comparable in magnitude to other terms in the meridional momentum balance implications about the role of the boundary layer capping in the adjustment to sst forcing are discussed

air sea heat exchanges characteristic of a prominent midlatitude oceanic front in the south indian ocean as simulated in a high resolution coupled gcm abstract an integration of a high resolution coupled general circulation model whose ocean component is eddy permitting and thus able to reproduce a sharp gradient in sea surface temperature sst is analyzed to investigate air sea heat exchanges characteristic of the midlatitude oceanic frontal zone the focus of this paper is placed on a prominent sst front in the south indian ocean which is collocated with the core of the southern hemisphere storm track time mean distribution of sensible heat flux is characterized by a distinct cross frontal contrast it is upward and downward on the warmer and cooler flanks respectively of the sst front acting to maintain the sharp gradient of surface air temperature sat that is important for preconditioning the environment for the recurrent development of storms and thereby anchoring the storm track induced by cross frontal advection of cold warm air associated with migratory atmospheric disturbances the surface flux is highly variable with intermittent en

ocean currents evident in satellite wind data satellite mounted radar scatterometers designed to quantify surface winds over the ocean actually measure the relative motion between the air and the ocean surface estimates of the wind stress from conventional surface wind measurements are usually derived neglecting ocean currents however when the relative motion is used the differences in the estimated stress can be as large as 50 near the equator and may even reverse sign during an el nino this assertion is supported by the strong relationship between the surface currents measured by the tropical atmosphere ocean tao array in the pacific ocean and the differences between the winds estimated from scatterometer data and those measured by tao anemometers the fact that the scatterometer measures relative motion and not wind alone makes scatterometer derived stress a more accurate representation of the boundary condition needed for both atmospheric and oceanic models than stress fields derived neglecting ocean currents

ocean frontal effects on the vertical development of clouds over the western north pacific in situ and satellite observations abstract a suite of shipboard and satellite observations are analyzed and synthesized to investigate the three dimensional structure of clouds and influences from sea surface temperature fronts over the western north pacific sharp transitions are observed across the kuroshio extension ke front in the marine atmospheric boundary layer mabl and its clouds the ocean s influence appears to extend beyond the mabl with higher cloud tops in altitude along the ke front than the surroundings in winter intense turbulent heat release from the ocean takes place on the southern flank of the ke front where the cloud top penetrates above the mabl and reaches the midtroposphere in this band of high cloud tops frequent lightning activity is observed the results of this study suggest a sea level pressure mechanism for which the temperature gradient in the mabl induces strong surface wind convergence on the southern flank of the ke front deepening the clouds there in early summer sea fog frequently occurs on

observations of sst induced perturbations of the wind stress field over the southern ocean on seasonal timescales the surface wind stress response to sea surface temperature sst over the latitude range 308 608 si n the southern ocean is described from the national aeronautics and space administration s quikscat scatterometer observations of wind stress and reynolds analyses of sst during the 2 yr period august 1999 to july 2001 while ocean atmosphere coupling at midlatitudes has previously been documented from several case studies this is the first study to quantify this relation over the entire southern ocean the spatial structures of the surface wind perturbations with wavelengths shorter than 108 latitude by 308 longitude are closely related to persistent spatial variations of the sst field on the same scales the wind stress curl and divergence are shown to be linearly related respectively to the crosswind and downwind components of the sst gradient the curl response has a magnitude only about half that of the divergence response this observed coupling is consistent with the hypothesis that sst modification of marine atmospheric boundary layer mabl stability affects vertical turbulent mixing of momentum inducing perturbations in the surface winds the nonequivalence between the responses of the curl and divergence to the crosswind and downwind sst gradients suggests that secondary circulations in the mabl may also play an important role by producing significant perturbations in the surface wind field near sst fronts that are distinct from the vertical turbulent transfer of momentum the importance of the wind stress curl in driving ekman vertical velocity in the open ocean implies that the coupling between winds and sst may have important feedback effects on upper ocean processes near sst fronts

sst induced surface wind variations over the brazil malvinas confluence satellite and in situ observations abstract the confluence of the brazil malvinas currents maintains strong sea surface temperature sst fronts in the midlatitude southwestern atlantic year round sst effects on near surface stability and surface wind variations are examined in this region using satellite and in situ datasets satellite observations show strong weak surface wind speeds over the warm brazil cold malvinas current a novel feature of this study is the construction of a high resolution surface meteorological dataset that is based on historical ship observations analysis of this new in situ dataset reveals an increased reduced sea air temperature difference over the brazil malvinas current indicating destabilization stabilization in the atmospheric boundary layer these results are consistent with the sst induced vertical mixing mechanism for wind adjustment the sst effect on the near surface atmosphere is observed both in the climatology and on interannual time scales in the brazil malvinas confluence along a zo

sst front anchored mesoscale feature of surface wind in the southern indian ocean using 28 year satellite borne special sensor microwave imager observations features of high wind frequency hwf over the southern indian ocean are investigated climatology maps show that high winds occur frequently during austral winter located in the open ocean south of polar front in subpolar region warm flank of the subantarctic front between 55 e 78 e and south of cape agulhas where westerly wind prevails the strong instability of marine atmospheric boundary layer accompanied by increased sensible and latent heat fluxes on the warmer flank acts to enhance the vertical momentum mixing thus accelerate the surface winds effects of sea surface temperature sst front can even reach the entire troposphere by deep convection hwf also shows distinct interannual variability which is associated with the southern annual mode sam during positive phase of the sam hwf has positive anomalies over the open ocean south of polar front while has negative anomalies north of the sst front a phase shift of hwf happened around 2001 which is likely related to the reduction of storm tracks and poleward shift of westerly winds in the southern hemisphere

on the role of sea surface temperature gradients in forcing low level winds and convergence in the tropics abstract we examine the importance of pressure gradients due to surface temperature gradients to low level p 700 mb flow and convergence in the tropics over time scales 1 month the latter plays a crucial role in determining the distribution of cumulonimbus convection and rainfall our approach is to consider a simple one layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically consistent with ecmwf analyzed data the top of the layer is taken at 700 mb the influence from higher levels is intentionally suppressed by setting horizontal pressure gradients and frictional stresses to zero at the top of the layer horizontal convergence within the layer is taken up by cumulonimbus mass flux however the development of the cumulonimbus mass flux is associated with a short relaxation time o hr roughly the development time for such convection during this short time horizontal convergence acts to redistribute mass so as to reduce horizontal pressur

a thermal front within the marine atmospheric boundary layer over the agulhas current south of africa composite aircraft observations aircraft cross section observations across the northern edge of the warm agulhas current to the south of africa are used to form composite results of mean and turbulent meteorological parameters over a 4 day period characterized by winter zonal westerlies across a sea surface temperature sst front of 8 c 40 km 1 near 35 s 23 e surface heat fluxes and wind stress increase fivefold the moist unstable marine atmospheric boundary layer is 400 m deeper on the warm side of the sst front and turbulent variances increase with sst in a logarithmic correlation r 0 76 a jetlike core of accelerated winds 17 m s 1 over the axis of warmest water is found its existence is thought to be due to secondary circulations set up by enhanced pressure gradients and baroclinic effects the sharp thermal front is quasi stationary and semipermanent during synoptic prefrontal conditions and zonal flows and lies approximately over the 200 m isobath in association with the agulhas current

spiral rainbands in a numerical simulation of hurricane bill 2009 part i structures and comparisons to observations abstractthis study examines spiral rainbands in a numerical simulation of hurricane bill 2009 this paper the first part of the study evaluates the structures of spiral rainbands and compares them to previous observations four types of spiral rainbands are identified principal secondary distant and inner rainbands principal rainbands tend to be stationary relative to the storm center while secondary rainbands are more transient and move around the storm center both principal and secondary rainbands are tilted radially outward with height and have many of the commonly observed kinematic features such as overturning secondary circulation and enhanced tangential velocity on their radially outward sides principal rainbands are bounded by very dry air on their radially outward sides distant rainbands are radially inward tilting convective features that have dense cold pools near the surface inner rainbands are made of shallow convection that appears to have originated from near the eyewall dif

the zonal asymmetry of the southern hemisphere winter storm track atmospheric general circulation model experiments have been performed to investigate how the significant zonal asymmetry in the southern hemisphere sh winter storm track is forced by sea surface temperature sst and orography an experiment with zonally symmetric tropical ssts expands the sh upper tropospheric storm track poleward and eastward and destroys its spiral structure diagnosis suggests that these aspects of the observed storm track result from rossby wave propagation from a wave source in the indian ocean region associated with the monsoon there the lower tropospheric storm track is not sensitive to this forcing however an experiment with zonally symmetric midlatitude ssts exhibits a marked reduction in the magnitude of the maximum intensity of the lower tropospheric storm track associated with reduced sst gradients in the western indian ocean experiments without the elevation of the south african plateau or the andes show reductions in the intensity of the major storm track downstream of them due to reduced cyclogenesis associated with the topography these results suggest that the zonal asymmetry of the sh winter storm track is mainly established by stationary waves excited by zonal asymmetry in tropical sst in the upper troposphere and by local sst gradients in the lower troposphere and that it is modified through cyclogenesis associated with the topography of south africa and south america

the influence of sea surface temperature on surface wind in the eastern equatorial pacific seasonal and interannual variability abstract the climate of the eastern pacific exhibits a pronounced equatorial asymmetry boundary layer air originating in the southern hemisphere trades crosses the equator and flows into the intertropical convergence zone itcz whose southern limit is nearly always located at least 4 to the north of the equator the sea surface temperature sst distribution is characterized by a prominent cold tongue centered 1 s a strong frontal zone centered 2 n and a warm eastward current centered near 5 n the surface wind field exhibits a pronounced horizontal divergence as the air flows northward across the oceanic frontal zone these features vary in strength in response to the annual cycle and the el nino southern oscillation phenomenon the northward cross equatorial surface winds the cold tongue and the frontal zone all tend to be strongest during the cold season july through november during the cold season of the coldest years when the cold tongue is most prominent the cross equatorial flow t

dynamically balanced absolute sea level of the global ocean derived from near surface velocity observations 1 the 1992 2002 time mean absolute sea level distribution of the global ocean is computed for the first time from observations of near surface velocity for this computation we use the near surface horizontal momentum balance the velocity observed by drifters is used to compute the coriolis force and the force due to acceleration of water parcels the anomaly of horizontal pressure gradient is derived from satellite altimetry and corrects the temporal bias in drifter data distribution ncep reanalysis winds are used to compute the force due to ekman currents the mean sea level gradient force which closes the momentum balance is integrated for mean sea level we find that our computation agrees within uncertainties with the sea level computed from the geostrophic hydrostatic momentum balance using historical mean density except in the antarctic circumpolar current a consistent horizontally and vertically dynamically balanced near surface global pressure field has now been derived from observations

a two way nested simulation of the oceanic circulation in the southwestern atlantic this article presents the results of a high resolution 1 12 two way nested simulation of the oceanic circulation in the southwestern atlantic region a comparison between the model results and extant observations indicates that the nested model has skill in reproducing the best known aspects of the regional circulation e g the volume transport of the acc the latitudinal position of the bmc the shelf break upwelling of patagonia and the zapiola anticyclone sensitivity experiments indicate that the bottom stress parameterization significantly impacts the mean location of the brazil malvinas confluence and the transport of the zapiola anticyclone the transport of the brazil current strengthens during the austral summer and weakens during the austral winter these variations are driven by the wind stress curl over the southwestern atlantic the variations of the transport of the malvinas current are out of phase with those of the brazil current most of the seasonal variability of this current is concentrated in the offshore portion of the jet the inshore portion has a weak seasonality that modulates the magnitude of the patagonian shelf break upwelling using passive tracers we show that most of the entrainment of deep waters into the shelf occurs in the southernmost portion of the patagonian shelf and along the inshore boundary of the brazil current shelf waters are preferentially detrained near the brazil malvinas confluence consistent with previous studies our simulation also shows that south of 42 s the malvinas current is composed of two jets which merge near 42 s to form a single jet farther north

spatial patterns of atmosphere ocean interaction in the northern winter abstract the variability of monthly mean sea surface temperature sst anomalies over the extratropical north atlantic and pacific and its relation to atmospheric circulation anomalies over the northern hemisphere during wintertime is investigated by applying eigenvector analysis to a 39 year dataset and correlating the time series of the resulting expansion coefficients with the hemispheric 500 mb height and sea level pressure fields in agreement with previous studies the simultaneous correlation between the tone series of the expansion coefficient of the first empirical orthogonal function eof 1 of north pacific sea surface temperature sst and the hemispheric 500 mb height field resembles the pacific north american pattern and the corresponding pattern for atlantic sst resembles the north atlantic oscillation in the vicinity of the conters of action of thew patterns the sst fluctuations associated with these modes explain on the order of half the variance of 500 mb height and slightly less of

diagnostics for near surface wind response to the gulf stream in a regional atmospheric model abstractthe mechanisms acting on near surface winds over the gulf stream are diagnosed using 5 yr outputs of a regional atmospheric model the diagnostics for the surface layer momentum vector its curl and its convergence are developed with a clear separation of pressure adjustment from downward momentum inputs from aloft in the surface layer system the results suggest that the downward momentum mixing mechanism plays a dominant role in contributing to the annual mean climatological momentum curl whereas the pressure adjustment mechanism plays a minor role in contrast the wind convergence is mainly due to the pressure adjustment mechanism this can be explained by the orientation of background wind to the sea surface temperature front the diagnostics also explain the relatively strong seasonal variation in surface layer momentum convergence and the small seasonal variation in curl finally the surface layer response to other western boundary currents is examined using a reanalysis dataset

quasi decadal variation in intensity of the western part of the winter subarctic sst front in the western north pacific the influence of kuroshio extension path state abstractvariations of the subarctic front saf which is extracted as a strong sea surface temperature sst gradient in the longitudinal band of 146 152 e were investigated over 30 winters january march from 1982 to 2011 using high spatial resolution satellite derived sst dataset and hydrographic observations the saf had little meridional movement in this longitudinal band lying between 40 and 41 n throughout the analysis period the saf intensity had a dominant quasi decadal time scale about 8 yr its intensity in the strong phase was up to about 50 higher than in the weak phase the saf intensity strongly reflected upper ocean conditions in the kuroshio oyashio confluence koc region just south of the saf in the strong saf phase large positive anomalies in both temperature and salinity were found in the koc region not only at the sea surface but also below 300 m and the water properties in the koc region were those of the kuroshio water the warm salty water in the koc region was supp

covariations of sea surface temperature and wind over the kuroshio and its extension evidence for ocean to atmosphere feedback abstract satellite microwave measurements are analyzed revealing robust covariability in sea surface temperature sst and wind speed over the kuroshio extension ke east of japan ocean hydrodynamic instabilities cause the ke to meander and result in large sst variations increased reduced wind speeds are found to be associated with warm cold sst anomalies this positive sst wind correlation in ke is confirmed by in situ buoy measurements and is consistent with a vertical shear adjustment mechanism namely an increase in sst reduces the static stability of the near surface atmosphere intensifying the vertical turbulence mixing and bringing fast moving air from aloft to the sea surface south of japan the kuroshio is known to vary between nearshore and offshore paths these paths are very persistent and can last for months to years as the kuroshio shifts its path coherent wind changes are detected from satellite data in particular winds are high south of tokyo when the kuroshio takes the near

interannual variability of the kuroshio extension system and its impact on the wintertime sst field altimetry data from the first 7 yr topex poseidon t p mission october 1992 september 1999 are analyzed to investigate the interannual variability in regions of the kuroshio extension and its southern recirculation gyre large scale interannual changes of the kuroshio extension system are characterized by the oscillation between an elongated state and a contracted state in the elongated state the kuroshio extension has a larger eastward surface transport a greater zonal penetration and a more northerly zonal mean path all these characteristics are closely connected to the presence of an intense zonally elongated southern recirculation gyre in its contracted state the kuroshio extension has a smaller eastward surface transport a more southerly mean path and is accompanied by a weaker southern recirculation gyre during the t p period the kuroshio extension changed from the elongated state in 1992 93 to the contracted state in 1996 97 and back to the elongated state since late 1997 in addition to these large scale changes the mesoscale eddy field also exhibited prominent interannual changes in the kuroshio extension region in the upstream region between the izu ridge and the shatsky rise the eddy kinetic energy level was generally low while the kuroshio extension was in its elongated state and high while in the contracted state downstream of the shatsky rise on the other hand the eke level was high low when the kuroshio extension was in the elongated contracted state the large scale interannual changes in the kuroshio extension system have a significant impact on the regional wintertime sst anomaly field the warm cold wintertime sst anomalies tend to persist in years when the kuroshio extension is in its elongated contracted state a diagnostic analysis of the surface ocean heat balance indicates that the nonseasonal geostrophic advection by the ocean circulation works to reduce increase the wintertime sst anomalies when the kuroshio extension changes from an elongated contracted state to a contracted elongated state the sst anomalies associated with the large scale changes of the kuroshio extension have an area averaged peak topeak amplitude of 18c and appear independent of the interannual sst changes in the tropical pacific ocean

global analysis of the pressure adjustment mechanism over sea surface temperature fronts using airs aqua data 1 we investigate the signatures of atmospheric pressure adjustment mechanism for surface wind convergence divergence over major sea surface temperature sst frontal regions using global observations of satellite sounding and scatterometer lower tropospheric air thickness which includes a sea level pressure component modified by air temperature in the marine atmospheric boundary layer is analyzed and the relation between the laplacian of the thickness and wind convergence are examined among four sst frontal regions in mid latitudes correlation between the thickness laplacian and wind convergence is the largest over the gulf stream followed by those for the agulhas return current and for the brazil malvinas current and relatively small but still significant over the kuroshio oyashio extension these correlations strongly suggest that the pressure adjustment mechanism ubiquitously plays an important role in air sea interaction over the global sst frontal regions furthermore air temperatures in the first two regions exhibit sst relating signatures even in the mid troposphere

atmospheric manifestation of tropical instability wave observed by quikscat and tropical rain measuring mission observations from two new spaceborne microwave instruments in 1999 clearly reveal the atmospheric manifestation of tropical instability waves north of the pacific equatorial cold tongue a unique zonal temporal band pass filter enables the isolation of the propagating signals and the determination of their phase differences the phase differences between the propagation of wind and sea surface temperature sst signals observed from space and the vertical wind profiles measured from a research ship are consistent with the hypothesis that the coupling between wind and sst is caused by buoyancy instability and mixing which reduces the wind shear in the atmospheric boundary layer the coupling causes higher evaporative cooling over the warm phase and infers a negative thermal feedback

two types of surface wind response to the east china sea kuroshio front abstracteffects of the sea surface temperature sst front along the east china sea kuroshio on sea surface winds at different time scales are investigated in winter and spring the climatological vector wind is strongest on the sst front while the scalar wind speed reaches a maximum on the warm flank of the front and is collocated with the maximum difference between sea surface temperature and surface air temperature sst sat the distinction is due to the change in relative importance of two physical processes of sst wind interaction at different time scales the sst front induced sea surface level pressure slp adjustment sf slp contributes to a strong vector wind above the front on long time scales consistent with the collocation of baroclinicity in the marine boundary layer and corroborated by the similarity between the thermal wind and observed wind shear between 1000 and 850 hpa in contrast the sst modulation of synoptic winds is more evident on the warm flank of the sst front large ther

improving estimates of the antarctic circumpolar current streamlines in drake passage abstract accurately resolving the mean antarctic circumpolar current acc is essential for determining southern ocean eddy fluxes that are important to the global meridional overturning circulation previous estimates of the mean acc have been limited by the paucity of southern ocean observations a new estimate of the mean surface acc in drake passage is presented that combines sea surface height anomalies measured by satellite altimetry with a recent dataset of repeat high resolution acoustic doppler current profiler observations a mean streamfunction surface height field objectively mapped from the mean currents is used to validate two recent dynamic height climatologies the new streamfunction has narrower and stronger acc fronts separated by quiescent zones of much weaker flow thereby improving on the resolution of acc fronts observed in the other climatologies distinct streamlines can be associated with particular acc fronts and tracked in time dependent maps of dynamic height this analysis

ocean atmosphere in situ observations at the brazil malvinas confluence region 1 this paper presents a description of marine atmospheric boundary layer mabl and oceanic boundary layer obl interactions at the brazil malvinas confluence although this region is known as one of the most energetic zones of the world ocean very few studies have addressed the mechanisms of oa interaction there based upon novel direct in situ simultaneous oa observations our results show that the obl mabl exchanges are closely correlated with the sea surface temperature sst field the heat fluxes range from 110 w m 2 over warm waters down to 18 w m 2 over cold waters higher heat fluxes and air sea temperature differences are associated with stronger near surface winds this suggests that the mabl is modulated at the synoptic temporal and spatial scale by the strong surface thermal gradients between the warm brazil and the cold malvinas falklands currents