interpretations of observed climatological patterns in stratospheric gravity wave variance observational analyses of gravity waves in the stratosphere have revealed various climatological patterns in gravity wave activity seasonal geographical and vertical variations have all been observed in this work a linear model of gravity wave propagation is applied to investigate the underlying causes of some of the observed patterns a collection of monochromatic gravity waves that represent a broad spectrum of wavenumbers and frequencies is input at 6 km altitude in the model propagation of the waves through realistic background atmospheric wind and stability fields is treated with linear ray theory and a simple saturation condition to limit amplitudes to stable values the wave spectrum at the 6 km source height is specified to be constant at all latitudes longitudes and times so the variability that appears at higher altitudes is due entirely to background atmosphere variations before the model results are compared to the observations the spectrum of waves is filtered in a way that mimics the limitations of each of the observation techniques the filtering is described in terms of vertical wavelength and is referred to as the observational filter in a vertically varying background wind gravity waves are doppler shifted in intrinsic frequency and refracted to different vertical wavelengths as they propagate vertically through the atmosphere the observational filter and the wave refraction effects can thus couple in interesting ways that have not been explicitly considered in previous work the model shows that this coupling can give rise to geographical seasonal and vertical variations in gravity wave observations without any variations in the spectrum or amplitude of gravity wave sources in the troposphere thus careful consideration of both the background wind profile and observational filter can greatly affect the interpretation of the observed climatological patterns in gravity wave activity

gravity wave and orographic wave activity observed around the antarctic and arctic stratospheric vortices by the cosmic gps ro satellite constellation 1 polar stratospheric gravity wave activity is studied using data from the constellation observing system for meteorology ionosphere and climate cosmic global positioning system radio occultation gps ro waves with vertical wavelengths of 2 to 15 km are considered the temperature variance 2 is used as a measure of wave activity and is studied on isentropic surfaces large intermittent orographic wave activity is identified during austral spring 2007 above the patagonian andes and the antarctic peninsula where 2 in the stratosphere increases by up to a factor of 5 for periods of 5 days to a few weeks the 2 are also investigated in equivalent latitudes to allow a direct comparison with the changing vortex structure the october 2007 2 inside the antarctic vortex boundary region at 400 600 k is one and a half times that outside the vortex this region of enhanced 2 descends in time and is not observed during the decay of the arctic vortex during the boreal winter of 2006 2007 orographic wave activity is observed above scandinavia and greenland an analysis of the 400 k and the 450 k levels in both hemispheres shows a strong relationship between enhanced 2 and the location of the vortex edge suggesting that the waves observed are propagating poleward and are guided to higher altitudes by the vortex the line of sight of the occultations shows a preference for north south alignment indicating that cosmic favors the detection of orographic waves above the north south oriented mountain ranges considered here

downward control of the mean meridional circulation and temperature distribution of the polar winter stratosphere abstract according to the downward control principle the extratropical mean vertical velocity on a given pressure level is approximately proportional to the meridional gradient of the vertically integrated zonal force per unit mass exerted by waves above that level in this paper a simple numerical model that includes parameterizations of both planetary and gravity wave breaking is used to explore the influence of gravity wave breaking in the mesosphere on the mean meridional circulation and temperature distribution at lower levels in the polar winter stratosphere the results of these calculations suggest that gravity wave drag in the mesosphere can affect the state of the polar winter stratosphere down to altitudes below 30 km the effect is most important when planetary wave driving is relatively weak that is during southern winter and in early northern winter in southern winter downwelling weakens by a factor of 2 near the stratopause and by 20 at 30 km when gravity wave drag is not included

a global morphology of gravity wave activity in the stratosphere revealed by the gps occultation data gps met using temperature profiles obtained by the gps met gps meteorology experiment from april 1995 to february 1997 we have extracted mesoscale temperature perturbations with vertical wavelengths ranging from 2 to 10 km and background brunt vaisala frequency squared n2 for each occultation event we can evaluate a potential energy ep which is assumed to be caused by atmospheric gravity waves the monthly mean values of ep at 15 20 km around japan showed an annual variation with an enhancement in winter which is consistent with the climatological behavior of the kinetic energy of gravity waves observed with the mu middle and upper atmosphere radar 34 9 n 136 0 e from 1985 to 1989 we have then derived the global distribution of ep at 20 30 km during northern hemisphere winter from november to february our analysis shows that the largest ep values are generally centered around the equator between 25 n and 25 s with considerable longitude variations longitudinal variations of ep at 20 30 km in a latitude range of 30 60 n are also analyzed resulting in larger ep values over the continents than over the pacific ocean using gps met data without antispoofing latitudinal variations of ep are determined in 15 45 km although large ep values are concentrated near the equator at 20 30 km ep tends to become larger at midlatitudes at 30 40 km and higher altitude regions at midlatitudes ep is found to be larger in winter months in both hemispheres height variations of ep indicate a decrease at 25 30 km and a monotonic increase above 30 km

satellite observations of atmospheric variances a possible indication of gravity waves the microwave limb sounder mls on the upper atmosphere research satellite has now produced the first global maps of small scale variances in the middle atmosphere initial analyses are presented here that suggest these variances are due to gravity waves and the technique used to extract gravity wave information from saturated radiance measurements is described observations at 30 80km altitudes show that the variances of horizontal scales less than 100km are strongly correlated with upper tropospheric convection surface topography and stratospheric jetstreams mls monthly averages during solstice periods suggest that the normalized variance amplitude grows exponentially with height in the stratosphere and saturates in the mesosphere as expected from wave breaking and dissipation at these altitudes

late quaternary grounded ice extent in the filchner trough weddell sea antarctica new marine geophysical evidence the last glacial maximum lgm ca 23 19 ka bp extent of grounded ice in the filchner trough a major cross shelf trough extending seaward from the filchner ice shelf in the southern weddell sea has been much debated here we present data from the first extensive multibeam swath bathymetry and sub bottom acoustic profiling surveys in the filchner trough that include several parallel survey lines with overlapping swaths we interpret these new data combined with published observations and radiocarbon dates from sediment cores as indicating that the grounding line in the filchner trough during the lgm advanced beyond the middle shelf probably to within 40 km of the shelf break and possibly reached the shelf break three different hypotheses are discussed that could reconcile this interpretation with interpretations based on ice coring and surface exposure age data that lgm ice surface elevations in areas draining into the filchner and ronne ice shelves were no more than a few hundred metres higher than today 1 ice plain conditions extended along most of the filchner trough 2 the ice shelf advanced and thickened so that it touched down on the continental shelf for a short period 3 lgm ice drainage pathways in the interior of the weddell sea embayment were different from those observed today

gravity waves around the subtropical jet of the southern winter in an atmospheric general circulation model 1 gravity wave gw activities around the subtropical jet of the southern winter june are analyzed using atmospheric general circulation model outputs of t106l60 in order to clarify roles of gws in maintaining the zonal mean zonal wind dominant gws are characterized with periods of 10 24 hours relative to the ground and with horizontal and vertical wavelengths of about 600 700 km and 2 2 4 4 km respectively these gws propagate both upward and downward from the jet and westward relative to the mean zonal wind most of the upward propagating waves do not reach the upper stratosphere due to negative vertical wind shear of the zonal wind in the lower stratosphere dominant upward fluxes of easterly momentum due to the non stationary gws extend zonally along 30 s above the jet remarkable ep flux convergence due mostly to these gws is seen around 100 hpa at 30 s and explains up to 30 of the total ep flux convergence

a statistical study of gravity waves in the polar regions based on operational radiosonde data gravity waves in the lower polar stratosphere are examined using operational radiosonde observations gathered from 33 stations over a period of 10 years both the potential and kinetic energies of the gravity waves vary annually and reach maxima in winter in the arctic and in spring in the antarctic in the antarctic spring a region of large gravity wave energy propagates downward following the movement of a zone of high static stability associated with southern hemispheric warming moreover the enhanced energy region and the high stability zone coincide in the horizontal plane and move gradually from 135 e 50 s to 45 w 70 s over the south pole the vertical and horizontal directions of wave propagation are examined using hodograph analysis in the vertical most gravity waves transfer energy upward in the arctic while the percentage of downward energy propagation is relatively high in winter and spring in the antarctic horizontally gravity waves propagate westward relative to the mean wind in the arctic while in the antarctic the dominant direction varies from station to station the correlation between gravity wave energy in the lower stratosphere and the mean wind is also examined in the arctic gravity wave energy is highly correlated with the surface wind though in the antarctic it correlates with the stratospheric wind these results suggest that gravity waves observed in the arctic are forced by topography whereas in antarctica some sources may exist in the stratosphere one such source candidate is likely to be the polar night jet

large potential energy of gravity waves over a smooth surface with little convection simulation and observation 1 a numerical experiment is conducted using an atmospheric general circulation model agcm to investigate the presence of the large potential energy over a region of low topography and little convective activity focusing on the tropical atlantic region 10 e to 20 w 0 to 20 s it is found that gravity waves with a time period of 24 hours are excited near the equator 5 15 n in a region of large moist heating extending vertically up to 10 13 km the gravity waves propagate upward from this region with a bias toward the south and are manifested as large energy fluxes in the cross equatorial region enhanced energy fluxes are therefore simulated at 20 30 km altitude over a region with no significant source of gravity waves and are confirmed using global positioning satellite meteorology gps met experiment data

gravity wave generation around the polar vortex in the stratosphere revealed by 3 hourly radiosonde observations at syowa station intensive radiosonde observations were performed at syowa station 69 0 s 39 6 e over about 10 days in each of march june october and december 2002 to examine inertia gravity wave characteristics in the antarctic lower stratosphere based on the 3 hourly observation data two dimensional i e vertical wavenumber versus frequency spectra of wind fluctuations were examined utilizing a double fourier transform method clear signals of gravity waves whose phases propagate upward suggesting downward energy propagation are detected in june and october when the polar night jet pnj was present on the other hand downward phase propagation i e upward energy propagation components are dominant in all months there is a spectral peak around the inertial frequency in a wide range of vertical wavenumbers in december when the background wind was weak whereas large spectral densities are distributed over lower frequency regions in june and october these spectral characteristics are consistent with the results obtained using a gravity wave resolving global circulation model gcm by sato et al dynamical characteristics are examined separately for upward and downward propagating gravity waves in june using a hodograph analysis method as a result it is found that upward and downward propagating wave packets observed simultaneously in the same height regions have similar horizontal wavelengths and phase velocities this fact suggests that these gravity waves are generated from the same source with a similar mechanism when the wave packets were observed both the local rossby number and the residual in the nonlinear balance equation estimated using ncep ncar reanalysis data are large around the pnj situated slightly to the lower latitudes of syowa station therefore it is likely that the observed inertia gravity waves are generated by a spontaneous adjustment around the geostrophically unbalanced pnj and propagate toward syowa station the possibility of spontaneous gravity wave generation around the pnj is confirmed by comparison with the gcm simulation by sato et al

transport and mixing in the extratropical tropopause region in a high vertical resolution gcm part ii relative importance of large scale and small scale dynamics abstract the relative roles of atmospheric motions on various scales from mesoscale to planetary scale in transport and mixing in the extratropical tropopause region are investigated using a high vertical resolution general circulation model gcm the gcm with a vertical resolution of about 300 m explicitly represents the propagation and breaking of gravity waves and the induced transport and mixing a downward control calculation shows that the eliassen palm e p flux of the gravity waves diverges and induces a mean equatorward flow in the extratropical tropopause region which differs from the mean poleward flow induced by the convergence of large scale e p fluxes the diffusion coefficients estimated from the eddy potential vorticity flux in tropopause based coordinates reveal that isentropic motions diffuse air between 20 k below and 10 k above the tropopause from late autumn to early spring while vertical mixing is strongly suppressed at around 10 15 k above the tropopause throughout the year t

oblique propagation of monsoon gravity waves during the northern hemisphere 2007 summer we present a combination of satellite observation and high resolution model output to understand monsoon convection as a source of high latitude mesospheric gravity waves gws the gws generated over the northern hemisphere nh monsoon region during the 2007 summer and the role of the winds in focusing these gws toward the high latitude middle atmosphere are analyzed using the saber timed satellite temperature data and the high resolution nogaps alpha model results in the nh above the stratosphere the monsoon gw momentum flux gwmf exhibits a poleward tilt that follows the slanted structure of the easterly jet the correlation coefficients 0 5 between the time series of nh tropical stratospheric gwmf and the global winds also have a slanted structure that coincide with the easterly jet confirming the modeling theory that stratospheric monsoon gws are refracted into the summer easterly jet and can reach the high latitude mesosphere since polar mesospheric clouds pmcs are sensitive indicators of changes in the polar summer mesosphere we compared the time series of tropical stratospheric gwmf to the pmc occurrence frequency of obtained from the cips aim satellite data to assess the influence of this wave focusing in the mesosphere there is a significant positive correlation between the high latitude pmc of and the tropical stratospheric gwmf suggesting a definite influence of monsoon gws on the high latitude mesosphere the disagreement in correlation at the end of the pmc season is attributed to the enhancement of the quasi 5 day planetary wave dominating over the influence of monsoon gws on pmcs

transport and mixing in the extratropical tropopause region in a high vertical resolution gcm part i potential vorticity and heat budget analysis abstract a high vertical resolution general circulation model gcm output has been analyzed to clarify transport and mixing processes in the extratropical tropopause region the high resolution gcm with a vertical resolution of about 300 m above the extratropical upper troposphere allows simulation of fine atmospheric structures near the tropopause such as the extratropical tropopause transition layer extl and the tropopause inversion layer til the high resolution gcm realistically simulates fine thermal and dynamic structures in the extratropical tropopause region the thickness and maximum stability of the simulated til are consistent with observations the high resolution output was analyzed using a zonal mean potential vorticity pv equation to identify dominant transport processes in the extratropical tropopause region in the northern hemisphere extratropics during winter mean downward advection sharpens the pv gradient between the tropopause and 20 k below it whereas latitudinal variati

gravity wave induced anomalous potential vorticity gradient generating planetary waves in the winter mesosphere abstractthis study shows that gravity wave gw forcing gwf plays a crucial role in the barotropic baroclinic instability that is frequently observed in the mesosphere and considered an origin of planetary waves pws such as quasi 2 day and quasi 4 day waves simulation data from a gw resolving general circulation model were analyzed focusing on the winter northern hemisphere where pws are active the unstable field is characterized by a significant potential vorticity pv maximum with an anomalous latitudinal gradient at higher latitudes that suddenly appears in the midlatitudes of the upper mesosphere this pv maximum is attributed to an enhanced static stability that develops through the following two processes 1 strong pws from the troposphere break in the middle stratosphere causing a poleward and downward shift of the westerly jet to higher latitudes and 2 strong gwf located above the jet simultaneously shifts and forms an upwelling in the midlatitudes causing a significant increase in

simulation of the eastward 4 day wave in the antarctic winter mesosphere using a gravity wave resolving general circulation model 1 the eastward moving 4 day wave in the antarctic winter mesosphere is investigated using a high resolution middle atmosphere general circulation model that directly simulates the spontaneous generation propagation and dissipation of gravity waves the results are also compared with the simulated seasonal march of the meridional structures of the westerly jet streams in the southern hemisphere upper stratosphere and mesosphere in order to investigate baroclinic barotropic instability as a possible excitation mechanism for the 4 day wave the model successfully reproduces the dynamically unstable double jet structure of the mesospheric westerly winds the simulated 4 day wave develops in association with the baroclinic and barotropic instability of the mesospheric mean flows and has similar characteristics to those observed at 50 60 s near the stratopause the 4 day wave has strong equatorward heat flux associated with strong baroclinicity in the antarctic winter mesosphere mainly attributable to poleward overturning circulation driven by gravity wave forcing eastward forcing due to the 4 day wave occurs within the double jet structure and offsets part of the westward forcing due to gravity waves such an effect partially acts to stabilize the unstable mean flow structure in the antarctic winter mesosphere

general aspects of a t213l256 middle atmosphere general circulation model 1 a high resolution middle atmosphere general circulation model gcm developed for studying small scale atmospheric processes is presented and the general features of the model are discussed the gcm has t213 spectral horizontal resolution and 256 vertical levels extending from the surface to a height of 85 km with a uniform vertical spacing of 300 m gravity waves gws are spontaneously generated by convection topography instability and adjustment processes in the model and the gcm reproduces realistic general circulation in the extratropical stratosphere and mesosphere the oscillations similar to the stratopause semiannual oscillation and the quasi biennial oscillation qbo in the equatorial lower stratosphere are also spontaneously generated in the gcm although the period of the qbo like oscillation is short 15 months the relative roles of planetary waves large scale gws and small scale gws in maintenance of the meridional structures of the zonal wind jets in the middle atmosphere are evaluated by calculating eliassen palm diagnostics separately for each of these three groups of waves small scale gws are found to cause deceleration of the wintertime polar night jet and the summertime easterly jet in the mesosphere while extratropical planetary waves primarily cause deceleration of the polar night jet below a height of approximately 60 km the meridional distribution and propagation of small scale gws are shown to affect the shape of the upper part of mesospheric jets the phase structures of orographic gws over the south andes and gws emitted from the tropospheric jet stream are discussed as examples of realistic gws reproduced by the t213l256 gcm

new gravity wave treatments for giss climate models previous versions of giss climate models have either used formulations of rayleigh drag to represent unresolved gravity wave interactions with the model resolved flow or have included a rather complicated treatment of unresolved gravity waves that while being climate interactive involved the specification of a relatively large number of parameters that were not well constrained by observations and also was computationally very expensive here the authors introduce a relatively simple and computationally efficient specification of unresolved orographic and nonorographic gravity waves and their interaction with the resolved flow comparisons of the giss model winds and temperatures with no gravity wave parameterization with only orographic gravity wave parameterization and with both orographic and nonorographic gravity wave parameterizations are shown to illustrate how the zonal mean winds and temperatures converge toward observations the authors also show that the specifications of orographic and nonorographic gravity waves must be different in the northern and southern hemispheres then results are presented where the nonorographic gravity wave sources are specified to represent sources from convection in the intertropical convergencezoneandspontaneousemissionfromjetimbalances finally astrategytoincludetheseeffectsin a climate dependent manner is suggested

gravity wave characteristics in the southern hemisphere revealed by a high resolution middle atmosphere general circulation model abstractgravity wave characteristics in the middle to high latitude southern hemisphere are analyzed using simulation data over 3 yr from a high resolution middle atmosphere general circulation model without using any gravity wave parameterizations gravity waves have large amplitudes in winter and are mainly distributed in the region surrounding the polar vortex in the middle and upper stratosphere while the gravity wave energy is generally weak in summer the wave energy distribution in winter is not zonally uniform but it is large leeward of the southern andes and antarctic peninsula linear theory in the three dimensional framework indicates that orographic gravity waves are advected leeward significantly by the mean wind component perpendicular to the wavenumber vector results of ray tracing and cross correlation analyses are consistent with this theoretical expectation the leeward energy propagation extends to several thousand kilometers which explains part of the gravity wave distribution aro

inertia gravity waves spontaneously generated by jets and fronts part i different baroclinic life cycles abstract the spontaneous generation of inertia gravity waves in idealized life cycles of baroclinic instability is investigated using the weather research and forecasting model two substantially different life cycles of baroclinic instability are obtained by varying the initial zonal jet the wave generation depends strongly on the details of the baroclinic wave s development in the life cycle dominated by cyclonic behavior the most conspicuous gravity waves are excited by the upper level jet and are broadly consistent with previous simulations of o sullivan and dunkerton in the life cycle that is dominated by anticyclonic behavior the most conspicuous gravity waves even in the stratosphere are excited by the surface fronts although the fronts are no stronger than in the cyclonic life cycle the anticyclonic life cycle also reveals waves in the lower stratosphere above the upper level trough of the baroclinic wave these waves have not been previously identified in idealized simulations the sensiti

the effect of horizontal resolution on gravity waves simulated by the gfdl skyhi general circulation model to examine the effects of horizontal resolution on internal gravity waves simulated by the 40 level gfdl skyhi general circulation model a comparison is made between the 3 and 1 resolution models during late december the stratospheric and mesospheric zonal flows in the winter and summer extratropical regions of the 1 model are much weaker and more realistic than the corresponding zonal flows of the 3 model the weaker flows are consistent with the stronger eliassen palm flux divergence epfd

mesoscale simulations of gravity waves during the 2008 2009 major stratospheric sudden warming 1 a series of 24 h mesoscale simulations of 10 km horizontal and 400 m vertical resolution are performed to examine the characteristics and forcing of gravity waves gws relative to planetary waves pws during the 2008 2009 major stratospheric sudden warming ssw just prior to ssw occurrence widespread westward propagating gws are found along the vortex s edge and associated predominantly with major topographical features and strong near surface winds momentum forcing due to gws surpasses pw forcing in the upper stratosphere and tends to decelerate the polar westerly jet in excess of 30 m s 1 d 1 with ssw onset pws dominate the momentum forcing providing decelerative effects in excess of 50 m s 1 d 1 throughout the upper polar stratosphere gws related to topography become less widespread largely due to incipient wind reversal as the vortex starts to elongate during the ssw maturation and early recovery the polar vortex eventually splits and both wave signatures and forcing greatly subside nonetheless during ssw westward and eastward propagating gws are found in the polar region and may be generated in situ by flow adjustment processes in the stratosphere or by secondary gw breaking the simulated large scale features agree well with those resolved in satellite observations and analysis products

recent developments in gravity wave effects in climate models and the global distribution of gravity wave momentum flux from observations and models recent observational and theoretical studies of the global properties of small scale atmospheric gravity waves have highlighted the global effects of these waves on the circulation from the surface to the middle atmosphere the effects of gravity waves on the large scale circulation have long been treated via parametrizations in both climate and weather forecasting applications in these parametrizations key parameters describe the global distributions of gravity wave momentum flux wavelengths and frequencies until recently global observations could not define the required parameters because the waves are small in scale and intermittent in occurrence recent satellite and other global datasets with improved resolution along with innovative analysis methods are now providing constraints for the parametrizations that can improve the treatment of these waves in climate prediction models research using very high resolution global models has also recently demonstrated the capability to resolve gravity waves and their circulation effects and when tested against observations these models show some very realistic properties here we review recent studies on gravity wave effects in stratosphere resolving climate models recent observations and analysis methods that reveal global patterns in gravity wave momentum fluxes and results of very high resolution model studies and we outline some future research requirements to improve the treatment of these waves in climate simulations copyright 2010 royal meteorological society and crown in the right of canada

energy enhancements of gravity waves in the antarctic lower stratosphere associated with variations in the polar vortex and tropospheric disturbances 1 gravity waves in the antarctic lower stratosphere are examined using original operational radiosonde data obtained at syowa station 69 0 s 39 6 e with fine vertical resolution in the lower stratosphere the temporal variation in gravity wave energy depends on height in the height region of 13 15 km just above the tropopause the seasonal variation in gravity wave energy is not evident the wave energy is rather enhanced when the absolute value of potential vorticity in the upper troposphere becomes small over syowa station this fact implies that tropospheric disturbances affect the dynamical processes of gravity waves there however the gravity wave energy in the height region of 15 25 km shows clear seasonal variation having a maximum in spring the time variation in gravity wave energy is examined in detail in terms of the polar vortex by using the equivalent latitude coordinate energy enhancements occur when the edge of the polar vortex approaches syowa station and the enhancements are especially large when the polar vortex breaks down in spring these results suggest that height variation in the background atmosphere leads to the difference of wave characteristics between the two height regions the enhancements of wave energy are partly explained as modification of the wave structure by the background wind speed and the static stability but it is also likely that enhancements of wave activity contribute to the energy enhancement at the edge of the polar vortex in spring

on the origins of mesospheric gravity waves 1 using hourly data from a three year simulation based on a gravity wave resolving general circulation model we have first inferred a global view of gravity wave sources and propagation affecting significantly the momentum balance in the mesosphere the meridional cross section of momentum fluxes suggests that there are a few dominant propagation paths originating from the subtropics in summer and the middle to high latitudes in winter these gravity waves are focused into the mesospheric jets in their respective seasons acting effectively to decelerate the jets the difference in the source latitudes likely contributes to the hemispheric asymmetries of the jets the horizontal distribution of the momentum fluxes indicates that the dominant sources are steep mountains and tropospheric westerly jets in winter and vigorous monsoon convection in summer the monsoon regions are the most important window to the middle atmosphere in summer because of the easterlies associated with the monsoon circulation

sources of gravity waves in the lower stratosphere above south pole 1 five year 2001 2005 high resolution radiosonde data were processed to obtain the gravity wave gw variabilities in the lower stratosphere over south pole sp our results show that gw activities in the lowermost section 10 15 km are strongest in may and september and weakest in the austral summer whereas in the altitude range of 15 25 km strongest weakest gw kinetic energy is observed around september january we also explored the relationships of gws to the synoptic scale variations in the troposphere and the ageostrophic motions in the upper troposphere over the antarctic which are expected to be significant mechanisms for gw generation a ray tracing model grograt was used to explore the relationship between gw propagation and the background field in the altitude of 15 25 km the annual cycle of gw activity resembles that of adjustment process below 15 km the annual cycle of gw activity has two peaks in may and september our analysis suggests that these two peaks are due to the variation of topographic gw generation and filtering of background atmosphere due to critical level filtering in the lowermost section topographic gws cannot propagate upward which makes the shape of gw annual cycle at higher altitudes closer to the annual cycle of adjustment processes the analysis suggests that the minimum of gw activity at sp during the austral summer may be due to the combination of weaker wave generation from adjustment processes associated with synoptic scale systems flow over topography and unfavorable background field for gw propagation

a global view of gravity waves in the martian atmosphere inferred from a high resolution general circulation model global characteristics of the small scale gravity wave gw field in the martian atmosphere obtained from a high resolution general circulation model gcm are presented for the first time the simulated gw induced temperature variances are in a good agreement with available radio occultation data in the lower atmosphere between 10 and 30 km the model reveals a latitudinal asymmetry with stronger wave generation in the winter hemisphere and two distinctive sources of gws mountainous regions and the meandering winter polar jet orographic gws are filtered while propagating upward and the mesosphere is primarily dominated by harmonics with faster horizontal phase velocities wave fluxes are directed mainly against the local wind gw dissipation in the upper mesosphere generates body forces of tens of m s 1 per martian solar day sol 1 which tend to close the simulated jets the results represent a realistic surrogate for missing observations which can be used for constraining gw parameterizations and validating gcm simulations

global distribution of atmospheric waves in the equatorial upper troposphere and lower stratosphere agcm simulation of sources and propagation 1 the global distribution sources and propagation of atmospheric waves in the equatorial upper troposphere and lower stratosphere were investigated using an atmospheric general circulation model with t106l60 resolution 120 km horizontal and 550 m vertical resolution the quasibiennial oscillation qbo with a period of 1 5 2 years was simulated well without gravity wave drag parameterization the zonal wave number versus the frequency spectra of simulated precipitation represent realistic signals of convectively coupled equatorial trapped waves eqws the temperature spectra in the stratosphere also indicate dominant signals of eqws eqws with equivalent depths in the range of 8 90 m from the n 1 mode to n 2 mode were extracted separately each eqw in the stratosphere generally corresponded well with the source of each convectively coupled eqw activity in the troposphere the propagations of kelvin waves and n 0 eastward westward propagating eqws are strongly influenced by the walker circulation and the phase of the qbo potential energy associated with eqws is generally larger in the westerly than in the easterly shear phase of the qbo eqws with vertical wavelengths 7 km contribute up to 30 of total potential energy 7 km over the equator at an altitude of 20 30 km gravity waves generated by cumulus convection with periods 24 h are clearly visible over areas of africa the amazon and around indonesia and result in localized pe distributions in areas short distances from the source region comparisons of the model results and recent satellite observations are discussed

effects of polar indirect circulation on superrotation and multiple equilibrium in long term agcm experiments with an idealized venus like forcing sensitivity to horizontal resolution and initial condition

numerical modeling of the excitation propagation and dissipation of primary and secondary gravity waves during wintertime at mcmurdo station in the antarctic

global measurements of stratospheric mountain waves from space temperatures acquired by the cryogenic infrared spectrometers and telescopes for the atmosphere crista during shuttle mission sts 66 have provided measurements of stratospheric mountain waves from space large amplitude long wavelength mountain waves at heights of 15 to 30 kilometers above the southern andes mountains were observed and characterized with vigorous wave breaking inferred above 30 kilometers mountain waves also occurred throughout the stratosphere 15 to 45 kilometers over a broad mountainous region of central eurasia the global distribution of mountain wave activity accords well with predictions from a mountain wave model the findings demonstrate that satellites can provide the global data needed to improve mountain wave parameterizations and hence global climate and forecast models

fine altitude resolution radar observations of upper tropospheric and lower stratospheric winds and waves abstract preliminary results of wind velocity measurements made using the arecibo 430 mhz radar are presented these measurements were made in the altitude range between 10 and 30 km with a time resolution of 1 2 min and an improved altitude resolution of 150 m a few interesting phenomena such as a quasi stationary wavy structure and short period sinusoidal oscillations are discussed

interactions between gravity waves and planetary scale flow simulated by the gfdl skyhi general circulation model abstract in order to study interactions between gravity waves and planetary flow in the middle atmosphere a 3 latitude by 3 6 longitude version of the 40 level gfdl skyhi general circulation model is analyzed using bihourly sampled output data it is shown by a space time spectral analysis that gravity waves in the mean zonal westerlies easterlies mainly consist of westward eastward moving components and carry easterly westerly momentum upward and decelerate the mean zonal westerlies easterlies in the mesosphere zonal momentum flux convergence due to gravity waves accounts for nearly all of the eliassen palm e p flux divergence in the summer mesosphere this convergence accounts for 30 50 of that in the winter upper mesosphere however this percentage is probably an underestimate since the convergence is significantly enhanced in a high resolution 1 1 2 model currently being integrated vertical propagation of gravity waves is affected not only by the mean zonal wind but also

the separated polar winter stratopause a gravity wave driven climatological feature abstract an examination of satellite derived temperatures reveals that the winter polar stratopause is usually elevated and warmer than the adjacent midlatitude stratopause this separated stratopause occurs in both hemispheres but is more pronounced and persistent in the southern winter it descends with time towards spring and exhibits week to week variability observational diagnostics and results from a two dimensional 2 d model suggest that gravity wave driving can account for this separated polar stratopause by driving a meridional circulation with downwelling over the winter pole in the model the solar heating pattern induces stronger winter westerlies than summer easterlies which leads to a stronger gravity wave driven circulation in the winter hemisphere spherical geometry and the high latitude location of the winter westerly jet combine to yield a concentrated region of downwelling model results suggest that descent of the temperature maximum with time is probably caused by wave mean f

application of deep learning to estimate atmospheric gravity wave parameters in reanalysis data sets gravity waves play an essential role in driving and maintaining global circulation to understand their contribution in the atmosphere the accurate reproduction of their distribution is important

sensitivity study for mesoscale simulations of gravity waves above antarctica during vorcore the observations from the vorcore campaign september 2005 january 2006 provide a unique dataset for the study of gravity waves in the lower stratosphere because of their wide coverage 150 000 observations from the south pole to about 40 s and of the quasi lagrangian nature of the superpressure balloons used numerical simulations with a mesoscale model are undertaken in order to investigate further the observed gravity waves their sources and the induced momentum fluxes the need for a high spatial resolution makes it necessary to find a compromise between the size of the model domain and the length of the simulations we describe preliminary simulations used to determine the best configuration of the model for this purpose and show that the simulations compare reasonably well with the observations model results complement the observations and provide new insights into orographic and non orographic wave sources copyright 2010 royal meteorological society

longitudinally dependent ozone increase in the antarctic polar vortex revealed by balloon and satellite observations the horizontal structure of processes causing increases in ozone in the antarctic polar vortex was examined using data measured in 2003 from an ozonesonde observation campaign at syowa station 39 68e 69 08s and from the improved limb atmospheric spectrometer ii ilas ii onboard the advanced earth observing satellite ii the ilas ii data are daily and distributed uniformly at 14 points in the zonal direction mostly at polar latitudes the antarctic ozone hole that developed in 2003 was one of the largest recorded the period of focus in this study is 26 september through 24 october when a strong polar vortex was situated in the stratosphere an ozone mixing ratio contour 1 0 ppmv moved downward near a height of 20 km during the period of focus this increase in ozone is likely to result from downward transport of ozone rich air originating from lower latitudes by brewer dobson circulation first the descent rate of the mixing ratio contour was estimated by taking the geometric height as the vertical coordinate for the deep vortex interior around 20 km a significant longitudinal dependence was observed an analysis using ecmwf operational data shows that this dependence can be approximately explained by longitudinally dependent vertical movements of the isentropes caused by a zonal wavenumber 1 quasi stationary planetary wave with amplitude and phases varying on a seasonal time scale next the descent rate was calculated around 500 k around 20 km by taking the potential temperature isentrope as the vertical coordinate the longitudinal dependence was still present using this coordinate meaning that the ozone mixing ratio and its increase are not constant on the isentropic layer even in the interior of the polar vortex a backward trajectory analysis showed that air parcels with large ozone mixing ratios were mostly transported from the polar vortex boundary region this result suggests that lateral transport mixing is important even before the breakup of the polar vortex results from a tracer tracer correlation analysis of o3 and long lived constituent n2o were also consistent with this inference the contribution of lateral mixing to the increase in ozone was estimated at about 17 6 4 that of the brewer dobson circulation around 20 km using the calculated descent rates the results of this study also imply that lagrangian downward motions in the vortex interior are not correctly estimated without accounting for lateral mixing even if the polar vortex is dynamically stable

equatorial quasi biennial oscillation influence on northern winter extratropical circulation 1 this study investigated the holton tan relationship between the equatorial quasi biennial oscillation qbo and the polar vortex as seen in the era 40 reanalysis and era interim analysis 1980 2004 25 years data sets and in ensemble simulated data sets five members covering the period 1980 2004 125 years by using the meteorological research institute chemistry climate model mri ccm and focusing on the northern hemisphere winter the primary tools employed were composite differences in zonal wind temperature and eliassen palm ep fluxes although not many global circulation models can simulate the qbo realistically the mri ccm which includes the interaction between qbo dynamics and the ozone hence heating distribution reproduces a self generated qbo that is fairly realistic in agreement with the finding of previous studies our results revealed that the conventional holton tan explanation that the equatorial winds in the lower stratosphere act as a waveguide for midlatitude planetary wave propagation cannot explain the winter circulation in either the era 40 data or the simulation although the composite differences in zonal wind and temperature show a slight yet statistically significant holton tan effect i e the stratospheric polar vortex is weaker and more disturbed under easterly qbo conditions the ep flux diagnostics do not show more poleward propagation in the midlatitude stratosphere rather planetary waves propagate more equatorward as well as more upward during the easterly phase of the qbo

global estimates of gravity wave momentum flux from high resolution dynamics limb sounder observations analyzed to derive global properties of gravity waves we describe a wavelet analysis technique that determines covarying wave temperature amplitude in adjacent temperature profile pairs the wave vertical wavelength as a function of height and the horizontal wave number along the line joining each profile pair the analysis allows a local estimate of the magnitude of gravity wave momentum flux as a function of geographic location and height on a daily basis we examine global distributions of these gravity wave properties in the monthly mean and on an individual day and we also show sample instantaneous wave events observed by hirdls the results are discussed in terms of previous satellite and radiosonde observational analyses and middle atmosphere general circulation model studies that parameterize gravity wave effects on the mean flow the high vertical and horizontal resolution afforded by the hirdls measurements allows the analysis of a wider range of wave vertical and horizontal wavelengths than previous studies and begins to show individual wave events associated with mountains and convection in high detail mountain wave observations show clear propagation to altitudes in the mesosphere

global observations of gravity waves from high resolution dynamics limb sounder temperature measurements a yearlong record of temperature amplitude and vertical wavelength 1 global observations of gravity waves have been performed using the high resolution dynamics limb sounder hirdls temperature data a background field that was derived by dynamically calculating 31 day 15 day means to block the stationary component and the slowly varying planetary scale waves was first subtracted from the hirdls temperature measurements an additional step was then taken to remove rapidly moving planetary scale waves by developing an along track temperature filter which was created by averaging the profiles within a 1000 km along track window finally each individual temperature perturbation vertical profile was analyzed using a fast fourier transform to estimate gravity wave temperature amplitudes and vertical wavelengths the investigation of the monthly mean gravity wave temperature amplitudes for the year 2006 found that gravity wave activity in the stratosphere is highly variable with season and can be very orographically dependent especially in the winter extratropics the monthly zonal means show that the peak vertical wavelengths correspond closely to the peak amplitudes the increasing amplitudes and vertical wavelengths are faster and generated at lower altitudes in the winter extratropical and high latitude stratosphere than those in the summer tropical stratosphere this is consistent with the lower source altitudes of orographic gravity waves in the extratropics and high latitudes and the higher source altitudes of convectively generated gravity waves in the tropics three cases were studied for the observed gravity waves over large mountain ranges using the european centre for medium range weather forecasts wind data investigations of episodes of enhanced gravity wave activity over the southern andes the cascade range and the rockies in winter months of 2006 indicate that orographic gravity waves refract downwind from the mountains and propagate along the direction of the intense winds by way of contrast observations of gravity waves around the himalayas show a strong relationship with the cyclones in that region

fine scale structure of the extratropical tropopause region 1 a vertically high resolved climatology of the thermal and wind structure of the extratropical tropopause region is presented the climatology is based on data from 80 u s radiosonde stations covering the period 1998 2002 time averages for each radiosonde station are computed using the tropopause as a common reference level for all vertical profiles within the mean a strong inversion at the tropopause in the mean vertical temperature gradient is uncovered that is temperature strongly increases with altitude within the lowermost stratosphere this tropopause inversion layer exists on average throughout the investigated extratropics about 30 n to 70 n accordingly the static stability parameter shows considerably enhanced values within the lowermost extratropical stratosphere compared to typical extratropical stratospheric values further aloft conventional averages are not able to capture the tropopause inversion layer mean profiles of the horizontal wind show behavior qualitatively corresponding to thermal wind balance winter and summer exhibit distinctly different climate states in the extratropical tropopause region an approximated potential vorticity is considered and found to be close to well mixed within the troposphere as well as within the tropopause inversion layer this suggests the view of the tropopause inversion layer as representing a dynamically active atmospheric layer some potential implications are discussed

wintertime temperature maximum at the subtropical stratopause in a t213l256 gcm 1 a wintertime temperature maximum can be observed at the subtropical stratopause but does not appear in the radiative equilibrium temperature distribution this structure was well simulated using a high resolution general circulation model and examined in detail the stratopause temperature is latitudinally maximized in the winter subtropics because of a strong downwelling of the meridional circulation from summer tropics to winter subtropics passing above the stratopause its strong meridional flow consists of two parts a strong poleward flow in the winter subtropics with nearly vertically aligned contours of absolute angular momentum m and a strong cross equatorial flow toward winter hemisphere above the tropical stratopause with nearly horizontally aligned m contours the strong poleward flow in the winter subtropics is driven by a large eliassen palm e p flux convergence in a small absolute vorticity region the large e p flux convergence is due to extratropical planetary waves and asymmetric inertial instability on the other hand the strong cross equatorial flow is induced along the m contour to satisfy mass continuity with the strong poleward flow in the winter subtropics and exists in the easterly phase of s sao with a small latitudinal gradient of m the easterly of s sao during its mature phase acts as a corridor for cross equatorial meridional circulation while cross equatorial meridional circulation contributes to driving the easterly of s sao in its development phase

gravity waves appearing in a high resolution gcm simulation global characteristics of gravity waves in the lower stratosphere are examined using a gcm with high resolution in both the horizontal t106 corresponding to about 120 km and the vertical 600 m the bottom boundary condition of the model is that of an aquaplanet with perpetual february sea surface temperature the simulated gravity waves are in good agreement with mesosphere stratosphere troposphere mst radar observations at a middle latitude on the gravity wave structure and on the frequency spectra as a function of height the frequency spectra of simulated wind and temperature fluctuations are also examined as a function of latitude large values of spectral density are observed at frequencies higher than the inertial frequency f in a weak wind region around 20 km which is consistent with the characteristics of internal gravity waves an isolated peak is observed near f for horizontal wind spectra at latitudes higher than 108 while the energy is distributed in a wide range of frequency at lower latitudes where f approaches zero further analysis is performed of those fluctuations having periods shorter than 24 h and those having vertical wavelengths smaller than 5 km these are frequently analyzed as gravity waves using observation data the distribution of energy and momentum fluxes in the latitude height section is examined the result indicates that short period waves mostly propagate upward and poleward from the equatorial region the wave energy reaches about 508 lat at the 27 km altitude a negative positive maximum of vertical flux of meridional momentum y9w9 is seen above the subtropical jet in the northern southern hemisphere for small vertical scale gravity waves this is consistent with the preferred equatorward propagation of the wave indicated by a statistical analysis based on mst radar observations the ratio of potential to kinetic energy maximizes over the equator and decreases poleward the eliassen palm flux divergence associated with gravity waves is decelerative above the subtropical jet albeit small

early cretaceous bimodal magmatism related epithermal mineralization a case study of the gaosongshan gold deposit in the northern lesser xing an range ne china abstract low sulfidation ls gold mineralization is partially associated with bimodal volcanism in origin sources of ore mineralized fluids and relevant dynamic processes remain poorly understood to better understand these issues a study including deposit geology petrology zircon u pb dating and element and sr nd hf isotope geochemistry of bimodal volcanic rocks at gaosongshan was conducted the bimodal volcanic rocks are composed of andesitic rocks basalt andesite andesite trachyandesite andesitic pyroclastic of the meifeng formation and overlying rhyolite lava of the fuminhe formation cut by equivalent porphyry stocks which contain pyrite bearing granular textured quartz cavity with a sugary appearance with trapped single phase magmatic fluids the andesitic suite formed at approximately 106 108 ma prior to eruption of the younger rhyolitic magmas 105 6 1 7 ma n 13 mswd 1 2 the andesites show calc alkaline affinities which is a subduction related characteristic and show moderate la ybn 7 91 11 36 and weakly negative europium anomalies 0 80 1 02 indicating a source in the asthenospheric mantle with varying contamination by both subduction and continental materials a type rhyolitic rocks are geochemically comparable to the andesitic suite and their higher la ybn 13 01 30 05 and lower eu eu 0 66 0 73 indicate evolved products of andesitic magmas the estimated oxygen fugacity of dry 1 2 water rhyolite lava is fmq 1 87 whereas rhyolite porphyry is more oxidized fmq 0 12 and water rich 2 5 2 8 with probably being water saturated at 2 0 2 4 km depths therefore it is assumed that the essential constraints of bimodal magmatism on epithermal gold mineralization are sequential processes from ascending and gradual differentiation of crustal level mantle derived basaltic magmas to releases of hydrothermal solutions from the silica rich magma reservoir at shallower levels most importantly the oxygen fugacity of and the fluid fluxes from dry rhyolitic melts are critical restricting parameters for the limited reserves at gaosongshan thus this research contributes objective evidence for investigations of deposit genesis and prospecting targets

a meridional scan of the stratospheric gravity wave field over the ocean in 2001 messo2001 1 in order to examine gravity wave characteristics over the ocean we conducted a radiosonde observation campaign to scan the stratosphere meridionally over the middle pacific with hakuho maru research vessel operated by the ocean research institute university of tokyo seventy vertical profiles of temperature winds and humidity were successfully obtained over a wide latitude range of 28 n to 48 s with an interval of 1 degree gravity wave energy and vertical wavenumber spectra were examined as a function of latitude gravity wave energy is maximized in the tropical region where the convection is active and in the middle latitude region where the subtropical westerly jet is situated the wave energy in the tropical region is greater than the climatology based on operational radiosonde observation over land regions the gravity wave amplitude does not necessarily increase with altitude in contradiction to simple vertical propagation the latitudinal distribution of wave energy rather suggests that gravity waves propagate meridionally toward higher latitudes an interesting feature is that a wave packet having large horizontal wind and temperature amplitudes is observed continuously over 7 days in the latitudinal region extending 26 degrees results of hodograph analysis indicate that the wave packet is due to an inertia gravity wave with horizontal and vertical wavelengths of about 1800 km and 4 5km respectively this inertia gravity wave is likely generated in association with vigorous convection in the intertropical convergence zone itcz in the northern hemisphere and propagated southward interhemispherically the results in this study show that there are strong nonstationary gravity wave sources over the ocean the importance of meridionally propagating gravity waves is discussed

giant porphyry deposits characteristics distribution and tectonic controls more than half of the 25 largest known porphyry copper deposits defined in terms of contained copper metal formed during three time periods the paleocene to eocene eocene to oligocene and middle miocene to pliocene these giant deposits are clustered within three provinces central chile northern chile and southwest arizona northern mexico other giant deposits occur in montana utah panama peru argentina irian jaya mongolia and iran compressive tectonic environments thickened continental crust and active uplift and erosion were associated with the formation of many of these deposits calc alkalic magmas are most favorable for the formation of giant porphyry copper deposits although several of the largest systems are associated with high k calc alkalic intrusions the 25 largest gold rich porphyry deposits are concentrated in the southwest pacific and south america with other occurrences in eurasia british columbia alaska and new south wales many of the deposits formed in the last 13 m y the largest of the deposits are associated with high k calc alkalic intrusions many calc alkalic porphyritic intrusions have also produced giant gold rich porphyries in the last 20 m y the formation of giant porphyry copper molybdenum and copper gold deposits in the circum pacific region has been closely associated with subduction of aseismic ridges seamount chains and oceanic plateaus beneath oceanic island and continental arcs in several examples these tectonic perturbations have promoted flat slab subduction crustal thickening uplift and erosion and adakitic magmatism coeval with the formation of well endowed porphyry and or epithermal mineral provinces similar tectonic features are inferred to be associated with the giant porphyry copper molybdenum provinces of northern chile eocene oligocene and southwest united states cretaceous paleocene topographic and thermal anomalies on the downgoing slab appear to act as tectonic triggers for porphyry ore formation other factors such as sutures in the overriding plate permeability architecture of the upper crust efficient processes of ore transport and deposition and in some cases formation and preservation of supergene enrichment blankets are also vital for the development of high grade giant ore deposits a low grade geochemical anomaly may be the final product of mineralization if ore forming processes do not operate efficiently even in the most favorable geodynamic settings

middle atmosphere simulated with high vertical and horizontal resolution versions of a gcm improvements in the cold pole bias and generation of a qbo like oscillation in the tropics abstract the large scale circulation in the geophysical fluid dynamics laboratory skyhi troposphere stratosphere mesosphere finite difference general circulation model is examined as a function of vertical and horizontal resolution the experiments examined include one with horizontal grid spacing of 35 km and another with 100 km horizontal grid spacing but very high vertical resolution 160 levels between the ground and about 85 km the simulation of the middle atmospheric zonal mean winds and temperatures in the extratropics is found to be very sensitive to horizontal resolution for example in the early southern hemisphere winter the south pole near 1 mb in the model is colder than observed but the bias is reduced with improved horizontal resolution from 70 c in a version with 300 km grid spacing to less than 10 c in the 35 km version the extratropical simulation is found to be only slightly affected by enhancements of the vertical resolution by contrast the tropical middle atmospheric s

a general circulation model study of the orographic gravity waves over antarctica excited by katabatic winds 1 in this study we simulated orographic gravity waves ogws over antarctica using a t213l250 general circulation model gcm the gcm has a fine vertical resolution of 300 m throughout the middle atmosphere the simulation was run for a 1 year period results from 21 28 june were primarily considered ogws are excited by katabatic winds that travel down the surface slopes of the antarctic ice sheet a strong eastward katabatic wind blows over the west coast of the ross sea at the approach of the synoptic scale upper tropospheric westerly jets a quasi stationary ogw is then excited above the coast and propagates upward into the mesosphere an ogw appears sporadically during the antarctic winter and spring its amplitude is determined by the strength of the eastward katabatic wind dissipation of ogws within the middle atmosphere results in a localized deceleration of westerly winds greater than 30 m s 1 d 1 this in turn modifies the horizontal circulation in the polar vortex strong vertical mixing occurs within the mesosphere and is associated with wave breaking large temperature fluctuations associated with the ogws affect the formation or suppression of polar stratospheric clouds in the lower stratosphere katabatic wind excitation is the most powerful source of gravity waves over antarctica around the time of the winter solstice

a very high resolution general circulation model simulation of the global circulation in austral winter abstract this paper discusses a simulation obtained with the geophysical fluid dynamics laboratory skyhi troposphere stratosphere mesosphere general circulation model run at very high horizontal resolution 60 km grid spacing and without any parameterization of subgrid scale gravity wave drag the results are for a period around the austral winter solstice and the emphasis is on the simulated southern hemisphere sh winter circulation comparisons are made with results obtained from lower horizontal resolution versions of the same model the focus in this paper is on two particularly striking features of the high resolution simulation the extratropical surface winds and the winter polar middle atmospheric vortex in the extratropical sh the simulated surface westerlies and meridional surface pressure gradients in the high resolution model are considerably stronger than observed and are stronger than those simulated at lower horizontal resolution in the middle atmosphere the high resolution model

using satellite observations to constrain parameterizations of gravity wave effects for global models abstract small scale gravity waves are common features in atmospheric temperature observations in satellite observations these waves have been traditionally difficult to resolve because the footprint or resolution of the measurements precluded their detection or clear identification recent advances in satellite instrument resolution coupled to innovative analysis techniques have led in the last decade to some new global datasets describing the temperature variance associated with these waves such satellite observations have been considered the best hope for quantifying the global properties of gravity waves needed to constrain parameterizations of their effects for global models although global maps of averaged gravity wave temperature variance have now been published from a variety of different instruments on earth orbiting platforms these maps have not provided the needed constraints the present paper first summarizes what has been learned from traditional temporally and spatially averaged analyse

growth of planetary waves and the formation of an elevated stratopause after a major stratospheric sudden warming in a t213l256 gcm 1 recovery processes after a major stratospheric sudden warming ssw with the formation of an elevated stratopause and a strong polar night jet are investigated using a gravity wave resolving gcm the major ssw that occurred in the gcm bears a strong resemblance to observations in january 2006 and january 2009 the recovery phase of the ssw in the gcm is divided into two stages in the first stage during about five days just after the ssw a large positive eliassen palm e p flux divergence associated with the growth of planetary waves contributes to the quick recovery of eastward wind above 2 hpa about 42 km which is likely due to baroclinic and or barotropic instabilities in the second stage over the next three weeks a prolonged westward wind in the lower stratosphere blocked upward propagation of gravity waves with westward intrinsic phase velocities it reduces the deceleration of eastward wind in the upper mesosphere and raises the breaking height of gravity waves since the height of westward gravity wave forcing also rises the polar stratopause created by the gravity wave driven meridional circulation is formed at an elevated height about 75 km compared to that before the ssw 55 65 km in addition the weaker westward gravity wave forcing in the upper mesosphere drives weaker downwelling around 1 hpa and forms a cold layer consequently the strong polar night jet forms at a higher altitude than before the ssw as a result of adjustment toward the thermal wind balance this indicates that these two stages provide eastward acceleration in different ways

low frequency inertia gravity waves in the stratosphere revealed by three week continuous observation with the mu radar continuous observations over three weeks were performed with the mu radar at shigaraki japan 35n 136e in april of 1995 by integrating radar echo spectra over 30 min after removing severe interferences winds were successfully estimated offline up to 24 km in the lower stratosphere it was found that inertia gravity waves with a period of about 20 h and a vertical wavelength of 3 5 km are dominant near 22 km in a region of weak background winds four wave packets were fitted to plane waves by a least squares method and wave parameters were estimated theoretically the inertia gravity waves propagate energy upward and their horizontal phase velocity is westward in the range 10 to 20 m s 1 the waves have large momentum fluxes of about 0 002 nm 2 this result suggests that inertia gravity wave drag may contribute to the formation of easterlies in the summer stratosphere

quantification of the gravity wave forcing of the migrating diurnal tide in a gravity wave resolving general circulation model 1 the interaction of gravity waves gws and the migrating diurnal tide are studied in a gw resolving general circulation model gcm by calculating the tidal components of zonal wind accelerations and equivalent rayleigh friction due to tidal induced gw dissipation two 15 day periods for perpetual equinoctial and solstice simulations are analyzed which are performed with the japanese atmospheric general circulation model for upper atmosphere research jaguar high resolution gcm the model can directly simulate gws with horizontal wavelengths greater than about 190 km and thus reproduce the general features of the mean winds and temperatures from the surface to the mesosphere and lower thermosphere mlt the amplitudes of the migrating diurnal tide are successfully simulated during both seasons and the tidal winds affect the altitudes of gw dissipation in the low latitude mlt the tidal component of gw forcing has maximal values of about 15 m s 1 d 1 near the maximal vertical shears of the tidal winds and generally works to shorten the vertical wavelength of the migrating diurnal tide the phase relationship between the tidal winds and the tidal induced gw forcing is not exactly 90 out of phase causing amplification suppression of the tide the gw forcing amplifies the migrating diurnal tide during the equinox while during the solstice it suppresses the tidal winds in the upper mesosphere of both hemispheres this difference in behavior can be attributed to a seasonal variation of the mean zonal winds because combination of the mean and tidal winds affects the altitudes of gw dissipation

southern hemisphere extratropical gravity wave sources and intermittency revealed by a middle atmosphere general circulation model abstractsouthern hemisphere extratropical gravity wave activity is examined using simulations from a free running middle atmosphere general circulation model called kanto that contains no gravity wave parameterizations the total absolute gravity wave momentum flux mf and its intermittency diagnosed by the gini coefficient are examined during january and july the mf and intermittency results calculated from the kanto model agree well with results from satellite limb and superpressure balloon observations the analysis of the kanto model simulations indicates the following results nonorographic gravity waves are generated in kanto in the frontal regions of extratropical depressions and around tropopause level jets regions with lower higher intermittency in the july midstratosphere become more less intermittent by the mesosphere as a result of lower level wave removal the gravity wave intermittency is low and nearly homogeneous throughout the sh middle atmosphere during january this indicates t

first successful hindcasts of the 2016 disruption of the stratospheric quasi biennial oscillation in early 2016 the quasibiennial oscillation in tropical stratospheric winds was disrupted by an anomalous easterly jet centered at 40 hpa a development that was completely missed by all operational extended range weather forecast systems this event and its predictability are investigated through 40 day ensemble hindcasts using a global model notable for its sophisticated representation of the upper atmosphere integrations starting at different times throughout january 2016 just before and during the initial development of the easterly jet were performed all integrations simulated the unusual developments in the stratospheric mean wind despite considerable differences in other aspects of the flow evolution among the ensemble members notably in the evolution of the winter polar vortex and the day to day variations in extratropical rossby waves key to prediction of this event is simulating the slowly evolving mean winds in the winter subtropics that provide a waveguide for rossby waves propagating from the winter hemisphere

frequency spectra and vertical profiles of wind fluctuations in the summer antarctic mesosphere revealed by mst radar observations continuous observations of polar mesosphere summer echoes at heights from 81 93 km were performed using the first mesosphere stratosphere troposphere incoherent scatter radar in the antarctic over the three summer periods of 2013 2014 2014 2015 and 2015 2016 power spectra of horizontal and vertical wind fluctuations and momentum flux spectra in a wide frequency range from 8 min 1 to 20 days 1 were first estimated for the antarctic summer mesosphere the horizontal vertical wind power spectra obey a power law with an exponent of approximately 2 1 at frequencies higher than the inertial frequency of 13 h 1 and have isolated peaks at about 1 day and a half day in addition an isolated peak of a quasi 2 day period is observed in the horizontal wind spectra but is absent from the vertical wind spectra which is consistent with the characteristics of a normal mode rossby gravity wave zonal meridional momentum flux spectra are mainly positive negative and large fluxes are observed in a relatively low frequency range from 1 day 1 to 1 h 1 a case study was performed to investigate vertical profiles of momentum fluxes associated with gravity waves and time mean winds on and around 3 january 2015 when a minor stratospheric warming occurred in the northern hemisphere a significant momentum flux convergence corresponding to an eastward acceleration of 200 m s 1 d 1 was observed before the warming and became stronger after the warming when mean zonal wind weakened the strong wave forcing roughly accorded with the coriolis force of mean meridional winds

gravity wave variations during the 2009 stratospheric sudden warming as revealed by ecmwf t799 and observations 1 ecmwf t799 is used to study gravity wave gw variations during the 2009 stratospheric sudden warming ssw in the arctic the magnitude and occurrence of gws correlate with the location and strength of the polar vortex that is strongly disturbed by planetary wave pw growth this location dependence on pw phase explains the observed gw variability during ssws during the development and the onset of ssw the zonal mean gw potential energy density gw ep increases on january 5 and 15 22 in association with the growth of pw wavenumber 1 and wavenumber 2 respectively as the initial prominent pw magnitude in the lower mesosphere progresses downward gw ep enhancement also seems to show a corresponding descent from january 5 22 gw ep peaks before the wind reversal occurrence and significantly weakens after the ssw these variations are confirmed by cosmic gps observations lidar data from antarctica are also used to validate gws as derived in ecmwf

quasi monochromatic inertia gravity waves in the lower stratosphere from mst radar observations 1 the frequency of occurrence of quasi monochromatic oscillations with periods near the inertial period is examined using hourly mean wind observations from the mst radars at white sands missile range new mexico and vandenberg air force base california spanning 6 years and 4 years respectively power spectral analyses show that the energy levels near the inertial frequency during summer are nearly constant with altitude from about 12 km up to the highest altitude available about 20 km while energy levels at lower frequencies decrease with altitude this decrease leads to a relative enhancement of energy near the inertial frequency during winter the relative enhancement near the inertial frequency is much smaller results from least squares curve fitting used to find the percent of wind variance explained pev by a single wave over data blocks 72 hours long and 2 km deep indicate that a quasi monochromatic oscillation is present when pev 25 during summer in the stratosphere over 50 of the cases have pev 25 the best fit waveform has mean period near 21 hours and vertical wavelength near 3 km the wind vectors exhibit anticyclonic rotation in time and with height consistent with upward propagating gravity waves the mean ratio of the intrinsic to the inertial frequency is about 1 3 in this data set and the associated mean horizontal wavelength of these waves is slightly over 1000 km

zonally non uniform distribution of equatorial gravity waves in an atmospheric general circulation model 1 the results from an atmospheric general circulation model without gravity wave gw drag parameterization include quasi biennial oscillation qbo like oscillations in the equatorial lower stratosphere the zonal distribution of gravity waves with periods of less than 3 days over the equatorial region is analyzed for 2 months july august during the westerly shear phase of the qbo the westerly acceleration of the qbo is associated with the zonal forcing due to resolved waves of all components and gws account for about 60 of the forcing the vertical flux of the zonal momentum of gws in the upper troposphere has a non uniform distribution large relatively small magnitude upward fluxes with westerly easterly momentum dominate in the eastern western hemisphere the wave momentum flux divergence also varies with longitude the westerly acceleration of the zonal wind due to gws in the eastern hemisphere is much greater than that in the western hemisphere

rayleigh lidar observations of gravity wave activity in the winter upper stratosphere and lower mesosphere above davis antarctica 69 s 78 e 1 gravity wave activity in the upper stratosphere and lower mesosphere uslm is investigated using temperature data retrieved from a rayleigh lidar at davis antarctica 69 s 78 e during the 2007 and 2008 winters the temporal and height variabilities of waves with ground based periods greater than 2 h and vertical wavelengths between 4 km and 20 km are analyzed stratospheric gravity wave potential energy per unit mass shows a weaker correlation with stratospheric winds at davis than that reported in the arctic gravity waves dissipate above 40 km during winter while there is no dissipation in the autumn mesosphere a separate analysis of gravity waves with ground based periods of 2 6 h revealed lower dissipation in the winter mesosphere the seasonal cycle of gravity wave activity is evident throughout the uslm with peak activity observed during winter the gravity wave potential energy and vertical wavenumber power spectral density at davis are similar to that recorded at other high latitude sites

three dimensional structures of tropical nonmigrating tides in a high vertical resolution general circulation model this paper investigates nonmigrating tides from the ground to the lower mesosphere using data from a high resolution general circulation model kanto gcm as well as observational data from the sounding of the atmosphere using broadband emission radiometry instrument on board the thermosphere ionosphere mesosphere energetics and dynamics satellite and from gps radio occultation measurements obtained with the cosmic formosat 3 mission we extract nonmigrating tides using a composite as a function of universal time in physical space without performing a zonal wave number decomposition the kanto gcm clearly demonstrates that tropical nonmigrating tides are regarded as gravity waves excited by diabatic heating enhanced over two major continents specifically africa and south america they propagate zonally in a direction away from their sources that is west and eastward propagating waves are dominant on the western and eastern sides of the continents respectively these characteristics are observed in two satellite data sets as well except that the amplitudes in the kanto gcm are larger than those in the observations seasonal variations of nonmigrating tides are also investigated it is suggested that filtering owing to the stratopause semiannual oscillation as well as diabatic heating in the troposphere is important for the seasonal variations of nonmigrating tides in the stratosphere and the lower mesosphere