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

stratospheric gravity wave simulation over greenland during 24 january 2005 1 the advanced regional prediction system forecast model is extended up to the stratopause and over the entire hemisphere to simulate gravity waves during 24 january 2005 with a 15 km horizontal resolution the simulation produces dominant gravity wave features near eastern greenland that are associated mainly with orographic forcing by the greenland terrain the simulated wave temperature perturbations compare favorably with radiance perturbations from nasa atmospheric infrared sounder observations in the upper stratosphere 40 50 km vertical overturning of the isentropes suggests the occurrence of wave breaking just east of greenland that leads to a tremendous reduction of wave amplitudes the associated flux divergence produces horizontal flow deceleration of 12 120 m s 1 day 1 and coincides with areas of depleted stratospheric wind speed suggesting strong interactions between orographic gravity waves and the polar vortex a simulation using the coarser 50 km horizontal resolution produces gravity waves of significantly weaker amplitudes

the propagation of mountain waves into the stratosphere quantitative evaluation of three dimensional simulations on 6 january 1992 measurements of a mountain wave with significant amplitude were taken over the southern tip of greenland during an er 2 flight at an altitude of about 20 km this work focuses on 3d numerical simulations of the wave generation and its propagation into the stratosphere during this event the sensitivity of the simulated mountain wave to surface friction and horizontal resolution is explored a nonhydrostatic model is used for experiments with horizontal resolutions of 12 4 and 1 3 km in all simulations the flow over the southern tip of greenland generates a mountain wave which propagates into the stratosphere changes of surface friction and horizontal resolution affect mostly the amplitude of the mountain wave increasing surface friction on the slopes reduces the amplitude of the excited orographic gravity wave horizontal diffusion required for numerical stability attenuates gravity waves during their propagation into the stratosphere increasing the horizontal resolution permits a smaller diffusion and thereby results in larger stratospheric wave amplitudes the experiment with increased surface friction at 1 3 km horizontal resolution shows the best agreement with the observational data of the wave in the stratosphere the differences between the simulated and measured amplitudes of vertical displacement and temperature anomaly are less than about 20 the disparity in vertical velocity is larger downward velocities were observed up to 4 8 m s21 and simulated up to 2 7 m s21 in the experiments with lower surface friction at 4 km resolution the accuracy regarding the amplitude of vertical displacement and temperature anomalies is similar but the simulated maximum downdraft is even weaker the other experiments with increased surface friction at 4 km resolution and normal friction at 12 km resolution significantly underestimate the wave amplitude the results of the experiments suggest that the generation of orographic gravity waves and their propagation into the stratosphere can be simulated in three dimensions in a realistic manner provided that the magnitude of the parameterized surface friction is in a realistic range and the horizontal resolution is sufficient

a study of the low frequency inertio gravity waves observed during the pyrenees experiment the purpose of this paper is to analyze and interpret the onset of some well characterized transient inertio gravity waves observed during the pyrex pyrenees experiment campaign the data used are the high resolution soundings launched every 6 hours on both sides of the ridge in agreement with other observations made during the field campaign certain among those soundings often show steady mountain waves it appears that those waves are often transients and are followed by well characterized inertio gravity waves propagating upward and downward from the level where the initial mountain waves are large to interpret those observations it is suggested that the observed inertio gravity waves result from the geostrophic adjustment of the large scale flow that follows the transit and eventually the breaking of the main mountain wave this hypothesis is supported by an analytical calculation of inertio gravity waves emission from a momentum deposit that lasts a finite time the spatial extent of this forcing are also finite and its maximum amplitude is a fraction of the measured mountain drag

equatorial stratospheric response to variations in deterministic and stochastic gravity wave parameterizations 1 the sensitivity of the equatorial stratospheric climate to variations in the gravity wave parameterization is examined in the unified model particular emphasis is placed on the response of the annual cycle and quasi biennial oscillation of zonal winds two classes of variations are considered the first consists of variations in the source strength of the classic deterministic formulation of a doppler spread doppler shifted gravity wave scheme the second consists of variations in the probability density function of the source strength parameter in a stochastic formulation of the same scheme the effects on stratospheric climate of variations in the source strength of a deterministic scheme can be predicted from theory in such a scheme when choosing the best possible value for the source strength a trade off between a proper representation of the quasi biennial oscillation and the annual cycle is inevitable implementation of a stochastic source strength in the resident gravity wave scheme is justified by the need to better represent the intermittent nature of the convective generation of gravity waves the most striking effect of the stochastic parameterization is the stabilization of the quasi biennial oscillation in multidecadal simulations we suggest that this is due to the ability of the stochastic gravity wave parameterization to deposit a larger portion of gravity wave drag in the middle stratosphere

gravity waves generated by deep tropical convection estimates from balloon observations and mesoscale simulations 1 convective gravity waves in the tropics are studied by analyzing in situ measurements from long duration stratospheric balloons launched during the preconcordiasi campaign 2010 and mesoscale simulations an improved temporal resolution of the observations as well as the balloon quasi lagrangian behavior allow an unprecedented investigation of the whole gravity wave spectrum first a case study of gravity waves generated by a developing cyclone tropical storm gelane february 2010 is carried out using observations complemented by numerical simulations with the weather research and forecast model with a resolution down to 1 km distributions of momentum fluxes obtained from both data show reasonable agreement and emphasize waves with short wavelengths 15 km and short periods 20 min still some differences are also found which can likely be related to errors of the modeled background flow second observations from the whole preconcordiasi flights are analyzed with an emphasis on gravity wave momentum fluxes their phase speed distribution has a robust shape with maximum fluxes with near zero ground based phase speeds yet significant momentum fluxes are also found for larger values yielding a mean phase speed of about 27 ms 1 the momentum fluxes are concentrated in short episodes with intense values and their intermittency is quantified using probability distribution functions and the gini coefficient 0 5 0 6 the relative importance of convective and topographic sources are investigated suggesting comparable intensities but a greater occurrence frequency of convective events waves emitted by tropical storm gelane do not stand out relative to other convective events

relevance of mountain wave cooling for the formation of polar stratospheric clouds over scandinavia mesoscale dynamics and observations for january 1997 the effect of mesoscale mountain wave induced temperature anomalies on the formation potential of polar stratospheric clouds above northern scandinavia is analyzed with a one month mesoscale model integration the simulation results are contrasted with synoptic scale analyses and compared with remote sensing and in situ observations the mesoscale mass flux of air parcels with temperatures below the threshold for cloud formation through a control volume is compared with its synoptic scale counterpart a classification of the synoptic scale flow into periods of large and small mountain wave activity in the stratosphere is proposed the derived classification will be used for a climatology of stratospheric mountain wave activity above scandinavia

quasi lagrangian superpressure balloon measurements of gravity wave momentum fluxes in the polar stratosphere of both hemispheres 1 superpressure balloons were flown in 2002 and 2005 in the winter polar vortices of both hemispheres the balloons can drift for months in the stratosphere acting as quasi lagrangian tracers of air parcel motions the meteorological datasets acquired are used to retrieve small scale internal atmospheric gravity wave parameters using wavelet techniques for the first time gravity wave momentum fluxes are estimated over wide geographical areas and the results will help constrain gravity wave parameterization schemes used in general circulation climate models the importance of mountain waves is confirmed with largest fluxes observed in the lee of greenland and the antarctic peninsula however significant momentum fluxes are also observed over the oceans showing the importance of other wave generation mechanisms

estimation of gravity wave momentum flux and phase speeds from quasi lagrangian stratospheric balloon flights part i theory and simulations a methodology for estimating gravity wave characteristics from quasi lagrangian observations provided by long duration superpressure balloon flights in the stratosphere is reviewed wavelet analysis techniques are used to detect gravity wave packets in observations of pressure temperature and horizontal velocity an emphasis is put on the estimation of gravity wave momentum fluxes and intrinsic phase speeds which are generally poorly known on global scales in the atmosphere the methodology is validated using monte carlo simulations of time series that mimic the balloon measurements including the uncertainties associated with each of the meteorological parameters while the azimuths of the wave propagation direction are accurately retrieved the momentum fluxes are generally slightly underestimated especially when wave packets overlap in the time frequency domain or for short period waves a proxy is derived to estimate by how much momentum fluxes are reduced by the analysis retrievals of intrinsic phase speeds are less accurate especially for low phase speed waves a companion paper part ii implements the methodology to observations gathered during the vorcore campaign that took place in antarctica between september 2005 and february 2006

observations and simulations of a large amplitude mountain wave breaking over the antarctic peninsula 1 a case study of a large amplitude orographic gravity wave occurring over the antarctic peninsula is presented based on observations from the vorcore balloon campaign and on mesoscale numerical simulations the vorcore campaign september 2005 to february 2006 consisted in the flight of 27 superpressure balloons in the core of the southern hemisphere stratospheric polar vortex at altitudes of 16 19 km from september 2005 to february 2006 on 7 october 2005 one of the balloons exploded as it was flying above the antarctic peninsula the observations collected by another balloon that was flying during the same time period above the peninsula suggest the presence of a very intense gravity wave peak to peak amplitude of the order of 25 30 m s 1 in zonal and meridional velocity disturbances the wave packet is likely undersampled in the balloon observations because of its high intrinsic frequency but the balloon data set is complemented with high resolution numerical simulations carried out with the weather research and forecast model the simulations are validated by comparison with the balloon measurements and show that the wave was breaking in the lower stratosphere at the time and height where the balloon exploded the simulations highlight several consequences of the mountain wave on the stratosphere forcing of the mean flow generation of secondary inertia gravity waves and turbulence and mixing in particular the momentum fluxes are calculated and are found to compare well with the estimates from balloon measurements the large values found are likely extreme values which raises the issue of their representativity to discuss this the balloon measurements are used in conjunction with operational analyses to estimate the frequency of such large amplitude gravity waves i e to provide an estimate of their intermittency

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

geochemistry and geochronology of proterozoic tholeiite dykes of east antarctica evidence for mantle metasomatism two episodes of tholeiite dyke emplacement have been identified in archaean high grade metamorphics of the napier complex in enderby land middle proterozoic amundsen dykes are typical continental tholeiites and most of the chemical variation in individual suites can be explained in terms of different degrees of partial melting and low pressure crystal fractionation group i amundsen tholeiites were derived from a relatively homogeneous source region 1 190 200 m y ago whereas that of the group ii amundsen tholeiites was chemically and isotopically heterogeneous group ii dykes have various degrees of enrichment in incompatible elements and commonly show normalised trace element abundance patterns with negative nb anomalies these features imply variable metasomatism of the source region by a volatile rich fluid phase rather than a melt of any observed igneous composition enriched in k rb ba th and possibly la and ce early proterozoic 2 350 48 m y tholeiites were emplaced at considerable depths in the crust during the waning stages of granulite facies metamorphism and include a high mg suite of possible komatiitic affinity ranging in composition from hypersthene rich tholeiite norite to quartz rich tholeiite they tend to have higher ratios of highly to moderately incompatible elements e g k zr k ce and larger nb anomalies i e higher k nb compared with middle proterozoic tholeiites suggesting derivation from more enriched source regions isotopic data are not compatible with significant crustal contamination but constrain source metasomatism to a time immediately before emplacement metasomatism of the source region of the much younger group i tholeiites may have been contemporaneous with that of the high mg suite

lidar observations of persistent gravity waves with periods of 3 10 h in the antarctic middle and upper atmosphere at mcmurdo 77 83 s 166 67 e persistent dominant and large amplitude gravity waves with 3 10 h periods and vertical wavelengths 20 30 km are observed in temperatures from the stratosphere to lower thermosphere with an fe boltzmann lidar at mcmurdo antarctica these waves exhibit characteristics of inertia gravity waves in case studies yet they are extremely persistent and have been present during every lidar observation we characterize these 3 10 h waves in the mesosphere and lower thermosphere using lidar temperature data in june from 2011 to 2015 a new method is applied to identify the major wave events from every lidar run longer than 12 h a continuous 65 h lidar run on 28 30 june 2014 exhibits a 7 5 h wave spanning 60 h and 6 5 h and 3 4 h waves spanning 40 and 45 h respectively over the course of 5 years 323 h of data in june reveal that the major wave periods occur in several groups centered from 3 5 to 7 5 h with vertical phase speeds of 0 8 2 m s these 3 10 h waves possess more than half of the spectral energy for 93 of the time a rigorous prewhitening postcoloring technique is introduced for frequency power spectra investigation the resulting spectral slopes are unusually steep 2 7 below 100 km but gradually become shallower with increasing altitude reaching about 1 6 at 110 km two dimensional fast fourier transform spectra confirm that these waves have a uniform dominant vertical wavelength of 20 30 km across periods of 3 5 10 h these statistical features shed light on the wave source and pave the way for future research

evidence for inertia gravity waves forming polar stratospheric clouds over scandinavia 1 at three successive days at the end of january 2000 the deutsches zentrum fur luft und raumfahrt dlr airborne lidar ozone lidar experiment explored mountain wave induced polar stratospheric clouds above the scandinavian mountain ridge global analyses and mesoscale modeling are applied to explain their complex internal structure and their day to day variability depending on the synoptical scale meteorological conditions stratospheric temperature anomalies of different amplitude and horizontal extent are generated by the upward propagating mountain waves short term excitation of about 6 hours resulted in localized stratospheric temperature anomalies directly above the mountain ridge as for 25 january 2000 in this case the elevation of the observed clouds differed not much from the synoptic scale clouds upstream above the norwegian sea on the other hand long lasting flow past the scandinavian mountain ridge formed huge 400 km horizontally extending stratospheric ice clouds in altitudes as much as 5 km above the elevation of the upstream clouds just 1 day later inertia gravity waves with horizontal wavelengths of about 350 km are responsible for their formation for the first time a predicted temperature minimum far downstream of the mountains could be proofed by the observation of an isolated stratospheric ice cloud above finland the observed particles are classified in terms of their measured optical properties such as backscatter ratio and depolarization in all cases mountain waves generated ice clouds in contrast to the nitric acid trihydrate tail of the ice cloud on 25 january the same classification results in a tail of liquid supercooled ternary solutions droplets 1 day later the particle structure downstream of the mountains is very complex and needs detailed microphyical modeling and interpretation

sensitivity of resolved mountain drag to model resolution for map case studies seven mountain wave case studies from the mesoscale alpine programme map have been used to investigate the behaviour of the resolved alpine pressure drag with model horizontal resolution three independent modelling systems show that the magnitude of the resolved surface pressure drag increases monotonically as the horizontal model resolution is increased from 125 km down to a few kilometres a substantial proportion of the drag will still need to be parametrized in the next generation of mesoscale models with horizontal resolutions of 3 or 4 km this is particularly true for the most important drag cases when the jet stream directly above the mountains produces larger wind speeds near mountain crest level resulting in much larger total alpine drags copyright 2006 royal meteorological society

large amplitude mountain wave breaking over greenland abstract a large amplitude mountain wave generated by strong southwesterly flow over southern greenland was observed during the fronts and atlantic storm track experiment fastex on 29 january 1997 by the noaa g iv research aircraft dropwindsondes deployed every 50 km and flight level data depict a vertically propagating large amplitude wave with deep convectively unstable layers potential temperature perturbations of 25 k that deformed the tropopause and lower stratosphere and a vertical velocity maximum of nearly 10 m s 1 in the stratosphere the wave breaking was associated with a large vertical flux of horizontal momentum and dominated by quasi isotropic turbulence the coupled ocean atmosphere mesoscale prediction system coamps nonhydrostatic model with four nested grid meshes with a minimum resolution of 1 7 km accurately simulates the amplitude location and timing of the mountain wave and turbulent breakdown finescale low velocity plumes that resemble wakelike structures emanate from highl

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

observation and analysis of a large amplitude mountain wave event over the antarctic peninsula 1 we use measurements from the atmospheric infrared sounder airs on the aqua satellite to observe the 3 dimensional structure of a gravity wave event over the antarctic peninsula and determine the horizontal and vertical wavelengths propagation direction and temperature amplitude and from these we estimate wave momentum flux using theoretical knowledge of the weighting functions and radiative transfer for airs radiance measurements at temperature sensitive channels in the infrared we derive a method of estimating wave temperature amplitude directly from the radiance measurements comparison of the radiance based temperature amplitudes to the temperature amplitude in airs retrieved temperature fields shows close agreement because the radiances have 3 times better horizontal resolution than the retrievals our analysis suggests we can routinely observe important geophysical properties of waves with horizontal wavelengths as short as 80 km using airs radiances we further analyze a nearly identical wave event appearing in the european centre for medium range forecasts ecmwf temperature and wind fields from both assimilation and forecast data analysis of the ecmwf data and nearby radiosonde wind profiles allows the interpretation as a mountain wave event forced by flow over the topography of the antarctic peninsula

evaluation of the lateral earth pressure coefficients at rest in granular soil deposits using the anisotropic components of s wave velocity abstract determination of the lateral earth pressure coefficients at rest k0 in natural soil deposits is an important issue in geotechnical and geological engineering in this study evaluation of this parameter in a granular soil deposit was examined by using two anisotropic components of the s wave velocity sv and sh wave components to this end thirteen pairs of p and s wave seismic refraction profiles were acquired at two different granular sites in iran the collected shot gathers were processed from which the sv and sh wave velocities were derived the sv wave velocities were obtained by using the multichannel analysis of surface waves masw method while the sh wave velocities were extracted by utilizing the multichannel analysis of love waves malw technique the reference k0 values in the soil deposits were calculated by the mayne and kulhawy s formula based on the friction angles and overconsolidation ratios ocr determined from laboratory tests the curves of the reference k0 values versus the sh sv velocity ratios at both sites strongly confirmed the feasibility of k0 evaluation from the velocity components to develop a global equation for k0 evaluation in granular soil deposits a general regression analysis was conducted on the obtained data from this study combined with those reported in the literature the results showed that reliable values of k0 can be estimated using the sh sv velocity ratios the findings of this study may appropriately serve as references for economic and non invasive in situ k0 identification in granular soil deposits using the surface wave methods

high resolution numerical model integrations to validate gravity wave drag parametrization schemes a case study a three dimensional non hydrostatic numerical model is used to simulate the lee wave event iop3 1800 gmt 14 october 1990 to 1200 gmt 15 october 1990 from the pyrex mountain experiment using high resolution with a horizontal gridlength of 1 5 km and a realistic terrain height specification the resulting model vertical velocity fields are compared directly with observations from aircraft flights the overall agreement of the model simulated wave structure with the aircraft data is very encouraging particularly given the high degree of nonlinearity and finite amplitude wave activity observed during this event given the very restrictive three dimensional coverage of the observations from the field experiment the numerical model results are used as surrogate observational data to give exhaustive three dimensional data over the whole model volume the model integrations are subsequently used to compute areally averaged surface pressure drags and height profiles of the vertical flux of horizontal momentum assuming these wave stresses to be an accurate representation of the real atmospheric stresses they are compared as a validation procedure against grid box flux values taken from a gravity wave drag parametrization scheme in a model with resolution 2 5 latitude by 3 75 longitude the drag scheme in question compares favourably with the model domain averaged stresses