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

analysis of the 15 december 2017 mw 6 5 and the 23 january 2018 mw 5 9 java earthquakes

on the relation between gravity waves and wind speed in the lower stratosphere over the southern ocean abstractthe relationship between gravity wave momentum fluxes and local wind speed is investigated for oceanic regions at high southern latitudes during austral spring the motivation is to better describe the gravity wave field by identifying a simple relationship between gravity waves and the large scale flow the tools used to describe the gravity waves are probability density functions of the gravity wave momentum fluxes three independent datasets covering high latitudes in the southern hemisphere springtime are analyzed simulations with a mesoscale model analyses from the european centre for medium range weather forecasts and observations from superpressure balloons of the concordiasi campaign in 2010 a remarkably robust relation is found with stronger momentum fluxes much more likely in regions of strong winds the tails of the probability density functions are well described as lognormal the median momentum flux increases linearly with background wind speed for winds stronger than 50 m s 1

secondary gravity wave generation over new zealand during the deepwave campaign multiple events during the deep propagating gravity wave experiment measurement program revealed mountain wave mw breaking at multiple altitudes over the southern island of new zealand these events were measured during several research flights from the national science foundation national center for atmospheric research gulfstream v aircraft utilizing a rayleigh lidar an na lidar and an advanced mesospheric temperature mapper simultaneously a flight on 29 june 2014 observed mws with horizontal wavelengths of 80 120 km breaking in the stratosphere from 10 to 50 km altitude a flight on 13 july 2014 observed a horizontal wavelength of 200 240 km mw extending from 20 to 90 km in altitude before breaking data from these flights show evidence for secondary gravity wave sgw generation near the breaking regions the horizontal wavelengths of these sgws are smaller than those of the breaking mws indicating a nonlinear generation mechanism these observations reveal some of the complexities associated with mw breaking and the implications this can have on momentum fluxes accompanying sgws over mw breaking regions

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

direct numerical simulation of the plumb mcewan laboratory analog of the qbo abstract the laboratory experiment of plumb and mcewan demonstrates the principal mechanism of periodically reversing winds observed in the stratosphere the quasi biennial oscillation qbo however despite numerous studies some aspects of the qbo and the connection to its laboratory analog remain unclear incorporating the rapidly undulating boundaries of the laboratory experiment into the numerical algorithm via time dependent curvilinear coordinates allows for the reproduction of the experimental setup while minimizing numerical uncertainties results are presented of the first direct numerical simulation of the phenomena that lead to the zonal mean flow reversal in the laboratory analog the aim of this research is to narrow the widening gap between the theoretical understanding of laboratory scale internal gravity wave processes and the complexity of global scale circulations a detailed study is presented on the parametric and numerical sensitivities of the oscillation the results confirm a numb

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

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

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

a systematic study of source time functions and moment tensors of intermediate and deep earthquakes 1 we developed an inversion algorithm to determine the source time function and moment tensor of intermediate and deep earthquakes from a set of teleseismic body wave records the method proceeds in two stages first a nonlinear inversion by simulated annealing is performed to simultaneously a align the waveforms in time b determine a common source time function and c measure a collection of observed station amplitudes the station amplitudes are then used in a second stage as secondary observables to invert for the moment tensors we perform three different inversions to estimate the complete moment tensor solution the pure deviatoric solution and the double couple solution all the calculations are extremely simple and in particular it is not necessary to compute synthetic seismograms the method requires well isolated phases at different stations which restricts its application to intermediate and deep events the algorithm is applied to the fdsn broadband records corresponding to the period 1990 2005 of worldwide intermediate and deep seismicity depth100 km of magnitude greater than 6 5 the source time functions are compared to those obtained from other studies of intermediate and deep events the moment tensors are also systematically compared to the harvard cmt and usgs solutions both show a very good agreement with previous studies

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

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

the gcm response to current parameterizations of nonorographic gravity wave drag abstract a comparison is undertaken of the response of a general circulation model gcm to the nonorographic gravity wave drag parameterizations of hines warner and mcintyre and alexander and dunkerton the analysis is restricted to a comparison of each parameterization s nonlinear dissipation mechanism since in principle this is the only component that differs between the schemes this is achieved by developing a new more general parameterization that can represent each of these dissipation mechanisms while keeping all other aspects of the problem identical the gcm simulations reveal differences in the climatological response to the three dissipation mechanisms these differences are documented for both tropopause and surface launch elevations of the parameterized waves the simulations also reveal systematic differences in the height at which momentum is deposited this behavior is investigated further in a set of experiments designed to reduce these systematic differences while leaving the det

the 26 may 2006 magnitude 6 4 yogyakarta earthquake south of mt merapi volcano did lahar deposits amplify ground shaking and thus lead to the disaster 1 indonesia is repeatedly unsettled by severe volcano and earthquake related disasters which are geologically coupled to the 5 7 cm a tectonic convergence of the australian plate beneath the sunda plate on saturday 26 may 2006 the southern coast of central java was struck by an earthquake at 2254 utc in the sultanate yogyakarta although the magnitude reached only mw 6 4 it left more than 6 000 fatalities and up to 1 000 000 homeless the main disaster area was south of mt merapi volcano located within a narrow topographic and structural depression along the opak river the earthquake disaster area within the depression is underlain by thick volcaniclastic deposits commonly derived in the form of lahars from mt merapi volcano which had a major influence leading to the disaster in order to more precisely understand this earthquake and its consequences a 3 month aftershock measurement campaign was performed from may to august 2006 we here present the first location results which suggest that the yogyakarta earthquake occurred at 10 20 km distance east of the disaster area outside of the topographic depression using simple model calculations taking material heterogeneity into account we illustrate how soft volcaniclastic deposits may locally amplify ground shaking at distance as the high degree of observed damage may have been augmented by the seismic response of the volcaniclastic mt merapi deposits this work implies that the volcano had an indirect effect on the level of earthquake destruction

the weathering of volcanic tephra and how they impact histosol development an example from south east iceland abstract little is known about the impact of tephra deposits from explosive volcanic eruptions on soil formation and weathering processes in organic soils the weathering of tephra of basaltic and rhyolitic origin and their impact on icelandic histosols were studied through a combination of physical chemical and mineralogical analyses two sampling sites were selected according to the presence of the light coloured rhyolitic tephra from the oraefajokull eruption in 1362 ce and a dark coloured basaltic vei ivotn tephra from 1477 ce in the volcanically active area south of vatnajokull in south east iceland the determining factor of pedogenesis in the investigated histosols is the om but the influence of tephra and aeolian material from external sources must be taken into consideration the soils are the result of altered plant residues and volcanic material tephra and aeolian material plant remnants as well as the soil itself are protected from decomposition by the prevailing anaerobic conditions a low soil ph and the repeated addition of inorganic matter clay formation is low while metal humus complexes are predominant feo fed ratios indicated a generally low degree of weathering being higher close to the basaltic tephra the mineralogy was dominated by plagioclase and pyroxene with quartz and zeolite as minor components in contrast to previous research on icelandic soils our investigations revealed layer silicates at both sites while we found evidence of smectite in the soils at kalfafell hydroxy interlayered minerals were found at reynivellir in the basaltic tephra traces of layer silicates could be verified in contrast the rhyolitic tephra did not show any pedogenic minerals suggesting that it had hardly altered since its deposition in 1362 ce it is not the chemical composition of the inorganic parent material but the location that may be an influencing factor on the formation of clay minerals in the investigated histosols

seasonal cycle of orographic gravity wave occurrence above small islands in the southern hemisphere implications for effects on the general circulation 1 orographic gravity waves generated by flow over the topography of small islands in the southern oceans have been observed from orbit with the atmospheric infrared sounder on the aqua satellite we examine the occurrence frequencies of these waves in the stratosphere at 40km above 14 islands and examine geographical and seasonal changes our results show that these small island mountain waves occur commonly in the stratosphere in the may september season though not every day differing seasonal variations are evident at different islands and the seasonal variations are closely related to latitude and prevailing wind patterns we also examine interannual variability in 2years of data and the relationships between occurrence frequencies momentum fluxes and stratospheric and surface winds the results suggest that stratospheric winds have a first order limiting effect on the observations of these island mountain waves in atmospheric infrared sounder airs data surface wind direction and island orographic relief have an additional but secondary influence on the island mountain wave occurrence frequencies in airs data the implications are that these wave events are extremely common and that on many days when the waves are not observed in airs data they have likely dissipated and induced a drag force on the atmosphere below the 40km observation level observations of momentum flux during these wave events also permit a first estimate of their importance to the general circulation of the southern hemisphere

alleviation of a systematic westerly bias in general circulation and numerical weather prediction models through an orographic gravity wave drag parametrization systematic westerly biases in the northern hemisphere wintertime flow of the meteorological office 15 layer operational model and 11 layer general circulation model are described evidence that the failure to parametrize subgrid scale orographic gravity wave drag may account for such biases is presented this evidence is taken from aircraft studies surface pressure drag measurements and studies of the zonally averaged momentum budget a parametrization scheme is described in which the surface stress is proportional to the near surface wind speed and static stability and to the variance of subgrid scale orography the stress is absorbed in the vertical by considering the influence of such gravity wave activity on static stability and vertical wind shear a richardson number dependent wave breaking formulation is devised and the vertical stress profile determined by a saturation hypothesis whereby the breaking waves are maintained at marginal stability it is shown that wave breaking preferentially occurs in the boundary layer and in the lower stratosphere results from a simple zonally symmetric model show how the adjustment to thermal wind balance with a wave drag in the stratosphere warms polar regions by adiabatic descent and decelerates the mean westerlies in the troposphere the influence of the parametrization scheme on integrations of the 11 layer model is described and found to be generally beneficial in a discussion of the reasons why this problem has only recently emerged it is suggested that the satisfactory northern hemisphere winter circulations of previous coarser general circulation models were due to a compensation implied by underestimating both the surface drag and the horizontal flux of momentum by explicitly resolved large scale eddies

tectonic features of the southern sumatra western java forearc of indonesia 1 multichannel reflection seismic profiles along the active sunda arc where the indo australian plate subducts under the overriding eurasian margin revealed two accretionary wedges the inner wedge i is of assumed paleogene age and the outer wedge ii is of neogene to recent age the inner wedge i is composed of tectonic flakes stretching from southeast sumatra across the sunda strait to northwest java implying a similar plate tectonic regime in these areas at the time of flake development during upper oligocene today wedge i forms the outer arc high and the backstop for the younger outer wedge ii the missing outer arc high of the southern sunda strait is explained by a combination of neogene transtension due to a clockwise rotation of sumatra with respect to java and by arc parallel strike slip movements the rotation created transtensional pull apart basins along the western sunda strait semangka graben as opposed to transpression and inversion on the eastern sunda strait within the new detected krakatau basin the arc parallel transpressional mentawai strike slip fault zone mfz was correlated from the sumatra forearc basin to the northwest java forearc basin off the sunda strait northward bending branches of the mfz are connected with the right lateral sumatra fault zone sfz along the volcanic arc segment on sumatra it is speculated that the sfz was attached to the cimandiri pelabuhan ratu strike slip fault of java prior to the presumed rotation of sumatra and that since the late lower miocene the main slip movement shifted from the volcanic arc position to the forearc basin area due to increasingly oblique plate convergence

momentum flux estimates for south georgia island mountain waves in the stratosphere observed via satellite abstract we show high resolution satellite observations of mountain wave events in the stratosphere above south georgia island in the remote southern atlantic ocean and compute the wave momentum fluxes for these events the fluxes are large and they imply important drag forces on the circulation small island orography is generally neglected in mountain wave parameterizations used in global climate models because limited model resolution treats the grid cell containing the island as ocean rather than land our results show that satellite observations can be used to quantitatively constrain mountain wave momentum fluxes and they suggest that mountain waves from island topography may be an important missing source of drag on the atmospheric circulation

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

sensitivity of the brewer dobson circulation and polar vortex variability to parameterized nonorographic gravity wave drag in a high resolution atmospheric model abstractthe role of parametrized nonorographic gravity wave drag nogwd and its seasonal interaction with the resolved wave drag in the stratosphere has been extensively studied in low resolution coarser than 1 9 2 5 climate models but is comparatively unexplored in higher resolution models using the european centre for medium range weather forecasts integrated forecast system at 0 7 0 7 resolution the wave drivers of the brewer dobson circulation are diagnosed and the circulation sensitivity to the nogw launch flux is explored nogws are found to account for nearly 20 of the lowerstratospheric southern hemisphere sh polar cap downwelling and for less than 10 of the lower stratospheric tropical upwelling and northern hemisphere nh polar cap downwelling despite these relatively small numbers there are complex interactions between nogwd and resolved wave drag in both polar regions seasonal cycle analysis reveals a temporal offset in the resolved and parametrized wave interaction the n

does strong tropospheric forcing cause large amplitude mesospheric gravity waves a deepwave case study the deepwave deep propagating wave experiment campaign was designed for an airborne and ground based exploration of gravity waves from their tropospheric sources up to their dissipation at high altitudes it was performed in and around new zealand from 24 may till 27 july 2014 being the first comprehensive field campaign of this kind a variety of airborne instruments was deployed onboard the research aircraft nsf ncar gulfstream v gv and the dlr falcon additionally ground based measurements were conducted at different sites across the southern island of new zealand including the dlr rayleigh lidar located at lauder 45 04 s 169 68 e we focus on the intensive observing period iop 10 on the 4 july 2014 when strong wsw winds of about 40 m s at 700 hpa provided intense forcing conditions for mountain waves at tropopause level the horizontal wind exceeded 50 m s and favored the vertical propagation of gravity waves into the stratosphere the dlr rayleigh lidar measured temperature fluctuations with peak to peak amplitudes of about 20 k in the mesosphere 60 km to 80 km msl over a period of more than 10 hours two research flights were conducted by the dlr falcon falcon flight 04 and 05 during this period with straight transects mt aspiring 2a over new zealand s alps at three different flight levels around the tropopause approx 11 km msl these research flights were coordinated with the gv research flight 16 where the largest mountain wave amplitudes at flight level approx 13 km msl were measured during deepwave additionally a first analysis of falcon s in situ flight level data revealed amplitudes in the vertical wind larger than 4 m s at all altitudes in the vicinity of the highest peaks of the southern alps here we present a comprehensive picture of the gravity wave characteristics and propagation properties during this interesting gravity wave event we use the airborne observations combined with a comprehensive set of ground based measurements consisting of 13 radiosoundings 1 5 hourly interval together with the dlr rayleigh lidar to cover the altitude range from the troposphere to the mesosphere high resolution 1 hourly ecmwf analyses and forecasts are used to estimate the propagation conditions of the excited mountain waves the goal of our investigation is to find out whether the large amplitude mesospheric gravity waves are caused by the strong tropospheric forcing

comparison of gravity waves in the southern hemisphere derived from balloon observations and the ecmwf analyses abstractthe increase of spatial resolution allows the ecmwf operational model to explicitly resolve a significant portion of the atmospheric gravity wave gw field but the realism of the simulated gw field in the ecmwf analyses still needs to be precisely evaluated here the authors use data collected during the concordiasi stratospheric balloon campaign to assess the representation of gws in the ecmwf analyses over antarctica and the southern ocean in spring 2010 the authors first compare the balloonborne gw momentum fluxes with those in ecmwf analyses throughout the campaign and find a correct agreement of the geographical and seasonal patterns however the authors also note that ecmwf analyses generally underestimate the balloon fluxes by a factor of 5 which may be essentially due to the spatial truncation of the ecmwf model intermittency of wave activity in the analyses and observations are found comparable these results are confirmed on two case studies dealing with orographic and nonorographi

gravity waves over antarctica and the southern ocean consistent momentum fluxes in mesoscale simulations and stratospheric balloon observations stratospheric balloons from the vorcore campaign have provided a unique description of the gravity wave field in the lower stratosphere above antarctica and the southern ocean during the austral spring of 2005 mesoscale simulations are carried out to analyze further the gravity wave field first the realism of the simulated waves is assessed by comparison to the observations a satisfactory overall agreement is found but different behaviour is noted for orographic waves overestimation in the simulations relative to the observations and non orographic waves underestimation second the gravity wave field is analyzed in more detail than was possible from observations alone it is necessary to distinguish and quantify orographic and non orographic waves separately orographic waves are larger and more intermittent yet affect only a limited geographical region hence although orographic sources stand out as hot spots for gravity waves their contribution to momentum fluxes entering the stratosphere is comparable to or smaller than the contribution of non orographic sources a diagnostic for intermittency the gini coefficient is proposed it clearly marks the distinction between orographic and non orographic sources intermittencies of 0 8 and 0 5 respectively sensitivity to resolution is quite small regarding the spatial structure of the gravity wave field but is significant for the amplitudes the momentum flux values increase by 2 when the horizontal resolution is doubled and possible biases of both simulations and observations are discussed nonetheless the good agreement between observations and simulations and the complementary information on the biases of each dataset promises that in the future these different estimates of gravity wave momentum fluxes may converge copyright 2012 royal meteorological society

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

estimation of gravity wave momentum flux and phase speeds from quasi lagrangian stratospheric balloon flights part ii results from the vorcore campaign in antarctica the stratospheric gravity wave field in the southern hemisphere is investigated by analyzing observations collected by 27 long duration balloons that flew between september 2005 and february 2006 over antarctica and the southern ocean the analysis is based on the methods introduced by boccara et al in a companion paper special attention is given to deriving information useful to gravity wave drag parameterizations employed in atmospheric general circulation models the balloon dataset is used to map the geographic variability of gravity wave momentum fluxes in the lower stratosphere this flux distribution is found to be very heterogeneous with the largest time averaged value 28 mpa observed above the antarctic peninsula this value exceeds by a factor of 10 the overall mean momentum flux measured during the balloon campaign zonal momentum fluxes were predominantly westward whereas meridional momentum fluxes were equally northward and southward a local enhancement of southward flux is nevertheless observed above adelie land and is attributed to waves generated by katabatic winds for which the signature is otherwise rather small in the balloon observations when zonal averages are performed oceanic momentum fluxes are found to be of similar magnitude to continental values 2 5 3 mpa stressing the importance of nonorographic gravity waves over oceans last gravity wave intermittency is investigated mountain waves appear to be significantly more sporadic than waves observed above the ocean

slab1 0 a three dimensional model of global subduction zone geometries 1 we describe and present a new model of global subduction zone geometries called slab1 0 an extension of previous efforts to constrain the two dimensional non planar geometry of subduction zones around the focus of large earthquakes slab1 0 describes the detailed non planar three dimensional geometry of approximately 85 of subduction zones worldwide while the model focuses on the detailed form of each slab from their trenches through the seismogenic zone where it combines data sets from active source and passive seismology it also continues to the limits of their seismic extent in the upper mid mantle providing a uniform approach to the definition of the entire seismically active slab geometry examples are shown for two well constrained global locations models for many other regions are available and can be freely downloaded in several formats from our new slab1 0 website http on doi gov d9arbs we describe improvements in our two dimensional geometry constraint inversion including the use of average active source seismic data profiles in the shallow trench regions where data are otherwise lacking derived from the interpolation between other active source seismic data along strike in the same subduction zone we include several analyses of the uncertainty and robustness of our three dimensional interpolation methods in addition we use the filtered subduction related earthquake data sets compiled to build slab1 0 in a reassessment of previous analyses of the deep limit of the thrust interface seismogenic zone for all subduction zones included in our global model thus far concluding that the width of these seismogenic zones is on average 30 larger than previous studies have suggested

implementation of a gravity wave source spectrum parameterization dependent on the properties of convection in the whole atmosphere community climate model waccm 1 this article describes the implementation of a new source spectrum parameterization for convectively generated gravity waves in the whole atmosphere community climate model version 2 waccm2 this parameterization is active in the tropics and is interactive with the underlying convection the gravity wave spectrum at each model grid point and time step is determined based on the convective heating depth tropospheric wind and the convective heating rate this parameterization introduces more realistic spatial and temporal distributions of gravity wave activity and yields gravity wave characteristics related to the underlying wave source we present the estimated gravity wave momentum flux phase speed spectra at 100 hpa as well as the gravity wave drag in the middle and upper atmosphere using the new source spectrum representation we also show the effects of this more physically based parameterization on the structure of the stratospheric and mesospheric semi annual oscillations of the zonal wind compared to a simulation with uniform gravity wave distribution we conclude that the interaction of the gravity wave parameterization with tropospheric characteristics is a positive step toward a more physical representation of the middle and upper atmosphere

transient mountain waves and their interaction with large scales abstract the impact of transient mountain waves on a large scale flow is examined through idealized numerical simulations of the passage of a time evolving synoptic scale jet over an isolated 3d mountain both the global momentum budget and the spatial flow response are examined to illustrate the impact of transient mountain waves on the large scale flow additionally aspects of the spatial response are quantified by potential vorticity inversion nearly linear cases exhibit a weak loss of domain averaged absolute momentum despite the absence of wave breaking this transient effect occurs because over the time period of the large scale flow the momentum flux through the top boundary does not balance the surface pressure drag moreover an adiabatic spatial redistribution of momentum is observed in these cases which results in an increase decrease of zonally averaged zonal momentum south north of the mountain for highly nonlinear cases the zonally averaged momentum field shows a region of flow de

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

gravity wave radiation and mean responses to local body forces in the atmosphere the authors determine the spectral linear solutions that arise in response to local 3d body forces and heatings in an idealized environment that turn on and off smoothly but not necessarily slowly over a finite interval in time the solutions include impulsive through slowly varying body forcings the forcings result in both a mean response which is typically significantly broadened spatially in one direction and a gravity wave response which allows the fluid to reach this state the gravity wave field depends on both the spatial attributes of the source and the forcing duration the frequency of the wave response is the characteristic source frequency formed from the source dimensions if the forcing frequency is greater than the characteristic frequency and is the forcing frequency otherwise the radiated gravity waves from zonal forcings have vertical wavelengths which are approximately twice the vertical extent of the forcing and horizontal wavelengths which are at least twice the horizontal extent of the forcing wave excitation is increasingly inefficient when the forcing frequency is smaller than the characteristic source frequency in addition the mean responses are not confined to the source region in general significant spatial broadening of the mean responses occurs if the source s frequency is high and low the responses are broadened horizontally and vertically respectively with the amount depending on the characteristic scales of the source if the body forcing is in the eastward direction then much or all of the ensuing zonal mean wind is eastward however for many realistic forcing scenarios a large percentage of the ensuing zonal wind flows westward these countersigned jets are displaced meridionally about the source thus spatially confined body forcings create both gravity wave and mean responses if the forcings are fast enough very slowly varying forcings create only mean responses

synoptic responses to mountain gravity waves encountering directional critical levels abstract a heuristic model is used to study the synoptic response to mountain gravity waves gws absorbed at directional critical levels the model is a semigeostrophic version of the eady model for baroclinic instability adapted by smith to study lee cyclogenesis the gws exert a force on the large scale flow where they encounter directional critical levels this force is taken into account in the model herein and produces potential vorticity pv anomalies in the midtroposphere first the authors consider the case of an idealized mountain range such that the orographic variance is well separated between small and large scale contributions in the absence of tropopause the pv produced by the gw force has a surface impact that is significant compared to the surface response due to the large scales for a cold front the gw force produces a trough over the mountain and a larger amplitude ridge immediately downstream it opposes somehow to the response due to the large scales of the mountain range whic

anatomy of the western java plate interface from depth migrated seismic images newly pre stack depth migrated seismic images resolve the structural details of the western java forearc and plate interface the structural segmentation of the forearc into discrete mechanical domains correlates with distinct deformation styles approximately 2 3 of the trench sediment fill is detached and incorporated into frontal prism imbricates while the floor sequence is underthrust beneath the decollement western java however differs markedly from margins such as nankai or barbados where a uniform continuous decollement reflector has been imaged in our study area the plate interface reveals a spatially irregular nonlinear pattern characterized by the morphological relief of subducted seamounts and thicker than average patches of underthrust sediment the underthrust sediment is associated with a low velocity zone as determined from wide angle data active underplating is not resolved but likely contributes to the uplift of the large bivergent wedge that constitutes the forearc high our profile is located 100 km west of the 2006 java tsunami earthquake the heterogeneous decollement zone regulates the friction behavior of the shallow subduction environment where the earthquake occurred the alternating pattern of enhanced frictional contact zones associated with oceanic basement relief and weak material patches of underthrust sediment influences seismic coupling and possibly contributed to the heterogeneous slip distribution our seismic images resolve a steeply dipping splay fault which originates at the decollement and terminates at the sea floor and which potentially contributes to tsunami generation during co seismic activity

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

interplate coupling model off the southwestern coast of java indonesia based on continuous gps data in 2008 2010 abstract we present an interplate coupling model of the australia java plate interface off the southwestern coast of java indonesia based on data from the indonesian permanent gps station network from 2008 to 2010 the majority of vertical data indicate uplift while the baseline change rate indicates coastal contraction in the middle of the network and coastal extension in the eastern part of the network using the rate of baseline length changes and the absolute rate of vertical displacements we apply a geodetic inversion method by yabuki and matsu ura 1992 from the inversion result we interpret the main source of the observed velocity in west java as resulting from contributions of 1 interplate coupling off ujung kulon pelabuhan ratu at 20 to 40 km depth with a slip rate range from 48 to 56 mm yr 2 interplate coupling off pangandaran at 37 to 45 km depth with a slip rate of 48 to 55 mm yr 3 afterslip off pangandaran within the rupture area of the 2006 m7 8 java earthquake in the depth range of 15 20 km with a slip excess rate of 57 61 mm yr the absence of a megathrust earthquake for at least 300 years in this region implies seismic moment accumulation during this time period of 1 6 10 21 nm mw 8 7 off ujung kulon pelabuhan ratu and 3 9 10 21 nm mw 8 3 off pangandaran unless episodic slow slips release tectonic stress

gravity wave forcing in the stratosphere observational constraints from the upper atmosphere research satellite and implications for parameterization in global models 1 global models that include parameterized gravity wave effects have an excessively broad range of tuning parameters to choose from that allow a very broad range of gravity wave momentum forcing distributions we derive a set of constraints on gravity wave characteristics near the tropopause from databased estimates of gravity wave effects in the stratosphere we use 5 6 years of upper atmosphere research satellite data and uk met office analyzed wind and temperature fields to first derive estimates of the gravity wave mean flow forcing in the stratosphere we then compare these estimates to a suite of gravity wave model calculations to infer the constraints on the gravity wave characteristics near the tropopause these constraints apply to the portion of the gravity wave spectrum that dissipates in the stratosphere and does not include those that dissipate and drive the mesosphere we focus on equatorial and extratropical regions separately and find substantially different wave characteristics between the two we also find a seasonal variation in gravity wave characteristics in the extratropics near the equator gravity waves assist in driving the quasibiennial and semiannual oscillations and our constraints on gravity waves likely include a blend of characteristics of both ordinary gravity waves and some kelvin wave modes in the extratropics gravity wave forcing primarily assists in the annual winter to summer transition from westward to eastward winds

strike slip faulting as a trigger mechanism for overpressure release through piercement structures implications for the lusi mud volcano indonesia piercement structures such as hydrothermal vent complexes pockmarks and mud volcanoes are found in various geological settings but are often associated with faults or other fluid focussing features this article aims to investigate and understand the mechanisms responsible for the formation of piercement structures in sedimentary basins and the role of strike slip faulting as a triggering mechanism for fluidization for this purpose four different approaches were combined fieldwork analogue experiments and math