long term atmospheric variability on uranus and neptune abstract long term photometric measurements of uranus and neptune through 2005 show variations in brightness for uranus much of the variation can be interpreted as seasonal i e caused by viewing angle changes of an oblate planet the photometry suggests that if seasonal variations on uranus are north south symmetric then the northern pole should begin to brighten in 2006 however seasonal aspect changes cannot explain all the variation the uranus observations require intrinsic atmospheric change furthermore uranus observations spanning many scale heights in the atmosphere may show similar change for neptune variations in sub solar latitude may explain the general shape of the long term light curve but significant deviations occur that have no explanation at present observations are needed over a longer temporal baseline than currently exists to fully characterize both atmospheres

convectively forced internal gravity waves results from two dimensional numerical experiments two dimensional numerical simulations were performed to investigate the nature of tropospheric internal gravity waves of the type which are observed to occur above active thermal convection over an unstable boundary layer these gravity waves are believed to be excited by a combination of pure thermal forcing and by the boundary layer eddies and cumulus clouds acting as obstacles to the flow in the presence of mean environmental wind shear large amplitude internal gravity waves were obtained in the simulations with amplitudes and horizontal scales similar to the 12 june 1984 aircraft observations over western nebraska this was a day with strong wind shear in the lowest 3 km above the ground and with scattered cumulus clouds topping the boundary layer the simulations show that there is significant difference between the early time solutions as might be predicted by linear theory and late time solutions for the boundary layer eddy structure a layer interaction occurs in which gravity waves of the stable layer are excited by the boundary layer convection there is evidence to suggest that this layer interaction occurs both with and without shear but that it is stronger in the presence of low level shear results indicate that shear or the obstacle effect is a more efficient generator of gravity waves than is the pure thermal forcing the simulations show that the gravity waves initially forced by the boundary layer eddies lead to a feedback mechanism that acts to organize the boundary layer eddies and the cumulus convection the solutions suggest that the character of fair weather convection moist or dry is a non local problem involving at times the full depth of the troposphere the clouds produced in the simulations have very little influence on the wave field or boundary layer eddy structure as they are relatively small cumuli on the other hand the clouds are strongly influenced by the interactions between the wave and eddy fields upshear growth of cumulus clouds similar to that which is frequently observed in nature is reproduced in the simulations the development of feeder feeder is used here in a dynamical sense only clouds on typically the upshear side of the cloud is found to be a result of the interaction between the gravity wave field and the dry and moist convection the relative phase velocity between the gravity waves and the cloud plays a crucial role in determining the character of the cumulus cloud growth in the present simulations these simulations suggest that the dynamics both internal and external to the boundary of a cumulus cloud is a complicated mix between wave dynamics and the usually considered convection dynamics a brief discussion of the implications of the present results to cloud boundary baroclinic instability dynamics is also presented

winds of neptune voyager observations of cloud motions high temporal and spatial resolution images acquired from voyager cameras have been used to measure cloud motions to improve the meridional profile of the zonal mean circulation on neptune a wide range of atmospheric periods between 12 and 21 hours is revealed by the average cloud motions consistent with the previous observations new observations have expanded latitudinal coverage improved the determination of streak motions especially near 30 n and added statistical weight to latitudes already covered by previous measurements both new and earlier observations have been subjected to quality control procedures to reduce dispersion caused by erroneous observations the resulting data set emphasizes short time intervals to maximize target recognition most reliable cloud targets last less than one neptune rotation many only a fraction of it a broad equatorial retrograde jet extends from approximately 50 s to at least 45 n the northernmost latitude at which discrete cloud features have been seen a relatively narrow prograde jet of at least 300 m s 1 is found near 70 s the wind observations have a high degree of variability some of which is due to variability of motions but at many latitudes it reflects observation errors arising from rapid evolution of neptune s clouds a bias observed in the measured meridional component is most likely due to a small discrepancy between the true rotation pole of neptune and the pole position used in the data reduction zonal motions and morphology suggest the global circulation to be symmetric about the equator

mjo related intraseasonal variation in the stratosphere gravity waves and zonal winds previous work has shown eastward migrating regions of enhanced temperature variance due to long vertical wavelength stratospheric gravity waves that are in sync with intraseasonal precipitation and tropopause wind anomalies associated with the madden julian oscillation mjo here the origin of these intraseasonal gravity wave variations is investigated with a set of idealized gravity wave resolving model experiments the experiments specifically test whether tropopause winds act to control gravity wave propagation into the stratosphere by a critical level filtering mechanism or play a role in gravity wave generation through an obstacle source effect all experiments use identical convective latent heating variability but the large scale horizontal wind profile is varied to investigate relationships between stratospheric gravity waves and zonal winds at different levels results show that the observed long vertical wavelength gravity waves are primarily sensitive to stratospheric zonal wind variations while tropopause wind variations have only a very small effect thus neither the critical level filter mechanism nor the obstacle source play much of a role in the observed intraseasonal gravity wave variations instead the results suggest that the stratospheric waves follow the mjo precipitation sources and tropopause wind anomalies follow the same sources we further find evidence of intraseasonal wave drag effects on the stratospheric circulation in reanalyzed winds the results suggest that waves drive intraseasonal stratospheric zonal wind anomalies that descend in altitude with increasing mjo phases 3 through 7 eastward anomalies descend further than westward suggesting that mjo related stratospheric waves cause larger eastward drag forces

observational study of ionospheric irregularities and gps scintillations associated with the 2012 tropical cyclone tembin passing hong kong

clouds and circulation on neptune implications of 1991 hst observations abstract images of neptune recorded by the hubble space telescope hst wide fields planetary camera in late 1991 provide a basis for the first significant comparison with the circulation results obtained from voyager 2 observations 2 years earlier the hst images using red f675w and methane band f889n filters contain isolated bright cloud features suitable for tracking atmospheric motions near planetocentric latitudes of 67 s 57 5 s 50 s 5 n and 27 n wind speeds inferred from the feature rotational periods are consistent with the latitudinal wind profile established by the 1989 voyager observations the latitudinal distribution of clouds also matches the voyager distribution reasonably well except for a notable lack of clouds between the equator and 40 s a region where the great dark spot gds and its companion cloud were observed in 1989 the 1991 hst images contain no cloud feature at any latitude with an integrated brightness comparable to the gds companion suggesting that the gds itself may not have survived its projected november 1990 arrival at neptune s equator

vertical wind shear in neptune s upper atmosphere explained with a modified thermal wind equation abstract we present observations of neptune taken in h 1 4 1 8 m and k 2 0 2 4 m bands on the nights of july 3 2013 and august 20 2014 from the 10 m w m keck ii telescope using nirc2 coupled to the adaptive optics ao system we track the positions of 100 bright atmospheric features over a 4 5 h window on each night to derive zonal velocities and wind profiles our results deviate from the smooth voyager zonal wind profile from sromovsky et al 1993 often by 100 200 m s and often by 3 10 times their estimated uncertainties besides what appears to be a random dispersion probably due to a mix of unaccounted for measurement errors eddy motions vertical wind shear and wave generated features that do not follow the mass flow there is also a systematic deviation that is wavelength dependent the h band profile is best described with a 73 106 m s shift towards the east for a retrograde flow i e a lessening of the retrograding velocities from the voyager profile at the equator the k band profile is consistent with voyager on both nights comparing h and k contribution functions and k h intensities suggests equatorial h band features are on average deeper than k band features the h band equatorial features also have greater eastward less negative velocities than k band features differences in zonal wind speed with depth at constant latitude and time imply vertical wind shear assuming the average variations in the zonal wind profiles result from wind shear over 3 5 scale heights we predict vertical wind shears between 1 0 and 2 2 m s km at the equator increasing with height the standard thermal wind equation and meridional thermal profile for neptune given by voyager iris spectra predict wind shear of the wrong sign relative to the observations we consider two effects that reconcile this inconsistency first we calculate the meridional temperature gradients at pressures outside the voyager iris narrow sensitivity window required to match our predicted wind shears second we generalize to a thermal wind equation that considers global methane variations and re derive the temperature structure needed to match the observed wind shear if methane is uniformly distributed or weakly varying the equator must be 2 15 k cooler than the mid latitudes below 1 bar if methane is strongly varying the equator can be 2 3 k warmer than the mid latitudes below 1 bar qualitatively consistent with observed temperature contrasts these findings may imply a stacked celled circulation pattern in neptune s troposphere and lower stratosphere

gravity waves generated by a tropical cyclone during the step tropical field program a case study overflights of a tropical cyclone during the australian winter monsoon field experiment of the stratosphere troposphere exchange project step show the presence of two mesoscale phenomena a vertically propagating gravity wave with a horizontal wavelength of about 110 km and a feature with a horizontal scale comparable to that of the cyclone s entire cloud shield wavelength of 250 km or greater the larger feature is fairly steady though its physical interpretation is ambiguous the 110 km gravity wave is transient having maximum amplitude early in the flight and decreasing in amplitude thereafter its scale is comparable to that of 100 to 150 km diameter cells of low satellite brightness temperatures within the overall cyclone cloud shield these cells have lifetimes of 4 5 to 6 hours aircraft flights through the anvil show that these cells correspond to regions of enhanced convection higher cloud altitude and upwardly displaced potential temperature surfaces a three dimensional transient linear gravity wave simulation shows that the temporal and spatial distribution of meteorological variables associated with the 110 km gravity wave can be simulated by a slowly moving transient forcing at the anvil top having an amplitude of 400 600 m a lifetime of 4 5 6 hours and a size comparable to the cells of low brightness temperature the forcing amplitudes indicate that the zonal drag due to breaking mesoscale transient convective gravity waves is definitely important to the westerly phase of the stratopause semiannual oscillation and possibly important to the easterly phase of the quasi biennial oscillation there is strong evidence that some of the mesoscale gravity waves break below 20 km as well the effect of this wave breaking on the diabatic circulation below 20 km may be comparable to that of above cloud diabatic cooling

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

dynamics of saturn s south polar vortex the camera onboard the cassini spacecraft has allowed us to observe many of saturn s cloud features we present observations of saturn s south polar vortex spv showing that it shares some properties with terrestrial hurricanes cyclonic circulation warm central region the eye surrounded by a ring of high clouds the eye wall and convective clouds outside the eye the polar location and the absence of an ocean are major differences it also shares properties with the polar vortices on venus such as polar location cyclonic circulation warm center and long lifetime but the venus vortices have cold collars and are not associated with convective clouds the spv s combination of properties is unique among vortices in the solar system

neptune s global circulation deduced from multi wavelength observations abstract we observed neptune between june and october 2003 at near and mid infrared wavelengths with the 10 m w m keck ii and i telescopes respectively and at radio wavelengths with the very large array images were obtained at near infrared wavelengths with nirc2 coupled to the adaptive optics system in both broad and narrow band filters between 1 2 and 2 2 m in the mid infrared we imaged neptune at wavelengths between 8 and 22 m and obtained slit resolved spectra at 8 13 m and 18 22 m at radio wavelengths we mapped the planet in discrete filters between 0 7 and 6 cm we analyzed each dataset separately with a radiative transfer program that is optimized for that particular wavelength regime at southern midlatitudes the atmosphere appears to be cooler at mid infrared wavelengths than anywhere else on the planet we interpret this to be caused by adiabatic cooling due to air rising at midlatitudes at all longitudes from the upper troposphere up to 0 1 mbar levels at near infrared wavelengths we find two distinct cloud layers at these latitudes a relatively deep layer of clouds presumably methane in the troposphere at pressure levels p 300 600 mbar which we suggest to be caused by the large scale upwelling and its accompanying adiabatic cooling and condensation of methane and a higher spatially intermittent layer of clouds in the stratosphere at 20 30 mbar the latitudes of these high clouds encompass an anticyclonic band of zonal flow which suggests that they may be due to strong but localized vertical upwellings associated with local anticyclones rather than plumes in convective i e cyclonic storms clouds at northern midlatitudes are located at the highest altitudes in the atmosphere near 10 mbar neptune s south pole is considerably enhanced in brightness at both mid infrared and radio wavelengths i e from 0 1 mbar levels in the stratosphere down to tens of bars in the troposphere we interpret this to be due to subsiding motions from the stratosphere all the way down to the deep troposphere the enhanced brightness observed at mid infrared wavelengths is interpreted to be due to adiabatic heating by compression in the stratosphere and the enhanced brightness temperature at radio wavelengths reveals that the subsiding air over the pole is very dry the relative humidity of h 2 s over the pole is only 5 at altitudes above the nh 4 sh cloud at 40 bar the low humidity region extends from the south pole down to latitudes of 66 s this is near the same latitudes as the south polar prograde jet signifying the boundary of the polar vortex we suggest that the south polar features spfs at latitudes of 60 70 are convective storms produced by baroclinic instabilities expected to be produced at latitudes near the south polar prograde jet taken together our data suggest a global circulation pattern where air is rising above southern and northern midlatitudes from the troposphere up well into the stratosphere and subsidence of dry air over the pole and equator from the stratosphere down into the troposphere we suggest that this pattern extends all the way from 0 1 mbar down to pressures of 40 bar

a study of the dynamics of the equatorial lower stratosphere by use of ultra long duration balloons 2 gravity waves in the late southern winter of 1998 centre national d etudes spatiales cnes the french space agency released six 10 m diameter superpressure balloons from a location near quito ecuador three balloons collapsed soon after launching but the remaining three drifted westward for a few weeks at altitudes between 19 and 20 km two of those balloons crossed the pacific ocean before falling above the maritime continent while the other completed a revolution around the earth and crossed the pacific for a second time before its final fall despite the small number and the relatively short duration of the flights the balloons provided a unique in situ data set for the lower equatorial stratosphere this part 1 of a two part paper describes this data set and analyzes outstanding features in the planetary scales part 2 focuses on gravity wave scale it is argued that balloon trajectories over the pacific are primarily determined by the westward drift during the easterly phase of the equatorial quasi biennial oscillation qbo and the meridional velocity field of a mixed rossby gravity yanai wave with an apparent period of 4 days and zonal wave number 4 this wave appears to have two episodes of amplification during the balloon flights it is also argued that the balloons show evidence of oscillations with periods between 2 and 4 days and of a kelvin wave with an apparent period close to 10 days and zonal wave number 1 in this way the balloon behavior provided a pictorial view of air parcel trajectory in the equatorial lower stratosphere it is stated that larger balloon campaigns can provide excellent in situ data sets for studies on the dynamics and composition of the middle atmosphere

a global view of stratospheric gravity wave hotspots located with atmospheric infrared sounder observations 1 the main aim of this study is to find and classify hotspots of stratospheric gravity waves on a global scale the analysis is based on a 9 year record 2003 to 2011 of radiance measurements by the atmospheric infrared sounder airs aboard nasa s aqua satellite we detect gravity waves based on 4 3 m brightness temperature variances our method focuses on peak events i e strong gravity wave events for which the local variance considerably exceeds background levels we estimate the occurrence frequencies of these peak events for different seasons and time of day and use the results to find local maxima or hotspots in addition we use airs radiances at 8 1 m to simultaneously detect convective events including deep convection in the tropics and mesoscale convective systems at middle latitudes we classify the gravity wave sources based on seasonal occurrence frequencies for convection but also by means of time series analyses and topographic data our study reproduces well known hotspots of gravity waves e g the andes and the antarctic peninsula however the high horizontal resolution of the airs observations also allows us to locate numerous mesoscale hotspots which are partly unknown or poorly studied so far most of these mesoscale hotspots are found near orographic features like mountain ranges coasts lakes deserts or isolated islands this study will help to select promising regions and seasons for future case studies of gravity waves

uranus southern circulation revealed by voyager 2 unique characteristics abstract revised calibration and processing of 1600 images of uranus by voyager 2 revealed dozens of discrete features south of 45 latitude where only a single feature was known from voyager images and none has been seen since tracking of these features over five weeks defined the southern rotational profile of uranus with high accuracy and no significant gap the profile has kinks unlike previous profiles and is strongly asymmetric with respect to the northern profile by sromovsky et al sromovsky l a fry p m hammel h b de pater i rages k a 2012 icarus 220 694 712 the asymmetry is larger than that of all previous data on jovian planets a spot that included the south pole off center rotated with a period of 12 24 h 2 h outside the range of all previous observations of uranus the region between 68 and 59 latitude rotated almost like a solid body with a shear that was about 30 times smaller than typical shears on uranus at lower latitudes features were sheared into tightly wound spirals as voyager watched the zone at 84 latitude was exceptionally bland reflectivity variations were only 18 ppm consistent with a signal to noise ratio estimated at 55 000 the low noise was achieved by smoothing over dozens of pixels per image and averaging 1600 images the presented data set in eight filters contains rich information about temporal evolution and spectral characteristics of features on uranus that will be the basis for further analysis

statistics of cold cumulonimbus anvils based on enhanced infrared photographs infrared photographs from the atlantic geosynchronous satellite enhanced to resolve cold anvil temperatures of tropical clouds are analyzed statistically to determine their spatial temporal variability during the nasa u2 flight experiment of 1980 diurnal dependence varies regionally indicating topographic control via low level convergence and release of convective instability anvil growth rates area covered and duration are discussed for individual and merging anvil systems gradients of anvil temperatures implied by infrared photographs are shown to be caused in part by radial decrease in anvil depth i e to emissivities less than 1 an error in cloud top temperature of 10c is caused by 10 reduction in emissivity errors are near zero in dense actively growing portions of the anvil

an investigation of spiral gravity waves radiating from tropical cyclones using a linear nonhydrostatic model abstracta recent study showed observational and numerical evidence for small scale gravity waves that radiate outward from tropical cyclones these waves are wrapped into tight spirals by the radia

role of gravity waves in triggering deep convection during toga coare the role of gravity waves in the initiation of convection over oceanic regions during the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare experiment is investigated first an autocorrelation method is applied to infrared temperature observations of convective events from satellite images it reveals that new deep convective cells often occur a few hours after a previous intense event at a typical distance of a few hundred kilometers such fast moving modes faster than 15 m s 21 are interpreted as the trace of gravity waves excited by previous convection and contributing to trigger further convection second the specific case of 11 12 december 1992 during which an active squall line is generated after the collapse of a previous mesoscale convective system mcs nearby is analyzed with a nonhydrostatic model the triggering of the second mcs is well reproduced explicitly owing to the use of the two way interactive grid nesting the convective source appears to emit pulses of gravity waves on a wide range of small scales on the contrary the troposphere response to the convective source exhibits a spectral simplicity a slowly evolving mode characterized by an ascent in the pbl and a compensating subsidence in the free troposphere favors shallow convection and inhibits deep convection respectively traveling modes propagating away from the convective source are characterized by a fast mode 50 m s21 and a slower mode 25 ms 21 associated with the convective and stratiform development of the source respectively in agreement with previous studies a budget analysis reveals the different factors leading to the deep convection triggering first an active pbl characterized by strong surface fluxes and mean ascent initiates shallow convection lasting about 2 h inhibited above by the subsiding motions maintaining a dry layer second horizontal advection of moist and cooler air at midlevels and detrainment from cumuli contribute to destroy the dry air layer capping the shallow convective layer finally vertical advection induced by the gravity waves passage modulates the vapor and temperature evolution ascending phases favor moistening and cooling whereas subsiding phases stop these effects delaying the deep convection onset the triggering occurs after a strong subsidence when the ascent phases of deep and shallow modes are combined

a model study of gravity waves over hurricane humberto 2001 abstract atmospheric gravity waves are known to influence global circulations understanding these waves and their sources help to develop parameterizations that include their effects in climate and weather forecasting models deep convection is believed to be a major source for these waves and hurricanes may be particularly intense sources simulations of hurricane humberto 2001 are studied using the fifth generation pennsylvania state university national center for atmospheric research psu ncar mesoscale model mm5 humberto is simulated at both tropical storm and hurricane stages fourier transform and wavelet analysis are employed to investigate wave characteristics and their behavior in the lower stratosphere the fourier analysis gives a regional view of storm affects whereas wavelet analysis gives a local picture of isolated events analysis of the movement of convective sources and local winds gives further insight into the mechanisms that can cause gravity waves convectively generated grav

source spectra information derived from u s high resolution radiosonde data 1 a ray tracing model is used to study the climatology of the source properties for gravity waves in the lower stratosphere using 8 years of u s high resolution radiosonde data if the simulated total energy density and zonal momentum flux correlate well with those two parameters derived from the observations simultaneously we claim a best fit is found eighty five stations with sufficient completeness and quality are analyzed and we are able to obtain best fit source spectra for 61 of them two conditions are found to be necessary to achieve a best fit first the kinetic energy density and the zonal momentum flux derived from observations need to be highly correlated second the source altitude needs to be located right below the lower stratosphere since the observed gravity waves represent the average climatology of the cumulative effect on a monthly average basis of the various time varying physical sources together with their propagation from different altitudes all the sources we found are anisotropic with most of momentum flux directed upstream of the dominant wind direction this might be caused by wave propagation effects or the nature of the sources themselves the latitudinal variation of the horizontal wavelength of the source spectra corresponds well with that derived independently from the observations but other variable parameters do not show obvious latitudinal dependence a source spectrum type representing convection works well for lower latitudes while another more general source works better for middle to high latitudes the central u s and the north american monsoon region are two regions where it is difficult to obtain best fit source spectra we suspect that the reason for this is that during the summer mesoscale convective systems are dominant sources for inertia gravity waves which may not be well represented by our chosen spectral source functions

small scale motions observed by aircraft in the tropical lower stratosphere evidence for mixing and its relationship to large scale flows abstract measurments of temperature and ozone from instrumental aircraft in the tropical lower stratosphere show the presence of small scale disturbances generated by 1 underlying cumulus convection and 2 kelvin helmholtz instability the disturbances associated with underlying convection have peak to peak vertical parcel excursions of 300 m flying conditions were smooth suggesting an ensemble of gravity waves and little or no turbulent mixing it is nevertheless possible that these waves break at other altitudes leading to turbulent mixing and net fluxes of vertically stratified tracers disturbances attributed to kh instability implied vertical parcel excursions of 300 400 m the disturbances coincided with rough flying conditions suggesting turbulent mixing a linear stability analysis of the atmospheric basic state defined by high resolution radiosondes shows fastest growing waves with horizontal wavelengths of 1 4 1 8 km consistent with the aircraft observations the strong shears responsible

effects of tropospheric wind shear on the spectrum of convectively generated gravity waves abstract the authors examine the effects of tropospheric wind shear on the phase speed spectrum of gravity waves generated by tropical convection a two dimensional cloud resolving model is used to perform numerous squall line simulations with the vertical shear of the horizontal wind varied in three layers of the troposphere several simplified simulations using prescribed heating are also performed to elucidate the interactions of wind shear with thermal forcing it is found that the dominant phase speed range of convectively generated stratospheric gravity waves is primarily determined by the vertical scale of the tropospheric heating and is then modified by the tropospheric wind the gravity wave spectrum is especially sensitive to shear in the upper troposphere through a mechanism similar to critical level filtering such shear acts to reduce the momentum flux of waves propagating in the same direction as the storm relative mean wind through interaction with convective turrets shear in the upper t

crustal heterogeneity as inferred from seismic coda wave decomposition by small aperture array observation abstract seismic coda waves have complex waveforms and are considered to be caused by 3 dimensional structural heterogeneities we carried out 3 component small aperture array observations of seismic coda waves from natural earthquakes in tsukuba central japan to decompose complex coda waveforms and to clarify the nature of crustal heterogeneity epicentral distances in the present study are less than 200 km the observational results are summarized as follows 1 the remarkable feature of the coda from natural earthquakes is the difference between the p coda and the s coda especially in the vertical component the p coda consists mainly of coherent p wave phases which have almost the same slowness vector as the initial p wave motion whereas the s coda is decomposed into incoherent phases with random propagation directions 2 coherency of waveforms among the array sensors of the vertical component rapidly becomes low from the high value of coherency of the direct s wave 3 in the two horizontal components radial and transverse ones both the p and s coda are decomposed into incoherent random phases 4 coherency in the early s coda of the horizontal components gradually becomes low compared to the vertical component these features indicate that s to p converted waves at horizontal boundaries of the structure are dominant in the p coda of the vertical component while the p coda of the horizontal components and the s coda consist of scattered waves from the lateral heterogeneity this interpretation leads to a model of crustal heterogeneity in which the degree of the lateral heterogeneity is smaller than the degree of vertical heterogeneity of layered structures

a novel technique for measuring lg attenuation results from eastern canada between 1 to 10 hz spectral amplitudes of regionally recorded lg waves are studied in detail between 0 6 and 10 hz using vertical component velocity seismograms of the eastern canada telemetered network stations and a supplementary seismic research observatory type station at glen almond gac quebec we find that the site responses vary among these stations by more than a factor of 3 within the frequency range of interest furthermore they are found to be strongly frequency dependent consequently it is essential that they be taken into consideration in studies of lg wave attenuation and lg source spectra of regionally recorded seismic events we present a new method of measuring interstation surface wave attenuation which is closely related to the conventional two station method while retaining all the desirable features of the conventional two station method the new technique which we will call the reversed two station method allows simple direct one parameter determination of the lg wave attenuation from sparse spectral data in a manner unaffected by station site effects and associated instrument error the reversed two station method is successfully tested over weakly attenuating short 53 to 210 km interstation paths in eastern canada a difficult experimental condition by normal standards the lg attenuation coefficient 0 6 to 10 hz in eastern canada is found to be frequency dependent and of the form f 0 0008 f 0 81 km 1 at higher frequencies the lg attenuation appears to be essentially frequency independent this latter finding is preliminarily interpreted as evidence that regionally recorded lg waves in the canadian shield are as in the case of lg waves propagating through the structurally complex appalachian province contaminated by the high frequency coda of sn waves the lg contamination over the shield paths becomes severe starting at 14 hz twice the frequency above which the lg signal propagating over the appalachian province becomes completely dominated by non lg arrivals

seeing double at neptune s south pole abstract keck near infrared images of neptune from ut 26 july 2007 show that the cloud feature typically observed within a few degrees of neptune s south pole had split into a pair of bright spots a careful determination of disk center places the cloud centers at 89 07 0 06 and 87 84 0 06 planetocentric latitude if modeled as optically thick perfectly reflecting layers we find the pair of features to be constrained to the troposphere at pressures greater than 0 4 bar by ut 28 july 2007 images with comparable resolution reveal only a single feature near the south pole the changing morphology of these circumpolar clouds suggests they may form in a region of strong convection surrounding a neptunian south polar vortex

double difference tomography the method and its application to the hayward fault california we have developed a double difference dd seismic tomography method that makes use of both absolute and relative arrival times by reducing systematic errors using the more accurate relative arrival times the method produces an improved velocity model simultaneously it yields event locations of a quality equivalent to those of the dd location method while avoiding simplifying assumptions of that method we test this method on a synthetic dataset and find that it produces a more accurate velocity model and event locations than standard tomography we also test this method on a hayward fault california earthquake dataset spanning 1984 1998 the earthquakes relocated by this method collapse to a thin line along the fault trace consistent with previous results the dd velocity model has sharper velocity contrasts near the source region than the standard tomography model

quantitative analysis of seismic fault zone waves in the rupture zone of the 1992 landers california earthquake evidence for a shallow trapping structure summary we analyse quantitatively a waveform data set of 238 earthquakes recorded by a dense seismic array across and along the rupture zone of the 1992 landers earthquake a grid search method with station delay corrections is used to locate events that do not have catalogue locations the quality of fault zone trapped waves generated by each event is determined from the ratios of seismic energy in time windows corresponding to trapped waves and direct s waves at stations close to and off the fault zone approximately 70 per cent of the events with s p times of less than 2 s including many clearly off the fault produce considerable trapped wave energy this distribution is in marked contrast with previous claims that trapped waves are generated only by sources close to or inside the landers rupture zone the time difference between the s arrival and trapped waves group does not grow systematically with increasing hypocentral distance and depth the dispersion measured from the trapped waves is weak these results imply that the seismic trapping structure at the landers rupture zone is shallow and does not extend continuously along strike by more than a few kilometres synthetic waveform modelling indicates that the fault zone waveguide has depth of approximately 2 4 km a width of approximately 200 m an s wave velocity reduction relative to the host rock of approximately 30 40 per cent and an s wave attenuation coefficient of approximately 20 30 the fault zone waveguide north of the array appears to be shallower and weaker than that south of the array the waveform modelling also indicates that the seismic trapping structure below the array is centred approximately 100 m east of the surface break

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

attenuation of lg waves in the new madrid seismic zone of the central united states using the coda normalization method abstract unique properties of coda waves are employed to evaluate the frequency dependent quality factor of lg waves using the coda normalization method in the new madrid seismic zone of the central united states instrument and site responses are eliminated and source functions are isolated to construct the inversion problem for this purpose we used 121 seismograms from 37 events with moment magnitudes m ranging from 2 5 to 5 2 and hypocentral distances from 120 to 440 km recorded by 11 broadband stations a singular value decomposition svd algorithm is used to extract q values from the data while the geometric spreading exponent is assumed to be a constant inversion results are then fitted with a power law equation from 3 to 12 hz to derive the frequency dependent quality factor function the final results of the analysis are q v lg f 410 38 f 0 49 0 05 for the vertical component and q h lg f 390 26 f 0 56 0 04 for the horizontal component where the term after sign represents one standard error for stations within the mississippi embayment with an average sediment depth of 1 km around the memphis metropolitan area estimation of quality factor using the coda normalization method is not well constrained at low frequencies f

model study of intermediate scale tropical inertia gravity waves and comparison to twp ice campaign observations abstracta 2 day inertia gravity wave igw was observed in high resolution radiosonde soundings of horizontal wind and temperature taken during the 2006 tropical warm pool international cloud experiment twp ice experiment in the darwin area the wave was observed in the stratosphere above darwin from 28 january to 5 february a similar wave event is observed in the european centre for medium range weather forecasts ecmwf operational data a comparison between the characteristics of the igw derived with the ecmwf data to the properties of the wave derived with the radiosonde data shows that the ecmwf data capture similar structure for this 2 day wave event but with a larger vertical wavelength a reverse ray tracing method is used to localize the source region using ecmwf data to define the atmospheric background conditions and wave properties observed in the soundings it is found that the 2 day wave event originated from deep convection in the indonesian region around 20 january the weather research

high resolution q 1 estimation based on extension of coda normalization method and its application to p wave attenuation structure in the aftershock area of the 2005 west off fukuoka prefecture earthquake m7 0 summary we developed a method for estimating the seismic wave attenuation 1 q in a seismically active region such as an aftershock area to estimate the attenuation factor between two adjacent hypocentres we employed two seismograms recorded at a station and calculate the ratio between two power spectra of direct waves normalized by those in the coda for both the events the coda normalization of the spectrum and the ratio between the two events minimize the possible influences of sources sites instruments and attenuation from the station to the hypocentral area the 1 q value can be estimated from the variation of the ratios of event pairs calculated at many stations for various traveltime differences between the even pairs this method involves double difference dd estimation from the logarithmic power spectra for estimating the 1 q structure employing a concept similar to the recently developed dd tomography for velocity structures we applied this method to the aftershock area of the 2005 west off fukuoka prefecture earthquake m7 0 in order to investigate the 1 q structure of p waves by using the spectra of the seismograms of 1781 events recorded at a dense seismic network deployed around the aftershock area we obtained the spatial variation of the 1 q value in this region the 1 q distribution thereby obtained suggests that there exists a high attenuation region around the edge of the main shock fault which could correspond to the segment boundary between the earthquake fault and the adjacent faults in addition we found that the initiation points of the main shock and aftershocks were located in a low attenuation region

modeling heterogeneous deviatoric stress field around the hypocentral area of the 2005 fukuoka earthquake m7 0 by spatially distributed moment tensors 1 recent studies on the stress field in a seismogenic zone revealed a heterogeneous feature around a fault to model the stress field around a fault zone we have developed an inversion method that can be applied to focal mechanism data on microearthquakes and slip data on faults the modeling scheme takes an objective approach without an a priori model such as the existence of faults or a magma source the stress variation resulting from inelastic deformation in a medium e g fault slip and magma intrusion can be expressed as equivalent body forces in the medium thus we attempted to model the stress field through the estimation of parameters of the regional stress and spatially distributed moment sources the method was applied to the focal mechanism data of the aftershocks of the 2005 fukuoka earthquake m7 0 in japan the direction obtained for the minimum regional principal stress i e nnw sse was as expected from the general tendency of the focal mechanisms the results revealed that the stress field was distorted by the fault slip in the middle segment of the earthquake fault the slip detected at the deep part of the fault is located away from the coseismic slip area suggesting a possibility of either preseismic or postseismic slip around the initiation point of the main shock rupture in contrast the stress accumulation rises at the folding point of the aftershock alignment and the stress relaxation area is found at the deeper edge where the largest aftershock occurred and strong heterogeneous medium exists

three dimensional attenuation structure beneath the northeastern japan arc estimated from spectra of small earthquakes abstract a fine scale three dimensional attenuation structure beneath the northeastern japan arc has been obtained using a joint inversion for source parameters site response and q values data used for this study are p wave spectra of microearthquakes occurring in the subducting pacific plate the subducting plate is found to have higher q values than the overlying mantle there is an along arc variation in the distribution of low q zones in the crust and the mantle wedge within the study area for the southern part of the study area low q zones are distributed in the crust beneath the volcanic front they extend into the mantle wedge and become deep toward the west that is toward the backarc region on the other hand the northern part of the study area has low q zones at two depth ranges at shallower depths just beneath the volcanic front and at the deeper part of the mantle wedge beneath the backarc region the region without active volcanoes along the volcanic front has relatively high mantle q values seismic activity in the lower plane of the double planed deep seismic zone is high beneath this relatively high q region of the mantle wedge spatial distribution of low q zones found in the present study is nearly consistent with that of the low velocity zones estimated from studies of travel times tomography partial melting zones in the mantle wedge whose existence has been suggested from the study of seismic velocity structure and laboratory experiments are located in the low q zones obtained in the present study these results suggest that spatial distribution of q values is closely related to heterogeneous distribution of temperature in the mantle wedge

near tropopause vertical motion within the trailing stratiform region of a midlatitude squall line abstract rawinsonde observations have been used to determine the flow structure in the vicinity of the tropopause atop the trailing stratiform precipitation region of an intense midlatitude squall line computations of vertical motion using the kinematic and thermodynamic methods show i upward motion in the mid to upper troposphere within the stratiform cloud and ii downward motion in a thin layer 2 3 km deep centered near the tropopause at cloud top the latter feature which has received little attention and explanation has recently been reported to exist above stratiform rain areas in the tropics as measured directly by a wind profiler on the tropical western pacific island pohnpei the thin layer of sinking at the top of the trailing stratiform region occurs along the sloping upper cloud boundary and is associated with downward sloping isentropes in the lower stratosphere to the rear of the convective line the deformation of the isentropes is associated with an upward bulging of the tropopause

clouds and aerosols on uranus radiative transfer modeling of spatially resolved near infrared keck spectra abstract we observed uranus in the near infrared h and k bands 1 47 2 38 m in 2010 and 2011 with the osiris imaging spectrograph on the keck ii telescope with adaptive optics in 2010 three years past the equinox we had a good view of the north polar region while still having access to southern latitudes down to 70 s in 2011 our observations focused on a moderately bright discrete cloud feature in the middle of the bright circumpolar band at 45 n the spatial and spectral resolution of our data allow us to retrieve atmospheric parameters between 65 s and 75 n via radiative transfer modeling we test vertical aerosol profiles with combinations of diffuse and compact scattering layers and find that we can reproduce our equatorial data for a range of cases provided the deepest detectable aerosol layer is compact and located between 2 and 3 bars with the higher cloud altitudes corresponding to models with higher methane deep volume mixing ratios using a parameterized atmosphere with a diffuse upper haze and a moderately compact lower cloud we find that both the haze and the cloud reach their maximal optical depth just north of the equator and thin toward the poles when we fix the abundance of methane with latitude we find that the bottom cloud shifts to shallower depths at higher latitudes in both hemispheres for a methane profile with a deep volume mixing ratio of 2 22 the cloud rises from the 3 bar level equatorward of 20 to above 2 bars by 60 however when we allow the tropospheric methane abundance to vary according to a parameterized vertical profile we find that the lower cloud depth is stable in latitude while the methane becomes increasingly depleted toward both poles in both cases we find denser aerosol layers and higher methane abundances in the northern hemisphere than the southern consistent with a seasonal post equinox trend in particular the bright band near 45 n is relatively undepleted in methane and represents a local peak in the opacity and altitude of the lower cloud the cloud feature we detected in 2011 falls in the middle of this band this feature extends from a depth of 1 3 bars up to the 0 5 bar level both ch4 and h2s are expected to condense below this level if the cloud has formed as the result of a convective upwelling event these are the most likely condensation species

satellite observed characteristics of midwest severe thunderstorm anvils abstract this paper presents analyses of the cloud top and anvil structure of severe thunderstorms as observed by goes for five sesame cases during 1979 and four non sesame cases during 1980 82 emphasis was placed on comparison of these observations with previous models and hypotheses for the so called v feature and thermal couplets in the infrared ir observations thermal couplets are comprised of a low temperature region generally at or upwind of the cloud summit old point near the vertex of the v and one or more higher temperature regions downshear of the cloud summit warm points within the interior of the v statistics of the various cloud top and anvil features were compiled and the different cases were compared all studied except one 8 june 1979 had the v feature the temperature difference between the claw in warm and cold points comprising the thermal couplet ranged from 7 to 17 c and the mean separation distance between these points was 21 44 km the observations also indicated th

fault zone attenuation of high frequency seismic waves we have developed a technique to measure seismic attenuation within an active fault zone at seismogenic depths utilizing a pair of stations and pairs of earthquakes spectral ratios are performed to isolate attenuation produced by wave propagation within the fault zone this empirical approach eliminates common source propagation instrument and near surface site effects the technique was applied to a cluster of 19 earthquakes recorded by a pair of downhole instruments located within the san andreas fault zone at parkfield california over the 1 40 hz bandwidth used in this analysis amplitudes are found to decrease exponentially with frequency furthermore the fault zone propagation distance correlates with the severity of attenuation assuming a constant q attenuation operator the s wave quality factor within the fault zone at a depth of 5 6 kilometers is 31 7 5 if fault zones are low q environments then near source attenuation of high frequency seismic waves may help to explain phenomenon such as fmax fault zone q may prove to be a valuable indicator of the mechanical behavior and rheology of fault zones specific asperities can be monitored for precursory changes associated with the evolving stress field within the fault zone the spatial and temporal resolution of the technique is fundamentally limited by the uncertainty in earthquake location and the interval time between earthquakes

temporal changes in p wave attenuation in the loma prieta rupture zone 1 clusters of recurring nearly identical microearthquakes have been recorded near loma prieta california such events make possible direct measurement of temporal changes in the attenuation operator t along fixed paths under what are tantamount to laboratory conditions analysis of almost 10 years of p wave data following the 18 october 1989 loma prieta california main shock m 7 0 reveals a large amplitude t increase within the first 3 weeks of the main shock a gradual t recovery toward its level prior to the main shock is seen in the years ensuing the results point to changes in porosity and fluid saturation taking place in parts of the main shock source volume stemming from coseismic crack opening and postseismic relaxation processes such as postseismic fluid flow into the cracks crack healing and rock compaction

small scale wind fluctuations in the tropical tropopause layer from aircraft measurements occurrence nature and impact on vertical mixing abstractthe contribution of turbulent mixing to heat and tracer transport in the tropical tropopause layer ttl is poorly constrained partly due to a lack of direct observations here the authors use high resolution 20 hz airborne measurements to study the occurrence and properties of small scale 100 m wind fluctuations in the ttl 14 19 km over the tropical pacific the fluctuations are highly intermittent and appear localized within shallow 100 m patches furthermore active turbulent events are more frequent at low altitude near deep convection and within layers of low gradient richardson number a case study emphasizes the link between the turbulent events and the occurrence of inertio gravity waves having small horizontal or vertical scale in order to evaluate the impact of the observed fluctuations on tracer mixing their characteristics are examined during active events they are in broad agreement with inertial range turbulence theory the motions are close to 3d isotropic and the sp

dehydration of the upper troposphere and lower stratosphere by subvisible cirrus clouds near the tropical tropopause the extreme dryness of the lower stratosphere is believed to be caused by freeze drying of air as it enters the stratosphere through the cold tropical tropopause previous investigations have been focused on dehydration occurring at the tops of deep convective cloud systems however recent observations of a ubiquitous stratiform cirrus cloud layer near the tropical tropopause suggest the possibility of dehydration as air is slowly lifted by large scale motions in this study we have evaluated this possibility using a detailed ice cloud model simulations of ice cloud formation in the temperature minima of gravity waves wave periods of 1 2 hours indicate that large numbers of ice crystals will likely form due to the low temperatures and rapid cooling as a result the crystals do not grow larger than about 10 m fallspeeds are no greater than a few cm s 1 and little or no precipitation or dehydration occurs however ice clouds formed by large scale vertical motions with lifetimes of a day or more should have fewer crystals and more time for crystal sedimentation to occur resulting in water vapor depletions as large as 1 ppmv near the tropopause we suggest that gradual lifting near the tropical tropopause accompanied by formation of thin cirrus may account for the dehydration

numerical simulations of interactions between gravity waves and deep moist convection abstract this study uses a numerical model to simulate deep convection both in the tropics over the ocean and the midlatitudes over land the vertical grid that was used extends into the stratosphere allowing for the simultaneous examination of the convection and the vertically propagating gravity waves that it generates a large number of trajectories are used to evaluate the behavior of tracers in the troposphere and it is found that the tracers can be segregated into different types based upon their position in a diagram of normalized vertical velocity versus displacement conditional sampling is also used to identify updrafts in the troposphere and calculate their contribution to the kinetic energy budget of the troposphere in addition fourier analysis is used to characterize the waves in the stratosphere it was found that the waves simulated in this study have similarities to those observed and simulated by other researchers finally this study examines the wave energy flux as a means to provid

vertical aerosol structure of neptune constraints from center to limb profiles abstract we present and analyze center to limb ctl profiles of the equatorial region of neptune extracted from images with good spatial resolution models of the quiescent atmosphere of neptune are consistent with at least two distinct cloud layers a thin stratospheric haze and a deep cloud the 8900 a ctl profile requires the presence of some material above the 5 mbar level assuming isotropic scattering the optical depth of the material is less than 0 15 for hazes with single scattering albedos larger than 0 6 ctl profiles at three methane bands could not be fitted simultaneously with a single scattering layer implying that there may be multiple haze layers the methane band data tolerate thin scattering hazes in the pressure level from 0 4 to 1 5 bars but the optical depths must be less than 0 05 again assuming isotropic scattering such a thin haze does not provide sufficient reflected flux at 6340 a a continuum region indicating the presence of another scattering layer deeper than 1 5 bars a bright cloud layer single scattering albedo near 1 with optical depth 3 0 at 2 6 bars provides a good fit to 6340 a reflectivity superposed on the quiescent atmosphere are discrete bright features the lack of detectable disk integrated variability at shorter wavelengths helps constrain the vertical aerosol structure of these bright regions specifically the difference of the bright feature from its surroundings in 1986 was probably caused by an increase in optical depth or height of a stratospheric haze layer

the gravity wave response above deep convection in a squall line simulation abstract high frequency gravity waves generated by convective storms likely play an important role in the general circulation of the middle atmosphere yet little is known about waves from this source this work utilizes a fully compressible nonlinear numerical two dimensional simulation of a midlatitude squall line to study vertically propagating waves generated by deep convection the model includes a deep stratosphere layer with high enough resolution to characterize the wave motions at these altitudes a spectral analysis of the stratospheric waves provides an understanding of the necessary characteristics of the spectrum for future studies of their effects on the middle atmosphere in realistic mean wind scenarios the wave spectrum also displays specific characteristics that point to low physical mechanisms within the storm responsible for their forcing understanding these forcing mechanisms and the properties of the storm and atmosphere that control them are crucial first steps toward developing

local wave propagation near the san jacinto fault zone southern california observations from a three component seismic array we present results from a study conducted to characterize the p and s wave trains and codas for local earthquakes observed near the san jacinto fault zone southern california the data were recorded by a small aperture three component seismic array and analyzed using a statistical array processing algorithm that provides estimates of the propagation direction apparent wavenumber and polarization characteristics for plane wave arrivals observed at the array the p codas for these local earthquake data are similar in that each is composed of predominantly p waves traveling in a direction subparallel to the path of the direct p arrivals these p coda exhibit a character consistent with propagation in a waveguide as opposed to propagation in a medium with randomly distributed isotropic scattering sources the s codas differ from the p codas in two dramatic ways 1 the s codas are composed of predominantly s waves and 2 the s coda waves arrive from more random spatially uniform directions the dramatic differences between the p and s codas provide compelling evidence that p and s coda are the product of distinctly different scattering mechanisms and therefore that the p and s codas provide information about different source characteristics and or structural features a third important observation concerning the s coda is that the direction of arrival spectra for the s codas differ from event to event considerably more so than do those of the p codas this observation is at odds with the conventional wisdom and suggests that the character of the s coda reflects a potentially complex interaction among several factors including but not limited to the source depth the source distance and the source radiation pattern

measurements of vertical eddy diffusivity across the tropopause using radio acoustic sounding system rass 1 a four day high temporal resolution mu radar rass data set was obtained under light wind conditions in august 1995 enabling retrieval of virtual temperatures up to 20 km this provided a unique opportunity to study the vertical eddy diffusivity k across the tropopause using rass brunt vaisala frequency n and radar spectral width co located six hourly radiosondes enabled calculation of k using radiosonde n and radar spectral width rass k decreased across the wmo tropopause from 0 39 0 05 m2s 1 in the uppermost kilometre of the troposphere to 0 27 0 03 m2s 1 in the lowermost kilometre of the stratosphere the equivalent radiosonde k were 0 43 0 06 m2s 1 and 0 31 0 07 m2s 1 respectively the wmo tropopause seems to provide a better definition than the cold point tropopause in separating the stratosphere from the troposphere when considering the mixing of minor constituents

seismic attenuation tomography of the source zone of the 2016 kumamoto earthquake m 7 3 we study the three dimensional seismic attenuation qp and qs structure in the source area of the 2016 kumamoto earthquake m 7 3 by using 18 296 tp and 29 668 ts data from 742 local earthquakes recorded by a dense seismic network consisting of 112 stations deployed in kyushu island our results show that significant low q high attenuation anomalies exist in the crust and mantle wedge beneath the volcanic front and back arc area which reflect hot and wet zones caused by convective circulation in the mantle wedge and dehydration of the young philippine sea phs slab the 2016 kumamoto earthquake occurred in a high q and high velocity high v zone in the upper crust which is surrounded and underlain by low q and low v anomalies in the lower crust and upper mantle these results suggest that the 2016 kumamoto earthquake took place in a brittle seismogenic layer in the upper crust but its rupture nucleation was affected by fluids and arc magma ascending from the mantle wedge in addition an obvious low q zone is revealed in the fore arc mantle wedge which reflects serpentinization of the fore arc mantle due to abundant fluids from the phs slab dehydration

source parameters and three dimensional attenuation structure from the inversion of microearthquake pulse width data qp imaging and inferences on the thermal state of the campi flegrei caldera southern italy the three dimensional p wave attenuation structure of the campi flegrei caldera and the estimate of source parameters for 87 local microearthquakes is obtained by the nonlinear inversion of pulse width and rise time measurements by using the method described by zollo and de lorenzo this issue source radii represent the better resolved parameters with values ranging from 70 m to 230 m the dip and strike angles defining fault orientations are usually affected by larger uncertainties and are well constrained only for 11 events the dip fault is usually confined in the range 30 60 with an average uncertainty of 12 the fault strikes mainly range between 60 and 60 and seem to define preferential directions oriented radially from the symmetry axis of the ground deformation stress drop estimates indicate rather low values 0 01 1 mpa which suggest low strength properties of the incoherent and brittle materials filling the caldera primarily yellow tuffs the three dimensional qp images obtained from the inversion of p pulse durations show two significant low qp anomalies between 0 and 1 km of depth in the north eastern sector and at 2 3 km of depth in the central eastern sector of the caldera the high degree of spatial correlation of the low qp zone and low vs as inferred by aster and meyer 1988 at 0 1 km in depth and other geophysical and geochemical observations suggest that this anomaly can be related to the presence of densely fractured porous and fluid filled rocks in the ne sector of the caldera the deeper low qp anomaly is interpreted as being related to a dominant thermal effect we used the surface and deep borehole temperature measurements available in the area to obtain a local calibration curve to convert qp in temperature at campi flegrei the retrieved t qp map shows a high thermal deep disturbance 450 500 c at depths between 2 and 3 km in the eastern sector of the caldera where the most recent eruptive activity is concentrated the present day temperature field retrieved by qp images has been interpreted by using a three dimensional thermal conduction model assuming an extended heat source initial temperature of 800 c located underneath the attenuation anomalous region the results indicate that the qp inferred temperature field can be related to the heat conduction effect of one or more molten bodies whose top should be at about 4 km depth consistent with recent seismic estimates of the magma chamber top at campi flegrei ferrucci et al 1992 this study suggests that the present thermal state and rock rheology of the inner caldera could be controlled by the cooling of molten bodies that originally intruded at depths of 1 4 1 6 km during one or more recent time of 10 kyr eruptive events

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

moment energy stress drop and source spectra of western united states earthquakes from regional coda envelopes we present a new method to estimate stable seismic source parameters such as energy moment and orowan stress drop using regional coda envelopes from as few as one broadband station we use the method to compute path and site corrected seismic moment rate spectra for 117 recent western united states earthquakes empirical green s function corrections were applied to our surface and body wave coda envelope measurements to generate s wave source spectra these source spectra provide stable single station estimates of radiated seismic energy es and seismic moment mo that for common events are in excellent agreement with network averaged estimates obtained using local and regional data teleseismic moment estimates are compatible with our regional results but teleseismic energy estimates appear to be nearly an order of magnitude low we estimated the seismic moment of events ranging between mw 2 2 and 7 3 and energy estimates for which we had measured at least 70 of the total energy generally events above mw 3 3 we use these estimates to examine the behavior of derived parameters such as the orowan stress drop 2 es mo while the earthquakes we studied have a small range in orowan stress drop generally between 0 1 and 20 mpa they show a strong tendency for orowan stress drop to increase with moment approximately as mo0 25 we believe this is a source effect and is not due to inadequate bandwidth or attenuation correction and note that this trend appears to continue for microearthquakes as described in a recent deep borehole study in southern california many of the large high stress drop earthquakes show complexity in their moment rate spectra near the corner frequency and cannot be fit by a simple square model instead above the first corner frequency the spectral decay ranges between f 1 0 and f 1 5 this leads to larger estimates of radiated energy than predicted with a simple square model and has implications for seismic hazard estimation coda envelopes have three main advantages over direct arrivals for estimating seismic moment and energy 1 coda amplitudes vary little with geology and source radiation anisotropy and allow accurate single station applications 2 path corrected coda amplitude measurements can be applied to very large regions allowing a comparison of source parameters throughout the western united states using a common methodology and stations 3 because long period coda can last for hours for large local and regional events it allows the analysis of seismograms with clipped early arrivals

vertical short scale structures in the upper tropospheric and lower stratospheric temperature and ozone at la reunion island 20 8 s 55 3 e the distribution and the nature of vertical short scale structures observed in ozone and temperature are investigated in the upper troposphere and the lower stratosphere at la reunion island located in the vicinity of the southern subtropical barrier by using wavelet based methods a climatology of dominant wavelike patterns with short vertical wavelengths reveals the presence of localized structures on both the ozone and the temperature perturbations extracted from ozonesonde and temperature data up to the middle stratosphere some case studies are presented to identify the nature of short scale structures with 1 to 5 km vertical wavelengths in the troposphere and the stratosphere a climatology of short scale structures induced by gravity waves and the horizontal advection shows that short scale structures are mainly detected in the middle and upper troposphere and in the lower stratosphere the weak value of the coefficient r z that links the ozone and temperature perturbations induced by gravity waves is a major limit to detecting such short scale structures above 21 km altitude some structures with vertical wavelengths ranging from 1 to 5 km are attributed to gravity waves produced by convection in summer and the subtropical jet in winter or quasi horizontal large scale motions from both sides of the subtropical barrier

regional body wave attenuation using a coda source normalization method application to mednet records of earthquakes in italy we develop a new methodology to determine apparent attenuation for the regional seismic phases pn pg sn and lg using coda derived source spectra the local to regional coda methodology mayeda 1993 mayeda and walter 1996 mayeda et al 2003 is a very stable way to obtain source spectra from sparse networks using as few as one station even if direct waves are clipped we develop a two step process to isolate the frequency dependent q first we correct the observed direct wave amplitudes for an assumed geometrical spreading next an apparent q combining path and site attenuation is determined from the difference between the spreading corrected amplitude and the independently determined source spectra derived from the coda methodology we apply the technique to 50 earthquakes with magnitudes greater than 4 0 in central italy as recorded by mednet broadband stations around the mediterranean at local to regional distances this is an ideal test region due to its high attenuation complex propagation and availability of many moderate sized earthquakes we find that a power law attenuation of the form q f q sub 0 f sup y fit all the phases quite well over the 0 5 to 8 hz band at most stations the measured apparent q values are quite repeatable frommore event to event finding the attenuation function in this manner guarantees a close match between inferred source spectra from direct waves and coda techniques this is important if coda and direct wave amplitudes are to produce consistent seismic results less

generation and trapping of gravity waves from convection with comparison to parameterization some parameterizations of gravity wave mean flow forcing in global circulation models gcms add realism by describing wave generation by tropospheric convection because the convection in gcms is itself a parameterized process these convectively generated wave parameterizations necessarily use many simplifying assumptions in this work the authors use a realistic simulation of wave generation by convection described in previous work which was validated by observations from the darwin area wave experiment dawex to test these assumptions and to suggest some possible improvements to the parameterizations in particular the authors find that wave trapping in the troposphere significantly modifies the spectrum of vertically propagating waves entering the stratosphere above convective wave sources and offer a linear method for computing wave transmission and reflection effects on the spectrum suitable for inclusion in the parameterizations the wave fluxes originate from both a time varying heating mechanism and an obstacle effect mechanism acting in the simulation methods for including both mechanisms in the parameterizations are described waves emanating from the obstacle effect remain very sensitive to the depth of penetration of latent heating cells into an overlying shear zone which will continue to make it difficult to accurately parameterize in a gcm where the convective cells are not resolved

occurrence frequency of convective gravity waves during the north american thunderstorm season 1 convective gravity waves are an important driver of the equator to pole circulation in the stratospheric summer hemisphere but their nature is not well known previous studies showing tight relationships between deep convection and convective waves mainly focus on tropical latitudes for midlatitudes most analyses are based on case studies here we present a new multiyear occurrence frequency analysis of convective waves at midlatitudes the study is based on radiance measurements made by the atmospheric infrared sounder airs satellite experiment during the north american thunderstorm season may to august in the years 2003 2008 for this study we optimized an existing algorithm to detect deep convection in airs data to be applicable at midlatitudes we also present a new detection algorithm for gravity waves in airs data based on a variance filter approach for 4 3 m brightness temperatures the new algorithm can detect plane wave perturbations in the altitude range from 20 to 65 km with vertical wavelengths larger than 15 km and horizontal wavelengths from 50 to 1000 km by analyzing spatial and temporal correlations of the individual airs observations it can be shown that more than 95 of the observed gravity waves in a core region over the north american great plains are related to deep convective clouds i e are likely being classified appropriately as convective waves we conclude that the core region is a good location to observe and characterize the properties of convective waves at midlatitudes the statistical analyses presented here are also valuable to validate parameterization schemes for convective gravity waves for completeness it should be mentioned that our analyses cover not only the u s midwest but the north american continent as well as the surrounding ocean regions in general our analysis also reveals interesting details about tropical convection and related gravity wave activity as well as the capability of the airs instrument to observe these

eastward propagating 2 to 15 day equatorial convection and its relation to the tropical intraseasonal oscillation anomalies of outgoing longwave radiation olr in 1980 1989 were examined in a narrow latitude band about the equator to elucidate the propagation and interaction of tropical intraseasonal oscillations tios and synoptic scale convective activity hovmoller diagrams of olr data reconstructed from two frequency bands corresponding to periods of 30 60 days and 2 15 days respectively revealed a clear distinction between the phase speed of eastward moving tios 3 7 m s 1 and that of eastward synoptic scale convection 10 13 m s 1 coherent propagation of tios from the indian to the western pacific oceans was often observed with temporary diminution of amplitude over the maritime continent propagation of high frequency anomalies was generally confined to an individual basin dominance of eastward propagating synoptic scale convection in the equatorial zone contrasts sharply with the westward propagation of off equatorial convergence zones interaction between the tio and high frequency activity resolved by daily olr was visible as a modest enhancement of eastward synoptic scale events and of high frequency activity in general during the convectively active phase of the tio

gravity wave characteristics over tromelin island during the passage of cyclone hudah 1 the time and spatial evolution of gravity wave characteristics are analysed using wavelets in vertical profiles of temperature and winds at tromelin island 15 53 s 54 31 e during the passage of the intense tropical cyclone hudah in the southern ocean indian basin in 2000 inertia gravity waves were observed in the upper troposphere and the lower stratosphere with dominant vertical wavelengths of 1 5 3 km horizontal wavelengths 2000 km and periods of 0 6 1 6 days large amounts of gravity wave energy were detected during landfalls of the tropical cyclone the distribution of total energy indicates that mesoscale convective structures such as tropical cyclones are important gravity wave sources in the upper troposphere

mesoscale disturbances in the tropical stratosphere excited by convection observations and effects on the stratospheric momentum budget abstract the importance of the momentum flux of topographically generated mesoscale gravity waves to the extratropical middle atmosphere circulation has been well established for over a decade estimates of the zonal forcing due to tropical mesoscale gravity waves however are hampered by lack of data on their primarily convective sources the advent of aircraft measurements over tropical convective systems now makes such estimates possible without the use of ad hoc assumptions about amplitudes and phase speeds aircraft measurements from nasa s 1980 panama and 1987 step australia missions show that convectively generated disturbances observed just above the tropopause have horizontal scales comparable to those of the underlying anvils about 50 100 km with peak to peak isentropic surface variations of about 300 400 m satellite imagery of tropical anvil evolution indicates a typical lifetime of about five hours assuming that each convective system s impact on the stratosphere can be modeled as a time

radiosonde observations of equatorial atmosphere dynamics over indonesia 2 characteristics of gravity waves this paper discusses the characteristics of gravity waves in the equatorial region revealed by analyzing radiosonde measurements of wind velocity and temperature fluctuations at 0 35 km with a height resolution of 150 m made every 5 7 hours between february 27 and march 22 1990 in east java indonesia we conducted hodograph analysis to delineate vertical and horizontal propagation characteristics and found that most gravity waves were generated in the middle of the troposphere and that they propagated upward into the stratosphere the amplitudes of wind velocity and temperature fluctuations due to gravity waves were larger in the stratosphere than in the troposphere the direction of horizontal propagation of gravity waves was rather uniformly distributed in the troposphere but it became eastward in the lower stratosphere being opposite to that of the mean winds because of quasi biennial oscillation the vertical wavenumber spectra of wind velocity were described fairly well by a saturated model spectrum although their amplitudes were smaller in the stratosphere a typical vertical wavelength was 2 2 5 km while the horizontal phase velocities were 5 7 and 12 m s in the troposphere and stratosphere respectively the amplitudes of small scale gravity waves were significantly larger in the equatorial stratosphere than at middle latitudes time height variation of the wind velocity variance due to gravity waves showed a clear correlation with that for high relative humidity which implies that cloud convection is an important mechanism of gravity wave generation in the equatorial region

isolating spatiotemporally local mixed rossby gravity waves using multi dimensional ensemble empirical mode decomposition tropical waves have relatively large amplitudes in and near convective systems attenuating as they propagate away from the area where they are generated due to the dissipative nature of the atmosphere traditionally nonlocal analysis methods such as those based on the fourier transform are applied to identify tropical waves however these methods have the potential to lead to the misidentification of local wavenumbers and spatial locations of local wave activities to address this problem we propose a new method for analyzing tropical waves with particular focus placed on equatorial mixed rossby gravity mrg waves the new tropical wave analysis method is based on the multi dimensional ensemble empirical mode decomposition and a novel spectral representation based on spatiotemporally local wavenumber frequency and amplitude of waves we first apply this new method to synthetic data to demonstrate the advantages of the method in revealing characteristics of mrg waves we further apply the method to reanalysis data 1 to identify and isolate the spatiotemporally heterogeneous mrg waves event by event and 2 to quantify the spatial inhomogeneity of these waves in a wavenumber frequency energy diagram in this way we reveal the climatology of spatiotemporal inhomogeneity of mrg waves and summarize it in wavenumber frequency domain the indian ocean is dominated by mrg waves in the period range of 8 12 days the western pacific ocean consists of almost equal energy distribution of mrg waves in the period ranges of 3 6 and 8 12 days respectively and the eastern tropical pacific ocean and the tropical atlantic ocean are dominated by mrg waves in the period range of 3 6 days the zonal wavenumbers mostly fall within the band of 4 15 with indian ocean has larger portion of higher wavenumber smaller wavelength components mrg waves

multi scale reasonable attenuation tomography analysis murat an imaging algorithm designed for volcanic regions abstract the attenuation of body wave amplitudes with propagation distance can be used to provide detailed tomographic images of seismic interfaces fluid reservoirs and melt batches in the crust the high sensitivity of body wave energies to high scattering structures becomes an obstacle when we try to apply attenuation tomography to small scale volcanic media where we must take into account the complexities induced by strong heterogeneous scattering topography and uncertain source modeling in the recorded wave fields the murat code uses a source and site independent coda normalization method to obtain frequency dependent measurements of p to coda and s to coda energy ratios the code inverts these data for both the geometrical spreading factor and the spatially dependent quality factors q providing additional attenuation information in the regions where velocity tomography is available the high sensitivity of coda waves to highly heterogeneous structures highlights zones of anomalous scattering which may corrupt amplitude dependent attenuation measurements and where basal assumptions of linear optics may go unfulfilled a multi step tomographic inversion increases the stability of the results obtained in regions of high heterogeneity e g the volcanic edifice by the inclusion of data corresponding to either sources or stations located in regions of lower heterogeneity on the other hand a mere increase in the number of rays entirely contained in the heterogeneous structures affects both the stability and the effective resolution of the results we apply the code to two small waveform datasets recorded at an active mount st helens and at a quiescent mount vesuvius volcano the results show that the seismicity located inside or under the volcanic edifice produces an increase of the low frequency energy ratios with travel time in both areas in our interpretation the anomalous concentration of energy which affects any waveform recorded on the cone produced inside the volcanic edifice or in the feeding system of the volcano is due to seismic source or medium dependent resonance the results also provide spatial and frequency limits on the feasibility of attenuation tomography in these two regions with larger datasets

gravity wave momentum flux in the lower stratosphere over convection this work describes a method for estimating vertical fluxes of horizontal momentum carried by short horizontal scale gravity waves lambda sub x 10 100 km using aircraft measured winds in the lower stratosphere we utilize in situ wind vector and pressure altitude measurements provided by the meteorological measurement system mms on board the er 2 aircraft to compute the momentum flux vectors at the flight level above deep convection during the tropical experiment of the stratosphere troposphere exchange project step tropical data from flight 9 are presented here for illustration the vertical flux of horizontal momentum these observations points in opposite directions on either side of the location of a strong convective updraft in the cloud shield this property of internal gravity waves propagating from a central source compares favorably with previously described model results

complex patterns of fluid and melt transport in the central andean subduction zone revealed by attenuation tomography abstract we present a high resolution 3 d model of p wave attenuation q p 1 for the central andean subduction zone data from 1500 mostly intermediate depth 60 250 km earthquakes recorded at three temporary seismic networks covering the forearc arc and backarc around 23 s were used for tomographic inversion the forearc is characterised by uniformly high q p values indicating low temperature rocks in accordance with low surface heat flow values prominent low q p anomalies are found beneath the magmatic arc and the backarc in the crust and mantle continuous regions of low q p connect earthquake clusters at 100 km and 200 km depth with zones of active volcanism in the arc and backarc fluids fluxed from the subducted oceanic lithosphere into the overlying mantle wedge where they induce melting explain our observations we propose that low q p regions indicate source and ascent pathways of metamorphic fluids and partial melts ascent of fluids and melts as imaged by seismic q p are not vertical as is often implicitely assumed instead sources of fluids are located at different depth levels and ascent paths are complex and exhibit significant variation within the study area the largest quaternary backarc volcano cerro tuzgle is fed by mantle melts which are imaged as a plume of low q p material that reaches to the strong earthquake cluster at 200 km depth

small scale gravity waves in the upper mesosphere and lower thermosphere generated by deep tropical convection a time dependent nonlinear fully compressible axisymmetric plane numerical model is used to simulate the generation of small scale gravity waves in the upper mesosphere and lower thermosphere by intense deep convection in the troposphere the simulations show that major convective storms in the tropics excite a broad spectrum of upper mesosphere lower thermosphere gravity waves above the storm centers the wave field includes a component that is guided in a thermal duct in the lower thermosphere and propagates horizontally outward from above the storm storms excite oscillations over the source which are initially confined to a stratospheric duct but leak into the thermospheric duct over time generating a long train of small scale ducted waves this ringing phenomenon persists for several hours after the storm has ended the ducted disturbances may propagate large distances from the source and explain observations of a strong summertime anisotropy favoring southward propagation of small scale waves observed in the airglow over adelaide more than 2000 km to the south of the storm events

general circulation model simulation of the semiannual oscillation of the tropical middle atmosphere abstract a study has been made of the evolution of the zonal mean zonal wind and temperature in a multiyear integration of the 40 level 3 3 6 resolution skyhi general circulation model gcm that has been developed at gfdl in the tropical upper stratosphere the mean wind variation is dominated by a strong semiannual oscillation sao the peak sao amplitude in the model is almost 25 m s 1 and occurs near the 1 mb level the phase of the sao near the stratopause is such that maximum westerlies occur shortly after the equinoxes these features are in good agreement with the available observations in addition the meridional width of the stratopause sao in the gcm compares well with observations a diagnostic analysis of the zonal mean momentum balance near the tropical stratopause was performed using the detailed fields archived during the gcm integration it appears that the easterly accelerations in the model sao are provided by a combination of i divergence of the meridional component of the el