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

foreland shortening and crustal balancing in the andes at 30 s latitude excellent surface exposures known benioff zone geometry a dynamic morphology and the availability of industry seismic reflection data all make the andes at 30 s an excellent transect for investigating crustal scale balanced sections 150 170 km of horizontal shortening has occurred in three major belts located between the trench and the foreland the thin skinned east verging precordillera of western argentina accounts for 60 75 of the total shortening and formed mostly since major volcanism ceased at 10 ma industry seismic reflection data show that the decollement of the precordillera belt is located anomalously deep at 15 km the belt is dominated by fault propagation folds and contains several prominent out of sequence thrust faults seismic stratigraphie analysis shows that miocene strata in the iglesia valley located between the precordillera and the crest of the andes accumulated in a piggy back basin onlap relations on the western side indicate that the high cordillera was uplifted as a major fault bend fold over a buried ramp thrusting in the two western belts both in the high cordillera of chile formed during the waning stages of arc volcanism 11 16 ma and account for 25 40 of the shortening the observed shortening is probably greater than can be accounted for with reasonable crustal thicknesses indicating the possibility of continental truncation or erosion along the plate margin or an anomalously thick root held down by the nearly flat subducted nazca plate our preferred crustal geometry puts the ramp between upper and lower crustal deformation west of the high topography requiring crustal scale tectonic wedging to thicken the crust beneath the crest of the andes this non unique model provides a simple explanation of the first order morphology of the andes at this latitude

the climatology of zonal wave numbers 1 and 2 planetary wave structure in the mlt using a chain of northern hemisphere superdarn radars the zonal wave components 1 and 2 were extracted from the meridional wind along the latitude band of 51 66 n for the years 2000 2008 using eight super dual auroral radar network superdarn radars spanning longitudes from 25 e to 150 w each extracted zonal component represents the superposition of all temporal periods with that zonal structure and indicates the total planetary wave energy available with that wave number the hovmoller diagrams show stationary as well as eastward and westward traveling planetary waves propagating in the background wind the method used to detect the zonal planetary wave components in the superdarn data are detailed and validated using uk meteorological office data which allows the evolution of s1 and s2 planetary wave energy between the stratosphere and mesosphere to be assessed the climatology of zonal wave number 1 and 2 planetary wave activity in the mesosphere lower thermosphere mlt is presented and compared to the activity in the stratosphere the mlt climatology of the mean wind anomalies shows stronger planetary wave activity during winter and weaker activity during summer with enhancement around midsummer and autumn equinox the climatology of the mean wind displays similar amplitudes apart from very strong s1 planetary wave amplitudes during summer in addition planetary wave activity during winters with major and minor stratospheric warming events are examined and contrasted

some forms of mountain peaks in the canadian rockies controlled by their rock structure abstract different mountain shapes in sedimentary sequences in the canadian rockies were enhanced by glacial erosion and have been modified post glacially by gravity driven slope processes slope modification by both glacial erosion and post glaciation landslides is related to slope geometry and rock structure particularly bedding dip five mountain peak shapes in monoclinal sequences each fall into different ranges of bedding dips 1 castellate and 2 matterhorn mountains occur in sub horizontal beds and their slopes are generally 35 65 and oblique to both bedding and joints 3 cuestas develop in gently to moderately dipping beds dip slopes and steeper normal escarpments form their cataclinal and anaclinal sides respectively with the dihedral angle between them about 90 4 hogbacks in moderately to steeply dipping beds have similar slope angles on both cataclinal and anaclinal slopes cataclinal slopes are either dip slopes or underdip slopes but anaclinal slopes are often steepened escarpments the dihedral angle between the slopes is usually slope gradients on a sample of 34 peaks are closely related to landslides particularly rock slides and rock topples these landslide modes are controlled by bedding dips

rapidly intensifying hurricane guillermo 1997 part i low wavenumber structure and evolution abstract the structure and evolution of rapidly intensifying hurricane guillermo 1997 is examined using airborne doppler radar observations in this first part the low azimuthal wavenumber component of the vortex is presented guillermo s intensification occurred in an environmental flow with 7 8 m s 1 of deep layer vertical shear as a consequence of the persistent vertical shear forcing of the vortex convection was observed primarily in the downshear left quadrant of the storm the greatest intensification during the 6 h doppler observation period coincided with the formation and cyclonic rotation of several particularly strong convective bursts through the left of shear semicircle of the eyewall some of the strongest convective bursts were triggered by azimuthally propagating low wavenumber vorticity asymmetries mesoscale budget analyses of axisymmetric angular momentum and relative vorticity within the eyewall are presented to elucidate the mechanisms contributing to guillermo s structural evol

zonal mean dynamics of extended recoveries from stratospheric sudden warmings abstractthe recovery of the arctic polar vortex following stratospheric sudden warmings is found to take upward of 3 months in a particular subset of cases termed here polar night jet oscillation pjo events the anomalous zonal mean circulation above the pole during this recovery is characterized by a persistently warm lower stratosphere and above this a cold midstratosphere and anomalously high stratopause which descends as the event unfolds composites of these events in the canadian middle atmosphere model show the persistence of the lower stratospheric anomaly is a result of strongly suppressed wave driving and weak radiative cooling at these heights the upper stratospheric and lower mesospheric anomalies are driven immediately following the warming by anomalous planetary scale eddies following which anomalous parameterized nonorographic and orographic gravity waves play an important role these details are found to be robust for pjo events as opposed to sudden warmings in general in that ma

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

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

eastern pacific hurricanes jimena of 1991 and olivia of 1994 the effect of vertical shear on structure and intensity abstract shear is a key inhibitor of tropical cyclone intensification although its signature is readily recognized in satellite imagery and theoretical or modeling studies provide some insight detailed observations have been limited airborne radar and in situ observations in hurricanes jimena of 1991 and olivia of 1994 are a step toward better understanding each storm was observed on two consecutive days initially both had small eyes 16 18 km radius and maximum winds of 57 m s 1 over sea surface temperatures sst 28 c in easterly environmental shear jimena maintained constant intensity or weakened gradually for 2 days in 13 20 m s 1 easterly shear olivia intensified in 8 m s 1 shear on the first day overnight the shear diminished to reverse and became westerly on the second day olivia weakened as the shear increased to 15 m s 1 from the west the storm moved over cooler sst and became surrounded by dryer air as convection weakened and the outer rainbands ceased to be effective barriers

downdrafts and the evolution of boundary layer thermodynamics in hurricane earl 2010 before and during rapid intensification abstractusing a combination of noaa p 3 aircraft tail doppler radar noaa and nasa dropsondes and buoy and drifter based sea surface temperature data different types of downdrafts and their infl

debris flow susceptibility mapping using frequency ratio and seed cells in a portion of a mountain international route dry central andes of argentina abstract debris flow and floods represent one of the main natural hazards that impact transport infrastructure causing serious damage economic losses and hinder regional economic development these processes are eventually associated with massive traffic cuts and direct damage to road structures to enable the prevention of such consequences this paper employs statistical modeling techniques various instability factors and geomorphological mapping to generate debris flow susceptibility maps in a portion of an important route on the dry andes of san juan in the agua negra river basin argentina a debris flows inventory map was prepared using satellite images and field checks the debris flows inventory was randomly divided into a model dataset 80 47 debris flows and remaining 20 12 debris flows data was used for validation purpose the instability factors chosen that influence debris flows occurrence were elevation slope angle slope aspect solar radiation topographic wetness index stream power index topographic position index melton ruggedness number terrain ruggedness index sediment transport capacity index plan curvature profile curvature lithology distance to road and proximity to stream using these factors six different models of debris flow susceptibility were calculated by frequency ratio fr lithology igneous complex was found to be important debris flows related factor in the study area the precision of the results was evaluated by receiver operating characteristic roc analysis according to the area under the curve auc the models of all flow track and natural breaks and all flow track and geometrical interval were 0 83 and 0 84 respectively showing a practically identical predictive capacity

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

morphometric characterization of a large scale rockslide and probable seismogenic origin of landslides on the western flank of central precordillera argentina abstract the distribution of late pleistocene to holocene rockslides in the western flank of the eastern mountain ranges of central precordillera 30 40 31 s has been analyzed to determine the triggering mechanisms the mode of failure was determined to be translational sliding this paper presents the results of research on one of the holocene rockslides located in the western flank of sierra de la dehesa which is composed of stratified limestones of early paleozoic age in order to characterize this slide high resolution satellite imagery interpretation was carried out along with the recognition of the landslide detachment zones and landslide bodies with the aim of reconstructing the pre slide topography the model proposed for this slide is a translational or planar slide as the mode of failure was along a broadly planar surface accompanied by shear or tensile fractures and joints the estimated rock volume involved is 1 24 mm 3 we compared rockslide occurrence patterns to slope topography lithology geological structures and seismicity records after analysis of the spatial relationships among all the slides and the distribution of seismic epicenters historical earthquakes and neighboring quaternary faults as seismogenic sources we hypothesize that these quaternary rockslides in the central precordillera have been triggered by shallow seismicity associated with active faults

combining airs and mls observations for three dimensional gravity wave measurement gravity waves play a critical role in transporting energy and momentum between the troposphere stratosphere and mesosphere satellite measurements provide a powerful tool to investigate these waves across the globe however many present methods cannot yield reliable estimates of wave momentum fluxes or the directions of these fluxes here we present a new method which addresses this problem by combining observations from atmospheric infrared sounder airs and microwave limb sounder mls in three dimensions the method allows direct estimation of horizontal and vertical wavelengths as well as wave amplitude this in turn allows estimation of both wave momentum flux and the full 3 d direction of propagation crucially including the horizontal direction the method thus allows separation of the data into for example eastward and westward momentum fluxes allowing estimation of the net atmospheric forcing due to these waves we illustrate this method with a proof of concept study over the andes arguably the largest source of gravity waves in the world we further critically assess the advantages and disadvantages of our method our study highlights the importance of the difference between net and absolute measures of momentum flux

a convective cell in a hurricane rainband abstract on 10 october 1983 the two noaa wp 3d aircraft completed a mission designed to provide airborne doppler radar data for a convective cell embedded in a weak rainband on the trailing side of hurricane raymond comparisons of the wind field produced from the pseudo dual doppler radar technique with in situ wind measurements suggest that the larger convective scale feature may be resolved if the sampling time is kept to a minimum the convective cell was found to move downband faster than any environmental winds but slightly slower than the winds found in the reflectivity core that delineates the cell in the core of the cell the tangential wind is increased and the radial inflow turns to outflow with respect to the circulation center the flow field demonstrates that the downband stratiform portion of a rainband is not from cells currently active since the updraft detrains upwind relative to the cell but rather it is due to the fallout from ice particles placed into the upper troposphere by clouds t

the evolution of hurricane humberto 2001 abstractin 2001 the national oceanic and atmospheric administration and the national aeronautical and space administration marshaled their resources to sample hurricane humberto for 3 successive days during the fourth convection and moisture experiment camex 4 humberto developed from a tropical storm into a category 2 hurricane despite the deep layer vertical shear of the environmental horizontal wind vws increasing markedly on the second and third days of sampling as exhibited in earlier studies the eyewall convection developed an azimuthal wavenumber 1 n 1 asymmetry as the vws increased horizontal divergence and vertical stability within 100 km of the eye exhibited persistent relationships to the vws vector the warm core evolved in an unexpected way the warm anomaly was initially located in the lower troposphere and built upward as the storm intensified the maximum temperature anomaly remained in the lower troposphere on all 3 days while the development of the upper tropospheric warm anom

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

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

objective determination of hurricane tracks from aircraft observations abstract an algorithm for location of hurricane centers by least squares using aircraft data has been developed as the aircraft traverses the eye lines of position normal to the wind are constructed each 100 m along its track an additional line of position is constructed normal to the track at the closest point of approach to the center the center coordinates are then chosen such that the sum of the squares of the normal distances from the center to the lines of position is minimized a cubic spline storm track is first constructed using centers based on winds in a coordinate system fixed to the earth a track based upon winds in moving storm centered coordinates may be obtained by transformation of the winds into such a coordinate system and iterative redetermination of the centers for intense hurricanes the centers can be located with an accuracy of 3 km and the mean motion over a period of four to six hours determined to within 4 of direction and 0 5 m s 1 of speed the details of the track osc

mountain wave drag in the stratosphere and mesosphere inferred from observed winds and a simple mountain wave parameterization scheme abstract a daily analysis of mountain wave propagation through observed global wind and temperature fields in january and august is presented winds and temperatures are obtained from the daily 18 level nmc climate analysis center mountain wave properties are deduced from a simple gravity wave parameterization scheme in which the effects of topographic anisotropy ridge orientation are explicitly included planetary waves in the northern winter stratosphere are found to play an important role in modulating the magnitude and distribution of inferred mountain wave drag in the middle atmosphere the aleutian anticyclone is found to effectively block mountain waves generated over western north america from reaching the mesosphere by inducing local mountain wave critical levels in the stratosphere stratospheric sudden warmings have a similar effect at all longitudes so that during months with sudden warmings have a similar effect at all longitudes so that during months with sudden warmings the average in

energy flux and wavelet diagnostics of secondary mountain waves abstract in recent years aircraft data from mountain waves have been primarily analyzed using velocity and temperature power spectrum and momentum flux estimation herein it is argued that energy flux wavelets i e pressure velocity wavelet cross spectra provide a more powerful tool for locating and classifying different types of mountain waves in the first part of the paper pressure velocity cross spectra using various linear mountain wave solutions are shown to be capable of disentangling collocated waves with different propagation directions and wavelength a field of group velocity vectors can also be determined in the second part the energy flux wavelet technique is applied to five cases of mountain waves entering the stratosphere from the terrain induced rotor experiment t rex in 2006 perturbation pressure along the flight track is determined using aircraft static pressure corrected hydrostatically with gps altitude in four of the cases collocated long up propagating and short down prop

orographic drag on islands in the nwp mountain grey zone the drag due to resolved and sub grid flow blocking and gravity waves is examined in simulations of flow over mountainous islands at grey zone resolutions in which the processes are neither well resolved or fully sub grid scale simulations of flows over narrow south georgia and broad new zealand mountain barriers are used to determine the behaviour of resolved and parametrized pressure drag and gravity wave momentum fluxes as a function of horizontal grid length analysis of the pressure drag in spectral space suggests that contributions from wavelengths shorter than 8 10 grid lengths are poorly resolved and that parametrization schemes should compensate for the missing drag from processes on these scales rather than strictly the sub grid scales the model performance for south georgia is such that the total resolved plus parametrized pressure drag is approximately invariant across a range of resolutions the parametrized resolved drag increases decreases as the grid length increases and the resolved and parametrized drag become comparable when the characteristic island wavelength is approximately 8 times the grid length this is not true when the same tuning of the drag parametrization is applied to new zealand in which case the parametrized drag increases too rapidly with increasing grid length however satisfactory results are obtained when the scheme is re tuned and it is shown that the optimal tuning for the two islands is consistent with scaling the sub grid orographic heights to be representative of the orography on longer length scales of up to 10 grid lengths the results suggest that drag schemes require orographic information on these longer scales rather than only the sub grid scale at the coarsest resolutions where the island wavelength and grid length are similar the parametrized drag is too small because the grid boxes are increasingly treated as sea points possible solutions to this problem are discussed

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

an extreme event in the eyewall of hurricane felix on 2 september 2007 abstractduring a routine penetration into hurricane felix late on 2 september 2007 noaa42 encountered extreme turbulence and graupel flight level horizontal wind gusts of over 83 m s 1 and vertical wind speeds varying from 10 m s 1 downward to 31 m s 1 upward and back to nearly 7 m s 1 downward within 1 min this led the plane to rise nearly 300 m and then return to its original level within that time though a dropwindsonde was released during this event the radars and data systems on board the aircraft were rendered inoperable limiting the amount of data obtained the feature observed during the flight is shown to be similar to that encountered during flights into hurricanes hugo 1989 and patricia 2015 and by a dropwindsonde released into a misovortex in hurricane isabel 2003 this paper describes a unique dataset of a small scale feature that appears to be prevalent in very intense tropical cyclones providing new evidence for eye eyewall mixing processes that may be related to intensity change

mountain waves and wakes generated by south georgia implications for drag parametrization high resolution simulations of flows over south georgia south atlantic are used to increase understanding of the likely influence of small isolated mountainous islands on the large scale flow and to ascertain the extent to which parametrization schemes can account for the missing drag in models where such islands are only partially resolved long duration 1 month austral winter forecasts with a horizontal grid spacing of 1 5 km are used to quantify the mountain wave momentum fluxes generated by the island and the low level drag associated with flow blocking dynamics the characteristics of the drag such as the occurrence of high and low drag states its dependence on wind direction and the spectral contributions to the mountain wave momentum flux are considered flow splitting and low level wave breaking are shown to be responsible for wake regions that extend for hundreds of kilometres from the island regions of deceleration are also evident in the stratosphere due to mountain wave dissipation the extent to which an orographic drag parametrization scheme can reproduce the drag is investigated by comparison with coarse resolution 15 km grid spacing simulations in which the orography is poorly resolved and a large proportion of the drag is parametrized it is demonstrated that the total of the resolved plus parametrized drag in these simulations closely resembles that at high resolution although it is underpredicted during instances of high drag simple modifications to the scheme which enhance the drag when the low level flow is approximately normal to the major axis of the subgrid orography are shown to rectify this the study demonstrates that at least for relatively simple isolated mountain ranges the drag and mountain wave momentum fluxes can be predicted in a deterministic sense by a well tuned parametrization scheme of suitable complexity although inclusion of stochastic effects might lead to yet further improvements

climatology of planetary waves in the northern stratosphere a 30 year record of subjectively analyzed daily temperature and geopotential height data from the lower and middle stratosphere 50 30 and 10 hpa is used to derive a climatology of planetary waves with zonal wavenumbers s 1 2 and 3 of temperature t and geopotential height z this should be useful as 1 a reference data set for intercomparison with shorter records and validation of general circulation models and 2 for fundamental understanding of the nature of stratospheric wave disturbances first seasonal december january and february statistics are presented the steady standing waves are strongest at 60 70 n and generally lead to northward eddy heat and momentum fluxes consistent with vertically propagating dissipated disturbances in broad agreement with previous studies based on shorter data sets at 30 hpa the stationary eddies provide about 50 60 of the net northward heat flux but the transients contribute a similar proportion to the net northward momentum flux statistical analysis of the transient wave amplitudes reveals unimodal distributions which are skew for higher wavenumbers transient variations in the eddy fluxes are shown to be mainly due to amplitude variations rather than changes in the barotropic or baroclinic structure of the eddies it is shown that changes in the geographical location of the waves contribute a considerable amount to the transience so that a composite mean based on the wave amplitude maximum contributes a much larger fraction of the net eddy fluxes than the stationary waves the importance of the long data record for these statistical distributions is emphasized by examining a 10 year subsample finally the occurrence of preferred flow regimes through the 30 year data record is examined neither trends nor definite links with possible external forcing mechanisms are found despite considerable low frequency biennial to decadal variability

low level kinematic thermodynamic and reflectivity fields associated with hurricane bonnie 1998 at landfall during 11 h on 26 august 1998 two noaa wp 3d aircraft deployed 85 global positioning system gps dropwindsondes within 2 of latitude of the circulation center of hurricane bonnie as it made landfall in north carolina about 75 of the sondes successfully collected data which were used to create a series of storm relative horizontal maps of kinematic and thermodynamic variables from 10 m to 2 km reflectivity fields were analyzed from the weather surveillance radar 1988 dopplers wsr 88ds located at wilmington and morehead city north carolina and the tail and lower fuselage radars aboard the wp 3ds gps sonde performance and deployment spacing is adequate to identify several aspects of the vortex these include 1 warm dry stable air in the offshore flow that results in reduced equivalent potential temperatures entering the southern portion of the eyewall 2 cooler air collocated with the upwelled water in the right rear quadrant and under the eyewall and 3 an atypical radial wind pattern with strong inflow southwest of the circulation center and outflow northeast of the center the strongly asymmetric structure found at 10 m becomes much more homogeneous by 2 km altitude no intense rainbands developed over land in the onshore flow nor did the bands in the onshore flow undergo any significant changes once they made landfall beyond the eyewall the offshore flow contained much less precipitation than the onshore portion of the storm characteristics beyond the eyewall appear to have been modulated by the proximity to land but hurricane intensity did not vary the authors infer that the lower energy content of the inflow was offset by the contraction of the eyewall

global survey of concentric gravity waves in airs images and ecmwf analysis concentric gravity waves cgws are atmospheric phenomena with ring shape perturbations originating in the troposphere they can propagate up to the ionosphere and thermosphere and dynamically couple the lower and upper atmosphere in this study we developed a novel ring detection algorithm to extract cgws from the atmosphere infrared sounder airs radiance data and the european center for medium range weather forecasting ecmwf analysis temperature in the stratosphere to produce the first global maps of such phenomena the algorithm is capable of estimating wave amplitude wavelength propagation direction and source location both airs and ecmwf data show a significant diurnal variation in wave propagation direction and generation in addition to strong seasonal variations in wavelength and amplitude occurrence of these ring waves is associated not only with tropical deep convections but also with summertime midlatitude convection wintertime extratropical jets and topography such as islands the high resolution ecmwf analysis data capture most of the cgw features but the wave amplitude is significantly weaker than airs observations showing few convectively generated cgws

application of logistic regression and frequency ratio in the spatial distribution of debris rockslides precordillera of san juan argentina abstract this study employs statistical modeling techniques and geomorphological mapping to analyze the distribution of debris rockslides in relation to altitude aspect slope angle lithology and distance to lineaments using optical remote sensing techniques with gis the study area includes a portion of the central precordillera of san juan around 32 s 69 w where few geomorphological studies have been conducted a debris rockslides inventory map was prepared using debris rockslides locations identified from satellite imageries a total of 35 debris rockslides were identified in an area of 288 13 km 2 with a total slide area of 6 36 km 2 all of the debris rockslides were rotational slides affecting upper ordovician and upper devonian deposits the volumes of debris rockslides were estimated using the sloping local base level technique that allows computing the possible pre rockslide topography and the bedrock deposits interface the relationship between the variables and the slide distribution was analyzed using the frequency ratio method and logistic regression models the analytical results show that lithology and slope exert major influences lithology is found to be the most important aspect in the study area

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

importance of the upper level warm core in the rapid intensification of a tropical cyclone 1 in this study the rapid intensification ri of tropical cyclone is examined using a 72 h cloud permitting prediction of hurricane wilma 2005 with a record breaking intensity of 882 hpa results show the formation of an upper level warm core from the descending air of stratospheric origin in the eye which coincides with the onset of ri it reaches the peak amplitude of more than 18 c from its initial conditions at the time of peak intensity the descending air is associated with the detrainment of convective bursts in the eyewall and it appears as perturbation cyclonic radial inflows above the upper outflow layer and causes the subsidence warming below we hypothesize that the upper divergent outflow layer favors the generation of a warm core by protecting it from ventilation by environmental flows use of the hydrostatic equation shows that the warm core of stratospheric origin contributes more than twice as much as the lower level warm column to the pressure change at the peak intensity of wilma results suggest that more attention be paid to the magnitude of storm relative flows and vertical wind shear in the upper troposphere rather than just vertical shear in the typical 850 200 hpa layer in order to reasonably predict the ri of tropical cyclones

mesoscale motion fields associated with a slowly moving gate convective band abstract the structure of the convective band of 14 september in the dense gate observing array is determined using wind and thermodynamic data primarily from multiple aircraft penetrations which are well distributed in the vertical and in time the well defined mesoscale features in the line which are 10 40 km in scale quasi two dimensional and persist for several hours determine the distribution of the convective scale features which are 5 km or less in size three dimensional not generally detectable for more than one flight leg at the leading edge a 30 km zone of strong ascent is computed from two dimensional continuity here lifting of the ambient air creates a favorable environment not found elsewhere for deep cumulonimbus clouds to develop their updrafts are weak 2 4 m s 1 on the average behind the updraft zone below 3 4 km is a broad descent zone it corresponds to the stratiform rain area and has little convection and some drying at lower levels on the average the mass flux by

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

antarctic nat psc belt of june 2003 observational validation of the mountain wave seeding hypothesis abstract satellite observations of polar stratospheric clouds pscs over antarctica in june 2003 revealed small nitric acid trihydrate nat particles forming suddenly along the vortex edge models suggest the trigger was mountain waves over the antarctic peninsula ap forming ice for nat nucleation we test this hypothesis by analyzing perturbations in stratospheric radiances from the atmospheric infrared sounder airs airs data show mountain waves over the ap on 10 14 june with no resolved wave activity before or after peak wave temperature amplitudes derived from independent 40 hpa channels all return values of 10 12 k in agreement with values used to model this nat event these observations support a nat wake from a small region of mountain wave activity over the ap as the source of this circumpolar nat outbreak

what is the source of the stratospheric gravity wave belt in austral winter abstractduring austral winter and away from orographic maxima or hot spots stratospheric gravity waves in both satellite observations and interim european centre for medium range weather forecasts ecmwf re analysis era interim data reveal enhanced amplitudes in a broad midlatitude belt extending across the southern ocean from east of the andes to south of new zealand the peak latitude of this feature slowly migrates poleward from 50 to 60 s wave amplitudes are much weaker across the midlatitude pacific ocean these features of the wave field are in striking agreement with diagnostics of baroclinic growth rates in the troposphere associated with midlatitude winter storm tracks and the climatology of the midlatitude jet this correlation suggests that these features of the stratospheric gravity wave field are controlled by geographical variations of tropospheric nonorographic gravity wave sources in winter storm tracks spontaneous adjustment emission from the midlatitude winter jet frontogenesi

low level inversions over the tropical pacific thermodynamic structure of the boundary layer and the above inversion moisture structure abstract the structure of the boundary layer over a broad region of the equatorial pacific is studied using dropwinsonde measurements made in january february may and june of 1979 low level inversions of sufficient strength to inhibit deep convection are found to be present in more than 50 of the soundings these inversions appear to play a critical role in regulating convective activity over the central and eastern pacific the tops of the inversions have an average pressure level of approximately 300 mb and show little latitudinal or longitudinal variation the majority of the inversion soundings approximately 70 have a reversal in the mixing ratio profile qreversal above the inversion that appears as a dry layer at the top of the inversion layer capped by a relatively moist layer this moist layer is on the average 2 g kg 1 more moist than the corresponding soundings that have no qreversal no systematic regional or temporal variations in the frequency of occurrence of the qreversal or the str

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

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

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

neotectonics and catastrophic failure of mountain fronts in the southern intra andean puna plateau argentina new cosmogenic nuclide exposure ages of rock avalanche deposits in front of sierra laguna blanca in the arid argentine puna plateau demonstrate the effects of westward propagation of reverse faulting and the influence of active faulting on slope oversteepening and subsequent gravitational collapse the 21 ne exposure ages of 8 superposed landslides with volumes 0 3 km 3 are between ca 150 and 430 ka and indicate an average recurrence interval of large gravitational mountain front failures of 27 5 k y for the ultimate 7 landslides landsliding did not occur after 150 ka along this sector of the sierra laguna blanca the termination of landsliding activity correlates with reverse fault propagation into the piedmont area of the sierra laguna blanca the exposure age of ca 130 ka of a tectonically uplifted terrace postdates initiation of fault activity in the piedmont region and the fault scarp height of 120 m indicates important continued uplift in the piedmont no further offsets occurred at the mountain front due to this lack of tectonic activity at the mountain front no further collapse has occurred indicating that in this environment catastrophic mountain front failure is mainly controlled by tectonically driven slope oversteepening

buoyancy of convective vertical motions in the inner core of intense hurricanes part ii case studies abstract this is the second of two papers on the buoyancy of convective vertical motions in the inner core of intense hurricanes this paper uses extensive airborne radar dropwindsonde and flight level observations in hurricanes guillermo 1997 and georges 1998 to illustrate typical azimuthal distribution of buoyant convection and demonstrate that the low level eye can be an important source region for buoyant eyewall convection in both hurricanes eyewall vertical velocity and radar reflectivity are asymmetric and exhibit persistent relationships with the direction of the environmental vertical wind shear mesoscale vertical motions exhibit a wavenumber 1 structure with maximum ascent downshear and weak descent upshear the mesoscale reflectivity maxima are located left of shear buoyant eyewall updraft cores and transient convective scale reflectivity cells are predominantly downshear and left of shear most eyewall downdraft cores that transport significant mass downward are located upshear nega

analyzing simulated convective bursts in two atlantic hurricanes part i burst formation and development abstractunderstanding the structure and evolution of the tropical cyclone tc inner core remains an elusive challenge in tropical meteorology especially the role of transient asymmetric features such as localized strong updrafts known as convective bursts cbs this study investigates the formation of cbs and their role in tc structure and evolution using high resolution simulations of two atlantic hurricanes dean in 2007 and bill in 2009 with the weather research and forecasting wrf model several different aspects of the dynamics and thermodynamics of the tc inner core region are investigated with respect to their influence on tc convective burst development composites with cbs show stronger radial inflow in the lowest 2 km and stronger radial outflow from the eye to the eyewall around z 2 4 km than composites without cbs asymmetric vorticity associated with eyewall mesovortices appears to be a major factor in some of the radial flow anomalies that lead to cb development the anomalous outfl

the application of gis based logistic regression for landslide susceptibility mapping in the kakuda yahiko mountains central japan as a first step forward in regional hazard management multivariate statistical analysis in the form of logistic regression was used to produce a landslide susceptibility map in the kakuda yahiko mountains of central japan there are different methods to prepare landslide susceptibility maps the use of logistic regression in this study stemmed not only from the fact that this approach relaxes the strict assumptions required by other multivariate statistical methods but also to demonstrate that it can be combined with bivariate statistical analyses bsa to simplify the interpretation of the model obtained at the end in susceptibility mapping the use of logistic regression is to find the best fitting function to describe the relationship between the presence or absence of landslides dependent variable and a set of independent parameters such as slope angle and lithology here an inventory map of 87 landslides was used to produce a dependent variable which takes a value of 0 for the absence and 1 for the presence of slope failures lithology bed rock slope relationship lineaments slope gradient aspect elevation and road network were taken as independent parameters the effect of each parameter on landslide occurrence was assessed from the corresponding coefficient that appears in the logistic regression function the interpretations of the coefficients showed that road network plays a major role in determining landslide occurrence and distribution among the geomorphological parameters aspect and slope gradient have a more significant contribution than elevation although field observations showed that the latter is a good estimator of the approximate location of slope cuts using a predicted map of probability the study area was classified into five categories of landslide susceptibility extremely low very low low medium and high the medium and high susceptibility zones make up 8 87 of the total study area and involve mid altitude slopes in the eastern part of kakuda mountain and the central and southern parts of yahiko mountain

a lagrangian trajectory view on transport and mixing processes between the eye eyewall and environment using a high resolution simulation of hurricane bonnie 1998 the transport and mixing characteristics of a large sample of air parcels within a mature and vertically sheared hurricane vortex are examined data from a high resolution 2 km horizontal grid spacing numerical simulation of real case hurricane bonnie 1998 are used to calculate lagrangian trajectories of air parcels in various subdomains of the hurricane namely the eye eyewall and near environment to study the degree of interaction transport and mixing between these subdomains it is found that 1 there is transport and mixing from the low level eye to the eyewall that carries air possessing relatively high values of equivalent potential temperature e which can enhance the efficiency of the hurricane heat engine 2 a portion of the low level inflow of the hurricane bypasses the eyewall to enter the eye and this air both replaces the mass of the low level eye and lingers for a sufficient time order 1 h to acquire enhanced entropy characteristics through interaction with the ocean beneath the eye 3 air in the mid to upper level eye is exchanged with the eyewall such that more than half the air of the eye is exchanged i n5hi nthis case of a sheared hurricane and 4 that one fifth of the mass in the eyewall at a height of 5 km has an origin in the mid to upper level environment where e is much less than in the eyewall which ventilates the ensemble average eyewall e by about 1 k implications of these findings for the problem of hurricane intensity forecasting are briefly discussed

a multiscale numerical study of hurricane andrew 1992 part ii kinematics and inner core structures despite considerable research understanding of the temporal evolution of the inner core structures of hurricanes is very limited owing to the lack of continuous high resolution observational data of a storm in this study the results of a 72 h explicit simulation of hurricane andrew 1992 with a grid size of 6 km are examined to explore the inner core axisymmetric and asymmetric structures of the storm during its rapid deepening stage based on the simulation a conceptual model of the axisymmetric structures of the storm is proposed most of the proposed structures confirm previous observations the main ingredients include a main inflow outflow in the boundary layer upper troposphere with little radial flow in between a divergent slantwise ascent in the eyewall a penetrative dry downdraft at the inner edge of the eyewall and a general weak subsiding motion in the eye with typical warming drying above an inversion located near an altitude of about 2 3 km the storm deepens as the axes of these features contract it is found that the inversion divides the eye of the hurricane vertically into two parts with a deep layer of warm dry air above and a shallow pool of warm moist air below the air aloft descends at an average rate of 5c m s 21 and has a residency time of several days in contrast the warm moist pool consists of air from the main inflow and penetrative downdrafts offset somewhat by the air streaming in a returning outflow into the eyewall in the lowest 2 km it is subject to the influence of the upward heat and moisture fluxes over the underlying warm ocean the warm moist pool appears to play an important role in supplying high ue air for deep convective development in the eyewall the penetrative downdraft is dry and originates from the return inflow in the upper troposphere and it is driven by sublimative evaporative cooling under the influence of the asymmetric radial inflow of dry cold air in the midtroposphere it penetrates to the bottom of the eye azimuthally downshear with a width often greater than 100 km in a radially narrow zone along the slantwise inner edge of the eyewall it is further shown that all the meteorological fields are highly asymmetric whereas the storm scale flow features a source sink couplet in the boundary layer and dual gyres aloft the inner core structures exhibit alternative radial inflow and outflow and a series of inhomogeneous updrafts and downdrafts all the fields tilt more or less with height radially outward and azimuthally downshear furthermore pronounced fluctuations of air motion are found in both the eye and the eyewall sometimes a deep layer of upward motion appears at the center of the eye all these features contribute to the trochoidal oscillation of the storm track and movement the main steering appears to be located at the midtroposphere 4 5 km and the deep layer mean winds represent well the movement of the hurricane

atypical thermodynamic profiles in hurricanes the global positioning system dropwindsondes deployed in hurricane bonnie on 26 august 1998 with supporting deployments in hurricanes mitch 1998 and humberto 2001 are used to identify three unusual thermodynamic structures in the lower cloud and subcloud layers two of these structures impact the energy content of the inflow and therefore the intensity of the hurricane first positive lapse rates of equivalent potential temperature are found near the top of the inflow these layers insulate the inflow from the negative impacts of entrainment mixing and promote rapid energy increases especially near the eyewall the second structure is a rapid decrease of equivalent potential temperature adjacent to the sea surface this is essentially a prominent surface layer that owes its existence to both higher moisture content and a superadiabatic lapse rate the steep lapse rate most often occurs under and near the eyewall where wind speeds at the surface exceed hurricane force the author speculates that water loading from spray increases the residence time of air parcels in the surface layer contributing to the creation of this structure the third feature is a moist absolutely unstable layer previously identified by bryan and fritsch for the midlatitudes these layers are found adjacent to the eyewall in rainbands and in the hub cloud within the eye and are evidence of mesoscale or vortex scale convergence and the very modest instabilities often found in the core of a hurricane

tropical cyclone eye thermodynamics in intense tropical cyclones sea level pressures at the center are 50 100 hpa lower than outside the vortex but only 10 30 hpa of the total pressure fall occurs inside the eye between the eyewall and the center warming by dry subsidence accounts for this fraction of the total hydrostatic pressure fall convection in the eyewall causes the warming by doing work on the eye to force the thermally indirect subsidence soundings inside hurricane eyes show warm and dry air aloft separated by an inversion from cloudy air below dewpoint depressions at the inversion level typically 850 500 hpa are 10 30 k rather than the 100 k that would occur if the air descended from tropopause level without dilution by the surrounding cloud the observed temperature and dewpoint distribution above the inversion can however be derived by 100 hpa of undilute dry subsidence from an initial sounding that is somewhat more stable than a moist adiabat it is hypothesized that the air above the inversion has remained in the eye since it was enclosed when the eyewall formed and that it has subsided at most a few kilometers the cause of the subsidence is the enclosed air s being drawn downward toward the inversion level as the air below it flows outward into the eyewall shrinkage of the eye s volume is more than adequate to supply the volume lost as dry air is incorporated into the eyewall or converted to moist air by turbulent mixing across the eye boundary the moist air below the inversion is in thermodynamic contact with the sea surface its moisture derives from evaporation of seawater inside the eye frictional inflow of moist air under the eyewall and from moist downdrafts induced as condensate mixes into the eye the moist air s residence time in the eye is much shorter than that of the dry air above the inversion the height of the inversion is determined by the balance between evaporation inflow and inward mixing on one hand and loss to the eyewall updrafts on the other

secondary generation of gravity waves associated with the breaking of mountain waves abstract the generation of small scale gravity waves associated with the breaking of mountain waves in the stratosphere has been simulated within a fully compressible nonhydrostatic two dimensional numerical model the model includes the mesosphere and offers sufficiently high spatial resolution to characterize the breaking and generation of gravity waves in the stratosphere the mean flow is initialized by cira86 at 40 n in february a bell shaped mountain with 30 km half width and 1 5 km height is located in the bottom of the modeled domain the primary wave forced by the mountain propagates into the stratosphere with amplitude increasing with height and subsequently breaks in the lower stratosphere after the primary wave breaking significant wave activity is simulated in the stratosphere these secondary waves are generated at both the upstream and the downstream edges of the breaking zone analysis is mostly focused on downstream small scale waves the horizontal and vertical wavelengths of the se

concentric eye walls secondary wind maxima and the evolution of the hurricane vortex abstract research aircraft observations in recent hurricanes support the model of shapiro and willoughby 1982 for the tropical cyclone s response to circularly symmetric convective heat sources convective rings in both nature and the numerical model the tangential wind commonly increases rapidly just inside the radius of maximum wind and decreases inside the eye near the central axis of the vortex thus both secondary outer wind maxima and eyewall wind maxima often contract as they intensify this response is independent of the horizontal spatial scale of the maximum an outer maximum is frequently observed to constrict about a pre existing eye and replace it this chain of events often coincides with a weakening or at least a pause in intensification of the vortex as a whole the concentric eye phenomenon is a common but by no means universal feature of tropical cyclones it is most frequently observed in intense highly symmetric systems

structural changes preceding rapid intensification in tropical cyclones as shown in a large ensemble of idealized simulations abstractstructural changes that precede rapid intensification ri of tropical cyclones tcs are examined in a full physics model by conducting a large ensemble 270 of idealized tc simulations the processes leading to ri in a representative case with moderate shear are consistent with previous studies for weakly sheared cases the most distinct changes are that the vortex tilt and the vortex size begin to decrease more rapidly 6 h before the onset of ri a vorticity budget analysis for the upper layer around the low level center reveals that the vertical vorticity is increased by vertical advection stretching and tilting terms before ri whereas the horizontal advection is small thus the upright vortex structure is not achieved through a vortex alignment process but rather is built upward by deep convection the ensemble simulations are generated by changing the intensity and size of the initial vortex the magnitude of vertical wind shear and the translation speed the ensemble members that show

the role of polygonal eyewalls in rapid intensification of typhoon megi 2010 abstracthigh resolution numerical experiments for typhoon megi 2010 in the western north pacific are conducted using the advanced research version of the weather research and forecasting wrf mo

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

buoyancy of convective vertical motions in the inner core of intense hurricanes part i general statistics abstract the buoyancy of hurricane convective vertical motions is studied using aircraft data from 175 radial legs collected in 14 intense hurricanes at four altitudes ranging from 1 5 to 5 5 km the data of each leg are initially filtered to separate convective scale features from background mesoscale structure convective vertical motion events called cores are identified using the criteria that the convective scale vertical velocity must exceed 1 0 m s 1 for at least 0 5 km a total of 620 updraft cores and 570 downdraft cores are included in the dataset total buoyancy is calculated from convective scale virtual potential temperature pressure and liquid water content using the mesoscale structure as the reference state core properties are summarized for the eyewall and rainband regions at each altitude characteristics of core average convective vertical velocity maximum convective vertical velocity and diameter are consistent with previous studies of hurricane convection most cores are superi

the giant paleolandslide deposits of tafi del valle tucuman province argentina abstract in the present study seven landslide deposits that took place during the pleistocene in the northern part of tafi del valle tucuman province argentina are described the recognition and mapping of them were carried out using satellite images aerial photograph interpretation and field survey the analysis of the area covered by the deposits and their runout distances were undertaken using aerial photographs at a scale of 1 50 000 and the software image tool all the deposits overcome the 106 m3 of volume with smaller coefficients of friction at 0 22 that gives an idea of the great mobility that they had reaching average speeds 100 km h these deposits could have originated as a consequence of a combination of internal slow deformation and fragmentation under periglacial conditions followed by a sudden collapse of the rock mass generated by strong earthquakes of magnitudes 6 at the base of the cumbres calchaquies ranges

low level thermodynamic kinematic and reflectivity fields of hurricane guillermo 1997 during rapid intensification abstract from 0600 utc 2 august to 1200 utc 3 august hurricane guillermo 1997 deepened by 54 hpa over the eastern north pacific ocean easily exceeding the thresholds that define rapid intensification ri the noaa wp 3ds observed a portion of this ri with similar two aircraft missions on consecutive days the aircraft jettisoned 70 successful global positioning system gps dropwindsondes or gps sondes which reveal how conditions in the lower troposphere on the octant to quadrant scale evolved within 250 km of the eye reflectivity fields demonstrate that the deepening is correlated with a spiraling in of the northern eyewall that reduces the eye diameter by 10 km this behavior contrasts the more uniform contraction witnessed during eyewall replacement cycles mixing between the lower eye and eyewall as detailed by other investigators appears to have triggered the reduction in the eye diameter after ri the eyewall remains asymmetrical with the tallest echo tops and heaviest rain rates located o

secondary gravity waves generated by breaking mountain waves over europe a strong mountain wave observed over central europe on 12 january 2016 is simulated in 2d under two fixed background wind conditions representing opposite tidal phases the aim of the simulation is to investigate the breaking of the mountain wave and subsequent generation of nonprimary waves in the upper atmosphere the model results show that the mountain wave first breaks as it approaches a mesospheric critical level creating turbulence on horizontal scales of 8 30 km these turbulence scales couple directly to horizontal secondary waves scales but those scales are prevented from reaching the hermosphere by the tidal winds which act like a filter initial secondary waves that can reach the thermosphere range from 60 to 120 km in horizontal scale and are influenced by the scales of the horizontal and vertical forcing associated with wave breaking at mountain wave zonal phase width and horizontal wavelength scales large scale nonprimary waves dominate over the whole duration of the simulation with horizontal scales of 107 300 km and periods of 11 22 minutes the thermosphere winds heavily influence the time averaged spatial distribution of wave forcing in the thermosphere which peaks at 150 km altitude and occurs both westward and eastward of the source in the 2 ut background simulation and primarily eastward of the source in the 7 ut background simulation the forcing amplitude is 2 that of the primary mountain wave breaking and dissipation this suggests that nonprimary waves play a significant role in gravity waves dynamics and improved understanding of the thermospheric winds is crucial to understanding their forcing distribution

mass movement in cordon de las osamentas de la flecha river basin san juan argentina abstract the de la flecha river basin is located to the southwest of san juan province at around 31 50 s 68 57 w in this area a total of twenty debris rock slides in the cordon de las osamentas were mapped and studied the mode of failure of each was determined to be a rotational slide the areal extent of the smallest observable landslide body is approximately 0 58 km2 and the largest is 367 76 km2 the slides were detected through high resolution satellite imagery interpretation digital elevation models and field surveys by identifying both the landslide detachment zones and landslide bodies based on the geographic information system gis the slides have varying controlling factors including lithology and slope which seem to be the main controlling factors in causing slope instability the spatial relationships among the landslides and the distribution of seismic epicentres historical earthquakes and quaternary faults maradona las osamentas papagayos faults la chilca and el mocho faults were analysed these gravitational movements were triggered by seismic shocks associated with active faults

two distinct regimes in the kinematic and thermodynamic structure of the hurricane eye and eyewall abstract using aircraft flight level data the present work demonstrates that the kinematic and thermodynamic distributions within the eye and eyewall of strong hurricanes are observed to evolve between two distinct regimes in the first regime angular velocity is greatest within the eyewall and relatively depressed within the eye in the second regime radial profiles of angular velocity are nearly monotonic with maxima found at the eye center considering sequential profiles within individual hurricanes the authors find that the evolution of the kinematic distribution is often marked by a transition from the first regime to the second the transition can occur in less than 1 h also noted during the transition are dramatic changes in the thermodynamic structure of the hurricane prior to the transition regime 1 the eye is typically very warm and dry and the equivalent potential temperature is often elevated within the eyewall and relatively depressed within the eye after the transition regime 2

an axisymmetric view of concentric eyewall evolution in hurricane rita 2005 abstractmultiplatform observations of hurricane rita 2005 were collected as part of the hurricane rainband and intensity change experiment rainex field campaign during a concentric eyewall stage of the storm s life cycle that occurred during 21 22 september satellite aircraft dropwindsonde and doppler radar data are used here to examine the symmetric evolution of the hurricane as it underwent eyewall replacement during the approximately 1 day observation period developing convection associated with the secondary eyewall became more symmetric and contracted inward latent heating in the emergent secondary eyewall led to the development of a distinct toroidal overturning circulation with inertially constrained radial inflow above the boundary layer and compensating subsidence in the moat region properties that are consistent broadly with the balanced vortex response to an imposed ring of diabatic heating outside the primary eyewall the primary eyewall s convection became more asymmetric during

reply to comments on nonlinear response of a tropical cyclone vortex to prescribed eyewall heating with and without surface friction in tcm4 implications for tropical cyclone intensification

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

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

mesoscale and convective scale characteristics of mature hurricanes part ii inner core structure of hurricane allen 1980 abstract the eyewall structure of hurricane alien is examined from analyses of multiple aircraft data on two days 5 and 8 august 1980 these data sets are unique in that for the first time three instrumented aircraft executed coordinated radial penetrations of the eyewall at multiple levels the data collected on 5 august illustrate the persistence of various features on horizontal scales 10 km over several hours composite cross sections constructed from the 8 august data show similar structure although the eye diameter had decreased to less than half that of 5 august the convergence of air in the eyewall was highly two dimensional this convergence supported organized ascent that was along the inner edge of the high reflectivity region and displaced inward several kilometers from the radius of maximum wind rmw a mean eyewall updraft of 5 6 m s 1 is computed from integration of the two dimensional continuity equation embedded within the two dimensional eyewall were cores of high reflectivity t

distribution of landslides along the andean active orogenic front argentinean precordillera 31 33 s abstract as one of the main environmental effects of earthquakes the distribution of landslides could reflect regional neotectonic activity to that end we carried out an inventory of landslides along the precordillera range 31 33 s comprising the most seismically active region of argentina main quaternary deformation is concentrated in this western central part of the country associated with active faults linked to intense shallow seismic activity

a numerical study of typhoon megi 2010 part i rapid intensification abstracttyphoon megi 15w was the most powerful and longest lived tropical cyclone tc over the western north pacific during 2010 while it shared many common features of tcs that crossed luzon island in the northern philippines megi experienced unique intensity and structural changes which were reproduced reasonably well in a simulation using the advanced research weather research and forecasting model arw wrf with both dynamical initialization and large scale spectral nudging in this paper processes responsible for the rapid intensification ri of the modeled megi before it made landfall over luzon island were analyzed the results show that megi experienced ri over the warm ocean with high ocean heat content and decreasing environmental vertical shear the onset of ri was triggered by convective bursts cbs which penetrate into the upper troposphere leading to the upper tropospheric warming and the formation of the upper level warm core in turn cbs with their roots inside of the eyewall in

application of frequency ratio and logistic regression to active rock glacier occurrence in the andes of san juan argentina this study employs statistical modeling techniques and geomorphological mapping to analyze the distribution of active rock glaciers in relation to altitude aspect slope lithology and solar radiation using optical remote sensing techniques with gis the study area includes a portion of the dry andes of the cordillera frontal of san juan around 30 s latitude where few geomorphological studies have been conducted over 155 rock glaciers have been identified and 85 are considered active the relationship between the variables and the rock glaciers distribution was analyzed using the frequency ratio method and logistic regression models the analytical results show that elevations 3824 m a s l a south facing or east facing aspect areas with relatively low solar radiation and slope between 2 and 20 favor the existence of the rock glaciers and demonstrate that lithology and slope exert major influences

polygonal eyewalls asymmetric eye contraction and potential vorticity mixing in hurricanes hurricane eyewalls are often observed to be nearly circular structures but they are occasionally observed to take on distinctly polygonal shapes the shapes range from triangles to hexagons and while they are often incomplete straight line segments can be identified other observations implicate the existence of intense mesovortices within or near the eye region is there a relation between polygonal eyewalls and hurricane mesovortices are these phenomena just curiosities of the hurricane s inner core circulation or are they snapshots of an intrinsic mixing process within or near the eye that serves to determine the circulation and thermal structure of the eye as a first step toward understanding the asymmetric vorticity dynamics of the hurricane s eye and eyewall region these issues are examined within the framework of an unforced barotropic nondivergent model polygonal eyewalls are shown to form as a result of barotropic instability near the radius of maximum winds after reviewing linear theory simulations with a high resolution pseudospectral numerical model are presented to follow the instabilities into their nonlinear regime when the instabilities grow to finite amplitude the vorticity of the eyewall region pools into discrete areas creating the appearance of polygonal eyewalls the circulations associated with these pools of vorticity suggest a connection to hurricane mesovortices at later times the vorticity is ultimately rearranged into a nearly monopolar circular vortex while the evolution of the finescale vorticity field is sensitive to the initial condition the macroscopic end states are found to be similar in fact the gross characteristics of the numerically simulated end states are predicted analytically using a generalization of the minimum enstrophy hypothesis in an effort to remove some of the weaknesses of the minimum enstrophy approach a maximum entropy argument developed previously for rectilinear shear flows is extended to the vortex problem and end state solutions in the limiting case of tertiary mixing are obtained implications of these ideas for real hurricanes are discussed

an air sea interaction theory for tropical cyclones part ii evolutionary study using a nonhydrostatic axisymmetric numerical model abstract in part i of this study an analytical model for a steady state tropical cyclone is constructed on the assumption that boundary layer air parcels are conditionally neutral to displacements along the angular momentum surfaces of the hurricane vortex the reversible thermodynamics implied by this assumption allows the mature storm to be thought of as a simple carnot engine acquiring heat at the high temperature ocean surface and losing heat near the low temperature tropopause although the oceanic heat source is universally recognized as the sine qua non for the mature hurricane there is also wide acceptance of conditional instability of the second kind cisk which makes no specific reference to surface heat fluxes as the formative mechanism this ambivalence is seen in that all numerical simulation studies find it essential to have transfer from the ocean surface yet all start from a conditionally unstable atmosphere the hypothesis put forward in part i based on the steady state theory is t

eye excess energy and the rapid intensification of hurricane lili 2002 abstract over 4 5 days noaa and u s air force personnel in reconnaissance aircraft deployed 44 global positioning system dropwindsondes gps sondes in the eye of hurricane lili 2002 the vertical profiles derived from these gps sondes were used to determine the evolution of the height of the inversion presence and height of the hub cloud the height of the lifted condensation layer and the depth of the mixed layer as lili deepened underwent rapid intensification ri and eventually rapid decay the lower portion of the eye moistened and the lapse rate became moist adiabatic the inversion layer rose as lili intensified and then quickly fell over 1500 m at the beginning of ri comparison of the equivalent potential temperature e of the eye with that in the eyewall revealed that like many other hurricanes the eye was a reservoir for the warmest e the authors define a variable called eye excess energy that is a function of the difference in e between the eye and the eyewall and the depth over