spatial modeling of discontinuous geologic attributes with geotechnical applications geologic data obtained by drilling investigations field measurements and laboratory tests are irregularly distributed with respect to location both horizontally and vertically spatial discontinuities impact soil classification hydraulic conductivity and chemical content in this study a three dimensional modeling method which combines the optimization principle method and a stochastic simulation method was developed optsim this method consists of three steps the transformation of geologic attributes into binary 0 or 1 under certain thresholds the three dimensional interpolation of these transformed binary data and the construction of conditional cumulative distribution functions ccdf by repeatedly changing the threshold and interpolation analysis the monte carlo method was then used to inversely determine the attributes from the constructed ccdfs three types of attribute expressed by value code and class were examined the optsim was applied to spatial modeling of geotechnical structures in the kumamoto plain southwest japan using two kinds of data lithologic units and physical soil properties resistivity data obtained by electric logging and the locations of screens were linked to geologic distribution the constructed model contributed to the location of chief aquifers and estimates of amount of shallow groundwater a combination of granular composition n value and water content was examined transgression and regression patterns following the last glacial stage were also inferred through this analysis in both applications discontinuities in lithologic units and soil properties resulting from fault movements and sea level changes were successfully expressed in the distribution models

critical levels and mixing layers induced by convectively generated gravity waves during cepex we study data from the central equatorial pacific experiment in particular the soundings providing temperature pressure wind and ozone profiles and we link them to the large scale conditions deduced from the analyses of the european centre for medium range weather forecasts to the west of the date line the mean wind shows a strong shear at the tropopause between the easterlies of the upper troposphere and the westerlies of the lower stratosphere these are conditions propitious to the formation of critical levels for quasi stationary gravity waves generated by deep convection the measured wind profiles show the main characteristics of the encounter of a wave with its critical level and in the ozone and potential temperature profiles the existence of a conspicuous mixing layer in the vicinity of this critical level our interpretation that the mixing layer is a consequence of the critical level is supported by numerical simulations with a nonlinear time dependent two dimensional model the occurrence of a mixing layer in the tropopause structure seems to be characteristic of large scale equatorial convective areas during westerly phases of the quasi biennial oscillation

a numerical study of three dimensional gravity waves triggered by deep tropical convection and their role in the dynamics of the qbo abstract a 3d mesoscale model is used to study the structure of convectively triggered gravity waves in the tropics and their role in the dynamics of the middle atmosphere simulations with three stratospheric background zonal wind cases are examined in the first case the background wind profile is constant the other two are representative of the easterly and westerly phases of the quasi biennial oscillation qbo spectral analysis is used to link the structure of the triggered gravity waves to the dominant vertical wavelength of the latent heating within the convection in the qbo wind shear cases upward propagating gravity waves are damped as they approach their critical layer the signature of critical layer absorption is clearly visible in the profiles of vertical momentum flux divergence in the simulations with open boundary conditions the response to vertical momentum flux divergence takes the form of large dynamic pressure differences between the east and west boundaries together with acceler

intensity of thunderstorm generated turbulence revealed by large eddy simulation thunderstorms are characterized by turbulent processes that constitute an important aviation hazard and cause vertical transport of atmospheric constituents turbulence occurs within cloud and in the surrounding clear air but despite its importance the characteristics of thunderstorm generated turbulence and its spatial distribution are poorly understood especially outside of cloud here we use large eddy simulation to characterize turbulence generated by a canonical thunderstorm the simulation identifies regions of notable three dimensional anisotropic turbulence more than 5 km above the storm in a shallow layer above the storm s anvil and a horizontally asymmetric pattern of weaker turbulence that extends more than 50 km horizontally away from the cloud our results provide the first continuous estimate of turbulence intensity in and around thunderstorms and represent a major step toward improved turbulence avoidance methods the results have broader implications for understanding the fundamental aspects of how thunderstorms affect their environment through vertical exchange processes

potential vorticity anomalies associated with squall lines abstract this study involves observations and model simulations of potential vorticity anomalies in the wake of midlatitude squall lines using data from the oklahoma kansas pre storm experiment we analyze potential vorticity fields near two squall lines one with and one without a trailing stratiform region from this observational analysis we suggest that squall lines with trailing stratiform regions can leave large positive midtropospheric potential vorticity anomalies in their wake to further interpret these observations we consider a two dimensional version of semigeostrophic theory formulated in isentropic and geostrophic coordinates which results in a simple potential pseudodensity inverse potential vorticity equation using apparent heat source fields that model those computed diagnostically from pre storm data we find that theory does indeed predict large midtropospheric potential vorticity anomalies for model squall lines with a trailing stratiform region but not for model squall lines t

influences of gravity waves on convectively induced turbulence cit a review thunderstorms are known to produce turbulence such turbulence is commonly referred to as convectively induced turbulence or cit and can be hazardous to aviation although this turbulence can occur both within and outside the convection out of cloud cit is particularly hazardous since it occurs in clear air and cannot be seen by eye or onboard radar furthermore due to its small scale and its ties to the underlying convection it is very difficult to forecast guidelines for out of cloud cit avoidance are available but they are oversimplified and can be misleading in the search for more appropriate and physically based avoidance guidelines considerable research has been conducted in recent years on the nature of the phenomenon and in particular its connection to gravity waves generated by the convection this paper reviews the advances in our understanding of out of cloud cit and its relation to convective gravity waves and provides several detailed examples of observed cases to elucidate some of the underlying dynamics

forcing of secondary waves by breaking of gravity waves in the mesosphere 1 previous simulations with a two dimensional cloud resolving model have shown that gravity waves generated by tropospheric convection can propagate into the mesosphere where they break and produce local heating and local accelerations the forcing associated with this wave breaking excites secondary gravity waves that propagate upward and downward away from the wave breaking region typical horizontal and vertical scales of individual centers of forcing caused by wave breaking are 25 km and 10 20 km respectively groups of individual forcing centers tend to be aligned along phase lines of the primary waves in the region east of the storm center the forcing groups move eastward and downward with the primary wave phase lines while individual forcing centers move upward to a first approximation the secondary gravity waves are a linear response to the localized momentum and thermal forcing associated with wave breaking though the forcing is itself generated by the nonlinear wave breaking process the secondary waves can be derived from knowledge of the temporal and spatial variability of the forcing

stationary gravity wave structure in flows with directional wind shear most theoretical studies of flow over mountains assume that the wind direction is constant for two dimensional orographic ridges this is not an issue since only the component of the wind across the ridge forces internal gravity waves a special case of rectilinear flow is when the wind component changes sign i e the wind direction changes discontinuously through 180 degrees such a point is a critical level for all stationary gravity waves for isolated three dimensional mountains the gravity wave response comprises waves of all azimuthal orientations and each of these may have a different critical level height depending on whether the wind backs or veers with height using a combination of ray tracing methods and stationary phase solutions the structure of the stationary hydrostatic gravity wave field generated by an isolated mountain is studied for a simple wind field which backs with height in contrast to the behaviour for unidirectional flow wave action does not accumulate indefinitely beneath the critical level but is continuously advected downwind by the component of the wind parallel to the phase lines instead of the wave energy becoming unbounded following a ray as in the 2d case the wave energy decays to zero along a trailing wake zone downwind of the mountain along phase lines this is just an extension of the asymptotic wake found in the linear solutions of smith for constant flow over an isolated mountain the work described here underlines the desirability of including the effects of selective critical level absorption in the gravity wave drag parametrization schemes of numerical weather prediction models

the influence of convectively generated thermal forcing on the mesoscale circulation around squall lines abstract the dynamical processes that determine the kinematic and thermodynamic structure of the mesoscale region around 2d squall lines are examined using a series of numerical simulations the features that develop in a realistic reference simulation of a squall line with trailing stratiform precipitation are compared to the features generated by a steady thermal forcing in a dry simulation with no microphysical parameterization the thermal forcing in the dry simulation is a scaled and smoothed time average of the latent heat released and absorbed in and near the leading convective line in the reference simulation the mesoscale circulation in the dry simulation resembles the mesoscale circulation in the reference simulation and around real squall lines it includes an ascending front to rear flow a midlevel rear inflow a mesoscale up and downdraft an upper level rear to front flow ahead of the thermal forcing and an upper level cold anomaly to the rear of the thermal forcing it is also shown t

the role of convectively generated rear inflow jets in the evolution of long lived mesoconvective systems abstract in this study the structure of convectively generated rear inflow jets and their role in the evolution of long lived mesoconvective systems are investigated through an analysis of idealized three dimensional simulations using a nonhydrostatic cloud model rear inflow jets are generated within these systems in response to the upshear tilting of the convective circulation as the horizontal buoyancy gradients along the back edge of the expanding system create a circulation that draws midlevel air in from the rear within this framework a wide range of rear inflow strengths and structures are produced depending on the magnitude of the ambient convective available potential energy cape and the vertical wind shear in general for environments characterized by weak to moderate vertical wind shear and weak to moderate cape the rear inflow jet descends and spreads along the surface well behind the leading edge of the gust front and the subsequent convective activity becomes weaker however for e

vertical fluctuation energy in united states high vertical resolution radiosonde data as an indicator of convective gravity wave sources 1 convectively generated internal gravity waves at extratropical latitudes are difficult to identify by climatological analysis of the temperature and horizontal wind fields from radiosonde profiles using traditional analysis methods here we show that by analyzing ascent rate profiles we define a new variable vertical fluctuation energy ve we can identify convection sources in climatological analyses analysis of a 9 year time series 1998 2006 of united states high vertical resolution radiosonde data shows that ve maximizes in summer in midlatitudes within the troposphere 2 8 9 km and peaks at local afternoon early evening during the summer over most of the contiguous united states furthermore the apparent dominant vertical wavelength based on fourier analysis of the low pass filtered ascent rate fluctuations also increase and decrease with ve both on diurnal and seasonal timescales ve in the lower stratosphere however does not show this same relationship to convection but analysis of the vertical wavelength does show some of the features seen in tropospheric ve unlike midlatitude stations ve within both the troposphere and the lower stratosphere over tropical western pacific island stations is highly correlated with convective precipitation and inversely correlated with outgoing longwave radiation we interpret this difference by using the 4 d gravity wave regional or global ray tracer ray tracing model with a source spectrum representative of a convection source

the role of vertical shear on aviation turbulence within cirrus bands of a simulated western pacific cyclone abstractat 0300 utc 9 september 2010 commercial aircraft traveling between tokyo and hawaii encountered regions of moderate and severe intensity turbulence at about 12 km elevation in or just above banded structures in the cirrus anvil associated with an oceanic cyclone located off the east coast of japan the generation mechanisms of the cirrus bands and turbulence are investigated using the advanced research weather research and forecasting model with five nested domains having a finest horizontal grid spacing of 370 m the simulation reproduces the satellite observed patterns of cloud brightness including the bands and suggests that synoptic scale vertical shear within the anvil cloud layer and radiative effects including longwave cooling at cloud top and warming at cloud base act together to produce banded structures within the southern edge of the cirrus cloud shield the character of the bands within the nearly neutral or convectively unstable layer of the cirrus shield is similar to boundary l

gravity waves compensating subsidence and detrainment around cumulus clouds abstract gravity waves play an important role in the redistribution of heat and moisture in a deep convecting cloud field we explore this role in a two dimensional numerical experiment on a simple moist convecting system consisting of an isolated long lasting nonprecipitating cloud in a calm atmosphere with no surface forcing the cloud develops a horizontally averaged density variation with height which is neutrally buoyant with respect to a moist adiabatic the buoyancy difference between the cloud and the undisturbed sounding produces circulations that can be understood as spreading gravity waves which adjust the environmental buoyancy to be equal to the cloud buoyancy by compensating subsidence unlike the circulations inside clouds this adjustment takes place without turbulent mixing hence the buoyancy adjustment time t1 during which the environment comes into rough buoyant equilibrium with the clouds is much shorter than the mixing time t2 which it takes a tracer initially concentrated at s

convection permitting simulations of the environment supporting widespread turbulence within the upper level outflow of a mesoscale convective system abstract widespread moderate turbulence was recorded on three specially equipped commercial airline flights over northern kansas near the northern edge of the extensive cirrus anvil of a nocturnal mesoscale convective system mcs on 17 june 2005 a noteworthy aspect of the turbulence was its location several hundred kilometers from the active deep convection i e large reflectivity regions of the mcs herein the mcs life cycle and the turbulence environment in its upper level outflow are studied using rapid update cycle ruc analyses and cloud permitting simulations with the weather research and forecast model wrf it is demonstrated that strong vertical shear beneath the mcs outflow jet is critical to providing an environment that could support dynamic e g shearing type instabilities conducive to turbulence comparison of a control simulation to one in which the temperature tendency due to latent heating was eliminated indicates that strong vertical shear and corresponding reductions in the l

analysis of a dryline during ihop implications for convection initiation abstract a detailed analysis of a dryline that formed on 22 may 2002 during the international h2o project ihop is presented the dryline was classified as a null case since air parcels lifted over the convergence boundary were unable to reach the level of free convection preventing thunderstorms from forming a secondary dryline associated with a distinct moisture discontinuity developed to the west of the primary dryline the primary dryline exhibited substantial along frontal variability owing to the presence of misocyclones this nonlinear pattern resembled the precipitation core gap structure associated with cold fronts during one of the analysis times although the misocyclones were positioned within the gap regions radar refractivity has been recently shown to accurately retrieve the low level moisture fields within the convective boundary layer however its use in forecasting the initiation of convection has been restricted to qualitative interpretations this study introduces the total derivati

a case study of gravity waves convective storms interaction 9 may 1979 abstract an analysis is presented of a series of severe storms which occurred in the north central united states on 9 may 1979 and whose spatial distribution and movement correlate well with observed gravity waves two gravity wave trains of 2 1 3 mb amplitude 2 5 3 3 h period and 240 265 km horizontal wavelength were isolated through power spectra analysis and cross correlation techniques applied to national weather service barograph traces the wave trains propagated in the 200 direction which coincided with the jet axis with a phase velocity of 20 30 m s 1c and within a 300 km wide band the storms were identified on enhanced infrared goes satellite pictures with the help of radar summaries these convective systems initially developed in nebraska and propagated north northeast at 25 m s 1 revealing wave like characteristics with a separation of 300 400 km the convective systems were closely linked to the observed wave trains with cell intensity height and associated rainfall maximized at the wa

an investigation of turbulence generation mechanisms above deep convection abstract an investigation of the generation of turbulence above deep convection is presented this investigation is motivated by an encounter between a commercial passenger aircraft and severe turbulence above a developing thunderstorm near dickinson north dakota on 10 july 1997 very high resolution two and three dimensional numerical simulations are used to investigate the possible causes of the turbulence encounter these simulations explicitly resolve the convection and the turbulence causing instabilities the configurations of the models are consistent with the meteorological conditions surrounding the event the turbulence generated in the numerical simulations can be placed into two general categories the first category includes turbulence that remains local to the cloud top and the second category includes turbulence that propagates away from the convection and owes its existence to the breakdown of convectively generated gravity waves in both the two and three dimensional calculations th

rear inflow in squall lines with trailing stratiform precipitation abstract the relative airflow and accompanying precipitation structure of squall lines trailed by mesoscale regions of stratiform rain are examined with emphasis on the occurrence of rear inflow i e the intrusion of environmental air into these storms across the trailing precipitation boundary three cases from kansas and oklahoma provide examples of strong rear inflow which crosses the back edge of the stratiform precipitation area at relative speeds exceeding 10 m s 1 the vertical profiles of relative flow at the trailing precipitation boundary of these three systems were remarkably similar with the rear inflow confined to a jet like layer centered at about 550 mb doppler radar data for two of these cases showed that the rear inflow jet occupied a continuous channel extending from middle levels at the back edge of the stratiform region to lower levels of the leading convective region where it merged with outflow from convective downdrafts to bolster the leading gust front strong front to rea

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

the synoptic setting and possible energy sources for mesoscale wave disturbances abstract thirteen case studies of mesoscale wave disturbances characterized by either a singular wave of depression or wave packets with periods of 1 4 h horizontal wavelengths of 50 500 km and surface pressure perturbation amplitudes of 0 2 7 0 mb are reviewed to isolate common synoptic features for these cases and to shed light on possible energy sources for the waves a strong thermal inversion in the lower troposphere north of a frontal boundary and a jet streak propagating toward a ridge axis in the upper troposphere are commonly observed in all the cases in general the area of wave activity is bounded by the jet axis to the west or northwest a surface front to the southeast an inflection axis between the trough and ridge axes to the southwest and the ridge axis to the northeast the conditions specified by lindzen and tung as being necessary to form a wave duct which include the existence of the lower tropospheric inversion seem to be met in many of these cases this suggests that a du

the holocene environmental changes in boreal fen peatland of northern mongolia reconstructed from diatom assemblages abstract the holocene hydrological changes of fen peatland in northern mongolia were reconstructed using diatom fossils with an aid of sphagnum leaf fossils analyses were conducted on three cores taken across the basin and reconstructed water environments were compared to find basin wide hydrological changes and climate anomalies the peatland has been covered by sedges during most of its 10 thousand years history but all cores showed common peatland hydrosere processes from fluvial environment in the early holocene period shallow marsh to present acidic fen peatland the establishment of fen peatland at 6 8 6 4 cal ka bp was marked synchronously by the shift of diatom and sphagnum taxa assemblages and this period was inferred as the onset of the mid holocene dry climate which is widely observed around mongolia the dry environment lasted until around 2 8 cal ka bp with a temporal wetter condition at 4 4 3 5 cal ka bp short term diatom trend shifts indicated temporal wetter environments at 8 7 8 4 8 0 7 6 2 4 2 1 1 2 0 5 cal ka bp and a dry environment at 0 4 0 2 cal ka bp these periods of hydrology changes were correlative with other studies in mongolia and east siberia so they would represent climate induced hydrological changes and those regions might share the same response to long term insolation changes or global climate anomalies however disagreements of climate data even within northern mongolian region suggest large influence of regional geography and the balance of evapotranspiration on climate behaviors as shown by recent dendrological paleoenvironment researches coherent differences of main taxa compositions between three cores were attributed to core site specific local hydrology mainly in terms of relative wetness from wettest core site accompanied by abundant planktonic diatom taxa to driest site with acidic peat indicator taxa timings and manners of temporal diatom trend shifts were also largely different between cores suggesting significant difference in each core site sensitivity to basin wide hydrology changes confirming the necessity of using multiple cores and proxies in peatland sediments to detect climate induced environmental changes

some effects of model resolution on simulated gravity waves generated by deep mesoscale convection abstract over the past decade numerous numerical modeling studies have shown that deep convective clouds can produce gravity waves that induce a significant vertical flux of horizontal momentum such studies used models with horizontal grid spacings of o 1 km and produced strong gravity waves with horizontal wavelengths greater than about 20 km this paper is an examination of how simulated gravity waves and their momentum flux are sensitive to model resolution it is shown that increases in horizontal resolution produce more power in waves with shorter horizontal wavelengths this change in the gravity waves spectra influences their vertical propagation in some cases gravity waves that were vertically propagating in coarse simulations become vertically trapped in fine simulations which strongly influences the vertical flux of horizontal momentum

vhf doppler radar observations of buoyancy waves associated with thunderstorms abstract the platteville vhf doppler radar located on the colorado piedmont near platteville colorado continuously measured the vertical wind velocity during a 12 day period in late july and early august 1981 measurements were made every 2 5 min on the average with range gates centered at 3 3 5 7 8 1 10 5 12 9 15 3 17 7 and 20 1 km above sea level periods of active thunderstorms were identified from the ppi maps from the national weather service 10 cm weather radar at limon colorado when no thunderstorm activity was present the vertical velocity fluctuations were small and erratic but a few hours after strong thunderstorm activity began large quasi sinusoidal wave trains with periods of about 40 min were observed power spectra of the vertical velocity time series showed enhancements at all frequencies during thunderstorm activity but for periods longer than 30 min the enhancements were larger particularly for the mid tropospheric range gates from 5 7 to 12 9 km some of the implication