an atmospheric solitary gust observed with a doppler radar a tall tower and a surface network abstract doppler radar and a 444 m tall instrumented tower provide a detailed view of the kinematic and thermodynamic structure of a solitary gust a study of the data fields and comparison with theoretical and laboratory work leads to the conclusion that the gust is an internal solitary wave of permanent form launched by a thunderstorm outflow onto an inversion layer formed by the passage of an earlier storm comparisons with results from fluid experiments and numerical models are made and the similarities are striking both observations show turbulent breakdown at the rear of the wave the ease with which solitary waves can be generated in experiments gives reason to believe that these nonlinear waves might be of considerable interest in the context of geophysical fluid dynamics

atmospheric gravity waves and aircraft turbulence encounters abstract we describe aircraft turbulence atmospheric gravity wave events which occurred during a 2 day period over the continental divide the waves are observed by two microbarograph networks an each side of the divide and last for several hours at a time we show them to be unstable modes of the jet stream corresponding to propagating internal gravity waves we also show that the position of aircraft reported turbulence coincides with the critical levels of the waves

pack ice drift off east antarctica and some implications three satellite tracke d data buoys were deployed between 700 and 800e south of 65 os in february march 1985 these buoys were subsequently trapped within the expanding seasonal sea ice and drifted with the ice the buoys measured air temperature and pressure and water temperatures to 100 m depth data from the buoys are used to describe the ice drift and environment within the winter sea ice zone in this region both north and south of the antarctic divergence additional preliminary data from a further six buoys deployed in the same area in march 1987 are also presented besides providing information on the broad scale drift of the ice in the prydz bay region data from the buoys have shown i the important role that ice drift plays in determining the autumn and winter expansion of antarctic sea ice ii the highly mobile nature of the ice even hundreds of kilometres from the ice edge iii the role that ocean bottom topography has in determining ice drift over the continental shelf and iv the modifying influence that an ice cover has on regional climate a qualitative assessment is made of importance of the major forces driving the ice data are insufficient for a detailed study dynamics

interpretation of ground based radiometric observations in terms of a gravity wave model an analysis is presented of 2 hour and 4 hour segments of data taken at denver colorado on february 3 1984 by a ground based radiometer designed and operated by the wave propagation laboratory of the national oceanic and atmospheric administration noaa the zenith viewing instrument has two moisture sensing and four temperature sensing channels it is demonstrated that a peak at a period of 10 min present in the spectra of the measured brightness temperature and of the derived geopotential heights thicknesses and vertically integrated water vapor content is due to an internal gravity wave generated by wind shear in the jet aloft this analysis shows that the radiometer has the sensitivity to detect such disturbances and that the mathematical inversion technique used to retrieve the geopotential field and other integrated quantities retains the derived information as well finally a linear expression is derived which relates the brightness temperature to the atmospheric temperature density humidity and cloud liquid perturbation fields

inertia gravity waves revealed in radiosonde data at jang bogo station antarctica 74 37 s 164 13 e 2 potential sources and their relation to inertia gravity waves

assessment and estimation of groundwater recharge for a catchment located in highland tropical climate in central ethiopia using catchment soil water balance swb and chloride mass balance cmb techniques two commonly applied groundwater recharge estimation techniques namely soil water balance swb and the chloride mass balance cmb methods were applied and compared to quantify and analyse groundwater recharge in the akaki catchment located in central ethiopia the semi distributed swb method estimated natural groundwater recharge at 105 mm a 10 of the mean annual areal precipitation maap the chloride mass balance method applied to the same catchment estimated mean annual groundwater recharge at 273 mm a 25 of the maap the swb recharge value is much less than the recharge estimated by cmb method highlighting the importance of preferential flow path recharge mechanism which is not captured by the swb method in situ permeability measurements undertaken as part of this research and an earlier investigation based on environmental isotopes have demonstrated that the catchment gets recharged both from direct and preferential flow recharge mechanisms which explains the discrepancy between recharge estimated through the two methods therefore swb model result which only takes into consideration the piston type flow recharge mechanism should be taken as the minimum possible groundwater recharge for the catchment characterized by fractured aquifers the mean recharge estimate from the two methods represents the maximum possible recharge estimate for the catchment investigated although calibration of the recharge estimates was not possible the swb recharge estimate is found to be highly sensitive to changes in precipitation input the findings of this research underline the fact that multiple recharge estimation methods are important to understand and capture possible recharge mechanisms and to reach to an acceptable recharge estimate

heavy rainfall associated with double low level jets over southern china part ii convection initiation abstractheavy rainfall that occurred at the south coast of china on 10 11 may 2014 was associated with a synoptic system related low level jet sllj and a boundary layer jet blj to clarify the

major ion hydrochemistry and environmental isotope signatures as a tool in assessing groundwater occurrence and its dynamics in a fractured volcanic aquifer system located within a heavily urbanized catchment central ethiopia summary hydrochemical and environmental isotope 2 h 18 o and 3 h data were used to characterize the groundwater flow occurrence and major ion chemistry in a complex fractured volcanic aquifer system located at the edge of the ethiopian rift the study has been supported by conventional hydrogeological mapping the result clearly indicates the presence of two distinct groundwater systems 1 the shallow groundwater characterized by low ionic concentration and in places isotopically enriched younger waters and 2 the deep thermal waters with relatively older age showing negative 18 o shifts and higher ionic concentration the deep groundwaters are manifested as thermal springs and deep confined and artisan wells mainly aligned along major regional faults the first group of groundwater is further divided into four subgroups indicating clear geo hydrological patterns along the groundwater flow path representing different lithologies residence time and anthropogenic influences the classification shows different degrees of rock water interaction and aquifer composition there are indications of aquifer recharge from highly evaporated surface waters this integrated study enabled to conceptualize the groundwater flow system vertically in to three zones namely shallow fast circulating fresh water mixed and moderately mineralized groundwaters representing the majority of wells and the deep old and mineralized thermal waters this study has very important implications on possible location and depth of future boreholes well head protection and in understanding the spread of pollutants that may originate from urban areas

a case study of the interaction of a mesoscale gravity wave with a mesoscale convective system abstractthis study documents the high amplitude mesoscale gravity wave mgw event of 7 march 2008 in which two mgws strongly impacted the sensible weather over a large portion of the southeast united states these mgws exhibited starkly contrasting character despite propagating within similar environments the primary i e long lived mgw was manifest by a solitary wave of depression associated with rapid sinking motion and adiabatic warming while the secondary short lived mgw was manifest by a solitary wave of elevation mgwel dominated by rising motion and moist adiabatic cooling genesis of the primary mgw occurred as a strong cold front arrived at the foot of mexico s high terrain and perturbed the appreciable overriding flow the resulting gravity wave became ducted in the presence of a low level frontal stable layer and caused surface pressure falls up to 4 hpa the mgw later amplified as it became coupled with a stratiform precipitation system which led to its evolution into an intense

mesoscale gravity waves and their environment in the central united states during storm fest abstract in an effort to better understand mesoscale gravity waves in winter storms in the central united states their frequency of occurrence wave characteristics the general conditions under which they occur and their effects upon the weather mesoscale surface and rawinsonde data as well as radar and satellite imagery collected during the storm scale operational and research meteorology fronts and experimental system test are analyzed in addition factors affecting the ability of objective surface map analysis to properly represent the waves are investigated thirteen coherent pressure pulse events with amplitudes of 0 2 4 0 mb and periods of 1 6 h were identified in the surface pressure data during the 6 weeks of the project involving 34 of the total hours investigated a variety of wave types occurred including wavelets wave trains and singular waves the three largest amplitude events were analyzed in detail using autospectral analysis and a barnes time to space conversion objective analysis

a mesoscale gravity wave event observed during ccope iii wave environment and probable source mechanisms abstract synoptic and special mesoscale observations taken during the cooperative convective precipitation experiment ccope are used to describe the multiscale environment of a gravity wave event understand the wave environment interactions that led to the development of severe thunderstorms and asses possible wave generation mechanisms the storms formed sequentially as a packet of gravity waves propagated across a stationary thunderstorm outflow boundary convection developed most rapidly in that part of the mesonetwork in which existed the combination of relatively high parcel buoyant energy weak restraining inversion strong storm downdraft potential and substantial vertical wind shear associated with a mesoscale jet streak synoptic scale analysis reveals that the waves were excited north of a stationary front and within the right exit region of the jet streak as it approached a stationary ridge in the 300 mb height field strong indications of unbalanced flow were diagnosed within the gravit

studies of quasi horizontally propagating gravity waves in the troposphere using the piura st wind profiler vhf profiler observations of the troposphere obtained over a flat desert in northern peru show the presence of strong quasi sinusoidal oscillations in the vertical wind velocity with periods of around 8 18 min these oscillations are a very typical feature of the vertical velocities over piura this paper presents an overview of the wave characteristics obtained at piura until this point including results obtained using two additional antennas built a few hundred meters to the west and south of the main antenna to measure horizontal wavelengths and phase velocities briefly the piura waves appear to have horizontal wavelengths of 1 3 km with either westward or eastward phase velocities in a ground based reference frame of 0 5 4 m s 1 their occurrence appears to be causally related to the magnitude of the easterly wind which blows over the andean cordillera some 60 km to the east of the site

a study of mountain lee waves using clear air radar the tropospheric and lower stratospheric response to flow over complex terrain is investigated using observations of vertical and horizontal motions made by a clear air doppler radar stationed at toulon in southern france analysis of the data has disclosed that episodic enhancements in the variability of vertical and horizontal velocities are due to lee waves excited by obstacles located within 5 km of the radar three separate cases of lee wave activity are studied two dimensional linear perturbation theory and existing three dimensional simulation results for appropriate parameter values are used as guides to check against the vertical structure observed by radar the magnitudes of vertical velocities observed during lee wave incidence are well within the range reported in previous observational and numerical simulation studies from a detailed examination of one of the cases of trapped waves the time variation observed by the radar of timescales of less than an hour has emerged as the likely result of small directional changes in the upstream winds causing a bodily rotation of the downstream three dimensional wave pattern centred on the wave generating obstacle the observed tendency of the vertical velocity perturbation to change sign with time above the radar location follows as a consequence of the presence of large horizontal gradients in the motion field which are inherent in the structure of three dimensional lee waves the temporal variability of the lee wave pattern has allowed the radar to sweep out a partial horizontal cross section revealing vertical circulation features that are broadly consistent with gravity wave behaviour however analysis of the effects of finite antenna beam spacing on the sampled data indicates that a spurious phase shift might have been introduced between the vertical and horizontal velocity perturbations observed in the cross section in contrast the measured vertical velocities are not seriously affected by finite beam width effects the lee waves examined in this study are quite moderate nevertheless this circumstance has provided a favourable opportunity to conduct a critical evaluation of the capabilities and limitations of this radar technique for observing lee wave phenomena in general we have been able to show clearly how the incidence and vertical structure of the waves respond to the synoptic scale situation in particular we have been able to distinguish between trapped and vertically propagating waves and to relate a transition between these wave types to synoptic scale changes in the static stability structure

sources of recharge at abu delaig sudan abstract various components of the water cycle in and around abu delaig a small town in a semiarid region of sudan have been investigated with geochemical and isotopic techniques to determine the sources of groundwater recharge rain samples total deposition during storms contain significant concentrations of dissolved solids for a continental site mean 4 6 mgl 1 for 1982 1985 the heaviest rains important for recharge tend to have the lowest chlorinities and are also the most negative isotopically wadi floods generally have lower chlorinity than the rainfall indicating the proportionally lower amounts of dust in the more intense rainfall events shallow ground waters at abu delaig have relatively evolved compositions higher mg ca ratios compared with rainfall and wadi floods yet they also contain tritium and retain isotopic signatures similar to the local rainfall they also have a distinctive chemistry compared with the deeper ground waters in the region and recharge from the former to the latter is considered to be insignificant ground waters in the unsaturated zone are saline and have isotopic compositions highly enriched in heavy isotopes compared with rainfall indicating strong evaporation the chloride balance indicates that mean recharge rates are 0 2 1 3 mm year 1 through the interfluve areas it is concluded that the only significant replenishable resources at abu delaig are from wadi recharge during floods and that direct regional recharge is insignificant fluctuations in the water table however lead to solutes from the lower unsaturated zone contributing to the chemistry of the shallow ground waters elsewhere it is possible that wadi recharge may be a possible route for deeper replenishment but this needs to be demonstrated by dedicated experiments

the life cycle of a mesoscale gravity wave as observed by a network of doppler wind profilers abstract for the first time an analysis has been made of the evolving vertical structure of a long lived mesoscale gravity wave that exerted a strong influence upon the precipitation distribution across a large area this paper describes this gravity wave system on 14 february 1992 which was observed using a combination of a surface mesonetwork digital satellite and radar imagery and several doppler wind profilers the resulting vertical structures are compared to the predictions of linear stability theory since the signature of the gravity waves in the profiler vertical beam data was often complicated by the presence of precipitation a kinematic method was developed for estimating the vertical air motions during these periods the resultant time height fields show vertical and horizontal winds that are consistent with a gravity wave conceptual model the microbarograph traces and the cloud and precipitation patterns in the early stages of development a strong vertically erect wave of depression

extraction of geopotential height and temperature structure from profiler and rawinsonde winds mesoscale height and temperature fields can be extracted from the observed wind field by making use of the full divergence equation mass changes associated with irrotational ageostrophic motions are retained for a nearly complete description of the height field above the boundary layer in the absence of friction the divergence equation includes terms composed of the components of the wind and a laplacian of the geopotential height field once the mass field is determined the thermal structure is obtained through application of the hypsometric equation in this paper an error analysis of this divergence method is undertaken to estimate the potential magnitude of errors associated with random errors in the wind data previous applications of the divergence method have been refined in the following ways i the domain over which the method is applied is expanded to encompass the entire storm fest domain ii wind data from 23 profiler and 38 rawinsonde sites are combined in the analysis iii observed profiler and rawinsonde data are interpolated to grid points through a modified objective analysis and iv the variation in elevation of the profiler sites is taken into account the results of the application of the divergence method to the combined wind data from profiler and rawinsonde sites show good agreement between the retrieved heights and temperatures and the observed values at rawinsonde sites standard deviations of the difference between the retrieved and observed data lie well within the precision of the rawinsonde instruments the difference field shows features whose magnitude is significantly larger than the errors predicted by the error analysis and these features are systematic rather than random in nature suggesting that the retrieved fields are able to resolve mesoscale signatures not fully captured by the rawinsonde data alone the divergence method is also applied solely to the profiler data to demonstrate the potential of the divergence method to provide mass and thermal fields on a routine basis at synoptic times when operational rawinsonde data are not available a comparison of the heights derived from the profiler winds with those independently measured by rawinsondes indicates that valuable information on the evolution of atmospheric height and temperature fields can be retrieved between conventional rawinsonde release times through application of the divergence method the implications of the results for applications of the method in weather analysis and in numerical weather prediction are discussed

review of wave turbulence interactions in the stable atmospheric boundary layer flow in a stably stratified environment is characterized by anisotropic and intermittent turbulence and wavelike motions of varying amplitudes and periods understanding turbulence intermittency and wave turbulence interactions in a stably stratified flow remains a challenging issue in geosciences including planetary atmospheres and oceans the stable atmospheric boundary layer sabl commonly occurs when the ground surface is cooled by longwave radiation emission such as at night over land surfaces or even daytime over snow and ice surfaces and when warm air is advected over cold surfaces intermittent turbulence intensification in the sabl impacts human activities and weather variability yet it cannot be generated in state of the art numerical forecast models this failure is mainly due to a lack of understanding of the physical mechanisms for seemingly random turbulence generation in a stably stratified flow in which wave turbulence interaction is a potential mechanism for turbulence intermittency a workshop on wave turbulence interactions in the sabl addressed the current understanding and challenges of wave turbulence interactions and the role of wavelike motions in contributing to anisotropic and intermittent turbulence from the perspectives of theory observations and numerical parameterization there have been a number of reviews on waves and a few on turbulence in stably stratified flows but not much on wave turbulence interactions this review focuses on the nocturnal sabl however the discussions here on intermittent turbulence and wave turbulence interactions in stably stratified flows underscore important issues in stably stratified geophysical dynamics in general

a comparative study of large amplitude gravity wave events abstract two large amplitude gravity waves were observed over the midwestern united states on 5 and 14 january 1989 during the university of illinois winter precipitation program on both days an extensive amount of data was recorded including data from two radars and a radiosonde facility the waves originated near missouri registered pressure fluctuations as large as 10 mb and produced distinct precipitation bands along their updraft regions the waves were long lived and maintained their identity over 1000 km a distance several times their wave lengths the synoptic features at the surface were dissimilar a deep cyclone was present on 5 january while a leeside trough was present on 14 january however the middle and upper tropospheric flow patterns were similar in both cases the axis of a trough was immediately upstream of the gravity wave genesis area and a jet streak had just propagated through the base of the trough toward a downstream ridge soundings taken near the gravity waves were re

groundwater recharge estimation using chloride deuterium and oxygen 18 profiles in the deep coastal sands of western australia the depth distributions of environmental chloride deuterium and oxygen 18 in the deep sands 20 m were monitored with a view to estimate average recharge to groundwater the investigated area is located on the southwestern coast of western australia and supports a perennial native woodland vegetation by using a steady state model based on the conservation of chloride the average areal recharge was estimated to be approximately 15 of the average precipitation 775 mm yr 1 whilst the cl concentration of groundwater was relatively uniform there was a considerable spatial variability in the depth distribution of cl in the unsaturated zone an approximate method of data analysis is developed application of this to cl data shows that possibly some 50 of the total annual recharge occurs via movement of water through preferred pathways thus bypassing the soil matrix stable isotope deuterium and oxygen 18 data show that there has been some isotopic enrichment due to evaporation of the rainfall but the extent of enrichment appears to be too small to estimate recharge rates reliably it is argued that relatively small isotopic enrichment occurs in the system studied since the direct evaporation from soil is a rather small component of the total evapotranspiration the observations on the depth distribution of isotopes qualitatively support the presence of a bimodal system for water movement through the profile as was suggested by the analysis of chloride data

observations of vertical velocity over illinois by the flatland radar a new vhf clear air doppler radar has been constructed in very flat terrain near urbana illinois this radar called the flatland radar as presently configured measures a profile of the vertical component of the wind velocity every 2 5 minutes it is found that typical time variances of vertical velocity over this very flat terrain are similar to the small variances observed during quiet periods near mountains the observed absence of extended periods of large variance supports the hypothesis that the active periods observed near mountains are mainly due to orographic effects the absence of such effects at flatland should facilitate the study of other meteorological processes for example in the case study presented here it is suggested that the vertical motions associated with large scale baroclinic storms are measurable by the flatland radar

analytical studies of low level internal gravity waves over the kanto plain associated with a stationary front abstract an observational analysis of the low level internal gravity waves over the kanto plain in japan on 17 october 1998 was performed the data from the doppler radar for airport weather draw as well as aircraft communications addressing and reporting system acars data of wind and temperature provided unique observations with high spatial and temporal resolutions and were used to analyze detailed wave structures and environmental conditions especially the wave trapping mechanism according to the data analysis the horizontal wavelength was approximately 7 km the ground relative phase speed of the waves was approximately 1 m s 1 and the direction of propagation was toward 50 ne the profiles from acars revealed that the scorer parameter decreased rapidly with height above 1500 m agl and became less than the horizontal wavenumber near 2600 m agl these results indicate that the atmosphere acts as a duct and the waves were trapped vertically and reflected downward the observed horizontal wa

horizontally propagating quasi sinusoidal tropospheric waves observed in the lee of the andes vhf profiler observations of the troposphere obtained over a flat desert in northern peru show the presence of strong quasi sinusoidal oscillations in the vertical wind velocity with periods of around 8 18 minutes these oscillations are a very consistent feature of the vertical velocities over piura and are also observed at other profiler locations this paper presents an overview of the wave characteristics obtained at piura until this point including results obtained using a second antenna built a few hundreds meters to the west of the main antenna to measure horizontal wavelengths and phase velocities briefly the piura waves appear to have horizontal wavelengths in the zonal direction of 5 10 m with either westward or eastward phase velocities in a ground based reference frame of 5 15 m s 1 their occurrence appears to be causally related to the magnitude of the easterly wind which blows over the andean cordillera some 60 km to the east of the site

a mesoscale gravity wave event observed during ccope part ii interactions between mesoscale convective systems and the antecedent waves abstract this paper presents the results of a very detailed investigation into the effects of preexisting gravity waves upon convective systems as well as the feedback effects of convection of varying intensity upon the waves the analysis is based on the synthesis of synoptic surface and barograph data with high resolution surface mesonetwork radar and satellite data collected during a gravity wave event described by koch and golus in part i of this series of papers use is also made of the synoptic barograph data and satellite imagery to trace the waves beyond the mesonetwork and thus determine their apparent source region just upstream of the mesonetwork it is shown that two of the gravity waves modulated convection within a weak squall line as they propagated across the line the other six waves remained closely linked with convective systems that they appeared to trigger however it is shown that the waves were not excited by convection furthermore the waves retained their signatures in the su

structure of an internal bore and dissipating gravity current as revealed by raman lidar abstract detailed moisture observations from a ground based raman lidar and special radiosonde data of two disturbances associated with a dissipating gust front are presented a synthesis of the lidar data with conventional meteorological data in conjunction with theoretical calculations and comparison to laboratory studies leads to the conclusion that the disturbances seen in both the lidar and accompanying barograph data represent a weak gravity current and an associated undular bore the disturbances display excellent coherence over hundreds of kilometers upstream of the lidar site bore formation occurs at the leading edge of the gust front coincidentally with the rapid weakening of the gravity current analysis suggests that the bore was generated by the collapse of the gravity current into a stable nocturnal inversion layer and subsequently propagated along this wave guide at nearly twice the speed of the gravity current the raman lidar provided detailed measurements of the vertical structure o

doppler sodar and radar wind profiler observations of gravity wave activity associated with a gravity current abstract observations from two doppler sodars and a radar wind profiler have been used in conjunction with data from a rawinsonde station and a mesoscale surface observation network to conduct a case study of a gravity current entering into an environment containing a nocturnal inversion and an elevated neutral layer on the basis of synoptic and mesoscale analyses it is concluded that the gravity current might have originated either as a scale contracted cold front or as a gust front resulting from thunderstorm outflows observed very near the leading edge of a cold front despite this ambiguity the detailed vertical structure of the gravity current itself is well resolved from the data moreover the vertical velocity measurements provided by the sodars and the radar wind profiler at high time resolution have given unique information about the height structure of gravity waves excited by the gravity current although only wave periods and not phase speeds or wavelengths are directly measured it is p

investigations of internal gravity waves using three vertically directed closely spaced wind profilers a network of three wind profilers spaced about 5 km apart was operated in southern france during the alpine experiment alpex program the wind profilers measured vertical motions and the experiment was designed to study traveling internal waves by comparing the vertical velocity fluctuations observed at each station the measured phase velocities together with the observed periods were used to deduce the horizontal wavelength of the waves only a relatively few cases of monochromatic waves could be identified using this array most of the waves that were detected had phase velocities opposite to the prevailing wind and had the speeds required to cause trapping as the intrinsic frequency was doppler shifted upward to the brunt vaisala frequency

a 4 yr climatology of pressure disturbances using a barometer network in central illinois this paper presents a climatology of coherent disturbances detected during 1991 95 by a network of barometers with a diameter of about 50 km located in a very flat terrain centered on the flatland atmospheric observatory in east central illinois an automatic wavelet based adaptive filter is used to extract the waveforms of all disturbance events with amplitudes larger than a frequency dependent threshold the extracted events cover characteristic temporal scales from about 30 min to 6 h that is the range that includes mesoscale disturbances that affect the weather and the forecasts the analysis resulted in two classes of events one class called coherent events or ces consists of disturbances that propagated coherently through the barograph network and for which the phase propagation velocity dominant period and horizontal wavelength could be estimated with good accuracy the propagation directions of 97 of the ces were between 08 and 1808 i e had an eastward component and the speeds of 96 were between 10 and 50 ms 21 with a mode at 25 30 m s21 the other class called incoherent events or ies consists of disturbances that had significant amplitudes but that did not propagate coherently across the network so that the propagation velocity could not be estimated this class consists of localized disturbances and wave packets with short periods and or wavelengths or with pressure signatures that were too different at the network stations the extracted events are attributed to gravity waves wave packets gravity currents pressure jumps solitary waves bores etc the rate of occurrence of events had a strong seasonal dependence with a maximum in fall and winter and a minimum in summer the ces occurred about 20 21 of the total time in fall and winter and 12 in summer while all events occurred 34 in both fall and winter and 23 in summer the seasonal dependence of events confirms the strong relation of these disturbances to the baroclinicity of the atmosphere concurrent vertical velocity fluctuations observed by the 50 mhz radar at the flatland atmospheric observatory showed that many of the large amplitude events extended up to at least 7 km the highest altitude reliably observed by the radar

origin evolution and finescale structure of the st valentine s day mesoscale gravity wave observed during storm fest part iii gravity wave genesis and the role of evaporation abstract on 14 february 1992 a long lived moderate amplitude mesoscale gravity wave formed in kansas during the storm scale operational and research meteorology fronts experiment systems test storm fest wave formation was evident in correlated surface pressure and wind fields the wave of depression accompanied by a weak rainband tracked across the state a wealth of data was collected on the mature wave as it passed over the storm fest dual doppler domain however the mechanism of genesis remained difficult to ascertain since wave formation occurred in a region of less comprehensive observations the genesis of the storm fest gravity wave is successfully simulated using the fifth generation pennsylvania state university national center for atmospheric research penn state ncar mesoscale model mm5 which was run at 6 km grid spacing in the innermost domain the lee cyclone movement dry airmass development and gravity wave formation over kansas were successfully captured by the model results

gravity waves and convection in colorado during july 1983 abstract in order to gain insight into the complex dynamics of a convective system interacting with a gravity wave train we have carried out an experiment in northeast colorado during july and august 1983 utilizing data from several program areas in noaa pressure data from the profs mesonetwork of microbarograph stations were combined with velocity profiles from the wave propagation laboratory uhf wind profiler st radar at stapleton airport in denver and convective cell location data from the nws limon weather radar several events were clearly visible in the microbarograph data from which four called events a b c and d in late july were selected for further study these events differed from each other in fundamental ways in each event the waves represent oscillations of a substantial depth of the troposphere and seem to appear and disappear together with the convective cells in events a and b the waves have a critical level and are probably unstable modes generated by wind shear in the jet s

a three year gravity wave climatology of the mesosphere and lower thermosphere over kauai a 3 year study of gravity wave variability covering 1991 1992 and 1993 was conducted using horizontal wind measurements collected by a partial reflection mf radar located on the island of kauai hawaii 22 n 160 w high echo return rates between 70 and 98 km provided ample time resolution for the study of gravity wave variability in this height range horizontal wind measurements were band pass filtered for periods between 20 min and 6 hours establishing a gravity wave band time series gravity wave variance and polarization calculations were carried out over various time frames and examined with regard to their response to season and background environment among the more interesting observed phenomena were the annual and semiannual oscillations in the gravity wave variances a significant diurnal and semidiurnal variability in the variances and an extended enhancement of these variances during the latter half of 1992 and the beginning of 1993

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