qlg tomography in colombia the crustal attenuation of lg waves in colombia was estimated and analyzed using local seismological data from the national seismological network of colombia rsnc the selected dataset comprises 510 crustal earthquakes with a total of 2928 ray paths this large dataset allowed us to invert for a regional average of qlg tomographic images for colombia and simultaneously source size for each event and site term at the seismological stations the computed regional average for qlg in the frequency band 0 5 5 0 hz was found to agree with the previously reported values in neighboring regions in order to resolve the lateral variation in the attenuation of lg waves in the crust independent tomographic inversions for 26 frequencies between 0 5 and 5 0 hz were conducted the resulting maps confirm that heterogeneities in the crust exist and that they are related to the large scale tectonic features in the country the highest attenuation in the region is linked to the presence of active volcanic arcs where the crust is weakened by partial melting relatively high attenuation is also found in zones where the crust is composed of accreted oceanic rocks and in regions with near surface low velocity sedimentary layers 2002 elsevier science b v all rights reserved

sea breezes shallow and deep on the california coast abstract analyses of doppler lidar data reveal sea breezes occurring on two different depth and time scales at monterey bay california on a day with offshore gradient flow indicated before sunrise and after sunset the lidar data used in this study consist of vertical cross sections and profiles of the westerly onshore wind component u in the morning after 0900 pst a shallow sea breeze formed which reached a depth of 300 m by noon starting in early afternoon a deeper sea breeze layer formed in the lowest kilometer and by late afternoon the shallow sea breeze blended into the deeper sea breeze and was no longer evident maximum speeds of 6 m s 1 in the shallow sea breeze occurred at the surface whereas those in the deep sea breeze also 6 m s 1 were about 300 m above the surface it is hypothesized that the shallow sea breeze is a local phenomenon responding to a more local temperature contrast between the sea and the region between the ocean and the mountain ranges the deeper sea breeze on the

evolution of the monterey bay sea breeze layer as observed by pulsed doppler lidar abstract as part of the land sea breeze experiment lasbex to study the sea breeze at monterey bay the pulsed doppler lidar of the noaa erl wave propagation laboratory performed vertical and nearly horizontal scans of the developing sea breeze on 12 days analyses of doppler velocity data from these scans revealed details on the growth of the sea breeze layer and on the horizontal variability of the sea breeze resulting from inland topography two days were selected for study when the ambient flow was offshore because the onshore flow of the sea breeze was easy to discern from the background flow sequences of vertical cross sections taken perpendicular to the coast showed the beginnings of the sea breeze beneath the land breeze at the coast and the subsequent growth of the sea breeze layer horizontally and vertically on one of the days a transient precursor a minor sea breeze appeared and disappeared before the main sea breeze began in midmorning other issues that the lidar was well suited to stud

the tertiary dynamics of the northern eastern alps austria changing palaeostresses in a collisional plate boundary abstract six tertiary deviatoric palaeostress tensor groups from 165 stations in the calcareous alps describe the upper crustal dynamics of the leading edge of the adriatic plate during protracted continental collision with the european lower plate palaeostress changes are correlated to the kinematic evolution of the plate boundary and to independently derived plate kinematic data of the alpine carpathian pannonian area each palaeostress direction is defined by 32 to 89 individual tensors which constrain 1 late eocene to oligocene nw directed compression during thrusting and dextral shearing on wnw striking faults nw directed compression along the northern margin of the adriatic plate is correlated to its n directed translation combined with a counterclockwise rotation 2a late eocene to early miocene n directed compression during n directed thrusting of penninic and helvetic units and the molasse 2b early to middle miocene n directed strike slip compression during the onset of eastward lateral extrusion the change from nw to n directed compression is interpreted to result from strain partitioning at the periadriatic fault which has formed the new adriatic plate boundary since the oligocene dextral shearing on this fault accommodated continued anticlockwise rotation and decoupled the northern eastern alps from the rotational component n directed compression in the calcareous alps paralleled the n directed translation of the adriatic plate 3 middle miocene ne directed compression of thrust and strike slip type during lateral extrusion ne directed compression in the calcareous alps resulted from the drag of the eastward extruding central eastern alps sinistral shear stress was transmitted across the ene trending salzach ennstal fault ne oriented 1 axes include 45 with the e w striking zone of distributed sinistral shear in the calcareous alps 4 middle miocene e directed extension associated with orogen parallel normal faulting of the central eastern alps e directed extension paralleled the direction of mass transfer towards the pannonian basin during lateral extrusion normal faulting was induced by reduced lateral confinement due to removal of material east of the alps on the large scale eastward motion was enabled by the e directed retreat of the eastern carpathian subduction zone 5 late miocene e directed compression orogen parallel compression obstructed lateral extrusion the stress change from extension to e directed compression was caused by the end of subduction retreat in the eastern carpathians due to dynamic changes in the subduction zone 6 n directed extension late to post miocene extension paralleled recent topographic slopes in the foothill of the eastern alps palaeostresses changes correspond to distinct phases in the kinematic evolution of the northern eastern alps and to the systematic formation and reactivation of major fault zones wnw striking faults changed deformation styles from dextral shear to dextral transpression reverse faulting and finally to sinistral shear the early to middle miocene salzach ennstal fault which formed the northern boundary of the extruded central eastern alps changed from sinistral transpression to sinistral shear sinistral transtension and finally to dextral shear

topographic slope as a proxy for seismic site conditions and amplification we describe a technique to derive first order site condition maps directly from topographic data for calibration we use global 30 arc sec topographic data and v s 30 measurements here v s 30 refers to the average shear velocity down to 30 m aggregated from several studies in the u s as well as in taiwan italy and australia v s 30 values are correlated against topographic slope to develop two sets of parameters for deriving v s 30 one for active tectonic regions where topographic relief is high and one for stable shields where topography is more subdued by taking the gradient of the topography and choosing ranges of slope that maximize the correlation with shallow shear velocity observations we can recover to first order many of the spatially varying features of sitecondition maps developed for california our site condition map for the low relief mississippi embayment also predicts the bulk of the v s 30 observations in that region despite rather low slope ranges we find that maps derived from the slope of the topography is often well correlated with other independently derived regional scale site condition maps but the latter maps vary in quality and continuity and subsequently also in their ability to match observed v s 30 measurements contained therein alternatively the slope based method provides a simple approach to uniform site condition mapping

3 d mapping of segmented active faults in the southern vienna basin abstract in this paper we present novel data on the location and kinematics of seismically active fault segments of the vienna basin transfer fault system in the southern vienna basin spatial mapping of active faults and kinematical analyses are based on commercial 3 d reflection seismic data geomorphological features such as tilted quaternary river terraces and fault scarps the geometry of subsided quaternary basins and published geodetic data accordingly active faulting in the southern vienna basin occurs partly by reactivation of the miocene fault system related to the formation of the vienna pull apart basin between c 17 and 8 ma two domains of quaternary and active faults can be distinguished with 1 predominantly strike slip and 2 mainly normal faulting 1 a seismically active ne striking sinistral strike slip fault zone with large negative flower structures is mapped at the south eastern margin of the basin subsidence within the reflection seismically imaged flower structure is documented by up to 1000 m of throw since pannonian times and the accumulation of up to 150 m thick quaternary gravels at the surface the fault zone is characterized by en echelon faults with some prominent scarps 2 major e dipping normal faults branch off from the transfer strike slip fault system the normal faults extend into the central and western part of the basin as well as into the urban area of vienna close to vienna the normal offset along such a normal fault is at minimum 300 m since pannonian times surface expressions of active normal faulting are tilted quaternary terraces of the danube river and tilted ancient land surfaces in the hanging wall of the normal faults the mapped active normal faults are kinematically linked by a common detachment horizon which is in contact with the seismically active strike slip zone along the south eastern border of the basin northeast of the vienna basin the seismically active zone continues as a straight line indicating a rather linear transfer fault zone than a pull apart step over geometry

an environmental reconstruction of the sediment infill of the bogota basin colombia during the last 3 million years from abiotic and biotic proxies abstract the lacustrine sediments of the intramontane basin of bogota 4 n 2550 m altitude were collected in a 586 m deep core funza 2 absolute datings show sediment infill started c 3 2 ma and continued almost without interruptions as a result of the balance between tectonic subsidence and sediment infill analysis of downcore changes in lithology grain size facies loss on ignition loi and hydrosere vegetation at 20 cm intervals along the core produced a 2200 sample record of basin dynamics and lake level changes with a temporal resolution from c 800 years during the last 1 5 ma to c 2000 years from 1 5 to 3 2 ma we recognized 11 discrete sedimentary facies that reflect 4 different depositional environments facies 1 and 2 correspond to lacustrine environment where the loi is 20 a fluvio lacustrine environment is represented by the facies 3 4 5 7 and 9 a fluvial environment is reflected by facies 6 8 and 10 basin infill started with accumulation in a fluvio lacustrine environment between 586 and 530 m below the present day sediment surface of the basin in the 530 to 325 m interval c 3 1 5 ma the basin contained mainly shallow water and swamps in combination with some fluvial activity the 325 5 m interval 1 5 0 028 ma shows almost uninterrupted lacustrine paleoenvironmental conditions the uppermost 5 m reflect a fluvial paleoenvironment deposited by the bogota river and its tributaries the downcore changing ratio between shallow water aquatics myriophyllum ludwigia polygonum cyperaceae and aquatics of deeper water isoetes is indicative of lake level changes isoetes as an indicator of high water levels is not consistent with fluvial and fluvio lacustrine depositional regimes several lithological discontinuities evidenced by the sharp transition from swamp deposits to fluvio lacustrine and fluvial deposits are present in the core in the interval from 530 to 325 m in particular it is plausible that swamp deposits have been eroded during episodes during which the water table quickly raised or during events of sudden coarse fluvial input into the basin

the evolution of lee wave rotor activity in the lee of pike s peak under the influence of a cold frontal passage implications for aircraft safety abstract a lee wave rotor system interacting with an approaching cold front in the lee of pike s peak near colorado springs colorado on 1 april 1997 is studied observationally and numerically dynamical effects associated with the approaching cold front caused the amplification of the evolving lee wave and rotor creating increasingly more hazardous flight conditions for nearby airports the rapidly evolving winds measured by a doppler lidar and 915 mhz wind profilers and simulated by the regional atmospheric modeling system rams produced light to moderate turbulence for a research aircraft making missed approaches at the colorado springs airport during the wave amplification phase as the cold front approached the foothills the lee wave rotor system ended abruptly reducing hazardous flight conditions the doppler lidar s detailed measurements of the lee wave rotor system allowed for an evaluation of rams ability to capture these complex wind features qualitative and quantitative comparisons betw

the spatial distribution of the lignite qualitative parameters and variant estimates of coal reserves the czech part of the vienna basin the aim of this article is to inform about the spatial distribution of the lignite qualitative parameters and total lignite reserves in the czech part of the vienna basin the south moravian lignite coalfield smlc the total reserves were estimated on the basis of several composed variant digital models of individual seams in four partial area of smlc calculations of the reserves resulted from the identified spatial distribution of chemical technological parameters obtained from the thousands analysis of samples taken from more than 4 000 exploration works the basic model of the deposit was so called geological model characterising genetic evolution of the deposit and defines the spatial positions of the coal seams subsequently developed variant economical models spatially define the selected areas by the quality of lignite expressed by the limits of ash yield based on the created models it was found that in the past just 3 7 depending on the variant model of the total lignite reserves smlc had been extracted the presented geological reserves are currently using the existing mining technologies only partially mineable

contributions of basin edge induced surface waves to site effect in the dinar basin southwestern turkey ground motion amplifications in the dinar basin and contributions of the surface waves generated from basin edges are investigated in frequency and time domains amplification functions are computed from the aftershock data of the october 1 1995 dinar earthquake mw 6 4 using the standard spectral ratio method which requires a pair of instruments one located at the site under investigation generally on alluvium and the other on a reference site preferably a nearby rock site first a time window covering the whole signal is used to compute the amplification function and successively the noise p wave s wave and the surface wave time windows are used in computation to observe their contributions to the amplification function it is seen that the maximum amplifications observed at about 2 0 hz on the amplification functions of the stations located in the basin are largely due to basin edge induced surface waves these waves have significantly increased the duration of signals recorded within the basin particularly on the vertical component records the amplitudes of surface waves are larger than the s wave amplitudes the periods of waves amplified maximally due to the basin structure coincide with the natural periods of 4 6 story buildings which were heavily damaged in dinar this indicates that the site effects may have been important regarding the damage which occurred during the dinar earthquake of october 1995

4d analogue modelling of transtensional pull apart basins abstract scaled sandbox models were used to investigate the 4d evolution of pull apart basins formed above underlapping releasing stepovers in both pure strike slip and transtensional basement fault systems serial sectioning and 3d volume reconstruction permitted analysis of the full 3d fault geometries results show that very different pull apart basins are developed in transtension compared to pure strike slip both types of models produced elongate sigmoidal to rhomboidal pull apart systems but the transtensional pull apart basins were significantly wider and uniquely developed a basin margin of en echelon oblique extensional faults dual opposing depocentres formed in the transtensional model whereas a single central depocentre formed in pure strike slip in transtension a distinct narrow graben system formed above the principal displacement zones pdzs cross basin fault systems that linked the offset pdzs formed earlier in the transtensional models sequential model runs to higher pdz displacements allowed the progressive evolution of the fault systems to be evaluated in cross section transtensional pull aparts initiated as asymmetric grabens bounded by planar oblique extensional faults with increasing displacement on the pdzs basin subsidence caused these faults to become concave upwards and lower in dip angle due to fault block collapse towards the interior of the basin in addition strain partitioning caused fault slip to become either predominantly extensional or strike slip the models compare closely with the geometries of natural pull apart basins including the southern dead sea fault system and the vienna basin austria

diagnosed characteristics of precipitation systems over taiwan during the may june 1987 tamex abstract characteristics of mei yu precipitating cloud systems over taiwan during the may june 1987 taiwan area mesoscale experiment tamex have been studied using sounding surface precipitation and radar data vertical motion has been computed over the island at 6 h intervals from 13 may to 15 june using a modification of the kinematic method that takes into account the mountainous lower boundary within a four station sounding polygon two primary characteristics of the precipitation have been found first the major rainfall event were linked to the passage of midlatitude disturbances and typically consisted of both deep convective and stratiform components deep convection was primarily prefrontal or frontal while the stratiform precipitation was postfrontal presumably in association with overrunning and orographic lifting second there was a pronounced diurnal variability in the rainfall vertical motion heating q1 and moistening q2 profiles have been used to define the character of the pr

a vs30 map for california with geologic and topographic constraints abstract for many earthquake engineering applications site response is estimated through empirical correlations with the time averaged shear wave velocity to 30 m depth v s 30 these applications therefore depend on the availability of either site specific v s 30 measurements or v s 30 maps at local regional and global scales because v s 30 measurements are sparse a proxy frequently is needed to estimate v s 30 at unsampled locations we present a new v s 30 map for california which accounts for observational constraints from multiple sources and spatial scales such as geology topography and site specific v s 30 measurements we apply the geostatistical approach of regression kriging rk to combine these constraints for predicting v s 30 for the v s 30 trend we start with geology based v s 30 values and identify two distinct trends between topographic gradient and the residuals from the geology v s 30 model one trend applies to deep and fine quaternary alluvium whereas the second trend is slightly stronger and applies to pleistocene sedimentary units the rk framework ensures that the resulting map of california is locally refined to reflect the rapidly expanding database of v s 30 measurements throughout california we compare the accuracy of the new mapping method to a previously developed map of v s 30 for california we also illustrate the sensitivity of ground motions to the new v s 30 map by comparing real and scenario shakemaps with v s 30 values from our new map to those for existing v s 30 maps online material california statewide v s 30 and shakemaps for loma prieta

shallow mesoscale flows at the north eastern adriatic coast a summertime anticyclonic situation over the northern part of the eastern adriatic coast is studied using a three dimensional nonhydrostatic mesoscale model the aim is to evaluate small scale variability such as mesoscale eddies sea breeze convergence zones czs and the coastal jet like flow in the thermally driven mesoscale circulations over very complex terrain the results show that the model reproduces main known features of the diurnal flow with certain local specific characteristics in addition to some new ones previously only somewhat qualitatively known after comparisons with measurements further analyses are performed by sensitivity tests in which topography and synoptic input are varied the simulations show a development of two diurnal intensive mesoscale eddies inside kvarner bay 20 km 20 km the night time deeper eddies exhibit anticlockwise rotation while the late afternoon shallow one shows the opposite rotation their appearance and dynamics are connected primarily to the coastline shape and topography meanwhile the large scale flow in the anticyclonic weather type as addressed here has small influence moreover a cz develops over istria and the island of krk as a result of merged sea breezes the intensity speed position and configuration of the sea breeze cells are examined the results also show that the topography is more important for the formation of the cz over the island of krk and for the coastal jet like flow between the island and mainland than for the istrian cz copyright 2006 royal meteorological society

the influence of mesoscale orography on a coastal jet and rainband abstract the role of mesoscale orography along the central california coast in the development and evolution of a coastal jet and rainband is investigated using a high resolution triply nested nonhydrostatic numerical model comparison of the model simulations which use horizontal grid increments of 5 and 2 km on the inner computational meshes with a coastal mesoscale observation network indicates that the finescale structure of the jet and rainband dynamics are adequately simulated although phase and orientation errors occur the observed and simulated near surface winds have maximum speeds that exceed 22 m s 1 and a direction nearly parallel to the coastline and topography force balance analysis indicates that blocking in the lowest 500 m and flow over the coastal range above this layer contribute to mesoscale pressure perturbations including pressure ridging upstream of the coastal mountains which forces the ageostrophic dynamics of the coastal jet pressure perturbations associated with the to

multiscale analysis of a meso β frontal passage in the complex terrain of the colorado front range abstract data from a mesoscale observing network are used to describe the evolution of a complex boundary between a dry air mass near the foothills of the rocky mountains and a shallow moist air mass over the eastern plains synoptic scale analyses revealed that the origin of the moist air mass was associated with lee cyclogenesis mesoscale analyses provided a detailed picture of a localized anticyclonic circulation that developed within the larger scale flow mixing ratio data from the mesoscale observing network indicated the position of the boundary between the air masses it is shown that the cooler moister air on the plains advanced toward and retreated away from the foothills during the evening eventually downslope winds that were opposing the motion of the mesoscale boundary decreased and the anticyclonic circulation on the plains became more organized on an even smaller scale doppler lidar measurements revealed characteristics of the wind flow associated with the mesofront and the interacti

a numerical study of the convection triggering and propagation associated with sea breeze circulation over hainan island based on high resolution numerical simulations the effects of sea breeze circulation sbc on associated convective initiation and propagation over hainan island are investigated the results show that the blocking of synoptic wind on the windward side of the mountains inhibits the occurrence of windward side valley breeze and sea breeze in the context of low mountains weak synoptic wind not only favors the combination of the sbc with the valley breeze circulation on the leeward side of the mountains but also makes the convergence zone between the synoptic wind and the leeward side combined circulation stay near the tops of the mountains leading to the accumulation of large quantities of water vapor taking place over the mountaintops the combined effect of enhanced water vapor and high temperatures over the mountaintops can result in the generation of much larger convective available potential energy cape than the surrounding areas the coupling of the large cape with the considerable converging ascending motion and abundant water vapor near the tops of the mountains promotes the occurrence of a strong convection band cb over the mountaintops during the cb propagation under the steering of synoptic wind the flow across the cb continuously and strongly opposes the sbc front and the fronts of the kelvin helmholtz billows behind resulting in successive and strong lifting motion as well as large quantities of water vapor and high cape near these fronts these lead to an apparent downstream wave like propagation of the cb

comparisons between mesoscale model terrain sensitivity studies and doppler lidar measurements of the sea breeze at monterey bay abstract a noaa environmental technology laboratory doppler lidar measured the life cycle of the land and sea breeze system at monterey bay california in 1987 during the land sea breeze experiment lasbex on days with offshore synoptic flow the transition to onshore flow the sea breeze was a distinct process easily detected by lidar finescale lidar measurements showed the reversal from offshore to onshore flow near the coast its gradual vertical and horizontal expansion and a dual structure to the sea breeze flow in its early formative stages initially a shallow 500 m sea breeze formed that later became embedded in a weaker onshore flow that was 1 km deep eventually these two flows blended together to form a mature sea breeze about 1 km deep regional atmospheric modeling system rams two dimensional simulations successfully simulated this dual structure of the sea breeze flow when both the coastal mountain range just east of monterey bay and the sierra nevada range peaking 300 km eas

contribution of dense array analysis to the identification and quantification of basin edge induced waves part ii application to grenoble basin french alps settled on a deep sediment filled valley the city of grenoble french alps faces important site effects large amplification and significant duration in crease of ground motion even for moderate size events in order to study multidi mensional site effects a very dense array composed of 29 three component seis mometers over a 1 km aperture was operated during spring 1999 in the center of the city a total of 18 events 6 local 4 regional and 8 teleseismic with an acceptable signal to noise ratio could be recorded over a 4 month period the complexity of the wave field and in situ seismic noise constraints led us to develop a procedure based on time frequency coherence and the multiple signal classification algorithm to iden tify and characterize wave arrivals cornou et al 2003 applying the procedure to the 18 records it is clearly indicated that ground motion inside the valley is domi nated by basin edge induced waves that carry 4 times more energy than the direct wave field regardless of the type of event considered in addition the basin induced wave field is composed of 60 rayleigh waves and 40 love waves when consid ering energy carried by the three components if one considers only the energy of horizontal components this proportion is 50 rayleigh waves and 50 love waves the diffraction phenomena are mostly constrained by the 3d structure of the basin regardless of the azimuth of the event a study of the relative contribution of 1d and 2d 3d effects on recorded ground motion suggests at least at frequencies below 1 hz that the difference between the standard spectral ratio and 1d transfer function or possibly the horizontal to vertical ratio receiver function and nakamura esti mates might be due mainly to laterally propagating waves

anomalous propagation of long period ground motions recorded in tokyo during the 23 october 2004 mw 6 6 niigata ken chuetsu japan earthquake unusually large 5 cm and prolonged shaking associated with long period ground motions at periods of about 7 sec were observed in central tokyo during the mw 6 6 niigata ken chuetsu earthquake of 23 october 2004 the long period ground motions caused significant resonance in high rise buildings of about 70 floors in height thus it is an urgent matter to understand the development and amplification properties of long period ground motions in tokyo associated with large earthquakes in this study we use numerous waveform records from 585 stations in a nationwide accelerometer network k net kik net and 495 intensity meters in the area around tokyo the data reveal that the long period ground motion is characterized in most part by a surface rayleigh wave generated at the northern edge of kanto basin and the surface wave is developed as propagating through a thick cover of sediments 3000 4000 m that overlies rigid bedrock to complement the observational data we conducted a large scale computer simu lation of seismic wave propagation by employing the earth simulator supercomputer with a detailed source slip model and a high resolution 3d sedimentary structural model of central japan the results of the computer simulation demonstrate that the anomalously prolonged ground shaking of the long period signal recorded in the center of tokyo occurred because of the stagnation of seismic energy resulting from the multipathing and focusing of rayleigh waves toward the bottom of the kanto basin from surrounding mountain regions with interaction to the 3d basin structure

evolution of lignite seams within the south moravian lignite coalfield based on certain qualitative data abstract this paper focuses on evolution of lignite seams the pannonian in the south moravian lignite coalfield smlc it is based on data analysis seam geometry ash yield sulfur content and lithology from more than 3300 boreholes and many channel samples the results show that the vienna basin in the pannonian period gradually developed into a freshwater bay in the early pannonian the sedimentary environment was tectonically calm the salinity of the sedimentary environment was changing as a consequence of recurring transgressions the studied area was under the influence of rivers flowing into the region from the west north and northeast in the upper part of zone b papp s classification of the pannonian sediments especially in the northern areas of the smlc suitable conditions for coal bearing sedimentation the kyjov seam occurred zones c f were characterized by simple or incomplete cyclic sedimentation processes the vienna basin opened and the subsidence between the steinberg fault zone and lu ice lan hot fault zone interconnected with the polesovice fault zone took place in the smlc at the beginning of zone f the swamp areas suitable for dub any seam formation developed in the smlc the coal forming conditions were repeatedly restored the sedimentary cycles with the coal bearing deposits occurred also in zone g however only in the central and southern parts of the smlc the increasing thickness of the deposits in zone g and the increasing number of cycles with lignitic layers in the southern part of the smlc indicate a shift of the suitable conditions for swamps towards the south and into the overlying rocks a distinct tectonic deformation of the lignite seam in the smlc started only in the pliocene when due to the change of the stress field in the vienna basin the rejuvenation of the tectonic zones of the pull apart system took place towards the ne sw and nw se to nnw sse

hydraulic aspects of fohn winds in an alpine valley this study examines the applicability of single layer hydraulic theory to alpine fohn winds in the example of the flow in the brenner pass region austria italy the south fohn is described as the gap flow over the pass and along the associated wipp valley numerical shallow water simulations for a wide range of initial conditions including shallow and deep fohn cases are discussed and compared with selected measurements collected within the mesoscale alpine programme map the observational analyses are based on doppler and aerosol backscatter lidar data for a specific fohn case and on surface observations and radiosoundings for all fohn cases observed within the 70 day map special observing period sop radiosoundings at a location upstream south and downstream north of the brenner pass reveal that the average map sop fohn case had subcritical flow south and nearly critical flow north of the brenner pass the hydraulic model indicates flow transition to a supercritical state near the pass a hydraulic jump 2 km further north mainly subcritical flow in the upper wipp valley except near the brenner and especially for shallow fohn a tendency to becoming supercritical in the lower wipp valley the model results suggest that the vertical topographic contraction exerts stronger control for the flow at the brenner gap than the lateral contraction in accordance with doppler lidar measurements the hydraulic model captures the decrease of the wind speed in the across valley direction from east to west in the northern part of the valley this asymmetric flow pattern is a result of the complex valley geometry rather than of the influence of upper level synoptic winds as suggested in a previous study for some observed cases the strength of the temperature inversion at the top of the fohn layer decreased across the brenner pass presumably due to entrainment processes consequently the reduced gravity decreased as well there are two major reasons for the only moderate agreement between the hydraulic parameters retrieved from soundings and those provided by the model the model assumes a constant value of reduced gravity and the calculation of hydraulic parameters for fohn cases without a strong and sharp temperature inversion is ambiguous essential flow patterns in the simulated fields such as the location of the pressure minimum and wind speed maxima compare well with the surface observations along a valley transect indications for a steeply amplified or breaking gravity wave resembling a hydraulic jump to the lee of the two mountain ridges are found in lidar observations as well as in the simulations copyright 2004 royal meteorological society

high resolution real time modeling of the marine atmospheric boundary layer in support of the aosn ii field campaign abstract the navy s coamps atmospheric model has been used to provide twice daily real time forecasts of 72 h duration in support of the aosn ii field campaign during august 2003 the model was configured with four grid meshes with a minimum horizontal grid increment of 3 km a statistical analysis of the model forecasts using available buoy observations demonstrates the skill of the atmospheric model predictions with characteristic wind speed rms and bias errors of 1 3 m s 1 and less than 0 5 1 0 m s 1 respectively and temperature rms errors of 1 2 c and biases typically less than 1 0 c the highest resolution mesh provides more accurate wind speed variances during the upwelling periods in the nearshore region where the wind speed gradients and diurnal variations are the largest persistent and strong low level winds from a northwesterly direction were associated with a mid tropospheric trough and jet stream that was substantially stronger than the overall mean monthly conditions during the relaxation periods which were relatively infrequent during august 2003 the trough was weaker than the mean conditions with a closed low west of the coast that resulted in southerlies near the coast during upwelling favorable conditions the mean marine inversion was substantially stronger than during the relaxation periods with the surface stress field exhibiting maxima in the lee of prominent coastal capes and topography particularly during the periods of strong larger scale low level flow the persistent mean stress pattern that is topographically locked yields maxima in the stress curl pattern that induce favorable regions of coastal upwelling near and downwind of the coastal promontories and headlands

empirical models for surface and body wave amplifications of response spectra in the bogota basin colombiaempirical models for surface and body wave amplifications of response spectra in the bogota basin