law for the distance between successive earthquakes 1 discovery of a new law for the three dimensional spatial distance between the foci of successive earthquakes is reported analyzing the seismic data taken between 1984 and 2001 in southern californian it is found that the cumulative distribution of the distances follows the modified zipf mandelbrot law showing complexity of geometry of the events

earthquake locations and three dimensional crustal structure in the coyote lake area central california previous work on the simultaneous inversion method has been improved and extended to incorporate iterative solution for earthquake locations and laterally heterogeneous structure approximate ray tracing and parameter separation are important elements of the improved method application of the method to p wave arrival time data recorded by stations of the u s geological survey central california network yields a three dimensional model for the velocity structure of the upper crust in an area encompassing the rupture zone of the coyote lake earthquake of august 1979 very strong correlations between the velocity model and the geology and gravity and magnetic anomalies are observed improved estimates of the locations of earthquakes in the study area are also determined the relocation of explosions indicates epicentral accuracies of the order of a kilometer or better based on the revised hypocentral locations it is concluded that the san andreas fault is vertical in this area with no actual offset between the epicenters and the fault trace in contrast the calaveras has two or more active fault surfaces one nearly vertical and another dipping 75 to the northeast

the mesoscale and microscale structure and organization of clouds and precipitation in midlatitude cyclones viii a model for the seeder feeder process in warm frontal rainbands abstract previous field studies have indicated that warm frontal rainbands form when ice particles from a seeder cloud grow as they fall through a lower level feeder cloud in this paper we present results from a parameterized numerical model of the growth processes that can lead to the enhancement of precipitation in a seeder feeder type situation the model is applied to two types of warm frontal rainbands in the first type 1 situation the vertical air motions are typical of those associated with slow widespread lifting in the vicinity of warm fronts in the second type 2 situation the vertical air motions are stronger and more characteristic of the mesoscale the model simulations show that in the type 1 situations the growth of the seed ice crystals within the feeder zone is due to vapor deposition the feeder zone in this case is slightly sub saturated with respect to water due to the presence of the seed crystals in regions where the feeder zone is not seeded from aloft snow cryst

cloud resolving model simulations of multiply banded frontal clouds an idealized two dimensional cloud resolving model is used to investigate the formation and temporal evolution of multiply banded clouds in frontal zones radar observations often show both upright and slantwise convection in the circulations associated with such bands the aim is to examine the interaction between upright and slantwise convection and to determine the mechanisms leading to multiple banding a warm bubble is used to initiate convection in the frontal zone which has an initial thermodynamic profile based on observations further triggering occurs and banded clouds evolve the initially upright plumes become tilted due to the so called am adjustment process upscale development observed multiple bands in frontal zones are frequently attributed to the release of conditional symmetric instability csi however in these simulations there is no evidence of the release of csi despite the fragmentation of slantwise bands into multiple layers in the mid troposphere successive triggering of upright convection is instead associated with a spreading cold pool driven by evaporative cooling in the slanted downdraughts triggering can occur on both the warm and cold air sides of the frontal zone and is sensitive to the microphysical parametrization used

effects of melting on frontogenesis abstract frontal precipitation systems are simulated with a 2d cloud model including ice phase microphysics despite the use of idealized frontogenetic forcing in the simulations some observed characteristics of frontal zones and their associated cloud and precipitation fields are reproduced in the simulations the effects of melting snow on surface frontogenesis is investigated it is found that the cooling effects of melting snow significantly accelerate surface frontogenesis in winter storm environments especially when the melting layer is close to the surface however the steady state surface frontal strength in the model is not sensitive to the melting effects finescale thermal and kinematic perturbations inside the frontal zone near the melting level quite similar to those recently reported in the literature are evident in the model results analysis of the model results suggests that cooling from melting snow may induce these thermal and kinematic perturbations and may enhance baroclinicity

mechanics of fold and thrust belts and accretionary wedges cohesive coulomb theory a critically tapered fold and thrust belt or submarine accretionary wedge is one that is on the verge of coulomb failure everywhere including its base where frictional sliding along a decollement is assumed to be occurring cohesion within a wedge can add significantly to the overall strength near the toe the effect of this is to decrease the near toe taper leading to a critical topographic profile that is concave upward if the decollement is planar we obtain an approximate self consistent solution for the state of stress within a thin skinned cohesive critical coulomb wedge and determine the relationship between the wedge taper and its strength and basal friction the theory is then applied to the presently deforming fold and thrust belt of western taiwan fitting of theoretical critical wedge shapes to topographic profiles and measurements of the step up angles of thrust faults from the basal decollement are used to constrain the taiwan wedge strength parameters an attractive assertion fully consistent with all the observations is that the mechanics of fold and thrust belts and accretionary wedges is governed by normal frictional and fracture strengths of rocks measured in the laboratory in particular if byerlee s law b 0 85 is adopted as the coefficient of sliding friction on the base we find a coefficient of internal friction 0 9 1 0 in the wedge and a wedge cohesion so 5 20 mpa other solutions having strengths and ambient stresses up to 4 times lower than this can also however satisfy the data

an analytic scaling law for the depositional growth of snow in thin mixed phase layer clouds in various practical problems such as assessing the threat of aircraft icing or calculating radiative transfer it is important to know whether mixed phase clouds contain significant liquid water content some mixedphase clouds remain predominantly liquid for an extended time whereas others glaciate quickly the glaciation rate of mixed phase layer clouds is thought to depend on various factors including number concentration of snow crystals terminal velocity of snow crystals and crystal habit type this paper attempts to quantify some of these factors by deriving scaling laws i e power laws for the mixing ratio and sedimentation flux of snow at cloud base the scaling laws are derived from the governing equation for snow mixing ratio they neglect aggregation of snow crystals and accretion of supercooled liquid by snow crystals the scaling laws permit arbitrary exponents and prefactors of the mass diameter and fall speed diameter power laws allowing flexibility in crystal habit properties the scaling laws are tested using idealized large eddy simulation les of three thin midlevel layer clouds the scaling laws agree adequately with the les over one order of magnitude for snow flux and over two orders of magnitude for snow mixing ratio they indicate for instance that in the present les cloud base snow flux and snow mixing ratio increase faster than linearly with increasing cloud thickness and supersaturation with respect to ice by varying the exponents and prefactors of the scaling laws one may explore the sensitivity of glaciation rate to habit type the relationship is complex but for the cloud cases examined dendrites tend to glaciate cloud more rapidly than plates

embedded cellular convection in moist flow past topography abstract marginally unstable air masses impinging upon a mountain ridge may lead to the development of a nominally stratiform orographic cloud with shallow embedded convection rainfall amounts and distribution are then strongly influenced by the convective dynamics in this study the transition from purely stratiform orographic precipitation to flow regimes with embedded convection is systematically investigated to this end idealized cloud resolving numerical simulations of moist flow past a two dimensional mountain ridge are performed in a three dimensional domain a series of simulations with increasing upstream potential instability shows that the convective dynamics may significantly increase precipitation amounts intensity and efficiency to an extent that cannot be replicated by two dimensional simulations under conditions of uniform upstream flow the embedded convection is of the cellular type it is demonstrated that simple stability measures of the upstream profile are poor predictors for

research aircraft observations and numerical simulations of a warm front approaching vancouver island abstract the mesoscale structure of the low level flow and the character of the turbulence are investigated for a warm front as it approached the prominent terrain of the pacific northwest in the vicinity of vancouver island flight level and airborne doppler radar measurements collected from a national oceanic and atmospheric administration p 3 research aircraft on 9 december 1995 during the coastal observation and simulation with topography experiment and high resolution numerical simulations performed with the naval research laboratory s nonhydrostatic coupled ocean atmosphere mesoscale prediction system coamps model have been used to document the warm front as it approached the coast and the structure of cool air trapped along vancouver island this air mass was capped by a flat thin transition zone of enhanced static stability and vertical wind shear the flow within the trapped air mass was oriented parallel to the terrain of vancouver island but appears to have been more an outflow from the s

asthenospheric imprints on the lithosphere in central mongolia and southern siberia from a joint inversion of gravity and seismology mobal experiment summary we present a joint inversion of gravity and teleseismic data to enlighten the lithospheric structures of the baikal mongolia region an area characterized by high topographic contrasts sporadic cenozoic volcanism extension and large transcurrent faulting in the vicinity of the baikal rift central asia the study uses a 1000 km long seismic transect that cross cuts the main tectonic structures from north to south namely the siberian platform tunka basin hangay dome and gobi altai belt the siberian platform depicts a high velocity lithosphere down to about 150 km we evidence strong velocity contrasts within the crust below the hangay dome and the tunka depression interpreted as a thickened crust a low velocity density region is located at various depths below the hangay dome thanks to the dense spatial coverage of gravity data we are able to define the 3 d geometry of this particular low velocity density anomaly the hangay dome anomalous body extends from 60 to 225 km depth at his largest point and slightly thins to no more than 40 km at its easternmost end a deep low velocity zone below 150 km with only a weak negative density contrast is observed on the eastern part of the transect we propose that the late cenozoic uplift of the whole mongolian plateau and associated rifting magmatism high heat flow and lithospheric thinning are not externally driven by the india asia collision but results from the interaction of two mantle plumes with the overlying lithosphere conversely recent faulting may be the major expression of the india asia collision in this region as well as n s striking rift basins that connect and interact with major strike slip faults such as the bolnai fault the comparison between time residuals of this experiment and the baikal rift seismic data shows an undeniable disproportion for the hangay anomaly the hangay time residuals are far more positive than through the baikal arguing for an asthenospheric signature that is not seen beneath the baikal rift furthermore the southern edge of the thick siberian cratonic lithosphere may favour the rise of a sublithospheric mantle flow at the contact with the baikal mongolia lithosphere

large scale atmospheric forcing by southeast pacific boundary layer clouds a regional model study abstract a regional model is used to study the radiative effect of boundary layer clouds over the southeast pacific on large scale atmosphere circulation during august october 1999 with the standard settings the model simulates reasonably well the large scale circulation over the eastern pacific precipitation in the intertropical convergence zone itcz north of the equator and marine boundary layer stratocumulus clouds to the south in a sensitivity experiment with the radiative effect of liquid clouds south of the equator over the eastern pacific artificially removed boundary layer clouds south of the equator almost disappear and precipitation in the itcz is reduced by 15 20 indicating that the stratocumulus clouds over the southeast pacific have both local and cross equatorial effects examination of the differences between the control and sensitivity experiments indicates that clouds exert a net diabatic cooling in the inversion layer in response to this cloud induced cooling an in situ anom

evolution structure cloud microphysical and surface rainfall processes of monsoon convection during the south china sea monsoon experiment abstract a two dimensional cloud resolving simulation is combined with dual doppler and polarimetric radar analysis to study the evolution dynamic structure cloud microphysics and rainfall processes of monsoon convection observed during the south china sea scs summer monsoon onset overall the model simulations show many similarities to the radar observations the rainband associated with the convection remains at a very stable position throughout its life cycle in the northern scs the reflectivity pattern exhibits a straight upward structure with little tilt the positions of the convective transition and stratiform regions produced by the model are consistent with the observations the major difference from the observations is that the model tends to overestimate the magnitude of updraft as a result the maximum reflectivity generated by the model appears at an elevated altitude the surface rainfall processes and associated thermodynamic dynamic and cloud microphysical processes are examine

new free air and bouguer gravity fields of taiwan from multiple platforms and sensors abstract we construct 1 1 grids of free air and bouguer gravity anomalies around taiwan with well defined error estimates for quality assessment the grids are compiled from land airborne and shipborne gravity measurements augmented with altimeter gravity at sea three sets of relative land gravity measurements are network adjusted and outlier edited yielding accuracies of 0 03 0 09 mgal three airborne gravity sets are collected at altitudes 5156 and 1620 m with accuracies of 2 57 2 79 mgal seven offshore shipborne gravity campaigns around taiwan and its offshore islands yield shallow water gravity values with 0 88 2 35 mgal accuracies all data points are registered with gps derived geodetic coordinates at cm dm accuracies allowing for precise gravity reductions and computing gravity disturbances the various datasets are combined by the band limited least squares collocation in a one step procedure in the eastern mountainous or offshore region bouguer anomalies and density contrasts without considering the oceanic or land topographic contribution are underestimated the new grids show unprecedented tectonic features that can revise earlier results and can be used in a broad range of applications

some insights into the characteristics and dynamics of the chilean low level coastal jet abstract the characteristics and dynamics of the chilean low level coastal jet cllcj are examined here through diagnosing real time mesoscale model forecasts in support of the variability of the american monsoon system vamos ocean cloud atmosphere land study vocals and additional sensitivity simulations the forecasted surface winds over the southeast pacific compare favorably with available observations according to the forecasts and sensitivity simulations the southeast pacific high pressure system seph plays a primary role in driving the cllcj the andes significantly intensify the cllcj mainly through interacting with the seph and anchoring a baroclinic zone along the chilean coast the land sea differential heating also enhances the cllcj by strengthening the coastal baroclinic zone based on the location of the seph center the cllcj can be separated into two types a strong forcing jet with the seph close to the central chilean coastline and a weak forcing jet with the seph centered fa

the relationship between seismic velocity and density in the continental crust a useful constraint summary plots of seismic velocity and density of rock samples show that a range of densities is possible for rocks of each seismic velocity and vice versa although a single linear relationship is often assumed in crustal gravity calculations because of the scatter whenever rocks of known seismic velocity are converted to density using this relationship a reduction is made to the resolving power of the resulting gravity calculation if these rocks reach thicknesses of more than a few kilometres then the uncertainties become significant when compared with the size of commonly observed gravity anomalies examples are considered from the north sea mississippi and carolina trough it is concluded that the use of a seismic velocity measurement as the only indication of rock density does not provide a useful constraint when attempting to reproduce observed gravity variations an appropriate model for isostatic compensation is probably the most important factor for successful predictions of crustal structure on the basis of gravity data

cooperative inversion of geophysical data geophysical inversion by iterative modeling involves fitting observations by adjusting model parameters both seismic and potential field model responses can be influenced by the adjustment of the parameters of the rock properties the objective of this cooperative in version is to obtain a model which is consistent with all available surface and borehole geophysical data al though inversion of geophysical data is generally non unique and ambiguous we can lessen the ambiguities by inverting all available surface and borehole data this paper illustrates this concept with a case history in which surface seismic data sonic logs surface gravity data and borehole gravity meter bhgm data are ad equately modeled by using least squares inversion and a series offorward modeling steps the traditional analysis of various geophysical data sets has been termed integrated interpretation such analysis has traditionally involved much processing modeling and subjec tive interpretation in order to develop a geologic model which is consistent with various surface and borehole geophysical data a method which automates some of the above pro cedures is least squares inversion this procedure perturbs an initial set of model parameters in order to fit the observed data least squares inversion is described in many papers in cluding those of jackson 1972 wiggins 1972 jupp and vozoff 1975 and lines and treitel 1984 this inversion technique could also be termed automated iterative mod eling in terms of modeling different geophysical data sets there are many possible approaches which allow inversion of a given data set and it is doubtful whether one single recipe will prove suitable for all problems nevertheless by jointly invert ing various types of geophysical observations we may lessen the extent of some of the ambiguities inherent in individual data sets lafehr 1984 gives a germane discussion of several reasons for this type of coordinated geophysical effort in the present study we define cooperative inversion as the esti mation of a subsurface model which is consistent with various independent geophysical data sets in the case discussed in this paper these data sets include surface and borehole observa tions of the seismic and gravity responses in our definition cooperative inversion may include either joint inversion or sequential inversion

diurnal variation of downslope winds in owens valley during the sierra rotor experiment abstract the impact of diurnal forcing on a downslope wind event that occurred in owens valley in california during the sierra rotors project srp in the spring of 2004 has been examined based on observational analysis and diagnosis of numerical simulations the observations indicate that while the upstream flow was characterized by persistent westerlies at and above the mountaintop level the cross valley winds in owens valley exhibited strong diurnal variation the numerical simulations using the coupled ocean atmosphere mesoscale prediction system coamps capture many of the observed salient features and indicate that the in valley flow evolved among three states during a diurnal cycle before sunrise moderate downslope winds were confined to the western slope of owens valley shallow penetration state surface heating after sunrise weakened the downslope winds and mountain waves and eventually led to the decoupling of the well mixed valley air from the westerlies aloft around local noon decoupled

simulated convective lines with parallel stratiform precipitation part i an archetype for convection in along line shear abstract this article the first of two describing convective lines with parallel stratiform ps precipitation addresses the basic kinematic and precipitation features of these systems the ps mode appears to be the preferred organizational structure in environments with line parallel vertical wind shear this archetype for long lived convective systems has received relatively little attention to date and yet it is frequently implicated in flash flooding because it entails both the along line movement of hydrometeors and back building convective development as a reality check this paper presents conventional observations of the wind and reflectivity fields associated with an archetypal ps system from 2 may 1997 thereafter analyses of idealized numerical simulations serve as the basis for a more detailed investigation of ps systems internal structures and processes the observations and simulations suggest several unique aspects of the ps structure the environment s vertically sheared 3d wind prof

pipe vesicles in basalt trails left by dense immiscible melt droplets sinking through a viscous basal thermal boundary layer abstract pipe vesicles tubular cavities found in the basal parts of p hoehoe lava flows worldwide constitute one of their fundamental primary structures like other vesicles pipe vesicles have been ascribed to gas bubbles whether rising buoyantly through viscous lava or trapped in an inward moving solidification front these models involve special and unrealistic conditions and still poorly explain characteristic features of pipe vesicles in a new model proposed here pipe vesicles are postulated to be hollow trails left by droplets of dense immiscible iron rich silicate or sulphide melt sinking through a viscous thermal boundary layer just above the lower chilled margin of a p hoehoe flow unit driven by gravity the droplets sink vertically in static lava but obliquely in mobile lava such as lava undergoing gravitational spreading viscous and fluid dynamic forces tend to deform the sinking droplets and resist their motion the characteristic inverted y inverted v and lambda shapes of individual pipe vesicles reflect downward branching with a large droplet breaking up in partially crystallized highly polymerized basalt in the basal thermal boundary layer pipe vesicles do not yield lava flow directions even on a local centimeters to meters scale but are indirect indicators of widespread liquid immiscibility processes in basalts and potential commercial fe cu ni mineralization as pipe vesicles are not vesicles cavities left by gas escape a new term is necessary and the term vermiform p hoehoe having good descriptive power but no genetic connonations is suggested for p hoehoe with pipe vesicles

seismic tomography constrained by bouguer gravity anomalies applications in western washington tomographic inversions for velocity variations in western washington indicate a high correlation with surface geology and geophysical measurements including gravity observations by assuming a simple linear relationship between density and velocity birch s law it is possible to calculate the gravity field predicted from the velocity perturbations obtained by local tomographic inversion while the predicted gravity matches observations in parts of the model the overall correlation is not satisfactory in this paper we suggest a method of constraining the tomographic inversion to fit the gravity observations simultaneously with the seismic travel time data the method is shown to work well with synthetic data in 3 dimensions where the assumption of birch s law holds strictly if the sources of the gravity anomalies are assumed to be spatially localized integration can be carried out over a relatively small volume below the observation points and sparse matrix techniques can be applied we have applied the constrained inversion method to western washington using 4 387 shallow earthquakes to depths of 40 0 km 36 865 raypaths convering a 150 250 km region and found that the gravitational constraints may be satisfied with minor effect on the degree of misfit to the seismic data

a convective vorticity vector associated with tropical convection a two dimensional cloud resolving modeling study 1 although dry moist potential vorticity e is a useful physical quantity for meteorological analysis it cannot be applied to the analysis of two dimensional 2 d simulations a new vorticity vector e convective vorticity vector cvv is introduced in this study to analyze 2 d cloud resolving simulation data associated with 2 d tropical convection the cloud model is forced by the vertical velocity zonal wind horizontal advection and sea surface temperature obtained from the tropical ocean global atmosphere toga coupled ocean atmosphere response experiment coare and is integrated for a selected 10 day period the cvv has zonal and vertical components in the 2 d x z frame analysis of zonally averaged and mass integrated quantities shows that the correlation coefficient between the vertical component of the cvv and the sum of the cloud hydrometeor mixing ratios is 0 81 whereas the correlation coefficient between the zonal component and the sum of the mixing ratios is only 0 18 this indicates that the vertical component of the cvv is closely associated with tropical convection the tendency equation for the vertical component of the cvv is derived and the zonally averaged and mass integrated tendency budgets are analyzed the tendency of the vertical component of the cvv is determined by the interaction between the vorticity and the zonal gradient of cloud heating the results demonstrate that the vertical component of the cvv is a cloud linked parameter and can be used to study tropical convection

microphysical properties of convectively generated fall streaks within the stratiform comma head region of continental winter cyclones abstractthis paper presents analyses of the microphysical structure of comma head stratiform precipitation in 14 continental cyclones focusing on fall streaks of hydrometeors produced by cloud top convective generating cells data were obtained at temperatures between 4 and 45 c using in situ instrumentation and the w band university of wyoming cloud radar all operated aboard the national science foundation national center for atmospheric research c 130 analyses are presented first for a case study of one cyclone followed by statistical analyses of the full dataset using radar based objective classifications the statistical percentile number concentrations averaged 1 9 times larger within the fall streaks compared to the regions between them and the corresponding ice water content and median mass diameter values averaged 2 2 and 1 1 times larger ice phase conditions were predominant within the stratiform precipitation with deposition and aggregation the primary ice growth mechanisms no distinc

instability characteristics of radar derived mesoscale organization modes within cool season precipitation near portland oregon abstractthe instability characteristics associated with different radar derived mesoscale organization modes are examined using six cool seasons of operational scanning radar data near portland oregon and operational sounding data from salem oregon additionally several years of microwave rain radar ka band vertically pointing radar data from portland and merwin washington are used to characterize the nature and occurrence of generating cells and fall streaks the combination of a new metric convective stratiform intermittency with the classification of radar reflectivity maps into convective and stratiform precipitation types was applied to periods when the freezing level was 1 4 km altitude this method distinguishes periods with embedded convective within stratiform mesoscale organization from those that were mostly convective or mostly stratiform mesoscale organization occurs in a continuum of states with predominantly stratiform structure occurring most frequently generating cells in the s

three dimensional vp and vs structural models associated with the active subduction and collision tectonics in the taiwan region summary 3 d vp and vs models for the crust and upper mantle beneath the taiwan area have been determined using selected high resolution earthquake data from an island wide seismic network and two local seismic arrays lateral structural variations in the upper crust as also evident from surface geology are responsible for the observed large traveltime residuals or station corrections prior shallow velocity information inferred from traveltime residuals and joint hypocentral determination jhd station corrections for the uppermost crust is essential to facilitate a reliable tomographic inversion a finite difference method that is efficient and accurate for a highly heterogeneous velocity structure is applied to calculate p and s wave traveltimes from the source to receiving stations all earthquakes in the taiwan central weather bureau s catalogue are then relocated using the resultant 3 d vp and vs models the depth of the moho varies significantly especially along the east west direction in the western coastal plain and western foothills the depth of the moho is around 35 km which deepens gradually eastward reaches a maximum depth of 55 km beneath the eastern central mountain range shallows up rapidly beneath the longitudinal valley and coastal range and merges with the thin philippine sea plate offshore of eastern taiwan in central taiwan the central mountain range is bounded to the east and west by two steeply westward dipping active faults from the upper crust to a depth of about 30 km therefore the uplifted and thickened central mountain range serves as a backstop for the converging eurasian and philippine sea plates the crust beneath the central mountain range is characterized by a brittle high velocity and seismically active upper crust 15 km and a ductile low velocity and aseismic mid to lower crust below 15 km most probably due to the high geothermal activity from the excess heat supplied from the hot upper mantle beneath the thin oceanic crust to the east from the surrounding hotter upper mantle beneath the thickened continental crust and from shear heating during active collision the collision zone in eastern taiwan is characterized by an active and steeply eastward dipping seismic zone along a region of low vp and high vp vs ratio near the taitung region in southeastern taiwan it transforms into an active westward steeply dipping seismic zone along a transition zone between the high vp and vs oceanic crust and the low vp and vs continental crust near hualien region in central eastern taiwan there is no apparent seismicity within many sedimentary basins imaged from the tomographic inversion however af ew basins are either bounded on one side by an active fault or are characterized by blind faults beneath the geometry of the subduction zone in northeastern taiwan can be clearly imaged from the relocated earthquake locations behind the subduction a region of low vp and high vp vs ratio at depths of 5 to 10 km can be identified beneath the tatun chilung volcano group indicating a potential magma reservoir two steeply dipping linear seismic zones in the volcano region may mark the upward escape paths of the magmatic materials in the region

lithospheric structure of taiwan from gravity modelling and sequential inversion of seismological and gravity data abstract using a bouguer anomaly map and a dense seismic data set we have performed two studies in order to improve our knowledge of the deep structure of taiwan first we model the bouguer anomaly along a profile crossing the island using simple forward modelling the modelling is 2d with the hypothesis of cylindrical symmetry second we present a joint analysis of gravity anomaly and seismic arrival time data recorded in taiwan an initial velocity model has been obtained by local earthquake tomography let of the seismological data the let velocity model was used to construct an initial 3d gravity model using a linear velocity density relationship birch s law the synthetic bouguer anomaly calculated for this model has the same shape and wavelength as the observed anomaly however some characteristics of the anomaly map are not retrieved to derive a crustal velocity density model which accounts for both types of observations we performed a sequential inversion of seismological and gravity data the variance reduction of the arrival time data for the final sequential model was comparable to the variance reduction obtained by simple let moreover the sequential model explained about 80 of the observed gravity anomaly new 3d model of taiwan lithosphere is presented

vertical velocity and physical structure of generating cells and convection in the comma head region of continental winter cyclones abstractthe vertical motion and physical structure of elevated convection and generating cells within the comma heads of three continental winter cyclones are investigated using the wyoming w band cloud radar mounted on the national science foundation national center for atmospheric research nsf ncar c 130 supplemented by analyses from the rapid update cycle model and weather surveillance radar 1988 doppler wsr 88d data the cyclones followed three distinct archetypical tracks and were typical of those producing winter weather in the midwestern united states in two of the cyclones dry air in the middle and upper troposphere behind the pacific cold front intruded over moist gulf of mexico air at lower altitudes within the comma head separating the comma head into two zones elevated convection in the southern zone extended from the cold frontal surface to the tropopause the stronger convective updrafts ranged from 2 to 7 m s 1 and downdrafts ranged from 2 to 6 m s 1 the horizontal scale of the

taiwan orogeny thin skinned or lithospheric collision abstract the taiwan orogeny is young and presently very active it provides an excellent environment for studying ongoing orogenic processes especially since the region is monitored intensively with dense seismological and geodetic networks and new studies aiming at deciphering shallow and deep structures in and around taiwan have been recently conducted or are being planned the available data can be used continually to test critically hypotheses of the taiwan orogeny hypotheses dealing with the mechanics of mountain building are basic to the understanding of taiwan orogeny and are particularly amenable to testing the widely cited thin skinned tectonics hypothesis was formulated to explain mainly the geologic and relatively shallow

orographic precipitation and air mass transformation an alpine example a case of orographic precipitation in the alps on 20 september 1999 was studied using several models along with rain gauge and radar data the objective of the study is to describe the orographic transformation of an air mass including multi scale aspects several new and some conventional diagnostic quantities are estimated including drying ratio precipitation efficiency buoyancy work condensed water residence time parcel changes in heat moisture and altitude and dominant space and time scales for the case considered the drying ratio was about 35 precipitation efficiency values are ambiguous due to repeated ascent and descent over small scale terrain the sign of buoyancy work changed during the event indicating a shift from stratiform orographic to weak convective clouds cloud water residence times are different for the two mesoscale models 400 compared to 1000 s due to different cloud physical formulations the two mesoscale models agree that the dominant spatial scale of lifting and precipitation is about 10 km smaller than the scale of the main alpine massif trajectory analysis of air crossing the alps casts doubt on the classic model of fohn few parcels exhibit classic pattern of moist ascent followed by dry descent parcels that gain latent heat descend only briefly before rising into the middle troposphere parcels that descend along the lee slope originate in the middle troposphere and gain little or even lose latent heat during the transit as parcels seek their proper buoyancy level downstream a surprising scrambling of the air mass occurs radar data confirm the model prediction that the rainfall field is tightly controlled by local terrain on scales as small as 10 km rather than the full 100 km cross alpine scale a curious pulsing of the precipitation is seen indicating either drifting moisture anomalies or weak convection copyright 2003 royal meteorological society

simulations of the extratropical transition of tropical cyclones contributions by the midlatitude upper level trough to reintensification abstract the extratropical cyclone development processes during the reintensification stage of an extratropical transition from a tropical cyclone tc are described using numerical simulations three control simulations without a tropical cyclone present examine the extratropical cyclogenesis associated with upper level troughs that are characterized as weak moderate and strong when no tropical cyclone is included in the simulation the minimum surface pressures attained with the weak moderate and strong troughs are 1003 991 and 977 mb respectively in all three cases the low tilts northwestward with height during intensification and the rainfall pattern and eventual occlusion are representative of classic extratropical cyclone development the interactions of a tropical cyclone with each of the three midlatitude circulation patterns are compared with the control simulations to illustrate the contributions to the extratropical transition of the tropical cyclone in the three trough with tc case

assimilation of simulated polarimetric radar data for a convective storm using the ensemble kalman filter part i observation operators for reflectivity and polarimetric variables abstract a radar simulator for polarimetric radar variables including reflectivities at horizontal and vertical polarizations the differential reflectivity and the specific differential phase has been developed this simulator serves as a test bed for developing and testing forward observation operators of polarimetric radar variables that are needed when directly assimilating these variables into storm scale numerical weather prediction nwp models using either variational or ensemble based assimilation methods the simulator takes as input the results of high resolution nwp model simulations with ice microphysics and produces simulated polarimetric radar data that may also contain simulated errors it is developed based on calculations of electromagnetic wave propagation and scattering at the s band of wavelength 10 7 cm in a hydrometeor containing atmosphere the t matrix method is used for the scattering calculation of raindrops and the rayleigh scattering approximation is applied to snow and ha

moho depth variation in taiwan from teleseismic receiver functions we determine lateral variation of moho discontinuity crustal thickness and vp vs ratios in the vicinity of taiwan by analyzing all the available teleseismic waveform data collected by the broadband array in taiwan for seismology network from 1998 to 2004 the crustal thickness and the average crustal vp vs ratio beneath each station are obtained by stacking ps ppps and ppss psps phases coherently the best estimated crustal thickness of taiwan from 27 broadband stations is 30 km on average the thinnest crust 11 15 km is found east of the longitude valley suture zone as part of the oceanic crust of the philippine sea plate in other places the crustal thickness varies from 17 19 km in northern taiwan to 32 39 km in the southwestern island the deepest moho is found to be 53 km beneath station sslb in central taiwan the average crustal vp vs ratio in taiwan is 1 74 with higher values of 1 74 1 99 in the north and lower values of 1 60 1 74 in the south the crustal thickness variation is supported by gravity measurements in taiwan and indicates that the collision between the philippine sea plate and eurasian plate in taiwan involves the whole crust the thin crust and high vp vs ratios in northern taiwan are believed to be related to the volcanism in tatun and keelung located in the southwestern extent of the okinawa trough

sensitivity of tropical pacific convection to dry layers at mid to upper levels simulation and parameterization tests abstract numerical forecast experiments are carried out to investigate the implications of observed moisture variability in the tropical pacific for deep convection the study uses a series of quasi cloud resolving model forecasts with a triple nested version of the naval research laboratory s coupled ocean atmosphere mesoscale prediction system coamps the forecasts are carried out for a dry tongue episode in the tropical western pacific in november 1998 during a 24 h forecast a number of convective cells develop in an area of deep convection near the edge of the simulated dry tongue in the coamps 3 km mesh inner grid which is located in the southern portion of the domain of the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare field program the forecast is repeated multiple times using a moisture profile from a toga coare dry tongue episode to modify the lateral boundary conditions for the 3 km mesh grid over layers of varying depth and altitude the entrai

sequential inversion of local earthquake traveltimes and gravity anomaly the example of the western alps summary we present a joint analysis of gravity anomaly and seismic arrival time data recorded in the western alps seismological data were collected by a network of 126 permanent and temporary stations implemented in 1996 a set of 550 local events has been recorded gravity data result from the addition of two new gravity surveys to an existing data base a published velocity model obtained by local earthquake tomography let was used to construct an initial 3 d gravity model using a linear velocity density relationship birch s law while the synthetic bouguer anomaly field calculated for this model has the same shape and wavelength as the observed anomaly its amplitude is strongly underestimated to derive a crustal velocity density model that accounts for both types of observations we performed a sequential inversion of seismological and gravity data the variance reduction of the arrival time data for the final sequential model was comparable to the variance reduction obtained by simple let moreover the sequential model explained 90 per cent of the observed gravity anomaly the main features of our model compared with the let model are 1 an important broadening of the high velocity anomaly associated with the high velocity high density ivrea body 2 a 10 km thick low velocity zone beneath the nappes of digne and castellane and 3 a high velocity zone at more than 25 km depth under the internal zone of the range

a nonhydrostatic mesoscale simulation of the 10 11 june 1994 coastally trapped wind reversal abstract during the summer months the california coast is under the influence of persistent northwesterly flow several times each summer this regime is disrupted by coastally trapped wind reversals ctwr in which the northwesterly flow is replaced by southerlies in a narrow zone along the coast controversy exists as to the physical mechanisms responsible for initiation and maintenance of ctwrs while it is clear that coastal terrain is important in creating the trapped response the precise role played by terrain is unclear in the present study these issues are investigated using a nonhydrostatic mesoscale model to simulate the 10 11 june 1994 ctwr event the results show that the model successfully reproduces many of the observed features of this event including anomalous vertical structure involving the relatively shallow boundary layer with a warm nearly neutral layer above the northward propagation of southerly flow in advance of a tongue of coastal stratus fog and a substantial reduction i

on the dynamics of tropical cyclone and trough interactions abstractthe interaction between a tropical cyclone tc and an upper level trough is simulated in an idealized framework using coupled ocean atmosphere mesoscale prediction system coamps for trop

tomographic imaging of lithospheric structures under taiwan abstract tomographic images of the crustal and mantle velocity structures under taiwan are obtained by simultaneous inversion of local earthquake p wave arrival times for hypocenters and p wave velocity structures in northern taiwan a high velocity zone coinciding with the wadati benioff zone can readily be identified as the subducted philippine sea plate the imaged zone dips toward the north at an angle of 40 from a depth range of 20 55 to 100 130 km an upper mantle low velocity wedge ranging from 40 to 80 km in depth exists above the subducted slab above this wedge is the ilan plain of northern taiwan which lies at the west end of the okinawa trough a well recognized back arc basin the crustal velocities under the plain are also relatively low the well defined high velocity zone and the low velocity wedge provide some constraints on the thermal structures of the subduction system under northern taiwan in tomographic images across the central section of taiwan thickening of the crust and up arching of the lower crustal materials under the central range are commonly observed the crust under the western foothills region is clearly thinner and the near surface low velocity layers are well developed the structures under the central range show that although the taiwan orogeny is quite young a root deeper in the north and shallowing to the south has formed the results of our tomography show that a significant portion of the lithosphere is involved in the taiwan orogeny

a synthesis of the geologic evolution of taiwan abstract the island arc of taiwan is composed of cenozoic geosynclinal sediments more than 10 000 m thick lying on a pre tertiary metamorphic basement pleistocene to miocene andesitic islands surround the main island and are related mostly to arc magmatism the penghu island group in the taiwan strait is covered with pleistocene flood basalt neogene shallow marine clastic sediments are exposed mainly in the western foothills with pleistocene andesitic extrusives at the northern tip and the northeastern offshore islands a thick sequence of paleogene to miocene argillitic to slaty metaclastic rocks underlies the western central range and forms the immediate sedimentary cover on the pre tertiary metamorphic complex to the east which represents an older mesozoic arc trench system the coastal range in eastern taiwan is a neogene andesitic magmatic arc including also a large variety of volcaniclastic and turbiditic sediments cenozoic taiwan is the site of arc continent collision where the luzon arc on the philippine sea plate overrides the chinese continental margin on the eurasian plate east and northeast of taiwan the polarity of subduction changes whereby the oceanic philippine sea plate is subducting beneath the ryukyu arc system on the eurasian plate continent arc collision in taiwan island is anomalous and may occur in a broad belt of deformation rather than along a well defined plate boundary or subduction zone

observations and numerical simulations of mountain waves in the presence of directional wind shear three research aircraft observed small amplitude gravity waves over the south western french alps on 13 november 1999 during the mesoscale alpine programme map radiosonde ascents and global positioning system dropsondes deployed by map research aircraft indicate that the upstream flow was characterized by topographic blocking below 2 km and low level directional wind shear associated with a synoptic scale depression that extended above the alpine crest the in situ vertical velocity data from the three research aircraft and backscatter from lidar onboard the low level and upper level aircraft exhibit gravity wave signatures in the lower troposphere that are characterized by relatively short horizontal wavelengths on a scale of 5 km or less the in situ flight level and backscatter data also suggest a rapid decrease in the wave amplitude with height due to a directional critical layer that partially absorbs wave energy in the lower to middle troposphere in concert with a decrease in the scorer parameter with height that traps the wave energy numerical simulation results obtained from the non hydrostatic coupled ocean atmosphere mesoscale prediction system model using a horizontal resolution of 556 m indicate the presence of low level wave breaking above the highest peaks and confirm the presence of trapped waves and a directional critical level results based on linear theory and nonlinear model simulations suggest that the absorption of wave energy associated with the directional critical layer has an important impact on the wave characteristics including the momentum flux copyright 2006 royal meteorological society

vertical variability of cloud hydrometeors in the stratiform region of mesoscale convective systems and bow echoes abstract during the bow echo and mesoscale convective vortex experiment the noaa p 3 research aircraft executed 17 spiral descents to the rear of convective lines to document the vertical variability of hydrometeors above within and below the stratiform melting layer ten spirals were behind lines that exhibited bowing at some stage in their evolution although quick descents on some spirals forced sampling of different particle zones clear trends with respect to temperature were seen for 16 spirals the ambient relative humidity with respect to ice was in the range of 100 4 at temperatures between 10 c and the melting layer but exhibited steady decreases below the melting layer to an average relative humidity with respect to water of 77 15 at 9 c in contrast one spiral conducted on 29 june 2003 directly behind a developing bow echo had a relative humidity with respect to ice averaging 85 at heights above the 0 c level and relative humidity with respect to ice further decreased below the

taiwan mountain building insights from 2 d thermomechanical modelling of a rheologically stratified lithosphere summary the taiwan orogen has long been regarded as a case example for studying mountain building in association with subduction processes in this paper we present a fully coupled thermomechanical modelling of the taiwan collision based on a realistic viscous elastic plastic rheology it satisfactorily reproduces available thermochronometric data long short term deformation patterns heat flux and erosion sedimentation distribution across the taiwan orogeny we found that a deep seated flux of asian crustal material into the orogenic wedge should be invoked to counter balance observed exhumation and erosion in the central range however in contrast with recent thermokinematic models of exhumation and deformation suggesting that underplating plays a significant role we show that most constraints on exhumation and deformation can be more straightforwardly interpreted by the frontal accretion of the rheologically layered asian crust we finally infer that such a model is in better agreement with the basic expectation that the hot young and buoyant chinese continental margin should hardly be subducted beneath the cold old and dense oceanic plate of the philippines sea

the role of cloud top generating cells and boundary layer circulations in the finescale radar structure of a winter cyclone over the great lakes abstractdata from airborne w band radar are used in conjunction with thermodynamic fields from the weather research and forecasting model and air parcel back trajectories from the hysplit model to investigate the finescale reflectivity vertical motion and airmass structure of the comma head of a winter cyclone in the vicinity of the great lakes cloud top generating cells formed along an upper level frontal boundary vertically separating dry air which 48 h earlier was located in the upper troposphere over south central canada from moist air which was located in the lower troposphere over the southeast united states the stronger updrafts within the generating cells had vertical velocities ranging from 1 to 3 m s 1 the generating cells were important to precipitation production within the comma head precipitation trails formed within the generating cells could sometimes be followed to the boundary layer before merging boundary layer air beneath the cyclone s comma head exhibited convective circulati

supercritical flow interaction within the cape blanco cape mendocino orographic complex abstract supercritical flow interaction occurring in the marine boundary layer between closely spaced coastal capes is investigated with a mesoscale numerical prediction model as an extension of previous work the u s navy s coupled ocean atmosphere mesoscale prediction system coamps is used to perform idealized model simulations with marine layers of varying upstream froude number to elucidate the different flow responses for a single convex bend the impact upon the supercritical flow of introducing a series of closely spaced coastal bends is then investigated the expansion fan is significantly reduced in magnitude and size by the formation of a compression wave at a blocking concave bend approximately 150 km downstream building upon the idealized marine layer response real data forecasts are then examined for several time periods of supercritical flow interaction between cape blanco oregon and cape mendocino california observations from the coastal waves 1996 cw96 field program were colle

geodetic and geophysical results from a taiwan airborne gravity survey data reduction and accuracy assessment 1 an airborne gravity survey was conducted over taiwan using a lacoste and romberg lcr system ii air sea gravimeter with gravity and global positioning system gps data sampled at 1 hz the aircraft trajectories were determined using a gps network kinematic adjustment relative to eight gps tracking stations long wavelength errors in position are reduced when doing numerical differentiations for velocity and acceleration a procedure for computing resolvable wavelength of error free airborne gravimetry is derived the accuracy requirements of position velocity and accelerations for a 1 mgal accuracy in gravity anomaly are derived gps will fulfill these requirements except for vertical acceleration an iterative gaussian filter is used to reduce errors in vertical acceleration a compromising filter width for noise reduction and gravity detail is 150 s the airborne gravity anomalies are compared with surface values and large differences are found over high mountains where the gravity field is rough and surface data density is low the root mean square rms crossover differences before and after a bias only adjustment are 4 92 and 2 88 mgal the latter corresponding to a 2 mgal standard error in gravity anomaly repeatability analyses at two survey lines suggest that gps is the dominating factor affecting the repeatability fourier transform and least squares collocation are used for downward continuation and the latter produces a better result two geoid models are computed one using airborne and surface gravity data and the other using surface data only and the former yields a better agreement with the gps derived geoidal heights bouguer anomalies derived from airborne gravity by a rigorous numerical integration reveal important tectonic features

velocity structure and seismicity of southeastern tennessee the seismic zone in southeastern tennessee is at the confluence of major crustal features which have been interpreted largely from potential data and their relation to seismicity could help us understand why major earthquakes sometimes occur in the eastern united states in this paper we solve for the previously unknown velocity structure of the upper crust by an inversion of travel time residuals from relocated earthquakes the gravity anomalies are included by using a linear relation between average anomalous density and average anomalous velocity the velocity model demonstrates that the seismicity is concentrated in areas of average to below average velocity and does not appear to be associated with one of the previously identified major crustal features the high velocity zones mark areas that are generally lacking in seismicity the association of earthquake hypocenters with regions of low velocity crustal rocks is consistent with other intraplate seismic zones and this association supports the conjecture that intraplate earthquakes occur in crust that may have been weakened the velocity anomalies at midcrustal depths do not support the new york alabama ny al lineament as a linear feature extending through southeastern tennessee and parallel to contours in gravity anomalies as originally proposed a continuation of the ny al lineament to the southwest requires either a 15 degree southwestward change in direction or a displacement to be consistent with the velocity anomalies the seismically active areas in southeastern tennessee do not appear to be constrained by the major crustal features but instead the seismicity is characterized by the distribution of hypocenters and their association with low velocity regions at midcrustal depths

two dimensional crustal structures of taiwan from gravity data to delineate the tectonic character of taiwan an island wide gravity survey of taiwan was conducted between 1980 and 1987 the bouguer anomaly map shows that in general isogals trend nne in consonance with the overall structural trend of the island with seismic and other geophysical data as constraints the subsurface density structures were modeled along three profiles across the major structural trends the gravity data are consistent with average continental moho depths of 26 km in the coastal plain and the western foothills 28 km underneath the coastal range in eastern taiwan and 33 km under the central range a lack of significant correlation of the bouguer anomalies with the topography implies dynamic rather than isostatic support of topography in the taiwan region

relevance of conditional symmetric instability in the interpretation of wide cold frontal rainbands a case study 20 may 1976 comparisons are made between the characteristics of rainbands observed in a frontal system using a c band doppler radar and dynamical mechanisms relevant on the mesoscale 100 km the orientation of these rainbands nearly aligned with the thermal wind suggests that symmetric instability may play a role in their formation this possible explanation of the precipitation is discussed

rheology and strength of the eurasian continental lithosphere in the foreland of the taiwan collision belt constraints from seismicity flexure and structural styles 1 deformation in western taiwan is characterized by variable depth frequency distribution of crustal earthquakes which are closely connected with along strike variations of tectonic styles thin or thick skinned around the peikang high a major inherited feature of the chinese margin to fit the calculated high crustal geotherm and the observed distribution of the crustal seismic activity a qz diorite and granulite composition for the upper and the lower crust is proposed we then model the plate flexure through te estimates using brittle elastic ductile plate rheology flexure modeling shows that the best fit combination of te boundary condition is for thrust loads acting at the belt front the calculated te vary in the range of 15 20 km these values are primarily a reflection of the thermal state of the rifted chinese margin inherited from the oligocene spreading in the south china sea however other mechanical properties such as the degree of crust mantle coupling and the thickness of the mechanically competent crust and mantle are considered south of the peikang high flexure modeling reveals lower te associated with thinner mechanically strong layers variable stress strain distribution associated with a higher degree of crust mantle decoupling is examined to explain plate weakening we first show that plate curvature cannot easily explain strength reduction and observed seismic activity additional plate boundary forces arising from the strong coupling induced by more frontal subduction of a buoyant crustal asperity i e the peikang high with the overriding plate are required favorably oriented inherited features in the adjacent tainan basin produce acceleration of strain rates in the upper crust and hence facilitate the crust mantle decoupling as attested by high seismic activity and thick skinned deformation the relative weakening of the lower crust and mantle then leads to weaken the lithosphere by contrast to the north more oblique collision and the lack of inherited features keep the lithosphere stronger this study suggests that when the eurasian plate enters the taiwan collision tectonic inheritance of the continental margin exerts a strong control on the plate deformation by modifying its strength

modeling of upwelling relaxation events with the navy coastal ocean model prediction system coamps tm coamps is a registered trademark of the naval research laboratory issues investigated in this study are ncom based model simulations of upwelling and relaxation events coupling to coamps use of sigma versus hybrid sigma z vertical grids and coupling with a larger scale model on the open boundaries the ncom simulations were able to reproduce the observed sequence of the upwelling and relaxation events which can be attributed in part to the good agreement between the observed and coamps winds comparisons with the mooring observations show that coamps overestimates shortwave radiation values which makes the ncom modeled ssts too warm in comparison with observations the ncom runs forced with different resolution atmospheric forcing 3 versus 9 km do not show significant differences in the predicted ssts and mixed layer depths at the mooring locations at the same time during the extended upwelling event the model runs forced with 3 and 9 km resolution coamps fields show differences in the surface circulation patterns which are the most distinct in the southern portion of the model domain the model run with 9 km forcing develops a northward flow along the coast which is not present in the run with 3 km forcing and in observations for example hf radar derived radials comparison of the wind patterns of the 3 and 9 km products shows a weakening of the 9 km wind stress along the southern coast of the ncom model domain which is responsible for the development of the artificial northward flow in the ncom run with 9 km forcing

modelling precipitation in frontal rainbands the main aim of this study is to establish the ability of a simple parametrization to represent adequately the microphysical processes acting in frontal rainbands in order to do this we compare it with a more detailed parametrization in conditions typical of warm frontal and narrow cold frontal rainbands simulations using a 2 dimensional diagnostic model indicate that a mixed phase parametrization is required in dynamical models of high resolution

the intense lee wave rotor event of sierra rotors iop 8 abstract a large amplitude lee wave rotor event observationally documented during sierra rotors project intensive observing period iop 8 on 24 26 march 2004 in the lee of the southern sierra nevada is examined mountain waves and rotors occurred over owens valley in a pre cold frontal environment in this study the evolution and structure of the observed and numerically simulated mountain waves and rotors during the event on 25 march in which the horizontal circulation associated with the rotor was observed as an opposing easterly flow by the mesonetwork of surface stations in owens valley are analyzed the high resolution numerical simulations of this case performed with the coupled ocean atmosphere mesoscale prediction system coamps run with multiple nested grid domains the finest grid having 333 m horizontal spacing reproduced many of the observed features of this event these include small amplitude waves above the sierra ridge decoupled from thermally forced flow within the valley and a l

velocity density properties of the lithosphere from three dimensional modeling at the geysers clear lake region california the analysis of travel time delays from 94 teleseisms recorded at the geysers clear lake california region reveals a broad area of delay centered at mount hannah and encompassing the geysers geothermal field a three dimensional velocity inversion of the delays indicates that the source of the delays is a low velocity body largely within the top 30 km of the lithosphere velocity decreases of as much as 20 are observed in the top 15 km near mount hannah and diminish with depth no significant velocity fluctuations are observed below 60 km the block model of velocity perturbations resulting from the teleseismic residual inversion is used to predict the observed bouguer gravity field by solving for the relation between velocity and density perturbation comparison between the predicted gravity and observed gravity indicates that the same body responsible for the teleseismic delays accounts for the long wave length 30 mgal bouguer gravity minima at mount hannah the results of the velocity density modeling suggest that the material beneath mount hannah and the geysers may be partially molten and somewhat more silicic than the surrounding medium supplemental table is available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington d c 20009 document j81 006 1 00 payment must accompany order

dynamical effects of ice sublimation in a frontal wave the dynamical role of ice sublimation in weather systems is briefly reviewed observations are presented from the fronts and atlantic storm track experiment fastex intensive observation period 16 that show variations of static stability humidity and mesoscale circulation corresponding to those associated theoretically with sublimation of ice precipitation it is thus suggested that the observations display the mechanism proposed by clough and franks in which forward mesoscale flows are associated with moist adiabatic descent supported by the sublimation cooling this mechanism was suggested as an important stage in the evolution of many mesoscale rain bands a set of three model simulations of the event has been made with versions of the mel office s unified model of these a mesoscale model integration with 11 km resolution and 45 levels clearly displays the symptoms and is diagnosed to demonstrate its consistency with the clough franks mechanism an integration omitting the cooling due to sublimation differs significantly from the full model experiment in the structure of low level wind fields frontal troughs and mesoscale precipitation distribution il is also demonstrated that the static stability transition mesoscale circulation and mid tropospheric potential vorticity perturbations are substantially weakened in this integration thus confirming that the clough franks mechanism is also operating in the numerical weather prediction nwp model we deduce from these studies that ice precipitation and its sublimation has a major role in determining mesoscale circulation and structure in mid latitude weather systems affecting stratification and the formation of features such as fronts and rain bands these are substantially affected by the fall and evaporation of ice crystals which are both important to temperature and moisture transports and the behaviour of nwp models on time scales of hours to days in our integrations dynamical feedback due to sublimation cooling coincided with extreme negative potential vorticity values and potentially conditional symmetric instability hence the anticyclonic motion occurring in the cloud head or deep cloud of the moist warm sector as in this case in moist warm sectors a substantial role for sublimation may be anticipated more generally particularly for air trajectories receiving most ice precipitation we suggest that the described phenomenon be referred to as sublimation enhanced descent or sed it is concluded that in view of tins demonstrated sensitivity substantial attention should be given to refining microphysical parametrizations in nwp models and that radar and sounding observations from the fastex experiment provide a suitable basis for validating these schemes

detailed lithospheric structure of an arc continent collision beneath taiwan revealed by joint inversion of seismological and gravity data the largest compilation of seismological and gravimetry data are combined in a sequential inversion to shed light on unresolved crustal structures in northern taiwan and southernmost ryukyu area our density and seismic velocity models reveal a nw se trending transfer zone tz between 23 25 n and 24 n this primary tz delimits major changes in the eurasian plate ep slab geometry and dynamics as well as first order crustal structure variations north of this tz the ep slab is breaking off from north to south as a result of 1 the extreme ep bending favouring plastic deformation 2 the stretching of the plate caused by the downward pull of the oceanic part of the slab versus the buoyancy of continental part of the plate still deforming in the taiwan orogen and 3 the indentation of the ep slab by the western slab edge of the philippine sea plate psp the change of ep slab dip angle is clearly observed in the density profiles the subvertical northernmost tip of ep slab allows asthenospheric upwelling through slab tear and subsequent invasion of the region beneath the longitudinal valley this process is migrating southward up to the tz which marks the transition to a different rheological behaviour the combination of deep arc continent collision clockwise asthenospheric toroidal flow and westward propagation of the southern okinawa rift results in a 100 clockwise rotation of the northernmost tip of the central range the eastward extrusion of this crustal block 90 km in diameter overlays and deflects the psp slab the indentation of the ep by the psp luzon arc thus results in complex lithospheric accommodation processes and structures

snow microphysical observations in shallow mixed phase and deep frontal arctic cloud systems snow particle size distributions particle size 400 m in the western arctic measured with in situ aircraft instrumentation during the surface heat budget of the arctic first isccp regional experiment arctic clouds experiment and mixedphase arctic cloud experiment are analysed three cases of shallow precipitating mixed phase boundary layer clouds and two cases of deep precipitating frontal clouds are examined overall the shallow cases had much lower values of particle concentration and ice water content than the deep cases indicating large differences in ice initiation and growth between these regimes within a given case for both the shallow and deep frontal systems and for the dataset as a whole crystal concentration had little correlation with temperature height despite an active aggregation process that was indicated by large aggregates 5 mm observed in four out of the five cases exponential size distributions are fitted to the observations allowing a direct comparison with the snow particle size distributions that are represented with exponential functions in many bulk microphysics schemes used in weather and climate models values of the fitted intercept parameter n0 are generally 2 10 times smaller for the shallow compared to the deep frontal cases as a result of differences in crystal concentration between these regimes values of n0 10 7 m 4 specified for snow in many bulk microphysics schemes are broadly consistent with fitted n0 for the deep cases but larger than values for the shallow cases the deep frontal cases also exhibit a relationship between n0 and temperature consistent with previous observations of midlatitude frontal systems however there are no consistent differences in n0 between the shallow and deep cases when partitioned by ice water content fitted values of slope parameter for the shallow and deep cases are generally consistent with previous studies of lower latitude cloud systems copyright c 2011 royal meteorological society

the improve 1 storm of 1 2 february 2001 part ii cloud structures and the growth of precipitation abstract on 1 2 february 2001 a strong cyclonic storm system developed over the northeastern pacific ocean and moved onto the washington coast this storm was one of several that were documented during the first field phase of the improvement of microphysical parameterization through observational verification experiment improve in the 1 2 february case soundings and wind profiler measurements showed that a wide cold frontal rainband was coincident with the leading edge of an upper level cold front in a classical warm occlusion ground based radar observations revealed the presence of subbands within the wide cold frontal rainband and two layers of precipitation generating cells within this rainband one at 5 7 km msl and the other at 9 10 km msl the lower layer of generating cells produced fallstreaks that were traced from the cells down to the radar bright band at 2 km msl observations suggest a connection between the subbands and the lower layer of generating cells a research aircraft equipped

new gravity anomaly map of taiwan and its surrounding regions with some tectonic interpretations abstract in this study we compiled recently collected from 2005 to 2015 and previously reported published and open access gravity data including land shipborne and satellite derived data for taiwan and its surrounding regions based on the cross over error analysis all data were adjusted and new free air gravity anomalies were obtained shedding light on the tectonics of the region to obtain the bouguer gravity anomalies the densities of land terrain and marine sediments were assumed to be 2 53 and 1 80 g cm3 respectively the updated gravity dataset was gridded with a spacing of one arc minute several previously unnoticed gravity features are revealed by the new maps and can be used in a broad range of applications 1 an isolated gravity high is located between the shoushan and the kaoping canyon off southwest taiwan 2 along the luzon arc both free air and bouguer gravity anomaly maps reveal a significant gravity discontinuity feature at the latitude of 21 20 n 3 in the southwestern okinawa trough the ne sw trending cross back arc volcanic trail cbvt marks the low high gravity anomaly both free air and bouguer boundary

electrification of stratiform regions in mesoscale convective systems part ii two dimensional numerical model simulations of a symmetric mcs abstract model simulations of a symmetric mesoscale convective system mcs observations discussed in part i were conducted using a 2d time dependent numerical model with bulk microphysics a number of charging mechanisms were considered based on various laboratory studies the simulations suggest that noninductive ice ice charge transfer in the low liquid water content regime characteristic of mcs stratiform regions is sufficient to account for observed charge density magnitudes and as much as 70 of the total charge in the stratiform region the remaining 30 is contributed by charge advection from the convective region the strong role of in situ charging is consistent with previous water budget studies which indicate that roughly 70 of the stratiform precipitation results from condensation in the mesoscale updraft thus both in situ charging and charge advection the two previously identified hypotheses appear to be important contributors to the electrical budget of the stratiform region the

observed microphysical evolution for two east coast winter storms and the associated snow bands abstractthis paper presents the observed microphysical evolution of two coastal extratropical cyclones 19 20 december 2009 and 12 january 2011 and the associated passage of heavy snowbands in the cyclone comma head the observations were made approximately 93 km east of new york city at stony brook new york surface microphysical measurements of snow habit and degree of riming were taken every 15 30 min using a stereo microscope and camera and snow depth and snow density were also recorded a vertically pointing ku band radar observed the vertical evolution of reflectivity and doppler vertical velocities there were rapid variations in the snow habits and densities related to the changes in vertical motion and depth of saturation at any one time a mixture of different ice habits was observed certain ice habits were dominant at the surface when the maximum vertical motion aloft occurred at their favored temperature for depositional growth convective seeder cells above 4 km msl resulted in relativel

surface microphysical observations within east coast winter storms on long island new york abstractsurface observations of ice habit and degree of riming were measured for 12 cyclone events over 3 winter seasons at stony brook new york on the northeast coast of the united states a total of 205 6 cm of snow accumulated during these storms with an average degree of riming of 1 25 out of 5 and snow to liquid ratio ranging from 3 1 to 17 1 there were consistent spatial patterns of habit and riming intensity relative to the cyclone structure cold type habits side planes and bullets commonly occurred within the outer comma head to the north and northeast of the cyclone center in the middle of the comma head moderately rimed dendrites plates and needles were observed close to the cyclone center heavy riming was observed with needles and graupel the western quadrant of the comma head had primarily plates and dendrites with little to no riming periods of light riming and high snow liquid ratios 13 1 are dominated by cold type habits dendrites and plates and have similar vertical m

ice crystal habits and growth processes in stratiform clouds with embedded convection examined through aircraft observation in northern china abstractice crystal habits and growth processes in two cases of stratiform clouds with embedded convection are investigated using data observed simultaneously from three aircraft on 18 april 2009 and 1 may 2009 as part of the beijing cloud experiment bce the results show that the majority of ice crystal habits found in the two cases at temperatures between 0 and 16 c included platelike needle column capped column dendrite and irregular a mixture of several ice crystal habits was identified in all of the clouds studied however the ice crystals recorded in the embedded convection regions contained more dendrites and possessed heavier riming degrees and the ice crystals identified in the stratiform clouds contained more hexagonal plate crystals both riming and aggregation processes played central roles in the broadening of particle size distributions psds and these processes were more active in embedded convection regions than in stratiform regions however riming was more prevalent in the

diagnosis of hydrometeor profiles from area mean vertical velocity data a simple one dimensional microphysical retrieval model is developed for estimating vertical profiles of liquid and frozen hydrometeor mixing ratios from observed vertical profiles of area mean vertical velocity in regions of convective and or stratiform precipitation the mean vertical velocity profiles can be obtained from doppler radar single and dual or other means the one dimensional results are shown to be in good agreement with two dimensional microphysical fields from a previous study sensitivity tests are performed

distribution and mechanisms of orographic precipitation associated with typhoon morakot 2009 abstractusing a combination of doppler radar observations and rain gauge data this study documents detailed aspects of the orographic precipitation associated with typhoon morakot 2009 rainfall distribution over underlying topographical features and possible physical mechanisms responsible for the observed orographic enhancement are explored the study region constitutes an approximately two dimensional south north oriented orographic barrier with higher wider lower narrower terrain features in its northern southern portions i e the northern and southern barriers upstream conditions were characterized by abundant typhoon background precipitation embedded within strong nearly saturated westerly to west southwesterly oncoming flow the observations show that a wide area of topographically enhanced precipitation and the rainfall maxima were confined to the windward slopes of the northern barrier whereas the strongest rainfall tended to occur near and or slightly downstream of the mountain c

a modeling study of moist and dynamic vorticity vectors associated with two dimensional tropical convection 1 moist qv mvv and dynamic dvv vorticity vectors are introduced to study 2 d tropical convection with 2 d cloud resolving simulation data the cloud model is forced by vertical velocity zonal wind horizontal advection and sea surface temperature data obtained from toga coare and is integrated for a selected 10 day period the mvv and dvv have zonal and vertical components in the 2 d x z frame analysis of zonally averaged and mass integrated quantities shows that the vertical zonal component of the mvv and the sum of the cloud hydrometeor mixing ratios are in phase with a correlation coefficient of 0 78 0 32 and the vertical zonal component of the dvv and the sum of the mixing ratios are in out of phase with a correlation coefficient of 0 52 0 62 indicating that the vertical component of the mvv and both zonal and vertical component of the dvv are closely associated with tropical convection the tendency equations for the mvv and dvv are derived and the zonally averaged and mass integrated tendency budgets are analyzed the tendency of the vertical component of the mvv is mainly determined by the interaction between the vorticity and the zonal gradient of condensational depositional heating the tendency of the zonal component of the dvv is controlled by the interaction between the vorticity buoyancy and vertical pressure gradient whereas the tendency of the vertical component is determined by the interaction between the vorticity and zonal pressure gradient

orographic precipitation forcing along the coast of northern california during a landfalling winter storm abstractthis study documents orographic precipitation forcing along the coastal mountains of northern california during the landfall of a significant winter storm over the period 16 18 february 2004 the primary observing asset is a scanning x band doppler radar deployed on the coast at fort ross california which provides low level e g below 1 km msl horizontal and vertical scans of radial velocity and reflectivity to characterize airflow and precipitation structures further context is provided by a wind profiling radar a radio acoustic sounding system rass balloon soundings buoys a gps receiver and surface meteorological sensors the winter storm is divided into two episodes each having pre cold frontal low level jet llj structures and atmospheric river characteristics episode 1 has a corridor of terrain trapped airflow tta that forms an interface with the llj the interface extends 25 km offshore in a 0 5 km vertical layer and the western edge of this interface near the ocean surf

three dimensional characteristics of stratospheric mountain waves during t rex abstract measurements from the national science foundation national center for atmospheric research nsf ncar gulfstream v g v obtained during the recent terrain induced rotor experiment t rex indicate marked differences in the character of the wave response between repeated flight tracks across the sierra nevada which were separated by a distance of approximately 50 km observations from several of the g v research flights indicate that the vertical velocities in the primary wave exhibited variations up to a factor of 2 between the southern and northern portions of the racetrack flight segments in the lower stratosphere with the largest amplitude waves most often occurring over the southern flight leg which has a terrain maximum that is 800 m lower than the northern leg multiple racetracks at 11 7 and 13 1 km altitudes indicate that these differences were repeatable which is suggestive that the deviations were likely due to vertically propagating mountain waves that varied systematically in am

the impact of horizontal grid spacing on the microphysical and kinematic structures of strong tropical cyclones simulated with the wrf arw model abstract using the advanced weather research and forecasting numerical model the impact of horizontal grid spacing on the microphysical and kinematic structure of a numerically simulated tropical cyclone tc and their relationship to storm intensity was investigated with a set of five numerical simulations using input data for the case of hurricane rita 2005 the horizontal grid spacing of the parent domain was systematically changed such that the horizontal grid spacing of the inner nest varied from 1 to 5 km by an increment of 1 km this while keeping geographical dimensions of the domains identical within this small range of horizontal grid spacing the morphology of the simulated storms and the evolution of the kinematic and microphysics field showed noteworthy differences as grid spacing increased the model produced a wider more tilted eyewall a larger radius of maximum winds and higher amplitude low wavenumber eyewall asymmetries the coarser resolution simulations also produced larger v

the role of vertically propagating gravity waves forced by melting induced cooling in the formation and evolution of wide cold frontal rainbands abstractrealistic mesoscale model simulations using the weather research and forecasting wrf model and idealized dry simulations were used to study the mechanisms responsible for the formation and evolution of wide cold frontal rainbands wcfrs associated with a wintertime cyclone that moved onto the washington coast the wrf simulation reproduced observed characteristics of three successively formed wcfrs including their spacing and movement as well as the timing of the formation of two wcfrs behind the first sensitivity experiments showed that melting induced cooling in the stratiform precipitation area behind the surface cold front was essential for the formation of the first and second wcfrs whereas the third wcfr was formed by the release of potential instability within an ascent forced by upper level frontogenesis enhanced frontal updrafts responsible for the first and second wcfrs were created by a superposition of a broad updraft caused by frontal dynamics and upward propagating gravity wav

improved seismic tomography offshore northeastern taiwan implications for subduction and collision processes between taiwan and the southernmost ryukyu summary to improve the resolution in imaging the 3 d vp and vp vs structures in the taiwan region especially offshore eastern taiwan we combine the arrival times from eleven ocean bottom seismometers obss and from seismic stations of the japan meteorological agency jma with those from the permanent stations of taiwan central weather bureau seismic network cwbsn and taiwan strong motion instrumentation program tsmip by doing so we have obtained a new 3 d tomographic model for taiwan and its surrounding regions with a better resolution especially in the area offshore northeastern taiwan we also used this new tomography model to relocate the hypocentres of the earthquakes in northeastern taiwan and determined the focal mechanisms of relatively large events our tomography results indicate that in the region northeast of taiwan the subducting oceanic philippine sea plate beneath the eurasian continental lithosphere is characterized by a high vp layer surrounded by lower vp areas this p wave velocity characteristics of the subducting slab provides a better constraint on the geometry of the subduction interface especially in its shallower portion in the hangingwall eurasian block above the subduction interface a vertically elongated high vp vs body appears to originate from the interface at depths between 100 and 140 km we suggest that it represents the partially melted materials that are related to the magmatic activity of the ryukyu volcanic arc

precipitation over concave terrain abstract many topographic barriers are comprised of a series of concave or convex ridges that modulate the intensity and distribution of precipitation over mountainous areas in this model based idealized study stratiform precipitation associated with stratified moist airflow past idealized concave ridges is investigated with a focus on windward blocking flow confluence and the associated precipitation enhancement it is found that flow confluence and precipitation enhancement by a concave ridge are controlled by the nondimensional ridge height m m nmhm u where nm is the moist buoyancy frequency hm is the maximum ridge height and u is the wind speed based on which three dynamical regimes can be defined in the linear regime m 0 4 a flow confluence zone is present over the upwind slope of the ridge vertex where precipitation is significantly enhanced the precipitation enhancement is due to the additional updraft driven by the horizontal flow convergence with a considerable contribution fr

deep structure of the baikal rift zone revealed by joint inversion of gravity and seismology 1 the question of plate boundary forces and deep versus shallow asthenospheric uplift has long been debated in intracontinental rift areas particularly in the baikal rift zone asia which is colder than other continental rifts as previous gravity and teleseismic studies support the dominance of opposing mechanisms in the baikal rift we reconsidered both data sets and jointly inverted them this more effective approach brings insight into location of the perturbing bodies related to the extension in this region our new joint inversion method allows for inverting the velocity density relationship with independent model parametrization we obtain velocity and density models that consistently show 1 crustal heterogeneities that coincide with the main tectonic features at the surface 2 a faster and denser cratonic mantle nw of lake baikal that we relate to the thermal contrast between old and depleted archean siberian platform and paleozoic orogenic belt sayan baikal belt 3 three dimensional topographic variations of the crust mantle boundary with well located upwarpings and 4 the lithosphere asthenosphere boundary uplift up to 70 km depth with a nw dip our resulting velocity and density models support the idea of a combined influence of lithospheric extension and inherited lithospheric heterogeneities for the origin of the baikal rift zone index terms 1234 geodesy and gravity regional and global gravity anomalies and earth structure 7218 seismology lithosphere and upper mantle 8122 citation tiberi c m diament j deverchere c petit mariani v mikhailov s tikhotsky and u achauer deep structure of the baikal rift zone revealed by joint inversion of gravity and seismology

seismic tomography of taiwan improved constraints from a dense network of strong motion stations in this study a large collection of 41 141 s p times from the untapped records of the taiwan strong motion instrumentation program tsmip network is combined with the p and s wave arrival times from the taiwan central weather bureau seismic network cwbsn to image the v p and v p v s structures beneath taiwan the records from the 680 tsmip stations throughout taiwan in the past 15 years enhance the path coverage and the resolution in the tomography inversions tremendously our result for the v p structure largely confirms previous studies but brings better constraint on the v p v s structure the colliding luzon volcanic arc is characterized by a belt of high v p and high v p v s with high seismicity that includes the offshore islands of lutao and lanyu and the coastal ranges in eastern taiwan at the depth between about 13 and 25 km this high v p v s belt can be traced to the subduction zone in the region between hualian and ilan in the deeper portion the shallow portions of the southwestern coastal plain and the pingtung region are also characterized by a belt of high v p v s with lower seismicity most of the events occurred at the base of the high v p v s zones we suggest that material strength in those regions may be too low to accumulate stress which may indicate water saturated young sediments finally the central range region is characterized by a low v p v s belt