thunderstorm genesis zones in the colorado rocky mountains as determined by traceback of geosynchronous satellite images abstract mountain thunderstorms often originate in preferred regions of the topography as shown qualitatively by pilot reports and more quantitatively by meteorological radar satellite and lightning detector studies to further investigate the phenomenon of mountain thunderstorm initiation we used time sequences of goes imagery to locate storms and to trace them back to their points of origin using three summers of data from days which started out clear we backtracked over 600 storms in the mountains of colorado and northern new mexico we plotted the origin points on a terrain map and drew contours of initiation frequency to identify regions with a high likelihood of producing thunderstorms we found that initiation sites tended to cluster into identifiable geographical locations or genesis zones consistent with findings based on the other data sources when cloud propagation effects were taken into account the locations of these genesis zones were also consistent with the locations of clusteri

a numerical study of the evolving convective boundary layer and orographic circulation around the santa catalina mountains in arizona part i circulation without deep convection abstract the daytime evolution of the thermally forced boundary layer bl circulation over an isolated mountain about 30 km in diameter and 2 km high is examined by means of numerical simulations validated with data collected in the cumulus photogrammetric in situ and doppler observations cupido field campaign two cases are presented one remains cloud free in the simulations and the second produces orographic convection just deep enough to yield a trace of precipitation the weather research and forecasting version 3 simulations at a resolution of 1 km compare well with cupido observations the simulations reveal a solenoidal circulation mostly contained within the convective bl but this circulation and especially its upper level return flow branch are not immediately apparent since they are overwhelmed by bl thermals a warm anomaly forms over the high terrain during the day but it is rather shallow and does not extend over the depth of the convective bl which bulges over the mountain low

pressure perturbations and upslope flow over a heated isolated mountain abstract surface and upper air data collected as part of the cumulus photogrammetric in situ and doppler observations cupido experiment during the 2006 monsoon season around the santa catalina mountains in southeast arizona are used to study the diurnal variation of the mountain scale surface convergence and its thermal forcing the thermal forcing is examined in terms of a horizontal pressure gradient force which is derived assuming hydrostatic balance the mountain is 30 km in diameter 2 km high and relatively isolated the environment is characterized by weak winds a deep convective boundary layer in the afternoon and sufficient low level moisture for orographic cumulus convection on most days the katabatic divergent surface flow at night and anabatic convergent flow during the day are in phase with the diurnal variation of the horizontal pressure gradient force which points toward the mountain during the day and away from the mountain at night the daytime pressure deficit over the mo

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

electroseismic and seismoelectric measurements of rock samples in a water tank an electromagnetic em or seismic wave can induce seismic or em waves because of the electrokinetic conversion based on the electric double layer in a fluid saturated porous medium we tested a new method for observing electroseismic and seismoelectric conversions in rock samples our method is designed to overcome the shortcoming of previous attempts to separate signals generated by a continuous electric or seismic source in a small container we first observed acoustic fields around electrodes excited by an electric pulse in a water tank or in a water saturated porous sample in our approach we immersed rock samples in a water tank and measure the seismic or electric responses using electric or acoustic pulses conveyed through the immersed electrodes or hydrophone we measured electroseismic and seismoelectric frequency responses in berea sandstone and westerly granite samples at a frequency range of 15 150 khz the measurements clearly separate the effects of the electric source background noises

pore scale modeling of electrical and fluid transport in berea sandstone the purpose of this paper is to test how well numerical calculations can predict transport properties of porous permeable rock given its 3d digital microtomography ct image for this study a berea 500 sandstone sample is used whose ct images have been obtained with resolution of 2 8 m porosity electrical conductivity permeability and surface area are calculated from the ct image and compared with laboratory measured values for transport properties electrical conductivity permeability a finite difference scheme is adopted the calculated and measured properties compare quite well electrical transport in berea 500 sandstone is complicated by the presence of surface conduction in the electric double layer at the grain electrolyte boundary a three phase conductivity model is proposed to compute surface conduction on the rock ct image effects of image resolution and computation sample size on the accuracy of numerical predictions are also investigated reducing resolution i e increasi

flow over heated terrain part ii generation of convective precipitation previous studies have shown that thunderstorms in the rocky mountain region have preferred areas in which to form there has been some indication that these areas depend on the midtropospheric wind direction a nonhydrostatic model with a terrain following horizontal grid is employed to investigate the initiation of precipitating convection over heated topography horizontally homogeneous meteorological conditions with no directional shear in the vertical wind profile are used the numerical simulations indicate that precipitating convection was more likely to be generated downwind of ridges than upwind of them initiation of these storms was more likely downwind of ridges with their long axis parallel to the wind direction than downwind of ridges with their long axis perpendicular to the wind direction in part i of this study it was shown that heating induced convergence is larger downwind of a ridge with its longer axis parallel to the wind direction for the orographic configuration of the rocky mountains total precipitation is maximized for southerly and northwesterly winds slower wind speeds are more likely and faster wind speeds are less likely to produce convective storms soundings with larger instability are more likely to produce convection the soundings with a greater temperature lapse rate produce more initiation locations and soundings with greater moisture produce greater amounts of precipitation even though a number of assumptions were made for this study the authors believe the results explain a significant amount of the observed variability in the initiation locations of precipitating convection in the rocky mountains during the summer because of the theoretical basis for this work detailed in part i of this study the authors believe it should explain convective initiation in other mountainous areas that are subject to strong solar heating

experimental measurements of the streaming potential and seismoelectric conversion in berea sandstone the streaming potential across a porous medium is induced by a fluid flow due to an electric double layer between a solid and a fluid when an acoustic wave propagates through a porous medium the wave pressure generates a relative movement between the solid and the fluid the moving charge in the fluid induces an electric field and seismoelectric conversion in order to investigate the streaming potential and the seismoelectric conversion in the same rock sample we conduct measurements with berea sandstone saturated by nacl solutions with different conductivities we measure the electric voltage streaming potential across a cylindrical sample in nacl solutions with different conductivities and under different pressures to determine the dc coupling coefficients we also measure the seismoelectric signals induced by acoustic waves with a berea sandstone plate at different frequencies and solution conductivities the pressures of the acoustic waves are calibrated with a standard hydrophone bruel 8103 at different frequencies 15 120 khz we calculate the quantitative coupling coefficients of the seismoelectric conversion at dc and at high frequencies with samples saturated by solutions with different conductivities when the berea sandstone sample is saturated by the nacl solution with 0 32 ms m in conductivity for example the dc and seismoelectric coupling coefficients at 15 khz are 0 024 v pa and 0 019 v pa respectively the seismoelectric coupling coefficient is an important and helpful parameter for designing a seismoelectric tool more experimental measurements of seismoelectric coupling coefficients in the frequency range of 100 hz to 15 khz are needed in the future

classification seasonality and persistence of low frequency atmospheric circulation patterns abstract orthogonally rotated principle component analysis rpca of northern hemisphere 1 month mean 700 mb heights is used to identify and describe the seasonality and persistence of the major modes of interannual variability the analysis is detailed and comprehensive in that 1 a high resolution approximately equal area 358 point grid is used for the virtually maximum possible 35 year period of record 2 a positive bias in the nmc data base in the early 1950s in the subtropics is largely eliminated for the first time and 3 homogeneous separate analyses of each month of the year are carried out detailing the mouth to month changes in the dominant circulation patterns winter results are similar to those of other recent rpca and teleconnection studies except that some less obvious patterns are identified and further detail of the better known patterns is provided two north south dipole patterns are found over the pacific ocean west pacific oscillation and east pacific pattern and over the atla

snow growth and transport patterns in orographic storms as estimated from airborne vertical plane dual doppler radar data abstractairborne vertical plane dual doppler cloud radar data collected on wind parallel flight legs over a mountain in wyoming during 16 winter storms are used to analyze the growth transport and sedimentation of snow in all storms the wind is rather strong such that the flow is unblocked the sampled clouds are mixed phase shallow and generally produce snowfall over the mountain only the 2d scatterers mean motion in the vertical along track plane below flight level is synthesized using one radar antenna pointing to nadir and one 30 forward of nadir this yields instantaneous cross mountain hydrometeor streamlines the dynamics of the orographic flow dominate the precipitation patterns across the mountain three patterns are distinguished the first two contain small convective cells either boundary layer bl convection or elevated convection the latter likely due to the release of potential instability in orographically lifted air in these patterns the cross mountain flow is relatively un

deep atmospheric response to the spring kuroshio over the east china sea abstractthe atmospheric response to the spring kuroshio front over the east china sea is investigated using a suite of high resolution satellite data and a regional atmospheric model the atmospheric response appears to extend beyond the marine atmospheric boundary layer with frequent occurrence of cumulus convection in spring quick scatterometer quikscat wind speed shows a clear effect of sea surface temperature sst with high low wind speed observed over the warm cold tongue this in phase relationship between sst and surface wind speed is indicative of sst influence on the atmosphere wind convergence is found on the warmer flank of the kuroshio front accompanied by a narrow rainband the analysis of satellite borne radar measurements indicates that deep convection appears over the kuroshio warm tongue in the spring season with enhanced convective precipitation frequent occurrence of cumulus convection and increased precipitation cloud tops in altitude these deep convective activities

boundary layer energy transport and cumulus development over a heated mountain an observational study abstract aircraft and surface measurements of the boundary layer transport of mass and moisture toward an isolated heated mountain are presented the data were collected around the santa catalina mountains in arizona 20 30 km in diameter during the north american monsoon on days with weak winds and cumulus congestus to cumulonimbus development over the mountain flights in the boundary layer around the mountain and surface station data indicate that mountain scale anabatic surface wind generally develops shortly after sunrise peaking at 1 m s 1 in strength close to solar noon there is some evidence for a toroidal heat island circulation with divergence in the upper boundary layer the aircraft data and mainly the diurnal surface temperature and pressure patterns confirm that this circulation is driven by surface heating over the mountain three case studies suggest that growth spurts of orographic cumulus and cumulonimbus are not preceded by enhanced mountain scale mass convergence near the surfac

the evolution of convective storms initiated by an isolated mountain ridge abstractthe evolution of convective storms over the black hills an isolated mountain ridge in south dakota and wyoming and a regional convection hotspot is investigated using a 10 yr observational climatology and quasi idealized numerical simulations radar observed diurnally forced mountain convection events are classified according to their maximum cell track length and duration which are quantified using an automated cell tracking algorithm environmental conditions during these events are obtained from operational radiosonde and model analysis data these data suggest that mountain forced convective cells generally struggle to survive in the convectively inhibited flow downwind of the black hills those cells that do survive downwind prefer environments with strong bulk vertical shear over the 0 6 km layer which favors organized multicellular or supercellular convection under slightly weaker shear the cells tend to dissipate rapidly as they propagate downwind relatively weak winds aloft when c

initiation of convection over the black forest mountains during cops iop15a doppler on wheels radar observations made during the convective and orographically induced precipitation study cops on 12 august 2007 showed that precipitating clouds only developed between the north south orientated murg and nagold valleys of the northern black forest the clouds produced moderate precipitation the weather research and forecasting wrf model run at 700 m horizontal resolution in the inner domain was able to simulate the location of the precipitation insight is therefore gained into the physical mechanisms responsible for the initiation and development of the convection convergence lines resulting from thermally driven flows constrained the initial location of the convection within warm and moist cores produced by heating on elevated surfaces the heaviest precipitation was later produced by secondary convection which was initiated within the cores at the boundary between cold pool outflows and thermal flows copyright 2011 royal meteorological society

daytime boundary layer evolution over mountainous terrain part 1 observations of the dry circulations abstract this paper presents the boundary layer structure which accompanies the development of daytime local wind systems in a broad mountain valley as revealed by cross sections of potential temperature it describes how this structure leads to the occurrence of a region of convergence to the downwind side of mountains previous studies based primarily on one dimensional sounding of potential temperature and horizontal winds have shown that profiles of static stability and the presence of winds aloft have an important effect on the manner in which daytime thermally forced wind systems develop in the present study two dimensional cross sections obtained from aircraft data vertical soundings and surface mesonet data show several relevant features in mid to late morning near the surface for example upslope winds form in a shallow mixed layer at the underside of the nocturnal inversion layer cold pool at elevations above the top of this cold pool convectively mixed surface winds exist the spat

numerical simulations of a gravity wave event over ccope part iii the role of a mountain plains solenoid in the generation of the second wave episode abstract mesoscale model simulations have been performed of the second episode of gravity waves observed in great detail in previous studies on 11 12 july 1981 during the cooperative convective precipitation experiment the dominant wave simulated by the model was mechanically forced by the strong updraft associated with a mountain plains solenoid mps as this updraft impinged upon a stratified shear layer above the deep well mixed boundary layer that developed due to strong sensible heating over the absaroka mountains the gravity wave was created this wave rapidly weakened as it propagated eastward however explosive convection developed directly over the remnant gravity wave as an eastward propagating density current produced by a rainband generated within the mps leeside convergence zone merged with a westward propagating density current in eastern montana the greatly strengthened cool pool resulting from this new convection then generated a bore wave that appeared to be continuous with the move

ocean frontal effects on the vertical development of clouds over the western north pacific in situ and satellite observations abstract a suite of shipboard and satellite observations are analyzed and synthesized to investigate the three dimensional structure of clouds and influences from sea surface temperature fronts over the western north pacific sharp transitions are observed across the kuroshio extension ke front in the marine atmospheric boundary layer mabl and its clouds the ocean s influence appears to extend beyond the mabl with higher cloud tops in altitude along the ke front than the surroundings in winter intense turbulent heat release from the ocean takes place on the southern flank of the ke front where the cloud top penetrates above the mabl and reaches the midtroposphere in this band of high cloud tops frequent lightning activity is observed the results of this study suggest a sea level pressure mechanism for which the temperature gradient in the mabl induces strong surface wind convergence on the southern flank of the ke front deepening the clouds there in early summer sea fog frequently occurs on

analysis of 2002 and 2003 warm season precipitation from the north american monsoon experiment event rain gauge network analyses of rainfall characteristics and their linkage to physiographic features are made from the north american monsoon experiment name event rain gauge network nern in northwest mexico the findings are based on the network configuration for the 2002 and 2003 warm seasons despite the relatively short record used a clearer structure of core region monsoon rainfall is beginning to emerge in agreement with earlier coarser scale studies the seasonal precipitation maximum overlies the western slope of the sierra madre occidental but does not strictly parallel a particular elevation band it is shown that the distance to the gulf of california and potentially the configuration of the terrain profile may also play an important role in determining where the axis of maximum precipitation lies the diurnal cycles of precipitation frequency and intensity are shown to have distinct relationships to terrain elevation that are qualitatively similar to those observed over the front range of the rocky mountains in the central western united states the relationship between precipitation and gulf surge events occurring during the summer of 2003 is also explored

numerical simulations of a gravity wave event over ccope part ii waves generated by an orographic density current a mesoscale numerical model and detailed observations are used to investigate the generation and maintenance of a mesoscale gravity wave event observed in eastern montana on 11 july 1981 during the cooperative convective precipitation experiment ccope it is shown that the interaction between an orographic density current and a mountain barrier leads to the generation of the gravity waves the simulation results suggest the following four stage conceptual model during stage i shortly after sunset the remnant up branch of a thermally driven upslope flow east of the rockies was driven back toward the mountain by the pressure gradient force associated with a cool pool over north dakota the nocturnal stable layer over eastern montana was strengthened during passage of this density current during the 1 2 h transition period of stage ii the advancing density current became blocked as it encountered the higher terrain an isentropic ridge developed above the original warm lee trough due to strong adiabatic cooling caused by the sustained upward motion in the presence of orographic blocking during stage iii an even stronger upward motion center formed to the east of the density current head updraft in response to an eastward horizontal pressure gradient force produced by the isentropic ridge in stage iv as the density current head collapsed and downward motion developed to the west of the original updraft in quadrature phase with the isentropic perturbation a gravity wave was generated this wave propagated eastward with the mean wind opposite to the motion of the earlier density current and was maintained by the strong wave duct established earlier by the density current thus the mountain plains circulation may at times generate mesoscale gravity waves and deep convection hours after diurnal heating has ended

crosshole seismoelectric measurements in borehole models with fractures laboratory experiments are performed in crossborehole models with fractures to investigate seismoelectric conversions in the fractures using an electrode in a borehole we measure the electric field induced by an acoustic wave and we investigate the relationship between the electric signal and the fracture aperture using ultrasonic fracture borehole models the experimental results confirm that a radiating electromagnetic em wave is induced by a guide wave at a fracture between an acoustic source and electric receiver boreholes the position of a vertical or inclined fracture between two boreholes can be determined using the arrival times of the em wave and the formation velocity by placing the acoustic source at a different depth and recording electric signals with real or synthetic arrays of acoustic and electric receivers in the second borehole crosshole seismoelectric measurements might be a technique for investigating fractures between boreholes more directly than traditional acoustic measurements

thermally forced low froude number flow past three dimensional obstacles abstract the present study extends the discussion of the flow of a density stratified fluid past three dimensional obstacles for froude number o 1 to flows past an isolated obstacle with heated cooled surface the study focuses on a response of thermally forced stratified flows representative of mesoscale flows past mountainous islands such as hawaii or taiwan in order to minimize the span of the parameter space uniform ambient wind and stratification axially symmetric bell shaped hills with moderate slopes representative of mesoscale mountains and a simple thermal forcing function that mimics natural effects over mountainous islands are assumed the earth s rotation surface friction viscosity dissipation and moisture are neglected with these simplifications flows can be characterized with two parameters the froude number and a characteristic scale of thermal forcing defined later in this paper the principal question addressed in this study is under what circumstances will a transition occur

using digital cloud photogrammetry to characterize the onset and transition from shallow to deep convection over orography an automated method for segmenting digital images of orographic cumulus and a simple metric for characterizing the transition from shallow to deep convection are presented the analysis is motivated by the hypothesis that shallow convection conditions the atmosphere for further deep convection by moistening it and preventing the evaporation of convective turrets through the entrainment of dry air time series of convective development are compared with sounding and surface data for 6 days during the summer of 2003 the observations suggest the existence of a threshold for the initiation of shallow convection based on the surface equivalent potential temperature and the saturated equivalent potential temperature above the cloud base this criterion is similar to that controlling deep convection over the tropical oceans the subsequent evolution of the convection depends on details of the environment surface fluxes of sensible and latent heat along with the transport of boundary layer air by upslope flow increase the surface equivalent potential temperature and once the threshold value is exceeded shallow convection begins the duration of the shallow convection period and growth rate of the deep convection are determined by the kinematic and thermodynamic structure of the mid and upper troposphere

seismoelectric measurements in a porous quartz sand sample with anisotropic permeability seismoelectric coupling coefficients are difficult to predict theoretically because they depend on a large numbers of rock properties including porosity permeability tortuosity etc the dependence of the coupling coefficient on rock properties such as permeability requires experimental data in this study we carry out a set of laboratory measurements to determine the dependence of seismoelectric coupling coefficient on permeability we use both an artificial porous sandstone sample with cracks built using quartz sand and berea sandstone samples the artificial sample is a cube with 39 porosity its permeability levels are anisotropic 14 7 d 13 8 d and 8 3 d in the x y and z directions respectively seismoelectric measurements are performed in a water tank in the frequency range of 20 khz 90 khz a piezoelectric p wave source is used to generate an acoustic wave that propagates through the sample from the three different x y and z directions the amplitudes of the seismoelectric signal induced by the acoustic waves vary with the direction the highest signal is in the direction of the highest permeability and the lowest signal is in the direction of the lowest permeability since the porosity of the sample is constant the results directly show the dependence of seismoelectric coefficients on permeability seismoelectric measurements with natural rocks are performed using berea sandstone 500 and 100 samples because the berea samples are nearly isotropic in permeability the amplitudes of the seismoelectric signals induced in the different directions are the same within the measurement error because the permeability of berea 500 is higher than that of berea 100 the amplitude of the seismoelectric signals induced in berea 500 is higher than those in berea 100 to determine the relative contributions of porosity and permeability on seismoelectric conversion we carried out an analysis using pride 1994 formulation and kozeny carman relationship the normalized amplitudes of seismoelectric coupling coefficients in three directions are calculated and compared with the experimental results the results show that the seismoelectric conversion is related to permeability in the frequency range of measurements this is an encouraging result since it opens the possibility of determining the permeability of a formation from seismoelectric measurements

structure of the marine atmospheric boundary layer over an oceanic thermal front semaphore experiment the structure des echanges mer atmosphere proprietes des heterogeneites oceaniques recherche experimentale semaphore experiment the third phase of which took place between october 4 and november 17 1993 was conducted over the oceanic azores current located in the azores basin and mainly marked at the surface by a thermal front due to the gradient of the sea surface temperature sst of about 1 to 2 c per 100 km the evolution of the marine atmospheric boundary layer mabl over the sst front was studied with two aircraft and a ship in different meteorological conditions for each case the influence of the incoming air direction with respect to the orientation of the oceanic front was taken into account during the campaign advanced very high resolution radiometer pictures did not show any relation between the sst field and the cloud cover the mabl was systematically thicker on the warm side than on the cold side the mean mabl structure described from aircraft data collected in a vertical plane crossing the oceanic front was characterized by 1 an atmospheric horizontal gradient of 1 to 2 c per 100 km in the whole depth of the mixed layer and 2 an increase of the wind intensity from the cold to the warm side when the synoptic wind blew from the cold side the surface sensible heat latent heat flux always increased from the cold to the warm sector owing to the increase of the wind and of the temperature specific humidity difference between the surface and the air turbulence increased from the cold to the warm side in conjunction with the mabl thickening but the normalized profiles presented the same structure regardless of the position over the sst front in agreement with the action de recherche programme te petite echelle and grande echelle model the mean temperature and momentum budgets were highly influenced by the horizontal temperature gradient in particular the strong ageostrophic influence in the mabl above the sst front seems linked with the secondary circulation due to the sst front

storm track response to ocean fronts in a global high resolution climate model synoptic atmospheric eddies are affected by lower tropospheric air temperature gradients and by turbulent heat fluxes from the surface in this study we examine how ocean fronts affect these quantities and hence the storm tracks we focus on two midlatitude regions where ocean fronts lie close to the storm tracks the north west atlantic and the southern ocean an atmospheric climate model of reasonably high resolution 50 km is applied in a climate length 60 year simulation in order to obtain stable statistics simulations with frontal structure in the sea surface temperature sst in one of the regions are compared against simulations with globally smoothed sst we show that in both regions the ocean fronts have a strong influence on the transient eddy heat and moisture fluxes not just in the boundary layer but also in the free troposphere local differences in these quantities between the simulations reach 20 40 of the maximum values in the simulation with smoothed sst averaged over the entire region of the storm track over the ocean the corresponding differences are 10 20 the effect on the transient eddy meridional wind variance is strong in the boundary layer but relatively weak above that the potential mechanisms by which the ocean fronts influence the storm tracks are discussed and our results are compared against previous studies with regional models aquaplanet models and coarse resolution coupled models

numerical modeling of diurnal convergence oscillations above sloping terrain abstract we document the development and sensitivity testing of a numerical model designed to predict diurnal cycles of boundary layer flows of synoptic horizontal scale above sloping terrain this application requires detailed vertical resolution of low level jets mixed layers and sharp inversions above terrain with large pointwise variations the truncation errors of the pressure gradient term are of special concern this term is computed using a thermodynamic state carried as a deviation from a standard state turbulent mixing is based upon a simplified diagnostic treatment the final model produces rather stable solutions because of the rather careful pressure gradient calculation and strong physical dissipation sensitivity testing indicates that the model prediction of diurnal convergence cycles depends upon soil parameters results are also sensitive to absolute rotation and mixing parameterizations but not equally sensitive to longwave radiative flux divergence applications over complex north a

streaming potential properties of westerly granite with applications this paper reports on laboratory measurements of the streaming potential properties of common minerals and in particular of westerly granite data are presented for these solids in contact with simple electrolytic solutions and in one case for temperature variation in the range 5 70 c for 1 1 electrolytes the ratio of the streaming potential coupling coefficient to fluid resistivity was approximately 4 mv atm m and for 2 1 electrolytes 2 mv atm m the effect of temperature was small 0 05 mv c temperature increase and indicates that the zeta potential was independent of temperature preliminary experimental results using mixed electrolytic solutions nacl cacl2 and two phase fluid flow are also described two phase flow can enhance streaming potentials by as much as a factor of 3 or 4 the laboratory data are used to interpret streaming potentials in geological problems such as earthquake prediction geothermal prospecting using the self potential method and surface conductivity contribution to the electrical resistivity of rocks

cloud resolving simulations of deep convection over a heated mountain abstract cloud resolving numerical simulations of airflow over a diurnally heated mountain ridge are conducted to explore the mechanisms and sensitivities of convective initiation under high pressure conditions the simulations are based on a well observed convection event from the convective and orographically induced precipitation study cops during summer 2007 where an isolated afternoon thunderstorm developed over the black forest mountains of central europe but they are idealized to facilitate understanding and reduce computational expense in the conditionally unstable but strongly inhibited flow under consideration sharp horizontal convergence over the mountain acts to locally weaken the inhibition and moisten the dry midtroposphere through shallow cumulus detrainment the onset of deep convection occurs not through the deep ascent of a single updraft but rather through a rapid succession of thermals that are vented through the mountain convergence zone into the deepening cloud mass emerging t

using borehole electroseismic measurements to detect and characterize fractured permeable zones in 1996 we measured stoneley wave induced electrical fields in an uncased water well drilled in fractured granite and diorite near hamilton massachusetts stoneley waves generated by sledgehammer blows to the surface casing produced a flow of pore fluid in permeable zones intersected by the borehole in turn this flow induced a streaming electrical field even though these electrical signals were very small tens of microvolts we were able to detect them using electrodes placed in the borehole after power line and telluric signals were canceled by remote referencing and notch filtering amplitude analysis of the electrical fields confirmed that they were induced by fluid flow in the fractured formation the normalized amplitudes of these electrical fields correlate with the fracture density log and agree with the theoretical model for this electroseismic phenomenon our biot theory based model predicts that borehole electroseismic measurements can be used to characterize permeable zones according t

permeability inversion from low frequency seismoelectric logs in fluid saturated porous formations in this paper a method is proposed to invert permeability from seismoelectric logs in fluid saturated porous formations from the analysis of both the amplitude and the phase of simulated seismoelectric logs we find that the stoneley wave amplitude of the ratio of the converted electric field to the pressure rep is sensitive to porosity rather than permeability while the tangent of the rep s phase is sensitive to permeability the rep s phase reflects the phase discrepancy between the electric field and the pressure at the same location in the borehole we theoretically derive the frequency dependent expression of the rep of the low frequency stoneley wave and find that the tangent of the rep s argument is approximately in inverse proportion to permeability we obtain an inversion formula and present the permeability inversion method by using the tangent of the rep s phase to test this method the permeabilities of different sandstones are inverted from the synthetic full waveform data of seismoelectric logs a modified inversion process is proposed based on the analysis of inversion errors by which the relative errors are controlled below 25 and they are smaller than those of the permeability inversion from the stoneley wave of acoustic logs

north atlantic oscillation effect on interannual variability in winter precipitation over the gulf stream abstractin winter the warm water of the gulf stream anchors a salient precipitation band previous studies suggested a close relationship between the sea surface temperature sst front and the pr

seismoelectric and seismomagnetic measurements in fractured borehole models seismoelectric and seismomagnetic fields generated by seismic waves in fluid saturated fractured borehole models are experimentally investigated with an electrode and a hall effect sensor in a borehole with a horizontal fracture the stoneley and flexural waves induce seismoelectric and seismomagnetic fields on the borehole wall and an electromagnetic wave propagating at light speed at the horizontal fracture in a borehole with a vertical fracture the acoustic field generated by a monopole or dipole source is similar to that in a borehole without a vertical fracture however the acoustic wave propagating along the vertical fracture induces seismoelectric and seismomagnetic fields whose apparent velocities are equal to that of a stoneley wave experimental results show that two different kinds of electric and magnetic fields are generated by acoustic waves in borehole models with horizontal and or vertical fractures one is an electromagnetic wave propagating with light speed the second is a stationary or localized seismoelectric and seismomagnetic field seismoelectric and seismomagnetic measurements might be a new logging technique for exploring fractures in a borehole

a stereo photogrammetric technique applied to orographic convection abstract this paper describes a technique for photogrammetric analysis of stereo pairs of images that is applied to the study of orographic convection the technique is designed for use with digital images and assumes detailed knowledge of the camera properties focal length and imaging chip and that the position and orientation are known as a first guess an iterative scheme using known landmarks on the frame is used to determine the camera orientation the scheme is accurate to 10 100 m at a distance of 15 km from the camera pair the transition from shallow to deep convection over the santa catalina mountains in southern arizona on 26 july 2005 is presented the three dimensional structure of the visible portion of the cloud is determined and compared with the composite reflectivity from the national weather service weather surveillance radar 1988 doppler radar and the tropopause height from the 1200 utc sounding in tucson arizona providing additional validation of the scheme the shallow to deep tr

seasonal evolutions of atmospheric response to decadal sst anomalies in the north pacific subarctic frontal zone observations and a coupled model simulation abstractpotential impacts of pronounced decadal scale variations in the north pacific sea surface temperature sst that tend to be confined to the subarctic frontal zone safz upon seasonally varying atmospheric states are investigated by using 48 yr observational data and a 120 yr simulation with an ocean atmosphere coupled general circulation model cgcm sst fields based on in situ observations and the ocean component of the cgcm have horizontal resolutions of 2 0 and 0 5 respectively which can reasonably resolve frontal sst gradient across the safz both the observations and cgcm simulation provide a consistent picture between sst anomalies in the safz yielded by its decadal scale meridional displacement and their association with atmospheric anomalies correlated with sst anomalies persistent in the safz from fall to winter a coherent decadal scale signal in the wintertime atmospheric circulation over the north pacific starts emerging in november and develops into an equivalent barotropic an

characteristics of the atlantic storm track eddy activity and its relation with the north atlantic oscillation abstract this study focuses on feedbacks of the high frequency eddy activity onto the quasi stationary circulation particularly with regard to the north atlantic oscillation nao the methodology consists of analyzing ncep ncar reanalysis data and sensitivity runs from a high resolution nonhydrostatic regional model consistent with recent studies results show that the jet displacement characteristic of the nao phenomenon depends strongly on the dynamics of the synoptic scale waves and the way they break positive and negative phases of the nao are closely related to anticyclonic and cyclonic wave breaking respectively indeed the high frequency momentum flux whose sign is directly related to the type of wave breaking is correlated with the nao index over the atlantic the peak of the momentum flux signal precedes that of the nao by a few days suggesting that wave breaking is triggering nao events two examples illustrate the significant impact of single storms in particular those occurring in the e