radar echoes from lightning and their microphysical environment 1 a uhf profiler radar has detected lightning echoes which occurred preferentially in a balance layer the stratum of mean zero doppler velocity with rising small ice particles and falling graupel and hail thus providing the conditions for collisional charging and lightning the results support prior findings of the role of the balance layer in lightning generation the 32 8 cm profiler radar is particularly well suited for these observations because the lightning echoes are not masked by the precipitation echoes thus allowing simultaneous measurement of the microphysical and kinematic properties

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

the vertical structure of toga coare convection part i radar echo distributions radar data collected by the 5 cm mit radar which was deployed aboard the r v vickers during the intensive observing period of the tropical ocean global atmosphere coupled ocean atmosphere response experiment are partitioned into convective and stratiform cartesian grid columns the vertical structure of convective echo is examined through the use of two variables echo top height and the height of the 30 dbz reflectivity contour the first of these variables has traditionally been used to describe the vertical structure characteristics of convection and the second has recently been linked to internal microphysical properties and lightning histograms of the relative frequency of convective only echo top heights and 30 dbz contour heights were constructed for the three cruises of the vickers with each cruise experiencing different phases of the intraseasonal oscillation iso cruise 1 which was dominated by the convectively inactive phase of the iso was characterized by the highest frequency of shallow convection based on echo top heights whereas cruise 2 which was dominated by a particularly well defined passage of the convective phase of the iso exhibited the tallest echo top heights cruise 3 convection was influenced by moderate westerly surface winds characteristic of postwesterly wind burst conditions and convection was of intermediate height when viewed as a function of internal vertical structure i e 30 db z contour height the frequency distributions vary less from cruise to cruise with cruises 1 and 2 having nearly identical distributions of convective 30 dbz contour heights furthermore when the contribution to convective rainfall is examined as a function of 30 dbz contour height it is seen that relatively more rain fell from vertically intense convection i e convection with tall 30 dbz contours during cruises 1 and 3 than during cruise 2 instantaneous correlations between rainfall rate and radar echo height were highly scattered about a mean value of about 0 55 whereas rainfall rate and 30 dbz contour height correlations peaked at about 0 8 and exhibited much less scatter

investigation of microphysical processes occurring in isolated convection during name abstracta major objective of the north american monsoon experiment name was to quantify microphysical processes within convection occurring near the steep topography of northwestern mexico a previous study compared examples of isolated convection using polarimetric radar data and noted a dependence on mixed phase processes via drop freezing and subsequent riming growth along the coastal plain and western slopes with an even greater role of melting ice in rainfall production over the highest terrain despite the higher frequency of these isolated cells compared to organized convective systems the latter were responsible for 75 of rainfall therefore this study seeks to evaluate the role of mesoscale organization on microphysical processes and describes the evolution of these systems as a function of topography similar to isolated convection both warm rain and ice based processes played important roles in producing intense rainfall in organized convection although similarities existed between cell

the relationship between lightning type and convective state of thunderclouds thunderstorm case studies and earlier observations are described which illuminate the relationship between cloud vertical development and the prevalence of intracloud ic and cloud to ground cg lightning a consistent temporal evolution starting with peak ic activity changing to predominant cg activity and concluding with strong outflow microburst suggests that ice is responsible for both the electrical i e lightning and dynamical i e microburst phenomena the ic activity is attributed to the updraft driven accumulation of graupel particles in the central dipole region and the subsequent cg activity to the descent of ice particles beneath the height of the main negative charge the subsequent descent and melting of ice particles beneath the height of the 0 c isotherm are associated with the acceleration of the downdraft and outflow the ic lightning precursor can provide a valuable short term 5 10 min warning for microburst hazard at ground level

cloud to ground lightning observations from toga coare selected results and lightning location algorithms abstract recently observations of electrified oceanic convection and associated cloud to ground cg lightning were obtained over the tropical western pacific ocean during toga coare tropical ocean global atmosphere coupled ocean atmosphere response experiment during coare observations of convection were made using a variety of instrument platforms including ship and airborne doppler radars an advanced lightning direction finder aldf network and a shipborne inverted electric field mill this study focuses on data collected by the coare aldf network fusion of those data with observations and the methods used to calculate accurate cg return stroke locations analysis of cg lightning data and doppler radar data indicates that lightning producing oceanic convection is characterized by deep vertically developed convective cells with radar reflectivities exceeding 30 dbz above the height of the 10 c level in several cases a peak in cg frequency occurred coincident with the descent of precipitation

radar observations of the kinematic microphysical and precipitation characteristics of two mcss in trmm lba 1 dual doppler and polarimetric radar observations are used to analyze two mesoscale convective systems mcss that occurred during the tropical rainfall measuring mission large scale biosphere atmosphere field campaign the mcss formed in different meteorological regimes based on profiles of atmospheric wind and thermodynamic data the first mcs event 26 january 1999 was a squall line that formed in low level easterly flow and had an intense leading line of convection in contrast the 25 february 1999 mcs formed in low level westerly flow and was best characterized by stratiform precipitation with embedded convective elements the radar analyses suggest that the mcss were distinct in terms of overall vertical structure characteristics in particular polarimetric radar cross sections indicated the presence of an active mixed phase zone in the easterly mcs that was largely absent in the westerly case the easterly mcs had considerably more precipitation ice in the middle to upper troposphere compared to the westerly mcs composite analyses showed that the easterly mcs had higher peak reflectivities and a smaller reflectivity gradient above the 08c level in convective regions of the storm compared to the westerly mcs event moreover mean profiles of both vertical air motion and vertical mass transport in the convective portion of the easterly mcs were larger over a factor of 2 at some heights below the 08 c level than those in the westerly event these observations suggest that the easterly and westerly wind regimes in the southwest amazon region produce convection with different vertical structure characteristics similar to regimes elsewhere in the global tropics e g maritime continent index terms 3314 meteorology and atmospheric dynamics convective processes 3329 meteorology and atmospheric dynamics mesoscale meteorology 3354 meteorology and atmospheric dynamics precipitation 1854 3374 meteorology and atmospheric dynamics tropical meteorology keywords microphysics tropical precipitation polarimetric radar mesoscale convective system

three dimensional kinematic and microphysical evolution of florida cumulonimbus part ii frequency distributions of vertical velocity reflectivity and differential reflectivity abstract high resolution radar data collected in florida during the convection and precipitation electrification experiment are used to elucidate the microphysical and kinematic processes occurring during the transition of a multicellular storm from convective to stratiform stages a statistical technique is employed to examine the evolving properties of the ensemble small scale variability of radar reflectivity vertical velocity and differential reflectivity over the entire storm differential radar reflectivity data indicate that the precipitation at upper levels was nearly glaciated early in the storm s lifetime dual doppler radar data show that throughout the storm s lifetime both updrafts and down drafts were present at all altitudes and that most of the volume of the radar echo contained vertical velocities incapable of supporting precipitation size particles thus the ensemble microphysical properties of the storm were increasingly dominated by particles falling in an environment of weak vertic

ice microphysical properties near the tops of deep convective cores implied by the gpm dual frequency radar observations abstractusing three years of observations from the dual frequency precipitation radar dpr aboard the global precipitation measurement gpm core observatory properties of the cores of deep conve

comparing the convective structure and microphysics in two sahelian mesoscale convective systems radar observations and crm simulations two mesoscale convective systems mcss observed during the african monsoon multidisciplinary analyses amma experimentaresimulatedusingthethree dimensional 3d goddardcumulusensemble model this studywasundertaken todeterminethe performance ofthe cloud resolving modelin representing distinct convective and microphysical differences between the two mcss over a tropical continental location simulations are performed using 1 km horizontal grid spacing a lower limit on current embedded cloudresolving models within a global multiscale modeling framework simulated system convective structure and microphysics are compared to radar observations using contoured frequency by altitude diagrams cfads calculated ice and water mass and identified hydrometeor variables vertical distributions of ice hydrometeors indicate underestimation at the mid and upper levels partially due to the inability of the model to produce adequate system heights the abundance of high reflectivity values below and near the melting level in the simulation led to a broadening of the cfad distributions observed vertical reflectivity profiles show thathighreflectivityis presentat greaterheights thanthe simulations produced thoughtto bea resultof using a single moment microphysics scheme relative trends in the population of simulated hydrometeors are in agreement with observations though a secondary convective burst is not well represented despite these biases the radar observed differences between the two cases are noticeable in the simulations as well suggesting that the model has some skill in capturing observed differences between the two mcss

global statistics of lightning in anvil and stratiform regions over the tropics and subtropics observed by the tropical rainfall measuring mission 1 the statistics of lighting in the anvil and stratiform regions of convective systems are summarized from tropical rainfall measuring mission trmm satellite observations from 1998 to 2009 the locations of lightning flashes in convective systems are determined by combining three dimensional precipitation radar pr observations with lightning flash center locations from lightning imaging sensor observations the geographical distributions of flashes in the anvil and stratiform regions of thunderstorms over the tropics and subtropics are presented flashes in stratiform regions are found to account for 5 6 of all lightning flashes observed within the trmm pr swath while flashes in nonraining anvil regions made up another 5 5 of the sample diurnally flashes in anvil regions peak earlier than flashes in stratiform regions 15 30 lt as opposed to 17 30 lt seasonal and regional variations of these flashes are discussed features in pr observations that likely contribute to charge separation are identified as contiguous areas with 6 km echoes exceeding 30 dbz lightning flashes are then assigned to one of these features by the nearest neighbor method convective properties of features linked with lightning in stratiform and nonraining anvil regions are then analyzed we find that features associated with lightning flashes in anvil regions are relatively weak and occur in small systems composed of a single convective region while flashes in the stratiform regions are also relatively weak but more likely occur in multicell systems about 15 of features with lightning are associated with at least one stratiform or anvil flash

main differences between thrust belts it is useful to differentiate between thrust belts that are related to east e dipping or west w dipping subduction more precisely these either follow or resist the overall eastward mantle flow detected by the hot spot reference frame because of the overall westward drift of the lithosphere we find in e dipping subduction that the basal decollement underlying the eastern plate reaches the surface and involves deep crustal rocks with w dipping subduction however we find that the basal decollement of the eastern plate is warped as well as subducted consequently thrust belts related to e or ne dipping subduction show conspicuous structural and morphologic relief involve deep crustal rocks and are associated with shallow foredeeps on the other hand thrust belts related to w or sw dipping subduction show relatively low structural and morphological relief involve only shallow upper crustal rocks and are associated with deep foredeeps as well as back arc extension the accretionary wedge foredeep back arc basin association is visualized as an overall eastward propagating tectonic wave the accretionary wedge forms in the frontal parts and generally below sea level this is followed by forward migrating extension that cuts the earlier accretionary wedge typically such a system occurs in the context of overall w dipping subduction and is characterized by an arcuate shape e g carpathians apennines barbados etc along the branches of the arc external transpression and internal transtension co exist but with different sense i e sinistral transpression contrasting with dextral transtension we also observe that with w dipping subduction the tangent to a pre deformation marker is descending into the foredeep at an angle in the range of 1 10 while with e or ne dipping subduction the same marker would rise towards the hinterland with typical angles of about 5 10 foredeep subsidence is mainly controlled by the load of the thrust sheets in thrust belts due to e or ne dipping subduction and by the roll back of the subduction hinge in accretionary wedges due to w dipping subduction subsidence or uplift rates in the foredeeps and accretionary wedges related to the two different types of subduction are very different providing different p t t paths in the two geodynamic realms the present shape and structure of the thrust belts belonging to one of these two general types may help us in reconstructing the location of thinned lithosphere and basin evolution in the past

the 29 june 2000 supercell observed during steps part i kinematics and microphysics this is a two part study that addresses the kinematic microphysical and electrical aspects of a severe storm that occurred in western kansas on 29 june 2000 observed during the severe thunderstorm electrification and precipitation study steps field campaign in this first part polarimetric and doppler radar data are used along with a simple particle growth model to examine the evolution of the kinematic and microphysical properties of the storm from its earliest developing phase through its mature and dissipating phases during its severe stage the storm exhibited frequent positive cloud to ground lightning strikes very large 5 cm hail and a tornado doppler derived winds radar reflectivity and hydrometeor classifications from the polarimetric data over a nearly 4 h period are presented it is shown that updraft velocity and vertical vorticity had to reach magnitudes of at least 10 m s 1 and 10 2 s 1 and occupy major portions of the storm before it could produce most of the observed severe storm characteristics furthermore the establishment of cyclonic horizontal flow around the right flank of the updraft core was essential for hail production most of the largest hail grew from near millimeter sized particles that originated in the mid to upper level stagnation region that resulted from obstacle like flow of environmental air around the divergent outflow from the upper part of the updraft these recycling embryonic particles descended around the right flank of the updraft core and reentered the updraft intermingling with other smaller particles that had grown from cloud base along the main low level updraft stream

some characteristics of thunderstorms over bathurst and melville islands near darwin australia a study defining the occurrence structure and evolution of maritime continent island thunderstorms over bathurst and melville islands near darwin australia is presented satellite data for the november december pre monsoon transition season show unambiguous records of island thunderstorms on at least 65 of days over the period 1978 1986 storms develop most commonly between 1230lst and 1530lst and radar data indicate a mean lifetime of 2 5 h non occurrence was found on only 7 of the days examined and was associated with a return to dry flow typical of the early transition season with middle level subsidence or suppressed conditions in the wake of previous convective activity environmental sounding data indicated that these maritime continent thunderstorms develop in a regime with moderate cape low to moderate shear and high moisture the dynamic regime is characteristic of multicellular storms examination of the evolution of the storms indicates the existence of a typical lifecycle but with considerable variability in detail initially the lifecycle is consistent with the multicellular storm concept but the developing storms tend to aggregate to form one or more mesoscale systems which in turn may develop into propagating squall lines in the mature stage the developing storms have preferred geographic regions of genesis and intensification over the islands and while motion of the storms is variable it is generally consistent with the mean surface to 700mb pressure weighted flow

electrical and multiparameter radar observations of a severe hailstorm using data from the 11 cm csu chill multiparameter radar the simultaneous evolution of the radar inferred precipitation structure and electrical characteristics of a severe hailstorm is investigated we compare the substorm point discharge current intracloud ic lightning flash rate cloud to ground cg lightning flash rate ground strike location and flash polarity to the progression of precipitation types and amounts this study is unique in that it presents multiparameter radar observations of a thunderstorm complex which exhibited an extremely high ic to cg ratio ic cg 20 70 and predominantly positive cg lightning over 74 after it became severe producing large hail and weak tornadoes in particular we investigate the reported relationship between large hail and positive cg lightning although a direct correlation is found between a rapid increase in ic cg the first positive cg lightning flashes and the initial production of hail aloft the temporal and spatial behavior of large hail and positive cg lightning appear to be anticorrelated as broad peaks in the positive cg flash rate lag relative maxima in the fallout of large hail by up to 30 min the majority of positive ground strikes were adjacent to the main precipitation core in a region of light rain and little or no hail at the surface aloft radar data indicated that ice crystals were aligned vertically in a strong electric field corona point observations at the surface indicate that these regions adjacent to the convective core were characterized by net positive charge aloft possible mechanisms to explain these observations are discussed

the relationship between precipitation and lightning in tropical island convection a c band polarimetric radar study one of the primary scientific objectives of the maritime continent thunderstorm experiment was to study cloud electrification processes in tropical island convection in particular the coupling between ice phase precipitation and lightning production to accomplish this goal a c band polarimetric radar was deployed in the tropics 11 68s 130 88e for the first time accompanied by a suite of lightning measurements using observations of the propagation corrected horizontal reflectivity and differential reflectivity along with specific differential phase rain and ice masses were estimated during the entire life cycle of an electrically active tropical convective complex known locally as hector over the tiwi islands on 28 november 1995 hector s precipitation structure as inferred from these raw and derived radar fields was then compared in time and space to the measured surface electric field cloud to ground cg and total lightning flash rates and ground strike locations during hector s developing stage precipitating convective cells along island sea breezes were dominated by warm rain processes no significant electric fields or lightning were associated with this stage of hector despite substantial rainfall rates aided by gust front forcing a cumulus merger process resulted in larger taller and more intense convective complexes that were dominated by mixed phase precipitation processes during the mature phase of hector lightning and the surface electric field were strongly correlated to the mixed phase ice mass and rainfall merged convective complexes produced 97 of the rainfall and mixed phase ice mass and 100 of the cg lightning as hector dissipated lightning activity rapidly ceased as evidenced from the multiparameter radar observations the multicell nature of hector resulted in the continuous lofting of supercooled drops to temperatures between 2108 and 2208c in discrete updraft cores during both the early and mature phases the freezing of these drops provided instantaneous precipitation sized ice particles that may have subsequently rimed and participated in thunderstorm electrification via the noninductive charging mechanism

cloud to ground lightning associated with the evolution of a multicell storm 1 the relationship of cloud to ground cg lightning strikes to the stages of updraft downdraft evolution is investigated in a multicell thunderstorm that occurred on 11 july 1989 during the north dakota thunderstorm project with only single doppler radar data available for this storm reflectivity and single doppler velocity signatures are used to identify individual cells within the storm and to deduce the stage of evolution within each cell cell evolution appeared to follow the thunderstorm project model of the late 1940s updraft growth and vertical development during the growing cumulus stage updraft peaking in the upper portion of the cell and rainy downdraft descending from the middle portion during the mature stage and lighter precipitation settling out during the dissipating stage on 11 july cells tended to occur in clusters each cluster consisting of growing mature and dissipating cells close together in both time and space no cg strikes were detected when the convective region of the storm contained only one cluster of cells all strikes occurred when there were two or more clusters of cells with only two exceptions strikes occurred in the convective region of the storm typically closer to growing mature cells than to dissipating cells these observations support the hypothesis that descending precipitation creates electrical conditions conducive to flashes reaching ground however these observations also suggest that the greater complexity of electrical structure due to the juxtaposition of several cells is especially conducive to cg flashes and can cause cg flashes to occur earlier in a new cell s life cycle than would otherwise be the case

the june 22 tropical squall line observed during copt 81 experiment electrical signature associated with dynamical structure and precipitation the tropical convection experiment copt 81 convection profonde tropicale was carried out near korhogo northern ivory coast during may and june 1981 the june 22 squall line was observed using meteorological and electrical equipment the frontal part was characterized by a heavy precipitation core associated with strong convection it was followed by a region of weak precipitation and a wide area of stratiform rain the characteristic of this squall line resides in the two dimensional structure of the observed three dimensional wind fields with intense convection ahead of the heavy precipitation core electrical measurements indicate that electrostatic field changes at ground level occurred in the weak precipitation zone and in the stratiform precipitation region no particular electrical activity was observed in the most convective but shallow part of the squall line a classical dipole structure appeared within the stratiform area the stationary electrical structure was coherent with the stationary dynamics and precipitation pattern of the squall line

tropical island convection in the absence of significant topography part i life cycle of diurnally forced convection abstract diurnally forced convection was observed over the tiwi islands north of the australian continent as part of the maritime continent thunderstorm experiment immature peninsula scale 5 15 km sea breezes were observed to initiate moist convection early each day principally through convergence that results from the confluence or collision of peninsula breeze fronts convection initiated by peninsula scale breezes usually fails to organize beyond a small cluster of cells and dissipates as a local event mature island scale 100 km breezes develop by late morning and subsequently play a pivotal role in the forcing and evolution of organized convection the initiation of mesoscale convective systems mcss is observed to be a direct consequence of breeze front collisions for only 20 of the days on which organized convection develops this is referred to as type a forcing and it occurs when normal convective development is delayed or otherwise suppressed type a forcing is nature s backup mech

a case study of convective organization into precipitating lines in the southwest amazon during the wetamc and trmm lba 1 a case study of convective development in the southwest amazon region during the wet season atmospheric mesoscale campaign wetamc and tropical rainfall measuring mission trmm large scale biosphere atmosphere lba experiment in amazonia is presented the convective development during 7 february 1999 is shown to occur during a period of very weak large scale forcing in the presence of topography and deforestation the available data include dual doppler radar analysis radiosonde launches and surface and boundary layer observations the observational analysis is complemented with a series of model simulations using the rams with 2 km resolution over a 300 km 300 km area forced by a morning radiosonde profile a comparison of the observed and simulated thermodynamic transformation of the boundary layer and of the formation of convective lines and of their kinematic and microphysical properties is presented it is shown that only a few very deep and intense convective cells are necessary to explain the overall precipitating line formation and that discrete propagation and coupling with upper atmosphere circulations may explain the appearance of several lines the numerical simulation indicates that topography may be the cause of initial convective development although later on the convective line is parallel to the midlevel shear there are indications that small scale deforestation may have an effect on increasing rainfall in the wet season when the large scale forcing is very weak

hydrometeor mass number and space charge distribution in a hector squall line 1 videosonde data from an australian squall line were combined with a radar echo profile to construct a conceptual model of hydrometeor mass number and space charge evolution two step hydrometeor growth modes were suggested low level warm rain frozen drop and high level graupel ice crystals a riming electrification mechanism successfully explained the charge distribution a warm rain frozen drop process was active in the forward area of the convective region and frozen drop growth was highly active near the 0 c level ice crystals which electrified frozen drops positively increased in number as they were lifted graupel growth was enhanced and additional charge separation occurred between ice crystals and graupel in the upper level large negative graupel fell at the rear of the convective region while positive ice crystals and small negative graupel were transported into the anvil the reason for high lightning frequencies in a squall line over a maritime continent is also discussed

convection and easterly wave structures observed in the eastern pacific warm pool during epic 2001 abstract during september october 2001 the east pacific investigation of climate processes in the coupled ocean atmosphere system epic 2001 intertropical convergence zone itcz field campaign focused on studies of deep convection in the warm pool region of the eastern pacific this study combines c band doppler radar sounding and surface heat flux data collected aboard the r v ronald h brown during epic to describe the kinematic and thermodynamic states of the itcz environment together with tendencies in convective structure lightning rainfall and surface heat fluxes as a function of 3 5 day easterly wave phase three easterly waves were observed at the location of the r v brown during epic 2001 wind and thermodynamic data reveal that the wave trough axes exhibited positively correlated u and winds a slight westward phase tilt with height and relatively strong weak northeasterly tropospheric shear following the trough ridge axis temperature and humidity perturbations exhibited mid to

a squall line in southern germany kinematics and precipitation formation as deduced by advanced polarimetric and doppler radar measurements abstract a multiscale analysis of a squall line system is reported in this paper it is shown that the squall line was initiated as part of a synoptic scale frontal zone the main emphasis then is on the polarimetric and doppler radar measurements which give insight into the meso and microscale structure of the kinematics and the precipitation microphysics especially within the new cells growing ahead of the squall line and within the main precipitation system the principal polarimetric measurements considered are the differential reflectivity zdr and a related new derived parameter termed the difference reflectivity or zdp which is useful in detection of rain ice mixed phase precipitation a limited amount of time series data have been analyzed to derive the specific differential phase kdp and the backscatter differential phase between horizontal and vertical polarizations a brief overview of the microphysical interpretation of these parameters is provided the newly grown clouds are identifi

a radar and electrical study of tropical hot towers abstract radar and electrical measurements for deep tropical convection are examined for both break period and monsoonal regimes in the vicinity of darwin australia break period convection consists primarily of deep continental convection whereas oceanic based convection dominates during monsoonal periods associated with the monsoon trough over darwin order of magnitude enhancements in lightning flash rates for the break period regime are associated with 10 20 db enhancements in radar reflectivity in the mixed phase region of the convection compared with the monsoonal regime the latter differences are attributed to the effect of convective available potential energy cape and its nonlinear influence on the growth and accumulation of ice particles aloft which are believed to promote charge separation by differential particle motions cape in turn is largely determined by the boundary layer wet bulb temperature modest differences 1 3 c in wet bulb potential temperature between land and s

when 4d seismic is not applicable alternative monitoring scenarios for the arab d reservoir in the ghawar field abstract ghawar the largest oilfield in the world produces oil from the upper jurassic arab d carbonate reservoir the high rigidity of the limestone dolomite reservoir rock matrix and the small contrast between the elastic properties of the pore fluids i e oil and water are responsible for the weak 4d seismic effect due to oil production a feasibility study was recently completed to quantify the 4d seismic response of reservoir saturation changes as brine replaced oil the study consisted of analysing reservoir rock physics petro acoustic data and seismic modelling a seismic model of flow simulation using fluid substitution concluded that time lapse surface seismic or conventional 4d seismic is unlikely to detect the floodfront within the repeatability of surface seismic measurements thus an alternative approach to 4d seismic for reservoir fluid monitoring is proposed permanent seismic sensors could be installed in a borehole and on the surface for passive monitoring of microseismic activity from reservoir pore pressure perturbations reservoir production and injection operations create these pressure or stress perturbations reservoir heterogeneities affecting the fluid flow could be mapped by recording the distribution of epicentre locations of these microseisms or small earthquakes the permanent borehole sensors could also record repeated offset vertical seismic profiling surveys using a surface source at a fixed location to ensure repeatability the repeated vertical seismic profiling could image the change in reservoir properties with production

evolution of microphysical structure of a subtropical squall line observed by a polarimetric radar and a disdrometer during opacc in eastern china the evolution of the microphysical structures of a subtropical squall line observed during the observation prediction and analysis of severe convection of china opacc field campaign in eastern china is documented in this paper the data collected from a c band polarimetric doppler radar reflectivity z differential reflectivity zdr and specific differential phase kdp and a disdrometer are used to investigate the variations of microphysical characteristics within the convective region during the formative intensifying and mature stages of the squall line the microphysical characteristics of the squall line are noticeably different among these three stages when the squall line develops from the formative stage to the mature stage its radar derived drop size distribution dsd in the convective region evolves from continental like convection to more maritime like convection contrary to previous studies the dsd characteristics of a convective line may not be simply locked to a geographical location but varied extensively throughout its life cycle the polarimetric radar derived liquid water content below the freezing level in the convective region is three times higher than the ice water content above the freezing level this in conjunction with a low cloud base 0 68 km and a high freezing level 5 km indicates a deep warm cloud layer and the dominance of the warm rain process within this squall line

aircraft observations of the influence of electric fields on the aggregation of ice crystals aircraft observations of ice crystal size and habit distributions in the cirrus outflow from deep convection at several geographic locations are reported in situ measurements were made in the outflow from maritime thunderstorms near kwajalein part of the marshall islands and of thunderstorms with more continental aerosol concentrations both in the united states and near darwin australia over the tiwi islands images of chain like aggregates of small ice crystals some with plate like shapes were observed with a state of the art microphysics probe in the outflow regions of continental storms that were typically highly electrified displaying lightning the chains were not found in the outflow regions of maritime storms that are typically less electrically active the striking similarity between these images and previous laboratory measurements of ice aggregation in electric fields are remarked upon this evidence is used to support the theory that chain aggregates of ice crystals may be common in fully glaciated regions of continental thunderstorms where ice particle number densities are high and their presence is due to the electric field alignment of ice crystals with subsequent enhancement of the aggregation process by dipole induction resulting in short range attractive inter particle forces it is not confirmed where in the storm the aggregates were typically formed however in the darwin thunderstorms they were noted to occur with the highest frequency towards the cirrus outflow base when the cirrus base altitude was high and generally decreased in frequency with increasing distance from the storm the potential consequences of electrically enhanced aggregation in continental storms and related electric field mechanisms along with the role of homogeneous freezing in intense thunderclouds are discussed copyright 2005 royal meteorological society

the vertical profile of radar reflectivity of convective cells a strong indicator of storm intensity and lightning probability abstract reflectivity data from doppler radars are used to construct vertical profiles of radar reflectivity vprr of convective cells in mesoscale convective systems mcss in three different environmental regimes the national center for atmospheric research cp 3 and cp 4 radars are used to calculate median vprr for mcss in the oklahoma kansas preliminary regional experiment for storm central in 1985 the national oceanic and atmospheric administration tropical ocean global atmosphere radar in darwin australia is used to calculate vprr for mcss observed both in oceanic monsoon regimes and in continental break period regimes during the wet seasons of 1987 88 and 1988 89 the midlatitude and tropical continental vprrs both exhibit maximum reflectivity somewhat above the surface and have a gradual decrease in reflectivity with height above the freezing level in sharp contrast the tropical oceanic profile has a maximum reflectivity at the lowest level and a very rapid decrease in reflectivity with he

electrically active hot towers in african easterly waves prior to tropical cyclogenesis abstract it has been hypothesized that intense convective scale hot towers play a role in tropical cyclogenesis via dynamic and thermodynamic feedbacks on the larger scale circulation in this study the authors investigate the role that widespread and or intense lightning producing convection i e electrically hot towers present in african easterly waves aews may play in tropical cyclogenesis over the east atlantic ocean the 700 hpa meridional wind from the ncep ncar reanalysis dataset was analyzed to divide the waves into northerly southerly trough and ridge phases the aews were subsequently divided into waves that developed into tropical storms i e developing and those that did not develop into tropical storms i e nondeveloping finally composites were created using various ncep variables lightning data gathered with the zeus network and worldwide lightning location network wwlln and brightness temperature data extracted from the nasa global merged infrared brightness temperatur