validating novel boundary conditions for three dimensional mechanics based restoration an extensional sandbox model example geomechanical restoration methods are dependent on boundary conditions to ensure geological consistency of the restored model in terms of geometry and strain classical restoration boundary conditions such as flattening a datum horizon may lead to inconsistent displacement and strain fields we restore a laboratory structural sandbox model with known deformation history to develop guidelines for definition of boundary conditions that produce improved results from geomechanical restorations the sandbox model has a basal silicone layer includes synkinematic deposition and is characterized by structures analogous to those found in suprasalt extensional environments the deformed geometry is interpreted from three dimensional tomography imaging and a time series of cross section tomography images provides a benchmark to quantify restoration error and inform boundary conditions we confirm that imposing a lateral displacement equal and opposite to far field tectonic shortening or extension provides a more accurate restoration however the amount of displacement may not be known in real cases we therefore test several established methods using only the unrestored geometries to assess the amount of shortening that should be used to guide geomechanical restorations an accurate estimation is provided by the area depth method and potentially by a dilatation analysis additionally novel fault compliance boundary conditions produce improved results in the vicinity of crossing and branching faults application of similar methods should produce improved restoration of natural geologic structures

transient luminous events above two mesoscale convective systems storm structure and evolution 1 two warm season mesoscale convective systems mcss were analyzed with respect to their production of transient luminous events tles mainly sprites the 20 june 2007 symmetric mcs produced 282 observed tles over a 4 h period during which the storm s intense convection weakened and its stratiform region strengthened tle production corresponded well to convective intensity the convective elements of the mcs contained normal polarity tripole charge structures with upper level positive charge 40 c midlevel negative charge 20 c and low level positive charge near the melting level in contrast to previous sprite studies the stratiform charge layer involved in tle production by parent positive cloud to ground cg lightning resided at upper levels this layer was physically connected to upper level convective positive charge via a downward sloping pathway the average altitude discharged by tle parent flashes during tle activity was 8 2 km above mean sea level msl 25 c the 9 may 2007 asymmetric mcs produced 25 observed tles over a 2 h period during which the storm s convection rapidly weakened before recovering later unlike 20 june tle production was approximately anticorrelated with convective intensity the 9 may storm which also had a normal tripole in its convection best fit the conventional model of low altitude positive charge playing the dominant role in sprite production however the average altitude discharged during the tle phase of flashes still was higher than the melting level 6 1 km msl 15 c based on these results it is inferred that sprite production and sprite parent positive charge altitude depend on mcs morphology

edge driven mechanical microplate models of strike slip faulting in the tibetan plateau 1 the india asia collision zone accommodates the relative motion between india and eurasia through both shortening and pervasive strike slip faulting to gain a mechanical understanding of how fault slip rates are driven across the tibetan plateau we develop a two dimensional linear elastic two stage deformable microplate model for the upper crust based on the behavior of an idealized earthquake cycle we use this approach to develop a suite of simple india asia collision zone models differing only in boundary conditions to determine which combination of edge forces and displacements are consistent with both the slip rate measurements along major tibetan faults as well as the geodetically observed extrusion of crustal material toward southeast asia model predictions for the altyn tagh 1 14 mm yr kunlun 3 10 mm yr karakorum 5 12 mm yr and haiyuan 3 5 mm yr faults are in agreement with geologically and geodetically inferred slip rates further models that accurately reproduce observed slip rate gradients along the altyn tagh and kunlun faults feature two critical boundary conditions 1 oblique compressive displacement along the himalayan range front west of the shillong plateau and 2 forcing in southeast asia additionally the ratio of internal block potency rate to the total potency rate for each microplate ranges from 28 to 79 suggesting a hybrid view of deformation in tibet as simultaneously localized on major faults and distributed at length scales 500 km

fractal density modeling of crustal heterogeneity from the ktb deep hole fractal or multifractal concepts have significantly enlightened our understanding of crustal heterogeneity much attention has focused on 1 f scaling natures of physico chemical heterogeneity of earth crust from fractal increment perspective in this study fractal density model from fractal clustering point of view is used to characterize the scaling behaviors of heterogeneous sources recorded at german ktb main hole and of special contribution is the local and global multifractal analysis revisited by using haar wavelet transform hwt fractal density modeling of mass accumulation generalizes the unit of rock density from integer e g g cm3 to real numbers e g g cm so that crustal heterogeneities with respect to source accumulation are quantified by singularity strength of fractal density in dimensional space from that perspective we found that the bulk densities of metamorphic rocks exhibit fractal properties but have a weak multifractality decreasing with the depth the multiscaling natures of chemical logs also have been evidenced and the observed distinct fractal laws for mineral contents are related to their different geochemical behaviors within complex lithological context accordingly scaling distributions of mineral contents have been recognized as a main contributor to the multifractal natures of heterogeneous density for low porosity crystalline rocks this finally allows us to use de wijs cascade process to explain the mechanism of fractal density in practice the proposed local singularity analysis based on hwt is suggested as an attractive high pass filtering to amplify weak signatures of well logs as well as to delineate micro lithological changes

hydrometeor enhanced tephra sedimentation constraints from the 18 may 1980 eruption of mount st helens 1 uncertainty remains on the origin of distal mass deposition maxima observed in many recent tephra fall deposits in this study the link between ash aggregation and the formation of distal mass deposition maxima is investigated through reanalysis of tephra fallout from the mount st helens 18 may 1980 msh80 eruption in addition we collate all the data needed to model distal ash sedimentation from the msh80 eruption cloud four particle size subpopulations were present in distal fallout with modes at 2 2 4 2 5 9 and 8 3 settling rates of the coarsest subpopulation closely matched predicted single particle terminal fall velocities sedimentation of particles 100 m was greatly enhanced predominantly through aggregation of a particle subpopulation with modal diameter 5 9 0 2 19 3 m mammatus on the msh80 cloud provided a mechanism to transport very fine ash particles with predicted atmospheric lifetimes of days to weeks from the upper troposphere to the surface in a matter of hours in this mechanism ash particles initiate ice hydrometeor formation high in the troposphere subsequently the volcanic cloud rapidly subsides as mammatus develop from increased particle loading and cloud base sublimation rapid fallout occurs as the cloud passes through the melting level in a process analogous to snowflake aggregation aggregates sediment en masse and form the distal mass deposition maxima observed in many recent volcanic ash fall deposits this work provides a data resource that will facilitate tephra sedimentation modeling and allow model intercomparisons

polar lightning and decadal scale cloud variability on jupiter although lightning has been seen on other planets including jupiter polar lightning has been known only on earth optical observations from the new horizons spacecraft have identified lightning at high latitudes above jupiter up to 80 n and 74 s lightning rates and optical powers were similar at each pole and the mean optical flux is comparable to that at nonpolar latitudes which is consistent with the notion that internal heat is the main driver of convection both near infrared and ground based 5 micrometer thermal imagery reveal that cloud cover has thinned substantially since the 2000 cassini flyby particularly in the turbulent wake of the great red spot and in the southern half of the equatorial region demonstrating that vertical dynamical processes are time varying on seasonal scales at mid and low latitudes on jupiter

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

multiscaling nature of sonic velocities and lithology in the upper crystalline crust evidence from the ktb main borehole the observed scaling of sonic logs is generally described using a monofractal model fractional brownian motion with hurst exponent typically between 0 1 and 0 2 or fractional levy motion even though such a description recognizes the existence of the self similarity of the logs it offers only a limited account of the actual symmetry as it misses the displayed heterogeneous fractality intermittency of the velocity increments is here observed and calls for the use of a multifractal description we quantify such a multifractality in the case of the p wave sonic log recorded at the ktb main borehole we also show that the associated lithology inferred from the gamma log has a multifractal distribution as well though characterized by a stronger intermittency it can be expected that the multifractality of the sonic log is partially induced by the lithology though the observed discrepancy in the degree of intermittency between the two logs indicates that the scaling symmetry of the seismic velocity is probably due to many different contributions such statistics for both sonic and gamma logs have important implications on our understanding of wave propagation and rock strength and permeability in the crystalline crust as they show the crust to be more heterogeneous than is usually modeled

thermal structure of jupiter s atmosphere near the edge of a 5 μm hot spot in the north equatorial belt thermal structure of the atmosphere of jupiter was measured from 1029 km above to 133 km below the 1 bar level during entry and descent of the galileo probe the data confirm the hot exosphere observed by voyager 900 k at 1 nanobar the deep atmosphere which reached 429 k at 22 bars was close to dry adiabatic from 6 to 16 bars within an uncertainty 0 1 k km the upper atmosphere was dominated by gravity waves from the tropopause to the exosphere shorter waves were fully absorbed below 300 km while longer wave amplitudes first grew then were damped at the higher altitudes a remarkably deep isothermal layer was found in the stratosphere from 90 to 290 km with t 160 k just above the tropopause at 260 mbar there was a second isothermal region 25 km deep with t 112 k between 10 and 1000 mbar the data substantially agree with voyager radio occultations the voyager 1 equatorial occultation was similar in detail to the present sounding through the tropopause region the voyager iris average thermal structure in the north equatorial belt neb approximates a smoothed fit to the present data between 0 03 and 400 mbar differences are partly a result of large differences in vertical resolution but may also reflect differences between a hot spot and the average neb at 15 4 bars probe descent velocities derived from the data are consistently unsteady suggesting the presence of large scale turbulence or gravity waves however there was no evidence of turbulent temperature fluctuations 0 12 k a conspicuous pause in the rate of decrease of descent velocity between 1 1 and 1 35 bars where a disturbance was also detected by the two radio doppler experiments implies strong vertical flow in the cloud seen by the probe nephelometer at p 0 6 bar measured temperatures were 3 k warmer than the dry adiabat possible evidence of radiative warming this could be associated with a tenuous cloud detected by the probe nephelometer above the 0 51 bar level for an ammonia cloud to form at this level the required abundance is 0 20 solar

kinematic microphysical and electrical aspects of an asymmetric bow echo mesoscale convective system observed during steps 2000 1 five hours of detailed observations of the asymmetric bow echo mesoscale convective system on 11 12 june 2000 during the steps project are presented data sources included polarimetric and doppler radars a vhf lightning mapper and the national lightning detection network nearly every 99 vhf lightning source occurred within 10 km of the convective line charge identification within the much of the convective line revealed evolution during the first 3 h from a normal polarity dipole upper positive charge near 9 km msl 30 c over mid level negative charge near 7 km 16 c to a normal polarity tripole with the addition of lower positive charge near 4 km 1 c during the final 2 h the charge structure resembled an inverted dipole with negative charge overlaying positive when the bow echo occurred during hour 2 part of the cells associated with severe winds developed an inverted tripolar charge structure and produced predominantly positive cloud to ground lightning stratiform lightning was infrequent normally initiating in the convective line and propagating rearward along two pathways a downward sloping upper pathway near 9 km and a more common constant altitude lower pathway near 6 km 10 c some flashes initiated within the stratiform region during this time but only after stratiform reflectivities increased significantly in the mixed phase region these flashes initiated near the bright band 4 km and tapped negative charge above and positive charge below possible mechanisms to explain the observations are discussed

the jal az zor escarpment as a product of complex duplex folding and strike slip tectonics a new study in kuwait northeastern arabian peninsula abstract the origin of jal az zor escarpment has been equivocal due to limited exposure and subsurface data the escarpment was assumed to be a result of differential weathering and erosion most recently mapping of basement lineaments suggested a deep fault system as a most likely cause the aim of this article is to use shallow seismic data acquired across various locations along the escarpment to investigate the underlying geology structural elements and link these features to surface observations to understand the near subsurface geology post stack time processing was applied to 2d seismic data acquired recently in the area the objective was to focus on the shallow intervals represented by the rus dammam and kuwait formations the analyses revealed a train of tight concentric folds that increase in stage development towards the escarpment in the dammam formation the shallower kuwait formation shows early stages of fault propagation folding as a result of the kuwait arch uplift towards the south of the escarpment we suggest that friction along the dammam formation upper contact detachment planes increased towards the south thus promoting the propagation of the fold reaching the surface resulting in the jal az zor escarpment that we see today structural kinematic analysis suggests that the jal az zor escarpment is also a principal displacement zone pdz that is dominated by dextral strike slip motion and exhibits a series of restraining bends positive flower structures and a horsetail splay 2d structural restoration and balancing suggest a total shortening magnitude of approximately 6 25 km considering the arabian and eurasian plates velocity vectors along with the relatively large amount of shortening this deformation initiated during the early pleistocene calabrian the presence of tight concentric and fault propagation folds combined with dextral strike kinematics introduce new complexities into the structural styles and assemblages of the area otherwise thought to follow the overall northern arabian peninsula tectonics

handling natural complexity in three dimensional geomechanical restoration with application to the recent evolution of the outer fold and thrust belt deep water niger delta volumetric restoration can provide crucial insights into the structural evolution of three dimensional 3 d petroleum systems a major limitation to its widespread application is the need to include complex architectures and realistic mechanics such as flexural slip we apply an implicit approach that allows for including unconformities thin and or pinched out layers in the models but that cannot explicitly localize slip along horizons to take advantage of this approach while accounting for flexural slip in 3 d restoration we investigate new geomechanical properties we consider flexural slip folding as a result of stacked rigid and thin weak layers which can be modeled using transversely isotropic properties we compare restorations of an anticline using transversely isotropic properties isotropic properties and a stack of rigid isotropic layers with nonfrictional slip between the layers our results show that transversely isotropic properties reasonably approximate flexural slip folding we use these new tools to model the evolution of a complex system located in the niger delta toe the system includes a detachment fold a fault bend fold and a structural wedge formed in series growth stratigraphy and erosional surfaces delimit the kinematics of deformation regional erosive surfaces 3 d gradients of fault slip and vertical variations in mechanical strength motivated the use of our new restoration techniques restoring two growth units results not only in reinforcing the interpretation that the area is behaving as a deforming thrust sheet at critical taper but also in highlighting coeval activity on both the hinterland structures and the toe of the thrust belt

three dimensional kinematic modeling of reversible fault and fold development in the current context of continuous supply of energy the discovery and development of new prospects will rely on our ability to detect reserves in deeper and structurally more complex formations these exploration areas stretch the capabilities of currently available three dimensional 3 d exploration software which cannot accommodate a realistic geometrical description of present day geological structures and the tectonic deformation steps correctly handling the kinematics of structural deformation and evaluating the pressure regime and temperature history at the scale of exploration will remain as challenges for several years to come in this article we focus on geometric aspects using a reversible kinematic approach to deform and restore faulted and folded structures kinematic modeling is a good alternative to the complexity of a mechanical approach and is sufficiently representative of the natural processes involved sedimentation erosion and compaction its reversibility ensures that the basin parameters need to be defined only once for both the restoration and the deformation steps the model describes the incremental development of the basin in space and time it is based on a hexahedral discretization process that is fully adapted and appropriate for thermal and fluid transfer different deformation modes flexural slip and vertical shear are mixed to integrate natural deformation more effectively the algorithm is validated using different geological examples of growing complexity up to curved normal and thrust faults the approach offers various prospects for improvement integrating both kinematic and mechanical constraints considering the challenges that the industry needs to overcome in future exploration the results of this approach are very encouraging and can be considered as a solution for solving the structural part of 3 d basin modeling in complex areas

lightning in the anvils of supercell thunderstorms abstractthis study uses data from the oklahoma lightning mapping array ok lma the national lightning detection network and the norman oklahoma koun prototype weather surveillance radar 1988 doppler wsr 88d radar to examine the evolution and structure of lightning in the anvils of supercell storms as they relate to storm dynamics and microphysics several supercell storms within the domain of the ok lma were examined to determine whether they had lightning in the anvil region and if so the time and location of the initiation of the anvil flashes were determined every warm season supercell storm had some flashes that were initiated in or near the stronger reflectivities of the parent storm and propagated 40 70 km downstream to penetrate well into the anvil some supercell storms also had flashes that were initiated within the anvil itself 40 100 km beyond the closest 30 dbz contour of the storm these flashes were typically initiated in one of three locations 1 coincident with a local reflec

evolution of the total lightning structure in a leading line trailing stratiform mesoscale convective system over houston texas 1 line normal vertical cross sections of houston lightning detection and ranging ldar vhf radiation sources and radar reflectivity provide new insights into the three dimensional total lightning structure and evolution of a leading line trailing stratiform llts mesoscale convective system mcs over houston texas on 31 october 2005 previous research examining only the mature stage of an mcs showed that the overwhelming majority of vhf lightning sources occurred in the convective region with a lightning pathway extending rearward and descending in altitude into the stratiform region this descending pathway was most likely associated with small charged ice particles advected from the convective line unlike previous research the lightning pathway observed during the evolution of the mcs on 31 october 2005 initially extended rearward 40 km at a nearly constant height of 9 10 km in less than an hour the lightning pathway evolved into a sloped pathway similar to that found by previous research with a horizontal extent between 50 to 60 km and downward descent of 4 to 5 km during the lightning pathway evolution radar analysis showed an increase of reflectivity in the midlevels of the stratiform region consistent with increased depositional and aggregational growth above the melting layer broadening increased range of values of radar reflectivity above the melting layer was most likely an indication of a strengthening mesoscale updraft in the stratiform region this strengthening updraft may have contributed to an increase in the growth of the small charge carrying ice crystals giving them a greater fall speed in addition the mesoscale updraft may have promoted an environment conducive to local stratiform region charge generation in the mixed phase region just above the melting layer

electrical evolution during the decay stage of new mexico thunderstorms 1 the electric field e at the ground beneath a thunderstorm often exhibits an end of storm oscillation eoso during the storm s decay phase in which e typically undergoes three polarity changes over a period of 30 75 min to determine why the surface e oscillates the timing of the eoso polarity changes of a multicellular storm in new mexico has been compared to a series of balloon radar and lightning data three in situ balloon soundings provide vertical profiles of e and inferred charge regions just before and during the eoso these data have been compared to the evolving precipitation structure determined from orthogonal range height scans of two radars and to several other parameters including lightning mapping array data before the eoso began the storm had the typical electrical structure of the late mature stage estimates of the total charge magnitudes in each of the principal regions before and during the eoso ranged from 7 to 33 c the comparisons indicate that surface e polarity changes during the eoso were 1 primarily owing to the successive fallout of three of the four principal charge regions in the storm s mature stage charge structure modified by 2 the growth or decay of the charge regions as they descended and 3 changes in the screening charges at the upper and lower cloud boundaries more limited data from two other decaying storms indicate that similar in cloud evolution was probably occurring during their eosos

jupiter s interior and deep atmosphere the initial pole to pole passes with the juno spacecraft on 27 august 2016 the juno spacecraft acquired science observations of jupiter passing less than 5000 kilometers above the equatorial cloud tops images of jupiter s poles show a chaotic scene unlike saturn s poles microwave sounding reveals weather features at pressures deeper than 100 bars dominated by an ammonia rich narrow low latitude plume resembling a deeper wider version of earth s hadley cell near infrared mapping reveals the relative humidity within prominent downwelling regions juno s measured gravity field differs substantially from the last available estimate and is one order of magnitude more precise this has implications for the distribution of heavy elements in the interior including the existence and mass of jupiter s core the observed magnetic field exhibits smaller spatial variations than expected indicative of a rich harmonic content

evolution of cloud to ground lightning characteristics and storm structure in the spearman texas tornadic supercells of 31 may 1990 abstract on 31 may 1990 four tornadic supercell storms formed sequentially near the intersection of a dryline and an outflow boundary in the northern texas panhandle staccato lightning flashes which have been hypothesized to be positive ground flashes were observed beneath the anvil of one storm during the most violent tornado that the storm produced evidence was found from a lightning mapping system that at least some of the staccato flashes were negative ground flashes although the four supercell storms on this day formed in approximately the same area traveled over roughly the same region and produced tornadoes and large hail the relationship between the genesis and evolution of tornadoes and the polarity and flash rates of ground flashes varied widely as in previous studies the second of the supercell storms had low precipitation supercell characteristics the third and fourth did not in previously studied storms ground flash activity in low precipitation supercell storms has always bee

relationships between lightning location and polarimetric radar signatures in a small mesoscale convective system abstract on 19 june 2004 the thunderstorm electrification and lightning experiment observed electrical microphysical and kinematic properties of a small mesoscale convective system mcs the primary observing systems were the oklahoma lightning mapping array the koun s band polarimetric radar two mobile c band doppler radars and balloonborne electric field meters during its mature phase this mcs had a normal tripolar charge structure lightning involved a midlevel negative charge between an upper and a lower positive charge and flash rates fluctuated between 80 and 100 flashes per minute most lightning was initiated within one of two altitude ranges 3 6 or 7 10 km msl and within the 35 dbz contours of convective cells embedded within the convective line the properties of two such cells were investigated in detail with the first lasting approximately 40 min and producing only 12 flashes and the second lasting over an hour and producing 105 flashes in both lightning was initiated in or nea

triggering of seismicity at short timescales following californian earthquakes 1 a method for measuring seismicity rate changes caused by the occurrence of major earthquakes in the surrounding crust is proposed it is based on a nonstationary poisson modeling of earthquake activity an estimate of the seismicity rate change and a probability measure of seismicity triggering following a large shock are derived and the removal of the influence of independent aftershock sequences of other nearby previous earthquakes is attempted without using more traditional declustering techniques the seismicity rate change estimator is corrected for its natural bias in favor of positive changes at short timescales that has so far strongly hindered measures of seismicity quiescences three californian earthquakes are examined using this method the 1989 m7 1 loma prieta the 1992 m7 3 landers and the 1994 m6 7 northridge earthquakes positive triggering is very commonly observed as expected but quiescence is however more seldomly obtained for timescales up to 100 days after the main shock this relative absence of quiescence as compared to typical predictions of coulomb modeling for example is also independently observed through direct correlation analyses of californian seismicity the possibility that the stresses caused by the main shock are spatially highly variable may explain these observations

nature and origin of upper crustal seismic velocity fluctuations and associated scaling properties combined stochastic analyses of ktb velocity and lithology logs the main borehole of the german continental deep drilling program ktb extends over 9000 m into a crystalline upper crust consisting primarily of interlayered gneiss and metabasite we present a joint analysis of the velocity and lithology logs in an effort to extract the lithology component of the velocity log covariance analysis of lithology log approximated as a binary series indicates that it may originate from the superposition of two brownian stochastic processes fractal dimension 1 5 with characteristic scales of 2800 m and 150 m respectively covariance analysis of the velocity fluctuations provides evidence for the superposition of four stochastic process with distinct characteristic scales the largest two scales are identical to those derived from the lithology confirming that these scales of velocity heterogeneity are caused by lithology variations the third characteristic scale 20 m also a brownian process is probably related to fracturing based on correlation with the resistivity log the superposition of these three brownian processes closely mimics the commonly observed 1 k decay fractal dimension 2 0 of the velocity power spectrum the smallest scale process characteristic scale 1 7 m requires a low fractal dimension 1 0 and accounts for 60 of the total rms velocity variation a comparison of successive logs from 6900 7140 m depth indicates that such variations are not repeatable and thus probably do not represent true velocity variations in the crust the results of this study resolve disparity between the differing published estimates of seismic heterogeneity based on the ktb sonic logs and bridge the gap between estimates of crustal heterogeneity from geologic maps and borehole logs

3d structural modelling of the southern zagros fold and thrust belt diapiric province 3d modelling of geological structures is a key method to improve the understanding of the geological history of an area and to serve as a drive for exploration geomodelling has been performed on a large 60000 km 2 area of the zagros fold and thrust belt of iran to reconcile a vast but heterogeneous dataset topography geological surface data and dips outcrop surveys and well and seismic data were integrated into the model the method was to construct a key surface maximizing the hard data constraints the oligo miocene top asmari layer was chosen as this formation was regionally deposited before the main zagros collision phase and because the numerous outcrops allow proper control of the bed geometry in the fold cores interpreted seismic data have been integrated to interpolate the surfaces at depth within the synclines several conceptual models of fold geometry have been applied to estimate the best way to convert seismic time signal to depth several deeper horizons down to palaeozoic strata were deduced from this key horizon by applying palaeo thickness maps during the construction the 3d interpolated surfaces could be reconverted to time using a velocity model and compared with previous seismic interpretations this exercise obliged us to revise some early interpretations of seismic lines that were badly tied to wells the 3d modelling therefore clearly improves regional interpretation in addition the 3d model is the only tool that allows drawing consistent cross sections in areas where there are no seismic lines emerging hormuz salt diapirs were added to the model dimensions and shapes of the individual diapirs were modelled using a statistical survey on the cropping out hormuz structures modelling reliably demonstrated that the diapirs when piercing show a constant mushroom shape whose diameter depends on the stratigraphic depth of observation this observation allowed us to exemplify relations between the pre existing diapirs and the anticlines of the area and to highlight the morphological changes from the inner onshore areas to the coastal and offshore areas in addition one of the surprising results of this study was the observation of the increasing diameter of the diapirs at the time of the zagros collision and folding event with growth strata and overhangs on the flanks of the diapirs

duration and extent of large electric fields in a thunderstorm anvil cloud after the last lightning 1 a series of balloon electric field e soundings and time correlated radar scans through the balloon locations are used to examine the evolution of charge and reflectivity inside a dissipating thunderstorm anvil the soundings cover a 75 min period during and after the final lightning flash in distant convection the first sounding measured large e magnitudes maximum 65 kv m 1 and significant charge densities of both polarities maximum 2 5 nc m 3 within and screening the anvil little change in the maximum e values occurred in the 30 min between the first and third soundings although altitudes and densities of some charge regions decreased with time maximum 0 6 nc m 3 screening charge regions were observed in close coincidence with 12 dbz radar reflectivity contours and interior positive charge was found in the reflectivity maxima of both anvil decks the fourth sounding ascended through visible but optically less dense cloud and no enhanced e values were detected overall the data indicate the interior positive charge region of the main anvil contained about 150 c and covered at least 250 km2 nearly 30 min after the last lightning flash potentially hazardous e values of 30 35 kv m 1 were measured at 9 9 10 2 km altitude a common jet aircraft cruising altitude more than 20 km away from and 32 min after the final lightning flash about 50 min after the last flash the main positive charge region contained an estimated 50 c and potentially hazardous e values associated with the anvil extended over at least 220 km2

palinspastic reconstruction of structure maps an automated finite element approach with heterogeneous strain existing methods for the palinspastic reconstruction of structure maps do not adequately account for heterogeneous rock strain and hence cannot accurately treat features such as fault terminations and non cylindrical folds we propose a new finite element formulation of the map reconstruction problem that treats such features explicitly in this approach a model of the map surface with internal openings that honor the topology of the fault gap network is constructed of triangular finite elements both model building and reconstruction algorithms are guided by rules relating fault gap topology to the kinematics of fault motion and are fully automated we represent the total strain as the sum of a prescribed component of locally homogeneous simple shear and a minimum amount of heterogeneous residual strain the region within which a particular orientation of simple shear is treated as homogenous can be as small as an individual element or as large as the entire map for residual strain calculations we treat the map surface as a hyperelastic membrane a globally optimum reconstruction is found that unfolds the map while faithfully honoring assigned strain mechanisms closes fault gaps without overlap or gap and imparts the least possible residual strain in the restored surface the amount and distribution of the residual strain serves as a diagnostic tool for identifying mapping errors the method can be used to reconstruct maps offset by any number of faults that terminate branch and offset each other in arbitrarily complex ways

sequential restoration and unstraining of structural cross sections applications to extensional terranes we restore cross sections using a strain minimization strategy that concentrates displacement on known faults and on slip systems within fault blocks growth strata are used to sequentially restore cross sections and the misfit of rigidly restored fault blocks is used to determine the internal strain within each fault block texture mapping allows data e g seismic profile photograph of an analog model or outcrop to be imaged onto the restored state and the image is translated rotated and unstrained during the restoration growth strata are stripped layer by layer to sequentially restore a cross section this approach determines the history of deformation including the activity of faults and the internal strain accumulated during each growth increment during each increment of growth a cross section is initially restored to a horizontal datum assuming that deformation is by rigid body translations and rotations of fault blocks fault blocks are unstrained by dividing them into smaller triangular elements that accommodate the internal deformation within each fault block translations and rotations of the smaller rigid elements within each fault block produce a least squares minimized best fit after attaining a best fit of rigid elements continuity is regained by moving initially coincident triangle vertices to a common centroid the change in shape of the triangular elements in regaining continuity is a measure of strain at that location assuming homogeneous strain within each triangular element sequential restoration and unstraining determines the spatial variation and temporal evolution of strain orientations and magnitudes calculated at each vertex during each increment of restoration the method is tested on an analog sandbox model of deformation in the hanging wall of a listric normal fault and on two seismic profiles a listric normal fault system from the gulf of mexico and a graben developed over salt from the north sea the sequential restoration accurately determines the sequence of faulting in the analog model and provides insights into the development of the natural examples the restoration method determines the orientations and magnitudes of strain which can be used to predict the orientation intensity and timing of small scale deformation features

electrical structure in thunderstorm convective regions 3 synthesis in this paper results from nearly 50 electric field soundings through convective regions of mesoscale convective systems mcss isolated supercells and isolated new mexican mountain storms are compared and synthesized these three types of thunderstorm convection are found to have a common basic electrical structure within convective updrafts the basic charge structure has four charge regions alternating in polarity and the lowest is positive outside updrafts of convection there are typically at least six charge regions alternating in polarity and the lowest is again positive among the three storm types there are differences in the heights and temperatures at which the basic four charge regions are found in updrafts the height temperature of the center of the main negative charge region averages 6 93 km 16 c in mcs convective region updrafts 9 12 km 22 c in supercell updrafts and 6 05 km 7 c in new mexican mountain storm updrafts in updraft soundings through all three storm types the center height of the main negative charge region increases with increasing average balloon ascent rate and updraft speed at a rate of about 0 3 km per 1 m s 1 with a correlation coefficient of 0 94 a schematic illustrates the basic four and six charge structure for thunderstorm convective regions and it is offered as an improved model for thunderstorm charge structure

variability of geophysical log data and the signature of crustal heterogeneities at the ktb summary small scale variations in geophysical borehole data re ect geological inhomogeneities in the earth s crust that is its petrological mineralogical and structural organization in this paper comprehensive geophysical log data from the boreholes of the german continental deep drilling program ktb are analysed they include electric radiogenic magnetic seismic and bulk properties of rocks the logs were recorded in crystalline basement down to 9 km depth with a sampling interval of 0 15 m we describe the vertical variability within the data series in order to relate their statistics to the small scale heterogeneities of the upper crust for each physical property spectral exponents b and hurst coe cients h were calculated power spectra indicate a scaling behaviour with b values mostly falling in the range 0 5 b 1 5 typical of 1 f noise however no particular values of b characterize the log data rescaled range analyses show long range correlations with persistence of the signals from metres to thousands of metres values of h ranging between 0 6 and 0 8 reveal the self a ne character of the data series all the log data present similar statistics suggesting a fractal variability of the physical properties of the earth s crust the inferred scale invariance helps to quantify the complexity of crustal heterogeneities

compatibility constraints on folded and faulted strata and calculation of total displacement using computational restoration unfold program abstract a balanced surface method is proposed that allows one to test the reliability of the interpretation of the structural geometry of folded and faulted strata it also estimates both the finite total displacement field linked to the folding and faulting processes and the finite displacement field linked to the folding the method describes a thin competent folded and faulted sedimentary layer using rigid triangular elements their sizes depending on the curvature of the surface the elements are laid flat and are automatically fit to form a horizontal surface which represents the initial state of the layer the degree of compatibility given by different indicators tests the reliability of the geometric fitting of the layer if folding and faulting occur without bed stretching or if this change is known and introduced as a parameter in the code a plausible interpretation can be perfectly retrodeformed just as a folded and torn sheet of paper may be smoothed with an iron the method has been applied to two natural examples in oil field regions using three or two dimensional depth migrated seismic data the main results reveal in general that the petroleum company s interpretations of the data were nonoptimal a careful reinterpretation of the seismic data was necessary to obtain balanced folded and faulted surfaces the estimation of the finite displacement fields revealed the compatibility between fold and fault deformation and also the strike slip movement or rotation associated with the deformation

galileo images of lightning on jupiter in october and november of 1997 the galileo solid state imager ssi detected lightning from 26 storms on the night side of jupiter more than half the surface area of the planet was surveyed the data include images of lightning against moonlit clouds illuminated by light from io and images of the same storm on the day and night sides the spatial resolution ranged from 23 to 134 km per pixel while the storms ranged in size up to 1500 km most storms were imaged more than once and they typically exhibit many flashes per minute the storms occur only in areas of cyclonic shear and near the centers of westward jets latitudes near 50 in both hemispheres are particularly active although the northern hemisphere has more lightning overall the greatest optical energy observed in a single flash was 1 6 10 10 j which is several times larger than terrestrial superbolts the average optical power per unit area is 3 10 7 w m 2 which is close to the terrestrial value the limited color information is consistent with line and continuum emission from atomic hydrogen and helium the intensity profiles of resolved lightning strikes are bell shaped with the half width at half maximum ranging from 45 to 80 km we used these widths to infer the depth of the strikes assuming that the appearance of each is the result of light scattering from a point source below the cloudtops we conclude that lightning must be occurring within or below the jovian water cloud the occurrence of lightning in regions of cyclonic shear has important implications for the dynamics of jupiter s atmosphere

prevalent lightning sferics at 600 megahertz near jupiter s poles lightning has been detected on jupiter by all visiting spacecraft through night side optical imaging and whistler lightning generated radio waves signatures1 6 jovian lightning is thought to be generated in the mixed phase liquid ice region of convective water clouds through a charge separation process between condensed liquid water and water ice particles similar to that of terrestrial cloud to cloud lightning7 9 unlike terrestrial lightning which emits broadly over the radio spectrum up to gigahertz frequencies10 11 lightning on jupiter has been detected only at kilohertz frequencies despite a search for signals in the megahertz range 12 strong ionospheric attenuation or a lightning discharge much slower than that on earth have been suggested as possible explanations for this discrepancy13 14 here we report observations of jovian lightning sferics broadband electromagnetic impulses at 600 megahertz from the microwave radiometer 15 onboard the juno spacecraft these detections imply that jovian lightning discharges are not distinct from terrestrial lightning as previously thought in the first eight orbits of juno we detected 377 lightning sferics from pole to pole we found lightning to be prevalent in the polar regions absent near the equator and most frequent in the northern hemisphere at latitudes higher than 40 degrees north because the distribution of lightning is a proxy for moist convective activity which is thought to be an important source of outward energy transport from the interior of the planet16 17 increased convection towards the poles could indicate an outward internal heat flux that is preferentially weighted towards the poles9 16 18 the distribution of moist convection is important for understanding the composition general circulation and energy transport on jupiter observations of broadband emission from lightning on jupiter at 600 megahertz show a lightning discharge mechanism similar to that of terrestrial lightning and indicate increased moist convection near jupiter s poles

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

electric fields cloud microphysics and reflectivity in anvils of florida thunderstorms into the interior electric fields very frequently increased abruptly from 1 to 10 kv m 1 even though the particle concentrations and radar reflectivity increased smoothly the abrupt increase in field usually occurred when the aircraft entered regions with a reflectivity of 10 15 dbz we suggest that the abrupt increase in electric field was because the charge advection from the convective core did not occur across the entire breadth of the anvil and because the advection of charge was not constant in time also some long lived anvils showed enhancement of electric field and reflectivity far downwind of the convective core screening layers were not detected near the edges of the anvils comparisons of electric field magnitude with particle concentration or reflectivity for a combined data set that included all anvil measurements showed a threshold behavior when the average reflectivity such as in a 3 km cube was less than approximately 5 dbz the electric field magnitude was 3 kv m 1 based on these

corona point measurements in a thundercloud at langmuir laboratory a meteorological radiosonde modified by the attachment of vertically oriented pointed metal rods and associated insrumentation was released beneath a thundercloud at langmuir laboratory new mexico in addition to information on temperature and winds the instrument provided an estimate of the vertical component of the cloud electric field by measurement of corona current induced in the rods charge volumes inferred from the sounding were 1 negative charge at 6 6 km msl temperature 12 c where northwesterly winds apparently advected the charge toward the cloud s most intense precipitation echoes 2 positive charge at 11 6 km msl 50 c where the winds flowed northward into the cloud s anvil 3 a 200 m thick screening layer of negative charge at the cloud s upper surface and 4 a small concentrated region of charge near the cloud base these charged regions were evident in volumes of low precipitation intensity log z 1 5 which were well away from the storm s convective center

the evolution of a severe mesoscale convective system cloud to ground lightning location and storm structure abstract cloud to ground lightning location data are correlated with the doppler radar observed structure of the evolution of a severe mesoscale convective system in oklahoma on 23 may 1981 while many of the results are not new this study is unique in that the evolution of electrical activity in a severe storm is compared to storm structure for most of the storm s life the first storm formed ahead of a mesoscale low pressure area located at the intersection of a front and a dryline and developed into a tornadic supercell in an environment of locally enhanced vertical shear ordinary cells subsequently formed both to the southwest and northeast of the supercell along the dryline and the front respectively and merged with the supercell to form a squall line having a trailing stratiform precipitation region with midlevel rear inflow it is shown that the cloud to ground flash rate in the convective region is related to the apparent strength of the updraft before the storm became a supercell the ligh

predicting strain using forward modelling of restored cross sections application to rollover anticlines over listric normal faults a strategy to predict strain across geological structures based on previous techniques is modified and evaluated and a practical application is shown the technique which employs cross section restoration combined with kinematic forward modelling consists of restoring a section placing circular strain markers on different domains of the restoration and forward modelling the restored section with strain markers until the present day stage is reached the restoration algorithm employed must be also used to forward model the structure the ellipses in the forward modelled section allow determining the strain state of the structure and may indirectly predict orientation and distribution of minor structures such as small scale fractures the forward model may be frozen at different time steps different growth stages allowing prediction of both spatial and temporal variation of strain the method is evaluated through its application to two stages of a clay experiment that includes strain markers and its geometry and deformation history are well documented providing a strong control on the results to demonstrate the method s potential it is successfully applied to a depth converted seismic profile in the central sumatra basin indonesia this allowed us to gain insight into the deformation undergone by rollover anticlines over listric normal faults

mesoscale circulations forced by melting snow part i basic simulations and dynamics abstract the melting of snow extracts latent heat of fusion from the environment the basic response of the atmosphere to this cooling by melting mechanism is investigated by using a nonlinear two dimensional numerical model it is found that the resultant melting induced circulations consist of a forced downdraft which spreads out laterally like a gravity current and transients which are gravity waves the characteristics of these mesoscale thermally driven circulations are studied under idealistic atmospheric conditions model results show that the melting associated with realistic precipitation rates up to 10 mm h 1 can induce horizontal wind perturbations of several meters per second and vertical motions of tens of centimeters per second since the gravity waves and the cold outflow current propagate away from the source they can have significant dynamic effects on the environment remote from the precipitation region moreover the melting induced near o c isothermal layer in the atmosphere alters

a model for large scale convective storms in jupiter 1 large scale convective storms are a common phenomenon in jupiter s atmosphere they are apparent in ground based and spacecraft images and may strongly affect the dynamics of the global atmosphere as well as the energy transport in the meteorological layer in this paper we analyze the outburst of a large convective storm system core 5000 km in the south equatorial belt seb that was observed at high spatial and temporal resolution by the voyager 1 spacecraft in 1979 we use a two dimensional 2 d model to study the interaction between cloud material brought up by moist convection and the environmental wind aided by previous 3 d models of jovian storms we can draw several qualitative and quantitative conclusions the evolution of this storm can be characterized by three phases 1 onset of the perturbation well reproduced by the growth of a single cell storm 2 an expanding phase in which the number of convective cells increases to 200 with updraft velocities limited to 50 m s and 3 a relatively sudden suppression of the convective activity leading to the disruption of large structures by the environmental wind furthermore we interpret the observations of the inner bright core as a well defined anticyclonic vortex with darker cloud material preferentially left southwest of the system finally we show that 1016 w are released by such a storm over its life cycle of 12 days and that the direct formation of a large scale anticyclonic vortex after the moist convective source has been removed is prevented by the environmental wind shear

air motion characteristics in the anvil of a severe thunderstorm during ccope abstract an analysis of aircraft measured data obtained in the lower portion of a high plains thunderstorm anvil is presented a wind shadow is still evident 5 to 7 core diameters downstream of the storm core the wind fluctuations are predominantly horizontal on large scales and isotropic on small scales little evidence for gravity waves is found in this convectively neutral region of the anvil small scale turbulence is encountered sporadically along cross anvil penetrations weak zones of smooth cloud edge downdraft are found along the lateral boundaries the power spectra of the wind components is shallower than the 5 3 value predicted for an inertial subrange turbulent cascade at the smallest scales resolved 2 km lightning is encountered triggered by the aircraft twice in different relatively turbulent regions far from the storm core where the temperature is 35 c and small graupel is present

a test of ice self collection kernels using aircraft data abstract aircraft observations from the cirrus regional study of tropical anvils and cirrus layers crystal florida area cirrus experiment face campaign obtained in the anvil of a large convective storm from 26 july 2002 are presented during this flight a lagrangian spiral descent was made allowing the evolution of the ice particle size distribution to be followed relative humidities during 1 km from 11 to 3 c of the descent were within 4 of ice saturation it was assumed that the ice particle size distribution was evolving through the process of aggregation alone three idealized ice ice collection kernels were used in a model of ice aggregation and compared to the observed ice particle size distribution evolution a geometric sweep out kernel a golovin sum of particle masses kernel and a modified golovin kernel sum of particle masses raised to a power the golovin kernel performed worst the sweep out kernel produced good agreement with the observations when a constant aggregation eff

restoration in plan view of faulted upper cretaceous and oligocene horizons and its bearing on the history of salt tectonics in the campos basin brazil abstract in the campos basin atlantic margin of brazil cretaceous and tertiary sediments show abundant evidence for thin skinned deformation above a layer of aptian salt near the coast there is a domain of downslope extension further offshore a domain of donwslope contraction thus we attribute the domainal pattern to gravitational gliding on the salt layer gravitational gliding appears to be driven primarily by surface slopes each material particle tends to move in the direction of steepest slope if topography is irregular particle paths diverge or converge deformation then differs from a plane strain and vertical cross sections cannot be individually balanced or restored we have therefore developed a method for restoring non plane deformation in extensional domains assuming that blocks between faults are rigid we restore stratigraphic horizons in plan view by least squares minimization of distances across fault separations cut off lenses obtaining fields of finite horizontal displacements for selected areas in the extensional domain of the campos basin where divergent gravitational gliding has led to extension in various horizontal directions we have restored two stratigraphie markers an upper cretaceous and an oligocene horizon for each horizon displacement vectors diverge seawards forming a fanlike pattern with a degree of mirror symmetry nevertheless there are major differences between the upper cretaceous and oligocene patterns both for faults and for displacements we infer that this resulted from the development during the tertiary of a propagating deltaic front whose sediment load drove the divergent gravitational gliding and induced a new fault pattern

rocket and balloon observations of electric field in two thunderstorms instruments that measure the intense electric field strengths in thunderclouds 100 kv m 1 are designed to minimize the production of ions by small electrical discharges coronas emanating from the instruments themselves the nearby charge of these ions would unpredictably disturb the natural field of the cloud in an attempt to assess this disturbance two different instruments one carried by a rocket and one carried by a balloon were launched on two occasions into thunderstorms in spite of differing trajectories the soundings were similar which gives us some confidence in both instruments in addition the measurements revealed some interesting features of the two storms each storm appeared to have six significant and distinct regions of charge the balloon soundings also revealed that lightning flashes temporarily increased the electric field strength above the thunderclouds at altitudes from 9 7 to 14 3 km by amounts up to 10 kv m 1 after which the fields decayed away in 50 to 125 s one pair of ascent and descent rocket soundings separated in time by a maximum of 60 s and horizontally by 1 to 3 km showed little change in the thunderstorm electric field between ground and 7 5 km altitude

analysis of voyager 2 images of jovian lightning abstract voyager 2 images have been examined and found to contain bright spots due to lightning activity that is confined to two narrow latitude bands centered at 49 n and 13 5 n latitude and to a single region near 60 n latitude no lightning activity is observed in the southern hemisphere even though a large area was observed with the same sensitivity as that used for northern hemisphere observations the brightest band of lightning activity occurs at 49 n but no unusual cloud features can be associated with this activity this result is consistent with the depth of the lightning activity being 80 km below the ammonia clouds and thus not producing readily observed disturbances in the visible clouds the secondary band of lightning activity that appears at 13 5 n is restricted in longitude to the disturbed zone one of the two storms found in this tropical band is very close to the location of a bright cloud feature that extends some 3 5 in latitude if it is assumed that the deflection of this feature is caused by the westerly flow of an air parcel over a hill in the potential temperature surface located at the 5 to 10 bar level then the air parcel moving over the hill would be forced to rise sufficiently high that the free convection level would be reached this situation could be the cause of the lightning activity in this region the energy dissipation rate by lightning activity in the voyager 2 images is 3200 w km2 when attenuation by clouds is considered the energy dissipation rate is approximately 50 greater than that found in the voyager 1 images the ratio of the energy dissipated by jovian lightning to the thermal flux available to drive convection motions is found to be three decades larger than the terrestrial ratio this value is similar to the ratio for the two planets found by ingersoll 1990 for the conversion of thermal energy flux to mechanical energy

origins of positive cloud to ground lightning flashes in the stratiform region of a mesoscale convective system 1 the origins of positive cloud to ground cg lightning in the stratiform region of a leading line trailing stratiform mesoscale convective system mcs are investigated platforms include radars nldn data and a vhf 3 d lightning mapping system this study examines a small asymmetric mcs that occurred near the colorado kansas border in june 2000 in this storm 39 of the 269 cgs produced over a nearly 5 hour period came to ground within the stratiform region of these 30 initiated in the leading convective line and propagated rearward before coming to ground nine other cgs originated within the stratiform region stratiform cgs were observed to propagate mostly horizontally through vertically thin layers the observations suggest that stratiform charge is a conduit for cg lightning from the convective line and can initiate cgs as well

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

lightning initiation in the anvils of two supercell storms 1 previous studies of lightning in anvil clouds have reported that flashes began in or near the storm core and propagated downwind into the anvil it had been thought that flashes could not be initiated far downwind in the anvil because anvil charge was thought to be produced mainly in the storm s deep updraft and to decrease with distance into the anvil here we report observations of the in cloud development of lightning flashes in the anvils of two supercell storms including the first observations of flashes that began in the anvil 30 100 km from the cores of the storms and propagated upwind back toward the cores interaction between charge regions in the two converging anvils of adjoining storms appeared to cause some of the distant flash initiations but a local charging mechanism in the anvil likely also contributed to the flash initiations all flashes that struck ground beneath the distant anvil transferred negative charge to ground instead of the positive charge usually transferred to ground there an apparent consequence of the parent storm having an inverted polarity electrical structure

polarimetric radar and aircraft observations of saggy bright bands during mc3e polarimetric radar observations increasingly are used to understand cloud microphysical processes which is critical for improving their representation in cloud and climate models in particular there has been recent focus on improving representations of ice collection processes e g aggregation and riming as these influence precipitation rate heating profiles and ultimately cloud life cycles however distinguishing these processes using conventional polarimetric radar observations is difficult as they produce similar fingerprints this necessitates improved analysis techniques and integration of complementary data sources the midlatitude continental convective clouds experiment mc3e provided such an opportunity quasi vertical profiles of polarimetric radar variables in two mc3e stratiform precipitation events reveal episodic melting layer sagging integrated analyses using scanning and vertically pointing radar and aircraft measurements reveal that saggy bright band signatures are produced when denser faster falling more isometric hydrometeors relative to adjacent times descend into the melting layer in one case strong circumstantial evidence for riming is found during bright band sagging times a bin microphysical melting layer model successfully reproduces many aspects of the signature supporting the observational analysis if found to be a reliable indicator of riming saggy bright bands could be a proxy for the presence of supercooled liquid water in stratiform precipitation which may provide important information for mitigating aircraft icing risks and for constraining microphysical models

chronologic modeling of faulted and fractured reservoirs using geomechanically based restoration technique and industry applications we have developed a geomechanically based restoration method to model reservoir deformation the approach founded on the finite element method simulates the physical behavior of the rock mass and considers heterogeneous material properties bedding slip and the mechanical interaction of faults to demonstrate the method s potential we analyze the deformation and fault growth in the hanging wall of a synsedimentary listric normal fault from a sand box model which provides an analog for evaluating complex faulted reservoirs the numerical model results are then analyzed to investigate the chronology of faulting the numerical model corresponds well to the physical model and provides additional insights about reservoir evolution and deformation the approach is also tested on a natural example of folding using outcrop data to study contractional deformation these examples illustrate how undetected faults and fractures reservoir compartmentalization hydrocarbon migration pathways and hydrocarbon traps can be understood in the context of tectonic processes and how this understanding can be exploited in decision making and reducing risk we conclude that the geomechanically based restoration of faulted and fractured reservoirs has significant potential for industry applications compared to common geometric restoration techniques which lack a mechanical basis

cross section restoration a tool to simulate deformation application to a fault propagation fold from the cantabrian fold and thrust belt nw iberian peninsula simulation of deformation in sections across tectonic structures can provide important information about the present day state of such structures a technique for simulation of deformation based on cross section restoration is presented the deformation parameters are calculated through a model that provides information in numerical format and the results are illustrated overlapping gridded images and diagrams on top of the sections across the structures in order to visualize their geological significance the validity of this method has been proved through its application to a structure formed in a contractional regime the structure analyzed is located in the cantabrian mountains nw iberian peninsula and consists of a fault propagation fold made up of carboniferous limestones the excellent outcrop of this structure allowed a complete geological cross section reconstruction and a detailed structural and kinematic analysis in order to obtain an accurate restoration the results furnished by the restoration technique about the deformation values and patterns are in agreement with small scale structures observed in the field as well as with the geometry and kinematics of the structure

the diurnal cycle of tropical convection the diurnal cycle of tropical convection is investigated with global cloud imagery constructed from 11 m radiance measurements taken aboard six satellites four harmonics of the diurnal cycle are resolved in the cloud imagery with about 50 km horizontal resolution to isolate deep convective activity from other processes which cause diurnal fluctuations in longwave radiance an index of deep convective activity is constructed by thresholding to brightness temperatures less than 230 k significant diurnal amplitude of deep convection is found only over tropical landmasses over the tropical oceans the diurnal cycle is weak and is barely discernible from the background red spectrum of convective variance nonetheless oceanic convection exhibits a systematic diurnal fluctuation with maximum intensity in the early morning nocturnal subsidence along the cloud free equator is postulated to play a role in forcing diurnal variation in the intertropical convergence zones other mechanisms are also implied to contribute as a similar early morning maximum in deep convection is seen even where no adjoining cloud free regions occur the diurnal cycle of deep convection is found to be organized on planetary scales predominantly in nonmigrating modes i e modes with phase speeds not equal to that of the sun the nonmigrating modes are postulated to be produced by the nonuniform distribution of convective centers the nonmigrating zonally symmetric component is found to be especially large while the role of this mode in forcing diurnal variations of the tropospheric circulation e g the hadley cell is questionable its role in modulating the ionospheric electric potential is well established discrepancies with the traditional notion that cloud to ground lightning is the dominant mechanism by which the earth is negatively charged are discussed in particular the probable role of nonlightning producing clouds e g the stratiform portion of convective complexes in diurnally modulating the negative charge on earth is discussed

quaternary seismo tectonic activity of the polochic fault guatemala 1 the polochic motagua fault system is part of the sinistral transform boundary between the north american and caribbean plates in guatemala and the associated seismic activity poses a threat to 70 of the country s population the aim of this study is to constrain the late quaternary activity of the polochic fault by determining the active structure geometry and quantifying recent displacement rates as well as paleo seismic events slip rates have been estimated from offsets of quaternary volcanic markers and alluvial fan using in situ cosmogenic 36cl exposure dating holocene left lateral slip rate and mid pleistocene vertical slip rate have been estimated to 4 8 2 3 mm y and 0 3 0 06 mm y respectively on the central part of the polochic fault the horizontal slip rate is within the range of longer term geological slip rates and short term gps based estimates in addition the non negligible vertical motion participates in the uplift of the block north of the fault and seems to be a manifestation of the regional far field stress regime we excavated the first trench for paleo seismological study on the polochic fault in which we distinguish four large paleo seismic events since 17 ky during which the polochic fault ruptured the ground surface

balanced cross section construction from seismic sections in areas of extensional tectonics abstract the application of the technique of balanced section construction initially developed for areas of compressional folding and faulting is reviewed with reference to extensional tectonics a number of examples are discussed where these techniques have been successfully applied in the north sea the interpretation of geoseismic sections is considered to be greatly assisted by careful application of geometrical balance and a consideration of strain even in areas of low crustal extensions the nature of seismic sections however places limitations on the validity of balancing which must be borne in mind with such interpretations and wherever possible the balancing of a geoseismic section should be confirmed by complete depth conversion the rapid testing of the integrity of the geoseismic section by attempting to balance the section at the interpretational phase can eliminate many problems as well as allowing the fullest use to be made of the geophysical information

localization and characterization of an active fault in an urbanized area in central guatemala by means of geoelectrical imaging article i nfo article history the polochic and motagua faults define the active plate boundary between the north american and caribbean plates in central guatemala a splay of the polochic fault traverses the rapidly growing city of san miguel uspantan that is periodically affected by destructive earthquakes this fault splay was located using a 2d electrical resistivity tomography ert survey that also characterized the fault damage zone and evaluated the thickness and nature of recent deposits upon which most of the city is built ert images show the fault as a 50 m wide near vertical low resistivity anomaly bounded within a few meters by high resistivity anomalies forward modeling reproduces the key aspects of the observed electrical resistivity data with remarkable fidelity thus defining the overall location geometry and internal structure of the fault zone as well as the affected lithologies our results indicate that the city is constructed on a 20 m thick surficial layer consisting of poorly consolidated highly porous water logged pumice this soft layer is likely to amplify seismic waves and to liquefy upon moderate to strong ground shaking the electrical conductivity as well as the major element chemistry of the groundwater provides evidence to suggest that the local aquifer might at least in part be fed by water rising along the fault therefore the potential threat posed by this fault splay may not be limited to its seismic activity per se but could be compounded its potential propensity to enhance seismic site effects by injecting water into the soft surficial sediments the results of this study provide the basis for a rigorous analysis of seismic hazard and sustainable development of san miguel uspantan and illustrate the potential of ert surveying for paleoseismic studies

cross section restoration and balancing as aid to seismic interpretation in extensional terranes structural cross sections in extensional terranes can be improved significantly by restoration and balancing principles originally developed for fold and thrust belts in rift basins and passive continental margins use of restoration techniques in analysis of growth faults elongate salt swells and other extensional structures results in geologically valid seismic interpretations sections must be in depth as opposed to two way time and oriented in the direction of material transport and decompaction must accompany restoration hanging wall deformation is characterized by different processes depending on the mechanical properties of the rocks being extended and can be approximated by various geometric and kinematic models antithetic faulting is analogous to antithetic shear combined antithetic and synthetic faulting is approximated by vertical shear domino style extension corresponds to rigid body rotation and flexural slip flow is modeled by bed length balance methods selection of the appropriate algorithm is crucial for proper restoration and balancing applications of these techniques illustrated here using seismic data from the gulf coast and north sea include 1 evaluating and adjusting seismic interpretations 2 projecting listric fault trajectories to depth 3 delineating more accurately the geometry and extent of hydrocarbon reservoirs 4 identifying new exploration leads 5 determining the deformation history of an area and 6 constraining the timing and direction of hydrocarbon migration and entrapment

fault scaling and 1 f noise scaling of seismic velocity fluctuations in the upper crystalline crust sonic logs are detailed measurements of the in situ seismic velocity along borehole walls power spectra of sonic logs typically decay approximately as the reciprocal of spatial frequency f regardless of the chemical composition geologic age and tectonic history of the probed lithologies data sequences of this type are fractal or scale invariant the origins of this uniform 1 f scaling of seismic structure are not clear particularly in low porosity crystalline rocks but faults fractures and cracks are considered to be important fault structures also follow fractal scaling laws and have significant effects on seismic velocity this paper presents a quantitative model that evaluates the role played by faults in determining the scaling laws of seismic velocity fluctuations the model is based on current knowledge of the structure and scaling properties of brittle faults and of associated regions of microcracking by approximating the relationship between crack density and velocity variation as linear this model yields a brownian power spectrum 1 f 2 for velocity perturbations across a single fault zone in a medium of otherwise constant velocity the power spectrum of velocity fluctuations induced by a population of faults is then obtained by superposing the corresponding brownian power spectra weighted according to the observed frequency size scaling relationship of brittle faults the results of this study indicate that the uniform 1 f scaling of velocity fluctuations in crystalline rocks seems to be linked to the correspondingly uniform scaling properties of fault structures

spectral analyses of the ktb sonic and density logs using robust nonparametric methods we use robust techniques to estimate power spectra coherences and transfer functions of the german continental deep drilling program ktb sonic and density logs and lithologically defined subsets thereof our results confirm the overall 1 wavelength decay of the power spectra inferred by parametric analyses but provide superior resolution and nonparametric estimates of errors and statistical significance we demonstrate the absence of any statistically meaningful coherence between the velocity logs from the main and pilot holes suggesting a spatially quasi isotropic upper crustal velocity structure also there is little coherence between the physical and caliper logs indicating that disturbances introduced by breakouts and uneven relief of the borehole wall mostly contribute to the uncorrelated portions of the velocity logs coherence between the gamma and physical logs is weak to absent indicating that the observed velocity and density fluctuations are dominated by the physical state of the rocks rather than by their petrological composition attempts to derive poisson s ratio and its variation with wavelength from the relationship between the shear and compressional velocity logs met with limited success but imply that caution should be exercised when comparing poisson s ratio derived from laboratory studies on samples representative of a region to crustal scale seismic determinations our preferred interpretation is that fluctuations in the physical logs in the intermediate wavelength range 10 150 m are dominated by cracks and their level of fluid saturation at larger wavelengths 50 150 m the effects of the petrology becomes more significant as shown by changes in slope of the power spectra and the emerging coherence between the vp and the gamma logs

aircraft observations of the origin and growth of very large snowflakes a new high volume precipitation probe capable of optically imaging particles up to about 5 cm was flown in a winter storm during the second canadian atlantic storms program casp ii dendritic crystals originating aloft in a region of weak convective instability were tracked and observed to aggregate into 4 5 cm snowflakes within an isothermal layer near 0 c the region containing the very large snowflakes was characterized by high radar reflectivities and rapid accumulation of snow at the surface

electrical structure and updraft speeds in thunderstorms over the southern great plains we have acquired 11 balloon soundings of the electric field and thermodynamics in large and sometimes severe and tornadic thunderstorms over the southern great plains the ascent rates of the balloons were used to divide the soundings into weak and strong updrafts all 11 soundings had magnitudes of charge densities and thicknesses of charge regions similar to those reported previously in small thunderstorms the five weak updraft soundings had complex charge structures of 7 9 charge regions below 10 km altitude the magnitude of the maximum measured electric field in these soundings was 100 150 k v m 1 the four soundings in strong updrafts had balloon ascent rates of at least 15 m s 1 for at least 1 km these soundings had simpler electrical structures of 3 5 charge regions below 10 km altitude their maximum measured electric fields ranged from 85 to 130 kv m 1 the data may support an earlier hypothesis that charge is elevated in strong updrafts in addition the data may suggest that simpler charge structures are associated with proximity to strong updrafts rather than with different storm types

electrical and polarimetric radar observations of a multicell storm in telex abstract on 28 29 june 2004 a multicellular thunderstorm west of oklahoma city oklahoma was probed as part of the thunderstorm electrification and lightning experiment field program this study makes use of radar observations from the norman oklahoma polarimetric weather surveillance radar 1988 doppler three dimensional lightning mapping data from the oklahoma lightning mapping array lma and balloon borne vector electric field meter efm measurements the storm had a low flash rate 30 flashes in 40 min four charge regions were inferred from a combination of lma and efm data lower positive charge near 4 km and midlevel negative charge from 4 5 to 6 km msl from 0 to 6 5 c were generated in and adjacent to a vigorous updraft pulse further midlevel negative charge from 4 5 to 6 km msl and upper positive charge from 6 to 8 km from 6 5 to 19 c were generated later in quantity sufficient to initiate lightning as the updraft decayed a negative screening layer was present near the storm top

small lightning flashes from shallow electrical storms on jupiter lightning flashes have been observed by a number of missions that visited or flew by jupiter over the past several decades imagery led to a flash rate estimate of about 4 10 3 flashes per square kilometre per year refs 1 2 the spatial extent of voyager flashes was estimated to be about 30 kilometres half width at half maximum intensity hwhm but the camera was unlikely to have detected the dim outer edges of the flashes given its weak response to the brightest spectral line of jovian lightning emission the 656 3 nanometre h line of atomic hydrogen1 3 6 the spatial resolution of some cameras allowed investigators to confirm 22 flashes with hwhm greater than 42 kilometres and to estimate one with an hwhm of 37 to 45 kilometres refs 1 7 9 these flashes with optical energies comparable to terrestrial superbolts of 0 02 1 6 1010 joules have been interpreted as tracers of moist convection originating near the 5 bar level of jupiter s atmosphere assuming photon scattering from points beneath the clouds 1 3 7 8 10 12 previous observations of lightning have been limited by camera sensitivity distance from jupiter and long exposures about 680 milliseconds to 85 seconds meaning that some measurements were probably superimposed flashes reported as one1 2 7 9 10 13 here we report optical observations of lightning flashes by the juno spacecraft with energies of approximately 105 108 joules flash durations as short as 5 4 milliseconds and inter flash separations of tens of milliseconds with typical terrestrial energies the flash rate is about 6 1 10 2 flashes per square kilometre per year more than an order of magnitude greater than hitherto seen several flashes are of such small spatial extent that they must originate above the 2 bar level where there is no liquid water14 15 this implies that multiple mechanisms for generating lightning on jupiter need to be considered for a full understanding of the planet s atmospheric convection and composition small lightning flashes detected on jupiter by juno have shallow origins above the 2 bar level of jupiter s atmosphere where temperatures are too low for liquid water to exist

3 d palinspastic restoration of normal faults in the inner moray firth implications for extensional basin development abstract balanced cross section techniques and the construction of a restored section permit 2 dimensional palinspastic restorations to be made in both compressional and extensional terraines in 3 dimensions an equivalent restoration can be made by assuming conservation of bedding plane area and considering the volume of a stratigraphic interval rather than its cross sectional area extensional basins displaying upper crustal listric normal faulting are particularly amenable to this approach computerised 3 d restorations have been made of the inner moray firth basin offshore scotland this basin is not isostatically compensated and was produced by 7 8 post triassic extension of which 2 5 3 is post jurassic above a detachment surface at 20 25 km depth close to the base of the crust limited lower crustal thinning and lithospheric stretching has affected the eastern part of the basin but this can account for no more than half of the measured upper crustal extension some of this shallow extension is probably coupled by low angle faults or shear zones into major zones of lithospheric stretching such as the north sea grabens where it may help account for discrepancies between estimates of lithospheric thinning and upper crustal extension

electric field measurements within a severe thunderstorm anvil the anvil cloud of a supercell severe storm in central oklahoma was penetrated by two free balloons carrying corona probes to measure electric fields the two balloons passed through the portion of the anvil upstream of the precipitation core and provided information on the charge concentrations and vertical thicknesses of the electric charge regions within the cloud the trajectories of the balloons relative to the storm were horizontally separated by approximately 35 km providing information on the horizontal extent of the charge regions contrary to the general assumption that anvil interiors are positively charged the results of the two flights indicate that extensive regions of both net positive and negative charge were present in the interior of the anvil net positive charge was observed in both balloon flights in the lower portion of the anvil interior the vertical thickness of the positive charge region was measured in each flight to be 1 6 and 2 3 km respectively a charge concentration of 0 2 nc m 3 was estimated from one of the flights net negative charge was observed by both balloons in the upper portion of the anvil interior the vertical thickness and charge concentration of the negative charge region were estimated from one flight to be 3 2 km and 0 1 nc m 3 respectively screening charge layers were identified at the upper and lower boundaries of the anvil with a typical thickness of a few hundred meters which is an order of magnitude greater than that calculated in a previous model we propose a conceptual model of the development of anvil charge regions based on our balloon measurements and previous observations of anvil dynamics in this model we suggest that the thicknesses of the anvil screening layers increase with distance from the precipitation core of the storm owing to turbulent mixing near the cloud boundaries and differences in the sedimentation rates of the cloud particles negative charge in the upper portion of the anvil interior results from the expansion of the upper negative screening layer into lower levels of the anvil cloud

observations and numerical simulations of the origin and development of very large snowflakes abstract the canadian atlantic storms program casp ii field experiment was conducted near st john s newfoundland canada during january march 1992 and it focused on the nature of winter storms analyses of casp ii aircraft surface satellite and radar observations collected during an intensive study of the origin and development of 9 mm h 1 precipitation containing 4 5 cm diameter snowflakes are compared in this article with results of the mm5 mesoscale and mitchell microphysical models mm5 simulations of the thermal kinematic and bulk microphysical fields were in good agreement with the observations this comparison provided the basis for extending the spatial and temporal scales of the aircraft observations to a larger scale domain using the model results the mitchell analytical numerical model was used to improve the understanding of the microphysical processes that led to the development of the very large snowflakes a synthesis of results using the different techniques leads to the co

mesoscale circulations forced by melting snow part ii application to meteorological features abstract various authors have proposed that the cooling associated with melting precipitation contributes significantly to the dynamics of mesoscale precipitation systems in this study we use the numerical model described in part i of this paper to investigate the effects of the cooling by melting mechanism in three specific situations rain snow boundaries the production of deep 0 c isothermal layers and the trailing stratiform region associated with mesoscale convective systems it is found that melting in the vicinity of a rain snow boundary produces a thermally indirect mesoscale vertical circulation that may be responsible for enhanced precipitation near a rain snow boundary melting in the presence of warm air advection above the melting layer and cold advection at and below it are necessary for producing deep 0 c layers within realistic times the dynamic effects of cooling associated with melting and evaporation in the stratiform region of a mature squall line system produce a mesoscale circul

on the cause of 1 f power spectral scaling in borehole sonic logs borehole logs provide in situ information about the scaling of fluctuations in the elastic properties of rock a surprising finding has been the widespread 1 f type 0 5 1 5 scaling of borehole sonic log power spectra yielding no clear correlation with geological age type or history raising questions about the reliability and origin of these findings ubiquitous fractures for example have been evoked as the most likely explanation of these results firstly we show that the smoothing effects of the logging tool must be taken into account in order to obtain reliable values of we then investigate the scaling properties of lithology only in perfectly exposed metamorphic rock by explicitly excluding fractures we find clear 1 f scaling for reconstructed velocity data based solely on lithological variations although fractures are certainly important in contributing to 1 f fluctuations in borehole logs intrinsic geology may also play a significant role

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

flexural unfolding of horizons using paleomagnetic vectors this paper introduces a new restoration method pmag3drest designed for complex folded structures non cylindrical non coaxial it combines paleomagnetic vectors and bedding markers setting up a reference system that allows deformed and undeformed surfaces to be related to one another we assume flexural conditions during the deformation consequently the stratigraphic horizons are considered to be globally developable surfaces with total area preservation except in specific deformation areas using paleomagnetism in the proposed restoration process pmag3drest helps to locate these areas with greater accuracy it is similar to other approaches based on triangulations but it forces the available paleomagnetic data to converge with the paleomagnetic reference vector during the restoration process our experiments use computer and analog models in which the deformed and undeformed surfaces are perfectly known this enables us to apply the restoration method to the deformed surface and compare the parameters of the restored surface with those of the initial undeformed surface to quantify the quality of the method paleomagnetic data anchor the surface leading to more accurate results

radiometric performance of the voyager cameras the voyager imaging experiment provided high quality data of jupiter and the galilean satellites with the two flyby trajectories in march and july of 1979 moderately accurate radio metric measurements have been made using these data this paper evaluates the radiometric results and describes the inflight and ground geometric and radiometric correction factors the radiometric quantities of intensity i and geometric albedo i f are derived and scaling factors for each of the filters are tabulated for correcting the calibrated data from the image processing laboratory at jpl in addition the key characteristics of both voyager 1 and voyager 2 cameras are tabulated

the extension of lightning flashes from thunderstorms near cape canaveral florida the horizontal distance that intracloud ic and cloud to ground cg lightning flashes extend from thunderstorms is presented for warm season nonsevere storms near cape canaveral fl the warning decision support system integrated information wdss ii software allowed us to ingest display and make distance calculations using radar reflectivity data from nearby national weather service offices and lightning information from the national lightning detection network and the local lightning detection and ranging network the flash distances were determined manually using a measuring tool within wdss ii six categories of flashes were investigated a cg flashes measured from the edge of the convective core 30 dbz to the ground strike location that is beneath the attached anvil b cg bolt from the blue flashes measured from cloud edge 0 dbz to the ground strike point that contains only 0 dbz overhead c cg bolt from the blue flashes as in category b but measured from the edge of the precipitation 18 dbz d ic flashes that exit a portion of the cloud that is not an anvil measured from cloud edge 0 dbz e ic flashes within anvils measured from the edge of convective precipitation 30 dbz to the termination point within the anvil and f ic flashes exiting the edge 0 dbz of anvils results for each category are presented in the forms of frequency distributions of distances and their cumulative frequency distributions

deep 0 c isothermal layers within precipitation bands over southern ontario isothermal layers having a temperature of 0 c and depths up to 1 km were measured within two precipitation bands occurring within autumn storms over southern ontario across these layers wind shears up to 0 02 s 1 existed and aggregation led to particles up to 20 mm in diameter melting and evaporation are proposed as contributing to the development of the layers

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

lightning location relative to storm structure in a leading line trailing stratiform mesoscale convective system 1 horizontal and line normal vertical cross sections and composite images of dallas fort worth lightning detection and ranging ldar ii vhf radiation sources and radar reflectivity over a 30 min period provide a unique perspective on lightning pathways within a leading line trailing stratiform llts mesoscale convective system mcs on 16 june 2002 the overwhelming majority of vhf lightning sources occurred within the leading convective line in a bimodal pattern in the vertical assuming that vhf source density maxima were most likely associated with positive charge then the ldar ii observations suggest that the gross charge structure of the convective region of the mcs was characterized by a tripole with net positive charge centered at 4 5 km agl 3 c and 9 5 km agl 35 c and net negative charge centered roughly in the relative minimum of the vhf source density maximum at 7 km agl 17 c a persistent lightning pathway and inferred positive charge zone sloped rearward by 40 50 km and downward by 4 5 km from the upper vhf source maximum in the convective line through the transition zone and into the radar bright band of the stratiform region in the stratiform region vhf lightning sources and inferred positive charge were concentrated in three layers centered at 4 5 6 and 9 km agl 2 c 11 c and 31 c respectively consistent with past electric field studies of symmetric llts mcss positive cloud to ground lightning flashes in the stratiform region were initiated in the convective line and followed the slanting pathway from the top of convective cores to the stratiform precipitation where they were horizontally extensive layered and highly branched the sloping lightning pathway was identical to hypothetical trajectories taken by snow particles these observations provide further support for the advection of charge on snow along the sloping pathway and the in situ generation of charge in the horizontal lightning layers as primary contributors to electrification and positive lightning production rearward of the convective line

a direct method for modeling and unfolding developable surfaces and its application to the ventura basin california n order to draw precise geological structures using scattered data it is relevant to use criteria that integrate the kinematic properties of the structure for example developable folds can be selected by the observation of constant length deformation markers by establishing an accurate drawing of these folds it is possible to precisely determine the geometrical limits of basin we have developed a program developable mesh that integrates these developability criteria this program first builds a 3d mesh using criteria that are based on the geometrical properties of developable surfaces it then slightly modifies the mesh to improve its developability this mesh is finally unfolded this program has been tested on a natural example of the lateral evolution of a thrust system to a fold structure red mountain area in the ventura basin this particular structure has been already balanced by a trial and error method unfold program this test confirms the validity of our approach the developable mesh program builds near perfect developable folded surfaces therefore it is geometrically coherent and can unfold these surfaces in a very short time moreover the program is faster and can construct more complex developable surfaces than other conventional unfolding techniques based on a common interpolator