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

gravity inversion of 2d bedrock topography for heterogeneous sedimentary basins based on line integral and maximum difference reduction methods based on the line integral li and maximum difference reduction mdr methods an automated iterative forward modelling scheme li mdr algorithm is developed for the inversion of 2d bedrock topography from a gravity anomaly profile for heterogeneous sedimentary basins the unknown basin topography can be smooth as for intracratonic basins or discontinuous as for rift and strike slip basins in case studies using synthetic data the new algorithm can invert the sedimentary basins bedrock depth within a mean accuracy better than 5 when the gravity anomaly data have an accuracy of better than 0 5 mgal the main characteristics of the inversion algorithm include 1 the density contrast of sedimentary basins can be constant or vary horizontally and or vertically in a very broad but ap rioriknown manner 2 three inputs are required the measured gravity anomaly accuracy level and the density contrast function 3 the simplification that each gravity station has only one bedrock depth leads to an approach to perform rapid inversions using the forward modelling calculated by li the inversion process stops when the residual anomalies the observed minus the calculated falls within an error envelope whose amplitude is the input accuracy level the inversion algorithm offers in many cases the possibility of performing an agile 2d gravity inversion on basins with heterogeneous sediments both smooth and discontinuous bedrock topography with steep spatial gradients can be well recovered limitations include 1 for each station position there is only one corresponding point vertically down at the basement and 2 the largest error in inverting bedrock topography occurs at the deepest points

3d gravity inversion of basement relief a depth dependent density approach we present a 3d gravity inversion technique based on the marquardt algorithm to analyze gravity anomalies attributable to basement interfaces above which the density contrast varies continuously with depth the salient feature of this inversion is that the initial depth of the basement is not a required input the proposed inversion simultaneously estimates the depth of the basement interface and the regional gravity background applicability and efficacy of the inversion is demonstrated with a synthetic model of a density interface we analyze the synthetic gravity anomalies 1 solely because of the structure 2 in the presence of a regional gravity background and 3 in the presence of both random noise and regional gravity background the inverted structure remains more or less the same regardless of whether the regional background is simulated with a second degree polynomial or a bilinear equation the depth of the structure and estimated regional background deviate only modestly from the assumed ones in the presence of random noise and regional background the analyses of two sets of real field data one over the chintalpudi subbasin india and another over the pannonian basin eastern austria yield geologically plausible models with the estimated depths that compare well with drilling data

observations of polarimetric signatures in supercells by an x band mobile doppler radar abstractpolarimetric weather radars significantly enhance the capability to infer the properties of scatterers within a resolution volume previous studies have identified several consistently seen polarimetric signatures in supercells observed in the central united states nearly all of these studies used data collected by fixed site s and c band radars because there are few polarimetric mobile radars relatively little has been documented in high resolution polarimetric data from mobile radars compared to s and c bands there has been very limited examination of polarimetric signatures at x band the primary focus of this paper is on one signature that has not been documented previously and one that has had little documentation at x band the first signature seen in at least seven supercell datasets collected by a mobile x band polarimetric radar consists of a narrow band of locally reduced reflectivity factor zh and differential reflectivity typically near the location where the hook echo attac

does wind shear cause hydrometeor size sorting abstractseveral recent studies have implicated vertical wind shear in producing steady state size sorting of a distribution of hydrometeors falling at their terminal velocity which varies as a function of hydrometeor diameter in particular this mechanism has been invoked to explain both the strength and storm relative orientation of the commonly observed differential reflectivity zdr arc in supercell thunderstorms however the actual role of the shear has not been fully clarified in this study a simple analytical model is used to show that the fundamental source of size sorting is the storm relative wind field itself and in particular its mean taken over the depth of the sorting layer wind shear is only strictly required for producing sustained size sorting in the special but common case of a precipitation source having a motion that lies on the hodograph such as with the environmental winds at the source level in supercells the precipitation source the rotating updraft does not necessari

modelling of sedimentary basins from gravity anomalies with variable density contrast summary the decrease of density contrast with depth in sedimentary basins could be approximated by a quadratic function the sedimentary basin is viewed as a number of outcropping vertical prisms put in juxtaposition at each observation point equations are derived for the gravity anomaly of a vertical prism for a quadratic density function the initial model is obtained by calculating the thicknesses of the prisms at each station by an infinite slab formula the differences between the observed anomalies and the anomalies of the initial model at each station are used to modify the initial model a computer program is developed for initial estimates and refinement of the model the method is applied to interpret the gravity anomaly of san jacinto graben california where sediments filling the graben have a density contrast that can be approximated to a quadratic function finally the convergence of the method is discussed

density currents in shear flows effects of rigid lid and cold pool internal circulation and application to squall line dynamics idealized density current models that contain a rigid lid developed in previous studies are evaluated it is shown through numerical experiments that a realistic stable layer placed at the level of the rigid lid acts very much like a rigid lid in confining the environmental flow to the levels below and in controlling the behaviour of density currents that propagate in the flow when this stable layer is replaced by a neutrally stable layer the behaviour of the density current is very different these results support the hypothesis that in the atmosphere the tropopause or a tropospheric inversion layer acts much like a rigid lid in the idealized density current models and the solutions of these models are applicable to organized quasi two dimensional convective systems such as squall lines in the atmosphere the effects of cold pool internal circulations on density current behaviour are also examined when a single circulation is present initially inside the cold pool the direction of circulation that gives rise to a smaller shear across the density interface leads to a smoother interface and a much more steady density current head large amplitude eddies develop along the interface when the direction of circulation is reversed when two layers of shear are initially present inside the cold pool the flow pattern inside the cold pool tends to be dominated by the circulation of the lower layer in this case the behaviour of the density interface and density current head depends on more than just the initial cross interface shear the overall flow pattern in the density current in which the cold pool circulation contains rearward flows at the ground level bears a close similarity to that found in mature squall line systems as shown by comparisons with a simulated squall line when the cold pool in a squall line is defined in terms of the equivalent potential temperature the solutions of idealized density currents in sheared flows become more readily applicable to squall lines copyright 2002 royal meteorological society

contrasting fluid flow patterns at the bufa del diente contact metamorphic aureole north east mexico evidence from stable isotopes impure limestones with interstratified metachert layers were contact metamorphosed and metasomatized by the bufa del diente alkali syenite massive marbles exhibit mineralogical and stable isotope evidence for limited fluid infiltration confined to a 17 m wide zone at the contact influx of magmatic brines along most metacherts produced up to 4 cm thick wollastonite rims according to calcite cc quartz qz wollastonite wo co2 and were observed at distances of up to 400 m from the contact the produced co2 exsolved as an immiscible low density co2 rich fluid chert protolith isotope compositions were 18o qz 27 30 and 18o cc 24 27 many wollastonites in infiltrated metacherts have low 18o ranging from 11 17 and confirm that decarbonation occurred in presence of a magmatic signatured fluid large gradients in 18o wo across the rims may reach 6 the 18o of remaining quartz is often lowered to 15 20 whereas caleites largely retained their original compositions the isotopic reversals of up to 10 between quartz and calcite along with reaction textures demonstrate non equilibrium between infiltrating fluid in the aquifer and the assemblage calcite quartz wollastonite this is compatible with the assumption of a down temperature flow of magmatic fluids that occurred exclusively in the remaining quarzite layer the 13c cc and 18o cc of marble calcites measured perpendicular to two metachert bands reveal significant isotopic alterations along distances of 4 5 cm and 7 5 cm from the wollastonite marble boundary only into the hanging wall marble suggesting an advection process caused by a fluid phase which movel upwards covariation trends of 13c cc and 18o cc across the alteration front indicate that this fluid was co2 rich mass balance calculations show that all co2 rich fluid produced by the decarbonation reaction was lost into overlying marble the metachert aquifers did not leak with respect to water rich fluids

impact of the dual polarization doppler radar data on two convective storms with a warm rain radar forward operator abstractthe dual polarization dual pol doppler radar can transmit receive both horizontally and vertically polarized power returns the dual pol radar measurements have been shown to provide a more accurate precipitation estimate compared to traditional radars in this study the horizontal reflectivity zh differential reflectivity zdr specific differential phase kdp and radial velocity vr collected by the c band advanced radar for meteorological and operational research armor are assimilated for two convective storms a warm rain scheme is constructed to assimilate zh zdr and kdp data using the three dimensional variational data assimilation 3dvar system with the advanced research weather research and forecasting model arw wrf the main goals of this study are first to demonstrate and compare the impact of various dual pol variables in initialization of real case convective storms and second to test how the dual pol fields may be better used with a 3dvar system the results show that the zh

dual polarization observations of microbursts associated with intense convection the 20 july storm during the mist project abstract a detailed case study of the microbrust producing storm on 20 july 1986 during the mist project is presented together with visual based on cloud photogrammetry and radar observations during the life cycle of the storm in particular multiparameter radar information is seen to have important implications for operational detection of this wind shear event noteworthy is the observation of a small shaft less than 1 km in horizontal dimensions of near zero differential reflectivity zdr surrounded by large positive zdr values in the main precipitation core within a microburst producing downdraft this zdrzm hole hole implies a strong localized downdraft composed of melting hail

a theory for strong long lived squall lines abstract we study herein the mechanics of long lived line oriented precipitating cumulus convection squall lines using two and three dimensional numerical models of moist convection these models used in juxtaposition enable us to address the important theoretical issue of whether a squall line is a system of special long lived cells or whether it is a long lived system of ordinary short lived cells our review of the observational literature indicates that the latter is the most consistent paradigm for the vast majority of cases but on occasion a squall line may be composed of essentially steady supercell thunderstorms the numerical experiments presented herein show that either type of squall line may develop from an initial line like disturbance depending on the magnitude and orientation of the environmental shear with respect to the line with shallow shear oriented perpendicular to the line a long lived line evolves containing individually short lived cells our analysis of this type o

three dimensional interpretation of gravity data from sedimentary basins using an exponential density depth function in mapping the topography of the basement of deep sedimentary basins by gravity modelling the accuracy can be improved by incorporating an exponential increase in density with depth for calculating the gravity effect of a three dimensional 3d structure with such an exponential density depth relation a frequency domain forward algorithm based on series expansion is presented the numerical evaluation of which can be performed efficiently by fast fourier transform the algorithm can be applied in a recursive procedure to give the inverse solution in terms of basement relief the inversion procedure is satisfactorily tested on a 2d synthetic example and a 3d field example of gravity data from the western margin of the pannonian basin in eastern austria where up to 2 2 km of tertiary sediments overlie an igneous or metamorphic basement the results are confirmed by basement intersections in several wells

deep crustal carbonates as co 2 fluid sources evidence from metasomatic reaction zones metasomatic reaction zones which developed at marble pelitic schist contacts in a granulite facies terrane in west greenland contain a consistent sequence of five mineralogical zones outward from the carbonates the zones are characterized by the assemblages grossular diopside meionite i meionite anorthite diopside ii anorthite diopside edenitic hornblende iii anorthite enstatite iv plagioclase almandine sillimanite v sphene is superceded by ilmenite between zones ii and iii quartz is present in all zones except zone i scapolite plagioclase clinopyroxene and mica exhibit a small degree of compositional variation which correlates with distance from the carbonate these small compositional variations are superimposed on a strong cao chemical potential gradient compositional features zone distributions and cao activity calculations demonstrate that the zones developed in response to cao diffusion along a chemical potential gradient of 2 kcal m the cao source appears to be carbonate rocks which release calcium as decarbonation reactions proceed the maximum volume of co2 released in this process and that released during discontinuous reactions in the marbles will contribute a total volume of co2 approximately equivalent to the volume of carbonate in the rock calculations demonstrate that a terrane consisting of as little as 8 carbonate will release sufficient co2 to result in complete dehydration of an amphibolite terrane at deep crustal conditions dehydration through co2 release will be accomplished either through rapid burial which would prevent both equilibration of mineral assemblages and co2 release at intermediate crustal levels or through diffusion driven metasomatic reactions which would lead to co2 release primarily at the high temperatures of deep crustal environments the latter process would be the dominant co2 source at deep crustal levels if carbonate rocks occur predominately as relatively thin layers

stable inversion of gravity anomalies of sedimentary basins with nonsmooth basement reliefs and arbitrary density contrast variations we present a new stable method for interpreting the basement relief of a sedimentary basin which delineates sharp discontinuities in the basement relief and incorporates any law known a priori for the spatial variation of the density contrast the subsurface region containing the basin is discretized into a grid of juxtaposed elementary prisms whose density contrasts are the parameters to be estimated any vertical line must intersect the basement relief only once and the mass deficiency must be concentrated near the earth s surface subject to the observed gravity anomaly being fitted within the experimental errors in addition upper and lower bounds on the density contrast of each prism are introduced a priori one of the bounds being zero and the method assigns to each elementary prism a density contrast which is close to either bound the basement relief is therefore delineated by the contact between the prisms with null and nonnull estimated density contrasts the latter occupying the upper part

evidence for pre regional metamorphic fluid infiltration of the lower calcsilicate unit reynolds range group central australia grandite garnet rich calcsilicate rocks from the lower calcsilicate unit of the regionally metamorphosed reynolds range group central australia crop out along a strike parallel section in which a transition zone from m22 amphibolite to granulite facies rocks is exposed across this transition the grandite rich layers do not show systematic changes in mineral assemblages compositions and modes or stable isotope compositions these layers are deformed by f22 folds that are associated with the peak of regional low pressure high temperature metamorphism therefore the grandite rich layers appear to pre date regional metamorphism and to have acted as closed chemical systems during prograde m22 metamorphism mineral assemblages in the grandite rich layers are consistent with their formation through the infiltration of oxidized water rich fluids xco2 0 1 0 3 log fo2 16 to 14 the stable isotope values of calcite 13c 4 2 to 0 8 0 pdb 18o 10 5 14 0 0 v smow and bulk silicate fractions 18o 6 1 to 10 8 of the grandite rich layers are most consistent with the infiltrating fluid being from a magmatic source it is most likely that fluid infiltration occurred during the pre m22 contact metamorphism m21 that affected much of the reynolds range group the preservation of these assemblages is probably due to their high variance and little pervasive fluid rock interaction having occurred during m22 the clinopyroxene and feldspar rich calcsilicate rocks that host the grandite rich layers contain poikiloblastic grandite garnet that formed during prograde m22 metamorphism thin marbles that locally occur with the grandite rich layers contain a third garnet generation that is post or late m22 this grossular rich garnet occurs in coronas around calcite plagioclase clinopyroxene wollastonite and scapolite these coronas are consistent with cooling and or compression however because the marble assemblages are themselves overprinted by m21 grandite rich layers the development of coronal garnet does not reflect a continuous p t t path rather it more probably reflects the partial re equilibration of m21 contact metamorphic assemblages to post m22 conditions

tilt depth method a simple depth estimation method using first order magnetic derivatives aeromagnetic data are routinely presented as contour or color shaded maps of the total magnetic intensity tmi an interpreter s task is to identify features anomalies contained within the map and qualitatively and or quantitatively interpret them into geologic structures at depth if the map contains anomalies that have large magnetic intensities the bodies might be considered to have large magnetizations or to be at shallow depths small amplitude anomalies superimposed on these anomalies could be masked or even missed by an interpreter thus the task of the interpreter is to use the spectral content of the anomalies to try and resolve these ambiguities part of this process is also to obtain estimates of the depth and shape of the body causing the anomalies

granulite facies amphibole and biotite equilibria and calculated peak metamorphic water activities samples located near the oregon dome anorthosite massif in the south central adirondack mountains new york contain the fluid buffering mineral assemblages amphibole clinopyroxene orthopyroxene quartz or biotite quartz orthopyroxene k feldspar these rocks were metamorphosed under granulite facies conditions t 725 750 c p 7 5 kbar during the grenville orogeny the mg rich nature of amphiboles micas and pyroxenes allow accurate calculation of water activities because corrections for the effects of solid solution are relatively small the activity of water was low during the peak of granulite facies metamorphism with h2o 0 15 0 14 wollastonite occurrences indicate that the co2 was low 0 3 in nearby rocks demonstrating that large quantities of co2 did not infiltrate in a pervasive manner the combination of low h2o with low co2 is consistent with the hypothesis that magmatic processes were dominant generating dry fluid absent conditions

calculation of co 2 activities using scapolite equilibria constraints on the presence and composition of a fluid phase during high grade metamorphism thermodynamic and phase equilibrium data for scapolite have been used to calculate co2 activities aco2 and to evaluate the presence or absence of a fluid phase in high grade scapolite bearing meta anorthosite granulites calc silicates and mafix xenoliths the assemblage scapolite plagioclase garnet quartz may be used to calculate or limit aco2 by the reaction meionite quartz grossular anorthite co2 granulites from four high grade terranes grenville province canada sargut belt india furua complex tanzania bergen arcs norway yield aco2 0 4 1 with most 0 7 for scapolite bearing granulites from the furua complex in which aco2 0 9 calculated h2o activities ah2o based on phlogopite dehydration equilibria are uniformly low 0 1 0 2 the aco2 calculated for meta anorthosite from the grenville province ontario ranges from 0 2 to 0 8 for grenville meta anorthosite also containing epidote the ah2o calculated from clinozoisite dehydration ranges from 0 2 to 0 6 calc silicates from the grenville sargur and furua terranes mostly yield aco2 1 the calculated fluid activities are consistent with metamorphism 1 in the presence of a mixed co2 h2o fluid phase in which co2 is the dominant fluid species but other c o h s species are minor 2 in the absence of a bulk fluid phase fluid absent metamorphism or 3 in the presence of a fluid bearing melt phase the results for many granulites and grenville meta anorthosite are consistent with the presence of a co2 rich mixed co2 h2o fluid phase in contrast the relatively restricted and low values of aco2 for calc silicates require an h2o rich fluid or absence of a fluid phase during metamorphism the range of values for xenoliths are most consistent with absence of a fluid phase the primary implication of these results is that a co2 rich fluid accounts for the reduced ah2o in scapolite bearing granulites however scapolite may be stable with a wide range of fluid compositions or in the absence of a fluid phase and the presence of scapolite is not a priori evidence of a co2 rich fluid phase in addition close association of scapolite free mafic granulites with scapolite bearing granulites having identical mineral compositions in the furua complex and the absence of scapolite from most granulite terranes implies that a co2 rich fluid phase is not pervasive on an outcrop scale or common to all granulite terranes

dehydration melting fluid buffering and decompressional p t path in a granulite complex from the eastern ghats india a suite of metapelites charnockites calc silicate rocks quartzo feldspathic gneisses and mafic granulites is exposed at garbham a part of the eastern ghats granulite belt of india reaction textures and mineral compositional data have been used to determine the p t x evolutionary history of the granulites in metapelites and charnockites dehydration melting reactions involving biotite produced quartzofeldspathic segregations during peak metamorphism however migration of melt from the site of generation was limited subsequent to peak metamorphism at c 860 c and 8 kbar the complex evolved through nearly isothermal decompression to 530 650 c and 4 5 kbar during this phase coronal garnet grew in the calc silicates while garnet in the presence of quartz broke down in charnockite and mafic granulite fluid activities during metamorphism were internally buffered in different lithologies in the presence of a melt phase the p t path of the granulites at garbham contrasts sharply with the other parts of the eastern ghats granulite belt where the rocks show dominantly near isobaric cooling subsequent to peak metamorphism

fluid evolution and transport during metamorphism evidence from the llano uplift texas a field petrologic and stable isotopic investigation of the marbles and calc silicates of the 1 15 b y valley spring gneiss documents the dilution of internally evolved co2 rich fluids by externally derived aqueous fluids introduced along channelways reaction textures within calcsilicates record the evolution through time of initially co2 rich fluids toward increasingly more aqueous compositions assemblage zonations within calc silicates require equilibration within local gradients of the mole fraction of co2 in the fluid and suggest that the infiltration of aqueous fluids was largely channelized along more permeable lithologies localized depletions in 13c and 18o corroborate petrologic evidence for channelized infiltration isotopic compositions reflect both devolatilization and the introduction of low 18o fluids estimated minimum oxygen equivalent fluid to rock ratios are near unity both mineralogical and stable isotopic systematics document the essential role of infiltration in driving decarbonation reactions during calc silicate formation the calc silicate assemblages which equilibrated with fluids of the lowest mole fraction of co2 record isotopic exchange equilibrium with fluids of 18o typical of those derived from normal granites as do the granitic aplites and pegmatites which transect most calcsilicate occurrences thus the infiltrating fluids are believed to be genetically linked to the intrusion of a suite of granitic plutons emplaced after the peak of regional metamorphism

gravity and magnetic field characteristics and hydrocarbon prospects of the tobago basin the tobago basin which is located offshore northern venezuela with a southern margin close to trinidad and tobago has an area of approximately 59 600 km2 the tobago basin has relatively favourable hydrocarbon prospects and to date exploration work has mainly concentrated on small areas of the southwestern portion of the basin to conduct a comprehensive study of the structural framework of the basin and the characteristics of the basement in order to identify prospective zones for hydrocarbon exploration shipborne measured and satellite measured gravity data shipborne measured magnetic data and aeromagnetic survey data were analysed a regularisation filtering method was used to separate and obtain regional and residual gravity and magnetic anomalies directional gradients of gravity and magnetic anomalies and the total horizontal gradient and vertical second derivative of gravity anomalies were employed to extract information about fault structures regression analysis methods were used to determine the basement depth the geological significance of the gravity and magnetic fields was examined the structural framework of the basin was assessed the basement depth was estimated and favourable hydrocarbon exploration prospects within the basin were identified the results show that the tobago basin contains complex structures consisting mainly of two groups of faults trending in northeasterly and northwesterly directions and that the major northeasterly trending faults control the main structural configuration and depositional system within the basin the basement of the tobago basin has deep rises and falls it can be divided into the following four secondary tectonic units the western sub basin the central uplift area the southern sub basin and the northeastern sub basin the central uplift area and northeastern sub basin are most likely to have developed hydrocarbon accumulations and should be targeted for further exploration

rapid 3 d forward model of potential fields with application to the palinuro seamount magnetic anomaly southern tyrrhenian sea italy 1 we show a set of forward model equations in the fourier domain for calculating the 3 d gravity and magnetic anomalies of a given 3 d distribution of density or magnetization one property of the potential field equations is that they are given by convolution products providing a very simple analytic expression in the fourier domain under this assumption the domain of the density or magnetization parameters is connected by a biunivoc relationship with the data space and potential field anomalies can be seen as filtered versions of the corresponding density or magnetization distributions a very fine spatial discretization can be obtained by using a large number of points within a unique 3 d grid where both the source distributions and field data are defined the main advantage of this formulation is that it dramatically reduces execution times providing a very fast forward model tool useful for modeling anomalies at different altitudes we use this method to evaluate an average magnetization of 8 a m for the palinuro seamount in the tyrrhenian sea southern italy thus performing a joint interpretation of morphological and newly acquired magnetic data

the dependence of numerically simulated convective storms on vertical wind shear and buoyancy abstract the effects of vertical wind shear and buoyancy on convective storm structure and evolution are investigated with the use of a three dimensional numerical cloud model by varying the magnitude of buoyant energy and one directional vertical shear over a wide range of environmental conditions associated with severe storms the model is able to produce a spectrum of storm types qualitatively similar to those observed in nature these include short lived single cells certain types of multicells and rotating supercells the relationship between wind shear and buoyancy is expressed in terms of a nondimensional convective parameter which delineates various regimes of storm structure and in particular suggests optimal conditions for the development of supercell type storms applications of this parameter to well documented severe storm cases agree favorably with the model results suggesting both the value of the model in studying these modes of convection as well as the value of this representation i

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

multiscale analysis of potential fields by a ridge consistency criterion the reconstruction of the bishop basement summary we use a multiscale approach as a semi automated interpreting tool of potential fields the depth to the source and the structural index are estimated in two steps first the depth to the source as the intersection of the field ridges lines built joining the extrema of the field at various altitudes and secondly the structural index by the scale function we introduce a new criterion called ridge consistency in this strategy the criterion is based on the principle that the structural index estimations on all the ridges converging towards the same source should be consistent if these estimates are significantly different field differentiation is used to lessen the interference effects from nearby sources or regional fields to obtain a consistent set of estimates in our multiscale framework vertical differentiation is naturally joint to the low pass filtering properties of the upward continuation so is a stable process before applying our criterion we studied carefully the errors on upward continuation caused by the finite size of the survey area to this end we analysed the complex magnetic synthetic case known as bishop model and evaluated the best extrapolation algorithm and the optimal width of the area extension needed to obtain accurate upward continuation afterwards we applied the method to the depth estimation of the whole bishop basement bathymetry the result is a good reconstruction of the complex basement and of the shape properties of the source at the estimated points

petrogenetic grids for metacarbonate rocks pressure temperature phase diagram projection for mixed volatile systems isothermal or isobaric phase diagram sections as a function of fluid composition x f are widely used for interpreting the genetic history of metacarbonate rocks this approach has the disadvantages that 1 the influence of a key metamorphic variable either pressure p or temperature t is obscured 2 the diagrams are inappropriate for systems that are not fluid saturated these problems are avoided by constructing phase diagram projections in which the volatile composition of the system is projected onto a p t coordinate frame i e a petrogenetic grid the univariant curves of such p t projections trace the conditions of the invariant points of isothermal or isobaric phase diagram sections thereby defining the absolute stability of high variance mineral assemblages with and without a coexistent fluid phase petrogenetic grids for metacarbonate rocks are most useful for the study of regional metamorphism and for systems in which fluid composition has not been externally controlled a calculated example of a p t projection for the system cao mgo sio2 h2o co2 suggests that many assemblages e g calcite tale enstatite fluid magnesite tremolite antigorite diopside dolomite and calcite forsterite tremolite in mixed volatile systems have stability fields that make them useful as p t indicators consideration of the principles governing projection topology demonstrates that the univariant curves around a fluid present invariant point cannot be oriented independently with respect to the direction of compositional variation in the fluid phase this has the interesting predictive implication that if the direction of compositional variation along one univariant curve around an invariant point is known then the direction of compositional variation along the remaining curves can be determined solely from topologic constraints the same constraints can be applied to systems containing simple mineral solutions or melts in order to predict compositional variations

gravity inversion of 2d basement relief using entropic regularization we have developed a gravity interpretation method for estimating the discontinuous basement relief of a sedimentary basin the density contrast between the basement and the sediments is assumed to be known and it could be either constant or vary monotonically with depth the interpretation model consists of a set of vertical juxtaposed prisms whose thicknesses are the parameters to be estimated we used the entropic regularization that combines the minimization of the first order entropy measure with the maximization of the zeroth order entropy measure of the solution vector we validated the method by applying it to synthetic data produced by a simulated basin bordered by high angle step faults we obtained a good definition of the relief particularly of the discontinuities we also applied the method to a profile across the buyuk menderes valley in west turkey and obtained a solution exhibiting a gravity fault with large slip on the northern border of the valley when applied to the interpretation of a discontinuous basement relief the method has a better performance than the global smoothness method it is comparable to the weighted smoothness method but it does not require the a priori knowledge about the maximum basin depth

garnet composition as a petrogenetic indicator an example from a marble calc silicate granulite interface at kondapalle eastern ghats belt india thep t fluid histories of aluminous garnet clinopyroxene bearing calc silicate granulites are commonly constrained through interpretation of sequential reaction textures based on activity corrected petrogenetic grids for model systems for example the widely used cas co2 h2o topologies application of these topologies to calc silicates of diverse bulk composition is limited by the fact that the role of clinopyroxene and hence of garnet composition in the garnet forming reactions is ignored or not adequately considered in this contribution the complexities that arise from the involvement of clinopyroxene in the garnet forming reactions are critically evaluated as an example the paragenetic relations and compositional features of clinopyroxene and coronitic garnet across paired scapolite and wollastonite dominated reaction zones scp cpx qtz cal qtz wo cal cpx scp developed between marble layers cal cpx wo scp and their host calc silicate granulite cpx pl qtz scp at an exposure in the high grade eastern ghats belt india are examined the microtextural features and systematic changes of modal and phase compositions across the profile indicate that clinopyroxene scapolite plagioclase quartz and calcite as well as wollastonite participated in the garnet forming reactions using the sub assemblage qtz cal cpx scp grt v in the system cao feo al2o3 sio2 co2 it is demonstrated that at the ambient p t xfluid conditions the reaction coefficients of the participating phases are uniquely defined by the garnet composition as a result the p t slope of a garnet forming reaction changes with the garnet composition with sharp changes at singular points across which one or more phases change their sides with respect to garnet in a given reaction to consider the consequences of these complexities on the reaction topology of calc silicate granulites a new petrogenetic grid for the system cao feo al2o3 sio2 co2 involving clinopyroxene has been constructed the effects of fluid composition co2 h2o o2 fluid pressure pfluid

simulated polarimetric fields of ice vapor growth using the adaptive habit model part ii a case study from the frost experiment abstracta new adaptive habit model ahm grows ice crystals through vapor deposition while evolving ice particle properties including shape and effective density the ahm provides an opportunity to investigate observed microphysical processes through the computation of polarimetric variables and corroboration with microphysical model output this study is unique because the polarimetric scattering calculations are computed using predicted microphysical parameters rather than a priori assumptions that are imposed within the scattering calculations in the forward simulator allowing for a more effective comparison to radar observations through the simulation of a case in the front range of the rocky mountains in colorado using the advanced research version of the weather research and forecasting model it is found that the ahm approximates ice mass shape cloud vertical structure and temporal evolution as reflected through polarimetric quantities compared to observations ahm reflectivity magnitudes are

bathymetric prediction from seasat altimeter data the linear response function technique is used to analyze two 1300 km tracks of seasat altimeter data and corresponding bathymetry in the musician seamounts region north of hawaii bathymetry and geoid height are highly correlated in the 50 to 300 km wavelength range a predictive filter is developed which can operate on seasat altimetry in poorly surveyed oceanic regions to indicate the presence of major bathymetrie anomalies modeling of the bathymetry geoid correlation in the musician region is attempted using the elastic plate model the flexural rigidity d of the plate is not well constrained by our data but appears to lie in the range 5 1021 n m 5 1022 n m at the time of loading since the musician seamounts and the crust on which they lie are both late cretaceous in age this value represents the effective flexural rigidity of very young lithosphere that was frozen in at the time of voicanism the modeling indicates that the general form of a predictive filter will strongly depend on various geologic parameters especially the effective flexural rigidity hence some a priori geologic constraints are necessary to estimate successfully the bathymetry from the altimeter data alternately if high quality bathymetry is available a crude estimate of the age of loading i e voicanism can be made from the altimeter data

the origins of granulites a metamorphic perspective although many recent reviews emphasize a uniformity in granulite pressure temperature p t conditions and paths granulites in reality preserve a spectrum of important petrogenetic features which indicate diversity in their modes of formation a thorough survey of over 90 granulite terranes or occurrences reveals that over 50 of them record p t conditions outside the 7 5 1 kbar and 800 50 c average granulite regime preferred by many authors in particular an increasing number of very high temperature 900 1000 c terranes are being recognized both on the basis of distinctive mineral assemblages and geothermobarometry petrogenetic grid and geothermobarometric approaches to the determination and interpretation of p t histories are both evaluated within the context of reaction textures to demonstrate that the large range in p t conditions is indeed real and that both near isothermal decompression itd and near isobaric cooling ibc p t paths are important amphibolite granulite transitions promoted by the passage of co 2 rich fluids as observed in southern india and sri lanka are exceptional and not representative of fluid related processes in the majority of terranes it is considered on the contrary that fluid absent conditions are typical of most granulites at or near the time of their recorded thermal maxima itd granulites are interpreted to have formed in crust thickened by collision with magmatic additions being an important extra heat source erosion alone is not however considered to be the dominant post collisional thinning process instead the itd paths are generated during more rapid thinning 1 2 mm yr exposure related to tectonic exhumation during moderate rate or waning extension ibc granulites may have formed in a variety of settings those which show anticlockwise p t histories are interpreted to have formed in and beneath areas of voluminous magmatic accretion with or without additional crustal extension ibc granulites at shallow levels very rapid 5 mm yr extensional thinning subsequent to collision it is suggested that the preservation of ibc paths rather than itd paths in many granulites is primarily related to the rate and timescale of extensional thinning of thickened crust and that hybrid itd to ibc paths should also be observed most ibc granulites and probably many itd granulites have not been exposed at the earth s surface as a result of the tectonic episodes which produced them but have resided in the middle and lower crust for long periods of time 100 2000 ma following these events the eventual exhumation of most granulite terranes only occur through their incorporation in later tectonic and magmatic events unrelated to their formation

polarimetric radar modeling of mixtures of precipitation particles with the advances of dual polarized radar techniques in meteorology it is now possible to deduce precipitation microphysical characteristics in far more detail than possible with reflectivity measurements alone radar parameters such as differential reflectivity and differential phase between horizontal and vertical polarizations have been studied in detail as well as linear depolarization ratio copolar correlation coefficient and backscatter differential phase while these parameters can be linked to certain microphysical properties of specific classes of precipitation such as raindrops or hail very little study has been directed at the practically important cases of mixtures of different types of precipitation particles such as rain hail graupel ice crystals and snow each type can have different size shape orientation and dielectric constant distributions the present treatment is rigorous and is based on the mueller matrix formulation radar parameters are derived from the averaged mueller matrix computations careful consideration is given to the orientation and size distributions of the different particle types after calculating single particle scattering characteristics some simple two component mixtures such as rain hail and ice crystals snow are considered finally a 2d numerical cloud model is used to simulate the rain hail graupel and snow fields of an evolving convective storm from which the radar parameters are derived for the initial peak and dissipating stages of the storm model computations are performed at c and s band frequencies

multiparameter radar measurements in colorado convective storms part ii hail detection studies abstract in this part ii paper we focus on hail detection using the ncar cp 2 radar measurements from which zh zdr ldr and dual frequency ratio can be derived a major feature of this paper relates to rigorous computations of multiparameter observables including circular polarization observables from model hail distributions and to consideration of propagation effects in moderate to intense rainfall multiparameter radar measurements of hail are presented using data gathered during the maypole 83 and 84 field programs these hail measurements are found to be consistent with model computations hail signature locations using zdr dual frequency ratio and ldr are shown to be in excellent agreement the vertical structure of zdr below the melting level ldr above the melting level and dual frequency ratio yield new and interesting information on hail shaft structure and vertical extent examples of radar data from maypole 84 are used to illustrate these inferences

insights into the evolving microphysical and kinematic structure of northeastern u s winter storms from dual polarization doppler radar abstractthe recent weather surveillance radar 1988 doppler wsr 88d network upgrade to dual polarization capabilities allows for bulk characterization of microphysical processes in northeastern u s winter storms for the first time in this study the quasi vertical profile qvp technique wherein data from a given elevation angle scan are azimuthally averaged and the range coordinate is converted to height is extended and applied to polarimetric wsr 88d observations of six northeast winter storms to survey their evolving bulk vertical microphysical and kinematic structures these analyses are supplemented using hourly analyses from the rapid refresh rap model regions of ascent inferred from qvps were consistently associated with notable polarimetric signatures implying planar crystal growth when near 15 c and riming and secondary ice production at higher temperatures the heaviest snowfall occurred most often when ascent and enhanced propagation differential phase shift occurred near 15 c

concept of effective density key to gravity depth determinations for sedimentary basins the gravity anomaly observed over a layered sedimentary basin is close to that calculated over a basin with the same configuration and depth but filled by homogeneous sediments with density equal to the effective weighted average density of the real layered basin therefore it is possible to calculate the effective density contrast of a basin from the residual gravity anomaly over it if the depth of the basin is known at least at one point assuming a mathematical function for density depth dependence an expression for the gravity depth dependence using the infinite slab bouguer formula can be developed this expression makes it possible to calculate the depth of a basin or an isopach map from gravity data an exponential function and a new hyperbolic density depth function and their gravity depth functions are analyzed and implemented for determining the depths of basins from gravity data for the san jacinto graben california and the tucson basin southern arizona the hyperbolic functions are m

modeling study of a tropical squall type convective line abstract a multidimensional and time dependent cloud scale model is used to investigate the dynamic and micro physical processes associated with convective and stratiform regions within a tropical squall type convective line the evolution of the total convective and stratiform portions of rainfall is also estimated by using model output a three dimensional version of the model covers a horizontal domain about 96 96 km2 frequently the horizontal extent of an observed stratiform region is over a few hundred kilometers therefore a two dimensional version of the model with a 512 km horizontal length is also used to incorporate a complete stratiform region two dimensional model result recapture many interesting features as observed in particular the fractional portion of stratiform rain as well as its fractional area coverage are in good agreement with observations a significant amount of ice particles melted to rain near the freezing level in the trailing part of the modeled squall system during i

low levelzdrsignatures in supercell forward flanks the role of size sorting and melting of hail abstractthe low levels of supercell forward flanks commonly exhibit distinct differential reflectivity zdr signatures including the low zdr hail signature and the high zdr arc the zdr arc has been previously associated with size sorting of raindrops in the presence of vertical wind shear here this model is extended to include size sorting of hail idealized simulations of a supercell storm observed by the norman oklahoma koun polarimetric radar on 1 june 2008 are performed using a multimoment bulk microphysics scheme in which size sorting is allowed or disallowed for hydrometeor species several velocity diameter relationships for the hail fall speed are considered as well as fixed or variable bulk densities that span the graupel to hail spectrum a t matrix based emulator is used to derive polarimetric fields from the hydrometeor state variables size sorting of hail is found to have a dominant impact on zdr and can result in a zdr arc from melting hail even when size sorting is disallowed in

metamorphic evolution of exhumed middle to lower crustal rocks in the mojave extensional belt southern california usa the waterman metamorphic complex of the central mojave desert was exposed as a consequence of early miocene detachment dominated extension however it has evidence consistent with a more extensive geological history that involves collision of a crustal fragment s tectonic thickening by overthrusting and two periods of extension the metamorphic complex contains granitoid intrusives and felsic mylonitic gneisses as well as polymetamorphic rocks that include marble calc silicate quartzite mafic granulite pyribolite amphibolite migmatite and biotite schist the latter group of rocks was affected by an initial series of high grade metamorphic events m1 and m2 and a localized lower grade overprint m3 the initial metamorphism m1 can be separated into two stages along its high grade p t path m1a a granulite facies metamorphism at 800 850 c and 7 5 9 kbar and mlb an upper amphibolite facies overprint at 750 800 c and 10 12 kbar m1a developed mineral assemblages and textures consistent with granulite facies conditions at a reduced activity of h2o and is associated with intense ductile deformation d1 and minor local partial melting m1b overprinted the granulite assemblages with a series of hydrous phases under conditions of increasing pressure and h2o activity and is accompanied by little or no deformation m2 developed at lower pressures and temperatures 650 750 c 4 5 5 5 kbar and is distinguished by a second local overprint of hydrous phases that reflects an input of aqueous fluids probably associated with the intrusion of a series of granitic dykes and veins effects of m3 are confined to the mitchel detachment zone an anastomosing early miocene detachment fault and are characterized by local ductile brittle deformation d2 of the pre existing high grade rocks and granitoid intrusives and by the production of mylonites and mylonitic gneisses under greenschist facies conditions 300 350 c 3 5 kbar the initial overprint m1a represents metamorphism devolatilization and minor partial melting of supracrustal rocks under granulite facies conditions as a consequence of tectonic and possibly magmatic thickening the increasing pressure transition of m1a to m1b reflects a period of continued compressional tectonism thrusting and influx of h2o in part locally related to crystallization of partial melts the near isothermal decompression between m1b and m2 probably represents a pre 112 ma extensional episode that may have been the result of a decompressional readjustment of a thickened crust following the initial extensional event the metamorphic complex remained at depths of 10 17 km for at least 90 ma until it was uplifted following miocene extension m3 develops locally in response to this second extensional period resulting from the early miocene detachment faulting

garnet coronas in scapolite wollastonite calc silicates from east antarctica the application and limitations of activity corrected grids calc silicate boudins within proterozoic granulite facies gneisses of the northern prince charles mountains east antarctica preserve a number of reaction textures including garnet coronas between calcite and scapolite garnet quartz coronas between scapolite and wollastonite and between plagioclase and wollastonite calcite quartz intergrowths in wollastonite and calcite plagioclase symplectites in scapolite these textures have been modelled using petrogenetic grids for reactions in the cao al2 o3 sio2 co2 system but with reduced mineral activities to account for additional components in real mineral compositions such fixed composition reduced activity grids are strictly valid only at the point in p t aco2 space where an assemblage last equilibrated and do not show the true positions of reactions away from this point because mineral compositions change with reaction progress in this case however mineral compositions close to end member values and low extents of reaction progress mean that compositional change was limited and the grids are good approximations to true pseudosections over the entire p t aco2 range of interest the grids show that the textures are consistent with near isobaric cooling from about 850 to 700d c at 7 kbar a p t path compatible with thermobarometric studies of other lithologies from the area phase relationships indicate that co2 activities were buffered by the local mineral assemblage during peak and retrograde metamorphism either under fluid absent conditions or within a non pervasive fluid phase previous studies of garnet coronas in scapolite wollastonite calc silicates have used qualitative grids based on limited experimental data to invoke garnet growth during water infiltration at high temperature but the grids used here show that garnet coronas can form on cooling without any need for water influx

a barometric response to late compression in the strangways metamorphic complex arunta block central australia evidence for four major deformation events d1 d4 and two metamorphic events m1 m2 is shown by granulite and amphibolite facies rocks of the strangways metamorphic complex central australia which is divided into two domains the ongeva granulites to the east and the anamarra granite domain to the west d1 and d2 produced layer parallel foliations with many of the effects of d1 overprinted by intense non coaxial shear during d2 low pressure granulite facies metamorphism m1 accompanied d1 2 at conditions of p 5 3 1 2 kbar and t 750 c the effects of m1 are characterized by s1 spinel quartz bearing assemblages with overprinting s2b sillimanite biotite magnetite assemblages implying approximately isobaric cooling effects of m2 are characterized by s1 2 cordierite pseudomorphed by orthopyroxene sillimanite biotite magnetite symplectites at conditions of p 7 5 0 8 kbar and t 800 c this retrograde increase in pressure was probably the result of crustal thickening during d3 which produced ne plunging f3 and f4 folds in the ongeva granulites and a widespread shear foliation in the anamarra granite domain the increase in pressure with m2 may reflect the beginning of a clockwise p t t path typical of collisional style tectonics sillimanite and orthopyroxene bearing ultramylonites were produced during d4 an extension event parallel to the d3 transport axis and probably related to crustal collapse after thickening during d3 wide n dipping shear zones d5 containing sillimanite kyanite staurolite and overprinting greenschist facies assemblages bound the strangways metamorphic complex these zones indicate a s directed sense of shear and were probably responsible for bringing the strangways metamorphic complex to higher crustal levels during both a probable late proterozoic event and the mid carboniferous alice springs orogeny

simulated polarimetric fields of ice vapor growth using the adaptive habit model part i large eddy simulations abstractthe bulk adaptive habit model ahm explicitly predicts ice particle aspect ratio improving the representation of microphysical processes and properties including ice liquid phase partitioning with the unique ability to predict ice particle shape and density the ahm is combined with an offline forward operator to produce fields of simulated polarimetric variables an evaluation of ahm forward simulated dual polarization radar signatures in an idealized arctic mixed phase cloud is presented interpretations of those signatures are provided through microphysical model output using the large eddy simulation mode of the weather research and forecasting model vapor grown ice properties are associated with distinct observable signatures in polarimetric radar variables with clear sensitivities to the simulated ice particle properties including ice number size and distribution shape in contrast the liquid droplet number has little influence on both polarimetric and microphysical variables in the

evolution of the continental crust in the proterozoic eastern ghats belt india and new constraints for rodinia reconstruction implications from sm nd rb sr and pb pb isotopes abstract for this study nd sr and pb isotope compositions were analyzed for ortho and paragneisses from the eastern ghats belt of india in order to determine its crust formation and crustal evolution this belt represents a proterozoic orogen that extends along the east coast of peninsular india and forms part of the mobile belts in east gondwana and rodinia the eastern ghats belt was affected by mesoproterozoic granulite facies metamorphism in the western segment western charnockite zone and a grenvillian regional scale high grade event in the central and eastern segments western khondalite zone charnockite migmatite zone and eastern khondalite zone as well as a local pan african overprint the results of the isotope studies are used for the large scale reconstruction of the indo antarctic part of the rodinia supercontinent based on nd model ages and pb isotope ratios from leached feldspars four crustal domains can be distinguished in the eastern ghats belt these domains can in part be correlated with the lithological division of the belt 1 the western charnockite zone south of the godavari graben is characterized by nd model ages between 2 3 and 2 5 ga for orthogneisses and 2 6 and 2 8 ga for metasediments domain 1 the pb isotopes are primitive indicating reworking of dominantly archean and mixing with minor proterozoic material 2 north of godavari graben nd model ages for orthogneisses are significantly higher with values ranging from 3 2 to 3 9 ga the pb isotopes are strongly retarded 3 the north eastern parts of the charnockite migmatite zone and western khondalite zone form a distinct and almost homogeneous crustal domain domain 3 with nd model ages between 1 8 and 2 2 ga 4 between the isotopically homogeneous terranes stretches a broad transition zone domain 2 enclosing parts of the western khondalite zone charnockite migmatite zone and eastern khondalite zone the nd model ages for metasediments 2 1 2 5 ga are younger than paragneiss ages of the adjoining western charnockite zone the nd model ages for orthogneisses 1 8 3 2 ga display a large spread which is consistent with the pb isotope signatures that indicate mixing of archean with proterozoic material the border zone between domain 3 and the archean eastern indian craton forms a second transition zone domain 4 characterized by metasediments with nd model ages between 2 2 and 2 8 ga and orthogneisses with model ages around 3 2 ga reworking of archean crustal material is most intense along the border zones of the belt and juvenile material is more dominant away from the orogenic front this scenario is indicative of an active continental margin setting for the two proterozoic episodes of orogenesis in the eastern ghats belt a correlation of domain 3 with the rayner complex and the prydz bay region antarctica for the early crustal evolution is supported by the similarity of the isotope signatures the napier complex is very different to the eastern ghats belt and an early joint evolution of these terranes is ruled out on the basis of the pb pb and sm nd systematics

two dimensional convection in non constant shear a model of mid latitude squall lines numerical simulations of two dimensional deep convection are analysed using analytical models extended to include shallow downdraughts and non constant shear the cumulonimbus are initiated by low level convergence created by a finite amplitude downdraught these experiments have constant low level shear and differ only in the profile of mid and upper level winds quasi steady convenction is produced if the mid and upper level flow has small shear and the low level shear is large the surface precipitation ismaximized for no intial relative relative flow aloft if stationary this storm p o can give prodigious locilized rainfall p o is the two dimentisonal equivalent of the supercell these results are placed in context with previous two dimensional simulations attention is drawn to the similiarity with previous two dimensional simulations attention is drawn to the similarity with squall lines in central and eastern u s a storm p o is analysed by construction of time averaged fields of streamfunction vorticity teperature and height deviation the smoothness of these fields suggests a conceptual model of the storm dynamics which involves cooperation between distinct charcteristic flows an overturning updraught a jump type updraught a shallow downdraught a low level rotor and a boundary layer an idealized analytical model is described by solution of the equations for steady convection these solutions for the remote flow are derived from energy conversation mass continuity and a momentum budget and they give relationships between the non dimensional parameteres of the problem it is apparent that the convection is a high froude or low richardson number flow demanding the existence of a cross storm pressure gradient inherent in this idealized model is a vortex sheet between updraught and down draught and it is considered that the dynamical instability of this sheet is related to complexities in the numerical simulation furthermore these results show that in two dimensions both non constant shear and a shallow downdraught are necessary to maintain steady convection

metamorphic evolution of calcsilicate granulites near battye glacier northern prince charles mountains east antarctica calcsilicate granulites of probable middle proterozoic age c 1000 1100 ma in the vicinity of battye glacier northern prince charles mountains east antarctica contain prograde metamorphic assemblages comprising various combinations of wollastonite scapolite clinopyroxene an rich plagioclase calcite quartz titanite and rarely orthoclase ilmenite phlogopite and graphite comparison of the prograde assemblages with calculated and experimentally determined phase relations in the simple cao al2o3 sio2 co2 h2o system suggests peak metamorphism at 835 c in the presence in wollastonite bearing assemblages at least of a co2 bearing fluid xco 0 3 at a probable pressure of 6 7 kbar well preserved retrograde reaction textures represent 1 breakdown of scapolite to anorthite calcite quartz 2 formation of grossular andradite garnet and locally 3 epidote both principally by reactions involving scapolite breakdown products and clinopyroxene 4 local coupled replacement of clinopyroxene and ilmenite by hornblende and titanite respectively and finally 5 local sericitization of prograde and retrograde plagioclase these retrograde reactions are interpreted to be the result of cooling and variable infiltration by h2o rich fluids possibly derived from crystallizing pegmatitic intrusions and segregations that may be partial melts which are common throughout the area

granulite facies metasomatism zoned calc silicate boudins from the rauer group east antarctica calc silicate boudins from the rauer group east antarctica were metamorphosed under granulite facies conditions during late proterozoic ca 1 000 ma m3 metamorphism boudin cores contain low to moderate aco2 assemblages including wollastonite grossularandradite grandite garnet clinopyroxene scapolite plagioclase quartz calcite petrological and stable isotopic evidence suggests that these core assemblages resulted from pre peak m3 infiltration of water rich fluids there is no evidence for a pervasive fluid phase under peak m3 conditions the boudins are separated from the surrounding fe rich pelites and semi pelites by a series of concentric high variance reaction zones developed under peak m3 conditions variations in mineral assemblage mineral composition and whole rock composition across these zones suggest that they formed by diffusional masstransfer controlled principally by a chemical potential gradient in ca across the original calc silicate paragneiss lithological boundary as a consequence of the nearcomplete decarbonation of the calc silicatesbefore the m3 peak development of the diffusion controlled reaction zones did not liberate significant co2 during granulite facies metamorphism similar calcite poor low aco2 calc silicate horizons in other granulite facies terrains are unlikely to have been important local fluid sources during deep crustal metamorphism

the tornadic supercell on the kanto plain on 6 may 2012 polarimetric radar and surface data assimilation with enkf and ensemble based sensitivity analysis abstracta tornadic supercell and associated low level mesocyclone lmc observed on the kanto plain japan on 6 may 2012 were predicted with a nonhydrostatic mesoscale model with a horizontal resolution of 350 m through assimilation of surface meteorological data horizontal wind temperature and relative humidity of high spatial density and c band doppler radar data radial velocity and rainwater estimated from reflectivity and specific differential phase with a local ensemble transform kalman filter with assimilation of both surface and radar data a strong lmc was successfully predicted near the path of the actual tornado when either surface or radar data were not assimilated however the lmc was not predicted therefore both surface and radar data were essential for successful lmc forecasts the factors controlling the strength of the predicted lmc defined as a low level maximum vertical vorticity were clarified by an ensemble based sensitivity analysis esa which is a new approach for ana

metamorphism of reduced granulites in low co 2 vapour free environment pervasive flooding of co2 has been proposed as the cause of granulite facies metamorphism that is capable of producing many distinctive characteristics of the deep continental crust reduced water activity orthopyroxene bearing assemblages depletion of large ion lithophile lil elements and dehydration1 6 the calculations presented here of c o h fluid composition for conditions of granulite facies metamorphism show that oxygen fugacity f o2 estimates from many terranes are sufficiently low that the addition of co2 rich fluid causes graphite to precipitate for values of pressure p and temperature t common to granulites and with f o2 slightly below the quartz fayalite magnetite buffer qfm the addition of co2 sufficient to grow 10 vol orthopyroxene requires the precipitation of 1 5 vol graphite as 0 1 vol graphite is readily recognizable but is not reported in most low f o2 granulites these rocks have not been flooded by co2 and low f h2o is probably due to extraction of a magma or recrystallization of an already dry rock7 8 granulite terranes may thus result from a combination of these three processes and the dominance of any one cannot now be demonstrated on a regional basis

calculation and application of clinopyroxene garnet plagioclase quartz geobarometers recently published thermodynamic and experimental data in a variety of chemical systems have been evaluated to derive gibbs free energies for hedenbergite and pyrope these were used to calculate the geobarometric equilibria

reactions and textures in wollastonite scapolite granulites and their significance for pressure temperature fluid histories of high grade terranes reaction textures in wollastonite scapolite calc silicates provide important evidence for pressure temperature fluid histories in granulites pressure temperature t aco2 and p aco2 diagrams calculated for appropriate mineral compositions using the internally consistent dataset of holland and powell 1990 are presented and used to provide a framework for interpretation of the reaction textures garnet rims replacing wollastonite and scapolite in calc silicate gneisses is a common texture in many granulite terranes this texture can plausibly be developed in post peak p t histories dominated by cooling e g near isobaric cooling and does not generally imply the infiltration of hydrous fluids examples from the arunta complex australia and the northern prince charles mountains antarctica are consistent with cooling without fluid influx at 7 8 kbar and aco2 of 0 3 0 5 contrasting textures involving the replacement of garnet by wollastonite scapolite or wollastonite plagioclase symplectites and the growth of wollastonite plagioclase rims or coronas on scapolite quartz boundaries can be interpreted as essentially closed system features and modelled through modal analysis of reaction products in the case of the rauer group antarctica near isothermal decompression from ca 8 to 6 kbar at 850 800 c and aco2 in the range 0 35 0 45 is indicated by these textures based on calculated p t aco2 grids in the cao al2o3 sio2 co2 casv and more complex systems calculated reactions producing wollastonite scapolite from garnet bearing assemblages do not involve decarbonation but may consume co2 with increasing temperature in the absence of calcite hence these calc silicates may act as co2 sinks on the prograde segments of clockwise p t paths conversely scapolite wollastonite granulites will act as sources of post peak co2 rich fluids liberated upon cooling and potentially trapped elsewhere as post peak carbonic fluid inclusions

fluid heterogeneity during granulite facies metamorphism in the adirondacks stable isotope evidence the preservation of premetamorphic whole rock oxygen isotope ratios in adirondack metasediments shows that neither these rocks nor adjacent anorthosites and gneisses have been penetrated by large amounts of externally derived hot co2 h2o fluids during granulite facies metamorphism this conclusion is supported by calculations of the effect of fluid volatilization and exchange and is also independently supported by petrologic and phase equilibria considerations the data suggest that these rocks were not an open system during metamorphism that fluid rock ratios were in many instances between 0 0 and 0 1 that externally derived fluids as well as fluids derived by metamorphic volatilization rose along localized channels and were not pervasive and thus that no single generalization can be applied to metamorphic fluid conditions in the adirondacks

depth to bedrock using gravimetry in the reno and carson city nevada area basins sedimentary basins can trap earthquake surface waves and amplify the magnitude and lengthen the duration of seismic shaking at the surface poor existing gravity and well data coverage of the basins below the rapidly growing reno and carson city urban areas of western nevada prompted us to collect 200 new gravity measurements by classifying all new and existing gravity locations as on seismic bedrock or in a basin we separate the basins gravity signature from variable background bedrock gravity fields we find an unexpected 1 2 km maximum depth trough below the western side of reno basin enhancement of the seismic shaking hazard would be greatest in this area depths throughout most of the rest of the truckee meadows basin below reno are less than 0 5 km the eagle valley basin below carson city has a 0 53 km maximum depth basin depth estimates in reno are consistent with depths to bedrock in the few available records of geothermal wells and in one wildcat oil well depths in carson city are consiste

arrested charnockite formation at kottavattam southern india at kottavattam southern kerala india late proterozoic homogeneous leptynitic garnet biotite gneisses of granitic composition have been transformed on a decimetric scale into coarse grained massive charnockite sensu stricto along a set of conjugate fractures transecting the gneissic foliation charnockitization post dates the polyphase deformation regional high grade metamorphism and anatexis and evidently occurred at a late stage of the pan african tectonothermal history geothermobarometric and fluid inclusion data document textural and chemical equilibration of the gneiss and charnockite assemblages at similar p lith t conditions 650 700 degrees c 5 6kbar in the presence of carbonic fluids internally buffered by reaction with graphite and opaque mineral phases x co2 0 7 0 6 x h2o 0 2 0 3 x n2 0 1 logf o2 l7 5 mineralogical zonation indicates that charnockitization of the leptynitic gneiss involved first the breakdown of biotite and oxidation of graphite in narrow outward migrating transition zones adjacent to the gneiss followed by the breakdown of garnet and the neoblastesis of hypersthene in the central charnockite zone compared to the host gneiss the charnockite shows higher concentrations of k na sr ba and zn and lower concentrations of mg fe ti v y zr and the hree with a complementary pattern in the narrow transition zones of biotite breakdown the p lith t x h2o data and chemical zonation patterns indicate charnockitization through subsolidus dehydration reaction in an open system subsequent residence of the carbonic fluids in the charnockite resulted in low grade alteration causing modification of the syn charnockitic elemental distribution patterns and the properties of entrapped fluids we favour an internally controlled process of arrested charnockitization in which during near isothermal uplift the release of carbonic fluids from decrepitating inclusions in the host gneiss into simultaneously developing fracture zones led to a change in the fluid regime from fluid absent in the gneiss to fluid present in the fracture zones and to the development of an initial fluid pressure gradient triggering the dehydration reaction

precipitation and evolution sensitivity in simulated deep convective storms comparisons between liquid only and simple ice and liquid phase microphysics abstract weisman and klemp suggested that their liquid only deep convective storm experiments should be repeated with a liquid ice microphysics scheme to determine if the solutions are qualitatively the same using a three dimensional nonhydrostatic cloud model such results are compared between three microphysics schemes the kessler liquid only scheme used by weisman and klemp a lin farley orville like scheme with liquid and ice parameterization li and the same lin farley orville like microphysics scheme but with only liquid processes turned on lr convection is simulated using a single thermodynamic profile and a variety of shear profiles the shear profiles are represented by five idealized half circle wind hodographs with arc lengths us of 20 25 30 40 and 50 m s 1 the precipitation cold pool characteristics and storm evolution produced by the different schemes are compared the kessler scheme produces similar accumulated precipitation over 2 h compared to lr for all shear regimes