wavelet scale analysis of mesoscale convective systems for detecting deep convection from infrared imagery wavelet scale analysis of mesoscale convective systems for detecting deep convection from infrared imagery

spectrum of pore types and networks in mudrocks and a descriptive classification for matrix related mudrock pores matrix related pore networks in mudrocks are composed of nanometer to micrometer size pores in shale gas systems these pores along with natural fractures form the flow path permeability network that allows flow of gas from the mudrock to induced fractures during production a pore classification consisting of three major matrix related pore types is presented that can be used to quantify matrix related pores and relate them to pore networks two pore types are associated with the mineral matrix the third pore type is associated with organic matter om fracture pores are not controlled by individual matrix particles and are not part of this classification pores associated with mineral particles can be subdivided into interparticle interp pores that are found between particles and crystals and intraparticle intrap pores that are located within particles organic matter pores are intrap pores located within om interparticle mineral pores have a higher probability of being part of an effective pore network than intrap mineral pores because they are more likely to be interconnected although they are intrap om pores are also likely to be part of an interconnected network because of the interconnectivity of om particles in unlithifed near surface muds pores consist of interp and intrap pores and as the muds are buried they compact and lithify during the compaction process a large number of interp and intrap pores are destroyed especially in ductile grain rich muds compaction can decrease the pore volume up to 88 by several kilometers of burial at the onset of hydrocarbon thermal maturation om pores are created in kerogen at depth dissolution of chemically unstable particles can create additional moldic intrap pores

observed evolution of tropical deep convective events and their environment abstract using a compositing technique the temporal progression of tropical convective systems and the mean atmospheric state in their vicinity is constructed from a time series of geostationary satellite and operational rawinsonde data the technique establishes the stage in the life cycle of convection prevailing at a given place and time by a simple objective method using time series of satellite brightness temperature tb histograms collected from a region surrounding the site soundings are classified according to their placement in the convective life cycle and composites formed that represent the areal mean state of the convecting atmosphere at each stage for several scales of horizontal averaging the temporal structure found here for the mesoscale mean atmosphere closely resembles existing observations of the horizontal structure of a tropical squall line albeit with certain reductions in amplitude and stabilization rate this supports the generality of previous findings that the physical m

formation of nanoporous pyrobitumen residues during maturation of the barnett shale fort worth basin abstract hydrocarbon generation reactions occur within organic rich shales as a response to thermal maturation here we report observations on samples from the organic rich mississippian barnett shale gas system fort worth basin texas usa at varying stages of thermal maturation a multiscale characterization was achieved using a combination of compositional organic geochemistry and spectromicroscopy techniques including synchrotron based scanning transmission x ray microscopy stxm and transmission electron microscopy tem we document the chemical evolution of the macromolecular structure of barnett shale kerogen with increasing maturity from an immature kerogen containing a significant aliphatic component and an important concentration of oxygen and sulfur containing functional groups to an overmature kerogen dominated by poorly condensed aromatic structures in addition to the presence of bitumen in samples of oil window maturity very likely genetically derived from thermally degraded kerogen the formation of nanoporous pyrobitumen has been inferred for samples of gas window maturity likely resulting from the formation of gaseous hydrocarbons by secondary cracking of bitumen compounds

a tropical squall line observed during the copt 81 experiment in west africa part 1 kinematic structure inferred from dual doppler radar data abstract this paper deals with the analysis of a tropical squall line observed on 22 june 1981 during the copt 81 convection profonde tropicale experiment the present part i is restricted to the study of the kinematic structure of the system which moved in a moderately unstable atmosphere faster than the environmental air at all levels at the observation time the squall line was in a mature stage the explicit description of the airflow within the system was inferred from dual and single doppler radar data the general characteristics of the squall line are found to be very similar to those of tropical squall lines observed during previous experiments such as vhimex or gate a large cloud system composed of an organized convective line ahead of an extensive trailing anvil cloud stratiform rain fast motion and long lasting structure and a well marked gust front signature at ground level the overall airflow presents a three dimensional structure at the leading edge convective scale updrafts a

the 11 august 2006 squall line system as observed from mit doppler radar during the amma sop on the evening of 9 august 2006 a mesoscale convective system mcs having a north south oriented squall line organization formed over the border between chad and nigeria it propagated westward intensified over nigeria on 10 august and reached niamey niger at 0320 utc on 11 august its passage over niamey was accompanied by dust lifting and was well tracked by the massachusetts institute of technology mit doppler radar the three dimensional structure of the airflow and precipitation pattern is investigated from regular radar volume scans performed every ten minutes between 0200 and 0321 utc the 3d wind components are deduced from the multiple doppler synthesis and continuity adjustment technique muscat applied to a set of three volume scans obtained over a time period of one hour which are equivalent to a three radar observation of the squall line when considering a reference frame moving with the system and the hypothesis of a stationary field results of the wind synthesis reveal several features commonly observed in tropical squall lines such as the deep convective cells in front of the system fed by the monsoon air and extending up to 15 km altitude and the well marked stratiform rain region at the rear associated with mesoscale vertical motions forward and trailing anvils are clearly identified as resulting from the outflow of air reaching the tropopause and transported to this level by the sloping convective updraughts occurring in a sheared environment in the northern part a deeper and stronger front to rear flow at mid levels is found to contribute to the rearward deflection of the leading line and to promote a broader over 300 km stratiform cloud region eddy vertical transports of the cross line momentum mainly accounts for the mid level flow acceleration due to a momentum redistribution from low to higher levels the height distribution of hydrometeors and their associated production terms derived from a one dimensional microphysical retrieval model indicate the distinct roles of the convective and stratiform regions in the formation of graupel and rain and the respective contributions of cold riming and warm coalescence melting processes cooling from melting and heating cooling from condensation evaporation processes yield a net decrease and increase of the potential temperature at low and mid to upper levels respectively with respect to an environmental thermodynamic profile taken three hours ahead of the analysis finally the upper level rearward flow could convey the non negligible proportion of ice particles farther from the leading deep convection to the trailing stratiform region thereby favouring the extent of this region

composite life cycle of maritime tropical mesoscale convective systems in scatterometer and microwave satellite observations this study examines scatterometer observed surface wind divergence and vorticity along with precipitable water pw across the life cycle of tropical maritime mesoscale convective systems mcss as resolved in 0 5 data simple composites were constructed around first appearances of cold 210 k cloud tops in infrared ir data at 3 hourly resolution many thousands of such events from the tropical indopacific in 2000 were used composites of subpopulations were also constructed by subdividing the dataset according to ir event size and duration as well as by prevailing values of pw and vorticity at a 5 scale the composite mcs life cycle here spans about a day and covers a few hundred kilometers with a remarkable sameness across subpopulations surface wind convergence and pw buildup lead cold cloud appearance by many hours afterward there are many hours of divergence indicative of downdrafts contrary to motivating hypotheses the strength of this divergence relative to convergence is scarcely different in humid and dry subpopulation composites normalized time series of composite vorticity show an evolution that seems consistent with vortex stretching by this convergence divergence cycle with peak vorticity near the end of the period of convergence 3 h prior to cold cloud appearance in rotating conditions the common 1 day mcs life cycle is superposed on large scale mean vorticity and convergence approximately in proportion which appear to be well scale separated covering the whole of the 48 h and 5 10 averages and are as strong as or stronger than the mcs signature

anvil productivities of tropical deep convective clusters and their regional differences abstractthe anvil productivities of tropical deep convection are investigated and compared among eight climatological regions using 4 yr of collocated and combined cloudsat and calipso data for all regions the convective clusters become deeper while they become wider and tend to be composed of multiple rainy cores two strong detrainment layers from deep convection are observed at 6 8 km and above 10 km which is consistent with the trimodal characteristics of tropical convection that are associated with different divergence cloud detrainment and fractional cloudiness the anvil productivity of tropical deep convection depends on the convection scale convective life stage or intensity and large scale environment anvil ice mass ratio related to the whole cluster starts to level off or decrease when the cluster effective scales weff the dimension of an equivalent rectangular with the same volume and height as the original cluster increase to about 200 km wide while the ratios of anvil scale and vo

the ribeira fluorite district southern brazil geological and geochemical ree sm nd isotopes characteristics the origin and evolution of different ore deposits grouped in the same district are often complex and may involve inheritance from crustal or mantle geochemical anomalies remobilization of former ore deposits and a polyphase hydrothermal history localized in a proterozoic basement in the parana state the ribeira fluorite district is such an example composed of three deposit types with distinct geological and geochemical characters emplaced at different periods from the late proterozoic to the cretaceous they are roughly aligned along a belt nearly 10 km in width and 50 km in length the southern boundary of which is a transcurrent fault two main ore facies are present 1 microcrystalline ore 0 1 mm grains and 2 macrocrystalline ore with a grain size of several millimetres the former results from the replacement of metalimestones or internal karstic sediments and the latter from microcrystalline ore dissolution and pore precipitation or recrystallization at least two different groups of source rocks can be proposed for the trapped ree in caf2 1 fluorite samples associated with the mato preto carbonatitic rocks display a slightly negative nd compatible with a mantle source and a ree pattern with the higher ree and la yb ratio in the district 2 other fluorites have a strongly negative nd 14 to 20 which indicates a crustal source that fluorine and ree have the same source is possible in strata bound and fracture filling deposits but is doubtful at mato preto the only economic fluorite deposit associated with carbonatite rocks in brazil this occurrence within a precambrian fluorite belt suggests that remobilization of a former strata bound deposit was a more significant metallogenic process than magmatic differentiation

development of organic porosity in the woodford shale with increasing thermal maturity abstract using a combination of focused ion beam milling and scanning electron microscopy we describe the evolution of secondary organic porosity in eight woodford shale late devonian early mississippian samples with mean random vitrinite reflectance values ranging from 0 51 ro to 6 36 ro organic porosity was observed to be absent in samples with vitrinite reflectance values of up to 0 90 ro with the first appearance of secondary pores starting with the 1 23 ro sample porosity in the organic matter was unexpectedly absent in a sample with a vitrinite reflectance of 2 00 ro however organic pores were again found in samples with higher thermal maturities porosity when present did not appear to be uniformly distributed among the organic matter that was within less than a micron of each other suggesting important differences in composition of the organic matter thin regions of organic matter were observed between grains raising the possibility that small amounts of the deposited organic matter were compacted between grains to form thin layers and or the structures are part of the secondary organic matter interpreted to be post oil bitumen which was left behind as a residue during oil migration through the shale some regions of porous organic matter appeared to be grain protected whereas others did not which indicates that these non protected porous organic regions may be stress supporting with porosity intact under in situ reservoir conditions these observations suggest that thermal maturity alone is insufficient to predict porosity development in organic shales and other factors such as organic matter composition complicate porosity development

an objective classification of saturn cloud features from cassini iss images abstract a k means clustering algorithm is applied to cassini imaging science subsystem continuum and methane band images of saturn s northern hemisphere to objectively classify regional albedo features and aid in their dynamical interpretation the procedure is based on a technique applied previously to visible infrared images of earth it provides a new perspective on giant planet cloud morphology and its relationship to the dynamics and a meteorological context for the analysis of other types of simultaneous saturn observations the method identifies 6 clusters that exhibit distinct morphology vertical structure and preferred latitudes of occurrence these correspond to areas dominated by deep convective cells low contrast areas some including thinner and thicker clouds possibly associated with baroclinic instability regions with possible isolated thin cirrus clouds darker areas due to thinner low level clouds or clearer skies due to downwelling or due to absorbing particles and fields of relatively shallow cumulus clouds the spatial associations among these cloud types suggest that dynamically there are three distinct types of latitude bands on saturn deep convectively disturbed latitudes in cyclonic shear regions poleward of the eastward jets convectively suppressed regions near and surrounding the westward jets and baroclinically unstable latitudes near eastward jet cores and in the anti cyclonic regions equatorward of them these are roughly analogous to some of the features of earth s tropics subtropics and midlatitudes respectively this classification may be more useful for dynamics purposes than the traditional belt zone partitioning temporal variations of feature contrast and cluster occurrence suggest that the upper tropospheric haze in the northern hemisphere may have thickened by 2014 the results suggest that routine use of clustering may be a worthwhile complement to many different types of planetary atmospheric data analysis

hydrocarbon potential of the barnett shale mississippian delaware basin west texas and southeastern new mexico the barnett shale mississippian in the delaware basin has the potential to be a prolific gas producer the shale is organic rich and thermally mature over large parts of the basin depths to the barnett range from 7000 ft 2133 m along the western edge of the basin to more than 18 000 ft 5486 m along the basin axis the barnett shale began generating petroleum about 250 ma and reached its maximum temperature about 260 ma present day thermal maturity is indicative of maximum burial and temperature wells in northern reeves county are in the gas window based on measured vitrinite reflectance values and kerogen transformation ratios the shale can be divided into an upper clastic unit and a lower limy unit by changes in resistivity the lower unit can be subdivided into five subunits by distinctive well log markers preliminary analyses suggest that intervals in the lower barnett marked by high resistivity and high neutron porosity readings on well logs have high gas contents areas in which to focus the future exploration in the lower barnett can be delineated by mapping a net resistivity greater than 50 ohm m the barnett shale contains significant gas resources in the delaware basin realizing the potential of these resources depends on the current efforts to optimize drilling and completion techniques for this shale gas play

characteristics of an african easterly wave observed during namma abstract the evolution of an african easterly wave is described using ground based radar and ancillary datasets from three locations in west africa niamey niger continental dakar senegal coastal and praia republic of cape verde oceanic the data were collected during the combined african monsoon multidisciplinary analyses amma and nasa amma namma campaigns in august september 2006 two precipitation events originated within the wave circulation and propagated with the wave across west africa mesoscale convective systems mcss associated with these events were identified at all three sites ahead of within and behind the 700 mb wave trough an additional propagating event was indentified that originated east of the wave and moved through the wave circulation the mcs activity associated with this event did not show any appreciable change resulting from its interaction with the wave the mcs characteristics at each site were different likely due to a combination of life cycle effects and

thermal maturity of the barnett shale determined from well log analysis intensive development with large scale fracturing treatments has made the barnett shale play newark east field in the fort worth basin the largest shale gas field in the world the mississippian barnett shale is an organic rich self sourced reservoir rock thermal maturity thickness and total organic carbon are the most important geological factors for commercial gas production from this shale formation the log derived thermal maturity index mi has been developed in an effort to better understand and predict hydrocarbon phases across the basin maturity index was calculated using three types of open hole logs neutron porosity deep resistivity and density porosity or bulk density the derivation of mi is based on the hypotheses that shale gas is generated and stored locally without apparent migration from outside sources and that the water saturation and the density of generated hydrocarbons decrease with an increase in thermal maturity maturity index correlates well with initial gas oil ratios gor from well production data based on this correlation an empirical relationship has been demonstrated for the fort worth basin this method is useful in understanding the thermal maturity levels of barnett shale source rock in the gas generation window mapping mi gor and gas heating value from hundreds of wells identifies the various maturity stages and areas of barnett shale that generate oil condensate wet gas or dry gas in the fort worth basin

geochemical variations in sedimentary organic matter within a homogeneous shale core tuscaloosa formation upper cretaceous mississippi u s a abstract geochemical analyses were conducted on samples collected from a 100 m core of the middle tuscaloosa formation from southwestern mississippi by studying a section that has uniform lithology and negligible differences in thermal maturity we can focus on parameters that reflect changes in depositional environment heterogeneity in the organic facies is observed at various intervals with different sampling density throughout the core a lithological transition between deep water prodeltaic shales and nearshore siltstones is marked by major perturbations in all measured geochemical parameters variations in the distribution of organic matter within the prodeltaic laminated shales are believed to reflect a shallowing event not obvious from the homogeneous lithology major heterogeneities in molecular distributions and concentrations are restricted to the tetra and pentacyclic terpanes while molecular parameters that are controlled or predominantly influenced by marine eukaryotic input show little variation these observations suggest that the chemistry and biota of the water column remained relatively constant during deposition of the laminated shales and although conditions at the sediment water interface remained dysaerobic the chemical environment appears to have varied enough to perturb communities and the diagenetic reactions of hopanoid hydrocarbons maturity dependent parameters based on the marine contribution exhibit little variation parameters based on pentacyclic triterpanes show a high degree of source dependency

intense convective systems in west africa and their relationship to the african easterly jet for may september 1998 convective systems in west africa were identified from observations by the tropical rainfall measuring mission satellite microwave imager at 85 ghz using re analysis data the 10 day average position of the african easterly jet aej was diagnosed from the 700 hpa zonal winds the distance from each convective system s centroid to the axis of the aej was calculated each convective system s minimum brightness temperatures were ranked so that intense convective systems were defined as those in the 10th percentile or lower the weak 10th percentile and intense convective systems were represented statistically as two separate populations the weak by the skewed gumbel distribution and the intense by the normal distribution from may to august the peak in activity of weak convective systems remained south of 10 n but shifted east of 10 e the peak in activity of the intense convective systems followed the seasonal migration of the aej northwards and became increasingly separate from the peak in activity of weak convective systems the majority of both weak and intense convective systems occurred within 0 50 of high terrain the high convective available potential energy high shear aej environment in the vicinity of high terrain appeared to have the greatest probability of generating intense convective systems in the study area copyright 2006 royal meteorological society

comparison of simulated and observed continental tropical anvil clouds and their radiative heating profiles abstractvertically pointing millimeter wavelength radar observations of anvil clouds extending from mesoscale convective systems mcss that pass over an atmospheric radiation measurement program arm field site in niamey niger are compared to anvil structures generated by the weather research and forecasting wrf mesoscale model using six different microphysical schemes the radar data provide the statistical distribution of the radar reflectivity values as a function of height and anvil thickness these statistics are compared to the statistics of the modeled anvil cloud reflectivity at all altitudes requiring the model to be statistically accurate at all altitudes is a stringent test of the model performance the typical vertical profile of radiative heating in the anvil clouds is computed from the radar observations variability of anvil structures from the different microphysical schemes provides an estimate of the inherent uncertainty in anvil radiative heating profiles all schemes underestima

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

deep convective system evolution over africa and the tropical atlantic in the tropical african and neighboring atlantic region there is a strong contrast in the properties of deep convection between land and ocean here satellite radar observations are used to produce a composite picture of the life cycle of convection in these two regions estimates of the broadband thermal flux from the geostationary meteosat 8 satellite are used to identify and track organized convective systems over their life cycle the evolution of the system size and vertical extent are used to define five life cycle stages warm and cold developing mature cold and warm dissipating providing the basis for the composite analysis of the system evolution the tracked systems are matched to overpasses of the tropical rainfall measuring mission satellite and a composite picture of the evolution of various radar and lightning characteristics is built up the results suggest a fundamental difference in the convective life cycle between land and ocean african storms evolve from convectively active systems with frequent lightning in their developing stages to more stratiform conditions as they dissipate over the atlantic the convective fraction remains essentially constant into the dissipating stages and lightning occurrence peaks late in the life cycle this behavior is consistent with differences in convective sustainability in land and ocean regions as proposed in previous studies the area expansion rate during the developing stages of convection is used to provide an estimate of the intensity of convection reasonable correlations are found between this index and the convective system lifetime size and depth

convection in gate the difficult problem of parameterizing tropical convection in large scale models of the atmosphere led to the global atmospheric research program s atlantic tropical experiment gate whose goal was to improve basic understanding of tropical convection and its role in the global atmospheric circulation a dense network of instrumented ships equipped with upper air sounding equipment and quantitative weather radars were located over the atlantic ocean in the intertropical convergence zone itcz just west of equatorial africa the ship network was supplemented by a fleet of research aircraft and a geosynchronous meteorological satellite the data obtained show that the deep convection in the itcz was concentrated in two types of cloud clusters rapidly moving squall clusters and slowly moving nonsquail clusters the clusters were characterized by large mid to upper level cloud shields or anvil clouds that emanated from penetrative cumulonimbus convection accompanying the deep cumulonimbus in each cluster was a log normal spectrum of smaller convective features ranging from moderate cumulonimbus down to tiny nonprecipitating cumulus the large cumulonimbus were typically grouped within a cluster into one or more mesoscale precipitation features or mpf s which were apparently triggered in mesoscale regions of intensified low level convergence as an mpf matured it developed a region of stratiform precipitation adjacent to its active deep convective cells the stratiform precipitation fell from the anvil cloud associated with the stratiform precipitation were a mesoscale downdraft below the anvil cloud and an apparent mesoscale updraft within the anvil cloud itself above the mesoscale downdraft these mesoscale drafts were distinct from the convective scale updrafts and downdrafts of the cumulus and cumulonimbus cells of the cluster downdrafts both convective scale and mesoscale filled the planetary boundary layer in the vicinity of cumulonimbus with stable air of low moist static energy these wakes of downdraft air exerted a strong control on where future convection broke out the results of gate show that to simulate the effects of tropical convection in large scale numerical models of the atmosphere a variety of phenomena must be accounted for including not only convective scale updrafts and downdrafts but anvil clouds with mesoscale updrafts and downdrafts downdraft induced boundary layer transformations and mesoscale convergence patterns experimentation with ways of including some of these features of tropical convection in large scale diagnostic and prognostic studies is under way but much work remains to be done

leading and trailing anvil clouds of west african squall lines the anvil clouds of tropical squall line systems over west africa have been examined using cloud radar data and divided into those that appear ahead of the leading convective line and those on the trailing side of the system the leading anvils are generally higher in altitude than the trailing anvil likely because the hydrometeors in the leading anvil are directly connected to the convective updraft while the trailing anvil generally extends out of the lower topped stratiform precipitation region when the anvils are subdivided into thick medium and thin portions the thick leading anvil is seen to have systematically higher reflectivity than the thick trailing anvil suggesting that the leading anvil contains numerous larger ice particles owing to its direct connection to the convective region as the leading anvil ages and thins it retains its top the leading anvil appears to add hydrometeors at the highest altitudes while the trailing anvil is able to moisten a deep layer of the atmosphere

the nature of porosity in organic rich mudstones of the upper jurassic kimmeridge clay formation north sea offshore united kingdom abstract analyses of organic rich mudstones from wells that penetrated the upper jurassic kimmeridge clay formation offshore united kingdom were performed to evaluate the nature of both organic and inorganic rock constituents and their relation to porosity in this world class source rock the formation is at varying levels of thermal maturity ranging from immature in the shallowest core samples to mature in the deepest core samples the intent of this study was to evaluate porosity as a function of both organic macerals and thermal maturity at least four distinct types of organic macerals were observed in petrographic and sem analyses and they all were present across the study area the macerals include in decreasing abundance 1 bituminite admixed with clays 2 elongate lamellar masses alginite or bituminite with small quartz feldspar and clay entrained within it 3 terrestrial vitrinite fusinite semifusinite grains and 4 tasmanites microfossils although pores in all maceral types were observed on ion milled surfaces of all samples the pores largely nanopores with some micropores vary as a function of maceral type importantly pores in the macerals do not vary systematically as a function of thermal maturity insofar as organic pores are of similar size and shape in both the immature and mature kimmeridge rocks if any organic pores developed during the generation of hydrocarbons they were apparently not preserved possibly because of the highly ductile nature of much of the rock constituents of kimmeridge mudstones clays and organic material inorganic pores largely micropores with some nanopores have been observed in all kimmeridge mudstones these pores particularly interparticle i e between clay platelets and intraparticle i e in framboidal pyrite in partially dissolved detrital k feldspar and in both detrital and authigenic dolomite are noteworthy because they compose much of the observable porosity in the shales in both immature and mature samples the absence of a systematic increase in organic porosity as a function of either maceral type or thermal maturity indicates that such porosity was probably unrelated to hydrocarbon generation instead much of the porosity within mudstones of the kimmeridge appears to be largely intraparticle and interparticle adjacent to inorganic constituents so the petroleum storage potential in these organic rich mudstones largely resides in inorganic pores

stress fields a key to oil migration a coherent oil migration model based on geomechanical considerations includes both the high molecular kerogen structure and the capillary properties of source rocks oil is squeezed from kerogen by compaction following oil generation this squeezing effect should be created by the differential stress maximum compressive stress minus least compressive stress acting on the kerogen which has been chemically broken up by oil formation in sedimentary bodies whose water is at hydrostatic pressure the migration of oil seems to involve two processes 1 lateral transfer by channeling into the more coarsely microporous layers of the source rocks from the oil generation site toward the geologic structure or lower pressured zone and 2 vertical transfer from source rock to eservoir by the opening or reopening of vertical fractures in the few areas such as structural tops where the least compressive stress is slightly greater than or equal to the pore pressure and where the capillary pressure increment 2 ggr r of oil in the microporosity exceeds the tensile strength of the rock in sedimentary bodies whose water is overpressured the pore pressure should be governed by the least compressive stress and thus migration should begin by oil transfers in a system of small open fractures and eventually in larger fractures the theory demonstrates the impossibility of oil being transferred to the reservoir under true tensile conditions negative effective compressive stress and thus explains the large asphaltic veins of southeastern turkey and the well known bitumen veins of the uinta basin

characteristics of west african and east atlantic cloud clusters a survey from gate abstract this article describes the size intensity trajectory lifetime and distribution of the gate cloud clusters of west africa and the eastern atlantic ocean and relates their distribution to the summer climate of the region sms 1 infrared and visible 3 h pictures for 85 days of gate starting 27 june 1974 were used it was found that over 500 clusters occurred size averaged 2 105 km2 lifetime one day although both were highly variable in general lifetime increased with maximum size the clusters occurred in a band oriented west southwest to east northeast over the ocean and eastward over land nodes were observed at intervals of 5 7 along the axis of maximum frequency of occurrence clusters at all latitudes moved generally westward having straighter tracks and faster speeds over land from july to september the axis of the cluster band shifted northward 100 300 km and tended to split over the ocean clusters on the northern flank of the band were associated with african easterly waves

evaluation of the model representation of the evolution of convective systems using satellite observations of outgoing longwave radiation 1 we introduce a technique for assessing the diurnal development of convective storm systems based on outgoing longwave radiation fields using the size distribution of the storms measured from a series of images we generate an array in the length scale time domain based on the standard score statistic it demonstrates succinctly the size evolution of storms as well as the dissipation kinematics it also provides evidence related to the temperature evolution of the cloud tops we apply this approach to a test case comparing observations made by the geostationary earth radiation budget instrument to output from the met office unified model run at two resolutions the 12 km resolution model produces peak convective activity on all length scales significantly earlier in the day than shown by the observations and no evidence for storms growing in size the 4 km resolution model shows realistic timing and growth evolution although the dissipation mechanism still differs from the observed data citation pearson k j r j hogan r p allan g m s lister and c e holloway 2010 evaluation of the model representation of the evolution of convective systems using satellite observations of outgoing longwave radiation j geophys res 115 d20206 doi 10 1029 2010jd014265

organic matter pores and oil generation in the tuscaloosa marine shale the upper cretaceous tuscaloosa marine shale tms is an oil play across central louisiana and southwest mississippi the lower tms is characterized by relatively high log resistivity 5 ohm m compared to the upper part and this elevated resistivity zone erz has become the primary target zone this study is to investigate the cause of variation in log resistivity based on the data of petrography mineralogy and organic matter property and porosity the results suggest that log resistivity is not controlled by mineralogy or porosity rather it is associated with oil generation during organic matter maturation total organic carbon toc content rock eval free hydrocarbon yield s1 and hydrogen index hi in the studied core increase with depth porosity within organic matter om measured by field emission scanning electron microscopy fe sem is also higher within the erz the correlated variations among toc content s1 values om porosity and log resistivity suggest that the higher log resistivity resulted from in situ oil generation and that the om pores were generated during oil generation thermal maturity varies little in the core whereas the downward increasing hi indicates an increasing abundance of oil prone type ii kerogen higher om porosity appears to be related to the greater proportion of type ii kerogen in the erz the data set demonstrates that higher contents of toc and oil prone kerogen are the combined factors for higher oil generation therefore higher log resistivity in the erz the study provides a quantitative relationship between om porosity and oil generation

geochemical evolution of organic rich shales with increasing maturity a stxm and tem study of the posidonia shale lower toarcian northern germany hydrocarbon generation and retention processes occurring within gas shales as a response to increases in thermal maturation are still poorly constrained while efforts have been directed at unravelling the resource potential composition and textures of these economically important unconventional systems their spatial variability in chemistry and structure is still poorly documented at the sub micrometer scale here we have characterized samples of the lower toarcian posidonia shale samples from northern germany at varying stages of thermal maturation using a combination of compositional organic geochemistry and spectromicroscopy techniques including synchrotron based scanning transmission x ray microscopy stxm we document geochemical and mineralogical heterogeneities down to the nanometer scale within the investigated samples as a function of their level of thermal maturity in particular authigenic albite crystals containing nanometric halite inclusions have been documented within the investigated mature and overmature samples the presence of such tracers of palaeobrine carbonate interactions supports a maturation scenario for the lower toarcian posidonia shale intimately related to ascending brine fluids rather than a maturation scenario solely resulting from high heat flows in addition various types of asphaltene and nso rich bitumen have been detected within the same samples very likely genetically derived from thermally degraded organic precursors furthermore the formation of nanoporous pyrobitumen has been inferred for samples of gas window maturity likely resulting from the formation of gaseous hydrocarbons by providing in situ insights into the fate of bitumen and pyrobitumen as a response to the thermal evolution of the macromolecular structure of kerogen the results reported here constitute an important step towards better constraining hydrocarbon generation processes during natural shale gas maturation

air motions and precipitation structure of an early summer squall line over the eastern tropical atlantic abstract the 28 june 1974 squall line over the ship army of the global atmospheric research programme s atlantic tropical experiment gate has been examined aircraft radar satellite sounding and surface data have been employed in the analysis this squall line is the third gate oceanic squall line to have been subjected to intensive case study analysis the vertical air motions and the relative amounts of convective and stratiform rain in this case were similar to those of the other two lines however this squall line moved more slowly without discrete jumps and the horizontal airflow relative to the system was quite different from that associated with the other two lines except at the surface the strong front to rear relative flow normal to the line observed at most levels in the other cases was absent with the relative flow tending instead to be parallel to the line in the low to middle troposphere relative flow parallel to the line from the north fed a post squall mesoscale downdraft in t

observed structure of mesoscale convective systems and implications for large scale heating mesoscale convective cloud systems that produce large amounts of rain in mid latitudes and most of the rain in the tropics consist of a combination of convective and stratiform cloud the convective regions contain numerous deep cells that are often but not always arranged in lines the stratiform region is an outgrowth of the convective ensemble it lies adjacent to the convective region and is seeded by ice particles detrained from convective towers sometimes it lies to the rear of a propagating convective line while on other occasions it surrounds the convection the heating of the large scale environment by a mesoscale convective system is affected by both the convective and stratiform regions although processes such as melting and radiation are important the net heating by a system is dominated by condensation and evaporation associated with vertical air motions this paper reviews recent observational evidence regarding the mean vertical motion profiles in the convective and stratiform regions of mesoscale convective systems and the implications of these mean motions for the vertical distribution of heating of the large scale environment in both the convective and the stratiform regions vertical motions have been determined by various techniques including composites of rawinsonde and aircraft wind data single and dual doppler precipitation radar analyses and wind profiler observations in stratiform regions these data consistently show mean vertical velocity that is upward in the upper troposphere and downward in the lower troposphere the level separating upward from downward motion is located from 0 to 2 km above the 0 c level depending on location within the stratiform region diagnostic calculations show that these vertical motion profiles imply heating of the upper troposphere and cooling of lower levels by stratiform region processes data on vertical motions in the convective regions are less consistent from case to case these data sometimes indicate that the mean vertical velocity in convective regions is maximum in the lower troposphere in other cases the data indicate a maximum in the high troposphere diagnostic calculations show that heating profiles diagnosed from these two types of profile are quite different the first having a maximum of heating in the lower troposphere while the second has a maximum in the middle troposphere although it is difficult to determine whether or not the differences in estimates arise from different types of observations analysis methods or sampling strategies it seems likely that they stem from differences in the large scale environment of the different mesoscale systems the ubiquitous occurrence of stratiform regions in mesoscale convective systems and hurricanes together with their consistent heating profiles which systematically concentrate heating in upper levels while cooling lower levels are a major consideration in evaluating the interaction of mesoscale systems with the large scale environment however the consistency of the stratiform profiles from case to case indicates that the variability of net convective plus stratiform heating profiles from case to case lies primarily in the variation of the convective region profiles from one case to another it is suggested that future work should focus on the convective region vertical profiles of vertical motion and heating and on the large scale environmental factors that may control the variation of these profiles from case to case

kerogen asphaltene sulfur relationships in sulfur rich monterey oils abstract monterey oils in the santa maria basin onshore and offshore are generally low maturity oils because of low thermal exposure relatively shallow burial for short times they are generated as heavy high sulfur oils because of the composition of the unusual type ii source kerogens which are exceptionally rich in organic sulfur 8 14 these high sulfur kerogens which we designate type ii s appear to generate oil at significantly lower thermal exposures than ordinary type ii kerogens with less than 6 s in contrast to common type ii kerogens which generate oil largely by cleavage at oxygen bridge groups and carbon carbon bonds eliminating co2 h2o and hydrocarbon fragments type ii s kerogens have an additional complement of weak bonds associated with bound sulfur the preferential cleavage at weak sulfur linkages tends to produce larger fragments leading to high initial amounts of asphaltenes resins and sulfur rich aromatics together with smaller amounts of saturated hydrocarbons elemental analyses of monterey kerogens and asphaltenes clearly support the concept that the asphaltenes are essentially fragments of kerogen cleaved sufficiently to be soluble or peptized in this heavy oil system solubilization of asphaltenes is attributed to their interactions with the abundant resins and aromatics this sysstem is sufficiently stable under source and reservoir conditions to allow expulsion and migration for reasonable distance without significant fractionation or changes in gross properties initial asphaltenes have essentially the same atomic h c ratios as the source kerogen but have significantlyy lower o c ratios and slightly lower s c ratios the n c ratios are nearly the same for kerogens and their derived asphaltenes with increasing maturity the h c ratios in asphaltenes decrease much like maturation changes in kerogen the s c ratio also decreases significantly however the o c ratios initially low in asphaltenes and n c ratios increase slightly due to material balance caused by other losses these element composition and atomic ratio relationships allow some important inferences concerning source kerogen composition from analysis of asphaltenes alone this can be useful when potential source rock samples are not available for analysis and or when a choice between alternate source rock possibilities must be made

porosity of devonian and mississippian new albany shale across a maturation gradient insights from organic petrology gas adsorption and mercury intrusion the evolution of porosity in shales with increasing maturity was examined in a suite of five new albany shale samples spanning a maturity range from immature vitrinite reflectance ro 0 35 to postmature ro 1 41 devonian to lower mississippian new albany shale samples from the illinois basin used in this study contain marine type ii kerogen having total organic carbon contents from 1 2 to 13 0 wt organic petrology co2 and n2 low pressure adsorption and mercury intrusion capillary pressure techniques were used to quantify pore volumes pore sizes and pore size distributions increasing maturity of the new albany shale is paralleled by many changes in the characteristics of porosity the total porosity of 9 1 vol in immature new albany shale decreases to 1 5 vol in the late mature sample whereas total pore volumes decrease from 0 0365 to 0 0059 cm3 g in the same sequence reversing the trend at even higher maturity the postmature new albany shale exhibits higher porosity and larger total pore volumes compared to the late mature sample with increasing maturity changes in total porosity and total pore volumes are accompanied by changes in pore size distributions and relative proportions of micropores mesopores and macropores porosity related variances are directly related to differences in the amount and character of the organic matter and mineralogical composition but maturity exerts the dominant control upon these characteristics we conclude that organic matter transformation due to hydrocarbon generation and migration is a pivotal cause of the observed porosity differences

anvil clouds of tropical mesoscale convective systems in monsoon regions the anvil clouds of tropical mesoscale convective systems mcss in west africa the maritime continent and the bay of bengal have been examined with trmm and cloudsat satellite data and arm ground based radar observations the anvils spreading out from the precipitating cores of mcss are subdivided into thick medium and thin portions the thick portions of anvils show distinct differences from one climatological regime to another in their upper portions the thick anvils of west africa mcss have a broad flat histogram of reflectivity and a maximum of reflectivity in their lower portions the reflectivity histogram of the bay of bengal thick anvils has a sharply peaked distribution of reflectivity at all altitudes with modal values that increase monotonically downward the reflectivity histogram of the maritime continent thick anvils is intermediate between that of the west africa and bay of bengal anvils consistent with the fact this region comprises a mix of land and ocean influences it is suggested that the difference between the statistics of the continental and oceanic anvils is related to some combination of two factors 1 the west african anvils tend to be closely tied to the convective regions of mcss while the oceanic anvils are more likely to be extending outward from large stratiform precipitation areas of mcss and 2 the west african mcss result from greater buoyancy so that the convective cells are more likely to produce graupel particles and detrain them into anvils copyright 2009 royal meteorological society

the west african squall line observed on 23 june 1981 during copt 81 kinematics and thermodynamics of the convective region abstract the squall line observed during the night of 23 24 june 1981 was one of the most intense events during the copt 81 convection profonde tropicale experiment conducted in may and june 1981 at korhogo in the northern ivory coast by french and ivorian research institutes the presquall environment possessed a very large convective instability with a stable layer in the lowest levels the presence of dry air in the midlevels which promoted the development of convective downdrafts and the unusually low altitude of the strong easterly winds which aided the development of a leading anvil above 6 km are two noteworthy characteristics of the environment of this squall line its mesoscale structure as deducted from radar data is similar to that previously observed for tropical squall lines convective updrafts and downdraft occur in the leading heavy precipitation region convective region and a mesoscale updraft and downdraft is found within and below the trailing mid to upper level anvil clouds

relationships between lightning and properties of convective cloud clusters 1 satellite observations of convective system properties and lightning flash rate are used to investigate the ability of potential lightning parameterizations to capture both the dominant land ocean contrast in lightning occurrence and regional differences between africa the amazon and the islands of the maritime continent as found in previous studies the radar storm height is tightly correlated with the lightning flash rate a roughly second order power law fit to the mean radar echo top height above the 0 c isotherm is shown to capture both regional and land ocean contrasts in lightning occurrence and flash rate using a single set of parameters recent developments should soon make it possible to implement a parameterization of this kind in global models parameterizations based on cloud top height convective rain rate and convective rain fraction all require the use of separate fits over land and ocean and fail to capture observed differences between continental regions

a practical model for organic richness from porosity and resistivity logs a practical method the delta log r technique for identifying and calculating total organic carbon in organic rich rocks has been developed using well logs the method employs the overlaying of a properly scaled porosity log generally the sonic transit time curve on a resistivity curve preferably from a deep reading tool in water saturated organic lean rocks the two curves parallel each other and can be overlain since both curves respond to variations in formation porosity however in either hydrocarbon reservoir rocks or organic rich non reservoir rocks a separation between the curves occurs using the gamma ray curve reservoir intervals can be identified and eliminated from the analysis the separation in organic rich intervals results from two effects the orosity curve responds to the presence of low density low velocity kerogen and the resistivity curve responds to the formation fluid in an immature organic rich rock where no hydrocarbons have been generated the observed curve separation is due solely to the porosity curve response in mature source rocks in addition to the porosity curve response the resistivity increases because of the presence of generated hydrocarbons the magnitude of the curve separation in non reservoirs is calibrated to total organic carbon and maturity and allows for depth profiling of organic richness in the absence of sample data this method allows organic richness to be accurately assessed in a wide variety of lithologies and maturities using common well logs

mesoscale convective systems 1 mesoscale convective systems mcss have regions of both convective and stratiform precipitation and they develop mesoscale circulations as they mature the upward motion takes the form of a deep layer ascent drawn into the mcs in response to the latent heating and cooling in the convective region the ascending layer overturns as it rises but overall retains a coherent layer structure a middle level layer of inflow enters the stratiform region of the mcs from a direction determined by the large scale flow and descends in response to diabatic cooling at middle to low levels a middle level mesoscale convective vortex mcv develops in the stratiform region prolongs the mcs and may contribute to tropical cyclone development the propagation of an mcs may have a discrete component but may further be influenced by waves and disturbances generated both in response to the mcs and external to the mcs waves of a larger scale may affect the propagation velocity by phase locking with the mcs in a cooperative mode the horizontal scale of an mcs may be limited either by a balance between the formation rate of convective precipitation and dissipation of stratiform precipitation or by the rossby radius of the mcv the vertical redistribution of momentum by an mcs depends on the size of the stratiform region while the net vertical profile of heating of the large scale environment depends on the amount of stratiform rain regional variability of the stratiform rain from mcss affects the large scale circulation s response to mcs heating

recurring patterns of total organic carbon and source rock quality within a sequence stratigraphic framework sequence stratigraphy has been combined with total organic carbon toc analysis from well logs core and cuttings to develop a model of toc accumulation in marine source rocks routine well profiling of toc in marine source rocks has revealed that recurrent patterns in the vertical distribution of toc occur that can be explained with sequence stratigraphic concepts the model assumes that the principle controls on organic carbon accumulation are 1 the presence of low oxygen conditions at the sediment water interface and 2 sedimentation rate under these circumstances toc will vary inversely with terrigenous clastic influx if accommodation is high clastic influx is low in distal locations and the resulting weight percent toc in basinal sediments is increased th maximum toc in a vertical profile through a single marine sequence probably correlates to the maximum flooding surface toc decreases above this surface due to increasing sediment dilution during highstand progradation and decreases below it with the higher sedimentation rate of the older transgressive systems tract commensurate with toc increase towards the maximum flooding surface the organic matter type becomes more marine and therefore increasingly oil prone several marine source rock examples are presented as well as a lacustrine example which also conforms to the marine model

vertical velocity in oceanic convection off tropical australia abstract time series of 1 hz vertical velocity data collected during aircraft penetrations of oceanic cumulonimbus clouds over the western pacific warm pool as part of the equatorial mesoscale experiment emex are analyzed for updraft and downdraft events called cores an updraft core is defined as occurring whenever the vertical velocity exceeds 1 m s 1 for at least 500 m a downdraft core is defined analogously over 19 000 km of straight and level flight legs are used in the analysis five hundred eleven updraft cores and 253 downdraft cores are included in the dataset core properties are summarized as distributions of average and maximum vertical velocity diameter and mass flux in four altitude intervals between 0 2 and 5 8 km distributions are approximately lognormal at all levels examination of the variation of the statistics with height suggests a maximum in vertical velocity between 2 and 3 km slightly lower or equal vertical velocity is indicated at 5 km near the freezing level virtual t

precipitation and mesoscale convective systems explicit versus parameterized convection over northern africa abstractprecipitating systems are analyzed during a dust event from 9 to 14 june 2006 over northern africa a common analysis is applied to satellite observations and two meso nh simulations one c

environments of deposition and petroleum geology of tuscaloosa group upper cretaceous south carlton and pollard fields southwestern alabama in southwestern alabama the lower tuscaloosa group upper cretaceous consists of two informally defined units the massive and pilot sand intervals the massive sand interval accumulated principally as sands in a wave dominated high destructive delta system these sandstones are structureless well sorted micaceous locally fossiliferous calcareous glauconitic fine grained and quartz rich containing angular to subangular quartz grains the massive sand interval unconformably overlies fluvial deltaic sediments of lower cretaceous strata the pilot sand interval which overlies the massive sand interval accumulated as shelf sands and clays during a marine transgression the sandstones are well sorted micaceous fossiliferous calcareous glauconitic very fine to fine grained and quartz rich containing sub angular to subrounded quartz grains the sandstones appear massive but may be structureless as a result of extensive bioturbation marine bivalves such as inoceramids are present in the sandstones and claystones the pilot sand interval is overlain by a marine claystone marine shale containing a diverse faunal assemblage of macroinvertebrates including ammonites inoceramids and other bivalves and a rich microfossil assemblage of planktonic foraminifera and calcareous nannofossils the marine shale accumulated in an open marine shelf environment petroleum traps in the tuscaloosa are structural traps involving salt anticlines south carlton field and extensional fault traps associated with salt movement pollard field reservoir grade porosity occurs in the massive and pilot sandstone units as primary intergranular porosity although tuscaloosa marine claystones contain significant amounts of organic carbon these rocks are thermally too immature to be the petroleum source rocks for the tuscaloosa crude oils in south carlton and pollard fields

identification of source rocks on wireline logs by density resistivity and sonic transit time resistivity crossplots source rock formations generally show a lower density a lower sonic transit time and a higher resistivity than other sediments of equal compaction and comparable mineralogy this phenomenon can be used to identify source rocks on wireline logs provided the source rocks have a minimum thickness within the resolution of the sondes used and are sufficiently rich in organic matter classification rules have been established to assist in the recognition of source rocks on a combination of logs because of the low density contrast between water and organic matter the method becomes inaccurate at high water saturations i e low compaction within limits the amount of organic matter contained in a sediment can be estimated from log anomalies when source rocks become mature free oil is present in addition to kerogen and the resistivity increases by a factor of 10 or more

life cycle variations of mesoscale convective systems over the americas abstract using goes 7 isccp b3 satellite data for 1987 88 the authors studied the evolution of the morphological and radiative properties of clouds over the life cycles of deep convective systems cs over the americas at both tropical and middle latitudes a deep convective cloud system is identified by adjacent satellite image pixels with infrared brightness temperatures tir 245 k 28 c that at some time contain embedded convective clusters that are defined by pixel values of tir 218 k 55 c the first part of the analysis computes parameters for each convective system that describe the system areal size number of convective clusters fractional convective area average and maximum size of the convective clusters shape eccentricity and orientation mean tir variance of tir tir gradient and the mean variance and gradient of collocated visible reflectances when available the second part of the analysis searches a 5 5 region centered on each convective system but in the subsequent

gregarious tropical convection abstract a beat source with a vertical profile like that of observed tropical mesoscale convective systems mcss is shown to cause through inviscid gravity wave dynamics upward displacement at low levels in a mesoscale region surrounding the heating typical values are 10 30 area contraction at the surface everywhere within 270 km of the heating 6 h after it starts as a result conditions near an existing mcs but beyond the area of mcs outflow become more favorable for the development of additional convection this theory predicts that cloud clusters should be gregarious infrared satellite imagery confirms that almost half of the cold cloudiness observed in a month over the oceanic warm pool region was contributed by just 14 objectively defined multiday supercluters

comment on formation of nanoporous pyrobitumen residues during maturation of the barnett shale fort worth basin by bernard et al 2012 abstract in their 2012 paper discussing the character of pores and organic matter in the mississippian barnett shale bernard et al 2012 identified only nonporous kerogen and nonporous solid bitumen in oil window maturity samples but nanoporous pyrobitumen in gas window maturity samples our examination of samples from the same wells shows that pores are also present in organic matter from oil window maturity samples we also argue that some of the pores we identified in gas window maturity samples are developed in organic matter that is unlikely to be pyrobitumen

multiscale variability of deep convection in relation to large scale circulation in toga coare deep convection over the indo pacific oceanic warm pool in the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare occurred in cloud clusters which grouped together in regions favoring their occurrence these large groups of cloud clusters produced large scale regions of satellite observed cold cloud top temperature this paper investigates the manner in which the cloud clusters were organized on time and space scales ranging from the seasonal mean pattern over the whole warm pool region to the scale of individual cloud clusters and their relationship to the large scale circulation and sea surface temperature sst the dominant convective variability was associated with the intraseasonal oscillation iso a large eastward propagating ensemble of cloud clusters marked the iso s progress the meridional structure of the iso was strongly affected by the seasonal cycle with a southward shift from the northern hemisphere in october november to the southern hemisphere in january february the sst had an intraseasonal signal in lagged quadrature with the cold cloudiness and rainfall in coare the sst increased decreased during the convectively suppressed active phases of the iso enhanced low level westerly winds occurred toward the later stages of the enhanced convection periods of the iso though not always centered at the equator the strongest westerlies tended to be located between two synoptic scale cyclonic gyres which were often not symmetric about the equator in the low level wind field this asymmetry in the anomalous equatorial low level westerlies may have different implications for the oceanic response in the coupled atmosphere ocean system than those centered on the equator the cyclonic gyres contained highly concentrated deep convection and in four cases the gyres developed into tropical cyclones within the envelope marking the convectively active phase of the iso cloud clusters were frequently concentrated into westward propagating disturbances with a local periodicity of similar to 2 days these 2 day disturbances have been identified in earlier spectral studies and appear to be related to westward propagating inertio gravity waves in coare they typically contained numerous cloud clusters which underwent a distinct diurnal cycle most of the cloud clusters embedded in the 2 day disturbances moved westward though some were stationary and a few moved eastward a cloud duster tracking program identified groups of clusters lime dusters that exhibited continuity in time and space in the most convectively active period of the iso the tracking program identified almost the entire iso cloud ensemble as a long lasting trackable superconvective system this observation indicates the lack of a distinct scale separation between convection and large scale disturbances during the most intense convective periods in coare

extreme convection of the near equatorial americas africa and adjoining oceans as seen by trmm abstractthis study documents the preferred location and diurnal cycle of extreme convective storms that occur in the tropical band containing the east pacific ocean central and south america the atlantic ocean and northern africa data from the tropical rainfall measuring mission trmm precipitation radar show three types of convective stratiform structures that constitute extreme convective events deep convective cores dccs wide convective cores wccs and broad stratiform regions bsrs interim ecmwf re analysis era interim data show the associated synoptic environmental factors associated with the occurrence of extreme convective features the dcc wcc and bsr echoes are associated with early middle and late stages of convective system development respectively and the statistics and timing of their occurrence are related to topography and life cycle behavior of the convection storms containing dcc occur primarily over the sudanian savannas of africa and near the mountains in northern

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

microstructural investigation of gas shales in two and three dimensions using nanometer scale resolution imaging the microstructure of gas shale samples from nine different formations has been investigated using a combination of focused ion beam fib milling and scanning electron microscopy sem backscattered electron bse images of fib cross sectioned shale surfaces show a complex microstructure with variations observed among the formations energy dispersive spectroscopy of the shale cross sections indicates that clay carbonate quartz pyrite and kerogen are the most prevalent components in the bse images areas of kerogen are observed interspersed with the inorganic grains pores are observed in both the kerogen and inorganic matrix with the size shape and number of pores varying among the shale samples by using fib milling and sem imaging sequentially and repetitively three dimensional 3 d data sets of sem images have been generated for each of the shale samples three dimensional volumes of the shales are reconstructed from these images by setting thresholds on the gray scale the kerogen and pore networks are segmented out and visualized in the reconstructed shale volumes estimates of kerogen and pore volume percentages of the reconstructed shale volumes have been made and range from 0 to 90 0 for the kerogen and 0 2 to 2 3 for pores estimates of pore size distributions suggest that although pores with radii of approximately 3 nm dominate in number they do not necessarily dominate in total volumetric contribution scanning electron microscopy images and 3 d reconstructions reinforce the facts that shales are quite different and that their microstructures are highly variable and complex

climatology and formation of tropical midlevel clouds at the darwin arm site abstracta 4 yr climatology of midlevel clouds is presented from vertically pointing cloud lidar and radar measurements at the atmospheric radiation measurement program arm site at darwin australia few studies exist of tropical midlevel clouds using a dataset of this length seventy percent of clouds with top heights between 4 and 8 km are less than 2 km thick these thin layer clouds have a peak in cloud top temperature around the melting level 0 c and also a second peak around 12 5 c the diurnal frequency of thin clouds is highest during the night and reaches a minimum around noon consistent with variation caused by solar heating using a 1 5 yr subset of the observations the authors found that thin clouds have a high probability of containing supercooled liquid water at low temperatures 20 of clouds at 30 c 50 of clouds at 20 c and 65 of clouds at 10 c contain supercooled liquid water the authors hypothesize that thin midlevel clouds formed at the melting level are formed differen