the prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models the accuracy of the predictions of distributed hydrological models must depend in part on the proper specification of flow pathways this paper examines some of the problems of deriving flow pathways from raster digital terrain data in the context of hydrological predictions using topmodel distributed moisture status is predicted in topmodel on the basis of spatial indices that depend on flow path definition the sensitivity of this index to flow path algorithm and grid size is examined for the case where the surface topography is a good indicator of local hydraulic gradients a strategy for the case where downslope subsurface flow pathways may deviate from those indicated by the surface topography is described with an example application

improvements in large scale drainage networks derived from digital elevation models 1 this paper presents an improved algorithm for deriving drainage networks for coarse gridded distributed hydrological models based on relatively fine resolution digital elevation models the proposed algorithm aims to reproduce actual drainage networks more closely when applied in regions with meandering rivers running in parallel and for cell sizes of the order of 10 kilometers to achieve this goal the cotat algorithm of reed 2003 was improved introducing another parameter related to the minimum upstream flow path into the cell besides the area threshold the proposed algorithm was tested by applying it to the catchments of the rivers tapajos 530 000 km 2 and grande 145 000 km 2 in south america results show that drainage networks are generally improved by the proposed algorithm needing only minor manual corrections

drizzle in stratiform boundary layer clouds part ii microphysical aspects abstract this is the second of two observational papers examining drizzle in stratiform boundary layer clouds part i details the vertical and horizontal structure of cloud and drizzle parameters including some bulk microphysical variables in this paper the focus is on the in situ size resolved microphysical measurements particularly of drizzle drops r 20 m layer averaged size distributions of drizzle drops within cloud are shown to be well represented using either a truncated exponential or a truncated lognormal size distribution the size resolved microphysical measurements are used to estimate autoconversion and accretion rates by integration of the stochastic collection equation sce these rates are compared with a number of commonly used bulk parameterizations of warm rain formation while parameterized accretion rates agree well with those derived from the sce initialized with observed spectra the autoconversion rates seriously disagree in some cases these disagreements need to be addr

cloud radar doppler spectra in drizzling stratiform clouds 1 forward modeling and remote sensing applications 1 several aspects of spectral broadening and drizzle growth in shallow liquid clouds remain not well understood detailed cloud scale observations of microphysics and dynamics are essential to guide and evaluate corresponding modeling efforts profiling millimeter wavelength cloud radars can provide such observations in particular the first three moments of the recorded cloud radar doppler spectra the radar reflectivity mean doppler velocity and spectrum width are often used to retrieve cloud microphysical and dynamical properties such retrievals are subject to errors introduced by the assumptions made in the inversion process here we introduce two additional morphological parameters of the radar doppler spectrum the skewness and kurtosis in an effort to reduce the retrieval uncertainties a forward model that emulates observed radar doppler spectra is constructed and used to investigate these relationships general analytical relationships that relate the five radar observables to cloud and drizzle microphysical parameters and cloud turbulence are presented the relationships are valid for cloud only cloud mixed with drizzle and drizzle only particles in the radar sampling volume and provide a seamless link between observations and cloud microphysics and dynamics the sensitivity of the five observed parameters to the radar operational parameters such as signal to noise ratio and doppler spectra velocity resolution are presented the predicted values of the five observed radar parameters agree well with the output of the forward model the novel use of the skewness of the radar doppler spectrum as an early qualitative predictor of drizzle onset in clouds is introduced it is found that skewness is a parameter very sensitive to early drizzle generation in addition the significance of the five parameters of the cloud radar doppler spectrum for constraining drizzle microphysical retrievals is discussed

north pacific cloud feedbacks inferred from synoptic scale dynamic and thermodynamic relationships abstract daily satellite cloud observations and reanalysis dynamical parameters are analyzed to determine how midtropospheric vertical velocity and advection over the sea surface temperature gradient control midlatitude north pacific cloud properties optically thick clouds with high tops are generated by synoptic ascent but two different cloud regimes occur under synoptic descent when vertical motion is downward during summer extensive stratocumulus cloudiness is associated with near surface northerly wind while frequent cloudless pixels occur with southerly wind examination of ship reported cloud types indicates that midlatitude stratocumulus breaks up as the boundary layer decouples when it is advected equatorward over warmer water cumulus is prevalent under conditions of synoptic descent and cold advection during winter poleward advection of subtropical air over colder water causes stratification of the near surface layer that inhibits upward mixing of moisture and suppresses cloudiness until a

origin of highly elongate calcite cemented concretions in some italian coastal beach and dune sands abstract highly elongate vertical and horizontal calcite cemented concretions in pleistocene shallow marine and coastal eolian sandstones are mixtures of terrigenous sand and carbonate biogenic grains cemented to various degrees by low mg calcite petrographic and stable carbon and oxygen isotopic data support the earlier hypothesis of mazzanti and parea 1979 that vertically oriented concretions formed by the precipitation of vadose meteoric water percolating downward toward the water table and that horizontal concretions were precipitated from phreatic groundwater flowing toward the coast many vertical concretions started growth as rhizocretions composed of micrite but enlarged and coalesced when equant sparry calcite was precipitated from percolating vadose water horizontal concretions cemented entirely by subequant calcite spar have coalesced into nearly completely cemented beds decimeter scale domains of curved horizontal concretion elements reflect the influence of adjacent phreatic flow domains each with their own particular flow paths aragonite and high mg calcite shells in the sands were the main source of carbon in calcite cement isotopically depleted 13c values of bulk samples 6 to 8 5o oo v pdb however require the input of a light carbon source probably soil co2 18o values of bulk samples are compatible with cementation chiefly by meteoric water at temperatures between 7 and 22 c the values are typical of air and inferentially groundwater temperatures today

influence of host rock texture on the morphology of carbonate concretions in a meteoric diagenetic environment abstract the integrated stratigraphic petrographic geochemical study of quaternary marine terraces that have undergone well constrained sea level and water table oscillation s over geologically short time periods can provide important clues on diagenetic processes at the marine continental interface the punta di i cani marine terrace quaternary saint florent corsica unconformably overlies the well cemented low permeability arenites of the miocene monte s angelo formation and is erosively overlain by unlithified high permeability holocene continental sediments the terrace is composed of a retrogradational fining upward succession from fluvial pebbly sandstone to beach and shoreface deposits the entire thickness of the terrace hosts concretions made of low mg calcite concretion geometry is linked to the sedimentological facies of the host sediment i massive fluvial pebbly sandstone at the base of the terrace contains knobby subhorizontal concretions somewhat resembling turbidite flute casts ii very low angle cross bedded well sorted beach deposits contain pipy subhorizontal concretions iii trough crossbedded upper shoreface deposits in the upper part of the terrace contain a subtle diagenetic lineation on the laminae locally obliterated by a patchy isotropic cementation overall the degree of cementation decreases from the bottom to the top of the terrace cement chemistry and morphology as well as stable carbon and oxygen isotopic signatures indicate that the concretions formed by precipitation of meteoric phreatic water flowing toward the coast elongate concretions are invariably parallel to the topographic gradient consistent with the notion that the growth of concretions was controlled by advection smectitic vadose cement is locally present its crosscutting relationships with calcite cement point to periodic oscillations of the water table the results of this study i show that elongate concretions can be used as interstitial paleoflow indicators and ii suggest that concretion geometry in an advection dominated diagenetic environment can depend on the small scale permeability distribution as suggested by the fact that each type of concretion is invariably associated with a specific sedimentary facies

observational constraints on the cloud thermodynamic phase in midlatitude storms the conditions under which supercooled liquid water gradually gives way to ice in the mixed phase regions of clouds are still poorly understood and may be an important source of cloud feedback uncertainty in general circulation model projections of long term climate change two winters of cloud phase discrimination cloud top temperature sea surface temperature and precipitation from several satellite datasets the nasa terra and aqua moderate resolution imaging spectroradiometer and the tropical rainfall measuring mission for the north atlantic and pacific ocean basins are analyzed to better understand these processes reanalysis surface pressures and vertical velocities are used in combination with a synoptic storm tracking algorithm to define storm tracks create composite storm dynamical and cloud patterns and examine changes in storm characteristics over their life cycles characteristically different storm cloud patterns exist in the atlantic and pacific and on the west and east sides of each ocean basin this appears to be related to the different spatial patterns of sea surface temperature in the two ocean basins glaciation occurs at very warm temperatures in the high thick heavily precipitating clouds typical of frontal ascent regions except where vertical velocities are strongest similar to previous field experiments outside frontal regions however where clouds are shallower supercooled water exists at lower cloud top temperatures this analysis is the first large scale assessment of cloud phase and its relation to dynamics on climatologically representative time scales it provides a potentially powerful benchmark for the design and evaluation of mixed phase process parameterizations in general circulation models and suggests that assumptions made in some existing models may negatively bias their cloud feedback estimates

reply to comments on a cloudsat calipso view of cloud and precipitation properties across cold fronts over the global oceans abstractin naud et al a compositing method was utilized with cloudsat calipso observations to obtain mean transects of cloud vertical distribution and surface precipitation across cold fronts and to examine their sensitivity to the large scale properties of the parent extratropical cyclone this reply demonstrates the value of compositing for evaluating numerical models and presents additional results that address the issue of the sensitivity of the initial results to the frontal detection methodology and the potential misclassification of occlusions as cold fronts here a sensitivity study of the cold front composite transects of cloud cover to the input datasets or the method utilized to locate the cold fronts demonstrates that these composite transects are robust and only marginally sensitive to cold front location methods the same conclusion is reached for the robustness of the contrast between northern and southern hemisphere cloud transects while occlusions cannot directly be flagged within th

nannobacterial alteration of pyroxenes in martian meteorite allan hills 84001 in martian meteorite allan hills alh 84001 this scanning electron microscope study was focused on the ferromagnesian minerals which are extensively covered with nanometer size bodies mainly 30 100 nm in diameter these bodies range from spheres to ovoids to caterpillar shapes and resemble both in size and shape nannobacteria that attack weathered rocks on earth and that can be cultured dense colonies alternate with clean smooth cleavage surfaces possibly formed later statistical study shows that the distribution of presumed nannobacteria is very clustered in addition to the small bodies there are a few occurrences of ellipsoidal 200 400 nm objects that are within the lower size range of normal earthly bacteria we conclude that the nanobodies so abundant in alh 84001 are indeed nannobacteria confirming the initial assertion of mckay et al 1996 however whether these bodies originated on mars or are antarctic contamination remains a valid question

boundary layer cloud and drizzle variability in the southeast pacific stratocumulus regime abstract the southeast pacific stratocumulus regime is an important component of the earth s climate system because of its substantial impact on albedo observational studies of this cloud regime have been limited but during the past 5 yr a series of cruises with research vessels equipped with in situ and remote sensing systems have provided unprecedented observations of boundary layer cloud and drizzle structures these cruises started with the east pacific investigation of climate epic 2001 field experiment followed by cruises in a similar area in 2003 and 2004 pan american climate studies pacs stratus cruises the sampling from these three cruises provides a sufficient dataset to study the variability occurring over this region this study compares observations from the 2004 cruise with those obtained during the previous two cruises observations from the ship provide information about boundary layer structure fractional cloudiness cloud depth and drizzle characteristics this study indicat

do stable isotopes in carbonate cement of mio pleistocene himalayan sediments record paleoecological and paleoclimatic changes non pedogenic carbonates such as carbonate cement and nodules in the sandstones are quite common in the terrestrial geological record unlike pedogenic carbonates their stable isotope ratios lack investigations for paleo climatic reconstructions the present investigation therefore explores the possibility of use of stable isotope studies of non pedogenic carbonates from the mb pleistocene siwalik group of sediments exposed in the ramnagar sub basin of the nw himalaya petrographic studies reveal the dominance of micrite fabric in carbonate nodules both of pedogenic and non pedogenic samples irrespective of specific stratigraphic unit however calcite as cement in the sandstones shows the dominance of micrite fabric in the younger in age sediments seventy two non pedogenic carbonate samples from the carbonate nodules and cement in the siwalik sandstones ranging in age between similar to 1 ma and 12 2 ma were analyzed for delta c 13 and delta o 18 values the delta c 13 values vary from 24 77 parts per thousand to 1 1 parts per thousand and delta o 18 values vary from 15 34 parts per thousand to 7 81 parts per thousand pedogenic and non pedogenic carbonates ranging in age between similar to 1 ma and 6 ma have largely similar delta c 13 values and the range of delta c 13 values indicate the dominance of c 4 type of vegetation however unlike pedogenic carbonates which showed the dominance of c 3 type of vegetation pre 7 ma on the basis of delta c 13 depleted isotopic values singh et al 2011 delta c 13 values are largely enriched in the corresponding aged non pedogenic carbonates revealing no information on specific type of vegetation likewise paleoprecipitational reconstructions from delta o 18 values in pedogenic carbonates showed a progressive increase in aridity from similar to 12 ma to recent excluding short term increases in rainfall monsoon intensity at around 10 ma 5 ma and 1 8 ma singh et al 2012 on the contrary such reconstructions are not possible from the delta o 18 values of non pedogenic carbonates and indeed the delta o 18 values of non pedogenic carbonates are largely depleted to as much as 6 parts per thousand from the corresponding pedogenic carbonates such differences in delta c 13 and delta o 18 values of non pedogenic carbonates from pedogenic carbonates are primarily due to the dependence of the former on groundwater conditions responsible for precipitating carbonate further a comparison of isotopic values between non pedogenic and pedogenic carbonates can be interpreted that post 6 ma and pre 6 ma non pedogenic carbonates were largely formed by shallow and deep groundwater conditions respectively the result of these investigative studies therefore suggests that the stable delta c 13 and delta o 18 values of non pedogenic carbonates unlike the pedogenic carbonates and irrespective of nature of calcite fabric showed their little importance in paleoclimatic and paleoecological reconstructions c 2014 elsevier b v all rights reserved

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

origin of spheroidal chert nodules drunka formation lower eocene egypt chert nodules of the drunka formation lower eocene are mostly spherical have diameters from 40 to 120 cm are quasi uniformly spaced 2 3 m apart in the plane of bedding have concentric internal structure and except for rare small 6 cm solid chert nodules are less than 85 chertified nodules formed after moderate alteration of limestone by meteoric water 18ocalcite 4 to 8 at shallow 100 m burial depths more extensive alteration of limestone 18o 10 to 16 by meteoric water followed nodule growth chertification was by low temperature meteoric water 18oquartz 18 in margins to 22 in nuclei at shallow burial depths meteoric water may have invaded the drunka formation in association with shelf progradation during the early eocene or during the development of a middle eocene unconformity replacement of carbonate mud by microcrystalline quartz was the dominant chertification process but fossils were replaced in part by fine grained equant megaquartz quartzine and chalcedony the last of these occurs in places as beekite opal a secreting marine organisms are the inferred source of silica but none are preserved there is no compelling evidence of an opal ct precursor so quartz may have formed by direct precipitation self organization processes of enigmatic character established the spacing pattern of the nodules and also the liesegang banded internal structure of the chert nodules nodules grew chiefly by diffusive supply of silica although one locality has elongate nodules that grew when there was some porewater advection chertification patterns and 18o values of both calcite and quartz indicate that nodule growth was complex and variable some nodules probably grew from the centre outwards many nodules however initially grew simultaneously across the entire nodule but late stage growth was predominantly at the outer margins or at selective internal sites

evaluation of the hydrometeor layers in the east and west pacific within isccp cloud top pressure optical depth bins using merged cloudsat and calipso data abstractthe international satellite cloud climatology project isccp provides a multidecadal and global description of cloud properties that are often grouped into joint histograms of column visible optical depth and effective cloud top pressure ptop it has not been possible until recently to know the actual distributions of hydrometeor layers within the isccp ptop bins distributions of hydrometeor layers within the isccp ptop conditional probability space using measurements from the cloudsat cloud profiling radar and the cloud aerosol lidar and infrared pathfinder satellite observations calipso lidar within two 40 40 regions in the eastern and western equatorial pacific over a 2 yr period are examined with the exception of thin cirrus and stratocumulus the authors show that of the ptop types that are commonly analyzed none of the types contain unique distributions of geometrically defined layer types but tend to be populated by diverse sets of hydrometeor layers whose bulk profile pro

mixed phase cloud phase partitioning using millimeter wavelength cloud radar doppler velocity spectra retrieving and quantifying cloud liquid drop contributions to radar returns from mixed phase clouds remains a challenge because the radar signal is frequently dominated by the returns from the ice particles within the radar sample volume we present a technique that extracts the weak cloud liquid drop contributions from the total radar returns in profiling cloud radar doppler velocity spectra individual spectra are first decomposed using a continuous wavelet transform the resulting coefficients of which are used to identify the region in the spectra where cloud liquid drops contribute by assuming that the liquid contribution to each doppler spectrum is gaussian shaped and centered on an appropriate peak in the wavelet coefficients the cloud liquid drop contribution may be estimated by fitting a gaussian distribution centered on the velocity of this peak to the original doppler spectrum the cloud liquid drop contribution to reflectivity the volume mean vertical air motion subvolume vertical velocity variance and ice particle mean fall speed can be estimated based on the separation of the liquid contribution to the radar doppler spectrum the algorithm is evaluated using synthetic spectra produced from output of a state of the art large eddy simulation model study of an arctic mixed phase cloud the retrievals of cloud liquid drop mode reflectivities were generally consistent with the original model values with errors less than a factor of 2 the retrieved volume mean vertical air velocities reproduced the updraft and downdraft structures but with an overall bias of approximately 0 06 m s 1 retrievals based on ka band atmospheric radiation measurement program zenith radar observations from barrow alaska during october 2011 are also presented

the spatial distribution and evolution characteristics of north atlantic cyclones a climatology of extratropical cyclones is produced using an objective method of identifying cyclones based on gradients of 1 km height wet bulb potential temperature cyclone track and genesis density statistics are analyzed and this method is found to compare well with other cyclone identification methods the north atlantic storm track is reproduced along with the major regions of genesis cyclones are grouped according to their genesis location and the corresponding lysis regions are identified most of the cyclones that cross western europe originate in the east atlantic where the baroclinicity and the sea surface temperature gradients are weak compared to the west atlantic east atlantic cyclones also have higher 1 km height relative vorticity and lower mean sea level pressure at their genesis point than west atlantic cyclones this is consistent with the hypothesis that they are secondary cyclones developing on the trailing fronts of preexisting parent cyclones the evolution characteristics of composite west and east atlantic cyclones have been compared the ratio of their upper to lower level forcing indicates that type b cyclones are predominant in both the west and east atlantic with strong upper and lower level features among the remaining cyclones there is a higher proportion of type c cyclones in the east atlantic whereas types a and c are equally frequent in the west atlantic

cloud overlap statistics the u s air force three dimensional nephanalysis 3dneph has been employed to analyze the vertical distribution of clouds and cloud overlap statistics during january 1979 over the north atlantic ocean 40 to 60 n the 3dneph integrates both satellite and conventional observations and gives what is probably the best available information on the vertical distribution of clouds this region was chosen because of the predominance of layered clouds and the high density of conventional observations the grid size of the 3dneph is 45 km and the data set was additionally averaged over three different grid sizes 90 221 and 442 km three cloud overlap assumptions that have been commonly used were tested namely the maximum minimum and random overlap assumptions for adjacent layers of the 3dneph that contained cloud the maximum overlap assumption performed the best accurately determining the total cloud cover to within the roundoff error for the layered cloud amounts in 82 of the cases for two or three cloud layers that were separated by clear interstices the random overlap assumption performed the best overall for all resolutions although there were systematic biases in the predicted cloud fraction which depend on the cloud fraction of the layers and on grid size for grid sizes 9o km random overlap resulted in a systematic underestimation of total cloud cover 5 random overlap performed worst when there were two layers with intermediate cloud fractions 30 70 the results of this study indicate that while random overlap performs reasonably well on average the systematic bias which depends on grid resolution and random discrepancies could result in significant errors when this approximation is used in general circulation modeling and cloud climatologies

observations of vertical velocity skewness within the marine stratocumulus topped boundary layer abstract during june and july 1987 the first isccp international satellite cloud climatology project regional experiment fire was conducted within the marine stratocumulus topped boundary layer off the coast of california one of the goals of the experiment was to investigate the structure of turbulent convection within the fire boundary layers the skewness of vertical velocity has proven to be a very useful statistic in the quest to understand this structure profiles of vertical velocity skewness from three turbulence flights conducted during fire are presented here these three flights were chosen because each represents a distinctly different pattern of vertical velocity skewness the observations of vertical velocity skewness from each of these flights are compared to the skewness statistics derived from a large eddy simulation les of a boundary layer whose profile of buoyancy flux is qualitatively similar to that found on the given fire flight plausible explanations are put forward in an eff

validation and sensitivities of frontal clouds simulated by the ecmwf model abstract clouds simulated by the european centre for medium range weather forecasts ecmwf model are composited to derive the typical organization of clouds surrounding a midlatitude baroclinic system comparison of this composite of about 200 cyclones with that based on satellite data reveals that the ecmwf model quite accurately simulates the general positioning of clouds relative to a low pressure center however the optical depths of the model s high low clouds are too small large relative to the satellite observations and the model lacks the midlevel topped clouds observed to the west of the surface cold front sensitivity studies with the ecmwf model reveal that the error in high cloud optical depths is more sensitive to the assumptions applied to the ice microphysics than to the inclusion of cloud advection or a change of horizontal resolution from 0 5625 to 1 69 lat this reflects the fact that in the ecmwf model gravitational settling is the most rapid process controlling the abundance of ic

mapping outlet points used for watershed delineation onto dem derived stream networks outlet point positions taken from hydrometric stations commonly do not coincide with stream locations extracted from digital elevation models dems this is a serious problem for accurate watershed delineation of data sets containing numerous outlets which is critical in regional scale studies that relate catchment characteristics to basin responses the advanced outlet repositioning approach aora presented here replicates the processes involved in manual outlet placement while reducing inefficiency and potential for blunders the technique uses water body names to identify locations for outlet repositioning that are consistent with nearby outlets the aora performance was compared against two existing automated techniques using 993 stations in seven basins in northwest england the aora had the fewest repositioning errors in each basin and nearly halved the overall number of errors in the data set compared with the second best method this work highlights the potential errors that may be present in studies that have employed existing automated watershed mapping methods

origin of the gypsum rich silica nodules moghra formation northwest qattara depression western desert egypt abstract gypsum rich silica nodules appear in two shale horizons of the moghra formation early miocene northwestern qattara depression western desert egypt these nodules are gray to milky white in colour mostly botroidal and rose like in shape and range in diameter from 2 to 7 5 cm the silica nodule bearing shale is composed mainly of smectite with a little minor kaolinite the silica nodules consist mainly of quartz and are composed of gypsum free matrix and gypsum rich megacrystalline quartz the matrix consists of microflamboyant quartz less than 36 m in diameter and chalcedony the megacrystalline quartz occurs as lenticular and prismatic forms length 90 250 m width 30 90 m the microprobe petrographic and sem examinations confirmed the occurrence of gypsum relics diameter 2 16 m within the megacrystalline quartz the chalcedony and mosaic microcrystalline quartz occurs as pore lining and pore filling cements the structure of the silica nodules begins with quartzine in its outer rim then gypsum free microcrystalline quartz in the middle part and ends with gypsum rich lenticular to prismatic megaquartz in the center field study petrographic examination and microprobe analysis reveal that the silica nodules were formed by silicification of precursor gypsum nodules deposited in a marginal sabkha environment under an arid climate the silicification selectively affected the gypsum nodules rather than the surrounding shale and occurred both through gypsum replacement and void filling transformation of isopachous chalcedony into mosaic microcrystalline quartz also occurred the texture of the silica minerals reflects the different physico chemical conditions under which they crystallized spherical nodules grew chiefly by the diffusive supply of the silica and elongated ones grew by pore water advection the integrated effect of climate ph salinity crack systems within the sediment and oscillation in the groundwater level and its chemical composition contributed to the formation of the nodules

spheroidal cannonballs calcite cemented concretions from the faiyum and bahariya depressions egypt evidence of differential erosion by sand storms

radar observations of updrafts downdrafts and turbulence in fair weather cumuli abstract observations from a 94 ghz radar are used to define the vertical structure of marine fair weather cumuli doppler spectra obtained from the radar provide mean vertical velocities as well as detailed spectral shapes that can be used to infer small scale vertical velocity shear illuminate cloud microphysical processes and provide estimates of turbulence dissipation rates these new observations facilitate the analysis and understanding of in cloud circulations and the physical processes involved since the cloud boundaries and dimensions are mapped along with the internal structure of the clouds coincident observations from a 915 mhz radar wind profiler were used to further define the turbulence structure in and around the clouds the observations document the detailed vertical and horizontal dimensions of updraft and downdraft circulations in the clouds observed the two cumuli studied in detail have similar circulation patterns an updraft core surrounded by downdrafts although the clouds ha

diagenesis of shallowly buried cratonic sandstones southwest sinai egypt abstract in spite of their age quartzose and feldspathic lower carboniferous sandstones deposited on the arabian shield in western sinai remain friable and porous average of 19 maximum of 25 except for strongly cemented ferricretes and silcretes these fluvial and shallow marine sandstones were not buried more than 1 5 km until late cretaceous and younger time when the deepest rocks reached 2 5 km owing to shallow burial depths and episodic exposure meteoric water dominated the pore system for most of geologic time iron oxides had multiple diagenetic stages and yield carboniferous and late cretaceous paleomagnetic signatures and oxygen isotopic data for authigenic quartz sparry calcite and kaolinite yield meteoric signatures the most significant diagenetic changes were 1 cementation by iron oxide that locally reaches 40 in groundwater ferricretes 2 reduction in porosity to 19 from an assumed original porosity 45 19 porosity was lost by compaction and 7 by cementation 3 generation of diagenetic quartzarenites by the loss of 7 detrital feldspar by kaolinization and dissolution and 4 development of three thin mature silcretes apparently by thermal groundwaters some outcrop samples have halite and gypsum cements of young but uncertain origin recycled from topographically higher younger rocks or from aerosols mature silcretes are strongly cemented by microcrystalline quartz multiply zoned syntaxial quartz and originally minor opal quartz overgrowths in most sandstones average only 2 2 but display a variety of textures and in places overprint isopachous opal now dissolved grain coats these features have more in common with incipient silcrete cement than normal burial quartz cement most silica was imported in groundwater

river reach length and slope estimates for large scale hydrological models based on a relatively high resolution digital elevation model application of regular grid based distributed hydrological models requires information related to river drainage networks such as flow directions flow accumulated areas basin delineation and length and slope of river reaches for every grid cell most of those data may be extracted automatically from digital elevation models dem however when dealing with large basins available dems are usually in higher spatial resolution than the model grid upscaling procedures have therefore been developed to extract low resolution flow directions and flow accumulated areas from relatively high resolution dems this paper presents a new methodology which extends the upscaling method to automatically extract length and slope of river reaches for large scale grid based hydrological models the proposed method is new and is believed to be the first attempt to produce such information automatically from dems the methodology was applied to parts of the uruguay river basin in south america using the globally wide available dem produced by the shuttle radar topography mission srtm 90m quality of results was assessed by comparing calculated river lengths with distances measured over vectorized river networks which were assumed to be correct it was shown that the proposed methodology adequately assigns river lengths to every model cell while ensuring that the whole length of the streams is considered the effect of dem resolution on calculated river length errors was analyzed by resampling the srtm dem to three different cell sizes with best results obtained for the higher resolution dem the modification of the original high resolution dem through the process known as stream burning was also tested largely improving the quality of the results finally optimal distance transforms were used for the calculation of distance increments instead of euclidean local distances giving results that were generally better the quality of results for calculated slope values could not be assessed because no reliable data were available for comparison

racoro continental boundary layer cloud investigations 3 separation of parameterization biases in single column model cam5 simulations of shallow cumulus climatically important low level clouds are commonly misrepresented in climate models the fast physics system testbed and research faster project has constructed case studies from the atmospheric radiation measurement climate research facility s southern great plain site during the racoro aircraft campaign to facilitate research on model representation of boundary layer clouds this paper focuses on using the single column community atmosphere model version 5 scam5 simulations of a multi day continental shallow cumulus case to identify specific parameterization causes of low cloud biases consistent model biases among the simulations driven by a set of alternative forcings suggest that uncertainty in the forcing plays only a relatively minor role in depth analysis reveals that the model s shallow cumulus convection scheme tends to significantly under produce clouds during the times when shallow cumuli exist in the observations while the deep convective and stratiform cloud schemes significantly over produce low level clouds throughout the day the links between model biases and the underlying assumptions of the shallow cumulus scheme are further diagnosed with the aid of large eddy simulations and aircraft measurements and by suppressing the triggering of the deep convection scheme it is found that the weak boundary layer turbulence simulated is directly responsible for the weak cumulus activity and the simulated boundary layer stratiform clouds increased vertical and temporal resolutions are shown to lead to stronger boundary layer turbulence and reduction of low cloud biases

a contour based topographic model for hydrological and ecological applications a digital model for discretizing three dimensional terrain into small irregularly shaped polygons or elements based on contour lines and their orthogonals is described from this subdivision the model estimates a number of topographic attributes for each element including the total upslope contributing area element area slope and aspect this form of discretization of a catchment produces natural units for problems involving water flow as either a surface or subsurface flow phenomenon the model therefore has wide potential application for representing the three dimensionality of natural terrain and water flow processes in the fields of hydrology sedimentology and geomorphology three example applications are presented and discussed they are the prediction of zones of surface saturation the prediction of the distribution of potential daily solar radiation and the prediction of zones of erosion and deposition in a catchment

unusual phosphate concretions related to groundwater flow in a continental environment abstract occurrence of phosphate cemented sandstone concretions in alluvial sand containing archaeological layers implies that they have formed during the last 2000 years morphology and petrography of the concretions indicates a relationship with groundwater cementation the phosphate cement of the concretions consists of concentric isopachous aureoles about 10 m thick that wrap the detrital grains aureoles are formed of collophane the cryptocrystalline or amorphous variety of hydroxyapatite geochemical modeling indicates that the apatite cement likely results from the leaching of a preexisting phosphate deposit bones in an acidic soil environment and the precipitation of dissolved phosphate under ph control at the mixing zone of down moving soil water with the calcite saturated groundwater

diagenetic origin of nodules in the sheepbed member yellowknife bay formation gale crater mars the sheepbed member of the yellowknife bay formation in gale crater contains millimeter scale nodules that represent an array of morphologies unlike those previously observed in sedimentary deposits on mars three types of nodules have been identified in the sheepbed member in order of decreasing abundance solid nodules hollow nodules and filled nodules a variant of hollow nodules whose voids have been filled with sulfate minerals this study uses mast camera mastcam and mars hand lens imager mahli images from the mars science laboratory curiosity rover to determine the size shape and spatial distribution of the sheepbed nodules the alpha particle x ray spectrometer apxs and chemcam instruments provide geochemical data to help interpret nodule origins based on their physical characteristics spatial distribution and composition the nodules are interpreted as concretions formed during early diagenesis several hypotheses are considered for hollow nodule formation including origins as primary or secondary voids the occurrence of concretions interpreted in the sheepbed mudstone and in several other sedimentary sequences on mars suggests that active groundwater systems play an important role in the diagenesis of martian sedimentary rocks when concretions are formed during early diagenetic cementation as interpreted for the sheepbed nodules they have the potential to create a taphonomic window favorable for the preservation of martian organics

the distribution and discrimination of shallow authigenic carbonate in the pliocene pleistocene palomas basin southern rio grande rift nine types of authigenic carbonate are present in the pliocene pleistocene alluvial fan and axial fluvial sediment of the palomas half graben in the southern rio grande rift pedogenic and other vadose carbonate includes 1 pedogenic carbonate of stage ii and stage iii morphology underlying bw and bt horizons 2 mudstones in which the carbonate nodules may be pedogenic or the result of shallow groundwater invasion of the vadose zone 3 pedogenic calcic nodules and tubules in eolian sand and 4 gully bed cement of proximal fan conglomerates formed by infiltration and evaporation of surface runoff shallow groundwater carbonate exists as 5 thin 30 50 cm massive beds with an upper fringe of nodules and tubules precipitated at the water table and in the capillary fringe 6 thick 1 5 3 m massive beds deposited by lateral flow of groundwater or at springs and 7 thin 30 cm calcified root mats associated with near surface water saturated sediment or springs phreatic spar cements 8 occupy the interstices of conglomerates and sandstones and locally exist as 9 oriented concretions groundwater carbonates are best developed near the toes of the large hanging wall derived alluvial fans whereas phreatic cement preferentially exists in footwall derived alluvial fan conglomerates pedogenic carbonate is distinguished from groundwater carbonate by the association with other diagnostic paleosol horizons a predominantly vertical arrangement of root traces peds desiccation cracks and calcic tubules and by gradational contacts the 13 c and 18 o values are similar among pedogenic and shallow groundwater carbonate although locally nodules in eolian sand and gully bed cement have higher 18 o values perhaps due to the effects of evaporation some phreatic cements may be distinguished from pedogenic and shallow groundwater carbonate by lower values of 13 c and 18 o authigenic carbonate in footwall derived alluvial fan sediment has consistently higher values of 13 c than that in hanging wall derived sediment which may reflect differences in vegetative type and or density on either side of the basin

cluster analysis of cloud properties over the southern european mediterranean area in observations and a model abstract this paper demonstrates how satellite observations of the cloudiness over a complex area such as the european mediterranean area can be classified into distinct cloud regimes by application of a k means clustering algorithm to pixel level cloud properties the study contrasts with previous approaches in the fact that the clustering is done on the cloud physical properties at the pixel level and not on statistics of these properties over a coarser grid a method to choose the number of clusters is described shallow cumulus stratocumulus and frontal clusters are robustly identified and associated environmental properties are described the approach helps to refine the diagnosis of errors in model simulations in addition to isolated classical errors of climate models lack of midlevel clouds overestimation of the cloud optical thickness and underestimation of the stratocumulus and a dramatic underestimation of the shallow cumulus clouds over land an underestimation of the boundary lay

concretion formation in volcaniclastic host rocks evaluating the role of organics mineralogy and geochemistry on early diagenesis abstract the upper part of the brushy basin member of the jurassic morrison formation in the four corners regions of the u s was deposited in an ephemeral alkaline saline lake system with copious input of volcanic ash that resulted in dynamic fluid rock interaction during early diagenesis three broad diagenetic facies defined by color and associated bioturbation features are interpreted red green and intermediate diagenetic facies reflect meter scale paleotopography red facies represent shallow water to subaerial oxidizing conditions green facies reflect saturated conditions and reducing pore water chemistry shortly after deposition and intermediate facies represent a combination of or rapid transition between the previous two conditions three categories of concretions are characterized based on mineralogy carbonate iron oxyhydr oxide and phosphate concretions variation in concretion mineralogy and morphology in the brushy basin member suggests that alkaline saline fluid chemistries created diagenetic microenvironments within a larger lake system to influence concretion precipitation however porosity and permeability are more important factors affecting concretion size morphology and mineralogy than host rock composition diagenetic fluid rock interactions in volcaniclastic sediments can be spatially variable even on tens of centimeters scale

carbonate cementation in a sequence stratigraphic framework upper cretaceous sandstones book cliffs utah colorado abstract three macroscopic diagenetic features can be recognized in the sandstones of the upper cretaceous desert member of the blackhawk formation and castlegate sandstone of the mesaverde group exposed in the book cliffs utah each of which have distinctive form geometry and stratigraphic distribution diagenetic alterations are 1 leached zones whitecaps up to 10 m thick beneath coal beds 2 large up to 8 m concretionary carbonate cemented bodies in amalgamated shoreface and thin fluvial sandstones and 3 thin up to 2 m laterally extensive carbonate cemented horizons beneath major marine flooding surfaces each feature has distinct petrographic and geochemical signatures and formed through discrete diagenetic processes large isolated carbonate cemented bodies are composed of ferroan dolomite most of which precipitated during early diagenesis field and petrographic data coupled with stable isotope data early cements 13c 2 5 to 3 4o oo vpdb 18o 7 8 to 12 0o oo vpdb 87sr 86sr 0 7078 later cements 13c 3 1 to 5 7o oo vpdb 18o 12 0 to 15 1o oo vpdb 87sr 86sr 0 7093 suggest precipitation from meteoric fluids input into sediments during times of relative sea level fall the source of carbonate for the dolomite cement was dissolution of detrital dolomite from beneath coals by organic acids and subsequent mobilization by meteoric fluids carbonate precipitation in laterally extensive cement horizons appears to have started as a result of hiatus in sediment accumulation during marine flooding events relative sea level rise cement precipitation in these horizons continued through sediment burial as a result of organic matter oxidation reactions in overlying organic rich mudstones the results of this study show a link between sedimentation related to changes in relative sea level and diagenesis leading to the potential for the development of process based predictive models of early diagenesis in depositional successions

a train based case study of stratiform convective transition within a warm conveyor belt abstractclouds are both produced by and interact with the mesoscale and synoptic scale structure of extratropical cyclones etcs in ways that are still not well understood cloud scale radiative and latent heating modifies the thermal environment leading to a response in the dynamics that can in turn feed back on cloud distribution and microphysical properties key to the structure of etcs is the warm conveyor belt wcb the poleward ascending airstream that produces the bulk of the clouds and precipitation this paper examines a long lived wcb that persisted over the western north atlantic ocean in nearly the same location for several days during this time the storm was sampled multiple times by nasa s a train satellite constellation and a clear transition from stratiform to convective clouds was observed examination of coincident temperature and water vapor data reveals destabilization of the thermodynamic profile after the cyclone reached maturity cloudsat radar reflectivity from two sequential

watershed delineation using hydrographic features and a dem in plain river network region watershed delineation is a required step when conducting any spatially distributed hydrological modelling automated approaches are often proposed to delineate a watershed based on a river network extracted from the digital elevation model dem using the deterministic eight neighbour d8 method however a realistic river network cannot be derived from conventional dem processing methods for a large flat area with a complex network of rivers lakes reservoirs and polders referred to as a plain river network region prnr in this study a new approach which uses both hydrographic features and dem has been developed to address the problems of watershed delineation in prnr it extracts the river nodes and determines the flow directions of the river network based on a vector based hydrographic feature data model the river network lakes reservoirs and polders are then used to modify the flow directions of grid cells determined by d8 approach the watershed is eventually delineated into four types of catchments including lakes reservoirs polders and overland catchments based on the flow direction matrix and the location of river nodes multiple flow directions of grid cells are represented using a multi direction encoding method and multiple outflows of catchments are also reflected in the topology of catchments the proposed approach is applied to the western taihu watershed in china comparisons between the results obtained from the d8 approach the stream burning approach and those from the proposed approach clearly demonstrate an improvement of the new approach over the conventional approaches this approach will benefit the development of distributed hydrological models in prnr for the consideration of different types and multiple inlets and outlets of catchments copyright 2015 john wiley sons ltd

cloud radar doppler spectra in drizzling stratiform clouds 2 observations and microphysical modeling of drizzle evolution sites is presented the evolution of the doppler spectra moments is consistent with the onset and growth of drizzle particles and can be used to assist modeling studies of drizzle onset and growth time height radar observations are used to exhibit the coherency of the doppler spectra shape parameters and demonstrate their potential to improve the interpretation and use of radar observations in addition a simplified microphysical approach to modeling the vertical evolution of the drizzle particle size distribution in warm stratiform clouds is described and used to analyze the observations the formation rate of embryonic drizzle droplets due to the autoconversion process is not calculated explicitly however accretion and evaporation processes are explicitly modeled the microphysical model is used as input to a radar doppler spectrum forward model and synthetic radar doppler spectra moments are generated three areas of interest are studied in detail early drizzle growth near the cloud top growth by accretion of the well developed drizzle and drizzle depletion below the cloud base due to evaporation the modeling results are in good agreement with the continental and maritime observations this demonstrates that steady state one dimensional explicit microphysical models coupled with a forward model and comprehensive radar doppler spectra observations offer a powerful method to explore the vertical evolution of the drizzle particle size distribution

distribution of upper cenozoic carbonate cemented sandstones kuche depression northwest china insights from high resolution borehole micro resistivity imaging abstract high resolution micro resistivity images are used to study the distribution of neoformed carbonate concretions in upper cenozoic shallowly buried fluvial sandstones in the kuche depression northwest china the carbonate concretions are high resistivity white facies on borehole images most of them occur as patches 1 40 cm thick and in shapes ranging from equant oblate to elongate these concretions contrast markedly with the poorly cemented or uncemented host sandstones which appear as dark to immediate grayscale facies on the images three patterns of occurrence of carbonate concretions are identified isolated concretions discontinuously cemented layers and continuously cemented layers most concretions occur in fine grained low permeability laminae suggesting that their growth was controlled more probably by diffusion transport rather than advective transport grain size lamination and distribution of intergranular clay all potentially influenced the selective distribution of carbonate cement in the sandstones shale interbeds and terrigenous carbonate rock fragments in the sandstones are potential sources of carbonate cement

the modification of sea surface temperature anomaly linear damping time scales by stratocumulus clouds abstractstratocumulus sc cloud cover is a persistent feature of the subtropical north and south atlantic it is well known that sc cloud cover increases with decreasing temperatures of the underlying sea surface and that an increase in cloud cover will cool the surface temperatures via increasing the local albedo otherwise known as the sc feedback in this study observations are used to quantify the magnitude and spatial structure of the sc feedback in the tropical extratropical atlantic ocean and investigate the role of the sc feedback in shaping the evolution of coupled modes of variability there the authors show that in the atlantic the sc feedback increases the time scales of newtonian cooling by 40 and in an idealized linear model of the tropical atlantic the dominant mode of coupled variability the atlantic meridional mode or dipole mode would experience no transient growth without the influence of the sc feedback on the surface temperature damping time scales this study also investigates at

arctic synoptic regimes comparing domain wide arctic cloud observations with cam4 and cam5 during similar dynamics 1 arctic cloud properties variability and sensitivity to surface conditions are strongly dependent on the synoptic regimes in which they exist and proper evaluation of modeled cloud properties against observations requires that the dynamic and thermodynamic environment be carefully accounted for in this study a k means clustering algorithm is used to sort arctic clouds observed by calipso into four distinct synoptic regimes three regimes largely associated with mid tropospheric subsidence or very weak uplift and separated by differences in lower tropospheric stability and one regime associated with mid tropospheric uplift boundary layer clouds are present within the three subsidence regimes with increases in stability relating to lower altitudes of the maximum cloud percentage in going from sea ice to open ocean the cloud amount increases at the lowest atmospheric level for all subsidence regimes except the least stable regime and the height of maximum low clouds rises for all subsidence regimes except the most stable regime within each synoptic regime clouds diagnosed from the calipso simulator in cam4 and cam5 forecast runs are then compared with observations compared with cam4 cam5 produces boundary layer clouds that are more similar to the observations and more closely captures the observed sensitivity of cloud properties to the underlying surface type however cam5 overestimates cloud percentages within the uplift regime the improved boundary layer turbulence and cloud microphysical parameterizations in cam5 yield a model that exhibits an improved sensitivity of arctic low level clouds to changes in lower tropospheric stability and surface type

automatically derived catchment boundaries and channel networks and their hydrological applications abstract a method of generating drainage networks and catchment boundaries from gridded ground elevation data a digital terrain model is presented the method includes an algorithm for coping with localised low points in the data the paper suggests two objective ways of comparing the conventionally mapped with the automatically generated drainage network emphasis is placed on the way that this approach is capable of benefiting a variety of hydrological applications in particular the automatic estimation of flow statistics from catchment characteristics

understanding the varied influence of midlatitude jet position on clouds and cloud radiative effects in observations and global climate models abstractthis study examines the dynamical mechanisms responsible for changes in midlatitude clouds and cloud radiative effects cre that occur in conjunction with meridional shifts in the jet streams over the north atlantic north pacific and southern oceans when the midlatitude jet shifts poleward extratropical cyclones and their associated upward vertical velocity anomalies closely follow as a result a poleward jet shift contributes to a poleward shift in high topped storm track clouds and their associated longwave cre however when the jet shifts poleward downward vertical velocity anomalies increase equatorward of the jet contributing to an enhancement of the boundary layer estimated inversion strength eis and an increase in low cloud amount there because shortwave cre depends on the reflection of solar radiation by clouds in all layers the shortwave cooling effects of midlatitude clouds increase with both upward vertical velocity anomalies and positive eis anomalies over midlatitude oce

the turbulence structure in a continental stratocumulus cloud from millimeter wavelength radar observations abstract the turbulent scale vertical velocity structure in a continental stratocumulus cloud is studied using a 3 mm wavelength doppler radar operating in a vertically pointing mode the radar observations provided 30 m sampling in the vertical with 2 s averages of 10 000 samples vertical velocity measurements were made continuously for an 8 h period and were further supported by measurements of cloud base height from a laser ceilometer and liquid water path from a microwave radiometer during the beginning of the observational period the cloud layer extended between 200 and 800 m the vertical velocity variance profiles evolved systematically over the period from a well defined peak in the upper part of the cloud layer of 0 7 m2 s 2 to a peak in the lower part of the cloud layer of 0 2 m2 s 2 as the layer became decoupled later in the observing period the vertical velocity skewness during the well coupled conditions was negative through most of the cloud consistent with the presence of relatively n

origin of giant calcite cemented concretions temple member qasr el sagha formation eocene faiyum depression egypt abstract the temple member of the qasr el sagha formation contains spheroidal calcite cemented concretions in sandstone ranging from 70 cm to 9 m in diameter although most are 1 to 4 m in diameter most concretions are solitary oblate spheroids but some are prolate coalesced joined laterally or are compound enclose smaller concretions half the concretions have domains with a fairly uniform center to center spacing of 4 6 m but half have domains of random spacing both clusters and segregated concretions or occur in parallel rows of coalesced concretions miocene marine carbonate shells now preserved only inside concretions were the source of calcite cement as further supported by carbon and strontium isotopic signatures of cement 13c 2 to 1o oo pdb 87sr 86sr 0 70765 to 0 70770 concretions formed at shallow burial depths in meteoric pore water most 18o values of calcite are from 4o oo to 2o oo pdb at temperatures probably between 10 and 20 c spheroidal uniformly spaced concretions formed where carbonate shells were uniformly distributed and where nucleation sites were influenced by low carbonate saturation levels and widely spaced sites or at sites established by some self organization process concretions in orthogonal rows in the plane of bedding probably formed where shells were concentrated during deposition randomly spaced concretions formed where shells were unevenly spaced or where nucleation of concretions was rapid some temple concretions reached exceptional size in less than 20 my owing to a combination of conditions large initial aragonite and mg calcite shell concentration widely spaced concretion growth sites locally presence of a stable hydrologic regime over a long period of time and possibly bacterially mediated precipitation of calcite

orographic cirrus in the global climate model echam5 1 a comparison of satellite data with simulations from global circulation models shows that there is a lack of cirrus cloud amount in large scale models above and in the lee of mountains the formation of orographic cirrus clouds due to gravity waves is usually not parameterized in large scale models to improve the simulation of such orographically excited cirrus clouds a coupling of the gravity wave dynamics and the cloud microphysics has been implemented in the climate model european centre hamburg 5 echam5 as homogeneous freezing of solution droplets strongly depends on the vertical velocity an increased vertical velocity due to gravity wave activity in the upper troposphere leads to the formation of cirrus clouds with higher ice crystal number densities a comparison of the new parameterization with measurements shows a better agreement with observations

surface based observations of mesoscale cumulus stratocumulus interaction during astex abstract data obtained from the island of santa maria in the azores during the atlantic stratocumulus transition experiment astex are used to describe cloud and boundary layer structure for a 24 h period on 15 june 1992 over the east central atlantic 37 n 25 10 w the evolution of the mesoscale cloud structure during a 24 h period in the vertical column above the surface site was characterized using a 94 ghz radar a laser ceilometer 3 h radiosonde ascents and surface micrometeorological instrumentation mesoscale circulations and drizzle were found to be key elements of the boundary layer clouds observed in this region during the late night and predawn hours of the study period a single layer of stratocumulus that averaged 200 m in thickness topped a well mixed marine boundary layer mesoscale cellular convection mcc which had ascending regions with horizontal dimensions of 7 km was observed during this period at sunrise decoupling was imposed on this mcc and extreme mesoscale variatio

fidelity of analytic drop size distributions in drizzling stratiform clouds based on large eddy simulations abstract cloud microphysical parameterizations and retrievals rely heavily on knowledge of the shape of drop size distributions dsds many investigations assume that dsds in the entire or partial drop size range may be approximated by known analytical functions the most frequently employed approximations of function are of the type of gamma lognormal khrgian mazin and marshall palmer at present little is known about the accuracy of these approximations the authors employ a dsd dataset generated by the cooperative institute for mesoscale meteorological studies large eddy simulation cimms les explicit microphysics model for stratocumulus cases observed during the atlantic stratocumulus transition experiment astex field project the fidelity of analytic lognormal and gamma type dsd functions is evaluated according to how well they represent the higher order moments of the drop spectra such as precipitation flux and radar reflectivity it is concluded that for boundary layer marine drizzling st

calcite cement distribution and its effect on fluid flow in a deltaic sandstone frontier formation wyoming precipitation of extensive calcite cement during burial diagenesis can strongly modify the depositional permeability of a sandstone reservoir and affect fluid flow during production to predict subsurface flow through cemented reservoirs permeability distributions used in fluid flow models must reflect this diagenetic overprint calcite cements in sandstones commonly occur as irregularly distributed concretions which makes it difficult to predict diagenetic permeability modifications in the subsurface from typically spaced wells outcrops can provide a continuous image of heterogeneity produced by concretionary calcite cements the size and distribution of calcite concretions were mapped in outcrops of the frewens sandstone frontier formation in central wyoming large tabular calcite concretions in this deltaic sandstone generally follow basinward inclined bedding median thickness of the concretions is 0 6 m length is 4 2 m and width is 5 3 m the highest cement fraction is in the high permeability facies at the top of the sandstone body concretion centers are approximately poisson distributed within the sandstone the upward increasing cement fraction is caused by upward increasing concretion size lateral variation in the fraction of the sandstone cemented by calcite has a normal distribution with a mean of 12 s 5 spatial distribution of calcite cement in the frewens sandstone was modeled using indicator geostatistics variograms were inferred from outcrop maps of cement indicator semivariograms of cement have a range of 30 m horizontally and 2 5 m vertically dimensions that correspond approximately to the size of the largest concretions stochastic images of cement were created using indicator simulation with vertically varying cement proportion flow models indicate that concretions make flow paths more tortuous and retard flow in the coarser facies near the top of the sandstone the fastest path through the sandstone is in the lightly cemented high net to gross center of the sandstone body because the cement mainly occurs within the highest permeability facies in the sandstone body a model based on depositional facies alone would overestimate upscaled permeability of the frewens sandstone

surface subsurface flow modeling with path based runoff routing boundary condition based coupling and assimilation of multisource observation data received 21 october 2008 revised 2 september 2009 accepted 16 september 2009 published 13 february 2010 1 a distributed physically based model incorporating novel approaches for the representation of surface subsurface processes and interactions is presented a path based description of surface flow across the drainage basin is used with several options for identifying flow directions for separating channel cells from hillslope cells and for representing stream channel hydraulic geometry lakes and other topographic depressions are identified and specially treated as part of the preprocessing procedures applied to the digital elevation data for the catchment threshold based boundary condition switching is used to partition potential atmospheric fluxes into actual fluxes across the land surface and changes in surface storage thus resolving the exchange fluxes or coupling between the surface and subsurface modules nested time stepping allows smaller steps to be taken for typically faster and explicitly solved surface runoff routing while a mesh coarsening option allows larger grid elements to be used for typically slower and more compute intensive subsurface flow sequential data assimilation schemes allow the model predictions to be updated with spatiotemporal observation data of surface and subsurface variables these approaches are discussed in detail and the physical and numerical behavior of the model is illustrated over catchment scales ranging from 0 0027 to 356 km 2 addressing different hydrological processes and highlighting the importance of describing coupled surfacesubsurface flow

oriented concretions ionian coast italy evidence of groundwater flow direction abstract highly elongate aligned calcite cemented concretions are present in exposed shallow marine pleistocene sands and gravels along the basilicata coast of the ionian sea southern italy concretions are shaped like rods pencils and cigars 0 5 3 cm in diameter and thin blades 031 cm thick and 1 5 cm wide most have aspect ratios greater than 5 and some reach 30 most concretions are in parallel laminated beds but a few are in cross stratified and ripple cross laminated beds concretions cut across foresets and inclined laminae the standard deviations of long axes at each of six localities with more than eight measurements are less than 7 the standard deviation of the orientation of concretions from 30 localities over a 400 km2 area is less than 17 previous interpretations for elongate carbonate concretions in sandstones include growth in the direction of groundwater flow growth parallel with current oriented grains and or paleocurrents and selective cementation in the troughs of wave ripples the basilicata concretions are oriented perpendicular to the local coastline and parallel with the direction of present day groundwater flow the groundwater flow direction was probably the same during the pleistocene the evidence indicates that the concretions grew parallel with groundwater flow and were not influenced by sedimentary structures or grain fabric the isotopic values 13c and 18o range from 10 to 1 pdb and from 5 to 3 pdb respectively and textures of calcite cement in the concretions indicate that the calcite was precipitated from meteoric groundwater nannobacteria may have mediated precipitation of calcite

cyclonic brine flow pattern recorded by oriented gypsum crystals in the badenian evaporite basin of the northern carpathian foredeep abstract in the middle miocene badenian within sulfate evaporites formed in the northern carpathian foredeep basin of poland ukraine and the czech republic the apices of the primary bottom grown gypsum crystals selenites are similarly aligned over broad areas and have a common azimuth this crystal orientation is interpreted as the product of a consistent direction of a brine inflow during gypsum crystallization and such a unique commonality is used as a tool for paleocurrent analysis in order to recognize both the local and the regional brine paleocurrents in the basin earlier sedimentologic and stratigraphic studies proved that these beds of oriented selenites were deposited at the same or nearly the same time in a brine not more than a few meters deep it is interpreted that the oriented selenites recorded only the mean flow within the basin mainly from the periods of mixing in the dry season lowstands when the whole brine column down to the bottom was ca sulfate oversaturated the measured paleocurrent vectors showed that the brines flowed along the marginal zone of the carpathian foredeep basin predominantly in a counterclockwise direction this longshore flow is interpreted as a typical cyclonic circulation analogous to those present in recent lakes and semi closed basins in the northern hemisphere where counterclockwise mean water drift is directly or indirectly forced by earth rotation the coriolis effect the detected brine flow directions do not reflect downslope gravity flow of dense brines into the central basinal depths or subbasins that were filling with the halite facies

abrupt cloud clearing of marine stratocumulus in the subtropical southeast atlantic we document rapid and abrupt clearings of large portions of the subtropical marine low cloud deck that have implications for the global radiation balance and climate sensitivity over the southeast atlantic large areas of stratocumulus are quickly eroded yielding partial or complete clearing along sharp transitions hundreds to thousands of kilometers in length that move westward at 8 to 12 meters per second and travel as far as 1000 kilometers from the african coast the westward moving cloudiness reductions have an annual peak in occurrence in the period from april through june the cloud erosion boundaries reduce cloud at 10 kilometer scale in less than 15 minutes move approximately perpendicular to the mean flow and are often accompanied by small scale wave features observations suggest that the cloud erosion is caused by atmospheric gravity waves

petrography and stable isotope geochemistry of oligocene miocene continental carbonates in south texas implications for paleoclimate and paleoenvironment near sea level abstract cenozoic sedimentary rocks in the southern texas gulf coastal plains contain abundant continental carbonates that are useful for reconstructing terrestrial paleoclimate and paleoenvironment in a region near sea level our field observations and thin section characterizations of the oligocene and miocene continental carbonates in south texas identified three types of pedogenic carbonates including rhizoliths carbonate nodules and platy horizons and two types of groundwater carbonates including carbonate cemented beds and carbonate concretions with distinctive macromorphologic and micromorphologic features based on preservations of authigenic microfabrics and variations of carbon and oxygen isotopic compositions we suggest these carbonates experienced minimal diagenesis and their stable isotopic compositions reflect paleoclimate and paleoenvironment in south texas our oligocene and miocene carbonate clumped isotope temperatures t 47 are 23 28 c slightly less than or comparable to the range of modern mean annual and mean warm season air temperature 21 27 c in the study area these t 47 values do not show any dependency on carbonate type or trends through time suggesting that groundwater carbonates were formed at shallow depths these data could indicate that air temperature in south texas was relatively stable since the early oligocene the reconstructed paleo surface water 18o values are similar to modern surface water which could indicate that meteoric water 18o values also remained stable since the early oligocene mean pedogenic carbonate 13c values increased 4 6 during the late miocene most likely reflecting an expansion of c4 grassland in south texas this study provides the first mid and late cenozoic continental records of paleoclimate and paleoecology in a low latitude near sea level region

the impact of diagenesis on the heterogeneity of sandstone reservoirs a review of the role of depositional facies and sequence stratigraphy diagenesis exerts a strong control on the quality and heterogeneity of most clastic reservoirs variations in the distribution of diagenetic alterations usually accentuate the variations in depositional porosity and permeability linking the types and distribution of diagenetic processes to the depositional facies and sequence stratigraphic framework of clastic successions provides a powerful tool to predict the distribution of diagenetic alterations controlling quality and heterogeneity the heterogeneity patterns of sandstone reservoirs which determine the volumes flow rates and recovery of hydrocarbons are controlled by geometry and internal structures of sand bodies grain size sorting degree of bioturbation provenance and by the types volumes and distribution of diagenetic alterations variations in the pathways of diagenetic evolution are linked to 1 depositional facies hence pore water chemistry depositional porosity and permeability types and amounts of intrabasinal grains and extent of bioturbation 2 detrital sand composition 3 rate of deposition controlling residence time of sediments at specific near surface geochemical conditions and 4 burial thermal history of the basin the amounts and types of intrabasinal grains are also controlled by changes in the relative sea level and therefore can be predicted in the context of sequence stratigraphy particularly in paralic and shallow marine environments changes in the relative sea level exert significant control on the types and extent of near surface shallow burial diagenetic alterations which in turn influence the pathways of burial diagenetic and reservoir quality evolution of clastic reservoirs carbonate cementation is more extensive in transgressive systems tract tst sandstones particularly below parasequence boundaries transgressive surface and maximum flooding surface because of the abundance of carbonate bioclasts and organic matter bioturbation and prolonged residence time of the sediments at and immediately below the sea floor caused by low sedimentation rates which also enhance the formation of glaucony eogenetic grain coating berthierine odinite and smectite formed mostly in tst and early highstand systems tract deltaic and estuarine sandstones are transformed into ferrous chlorite during mesodiagenesis helping preserve reservoir quality through the inhibition of quartz cementation the infiltration of grain coating smectitic clays is more extensive in braided than in meandering fluvial sandstones forming flow barriers in braided amalgamated reservoirs and may either help preserve porosity during burial because of quartz overgrowth inhibition or reduce it by enhancing intergranular pressure dissolution diagenetic modifications along sequence boundaries are characterized by considerable dissolution and kaolinization of feldspars micas and mud intraclasts under wet and warm climates whereas a semiarid climate may lead to the formation of calcrete dolocrete cemented layers turbidite sandstones are typically cemented by carbonate along the contacts with interbedded mudrocks or carbonate mudstones and marls as well as along layers of concentration of carbonate bioclasts and intraclasts commonly hybrid carbonate turbidite arenites are pervasively cemented proximal massive turbidites normally show only scattered spherical or ovoid carbonate concretions improved geologic models based on the connections among diagenesis depositional facies and sequence stratigraphic surfaces and intervals may not only contribute to optimized production through the design of appropriate simulation models for improved or enhanced oil recovery strategies as well as for co2 geologic sequestration but also support more effective hydrocarbon exploration through reservoir quality prediction

extraction and representation of nested catchment areas from digital elevation models in lake dominated topography this paper presents a new method for extracting flow directions contributing upslope areas and nested catchments from digital elevation models in lake dominated areas existing tools for acquiring descriptive variables of the topography such as surface flow directions and contributing areas were developed for moderate to steep topography these tools are typically difficult to apply in gentle topography owing to limitations in explicitly handling lakes and other flat areas this paper addresses the problem of accurately representing general topographic features by first identifying distinguishing features such as lakes in gentle topography areas and then using these features to guide the search for topographic flow directions and catchment marking lakes are explicitly represented in the topology of a watershed for use in water routing nonlake flat features help guide the search for topographic flow directions in areas of low signal to noise this combined feature based and grid based search for topographic features yields improved contributing areas and watershed boundaries where there are lakes and other flat areas lakes are easily classified from remotely sensed imagery which makes automated representation of lakes as subsystems within a watershed system tractable with widely available data sets

on using the relationship between doppler velocity and radar reflectivity to identify microphysical processes in midlatitudinal ice clouds 1 ground based 35 ghz profiling doppler cloud radar observations of ice clouds were used to derive the power law relation between doppler velocity vd and radar reflectivity z vd azb by removing the vertical air motion from vd the power law can be rewritten as vt azb with vt being the reflectivity weighted particle terminal fall velocity profiles of this relation are variable with height an attempt was made to relate this variability to the dominant microphysical processes in different layers of the cloud based on that the possibility of using profiles of the parameters a and b to distinguish different microphysical regimes was explored the methodology was applied to long term measurements january 1997 to december 2010 at the atmospheric radiation measurement site in the southern great plains principal component analysis was used to determine the modes of the profiles that explain most of the observed variance in the observations profile averaged means and standard deviations of parameters a and b amounted to 0 65 0 42 and 0 03 0 19 respectively furthermore three commonly used microphysical relations related to bulk quantities were used to determine values of a and b these results were found to compare reasonably well with the values obtained from the radar observations finally microphysical considerations showed that radar derived values of parameter b can be explained in terms of particle size distribution moment changes

digital elevation model networks demon a model of flow over hillslopes for computation of contributing and dispersal areas current algorithms for computing contributing areas from a rectangular grid digital elevation model dem use the flow routing model of o callaghan and mark 1984 which has two major restrictions 1 flow which originates over a two dimensional pixel is treated as a point source nondimensional and is projected downslope by a line one dimensional moore and grayson 1991 and 2 the flow direction in each pixel is restricted to eight possibilities we show that large errors in the computed contributing areas result for any terrain topography divergent convergent or planar we present a new model called digital elevation model networks demon which avoids the above problems by representing flow in two dimensions and directed by aspect demon allows computation of both contributing and dispersal areas demon offers the main advantage of contour based models e g moore et al 1988 the representation of varying flow width over nonplanar topography while having the convenience of using rectangular grid dems

the assignment of drainage direction over flat surfaces in raster digital elevation models abstract drainage direction assignment over flat surfaces in raster digital elevation models dem has been a stubborn problem for dem processing methods a new approach that improves upon current methods of flat surface treatment is presented the approach is based on the recognition that in natural landscapes drainage is generally away from higher and towards lower terrain to produce such a drainage dem elevations of a flat surface are modified to impose two gradients one away from higher terrain and one towards lower terrain subsequent processing of the dem produces a drainage pattern over the flat surface that is topographically consistent and exhibits flow convergence properties the proposed approach is not restricted by the shape of the flat surface the number of outlets on its edge or the complexity of the surrounding topography a comparison with the drainage pattern of an established method that displays the parallel flow problem shows significant improvements in producing realistic drainage patterns the proposed approach extends automated dem processing to digital landscapes for which existing methods cannot provide adequate flow directions over flat surfaces to conduct a drainage analysis the necessary algorithmic details for implementation of the approach are provided 1997 elsevier science b v

oriented carbonate concretions in a paleoaquifer insights into geologic controls on fluid flow oriented carbonate concretions appear to provide a powerful new tool in the evaluation of flow through heterogeneous aquifers calcite cement forms elongate bodies of indurated rock that have distinct and mappable spatial orientations we have mapped 200 of these concretion orientations as well as the hydrogeologic characteristics of the host sediments in outcrops of the pliocene pleistocene sierra ladrones formation in central new mexico the average azimuthal concretion orientations is 150 which is consistent with the southeasterly groundwater flow suggested by past and present basin geometry using a first order approximation the dimensionless transverse velocity is estimated from the orientation data the spatial correlation structure of the dimensionless transverse velocity is distinctly different in the two units investigated however both are consistent with existing stochastic models the differences between the units and the similarities with theoretical models suggest that concretion orientations can be used to study how fluids flow through heterogeneous systems over scales ranging from centimeters to tens of kilometers

martian microfossils in lunar meteorites one of the five lines of evidence used by mckay et al 1996 for relic life in the martian meteorite allan hills alh 84001 was the presence of objects thought to be microfossils these ovoid and elongated forms are similar to structures found in terrestrial rocks and described as nanobacteria folk 1993 mcbride et al 1994 using the same procedures and apparatus as mckay et al 1996 we have found structures on internal fracture surfaces of lunar meteorites that cannot be distinguished from the objects described on similar surfaces in alh 84001 the lunar surface is currently a sterile environment and probably always has been however the lunar and martian meteorites share a common terrestrial history which includes many thousands of years of exposure to antarctic weathering although we do not know the origin of these ovoid and elongated forms we suggest that their presence on lunar meteorites indicates that the objects described by mckay et al 1996 are not of martian biological origin

an analysis of cloud cover in multiscale modeling framework global climate model simulations using 4 and 1 km horizontal grids 1 over the past few years a new type of global climate model gcm has emerged in which a two dimensional or small three dimensional cloud resolving model is embedded into each grid cell of a gcm this approach is frequently called the multiscale modeling framework mmf but is also known as a cloud resolving convection parameterization or a superparameterization in this article we compare joint histograms of cloud top height and optical depth from the mmf with those being produced by the international satellite cloud climatology project isccp and from the multiangle imaging spectroradiometer misr while the form of the isccp and misr data sets is conceptually similar the satellite sensors and the algorithms differ with the result that the joint histograms can differ quite significantly even when viewing exactly the same clouds the analysis takes advantages of the strengths of each data set as well as the differences in these data which for example allow one to characterize the amount of some multilayer clouds mmf simulation runs with three different resolutions are analyzed one simulation is run using a 4 km horizontal grid with 26 vertical levels on a stretched grid a second simulation is run with a 1 km horizontal grid and the same 26 vertical levels and a third simulation is run with a 1 km horizontal grid and 52 vertical levels the analysis shows that the mmf reproduces the broad pattern of tropical convergence zones subtropical belts and midlatitude storm tracks as observed by isccp and misr however the model has several significant shortcomings perhaps most seriously it significantly underpredicts the amount of low level cloud in most regions the simulation with a 1 km horizontal grid and 52 vertical layers is found to improve modestly several aspect of the mmf low level cloud cover the model output is obtained using isccp and misr instrument simulators and the role of horizontal resolution in the instrument simulators is examined