relating the hydraulic properties of a fractured rock mass to seismic attributes theory and numerical experiments numerical experiments are conducted to establish how the properties of a seismic signal are related to the hydraulic properties of a fractured rock mass a hybridized reflectivity method is developed and used to compute a 1d synthetic seismogram for a geologic section which consists of a series of layers with one of the layers consisting of fractures seismic attributes notably instantaneous amplitude frequency and bandwidth are computed for a reflected seismic energy from a fractured zone with known distribution of fracture parameters fracture length aperture and spacing the permeability of the fractured zone is computed using a discrete fracture model the synthetic seismogram is computed using the modified displacement discontinuity model mdd which accounts for fracture opening and finite lengths of fractures a significant correlation is established between the seismic attributes and fractured rock mass permeability all the seismic attributes tend to increase with increase in permeability the correlation is significant enough to establish a meaningful empirical relation between seismic attributes and fracture permeability

airborne doppler radar and sounding analysis of an oceanic cold front abstract an analysis of a cold front over the eastern atlantic ocean based on airborne doppler wind syntheses and dropsonde data is presented the focus and unique aspect of this study is a segment of the front that was near the center of the cyclone the dual doppler wind synthesis of the frontal zone combined with an average dropsonde spacing of 30 km covers a total distance of 450 km in the cross frontal direction the finescale resolution and areal coverage of the dataset are believed to be unprecedented the cold front was characterized by a distinct wind shift and a strong horizontal temperature gradient the latter was most intense aloft and not at the surface in contrast to the classical paradigm of surface cold fronts the shear of the alongfront component of the wind was relatively uniform as a function of height within the frontal zone this observation is contrary to studies suggesting that frontal zones decrease in intensity above the surface the surface convergence within the frontal zon

a comparison of the vorticity dynamics governing the oceanic bomb cyclone of 4 5 january 1989 and the super derecho of 8 may 2009

enhancement of extratropical cyclogenesis by a mesoscale convective system abstract considerable progress has been made in the past decades on understanding the life cycle of rapidly deepening winter cyclones however little attention has been paid to the role that mesoscale convective systems mcss play during extratropical cyclogenesis within weak baroclinic environments in this study the impact of an mcs on the subsequent surface cyclogenesis is investigated by extending the previously documented 21 h simulation of the 10 11 june 1985 pre storm squall line to 36 hours the model reproduces the meteorological events from the initiation to the dissipation of the squall system and then to the formation of a surface cyclone and the amplification of midlevel baroclinic waves as verified against all available observations it is found that the squall line is initiated ahead of a weak surface cold front with the aid of baroclinic forcing once initiated however the prefrontal squall system is primarily driven by the interaction of convectively generated circulations with a co

the vertical structure of mesoscale convective vortices abstract simulations of two cases of developing mesoscale convective vortices mcvs are examined to determine the dynamics governing the origin and vertical structure of these features although one case evolves in strong vertical wind shear and the other evolves in modest shear the evolutions are remarkably similar in addition to the well known mesoscale convergence that spins up vorticity in the midtroposphere the generation of vorticity in the lower troposphere occurs along the convergent outflow boundary of the parent mesoscale convective system mcs lateral transport of this vorticity from the convective region back beneath the midtropospheric vorticity center is important for obtaining a deep column of cyclonic vorticity however this behavior would be only transient without a secondary phase of vorticity growth in the lower troposphere that results from a radical change in the divergence profile favoring lower tropospheric convergence following the decay of the nocturnal mcs subsequent con

investigation of the relationship between permafrost distribution in nw europe and extensive winter sea ice cover in the north atlantic ocean during the cold phases of the last glaciation atmospheric model simulations with different extents of sea ice are compared with reconstructed european mean annual temperatures derived from permafrost indicators analysis of the results suggest that during cold phases of the last glacial the southern margin of permafrost in western europe was controlled by the latitude of the winter sea ice margin in the north atlantic ocean in this case reconstructions of permafrost extent in europe may be used to constrain past winter sea ice conditions in the north atlantic ocean accordingly extensive north atlantic sea ice cover southwards to at least 50degreesn is inferred during four phases of the last glaciation 1 early pleniglacial 74 59 cal kyr bp 2 the hasselo stadial 41 5 40 cal kyr bp 3 the lgm 23 19 cal kyr bp and 4 the younger dryas 12 7 11 5 cal kyr bp the extensive sea ice cover for the phase of maximum cold disagrees with recent studies suggesting a relatively warm north atlantic during the lgm while it agrees with the original climap reconstruction moreover the estimate for the younger dryas cooling conflicts with reconstructions based on marine proxy data c 2002 elsevier science ltd all rights reserved

pseudogleyed loess derivates the most common soil parent materials in the pannonian region of croatia abstract loess derived sediments represent the most widespread soil parent materials in the pannonian region of croatia pseudogley as the most common soil type in this region developed mainly on such parent materials pseudogleys largely correlate with the wrb reference soil group of stagnosols on the general soil map of croatia at scale 1 50 000 gsm of croatia the distinction is made between pleistocene loams pl and loess as pseudogley parent materials the initial purpose of this research was to investigate if the criteria for this distinction were clear and consistent and if the terms used for labeling these parent materials were adequate hence we investigated parent materials of 18 pseudogleys across 6 different locations three on loess and three on pl in the pannonian region of croatia we analyzed their morphology including micromorphology of three representative parent materials particle size distribution total porosity ph and mineral assemblages by modal analysis of three representative parent materials following these analyses no systematic differences between the loess parent materials and the pl parent materials were found additionally it was concluded that due to significant geogenetic and or pedogenetic alterations of all studied parent materials none of them should be labeled simply as loess hence parent material at one location was labeled as leached loess derivate and parent materials at all other locations were labeled as pseudogleyed loess derivates both types of parent materials were described in detail and defined in addition the terminology and the classification of loess derived parent materials in general was proposed the analyzed pseudogleyed loess derivates were not completely uniform across the investigated locations primarily this was due to the polygenesis of loess reflected by differences in particle size distributions and compositions of light and heavy mineral fractions secondarily it was due to the 600 1100 mm map gradient along the study region reflected by differences in ph values and properties of redoximorphic features although pedogenesis of the investigated parent materials might have started already during the late glacial and have continued throughout the holocene at varying and overall decreasing rates their morphology indicates that pseudogleization and lessivage are still active processes which occur simultaneously in the analyzed parent materials and agree with the present climate

a family of frontal cyclones over the western atlantic ocean part i a 60 h simulation despite marked improvements in the predictability of rapidly deepening extratropical cyclones many operational models still have great difficulties in predicting frontal cyclogenesis that often begins as a mesoscale vortex embedded in a large scale parent cyclone system in this paper a 60 h simulation and analysis of a family of frontal cyclones that were generated over the western atlantic ocean during 13 15 march 1992 are performed using the pennsylvania state university national center for atmospheric research mesoscale model with a fine mesh grid size of 30 km although it is initialized with conventional observations the model reproduces well the genesis track and intensity of the frontal cyclones their associated thermal structure and precipitation pattern as well as their surface circulations as verified against the canadian meteorological centre analysis and other available observations it is shown that each frontal cyclone is initiated successively to the southwest of its predecessor in the cold sector first appearing as a pressure trough superposed on a baroclinically unstable basic state in the lowest 150 300 hpa then it derives kinetic energy from the low level available potential energy as it moves over an underlying warm ocean surface with weak static stability toward a leading large scale frontal zone and deepens rapidly by release of latent heat occurring in its own circulations one of the frontal cyclones originating in the cold air mass deepens 44 hpa in 42 h and overwhelms the parent cyclone after passing over the warm gulf stream water into the leading frontal zone these cyclones have diameters ranging from 500 to 1100 km as denoted by the last closed isobar and are spaced 1000 1400 km apart between their circulation centers during the mature stage they begin to establish their own cold warm frontal circulations once their first closed isobars appear thus distorting the leading large scale frontal structures and altering the distribution and type convective versus stratiform of precipitation it is found that the frontal cyclones accelerate and experience their central pressure drops as they move from high to low pressure regions toward the parent cyclone center and then they decelerate and fill as they travel away from the parent cyclone their spatial and temporal scales vertical structures as well as deepening mechanisms are shown to differ significantly from those typical extratropical cyclones as previously studied

effects of fractures on seismic wave velocity and attenuation the effects of fractures on the seismic velocity and attenuation of a rock are investigated using theoretical results and experimental data fractures in a rock mass influence the traveltimes and amplitudes of seismic waves that have propagated through them the displacement discontinuity model recently employed in fracture investigations is modified to describe the effect of fractures on seismic wave velocity and attenuation this new model the modified displacement discontinuity model mdd is formulated in a way analogous to transmission line analysis the fractures are treated as transmission lines for the passage of seismic waves the mdd takes into consideration realistic fracture parameters which include the fracture length the fractional area of a fracture surface in contact and the nature of the infilling material a single fracture of varying geometric and material properties is shown to affect dramatically the transmission properties of a propagating waveform and hence the seismic velocity and attenuation these effects have been shown to result in a frequency dependent velocity and attenuation the sensitivity of the fracture parameters to seismic wave velocity and attenuation was investigated and interesting results were obtained fracture parameters used in designing experimental models consisting of synthetically manufactured cracks were fed into the mdd and a well known crack model hudson s model for comparison velocities as a function of the incident wave angle were obtained from both numerical models and were compared with the results from the experimental modelling for p waves the mdd model results show better agreement with those of the experimental model for all crack densities investigated than those from hudson s model

tracing the origin of loess in hungary with the help of heavy mineral composition data abstract heavy mineral composition of the fine sand fraction in the hungarian loess sediments provides important data about the closer sources of the loess in the carpathian basin quantitative detrital heavy mineral compositions of 216 loess loess like sediment and paleosol samples were compared to each other and to recent fluvial sands and different cenozoic sands and sandstones of hungary using statistical methods cluster analysis principal component analysis and discriminant analysis usually garnet is the most frequent detrital heavy mineral in the studied loess sections followed by chlorite magnetite epidote and amphiboles old loess and young loess have similar compositions indicating uniform or similar sources based on the similarities the garnet rich loess sediments could originate from aeolian reworking of the floodplain sediments of the danube and other rivers of transdanubia and the local cenozoic sands of the uplifting transdanubian central range and transdanubian hilly region the biotite and tourmaline rich loess in south transdanubia and the loess with high pyroxene content in the north hungarian range had some material from nearby sources weathered granitoids and volcanic rocks respectively or sediments of local rivers which carried detritus of these rocks the new results presented in this paper confirm numerous earlier ideas about the origin of loess in the carpathian basin but also suggest newly identified sources of the loess particles at several locations

parent material influence on soil distribution and genesis in a paleudult and kandiudult complex southeastern usa parent materials greatly influence soil development and the distribution of soils on the southeastern us coastal plain we examined the physical chemical and mineralogical properties of 11 pedons in a 1 ha plot on the upper coastal plain of georgia usa uniformity of parent materials was assessed by sand grain size characteristics the soils have sandy epipedons of variable thickness and argillic horizons of variable texture six of the pedons also have kandic horizons they are classified us soil taxonomy in psammentic grossarenic arenic and typic subgroups of paleudults and kandiudults loamy pedons possess argillic horizons with two distinct increases in clay and greater differences between eluvial and illuvial horizons than sandy pedons the upper boundary of the argillic horizon is approximately parallel to the present geomorphic surface suggesting that it is associated with the contemporary surface discontinuities identified by changes in sand grain size ratios and plots of the third skewness and fourth kurtosis moments of sand grain distribution roughly correspond to the bottom of the solum our data suggest that there are both eolian and fluvial components in the solum whereas subjacent horizons are completely derived from fluvial deposits sandier pedons have greater gibbsite kaolinite ratios possibly because greater permeability has enhanced leaching and si loss our data suggest parent materials largely control soil distribution over this plot

geochemical characterization and origin of southeastern and eastern european loesses serbia romania ukraine abstract the loess paleosol sections of batajnica stari slankamen serbia mircea voda romania and stary kaydaky ukraine were geochemically characterized based on discriminant analysis of major and trace elements the ratios of al ti fe ti and al fe the a cn k ternary plot and element enrichment depletion relative to the average composition of the upper continental crust the origin of the loess material in the southern pannonian basin vojvodina the lower danube basin dobrudja and the dnieper area was evaluated by comparison with the representative element composition of possible source areas and by considering the geomorphodynamic setting also the background values of the initial magnetic susceptibility of the loesses were taken into account for the lower danube basin dobrudja and the ukraine paleowind direction was reconstructed based on the geographic distribution of sandy soil texture and dunes related to river systems finally loesses were evaluated as possible samples of the average upper continental crust our results show that danube and dnieper loess areas can be clearly distinguished the former reveal higher al and fe contents the latter higher si zr hf content and indications of effective mineral and grain size sorting we can confirm that vojvodina loess originated from danube alluvial material and loess of the dnieper area from glaciofluvial sediments of the fennoscandinavian ice sheet the dobrudja loess derived also predominantly from danube alluvium but shows significant contribution of a second loess source probably the glaciofluvial sediments of the ukraine this was forced by northerly katabatic winds from the fennoscandinavian ice sheet whereas wnw winds prevailed in the western walachian plain the studied loesses reflect the average composition of the upper continental crust yet biases exist due to selective mineral element enrichment and depletion in the course of previous sedimentary recycling phases respectively material of all studied loess deposits seems to derive originally from sedimentary rocks

development of texture contrast soils by a combination of bioturbation and translocation abstract soils and weathering profiles in a wide variety of parent materials and environmental settings exhibit coarse over fine vertical textural contrasts where these cannot be attributed to inherited texture contrasts or erosion deposition the most common explanations are based on translocation eluviation illuviation which removes clays from surface layers and deposits them in the subsoil or bioturbation where preferentially fine material is delivered to the surface by organisms from whence erosional winnowing creates a coarse surface layer in some soils of the lower coastal plain of north carolina u s a neither explanation is sufficient to explain the observed texture contrasts a heuristic model based on a combination of translocation of fine material from surface to subsoil and bioturbation driven delivery and recycling of material to the surface can explain the observed vertical textural contrasts the key elements in the model are coastal plain sediments which include some fine material eluviation illuviation by percolating water delivery of additional fine and mixed grain size material to surface by bioturbation making it available for translocation concentration of fine material originally scattered throughout the parent material in a b horizon and maintenance of vertical moisture fluxes by bioturbation the model is supported by morphological evidence of the key mechanisms argillic horizons that are finer than both the surface layers and underlying parent material evidence that argillic horizon formation is not limited by the rate of clay synthesis and the absence of texture contrasts in nearby soils formed from dune sands which lack fines

holocene loess deposition and soil formation as competing processes matanuska valley southern alaska although loess paleosol sequences are among the most important records of quaternary climate change and past dust deposition cycles few modern examples of such sedimentation systems have been studied stratigraphic studies and 22 new accelerator mass spectrometry radiocarbon ages from the matanuska valley in southern alaska show that loess deposition there began sometime after f6500 14 c yr b p and has continued to the present the silts are produced through grinding by the matanuska and knik glaciers deposited as outwash entrained by strong winds and redeposited as loess over a downwind distance of f40 km loess thickness sand content and sand pluscoarse silt content decrease whereas fine silt content increases loess deposition was episodic as shown by the presence of paleosols at distances 10 km from the outwash plain loess source stratigraphic complexity is at a maximum i e the greatest number of loesses and paleosols at intermediate 10 25 km distances from the loess source surface soils increase in degree of development with distance downwind from the source where sedimentation rates are lower proximal soils are entisols or inceptisols whereas distal soils are spodosols ratios of mobile cao k2o and fe2o3 to immobile tio2 show decreases in surface horizons with distance from the source thus as in china where loess deposition also takes place today eolian sedimentation and soil formation are competing processes study of loess and paleosols in southern alaska shows that particle size can vary over short distances loess deposition can be episodic over limited time intervals and soils developed in stabilized loess can show considerable variability under the same vegetation d 2004 university of washington all rights reserved

aeolian silt contribution to soils on mountain slopes mt śleza southwest poland this paper evaluates the possible contribution of aeolian silt to soils of mt leza southwest poland silt loam textures are common across lower silesia and are often confused with silt clay loam especially at the outer boundaries with thin loess deposits eight study sites with different thicknesses of silt loam mantles that are covered and or mixed with underlying sediments were examined in the field to test our hypothesis we analyzed the particle size and geochemistry of representative horizons concentrations of major and trace elements as well as their cross ratios confirmed the aeolian origin of silt loam materials and clearly distinguished them from basal sediments there is a clear relationship between the presence and depth of aeolian mantles and mixing zones with the type of underlying material furthermore the incorporation of aeolian silt to regoliths soils was a main agent initiating and stimulating clay translocation leading to the formation of an argic horizon below the silt mantles mixing aeolian silt with acid granite regoliths and further illuviation resulted in the formation of alisols while silt contributions to serpentine sediments resulted in development of skeletic luvisols soils receiving very weak input of aeolian silts remain as leptosols cambisols

transmission of seismic waves across single natural fractures fractures and other nonwelded contacts are important mechanical and hydrological features of rock masses their effects on seismic wave propagation can be modeled as a boundary condition in the seismic wave equation seismic stress is continuous across such a boundary but seismic particle displacement and seismic particle velocity are not the complete solutions for seismic wave reflection conversion and transmission across a displacement and velocity discontinuity between two half spaces with different densities and elastic properties are derived for all angles of the incident wave the ratio between the seismic stress across this boundary and the seismic particle displacement and velocity are described by a specific stiffness and a specific viscosity respectively a displacement discontinuity results in frequency dependent reflection and transmission coefficients and a frequency dependent group time delay the velocity discontinuity results in frequency independent coefficients and zero delay results of laboratory experiments on compressional and shear wave transmission across three different natural fractures in a quartz monzonite are described measurements were made at different effective stresses under dry and saturated conditions at room temperature it is shown that the effect of these fractures on the spectral amplitudes for compressional and shear pulses transmitted across these fractures are described well by a displacement discontinuity for compressional pulses under dry and saturated conditions and by a combined displacement and velocity discontinuity for shear wave pulses under dry and saturated conditions values of specific stiffness and specific viscosity vary between fractures and increase with increasing effective stress as does the static specific stiffness of these fractures changes in the spectral amplitudes of transmitted pulses are also analyzed in terms of attenuation using the seismic quality factor q which is found to be a function of frequency

the genesis of severe long lived bow echoes abstract a series of idealized simulations using a nonhydrostatic cloud model is used to investigate the genesis of bow echoes a bow shaped system of convective cells that is especially noted for producing long swaths of damaging surface winds it is hypothesized that severe long lived bow echoes represent a dynamically unique form of mesoconvective organization being produced for a restricted range of environmental conditions including a convective available potential energy cape of at least 2000 m2 s2 and vertical wind shears of at least 20 m s 1 over the lowest 2 5 5 km agl the key structural features include a 40 100 km long bow shaped segment of convective cells with a strong rear inflow jet extending to the leading edge of the bow at 2 3 km agl and cyclonic and anticyclonic eddies referred to as bookend vortices on the northern and southern flanks of the bowed segment respectively this structure characteristically develops three to four hours into the lifetime of a convective system a

tracking textural mineralogical and geochemical signatures in soils developed from basalt derived materials covered with loess sediments sw poland abstract this study investigates the scale of inheritance of signatures typical of loess and basalt derived substrates in soils having both components present as parent material due to past periglacial processes based on field description particle size distribution mineralogy heavy minerals and clay minerals as well as geochemistry we track the signal of both materials local basalt derived and loess derived estimate the maximum thickness of loess mantles and mixed zones having both loess and basaltic components and note the presence or absence of basal layers without allochtonous additions the results show that geochemistry and heavy minerals are the most reliable proxies for a verification of aeolian silt contributions and to define individual layers in complex soil parent materials soil formation in the studied landscape depends on the type of slope sediments typical fine grained weathering of basalt without input from aeolian silt would promote rather vertic development however in thick loess deposits as well as in thin silt textured materials superimposed on clay loam beds clay illuviation dominates development of argic horizons however results in decreasing permeability promoting water stagnation and enhanced degradation processes in clay rich subsoil instead of luvisols stagnosols and retisols developed in the study regions basaltic block covers mixed with loess host cambic horizons based on our findings it seems that at the edge of thin loess deposits no soils exist that developed exclusively from basaltic parent materials

patterns of precipitation and mesolow evolution in midlatitude mesoscale convective vortices abstract surface pressure manifestations of mesoscale convective vortices mcvs that traversed oklahoma during the periods may august 2002 05 are studied using the weather surveillance radar 1988 doppler wsr 88d the oklahoma mesonet and the noaa profiler network data forty five mcvs that developed from mesoscale convective systems mcss have been investigated 28 62 of which exhibit mesolows detectable at the surface within this group three distinct patterns of precipitation organization and associated mesolow evolution have been identified the remaining 17 38 of the cases do not contain a surface mesolow two repeating patterns of precipitation organization are identified for the latter group the three categories of mcvs possessing a surface mesolow are as follows nineteen are classified as rear inflow jet mcvs and tend to form within large and intense asymmetric mcss rear inflow into the mcs enhanced by the development of an mcv on the left hand side relative to system motion pro

loess chronostratigraphy in eastern croatia a luminescence dating approach abstract in eastern croatia impressive loess palaeosol successions up to 30 m thick are exposed along the steep cliffs of the danube river between zmajevac and sarengrad the croatian loess record provides an excellent high resolution archive of climate and environmental change providing evidence for the interaction between accumulation and erosion of aeolian and fluvial sediments during the middle and late pleistocene sedimentological and pedological investigations including granulometry carbonate content and total organic carbon content and infrared optically stimulated luminescence irsl dating were carried out on samples collected from the loess sections at zmajevac erdut and sarengrad the loess successions are intercalated by at least four palaeosols or pedocomplexes which very likely correlate with middle and upper pleistocene interstadials and interglacials in all sediment successions investigated alluvial sediments are intercalated in the loess deposits indicating periods of fluvial activity the stratigraphically youngest alluvial sediments are exposed at the erdut section loess sandwiching these alluvial sediments yielded irsl age estimates of 61 5 6 2 and 53 8 5 4 ka the irsl age estimates give evidence for periods of increased accumulation of dust during the middle and late pleniglacial correlating with oxygen isotope stage ois 3 and ois 2 respectively during the penultimate glaciation and at least the antepenultimate glaciation however it is likely that irsl age estimates 60 ka are underestimated

polygenetic soil formation on late glacial loess on the susak island reflects paleo environmental changes in the northern adriatic area abstract a polygenetic soil formed on late glacial loess on the island of susak was investigated by means of high resolution depth approach to give pedosedimentary and palaeoenvironmental reconstructions of the late glacial holocene pedosequence the complete polygenetic profile a 2c1 2c2 3btb 4ck defined as eutric leptic regosol geoabruptic siltic ruptic over argic horizon over loess deposit is a result of the interaction of the sediments loess with environmental conditions from the late glacial throughout the holocene both normal pedogenesis and erosion sedimentation driven pedogenesis influenced its development therefore this profile bears valuable imprints of climate vegetation land surface and land use changes in this part of the adriatic area for the time period covering the past 16 ka the 4ck horizon is a remnant of an a c soil profile whose incipient formation corresponds to a steppe like palaeo vegetation and a semi humid to semi arid palaeo climate the 3btb horizon has blocky structure common clay coatings and infillings that are related to the walls of channel macrovoids increased cia al si and ba sr ratios due to the increase of the al and clay contents highest fet fed mnt and mnd values due to abundant redox concentrations and specific clay mineralogy since the obtained age of the loess deposit 4ck horizon underlying the 3btb horizon is 16 1 1 3 ka can be correlated to the late glacial maximum i e ois 2 we find that the period of the bolling allerod warming might have enabled the formation of the highly weathered 3btb horizon within a luvisol like soil after the period of surface stability a period of forest decay and surface instability took place resulting with the erosion of the luvisol the 3btb horizon was then covered with a homogeneous loess material whose deposition can presumably be related to the younger dryas period inside of which the horizons 2c1 and 2c2 are recognized both these horizons are negligibly affected by pedogenesis and contain artefacts the incipient soil formation in the upper part of the profile along with the irregular lower boundary of the a horizon and the lithic discontinuity between the a horizon and the 2c1 horizon points to the possibility of a very recent and minor aeolian deposition however one should not overlook the potential impacts of human activities and or colluvial depositions on the properties of the a 2c1 and 2c2 horizons

derecho and mcs development evolution and multiscale interactions during 3 5 july 2003 abstract from 3 to 5 july 2003 during the bow echo and mesoscale convective vortex experiment bamex multiple mesoscale convective systems mcss 1 and 2 and derechos derechos an as a bw and be progressed across a preferred upper midwest corridor the derechos evolved in a favorable synoptic scale environment however the environmental details associated with each derecho such as the characteristics of the initial surface boundary the formation position relative to the upper level jet stream the presence of an upper level mesoscale disturbance and the cape shear environment varied from derecho to derecho the mcss and derechos composed three distinct convective episodes multiple mesoscale interactions between the mcss and derechos and the environment altered the character and longevity of these episodes the first convective episode consisted of derecho a which formed from merging derechos an and as northern and southern systems respectively the 200 hpa deep cold pool associated with d

the generation and propagation of a nocturnal squall line part i observations and implications for mesoscale predictability abstract the initiation and forcing of a squall line on 26 27 may 1985 near wichita kansas is examined the squall line is secondary convection in the sense that it is preceded in the diurnal cycle by other mesoscale convective systems the squall fine develops in synoptic conditions frequently associated with convective weather in the central united states this includes moderate shear moderate to high convective available potential energy a quasi stationary dryline a low level southerly jet and an 85 kpa moist tongue the initiation of free convection is specifically attributed to a gust front that propagates into a low level jet with attendant horizontal vorticity convergence and moisture the gust front initially propagates as a gravity current and subsequently as an internal undular bore observations of gravity currents gravity waves and the collision of radar echo boundaries provide valuable clues for short period forecasting they establish the presence of potential triggering mechanism

detection and prediction of warm season midtropospheric vortices by the rapid update cycle the authors perform a statistical and dynamical analysis of midtropospheric mesoscale vortices captured by analyses from the rapid update cycle version 2 ruc 2 during the period 1 may to 31 august 1999 a total of 203 vortices meeting conditions of an automated algorithm were found of these 86 were observed to form within organized convection and were termed mesoscale convective vortices mcvs mcvs were favored over a broad area from eastern colorado and western nebraska to the mississippi river valley essentially collocated with the loci of organized convection the remaining 117 vortices termed dry vortices clustered in the immediate lee of the rocky mountains and over the southeastern united states vortices arising from convection had considerably greater intensity and longevity than dry vortices they were roughly five times more likely to be involved with the triggering of new convection a relationship was found between intensity and longevity such that there appears to be a maximum vortex lifetime that can be estimated from its maximum intensity vortices arising from convection had markedly greater humidity and water vapor mixing ratio underneath their centers compared to dry vortices consistent with many dry vortices having a topographic origin and mcvs arising from organized convection parameters such as horizontal scale background vertical wind shear and horizontal deformation were not systematically related to intensity or longevity prediction of mesoscale vortices by the ruc 2 was examined for a subsample of all cases in general the ruc 2 was able to predict the evolution of vortices once analyzed but had virtually no skill at predicting 12 h in advance the formation of the vortices however forecasts of organized convection should still benefit from accurate predictions of long lived vortex tracks

postlandfall tropical cyclone reintensification in a weakly baroclinic environment a case study of hurricane david september 1979 abstract an analysis is conducted from a potential vorticity pv perspective of the reintensification of tropical storm david over the northeastern united states in september 1979 david a major long lived hurricane originated near the cape verde islands in late august 1979 it made final landfall in georgia on 4 september 1979 and weakened rapidly thereafter the noteworthy aspect of david was its subsequent reintensification approximately 27 h after landfall as a warm core disturbance in a weakly baroclinic environment in this regard the redevelopment of david is unlike the classical extratropical transformation of a tropical storm in a strongly baroclinic environment that has been documented in the literature the authors analysis of the evolution of the dynamical tropopause subsequent to storm landfall revealed that david reintensified in response to tropopause lifting upward displacement of the dynamic tropopause ahead of a nondeepening and otherwise very weak upper tropospheric disturbance

magnetic mineralogy of soils across the russian steppe climatic dependence of pedogenic magnetite formation formation of ferrimagnets in well drained buffered unpolluted soils appears to be related to climate and especially rainfall if robust this magnetism rainfall couple can be used to estimate past rainfall from buried soils particularly the multiple soils of the quaternary loess soil sequences of central asia however dispute exists regarding the role of climate vs dust flux for the magnetic properties of modern loessic soils here we examine the mineralogical basis of the magnetism rainfall link for a climate transect across the loess mantled russian steppe where critically dust accumulation is minimal at the present day magnetic and independent mineralogical analyses identify in situ formation of ferrimagnets in these grassland soils increased ferrimagnetic concentrations are associated with higher annual rainfall xrd and electron microscopy show the soil formed ferrimagnets are ultrafine grained 50 nm and pure ferrimagnetic contributions to ma ssbauer spectra range from 17 in the parent loess to 42 for a subsoil sample from the highest rainfall area total iron content varies little but the systematic magnetic increases are accompanied by decreased fe2 content reflecting increased silicate weathering for this region parent materials are loessial deposits topography is rolling to flat and duration of soil formation effectively constant the variations in soil magnetic properties thus predominantly reflect climate and its co variant organic activity statistical analysis identifies strongest relationships between rainfall and magnetic susceptibility and anhysteretic remanence this magnetic response correlates with that of the modern soils across the chinese loess plateau such correlation suggests that the rainfall component of the climate system not dust flux is a key influence on soil magnetic properties in both these regions

discrete frontal propagation in a nonconvective environment abstract surface discrete frontal propagation in a wintertime nonconvective environment is documented using conventional surface and upper air data and simulated using the psu ncar mesoscale model synoptic and mesoscale surface analyses show a cold front associated with a synoptic scale low pressure system propagating from northwest to southeast across the central united states apparently discrete frontal propagation occurs when the surface front dissipates and a new front forms approximately 500 km ahead of the original front with no compelling evidence of frontal passage in the intervening space upper air analyses indicate the infusion of three different airstreams into the frontal region resulting in the formation of a ribbon of low static stability air parallel to and several hundred kilometers in advance of the original front this static stability structure appears to be involved in the observed evolution of the front the development of precipitation over the intervening zone between the old

geogenesis pedogenesis and multiple causality in the formation of texture contrast soils abstract coarse over fine vertical texture contrasts vtc are common in soils and weathering profiles in a variety of environmental settings including many where inheritance or surficial processes alone cannot account for them a multiple causality model is presented here which shows that texture contrasts can form in response to a combination of ubiquitous phenomena there are six key elements downward translocation by water erosional winnowing soil mixing by bioturbation the tendency for surface clay additions to be mobilized while subsurface clays are more likely to remain in place and biological facilitation of moisture flux no element alone is sufficient to create a vtc but not all are necessary in any given regolith the model is illustrated by application to case studies in the ouachita mountains arkansas ridgetops in eastern kentucky the lower coastal plain of north carolina and the upper coastal plain of east texas the implications for interpretation of soils paleosols and weathering profiles is that the presence of a textural contrast by itself does not connote any particular set of geogenic or pedogenic processs or controls texture contrasts may be geogenic pedogenic or both given the widespread occurrence of the mechanisms of the multiple causality model vertical texture contrasts are inevitable

pleistocene environmental dynamics recorded in the loess of the middle and lower danube basin abstract the substantial loess deposits of the middle and lower danube basin in southeastern europe represent one of the thickest and most comprehensive terrestrial palaeoenvironmental records on the continent yet are also the least well understood environmental conditions over the last million years have resulted in relatively continuous deposits uninterrupted by glaciation and tundra conditions which nevertheless reflect oscillations between relatively warm humid interglacial and cold dry glacial intervals this relative environmental stability may have proven important for hominins migrating into and through the region the loess stratigraphy comprises distinct loess paleosol sequences reflecting glacial interglacial phases which can be quantified for intensity using environmental magnetism and geochemistry these phases are emphasised by variations in vegetation and malacofauna which respond to climatic change the loess deposits demonstrate broadly similar sedimentological characteristics across the basin danubian loess deposits initiated in response to the tectonic formation of the pannonian basin retreat of the large palaeolakes and increased sediment supply from the danube the period from 1 ma 500 ka mis 27 13 was characterised by alternating loess deposition and pedogenesis during glacial and interglacial periods respectively in response to relatively humid forested conditions this period represents the opening of the danube corridor and provides the backdrop for initial hominin arrival into europe after 500 ka and particularly after mis 9 loess accumulation rates increased in response to relatively more steppic arid environments mis 9 and 13 15 were the most humid phases of the last 600 ky the mis 5 interglacial period was the warmest and relatively most humid period preceding the holocene and was followed by substantially increased loess accumulation during mis 4 which may be linked to north atlantic circulation the complexity of the mis 3 interstadial paleosol suggests that conditions were not uniformly warm and wet during this time mis 3 corresponds with the first arrival of anatomically modern humans to europe the last glacial maximum and younger dryas of mis 2 were characterised by substantially increased loess accumulation indicating cold steppe environments most likely influenced by the north atlantic although conditions were sufficiently mild that the region acted as a refugium for thermophilic biota as may also have been the case for most of the pleistocene glacial cycles the holocene soil represents relatively wamer and more humid conditions corresponding to the current interglacial

albeluvisol development with time in loamy marine sediments of southern norway abstract this paper reports a study on soil development in loamy marine sediments on both sides of the oslofjord vestfold ostfold this region has been subject to steady glacio isostatic uplift during the whole holocene hence land surface age continuously increases from the coast inland several sea level curves based on radiocarbon datings enable estimation of land surface age for all locations clay illuviation starts in less than 1650 years e horizons become lighter with age but their lower boundary stays around 40 cm for more than 10 000 years albeluvic tongues develop between 4600 and 6200 years initially they form along intersections of cracks as preferential flow and leaching along the cracks continues the tongues increase in length and width progressively consuming the prisms between the cracks in the upper bt horizon the fe d fe t ratios weighted means of the upper meter show a clear linear increase with soil age and may be used for pedo dating i e for estimating the ages of non dated land surfaces covered with similar sediments in contrast the logarithmic decrease of base saturation and ph with rapid changes in the first time but only very slight changes between 2000 and 10 000 years makes these parameters unsuitable for pedo dating

rainfall occurrence in the u s warm season the diurnal cycle the diurnal occurrence of warm season rainfall over the u s mainland is examined particularly in light of forcings at multiple scales the analysis is based on a radar dataset of 12 seasons duration covering the u s mainland from the continental divide eastward the dataset resolves 2 km features at 15 min intervals thus providing a detailed view of both large and regional scale diurnal patterns as well as the statistics of events underlying these patterns the results confirm recent findings with respect to the role of propagating rainfall systems and the high frequency at which these are excited by sensible heating over elevated terrain between the rockies and the appalachians 60 of midsummer rainfall occurs in this manner most rainfall in the central united states is nocturnal and may be attributed to the following three main forcings 1 the passage of eastward propagating rainfall systems with origins near the continental divide at 105 w 2 a nocturnal reversal of the mountain plains solenoid which is associated with widespread ascent over the plains and 3 the transport of energetic air and moisture convergence by the great plains low level jet other features of interest include effects of the appalachians semidiurnal signals of regional significance and the impact of breezes along the gulf of mexico a modest effort was put forth to discern signals associated with el nino and the southern oscillation while tendencies in precipitation patterns are observed the record is too short to draw conclusions of general significance

assessing the applicability of the tropical convective stratiform paradigm in the extratropics using radar divergence profiles abstractlong term radar observations from a subtropical location in southeastern texas are used to examine the impact of storm systems with tropical or extratropical characteristics on the large scale circulation climatological vertical profiles of the horizontal wind divergence are analyzed for four distinct storm classifications cold frontal cf warm frontal wf deep convective upper level disturbance dc uld and nondeep convective upper level disturbances nc uld dc uld systems are characterized by weakly baroclinic or equivalent barotropic environments that are more tropical in nature while the remaining classifications are representative of common midlatitude systems with varying degrees of baroclinicity dc uld systems are shown to have the highest levels of nondivergence lnd and implied diabatic heating maxima near 6 km whereas the remaining baroclinic storm classifications have lnd altitudes that are about 0 5 1 km lower analyses of climatological mean divergence profiles are also s

a numerical investigation of a convectively generated inertially stable extratropical warm core mesovortex over land part i structure and evolution abstract a 36 h nested grid numerical simulation of the life cycle of a convectively generated inertially stable warm core mesovortex is presented the vortex evolved from a mesoscale convective complex that developed from a squall line over oklahoma during 7 8 july 1982 a modified version of the pennsylvania state university national center for atmospheric research mesoscale hydrostatic model with a fine mesh grid resolution of 25 km is utilized for this study the model simultaneously incorporates parameterized convection and a grid resolved convective scheme containing the effects of hydrostatic water loading condensation evaporation freezing melting and sublimation genesis intensification and maintenance of a low to midtropospheric closed meso scale cyclone as well as the associated surface pressure perturbations the evolution of moist convection and the distribution and magnitude of total rainfall are simulated by the model similarly the observed amplification of a 700 mb meso sc

mineralogical and geochemical characteristics of quaternary sediments from the island of susak northern adriatic croatia middle and upper pleistocene loess palaeosol sequences up to 90 m thick are exposed on the island of susak located in the northern adriatic sea in croatia during glacial times the sea level was up to about 120 m lower and a significant part of the adriatic became land the source area of the primary aeolian sediments was in the vicinity of the island and is related to the southward extended river po plain the loess has a mainly clayey to sandy silt or sand grain size and is intercalated by at least three tephras numerous palaeosols and calcareous segregations the heavy mineral association points to metamorphic and igneous rocks from alpine regions as source material of the loess geochemical and mineralogical properties of loess and palaeosols differentiate one from another and reflect the intensity of weathering and pedogenesis the oldest tephra contains vitroclasts and serrated clinopyroxene while the middle and the youngest tephra along with vitroclasts contain idiomorphic augite as diagnostic volcanic features based on bulk rock and vitroclast chemistry morphology of pyroxenes and the age of the loess sandwiching the tephra the potential source of this volcanic material could very likely be the campanian or aeolian volcanic province in southern italy infrared stimulated luminescence dating results show that the major part of the aeolian deposits including the tephra layers correlates to mis 3 mis 5

baroclinic transition of a long lived mesoscale convective vortex abstract the period 5 15 june 2003 during the field phase of the bow echo and mesoscale convective vortex mcv experiment bamex was noteworthy for the wide variety of mesoscale convective systems mcss that occurred of particular interest was a long lived mcv that formed in the trailing stratiform region of an mcs over west texas at 0600 utc 10 june this mcv was noteworthy for its i longevity as it can be tracked from 0600 utc 10 june to 1200 utc 14 june ii development of a surface cyclonic circulation and attendant 2 to 4 hpa sea level pressure perturbation iii ability to retrigger convection and produce widespread rains over several diurnal heating cycles and iv transition into a baroclinic surface cyclone with distinct frontal features baroclinic transition defined here as the acquisition of surface fronts occurred as the mcv interacted with a remnant cold front left behind by a predecessor extratropical cyclone over the great lakes region although the mcv developed well def

the loess cover of northeastern wisconsin abstract we present the first study of the distribution genesis and paleoenvironmental significance of late pleistocene loess in northeastern wisconsin and adjacent parts of michigan s upper peninsula loess here is commonly 25 70 cm thick upland areas that were deglaciated early and remained geomorphically stable preferentially accumulated loess by providing sites that were efficient at trapping and retaining eolian sediment data from 419 such sites indicate that the loess was mainly derived from proglacial outwash plains and to a lesser extent hummocky end moraines within and near the region particularly those toward the east of the loess deposits most of the loess was transported on katabatic winds coming off the ice sheet which entrained and transported both silt and fine sands the loess fines markedly and is better sorted distal to these source regions only minimal amounts of loess were deposited in this area via westerly winds this research 1 reinforces the observation that outwash plains and end moraines can be significant loess sources 2 provides evidence for katabatic winds as significant eolian transport vectors and 3 demonstrates that the loess record may be variously preserved across landscapes depending on where and when geomorphically stable sites became available for loess accumulation

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

the mesoscale forcing of a midlatitude upper tropospheric jet streak by a simulated convective system part i mass circulation and ageostrophic processes abstract the mutual forcing of a midlatitude upper tropospheric jet streak by organized mesoscale adiabatic and diabatic processes within a simulated convective system scs is investigated using isentropic diagnostics results from a three dimensional numerical simulation of an scs are examined to study the isallobaric flow field modes of dominant ageostrophic motion and stability changes in relation to the mutual interdependence of adiabatic processes and latent heat release isentropic analysis affords an explicit isolation of a component of isallobaric flow associated with diabatic processes within the scs prior to convective development within the simulation atmospheric destabilization occurs through adiabatic ageostrophic mass adjustment and low level convergence in association with the preexisting synoptic scale upper tropospheric jet streak the scs develops in a baroclinic zone and quickly initiates a vigorous mass circulation by the mature stage a pronounced vertical couplet of low level

storm track dynamics this paper reviews the current state of observational theoretical and modeling knowledge of the midlatitude storm tracks of the northern hemisphere cool season observed storm track structures and variations form the first part of the review the climatological storm track structure is described and the seasonal interannual and interdecadal storm track variations are discussed in particular the observation that the pacific storm track exhibits a marked minimum during midwinter when the background baroclinicity is strongest and a new finding that storm tracks exhibit notable variations in their intensity on decadal timescales are highlighted as challenges that any comprehensive storm track theory or model has to be able to address physical processes important to storm track dynamics make up the second part of the review the roles played by baroclinic processes linear instability downstream development barotropic modulation and diabatic heating are discussed understanding of these processes forms the core of our current theoretical knowledge of storm track dynamics and provides a context within which both observational and modeling results can be interpreted the eddy energy budget is presented to show that all of these processes are important in the maintenance of the storm tracks the final part of the review deals with the ability to model storm tracks the success as well as remaining problems in idealized storm track modeling which is based on a linearized dynamical system are discussed perhaps on a more pragmatic side it is pointed out that while the current generation of atmospheric general circulation models faithfully reproduce the climatological storm track structure and to a certain extent the seasonal and enso related interannual variations of storm tracks in depth comparisons between observed and modeled storm track variations are still lacking

loess palaeosol section in sarengrad croatia a qualitative discussion on the correlation of the geochemical and magnetic susceptibility data abstract the sarengrad loess section is located on the south bank of the danube river in the easternmost part of croatia the published lithostratigraphical results including grain size total organic content calcium carbonate content and luminescence dating results are complemented by geochemical content of major and trace elements and acidity and magnetic susceptibility studies throughout the section four palaeosols are intercalated in the loess the oldest hydromorphic one is covered by laminated alluvial sediments and loess the second palaeosol is an argillic dark brown soil with the highest value of the profile and the other two palaeosols are brownish and less developed geochemical characteristics and ms signals of the palaeosols explain both the main characteristics and degree of pedogenesis palaeosol horizons could be clearly distinguished from loess based on the content of major and trace elements and on weathering coefficients such as ba sr and cao na 2 o mgo k 2 o al 2 o 3 irsl age estimates of 86 6 8 6 and 55 3 5 5 ka indicate that most of the middle and upper pleniglacial loess record is missing at the sarengrad section however the loess palaeosol sequence at sarengrad has a very detailed record correlating with mis 4 5

an integrated view of the 1987 australian monsoon and its mesoscale convective systems i horizontal structure this observational study is organized around three issues the forcing of the monsoon flow by embedded deep convection the thermodynamic conditions that support the convection and the structures of the mesoscale convective systems mcss that constitute much of the deep convection the monsoon convective cloudiness occurred predominantly offshore over the earth s warmest waters week long periods of widespread deep convection caused cycles of monsoon spin up culminating in tropical cyclone formation momentum transports by the convection also created smaller scale vortex pairs in the upper troposphere sounding data suggest that the convection was modulated by low level processes not by large scale deep forced ascent triggering by mesoscale boundary layer cold pool boundaries and coastlines determined specifically where convection occurred while several positive feedbacks acted to keep regional thermodynamic conditions favourable hence monsoon convection once initiated persisted as self exciting superclusters composed at any instant of many distinct mcss the observed mcss all contained areas of deep convection and stratiform precipitation areas stratiform precipitation usually evolved in place from convective cells although precipitation also occasionally fell from overhanging anvils created by upper level shear the mcss within similar synoptic wind environments tended to have similar mesoscale structures this fact reflects the effects illustrated herein of environmental winds upon the relative motions of cold pools which trigger new convective cells and stratiform precipitation areas which evolve from old convective cells

cold fronts with and without prefrontal wind shifts in the central united states time series of cold fronts from stations in the central united states possess incredible variety for example time series of some cold fronts exhibit a sharp temperature decrease coincident with a pressure trough and a distinct wind shift other time series exhibit a prefrontal trough and wind shift that precedes the temperature decrease associated with the front by several hours in early march 2003 two cold fronts passed through oklahoma city oklahoma okc representing each of the above scenarios the cold front on 4 march was characterized by a coincident sharp wind shift pressure trough and a strong temperature decrease of 108c in 2 min on the other hand the cold frontal passage on 8 march was characterized by a prefrontal wind shift occurring over a 7 h period before the temperature decrease of 108c in 2 h twelve hours before frontal passage at okc both fronts had the same magnitude of the horizontal potential temperature gradient and petterssen frontogenesis by the time of frontal passage at okc the magnitude of the horizontal potential temperature gradient for the 4 march front was double that of the 8 march front and the frontogenesis was nearly four times as great the simultaneity of the surface horizontal potential temperature gradient and deformation and convergence maxima coincident with the wind shift was primarily responsible for the greater strength of the cold front in okc on 4 march compared to that on 8 march whether a prefrontal wind shift occurred was determined by the timing and location of cyclogenesis in the central united states on 4 march a cyclone was adjacent to the slope of the rocky mountains and developed on the cold front as it moved through oklahoma permitting greater frontogenesis and resulting in a cold frontal passage at okc with a simultaneous temperature decrease and wind shift on 8 march the cyclone moved eastward through oklahoma before the arrival of the cold front resulting in a prefrontal wind shift associated with the northerlies behind the cyclone followed by the frontal passage a 2 yr climatology of cold frontal passages at okc supports the results from the two cases above indicating that the timing and location of cyclogenesis was responsible for these two different cold frontal structures these results imply that for situations resembling those of this study the prefrontal trough is not directly associated with the cold front but is caused by external processes related to the lee troughing

climate vs parent material which is the key of stagnosol diversity in croatia abstract stagnosols are the most widespread soils in the pannonian region of croatia in croatia they are referred to as pseudogleys and considered to form primarily by normal top down pedogenesis however the formation of their non calcareous loess parent materials probably involved different sources transports and depositional environments we aimed to determine the courses of soil formation and the characteristics of three stagnosol profiles studied along the mean annual precipitation map gradient 700 1100 mm in the pannonian region of croatia we found that soil redoximorphic features formed in situ by ongoing pseudogleization vertical trends for the clay silt and coarse fine silt ratios pointed to top down pedogenesis however high organic c content at the bottom of one soil profile is the result of erosion sedimentation processes whereas high clay content in the subsoil of another profile was largely the result of sedimentation in a shallow paleo lake therefore some croatian stagnosols should be considered polygenetic each soil profile was classified using the wrb system and the new wrb 2014 version proved more suitable than the previous one wrb 2006 however suggestions for improvements are given in line with the map gradient were several morphological and only two chemical ph and base saturation soil characteristics organic c content did not correspond to map due to variability of forest topsoils clay content and cec did not agree with map due to variability of loess parent materials across the pannonian region of croatia the existence of more than one source of loess material confirmed by the modal analysis and the differences in depositional paleo environments resulted in slightly different mechanical compositions of the investigated parent materials we concluded that both climate and parent material must be regarded as key factors for the formation and characteristics of stagnosols in the pannonian region of croatia and the wider southwestern pannonian basin

complex seismic trace analysis of thin beds displays of complex trace attributes can help to define thin beds in seismic sections if the wavelet in a section is zero phase low impedance strata whose thicknesses are of the order of half the peak to peak period of the dominant seismic energy show up as anomalously high amplitude zones on instantaneous amplitude sections these anomalies result from the well known amplitude tuning effect which occurs when reflection coefficients of opposite polarity a half period apart are convolved with a seismic wavelet as the layers thin to a quarter period of the dominant seismic energy thinning is revealed by an anomalous increase in instantaneous frequency this behavior results from the less well known but equally important phenomenon of frequency tuning by beds which thin laterally instantaneous frequency reaches an anomalously high value when bed thickness is about a quarter period and remains high as the bed continues to thin in this paper complex trace analysis is applied to a synthetic model of a we

elastic wave propagation in media with parallel fractures and aligned cracks a model of parallel slip interfaces simulates the behaviour of a fracture system composed of large closely spaced aligned joints the model admits any fracture system anisotropy triclinic the most general monoclinic orthorhombic or transversely isotropic and this is specified by the form of the 3 3 fracture system compliance matrix the fracture system may be embedded in an anisotropic elastic background with no restrictions on the type of anisotropy to compute the long wavelength equivalent moduli of the fractured medium requires at most the inversion of two 3 3 matrices when the fractures are assumed on average to have rotational symmetry transversely isotropic fracture system behaviour and the background is assumed isotropic the resulting equivalent medium is transversely isotropic and the effect of the additional compliance of the fracture system may be specified by two parameters in addition to the two isotropic parameters of the isotropic background dilute systems of flat aligned microcracks in an isotropic background yield an equivalent medium of the same form as that of the isotropic medium with large joints i e there are two additional parameters due to the presence of the microcracks which play roles in the stress strain relations of the equivalent medium identical to those played by the parameters due to the presence of large joints thus knowledge of the total of four parameters describing the anisotropy of such a fractured medium tells nothing of the size or concentration of the aligned fractures but does contain information as to the overall excess compliance due to the fracture system and its orientation as the aligned microcracks which were assumed to be ellipsoidal with very small aspect ratio are allowed to become non fiat i e have a growing aspect ratio the moduli of the equivalent medium begin to diverge from the standard form of the moduli for flat cracks the divergence is faster for higher crack densities but only becomes significant for microcracks of aspect ratios approaching 0 3

the role of climate and vegetation in weathering and clay mineral formation in late quaternary soils of the swiss and italian alps nteractions between climate and soil remain ambiguous particularly when silicate weathering and clay mineral formation and transformation rates are considered in relation to global climate changes recent studies suggest that climate affects weathering rates much less than previously thought here we show that the climate in the central european alps has a significant but indirect influence on the weathering of soils through vegetation the pattern of element leaching and mineral transformations is not only due to precipitation and temperature element leaching was greatest in subalpine forests near the timberline weathering is lessened at higher and lower altitudes vegetation therefore contributes significantly to weathering processes the highest accumulation of organic matter was found in climatically cooler sites subalpine range where the production of organic ligands which enhance weathering is greatest patterns of smectite formation and distribution had strong similarities to that of the elemental losses of fe and al r 0 69 p 0 01 or base cations r 0 58 p 0 05 higher precipitation rates and the production of organic chelating compounds in the soil promoted the appearance of smectites the relationship between climate element leaching fe al ca mg k na and smectite formation is strongly nonlinear and driven by the podzolisation process which is more pronounced near the timberline because of the bioclimatic constellation climate warming will probably in the future lead to a decrease in som stocks in the subalpine to alpine range because of more favourable conditions for biodegradation that would also affect weathering processes

the extratropical transition and precipitation distribution of hurricane floyd 1999 abstract several recent landfalling tropical cyclones e g dennis floyd and irene 1999 have highlighted a need for a refinement in the forecasting paradigms and techniques in the area of quantitative precipitation forecasting floyd proved to be a particularly challenging forecast problem as it was accompanied by catastrophic flooding over large regions of the east coast in spite of its relatively quick northward movement the extent and intensity of the precipitation distribution was strongly modulated by the storm s interaction with a midlatitude trough in an attempt to better understand and quantify the relevant dynamics during this interaction potential vorticity pv and quasigeostrophic perspectives are utilized as floyd approached the east coast precipitation shifted to the left of the storm track due to the presence of a deep midlatitude trough in the ohio valley the juxtaposition of a cold core pv anomaly associated with the midlatitude trough and a warm core pv anomaly associated with

soil development along an elevational transect in the western sierra nevada california soil development along an elevational transect on the western slopes of the the central sierra nevada was investigated to assess the effects of climate on soil properties and processes the transect of seven soils formed in granitic residuum spans elevations from 198 to 2865 m with mean annual temperature and precipitation differences of 13 c 3 9 16 7 and 94 cm 33 127 respectively soil ph decreased by about two units and base saturation decreased from 90 to 10 with increasing elevation concentrations of organic c in the solum increased with elevation with the largest single increase occurring between the oak woodland 5 6 kg c m2 and mixed conifer sites 10 15 kg c m2 clay mineralogy showed a general trend of desilication and hydroxy al interlayering of 2 1 layer silicates with increasing elevation the degree of chemical weathering based on clay and secondary fe oxide concentration in the solum showed a maximum clay 536 kg m2 and fe oxides 24 kg m2 at mid elevations having intermediate levels of precipitation and temperature while some soil properties show a continuous progression e g organic carbon base saturation clay mineralogy with elevation other properties e g ph soil color clay and secondary fe oxide concentrations show a pronounced change threshold type step over a short distance at about 1600 m the explanation for the abrupt nature of this shift is not known however it coincides with the approximate elevation of the present day average effective winter snow line

the march 1993 superstorm cyclogenesis incipient phase synoptic and convective scale flow interaction and model performance abstract the incipient stages of the 12 14 march 1993 superstorm ss93 cyclogenesis over the gulf of mexico are examined noteworthy aspects of ss93 include 1 it is the deepest extratropical cyclone ever observed over the gulf of mexico during the 1957 96 period and 2 existing operational prediction models performed poorly in simulating the incipient cyclogenesis over the northwestern gulf of mexico a dynamic tropopause dt analysis shows that ss93 is triggered by a potent potential vorticity pv anomaly as it crosses extreme northern mexico and approaches the gulf of mexico the low level environment over the western gulf of mexico is warmed moistened and destabilized by a persistent southerly flow ahead of the approaching pv anomaly ascent and a lowering of the dt associated with a lowering of the potential temperature ahead of the pv anomaly contributes to further destabilization that is realized in the form of a massive convective outbreak an examination of the national centers for envi

midlevel cyclonic vortices generated by mesoseale convective systems abstract despite the large number of convective systems that occur over the central united states every year there are typically only a few well defined midlevel vortices apparent in satellite imagery after the overlying anvil debris from some convective complexes has dissipated or advected away a climatology of mesoscale convectively generated vortex mcv events for 1981 1988 is presented and the synoptic setting in which the circulation becomes apparent is discussed proximity sounding data from numerous cases are used to examine features of the kinematic and thermodynamic setting of mcvs at various lifelycle stages defined by satellite imagery features ofthe large scale environment that appear conducive to the formation and longevity of mcvs include weak flow weak vertical shear weak background relative vorticity and intense horizontal and vertical moisture gradients the rapid mesovortex generation observed can be explained by the stretching term of the vorticity equation most mcvs emerge fro

coherent regeneration and the role of water vapor and shear in a long lived convective episode abstract in a recent radar based climatological study of warm season precipitation over the continental united states carbone et al found a high frequency of long lived coherent rainfall episodes many of the events were of longer duration than normally associated with mesoscale convective complexes and exhibited phase speeds 10 m s 1 in excess of the phase speed associated with synoptic systems the observations led to the speculation that cold pool dynamics and wavelike propagation mechanisms were responsible for the longevity of the systems one of the long lived episodes included in the statistics of the carbone et al study is described here occurring on 14 15 july 1998 the system lasted 50 h and traveled over 2800 km at its peak intensity the system was a bow echo producing damaging wind large hail and local flash flooding an interesting aspect of the event was an abrupt 90 turn in the storm s orientation and propagation vector midway through its life the environmental factors that led t

diabatic divergence profiles in western pacific mesoscale convective systems abstract heating in the atmosphere can be expressed as diabatic divergence d which is nearly equal to the actual horizontal divergence in tropical convection high quality profile measurements from airborne doppler radar purls in ten mesoscale convective systems mcs observed during toga coare are examined and the mean profile is compared with rawinsonde array measurements young convective features have strong near surface convergence while older cells with better developed downdrafts and stratiform precipitation areas have their peak convergence aloft in the mean then surface flow is only weakly convergent or oven divergent so that the main convergence into mcss is deep and peaked aloft with a sharp melting convergence at 0 c divergence prevails above 10 km altitude but was undersampled by the radar unusual but well sampled observations in the purl dataset include a persistent widespread profile feature in one well sampled mcs a cyclone rainband oscillatory reverberations c

modeled and observed variations in storm divergence and stratiform rain production in southeastern texas abstractstorm divergence profiles observed by an s band doppler radar are compared to ensemble simulations of 10 disparate precipitating systems occurring in warm season weakly baroclinic and strongly baroclinic environments in southeastern texas eight triply nested mesoscale model simulations are conducted for each case using single and double moment microphysics with four convective treatments i e two convective parameterizations and explicit versus parameterized convection at 9 km observed and simulated radar reflectivities are objectively separated into convective stratiform and nonprecipitating anvil columns and comparisons are made between ensemble mean echo coverages and levels of nondivergence lnds in both the model and observations storms occurring in less baroclinic environments have more convective rain area less stratiform rain area and more elevated divergence profiles the model ensemble and observations agree best for well organized leading line trailing stratiform systems

jetlet formation from diabatic forcing with applications to the 1994 palm sunday tornado outbreak abstract the three dimensional responses of simple stably stratified barotropic and baroclinic flows to prescribed diabatic forcing are investigated using a dry hydrostatic primitive equation numerical model the north carolina state university geophysical fluid dynamics model a time dependent diabatic forcing is utilized to isolate the effects of latent heat release in a midlatitude convective system examination of the mass momentum adjustments to the diabatic forcing is performed with a focus on the development of an isolated midlevel wind maximum the results of both cases suggest the formation of a midlevel wind maximum in the form of a perturbation meso scale cyclone which later propagates downstream as the heating is decreased the scale of the perturbation cyclone remains at a sub rossby radius of deformation length scale therefore the mass perturbations adjust to the wind perturbations as the mesocyclone propagates downstream transverse vertical circulations which favor ascent on the r

mechanisms supporting long lived episodes of propagating nocturnal convection within a 7 day wrf model simulation abstract a large domain explicit convection simulation is used to investigate the life cycle of nocturnal convection for a one week period of successive zonally propagating heavy precipitation episodes occurring over the central united states similar to climatological studies of phase coherent warm season convection the longest lived precipitation episodes initiate during the late afternoon over the western great plains 105 100 w reach their greatest intensity at night over the central great plains 100 95 w and typically weaken around or slightly after sunrise over the midwest 95 85 w the longest lived episodes exhibit average zonal phase speeds of 20 m s 1 consistent with radar observations during the period composite analysis of the life cycle of five long lived nocturnal precipitation episodes indicates that convection both develops and then propagates eastward along an east west oriented lower tropospheric frontal zone an elevated 2 km deep layer of high e air helps sustain convect

numerical simulation of elastic wave propagation in fractured rock with the boundary integral equation method this paper describes a boundary integral equation method for simulating two dimensional elastic wave propagation in a rock mass with nonwelded discontinuities such as fractures joints and faults the numerical formulation is based on the three dimensional boundary integral equations that are reduced to two dimensions by numerical integration along the axis orthogonal to the plane of interest the numerical technique requires the assembly and solution of the coefficient matrix only for the first time step resulting in a significant reduction in computational time nonwelded discontinuities are each treated as an elastic contact between blocks of a fractured rock mass across such an elastic contact seismic stresses are continuous and particle displacements are discontinuous by an amount which is proportional to the stress on the discontinuity and inversely to the specific stiffness of the discontinuity simulations demonstrate that such formulated boundary element method successfully models elastic wave propagation along and across a single fracture generated by a line source

the synoptic setting and possible energy sources for mesoscale wave disturbances abstract thirteen case studies of mesoscale wave disturbances characterized by either a singular wave of depression or wave packets with periods of 1 4 h horizontal wavelengths of 50 500 km and surface pressure perturbation amplitudes of 0 2 7 0 mb are reviewed to isolate common synoptic features for these cases and to shed light on possible energy sources for the waves a strong thermal inversion in the lower troposphere north of a frontal boundary and a jet streak propagating toward a ridge axis in the upper troposphere are commonly observed in all the cases in general the area of wave activity is bounded by the jet axis to the west or northwest a surface front to the southeast an inflection axis between the trough and ridge axes to the southwest and the ridge axis to the northeast the conditions specified by lindzen and tung as being necessary to form a wave duct which include the existence of the lower tropospheric inversion seem to be met in many of these cases this suggests that a du

the characteristics of cultivated soils developed from coastal paleosand korcula island croatia the problem of maintaining soil quality and fertility of soil developed from pleistocene eolian sand deposits arises from improper management and conservation of the highly fragile sandy soil environment the research was undertaken to determine howvarious aspects of cultivated soil fertility can be related to specific pedological and geological factors and which one of these relationships plays an essential role in lumbarda polje korcula island croatia soil survey was done by examining and sampling one hundred locations to the depth of 100 cm within 40 ha of the winegrowing site geostatistical analysis was applied to characterize the spatial variability and produce the soil map of the area soil profiles were sampled for laboratory analysis including physicochemical characteristics and mineralogy modal analysis and petrographic microscopy of soil concretions were conducted as well two soil units su were identified both containing more than 80 sand su1 hypoluvic arenosols and su2 haplic arenosols fao 2006 in su1 reddish brown color originated from fe oxide coatings on sand grains whereas su2 is characterized by the rise of ph with depth and the presence of calcite as a cementing material cation exchange capacity was significantly higher in su2 the documented variability of element content and distribution in the soil profiles indicates differentweathering stages of the sandy layers diagrams of cr v and co v ratios indicate different origin of sand deposits light mineral fraction is dominant in both su most of the sand grains are intensively weathered and well rounded indicating long transportation from the source area the results of mineralogical and geochemical characterization of lumbarda polje grapevine growing site are applicable and useful to future studies that involve fingerprinting regional wines

relative roles of elevated heating and surface temperature gradients in driving anomalous surface winds over tropical oceans abstract elevated heating by cumulus convection and sea surface temperature gradients are both thought to contribute to surface winds over tropical oceans the relative strength and role of each mechanism is examined by imposing forcing derived from data on a linear primitive equation model with idealized parameterizations for the two forcings and comparing the response with observed surface winds two test cases are studied one related to the el nino southern oscillation and the other related to the dipole mode in the tropical atlantic it is found that in both cases elevated heating dominates the surface zonal wind response and contributes significantly to the meridional wind response especially in the subtropics and the south pacific and south atlantic convergence zone regions surface temperature gradients dominate the meridional wind forcing in regions near the equator with strong meridional temperature gradients

provenance and formation of the red palaeosol and lithified terra rossa like infillings on the island of susak a high resolution and chronological approach abstract red palaeosol rp covering the carbonate basement exposed at the bottom of the loess section and lithified terra rossa like materials situated in cavities ltr1 and karstified fissures ltr2 in cretaceous limestones were investigated by means of high resolution approach to give a systematic and deeper palaeopedological insight into reddish materials and the exposed red palaeosols on the island of susak both selected geochemical indicators of weathering al si na k al and fed fet and provenance la ce as well as detailed mineralogical analysis clearly showed differences among ltr1 ltr2 and rp respectively ltr1 and ltr2 represent erosional remains of different soils that existed on the surface of the limestone bedrock prior to the formation of the rp ltr2 has the highest ztr zircon tourmaline rutile index index and contains bauxite minerals gibbsite and boehmite clays kaolinite and mixed layer clay minerals and haematite ltr2 bears characteristics of reworked bauxitic materials mixed with other soils that existed on the surface of the carbonate basement those materials might have been mixed and transported until they were captured in the karstified fissure and subsequently interlocked with calcite veins and lithified this might have happened from the eocene age on our attempt to resolve the age of ltr2 formation more precisely using palaeomagnetic investigations did not give unambiguous results because the extremely viscous behaviour of the ltr2 samples hinders the acquisition of a stable remanent magnetisation if we exclude the secondary calcite ltr1 bears typical mineralogical and geochemical characteristics e g fed fet ratio similar to those of istrian terra rossa insoluble residues of cretaceous limestone might have been the main parent materials for the ltr1 formation while the most likely additional fluxes influencing terra rossa formation on the island of susak were aeolian dust and flysch the erosion remains ended in limestone cavities and were mixed with cm to dm sized angular and subangular limestone clasts and subsequently interlocked with calcite veins and lithified the investigated rp profile comprised the following mineral horizons bwb1 bwb2 bwb3 r the rp formed in a lithologically uniform material that dominantly presents a mixture of loess and partly remains of older soils e g rounded clay coatings not related to macrovoids that existed on the surface of the cretaceous limestone fed fet ratio in rp reflects a low degree of weathering of fe containing primary silicates therefore we can conclude that the rp does not fit a rather limited variation of selected fe oxide characteristics typical for terra rossa the investigated rp was classified independently of the overlying material the full name of the palaeosol that we classified is as follows hypereutric chromic cambisol episiltic endoloamic since no reversal of the emf was recorded in the rp we concluded that the rp formed during the brunhes epoch luminescence dating was applied to establish the age of the rp based on the acquired data we assume that the rp very likely formed during the penultimate interglacial ois7

dust flux estimates for the last glacial period in east central europe based on terrestrial records of loess deposits a review loess paleosol sequences are significant records of the mineral dust cycle of glacial interglacial periods as dust particles give rise to direct and indirect radiative forcing obtaining a reliable picture of the global and regional patterns of mineral dust fluxes during glacial periods can lead to a better understanding of the contribution of mineral dust to past climate changes recent progress in absolute dating of loess deposits in the carpathian basin in east central europe made it possible to provide correct aeolian flux estimates for the last glacial period marine isotope stage mis 2 mass accumulation rates mars from chronological data of 33 loess sites exhibited a wide range of values from 150 to 1422 g m 2 a 1 centered around median and mean values of 338 and 417 g m 2 a 1 marpm10marpm10 and marpm2marpm2 estimates have been also calculated using grain size measurements of many loess samples and loess mars in order to facilitate comparison with models and since particles larger than 10 m have a negligible radiative effect here we show that some previous model simulations of the dust cycle at the last glacial maximum lgm significantly underestimated the real aeolian flux ranges of our estimates marpm10 34 324marpm10 34 324 and marpm2 9 3 88 2gm 2a 1 in east central europe for this reason some simulations of dust induced direct radiative forcing of the lgm climate failed to yield reliable results for this mid latitude region as they have been based on three dimensional dust field models that are not capable of estimating the real aeolian fluxes in central europe a recent global model of top of the atmosphere toa radiative forcing by mineral aerosols at the lgm that has been based on more realistic parameterization of dust sources transport and deposition revealed zonally averaged surface cooling of 2 c for the latitudes of our study area this surface cooling and toa radiative forcing 2 to 3 w m 2 are greater than recognized in other models and draws our attention to the importance of further modeling the impact of mineral dust on lgm climate in order to gain insight into the spatial pattern of radiative forcing and better understand resulting climate response in mid latitude loess regions such as east central europe

abrupt chemical weathering increase across the permian triassic boundary previous studies have suggested a variety of causes for the end permian extinction event including a bolide impact flood basalt volcanism methane clathrate dissociation or some combination of catastrophic processes one common feature of these hypotheses is the prediction of an enhanced earliest triassic greenhouse new high resolution geochemical results from graphite peak antarctica support an abrupt increase in chemical weathering in the earliest triassic among otherwise genetically similar paleosols of similar provenance relative to the latest permian paleosols the earliest triassic paleosol exhibits greater leaching greater accumulation of immobile rees and evidence of lower soil po2 with no evidence of an erosional unconformity between the paleosols which are separated by 15 cm stratigraphically these results support a rapid shift perhaps 10 000 years to an earliest triassic greenhouse and a role for methane release in the extinction event and its aftermath

the evolution of the 10 11 june 1985 pre storm squall line initiation development of rear inflow and dissipation abstract mesoscale analysis of surface observations and mesoscale modeling results show that the 10 11 june squall line contrary to prior studies did not form entirely ahead of a cold front the primary environmental features leading to the initiation and organization of the squall line were a low level trough in the lee of the rocky mountains and a midlevel short wave trough three additional mechanisms were active a southeastward moving cold front formed the northern part of the line convection along the edge of cold air from prior convection over oklahoma and kansas formed the central part of the line and convection forced by convective outflow near the lee trough axis formed the southern portion of the line mesoscale model results show that the large scale environment significantly influenced the mesoscale circulations associated with the squall line the qualitative distribution of along line velocities within the squall line is attributed to the larger scale circulations associated with the le

potential vorticity anomalies associated with squall lines abstract this study involves observations and model simulations of potential vorticity anomalies in the wake of midlatitude squall lines using data from the oklahoma kansas pre storm experiment we analyze potential vorticity fields near two squall lines one with and one without a trailing stratiform region from this observational analysis we suggest that squall lines with trailing stratiform regions can leave large positive midtropospheric potential vorticity anomalies in their wake to further interpret these observations we consider a two dimensional version of semigeostrophic theory formulated in isentropic and geostrophic coordinates which results in a simple potential pseudodensity inverse potential vorticity equation using apparent heat source fields that model those computed diagnostically from pre storm data we find that theory does indeed predict large midtropospheric potential vorticity anomalies for model squall lines with a trailing stratiform region but not for model squall lines t

baroclinicity influences on storm divergence and stratiform rain subtropical upper level disturbances abstract divergence structures associated with the spectrum of precipitating systems in the subtropics and midlatitudes are not well documented a mesoscale model is used to quantify the relative importance different baroclinic environments have on divergence profiles for storms primarily caused by upper level disturbances in southeastern texas a subtropical region the divergence profiles simulated for a subset of the modeled storms are consistent with those calculated from an s band doppler radar realistic convective and stratiform divergence signals are also generated when applying a two dimensional convective stratiform separation algorithm to reflectivities derived from the mesoscale model although the model appears to underestimate stratiform rain area divergence profiles from the modeled precipitating systems vary in magnitude and structure across the wide range of baroclinicities common in southeastern texas barotropic storms more characteristic of the tropics generate the most elevated diver

composition properties and formation of pseudogley on loess along a precipitation gradient in the pannonian region of croatia abstract three pseudogley profiles stagnic cutanic albeluvisol dystric siltic stagnic cutanic albeluvisol eutric siltic and luvic stagnosol hypereutric siltic were studied along the 700 1000 mm mean annual precipitation map gradient in the pannonian region of croatia the aim was to compare their composition and properties and to determine the major processes of their formation as well as to show whether investigations of pseudogley climosequences in this part of pannonian basin are feasible all three soil profiles were formed in situ from initially vertically homogeneous previously cycled and post depositionally modified loess deposits of same provenance given their morphology texture geochemical ratios and mineralogy substantial morphological and physical a horizons colors eg horizons thicknesses colors bulk densities and porosities btg horizons redoximorphic features as well as chemical soil properties ph base saturation topsoil organic c content corresponded to the precipitation gradient on the other hand due to slight differences between their parent materials clay content and cec values of the investigated profiles did not increase with the increase of map nevertheless processes of acidification and pseudogleying were found to be least pronounced at the location with the lowest map and most pronounced at the location with the highest map intensity of lessivage as one of major pedogenetic processes in all three investigated pseudogleys did not correspond to the precipitation gradient since it was more a function of soil ph and clay mineralogy than map the three pedogenetic processes were recognized on the basis of obtained ph base saturation cia chemical index of alteration and ti al values as well as soil texture morphology presence and characteristics of clay coatings and redoximorphic features and phyllosilicate dynamics comminution of chlorite into the clay fraction vermiculitization smectite translocation observed along the investigated profiles given the uneven environmental conditions of loess depositions across the pannonian region of croatia and the resulting incomplete uniformity of loess parent materials investigations of pseudogley climosequences in this part of the pannonian basin should be approached with caution

linear response of a stratified tropical atmosphere to convective forcing abstract the three dimensional response of the tropical atmosphere to an isolated heat source is investigated using a primitive equation model linearized about a resting basic state on an equatorial plane the model equations are solved by applying vertical and horizontal normal mode transforms the thermal forcing was chosen to simulate the convection which occurs over tropical south america during the southern hemisphere summer the vertical dependence of the forcing is such that the heating is zero at the top and bottom boundaries with a variable level of maximum beating the model results with steady forcing are compared with the average circulation over tropical south america for a 19 day period in the southern hemisphere summer of 1979 and it is shown that the model reproduces many aspects of the observed circulation the partition of the energy of the steady state response between the vertical modes is calculated and it is shown that the internal mode with an equivalent depth of 208 m is domina

is midlatitude convection an active or a passive player in producing global circulation patterns abstract the ability of persistent midlatitude convective regions to influence hemispheric circulation patterns during the northern hemisphere summer is investigated global rainfall data over a 15 yr period indicate anomalously large july total rainfalls occurred over mesoscale sized midlatitude regions of north america and or southeast asia during the years of 1987 1991 1992 and 1993 the anomalous 200 hpa vorticity patterns for these same years are suggestive of rossby wave trains emanating from the regions of anomalous rainfall in the midlatitudes results from an analysis of an 11 yr mean monthly 200 hpa july wind field indicate that in the climatological mean rossby waveguides are present that could assist in developing a large scale response from mesoscale sized regions of persistent convection in the midlatitudes this hypothesis is tested using a barotropic model linearized about the 200 hpa july time mean flow and forced by the observed divergence anomalies the model results are in qualit

formation of the enhanced v infrared cloud top feature from high resolution three dimensional radar observations the responsible mechanism for the formation of the enhanced v infrared cloud top feature observed above tropopause penetrating thunderstorms is not well understood a new method for the combination of volumetric radar reflectivity from individual radars into three dimensional composites with high vertical resolution 1km is introduced and used to test various formation mechanisms proposed in the literature for analysis a set of 89 enhanced v storms over the eastern continental united states are identified in the 10 yr period from 2001 to 2010 using geostationary satellite data the background atmospheric state from each storm is determined using the interim ecmwf re analysis era interim and radiosonde observations in conjunction with the infrared temperature fields analysis of the radar data in a coordinate relative to thelocationoftheovershootingconvectivetopandinaltitudesrelativetothetropopausesuggeststhataboveanvil stratospheric cirrus clouds are the most likely mechanism for the formation of the enhanced v

diabatically driven discrete propagation of surface fronts a numerical analysis discrete frontal propagation has been identified as a process whereby a surface front discontinuously moves forward without evidence of frontal passage across a mesoscale region numerical simulations are employed to examine the upper level evolution of a discrete frontal propagation event and to explore the processes that were responsible for the discrete movement model results indicate that a frontal pressure trough was not able to penetrate through a deep surface based layer of cool air created by a precipitating convective system several hundred kilometers in advance of the front meanwhile a new low level baroclinic zone formed well ahead of the front along the southern side of the cool layer as the midlevel front moved continuously over the cool layer a new low level front developed in the new baroclinic zone and the original low level front dissipated at the surface the simulated front did not pass through the cool layer frontogenesis terms reveal that the prefrontal circulation that becomes the new frontal circulation initially forms directly from diabatic frontogenesis daytime heating in the prefrontal boundary layer and cooling from thunderstorms combine to create a thermal gradient and a mesoscale pressure perturbation winds turn in response to the altered pressure field and form a convergent boundary resulting in kinematic frontogenesis the boundary subsequently undergoes rapid intensification sensitivity studies were conducted in which latent heating due to precipitation was withheld and the influence of clouds on the radiation scheme was ignored in a simulation with both of these effects withheld the original front passes continuously through the region that is there is no discrete propagation thus diabatic processes associated with a large complex of thunderstorms were necessary to induce the discrete frontal propagation in this case this conclusion contrasts with previous studies where fronts were observed to propagate discretely in dry environments

overview of ophiolites and related units in the late palaeozoic early cenozoic magmatic and tectonic development of tethys in the northern part of the balkan region abstract the northern balkan peninsula including serbia montenegro bosnia croatia and the former yugoslavian republic of macedonia represents an excellent region for the study of tectonic processes related to mesozoic tethyan ophiolite genesis and emplacement we first summarise the main tectonic units of the northern balkan peninsula and then use this information to discuss tectonic processes including rifting sea floor spreading ophiolite genesis and emplacement melange accretion ocean basin closure and collision we then discuss alternative models of ophiolite genesis and emplacement for the region and suggest that multi ocean basin interpretations fit the data better than single ocean basin interpretations rifting of adria gondwana during the triassic created a rift in the south budva zone and opened a triassic oceanic basin further north dinaride ocean occurrences of inferred sub continental mantle lithosphere in the dinaride ophiolite belt e g zlatibor may record extensional exhumation within an ocean continent transition zone bordering the adria dinaride continent this was followed by emplacement together with ophiolites and melange during upper jurassic early cretaceous time upper triassic radiolarites and mid ocean ridge type basalts formed at a spreading ridge after continental break up the oceanic lithosphere of the dinaride ophiolite belt was partly generated above a subduction zone the metamorphic soles of the dinaride ophiolites formed during mid late jurassic mainly based on k ar dating widespread melange that is associated with the ophiolites represents a subduction complex controlled by tectonic accretion and sedimentary reworking in trench and fore arc basin settings a possible cause of jurassic dinaride ophiolite emplacement was collision of a subduction trench with a continental margin further north mesozoic oceanic lithosphere subducted northeastwards present coordinates opening a late jurassic marginal basin in the main vardar zone the dinaride ocean in the south closed during late jurassic early cretaceous time tithonian berriasian deformed oceanic crust melange and magmatic arc rocks further north main vardar zone were transgressed by mainly clastic sediments during the early cretaceous however part of the vardar ocean vardar zone western belt or sava zone remained partially open until latest cretaceous time generally northward subduction within this remnant ocean triggered further supra subduction zone ophiolite genesis during the late cretaceous the ocean closed by the maastrichtian followed by early cenozoic regional scale southward thrusting that locally intercalated older and younger mesozoic ophiolites and melanges future progress particularly depends on determining the crystallisation ages of the ophiolites obtaining better structural data on the direction of initial ophiolite emplacement and unravelling the palaeozoic tectonic development of the eurasian continental margin

use of multifractal seismic waveform parameters to characterize the hydraulic properties of fractured media numerical experiments summary the multifractal characteristics of seismic waveforms that have propagated through fractured media were studied using numerical experiments the study suggests that multifractal waveform parameters i e information dimension correlation dimension curvature and range indices bear correlations with the hydraulic properties of the fractured media the characteristic waveform parameters were estimated from a multifractal analysis of 1 d synthetic seismograms generated using a variation of the reflectivity method waveforms from fractured zones were obtained by a superposition of reflections from horizontal fractures with a varying distribution of fracture length aperture and spacing the constructive and destructive interferences of the composite reflections from the fractures in the fractured layer result in waveforms that possess multifractal attributes the characteristic parameters extracted from the waveforms are shown here to correlate with the hydraulic properties of the fractured rockmass which include the fracture permeability the discontinuity index and the fracture density parameter

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

doppler radar observations of mesoscale wind divergence in regions of tropical convection abstract a simple new analysis method for large single doppler radar datasets is presented using data from several tropical field experiments a cylindrical grid is chosen to respect both the geophysical importance of altitude and the radar importance of range and azimuth horizontal and temporal fine structure are sacrificed by compiling data as hourly histograms in 12 24 36 spatial grid cells of 15 azimuth 8 km horizontal range 500 m height respectively mean doppler radial velocity in each region is automatically unfolded dealiased using a simple histogram method and fed into a velocity azimuth display vad analysis the result is a set of hourly horizontal wind and wind divergence profiles with associated error estimates for circles of different radii centered on the radar these divergence profiles contain useful heating profile information in many weather situations not just occasional cases of uniform widespread rainfall consistency of independent estimates for concentric circl

late pleistocene loess palaeosol sequences in the vojvodina region north serbia late pleistocene loess palaeosol sequences are widespread in the vojvodina region with thicknesses reaching a maximum of about 20 m our investigations include more than 40 of these loess sections geochronology of the last glacial loess palaeosol sequences based on lumines cence dating and amino acid racemisation provides correlations between upper pleistocene loess palaeosol sediments in vojvodina and comparable deposits at other european localities sedimentary logs of magnetic susceptibility grain size measurements and carbonate content combined with malacological evidence indicate two main relatively cold and arid phases during the last glacial period related to intensive accumulation of loess units l1l1 and l1l2 as well as many brief episodes of dry and windy climatic conditions suggesting a possible relationship with cold events recorded in the north atlantic region generally late pleistocene climate in the region was dry and relatively warm compared with glacial period sites in central europe and was characterised by sharp differences between glacial and interglacial modes new data and interpretations presented in this study emphasise the significance of loess palaeosol sequences in vojvodina for the reconstruction of the temporal and spatial evolution of late pleistocene palaeoclimate in this part of europe copyright 2007 john wiley sons ltd

initiation of precipitation episodes relative to elevated terrain abstract the western and central united states experience a pronounced diurnal cycle in rainfall during the warm season over the higher terrain west of 105 w most precipitation occurs in the afternoon whereas the central united states experiences more nocturnal events this coherent phase transition between the rocky mountains and the u s great plains is well defined for all warm seasons between 1996 and 2003 provided that the rainfall observations are remapped relative to the elevated terrain in the western united states prior to north south averaging due to the westward shift of the continental divide north of 42 n and its intersection with the warm season storm track for 2002 the diurnal coherence greatly improves after remapping the 2002 rainfall observations this speaks to the long range influence of orography on precipitation frequency and suggests that the primary east west corridor of precipitation for an individual warm season intersects the cordillera over a fairly narrow latitude range

spatial predictions of geological rock mass properties based on in situ interpretations of multi dimensional seismic data abstract the article presents a statistical approach to characterize and predict engineering geological conditions in the up to 2000 m deep faido tunnel and gotthard base tunnel in switzerland seismic investigations were conducted to improve the technology of interpreting seismic tomographic images overall the goal of this study was to predict spacial maps of geological rock mass properties such as uniaxial compressive strength or total fracture spacing by using up to six seismic features in combination e g compression wave and shear wave velocities and dynamic poisson s ratio self organizing mapping som an artificial intelligent method was used for the purposes of interpreting multi dimensional geophysical attributes derived from seismic profiles of tomographic images along tunnel sidewalls the som method was applied in the faido tunnel to delineate complex physical relations between the geological and seismic parameters then the method was applied to predict geological properties around a segment of the gotthard base tunnel with unknown geological geotechnical conditions the results illuminate that correlation analyses pairwise parameter classification are substantially less powerful than the som method multi parameter classification in order to interpret geological features from seismic in situ data moreover predicted spatial distributions of the total fracture spacing and the uniaxial compressive strength for example corresponded well with drill core and tunnel mapping results the som approach was a helpful tool for practitioners in predicting zones of instabilities and geological complexity during underground excavation processes of the gotthard base tunnel it is suggested to use such an interpretation method as decision support for purposes of sub surface exploration and long term geophysical monitoring of large scale geoengineering projects such as disposals of nuclear waste and greenhouse gases or geopower plants for renewable energy geothermal biosoils