the record los angeles heat event of september 2010 1 synoptic scale meso β scale analyses of interactive planetary wave breaking terrain and coastal induced circulations on 27 september 2010 the los angeles civic center reached its all time record maximum temperature of 45 c before 1330 ldt with several other regional stations observing all time record breaking heat early in that afternoon this record event is associated with a general circulation pattern predisposed to hemispheric wave breaking three days before the event wave breaking organizes complex terrain and coastal induced processes that lead to isentropic surface folding into the los angeles basin the first wave break occurs over the western two thirds of north america leading to trough elongation across the southwestern u s collocated with this trough is an isentropic potential vorticity filament that is the locus of a thermally indirect circulation central to warming and associated thickness increases and ridging westward across the great basin in response to this circulation two subsynoptic wave breaks are triggered along the pacific coast and the ipv filament is coupled to the breaking waves and the interaction produces a subsynoptic low pressure center and a deep vortex aloft over the southeastern california desert this coupling leads to advection of an elevated mixed layer over point conception the night before the record breaking heat that creates a coastally trapped low pressure area southwest of los angeles the two low pressure centers create a low level pressure gradient and east southeasterly jet directed offshore over the los angeles basin by sunrise on the 27th this allows the advection of low level warm air from the inland terrain towards the coastally trapped disturbance and descending circulation resulting in record heating

high resolution characterization of vadose zone dynamics using cross borehole radar characterization of the dynamics of moisture migration in the unsaturated zone of aquifers is essential if reliable estimates of the transport of pollutants threatening such aquifers are to be made electrical geophysical investigation techniques such as ground penetrating radar offer suitable methods for monitoring moisture content changes in the vadose zone moreover these tools permit relatively large measurement scales appropriate for hydrological models of unsaturated processes and thus they offer a distinct advantage over conventional measurement approaches ground penetrating radar when applied in transmission mode between boreholes can provide high resolution information on lithological and hydrological features the technique may be applied in tomographic mode and in a much simpler vertical profile mode both modes of measurement have been utilized using two boreholes 5 m apart located at a field site in the uk sherwood sandstone aquifer radar transmission measurements have been used to characterize the change in moisture content in unsaturated sandstone due to controlled water tracer injection continual monitoring of cross borehole radar measurements over an 18 month period has also permitted determination of travel times of natural loading to the system and has revealed the impact of subtle contrasts in lithology on changes in moisture content over time the time series of inferred moisture contents show clearly wetting and drying fronts migrating at a rate of approximately 2 m month 1 throughout the sandstone

radiative transfer mixing models of meteoritic assemblages 1 a spectral mixing model for the expected conditions on asteroid surfaces based on hapke s radiative transfer theory for intimate mixtures is presented this model calculates the visible near infrared reflectance spectrum of an intimate mixture incorporating the modal mineralogy the mineral chemistry the particle size and the degree of space weathering as factors and includes an improved treatment for the spectral effects of coarse grained fe ni metal this model can reproduce the spectra of geologically plausible mixtures of silicate components and meteorites with known mineral abundances chemistry and particle sizes we compare the model spectral effects of the coarse grained fe ni metal naturally present on asteroid surfaces to the spectral effects of submicroscopic iron produced by lunar style space weathering the model spectral effects of large asteroid surface concentrations of coarse grained fe ni metal are similar to the spectral effects of smfe in some cases we model the composition of asteroid 4 vesta and find it to be consistent with a minimally space weathered eucritic composition finally we predict the spectral properties of some example of ordinary chondrite parent bodies when modeled with particle sizes matching the optically dominant particle size of the lunar surface and minimal abundances of smfe these model ordinary chondrite parent bodies plot outside the s iv asteroid field on a band area ratio versus band i center plot we find that a combination of larger particle sizes and increased smfe abundances is the most effective way to move these models into the s iv field

s type asteroids ordinary chondrites and space weathering the evidence from galileo s fly bys of gaspra and ida new observations of the s type asteroids gaspra and ida especially by the galileo spacecraft demonstrate that a space weathering process operates which modifies the reflectance spectra of fresh material to be redder straighter and have shallower absorption bands the weathering process appears similar to but less potent than that observed on the moon it operates in the sense that it would tend to convert spectra of ordinary chondrites oc to having the spectral traits of s type asteroids these results appear to resolve the major obstacles of the long standing s type conundrum about the provenance of ordinary chondrite meteorites a wide body of recent research which is reviewed here builds on previous meteoritical evidence to support a new developing consensus that the larger s type asteroids are a diverse assortment of silicaceous assemblages which includes the ordinary chrondite parent bodies recent fairly realistic laboratory simulations of space weathering processes have changed oc spectra to resemble s type spectra j f bell s highly regarded earlier paradigm that oc parent bodies would be found only among sub 10 km main belt asteroids has been tested by an extensive observational survey by r binzel and his proteges the result is that no small main belt analog for the ocs has been found not even the somewhat oc like object boznemcova this article reviews the history of the s type conundrum which set the stage for galileo s historic flybys i review the findings about gaspra and ida including results about their geology their geophysical structure and probable origins and about ida s small moonlet dactyl density constraints on ida set by dactyl s orbit rule out for ida at least the classic view of s types as metallic stripped cores of differentiated precursor asteroids new analysis of the galileo spectral images of ida is presented that provides strong evidence that space weathering occurs on ida and that ida and the koronis family asteroids in general are plausibly oc like in composition after reviewing 1990s developments on the s type conundrum i advocate a new perspective that the ordinary chondrite parent bodies are among the s type asteroids a diverse grouping that also contains other silicaceous and silicate metal assemblages presumably including various stony irons and primitive achondrites represented in meteorite collections gaspra may be such a metal rich assemblage

ground penetrating radar and its use in sedimentology principles problems and progress abstract ground penetrating radar gpr also referred to as ground probing radar surface penetrating radar subsurface radar georadar or impulse radar is a noninvasive geophysical technique that detects electrical discontinuities in the shallow subsurface

dynamics of mild strombolian activity on mt etna abstract here we report the first measurements of gas masses released during a rare period of strombolian activity at the bocca nuova crater mt etna sicily uv camera data acquired for 195 events over an 27 minute period 27th july 2012 indicate erupted so2 masses ranging from 0 1 to 14 kg per event with corresponding total gas masses of 0 1 to 74 kg thus the activity was characterised by more frequent and smaller events than typically associated with strombolian activity on volcanoes such as stromboli events releasing larger measured gas masses were followed by relatively long repose periods before the following burst a feature not previously reported on from gas measurement data if we assume that gas transport within the magma can be represented by a train of rising gas pockets or slugs then the high frequency of events indicates that these slugs must have been in close proximity in this case the longer repose durations associated with the larger slugs would be consistent with interactions between adjacent slugs leading to coalescence a process expedited close to the surface by rapid slug expansion we apply basic modelling considerations to the measured gas masses in order to investigate potential slug characteristics governing the observed activity we also cross correlated the acquired gas fluxes with contemporaneously obtained seismic data but found no relationship between the series in line with the mild form of manifest explosivity

towards realistic aquifer models three dimensional georadar surveys of quaternary gravel deltas singen basin sw germany abstract understanding sedimentary heterogeneities has nowadays become crucial for sophisticated aquifer management the methods used so far for aquifer characterization e g pump test coring analysis cannot provide the needed resolution for a sufficient prediction of the subsurface properties e g sudicky 1986 this calls for the application of the outcrop analogue approach to aquifers e g macfarlan et al 1994 aigner 1995 in this project we used georadar ground penetrating radar or gpr to acquire the subsurface information for high resolution three dimensional images and radar facies mapping of glaciolacustrine delta sediments in the singen basin sw germany a three dimensional reconstruction of sedimentary heterogeneities for a detailed aquifer characterisation becomes possible by combining gpr profiling and outcrop information a case study is presented showing a complex three dimensional architecture of a quaternary gravel body consisting of the following three types of architectural elements 1 glaciolacustrine delta foresets 2 erosional surfaces with scour pool fills and 3 horizontal glaciofluvial gravel sheets although this seems a relatively simple architectural inventory the three dimensional georadar profiling shows considerable internal heterogeneities the radar data are interpreted following the seismic stratigraphic approach i e the delineation of radar facies types and of radar sequences the three dimensional heterogeneities are visualized by means of time slices 3 d block or chair diagrams or series of radar facies maps

exploring the interplay between infiltration dynamics and critical zone structures with multiscale geophysical imaging a review abstract infiltration is the process of water entering into and routings through the subsurface it has a profound impact on water flux in the earth s critical zone cz influencing phenomena such as overland flow stream generation plant available water and groundwater recharge as well as the associated cz processes and functions of weathering erosion slope stability and food production however reliable measurement of infiltration in structured geomedia soils and regolith with hidden subsurface features remain challenging the increasing availability of geophysical techniques has helped them emerge as viable options for minimally invasive determination of infiltration at the pedon to hillslope or catchment scales geophysical methods replace the educated guesswork of interpreting field data from traditional infiltrometers with direct visualization and quantification this paper provides a comprehensive literature review of various applications of geophysical techniques used to 1 visualize infiltration relevant structures 2 monitor non uniform or preferential infiltration patterns and 3 map soil moisture distribution after infiltration it then proposes a new conceptualization form and function dualism for subsurface hydrology to link preferential infiltration to cz structures with the goal of formulating more realistic infiltration theories related to subsurface structural heterogeneity the characterization of both subsurface structures form and infiltration dynamics function via geophysical imaging should help infiltration models currently emphasizing macroscale behaviors rooted in the continuum concept expand to accommodate the microscale nature of preferential flow integrating multiple geophysical approaches and developments into the new generation of geophysical techniques will further enhance our ability to see into the fabric of the subsurface and capture the dynamics of non uniform infiltration through the hidden half of the cz this approach offers exciting opportunities for understanding the complex interactions between cz structures and cz processes

using two and three dimensional georadar methods to characterize glaciofluvial architecture abstract the threat of pollution in the shallow subsurface has led to an increasing need to understand how complex heterogeneities in gravel aquifers influence groundwater transport to characterize these heterogeneities we have conducted extensive two dimensional 2 d and three dimensional 3 d ground penetrating radar gpr or georadar surveys in two quarries within the rhine valley of northeastern switzerland the quarries comprised gravel and sand deposited in a proglacial braided river system that followed the maximum wurm stage glaciation after the surveys the terrace walls beneath the two study sites were photographed as they were being excavated by combining information extracted from the 2 and 3 d georadar images with the outcrop photographs it was possible to correlate georadar facies with the various glaciofluvial architectural elements the dominant elements were scour pools formed at or near the confluences of two stream channels and horizontally bedded and massive gravel sheets deposited during moderate to high water flow conditions and exposed during low flow conditions architectural elements were generally elongated parallel to the mean flow directions of the ancient river system variations in the strike of their long axes reflected lateral and vertical changes in the local flow direction time slices showed structural trends not evident on 2 d georadar images and photographs data interpretation was quicker more complete and less ambiguous when georadar facies analyses were based on a combination of georadar vertical profiles and time slices than when based on georadar vertical profiles alone

surface lithologic heterogeneity of asteroid 4 vesta abstract high precision spectrophotometry of 4 vesta the third largest asteroid was used to establish the surface composition of this body and to investigate mineralogical variations across its surface the average surface of vesta is analogous to howardite and or polymict eucrite assemblages regolith derived members of the hed meteorite suite which consist of a eucrite matrix containing differing amounts of a diogenite component color and or spectral changes which exhibit a consistent relationship to rotational phasing are evident in 16 of 18 studies of vesta dating back to 1929 including the present work after elimination of possible sources of spurious spectral or color changes it is concluded that these variations arise from hemispheric variations in surface materials and hence provide a means of spatially resolving subhemispheric compositional units on the surface of vesta the background surface of vesta is a relatively dark howardite or polymict eucrite pyroxene plagioclase assemblage with several compositionally distinct bright regions clustered in one hemisphere viewed around the maximum in vesta s lightcurve these include what appears to be an olivine bearing unit suggested name leslie formation located near vesta s equator which probably represents an impact basin and or its associated ejecta that penetrated through the basaltic crust other high albedo compositional units including an apparently low calcium eucrite region and several diogenite pyroxenite regions at least one located near the southern pole may be smaller shallower impact basins by analogy to the eucrite meteorites which represent surface flows or shallow intrusions and which constitute the major component of the regolith derived howardites and polymict eucrites we conclude that the howardite polymict eucrite units represent a regolith gardened original surface of vesta it is probable that the low albedo of the background surface on vesta is due to an age related darkening effect similar to that inferred from the galileo images of gaspra and ida this mechanism is consistent with the correlation of absorption feature intensity with the lightcurve vesta appears to have an old eucritic surface darkened with age and represented among the meteorites by the regolith derived howardites and polymict eucrites on which several impacts on one hemisphere have exposed fresher brighter diogenite and olivine bearing material based on qualitative analysis of the mineralogical variations as a function of rotation a generalized lithologic map of vesta was produced there is reasonable control on the longitude of lithologic features but little control on their latitudes except where specifically noted in producing this map discrete circular features were used on the plausible assumption that impacts have been the most important geologic process on this surface for most of the age of the solar system the shape of the features has thus been assumed rather than derived and is subject to future revision as data improve

gap flows through idealized topography part ii effects of rotation and surface friction numerical simulations are conducted of geostrophically balanced flow over an isolated mountain cut by a horizontal gap the relative importance of the along gap synoptic scale pressure gradient and terraininduced mesoscale circulations for the generation of gap winds was examined by changing the direction of the synoptic scale wind relative to the topography in all cases the forcing associated with mesoscale circulations generated by the mountain was at least as significant as the synoptic scale pressure gradient in the cases where a component of the large scale flow was directed perpendicular to the ridge the dynamics were dominated by either the vertical momentum fluxes due to mountain lee waves or by mesoscale pressure gradients associated with upstream blocking or lee troughing mesoscale circulations were also important when the large scale flow was parallel to the ridge because surface friction turned the low level winds toward the high pressure side of the ridge partially blocking the flow and enhancing the along gap pressure gradient the flow in the interior of a very long uniform gap was also simulated for a case with the synoptic scale winds parallel to the ridge so that the synoptic scale pressure gradient was down the gap the flow in the interior of the long gap was not horizontal and not in a simple dynamical balance between acceleration the pressure gradient force and surface friction even the flow in the lowest 150 m was gradually subsiding subsidence and lateral momentum flux convergence at low levels near the center of the gap were important contributors to the mass and along gap momentum budgets

space weathering on airless bodies resolving a mystery with lunar samples using new techniques to examine the products of space weathering of lunar soils we demonstrate that nanophase reduced iron npfe0 is produced on the surface of grains by a combination of vapor deposition and irradiation effects the optical properties of soils both measured and modeled are shown to be highly dependent on the cumulative amount of npfe0 which varies with different starting materials and the energetics of different parts of the solar system the measured properties of intermediate albedo asteroids the abundant s type asteroids in particular are shown to directly mimic the effects predicted for small amounts of npfe0 on grains of an ordinary chondrite regolith this measurement and characterization of space weathering products seems to remove a final obstacle hindering a link between the abundant ordinary chondrite meteorites and common asteroids

impact excavation on asteroid 4 vesta hubble space telescope results hubble space telescope images of asteroid 4 vesta obtained during the favorable 1996 apparition show an impact crater 460 kilometers in diameter near the south pole color measurements within the 13 kilometer deep crater are consistent with excavation deep into a high calcium pyroxene rich crust or olivine upper mantle about 1 percent of vesta was excavated by the crater formation event a volume sufficient to account for the family of small vesta like asteroids that extends to dynamical source regions for meteorites this crater may be the site of origin for the howardite eucrite and diogenite classes of basaltic achondrite meteorites

threshold relations in subsurface stormflow 2 the fill and spill hypothesis analysis of subsurface stormflow from 147 storms at the 20 m long trench in the panola mountain research watershed by tromp van meerveld and mcdonnell 2006a showed that there was a distinct 55 mm precipitation threshold for significant subsurface stormflow production this second paper in the series investigates the processes responsible for this threshold response we installed a dense spatial array of maximum rise crest stage gauges and recording wells on the hillslope and studied the temporal and spatial patterns of transient saturation at the soil bedrock interface and its relation to subsurface stormflow measured at the trench face results show that while transient groundwater developed on parts of the hillslope during events smaller than 55 mm it was not until more than 55 mm of rain fell before bedrock depressions on the hillslope were filled water spilled over microtopographic relief in the bedrock surface and the subsurface saturated areas became connected to the trench when connectivity was achieved the instantaneous subsurface stormflow rate increased more than fivefold compared to before the subsurface saturated areas were connected to the trench face total subsurface stormflow was more than 75 times larger when connectivity was achieved compared to when connectivity was not achieved the fill and spill hypothesis presented in this paper is a process explanation for the observed threshold behavior of tromp van meerveld and mcdonnell 2006a thereby linking patterns and processes

interactions of north pacific tropical midlatitude and polar disturbances resulting in linked extreme weather events over north america in october 2007 abstractthis study uses observations and model reanalyses to examine the multiscale processes associated with four high impact extreme weather events ewes over north america during late october 2007 the ewes consisted of wind driven wildfires in california prolonged anomalous cold conditions in mexico linked to two cold surges heavy rainfall in the eastern united states and severe flood producing heavy rainfall in southern mexico the ewes involved a pronounced large scale flow reconfiguration across the north pacific and north america in conjunction with the formation of a high amplitude rossby wave train the flow reconfiguration involved perturbations to the north pacific jet stream linked to polar midlatitude and tropical disturbances including three tropopause level polar disturbances originating over northeastern asia transient extratropical cyclones a diabatic rossby vortex and western north pacific tropical cyclone kajiki eulerian and lagrangian diagnostics indicate that ridge amplifi

subsurface lateral preferential flow network revealed by time lapse ground penetrating radar in a hillslope subsurface lateral preferential flow lpf has been observed to contribute substantially to hillslope and catchment runoff however the complex nature of lpf and the lack of an appropriate investigation method have hindered direct lpf observation in the field thus the initiation persistence and dynamics of lpf networks remain poorly understood this study explored the application of time lapse ground penetrating radar gpr together with an artificial infiltration to shed light on the nature of lpf and its dynamics in a hillslope based on our enhanced field experimental setup and carefully refined gpr data postprocessing algorithms we developed a new protocol to reconstruct lpf networks with centimeter resolution this is the first time that a detailed lpf network and its dynamics have been revealed noninvasively along a hillslope real time soil water monitoring and field soil investigation confirmed the locations of lpf mapped by time lapse gpr surveys our results indicated the following 1 increased spatial variations of radar signals after infiltration suggested heterogeneous soil water changes within the studied soil which reflected the generation and dynamics of lpf 2 two types of lpf networks were identified the network at the location of soil permeability contrasts and that formed via a series of connected preferential flow paths and 3 the formation and distribution of lpf networks were influenced by antecedent soil water condition overall this study demonstrates clearly that carefully designed time lapse gpr surveys with enhanced data postprocessing offer a practical and nondestructive way of mapping lpf networks in the field thereby providing a potentially significant enhancement in our ability to study complex subsurface flow processes across the landscape

the non invasive characterization of pumping induced dewatering using ground penetrating radar abstract ground penetrating radar gpr profiling is a non invasive geophysical technique that has been used by endres et al ground water 38 2000 566 to successfully image pumping induced drainage in an unconfined aquifer however the drained water volume calculated from the gpr data was significantly less than the actual pumped volume to investigate the reasons for this discrepancy a seven day pumping test and five day recovery test was performed at canadian forces base borden in ontario canada a dense spatial coverage of gpr profiles was used to better quantify variations in drainage due to small scale aquifer heterogeneity in addition a neutron moisture content probe was used to directly observe drainage and the soil moisture profile at a sealed well near the pumping well neutron logging indicated that the transition zone translated downward during pumping without undergoing significant extension comparison of the gpr and neutron derived transition zone drawdowns show nearly equal responses both of these observations support the hypothesis that the behaviour of the gpr reflection is an accurate measure of the transition zone response in contrast transition zone drawdown obtained from both gpr and neutron logging are significantly delayed relative to potentiometric drawdown resulting in an extended capillary fringe the drained water volume was determined from the gpr derived transition zone drawdown data using a number of different approaches methods that incorporated information about spatial variations in drainage gave larger estimates of drained water volume however those estimates were still lower than the actual pumped volume the unaccountable volume of water could be a result of several factors aquifer heterogeneity may still not be adequately represented by the increased gpr coverage and or leakage from the underlying aquitard may be providing a significant volume of water

imaging rainfall drainage within the miami oolitic limestone using high resolution time lapse ground penetrating radar 1 the vadose zone of the miami limestone is capable of draining several centimeters of rainfall within a fraction of an hour once the water enters the ground little is known about the flow paths in the oolitic rock a new rotary laser positioned ground penetrating radar gpr system enables centimeter precise and rapid acquisition of time lapse surveys in the field two dimensional 2 d gpr time lapse surveying at a 3 min interval before during and after rainfall shows how buried sand filled dissolution sinks efficiently drain the bulk of the rainwater hourly repeated 3 d imaging of a dissolution sink in response to surface infiltration shows how the wetting front propagates at a rate of 0 6 1 2 m h traversing the 5 m thick vadose zone within hours at the same time some of the water migrates laterally into the host rock guided by stratigraphic unit boundaries average lateral propagation measured over a 28 hour period was of the order of 0 1 m h on a seasonal time frame redistribution involves the entire rock volume comparing 3 d surveys acquired after wet summer and dry winter conditions shows good gpr event correspondence but also time shifts up to 20 ns caused by the change of overall water content within the vadose zone high precision time lapse gpr imaging can therefore be used to noninvasively characterize natural drainage inside the vadose zone ranging from transient loading to seasonal variation

olivine or impact melt nature of the orange material on vesta from dawn abstract nasa s dawn mission observed a great variety of colored terrains on asteroid 4 vesta during its survey with the framing camera fc here we present a detailed study of the orange material on vesta which was first observed in color ratio images obtained by the fc and presents a red spectral slope the orange material deposits can be classified into three types a diffuse ejecta deposited by recent medium size impact craters such as oppia b lobate patches with well defined edges nicknamed pumpkin patches and c ejecta rays from fresh looking impact craters the location of the orange diffuse ejecta from oppia corresponds to the olivine spot nicknamed leslie feature first identified by gaffey gaffey m j 1997 icarus 127 130 157 from ground based spectral observations the distribution of the orange material in the fc mosaic is concentrated on the equatorial region and almost exclusively outside the rheasilvia basin our in depth analysis of the composition of this material uses complementary observations from fc the visible and infrared spectrometer vir and the gamma ray and neutron detector grand several possible options for the composition of the orange material are investigated including cumulate eucrite layer exposed during impact metal delivered by impactor olivine orthopyroxene mixture and impact melt based on our analysis the orange material on vesta is unlikely to be metal or olivine originally proposed by gaffey gaffey m j 1997 icarus 127 130 157 analysis of the elemental composition of oppia ejecta blanket with grand suggests that its orange material has 25 cumulate eucrite component in a howarditic mixture whereas two other craters with orange material in their ejecta octavia and arruntia show no sign of cumulate eucrites morphology and topography of the orange material in oppia and octavia ejecta and orange patches suggests an impact melt origin a majority of the orange patches appear to be related to the formation of the rheasilvia basin combining the interpretations from the topography geomorphology color and spectral parameters and elemental abundances the most probable analog for the orange material on vesta is impact melt

hydrological response of weathered clay shale slopes water infiltration monitoring with time lapse electrical resistivity tomography this work presents an attempt to monitor water infiltration and subsurface flow within a clay shale landslide using time lapse electrical resistivity tomography ert a rainfall experiment was carried out on a plot of 100 m2 at the laval landslide in the draix experimental catchments ore draix south french alps in order to characterize the spatial and temporal development of water circulation in the soil and to identify when steady state flow conditions are reached the experiment was conducted during 67 h with initial unsaturated conditions in the slope the apparent electrical resistivity values were inverted with a time lapse approach using several cross models the results indicate a significant decrease in resistivity 18 compared to the initial state in the rain plot downslope progression of negative resistivity anomalies is imaged suggesting that vertical and subsurface lateral flows have developed about 21 h after the start of the rain experiment a constant level of resistivity values is observed indicating that the hydrological system reached steady state flow conditions this observation is consistent with ground water level observations and chemical tracer analysis computed differences in time of steady state conditions highlight possible preferential flows near the landslide toe a hydrological concept of functioning of the slope is proposed and apparent saturated hydraulic conductivity ks of 1 7 10 4 m s 1 is computed from the steady state times this study demonstrates the potentiality of ert monitoring to monitor water infiltration in clay shale slopes and the high water transfer capacity of reworked clay shale material

the sundowner winds experiment swex pilot study understanding downslope windstorms in the santa ynez mountains santa barbara california abstractsundowner winds are downslope gusty winds often observed on the southern slopes of the santa ynez mountains sym in coastal santa barbara sb california they typically peak near sunset

three dimensional sedimentary architecture of a large mid channel sand braid bar jamuna river bangladesh the three dimensional subsurface alluvial architecture of a large approximately 3 km long 1 km wide 12 m high mid channel sand braid bar in the jamuna river bangladesh is described evolution of the bar and its depositional characteristics are assessed from a unique combination of ground penetrating radar surveys vibracoring and trenching that are allied to a series of bathymetric surveys taken during growth of the bar over a 29 month period this methodology permits identification of the formative processes of different packages of braid bar sedimentation and provides a facies model for deposition within the entire bar mid channel bar growth occurred in a region of flow expansion and was probably initiated by the stalling and amalgamation of large dunes these dunes created a bar core that grew by i propagation of a downstream accreting slipface ii vertical accretion through stacking of dunes on both bar stoss and top and iii lateral accretion on the bar margins during recession of the flood hydrograph braid bar sedimentation is dominated by four radar facies 1 large scale predominantly planar dipping reflections interpreted as cross stratification up to 8 m in height and greater than 100 m in width that is produced by the cross channel migration of bar margins 2 medium scale trough shaped and planar discontinuous reflections interpreted as cross stratification up to 4 m in height and 300 m wide that is deposited from large sinuous crested sand dunes 3 discontinuous reflections up to 2 m high and 30 m wide interpreted as small scale trough cross stratification that is the product of smaller sinuous crested dunes and 4 high amplitude undulating reflections interpreted as mud drapes deposited in regions of slow flow often in the bar tail region at low stage dune size decreases vertically within the bar in response to the progressively shallower flows on the emerging bar top later evolution of the bar as one anabranch channel became dominant created a 1 5 km extension to the bar tail with an 8 m high angle of repose bar margin slipface formed by flow transverse to the long axis of the bar seven styles of deposition can be defined that constitute the alluvial architecture bar margin slipface vertical accretion in channel bar top vertical accretion upstream accretion lateral accretion downstream accretion and low stage mud drapes a model of braid bar sedimentation is presented that shares many similarities with previous studies of smaller sand bed braid bars with the dominance of dune scale cross stratification the presence of large scale bar margin cross stratification and the occurrence of lateral vertical upstream and downstream accretion however the contribution of the bar margin facies to the preserved stratigraphy highlighted herein may have been underestimated in previous models of braided rivers in which the braid bars were migrating slowly this study suggests a scale invariance in several aspects of mid channel bar sedimentation in sand bed rivers and proposes a model of braid bar sedimentation that may be applied widely within studies of braided alluvial architecture

pairing geophysical techniques improves understanding of the near surface critical zone visualization of preferential routing of stemflow along coarse roots abstract there is compelling evidence from aboveground observations that trees considerably affect precipitation partitioning through the critical zone however due to the lack of appropriate methods the role of root systems the hidden half of trees on redistributing precipitation and infiltration into and routing through the soil remains inadequately visualized and understood here we designed a novel experiment to pair two non invasive geophysical techniques ground penetrating radar gpr and electrical resistivity tomography ert to trace stemflow through the soil in a forested hillslope after water was released on the trunk of an american beech fagus grandifolia ehrh to induce stemflow we used gpr to locate lateral coarse roots and gpr and ert together to confirm the wetting areas in response to the non uniform transport of stemflow signal changes between time lapse geophysical images were used to reveal both the response time and location of stemflow infiltration into and redistribution through the soil this first known study to investigate the subsurface routing of stemflow by combining gpr and ert revealed that the belowground funneling of stemflow along laterally oriented coarse roots transported water 2 8 m downslope from the study tree in 30 min after stemflow was initiated in situ excavation validated the distribution of lateral roots and lateral root derived preferential flow paths identified in geophysical images confirming the utility of pairing gpr and ert to gain insights into the temporal dynamics and spatial distribution of subsurface routing of stemflow the proposed method visualized and confirmed the funneling effect of roots on belowground water redistribution that contributed to subsurface lateral flow pairing gpr and ert provides a useful combination of geophysical methods to advance our understanding of the complex interactions between plant and soil such as the role of tree roots in soil hydrological process by revealing areas of funneling in the hidden part of the critical zone

space weathering from mercury to the asteroid belt the variety of evidence bearing on the nature of space weathering is reviewed the effects of space weathering include spectral darkening reddening and subdued absorption bands and the distinctive magnetic electron spin resonance caused by single domain metallic iron particles ever since the apollo missions two paradigms have dominated the thinking of the planetary science community concerning space weathering 1 the optical effects are caused by impact vitrified glass in agglutinates and 2 the submicroscopic metallic iron results from the reduction of ferrous iron by the impact melting of minerals whose surfaces have been saturated with hydrogen from the solar wind however studies carried out since the apollo program showed that both of these paradigms are invalid a hypothesis first suggested by the author and his colleagues 26 years ago but not generally accepted at that time now appears to be essentially correct both the optical and magnetic effects are caused by metallic iron particles smaller than the wavelength in ubiquitous vapor deposited coatings on soil particle surfaces and inside agglutinates the vapor is generated by both solar wind sputtering and micrometeorite impact vaporization and injected preferentially downward into the porous regolith the iron is reduced by a physical process the selective loss of oxygen that occurs during deposition of the vapor and does not require heating melting or a reducing environment a mathematical theory that describes the optical effects of the submicroscopic iron quantitatively is derived and applied to the regoliths of the moon mercury and an s asteroid

correlation between rock fabrics and physical properties of carbonate reservoir rocks three carbonate core samples from an oil and gas reservoir of the nw german basin were chosen to study the correlation between rock fabrics and physical properties of reservoir rocks detailed fabric analyses and texture investigations were carried out as well as laboratory measurements of different physical properties e g density porosity permeability electrical conductivity seismic compressional and shear wave velocities although the three core samples come from a similar depositional facies they show great differences in the occurrence and three dimensional distribution of the rock fabric elements these heterogeneities are the result of various diagenetic and tectonic processes for the correlation between the rock fabrics and the physical properties four main rock fabric types have to be considered a major constituents e g fossils ooides peloides and crystals b pore space with different pore types c fractures and d stylolites the results of the correlation clearly show that the values and anisotropies of the petrophysical properties are fairly related to the observed fabric elements with their different arrangements spatial distributions and preferred orientations these results also provide a fundamental understanding of the petrophysical responses such as seismics to the different geological features e g fractures and their dynamic changes with pressure which can be converted to different depths the knowledge gained from such correlations may lead to an improved interpretation of geophysical data for hydrocarbon exploration and production and therefore to an advanced reservoir characterization

on the surface wind speed probability density function over complex terrain 1 the physical mechanisms determining the shape of the surface wind speed probability density function over complex terrain are investigated using observations from a dense mesoscale network and a high spatial resolution mesoscale simulation for the 1992 to 2005 period results indicate that the atmospheric stability plays a major role in controlling the shape of the wind speed distribution but its effects are strongly modulated by the contribution of different atmospheric scales of motion such as the mesoscale or synoptic scale the local topographic features further modulate the relative contribution of each mechanism as a consequence of the complicated interaction of these atmospheric processes the surface wind speed distribution can present a complicated shape that is not always expected to fit a unimodal weibull type distribution over complex terrain regions

ground penetrating radar investigation of a lake bonneville deita provo level brigham city utah field experiments carried out in the brigham sand and gravel company pit near brigham city utah show an impressive similarity between observed gravelly deltaic foreset facies in highwall exposures and inclined reflections detected by ground penetrating radar gpr beneath the pit floor the radar indicates additional inclined strata more than 30 m deep in a test to compare different antenna frequencies 50 100 and 200 mhz using a 400 v transmitter 50 mhz antennas are capable of detecting gravel facies in excess of 30 m whereas signal loss for the 100 and 200 mhz antennas occurs below 23 and 17 m respectively though providing higher resolution

monitoring of the soil moisture regime of an earth filled dam by means of electrical resistance tomography close range photogrammetry and thermal imaging small earthen dams usually lack a detailed monitoring system that would provide high resolution data concerning changes in seepage flow geophysical methods and remote sensing are useful techniques for non destructive and non invasive investigation of subsurface processes we have utilized a combination of electrical resistivity tomography ert close range photogrammetry and unmanned aerial vehicle uav thermal imaging techniques to detect specific superficial and internal structures of a historical earth filled dam longitudinal and transversal profiles of a typical fishpond dam in the czech republic were measured the dam was constructed during the fifteenth century but has since gone through some minor reconstruction the aims of the applied geophysical methods are to detect and localize the boundary of the dam foundation new earth material from reconstruction the cone of water depression the reservoir s outlet location potential internal erosion cavities and heterogeneity in water content pattern and any other anomalies the primary results show that ert is suitable to detect dam stratification and large anomalies the uav monitoring system provided reliable data for a surface temperature distribution map which corresponded well to topsoil water content and electrical resistivity

the role of katabatic winds on the antarctic surface wind regime abstract antarctica is known for its strong and persistent surface winds that are directed along topographic pathways surface winds are especially strong during the winter period the high directional constancy of the wind and the close relationship of the wind direction to the underlying terrain can be interpreted as evidence of katabatic wind activity observations show that the directional constancy of the antarctic surface wind displays little seasonal variation summertime winds cannot be expected to contain a significant katabatic component owing to enhanced solar heating of the ice slopes observations also show that the coastal environs are subjected to wide variation in atmospheric pressure associated with frequent cyclone activity the robust unidirectional nature of the antarctic surface wind throughout the year implies that significant topographic influences other than those from katabatic forcing must be acting idealized numerical simulations have been performed to illustrate the potential

hydrological connectivity of soil pipes determined by ground penetrating radar tracer detection soil pipes are common and important features of many catchments particularly in semi arid and humid areas and can contribute a large proportion of runoff to river systems they may also signi cantly in uence catchment sediment and solute yield however there are often problems in nding and de ning soil pipe networks which are located deep below the surface ground penetrating radar gpr has been used for non destructive identi cation and mapping of soil pipes in blanket peat catchments while gpr can identify subsurface cavities it cannot alone determine hydrological connectivity between one cavity and another this paper presents results from an experiment to test the ability of gpr to establish hydrological connectivity between pipes through use of a tracer solution sodium chloride was injected into pipe cavities previously detected by the radar the gpr was placed downslope of the injection points and positioned on the ground directly above detected soil pipes the resultant radargrams showed signi cant changes in re ectance from some cavities and no change from others pipe waters were sampled in order to check the radar results changes in electrical conductivity of the pipe water could be detected by the gpr without data post processing when background levels were increased by more than approximately twofold it was thus possible to rapidly determine hydrological connectivity of soil pipes within dense pipe networks across hillslopes without ground disturbance it was also possible to remotely measure travel times through pipe systems the passing of the salt wave below the gpr produced an easily detectable signal on the radargram which required no post processing the technique should allow remote sensing of water sources and sinks for soil pipes below the surface the improved understanding of owpath connectivity will be important for understanding water delivery solutional and particulate denudation and hydrological and geomorphological model development copyright 2004 john wiley sons ltd

optical effects of space weathering the role of the finest fraction the optical properties of lunar softs are different than those of rocks from which they are derived as a consequence of lunar space weathering soils are darker and exhibit a distinctive red sloped continuum and weaker mineral absorption bands the accumulation of dark glass welded aggregates agglutinates has been thought to account for these optical effects of space weathering on lunar soils spectroscopic analyses of agglutinate separates and size fractions for a suite of lunar softs presented here indicate that the agglutinate paradigm is insufficient to fully account for lunar optical alteration it is the finest fraction of lunar soils 25 gm which constitute 25 wt that dominates the optical properties of the bulk soil unlike size fractions of most silicates for which the finest fraction is the brightest the lunar soil size fractions all have comparable albedos in the short wavelength visible in the near infrared however it is the finest fraction that exhibits the steep red continuum and weak absorption bands the properties of the finest fraction cannot be duplicated by preparing a fine fraction by grinding larger agglutinate rich soil particles these results suggest space weathering on airless bodies is dominated by surface correlated processes perhaps associated with the development of fine grained fe o on or near the surface of grains and the accumulation of the larger agglutinates is not necessarily required to account for lunar optical alteration

geologic mapping of vesta from 1994 hubble space telescope images we utilize the 56 images of asteroid 4 vesta obtained through four mineralogically diagnostic filters by the hubble space telescope zellneret al 1997 icarus to construct a geologic map vesta s surface is found to be geologically diverse and to be dichotomous at a hemispheric scale the eastern hemisphere longitude definition from thomaset al 1997 icarus is dominated by units interpreted to be impact excavated plutonic material composed of magnesium rich and calcium poor pyroxene the mineralogy of this region is most analogous to diogenite meteorites several eastern hemisphere units which have the deepest and broadest 1 m absorption bands may contain a substantial olivine component the locations of these units are consistent with a previous map based on rotationally resolved groundbased spectroscopy gaffey 1997 icarus the western hemisphere is dominated by units interpreted to consist of a single component of iron rich and relatively calcium rich pyroxene analogous to surface basalts such as eucrite meteorites we investigate the spectral properties of 20 representative surface regions and find a correlation between the 1 m absorption band depth and albedo the units with lower albedos have shallower band depths such a relation could arise from differences in lithologies differences in surface particle sizes or from a weathering effect which decreases albedo and band depth over time because of vesta s geologic diversity and hemispheric dichotomy it is apparent that any major impact events such as those possibly related to the formation of the vesta family binzel and xu 1993 science260 186 191 did not globally resurface the planet the spectral evidence for remnants of a basaltic crust implies that the oldest units on the surface date back to the time of their emplacement most likely 4 5 byr ago if a weathering process exists which alters the albedo then the lowest albedo units such as the feature with the proposed name olbers most likely represent remnants of vesta s ancient basaltic crust

three dimensional ground penetrating radar imaging of sedimentary structures fractures and archaeological features at submeter resolution contemporary geoscientific shallow subsurface assessment chiefly relies on outcrops drilling excavations and sometimes geophysics often the information gathered is insufficient to accurately characterize the archaeological and or geologic record and ongoing shallow subsurface processes that affect a variety of economic and environmental aspects of our society the extra effort of acquiring very dense ground penetrating radar gpr survey grids and three dimensional 3d data processing transforms uncorrelatable and uninterpretable gpr signals into clear images of complex shallow subsurface anatomy with an unprecedented resolution here we present two examples of noninvasive 3d shallow subsurface imaging example 1 images decimeter to meter scale sedimentary structures in a pleistocene oolite shoal barrier bar setting example 2 images the fracture network in a triassic limestone quarry denser than quarter wavelength grid acquisition in combination with 3d migration processing focuses scattered energy and removes out of plane reflections in addition to conventional vertical cross sections horizontal depth slices and data volume animations reveal previously unseen diagnostic patterns of past human activities laterally changing depositional processes and fracture networks including near vertical joints with millimeter apertures

significance of stemflow in groundwater recharge 2 a cylindrical infiltration model for evaluating the stemflow contribution to groundwater recharge a primary model for evaluating the effect of stemflow on groundwater recharge has been developed the model a cylindrical infiltration model ci model is based on the infiltration area of stemflow induced water instead of canopy projected area for determining the stemflow inputs to the soil surface the estimated ratio of recharge rate by stemflow to the total recharge rate determined with this model agrees closely with values obtained from the mass balance of chloride in subsurface waters this primary model is considered to be useful for estimating the effect of stemflow on groundwater recharge

analysis of the long term surface wind variability over complex terrain using a high spatial resolution wrf simulation this work uses a wrf numerical simulation from 1960 to 2005 performed at a high horizontal resolution 2 km to analyze the surface wind variability over a complex terrain region located in northern iberia a shorter slice of this simulation has been used in a previous study to demonstrate the ability of the wrf model in reproducing the observed wind variability during the period 1992 2005 learning from that validation exercise the extended simulation is herein used to inspect the wind behavior where and when observations are not available and to determine the main synoptic mechanisms responsible for the surface wind variability a principal component analysis was applied to the daily mean wind two principal modes of variation accumulate a large percentage of the wind variability 83 7 the first mode reflects the channeling of the flow between the large mountain systems in northern iberia modulated by the smaller topographic features of the region the second mode further contributes to stress the differentiated wind behavior over the mountains and valleys both modes show significant contributions at the higher frequencies during the whole analyzed period with different contributions at lower frequencies during the different decades a strong relationship was found between these two modes and the zonal and meridional large scale pressure gradients over the area this relationship is described in the context of the influence of standard circulation modes relevant in the european region like the north atlantic oscillation the east atlantic pattern east atlantic western russia pattern and the scandinavian pattern

space weathering on eros constraints from albedo and spectral measurements of psyche crater we present combined multi spectral imager msi 0 95 m and near infrared spectrometer nis 0 8 2 4 m observations of psyche crater on s type asteroid 433 eros obtained by the near earth asteroid rendezvous near shoemaker spacecraft at 5 3 km in diameter psyche is one of the largest craters on eros which exhibit distinctive brightness patterns consistent with downslope motion of dark regolith material overlying a substrate of brighter material at spatial scales of 620 m spectrum psyche crater wall materials exhibit albedo contrasts of 32 40 at 0 946 m associated spectral variations occur at a much lower level of 4 8 2 4 we report results of scattering model and lunar analogy investigations into several possible causes for these albedo and spectral trends grain size differences olivine pyroxene and troilite variations and optical surface maturation we find that the albedo contrasts in psyche crater are not consistent with a cause due solely to variations in grain size olivine pyroxene or lunar like optical maturation a grain size change sufficient to explain the observed albedo contrasts would result in strong color variations that are not observed olivine and pyroxene variations would produce strong band correlated variations that are not observed a simple lunar like optical maturation effect would produce strong reddening that is not observed the contrasts and associated spectral variation trends are most consistent with a combination of enhanced troilite a dark spectrally neutral component simulating optical effects of shock and lunar like optical maturation these results suggest that space weathering processes may affect the spectral properties of eros materials causing surface exposures to differ optically from subsurface bedrock however there are significant spectral differences between eros proposed analog meteorites ordinary chondrites and or primitive achondrites and eros freshest exposures of subsurface bright materials after accounting for all differences in the measurement units of our reflectance comparisons we have found that the bright materials on eros have reflectance values at 0 946 m consistent with meteorites but spectral continua that are much redder than meteorites from 1 5 to 2 4 m most importantly we calculate that average eros surface materials are 30 40 darker than meteorites

quantitative nondestructive estimates of coarse root biomass in a temperate pine forest using 3 d ground penetrating radar gpr coarse root biomass was estimated in a temperate pine forest using high resolution 1 ghz 3 d ground penetrating radar gpr gpr survey grids were acquired across a 400 m2 area with varying line spacing 12 5 and 25 cm root volume and biomass were estimated directly from the 3 d radar volume using isometric surfaces calculated with the marching cubes algorithm empirical relations between gpr reflection amplitude and root diameter were determined for 14 root segments 0 1 10 cm diameter reburied in a 6 m2 experimental test plot and surveyed at 5 25 cm line spacing under dry and wet soil conditions reburied roots 1 4 cm diameter were detectable as continuous root structures with 5 cm line separation reflection amplitudes were strongly controlled by soil moisture and decreased by 40 with a two fold increase in soil moisture gpr line intervals of 12 5 and 25 cm produced discontinuous mapping of roots and gpr coarse root biomass estimates 0 92 kgcm 2 were lower than those obtained previously with a site specific allometric equation due to non detection of vertical roots and roots 1 5 cm diameter the results show that coarse root volume and biomass can be estimated directly from interpolated 3 d gpr volumes using a marching cubes approach but mapping of roots as continuous structures requires high inline sampling and line density 5 cm the results demonstrate that 3 d gpr is viable approach for estimating belowground carbon and for mapping tree root architecture this methodology can be applied more broadly in other disciplines e g archaeology civil engineering for buried structures

diagnosis of the katabatic wind influence on the wintertime antarctic surface wind field from numerical simulations abstract katabatic winds have long been recognized as one of the key climatic variables of the low level antarctic environment antarctic surface winds display a high degree of persistence with mean directions related to the local topographic configuration of the ice sheet consistent with katabatic forcing continental orography also constrains the atmospheric boundary layer motions through blocking and cold air damming finally the coastal rim about the antarctic continent is among the most active baroclinic zones on earth the establishment of the low level wind field over antarctica is thus potentially the result of a number of interacting processes to quantify the forcing of the wintertime surface wind field over the antarctic continent two numerical strategies are presented first idealized numerical simulations are conducted to illustrate the strong orographic control of the low level wind field second a series of daily numerical simulations using the fifth generation pennsylvania state unive

evidence of space weathering in regolith breccias ii asteroidal regolith breccias space weathering products such as agglutinates and nanophase iron bearing rims are easily preserved through lithification in lunar regolith breccias thus such products if produced should be preserved in asteroidal regolith breccias as well a study of representative regolith breccia meteorites fayetteville h4 and kapoeta howardite was undertaken to search for physical evidence of space weathering on asteroids amorphous or npfe 0 bearing rims cannot be positively identified in fayetteville although possible glass rims were found extensive friction melt was discovered in the meteorite that is difficult to differentiate from weathered materials several melt products including spherules and agglutinates as well as one irradiated rim and one possible npfe 0 bearing rim were identified in kapoeta the existence of these products suggests that lunar like space weathering processes are or have been active on asteroids

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

extreme temperature and precipitation events in march 2015 in central and northern chile from 18 to 27 march 2015 northern central and southern chile experienced a series of extreme hydrometeorological events first the highest surface air temperature ever recorded in santiago with reliable records dating to 1877 36 8 c at quinta normal was measured at 15 47 local time on 20 march 2015 immediately following this high heat event an extreme precipitation event with damaging streamflows from precipitation totals greater than 45 mm occurred in the semiarid and hyperarid atacama regions finally concurrent with the heavy precipitation event extremely warm temperatures were recorded throughout southern chile these events were examined from a synoptic perspective with the goal of identifying forcing mechanisms and potential interaction between each analysis which provides operational context by which to identify and predict similar events in the future primary findings were as follows 1 record warm temperatures in central chile resulted from anomalous lower troposphere ridging and easterly downslope flow both of which developed in response to an anomalous midtroposphere ridge trough pattern 2 a cutoff low with anomalous heights near one standard deviation below normal slowly moved east and was steered ashore near 25 s by circulation around a very strong ridge anomalies more than 3 standard deviations above normal centered near 60 s 3 anomalously high precipitable water content 20 mm above climatological norms over the peruvian bight region was advected southward and eastward ahead of the cutoff low by low level northwesterly flow greatly enhancing observed precipitation over northern chile

vesta s uv lightcurve hemispheric variation in brightness and spectral reversal abstract spectra of asteroid 4 vesta obtained in october 1990 with the international ultraviolet explorer are reanalyzed and reinterpreted a large portion of the eastern hemisphere based on the prime meridian definition of thomas et al 1997a is darker at uv wavelengths than much of the western hemisphere the uv lightcurve is in contrast with the visible lightcurve which shows that the eastern hemisphere is brighter than the western these iue spectra of vesta thus may be evidence for the spectral reversal first seen on the moon by apollo 17 where the visibly brighter lunar highlands are darker than the maria at far uv wavelengths this effect was linked to space weathering when it was noted wagner et al 1987 that the spectral reversal appears in the laboratory spectra of lunar soils but not powdered lunar rocks we investigate vesta s uv lightcurve and spectral reversal and its possible connection with space weathering the addition to grain coatings of small amounts of submicroscopic iron smfe through vapor deposition causes drastic spectral changes at uv visible wavelengths hapke 2001 while the longer wavelength spectrum remains largely unaffected other laboratory results e g hiroi and pieters 1998 indicate that the uv visible wavelength range is affected by simulated weathering processes in a manner similar to what is seen on vesta it is likely that vesta has experienced relatively minor amounts of space weathering as indicated by the spectral reversal along with the subtle visible near infrared weathering effects e g binzel et al 1997

santa ana winds of southern california their climatology extremes and behavior spanning six and a half decades santa ana winds saws are an integral feature of the regional climate of southern california northern baja california region but their climate scale behavior is poorly understood in the present work we identify saws in mesoscale dynamical downscaling of a global reanalysis from 1948 to 2012 model winds are validated with anemometer observations saws exhibit an organized pattern with strongest easterly winds on westward facing downwind slopes and muted magnitudes at sea and over desert lowlands we construct hourly local and regional saw indices and analyze elements of their behavior on daily annual and multidecadal timescales saws occurrences peak in winter but some of the strongest winds have occurred in fall finally we observe that saw intensity is influenced by prominent large scale low frequency modes of climate variability rooted in the tropical and north pacific ocean atmosphere system

aquifer architecture analysis using ground penetrating radar triassic and quaternary examples s germany applying the concept of analogue studies long used in reservoir characterization outcrop analogues in two aquifer units of southern germany have been investigated upper triassic keuper alluvial sandstones stubensandstein and quaternary glaciofluvial gravels architectural element analysis of the outcrops is combined with ground penetrating radar profiles derived a few meters behind the outcrop walls such calibration is used to better understand the three dimensional sedimentary architecture many sedimentary units at the same time represent hydraulic flow units and are characterized by specific radar signatures this approach leads to promising results not only in unconsolidated aquifers but also in fully consolidated sedimentary rocks our studies will lead to a database with which more realistic predictions of the hydraulic behaviour of sedimentary aquifers systems needed for numerical hydrogeological simulations will be possible

ground penetrating radar monitoring of a controlled dnapl release 200 mhz radar a controlled release of tetrachloroethylene was performed in a saturated natural sandy aquifer to evaluate the effectiveness of various geophysical techniques for detecting and monitoring dense nonaqueous phase liquids dnapls in the subsurface tetrachloroethylene typical of most dnapls has a low relative dielectric permittivity 2 3 which contrasts with the high relative permittivity 80 of the pore water it displaces making it a potential target for detection by ground penetrating radar gpr gpr data were acquired using 200 mhz antennas radar sections collected at different times over the same spatial location clearly show the changes induced by the movement of dnapl in the subsurface temporal changes can be examined through the evolution of a radar data trace collected at a single spatial location normal moveout analysis of common midpoint cmp data demonstrates induced changes in electromagnetic em wave velocities of up to 30 percent caused by the presence of dnapl the distribution o

effect of soil roughness on the inversion of off ground monostatic gpr signal for noninvasive quantification of soil properties we report on a laboratory experiment that investigates the effect of soil surface roughness on the identification of the soil electromagnetic properties from full wave inversion of ground penetrating radar gpr data in the frequency domain the gpr system consists of an ultrawide band stepped frequency continuous wave radar combined with an off ground monostatic horn antenna radar measurements were performed above a rectangular container filled with a loose sandy soil subject to seven water contents and four random surface roughnesses including a smooth surface as reference compared to previous studies we have reduced the modeling error of the gpr signal for the smooth surface case thanks to improved antenna transfer functions by solving an overdetermined system of equations based on six model configurations instead of only three then the continuously increasing effect of surface roughness on the radar signal with respect to frequency is clearly observed in close accordance with rayleigh s criterion both the radar signal and the inversely estimated parameters are not significantly affected if the surface protuberances are smaller than one eighth of a wavelength in addition when this criterion is not respected errors are made in the estimated parameters but the inverse solution remains stable this demonstrates the promising perspectives for application of gpr for noninvasive water content estimation in agricultural and environmental field applications

presidential address presented 2000 august 28 chicago illinois usa the eucrite vesta story many lines of evidence indicate that meteorites are derived from the asteroid belt but in general identifying any meteorite class with a particular asteroid has been problematical one exception is asteroid 4 vesta where a strong case can be made that it is the ultimate source of the howardite eucrite diogenite hed family of basaltic achondrites visible and near infrared reflectance spectra first suggested a connection between vesta and the basaltic achondrites experimental petrology demonstrated that the eucrites the relatively unaltered and unmixed basaltic achondrites were the product of approximately a 10 melt studies of siderophile element partitioning suggested that this melt was the residue of an asteroidal scale magma ocean mass balance considerations point to a parent body that had its surface excavated but remains intact modern telescopic spectroscopy has identified kilometer scale vestoids between vesta and the 3 1 orbit orbit resonance with jupiter dynamical simulations of impact into vesta demonstrate the plausibility of ejecting relatively unshocked material at velocities consistent with these astronomical observations hubble space telescope images show a 460 km diameter impact basin at the south pole of vesta it seems that nature has provided multiple free sample return missions to a unique asteroid major challenges are to establish the geologic context of the hed meteorites on the surface of vesta and to connect the remaining meteorites to specific asteroids

first disk resolved spectroscopy of 4 vesta abstract vesta the second largest main belt asteroid will be the first to be explored in 2011 by nasa s dawn mission it is a dry likely differentiated body with spectrum suggesting that is has been resurfaced by basaltic lava flows not too different from the lunar maria here we present the first disk resolved spectroscopic observations of an asteroid from the ground we observed 4 vesta with the eso vlt adaptive optics equipped integral field near infrared spectrograph sinfoni as part of its science verification campaign the highest spatial resolution of 90 km on vesta s surface was obtained during excellent seeing conditions 0 5 in october 2004 we observe spectral variations across vesta surface that can be interpreted as variations of either the pyroxene composition or the effect of surface aging we compare vesta s 2 m absorption band to that of howardite eucrite diogenite hed meteorites that are thought to originate from vesta and establish particular links between specific regions and hed subclasses the overall composition is found to be mostly compatible with howardite meteorites although a small area around 180 e longitude could be attributed to a diogenite rich spot we finally focus our spectral analysis on the characteristics of vesta s bright and dark regions as seen from hubble space telescope s visible and keck ii s near infrared images

numerical study of convection observed during the winter monsoon experiment using a mesoscale two dimensional model abstract a two dimensional version of the pennsylvania state university mesoscale model has been applied to winter monsoon experiment data in order to simulate the diurnally occurring convection observed over the south china sea the domain includes a representation of part of borneo as well as the sea so that the model can simulate the initiation of convection also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle this allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck which typically occupies several hundred kilometers of the domain frank and cohen s cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area the major conclusions are ice phase processes are important in determining the level of maximum large scale heating and vertical motion because there is a strong anvil componen

local and synoptic mechanisms causing southern california s santa ana winds the atmospheric conditions that lead to strong offshore surface winds in southern california commonly referred to as santa ana winds are investigated using the north american regional reanalysis and a 12 year 6 km resolution regional climate simulation of southern california we first construct an index to characterize santa ana events based on offshore wind strength this index is then used to identify the average synoptic conditions associated with santa ana events a high pressure anomaly over the great basin this pressure anomaly causes offshore geostrophic winds roughly perpendicular to the region s mountain ranges which in turn cause surface flow as the offshore momentum is transferred to the surface we find however that there are large variations in the synoptic conditions during santa ana conditions and that there are many days with strong offshore flow and weak synoptic forcing this is due to local thermodynamic forcing that also causes strong offshore surface flow a large temperature gradient between the cold desert surface and the warm ocean air at the same altitude creates an offshore pressure gradient at that altitude in turn causing katabatic like offshore flow in a thin layer near the surface we quantify the contribution of synoptic and local thermodynamic mechanisms using a bivariate linear regression model and find that unless synoptic conditions force strongly onshore winds the local thermodynamic forcing is the primary control on santa ana variability