flow to a heated borehole in porous thermoelastic rock analysis exact solutions are obtained for fluid flow induced by the heating of a borehole the rock is modeled as a fluid saturated porous thermoelastic medium the temperature and pore pressure fields are governed by a pair of diffusion equations which are coupled through a source term in the pressure equation proportional to the temperature rate the pressure profile exhibits a maximum that grows in magnitude and propagates away from the borehole for a constant heat flux applied as an instantaneous step the fluid flux to the borehole takes a finite initial value and decays monotonically when the heat flux exhibits a finite rise time the fluid flux is initially zero rises to a maximum and then decays at late time the inverse of the fluid flux is linear in ln t this observation can be exploited to estimate the permeability and fluid diffusivity of low permeability rock sample calculations are shown for westerly granite

a geologic evaluation of thermal properties for the elysium and aeolis quadrangles of mars thermal inertias with spatial resolutions as small as 2 by 5 km were combined in a regional study of the elysium and aeolis quadrangles of mars 30 n to 30 s 180 w to 225 w the range of thermal inertias obtained was 1 14 10 3 cal cm 2 s k 1 41 84 j m 2 s k 1 with the lowest values corresponding to the elysium rise and the highest values correlating with dark patches of aeolian material in the southern highlands the thermal properties obtained from the high spatial resolution measurements are essentially identical to the results obtained from data with much poorer spatial resolution indicating a regional homogeneity of surface properties at scales greater than 5 km aeolian features both dark patches and bright materials associated with topographic obstacles such as craters have higher thermal inertias than do their surroundings other surface features do not display distinctive thermal properties even when clearly resolved from their surroundings comparison of the thermal inertias with global data sets shows a pronounced inverse correlation with albedo consistent with globally observed trends and brightnesses at red green and violet wavelengths but no prominent correlation with elevation thermal inertias for individual geologic units within the two quadrangles appear to be more strongly controlled by the location of the terrain in either the northern plains or the southern highlands than by properties intrinsic to the unit

consolidation of fissured clays a numerical model for consolidation of fissured clays on the basis of the double porosity concept is presented as applications of the model two numerical examples are analysed a one dimensional soil column and a strip loading on a two dimensional medium of a fissured clay it is shown that in comparison to an equivalent single porosity model the settlement in a double porosity medium is delayed due to the slow dissipation of excess fluid pressure in the clay matrix in addition three distinct time periods are identified in the consolidation of a fissured clay the characteristic of each period are discussed and the parameters affecting these periods are highlighted moreover it is shown that the mandel cryer effect which is often discussed in relation to consolidation of soils treated as single porosity material may not develop in fissured clays nous presentons un modele numerique pour la consolidation des argiles fissurees sur la base du concept de double porosite en applications du mod acu

some observational constraints on the global scale wind systems of mars wind direction measurements from a variety of indicators taken over several mars years and covering the entire planet have been collected these include observations of lee wave clouds not previously studied the data exhibit a high degree of consistency and seasonal reproducibility making it possible to interpret most of the observations in terms of the zonally symmetric circulation of mars we examine these data in the context of the constraints the observed wind directions place upon the thermal and polar cap mass flux fields which force the flows within the limitations of the data set mid and high latitude winds appear to be controlled by the thermal field during mid and late summer and winter and in the northern hemisphere during early spring and early summer at other times the cap flows dominate at high latitudes the strongest yearly winds are probably generated by cap formation in the north and cap recession in the south the hemispheric asymmetry seems to result primarily from the effects of global dust storms on the north polar cap turning of the prograde wind from poleward to equatorward in midautumn is observed consistent with reduced poleward mass flux and increased meridional temperature gradient at that time the latitudinal extent of the equatorial hadley cell when observed is probably larger than that predicted by nearly inviscid models of low latitude circulation the cross equational hadley cell and high latitude poleward flows which occur in both hemispheres during the summer seasons may set additional constraints on the thermal forcing mechanisms at these times

thermal studies of martian channels and valleys using termoskan data the termoskan instrument on board the phobos 88 spacecraft acquired the highest spatial resolution thermal infrared emission data ever obtained for mars included in the thermal images are 2 km pixel midday observations of several major channel and valley systems including significant portions of shalbatana ravi al qahira and ma adim valles the channel connecting valles marineris with hydraotes chaos and channel material in eos chasma termoskan also observed small portions of the southern beginnings of simud tiu and ares valles and some channel material in gangis chasma simultaneous broadband visible reflectance data were obtained for all but ma adim vallis we find that most of the channels and valleys have higher thermal inertias than their surroundings consistent with previous thermal studies we show for the first time that the thermal inertia boundaries closely match flat channel floor boundaries also buttes within channels have inertias similar to the plains surrounding the channels suggesting the buttes are remnants of a contiguous plains surface lower bounds on typical channel thermal inertias range from 8 4 to 12 5 10 3 cal cm 2 s 1 2 k 1 352 to 523 in si units of j m 2 s 1 2 k 1 lower bounds on inertia differences with the surrounding heavily cratered plains range from 1 1 to 3 5 46 to 147 si atmospheric and geometric effects are not sufficient to cause the observed channel inertia enhancements we favor nonaeolian explanations of the overall channel inertia enhancements based primarily upon the channel floors thermal homogeneity and the strong correlation of thermal boundaries with floor boundaries however localized dark regions within some channels are likely aeolian in nature as reported previously most channels with increased inertias have fretted morphologies such as flat floors with steep walls eastern ravi and southern ares valles the only major channel sections observed that have obvious catastrophic flood bedforms do not have enhanced inertias therefore we favor fretting processes over catastrophic flooding for explaining the inertia enhancements we postulate that the inertia enhancements were caused either by the original fretting process or by a process involving the bonding of fines due to an increased availability of water either initially or secondarily

interaction of ocean temperature advection surface heat fluxes and sea ice in the marginal ice zone during the north atlantic oscillation in the 1990s a modeling study 1 a moderately fine resolution 0 4 40 vertical levels global coupled ice ocean model was configured and run for 24 years 1979 2002 forced with high frequency national center for environmental prediction national center for atmospheric research ncep ncar atmospheric fluxes the model consists of the los alamos national laboratory parallel ocean program pop and sea ice model cice the fidelity of the simulated mean climatological state and variability of key variables such as ice concentration total ice area ice thickness and drift were compared to observational data sets from satellite and ice drift buoy measurements basin scale changes in the lower atmosphere surface ocean sea ice in the simulated arctic and nordic seas before and after the north atlantic oscillation nao phase switch in 1995 were examined using winter composite analyses over the period 1990 1999 ice cover changes between the two nao phases were consistent with observations in that reduced concentrations were found in the nordic and barents seas and increased values occurred in the labrador sea next we regionally evaluated the relative importance of winter anomalies of upper ocean mixed layer net heat fluxes and of ocean temperature advection on marginal ice zone variability in the irminger greenland and barents seas for this ten year period we found that the net heat flux winter anomaly was at least four times more important than the winter anomaly of ocean temperature advection in the greenland and barents seas while it was twice as important in the irminger sea the ekman ocean temperature advection component generally dominated the geostrophic component in all three regions

ocean surface wave evolvement in the arctic basin 1 recent basin scale changes to the compactness and thickness of arctic sea ice foreshadow that encroaching swells and locally generated waves will exert more influence there in the future indeed it is conceivable that waves may have already hastened the adjustments observed by breaking up ice floes yet waves advancing in sea ice attenuate due to being scattered from ice thickness variations and damped by ice inelasticity turbulence and friction while past research focuses on scattering by unnaturally perfect features in the ice the model reported herein assimilates realistic basin scale swathes of heterogeneous ice and parameterizes damping by way of example we show how an ocean wave train evolves during its passage in an 1670 km long arctic sea ice profile obtained from submarine

borehole stability analysis in a thermoporoelastic dual porosity medium the problem of diffusion and mass transfer in dual porous media is considered in a threephase framework the solid phase is assumed to contain two distinct cavities filled with fluid the porous mixture is composed of two overlapping media the porous blocks and the fissure network the fluid can transfer between the cavities due to fluid pressure difference in addition hydraulic and thermal diffusions take place through the mixture a global understanding of mass transfer diffusion and deformation is provided the governing equations associated with these phenomena are presented for a mixture in thermal equilibrium the finite element approximation of the governing equations is formulated and applied to the stability analysis of a vertical borehole a parametric analysis is carried out to evaluate the influence of mass transfer on the pressure profiles of the fluids around the borehole permeable and a semipermeable boundary conditions are compared to predict the potential for failure of the wellbore under drained and partially undrained conditions

multiscale insights into borehole instabilities in high porosity sandstones this paper presents a multiscale analysis of the classical borehole instability problem in high porosity sandstones using a hierarchical multiscale approach a rigorous two way message passing coupling of finite element method and discrete element method is employed where the finite element method is employed to solve a boundary value problem and the constitutive material responses required at each of its integration points are derived by the discrete element method solution to an embedded representative volume element instead of by using an assumed phenomenological model we employ this multiscale approach to examine the successive failure of a borehole subjected to gradually decreased support stresses at the inner borehole wall or increased far field stresses to reproduce the material behavior of high porosity sandstone representative volume elements with a high porosity structure and interparticle bonds are generated it is found that stress concentration triggers the initial failure at the borehole wall and the subsequent failure in form of deformation bands is driven by further stress concentration ahead of the band tips the failure pattern around the borehole varies with initial stress state and global loading path the comparison of the local stress paths of the initial failure points in various cases reveals that the change of failure pattern from shear failure to mixed mode failure and to compaction failure is dominated by the increased mean stress cross scale parametric studies show that the failure mode changes from clear compaction bands to multiple arrays of shear bands by changing the high porosity specimen to a low porosity one the increase in cohesion strength expands the yield locus and enlarges the critical mean stress between different failure patterns hence the failure mode may change from compaction failure to mixed mode failure or from mixed mode failure to shear failure due purely to the increased cohesion strength the qualitative comparisons indicate greater length larger area and more severe damage of the diametrically opposite failure with the increase in minor principal stress 0 and principal stress ratio the diametrically opposite failure mode is found a good indicator for 0 direction but it may also occur under hydrostatic far field stress due to material anisotropy

global duricrust on mars analysis of remote sensing data global remote sensing data for mars are analyzed to obtain a simple self consistent model for the surface layer the data sets discussed include radar cross section measurements at several wavelengths radio whole disk thermal emission observations at two wavelengths the global distribution of thermal inertia deviations of diurnal temperatures from those of a homogeneous model and thermal spectral estimates of surface rock abundance and of the thermal inertia of the nonrocky component of the surface the data sets which most constrain the interpretation are the rock abundance map and the correlation of thermal inertia with radar cross section these require the rock abundance to not vary significantly from place to place and simultaneously require the density and thermal inertia of the fines to vary in a consistent manner the simplest model which can explain all of the data involves a global case hardened crust duricrust which varies spatially in its degree of formation in general low thermal inertia regions have a poorly developed crust and highinertia regions have a well developed crust there are however regions that consist of coarse particles and which do not fit this model e g chryse this model is consistent with the ages of low inertia regions and with aeolian mechanisms for their development the duricrust is thought to form via the mobilization of salt ions within a layer of water adsorbed within the regolith and its formation may be associated with the exchange of water between the regolith and atmosphere which occurs on the 105 and 106 year time scale

30 year satellite record reveals contrasting arctic and antarctic decadal sea ice variability a 30 year satellite record of sea ice extents derived mostly from satellite microwave radiometer observations reveals that the arctic sea ice extent decreased by 0 30 0 03 x 10 exp 6 square kilometers per 10 yr from 1972 through 2002 but by 0 36 plus or minus 0 05 x 10 exp 6 square kilometers per 10yr from 1979 through 2002 indicating an acceleration of 20 in the rate of decrease in contrast the antarctic sea ice extent decreased dramatically over the period 1973 1977 then gradually increased over the full 30 year period the antarctic ice extent decreased by 0 15 plus or minus 0 08 x 10 exp 6 square kilometers per 10 yr the trend reversal is attributed to a large positive anomaly in antarctic sea ice extent in the early 1970 s an anomaly that apparently began in the late 1960 s as observed in early visible and infrared satellite images

a mathematical model for consolidation in a thermoelastic aquifer due to hot water injection or pumping a mathematical model is developed for the areal distribution of fluid pressure temperature land subsidence and horizontal displacements due to hot water injection into thermoelastic confined and leaky aquifers the underlying assumption is that the aquifer is thin in relation to the horizontal distances of interest and hence all dependent variables of interest are average over the thickness values the solid matrix is assumed to be thermoelastic following the development of three dimensional conservation of mass and energy equations and equilibrium equations in terms of horizontal and vertical displacements the mathematical model is derived by averaging the three dimensional model over the vertical thickness of the aquifer subject to conditions of plane total stress the effects of viscous dissipation and compressible work have been included in the formulation the resulting averaged coupled equations are in terms of pore water pressure temperature and vertical and horizontal displacements which are functions of x y and t only the equations are nonlinear and have to be solved simultaneously due to the coupling that exists among them equations and appropriate boundary conditions in radial coordinates have also been presented for an example of a single injecting or pumping well

wind streaks on mars meteorological control of occurence and mode of formation abstract why do some craters on mars produce depositional wind streaks while others produce erosional ones there is no evidence to suggest that crater morphology or topography plays the determining role some craters can form either type of streak at different times of the martian year suggesting that the controlling factor is meteorological we propose that atmospheric stability is the determining factor a stable atmosphere should lead to blocking of the wind flow by crater rims producing wind shadows over distances comparable to those of observed bright streaks such conditions should prevail in a belt about the equator at the time of major dust storms as the atmosphere becomes more transparent following the end of the dust storms the rate of surface heating increases and the stability of the atmosphere is reduced under such conditions blocking is not expected flow over obstacles results in increased surface stress downwind conditions which encourage the formation of erosional dark streaks these ideas are shown to be consistent with the seasons at which erosional and depositional streaks are formed as well as with their distribution on the planet specifically the scheme explains why craters which have both erosional and depositional streaks occur only within a very restricted latitude belt

thermal inertia mapping of mars from 60 s to 60 n twenty micrometer brightness temperatures are used to derive the thermal inertia for 81 of the martian surface between latitudes 60 these data were acquired by the two viking infrared thermal mappers in 1977 and 1978 following the two global dust storms of 1977 the spatial resolution used is 2 in latitude by 2 in longitude and the total range in derived inertia is 1 to 15 10 3 cal cm 2 sec 12 k 1 the distribution of thermal inertia is strongly bimodal with all values of thermal inertia less than 4 10 3 cal cm 2 sec 12 k 1 being associated with three disjoint bright regions mostly in the northern hemisphere sufficient dust is raised in global storms to provide fine material adequate to produce these low inertia areas but the specific deposition mechanism has not been defined at the low resolution used no complete exposures of clean rock were found there is some tendency for darker material to be associated with higher thermal inertia although the trend is far from one to one the distribution of high and low inertia areas is sufficiently nonrandom to produce a variation in whole disk brightness temperature with central meridian longitude this variation and the change in surface kinetic temperature associated with dust storms are factors in establishing the whole disk brightness temperature at radio and infrared wavelengths and will be important for those who use mars as a calibration source

daily temperature variations on mars the viking infrared thermal mapper irtm has measured the infrared brightness temperature of mars for more than a full martian year the daily variation of the 20 m brightness temperature can be predicted to within 5 k for most of the martian surface during any season if the radiometric albedo and the thermal inertia of the model are allowed to increase with increasing atmospheric dust opacity however for approximately 32 of the martian surface area no values of thermal inertia or albedo can fit the thermal observations these temperature anomalies isolate one large region on mars which connects the low thermal inertia regions of arabia tharsis and elysium the anomalies do not correlate with elevation geologic units morphology or atmospheric dust content all regions with lambert albedo less than 0 18 can be well fit with the standard thermal model but all areas with albedo greater than 0 28 are anomalous there is a strong inverse correlation between the magnitude of the anomaly and the thermal inertia this correlation indicates that some surface property is responsible for the anomaly in the anomalous region the observed temperatures are warmer in the morning cooler late in the afternoon and decrease more slowly during the night than the viking model temperatures of all the physical processes likely to occur on mars but not included in the viking thermal model only a layered soil can explain the observations a low thermal inertia layer covering a high thermal inertia material will heat up quickly in the morning and cool down quickly in the afternoon at night the high thermal inertia material will moderate the temperature a possible interpretation for the layering deduced from the irtm observations is a layer of aeolian deposited dust about one thermal skin depth thick 1 to 4 cm covering a duricrust because dust accumulates in some areas after every global dust storm the duricrust must be actively forming a one thermal skin depth dust layer covering a duricrust is compatible with viking lander observations irtm spectral observations and viking orbiter imaging

borehole stability analysis accounting for anisotropies in drilling to weak bedding planes abstract borehole instabilities pose significant challenges to drilling and completion operations particularly in regions with weak bedding planes and pre existing fractures where formations have strong anisotropies the bedding planes rock anisotropy and their impacts on horizontal stresses are considered in the proposed model to improve borehole stability modeling this improved model enables to calculate borehole failures and minimum mud weight along borehole trajectories with various drilling orientations versus bedding directions laboratory test data of rock compressive strengths are analyzed and a new correlation is developed to allow for predicting uniaxial compressive strengths in weak rocks from sonic velocities time dependent rock compressive strength is also examined to analyze the wellbore failure evolution with time the slip failure gradient in the weak planes is derived which can be used to model wellbore sliding shear failure in the planes of weakness the mud weight applied to prevent borehole shear failures in both intact rocks and ones with weak bedding planes can be obtained from the proposed model

regional dust deposits on mars physical properties age and history major dust storms on mars play an important role in the deposition and removal of fine dust material thermal radar and visual remote sensing observations provide important constraints on the martian regolith which have been used to determine the location and physical properties of regional dust deposits these deposits are located in three northern equatorial regions tharsis 20 s to 50 n 60 to 190 w arabia 5 s to 30 n 300 to 360 w and elysium 10 to 30 n 210 to 225 w they are covered by fine 2 40 m bright albedo 0 27 particles with fewer exposed rocks and coarse deposits than found elsewhere dust is currently deposited uniformly throughout the equatorial region at a rate of 40 m global storm over geologic time the rate of accumulation may vary from 0 to 250 m yr due to changes in atmospheric conditions produced by orbital variations dust deposited during global storms is subsequently removed only from dark regions resulting in a net accumulation in the low inertia bright regions the thickness of these current dust deposits is 0 1 2 m the thermal inertia places a lower limit of 0 1 m on the thickness of these deposits while the sparse but ubiquitous presence of exposed rocks and the degree of visible mantling indicate that the thickness is less than 5 m dual polarization radar observations of a very rough texture in tharsis are consistent with this model with a 2 m thick dust layer burying most of the surface rocks but permitting radar sampling of the rough subsurface based on their thickness and rate of accumulation the age of these deposits is 105 106 years suggesting a cyclic process of deposition and removal one possible cause may be cyclic variations in the magnitude and location of maximum wind velocities related to variations in mars orbit at present perihelion and maximum wind velocities occur in the south whereas regional dust deposits occur in the north suggesting net transport from south to north orbital parameters oscillate with periods ranging from 5 104 to 106 years the agreement between these periods and the dust deposit age suggests a possible link at different stages in orbit evolution maximum wind velocities will occur in the north with subsequent erosion and redistribution of the accumulated fines based on this model much of the uppermost martian surface is very young and is being continually reworked

analysis of the projected regional sea ice changes in the southern ocean during the twenty first century using the set of simulations performed with atmosphere ocean general circulation models aogcms for the fourth assessment report of the intergovernmental panel on climate change ipcc ar4 the projected regional distribution of sea ice for the twenty first century has been investigated averaged over all those model simulations the current climate is reasonably well reproduced however this averaging procedure hides the errors from individual models over the twentieth century the multimodel average simulates a larger sea ice concentration decrease around the antarctic peninsula compared to other regions which is in qualitative agreement with observations this is likely related to the positive trend in the southern annular mode sam index over the twentieth century in both observations and in the multimodel average despite the simulated positive future trend in sam such a regional feature around the antarctic peninsula is absent in the projected sea ice change for the end of the twenty first century the maximum decrease is indeed located over the central weddell sea and the amundsen bellingshausen seas in most models changes in the oceanic currents could play a role in the regional distribution of the sea ice especially in the ross sea where stronger southward currents could be responsible for a smaller sea ice decrease during the twenty first century finally changes in the mixed layer depth can be found in some models inducing locally strong changes in the sea ice concentration

an analysis of the atmospheric processes driving the large scale winter sea ice variability in the southern ocean the response of the sea ice in the southern ocean to the variability of the atmosphere on the period 1979 2004 is investigated using both model and observational data on the one hand our results show that in line with previous investigations the classical modes of atmospheric variability do not explain a large part of the winter sea ice extent variability integrated over the entire southern ocean on the other hand the regression between the ice extent and the atmospheric pressure displays a pattern with low pressure areas over the south atlantic over the indian ocean and on the southwestern part of the pacific ocean and a high pressure area over the antarctic region extending toward both the southeastern pacific and the region south of australia this pattern which does not correlate significantly with any of the known modes of atmospheric variability induces changes in the sea ice extent by influencing the air temperature the ice production and both the meridional and the zonal ice velocity however there is no clear link between the different centers of action of this pattern furthermore the correlation of the sea ice extent between the different sectors is generally low as a conclusion we must consider that the sea ice extent in the southern ocean over the last 30 years does not behave as a single entity its variability is the result of the combination of regional sea ice changes each sector should thus be examined separately

the thermal stability of near surface ground ice on mars the existence of subsurface water ice on mars has been predicted in several theoretical studies1 5 but there are no definitive observations of its present distribution geomorphic features on the surface of mars have been widely interpreted as evidence for the presence of ground ice6 12 but many of these features are found at near equatorial latitudes where thermal models have predicted that near surface water ice should not be stable under present climate conditions3 13 14 here i present the results of thermal calculations which show that observed geographic variations in the thermal and reflectance properties of martian soils significantly affect subsurface temperatures my results indicate that in certain regions ground ice deposits could exist much closer to the surface and much closer to the equator than previously thought in the future these deposits could be a valuable resource for human exploration15

coupling effects in double porosity media with deformable matrix 1 the significance of the microscopic coupling effects on the macroscopic response of double porosity media is investigated in reference to the consolidation of fissured clays the basic findings of the investigation are validated through a set of laboratory test data

a model assessment of satellite observed trends in polar sea ice extents 1 for more than three decades now satellite passive microwave observations have been used to monitor polar sea ice here we utilize sea ice extent trends determined from satellite data for both the northern and southern hemispheres for the period 1972 73 2004 and assess and interpret them using results from simulations by eleven climate models in the northern hemisphere nh observations show a statistically significant decrease of sea ice extent and an acceleration of sea ice retreat during the past three decades however from the modeled natural variability of sea ice extents in control simulations we conclude that the acceleration is not statistically significant and should not be extrapolated into the future most of the models like the observations show an absence of a prominent seasonal cycle in the trend values both observations and model simulations show that climate variability in sea ice extent in the southern hemisphere sh is much larger than in the nh and that the sh sea ice extent trends are not statistically significant citation vinnikov k y d j cavalieri and c l parkinson 2006 a model assessment of satellite observed trends in polar sea ice extents geophys res lett 33 l05704 doi 10 1029 2005gl025282

dual porosity poroelastic analyses of wellbore stability this paper presents a numerical solution of dual porosity poroelastic formulations that couple solid deformations with fluid flow in both matrix and fracture systems of naturally fractured reservoirs the finite element numerical method was applied to solve the inclined wellbore problem in which mud weight was considered for both permeable and impermeable boundary conditions failure criteria relevant to tensile collapse and shear failure modes were introduced into the numerical model and resulting failure areas around boreholes were subsequently defined several related applications including the stability of inclined and horizontal wellbores under various in situ stress regimes were evaluated upper and lower mud weight bounds and the most stable borehole orientations were determined the best trajectory selections for horizontal boreholes were also investigated

apparent thermal inertia and the surface heterogeneity of mars abstract thermal inertia derivation techniques generally assume that surface properties are uniform at horizontal scales below the footprint of the observing instrument and to depths of several decimeters consequently surfaces with horizontal or vertical heterogeneity may yield apparent thermal inertia which varies with time of day and season to investigate these temporal variations we processed three mars years of mars global surveyor thermal emission spectrometer observations and produced global nightside and dayside seasonal maps of apparent thermal inertia these maps show broad regions with diurnal and seasonal differences up to 200 j m 2 k 1 s 1 2 at mid latitudes 60 s to 60 n and 600 j m 2 k 1 s 1 2 or greater in the polar regions we compared the seasonal mapping results with modeled apparent thermal inertia and created new maps of surface heterogeneity at 5 resolution delineating regions that have thermal characteristics consistent with horizontal mixtures or layers of two materials the thermal behavior of most regions on mars appears to be dominated by layering with upper layers of higher thermal inertia e g duricrusts or desert pavements over fines prevailing in mid latitudes and upper layers of lower thermal inertia e g dust covered rock soils with an ice table at shallow depths prevailing in polar regions less common are regions dominated by horizontal mixtures such as those containing differing proportions of rocks sand dust and duricrust or surfaces with divergent local slopes other regions show thermal behavior that is more complex and not well represented by two component surface models these results have important implications for mars surface geology climate modeling landing site selection and other endeavors that employ thermal inertia as a tool for characterizing surface properties

eolian intracrater deposits on mars physical properties and global distribution abstract an investigation of martian intracrater materials has been made using their thermophysical properties as derived from viking irtm observations over one fourth of all craters larger than 25 km in diameter between 50 s and 50 n have localized deposits of coarse material on the floor which are associated with dark splotches seen visually assuming homogeneous unconsolidated materials the measured thermal inertias of these deposits i 0 003 10 3 to 0 026 10 3 cal cm 2 sec 1 2 k 1 imply effective grain sizes ranging from 0 1 mm to 1 cm with a modal value of 0 9 mm these deposits are coarser and darker than the surrounding terrains and the majority of the martian surface but are not compositionally distinct from materials with similar albedos they occur more frequently in the south in regions of relatively coarse material 0 2 to 2 mm and in relatively dark areas these features most likely formed by entrapment of marginally mobile material which can be transported into but not out of crater depressions by the wind very few have recognizable dune forms those that do have effective grain sizes less than 0 5 mm the majority of the splotch deposits are coarser than the dune forming materials found in the north polar region and inside extreme southern latitude craters and probably form low broad zibar dunes or lag deposits intracrater deposits are noticeably lacking from the interior of the large northern hemisphere low inertia region of arabia 10 s to 30 n 300 to 360 w interpreted to be a sink for suspended dust but do occur around the perimeter of this region this distribution suggests that the intracrater features have been buried in the interior of arabia and that the dust deposit is less extensive at the margins and may currently be expanding the occurrence of regional dust deposits in the north may be related to the maximum wind activity currently occurring in the southern hemisphere and suggests that the location of regional sinks may migrate with time as the solar insolation maximum migrates

evaluation of the simulation of the annual cycle of arctic and antarctic sea ice coverages by 11 major global climate models 1 comparison of polar sea ice results from 11 major global climate models gcms and satellite derived observations for 1979 2004 reveals that each of the models is simulating annual cycles that are phased at least approximately correctly in both hemispheres each is also simulating various key aspects of the observed ice cover distributions such as winter ice not only throughout the central arctic basin but also throughout hudson bay despite its relatively low latitudes however some of the models simulate too much ice others simulate too little ice in some cases depending on hemisphere and or season and some match the observations better in one season versus another several models do noticeably better in the northern hemisphere than in the southern hemisphere and one does noticeably better in the southern hemisphere in the northern hemisphere all simulate monthly average ice extents to within 5 1 106 km2 of the observed ice extent throughout the year in the southern hemisphere all except one simulate the monthly averages to within 6 3 106 km2 of the observed values all the models properly simulate a lack of winter ice to the west of norway however most obtain more ice immediately north of norway than the observations show suggesting an under simulation of the north atlantic current the spread in monthly averaged ice extents among the 11 model simulations is greater in the southern hemisphere than in the northern hemisphere and greatest in the southern hemisphere winter and spring

insights into complex layered ejecta emplacement and subsurface stratigraphy in chryse planitia mars through an analysis of themis brightness temperature data layered ejecta craters on mars have been interpreted to indicate the presence of volatiles in the substrate making them important targets for the investigation of sites of astrobiological significance if the ejecta are associated with the presence of water in the substratum specific surface grain size trends are expected in this study we explore the distribution of grain sizes in the layered ejecta of impact craters located in chryse planitia using thermal emission imaging system themis thermal infrared data ejecta grain size trends in conjunction with ejecta mobility and lobateness values are applied to assess the degree of surface flow of the ejecta and in turn to constrain the plausible volatile abundance cohesion and fine particle content of the target materials craters with a larger fraction of small grain sizes in their ejecta showed greater ejecta mobility and lobateness consistent with a water rich and or a low cohesion target craters displaying decreasing grain size with increasing radius had smaller diameters and lower ejecta mobility and lobateness indicating only a minimal component of surface ejecta flow ejecta grain size trends varied with crater diameter from which the presence of vertical compositional stratigraphy in chryse planitia is inferred and interpreted our observations are synthesized into a number of plausible geologic scenarios for chryse planitia

occurrence dates of north atlantic tropical storms and hurricanes 2005 in perspective 1 this paper compares dates of the nth storm 1st 2nd etc in sequence for all tropical storms and hurricanes in the north atlantic basin from 1851 2005 the year 2005 stands out as a season that got off to an early start remained active throughout the season and set many records for earliest occurrence dates for the nth named storm exceptionally warm sea surface temperatures may help explain the record breaking season of 2005 other seasons with storms with early dates of occurrence include 1887 1933 1936 and 1995 all of these seasons are associated with a positive phase of the atlantic multidecadal oscillation

porothermoelastic effect on wellbore stability in transversely isotropic medium subjected to local thermal non equilibrium abstract provided that the hydraulic boundary conditions at the wellbore wall are identified as permeable pbc and impermeable impbc and that the assumption of plane strain holds the present paper formulates a newly porothermoelastic analytical solution which is based on the thermodynamic principles in laplace space domain for inclined borehole the adopted linear porothermoelastic model embodies the transient heat transfer process in the presence of local thermal non equilibrium ltne during the derivation the solution is available for the cases where the wellbore axis of inclined wellbore is perpendicular to the isotropic plane of the low permeable transversely isotropic porous medium under non hydrostatic stress field condition the wellbore problem is decomposed into axisymmetric and deviatoric loading cases the numerical results of the time dependent distributions of field variables are obtained by virtue of performing the inversion technique for laplace transforms an integrated geomechanical wellbore stability model is proposed which is not only comprised by the abovementioned new porothermoelastic solution but also associated with the theoretical derivations of strength criteria to evaluate the rock to shear failure which include mogi coulomb criterion and single weak plane criterion when a horizontal borehole is drilled along the direction of in the minimum horizontal in situ stress the numerical comparative analyses in the present paper examine the combined influence of material anisotropy and thermal effect which embody in the ltne and local thermal equilibrium lte models on the thermally induced pore pressure stresses and the shear and tensile failure regions around the wellbore

sea surface temperature variability in the tropical southeast atlantic ocean and west african rainfall 1 evidence is presented of a connection between sea surface temperature sst variability in the tropical southeast atlantic ocean off angola and boreal summer rainfall over coastal west africa the strongest relationships exist between april may sst in the angola benguela frontal zone area may june latent heat fluxes in this area and july august rainfall over the region 5 w 5 e 5 n 10 n anomalously wet summers in this region are also characterised by a weaker african easterly jet a stronger tropical easterly jet and in many cases reduced rainfall further north over the southern sahel

the impact of martian mesoscale winds on surface temperature and on the determination of thermal inertia radiative control of surface temperature is a key characteristic of the martian environment and its low density atmosphere here we show through meteorological modeling that surface temperature can be far from radiative equilibrium over numerous sloping terrains on mars where nighttime mesoscale katabatic winds impact the surface energy budget katabatic circulations induce both adiabatic atmospheric heating and enhancement of downward sensible heat flux which then becomes comparable to radiative flux and acts to warm the ground through this mechanism surface temperature can increase up to 20 k one consequence is that warm signatures of surface temperature over slopes observed through infrared spectrometry cannot be systematically associated with contrasts of intrinsic soil thermal inertia apparent thermal inertia maps retrieved thus far possibly contain wind induced structures another consequence is that surface temperature observations close to sloping terrains could allow the validation of model predictions for martian katabatic winds provided contrasts in intrinsic thermal inertia can be ruled out the thermal impact of winds is mostly discussed in this paper in the particular cases of olympus mons lycus sulci and terra meridiani but is generally significant over any sloped terrains in low thermal inertia areas it is even general enough to apply under daytime conditions thereby providing a possible explanation for observed afternoon surface cooling and to ice covered terrains thereby providing new insights on how winds could have shaped the present surface of mars