the influence of fluid sensitive dispersion and attenuation on avo analysis summary analysis of seismic data suggests that hydrocarbon deposits are often associated with higher than usual values of attenuation but this is generally ignored during amplitude versus offset avo analysis the effect can be modelled with equivalent medium theory based on the squirt flow concept but the excess attenuation is associated with strong velocity dispersion consequently when we study reflections from the interface between such an equivalent medium and an elastic overburden we find that the reflection coefficient varies with frequency the impact of this variation depends on the avo behaviour at the interface class i reflections tend to be shifted to higher frequency while class iii reflections have their lower frequencies amplified we calculate synthetic seismograms for typical models using the reflectivity method for materials with frequency dependent velocities and attenuations and find that these effects are predicted to be detectable on stacked data two field data sets show frequency anomalies similar to those predicted by the analysis and we suggest that our modelling provides a plausible explanation of the observations

well based hydraulic and geochemical monitoring of the above zone of the co2 reservoir at ketzin germany in order to detect hydraulic and geochemical impact on the groundwater directly above the co2 storage reservoir at the ketzin pilot site continuous monitoring using an observation well is carried out the target depth 446 m below ground level bgl of the well is the exter formation upper triassic rhaetian which is the closest permeable stratigraphic overlying formation to the co2 storage reservoir 630 636 m bgl at well location the monitoring concept comprises evaluation of hydraulic conditions temperature water chemistry gas geochemistry and 13c values this is achieved by a tubing inserted inside the well with installed pressure sensors and a u tube sampling system so that pumping tests or additional wireline logging can be carried out simultaneously with monitoring the aquifer was examined using a pump test the observation well is hydraulically connected to the regional aquifer system and the permeability of about 1 8 d is comparatively high between sept 2011 and oct 2012 a pressure increase of 7 4 kpa is observed during monitoring under environmental conditions drilling was carried out with drilling mud on carbonate basis the concentration of residual drilling mud decreases during the pump test but all samples show a residual concentration of drilling mud the formation fluid composition is recalculated with phreeqc and is comparable to the literature values for the exter formation the gas partial pressure is below saturation at standard conditions and the composition is dominated by n2 similar to the underlying storage reservoir prior to co2 injection the impact of residual drilling mud on dissolved inorganic carbon and the respective 13c values decreases during the monitoring period the pristine isotopic composition cannot be determined due to calcite precipitation no conclusive results indicate a leakage from the underlying co2 storage reservoir

reservoir characterization of a co2 storage aquifer the upper triassic stuttgart formation in the northeast german basin abstract ketzin in the northeast german basin negb is the site for pilot injection of co 2 co 2 sink project into a saline aquifer the upper triassic stuttgart formation situated at a depth of about 630 700 m this paper reports the baseline characterization of the reservoir formation based on new core material and well logs obtained from one injection well and two observations wells drilled at a distance from 50 m to 100 m from each other the reservoir is lithologically heterogeneous and made up by fluvial sandstones and siltstones interbedded with mudstones showing remarkable differences in porosity the thickest sandstone units are associated with channel sandstone whose thickness varies over short lateral distances in depth petrographic mineralogical mineral chemical and whole rock geochemical analysis were performed focusing on the sandstone intervals which display the best reservoir properties for co 2 injection the dominantly fine grained and well to moderately well sorted immature sandstones classify as feldspathic litharenites and lithic arkoses quartz 22 43 wt plagioclase 19 32 wt and k feldspar 5 13 wt predominate mineralogically muscovite plus illite and mixed layer minerals are omnipresent 4 13 wt quartz feldspar as well as meta sedimentary and volcanic rock fragments comprise the most abundant detrital components which often are rimmed by thin early diagenetic coatings of ferric oxides and locally of clay minerals feldspar grains may be unaltered and optically clear partially to completely dissolved partially altered to sheet silicates mainly illite or albitized analcime and anhydrite constitute the most widespread often spatially associated pore filling cement minerals authigenic dolomite barite and coelestine is minor the percentage of cements ranges in total from about 5 vol to 32 vol except of samples intensely cemented by anhydrite and analcime total porosities of the sandstones range from 13 to 26 the fraction of intergranular porosity varies between 12 and 21 about 1 5 porosity has been generated by dissolution of detrital plagioclase k feldspar and volcanic rock fragments the comparatively large modal abundance of feldspars micas chlorite clay minerals fe ti oxides and analcime account for the richness in ti al fe mg na and k and the paucity in si of the stuttgart sandstones relative to mature sandstones altogether these sandstones are comparatively rich in minerals that may potentially react with the injected co 2

atmospheric pressure response to mesoscale sea surface temperature variations in the kuroshio extension region in situ evidence several research cruises were conducted across the kuroshio extension front to examine the low level atmospheric responses to mesoscale variations in sea surface temperature sst surface meteorological observations including sea level pressure slp and sst were collected at two moored buoys that were located on either side of the kuroshio extension and from a research vessel as it moved between the two buoys during the various cruises spatial perturbations in slp along the ship transects calculated by subtracting moored buoy slp from that of the moving ship tend to be positive negative where sst is lower higher on spatial scales of about 100 km and the magnitude of these slp perturbations near the sst front can exceed 1 0 hpa radiosonde data also show that the atmospheric boundary layer thins thickens over lower higher sst although the contribution of across track component in the wind cannot be calculated the along track component of divergence suggests low level convergence over higher sst the thermally induced pressure gradient is important in the momentum budget suggesting that sea breeze like local circulations formed over the sst fronts indeed the pressure adjustment mechanism can sometimes dominate even on a scale of 100 km although it is not always observed the time scale in which the boundary layer thickness adjusted to sst is estimated to be 1 day or less

sea level pressure minimum along the kuroshio and its extension abstractatmospheric effects of sea surface temperature sst fronts along the kuroshio and kuroshio extension k ke are investigated by examining spatial characteristics of the climatological sea level pressure slp surface winds and surface heat flux q fields based on an in situ observation dataset a hydrostatic effect of the sst front is observed during the northwesterly monsoon characterized by a westward extending low slp wedge trough slightly south of the peak in q along the k ke ageostrophic surface westerlies crossing slp isobars toward a trough center are found north of the low slp wedge apparently because of the eastward acceleration by the vertical mixing effect this feature of the ageostrophic winds is less pronounced south of it a north south asymmetry arising as vertical mixing accelerates decelerates eastward ageostrophic winds north south of it while the slp trough near the sst front is found nearly year round except for summer its meridional location seasonally migrates pr

air sea interaction effects in the lower troposphere across the north wall of the gulf stream abstract significant atmospheric and oceanographic differences have often been observed in the regions lying on either side of the north wall of the gulf stream satellite visible range sensors have revealed changes in reflectivity across the gulf stream believed to be due to changes in sea state that are related to these atmospheric and oceanic differences in addition lines of low level cloud paralleling the edge of the gulf stream have been observed to persist in satellite imagery for several days at a time anomalous radar propagation also has been noted to occur in these same regions in an attempt to document the interrelation of these phenomena the lower atmosphere over the north wall of the gulf stream was studied on two separate occasions sea state photography and measurements of sea surface temperature air temperature dew point temperature and atmospheric pressure were made by an instrumented rp 3a aircraft flying at various altitudes from the gulf stream across the north wall and onto

the influence of sea surface temperature on surface wind in the eastern equatorial pacific weekly to monthly variability abstract temporal correlations between near equatorial surface wind and sea surface temperatures sst at 11 w in the eastern pacific ocean are investigated using data from an array of moored sensors between 5 n and 5 s the signature of tropical instability waves with periods of 20 30 days is apparent in time series of sst and both the meridional and zonal wind components results indicate the existence of a band of pronounced horizontal divergence in the surface wind field associated with the large meridional sst gradient equatorial front normally located just north of the equator perturbations of the equatorial front by the instability waves induce fluctuations in the overlying winds evidence of the air sea coupling is stronger in time series of the meridional gradients of wind and sst than between time series of the variables themselves the meridional differencing serves as a high pass filter in the space domain which removes planetary scale wind fluctuations that are unrelated to the local sst

evidence for sst forced anomalous winds revealed from simultaneous radiosonde launches from three ships across the kuroshio extension front abstractsimultaneous launches of radiosondes were conducted from three research vessels aligned meridionally across a sea surface temperature sst front on the flank of the kuroshio extension the soundings carried out every 2 h over 5 days in early july 2012 provided a unique opportunity in capturing unambiguous data on anomalous easterly winds derived from a pronounced meridional sst gradient the data indicate that a meridional contrast in surface heat fluxes from the underlying ocean enhanced the air temperature anomaly across the sst front which was observed from the surface up to 300 m altitude correspondingly high and low pressure anomalies that reached 800 m altitude formed on the north and south sides of the sst front respectively these temperature and pressure anomalies were maintained even during the passage of synoptic scale disturbances although the free tropospheric winds are overall westerly winds below the 1000 m level were easterly due to geostrophic anomalies driven by the northw

multiyear measurements of the oceanic and atmospheric boundary layers at the brazil malvinas confluence region 1 this study analyzes and discusses data taken from oceanic and atmospheric measurements performed simultaneously at the brazil malvinas confluence bmc region in the southwestern atlantic ocean this area is one of the most dynamical frontal regions of the world ocean data were collected during four research cruises in the region once a year in consecutive years between 2004 and 2007 very few studies have addressed the importance of studying the air sea coupling at the bmc region lateral temperature gradients at the study region were as high as 0 3 c km 1 at the surface and subsurface in the oceanic boundary layer the vertical temperature gradient reached 0 08 c m 1 at 500 m depth our results show that the marine atmospheric boundary layer mabl at the bmc region is modulated by the strong sea surface temperature sst gradients present at the sea surface the mean mabl structure is thicker over the warmside of the bmc where brazil current bc waters predominate the opposite occurs over the coldside of the confluence where waters from the malvinas falkland current mc are found the warmside of the confluence presented systematically higher mabl top height compared to the coldside this type of modulation at the synoptic scale is consistent to what happens in other frontal regions of the world ocean where the mabl adjusts itself to modifications along the sst gradients over warm waters at the bmc region the mabl static instability and turbulence were increased while winds at the lower portion of the mabl were strong over the coldside of the bc mc front an opposite behavior is found the mabl is thinner and more stable our results suggest that the sea level pressure slp was also modulated locally together with static stability vertical mixing mechanism by the surface condition during all cruises sst gradients at the bmc region modulate the synoptic atmospheric pressure gradient postfrontal and prefrontal conditions produce opposite thermal advections in the mabl that lead to different pressure intensification patterns across the confluence

a new energy density calculation method for reservoir delineation using seismic low frequency signal abstract in comparison to high frequency signals low frequency seismic signals suffer less from scattering and intrinsic attenuation during wave propagation penetrate deeper strata and thus can provide more energy information related to the hydrocarbon reservoirs based on the asymptotic representation for the frequency dependent reflections in the fluid saturated pore elastic media we first derive a novel equation of the reservoir energy density and present an efficient workflow to calculate the reservoir energy density using low frequency seismic data then within a low frequency range from 1 to 30 hz we construct an objective function to determine the optimal frequency using the energy densities calculated from the post stack seismic traces close to the wells next we can calculate the reservoir energy density using the instantaneous spectra of optimal frequency at the low frequency end of the seismic spectrum tests on examples for synthetic and field data demonstrate that the proposed reservoir energy density can produce high quality images for the fluid saturated reservoirs and it produces less background artefacts caused by elastic layers this method provides a new way to detect the location of hydrocarbon reservoirs and characterize their spatial distribution

the use of tracers to assess drill mud penetration depth into sandstone cores during deep drilling method development and application for the utilization of deep saline aquifers in the frame of geotechnical use such as geological sequestration of co2 h2 or energy storage a baseline characterization of pristine reservoir rock cores is required to monitor changes in the indigenous microbial communities and pore fluids and to study alterations in rock characteristics resulting from interaction with geological storage technologies however drilling procedures and technical fluids particularly drill mud are sources of core contamination to measure the penetration of drill mud into the cores three tracers fluorescein microspheres and 4 6 diamidino 2 phenylindole stained bacteria were tested under laboratory conditions the flow of drill mud into core samples was induced by applying uniaxial pressure differentials to the core and the penetration depth was microscopically determined for each tracer fluorescein was extracted from the rock samples and quantified fluorometrically the results indicate that all tested tracers are suitable for tracking drill mud penetration the actual penetration depth seems to be related to differences in mineral composition and texture as well as microfractures among all tested tracers fluorescein labelling is the simplest cheapest and most accurate method for analyzing the contamination of rock cores by technical fluids the application of this tracer was successfully applied during two deep drilling campaigns at the co2 storage pilot site in ketzin germany the results highlight that the use of tracers is indispensable to ensure the quality of core samples for microbiological and biogeochemical analysis

midlatitude wind stress sea surface temperature coupling in the vicinity of oceanic fronts the influences of strong gradients in sea surface temperature on near surface cross front winds are explored in a series of idealized numerical modeling experiments the atmospheric model is the naval research laboratory coupled ocean atmosphere mesoscale prediction system coamps model which is fully coupled to the regional ocean modeling system roms ocean model a series of idealized two dimensional model calculations is carried out in which the wind blows from the warm to cold side or the cold to warm side of an initially prescribed ocean front the evolution of the near surface winds boundary layer and thermal structure is described and the balances in the momentum equation are diagnosed the changes in surface winds across the front are consistent with previous models and observations showing a strong positive correlation with the sea surface temperature and boundary layer thickness the coupling arises mainly as a result of changes in the flux richardson number across the front and the strength of the coupling coefficient grows quadratically with the strength of the cross front geostrophic wind the acceleration of the winds over warm water results primarily from the rapid change in turbulent mixing and the resulting unbalanced coriolis force in the vicinity of the front much of the loss gain of momentum perpendicular to the front in the upper and lower boundary layer results from acceleration deceleration of the flow parallel to the front via the coriolis term this mechanism is different from the previously suggested processes of downward mixing of momentum and adjustment to the horizontal pressure gradient and is active for flows off the equator with sufficiently strong winds although the main focus of this work is on the midlatitude strong wind regime calculations at low latitudes and with weak winds show that the pressure gradient and turbulent mixing terms dominate the cross front momentum budget consistent with previous work

mesoscale wind stress sst coupled perturbations in the kuroshio extension abstract mesoscale perturbations of wind stress ms and sea surface temperature sstms in the kuroshio extension ke are analyzed using long term high resolution satellite observations mesoscale wind stress and sst perturbations are first extracted using a locally weighted regression loess method and then analyzed using statistical methods including linear regression singular value decomposition svd and the inverse method the coupling coefficient between mesoscale wind stress magnitude ms and sstms and those between mesoscale wind stress divergence curl and downwind crosswind sst gradients exhibit distinct seasonal variability with large values in winter and small values in summer consistent with previous studies the three leading svd modes for ms and sstms show highly consistent variability in both spatial patterns and temporal expansion coefficients and the temporal expansion coefficients exhibit distinct seasonal and interannual variability these modes are associated with inherent seasonal variability of ms and sstms and interannual variability of the ke jet dynamic state based on the observed coupling relationships between wind stress divergence curl and downwind crosswind sst gradients an empirical model for mesoscale wind stress vector perturbations x y ms f sst is established this model solves x y ms from their divergence and curl estimated from sst gradient data using an inverse method this newly established x y ms f sst model produces reasonably consistent solutions compared to the one established based on the empirical relationship between ms and sstms furthermore this model could separate divergence only and curl only wind stress perturbations to study their respective effects and thus is promising and will contribute to ocean dynamic analyses

the low frequency gas shadow on seismic sections about six years ago greg partyka and his colleagues at amoco research showed how an old technique the fourier transform could be used effectively for seismic interpretation and visualization this idea has come to be known as spectral decomposition in recent years many spectral decomposition techniques have been developed and utilized for stratigraphic analysis and direct hydrocarbon detection with the refined spectral decomposition techniques now available the low frequency shadow beneath gas reservoirs is another old idea that has renewed importance and interest in the exploration community almost a decade ago dan ebrom studied a variety of possible mechanisms for the low frequency shadow and why it might be associated with hydrocarbons he presented his analysis at the 1996 seg summer research workshop

atmospheric boundary layer adjustment to the synoptic cycle at the brazil malvinas confluence south atlantic ocean 1 this study analyzes and discusses atmospheric boundary layer vertical profiles of potential temperature specific humidity and wind speed at each of the sides of the brazil malvinas confluence in the southwestern atlantic ocean such confluence is characterized by the meeting of water masses with very different characteristics the southern waters of the malvinas current can be several degrees colder and appreciably less salty than the northern brazil current waters at the same time a synoptic cycle can be identified at the region marked by the successive passages of frontal systems and extratropical cyclones the different phases of the synoptic cycle lead to different thermal advections at the confluence causing respective different patterns of atmospheric boundary layer adjustment to the surface heterogeneity induced by the confluence in the present study this adjustment along the synoptic cycle is analyzed using data from five experiments performed across the confluence from 2003 to 2008 in each of the campaigns a number of soundings were launched from a ship at both sides of the confluence a climatological analysis with respect to the closest frontal passage is presented and it suggests that the observations collected at each of the years analyzed are referent to a different day of the synoptic cycle the average profiles at each side of the confluence are in agreement with previous modeling studies of warm and cold thermal advection patterns over an oceanic front furthermore our study shows that peculiar transitional characteristics are also observed between the conditions of well established warm and cold advection at many phases of the synoptic cycle a strongly stratified boundary layer occurs at one or both sides of the confluence some of the observed characteristics such as a large moisture accumulation near the surface suggest that existing sensible and latent heat fluxes parameterizations fail under very strong stratifications and the consequences of this deficiency are analyzed

reservoir permeability from seismic attribute analysis in case of porous fluid saturated medium the biot s poroelasticity theory predicts a movement of the pore fluid relative to the skeleton on seismic wave propagation through the medium this phenomenon opens an opportunity for investigation of the flow properties of the hydrocarbon saturated reservoirs it is well known that relative fluid movement becomes negligible at seismic frequencies if porous material is homogeneous and well cemented in this case the theory predicts an underestimated seismic wave velocity dispersion and attenuation based on biot s theory helle et al 2003 have numerically demonstrated the substantial effects on both velocity and attenuation by heterogeneous permeability and saturation in the rocks besides fluid flow effect the effects of scattering gurevich et al 1997 play very important role in case of finely layered porous rocks and heterogeneous fluid saturation we have used both fluid flow and scattering effects to derive a frequency dependent seismic attribute which is proportional to fluid mobility and applied it for analysis of reservoir permeability

seismic attenuation due to wave induced flow analytical expressions for three p wave attenuation mechanisms in sedimentary rocks are given a unified theoretical framework two of the models concern wave induced flow due to heterogeneity in the elastic moduli at mesoscopic scales scales greater than grain sizes but smaller than wavelengths in the first model the heterogeneity is due to lithological variations e g mixtures of sands and clays with a single fluid saturating all the pores in the second model a single uniform lithology is saturated in mesoscopic patches by two immiscible fluids e g air and water in the third model the heterogeneity is at microscopic grain scales broken grain contacts and or micro cracks in the grains and the associated fluid response corresponds to squirt flow the model of squirt flow derived here reduces to proper limits as any of the fluid bulk modulus crack porosity and or frequency is reduced to zero it is shown that squirt flow is incapable of explaining the measured level of loss 10 sup 2 q sup 1 10 sup 1 within the seismic band of frequencies 1 to 10 sup 4 hz however either of the two mesoscopic scale models easily produce enough attenuation to explain the field data

role of the gulf stream and kuroshio oyashio systems in large scale atmosphere ocean interaction a review abstract ocean atmosphere interaction over the northern hemisphere western boundary current wbc regions i e the gulf stream kuroshio oyashio and their extensions is reviewed with an emphasis on their role in basin scale climate variability sst anomalies exhibit considerable variance on interannual to decadal time scales in these regions low frequency sst variability is primarily driven by basin scale wind stress curl variability via the oceanic rossby wave adjustment of the gyre scale circulation that modulates the latitude and strength of the wbc related oceanic fronts rectification of the variability by mesoscale eddies reemergence of the anomalies from the preceding winter and tropical remote forcing also play important roles in driving and maintaining the low frequency variability in these regions in the gulf stream region interaction with the deep western boundary current also likely influences the low frequency variability surface heat fluxes damp the low frequency sst anomalies ove

phase shifted based numerical method for modeling frequency dependent effects on seismic reflections the significant velocity dispersion and attenuation has often been observed when seismic waves propagate in fluid saturated porous rocks both the magnitude and variation features of the velocity dispersion and attenuation are frequency dependent and related closely to the physical properties of the fluid saturated porous rocks to explore the effects of frequency dependent dispersion and attenuation on the seismic responses in this work we present a numerical method for seismic data modeling based on the diffusive and viscous wave equation dvwe which introduces the poroelastic theory and takes into account diffusive and viscous attenuation in diffusive viscous theory we derive a phase shift wave extrapolation algorithm in frequencywavenumber domain for implementing the dvwe based simulation method that can handle the simultaneous lateral variations in velocity diffusive coefficient and viscosity then we design a distributary channels model in which a hydrocarbon saturated sand reservoir is embedded in one of the channels next we calculated the synthetic seismic data to analytically and comparatively illustrate the seismic frequency dependent behaviors related to the hydrocarbon saturated reservoir by employing dvwe based and conventional acoustic wave equation awe based method respectively the results of the synthetic seismic data delineate the intrinsic energy loss phase delay lower instantaneous dominant frequency and narrower bandwidth due to the frequency dependent dispersion and attenuation when seismic wave travels through the hydrocarbon saturated reservoir the numerical modeling method is expected to contribute to improve the understanding of the features and mechanism of the seismic frequency dependent effects resulted from the hydrocarbon saturated porous rocks

seismic low frequency effects in monitoring fluid saturated reservoirs there is a complex relationship between seismic attributes including the frequency dependence of reflections and fluid saturation in a reservoir observations in both laboratory and field data indicate that reflections from a fluid saturated layer have an increased amplitude and delayed traveltime at low frequencies when compared with reflections from a gas saturated layer comparison of laboratory modeling results with a diffusive viscous theory model show that low 5 values of the quality factor q can explain the observations of frequency dependence at the field scale conventional processing of time lapse vsp data found minimal changes in seismic response of a gas storage reservoir when the reservoir fluid changed from gas to water lowfrequency analysis found significant seismic reflectionattribute variation in the range of 15 50 hz the field observations agree with effects seen in laboratory data and predicted by the diffusive viscous theory one explanation is that very low values of q are the result of internal diffusive losses caused by fluid flow this explanation needs further theoretical investigation the frequencydependent amplitude and phase reflection properties presented in this paper can be used for detecting and monitoring fluid saturated layers

barometric pressure variations associated with eastern pacific tropical instability waves abstract barometric pressure surface temperature and wind time series in the eastern equatorial pacific are analyzed to determine if oceanic tropical instability wave tiw sea surface temperature variations cause barometric pressure gradients large enough to influence the atmospheric boundary layer during the study period from april 2001 to september 2002 11 tiws propagated westward past 110 w causing a spectral peak at 20 30 days in the sea surface temperature sst meridional difference between 2 n 110 w and 0 110 w likewise the meridional pressure difference also had a spectral peak in the 20 30 day tiw band cross spectral analysis shows that within the tiw band sst induced pressure variations were roughly 0 1 hpa c 1 in magnitude the resulting pressure gradient force is comparable in magnitude to other terms in the meridional momentum balance implications about the role of the boundary layer capping in the adjustment to sst forcing are discussed

air sea heat exchanges characteristic of a prominent midlatitude oceanic front in the south indian ocean as simulated in a high resolution coupled gcm abstract an integration of a high resolution coupled general circulation model whose ocean component is eddy permitting and thus able to reproduce a sharp gradient in sea surface temperature sst is analyzed to investigate air sea heat exchanges characteristic of the midlatitude oceanic frontal zone the focus of this paper is placed on a prominent sst front in the south indian ocean which is collocated with the core of the southern hemisphere storm track time mean distribution of sensible heat flux is characterized by a distinct cross frontal contrast it is upward and downward on the warmer and cooler flanks respectively of the sst front acting to maintain the sharp gradient of surface air temperature sat that is important for preconditioning the environment for the recurrent development of storms and thereby anchoring the storm track induced by cross frontal advection of cold warm air associated with migratory atmospheric disturbances the surface flux is highly variable with intermittent en

ocean frontal effects on the vertical development of clouds over the western north pacific in situ and satellite observations abstract a suite of shipboard and satellite observations are analyzed and synthesized to investigate the three dimensional structure of clouds and influences from sea surface temperature fronts over the western north pacific sharp transitions are observed across the kuroshio extension ke front in the marine atmospheric boundary layer mabl and its clouds the ocean s influence appears to extend beyond the mabl with higher cloud tops in altitude along the ke front than the surroundings in winter intense turbulent heat release from the ocean takes place on the southern flank of the ke front where the cloud top penetrates above the mabl and reaches the midtroposphere in this band of high cloud tops frequent lightning activity is observed the results of this study suggest a sea level pressure mechanism for which the temperature gradient in the mabl induces strong surface wind convergence on the southern flank of the ke front deepening the clouds there in early summer sea fog frequently occurs on

on the role of sea surface temperature gradients in forcing low level winds and convergence in the tropics abstract we examine the importance of pressure gradients due to surface temperature gradients to low level p 700 mb flow and convergence in the tropics over time scales 1 month the latter plays a crucial role in determining the distribution of cumulonimbus convection and rainfall our approach is to consider a simple one layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically consistent with ecmwf analyzed data the top of the layer is taken at 700 mb the influence from higher levels is intentionally suppressed by setting horizontal pressure gradients and frictional stresses to zero at the top of the layer horizontal convergence within the layer is taken up by cumulonimbus mass flux however the development of the cumulonimbus mass flux is associated with a short relaxation time o hr roughly the development time for such convection during this short time horizontal convergence acts to redistribute mass so as to reduce horizontal pressur

frequency dependent velocity analysis and offset dependent low frequency amplitude anomalies from hydrocarbon bearing reservoirs in the southern north sea norwegian sector abstractour aim was to identify some of the characteristics of low frequency anomalies specifically we have looked in 3d broadband data from the north sea for any offset dependence in these anomalies and any frequency related change in normal moveout nmo velocity that could influence stacking power over different frequencies after high resolution spectral decomposition two types of low frequency anomaly have been identified associated with hydrocarbon bearing reservoirs 1 at the reservoir top and 2 below the reservoir with a time delay of approximately 100 200 ms both types of anomalies indicate offset dependence on the near offset stacks they are relatively strong but they tend to be absent on the far offset stacks in addition horizon velocity analysis which was performed along the horizons picked at the tops of reservoir and nonreservoir intervals has revealed frequency dependent nmo velocity for nonreservoir events we found no significant difference between the nmo velocities fo

comparison of the microbial community composition of pristine rock cores and technical influenced well fluids from the ketzin pilot site for co2 storage two geological formations at the co2 storage pilot site in ketzin germany were geochemically and microbiologically characterized to further evaluate changes resulting from co2 injection well fluids were collected from both stuttgart storage formation 650 m depth and exter formations 400 m depth overlying the caprock either through pump tests or downhole samplings rock samples were retrieved during a deep drilling into the exter formation and primarily comprised quartz ferrous dolomite or ankerite calcite analcime plagioclase and clay minerals as determined through x ray diffraction analyses in the rocks the total organic carbon toc which potentially contributes to microbial growth was mostly below 1000 mg kg 1 the geochemical characterization of fluids revealed significant differences in the ionic composition between both formations the microbial characterization was performed through fluorescence in situ hybridization and 16s rrna gene fingerprinting in the fluids obtained from the stuttgart formation the microbial activity was affected by the relatively high toc introduced by the organic drill mud the total cell counts were approximately 106 cells ml 1 the microbial community was characteristic of a saline deep biosphere environment enriched through increased carbon availability with sulfate reducing bacteria as the most abundant microorganisms up to 60 of total cells species belonging to halophilic halotolerant proteobacteria and firmicutes were primarily detected in exter formation rocks proteobacteria and actinobacteria were detected these data provide an explicit reference to further evaluate environmental changes and community shifts in the reservoir during co2 storage and provide information for evaluating the storage efficiency and reliability

influence of drill mud on the microbial communities of sandstone rocks and well fluids at the ketzin pilot site for co2 storage at a pilot site for co2 storage in ketzin germany a drastic decrease in injectivity occurred in a well intended for injection this was attributed to an obstruction of the pore throats due to microbial degradation of the organic drill mud and subsequent iron sulfide fes precipitation in the highly saline brine 240 g l 1 to better understand the biogeochemical processes the response of the autochthonous microbial community to drill mud exposure was investigated pristine cores of two aquifers with different salinity were incubated under simulated in situ conditions 50 bar 40 c and 45 bar 25 c respectively and co2 atmosphere for the first time rock cores obtained from the co2 plume of the storage formation were investigated the influence of acetate as a biodegradation product of drill mud polymers and the effectiveness of a biocide were additionally tested increased microbial diversities were observed in all long term 8 20 weeks incubations even including biocide biofilm like structures and small round shaped minerals of probable microbiological origin were found the results indicate that the microbial community remains viable after long term co2 exposure microorganisms hydrolyzing cellulose polymers e g burkholderia spp variovorax spp biodegraded organic components of the drill mud and most likely produced low molecular weight acids although the effects of drill mud were less strong as observed in situ it was demonstrated that acetate supports the growth of sulfate reducing bacteria i e desulfotomaculum spp the microbial induced precipitation of amorphous fes reduced the injectivity in the near well area therefore when using organic drill mud the well must be cleaned intensively to minimize the hazards of bacterial stimulation

the influence of sea surface temperature on surface wind in the eastern equatorial pacific seasonal and interannual variability abstract the climate of the eastern pacific exhibits a pronounced equatorial asymmetry boundary layer air originating in the southern hemisphere trades crosses the equator and flows into the intertropical convergence zone itcz whose southern limit is nearly always located at least 4 to the north of the equator the sea surface temperature sst distribution is characterized by a prominent cold tongue centered 1 s a strong frontal zone centered 2 n and a warm eastward current centered near 5 n the surface wind field exhibits a pronounced horizontal divergence as the air flows northward across the oceanic frontal zone these features vary in strength in response to the annual cycle and the el nino southern oscillation phenomenon the northward cross equatorial surface winds the cold tongue and the frontal zone all tend to be strongest during the cold season july through november during the cold season of the coldest years when the cold tongue is most prominent the cross equatorial flow t

sea breeze like winds across the north wall of the gulf stream an analytical model sea breeze like winds have been observed on the warmer side of the gulf stream when synopticscale winds blow from cool shelf water toward a warm water surface sweet et al 1981 it is shown that a simple thermally driven analytical model can explain satisfactorily the increase in wind speed from the cold to the warmer water side as resulting from horizontal temperature gradient across the gulf stream

dynamical analyses of marine atmospheric boundary layer structure near the gulf stream oceanic front the effects of the sea surface temperature s s t front at the edge of the gulf stream on the marine atmospheric boundary layer mabl are investigated using a numerical model to study the modification effects of an oceanic front on the mabl structure the situation simulated is flow from over cold shelf water to over the warm water of the gulf stream the initial temperature and humidity profiles of the air are specified to be near neutral over the cold water and are therefore typical of undisturbed conditions the differential in s s t across the oceanic front creates a horizontal variation in the surface perturbation pressure and the stability the surface perturbation pressure and turbulent fluxes modulate the flow and produce horizontal variations in horizontal wind components with associated vertical motions a thermally direct cell is produced as a result of the s s t difference across the front the isotherms slope upward towards the warm water entrainment of inversion layer air and upward vertical motion over the warm water cause the mabl to be deeper there a layer of cloud forms over warm water and is associated with mixed layer deepening rather than lowering of the condensation level turbulent fluxes in the mabl show considerable spatial variation surface stress is much larger over the front and over the warm water than over the cold water this is mostly caused by wind speed changes associated with the front changes in the drag coefficient due to changes in surface roughness and stability are much less important mean budgets for temperature and total water indicate that there is a balance between horizontal advection and turbulent flux divergence the u momentum budget shows that once the geostrophic balance terms are subtracted the balance is mainly between the pressure gradient force associated with the induced temperature field and turbulent friction with horizontal advection and the coriolis force acting on the geostrophic departure playing minor roles the v momentum budget shows a balance between horizontal advection coriolis force and friction although there are few data for comparison the results are in qualitative agreement with observations in the area this study shows that the s s t front at the gulf stream edge produces marked local changes in the nearby atmospheric surface layer

low frequency reflections from a thin layer with high attenuation caused by interlayer flow the 1d interlayer flow or white s model is based on biot s theory of poroelasticity and explains low frequency seismic wave attenuation in partially saturated rocks by wave induced fluid flow between two alternating poroelastic layers each saturated with a different fluid we have developed approximate equations for both the minimum possible value of the quality factor q and the corresponding fluid saturation for which q is minimal the simple approximate equations provide a better insight into the dependence of q on basic petrophysical parameters and allow for a fast assessment of the minimal value of q the approximation is valid for a wide range of realistic petrophysical parameter values for sandstones partially saturated with gas and water and shows that values of q can be as small as two we ap plied the interlayer flow model to study the reflection coefficient of a thin i e between 6 and 11 times smaller than the incident wavelength layer that is partially saturated with gas and water

observations of marine atmospheric boundary layer transitions across the summer kuroshio extension abstract the baiu and kuroshio extension ke fronts both zonally oriented and nearly collocated east of japan are the dominant summertime features of the atmosphere and ocean respectively over the midlatitude northwest pacific an atmospheric sounding campaign was conducted on board the r v roger revelle during the 2005 summer transects of soundings across the ke front are analyzed to study its effects on the atmosphere along with continuous surface meteorological and ceilometer cloud base observations while the ke front remained nearly stationary during the cruise the baiu front displayed large meridional displacements that changed wind direction across the ke front the presence of sharp sea surface temperature sst gradients anchored by the ke enhanced the thermal and moisture advection causing substantial changes in the marine atmospheric boundary layer mabl structure when the baiu front was displaced north of the ke front southwesterly winds advected warm humid air from the subtropics

cloud response to the meandering kuroshio extension front abstracta unique set of observations on board research vessel r v mirai in april 2010 captured a striking cloud hole over a cold meander of the kuroshio extension ke east of japan as corroborated by atmospheric soundings ceilometer shipboard radiation data and satellite cloud images distinct differences were also observed between the warm meander farther to the north and warm water south of the ke the atmosphere is highly unstable over the warm meander promoting a well mixed marine atmospheric boundary layer mabl and a layer of solid stratocumulus clouds capped by a strong inversion over the warm water south of the ke mabl deepens and is decoupled from the ocean surface scattered cumulus clouds develop as captured by rapid variations in ceilometer derived cloud base the results show that the meandering ke front affects the entire mabl and the clouds such atmospheric response can potentially intensify the baroclinicity in the lower atmosphere

numerical simulation of boundary layer structure and cross equatorial flow in the eastern pacific abstract recent observations from spaceborne microwave sensors have revealed detailed structure of the surface flow over the equatorial eastern pacific in the boreal fall season a marked acceleration of surface wind across the northern sea surface temperature sst front of the cold tongue is a prominent feature of the regional climate previous studies have attributed the acceleration to the effect of enhanced momentum mixing over the warmer waters a high resolution numerical model is used to examine the cross frontal flow adjustment in a comprehensive comparison the model agrees well with many observed features of cross equatorial flow and boundary layer structure from satellite tropical atmosphere ocean tao moorings and the recent eastern pacific investigation of climate processes epic campaign in particular the model simulates the acceleration across the sst front and the change from a stable to unstable boundary layer analysis of the model momentum budget indicates that the hydrostatic

modulation mechanisms of marine atmospheric boundary layer at the brazil malvinas confluence region 1 the influence of the brazil malvinas confluence bmc region on the marine atmospheric boundary layer mabl is investigated through in situ data analysis of five different cruises 2004 to 2008 and numerical experiments with a regional atmospheric model two different groups of numerical experiments were performed in order to evaluate the relevance of static stability and hydrostatic balance physical mechanisms for the mabl instability the first group used monthly climatological sea surface temperature sst as bottom boundary condition while the second used daily updated advanced microwave scanning radiometer eos sst data together with radiosondes and surface data assimilation a reasonable agreement between numerical results and quikscat wind data was observed through correlation coefficients and mean square error values in terms of the horizontal structure of the mabl stronger winds were found over the warm side of the bmc region as well as over the thermal front itself which supports the coexistence of both modulation mechanisms the analyzed patterns of surface atmospheric thermal advection showed a clear interaction between the synoptic and regional scales the signature of the oceanic thermal front almost meridionally oriented on the air temperature at 2 m makes the temperature advection strongly determined by the zonal component of the wind the analysis of momentum budget terms did not show a clear and reasonable explanation of the existence or predominance of the modulation mechanisms and it also suggested the relevance of other effects such as the idea based on unbalanced coriolis force and turbulence friction effects

global analysis of the pressure adjustment mechanism over sea surface temperature fronts using airs aqua data 1 we investigate the signatures of atmospheric pressure adjustment mechanism for surface wind convergence divergence over major sea surface temperature sst frontal regions using global observations of satellite sounding and scatterometer lower tropospheric air thickness which includes a sea level pressure component modified by air temperature in the marine atmospheric boundary layer is analyzed and the relation between the laplacian of the thickness and wind convergence are examined among four sst frontal regions in mid latitudes correlation between the thickness laplacian and wind convergence is the largest over the gulf stream followed by those for the agulhas return current and for the brazil malvinas current and relatively small but still significant over the kuroshio oyashio extension these correlations strongly suggest that the pressure adjustment mechanism ubiquitously plays an important role in air sea interaction over the global sst frontal regions furthermore air temperatures in the first two regions exhibit sst relating signatures even in the mid troposphere

seismic modeling of low frequency shadows beneath gas reservoirs abstractp wave amplitude anomalies below reservoir zones can be used as hydrocarbon markers some of those anomalies are considerably delayed relatively to the reflections from the reservoir zone high p wave attenuation and velocity dispersion of the observed p waves cannot justify such delays the hypothesis that these amplitude anomalies are caused by wave propagation through a layered permeable gaseous reservoir is evaluated the wave propagation through highly interbedded reservoirs suggest an anomalous amount of mode conversions between fast and slow p waves the converted p waves which propagated even a short distance as slow p waves should be significantly delayed and attenuated comparatively with the fast p wave reflections the amplitudes and arrival time variations of conventional and converted p wave reflections at low seismic frequencies were evaluated by means of an asymptotic analysis the calculations confirmed that the amplitude anomalies due to converted p waves are noticeably delayed

modeling the effect of multiple sets of mesoscale fractures in porous rock on frequency dependent anisotropy this study models the seismic response of porous rock containing two fracture sets with different orientations sizes and connectivities modeling demonstrates frequency dependent anisotropy controlled by two characteristic frequencies that are defined by fluid mobility and the length scales of the fractures fracture related dispersion and attenuation typically occur over a wider frequency band than is seen in the case of a single fracture set when one set of fractures is modeled as being sealed the azimuthal variation of velocity and attenuation can be different with the azimuth of minimum attenuation coinciding with the strike direction of the open fracture set the results should support attempts to differentiate between open and closed fractures on the basis of seismic measurements

reservoir imaging using low frequencies of seismic reflections there are numerous laboratory and field examples in which low frequency components of reflected seismic waves show surprising imaging capabilities ironically such components are often filtered out as useless in conventional data processing however as we demonstrate below this part of the signal contains the most important information about the reservoir

on the importance of midlatitude oceanic frontal zones for the mean state and dominant variability in the tropospheric circulation 1 observations indicate that midlatitude weather systems are organized into storm tracks near oceanic frontal zones with pronounced sea surface temperature sst gradients a pair of atmospheric general circulation model experiments with zonally uniform sst profiles prescribed show that their observed collocation is not fortuitous in one experiment a storm track is anchored around a midlatitude sst front that maintains near surface thermal gradients and energizes eddies westerly momentum transport by eddies produces a well defined polar front jet along the front even in winter when a subtropical jet stream intensifies in the other experiment removal of the sst front leads to a substantial weakening in eddy activity and the pfj especially in winter it also leads to a weakening of the annular mode the dominant mode of westerly jet variability and its notable structural distortion in winter though idealized our experiments suggest the importance of midlatitude oceanic fronts for the tropospheric circulation and its variability

fluid mobility and frequency dependent seismic velocity direct measurements the influence of fluid mobility on seismic velocity dispersion is directly observed in laboratory measurements from seismic to ultrasonic frequencies a forceddeformation system is used in conjunction with pulse transmission to obtain elastic properties at seismic strain amplitude 10 7 from 5 hz to 800 khz varying fluid types and saturations document the influence of pore fluids the ratio of rock permeability to fluid viscosity defines mobility which largely controls pore fluid motion and pore pressure in a porous medium high fluid mobility permits pore pressure equilibrium either between pores or between heterogeneous regions resulting in a low frequency domain where gassmann s equations are valid in contrast low fluid mobility can produce strong dispersion even within the seismic band here the low frequency assumption fails since most rocks in the general sedimentary section have very low permeability and fluid mobility shales siltstones tight limestones etc most rocks are not in the lowfrequency domain even at seismic frequencies only those rocks with high permeability porous sands and carbonates will remain in the low frequency domain in the seismic or sonic band

ocean atmosphere in situ observations at the brazil malvinas confluence region 1 this paper presents a description of marine atmospheric boundary layer mabl and oceanic boundary layer obl interactions at the brazil malvinas confluence although this region is known as one of the most energetic zones of the world ocean very few studies have addressed the mechanisms of oa interaction there based upon novel direct in situ simultaneous oa observations our results show that the obl mabl exchanges are closely correlated with the sea surface temperature sst field the heat fluxes range from 110 w m 2 over warm waters down to 18 w m 2 over cold waters higher heat fluxes and air sea temperature differences are associated with stronger near surface winds this suggests that the mabl is modulated at the synoptic temporal and spatial scale by the strong surface thermal gradients between the warm brazil and the cold malvinas falklands currents