the miocene pliocene hiatus in the southern north sea basin northern belgium revealed by dinoflagellate cysts a palynological analysis with marine palynomorphs dinoflagellate cysts acritarchs green algae and terrestrial palynomorphs pollen and spores of the kasterlee and poederlee formations provides new insights in the depositional history at the southern border of the north sea basin northern belgium around the miocene pliocene transition dinoflagellate cyst stratigraphy constrains the age of the kasterlee formation in the oud turnhout borehole between 7 5 and 5 32 ma the upper boundary of the formation can be correlated with sequence boundary me2 at 5 73 ma of hardenbol and co workers which further constrains its age to the time interval 7 5 5 73 ma the palynomorph assemblages reflect a near coast depositional environment where present the kasterlee formation thus terminates the miocene series in northern belgium the overall shallow nature of the latest miocene deposits is related to a sea level lowering caused by the onset of globally cooling conditions for the first time palynology is applied to estimate the age of the poederlee formation suggesting it was deposited during the mid pliocene warm period dinoflagellate cysts and sequence stratigraphy together constrain the age of the unit between 3 21 and 2 76 ma and possibly even between 3 21 and 3 15 ma the poederlee formation was deposited in neritic environments which shoaled in the upper part of the unit as a consequence of the decreasing availability of accommodation space we demonstrate that the magnitude of the hiatus between the miocene and pliocene series varies strongly at the southern boundary of the north sea basin and lasts in the antwerp area c 3 2 million years and c 2 52 million years in the campine area

how porosity and permeability vary spatially with grain size sorting cement volume and mineral dissolution in fluvial triassic sandstones the value of geostatistics and local regression although it is well known that sandstone porosity and permeability are controlled by a range of parameters such as grain size and sorting amount type and location of diagenetic cements extent and type of compaction and the generation of intergranular and intragranular secondary porosity it is less constrained how these controlling parameters link up in rock volumes within and between beds and how they spatially interact to determine porosity and permeability to address these unknowns this study examined triassic fluvial sandstone outcrops from the uk using field logging probe permeametry of 200 points and sampling at 100 points on a gridded rock surface these field observations were supplemented by laser particle size analysis thin section point count analysis of primary and diagenetic mineralogy quantitative xrd mineral analysis and sem edax analysis of all 100 samples these data were analyzed using global regression variography kriging conditional simulation and geographically weighted regression to examine the spatial relationships between porosity and permeability and their potential controls the results of bivariate analysis global regression of the entire outcrop dataset indicate only a weak correlation between both permeability porosity and their diagenetic and depositional controls and provide very limited information on the role of primary textural structures such as grain size and sorting subdividing the dataset further by bedding unit revealed details of more local controls on porosity and permeability an alternative geostatistical approach combined with a local modeling technique geographically weighted regression gwr subsequently was used to examine the spatial variability of porosity and permeability and their controls the use of gwr does not require prior knowledge of divisions between bedding units but the results from gwr broadly concur with results of regression analysis by bedding unit and provide much greater clarity of how porosity and permeability and their controls vary laterally and vertically the close relationship between depositional lithofacies in each bed diagenesis permeability and porosity demonstrates that each influences the other and in turn how understanding of reservoir properties is enhanced by integration of paleoenvironmental reconstruction stratigraphy mineralogy and geostatistics

spatial characterization of the hydraulic conductivity using direct push injection logging 1 detailed information on the spatial structure of hydraulic conductivity k is important for understanding and predicting groundwater flow and transport direct push injection logging dpil is a promising technology for rapid measurement of k in unconsolidated formations this technology was used to gain information on the highly heterogeneous aquifer at the lauswiesen test site in germany using a large body of dpil and direct push slug testing measurements we characterize the structure of k on scales not previously possible two new applications of dpil are put forward 1 use of raw dpil measurements of relative conductivity kr to characterize the spatial distribution of k and 2 transformation of kr measurements to k values based on their statistical moments the dpil results are compatible to those obtained using more conventional methodologies the main achievement of the methodology is the possibility to delineate deterministic aquifer subunits as well as the identification of the statistical parameters of the log conductivity for each subunit in particular the horizontal integral scale i a parameter affecting solute transport is difficult and costly to identify using other approaches nevertheless further studies are needed to clarify questions on low kr measurements and the nature of the relationship between kr and k

tracer exchange between tropics and middle latitudes the interaction between the tropics and middle latitudes is studied using a tracer emitted at 50 hpa along a great circle route between los angeles usa and sydney australia though designed to examine the impact of stratospheric aircraft the study more generally addresses the transport between tropics and middle latitudes for a three month period from january through march 1989 the results show that air is transported from the tropics to middle latitudes by planetary scale and tropospheric cyclonic scale waves except for intrusions by these wave events the tropics are substantially isolated throughout the lower stratosphere these waves draw material out of the tropics which ends up in the middle latitude westerly jets with little material entering the winter polar latitudes prior to the springtime transition the summer southern hemisphere is characterized by tracer being drawn out in streamers that extend from north and west to south and east the material in the tropics is zonally asymmetric the material that reaches the troposphere comes down in the synoptic scale eddies and is concentrated in the middle latitude jet stream these characteristics are similar to those observed during the dispersion of volcanic clouds

geohydrological research in relation to radioactive waste disposal in an argillaceous formation abstract since 1974 the belgian nuclear research establishement sck cen at mol has been studying the suitability of the boom clay formation as a potential host formation for wastes arising from the belgian nuclear power production this paper presents the method developed to evaluate from the point of view of the regional hydrology the capacity of the boom clays for confining radioactive waste products this method consist of four successive steps 1 a reconnaissance of the geological and hydrogeological structure 2 the development of a numerical model to interpret the field observations 3 the construction of an appropriate migration model that uses the results obtained by the hydrodynamic model and finally 4 the simulation of the consequences of possible changes in the hydrogeological system due to natural geological evolution the analysis also stresses the role of confining layers in multilayered aquifer systems and the importance of leakage flow on a regional scale

on the use of cycle thickness diagrams as records of long term sealevel change during accumulation of carbonate sequences analysis of variation in changing rates of accommodation space creation as represented by stratigraphic thickness has become an integral part of ongoing investigations into the origin of ancient meter scale upward shoaling cyclic marine carbonates groupings of thicker than average and thinner than average cycles within long stratigraphic sections have been thought to represent the influence of long term eustatic sealevel variation on rates of accommodation space creation under conditions of constant basin subsidence statistical analysis demonstrates that a large percentage of early paleozoic cyclic carbonate sequences contain thickness distributions indistinguishable from those anticipated for random associations of cycles and that only a few have characteristics commensurate with long term changes in rate of accommodation space creation moreover in those cases where some extraneous control is suggested computational considerations readily demonstrate that change in subsidence rate and or diffe

frozen in anticyclones occurring in polar northern hemisphere during springtime characterization occurrence and link with quasi biennial oscillation during winter the polar vortex forms a dynamical barrier in the arctic stratosphere which prevents large scale exchanges between the high latitude and tropical regions nevertheless the occurrence of thin tropical air mass intrusions at the edge of the polar vortex have in fact been detected and modeled these structures could play an important role in improving our knowledge of the balance between chemical and dynamical processes associated with the ozone budget after the final stratospheric warming in springtime the breakdown of the polar vortex occurs and the summer circulation starts to develop air mass intrusions from the tropics can be trapped at polar latitudes and persist until august in the anticyclone advected by summer easterlies these structures named frozen in anticyclones friacs have already been observed in 2003 and 2005 by mipas envisat and mls aura tracer measurements we present here a new case of friac in 2007 highlighted using mls aura measurements in order to better understand the dynamical conditions required for such events and the associated processes we performed a climatology of tropical air mass intrusions using a potential vorticity contour advection model this climatology reveals a preferred path for exchanges between the polar and tropical stratospheres using era iterim wind and temperature reanalysis from ecmwf we have established links between friac occurrences and rossby wave activity there is evidence that friacs can exist if no major sudden stratospheric warming occurs during the polar vortex phase and their development seems favorable if the tropical quasi biennial oscillation is in the easterly phase

a high resolution one layer model of breaking planetary waves in the stratosphere numerical integrations of a one layer hemispheric model of the winter stratosphere have been carried out at very high resolution of the order of a fraction of a degree of latitude the numerical experiments simulate planetary wave breaking and polar vortex erosion under conditions far closer to the real winter stratosphere than those assumed in earlier critical layer models the model has implications for stratospheric photochemistry and the antarctic ozone hole problem

quasi biennial and semi annual oscillations in equatorial wind fields constructed by data assimilation since october 1991 the u k meteorological office has used the technique of data assimilation to produce global meteorological analyses of the troposphere and stratosphere these analyses are constructed from conventional meteorological measurements in the troposphere and lower stratosphere and temperature soundings from noaa polar orbiting satellites the analyses show very clear quasi biennial and semi annual oscillations in equatorial winds the quasi biennial oscillation has its maximum amplitude of about 20 ms 1 near 30 hpa and exhibits descending easterly and westerly shear zones analysed winds compare well with radiosonde observations in the lower stratosphere the semi annual oscillation has its peak amplitude of about 30 ms 1 near the stratopause winds near the equatorial stratopause show strong longitudinal variations on a planetary scale during both the westerly and easterly phases of the semi annual oscillation

air permeameter investigation of surficial dune structures in the nebraska sand hills a permeameter was designed and constructed and its theory of operation was developed it has a subsurface probe for internal permeability measurements in poorly consolidated sediments it was used to measure the permeability of sand at five depths in the upper 1 3 m 4 3 ft of structural features on a large vegetated composite crescentic dune in the nebraska sand hills permeability measurements were taken at 34 locations on the dune s steep leeward face its long windward slope fans below the leeward face blowouts peaks crests transverse ridges benches and the heads of gullies correlation of the permeabilities with the morphology of the dune is illustrated by a plot of the depth averaged permeabilities and dune profile along a transect perpendicular to the lee face some of the permeabilities do not match the values anticipated on the basis of the theory of sedimentation and experimental results for active crescentic dunes although the large scale features of the dune studied were evidently because of the original eolian sedimentation the permeability was found to be strongly influenced by dune degradation processes involving running water and animal activity

sage ii measurements of early pinatubo aerosols sage ii satellite measurements of the mt pinatubo eruption cloud in the stratosphere during june july and early august 1991 show that aerosols in the tropics reached as high as 29 km altitude with most of the cloud between 20 and 25 km the most optically thick portions of the cloud covered latitudes from 10 s to 30 n during the early part of this period by late july high stratospheric optical depths were observed to at least 70 n with the high values north of about 30 n from layers below 20 km high pressure systems in both hemispheres were observed to be correlated with the movement of volcanic material at 21 km into the westerly jet stream at high southern latitudes and similarly to high northern latitudes at 16 km by august the entire southern hemisphere had experienced a 10 fold increase in optical depth relative to early july due to layers above 20 km initial mass calculations using sage ii data place the aerosol produced from this eruption at 20 to 30 megatonnes well above the 12 megatonnes produced by el chichon

variability of sedimentary sequence numerical modeling of the deposition erosion process reinterpretation of field studies of bedload transport allowed some power law relations to be obtained between different quantities they were taken as a basis for the construction of a numerical model simulating bedload transport the deposition erosion process is presented as a sequence of individual events with intensities distributed according to a power law characteristic of the regime of self organized criticality the model output sedimentary cross sections with the model age of each of its elements is rich in features resulting from the non linearity of the underlying process analysis of the results of a series of numerical experiments provided an estimation of scale invariance of model sedimentary structures in space and time these data are tested against observed regularities of spaciotemporal variability of real sedimentary sequences good agreement of these data makes it possible to extrapolate the scaling relations obtained to larger scales

geological modeling of submeter scale heterogeneity and its influence on tracer transport in a fluvial aquifer 1 we developed a new model of aquifer heterogeneity to analyze data from a single well injection withdrawal tracer test conducted at the macrodispersion experiment made site on the columbus air force base in mississippi usa the physical heterogeneity model is a hybrid that combines 3 d lithofacies to represent submeter scale highly connected channels within a background matrix based on a correlated multivariate gaussian hydraulic conductivity field the modeled aquifer architecture is informed by a variety of field data including geologic core sampling geostatistical properties of this hybrid heterogeneity model are consistent with the statistics of the hydraulic conductivity data set based on extensive borehole flowmeter testing at the made site the representation of detailed small scale geologic heterogeneity allows for explicit simulation of local preferential flow and slow advection processes that explain the complex tracer response from the injection withdrawal test based on the new heterogeneity model advective dispersive transport reproduces key characteristics of the observed tracer recovery curve including a delayed concentration peak and a low concentration tail importantly our results suggest that intrafacies heterogeneity is responsible for local scale mass transfer

simulations of fall and early winter in the stratosphere mechanistic model simulations of fall early winter in the northern november and december and southern may and june stratosphere are compared with observational analyses to examine the skill of the model in simulating the state of the stratosphere including both means and variability in key fields during six winters while detailed success varies from year to year the model produces a realistic climatology of and variability in the evolution of winds geopotential heights temperatures and wave propagation in the early winter stratosphere the variability and mean fields agree well with those in longer data records the northern hemisphere nh simulations show a small cold bias when averaged over the 6 years while the southern hemisphere sh simulations show a larger warm bias greater detailed success in simulations of alternate nh winters suggests the possibility of greater model skill during the westerly quasi biennial oscillation phase although the short record and complexity of interactions between tropics and high latitudes preclude definitive identification of such a relationship a prominent failing of the model when using rayleigh friction to parametrize gravity wave drag is an inability to correctly reproduce the latitudinal structure of the stratospheric jet above about 7 hpa this failing can be alleviated by using a non orographic gravity wave drag parametrization at the expense of frequently degrading agreement of planetary wave phases and amplitudes the success of the model in reproducing realistic climatology and variability makes these simulations useful for more detailed studies of transport and vortex evolution in early winter interhemispheric comparisons show that the early winter circulations are qualitatively similar in the nh and sh they are dominated by a strengthening vortex with most wave activity being in wave 1 they both have minor warmings in a preferred location and clustered around a preferred time early december early june in the nh sh variability in the flow shows a crescent pattern of maximum variations near 60 80 latitude centred at the location of the minor warmings over the dateline in the nh and in the south pacific in the sh interhemispheric differences are primarily in the magnitude of the variability with a more symmetric circulation and weaker minor warmings in the sh this is in contrast to later in the winter when large qualitative interhemispheric differences have been seen copyright 2002 royal meteorological society

landscape evolution and changes in soil hydraulic properties at the decadal centennial and millennial scale a case study from the campine area northern belgium abstract soil hydraulic properties evolve over time as a result of soil formation processes we investigated the rate and circumstances of change in soil hydraulic properties as a result of soil and landscape evolution that took place over a period of a few decades to several thousands of years to this end a sediment soil sequence in which different sandy landscapes and associated soils are preserved was studied with respect to its geomorphological and pedohydrological characteristics three stages of soil development corresponding to specific landscapes were observed within a 2 m deep profile 1 a stabilisation surface within an active drift sand landscape 2 an a horizon that developed on a stabilised drift sand landscape and 3 a pronounced podzol that developed in a stabilised landscape from the last glacial measurement of soil physical properties was conducted including grain size analysis organic carbon content soil water retention characteristic and hydraulic conductivity using constant head and air permeability analyses age control of soil horizons and vegetation history were obtained from optically stimulated luminescence osl dating radiocarbon 14c dating pollen analysis and historical archives the results suggest a strong relationship between landscape evolution soil development and hydraulic properties small changes in hydraulic properties may already be observed on a decadal and centennial scale while long term podzolisation processes may decrease the hydraulic conductivity of parent material up to three orders of magnitude in several thousands of years it is concluded that combination of geomorphological and pedohydrological analyses of sediment soil archives may provide a unique means to gain insight into the rate and extent of past changes in soil hydraulic properties and the consequences of future hydrological changes as a result of these evolving properties

a new chemical lagrangian model of the stratosphere clams 1 formulation of advection and mixing 1 recent satellite observations and dynamical studies have demonstrated the existence of filamentary structures in chemical tracer fields in the stratosphere it is also evident that such features are often below the spatial resolution of the highest resolution eulerian models that have been used up to the present time these observations have motivated the development of a novel chemical lagranigan model of the stratosphere clams that is based on a lagrangian transport of tracers the description of clams is divided into two parts part 1 this paper concentrates on the lagrangian dynamics i e on the calculation of trajectories and on a completely new mixing algorithm based on a dynamically adaptive grid while part 2 describes the chemical integration and initialization procedure the mixing of different air masses in clams is driven by the large scale horizontal flow deformation and takes into account the mass exchange between the nearest neighbors determined by delaunay triangulation here we formulate an isentropic i e two dimensional version of the model and verify the mixing algorithm using tracer distributions measured during the space shuttle crista 1 experiment where highly resolved stratospheric structures were observed in early november 1994 a comparison of the measured southern hemispheric n2o distribution with clams results allows the intensity of simulated mixing to be optimized the long term robustness of the transport scheme is investigated in a case study of the 1996 1997 northern hemisphere polar vortex this study further provides a dynamical framework for investigations of chemical arctic ozone destruction discussed in part 2

the evaluation of winds from geopotential height data in the stratosphere abstract several methods of obtaining horizontal wind fields in the extratropical stratosphere from geopotential height data are evaluated and compared to geostrophic estimates with focus on the poleward fluxes of momentum and heat and on the resulting eliassen palm ep flux divergence estimates winds derived from a coupled iterative solution of the zonal and meridional momentum equations balance winds are proposed and tested in addition to winds derived from linearizing these equations about the zonal mean flow linen winds comparison of the different analysis methods are made for a general circulation model simulation of the northern hemisphere nh winter stratosphere and for nh and southern hemisphere sh winter observational data the balance and linear wind estimates of poleward momentum flux are similar and substantially smaller than geostrophic values in the high latitude stratosphere neglect of local curvature effects is the primary cause of the geostrophic overestimate the relati

possible evidence for underlying non linear dynamics in steep faced glaciodeltaic progradational successions steep faced glaciodeltaic progradational successions are often studied in order to reconstruct the behaviour of the glacial feeder system or changes in the sediment sink this paper analyses the magnitude and frequency of depositional events associated with steep faced glacier fed progradational successions recorded in scandinavia and ireland the successions exhibit depositional patterns that may be interpreted as a function of underlying non linear dynamics a number of the sequences display fractal scaling in the frequency and thickness of foreset units other successions demonstrate chaotic patterns and strong relationships between delta front angle and bed thicknesses suggesting that the progradation of such sequences is self organized and to an extent occurs independently of forcing by the feeder system that provides sediment to the delta front these patterns of sedimentation appear to be a function of the steepness of the delta front and or the textural characteristics of the sediment this paper provides further evidence for the simultaneous presence of order and chaos in earth surface processes and calls into question the extent to which palaeoenvironmental reconstructions may be made from steep faced progradational successions copyright 2000 john wiley sons ltd

modeling the quasi biennial oscillation s effect on the winter stratospheric circulation abstract the influence of the equatorial quasi biennial oscillation qbo on the winter middle atmosphere is modeled with a mechanistic global primitive equation model the model s polar vortex evolution is sensitive to the lower stratosphere s tropical winds with the polar vortex becoming more less disturbed as the lower stratospheric winds are more easterly westerly this agrees with the observed relationship between wintertime polar circulation strength and the phase of the qbo in the lower stratosphere in these experiments it is the extratropical planetary rossby waves that provide the tropical extratropical coupling mechanism more easterly tropical winds in the lower stratosphere act to confine the extratropical rossby waves farther north and closer to the vortex at the qbo altitudes weakening the vortex relative to the case of westerly qbo phase while the qbo winds occur in the lower stratosphere the anomaly in the polar vortex strength is strongest at higher levels

quantitative diagnostics of mixing in a shallow water model of the stratosphere two different approaches are applied to quantify mixing in a shallow water model of the stratosphere these are modified lagrangian mean mlm theory and a technique referred to as reverse domain filling with local gradient reversal rdf lgr the latter is similar to a previously existing technique using contour advection and contour surgery it is first proved that in an inviscid shallow water atmosphere subject to mass sources and sinks if the mass enclosed by a potential vorticity pv contour is steady in time then the integral of the mass source over the area enclosed by the contour must be zero next the mlm and rdf lgr approaches are used to diagnose the time averaged transport across pv contours in the model simulations the model includes a sixth order hyperdiffusion on the vorticity field except in a thin outer entrainment zone the hyperdiffusion term has only a very weak effect on the mlm mass budget of the polar vortex in the entrainment zone the hyperdiffusion term has a significant effect the rdf lgr results capture this behavior providing good quantitative estimates of the hyperdiffusion term which is equivalent to the degree of radiative disequilibrium at a pv contour this agreement shows that the main role of the hyperdiffusion is to mop up the filaments that are produced by the essentially inviscid large scale dynamics all calculations are repeated for two values of the hyperdiffusion coefficient that differ by a factor of 50 with little difference in the results this suggests that the amount of material entrained from the vortex edge into the surf zone does not depend on the details of the small scale dissipation as long as it is sufficiently weak and has some degree of scale selectivity

stratospheric transport by planetary wave mixing as observed during crista 2 1 planetary waves drive the mean meridional circulation of the stratosphere and at the same time facilitate quasi horizontal mixing of trace gases this paper presents significant day to day variability of stratospheric trace gas fields associated with large planetary wave activity observed during the second mission of the cryogenic infrared spectrometers and telescopes for the atmosphere crista experiment geopotential height data of the uk met office show that the crista 2 observations in the southern hemisphere winter were made during a period of extremely large amplitudes of both wave 1 and wave 2 the planetary wave 1 usually a quasi stationary feature moved eastward with the traveling planetary wave 2 the large amplitudes of both wave 1 and wave 2 led to a significant displacement of the edge of the polar vortex toward the tropics down to 30 s as a result of the large wave amplitudes and favorable phase alignment the anticyclone drawing up tropical air was unusually strong and thus considerable wave induced trace gas flux from the tropics toward midlatitudes was observed mainly in the form of a pronounced planetary scale tongue advected out of the tropics around the vortex and into the anticyclone quantitative transport calculations based on a sequential data assimilation system highlight the importance of such transport events for trace gas eddy flux in the southern hemisphere winter stratosphere

upper stratospheric circulations in the two hemispheres observed by satellites a global analysis is made of upper stratospheric circulations with the aid of nimbus 5 and tiros n satellite observations in order to make a comparison of characteristics between the northern hemisphere nh and the southern hemisphere sh it is shown that the reversal of north south gradient of the zonal mean temperature at the stratopause level is always observed in higher latitudes of the sh winter while the temperature gradient of the nh winter is variable because of the occurrence of sudden warmings consequently due to the thermal wind relation the polar night westerlies of the sh stratosphere are generally stronger than those of the nh stratosphere in association with this difference the activity of transient planetary waves of wavenumber 2 is striking in the sh in contrast to the predominance of steady waves in the nh finally the interrelation between the zonal mean field and planetary waves in the upper stratosphere is briefly discussed

small scale diagenetic facies heterogeneity controls porosity and permeability pattern in reservoir sandstones the fluvial aeolian upper rotliegend sandstones from the bebertal outcrop flechtingen high germany are the famous reservoir analog for the deeply buried upper rotliegend gas reservoirs of the southern permian basin while most diagenetic and reservoir quality investigations are conducted on a meter scale there is an emerging consensus that significant reservoir heterogeneity is inherited from diagenetic complexity at smaller scales in this study we utilize information about diagenetic products and processes at the pore and plug scale and analyze their impact on the heterogeneity of porosity permeability and cement patterns eodiagenetic poikilitic calcite cements illite iron oxide grain coatings and the amount of infiltrated clay are responsible for mm to cm scale reservoir heterogeneities in the parchim formation of the upper rotliegend sandstones using the petrel e p software platform spatial fluctuations and spatial variations of permeability porosity and calcite cements are modeled and compared offering opportunities for predicting small scale reservoir rock properties based on diagenetic constraints

the gradient genesis of stratospheric trace species in the subtropics and around the polar vortex abstract mechanisms that control the formation and decay of meridional gradients in stratospheric trace species in the subtropics and around the polar vortex are investigated using a gradient genesis equation that uses mass weighted isentropic zonal means application of this method to global nitrous oxide n2o data output from a global chemical transport model shows that mean vertical transport increases the meridional tracer gradient from the subtropics to midlatitudes through the shearing deformation particularly related to overturning of the brewer dobson circulation mean meridional transport advects the subtropical tracer gradient toward midlatitudes while the eddy stairstep effect steepening at the edge of the well mixed region because of a meridional gradient in the diffusion coefficient increases the tracer gradient in the subtropics and around the polar vortex mechanisms controlling the evolution of the tracer gradients in the subtropics differ between spring and autumn the autumnal subtr

a comparative study of three dimensional hydraulic conductivity upscaling at the macro dispersion experiment made site columbus air force base mississippi usa simple averaging simple laplacian laplacian with skin and non uniform coarsening are the techniques investigated in this comparative study of three dimensional hydraulic conductivity upscaling the reference is a fine scale conditional realization of the hydraulic conductivities at the macro dispersion experiment site on columbus air force base in mississippi usa this realization was generated using a hole effect variogram model and it was shown that flow and transport modeling in this realization at this scale can reproduce the observed non fickian spreading of the tritium plume the purpose of this work is twofold first to compare the effectiveness of different upscaling techniques in yielding upscaled models able to reproduce the observed transport behavior and second to demonstrate and analyze the conditions under which flow upscaling can provide a coarse model in which the standard advection dispersion equation can be used to model transport in seemingly non fickian scenarios specifically the use of laplacian based upscaling technique coupled with a non uniform coarsening scheme yields the best results both in terms of flow and transport reproduction for this case study in which the coarse blocks are smaller than the correlation ranges of the fine scale conductivities

fine scale study of a thick stratospheric ozone lamina at the edge of the southern subtropical barrier a large scale transport event resulting in a thick ozone lamina originating from midlatitudes is observed in the tropical stratosphere over reunion island 55 e 21 s this isentropic transport was detected from stratospheric balloon borne ozone measurements that showed the occurrence of the lamina and was investigated using different tools based on ertel s potential vorticity epv analyses an original software dybal using surface coordinate and the equivalent length of epv contours as diagnostic tools in conjunction with high resolution outputs from an epv advection model mimosa allows us to specify the origin of the lamina the results indicate that a broad layer of stratospheric air was isentropically advected from midlatitudes across the southern edge of tropical reservoir and reached reunion island on 12 july 2000 in addition eliassen palm s flux vectors calculated from ecmwf analysis show that planetary wave activity was quite large during that time period with wave breaking occurring around 30 km and could have driven that exchange in contrast with analyses of filamentation events based on model and satellite data the present study focuses on a fine scale vertical survey from in situ measurements the filament reported in this paper is characterized by a large vertical extension and is located around the maximum of ozone concentration in the tropical stratosphere 600 k the analysis of such events poorly documented in the tropics could complement satellite studies and contribute to a better determination of the transport between the tropics and the midlatitudes

on the subtropical edge of the stratospheric surf zone abstract the formation of a subtropical transport barrier in the wintertime stratosphere is investigated in the context of a high resolution shallow water model in which rossby waves are topographically forced on a zonally symmetric basic state two sets of experiments are performed in the first adiabatic set no dissipation or forcing of the mean state is imposed in the second set the layer thickness is relaxed to an equilibrium state taken to be representative of middle stratospheric radiative equilibrium temperatures it is found that in the adiabatic case only a very weak subtropical barrier forms for forcing amplitudes that generate realistically steep potential vorticity gradients at the edge of the polar vortex the vigorous wave breaking in the surf zone generates secondary waves that spread and in turn break well into the summer hemisphere in contrast the inclusion of relaxation to a realistic thermal equilibrium leads to the formation of a subtropical region of steep pv gradients the

evolution of the stratospheric aerosol in the northern hemisphere following the june 1991 volcanic eruption of mount pinatubo role of tropospheric stratospheric exchange and transport since the eruption of mount pinatubo in june 1991 measurements of particle size and concentration have intermittently been carried out from an er 2 aircraft at altitudes of up to 21 km at midlatitudes and high latitudes in the northern hemisphere they show the evolution and purge of the volcanic aerosol to be due to an interaction of aerosol mechanics with tropospheric stratospheric exchange processes transport and mixing during the first 5 months after the eruption the volcanic plume spread to higher latitudes in laminae and filaments producing steep spatial gradients in the properties of the stratospheric aerosol at the same time the concentration of newly formed particles in the plume rapidly decreased toward background values as a result of coagulation while particle size and aerosol surface area continued to increase by december 1991 the particle number mixing ratios and aerosol surface area mixing ratios had become spatially uniform over a wide range of latitudes above 18 km the surface area mixing ratios peaked in this region of the stratosphere at 35 times their background values in the winter of 1992 the corresponding condensed mass mixing ratio enhancement was by a factor of 200 after the winter of 1992 a gradual removal of the volcanic mass began and initially was dominated by sedimentation above 18 km the aerosol surface area mixing ratio thus decreased by an order of magnitude over 2 5 years and the aerosol volume or condensed mass mixing ratio decayed by an order of magnitude over approximately 1 7 years below 18 km the purging of the pinatubo aerosol at mid latitudes appeared sporadic and disorderly and was strongly influenced by episodal rapid quasi isentropic transport and dilution by tropical air of tropospheric origin having high condensation nuclei mixing ratios but low mixing ratios of aerosol surface area or condensed mass compared to the volcanic aerosol

combining geologic process models and geostatistics for conditional simulation of 3 d subsurface heterogeneity 1 the goal of simulation of aquifer heterogeneity is to produce a spatial model of the subsurface that represents a system such that it can be used to understand or predict flow and transport processes spatial simulation requires incorporation of data and geologic knowledge as well as representation of uncertainty classical geostatistical techniques allow for the conditioning of data and uncertainty assessment but models often lack geologic realism simulation of physical geologic processes of sedimentary deposition and erosion process based modeling produces detailed geologically realistic models but conditioning to local data is limited at best we present an aquifer modeling methodology that combines geologic process models with object based multiple point and variogram based geostatistics to produce geologically realistic realizations that incorporate geostatistical uncertainty and can be conditioned to data first the geologic features of grain size or facies distributions simulated by a process based model are analyzed and the statistics of feature geometry are extracted second the statistics are used to generate multiple realizations of reduced dimensional features using an object based technique third these realizations are used as multiple alternative training images in multiple point geostatistical simulation a step that can incorporate local data last a variogram based geostatistical technique is used to produce conditioned maps of depositional thickness and erosion successive realizations of individual strata are generated in depositional order each dependent on previously simulated geometry and stacked to produce a fully conditioned three dimensional facies model that mimics the architecture of the process based model we demonstrate the approach for a typical subsea depositional complex

midlatitude and high latitude n2o distributions in the northern hemisphere in early and late arctic polar vortex breakup years 1 simulated n2o distributions at midlatitudes and high latitudes in the northern hemisphere are analyzed in early and late vortex breakup years with the probability distribution function pdf technique the data are from a center for climate system research national institute for environmental studies ccsr nies nudging chemical transport model ctm for 24 years from 1979 to 2002 results show that there is a large difference in midlatitude and high latitude n2o concentrations on the 600 k isentrope between early and late vortex breakup years in the early breakup years the n2o concentration with the maximum area shows low values in the lower stratosphere in the springtime after the vortex breakup in the late breakup years the maximum area concentration shows constant high values from the winter to the summer our analyses show that the winter and springtime meridional circulation is a main factor for these differences in n2o concentration in the early breakup years a larger eddy heat flux causes a stronger winter meridional circulation and a stronger downward advection of low n2o concentration air at higher altitudes to the lower stratosphere which leads to the low values of n2o concentration in the lower stratosphere in late winter and early spring inside the arctic vortex however the importance of vertical advection is smaller than or comparable to other processes such as horizontal divergence and subgrid scale motions these results are consistent with the previous studies on tracer distribution which showed that not only the vertical advection but also the horizontal eddy transport are important for tracer concentration tendency in the polar vortex

synoptic scale study of the arctic polar vortex s influence on the middle atmosphere 1 observations 1 we present nightly rayleigh lidar temperature measurements of the high latitude middle atmosphere taken at three arctic sites over similar time periods in midwinter the four reported case studies depict changes in the thermal structure of the stratosphere and lower mesosphere over a period of days to weeks that can be attributed to movement and interaction of the polar vortex the aleutian high and planetary waves as evidenced from the national center for environmental prediction tropospheric and stratospheric analyses in cases where substantial i e large horizontal scale movement of the vortex is observed it is noted that regional middle atmospheric arctic temperatures can change by tens of degrees in other cases we show that even very subtle i e small horizontal scale movement of the vortex system over similar timescales can result in notable temperature changes in the regional middle atmosphere it appears that the observed events are dependant on the location strength and structure of the polar vortex and aleutian high all of these synoptic scale measurements indicate a change in the local dynamical structure of the middle atmosphere and are discussed in regards to this issue

a fractal model for the distribution of stratigraphic hiatuses several recent studies have suggested that there is a negative log linear relationship between sedimentation rates and the time span over which they are measured i e measured sedimentation rates are slow when measured over long time spans and rapid when measured over short time spans this relationship may be due to the inclusion of more and longer hiatuses over long time spans this paper proposes a mathematical model consistent with this relationship that is based upon the fractal cantor bar this model allows the estimation of the relative number and durations of stratigraphic hiatuses within a given section

trace gas transport in the arctic vortex inferred from atmos atlas 2 observations during april 1993 measurements of the long lived tracers ch4 n2o and hf from the atmospheric trace molecule spectroscopy atmos instrument during the atmospheric laboratory for science and applications 2 atlas 2 space shuttle mission in april 1993 are used to infer average winter descent rates ranging from 0 8 km month at 20 km to 3 2 km month at 40 km in the arctic polar vortex during the 1992 93 winter descent rates in the mid stratosphere are similar to those deduced for the antarctic vortex using atmos atlas 3 measurements in november 1994 but the shorter time period of descent in the arctic leads to smaller total distances of descent strong horizontal gradients observed along the vortex edge indicate that the arctic vortex remains a significant barrier to transport at least until mid april in the lower to middle stratosphere

field evaluation of methods for determining hydraulic conductivity from grain size data summary determination of hydraulic conductivity k and its variation in space is often a major objective of hydrogeological site investigations however measurement of k at a high spatial resolution in sedimentary aquifers is a challenge there are a number of field methods that can be used to determine k although they differ greatly in terms of their spatial resolution one commonly used approach is to estimate k from grain size analyses but the reliability of the resulting k estimates is unclear the aims of this study are to compare frequently used formulas for the determination of k from grain size data for a broad range of sediment types and to evaluate how well these methods predict k sonic sampling was used to obtain minimally disturbed cores in a highly heterogeneous sedimentary aquifer and k values of grain size analyses from 108 core samples were calculated despite the high correlation of calculated k derived from different formulas mean k values differed by several orders of magnitude between the formulas for the evaluation of the reliability of the k estimates high resolution direct push slug tests dpsts were also performed in the close vicinity of the cores a high correlation between ln k dpst and ln k grain size was found for most of the applied formulas nevertheless sample heterogeneity i e the presence of small clay layers in a generally highly permeable sample led to k grain size estimates that were significantly smaller than the k dpst estimates based on these results the applied formulas appear to be suitable for an initial assessment of aquifer k however considering the difference in calculated k mean values results are not sufficiently reliable for the high resolution analyses of k variations needed for flow or transport modeling

zonal jets as transport barriers in planetary atmospheres abstract the connection between transport barriers and potential vorticity pv barriers in pv conserving flows is investigated with a focus on zonal jets in planetary atmospheres a perturbed pv staircase model is used to illustrate important concepts this flow consists of a sequence of narrow eastward and broad westward zonal jets with a staircase pv structure the pv steps are at the latitudes of the cores of the eastward jets numerically simulated solutions to the quasigeostrophic pv conservation equation in a perturbed pv staircase flow are presented these simulations reveal that both eastward and westward zonal jets serve as robust meridional transport barriers the surprise is that westward jets across which the background pv gradient vanishes serve as robust transport barriers a theoretical explanation of the underlying barrier mechanism is provided it is argued that transport barriers near the cores of westward zonal jets across which the background pv gradient is small are found in jupi

tropical mixing barriers in the lower stratosphere in the geophysical fluid dynamics laboratory skyhi model large scale isentropic mixing in the tropical lower stratosphere is investigated by computing lagrangian trajectories using winds from the geophysical fluid dynamics laboratory skyhi general circulation model the use of model simulated winds avoids some problems with analyzed winds in the tropics during the solstitial seasons a weak mixing zone is present in the tropics in the model simulations the weak mixing zone is relatively isolated from the midlatitude surf zones in the northern and southern hemispheres by two mixing barriers a strong one on the summer hemisphere side and a weak one on the winter side the mixing barriers vary seasonally in response to seasonal variations of the tropical zonal mean zonal flow and wave spectrum the roles of the zonal mean flow and of different parts of the wave spectrum in meridional transport are tested using filter techniques effective meridional diffusion coefficients are calculated by using filtered and antifiltered winds i e winds with selected spatial scales either attenuated or amplified the results suggest that mixing in the tropical easterlies occurs near the critical layers for the large scale zonal wavenumber 10 westward moving waves which is where the waves would be expected to break wave spectrum analysis indicates that during the solstitial seasons there is a zone in the tropics exactly matching the weak mixing zone where there is relatively little power in westward moving waves the tropical mixing barriers are a result of the relative lack of such waves

an update on dynamical changes in the arctic and antarctic stratospheric polar vortices dynamical changes in the arctic and antarctic lower stratosphere from autumn to spring were analysed using the ncep ncar era40 and fub stratospheric analyses for three periods 1979 1999 1979 2005 and 1965 2005 we found a weakening of the arctic vortex in winter and a strengthening in spring between 1979 1980 and 1998 1999 with corresponding changes in the zonal mean circulation the vortex formed earlier in autumn and broke down later in spring these changes however were statistically not significant due to the high interannual dynamical variability in northern hemisphere nh winter and spring and the relatively short time series in the antarctic the vortex formed earlier in autumn intensified in late spring and broke down later the changes of the antarctic vortex were at all levels and for both autumn and spring transitions larger and more significant than the changes of the arctic vortex these changes of the 1980s and early to mid 1990s were however not representative of a long term change the dynamically more active winters in the arctic and antarctic since 1998 1999 led to an enhanced weakening of the polar vortex in winter and to a reduction of the polar vortex intensification in spring as two of the recent arctic major warmings occurred rather early in winter the polar vortex could recover in late winter and the delay in spring breakdown further increased in contrast the increase in antarctic vortex persistence did no longer appear when including the recent winters due to the dominant impact of the three recent dynamically active antarctic winters in 2000 2002 and 2004 the long term changes of 1965 1966 2005 were smaller in amplitude and partly opposite to the trends since the 1980s there is no significant long term change in the arctic vortex lifetime or spring persistence while the antarctic vortex shows a long term deepening and shift towards later spring transitions the changes in the stratospheric dynamical situation could be attributed in both hemispheres to changes in the dynamical forcing from the troposphere

laminae in the tropical middle stratosphere origin and age estimation in situ measurements of n 2 o and o 3 aboard the observations from the middle stratosphere oms balloon payload in the tropics are presented in november 1997 at 7 s very distinct laminated structures in the n 2 o profile were observed in contrast to earlier studies based solely on o 3 profiles the laminae probably are an observation of rossby wave breaking events that lead to transport of mid latitude air into the tropics using a photochemical model of the ozone response within those air parcels their residence time in the tropics is estimated to be 4 to 6 weeks in february 1997 at 7 s a similar vertical profile of n 2 o revealed no mid latitude laminae we present dynamical arguments to support the existence of such laminae in november but not in february

the seasonal evolution of planetary waves in the southern hemisphere stratosphere and troposphere seasonality in planetary wave structure in the southern hemisphere stratosphere and troposphere 1000 1 mb is studied based on eight years 1979 1986 of daily geopotential data emphasis is placed on the distinctive seasonality in the stratosphere along with tracing the stratospheric fluctuations into the troposphere time filtering is used to separate stationary and transient components maximum geopotential height variance is observed in the middle to upper stratosphere in late winter spring with a distinct secondary smaller maximum in late fall early winter these maxima sandwich the strongest mid winter zonal winds this sequence occurs approximately one month earlier in the upper stratosphere two corresponding peaks are observed in stratospheric zonal mean wind and temperature fluctuations the two maxima in stratospheric wave variance are not in agreement with observed seasonal changes in quasi geostrophic refractive index of the zonal mean flow the stratospheric geopotential variance maxima result from nearly equal amounts of stationary and transient zonal wave 1 fluctuations with transient wave 2 also contributing during late winter stationary wave 1 shows intriguing seasonal evolution the early winter maximum is predominantly equivalent barotropic whereas that of late winter spring is highly baroclinic in the stratosphere stratospheric poleward fluxes of heat and momentum both exhibit pronounced maxima during september october these result primarily from the stationary wave 1 contributions and the transients assume a secondary role although not as pronounced as the stationary wave seasonality seasonal differences in transient wave behaviour are also documented including three dimensional propagation characteristics and wave mean flow interaction diagnostics

on the interaction of geology measurement and statistical analysis of small scale permeability measurements sedimentary rocks exhibit small scale mm permeability variations which can be detected with a probe permeameter the structure of the laminations may provide evidence about the characteristics of the measurement device the statistical interpretation of these measurements using averages and variograms is enhanced when the geological character of the rock is taken into consideration the three aspects of rock characterization namely geology measurement and statistical analysis are best assessed in concert this theme is illustrated using probe data taken from sections of the rannoch and etive formations northern north sea

on the origin of polar vortex air forward and backward three dimensional stratospheric polar vortex trajectory computations between fall and spring for each of the years 1992 1993 through 1999 2000 in the northern hemisphere and the years 1992 1999 in the southern hemisphere have been carried out we find that the forward and backward trajectories give very different pictures of polar vortex descent the backward trajectories show a complex distribution of parcels in which one population originates in the upper stratosphere and mesosphere and experiences considerable descent in the polar regions while the remaining parcels originate at lower altitudes of the middle and lower stratosphere and are mixed into the polar regions during vortex formation the forward trajectory calculations do not show this second population since the parcels in the forward calculation originate within the protovortex the amount of descent experienced by the first population shows little variability from year to year while the computed descent and mixing of the remaining parcels show considerable interannual variability due to the varying polar meteorology spring methane values reconstructed from halogen occultation experiment haloe fall data and the back trajectories compare fairly well with typical haloe spring values these results imply that using a comparison between prewinter and postwinter tracer profiles to estimate the amount of descent over the fall to spring time period might result in unrealistically large values of descent since the fall profiles are not representative of the same air as the spring profiles additional back trajectory calculations of descent in the lower stratosphere over 3 month time periods from spring to midwinter show that very little mixing occurs at these times and altitudes in the northern hemisphere during winters when the vortex is undisturbed and in the southern hemisphere for all years studied thus for this shorter time period tracking constant mixing ratios of tracers within the vortex should give reasonable estimates of descent amounts except for years when there are meteorological disturbances in the northern hemisphere

meteorology of the polar vortex spring 1997 the 1996 1997 northern hemisphere spring polar vortex was very strong cold and symmetric somewhat similar to those found in the antarctic spring vortex the vortex did not form until late in december and was very symmetric from february into late april the spring vortex was characterized by record low temperatures record low ozone amounts as measured from the total ozone mapping spectrometer toms instruments and a wide band of strong winds in the lower stratosphere spring wave activity was greatly reduced with 100 hpa february march eddy heat fluxes that were lower by a factor of 2 from any previously observed values over the last 18 years

relevance of mountain wave cooling for the formation of polar stratospheric clouds over scandinavia mesoscale dynamics and observations for january 1997 the effect of mesoscale mountain wave induced temperature anomalies on the formation potential of polar stratospheric clouds above northern scandinavia is analyzed with a one month mesoscale model integration the simulation results are contrasted with synoptic scale analyses and compared with remote sensing and in situ observations the mesoscale mass flux of air parcels with temperatures below the threshold for cloud formation through a control volume is compared with its synoptic scale counterpart a classification of the synoptic scale flow into periods of large and small mountain wave activity in the stratosphere is proposed the derived classification will be used for a climatology of stratospheric mountain wave activity above scandinavia

aquifer structure identification using stochastic inversion this study presents a stochastic inverse method for aquifer structure identification using sparse geophysical and hydraulic response data the method is based on updating structure parameters from a transition probability model to iteratively modify the aquifer structure and parameter zonation the method is extended to the adaptive parameterization of facies hydraulic parameters by including these parameters as optimization variables the stochastic nature of the statistical structure parameters leads to nonconvex objective functions a multi method genetically adaptive evolutionary approach amalgam so was selected to perform the inversion given its search capabilities results are obtained as a probabilistic assessment of facies distribution based on indicator cokriging simulation of the optimized structural parameters the method is illustrated by estimating the structure and facies hydraulic parameters of a synthetic example with a transient hydraulic response

ground based observations of arctic o3 loss during spring and summer 1997 ground based solar absorption spectra were measured from fairbanks alaska 65 n 148 w from march to september 1997 by the jet propulsion laboratory jpl mkiv fourier transform infrared ftir spectrometer the derived column abundances of 03 declined by 35 over this period 20 in april and may and 15 during the summer whereas those of hf a long lived tracer changed by less than 5 high latitude summertime balloon observations reveal similar shapes for the volume mixing ratio profiles of o 3 and hf in the lower stratosphere where most of their column abundance resides vertical transport should therefore have similar effects on the column abundances of o 3 and hf data from the halogen occultation experiment haloe show a poleward decrease in the o 3 hf ratio at all stratospheric altitudes so that any reductions in column o 3 due to horizontal meridional transport would have been accompanied by even larger reductions in column hf therefore the observed column o 3 decrease must be the result of chemical loss processes column measurements of other atmospheric gases show a summertime maximum in the no x no y column ratio and little change in the chlorine partitioning we conclude that most of the reduction in column o 3 over fairbanks from march to september 1997 was likely driven by no x chemistry these conclusions are supported by the similar behavior of column abundances measured by another ground based ftir spectrometer based in ny alesund spitsbergen 79 n 12 e

atmos atlas 3 observations of long lived tracers and descent in the antarctic vortex in november 1994 observations of the long lived tracers n2o ch4 and hf obtained by the atmospheric trace molecule spectroscopy atmos instrument in early november 1994 are used to estimate average descent rates during winter in the antarctic polar vortex of 0 5 to 1 5 km month in the lower stratosphere and 2 5 to 3 5 km month in the middle and upper stratosphere descent rates inferred from atmos tracer observations agree well with theoretical estimates obtained using radiative heating calculations air of mesospheric origin n2o 5 ppbv was observed at altitudes above about 25 km within the vortex strong horizontal gradients of tracer mixing ratios the presence of mesospheric air in the vortex in early spring and the variation with altitude of inferred descent rates indicate that the antarctic vortex is highly isolated from midlatitudes throughout the winter from approximately 20 km to the stratopause the 1994 antarctic vortex remained well isolated between 20 and 30 km through at least mid november

subtropical stratospheric mixing linked to disturbances in the polar vortices randel et al 1 have observed tongues of stratospheric air stretching from the tropics into middle latitudes and conclude that such events may be responsible for transporting significant amounts of stratospheric air across the tropical mid latitude barrier2 here i examine the movements of air parcels during these events using high resolution contour trajectory calculations my calculations suggest that the tongues of tropical air are associated with disturbances of the stratospheric polar vortices the edge of the disturbed polar vortex reaches low latitudes and draws a long tongue of tropical air around the vortex into middle latitudes this process occurs in the winter of both hemispheres although the edge of the larger antarctic polar vortex reaches farther toward the equator and draws up material from lower latitudes than its arctic counterpart

development of the polar vortex in the 1999 2000 arctic winter stratosphere the 1999 2000 arctic stratospheric vortex was unusually cold especially in the early winter lower stratosphere with a larger area near polar stratospheric cloud formation temperatures in dec and jan and much lower temperatures averaged over nov jan than any previously observed arctic winter in nov and early dec there was a double jet in the upper stratosphere with the anticyclone cutoff in a region of cyclonic material by late dec there was a discontinuous vortex large in the upper stratosphere small in the lower stratosphere evolving to a strong continuous relatively upright vortex by mid jan this vortex evolution in 1999 2000 is typical of that in other cold early winters despite unusually low temperatures the lower stratospheric vortex developed more slowly than in previous unusually cold early winters and was weaker than average until late dec

estimation of completeness of stratigraphical sections using empirical data and theoretical models the completeness of a stratigraphical section is the fraction of time intervals of some specified length t that have left a record a record is left when some sediment is deposited during the interval and is not subsequently eroded a complete section contains no hiatuses longer than t the completeness of a section varies with t and its accumulation rate varies with the length of the time span over which it is measured plots of measured accumulation rate against time span are an empirical means of estimating completeness simple theoretical models help extrapolate meagre data and identify bias completeness at time scale t can depend upon three general properties of the accumulation history the age of the section the long term net accumulation rate drift and the unsteadiness of the sedimentation rate the way unsteadiness is measured depends upon the kinds of fluctuations that can be recognized in the accumulation rate to describe random fluctuations a standard deviation of rates is sufficient one dimensional brownian motion is a model of random fluctuations that explains many aspects of stratigraphical completeness regular periodic fluctuations in accumulation rate may be described in terms of wavelength and amplitude completeness is an increasing function of t drift and in the periodic case the wavelength of fluctuations it decreases with increasing standard deviation of accumulation rate and the amplitude of periodic fluctuations the completeness and thickness of stratigraphical sections are weakly positively associated

intrusions into the lower stratospheric arctic vortex during the winter of 1991 1992 investigations of the kinematics of the lower stratospheric arctic vortex during the winter of 1991 1992 using the contour advection with surgery technique reveal three distinct events in which there was substantial intrusion of midlatitude air into the vortex in apparent contradiction of the view that the polar vortex constitutes an isolated air mass two of these events in late january and mid february were well documented they were predicted in high resolution forecasts by the european centre for medium range weather forecasts most clearly in experimental forecasts with reduced diffusion direct confirmation of the presence of the intrusions and of their calculated locations was provided by aerosol observations from the airborne differential absorption laser lidar aboard the nasa dc 8 taken as part of the second airborne arctic stratospheric expedition campaign aerosol rich air of midlatitude origin was seen in the expected position of the intrusions the reality of the february event was also confirmed by in situ measurements from the nasa er 2 such events may be significant for the chemical processes taking place within the winter vortex the intrusions were evidently related to the meteorology of the northern stratosphereduring this winter and in particular to persistent tropospheric blocking over the northeastern atlantic ocean and western europe and concomitant ridging into the lower stratospheric vortex in this region nevertheless preliminary investigations have indicated that such events are not uncommon in other northern hemisphere winters although no such events were found in the southern hemisphere during the antarctic winter of 1987

the value of grain size hydraulic conductivity estimates comparison with high resolution in situ field hydraulic conductivity hydraulic conductivity is commonly estimated from grain size characteristics of unconsolidated sediments we present an extensive set of air permeability and grain size measurements from a heterogeneous aquifer these data are unique in that the hydraulic conductivity measurements are made on undisturbed in situ sediment and like the grain size measurements have a small sample volume size 1200 cm hydraulic conductivity estimated from grain size has a higher mean and a lower variance than direct measurements while grain size estimates of hydraulic conductivity do not correspond well to field measured hydraulic conductivity spatial correlation of the two data sets is quite similar

modeling the quasi biennial oscillation s influence on isentropic tracer transport in the subtropics tracer transport in the lower stratosphere is investigated using an off line semi lagrangian transport model and winds from a mechanistic three dimensional middle atmosphere model interpolated to the 650 k isentropic surface over a winter season by comparing two simulations the effect of the quasi biennial oscillation s qbo s easterly or westerly wind phases on low latitude transport is examined especially regarding the formation of an apparent subtropical transport barrier at the equatorward edge of the surf zone the tracer field is diffused less than potential vorticity pv and shows sharper gradients and finer structures developing over the winter in both qbo phases the winter extratropical surf zone is bounded by large tracer gradients equatorward of about 15 latitude the inability of quasi stationary rossby waves to propagate into qbo easterlies leads to a much sharper edge forming between the rapidly stirred extratropical surf zone and the relatively unstirred tropics during the easterly qbo phase than occurs during the westerly qbo phase in the westerly phase some rossby wave activity can propagate across the equatorial westerlies and break on reaching the summer hemisphere easterly winds causing mixing there simulations using a tracer initially confined to the tropics show that more tropical air is mixed out to the winter extratropics by rossby wave stirring when the qbo phase is easterly despite the sharper band of stronger tracer or pv gradient which separates the tropics and the winter extratropics in this phase while air was mixed out of the tropics in both qbo phase simulations neither qbo phase simulation showed extratropical air being irreversibly mixed into the tropics these results are related to observations of the tropical reservoir of stratospheric aerosols especially the dynamics and transport of its winter hemisphere boundary

relating small scale sedimentary structures and permeability in a cross bedded aquifer summary the objective of this study is to investigate the relation between small scale sedimentary structures and permeability in the brussels sands formation an early middle eocene shallow marine sand deposit in central belgium that constitutes a major groundwater source in the region a field campaign was carried out consisting of field observations of the sedimentary structures and in situ measurements of air permeability the sedimentary structures were interpreted sketched digitally photographed and measured in a representative outcrop additionally a total of 2750 cm scale air permeability measurements were carried out in situ analysis of the spatial distribution of sedimentary structures and permeability shows that clay rich sedimentary features such as bottomsets and distinct mud drapes exhibit a different statistical and geostatistical permeability distribution compared to the other lithofacies in the cross bedded sands spatial analysis of the air permeability data shows that permeability anisotropy in the cross bedded lithofacies is dominated by the foreset lamination orientation these results show that small scale sedimentary heterogeneity strongly influences the local spatial distribution of the hydraulic properties and results in permeability heterogeneity and stratification that would produce anisotropy in upscaled permeability values

the extraordinarily strong and cold polar vortex in the early northern winter 2015 2016 the arctic polar vortex in the early winter 2015 16 was the strongest and coldest o f the la st 68 years using global reanalysis data satellite observations and mesospheric radar wind measurements over northern scandinavia we investigate the characteristics of the early sta g e polar vortex and relate them to previous winters we found a correlation between the planetary wave pw activity and the strength and temperature of the northern polar vor tex in the stratosphere and mesosphere in nov d ec 2015 a reduced pw generation in the troposphere and a stronger pw filtering in the troposphere and stratosphere caused by stronger zonal winds in mid latitudes resulted in a stronger polar vortex thi s effect was strengthened by the equator ward shift of pws due to the strong zonal wind in polar latitudes resulting in a southward shift of the eliassen palm flux divergence and hence inducinga decreased deceleration of th e polar vortex by pws

rossby wave breaking and transport between the tropics and extratropics above the subtropical jet abstractrossby wave breaking is an important mechanism for the two way exchange of air between the tropical upper troposphere and lower stratosphere and the extratropical lower stratosphere the authors present a 30 yr climatology 1981 2010 of anticyclonically and cyclonically sheared wave breaking events along the boundary of the tropics in the 350 500 k potential temperature range from ecmwf interim re analysis era interim lagrangian transport analyses show net equatorward transport from wave breaking near 380 k and poleward transport at altitudes below and above the 370 390 k layer the finding of poleward transport at lower levels is in disagreement with previous studies and is shown to largely depend on the choice of tropical boundary in addition three distinct modes of transport for anticyclonic wave breaking events are found near the tropical tropopause 380 k poleward equatorward and symmetric transport associated with cyclonic wave breaking events however is predominantly poleward

transport out of the lower stratospheric arctic vortex by rossby wave breaking the fine scale structure in lower stratospheric tracer transport during the period of the two arctic airborne stratospheric expeditions january and february 1989 december 1991 to march 1992 is investigated using contour advection with surgery calculations these calculations show that rossby wave breaking is an ongoing occurrence during these periods and that air is ejected from the polar vortex in the form of long filamentary structures there is good qualitative agreement between these filaments and measurements of chemical tracers taken aboard the nasa er 2 aircraft the ejected air generally remains filamentary and is stretched and mixed with midlatitude air as it is wrapped around the vortex this process transfers vortex air into midlatitudes and also produces a narrow region of fine scale filaments surrounding the polar vortex among other things this makes it difficult to define a vortex edge the calculations also show that strong stirring can occur inside as well as outside the vortex

bedload transport of fine gravel observed by motion picture photography motion pictures taken at duck creek a clear stream 6 5 m wide and 35 cm deep near pinedale wyoming provide detailed quantitative information on both the modes of motion of individual bedload particles and the collective motions of large numbers of them bed shear stress was approximately 6 pa 60 dynes cm 2 which was about twice the threshold for movement of the 4 mm median diameter fine gravel bed material and transport was almost entirely as bedload the displacements of individual particles occurred mainly by rolling of the majority of the particles and saltation of the smallest ones and rarely by brief sliding of large angular ones entrainment was principally by rollover of the larger particles and liftoff of the smaller ones and infrequently by ejection caused by impacts whereas distrainment was primarily by diminution of fluid forces in the case of rolling particles and by collisions with larger bed particles in the case of saltating ones the displacement times averaged about 0 2 0 4 s and generally were much shorter than the intervening repose times the collective motions of the particles were characterized by frequent brief localized random sweep transport events of very high rates of entrainment and transport which in the aggregate transported approximately 70 of the total load moved these events occurred 9 of the time at any particular point of the bed lasted 1 2 s affected areas typically 20 50 cm long by 10 20 cm wide and involved bedload concentrations approximately 10 times greater than background the distances travelled during displacements averaged about 15 times the particle diameter despite the differences in their dominant modes of movement the 8 16 mm particles typically travelled only about 30 slower during displacement than the 2 4 mm ones whose speeds averaged 21 cm s 1 particles starting from the same point not only moved intermittently downstream but also dispersed both longitudinally and transversely with diffusivities of 4 6 and 0 26 cm 2 s 1 respectively the bedload transport rates measured from the films were consistent with those determined conventionally with a bedload sampler the 2 4 mm particles were entrained 6 times faster on finer areas of the bed where 8 16 mm particles covered 6 of the surface area than on coarser ones where they covered 12 even though 2 4 and 4 8 mm particles covered practically the same percentage areas in both cases the 4 8 and 8 16 mm particles in contrast were entrained at the same rates in both cases to within the statistical uncertainty the rates of distrainment balanced the rates of entrainment for all three sizes and were approximately proportional to the corresponding concentrations of bedload

quantifying stratigraphic completeness a probabilistic approach using paleomagnetic data although sedimentary hiati of variable magnitude are abundant in most stratigraphic sections quantification of the degree of completeness for individual sections has proven difficult a new method of estimating stratigraphic completeness is developed for sections that preserve a detrital remanent magnetic reversal history because the timing of geomagnetic reversals is independent of sedimentation events the distribution of reversals in a stratigraphic section can be used to evaluate completeness the most direct method in which sections are sampled at the top and base of each stratigraphic unit evaluates the frequency of reversals within units versus at unit contacts the more complete a section the greater the probability that reversals occurred during depositional events and are recorded as within unit reversals the less complete a section the greater the probability that reversals occurred during depositional hiati and are recorded as unit contact reversals monte carlo simulations suggest that

use of cpt and other direct push methods for hydro stratigraphic aquifer characterization a field study every environmental site investigation aims at delineating near surface hydro stratigraphic units and their characterization to determine the type and hydraulic properties of sedimentary deposi

observations of vertically thick polar stratospheric clouds and record low temperature in the arctic vortex on 12 and 13 january 2001 backscatter sondes launched at sodankyla finland 67 n 27 e detected an extraordinarily thick polar stratospheric cloud layer of more than 8 km vertical extent on these days the polar vortex passed over northern scandinavia this provided synoptic scale low stratospheric temperatures leading to the formation of both liquid and solid phase particles two days later on 15 january 2001 a regular radiosonde measured record low temperature of 176 7 k at an altitude of 25 2 km at the vortex edge high vertical resolution radiosonde profiles and meteorological analyses indicate strong mountain wave activity on this day this provides further evidence that the coldest temperatures in the arctic lower stratosphere occur as a consequence of mountain wave cooling under cold synoptic scale background conditions

modulation of antarctic vortex composition by the quasi biennial oscillation using a decade of aura microwave limb sounder observations we show distinctly different n2o distributions in southern hemisphere winter that depend on the phase of the quasi biennial oscillation qbo composites of the nitrous oxide n2o anomalies calculated for westerly and easterly phases show that qbo generated variability originating in the subtropical middle stratosphere fills the midlatitude surf zone by late winter after the spring vortex breakup the anomaly is transported to the antarctic where it remains until the next vortex forms in fall trapped in the newly formed vortex the anomaly descends in isolation through fall and winter arriving in the antarctic lower stratosphere in september about 1 year after it formed this transport pathway explains previously reported variability of n2o and inorganic chlorine cly inside the antarctic vortex and demonstrates that the middle stratosphere qbo affects ozone depletion by modulating antarctic cly

the usefulness of outcrop analogue air permeameter measurements for analyzing aquifer heterogeneity quantifying outcrop hydraulic conductivity and its spatial variability saturated hydraulic conductivity k is one of the most important parameters determining groundwater flow and contaminant transport in both unsaturated and saturated porous media although several well established laboratory methods exist for determining k in situ measurements of this parameter remain very complex and scale dependent often the limited accessibility of subsurface sediments for sampling means an additional impediment to our ability to quantify subsurface k heterogeneity one potential solution is the use of outcrops as analogues for subsurface sediments this paper investigates the use of air permeameter measurements on outcrops of unconsolidated sediments to quantify k and its spatial heterogeneity on a broad range of sediment types the neogene aquifer in northern belgium is used as a case study for this purpose to characterize the variability in k 511 small scale air permeability measurements were performed on outcrop sediments representative over five of the aquifer s lithostratigraphic units from these measurements outcrop scale equivalent k tensors were calculated using numerical upscaling techniques validation of the air permeameter based k values by comparison with laboratory constant head k measurements reveals a correlation of 0 93 overall the results indicate that hand held air permeameters are very efficient and accurate tools to characterize saturated k as well as its small scale variability and anisotropy on a broad range of unconsolidated sediments the studied outcrops further provided a qualitative understanding of aquifer hydrostratigraphy and quantitative estimates about k variability at the centimetre scale to metre scale copyright 2013 john wiley sons ltd

coupling of the quasi biennial oscillation and the extratropical circulation in the stratosphere through planetary wave transport abstract a significant fraction of the interannual variability of the wintertime stratosphere in the northern hemisphere is related to the quasi biennial oscillation qbo in tropical winds disturbed conditions of the polar night vortex are favored in years when the winds over the equator are easterly more quiescent conditions prevail at high latitudes when the phase of the tropical qbo is westerly the effects of tropical winds on the extratropical circulation are studied in the equivalent barotropic framework on the sphere calculations are performed with the tropical flow representative of easterly and westerly phases of the qbo with planetary wave forcing representative of conditions in the lower stratosphere the wintertime polar vortex is highly disturbed during the easterly phase of the qbo the evolution taking the form of a canadian warming in contrast more quiescent conditions prevail with the same forcing but with tropical winds representative of the westerly phase of the qbo the vortex

quantification of filaments penetrating the subtropical barrier a method based on contour advection is introduced that aims to quantify the formation of filaments both equatorward and poleward of the subtropical barrier it is applied to diagnosed potential vorticity fields for every day of january and february in 1997 and 1998 an isosurface of modified potential vorticity is found to represent the region of largest isentropic gradients of potential vorticity and is hence assumed as the tropopause tropopause penetrating structures filaments forming in contour advected potential vorticity fields are identified and statistics of the abundance of such structures are derived filamentation as measured by this method exhibits a large temporal variability on the scale of days to weeks for example tropospheric cutoff systems developing in the wake of rossby wave breaking events cause strong filamentation to occur in the lowermost stratosphere the timescales governing filamentation are a function of altitude reflecting the differing types and amplitudes of waves inducing filamentation at different isentropic levels zonal asymmetries arise as rossby waves favorably break near the end of the north atlantic storm track a difference in the intensities of filamentation in january and february of 1997 and 1998 suggests that the relatively low values of ozone in the lowermost stratosphere observed in 1997 are related to increased filamentation induced stratosphere troposphere exchange compared to 1998 for example around 30 more filaments are found in the hemispheric and bimonthly mean at the 330 k isentropic surface in january and february of 1997 than during the same months of 1998 single events can represent most of the filamentation occurring in a month and hence interannual variability in the frequency of filamentation can be considerable

the upper miocene of the southern north sea basin northern belgium a palaeoenvironmental and stratigraphical reconstruction using dinoflagellate cysts organic walled palynomorph assemblages from the kasterlee formation in northern belgium provide new insights into the late miocene depositional history and palaeoenvironments of the southernmost north sea basin ranges of key dinoflagellate cysts constrain the unit between 7 5 and 5 32 ma that is a latest tortonian to messinian age the palynomorph assemblage is characterized amongst others by geonettia clineae an opportunistic species that thrives in mesotrophic coastal embayments with a low sediment influx this environmental setting is corroborated by the notable presence of gramocysta verricula a species with preference for shallow marine environments the occurrence of species of the fresh water green alga pediastrum indicates manifest river discharge in a near shore environment or embayment the coastal depositional environment mirrored by the palynomorphs of the kasterlee formation succeeds the distinct transgressive and fully marine environments of the underlying diest formation in the campine area the results from the palynological study combined with lithological and geophysical data show that both upper miocene formations are two distinct depositional cycles separated by an erosional or regressive phase the upper boundary of the kasterlee formation is correlated with the me2 sequence boundary at 5 73 ma the kasterlee formation is herein formally moved from the lower pliocene series to the upper miocene series the coastal environment probably characterized by a shoaling phase recorded at the border of the southern north sea basin matches the global record of regressive phases in messinian sedimentary sequences which are linked to cooling and increasing global ice volume

seasonal variation of isentropic transport out of the tropical stratosphere the seasonal variation of the isentropic transport out of the tropical stratosphere is examined using contour advection calculations with winds from meteorological analyses for the period july 1991 to june 1994 calculations using winds from three different meteorological analyses are compared there is good qualitative agreement between the different calculations for extratropical structures but not for structures in the tropics there is also reasonable agreement between area diagnostics for transport out of the tropics derived from these calculations transport out of the tropics occurs in rossby wave breaking events in which filaments of tropical air are drawn into middle latitudes in all years these wave breaking events occur during the fall to spring period when there are westerlies throughout middle latitudes late september to early may in the northern hemisphere this includes periods before the formation of and after the breakup of the polar vortex in the northern hemisphere the rate of transport out of the tropics during fall to spring fluctuates around a constant value whereas in the southern hemisphere there is a relatively quiet midwinter period with maxima in the transport in early and late winter