analysis of vadose zone inhomogeneity toward distinguishing recharge rates solving the nonlinear interface problem with newton method citation steward d r 2016 analysis of vadose zone inhomogeneity toward distinguishing recharge rates solving the nonlinear interface problem with newton method water resources research 52 11 8756 8774 doi 10 1002 2016wr019222

sst anomalies of enso and the madden julian oscillation in the equatorial pacific this study explores whether anomalies of sea surface temperature sst in the equatorial pacific during warm events of el nino southern oscillation enso are related to the madden julian oscillation mjo an index is derived from surface wind data of a global model reanalysis to measure forcing of oceanic kelvin waves by wind stress associated with the mjo this kelvin wave forcing index of the mjo is used to relate interannual anomalies in seasonal activity of the mjo to interannual anomalies in equatorial sst for the 1980 99 time period evidence is found showing that during enso warm events stronger kelvin wave forcing in the western pacific precedes greater sst anomalies in the eastern pacific by 6 12 months no such evidence however can be found for the period of 1950 79 the result suggests that during enso warm events amplitudes of sst anomalies in the eastern pacific can be affected by the mjo at least for the 1980 99 period through its seasonal activity of kelvin wave forcing a possible mechanism for such an mjo enso relationship is described how enso prediction can be benefited from the precursory signals of the mjo is discussed

dynamics and thermodynamics of a warming event in a coupled tropical atmosphere ocean model abstract a simple coupled ocean atmosphere model similar to that of zebiak and cane is used to examine the dynamic and thermodynamic processes associated with el nino southern oscillation enso the model is run for 300 years the interannual variability which results is regular with a period of either 3 or 4 years quantized by the annual cycle the amplitude 1 5 m s 1 wind and 2 c sst anomalies period and structure of the interannual variability compare well with observations the model warm event is initiated in the spring prior to the event peak and is well described as an instability of the coupled system during instability growth the sea surface temperature sst anomaly is primarily generated by vertical upwelling processes the sst anomaly can be approximately described by the expression t t kth t where t is the sst anomaly t time h the upper layer thickness pycnocline perturbation and an effective damping time which includes heat loss to the atmosphere kt parameterizes

the seepage exclusion problem for sloping cylindrical cavities solutions of the seepage exclusion problem for sloping cylinders of arbitrary cross section are simply deduced from those for horizontal cylinders the three dimensional flow field around sloping cylinders may be specified by two scalar functions of two space coordinates liability to water entry from downward unsaturated seepage decreases as the slope of the cylinder axis increases

problems of seepage to empty ditch and drain analytical solutions for the maximum area of the cross section of a drain ditch and a mole drain are obtained in the case of seepage to a ditch from an underflooded soil surface the extreme curve is represented by a semicircle with a constant value of flow velocity along the curve seepage to a system of empty horizontal drains is studied for one of three possible patterns of water tables at low values of infiltration to a phreatic surface the drain of a maximum area is nearly circular

is enso a cycle or a series of events 1 after early ideas that saw el ninos as isolated events the advent of coupled models brought the conception of enso as a cycle in which each phase led to the next in a self sustained oscillation twenty two years of observations that represent the el nino and la nina peaks east pacific sst and the memory of the system zonal mean warm water volume suggest a distinct break in the cycle in which the coupled system is able to remain in a weak la nina state for up to two years so that memory of previous influences would be lost similarly while the amplitude of anomalies persists from the onset of a warm event through its termination there is no such persistence across the la nina break these observations suggest that el ninos are in fact event like disturbances to a stable basic state requiring an initiating impulse not contained in the dynamics of the cycle itself

distributed of downward flux in unsaturated heterogeneous hydrogeology environments we used the finite element computer program unsat2 to quantify the horizontal distribution of unsaturated downward flux in porous tuff as a function of hydrogeologic heterogeneities under two different recharge rates the distribution of downward flux is important because it influences ground water travel time at a potential geologic repository for high level radioactive wastes hydraulic properties of the topopah spring member of the paintbrush tuff formation at yucca mountain nevada were selected for use in the eight simulations that were conducted all simulations were run essentially to steady state referred to herein as quasi steady state the simulations show that 1 heterogeneities in an isotropic porous rock matrix will cause downward flux to be distributed nonuniformly 2 zones in which saturated matrix hydraulic conductivity is less than the downward flux tend to develop positive pressures that may divert flow into fractures if they exist 3 one dimensional analysis of vertical flow in the unsaturated zone is insufficient to ensure that fracture flow does not occur even if the true magnitude of vertical flux is known and 4 the true spatial distribution of hydraulic conductivity above the regional water table must be determined in order to obtain the true spatial distribution of downward flux this analysis assumes constant spatial and temporal distribution of recharge for each simulation but the differences among simulations verify the fact that changing recharge rates also play a significant role in the distribution of downward flux owing to the influence of recharge rate on the development of positive pore pressures in the otherwise unsaturated rock the primary significance of this research is as follows 1 we have introduced a new method of unsat2 time step control that facilitates convergence even in complex large scale partially saturated hydrogeologic environments previous studies have experienced convergence problems with unsat2 under complex hydrogeologic conditions 2 nonuniform downward flow should be anticipated in heterogeneous hydrogeologic environments at a heterogeneity scale of 50 m and a model scale of hundreds of meters even if recharge is uniform spatially 3 the impact of heterogeneities in the unsaturated zone on downward flux can now be quantified 4 hydrogeologic heterogeneities can create zones of positive pressure and consequent possible fracture flow in the unsaturated zone even when the recharge rate is less than the average saturated hydraulic conductivity but most certainly when the recharge rate exceeds saturated hydraulic conductivity 5 this type of study provides a basis for designing hydrogeologic property testing programs and recharge distribution testing programs that are compatible with the design of models that can characterize downward flux 6 this work shows that field documentation of the absence of positive pressures above the water table constitutes the best evidence of exclusive matrix flow absence of fracture flow within yucca mountain if positive pressures are encountered in the field then fracture flow probably exists within yucca mountain

seepage into a mountain tunnel and rain infiltration abstract to clarify the processes governing recharge of rainwater into an unconfined aquifer in a mountain basin the seepage rate of water into a mountain tunnel was monitored continuously between may 1988 and december 1991 in yura wakayama western japan the electrical conductivity and ionic composition of the seepage water was also measured regularly from june 1989 the mountain is composed of fractured sedimentary rocks such as sandstones and cherts seepage appeared only at specific locations on the roof of the tunnel seepage was measured through overlying sandstones of 10 m depth and cherts of 5 m depth time variations in the discharge suggested that seepage is formed both by rapid flow and basic flow components which correspond to the so called fissure flow and matrix flow this was confirmed by analysis of time variations in the concentration of chemical species in the seepage water fissure flow contributes the initial increment of seepage discharge immediately after the occurrence of rainfall and its velocity for sandstone can be represented by a function only of water content n is constant and larger in winter than in summer but n remains constant at approximately two infiltration time in fissures through the base of the cherts is negligible compared with that through the overlying soil layer whereas matrix flow through sandstones persists through the year for cherts it disappears within a week after rainfall events and its decay is dependent on the seasonal magnitude of evapotranspiration the behavior of the matrix flow for sandstones can be analyzed through a kinematic wave model as can the fissure flow

methodology for bounding calculations of nuclear criticality of fissile material accumulations external to a waste container at yucca mountain nevada abstract the possibility of nuclear criticality however remote in the vicinity of the proposed repository at yucca mountain nevada generates justified concerns and may impact the performance of the repository a heuristic approach is presented here for determining the amount spatial distribution and other characteristics of fissile material accumulation in the rock beneath a waste package that could contribute to such an event this study is concerned primarily with waste packages containing special spent fuel from the department of energy and high level nuclear waste glass mixing with less alkaline waters and the subsequent drop in ph is the mechanism that is most efficient for precipitating fissile material from the waste package internal leachate in contrast to natural deposits in which redox changes are the main precipitation driver external accumulation size is determined by 1 computing the chemical composition of the leachate leaving a package as its internal materials degrade with the batch geochemical code eq3 6 2 determining precipitation of fissile material into mineral phases using the 1d geochemical code phreeqc as the effluent mixes with percolation water and 3 heuristically scaling results to a 3d volume and computing the criticality coefficient using the code mcnp loci for accumulation are the multiple lithophysal cavities and the fracture system a bounding conservative approach is used by necessity in step 3 nuclear criticality is sensitive to small variations in the distribution of fissile material and parameters of natural systems vary by orders of magnitude because the most likely combinations of parameters are not conducive to nuclear criticality this study focuses on extreme values of parameter probabilistic distributions such as limited flow into the package associated with a large percolation rate combinations of material degradation rates favoring actinide release and very high host rock porosity values by considering these combinations most favorable to criticality but unlikely it was concluded that external nuclear criticality is not a concern at the proposed repository

simulations of the last glacial maximum ice sheet surface climate implications for the interpretation of ice core air content this paper reports on analyses of the surface pressure surface wind and seasonality of temperature and precipitation in the central parts of greenland and antarctica as simulated by different general circulation models gcms for the present and for the last glacial maximum lgm climates these parameters in addition to the mean surface temperature influence the air content of the ice either directly or through their influence on the pore volume to correctly interpret the air content of the ice in terms of past ice sheet elevation changes the variations of these parameters must therefore be known most of the simulations discussed here have been carried out within the framework of the paleoclimate modeling intercomparison project moreover a stretched grid gcm has been used with a high resolution over the ice sheets we show that not taking into account changes of surface pressure at constant altitude between the lgm and today leads to an overestimation of past ice sheet elevation up to 150 m while wind speed changes are too weak to have a significant influence on ice core air content the results concerning changes of the amplitude or phase of the seasonal variations of precipitation and temperature are somewhat ambiguous most but not all of the models suggest an intensification of the seasonal cycle of surface temperatures over central greenland and to a lesser extent over central east antarctica neglecting these changes might lead to an underestimation of past elevation by up to 140 m for the greenland ice sheet but this number is subject to large uncertainties

role of non linear oceanic processes in the response to westerly wind events new implications for the 1997 el nino onset in march 1997 a strong westerly wind event wwe occurred in the western equatorial pacific prior to the 1997 1998 el nino event it produced downwelling kelvin waves that interacted non linearly with the surface temperature salinity and zonal current fronts located at the eastern edge of the warm fresh pool eewp this non linear interaction locally increased zonal currents by a factor of three compared to a theoretical linear response and advected the eewp at an unexpected rate 1m s to which the ocean atmosphere coupled system may have been responding rapidly to trigger el nino conditions

atmospheric circulation around the greenland crest the greenland ice sheet program 2 gisp2 required meteorological support for the layout of the field camp ice core site landing strip snow sampling sites and air sampling sites an automatic weather station installed in may 1987 provided the initial data for the support of several components of the program using the 2 year wind speed and direction distributions the automatic weather station aws network was expanded to six sites with four sites located approximately 100 km from the highest point in greenland in the cardinal directions and sites located at gisp2 and at the air sampling site the wind direction and speed wind roses for august and september 1994 show that there is considerable variation in the wind field around the greenland crest the constancy ratio of the vector wind speed to the scalar wind speed of the monthly wind vectors was lowest at the southern site and increased as one moved clockwise around the crest to the eastern site vorticity and divergence were determined from triangles formed by three aws sites the mean horizontal divergence for august and september 1994 was 1 4 x 10 5 s 1 and the vorticity was 3 7 x 10 5 s 1 apparently the flow around the greenland crest is most influenced by topography when the 500 hpa contours indicate a pressure ridge over central greenland the surface winds showed anticyclonic flow positive horizontal divergence and negative vertical vorticity in the mean this configuration indicates the presence of an inversion wind especially at the sites located on the slopes to the west and east of the crest

groundwater flow patterns in the vicinity of underground openings in unsaturated rock abstract a two dimensional modeling scheme is utilized herein to analyze the effects of mined out underground openings on groundwater flow patterns in unsaturated rocks a series of modeling results is presented using the finite element computer program unsat2 to simulate steady groundwater flow that initially is vertical and downward model output is analyzed for 1 variations in the direction of groundwater flow caused by the mined out openings 2 the distribution of pressure head as produced by the openings 3 variables that affect the rate of predicted groundwater inflow into the openings modeling results indicate that 1 mined out openings will alter the pattern of groundwater flow in the unsaturated zone 2 the hydraulic effects are dependent on the hydrogeology of the rocks and on the geometry of the mined out openings 3 inflow of groundwater into mined out openings is possible in the otherwise unsaturated zone including mines developed in homogeneous rocks 4 groundwater inflow into the mined out openings can occur at values of downward flux that are smaller in magnitude than the saturated hydraulic conductivity of the surrounding rock 5 the temporal and spatial distribution of flux through the topopah spring member of the paintbrush tuff is the most critical factor regarding the occurrence of mine water inflow in the otherwise unsaturated tuff at yucca mountain nd u s a

unsaturated quasi linear flow analysis in v shaped domains abstract an explicit essentially 2d solution for steady unsaturated seepage flow from infinity to a corner with boundaries kept at constant suction is obtained for the kirchhoff potential by the method of separation of variables a system of coordinates coinciding with the corner boundaries is selected distributions of the pressure stream lines and velocities are derived non existence of steady flows at certain corner orientations deflection of the incident flow by slanted boundaries and inflection points on the stream lines close to the vertex are discussed one dimensional limit for zones far from the trough is examined refraction and further collimation of the upper 2d flow in the second underlying porous medium with implications to geotechnical capillary barriers is studied a vadose zone originated accretion is matched with a saturated wing which appears on a slanted bedrock mathematically this matching is done by linking the dupuit forchheimer and quasi linear models a tilted water table is shown to entrain the recharging moisture with curvilinear stream lines in the unsaturated zone

vapor phase transport in the near drift environment at yucca mountain 1 a key issue regarding the performance of the potential high level radioactive waste repository at yucca mountain nevada is the likelihood of precipitation percolating a vertical distance of 300 m through fractured unsaturated rock into drifts containing waste packages water enhances waste package corrosion and is required for transport of released radionuclides to evaluate the propensity for seepage into tunnels at yucca mountain a 5 m diameter 2 7 km long tunnel commonly referred to as the cross drift cd was excavated in 1998 branching off from the main exploratory studies facility tunnel sections of this tunnel have been isolated from ventilation for extended periods over the last 4 years we present continuous measurements of relative humidity and temperature and periodic observations of liquid water in the cd over two periods during this observation duration the terminal section of the drift was partitioned into four sections by bulkheads and ventilation to these sections was minimized to a few days we compare these observations to results from analytical and numerical models to investigate processes associated with the movement of water vapor between the tunnel bore and the surrounding fractured rock formation observations from this effort indicate that fractures can be primary paths for unsaturated zone vapor flow in the immediate vicinity of emplacement drifts observations measurements and analysis indicate the need for a model that includes fracture dominated vapor transport as a significant contributor to total water flow into the drifts

hydrologic issues associated with nuclear waste repositories significant progress in hydrology especially in subsurface flow and solute transport has been made over the last 35 years because of sustained interest in underground nuclear waste repositories the present paper provides an overview of the key hydrologic issues involved and to highlight advances in their understanding and treatment because of these efforts the focus is not on the development of radioactive waste repositories and their safety assessment but instead on the advances in hydrologic science that have emerged from such studies work and results associated with three rock types which are being considered to host the repositories are reviewed with a different emphasis for each rock type the first rock type is fractured crystalline rock for which the discussion will be mainly on flow and transport in saturated fractured rock the second rock type is unsaturated tuff for which the emphasis will be on flow from the shallow subsurface through the unsaturated zone to the repository the third rock type is clay rich formations whose permeability is very low in an undisturbed state in this case the emphasis will be on hydrologic issues that arise from mechanical and thermal disturbances i e on the relevant coupled thermo hydro mechanical processes the extensive research results especially those from multiyear large scale underground research laboratory investigations represent a rich body of information and data that can form the basis for further development in the related areas of hydrologic research

an advective reflective conceptual model for the oscillatory nature of the enso recent findings about zonal displacements of the pacific warm pool required a notable modification of the delayed action oscillator theory the current leading theory for the el nino southern oscillation enso simulations with a linearized coupled ocean atmosphere model resulted in 3 to 6 year enso like oscillations with many of the variable model parameters found to be very close to their observed values this simple model suggests that ocean processes that are ignored or underestimated in the delayed action oscillator theory such as zonal current convergence zonal advection of sea surface temperature and equatorial wave reflection from the eastern ocean boundary are fundamental to the development of the enso in particular to its manifestations in the central equatorial pacific

observations of warm water volume changes in the equatorial pacific and their relationship to el nino and la nina abstract this paper describes observed changes in surface winds sea surface temperature sst and the volume of water warmer than 20 c wwv in the equatorial pacific ocean for the period 1980 99 the purpose is to test recent hypotheses about the relationship between variations in wwv and the el nino southern oscillation enso cycle the results confirm inferences based on theory models and previous empirical analyses using proxy data namely sea level that enso involves a recharge and discharge of wwv along the equator and that the cyclic nature of enso results from a disequilibrium between zonal winds and zonal mean thermocline depth the authors also find that the magnitude of enso sst anomalies is directly related to the magnitude of zonal mean wwv anomalies furthermore for a given change in equatorial wwv the corresponding warm el nino sst anomalies are larger than the corresponding cold la nina anomalies this asymmetry between the warm and cold phases of the enso cycle implies differences

wintertime surface winds over the greenland ice sheet abstract clear sky wintertime surface winds over the greenland ice sheet are simulated with a three dimensional mesoscale numerical model it is shown that the simulated winds blow from the broad gently sloped interior to the steep coastal margins this general wind pattern is similar to that found over antarctica due to the same governing dynamics the longwave radiational cooling of the sloping ice terrain is the key driving force of this cold airflow in some coastal areas the downslope winds converge into large fjords such as kangerlussuaq and sermilik this is consistent with the frequent presence in these areas of warm signatures on cloud free thermal infrared satellite images that are generated by katabatic winds the shape of the greenland ice sheet plays an important role in directing the flow of the surface winds the study demonstrates that the surface wind pattern is only moderately affected by climatological flow around and over the ice sheet the mass redistribution associated with the kat

response of equatorial oceans to periodic forcing oscillating wind with a period p induce variability with the following characteristics in the upper few hundred meters of the equatorial zone 5 sup 0 n to 5 sup 0 s of the ocean 1 p 10 days these winds fluctuate too rapidly to generate strong currents and excite primarily waves 2 10 days 150 days the amplitude of variability is almost independent of frequency an equilibrium response which is in phase with the forcing and which corresponds to a succession of steady states is approached asymptotically these time scales are for a basin 5000 km wide if the width of the basis exceeds 5000 km then the 150 daytime scale increases in the deep ocean below the thermocline motion corresponds to propagating waves generated by the divergence of the nonlinear currents in the upper ocean

dynamic role of a westerly wind burst in triggering an equatorial pacific warm event abstract dynamical impacts of a strong westerly wind burst wwb are studied using an ocean atmosphere coupled simulation in which an intense westerly wind burst is introduced the ocean response includes local and remote components with the development of a zonal surface jet and the appearance of positive sea surface temperature anomalies in the eastern pacific as observed during the triggering of the 1997 98 el nino remote warming results from the eastward propagation of a subsurface temperature anomaly generated in the western pacific a detailed heat budget helps to describe and understand the major mechanisms taking part to the formation of the subsurface temperature anomaly in the western pacific contributing to its eastward propagation and leading to the surface warming simulated in the eastern pacific advective contributions are proved to be widely predominant in the heat budget further decomposition of advective terms into linear and nonlinear parts allows insights into the role of mean stat

introduction to special section synoptic and mesoscale weather systems in the polar regions this special section consists primarily of papers contributed to symposium m 9 on synoptic and mesoscale weather systems in the polar regions at the xxi general assembly of the international union of geodesy and geophysics which was held in boulder colorado during july 1995 the symposium was convened by john turner of the british antarctic survey and erik rasmussen of the university of copenhagen high latitude meteorology is in a period of rapid transition away from being a generally neglected area of atmospheric science with the general understanding that the atmospheric and oceanic circulation is to first order driven by the thermal contrast between the equatorial heat source and the polar heat sinks it no longer seems appropriate to deemphasize the role of the polar regions in climate variability and change however the natures of the arctic and antarctic are profoundly different the ice covered and land locked arctic ocean contrasts with the elevated and extensive antarctic ice sheets that are surrounded by the southern ocean the very different geographic characteristics limit the similarities between these two regions polar atmospheric studies have been hampered by the remoteness of these areas their demanding climate and the shortage of observations the increasingly accurate and expanding range of variables derived from satellite observations combined with the development and widespread deployment of automatic weather stations and drifting buoys is decreasing the data void numerical modeling is becoming an important analysis tool in particular data assimilation is emerging as an important approach to integrate diverse and sparse data sources into a coherent description of the threedimensional time dependent atmospheric circulation the trend is away from broad scale studies to more detailed investigations such as the surface heat budget of the arctic ocean sheba moritz and perovich 1996 and the first regional observing study of the troposphere frost turner et al 1996 the first project addresses the energy exchanges among the atmosphere sea ice and upper arctic ocean frost is directed toward examining and improving the performance of weather forecast models poleward of 50os latitude the symposium was designed to advance the understanding of the role of the polar atmospheres in the general circulation by better resolving synoptic and mesoscale circulation systems in high latitudes emphasis was placed on describing their structure dynamics and climatology in

the three dimensional structure of an upper ocean vortex in the tropical pacific ocean in the equatorial pacific ocean easterly trade winds and the earth s rotation combine to drive surface currents away from the equator thereby causing cold nutrient rich subsurface water to upwell the front1 that forms between this upwelled water and warmer waters north of the equator is sometimes visible as a spectacular line in the sea 2 between 2 and 6 n westward propagating cusp shaped disturbances observed along this front3 have been attributed to the effect of dynamical instabilities in the system of zonal equatorial currents4 11but the connection between these phenomena remains unclear here we report extensive measurements from shipboard sensors satellite and drifting buoys which reveal the three dimensional structure of an anticyclonic eddy or vortex 500 km in diameter and centred at 4 n we suggest that cusp shaped disturbances of the front are caused by trains of large amplitude vortices which are driven by instability of the mean zonal shear we show that these vortices not only play an important role in the meridional transport of heat salt and momentum but are also associated with regions of intense horizontal convergence along the front where dramatic concentrations of marine life are observed

considerations for measuring pressure head and water content in inclined boreholes 1 angled boreholes have been proposed to improve water content and pressure head monitoring in deep vadose zones by reducing the impact of the borehole on measurements by placing sensors below undisturbed soil however the borehole casing distorts the flow field which may impact measurements made with sensors placed on or in the boreholes we examined a wide range of soil types background fluxes and casing radii and angles of inclination to predict the error in water content and pressure head measurements that arise due to this flow disruption under unit gradient flow we found that placing pressure head and water content sensors 110 and 120 from the top of the borehole respectively minimizes the effects of flow perturbation under some conditions it may be possible to use the perturbation of the flow field caused by the casing to estimate hydraulic parameter values

tropical instability wave variability in the pacific and its relation to large scale currents abstract shipboard acoustic doppler current profiler adcp derived zonal currents from 170 to 110 w are assembled into composite seasonal and enso cycles to produce detailed representations of large scale ocean flow regimes that favor tropical instability waves tiws the instability favorable portion of these cycles namely the august october period of the seasonal cycle and the pre december period of the enso cold phase both have intense westward flow in the south equatorial current most particularly the branch north of the equator secn and strengthened eastward flows in the north equatorial countercurrent necc and the equatorial undercurrent euc taken together these flows enhance current shear in the two regions generally associated with tiw activity namely the cyclonic and anticyclonic shear regions located to the south and north of the secn respectively direct correlation of adcp currents and ctd densities to an instability index derived from equatorial 13 30 day meridional velocit

heat content variability related to enso events in the pacific abstract anomaly fields of upper ocean heat content ohc in the pacific basin from 30 s to 60 n over a 45 yr period are analyzed with special reference to their relationship with el nino southern oscillation enso events in the present study for convenience the ohc is defined as vertically averaged temperature from the sea surface to 300 m depth based on a cluster analysis it is found that interannual variability with a period of 3 6 yr is dominant in the eastern and western tropical pacific while multidecadal variability with a period of approximately 20 yr is dominant in mid to high latitudes in order to focus attention on the relationship between ohc anomalies and enso events 3 6 yr variations are extracted by a bandpassed filtering with half power points at 3 and 6 yr periods the result clearly shows the cyclic and anticlockwise propagation of ohc anomalies on the circuit in the northern tropical pacific that is an eastward propagation along the equator a northward propagation at the e

hydrologic processes in a low gradient source area discharge piezometric and other field observations from a 3 year monitoring program indicate that runoff from a low gradient source area in marin county california is controlled by the interaction of throughflow macropore flow and saturation overland flow throughflow response integrates multiple storm events and exhibits both seasonal trends and rapid response to midwinter storms upon saturation of highly conductive near surface soils after saturation of the deeper colluvium along the hollow axis macropore flow responds rapidly to individual storm events and locally provides a ceiling to piezometric response saturation overland flow occurs along the axis of the unchanneled valley only during large storms when both soil matrix and macropore transmissivity are exceeded during large runoff producing storms saturation overland flow extends continuously over most of the unchanneled valley axis during smaller runoff producing events however ground surface saturation may be discontinuous reflecting either variations in the conductivity of the underlying soil bedrock or a variable soil thickness along the hollow axis results of this study document a sequence of flow path activation in which the temporal distribution of rainfall events within a season determines both the mechanism and magnitude of runoff generation

low frequency modes of tropical ocean dynamics abstract basinwide very low frequency vlf modes with zonal uniformly deepening and shoaling of the equatorial thermocline are found as solutions of linear shallow water equations with the meridional basin boundaries under an equatorial plane they can be understood as the free heat content recharge oscillations the interannual vlf modes had been recognized as the essential part of the coupled recharge oscillator theory for the el nino southern oscillation it is suggested that the decadal vlf modes may also be transformed into coupled modes relevant to the pacific decadal climate variability through the ocean atmosphere interaction in the tropics

on the role of meridional wind anomalies in a coupled model of enso the role of the meridional wind anomalies on the el nino southern oscillation as simulated by a simple coupled tropical pacific ocean atmosphere model is investigated it is found that these anomalies play a key role in maintaining finite amplitude interannual variability in the coupled simulations when the meridional wind stress anomalies are not allowed to feed back to the ocean the simulated oscillations are damped out within a few years this happens irrespective of initial conditions during a warm cold event the simulated meridional wind stress anomalies drive convergent divergent surface currents in the equatorial east pacific inducing downwelling upwelling anomalies that act to strongly reinforce the sst and wind anomalies this is in contrast to the model zonal wind stress anomalies which due to the tendency to reverse sign in the eastern pacific induce upwelling downwelling anomalies in the east and sst patterns with weaker net positive feedback observed wind stress anomalies present some similarity with those simulated by the coupled model in the near equatorial region the zonal component reverses sign between the central and the eastern pacific there the meridional component induces a vertical current anomaly of opposite sign and similar magnitude to that induced by the zonal one these features suggest the importance of meridional wind stress anomalies in the real climate system

the role of reversed equatorial zonal transport in terminating an enso event abstractthis study shows the sudden basinwide reversal of anomalous equatorial zonal transport above the thermocline at the peaking phase of enso triggers rapid termination of enso events the anomalous equatorial zonal transport is controlled by the concavity of anomalous thermocline meridional structure across the equator during the developing phase of enso opposite zonal transport anomalies form in the western central and central eastern equatorial pacific respectively both are driven by the equatorial thermocline anomalies in response to zonal wind anomalies over the western central equatorial ocean at this stage the anomalous zonal transport in the east enhances enso growth through zonal sst advection in the mature phase of enso off equatorial thermocline depth anomalies become more dominant in the eastern pacific because of the reflection of equatorial signals at the eastern boundary as a result the meridional concavity of the thermocline anomalies is reversed in the east this change reve

northeast monsoon rainfall variability over the southern peninsular india associated with multiyear la nina events the present study examines the variability of northeast monsoon nem rainfall over the southern peninsular india spi associated with multiyear la nina events using observations and coupled model inter comparison project phase 5 cmip5 models the analysis is carried out for nem season october december of two successive la nina years referred to as the first and second year during the period 1900 2010 observations show that despite noticeable weakening in the equatorial pacific cooling from the first year to the second year strong la nina teleconnections and the rainfall deficiency over the spi region remains the same in most of the multiyear la nina events 70 in the first year zonally protracted low level cyclonic circulation over the north indian ocean nio region induces northwesterly wind anomalies over spi region negative moisture anomalies corroborated by northwesterlies and subsidence cause deficient rainfall over this region on the other hand the western flank of nio cyclonic circulation is pushed towards indian longitudes in the second year inducing dry northerlies over spi region development of low level divergent flow over the western tropical indian ocean and eastward migration of convergence zone from bay of bengal are found to be responsible for the shift in circulation pattern these anomalous circulations together with low moisture content are responsible for deficit nem rainfall in the second year differences in circulation patterns noted in the first and second year are associated with changes in the la nina related sst patterns over the equatorial pacific and modulation of the upper lower level convergence divergence zones analysis reveals that most of the cmip5 models have tendency to simulate excess rainfall over the spi region in 70 100 of multiyear la nina events unlike in the observations 30 of events the possible reasons for the simulation of such positive rainfall anomalies are explored in the present study

water exclusion from tunnel cavities spanning a water table abstract the vertical downward flow of water in unsaturated soils is perturbed by the presence of cavities analysis of the flow problem has shown that there is for a given situation a critical shape of a cavity for it to exclude water entry when the soil water pressure at the cavity wall is everywhere the air entry value for the soil and the cavity wall is a streamline in this note cavities spanning a water table are considered when the water table is caused by artesian pressure in a water bearing substratum building on previous analysis critical shapes for such cavities are obtained for particular circumstances thus showing that situations can exist for cavities not to fill with water although protruding below the water table it is noted that the analysis used to obtain a solution to this problem is the same as that for the groundwater seepage problem of water movement to a water bearing substratum under pressure from infinite ponded water regions separated by a long island strip

analytic element solutions for seepage towards topographic depressions abstract point and line singularities are superposed with incident unidirectional saturated and unsaturated flows the resulting isobars of 3d laplacian or advective dispersion equation fields model either seepage face dimples and rills on a tilted hillslope or an undulated top of the vadose zone above a stagnant water table the reconstructed shapes of isobars are conchoidal i e convex concave all flow characteristics drawdowns velocity and kirchhoff potential distributions dimple sizes are calculated either explicitly or by elementary computer algebra routines

interannual variability of meridional heat transport in a numerical model of the upper equatorial pacific ocean abstract the interannual heat budget of the pacific equatorial upwelling zone is studied using a primitive equation a reduced gravity model of the upper pacific equatorial ocean the model is forced with monthly mean fsu winds from 1971 to 1990 a meridional overturning cell transports heat poleward with poleward flowing warm surface water compensated by colder deeper equatorward flow a horizontal cell transports heat equatorward as warmer equatorward flow which enters the equatorial zone near the western boundary to feed the equatorial undercurrent is compensated by colder poleward flow in the eastern basin the heat transported by transient eddies is equatorward heat transport anomalies from the 20 year mean balance the time rate of change of heat content on interannual and seasonal timescales anomalies of surface heat flux do not contribute significantly to the interannual heat budget although each simulated enso event develops differently similarities in the interannual heat budget emerge he

seepage into an underground opening constructed in unsaturated fractured rock under evaporative conditions 1 liquid release tests performed in boreholes above an underground opening constructed in unsaturated fractured rock are used in this study to evaluate seepage into a waste emplacement drift evidence for the existence of a capillary barrier at the ceiling of the drift is presented based on field observations including spreading of the wetting front across the ceiling and water movement up fractures exposed in the ceiling before seepage begins the capillary barrier mechanism has the potential to divert water around the opening resulting in no seepage when the percolation flux is at or below the seepage threshold flux liquid release tests are used to demonstrate that a seepage threshold exists and to measure the magnitude of the seepage threshold flux for three test zones that seeped the seepage data are interpreted using analytical techniques to estimate the test specific strength of the rock capillary forces 1 that prevent water from seeping into the drift evaporation increases the seepage threshold flux making it more difficult for water to seep into the drift and producing artificially inflated 1 values with adjustments for evaporation the minimum test specific threshold is 1600 mm yr with a corresponding 1 value of 0 027 m

long term observations of tropical instability waves abstract reynolds sea surface temperature sst data showing tropical instability waves tiws in the tropical pacific are analyzed along with current measurements from the tropical atmosphere ocean tao buoy array and wind speeds from the european remote sensing satellite ers 1 and 2 scatterometers tiws are visible as undulations in the sst cold fronts that delineate the northern and southern boundaries of the cold tongue in the equatorial pacific the sst pattern results from advection of the sst front by instabilities in the near surface equatorial currents although the waves are seen on both sides of the pacific cold tongue and north of the equator in the atlantic they are most intense and thereby most observable in the north equatorial pacific the combination of data used in this analysis provides information about these waves the factors controlling them and their coupling to the atmosphere on annual and interannual timescales on annual timescales the tiws generally establish a strong

direct measurements of upper ocean currents and water properties across the tropical pacific during the 1990s abstract meridional sections of upper ocean zonal currents potential temperature and salinity are estimated at ten longitudes from 143 e to 95 w using conductivity temperature depth and acoustic doppler current profiler data from 172 synoptic sections taken in the tropical pacific between 138 e and 86 w mostly in the 1990s data reduction is carried out in a potential isopycnal and mixed layer framework to preserve a sharp pycnocline a mixed layer water property extrema and velocity extrema mean zonal currents potential temperatures and salinities are produced at each longitude the seasonal cycles of these fields are also estimated as well as a simple el nino southern oscillation enso cycle zonal sections along the equator are also presented properties of the near equatorial zonal currents including transports temperatures and salinities are estimated separately from the synoptic sections the seasonal cycles of these quantities and their correlations with the southern oscillation index are investigated the work is distinguished from most existing literature in that direct estimates of zonal velocity are combined with contemporaneous temperature and salinity data allowing trans pacific estimates of near equatorial current transports and properties including those of the northern branch of the south equatorial current the new guinea coastal undercurrent and the equatorial undercurrent

unsaturated flow and transport through a fault embedded in fractured welded tuff 1 to evaluate the importance of matrix diffusion as a mechanism for retarding radionuclide transport in the vicinity of a fault located in unsaturated fractured rock we carried out an in situ field experiment in the exploratory studies facility at yucca mountain nevada this experiment involved the release of 82 000 l of water over a period of 17 months directly into a near vertical fault under both constant positive head at 0 04 m and decreasing fluxes a mix of conservative tracers pentafluorobenzoic acid pfba and bromide applied in the form of lithium bromide was released along the fault over a period of 9 days 7 months after the start of water release along the fault as water was released into the fault seepage rates were monitored in a large cavity excavated below the test bed after the release of tracers seepage water was continuously collected from three locations and analyzed for the injected tracers observations of bromide concentrations in seepage water during the early stages of the experiment and bromide and pfba concentrations in the seepage water indicate the significant effects of matrix diffusion on transport through a fault embedded in fractured welded rock

unsaturated seepage and subterranean holes conspectus and exclusion problem for circular cylindrical cavities this paper introduces the general theory of water exclusion from or entry into subterranean holes from steady uniform downward unsaturated seepage buried holes serve as obstacles to the flow and so increase water pressure at parts of the hole surface when downward seepage is fast enough and or the hole is large enough water pressure increases to the point where a seepage surface forms and water enters the hole contrary to the conventional picture drawn from capillary statics hydrodynamics shows that the larger the hole the more vulnerable it is to water entry cavity shape is important also applications include optimal design of configurations of tunnels and underground repositories e g for nuclear wastes against entry of seepage water the theory also embraces the disturbance of seepage flows by buried impermeable obstacles such as stones and structures the quasi linear exclusion problem for circular cylindrical cavities is solved both exact solutions and simple asymptotic results are found and graphs and tables presented the moisture field about the cavity exhibits upstream and downstream stagnation points and retarded regions roof drip lobes in which the moisture content and downward flow velocity are augmented by water essentially deflected from the cavity roof and the dry shadow region of reduced moisture content and flow velocity essentially sheltered by the cavity a practical consequence is that we can establish for any given combination of downward seepage velocity cavity radius saturated hydraulic conductivity k1 and sorptive number whether or not seepage water will enter a cylindrical cavity

seepage into drifts and tunnels in unsaturated fractured rock 1 methods for obtaining estimates of seepage into drifts and tunnels excavated in unsaturated fractured rocks are of interest for engineering and environmental applications for uniform porous media a tunnel surface may present a capillary barrier promoting water diversion around the opening through the porous matrix hence reducing seepage into the opening the presence of fractures intersecting the opening complicates flow behavior and presents a challenge to seepage prediction we present a simple and physically based model for seepage estimation that preserves key physical processes associated with fracture flow while avoiding complexity of detailed fracture network characterization the processes of film and capillary driven flows are combined with a geometrically tractable representation of the dual continuum fractured rock with two disparate populations of matrix pores and fracture apertures the large disparity in capillary forces between matrix and fractures rules out matrix seepage based on philip s theory we obtain estimates of seepage fraction for a given percolation flux from consideration of the hydraulic conductivity of the fracture domain only similar to previous studies the new model shows existence of a percolation threshold for onset of seepage the new model also exhibits a steep increase in seepage with increase in percolation flux that reflects the role of fracture film flow in addition to consideration of physically based flow processes computations for the proposed analytical model can be performed with common spreadsheet software which is a distinct advantage over numerical equivalent porous media approaches that require a powerful computational environment excessive computation time and thorough characterization of the fracture domain

surface roughness on the greenland ice sheet from airborne laser altimetry high resolution airborne laser altimetry is used to determine the small scale surface relief in central greenland and estimate the contribution from spatial noise to stratigraphic records the standard deviation of the surface roughness is 1 6 cm water equivalent corresponding to a standard deviation of annual layer thickness of 2 3 cm we this estimate agrees with an independent assessment of the spatial variability 2 5 cm we based on nine shallow ice cores the agreement suggests that the statistical nature of the surface in central greenland remains unchanged throughout the year by conducting airborne altimetry around proposed drilling sites the expected noise level in the core can be evaluated and sites selected where this level is lowest

a western pacific oscillator paradigm for the el nino southern oscillation a data based hypothesis is presented on the mechanism of the el nino southern oscillation enso a major determinant of interannual global climate variability the hypothesis emphasizes the importance of off equator sea surface temperature and sea level pressure variations west of the dateline for initiating equatorial easterly winds over the far western pacific these winds compete with westerly winds over the equatorial central pacific enabling the coupled ocean atmosphere system to oscillate consistent with this hypothesis an analogical oscillator model is constructed that produces enso like oscillations the proposed mechanism differs from the delayed oscillator paradigm in that wave reflection at the western boundary is not a necessary condition for the coupled ocean atmosphere system to oscillate

shortwave feedbacks and el nino southern oscillation forced ocean and coupled ocean atmosphere experiments changes in tropical sea surface temperature sst can produce changes in cloudiness that modify incoming solar shortwave sw radiation which in turn affects sst the effects of this negative feedback on pacific interannual variability are examined in forced ocean model and hybrid coupled ocean atmosphere model simulations two empirical schemes are used to model the large scale low frequency response of surface sw to sst anomalies the first scheme attempts to account for the nonlocal nature of the atmospheric response to sst based on patterns of covariability analyzed through singular value decomposition in the observations the primary coupled mode of variability is composed of a sw anomaly in the central pacific that covaries with anomalous sst in the eastern pacific this is applied in the model as a nonlocal sw feedback the second scheme examines the effects of a purely local feedback with a spatially varying coefficient of magnitude chosen similar to the first scheme in almost all cases the second scheme behaved similarly to the first presumably because the correlation scale of sst is large enough for el nino southern oscillation enso dynamics that there is little sensitivity to the local approximation in the sw feedback in simulations forced by time series of observed wind stress the sw feedback induced very minor sst damping results from a simplified heat budget analysis showed that while the sw feedback increased the local heat flux damping on sst it also induced a mean shallowing of the mixed layer the resulting changes in both the local mean vertical temperature gradient and the zonal velocity response to the wind stress acted to oppose the local heat flux damping effects when observed sw anomalies were applied to forced simulations the simulated sst anomalies were modified as expected and agreement with observed sst improved in coupled simulations the sw feedbacks had greater impact than in the case of specified stress the main effects were to decrease the magnitude of the warm and cold sst anomalies in the central pacific while leaving the pattern and evolution of enso anomalies essentially unchanged elsewhere the sw feedbacks thus produce a modest improvement of the model enso sst pattern compared with observations although they tended to shorten the period of the model enso cycle overall the results suggest that large scale sw feedbacks are of quantitative importance to simulating some aspects of the enso cycle but are not critical to the overall occurrence of the phenomenon

dripping into unsaturated rock underground excavations literature review and geologic and hydrogeologic setting description a literature review of dripping in underground constructions in deep unsaturated geologic media was performed as part of a phased study the objective is to develop and test a formulation that can be used for studying unsaturated flow through rough multi segmented fractures with emphasis on predicting dripping initiation time geologic and hydrogeologic setting for the yucca mountain ym and its exploratory studies facility which is the site where the model will be tested are described

reply to comment by stefan finsterle on seepage into drifts and tunnels in unsaturated fractured rock keywords flow cavities reference epfl article 168697doi 10 1029 2006wr005008 record created on 2011 09 05 modified on 2016 08 09

experimental observation of the drift shadow effect using x ray absorption imaging summary x ray absorption imaging is used to test the concept of the drift shadow in geological samples the drift shadow model predicts that water travels around underground tunnels or drifts leaving areas of high saturation along the sides of the drift roof drip lobe and an area of low saturation beneath the drift drift shadow the drift shadow model could impact nuclear waste repositories designed with open tunnels such as yucca mountain by impacting the flux available to transport waste beneath the repository however without strong evidence for the drift shadow effect it is difficult to justify its inclusion in performance assessment calculations twelve experiments were run looking at the impact of fracture aperture inflow rate and geological heterogeneity on flow in the vicinity of a drift test cells of dimensions 10 1 cm 15 0 cm 2 5 cm were constructed using geological samples relevant to the yucca mountain project a semi circle of sample was removed from one side of the cell creating an artificial drift assuming symmetry an artificial fracture was created through the middle of each test cell parallel to the face of the sample potassium iodide tracer solution was dripped into the artificial fracture at the top of the sample x ray imaging allowed for visualization of the tracer flow paths over the duration of the experiment in addition samples were collected at the bottom of the flow cell to determine the lateral distribution of the outflow results showed distinct flow paths of tracer solution around the drift followed by shedding at the edge of the drift roof drip lobes as predicted by the drift shadow model in addition the distribution of discharge under the drift supported the drift shadow model with less discharge directly under the drift and greater discharge to the side of the drift in most experiments in the experiments with smaller fracture apertures and lower flow rates discharge beneath the drift was greater than expected than if flow was uniformly vertical indicating that under certain conditions some water could be carried back under the drift due to capillary action very low mass discharge into the drift generally less than 1 of the inflow mass along with the x ray images of the tracer flow paths provide evidence that the drift is acting as a capillary barrier x ray imaging also showed that heterogeneities have some control on the flow paths experimental results such as these coupled with numerical modeling that better quantifies the effects of heterogeneities and uncertainties in input parameters may allow performance assessment calculations to include the impact of the drift shadow on radionuclide transport if implemented such studies could lead to improved natural barrier performance in future calculations

surface airflow over east antarctica abstract surface winds over the antarctic interior occur mainly due to the strong radiational cooling of the ice slopes as a consequence such winds exhibit a high degree of persistence with a predominant direction closely related to the terrain orientation using detailed contour maps of the interior ice topography and representative values of the mean wintertime strength of the temperature inversion it is possible to infer the terrain induced accelerations a simple diagnostic equation system is formulated from which a time averaged surface airflow pattern of east antarctica is generated the results appear consistent with observations the occurrence of localized anomalously strong katabatic winds is explained as a result of typographically forced patterns of cold air convergence depicted in the airflow analysis

critical tunnel cavities for water exclusion in green and ampt and gardner soils 1 the limiting case of the analytical solution for the downward flow of water in a green and ampt soil around a tunnel cavity of critical shape resting on a permeable substratum at infinite depth gives the shape of the cavity and also the shape of the fringe surface of the surrounding tension saturated region as parabolas the cavity shape is compared with the parabolic shape obtained analytically for the water exclusion from a critical tunnel cavity in a gardner soil of infinite extent where parabolic isobaric surfaces surround the cavity the results are used to relate the parameters in the two models they also add confidence for their use in soil hydrology

estimation of the role of obstacles in the downslope soil flow with a simple erosion model the analytical solution and its approximation with the lattice boltzmann model abstract the description of a downslope soil particle flow is usually assumed to be uniform nevertheless the presence of obstacles like stones rock outcrops or plants hinders the uniformity of the flow culling in 1983 proposed an analytical solution for the advective dispersive flow of soil particles around circular and elliptical cross section obstacles in this paper the culling solution is extended using a more versatile numerical method based on the integration of the transport equations at the mesoscopic level the lattice boltzmann model lbm two lbms are used for the description of the flow components the first lbm simulates the advection component and the second one the diffusion component the distribution of soil or any tracer particles produced by the model is similar to the prediction of the analytical solution the lbm has a greater flexibility for the study of intricate geometries allowing more irregular boundary conditions closer to field situations the model has been applied to the analysis of the flow of soil or any tracer particles around several obstacles such as the trunks in a forest or a regular plantation

observations of 20 day period meridional current oscillations in the upper ocean along the pacific equator abstract prominent oscillations of the meridional current with a mean period of approximately 20 days have been observed in the upper ocean over several years from may 1979 to october 1985 using moored current measurements along the pacific equator at 95 110 124 140 w and 152 w as well as off but near the equator at 110 and 140 w the fluctuations are relatively narrowband 0 005 cpd in frequency a 95 statistically significant peak in power spectra of meridional current occurred at 110 124 and 140 w but not at 95 and 152 w where the spectral peaks were smaller the dominant wave period decreased by about 4 from 110 to 140 w maximum amplitude was measured at 124 w the amplitude above 80 m was maximum at the equator and decreased poleward from the equator at 15 m the annual averaged root mean square amplitude was about 20 5 cm s 1 and individual peak to trough values reached 150 cm s 1 the wave amplitude decreased with depth and the wave was essentially confined to the upper 80 m

monthly period oscillations in the pacific north equatorial countercurrent monthly period oscillations in temperature and velocity in the vicinity of the north equatorial countercurrent along 140 w are examined using moored time series data collected during 1988 1989 these oscillations which presumably derive their energy from instability of the large scale shear of the zonal equatorial current system are found to be energetic across a broad band of periods of about 15 50 days along 7 n wavelike motions at these periods propagate westward with a phase speed of about 30 40 cm s 1 and a zonal wavelength of 750 1150 km the oscillations are approximately in geostrophic balance with the thermal field with the velocity vector rotating anticyclonically around westward propagating high sea level centers zonal volume transport variations associated with these waves between 5 and 9 n at 20 180 m depth have a standard deviation of about 4 1 sv with peak to peak changes in some instances approaching 20 sv maximum temperature variance along 140 w occurs between 5 and 7 n at 100 150 m depth in a region of strong mean vertical and meridional temperature gradient associated with a thermocline sloping upward to the north at the surface maximum temperature variability occurs from 2 to 5 n in the vicinity of the strong sea surface temperature front north of the equator analysis of the upper ocean temperature balance at 7 n 140 w reveals that meridional advection is important both in the surface layer and in the thermocline vertical advection estimated using vertical velocity calculated from a simplified linear vorticity balance is also important in the thermocline where it contributes a variance comparable to that of meridional advection zonal advection is likely to be significant in the upper 80 m below which it is probably of secondary importance compared to meridional and vertical advection one consequence of advection in the temperature balance is that variance is shifted toward lower frequencies in temperature vis a vis velocity spectra this red shift may account for the apparent difference between periods for instability waves inferred from near equatorial meridional velocity spectra and slightly longer periods reported for oscillations of the sea surface temperature front north of the equator based on satellite imagery

pausing of the enso cycle a case study from 1998 to 2002 abstract the heat balance of the surface mixed layer is analyzed at the eastern equatorial pacific ocean 0 140 w in order to examine the transition from the 1998 la nina to the 2002 el nino the data used are observations from the tropical atmosphere ocean triangle trans ocean buoy network tao triton results show that interannual variation of eddy heat flux due to tropical instability waves slows the transition from la nina to el nino previous studies have described this slow transition as a pausing period of the enso cycle that is la nina lingers and el nino does not immediately appear despite a deepened thermocline heat balance analysis shows that the vertical heat advection anomaly and surface heat flux anomaly warm the mixed layer from 1999 to 2002 these warming anomalies cause the rise of the mixed layer temperature anomaly in the transition from la nina to el nino in contrast a cooling anomaly of the horizontal heat advection reduces the warming anomaly and slows down the transition fr