what kind of stratospheric sudden warming propagates to the troposphere 1 the factors affecting the downward propagation of stratospheric sudden warming ssw events to the troposphere are studied through composite analysis of 45 year reanalysis data from the european centre for medium range weather forecasts during the growth stage of ssw events that propagate into the troposphere exhibit enhanced upward flux of the wavenumber 2 wave while events that do not propagate downward display reduced wavenumber 2 flux in both events upward flux of the wavenumber 1 wave is enhanced but the enhancement is stronger in the non propagating event the composite for propagating events reveals a negative eurasian pattern of horizontal geopotential anomalies in the troposphere during the growth stage and a negative arctic oscillation pattern following the event while non propagating events are preceded by a positive eurasian pattern in both types of event the tropospheric anomalies are generated mainly by tropospheric planetary wave forcing prior to the emergence of ssw

characteristic patterns of variability of sea level pressure in the northern hemisphere abstract seasonal and annual mean sea level pressures for the northern hemisphere have been analyzed to determine the dominant modes of interannual and longer period variability using monthly sea level pressure analyses as revised by trenberth and paolino 1980 empirical orthogonal function eof analysis is used to reveal the modes which explain most of the variance for the period 1925 77 in winter kutzbach s 1970 eof 1 for january remains the dominant mode and a closely related pattern dominates all seasons and the annual means although there are differences in detail in each season the dominant mode is basically a high latitude zonal index type pattern with departures in pressure at high latitudes corresponding to anomalies of opposite sign in low latitudes eof 1 is linked to the north atlantic oscillation but the north south fluctuations in mass also occur in the pacific and to a lesser extent elsewhere time series associated with this pattern have highly significant spectral peaks at the

direct measurements of floodwater infiltration into shallow alluvial aquifers the relationship between floodwater infiltration and groundwater recharge of a shallow alluvial aquifer in a hyper arid desert was studied in the arava valley israel the study implemented an experimental system that simultaneously monitors all three hydrological domains controlling the recharge process 1 floodwater stages on land surface 2 water content variations in the deep vadose zone and 3 groundwater response to the infiltration this experimental system makes use of a new technique for installing flexible time domain reflectometry probes for continuous monitoring of the vadose zone moisture profiles water infiltration was monitored in controlled infiltration experiments and during a natural flood the monitoring setup allowed real time tracking of the wetting front propagation velocities and assessment of water fluxes through the vadose zone the results revealed a complex infiltration process that includes matrix and preferential flow together with lateral flow

geochemistry and geochemical modeling of unsaturated zone in a tropical region in urânia sao paulo state brazil summary the geochemistry of a thick unsaturated zone in a tropical region in ur nia sao paulo state brazil has been investigated the site was instrumented for pressure head measurements and pore water sampling above the water table at 9 5 m depth the composition of the solid phase was determined by x ray diffraction optical microscopy sem and microprobe and icp aes analyses of decomposed samples the unsaturated zone is composed mainly of clayey sand and can be subdivided into three zones a shallow zone down to depth of 2 m corresponding to the evaporation line an intermediate zone between 2 and 7 m where small wetting fronts dissipate and only longer recharge events are evidenced by changes of pressure head and a deep zone between 7 and 9 5 m where pressure heads are generally stable based on data collected during the recharge period in year 2000 the response time of water table to recharge event was of 3 months the solid phase is in an advanced stage of weathering and quartz and kaolinite are principal minerals pore water has a low mineralization and can be characterized as ca hco 3 type with high concentrations of nitrate at shallow depth the main factors that have an impact on pore water chemistry are 1 atmospheric input and nitrate pollution due to human activities 2 evaporation down to a depth of 2 m 3 plant respiration down to a depth of 7 m 4 dissolution of primary silicate minerals such as feldspars and the formation of secondary minerals like kaolinite and 5 adsorption and cation exchange analysis of the solid phase suggests that ferric oxides and hydroxides provide the principal adsorption surfaces inverse geochemical modeling yielded non unique results and both dissolution precipitation of silicates plus cation exchange and dissolution precipitation of amorphous silica plus cation exchange were able to match changes of water chemistry along the presumed flow path

the life cycle of the northern hemisphere sudden stratospheric warmings motivated by recent evidence of strong stratospheric tropospheric coupling during the northern hemisphere winter this study examines the evolution of the atmospheric flow and wave fluxes at levels throughout the stratosphere and troposphere during the composite life cycle of a sudden stratospheric warming the composite comprises 39 major and minor warming events using 44 years of ncep ncar reanalysis data the incipient stage of the life cycle is characterized by preconditioning of the stratospheric zonal flow and anomalous quasistationary wavenumber 1 forcing in both the stratosphere and troposphere as the life cycle intensifies planetary wave driving gives rise to weakening of the stratospheric polar vortex and downward propagation of the attendant easterly wind and positive temperature anomalies when these anomalies reach the tropopause the life cycle is marked by momentum flux and mean meridional circulation anomalies at tropospheric levels that are consistent with the negative phase of the northern hemisphere annular mode the anomalous momentum fluxes are largest over the atlantic half of the hemisphere and are associated primarily with waves of wavenumber 3 and higher

recharge of aquifers by flood events in an arid region the process of aquifer recharge by flood events in an arid region was investigated as applied to the hazeva formation the karkom graben the wadi paran watershed israel the hydrological model was established as a complex system with due regard for groundwater and transmission losses of surface runoff it was based on a previously outlined hydrogeological model of the karkom graben and a model of transmission losses in arid watercourses under conditions of data deficiency proceeding from calculation of groundwater balances the contribution of surface runoff as a decisive balance component was confirmed the main characteristics of aquifer regimes such as changes in storage volume and groundwater level as well as lateral flow were all found to be dependent upon the net extraction rate i e pumpage discounting replenishment by flood events analysis and physical interpretation of model parameters enabled assessment of the influence of groundwater extraction on aquifer recharge this became apparent as increasing absorption capacity and recharge availability of the aquifer as a result of the groundwater abstraction copyright 2002 john wiley sons ltd

characterising deep vadose zone water movement and solute transport under typical irrigated cropland in the north china plain understanding the dynamics and mechanisms of soil water movement and solute transport is essential for accurately estimating recharge rates and evaluating the impacts of agricultural activities on groundwater resources in a thick vadose zone 0 15 m under irrigated cropland in the piedmont region of the north china plain soil water content matric potential and solute concentrations were measured based on these data the dynamics of soil water and solutes were analysed to investigate the mechanisms of soil water and solute transport the study showed that the 0 15 m vadose zone can be divided into three layers an infiltration and evaporation layer 0 2 m an unsteady infiltration layer 2 6 m and a quasi steady infiltration layer 6 15 m the chloride nitrate and sulphate concentrations all showed greater variations in the upper soil layer 0 1 m compared to values in the deep vadose zone below 2 m the average concentrations of these three anions in the deep vadose zone varied insignificantly with depth and approached values of 125 242 and 116 mg l the accumulated chloride sulphate and nitrate was 2179 113 1760 383 and 4074 421 kg ha respectively the soil water potential and solute concentrations indicated that uniform flow and preferential flow both occurred in the deep vadose zone and uniform flow was the dominant mechanism of soil water movement in this study the piston like flow velocity of solute transport was 1 14 m yr and the average value of calculated leached nitrate nitrogen was 107 kg ha yr below the root zone the results can be used to better understand recharge processes and improve groundwater resources management this article is protected by copyright all rights reserved

teleconnections in the geopotential height field during the northern hemisphere winter abstract contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on earth referred to as teleconnections in this paper are studied in an attempt to identify and document recurrent spatial patterns which might be indicative of standing oscillations in the planetary waves during the northern hemisphere winter with time scales on the order of a month or longer a review of existing literature on the subject reveals the existence of at least four such patterns the north atlantic and north pacific oscillations identified by walker and bliss 1932 a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes first noted by lorenz 1951 and what we will refer to as the pacific north american pattern which has been known to operational long range forecasters in this country since the 1950 s a data set consisting of nmc monthly mean sea level pressure and 500 mb height analyses for a 15 year period is used as a basis fo

evaluating the recharge mechanism of the lower kuiseb dune area using mixing cell modeling and residence time data summary a mixing cell approach was extended by a method incorporating mean cell residence times derived from 14c to further constrain and validate the modeling results this extended approach was used to model the groundwater system of the lower kuiseb dune area in namibia the kuiseb river is a 560 km long ephemeral river that crosses the namib desert from east to west transmission losses from the riverbed during flood events are an important source of groundwater recharge to the underlying aquifer system the lower kuiseb area is located in a hyper arid region with annual precipitation less than 25 mm yr hydrochemical data from 13 wells in the area were used in the mixing cell model mcm end members were identified as sources for the groundwater found in the lower kuiseb including inflow from the crystalline basement plateau north of the kuiseb as well as floodwater from the kuiseb river a conceptual groundwater recharge and flow model was developed and then inverse mixing cell modeling was carried out using hydrochemical tracers this approach generally allows for several possible solutions after completing the inverse modeling a forward mixing cell model was developed by varying the mean residence time of each cell to fit calculated 14c data to the measured 14c data this new approach joins previously developed methods solely based on conservative mixing or residence time optimization based on the results of the model the fraction of floodwater in different sections of the lower kuiseb groundwater systems was calculated ranging from 61 to 98 2 in addition to floodwater groundwater inflow from the crystalline basement north of the kuiseb was shown to contribute to the lower kuiseb aquifer accounting for salinization during periods without flooding

qualitative and quantitative evaluation of the influence of anthropic pressure on subsidence in a sedimentary basin near rome this paper presents the results of analyses measuring variations in anthropic pressure and the influence of anthropic pressure on the variations in subsidence rates from 1954 to 2005 in the tivoli guidonia area located to the east of rome italy in the last 60 years this area underwent exceptional demographic growth as well as an increase in the quarrying and hydrothermal industries the calculation of the increase in anthropic pressure was based on two factors the expansion of built up areas and the increase in quarrying photogrammetric techniques permitted a multi temporal analysis of aerial photos taken in 1954 1985 1993 1998 and 2005 the aim of this analysis was to estimate the increase in both urban surface area and travertine quarrying non conventional techniques such as the reconstruction of photograms using photo retouching software allowed for the use of aerial photos from 1954 these photos were fundamental for establishing a medium term evaluation of anthropic activity in the area the results of the photogrammetric analysis were compared to the phases of acceleration and stabilization in subsidence phenomena deduced from a radar interferometry study published by the italian ministry of the environment this comparison showed a close relationship between the rise and temporary halt of anthropic development and the rise and fall of subsidence rates furthermore data on the distribution of private wells in the study area variations in the groundwater table level and the precipitation regime were analyzed but although helpful in defining the geological context and considerable transformations of the territory they were considered as qualitative data due to the lack of systematic measures or an unclear relationship to the variations in subsidence rate despite the difficulties involved in evaluating both the amount of anthropic pressure and the role of different human activities on environmental change it was possible to estimate the variations in anthropic pressure and their influence on potentially dangerous geological processes

review and comparison of models for describing non equilibrium and preferential flow and transport in the vadose zone abstract in this paper we review various approaches for modeling preferential and non equilibrium flow and transport in the vadose zone existing approaches differ in terms of their underlying assumptions and complexity they range from relatively simplistic models to more complex physically based dual porosity dual permeability and multi region type models a relatively simple dual porosity flow model results when the richards equation is combined with composite double hump type equations for the hydraulic properties to account for both soil textural matrix and soil structural fractures macropores peds effects on flow the simplest non equilibrium flow model a single porosity model which distinguishes between actual and equilibrium water contents is based on a formulation by ross and smettem soil sci soc am j 64 2000 1926 that requires only one additional parameter to account for non equilibrium a more complex dual porosity mobile immobile water flow model results when the richards or kinematic wave equations are used for flow in the fractures and immobile water is assumed to exist in the matrix we also discuss various dual permeability models including the formulation of gerke and van genuchten water resour res 29 1993a 305 and the kinematic wave approach as used in the macro model of jarvis technical description and sample simulations department of soil science swedish university of agricultural science uppsala sweden 1994 51 both of these models invoke terms accounting for the exchange of water and solutes between the matrix and the fractures advantages and disadvantages of the different models are discussed and the need for inter code comparison is stressed especially against field data that are sufficiently comprehensive to allow calibration validation of the more complex models and to distinguish between alternative modeling concepts several examples and comparisons of equilibrium and various non equilibrium flow and transport models are also provided

the statistical connection between tropospheric and stratospheric circulation of the northern hemisphere in winter abstract the associated anomaly patterns of the stratospheric geopotential height field and the tropospheric geopetential and temperature height fields of the northern hemisphere are determined applying the canonical correlation analysis with this linear multivariate technique the coupled modes of variability of lime series of two fields are isolated in the space of empirical orthogonal functions the one dataset is the 50 hpa geopotential height field the other set consists of different height fields of the tropospheric pressure levels 200 500 700 and 850 hpa and the temperature of the 850 hpa pressure level for the winter months december january february two natural coupled modes a barotropic and a baroclinic one of linear relationship between stratospheric and tropospheric circulation are found the baroclinic mode describes a connection between the strength of the stratospheric cyclonic winter vortex and the tropospheric circulation over the north atlantic the corresponding temperature

characterizing stratospheric polar vortex variability with computer vision techniques computer vision techniques are used to characterize the arctic stratospheric polar vortex in 38 years of reanalysis data such techniques are typically applied to analyses of digital images but they represent powerful tools that are more widely applicable basic techniques and considerations for geophysical applications are outlined herein segmentation descriptive and tracking algorithms are combined in the characterization and analysis of vortex evolution using algorithms for region tracking cave art package which was developed to comprehensively describe dynamical and geometrical evolution of polar vortices cave art can characterize and track multiple vortex regions through time providing an extensive suite of region moments and edge diagnostics for each cave art is valuable for identifying vortex splitting events including but not limited to previously cataloged vortex split sudden stratospheric warmings an algorithm for identifying such events detects 52 potential events between 1980 2017 of these 38 are subjectively classified as distinct split like events the algorithm based on cave art is also compared with moments based methods previously used to detect split events furthermore vortex edge averaged windspeeds from cave art are used to define extreme weak and strong polar vortex events over multiple vertical levels this allows characterization of their occurrence frequencies and extents in time and altitude weak and strong events show distinct signatures in cave art diagnostics in contrast to weak events strong vortices are more cylindrical and pole centered and less filamented than the climatological state these results from cave art exemplify the value of computer vision techniques for analysis of geophysical phenomena

role of medium scale waves on the southern annular mode 1 we examined the role of short period waves on the southern annular mode sam through analysis of 6 hourly reanalysis data of the european centre for medium range weather forecasts ecmwf era interim we focused on medium scale waves those with periods shorter than about 6 days although medium scale waves generally have much smaller amplitudes than synoptic waves they have a much higher correlation with the sam index as a result about one third of wave driven meridional circulation and zonal wind acceleration associated with the sam is generated by medium scale waves their contribution is large in spite of their climatologically smaller amplitude moreover two thirds of sam related meridional circulation and zonal wind acceleration comes from waves of periods shorter than about 3 days our analysis demonstrates a positive feedback between westerly winds around 60 s and amplification of synoptic and medium scale waves which sustains hemispheric sam variability for the feedback process between zonal wind and waves baroclinic conversion is a key process to both synoptic waves and medium scale waves our analysis also shows that wave forcings calculated from daily data explain only half of the total forcings and that the contribution from short period waves is very significant around 50 s

glacier change in western north america influences on hydrology geomorphic hazards and water quality the glaciers of western canada and the conterminous united states have dominantly retreated since the end of the little ice age lia in the nineteenth century although average rates of retreat varied from strong in the first half of the twentieth century with glaciers stabilizing or even advancing until 1980 and then resuming consistent recession this retreat has been accompanied by statistically detectable declines in late summer streamflow from glacier fed catchments over much of the study area although there is some geographical variation over recent decades glaciers in northwest bc and southwest yukon have lost mass dominantly by thinning with relatively low rates of terminal retreat and glacier fed streams in that region have experienced increasing flows in many valleys glacier retreat has produced geomorphic hazards including outburst floods from moraine dammed lakes mass failures from oversteepened valley walls and debris flows generated on moraines in addition to these hydrologic and geomorphic changes evidence is presented that glacier retreat will result in higher stream temperatures possibly transient increases in suspended sediment fluxes and concentrations and changes in water chemistry with climate projected to continue warming over the twenty first century current trends in hydrology geomorphology and water quality should continue with a range of implications for water resources availability and management and hydroecology particularly for cool and cold water species such as salmonids copyright 2008 john wiley sons ltd

estimating groundwater recharge using deep vadose zone data under typical irrigated cropland in the piedmont region of the north china plain summary groundwater recharge can be accurately estimated by understanding the soil water flow process in the deep vadose zone in this study soil water content and soil matric potential were measured in situ in the deep vadose zone 8 m under typical irrigated cropland in the piedmont region of the north china plain and were used to analyze the soil water dynamics and calibrate a transient matric flow model using the calibrated model the long period average groundwater recharge was estimated and the influences of the lower boundary depth and time scale length of study period on the recharge were assessed the study showed that the response time of the water table with a buried depth of 42 m to water input might be no more than 1 year because the velocity of the wetting front could be as high as 0 13 m day below the root zone however the lag time could be more than 15 years because of the slower velocity of the soil water displacement the variation in the recharge flux with depth was significant over shorter time scales therefore for more representative estimated recharge with a maximum deviation less than 20 from the 38 year mean value research should be conducted over a long period 12 years however the average annual recharge showed almost no change with depth at the 38 year scale and a depth of 2 m below ground surface could be used as an interface for estimating recharge at the 38 year scale the simulated annual recharge at a depth of 2 m ranged from 59 mm to 635 mm with a mean value of 200 mm the variation in water input precipitation and irrigation was the main reason for the variation in annual recharge at the depth of 2 m this approach improves our understanding of the recharge process in the deep vadose zone in this region and the results of this work could aid development of effective groundwater resources management

a major stratospheric sudden warming event in january 2009 abstract the major stratospheric sudden warming ssw event of january 2009 is analyzed using the japan meteorological agency jma climate data assimilation system jcdas this ssw event is characterized by the extraordinary predominance of the planetary scale wave of zonal wavenumber 2 wave 2 the total amount of the upward eliassen palm ep flux for wave 2 was the strongest since the winter of 1978 79 it is found that the remarkable development of the upper troposphere ridge over alaska played important roles in the ssw in january 2009 during the first development stage the ridge excited wave packets upward as well as eastward over around alaska the eastward propagating packets intensified a trough over eastern siberia which led to the development of the planetary wave over eastern siberia during the second development stage the results of this study indicate that the pronounced wave 2 pattern observed in the stratosphere was brought about by accumulative effects of rather localized propagati

water recharge and solute transport through the vadose zone of fractured chalk under desert conditions this study focuses on water flow and solute migration through unsaturated fractured chalk in an arid area the chalk underlies a major industrial complex in the northern negev desert where groundwater contamination has been observed four dry drilling holes were bored through the vadose zone core and auger samples collected at 30 to 50 cm intervals were used for chemical and isotopic analyses enabling the construction of the following profiles 1 a tritium profile to estimate the rate of water flow through the unsaturated zone 2 oxygen 18 and deuterium profiles to assess the evaporation of water at land surface before percolation and in the upper part of the vadose zone after infiltration and 3 chloride and bromide profiles as tracers for inert solutes and pollutants the tritium and bromide profiles showed the rate of infiltration through the unsaturated matrix to be very slow 1 6 11 cm yr the chemical and isotopic data from the core holes suggested that the pore water changes characteristics with depth close to land surface the pore water is strongly evaporated 18o 5 94 and highly concentrated 29 meq cl 100 g rock but changes gradually with depth to amore dilute concentration 4 meq cl 100 g rock and isotopically depleted composition 18o 4 4 closer to the isotopic composition of precipitation and groundwater nearby monitoring wells have shown anthropogenic contribution of heavy metals organic compounds and tritium nativ and nissim 1992 a conceptual model is proposed in which a small portion of the rainwater percolates downward through the matrix while a larger percentage of the percolating water moves through preferential pathways in fractures the water flowing through the fractures penetrates the matrix across the fracture walls where it increases the tritium concentrations depletes the stable isotopic composition and dilutes the salt concentrations the observed rapid downward migration of tritium and heavy metals through the profuse fractures makes the chalk inefficient as a hydrologic barrier

the connection between extreme stratospheric polar vortex events and tropospheric blockings the variations of tropospheric blockings and their connections with the stratospheric polar vortex during different stages of the life cycle of extreme stratospheric polar vortex events i e strong vortex sv events and weak vortex wv events are investigated the blocking frequency decreases over the euro atlantic sector and increases over the western north pacific during the onset and maturation stages of sv events there are more blocking days over the western north pacific and weakened upward planetary wave fluxes in the stratosphere during the maturation stage of shorter time scale sv events than during longer time scale sv events and the weakening of the upward planetary wave fluxes mainly results from the linear wave interference effect the blocking frequency is increased over the euro atlantic sector during the decline stage of sv events this increase is found to be related to the descending stratospheric zonal wind anomalies and the poleward displacement of the eddy driven jet stream which lasts for about 10 days and is associated with the descending positive stratospheric northern annular mode nam anomalies the increased blocking frequency leads to an enhancement of the planetary wave fluxes in the stratosphere via both the linear wave interference for shorter time scale sv events and nonlinear wave interference for longer time scale sv events effect the changes of the blocking frequency during the growth stage of wv events are almost opposite to those observed during the onset and maturation stages of sv events the blocking frequency decreases over the euro atlantic sector after the central dates of wv events which are related to the descending stratospheric zonal wind anomalies and the equatorward displacement of the eddy driven jet stream preceded by the descending negative stratospheric nam anomalies about 10 days we found that the nonlinear wave interference begins to make a considerable contribution to the weakening of the upward wave fluxes in the stratosphere after the central date of wv events and this is not emphasized in previous literature

spatial variability of sea level pressure and 500 mb height anomalies over the southern hemisphere abstract the spatial variability of mean sea level pressure slp and 500 mb height anomalies over the southern hemisphere during summer djf and winter jja is determined using eigenvector analysis based on daily synoptic maps from 1972 to 1979 the patterns of spatial distribution of pressure and height anomalies are further verified and examined by means of station data and the eigenvectors are compared between the seasons and to those found for the northern hemisphere the first eigenvector shows that midlatitude anomalies of slp and 500 mb height are of an opposite sign to those found over and around antarctica the pattern is highly barotropic and suggests strengthening and weakening of the zonal wind in alternating latitude belts the 500 mb height differences are calculated for five midlatitude to antarctic station pairs using data from the late 1950 s onward these latitudinal height differences are also used to describe the association between the hemispheric westerlies and the southern oscil

the interannual variability of the surface eddy kinetic energy in the labrador sea abstract the variability of the surface eddy kinetic energy eke in the labrador sea is investigated with a suite of numerical integrations using a regional ocean model simulations are performed over the period 1980 2001 and are compared to satellite observations over the last 9 years the surface eke pattern in the basin is dominated by a region along the west coast of greenland where eddies mainly anticyclonic are formed by instability of the main currents flowing over the continental slope consistent with previous idealized results here the interannual changes are linked to the shear of the incoming boundary current system imposed as boundary condition to the model domain the highly variable strength of the east greenland current at the northeast boundary derived from the simple ocean data assimilation soda reanalysis strongly influences the vortex formation in the center of the labrador sea where deep convection occurs a statistically significant portion of the modeled interannual surface eke variability is correlated with the local atmospheric forcing and both heat and wind fluxes play an important role and can be adopted as predictors at a lag of 2 3 months the arctic oscillation index can also be used as a remote indicator of the atmospheric fluxes but with lower skill than local measurements in contrast the north atlantic oscillation index does not correlate significantly with the surface eke at intraseasonal and interannual scales the analysis of altimeter data over the 1993 2001 supports the existence of this asymmetry between the regime locally forced by the atmosphere in the central basin and the regime remotely forced by the incoming boundary current along the west greenland coast those results have important implications for monitoring and predicting the surface eddy kinetic energy variability in the labrador sea

the amplification of height wave 1 in january 1979 a characteristic precondition for the major warming in february abstract the development in time and space of the planetary scale height waves 1 and 2 and of the mean zonal flow is described for the winter 1978 79 it is concluded that this winter supports earlier observational results the anomalous amplification of height wave 1 in the stratosphere concurrent with a distinct minimum of height wave 2 is a characteristic precondition for the development of a major warming if later the breakdown itself concurs with the development of height wave 2 the amplification of height wave 1 before is needed insofar as it changes the zonal flow i e displaces the stratospheric jet poleward to favor propagation of height wave 2

enso like interdecadal variability 1900 93 a number of recent studies have reported an enso like eof mode in the global sea surface temperature sst field whose time variability is marked by an abrupt change toward a warmer tropical eastern pacific and a colder extratropical central north pacific in 1976 77 the present study compares this pattern with the structure of the interannual variability associated with the enso cycle and documents its time history back to 1900 the analysis is primarily based on the leading eofs of the sst anomaly and anomaly deviation fields in various domains and the associated expansion coefficient or principal component time series which are used to construct global regression maps of sst sea level pressure slp and a number of related variables the use of anomaly deviations i e departures of local sst anomalies from the concurrent global mean sst anomaly reduces the influence of global mean sst trends upon the structure of the eofs and their expansion coefficient time series an important auxiliary time series used in this study is a southern oscillation index based on marine surface observations by means of several different analysis techniques the time variability of the leading eof of the global sst field is separated into two components one identified with the enso cycle related variability on the interannual timescale and the other a linearly independent residual comprising all the interdecadal variability in the record the two components exhibit rather similar spatial signatures in the global sst slp and wind stress fields the sst signature in the residual variability is less equatorially confined in the eastern pacific and it is relatively more prominent over the extratropical north pacific the corresponding slp signature is also stronger over the extratropical north pacific and its counterpart in the cold season 500 mb height field more closely resembles the pna pattern the amplitude time series of the enso like pattern in the residual variability reflects the above mentioned shift in 1976 77 as well as a number of other prominent features including a shift of opposite polarity during the 1940s

tropical upper tropospheric potential vorticity intrusions during sudden stratospheric warmings abstractthe intrusion of lower stratospheric extratropical potential vorticity into the tropical upper troposphere in the weeks surrounding the occurrence of sudden stratospheric warmings ssws is examined the analysis reveals that ssw related pv intrusions are significantly stronger penetrate more deeply into the tropics and exhibit distinct geographic distributions compared to their climatological counterparts while climatological upper tropospheric and lower stratospheric utls pv intrusions are generally attributed to synoptic scale rossby wave breaking it is found that ssw related pv intrusions are governed by planetary scale wave disturbances that deform the extratropical meridional pv gradient maximum equatorward as these deformations unfold planetary scale wave breaking along the edge of the polar vortex extends deeply into the subtropical and tropical utls in addition the material pv deformations also reorganize the geographic structure of the utls waveguide which alters where synopti

transmission losses infiltration and groundwater recharge through ephemeral and intermittent streambeds a review of applied methods summary aquifer recharge through ephemeral streambeds is believed to be a major source of groundwater recharge in arid areas however comparatively few studies quantify this streamflow recharge this review synthesizes the available field based aquifer recharge literature from arid regions around the world seven methods for quantifying ephemeral and intermittent stream infiltration and aquifer recharge are reviewed controlled infiltration experiments monitoring changes in water content heat as a tracer of infiltration reach length water balances floodwave front tracking groundwater mounding and groundwater dating the pertinent temporal and spatial scales as well as the advantages and limitations of each method are illustrated with examples from the literature comparisons between the methods are used to highlight appropriate uses of each field method with emphasis on the advantages of using multiple methods within a study in order to avoid the potential drawbacks inherent in any single method research needs are identified including quantitative uncertainty analysis long term data collection and analysis understanding of the role of riparian vegetation and reconciliation of transmission losses and infiltration estimates with actual aquifer recharge

hidden carbon sink beneath desert for decades global carbon budget accounting has identified a missing or residual terrestrial sink i e carbon dioxide co2 released by anthropogenic activities does not match changes observed in the atmosphere and ocean we discovered a potentially large carbon sink in the most unlikely place on earth irrigated saline alkaline arid land when cultivating and irrigating arid saline lands in arid zones salts are leached downward simultaneously dissolved inorganic carbon is washed down into the huge saline aquifers underneath vast deserts forming a large carbon sink or pool this finding points to a direct rapid link between the biological and geochemical carbon cycles in arid lands which may alter the overall spatial pattern of the global carbon budget

differential compaction mechanism for earth fissures near casa grande arizona precise gravity measurements indicate that earth fissures or tension cracks caused by ground water withdrawal within a 10 km 2 area southeast of casa grande arizona are associated with relief on the buried interface between the alluvial aquifer and underlying bedrock all of the fissure zones which have a cumulative length of 8 7 km occur above either ridges or steps in the bedrock surface intersecting fissure zones overlie intersecting bedrock features and the angle of intersection of the zones accurately reflects the angle between the bedrock features these relations suggest that the fissures are forming in response to localized differential compaction caused by localized variations of aquifer system thickness topographic profiles across fissures on undisturbed desert floor confirm differential compaction proportional to the variations in aquifer thickness the occurrence of the fissures at points of maximum convex upward curvature in profiles of both the topographic and buried bedrock surfaces indicates that the fissures result from tensile strains caused by bending of the strata above the buried bedrock features in response to the differential compaction tensile strains at failure are estimated to range from 0 02 to 0 2 on the basis of modeling of the bending process

solute transport in the vadose zone and groundwater during flash floods events were investigated in the lower reach of the kuiseb river namibia and in controlled column experiments simultaneous measurements of water level and electrical conductivity of the ood water in the stream channel and in the groundwater together with variations in the vadose zone water content temperature and pressure proles allowed a detailed analysis of the various mechanisms governing solute transport in the subsurface during ash oods the results indicated that on the land surface ash oods emit at their wetting fronts instantaneous compression waves that propagate downward through the unsaturated zone to the water table these compression waves generate abrupt solute displacement events in the groundwater immediately after the arrival of the ood on the land surface long before deep percolation and groundwater recharge begin each ood event launches into the vadose zone a wetting front that propagates down through the vadose zone and recharges the groundwater upon arrival at the water table therst wetting front of each ood season leaches out soluble salts that have accumulated in the vadose zone during the dry season however water percolation through the unsaturated zone does not leach out the entire soluble salt capacity of the sediment even if percolation takes place under high water head ooding conditions for long periods the incomplete leaching of the unsaturated zone by the percolating water releases soluble salts into the groundwater during every recharge event as a result of the rise of the water table into the vadose zone this process results in a temporal increase of the groundwater electrical conductivity ec

processes governing natural land subsidence in the shallow coastal aquifer of the ravenna coast italy abstract we identified the processes governing natural land subsidence in a shallow coastal aquifer near ravenna north eastern italy by analysing the relationships among different data set time series water table level rainfall drainage sea level etc and establishing the correlations with vertical ground motion observed at a high resolution settlement gauge for the first time we establish the relationships between water table fluctuations and vertical displacement in a real field dataset as well as demonstrate the important contribution of primary consolidation and aquifer stratigraphy to natural land subsidence our study highlights the presence of three deformation components related to different processes controlling land subsidence elastic delayed elastic and irreversible plastic components the elastic and delayed elastic components are closely related to water table fluctuations that change the effective stress in two portions of the coastal aquifer at a daily in the sandy unconfined portion and seasonal time scales in the finely layered clay rich semiconfined prodelta portion respectively the irreversible component represents the trend in the land subsidence time series and is due to primary consolidation pore water pressure dissipation of the fine grained prodelta levels above where the settlement gauge is located the amplitudes of the elastic component can be up to 0 2 0 3 mm whereas the amplitude of the delayed elastic component reaches 0 89 mm the primary consolidation rate of deformation is 0 9 mm year and constrains the likely age of prodelta sediments deposition to 1300 2800 years before present the average degree of consolidation for the prodelta sediments varies from 0 8 to 0 99 according to consolidation coefficients varying from 1 58 to 3 15 m2 year which are accepted values in the literature our analysis point out that primary consolidation in the shallow fine grained sediments of the shallow coastal aquifer is still ongoing the delayed elastic land subsidence rate has similar magnitude to that due to primary consolidation and is likely connected to poroelastic effects in the prodelta sequence following seasonal variations in water table our findings are important for planning land subsidence management and monitoring strategies especially where the surface aquifer structure is heterogeneous due to different depositional settings

effect of stratospheric sudden warming and vortex intensification on the tropospheric climate 1 the effect of stratospheric sudden warming ssw and vortex intensification vi on the tropospheric climate is examined through composite analysis of the observational data specifically examined in the present study is the eulerian meridional circulations associated with ssw and vi it is found that prominent signal in the troposphere tends to appear associated with the occurrence of ssw and vi the patterns created are very similar between ssw and vi except for the polarity in the high latitude region the pattern similar to the arctic oscillation ao is created before and after the occurrence of ssw and vi with changing polarities in the tropics convection tends to enhance in the southern hemisphere northern hemisphere tropics after the occurrence of ssw vi these signals are created through three prominent cells of the anomalous eulerian meridional circulation that extends from polar cap to the tropical southern hemisphere the mechanism for the formation of the cells associated with ssw and vi is also discussed

instrumental monitoring of the subsidence due to groundwater withdrawal in the city of murcia spain this paper presents the results of investigations of the generalized subsidence occurring in and around the city of murcia spain based on this research this is the first integrated investigation of its type performed in spain the phenomenon of ground consolidation in the city of murcia leads to the appearance of severe cracking and settlement in buildings subsidence is the result of two factors on the one hand the nature of the ground in this area as it is made of recent deposits of clay and soft limes filled in with clay lime backfills in the top layers on the other hand the increase in groundwater withdrawal during the 1992 95 drought led to a decrease in the water level of a magnitude never before recorded in the city the risk prevention management suggested convenience of the installation of a measurement network to study and follow the phenomena of the subsidence to quantify it and to calibrate this theoretical model this network is composed of extensometers and piezometers the best devices to measure moderate ground movements which is the case of murcia the first phase phase i of this study of ground settlement in the metropolitan area of murcia involved the installation of a network with 22 extensometers and taking the first measurement series in a second phase phase ii during a period of 4 years measurements with extensometers were performed to make the analysis and calibration of the theoretical model experience and data analysis showed the convenience of installation of new control points with an incremental extensometer and a piezometer in close position with the aim of precisely correlating piezometric levels with the observed subsidence the third phase phase iii started in 2007 a new control technique based on radar interferometry insar is being employed to provide information about subsidence in areas not previously monitored

visco elasto plastic compaction of aquitards due to groundwater withdrawal in shanghai china long term excessive groundwater withdrawal can cause aquifer systems to compact and land subsidence ensues the compaction of aquitards lags behind the change of groundwater level in adjacent aquifers which is attributed to low hydraulic conductivity and great creep deformation of aquitards under the condition of groundwater withdrawal aquitard clays may compact visco elastically elasto plastically or visco elasto plastically depending on the effective stress history they have experienced laboratory data manifest that aquitard clays have a similar constitutive relationship to aquifer sands therefore the double yielding visco elasto plastic mechanical model proposed for aquifer sands is applicable to aquitard clays a fully coupled one dimensional visco elasto plastic compaction model is constructed for aquitards to predict their compaction by integrating the double yielding mechanical model with the flow governing equation of groundwater the comprehensive compaction model not only makes the groundwater flow and soil deformation coupled but also takes into account the complex deformation characteristics of aquitard units under long term groundwater withdrawal such as creep and plastic deformation under reloading

long term coordinated changes in the convective activity of the north atlantic the north atlantic is a peculiarly convective ocean the convective renewal of intermediate and deep waters in the labrador sea and greenland iceland sea both contribute significantly to the production and export of north atlantic deep water thus helping to drive the global thermohaline circulation while the formation and spreading of 18 degree water at shallow to intermediate depths off the us eastern seaboard is a major element in the circulation and hydrographic character of the west atlantic for as long as time series of adequate precision have been available to us it has been apparent that the intensity of convection at each of these sites and the hydrographic character of their products have been subject to major interannual change as shown by aagaard 1968 clarke et al 1990 and meincke et al 1992 for the greenland sea in the ows bravo record from the labrador sea eg lazier 1980 et seq and at the panulirus hydrostation s site in the northern sargasso off bermuda eg jenkins 1982 talley and raymer 1982 this paper reviews the recent history of these changes showing that the major convective centres of the greenland and labrador seas are currently at opposite convective extrema in our postwar record with vertical exchange at the former site limited to 1000 m or so but with labrador sea convection reaching deeper than previously observed to over 2300 m as a result greenland sea deep water has become progressively warmer and more saline since the early 70 s due to increased horizontal exchange with the arctic ocean through fram strait while the labrador sea water has become progressively colder and fresher over the same period through increased vertical exchange most recently convection has become deep enough there to reach into the more saline nadw which underlies it so that cooler but now saltier and denser lsw has resulted

aura microwave limb sounder observations of the northern annular mode from the mesosphere to the upper troposphere 1 vertical structure and evolution of the wintertime northern hemisphere annular mode nam the first empirical orthogonal function eof of geopotential height anomalies are constructed from the 2005 2009 aura microwave limb sounder mls measurements in the entire middle atmosphere between 316 hpa 9 km and 0 001 hpa 90 km this is the first report of nam structure extending into the mesosphere the mode appears to be robust and it accounts for up to 70 of middle atmospheric variance before decreasing in the upper mesosphere the vertical connection of the nam modes suggests strong dynamic coupling between the mesosphere and stratosphere time evolution of the nam suggests that the significant nam anomalies typically appear first in the mesosphere and progress downward nam patterns derived from mls observations are consistent with those derived from long term reanalysis below the middle stratosphere the nam indexes show the mesospheric cooling signals during the major stratospheric sudden warmings ssws in 2006 and 2009

stratosphere troposphere evolution during polar vortex intensification stratosphere troposphere evolution associated with polar vortex intensification vi events is examined during the northern hemisphere winter the incipient stage of a vi event is marked by anomalously low wave activity and descending westerly anomalies over the depth of the polar stratosphere reduced poleward planetary wave heat flux occurs as the circumpolar wind becomes strongest and pressure anomalies penetrate toward the surface descending pressure patterns project strongly onto the positive state of the northern hemisphere annular mode nam concurrently anomalous poleward momentum flux develops in the upper troposphere and the related tropospheric mean meridional circulation maintains the attendant wind and temperature anomalies against surface drag the gross behavior of the composite vi event is similar in shape but opposite in sign to that associated with sudden stratospheric warming events ssws however the descent of the wind and temperature anomalies over the vi life cycle is generally weaker and slower than its ssw counterpart preceding the maximum vortex anomaly similarly after the maximum wind event the weakening of the winds is faster than the strengthening of the winds after a ssw this is because stratospheric wind reduction anomalies are produced by wave driving which can be rapid and increases in wind speed are associated with the radiative cooling of the polar cap which happens more gradually while the contributions of the anomalous momentum fluxes by the quasi stationary and synoptic eddies are similar to ssws the much stronger anomalous momentum flux observed during vi can be attributed to the larger role of eddies with timescales between 15 and 40 days and of wave number 2 scale notable differences between vi and ssw appear in the tropical region in particular anomalous vortex intensification seems to occur preferentially during la nina conditions

influence of volcanic eruptions on the troposphere through stratospheric dynamical processes in the northern hemisphere winter it has been suggested that the zonal mean stratospheric zonal wind anomalies can propagate downward into the troposphere producing considerable changes on the other hand volcanic aerosols are thought to produce a stronger polar vortex in the winter stratosphere if these suggestions are correct the influence of volcanic eruptions can be expected to produce changes in the northern hemisphere winter troposphere through stratospheric process in the present study this idea is examined by analyzing changes in the january circulation after three recent volcanic eruptions regional features of observed changes in tropospheric temperatures due to volcanic eruptions can be explained by the changes in the propagation of stationary waves associated with dipole type anomalies in the zonal mean zonal winds which are similar to those observed in a previous work on the influence of polar night jet

the arctic oscillation signature in the wintertime geopotential height and temperature fields the leading empirical orthogonal function of the wintertime sea level pressure field is more strongly coupled to surface air temperature fluctuations over the eurasian continent than the north atlantic oscillation nao it resembles the nao in many respects but its primary center of action covers more of the arctic giving it a more zonally symmetric appearance coupled to strong fluctuations at the 50 hpa level on the intraseasonal interannual and interdecadal time scales this arctic oscillation ao can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft it is proposed that the zonally asymmetric surface air temperature and mid tropospheric circulation anomalies observed in association with the ao may be secondary baroclinic features induced by the land sea contrasts the same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature sea level pressure and 50 hpa height over the past 30 years parts of eurasia have warmed by as much as several k sea level pressure over parts of the arctic has fallen by 4 hpa and the core of the lower stratospheric polar vortex has cooled by several k these trends can be interpreted as the development of a systematic bias in one of the atmosphere s dominant naturally occurring modes of variability

insar derived digital elevation models for terrain change analysis of earthquake triggered flow like landslides based on alos palsar imagery earthquakes can directly trigger multiple simultaneous slope failures in mountainous regions among these slope failures flow like landslides with high velocities and long run outs can result in damage that is more destructive than other types of landslides timely and accurate recognition of the locations and magnitudes of flow like landslides is essential for post disaster relief synthetic aperture radar sar sensors are suitable for deformation monitoring because of their capability to operate at day or night and in all weather conditions interferometric synthetic aperture radar insar is an advanced technique that extracts three dimensional terrain and changes information from the radar images at a regional scale the focus of this study is the donghekou landslide debris flow that was triggered by the 2008 wenchuan earthquake alos palsar remote satellite images were interpreted by insar to generate digital surface elevation models a comparison of data from a typical insar configuration with field survey data proves that the former is an effective method for rapidly detecting flow like landslides in a mountainous area the comparison also shows that the accuracy of the results is closely related to the correlation between the satellite radar images used and further that the study accuracy would improve with the inclusion of better correlation in this way representations of pre and post landslide terrains could be generated for use in numerical simulations the insar method has particular significance for areas without terrain data prior to slope failure and can provide basic data for landslide hazard assessments

impact of switching crop type on water and solute fluxes in deep vadose zone switching crop type and consequently changing irrigation and fertilization regimes lead to alterations in deep percolation and solute concentrations of pore water herein observations from the deep vadose zone and model simulations demonstrate the changes in water chloride and nitrate fluxes under a commercial greenhouse following the change from tomato to lettuce cropping the site located above a phreatic aquifer was monitored for 5 years a vadose zone monitoring system was implemented under the greenhouse and provided continuous data on both temporal variations in water content and chemical composition of the pore water at multiple depths in the deep vadose zone up to 20 m following crop switching a significant reduction in chloride concentration and dramatic increase in nitrate were observed across the unsaturated zone the changes in chemical composition of the vadose zone pore water appeared as sequential breakthroughs across the unsaturated zone initiating at land surface and propagating down toward the water table today 3 years after switching the crops penetration of the impact exceeds 10 m depth variations in the isotopic composition of nitrate 18o and 15n in water samples obtained from the entire vadose zone clearly support a fast leaching process and mobilization of solutes across the unsaturated zone following the change in crop type water flow and chloride transport models were calibrated to observations acquired during an enhanced infiltration experiment forward simulation runs were performed with the calibrated models constrained to tomato and lettuce cultivation regimes as surface boundary conditions predicted chloride and nitrate concentrations were in agreement with the observed concentrations the simulated water drainage and nitrogen leaching implied that the observed changes are an outcome of recommended agricultural management practices

provenance of terrigenous detritus of the surface sediments in the bering and chukchi seas as derived from sr and nd isotopes implications for recent climate change in the arctic regions abstract strontium and nd isotope analysis of the detrital fractions extracted from the marginal sea sediments in the arctic was applied to examine regional and temporal changes in the inflow and transportation of terrigenous material in the chukchi and bering seas over the past 100 years regional distributions of the sr and nd isotopes of the surface sediments show higher sr isotope ratios and lower nd isotope ratios in the chukchi sea 87 sr 86 sr 0 7106 0 7150 e nd 10 1 to 8 3 and lower sr isotope ratios and higher nd isotope ratios in the eastern bering sea 0 7045 0 7109 8 6 to 3 0 in addition the rb and sr contents and ree patterns e g eu eu changed noticeably across the bering strait these variations mean that the sediments in the bering and chukchi seas have clearly distinct sources the terrigenous detritus in the chukchi sea is mainly derived from northeastern siberia 87 sr 86 sr 0 711 e nd 9 and bering strait inflow essentially from the yukon river and additionally from the mackenzie river basin including the canadian shield 0 732 0 734 14 the detritus in the eastern bering sea mainly consists of two components the continental material from the yukon river basin mainly underlain by mesozoic and paleozoic rocks in the alaskan mainland 0 708 0 709 9 to 8 and the aleutian arc volcanics 0 703 6 to 10 transported northward by the alaska coastal and bering shelf waters the eastern bering sediments over the past 100 years show slight variations of the sr isotope ratio and relatively wide variations of the nd isotope ratio and the variations and trends of the time series of the northeastern bering sea in the sr nd isotope diagram are probably controlled by changes in the grain size of the detritus from the yukon river basin some of the e nd time series show periodic fluctuations correlating with the annual mean surface air temperature sat for the arctic the e nd value is low in the high sat period and high in the low sat period in the warm period the yukon river was likely to supply a higher amount of the fine grain material with a relatively low e nd value such as surficial overburden probably because partial melting of continental glaciers and permafrosts in the alaskan mainland increased more detailed analysis with high time resolution is needed to clearly understand the effects the sat have on the arctic continental and marine environments