a general rule for synoptic eddy feedback onto low frequency flow in this study scale interaction between synoptic eddies and low frequency flow is investigated it is demonstrated here that there is a general rule the left hand rule that describes synoptic eddy feedback onto low frequency flow the rule is that low frequency anomalies systematically stir and deform the transient eddies in such a way that the irrotational eddy vorticity fluxes are directed preferentially about 90 toward the left hand side of the low frequency flow thus this eddy feedback plays a positive role in maintaining and prolonging low frequency flow under the stormy atmosphere similarly we show that the irrotational eddy temperature and moisture fluxes are also directed preferentially about 90 toward the left hand side of the low frequency flow in the northern hemisphere the eddy temperature fluxes and their vertical structure play a positive role in reinforcing the low frequency flow in the low levels the moisture fluxes play a role in enhancing low frequency flow by providing eddy induced moisture convergence and divergence

evaluation of treated and un treated nubia sandstone using ultrasonic as a non destructive technique deterioration factors both exogenous and endogenous are major sources of damaging monumental stones in egypt in the current study the change state of one of the major egyptian stones nubia sandstone is investigated and evaluated before and after consolidation by the use of wave velocity as a new method for detecting its elasticity modulus wave velocity propagation vp is one of the most important and effective methods for estimating the durability of monumental stones without using any other harmful method as a compressive strength this technique is usually used for a number of purposes the first of which is the qualification of masonry building through its morphology and detection of internal defects e g voids and cracks the second is the examination of the changes of material physical properties and the control conservation procedures third it is used with some samples of nubia sandstone for a laboratory test the study concludes that the durability of samples increases due to the increase of material compacting as a direct result of using consolidant materials using the vp as a non destructive technique in examining monumental materials gives the same results of other harmful techniques

solutions of the inherent problem of the equivalence in direct current resistivity and electromagnetic methods through global optimization and joint inversion by successive refinement of model space the problem of equivalence in direct current dc resistivity and electromagnetic methods for a thin resistive and conducting layer is well known attempts have been made in the past to resolve this problem through joint inversion however equivalence still remains an unresolved problem in the present study an effort is made to reduce non uniqueness due to equivalence using global optimization and joint inversion by successive refinement of the model space a number of solutions derived for dc resistivity data using very fast simulated annealing global inversion that fits the observations equally well follow the equivalence principle and show a definite trend for a thin conductive layer the quotient between resistivity and thickness is constant while for a resistive one the product between these magnitudes is constant three approaches to obtain very fast simulated annealing solutions are tested in the first one layer resistivities and thicknesses are optimized in a linear domain in the second layer resistivities are optimized in the logarithmic domain and thicknesses in the linear domain lastly both layer resistivities and thicknesses are optimized in the logarithmic domain only model data from the mean models corresponding to very fast simulated annealing solutions obtained for approach three always fit the observations the mean model defined by multiple very fast simulated annealing solutions shows extremely large uncertainty almost 100 in the final solution after inversion of individual dc resistivity or electromagnetic em data sets uncertainty associated with the intermediate resistive and conducting layers after global optimization and joint inversion is still large in order to reduce the large uncertainty associated with the intermediate layer global optimization is performed over several iterations by reducing and redefining the search limits of model parameters according to the uncertainty in the solution the new minimum and maximum limits are obtained from the uncertainty in the previous iteration though the misfit error reduces in the solution after successive refinement of the model space in individual inversion it is observed that the mean model drifts away from the actual model however successive refinement of the model space using global optimization and joint inversion reduces uncertainty to a very low level in 4 5 iterations this approach works very well in resolving the problem of equivalence for resistive as well as for conducting layers the efficacy of the approach has been demonstrated using dc resistivity and em data however it can be applied to any geophysical data to solve the inherent ambiguities in the interpretations

time domain electromagnetic imaging of a clayey confining bed in a brackish environment a case study in the kairouan plain aquifer kelbia salt lake tunisia the semi arid plio quaternary aquifer of the kairouan plain is located in the central part of tunisia in this region the main form of human activity is extensive agriculture the few lithological logs in this area indicate that the aquifer is divided into two groundwater reservoirs separated by a confining clay layer in the shallower groundwater reservoir the electrical conductivity of the water is close to 1 200 ms m that is 3 to 4 times higher than that of the deeper aquifer which is currently used for irrigation recently an increase in salinity has been observed which is producing significant difficulties with irrigation in order to determine the geometry of the confining clay layer and assess the potential connectivity between both reservoirs time domain electromagnetic tdem and vertical electrical soundings surveys were carried out in the extremely conductive environment electrical resistivities 10 m of the sebkha kelbia the tdem survey produced the first geophysical map of this near surface aquifer system

layered and laterally constrained 2d inversion of resistivity data in a sedimentary environment quasi layered models often can represent the actual geology more accurately than smooth minimum structure models we present a 2d inversion scheme with lateral constraints and sharp boundaries lci for continuous resistivity data all data and models are inverted as one system producing layered solutions with laterally smooth transitions the models are regularized through lateral constraints that tie interface depths or thicknesses and resistivities of adjacent layers a priori information used to resolve ambiguities and to add for example geological information can be added at any point of the profile and migrates through the lateral constraints to parameters at adjacent sites similarly information from areas with well resolved parameters migrates through the constraints to help resolve areas with poorly constrained parameters the estimated model is complemented by a full sensitivity analysis of the model parameters supporting quantitative evaluation of the inversion result a simple synthetic model proves the need for a quasilayered 2d inversion when compared with a traditional 2d minimum structure inversion a 2d minimum structure inversion produces models with spatially smooth resistivity transitions making identification of layer boundaries difficult a continuous vertical electrical sounding field example from sweden with a depression in the depth to bedrock supports the conclusions drawn from the synthetic example a till layer on top of the bedrock hidden in the traditional inversion result is identified using the 2d lci scheme furthermore the depth to the bedrock surface is easily identified for most of the profile with the 2d lci model which is not the case with the model from the traditional minimumstructure inversion

multi model changes in el nino teleconnections over north america in a future warmer climate previous studies with single models have suggested that el nino teleconnections over north america could be different in a future warmer climate due to factors involving changes of el nino event amplitude and or changes in the midlatitude base state circulation here we analyze a six member multi model ensemble three models with increasing future el nino amplitude and three models with decreasing future el nino amplitude to determine characteristics and possible changes to el nino teleconnections during northern winter over the north pacific and north america in a future warmer climate compared to observed el nino events all the models qualitatively produce general features of the observed teleconnection pattern over the north pacific and north america with an anomalously deepened aleutian low a ridge over western north america and anomalous low pressure over the southeastern united states however associated with systematic errors in the location of sea surface temperature and convective heating anomalies in the central and western equatorial pacific the models anomaly patterns are shifted to the west the anomalous low pressure center in the north pacific is weaker and shifted somewhat south compared to the observations for future el nino events two different stabilization experiments are analyzed one with co2 held constant at year 2100 concentrations in the sres a1b scenario roughly doubled present day co2 and another with co2 concentrations held constant at 4xco2 consistent with the earlier single model results the future el nino teleconnections are changed in the models with a weakened as well as an eastward and northward shifted anomalous low in the north pacific this is associated with weakened anomalous warming over northern north america strengthened cooling over southern north america and precipitation increases in the pacific northwest in future events compared to present day el nino event teleconnections these changes are consistent with the altered base state upper tropospheric circulation with a wave 5 pattern noted in previous studies that is shown here to be consistent across all the models whether there are projected future increases or decreases in el nino amplitude the future teleconnection changes are most consistent with this anomalous wave 5 pattern in the models with future increases of el nino amplitude but less so for the models with future decreases of el nino amplitude

geophysical surveys for identifying saline groundwater in the semi arid region of the central altiplano bolivia in the central part of the bolivian altiplano the shallow groundwater presents electrical conductivities ranging from 0 1 to 20 ms cm in order to study the origin of this salinity pattern a good knowledge is required of the geometry of the aquifer at depth in this study geophysics has been used to complement the sparse data available from drill holes one hundred time domain electromagnetic tdem soundings were carried out over an area of 1750 km2 about 20 geological logs were available close to some of the tdem soundings three intermediate results were obtained from the combined data i the relationship between the electrical conductivity of the groundwater and the formation resistivity ii geoelectrical cross sections and iii geoelectrical maps at various depths the limited data set shows a relationship between resistivity and the nature of the rock from the cross sections a conductive substratum with a resistivity of less than 1 m was identified at most of the sites at depths ranging from 50 to 350 m this substratum could be a clay rich formation containing brines using derived relationships maps of the nature of the formation sandy intermediate and clayey sediments were established at depths of 10 and 50 m discrimination between sand and clays was impossible where groundwater conductivity is high 3 ms cm in the central part of the area where the groundwater conductivity is low sandy sediments are likely to be present from the surface to a depth of more than 200 m clayey sediments are more likely to be present in the south east and probably constitute a hydraulic barrier to groundwater flow in conclusion the study demonstrates the efficiency of the tdem sounding method to map conductive zones copyright 2001 john wiley sons ltd

teleconnective response of the pacific north american region atmosphere to large central equatorial pacific sst anomalies abstract a prominent year round ensemble response to a global sea surface temperature sst anomaly field fixed to that for january 1992 near the peak of a major warm el nino southern oscillation episode was observed in a 20 yr integration of the general circulation model used for operational seasonal prediction by the u s national weather service this motivated a detailed observational reassessment of the teleconnections between strong sst anomalies in the central equatorial pacific ocean and pacific north america region 700 hpa heights and u s surface temperatures and precipitation the approach used consisted of formation of monthly mean composites formed separately from cases in which the sst anomaly in a key area of the central equatorial pacific ocean was either large and positive or large and negative extensive permutation tests were conducted to test null hypotheses of no signal in these composites the results provided a substantial case for the presence of teleconnections to either the pos

spatial delineation of groundwater salinity using deep time domain electromagnetic geophysical measurements a feasibility study 1 the objective of this study was to delineate the spatial distribution of fresh brackish and saline groundwater bodies as well as brine beneath the judea desert israel we used the deep time domain electromagnetic tdem geophysical system cycle 5m which provides the maximum exploration capability to depths 1 5 2 km below land surface the study was conducted at 21 locations at the desert plateau where fresh groundwater flows through the upper aquifers from the replenishment area at the judea mountains toward the dead sea springs in deeper aquifers brackish and saline groundwater bodies exist which originated from lakes and lagoons that existed at the dead sea rift valley during the pleistocene and pliocene respectively it was found that within carbonate formations fresh groundwater c 103 ppm total dissolved solids tds is characterized by a resistivity of more than 15 m brackish groundwater 103 c 104 ppm tds is characterized by 5 15 m saline groundwater 104 c 105 ppm tds is characterized by 0 5 5 m and brine 105 c ppm tds is characterized by less than 0 5 m

quasi 2d block inversion of large scale surface nuclear magnetic resonance profile data using a laterally constrained model abstractthe water content of underground structures can be imaged using surface nuclear magnetic resonance nmr in one dimension two dimensions or recently three dimensions the maximum efficiency can be obtained with a coincident loop configuration in a large scale area although the resolution is limited we have developed a quasi 2d block inversion to characterize a horizontal continuous underground aquifer using a laterally constrained model to improve the resolution of thin aquifers and deep aquifers through the simulation of flat surface and irregular surface models a horizontally layered aquifer with continuously variable water content and t2 can be imaged through quasi 2d block inversion which is more optimized than the traditional 1d block or 1d or 2d smooth inversion methods finally using a series of profile data obtained from surface nmr field measurements in mongolia we determine that quasi 2d block inversion based on a laterally constrained model can significantly improve the disco

seismic investigations of buried tunnel valleys on and offshore denmark tunnel valleys on and offshore denmark have been investigated based on a database of 1000 km two dimensional 2d onshore seismic data 5600 km 2d offshore seismic data and 1200 km2 three dimensional 3d offshore seismic data from the 2d data we identified 216 onshore and 674 offshore seismic tunnel valley intersections and 55 individual valleys were identified from three 3d surveys the majority of the valleys have depths ranging from 50 to 200 m and widths between 500 and 1500 m up to seven generations of tunnel valleys were identified indicating repeated erosion and deposition within the study area the valleys were most likely formed by subglacial meltwater erosion during the last three glaciations statistical analyses conducted on the data show that there are no significant differences between the onshore and offshore valleys with respect to their depth and shape they share morphological and structural characteristics the onshore seismic data have been analysed in conjunction with lithological information from boreholes the analyses show that tunnel valley bottoms terminate equally commonly in substrates dominated by clay and sand and that the valley shapes are similar for the two substrates the geological society of london 2012

diverse influences of enso on the east asian western pacific winter climate tied to different enso properties in cmip5 models the influence of el nino southern oscillation enso on the east asian western pacific eawp climate in boreal winter is investigated in the phase 5 of the coupled model intercomparison project cmip5 model results and then compared to that in the phase 3 cmip3 results in particular the role played by the differences among models in enso properties including the amplitude and longitudinal extension of enso s sea surface temperature sst pattern is analyzed results show that an eastward shrinking of enso s sst pattern leads to quite weak circulation and climatic responses over the eawp regions in the models on the contrary a westward expansion of the sst pattern shifts the anomalous walker circulation too far west the resultant precipitation anomalies and lower tropospheric atmospheric rossby wave responses both extend unrealistically into the indian ocean and the hemispheric asymmetry of the rossby wave response is missing all these features lead to unrealistic climatic impacts of ensoover the eawp regions in contrasttothe abovetwocases areasonablelongitudinalextensionof enso s sst pattern corresponds to better enso teleconnections over the eawp regions nevertheless the atmospheric responses over the western pacific are still located farther west than observed implying a common bias of cmip5 models in this case a larger amplitude of enso variability to some extent helps to reduce model biases and facilitate better climatic responses to enso in the eawp regions compared with cmip3 models cmip5 models perform better in representing enso s impacts on the east asian winter climate

indian ocean capacitor effect on indo western pacific climate during the summer following el nino significant climate anomalies persist through the summer june august after el nino dissipates in spring over the equatorial pacific they include the tropical indian ocean tio sea surface temperature sst warming increased tropical tropospheric temperature an anomalous anticyclone over the subtropical northwest pacific and increased mei yu baiu rainfall over east asia the cause of these lingering el nino effects during summer is investigated using observations and an atmospheric general circulation model gcm the results herein indicate that the tio warming acts like a capacitor anchoring atmospheric anomalies over the indo western pacific oceans it causes tropospheric temperature to increase by a moist adiabatic adjustment in deep convection emanating a baroclinic kelvin wave into the pacific in the northwest pacific this equatorial kelvin wave induces northeasterly surface wind anomalies and the resultant divergence in the subtropics triggers suppressed convection and the anomalous anticyclone the gcm results support this kelvin wave induced ekman divergence mechanism in response to a prescribed sst increase over the tio the model simulates the kelvin wave with low pressure on the equator as well as suppressed convection and the anomalous anticyclone over the subtropical northwest pacific an additional experiment further indicates that the north indian ocean warming is most important for the kelvin wave and northwest pacific anticyclone a result corroborated by observations these results have important implications for the predictability of indo western pacific summer climate the spatial distribution and magnitude of the tio warming rather than simply whether there is an el nino in the preceding winter affect summer climate anomalies over the indo western pacific and east asia

insights on the structural control of a neogene forearc basin in northern chile a geophysical approach abstract the comprehensive study of intramountain basins located in the coastal cordillera of the continental emergent andean forearc in northern chile enables the better understanding of the nature and evolution of the upper crustal deformation during the neogene and quaternary a case study is the extensive extensional half graben alto hospicio basin the basin is cut by the coastal cliff which exposes the deformed neogene basin fill also exposed are several structural systems some of which affect quaternary surfaces the results of the integrated geophysical surveys electromagnetic transient and gravity allow us to fully constrain the geometry of the alto hospicio basin and the lithological relationship between the subsurface geological units the structural geology analysis assesses the deformation regimes affecting the faults present in the basin and surrounding area altogether evidence a change in the deformation regime from an ew extensional deformation during the miocene pliocene to a ns compression in the quaternary as is presented in this study we suggest this deformation change is related to a small change in the convergence vector orientation during the pliocene

fast approximate 1d modelling and inversion of transient electromagnetic data a novel fast and approximate forward modelling routine for time domain electromagnetic responses is presented it is based on the separation of the forward problem into a configuration independent part mapping conductivity as a function of depth onto apparent conductivity as a function of time and a configuration dependent part i e the half space step response the response of a layered model is then found as the half space response for a half space conductivity equal to the apparent conductivity the mapping is ten times faster than traditional accurate forward modelling routines and through stochastic modelling it is found that the standard deviation of the modelling error is 0 7 the forward mapping lends itself to integration in a modern state of the art inversion formulation in exactly the same way as traditionally computed responses and a field example is included where inversion results using the approximate forward response are compared with those of an accurate forward response for helicopterborne transient electromagnetic data in addition to being used in its own right in inversion of transient data the speed and accuracy of the approximate inversion mean that it is well suited for quality control and fast turnaround data delivery of survey results to a client it can also be used in hybrid inversion formulations by supplying initial iterations and high quality derivatives in an inversion based on accurate forward modelling

comparing electromagnetic and seismic geophysical methods estimating the depth to water in geologically simple and complex arid environments abstract an integrated electromagnetic em and seismic geophysical study was performed to evaluate non invasive approaches to estimate depth to shallow groundwater i e

detecting unfrozen sediments below thermokarst lakes with surface nuclear magnetic resonance 1 a talik is a layer or body of unfrozen ground that occurs in permafrost due to an anomaly in thermal hydrological or hydrochemical conditions information about talik geometry is important for understanding regional surface water and groundwater interactions as well as sublacustrine methane production in thermokarst lakes due to the direct measurement of unfrozen water content surface nuclear magnetic resonance nmr is a promising geophysical method for noninvasively estimating talik dimensions we made surface nmr measurements on thermokarst lakes and terrestrial permafrost near fairbanks alaska and confirmed our results using limited direct measurements at an 8 m deep lake we observed thaw bulb at least 22 m below the surface at a 1 4 m deep lake we detected a talik extending between 5 and 6 m below the surface our study demonstrates the value that surface nmr may have in the cryosphere for studies of thermokarst lake hydrology and their related role in the carbon cycle

barotropic models of the extratropical response to el nino abstract a series of linear and nonlinear barotropic models are used to interpret the extratropical response to el niflo equatorial surface temperatures as simulated by an atmospheric general circulation model gcm the divergence time mean vorticity tendency due to transients and the zonal mean tlow are specified from the gcm and the deviation of the streamfunction from its zonal mean at an upper tropospheric level is predicted nonlinearsteady state models suggest that the extratropical wave train is primarily forced from the central rather than the western pacific and that subtropical divergence anomalies are of more importance than tropical anomalies these nonlinear solutions can be reproduced with little loss in accuracy by linearizing about the zonally asymmetric climatological flow if one linearizes about the zonally symmetric flow the part of the solution forced from thewestern pacific deteriorates significantly the solution in the tropics and subtropics also deteriorates if advection of v

role of the enso indian ocean coupling on enso variability in a coupled gcm warming are only confined to the io and it has little impact on the tropical pacific during the boreal winter when the el nino is in its mature phase the anomalous warming extends eastward to cover the entire tropical io and the anomalous easterlies extend into the western pacific wp the anom alous easterlies in the wp generate oceanic upwelling kelvin waves which propagate eastward and accelerate the decay of the warm sst in the eastern pacific as a result the el nino is rapidly terminated and a la nina develops within one year from the el nino mature phase they concluded that the interaction between enso and the io may generate a biennial tendency for enso 4 the samples used for the composite analysis by kk06 are rather limited due to the relatively short length of the observational data in this study we intended to analyze a longer 200 yr data set obtained from the simulation of a sintex f scale interaction experiment frcgc cou pled gcm in order to verify the enso io feedback hypoth esis itturnsoutthatthefeedbackprocessbetweenensoand the io is quite plausible not only from observations but also from the state of the art coupled gcm

a moist linear baroclinic model coupled dynamical convective response to el nino a newly developed linear baroclinic model lbm and its application to the tropical enso teleconnection is described the model based on primitive equations linearized about the observed zonally varying basic state in northern winter involves linear schemes for the cumulus convection and surface sensible and latent heat fluxes referred to as the moist lbm this enables us to solve a steady state response of the coupled dynamical convective system to a given sst anomaly which is fairly different from the conventional dry lbm linear representation of the convection is acceptable for a realistic range of sst anomalies reproducing well the rossby wave train computed in the conventional lbm forced by a tropical heating the moist lbm is used to examine the formation mechanisms of an anomalous low level anticyclone near

relative roles of equatorial central pacific and western north pacific precipitation anomalies in enso teleconnection over the north pacific it is shown here that the teleconnections of el nino southern oscillation enso are contributed by two anomalous precipitation forcings in the equatorial central pacific cp 160 e 120 w 5 s 5 n and western north pacific wnp 110 e 150 e 0 n 20 n the positive cp precipitation anomalies induce a prevailing cyclonic flow over the north pacific 120 e 110 w 20 n 70 n whereas the negative wnp precipitation forcing tends to induce anticyclonic anomalies over the kuroshio extension region and north pacific it is demonstrated that the equatorial cp and wnp precipitation anomalies play relative roles in generating atmospheric teleconnections over the north pacific which can be determined by the competing responses to the cp and wnp precipitation anomalies the reconstructed teleconnection patterns based on only the two tropical forcings capture the majority of the subseasonal evolution of the enso teleconnection in addition we find that the diversity of inter enso events in the atmospheric teleconnection can be better explained by considering the relative roles of the cp and wnp precipitation anomalies

application of transient electromagnetic and audio magnetotelluric methods for imaging the monte real aquifer in portugal fifty transient electromagnetic tem and 15 audio magnetotelluric amt soundings were carried out in the west central part of portugal over an area of approximately 40 km2 to characterize the geological formations associated with the monte real aquifer in order to 1 assess the spatial extent of the aquifer 2 detect the zones of higher water productivity and 3 evaluate the aquifer salinization risk the dimensionality and strike direction of the amt profiles were studied using phase tensor analysis and the amt data was inverted using a two dimensional 2d nonlinear conjugate gradient algorithm in addition the tem soundings were inverted using a one dimensional 1d levenberg marquardt technique in order to obtain 1d layered earth resistivity models the tem results reveal that the aquifer is not uniform in the study area a more resistive zone is evident in the north and northeast of the investigated area where we expect to have higher productivity on the other hand the amt models suggest that the aquifer basement is probably located at a depth of more than 800 m based on the results of this investigation no traces of saltwater intrusion were found for the monte real aquifer therefore we assume that the risk of saltwater intrusion is small in the study area

interactive feedback between enso and the indian ocean abstract a feedback process of the indian ocean sst on enso is investigated by using observed data and atmospheric gcm it is suggested that warming in the indian ocean produces an easterly wind stress anomaly over indonesia and the western edge of the pacific during the mature phase of el nino the anomalous easterly wind in the western pacific during el nino helps a rapid termination of el nino and a fast transition to la nina by generating upwelling kelvin waves thus warming in the indian ocean which is a part of the el nino signal operates as a negative feedback mechanism to enso this indian ocean feedback appears to operate mostly for relatively strong el ninos and results in a la nina one year after the mature phase of the el nino this 1 yr period of phase transition implies a possible role of indian ocean enso coupling in the biennial tendency of the enso atmospheric gcm experiments show that indian ocean sst forcing is mostly responsible for the easterly wind anomalies in the western pacific

parameter estimation and fault detection by three component seismic and geoelectrical surveys in a coal mine three component seismic and geoelectrical in mine surveys were carried out in lyukobanya colliery near miskolc hungary to determine the in situ petrophysical parameter distributions and to detect inhomogeneities in the coal seam the seismic measurements comprise an underground vertical seismic profile using body waves and an in seam seismic amplitude depth distribution and transmission survey using channel waves the geoelectrical measurements are based on the drift and seam sounding method interval traveltime amplitude multiple filter and polarization analysis methods are applied to the seismic data they lead to a five layer model for the strata including the coal seam the coal seam and two underlying beds act as a seismic waveguide the layer sequence supports the propagation of both normal and leaky mode channel waves of the love and rayleigh type a calculation of the total reflected energy for each interface using knott s energy coefficients shows that the velocity ranges of high reflection energy and of normal and leaky mode wavegroups coincide the excitation of wavegroups strongly depends on the seismic source a simultaneous inversion of a geoelectrical drift and seam sounding survey prevents misinterpretations of the seismic data by clearly identifying the low velocity coal seam as a high resistivity bed calculations of dispersion and sounding curves improve the resolution of the slowness and resistivity in each layer both diminished amplitudes and distortions in the polarization of transmission seismo grams and decreasing resistivities in a geoelectrical pseudosection of the coal seam are related to an inhomogeneity a calculation of synthetic seismograms for love and rayleigh channel waves with the finite difference and the alekseev mikhailenko method agrees well with the field data for the main features i e particular arrivals in the wave train wavegroups velocities and symmetries or asymmetries this in mine experiment demonstrates that the simultaneous acquisition processing and interpretation of seismic and geoelectrical data improve the lithological interpretation of petrophysical parameter distributions coal seam inhomogeneities can also be detected more reliably by the two independent surveys than by one alone

optimized fast hankel transform filters in the linear digital filter theory for calculation of hankel transforms it is possible to find explicit series expansions for the filter coefficients a method is presented for optimizing the hankel filters calculated in this way for a certain desired accuracy of computation the sampling density and filter length are minimized by choosing the parameters determining the filter characteristics according to the analytical properties of the input function a new approach to the calculation of the filter coefficients has been developed for these optimized filters the length of the filters may be further reduced by introducing a shift in the sampling scheme

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

interactive feedback between enso and the indian ocean in an interactive ensemble coupled model an interactive feedback between enso and the indian ocean is investigated using a center for ocean land atmosphere studies cola interactive ensemble coupled model from a long term simulation of the coupled gcm it is shown that el nino events terminate relatively rapidly when the indian ocean sst is anomalously warm the anomalous indian ocean warming induces the anomalous easterlies over the western pacific by modulating the walker circulation in turn the anomalous easterlies generate oceanicupwelling kelvin waves over the western pacific which propagate eastward and accelerate the decay of the warm sst in the eastern pacific as a result el nino terminates relatively quickly and the phase transition from el nino to la nina progresses rapidly these interactive processes are consistent with those derived from the previous observational analyses

electromagnetic and geological transect across permafrost terrain mackenzie river delta canada the time domain electromagnetic tdem method provides a surface geophysical technique suitable for interpreting deep permafrost conditions this paper describes profiles collected in early spring in a transitional area of the mackenzie delta arctic canada with differing permafrost conditions and surficial geology these data augment previously published profiles and allow the construction of a 30 km long tdem transect from the holocene age mackenzie delta in the southwest to the pleistocene age tuktoyaktuk coastlands in the northeast the geoelectric section produced from the tdem data is interpreted in terms of permafrost distribution this interpretation provided a basis for inferring lithologic changes unconsolidated non ice bonded unfrozen sediment has resistivities less than 10 ohm m partially ice bonded sediment ranges in resistivity from 10 to 40 ohm m ice bonded frozen sediment has resistivities from 30 to 300 ohm m bedrock has low resistivities from 5 to 15 ohm m interpretation of the geoelectric section derived from both the shallow 500 m tdem data suggests that the main body of permafrost increases in thickness from 50 to 500 m over a few kilometers a horizontally persistent unfrozen zone talik is situated from 50 to 100 m in depth within the main body of permafrost ice bonding models derived from the tdem surveys provide constraints on the geologic history of the mackenzie delta

el nino east asian monsoon teleconnection and its diversity in cmip5 models in this study we assess the performance of state of the art coupled models in reproducing el nino diversity and its impacts on the east asian summer monsoon easm based on simulations taken from the coupled model intercomparison project phase 5 cmip5 all of the 17 models used in this study are identified to give reasonable eastern pacific ep el nino related sea surface temperature anomalies ssta and anomalous walker circulation compared with observations whereas one third of the models fail to reproduce the walker circulation anomalies for central pacific cp el nino in these models negative ssta over the eastern to central pacific are found to be too strong while positive ssta shift to the western pacific during cp el nino there is thus sinking rising motion over the central western part of the pacific basin implying westward displaced anomalous walker cells relative to the observed this results in simulated low level cyclonic flow and positive rainfall anomalies over the far western north pacific south china sea during and after the peak phase of cp el nino which are opposite to the observed anomalous climate state the other two thirds of models with realistic cp el nino related anomalous walker cell can better reproduce the corresponding wind circulation and rainfall anomalies over east asian ea region the contrasting cp el nino related teleconnection among models mainly arises from the different simulated cp el nino ssta which in turn determine the circulation anomalies through a gill type response further analyses reveal that in the mean state of models with erroneous teleconnection there exists a large cold sst bias over the eastern pacific the stronger walker circulation and possibly the stronger bjerknes feedback might be responsible for the overly negative ssta associated with cp el nino in the vicinity our results highlight the sensitivity of el nino ea climate linkage to the oceanic state in models especially for cp el nino events

how well do climate models simulate atmospheric teleconnctions over the north pacific and east asia associated with enso during the el nino and la nina mature phase atmospheric teleconnections over the north pacific and east asia vary considerably on sub seasonal time scales and are strongly phase locked to the sub seasonal evolution in this study we investigate how well climate models that participated in the coupled model intercomparison project phase 5 cmip5 simulate the sub seasonal evolution of teleconnections over the north pacific and east asia associated with el nino southern oscillation enso in the observations there is a prominent anticyclone anomaly over the kuroshio extension region i e kuroshio anticyclone which significantly affects east asian climate in the early winter november december of el nino years however in january the kuroshio anticyclone suddenly disappears and a cyclonic flow dominates over the north pacific it is found here that the cmip5 models simulate the overall extratropical teleconnection patterns but they fail to reproduce some of these sub seasonally varying features in atmospheric circulation for example the models tend to simulate a weaker kuroshio anticyclone in the early winter during el nino phases and fail to capture the abrupt decay of the kuroshio anticyclone in the late winter we demonstrate here that these systematic errors in enso teleconnection can be explained by systematic errors in tropical precipitation associated with enso that is negative precipitation anomalies over the western north pacific wnp are too weak in the models compared to that in the observations and their amplitude tends to be strengthened from december to the following january while they are weakened in the observations in addition analyses on the inter model diversity strongly support that relative magnitudes of wnp and central pacific precipitation anomalies are critical for determining sub seasonal evolution of enso teleconnections over the north pacific and east asia

inversion of band limited tem responses it is shown that the electromagnetic em spectrum is characterized by strong amplitude modulated transmitters operating in the target bandwidth of transient electromagnetic tem measurements as these transmitters cause significant noise in tem soundings it is mandatory to band limit the input signals to improve the signal to noise ratio and thereby the depth of exploration band limitation will distort the tem responses which leads to erroneous inversion results if the applied low pass filters are not accounted for in the inversion scheme we incorporate the low pass filters in the inversion scheme and test the inversion approach on theoretical and field data inversion of band limited theoretical responses results in recovery of erroneous resistivity models if the filters are not included in the inversion scheme by contrast inversion of band limited theoretical and field data for which the applied low pass filters are included in the inversion scheme leads to recovery of similar resistivity models independent of the applied cut off frequencies

combination mode dynamics of the anomalous northwest pacific anticyclone abstractnonlinear interactions between enso and the western pacific warm pool annual cycle generate an atmospheric combination mode c mode of wind variability the authors demonstrate that c mode dynamics are responsible for the development of an anomalous low level northwest pacific anticyclone nwp ac during el nino events the nwp ac is embedded in a large scale meridionally antisymmetric indo pacific atmospheric circulation response and has been shown to exhibit large impacts on precipitation in asia in contrast to previous studies the authors find the role of air sea coupling in the indian ocean and northwestern pacific only of secondary importance for the nwp ac genesis moreover the nwp ac is clearly marked in the frequency domain with near annual combination tones which have been overlooked in previous indo pacific climate studies furthermore the authors hypothesize a positive feedback loop involving the anomalous low level nwp ac through el nino and c mode interactions the development o

pacific east asian teleconnection how does enso affect east asian climate observational evidence is presented to show a teleconnection between the central pacific and east asia during the extreme phases of enso cycles this pacific east asian teleconnection is confined to the lower troposphere the key system that bridges the warm cold events in the eastern pacific and the weak strong east asian winter monsoons is an anomalous lower tropospheric anticyclone cyclone located in the western north pacific the western north pacific wind anomalies develop rapidly in late fall of the year when a strong warm or cold event matures the anomalies persist until the following spring or early summer causing anomalously wet dry conditions along the east asian polar front stretching from southern china northeastward to the east of japan kuroshio extension using atmospheric general circulation and intermediate models the authors show that the anomalous philippine sea anticyclone results from a rossby wave response to suppressed convective heating which is induced by both the in situ ocean surface cooling and the subsidence forced remotely by the central pacific warming the development of the anticyclone is nearly concurrent with the enhancement of the local sea surface cooling both the anticyclone and the cooling region propagate slowly eastward the development and persistence of the teleconnection is primarily attributed to a positive thermodynamic feedback between the anticyclone and the sea surface cooling in the presence of mean northeasterly trades the rapid establishment of the philippine sea wind and sst anomalies implies the occurrence of extratropical tropical interactions through cold surge induced exchanges of surface buoyancy flux the central pacific warming plays an essential role in the development of the western pacific cooling and the wind anomalies by setting up a favorable environment for the anticyclone sst interaction and midlatitude tropical interaction in the western north pacific

a survey of current trends in near surface electrical and electromagnetic methods electricalandelectromagnetice emmethodsfornearsurface investigations have undergone rapid improvements over the past few decades besides the traditional applications in groundwater investigations natural resource exploration and geological mapping a number of new applications have appeared these include hazardous waste characterizationstudies precision agricultureapplications archeological surveys and geotechnical investigations the inclusion of microprocessors in survey instruments development ofnewinterpretationalgorithms andeasyaccesstopowerful computers have supported innovation throughout the geophysical community and the e em community is no exception most notable are development of continuous measurement systems that generate large dense data sets efficiently these have contributed significantly to the usefulness of e em methods by allowing measurements over wide areas without sacrificing lateral resolution the availability of theseluxuriantdatasetsinturnspurreddevelopmentofinterpretation algorithms including laterally constrained 1d inversionaswellasinnovative2d and3d inversionmethods taken together these developments can be expected to improve the resolution and usefulness of e em methods and permit them to be applied economically the trend is clearly towarddensesurveyingoverlargerareas followedbyhighly automated post acquisition processing and interpretation to provide improved resolution of the shallow subsurface in a cost effectivemanner

joint inversion of aquifer test mrs and tem data this paper presents two methods for joint inversion of aquifer test data magnetic resonance sounding mrs data and transient electromagnetic data acquired from a multilayer hydrogeological system the link between the mrs model and the groundwater model is created by tying hydraulic conductivities k derived from mrs parameters to those of the groundwater model method 1 applies k estimated from mrs directly in the groundwater model during the inversion method 2 on the other hand uses the petrophysical relation as a regularization constraint that only enforces k estimated for the groundwater model to be equal to mrs derived k to the extent that data can be fitted both methodologies can jointly calibrate parameters pertaining to the individual models as well as a parameter pertaining to the petrophysical relation this allows the petrophysical relation to adapt to the local conditions during the inversion the methods are tested using a synthetic data set as well as a field data set in combination the two case studies show that the joint methods can constrain the inversion to achieve estimates of k decay times and water contents for a leaky confined aquifer system we show that the geophysical data can assist in determining otherwise insensitive k and vice versa based on our experiments and results we mainly advocate the future application of method 2 since this seems to produce the most reliable results has a faster inversion runtime and is applicable also for linking k of 3 d groundwater flow models to multiple mrs soundings

role of off equatorial sst in el nino teleconnection to east asia during el nino decaying spring observational evidences are presented to show significant differences in pacific east asian pea teleconnections during the el nino decaying period depending on the northern off equatorial sea surface temperature sst conditions on the basis of the northern off equatorial central pacific sst nocp index we separate el nino events into two groups distinctive differences are observed between the two groups not only in tropical features but also in mid latitude teleconnections in particular the nocp index is closely related to the strength of the local feedback between the sst anomalies and the anticyclonic flow over the western north pacific wnp during the ensuing spring of the el nino events because the wnp anticyclone tends to persist until boreal spring in the case of negative nocp diabatic cooling due to the reduced precipitation over the wnp induces anticyclonic flow over the kuroshio extension region via a rossby wave response which leads to warm and wet conditions over east asia however because the wnp anticyclone decays early in the case of positive nocp cyclonic circulation exists over the north pacific which leads to cold and dry conditions over east asia consequently the maintenance of the wnp anticyclone during the el nino decaying period may explain the discrepancy in the pea teleconnections in various types of el nino accordingly the nocp index could be a possible predictor for boreal spring climate conditions over east asia

joint inversion of geophysical data summary by jointly inverting several different kinds of geophysical measurements at a site we avoid some of the ambiguity inherent in the individual methods we show how this can be done for the combination of dc resistivity and magnetotelluric measurements on a layered medium by considering a simple 3 layer model the combination resolves the resistivity of the thin resistive second layer even though neither of the two methods can do so alone the method is then applied to field data from a shallow sedimentary basin a blind zone occurs beneath a thick near surface conductive shale by a study of the eigenvalue structure of the model it can be seen that resolution in this zone would be slightly enhanced by higher frequency magnetotelluric data but additional dc data at larger spacing would yield no improvement

airborne and ground geophysical mapping of coastal clays in eastern friesland germany coastal areas such as the german bight are at risk from storms and rising sea level that may affect the hydrogeologic setting because knowledge of the distribution of clayey sediments is important for understanding the current status of this dynamic setting the german federal institute for geosciences and natural resources bgr has focused on geophysical research projects on the north sea coast applying airborne and ground geophysics the airborne system operated by bgr was used to survey a 20 by 31 km large coastal area in eastern friesland germany including the islands of langeoog and spiekeroog helicopter borne electromagnetic hem data were collected at six frequencies in addition the leibniz institute for applied geophysics commissioned a skytem survey covering a 2 km wide north south strip on the island of langeoog ground geophysical methods such as transient electromagnetics tem and magnetic resonance soundings mrs were used to investigate the hydrogeologic setting in greater detail onshore the airborne electromagnetic results clearly outlined a complex electrically conductive pattern occurring at a shallow depth comparison with borehole results provided by the state authority for mining energy and geology confirmed that these conductors were caused by clayey material particularly down to an approximate 20 m depth this pattern continues offshore and it is likely that the saltwater is linked to stripes of clayey sediments and the fresh groundwater flows out to the wadden sea in between on the islands the hem results revealed the freshwater lenses and showed some indications for clay layers within these freshwater lenses the application of tem and mrs helped to distinguish lithology from salinity and confirmed the existence of these clay layers we demonstrated the usefulness of combining the spatial airborne data with geophysical and borehole data available at sparsely distributed sites on the ground to investigate hydrogeologic settings

combining tem resistivity joint inversion and magnetic data for groundwater exploration application to the northeastern part of greater cairo egypt this paper presents the combination of two complementary methods magnetic and joint inversion of resistivity tem data as an effective approach to characterize groundwater reservoirs twenty stations of transient electromagnetic tem and vertical electrical soundings ves were measured and interpreted using a joint inversion technique to evaluate the subsurface low resistivity zones connected to the groundwater reservoir a complementary survey including 871 land magnetic stations was carried out at the same area to detect the upper surface of the basaltic sheet which represents the bottom of the miocene aquifer in the study area the geological log from one borehole drilled in the zone was used to partially calibrate the calculated models the results revealed that the study area consists of five different geological units with ages ranging from paleogene oligocene to quaternary the methodology provides good results at a very low cost when compared with drilling boreholes

piecewise 1d laterally constrained inversion of resistivity data in a sedimentary environment layered models are often capable of representing the actual geology more accurately than smooth minimum structure models furthermore interval thicknesses and resistivities are often the parameters to which non geophysicist experts can relate and base decisions on when using them in waste site remediation groundwater modelling and physical planning we present a laterally constrained inversion scheme for continuous resistivity data based on a layered earth model 1d all 1d data sets and models are inverted as one system producing layered sections with lateral smooth transitions the models are regularized through laterally equal constraints that tie interface depths and resistivities of adjacent layers prior information e g originating from electric logs migrates through the lateral constraints to the adjacent models making resolution of equivalences possible to some extent information from areas with well resolved parameters will migrate through the constraints in a similar way to help resolve the poorly constrained parameters the estimated model is complemented by a full sensitivity analysis of the model parameters supporting quantitative evaluation of the inversion result examples from synthetic 2d models show that the model recognition of a sublayered 2d wedge model is improved using the laterally constrained inversion approach when compared with a section of combined 1d models and when compared with a 2d minimum structure inversion case histories with data from two different continuous dc systems support the conclusions drawn from the synthetic example

improvement in mrs parameter estimation by joint and laterally constrained inversion of mrs and tem data we developed a new scheme for joint and laterally constrained inversion lci of magnetic resonance sounding mrs data and transient electromagnetic tem data which greatly improves the estimation of the mrs model parameters during the last few decades electrical and electromagnetic methods have been widely used for groundwater investigation but they suffer from some inherent limitations for example equivalent layer sequences furthermore the water content information is only empirically correlated to resistivity of the formation mrs is a noninvasive geophysical technique that directly quantifies the water content distribution from surface measurements the resistivity information of the subsurface is obtained from a complementary geophysical method such as tem or dc resistivity methods the conventional inversion of mrs data assumes the resulting resistivity structure to be correct and considers a constant mrs kernel through the inversion we found that this assumption may introduce an error to the forward modeling and consequently could result in erroneous parameter estimations in the inversion process we investigated the advantage of tem for the joint inversion compared to dc resistivity a fast and numerically efficient mrs forward routine made it possible to invert the mrs and tem data sets simultaneously along profiles furthermore by application of lateral constraints on the model parameters lateral smooth 2d model sections could be be obtained the simultaneous inversion for resistivity and mrs parameters led to a more reliable and robust estimation of all parameters and the mrs data diminished the range of equivalent resistivity models we examined the approach through synthetic data and a field example in denmark where good agreement with borehole data was demonstrated with clear correlation between the relaxation time

identification of the shallow subsurface succession and investigation of the seawater invasion to the quaternary aquifer at the northern part of el qaa plain southern sinai egypt by transient electromagnetic data the phenomenon of seawater invasion is a very common and widespread environmental problem that is present in the majority of egyptian coastal aquifers saltwater intrusion may occur due to human activities and by natural events such as climate change and sea level rise el qaa plain is a structural depression trending nnw sse parallel to the main rift system of the gulf of suez the quaternary aquifer in el qaa plain is the main source for water supply in this region so this study has been conducted to shed more light on the description of the subsurface section and marking out the invasion of seawater to this aquifer at the northern part of el qaa plain in this concern transient electromagnetic data were measured at 52 stations arranged along 2 parallel profiles 10 km apart trending ne sw to cross the major course of the plain and to be approximately perpendicular to the coast line of the suez gulf in addition information from a nearby borehole was used to confirm the results of transient electromagnetic data interpretation two apparent resistivity pseudosections and two geoelectrical cross sections were constructed along the selected profiles investigation of these sections revealed that four geoelectrical layers could be detected in the shallow subsurface medium at the studied area and the quaternary aquifer has been affected by seawater invasion at the western and middle parts besides three faults striking approximately nw se parallel to the major track of the plain were inferred from this study these faults may be controlling the groundwater accumulation and flow in this area

joint inversion of seismic and geoelectric data recorded in an underground coal mine1 until the present time the rock coal rock layer sequence and offsets in coal seams in underground coal mines have been detected with the aid of seismic waves and geoelectric measurements in order to determine the geometrical and petrophysical parameters of the coal seam situation the data recorded using seismic and geoelectric methods have been inverted independently in consequence the inversion of partially inaccurate data resulted in a certain degree of ambiguity this paper presents the first results of a joint inversion scheme to process underground vertical seismic profiling data geolectric resistivity and resistance data the joint inversion algorithm makes use of the damped least squares method and its weighted version to solve the linearized set of equations for the seismic and geolectric unknowns in order to estimate the accuracy and reliability of the derived geometrical and petrophysical layer parameters both a model covariance matrix and a correlation matrix are calculated the weighted least squares algorithm is based on the method of most frequent values mfv the weight factors depend on the difference between measured data and those calculated by an iteration process the joint inversion algorithm is tested by means of synthetic data compared to the damped least squares algorithm the mfv inversion leads to smaller estimation errors as well as lower sensitivities due to the choice of the initial model it is shown that compared to an independent inversion the correlation between the model parameters is definitely reduced while the accuracy of the parameter estimation is appreciably increased by the joint inversion process thus the ambiguity is significantly reduced finally the joint inversion algorithm the mfv method is applied to underground field data the model parameters can be derived with a sufficient degree of accuracy even in the case of noisy data

hydrogeophysical investigations in the western and north central okavango delta botswana based on helicopter and ground based transient electromagnetic data and electrical resistance tomography abstractthe okavango delta is a huge alluvial megafan in northwestern botswana despite numerous geologic geochemical geophysical and hydrologic investigations over the past half century the sedimentary units underlying the delta are largely unknown to address this issue helicopter transient electromagnetic data htem have been collected across the entire delta and coincident ground based electrical resistance tomographic ert and transient electromagnetic tem data have been acquired at two locations one along the delta s western margin and one in its north central region inversions of the htem data have yielded three layer resistivity models in which a relatively homogeneous conductive layer is sandwiched between two resistive layers the three layer htem model is reproduced in models obtained from independently and jointly inverting the ground based data the conductive layer s low resistivities and depths to its upper and lower boundaries are practically equal in the htem and ground based m

on the persistence of decadal sst anomalies in the north atlantic abstract historical wintertime sea surface temperature sst data show that a sandwich pattern dominates on the decadal timescales in the north atlantic at least after the 1970s the authors investigated how such decadal sst anomalies can survive against local thermal feedback which acts to dampen them rapidly at the surface winter sst anomalies have a negligible projection with the subsequent summer anomalies while they show a significant projection with the sst anomalies in the next winter on the other hand observed summer temperature anomalies below the mixed layer tend to have the same sign as the previous winter sst anomalies although the magnitude of the former is roughly one third of the latter this suggests that a reemergence mechanism of sst anomalies associated with the seasonal cycle of the mixed layer depth mld which has been verified by alexander and deser helps maintain the decadal sst anomalies in order to examine this scenario a mixed layer model driven by daily atmospheric d

winter precipitation variability over korean peninsula associated with enso in this study winter precipitation variability associated with the el nino southern oscillation enso over the korean peninsula was investigated using a 5 pentad running mean data because significant correlation pattern cannot be revealed using seasonal mean data it was found a considerably significant positive correlation between nino3 sea surface temperature and precipitation during early winter from mid november to early december when the correlation coefficient is close to 0 8 in early december the correlation is distinctively weakened during late winter it is demonstrated that such sudden intraseasonal change in relation to enso is associated with the presence of anticyclonic flow over the kuroshio extension region kuroshio anticyclone in early winter there is strong southerly wind over the korean peninsula which is induced by the philippine sea anticyclone and kuroshio anticyclone however in january although the philippine sea anticyclone develops further the kuroshio anticyclone suddenly disappears as a result the impact of enso is considerably weakened over the korean peninsula these results indicate that the kuroshio anticyclone during el nino peak phase plays a critical role by strongly affecting northeast asia climate including the korean peninsula in addition it is also found that there are distinctive interdecadal changes of the relationship between enso and precipitation over the korean peninsula in particular the strong correlation in early winter is clearer in the recent 30 years than that in the previous period of 1950 1979

el nino modoki and its possible teleconnection 1 using observed data sets mainly for the period 1979 2005 we find that anomalous warming events different from conventional el nino events occur in the central equatorial pacific this unique warming in the central equatorial pacific associated with a horseshoe pattern is flanked by a colder sea surface temperature anomaly ssta on both sides along the equator empirical orthogonal function eof analysis of monthly tropical pacific ssta shows that these events are represented by the second mode that explains 12 of the variance since a majority of such events are not part of el nino evolution the phenomenon is named as el nino modoki pseudo el nino modoki is a classical japanese word which means a similar but different thing the el nino modoki involves ocean atmosphere coupled processes which include a unique tripolar sea level pressure pattern during the evolution analogous to the southern oscillation in the case of el nino hence the total entity is named as el nino southern oscillation enso modoki the enso modoki events significantly influence the temperature and precipitation over many parts of the globe depending on the season the impacts over regions such as the far east including japan new zealand western coast of united states etc are opposite to those of the conventional enso the difference maps between the two periods of 1979 2004 and 1958 1978 for various oceanic atmospheric variables suggest that the recent weakening of equatorial easterlies related to weakened zonal sea surface temperature gradient led to more flattening of the thermocline this appears to be a cause of more frequent and persistent occurrence of the enso modoki event during recent decades

on determining uncertainties of magnetic resonance sounding estimated transmissivities for groundwater modeling abstract the nuclear magnetic resonance sounding mrs method is used increasingly as a tool for hydrological investigations compared to other geophysical methods the advantage of mrs is that it is directly sensitive to the presence of water in the subsurface data interpretations can also be used to get information about the subsurface pore structures which under special conditions can be related to hydraulic properties such as aquifer transmissivity however to broaden the usage of this information in hydrological modeling the uncertainties related to these transmissivity estimates must be determined otherwise properly balanced weights cannot be given to the prior information obtained from mrs transmissivity estimates as compared to the hydrological data sets when used for groundwater model calibration we have developed a methodology to estimate the uncertainties of mrs based transmissivity estimates compared to previous studies the methodology is well defined and it takes into account import

delimiting a saline water zone in quaternary fluvial alluvial deposits using transient electromagnetic a case study in punata bolivia the semiarid punata alluvial fan is located in the central part of bolivia the main activity of this region is the extensive agriculture and groundwater is the main water supply local villagers who use groundwater reported that in some places groundwater has a salty taste in order to investigate the origin of this problem several tem soundings were performed in the study area and they were complemented with ert surveys the results show top layers with resistivity values ranging from 30 to 200 m and a bottom layer with resistivity values ranging from 1 to 20 m which might be interpreted as the main aquifer and a layer with high clay content respectively between the top and bottom layer a transition zone with saline water has been identified with resistivity values ranging from 0 1 to 1 m the origin of this closed basin brine might be a product of the evaporation of paleolakes during the lower pliocene where saline clays were deposited this study demonstrated the effectiveness of tem sounding for mapping very low resistivity zones such as saline water

experimental studies on the effects of fracture on the p and s wave velocity propagation in sedimentary rock calcarenite del salento abstract experimental studies were carried out in laboratory in order to investigate the effects of fracture on compressional p wave and shear s wave velocity propagation and therefore the relations between seismic properties and rock mass parameters the discontinuity index i d fracture density parameter c linear fracture parameter and the rock quality designation rqd were used to describe the rock mass parameters these parameters are analyzed and then related to the seismic properties four vertical aligned fractures were created on an intact calcarenite block 0 6 m long 0 4 m thick and 0 4 m width by sawing the measures were carried out in four different blocks of cacarenite having the same physical properties and in four different phases in first block the fractures were filled with air in the second block the fractures were filled with terra rossa in third block the fractures were filled with wet terra rossa and in the fourth block the fractures were filled with clay the test results were statistically analysed using the method of least squares regression and polynomial relationships with high correlation coefficient were found between the fractured rock parameters and p wave s wave velocities and v p v s ratio the investigations suggest that the p wave and s wave velocities decrease with increasing the fracture parameters while the v p v s ratio increases with decreasing the fracture parameters furthermore the results of the experimental studies were applied on the seismic refraction tomography data acquired in a great measurements campaign undertaken in the adriatic salentina coast south italy in order to monitor the coastal erosion the geophysical results using the polynomial relationships between the fractured rock parameters and p wave velocity are in good agreement with the geomorphological and geological results

electromagnetic soundings in the sedimentary basin of southern ontario a case history the results of electrical and electromagnetic em soundings conducted in the sedimentary basin of southern ontario are presented the sounding sites are located strategically to take advantage of the dipping nature of the sediments a progressive study being undertaken from shallow to deep sections the vertical magnetic field transfer function estimated with a pseudonoise source em system and conventional schlumberger apparent resistivity are jointly inverted for each site the layered earth model containing the minimum number of layers is fitted to the data the joint inversion enables up to eight distinct layers to be identified at some sites the nonuniquenesses or ambiguities in each model for example s conductivity thickness product equivalence of a deep thin conductive layer are revealed through an eigensolution analysis the intrinsic ambiguities of the models of the deeper sections are resolved by a systematic progressive site to site correlation of electrical units across the basin for example the conductivity of a conductive unit is measurable when it is at a shallow depth in a deeper section if the unit appears as a thin layer it is assigned this value of conductivity removing the s equivalence ambiguity the individual inversions combined with the site to site correlation produce an overall electrical model of the basin consistent with the known geologic section

advanced aquifer characterization for optimization of managed aquifer recharge managed aquifer recharge mar will play an increasingly important role in solving water scarcity the performance of mar systems depends primarily upon local hydrogeology greatest opportunities for improvement in the implementation of mar systems lie in the targeted application of conventional and advanced technologies to improve aquifer characterization surface geophysics e g ves tdem and seismic reflection and refraction generally provide low resolution but areal extensive data on subsurface hydrogeology times series of relative microgravity measurements have been used to map changes in both vadose and phreatic zone storage and to augment monitoring well systems surface nuclear magnetic resonance nmr has the potential to provide quantitative data on water filled porosity and pore size distribution and in turn an estimate of hydraulic conductivity standard borehole geophysical logging techniques can provide coarse scale data on aquifer heterogeneity advanced borehole logging techniques such as nmr microresistivity imaging and gamma ray spectroscopy have been used in mar projects in the usa and uae to provide fine scale petrophysical data e g porosity porosity types and pore size distribution groundwater modeling is used in mar investigations to evaluate system feasibility and to optimize system design and operation opportunities to improve groundwater modeling exist through the application of advanced reservoir simulation platforms that allow for the processing and integration of available lithological geophysical and aquifer testing data and their subsequent incorporation into groundwater flow models advanced groundwater modeling programs are available that allow for the simulation of complex aquifers such as dual porosity systems and variable density

transient electromagnetic sounding for groundwater the feasibility of using the transient electromagnetic sounding ts or tdem method for groundwater exploration can be studied by means of numerical models as examples of its applicability to groundwater exploration we study four groundwater exploration problems 1 mapping of alluvial fill and gravel zones over bedrock 2 mapping of sand and gravel lenses in till 3 detection of salt or brackish water interfaces in freshwater aquifers and 4 determination of hydrostratigraphy these groundwater problems require determination of the depth to bedrock location of resistive high porosity zones associated with fresh water determination of formation resistivity to assess water quality and determination of lithology and geometry respectively the ts method is best suited for locating conductive targets and has very good vertical resolution unlike other sounding techniques where the receiver transmitter array must be expanded to sound more deeply the depth of investigation for the ts method is a

the role of tropical mean state biases in modeled winter northern hemisphere el nino teleconnections abstractthe role of tropical mean state biases in el nino southern oscillation teleconnections in the winter northern hemisphere is examined in coupled general circulation models from phase 5 of th

integrated geophysical studies to elicit the subsurface structures associated with uranium mineralization around south purulia shear zone india a review abstract south purulia shear zone in india is an important zone that hosts uranium mineralization since detailed geophysical studies have not been carried out in this region an integrated geophysical study using self potential resistivity very low frequency electromagnetic and radiometric methods was performed to identify the subsurface structures that could host the hydrothermally altered uranium deposits in the area the study reveals the wide and large magnitude of negative self potential anomaly across the south purulia shear zone the peak negative self potential anomalies are correlated with the low gravity and low resistivity anomalies measured along various profiles the low self potential gravity and low resistivity anomaly zones are also correlated with conducting zones inferred from very low frequency electromagnetic measurements interpretation of self potential data reveals multiple thick sheet type vertical and or inclined structures which might be associated with uranium mineralization schlumberger resistivity sounding data reveals an increasing trend of apparent resistivity with current electrode separations depth apparent conductance measured simultaneously with resistivity measurement reveals an increase in current flow of current as depth increases this exhibits the presence of thin conducting layers at these depths which is not reflected in resistivity sounding data due to suppression problem also this conducting layer is consistent in various soundings and is connected from raghunathpur to the south purulia shear zone correlation of very low frequency and self potential data shows that the structures are comparable and a radiometric profile also advocate that the conducting structure is associated with radioactive minerals these structures are likely to be mineralized zones as hydro uranium anomaly has also been reported from various locations in the area moreover drilling results at a specific mine near the study area also confirms the presence of uranium mineralization the hydrothermal activity associated with uranium mineralization seems to be still active in the area such combined geophysical studies are essential to understand this highly complex shear zone for the economic exploitation of its natural resources

an integrated magnetotelluric and gamma exploration of groundwater in fractured granite for small scale freshwater supply a case study from the boshan region shandong province china exploration and use of groundwater in hard rocks is a difficult but yet a significant issue especially when the local surface water source is polluted in this study integrated geophysical and nuclear methods are used to delineate groundwater bearing zones in a granite terrain in the boshan region shandong province china structural analysis showed that fractures extend in a nw se direction which is the same as the direction of river valley a controlled source audio frequency magnetotelluric survey conducted along the river valley indicated several different low resistivity anomalies or potential water bearing fracture zones they are seated at depth ranges down to 400 m from the surface along the river valley the locations of deep water bearing zones were further confirmed by higher gamma radiation measurements found near the river valley a fault with a nw se strike near the river was deduced as an anomalous water bearing zone two tube wells were drilled targeting at the water bearing zone that has achieved single well water yield greater than 360 m3 day the well water was sampled for water chemistry and stable isotope analyses shallow groundwater samples show similar water chemistry and isotopic feature to river water indicating connection between the two deep groundwater from the water bearing fracture zones is not hydraulically connected with shallow groundwater ensuring safety of the deep groundwater in the granite from being affected by the polluted shallow groundwater or river water integrated geophysical and gamma exploration methods helped to identify two disconnected groundwater systems offering an alternative freshwater source for the region if shallow groundwater or surface water is polluted

sharp spatially constrained inversion with applications to transient electromagnetic data time domain electromagnetic data are conveniently inverted by using smoothly varying 1d models with fixed vertical discretization the vertical smoothness of the obtained models stems from the application of occam type regularization constraints which are meant to address the ill posedness of the problem an important side effect of such regularization however is that horizontal layer boundaries can no longer be accurately reproduced as the model is required to be smooth this issue can be overcome by inverting for fewer layers with variable thicknesses nevertheless to decide on a particular and constant number of layers for the parameterization of a large survey inversion can be equally problematic here we present a focusing regularization technique to obtain the best of both methodologies the new focusing approach allows for accurate reconstruction of resistivity distributions using a fixed vertical discretization while preserving the capability to reproduce horizontal boundaries the formulation is flexible and can be coupled with traditional lateral spatial smoothness constraints in order to resolve interfaces in stratified soils with no additional hypothesis about the number of layers the method relies on minimizing the number of layers of non vanishing resistivity gradient instead of minimizing the norm of the model variation itself this approach ensures that the results are consistent with the measured data while favouring at the same time the retrieval of horizontal abrupt changes in addition the focusing regularization can also be applied in the horizontal direction in order to promote the reconstruction of lateral boundaries such as faults we present the theoretical framework of our regularization methodology and illustrate its capabilities by means of both synthetic and field data sets we further demonstrate how the concept has been integrated in our existing spatially constrained inversion formalism and show its application to large scale time domain electromagnetic data inversions

the late fall extratropical response to enso sensitivity to coupling and convection in the tropical west pacific abstract the extratropical response to el nino in late fall departs considerably from the canonical el nino signal observational analysis suggests that this response is modulated by anomalous forcing in the tropical west pacific twp so that a strong fall el nino teleconnection is more likely when warm sst conditions and or enhanced convection prevail in the twp while these twp sst anomalies may arise from noise and or long term variability they may also be generated by differences between el nino events through variations in the tropical atmospheric bridge this bridge typically drives subsidence west of the date line and enhanced trade winds over the far twp which cool the ocean in late fall however some relatively weaker and or more eastward shifted el nino events produce a correspondingly weakened and displaced tropical bridge which results in no surface cooling and enhanced convection in the twp because the north pacific circulation is very sensitive to forcing from the twp at this time

origins of honeycomb weathering the role of salts and wind honeycomb weathering is a common surface phenomenon affecting a variety of rocks in a range of environments it develops on building stones and it shapes ocean cliffs rocks in hot deserts and arctic landscapes honeycomb weathering may also help alter rocks on other planets such as mars although first noted in the nineteenth century its origins are still not well understood and a dearth of laboratory experiments testing the many theories proposed for its development has added to the ambiguity incipient honeycomb weathering in a homogeneous limestone has been experimentally reproduced by wind exposure and salt crystallization our experiments show that heterogeneous wind flow over a stone surface is important in the development of this weathering pattern wind promotes evaporative salt growth between grains on a stone surface resulting in the development of small randomly distributed cavities a reduction in air pressure within the cavities results in increased wind speed and rapid evaporation a high evaporation rate and evaporative cooling of the saline solution in the cavity leads to more rapid and greater granular disintegration than in the surrounding areas it seems that this local supersaturation and subsequent buildup of salt crystallization pressure ultimately result in the formation of honeycomb features for the first time these experimental results demonstrate the close relationship between salts wind and honeycomb weathering they also offer new ways to understand the genesis of this striking and sometimes harmful weathering pattern

extra tropical atmospheric response to enso in the cmip5 models the seasonal mean extra tropical atmospheric response to el nino southern oscillation enso is assessed in the historical and pre industrial control cmip5 simulations this analysis considers two types of el nino events characterized by positive sea surface temperature sst anomalies in either the central equatorial pacific cp or eastern equatorial pacific ep as well as ep and cp la nina events characterized by negative sst anomalies in the same two regions seasonal mean geopotential height anomalies in key regions typify the magnitude and structure of the disruption of the walker circulation cell in the tropical pacific upper tropospheric enso teleconnections and the polar stratospheric response in the cmip5 ensembles the magnitude of the walker cell disruption is correlated with the strength of the mid latitude responses in the upper troposphere i e the north pacific and south pacific lows strengthen during el nino events the simulated responses to el nino and la nina have opposite sign the seasonal mean extra tropical upper tropospheric responses to ep and cp events are indistinguishable the enso responses in the merra reanalysis lie within the model scatter of the historical simulations similar responses are simulated in the pre industrial and historical cmip5 simulations overall there is a weak correlation between the strength of the tropical response to enso and the strength of the polar stratospheric response enso related polar stratospheric variability is best simulated in the high top subset of models with a well resolved stratosphere