diagnosis of the downstream ridging associated with extratropical transition using short term ensemble forecasts abstract the dynamical mechanisms that led to downstream ridging during the extratropical transition et of typhoons tokage and nabi are evaluated using data drawn from a cycling ensemble kalman filter coupled with the weather research and forecasting model wrf during both transitions the ensemble covariances indicate that the 350 k potential vorticity pv at the apex of the ridge which is used to define the ridge structure is proportional to the amount of precipitation along the baroclinic zone to the northeast of the tropical cyclone tc and at some times to the upper tropospheric divergence above the tropical cyclone multivariate regression calculations indicate that the frontal precipitation has the largest impact on the ridge amplitude and area during tokage s transition while the tc divergence has roughly equal impact during some times of nabi s transition the amount of precipitation along the baroclinic zone is modulated by the lower tropospheric frontogenesis and moisture flux on the

geochemical and isotopic study of surface and groundwaters in ain bou mourra basin central tunisia abstract a comprehensive study of the hydrogeological framework and groundwater resources using chemical and isotope methods was recently carried out in the ain bou mourra basin central tunisia in this area surface water in rivers is seasonal and therefore groundwater is the perennial source of water supply for domestic and agricultural purposes a great dam and several harvesting features have been built within a national water management strategy in order to increase the overall water availability in the basin in this study groundwaters from the paleogene neogene formations in the ain bou mourra together with rain and surface waters have been analyzed in order to investigate the mineralization processes water origin and recharge sources chemical data indicate that surface and groundwater samples show a large spatial variability of chemical facies most of the groundwaters are slightly to moderately mineralized and are of ca mg cl so4 water type induced mainly by feldspar and silicate weathering dissolution of evaporitic and carbonate minerals and cation exchange reactions data inferred from 18o and deuterium isotopes in groundwater samples indicated recharge with modern rainfall water characterized by lower 18o and 2h values is interpreted as recharged by non evaporated rainfall originating from mediterranean air masses at higher altitude however water with relatively enriched 18o and 2h contents is thought to reflect the occurrence of an evaporation process related to the long term practice of flood irrigation the investigated surface water samples collected from the dam river hill reservoirs and pumped storage water power plant are affected by a significant evaporation and reveal large seasonal variations which could be controlled by the water volume changes in the open surface reservoirs and the meteorological conditions during evaporation condensation and precipitation considerable tritium concentration in groundwaters allowed qualitative identification of the present day component it is assumed that this component is supplied by recent precipitation at the oligocene miocene outcrops of the study area data revealed the existence of high 14c activities in groundwaters reservoir of dissolved carbon is simultaneously depleted in 13c reflecting the domination of co2 produced by c4 plants in formation of carbonate mineralization of analyzed waters

interaction of a tropical cyclone with a high amplitude midlatitude wave pattern waviness analysis trough deformation and track bifurcation an idealized scenario of extratropical transition et is investigated in which a tropical cyclone interacts with a high amplitude upper level wave pattern and well developed surface cyclones early during the interaction the external forcing of the upper level wave by the et system is quantified based on a metric for the waviness of the midlatitude flow local amplification of the wave pattern is diagnosed associated prominently with the trough downstream of et this amplified trough however exhibits pronounced anticyclonic breaking and thus in contrast to many previous et studies it is not clear that the amplification of the upper level wave propagates into the farther downstream region subsequently the et system merges with the upstream cyclone the upstream trough undergoes strong deformation and cyclonic breaking associated with straining due to the cyclonic circulation of the et system with the decay of this trough the et system weakens considerably and the upper level wave pattern changes locally to a zonal flow orientation this zonal flow pattern then extends into the downstream region and promotes the decay of the downstream baroclinic systems as in previous studies the evolution of et exhibits large sensitivity to the initial location of the tropical cyclone examining the steering flow s topology i e identifying the stagnation points and the streamlines emanating from these points helps to identify three different regimes a no et regime and two et regimes reminiscent of the northwest and northeast patterns respectively introduced previously by harr et al a stagnation point located on the axis of the upstream trough governs the bifurcation into no et and et regimes a stagnation point located on the axis of the downstream ridge governs the bifurcation into northwest and northeast patterns

twenty years of groundwater evolution in the triassic sandstone aquifer of lorraine impacts on baseline water quality abstract the lorraine triassic sandstone aquifer ltsa which has already been the subject of a chemical and radioisotopic study 1979 is used to investigate the impacts of 20 a of large scale pumping on baseline water quality in parallel new sampling of the aquifer 2001 provides new inorganic geochemical data including trace elements that allow improving the knowledge of baseline conditions and hydrochemical functioning of a major sandstone aquifer the good correlation between 14 c activities temperature and depth along the main flow line indicate regular downgradient trends and possible water stratification unreactive tracers mainly stable isotope ratios 18 o and 2 h as well as c isotopes are used to define a timescale for the aquifer showing two groups of groundwater namely of modern and holocene age and late pleistocene age with a mixing zone baseline quality is then represented by a wide range of concentrations mainly the result of time dependent water rock interaction as already observed elsewhere in triassic sandstone aquifers some trace elements such as li rb cs which are not limited by solubility constraints show linear trends during saturated flow downgradient the chemistry is also specifically characterised by a regular increase in na and cl and locally so 4 as a result of evaporite dissolution related to overlying or basement limits the aquifer is mostly oxidising with a redox boundary marked by u decrease some 40 km from outcrop groundwater abstraction since the 1970s has created a strong lowering 10 150 m of the water table especially from 1970 to 1980 based on nine boreholes previously sampled in 1979 a decreasing evolution in radiocarbon content of the tdic together with significant evolution of 18 o content indicate that old groundwater has moved upgradient the major difference in terms of baseline evolution is observed using cl and na concentration and locally so 4 indicating an increasing influence of water circulation involving overlying or basement formations or of mixing with permian waters from the point of view of aquifer management the perceptible no 3 increase could provide information on the progress of any contamination under the aerobic conditions in addition the few key elements indicators of disequilibrium related to overlying or deep waters should be included in regular monitoring programmes

evaluation of salt sources and loads in the upland areas of the murray darling basin australia estimates of catchment salt balances throughout the murray darling basin mdb suggest mobilization of salt stores and generally increasing stream salinities it is widely assumed these salts are rainfall deposited cyclic salts of marine aerosol origin concentrated by evapotranspiration stored in groundwaters and mobilized by clearing of native vegetation in this paper the assumptions about the sources of salts in upland catchments in the south eastern region of the mdb are re evaluated the estimation of dissolved salts is re examined using electrical conductivity ec the assessment of stream salt loads from sporadic ec measurements and the sources of salts in upland catchments it is concluded that although evapotranspiration plays a significant role in the concentrations of salts in the lower mdb mineral weathering is a major contributor to stream salt loads in upland rivers of the mdb that supply over 80 of surface runoff to the murray river copyright 2009 john wiley sons ltd

a modern isotope record of changes in water and carbon budgets in a groundwater fed lake blue lake south australia groundwater is often a major component of lake water and chemical balances alteration in catchment subsurface water balances through land use change and pumping can affect lake biogeochemical cycles through changes in groundwater flow rates we present a modern 200 yr sediment isotope record d 18 ocarb d 13 ccarb and d 13 corg o f changes to the water and carbon budget of blue lake which is situated in karstic limestone in south australia and is mostly fed by groundwater the 3 5 decrease in d 18 ocarb and d 13 ccarb deposited in lake sediments since 1850 reflects higher rates of groundwater through flow due to rainfall variability land use change and increased rates of pumping over the past 40 yr calculated water residence times based on the isotopic data were 23 6 2 yr before 1850 and decreased by the late twentieth century to 8 6 2 yr concomitant dissolved inorganic carbon dic residence times were 3 8 and 2 2 yr respectively although burial rates of caco3 have increased by about threefold over the past 40 yr there is no evidence that substantial changes in organic carbon deposition has occurred the shorter dic residence time is largely due to increased input and higher co2 evasion rates about 88 of ccarb and 96 of corg generated within the water column is remineralized but the isotopic composition is essentially unaltered in the sediments the measured variations in d 13 ccarb and d 13 corg of sediments are thought to reflect changes to dic residence time and increased co2 aq concentrations rather than changes in lake productivity

transport of soluble salts in a large semiarid basin river murray australia median annual concentrations of cl so4 hco3 na k mg and ca increase greatly downstream in the river murray along its 2500 km route to the sea chloride increases from less than 2 mg l 1 near the headwaters to about 170 mg l 1 near the downstream end of the main channel water near the head of the river has hco3 balanced by similar equivalents of na ca and mg while higher salinity water in the downstream half of the river is dominated by na and cl sources of these dissolved ions include a sea derived airborne salts contributing essentially all of the cl br and 80 of the na and b rock derived ions from weathering of sedimentary rock and soil minerals contributing most of the observed hco3 80 of the ca and 20 25 of the mg and so4 much of the change in chemistry along the axis of the murray is due to influx of saline groundwater which has a major ion composition similar to sea water inflows of irrigation drainage water also enhance downstream transport of salts especially hco3 the stable isotope composition of the river murray 2h and 18o begins with relatively depleted heavy isotope abundances 47 8 in the uplands of the southeastern margin of the murray darling basin increasing steadily by 30 and 6 respectively due to evaporative enrichment from river surfaces and influx of drainage returned from irrigation diversions despite the similarity of groundwater major ion chemistry to that of sea water stable isotope compositions of groundwaters clearly demonstrate that water molecules from past marine incursions have been completely flushed from the system similarly the cl br ratios of groundwaters are not appreciably different from seawater values indicating that dissolution of fossil evaporites does not contribute significant salt to the groundwaters or the river

on the role of a rossby wave train during the extratropical transition of hurricane helene 2006 three successive interactions of hurricane helene 2006 with a rossby wave train during the extratropical transition of helene over the north atlantic were investigated numerical experiments were performed with different horizontal resolutions and configurations over a domain that stretches from the eastern pacific to the western mediterranean to encompass helene and the whole rossby wave train in particular a cloud resolving run offered an explicit representation of strong diabatic effects involved in the three successive interactions while the circulation and moisture anomaly of helene were essential to its own reintensification it is shown that the rossby wave train played an important role in the track and intensity of helene and in explosive cyclogenesis downstream first the rossby wave train steered helene in such a way that a small difference in phasing resulted in large errors in the track of helene only a run at kilometre scale was able to correctly forecast the 5 day track of helene second through the formation of three filaments the rossby wave train created a quasi diurnal cycle in the intensity of helene helene responded with strong diabatic activity that prevented the superposition of an upstream trough and enhanced a downstream ridge finally model errors in the outflow of helene propagated downstream with the group speed of the rossby wave train leading to the loss of predictability of a tropical like cyclone over the mediterranean this study suggests that in addition to the horizontal resolution uncertainty from the model microphysics and from initial conditions need to be characterized to improve mid range forecast downstream from an extratropical transition copyright 2012 royal meteorological society

dynamics of rossby wave packets in a quantitative potential vorticity potential temperature framework abstractrossby wave packets rwps have been associated with increased atmospheric predictability but also with the growth and propagation of forecast uncertainty to address the important question of under which conditions rwps imply high and low predictability a potential vorticity potential temperature pv framework is introduced to diagnose rwp dynamics finite amplitude rwps along the midlatitude waveguide are considered and are represented by the synoptic scale wavelike undulations of the tropopause the evolution of rwps is examined by the amplitude evolution of the individual troughs and ridges troughs and ridges are identified as pv anomalies on levels intersecting the midlatitude tropopause by partitioning the pv tendency equation individual contributions to the amplitude evolution are identified a novel aspect is that the important role of the divergent flow and the diabatic pv modification is quantified explicitly arguably prominent upper tropospheric divergent flow is associated

the impact of extratropical transition on the downstream flow an idealized modelling study with a straight jet the interaction of a tropical cyclone undergoing extratropical transition et with the midlatitude synoptic scale flow is investigated using full physics numerical experiments with idealized initial conditions the emphasis is on the impact on the midlatitude flow downstream of the et event the midlatitude flow is represented by a balanced straight jet stream as the tropical cyclone approaches the jet a ridge trough couplet and a distinct jet streak form in the upper level flow a midlatitude cyclone develops rapidly downstream of the et system and the further evolution is characterized by downstream baroclinic development based on hovmoller diagrams the upper level development is interpreted as the excitation and subsequent dispersion of a rossby wave train on the potential vorticity gradient associated with the jet the characteristics of this wave train are sensitive to the structure of the jet and to moist processes in the midlatitudes the tropical cyclone undergoing et acts as a sustained forcing for the wave train and the structure of the et system impacts the development most significantly one to two wavelengths downstream of et piecewise inversion of potential vorticity complemented by the partitioning of the flow into its rotational and divergent parts is applied to assess the impact of the et system quantitatively both the cyclonic circulation and the outflow of the tropical cyclone are important contributors to the formation and amplification of the ridge trough couplet the outflow anomaly reduces the eastward motion of the ridge trough couplet significantly and thus promotes phase locking between the tropical cyclone and the upper level pattern copyright 2008 royal meteorological society

oxygen isotopes and sea level from the time that detailed oxygen isotope records derived from foraminifera living in the constant temperature environment of the abyssal ocean became available there has been a discrepancy between the ice volume record that these records imply and that derived from the altitude of dated coral terraces around the world here we re examine the data and conclude that the temperature of the abyssal ocean has been an actively varying component of the climate system

the resonant interaction of a tropical cyclone and a tropopause front in a barotropic model part ii frontal waves abstract the influence of frontal waves on the interaction of a tropical cyclone and a tropopause front is investigated in an idealized framework in a nondivergent barotropic model the front is represented by a vorticity step with a superimposed sinusoidal perturbation this gives rise to a jet that meanders to the north and south and can be viewed as a sequence of upper level troughs and ridges the model evolution depends sensitively on the position of the cyclone relative to the troughs and ridges here a bifurcation point is identified that is located on the trough axis at a distance where the zonal speed of the background flow equals the phase speed of the wave arbitrarily small displacements from this position determine whether a cyclone is advected toward the front or repelled only a limited range of wavelengths can lead to track bifurcations the largest effects are obtained for resonant frontal waves propagating with a phase speed matching the initial zonal translation speed of the cyclone we

groundwater flow regime within the gambier embayment of the otway basin australia evidence from hydraulics and hydrochemistry a conceptual groundwater flow model for the cainozoic sequence of the gambier embayment of the otway basin south australia is developed using hydraulic head distribution environmental isotopes and hydrochemical data local flow cells occur within the upper sequence of the gambier unconfined aquifer and are recognised by local relief of the water table and as rapid lateral variations in chloride 14c 2h and 18o concentrations indicating that regional flow is not dominant in the upper portion of the unconfined aquifer these localised systems are topographically controlled and have developed in response to undulating stranded coastal dune ridges of the bridgewater formation recharge areas correspond to dune highs while discharge is focused towards the lower lying interdunal regions total dissolved solids concentrations are controlled by evapotranspiration processes during recharge and ion ratios are modified by water rock interactions within the groundwater system groundwaters are more dilute in the southern section of the basin where the surplus of precipitation over evapotranspiration in the winter months is greater than that in the northern section of the basin a regional flow system with interaquifer mixing has developed within the confined dilwyn aquifer system recharge to the dilwyn aquifer has been identified downgradient from the basin margin via downward leakage from an intermediate flow system within the gambier unconfined aquifer to the deeper regional flow system of the confined dilwyn aquifer interaquifer mixing appears to be geologically controlled in the south by the elevated gambier axis and in the north by the kanawinka fault downgradient of the zero head difference line lateral flow appears to be the dominant transport mechanism within the dilwyn aquifer as indicated by constant chloride concentrations monotonic decrease in radiocarbon concentration and more negative 2 and 18 o composition

convection in an african easterly wave over west africa and the eastern atlantic a model case study of helene 2006 convective systems embedded in an african easterly wave aew over west africa and the eastern atlantic in september 2006 are investigated the study is based on cosmo model runs with a horizontal resolution of 2 8 km the developing mature and decaying phases of a mesoscale convective system over land are identified over the ocean the convection consists of the development and decay of short lived systems there are significant differences between the structure of convection over land and water over land the updraught heating and vertical vorticity are tilted in the vertical over water the convective cores are upright and collocated with positive relative vorticity the atmosphere is drier at mid levels over land and stronger shear downdraughts and a distinct cold pool occur the influence of the convective systems on their environment is assessed with potential temperature and relative vorticity budgets for regions encompassing the convective systems during the convective system s life cycle the relative vorticity increased at the height of the african easterly jet over land due to the eddy flux term whereas the relative vorticity maximum over the ocean moved downwards with time due to stretching high values of low level relative vorticity were seen over the ocean before the aew trough crossed the west african coast the low level circulation that developed as a positive low level vorticity anomaly associated with the westward extension of the saharan heat low moved over the atlantic and southwestwards in addition positive vorticity associated with the low level monsoon flow contributed to this circulation the cyclogenesis of hurricane helene was initiated when the mid level vorticity anomaly of the aew moved over the low level circulation initiating convection and enhancing the low level vorticity through vortex stretching copyright 2010 royal meteorological society

geochemistry and14c dating of groundwaters from jurassic aquifers of north aquitaine basin france twenty seven samples from a confined lower middle jurassic aquifer and an unconfined oxfordian aquifer of the north aquitaine basin france have been analysed for their major elements br 18o 2h 13c and14c contents hydrochemistry indicates 1 a dissolution of carbonate and anhydrite near the recharge zone and 2 a dilution of a saline water derived from a seawater halite mixing in the deeper part of the aquifer the mixing is also visible in a 18o vs cl diagram in which two different groups appear recent waters and old waters indicating a mixing process between fresh and saline groundwaters the composition of the saline water is likely to be 34 100 11 200 ppm in cl 70 20 ppm in br and more than 3 5 07 vs smow in18o 13c contents indicate 1 a c exchange with caco3 matrix for groundwaters near the recharge zone and 2 a participation of organic matter in the deep part of the aquifer residence times for waters near the area of the aquifer outcrop correspond to holocene and late pleistocene periods the depletion in stable isotopes of 10 to 15 000 y b p waters show a late glacial period infiltration to the aquifer after a distance of about 10 km in the aquifer the14c activities are 0 pmc showing the presence of old groundwaters

late pleistocene and holocene sea level change along the australian coast abstract tectonically the australian continent is relatively stable and as such it provides a good platform for studying late pleistocene and holocene sea level change the observations indicate that present sea level was reached at about 6000 years ago and that since then level has remained constant to within a few metres considerable spatial variability in the amplitude of the emergence and in the time at which sea levels first reached their present values have been observed spatial variability has also been observed in the sea level during the last glacial maximum and during the late phase of the holocene transgression much of this variaiblity is the result of the earth s adjustment to the glacial melting in the late pleistocene early holocene time and the concomitant distribution of this meltwater into the oceans conclusions that are drawn from matching observations with this glacio hydro isostatic model include the following 1 the mantle viscosity increases with depth the average upper mantle viscosity is about 2 3 10 20 pa s and the average lower mantle defined as below 670 km depth viscosity is about 10 22 pa s the average lithospheric thickness for the coastal and offshore region is about 70 80 km lateral variations in these mantle parameters are indicated 2 the addition of melwater into the oceans did not cease 6000 years ago but continued at a reduced rate up to more recent times adding an amount of water equivalent to a 3 m sea level rise in this interval 3 the amplitude of the holocene emergence is a function inter alia of coastal geometry and significant variations occur over distances of a few hundred kilometres and more holocene highstands of 1 2 m are generally well developed at the continental margins but are less well developed or do not developed at all at offshore islands and reefs 4 variations in the time of maximum emergence also occur being earlier at upstream tidal river sites than at coastal sites at offshore reefs or islands the sea level curve lags the coastal curves by 1000 years or more 5 considerable spatial variability occurs in the sea levels at the time of the last glacial maximum with variations of up to 30 m occurring across the continental shelves 6 there is generally no need to invoke tectonic movements to explain the sea level data along the australian coast but possible exceptions occur for the perth region and for tasmania

radiocarbon dating of groundwater of the aquifer confined in the lower triassic sandstones of the lorraine region france abstract blavoux b and olive ph 1981 radiocarbon dating of groundwater of the aquifer confined in the lower triassic sandstones of the lorraine region france in w back and r letolle guest editors symposium on geochemistry of groundwater 26th international geological congress j hydrol 54 167ndash 183 stable isotope and groundwater chemistry analyses on samples from about 40 boreholes in the lorraine region eastern france are used to evaluate the paleohydrological regime of the lower triassic sandstone aquifer in the study of the mechanisms of the general water dynamics of the aquifer at present in this sandstone aquifer the estimation of the 14 c activity a 14 in the total dissolved carbon tdc to 100 of modern carbon is justified by the absence of carbonates in the reservoir and by the 13 c contents in the tdc a significant relation could be determined between the 14 c activity in the tdc and 13 c a 14 7 7 13 59 6 this gradual enrichment of the tdc with 13 c results from the escape of the dissolved co 2 the meaning of the radiometric age is discussed as a function of piston and exponential type flows the study of the stable isotopes 18 o and 2 h revealed two water families the most recent waters have 18 o values higher by 1 0 than the more than 10 4 yr old waters this 1 0 discontinuity corresponds to the improvement of weather conditions during the holocene which amounts to 2 5 c the isochrons of the aquifer reveal the existence of hydrogeological sections bounded by faults where the rates of circulation are different

palaeorecharge conditions of the deep aquifers of the northern aquitaine region france summary the study was carried out in the northern part of the aquitaine basin extending in southwest france the basin has been intensively exploited for various purposes for many years although the geological context is well known there are still some gaps in the knowledge about the hydrogeochemical regime groundwater average residence time and the palaeohydrological conditions prevailing during the recharge period which would help to secure sustainable exploitation of the resources environmental isotopes 18 o 2 h 3 h 13 c together with radiocarbon were used to evaluate hydrochemical evolution residence time and palaeorecharge conditions for jurassic cretaceous and eocene aquifers radiocarbon activity in the aquifers varies widely between 0 and 94 pmc after radiocarbon corrections the ages indicate both modern and old waters sometimes exceeding the limit for 14 c dating the fontes and garnier model is best adapted to the specificity of the carbonate system the content in stable isotopes of water is varying between 7 7 and 4 9 for 18 o and 52 3 to 29 6 for 2 h the wide ranges of stable isotopic values imply variable climatic conditions a group of isotopically depleted samples was detected indicating colder climatic conditions during the recharge radiocarbon ages calculation together with isotopic signature point out that the depletion in stable isotopic values fits the period between 20 and 15 ka b p and therefore indicate the last glacial maximum lgm according to the correction model the transition from pleistocene to holocene would occur between 15 and 12 ka b p palaeohydrological data from the northern aquitaine basin does not confirm a significant hiatus in the recharge history the recharge conditions in south europe seem to have occurred under discontinuous permafrost conditions as documented by many palaeoclimatological archives this is in favour of an uninterrupted recharge of the confined aquifers of northern aquitaine basin such information should be considered by modellers in their attempts to simulate the hydrogeological functioning of large confined aquifers on the very long time range

extratropical transition of tropical cyclones over the western north pacific part ii the impact of midlatitude circulation characteristics abstract two characteristic midlatitude circulation patterns labeled northwest and northeast are found to be associated with extratropical transition et of tropical cyclones over the western north pacific ocean although in both cases the tropical cyclone moves poleward ahead of a midlatitude trough the primary midlatitude circulation is either that trough or is a large quasi stationary cyclone to the northeast of the poleward moving tropical cyclone transition into a northwest pattern typically results in the development within 36 h of an intense extratropical cyclone that moves north northeast a tropical cyclone that moves into a northeast pattern enters into strong zonal flow between the primary midlatitude circulation and the subtropical ridge to the southeast these systems move rapidly eastward and do not intensify significantly during the 36 h following transition in part i of this study the et of typhoon ty david 1997 and the et of ty opal 1997 were investigated in terms of the form

carbon 14 and stable isotope data for an area in the murray basin its use in estimating recharge measurements of the carbon 14 concentration of water in 33 boreholes in a saline unconfined aquifer in southern australia have been interpreted to show that local recharge under natural conditions has a mean annual value which falls between 0 1 and 0 2 mm yr 1 the chloride concentration of groundwater is log normally distributed suggesting that its source is rainfall the estimate of mean annual recharge to the aquifer made using chloride is 0 25 mm yr 1

a survey of groundwater levels and hydrogeochemistry in irrigated fields in the karamay agricultural development area northwest china implications for soil and groundwater salinity resulting from surface water transfer for irrigation analysis of the water budget along with hydrochemistry and stable isotopes in shallow groundwater were carried out in the karamay agricultural development area kada in order to assess the impact of transfer of irrigation water from the irtysh river in particular in relation to the mechanisms of salinization and the nature of the water table regime in terms of aquifer dynamics the addition of the irrigation water without any groundwater abstraction has caused a sharp rise in the water table is and the development of serious soil salinity together with an almost complete attenuation of inter seasonal water table oscillations the mean rise in the groundwater table from september 1997 to october 2009 was 6 9 m representing an accumulated total water storage change of close to 150 million cubic meters the analysis of aquifer water budget shows that infiltration of irrigation water occupied over 90 of the total recharge of the groundwater in the kada sources of groundwater recharge and mechanisms of salinization in the kada were also investigated using geochemical and isotopic techniques the groundwater is characterized by cl so 4 na type generally becoming more na and cl dominated with increasing salinity the total dissolved solids tds content of the groundwater ranges from 0 5 g l to over 65 g l with greater tds values in areas of low topographic relief and shallow water tables where the sediments are more permeable e g due to the presence of palaeochannels tds values are generally lower and the seasonal water table fluctuations greater the ratios of k cl ca cl na cl and mg cl decrease with increasing cl concentrations especially in the shallow groundwater from 10 to 15 m depth indicating hydrogeochemical evolution via minor water rock interaction feldspar weathering and significant evaporation the stable isotopic compositions show a characteristic evaporation effect in the shallow groundwater and confirm that direct infiltration of precipitation is generally not a volumetrically important source of recharge to the shallow aquifer preferential recharge of river water after irrigation events and or precipitation from rare heavy rain events is likely responsible for the depleted 2 h and 18 o values in some of the groundwater samples the negative relationship between deuterium excess and 18 o values indicates that even in groundwater with relatively depleted 2 h and 18 o values evaporation has occurred to a significant degree careful management of water quantity and quality and implementation of salinity management strategies are considered necessary in order to reduce the risk of further salt accumulation and damage to farming and local ecosystems

understanding the salinisation process for groundwater in an area of south eastern australia using hydrochemical and isotopic evidence abstract increases in groundwater salinity down gradient are a common occurrence in catchments throughout australia exacerbating the effects of dryland salinisation in discharge areas groundwater hydrochemical and isotopic data from the willaura catchment in south eastern australia which is affected by both primary natural and secondary human induced salinity allowed the factors that cause the down gradient trend in salinisation within this catchment to be determined the overall salinity of the groundwater 0 8 70 ms cm is controlled by evapotranspiration which concentrates cyclic salts in the unsaturated zone greatly increasing the salinity of the soil water to 3700 6400 mg l cl the progressive addition of this saline soil water to fresher groundwaters recharged on the catchment margins causes a gradual increase in salinity down gradient the groundwater stable isotope compositions show that most recharge occurs in winter and spring groundwater salinities increase around the saline lakes of the discharge zone due to direct evaporation from shallow watertables and minor dissolution of halite as indicated by cl br ratios mineral water interactions within the aquifers cause a slight overall reduction in salinity conversion of kaolinite to smectite and illite and cation exchange of na for ca2 on smectites cause na cl mg2 cl k cl si cl and hco3 cl ratios to progressively decline and ph to gradually increase down gradient oxidation of organic matter causes a strong decrease in the redox potential of the groundwaters down gradient the groundwater ages increase from modern containing tritium on the catchment margins to 8000 years based on 14c dating at the end of the 25 km flow path the older groundwaters are isotopically heavier than the younger waters probably due to recharge during a wetter climate in the early holocene the groundwater ages show clearly that the progressive addition of saline soil water causing groundwaters to become more saline down gradient has occurred throughout the holocene and may explain the occurrence of primary salinisation within many australian catchments

oval intensification event observed by stare and viking optical emissions and electron flow patterns in the auroral oval evening sector have been investigated in the 30 min interval prior to a major auroral intensification the stare radar and viking uv image data were combined to give a dynamical picture of the auroral ionosphere just to the west of the intensification region which was bordered on its eastward side by the foot of a high latitude polar arc half an hour prior to the main intensification an auroral arc appeared equatorward of a band of eastward electrojet which in turn was equatorward of another discrete arc system the appearance of the new arc system was accompanied by a second eastward electrojet further equatorward within minutes of this appearance the older electrojet and arc system faded and the new system moved poleward to replace it this precursor activity was followed by a major intensification a substorm to the east of the foot of the high latitude polar arc it is speculated that the precursor is linked to changes in the current distribution in the near earth nightside magnetosphere prior to the substorm onset

transient hydrological conditions implied by chloride mass balance in southeast australian rivers a robust correlation between electrical conductivity ec values and cl concentrations in river water from southeast australia allows detailed cl fluxes to be calculated from continuous ec and river discharge records many victorian rivers export significantly more cl than is delivered to their catchments by rainfall cl is defined as the mass of cl exported in the rivers relative to that input by rainfall over a multi year period cl 100 indicates that the river exports the same mass of cl as is input by rainfall there is a systematic relationship between catchment type and cl rivers draining cleared plains have cl values between 50 and 750 rivers draining volcanic plains have cl values of 770 1600 whereas rivers with large forested upland catchments have cl values of 50 110 these values are minima as they do not account for cl exported by groundwater from the catchments the calculations are based on long term up to 22 year records that span drought and high rainfall periods the magnitude of cl is far higher than can be explained by errors in the calculations or variability in rainfall and runoff and cl br ratios preclude halite dissolution as a source of cl the excess cl reflects hydrological changes in the catchments land clearing on the cleared plains has caused the rise of regional water tables which results in the export of cl from saline groundwater via increased baseflow to the river systems drainage systems on the volcanic plains are re establishing following impoundment by recent 4 5 ma lava flows cl which accumulated in shallow groundwater around saline lakes and marshes developed on these volcanic plains is now being exported via the rivers the upland catchments have undergone less landscape change and may be in chemical balance the methodology outlined here provides a straightforward assessment of whether catchments are in chemical balance that may in turn indicate whether they are undergoing hydrological changes

vortex vortex interaction between hurricane nadine 2012 and an atlantic cut off dropping the predictability over the mediterranean operational ensemble forecasts for the western mediterranean exhibited high uncertainty while hurricane nadine was moving slowly over the eastern north atlantic in september 2012 the forecasts showed a bifurcation in the track of nadine a significant fraction predicting its landfall over the iberian peninsula and a high spread in the synoptic conditions downstream the forecast uncertainty was a major issue for planning observations during the first special observation period sop1 of the hydrological cycle in the mediterranean experiment hymex clustering the ensemble forecast of the european centre for medium range weather forecasts reveals two scenarios for interaction between nadine and an atlantic cut off which controls both the track of nadine and the synoptic conditions downstream the observed scenario of weak interaction is characterized by nadine moving westward and the cut off moving eastward the cut off then triggers precipitation over the cevennes in southeastern france the contrasting scenario of strong interaction is characterized by nadine and the cut off rotating around each other over the atlantic nadine then either merges with the cut off or makes landfall over the iberian peninsula the interaction between nadine and the cut off mimics the vortex vortex interaction previously observed between two tropical cyclones or two upper level vortices it differs from the usual interaction between a tropical cyclone and a larger trough during extratropical transition a critical distance of about 1000 km between nadine and the cut off distinguishes between the cases of weak and strong interaction in the ensemble forecast shifting the initial position of nadine in meso nh numerical experiments confirms the critical distance and suggests a bifurcation point in the relative position of nadine and the cut off the high forecast sensitivity to the vortex vortex interaction resulted in the lowest predictability over the mediterranean during the whole hymex sop1

differences in groundwater and chloride residence times in saline groundwater the barwon river catchment of southeast australia abstract the residence times of groundwater and chloride and the processes contributing to the development of saline total dissolved solids tds up to 45 379 mg l groundwater within the barwon river catchment of southeast australia were investigated using major ion stable isotope 18 o 2 h and 13 c and radioactive isotope 3 h 14 c 36 cl geochemistry the elevated groundwater salinity in the region is primarily due to evapotranspiration and recycling of solutes in saline lakes with minor contributions from weathering of halite silicate and calcite minerals groundwater residence times estimated from 14 c vary from modern to 20 ka for groundwater with lower 14 c activities the estimated residence times vary significantly depending on the assumed flow model and the 14 c activity of recharge chloride residence times downgradient of lake murdeduke a saline through flow lake in the centre of the catchment are greater than the corresponding groundwater residence times due to the recycling of cl within the lake precise estimates of chloride residence time could not be determined using 36 cl due to r 36 cl in precipitation being lower than that of groundwater this is most likely due to r 36 cl values in rainfall having been higher in the past than they are at present due to climate variability 18 o 2 h and 13 c values also suggest that the region has experienced increasingly more evaporative conditions with time the results of this study demonstrate that while cl is a useful tracer of hydrological processes it must be applied carefully in arid and semi arid regions of the world in particular recharge rates calculated using chloride mass balance may be underestimated where recycling of cl has occurred

geochemical mass balance and oxygen isotope constraints on silcrete formation and its paleoclimatic implications in southern australia abstract two geographically distinct silcrete associations are present in southern australia inland and eastern these were sampled in central south australia and central victoria respectively at each site both silicified and immediately adjacent unsilicified parent material were collected analytical data from these pairs were used to construct isocons assuming zr immobility and to calculate the volume change and amount of silica introduced during silicification these results together with whole rock oxygen isotope compositions were used to determine the 18o of the introduced silica the results show that the eastern silcretes in central victoria are probably linked genetically to the associated basalts weathering of which supplied the introduced silica this conclusion is based on the close spatial connection between the two as well as the substantial amount of introduced silica in the silcretes greater than in the inland silcretes resulting in volume increases in some eastern silcretes oxygen isotopic calculations for the silcretes indicate that the silica precipitated from groundwaters at temperatures slightly higher than present conditions silcrete formation apparently occurred during the miocene and pliocene basalts in victoria younger than pliocene lack associated silcrete and may reflect the much wetter climate in southeastern australia at that time the inland silcretes of central south australia can be divided into pedogenic the most common and groundwater varieties the pedogenic silcretes which show typical soil features like columnar and nodular textures contain moderate amounts of introduced silica that precipitated by evaporation from saline groundwaters for the groundwater silcretes which have massive textures and formed at or close to the water table insufficient data are available to determine the mode of formation the inland pedogenic silcretes have probably been forming from the eocene miocene to the present implying that conditions of seasonally high evaporation have occurred in central australia during this time period thus silcrete formation depends on a complex interplay between climate and silica supply and it is impossible to generalize that the presence of silcrete is indicative of a particular climate likewise the elemental composition of silcretes particularly ti content is not necessarily of climatic significance nevertheless detailed geochemical and oxygen isotopic studies of a silcrete and its parent material can elucidate the mechanisms of silcrete formation and if evaporation is indicated as a major factor in silcrete formation then the climate at the time was likely to have been at least seasonally arid

using groundwater geochemistry and environmental isotopes to assess the correction of 14c ages in a silicate dominated aquifer system summary the use of 14c to constrain groundwater residence times requires careful correction of 14c activities a14c and an assessment of the degree of inter aquifer mixing in groundwater of the campaspe valley in the southern murray basin australia 13c values of dissolved inorganic carbon dic range from 18 to 2 using these 13c values to correct 14c ages assuming that dissolution of or exchange with matrix calcite had occurred implies that locally 90 of the dic is derived from carbonates in turn this suggests that low salinity groundwater in the deeper confined calivil renmark formation up to 50 60 km from the basin margins in the campaspe valley has a component of modern recharge which would require that widespread leakage from the overlying shepparton formation had occurred however 87sr 86sr ratios and major ion geochemistry of groundwater imply that negligible inter aquifer mixing has occurred and that calcite dissolution is a very minor process the variable 13c values are most probably due to methanogenesis via reduction of co2 in the groundwater that results in the residual dic being enriched in 13c as methanogenesis by this mechanism has only a minor impact on a14c uncorrected 14c ages are a better estimate of groundwater residence times groundwater in the north of the campaspe valley has a residence time of 9 13 ka which agrees with ages calculated from head gradients and hydraulic conductivities calivil renmark groundwater from the adjacent pyramid hill region in an area where the aquifers contain lower hydraulic conductivity sediments is substantially older up to 20 25 ka the age of groundwater from the shepparton formation increases irregularly with depth with ages of in excess of 25 ka recorded at its base this study illustrates the need to fully understand hydrogeological processes in order to correct 14c ages especially in silicate dominated aquifers where dissolution of carbonates may not be the major process controlling 13c values

constraining groundwater recharge and the rate of geochemical processes using tritium and major ion geochemistry ovens catchment southeast australia summary constraining recharge is essential for understanding and managing groundwater systems this study uses high precision tritium 3 h concentrations together with major ion and environmental isotope sr c o h geochemistry to constrain rates of recharge and geochemical processes in the ovens catchment of the southeast murray basin australia 3 h concentrations of groundwater in the ovens catchment decline with depth but not with position in the catchment implying that recharge occurs over broad areas recharge rates calculated using an exponential piston flow model are 120 180 mm yr in the coarse grained alluvial gravels of the upper and middle ovens and 30 45 mm yr in the finer grained sediments of lower ovens these recharge rates are similar to those calculated from the response of shallow bore hydrographs to rainfall the geochemistry of groundwater with low 60 160 mg l total dissolved solids tds from the upper and middle ovens indicates that dissolution of both silicate minerals and calcite has occurred major ion geochemistry 87 sr 86 sr ratios and 13 c values in the upper and middle ovens groundwater are correlated with groundwater residence times and constrain the progress of mineral reactions dissolution of silicates with high 87 sr 86 sr ratios biotite and k feldspar occurs prior to dissolution of silicates with low 87 sr 86 sr ratios plagioclase and calcite mineral dissolution mainly occurs in the upper 20 m of the aquifer system with relatively little change in geochemistry deeper in the flow system groundwater from the lower ovens has higher tds contents 600 9600 mg l due to higher degrees of evapotranspiration although a correlation between tds and groundwater residence times exists it is more likely to reflect differential recharge rates and not the rate of evapotranspiration the conclusion that recharge occurs across the ovens catchment indicates that protection of groundwater from surface contamination is dependent on the protection and management of large areas

a compartmental mixing cell approach for the quantitative assessment of groundwater dynamics in the otway basin south australia abstract transient groundwater fluxes as calculated by a groundwater flow model modflow are used as input into a compartmental mixing cell cmc model to simulate the transport of hydrochemical and isotopic species in regional groundwater systems good agreement between modeled and measured concentrations of solutes in groundwater provides greater confidence in estimating aquifer parameters for the flow model the cmc model is currently developed for multi layered groundwater systems and allows for both recharge to the uppermost aquifer and upward or downward leakage between individual aquifers the combination of the cmc approach and modflow allows chemical and hydraulic data to be analysed simultaneously to allow for improved conceptualization of the groundwater system the use of transient fluxes reflects the temporal scale and variability of the chemical tracers as well as the temporal variability of hydraulic conditions the model is applied to a transect in the gambier embayment of the otway basin in south australia to quantify mixing between two main aquifer systems this groundwater system is hydraulically connected to the ocean in the west and as a result would have been affected by sea level changes over the last 30 000 yr radiocarbon simulations helped to quantify a major zone of downward leakage to the confined aquifer with modeled rates of leakage ranging 2 9 mm yr

the hydrogeology hydrochemistry and environmental isotopes of the campaspe river aquifer system north central victoria australia the campaspe river hydrogeological system of north central victoria consists of two major units 1 the tertiary deep lead aquifer a combination of the renmark group and calivil formation which forms the major aquifer of the region and 2 the plio pleistocene shepparton formation which forms a complex aquitard aquifer system on top of the deep lead recharge to the deep lead aquifer is twofold 1 a major component of recharge occurs along the southern reaches of the campaspe river where the overlying shepparton formation is thin and becomes more permeable and 2 recharge occurs by vertical downward movement of water from the shepparton formation whose heads are everywhere higher than those of the deep lead natural discharge from the system occurs further to the northwest beyond the murray river salinity gradually increases down gradient in the deep lead with an abrupt increase to greater than 6000 mg l 1 total dissolved solids close to the murray river except in the goornong area in the south which appears to be separated from the main deep lead system this increase is characterised by a certain hydrochemical evolution of the water wherein very fresh recharge with a mnacl 1 0 changes to an oceanic type composition while still in the low salinity range this is due largely to concentration of the original solutes in the system and is the consequence of salt remobilisation within the catchment the shepparton formation waters on the other hand are characterised by disorder namely fresh to saline water juxtaposed both horizontally and vertically heads in both the shepparton formation and the deep lead had been increasing at the rate of about 15 20 cm yr 1 for at least several decades the advent of large scale withdrawal from the deep lead in the early 1980s has arrested this trend in the northern and central portions of the area a decline in aquifer pressures is evident this decline will induce increased leakage from the shepparton formation down into the deeper aquifer and such leakage could possibly result in a degradation of its water quality stable isotope data indicate that under the existing hydrologic regime little irrigation drainage water has penetrated to the deep system

delivery of marine chloride in precipitation and removal by rivers in the murray darling basin australia abstract rising groundwater tables and increasing river salinities are major problems in the semi arid murray darling m d drainage basin of se australia chemical data from precipitation rivers and groundwaters are integrated here to estimate chloride fluxes in the context of dramatic alteration of the hydrologic balance in the basin initiated during european settlement approximately 150 years ago our analysis indicates that about half of cl deposition from the atmosphere in the western murray basin is derived from resuspended regional continental dust resulting in high ca na ratios in bulk precipitation samples estimates of recent marine deposition of cl to the m d basin were made by excluding rainfall data from sites having high ca na ratios basin wide budgets for cl delivery from the atmosphere and removal by rivers indicate that the darling basin retains about 90 of current annual input of marine cl whereas the river murray exports two to three times current annual input to the murray basin exclusive of the darling some implications from this study are as follows 1 1 re evaluation of net marine cl input by rain implies that recent model calculations of 36 cl cl inputs from the atmosphere to the murray basin may differ significantly from actual values in particular net 36 cl cl input ratios from the atmosphere to the western murray basin may be a factor of two higher than those derived assuming all cl in rain is of recent marine origin 2 2 the very large inventories of salt within the two catchments especially the saline groundwaters of the murray basin accumulated over very long periods probably of the order of a few million years the current rearrangements of stored salinity as a result at least in part of human perturbations of the hydrologic balance are likely to continue for an extended period because of the massive quantities of salts involved and thus present major limitations on options for long term management of the m d basin

groundwater reorganization in the floridan aquifer following holocene sea level rise sea level fluctuations can have a profound impact on coastal groundwater circulation the geochemistry of groundwater in the floridan aquifer system suggests that the fresh water in the upper aquifer was emplaced primarily during the last glacial period when sea level was more than 100 m lower than at present

effects of cloud diabatic heating on the early development of the fastex iop17 cyclone a set of numerical simulations is used to study the first development phase of the fastex cyclone a particularly well sampled frontal cyclone system that developed on the trailing front of a primary large scale baroclinic wave during intensive observation period 17 iop17 of fastex the fronts and atlantic storm track experiment the role of diabatically induced vertical circulations is investigated with a combination of diagnostic tools including a generalized omega equation and keyser s psi vector technique applied to the model outputs the full physics simulation shows a good agreement with observed data particularly the splitting of the upper level flow into a pair of jet streaks analysis of the contributions to the vertical ageostrophic transverse circulations near the jet streak pair structure shows that a positive feedback exists between the storm s dynamical configuration and the diabatic processes in the second part of the paper this interpretation is confirmed by a sensitivity analysis excluding cloud processes results suggest that after initial baroclinic growth the storm evolves towards a purely diabatic deepening regime leading to a diabatic rossby wave mechanism as proposed by recent wave cisk conditional instability of the second kind theoretical studies

time to reach near steady state in large aquifers 1 a new analytical solution of the flow equation has been developed to estimate the time to reach a near equilibrium state in mixed aquifers i e having unconfined and confined portions following a large hydraulic perturbation near equilibrium is defined as the time for an initial aquifer perturbation to dissipate by an average 95 across the aquifer the new solution has been obtained by solving the flow system of a simplified conceptual model of a mixed aquifer using laplace transforms the conceptual model is based on two assumptions 1 the groundwater flow can be reduced to a horizontal 1 d problem and 2 the transmissivity a function of the saturated thickness is assumed constant on the unconfined portion this new solution depends on the storativity of the unconfined portion the lengths of the unconfined and confined portions and the transmissivity assumed to be constant and equal in both portions of the mixed aquifer this solution was then tested and validated against a numerical flow model where the variations of the saturated thickness and therefore variations of the transmissivity were either ignored or properly modeled the agreement between the results from the new solution and those from the numerical model is good validating the use of this new solution to estimate the time to reach near equilibrium in mixed aquifers this solution for mixed aquifers as well as the solutions for a fully confined or fully unconfined aquifer has been used to estimate the time to reach near equilibrium in 13 large aquifers in the world for those different aquifers the time to reach near equilibrium ranges between 0 7 kyr to 2 4 107 kyr these results suggest that the present hydraulic heads in these aquifers are typically a mixture of responses induced from current and past hydrologic conditions and thus climate conditions for some aquifers the modern hydraulic heads may in fact depend upon hydrologic conditions resulting from several past climate cycles

a phase locking perspective on rossby wave amplification and atmospheric blocking downstream of recurving western north pacific tropical cyclones abstractthe extratropical transition et of tropical cyclones tcs can significantly influence the evolution of the midlatitude flow however the interaction between recurving tcs and upstream u

mapping using the tsyganenko long magnetospheric model and its relationship to viking auroral images the tsyganenko long magnetospheric model 1987 has been used in conjunction with ultra violet images taken by the viking spacecraft to investigate the relationship of the auroral distribution to different magnetospheric regions the model describes the large scale structure of the magnetosphere reasonably well for dipole tilt angles near zero but it appears to break down at higher tilt angles even so a wide variety of auroral configurations can be accurately described by the model it appears that the open closed field line boundary is a poor indicator of auroral arc systems with the possible exception of high latitude polar arcs the auroral distribution typically called the oval maps to a region in the equatorial plane quite close to the earth and can be approximately located by mapping the model current density maximum from the equatorial plane into the ionosphere although the model may break down along the flanks of the magnetotail the large scale auroral distribution generally reflects variations in the near earth region and can be modeled quite effectively

rossby wave packets on the midlatitude waveguide a review abstractrossby wave packets rwps are rossby waves for which the amplitude has a local maximum and decays to smaller values at larger distances this review focuses on upper tropospheric transient rwps along the midlatitude jet stream their central characteristic is the propagation in the zonal direction as well as the transfer of wave energy from one individual trough or ridge to its downstream neighbor a process called downstream development these rwps sometimes act as long range precursors to extreme weather and presumably have an influence on the predictability of midlatitude weather systems the paper reviews research progress in this area with an emphasis on developments during the last 15 years the current state of knowledge is summarized including a discussion of the rwp life cycle as well as rossby waveguides recent progress in the dynamical understanding of rwps has been based in part on the development of diagnostic methods these methods include algorithms to identify and track rwps

a chemical model for the evolution of australian sodium chloride lake brines abstract we present a chemical model which calculates the composition of waters as they are progressively concentrated from various starting compositions to determine the important processes leading to the development of na cl type brines typical of australia the model can be extended to other continental settings which are characterised by low rainfall low topographic relief and highly weathered regolith the model extends previous brine evolution models to include clay mineral solution reactions as a means of controlling aqueous silica concentrations and we suppress k concentrations via clay mineral interactions our model also evaluates the importance of elevated partial pressures of co2 which mimics situations encountered in groundwaterfed systems several important controls on major ion evolution were observed 1 1 initial ca alkalinity ratios must be greater than 0 5 to generate cl rich brines of circum neutral ph one thousand fold concentration of average australian river water ca alk 0 31 generates alkaline high ph brines while the same ionic strength brine derived from mean australian rainwater ca alk 1 2 generates a brine which is two orders of magnitude lower in alkalinity 2 2 elevated pco2 values which occur in subsurface waterssuppresses precipitation of carbonate minerals this allows ca to build up more quickly thereby accelerating the onset of gypsum precipitation 3 3 aqueous silica concentrations are controlled by equilibrium with clay minerals in the dilute waters but reach amorphous silica saturation in concentrated brines because of the reduced activity of the neutral sio2 aq species in high ionic strength brines 4 4 continual dissolution and reprecipitation of salts in the groundwaters or efflorescent crusts are responsible for minor and trace element ratios very different from that of the initial starting waters

the extratropical transition of hurricane irene 1999 a potential vorticity perspective extratropical transition et of tropical cyclones is common in all ocean basins where tropical cyclones recurve polewards after the tropical cyclone experiences et a rapid deepening can take place resulting in the development of a very large and deep extratropical cyclone the et of hurricane irene 1999 was an example of such an explosive et irene formed in the caribbean and experienced et as it moved poleward resulting in a low pressure system which deepened 39 hpa in 24 hours according to the met office analyses the extent to which the hurricane was responsible for the explosive extratropical development has been determined by performing met office unified model forecasts from initial states with and without the hurricane the circulation and temperature anomalies associated with the hurricane were removed from the initial state using potential vorticity inversion the moisture anomaly co located with the hurricane core was also removed the results show that an extratropical cyclogenesis event takes place regardless of the presence of the hurricane in the initial conditions however the hurricane makes a significant difference to the track and central mean sea level pressure evolution of the resulting extratropical cyclone when irene was present the track of the extratropical cyclone was more zonal and the cyclone deepening rate was twice as fast as when irene was not present these effects appear to be particularly associated with a negative potential vorticity anomaly and enhanced divergent flow in the region of the upper level outflow of the transforming hurricane rather than with the hurricane vortex results also show that the presence of the hurricane resulted in a significant downstream surface low development in the eastern atlantic copyright 2004 royal meteorological society

oval intensifications associated with polar arcs the existence of large scale auroral forms in the high latitude region poleward of the auroral oval has generated much interest in recent years because of the implications these forms have for magnetospheric topology often these so called polar cap arcs are observed to be connected to auroral regions which are identified with plasma sheet particle populations these connection points are sometimes associated with intensifications in the auroral distribution observations with the viking uv imager show that these intensifications are highly dynamic on time scales of minutes being sometimes suggestive of substorms the polar arcs may move in response to the dynamics of the intensification or else remain spatially fixed

the role of soil organic matter in the geochemical cycling of chloride and bromide abstract chloride to bromide ratios were determined for rainfall in western australia and groundwaters and surface waters from a number of catchments in western australia victoria and queensland the ratio in rainfall though showing a large short term scatter on average reflected the ratio in ocean water groundwaters and surface waters often showed characteristic differences in cl br presumably associated with the cycling of bromide through soil organic matter to prove this association it is shown that in the leachate of saturated small columns of soil the cl br ratio is governed by chloride and bromide released from decomposing organic matter on leaching the columns of soil the cl br weight ratio decreased rapidly from a high 300 reflecting rainfall to a low 10 reflecting the ratio of chlorine to bromine bound to soil organic matter

paleoclimatic investigations using isotopic signatures of the late pleistocene holocene groundwater of the stratified aquifers in kuwait abstract the study attempts to determine paleo recharge sources for two major aquifer units of kuwait namely kuwait group aquifer kga and dammam formation dfm were collected and analyzed for major ions and isotopes the obtained results of 14c ages indicated that the groundwater samples ranged from 31 9 ky to 3 9 ky in dfm and 23 3 ky to 0 8 ky in kga the variations in 18o signatures with respect to age reflected that there were two major sources of rainwater such as enriched southern indian ocean monsoon and the depleted northwesterly mediterranean vapor source the samples found to show variations during the three marine isotopic stages mis 1 3 heinrich events bolling allerod and dryas time periods in both aquifers a shift in the intertropical convergence zone itcz was witnessed in the groundwater of both aquifers from 7 8 ky to 4 9 ky the variation in the holocene climate is mainly due to the influence of tropospheric easterly jet governed by the swing in itcz as a result of holocene volcanism the mean 18o values of dfm samples 3 81 reflect depletion than kga samples 2 31 and the d excess values were 0 95 and 2 05 respectively thus it could be inferred that the dfm was predominantly recharged during late pleistocene period and it was in a relatively cooler climate than recharge environment of kga the study infers that kga was recharged between 26on and 26 8on latitudes and that of the dfm was noted to be recharged south west of kuwait in two different patches between 25 8on and 26 2on and 26 7on 27 4on latitudes during late pleistocene the kga was concluded to be recharged between 25 5on and 27 5on latitudes south of kuwait during holocene

thermal history of michigan basin and southern canadian shield from apatite fission track analysis apatite fission track ages and confined length distributions were collected from 38 basement outcrop and 5 basement drillcore samples in order to reconstruct the phanerozoic thermal history of the michigan basin and southern canadian shield the apatite data indicate two periods of thermal activity in the region triassic heating cooling that affected the basin and adjacent shield and cretaceous or post cretaceous heating cooling that primarily affected the basin the magnitude timing and cause of cretaceous thermal activity cannot be identified with the present data model calculations suggest that some of the shield samples and probably all of the basin samples were heated to temperatures of at least 90c just prior to relatively rapid cooling in the triassic available stratigraphic and geochemical constraints suggest that these elevated temperatures were the result of burial by an additional 2 5 km of late paleozoic probably pennsylvanian and permian sediments it is likely that the basin was buried during the alleghenian orogeny as observed for the adjacent appalachian basin

the downstream impact of tropical cyclones on a developing baroclinic wave in idealized scenarios of extratropical transition the interaction of a tropical cyclone with a developing baroclinic wave is investigated in an idealized scenario of extratropical transition et the impact of et is examined by comparing and analyzing two numerical baroclinic wave experiments a traditional experiment in which baroclinic development is excited by a localized upper level perturbation on a realistic jet profile and an experiment in which additionally a model tropical cyclone is inserted south of the jet at the initial time et occurs in a wavy upper level flow while baroclinic surface systems are still weak the characteristic direct impact of et on the midlatitude flow is the formation of a distinct jet streak and the amplification of a ridge trough couplet in the adjacent downstream region the subsequent rapid cyclogenesis downstream is a direct consequence of these upper level flow modifications this faster and stronger development constitutes the amplification of the leading edge of downstream development both the upper level wave pattern and the surface development are subsequently amplified in the region further downstream the formation of the ridge adjacent to the intensified downstream cyclone is analyzed in detail to elucidate the next stage in the downstream dispersion of the et impact ridge building in the et scenario exhibits characteristics distinct from those in the life cycle experiment wave breaking feedback from the modified low level frontal structure and diabatic processes all contribute to the high amplitude wave pattern downstream of et the downstream impact of et is highly sensitive to the initial storm location and intensity the considerable amplification of the leading edge found in the reference experiment is the most widespread and rapidly propagating impact we thus speculate that this leading edge represents an optimal location of the midlatitude circulation where et can lead to the most significant impact on the downstream flow copyright 2010 royal meteorological society

the extratropical transition of tropical cyclones part i cyclone evolution and direct impacts abstractextratropical transition et is the process by which a tropical cyclone upon encountering a baroclinic environment and reduced sea surface temperature at higher latitudes transforms into an extratropical cyclone this process is influenced by and influences phenomena from the tropics to the midlatitudes and from the meso to the planetary scales to extents that vary between individual events motivated in part by recent high impact and or extensively observed events such as north atlantic hurricane sandy in 2012 and western north pacific typhoon sinlaku in 2008 this review details advances in understanding and predicting et since the publication of an earlier review in 2003 methods for diagnosing et in reanalysis observational and model forecast datasets are discussed new climatologies for the eastern north pacific and southwest indian oceans are presented alongside updates to western north pacific and north atlantic ocean climatologies advances in understanding and in some cases mode

the impact of tropical remnants on extratropical cyclogenesis case study of hurricanes danielle and earl 1998 abstract the importance of remnant tropical cyclone tc circulation and moisture structures is investigated for a simultaneous extratropical transition et event involving ex hurricanes danielle and earl september 1998 although both storms undergo prolonged periods of reintensification following et the forcings involved in each of their redevelopment processes differ fundamentally a review of the tropical and baroclinic et modes in the north atlantic stresses the importance of jet front structures to the nature of the reintensification process ex hurricane danielle begins to redevelop in the eastern half of the basin in the downstream poleward sector of an intensifying polar jet the system undergoes a tropical mode of reintensification resulting in a troposphere deep warm environment surrounding the storm devoid of near surface fronts and maintained by strong tropopause folds at its periphery ex hurricane earl reintensifies near the eastern seaboard according to a baroclinic mode under the i

constraining modern and historical recharge from bore hydrographs 3h 14c and chloride concentrations applications to dual porosity aquifers in dryland salinity areas murray basin australia summary water table fluctuations and renewal rates based on 3h and 14c concentrations in bores screened within 5 m of the water table were used to estimate recharge rates in five dryland salinity areas in northern victoria australia given the resolution of each technique both methods yield broadly similar results of 4 90 mm yr up to 14 of modern rainfall that reflect the recharge rates following land clearing over the last 200 years deeper bores show mixing of modern recharge with older water flowing laterally through the aquifers recharge estimates based on cl concentrations are up to two orders of magnitude lower

environmental isotopes as indicators of inter aquifer mixing wimmera region murray basin southeast australia abstract complex groundwater flow systems in confined aquifers that result from geological structures stratigraphic changes or the absence of efficient aquitards are difficult to constrain using physical parameters alone despite a relatively simple aquifer configuration the distribution of groundwater total dissolved solids tds concentrations 13c values 87sr 86sr ratios and 14c activities a14c in groundwater in the wimmera region of the southern murray basin implies that considerable inter aquifer flow has occurred given the presence of both silicate and carbonate aquifers 13c values and 87sr 86sr ratios are the key parameters that demonstrate inter aquifer flow locally between 40 and 95 of water from one aquifer has infiltrated the underlying aquifer homogenising many aspects of the groundwater geochemistry groundwater residence times estimated from a14c range from modern to 30 ka and the distribution of 14c residence times confirm that inter aquifer flow is regional scale and long term recharge of the deepest aquifers occurs across a broad region and not solely at the basin margins vertical leakage rates are 6 10 10 3 m year and long term recharge rates 0 1 0 2 mm year

downstream development associated with the extratropical transition of tropical cyclones over the western north pacific abstract the movement of a tropical cyclone into the midlatitudes involves interactions among many complex physical processes over a variety of space and time scales furthermore the extratropical transition et of a tropical cyclone may also result in a high amplitude rossby wave response that can extend to near hemispheric scales after an et event occurs over the western portion of a northern hemisphere ocean basin the high amplitude downstream response often forces anomalous midlatitude circulations for periods of days to a week these circulations may then be related to high impact weather events far downstream of the forcing by the et event in this study downstream development following et events over the western north pacific ocean is examined local eddy kinetic energy analyses are conducted on four cases of north pacific tropical cyclones of varying characteristics during et into varying midlatitude flow characteristics during 15 july 30 september 2005 the goal is to examine the impact of e

hydrogeochemical and isotopic constraints on the origins of dryland salinity murray basin victoria australia abstract combined hydrogeological and hydrogeochemical data allow flow systems and the origins of solutes in the honeysuckle creek area of the southeastern murray basin which is an area affected by dryland salinity to be constrained recharge occurs both on the uplands that are composed of fractured violet town volcanic rocks and the riverine plain that comprises sediments of the shepparton and coonambidgal formations groundwater from the violet town volcanics has low salinity 20 mmol l groundwater has intermediate cl br ratios 600 1000 which indicate that the high salinities do not simply result from halite dissolution rather mixing of groundwater homogenises cl br ratios and evaporation as a consequence of a shallow water table is the dominant process that increases salinity oxygen and h isotopes also indicate that mixing and evaporation have occurred these results indicate that land use over the whole region not just the uplands needs to be considered in any salinity management plans additionally future development of salinity is controlled by depth to the water table on the plains and the efficiency of recharge rather than by salt stores halite or brines in the unsaturated zone

decoupling of solutes and water in regional groundwater systems the murray basin australia documenting the origins residence times and movement of groundwater and the solutes that it contains is critical to understanding hydrogeological systems this study uses cl mass balance to determine the cl accession time i e the time required for cl to accumulate and cl to estimate the residence times of cl in the victorian portion of the murray basin southeast australia much of the murray basin contains saline groundwater with total dissolved solids tds concentrations commonly 14 000 mg l and locally up to 300 000 mg l the total mass of cl stored in the victorian portion of the basin is estimated as between 12 400 and 47 100 mt using present day rainfall totals and cl concentrations in rainfall the cl accession time is 170 to 650 ka aquifer thicknesses and groundwater salinity both increase westwards in this part of the murray basin consequently the cl accession times increase westward from 0 1 0 6 ka to 286 1080 ka by contrast c activities of the majority of the groundwater are 2 pmc and commonly much higher notwithstanding the difficulty in correcting c residence times the widespread occurrence of groundwater with above background c activities implies that groundwater residence times are generally 30 ka which is substantially shorter than the cl accession times rcl the ratio of cl to total cl 10 values of the groundwater are between 20 and 230 and are uncorrelated with cl concentrations while it is difficult to determine precise cl residence times the observation that the rcl values are significantly higher than those that represent secular equilibrium with the aquifer matrix rcl of 5 to 10 indicates that they are up to a few hundred thousand years and similar to the cl accession times the rcl values together with the geology of the aquifers stable isotope ratios and major ion geochemistry precludes halite dissolution incorporation of connate water or the long term diffusion of cl from clays as mechanisms of producing the elevated cl concentrations rather it is most likely that the high cl concentrations result from recycling of solutes in saline lakes and playas or repeated cycles of evapotranspiration in the unsaturated zone

constraining groundwater flow residence times inter aquifer mixing and aquifer properties using environmental isotopes in the southeast murray basin australia environmental isotopes particularly d 18 o d 2 h and d 13 c values 87 sr 86 sr ratios and a 14 c constrain geochemical processes recharge distribution and rates and inter aquifer mixing in the riverine province of the southern murray basin due to methanogenesis and the variable d 13 c values of matrix calcite d 13 c

genetic identification of the saline origins of groundwaters in israel by means of minor elements abstract b f and sr in natural groundwaters of israel tend either to correlate with salinity or to show consistently high concentrations rising from a ppb to a ppm level as salinity increases their relations to cl na and ca as well as their mutual relationship can be used to identify the origin of the salinity the division of the waters into genetic groups which generally coincide with their geographical distribution is based on m b m cl vs mcl and m f m cl vs m na m cl plots as well as by m sr m ca ratios the water groups defined in this way exhibit various salinities each indicative of the processes involved in their evolution namely evaporation leaching and dilution seawater and brines or reflect the geothermal origin these water types are subdivided into two major groups 1 1 the western catchment of which the mediterranean sea is the base level and 2 2 the eastern catchment of which the land locked jordan dead sea rift valley is a lower base level this complex hydrogeological system has a multiple origin of salinity and has evolved through combinations of the above mentioned processes

remote impact of north atlantic hurricanes on the mediterranean during episodes of intense rainfall in autumn 2012 autumn is the most favourable season for tropical cyclones to undergo extratropical transition and interact with the midlatitude flow over the north atlantic autumn is also the season when intense rainfall over the mediterranean is often triggered by rossby wave breaking the impact of tropical cyclones on downstream wave breaking is investigated here during three episodes of intense rainfall which were the target of hymex hydrological cycle in mediterranean experiment in autumn 2012 five day simulations of hurricanes leslie rafael and sandy were performed with the meso nh model in a domain encompassing the north atlantic and the mediterranean control simulations were compared to simulations in which the hurricanes were filtered out from the initial conditions in each case the hurricane locally impeded the forward progression of an upstream trough then reintensified as an extratropical cyclone during the wrap up of the trough the local impact of leslie and rafael on the midlatitude flow quickly propagated downstream along a polar jet and amplified rossby wave breaking but decreased the intensity of the forecast precipitation over the mediterranean the local impact of sandy propagated downstream along a subtropical jet in addition to the polar jet and resulted in a weak impact of the forecast precipitation on the mediterranean this study suggests that the interaction of tropical cyclones with the midlatitude flow over the western north atlantic may be considered a perturbation to rather than a source of downstream wave breaking

cyclogenesis downstream of extratropical transition analyzed by q vector partitioning based on flow geometry abstractduring extratropical transition et tropical cyclones exert a significant impact on the midlatitude circulation archetypical features of this impact are jet streak formation amplification of the downstream trough and modification of the associated downstream cyclogenesis this study investigates the relative importance of the jet streak and the upper level trough for cyclone development by quantifying the respective contributions to midtropospheric vertical motion using the q vector partitioning by j c jusem and r atlas their framework is here extended from quasigeostrophic theory to alternative balance the q vector under alternative balance involves the nondivergent wind instead of the geostrophic wind and therefore represents more accurately the balanced dynamics associated with vertical motion in particular downstream of et where the flow often exhibits significant curvature associated with the amplified trough an idealized et scenario and three real cases the cyclones downstream

climatic and lithologic controls on the temporal and spatial variability of co2 consumption via chemical weathering an example from the australian victorian alps abstract a detailed geochemical study on river waters of the australian victorian alps was carried out to determine i the relative significance of silicate carbonate evaporite and sulfide weathering in controlling the major ion composition and ii the factors regulating seasonal and spatial variations of co2 consumption via silicate weathering in the catchments major ion chemistry implies that solutes are largely derived from evaporation of precipitation and chemical weathering of carbonate and silicate lithologies the input of solutes from rock weathering was determined by calculating the contribution of halite dissolution and atmospheric inputs using local rain and snow samples despite the lack of carbonate outcrops in the study area and waters being undersaturated with respect to calcite the dissolution of vein calcite accounts for up to 67 of the total dissolved cations generating up to 90 of dissolved ca and 97 of mg dissolved sulfate has 34s values of 16 to 20 cdt indicating that it is derived predominantly from atmospheric deposition and minor gypsum weathering and not from bacterial reduction of fes2 this militates against sulphuric acid weathering in victorian rivers ratios of si vs the atmospheric corrected na and k concentrations range from 1 1 to 4 3 suggesting incongruent weathering from plagioclase to smectite kaolinite and gibbsite estimated long term average co2 fluxes from silicate weathering range from 0 012 106 to 0 039 106 mol km2 yr with the highest values in rivers draining the basement outcrops rather than sedimentary rocks this is about one order of magnitude below the global average which is due to low relief and the arid climate in that region time series measurements show that exposure to lithology high physical erosion and long water rock contact times dominate co2 consumption fluxes via silicate weathering while variations in water temperature are not overriding parameters controlling chemical weathering because the atmospheric corrected concentrations of na k and mg act non conservative in victorian rivers the parameterizations of weathering processes and net co2 consumption rates in particular based on major ion abundances should be treated with skepticism

predictability of a mediterranean tropical like storm downstream of the extratropical transition of hurricane helene 2006 the extratropical transition et of a tropical cyclone is known as a source of forecast uncertainty that can propagate far downstream the present study focuses on the predictability of a mediterranean tropical like storm medicane on 26 september 2006 downstream of the et of hurricane helene from 22 to 25 september while the development of the medicane was missed in the deterministic forecasts from the european centre for medium range weather forecasts ecmwf initialized before and during et it was contained in the ecmwf ensemble forecasts in more than 10 of the 50 members up to 108 h lead time the 200 ensemble members initialized at 0000 utc from 20 to 23 september were clustered into two nearly equiprobable scenarios after the synoptic situation over the mediterranean in the first and verifying scenario helene was steered northeastward by an upstream trough during et and contributed to the building of a downstream ridge a trough elongated farther downstream toward italy and enabled the development of the medicane in 9 of 102 members in the second and nonverifying scenario helene turned southeastward during et and the downstream ridge building was reduced a large scale low over the british isles dominated the circulation in europe and only 1 of 98 members forecasted the medicane the two scenarios resulted from a different phasing between helene and the upstream trough sensitivity experiments performed with the meso nh model further revealed that initial perturbations targeted on helene and the upstream trough were sufficient in forecasting the warm core medicane at 84 and 108 h lead time

geochemical evidence for efficient aquifer isolation over geological timeframes aquitards layers of rock having low permeability have been suggested as potential long term reservoirs for toxic materials such as nuclear or chemical waste but information about the isolation properties of aquitard layers is essential to evaluate whether they can indeed be used safely as reservoirs here we investigate the long term mobility of groundwaters between two aquifers surrounding an aquitard layer in the eastern recharge area of the paris basin france using helium isotopes as a geochemical tracer the deeper trias sandstone aquifer which lies above the crystalline basement accumulates radiogenic 4he and primordial 3he from large regions of the crust and mantle at rates comparable to the degassing of the whole crust1 and of mid ocean ridges2 we show that the overlying carbonate dogger aquifer which is separated from the trias aquifer by an aquitard layer consisting of a 600 m succession of shales and clays is stagnant and has been extremely well isolated from the trias over the past several million years this finding together with previous studies at the centre of the paris basin3 4 shows that diffusive mass transfer across aquitards is negligible and that cross formational flow in basins takes place preferentially in faulted areas

orographic controls on rain water isotope distribution in the mount lofty ranges of south australia summary hydrogen and oxygen isotopes of water are common environmental tracers used to investigate hydrological processes such as evaporation vegetation water use surface water groundwater interaction and groundwater recharge the water isotope signature in surface water and groundwater evolves from the initial rain signature in mountain terrain rain water stable isotope composition spatially varies due to complex orographic precipitation processes many studies have examined the isotope elevation relationships while few have quantitatively investigate the terrain aspect and slope effect on rain isotope distribution in this paper we examine the orographic effects more completely including elevation terrain slope and aspect on stable isotope distribution in the mount lofty ranges mlr of south australia using a multivariate regression model the regression of precipitation isotope composition suggests that orographic effects are the dominant controls on isotope spatial variability about 75 of spatial variability in 18 o and deuterium excess is represented by the regression using solely orography related variables elevation terrain aspect and slope with about 25 of 18 o spatial variability attributed to the terrain aspect and slope effect the lapse rate is about 0 25 for every 100 m at both windward and leeward slopes however at the same elevation 18 o at the leeward slope eastern mlr is 0 5 larger than that at the windward slope the difference can be explained by different mechanisms continuous rain out processes on the windward side and sub cloud evaporation on the leeward side both 18 o and deuterium excess maps 1 km resolution are constructed based on the regression results for the mlr both maps are consistent with groundwater of local precipitation origin and useful to examine groundwater recharge

groundwater residence time and palaeohydrology in the otway basin south australia 2h 18o and 14c data stable isotopes 2h 18o and 13c and radiocarbon 14c have been used in conjunction with chemical data to evaluate recharge mechanisms groundwater residence time and palaeohydrology within the confined dilwyn sand aquifer in the gambier embayment of the otway basin this aquifer does not receive recharge down gradient of the hydraulic hinge line and data have been interpreted along two discrete flow lines the mean residence time of groundwater determined by 14c in the confined aquifer from the hydraulic hinge position to the sea a distance of about 50 km along an inferred flow path is approximately 12 800 years the corresponding hydraulic travel time calculated from darcy s law is approximately 49 000 years the apparent discrepancy may be a result of eustatic sea level lowering during the last glacial because the groundwater system is hydraulically connected to the sea lower sea level would result in increased gradients and a decrease in groundwater residence time variations in stable isotopic composition along flow lines suggest a number of recharge mechanisms stable isotope data indicate progressive depletion of 2h and 18o in the groundwaters over the past 30 000 years groundwaters older than about 10 000 years b p were recharged either during a cooler climate climatic regime lower precipitation evapotranspiration and temperature and or the vapour source s had travelled over greater continental mass than those recharged over the past 10 000 years lower chloride concentrations in some of the older groundwaters indicate lower evapotranspiration rates in the recharge areas before 10 000 years ago

past changes to isotopic and solute balances in a continental playa clues from stable isotopes of lacustrine carbonates in many salt lakes around the world the relative abundance of preserved authigenic minerals is different from that predicted from solute mass balance calculations conventional mass balance models assume that chloride behaves conservatively over long periods of time and fail to take into account the role of diffusion deflation and fractional crystallisation dissolution of salts an alternative approach is to use oxygen isotopes as these reflect directly water molecule rather than solute concentrations and have the added advantage of providing a palaeohydrological record in lacustrine carbonates we present a steady state stable isotope model in conjunction with stable isotopic measurements of sub surface brines regional groundwaters and carbonate deposits from the lake malata lake greenly playa complex in south australia to estimate the apparent leakage and palaeoleakage from these superficially closed playa lakes the steady state model calculations using the present and compositions of the lake brines and inflowing groundwater suggest that the apparent present day leakage for the complex is 75 to 90 of inflow 35 times that calculated from cl and br under such conditions only low magnesian calcite precipitates and the lake water experiences reduced effects of evaporation gas and vapour exchange and consequently reduced isotopic and chemical enrichment further our model shows that calcite becomes increasingly mg rich until leakage is reduced to 55 to 70 of inflow a condition favourable for dolomitisation and of the lacustrine carbonates show excursions on the order of 5 over the length of a 2 3 m core indicating that the lake complex has varied from being throughflow dominated presence of low mg calcite relatively depleted in and to evaporation dominated high mg calcite dolomite relatively enriched in and throughout late quaternary our estimates of leakage fractions are consistent with the observed mineralogical suite but there remains a discrepancy between apparent closure indicated by the presence of the highly saline brine reservoir 1 leakage and high rates of throughflow inferred from stable isotope data we propose that the brine was formed by winter time re solution of a seasonal halite crust which forms during summer dominated evaporative discharge recirculation of the secondary brine and mixing with regional groundwater may decouple the solute cycle from the water cycle in many playa lakes the end result is a partially mixed brine characterised by nearly conserved solutes but with isotopic signatures indicative of brine rainfall groundwater interactions

origin of the shallow groundwater system in the southern voltaian sedimentary basin of ghana an isotopic approach the development and management of groundwater resources require an ability to understand and identify the recharge source to the groundwater system stable and radioactive isotope data have been used to investigate the source of recharge and the age of the shallow groundwater system within the southern voltaian sedimentary basin svsb of ghana as part of an on going groundwater development project the tritium concentrations in the groundwater samples are very low and range from less than 1 7 2 t u while measured 14c content ranges from 43 to 108 modern carbon the tritium concentration of rainfall ranges from less than 1 4 t u the 18o values of groundwater samples range from 4 2 to 2 6 while the d values range from 21 to 10 stable isotopic data of the groundwater samples lie either on or close to the global meteoric water line gmwl on the d 18o plot and indicate that the shallow groundwater in the area is derived from meteoric water that has undergone no significant degree of kinetic evaporation during recharge no indication of paleo recharge can be inferred from the 18o and 2h composition of the groundwater current tritium concentration in the groundwater is generally low however it proved useful in the qualitative identification of modern recharge radiocarbon deduced ages range from about b p to modern and indicate young recharge to the shallow groundwater system

environmental isotope hydrology of salinized experimental catchments deuterium oxygen 18 tritium and chloride concentrations were used in three salinized experimental catchments to gain insight into the mechanism of solute concentration and flow processes in the saturated and unsaturated zones the three experimental catchments were studied because of their location in different rainfall regions their status with respect to clearing of native vegetation and with respect to secondary salinization two uncleared catchments have average annual rainfalls of approximately 820 and 1220 mm respectively the third cleared catchment has an annual rainfall of 650 750 mm this catchment was in an advanced state of secondary salinization and displayed large areas of saline groundwater discharge with halite encrustation at the ground surface the stable isotope compositions of the solution phase in solute bulge profiles in the unsaturated zone showed a close agreement with the amount weighted mean isotopic composition of rainfall and only surficial evidence of isotopic enrichment due to evaporation evaporation from the soil surface plays a minor role as a mechanism of solute concentration in the unsaturated zone the dominant process of solute concentration in the unsaturated zone was ion exclusion during uptake of water by tree roots which was evidently a solute but not isotope fractionating process tritium analyses of unsaturated zone water and grondwater indicated movement of recent recharge to 7 10 m depth at the low rainfall site but over the full depth of the 15 m unsaturated zone at the higher rainfall site the variability in 18o and 2h values of groundwaters was used in association with chloride concentrations to provide information on mixing characteristics of groundwaters within the catchments

the influence of the downstream state on extratropical transition hurricane earl 1998 case study abstract the multitude of tropical extratropical interactions that occur during an extratropical transition et complicate the prediction and diagnosis of these extreme events this study focuses on the analysis of a double et and reintensification event that took place between 5 and 7 september 1998 ex hurricanes earl and danielle reintensified rapidly over the western and eastern north atlantic respectively a set of simulations designed to test the sensitivity of earl s et to features in the downstream state was run using a set of idealizations for a numerical model s initial and boundary conditions downstream of ex hurricane earl dynamic tropopause analyses and the pv thinking paradigm applied under the eady model highlight important developmental and structural differences between the tests in fact two distinct solution modes are diagnosed both in the control and in the sensitivity tests earl s et proceeds according to a baroclinic mode of redevelopment whereas danielle displays distinct

numerical analysis of a mediterranean hurricane over southeastern italy abstract the presence of a subsynoptic scale vortex over the mediterranean sea in southeastern italy on 26 september 2006 has been recently documented by the authors the transit of the cyclone over land allowed an accurate diagnosis of the structure of the vortex based on radar and surface station data showing that the cyclone had features similar to those observed in tropical cyclones to investigate the cyclone in greater depth numerical simulations have been performed using the weather research and forecasting wrf model set up with two domains in a two way nested configuration model simulations are able to properly capture the timing and intensity of the small scale cyclone moreover the present simulated cyclone agrees with the observational analysis of this case identifying in this small scale depression the typical characteristics of a mediterranean tropical like cyclone an analysis of the mechanisms responsible for the genesis development and maintenance of the cyclone has also been p

geochemical and isotopic characterization of groundwater from the paleogene limestone aquifer of the upper jezireh syria this research aims to evaluate the groundwater resources of paleogene aquifer in the upper jazireh area syria in terms of chemical water type recharge zones and water ages the results show that the main recharge zones for the paleogene aquifer range between 650 and 900 m a s l which coincide with the outcrop of the karstified limestone in the mardin uplift the chemical and isotopic behaviors of groundwater together with radiometric 14c reflect the existence of three different groundwater groups 1 the fresh and cold water percolating in short and shallow flow paths for which the main replenishment processes are recent 2 the brackish and thermal water containing certain amounts of h2s gas that percolate in longer and deeper flow paths for which the main replenishment processes occurred during the palaeoclimatic humid conditions of pleistocene time placed at 10 18 ka bp 3 the brackish and admixed thermal groundwater with intermediate 14c age which seems to be formed as a result of mixing between the previous two groups

hurricane vortex dynamics during atlantic extratropical transition abstract simulations of six atlantic hurricanes are diagnosed to understand the behavior of realistic vortices in varying environments during the process of extratropical transition et the simulations were performed in real time using the advanced research weather research and forecasting wrf model arw using a moving storm centered nest of either 4 or 1 33 km grid spacing the six simulations ranging from 45 to 96 h in length provide realistic evolution of asymmetric precipitation structures implying control by the synoptic scale primarily through the vertical wind shear the authors find that as expected the magnitude of the vortex tilt increases with increasing shear but it is not until the shear approaches 20 m s 1 that the total vortex circulation decreases furthermore the total vertical mass flux is proportional to the shear for shears less than about 20 25 m s 1 and therefore maximizes not in the tropical phase but rather during et this has important implications for predictin

cl br ratios and environmental isotopes as indicators of recharge variability and groundwater flow an example from the southeast murray basin australia abstract systematic variations in cl br ratios together with r 36 cl values 14 c activities and 18 o values reflect differences in groundwater recharge and define groundwater flow paths in the riverine province of the southeast murray basin in groundwater from the shallowest shepparton formation homogenisation of cl br and 18 o values and a decline in 14 c activities with depth imply that vertical flow dominates the 14 c activities define variations in pre land clearing recharge in the palaeovalleys of present day rivers deep leads which contain sandier sediments higher recharge 0 5 to 1 4 mm year produced relatively fresh groundwater tds 36 cl values in groundwater from the goulburn subcatchment zones of groundwater with variable cl br ratios in the deeper calivil renmark aquifer also allow the detection of rapid leakage from the surface that has the potential to compromise groundwater resources

6000 years of environmental changes recorded in blue lake south australia based on ostracod ecology and valve chemistry abstract a 4 m long core taken from the freshwater blue lake crater near the township of mount gambier in southeastern south australia provided a high resolution palaeoclimatic record for the last six millennia accelerator mass spectrometry ams radiocarbon 14 c dates were obtained from organic plant fibres and biogenic carbonates from the laminated sequence of the core and from a modern water sample large discrepancies between the radiocarbon ages determined from plant fibres and biogenic carbonates indicate the presence of a time variable lacustrine reservoir which is consistent with what is known of the lake s hydrology ostracod assemblages associated with stable isotope 13 c 18 o analyses and in combination with mg ca sr ca and na ca analyses done on ostracod valves infer salinity temperature and water level changes in blue lake over the last 6 millenia the influence of local aquifers through time has also been determined from the na ca of ostracod valves approximately 900 year cycles are evident in the 13 c record from 5 4 ka to 1 8 ka the history of blue lake records an initial period of high hydrological variability around 6 ka becoming increasingly deeper as groundwater flowed into the basin by 4 ka the lake had reached steady state with the lake level fluctuating by as much as 9 m although significant geochemical variations represent temperature fluctuations until european settlement near the lake in 1839

a cyclone phase space derived from thermal wind and thermal asymmetry abstract an objectively defined three dimensional cyclone phase space is proposed and explored cyclone phase is described using the parameters of storm motion relative thickness asymmetry symmetric nonfrontal versus asymmetric frontal and vertical derivative of horizontal height gradient cold versus warm core structure via the thermal wind relationship a cyclone s life cycle can be analyzed within this phase space providing substantial insight into the cyclone structural evolution an objective classification of cyclone phase is possible unifying the basic structural description of tropical extratropical and hybrid cyclones into a continuum stereotypical symmetric warm core tropical cyclone and asymmetric cold core extratropical cyclone life cycles are illustrated using 1 navy operational global atmospheric prediction system nogaps operational analyses and 2 5 ncep ncar reanalyses the transitions between cyclone phases are clearly illustrated within the phase space including extratro

14c age reassessment of groundwater from the discharge zone due to cross flow mixing in the deep confined aquifer abstract in a groundwater flow system the age of groundwater should gradually increase from the recharge zone to the discharge zone within the same streamline however it is occasionally observed that the groundwater age becomes younger in the discharge zone in the piedmont alluvial plain and the oldest age often appears in the middle of the plain a new set of groundwater chemistry and isotopes was employed to reassess the groundwater 14c ages from the discharge zone in the north china plain ncp carbonate precipitation organic matter oxidation and cross flow mixing in the groundwater from the recharge zone to the discharge zone are recognized according to the corresponding changes of hco3 or dic and 13c in the same streamline of the third aquifer of the ncp the effects of carbonate precipitation and organic matter oxidation are calibrated with a 13c mixing model and dic correction but these corrected 14c ages seem unreasonable because they grow younger from the middle plain to the discharge zone in the ncp the relationship of cl content and the recharge distance is used to estimate the expected cl content in the discharge zone and ln a14c cl is proposed to correct the a14c in groundwater for the effect of cross flow mixing the 14c ages were reassessed with the corrected a14c due to the cross flow mixing varying from 1 25 to 30 58 ka and the groundwater becomes older gradually from the recharge zone to the discharge zone the results suggest that the reassessed 14c ages are more reasonable for the groundwater from the discharge zone due to cross flow mixing

using 3h and 14c to constrain the degree of closed system dissolution of calcite in groundwater abstract this study uses 3h concentrations 14c activities a14c 87sr 86sr ratios and 13c values to constrain calcite dissolution in groundwater from the ovens catchment se australia taken in isolation the 13c values of dissolved organic c dic and 87sr 86sr ratios in the ovens groundwater imply that there has been significant calcite dissolution however the covariance of 3h and 14c and the calculated initial 14c activities a014c imply that most groundwater cannot have dissolved more than 20 of 14c free calcite under closed system conditions rather calcite dissolution must have been partially an open system process allowing 13c and 14c to re equilibrate with co2 in the unsaturated zone recognising that open system calcite dissolution has occurred is important for dating deeper groundwater that is removed from its recharge area in this and other basins the study is one of the first to use 14c and 3h to constrain the degree of calcite dissolution and illustrates that it is a valuable tool for assessing geochemical processes in recharge areas

a comparison of the downstream predictability associated with et and baroclinic cyclones abstractthe impact of the extratropical transition et of tropical cyclones and baroclinic cyclogenesis in the western north pacific wnp atlantic and southern indian ocean sio basins on the predictability of the downstream midlatitude flow is assessed using 30 years of cases from the global ensemble forecast system gefs reforecast version 2 in all three basins et is associated with statistically larger 500 hpa geopotential height forecast standard deviation sd compared to the forecast climatology the higher sd values originate from where the tc enters the midlatitudes and spread downstream at the group velocity of the associated wave packet of the three basins wnp et is associated with the largest amplitude and longest lasting sd anomalies forecasts initialized 2 4 days prior to the onset of et have larger sd anomalies compared to forecasts initialized during or after the onset of et by contrast the region of positive sd anomaly associated with winter baroclinic cyclones is confined to

palaeohydrology and future climate change since the mid 1980s there has been growing concern that increasing concentrations of so called greenhouse gases will lead to global warming changes to regional climates and hence impacts on the environment society and economy the united nations environment program and the world meteorological organization in 1987 set up the intergovernmental panel on climate change ipcc which has reported on climate change predictions ipcc 1990a 1992a the possible impacts of climate change ipcc 1990b 1992b and strategies for mitigating the effects of climate change ipcc 1991 the ipcc second assessment is scheduled for publication in 1996 climate change science is essentially predictive it is trying to predict conditions during the twenty first century by far the most common approach is based around the use of global climate models gcms these numerical simulation models are used to predict the global and regional climatic effects of changing greenhouse gas concentrations and many climate change impact studies use scenarios based in some way on gcm simulations these scenarios are then used to perturb current climatic time series and fed through a catchment hydrological model to simulate river flows and other hydrological properties e g bultot et al 1988 lettenmaier gan 1990 arnell reynard 1993 and many others the two major problems with this approach lie in the definition of credible catchment scale scenarios from gcm simulations and the development of realistic hydrological simulation models the latter problem is fundamental to hydrological simulation whilst the former is peculiar to climate change impact assessments and arises for two reasons first gcms do not at present represent all the climatic processes in a realistic manner particularly those relating to the development of clouds and the interactions between the atmosphere and the land surface and second gcms operate at a very coarse spatial resolution some important atmospheric processes such as the development of meso scale circulation patterns and convective storms are therefore not simulated particularly well and whilst gcms can simulate large scale atmospheric features well regional and local climates are often not well reproduced the coarse spatial resolution also means that gcm output has to be interpolated down to the catchment scale a variety of techniques of varying degrees of sophistication have been used or proposed ranging from simple statistical interpolation through empirical relationships between large scale and local climate to the use of nested regional climate simulation models but all rely ultimately on the reliability of the gcm simulations of large scale climatic features arnell 1995a the other popular approach to climate impact assessment uses the past as an analogue for the future one variant uses the instrumental period in practice the last century another uses historical data and a third uses palaeoclimatic reconstructions

the extratropical transition of tropical cyclone edisoana 1990 abstractdocumentation of southwest indian ocean swio tropical cyclones tcs and extratropical transition et events is sparse in the refereed literature the authors present a climatology of swio tc and et events for 1989 2013 the swio averages 9 tropical cyclones tcs per year in this modern era of these tcs 44 undergo extratropical transition et or four per year a case study of tc edisoana 1990 the most rapidly intensifying swio post et tc between 1989 and 2013 shows that extratropical interactions began when an approaching trough embedded in the subtropical jet stream stj induced et on 7 march as edisoana underwent et a subtropical ridge downstream amplified in response to poleward directed positive potential vorticity pv advection associated with diabatically convectively driven upper level outflow from tc edisoana this amplifying lower latitude ridge phased with a lower amplitude higher latitude ridge embedded in the polar front jet pfj resulting in the merger of the t