the role of the tropical west pacific in the extreme northern hemisphere winter of 2013 2014 in the 2013 14 winter the eastern usa was exceptionally cold the bering strait region was exceptionally warm california was in the midst of drought and the uk suffered severe flooding it has been suggested that elevated ssts in the tropical west pacific twpac were partly to blame due to their producing a rossby wavetrain that propagated into the extratropics we find that seasonal forecasts with the tropical atmosphere relaxed towards a reanalysis give 2013 14 winter mean anomalies with strong similarities to those observed in the northern hemisphere indicating that low latitude anomalies had a role in the development of the extremes relaxing just the twpac produces a strong wavetrain over the north pacific and north america in january but not in the winter mean this suggests that anomalies in this region alone had a large influence but cannot explain the extremes through the whole winter we also examine the response to applying the observed twpac sst anomalies in two atmospheric general circulation models we find that this does produce winter mean anomalies in the north pacific and north america resembling those observed but that the tropical forcing of rossby waves due to the applied sst anomalies appears stronger than that in reanalysis except in january therefore both experiments indicate that the twpac influence was important but the true strength of the twpac influence is uncertain none of the experiments indicate a strong systematic impact of the twpac anomalies on europe

semi analytical solution for a slug test in partially penetrating wells including the effect of finite thickness skin this paper presents a new semi analytical solution for a slug test in a well partially penetrating a confined aquifer accounting for the skin effect this solution is developed based on the solution for a constant flux pumping test and a formula given by peres and co workers in 1989 the solution agrees with that of cooper and co workers and the kgs model when the well is fully penetrating the present solution can be applied to simulate the temporal and spatial head distributions in both the skin and formation zones it can also be used to demonstrate the influences of skin type or skin thickness on the well water level and to estimate the hydraulic parameters of the skin and formation zones using a least squares approach the results of this study indicate that the determination of hydraulic conductivity using a conventional slug test data analysis that neglects the presence of a skin zone will give an incorrect result if the aquifer has a skin zone

storm track dynamics this paper reviews the current state of observational theoretical and modeling knowledge of the midlatitude storm tracks of the northern hemisphere cool season observed storm track structures and variations form the first part of the review the climatological storm track structure is described and the seasonal interannual and interdecadal storm track variations are discussed in particular the observation that the pacific storm track exhibits a marked minimum during midwinter when the background baroclinicity is strongest and a new finding that storm tracks exhibit notable variations in their intensity on decadal timescales are highlighted as challenges that any comprehensive storm track theory or model has to be able to address physical processes important to storm track dynamics make up the second part of the review the roles played by baroclinic processes linear instability downstream development barotropic modulation and diabatic heating are discussed understanding of these processes forms the core of our current theoretical knowledge of storm track dynamics and provides a context within which both observational and modeling results can be interpreted the eddy energy budget is presented to show that all of these processes are important in the maintenance of the storm tracks the final part of the review deals with the ability to model storm tracks the success as well as remaining problems in idealized storm track modeling which is based on a linearized dynamical system are discussed perhaps on a more pragmatic side it is pointed out that while the current generation of atmospheric general circulation models faithfully reproduce the climatological storm track structure and to a certain extent the seasonal and enso related interannual variations of storm tracks in depth comparisons between observed and modeled storm track variations are still lacking

was the north american extreme climate in winter 2013 14 a sst forced response this study analyzed the possible causes of the atmospheric circulation anomalies responsible for the severe north american na climate in the winter 2013 14 the seasonal december january february mean circulation anomalies characterized by an extremely strong ridge off the west coast of na and an intense trough over the continental us appeared as a part of wave train across the north pacific na and north atlantic the lack of heating circulation response relationship in the tropics however suggested that the wave train might not be a direct response to tropical heating meanwhile dramatic month to month variations of the atmospheric circulation over the northeastern pacific excluded the possibility that the underlying sea surface temperature sst anomalies played a dominant role a further examination of monthly mean circulation patterns suggests that the wave train was initiated by a heating cooling dipole at the equatorial pacific in december 2013 and subsequently was maintained and modified by the extratropical atmospheric internal dynamics in following months the evolution of tropical heating from december 2013 to february 2014 was associated with the madden julian oscillation mjo instead of a quasi steady response to underlying sst anomalies some features of the circulation anomalies in the extratropics for the season can be captured by an atmospheric general circulation model agcm forced with observed sst but a lack of persistent heating circulation response relationship in the tropics implied a crucial role of internal variability to extreme na climate anomalies in the winter 2013 14

hydraulics of horizontal wells in fractured shallow aquifer systems abstract an analysis of groundwater hydraulic head in the vicinity of a horizontal well in fractured or porous aquifers considering confined leaky confined and water table aquifer boundary conditions is presented solutions for hydraulic heads in both leaky confined and water table aquifers are provided the fracture model used in this study is the standard double porosity model the aquitard storage is included in the formula solutions for the confined and unconfined conditions fractured and porous conditions wellbore storage and skin effect are compared several findings of this study are 1 the influence of wellbore storage and skin upon the drawdown for a fractured confined aquifer is similar to that for a porous confined aquifer 2 aquitard storage affects the intermediate time the most by delaying the drawdown and 3 there is a significant difference between the type curves of fractured and porous confined aquifers in most aquifer boundary conditions because of the contribution of matrix storage and such a difference disappears at the later time

enso prediction one year in advance using western north pacific sea surface temperatures 1 we present evidence that the de trended boreal winter sea surface temperature anomalies ssta in the western north pacific wnp are a skillful predictor for the development of the el nino southern oscillation enso by the following winter the wnp shares some similarities with the meridional mode mm located in the subtropical central and eastern north pacific both are linked to off equatorial ssta and low level wind anomalies and both appear to be strongly related to wintertime variability in the north pacific oscillation npo however in contrast with the mm the wnp is associated with an opposite signed ssta dipole located off southeastern asia and in the western tropical pacific which is accompanied by equatorial winds that may influence the level of oceanic kelvin wave activity that precedes enso events

laplace domain solutions for radial two zone flow equations under the conditions of constant head and partially penetrating well a mathematical model is presented for a constant head test performed in a partially penetrating well with a finite thickness skin the model uses a no flow boundary condition for the casing and a constant head boundary condition for the screen to represent the partially penetrating well the laplace domain solutions for the dimensionless flow rate at the wellbore and the hydraulic heads in the skin and formation zones are derived using the laplace and finite fourier cosine transforms the solutions of hydraulic heads have been shown to satisfy the governing equations related boundary conditions and continuity requirements for the pressure head and flow rate at the interface of the skin zone and undisturbed formation in addition an efficient algorithm for evaluating those solutions is also presented the dimensionless flow rates obtained from new solutions have been shown to be better than those of novakowski s solutions especially when the penetration ratio is large

factors determining the extratropical response to equatorial diabatic heating anomalies abstract the steady linear response of a spherical baroclinic atmosphere to an equatorial diabatic heat source having a simple horizontal and vertical structure is examined this source is imposed upon representative zonally symmetric as well as zonally varying flows during the boreal winter two climatologies are considered one is a 6 year average of global observations analyzed at the european centre for medium range weather forecasts ecmwf the other is a 30 year average taken from a general circulation model gcm run at the geophysical fluid dynamics laboratory in princeton the extratropical response is found to be very sensitive to the basic state around which the governing primitive equations are linearized and in the case of the ecmwf climatology to the longitudinal position of the source with respect to the climatological waves there is also some sensitivity to the vertical level of maximum heating although again this is more evident in the case of the ecmwf basic state these results ar

use of cumulative volume of constant head injection test to estimate aquifer parameters with skin effects field experiment and data analysis 1 in a silty sand aquifer constant head injection tests chits were performed for the determination of aquifer parameters in a chit the test well is overflowed by the injection of surface water the difference between the injection flow and the overflow measured by an automated system directly yields the cumulative volume vw t that enters the aquifer therefore the method of using vw t in determining the aquifer transmissivity and the storage coefficient is developed where well skin effects are taken into account the semilog plot of t vw t is useful in indicating whether well skin exists around the constant head pumping well if well skin is absent the semilog plot of t vw t shows a straight line at large times from which the transmissivity and the storage coefficient can be determined if well skin exists the semilog plot of t vw t exhibits two straight line sections occurring at small and large times respectively then only the transmissivity can be determined from the slope of the large time straight line in this event aquifer drawdown buildup observed at observation wells is needed for the determination of the storage coefficient in fact both the transmissivity and the storage coefficient can be determined with aquifer drawdown buildup normalized with respect to vw t regardless of well skin around the constant head pumping well once t and s are known the skin factor of the constant head pumping well can be obtained from t vw t

skin effect on single well push pull tests with the presence of regional groundwater flow abstract single well push pull swpp test is one of the most important ways to estimate flow and transport parameters e g porosity dispersivity regional groundwater flow velocity usually the wellbore is surrounded by a finite thickness skin such as a gravel pack the positive skin has a smaller hydraulic conductivity than the aquifer formation zone and the negative skin has a greater one in this study a numerical model of a swpp test considering skin effects was established using the finite element comsol multiphysics program to estimate aquifer parameters several important results were obtained firstly regional groundwater velocity affects the types of breakthrough curves btcs through changing the flow pattern secondly a positive or negative skin leads to a slower or faster tracer transport process and a smaller ratio between the hydraulic conductivity of the skin and that of the aquifer formation zone results in greater solute plume retardation in the skin zone thirdly a larger thickness of the positive skin leads to a higher tracer concentration around the well and the opposite is true if the skin is negative besides the model of leap and kaplan 1988 underestimates the regional groundwater velocity for the second type of btcs and a larger longitudinal dispersivity can lead to a greater error where the second type of btcs has a rising limb at early stage followed by a falling limb at late stage the general conclusion is that the estimations of groundwater velocity from swpp tests are also affected by skin effects

mechanisms determining the atmospheric response to midlatitude sst anomalies abstract previous gcm experiments demonstrated that a model atmosphere produces two different responses to a midlatitude warm sst anomaly over the pacific under perpetual january and february conditions to elucidate the mechanisms responsible for the different gcm responses and their dependence on the background flow experiments with two idealized models are conducted experiments with a linear baroclinic model reveal that the gcm responses at equilibrium are primarily maintained by the anomalous eddy forcing the anomalous flow induced directly by an idealized initial heat source exhibits little sensitivity to the background flow eddy feedbacks on the heating induced anomalous flow are examined using a linear storm track model the anomalous eddy forcing produced by the storm track model is sensitive to the basic state the eddy forcing in january acts to shift the heating induced upper level ridge toward the northeast of the gulf of alaska while in february it acts to reinforce the ridge this sugge

an analytical solution of two dimensional reactive solute transport in an aquifer aquitard system 1 this article presents an analytical study of two dimensional reactive solute transport in an aquifer aquitard system advection longitudinal and vertical dispersion first order irreversible decay and linear sorption are included for aquifer transport advection vertical diffusion first order irreversible decay and linear sorption are considered for aquitard transport this study solves transport equations in the aquifer and aquitards simultaneously and maintains continuities of concentration and mass flux at the aquifer aquitard interfaces the transport equations are first solved in laplace domain and the solutions are then inverted numerically to yield solutions in the real time domain the zhan solution concentration profiles in the aquifer and the aquitards are obtained and mass transported to the aquitards is also calculated closed form steady state solutions of concentration and mass have been obtained the zhan solution is compared with solutions derived with the averaged volumetric sink source approach the aa solution the aa solution substantially overestimates the concentration and the mass in the upper aquitard when an upward velocity exists in the aquitard the penetrating depths of the solute in the aquitard are similar for the aa solution and the zhan solution

compounding effects of warm sea surface temperature and reduced sea ice on the extreme circulation over the extratropical north pacific and north america during the 2013 2014 boreal winter unprecedented atmospheric circulations with extreme weather were observed in the extratropical northern hemisphere during the winter of 2013 2014 the anomalous circulations were the manifestation of the pacific pattern or the north pacific oscillation western pacific pattern but with extremely large amplitude simulation results suggest that the anomalous atmospheric circulations were constructively induced by anomalous sea surface temperature in the tropical pacific and extratropical north pacific as well as the low sea ice concentration in the arctic natural variability played a major role in inducing the anomaly pattern whereas the anomalously warm sea surface temperature and low arctic sea ice concentration in the bering sea contributed to the intensity if the anthropogenic warming has a significant impact on causing the synchronization of the aforementioned anomalies in sea surface temperature and sea ice concentration and this trend continues severe winters similar to that in 2013 2014 may occur more frequently in the future

climatic and geomagnetic influences on the lac du bouchet palaeomagnetic sv record through the last 110 000 years abstract palaeomagnetic secular variation records stacked from five cores 20 m long extend back through the last glacial cycle to 100 000 years ago the time scale has been constructed from conventional and accelerator radiocarbon ages back to 45 ka bp and beyond this by comprehensive pollen studies which identify forest and steppe cycles that have been related to marine oxygen isotopic stages 4 and 5 spectral analyses of the intensity and directional records using both fourier and maximum entropy methods reveal strong low frequency components which fall in the range of the milankovitch obliquity and precession periodicities 40 20 ka it is concluded that although part of this signal may have fed indirectly into the natural remanence via the influence of climatic change on sediment facies part has been impressed directly by perturbation of the geomagnetic dynamo process at the core boundary by variations in the earth s obliquity and precession these long periods envelop a well defined pattern registered also by the independent mackereth core stack back to 50 ka bp of irregular secular oscillations of the geodynamo with periods of a few thousands of years

a preliminary palaeomagnetic study of the holocene and late wurmian sediments of lac du bouchet haute loire france summary lac du bouchet is a small maar type lake located at 45 n 4 e in central france the bottom sediments have been sampled down to a depth of 6 m with mackereth type corers a chronology has been established from pollen analytical and diatom zonations and by radiocarbon age determinations throughout the period covered which runs from 22 000 years ago through to the present time declination and inclination variations consist of oscillations of up to about 30 amplitude no abnormally large amplitude excursions in direction are recorded the main contribution of this study is the extension of the european secular variation sv records to the interval from 13000 bp years before present to 22000 bp the sediments deposited through this interval ancient dryas intc wurm originated from the erosion of the internal walls of the volcano spectrum analyses of the declination and inclination curves from 13000 to 22000 bp reveal peaks at periods of 3000 4000 1800 1150 and 700 yr cross spectrum analysis shows strong coherence of the two signals at the longest of these periods the phase relationship of all these peaks indicates clockwise rotation of the palaeomagnetic vector possibly suggesting westward drifting sources although the palaeomagnetic sv record through the holocene 0 10300 bp is compressed into 1 7m of highly organic sediments the principal features exhibited by the type curves established for uk can be identified and the resulting magnetic ages are consistent with the palynology the sense of rotation of the magnetic vector is biased equally in both senses the late glacial 10300 bp to 13000 bp is characterized by oscillating climatic conditions recent dryas allerod and bolling which resulted in poorly resolved and probably discontinuous palaeomagnetic sv records which show a strong bias to anti clockwise rotation all ages are given in radiocarbon years

constant head test at a partially penetrating well in an aquifer aquitard system abstract an analytical model for describing pumping induced drawdown by constant head test at a partially penetrating well in a leaky confined aquifer is developed by treating the leakage of aquitard storage as an interface phenomenon rather than an volumetric effect which is the novel and never developed so far three different cases of remote lateral boundaries are considered in the model the new drawdown solution in laplace space is obtained and inverted into time domain solution utilizing the stehfest method the semi analytical solutions for well discharge are then obtained under three different cases analytical solutions in laplace and time domains are developed for calculating the total leakage rate and volume across the aquitard aquifer interface due to constant head test at a partially penetrating well in a leaky confined aquifer and such solutions are of great use for groundwater resource management based on the newly developed solutions the distribution of wellbore flowrate and aquitard leakage are explored and the sensitivity analysis is conducted to identify the most important controlling factor the sensitivity analysis shows that the wellbore flowrate and the drawdown in infinite case 1 finite case 2 and closed case 3 leaky confined aquifer systems are both sensitive to the variation of well partial penetration well radius and aquifer anisotropic ratio during the whole pumping period and they are most sensitive to the change of outer boundary distance at late time for case 3 the effect of the outer boundary on the drawdown or wellbore flowrate is more significant for a shorter outer boundary distance

relationships between organo mineral supply and early diagenesis in the lacustrine environment a study of surficial sediments from the lac du bouchet haute loire france the relationships between organo mineral composition and early diagenetic processes in surface 50 cm sediments from the lac du bouchet haute loire france are presented parallel pore water studies reveal downcore increases in dissolved organic carbon inorganic carbon and ch4 illustrating the dominant methanogenetic degradation but also highlighting regions of enhanced degradation due to sulphate reduction confirmed by solid phase sulphur and pyrite distributions three sedimentary facies are observed ia 0 25 cm where the majority of compaction and degradation of the organic matter by diagenesis occurs in the absence of any significant change in the type of organic material or sedimentation rate ib 25 40 cm characterised by an increased grain size and diatom abundance ii below 40 cm whose base dates at 2500 350 bp i e within the sub atlantic shows high organic carbon contents and large grain size autochthonous amorphous organic matter is the dominant petrographical organic component whereas pedogenetic allochthonous amorphous organic matter is slightly enriched in facies ii and ia this is coincident with the disappearance of the spores and pollen and suggests a greater continental runoff from the surrounding basin at these times proportions of kaolinite chlorite and illite content do not vary greatly indicating that the detrital input has not changed significantly over the last 2500 years downcore decreases in the sial curve proxy for biogenic silica parallel those of total organic carbon suggesting the dissolution of solid phase silica over time the anthropogenic deforestation and consequent greater nutrient runoff into the oligotrophic lake encouraged an increased production of diatoms around 30 cm the increased sedimentation rate at the beginning of the sub atlantic facies ii as a result of greater continental runoff due to installation of present climatic conditions enhanced the preservation of the organic material by reducing the dia genetic effects and by increasing the proportion of diagenetically inert and relatively resistant organic matter these findings underline the critical role that bulk sedimentation rate and the nature of organic matter play in the final determination of sediment composition both in terms of input and in post depositional degradation

radial groundwater flow to a finite diameter well in a leaky confined aquifer with a finite thickness skin a mathematical model that describes the drawdown due to constant pumpage from a finite radius well in a two zone leaky confined aquifer system is presented the aquifer system is overlain by an aquitard and underlain by an impermeable formation a skin zone of constant thickness exists around the wellbore a general solution to a two zone leaky confined aquifer system in laplace domain is developed and inverted numerically to the time domain solution using the modified crump 1976 algorithm the results show that the drawdown distribution is significantly influenced by the properties and thickness of the skin zone and aquitard the sensitivity analyses of parameters of the aquifer and aquitard are performed to illustrate their effects on drawdowns in a two zone leaky confined aquifer system for the negative skin case the drawdown is very sensitive to the relative change in the formation transmissivity for the positive skin case the drawdown is also sensitive to the relative changes in the skin thickness and both the skin and formation transmissivities over the entire pumping period and the well radius and formation storage coefficient at early pumping time copyright 2009 john wiley sons ltd

on the relationship between tropical and north pacific sea surface temperature variations abstract empirical orthogonal function analysis of winter sea surface temperature sst anomalies over the pacific domain 60 n 20 s reveals an el nino southern oscillation enso mode that is linked to the eastern north pacific and a north pacific mode that is linearly independent of enso the north pacific mode exhibits maximum amplitude and variance explained along 40 n west of 170 w ssts in this region have decreased by 1 5 c from 1950 to 1987 the cooling in winter has been associated with a strengthening of the overlying westerly winds

non detrital si concentrations as an estimate of diatom concentrations in lake sediments and suspended material abstract this paper evaluates a method based on normalization with al to estimate the concentration of diatoms in suspended and deposited sediments provided that al exists primarily in the detrital phase one can calculate the fraction of non detrital si i e biogenic si suspended matter and sediment in two lakes in northern sweden have been analyzed results from the normalization method are compared with microscope count data the results from the two methods differ somewhat partly dissolved diatom frustules may explain part of this discrepancy these remnants can hardly be recognized as diatoms therefore they are not counted during the microscopic analysis although they contribute to the concentration of biogenic si another factor is the differences in si content among different types of diatoms we show that the calculated concentrations of non detrital si are good estimates of the diatom concentrations by using normalization as a tool reasonable estimates of the stocks of biogenic si can be obtained rapidly using these estimates as a guide sites where considerable changes in diatom productivity and or dissolution rates have occurred can be identified

a mobile immobile model for reactive solute transport in a radial two zone confined aquifer abstract a mobile immobile model mim of reactive solute transport for an injection well was investigated in a radial two zone confined aquifer system made up of the aquifer formation zone and the wellbore skin zone evolving from mud invasion or extensive well development fundamental transport processes such as advection radial dispersion first order reaction linear sorption and first order mass transfer between the mobile and immobile domains were considered the laplace transform and numerical inverse laplace methods were used to solve the model while the skin effect on the spatial concentration distribution as well as breakthrough curves btcs were analyzed the results indicate that a larger dispersivity or smaller effective porosity in the skin zone result in higher values of btcs at the early injection stage lower values at the late stage and higher peak values of btcs however an abrupt change for the spatial concentration distribution was observed at the interface of the skin and aquifer formation zones due to the dispersivity change in the skin zone it was also found that a larger mass transfer coefficient of the skin zone results in smaller values of btcs at the early injection stage but higher at the late stage the general conclusion is that the possible impacts of skin on radial solute transport are significant and should be taken into consideration in tracer injection tests

solution for flow rates across the wellbore in a two zone confined aquifer a closed form solution for transient flow rates across the wellbore in a confined aquifer is derived from a two zone radial ground water flow equation subject to the boundary condition of keeping a constant head at the well radius an aquifer may be considered as a two zone system if the formation properties near the wellbore are significantly changed due to the well construction and or well development an efficient numerical approach is used to evaluate this newly derived solution values of the transient flow rate are provided in a tabular form and compared with those obtained by numerical inversion for the laplace domain solution the results show that the two solutions are in good agreement this newly derived solution can be used not only for predicting the transient flow rate across the wellbore but also for identifying the effects of a skin with a finite thickness on the estimation of transient flow rates in a ground water system with two different formation properties

sedimentation rate and early diagenesis of particulate organic nitrogen and carbon in aydat lake puy de dome france abstract a core of low compacted sediment from a eutrophic lake aydat lake was extracted in order to study the early diagenesis of particulate organic carbon and nitrogen we use a simple model where the advection rate was estimated with the classical 210 pb method we show that the 210 pb data are not sufficient by themselves to provide a correct estimation of this parameter but a model which includes the sediment compaction leads to a better understanding of the sedimentation process compaction is also taken into account in the diagenetic model which allows us to make an estimation of the carbon and nitrogen mineralization rates

extension of the lac du bouchet palaeomagnetic record over the last 120 000 years a high resolution profile of the palaeomagnetic variations recorded in the upper 20 m of the lac du bouchet sedimentary sequence has been reconstructed from several parallel mackereth and livingstone type cores inter core correlations were established by comparing individual core profiles of magnetic susceptibility individual records of af cleaned directions were then stretched to a common depth scale and merged the mean record was then filtered and smoothed in order to reduce the background noise accelerator radiocarbon determinations and pollen analyses show that the sequence covers the last interglacial glacial cycle back to ca 120 kyr b p and allow to perform a depth to time transformation there is a noted absence of widely divergent directions back to 90 kyr b p it is estimated that the recorded signal a pdrm signal represents the geomagnetic input signal attenuated by about 19 it follows that the excursions reported for the laschamp and olby lavas if they existed at all must have been of rather short duration two durable excursions appear in narrow diameter sections at the base of three independent cores b c and d while a reverse to normal transition is possibly documented in the lowermost meter core d this part of the sequence is dated from the recognition of major climatic events related to the 18 o isotopic stages defined in the oceanic record between 116 and 95 kyr this introduces the possibility of new excursions at ca 104 and 95 kyr i e immediately after the recovery of normal polarity documenting the end of the blake event

pacific sea surface temperature and the winter of 2014 it is shown from historical data and from modeling experiments that a proximate cause of the cold winter in north america in 2013 2014 was the pattern of sea surface temperature sst in the pacific ocean each of the three dominant modes of sst variability in the pacific is connected to the tropics and has a strong expression in extratropical sst and weather patterns beginning in the middle of 2013 the third mode of sst variability was two standard deviations positive and has remained so through january 2015 this pattern is associated with high pressure in the northeast pacific and low pressure and low surface temperatures over central north america a large ensemble of model experiments with observed ssts confirms that sst anomalies contributed to the anomalous winter of 2014

on the role of tropical ocean forcing of the persistent north american west coast ridge of winter 2013 14a abstractthe causes of the high pressure ridge at the north american west coast during winter 2013 14 the driest winter of the recent california drought are examined the ridge was part of an atmosphere ocean state that included anomalies defined relative to a 1979 2014 mean of circulation across the northern hemisphere warm sea surface temperatures ssts in the tropical western and northeastern pacific and the south indian ocean and cool ssts in the central tropical pacific the sst anomalies differ sufficiently between datasets that when used to force atmosphere models the simulated circulation anomalies vary notably in realism recognizing uncertainty in the sst field the authors use idealized tropical sst anomaly experiments to identify an optimal combination of sst anomalies that forces a circulation response that best matches observations the optimal sst pattern resembles that observed but the associated circulation pattern is much weaker than observed suggesting an important but limited

dynamics of stationary wave anomalies during the 1986 87 el nino the dynamics of the wintertime atmospheric response to the 1986 87 el nino sst anomalies is studied a gcm used for this purpose simulates a wave train over the pacific north american pna region that agrees closely in amplitude with that observed but phase shifted 30 to the east linear baroclinic model experiments are performed in order to determine the origin of the gcm and observed stationary wave anomalies with particular focus on the cause for gcm failure diagnostics with the linear model reveal that the gcm and observed wave train anomalies are maintained by very different processes in the gcm the forcing due to tropical diabatic heating and transient vorticity fluxes are equally important over the pna region in the observations the transient vorticity fluxes assume the primary role the cause for these discrepancies is traced to the different dynamic influences of suppressed rainfall near indonesia the associated diabatic cooling is found to excite a large amplitude wave train over the pna region in the gcm while no significant extratropical response to cooling is found in the observations the combined effects of the diabatic cooling and the reorganization of the storm track transients by the remotely forced wave train acts to shift the gcm s wave train well to the cast of that observed due to uncertainties in the observed diabatic forcing however it is not clear to what extent the gcm s failure is due to errors in the simulated anomalous forcing and or to the gcm s mean climate error

simulating the atmospheric response to the 1985 87 el nino cycle abstract the atmospheric response to the evolution of global sea surface temperatures ssts from 1985 to 1987 is studied using the ncar community climate model ccm1 five separate 2 year integrations are performed and results are presented for the ensemble averaged response during the pre el nino 1985 86 winter and the mature el nino 1986 87 winter no skill is found in ccm1 s simulation for 1985 86 the simulation for the following winter when tropical pacific sst anomalies approached 2 c is more successful a large amplitude wave train extends poleward and eastward from the location of anomalous central pacific convection in ccm1 although the model s wave train is shifted 30 too far east compared to observations a linear barotropic stationary wave model is used to diagnose ccm1 s response during 1986 87 the eastward shifted pna response is easily excited by a dipole pattern of upper level forcing with convergence over the western tropical pacific and divergence over the central tropical pacifi

the north pacific oscillation west pacific teleconnection pattern mature phase structure and winter impacts abstract the north pacific oscillation npo in sea level pressure and its upper air geopotential height signature the west pacific wp teleconnection pattern constitute a prominent mode of winter midlatitude variability the npo wp its mature phase expression is identified from principal component analysis of monthly sea level pressure variability as the second leading mode just behind the pacific north american variability pattern npo wp variability primarily on subseasonal time scales is characterized by a large scale meridional dipole in slp and geopotential height over the pacific and is linked to meridional movements of the asian pacific jet and pacific storm track modulation the hemispheric height anomalies at upper levels resemble the climatological stationary wave pattern attributed to transient eddy forcing the npo wp divergent circulation is thermal wind restoring pointing to independent forcing of jet fluctuations intercomparison of sea level pressure geopotential height and zonal

a diagnostic and modeling study of the monthly mean wintertime anomalies appearing in a 100 year gcm experiment abstract the nature of simulated atmospheric variability on monthly time scales has been investigated by analyzing the output from a 100 year integration of a spectral gcm with rhomboidal wavenumber 15 truncation in this experiment the seasonally varying climatological sea surface temperature was prescribed throughout the world oceans the principal modes of variability in the model experiment were identified by applying a rotated empirical orthogonal function eof analysis to the northern hemisphere monthly averaged 515 mb geopotential height for the winter season november through march the individual leading spatial modes are similar to the observed north south dipoles over the north atlantic and north pacific as well as wavelike patterns in the pacific north american and northern asian sectors quasigeostrophic geopotential tendencies forced by synoptic scale 2 5 6 day eddy vorticity and heat fluxes were computed for those months when the individual eof modes are particularly active the comp

variability of the baroclinic and barotropic transient eddy forcing associated with monthly changes in the midlatitude storm tracks abstract the heat and vorticity transports by synoptic scale eddies at various levels between 1000 and 100 mb have been compiled for each winter month of the 1966 84 period using time filtered daily analyses produced by the u s national meteorological center these circulation statistics were used to compute the three dimensional distributions of the quasigeostrophic geopotential tendency and vertical motion induced by baroclinic and barotropic eddy processes in individual months the latter fields serve as the basis for describing the synoptic scale eddy forcing associated with the leading modes of month to month variability of the storm tracks over the north pacific and north atlantic these modes are associated with the meridional displacements of the storm track axes from their climatological positions the placement of a storm track at a certain latitude in a certain month is accompanied by enhanced convergence of eddy heat fluxes poleward of in the tropospheric column poleward of the storm tra

causes of extreme ridges that induce california droughts abstractcalifornia droughts are often caused by high amplitude and persistent ridges near and off the west coast of north america without apparent connections with enso here with a hierarchy of climate models it is demonstrated that extreme ridges in this region are associated with a continuum of zonal wavenumber 5 circumglobal teleconnection patterns that originate from midlatitude atmospheric internal dynamics although tropical diabatic heating anomalies are not essential to the formation and maintenance of these wave patterns certain persistent heating anomalies may double the probability of ridges with amplitudes in the 90th percentile occurring on interannual time scales those heating anomalies can be caused by either natural variability or possibly by climate change and they do not necessarily depend on enso the extreme ridges that occurred during the 2013 14 and 2014 15 winters could be examples of ridges produced by heating anomalies that are not associated with enso this mechanism could p

the generation of global rotational flow by steady idealized tropical divergence abstract tropical convective heating is balanced on the large scale by the adiabatic cooling of ascent the horizontal divergence of the wind above this heating may be viewed as driving the upper tropospheric rotational wind field a vorticity equation model is used to diagnose this relationship it is shown that because of the advection of vorticity by the divergent component of the flow the rossby wave source can be very different from the simple fd source often used in particular an equatorial region of divergence situated in easterly winds can lead to a rossby wave source in the subtropical westerlies where it is extremely effective this part of the source can be relatively insensitive to the longitudinal position of the equatorial divergence a divergence field which is asymmetric about the equator can lead to a quite symmetric rossby wave source for a steady frictionless flow the rossby wave source averaged over regions within closed streamfunction or absolute vorticity contours is under cert

cooperative effects of tropical pacific and atlantic sst forcing in southern china winter precipitation variability this study investigates the variability of winter precipitation over southern china sc and the impacts of sea surface temperature sst forcing in the tropical pacific and atlantic oceans the sc winter precipitation displays two major spatial modes a same sign mode with the maximum center located in southeastern china and a north south dipole mode with opposite variations between the lower reach of the yangtze river and the southeastern coast of china both modes are associated with the variation of the western north pacific wnp anticyclone the same sign mode is associated with canonical el nino through the pacific east asian teleconnection in the lower troposphere the north south dipole mode is subject to the impact of the western pacific warm pool associated with the central pacific el nino and equatorial atlantic forcing the influence of equatorial atlantic warming is through an upper tropospheric zonal wave pattern from the tropical atlantic to the mid latitudes of east asia both the tropical pacific and atlantic oceanic forcing induce a north south dipole pattern of winter precipitation anomalies over sc by affecting the northward extension of the wnp anticyclone moreover the observed statistical relationship between the dipole mode and the equatorial atlantic sst anomalies is present in hindcasts forecasts of the ncep climate forecast system version 2 cfsv2 confirming a potential source of the predictability of the north south dipole like variation of the winter precipitation in sc

what drove the pacific and north america climate anomalies in winter 2014 15 in late 2014 and early 2015 the canonical atmospheric response to the el nino and southern oscillation enso event was not observed in the central and eastern equatorial pacific although nino3 4 index exceeded the threshold for a weak el nino in an effort to understand why it was so this study deconvoluted the observed 2014 15 december january february djf mean sea surface temperature sst precipitation and 200 hpa stream function anomalies into the leading patterns related to the principal components of djf sst variability it is noted that the anomalies of these variables were primarily determined by the patterns related to two sst modes one is the north pacific mode npm and the other the enso mode the npm was responsible for the apparent lack of coupled air sea relationship in the central equatorial pacific and the east west structure of the circulation anomalies over north america while the enso mode linked to ssts in the central and eastern equatorial pacific as well as the circulation in the central equatorial pacific further the enso signal in djf 2014 15 likely evolved from the npm pattern in winter 2013 14 its full development however was impeded by the easterly anomalies in the central equatorial pacific that was associated with negative sst anomalies in the southeastern subtropical pacific in addition the analyses also indicates that the sst anomalies in the nino3 4 region alone were not adequate for capturing the coupling of oceanic and atmospheric anomalies in the tropical pacific due to the fact that this index cannot distinguish whether the sst anomaly in the nino3 4 region is associated with the enso mode or npm or both

lacustrine organic fluxes and palaeoclimatic variations during the last 15 ka lac du bouchet massif central france to assess the influence of climatic changes on organic lacustrine sedimentation two cores recovered from the centre of the lac du bouchet were studied by petrographical palynofacies and geochemical methods only core ldb h was used for estimation of the organic fluxes the variation of these fluxes with climo stratigraphic periods showed low organic fluxes during the lateglacial an increase at the beginning of the holocene a minimum at the end of the atlantic period resulting from the climatic cooling and a maximum at the end of the sub boreal related to the installation of the present climatic conditions

spatial patterns of atmosphere ocean interaction in the northern winter abstract the variability of monthly mean sea surface temperature sst anomalies over the extratropical north atlantic and pacific and its relation to atmospheric circulation anomalies over the northern hemisphere during wintertime is investigated by applying eigenvector analysis to a 39 year dataset and correlating the time series of the resulting expansion coefficients with the hemispheric 500 mb height and sea level pressure fields in agreement with previous studies the simultaneous correlation between the tone series of the expansion coefficient of the first empirical orthogonal function eof 1 of north pacific sea surface temperature sst and the hemispheric 500 mb height field resembles the pacific north american pattern and the corresponding pattern for atlantic sst resembles the north atlantic oscillation in the vicinity of the conters of action of thew patterns the sst fluctuations associated with these modes explain on the order of half the variance of 500 mb height and slightly less of

persistence and predictions of the remarkable warm anomaly in the northeastern pacific ocean during 2014 16 abstractin this work the evolution and prediction of the persistent and remarkable warm sea surface temperature anomaly ssta in the northeastern pacific during october 2013 june 2016 are examined based on experiments with an atmospheric model the possible contribution of sstas in different ocean basins to the atmospheric circulation anomalies is identified further through verifying the real time forecasts current capabilities in predicting such an extreme warm event with a state of the art coupled general circulation model are assessed during the long lasting warm event there were two warm maxima in the area averaged ssta around january 2014 and july 2015 respectively the warm anomaly originated at the oceanic surface and propagated downward and reached about 300 m model experiments forced by observed sst suggest that the long persistence of the atmospheric anomalies in the northeastern pacific as a whole may be partially explained by sst forcing particularly in the tropical pacific ocean ass

constant head test in a leaky aquifer with a finite thickness skin summary constant head test is a commonly used aquifer testing method in groundwater hydrology a mathematical model for constant head test in a leaky aquifer with a finite thickness skin was developed in this study three different aquifer aquitard systems were considered and the laplace domain solutions were obtained and then inverted numerically with the stehfest method to yield the time domain solutions the well discharges for different cases were computed and a sensitivity analysis of the well discharge on different parameters was performed the results indicated that the dimensionless transmissivity of the aquitard had little effect on the well discharge at early times while a larger transmissivity of the aquitard leaded to a larger well discharge at late times the well discharge for the positive skin was smaller than that without the skin while the well discharge for the negative skin was larger than that without the skin where positive and negative skins refer to the cases in which the permeability values of the skin zones are less and greater than that of the formation zone respectively a thicker skin resulted in a smaller well discharge for the positive skin case but leaded to a larger well discharge for the negative skin case at late times we also found that the drawdown for the positive skin case was less than that for the negative skin case at the same time and a positive skin might result in delayed response of the aquifer to pumping the sensitivity analysis indicated that the well discharge was sensitive to the properties of the skin zone but not sensitive to the properties of the aquitards for the aquifer aquitard system presented in this study