horizontal wells in shallow aquifers field experiment and numerical model this paper is concerned with horizontal wells in shallow aquifers information about a field test is presented and the development of appropriate conceptual and computational models is discussed particular attention is paid to the processes of flow from the aquifer into the horizontal well and the hydraulic conditions within the well a combined computational model representing the aquifer and the horizontal well is developed this methodology is used to study a horizontal well in a shallow coastal aquifer a detailed pumping test is analysed using the combined model the combined model is then used to predict the consequences of increasing the abstraction lengthening the well or using the horizontal well for an extended period when there is no recharge the results from the combined model indicate that the commonly adopted assumptions of either a uniform flux into the well or a constant head along the well are not suitable for this field problem

wavenumber frequency spectra of inertia gravity and mixed rossby gravity waves in the equatorial pacific ocean abstractin the 1970s and 1980s there was considerable interest in near equatorial variability at periods of days to weeks associated with oceanic equatorial inertia gravity waves and mixed rossby gravity waves at that time the measurements available for studying these waves were much more limited than today most of the available observations were from scattered island tide gauges and a handful of short mooring records more than a decade of the extensive modern data record from the tropical atmosphere ocean tao triangle trans ocean buoy network triton mooring array in the pacific ocean is used to reexamine the internal wave climate in the equatorial pacific with a focus on interpretation of the zonal wavenumber frequency spectrum of surface dynamic height relative to 500 decibars at periods of 3 15 days and zonal wavelengths exceeding 30 of longitude to facilitate interpretation of the dynamic height spectrum and identification of equatorial wave modes the spectrum is decomposed into separate

equatorial inertia gravity waves observed in topex poseidon sea surface heights we report an evaluation of the ability of the topex poseidon altimeter to observe equatorial inertia gravity waves in the central pacific aliasing problems limit us to examining meridional mode two but this mode is an energetic one in the pacific basin these estimates of the temporal potential energy modulations are compared with estimates from tide gauges in the tropical pacific and we find that the time series obtained at these points show good agreement

variations in the zn si record over the last interglacial glacial transition we examined the zinc content of diatom frustules as an indicator of past changes in surface seawater zn2 concentration zn si data of samples from three cores located in the south atlantic sector of the southern ocean spanning the last interglacial glacial transition are presented changes in the zn si record are linked to changes in the surface water zn2 concentration the source of variation in zn2 concentration appears to be via changes in deep water upwelling and circulation we rule out changes in phytoplankton productivity and aeolian dust input as a source of variation in the zn si record likewise the zn si data are not linked to shifts in the diatom species composition of the sediment or sediment preservation effects the zn si results presented do not support the zinc hypothesis there is no link between the uptake of co2 by phytoplankton as inferred from the 13c record and the zn si record

observations of the vertical structure of the eddy field in the kuroshio extension normalized kinetic energy frequency distributions at a site in the kuroshio extension along 152 e are independent of depth as a good first approximation the lowest frequencies are strongly vertically coherent from 350 to 6000 m depths nominal none of the other vertical sets of time series previously examined possess these characteristics to such a degree coherence being typically much lower between the thermocline and abyssal depths with spectral shape changing significantly as well the vertical distributions of eddy kinetic energy at this kuroshio extension site and for the gulf stream along 55 w are very similar if a depth independent contribution of approximately 100 cm2 s 2 be added to the former the latter observation suggests the existence of a more energetic weakly depth dependent component for the eddy field in the north atlantic than for the north pacific at special locations in the vicinity of their mid latitude jets possibly a signature of distinct instability mechanisms

trace metal concentrations in the ross sea and their relationship with nutrients and phytoplankton growth abstract dissolved and particulate trace metal concentrations dissolved fe zn cd co cu and ni particulate fe mn and al were measured along two transects in the ross sea during austral summer of 1990 total fe concentrations in southern ross sea and inshore waters were elevated 3 5 times that of northern waters dissolved zn cd and co concentrations were lower by factors of 4 5 3 5 and 1 6 in southern surface waters relative to northern waters dissolved cu and ni concentrations were similar in both areas elevated fe concentrations coincided with areas of increased productivity phytoplankton biomass and nutrient drawdown indicating that fe is an important factor controlling the location of phytoplankton blooms in the ross sea particulate concentrations of fe mn and al indicate two possible sources of iron to the ross sea resuspension of continental shelf sediments and iron incorporated in annual sea ice and released with meltwaters

winter time dissolved iron and nutrient distributions in the subantarctic zone from 40 52s 155 160e 1 in hnlc oceanic regions iron fe controls phytoplankton productivity yet large gaps remain in our understanding of iron s biogeochemical cycle here we present the first comprehensive winter dataset for dissolved fe dfe and nitrate no3 distributions 0 1000 m depth between 40s 52s which transects the subantarctic zone saz west of new zealand surface concentrations 0 2 nmol fe kg 1 were conspicuously low i e probably biologically limiting even at winter reserve levels at frontal zones between 43s subtropical front and 51s subantarctic front a fivefold range in fe no3 molar ratios was observed along the transect with subtropical waters where blooms occur having the highest ratios in subsurface waters the major wintertime supply of dfe in the saz is from ekman advection of waters from the south but calculated source water dfe is 0 2 nmol fe kg 1 suggesting that mixed layer dfe concentration is controlled by how long these southern waters remain at the surface 3 years

barotropic rossby waves radiating from tropical instability waves in the pacific ocean abstracttropical instability waves are triggered by instabilities of the equatorial current systems and their sea level signal with peak amplitude near 5 n is one of the most prominent features of the dynamic topography of the tropics cross spectral analysis of satellite altimetry observations shows that there is sea level variability in the pacific ocean as far north as hawaii i e 20 n that is coherent with the sea level variability near 5 n associated with tropical instability waves within the uncertainty of the analysis this off equatorial variability obeys the dispersion relation for nondivergent barotropic rossby waves over a fairly broad range of periods 26 38 days and zonal wavelengths 9 23 of longitude that are associated with tropical instability waves the dispersion relation and observed wave properties further suggest that the waves are carrying energy away from the instabilities toward the north pacific subtropical gyre which together with the observed coherence of the sea

mid latitude mesoscale variability neither homogeneous quasi geostrophic turbulence nor the effect of eddies on the interior ocean circulation remains the major focus of mesoscale research as was the case for much of the preceding 20 years following identification of the phenomena concentration on basin wide geographical exploration of eddy properties was rather well established by 1978 over the last few years a promising zero order description and rationalization of the mesoscale field has become available that is eddy energy is largest near strong flows intensification not only in western boundary currents but along their mid latitude open ocean extension roughly as indicated by gyre scale numerical models where eddies develop as a result of instability processes in the mid latitude jet and recirculation regimes and then propagate into the ocean interior our point of view is that mesoscale eddies drive recirculations but do not play a crucial role in the dynamics of the mean flow in the ocean interior in the north atlantic for example the idea is that the downstream increase in transport of the gulf stream is eddy driven but not the flow through the florida straits in addition the fluctuating response to forcing by variable winds may now be widely perceived as forming the horizontally homogeneous background signal in subtropical gyres the time dependent field associated with thermohaline flows at abyssal depths also has a special character

tropical instability wave energetics observations from the tropical instability wave experiment ocean velocity data from an array of subsurface moorings deployed from may 1990 to june 1991 during the tropical instability wave experiment are used to study the energetics of planetary waves in the vicinity of the equator at 1408w such waves observed from august to december 1990 were initiated by barotropic instability arising primarily from the cyclonic shear region of the south equatorial current and equatorial undercurrent just north of the equator subsequently local barotropic production continued to maintain and modulate these tropical instability waves through a combination of cyclonic shear and meridional velocity component divergence just north of the equator the end of the wave season coincided with the propagation past the array of a large intraseasonal kelvin wave

stream depletion rate for a radial collector well in an unconfined aquifer near a fully penetrating river the stream depletion rate sdr is computed for a radial collector well installed in a semi infinite anisotropic homogeneous unconfined aquifer near a fully penetrating stream with a streambed with reduced conductivity for small pumping rates dimensional analysis and other arguments allow the sdr to be expressed as a function of eight parameters that describe the effect of properties of the aquifer and streambed as well as the configuration and placement of the well the calculations employ some results from huang et al 2012 j hydrol who expressed the sdr as a quintuple integral but by computing four of the integrals analytically the present solution requires less computational effort analytical calculation shows that the sdr in steady state does not depend on the streambed properties or any other parameters given enough time the flow through the streambed will equal the pumping rate of the well values of sdr are supported by comparing to previous solutions for special cases corresponding to appropriate limiting values of the parameters effects of the eight dimensionless parameters are studied systematically the properties of the streambed anisotropy of the aquifer and the position of the well affect the sdr more strongly than the orientation length and depth of the laterals

flow to a horizontal well in an aquitard aquifer system a horizontal well is sometime installed in an aquifer beneath a water reservoir to get significant amount of groundwater with better quality an aquitard often separates the surface water body from the underneath aquifer previous studies in vertical wells related to this subject treated leakage from the aquitard as a volumetric source term in the governing equation of flow in the main aquifer a hypothesis termed hantush s approximation for partially penetrating wells in this study flow in the aquitard and aquifer is treated as two systems which are linked through the continuity of flux and head at the aquitard aquifer boundary in particular we treat leakage as a boundary at the aquitard aquifer interface not as a volumetric source the leakage induced by the pumping horizontal well depends on several parameters such as the aquitard thickness the vertical hydraulic conductivity of the aquitard the aquitard specific storage the well location and the well length in general we find that the solution based on the hantush s approximation to some extent deviates from that obtained based on the actual scenario of leakage through the interface during the transient flow condition particularly at the early time for steady state flow the hantush s approximation works reasonably well under realistic conditions of aquitard thickness and hydraulic conductivity as long as the aquitard thickness is relatively thick aquitard aquifer ratio greater than 0 001 this approximation also works reasonably well under realistic horizontal well length and well location as long as the well is not too close to the aquitard aquifer boundary q 2005 elsevier b v all rights reserved

instability waves observed on the equator in the atlantic ocean during 1983 a packet of surface confined westward propagating waves apparently generated by barotropic instability of the surface currents was observed in the equatorial atlantic during 1983 initial wavenumber analyses and energetics calculations are presented local working by the horizontal reynolds stress was large enough and at the correct time to account for the wave packet s existence the amplitude of the waves was comparable to the mean currents implying that the waves are of primary importance in the momentum balance of the seasonally varying equatorial surface currents

an analytical solution for tidal fluctuations in unconfined aquifers with a vertical beach 1 the perturbation technique has been commonly used to develop analytical solutions for simulating the dynamic response of tidal fluctuations in unconfined aquifers however the solutions obtained from the perturbation method might result in poor accuracy for the case of the perturbation parameter being not small enough in this paper we develop a new analytical model for describing the water table fluctuations in unconfined aquifers based on laplace and fourier transforms in the new approach the mean sea level is used as the initial condition and a free surface equation neglecting the second order slope terms as the upper boundary condition numerical results show that the present solution agrees well with the finite different model with the second order surface terms unlike teo et al s 2003 approximation which restricts on the case of shallow aquifers the present model can be applied to most of the tidal aquifers except for the very shallow one in addition a large time solution in terms of sine function is provided and examined graphically with four different tidal periods

on the formation of a subsurface weakly sheared laminar layer and an upper thermocline strongly sheared turbulent layer in the eastern equatorial pacific interplays of multiple time scale equatorial waves

seasonal modes of surface cooling in the gulf of guinea a numerical simulation of the tropical atlantic ocean indicates that surface cooling in upwelling zones of the gulf of guinea is mostly due to vertical mixing at the seasonal scale the spatial structure and the time variability of the northern and southern branches of the south equatorial current sec and of the guinea current are correlated with the timing and distribution of turbulent heat fluxes in the gulf of guinea through modulation of the velocity shear at the subsurface these surface currents control the vertical turbulent exchanges bringing cold and nutrient rich waters to the surface this mechanism explains the seasonality and spatial distribution of surface chlorophyll concentrations better than the generally accepted hypothesis that thermocline movements control the nutrient flux the position of the southern sec explains why the cold tongue and high chlorophyll concentrations extend from the equator to 4 s in the southeastern part of the basin

distribution of reynolds stress carried by mesoscale variability in the antarctic circumpolar current satellite altimeter data collected by the u s navy s geosat exact repeat mission were used to investigate turbulent stress resulting from the variability of surface geostrophic currents in the antarctic circumpolar current the altimeter measured sea level along the subsatellite track the variability of the along track slope of sea level is directly proportional to the variability of surface geostrophic currents in the cross track direction we used the two components of the slope at points where the satellite ground tracks cross to calculate orthogonal components of the current s variability because the grid of crossover points is dense at high latitudes the satellite data could be used for mapping the temporal and spatial variability of the current two and a half years of data were used to compute the statistical structure of the variability leading to a better understanding of the role of variability in the dynamics of the current the statistics included the probability distribution functions for each component of the current the time lagged auto correlation functions of the variability and the reynolds stress produced by the variability the results demonstrate that stress is correlated with bathymetry in some areas the distribution of negative stress indicate that eddies contribute to an acceleration of the mean flow strengthening the hypothesis that baroclinic instability makes important contributions to strong oceanic currents

the three dimensional circulation near the eastern north pacific subtropical front abstract the purpose of our study is to describe and compute the large scale three dimensional circulation near the subtropical front in the eastern north pacific along 31 n this was accomplished through the use of four extensive hydrographic surveys historical wind stress data and also the movement of surface drifters our results indicate that in wintertime surface water sinks on the north side of the front and rises on its south side during the summer however the subtropical salty surface water overflows the frontal area to the north potential vorticity and heat are best conserved in a vertical flow pattern where the annual mean ekman convergence sinks to a depth of 300 m and water upwells throughout the main thermocline the computed horizontal flow below 700 m amounts to less than 0 6 cm s 1 both strength and direction depend greatly on the treatment of noise within the data set and also on the conservation statement that is specified in addition to geostrophic and hydrostatic dynamics a q

assessing past changes in bioavailable zinc from a terrestrial zn si opal record historical changes in bioavailable zn concentrations of the surface waters of lake geneva were assessed by analyzing the zinc content of fossil diatoms the measured ratios of zn to si in the opal zn si opal were consistent with both data obtained for cultured freshwater diatoms that were representative of lake geneva and with field data reconstructed variations suggested that increased zn uptake by phytoplankton occurred in the period from 1960 1980 resulting from an increased loading of zn to the lake nonetheless observed concentrations were sufficiently low that no adverse effects were expected on the pelagic community the data presented here suggest that zn si opal records may become a valuable tool to assess past changes in bioavailable zn concentrations in freshwater systems

internal tides near the kermadec ridge abstract current meter data from the woce pcm 9 array extending 1000 km eastward from the kermadec ridge northeast of new zealand are used to investigate the internal tide a high degree of spatial and temporal variability in the semidiurnal tide but not in the diurnal tide suggests that there is a conversion from barotropic to baroclinic tidal energy at the semidiurnal periods comparison between observed tidal constituents and those predicted by the tpxo 3 model indicates that the model may be used as an estimate of the barotropic tide once the barotropic tide has been removed the remaining semidiurnal energy propagates predominantly at the first vertical mode phase speed of 3 5 m s 1 consistent with linear theory a frequency domain empirical orthogonal function analysis is used to extract signals that have phase propagation consistent with a coherent internal tide these modes represent a phase locked semidiurnal internal tide having about 0 65 of the baroclinic energy tidal energies at the m2

variability in horizontal current velocities in the central and eastern equatorial atlantic in 2002 1 near surface current velocity data from the pilot research moored array in the tropical atlantic at 23 w in the year 2002 were re examined and compared to simultaneous unpublished velocity data at 10 w near the surface strong 7 day period fluctuations were observed in the zonal velocity component and in temperature records at 23 w the large temperature fluctuations near the thermocline depth suggest a vertical velocity component at the same 7 day period the 7 day period signals occurred in june july simultaneously with the seasonal upwelling the meridional velocity component presented similar spectral contents at 23 w and at 10 w two distinguishable quasiperiodic signals were observed in the meridional component at both locations the first signal occurred in the spring had a periodicity of about 14 days was subsurface intensified and had the characteristics of a mixed rossby gravity wave the second signal occurred three times in the year once in winter 2001 2002 another in summer and another during fall 2002 had a periodicity of about 20 days was strongest close to the surface and was the result of the passage of tropical instability waves tiws satellite sea surface temperature sst data show the same periodicities as the meridional velocity records and present a spatial structure in accordance with the tiw sst signature the summer of 2002 showed different tiw sst patterns depending upon location suggesting the existence of different types of tiws overall variability in the current meter data for the year 2002 was mainly due to current instabilities except around boreal spring where intraseasonal variability in surface winds was strongest

a comment on long waves in the pacific ocean abstract surface currents near the equator in the eastern pacific ocean fluctuate with periods of 21 30 days channel model experiments determined that these changes in oscillations are attributed to variations in the intensity of the south equatorial current

evidence for the maintenance of slowly varying equatorial currents by intraseasonal variability recent evidence from mooring data in the equatorial atlantic reveals that semi annual and longer time scale ocean current variability is close to being resonant with equatorial basin modes here we show that intraseasonal variability with time scales of 10 s of days provides the energy to maintain these resonant basin modes against dissipation the mechanism is analogous to that by which storm systems in the atmosphere act to maintain the atmospheric jet stream we demonstrate the mechanism using an idealised model set up that exhibits equatorial deep jets the results are supported by direct analysis of available mooring data from the equatorial atlantic ocean covering a depth range of several thousand meters the analysis of the mooring data suggests that the same mechanism also helps maintain the seasonal variability

the zn abundance and isotopic composition of diatom frustules a proxy for zn availability in ocean surface seawater we have developed cleaning methods for extracting diatomopal from bulk marine sediment samples for measurement of both zinc zn abundance and isotope composition this cleaning technique was then applied to a set of holocene core top samples from the southern ocean the measured 66zn reported relative to the jmclyon standard and zn si ratios from the southern ocean diatomopal samples range from 0 7 to 1 5 and from 14 to 0 9 mol mol respectively the zn abundance and isotope composition data show a clear correlation with opal burial rates and other oceanographic parameters in common with previous work we interpret the systematic changes in the zn si ratio to be linked to the variability in the concentrations of bioavailable zn in the ambient surface seawater where the diatom opal is formed this variability is likely to be primarily controlled by the degree to which zn is taken up into phytoplankton biomass the observed systematic pattern in the 66zn compositions of the diatomopal core top samples is similarly likely to reflect changes in the 66zn composition of the ambient zn in the surface waters above the core top sites which is progressively driven towards isotopically heavier values by preferential incorporation of the lighter isotopes into phytoplankton organic material thus the systematic relationship between zn isotopes and abundance observed in the core top diatomopal samples suggests a potential tool for investigating the biogeochemical cycling of zn in the past surface ocean for down core diatomopal material in this respect it may be possible to test hypotheses that attribute variations in atmospheric co2 on glacial interglacial timescales to the degree to which trace metals limited primary productivity in hnlc zones

glacial interglacial co2 change the iron hypothesis several explanations for the 200 to 280 ppm glacial interglacial change in atmospheric co2 concentrations deal with variations in southern ocean phytoplankton productivity and the related use or nonuse of major plant nutrients an hypothesis is presented herein in which arguments are made that new productivity in today s southern ocean 7 4 1013g yr 1 is limited by iron deficiency and hence the phytoplankton are unable to take advantage of the excess surface nitrate phosphate that if used could result in total southern ocean new production of 2 3 1015 g c yr 1 as a consequence of fe limited new productivity holocene interglacial co2 levels preindustrial are as high as they were during the last interglacial 280 ppm in contrast atmospheric dust fe supplies were 50 times higher during the last glacial maximum lgm because of this fe enrichment phytoplankton growth may have been greatly enhanced larger amounts of upwelled nutrients may have been used and the resulting stimulation of new productivity may have contributed to the lgm drawdown of atmospheric co2 to levels of less than 200 ppm background information and arguments in support of this hypothesis are presented

geographical variability of the first baroclinic rossby radius of deformation global 1 83 18 climatologies of the first baroclinic gravity wave phase speed c1 and the rossby radius of deformation l1 are computed from climatological average temperature and salinity profiles these new atlases are compared with previously published 5 83 58 coarse resolution maps of l1 for the northern hemisphere and the south atlantic and with a 1 83 18 fine resolution map of c1 for the tropical pacific it is concluded that the methods used in these earlier estimates yield values that are biased systematically low by 5 15 owing to seemingly minor computational errors geographical variations in the new high resolution maps of c1 and l1 are discussed in terms of a wkb approximation that elucidates the effects of earth rotation stratification and water depth on these quantities it is shown that the effects of temporal variations of the stratification can be neglected in the estimation of c1 and l1 at any particular location in the world ocean this is rationalized from consideration of the wkb approximation

the baroclinic stability of the atlantic north equatorial current abstract polymode array iii cluster c was a collection of four current meter moorings that were placed in the atlantic north equatorial current for one year in may 1978 they were designed to look for indications of baroclinic instability such as downgradient eddy heat fluxes and upward phase propagation however fu keffer and other investigators find that the eddy heat fluxes tended to be more across gradient and sometimes even upgradient they also find only slight indications of upward phase propagation in this study the linear stability model of gill et al is applied to determine the expected heat fluxes and the modal shapes and scales due to linear amplification it appears that the expected fluxes should be detectable modal shapes are similar to the observed shapes but the fastest growing mode is only about half the size of the observed correlation scale although these discrepancies could be explained by simple statistical variability the supercriticality of the mean flow the large obser

rossby gravity waves in the central equatorial pacific ocean during the norpax hawaii to tahiti shuttle experiment spectra of sea level and current taken from the central pacific during the norpax experiment contain broad peaks centered around 10 day periods zonal dispersion shows these peaks to be caused by rossby gravity waves an empirical orthogonal function eof analysis indicates that 44 of the variance can be attributed to these rossby gravity waves and they show clear temporal modulation in amplitude there is no evidence that the rossby gravity waves are generated locally but coherence between the eof and a modeled response to winds from kapingamarangi island allowing for dispersion suggests that these waves are generated by meridional wind stress in the west pacific

modes of covariability between sea surface temperature and wind stress intraseasonal anomalies along the coast of peru from satellite observations 2000 2008 1 the tropical rainfall measuring mission microwave imager sea surface temperature sst and quikscat wind stress satellite data are used to investigate the intraseasonal upwelling variability along the coat of peru over the period 2000 2008 two regions of peak variance correspond to the central peru region pisco region 15 s and the northern peru region piura region 5 s a covariance analysis reveals a significant coherency between winds and sst anomalies off pisco consistent with ekman pumping and transport dynamics the upwelling cell consists in a meridionally extended fringe of colder warmer water extending as far as 250 km from the coast at 15 s in the piura region the intraseasonal covariability pattern is represented by two modes one relevant to the direct ekman dynamics and the other one associated with the remote forcing of intraseasonal oceanic kelvin wave two regimes of variability are evidenced a low period regime 10 25 days is the signature of ekman transport pumping dynamics and is remotely forced by the migratory atmospheric disturbances across the southeastern pacific anticyclone a high period regime 35 60 day band is associated with the combined forcing of oceanic equatorial kelvin waves and migratory atmospheric disturbances in the midlatitudes in particular the modes of covariability exhibit a prominent 50 day period energy peak it is shown that this period arises from the impact of the first two baroclinic modes kelvin wave with the second baroclinic mode kelvin wave being more influential on the piura region

intraseasonal modulation of the surface cooling in the gulf of guinea abstracta regional numerical model of the tropical atlantic ocean and observations are analyzed to investigate the intraseasonal fluctuations of the sea surface temperature at the equator in the gulf of guinea results indicate that the seasonal cooling in this region is significantly shaped by short duration cooling events caused by wind forced equatorial waves mixed rossby gravity waves within the 12 20 day period band inertia gravity waves with periods below 11 days and equatorially trapped kelvin waves with periods between 25 and 40 days in these different ranges of frequencies it is shown that the wave induced horizontal oscillations of the northern front of the mean cold tongue dominate the variations of mixed layer temperature near the equator but the model mixed layer heat budget also shows that the equatorial waves make a significant contribution to the mixed layer heat budget through modulation of the turbulent cooling especially above the core of the equatorial undercurrent euc the tu

interaction of the atlantic equatorial cold tongue and the african monsoon the seasonal cycle of equatorial atlantic sea surface temperature sst is characterized by a rapid cooling from april to july coinciding with the onset of the west african summer monsoon and followed by a slow warming that lasts 3 times longer two ensemble simulations are carried out with an atmospheric general circulation model to investigate the mechanisms for the wind changes that cause this rapid oceanic cooling and its feedback onto the african monsoon in the control simulation sst is globally prescribed in its full climatological seasonal cycle while in the second simulation equatorial atlantic sst is held constant in time from 15 april onward comparison of these simulations indicates that the equatorial cooling exerts a significant influence on the african monsoon intensifying the southerly winds in the gulf of guinea and pushing the continental rainband inland away from the guinean coast the intensification of the cross equatorial southerlies associated with the onset of the african monsoon in turn triggers the oceanic cooling in the east the equatorial easterlies are also important for the seasonal cooling by inducing local upwelling and raising the thermocline in the east three mechanisms are identified for the easterly wind acceleration in the equatorial atlantic in boreal summer first the monsoon rainfall distribution is such that it induces zonal sea level pressure gradients and easterly anomalies in the eastern atlantic second the strong cross equatorial southerlies advect the easterly momentum from the south into the equator finally zonal pressure gradients associated with the equatorial ocean cooling accelerate surface easterly winds in the middle and western atlantic this interaction of equatorial sst and zonal wind causes their westward copropagation analogous to that in the equatorial pacific

groundwater flow to a general well configuration in an unconfined aquifer overlying a fractured bedrock abstract unconfined aquifers sometimes overlie fractured bedrocks consisting of unconfined fractured aquifer systems pumping induced hydrodynamics in such aquifer systems has not received much attention as in other types of aquifer systems this paper aims to obtain semi analytical solutions of flow to a general well configuration in such an unconfined fractured two layer aquifer system the examples of general well configuration specifically discussed here include 1 a horizontal well 2 a vertical well 3 a vertical well with one horizontal collector and 4 a vertical well with two horizontal collectors which are perpendicular with each other the methodology is general and can be extended to other types of wells with minor modifications of solutions developed in this study the point sink source solution is first obtained using double infinite fourier and laplace transformations where sink is for pumping and source is for injection the line sink source solution is then obtained via integrating the point sink source along the desired direction and following the principle of superposition the de hoog numerical inverse laplace transform and gaussian quadrature are used to obtain time domain dimensionless drawdown solutions the instantaneous drainage of water table and the inter porosity flow of the underlying fractured aquifer are taken into account the effects of the length of horizontal well on dimensionless drawdown and dimensionless drawdown derivative and scaled sensitivity of the hydraulic parameters of the underlying fractured aquifer are explored the dimensionless drawdowns and drawdown derivatives of a vertical pumping well a vertical well with a single horizontal collector and a vertical well with two perpendicular horizontal collectors are also compared the scaled sensitivity of dimensionless drawdown to the hydraulic parameters of the underlying fractured aquifer of these different pumping well structures is explored the results of this study can be used to evaluate the hydraulic parameters using the drawdown data collected during a pumping test performed in a general well configuration in a unconfined fractured two layer aquifer system furthermore the presented solutions can be utilized to design the pumping well to minimize drawdown in low permeability or thin aquifers by eliminating the inter porosity flow term from the underlying fractured aquifer the solutions are applicable to groundwater flow to a pumping well in leaky aquifers

the equatorial source of propagating variability along the peru coast during the 1982 1983 el nino using data obtained from tide gages in south america current meters along the equator and the peru coast and an array of pressure gages and inverted echo sounders within and around the galapagos archipelago we have analyzed the equatorial origin of coastal trapped waves observed by cornejo rodriquez and enfield this issue along the peru coast during the intense 1982 1983 el nino the propagating fluctuations along the coast were much stronger at that time than either before or after the el nino and the variability was not locally forced by coastal winds we find that the coastal variability was also more energetic during previous el nino occurrences at periods of 1 2 weeks the meridional component of currents on the equator is up to an order of magnitude more energetic than the zonal fluctuations and is consistently associated with sea level that fluctuates antisymmetrically between hemispheres at periods longer than 2 weeks the zonal velocity component is more energetic and the cross equatorial sea level variability is symmetric the meridional and zonal phase structures of cross spectra involving the currents and sea level establish the 1 to 2 week equatorial fluctuations as mixed rossby gravity yanai waves of low wave number with infinite phase speed standing oscillations in the middle of the band 10 days the corresponding structures for longer periods are consistent with nondispersive kelvin waves frequency domain eof modes of the sea level and current data establish the mixed rossby gravity waves as the principal source of the strong trapped wave variability in the 1 to 2 week band along the ecuador peru coast during the 1982 1983 el nino episode

comment on rossby gravity waves in the central equatorial pacific ocean during the norpax hawaii to tahiti shuttle experiment by s m chiswell and r lukas

seasonal heat balance in the upper 100 m of the equatorial atlantic ocean the variability of sea surface temperature sst in the equatorial atlantic is characterized by strong cooling in may june and a secondary cooling in november december a numerical simulation of the tropical atlantic is used to diagnose the different contributions to the temperature tendencies in the upper ocean right at the equator the coolest temperatures are observed between 20 w and 10 w due to enhanced turbulent heat flux in the center of the basin this results from a strong vertical shear at the upper bound of the equatorial undercurrent euc cooling through vertical mixing exhibits a semiannual cycle with two peaks of comparable intensity during the first peak in may june vertical mixing drives the sst while during the second peak in november december the strong heating due to air sea fluxes leads to much weaker effective cooling than during boreal summer seasonal cooling events are closely linked to the enhancement of the vertical shear just above the core of the euc which appears to be not driven directly by the strength of the euc but by the strength and the direction of the surface current the vertical shear is maximum when the northern branch of the south equatorial current is intense the surface cooling in the eastern equatorial atlantic is not as marked as in the center of the basin mean thermocline and euc rise eastward but a strong stratification caused by the presence of warm and low saline surface waters limits the vertical mixing to the upper 20 m and disconnects the surface from subsurface dynamics

a comparison of the mid latitude eddy fields in the western north atlantic and north pacific oceans abstract latitudinal distributions of estimates of eddy kinetic energy and off diagonal component of the horizontal reynolds stresses are demonstrated to have similar shapes at corresponding generally western locations but at much different depths in the mid latitude north atlantic and north pacific oceans this comparison is based on direct current measurements at abyssal depths in the north atlantic along 55 w and on indirect estimates of upper level velocity differences in the vertical for the north pacific between the izu or izu ogasawara or south honshu ridge and the shatsky rise these sections span the more energetic segments of the kuroshio extension and gulf stream systems

analysis of pumping induced unsaturated regions beneath a perennial river 1 the presence of an unsaturated region beneath a streambed during groundwater pumping near streams can reduce the pumping capacity change flow paths and alter the types of biological transformations in the streambed sediments a three dimensional multiphase flow model of two horizontal collector wells along the russian river near forestville california was developed to investigate the impact of varying the ratio of the aquifer to streambed permeability on 1 the formation of an unsaturated region beneath the stream 2 the pumping capacity 3 stream water fluxes through the streambed and 4 stream water traveltimes to the collector wells the aquifer to streambed permeability ratio at which the unsaturated region was initially observed ranged from 10 to 100 the size of the unsaturated region beneath the streambed increased as the aquifer to streambed permeability ratio increased the simulations also indicated that for a particular aquifer permeability decreasing the streambed permeability by only a factor of 2 3 from the permeability where desaturation initially occurred resulted in reducing the pumping capacity in some cases the stream water fluxes increased as the streambed permeability decreased however the stream water residence times increased and the fraction of stream water that reached that the wells decreased as the streambed permeability decreased indicating that a higher streambed flux does not necessarily correlate to greater recharge of stream water around the wells

interannual variations of atlantic tropical instability waves 1 observations are used to develop metrics for interannual tropical instability wave tiw variability in the atlantic and to relate that variability to larger scale processes the analysis is partitioned into different latitude bands to distinguish between off equatorial 5 s 2 n and 5 n and near equatorial 2 s and 0 tiws tiw metrics based on sea surface temperature sst and sea level anomaly sla fluctuations are compared against interannual anomalies of sst in the cold tongue region to examine the role of barotropic shear instabilities in modulating the intensity of a tiw season wind stress and near surface current indices are developed in regions where the shear between the equatorial undercurrent euc and the northern branch of the south equatorial current nsec and between the nsec and the north equatorial countercurrent necc are expected to be largest good agreement is found between the sst and sla tiw metrics along the off equatorial latitude bands and interannual variations of both metrics can largely be attributed to barotropic shear instabilities in particular years with low high tiw variance along the off equatorial latitude bands are associated with anomalously warm cold ssts in the cold tongue region weak strong wind stress divergence and curl in the euc nsec region and weak strong zonal current shear in the nsec necc region in contrast in the near equatorial latitude bands poor agreement is found between interannual tiw activity based on the sst and sla metrics and near equatorial tiw variability cannot be explained by the large scale sst wind stress divergence and curl and current shear indices

why were sea surface temperatures so different in the eastern equatorial atlantic in june 2005 and 2006 abstract a comparison of june 2005 and june 2006 sea surface temperatures in the eastern equatorial atlantic exhibits large variability in the properties of the equatorial cold tongue with far colder temperatures in 2005 than in 2006 this difference is found to result mainly from a time shift in the development of the cold tongue between the two years easterlies were observed to be stronger in the western tropical atlantic in april may 2005 than in april may 2006 and these winds favorably preconditioned oceanic subsurface conditions in the eastern atlantic however it is also shown that a stronger than usual intraseasonal intensification of the southeastern trades was responsible for the rapid and early intense cooling of the sea surface temperatures in mid may 2005 over a broad region extending from 20 w to the african coast and from 6 s to the equator this particular event underscores the ability of local intraseasonal wind stress variability in the gulf of guinea to initiate the cold tongue seaso

wind driven meridional eddy heat flux in the gulf of guinea seasonal response of the equatorial atlantic programme francais ocean et climat dans l atlantique equatorial data for 1984 are analyzed to estimate heat fluxes in the interior of the gulf of guinea between 1 n and 4 n in this region during may july the mixed layer roughly 35 m deep cools uniformly by nearly 4 c in 3 months representing a mean rate of heat loss of approximately 70 w m2 climatic heat budget calculations by hastenrath and lamb 1978 show a surface flux heat loss of 30 w m2 during this time this suggests that although surface flux makes a significant contribution to the mixed layer cooling additional divergent heat flux is required to balance the local heat budget all advective and diffusive terms are estimated to be small except for the meridional eddy heat flux v t the cospectrum of v and t has a peak near 15 days at this frequency v is coherent with the meridional wind the thermocline displacements forced by this meridional wind are nearly antisymmetric about the equator the frequency meridional length scale and asymmetry of these fluctuations suggest that a second baroclinic rossby gravity wave is being locally forced thus in the interior of the gulf of guinea the eddy flux driven by the fortnightly wind fluctuations makes a significant contribution to the cooling of the mixed layer during the seasonal upwelling this is in contrast to the central and western equatorial atlantic ocean where a meridional heat flux is produced by 25 to 30 day fluctuations generated by current instabilities

changes in micronutrient supply to the surface southern ocean atlantic sector across the glacial termination major deepwater masses upwell and reach the surface in the southern ocean forming an important conduit supplying nutrients and micronutrients to the surface and playing a key role in the regulation of global climate through ocean atmosphere gas exchange here we reconstruct changes in micronutrient distribution in this region in response to past changes in upwelling oceanic mixing and sea ice seasonality we present two downcore zn si opal records from the scotia sea and drake passage region which we interpret in the context of micronutrient distribution in the atlantic sector of the southern ocean over the last glacial termination previous work shows that micronutrient availability in the surface waters in the south atlantic appear to be controlled dominantly by upwelling and mixing of micronutrient rich deepwaters which are additionally fuelled by the terrestrial sediment sources of the scotia arc and south georgia this is supported by our reconstructions which show micronutrient availability to the west of the scotia arc and south georgia are consistently lower than to the east over the last glacial termination due to downstream transport and mixing into surface waters of continentally derived material in the antarctic circumpolar current micronutrient availability in this region was at a minimum from 20 to 25 ky bp coinciding with maximum sea ice coverage and increased due to an expansion of the seasonal sea ice zone and increased mixing of subsurface waters our findings are consistent with largely diminished upwelling of micronutrients during the maximum glacial extent and reduced mixing due to the presence of persistent sea ice during the deglacial there was an increase in micronutrient availability as well as other nutrients and inorganic carbon within the antarctic circumpolar current as a result of an increase in deep oceanic upwelling mixing and strengthened zonal transport

near surface current and temperature variability observed in the equatorial atlantic from drifting buoys we examine data from 23 surface drifters which were deployed between june 1983 and july 1984 at 4 w 1 5 4 s the drifters were equipped with a window shade drogue centered at 15 m depth and in most cases a 117 m long thermistor chain drift data indicate a westward south equatorial current with typical speeds of about 20 cm s 1 south of the equator maximum westward flow of 30 40 cm s 1 occurred in june through september of 1983 and 1984 consistent with climatology near zero westward flow which was significantly weaker than was expected from climatology by about 20 cm s 1 occurred from february to april 1984 this probably represents real interannual variability and may be related to the fact that the equatorial atlantic was warmer than usual in the spring and summer of 1984 energetic variations on time scales of o 1 month and less and space scales of o 100 km and less are ubiquitous in the drift and temperature data kinetic energy levels associated with these variations south of the equator are typically 100 cm2 s 2 with slightly higher values in boreal summer energy levels north of the equator are about 500 cm2 s 2 on the basis of data available only during the boreal summer and fall the sources of this energy include inertia gravity waves instabilities of the general circulation and other phenomena for which there is no simple explanation

sea surface cooling at the equator by subsurface mixing in tropical instability waves changes in the sea surface temperature of equatorial waters have critical effects on the large scale atmospheric circulation shipboard measurements of turbulence kinetic energy dissipation rate indicate that seasonal surface cooling in the central equatorial pacific may be largely caused by mixing induced by tropical instability waves

variability in equatorial pacific sea surface topography during the verification phase of the topex poseidon mission l abstract as part of the verification phase of the topewposeidon mission 10 day gridded fields of altimeter data derived from topex geophysical data records are compared with 10 day gridded fields of dynamic height derived from more than 60 moorings of the tropical ocean and global atmosphere tropical atmosphere ocean toga tao array in the equatorial pacific ocean access to tao data in real time permits the first 500 days of the topewposeidon mission to be placed in the context of complementary in situ measurements of surface winds sea surface temperatures and upper ocean thermal structure as well as the time history of these variables prior to launch analysis of the space time structure in the topex and tao surface topography data indicates sea level variability primarily due to equatorial kelvin wave activity generated by intense wind bursts west of the date line in association with the 1991 1993 el nino cross correlations between the two data sets are generally 0 7 witha rms differences 5 cm north of the equator in the central and eastern pacific

zn si records in diatom opal from prydz bay east antarctica abstract the zn si records of diatom opal from prydz bay were investigated the results show that the zn si ratios range from 8 to 53 mol mol 1 the ratio from the continental slope is higher than those from the shelf the difference in zn si records could be attributed to the change of bioavailable zn via the upwelling of zn2 rich deep water or the influence of oceanic water on the slope however phytoplankton productivity influences zn si records on the continental shelf increased productivity leads to elevated zn pumping and eventually to higher zn si ratio in diatom opal in this case it is suggested that zn si proxy could be a signal of marine productivity on the continental shelf of prydz bay the down core profile of zn si records shows an increase in marine productivity over the last century

eastern equatorial pacific response to three composite westerly wind types it has been suggested recently that episodes of westerly wind near the international date line in the western pacific tend to fall into one of four types three of the types have enough equatorial zonal wind variation to be able to induce an eastern pacific response by forcing equatorial waves in this note we examine the central and eastern pacific waveguide response to idealized representations of these three types of westerly wind episodes using a combination of linear theory and results from an ocean general circulation model the idealized westerly wind types are the c type maximum anomalies centered on the equator the n type maximum anomalies just north of the equator and the s type maximum anomalies just south of the equator the composite c type event excites equatorially trapped kelvin pulses that alter sea surface temperature in the central and eastern pacific warm anomalies caused by the c type episode have approximately equal contributions from a zonal advection of heat by the kelvin pulses and a meridional advection of heat by an altered instability wave field because the center of forcing of the s type event is displaced off of the equator the kelvin pulses excited by the s type episode have smaller amplitude than those of the c type episode even though the maximum wind anomaly is the same in the two cases the s type anomaly also excites weak rossby gravity waves that can propagate into the eastern pacific because the rossby gravity waves are dispersive their amplitude diminishes as the waves propagate into the eastern pacific the n type episode as observed in winds from the western tropical pacific is much weaker and of shorter duration than the c and s types and therefore excites only a very weak eastern pacific response although all types of westerly wind excite a local western pacific response only the c and s type events excite a significant eastern pacific response

a climatology of waves in the equatorial region abstract propagating anomalies of moisture and moist deep convection in the tropics are organized into a variety of large scale modes these include but are not limited to the so called intraseasonal oscillations convectively coupled waves similar to those predicted by shallow water theory on the equatorial beta plane and tropical depression type disturbances along with the annual and diurnal cycles these modes act and interact to control much of the variance of tropical convection analyses of 10 yr of outgoing longwave radiation olr and precipitable water pw data are carried out to develop comparative climatologies of these wavelike modes the analysis relaxes the commonly used cross equatorial symmetry constraints which allows study of the portions of the wavelike processes that are asymmetric across the equator mean background states are found for olr and for pw as functions of day of the year examination of anomalies together with the background reveals much about how the waves are affec

energy and heat fluxes due to vertically propagating yanai waves observed in the equatorial indian ocean shipboard current measurements in the equatorial indian ocean in october and november of 2011 revealed oscillations in the meridional velocity with amplitude 0 10m s these were clearest in a layer extending from 300 to 600 m depth and had periods near 3 weeks phase propagation was upward measurements from two sequential time series at the equator four meridional transects and one zonal transect are used to identify the oscillation as a yanai wave packet and to establish its dominant frequency and vertical wavelength the doppler shift is accounted for so that measured wave properties are translated into the reference frame of the mean zonal flow we take advantage of the fact that in the depth range where the wave signal was clearest the time averaged current and buoyancy frequency were nearly uniform with depth allowing application of the classical theoretical representation of vertically propagating plane waves using the theory we estimate wave properties that are not directly measured such as the group velocity and the zonal wavelength and phase speed the theory predicts a vertical energy flux that is comparable to that carried by midlatitude near inertial waves we also quantify the wave driven meridional heat flux and the stokes drift

an analytical solution for a radial collector well near a stream with a low permeability streambed summary radial collector wells are often constructed near a stream to obtain more water and produce smaller drawdown in comparison with traditional vertical wells this paper aims at developing a mathematical model for describing head distributions induced by pumping in a radial collector well near a stream in an unconfined aquifer a low permeable streambed between the stream and the aquifer is considered the first order free surface equation is used to describe the movement of water table a point sink solution of the model is developed first by a general transform combining fourier sine and cosine transforms and then by fourier transform and laplace transform the transient solution of head distributions for different well types such as the horizontal well or radial collector well can be obtained by integrating the point sink solution along the well based on darcy s law and the developed solution an equation for temporal stream depletion rate describing filtration from the stream is then obtained the steady state solutions for filtration can be obtained from the transient solution when neglecting the exponential term associated with time it is found that steady state filtration depends only on the ratio of streambed permeability over aquifer permeability steady state filtration equals water extraction from a well when the ratio is larger than 10 2 the streambed is regarded as completely impermeable when the ratio is less than 10 7 additionally the lowest water table happens near the well before occurrence of filtration the lowest water table moves landward and away from the well after filtration occurs

generation of tropical instability waves in the atlantic ocean the spatial and temporal distributions of tropical instability waves tiws in the atlantic ocean are investigated using a combination of current observations with moored instruments deployed at the equator at 23 w and a realistic eddy resolving 1 12 general circulation model of the atlantic ocean the meridional and vertical shears of the zonal current system contribute to the eddy production rates and thus to the generation of tiws in the central tropical atlantic ocean in the southern hemisphere tiws are forced only by baroclinic instability associated with the vertical shear of the central part of the south equatorial current sec in the northern hemisphere baroclinic instability due to the vertical shear of the northern sec nsec as well as barotropic instabilities due to horizontal shears of the equatorial undercurrent euc nsec and nsec north equatorial countercurrent necc contribute to the generation of the tiws since seasonal changes of the instability production rates related to the euc nsec are comparable low while the rates related to the nsec necc are high we suggest that the seasonality of the necc dominates the seasonal modulation of the tiws

distribution of diatoms in surface sediments of prydz bay antarctica abstract four diatom assemblages are identified from the surface sediments of prydz bay and the mac robertson shelf using multivariate analysis a coastal assemblage is characterised by the sea ice diatoms fragilariopsis curta f angulata f cylindrus and pseudonitzschia turgiduloides a continental shelf assemblage is characterised by sea ice and ice edge diatoms and an oceanic assemblage is characterised by the open water diatoms fragilariopsis kerguelensis thalassiosira lentiginosa t gracilis var expecta and trichotoxin reinboldii the cape darnley assemblage contains both sea ice and open water diatoms but all are characteristically large and heavily silicified multiple regression has been used to identify the relationships between the diatom assemblages and known environmental variables there are strong correlations between the coastal shelf and oceanic assemblages and ecological conditions including latitude sea ice distribution and ocean currents the cape darnley assemblage is thought to represent an assemblage from which the smaller and more lightly silicified species have been removed by current winnowing

interannual long equatorial waves in the tropical atlantic from a high resolution ocean general circulation model experiment in 1981 2000 we investigate the tropical atlantic vertical structure variability 1981 2000 based on the clipper ocean general circulation model ogcm we aim at determining to what extent the observed interannual variability can be explained by the low frequency wave dynamics the linear vertical modes of the ogcm climatological stratification are estimated along the equator the baroclinic mode contributions to surface zonal current and sea level anomalies are calculated and analyzed at interannual timescales the second baroclinic mode is the most energetic the first third mode exhibits a variability peak in the west east the summed up contribution of the high order baroclinic modes 4 6 is as energetic as the gravest modes and is largest in the east wave components are then derived by projection onto the associated meridional structures the effect of longitudinal boundaries near the equator is taken into consideration equatorial kelvin and rossby waves propagations with phases speed close to the theory are identified for the first three baroclinic modes the comparison with a multimode linear simulation corroborates the propagating properties of the ogcm waves coefficients an estimation of the meridional boundary reflection efficiency indicates that wave reflections take place at both boundaries a 65 reflection efficiency is found at the eastern boundary our study suggests that low frequency wave dynamics is to a large extent at work in the tropical atlantic on the basis of what is known on the pacific el nino southern oscillation mode this may provide a guidance for investigating ocean atmosphere mechanisms that can lead to the atlantic zonal equatorial mode

the distribution of dissolved zinc in the atlantic sector of the southern ocean the distribution of dissolved zinc zn was investigated in the atlantic sector of the southern ocean in the austral autumn of 2008 as part of the ipy geotraces expedition zero drake research focused on transects across the major frontal systems along the zero meridian and across the drake passage there was a strong gradient in surface zinc concentrations observed across the antarctic polar front along both transects and high zinc levels were found in surface waters throughout the southern ocean vertical profiles for dissolved zinc showed the presence of local minima and maxima in the upper 200 m consistent with significant uptake by phytoplankton and release by zooplankton grazing respectively highest deep water zinc concentrations were found in the centre of the weddell gyre associated with central intermediate water ciw a water mass which is depleted in o2 elevated in co2 and is regionally a cfc minimum our data suggests that the remineralization of sinking particles is a key control on the distribution of zn in the southern ocean disappearance ratios of zinc to phosphate zn p in the upper water column increased southwards along both transects and based on laboratory studies they suggest slower growth rates of phytoplankton due to iron or light limitation zinc and silicate were strongly correlated throughout the study region but the disappearance ratio zn si was relatively uniform overall except for the region close to the ice edge on the zero meridian

dynamics of intraseasonal sea level and thermocline variability in the equatorial atlantic during 2002 03 abstract satellite and in situ observations in the equatorial atlantic ocean during 2002 03 show dominant spectral peaks at 40 60 days and secondary peaks at 10 40 days in sea level and thermocline within the intraseasonal period band 10 80 days a detailed investigation of the dynamics of the intraseasonal variations is carried out using an ocean general circulation model namely the hybrid coordinate ocean model hycom two parallel experiments are performed in the tropical atlantic ocean basin for the period 2000 03 one is forced by daily scatterometer winds from the quick scatterometer quikscat satellite together with other forcing fields and the other is forced by the low passed 80 day version of the above fields to help in understanding the role played by the wind driven equatorial waves a linear continuously stratified ocean model is also used within 3 s 3 n of the equatorial region the strong 40 60 day sea surface height anomaly ssha and thermocline variability result mainly from the

the hawaii to tahiti shuttle experiment the shuttle experiment conducted between hawaii and tahiti from january 1979 to june 1980 was designed to observe the changing equatorial ocean structure and circulation to study the variations and interactions of the four major equatorial ocean currents and to develop a scientific basis for their monitoring by simple observations of thermal structure and sea level preliminary analyses of the results show that the equatorial thermal structure remains intact during a normal year and that only the positions and intensities of the currents are subject to change the water transport of the equatorial undercurrent varied from 25 x 106 cubic meters per second in january to 51 x 106 cubic meters per second in july but also exhibited strong short term pulsations the equatorial surface flow responded strongly to the winds at periods of 1 month and longer an array of drifter buoys in the equatoral countercurrent was subject to very little dispersion while traveling over 4500 kilometers in 4 months low frequency fluctuations in the north equatorial countercurrent can be monitored by means of the difference in sea level between fanning and majuro

equatorially trapped rossby waves in the presence of meridionally sheared baroclinic flow in the pacific ocean topex poseidon altimeter data are analyzed for the 8 5 year period november 1992 to may 2001 to investigate the sea surface height ssh and geostrophic velocity signatures of quasi annual equatorially trapped rossby waves in the pacific the latitudinal structures of ssh and both components of geostrophic velocity are found to be asymmetric about the equator across the entire pacific with larger amplitude north of the equator the westward phase speeds are estimated by several different methods to be in the range 0 5 0 6 m s 1 these observed characteristics are inconsistent with the classical theory for first vertical first meridional mode equatorially trapped rossby waves which predicts a phase speed of about 0 9 m s 1 with latitudinally symmetric structures of ssh and zonal velocity and antisymmetric structure of meridional velocity the observations are even less consistent with the latitudinal structures of ssh and geostrophic velocity components for other modes of the classical theory the latitudinal asymmetries deduced here have also been consistently observed in past analyses of subsurface thermal data and altimeter data and have been variously attributed to sampling errors in the observational data a superposition of multiple meridional rossby wave modes asymmetric forcing by the wind and forcing by cross equatorial southerly winds in the eastern pacific we propose a different mechanism to account for the observed asymmetric latitudinal structure of low frequency equatorial rossby waves from the free wave solutions of a simple 1 5 layer model it is shown that meridional shears in the mean equatorial current system significantly alter the potential vorticity gradient in the central and eastern tropical pacific the observed asymmetric structures of sea surface height and geostrophic velocity components are found to be a natural consequence of the shear modification of the potential vorticity gradient the mean currents also reduce the predicted westward phase speed of first meridional mode rossby waves improving consistency with the observations

observations of the dispersion characteristics and meridional sea level structure of equatorial waves in the pacific ocean spectral techniques applied to altimetry data are used to examine the dispersion relation and meridional sea level structure of wavelike variability with periods of about 20 to 200 days in the equatorial pacific ocean zonal wavenumber frequency power spectra of sea surface height when averaged over about 7 s 7 n exhibit spectral peaks near the theoretical dispersion curves of first baroclinic mode equatorial kelvin and rossby waves there are distinct statistically significant ridges of power near the first and second meridional mode rossby wave dispersion curves sea level variability near the theoretical kelvin wave and first meridional mode rossby wave dispersion curves is dominantly but not perfectly symmetric about the equator while variability near the theoretical second meridional mode rossby wave dispersion curve is dominantly antisymmetric these results are qualitatively consistent with expectations from classical or shear modified theories of equatorial waves the meridional structures of these modes resemble the meridional modes of equatorial wave theory but there are some robust features of the meridional profiles that were not anticipated the meridional sea level structure in the intraseasonal kelvin wave band closely resembles the theoretically expected gaussian profile but sea level variability coherent with that at the equator is detected as far away as 11 75 s possibly as a result of the forced nature of these kelvin waves both first and second meridional mode rossby waves have larger amplitude in the northern hemisphere the meridional sea level structure of tropical instability waves closely resembles that predicted by lyman et al using a model linearized about a realistic equatorial zonal current system

reply to comment on rossby gravity waves in the central equatorial pacific ocean during the norpax hawaii to tahiti shuttle experiment by s m chiswell and r lukas

observations of eastward propagation of atmospheric intraseasonal oscillations from the pacific to the atlantic received 19 april 2010 revised 20 september 2010 accepted 29 september 2010 published 19 january 2011 1 significant 40 60 day intraseasonal variability in surface winds sea level and thermocline depth were observed in the tropical atlantic during the atlantic nino year of 2002 satellite derived quikscat winds and noaa outgoing longwave radiation olr measurements for the period of 2000 2006 together with reanalysis of winds from a longer record are analyzed to understand the sources of this 40 60 day wind variability and the global propagation of the madden julian oscillation mjo surface signatures the results demonstrate that the mjo propagated eastward from the indo pacific ocean to the atlantic during winter and spring of 2002 causing 40 60 day wind variations in the equatorial atlantic the isthmus of panama appears to be a dominant pathway for these surface wind anomalies to propagate into the atlantic where they can produce important climate impacts this result is consistent with previous work that has demonstrated a strong mjo influence on the north american monsoon nam region and complements other work demonstrating the propagation of intraseasonal wind anomalies and accompanying sea level pressure signals associated with dry equatorial kelvin waves that reach the caribbean through the panama gap the mjo is also shown to have a large influence on the subtropical atlantic ocean seasonality of the mjo impact on atlantic surface winds is investigated using data from an extended record and the most direct influence is found to be during boreal winter and spring with a delayed influence during summer and fall

semi analytical solutions of discharge variation of a qanat in an unconfined aquifer subjected to general areal recharge and nearby pumping well discharge abstract qanat is a type of drain that extract water from aquifers by gravity significant amount of fresh water used in middle east and other parts of the world are supplied by qanats despite their importance discharge variation of these type of wells received almost no attention the aim of this research is to obtain a laplace domain solution of discharge variation of a qanat installed in an anisotropic unconfined aquifer subjected to arbitrary areal recharge and nearby pumping well s discharge a new semi analytical solution of drawdown is obtained first to implement the effects of arbitrary areal recharge and nearby pumping well s using the principle of superposition then the discharge variation solution of the qanat is obtained from the drawdown solution to establish a constant head boundary condition at the qanat periphery the qanat is discretized into several segments the results of this study are presented in dimensionless discharge dimensionless time curves the effects of hydraulic as well as geometric parameters on the discharge variation of the qanat due to arbitrary areal recharge falling of water table from its initial position and discharge of nearby wells are explored we also investigate the influences of distance and screen depth and location of the nearby well on the discharge variation of the qanat the results of this study can be utilized for multiple purposes 1 to predict discharge of qanat in response to rainfall and nearby pumping well s 2 to estimate the aquifer parameters using hydrograph of the qanat 3 to determine optimal location and pumping pattern of the nearby wells to minimize their influences on the discharge of the qanat 4 to calculate water budget of aquifers drained by a qanat the equation presented in this work can also be used to estimate discharge of a horizontal drain installed in cropland subjected to arbitrary irrigation pattern

variability of the mixed layer heat budget in the eastern equatorial atlantic during 2005 2007 as inferred using argo floats we examine the variability of the sea surface temperatures in the eastern equatorial atlantic during 2005 2007 by using argo profiling floats prediction and research moored array in the atlantic buoys and satellite in situ and atmospheric data sets the eastern equatorial atlantic characterized by shallow mixed layers all yearlong is divided into nine boxes of nearly equal surface area with respect to the dynamics and thermodynamics in this region monthly mixed layer heat budgets are computed in each box from 10 day argo profiles in all the boxes the net surface heat flux is one of the main causes of the seasonal evolution of sea surface temperatures for the 3 studied years the amount of short wave radiation penetrating through the base of the mixed layer and horizontal heat advection may locally contribute to the temperature variability while entrainment has a weaker contribution to balance the heat budget a residual term exists which includes all processes that cannot be calculated with observations as well as the possible errors in the other terms this residual is more intense in the cold tongue and the northern region and exhibits a clear seasonal cycle with minimum negative values in boreal summer and maximum values in winter this residual compares well with available observations of vertical turbulent mixing collected during etude de la circulation oceanique et des echanges ocean atmosphere dans le golfe de guinee campaigns 2005 2007 in the eastern equatorial atlantic when assuming that the residual is mostly associated with vertical turbulent mixing it can be conjectured that turbulent mixing is a significant cooling source in the cold tongue and north of the equator

sources of interannual baroclinic waves in the eastern subtropical north pacific abstract subsurface temperature and surface salinity observations along the great circle transect between san francisco and honolulu are used to investigate the source of annual baroclinic long waves in the eastern subtropical north pacific ocean long term mean 15 day values 1966 74 of depth of the 9 c isotherm indicative of thermocline depth and of surface salinity are each fit by least squares method with a time varying cosine yielding phase and amplitude of the mean annual cycle at standard locations every 92 6 km 50 mi along the transect local wind stress curl is expected to influence the observed depth of the 9 c isotherm through the mechanism of ekman pumping therefore its annual cycle is computed in a manner like that of the depth of the 9 c isotherm and its effect removed from the latter the residual annual cycle has phase and amplitude profiles along the transect that closely resemble that of model annual baroclinic long waves emanating from a line source of large amplitude wind st

monitoring the 1979 1985 equatorial pacific current transports with expendable bathythermograph data geostrophic transports of the major equatorial currents including the equatorial undercurrent and the south equatorial current have been estimated on a bimonthly basis in the central and western pacific over the 1979 1985 period this was made possible by a collection of carefully checked expendable bathythermograph xbt data and a few hydrocast and conductivity temperature depth data this collection considerably improved the number and quality of temperature profiles of the original institut francais de recherche scientifique pour le developpement en cooperation orstom scripps institute of oceanography tropical pacific xbt ship of opportunity program the temperature profiles were first grouped independently of longitude in regions around mean xbt tracks dynamic heights were then calculated relative to 400 db through a t s relationship deduced from the climatological levitus file geostrophic currents were calculated along the roughly south north oriented fiji hawaii and new caledonia japan mean xbt tracks using a specific technique this technique which combines fourier filtering in the meridional direction and in time also ensures the continuity across the equator between geostrophic currents deduced from the first and second derivatives of the meridional pressure field the filter coefficients in the meridional direction were determined through an adjustment of geostrophic currents to directly measured currents using the mean of data collected along 165 e during six tropical ocean and global atmosphere toga orstom cruises finally transports of the main equatorial currents were computed in a subjective way between 20 n and 20 s 0 400 m using monthly charts of geostrophic currents along the two mean xbt tracks the transports in the central pacific were compared to the transports derived from the semicontinuous direct current measurements taken during the hawaii tahiti shuttle experiment in 1979 1980 and during the line island profiling project pacific equatorial ocean dynamics experiment in 1982 1983 reasonable agreement demonstrates that it is possible to use xbt data for transport indexes of the major equatorial currents in the central and western pacific

horizontal reynolds stresses in the central equatorial pacific seven 13 month long current records from the north pacific experiment hawaii to tahiti shuttle experiment during 1979 1980 were analyzed to investigate eddy energetics of the upper ocean within 75 km of the equator profiling current meter data from the experiment were also used in an attempt to relate the eddy motions to the mean zonal flow the current fluctuations are highly anisotropic with zonal current dominating after removal of a linear trend plus annual and semiannual harmonics the residual high frequency current fluctuations are much more nearly isotropic the high frequency eddy kinetic energy decreases by a factor of 2 over the upper 250 m and at 100 m has a relative minimum on the equator the seasonal time scale eddy kinetic energy shows a much more dramatic decrease below the thermocline with the exception of tidal peaks the spectra of zonal current are red while meridional current spectra show a flattening at the lowest resolvable frequencies meridional current was non stationary with an energetic packet of 10 to 15 day period oscillations occurring in early 1980 the off diagonal component of the reynolds stress tensor u calculated from the high frequency residuals is everywhere positive decreasing from north to south and with depth the implied cross equatorial flux of zonal momentum is at odds with eddy viscosity parameterizations which relate u to the mean meridional shear of the zonal current the observed distribution of reynolds stresses might be explained by radiation of energy from an instability of the portion of the south equatorial current north of the equator in all cases the high frequency u time series are significantly skewed toward positive values and show no evidence of periodicity indicating that the process es responsible is are intermittent and broadband this is consistent with the instability mechanism

rossby wave analysis of subsurface temperature fluctuations along the honolulu san francisco great circle abstract seven years of xbt observations collected between honolulu and san francisco reveal subsurface temperature fluctuations with strong in phase vertical coherence and fair horizontal coherence over 1000 km distance their annual and semi annual harmonics exhibit randomness of phase suggesting that the fluctuations are modeled better as a stochastic process than as a deterministic signal cross spectral fitting of a stochastic first baroclinic mode rossby wave model to the fluctuations demonstrates the rossby waves could be producing 50 60 of the observed subsurface covariance at periods exceeding nine months phase is seen to propagate northwestward and energy westward and southwestward the corresponding sea surface velocities and sea level fluctuations are of the order 1 cm s 1 and 1 5 cm

tropical instability wave kinematics observations from the tropical instability wave experiment the kinematics of planetary waves originating from instability of the nearsurface equatorial currents are reported on using velocity measurements from an array of acoustic doppler current profilers deployed in the equatorial pacific during the tropical instability wave experiment a distinctive wave season was observed from august to december 1990 with wave energy confined primarily above the core of the equatorial undercurrent particle motions in the horizontal plane are described by eccentric ellipses oriented toward the north but tilting into the cyclonic shear of the south equatorial current the tilt is maximum near the surface just north of the equator and decreases to the south and with depth the distribution of wave variance is narrowband in both frequency and zonal wavenumber with central period zonal wavelength and westward directed phase propagation estimated to be 500 hours 1060 km and 59 cm s 1 respectively neither the meridional nor the vertical wavenumber component is statistically different from zero these results generally agree with previous findings on tropical instability waves from the atlantic and pacific oceans and in the undersampled arena of geophysical measurements they provide an example where statistical inference is supported by an ensemble of independent measurements

opal zn si ratios as a nearshore geochemical proxy in coastal antarctica during the last 50 years the antarctic peninsula has experienced rapid warming with associated retreat of 87 of marine and tidewater glacier fronts accelerated glacial retreat and iceberg calving may have a significant impact on the freshwater and nutrient supply to the phytoplankton communities of the highly productive coastal regions however commonly used biogenic carbonate proxies for nutrient and salinity conditions are not preserved in sediments from coastal antarctica here we describe a method for the measurement of zinc to silicon ratios in diatom opal zn si opal which is a potential archive in antarctic marine sediments a core top calibration from the west antarctic peninsula shows zn si opal is a proxy for mixed layer salinity we present down core zn si opal paleosalinity records from two rapidly accumulating sites taken from nearshore environments off the west antarctic peninsula which show an increase in meltwater input in recent decades our records show that the recent melting in this region is unprecedented for over 120 years

impact of isopycnal mixing on the tropical ocean circulation the sensitivity of tropical ocean dynamics to the ocean lateral mixing orientation is explored using a z coordinate climate type ocean general circulation model compared to a simulation using horizontal mixing on both tracers and dynamics hor a rotation of the tracer tensor in which mixing occurs along isopycnals isot improves the structure of the off equatorial density field which consequently enhances the off equatorial circulation through geostrophy however the dynamics at the equator in isot are degraded compared to observations as the upper part of the equatorial undercurrent euc is too deep and the south equatorial current sec is too intense next isopycnal diffusion on momentum is implemented isomt an examination of the momentum balance at the equator shows that this change in lateral diffusion direction significantly reduces the meridional diffusive flux of momentum at the top of the euc this intensifies the euc which in turn weakens the sec along the equator through vertical diffusion the equatorial degradations observed in isot disappear compared to isot and hor the separation of the two sec branches and the equatorial current magnitude in the surface layers are much better reproduced moreover in contrast to the results from isot and hor isopycnal momentum mixing allows the existence of both horizontal up gradient and down gradient eddy momentum fluxes notably improving the vertical profile of the lateral viscosity term the isomt experiment is therefore shown to be the closest to observations these results suggest that isopycnal mixing should be used on both tracers and momentum to better simulate the observed eddy effects and the tropical circulation in climate models

significance of hydraulic head gradients within horizontal wells in unconfined aquifers of limited saturated thickness summary horizontal wells can be used to withdraw water from shallow aquifers frequently there is a substantial hydraulic gradient within the horizontal well this paper considers the significance of the hydraulic head distribution for horizontal wells in shallow aquifers and estimates the inflows of groundwater along the length of the well conceptual and computational models are developed to represent time variant regional groundwater flow convergent flows towards and into the horizontal well and hydraulic conditions within the well are also included a case study of a 300 m long horizontal well curved in plan in an aquifer of limited saturated thickness is used to illustrate the approach field monitoring indicates significant drawdowns in groundwater heads in the vicinity of the well substantial difference in hydraulic head between the pump end and the far end of the well are also identified successful comparisons are made between field and model results from the numerical models groundwater inflows along the well are estimated inflows at the pump end are about four times the inflows towards the far end the effect of reducing the length of the well is explored

oscillations of dynamic topography in the eastern equatorial pacific abstract for 14 months in 1980 81 surface dynamic height was monitored with inverted echo sounders at five sites from 0 to 9 n along 110 w these records show that the sec necc equatorial current system was well developed during the boreal summer and fall but weak and irregular during winter and spring when westward flow associated with the nec extended as far south as 6 n superimposed on the mean dynamic topography of this region are energetic 20 to 80 day oscillations longer periods being associated with higher latitudes near the equatorial ridge 5 n these oscillations have predominantly monthly periods and amplitude of 10 dyn cm comparable to the mean dynamic height difference across the necc the broad in phase meridional extent of these monthly oscillations implies that the principal mode of ridge variation is vertical undulation rather than meridional meandering producing large in phase monthly modulations in transport of the sec and necc oscillations or the equatorial ridge are correla

cross equatorial structure and temporal modulation of intraseasonal variability at the surface of the tropical atlantic ocean intraseasonal variability 10 50 days in the equatorial atlantic ocean is analyzed from multiyear 1999 2005 satellite gridded products of sea level anomalies sla and sea surface temperature sst two regions with distinct intraseasonal variability have been identified the first one west of 10 degrees w is dominated by westward propagating anomalies with maximum values in sla along 5 degrees n and in sst along 2 degrees n they occur in boreal summer with periods of 25 50 days and are known to correspond to tropical instability waves tiws we show that tiws have also a signature though weaker south of the equator especially along 5 degrees s in sla northern and southern anomalies propagate together westward being mostly out of phase suggesting that equatorial wave dynamics is involved in tiws variability an sst signature of tiws is also observed near 2 degrees s in quadrature with sst anomalies detected in the northern hemisphere the interannual modulations of the tiw signature in sla and sst are compared and discussed the second dominant intraseasonal signal is only seen east of 10 degrees w in sst and corresponds to an equatorially trapped variability confined to the gulf of guinea with periods between 10 and 20 days this signal is present in boreal summer when an intense sst front is observed just north of the equator intraseasonal variability with comparable periods is also observed in the meridional wind stress throughout the year comparison of sst and meridional wind stress anomalies suggests that the 10 to 20 day variability in sst is forced by the wind stress but seasonally modulated by the presence of the sst front

diagnosing ocean wave turbulence interactions from space numerical studies indicate that interactions between ocean internal gravity waves especially those textless100 km and geostrophic or balanced motions associated with mesoscale eddy turbulence involving eddies of 100 300 km impact the ocean s kinetic energy budget and therefore its circulation results from these studies have never been confirmed by observations in regional or basin scale domains here we show that internal gravity waves have a spectral signature on sea surface height during summer that significantly differs from that of balanced motions these spectral differences lead us to propose a new dynamical framework that quantifies the interactions between internal gravity waves and balanced motions in physical space from sea surface height snapshots and in particular the energy exchanges between them our results using this dynamical framework highlight the strong potential of future satellite altimeter missions to make critical advances in assessing the ocean s kinetic energy budget from observations in large domains

paleo ocean chemistry records in marine opal implications for fluxes of trace elements cosmogenic nuclides 10be and 26al and biological productivity abstract here we provide evidence suggesting that marine diatom opal contains not only a high fidelity record of dissolved oceanic concentrations of cosmic ray produced radionuclides 10 be and 26 al but also a record of temporal variations in a large number of trace elements such as ti fe zn and mn this finding is derived from measurements in purified biogenic opal that can be separated from detrital materials using a newly developed technique based on surface charge characteristics initial results from a sediment core taken near the present day position of the antarctic polar front odp site 1093 show dramatic changes in the intrinsic concentrations of be al ti fe mn and zn in the opal assemblages during the past 140 kyr bp the results imply appreciable climatically controlled fluctuations in the level of bioreactive trace elements the time series of total be al ti fe and 10 be in the sediment core are all well correlated with each other and with dust records in the polar ice cores the observations suggest that a significant flux of these trace metals to oceans is contributed by the aeolian dust in this case presumably from the patagonia this observation also allows determination of fluxes of dust contributed 10 be to the antarctica ice sheets however our data show that the relationships among the various metals are not perfectly linear during periods of higher dissolved concentrations of trace elements indicated by fe and ti the relative concentrations of bioreactive elements be al mn and zn are decreased by contrast the fe zn and fe mn ratios decrease significantly during each transition from cold to warm periods the relative behavior could be consistent with any of the following processes i enhanced biological productivity due to greater supply of the bioreactive elements e g zn during cold periods ii increased biological and inorganic scavenging of particle active elements e g be and al during early interglacial periods iii differential uptake removal of the metals by the various diatom taxa whose relative productivity or growth rate changes with large scale climate in any case with one sedimentary phase and in single sedimentary sections we now have the potential to compare directly a proxy for aeolian input of micronutrients e g fe or ti with a proxy for production e g 26 al al ratios we expect that studies of the temporal records of trace elements and cosmogenic nuclides in contrasting regions of upwelling and productivity which exhibit different sensitivities to global climate fluctuations and micronutrient inputs would lead to a direct and comprehensive test of ideas such as the hypothesis of iron control of atmospheric carbon dioxide martin j h 1990 glacial interglacial co 2 change the iron hypothesis paleoceanography 5 1 13 our present data from a single site do not show that increases in dissolved fe concentrations per se were responsible for increased biological productivity however a much clearer picture of the effect of increased dust fluxes should emerge when we have data for trace elements and the cosmogenic nuclides 10 be and 26 al from various oceanic provinces

coupling between the atlantic cold tongue and the west african monsoon in boreal spring and summer 1 the formation of the atlantic cold tongue act is the dominant seasonal sea surface temperature signal in the eastern equatorial atlantic eea a comprehensive analysis of variability in its spatial extent temperature and onset is presented then the physical mechanisms which initiate act onset as well as the feedbacks from the act to the maritime boundary layer and how the act influences the onset of the west african monsoon wam are discussed we argue that in the eea the air sea coupling between the act and wam occurs in two phases from march to mid june the act results from the intensification of the southeastern trades associated with the st helena anticyclone steering of surface winds by the basin shape of the eea imparts optimal wind stress for generating the maximum upwelling south of the equator during the second phase mid june august wind speeds north of the equator increase as a result of the northward progression of the intensifying trades and as a result of significant surface heat flux gradients produced by the differential cooling between the act and the tropical waters circulating in the gulf of guinea gg it is anticipated that the atmospheric divergence induced at low levels north of the equator reduces convection over the gg and that increased northward winds shift convection over land correlations between the act and the wam onset dates over the last 26 years 1982 2007 measure as much as 0 8 this suggests that the act plays a key role in the wam onset

base flow recession from unsaturated saturated porous media considering lateral unsaturated discharge and aquifer compressibility unsaturated flow is an important process in baseflow recessions and its effect is rarely investigated a mathematical model for a coupled unsaturated saturated flow in a horizontally unconfined aquifer with time dependent infiltrations is presented the effects of the lateral discharge of the unsaturated zone and aquifer compressibility are specifically taken into consideration semi analytical solutions for hydraulic heads and discharges are derived using laplace transform and cosine transform the solutions are compared with solutions of the linearized boussinesq equation lb solution and the linearized laplace equation ll solution respectively a larger dimensionless constitutive exponent d a smaller retention capacity of the unsaturated zone leads to a smaller discharge during the infiltration period and a larger discharge after the infiltration the lateral discharge of the unsaturated zone is significant when d 1 and becomes negligible when d d 100 the compressibility of the aquifer has a non negligible impact on the discharge at early times for late times the power index b of the recession curve dq dt aqb is 1 and independent of d where q is the baseflow and a is a constant lumped aquifer parameter for early times b is approximately equal to 3 but it approaches infinity when t 0 the present solution is applied to synthetic and field cases the present solution matched the synthetic data better than both the ll and lb solutions with a minimum relative error of 16 for estimate of hydraulic conductivity the present solution was applied to the observed streamflow discharge in iowa and the estimated values of the aquifer parameters were reasonable

observations of inertia gravity waves in the atlantic from inverted echo sounders during fgge abstract the study is based on observations from inverted echo sounders anchored near the equator in the western atlantic ocean it appears to be a good method of detecting inertia gravity waves with large vertical scale the spectral analysis of the records shows variable spectral density levels in the band of 2 5 days three of the four inverted echo sounder ies records show an increase in the variance centered at 3 75 days in addition two sounders deployed during the latter half of the year stronger winds also show a peak in the variance at 2 14 and 2 31 days the most likely interpretation of the spectral peak at 3 75 days is an atmospherically forced vertically propagating inertia gravity wave with a meridional structure given by the n 3 mode the corresponding equivalent depth is h 0 7 m and the vertical wavelength is 730 m the energy density estimated from the variance in the ies records is e 0 7 103 j m 2