observations of variability on synoptic timescales in the east pacific itcz abstract data obtained in the eastern pacific intertropical convergence zone itcz during the tropical eastern pacific process study tepps show a 3 6 day variability the noaa ship ronald h brown collected surface meteorological observations c band doppler radar volumes atmospheric soundings and rainfall data while on station at 7 8 n 125 w from 8 23 august 1997 the 3 6 day variability was a prominent timescale in the meridional wind and humidity data the maxima of the surface to 700 mb meridional wind anomalies were 5 12 m s 1 maxima of the moisture anomalies at the same levels were 1 3 g kg 1 in phase with the low level southerlies while upper level moisture lagged the southerlies by less than a day the radar indicated a close connection between precipitation in the vicinity of the ship and the meridional wind with the precipitation occurring when the surface southerlies were strongest the meridional and zonal wind components had a maximum of 850 450 mb wind shear during the southerly e

chemistry of rainwater in the massif central france a strontium isotope and major element study atmospheric aerosols sea salt crustal dust and biogenic aerosols are the primary source of dissolved species in rainwater as well as one of the sources of dissolved species in river water chemical weathering studies require quantification of this atmospheric input the crustal component of atmospheric input can have various origins both distant and local the proportions of the various inputs marine distant or local are determined in this study strontium isotope ratios and ca na k mg al cl so4 no3 and sr concentrations were measured in rainwater samples collected in the massif central france over a period of one year each sample collected automatically represents a monthly series of rain events chemical composition of the rainwater samples varied considerably and the 87sr 86sr ratios ranged between 0 709198 and 0 713143 using na as an indicator of marine origin and al for the crustal input in rain samples the proportion of marine and crustal elements was estimated from elemental ratios a marine origin of 4 to 100 of cl of 0 6 to 20 of the so4 of 1 to 10 of ca 1 to 40 of k 4 to 100 of mg and 1 to 44 of sr was determined strontium isotopes were used to characterize the crustal sources the 87sr 86sr ratios of the crustal sources varied considerably from 0 7092 to 0 71625 and indicate the occurrence of multiple sources for the crustal component in the analysed rainwaters

the annual cycle in equatorial convection and sea surface temperature abstract the coupled atmosphere ocean system in the equatorial eastern pacific and atlantic exhibits a distinct annual cycle that is reflected in contrasting conditions at the times of the two equinoxes the contrasts are so strong that they dominate the annual march of zonally averaged outgoing longwave radiation for the equatorial belt the march equinox corresponds to the warm season when the equatorial cold tongues in the eastern pacific and atlantic are absent with the onset of summer monsoon convection over colombia central america and west africa in may june northward surface winds strengthen over the eastern pacific and atlantic the equatorial cold tongues reappear and the marine convection shifts from the equatorial belt to the intertropical convergence zones itczs along 8 n as the northern summer program the itczs remain strong and shift northward to new 10 n while sea surface temperature sst continues to drop over the cold tongues and the southern tropics perhaps in response to the

resonant forcing of mixed layer inertial motions by atmospheric easterly waves in the northeast tropical pacific abstract westward propagating atmospheric easterly waves contribute to much of the variability of the low level wind fields within the northeast tropical pacific with the dominant period of these waves 3 5 days close to the local inertial period 2 4 days at 12 n to 5 7 days at 5 n there is the expectation that the associated winds may resonantly force mixed layer inertial motions in this region the authors test this hypothesis using a simple slab model and roughly 4 yr of wind data from four noaa tropical atmosphere ocean eastern pacific investigation of climate processes tao epic buoys along 95 w at 12 10 8 and 5 n the degree of resonance is determined by comparing model simulations using observed wind stress with simulations forced with reversed rotation wind stress results strongly indicate that pacific easterly waves pews resonantly force inertial motions in the region this resonance shows both significant seasonality and latitudinal dependence that appears to be related to the me

tracking and mean structure of easterly waves over the intra americas sea abstract easterly waves ews are prominent features of the intertropical convergence zone itcz found in both the atlantic and pacific during the northern hemisphere summer and fall where they commonly serve as precursors to hurricanes over both basins a large proportion of atlantic ews are known to form over africa but the origin of ews over the caribbean and east pacific in particular has not been established in detail in this study reanalyses are used to examine the coherence of the large scale wave signatures and to obtain track statistics and energy conversion terms for ews across this region regression analysis demonstrates that some ew kinematic structures readily propagate between the atlantic and east pacific with the highest correlations observed across costa rica and panama track statistics are consistent with this analysis and suggest that some individual waves are maintained as they pass from the atlantic into the east pacific whereas others are generated locally in the caribbean a

chemistry of marine aerosol over the tropical and equatorial pacific aerosols from the marine boundary layer were collected during a cruise from the peru ecuador shelf through the equatorial and tropical pacific to the hawaiian islands a variety of samplers of different design and independent analytical techniques were used to validate the results obtained on large particles little or no chloride deficiency relative to seawater composition was observed while on submicrometer particles as much as 40 of chloride had been lost a silicate component with a composition similar to the crustal average was associated with sea salt particles as an internal mixture along the peru coast substantial concentrations of cu zn as and pb were found which must be related to large emissions from the metallurgical industry in that region high levels of selenium in the remote equatorial region suggest a biological source of volatile selenium in this area of high productivity the concentrations of excess sulfate were found to be consistent with the flux of dimethylsulfide determined on the same cruise the presence of soot carbon particulate organic carbon and fine excess potassium showed evidence of long range transport of combustion derived aerosols to this remote region enhanced soot and crustal elements in the intertropical convergence zone suggest downward mixing of materials transported in the upper troposphere in this region of active vertical exchange

case studies of developing east pacific easterly waves this paper contains a study of developing east pacific easterly waves observed during the summer of 1991 with aircraft in situ and radar data and geosynchronous infrared satellite imagery the circulation and divergence profiles surface momentum and entropy fluxes as well as 700 mb and 975 mb saturated and actual equivalent potential temperatures were measured repeatedly for three disturbances that evolved into east pacific hurricanes as the disturbances develop the level of maximum updraught mass flux decreases which leads to increased convergence at low levels this process appears to be coupled to an increase in the mid level relative humidity which in turn suppresses the development of convective downdraughts comparison of the respective tendencies of convergence and surface friction to spin up and spin down a developing disturbance suggests that friction is unimportant in the early stages of development however as the surface circulation develops the two effects become comparable in magnitude if surface friction is deposited through a fairly deep layer of the troposphere the observations appear to rule out boundary layer ekman balance in these developing systems though more accurate observations of the eddy fluxes of absolute vorticity into such systems are needed to answer this question with certainty

synoptic scale disturbances near the equator abstract a spectral analysis of winds analyzed and initialized at the european centre for medium range weather forecasts reveals an abundance of power in the 850 mb meridional wind along the equator with periods near four days the power is mostly in the westward propagating component using high pass filtered data it is shown that the waves have westward phase and eastward group propagation relative to the mean wind the longest wavelengths are found over the pacific ocean while the shortest are found over the convectively variable regions of indonesia south america and africa mean phase speeds at 850 mb are positively correlated with the mean wind on the equator at 500 mb and below and negatively correlated with the mean wind above that level the effective advecting zonal wind of the disturbances seems to be the density weighted average of the lower troposphere the structure of the disturbances bears resemblance to the expected structure of an equatorially trapped mixed rossby gravity wave over t

horizontal and vertical structure of easterly waves in the pacific itcz abstract outgoing longwave radiation olr and low level wind fields in the atlantic and pacific intertropical convergence zone itcz are dominated by variability on synoptic time scales primarily associated with easterly waves during boreal summer and fall this study uses spectral filtering of observed olr data to capture the convective variability coupled to pacific easterly waves filtered olr is then used as an independent variable to isolate easterly wave structure in wind temperature and humidity fields from open ocean buoys radiosondes and gridded reanalysis products the analysis shows that while some pacific easterly waves originate in the atlantic most of the waves appear to form and strengthen within the pacific pacific easterly waves have wavelengths of 4200 5900 km westward phase speeds of 11 3 13 6 m s 1 and maximum meridional wind anomalies at about 600 hpa a warm moist boundary layer is observed ahead of the waves with moisture lofted quickly through the troposphere by deep co

dynamics of the shallow meridional circulation around intertropical convergence zones the generally accepted view of the meridional circulation in the tropical east pacific is that of a single deep overturning cell driven by deep convective heating in the intertropical convergence zone itcz similar to the zonal mean hadley circulation however recent observations of the atmosphere from the tropical eastern pacific have called this view into question in several independent datasets significant meridional return flows out of the itcz region were observed not only at high altitudes but also at low altitudes just above the atmospheric boundary layer this paper presents a theory and idealized simulations to understand the causes and dynamics of this shallow meridional circulation smc fundamentally the smc can be seen as a large scale sea breeze circulation driven by sea surface temperature gradients when deep convection is absent in the itcz region a simple model of this circulation is presented using observed values the sea breeze model shows that the pressure gradient above the boundary can indeed reverse leading to the pressure force that drives the shallow return flow out of the itcz the weather research and forecast model wrf is used to simulate an idealized hadley circulation driven by moist convection in a tropical channel the smc is reproduced with reasonable similarity to the circulation observed in the east pacific the simulations confirm that the smc is driven by a reversal of the pressure gradient above the boundary layer and that the return flow is strongest when deep convection is absent in the itcz and weakest when deep convection is active the model also shows that moisture transport out of the itcz region is far greater in the low level shallow return flow than in the high altitude return flow associated with the deep overturning and that a budget for water transport in and out of the itcz region is grossly incomplete without it much of the moisture carried in the shallow return flow is recycled into the boundary layer but does not appear to contribute to enhanced cloudiness in the subtropical stratocumulus poleward of the itcz

variations in precipitating convective feature populations with itcz width in the pacific ocean abstractmany recent studies have aimed to better understand changes in the characteristics of the intertropical convergence zone itcz including itcz location width and precipitation intensity

detecting subsurface groundwater flow in fractured rock using self potential sp methods in the wine district of clare valley in south australia the natural voltage sp signal generated by fluid flow in fractured rock during a pumping test was carefully monitored by time continuous measurements from ten electrode locations surrounding the pumping well the drawdown cone produced by pumping was determined on the basis of the sp measurements together with laboratory measurements of the grain boundary zeta potential such measurements allowed calculation of the fractured rock aquifer s transmissivity and average permeability results were confirmed by piezometer measurements to the extent that data were available the study has revealed that sp signals generated during pumping tests are of a complex nature however if the pumping test is sufficiently long to allow the signal to stabilise and careful field procedures are in place then sp measurements have the potential to add significant hydrogeological information sp measurements are relatively easy and cheap and are contrary to traditional methods not restricted to the locations of existing piezometers which is particularly useful in fractured rock aquifers

an observational study of easterly waves over the eastern pacific in the northern summer using fgge data abstract fgge revel iii b data provided by the european centre for medium range weather forecasts and the outgoing longwave radiation data measured by satellites are used to investigate observationally relationships between deep cloud activity and large scale meteorological fields during the northern hemisphere summer may september of 1979 over the eastern pacific aside from the summer monsoon area over southern and eastern asia the eastern pacific is the area where strong deep convection frequently develops in the northern summer this is also one of the tropical ocean areas that have been least explored meteorologically a power spectral analysis using the maximum entropy method is made for the meridional wind component at 850 mb at various grid points in the analysis domain for each mouth from may through september the waves with a period of 4 6 days are not only stronger in july and august than those of other months but active in the regions of 100 130 w in the eastern pacific and 130 160 e i

characterization of the atmospheric aerosol over the eastern equatorial pacific by using a polyester sailboat as sampling platform a series of duplicate aerosol samples was collected by cascade impactors on a trip from panama to tahiti in 1979 elemental analysis mainly by particle induced x ray emission pixe indicated in the samples collected between panama and the galapagos islands the presence of a substantial crustal component 0 4 g m3 fine cu 0 4 ng m3 and zn 0 6 ng m3 and excess fine s and k 100 and 2 4 ng m3 respectively in addition to the major sea salt elements the crustal component and fine cu and zn are suggested to result from natural continental sources i e eolian dust transport from the american continents and perhaps geothermal emissions samples collected west of the galapagos islands in the southern trades showed significantly lower concentrations for the nonseawater components the average si and fe levels were as low as 4 8 and 3 3 ng m3 corresponding to a maximum of 0 066 g m3 for an assumed mineral dust component whereas heavy metal concentrations were all below the detection limits typically ranging from 0 05 to 0 15 ng m3 for v cr mn ni cu zn and se excess fine s decreased to a mean of 46 ng m3 a level similar to those reported for other remote marine and continental locations this all indicates that the marine atmosphere west of the galapagos was little influenced by natural continental source processes or by anthropogenic emissions under these truly marine conditions several concentration ratios of the major seawater elements were significantly different from those in bulk seawater ca sr and s in 1 m diameter particles were enriched relative to k and na with the enrichment being substantially more pronounced up to 50 or higher for l 4 m diameter particles than for particles 4 m comparison of these data with a similar data set from samples collected over the atlantic indicates that the departures from seawater composition are significantly larger for the pacific differences in sea to air fractionation processes probably involving binding of divalent cations to organic matter in the oceanic surface microlayer are suggested as being responsible for these observations

the origin and dispersion characteristics of the observed tropical summertime synoptic scale waves over the western pacific abstract the origin initiation and dispersion behavior of the observed summertime synoptic scale disturbances in the tropical western pacific are studied these westward propagating disturbances have the strongest growth rate over the region of 130 160 e off the equator the three dimensional wave activity flux associated with a wave packet in the vicinity of this region is computed in general wave activity is directed westward there is accumulation of activity flux which gives rise to the amplification of waves in the low levels such accumulation can be attributed to the convergence of both the mean flow and the intrinsic group velocity diabatic forcing also contributes to the growth of disturbances and is most important in the 500 600 hpa layer along the east west oriented storm tracks of the synoptic scale disturbances there are two different dynamical regimes west of 150 e enhanced convection is associated with increased specific humidity at the top of the planetary boundary layer an

observations of a convectively coupled kelvin wave in the eastern pacific itcz abstract a case study of a convectively coupled kelvin wave in the eastern pacific intertropical convergence zone itcz is presented as observed during the 1997 pan american climate studies pacs tropical eastern pacific process study tepps the large scale convective envelope associated with this disturbance with a zonal scale of approximately 1000 2000 km propagates eastward at 15 m s 1 along the mean convective axis of the itcz this envelope consists of many smaller scale westward moving convective elements with zonal scales on the order of 100 500 km as the convectively coupled kelvin wave disturbance propagates eastward it exerts a strong control on local convection radar and vertical profiler data collected aboard the noaa r v ronald h brown during the wave passage show that convection deepens rapidly as the kelvin wave approaches from the west progressing from isolated shallow cumuli to organized deep convective features within just 12 h initially rainfall in the vicinity of the s

three dimensional structure and dynamics of african easterly waves part i observations the mean structure of african easterly waves aews over west africa and the adjacent atlantic is isolated by projecting dynamical fields from reanalysis and radiosonde data onto space time filtered satellite derived outgoing longwave radiation these results are compared with previous studies and an idealized modeling study in a companion paper which provides evidence that the waves bear a close structural resemblance to the fastest growing linear normal mode of the summertime basic state flow over africa there is a significant evolution in the three dimensional structure of aews as they propagate along 10 n across west africa at this latitude convection occurs in northerly flow to the east of the greenwich meridian then shifts into the wave trough and finally into southerly flow as the waves propagate offshore into the atlantic itcz in contrast to the north of the african easterly jet along 15 n convection remains in southerly flow throughout the waves trajectory along 10 n over west africa the location of convection is consistent with the adiabatic dynamical forcing implied by the advection of perturbation vorticity by the mean thermal wind in the zonal direction as in the companion paper offshore and along 15 n the relationship between the convection and dynamics is more complex and not as easily explained in terms of dynamical forcing alone

on the distribution of copper nickel and cadmium in the surface waters of the north atlantic and north pacific ocean concentrations of copper nickel and cadmium have been determined for about 250 surface water samples nonupwelling open ocean concentrations of these metals are cu 0 5 1 4 nmol kg ni 1 2 nmol kg and cd less than 10 pmol kg in the equatorial pacific upwelling zone concentrations of ni 3 nmol kg and cd 80 pmol kg are higher than in the open ocean but cu 0 9 nmol kg is not significantly enriched metal concentrations are higher in cool nutrient rich eastern boundary currents cu 1 5 nmol kg ni 3 5 nmol kg and cd 30 50 pmol kg copper is distinctly higher in the coastal waters of the gulf of panama 3 4 nmol kg and also higher in the shelf waters north of the gulf stream 2 5 nmol kg these copper enrichments may be caused by copper remobilized from mildly reducing shelf sediments and maintained by a coastal nutrient trap in the open ocean events of high cu water 1 5 3 5 nmol kg are seen on scales up to 60 km presumably these are due to the advection of coastal water into the oceanic interior the lowest copper concentrations in the north pacific central gyre 0 5 nmol kg bruland 1980 are lower than in the sargasso sea 1 3 nmol kg while for nickel the lowest concentrations are 2 nmol kg in both the north pacific and the north atlantic nickel and cadmium while generally correlated with the nutrients in surface waters show distinct regional changes in their element nutrient correlations the residual concentrations of trace metals in the surface waters of the ocean can be explained if biological discrimination against trace metals relative to phosphorus increases as productivity decreases

variability in the southerly flow into the eastern pacific itcz abstract during boreal summer and fall there is a strong southerly boundary layer flow across the equator into the east pacific intertropical convergence zone itcz the modulation of this flow on synoptic to seasonal time scales is studied using an index of meridional pressure difference between the equator and the itcz along 95 w two complementary datasets from the east pacific investigation of climate epic are used to study eastern pacific variability daily measurements of sea level pressure slp from tropical atmosphere ocean toa array buoys from may to november 2001 provide temporal coverage and eight flights by a c 130 aircraft during september to october 2001 document the associated modulation of lower tropospheric vertical structure the principal mode of variability of the perturbation slp along 95 w from 1 s to 12 n derived by principal component analysis from either the eight flights pc1c 130 or from daily tao buoy observations pc1 explains 77 of the meridional pressure gradien

types and genesis of induced polarization anomalies in the water rich structures of the taian karst area from december 2010 to april 2011 agricultural production in north china and huang huai basin experienced difficulties because of severe drought based on samples from the development of deep karst groundwater resources a set of laws has been established to reflect the types and genesis of induced polarization ip anomalies in a range of water rich karst structures in taian area the curves of ip anomalies in the water rich structures can be classified into ramps slow downs low resistance platforms and low resistance v patterns ip anomalies observed in apparent resistivities contours can be classified as low resistance steps low resistance gradients and low resistance u patterns in water rich areas hosted mainly in caves ip anomalies include low apparent resistivity low visible polarization low half decay time low attenuation and low multi parameter synchroneity these water rich areas mainly consist of fault structures where the ip anomalies have a low apparent resistivity and low vision polarization and exhibit relatively long half decay time maximum attenuation value exceptions apparent resistivities and multi parameter reverse phase anomalies

observed structure of mesoscale convective systems and implications for large scale heating mesoscale convective cloud systems that produce large amounts of rain in mid latitudes and most of the rain in the tropics consist of a combination of convective and stratiform cloud the convective regions contain numerous deep cells that are often but not always arranged in lines the stratiform region is an outgrowth of the convective ensemble it lies adjacent to the convective region and is seeded by ice particles detrained from convective towers sometimes it lies to the rear of a propagating convective line while on other occasions it surrounds the convection the heating of the large scale environment by a mesoscale convective system is affected by both the convective and stratiform regions although processes such as melting and radiation are important the net heating by a system is dominated by condensation and evaporation associated with vertical air motions this paper reviews recent observational evidence regarding the mean vertical motion profiles in the convective and stratiform regions of mesoscale convective systems and the implications of these mean motions for the vertical distribution of heating of the large scale environment in both the convective and the stratiform regions vertical motions have been determined by various techniques including composites of rawinsonde and aircraft wind data single and dual doppler precipitation radar analyses and wind profiler observations in stratiform regions these data consistently show mean vertical velocity that is upward in the upper troposphere and downward in the lower troposphere the level separating upward from downward motion is located from 0 to 2 km above the 0 c level depending on location within the stratiform region diagnostic calculations show that these vertical motion profiles imply heating of the upper troposphere and cooling of lower levels by stratiform region processes data on vertical motions in the convective regions are less consistent from case to case these data sometimes indicate that the mean vertical velocity in convective regions is maximum in the lower troposphere in other cases the data indicate a maximum in the high troposphere diagnostic calculations show that heating profiles diagnosed from these two types of profile are quite different the first having a maximum of heating in the lower troposphere while the second has a maximum in the middle troposphere although it is difficult to determine whether or not the differences in estimates arise from different types of observations analysis methods or sampling strategies it seems likely that they stem from differences in the large scale environment of the different mesoscale systems the ubiquitous occurrence of stratiform regions in mesoscale convective systems and hurricanes together with their consistent heating profiles which systematically concentrate heating in upper levels while cooling lower levels are a major consideration in evaluating the interaction of mesoscale systems with the large scale environment however the consistency of the stratiform profiles from case to case indicates that the variability of net convective plus stratiform heating profiles from case to case lies primarily in the variation of the convective region profiles from one case to another it is suggested that future work should focus on the convective region vertical profiles of vertical motion and heating and on the large scale environmental factors that may control the variation of these profiles from case to case

atmospheric trace elements at enewetak atoll 2 transport to the ocean by wet and dry deposition the concentrations of trace elements in precipitation and dry deposition are presented for samples collected at enewetak atoll 11 n 162 e during searex experiments in 1979 the concentrations of al sc mn fe co and th in rain are dominated by crustal material and for these elements wet deposition evidently exceeds dry deposition for most of these elements the present rates of atmospheric deposition at enewetak are similar to their mean rate of accumulation in sediments over the past 5 10 000 years suggesting that the air to sea exchange of particles is closely tied to the sedimentary cycle of the mid pacific noncrustal sources govern the concentrations of pb zn cu se and cd in wet and dry deposition samples analyses of dry deposition collected from a flat plastic plate indicate that the amount of material recycled from the sea surface varies markedly between samples and even though these estimates do not necessarily reflect the dry deposition to the ocean surface the results suggest that recycled sea spray often amounts to more than 50 of the total dry deposition of the enriched elements recycled sea spray also makes up a significant fraction of the total wet deposition of the enriched elements the net deposition rates of elements such as cu and zn are greater than or equal to their inputs from vertical mixing but the net deposition of pb clearly exceeds the input from upwelling the current net deposition rates of the enriched elements are also similar to their rates of removal to sediments these results indicate that air sea exchange processes may significantly affect the chemistry of trace metals in the open ocean

mesoscale convective systems 1 mesoscale convective systems mcss have regions of both convective and stratiform precipitation and they develop mesoscale circulations as they mature the upward motion takes the form of a deep layer ascent drawn into the mcs in response to the latent heating and cooling in the convective region the ascending layer overturns as it rises but overall retains a coherent layer structure a middle level layer of inflow enters the stratiform region of the mcs from a direction determined by the large scale flow and descends in response to diabatic cooling at middle to low levels a middle level mesoscale convective vortex mcv develops in the stratiform region prolongs the mcs and may contribute to tropical cyclone development the propagation of an mcs may have a discrete component but may further be influenced by waves and disturbances generated both in response to the mcs and external to the mcs waves of a larger scale may affect the propagation velocity by phase locking with the mcs in a cooperative mode the horizontal scale of an mcs may be limited either by a balance between the formation rate of convective precipitation and dissipation of stratiform precipitation or by the rossby radius of the mcv the vertical redistribution of momentum by an mcs depends on the size of the stratiform region while the net vertical profile of heating of the large scale environment depends on the amount of stratiform rain regional variability of the stratiform rain from mcss affects the large scale circulation s response to mcs heating

trace element concentrations elemental ratios and enrichment factors observed in aerosol samples collected during the us geotraces eastern pacific ocean transect gp16 abstract atmospheric deposition is an important source of bioactive trace elements to the open ocean but observations of this flux are sparse atmospheric deposition of aerosol iron is of particular interest as it can play an important role in supporting primary production in the global ocean yet it represents a key uncertainty that hampers accurate numerical modeling of the marine iron cycle we report concentrations of atmospheric trace elements from samples collected as part of the 2013 us geotraces gp16 zonal transect of the eastern pacific ocean the cruise transected a relatively dusty region which coincided with the peruvian upwelling zone before entering the much less dusty region of the subtropical gyre the aerosol chemical composition and elemental ratios indicate crustal sources for al ti v mn and fe while the analyses suggest that cu cd and pb originate from anthropogenic emissions dry deposition fluxes were calculated by applying characteristic deposition velocities based on the expected particle size associated with each element bulk deposition which includes wet and dry deposition was calculated using the inventory of 7be in the upper water column soluble aerosol iron flux estimates were compared with vertical iron fluxes within the water column to assess the relative importance of atmospheric deposition to the marine iron cycle in the region atmospheric deposition was insignificant relative to the upwelling input of iron in the areas near the continental sources but increased in relative importance seaward of the coastal upwelling zone even as the magnitude of deposition decreased away from the coast this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

anomalous spontaneous electrical potential characteristics of epi karst in the longrui depression southern guangxi province china this paper examines the use of the temporal and spatial distribution of natural electric fields in karst depressions to detect shallow groundwater resources under specific osmotic pressures vadose water is filtered through the soil layer and supplies deep karst water through pipes or underground rivers along the carbonate dissolution fracture network as a result a natural electric field is generated by ions at the interface between conductive soil and rock layers detecting this natural electric field can be used as a research method for shallow karst water exploration this method has been applied to a karst depression in longrui china and the results show that an anomalous zone with electric potential values of 60 mv to 80 mv occurs in the center of the depression the anomalous zone has an s shaped north to south distribution with a width of about 40 m changes in the plane of the anomalous zone indicate differences in shallow karst development in depressions and hydrogeological drilling reveals shallow caves sags and fault zones that correspond with the natural potential anomalies at different depths in the longrui depression additionally advancement of boreholes reveals a water yield of 60 m3 h this highlights the effectiveness of using the natural electric field method to detect karst water in epi karst areas

observation of 3 6 day meridional wind oscillations over the tropical pacific 1973 1992 horizontal structure and propagation abstract twenty years of rawinsonde data 1973 1992 were examined in conjunction with european centre for medium range weather forecasts ecmwf analyses and outgoing longwave radiation olr in 1980 1989 to determine the horizontal structure propagation and convective coupling of 3 6 day meridional wind oscillations over the tropical pacific wave properties from ecmwf data determined by lag correlation with respect to rawinsonde or ecmwf principal components were consistent with what could be determined from the sparse rawinsonde network alone gridded analyses allowed a clearer distinction between equatorially trapped rossby gravity waves rgw and off equatorial tropical depression td disturbances so that the contrasting properties of these waves including their seasonal and interannual variation could be studied in better detail significant correlations with olr were found increasing in magnitude from eastern to western pacific the apparent group propagation of disturbances was equator

the influence of amazon rainfall on the atlantic itcz through convectively coupled kelvin waves abstract using outgoing longwave radiation olr and tropical rainfall measuring mission trmm daily rain rate data systematic changes in intensity and location of the atlantic intertropical convergence zone itcz were detected along the equator during boreal spring it is found that the changes in convection over the tropical atlantic may be induced by deep convection in equatorial south america lagged regression analyses demonstrate that the anomalies of convection developed over the land propagate eastward across the atlantic and then into africa the eastward propagating disturbances appear to be convectively coupled kelvin waves with a period of 6 7 5 days and a phase speed of around 15 m s 1 these waves modulate the intensity and location of the convection in the tropical atlantic and result in a zonal variation of the atlantic itcz on synoptic time scales the convectively coupled kelvin wave has substantial signals in both the lower and upper troposphere both a reanalysis dataset and the qui

characteristics of tropical convection over the ocean near kwajalein radar observations have been analyzed to determine characteristics of convection over the oceanic region around kwajalein in the tropical western pacific generally the echo areas heights and durations exhibited lognormal distributions heights were greater under conditions of higher midtropospheric humidity and correlated with echo area with a wide spread of values mergers and splits often truncated echo lifetimes the most surprising result was the distribution of orientation angles of echo lines which statistically verify the shear parallel and shear normal modes of convective line organization seen elsewhere over tropical oceans the two modes typically coexisted within the area of radar coverage indicating a potential difficulty in predicting line orientation in terms of large scale variables the largest members of the echo population were mesoscale convective systems mcss which had large stratiform components they occurred in environments of increased humidity and higher midlevel buoyancy associated with westward propagating synoptic scale disturbances mcss moved with the easterlies in low to midlevels and exhibited the jump updraft overturning updraft and subsiding midlevel inflow characteristic of tropical oceanic mcss the kwajalein experiment kwajex radar echo population resembles that of the eastern tropical atlantic in terms of the shapes of the distributions of area height and lifetime the prevalence of echo mergers and splits and the tendency to form shear parallel and shear normal lines these characteristics appear to be endemic to oceanic convective populations large scale conditions appear to modulate these basic population characteristics rather than qualitatively alter them

convection and easterly wave structures observed in the eastern pacific warm pool during epic 2001 abstract during september october 2001 the east pacific investigation of climate processes in the coupled ocean atmosphere system epic 2001 intertropical convergence zone itcz field campaign focused on studies of deep convection in the warm pool region of the eastern pacific this study combines c band doppler radar sounding and surface heat flux data collected aboard the r v ronald h brown during epic to describe the kinematic and thermodynamic states of the itcz environment together with tendencies in convective structure lightning rainfall and surface heat fluxes as a function of 3 5 day easterly wave phase three easterly waves were observed at the location of the r v brown during epic 2001 wind and thermodynamic data reveal that the wave trough axes exhibited positively correlated u and winds a slight westward phase tilt with height and relatively strong weak northeasterly tropospheric shear following the trough ridge axis temperature and humidity perturbations exhibited mid to

combined microgravity electrical resistivity tomography and induced polarization to detect deeply buried caves algaidilla cave southern spain abstract the suitability of the combined microgravity and electrical tomography to detect and characterize caves deeply buried in limestones is tested we have selected the buried algaidilla cave in the estepa range western betic cordillera which is partially submerged below the water table and which was intersected between 26 and 66 m in depth by two boreholes at that location microgravity electrical resistivity tomography ert and induced polarization ip data was collected along four profiles algaidilla cave is associated with a 0 5 mgal residual gravity anomaly minimum microgravity models reveal an approximately horizontal n s elongated shape with a maximum length of 150 m and a width of 40 m resistivity variations provide information on the cave sectors remaining above as well as below the water table forward modeling and depth of investigation doi support the suitability of ert to constrain the cave geometry the cave is identified as having an intermediate to low resistivity feature which approximately matches the 250 m contour line along its ceiling in addition induced polarization models show high chargeability anomalies probably associated with decalcification clays the location and approximately geometry of algaidilla cave estimated from geophysical modeling suggests that nearby overburden may develop cave ins and collapse sinkholes microgravity is proved as a powerful tool to detect caves at this depth but this method alone fails to estimate the geometry ert results delineate the cavity both above and below the water table although the deepest sectors of the models should be interpreted with caution since they are less constrained by the data below the water table the cavity shows great resistivity contrast with regard to the background carbonate in addition this study points out the usefulness of the ip method for detecting decalcification clays often present at the base of karstic caves

potential vorticity easterly waves and eastern pacific tropical cyclogenesis abstract a significant sign reversal in the meridional potential vorticity gradient was found during the summer of 1991 on the 310 k isentropic surface near 700 mb over the caribbean sea the charney stern necessary condition for instability of the mean flow is met in this region it is speculated that the sign reversal permits either invigoration of african waves or actual generation of easterly waves in the caribbean during the same season a correlation existed between the strength of the negative potential vorticity gradient in the caribbean and subsequent cyclogenesis in the eastern pacific the meridional pv gradient convective heating measured by outgoing longwave radiation data and eastern pacific cyclogenesis all varied on the timescale of the madden julian oscillation mjo it is hypothesized that upstream wave growth in the dynamically unstable region provides the connection between the mjo or any other convective forcing and the associated enhanced downstream tropical cyclogenesis

origins and mechanisms of eastern pacific tropical cyclogenesis a case study the genesis of hurricane hernan 1996 in the eastern pacific was investigated using gridded analyses from the european centre for medium range weather forecasts and gridded outgoing longwave radiation hernan developed in association with a wave in the easterlies that could be tracked back to africa in longitude time plots of the filtered y component of the wind 2 6 day period at 700 mb the wave crossed central america near lake nicaragua with little change in its southwest northeast tilt but the most intense convection shifted from near the wave axis in the caribbean to west of the wave axis in the pacific the wave intensified as it moved through a barotropically unstable background state defined by a low pass filter with a 20 day cutoff in the western caribbean and eastern pacific a surge in the southwesterly monsoons and enhanced convection along 108n occurred to the west of the 700 mb wave in the pacific and traveled with the wave this had the effect of enhancing low level vorticity over a wide region ahead of the 700 mb wave available evidence suggests that additional low level vorticity was produced by enhanced flow from the north through the isthmus of tehuantepec as the 700 mb wave approached depression formation did not occur until 6 12 h after the 700mb wave reached this region of large low level vorticity in the gulf of tehuantepec eastern pacific sst and vertical wind shear magnitude are typically favorable for tropical cyclone development in northern hemisphere summer and early fall because the favorable mountain interaction and the surge in the low level monsoons appear to relate directly to the wave in the easterlies it is argued that the strength of such waves reaching central america from the east is the single most important factor in whether subsequent eastern pacific cyclogenesis occurs possible parallels with western pacific cyclogenesis are discussed

barotropic aspects of itcz breakdown abstract in satellite images the itcz intertropical convergence zone is sometimes observed to undulate and break down into a series of tropical disturbances tropical cyclones may later develop within these disturbances and move into higher latitudes allowing the itcz to reform it has been proposed that itcz breakdown results from a convectively modified form of combined barotropic and baroclinic instability of the mean flow an unstable mean flow can be produced by itcz convection in just a couple of days in this sense the itcz produces favorable conditions for its own instability and breakdown in this study a nonlinear shallow water model on the sphere is used to simulate barotropic aspects of itcz breakdown in the shallow water model the itcz is simulated by a prescribed zonally elongated mass sink near the equator the mass sink produces a cyclonic potential vorticity pv anomaly that has a reversed meridional pv gradient on its poleward side according to the ripa theorem a flow that has a