small scale waves encountered during aase variability on scales of 200 km or less in the lower stratosphere is examined using potential temperature data collected during the aase campaign enhanced variability is found over regions containing topography presumably due to gravity waves the effect of gravity wave critical levels on topographically induced variability is examined a significant reduction in variability is found when a critical level is present

eof analysis and modeling of gps tec climatology over north america an empirical ionospheric model of the total electron content tec over north america 20 60 n 40 140 w is constructed using the gps tec data collected by massachusetts institute of technology mit haystack observatory during the years 2001 2012 this model is based on an analysis of quiet time monthly averages using the empirical orthogonal function eof decomposition technique allowing for separation of spatial and temporal variations the importance of different types of spatial temporal variations to the overall tec variability can be well represented by the characteristics of eof basis functions and associated principal components coefficients with various modes the mode one eof decomposition constitutes 97 5 of the total variance and therefore represents the essential feature of north america spatial and diurnal variation of the tec the mode two eof as reported in an earlier study reveals a large and significant symmetric longitudinal variation of the ionosphere organized with respect to magnetic declination the mode three eof decomposition shows midlatitude latitudinal structure that varies with season in a manner very similar to the so called winter anomaly because of the quick convergence of eof decomposition modes the first four eof modes are utilized for constructing a tec empirical model for each of the eof modes the temporal variations are expressed analytically in terms of local time season and solar activity and the spatial variations by cubic spline functions an analysis of accuracy and quality indicates that this regional empirical tec model can reflect the majority of the quiet time monthly means and represent characteristic temporal spatial variations in the north america

structure and dynamics of the benguela low level coastal jet generations of coupled atmosphere ocean general circulation models have been plagued by persistent warm sea surface temperature sst biases in the southeastern tropical atlantic the sst biases are most severe in the eastern boundary coastal upwelling region and are sensitive to surface wind stress and wind stress curl associated with the benguela low level coastal jet bllcj a southerly jet parallel to the angola namibia coast however little has been documented about this atmospheric source of oceanic bias here we investigate the characteristics and dynamics of the bllcj using observations reanalyses and atmospheric model simulations satellite wind products and high resolution reanalyses and models represent the bllcj with two near shore maxima one near the angola benguela front abf at 17 5 s and the other near 25 27 5 s whereas coarse resolution reanalyses and models represent the bllcj poorly with a single broad more offshore maximum model experiments indicate that convex coastal geometry near the abf supports the preferred location of the bllcj northern maximum by supporting conditions for a hydraulic expansion fan intraseasonal variability of the bllcj is associated with large scale variability in intensity and location of the south atlantic subtropical high through modulation of the low level zonal pressure gradient

local atmospheric forcing during the coastal ocean dynamics experiment 1 a description of the marine boundary layer and atmospheric conditions over a northern california upwelling region as part of the coastal ocean dynamics experiment code meteorological instruments were deployed on buoys and at coastal stations and instrumented aircraft flights and coastal soundings were made to study the three dimensional structure of the marine boundary layer over the continental shelf off northern california during the 1981 and 1982 upwelling seasons these measurements show that after the atmospheric spring transition the airflow in the marine layer is dominated by the north pacific high and the surface wind field over the shelf is characterized by periods of strong 7 15 m s upwelling favorable alongshelf winds lasting for up to 30 days interrupted by shorter periods of much weaker winds directed either equatorward or poleward these periods of weak or reversed winds typically last several days and are called wind relaxations even though they are primarily associated with coastally trapped perturbations of the marine layer along the central and northern california coast and not with a large scale weakening of the north pacific high the atmospheric boundary layer measurements made in code suggest a simple conceptual model which can explain much of the physiology or structure of the marine layer and associated surface wind field during periods of persistent upwelling favorable winds during these periods which represent the quasi steady state regime during the upwelling season the inversion base of the marine layer drops eastward toward the coast until it intersects the coastal mountain range at a height of several hundred meters and the associated thermal wind produces an alongshelf wind jet which has a maximum speed just below the inversion base turbulent mixing tends to homogenize any stratification in the marine layer beneath the jet and couple the jet to the ocean surface producing strong upwelling favorable winds over the shelf day night heating cooling over the narrow coastal strip beneath the marine layer generates a weak cross coast secondary circulation which causes the core of the alongshelf jet to drop in elevation and shift onshore this diurnal change in the marine layer structure explains both the daytime acceleration of the surface winds observed over and near the coast and its offshore decay and the associated offshore increase in the subdiurnal alongshelf wind thus the quasi steady component of the wind stress has a significant curl over the inner shelf during periods of active upwelling this mean summer atmospheric boundary layer regime is occasionally interrupted by synoptic and or mesoscale events or anomalous conditions analysis of the code observations suggests five types of events two primarily synoptic scale conditions which lead to stronger than normal upwelling favorable winds over the shelf and three primarily mesoscale events which lead to wind relaxation about half of the wind relaxation events observed in 1981 and 1982 are believed to be associated with either coastal trapped gravity currents or internal kelvin waves which propagate north ward in the marine layer along the central and northern california coastal mountain range

tropical atlantic biases in ccsm4 abstractthis paper focuses on diagnosing biases in the seasonal climate of the tropical atlantic in the twentieth century simulation of the community climate system model version 4 ccsm4 the biases appear in both atmospheric and oceanic components mean sea level pressure is erroneously high by a few millibars in the subtropical highs and erroneously low in the polar lows similar to ccsm3 as a result surface winds in the tropics are 1 m s 1 too strong excess winds cause excess cooling and depressed ssts north of the equator however south of the equator sst is erroneously high due to the presence of additional warming effects the region of highest sst bias is close to southern africa near the mean latitude of the angola benguela front abf comparison of ccsm4 to ocean simulations of various resolutions suggests that insufficient horizontal resolution leads to the insufficient northward transport of cool water along this coast and an erroneous southward stretching of the abf a similar proble

attribution and impacts of upper ocean biases in ccsm3 the largest and potentially most important ocean near surface biases are examined in the community climate system model coupled simulation of present day conditions they are attributed to problems in the component models of the ocean or atmosphere or both tropical biases in sea surface salinity sss are associated with precipitation errors with the most striking being a band of excess rainfall across the south pacific at about 8 s cooler than observed equatorial pacific sea surface temperature sst is necessary to control a potentially catastrophic positive feedback involving precipitation along the equator the strength of the wind driven gyres and interbasin exchange is in reasonable agreement with observations despite the generally too strong near surface winds however the winds drive far too much transport through drake passage 190 sv 1 sv 10 6 m 3 s 1 but with little effect on sst and sss problems with the width separation and location of western boundary currents and their extensions create large correlated sst and sss biases in midlatitudes ocean model deficiencies are suspected because similar signals are seen in uncoupled ocean solutions but there is no evidence of serious remote impacts the seasonal cycles of sst and winds in the equatorial pacific are not well represented and numerical experiments suggest that these problems are initiated by the coupling of either or both wind components the largest mean sst biases develop along the eastern boundaries of subtropical gyres and the overall coupled model response is found to be linear in the south atlantic surface currents advect these biases across much of the tropical basin significant precipitation responses are found both in the northwest indian ocean and locally where the net result is the loss of an identifiable atlantic intertropical convergence zone which can be regained by controlling the coastal temperatures and salinities biases off south america and baja california are shown to significantly degrade precipitation across the pacific subsurface ocean properties on both sides of the equator and the seasonal cycle of equatorial sst in the eastern pacific these signals extend beyond the reach of surface currents so connections via the atmosphere and subsurface ocean are implicated other experimental results indicate that the local atmospheric forcing is only part of the problem along eastern boundaries with the representation of ocean upwelling another likely contributor

diagnosis of the tropical atlantic near equatorial sst bias in a directly coupled atmosphere ocean general circulation model 1 the current generation of non flux corrected coupled atmosphere ocean general circulation models cgcms have trouble correctly simulating the sign of the annual mean near equatorial east to west gradient of sea surface temperature sst in the atlantic ocean this model pathology is of concern because the distribution of tropical oceanic precipitation is related to the near equatorial sst distribution the tropical oceanic precipitation in turn influences local and remote precipitation over the tropical land areas through various teleconnection mechanisms therefore understanding and eventually fixing this model error is of interest in this study the cause of the atlantic equatorial sst gradient error in one cgcm is investigated using forced experiments with the cgcm ocean component model these experiments show that the most likely candidate for this error is the too weak zonal wind stress along the equator in the coupled model this wind stress error affects the sst along the equator in two ways first it leads to a deepening of the thermocline in the eastern part of the basin and a shallowing in the western part second the weak zonal stress leads to a vertical velocity distribution at the based of the mixed layer that is too weak in the eastern and central atlantic and too strong in the western atlantic both of these errors lead to insufficient cooling of the eastern near equatorial mixed layer and erroneously enhanced cooling in the western near equatorial mixed layer

tide induced ground water flow in deep confined aquifer water elevation variation in rivers can be large due to tides even far away from the coastline for deep confined aquifers the possibility of leakage from rivers is small nevertheless the fluctuation of river elevation can induce a stress change in soil and in turn can induce ground water flow below the present study focuses on the effect of the fluctuation assuming the time scale for consolidation is much larger than that of the ground water the total stress change in the deep confined aquifer affects the water pressure head through deformable soil medium if the subsurface profile contains only one dominant confined aquifer a vertically averaged one dimensional problem with periodic total stress change and constant line pumping is examined the governing equation is a linear diffusion equation with time varying forcing terms laplace transform and fourier transform are invoked the response distribution in space is of the error function type the pumping effect can be superimposed due to linearity away from the loading deeper aquifers rather than those close to the ground surface are affected by the dynamic loading pressure peaks appear earlier for location farther away from the loading field data support the model

dewatering induced subsidence during excavation in a shanghai soft deposit foundation dewatering has become a major cause of land subsidence in shanghai the burial depth of foundations in relation to geotechnical construction works is less than 75 m and the corresponding groundwater includes phreatic low pressure artesian and the first confined aquifers based on the geological and hydrogeological conditions beneath shanghai methods of dewatering may be divided into three modes and further five patterns according to the insertion depth of the dewatering retaining system the most common dewatering mode aims to reduce the water pressure in the confined aquifer by setting the dewatering wells inside the pit whilst the retaining walls are buried in the confined aquifer and partially cut off the confined aquifer layer to predict the settlement due to foundation dewatering numerical models are generally adopted which are similar to those used to predict land subsidence induced by regional groundwater withdrawal however since foundation dewatering is conducted along with the setting of retaining walls and foundation pit excavation which differs from regional groundwater withdrawal interactions between the retaining wall dewatering well the dewatering excavation and dewatering recharge are important factors affecting the analytical model since the grading of the shallow soil layers is different stratified settlement characteristics of the shallow soil strata and seepage erosion which results in additional deformation need to be given particular consideration

three dimensional kinematic and microphysical evolution of florida cumulonimbus part i spatial distribution of updrafts downdrafts and precipitation abstract this paper is the first in a three part study that examines the kinematic and microphysical evolution of florida cumulonimbus and focuses on the convective to stratiform transition of the storm this first paper lays the groundwork for the subsequent papers by defining the problem under study delineating the setting for the storm and describing the spatial distribution of updrafts downdrafts and precipitation high resolution radar data of a typical line of storms associated with the florida sea breeze is the centerpiece of this study the high resolution data reveal details of the internal structure of the squall line that were beyond the resolution of previous squall line studies radar reflectivity filled in between cells at upper levels as the storm evolved reflectivity values were only weakly associated with updraft and downdraft magnitude the updrafts and downdrafts in the storm tended to be irregular in their three dimensional shape and less than 5 km in horizontal extent at any giv

on the origin of equatorial atlantic biases in coupled general circulation models many coupled ocean atmosphere general circulation models gcms suffer serious biases in the tropical atlantic including a southward shift of the intertropical convergence zone itcz in the annual mean a westerly bias in equatorial surface winds and a failure to reproduce the eastern equatorial cold tongue in boreal summer the present study examines an ensemble of coupled gcms and their uncoupled atmospheric component to identify common sources of error it is found that the westerly wind bias also exists in the atmospheric gcms forced with observed sea surface temperature but only in boreal spring during this time sea level pressure is anomalously high low in the western eastern equatorial atlantic which appears to be related to deficient excessive precipitation over tropical south america africa in coupled simulations this westerly bias leads to a deepening of the thermocline in the east which prevents the equatorial cold tongue from developing in boreal summer thus reducing atmospheric model errors during boreal spring may lead to improved coupled simulations of tropical atlantic climate

a case history of field pumping tests in a deep gravel formation in the taipei basin taiwan 33 large diameter wells embedded in 2 m thick 63 m deep diaphragm walls were constructed to reduce both the uplift pressures and the groundwater inflow during the excavations as the actual thickness of the pumped aquifer is unknown the installed wells are regarded as partial penetration wells single well and multi well pumping tests were conducted in the deep gravel formation of taipei basin to derive the hydraulic parameters and to investigate the drawdown characteristics at both the construction and remote sites however the tidal effect on the drawdown of both the pumping well and nearby observation wells was found significant additionally wellbore storage skin and leakage need to be taken into account for deriving the hydraulic parameters hence a method to remove these five factors influencing the drawdown curve is developed which takes advantage from the late time characteristics of drawdown data and the early time behavior of drawdown some currently available semi log graphic techniques are therefore proven applicable for parameter determination validity of the proposed method is verified by the good agreement between the calculated and the measured drawdown of both the pumping well and observation well

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

an investigation of gravity wave activity in the low latitude upper mesosphere propagation direction and wind filtering horizontal phase speeds of up to 80 m s 1 the large scale band wave patterns horizontal wavelength between 10 and 60 km exhibited a clear seasonal dependence on the horizontal propagation direction propagating toward the southeast during the summer months and toward the northwest during the winter the direction of propagation was observed to change abruptly around the equinox period in mid march and at the end of september using a numerical simulation of gravity wave propagation in a seasonally variable climatological wind field we have determined that the observed anisotropy in the wave propagation directions can be attributed to a strong filtering of the waves in the middle atmosphere by stratospheric winds index terms 0310 atmospheric composition and structure airglow and aurora 3332 meteorology and atmospheric dynamics mesospheric dynamics 3360 meteorology and atmospheric dynamics remote sensing keywords airglow winds gravity waves wind filtering imager

the low level jet off the west coast of subtropical south america structure and variability abstract the subtropical anticyclone over the southeast pacific drives low level southerly flow along the west coast of south america in turn the alongshore flow induces coastal upwelling that supports a wealth of fishery resources within this region satellite data marine reports and coastal observations indicate the existence of a southerly coastal jet i e a maximum of wind speed off central chile 26 36 s the mean features and variability of this southerly jet is documented in this work using 4 yr of satellite derived sea surface winds complemented by satellite derived cloud amount fields and atmospheric reanalysis furthermore analysis of in situ data and model results of a well defined jet event during october 2000 allows a preliminary description of the jet s three dimensional structure and a comparison with the northerly jet off the coast of california southerly jet events off central chile occur year round but they are more frequent during spring summer over 60 of the time the

respective roles of remote and local wind stress forcings in the development of warm sst errors in the south eastern tropical atlantic in a coupled high resolution model processes involved in the development of the warm sea surface temperature sst bias in the tropical south eastern atlantic seta in a high resolution hr version of the cnrm cm model are evaluated based on full field initialized seasonal hindcasts starting at 1 february of each year for 2000 2009 whereas the initial sst growth is likely associated with local atmospheric forcing its further development is due to remote oceanic processes a mixed layer heat budget analysis in seta indicates a spurious warm horizontal advection observed as far as south of 25 s that appears at the beginning of march it is associated with an erroneous oceanic mean state at the equator resulting from the mean equatorial westerly wind bias a sensitivity experiment with corrected wind stress over the equatorial region suggests that the remote forcing explains about 57 of the seta sst bias in march may comparison with a lower resolution lr version of the model reveals that in general similar processes are responsible for the sst bias in both models a strong reduction of the bias in the hr model is observed only over the near coastal southern benguela region due to a better representation of atmospheric and oceanic processes controlling the coastal upwelling overall the results of the inter comparison of the seta sst bias evolution in different sensitivity experiments performed in this study can be interpreted in terms of the relative contributions of erroneous warm horizontal advection associated with equatorial forcing and cold horizontal advection associated with local offshore ekman transport

land atmosphere ocean interactions in the southeastern atlantic interannual variability land atmosphere ocean interactions in the southeastern south atlantic and their connections to interannual variability are examined using a regional climate model coupled with an intermediate level ocean model in austral summer zonal displacements of the south atlantic subtropical high sash can induce variations of mixed layer currents in the benguela upwelling region through surface wind stress curl anomalies near the namibian coast and an eastward shifted sash is related to the first pacific south american mode when the sash is meridionally displaced mixed layer vertically integrated ekman transport anomalies are mainly a response to the change of alongshore surface wind stress the latitudinal shift of the sash tends to dampen the anomalous alongshore wind by modulating the land sea thermal contrast while opposed by oceanic diffusion although the position of the sash is closely linked to the phase of el nino southern oscillation enso and the southern annular mode sam in austral summer an overall relationship between benguela upwelling strength and enso or sam is absent during austral winter variations of the mixed layer ekman transport in the benguela upwelling region are connected to the strength of the sash through its impact on both coastal wind stress curl and alongshore surface wind stress compared with austral summer low level cloud cover change plays a more important role although wintertime sea surface temperature fluctuations in the equatorial atlantic are strong and may act to influence variability over the northern benguela area the surface heat budget analysis suggests that local air sea interactions dominate

identifying robust transport features of the upper tropical troposphere multimodel ensembles of back trajectories calculated from four different analysis data sets and two different trajectory formulations diabatic and kinematic are analyzed to investigate seasonal mean boundary layer to tropopause 100 hpa transport in the tropics transport paths are separated into two legs convective uplift boundary layer to detrainment and radiative ascent detrainment to tropopause the following three diagnostic measures are used source location source to tropopause transport time and the source influence i e the fraction of air with short transport times at 100 hpa ensemble means and standard deviations identify robust features i e common to all ensemble members while experimental hybrid calculations explain model to model discrepancies convective uplift is a major contributor to uncertainties in boundary layer to tropopause transport times and source locations spatial patterns of boundary layer influence at 100 hpa are nevertheless robust detrainment to tropopause transport times are robust despite substantial model to model variations of convective detrainment height because ascent rates are faster at low altitudes than at high altitudes detrainment to tropopause transport also has robust horizontal spatial patterns for both convective sources and convective influence particularly during boreal winter most model to model discrepancies occur at small spatial scales and are associated with differing distributions of convection the location of maximum convective influence associated with the asian summer monsoon is a notable exception this exceptionally large discrepancy is associated primarily with radiative ascent the fact that the observed maxima of important tropospheric constituents are collocated with the maximum convective influence for the diabatic calculations but not for the kinematic calculations suggests that diabatic trajectories could be more reliable in this region

organization of tropical convection in low vertical wind shears the role of water vapor abstract a modeling study is conducted to gain insight into the factors that control the intensity and organization of tropical convection and in particular to examine if organization occurs in the absence of factors such as vertical wind shear or underlying sea surface temperature sst gradient the control experiment integrates a cloud resolving model for 15 days using a 3d domain exceeding 1000 km in length with no imposed winds and horizontally uniform sst and forcing for convection after 2 days of random activity the convection organizes into clusters with dimensions of approximately 200 km convective systems propagate through the clusters at speeds of 2 3 m s 1 while the clusters themselves propagate at minimal speeds of around 0 5 m s 1 examining the thermodynamic structure of the model domain it is found that the convective free bands separating the clusters are very dry throughout the troposphere and due to virtual temperature effects are correspondingly warmer in the lower tropospher

one dimensional time dependent modeling of gate cumulonimbus convection abstract a one dimensional time dependent cumulonimbus model is designed that unlike in previous one dimensional models simulates cloud top heights vertical velocities and water contents that are reasonably consistent with those observed in real convective cores the model successfully simulates deep tropical oceanic cumulonimbus with results that are in agreement with aircraft observations of vertical velocity observations of radar reflectivity and three dimensional model simulations these results are achieved by improving the parameterizations of the following physical processes vertical mixing through the inclusion of an overturning thermal circulation near cloud top lateral entrainment by modifying the assumed shape of the cloud initiating convection with sustained boundary layer forcing that resembles the lifting by gust fronts associated with tropical oceanic cumulonimbus and making the pressure perturbation internally consistent with the horizontal distribution of vertical velocity in th

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

field tests of pumping recharge technology for deep confined aquifers and its application to a deep excavation abstract the execution of deep excavation above confined aquifers asks for dewatering measurements to reduce the hydrostatic pressure so that the safety of the deep excavation can be assured dewatering will inevitably cause deformations in the surrounding strata to reduce the dewatering induced strata movement an innovative pumping recharge technology has been developed in which the dewatering is carried out in the excavation and the recharge is conducted near the protected facilities however the capacity and efficiency of this technology in deep confined aquifers need to be further investigated this paper presents two in situ pumping recharge tests in a deep confined aquifer under a deep foundation pit the feasibility of artificial recharge in the deep confined aquifer has been verified by conducting a single well pumping and multi well recharge test with different discharge and injection rates then a multi well pumping recharge test was carried out in accordance with the requirement and circumstance of construction to evaluate the capacity and efficiency of recharge in controlling the drawdown and ground settlement the results showed that multi well recharge could form a water curtain which has a water proof function to reduce the groundwater drawdown meanwhile by controlling the groundwater head of the confined aquifer during the recharge the pumping induced settlement of the surrounding area can be reduced or even eliminated the pumping effect in the pit would be affected by the recharge around the protected facilities so it is necessary to take in situ pumping recharge tests to determine the layout of wells and the discharge and injection rate finally the artificial recharge was applied to the construction of a deep excavation in shanghai and the drawdown and the ground settlement around the protected buildings were effectively controlled by recharge

thermodynamic and circulation characteristics of winter monsoon tropical mesoscale convection abstract during the december 1978 field phase of the international winter monsoon experiment winter monex a regular diurnal cycle of deep convective activity occurred over the south china sea immediately to the north of borneo the convection was initiated during the late night hours by convergence of the low level northeast monsoon flow with the land breeze along borneo s north coast the precipitation feature that developed was characterized during its mature stage by a nearly continuous stratiform cloud referred to here as a mesoscale anvil of 100 500 km dimension extending from the mid troposphere 5 km to near the tropopause 17 km using rawinsonde data from the sounding network thermodynamic and circulation characteristics of the convection are documented mesoscale upward motion is found to within the anvils with a mcsomc downdraft below producing a warm dry region over a lame area just above the boundary layer air flow relative to the anvil on both its leading and trailing edges i

three dimensional kinematic and microphysical evolution of florida cumulonimbus part ii frequency distributions of vertical velocity reflectivity and differential reflectivity abstract high resolution radar data collected in florida during the convection and precipitation electrification experiment are used to elucidate the microphysical and kinematic processes occurring during the transition of a multicellular storm from convective to stratiform stages a statistical technique is employed to examine the evolving properties of the ensemble small scale variability of radar reflectivity vertical velocity and differential reflectivity over the entire storm differential radar reflectivity data indicate that the precipitation at upper levels was nearly glaciated early in the storm s lifetime dual doppler radar data show that throughout the storm s lifetime both updrafts and down drafts were present at all altitudes and that most of the volume of the radar echo contained vertical velocities incapable of supporting precipitation size particles thus the ensemble microphysical properties of the storm were increasingly dominated by particles falling in an environment of weak vertic

the marine atmospheric boundary layer jet in the coastal ocean dynamics experiment the vertical and horizontal structure of the atmospheric boundary layer near the northern california coast was investigated during spring upwelling conditions as part of the 1981 coastal ocean dynamics experiment two daytime aircraft flights were devised to measure mean and turbulent quantities for 25 km tracks along and across the continental shelf from 30 to 1200 m altitude the pacific high offshore and an inland thermal low characterized the synoptic situations and equatorward winds resulted which produced intense ocean upwelling the wind profile was found to be jet shaped maximum wind speeds were 25 m s 1 and 16 m s 1 at 400 and 100 m respectively in the two flights above and below the heights of the jet speed maxima the wind speed decreased rapidly sharp density inversions existed at the levels of the peak wind speeds in one flight the inversion also sloped down toward the coast turbulence was effectively confined below the inversions strong zonal temperature gradients above the inversion between the hot land and cool marine air caused a thermal wind for which the wind speed decreased with height below the inversion turbulent stress divergence was large and effective in transferring the horizontal momentum of the wind to the sea slowing the wind there was also a small thermal wind below the inversion but opposite to the one above owing to the well mixed air temperature following the sea surface temperature which was cold at the coast and relatively warmer offshore owing to the upwelling these effects explain the jet shaped wind profile the mean momentum equations show that an acceleration toward the coast can balance the pressure gradient coriolis and turbulent stress divergence forces and there were some observations to support this complete balance was not obtained for the turbulent kinetic energy budget inferred dissipation rates were too large

using partial penetrating wells and curtains to lower the water level of confined aquifer of gravel abstract to address the difficulties of penetrating and dewatering of a deep and thick confined aquifer of gravel a dewatering approach that considers the anisotropic hydraulic conductivity of aquifer co work of partial penetrating curtains and partial penetrating pumping wells was developed using the deep foundation pit of the southern ventilation shaft of metro line 1 in hangzhou china as an example a numerical simulation model based on finite difference method was established to invert the parameters and determine the co work of partial penetrating curtains and wells the anisotropic characteristic of the aquifer indicated that the three dimensional flow caused by partial penetrating wells produced bigger drawdown by co working with the partial penetrating wells the partial penetrating curtains changed the horizontal flow to a vertical one lengthened the flow path and consumed more energy to produce bigger drawdown three simulation schemes with different lengths depths of well screen and pumping rates were performed the results indicated that a short screen for the pumping well embedded by curtains resulted in the biggest drawdown with minimum pumping rate based on numerical simulations four pumping wells with 4 m long screens embedded by curtains were installed inside the excavation zone the water level declined to the required drawdown which indicated that the approach is feasible and can provide solutions to problems on similar projects

variability in satellite winds over the benguela upwelling system during 1999 2000 1 wind stress variability over the benguela upwelling system is considered using 16 months 01 august 1999 to 29 november 2000 of satellite derived quikscat wind data variability is investigated using a type of artificial neural network the self organizing map som and a wavelet analysis the som and wavelet analysis are applied to an extracted data set to find that the system may be divided into six discrete wind regimes the wavelet power spectra for these wind regions span a range of frequencies from 4 to 64 days with each region appearing to contain distinct periodicities to the north 10 23 5 s the majority of the power occurs during austral winter with a 4 16 day periodicity further investigation of national centers for environmental prediction reanalysis outgoing longwave radiation data indicates that the winter intensification of wind stress off the angolan coast is linked with convective activity over equatorial west africa the summer activity appears to be linked with the intensification of the angolan heat low convective activity over the congo basin appears to impact upon wind stress variability off the angolan coast throughout the year farther south 24 35 s the majority of the power occurs in the summer here a bimodal distribution occurs with peaks of 4 12 and 25 50 days the southernmost regions appear to be forced at higher frequencies by both midlatitude cyclones austral winter and mesoscale coastal lows austral summer at lower frequencies eastward propagating periodic wind events that originate over eastern south america appear to be important to the forcing of wind stress over the southern benguela

sensitivity of tropical atlantic climate to mixing in a coupled ocean atmosphere model the sensitivity of tropical atlantic climate to upper ocean mixing is investigated using an ocean only model and a coupled ocean atmosphere model the upper ocean thermal structure and associated atmospheric circulation prove to be strongly related to the strength of upper ocean mixing using the heat balance in the mixed layer it is shown that an excessively cold equatorial cold tongue can be attributed to entrainment flux at the base of the oceanic mixed layer that is too large enhanced entrainment efficiency acts to deepen the mixed layer and causes strong reduction in the upper ocean divergence in the central equatorial atlantic as a result the simulated sea surface temperature thermocline structure and upwelling velocities are close to the observed estimates in the coupled model the seasonal migration of the intertropical convergence zone itcz reduces when the entrainment efficiency in the oceanic mixed layer is enhanced the precipitation rates decrease in the equatorial region and increase along 10 n resulting in a more realistic atlantic marine itcz the reduced meridional surface temperature gradient in the eastern tropical atlantic prohibits the development of convective precipitation in the southeastern part of the tropical atlantic also the simulation of tropical atlantic variability as expressed in the meridional gradient mode and the eastern cold tongue mode improves when the entrainment efficiency is enhanced

high resolution mapping of tec perturbations with the gsi gps network over japan two dimensional total electron content tec perturbations over japan are mapped with the geographical survey institute gsi gps network geonet gps earth observation network its spatial resolution is 0 15 latitude 0 15 longitude and temporal resolution is 30 seconds two dimensional tec observations with these high resolutions revealed spatial structures and temporal evolutions of traveling ionospheric disturbances tids in the nighttime mid latitude ionosphere on july 03 1997 a preliminary result of the tec perturbation mapping indicates that it would be a strong tool to investigate the ionospheric structures in detail coordinated observations with other ionospheric observation techniques such as incoherent scatter is radars airglow imagers and ionosondes are needed to clarify the vertical structure of the ionosphere

gnss observations of ionospheric variations during the 21 august 2017 solar eclipse u s national science foundation grant nasa grant nasa lws funding support muri grant onr

underestimation of deep convective cloud tops by thermal imagery 1 the most common method of ascertaining cloud heights from space is from thermal brightness temperatures deep convective clouds of high water content are expected to radiate as black bodies here thermal cloud top estimates from goes 8 are compared with direct estimates of where the top should be sensed based on colocated goddard cloud physics lidar cpl observations collected during the cirrus regional study of tropical anvils and florida area cirrus experiment crystal face goes 8 cloud top heights are consistently 1 km lower than the visible cloud top estimates from the lidar even though the latter take into account the finite visible opacity of the clouds and any overlying thin cirrus layers and are often far below the position of highest detected cloud the low bias in thermal estimates appears to get worse for the tallest clouds perhaps by an additional kilometer and depends little on cloud albedo the consistency of the bias over multiple satellites suggests that cloud retrievals are affected by an unexpected radiative transfer issue

convective circulations induced by surface heterogeneities a simple theory for convective circulations induced by surface heterogeneities is proposed the theory is based on the thermodynamics of heat engines and provides a simple physical explanation for the general characteristics of circulations forced by surface inhomogeneities in sloping terrains in particular the theory is applied to a mesoscale circulation induced by deforestation it predicts that the intensity of the mesoscale convective circulation forced by deforestation depends on the difference of the near surface nonadiabatic temperature and humidity between the forest and cleared regions and on the depth of the convective boundary layer the theory was successfully tested against observations made during a field experiment in the amazon forest and a nearby clearing

response of the summer marine layer flow to an extreme california coastal bend abstract a summer wind speed maximum extending more than 200 km occurs over water around point conception california the most extreme bend along the u s west coast the following several causes were investigated for this wind speed maximum 1 synoptic conditions 2 marine layer hydraulic flow effects 3 diurnal variations 4 mountain leeside downslope flow 5 sea surface temperature structure and 6 island influence synoptic conditions set the general wind speed around point conception and these winds are classified as strong moderate or weak the strong wind condition extends about point conception reaching well offshore toward the southwest and the highest speeds are within 20 km to the south moderate wind cases do not extend as far offshore and they have a moderate maximum wind speed that occurs over a smaller area in the western mouth of the santa barbara channel the weak wind speed case consists of light and variable winds about point conception each category occurs about one third

thunderstorm cloud top dynamics as inferred from satellite observations and a cloud top parcel model abstract a lagrangian model applicable to the overshooting region of thunderstorm tops is used to describe the temperature height path taken by updraft core parcels as they penetrate above the tropopause reach their maximum height and descend in the periphery of the convective tower the model is run under a variety of ambient and in cloud conditions in order to simulate certain temperature height relationships observed in satellite observations observations indicate that in the majority of observed storm tops the satellite observed cold point in the ir brightness temperature tb field is collocated with the highest point in the convective overshooting region and the tb height relations are near adiabatic the parcel model quantitatively reproduces this type of relationship for model runs where the mixing parameter is relatively small another type of storm has a close in cold warm tb couplet with a dimension of approximately 20 40 km and a v shaped cold tb pattern in some cases of these v shaped st

characteristics of groundwater seepage with cut off wall in gravel aquifer i field observations1 this paper presents a case history of the leakage behavior during dewatering tests in the gravel strata of an excavation pit of a metro station in hangzhou china the groundwater system at the tes

mjo like coherent structures sensitivity simulations using the cloud resolving convection parameterization crcp abstract interaction between equatorially trapped disturbances and tropical convection is investigated using a nonhydrostatic global model that applies the cloud resolving convection parameterization crcp the crcp represents subgrid scales of the global model by embedding a 2d cloud resolving model in each column of the global model the modeling setup is a constant sst aquaplanet with the size and rotation of earth in radiative convective quasi equilibrium the global atmosphere is assumed to be initially at rest no large scale organization of convection is present outside the equatorial waveguide inside the waveguide on the other hand the model simulates spontaneous formation of coherent structures with deep convection on the leading edge and strong surface westerly winds to the west the westerly wind bursts these coherent structures resemble the madden julian oscillation mjo observed in the terrestrial tropics and are present in simulations applying prescribed and interactive radiation an

dynamics of the low level jet off the west coast of subtropical south america the subtropical west coast of south america is under the influence of the southeast pacific anticyclone year round which induces persistent southerly winds along the coast of north central chile these winds often take the form of a low level coastal jet in many aspects similar to the coastal jet existing off the california coast extensive diagnostics of mesoscale model results for a case in october 2000 are used here to describe the mean momentum budget supporting the coastal jet the jet appears to occur when midlatitude synoptic conditions induce a northerly directed pressure gradient force along the coast of northcentral chile the very steep coastal terrain precludes the development of a significant easterly low level wind that would geostrophically balance the pressure gradient instead the meridional flow accelerates until turbulent friction in the marine boundary layer balances the meridional pressure gradient the resulting force balance is semigeostrophic with geostrophy valid only in the zonal cross shore direction at higher levels the topographic inhibition of the easterlies relaxes and a small easterly flow ensues which turns out to be very important in the temperature and stability budgets of the layer capping the marine boundary layer

airglow observations of nighttime medium scale traveling ionospheric disturbances from yonaguni statistical characteristics and low latitude limit the characteristics of nighttime medium scale traveling ionospheric disturbance mstid features observed over yonaguni 24 5 n 123 0 e 19 3 n dip latitude japan are studied using all sky imaging of oi 630 0 nm airglow emission the uniqueness of these observations is that the area observed by the imager covers the transition region between low to middle latitudes in the ionosphere typical low latitude limit of midlatitude type nighttime mstids possessing phase front alignments along the northwest to the southeast occurs in this region these mstid features are rarely sighted at dip latitudes below 15 we selected 2 year period for analysis in which 1 year corresponded to the solar minimum conditions and another year to the solar maximum conditions the mstids were observed to extend to farther lower latitudes during the solar minimum conditions than during the solar maximum periods their observed range of wavelengths phase velocities phase front alignment and propagation directions are similar to those observed at typical midlatitude sites however on many occasions the phase fronts of the observed mstids did not extend over the whole field of view of the imager indicating that some process inhibits their extension to further lower latitudes detailed investigation suggests that the poleward propagating enhancement of airglow intensity probably associated with the midnight pressure bulge causes the mstid features to disappear when they reach lower latitudes later in the night when the mstids reach lower latitudes well before midnight they are found to be inhibited by the equatorial ionization anomaly crest region

sixteen year variation of horizontal phase velocity and propagation direction of mesospheric and thermospheric waves in airglow images at shigaraki japan we analyzed the horizontal phase velocity of gravity waves and medium scale traveling ionospheric disturbances mstids by using the three dimensional fast fourier transform method developed by matsuda et al 2014 for 557 7 nm altitude 90 100 km and 630 0 nm altitude 200 300 km airglow images obtained at shigaraki mu observatory 34 8 n 136 1 e dip angle 49 over 16 years from 16 march 1999 to 20 february 2015 the analysis of 557 7 nm airglow images shows clear seasonal variation of the propagation direction of gravity waves in the mesopause region in spring summer fall and winter the peak directions are northeastward northeastward northwestward and southwestward respectively the difference in east west propagation direction between summer and winter is probably caused by the wind filtering effect due to the zonal mesospheric jet comparison with tropospheric re analysis data shows the difference in north south propagation direction between summer and winter is caused by differences in the latitudinal location of wave sources due to convective activity in the troposphere relative to shigaraki the analysis of 630 0 nm airglow images shows that the propagation direction of mstids is mainly southwestward with a minor northeastward component throughout the 16 years a clear negative correlation is seen between the yearly power spectral density of mstids and f10 7 solar flux this negative correlation with solar activity may be explained by the linear growth rate of the perkins instability and secondary wave generation of gravity waves in the thermosphere

gps tec response to the 22 july 2009 total solar eclipse in east asia 1 the longest total solar eclipse of this century occurred in east and south asia on 22 july 2009 the eclipse was accompanied with a medium magnetic storm whose main phase onset occurred 27 min after the passage of the moon s umbral shadow using tec data from 60 gps stations we construct differential tec maps to investigate the ionosphere response to the solar eclipse in central china in the range of 26 n 36 n 108 e 118 e i e the magnetic latitude 15 n 25 n during the eclipse s totality a shadow in the ionosphere shown as tec depletion area was formed 100 km south of the moon s umbral path with a maximum decrease of 5 tecu the tec depletion area moved eastward following the movement of the totality area with a time lag of 10 min enhancements of tec due to the storm are observed after the main phase onset the relative drop of tec due to the solar eclipse is evidently larger at lower latitudes than that at higher ones and around noontime than that in the morning by modeling work we find that the latitudinal dependence of the tec response may result from latitudinal variation of magnetic inclination which influences the diffusion of ionization among different layers besides the local time dependence of tec response is closely related to the local time variation of background atmosphere density which affects the electron loss efficiency in the ionosphere

deep convective cloud top heights and their thermodynamic control during crystal face 1 infrared 11 m radiances from goes 8 and local radiosonde profiles collected during the cirrus regional study of tropical anvils and cirrus layers florida area cirrus experiment crystal face in july 2002 are used to assess the vertical distribution of florida area deep convective cloud top height and test predictions as to its variation based on parcel theory the highest infrared tops z11 reached approximately to the cold point at 15 4 km though these are uncertain by about 1 km due to unknown cloud environment temperature differences since lidar shows that visible tops are generally 1 km or more above z11 visible cloud tops frequently penetrated the lapse rate tropopause 15 km further since tropospheric ice concentrations were typically present up to 1 km above the visible tops lofting of moisture through the mean cold point was probably common morning clouds and those near key west rarely penetrated the tropopause as in previous studies nonentraining parcel theory fails to explain either of these results though it does show promise in explaining day to day variations over the peninsula moisture variations above the boundary layer account for much of the day to day z11 variability especially over the oceans in all locations a 20 increase in mean mixing ratio between 750 and 500 hpa was associated with about 1 km deeper maximum cloud penetration other things being equal this sensitivity is too large to explain by simple dilution of parcel buoyancy through mixing implying microphysical or dynamical feedbacks on cloud development the evident influence of midtropospheric humidity on the depth of the tropical troposphere suggests an interesting climate feedback possibility for stabilizing midtropospheric relative humidity

multievent analysis of oscillatory motion of medium scale traveling ionospheric disturbances observed by a 630 nm airglow imager over tromso

evidence of mesospheric gravity waves generated by orographic forcing in the troposphere 1 we report on the first imaging observations of stationary mesospheric gravity waves in the three nightglow emissions of oh 695 1050 nm na 589 3 nm and o 1s 557 7 nm the waves were observed in all sky images at the el leoncito observatory elo argentina 31 8 s 69 3 w during the period of 1 8 july 2008 over the course of each night the band like wave features exhibited a zero or near zero observed horizontal phase speed and had lifetimes of several hours these factors coupled with the winds measured locally and the orientation of the waves to the andes mountain range located nearby suggested that the waves were mountain waves generated by 70 ms 1 eastward winds flowing over the andes

medium scale gravity wave activity in the bottomside f region in tropical regions thermospheric gravity waves gws in the bottomside f region have been proposed to play a key role in the generation of equatorial plasma bubbles epbs however direct observations of such waves are scarce this study provides a systematic survey of medium scale 620 km neutral atmosphere perturbations at this critical altitude in the tropics using 4 years of in situ gravity field and steady state ocean circulation explorer satellite measurements of thermospheric density and zonal wind the analysis reveals pronounced features on their global distribution and seasonal variability 1 a prominent three peak longitudinal structure exists in all seasons with stronger perturbations over continents than over oceans 2 their seasonal variation consists of a primary semiannual oscillations sao and a secondary annual oscillation ao the sao component maximizes around solstices and minimizes around equinoxes while the ao component maximizes around june solstice these gw features resemble those of epbs in spatial distribution but show opposite trend in climatological variations this may imply that stronger medium scale gw activity does not always lead to more epbs possible origins of the bottomside gws are discussed among which tropical deep convection appears to be most plausible

applicability of method to estimate transmissivity based on yield drawdown analysis in mountainous fractured rock aquifers a case study in taiwan abstract the observation of yield drawdown response in the course of pumping test as well as its derived application for aquifer characterization is an essential practice in a geotechnical investigation on the basis of that for providing a reasonable estimate of aquifer transmissivity on site a number of empirical models have therefore been proposed yet the majority of previous studies are conducted based on investigations at homogeneous alluvial plain very few particularly in the case of taiwan are carried out focusing on mountainous fractured rock aquifers aiming to address this problem the observation data of 53 pumping tests obtained from a multi years in situ geological investigation program are analyzed and the applicability of empirical log log linear relationship between t and q s is examined our analysis reveals that the yield drawdown responses derived from different geologic formations are quantitatively distinct and those empirical rules derived from the alluvial landform should be used with care when applying in mountainous fractured rock aquifers based on the analysis of statistical results in our study with a systematic investigation and clarification of the q s relationship in advance a satisfactory and cost effective solution is obtained

causes of the large warm bias in the angola benguela frontal zone in the norwegian earth system model we have investigated the causes of the sea surface temperature sst bias in the angola benguela frontal zone abfz of the southeastern atlantic ocean simulated by the norwegian earth system model noresm similar to other coupled models noresm has a warm sst bias in the abfz of up to 8 c in the annual mean our analysis of noresm reveals that a cyclonic surface wind bias over the abfz drives a locally excessively strong southward 0 05 m s relative to observation angola current displacing the abfz southward a series of uncoupled stand alone atmosphere and ocean model simulations are performed to investigate the cause of the coupled model bias the stand alone atmosphere model driven with observed sst exhibits a similar cyclonic surface circulation bias while the stand alone ocean model forced with the reanalysis data produces a warm sst in the abfz with a magnitude approximately half of that in the coupled noresm simulation an additional uncoupled sensitivity experiment shows that the atmospheric model s local negative surface wind curl generates anomalously strong angola current at the ocean surface consequently this contributes to the warm sst bias in the abfz by 2 c compared to the reanalysis forced simulation there is no evidence that local air sea feedbacks among wind stress curl sst and sea level pressure slp affect the abfz sst bias turbulent surface heat flux differences between coupled and uncoupled experiments explain the remaining 2 c warm sst bias in noresm ocean circulation upwelling and turbulent heat flux errors all modulate the intensity and the seasonality of the abfz errors

do the tallest convective cells over the tropical ocean have slow updrafts far from continents a few storms lift precipitation size ice particles into the stratosphere 17 to 18 km above the tropical ocean this study is the first to examine the observed properties of a large sample of these extremely tall convective storm cells the central questions in this study are whether the unusually tall ocean cells have the slow updrafts known to be typical of oceanic convection and if so how can these tall cells reach such extreme heights the precipitation radar on the tropical rainfall measuring mission trmm satellite observed 174 extremely tall oceanic cells from 1998 to 2007 relative updraft intensity is inferred from 17 km tall oceanic cells having on average a 7 km lower 40 dbz radar reflectivity height and an order of magnitude less lightning than do equally tall cells over the sahel region of africa a region known for vigorous convective updrafts despite some ambiguity the potential temperature and lapse rate of the ncep reanalysis suggest that the environment in which these oceanic cells form is conducive to modest updrafts reaching extreme heights extrapolating based on the limited coverage of the trmm satellite radar it is likely that such extremely tall cells occur more often than once each day somewhere over the tropical ocean

the benguela upwelling system quantifying the sensitivity to resolution and coastal wind representation in a global climate model abstractof all the major coastal upwelling systems in the world s oceans the benguela located off southwest africa is the one that climate models find hardest to simulate well this paper investigates the sensitivity of upwelling processes and of sea surface temperature sst in this region to resolution of the climate model and to the offshore wind structure the community climate system model version 4 is used here together with the regional ocean modeling system the main result is that a realistic wind stress curl at the eastern boundary and a high resolution ocean model are required to well simulate the benguela upwelling system when the wind stress curl is too broad as with a 1 atmosphere model or coarser a sverdrup balance prevails at the eastern boundary implying southward ocean transport extending as far as 30 s and warm advection higher atmosphere resolution up to 0 5 does bring the atmospheric jet closer to the coast but there can be too strong a wind stress curl the most

atmospheric gravity waves observed in the nightglow following the 21 august 2017 total solar eclipse nighttime airglow images observed at the low latitude site of sao joao do cariri 7 4s 36 5w showed the presence of a medium scale atmospheric gravity wave agw associated with the

the marine layer off northern california an example of supercritical channel flow abstract during the spring and summer northerly winds driven by the north pacific high pressure system are prevalent over the northern california continental shelf only interrupted for periods of a few days when weak or southerly winds occur in the course of the coastal ocean dynamics experiment code fixed station and observations were made to describe the temporal and spatial structure of the lower atmosphere and their relation to the strong upwelling of coastal waters in a region extending up to 40 km offshore and 100 km along the coast these observations suggest that atmospheric conditions during the spring and summer usually fall into one of three categories the surface wind can be everywhere weak pattern 1 it can blow at large speeds in a uniform pattern pattern 2 or finally the structure of the northerly surface wind can be complex with large changes in the wind speed and corresponding changes in the surface pressure over short spatial scales pattern 3 the latter pattern which o

medium scale traveling ionospheric disturbances affecting gps measurements spatial and temporal analysis 1 in this work we present a simple technique to estimate the medium scale traveling ionospheric disturbances mstids characteristics such as occurrence velocity vertical propagation with periods lower than 20 min and its application to a set of gps data both temporally and spatially representative near one solar cycle and four local networks in the northern and southern hemispheres respectively some of the main results presented in this paper are the mstids which occur at daytime in local winter and nighttime in local summer related to the solar terminator and modulated by the solar cycle they present equatorward from 100 to 400 m s and westward 50 to 200 m s horizontal propagation velocities respectively the corresponding periods are compatible higher with the theoretical prediction which is given by the neutral atmosphere

generation of mesoscale gravity waves in upper tropospheric jet front systems abstract multiply nested mesoscale numerical simulations with horizontal resolution up to 3 3 km are performed to study the generation of mesoscale gravity waves during the life cycle of idealized baroclinic jet front systems long lived vertically propagating mesoscale gravity waves with horizontal wavelengths 100 200 km are simulated originating from the exit region of the upper tropospheric jet streak in a manner consistent with past observational studies the residual of the nonlinear balance equation is found to be a useful index in diagnosing flow imbalance and predicting wave generation the imbalance diagnosis and model simulations suggest that balance adjustment as a generalization of geostrophic adjustment is likely responsible for generating these mesoscale gravity waves it is hypothesized that through balance adjustment the continuous generation of flow imbalance from the developing baroclinic wave will lead to the continuous radiation of gravity waves

oceanic origin of southeast tropical atlantic biases most coupled general circulation models suffer from a prominent warm sea surface temperature bias in the southeast tropical atlantic ocean off the coast of africa the origin of the bias is not understood and remains highly controversial previous studies suggest that the origin of the bias stems from systematic errors of atmospheric models in simulating surface heat flux and coastal wind or poorly simulated coastal upwelling in this study we show using different reanalysis and observational data sets combined with a set of eddy resolving regional ocean model simulations that systematic errors in ocean models also make a significant contribution to the bias problem in particular 1 the strong warm bias at the angola benguela front that is maintained by the local wind and the convergence of angola and benguela currents is caused by an overshooting of the angola current in ocean models and 2 the alongshore warm bias to the south of the front is caused by ocean model deficiencies in simulating the sharp thermocline along the angola coast which is linked to biases in the equatorial thermocline and the complex circulation system within the benguela upwelling zone

rainfall morphology in florida convergence zones a numerical study abstract central florida is the ideal test laboratory for studying convergence zone induced convection the region regularly experiences sea breeze fronts and rainfall induced outflow boundaries the focus of this study is convection associated with the commonly occurring convergence zone established by the interaction of the sea breeze front and an outflow boundary previous studies have investigated mechanisms primarily affecting storm initiation by such convergence zones few have focused on rainfall morphology yet these storms contribute a significant amount of precipitation to the annual rainfall budget low level convergence and midtropospheric moisture have been shown to be correlated with rainfall amounts in florida using 2d and 3d numerical simulations the roles of low level convergence and midtropospheric moisture in rainfall evolution are examined the results indicate that area and time averaged vertical moisture flux vmf at the sea breeze front outflow convergence zone is directly and

spaced transmitter measurements of medium scale traveling ionospheric disturbances near the equator 1 the motion of medium scale traveling ionospheric disturbances mstids was measured for 1 year from the eastern tip of brazil about 10 degrees south of the magnetic and geographic equators using spaced fixed frequency radio transmitters the motion was very similar during all of the year the daytime average direction was towards 150 azimuth clockwise from north and speed was typically in the range 150 300 m s the azimuth varied only slightly during the day being slightly more easterly during evening morning hours during winter months there were also some tids whose motion was northward none of the known sources for mstids fits well with mstids having these velocity patterns a possible unconfirmed source is the inter tropical convergence zone itcz

vertical velocity in oceanic convection off tropical australia abstract time series of 1 hz vertical velocity data collected during aircraft penetrations of oceanic cumulonimbus clouds over the western pacific warm pool as part of the equatorial mesoscale experiment emex are analyzed for updraft and downdraft events called cores an updraft core is defined as occurring whenever the vertical velocity exceeds 1 m s 1 for at least 500 m a downdraft core is defined analogously over 19 000 km of straight and level flight legs are used in the analysis five hundred eleven updraft cores and 253 downdraft cores are included in the dataset core properties are summarized as distributions of average and maximum vertical velocity diameter and mass flux in four altitude intervals between 0 2 and 5 8 km distributions are approximately lognormal at all levels examination of the variation of the statistics with height suggests a maximum in vertical velocity between 2 and 3 km slightly lower or equal vertical velocity is indicated at 5 km near the freezing level virtual t

climatology of medium scale traveling ionospheric disturbances observed by a gps network in central china 1 the 15 month climatology of medium scale traveling ionospheric disturbances mstids during a solar minimum period has been constructed from observations of a dense gps receiver array in central china in total 793 mstid events are identified with peaks in occurrence at 1500 lt and 0100 lt the occurrence of mstids decreases following an increase in geomagnetic activity with 46 of the mstids occurring in the daytime daytime mstids are characterized by a major occurrence maximum around the winter solstice and by an equatorward propagation direction the period phase velocity azimuth and amplitude of daytime mstids are 20 60 min 100 400 m s 130 270 and 0 8 1 5 respectively the remaining 54 of the mstids occurred at night and were characterized by a peak in occurrence at the summer solstice and by a southwestward propagation direction the period phase velocity azimuth and amplitude of nighttime mstids are 20 70 min 50 230 m s 170 300 and 2 7 respectively the propagation directions and the seasonal behaviors support the view that daytime mstids are an ionospheric manifestation of atmospheric gravity waves from the lower atmosphere while a possible excitation mechanism of nighttime mstids is the electrodynamics process caused by plasma instability in the f layer

semi analytical solution to pumping test data with barrier wellbore storage and partial penetration effects abstract there exist some difficulties in determining aquifer parameters based on pumping test data within a partially penetrated retaining walls using traditional cooper jacob method many other site specific factors such as the effect of partially penetrating well and the large diameter of the wells cannot easily be accommodated in theoretical well formulae the semi log drawdown time curves affected by the effects of barrier wellbore storage and partial penetration well can be characterised by four distinct stages of drawdown i stage i drawdown is unaffected by the barrier ii stage ii drawdown is significantly influenced by the barrier iii stage iii the drawdown time curve runs parallel to that deduced from greenfield conditions and iv stage iv the drawdown becomes a constant value to handle the four distinct stages of drawdown a semi analytical method using the slope of the late time drawdown asymptote of stage iii for determining the transmissivity is proposed the horizontal intercept resulting from an extension of the late time drawdown asymptote from stage ii is used for determining the storage coefficient pumping test data from a case history are analysed using the proposed semi analytical method and the results obtained are compared with those deduced from the numerical simulation the comparison between the analytical results and those obtained from the numerical simulation appeared satisfactory

seasonal variability of the mauritania current and hydrography at 18 n extensive field campaigns in the mauritanian upwelling region between 2005 and 2016 provide the database for analyzing the seasonal variability of the eastern boundary circulation ebc and associated water mass distribution at 18 n the data set includes shipboard upper ocean current hydrographic and oxygen measurements from nine research cruises conducted during upwelling december to april and relaxation may to july seasons during the upwelling season the ebc closely resembles a classical eastern boundary current regime with a poleward undercurrent flowing beneath an equatorward coastal jet in contrast elevated poleward flow exceeding 30 cm s and extending from the surface down to 250 m depth is observed during the relaxation season the pronounced seasonal variability of the across shore structure of the ebc can be related to local wind forcing and is in general agreement with sverdrup balance the ebc transport is correlated to the wind stress curl leading the transport by 7 days the short lead time suggests a fast response of locally forced waves adjusting the ebc to wind forcing the seasonal and vertical water mass distribution is presented based on hydrographic observations the meridional oxygen distribution and corresponding water mass partitioning into south and north atlantic central water masses reveal a possible northerly ventilation pathway in the deeper layers of the central water stratum our results suggest that the poleward surface flow and the poleward undercurrent both are a consequence of the cyclonic wind stress curl forcing and thus propose to name it the mauritania current

a model study of the angola benguela frontal zone sensitivity to atmospheric forcing 1 a regional ocean model is applied to the tropical south east atlantic ocean in order to investigate the sensitivity of the intensity and position of the angola benguela frontal zone the results suggest that the position of the angola benguela frontal zone is mainly determined by opposing northward and southward flow within 2 degrees off the coast the windstress curl plays a major role in altering the position of the angola benguela frontal zone as it controls the southeastward flow of the south equatorial counter current the opposing northward flow is mainly the result of geostrophic adjustment to coastal upwelling driven by the meridional windstress the strength of the frontal zone is found to be related to the strength of the southerly windstress that controls the coastal upwelling

damping of large scale traveling ionospheric disturbances detected with gps networks during the geomagnetic storm 1 large scale traveling ionospheric disturbances lstids during the geomagnetic storm on 22 september 1999 were studied using total electron content tec data from the gps earth observation network geonet in japan international gps service igs and continuously operating reference stations cors in the united states the damping rates of the lstids were precisely derived in several local time sectors and were found to depend on values of the background tec this indicates that the dominant physical mechanism of the lstids damping is the ion drag effect by the background ionosphere the high resolution tec data from geonet revealed that two successive lstids were damped significantly as they traveled equatorward in the dawn sector the ratio of the perturbation component of tec to the background component i i0 decreased exponentially with the damping rate of 0 89 1000 km and 0 77 1000 km we studied also the amplitude of i i0 at high latitudes using igs data and found that the damping rates of lstids at high latitudes tended to be smaller than those at midlatitudes global tec observations during this geomagnetic storm by the igs and cors networks detected that several lstids propagated also equatorward in the afternoon sector and in the night sector the lstids in the afternoon sector were most damped with the damping rate of 1 04 1000 km which corresponds to the e folding length of 961 km the damping rate of lstids in the night sector was found to be small the lstids had a tendency to be damped rapidly in the regions where background tec was large this dependence of the damping rate on latitude and local time indicates that this intense damping of lstids was caused mainly by the ion drag effect that is proportional to the ion collision frequency the relation between the damping rates and the background tec derived from the observation are consistent with those estimated with a theoretical calculation of the gravity wave damping by the ion drag effect the worldwide distribution of gps receivers enabled us to estimate the longitudinal extent of these lstids the zonal width of lstids in the dawn sector was narrower than 45 in longitude 2 900 km around 55 n and wider than 20 in longitude 1 800 km around 40 n these widths were narrower than those reported in previous studies

supercritical marine layer flow along a smoothly varying coastline abstract a model for hydraulically supercritical atmospheric marine layer flow along a smoothly varying coastline is formulated and solved numerically the model is motivated by a recent comparison of code observations to a simple hydraulic theory which suggested the presence of an expansion fan and a compression jump downstream of topographic features the marine layer is modeled as a homogeneous rotating fluid layer decelerated by surface friction and forced by imposed upper level pressure gradients the equations are solved by a characteristic based gridpoint scheme the results indicate that the expansion fan is a robust feature that persists under most conditions in the present more realistic model but is dramatically altered in structure by the presence of friction while the jump may weaken rapidly offshore due mainly to offshore variations of the layer height upstream of the jump the agreement between observations and model predictions is good enough to suggest that a first order description of

convective influence on the heat balance of the tropical tropopause layer a cloud resolving model study the tropical tropopause layer ttl and in particular the cold point tropopause has been previously suggested as a feature decoupled from convection using a cloud resolving model the authors demonstrate that convection in fact has a cooling effect in the ttl that significantly affects its thermal structure in particular the cold point is found to be strongly tied to the convective cooling maximum the authors interpret these as natural features of an entrainment layer such as the ttl the recognition that the cold point tropopause is strongly tied to rather than decoupled from convection suggests that dehydration processes at the cold point cannot be assumed as gradual and the effect of convection may not be ignored

transient flow of water to a well in an unconfined aquifer applicability of some conceptual models currently available methods for interpreting data from unconfined aquifers are based on analytical solutions which restrict attention to flow in the saturated zone and account for drainage of water from the unsaturated zone through a source term the parameter specific yield sy is assumed to dictate the total quantity of water that is derivable through the desaturation process it is commonly assumed that flow in the unsaturated zone has little effect on flow in the saturated zone and therefore that all the drainable water is instantly delivered at the water table as it declines in response to pumping in a model proposed in 1954 boulton empirically assumed that the drainable water associated with sy is released gradually at the water table as an exponential function of time this concept of boulton is similar to the notion of first order kinetics frequently used to handle chemical transformations boulton s model is considered by some to have no physical basis numerical experiments performed on sand columns with reasonable properties suggest that vertical drainage of water at the water table due to a falling water table is a time dependent process which is mathematically more complex than a simple exponential relation although boulton did not provide a rational physical explanation his exponential assumption has some merit in that it implicitly provides for a time dependent drainage process which seems to occur in the unsaturated zone however the simple exponential approximation is not adequate to account for what is seemingly a complex process it appears that a physically comprehensive model of radial flow in an unconfined aquifer will combine time dependent drainage from above the water table with vertical components of flow in the saturated zone an additional assumption frequently made is that the well can be treated as a line source results from numerical experiments suggest that caution is in order before neglecting effects of well bore storage in interpreting data from tests on unconfined aquifers

long term study of medium scale traveling ionospheric disturbances using o i 630 nm all sky imaging and ionosonde over brazilian low latitudes 1 in this paper we report a long term study of medium scale traveling ionospheric disturbance mstid occurrence using all sky images of o i 630 nm airglow emission our study is based on a 10 5 year data series in which 5 5 years compound a new data set the images were obtained by an all sky imager installed at cachoeira paulista 22 7 s 45 w 15 s magnetic latitude our results show the greatest occurrence of mstids during solar minimum and a minor occurrence rate during descending and ascending solar activity periods during solar maximum we have not detected mstid signatures on all sky images all detected events have occurred during geomagnetically quiet conditions simultaneous measurements using both all sky images and ionograms obtained at the same site show the occurrence of spread f and a sharp rise in the ionospheric f layer at the same time as dark bands are optically registered over the zenith it is possible that for certain weaker events the ionosonde may resolve bands that are not sufficiently raised to cause darkening of the all sky images in order to investigate this possibility we have conducted a study using only ionograms for a 1 year period march 2000 february 2001 during solar maximum when we have not seen any mstid events in the all sky images as we conjectured mstids also occur during solar maximum and the risings of the ionospheric f layer are not able to disturb the airglow layer during such events

the vertical profile of radar reflectivity of convective cells a strong indicator of storm intensity and lightning probability abstract reflectivity data from doppler radars are used to construct vertical profiles of radar reflectivity vprr of convective cells in mesoscale convective systems mcss in three different environmental regimes the national center for atmospheric research cp 3 and cp 4 radars are used to calculate median vprr for mcss in the oklahoma kansas preliminary regional experiment for storm central in 1985 the national oceanic and atmospheric administration tropical ocean global atmosphere radar in darwin australia is used to calculate vprr for mcss observed both in oceanic monsoon regimes and in continental break period regimes during the wet seasons of 1987 88 and 1988 89 the midlatitude and tropical continental vprrs both exhibit maximum reflectivity somewhat above the surface and have a gradual decrease in reflectivity with height above the freezing level in sharp contrast the tropical oceanic profile has a maximum reflectivity at the lowest level and a very rapid decrease in reflectivity with he

medium scale traveling ionospheric disturbances detected with dense and wide tec maps over north america 1 nighttime and daytime medium scale traveling ionospheric disturbances mstids are detected with dense and wide detrended total electron content tec maps over north america using multiple gps receiver networks the tec maps cover a wide region of 60 130 w and 24 54 n 30 65 n in geomagnetic latitude and have a spatial resolution of 1 05 1 05 in latitude and longitude 0 15 0 15 with 7 7 pixel smoothing and a temporal resolution of 30 seconds the tec maps reveal for the first time that the nighttime mstids propagate southwestward with 200 500 km wavelengths over north america and have wavefronts longer than 2 000 km we also observe that daytime mstids with 300 1 000 km wavelengths propagate southeastward until mid afternoon and southwestward in the late afternoon in the mid to late afternoon these mstids propagating in the different directions are superimposed the tec maps can be a new powerful tool to investigate the mstids

ionospheric symmetry caused by geomagnetic declination over north america 1 we describe variations in total electron content tec in the north american sector exhibiting pronounced longitudinal progression and symmetry with respect to zero magnetic declination patterns were uncovered by applying an empirical orthogonal function eof decomposition procedure to a 12 year ground based american longitude sector gps tec data set the first eof mode describes overall average tec while the strong influence of geomagnetic declination on the midlatitude ionosphere is found in the second eof mode or the second most significant component we find a high degree of correlation between spatial variations in the second eof mode and vertical drifts driven by thermospheric zonal winds along with well organized temporal variation results strongly suggest a causative mechanism involving varying declination with longitude along with varying zonal wind climatology with local time season and solar cycle this study highlights the efficiency and key role played by the geomagnetic field effect in influencing mesoscale ionospheric structures over a broad midlatitude range

flow to a well of finite diameter in a homogeneous anisotropic water table aquifer a laplace transform solution is presented for the problem of flow to a partially penetrating well of finite diameter in a slightly compressible water table aquifer the solution which allows for evaluation of both pumped well and observation piezometer data accounts for effects of well bore storage and skin and allows for the noninstantaneous release of water from the unsaturated zone for instantaneous release of water from the unsaturated zone the solution approaches the line source solution derived by neuman as the diameter of the pumped well approaches zero delayed piezometer response which is significant during times of rapidly changing hydraulic head is included in the theoretical treatment and shown to be an important factor in accurate evaluation of specific storage by means of a hypothetical field example it is demonstrated that evaluations of specific storage ss using classical line source solutions may yield values of ss that are overestimated by a factor of 100 or more depending upon the location of the observation piezometers and whether effects of delayed piezometer response are included in the analysis theoretical responses obtained with the proposed model are used to suggest methods for evaluating specific storage