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

seismic models of a prograding carbonate platform vercors south east france abstract the southern vercors area south east france displays superb exposures of a lower cretaceous prograding carbonate platform these exposures allow a geometrical sequence analysis to be combined with detailed outcrop observations two dimensional seismic modelling techniques were used to determine the seismic response of three of these exposures the montagnette the archiane valley and the rocher de combau the outcrops display prograding and retreating series of clinoforms interfingering with fine grained basinal sediments photographs from different angles of view combined with detailed field observations were used to construct lithological profiles with a resolution of f few metres p wave velocities and bulk densities were measured from cored hand specimens and selected values were assigned to lithostratigraphic units in each profile the vertical incidence modelling technique was then used to compute migrated time sections of reflectivity these were convolved with source wavelets of different frequencies to produce the final synthetic seismic profiles none of the modelled outcrop geometries is correctly portrayed seismically at 25 50 hz frequencies not only do the synthetic seismic profiles show less detail they also show misleading geometries in most seismic models for instance pseudo unconformities are present that correspond to rapid changes in dip and in facies in outcrop furthermore the seismic tool is not able to resolve between stratal patterns punctuated by unconformities and those with gradual shifts in facies belts accompanied by complex interfingering relationships this implies that an unconformity recognized on a real seismic line should not automatically be assumed to represent a true stratal unconformity large outcrops are often used to show the validity of sequence stratigraphy a concept mainly based on the analysis of seismic lines this study however shows that there is no one to one relationship between geometries observed in outcrop and in seismic lines seismic modelling of outcrops therefore provides a means for evaluating outcrop geometries in terms of seismic stratigraphy

3 d characterization of a clastic reservoir analog from 3 d gpr data to a 3 d fluid permeability model a three dimensional 3 d 100 mhz ground penetrating radar gpr data volume is the basis of in situ characterization of a fluvial reservoir analog in the ferron sandstone of east central utah we use the gpr reflection times to image the bounding surfaces via 3 d velocity estimation and depth migration and we use the 3 d amplitude distribution to generate a geostatistical model of the dimensions orientations and geometries of the internal structures from the surface down to 12 m depth each sedimentological element is assigned a realistic fluid permeability distribution by kriging with the 3 d correlation structures derived from the gpr data and which are constrained by the permeabilities measured in cores and in plugs extracted from the adjacent cliff face the 3 d gpr image shows that gpr facies changes can be interpreted to locate sedimentological bounding surfaces even when the surfaces do not correspond to strong gpr reflections the site contains two main sedimentary regimes the upper 5 m co

giant carbonate mud mounds in the southern rockall trough seismic profiles sidescan sonar data bottom photography and sampling proved for the first time that there are giant carbonate mounds bioherms in the rockall trough the pelagia mounds on the northern porcupine bank are relatively isolated whereas most of the logachev mounds on the southeast rockall bank form a field of closely spaced contiguous mounds they are all found on the upper slope at depths between about 500 and 1200 m and as a result of this study about 500 have been mapped they have a variety of shapes and the larger ones are very steep sided up to 350 m high and 2 km wide at the base sediment samples show that the mounds consist of pale coloured muds mainly aragonite usually with live and or dead cold water corals at the seafloor and with buried dead corals coral thickets appear to be detected as a brush like signature on high resolution profiles and as a speckled pattern on high resolution sidescan sonar records shelly sands are found on the seabed between the mounds currents in the mound areas are strong enough to transport sands along slope as medium sized sand waves and to prevent pelagic deposition thus providing surfaces for initial coral settlement by the winnowing of fines to leave glacial dropstones and exposed rocks these observations show that the poleward directed upper slope current of the eastern north atlantic extends further south than hitherto known and that there is a southwesterly directed current on rockall bank there are waves on the logachev mounds with a wavelength of about 20 30 m that are thought to be moulded in carbonate muds by across slope directed internal tidal currents and or cascading currents mounds develop above erosional surfaces seen on seismic data the huge amount of carbonate mud seems to be produced by the rapid growth and breakdown of cold water corals living in a very favourable environment intermediate nepheloid layers formed upstream by the strong currents may provide the food source for the deep water suspension feeders conditions for giant mound growth require an ideal balance between current speed and sedimentation rate among other factors no evidence for the suggested link to methane seepage has been found so far

coupled dynamic thermodynamic forcings during tropical cyclogenesis part i diagnostic framework abstracta diagnostic framework to investigate the role of processes around and during tropical cyclogenesis is presented the key framework metric is the ratio of bulk differences of moist entropy over differences of angular momentum between an inner and outer region of a tropical disturbance or cyclone this ratio is hypothesized to decrease and become negative as both the high entropy core and low level vortex in the inner region amplify during tropical cyclogenesis the time tendency of this ratio can be split into two forcings a moist entropy forcing and an angular momentum forcing each forcing can be further divided into components comprising differences in net advective fluxes and nonadvective boundary fluxes of moist entropy or angular momentum between each region the framework provides a comprehensive way to compare the relative importance of processes leading to tropical cyclogenesis in a tractable consistent manner suggestions on how to apply the framework to numerical model output are given

the effect of vertical shear orientation on tropical cyclogenesis the effect of the relative orientation of the vertical wind shear to the surface wind on tropical cyclogenesis is explored in environments of radiative convective equilibrium rce through numerical simulation this study serves as a companion paper to an earlier study on the thermodynamics of genesis in rce it is found when the mean surface wind and shear are aligned a negative surface wind anomaly arises from the superposition of the mean and vortex surface flows left of the shear vector the resulting weak surface enthalpy fluxes and up shear quasi balanced subsidence leads to dry air being located cyclonically down wind of the down shear convective anomaly thus convection is inhibited from propagating cyclonically around the core leading to a large down shear vortex tilt conversely in a counter aligned orientation the negative surface wind anomaly and driest air is found right of the shear vector hence the driest air rotates into the down shear flank where it moistened by shear organized convection furthermore the boundary layer is relatively moist left of shear due to the positive surface wind anomaly therefore promoting the cyclonic propagation from down shear and constraining the magnitude of the vortex tilt genesis is intimately tied to the magnitude of the tilt and is found to occur once the mid level vortex has precessed into the up shear flank for smaller values of maximum tilt vortex precession is comparatively rapid aided by showerhead moistening provided by the up shear advection of frozen condensate aloft with the up shear flank pre moistened rapid precession of the mid level vortex at smaller radii leads to near saturation on the mesoscale and the onset of rapid intensification when the magnitude of the tilt is quite large precession is much slower and the showerhead effect is significantly reduced until just prior to the emergence of the mid level vortex in the up shear flank copyright 2011 royal meteorological society

evaluation of pinnacle reef distribution at shallow subsurface using integrated geophysical methods a case study from the upper kimmeridgian spain abstract the well exposed outcrops of the upper kimmeridgian shallow marine carbonates at jabaloyas iberian chain ne spain permit the evaluation of geophysical methods for the identification of sedimentary facies direct measurement of magnetic susceptibility in facies and detailed grids of magnetometry electromagnetic multifrequency and ground penetrating radar 50 500 mhz antennas have been performed in two study areas where the upper kimmeridgian rocks are nearly horizontal magnetometry indicates negative anomalies in residual magnetic field and vertical magnetic gradient related to reef pinnacles and faults electromagnetic data reveal that positive anomalies of apparent conductivity correlate with non reefal facies the areal distribution of magnetometry and em data does not permit the unequivocal identification of pinnacles and faults at the studied area by contrast ground penetrating radar profiles and maps of relative reflectivity in two way travel time slices are useful for the identification of faults hyperbolic anomalies and reefal and non reefal facies radar facies a and b respectively the integration of geophysical data mainly ground penetrating radar has permitted the 3d reconstruction of reef pinnacles and its tectonic framework

contourite drifts moats and channels in the upper cretaceous chalk of the danish basin during the late cretaceous high global sea level meant that most of the nw european craton was flooded by the deep epeiric chalk sea the classical paradigm for chalk deposition envisages a quiet rain of minute skeletal debris of coccolithophorid algae and other pelagic organisms deposited as horizontal flat lying pelagic oozes with local redeposition by slumps slides and debris flows along faults and other structural features seismic data from the danish basin and elsewhere necessitate a revision of this paradigm these demonstrate that the chalk sea floor had a considerable relief commonly of more than a hundred metres amplitude comprising moats drifts mounds and channels seismic sections from the kattegat sea illustrate the development in the maastrichtian of a deep moat adjacent to a topographic ridge formed over the inverted nw se trending sorgenfrei tornquist zone the moat was up to 120 m deeper than its sw flank which was formed by an internally complex elongate drift up to 20 km wide with an estimated length of ca 200 km smaller mound like features channels and clinoform beds are superimposed on the large scale relief the sea floor relief is interpreted to have formed in response to persistent bottom currents flowing parallel to bathymetric contours the initial build up of the broad gently convex up sheeted drift was controlled by relatively low velocity bottom currents the region of highest current velocity was gradually shifted ne wards towards the inversion zone ridge resulting in the formation of the deep moat flanked by the elongate drift the current is interpreted to have flowed from the se towards nw on the basis of the internal architecture of the elongate drift and the nw ward branching and decrease in moat relief the architecture and morphology of the moat drift and other features of the chalk sea floor are in all aspects similar to contourite systems of modern continental margins it is accordingly proposed that the fundamental physical oceanographic concept contour currents and their resulting contourite drifts is extended to include the deep epeiric seas which covered nw europe during the late cretaceous

revisiting the balanced and unbalanced aspects of tropical cyclone intensification abstractthe balanced and unbalanced aspects of tropical cyclone tc intensification are revisited with the balanced contribution diagnosed with the outputs from a full physics model simulation of a tc using the sawyer eliassen se equation the results show that the balanced dynamics can well capture the secondary circulation in the full physics model simulation even in the inner core region in the boundary layer the balanced dynamics can largely explain the intensification of the simulated tc the unbalanced dynamics mainly acts to prevent the boundary layer agradient flow in the inner core region from further intensification although surface friction can enhance the boundary layer inflow and make the inflow penetrate more inward into the eye region contributing to the eyewall contraction the net dynamical effect of surface friction on tc intensification is negative the sensitivity of the balanced solution to the procedure used to ensure the ellipticity condition for the se equation is also examine

enhanced marine productivity off western north america during warm climate intervals of the past 52 k y studies of the santa barbara basin off the coast of california have linked changes in its bottom water oxygen content to millennial scale climate changes as recorded by the oxygen isotope composition of greenland ice through the use of detailed records from a sediment core collected off the magdalena margin of baja california mexico we demonstrate that this teleconnection predominantly arose from changes in marine productivity rather than changes in ventilation of the north pacific as was originally proposed

westward propagating predecessors of monsoon depressions abstract by examining maps of 24 h change of sea level pressure during july and august over the 10 year period 1969 78 we find that 45 87 of the 52 lows and depressions that formed in the bay of bengal were associated with predecessor disturbances coming from the cast in 12 23 instances the predecessor was associated with a typhoon or named tropical storm in the south china sea while the remaining 33 64 were weaker systems originating over a broad region of land and sea from examination of time sections over the same period from eastern thailand to the burmese coast we identified 50 westward moving disturbances with consider able vertical extent of which 64 developed into lows or depressions on reaching the bay in 60 of the 50 instances the disturbance could be traced to the south china sea 32 being typhoons and named tropical storms and 28 weaker circulations the remaining 40 of the 50 disturbances appeared to originate over land for the three stations along the section line cr

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

momentum flux by lines of cumulonimbus over the tropical oceans abstract examination of aircraft and rawinsonde data gathered in nine tropical mesoscale convective line cases indicates that all but two lines systematically increased front to rear momentum at heights greater than about 4 km and rear to front momentum at lower levels where front is defined as the direction toward which the line is moving the convective lines were characterized by a leading 10 20 km wide band of convective clouds and a trailing region of stratiform cloudiness most wore propagating lines moving into the wind at all levels consistent with mixing length theory the vertical transport of the horizontal wind component parallel to the lines was down the vertical gradient of the component resulting in a decrease of its vertical shear smaller more random cloud groups and the upper portions of a convective line with isolated towers transported both components of horizontal momentum downgradient normalization of the vertical flux of horizontal momentum normal to the line u w su

the role of vortical hot towers in the formation of tropical cyclone diana 1984 abstract a high resolution 3 km horizontal grid spacing near cloud resolving numerical simulation of the formation of hurricane diana 1984 is used to examine the contribution of deep convective processes to tropical cyclone formation this study is focused on the 3 km horizontal grid spacing simulation because this simulation was previously found to furnish an accurate forecast of the later stages of the observed storm life cycle the numerical simulation reveals the presence of vortical hot towers or cores of deep cumulonimbus convection possessing strong vertical vorticity that arise from buoyancy induced stretching of local absolute vertical vorticity in a vorticity rich prehurricane environment at near cloud resolving scales these vortical hot towers are the preferred mode of convection they are demonstrated to be the most important influence to the formation of the tropical storm via a two stage evolutionary process i preconditioning of the local environment via diabatic production of mul

a comparison of observed and model derived structures of caribbean easterly waves abstract a linear primitive equation model has been used to test the hypothesis that the vertical structure of observed caribbean easterly waves is determined by the interaction between convective heating and the environmental wind the model determines the response to a propagating heat source in a specified basic state the model allows for the inclusion of diffusion and cumulus momentum transports the linear perturbations are assumed to have the form of a single fourier component in the zonal direction the frequency and zonal wavelength of the disturbance are taken from observations of the three dimensional structure of a series of caribbean easterly waves made by shapiro the structure of the basic state zonal wind assumed to be a function of height is based on observations near the latitude of largest observed wave amplitude the maximum heating rate is 5 k day 1 centered at about 19 n very good agreement is found between the model derived vertical structure of the waves and that observed by sh

tropical cyclone environments over the northeastern and northwestern pacific based on era 15 analyses abstract this study uses a 1 1 lat long dataset extracted from ecmwf reanalyses for the 15 yr period 1979 93 era 15 to composite environmental characteristics and flow features in the vicinity of named tropical cyclones tcs in the eastern and western north pacific ocean basins tropical cyclones are partitioned into one of four classifications as they pass by selected locations along the axes of maximum frequency and tc tracks weak w strong s intensifying i or dissipating d results of this study show that peak values of rising motion within the same classification are greater for tc composites in the western pacific than for those in the eastern pacific the level of maximum rising motion was at or above the 500 hpa level for all locations and classifications except for the ss at our northernmost point 25 n 130 e in the western pacific their maximum upward motion occurred at 700 hpa it is also found that the latter systems contrary to all other points were located in a reg

direct observations of atmospheric boundary layer response to sst variations associated with tropical instability waves over the eastern equatorial pacific tropical instability waves tiws with a typical wavelength of 1000 km and period of 30 days cause the equatorial front to meander and result in sst variations on the order of 18 28c vertical soundings of temperature humidity and wind velocity were obtained on board a japanese research vessel which sailed through three fully developed sst waves from 1408 to 1108w along 28n during 21 28 september 1999 a strong temperature inversion is observed throughout the cruise along 28n capping the planetary boundary layer pbl that is 1 1 5 km deep temperature response to tiw induced sst changes penetrates the whole depth of the pbl in response to an sst increase air temperature rises in the lowest kilometer and shows a strong cooling at the mean inversion height as a result this temperature dipole is associated with little tiw signal in the observed sea level pressure slp the cruise mean vertical profiles show a speed maximum at 400 500 m for both zonal and meridional velocities sst based composite profiles of zonal wind velocity show weakened intensified vertical shear within the pbl that is consistent with enhanced reduced vertical mixing causing surface wind to accelerate decelerate over warm cold ssts taken together the temperature and wind soundings indicate the dominance of the vertical mixing over the slp driving mechanism based on the authors measurements a physical interpretation of the widely used pbl model proposed by lindzen and nigam is presented

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

the vertical structure of mesoscale convective vortices abstract simulations of two cases of developing mesoscale convective vortices mcvs are examined to determine the dynamics governing the origin and vertical structure of these features although one case evolves in strong vertical wind shear and the other evolves in modest shear the evolutions are remarkably similar in addition to the well known mesoscale convergence that spins up vorticity in the midtroposphere the generation of vorticity in the lower troposphere occurs along the convergent outflow boundary of the parent mesoscale convective system mcs lateral transport of this vorticity from the convective region back beneath the midtropospheric vorticity center is important for obtaining a deep column of cyclonic vorticity however this behavior would be only transient without a secondary phase of vorticity growth in the lower troposphere that results from a radical change in the divergence profile favoring lower tropospheric convergence following the decay of the nocturnal mcs subsequent con

role of cumulus congestus in tropical cyclone formation in a high resolution numerical model simulation abstractthe role of cumulus congestus shallow and congestus convection in tropical cyclone tc formation is examined in a high resolution simulation of tropical cyclone fay 2008 it is found that cumulus congestus plays a dominant role in moistening the lower to middle troposphere and spinning up the near surface circulation prior to genesis while deep convection plays a key role in moistening the upper troposphere and intensifying the cyclonic circulation over a deep layer the transition from the tropical wave stage to the tc stage is marked by a substantial increase in net condensation and potential vorticity generation by deep convection in the inner wave pouch region this study suggests that tc formation can be regarded as a two stage process the first stage is a gradual process of moisture preconditioning and low level spinup in which cumulus congestus plays a dominant role the second stage commences with the rapid development of deep convection in the inner pouch region after the air colum

convective forcing in the intertropical convergence zone of the eastern pacific abstract one of the goals of the east pacific investigation of climate year 2001 process study epic2001 was to understand the mechanisms controlling the forcing of deep atmospheric convection over the tropical eastern pacific an intensive study was made of convection in a 4 4 square centered on 10 n 95 w in september and october of 2001 this is called the intertropical convergence zone itcz study region because it encompasses the eastern pacific intertropical convergence zone starting from an analysis of the theoretical possibilities and a plethora of dropsonde in situ radar and satellite data it is found that newly developing convection occurs where a deep layer of air of order 1 km deep or deeper is conditionally unstable with only weak convective inhibition shallower conditionally unstable layers are associated with numerous small clouds but do not seem to produce deep convection the occurrence of deep convection over the itcz study region is presumably related to the propensity

the three dimensional structure of synoptic scale disturbances over the tropical atlantic abstract twice daily analyses of low level and 200 mb winds over the tropical atlantic region archived by the national hurricane center are used to diagnose the structure of synoptic scale disturbances in the 3 5 day period band the large scale disturbances extracted by a complex empirical orthogonal function technique are found to have a preferred shift at 200 mb relative to the low level troughs of somewhat less than one quarter cycle the presentation concentrates on july 1975 during which a repeated series of strong disturbances propagated through the region the relationship between these disturbances and systems in the eastern pacific is discussed an analysis of the vorticity propagation characteristics for the disturbances during the month indicates a very different balance from level to level at the lower level advection by the mean wind plays a major rate at 200 mb the meridional advection of mean vorticity is more inportant rawinsonde data from several island stations are used to res

external influences on hurricane intensity part iii potential vorticity structure abstract the interaction of hurricane elena 1985 with a baroclinic wave was reexamined using both potential vorticity pv and a formulation for eliassen palm fluxes in cylindrical coordinates the hurricane began to deepen rapidly as a narrow upper level positive pv anomaly became nearly superposed over the low level center the intensification appeared to represent an evaporation wind feedback activated by constructive interference of the pv anomalies enhanced convection associated with this process eroded the upper pv anomaly and prevented it from crossing the hurricane and reversing the intensification the eliassen palm flux divergence showed that maximum eddy activity remained in the upper troposphere prior to the reintensification this activity was produced in part because the action of the outflow anticyclone of the hurricane contributed to synoptic scale wave breaking the upper level pv anomaly that approached the center was much narrower in extent than the original synoptic scale trough th

intensification of hurricane sandy 2012 through extratropical warm core seclusion abstracthurricane sandy s landfall along the new jersey shoreline at 2330 utc 29 october 2012 produced a catastrophic storm surge stretching from new jersey to rhode island that contributed to damage in excess of 50 billion the sixth costliest u s tropical cyclone on record since 1900 and directly caused 72 fatalities hurricane sandy s life cycle was marked by two upper level trough interactions while it moved northward over the western north atlantic on 26 29 october during the second trough interaction on 29 october sandy turned northwestward and intensified as cold continental air encircled the warm core vortex and sandy acquired characteristics of a warm seclusion the aim of this study is to determine the dynamical processes that contributed to sandy s secondary peak in intensity during its warm seclusion phase using high resolution numerical simulations the modeling results show that intensification occurred in response to shallow low level convergence below 850 hpa that was consistent with th

energetics of east pacific easterly waves during intraseasonal events abstractthe background atmospheric state of the east pacific warm pool in which easterly waves develop varies dramatically on intraseasonal time scales east pacific intraseasonal variability is well known to modulate local convective and circulation patterns westerly easterly intraseasonal phases are associated with westerly easterly low level wind and positive negative convective anomalies this study investigates the perturbation available potential energy pape and perturbation kinetic energy pke budgets of easterly waves composited during westerly easterly and neutral intraseasonal phases respectively the mechanisms magnitudes locations and vertical structures of easterly waves are shown to strongly vary as a function of intraseasonal phase easterly waves draw energy from low level barotropic conversion regardless of phase although the location and magnitude of the conversion varies strongly during neutral and westerly intraseasonal phases the generation of pape associated with

ground penetrating radar imaging of carbonate mound structures and implications for interpretation of marine seismic data images of carbonate mound structures in denmark and sweden are obtained from ground penetrating radar gpr reflections and outcrop analysis the gpr data are collected in limestone quarries and provide a depth penetration of about 10 m 33 ft and a vertical resolution of about 0 5 m 1 6 ft the mounds are part of the northwest european upper cretaceous danian lower paleocene chalk group and they are similar to each other in terms of architecture spatial distribution and size with widths and lengths of 30 60 m 100 200 ft and heights of 5 10 m 16 33 ft seismic reflection images from the sea of kattegat between sweden and denmark and the north sea show large 500 1000 m 1640 3280 ft wide and 50 100 m 160 330 ft high moundlike carbonate structures interpretations of such large mounds conflict with the gpr and outcrop observations we address these conflicting observations we construct realistic reference models of carbonate mound complex geometries based on the results of the gpr measurements and outcrop analysis and calculate synthetic seismic sections for the models the modeling results show that the size of individual mounds is below the seismic resolution of 10 25 m 33 82 ft and that interference effects caused by stacks of mounds may explain the observed large moundlike structures our findings are important for the interpretation of seismic images of carbonate mound structures carbonate mound buildups may form traps and correct seismic interpretation of mound complex geometry may be essential for evaluation of the nature and reservoir potential of such structures

local and remote atmospheric response to tropical instability waves a global view from space a la nina took place in the equatorial pacific in 1999 and strong tropical instability waves tiws developed causing large meanders of a sea surface temperature sst front between the equator and 3 n high resolution satellite measurements are used to describe the variability of sst surface wind velocity column integrated water vapor cloud liquid water and precipitation associated with these strong tiws in 1999 coherent ocean atmosphere patterns emerge in both the pacific and atlantic revealing rich regional characteristics in the far eastern pacific southeasterly trades strengthen weaken over positive negative sst anomalies apparently due to enhanced reduced mixing with high speed winds aloft in the central pacific we find evidence that sst induced sea level pressure changes also contribute substantially to wind fluctuations similar sst wind covariability also exists in the southern hemisphere along 2 s but the wind variability induced by unit sst anomaly is much larger than that north of the equator in the central pacific where the equatorial front is broad the northern sst pattern has a large meridional scale and reaches as far north as 6 n further to the north in the intertropical convergence zone itcz where local sst anomalies are small significant variability is found in clouds and precipitation which is further correlated with surface wind convergence in the atlantic tiw signals in sst are strongly trapped near the equator but they induce significant remote response in the itcz which takes a more southern position than its pacific counterpart and thus more susceptible to tiw influence

appraisal of recent theories to understand cyclogenesis pathways of tropical cyclone madi 2013 the present study aims to examine the new understanding of cyclogenesis by analyzing the genesis sequence of formation of a very severe cyclonic storm madi 6 13 december 2013 that occurred over the bay of bengal we have generated a high resolution 18 km 6 km and 2 km analysis using three dimensional variational data assimilation technique and weather research and forecasting model the genesis sequence of madi cyclone is analyzed using the concepts in the marsupial theory and other theories of tropical cyclone formation major results are as follows the developed analysis is found useful for tracking the movement of westward moving parent disturbance from 15 days prior to the genesis identifying developed pouch region in the lagrangian frame of reference understanding the evolution of the pouch and convection within the pouch region and for the study of intensification inside the pouch region also large scale priming of environment concurs with the hypotheses of the marsupial theory of tropical cyclogenesis the analysis of dynamical and thermodynamical processes within the pouch region showed gradual moistening uplifting of moisture diabatic heating causing buoyant convection in the vorticity rich environment followed by vortex tube stretching development of convection heavy precipitation strengthening of lower level convergence and hence spin up during a day or two preceding the genesis of madi cyclone in general it is concluded that intensification within pouch region during the cyclogenesis phase followed the marsupial paradigm and bottom up mechanism

a vortex based perspective of eastern pacific tropical cyclone formation tropical cyclone formation over the eastern pacific during 2005 and 2006 was examined using primarily global operational analyses from the national centers for environmental prediction this paper represents a vortex view of genesis adding to previous work on tropical cyclone formation associated with tropical waves between 1 july and 30 september during 2005 and 2006 vortices at 900 hpa were tracked and vortex following diagnostic quantities were computed vortices were more abundant during periods of an enhanced hadley circulation with monsoon westerlies around 10 n in the lower troposphere this zonally confined hadley circulation was significantly stronger during the genesis of developing vortices developing vortices were stronger at the outset with a deeper potential vorticity maximum compared to nondeveloping vortices this implies that developing disturbances were selected early on by favorable synoptic scale features the characteristic time mean reversal of the meridional gradient of absolute vorticity in the lower troposphere was found to nearly vanish when the aggregate contribution of strong vortices was removed from the time mean vorticity this finding implies that it is difficult to unambiguously attribute development to a preexisting enhancement of vorticity on the synoptic scale the time mean enhancement of cyclonic vorticity primarily results from the accumulated effect of vortices it is suggested that horizontal deformation in the background state helps distinguish developing vortices from nondevelopers and also biases the latitude of development poleward of the climatological itcz axis

precipitation and kinematic structure of an oceanic mesoscale convective system part i convective line structure abstract the precipitation thermodynamic and kinematic structure of an oceanic mesoscale convective system is studied using airborne doppler and in situ flight level data collected by the noaa p 3 aircraft the system a well organized stationary north south convective line was located near the east coast of taiwan in part i the basic structure of the line is documented with both datasets a procedure revealing the strengths and weakness of both approaches the doppler data reveal that the warm moist air feeding the line enters from the east side most updrafts associated with the leading edge of the convective line tilt westward below 5 km and then eastward above 5 km this change of tilt corresponds to a change in the sign of the vertical flux of east west momentum to the east of the leading edge a 10 km wide zone of strong mesoscale descent is seen the band is not a complete barrier to the low level southeasterly flow and at times and places along the line the inflowing air can move throu

the interaction of planetary scale tropical easterly waves with topography a mechanism for the initiation of tropical cyclones abstract the interaction of a basic state flow consisting of a planetary scale easterly wave superimposed on a uniform easterly zonal wind with an isolated topographic feature is examined by numerical integration of the shallow water equations in an equatorial beta plane channel the topographic parameters are chosen to represent the sierra madre mountains of mexico the zonal wavelength and phase speeds of the basic state easterly waves are chosen to correspond with previously published observations the topographic modification of a slow rossby mode in which the basic state vorticity maximum is located near 15 latitude is characterized by the generation of a cyclonic vorticity maximum in the lee of the mountain which extends the entire length of the ridge and a secondary maximum which propagates downstream a fast mixed rossby gravity mode in which the vorticity maximum is located at the equator interacts less strongly with the mountain with a lee vorticity maximum that is confined near the southern

roles of the synoptic scale wave train the intraseasonal oscillation and high frequency eddies in the genesis of typhoon manyi 2001 abstractexperiments using the weather research and forecasting wrf model were conducted to investigate the effects of multiscale motions on the genesis of typhoon manyi 2001 in the western north pacific the precursor signal associated with this typhoon genesis was identified as a northwest southeast oriented synoptic scale wave train swt the model successfully simulated the genesis of the typhoon in the wake of the swt further experiments were conducted to isolate the effects of the swt the intraseasonal oscillation iso and high frequency shorter than 3 days eddies in the typhoon formation removing the swt in the initial and boundary conditions eliminates the typhoon genesis this points out the importance of the swt in the typhoon genesis it was noted that the swt strengthened the wake cyclone through southeastward energy dispersion the strengthening wake cyclone triggered multiple episodes of strong sustained convective updrafts leading to aggregation of vertical vorticity and formatio

porewater ph and authigenic phases formed in the uppermost sediments of the santa barbara basin abstract in this paper porewater and solid phase analyses are used in combination with in situ o 2 and ph microelectrode measurements to characterize early diagenetic processes in the uppermost sediments of the santa barbara basin california rapid reduction of dissolved oxygen nitrate solid phase manganese and iron and dissolved sulfate is observed between sediment depths of 0 and 2 cm reductive solubilization of ferric iron phases releases fe 2 adsorbed phosphate and fluoride to the porewaters and contributes to a sharp increase in porewater ph between 2 and 4 cm sulfate reduction rates peak ph levels off and acid volatile sulfides and pyrite become the dominant forms of solid phase iron saturation state calculations which depend largely on ph indicate that the porewaters of the santa barbara basin become saturated with respect to carbonate fluorapatite and calcite within the first 0 25 mm of the sediment and are highly supersaturated by and below 2 cm in spite of this result porewater evidence of phosphate and fluoride removal into a solid phase is observed only in the first 5 cm of some cores whereas dissolved ca profiles suggest dispersed calcite precipitation throughout the sediment column this finding is interpreted as an indication of the nonsteady state nature of the surface reactions that may given sufficient nucleation sites and time lead to carbonate fluorapatite genesis in anoxic sediments finally microelectrode ph profiles from two other basins in the california borderlands are presented these demonstrate that the porewaters of the santa barbara basin are more alkaline than those of other basins this outcome is attributed to the lack of particle mixing and a unique interplay between fe liberation and fes precipitation reactions in the santa barbara basin

barometric pressure variations associated with eastern pacific tropical instability waves abstract barometric pressure surface temperature and wind time series in the eastern equatorial pacific are analyzed to determine if oceanic tropical instability wave tiw sea surface temperature variations cause barometric pressure gradients large enough to influence the atmospheric boundary layer during the study period from april 2001 to september 2002 11 tiws propagated westward past 110 w causing a spectral peak at 20 30 days in the sea surface temperature sst meridional difference between 2 n 110 w and 0 110 w likewise the meridional pressure difference also had a spectral peak in the 20 30 day tiw band cross spectral analysis shows that within the tiw band sst induced pressure variations were roughly 0 1 hpa c 1 in magnitude the resulting pressure gradient force is comparable in magnitude to other terms in the meridional momentum balance implications about the role of the boundary layer capping in the adjustment to sst forcing are discussed

external influences on hurricane intensity part i outflow layer eddy angular momentum fluxes abstract outflow layer winds were objectively analyzed every 12 h for 6 days during the life cycle of hurricane elena 1985 a high correlation was found between angular momentum fluxes by azimuthal eddies at large radii and central pressure changes in the storm 27 33 h later momentum flux by eddies exceeded that by the azimuthal mean outside the 800 km radius while vortex spinup by the eddies reached instantaneous magnitudes as large as 25 m s 1 day outflow maxima and minima repeatedly appeared more than 1000 km from the hurricane center and tracked inward with time the results provide evidence of significant environmental control on the behavior of the storm after reaching hurricane strength elena experienced a major secondary intensification associated with a large inward cyclonic eddy momentum flux produced by the passage of a middle latitude trough north of the hurricane an outflow maximum appeared radially inside of the eddy momentum source consistent with balanced vortex theory and tracke

mixed rossby gravity waves and western pacific tropical cyclogenesis part i synoptic evolution abstract a large amplitude mixed rossby gravity wave packet is identified in the western pacific using 6 10 day bandpass filtered winds individual disturbances of 2300 3000 km wavelength propagated westward as the packet moved slowly eastward the packet first appeared and subsequently amplified within a region of active convection associated with the madden julian oscillation mjo which was isolated by low pass filtered outgoing longwave radiation the packet lasted about 5 weeks then rapidly dispersed as the active mjo moved away from it to the east west of 150 e individual disturbances within the packet turned northwestward away from the equator indicating an apparent transition from mixed rossby gravity waves to off equatorial tropical depression td type disturbances cyclones filled with cloud and anticyclones cleared during the transition nevertheless convective structure consistent with mixed rossby gravity waves remained outside the circulation centers and three tropical cyclones for

thermodynamic aspects of tropical cyclone formation abstractthe thermodynamic aspects of tropical cyclone tc formation near the center of the wave pouch a region of approximately closed lagrangian circulation within the wave critical layer are examined through diagnoses of a high resolution numerical simulation and dropsonde data from a recent field campaign it is found that the meso area near the pouch center is characterized by high saturation fraction small difference in equivalent potential temperature e between the surface and the middle troposphere and a short incubation time scale updrafts tend to be more vigorous in this region presumably because of reduced dry air entrainment while downdrafts are not suppressed the thermodynamic conditions near the pouch center are thus critically important for tc formation the balanced responses to convective and stratiform heating at the pregenesis stage are examined using the sawyer eliassen equation deep convection is concentrated near the pouch center the strong radial and vertical gradients o

from detached to attached carbonate buildup complexes 3d seismic data from the upper palaeozoic finnmark platform southwestern barents sea abstract carbonate buildups were abundant during the palaeozoic three dimensional seismic data from the finnmark platform barents sea has been used to reconstruct the evolution of laterally extensive carbonate buildup complexes in space and time the results suggest that the location of upper palaeozoic warm and cool water carbonate buildups from the finnmark platform is controlled by faults and the sea floor morphology at the time of their growth a fluctuating sea level affected the growth of the carbonate buildups but they also influenced their own environment by forming lagoons atoll like ridges and possibly areas with restricted circulation warm water carbonate buildups forming ridges and isolated mounds occur in the gipsdalen group latest serpukhovian mid sakmarian where they initially grew in a detached platform setting the carbonate buildups are several tens of kilometres long up to 2 5 km wide and 300 m thick and interpreted to consist of vertically stacked complexes of sub seismic scale carbonate buildups evaporites were deposited and later subject to karstification possibly during a period of sub aerial exposure before a transgression and the subsequent carbonate deposition and buildup growth bridged the detached platform with the attached platform in the bjarmeland group lower permian 0 35 4 8 km wide 1 5 27 km long and 60 420 m thick cool water bryozoan dominated straight sinuous and continuous carbonate ridges or atoll like ridges are located on top of the warm water carbonate structures three dimensional maps of upper palaeozoic carbonate buildups document their geomorphology distribution and size through time the lateral and vertical growth of carbonate buildups has been reconstructed revealing how their distribution changed over time and with changing environmental settings

interpretation of reflection attributes in a 3 d gpr survey at vallee d ossau western pyrenees france to study the attributes of reflected radar waves a 3 d ground penetrating radar gpr data set was recorded processed with promax 3 d seismic processing software and analyzed with stratimagic 3 d seismic interpretation software the zone studied was an old glacial valley vallee d ossau western pyrenees where fluvio glacial deposits 8 10 m thick overlay a karstic limestone bedrock reflections were picked to 250 ns 9 m depth with velocity 0 07 m ns analysis of the isochron map of the bedrock surface reflector showed north south undulations corresponding to the displacement of the old glacier together with sharp discontinuities interpreted as local faults or karstic zones amplitude variations along the reflector were interpreted as being from water saturation and the nearby north south alignment of springs at the surface in the fluvio glacial deposits paths of old channels were also imaged using amplitude analysis the radar wave amplitude attenuation was also characterized within the d

coastal upwelling in the california current system abstract coastal upwelling in the california current system has been the subject of large scale studies off california and baja california and of small scale studies off oregon recent studies of the winds along the entire coast from 25 n to 50 n indicate that there are significant along shore variations in the strength of coastal upwelling which are reflected in the observed temperature distribution active upwelling appears to be restricted to a narrow coastal band about 10 25 km wide along the entire coast but the region influenced by coastal upwelling may be much wider intensive observations of the upwelling zone during summer off oregon show the presence of a southward coastal jet at the surface a mean vertical shear a poleward undercurrent along the bottom and persistently sloping isopycnals over the continental shelf most of the upwelling there occurs during relatively short periods several days long of upwelling favorable winds during the upwelling season off oregon the offshore ekman transport is carried by the surface ekman layer and the onshore return flow occurs through a quasi geostrophic interior it is not known whether the structure and dynamics observed off oregon are typical of the upwelling zone along the entire coast though some of the same features have been observed off baja california current and future research will eventually show whether the oregon results are also applicable in the region of persistently strong upwelling favorable winds off northern california and in the region of complex bathymetry off central and southern california

rotating convective disturbances in the trades observations of rotating convective disturbances in the trade wind region just east of hawaii are presented rotation results from stretching of vertical ambient vorticity in the convective regions surface friction is shown to play a significant dissipative role in these disturbances ekman pumping associated with the rotation is probably only of secondary importance convection is found to be associated with weak local maxima in the boundary layer equivalent potential temperature this suggests that convection occurs where such anomalies make the buoyancy of surface parcels larger than average convective available potential energies are found to be small which means that such equivalent potential temperature anomalies are important in determining parcel buoyancy it is hypothesized that mesoscale circulations induced by the ascending motion of convection reinforce the anomalies resulting in the intensification of the circulations the equivalent potential temperature of the boundary layer results from a balance between surface fluxes and entrainment from above ascending motion apparently reduces entrainmcnt thus allowing the equivalent potential temperature to rise whereas subsidence has the opposite effect

a vortical hot tower route to tropical cyclogenesis abstract a nonhydrostatic cloud model is used to examine the thermomechanics of tropical cyclogenesis under realistic meteorological conditions observations motivate the focus on the problem of how a midtropospheric cyclonic vortex a frequent by product of mesoscale convective systems during summertime conditions over tropical oceans may be transformed into a surface concentrated warm core tropical depression as a first step the vortex transformation is studied in the absence of vertical wind shear or zonal flow within the cyclonic vorticity rich environment of the mesoscale convective vortex mcv embryo the simulations demonstrate that small scale cumulonimbus towers possessing intense cyclonic vorticity in their cores vortical hot towers vhts emerge as the preferred coherent structures the vhts acquire their vertical vorticity through a combination of tilting of mcv horizontal vorticity and stretching of mcv and vht generated vertical vorticity horizontally localized and exhibiting conve

the formation of hurricane humberto 2001 the importance of extra tropical precursors the authors examine the formation of hurricane humberto 2001 in the atlantic basin precursor disturbances originating in the extratropics appear critical for inducing tropical cyclogenesis one precursor near the tropopause arose during the development of hurricane erin on 7 september and could be tracked continuously for 12 days until 1200 utc 19 september a fully explicit numerical simulation with the psu ncar mesoscale model produces a generally realistic evolution of the developing storm during a 4 day period beginning 0000 utc 19 september diagnostics of the simulations reveal that moderate vertical shear was crucial for organizing convection and this shear was enhanced on the periphery of an upper level vortex within a lower to mid tropospheric baroclinic zone downdraughts and evaporative cooling produced a rearward propagating bore that organized new convection in a notably moistened environment with small cape vorticity generation maximized near 1 km above mean sea level and the vortex built upward with time this evolution contrasts markedly with downward development conceptual models of tropical cyclogenesis and points to the crucial need for observations in the lower troposphere before depression formation convective scale dynamics were governed by intense convective cores which produced most of the diabatic heating and lower tropospheric vertical vorticity they were constrained by vertical shear to populate the downshear left quadrant of the vortex and therefore their collective behaviour was organized despite being quasi random within the favoured region ultimately the shear that helped organize the convection in the developing depression hampered humberto s subsequent intensification copyright 2006 royal meteorological society

factors controlling elastic properties in carbonate sediments and rocks carbonate sediments are prone to rapid and pervasive diagenetic alterations that change the mineralogy and pore structure within carbonate rocks in particular cementation and dissolution processes continuously modify the pore structure to create or destroy porosity in extreme cases these modifications can completely change the mineralogy from aragonite calcite to dolomite or reverse the pore distribution whereby original grains are dissolved to produce pores as the original pore space is filled with cement to form the rock figure 1 all these modifications alter the elastic properties of the rock and therefore the sonic velocity the result is a dynamic relationship among diagenesis porosity pore type and sonic velocity the result is a wide range of sonic velocity in carbonates in which compressional wave velocity vp ranges from 1700 to 6600 m s and shear wave velocity vs from 600 to 3500 m s

the diurnal cycle of tropical convection the diurnal cycle of tropical convection is investigated with global cloud imagery constructed from 11 m radiance measurements taken aboard six satellites four harmonics of the diurnal cycle are resolved in the cloud imagery with about 50 km horizontal resolution to isolate deep convective activity from other processes which cause diurnal fluctuations in longwave radiance an index of deep convective activity is constructed by thresholding to brightness temperatures less than 230 k significant diurnal amplitude of deep convection is found only over tropical landmasses over the tropical oceans the diurnal cycle is weak and is barely discernible from the background red spectrum of convective variance nonetheless oceanic convection exhibits a systematic diurnal fluctuation with maximum intensity in the early morning nocturnal subsidence along the cloud free equator is postulated to play a role in forcing diurnal variation in the intertropical convergence zones other mechanisms are also implied to contribute as a similar early morning maximum in deep convection is seen even where no adjoining cloud free regions occur the diurnal cycle of deep convection is found to be organized on planetary scales predominantly in nonmigrating modes i e modes with phase speeds not equal to that of the sun the nonmigrating modes are postulated to be produced by the nonuniform distribution of convective centers the nonmigrating zonally symmetric component is found to be especially large while the role of this mode in forcing diurnal variations of the tropospheric circulation e g the hadley cell is questionable its role in modulating the ionospheric electric potential is well established discrepancies with the traditional notion that cloud to ground lightning is the dominant mechanism by which the earth is negatively charged are discussed in particular the probable role of nonlightning producing clouds e g the stratiform portion of convective complexes in diurnally modulating the negative charge on earth is discussed

an investigation of composite dropsonde profiles for developing and nondeveloping tropical waves during the 2010 predict field campaign abstractcomposite dropsonde profiles are analyzed for developing and nondeveloping tropical waves in an attempt to improve the understanding of tropical cyclogenesis these tropical waves were sampled by 25 reconnaissance missions during the 2010 pre depression investigation of cloud systems in the tropics predict field campaign comparisons are made between mean profiles of temperature mixing ratio relative humidity radial and tangential winds relative vorticity and virtual convective available potential energy cape for genesis and nongenesis cases genesis soundings are further analyzed in temporal progression to investigate whether significant changes in the thermodynamic or wind fields occur during the transition from tropical wave to tropical cyclone significant results include the development of positive temperature anomalies from 500 to 200 hpa 2 days prior to genesis in developing waves this is not observed in the nongenesis mean progressive mesoscale moistening of the column is observe

understanding the vertical structure of potential vorticity in tropical depressions author s murthy vs boos wr abstract 2019 royal meteorological society potential vorticity pv has been used to understand the intensification and motion of a variety of tropical vortices here atmospheric reanalyses and idealized models are used to understand how the vertical structures of moist convective heating and adiabatic advection jointly shape the vertical structures of pv in tropical depressions observationally based estimates reveal a top heavy pv structure in tropical depressions contrasting with bottom heavy structures of absolute vorticity and diabatic pv generation these distinct vertical structures are reproduced in an axisymmetric model which employs the weak temperature gradient approximation for conceptual simplicity and is forced by stratiform and deep convective heating when applied in isolation the stratiform and deep convective heatings produce pv maxima at 500 hpa and near the surface respectively when these two heatings are applied simultaneously interactions between the stratiform and deep convective modes enhance the adiabatic advective tendencies produced by the transverse circulation making the pv distribution more top heavy in the lower and middle troposphere radial advection also greatly reduces the radius of the pv structure relative to that of the imposed heating consistent with structures in observed tropical depressions the implications of these differences in radial structures for using the flux form of the relevant conservation equations e g for pv substance or absolute vorticity are discussed

mesoscale observations of the genesis of hurricane dolly 1996 abstract recent numerical studies of tropical cyclone genesis suggest a new paradigm for how the surface vortex is established based on a highly nonaxisymmetric mechanism involving the interaction of low level cyclonic circulations generated by deep cumulonimbus convection a reexamination of mesoscale observations during the genesis of hurricane guillermo 1991 confirms the presence of multiple cyclonic circulations more recently airborne doppler radar wind observations during the genesis of atlantic hurricane dolly 1996 also reveal multiple lower to middle tropospheric mesoscale cyclonic circulations during sequential 15 20 min compositing periods a particularly well organized but initially weak mean tangential wind of 7 m s 1 low level cyclonic vortex embedded within the pre dolly tropical disturbance is observed coincident with deep vertically penetrating cumulonimbus convection the earliest observations of this vortex show the peak circulation near 2 km height with a mean diameter of 30 4

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

genesis of pre hurricane felix 2007 part i the role of the easterly wave critical layer abstract the formation of pre hurricane felix 2007 in a tropical easterly wave is examined in a two part study using the weather research and forecasting wrf model with a high resolution nested grid configuration that permits the representation of cloud system processes the simulation commences during the wave stage of the precursor african easterly wave disturbance here the simulated and observed developments are compared while in part ii of the study various large scale analyses physical parameterizations and initialization times are explored to document model sensitivities in this first part the authors focus on the wave vortex morphology its interaction with the adjacent intertropical convergence zone complex and the vorticity balance in the neighborhood of the developing storm analysis of the model simulation points to a bottom up development process within the wave critical layer and supports the three new hypotheses of tropical cyclone formation proposed recently by dunkerton montgome

planetary and synoptic scale influences on eastern pacific tropical cyclogenesis abstract the structure and evolution of lowpass filtered background flow and synoptic scale easterly waves were examined during the 1991 eastern pacific hurricane season active and inactive cyclogenesis periods conformed well to the sign of the near equatorial lowpass filtered 850 mb zonal wind anomaly consistent with the recent results of maloney and hartmann this behavior emphasizes the importance of westerly wind bursts associated with the madden julian oscillation mjo in creating an environment favorable for eastern pacific tropical cyclogenesis synoptic scale easterly waves reached the western caribbean and eastern pacific regularly from upstream usually from africa the amplitude of waves leaving africa had little correlation with the likelihood of a wave producing an eastern pacific storm rather easterly waves intensified and tropical depressions formed during the convectively active phase of the mjo in the western caribbean and eastern pacific wave growth measured by strengthening o

on the convective coupling and moisture organization of east pacific easterly waves abstractprocesses associated with the local amplification of easterly waves ews in the east pacific warm pool are explored developing ews favor convection in the southwest and northeast quadrants of the disturbance in nascent ews convection favors the southwest quadrant as the ew life cycle progresses convection in the northeast quadrant becomes increasingly prominent and southwest quadrant convection wanes the ew moisture budget reveals that anomalous meridional winds acting on the mean meridional moisture gradient of the itcz produce moisture anomalies supportive of convection in the southwest quadrant early in the ew life cycle as ews mature moisture anomalies on the poleward side of the ew begin to grow and are supported by the advection of anomalous moisture by the mean zonal wind in the southwest and northeast portions of the wave where convection anomalies are favored lower tropospheric vorticity is generated locally through vertical stretching that supports a horizontal tilt of the wav

detailed internal architecture of a fluvial channel sandstone determined from outcrop cores and 3 d ground penetrating radar example from the middle cretaceous ferron sandstone east central utah ideally characterization of hydrocarbon reservoirs requires information about heterogeneity at a submeter scale in three dimensions detailed geologic information and permeability data from surface and cliff face outcrops and boreholes in the alluvial part of the ferron sandstone are integrated here with three dimensional 3 d ground penetrating radar gpr data for analysis of a near surface sandstone reservoir analog in fluvial channel deposits the gpr survey covers a volume with a surface area of 40 x 16 5 m and a depth of 12 m five architectural elements are identified and described in outcrop and well cores using a sixfold hierarchy of bounding surfaces internally the lower four units consist of fine grained parallel laminated sandstone and the upper unit consists of medium grained trough cross bedded sandstone the same sedimentary architectural elements and associated bounding surfaces are distinguished in the gpr data by making use of principles developed in seismic stratigraphic analysis to facilitate comparison of geologic features in the depth domain and radar reflectors in the time domain the radar data are depth migrated the gpr interpretation is carried out mainly on migrated 100 mhz data with a vertical resolution of about 0 5 m measures of the spatial continuity and variation of the first and second order bounding surfaces are obtained by computing 3 d experimental variograms for each architectural element each radar begin page 1584 facies the maximum correlation length of the dominant internal features ranges between 4 and 6 m and the anisotropy factor ranges between 0 6 and 0 95

prediction and diagnosis of tropical cyclone formation in an nwp system part i the critical role of vortex enhancement in deep convection this is the first of a three part investigation into tropical cyclone tc genesis in the australian bureau of meteorology s tropical cyclone limited area prediction system tc laps an operational numerical weather prediction nwp forecast model the primary tc laps vortex enhancement mechanism is presented in part i the entire genesis process is illustrated in part ii using a single tc laps simulation and in part iii a number of simulations are presented exploring the sensitivity and variability of genesis forecasts in tc laps the primary vortex enhancement mechanism in tc laps is found to be convergence stretching and vertical advection of absolute vorticity in deep intense updrafts which result in deep vortex cores of 60 100 km in diameter the minimum resolvable scale is limited by the 0 15 horizontal grid spacing on the basis of the results presented it is hypothesized that updrafts of this scale adequately represent mean vertical motions in real tc genesis convective regions and perhaps that explicitly resolving the individual convective processes may not be necessary for qualitative tc genesis forecasts although observations of sufficient spatial and temporal resolution do not currently exist to support or refute this proposition relatively large scale 30 km and greater lower to midlevel tropospheric convergent regions have been observed in tropical oceanic environments during the global atmospheric research programme garp atlantic tropical experiment gate the equatorial mesoscale experiment emex and the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare and regions of extreme convection of the order of 50 km are often remotely observed in tc genesis environments these vortex cores are fundamental for genesis in tc laps they interact to form larger cores and provide net heating that drives the system scale secondary circulation which enhances vorticity on the system scale akin to the classical eliassen problem of a balanced vortex driven by heat sources these secondary vortex enhancement mechanisms are documented in part ii in some recent tc genesis theories featured in the literature vortex enhancement in deep convective regions of mesoscale convective systems mcss has largely been ignored instead they focus on the stratiform regions while it is recognized that vortex enhancement through midlevel convergence into the stratiform precipitation deck can greatly enhance midtropospheric cyclonic vorticity it is suggested here that this mechanism only increases the potential for genesis whereas vortex enhancement through low to midlevel convergence into deep convective regions is necessary for genesis

in situ initiation of east pacific easterly waves in a regional model abstractthe in situ generation of easterly waves ews in the east pacific epac is investigated using the weather research and forecasting wrf model the sensitivity of the model to the suppression of ew forcing by locally generated convective disturbances is examined specifically local forcing of ews is removed by reducing the terrain height in portions of central and south america to suppress robust sources of diurnal convective variability most notably in the panama bight high terrain contributes to the initiation of mesoscale convective systems in the early morning that propagate westward into the epac warm pool when such mesoscale convective systems are suppressed in the model ew variance is significantly reduced this result suggests that epac ews can be generated locally in association with higher frequency convective disturbances and these disturbances are determined to be an important source of epac ew variability however epac ew variability is not completely eliminated in such sensi

cenozoic evolution of the eastern danish north sea this paper provides a review of recent high resolution and conventional seismic investigations in the eastern danish north sea and describes their implications for the development of the eastern north sea basin the results comprise detailed time structure maps of four major unconformities in the eastern danish north sea the top chalk surface mid paleocene near top oligocene the mid miocene unconformity and base quaternary the maps show that the eastern danish north sea has been affected by faulting and salt diapirism throughout the cenozoic carbonate mounds erosional valleys and pockmark or karst like structures were identified at the top of the upper cretaceous danian chalk group strike parallel erosional features and depositional geometries observed at near top oligocene and at the mid miocene unconformity indicate that these major sequence boundaries can be attributed to large scale lateral changes in sediment supply directions increases in sediment flux to the southeastern north sea at the eocene oligocene transition and in the post middle miocene appear to correlate with similar events world wide and with long term 18o increases indicating forcing by global factors i e eustasy and climate stratal geometries observed on the seismic data indicate that the so called neogene uplift of the eastern danish north sea may have been hundreds of metres less than previously suggested it is argued that late cenozoic uplift of the basin margin and of mountain peaks in southern norway may have been caused entirely by isostatic uplift of the crust in response to accelerated late cenozoic denudation and dissection of topography created in the paleogene the late cenozoic periods of accelerated denudation and incision rates were most likely driven by climatic deterioration and long term eustatic lowering rather than active late cenozoic tectonics the cause of which is conjectural a series of shallow thrust structures and an associated system of deep buried valleys were mapped thrust faulting most likely occurred in response to gravitational loading at the margin of an advancing ice sheet and it was followed by deep incision due to subglacial melt water erosion probably during the elsterian glaciation

multiscale variability of the flow during the north american monsoon experiment abstract the 2004 north american monsoon experiment name provided an unprecedented observing network for studying the structure and evolution of the north american monsoon this paper focuses on multiscale characteristics of the flow during name from the large scale to the mesoscale using atmospheric sounding data from the enhanced observing network the onset of the 2004 summer monsoon over the name region accompanied the typical northward shift of the upper level anticyclone or monsoon high over northern mexico into the southwestern united states but in 2004 this shift occurred slightly later than normal and the monsoon high did not extend as far north as usual consequently precipitation over the southwestern united states was slightly below normal although increased troughiness over the great plains contributed to increased rainfall over eastern new mexico and western texas the first major pulse of moisture into the southwest occurred around 13 july in association with a strong gulf of californi

the cretaceous palaeogene boundary at stevns klint denmark inversion tectonics or sea floor topography the cretaceous palaeogene boundary interval is exposed over 12 km in the coastal cliff stevns klint denmark an important lowermost danian hardground has been interpreted as an originally horizontal marine abrasion surface its present elevation varies from a few metres below to about 35 m above sea level this relief has traditionally been considered as resulting from late or post danian laramide folding new seismic profiles offshore stevns klint show however that the base chalk reflector is not folded is remarkably planar and has a gentle northward dip thus the folding hypothesis cannot be upheld seismic stratigraphic analysis of the chalk group necessitates a fundamental revision of general ideas of chalk deposition a highly irregular sea floor topography was formed at many levels and includes broad valleys ridges channels drifts and mounds a system of major wnw ese oriented valleys and ridges can be traced into the succession exposed in stevns klint and further inland where it corresponds to the relief of the cretaceous palaeogene boundary the marked topographic elements of the chalk sea floor are elongate with a wnw orientation roughly parallel to the axis of the danish basin and to the sorgenfrei tornquist zone forming the ne border of the basin the sea floor relief undoubtedly reflects the influence of strong contour parallel bottom currents the cretaceous palaeogene boundary succession at stevns klint was thus developed on an underlying sea floor topographic relief of about 40 m recognition of the highly irregular current influenced topography of the late cretaceous sea floor stands in marked contrast to the conventional picture of quiet pelagic deposition of the chalk

three dimensional architecture and development of danian bryozoan mounds at limhamn south west sweden using ground penetrating radar bryozoan mounds from the middle danian lower palaeocene of the danish basin represent a possibly new class of non cemented skeletal mounds the sedimentology and palaeoecology of the mounds have recently been studied in detail three dimensional images of middle danian bryozoan mound structures in the limhamn limestone quarry south west sweden obtained from combined reflected ground penetrating radar signals and outcrop analysis provide new information about the architecture and growth development of such mounds the mounds are composed of bryozoan limestone and dark grey to black flint bands which outline mound geometries ground penetrating radar data sections are collected over a 120 m by 60 m grid of data lines with trace spacing of 0 25 m providing a depth penetration of 7 to 12 m and a vertical resolution of ca 0 30 m the ground penetrating radar images outline the geometry of the internal layering of the mounds which typically have widths and lengths of 30 to 60 m and heights of 5 to 10 m mound architecture and growth show great variability in the ground penetrating radar images small scale mound structures with a palaeorelief of only a few metres may constitute the basis for growth of larger mounds the outermost beds of the individual mounds are commonly characterized by sub parallel to parallel reflections which have a circular to slightly oval appearance in map view the mounds are mainly aggrading and do not show clear signs of pronounced lateral migration during growth although some mound structures indicate a preferential growth direction towards the south growth patterns interpreted from the ground penetrating radar images suggest that the palaeocurrents in the study area may have shown great variability even on a small scale this observation is in contrast to results from studies of extensive slightly older early danian mound complexes exposed in coastal cliffs at stevns klint and karlby klint located 50 and 200 km away from the study area respectively at these locations the mounds show a remarkably uniform development and typically are asymmetrical clearly showing migration directions towards the south these differences in mound geometry may be the result of differences in the current systems and water depths that existed during formation of the early and middle danian mounds respectively the mounds at limhamn were located closer to the basin margin in shallower water than those at stevns klint and karlby klint in addition the difference in mound architecture may be due to the occurrence of non layered irregular coral mounds intercalated with the bryozoan mounds at limhamn

the genesis of hurricane guillermo texmex analyses and a modeling study abstract the transformation of a mesoscale convective system into hurricane guillermo was captured by aircraft and doppler wind data during the tropical experiment in mexico the early phase of the system evolves in a way very similar to previously documented mesoscale convective systems with a midlevel mesocyclone developing in the stratiform precipitation region more unusually the cyclone extends to low altitudes a weak cyclone is discernable even in the 300 m altitude wind field after another day of evolution a small surface based warm core cyclone is observed to develop within the relatively cold air associated with the mesocyclone aloft this mesocyclone develops into a hurricane over the subsequent day a nonhydrostatic axisymmetric numerical model is used to explore the evolution of the initially cold core midlevel vortex into a tropical cyclone a mesoscale midlevel showerhead is switched on in an initially quiescent tropical atmosphere overlying a warm ocean surface evaporation of t

initial development and genesis of hurricane dolly 2008 abstract based on a successful cloud resolving simulation with the weather research and forecasting model this study examines key processes that led to the early development of hurricane dolly 2008 the initial development of dolly consisted of three stages i an initial burst of convection ii stratiform development dry intrusion and thermodynamic recovery and iii reinvigoration of moist convection and rapid intensification advanced diagnosis of the simulation including the use of vorticity budget analysis contour frequency analysis diagrams and two dimensional spectral decomposition and filtering suggests that the genesis of dolly is essentially a bottom up process the enhancement of the low level vorticity is mainly ascribed to the stretching effect which converges the ambient vorticity through stretching enhanced by moist convection in the rapid intensification stage smaller scale positive vorticity anomalies resulting from moist convection are wrapped into the storm center area u

climatically related millennial scale fluctuations in strength of california margin oxygen minimum zone during the past 60 k y a strong oxygen minimum zone omz currently exists along the california margin because of a combination of high surface water productivity and poor intermediate water ventilation however the strength of this omz may have been sensitive to late quaternary ocean circulation and productivity changes along the margin although sediment lamination strength has been used to trace ocean oxygenation changes in the past oxygen levels on the open margin are not sufficiently low for laminations to form in these regions benthic foraminifera are highly sensitive monitors of omz strength and their fossil assemblages can be used to reconstruct past fluctuations benthic foraminiferal assemblages from ocean drilling program site 1017 off point conception exhibit major and rapid faunal oscillations in response to late quaternary millennial scale climate change dansgaard oeschger cycles on the open central california margin these faunal oscillations can be correlated to and are apparently synchronous with those reported from santa barbara basin together they represent major fluctuations in the strength of the omz which were intimately associated with global climate change weakening perhaps disappearing during cool periods and strengthening during warm periods these rapid major omz strength fluctuations were apparently widespread on the northeast pacific margin and must have influenced the evolution of margin biota and altered biogeochemicalmore cycles with potential feedbacks to global climate change less

nitrogen isotope and productivity variations along the northeast pacific margin over the last 120 kyr surface and subsurface paleoceanography 1 glacial interglacial changes in sedimentary 15n over the last 120 kyr display a remarkably similar pattern in timing and amplitude in core records extending from the denitrification zone in the eastern tropical north pacific etnp where subsurface denitrification is active to the oregon margin where no denitrification occurs today low 15n values 4 6 generally characterize glacial stages 2 and 4 and higher 15n values 7 10 are representative of the holocene millennial scale periods within stage 3 and stage 5 the inferred synchroneity of 15n variations along the entire margin implies that the nitrate isotopic signal produced in the oxygen poor subsurface waters in the etnp is rapidly advected northward and recorded at sites far beyond the boundaries of the modern denitrification zone similar to 15n primary production indicators percent corg ba al and percent opal show glacial interglacial as well as millennial scale variations along the ne pacific margin with higher primary production during warm periods however the relative phasing between 15n and paleoproduction tracers within individual records changes latitudinally whereas 15n and primary production vary approximately synchronously in the midlatitudes production lags 15n in the etnp by several kiloyears this lag calls for a new understanding of the processes driving denitrification in the etnp we suggest that oxygen input by the equatorial undercurrent as well as local organic matter flux controls denitrification rates in the etnp moreover the differences in relative timing point to a time transgressive development of upwelling favorable winds along the ne pacific margin after the last glaciation with those in the north developing several kiloyears earlier

observational analysis of tropical cyclogenesis in the western north pacific part i structural evolution of cloud clusters abstract this paper is the first of a two part series summarizing recent attempts to advance omit understanding of the physical processes associated with tropical cyclone formation in the western north pacific a combination of rawinsonde composite and individual case analyses are shown for both pre cyclone tropical cloud clusters genesis and those prominent cloud cluster that do not develop into tropical cyclones nongenesis this research is an extension of previous works at colorado state university by mcbride zehr and love the first part of the study concerns the structural evolution of the genesis cloud clusters and nongenesis cloud clusters results show that nongenesis cloud clusters have about the same mean vertical motion and cumulus activity as the genesis cloud clusters however genesis cloud clusters are found to have much stronger middle to low level cyclonic circulation extending over a radius 2 8 outward from the center the buildup of this strong precyclogenesis circulation is ass

tropical cyclone formation in a sheared environment a case study abstract the development of hurricane danny 1997 from depression to hurricane was examined using cloud to ground lightning data reconnaissance aircraft data and satellite imagery vertical wind shear between 850 and 200 hpa of 5 11 m s 1 produced persistent downshear convective outbreaks that became progressively more intense and closer to the center during the development early in the period the storm intensified steadily in the presence of this downshear convection during the last and most intense outbreak a second vortex appeared to develop within the convection evidence is presented that the new downshear vortex became the dominant vortex and absorbed the original based on these events it is hypothesized that the presence of moderate vertical wind shear accelerated the early development process equivalent potential temperature fields within 500 m of the surface were examined only well after the period of vortex interaction did the characteristic mature tropical cyclone radial profile of eq

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

development of synoptic scale disturbances over the summertime tropical northwest pacific abstract this study addresses the origin of the synoptic scale disturbances that occur in the tropical western north pacific ocean wp region in northern hemisphere summer these have been called easterly waves and tropical depression type td disturbances this analysis uses the national center for environmental prediction national center for atmospheric research reanalysis dataset by performing a regression analysis on several terms in the vorticity equation at 850 hpa it is shown that the td disturbances propagate approximately as barotropic rossby waves at 850 hpa given this ray tracing calculations and the wave activity diagnostic introduced by plumb are used to show that wave accumulation is a promising candidate for the initial development mechanism of the td disturbances the expected local growth rate from this mechanism is simply the convergence of the group velocity which reaches values corresponding to a growth timescale of 3 days this convergence is dominated by but somewhat lar

spectral induced polarization of limestones time domain field data frequency domain laboratory data and physicochemical rock properties with advances in data acquisition and processing methods spectral inversion of time domain td induced polarization ip data is becoming more common geological interpretation of inverted spectral parameters for instance cole cole parameters often relies on results from systematic laboratory measurements these are most often carried out with frequency domain fd systems on sandstone samples however the two different methods of measuring the spectral ip response differ in both measurement technique and scale one of the main objectives of this study is thus to perform a direct comparison of inverted spectral parameters from td ip field data with fd ip spectra from laboratory measurements to achieve this field measurements were carried out before a 50 m long rock core was drilled down along one of the measurement lines solid parts of the core were vacuum sealed in plastic bags to preserve the natural groundwater in the samples after which the core samples were measured with fd spectral ip in laboratory the results showed that the inverted cole cole parameters closest to the borehole were comparable to the ip spectra measured at the core samples despite differences in measurement techniques and scale the field site chosen for the investigation was a limestone succession spanning over a well known lithological boundary the cretaceous palaeogene boundary little is known in previous research about varying spectral ip responses in limestones and an additional objective of this study was therefore to investigate possible sources of these variations in the laboratory the ip spectra were interpreted in light of measured lithological and physicochemical properties the carbonate texture differed strongly across the cretaceous palaeogene boundary from fine grained calcareous mudstone cretaceous to more well lithified and coarse grained wackestone and packstone palaeogene both laboratory and field spectral ip results showed that these differences cause a large shift in measured bulk conductivity across the boundary furthermore carbonate mound structures with limestone grains consisting mainly of cylindrical bryozoan fragments could be identified in the inverted cole cole parameters as anomalies with high relaxation times a general conclusion of this work is that limestones can give rise to a wide range of spectral responses the carbonate texture and the dominant shape of the fossil grains seem to have important control over the electrical properties of the material a main conclusion is that the inverted cole cole parameters from the field scale td ip tomography were comparable to the magnitude and shape of fd ip spectra at low frequencies this opens up large interpretational possibilities as the comprehensive knowledge about relationships between lithological properties and ip spectra from laboratory research can be used for field data interpretation less

multiscale variability of deep convection in relation to large scale circulation in toga coare deep convection over the indo pacific oceanic warm pool in the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare occurred in cloud clusters which grouped together in regions favoring their occurrence these large groups of cloud clusters produced large scale regions of satellite observed cold cloud top temperature this paper investigates the manner in which the cloud clusters were organized on time and space scales ranging from the seasonal mean pattern over the whole warm pool region to the scale of individual cloud clusters and their relationship to the large scale circulation and sea surface temperature sst the dominant convective variability was associated with the intraseasonal oscillation iso a large eastward propagating ensemble of cloud clusters marked the iso s progress the meridional structure of the iso was strongly affected by the seasonal cycle with a southward shift from the northern hemisphere in october november to the southern hemisphere in january february the sst had an intraseasonal signal in lagged quadrature with the cold cloudiness and rainfall in coare the sst increased decreased during the convectively suppressed active phases of the iso enhanced low level westerly winds occurred toward the later stages of the enhanced convection periods of the iso though not always centered at the equator the strongest westerlies tended to be located between two synoptic scale cyclonic gyres which were often not symmetric about the equator in the low level wind field this asymmetry in the anomalous equatorial low level westerlies may have different implications for the oceanic response in the coupled atmosphere ocean system than those centered on the equator the cyclonic gyres contained highly concentrated deep convection and in four cases the gyres developed into tropical cyclones within the envelope marking the convectively active phase of the iso cloud clusters were frequently concentrated into westward propagating disturbances with a local periodicity of similar to 2 days these 2 day disturbances have been identified in earlier spectral studies and appear to be related to westward propagating inertio gravity waves in coare they typically contained numerous cloud clusters which underwent a distinct diurnal cycle most of the cloud clusters embedded in the 2 day disturbances moved westward though some were stationary and a few moved eastward a cloud duster tracking program identified groups of clusters lime dusters that exhibited continuity in time and space in the most convectively active period of the iso the tracking program identified almost the entire iso cloud ensemble as a long lasting trackable superconvective system this observation indicates the lack of a distinct scale separation between convection and large scale disturbances during the most intense convective periods in coare

extreme convection of the near equatorial americas africa and adjoining oceans as seen by trmm abstractthis study documents the preferred location and diurnal cycle of extreme convective storms that occur in the tropical band containing the east pacific ocean central and south america the atlantic ocean and northern africa data from the tropical rainfall measuring mission trmm precipitation radar show three types of convective stratiform structures that constitute extreme convective events deep convective cores dccs wide convective cores wccs and broad stratiform regions bsrs interim ecmwf re analysis era interim data show the associated synoptic environmental factors associated with the occurrence of extreme convective features the dcc wcc and bsr echoes are associated with early middle and late stages of convective system development respectively and the statistics and timing of their occurrence are related to topography and life cycle behavior of the convection storms containing dcc occur primarily over the sudanian savannas of africa and near the mountains in northern

formation of atlantic hurricanes from cloud clusters and depressions abstract the role of large scale eddy processes in the transformation of cloud clusters and depressions into hurricanes is investigated by using different initial conditions in numerical integrations of the naval research laboratory limited area hurricane model with initial conditions specified from the colorado state university composite datasets of professor william gray for atlantic nondeveloping cloud clusters wave trough clusters and depressions no hurricane formation takes place in any of the model integrations with initial conditions specified from the datasets for atlantic developing cloud clusters and depressions a hurricane develops in the course of each model integration one characteristic difference between the developing and nondeveloping disturbances is that the former exhibit large well organized eddy flux convergences of angular momentum associated with wavelike disturbances in the upper troposphere and lower stratosphere whereas the latter exhibit weak poorly organized eddy momen

momentum transport by a line of cumulonimbus abstract the vertical transport of horizontal momentum normal to a line of cumulonimbus observed during gate on 14 september 1974 is against the vertical momentum gradient contrary to the predictions of mixing length theory data from repeated aircraft passes normal to the line s axis at heights from 0 15 to 5 5 km are used to document the flux and determine its source the flux is concentrated in roughly a 25 km wide active zone just behind the leading edge of the line in kilometer scale convective updrafts accelerated upward by buoyancy and toward the rear of the line by mesoscale pressure forces the fall in mesoscale pressure from the leading edge to the rear of the active zone is mainly hydrostatic resulting from relatively high virtual temperatures and the 60 degree tilt of the leading edge from the vertical with the clouds at the surface well ahead of those aloft evaluation of the terms in the momentum flux generation equation confirms that the above process reflected by the velocity buoyan

quaternary bryozoan reef mounds in cool water upper slope environments great australian bight bryozoan reef mounds are common features in the geological record occurring within mid ramp slope paleoenvironments especially in paleozoic carbonate successions but until now have not been recorded from the modern ocean recent scientific drilling in the great australian bight ocean drilling program leg 182 has confirmed the existence of shallow subsurface bryozoan reef mounds in modern water depths of 200 350 m these structures have as much as 65 m of synoptic relief and occur both as single mounds and as mound complexes they are unlithified have a floatstone texture and are rich in delicate branching encrusting and or nodular arborescent flat robust branching fenestrate and articulated zooidal bryozoan growth forms the muddy matrix is composed of foraminifers serpulids fecal pellets irregular bioclasts sponge spicules and calcareous nannofossils the 14c accelerator mass spectrometry dates of 26 6 35 1 ka indicate that the most recent mounds the tops of which are 7 10 m below the modern seafloor flourished during the last glacial lowstand but perished during transgressive sea level rise this history reflects changing oceanographic current patterns strong upwelling during lowstands and reduced upwelling and lowered trophic resources during highstands large specimens of benthic foraminifers restricted to the mounds confirm overall mesotrophic growth conditions the mounds are similar in geometry scale general composition and paleoenvironments to older structures but lack obvious microbial influence and extensive synsedimentary cementation such differences reflect either short term local conditions or long term temporal changes in ocean chemistry and biology

deep onshore reflection seismic imaging of the chalk group strata using a 45 kg accelerated weight drop and combined recording systems with dense receiver spacing the chalk group forms important hydrocarbon reservoirs offshore and water aquifers onshore denmark within a day of fieldwork a 450 m long reflection seismic profile was acquired onshore in an are