geochemistry of cassiterite and wolframite from tin and tungsten quartz veins in portugal cassiterite and wolframite compositions from snnw and wnsn bearing quartz veins in northern and central portugal are compared to provide evidence on fluid compositions in snnw bearing quartz veins euhedral cassiterite shows sequences of alternating parallel darker and lighter zones the darker zones are pleochroic oscillatory zoned exhibit exsolutions of columbite and ixiolite and are richer in nb ta and fe than the lighter zones which consist of nearly pure sno2 cassiterite from wnsn bearing quartz veins is usually zoned with homogeneous and slightly pleochroic darker zones which are chemically similar to lighter zones bothzoneshaveinclusionsofrutileandrareilmenite thedarkerzonesofcassiteritefrom theformer veins arericherin nb taandfe contents and poorer in ti than the darker and lighter zones of cassiterite from the latter veins this is attributed to differences in the composition of magmatic hydrothermal fluids wolframite compositions from snnw and wnsn bearing quartz veins do not show any significant distinction because they precipitate from relatively similar magmatic hydrothermal fluids in some deposits most wolframite crystals are homogeneous but others are heterogeneous inner patches rich in a hubnerite component rarely occur in crystals from the filharoso and panasqueira deposits zoned crystals showing an increase in fe and a decrease in mn from core to rim were found in the vale das gatas deposit complex oscillatoryzonedcrystals occur inthe carris deposit later wolframite contains inclusions ofscheelite partially replaces itand is richer in fe and poorer in mn than earlier wolframite wolframite from snnw bearing quartz veins in the argozelo deposit and wnsn bearing quartz veins from vale das gatas and panasqueira deposits has significant nb content this does not depend on the fe and mn content of the wolframite but w content is negatively correlated with nb content only very rare single crystals of wolframite show an increase in w and a decrease in nb from core to rim snnw bearing quartz veins contain wolframite poorer in nb than the darkerzones of cassiterite which exsolved columbite andixiolite inwnsn bearing quartz veins from panasqueira and vale das gatas the wolframite has a higher nb content than the cassiterite which contains rutile inclusions enriched in nb because cassiterite and wolframite are derived from two distinct magmatic hydrothermal fluids of different age the fluid responsible for wolframite precipitationwillhaveasimilarcompositiontothatresultingfromtheevolutionofthefluidresponsibleforcassiteriteprecipitationinthe

the genesis of severe long lived bow echoes abstract a series of idealized simulations using a nonhydrostatic cloud model is used to investigate the genesis of bow echoes a bow shaped system of convective cells that is especially noted for producing long swaths of damaging surface winds it is hypothesized that severe long lived bow echoes represent a dynamically unique form of mesoconvective organization being produced for a restricted range of environmental conditions including a convective available potential energy cape of at least 2000 m2 s2 and vertical wind shears of at least 20 m s 1 over the lowest 2 5 5 km agl the key structural features include a 40 100 km long bow shaped segment of convective cells with a strong rear inflow jet extending to the leading edge of the bow at 2 3 km agl and cyclonic and anticyclonic eddies referred to as bookend vortices on the northern and southern flanks of the bowed segment respectively this structure characteristically develops three to four hours into the lifetime of a convective system a

the sedimentary structure of linear sand dunes linear sand dunes dunes that extend parallel to each other rather than in star like or crescentic forms are the most abundant type of desert sand dune1 but because their development and their internal structure are poorly understood they are rarely recognized in the rock record2 models of linear dune development2 3 4 5 6 have not been able to take into account the sub surface structure of existing dunes but have relied instead either on the extrapolation of short term measurements of winds and sediment transport or on observations of near surface internal sedimentary structures from such studies it has not been clear if linear dunes can migrate laterally2 7 8 here we present images produced by ground penetrating radar showing the three dimensional sedimentary structure of a linear dune in the namib sand sea where some of the world s largest linear dunes are situated these profiles show clear evidence for lateral migration in a linear dune moreover the migration of a sinuous crest line along the dune produces divergent sets of cross stratification which can become stacked as the dune height increases and large linear dunes can support superimposed dunes that produce stacked sets of trough cross stratification these clear structural signatures of linear dunes should facilitate their recognition in geological records

a diabatically driven mesoscale vortex in the lee of the tibetan plateau abstract an analysis of a diabatically driven and long lived midtropospheric vortex in the lee of the tibetan plateau during 24 27 june 1987 is presented the large scale conditions were characterized by the westward expansion of the 500 mb western pacific subtropical high and the amplification of a trough in the lee of the plateau embedded within the lee trough three mesoscale convective systems mcss developed a vortex emerged following the dissipation of one mcs with its strongest circulation located in the 400 500 mb layer low level warm advection and surface sensible and latent heating contributed to the convective initiation weak wind and weak ambient vorticity conditions inside the lee trough provided a favorable environment for these mcss and the vortex to develop and evolve the organized vortex circulation featured a coherent core of cyclonic vorticity extending from near the surface to 300 mb with virtually no vertical tilt the air in the vicinity of the vortex was very moist and the

structure of a midtropospheric vortex induced by a mesoscale convective system on 9 june 1988 a mesoscale 200 km diameter convectively generated vortex mcv passed through the colorado wind profiling network the generating convective system which was too small to meet maddox s mesoscale convective complex criteria developed beneath a high amplitude mid and upper level ridge axis profiler winds obtained within the stratiform region of the convective system and near the center of the ensuing mcv form the basis of this study with the addition of satellite including rapid scan images and conventional and doppler radar data this vortex was well observed over its entire life cycle the slowly moving vortex was observed by the flagler 50 mhz profiler for more than 16 h for a portion of this period the circulation was quasi steady hence the spatial structure of the vortex was depicted by timeto space conversion of the profiler data the results show a strong coherent circulation with maximum tangential speeds greater than 16 m s21 at 6 km above mean sea level msl and at radii of 50 70 km corresponding relative vorticity was more than three times as large as the local coriolis parameter the long duration and the apparent dominance of vorticity over divergence suggest that the flow in the vortex was in a quasi balanced state hence the temperature perturbation necessary to support the tangential velocity distribution was computed assuming gradient balance in the radial direction the resulting estimated temperature structure showed a warm core with a magnitude of 2 38c at 7 3 km msl and a cold core below 6 3 km msl the associated potential vorticity pv structure at the vortex center consisted of a lens of high pv with a maximum at 6 3 km msl and relative minima above and below this height

genesis of w mo mineralization in the xiaoliugou and ta ergou ore fields north qilian orogen nw china constraints from fluid inclusions and s pbhond isotopes abstract tungsten molybdenite w mo polymetallic mineralization are intensely developed in the western section of the north qilian orogen nw china represented by the xiaoliugou and ta ergou ore fields in this study fluid inclusion microthermometric and s pb h o nd isotopic analyses were conducted on the w mo ores to shed insights into the genesis of the mineralization belt the ore fields are characterized by abundant liquid vapor two phase inclusions which have medium high temperature salinity 200 320 c and 4 10 wt nacl equiv the consistent 18ov smow 7 7 to 13 1 and 2hv smow 88 1 to 49 4 values of quartz and muscovite indicate that the ore forming fluid originated from granitic intrusion but mixed with meteoric water typical 34s values of their sulfide ores range from 6 to 18 and the ore related granites 206pb 204pb 18 18 26 61 207pb 204pb 15 51 16 02 208pb 204pb 37 60 39 77 and sulfides 206pb 204pb 17 97 20 06 207pb 204pb 15 42 16 64 208pb 204pb 37 39 41 06 have variable pb pb ratios indicating both magmatic rocks and meta sedimentary rocks contributed to the mineralization the negative nd values end t 9 0 to 3 2 and old two stage nd model ages tdm2 1517 to 1901 ma of the scheelites suggest that the ore forming materials may have been derived from old crust together with the granitic magma an isochron age of 422 42 ma initial 143nd 144nd 0 511701 0 000046 has been yielded by the scheelite sm nd dating from the ta ergou ore field implying the 450 420 ma magmatic hydrothermal event resulted in the intense w mo mineralization in the north qilian especially in the western section of this orogen consequently we propose a multi metal coupled mineralization model to illustrate the mineralization process of the ore fields which involving the formation of ore source beds wall rocks in proterozoic and the intrusion of granites in early paleozoic this research highlights the use of multiple isotopic methods in revealing complex fluid evolutionary process of large scale w mo deposits

warm core vortex amplification over land abstract a convectively generated mesoscale vortex that was instrumental in initiating and organizing five successive mesoscale convective systems over a period of three days is documented two of these convective systems were especially intense and resulted in widespread heavy rain with localized flooding based upon radar and satellite data the detectable size of the vortex became much larger following the strong convective developments nearly tripling its initial diameter over its three day life cycle during nighttime when convection typically intensified within the vortex movement of the system tended to slow following dissipation of the convection in the morning the daytime movement accelerated cross sections of potential vorticity taken through the vortex center clearly show a maximum at midlevels and a well defined minimum directly above the vortex and the potential vorticity maximum were essentially colocated and the system was nearly axisymmetric in the vertical over the three day life

mechanisms for quasi stationary behavior in simulated heavy rain producing convective systems abstract in this study idealized numerical simulations are used to identify the processes responsible for initiating organizing and maintaining quasi stationary convective systems that produce locally extreme rainfall amounts of particular interest are those convective systems that have been observed to occur near mesoscale convective vortices mcvs and other midlevel circulations to simulate the lifting associated with such circulations a low level momentum forcing is applied to an initial state that is representative of observed extreme rain events the initial vertical wind profile includes a sharp reversal of the vertical wind shear with height indicative of observed low level jets deep moist convection initiates within the region of mesoscale lifting and the resulting convective system replicates many of the features of observed systems the low level thermodynamic environment is nearly saturated which is not conducive to the production of a strong surface cold pool yet the convection qui

patterns of precipitation and mesolow evolution in midlatitude mesoscale convective vortices abstract surface pressure manifestations of mesoscale convective vortices mcvs that traversed oklahoma during the periods may august 2002 05 are studied using the weather surveillance radar 1988 doppler wsr 88d the oklahoma mesonet and the noaa profiler network data forty five mcvs that developed from mesoscale convective systems mcss have been investigated 28 62 of which exhibit mesolows detectable at the surface within this group three distinct patterns of precipitation organization and associated mesolow evolution have been identified the remaining 17 38 of the cases do not contain a surface mesolow two repeating patterns of precipitation organization are identified for the latter group the three categories of mcvs possessing a surface mesolow are as follows nineteen are classified as rear inflow jet mcvs and tend to form within large and intense asymmetric mcss rear inflow into the mcs enhanced by the development of an mcv on the left hand side relative to system motion pro

failed cyclogenetic evolution of a west african monsoon perturbation observed during amma sop 3 abstract the so called perturbation d was a nondeveloping west african disturbance observed near dakar senegal during special observing period sop 3 of the african monsoon multidisciplinary analysis amma in september 2006 its mesoscale environment is described with the dropsonde data obtained during flights on three successive days with the service des avions francais instrumentes pour la recherche en environnement falcon 20 aircraft processes involved in this evolution are studied qualitatively with ecmwf reanalyses and meteosat 9 images the evolution of perturbation d was the result of an interaction between processes at different scales such as the african easterly jet aej a midtropospheric african easterly wave aew a series of mesoscale convective systems the monsoon flow dry low to midlevel anticyclonic saharan air and a midlatitude upper level trough the interaction between these processes is further investigated through a numerical simulation conducted with the french nonhydro

diurnal evolution and structure of long lived mesoscale convective vortices along the mei yu front over the east china plains abstractthe structure and diurnal evolution of long lived eastward propagating mesoscale convective vortices mcvs along typical summertime mei yu fronts over the east china plains are investigat

a numerical study of the genesis of extratropical convective mesovortices part i evolution and dynamics abstract the purpose of this study is to understand the genesis of extratropical convective mesovortices and the large scale environmental features that influence the vortex formation a hypothesis is proposed that mesovortices form in the stratiform rain regions of mesoscale convective systems mcss due to the reduction of static stability that reduces the effective local rossby radius in such regions a conceptual model of the mesoscale convective cyclogenesis is introduced which describes the three stages of the mesovortex formation a modified version of the pennsylvania state university national center for atmospheric research three dimensional hydrostatic mesoscale model is used to simulate mesovortex genesis in analytically generated pre mcs large scale environments the model simultaneously incorporates parameterized convection and a grid resolvable convective scheme containing the effects of hydrostatic water loading condensation evaporation freezing melting and sublimation a control si

doppler radar observations of an asymmetric mesoscale convective system and associated vortex couplet abstract a study of the 28 may 1985 asymmetric mesoscale convective system mcs observed during pre storm is presented dual doppler analysis revealed a well defined cyclonic mesovortex in the northern portion of the stratiform region in accord with previous studies on this type of circulation at maximum extent the closed cyclonic circulation had a diameter of approximately 80 km and a depth of 7 km a smaller anticyclonic circulation was present to the south of the cyclonic vortex counterrotating vortices in asymmetric mcss have been identified in recent modeling studies however prior to this study observational confirmation of the anticyclonic vortex has been elusive

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

regional and local variations in the composition of the wolframite series from sw japan and possible factors controlling compositional variations the regional and local variations in the composition of the wolframite series associated with the ilmeniteseries and magnetite series granitoids in the inner zone of sw japan were investigated using x ray diffraction and microprobe analyses it is concluded that the variation in mn fe ratios in the source materials granitic magmas in most cases is the dominant factor controlling the regional variation in the wolframite compositions while as exemplified by the kaneuchi mine kyoto prefecture the wallrock chemistry and ph of ore fluids are responsible for the local variation within a single vein system within a fresh euhedral crystal from the mine only slight compositional variation of less than 3 mole mnwo4 is found in the form of oscillatory zoning this study combined with the fluid inclusion research indicates that the wolframite compositions mn fe ratios cannot be used as a geothermometer

detection and prediction of warm season midtropospheric vortices by the rapid update cycle the authors perform a statistical and dynamical analysis of midtropospheric mesoscale vortices captured by analyses from the rapid update cycle version 2 ruc 2 during the period 1 may to 31 august 1999 a total of 203 vortices meeting conditions of an automated algorithm were found of these 86 were observed to form within organized convection and were termed mesoscale convective vortices mcvs mcvs were favored over a broad area from eastern colorado and western nebraska to the mississippi river valley essentially collocated with the loci of organized convection the remaining 117 vortices termed dry vortices clustered in the immediate lee of the rocky mountains and over the southeastern united states vortices arising from convection had considerably greater intensity and longevity than dry vortices they were roughly five times more likely to be involved with the triggering of new convection a relationship was found between intensity and longevity such that there appears to be a maximum vortex lifetime that can be estimated from its maximum intensity vortices arising from convection had markedly greater humidity and water vapor mixing ratio underneath their centers compared to dry vortices consistent with many dry vortices having a topographic origin and mcvs arising from organized convection parameters such as horizontal scale background vertical wind shear and horizontal deformation were not systematically related to intensity or longevity prediction of mesoscale vortices by the ruc 2 was examined for a subsample of all cases in general the ruc 2 was able to predict the evolution of vortices once analyzed but had virtually no skill at predicting 12 h in advance the formation of the vortices however forecasts of organized convection should still benefit from accurate predictions of long lived vortex tracks

case study of an intense african easterly wave abstract the life cycle of an intense african easterly wave aew over the african continent is examined using european centre for medium range weather forecasts ecmwf operational analyses meteosat satellite images and synoptic observations this system the strongest aew of 2000 can be tracked from central north africa into the eastern atlantic ocean where it is associated with the genesis of hurricane alberto synoptic analysis of the kinematic and thermodynamic fields is supplemented by analysis of potential vorticity pv allowing exploration at the role of multiple scales in the evolution of this aew the authors analysis promotes the division of the aew life cycle into three distinctive phases i initiation the aew development is preceded by a large convective event composed of several mesoscale convective systems over elevated terrain in sudan this convection provides a forcing on the baroclinically and barotropically unstable state that exists over tropical north africa ii baroclini

potential vorticity anomalies associated with squall lines abstract this study involves observations and model simulations of potential vorticity anomalies in the wake of midlatitude squall lines using data from the oklahoma kansas pre storm experiment we analyze potential vorticity fields near two squall lines one with and one without a trailing stratiform region from this observational analysis we suggest that squall lines with trailing stratiform regions can leave large positive midtropospheric potential vorticity anomalies in their wake to further interpret these observations we consider a two dimensional version of semigeostrophic theory formulated in isentropic and geostrophic coordinates which results in a simple potential pseudodensity inverse potential vorticity equation using apparent heat source fields that model those computed diagnostically from pre storm data we find that theory does indeed predict large midtropospheric potential vorticity anomalies for model squall lines with a trailing stratiform region but not for model squall lines t

wolframite solubility and precipitation in hydrothermal fluids insight from thermodynamic modeling abstract wolframite a solid solution series between hubnerite mnwo4 and ferberite fewo4 is the main tungsten bearing ore mineral in vein type tungsten deposits much progress has been made on characterizing the mineralizing fluids precipitating wolframite but it remains poorly understood what are the mechanisms depositing wolframite effectively and the variables controlling mn fe ratios in wolframite this study examines chemical controls on wolframite solubility in hydrothermal fluids and mn fe ratios in wolframite using thermodynamic models for fluids in the systems of w mn cl na o h and w fe cl na o h the fluid buffered models are established based on the characteristics of vein type tungsten deposits the modeling results indicate that solubilities of hubnerite and ferberite in hydrothermal fluids at typical w mineralizing conditions 300 400 c 500 1500 bars 5 15 wt nacl equivalent ph 4 6 reach up to hundreds of ppm the predominant tungsten manganese and iron species in fluids are h w o 4 m n c l 2 0 and f e c l 4 2 respectively an increase in ph and a decrease in fluid temperature and salinity are efficient mechanisms precipitating hubnerite and ferberite from acidic hydrothermal fluids hubnerite and ferberite are also significantly dissolved in alkaline hydrothermal fluids but their solubilities in alkaline fluids are insensitive to fluid temperature and salinity this may affect w mineralization at stages with different ph levels e g the greisen stage and the alkaline stage the mn fe ratio of mineralizing fluids is the principal variable controlling mn fe ratios in wolframite more supply of fe than mn from the fertile magma tends to produce fe rich mineralizing fluids this may be one of reasons why ferberite is more common than hubnerite in tungsten deposits and why hubnerite is more likely to precipitate at an early stage

long lived mesoconvective vortices and their environment part ii induced thermodynamic destabilization in idealized simulations abstract idealized numerical simulations are used to quantify the effect of quasi balanced lifting arising from the interaction of the ambient vertical shear with midtropospheric cyclonic vortices mcvs generated by mesoscale convective systems on thermodynamic destabilization over a range of ambient vertical shear strengths and vortex characteristics observed in part i maximum upward displacements occur beneath the midtropospheric potential vorticity anomaly near the radius of maximum tangential vortex winds the location of the region of upward displacements relative to the ambient vertical shear vector depends on the relative strength of the vortex tangential flow and the ambient vertical shear and ranges from downshear for vortices of moderate strength in strong ambient vertical shear to 90 to the left of downshear for strong vortices in weak ambient vertical shear although significant upward displacements occur most rapidly with small vortices in strong ambient vertical shear maximum upward di

imbalance in a mesoscale vortex within a midlatitude continental mesoscale convective system abstract the authors examine the degree of hydrostatic and gradient balances in a mesoscale convective vortex mcv in the stratiform region of a mesoscale convective system mcs that crossed oklahoma on 1 august 1996 results indicate that the mcv was partially unbalanced because the cool layer at the base of its core was too cool and too shallow to balance the tangential winds about the mcv s axis the apparent imbalance may have been due to strong unsteady forcing on the vortex insufficient or unrepresentative data approximations used in the analysis or reasons that are unknown

formation of long lived summertime mesoscale vortices over central east china semi idealized simulations based on a 14 year vortex statistic abstractregions around dabie mountain dbm in the yangtze river basin yrb are the source of a mesoscale vortex the dabie vortex dbv based on a 14 yr statistical study 11 long lived heavy rain producing dbvs were composited for convection permitting semi idealized simulations a control simulation initialized 12 h before the composite vortex formation successfully reproduced a dbv with all the salient characteristics of the 11 events sensitivity experiments were designed to understand the impacts of large scale environmental conditions regional topography and latent heating on dbv formation the main results were as follows i supposition of a 500 hpa shortwave trough with an east west oriented lower level transversal trough around the dbm is crucial for the formation of vortices a nocturnal lower level jet on the southern side of the transversal trough accelerates dbv formation by enhancing convergence triggering sustaining convection and producing cyclonic vorticity ii during the si

mesoscale convective vortex that causes tornado like vortices over the sea a potential risk to maritime traffic abstractstrong gusty winds in a weak maritime extratropical cyclone ec over the tsushima strait in the southwestern sea of japan capsized several fishing boats on 1 september 2015 a c band doppl

a mesoscale convective complex generated inertially stable warm core vortex abstract a long lived mesoscale convectively generated vortex mcv associated with a mesoscale convective complex mcc is documented the mcv with a rossby number of approximately 0 5 is investigated as a feature intrinsic to the organization of the mcc on 6 7 july 1982 a particularly large and intense mcc developed in a region of high convective available potential energy cape but weak vertical wind shear bulk richardson number 150 and weak advection of temperature and vorticity convection initially was organized in a narrow line with elements propagating relative to the mean environmental flow these elements subsequently developed a large semicircular area of stratiform precipitation and a surface mesolow to the rear heavy rain fell over a broad area amounts as great as 10 9 cm accompanied by flooding were reported in central oklahoma as the large semicircular rain area dissipated a three layered structure became evident a large upper tropospheric anticyclone a rain cooled mesoscale h

numerical simulation of the meso β scale structure and evolution of the 1977 johnstown flood part ii inertially stable warm core vortex and the mesoscale convective complex abstract a mesoscale warm core vortex associated with the mesoscale convective complex mcc that produced the 1977 johnstown flood is examined using a three dimensional nested grid model simulation of the flood episode in the simulation the vortex plays a key role in determining the evolution of the mcc a squall line and the distribution of heavy precipitation the vortex has a space scale of 100 200 km in diameter and a time scale of more than 18 hours its low pressure center extends from the midtroposphere down to the surface and its maximum vorticity occurs between 850 and 700 mb a pool of cool moist downdraft air develops in the surface to the 850 mb layer beneath the warm core while a cold dome forms in the vicinity of the tropopause above the warm core following forcing from repeated deep convection prior to model initial time the vortex is initiated by mesoscale ascent associated with a traveling meso scale wave genesis takes place in a nearly saturated slightly conditionally unstabl

a subtropical oceanic mesoscale convective vortex observed during sowmex timrex abstractthis study examines a subtropical oceanic mesoscale convective vortex mcv that occurred from 1800 utc 4 june to 1200 utc 6 june 2008 during intensive observing period iop 6 of the southwest monsoon experiment sowmex and the terrain influenced monsoon rainfall experiment timrex a dissipating mesoscale convective system reorganized within a nearly barotropic vorticity strip which formed as a southwesterly low level jet developed to the south of subsiding easterly flow over the southern taiwan strait a cyclonic circulation was revealed on the northern edge of the mesoscale rainband with a horizontal scale of 200 km an inner subvortex on a scale of 25 30 km with maximum shear vorticity of 3 10 3 s 1 was embedded in the stronger convection the vortex relative southerly flow helped create local potential instability favorable for downshear convection enhancement strong low level convergence suggests that stretching occurred within the mcv higher e air associated with significant pot

the formation of a cooling induced mesovortex in the trailing stratiform region of a midlatitude squall line abstract there have been some ambiguities in recent observational studies as to whether midlevel mesovortices are induced by latent heating or cooling and develop in the descending or ascending portion of mesoscale convective systems mcs s in this study a comprehensive examination of a cooling induced mesovortex in the trailing stratiform region of a midlatitude squall line that occurred on 10 11 june 1985 during the preliminary regional experiment for storm central pre storm is presented using a 20 h high resolution simulation of the squall system this cooling induced midlevel vortex originates from the preexisting cyclonic vorticity associated with a traveling meso scale short wave the vortex is intensified in the descending rear to front rtf inflow as a result of continued sublimative melting and evaporative cooling in the stratiform region it decouples from the front to rear ftr ascending and anticyclonic flow in the upper troposphere during the formative stage the vortex tilts northw

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

environment and early evolution of the 8 may 2009 derecho producing convective system abstractthis study documents the complex environment and early evolution of the remarkable derecho that traversed portions of the central united states on 8 may 2009 central to this study is the comparison of the 8 may 2009 derecho environment to that of other mesoscale convective systems mcss that occurred in the central united states during a similar time of year synoptic scale forcing was weak and thermodynamic instability was limited during the development of the initial convection but several mesoscale features of the environment appeared to contribute to initiation and upscale growth including a mountain wave a midlevel jet streak a weak midlevel vorticity maximum a denver cyclone and a region of upper tropospheric inertial instability the subsequent mcs developed in an environment with an unusually strong and deep low level jet llj which transported exceptionally high amounts of low level moisture northward very rapidly destabilized the lower troposphere and enhanced frontogenetica

surface cyclogenesis from convectively driven amplification of midlevel mesoscale convective vortices mesoscale convective vortices mcvs are midtropospheric warm core cyclonic circulations that often develop in the stratiform region of mesoscale convective systems typically divergent anticyclonically circulating mesoscale cold anomalies appear both above and below the mcv the upper level cold anomaly is usually found near the tropopause while the low level anomaly is surface based and exhibits locally higher pressure one aspect of mcvs that has received much attention recently is the role that they may play in tropical cyclogenesis of special interest is how an mcv amplifies when deep convection redevelops within the borders of its midlevel cyclonic circulation and how the amplified mcv transforms the divergent surface based cold pool with anomalously high surface pressure into a convergent cyclonic circulation with anomalously low pressure the pennsylvania state university national center for atmospheric research fifth generation mesoscale model is used to simulate an mcv that was instrumental in initiating within the borders of the midlevel vortex s circulation several successive cycles of convective development and decay over a 2 day period after each cycle of convection both the horizontal size of the cyclonic circulation and the magnitude of the potential vorticity associated with the vortex were observed to increase the simulation reproduces the development and evolution of the mcv and associated convective cycles mesoscale features responsible for the initiation of convection within the circulation of the vortex and the impact of this convection on the structure and evolution of the vortex are investigated a conceptual model is presented to explain how convective redevelopment within the mcv causes low level heights to fall and cyclonic vorticity to grow downward to the surface applying this conceptual model to a tropical marine environment is also considered

mesoscale convective vortices observed during bamex part ii influences on secondary deep convection abstract observations from the bow echo and mesoscale convective vortex mcv experiment are used to examine the role of the five mesoscale convective vortices described in part i on heavy precipitation during the daytime heating cycle persistent widespread stratiform rain without deep convection occurs for two strong mcvs in conditionally stable environments with strong vertical shear two other mcvs in moderate to strong vertical shear have localized redevelopment of deep convection termed secondary convection on their downshear side where conditional instability exists the strongest of the five mcvs occurs in weak vertical shear and has widespread secondary convection which is most intense on its conditionally unstable southeast periphery the two mcvs with only localized secondary convection have well defined mesoscale vertical motion couplets with downshear ascent and upshear descent above the planetary boundary layer pbl although the amplitude is significantly greater the kinematically der

ore forming mechanism of quartz vein type w sn deposits of the xitian district in se china implications from the trace element analysis of wolframite and investigation of fluid inclusions abstract the xitian w sn district is located in eastern hunan province of se china and comprises the heshuxia goudalan and longshang w sn deposits our study on the occurrence mineral assemblage and geochemistry of the orebodies shows that quartz vein orebodies are dominant mode of mineralization and can be divided into three stages stage i quartz molybdenite wolframite i stage ii quartz wolframite ii polymetallic sulfides and stage iii quartz pyrite fluorite the elements nb ta sc sn zn cr v mo cu and zr are abundant in both wolframite i and wolframite ii wolframite i contains higher concentrations of nb 1408 9245 ppm ta 241 2407 ppm and sc 123 521 ppm than wolframite ii nb 144 1080 ppm ta 3 76 315 ppm and sc 1 86 11 44 ppm these results indicate that wolframite i was formed closer to the host rock and at a greater ore forming depth than wolframite ii the total ree concentrations of wolframite i and ii range from 34 96 to 133 36 ppm and 21 30 to 43 73 ppm respectively both wolframite i and wolframite ii have low lree concentrations 0 00 0 05 and 0 08 8 18 ppm respectively and high hree concentrations 34 96 133 31 and 21 23 41 87 ppm respectively the enrichment of hrees in wolframite may be due to the fact that the sizes of the hrees3 0 94 1 02 a in combination with nb5 or ta5 0 72 a are closer to that of w6 0 68 a in combination with ca2 1 08 a or mg2 0 80 a than that of the lrees3 1 03 1 13 a making the coupled substitution easier a study of fluid inclusions in the coexisting gangue minerals shows that the homogenization temperatures of the fluid inclusions decrease from stage i to stage iii stage i 187 382 c average 275 c stage ii 122 278 c average 175 c stage iii 92 172 c average 139 c whereas the salinities of the fluid inclusions increase from stages i to ii and decrease from stages ii to iii stage i 1 8 18 2 wt nacleqv average 10 3 wt nacleqv stage ii 7 3 24 4 wt nacleqv average 14 9 wt nacleqv stage iii 0 2 5 3 wt nacleqv average 1 5 wt nacleqv raman spectroscopy reveals that the fluid inclusions mainly contain h2o co2 is minor and h2s ch4 and n2 are rare we conclude that the formation of wolframite was driven by post magmatic thermodynamic processes the ore forming fluid flowed through a multi fractured low pressure zone in the fault system in the district and a temperature pressure decrease led to fluid immiscibility characterized by co2 escaping in a low ph and high eh environment in stage i crust mantle mixed fluid and meteoric water mixing in stage ii and natural cooling of the fluid system in stage iii

circulations associated with a mature to decaying midlatitude mesoscale convective system part ii upper level features abstract the vertical structure of a midtropospheric mesovortex that developed during the decay of a midlatitude mesoscale convective system over kansas and oklahoma on 23 24 june 1985 is documented surface rawinsonde wind profiler and dual doppler data are used to define its structure as has been observed in other midlatitude and tropical cases the mesovortex occurred within the trailing stratiform precipitation region of a squall line system it was associated with a preexisting synoptic scale short wave trough and as the circulation developed it deformed the back edge of the stratiform precipitation region into a hooklike pattern the 100 200 km mesovortex was confined to the midtroposphere 3 8 km with a maximum amplitude just above the 0 c level the vortex axis sloped toward the northeast but its orientation changed hour by hour over the 2 h period of dual doppler coverage overall the mesovortex was warm core although its thermal structure was complex and apparently significantly infl

midlevel cyclonic vortices generated by mesoseale convective systems abstract despite the large number of convective systems that occur over the central united states every year there are typically only a few well defined midlevel vortices apparent in satellite imagery after the overlying anvil debris from some convective complexes has dissipated or advected away a climatology of mesoscale convectively generated vortex mcv events for 1981 1988 is presented and the synoptic setting in which the circulation becomes apparent is discussed proximity sounding data from numerous cases are used to examine features of the kinematic and thermodynamic setting of mcvs at various lifelycle stages defined by satellite imagery features ofthe large scale environment that appear conducive to the formation and longevity of mcvs include weak flow weak vertical shear weak background relative vorticity and intense horizontal and vertical moisture gradients the rapid mesovortex generation observed can be explained by the stretching term of the vorticity equation most mcvs emerge fro

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

moist surface frontogenesis associated with interior potential vorticity anomalies in a semigeostrophic model abstract we previously examined surface frontogenesis as an initial value problem in a dry inviscid semigeostrophic eady model focusing on the frontal dynamics associated with interior potential vorticity anomalies this work explores frontogenesis associated with potential vorticity anomalies in the presence of latent heat release using a generalization of the two dimensional semigeostrophic eady model that insures that the heating term gives correct asymptotic behavior at high and low temperatures a variety of initial conditions are considered in which upper level potential vorticity disturbances induce strong positive potential vorticity anomalies near the lower surface with uniform interior potential vorticity baroclinic coupling between the upper and surface induced disturbance is weak despite a near neutral moist stability on the other hand examples of initial disturbances with interior potential vorticity show greatly enhanced baroclinic coupling between upper and lower disturbances comparis

development of an intense warm core mesoscale vortex associated with the 8 may 2009 super derecho convective event abstractin this study the dynamical processes contributing to warm core meso scale vortex formation associated with the 8 may 2009 super derecho are examined utilizing two complementary quasi lagrangian approaches a circulation budget and backward trajectory analyses applied to a fortuitous numerical simulation of the event warm core meso scale vortex formation occurs in a deeply moist potentially stable environment that is conducive to the development of near surface rotation and is somewhat atypical compared to known derecho supporting environments air parcels in the vicinity of the developing vortex primarily originate near the surface in the streamwise vorticity rich environment associated with the vertical wind shear of the low level jet immediately to the east of the eastward moving system cyclonic vertical vorticity is generated along inflowing air parcels primarily by the ascent induced tilting of streamwise vorticity and amplified primarily by ascent induced vortex tube stretching de

a midlatitude squall line with a trailing region of stratiform rain radar and satellite observations abstract a squall line exhibiting an extensive trailing region of stratiform precipitation passed over the observational network of the national severe storms laboratory on 22 may 1976 satellite imagery and conventional radar observations document its evolution from a broken line of thunderstorms to a system of mesoscale proportions and single doppler radar observations describe aspects of its mature structure satellite measurements of cloud top temperature showed the system to be a mesoscale convective complex mcc the life cycle of the system exhibited the stages of development seen in tropical cloud clusters at maturity two prominent mesoscale flow regimes were identified at midlevels one marked by inflow into the system s front and continuing toward its rear and another associated with inflow entering the extreme rear of the system the rear inflow was associated with a cyclonic midlevel vortex in the stratiform precipitation region it produced a concavity or notch in the back edge of th

formative stage of a long lived mesoscale vortex observed by airborne doppler radar abstract the formative stage of a long lived mesoscale cyclonic vortex was captured by the noaa p 3 aircraft as it investigated a developing mesoscale convective system mcs near the southeastern coast of taiwan on 16 june 1987 during the taiwan area mesoscale experiment the supporting environment of the mesovortex was characterized by an exceptionally moist atmosphere and moderate ambient vertical shear through a deep layer from the near surface to 6 km with much weaker shear and winds aloft in addition a pronounced low level mesoscale shear convergence zone which resulted from the interaction of southeasterly flow with northeasterly flow confined to the near coast region existed in the vicinity of the observed mesovortex composite three dimensional wind fields derived via pseudo dual doppler synthesis show the vortex had a horizontal diameter expanding from 40 km to 70 km in the lower to midtroposphere respectively and exhibited considerable tilt through this layer contrary to previously d

the kinematics of a midlatitude continental mesoscale convective system and its mesoscale vortex the authors present a unique scale discriminating study of the environment relative circulations within a mesoscale convective system mcs and mesoscale convective vortex mcv the mcs a leading convective line and trailing stratiform region that became asymmetric passed through the national oceanic and atmospheric administration noaa profiler network npn in kansas and oklahoma on 1 august 1996 the mcv appeared in the mcs s stratiform region just prior to the system s mature stage and grew to a depth of over 12 km as the mcs dissipated the mcv did not apparently survive to the next day a spatial bandpass filter was used to divide observed wind into a component that was predominantly synoptic background wind and a component that was predominantly a mesoscale perturbation on that background wind a mesoscale updraft mesoscale downdraft and divergent outflows in the lower and upper troposphere were evident after the synoptic background wind was removed so these four circulations were internal and fundamental to the mcs the mesoscale perturbation in wind in the middle troposphere extended farther behind the mcs than ahead of it consistent with analytic studies and numerical simulations of gravity waves generated by heat sources characteristic of mcss with leading convective lines and trailing stratiform regions deepening of the mcv appeared to be reflected in the vertical wind shear at the vortex s center as the mcv strengthened the mesoscale shear through its lower part decreased perhaps as wind became more vortical at increasing altitudes mesoscale and synoptic vertical shears were of similar magnitude so an average of environmental soundings outside an mcs probably does not accurately represent the shear that affects an mcv this suggests the need to reevaluate how the kinematical settings of mcvs are diagnosed

architectural elements and bounding surfaces in fluvial deposits anatomy of the kayenta formation lower jurassic southwest colorado abstract three well exposed outcrops in the kayenta formation lower jurassic near dove creek in southwestern colorado were studied using lateral profiles in order to test recent regarding architectural element analysis and the classification and interpretation of internal bounding surfaces examination of bounding surfaces within and between elements in the kayenta outcrops raises problems in applying the three fold classification of allen 1983 enlarging this classification to a six fold hierarchy permits the discrimination of surfaces intermediate between allen s second and third order types corresponding to the upper bounding surfaces of macroforms and internal erosional reactivation surfaces within the macroforms examples of the first five types of surface occur in the kayenta outcrops at dove creek the new classifications is offered as a general solution to the problem of description of complex three dimensional fluvial sandstone bodies the kayenta formation at dove creek consists of a multistorey sandstone body including the deposits of lateral and downstream accreted macroforms the storeys show no internal cyclicity neither within individual elements nor through the overall vertical thickness of the formation low paleocurrent variance indicates low sinuosity flow whereas macroform geometry and orientation suggest low to moderate sinuosity the many internal minor erosion surfaces draped with mud and followed by intraclast breccias imply frequent rapid stage fluctuation consistent with variable seasonal monsonal ephemmeral flow the results suggest a fluvial architecture similar to that of the south saskatchewan river through with a three dimensional geometry unlike that interpreted from surface studies of that river

mesoscale convective vortices observed during bamex part i kinematic and thermodynamic structure abstract five cases of mesoscale convective vortices mcvs are described from observations collected during the bow echo and mcv experiment bamex over the central united states during the period from 20 may to 6 july 2003 in the present paper the kinematic and thermodynamic structure of each vortex and its environment are emphasized data consist of bamex dropsondes the national oceanic and atmospheric administration profiler network and national weather service soundings in addition weather surveillance radar 1988 doppler observations documented the signatures of nascent mcvs within nocturnal convection systems as well as the spatial pattern of convection within mcvs during the following day the vertical structure of each vortex was highly dependent on the vertical shear and the presence of upper tropospheric cyclonic vorticity anomalies in strong shear a pronounced downshear tilt of the vortex was evident but with the presence of an upper tropospheric trough the tilt was upshear in the upp

baroclinic transition of a long lived mesoscale convective vortex abstract the period 5 15 june 2003 during the field phase of the bow echo and mesoscale convective vortex mcv experiment bamex was noteworthy for the wide variety of mesoscale convective systems mcss that occurred of particular interest was a long lived mcv that formed in the trailing stratiform region of an mcs over west texas at 0600 utc 10 june this mcv was noteworthy for its i longevity as it can be tracked from 0600 utc 10 june to 1200 utc 14 june ii development of a surface cyclonic circulation and attendant 2 to 4 hpa sea level pressure perturbation iii ability to retrigger convection and produce widespread rains over several diurnal heating cycles and iv transition into a baroclinic surface cyclone with distinct frontal features baroclinic transition defined here as the acquisition of surface fronts occurred as the mcv interacted with a remnant cold front left behind by a predecessor extratropical cyclone over the great lakes region although the mcv developed well def

influence of balanced motions on heavy precipitation within a long lived convectively generated vortex abstract the forcing of heavy precipitation within a long lived convectively generated mesoscale vortex mcv is investigated with the aid of diagnoses from rapid update cycle gridded analyses organized convection within the mcv followed a distinct diurnal cycle which featured organized mesoscale convective systems mcss that matured overnight near the mcv center on successive days the mcv was typically most intense in the middle troposphere but intensified within the lower troposphere during the episodes of organized nocturnal convection the lower tropospheric vertical shear was an important organizing factor in mcs development and sustenance in the sense that its interaction with the cold temperature anomaly beneath the mcv center determined where balanced lower tropospheric ascent occurred from trajectory analyses we estimate that balanced ascent accounted for approximately half of the total vertical displacement of the thermodynamically unstable air that eventually composed elevated saturated

mesoscale organization of springtime rainstorms in oklahoma abstract radar reflectivity and raingage data obtained during six springtimes indicate the types of mesoscale organization that occur in association with major rain events in oklahoma at least 25 mm of rain in 24 h over an area exceeding 12 500 km2 in these storms the primary rain area is found to be a contiguous region of precipitation 10s to 100s of km in scale that consists partly of deep convection and partly of stratiform rain the patterns of rain formed by the convective and stratiform areas comprise a continuous spectrum of mesoscale structures about two thirds of the cases examined exhibited variations on the type of organization in which convective cells arranged in a moving line are followed by a region of stratiform rain storm organization was graded according to the degree to which it matched an idealized model of this leading line trailing stratiform structure the precipitation pattern was further graded according to whether its structure was relatively symmetric with respect to an a

genesis and development of spring rainstorms in northern southeast asia southwest china northern indochina and the northern south china sea abstractduring may and june the monsoon rainfall in northern southeast asia is primarily produced by rainstorms at the mature stage these storms coupled with a midtropospheric subsynoptic scale trough produce rainfall 50 mm 6 h 1 and exhibit a cyclonic surface vortex with a scale o 102 km rainstorms during the period of 1979 2016 are identified with station and satellite observations along with assimilation data several dynamic processes of rainstorm geneses are disclosed by an extensive analysis 1 maximum occurrence of rainstorm geneses is located in the midtroposphere of two regions northern vietnam southwestern china and the northern south china sea but eventually penetrates downward to the surface 2 the environment favorable for rainstorm genesis is a southwest northeast oriented narrow trough formed by the confluence of the midtropospheric northeasterly around the eastern tibetan plateau and the lower tropospheric monsoon southwesterlies because the criterion for charney stern i

high winds generated by bow echoes part ii the relationship between the mesovortices and damaging straight line winds airborne radar analysis of a mesovortex that developed near the apex of a bow echo is presented the mesovortex was shown to play a critical role in determining the location of intense straight line wind damage at the surface the perturbation pressure gradient force in natural coordinates along the parcel path accelerated the horizontal winds however intense mesovortices modified the low level outflow and largely determined the locations where the strongest winds occurred regions of maximum winds are accounted for as a superposition of the vortex and the flow in which it is embedded the strongest winds occur on the side of the vortex where translation and rotation effects are in the same direction this model explains the observed tongue of high wind speeds that were confined to the periphery of the mesovortex the origin of the mesovortex is also examined similarities and differences of this bow echo event with recent modeling studies are presented

three dimensional evolution of simulated long lived squall lines abstract simulations of squall lines using nonhydrostatic convection resolving models have been limited to two dimensions or three dimensions with the assumption of along line periodicity the authors present 3d nonhydrostatic convection resolving simulations produced using an adaptive grid model where the lines are finite in length and the restriction to along line periodicity is removed the base state for the simulations is characterized by weak shallow shear and high convective available potential energy cape an environment in which longlived midlatitude mesoscale convective systems mcss are observed the simulated systems bear strong resemblance to many observed systems suggesting that large scale forcing absent in the horizontally homogeneous environment is not needed to produce many of the distinguishing features of midlatitude mcss in simulations without coriolis forcing the presence of line ends leads to mature symmetric systems characterized by a central region of strong convectio

modeled and observed variations in storm divergence and stratiform rain production in southeastern texas abstractstorm divergence profiles observed by an s band doppler radar are compared to ensemble simulations of 10 disparate precipitating systems occurring in warm season weakly baroclinic and strongly baroclinic environments in southeastern texas eight triply nested mesoscale model simulations are conducted for each case using single and double moment microphysics with four convective treatments i e two convective parameterizations and explicit versus parameterized convection at 9 km observed and simulated radar reflectivities are objectively separated into convective stratiform and nonprecipitating anvil columns and comparisons are made between ensemble mean echo coverages and levels of nondivergence lnds in both the model and observations storms occurring in less baroclinic environments have more convective rain area less stratiform rain area and more elevated divergence profiles the model ensemble and observations agree best for well organized leading line trailing stratiform systems

evolution and structure of the 6 7 may 1985 mesoscale convective system and associated vortex abstract observations collected during the oklahoma kansas pre storm experiment are used to document the evolution and structure of the mesoscale convective system mcs that occurred on 6 7 may 1985 the storm began when a short squall line developed in an area of preexisting thunderstorm activity thunderstorm updrafts along the squall line lifted warm moist air with its southerly momentum to the upper troposphere a broad region of convective outflow and a meso scale updraft region with a mean vertical velocity in excess of 15 10 3 mb s 1 were created a stratiform rain area with an embedded mesovortex formed behind the squall line the vortex resided beneath the deepest upper level outflow the mesovortex altered the wind field and consequently became the principal organizational feature within the mcs a descending current from the storm s rear that depending on location extended from 1 km to the upper troposphere was intensified and focused by the vortex the descending rear inflow had a peak

cloud resolving simulations of mesoscale vortex intensification and its effect on a serial mesoscale convective system abstract the authors performed numerical simulations of the 27 28 may 1998 mesoscale convective vortex mcv and mesoscale convective system mcs to understand how the mcv modulated the convection and how the convection intensified the vortex the fifth generation pennsylvania state university national center for atmospheric research psu ncar mesoscale model mm5 was used initialized with the analysis from the rapid update cycle version 2 ruc 2 and nested to achieve 1 5 km grid spacing covering the mcs the model successfully simulated a north south convective band that formed near the center of the mcv in the early evening the simulation then correctly reoriented the convection along a roughly east west line in response to northward transport of warm conditionally unstable air within the nocturnal low level jet balanced vertical motion was found to contribute substantially to mesoscale lifting and thermodynamic destabilization which localized the convection horizontal transport of moist uns

genetic types mineralization styles and geodynamic settings of mesozoic tungsten deposits in south china abstract south china hosts the most abundant and largest tungsten w deposits in the world being a famous w metallogenic region located at the eastern part of the south china block which was formed by amalgamation of the yangtze and cathaysia blocks during the neoproterozoic these w deposits were mainly formed during the mesozoic the w mineralization is dominanted by greisen quartz vein skarn and porphyry types all of which are genetically related to the evolution of highly fractionated granitoids four episodes of w mineralization are recognized 1 late triassic 230 210 ma in the central and western parts of south china 2 middle jurassic ca 170 ma to early cretaceous ca 140 ma in the interior of south china with the mineralization being concentrated in southern jiangxi province between 165 and 150 ma 3 early cretaceous 136 120 ma with deposits across south china and 4 late cretaceous 100 80 ma mainly in the southwestern parts of south china these four periods of mineralization are closely related to the closure of paleo tethys and subduction of the paleo pacific plate in the late triassic these two events caused local extensional environments facilitating emplacement of the peraluminous granitoids and formation of the w deposits in the middle jurassic break off of the subducting oceanic plate resulted in emplacement of highly fractionated granites in the nanling region later anticlockwise rotation of the paleo pacific plate created widespread s type granitoids and associated middle jurassic to early cretaceous w mineralization in the interior of south china since 136 ma rollback of the subducting pacific plate resulted in weak w mineralization across south china finally a change of direction in the retreating plate from se to ese resulted in intensive mineralization of the southwestern part of south china

mesoscale convective vortex formation in a weakly sheared moist neutral environment abstract idealized simulations of a diabatic rossby vortex drv in an initially moist neutral baroclinic environment are performed using the fifth generation national center for atmospheric research pennsylvania state university ncar psu mesoscale model mm5 the primary objective is to test the hypothesis that the formation and maintenance of midlatitude warm season mesoscale convective vortices mcvs are largely influenced by balanced flow dynamics associated with a vortex that interacts with weak vertical shear as a part of this objective the simulated drv is placed within the context of the bow echo and mesoscale convective vortex experiment bamex field campaign by comparing its tangential velocity radius of maximum winds cape and shear with the mcvs observed in bamex the simulations reveal two distinct scales of development at the larger scale the most rapidly growing moist baroclinic mode is excited and exponential growth of this mode occurs during the simulation embedded within the

baroclinic instability in an environment of small stability to slantwise moist convection part i two dimensional models abstract in the semigeostrophic system the growth rate of baroclinic waves varies with the inverse square root of the potential vorticity which acts as the effective static stability recent observations in the ascent regions of middle latitude cyclones show that the effective potential vorticity for saturated air is very near zero in this paper we examine the structure and rate of growth of baroclinic cyclones when the effective potential vorticity is small for upward saturated displacements but large in regions of descent analytic solutions for two dimensional disturbances in a two layer semigeostrophic model and numerical simulations using a multilevel semigeostrophic model show that when the effective potential vorticity is small in regions of upward motion growth rates are modestly increased and the region of ascent intensifies and collapses onto a thin ascending sheet in the limit of zero moist potential vorticity the fastest growing wave has a finite growth rate which is about 2 5 times the