stratospheric gravity waves generated by multiscale tropical convection abstract the generation of gravity waves by multiscale cloud systems evolving in an initially motionless and thermodynamically uniform environment is explored using a two dimensional cloud system resolving model the simulated convection has similar depth and intensity to observed tropical oceanic systems the convection self organizes into preferred horizontal and temporal scales involving weakly organized propagating cloud clusters the multiscale systems generate a broad spectrum of gravity waves with horizontal scales that range from the cloud system scale up to the cloud cluster scale the gravity waves with the largest horizontal scale play an important role in modifying layered tropospheric inflow and outflow to the cloud systems which in turn influence the multiscale convective organization slower moving short scale gravity waves make the strongest individual contribution to the vertical flux of horizontal momentum and cause a robust peak in the momentum flux spectrum that corresponds to the lif

the nature and genesis of gold silver tellurium mineralization in the metaliferi mountains of western romania precious metal au ag and base metal pb zn deposits in the metaliferi mountains of western romania occur in steeply clipping quartz ca mn carbonate veins which are hosted by miocene andesitic stocks and lava flows and surrounding sedimentary rocks the deposits consist predominantly of sulfides pyrite chalcopyrite sphalerite galena sulfosalts of as and sb and a diverse range of au ag tellurides the igneous host rocks have undergone mild pervasive propylitic alteration whereas immediately adjacent to the veins the wall rock alteration assemblages consist of quartz sericite k feldspar calcite and pyrite fluid inclusion stable isotope and thermodynamic data suggest that the majority of the mineralization and hydrothermal alteration in these deposits was caused by loci salinity 0 5 wt nacl equiv medium temperature 200 degrees 300 degrees c near neutral ph 5 6 fluids which underwent occasional boiling the fluid inclusion and stable isotope data support a model in which a metal bearing magmatic fluid was exsolved from a crystallizing calc alkaline melt and ascended to higher levels in the crust undergoing some isotopic exchange with surrounding sedimentary rocks but limited mixing with ground waters although the deposits in this part of the romanian carpathians exhibit many of the geologic characteristics of classic low sulfidation volcanic hosted au ag epithermal deposits they seem to have formed from essentially magmatic waters and there is little evidence for the incorporation of meteoric fluids into the hydrothermal system

momentum and mass transport by convective bands comparisons of highly idealized dynamical models to observations the importance of the vertical transport of horizontal momentum by convective clouds has been documented in studies of momentum budgets e g shapiro and stevens 1980 sui and yanai 1986 furthermore it is obvious that the boundary layer wind itself and hence surface heat moisture and momentum transports is affected by deep convection most of the airsea transfer in tropics is concentrated in regions with deep convection

role of basement in epithermal deposits the kushikino and hishikari gold deposits southwestern japan abstract the magma ore deposit relationship of most low sulfidation epithermal ore deposits is still unclear partly because many stable isotopic studies of such deposits have indicated the predominance of meteoric waters within hydrothermal fluids however it is certainly true that hydrothermal systems are ultimately driven by magmatic intrusions and epithermal gold deposits might therefore be produced by magmatic activity even in deposits having has no obvious links to a magma we re examine the genesis of two typical low sulfidation epithermal gold deposits the kushikino and hishikari deposits using structural simulations and isotope data many epithermal gold deposits including the kushikino and hishikari deposits have been discovered in kyushu southwestern japan the kushikino deposit comprises fissure filling veins within neogene andesitic volcanics that overlie unconformably cretaceous sedimentary basement the veins consist of gold and silver bearing quartz and calcite with minor amounts of adularia sericite and sulfides although carbon and oxygen isotopic data for the veins indicate a meteoric origin of the ore fluid finite element simulations suggest that the vein system might have formed in direct response to magma intrusion in particular geophysical data suggest that intruding magma has uplifted the basement rocks thereby producing fractures and veins and a positive bouguer anomaly and providing the heat necessary to drive an ore forming hydrothermal system the second component of this study has been to investigate the nature and evolution of the kushikino and hishikari epithermal systems isotope data document the geochemical evolution of the hydrothermal fluids we conclude that the existence of sedimentary basement rocks at depth might have affected the strontium and carbon isotopic ratios of the kushikino and hishikari ore fluids the 87 sr 86 sr ratios and 13 c 18 o trend reveal that major ore veins in the hishikari deposit can be distinguished from shallow barren veins it was suggested isotopically that fluids responsible for the barren veins in nearby shallow and barren circulation systems were only controlled by the shallow host rocks such multi isotope systematics provide a powerful tool with which to determine the center of hydrothermal activity and thereby document the evolution of hydrothermal fluids

a numerical study of three dimensional gravity waves triggered by deep tropical convection and their role in the dynamics of the qbo abstract a 3d mesoscale model is used to study the structure of convectively triggered gravity waves in the tropics and their role in the dynamics of the middle atmosphere simulations with three stratospheric background zonal wind cases are examined in the first case the background wind profile is constant the other two are representative of the easterly and westerly phases of the quasi biennial oscillation qbo spectral analysis is used to link the structure of the triggered gravity waves to the dominant vertical wavelength of the latent heating within the convection in the qbo wind shear cases upward propagating gravity waves are damped as they approach their critical layer the signature of critical layer absorption is clearly visible in the profiles of vertical momentum flux divergence in the simulations with open boundary conditions the response to vertical momentum flux divergence takes the form of large dynamic pressure differences between the east and west boundaries together with acceler

effects of tropospheric wind shear on the spectrum of convectively generated gravity waves abstract the authors examine the effects of tropospheric wind shear on the phase speed spectrum of gravity waves generated by tropical convection a two dimensional cloud resolving model is used to perform numerous squall line simulations with the vertical shear of the horizontal wind varied in three layers of the troposphere several simplified simulations using prescribed heating are also performed to elucidate the interactions of wind shear with thermal forcing it is found that the dominant phase speed range of convectively generated stratospheric gravity waves is primarily determined by the vertical scale of the tropospheric heating and is then modified by the tropospheric wind the gravity wave spectrum is especially sensitive to shear in the upper troposphere through a mechanism similar to critical level filtering such shear acts to reduce the momentum flux of waves propagating in the same direction as the storm relative mean wind through interaction with convective turrets shear in the upper t

large scale organization of tropical convection in two dimensional explicit numerical simulations the large scale organization of tropical deep convection is investigated in idealized two dimensional cloud resolving simulations a 20 000 km periodic computational domain allows interactions among moist convection mesoscale organization and surface exchange on a wide range of scales a uniform 10 m s 1 easterly wind and a uniform sea surface temperature of 30 c are assumed a prescribed temperature tendency mimicking the mean radiative cooling of the tropical troposphere is used in this pilot study the large scale organization of convection resembles the observed tropical atmosphere as well as results from some previous numerical studies using parametrized convection the simulation highlights mesoscale convective systems with horizontal scales of several hundred kilometres moving east to west with speeds similar to the mean flow and an envelope of convection with a horizontal extent of a few thousand kilometres and propagating west to east the propagation speed of the large scale envelope compares well with the phase velocitites of convectively coupled kelvin waves observed in the equatorial waveguide convective momentum transport and the impact of convective systems on temperature and moisture near the surface are key processes responsible for the large scale organization of convection these results are discussed in the context of recent observations and numerical studies of convection organization in the tropics

organizational modes of midlatitude mesoscale convective systems this paper discusses common modes of mesoscale convective organization using 2 km national composite reflectivity data the authors investigated linear mesoscale convective systems mcss that occurred in the central united states during may 1996 and may 1997 based upon the radar observed characteristics of 88 linear mcss the authors propose a new taxonomy comprising convective lines with trailing ts leading ls and parallel ps stratiform precipitation while the ts archetype was found to be the dominant mode of linear mcs organization the ls and ps archetypes composed nearly 40 of the studied population in this paper the authors document the characteristics of each linear mcs class and use operational surface and upper air data to describe their different environments in particular wind profiler data reveal that the stratiform precipitation arrangement associated with each class was roughly consistent with the advection of hydrometeors implied by the mean middle and upper tropospheric storm relative winds which were significantly different among the three mcs modes case study examples are presented for both the ls and ps classes which have received relatively little attention to this point as well the authors give a general overview of the synoptic scale meteorology accompanying linear mcss in this study which was generally similar to that observed by previous investigators

small scale variations of 87 sr 86 sr isotope composition of barite in the madjarovo low sulphidation epithermal system se bulgaria implications for sources of sr fluid fluxes and pathways of the ore forming fluids the madjarovo ore district is located in the volcanic rocks of the oligocene madjarovo shield volcano and underlying precambrian and palaeozoic high grade metamorphic rocks of the rhodope massif bulgaria it is situated in the eastern part of a large tertiary magmatic metallogenic belt which resulted from the cretaceous collision of serbo macedonian and rhodope massifs with the pelagonian microplate the low sulphidation base and precious metal mineralisation at madjarovo 32 1 ma formed shortly after the cessation of the shoshonitic and high k calc alkaline volcanic and intrusive activity 32 6 32 2 ma and is spatially and temporally related to late monzonite trachyte intrusions the strontium isotope composition of five barite samples hosted in the volcanic sequence is used to characterise the source s of sr in associated base and precious metal mineralisation and to infer fluid fluxes and pathways of the ore forming fluids the 87sr 86sr compositions for barite samples from ore veins fall in the range 0 70854 0 70955 with the lowest and highest values found in the smaller brecciated veins barite from a thin vein in the basal latite lava flow has the most radiogenic 87sr 86sr isotope composition likely reflecting the involvement of more radiogenic metamorphic basement rocks the least radiogenic composition was determined for barite from a similar vein high in the volcanic pile 500 600 m above the metamorphic basement barites from large veins taken from different stratigraphic positions in the host lavas have almost identical isotopic compositions in the range 0 70883 0 70899 the 87sr 86sr values for barite within the deposit are higher than those for host magmatic rocks 0 70775 0 70863 but lower than those of the metamorphic basement 0 7110 0 7278 it is concluded that strontium in the fluids is a mixture of predominantly magmatic strontium and a variable amount of more radiogenic sr from the metamorphic basement rocks the ore bearing fluid may have been derived from a shallow 1 4 km silicic pluton with an initial 87sr 86sr value 0 7080 because of the short distance to the site of deposition the fault focused ore fluids maintained homogeneous strontium predominantly magmatic strontium isotope ratios with slight contribution s of more radiogenic strontium from the metamorphic basement rocks larger variations in the small brecciated veins can be explained by more extensive fluid rock interaction with local host metamorphic or volcanic rocks

effects of vertical wind shear on the cumulus transport of momentum observations and parameterization abstract dynamical effects of organized cumulus convection on its environment with vertical wind shear are studied analyses of the wind field and momentum budget residual for mesoscale convective systems observed during sesame and pre storm reveal systematic differences in the vertical transport of horizontal momentum between mesoscale convective complex mcc and squall line cases in the mcc a distinct minimum in wind speed appears over the area of intense convection and the momentum budget residual acts to decelerate the environmental wind and to reduce the upper level vertical shear therefore the inferred vertical transport of momentum in the mcc is downgradient in the upper layer on the other hand in the squall line there is no wind speed minimum and the upper level vertical shear of the line normall component of the environmental wind increases as convection develops thus the vertical transport of momentum normal to the squall line is upgradient in the upper layer although the transport of

convection initiation by density currents role of convergence shear and dynamical organization abstract steady state analytic models establish two key points concerning the impact of vertical shear on density currents and the implication for convection initiation first shear decreases the horizontal convergence and therefore the mean ascent associated with downshear propagating currents second shear has a basic effect on the dynamical organization if the downshear current travels at the speed of the ambient flow at a critical steering level an overturning circulation provides deep lifting although mean ascent is increased by shear in the case of upshear propagating currents the lifting is comparatively shallow because jumplike ascent occurs rather than deep overturning the convection initiation mechanism involving the downshear current is therefore very different from the upshear case these basic principles are borne out in two dimensional numerical simulations density currents generated by a stationary cold source imposed on an initially horizontally homogeneous sheared and neutra

cloud resolving modeling of cloud systems during phase iii of gate part ii effects of resolution and the third spatial dimension abstract two and three dimensional simulations of cloud systems for the period of 1 7 september 1974 in phase iii of the global atmospheric research programme garp atlantic tropical experiment gate are performed using the approach discussed in part i of this paper the aim is to reproduce cloud systems over the gate b scale sounding array comparison is presented between three experiments driven by the same large scale conditions i a fully three dimensional experiment ii a two dimensional experiment that is an east west section of the three dimensional case and iii a high resolution version of the two dimensional experiment differences between two and three dimensional frameworks and those related to spatial resolution are analyzed the three dimensional experiment produced a qualitatively realistic organization of convection nonsquall clusters a squall line and scattered convection and transitions between regimes were simulated the two dimensional experiments produced convective organ

multicell squall line structure as a manifestation of vertically trapped gravity waves abstract two dimensional and three dimensional simulations of a midlatitude squall line with a high resolution non hydrostatic model suggest that the multicellular structure of the storm may be associated with gravity waves generated by convection time lapse display of model output demonstrates that the commonly described cut off process is actually a gravity wave phenomenon the convective cells arise as gravity waves which are forced by continuous strong low level convergence at the storm s gust front the waves propagate to both sides of the gust front the stronger westward front to rear mode dominates at the mature stage of the squall line continuous low level updraft is generated at the nose of the cold pool which propagates at the speed of a density current updraft cells periodically break away from this persistent low level gust front updraft and move at phase speeds of their associated gravity waves not at the surrounding airflow speeds as implied by the traditional multicell model lin

multiscale convective wave disturbances in the tropics insights from a two dimensional cloud resolving model abstract multiscale convective wave disturbances with structures broadly resembling observed tropical waves are found to emerge spontaneously in a nonrotating two dimensional cloud model forced by uniform cooling to articulate the dynamics of these waves model outputs are objectively analyzed in a discrete truncated space consisting of three cloud types shallow convective deep convective and stratiform and three dynamical vertical wavelength bands model experiments confirm that diabatic processes in deep convective and stratiform regions are essential to the formation of multiscale convective wave patterns specifically upper level heating together with low level cooling serves to preferentially excite discrete horizontally propagating wave packets with roughly a full wavelength structure in troposphere and dry phase speeds cn in the range 16 18 m s 1 these wave packets enhance the triggering of new deep convective cloud systems via low level destabilization the new convection in turn caus

1 subduction slab detachment and mineralization the neogene in the apuseni mountains and carpathians abstract the inner carpathians comprise several distinct neogene late stage orogenic pb zn cu ag au ore districts the mineral deposits in these districts are closely related to volcanic and subvolcanic rocks and represent mainly porphyry and epithermal vein deposits which formed within short periods of time in each district here we discuss possible geodynamic and structural controls that suggest why some of the neogene volcanic districts within the carpathians comprise abundant mineralization while others are barren the neogene period has been characterized by an overall geodynamic regime of subduction where primary roll back of the subducted slab and secondary phenomena like slab break off and the development of slab windows could have contributed to the evolution location and type of volcanic activity structural features developing in the overlying lithosphere and visible in the carpathian crust such as transtensional wrench corridors block rotation and relay structures due to extrusion tectonics have probably acted in focusing hydrothermal activity as a result of particular events in the geodynamic evolution and the development of specific structural features mineralization formed during fluid channelling within transtensional wrench settings and during periods of extension related to block rotation in the slovakian ore district of the western carpathians neogene volcanism and associated mineralization were localized by sinistral ne trending wrench corridors which formed part of the extruding alcapa block the baia mare ore district in the eastern carpathians reflects a transtensional wrench setting on distributed oversteps close to the termination of the dragos voda fault there mineralization was spatially controlled by the transtensional dragos voda master fault and associated cross fault systems the golden quadrangle cu au ore district of the southern apuseni mountains reflects an unusual rotated transtensional extensional setting close to the termination of a graben system there fluid flow was probably localized by fault propagation at the inner tip of the graben system the spatial and temporal evolution of the magmatism and its changing geochemical signature from n w to s e strongly suggests a link with the contemporaneous northeastward roll back of the subducted slab and a progressive southeastward detachment during accelerating roll back this geodynamic evolution is further supported by the present day overall and detailed mantle lithospheric density images the present day heat flow patterns the crustal architecture and its interpreted evolution and the spatial and temporal evolution of depocentres around the carpathian arc in contrast to all these features the mineral deposits in the west carpathians east carpathians and apuseni mountains are too synchronous with respect to their individual volcanic history and contrast too much with younger volcanics of similar style but barren in southeastern parts of the carpathians to simply link them directly to the slab evolution in all three districts the presence of magmatic fluids released from shallow plutons and their mixing with meteoric water were critical for mineralization requiring transtensional or extensional local regimes at the time of mineralization possibly following initial compressional regimes these three systems show that mineralization was probably controlled by the superposition of favourable mantle lithospheric conditions and partly independent evolving upper crustal deformation conditions in the 13 to 11 ma period the dominant mineralization formed all across the carpathians and was superimposed on structurally favourable crustal areas with at that time volcanic hydrothermal activity the period may reflect the moment when the upper part of the crust failed under lithospheric extension imposed by the slab evolution this crustal failure would have fragmented the overriding plate possibly breaking up the thermal lid to provoke intensive fluid flow in specific areas and allowed subsequent accelerated tectonic development block rotation and extrusion of a family of sub blocks that are arbitrarily regarded as the tisia dacia or alcapa blocks even though they have lost their internal entity

numerical modeling of gravity wave generation by deep tropical convection although convective clouds are known to generate internal gravity waves the mechanisms responsible are not well understood the present study seeks to clarify the dynamics of wave generation using a high resolution numerical model of deep convection over the tiwi islands australia the numerical calculations presented explicitly resolve both the mesoscale convective cloud cluster and the gravity waves generated as the convective clouds evolve they excite gravity waves which are prominent features of the model solutions in both the troposphere and stratosphere the source location is variable in time and space but is related to the development of individual convective cells the largest amplitude gravity waves are generated when the cloud tops reach the upper troposphere a new analysis technique is introduced in which the nonlinear terms in the governing equations are taken as the forcing for linear gravity waves the analysis shows that in the present calculation neither the shear nor the diabatic heating are the dominant forcing terms instead the wave source is most easily understood when viewed in a frame of reference moving with the wind at the level of neutral buoyancy whereupon the source may be described as a vertically oriented oscillating convective updraft this description is consistent with the properties of the modeled stratospheric waves

impact of a convectively forced gravity wave drag parameterization in ncar ccm3 a parameterization of gravity wave drag forced by subgrid scale cumulus convection gwdc proposed by chun and baik is implemented into the national center for atmospheric research community climate model ncar ccm3 and its effect on perpetual january and july climate is investigated the cloud top gravity wave stress is concentrated in the intertropical convergence zone where persistent deep cumulus clouds exist the resultant zonal wind acceleration due to the breaking of convectively forced gravity waves is predominantly found in the tropical lower stratosphere with westerly acceleration above cloud top and easterly acceleration just below it since the parameterized gravity waves are stationary relative to convective clouds wave breaking occurs mainly in the tropical lower stratosphere where the zonal wind is weak enough for wave saturation it is shown that the gwdc parameterization significantly alleviates the systematic model biases of zonal mean zonal wind and temperature in particular excessive easterlies in the tropical stratosphere and excessive cold temperatures in the tropical lower stratosphere are reduced by more than 50 by including the gwdc parameterization the horizontal wind divergence field in the tropical upper troposphere and lower stratosphere is also significantly improved with the gwdc parameterization the impact of the gwdc parameterization extends to mid to high latitudes through planetary wave activity in the winter hemisphere the increased amplitude of zonal wavenumber 3 in the january northern hemisphere and the increased amplitude of zonal wavenumber 2 in the july southern hemisphere lead to significant improvements in model performance the impact of the gwdc parameterization on eliassen palm ep flux divergence forcing by stationary waves is generally opposite to that by transient waves in the extratropics especially in the northern hemisphere wintertime hence the zonal mean zonal wind change by the gwdc parameterization occurs mainly in the tropics by direct gravity wave drag forcing

representing convective organization in prediction models by a hybrid strategy the mesoscale organization of precipitating convection is highly relevant to next generation global numerical weather prediction models which will have an intermediate horizontal resolution grid spacing about 10 km a primary issue is how to represent dynamical mechanisms that are conspicuously absent from contemporary convective parameterizations a hybrid parameterization of mesoscale convection is developed consisting of convective parameterization and explicit convectively driven circulations this kind of problem is addressed for warm season convection over the continental united states although it is argued to have more general application a hierarchical strategy is adopted cloud systemresolving model simulations represent the mesoscale dynamics of convective organization explicitly and intermediate resolution simulations involve the hybrid approach numerically simulated systems are physically interpreted by a mechanistic dynamical model of organized propagating convection this model is a formal basis for approximating mesoscale convective organization stratiform heating and mesoscale downdraft by a first baroclinic heating couplet the hybrid strategy is implemented using a predictor corrector strategy explicit dynamics is the predictor and the first baroclinic heating couplet the corrector the corrector strengthens the systematically weak mesoscale downdrafts that occur at intermediate resolution when introduced to the betts miller janjic convective parameterization this new hybrid approach represents the propagation and dynamical structure of organized precipitating systems therefore the predictor corrector hybrid approach is an elementary practical framework for representing organized convection in models of intermediate resolution

characterization of momentum transport associated with organized moist convection and gravity waves abstract tropical convection is inherently multiscalar involving complex fields of clouds and various regimes of convective organization ranging from small disorganized cumulus up to large organized convective clusters in addition to being a crucial component of the atmospheric water cycle and the global heat budget tropical convection induces vertical fluxes of horizontal momentum there are two main contributions to the momentum transport the first resides entirely in the troposphere and is due to ascent descent and organized circulations associated with precipitating convective systems the second resides in the troposphere stratosphere and farther aloft and is caused by vertically propagating gravity waves both the convective momentum transport and the gravity wave momentum flux must be parameterized in general circulation models yet in existing parameterizations these two processes are treated independently this paper examines the relationship between the convective momentum transport and

organized convective systems in the tropical western pacific as a process in general circulation models a toga coare case study we examine the large scale effects of organized convective systems in the tropical western pacific observed during the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare in a case study approach we examine realizations of a supercluster associated with the onset of the december 1992 westerly wind burst in the t213 operational medium range weather forecasting model of the european centre for medium range weather forecasts ecmwf we idealize a supercluster as a hierarchy of three interacting scales namely organized cumulonimbus c 1 mesoscale convective systems c 2 and the supercluster component c 3 it is shown that the ecmwf model represents this hierarchy as a c 3 like surrogate whose influence dominates the effect of parametrized convection this causes over prediction of the model tendencies which in the case of zonal momentum is explained in elementary terms the structure of the resolved scale momentum flux is explained by moncrieff s 1992 archetypal theory of organized convection which has been verified against observations and cloud resolving model data sets the parametrization of subgrid scale convective momentum flux in the ecmwf model based on a momentum mixing concept produces subgrid scale tendencies that are physically different from transports associated with cumulonimbus convection in a shear flow we outline a strategy for parametrizing the momentum flux by the c 1 component based on the archetypal model the c 2 component which is part resolved and part parametrized is at odds with the assumptions of scale separation underpinning parametrization it is argued that this component should be represented as part of the prognostic treatment of convectively generated cirrus finally we suggest cloud resolving modelling studies to further quantify the structure and large scale impact of superclusters in a westerly wind burst environment ranging from idealized models to models having data assimilation capability

parametrization of momentum transport by convection ii tests in single column and general circulation models diagnostics derived from cloud resolving model simulations in part i of this study relating to the vertical transport of horizontal momentum by convection are used to develop a parametrization of convective momentum transports for deep convection based upon the mass flux convection scheme discussed by gregory and rowntree the importance of cloud pressure gradients to the flow within the cloud is emphasised and a simple method of representing their effect is suggested the scheme is able to reproduce the fluxes derived from the cloud resolving model studies where cloud organization by the flow is unimportant inclusion of the parametrization in a version of the meteorological office unified model demonstrates that convective momentum transports play a large role in the momentum balance of the atmosphere generally simulation of the mean atmospheric circulation by the unified model is improved by the inclusion of such transports

implementation of a gravity wave source spectrum parameterization dependent on the properties of convection in the whole atmosphere community climate model waccm 1 this article describes the implementation of a new source spectrum parameterization for convectively generated gravity waves in the whole atmosphere community climate model version 2 waccm2 this parameterization is active in the tropics and is interactive with the underlying convection the gravity wave spectrum at each model grid point and time step is determined based on the convective heating depth tropospheric wind and the convective heating rate this parameterization introduces more realistic spatial and temporal distributions of gravity wave activity and yields gravity wave characteristics related to the underlying wave source we present the estimated gravity wave momentum flux phase speed spectra at 100 hpa as well as the gravity wave drag in the middle and upper atmosphere using the new source spectrum representation we also show the effects of this more physically based parameterization on the structure of the stratospheric and mesospheric semi annual oscillations of the zonal wind compared to a simulation with uniform gravity wave distribution we conclude that the interaction of the gravity wave parameterization with tropospheric characteristics is a positive step toward a more physical representation of the middle and upper atmosphere

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

hydrothermal alteration associated with gold mineralization in the southern apuseni mountains romania preliminary sr isotopic data precious metal mineralization in the southern apuseni mountains of western romania is hosted by mid miocene 14 ma andesitic stocks and lava flows the mineralized veins are surrounded by aureoles of hydrothermal alteration consisting of quartz sericite k feldspar pyrite and calcite the alteration process caused a total homogenization of initial 87sr 86sr in the rocks ages determined for the hydrothermal alteration are 13 7 15 7 ma indicating that hydrothermal alteration immediately followed igneous activity furthermore a large influx of radiogenic sr took place during alteration this sr probably being derived from the hydrothermal leaching of continental meta sedimentary rocks in the basement

a theory for strong long lived squall lines revisited based on the analysis of idealized two and three dimensional cloud model simulations rotunno et al hereafter rkw and weisman et al hereafter wkr put forth a theory that squall line strength and longevity was most sensitive to the strength of the component of low level 0 3 km agl ambient vertical wind shear perpendicular to squall line orientation an optimal state was proposed by rkw based on the relative strength of the circulation associated with the storm generated cold pool and the circulation associated with the ambient shear whereby the deepest leading edge lifting and most effective convective retriggering occurred when these circulations were in near balance since this work subsequent studies have brought into question the basic validity of the proposed optimal state based on concerns as to the appropriate distribution of shear relative to the cold pool for optimal lifting as well as the relevance of such concepts to fully complex squall lines especially considering the potential role of deeper layer shears in promoting system strength and longevity in the following the basic interpretations of the rkw theory are reconfirmed and clarified through both the analysis of a simplified two dimensional vorticity streamfunction model that allows for a more direct interpretation of the role of the shear in controlling the circulation around the cold pool and through an analysis of an extensive set of 3d squall line simulations run at higher resolution and covering a larger range of environmental shear conditions than presented by wkr

thickness and spatial distribution of veins in a porphyry copper deposit rosia poieni romania abstract a statistical analysis of the vein thickness distributions of veins in the rosia poieni porphyry copper deposit romania indicates that vein thickness data conform to a power law distribution whereas the spatial distribution of veins follows a negative exponential law a high clustering of the veins is indicated by both the spacing distribution and the cv values the similar vein densities observed at the open pit scale are representative of a saturation level of vein nucleation differences in the spacing distribution and in the mean vein thickness are explained by different initial nucleation rates in the deepest and the lowest parts of the porphyry copper the highly clustered organization of the system is explained by vein linkage processes during their growth and modification of the fluid pressure and local stress during the hydrofracturing

kinematic characteristics of air flowing into and out of precipitating convection over the west pacific warm pool an airborne doppler radar survey air flowing into and out of 25 cloud systems over the west pacific warm pool was sampled by doppler radars on board two noaa wp 3d aircraft and the ncar electra aircraft during the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare in convective cells updraught inflows and downdraught outflows tended to be positioned adjacent to each other at sharp updraught downdraught interfaces sloping at various angles and directions the updraught inflows were sometimes shallow and sometimes deep often extending well above the boundary layer downdraught outflow magnitudes were usually stronger than updraught inflows and the horizontal directions of the inflow and outflow were frequently offset from each other at angles of 90 in stratiform precipitation regions the dominant airflow features were descending mid level inflows located at the bases of anvils and often extending into the interior of the precipitation system these stratiform inflows originated at levels between 5 and 10 km and descended to about 3 km a few extended down to the surface stratiform inflows were typically strong and sandwiched between weaker stratiform outflows at upper and lower altitudes the stratiform region inflow and outflow directions were frequently offset by 90 in the horizontal the mid level inflow currents entered the stratiform regions horizontally from a direction similar to that of the large scale ambient wind the mid level stratiform inflow tended to occur in the same vertical plane as the convective downdraught outflow although the mid level stratiform inflow appeared to be slowed by horizontal pressure gradients before connecting with the convective downdraught outflow in other respects the mesoscale systems differed from a simplified two dimensional model of airflow the systems moved primarily by discrete propagation and updraughts and downdraughts tended to have orthogonal horizontal relative airflow

mineralogy and geochemistry of pb sb as sulfosalts from coranda hondol ore deposit romania conditions of telluride deposition abstract electron microprobe analyses are reported on newly identified occurrences of pb sb as sulfosalts from the coranda hondol ore deposit certej area south apuseni mountains romania the coranda hondol deposit is an intermediate sulfidation au ag epithermal system hosted in propylitic altered andesitic rocks covered by cretaceous and neogene sediments the main base metal sulfides are sphalerite pyrite and galena subordinate amounts of chalcopyrite arsenopyrite pyrrhotite marcasite tetrahedrite tennantite bournonite seligmannite geocronite jordanite stibnite and au ag tellurides complete the paragenetic sequence gangue minerals are quartz calcite and barite hydrothermal alteration is expressed as pyritisation silicification potassic alteration carbonitisation and phyllic or sericitic alteration minerals of the bournonite seligmannite and geocronite jordanite series are described for the first time in samples from different levels of the coranda hondol open pit both series show chemical variations in terms of sb as sb ratio and display a general spatial trend within the deposit in which the sb content of both series tends to increase towards upper levels textural relationships between the two sulfosalt series and their chemical variations suggest that the presence of sb in hydrothermal fluids favors precipitation of bournonites whereas as favors precipitation of jordanites compositions of minerals from the bournonite seligmannite and geocronite jordanite series extend from bnn35 to bnn98 and from gcn14 to gcn76 respectively back scattered electron imaging reveals grain scale compositional heterogeneity in bournonite seligmannite seen as concentric and layered oscillatory zoning patterns these zoning patterns were observed only in the upper parts of the deposit and suggest an increasing as content in late fluids trace elements te se and fe are preferentially incorporated into sb rich members of bnn slg series this is consistent with the association of gold silver tellurides and bournonites identified at the coranda hondol deposit variable conditions within the coranda hondol hydrothermal system suggest that precipitation of au ag tellurides occurred via two possible mechanisms i te vapor condensation into precious metal brines during boiling and ii by fluid throttling with periodic release of volatiles

coupling of convective momentum transport with convective heating in global climate simulations abstract the effects of convective momentum transport cmt on global climate simulations are examined in this study comparison between two sets of 20 yr 1979 98 integration using the ncar community climate model version 3 ccm3 illustrates that the inclusion of cmt in the convection scheme systematically modifies the climate mean state over the equatorial region the convective momentum tendencies slow down the equatorward flow at higher latitudes near the surface and weaken the equatorial convergence and convection this reduces the convective heating and drying around the equator and produces an improved meridional distribution within the upward branch of the hadley circulation the major heating peak during the boreal winter is moved to south of the equator at about 10 s which is closer to the heat budget residuals of the ecmwf reanalysis data the responses of meridional wind to the reduced heating result in the secondary meridional circulation within the intertropical convergence zone

climatology of summer midtropospheric perturbations in the us northern plains part ii large scale effects of the rocky mountains on genesis propagating convective storms across the us northern plains are often coupled with preexisting midtropospheric perturbations mps initiated over the rocky mountains a companion study part i notes that such mps occur most commonly at 12 utc early morning and 00 utc late afternoon using a regional reanalysis and a general circulation model gcm this study investigates how such a bimodal distribution of the mp frequency is formed the results point to two possible mechanisms working together while each has a different timing in terms of maximum effect the diurnal evolutions between the midtropospheric flows over the rockies and over the great plains are nearly out of phase due to inertial oscillation during the nighttime the westerly flows at 700 500 mb over the rockies intensify while flows at the same level over the great plains turn easterly these two flows converge over the eastern rockies and induce cyclonic vorticity through vortex stretching after sunrise the convergence dissipates and the cyclonic vorticity is redistributed by horizontal vorticity advection moving it downstream this process creates a climatological zonally propagating vorticity signal which in turn facilitates the early morning mp genesis at 12 utc the analysis also reveals marked dynamic instability conducive to subsynoptic scale disturbances in the midtroposphere over the rockies strong meridional temperature gradients appear over the north facing slopes of the rockies due to terrain heating to the south and the presence of cooler air to the north this feature along with persistent vertical shear creates a charney stern type of instability i e sign changes of the meridional potential vorticity gradient meanwhile the development of terrain boundary layer reduces the rossby deformation radius which subsequently enhances the likelihood for baroclinic short waves such effects are most pronounced in the late afternoon and therefore are supportive to the mp genesis around 00 utc examination of gcm experiments with and without orography further supports the critical role of the rocky mountains and its associated boundary layer impacts on the formation of mps

some effects of model resolution on simulated gravity waves generated by deep mesoscale convection abstract over the past decade numerous numerical modeling studies have shown that deep convective clouds can produce gravity waves that induce a significant vertical flux of horizontal momentum such studies used models with horizontal grid spacings of o 1 km and produced strong gravity waves with horizontal wavelengths greater than about 20 km this paper is an examination of how simulated gravity waves and their momentum flux are sensitive to model resolution it is shown that increases in horizontal resolution produce more power in waves with shorter horizontal wavelengths this change in the gravity waves spectra influences their vertical propagation in some cases gravity waves that were vertically propagating in coarse simulations become vertically trapped in fine simulations which strongly influences the vertical flux of horizontal momentum