impact of high potential vorticity intrusions into the tropical upper troposphere in south atlantic on precipitation over northeast brazil 1 interannual variations of high potential vorticity intrusions at 10 s in the upper troposphere during ndjfm are shown to be negatively correlated with rainfall over northern northeast brazil neb that is higher intrusions associated with stronger equatorial westerlies may provoke droughts higher intrusions lead to the formation of an anomalous cyclonic vortex over neb which causes convergence in the upper troposphere and sinking motion at lower levels the number of intrusions in ndjfm has highest correlation significant at 99 confidence level with the rainfall of the principal rainy season in fmam

impacts of convectively coupled kelvin waves on environmental conditions for atlantic tropical cyclogenesis abstracthigh amplitude convectively coupled equatorial atmospheric kelvin waves cckws are explored over the tropical atlantic during the boreal summer 1989 2009 focus is given to the atmospheric environmental conditions that are important for tropical cyclogenesis cckws are characterized by deep westerly vertical wind shear to the east of its convectively active phase and easterly vertical wind shear to the west of it this dynamical signature increases vertical wind shear over the western tropical atlantic ahead of the convectively active phase and reduces vertical wind shear after its passage the opposite is true over the eastern tropical atlantic where the climatological vertical wind shear is easterly positive total column water vapor tcwv anomalies progress eastward with the convectively active phase of the cckw whereas negative tcwv anomalies progress eastward with the convectively suppressed phase during the passage of the convectively active phase of the cckw a zonally oriented strip o

climatology of vertical wind shear over the tropical atlantic abstract the spatiotemporal variability of the 200 850 hpa vertical wind shear over the tropical atlantic is examined for a period of 46 yr this work extends and updates past studies by considering a longer data record as well as a tropospheric deep measure of vertical wind shear composite fields are constructed to illustrate the spatial pattern of the large scale circulation associated with the mean and extreme cases of vertical shear within the tropical atlantic the contemporaneous relationship of vertical shear with el nino southern oscillation enso and sahel precipitation are also examined while the enso shear correlation appears to have slightly strengthened during the past decade the sahel shear correlation has become significantly degraded a combined empirical orthogonal function eof analysis of the zonal and meridional components of the vertical shear reveals interannual and multidecadal modes the leading eof exhibits mainly interannual variability and is highly correlated with enso th

a case study of an outbreak of twin tropical cyclones abstract previous studies have found that twin tropical cyclogenesis typically occurs 2 3 times a year in the pacific ocean during october 1997 however three sets of twin tropical cyclones developed in the central pacific within a single month tropical cyclone archives indicate that this is the only such outbreak from 1969 to 2006 this case study explores the background and synoptic conditions that led to this unique event all three twin tropical cyclogenesis events occurred within a broad and long lasting envelope of warm water low surface pressure active convection and weak or easterly vertical shear westerly winds at the equator and trade easterlies farther poleward created strips of cyclonic vorticity through a deep layer a low pass filter showed that these favorable conditions shifted eastward with time at 1 2 m s 1 in addition to the gradual eastward movement the equatorial westerlies and convection were modulated by higher frequency westward propagation these anomalies appear to have

biogeomorphic relationships between slope processes and globular grimmia mosses in haleakala s crater maui hawai i abstract globular mosses were found in haleakala s crater maui at five locations between 2175 and 2725 m the highest altitude site with abundant epilithic mosses growing on alkali olivine basalt outcrops and a large mossball population was studied mossballs form when moss cushions are dislodged from rocks but continue growing unattached to substrate detachment agents include rainsplash desiccation wind frost and disturbance by birds dark rumped petrels that burrow nests under outcrops or by goats when loosened moss polsters are transported down steep 26 34 slopes by different geomorphic processes including frost mainly needle ice activity runoff and wind mossballs contained two species grimmia trichophylla grev and grimmia torquata drumm growing separately or commingled weight size and various shape indices were determined for 260 specimens shape and size were correlated larger mosses become less spheroidal because heavier specimens are less disturbed by needle ice remaining immobile for increasingly longer time periods thus becoming flattened distance of downslope transport from source rockwalls was measured for 330 specimens 83 shifted 100 cm but only 5 had moved 200 839 cm heavier mossballs moved short distances thus 88 of all biomass remained within 200 cm from outcrops substrate soils were compared with those within globoids surface site soils were much coarser than mossball grains twelve substrate samples had on average 21 3 gravel 2 mm 6 1 fines 0 063 mm and 2 1 organic matter in contrast 12 mossballs contained this area is frequently subjected to freezing temperatures while fog interception from incoming tradewinds contributes significant moisture amounts to precipitation ground disturbance by frost activity seemed significant needle ice grows frequently on this slope as evidenced by widespread presence of miniature sorted stripes striated soils fine earth flags below stones gaps around stones and fine soil raised patches observed during multiple visits biogeomorphic interactions between mossballs and substrate at haleakala are briefly discussed from the perspective of self organized criticality and interpreted to represent a self replicating moss dispersal system dependent on slope geomorphic processes

the evolution of vortex tilt and vertical motion of tropical cyclones in directional shear flows abstractrecent studies have demonstrated the importance of moist dynamics on the intensification variability of tropical cyclones tcs in directional shear flows here we propose that dry dynamic

the role of cumulus convection in hurricanes and its representation in hurricane models this paper reviews our understanding of the role of cumulus convection in hurricanes as well as the various convective parameterization schemes that have been used in hurricane models elementary principles show that the primary tangential circulation of a vortex intensifies as rings of rotating air converge inward while conserving their absolute angular momentum thus intensification requires a mechanism to produce enough flow convergence above the surface boundary layer to counter the divergence induced there by the boundary layer itself typically such convergence is associated with the inward branch of the secondary circulation and is produced by an unbalanced negative radial gradient of buoyancy above the boundary layer resulting from condensational heating in the inner region of the vortex the fact that such buoyancy gradients are produced by all the parameterization schemes as well as by explicit schemes for latent heat release explains why all the models are able to simulate hurricane intensification with some degree of realism in a weak vortex the secondary circulation is dominated by buoyant forcing but as the vortex intensifies the contribution from surface friction increases until in the mature stage the buoyantly induced convergence must closely balance the frictionally induced divergence just above the boundary layer only a handful of the more recent hurricane models and only two of those in which convection is parameterized represent the effects of convective downdrafts these downdrafts cool and dry the subcloud layer tending to suppress further convection so that acting alone they would serve as a brake on hurricane intensification the strength of downdrafts decreases when the middle tropospheric relative humidity increases as a result of sustained cumulus convection over an area if surface wind speeds are high enough surface fluxes of sensible and latent heat can more than counteract the cooling and drying effects of convective downdrafts allowing continued warming of the troposphere in the inner region of the vortex so that vortex intensification can proceed accordingly the surface fluxes provide the energy source for the hurricane while convection transfers this energy vertically through the troposphere creating a suitable radial gradient of buoyancy to drive the secondary circulation of the vortex

rapidly intensifying hurricane guillermo 1997 part i low wavenumber structure and evolution abstract the structure and evolution of rapidly intensifying hurricane guillermo 1997 is examined using airborne doppler radar observations in this first part the low azimuthal wavenumber component of the vortex is presented guillermo s intensification occurred in an environmental flow with 7 8 m s 1 of deep layer vertical shear as a consequence of the persistent vertical shear forcing of the vortex convection was observed primarily in the downshear left quadrant of the storm the greatest intensification during the 6 h doppler observation period coincided with the formation and cyclonic rotation of several particularly strong convective bursts through the left of shear semicircle of the eyewall some of the strongest convective bursts were triggered by azimuthally propagating low wavenumber vorticity asymmetries mesoscale budget analyses of axisymmetric angular momentum and relative vorticity within the eyewall are presented to elucidate the mechanisms contributing to guillermo s structural evol

recent changes in the precipitation driving processes over the southern tropical andes western amazon analyzing december february djf precipitation in the southern tropical andes sta 12 circ hbox s 20 circ hbox s 3000 m a s l allows revisiting regional atmospheric circulation features accounting for its interannual variability over the past 35 years 1982 2018 in a region where in situ rainfall stations are sparse the chirps precipitation product is used to identify the first mode of interannual djf precipitation variability pc1 andes a network of 98 rain gauge stations further allows verifying that pc1 andes properly represents the spatio temporal rainfall distribution over the region in particular a significant increase in djf precipitation over the period of study is evident in both in situ data and pc1 andes using the era interim data set we found that aside from the well known relationship between precipitation and upper level easterlies over the sta pc1 andes is also associated with upward motion over the western amazon wa a link that has not been reported before the ascent over the wa is a component of the meridional circulation between the tropical north atlantic and western tropical south america wtsa 80 circ hbox w 60 circ hbox w 35 circ hbox s 10 circ hbox n indeed the precipitation increase over the last 2 decades is concomitant with the strengthening of this meridional circulation an intensified upward motion over the wa has moistened the mid troposphere over wtsa and as a consequence a decreased atmospheric stability between the mid and the upper troposphere is observed over this region including the sta we further show that over the last 15 years or so the year to year variability of sta precipitation periodicity 8 years has been significantly associated with upward motion over the wa while upper level easterlies are no longer significantly correlated with precipitation these observations suggests that the sta have experienced a transition from a dry to a wet state in association with a change in the dominant mode of atmospheric circulation in the former dominant state zonal advection of momentum and moisture from the central amazon associated with upper level easterlies is necessary to develop convection over the sta since the beginning of the 21st century djf precipitation over the sta seems to respond directly and primarily to upward motion over the wa beyond improving our understanding of the factors influencing sta precipitation nowadays these results point to the need of exploring their possible implications for the long term evolution of precipitation in a context of global warming

the role of storm relative advection of absolute angular momentum in strengthening of atlantic tropical cyclones 1 this study examined absolute angular momentum tendency in atlantic tropical cyclones each advective and torque term in the storm relative eulerian absolute angular momentum tendency equation was calculated in a storm relative reference frame using modeled and observational data 18 storms between 2004 and 2006 were simulated using the hurricane weather research and forecast model in addition the storm relative advection of absolute angular momentum was calculated using reconnaissance aircraft wind data from 12 atlantic hurricanes which occurred between 2003 and 2007 through methods of statistical correlation categorical composition and linear regression it was found that mid level horizontal advection of relative angular momentum was most relevant to 12 hour strength change in the modeled tropical cyclones mid level horizontal advection of relative angular momentum was most relevant to intensity change in the observed hurricanes while mid level advection of earth s angular momentum was found to be most closely related to strength change in observed hurricanes

on the influences of vertical wind shear on symmetric tropical cyclone structure derived from amsu abstract axisymmetric temperatures and gradient balanced winds associated with tropical cyclones derived from the advanced microwave sounding unit are stratified by the 24 h averaged vector difference of the horizontal wind between 200 and 850 hpa or vertical wind shear using 186 total cases that are limited to tropical cyclones with intensities greater than 33 m s 1 or mature and are located over sea surface temperatures greater than 26 4 c vertical wind shear based composites are created results show that as the vertical wind shear increased the upper level warm core structure associated with the tropical cyclone descended resulting in a shallower balanced vortex these observationally based results are presented in the context of recent mesoscale modeling results of the effect of shear on tropical cyclone structure

a balanced tropical cyclone test case for agcms with background vertical wind shear abstractthis paper presents a balanced tropical cyclone tc test case designed to improve current understanding of how atmospheric general circulation model agcm configurations affect simulated tc development and behavior it consists of an analytic initial condition comprising two independently balanced components the first provides a vortical tc seed while the second adds a planetary scale zonal flow with height dependent velocity and imposes background vertical wind shear vws on the tc seed the environmental flow satisfies the steady state hydrostatic primitive equations in spherical coordinates and is in balance with other background field variables e g temperature surface geopotential the evolution of idealized tcs in the test case framework is illustrated in 10 day simulations performed with the community atmosphere model version 5 1 1 cam 5 1 1 environmental wind profiles with different magnitudes directions and vertical inflection points are applied to ensure that the technique

eastern pacific hurricanes jimena of 1991 and olivia of 1994 the effect of vertical shear on structure and intensity abstract shear is a key inhibitor of tropical cyclone intensification although its signature is readily recognized in satellite imagery and theoretical or modeling studies provide some insight detailed observations have been limited airborne radar and in situ observations in hurricanes jimena of 1991 and olivia of 1994 are a step toward better understanding each storm was observed on two consecutive days initially both had small eyes 16 18 km radius and maximum winds of 57 m s 1 over sea surface temperatures sst 28 c in easterly environmental shear jimena maintained constant intensity or weakened gradually for 2 days in 13 20 m s 1 easterly shear olivia intensified in 8 m s 1 shear on the first day overnight the shear diminished to reverse and became westerly on the second day olivia weakened as the shear increased to 15 m s 1 from the west the storm moved over cooler sst and became surrounded by dryer air as convection weakened and the outer rainbands ceased to be effective barriers

the influence of surface volcaniclastic layers from haleakala maui hawaii on soil water conservation this study focuses on the soils and surficial volcaniclastic layers of haleakala s crater maui hawaii the main objective is to assess the effects of covers with fragments of various sizes ash cinder lapilli on soil water conservation soil and gravel samples were collected in haleakala national park from a site at 2505 m where the hawaiian silversword a giant rosette plant grows densely on pyroclastic materials an evaporation experiment lasting 22 days showed a gradual drop in seven pairs of soil samples initially at field capacity one set of samples was left bare the other was covered by gravel mulches gm these resulted in lengthening of t100 total desiccation time by a factor of 2 3 5 2 bare soils dried after 70 140 h but drying time under gravel was 246 509 h mean grain size mz and sorting had the greatest influence on evaporation rates coarse lapilli mz 13 8 mm were less effective than fine ash mz 2 9 3 8 mm in preventing water losses while medium grained cinder mz 4 5 2 mm produced the greatest water savings lapilli mean 0 48 and ash 0 6 were moderately to well sorted cinders with a broader grain size range 1 13 were poorly sorted this allowed infilling of large interstices between coarse fragments by smaller grains effectively reducing pore size and therefore evaporation rates a second experiment determined water storage and rates of water loss by mulches wetting occurred swiftly within 3 4 min all gravel types were dry within 26 h this drying process is important for water conservation as it effectively prevents further water loss from the mulch surface larger fragments stored less water this is related to their surface area weight ratio which increases for smaller particles thus fine ash or cinder grains with a high total area intercept more water than larger lapilli a 5 cm thick layer of ash intercepted an average of 6 8 mm of rain slightly more than the same depth of cinder 6 3 mm but lapilli retained only 4 7 mm therefore light rainfall events are more likely to contribute water to soil under lapilli than below finer pyroclastic material volcaniclastic covers serve an important ecological role in haleakala by prolonging periods of water availability to plants thus allowing hawaiian silverswords to grow for longer time spans

azimuthal distribution of deep convection environmental factors and tropical cyclone rapid intensification a perspective from hwrf ensemble forecasts of hurricane edouard 2014 abstractforecasts from the operational hurricane weather research and forecasting hwrf based ensemble prediction system for hurricane edouard 2014 are analyzed to study the differences in both the tropical cyclone inner core structure and large scale environment between rapidly intensifying ri and non intensifying ni ensemble members an analysis of the innercore structure reveals that as deep convection wraps around from the downshear side of the storm to the upshear left quadrant for ri members vortex tilt and asymmetry reduce rapidly and ri occurs for ni members deep convection stays trapped in the downshear downshear right quandrant and storms do not intensify the budget calculation of tangential wind tendency reveals that the positive radial eddy vorticity flux for ri members contributes significantly to spinning up the tangential wind in the middle and upper levels and reduces vortex tilt the negative eddy vorticity flux for ni members spins down the tangential wind in the middle and u

steady as a rock biogeomorphic influence of nurse rocks and slope processes on kūpaoa dubautia menziesii shrubs in haleakalā crater maui hawai i abstract this study examines biogeomorphic interactions between nurse rocks slope processes and 300 k paoa dubautia menziesii shrubs in haleakal crater maui hawai i research objectives were to assess the association of k paoa with substrates upslope and downslope of plants and proximity to the closest rock uphill contrast shrub substrate relationships with site frequency of sediment types measure surface soil shear strength and compressibility on 50 paired locations near boulders and investigate the aggregation characteristics and spatial patterns of k paoa in relation to rock and substrate variation data analyzed came from three 100 plant surveys at 3 sites a plant census at 2720 2975 m altitude and wandering quarter transects wqts across two areas 2610 2710 m ground sediment cover was estimated along four phototransects on these sites data for the three 100 plant surveys included substrate type outcrops blocks cobbles pebbles exposed soil organic litter upslope from each plant and distance to the largest rock upslope the two surveys examined along wqts included substrate type found downslope from k paoa plant height plant diameters across and along the slope and distance between successively censused plants most plants grew downslope of nurse rocks 74 were adjacent to blocks or outcrops and 17 near cobbles plants showed avoidance for finer substrates only 5 3 and 2 7 grew on near bare soils and pebbles respectively about 92 of k paoa were 10 cm downslope of rocks 89 grew 2 cm away and 83 in direct contact with a rock some seedlings also grew on pukiawe leptecophylla tameiameiae nurse plants several stable rock microsites protected plants from disturbance by slope processes causing debris shift site sediments were significantly finer than substrates near plants shrubs grew preferentially adjacent to boulders 20 cm wide which were more common near plants than across sites soils downslope of 50 boulders mean 41 3 cm showed higher shear strength and compressibility than soils along rock sides these boulder dams stop descending debris steadily deflecting them toward rock sides whereas protected soils downslope of blocks are infrequently disturbed and develop into downslope elongated clast free fine earth flags k paoa were uniformly dispersed across slopes showing a single phase mosaic arrangement without apparent aggregation slopes where k paoa grows had a relatively uniform distribution of surface sediments observed k paoa patterns may have resulted from the array of microsites generated by surface rocks and sediments as shrubs simply responded to such spatial structure

effects of vertical wind shear on the intensity and structure of numerically simulated hurricanes a series of numerical simulations of tropical cyclones in idealized large scale environments is performed to examine the effects of vertical wind shear on the structure and intensity of hurricanes the simulations are performed using the nonhydrostatic pennsylvania state university national center for atmospheric research fifth generation mesoscale model using a 5 km fine mesh and fully explicit representation of moist processes when large scale vertical shears are applied to mature tropical cyclones the storms quickly develop wavenumber one asymmetries with upward motion and rainfall concentrated on the left side of the shear vector looking downshear in agreement with earlier studies the asymmetries develop due to the storm s response to imbalances caused by the shear the storms in shear weaken with time and eventually reach an approximate steady state intensity that is well below their theoretical maximum potential intensity as expected the magnitude of the weakening increases with increasing shear all of the storms experience time lags between the imposition of the large scale shear and the resulting rise in the minimum central pressure while the lag is at most a few hours when the storm is placed in very strong 15 m s21 shear storms in weaker shears experience much longer lag times with th e5ms 21 shear case showing no signs of weakening until more than 36 h after the shear is applied these lags suggest that the storm intensity is to some degree predictable from observations of largescale shear changes in all cases both the development of the asymmetries in core structure and the subsequent weakening of the storm occur before any resolvable tilt of the storm s vertical axis occurs it is hypothesized that the weakening of the storm occurs via the following sequence of events first the shear causes the structure of the eyewall region to become highly asymmetric throughout the depth of the storm second the asymmetries in the upper troposphere where the storm circulation is weaker become sufficiently strong that air with high values of potential vorticity and equivalent potential temperature are mixed outward rather than into the eye this allows the shear to ventilate the eye resulting in a loss of the warm core at upper levels which causes the central pressure to rise weakening the entire storm the maximum potential vorticity becomes concentrated in saturated portions of the eyewall cloud aloft rather than in the eye third the asymmetric features at upper levels are advected by the shear causing the upper portions of the vortex to tilt approximately downshear the storm weakens from the top down reaching an approximate steady state intensity when the ventilated layer can descend no farther due to the increasing strength and stability of the vortex at lower levels

genesis of the northeast brazil upper tropospheric cyclonic vortex a primitive equation barotropic instability study abstract the primitive equation barotropic unstable linear normal modes are computed using an eigenvalue approach for daily latitudinal profiles of zonal flow in the upper tropospheric layer of 100 350 hpa before and after formation of cyclonic vortices during january 1993 and november 2001 off the coast of northeast brazil the wave kinetic energy equation for u and motion is presented equations are derived to isolate the contribution of divergence and other dynamical processes in the movement and growth of unstable modes numerical accuracy and physical nature of unstable modes are tested in a short span of 2 3 days prior to formation of vortices a progressive and a sharp intensification of the basic flow shear zone and its barotropic instability are seen with time the horizontal structure momentum transport and zonal and meridional scales of the most unstable normalized wave are obtained and compared with the vortex extracted from the 200 hpa observed winds using a bandpass smoother a close

subepithermal au pd mineralization associated with an alkalic porphyry cu au deposit mount milligan quesnel terrane british columbia canada at the mount milligan cu au porphyry deposit quesnel terrane british columbia canada barren and weakly mineralized late stage hydrothermal veins occur in volcanic rocks adjacent to zones of cu au porphyry mineralization and have overprinted the porphyry stage veins the earliest of the late stage hydrothermal veins are barren and consist of quartz pyrite carbonate chlorite tourmaline these veins are similar to transitional to late stage hydrothermal veins in other alkaline porphyry cu au deposits and we consider these to be the equivalent of transitional post porphyry pre epithermal quartz sericite pyrite veins in calc alkaline porphyry environments a later generation of volumetrically minor mineralized veins are composed of pyrite hg and as bearing quartz carbonate chlorite and contain early electrum arsenopyrite tetra hedrite tennantite platinum group element pge tellurides galena sphalerite barite and chalcopyrite as inclusions in pyrite and a later assemblage of electrum pge tellurides arsenides and antimonides galena sphalerite chalcopyrite and various au ag te bi minerals in annealed fractures and open space infillings in quartz and pyrite metal precipitation in these veins was temporally and spatially associated with the deposition and later recrystallization of pyrite primary fluid inclusions in quartz in the barren and weakly mineralized veins are two phase l v homogenize to liquid over a narrow range in t 170 270 c n 96 12 veins and show a wide range in salinity 4 2 wt nacl equiv to 28 7 wt cacl2 equiv when all samples are considered however individual veins show narrow ranges in salinity and homogenization temperature la icp ms analyses indicate that the fluids were highly enriched in as to 2 260 ppm sb to 230 ppm b to 5 400 ppm au 1 2 ppm and pd 0 5 1 ppm but depleted in cu 80 ppm compared to typical porphyry stage fluids metal ratios in the fluids overlap with bulk rock metal ratios in the mineralized veins the inclusions are interpreted to contain a contracted magmatic vapor produced by boiling that lost cu during the formation of porphyry stage veins at depth fluids show decreasing b as sb and increasing sr ca and salinity with time stable c o and h isotope analyses of vein minerals indicate that mixing of this magmatic fluid with meteoric water was not responsible for metal deposition rather metal precipitation was possibly the result of mixing of the magmatic derived fluid with a heated saline groundwater the precious and accessory metal mineralogy of the hydrothermal veins is similar to that found in low to intermediate sulfidation epithermal systems fluid inclusion microthermometry and chlorite thermometry constrain the approximate formation conditions of the veins between 200 and 1 500 bars and 240 and 280 c after the formation of the mineralized veins circulation of low salinity metal depleted fluids occurred these latest stage fluids may have formed by mixing of the saline magmatic fluid groundwater hybrid with meteoric water the results of this study suggest a genetic link between porphyry stage events and the deposition of au and pge in late stage veins in an alkalic igneous environment recognition of hydrothermal processes involving the transport of au pge as sb bi te b rich fluids in the subepithermal regimes implies that low sulfidation epithermal au deposits may have been present in the shallower parts of the magmatic hydrothermal complex and that there is potential for the discovery of pge rich epithermal veins in less deeply exhumed terranes on the other hand the formation of high grade low sulfidation epithermal au pge deposits may be prohibited if porphyry epithermal transitional fluids precipitate ore metals through mixing with groundwater prior to reaching the level where meteoric water mixing and epithermal boiling normally occur

numerical simulation of tropical cyclone mora using a regional coupled ocean atmospheric model tropical storms ts are highly sensitive to the behavior of nearby oceans and the only way to improve their predictability is to include all the possible factors contributing to their genesis and motion the present study evaluates the response of air sea coupling on ts mora which occurred during the pre monsoon season of 2017 mora is simulated using a non hydrostatic regional atmospheric modeling system coupled to a regional ocean modeling system model the observations show a low level rossby wave in the atmosphere during the storm genesis there was also evidence of increased sea surface height simultaneously in the form of a downwelling kelvin wave at the west coast of the bay of bengal the present study emphasizes the relationship between near surface oceanic and atmospheric circulation patterns we have tried to elucidate the process with the help of dynamical equations and model solutions we also analyze the pivotal role of the atmospheric rossby wave in the formation of the coastal kelvin wave the kelvin wave seems to produce a warm pool required to form a low pressure system which further gave rise to the tropical storm mora the changes in the temperature and salinity profile within the ocean subsurface layers during storm passage are further used for inferences regarding the vertical structure of the upper ocean due to wind generated mixing the model analysis reveals that the ocean and atmospheric counterparts responsible for storm genesis are well recorded in the coupled model when compared to the observations it was found that air sea coupling in the model made it possible to realistically capture ocean and atmospheric responses

the development of tropical cyclones in the north west of australia case studies of developing and non developing tropical depressions in the north west australian region during the 1979 80 and 1980 81 cyclone seasons have been constructed using conventional and satellite observations these show that enhanced low level winds can occur during the lifetime of non developing disturbances and are not exclusively associated with cyclogenesis both types of system possessed lower level cyclonic circulations and there was an overlapping such that non developing storms could have stronger circulations than some developers at upper levels development was associated with the subtropical ridge being situated over the surface position of the disturbance in contrast the ridge tended to be located southwards of non developers these findings are supported by calculations of area averaged vorticity at 850 and 200 mb cross sections of zonal winds show that non developing systems could exhibit weaker vertical wind shears than some developing storms developers had only moderate shears at worst and maintained a well organized lower cyclonic circulation such features are consistent with both classes of disturbance existing within the monsoon shearline non development was caused by interactions with large scale flows in the southern hemisphere that prevented the necessary conditions for cyclogenesis from being all fulfilled this suggests a need for greater understanding of the influence of mid latitude events on depressions within the monsoon trough

a preliminary study of summertime tropospheric circulation patterns over south america estimated from cloud winds abstract cloud winds obtained from sms i geostationary satellite images for the southern hemisphere summer time are used to describe the tropospheric circulation over tropical and subtropical south america these data provide good spatial and temporal coverage over south america for at least two levels in the troposphere the summertime circulation derived from cloud winds is similar in pattern to that obtained from sparse conventional winds but is more intense the major features of the time averaged circulation at the upper level 300 100 mb are an intense quasi stationary anticyclone trough system extending over most of south america north of 35 s a band of easterly flow near 10 s and strong cross equatorial northward flow between 60 and 80 w longitudes at the lower level 900 700 mb the major features are the northerly and northwesterly jet type flow along the eastern slopes of the central andes and northeasterly trades over much of the remainder of the continental region to the north and cast

ice core palaeoclimate records in tropical south america since the last glacial maximum ice core records spanning the last 25 000 yr from the tropical andes of south america are reviewed these records from quelccaya huascaran and sajama present a high temporal resolution picture of both the late glacial stage lgs and the holocene climatic and environmental conditions in the south american andes late glacial stage conditions at high elevations appear to have been cooler than today although the magnitude of the inferred cooling differs with the particular proxy used e g snowline depression pollen ice cores insoluble dust and anion concentrations in the ice cores reveal that lgs hydrological conditions in the tropics 9 s were much drier than today whereas in the subtropics 18 s lgs conditions were much wetter this probably reflects the migration of the tropical hadley cell in response to a different meridional temperature gradient low nitrate concentrations in the lgs ice from both huascaran and sajama suggest that the amazon basin forest cover may have been much less extensive discussed is the conundrum surrounding the use of d 18 o as a palaeothermometer in the tropics where temperatures exhibit little seasonal variation yet the ice core records suggest that d 18 o records temperature variations on decadal to millennial time scales finally evidence is presented for a strong twentieth century warming copyright 2000 john wiley sons ltd

gold abundance and an aluminosilicate rich alteration zone in the val d or mining district abitibi quebec examples of the fossil geothermal fields abstract investigation of gold abundance in a gold rich mining district by accurate analytical techniques e g instrumental neutron activation and or radiochemical neutron activation shows that gold is anomalously distributed in some parts of the val d or mining district of quebec it is possible to distinguish 1 background values 1 4 3 5 ppb au 2 zones of primarily anomalous gold values around the lamaque sigma mines median 15 ppb au 3 enrichment halos around gold orebodies median 70 ppb au 4 secondary gold enrichment in shear zones and 5 high background values for the east sullivan monzonitic stock the bourlamaque batholith is considered to be a gold enriched intrusion because of areas shear zones that are anomalously enriched in gold median 10 ppb au it is concluded that there are auriferous geological units in the val d or mining district such as the bourlamaque batholith and val d or formation the latter contains the lamaque sigma gold mines representing 49 6 of the total gold production in the district it is interpreted that the val d or formation is part of a central volcanic complex within an island arc system that the centre of this complex is located in the main lamaque plug and that this environment may be compared to high temperature active geothermal systems which are commonly responsible for the formation of epithermal gold deposits the lamaque sigma area is considered to be a fossil geothermal field potentially explaining the anomalous gold values in addition a dumortierite bearing aluminosilicate rich zone of hydrothermal alteration in the val d or mining district is considered as for other similar occurrences to be the result of hydrothermal alteration within a geothermal field producing an al and si rich leached protholith which has subsequently been metamorphosed and deformed a model is proposed for the formation of the gold deposits within the primary gold rich environment by mobilisation of gold in the volcanic rocks due to metamorphism and deformation therefore two distinct and successive events are postulated 1 gold rich synvolcanic geothermal activity and 2 late remobilisation from the host rocks followed by deposition of gold ore within favourable structures

angular momentum transports in tropical cyclones angular momentum budget equations are developed for eulerian and lagrangian cylindrical coordinate systems centred on a tropical cyclone all non friction terms are reduced to boundary transports and the effects of cyclone motion in the eulerian coordinate system are isolated a number of intensifying and weakening composite northwest pacific cyclones are used to illustrate the physical role and relative importance of each process in the maintenance or destruction of tropical cyclones at various intensity stages

does a monsoon climate exist over south america the climatology and the basic state of the summertime circulation and rainfall over south america are studied using assimilation products from the data assimilation system of goddard earth observing system 1 geos1 and satellite derived rainfall results indicate the existence of a regional summer monsoon circulation regime induced by strong diabatic heating over the subtropical south american highland centered at the altiplano plateau sensitivity of the results to the assimilation scheme is tested by comparing that with the national centers for environmental prediction ncep reanalysis and with satellite rainfall estimates results show general agreement between the model produced rainfall anomaly and the satellite estimates as well as consistency between the basic circulation features in the geos 1 and the ncep reanalyses a case study of 1989 90 south american summer monsoon sasm reveals the following characteristics 1 in late spring the onset of sasm is signaled by an abrupt merging of the upper tropospheric double westerly jets one in the subtropics and the other in the subpolar region into a single jet in the midlatitudes this is followed by the establishment of a vortex to the southeast of altiplano and occurrence of heavy precipitation over subtropical eastern brazil 2 during the mature phase of sasm the heavy rainfall zone moves over the altiplano plateau and the southernmost brazilian highland the fully established sasm features are the following a an enhancement of equatorial north atlantic trade wind which emanates from the sahara high and crosses the equator over the south american continent b a buildup of strong northwesterlies along the eastern side of the tropical andes and c development of the south atlantic convergence zone in the southernmost position with strong convective activity meanwhile the upper tropospheric return flow emerges from an anticyclone formed over the altiplano plateau crosses the equator and sinks over northwestern africa 3 the withdrawal of sasm in late summer is signaled by the resplitting of the midlatitude westerly jet at the same time the low level northwest monsoon flow diminishes reducing the moisture supply and leading to the termination of heavy precipitation over the subtropical highland results also show that the above mentioned characteristics of sasm are clearly linked to the tropospheric temperature changes over the central south american highland sensible versus latent heating over the highland are bound to play an important role in the evolution of sasm to provide further support of presence of a monsoon climate over south america sasm is compared and contrasted to the classic east asian summer monsoon easm many similar features including evolution characteristics between the two systems have been identified contrasting aspects of the sasm from the easm are also discussed it is pointed out that a number of monsoonal characteristics of the climate of south america such as the seasonal reversal of the low level wind become apparent only when the strong annual mean wind is removed based on the characteristic features and their evolution the authors conclude that a monsoon climate does exist over south america

structure and evolution of the large scale flow and an embedded upper tropospheric cyclonic vortex over northeast brazil horizontal structure and evolution of large scale flow and an embedded synoptic scale cyclonic vortex over northeast brazil as separate systems and dynamical interaction between them are studied at 200 hpa a quasistationary cyclonic vortex with its average position at 10 8s and 358w that formed and remained active during 5 10 january 1993 is selected for the investigation the evolution of large scale flow in the prevortex period 1 4 january is also explored an efficient and effective scale separation technique is developed and used to separate the large scale flow and embedded synoptic scale vortex it is shown that a strong positive shear zone developed in the latitude domain 17 58 7 58s within the south atlantic trough region before the vortex formation the shear zone has a characteristic meridional zonal scale of 1000 km 3000 km and satisfies strongly the necessary condition for barotropic instability it is identified that the development of a strong shear zone is associated with the intensification of a bolivian anticyclone and associated ridge and their eastward shift and intensification of the south atlantic trough east west orientation of the atlantic trough and the presence of a transient trough over the equatorial atlantic ocean the average structure of vortex including zonal and meridional characteristic scales is computed from the synoptic bandpass flow the vortex is identified as a nonlinear wave packet with an average zonal wavelength of 2750 km and it is confined to a latitude belt of about 17 58 the vortex shows a strong westward tilt with latitude the convergence zone is located to its southwest and it is a weak cold cored system maximum cyclonic vorticity of the vortex is 23 24 3 1025 s 21 which is comparable to the value for embedding flow the momentum transports due to the vortex large scale eddy and the vortex large scale eddy interaction are computed it is found that the vortex and vortex large scale eddy westerly momentum transports are southward down the gradient of embedding zonal flow and their divergence convergence is located over the latitudes of large scale westerlies easterlies the sensible heat transports are weak it is noted that the vortex large scale flow interaction leads to the weakening of the shear zone and restoration of the large circulation features to their january 1993 mean configuration which have undergone significant deviation during the prevortex period the signature of vortex large scale interaction is also seen in the evolution of dynamical parameters y and n2 q square of refractive index parameter

tropical cyclone convection the effects of a vortex boundary layer wind profile on deep convection we describe idealized numerical model experiments to study the effects of a vortex boundary layer wind profile on the generation of vertical vorticity in tropical deep convection situations are considered in which there is either no vertical shear above the boundary layer or negative vertical shear appropriate to a warm cored vortex deep convection growing in these environments develops dipole structures of vertical vorticity in which the cyclonic gyre is favoured and persists longer than the anticyclonic one the orientation of the dipole at a particular height is determined partly by that of the ambient horizontal vortex lines which rotate with height and also by the vertical advection of vertical vorticity from below an increase in the magnitude of boundary layer shear enhances the distortion of the initial thermal weakening its subsequent ascent rate this effect is detrimental to vertical vorticity production by stretching but because the increase in shear implies an increase in the magnitude of horizontal vorticity that can be tilted its net effect on the vertical vorticity production by tilting cannot be foreseen in the calculations described the effect of the increased horizontal vorticity dominates so that updraughts rising in stronger vertical shear have larger vertical vorticity maxima despite smaller vertical velocity maxima with negative vertical shear above the boundary layer the vorticity dipole reverses in sign with height as in a recent study of the effects of unidirectional shear the results provide a basis for appraising a recently proposed conceptual model for the inward contraction of eyewall convection in tropical cyclones as well as a starting point for developing an improved understanding of the formation of a vorticity monopole during tropical cyclogenesis

rock fragments in top soils significance and processes this introductory paper reviews various aspects of rock fragments in top soils such information is required for various reasons and in particular for predicting the impact of climatic or landuse changes on the response of these soils particular attention is paid to the definition and measurement of rock fragment content in top soils the density of soils containing rock fragments the spatial distribution and movement of rock fragments in top soils the effects of rock fragments on some key hydrological processes thermal properties of top soils physical soil degradation soil erosion and soil productivity

annual cycle of upper air circulation and convective activity over the tropical americas a combination of novel data sets including satellite derived outgoing longwave radiation and highly reflective clouds rain gauge records and upper air analyses of the european centre for medium range weather forecasts have been evaluated in context to reappraise the multiyear mean convective activity and circulation and their annual cycle variations over the tropical americas in austral summer a maximum of 200 mbar geopotential height anticyclonic vortex in the wind field and extremum of stream function are located over the western part of the amazon basin well to the west of the extremum of the velocity potential to the north of that and the nucleus of the most intense convection and rainfall the major upper tropospheric divergence is found over northern south america from this outflow is directed primarily northward into an area of strongest convergence situated over the equatorward side of the north atlantic surface high in the evolution from austral to boreal summer the high over western amazonia vanishes and the centers of strongest convection upper tropospheric velocity potential and divergence establish themselves in the realm of the intertropical convergence zone over the eastern equatorial pacific with outflow directed mainly into a broad zone of upper tropospheric convergence in the southern hemisphere after the height of the boreal summer the centers of convection and velocity potential develop again over southeastern amazonia and the upper tropospheric high and weak anticyclone separately form again over the western portion of the amazon basin

chaco low level jet events characterization during the austral summer season 1 previous studies showed a relationship between convection maxima and the convergence of vapor flux over southeastern south america nicolini and saulo 2000 explored the hypothesis of an intensification of this mutual dependency during the chaco jet events they defined these events as extreme cases of low level jets east of the andes that penetrate southernmost to 25 s using eta operative products during the 1997 1998 austral warm season the interest of the present paper centers on the climatic characterization of the chaco jet events cjes and the possibility of researching this hypothesis using the european centre for medium range weather forecasts reanalyses era which cover a 15 year period 1979 1993 the cjes represent a subensemble of low level jet events east of the andes that are infrequent in the era data set their duration varies from 1 to 10 days more frequently extending from 1 to 5 days the outstanding features of the circulation and the thermodynamic field that represent this ensemble are a maximum contrast of air masses in a latitude close to 39 s the presence of a trough centered on 70 w within a baroclinic wave train penetrating from the pacific ocean and a maximum of heat and moisture over northen argentina and paraguay during the cjes there is an important flux of moisture and convergence at low and mid levels that is about 10 times more intense than the summer mean the intensity found in the water vapor flux anomaly reinforces the importance of studying these episodes for the purpose of determining the water balance over southeastern south america the statement that the cjes represent an important characteristic of the southeastern south american climate is founded on the fact that although the cjes only represent 17 of the austral summer days they account for a significant fraction of the precipitation a maximun of 55 over northeastern argentina however it is indispensable to contrast these results with future field experiments to test the hypothesis addressed in this paper

influence of substrate on the distribution of the hawaiian silversword argyroxiphium sandwicense dc in haleakala maui hi the spatial patterns of the hawaiian silversword argyroxiphium sandwicense dc were studied in haleakala maui hi the silversword is a giant rosette plant nearly brought to extinction by human impact and goat browsing during the 1920s but stern protection has resulted in the resurgence of plant populations silversword regeneration is occurring vigorously in soils with surficial layers of volcaniclastic fragments ten sites with sizable silversword populations and the associated substrates were examined in haleakala s crater between 2175 and 2755 m at each site the population structure of 100 plants was determined along wandering quarter transects which limit sampling bias substrates where rosettes were rooted and the size of the biggest stone fragments upslope and downslope from the plant s base were determined volcaniclastic substrates were examined with photographs along 12 m long transverse transects fine debris samples gravel and pebbles were analyzed by mechanical sifting of surficial fragments gathered from 15 15 cm miniplots volcaniclastic fragments in silversword areas have different sources i most were ejected during eruptions yielding pyroclastic materials ash to blocks that built cinder cones on haleakala s crater ii on steep slopes weathering of olivine alkali basalt outcrops and subsequent mass wasting of rock fragments contributed a mantle of clasts to slopes below iii on some cinder cones welded spatter was produced during late eruptive stages this coalesced into ruff like agglutinate layers around crater rims called pohaku o hanalei wreath of stones agglutinate deposits weather gradually supplying clasts that roll downhill and accumulate on cone flanks iv on weathered aa lava flows stone fragments and rocky crags abound along eroding lava flow ridges associated with vegetation but the intervening troughs covered with fine ash and cinder remain bare silversword population structures indicate healthy regeneration all populations display a typical pattern of decreasing silversword numbers with increasing size age nearly 65 of the rosettes are rooted near cobbles 5 10 cm long or pebbles 2 5 5 cm and 23 grow at the base of blocks 10 cm or outcrops 9 of the plants are on gravel 2 5 cm but only 1 have germinated on sandy soil without granules or stones 2 of the silverswords grow on organic litter of dead rosettes plants on six sites showed noticeable differences in clast size between their upslope and downslope sides particles are significantly larger upslope from rosettes this suggests that successful seedlings germinate below clasts which deflect finer downslope moving sediment thus protecting young plants from burial by descending debris statistical tests indicate a few blocks above plants may have been stopped by adult rosettes such a relationship underscores the dynamic nature of steep cinder and rubble talus slopes regularly affected by dry debris slides frost creep and other mass wasting processes slope instability is also evinced by i common bending and deformation of silversword roots particularly in seedlings which trail upslope ii pronounced downhill tilting and asymmetry of tall rosettes on steep gradients iii presence of accumulated fine debris steps 9 9 13 8 cm thick upslope from plants and blocks iv ubiquitous fine earth flags exposed below embedded blocks which intercept descending debris and deflect it laterally v widespread miniature sorted stripes

hurricane juan 2003 part i a diagnostic and compositing life cycle study abstract a detailed analysis of the complex life cycle of hurricane juan in 2003 is undertaken to elucidate the structures and forcings that prevailed over the period leading up to the hurricane s landfall in halifax nova scotia canada despite the presence of easterly wave precursors hurricane juan s initial development is shown to occur in a baroclinic environment beneath a low latitude potential vorticity streamer this feature interacts with a lower level shear line as the incipient vortex begins to effectively focus ascent and convection the system undergoes a slow tropical transition over a period of several days as the deep layer shear over the developing storm decreases the hurricane is repeatedly perturbed by subsynoptic scale waves traveling along the leading edge of a large upstream trough however hurricane juan maintains its tropical structure despite its relatively high formation latitude 28 n and its northward trajectory the unusual persistence of the storm s tropical nature as i

influence of equatorial waves on the genesis of super typhoon haiyan 2013 abstractthe influence of equatorial wave disturbances on the genesis of super typhoon haiyan 2013 is investigated through spectral composite and ensemble sensitivity analysis of various observational datasets in combination with predictions from an operational ensemble under the favorable large scale environmental conditions of the asian monsoon combined with the madden julian oscillation mjo the incipient haiyan develops from a cyclonic disturbance that originates from a train of westward propagating mixed rossby gravity mrg waves haiyan eventually develops in the monsoon trough region at the leading edge of the moist mjo phase that has strong low level convergence high moisture content and weak shear along with high sea surface temperature these favorable environmental conditions promote the intensification of deep moist convection that facilitates the development of the cyclonic disturbance from an mrg wave into a tropical depression which later intensifies rapidly into super typhoon ha

the alkaline porphyry associated yao an gold deposit yunnan china rare earth element and stable isotope evidence for magmatic hydrothermal ore formation the yao an vein type gold deposit is located in the ailaoshan jinshajiang alkaline intrusive belt yunnan province china and is associated both in time and space with 33 5 1 0 ma old alkaline intrusions the gold mineralization is associated with potassic wall rock alteration the ree distribution patterns of secondary k feldspar are generally similar to those of the igneous perthite but with about seven times higher total ree abundances the alteration is ascribed to a high ree magmatic fluid derived from the yao an alkaline intrusive suite the hydrothermal yao an gold deposit formed during two gold bearing stages i e a sulfide pyrite stage and a sulfide oxide stage pyrite specularite the ree abundance of early stage i pyrite is relatively high with strong enrichment in lree la yb n of 40 290 generally positive eu anomalies eu eu 0 86 1 55 and ree patterns very similar to those of secondary feldspar in contrast the later stage ii pyrite has much lower ree concentrations and lower la yb n of 5 5 11 8 eu eu of 0 49 0 76 and flat chondrite normalized spidergram patterns the stage i pyrite has 34s in the range of 2 2 to 3 2 and overlaps with regionally distributed pyrite in least altered syenite porphyry in contrast stage ii pyrite has much higher 34s values between 7 8 and 16 5 carbon isotope data for four samples from stage ii revealed 13c pdb values between 6 and 8 these stable isotope and ree data suggest that magmatic fluids of the alkaline intrusions caused both potassic alteration and stage i sulfide mineralization the system evolved from stage i to stage ii mineralization by influx of meteoric fluids with relatively heavier sulfur although calcite carbon isotope data suggest that the co2 remained dominantly of magmatic origin

biogeomorphic influence of soil depth to bedrock volcanic ash soils and surface tephra on silversword distribution haleakalā crater maui hawai i abstract this research examines the spatial distribution of haleakal silverswords argyroxiphium sandwicense dc subsp macrocephalum over basaltic a lava flows at silversword loop haleakal crater maui hawai i the overall study goal is to situate an extensive field data set within an historical geomorphic framework to propose a conceptual biogeomorphic model of landscape development at silversword loop landscape features were investigated along two belt transects 111 120 m long crossing lava flow deposits at 2175 m the lava flows 4 5 km long originated 2700 ybp at pu u o m ui a large cinder cone transects consist of contiguous 3 3 m 9 m2 quadrats plot data include topographic profiles soil depth to bedrock size of surface tephra determined by photosieving and plant density 23 soil samples were analyzed within 10 profiles weathered lava outcrops tephra blocks 10 cm and cobbles 5 10 cm cover lava flow ridges the gently sloping flanks of lava flow deposits merge into intervenient concave troughs filled with volcanic ash and small tephra soils along ridges are thin 17 cm whereas profiles on troughs are deeper 110 cm soils are sandy volcanic inceptisols lithic typic and aridic lithic haplustepts averaging 21 6 gravel 96 8 sand and 3 2 fines silt clay mean organic matter is just 0 92 these soils provide low water retention 23 2 at field capacity and rapid infiltration deeper trough soils are largely devoid of plants in contrast silverswords are virtually restricted to shallow soils on lava flow crests where they densely cluster about outcrops and blocks 90 of plants grow on soils 40 cm deep and 71 3 occupy plots with 40 ash cover 84 4 of rosettes are rooted on outcrops or near stones only 4 4 grow on soil and 11 2 germinated on plant litter patterns of lava flow weathering and soil depth to bedrock control silversword distribution at silversword loop shallow basalt bedrock and outcrops restrict soil drainage providing a perched water table that silversword roots can exploit surface blocks also provide safe stable microhabitats thus rosettes grow preferentially near stones geomorphological pedological and ecological data are integrated into a biogeomorphic sequence of soil development and landscape evolution at silversword loop for the past three millennia first through the eruptions and ash deposits of pu u o m ui followed 970 940 bp by pyroclastic activity in hal li i and ka lu u o ka o o cinder cones

tropical cyclogenesis a comparative study of two depressions in the northwest of australia a comparative study of two cloud clusters in the north west of australia highlights synoptic influences on tropical cyclogenesis although both clusters developed over land in the same region the large scale flow was conducive to the subsequent development of one cluster into tropical cyclone enid and suppressed the development of the other cluster the non developing low was under strong upper easterlies from an upper tropospheric ridge an upper trough in the subtropical westerlies later split the ridge bringing light and divergent upper winds over the low level monsoonal trough this facilitated the development and intensification of a low level cyclonic circulation tropical cyclone enid

allard stock la plata mountains colorado an alkaline rock hosted porphyry copper precious metal deposit the allard stock which hosts a porphyry cu ag au pt metals deposit is an epizonal laramide pluton at the southwest end of the colorado mineral belt the stock and associated mineralization evolved by a complex interaction of igneous and metasomatic processes as follows stage 1 forceful emplacement of syenite plutons stage 2 intense hydrothermal argillization of stage 1 syenites stage 3 intrusion of mafic syenite plutons some of which are layered along shear zones stage 4 violent escape of volatiles producing intrusive breccia pipes stage 5 intense k metasomatic alteration of the older stock units with production of a fenitelike alteration halo extending 1000 m beyond the stock and simultaneous intrusion of carbonate bearing alkali feldspar dikes stage 6 emplacement of trachyte syenite pegmatite and mafic pegmatite dikes stage 7 deposition of metallic minerals sanidine quartz calcite and fluorite as veinlets and disseminated replacement masses from hydrothermal solutions the stock

the role of tephra covers on soil moisture conservation at haleakala s crater maui hawai i abstract the influence of tephra covers on soil water was studied in haleakala maui hawai i during two summers eight sites with tephra layers and silverswords argyroxiphium sandwicense dc were sampled at 2415 2755 m at each site eight paired sample sets were obtained in bare soils and under adjacent tephra at three depths tephra were sharply separated from underlying soils and showed prominent vertical stratification tephra clast size distribution was assessed by photosieving and on interstitial gravel samples stones included 45 6 cobbles 29 4 pebbles and 25 blocks moisture content increased with depth in both positions but soils below tephra had more water at all depths than exposed areas surface soils beneath tephra contained 83 more water than bare ground soils at 5 10 cm had 106 greater moisture under rocks but only 70 at 10 15 cm differences between plots were statistically significant p all soils were coarse with 20 gravel and 94 sand most fine material 0 063 mm was silt as clay content was negligible organic matter percentage was low 1 65 bulk density and porosity were associated with moisture variation both in tephra insulated and bare soils 80 of field moisture was statistically p

gold mineralization in the northern margin of the north china craton influence of alkaline magmatism and regional tectonic during middle paleozoic mesozoic abstract the northern margin of north china craton nncc has undergone multiple tectonic and magmatic episodes associated with numerous gold mineralization during devonian to cretaceous the origin of gold mineralization is a subject of debate in the nncc but there is a consensus on a metamorphic hydrothermal origin and a magmatic hydrothermal origin for this study we focused on four gold districts including the daqingshan zhangjiakou west liaoning and changbaishan from west to east we specifically constrain the link between the hadamengou dongping jinchanggouliang erdaogou and haigou gold deposits and their magmatic episodes the dahuabei and haigou granites and dongping syenite rocks have an alkaline affinity in contrast the xitaizi jinchanggouliang and xiaoxigou granites as well as the duimiangou quartz monzonites are calc alkaline with high alkaline rocks they are predominantly metaluminous and high fractionated i type granites except the xiaoxigou granite which is a type granites with peraluminous nature this indicates a variable mixing between depleted mantle derived mafic magma and ancient crust derived magma the magmatic events overlap the gold mineralization episodes in the nncc we have identified four magmatic episodes during middle paleozoic to mesozoic at 400 320 ma 245 221 ma 199 161 ma and 143 125 ma on the other hand gold mineralization was emplaced from carboniferous to cretaceous 390 110 ma with a peak in the middle jurassic 170 160 ma the available sulfur oxygen and carbon isotopic data from the studied nncc gold deposits suggest that the ore forming fluids were derived from a mixture of magmatic fluids and meteoric waters that flow in the wall rocks except for the hadamengou and jinchanggouliang gold deposits both late deposits present a multi source involving organic matter and other regional crustal rocks as shown by their positive 34s values 0 6 18 5 the intrusive rocks and sulfides in the nncc display similar lead isotope data suggesting that the lead isotopes might have similar origin the gold forming materials resulting from the mixing of these fluids are the product of several alkaline magmatism activities in this region hence this study has proved that gold mineralization is spatially and temporally related to the alkaline magmatism in the nncc the dominant tectonic events in the nncc are marked by post collisional or anorogenic geodynamical setting which is characterized by high alkaline features and andean type arc related to subduction geodynamical setting and characterized by calc alkaline features of the studied rocks both tectonic events are controlled by 1 the collision between the ncc and the bainaimiao arc 2 the subduction of the paleo asian ocean plate beneath the ncc 3 the collision between the siberian craton and the ncc and 4 the subduction of the western paleo pacific beneath the ncc these tectonic regimes are expressed by a transitional regime changing from compression to extension at western and an extensional regime at western and eastern parts of the nncc respectively

intensification of tropical cyclone like vortices in uniform zonal background flows the effect of uniform zonal background flows on the intensification of tropical cyclone like vortices is investigated using a numerical three layer shallow water model that includes parametrizations of convection sea surface energy exchange and boundary layer friction calculations on an f plane showed that during the developing stage an initially weak vortex intensified more rapidly in the presence of a uniform zonal background flow compared to an environment at rest the uniform zonal background flow resulted in increased boundary layer convergence collocated with increased boundary layer mixing ratio as a result of surface moisture fluxes producing stronger convection and more rapid intensification after the vortex achieved hurricane strength in the presence of an easterly westerly background flow a region of convectively stable air formed to the south north of the vortex centre as a result of small values of surface moisture flux and the downward transport of relatively dry middle layer air this convectively stable air penetrated slowly into regions of boundary layer convergence thereby weakening convection and reducing the maximum intensity of the vortex compared to the case without background flow this effect was more pronounced for stronger background flows calculations on a plane showed that a westerly background flow is more favourable for intensification than an easterly background flow of the same strength in the former the vortex always moved into a region of convectively unstable air whereas in the latter the vortex progressively moved into a region of convectively stable air produced by subsidence and drying of the boundary layer because of the relatively high vortex drift speed in the easterly background flow case there was not sufficient time for surface moisture fluxes to moisten the boundary layer air rapidly enough to eliminate the convectively stable region ahead of the vortex resulting in the overall weakening of convective activity and a less intense storm than in the westerly flow case the foregoing calculations suggest that the imposed background flow affects the development of the vortices in the shallow water model by establishing an environment in which boundary layer convergence and surface moisture fluxes may interact to produce stratifications that either enhance or suppress convection the occurrence of which is necessary for the intensification of the vortices in the model

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

isotope geochemistry of the northeast zone mount polley alkalic cu au ag porphyry deposit british columbia a case for carbonate assimilation mount polley is a late triassic 205 ma alkalic porphyry cu au ag deposit 226 3 thousand tonnes t cu 21 5 t au and 65 1 t ag hosted by silica undersaturated to silica saturated monzonitic intrusions of the mount polley complex located in british columbia canada the northeast ore zone at mount polley is hosted by magmatic hydrothermal breccia copper and precious metals occur in sulfide minerals primarily as coarse to fine grained breccia cement local wall rocks include equigranular to porphyritic diorite monzodiorite and monzonite alteration breccia cement and veins of the northeast ore zone formed in five paragenetic stages prebreccia stage 1 brecciation and main stage mineralization stage 2 late stage mineralization stage 3 unmineralized postbreccia dikes and veins stage 4 and epithermal style veins stage 5 intense pervasive k and fe metasomatism calcite and calc silicate alteration occurred prior to brecciation caused by the intrusion of megacrystic k feldspar phyric monzonite stage 2 fluids were silica undersaturated high temperature 350 c co2 enriched and of near neutral to alkaline ph potassic sodic and calc potassic assemblages precipitated with mineralization during stage 2 with moderate temperatures at the deposit periphery and in stages 3 and 4 evidence for more acidic and lower temperature conditions is preserved in stage 5 veins the 34ssulfide isotope compositions of stages 2 and 3 chalcopyrite pyrite and bornite range from 7 1 to 1 4 sulfur isotope compositions of anhydrite and gypsum are mostly between 6 2 and 9 8 these values together with the presence of hematite are consistent with deposition from an oxidized sulfate dominant high temperature magmatic hydrothermal fluid limited sulfur isotope geothermometry indicates that cu sulfides precipitated at temperatures from 480 to 250 c hydrothermal calcite occurs in all paragenetic stages at mount polley calcite 13c values range from 0 2 to 10 5 and 18o values from 4 0 to 20 9 the enriched c o isotope values are not consistent with simple precipitation from an entirely magmatic source of hydrothermal fluid interaction of the fluid and or magma with limestone is considered a likely process to explain the c and o isotope signature lead isotope data suggest mixing of mantle and crustal sources during mineralization main stage chalcopyrite and pyrite as well as late stage galena have 206 204pb values of 18 77 to 18 92 207 204pb of 15 56 to 15 59 and 208 204pb of 38 22 to 38 32 strontium isotope data 0 70331 0 70371 provide evidence of a strongly depleted mantle source of sr with minor crustal input epsilon nd values for main stage apatite range between 5 9 and 6 5 also indicating a depleted mantle source stage 5 carbonate 206 204pb values of 18 96 to 19 04 207 204pb of 15 57 to 15 59 and 208 204pb of 38 26 to 38 36 suggest superposition of an epithermal system onto the northeast ore zone potentially as late as 100 m y after breccia formation the data presented are consistent with the hypothesis that the silica undersaturated alkalic mount polley complex formed due to carbonate assimilation prior to mineralization this process can explain the 13c 18o isotope data calcite precipitation concurrent with cu au mineralization and silica undersaturation of the magma the co2 released during assimilation of carbonate also could have promoted magmatic hydrothermal brecciation silica undersaturated alkalic porphyry systems may preferentially form in arc terranes built on a carbonate bearing substrate

interactions between simulated tropical cyclones and an environment with a variable coriolis parameter abstract numerical simulations of tropical cyclones are performed to examine the effects of a variable coriolis parameter on the structure and intensity of hurricanes the simulations are performed using the nonhydrostatic fifth generation pennsylvania state university national center for atmospheric research mesoscale model using a 5 km fine mesh and fully explicit representation of moist processes when a variable conolis parameter f environment is applied to a mature tropical cyclone a persistent north northwesterly shear develops over the storm center as a result of an interaction between the primary circulation of the storm and the gradient in absolute vorticity as a result the variable f storm quickly develops a persistent wavenumber 1 asymmetry in its inner core structure with upward motion and rainfall concentrated on the left side of the shear looking downshear in agreement with earlier studies in comparison the constant f storm develops weak transient asymmetries in structure that are

a statistical perspective on wind profiles and vertical wind shear in tropical cyclone environments of the northern hemisphere abstracta statistical analysis of tropical cyclone tc environmental wind profiles is conducted in order to better understand how vertical wind shear influences tc intensity change the wind profiles are computed from global atmospheric reanalyses around the best track locations of 7554 tc cases in the northern hemisphere tropics mean wind profiles within each basin exhibit significant differences in the magnitude and direction of vertical wind shear comparisons between tc environments and randomly selected non tc environments highlight the synoptic regimes that support tcs in each basin which are often characterized by weaker deep layer shear because weaker deep layer shear may not be the only aspect of the environmental flow that makes a tc environment more favorable for tcs two new parameters are developed to describe the height and depth of vertical shear distributions of these parameters indicate that in both tc and non tc environments vertical shear most frequently occurs in shallow layer

midsummer low level circulation and precipitation in subtropical south america and related sea surface temperature anomalies in the south atlantic abstract the midsummer interannual variability of the low level tropospheric circulation and of the precipitation field in subtropical south america sa associated to the sea surface temperature sst anomalies in the western subtropical south atlantic ocean wssa is investigated using reanalyses regional precipitation datasets and monthly ssts the region of the wssa where sst has the strongest relation with precipitation in subtropical sa was identified using canonical correlation analysis this region extends from 20 to 30 s and from 30 to 50 w composites corresponding to extreme ssts in this area show two well differentiated patterns in the low level circulation and in the precipitation fields in the composite corresponding to the more positive sst anomalies in this area the mainstream of the low level flow and of the moisture transport from the continental low latitudes starts to follow a southeastward direction at 10 s and converges with the west flow at 35 s over the atlantic ocean on t

pge geochemistry of the fengshan porphyry skarn cu mo deposit hubei province eastern china abstract the fengshan cu mo deposit is located in the western part of the jiurui cu au mo district in the late mesozoic middle lower yangtze river metallogenic belt yrmb eastern china the mineralization is spatially associated with the fengshan granodiorite porphyry stock 149 138 ma where two types of ore bodies porphyry skarn occur the fengshan deposit is located on the yangtze craton i e in an intracontinental extensional environment a geological setting not considered by previous studies of pge abundance and distribution in porphyry systems for the present investigation the pge geochemistry of fourteen samples of the granodiorite ore and flotation concentrates were determined by icp ms after preconcentration by the lead fire assay technique from large 30 g samples a maximum of 32 ppb pd and 81 2 ppb pt is reported for the molybdenum flotation concentrate cu au pt pd contents from flotation concentrate samples are almost 1 to 2 orders of magnitude higher than those reported for ore samples this is especially true for the pt content covariant diagrams of cu and mo with noble metals au ag pt and pd reveal weak correlation between cu vs au ag and mo vs pt also au shows a slightly positive relationship with pt and pd it is apparent that pd and pt contents of flotation concentrate from the fengshan deposit are considerably lower than those reported for porphyry deposits in an island arc setting however au and ag appear to be elevated in the fengshan deposit the intrusion derived from an enriched mantle source high oxygen fugacity fo2 and liberation of mantle sulfates during partial melting are the first steps for pge enrichment in porphyry cu deposits however the fengshan granodiorite was most likely generated by partial melting of enriched mantle that was previously metasomatized by slab melts related to an ancient subduction system au pt and pd in potassic alteration zones and or endocontact zones are transported as an aqueous chloride complex in high temperature hypersaline fluid in contrast au pt and pd would be transported by bisulfide complex in low temperature intermediate salinity fluid in phyllic alteration zones and or exocontact marble that is distinctly different from the porphyry cu deposits in an island arc environment where intrusion derived directly from slab melting and pd and pt are transported only as chloride complexes

tropical convection the effects of ambient vertical and horizontal vorticity we present a series of idealized numerical model experiments to investigate aspects of deep convection in tropical depressions including the effects of boundary layer wind structure on storm structure especially on vertical vorticity production and updraught splitting and the combined effects of horizontal and vertical shear on vertical vorticity production with and without background rotation in warm cored disturbances such as tropical depressions the vertical shear and horizontal vorticity change sign at some level near the top of the boundary layer so that unlike in the typical middle latitude supercell storm the tilting of horizontal vorticity by a convective updraught leads not only to dipole patterns of vertical vorticity but to a reversal also in sign of the updraught rotation with height this finding has implications for understanding the merger of convectively induced vorticity anomalies during vortex evolution ambient cyclonic horizontal shear and or cyclonic vertical vorticity favour amplification of the cyclonically rotating gyre of the dipole consistent with an earlier study storm splitting occurs in environments with pure horizontal shear as well as pure vertical shear but the morphology of splitting is different in both situations splitting is found to require a relatively unstable sounding and relatively strong wind shear

summertime precipitation variability over south america role of the large scale circulation abstract the observed large scale circulation mechanisms associated with summertime precipitation variability over south america are investigated particular attention is paid to the altiplano where a close relationship has been observed between rainfall and the position and intensity of the bolivian high empirical orthogonal function eof correlation and composite analyses suggest that on intraseasonal timescales typically 5 20 days rainy periods on the altiplano are associated with at least three types of circulation anomalies involving either extratropical cyclones cold core lows or the westward enhancement of the south atlantic high in each instance the primary support for high rainfall rates is a moist poleward flow at low levels along the eastern flank of the central andes in association with the south atlantic convergence zone sacz the warm low level flow along the sacz also inflates the overlying atmospheric column resulting in an intensification and southward shift of the bolivi

biogeomorphological influence of slope processes and sedimentology on vascular talus vegetation in the southern cascades california abstract the vascular vegetation of alpine talus slopes between 2035 and 3095 m altitude was studied at lassen volcanic national park california in the cascade range taluses show a diverse flora with 79 plant species growth forms include coniferous trees shrubs suffrutices herbs graminoids and ferns spatial patterns of plant distribution were studied along 40 point intercept transects plant cover was low 0 32 7 on all slopes spatially variable and showed no consistent trends sedimentological characteristics were determined by photosieving next to 1500 plants this census indicated preferential plant growth on blocks and cobbles with 43 2 and 23 3 of the plants growing on these stones respectively fewer specimens were rooted on pebbles 13 or on stone free gravel areas 20 5 growth forms displayed different substrate preferences 92 5 of the shrubs and 83 of the suffrutices colonized blocks or cobbles but only 57 2 of the herbs and 59 8 of the graminoids grew on large stones plants are associated with large clasts because 1 coarse talus is more stable than fine sediment areas which are more frequently disturbed by various geomorphic processes and 2 large stones help conserve substrate water beneath them while moisture quickly evaporates from fine debris root patterns were studied for 30 plant species 10 specimens for each species were excavated and inspected and several root growth ratios calculated all species exhibited pronounced root asymmetry as roots for most plants grew upslope from their shoot base for 23 species all specimens had 100 of their roots growing upslope for the other 7 species 92 2 99 3 of below ground biomass extended uphill this uneven root distribution is ascribed to continual substrate instability and resulting talus shift as cascading debris progressively buries roots and stems plants are gradually pushed and or stretched downhill various disturbance events affect root development slope erosion following rubble removal often exposes plant roots debris deposition can completely bury plants some may survive sedimentation producing new shoots that grow through accumulated debris shrubs may propagate by layering as adventitious roots develop along buried stems or produce new clones along their roots slope processes may damage and transport plant pieces downhill some species can sprout from severed displaced root or stem fragments vegetation interacts with several geomorphic processes including debris flows grain flows rockfall snow avalanches frost creep and runoff larger plants may alter local patterns of debris movement and deposition damming cascading debris on their upslope side and deflecting sediments laterally to plant margins where they form narrow elongated stone stripes

new insights into the rainfall variability in the tropical andes on seasonal and interannual time scales in this study we analyze the atmospheric mechanisms associated with the main rainfall patterns in the tropical andes 20 circ hbox s 1 circ hbox n on seasonal and interannual time scales using a homogeneous and high spatial resolution precipitation data set 0 05 circ times 0 05 circ at monthly time step chirps 1981 2016 in situ precipitation from 206 rain gauge stations power spectrum and eof analysis we identify three andean regions characterized by specific seasonal and interannual rainfall modes the equatorial andes ea 5 circ hbox s 1 circ hbox n the transition zone tz 8 circ hbox s 5 circ hbox s and the southern tropical andes sta 20 circ hbox s 8 circ hbox s on seasonal time scales the main mode of precipitation in the ea and sta are characterized by a unimodal regime while the tz is represented by a bimodal regime the ea and the tz share the same wet season in the february april period which is associated with a weakened walker cell the southerly position of the intertropical convergence zone itcz and a strong westward humidity transport from the equatorial amazon this latter mechanism and a reduced elevation of the andes are associated with the october november wet season in the tz the presence of the bolivian high and the northward extension of the low level jet are associated with the precipitation over andean regions between 20 circ s and 8 circ s in the december march period on interannual time scales extreme monthly wet events emwe in the sta tz are related to convection over the western equatorial amazon during the december march february april period showing an atmospheric relationship between the amazon and the andes extreme monthly dry events emde in the tz and in the ea during the february april period are related to a strengthened walker cell especially in the eastern pacific in addition emwe emde in the ea are associated with an anomalous southward northward displaced eastern pacific itcz moreover we find a relationship between precipitation at higher elevations in the andes north of 10 circ hbox s and easterly winds at 200 hpa during february april emwe finally extreme monthly events in the ea sta are related to sea surface temperature anomalies in the western central equatorial pacific

examining the roles of the easterly wave critical layer and vorticity accretion during the tropical cyclogenesis of hurricane sandy abstractthe tropical cyclogenesis sequence of hurricane sandy is examined it is shown that genesis occurs within a recirculating kelvin cat s eye flow of a westward propagating tropical wave the cat s eye flow is able to provide a protective environment for the mesoscale vortex to grow and is characterized by gradual column moistening and increased areal coverage of deep cumulus convection these findings are generally consistent with a recently proposed tropical cyclogenesis sequence referred to as the marsupial paradigm sandy s cyclogenesis provides a useful illustration of the marsupial paradigm within a partially open recirculating region with the opening located south of the pouch center it is suggested that the opening acts to enhance the genesis process because it is adjacent to an environment characterized by warm moist air conditions favorable for tropical cyclogenesis from a dynamical perspective accretion of low level cyclonic vorticity filaments into the developing vortex from sever

a numerical study on the effects of environmental flow on tropical storm genesis abstract the role of the environmental wind in tropical storm genesis is studied using a numerical simulationmodel the model used is an 11 level primitive equation model covering a channel domain of 25 span withopen lateral boundaries at 5 5 and 30 5 n a number of experiments were integrated for 96 h in which theinitial zonal mean flow was specified differently the superposed initial wave disturbances were identicalin all experiments the dynamic coupling between the upper level winds and the low level movement of the disturbance wasfound to be an important factor in explaining the role of the environmental wind in storm genesis anotherimportant factor is the impact of the low level winds on the latent energy supply this supply is affectedby the relative inflow into a disturbance and by the transfer of momentum from aloft into the boundarylayer in a large area surrounding the disturbance according to the model results the storm genesis potential is definitely biased toward easterly verticalshear

hot soils and cooler stones geoecological influence of volcanic tephra and boulders on soil temperature and significance for plant distribution in haleakalā crater maui hawai i abstract this project i investigates the geoecological influence of boulders and their dimensions thickness length on maximum daily soil temperatures beneath them at two sites 2175 and 2685 m in haleakal crater maui ii contrasts temperatures in bare volcanic ash soils with adjacent substrates covered by reddish tephra at 7 study sites 2170 2735 m these encompass most of the altitudinal range of k paoa and silversword two common plants in this mountain area and iii analyzes effects of tephra depth on soil maxima midday soil temperatures were measured with thermocouple thermometers 5 cm recording thermographs also monitored temperatures continuously in various contrasting substrates for 8 day periods both boulders and tephra substantially decreased soil maxima bare soil highs n 100 reached 47 6 c mean 37 2 4 4 c maxima below boulders n 40 4 109 cm thick 6 265 cm long peaked at 20 5 c mean 16 0 2 54 c whereas 80 readings under tephra 9 95 mm depth reached 32 0 c mean 25 2 5 2 c larger boulders were most effective in lowering temperatures spearman and kendall correlation tests indicate block thickness was slightly more important p p p values caused greater albedo higher tephra reflectivity helped reduce absorption of solar radiation and consequently soils remained cooler below stones such temperature reduction is ecologically significant for plant survival on stone covered areas as soil maxima 35 c may be deleterious to seed and or seedling survival

a preliminary study of pge in the late caledonian loch borralan and loch ailsh alkaline pyroxenite syenite complexes north west scotland the siluro ordovician loch borralan c 430 ma and loch ailsh complexes c 439 ma comprise a suite of intrusive rocks ranging in composition from clinopyroxenites through potassic melasyenites to quartz syenites the rock suite at loch borralan also includes nepheline syenite geochemical data in the literature indicate that the intrusions are alkaline with pronounced enrichments in lile and lree relative to contemporaneous calc alkaline magmatic centres further to the south east although they share similar high lile nb subduction related characteristics the loch borralan complex is associated with marginal gravity and magnetic anomalies which can be interpreted in terms of a shallow body less than 400 m thick analysis of rocks and drill core revealed widespread elevated pt and pd values in pyroxenites and syenites in both complexes the highest concentrations up to about 900 ppb pt pd occur in pyroxenites in the loch borralan complex extensive archived drill core provides an excellent section through the marginal pyroxenites which host the pge at loch borralan the pyroxenites show unusual petrological features early clinopyroxene is followed by biotite apatite magnetite sphene and plagioclase with later garnet which might be metasomatic in origin sulphides occur in minor amounts high temperature shearing produced local granulation and mylonitisation later brittle deformation caused extensive micro fracturing and the introduction of minor carbonate veining platinum group minerals pgm were located in a number of samples with high pge assay values these occur as clusters of grains around 1 2 m in diameter and are difficult to identify uniquely a few grains appear to be magmatic these are pt and ptpd sulphides that occur enclosed in clinopyroxene or garnet all other grains occur in late fractures or along grain boundaries these include sperrylite ptas2 pd antimonides and pdbi tellurides along with hessite ag2te they occur in microfractures accompanied by carbonate and barite and fine grained sulphides and are probably of secondary origin the pge in the pyroxenites may have been introduced during the magmatic phase of the intrusion but the observed distribution of pgm results from low temperature hydrothermal remobilisation following brittle deformation and introduction of fluids

on the origin of the bolivian high and related circulation features of the south american climate abstract the climatological structure in the upper tropospheric summertime circulation over south america is diagnosed using a gcm with and without south american topography a linear model and observational data emphasis is placed on understanding the origin of observed features such as the bolivian high and the accompanying nordeste low to the east results from the linear model indicate that these two features are generated in response to precipitation over the amazon basin central andes and south atlantic convergence zone with african precipitation also playing a crucial role in the formation of the nordeste low the direct mechanical and sensible heating effects of the andes are minimal acting only to induce a weak lee trough in midlatitudes and a shallow monsoonal circulation over the central andes in the gcm the effects of the andes include a strengthening of the bolivian high and northward shift of the nordeste low primarily through changes in the precipitation field the position of

palladium platinum and gold distribution in porphyry cu mo deposits of russia and mongolia the porphyry cu mo deposits in the southern siberian craton and northern mongolia including subduction collision and rift related igneous series of early paleozoic to mesozoic age are all characterized by varying crustal contribution to their parent magmas and the presence of explosive breccias precious metal and associated element contents are reported for mineralized samples sulphide concentrates and chalcopyrite molybdenite flotation concentrates from porphyry cu mo intrusions of russia sora aksug and zhireken and mongolia erdenetiun obo average pge contents in rocks are 17 ppb pd and 22 ppb pt in the aksug deposit 13 ppb pd and 10 ppb detection limit pt in the sora 14 ppb pd and 21 ppb pt in the erdenetuin obo and 18 ppb pd and 28 ppb pt in the zhireken deposit average gold content in rocks is 61 ppb in the aksug deposit 17 ppb in the sora 21 ppb in the erdenetuin obo and 30 ppb in the zhireken deposit the highest average 2 3 ppm ag was recorded in the rocks of the sora deposit in general the precious metal distribution in the studied deposits has no apparent relationship with the alteration types the molybdenum content in rocks ranges between 1 and 128 ppm mo in the aksug deposit from 1 to 5400 ppm mo in the sora deposit from 2 to 755 ppm mo in the erdenetuin obo deposit and from 3 to 1530 ppm mo in the zhireken deposit the average copper content in rocks is 1540 ppm in the aksug deposit 460 ppm in the sora deposit 1460 ppm in the erdenetuin obo deposit and 220 ppm in the zhireken deposit the cu mo ratios are highest in the aksug and erdenetuin obo deposits and lowest in the sora and zhireken deposits the correlation matrix for selected major and trace element data on mineralized samples and sulphide concentrates 34 samples indicates that precious metals are associated with either chalcopyrite or molybdenite copper shows a strong positive correlation with au and pd r 0 91 while mo shows a strong positive correlation with pt r 0 98 in addition mo exhibits a strong positive correlation with w r 0 94 an interelement positive correlation between precious metals is 0 57 ag au the pd and pt contents of both chalcopyrite and molybdenite in flotation concentrates are low varying from 9 to 83 ppb pd and from 10 to 110 ppb pt the highest values recorded are 924 ppb pd in sulphide concentrates from the aksug deposit and 684 ppb pd and 299 ppb pt in sulphide concentrate from breccia of the zhireken deposit the highest gold content 5450 ppb au is in chalcopyrite flotation concentrate from the aksug deposit whereas in the majority of concentrates the gold content is in the order of a few hundreds parts per billion the relatively low contents and limited variation of the precious metal contents in the individual deposits of russia and mongolia point to the essential role of the composition of the source and composition of parent magmas

platinum solubility and partitioning in a felsic melt vapor brine assemblage abstract the solubility and partitioning of pt in a s free vapor brine rhyolite melt pt metal assemblage has been quantified at 800 c f o 2 nno and pressures of 100 and 140 mpa vapor and brine were sampled at run conditions by trapping these phases as glass hosted fluid inclusions as the melt cooled through the glass transition temperature the vapor and brine were in equilibrium with the melt at the time of trapping and thus represent fluids which were sampled at the termination of each experimental run the microthermometrically determined salinities of vapor and brine are 2 and 63 wt nacl eq and 9 and 43 wt nacl eq at 100 and 140 mpa respectively platinum solubilities in vapor brine and glass i e quenched melt were quantified by using laser ablation inductively coupled plasma mass spectrometry la icp ms equilibrium is discussed with reference to the major and trace element concentrations of glass hosted fluid inclusions as well as the silicate melt over run times that varied from 110 to 377 h at 140 mpa and 159 to 564 h at 100 mpa platinum solubility values 1 in h2o saturated felsic melt are 0 28 0 13 g g and 0 38 0 06 g g at 140 and 100 mpa respectively platinum solubility values 1 x at 140 and 100 mpa respectively in aqueous vapor are 0 91 0 29 g g and 0 37 0 17 g g and in are brine 16 10 g g and 3 3 1 0 g g the measured solubility data were used to calculate nernst type partition coefficients for pt between vapor melt brine melt and vapor brine the partition coefficient values 1 x for vapor melt brine melt and vapor brine at 140 mpa are 2 9 1 0 67 27 and 0 13 0 05 and at 100 mpa are 1 0 0 2 6 8 2 4 and 0 15 0 05 the partitioning data were used to model the pt scavenging capacity of vapor and brine during the crystallization driven degassing i e second boiling of a felsic silicate melt over a depth range i e 3 6 km consistent with the evolution of magmatic hydrothermal ore deposits model calculations suggest that aqueous vapor and brine can scavenge sufficient quantities of pt and by analogy other platinum group elements pge to produce economically important pge rich magmatic hydrothermal ore deposits in earth s upper continental crust

tropical cyclone genesis in a global numerical weather prediction model abstract the physical processes responsible for tropical cyclone genesis over the western north pacific are investigated using the operational analyses of the u k meteorological office global model for the years 1992 93 the analyses are divided into two groups depending on whether a particular analysis led to the prediction of a real genesis in the atmosphere composites of the winds at 850 and 200 hpa from the analyses that fall into each of the two groups the successful and failed predictions are then made and compared it is found that about 3 days prior to genesis the low level trades north of the pregenesis vortex begin to strengthen one day later an upper level westerly trough and or the tropical upper tropospheric trough tutt starts to encroach toward the pregenesis cluster the low level trades near the cluster continue to intensify and a surge of southwesterly winds occurs to the south of the cluster on the day before genesis the southwesterlies become the dominant low level feature a

palladium platinum and gold concentration in porphyry copper systems of greece and their genetic significance compilation of new and published data on precious metal and associated trace element contents in mineralized porphyry copper intrusions of greece indicates that the pd content in the potassic propylitic zone of the skouries deposit is relatively high ranging between 60 and 200 ppb average 110 ppb whereas in the porphyry copper intrusions of gerakario and pontokerasia it is very low 3 ppb pd the oxidized zone of fissoka op 65 exhibits low pd and cu contents but higher au te as pb and zn contents the pt content is much lower than pd in the porphyry copper intrusions studied the pd pt ratio in the skouries deposit ranges from 9 to 60 while it is much lower 2 in the mineralized samples from fissoka gerakario and pontokerasia a decrease of the pd content and pd pt ratio with increasing te as pb and zn content may indicate that the pd distribution in porphyry copper systems is effected by the evolution of the magma hydrothermal system also mineralogical and geochemical data on the skouries deposit coupled with textural relations between base metal sulphides pgm and au ag tellurides indicate that the main pd bearing mineral merenskyite is associated with the vein type chalcopyrite or bornite and was deposited during the main stage of mineralization the high magmatic oxidation state and the magmatic features of the hydrothermal system limited participation of meteoric portion in the skouries intrusion may be a strong control of its pd potential assuming that pd is mainly associated with chalcopyrite in the porphyry copper deposits the calculated pd from measured pd contents in chalcopyrite average 3300 ppb pd are relatively high and comparable to that in the chalcopyrite concentrate made after the processing of large composite drill hole samples 2400 ppb pd to 21 wt cu it is considered to be an encouraging economic factor for pd as a by product probably along with au although the main product is cu

scale interactions during the formation of typhoon irving the development of typhoon irving is investigated using a variety of data including special research aircraft data from the tropical cyclone motion tcm 92 experiment objective analyses satellite data and traditional surface and sounding data the development process is treated as a dry adiabatic vortex dynamics problem and it is found that environmental and mesoscale dynamics mutually enhance each other in a cooperative interaction during cyclone formation synoptic scale interactions result in the evolution of the hostile environment toward more favorable conditions for storm development mesoscale interactions with the low level large scale circulations and with other midlevel mesoscale features result in development of vorticity in the midlevels and enhancement of the low level vorticity associated with the developing surface cyclone multiple developments of mesoscale convective systems after the storm reaches tropical depression strength suggests both an increase in low level confluence and a tendency toward recurrent development of associated mesoscale convective vortices this is observed in both aircraft data and satellite imagery where subsequent interactions including mergers with the low level tropical depression vortex are observed a contour dynamics experiment suggests that the movement of mesoscale convective systems in satellite imagery corresponds well to the movement of their associated midlevel vortices results from a simple baroclinic experiment show that the midlevel vortices affect the large scale low level circulation in two ways 1 initially interactions between midlevel vortices produce a combined vortex of greater depth 2 interaction between midlevel vortices and the low level circulation produces a development downward of the midlevel vorticity this strengthens the surface vortex and develops a more cohesive vortex that extends from the surface through the midtroposphere

the large scale environments of the global populations of mesoscale convective complexes abstract the mean genesis environment was constructed for each of five mesoscale convective complex mcc population centers around the world africa australia china south america and the united states it is found that the environments are very similar and exhibit many of the same dynamic and thermodynamic structures that are present with systems in the united states in particular mccs initiate within prominent baroclinic zones characterized by locally large values of lower tropospheric vertical wind shear and convective available potential energy cape typically a low level jet of air with low static stability high equivalent potential temperature oriented nearly perpendicular to the baroclinic zone intrudes into the genesis region and is forced to ascend over a relatively shallow surface based layer of relatively cool air pronounced warm advection accompanied by strong lower tropospheric veering overlays the surface based cool layer a local maximum in absolute humidity and a local minimu

electrically active hot towers in african easterly waves prior to tropical cyclogenesis abstract it has been hypothesized that intense convective scale hot towers play a role in tropical cyclogenesis via dynamic and thermodynamic feedbacks on the larger scale circulation in this study the authors investigate the role that widespread and or intense lightning producing convection i e electrically hot towers present in african easterly waves aews may play in tropical cyclogenesis over the east atlantic ocean the 700 hpa meridional wind from the ncep ncar reanalysis dataset was analyzed to divide the waves into northerly southerly trough and ridge phases the aews were subsequently divided into waves that developed into tropical storms i e developing and those that did not develop into tropical storms i e nondeveloping finally composites were created using various ncep variables lightning data gathered with the zeus network and worldwide lightning location network wwlln and brightness temperature data extracted from the nasa global merged infrared brightness temperatur

multiscale analysis of the summertime precipitation over the central andes precipitation over the central andes in south america exhibits a marked annual march with most of the rainfall concentrated during the austral summer season december february when the atmospheric circulation favors the uplifting of moist air from the lowlands to the east of the mountain range within its rainy season the central andes experiences week long rainy and dry episodes the large scale and local conditions during these episodes are investigated using satellite imagery reanalyzed atmospheric fields and in situ data despite the deep layer of conditional instability prevalent during most summertime afternoons deep convection can occur only on those days in which the mixing ratio within the local boundary layer exceeds some threshold 7gk g 21 yielding saturation of near surface air parcels rising more than 600 m above ground convective cloudiness anomalies over the central andes extend southeastward and tend to be concurrent with anomalies of opposite sign over the eastern part of the continent rainy dry episodes are also associated with anticyclonic cyclonic anomalies centered over subtropical south america that extend through the depth of the troposphere accompanied by easterly westerly wind anomalies over the central andes these anomalies are presumably forced by planetary waves originating in the southern hemisphere extratropics to gain insight into the regional processes linking the large scale and local conditions the pennsylvania state university national center for atmospheric research mesoscale model version 5 2 was used to simulate contrasting rainy and dry episodes the most marked and relevant differences are the strength and extent of diurnally varying flow over the eastern slope of the andes during the rainy simulation strong easterly winds reach the upper part of the slope by midmorning initiating an intrusion of warm and moist air high ue air originating in the eastern lowlands into the central andes in the dry case the moisture transport from the east is restricted to the eastern slope of the andes and the central andes is flooded by low ue air from the western foothills that cannot support deep convection even in the presence of localized updrafts the momentum balance based on the model output indicates that turbulent momentum mixing from aloft determined by the large scale anomalies of the upper level flow into the convective boundary layer is the leading term causing the differences in the daytime upslope flow and hence moisture transport over the upper part of the eastern side of the andes between rainy and dry simulations