locating and quantifying geological uncertainty in three dimensional models analysis of the gippsland basin southeastern australia abstract geological three dimensional 3d models are constructed to reliably represent a given geological target the reliability of a model is heavily dependent on the input data and is sensitive to uncertainty this study examines the uncertainty introduced by geological orientation data by producing a suite of implicit 3d models generated from orientation measurements subjected to uncertainty simulations the resulting uncertainty associated with different regions of the geological model can be located quantified and visualised providing a useful method to assess model reliability the method is tested on a natural geological setting in the gippsland basin southeastern australia where modelled geological surfaces are assessed for uncertainty the concept of stratigraphic variability is introduced and analysis of the input data is performed using two uncertainty visualisation methods uncertainty visualisation through stratigraphic variability is designed to convey the complex concept of 3d model uncertainty to the geoscientist in an effective manner uncertainty analysis determined that additional seismic information provides an effective means of constraining modelled geology and reducing uncertainty in regions proximal to the seismic sections improvements to the reliability of high uncertainty regions achieved using information gathered from uncertainty visualisations are quantified in a comparative case study uncertainty in specific model locations is identified and attributed to possible disagreements between seismic and isopach data further improvements to and additional sources of data for the model are proposed based on this information finally a method of introducing stratigraphic variability values as geological constraints for geophysical inversion is presented

stratosphere and lower mesosphere wind observation and gravity wave activities of the wind field in china using a mobile rayleigh doppler lidar since the mobile rayleigh doppler lidar of the university of science and technology of china was developed in 2013 more than 100 days of valid nighttime wind data from 15 to 60 km altitude were obtained during recent 3 years the observation locations cover the northwest midlatitude of china delingha 37 371 n 97 374 e xinzhou 38 425 n 112 729 e and jiuquan 39 741 n 98 495 e recently we have extracted perturbations of the wind profiles from the wind field measurements and we have found that inertia gravity waves and mountain waves existed at the same time the results of wind field and several gravity waves cases are shown in this paper typical characteristics of the gravity waves are analyzed in this midlatitude area of china a 2 d fast fourier transform of the wind perturbation shows that a dominant stationary wave mode and a downward wave mode exist simultaneously in the spectrum a band pass 2 d filter was applied to the spectrum followed by inverse fast fourier transform to separate inertia gravity waves from stationary mountain waves the horizontal wavelength is retrieved using hodograph methods indicating that the inertia waves are generated thousands of kilometers away observed mountain waves from a combination of vertical wind and leaned line of sight wind measurements show a small angle leaned wave front from the horizontal direction this kind of gravity wave observation of the stratospheric wind field and its wave patterns is rare and significant for the study of atmospheric dynamics

large amplitude mountain waves in the mesosphere observed on 21 june 2014 during deepwave 1 wave development scales momentum fluxes and environmental sensitivity

modelling the generation of gravity waves by a maritime continent thunderstorm observed wind and temperature profiles are used to initialize a model calculation of a maritime continent thunderstorm and the numerical solution is used to explore the effect of tropospheric shear on the gravity wave generation the resultant convective system is qualitatively similar to that observed the modelled gravity waves propagate away from the cloud with wave fronts that are approximately circular implying that the convective clouds do not generate waves which propagate in a preferred direction the gravity wave generation is related to the oscillation of the convective updraughts about their level of neutral buoyancy while the general features of the gravity waves are similar in most respects to a previous study which used an idealized wind profile the frequency of the gravity waves is doppler shifted by the tropospheric wind shear the result is a much broader power spectrum in comparison to the idealized cases

the effect of small scale hills on orographic drag the purpose of this study is to investigate the extent to which the presence of hills with relatively short horizontal scales can influence the drag due to mountain waves and flow blocking exerted on the flow by larger scale mountains numerical simulations of stratified flow over mountains are presented for flow over orography described by the linear superposition of broad mountains whose length scales are large enough to generate mountain waves and narrow corrugations whose wavelengths fall below the minimum horizontal wavelength for stationary gravity waves results are presented for both two and three dimensional mountain shapes and for a range of corrugation heights it is shown that the corrugations can significantly reduce the amplitude of the mountain waves generated by the broader mountain or they can suppress the unsteadiness of the wake when these mechanisms make an important contribution to the total drag this implies a significant drop in the total drag compared to the sum of the contributions from the two scales of orography from the point of view of drag parametrization the extent to which the effect of the small scale hills can be represented via an effective roughness length is investigated crown copyright 2007 reproduced with the permission of her majesty s stationery office published by john wiley sons ltd

comprehensive simulation of the middle atmospheric climate some recent results this study discusses the results of comprehensive time dependent three dimensional numerical modelling of the circulation in the middle atmosphere obtained with the gfdl skyhi troposphere stratosphere mesosphere general circulation model gcm the climate in a long control simulation with an intermediate resolution version 3 in horizontal is briefly reviewed while many aspects of the simulation are quite realistic the focus in this study is on remaining first order problems with the modelled middle atmospheric general circulation notably the very cold high latitude temperatures in the southern hemisphere sh winter spring and the virtual absence of a quasi biennial oscillation qbo in the tropical stratosphere these problems are shared by other extant gcms it was noted that the sh cold pole problem is somewhat ameliorated with increasing horizontal resolution in the model this suggests that improved resolution increases the vertical momentum fluxes from the explicitly resolved gravity waves in the model a point confirmed by detailed analysis of the spectrum of vertical eddy momentum flux in the winter sh extratropics this result inspired a series of experiments with the 3 skyhi model modified by adding a prescribed zonally symmetric zonal drag on the sh winter westerlies the form of the imposed momentum source was based on the simple assumption that the mean flow drag produced by unresolved waves has a spatial distribution similar to that of the eliassen palm flux divergence associated with explicitly resolved gravity waves it was found that an appropriately chosen drag confined to the top six model levels above 0 35 mb can lead to quite realistic simulations of the sh winter flow including even the stationary wave fields through august but that problems still remain in the late winter springtime simulation while the imposed momentum source was largely confined to the extratropics it produced considerable improvement in the simulation of the equatorial semiannual oscillation with both the easterly and westerly phases being somewhat more intense than in the control simulation a separate experiment was conducted in which the skyhi model was simplified so that it had no topography and so that the seasonal cycle was frozen in perpetual equinox conditions these changes result in a model that has much reduced interhemispheric asymmetry this model spontaneously produces a long period mean flow oscillation of considerable amplitude in the tropical upper stratopause the implication of this result for the general issue of obtaining a qbo in comprehensive gcms is discussed

a gravity wave drag matrix for complex terrain abstractwe propose a simplified scheme to predict mountain wave drag over complex terrain using only the regional average low level wind components u and v the scheme is tuned and tested on data f

aircraft measurements of mountain waves and their associated momentum flux over the british isles the hercules and canberra aircraft of the meteorological research flight have made a number of flights to investigate mountain waves over different mountainous areas of the british isles results from five flight days are presented in this study for each flight day the observed values of the dominant wavelength and the wave amplitude as a function of height were compared with the values predicted by two dimensional linear lee wave theory good agreement was obtained in four of the five cases measurements of the vertical flux of horizontal momentum show that the largest values were obtained when the wavelength was 20 9 km and the waves were only weakly trapped on this occasion the flux was observed to be constant with height in the range over which measurements were made supporting a theoretical result of eliassen and palm the value 0 35nm 2 is comparable with some aircraft measurements made over the rocky mountains

mountain drag along the gotthard section during alpex abstract an estimate of the time variation of the pressure drag component across the inner portion of the st gotthard section of the alps is derived for the special observational period march april 1982 of the alpex project surface pressure data obtained from a purpose designed mesoscale array of microbarograph stations are used and the results indicate that this drag component amounted to a value per unit area that varied on the order of 5 pa with a mean 0 78 pa it is shown that the phase variations of the time trace of the drag are directly related to synoptic scale flow developments however the magnitude of the drag is substantially influenced by mesoscale effects further an indication is given of the contribution to the drag of the effects of diurnal variation vertically propagating buoyancy waves and low level flow blocking deflection the order of magnitude of these drag values notwithstanding the potential errors in the estimates indicates that the alps exert a substantial influenc

january and july simulations with a spectral general circulation model abstract we describe the results of january and july simulations carded out with a nine level spectral model employing a rhomboidal truncation at wavenumber 15 sea surface temperature sea ice distribution and solar zenith angle are held constant in each simulation the model includes interactive clouds and radiative processes after ramanathan et al 1983 selected fields are shown which highlight the model s strengths and weaknesses the latitude height distribution of the zonal wind is successfully simulated the model captures the separation between the wintertime westerly jets in the troposphere and stratosphere and thus simulates the sign reversal in the vertical wind shear across the jet axis in the upper troposphere in addition to the zonal wind we show also the zonally averaged temperature meridional wind and vertical velocity regional distributions of sea level pressure surface air temperature precipitation and a number of other fields defined at various pressure levels are compared in

core concept to improve weather and climate models researchers are chasing atmospheric gravity waves on september 3 2018 an unpowered experimental sailplane made history by flying into the stratosphere after leaving from el calafate a town near the southern patagonian ice field in argentina glider pilots jim payne and tim gardner surfed on enormous airborne waves emanating from the andes mountains they achieved a world record height of 23 203 meters higher than a lockheed u 2 spy plane s cruising altitude no other unpowered aircraft has ever achieved such elevation it was a feat made possible by not just human ingenuity but also the incredible strength of a phenomenon known as atmospheric gravity waves atmospheric gravity waves seen here over the indian ocean via the moderate resolution imaging spectroradiometer housed in nasa s terra satellite emerge when parcels of air are forced upward image credit jacques descloitres modis rapid response team nasa gsfc unlike the similarly named and perhaps more famous cosmic gravitational waves which are ripples in the fabric of space time atmospheric gravity waves are a wholly terrestrial occurrence they emerge when parcels of air are forced upward for instance by a tall mountain range moving from a dense atmospheric layer to a thinner one the heavier blobs of air then succumb to the force of gravity and fall back down resulting in a periodic oscillation that can carry energy and momentum over vast distances they are the smallest atmospheric waves that researchers study generally between a few hundred meters and a few hundred kilometers in size but their cumulative effects can be dramatic the actions of atmospheric gravity waves bring energy from the troposphere the lowest atmospheric layer which ends at an altitude of about 10 kilometers out past the edge of space 500 or more kilometers above earth s surface they play important roles in daily weather as well as long term climate fluctuations decelerating powerful jet streams and affecting the circulating

gravity waves around the subtropical jet of the southern winter in an atmospheric general circulation model 1 gravity wave gw activities around the subtropical jet of the southern winter june are analyzed using atmospheric general circulation model outputs of t106l60 in order to clarify roles of gws in maintaining the zonal mean zonal wind dominant gws are characterized with periods of 10 24 hours relative to the ground and with horizontal and vertical wavelengths of about 600 700 km and 2 2 4 4 km respectively these gws propagate both upward and downward from the jet and westward relative to the mean zonal wind most of the upward propagating waves do not reach the upper stratosphere due to negative vertical wind shear of the zonal wind in the lower stratosphere dominant upward fluxes of easterly momentum due to the non stationary gws extend zonally along 30 s above the jet remarkable ep flux convergence due mostly to these gws is seen around 100 hpa at 30 s and explains up to 30 of the total ep flux convergence

possible effects of breaking gravity waves on the circulation of the middle atmosphere of mars a simplified quasi geostrophic beta plane dynamical model of the zonal mean flow is used to investigate the possible effects of breaking internal gravity waves on the circulation in the middle atmospheric region 10 100 km altitude of mars the gravity wave parameterization employed is basically the saturation parameterization of lindzen 1981 which has been utilized in several terrestrial modeling studies numerical simulations are performed for a range of plausible values of the gravity wave parameters and for different representations of the mean flow thermal forcing with a focus on the effects of topographically forced stationary gravity waves on the winter hemisphere circulation the results of the model simulations show that breaking gravity waves of intermediate horizontal scales 100 1000 km wavelengths could act to close off the winter westerly circumpolar jet in the 40 80 km altitude region and induce strong high latitude warming at these levels the latter could explain recent thermal measurements indicating that martian winter polar latitudes may be very warm far above radiative equilibrium in this middle atmospheric region deming et al 1986 for the most plausible range of parameter values breaking gravity waves do not induce much warming below 40 km consistent with available data showing that winter high latitudes are normally very cold at lower levels several dust storm cases indicate that breaking gravity waves possibly could act to induce a very large polar warming at relatively low altitudes such as was observed during the 1977 winter solstice dust storm however quite large gravity wave amplitudes and or relatively long horizontal wavelengths are required for such strong low level effects thermal forcing associated with dust heating might be a source for such anomalous gravity wave activity during a global dust storm summer simulations indicate that breaking gravity waves might alter the mean flow at somewhat higher levels than in the winter hemisphere as a consequence of the presence of westerlies in the lower atmosphere this could explain the presence of a warm summer pole in the recent 50 80 km thermal measurements of deming et al several aspects of the results relating to the middle atmospheric circulation and the polar warming phenomenon are discussed the possible importance of breaking gravity waves for constituent transports in the middle atmosphere of mars is also briefly considered

observations of the site dependency of the morning wind and the role of gravity waves in the transitions values of 10 m wind speed have been plotted against screen temperature during morning warming and averaged over several years for a number of sites within great britain when the temperature is referenced to that at the time of the coming evening transition the plots give consistent lines with a gradient dependent on geostrophic wind however the gradient for a given geostrophic wind varies between sites comparison with similar plots made during evening cooling shows that the wind plot against temperature increases relatively abruptly at some stage during the early hours of the morning and then increases to its midday maximum with a reduced wind temperature gradient to that in the evening however as with the evening plots the gradients of the morning plots increase in hillier terrain the effect of wind direction on the gradients during morning and evening is also described in order to verify that the effect of topography on the plots is consistent a one dimensional numerical model is used to simulate both transitions it is shown that external drag factors such as form drag in the region of low hills are not sufficient to explain the observations only an external drag of the type given by a simple formulation of gravity wave generation and absorption within the stable boundary layer gives good agreement with the observations this suggests that an important factor causing the wind to drop during the evening cooling is gravity wave drag and its relative absence due to the near surface convective layer is a factor during the morning wind increase

a palaeoclimate model for the kimmeridgian abstract most attempts at using numerical general circulation model gcm to simulate mesozoic climates have studied the late cretaceous and have focused on the enigmaof apparently equable global climates however this climate regime lasted throughout the mesozoic and it is of interest to examine other periods we present the results of an integration for the late jurassic using a relatively detailed and high resolution model there is generally good agreement between the model climate and the existing geological data in particular the simulation predicts no permanent ice cover near either pole arid conditions over the southwestern usa seasonally arid climate over southern europe and winter storminess over europe and australia however the surface temperatures over siberia and southeastern gondwanaland drop below zero for a significant part of the winter

parameterizing tidal dissipation over rough topography the traditional model of tidal dissipation is based on a frictional bottom boundary layer in which the work done by bottom drag is proportional to a drag coefficient and the velocity cubed however away from shallow coastal regions the tidal velocities are small and the work done by the bottom boundary layer can account for only weak levels of dissipation in the deep ocean the energy flux carried by internal waves generated over rough topography dominates the energy transfer away from barotropic flow a parameterization for the internal wave drag over rough topography is included as a dissipative mechanism in a model for the barotropic tides model results suggest that the inclusion of this dissipation mechanism improves hydro dynamical models of the ocean tide it also substantially increases the amount of modeled tidal dissipation in the deep ocean bringing dissipation levels there into agreement with recent estimates from topex poseidon altimetry data

regional to global evolution of impacts of parameterized mountain wave drag in the lower stratosphere abstractmountain ranges are regional features on earth as are the regions of mountain wave drag mwd exerted by dissipating atmospheric gravity waves generated by flow over them however these r

sensitivity of medium range weather forecasts to the use of an envelope orography the performances of grid square mean and enhanced envelope orographies are compared in a set of 10 day forecasts performed using the ecmwf spectral model at horizontal resolutions t21 t42 t63 and t106 twenty four cases chosen at monthly intervals from may 1983 to april 1985 are examined and for diagnosis of results for the northern hemisphere these are divided into 12 winter november to april and 12 summer may to october situations the winter results in many respects confirm those of previous studies apart from t21 resolution use of the envelope orography in this season is clearly beneficial in general and synoptic assessment illustrates how mountain barrier effects are better represented by the envelope conversely in summer the envelope has a detrimental effect according to some though not all measures at t42 and t63 resolutions though not at t106 this appears to be at least in part due to the more northerly position of the northern hemisphere jet in summer which interacts with mountains that are less of a barrier with t106 giving a better separation of the localized orographic features of these regions some problems are seen at all seasons with the envelope representation of the asian relief results for the southern hemisphere are not surprisingly generally less sensitive to the representation of mountains the principal impact coming from the southern andes and antarctic peninsula to the south a small beneficial impact of the envelope orography is found in the tropics in individual cases the use of envelope rather than mean orographv gives rise to local forecast differences near mountains which tend to propagate and amplify principally on synoptic scales following the upper level flow much of the hemisphere can be influenced in 7 10 days ensemble and time averaged errors are generally reduced by use of the envelope though not dramatically and not at all locations

crustal evolution of northeastern yeongnam massif korea revealed by shrimp u pb zircon geochronology and geochemistry abstract paleoproterozoic igneous activity and metamorphism are widespread in north china and korean peninsula as a part of a precambrian tectonic unit located in the southeastern margin of korea the northeastern yeongnam massif consists mainly of metasedimentary rocks and granitoids such as the buncheon granite gneiss hongjesa granite and leucogranite here we present their shrimp zircon u pb ages and geochemical compositions magmatic oscillatory zones of zircon grains from the buncheon granite gneiss yielded a concordia age of 1990 5 ma the detrital zircon analyses of metasedimentary rocks tightly constrain the depositional age between 2 02 ga and 2 00 ga subsequently the igneous and detrital zircons were overgrown during a metamorphic overprint at ca 1 95 ga dark cathodoluminescent metamorphic rims of zircon grains from the metasedimentary rocks and buncheon granite gneiss are dated at 1 89 to 1 84 ga which is contemporaneous with the emplacement age of leucogranite all granitoids are peraluminous and show distinct eu negative anomalies also the initial whole rock end values of the granitoids are consistently negative such geochemical features are indicative of recycled crustal source rocks with residual plagioclase the granitoids are enriched in large ion lithophile elements and depleted in high field strength elements in their normalized trace element patterns which is typical of subduction zone magmas our compilation of the literature shows that the yeongnam massif lacks late archean and neoproterozoic igneous or metamorphic phases which are well recorded in the other two precambrian massifs in korea namely the gyeonggi and nangrim massifs all three massifs however show a strong metamorphic imprint at ca 1 85 ga possibly associated with the formation of the supercontinent columbia there remain ambiguities on the correlation between korean and chinese precambrian tectonic units considering discrepancies in the geochronological framework of magmatism and metamorphism

some aspects of the effect of surface friction on flows over mountains the effect of surface friction on flow over mountains in stratified fluids is investigated using a two dimensional version of the naval research laboratory s non hydrostatic coupled ocean atmosphere mesoscale prediction system coamps without surface friction flow over a mountain attains a maximum speed at the surface on the lee slope with surface friction the flow speed vanishes at the surface and reaches a maximum near the top of the boundary layer bl corresponding to this wind distribution is a shallow layer of very large vertical wind shear beneath the jet maximum and a weaker but deeper sheared layer elsewhere this strong shear generates maximum turbulent kinetic energy tke at the jet maximum region meanwhile the buoyancy effect associated with the mountain gravity wave inhibits the production of the tke above the jet maximum region the combined effects of shear and buoyancy lead to a very shallow bl on the lee slope in general surface friction reduces the amplitude of mountain gravity waves comparison of the flow fields with the outline of the bl height indicates that flow characteristics correspond closely to the distribution of the bl height it is hypothesized that the reduction in mountain wave amplitude in the presence of surface friction is due to the reduction in the slope of the bl height as compared to the terrain height for narrower and or higher mountains the bl height exhibits a secondary peak on the lee side that further modifies the wave simulations using the bl height as a solid mountain without surface friction confirm that characteristics of flow over the mountain are associated with the distribution of bl height rather than the terrain height field as the non dimensional mountain height increases the magnitude of the effect of surface friction decreases due to decreasing bl depth on the lee side with the result that the bl height profile becomes closer to the terrain height field the effect of surface friction on asymmetric mountains is also investigated without surface friction the pressure drag shows distinctive reduction with a secondary peak on the downstream side but the effect is less when the secondary peak is on the upstream side with surface friction all three mountains have similar pressure drag corresponding to their similar bl height profiles copyright 2003 royal meteorological society

sensitivity of the asian summer monsoon to aspects of sea surface temperature anomalies in the tropical pacific ocean summary the response of both the time of onset and the strength of the asian summer monsoon to regional aspects of the sea surface temperature sst anomalies in the tropical pacific ocean associated with el nifio southern oscillation enso has been investigated through a series of sensitivity experiments with the universities global atmospheric modelling programme ugamp general circulation model ugcm this paper builds on the work of ju and slingo 1995 and on their hypothesis that the relationship between the asian summer monsoon and enso involved the latitudinal position and strength of the tropical convective maximum tcm over indonesia and the west pacific in the preceding spring the inference from their results was that the modulation of the tcm might be associated either with changes in the walker circulation through the influence of the east pacific sst anomalies or with changes in the local hadley circulation associated with the in situ sst anomalies in the west pacific the investigation has focused on the particular contrasting years of 1983 and 1984 the experiments described in this paper are designed to isolate the effects of the principal sst anomalies in the east and central pacific associated with el niiio la nifia from those of opposite sign which develop in the west pacific as a complementary pattern during the mature phase of el nifiola niba the results of the experimentation suggest that at least for the test cases of 1983 and 1984 the modulation of the walker circulation with implied additional subsidence over the eastern hemisphere is the dominant mechanism whereby the asian summer monsoon is weakened during el nifio years however the late onset during el nifio years may also be associated with the complementary cold sst anomalies in the west pacific which delay the northwards transition of the tcm during la nifia the modulation of the walker circulation appears not to be the controlling factor which determines the stronger monsoons the ugcm results suggest that the complementary warm sst anomalies in the west pacific enhance the tcm and it is this in situ response by the tcm that leads to an early onset and stronger monsoon the importance of warm anomalies in the west pacific in the development of a strong monsoon has been investigated further through a case study of the 1994 season the year 1994 was an el nifio year in which the monsoon was unexpectedly active but which was also marked by wanner than normal ssts in the west pacific the sensitivity experiments have also elucidated the role of el nibo in influencing the precursory signature of stronger subtropical westerlies over india and south east asia during the winter and spring preceding weak monsoons the results suggested that the equatorwards shift of the subtropical jet is a remote response to the warm sst anomalies in the central and east pacific associated with el nifio

simulations of fall and early winter in the stratosphere mechanistic model simulations of fall early winter in the northern november and december and southern may and june stratosphere are compared with observational analyses to examine the skill of the model in simulating the state of the stratosphere including both means and variability in key fields during six winters while detailed success varies from year to year the model produces a realistic climatology of and variability in the evolution of winds geopotential heights temperatures and wave propagation in the early winter stratosphere the variability and mean fields agree well with those in longer data records the northern hemisphere nh simulations show a small cold bias when averaged over the 6 years while the southern hemisphere sh simulations show a larger warm bias greater detailed success in simulations of alternate nh winters suggests the possibility of greater model skill during the westerly quasi biennial oscillation phase although the short record and complexity of interactions between tropics and high latitudes preclude definitive identification of such a relationship a prominent failing of the model when using rayleigh friction to parametrize gravity wave drag is an inability to correctly reproduce the latitudinal structure of the stratospheric jet above about 7 hpa this failing can be alleviated by using a non orographic gravity wave drag parametrization at the expense of frequently degrading agreement of planetary wave phases and amplitudes the success of the model in reproducing realistic climatology and variability makes these simulations useful for more detailed studies of transport and vortex evolution in early winter interhemispheric comparisons show that the early winter circulations are qualitatively similar in the nh and sh they are dominated by a strengthening vortex with most wave activity being in wave 1 they both have minor warmings in a preferred location and clustered around a preferred time early december early june in the nh sh variability in the flow shows a crescent pattern of maximum variations near 60 80 latitude centred at the location of the minor warmings over the dateline in the nh and in the south pacific in the sh interhemispheric differences are primarily in the magnitude of the variability with a more symmetric circulation and weaker minor warmings in the sh this is in contrast to later in the winter when large qualitative interhemispheric differences have been seen copyright 2002 royal meteorological society

kinetic controls on the partitioning of trace elements between silicate and sulfide liquids mass transfer between sulfide and silicate liquids is often discussed elements pge has resulted from liquation immiscible by reference to a mass ratio between hypothetical liquid reservoirs liquid phase separation of sulfide liquid from mafic or at equilibrium defined as r in an open system not at equilibrium ultramafic silicate magma a central assumption of modthe mass of silicate melt from which a growing sulfide droplet els of magmatic sulfide deposit formation is that the base appears to have scavenged chalcophile elements will depend on metals and pge are strongly partitioned into the sulfide diffusivities di and dfes of the element and of the fes component melt previous discussions of the process by which sulfide in the silicate melt respectively on the degree of supersaturation of liquids become enriched in chalcophile metals have fothe melt with fes c o on the radius a of the droplet and on the cused almost exclusively on models in which coexisting velocity v with which the droplet is advected through the melt so bodies of sulfide and silicate melt are considered to be that in equilibrium at all times the intent of this paper is to demonstrate that natural sulfide deposits preserved in igneous rocks will in many r 1 c fes o di 1 2 adiv dfes 1 2 adfesv instances record metal distributions that never attained equilibrium as a result of the kinetic constraints on metal chalcophile elements are expected to show inter element variations partitioning between phases the consequences are that in d spanning several orders of magnitude in some melts leading different elements will seem to show evidence for equito large inter element variations in effective r in a given sulfide libration at different silicate sulfide mass ratios within body these variations in effective r will lead to spatial separations single sulfide bodies i describe the time dependent evolubetween zones of maximum enrichment of chalcophile elements tion of metal distributions in silicate sulfide melt systems produced during fractional segregation of sulfide in layered intrusions starting with analytical solutions for simple boundary whereas it has proven impossible to model the generation of spatially conditions and then adapting them to more complex offset stratiform horizons in the australian munni munni layered systems as numerical models intrusion using equilibrium partition coefficients the present kinetic model reproduces the observed patterns with great fidelity

the santa rita nickel sulfide deposit in the fazenda mirabela intrusion bahia brazil geology sulfide geochemistry and genesis the santa rita ore zone within the fazenda mirabela intrusion is an unusual example of high tonnage magmatic ni cu pge sulfide mineralization developed as a stratiform layer within the main cumulus sequence of a layered intrusion the intrusion as a whole is about 4 2 5 km in outcrop dimensions and at least 3 km in original maximum stratigraphic thickness with an original boat shaped morphology the ore zone comprises a 50 to 200 m thick interval containing up to 5 wt percent disseminated sulfides within a sequence of mostly unaltered harzburgites and orthopyroxenites this orthopyroxene dominated sequence lies between the dominantly olivine rich cumulates that comprise the lower half of the intrusion and the gabbroic cumulates that make up the upper half sulfide tenor variations and silicate host rock compositions have been derived from a very large database of continuous assays of more than 500 diamond drill cores consistent patterns of sulfide tenor gradually decreasing ni from over 20 to about 10 wt percent near constant cu and gradually decreasing pges with cyclically varying pt pd ratios are found within the santa rita ore zone across the entire intrusion and display relatively little lateral variability the position of the sulfide mineralization envelope within the harzburgite orthopyroxenite package migrates to higher stratigraphic levels from the northern to the southern margin of the intrusion maximum grades and thicknesses correlate with the maximum thickness of orthopyroxene bearing cumulates asymmetrically disposed toward the southern margin of the intrusion nickel tenors of the sulfides range from 15 to 25 wt percent exceptionally high for rocks with relatively low values of mgo mgo feo and are closer to the typical values observed in komatiite hosted deposits although cu tenors typically 5 8 wt are much higher than komatiite values sulfide pge tenors range from less than 100 ppb to greater than 10 ppm of both pt and pd with maximum values in s poor rocks at the base of the sulfide bearing interval pges become significantly more depleted toward the top of the santa rita zone we attribute these features along with the localization of the sulfide bearing interval at the contact between ultramafic and mafic cumulates to mixing of an initially s undersaturated moderately ni enriched resident magma with a relatively low ni pge depleted significantly lower temperature replenishing magma charged with suspended sulfide liquid droplets

intraseasonal and interannual variability of the quasi 2 day wave in the northern hemisphere summer mesosphere this study uses global synoptic meteorological fields from a high altitude data assimilation system to investigate the quasi 2 day wave q2dw and migrating diurnal tide during the northern hemisphere nh summers of 2007 2009 by applying a two dimensional fast fourier transform to meridional wind and temperature fields we identify q2dw source regions and diagnose propagation of q2dw activity into the upper mesosphere and lower thermosphere we find that the q2dw in nh summer is composed primarily of westward propagating zonal wave number 3 and wave number 4 components that originate within baroclinically unstable regions along the equatorward flank of the summer midlatitude easterly jet the amplitude of the wave number 3 q2dw tends to peak in july while the amplitude of the wave number 4 q2dw tends to peak in late june and again in early august the seasonal mean q2dw amplitudes are largest in 2009 when the amplitude of the migrating diurnal tide in the upper mesosphere near 30 n was relatively weak however there is no evidence of rapid amplification of the q2dw via nonlinear interaction with the diurnal tide instead variations of q2dw amplitudes during nh summer appear to be linked to variations in the strength and location of the mesospheric easterly jet from one summer to the next with a stronger jet producing larger q2dw amplitudes linear instability model calculations based on the assimilated wind fields indicate that the fastest growing modes are zonal wave numbers 3 and 4 with periods near 2 days that originate in the vicinity of the easterly jet

a three dimensional mountain wave imaged in satellite radiance throughout the stratosphere evidence of the effects of directional wind shear swath scanned thermal radiances from the advanced microwave sounding units amsu a on the noaa and aqua satellites are used to image the horizontal temperature structure of a long wavelength mountain wave that formed over southern scandinavia on 14 january 2003 data from all six stratospheric channels show this wave propagating through the full depth of the stratosphere in channels 9 11 altitudes 20 90 hpa the imaged wave has a phase structure broadly consistent with a stationary wave radiated by the southeastward flow over and above the quasi elliptical terrain of southern norway channel 12 radiances at 10 hpa however show a remarkable abrupt change in imaged wave structure the horizontal wavelength contracts phase lines rotate anticlockwise by 30 40 and peak activity migrates to the south to lie over denmark and northern germany similar structure persists in channels 13 and 14 at 2 5 hpa with progessively increasing radiance amplitudes these features are stable over the 10 hours of amsu a measurements from five separate overpasses and are validated against independent radiances acquired by the atmospheric infrared sounder airs and retrieved airs amsu a temperature profiles from the aqua overpass this change at the channel 11 12 interface coincides with an onset of anticlockwise rotation backing and intensification of background stratospheric winds with height fourier ray and spatial ray modelling incorporating these directionally sheared winds and simplified orographic forcing reproduce the salient features of the observations but only after wave induced temperature perturbations have been converted to channel radiances using a forward model the differential visibility of various components of this three dimensional mountain wave to the amsu a channel weighting functions has a first order impact on the observations at heights above 10 hpa once that is factored in the combined observations and modelling provide direct experimental support for the shutts model s predictions of how backing wind vectors affect the vertical evolution of three dimensional mountain waves implications of these observations for orographic gravity wave drag parametrization are briefly discussed copyright 2007 royal meteorological society

a review of gravity wave saturation processes effects and variability in the middle atmosphere this paper provides a review of our current understanding of the processes responsible for gravity wave saturation as well as the principal effects and variability of saturation in the lower and middle atmosphere we discuss the theoretical and observational evidence for linear and nonlinear saturation processes and examine the consequences of saturation for wave amplitude limits momentum and energy fluxes the diffusion of heat and constituents and the establishment of a near universal vertical wavenumber spectrum recent studies of gravity wave variability are reviewed and are seen to provide insights into the significant causes of wave variability throughout the atmosphere

observation of the airflow over the alps during a foehn event a detailed analysis is presented of the large scale mesoscale and local features of a south foehn event in the alps on 8 november 1982 on this day with a substantial cross mountain flow instrumented aircraft made programmed flights back and forth across the alps between southern germany and northern italy rawinsonde observations were used to complete the data set a mesoscale double mountain wave with an amplitude of 1 km was found in the upper troposphere in the mid troposphere above the inn valley a rather pronounced wave with an amplitude of 2 km and a wavelength of 50 km was analysed this wave was close to overturning the foehn turned out to be accompanied by low wave drag at high levels and with strong wave drag at lower levels downward southerly westerly momentum flux was evaluated to be 0 3 0 1 pa mountain drag was estimated to be between 1 6 and 6 7pa light to moderate turbulence was observed immediately to the lee in a low level turbulence zone over the region of strong gusty surface winds finally special attention has been devoted to the similarities and possible differences between foehn in the alps and chinook in the rocky mountains

sensitivity of the eddy momentum flux to meridional resolution in atmospheric gcms abstract gcm experiments with zonally symmetric climates are used to demonstrate that the increase in the meridional eddy momentum fluxes and zonal surface winds that occurs when resolution is increased is primarily due to the increase in meridional rather than zonal resolution it is argued that the sensitivity to meridional resolution reflects the need to resolve the small scales generated in the rossby wave field as waves radiate from the midlatitude baroclinic eddy source region into regions with small mean winds some additional experiments highlight the sensitivity of surface winds and eddy momentum fluxes to the subgrid scale horizontal mixing formulation in low revolution models

an intercomparison of model predicted wave breaking for the 11 january 1972 boulder windstorm abstract two dimensional simulations of the 11 january 1972 boulder colorado windstorm obtained from 11 diverse nonhydrostatic models are intercompared with special emphasis on the turbulent breakdown of topographically forced gravity waves as part of the preparation for the mesoscale alpine programme field phase the sounding used to initialize the models is more representative of the actual lower stratosphere than those applied in previous simulations upper level breaking is predicted by all models in comparable horizontal locations and vertical layers which suggests that gravity wave breaking may be quite predictable in some circumstances characteristics of the breaking include the following pronounced turbulence in the 13 16 km and 18 20 km layers positioned beneath a critical level near 21 km a well defined upstream tilt with height and enhancement of upper level breaking superpositioned above the low level hydraulic jump sensitivity experiments indicate that the structure of the wave bre

improved general circulation models of the martian atmosphere from the surface to above 80 km we describe a set of two new generation general circulation models of the martian atmosphere derived from the models we originally developed in the early 1990s the two new models share the same physical parameterizations but use two complementary numerical methods to solve the atmospheric dynamic equations the vertical resolution near the surface has been refined and the vertical domain has been extended to above 80 km these changes are accompanied by the inclusion of state of the art parameterizations to better simulate the dynamical and physical processes near the surface boundary layer scheme subgrid scale topography parameterization etc and at high altitude gravity wave drag in addition radiative transfer calculations and the representation of polar processes have been significantly improved we present some examples of zonal mean fields from simulations using the model at several seasons one relatively novel aspect previously introduced by wilson 1997 is that around northern winter solstice the strong pole to pole diabatic forcing creates a quasi global angular momentum conserving hadley cell which has no terrestrial equivalent within such a cell the coriolis forces accelerate the winter meridional flow toward the pole and induce a strong warming of the middle polar atmosphere down to 25 km this winter polar warming had been observed but not properly modeled until recently in fact thermal inversions are generally predicted above one and often both poles around 60 70 km however the mars middle atmosphere above 40 km is found to be very model sensitive and thus difficult to simulate accurately in the absence of observations

mountain waves and wakes generated by south georgia implications for drag parametrization high resolution simulations of flows over south georgia south atlantic are used to increase understanding of the likely influence of small isolated mountainous islands on the large scale flow and to ascertain the extent to which parametrization schemes can account for the missing drag in models where such islands are only partially resolved long duration 1 month austral winter forecasts with a horizontal grid spacing of 1 5 km are used to quantify the mountain wave momentum fluxes generated by the island and the low level drag associated with flow blocking dynamics the characteristics of the drag such as the occurrence of high and low drag states its dependence on wind direction and the spectral contributions to the mountain wave momentum flux are considered flow splitting and low level wave breaking are shown to be responsible for wake regions that extend for hundreds of kilometres from the island regions of deceleration are also evident in the stratosphere due to mountain wave dissipation the extent to which an orographic drag parametrization scheme can reproduce the drag is investigated by comparison with coarse resolution 15 km grid spacing simulations in which the orography is poorly resolved and a large proportion of the drag is parametrized it is demonstrated that the total of the resolved plus parametrized drag in these simulations closely resembles that at high resolution although it is underpredicted during instances of high drag simple modifications to the scheme which enhance the drag when the low level flow is approximately normal to the major axis of the subgrid orography are shown to rectify this the study demonstrates that at least for relatively simple isolated mountain ranges the drag and mountain wave momentum fluxes can be predicted in a deterministic sense by a well tuned parametrization scheme of suitable complexity although inclusion of stochastic effects might lead to yet further improvements

sources of gravity waves in the lower stratosphere above south pole 1 five year 2001 2005 high resolution radiosonde data were processed to obtain the gravity wave gw variabilities in the lower stratosphere over south pole sp our results show that gw activities in the lowermost section 10 15 km are strongest in may and september and weakest in the austral summer whereas in the altitude range of 15 25 km strongest weakest gw kinetic energy is observed around september january we also explored the relationships of gws to the synoptic scale variations in the troposphere and the ageostrophic motions in the upper troposphere over the antarctic which are expected to be significant mechanisms for gw generation a ray tracing model grograt was used to explore the relationship between gw propagation and the background field in the altitude of 15 25 km the annual cycle of gw activity resembles that of adjustment process below 15 km the annual cycle of gw activity has two peaks in may and september our analysis suggests that these two peaks are due to the variation of topographic gw generation and filtering of background atmosphere due to critical level filtering in the lowermost section topographic gws cannot propagate upward which makes the shape of gw annual cycle at higher altitudes closer to the annual cycle of adjustment processes the analysis suggests that the minimum of gw activity at sp during the austral summer may be due to the combination of weaker wave generation from adjustment processes associated with synoptic scale systems flow over topography and unfavorable background field for gw propagation

the impact of abyssal mixing parameterizations in an ocean general circulation model a parameterization of vertical diffusivity in ocean general circulation models has been implemented in the ocean model component of the community climate system model ccsm the parameterization represents the dynamics of the mixing in the abyssal ocean arising from the breaking of internal waves generated by the tides forcing stratified flow over rough topography this parameterization is explored over a range of parameters and compared to the more traditional ad hoc specification of the vertical diffusivity diapycnal mixing in the ocean is thought to be one of the primary controls on the meridional overturning circulation and the poleward heat transport by the ocean when compared to the traditional approach with uniform mixing the new mixing parameterization has a noticeable impact on the meridional overturning circulation while the upper limb of the meridional overturning circulation appears to be only weakly impacted by the transition to the new parameterization the deep meridional overturning circulation is significantly strengthened by the change the poleward ocean heat transport does not appear to be strongly affected by the mixing in the abyssal ocean for reasonable parameter ranges the transport of the antarctic circumpolar current through the drake passage is related to the amount of mixing in the deep ocean the new parameterization is found to be energetically consistent with the known constraints on the ocean energy budget

origin of ultra nickeliferous olivine in the kevitsa ni cu pge mineralized intrusion northern finland the 2 058 4 ma mafic ultramafic kevitsa intrusion is located in the central lapland greenstone belt northern finland it is hosted by a paleoproterozoic volcano sedimentary sequence that contains komatiitic volcanic rocks and sulfide and graphite rich black schists economic ni cu pge sulfide mineralization occurs in the middle part of the ultramafic lower unit of the intrusion two main types of ore are distinguished normal and ni pge ores the normal ore is characterized by 2 to 6 vol disseminated sulfides and average ni and cu grades of 0 3 and 0 42 wt respectively ni cu 1 the ni pge ore has broadly similar sulfide contents but a higher ni grade and lower cu grade as a result the ni cu ratio reaches 15 much higher than in the normal ore the ni pge ores occur as irregular discontinuous lense like bodies in the ultramafic rocks notably the olivines in the ni pge ore contain extremely high ni contents of up to 14 000 ppm which is significantly higher than the ni content of olivine in other mafic ultramafic igneous rocks globally up to 5 000 ppm and in harmony with the associated ni rich sulfide assemblage containing pentlandite millerite and pyrite microprobe mapping of olivine from the ni pge ore suggests relatively low and homogeneous s contents and homogeneous distribution of ni mg fe which is inconsistent with the presence of sulfide inclusions in the olivine grains or diffusion of ni from interstitial sulfides into the olivine grains we therefore conclude that ni substitutes for mg in the olivine lattice the clinopyroxenes from the ni pge ore also have unusually high ni concentrations reaching 1 500 ppm and show a positive correlation with the nickel content of the associated olivine the nicpx niolivine is 0 1 to 0 2 corresponding to high t partitioning of ni between clinopyroxene and olivine k d of 20 can account for the partitioning of nickel between olivine and the sulfide phase consistent with magmatic equilibration these data suggest that the olivine clinopyroxene and sulfides all crystallized from a basaltic magma with an unexceptionally high ni content ranging from 300 to 1 100 ppm the ni pge ores are spatially associated with ultramafic xenoliths olivine in these ultramafic xenoliths have relatively high fo contents up to 90 mol and high ni contents up to 5 200 ppm suggesting that the xenoliths formed from a komatiitic parental magma it is proposed that assimilation by the kevitsa magma of massive or semi massive sulfides associated with komatiitic rocks elevated the ni content of the magma and resulted in the formation of ni pge ores and related extremely ni rich olivines

structure of the outokumpu ore district and ophiolite hosted cu co zn ni ag au sulfide deposits revealed from 3d modeling and 2d high resolution seismic reflection data abstract the outokumpu district within the north karelia schist belt in eastern finland hosts a number of cu co zn ni ag au sulfide deposits that are associated with palaeoproterozoic ophiolitic metaserpentinites derived from depleted mantle peridotites that were subsequently tectonically interleaved with allochthonous metaturbidites the metaperidotites have been extensively metasomatized to quartz carbonate calc silicate rocks of the outokumpu assemblage the outokumpu area has been affected by a multiple phase tectonic history comprising various phases of folding and shearing followed by several faulting events future exploration has to expand the search into deeper areas and requires knowledge of the subsurface geology in order to unravel the complex structure 3d geologic models of different scales have been built using a variety of information including geological aeromagnetic and gravity maps digital terrain models and mine cross sections as well as data like drill core logs combined with observations from underground mine galleries structural measurements aeromagnetic data and seismic surveys for crustal structures data from seismic surveys lines have been reprocessed for our purpose both deposit scale and regional scale models allow the reconstruction of a sequence of structural events the mined ore has formed during remobilization of a proto ore and is closely related to shear zones thrusts that truncate the outokumpu assemblage later faults dismembered the ore explaining the variable depth of the different ore bodies along the outokumpu ore zone on larger scale at least four km scale thrust sheets separated by major listric shear zones can be identified in the ore belt which are internally further imbricated by subordinate shear zones these thrusts separate a number of lens shape metaperidotite bodies that are probably surrounded by outokumpu assemblage rocks thrust stacking was followed by at least three stages of faulting that divided the ore belt into fault bounded blocks with heterogeneous displacements i faulting along nw dipping faults with unresolved kinematics ii reverse faulting along c 50 60 se dipping faults and iii sw ne to ssw nne striking faults which may have formed at an earlier stage and have been reactivated the specific outokumpu alteration assemblage around metaperidotite bodies combined with shear zones acting as path ways for fluids are the main vectors to mineralization seismic reflection data do not provide a simple tool to directly detect the sites of outokumpu assemblage bodies at depth but they identify strong reflector zones which are characteristic for though not exclusive to the assemblage shear zones can be recognized as curved dislocations in the seismic lines our study shows that 3d modeling when used in combination with surface geology and other geophysical data and good knowledge about the structural evolution clearly improves the interpretation of reflectors and enables the identification of strong reflector packages as outokumpu assemblage that due to absent geological control have first been mapped as unknown reflector it thus enhances the chances for locating potentially economic horizons at depth and to delineate target areas for detailed exploration

dynamics and predictability of downward propagating stratospheric planetary waves observed in march 2007 abstractthe predictability of a downward propagating event of stratospheric planetary waves observed in early march 2007 is examined by conducting ensemble forecasts using an agcm it is determined that the predictable period of this event is about 7 days regression analysis using all members of an ensemble forecast also reveals that the downward propagation is significantly related to an amplifying quasi stationary planetary scale anomaly with barotropic structure in polar regions of the upper stratosphere moreover the anomaly is 90 out of phase with the ensemble mean field hence the upper stratospheric anomaly determines the subsequent vertical propagating direction of incoming planetary waves from the troposphere by changing their vertical phase tilt which depends on its polarity furthermore the regressed anomaly is found to have similar horizontal structure to the pattern of greatest spread among members of the predicted upper stratospheric height field and the spread growth rate reaches a m

interactions between mesoscale and submesoscale gravity waves and their efficient representation in mesoscale resolving models abstractas present weather forecast codes and increasingly many atmospheric climate models resolve at least part of the mesoscale flow and hence also internal gravity waves gws it is natural to ask whether even in such configurations subgrid scale gws might impact the resolved flow and how their effect could be taken into account this motivates a theoretical and numerical investigation of the interactions between unresolved submesoscale and resolved mesoscale gws using boussinesq dynamics for simplicity by scaling arguments first a subset of submesoscale gws that can indeed influence the dynamics of mesoscale gws is identified therein hydrostatic gws with wavelengths corresponding to the largest unresolved scales of present day limited area weather forecast models are an interesting example a large amplitude wkb theory allowing for a mesoscale unbalanced flow is then formulated based on multiscale asymptotic analysis utilizing a proper scale separation parameter purely vertical propagation

reduction of systematic forecast errors in the ecmwf model through the introduction of an envelope orography day 1 forecast errors in the ecmwf model geopotential height fields during wintertime show a distinctive and highly reproducible signature with negative biases over the major mountain barriers these biases are largest on days when the 500mb flow over the mountains is strong and they tend to shift position from day to day so as to remain close to the region where the jet stream crosses the mountain barrier these systematic errors evolve through the forecast interval until by day 10 they assume an equivalent barotropic structure which strongly resembles the upper level stationary wave pattern but has the opposite sign which indicates that the model does not have sufficient presumably orographic forcing to maintain the stationary waves the time evolution of the systematic error pattern is investigated by means of a series of experiments with a barotropic model in which the observed mean wintertime 300 mb flow is perturbed by a steady forcing derived from the day 1 forecast error pattern the day 10 error patterns as simulated by the barotropic model bear a strong similarity to the observed ones the forcing in the vicinity of the northern rockies makes a particularly large contribution to the simulated day 10 error pattern whereas that in the himalaya region appears to be relatively less important the impact of an enhanced orography upon the climate of the ecmwf model is investigated by carrying out a pair of extended integrations out to 50 days the control run is based on the conventional average type orography used for operational forecasting the other run is based on an envelope orography constructed by adding to the conventional grid square averaged orography an increment proportional to the standard deviation of the sub grid scale variance results for this one rather short pair of integrations suggest that the envelope orography may be capable of yielding a more realistic simulation of the observed wintertime flow pattern particularly with respect to features in the pacific and western north american sectors certain aspects of the zonally averaged circulation are also more realistic in this envelope simulation a series of 21 successive ten day forecast integrations has also been carried out with this envelope orography from february 1982 data results indicate that the introduction of the envelope orography results in a slight degradation of the short range forecasts together with a distinct improvement of the forecast beyond four days the beneficial impact towards the end of the forecast interval appears to be large enough to increase the forecast usefulness by perhaps as much as half a day

application of deep learning to estimate atmospheric gravity wave parameters in reanalysis data sets gravity waves play an essential role in driving and maintaining global circulation to understand their contribution in the atmosphere the accurate reproduction of their distribution is important

observations and numerical simulations of mountain waves in the presence of directional wind shear three research aircraft observed small amplitude gravity waves over the south western french alps on 13 november 1999 during the mesoscale alpine programme map radiosonde ascents and global positioning system dropsondes deployed by map research aircraft indicate that the upstream flow was characterized by topographic blocking below 2 km and low level directional wind shear associated with a synoptic scale depression that extended above the alpine crest the in situ vertical velocity data from the three research aircraft and backscatter from lidar onboard the low level and upper level aircraft exhibit gravity wave signatures in the lower troposphere that are characterized by relatively short horizontal wavelengths on a scale of 5 km or less the in situ flight level and backscatter data also suggest a rapid decrease in the wave amplitude with height due to a directional critical layer that partially absorbs wave energy in the lower to middle troposphere in concert with a decrease in the scorer parameter with height that traps the wave energy numerical simulation results obtained from the non hydrostatic coupled ocean atmosphere mesoscale prediction system model using a horizontal resolution of 556 m indicate the presence of low level wave breaking above the highest peaks and confirm the presence of trapped waves and a directional critical level results based on linear theory and nonlinear model simulations suggest that the absorption of wave energy associated with the directional critical layer has an important impact on the wave characteristics including the momentum flux copyright 2006 royal meteorological society

alleviation of a systematic westerly bias in general circulation and numerical weather prediction models through an orographic gravity wave drag parametrization systematic westerly biases in the northern hemisphere wintertime flow of the meteorological office 15 layer operational model and 11 layer general circulation model are described evidence that the failure to parametrize subgrid scale orographic gravity wave drag may account for such biases is presented this evidence is taken from aircraft studies surface pressure drag measurements and studies of the zonally averaged momentum budget a parametrization scheme is described in which the surface stress is proportional to the near surface wind speed and static stability and to the variance of subgrid scale orography the stress is absorbed in the vertical by considering the influence of such gravity wave activity on static stability and vertical wind shear a richardson number dependent wave breaking formulation is devised and the vertical stress profile determined by a saturation hypothesis whereby the breaking waves are maintained at marginal stability it is shown that wave breaking preferentially occurs in the boundary layer and in the lower stratosphere results from a simple zonally symmetric model show how the adjustment to thermal wind balance with a wave drag in the stratosphere warms polar regions by adiabatic descent and decelerates the mean westerlies in the troposphere the influence of the parametrization scheme on integrations of the 11 layer model is described and found to be generally beneficial in a discussion of the reasons why this problem has only recently emerged it is suggested that the satisfactory northern hemisphere winter circulations of previous coarser general circulation models were due to a compensation implied by underestimating both the surface drag and the horizontal flux of momentum by explicitly resolved large scale eddies

in situ strontium and sulfur isotope investigation of the ni cu pge sulfide ore bearing kevitsa intrusion northern finland the 2 06 ga kevitsa mafic ultramafic intrusion in northern finland hosts a large disseminated ni cu pge deposit the deposit occurs in the ultramafic olivine pyroxene cumulates and shows a range in ni tenors varying from 4 7 wt regular ore to 10 wt ni pge ore there are also a metal poor sulfide mineralization false ore and contact mineralization that are uneconomic ni tenor 0 7045 in comparison to the estimated depleted mantle sr isotope ratio of 0 702 at 2 06 ga the sulfur 34s values are generally higher than 2 which together with the sr isotope data imply involvement of crustal material in the genesis of the kevitsa intrusion and its ores the 87sr 86sr i values obtained from the ore bearing domain of the intrusion show stratigraphic variation and exceed 0 7050 with the maximum value reaching up to 0 7109 in contrast in rocks around the ore domain the initial sr isotope compositions remain more or less constant 0 7047 0 7060 throughout the intrusive stratigraphy the isotope data suggest that the ore bearing domain of the intrusion represents a dynamic site with multiple injections of variably contaminated magma whereas the surrounding part of the intrusion experienced a less vigorous emplacement history no correlation is observed between the strontium and sulfur isotope compositions this is explained by bulk assimilation of the silicate magma in a deeper staging magma chamber and variable assimilation of sulfur during magma transport into the kevitsa magma chamber the low level of metals in false ore and the ni depleted nature of its olivine suggest that some sulfides may have precipitated and deposited in the feeder conduit during the initial stage of magma emplacement cannibalization of early formed sulfides by later magma injections may have been important in the formation of the economic ore deposit

a comparison of the impact of an envelope orography and of a parametrization of orographic gravity wave drag on model simulations results are presented from extended annual cycle integrations of the meteorological office 11 layer atmospheric general circulation model an 8 year control integration produces a good simulation in the southern hemisphere in both summer and winter and also in the northern hemisphere in summer in northern winter however there is excessive westerly near surface flow polewards of about 40 n it is argued that this indicates a lack of orographic forcing of the flow by the major mountain ranges two solutions which have been proposed for this problem are investigated the first is envelope orography and the second is a parametrization of the effects of orographic gravity wave drag each was included separately in 3 1 2 year integrations in parallel with the control both produce substantial changes in the model s climatology but envelope orography does not improve the westerly problem over the european area and it also degrades the summer circulation the gravity wave drag scheme however gives results which in general are in very good agreement with the observations in both hemispheres and seasons comparison of the zonally averaged torques from the three experiments demonstrates that with envelope orography the northern hemisphere near surface westerlies are reduced because of a dramatic increase in the mountain pressure torque in the experiment with the gravity wave scheme however the reduction is due to the gravity wave drag and the mountain torque is similar in magnitude to that in the control a study of the variability of the 500mb height fields on synoptic timescales demonstrates the improvement in the positions of the northern hemisphere storm tracks in this integration some remaining errors in the simulations are identified particularly in the stratosphere finally it is argued that despite these results it may be too early to come to a final conclusion as to the role of gravity wave drag in the general circulation and also as to the relative importance of dynamical and radiative processes in the polar winter stratosphere

an assessment of a mountain wave parametrization scheme using satellite observations of stratospheric gravity waves gravity wave induced temperature fluctuations predicted by a mountain wave parametrization scheme are compared with observed stratospheric temperature fluctuations from the high resolution dynamics limb sounder hirdls instrument the focus of the study is on the southern andes region during the month of august 2006 the comparison reveals that while the mean amplitude of temperature fluctuations predicted by the parametrization is broadly consistent with those observed by hirdls there are significant differences for individual cases ray tracing calculations performed for these cases suggest that these differences are likely to be associated with horizontal propagation of mountain waves which is not represented by current column based parametrization schemes the results presented in this note suggest that this is a deficiency of mountain wave parametrization schemes that may affect models at resolutions typical of both climate and numerical weather prediction modelling copyright 2011 royal meteorological society and british crown copyright the met office

long term budget of zonal momentum in the free atmosphere over europe in winter two sets of aerological data are used to study the time averaged budget of the zonal momentum in the free atmosphere over europe in winter in many respects the budget appears to be different from that reported by holopainen et al 1980 for north america over europe the coriolis force associated with the southward directed ageostrophic meridional flow tends to decrease the westerly momentum a compensating effect is caused by horizontal momentum flux convergence which takes place in the zonal as well as in the meridional plane and is due mainly to transient flow systems large scale turbulence the residual term in the momentum budget indicates that over europe the sub grid scale processes on the average cause a small accelerating effect on the large scale zonal flow in the upper troposphere the residual force over the mountainous region of europe 5 e 30 e 45 n 50 n is a decelerating one in agreement with the results for the corresponding area of north america

global observations of gravity waves from high resolution dynamics limb sounder temperature measurements a yearlong record of temperature amplitude and vertical wavelength 1 global observations of gravity waves have been performed using the high resolution dynamics limb sounder hirdls temperature data a background field that was derived by dynamically calculating 31 day 15 day means to block the stationary component and the slowly varying planetary scale waves was first subtracted from the hirdls temperature measurements an additional step was then taken to remove rapidly moving planetary scale waves by developing an along track temperature filter which was created by averaging the profiles within a 1000 km along track window finally each individual temperature perturbation vertical profile was analyzed using a fast fourier transform to estimate gravity wave temperature amplitudes and vertical wavelengths the investigation of the monthly mean gravity wave temperature amplitudes for the year 2006 found that gravity wave activity in the stratosphere is highly variable with season and can be very orographically dependent especially in the winter extratropics the monthly zonal means show that the peak vertical wavelengths correspond closely to the peak amplitudes the increasing amplitudes and vertical wavelengths are faster and generated at lower altitudes in the winter extratropical and high latitude stratosphere than those in the summer tropical stratosphere this is consistent with the lower source altitudes of orographic gravity waves in the extratropics and high latitudes and the higher source altitudes of convectively generated gravity waves in the tropics three cases were studied for the observed gravity waves over large mountain ranges using the european centre for medium range weather forecasts wind data investigations of episodes of enhanced gravity wave activity over the southern andes the cascade range and the rockies in winter months of 2006 indicate that orographic gravity waves refract downwind from the mountains and propagate along the direction of the intense winds by way of contrast observations of gravity waves around the himalayas show a strong relationship with the cyclones in that region

alignment of mountain wave patterns above wales a vhf radar study during 1990 1998 mountain waves must be parameterized in numerical models of the atmosphere but long term obervations of their characteristics are sparse in this study a large data set from the vhf radar at aberystwyth 52 42 n 4 00 w during the years 1990 1998 is used to investigate the relation between background wind direction local topography and the mountain wave alignment the horizontal wave vector of the mountain waves is on average found to be biased 10 anticlockwise from the wind direction in the lower troposphere near 2 km altitude and biased 20 clockwise from the wind direction near the ground this can be explained if the wave launching height where the background wind speed and direction values can be assumed responsible for generating the waves lies within the boundary layer where the wind has only partly rotated between its direction near ground level and its direction in the free troposphere above the boundary layer on average and for most background wind directions at aberystwyth the wind direction within the boundary layer is a more important influence on wave alignment than the orientation of upstream mountain ridges the relative height of the mountain peaks and the boundary layer may affect the average alignment of mountain waves and therefore the wave stress by as much as 30

simplifying drill hole domains for 3d geochemical modelling an example from the kevitsa ni cu pge deposit abstract a 3d geology model is a simplified version of the true geology designed to give a visual summary of the geometry and distribution of major geological elements in a specified region drill holes provide detailed data of the subsurface that can be classified into geological units that are the fundamental elements of the 3d model due to software limitations upscaling lumping is usually required to reduce the number of geological units in the drill holes prior to model building upscaling is a subjective process which means that different geologists will group in different ways and will typically not record the rationale behind their decision this means the experiment is not reproducible in our study we use a method of upscaling geological units in this case based on assay data using the continuous wavelet transform cwt and tessellation methods this method reduces subjectivity and can easily be repeated e g on an updated or new drill hole by using the same parameters ensuring that the upscaling process is consistent over all drill hole data we apply this technique to a large assay database 90 000 samples from the kevitsa nickel copper platinum group element pge deposit in finland the kevitsa ni cu pge disseminated sulfide orebody is hosted in a proterozoic layered intrusion in northern finland internal geological subdivision and correlation within the intrusion is very difficult to do consistently using lithological observations owing to general homogeneity of rock types and an overprint of alteration but distinct variability is evident in ni and pge sulfide tenors in its raw form the tenor variation dataset appears noisy and unsystematic we have applied the tessellation method to classifying ore types based on tenor variations consistently and objectively reducing the number of units in each drill hole to create a simplified 3d model of the orebody our results reveal shallow inward dipping cryptic layering defined by sulfide composition which are interpreted as reflecting an increase in ni and pge tenor with time during emplacement of the sulfide bearing cumulates we interpret this as a progressive increase in silicate sulfide mixing efficiency r factor as the intrusion developed from an interconnected sill sediment complex choked with country rock inclusions into a freely convecting magma chamber based on this case study we show that the tessellation method can add considerable value by distinguishing the wood from the trees in large 3d geochemical databases the method may be widely applicable in other ni cu pge deposits where tenor variations appear at first sight to be chaotic and uninterpretable

simulation of the semi annual oscillation of the equatorial middle atmosphere using the extended ugamp general circulation model the semi annual oscillation sao is examined in two runs of a middle atmosphere general circulation model the first run pgw includes a parametrization of gravity waves with zero phase speed only whilst the second run agw also includes gravity waves with phase speeds of 20 m s 1 run pgw successfully simulates equatorial saos near the stratopause and in the mid to upper mesosphere however the zonal winds at all heights are easterly and the amplitude of the oscillation is too weak by up to 15 m s 1 near the stratopause and too strong by about 45 m s 1 in the upper mesosphere the corresponding saos in run agw however have amplitudes that are within 5 m s 1 of those observed by rocketsondes and have a pattern of easterly and westerly winds that are in reasonable agreement with the observations zonal mean momentum budget studies show that both at the stratopause and in the mid to upper mesosphere the westerly phase of the oscillation in run agw is stronger than in run pgw owing to an increase in total eddy forcing associated with the introduction of the 20 m s 1 phase speed gravity wave the easterly phase of the stratopause oscillation on the summer side of the equator is driven by advection of easterlies across the equator however on the winter side of the equator the net zonal forcing is westerly in may but easterly in november since easterly eddy forcing associated with extratropical planetary waves is stronger in november than in may the easterly phase of the mid to upper mesosphere oscillation is forced by contributions from both the residual circulation and eddy forcing the eddy forcing contribution is more easterly than in other modelling studies owing to weaker kelvin wave activity and to easterly forcing associated with model diurnal tides introduction of the 20 m s 1 gravity waves also improves the simulation of an n2o like tracer in run agw a double peak of tracer is present in april in reasonable agreement with observations but this feature is absent in run pgw

what triggers the transition of palaeoenvironmental patterns in china the tibetan plateau uplift or the paratethys sea retreat abstract geological research has illustrated the transition of palaeoenvironmental patterns by the earliest miocene from a planetary wind dominant type to a monsoon dominant type indicating that the east asian monsoon became markedly intensified and played a leading role in the east asian climate from a modeling point of view the pioneering research using the reduced number of scenarios had demonstrated that both the tibetan plateau uplift and the paratethys sea retreat were important for understanding the asian monsoon evolution however the sensitivity of the paratethys retreat to the east asian climate still needs further studies based on the more detailed scenarios thirty numerical experiments under the six paratethys sea and the five tibetan plateau conditions illustrate the shifts from zonal climate to the monsoon climate in east asia the results confirm again that both the paratethys retreat and the tibetan plateau uplift play important roles in the formation of the monsoon dominant environmental pattern and show that the paratethys retreat can strengthen the east asian monsoon and greatly increase humidity and aridity respectively in the monsoon areas and northwest china which is similar to the impact of the tibetan plateau uplift on the east asian climate furthermore the fact that the paratethys sea retreats to the turan plate is found to be the key criterion for the palaeoenvironmental patterns transition in china the shrinkage of paratethys sea leads to the reconstructions of the pressure system and the atmospheric circulations which result in the variations of precipitation and the transition of palaeoenvironmental patterns

tides in the mesopause region over antarctica comparison of whole atmosphere model simulations with ground based observations almost a quarter century ago first optical and radar observations from the south pole revealed rich dynamics unexpected from classical tidal theory a strong semidiurnal wind oscillation was detected near the mesopause implying substantial deviations from the classical view that the semidiurnal variation is dominated by the migrating tide subsequent systematic observations exhibited large seasonal variations of both the diurnal and semidiurnal tide with dramatic reduction in amplitude from summer to winter first numerical simulations with a realistic general circulation model extending into the lower thermosphere indicated the presence of nonmigrating tides with substantial amplitudes in the polar regions however direct model data comparisons have been limited to idealized linear models here whole atmosphere model wam simulations for january and july are compared with available wind climatologies based on multiyear radar observations at different locations in antarctica as well as with first summertime lidar measurements of temperature the diurnal tide simulation agrees well with most of the independent radar and satellite wind observations in both seasons the strong semidiurnal tide comprised of migrating and nonmigrating components is well reproduced in summer while in winter the model tends to overestimate the amplitudes over the continental edge besides model validation a self consistent numerical solution also enables cross validation of observations made with different instruments at different locales

a meridional scan of the stratospheric gravity wave field over the ocean in 2001 messo2001 1 in order to examine gravity wave characteristics over the ocean we conducted a radiosonde observation campaign to scan the stratosphere meridionally over the middle pacific with hakuho maru research vessel operated by the ocean research institute university of tokyo seventy vertical profiles of temperature winds and humidity were successfully obtained over a wide latitude range of 28 n to 48 s with an interval of 1 degree gravity wave energy and vertical wavenumber spectra were examined as a function of latitude gravity wave energy is maximized in the tropical region where the convection is active and in the middle latitude region where the subtropical westerly jet is situated the wave energy in the tropical region is greater than the climatology based on operational radiosonde observation over land regions the gravity wave amplitude does not necessarily increase with altitude in contradiction to simple vertical propagation the latitudinal distribution of wave energy rather suggests that gravity waves propagate meridionally toward higher latitudes an interesting feature is that a wave packet having large horizontal wind and temperature amplitudes is observed continuously over 7 days in the latitudinal region extending 26 degrees results of hodograph analysis indicate that the wave packet is due to an inertia gravity wave with horizontal and vertical wavelengths of about 1800 km and 4 5km respectively this inertia gravity wave is likely generated in association with vigorous convection in the intertropical convergence zone itcz in the northern hemisphere and propagated southward interhemispherically the results in this study show that there are strong nonstationary gravity wave sources over the ocean the importance of meridionally propagating gravity waves is discussed

seasonality and interannual variability of the westerly jet in the tibetan plateau region abstract in this study 40 yr ecmwf re analysis era 40 data are used for the description of the seasonal cycle and the interannual variability of the westerly jet in the tibetan plateau region to complement results based on the analysis of monthly mean horizontal wind speeds an occurrence based jet climatology is constructed by identifying the locations of the jet axes at 6 hourly intervals throughout 1958 2001 thus a dataset describing the highly transient and localized features of jet variability is obtained during winter and summer the westerly jet is located respectively to the south and north of the tibetan plateau during the spring and autumn seasons there are jet transitions from south to north and vice versa the median dates for these transitions are 28 april and 12 october the spring transition is associated with large interannual variations while the fall transition occurs more reliably within a 3 week period the strength of the jet exhibits a peculiar seasonal cycle during northw

interpretation of winter warming on northern hemisphere continents in 1977 94 abstract northern hemisphere december march near surface temperature and pressure anomalies during 1977 94 relative to those during 1946 76 are considered to a first approximation these anomalies can be decomposed into two components the first one reaches its maximum during 1977 88 the main features of the anomalies of 1977 88 can be obtained as the atmospheric general circulation model agcm response to sea surface temperature anomalies observed during that period the second component reaches its maximum in 1989 94 the main features of anomalies of 1989 94 relative to 1977 88 can be obtained as the agcm response to lower stratosphere ozone depletion observed in 1989 94

effects of hydrous alteration on the distribution of base metals and platinum group elements within the kevitsa magmatic nickel sulphide deposit abstract platinum and nickel are commonly assumed to be immobile in most conditions especially during low temperature hydrothermal alteration however only a small number of studies have rigorously tested this assumption the ni cu pge sulphide ore body hosted by the kevitsa intrusion northern finland provides a natural laboratory to study the behaviour of base metals and platinum group elements pge during low temperature alteration this ca 2060 ma mafic ultramafic intrusion located in the central lapland greenstone belt hosts disseminated ni cu pge sulphide mineralisation in the middle part of the main ultramafic body the mineralisation which contains a range of ni cu and pge grades is affected by three main alterations serpentinisation amphibolitisation and epidotisation and is cross cut by various types of veins the effect of the circulation of hydrothermal fluids on the distribution of base metals and pge was studied at two different scales interrogation of an extensive deposit wide assay database provided information on the deposit scale kilometre scale effect of these different alteration styles and a detailed study involving laboratory x ray fluorescence xrf portable xrf and micro xrf mapping of drill core samples containing cm scale cross cutting veins provided information on the small scale centimetre to decimetre scale remobilisation of base metals and pges results show that the hydration and carbonation of the kevitsa mineralised mafic ultramafic intrusion did not significantly affect the distribution of ni and pge at scales larger than a few mm and that cu and au are the only metals that are affected by small to large scale remobilisation from centimetre to kilometre scale

a general circulation model study of the orographic gravity waves over antarctica excited by katabatic winds 1 in this study we simulated orographic gravity waves ogws over antarctica using a t213l250 general circulation model gcm the gcm has a fine vertical resolution of 300 m throughout the middle atmosphere the simulation was run for a 1 year period results from 21 28 june were primarily considered ogws are excited by katabatic winds that travel down the surface slopes of the antarctic ice sheet a strong eastward katabatic wind blows over the west coast of the ross sea at the approach of the synoptic scale upper tropospheric westerly jets a quasi stationary ogw is then excited above the coast and propagates upward into the mesosphere an ogw appears sporadically during the antarctic winter and spring its amplitude is determined by the strength of the eastward katabatic wind dissipation of ogws within the middle atmosphere results in a localized deceleration of westerly winds greater than 30 m s 1 d 1 this in turn modifies the horizontal circulation in the polar vortex strong vertical mixing occurs within the mesosphere and is associated with wave breaking large temperature fluctuations associated with the ogws affect the formation or suppression of polar stratospheric clouds in the lower stratosphere katabatic wind excitation is the most powerful source of gravity waves over antarctica around the time of the winter solstice

a general circulation model study of a tropopause folding event at middle latitudes the uk universities global atmospheric modelling programme general circulation model ugcm has been run at high horizontal resolution to investigate a tropopause folding event at middle latitudes geopotential height potential vorticity and specific humidity distributions were diagnosed from the model and showed a realistic representation of the synoptic development of the cut off low associated with the tropopause fold the model also successfully portrayed the frontogenesis associated with tropopause folding and represented both the upper level frontal region and the corresponding jet streaks as they progressed through the region of the developing trough a series of vertical cross sections at the ends of the jet streaks demonstrated that a fold could be captured by the ugcm using potential vorticity and specific humidity although more small scale features were evident in the specific humidity contours than in the corresponding potential vorticity fields the corresponding baroclinic zone was also resolved although both the slope and thickness were rather larger than sometimes observed both the spatial and temporal extent of the fold compared well with observations in addition the model simulated the ageostrophic winds in the entrance exit and middle streak regions a direct circulation was obtained at the entrance and an indirect circulation at the exit region of the jet streak in good agreement with theory and with observational data a combination of confluence cold advection and curvature was responsible for the forcing of the ageostrophic motion at the jet entrance whereas the forcing at the jet exit was attributed mainly to diffluence and curvature q vectors were employed to investigate the vertical motion in the vicinity of the fold and showed the precise positions of descent corresponding to the fold along the entire length of the jet streak finally a tropopause fold around a jet that was not subject to the development of strong baroclinic instabilities was reproduced by the model it was smaller in size than the fold of the cyclonic trough a q vector analysis confirmed the position of the small fold along the jet and revealed large scale ascending motion that may have been responsible for the small size of fold the possibility of using the model to yield a realistic estimate of the transfer of air from the stratosphere to the troposphere in a tropopause folding event at mid latitudes is discussed

a study of wintertime circulation anomalies during past el nino events using a high resolution general circulation model i influence of model climatology in this paper the response of an 11 layer general circulation model gcm to an enhanced composite el nino sea surface temperature s s t anomaly is studied the integrations were run for 540 days in a perpetual january mode and had either mean or envelope orography a basic objective of this paper is to study the influence of model climatology on the response to a tropical s s t anomaly this was done both by comparing our results with those from a lower resolution gcm the ncar community climate model with an identical s s t anomaly and by performing control and anomaly integrations with both mean and envelope orography the specification of orography strongly influences the strength of the mean zonal flow and stationary and transient wave activity in our model whereas the runs with envelope orography produced an anomalous pacific north american pna teleconnection pattern in the northern hemisphere the runs with mean orography did not in the extratropical southern hemisphere our model produced a statistically significant response which had a substantial zonally symmetric component by contrast the ncar model with weaker zonal flow produced a weaker and mainly statistically insignificant response in the southern hemisphere finally in the tropics over the central and eastern pacific the anomalous rainfall and vorticity fields correlated strongly with the corresponding fields in the control integration overall therefore we conclude that a gcm s response is strongly sensitive to the basic model climatology in trying to understand dynamically the gcm response it was concluded that the pna pattern may not simply be the result of rossby wave dispersion from a tropical source the pna pattern may also be associated with a combination of two separate influences the interaction with the anomalous mean flow of enhanced storm track activity over the pacific and with orography on the north american continent the implications of the model s tropical response for simple linear theory were also discussed in these composite el nino anomaly experiments enhanced rainfall and upper divergence occurred well to the west of the upper tropical anticyclone pairs implying that a sverdrup type balance in the vorticity equation cannot hold it is suggested that the strength of the anomalous vortex stretching term could be a small residual compared with the horizontal advection terms and that a simple linear relationship between anomalous latent heating and the position and strength of the anomalous anticyclone pairs is not always valid an alternative qualitative explanation for the relative position of these anticyclone pairs is given in terms of a reduction in the zonally asymmetric component of upper tropospheric vorticity across the tropical pacific whilst the position of the rainfall maximum is located close to the s s t maximum

upstream cyclone influence on the predictability of block onsets over the euro atlantic region abstractatmospheric blocking has been shown to be a phenomenon that models struggle to predict accurately particularly the onset of a blocked state following a more zonal flow this struggle is i

s saturation history of nain plutonic suite mafic intrusions origin of the voisey s bay ni cu co sulfide deposit labrador canada the voisey s bay deposit is hosted in a 1 34 ga intrusion composed of troctolite olivine gabbro and ferrogabbro the sulfide mineralization is associated with magmatic breccias that are enveloped by weakly mineralized olivine gabbros and troctolites and also occurs as veins along structures in adjacent paragneiss a dyke is connected to the base of the north wall of the eastern deeps intrusion and the entry point of this dyke into the chamber is the locus of the eastern deeps nickel sulfide deposit a detailed exploration in the area between the eastern deeps and the ovoid has shown that these intrusions and ore deposits are connected by a splayed dyke the eastern deeps deposit is surrounded by a halo of moderately to weakly mineralized variable textured troctolite vtt that reaches a maximum thickness above the axis of the eastern deeps deposit along the northern wall of the eastern deeps intrusion the massive sulfides and breccia sulfides are petrologically and chemically different when compared to the disseminated sulfides in the vtt and there is a marked break in ni tenor of sulfide between the two sulfides hosted in the dyke tend to have low metal tenors ni 100 2 5 3 5 sulfides in eastern deeps massive and breccia ores have intermediate ni tenors ni 100 3 5 4 and disseminated sulfides in overlying rocks have high ni tenors ni 100 4 8 four principal processes control the compositions of the voisey s bay sulfides coarse grained loop textured ores consisting of pyrrhotite crystals separated by chalcopyrite and pentlandite exhibit a two orders of magnitude variation in the pd ir ratio which is due to mineralogical variations where pentlandite is enriched in pd and ir is dispersed throughout the mineral assemblage a decrease in ir and rh from the margin of the ovoid toward cubanite rich parts at the central part of the ovoid is consistent with fractionation of the sulfide from the margins toward the center of the ovoid the ovoid ores have higher ni and pd tenor than the eastern deeps massive sulfides this is consistent with both a higher r factor and greater degree of silicate parental magma evolution in the ovoid than the eastern deeps the disseminated sulfides surrounding the eastern deeps deposit have some of the highest ni and pd tenors at voisey s bay which are indicative of not only more primitive magmas but also higher r factors than the ovoid or the eastern deeps vtt and normal textured troctolite of the eastern deeps that contain trace sulfide have 0 1 3 ppb pt and 0 1 3 ppb pd whereas weakly to heavily mineralized variable troctolites in the same unit have one to two orders of magnitude higher abundances of pt and pd troctolites and olivine gabbros from other parts of the voisey s bay intrusion and other nain plutonic suite intrusions including the kiglapait newark bay barth island mushua and nain bay south intrusion also have low platinum group element abundances although it is possible that this is a signature of a widespread sulfide saturation event that pre dated ore formation at voisey s bay it is more likely that platinum group element pge depletion is a product of the source melting process where low degrees of melting resulted in the retention of pge in the mantle source if so this indicates that pge depletion should be used with caution as an exploration tool in the nain plutonic suite

implications of regime transitions for mountain wave breaking predictability abstract a suite of high resolution two dimensional ensemble simulations are used to investigate the predictability of mountain waves wave breaking and downslope windstorms for relatively low hills and mountains perturbation growth is weak and ensemble spread is small gravity waves and wave breaking associated with higher mountains exhibit rapid perturbation growth and large ensemble variance near the regime boundary between mountain waves and wave breaking a bimodal response is apparent with large ensemble variance several ensemble members exhibit a trapped wave response and others reveal a hydraulic jump and large amplitude breaking in the stratosphere the bimodality of the wave response brings into question the appropriateness of commonly used ensemble statistics such as the ensemble mean in these situations small uncertainties in the initial state within observational error limits result in significant ensemble spread in the strength of the downslope wind speed wave breaking and wave mom

global and seasonal distribution of gravity wave activity in mars lower atmosphere derived from mgs radio occultation data 1 temperature profiles from mars global surveyor mgs radio occultation measurements reveal vertical wave structures assumed to be atmospheric gravity waves in mars lower atmosphere for each vertical temperature profile derived from a radio occultation measurement wave energy density is calculated and results are locally averaged to derive a global distribution of gravity wave activity global distributions are determined for all values of solar longitude and for solar longitudes corresponding to northern summer and winter to show seasonality and for vertical wavelengths less than 10 km to remove the contribution from thermal tides which dominate in the martian tropics at larger vertical wavelengths the global energy density patterns show significant wave activity over the tropics and the mountainous tharsis region averaged over all seasons and enhanced activity in northern summer compared to winter for the most part the observed data does not correlate well with the orographic forcing schemes used to model gravity waves in general circulation models for mars suggesting that wave sources other than orography play an important role on mars

the influence of antarctica on the momentum budget of the southern extratropics the antarctic plateau acts as a strong heat sink for the global climate cooling the atmosphere and radiating energy to space a cold dense atmospheric boundary layer is formed strong surface winds are formed as the boundary layer drains off the plateau these drainage winds and the eddy fluxes necessary to maintain them are analysed in a general circulation model gcm the drainage flow is well represented in the gcm the associated mean meridional circulation is analysed in isentropic coordinates the momentum budget over antarctica reveals a balance between the eliassen palm flux convergence and the coriolis torque exerted by the mean meridional mass flux both vertical and horizontal components of the eliassen palm flux contribute the vertical component being the greater

aircraft measurements of wave momentum flux over the colorado rocky mountains results are presented from a programme designed to measure the momentum flux associated with standing gravity waves over the central rocky mountains of north america the purpose was to determine momentum losses from the westerlies as they cross a mountainous section of the northern hemisphere where wave drag is believed to be substantial the data from one to three instrumented aircraft operating on 20 flight days mostly during january to march of 1973 are in reasonably good conformity with linear wave theory and also correlate well with surface measurements of downslope winds downward westerly momentum flux averaged 0 5 1 0 dynes cm 2 0 05 0 1 pa the mean westerly flow on the flight days was near the climatological mean for the period of the project although the mean flow over this period as a whole was much weaker than the climatological mean

a case study of lee waves over the lake district in northern england the structure and intensity of stationary orographically forced over the lake district and northern pennines on he afternoon of 26 november 1991 is determined through a combination of field observations and high resolution numerical modelling observations were provided by the meteorological office s c130 aircraft at four different levels and by five radisondes of differing ascent rates released in rapid succession from an observing station located on the cumbrian coast vertical velocity was inferred from both of these data sources and with the help of satellite imagery it was possible to build up a comprehensive picture of the lee wave structure in addition a non hydrostatic primitive equation model was run with a 2 km grid covering a 180 km square region of the northern pennines in an attempt to simulate the gravity wave motion observed the model was initialized with an upstream profile formed by merging a descent profile obtained from the aircraft with one from the sondes the model orography was defined using a terrain height data set with 500 m resolution and with some smoothing to the model grid after about four hours of integration the model achieves a quasi steady state with strong lower tropospheric lee waves verification on the model response was sought by comparing the vertical velocity in the model along the paths of the aircraft and sondes with that actually deduced from the observations the overall agreement of the simulated amplitude and phase of the lee waves with that observed is very encouraging as found in a different case study shutts 1992 the success of the model in predicting lee wave motion gives strong support for the use of these models for the development of gravity wave drag parametrization schemes the domain averaged surface frictional stress was found to be much larger than the wave drag and consistent with the high roughness lengths likely in the case of mountainous terrain

nondissipative and dissipative momentum deposition by mountain wave events in sheared environments abstractmountain waves mws are generated during episodic cross barrier flow over broad spectrum terrain however most mw drag parameterizations neglect transient broad spectrum dynamics here

high resolution numerical model integrations to validate gravity wave drag parametrization schemes a case study a three dimensional non hydrostatic numerical model is used to simulate the lee wave event iop3 1800 gmt 14 october 1990 to 1200 gmt 15 october 1990 from the pyrex mountain experiment using high resolution with a horizontal gridlength of 1 5 km and a realistic terrain height specification the resulting model vertical velocity fields are compared directly with observations from aircraft flights the overall agreement of the model simulated wave structure with the aircraft data is very encouraging particularly given the high degree of nonlinearity and finite amplitude wave activity observed during this event given the very restrictive three dimensional coverage of the observations from the field experiment the numerical model results are used as surrogate observational data to give exhaustive three dimensional data over the whole model volume the model integrations are subsequently used to compute areally averaged surface pressure drags and height profiles of the vertical flux of horizontal momentum assuming these wave stresses to be an accurate representation of the real atmospheric stresses they are compared as a validation procedure against grid box flux values taken from a gravity wave drag parametrization scheme in a model with resolution 2 5 latitude by 3 75 longitude the drag scheme in question compares favourably with the model domain averaged stresses

pressure drag and momentum fluxes due to the alps ii representation in large scale atmospheric models a three dimensional numerical model with interactive grid nesting is used to study the pressure drag and associated momentum fluxes due to the alpine complex for a specified upstream wind and static stability profile four basic questions are addressed which are relevant to the problems of flow description in the vicinity of mountains and the impact of orography in the context of mesoscale numerical weather prediction and general circulation models i what is the dependence of basic quantities such as the pressure drag on the model s horizontal resolution ii is there a need for non hydrostatic dynamics to account properly for the flow characteristics near steep mountains iii is there an effective role for enhanced orography such as an envelope formulation iv might a gravity wave drag parametrization scheme be able to represent adequately the highest resolution fluxes and surface drag in a much coarser resolution model a series of experiments with both hydrostatic and non hydrostatic models at resolutions of 80 40 20 10 and 5 km is analysed and two of these experiments are repeated with an envelope orography it is concluded that hydrostatic simulations are sufficient to describe the basic dynamics even at 5 km resolution however there is a strong dependence of the drag and momentum fluxes on resolution with the drag at 80 km resolution being almost half that at the highest resolution it is also shown that the use of an envelope orography at coarser resolutions can compensate significantly for the drag under estimation but is less effective in representing the vertical stress profiles or the direction of the stress vectors which are systematically in error at the coarsest resolution the potential role of gravity wave drag is confirmed and possible improvements considered it is suggested that both envelope orography and gravity wave drag may make a significant contribution until resolutions are as high as 10 to 20 km

the tropospheric response to tropical and subtropical zonally asymmetric torques analytical and idealized numerical model results abstractthe tropospheric response to prescribed tropical and subtropical zonally asymmetric torques which can be considered as idealizations of vertical momentum transfers by orographic gravity waves or convection is investigated the linear analytical gill model response to westward upper tropospheric torques is compared to the response to a midtropospheric heating which is a familiar point of reference the response to an equatorial torque projects onto a kelvin wave response to the east that is of opposite sign to the response to the east of the heating at upper levels in contrast the torque and heating both produce rossby gyres of the same sign to the west of the forcing and the zonal mean streamfunction responses are identical when the forcings are shifted into the northern hemisphere the streamfunction responses have opposite signs there is upwelling in the southern northern hemisphere in response to the torque heating the nonlinear response to westward torques was explored in idealized