the seasonal cycle of lower tropospheric gravity wave activity at davis antarctica 69 s 78 e abstracta vhf wind profiling radar located at davis in coastal east antarctica 69 s 78 e collected data from september 2009 to august 2011 in the lower troposphere gravity wave activity is quantified using the radar s wind velocity variances era interim and antarctic mesoscale prediction system amps forecast output are used to understand the gravity wave activity in the context of the synoptic scale meteorology and to identify the likely source of the observed gravity waves the seasonal cycle of lower tropospheric gravity wave activity 2 0 3 2 km altitude obtained from the radar data for waves with ground based periods of 16 min 12 8 h reveals a maximum in winter and a minimum in summer the largest gravity wave activity corresponds in time to the presence of a surface depression centered north of davis that directs strong northeasterly winds along the antarctic coastline case studies indicate that these winds interact with an ice ridgeline located around 60 km northeast and upwind of davis th

inertia gravity waves observed in the lower stratosphere over macquarie island abstract this study examines the properties of inertia gravity waves observed in the lower stratosphere over macquarie island how these properties vary with season and the likely source of the waves the waves are observed in high resolution upper air ozonesonde soundings of wind and temperature released from macquarie island during the 1994 ashoe maesa program the properties of the inertia gravity waves observed in the soundings are quantified using hodograph and rotary spectral analyses the analyzed waves have horizontal wavelengths between 100 and 1000 km vertical wavelengths between about 1 and 7 km intrinsic frequencies between f and 2f and horizontal trace speeds between 50 and 30 m s 1 there appears to be a seasonal cycle in the inertia gravity wave activity in the lower stratosphere the minimum being in the austral winter when the background zonal flow is strong and westerly and its vertical shear is positive in contrast the variance of the horizontal perturbation winds does not show a

a climatological study of short period gravity waves and ripples at davis station antarctica 68 s 78 e during the austral winter february october period 1999 2013 a scanning radiometer deployed at davis station antarctica 68 s 78 e has been recording infrared 1 10 1 65 m images of a small region 24 km 24 km of the zenith night sky once per minute each austral winter night since february 1999 these images have been processed to extract information on the passage of gravity waves gws horizontal wavelength h 15 km and ripples h 15 km over the observing station phase speeds periods horizontal wavelengths and predominant propagation directions have been deduced observed speeds were found to be highly correlated with horizontal wavelengths as has been reported in previous studies reverse ray tracing of the detected gws only enabled us to identify four distinct groups on average only 15 of waves detected can be traced back to the troposphere and a large proportion 45 were not successfully reverse traced substantially below the airglow layer two smaller groups were found to reach a termination condition for reverse ray tracing at altitudes near 50 km and 75 km of those that reached the termination altitude in the troposphere 10 km most of the end points fell within a radius of 300 km of the station with a very pronounced concentration of wave initiation to the north west at approximately of the observing point the predominant direction of propagation was southward and they were observed throughout the year recent reports suggest the interaction of planetary waves with the background wind field as a potential source for these waves

the origin of rapakivi texture by sub isothermal decompression abstract the rapakivi texture plagioclase mantled k feldspar ovoids rounded quartz megacrysts and euhedral plagioclase megacrysts in a more fine grained granitic matrix has been studied in five proterozoic 1 64 1 55 ga anorogenic rapakivi granite batholiths in the fennoscandian shield with emphasis on mineral stability and inherited cores k feldspar ovoids and rounded quartz megacrysts with deep embayments consist principally of a core zone and an outer melted and recrystallized zone when the k feldspar ovoids are mantled by plagioclase the outermost part of the mantle is homogeneous but towards the k feldspar a skeletal texture develops intensive parameters obtained from different textural positions show that mineral inclusions in cores of the k feldspar ovoids and quartz megacrysts were formed at low t 680 720 c and high p 5 6 kbar conditions while inclusions in the periphery of ovoids and the plagioclase mantles display high t 780 c and intermediate to low p 3 5 1 kbar the lowest p is comparable to that during solidification of the matrix the total water equivalent of the volatile content in the magma has been calculated as 2 5 the amount of solids in the magma at 1 kbar has been estimated as 40 theoretical calculations and experimental data for mineral stabilities in granitic systems suggest that the texture formed when a crystal saturated kfsp qtz pl 60 and volatile undersaturated a type granite magma was transported under approximately constant temperature 760 780 c from the lower middle crust 5 6 kbar to upper crustal levels according to phase stabilities in the eutectoid granite system quartz and k feldspar were resorbed but plagioclase remained stable and precipitated during this sub isothermal rise of magma textural presence of disequilibrium textures and mineralogical presence of different mineral assemblages including relics evidence of a sub isothermal rise of the rapakivi magmas is better preserved in subvolcanic and contact varieties of rapakivi granites than in the more deep seated rapakivi granites formed by slow cooling

downward control of the mean meridional circulation and temperature distribution of the polar winter stratosphere abstract according to the downward control principle the extratropical mean vertical velocity on a given pressure level is approximately proportional to the meridional gradient of the vertically integrated zonal force per unit mass exerted by waves above that level in this paper a simple numerical model that includes parameterizations of both planetary and gravity wave breaking is used to explore the influence of gravity wave breaking in the mesosphere on the mean meridional circulation and temperature distribution at lower levels in the polar winter stratosphere the results of these calculations suggest that gravity wave drag in the mesosphere can affect the state of the polar winter stratosphere down to altitudes below 30 km the effect is most important when planetary wave driving is relatively weak that is during southern winter and in early northern winter in southern winter downwelling weakens by a factor of 2 near the stratopause and by 20 at 30 km when gravity wave drag is not included

gravity wave excitation during the coastal transition of an extreme katabatic flow in antarctica abstractthe offshore extent of antarctic katabatic winds exerts a strong control on the production of sea ice and the formation of polynyas in this study we make use of a combination of ground ba

the specific case of the mid proterozoic rapakivi granites and associated suite within the context of the columbia supercontinent abstract rapakivi granites and the associated suite anorthosite mangerite and charnockite that developed during the mid proterozoic escape the global rules that control usual granitic magma formation about 40 points that characterise the proterozoic magmatism confirm the originality of the magmatism rapakivi granites developed without a global orogenic context within the supercontinent columbia the intrusions extend from the east european shield to the western us through fennoscandia greenland and labrador other occurrences in the amazonian shield australia or south china are less well documented they show no definite trend in age or chemistry that would explain large scale mantle plume effects a mantle upwelling of material is contradictory with the re assembly of a supercontinent because it occurred before this magmatic episode 1 9 1 8 ga at 1 7 ga the supercontinent columbia amalgamated with the collision of the yapavai and mazatzal provinces a model is suggested that takes into account the supercontinent re assembly defining a downwelling flow in the mantle that anchors the continent above it in contrast to a material flow heat is still delivered to the base of the continental lithosphere and is focused toward the juvenile suture zone the base of the crust must reach 1200 1300 c before producing anorthosite magmas under such a high temperature gradient lasting over a long time magmas are transferred toward the upper crust giving the thin 5 km and square shape 100 km that the intrusions presently have heat delivery is essentially conductive leading to long time spans for intrusions the presence of the supercontinent immobile over a descending cell poloidal mode of convection developed a tangential force toroidal mode of convection that partly split the continent through strike slip deformation due to plate rotation it developed progressively between 1 57 and 1 3 ga starting from fennoscandia and then passing to amazonia western us and labrador in a clockwise sense the associated rotation induced sinistral shear manifested by small scale shear zones and the orientation of late magmatic facies topaz bearing granites in each province the proterozoic magmatism appears to be unique because it requires a supercontinent with a zone of juvenile crust surrounded by older cratons the present moho still shows remnants of this process having bumpy undulations that may reach 22 km in amplitude over a distance of 200 km

multi stage emplacement of the gotemar pluton se sweden new evidence inferred from field observations and microfabric analysis including cathodoluminescence microscopy the emplacement of the mesoproterozoic gotemar pluton into paleoproterozoic granitoid host rocks of the transscandinavian igneous belt is re examined by microfabric analysis including cathodoluminescence microscopy field data on the pluton host rock system are used to strengthen the model the gotemar pluton situated on the baltic shield of se sweden is a horizontally zoned tabular structure that was constructed by the intrusion of successive pulses of magma with different crystal melt ratios at an estimated crustal depth of 4 8 km initial pluton formation involved magma ascent along a vertical dike which was arrested at a mechanical discontinuity within the granitoid host rocks this led to the formation of an initial sill subsequent sill stacking and their constant inflation resulted in deformation and reheating of existing magma bodies which also raised the pluton roof this multi stage emplacement scenario is indicated by complex dike relationships and the occurrence of several generations of quartz si metasomatism the sills were charged by different domains of a heterogeneous magma chamber with varying crystal melt ratios ascent or emplacement of magma with a high crystal melt ratio is indicated by syn magmatic deformation of phenocrysts complex crystallization fabrics e g oscillatory growth zoning caused by high crystal defect density overgrowth and replacement features resorbed and corroded crystal cores rapakivi structure are mostly related to processes within the main chamber that is repeated magma mixing or water influx

a statistical study of gravity waves in the polar regions based on operational radiosonde data gravity waves in the lower polar stratosphere are examined using operational radiosonde observations gathered from 33 stations over a period of 10 years both the potential and kinetic energies of the gravity waves vary annually and reach maxima in winter in the arctic and in spring in the antarctic in the antarctic spring a region of large gravity wave energy propagates downward following the movement of a zone of high static stability associated with southern hemispheric warming moreover the enhanced energy region and the high stability zone coincide in the horizontal plane and move gradually from 135 e 50 s to 45 w 70 s over the south pole the vertical and horizontal directions of wave propagation are examined using hodograph analysis in the vertical most gravity waves transfer energy upward in the arctic while the percentage of downward energy propagation is relatively high in winter and spring in the antarctic horizontally gravity waves propagate westward relative to the mean wind in the arctic while in the antarctic the dominant direction varies from station to station the correlation between gravity wave energy in the lower stratosphere and the mean wind is also examined in the arctic gravity wave energy is highly correlated with the surface wind though in the antarctic it correlates with the stratospheric wind these results suggest that gravity waves observed in the arctic are forced by topography whereas in antarctica some sources may exist in the stratosphere one such source candidate is likely to be the polar night jet

evolution and facies architecture of paleogene surtseyan volcanoes on chatham islands new zealand southwest pacific ocean abstract this paper reports for the first time phreatomagmatic deposits and preserved surtseyan tuff cones in the chatham islands new zealand fieldwork has located the relicts of at least six closely spaced paleogene surtseyan cones and associated volcaniclastic sediments within the red bluff tuff formation the complete stratigraphic section of the cones consists of two parts 1 the lower part represents volcanic aggradational processes that constructed tuff cones in a short period of time and is composed of a bedded interval of explosively fragmented vesicular glassy basaltic pyroclasts ash and lapilli sizes as well as feeder dykes pillow lavas and pillow sills and 2 the upper part represents the rapid denudation of these cones by shallow marine currents or gravity flows reflecting the instability of the tephra pile forming the cones and a much later marine faunal colonization stage e g corals brachiopods molluscs etc erosion could have occurred almost immediately after or even during the emplacement of the volcanic pile similar to what occurred at surtla vent a satellite submerged cone of the basaltic island volcano surtsey iceland the waiareka deborah volcanics bridge point aorere point and lookout bluff surtseyan cones otago new zealand and marion and prince edward islands southwest indian ocean amongst others by contrast the complete faunal colonization and stabilization of a diverse marine community could have taken hundreds or perhaps even thousands of years to reach their acme following the volcanic pulses the structural textural and compositional characteristics of the red bluff tuff formation support a phreatomagmatic mode of fragmentation similar to that at surtsey volcano iceland the red bluff tuff sequence represents one of the most complete marine tuff cones described in the geologic record

a gravity wave climatology for antarctica compiled from challenging minisatellite payload global positioning system champ gps radio occultations 1 the seasonal geographical and altitudinal dependence of gravity wave activity in the lower stratosphere over antarctica is presented gravity wave activity is estimated by calculating potential energy ep from radio occultation profiles obtained by the challenging minisatellite payload global positioning system champ gps experiment significant seasonal variation of wave activity is observed smaller wave activity in summer is attributed to waves with small phase velocities experiencing critical level filtering at other times of the year when wave activity is large less filtering occurs and the strong background wind is likely to cause doppler shifting of waves to longer vertical wavelengths which can reach larger amplitudes before saturating relationships between gravity wave activity and geographic location indicate that topography is a strong source for wave activity especially over the antarctic peninsula however wind rotation in this area was found to reduce the wave energy in summer at certain altitudes a strong enhancement of wave energy is observed at the edge of the polar vortex again reduced critical level filtering and doppler shifting in the area of the jet are likely to be major causes for this finding possible limitations to this study due to observational filtering are discussed

mesospheric momentum flux studies at adelaide australia observations and a gravity wave tidal interaction model abstract we present here the results of an analysis of gravity wave momentum fluxes in the mesosphere and lower thermosphere inferred using a dual beam doppler radar near adelaide australia during june 1984 our analysis reveals that over 70 of the momentum flux and of the inferred zonal drag was due to gravity waves with observed periods less than one hour this suggests that it is the gravity waves with high intrinsic frequencies and small horizontal scales that are most effective at transporting momentum into the middle atmosphere the temporal variations in the momentum flux and flux divergence due to high frequency motions were also examined in detail in addition to daily variability a strong diurnal modulation was observed to occur this was found to be correlated with the phase of large amplitude diurnal tidal motions as a result of these observations a gravity wave tidal interaction model was proposed which accounts for all of the major features of the observed data including a reduction i

observations and fine scale model simulations of gravity waves over davis east antarctica 69 s 78 e large vertical velocities were observed throughout the troposphere at davis east antarctica on 18 february 2014 by a vhf wind profiling radar simulations using the met office unified model at 2 2 0 5 and 0 1 km horizontal grid spacing were able to broadly capture the location timing and magnitude of the observed velocities as well as reveal that they are due to small scale orographic gravity waves resulting from the interaction between the coastal topography and strong easterly winds associated with a synoptic scale cyclone situated to the north the simulations indicated that the gravity waves are responsible for i temperature fluctuations which coincided with satellite observed cloud variations in the vicinity of davis suggesting that they have a crucial role in the formation of cirrus clouds and ii large vertical momentum fluxes in the troposphere the waves are prevented from propagating into the stratosphere by the background winds turning from near surface easterlies to lower stratospheric northerlies as well as illuminating and quantifying the role that weather systems have in producing orographic gravity waves along the east antarctic coastline studies such as this should be exploited to improve the representation of key localized atmospheric processes in global climate models

stratospheric gravity wave simulation over greenland during 24 january 2005 1 the advanced regional prediction system forecast model is extended up to the stratopause and over the entire hemisphere to simulate gravity waves during 24 january 2005 with a 15 km horizontal resolution the simulation produces dominant gravity wave features near eastern greenland that are associated mainly with orographic forcing by the greenland terrain the simulated wave temperature perturbations compare favorably with radiance perturbations from nasa atmospheric infrared sounder observations in the upper stratosphere 40 50 km vertical overturning of the isentropes suggests the occurrence of wave breaking just east of greenland that leads to a tremendous reduction of wave amplitudes the associated flux divergence produces horizontal flow deceleration of 12 120 m s 1 day 1 and coincides with areas of depleted stratospheric wind speed suggesting strong interactions between orographic gravity waves and the polar vortex a simulation using the coarser 50 km horizontal resolution produces gravity waves of significantly weaker amplitudes

vhf radar observations of gravity wave production by cold fronts over southern australia abstract four extended observational campaigns were conducted during august and november 1988 with an st stratosphere troposphere radar in southern australia during the passage of cold fronts over the system giving around 30 days of three dimensional wind measurements with 15 min time and 0 5 km height resolution over the 2 11 5 km height range order of magnitude increases in the variance of time fluctuating wind velocities were measured during frontal passages which are definitively ascribed to gravity waves the time height morphology of the horizontal and vertical velocity fluctuations differed bursts of horizontal velocity variance u 2 2 10 100 m2 s 2 arose at upper levels about a day before the frontal boundary arrived and this activity gradually extended to lower heights as the front neared the arrival of the frontal boundary marked a sudden reduction in this activity after the frontal boundary passed reduced activity persisted for 12 hours after which bursts in u 2 2 returne

sr nd isotopic constraints on the petrogenesis of the central bohemian pluton czech republic the sr nd isotopic data for selected granitoids of the central bohemian pluton show a broad negative correlation with the total range of 87sr 86sr 330 0 7051 0 7129 and nd330 0 2 to 8 9 the older intrusions have more depleted sr nd compositions and calc alkaline geochemistry sazava suite whereas the younger intrusions shift towards k rich calc alkaline blatna suite and shoshonitic rocks icany and certovo b emeno suites with more evolved isotopic signatures the distribution of the data is interpreted as reflecting a diversity of sources and processes rather than a single progressive crustal contamination trend the sazava suite could have originated by partial melting of metabasites or of a mantle source with an isotopic composition close to bulk earth or by hybridization of crustally derived tonalitic and mantle derived magmas variation within the blatna suite is modelled by mixing between a moderately enriched 87sr 86sr 330 0 708 nd330 3 mantle component with either an isotopically evolved metasedimentary component or with more evolved magmas of the suite the icany suite was most probably produced by partial melting of peraluminous lithologies possibly of the adjacent moldanubian unit the certovo b emeno suite evolved from strongly enriched mantle derived magmas 87sr 86sr 330 0 7128 end330 7 either through closed system fractional crystallization or interaction with magma corresponding to leucogranites of the central bohemian pluton

petrology and textural evolution of granites associated with tin and rare metals mineralization at the pitinga mine amazonas brazil abstract the agua boa and madeira igneous complexes at the pitinga mine were emplaced into acid volcanic rocks of the paleoproterozoic iricoume group and host major tin rare metal zr nb ta y ree and cryolite mineralization the igneous complexes are elongate ne sw and each is composed of three major facies that in order of emplacement include porphyritic and equigranular rapakivi granite and biotite granite in both igneous complexes followed by topaz granite in the agua boa igneous complex abic and albite granite in the madeira igneous complex mic rapakivi porphyritic and granophyric textures observed in the granites are interpreted to reflect multiple stages of crystallization at different pressures depths decompression during ascent shifted the magmas into the plagioclase stability field causing partial resorption of quartz with subsequent growth at lower pressure fluid saturation and separation probably occurred after final emplacement at shallow levels temperature and pressure estimates based on phase relations and zircon concentrations range from a maximum of 930 c and 5 kbar for the rapakivi granites to below 650 c and 1 kbar for the peralkaline albite granite this suggests initial crystallization of early intrusive phases at around 15 km depth with final emplacement of more volatile rich crystal mush at a depth of 0 5 1 km accessory minerals including zircon thorite monazite columbite tantalite cassiterite bastnaesite and xenotime are present in almost all facies of the agua boa and madeira igneous complexes attesting to the highly evolved character of the magmas the presence of magnetite and or primary cassiterite indicate crystallization under oxidizing conditions above the nno buffer the evolutionary sequence and nd isotope characteristics t dm 2 2 2 4 ga of the pitinga granites are similar to those of other proterozoic rapakivi granites however petrographic geochemical and nd isotopic data e nd initial 2 1 to 0 5 suggest that the different facies of the pitinga granites were derived from different crustal sources with variable input of a mantle component

polar mesosphere and lower thermosphere dynamics 1 mean wind and gravity wave climatologies 1 mean wind and gravity wave climatologies are presented for the polar mesosphere and lower thermosphere mlt the data were derived using mf radars at davis 69 s 78 e and syowa 69 s 40 e in the antarctic and poker flat 65 n 147 w and andenes 69 n 16 e in the arctic the dynamics of the antarctic mlt are found to be significantly different from the arctic mlt summer maxima in both the westward and equatorward winds occur closer to the solstice in the antarctic than in the arctic the greater symmetry around the solstice suggests radiative effects may play a greater role in controlling the state of the antarctic mlt than in the arctic where dynamical effects appear to be more important gravity wave observations also suggest that wave drag may be greater in the arctic than in the antarctic the equatorward flow near the mesopause persists later in summer in the arctic than in the antarctic as do observations of polar mesospheric clouds and polar mesospheric summer echoes all three phenomena begin at about the same time in each hemisphere but end later in the arctic than in the antarctic it is proposed that the magnitude of the meridional winds can be used as a proxy for gravity wave driving and the consequent adiabatic cooling in the mlt seasonal variations in gravity wave activity are predominately combinations of annual and semiannual components significant hemispheric differences are observed for both the timing and magnitude of these seasonal variations

the orestes melt zone mcmurdo dry valleys antarctica spatially distributed melting regimes in a contact melt zone with implications for the formation of rapakivi and albite granites

syn tectonic emplacement of the late mesozoic laojunshan granite pluton in the eastern qinling central china an integrated fabric and geochronologic study abstract the porphyritic monzogranite of laojunshan eastern qinling in central china forms a w e elongated pluton characterized by a varying abundance of cm scale potassium feldspar kfs megacrysts with or without plagioclase mantles mafic microgranular enclaves mmes and associated mafic dykes the measurements of the shape preferred orientation of kfs megacrysts and the tiling of megacrystic pairs throughout the pluton suggest that these megacrysts constitute magmatic foliations subparallel to the pluton s margin possibly resulting from eastward non coaxial magmatic flow felsic mafic magma mixing and mingling were important during magma emplacement as indicated by abundant mmes coeval mafic dykes and disequilibrium textures within kfs megacrysts quantitative analyses of the crystal size distribution and the in situ chemistry of kfs megacrysts revealed that the temperature fluctuation in the deep magma chamber and the resultant textural coarsening are the most likely important mechanisms for the growth of kfs megacrysts the syn tectonic and two main stage emplacement of the pluton in a sinistral transtensional regime is inferred by the mechanical coupling between magmatic submagmatic solid state fabrics in the pluton and wall rock deformations as well as zircon u pb dating results which produce eastward younging emplacement ages spanning from 122 ma to 119 ma combined with other studies our work supports the idea that the qinling dabie orogen was in a sinistral transtensional regime during the early cretaceous which may correspond to the eastward extrusion tectonics in eastern china

zircon as a proxy for the magmatic evolution of proterozoic ferroan granites the wiborg rapakivi granite batholith se finland

fingerprinting feldspar phenocrysts using crystal isotopic composition stratigraphy implications for crystal transfer and magma mingling in s type granites microsampling of cm scale feldspar crystals within an s type granite from the lachlan fold belt of southeastern australia has revealed complex internal sr and nd isotopic variations the observed isotopic zonations are in part interpreted as recording feldspar crystallisation in a dynamically mixing magma system the isotopic composition of which was varying in response to the influx of more mafic and isotopically more mantle like magmas the latter stages of which are now represented in modified form by microgranular enclaves similar core to rim isotopic variations in feldspar megacrysts from a microgranular enclave and the adjacent host granite strongly suggest megacrysts in the enclave were transferred from the granitic magma during crystallisation feldspar rims have higher 87sr 86sri and lower nd i than adjacent whole rock analyses but match those of mineral separates from the surrounding enclave matrix this suggests that the final stages of megacryst growth occurred in the presence of a component that had previously interacted with a high 87sr 86sr low nd i component such as metasedimentary wall rocks isotopic heterogeneities are also presererved within different mineral phases in the enclave matrix suggesting that differing phases grew at differing stages of equilibration between the enclave magma and its host granitic magma our results reveal major isotopic heterogeneities on a single crystal and also inter mineral scale in a pluton which shows well constrained evidence for magma mingling these results indicate the suitability of feldspars as recorders of isotopic change in magmatic systems even those which have cooled slowly in the plutonic environment and suggest that much heterogeneity in plutonic systems may be overlooked on a whole rock scale

paleomagnetic and rock magnetic evidence for inverse zoning in the parguaza batholith southwestern venezuela and its implications about tectonics of the guyana shield abstract we report paleomagnetic and rock magnetic data from the rapakivi granites of the parguaza batholith guyana precambrian shield southwestern venezuela these results suggest that the pluton is inversely zoned with respect to the cooling ages in order to explain such an age pattern tentative structural settings are proposed placing the parguaza intrusions in a plate tectonic context six sites were sampled along a 200 km transect that cuts through the northern lobe of the batholith thermomagnetic curves x ray diffraction and fluorescence hysteresis loops thermal and alternating field af intensity plots transmission tem and scanning sem electron microscope analyses and konigsberger ratios qn values were used to identify the different magnetic mineralogies and their distribution of grain sizes magnetite titanomagnetite near magnetite in composition and deuteric hematite are the three carriers of natural remanent magnetizations nrms in these rocks magnetic granulometry indicators such as konigsberger ratios qn values suggest the dominant presence of single domain magnetites with average grain sizes grading from finer to coarser away from the center of the transect the paleomagnetic results reveal the existence of two primary thermoremanent and or thermochemical magnetizations trms tcrms for sites csp 3 pi 2 and pi 4 decl 328 incl 21 k 15 95 11 4 and site csp 2 pi 1 and pi 3 decl 16 incl 87 k 10 95 13 respectively there is also a poorly defined g3r2 magnetization decl 284 incl 86 k 6 95 27 found in sites csp 2 pi 1 and pi 3 the overlap of coercivities and the unblocking temperatures spectra probably resulting from the coexistence of primary single domain magnetic mineralogies with secondary exsolutions of single domain like ti poor fe rich regions almost pure magnetite in multidomain titanomagnetite grains in most cases precludes the complete resolution of hybrid g1 n r or g3 n r the relative ages for these components were determined using a map of rb sr model age chrontours g1 and g3 are the older and the younger trms tcrms respectively and were acquired at two discrete moments of the batholith s geological history the final map resulting from integrating the paleomagnetic and rb sr data shows an age pattern for this batholith and the rest of the intrusions that belong to the parguaza igneous complex that could be explained either as the effect of inverse cooling of a single intrusive body the sequential emplacement of magmas controlled by normal faulting or an internal tectonism resulting in a system of ne trending horsts and grabens cutting through the pluton because of its feasibility and agreement with the most recent theories about the tectonic evolution of the guyana shield we favor the latter hypothesis

p t conditions of crystallization and origin of plagioclase mantled alkali feldspar megacrysts in the mesozoic granitoids in the qinling orogen china abstract the qinling orogen between the north china and south china cratons was intruded at 211 217 ma by calc alkaline quartz monzonitic to monzogranitic plutons characterized by i to a type geochemistry and in many places contain plagioclase mantled alkali feldspar megacrysts rapakivi texture sensu lato the felsic rocks contain mafic to intermediate magmatic enclaves suggestive of mingling and mixing of mafic and felsic magmas the p t conditions of crystallization have been determined for early mineral assemblages inner parts of alkali feldspar megacrysts and their plagioclase quartz amphibole and biotite inclusions and late assemblages matrix minerals of the rapakivi textured granitoids al contents in amphibole from the early and late mineral assemblages yield pressures of 1 2 3 0 and 0 7 3 0 kbar respectively and indicate only minor pressure change between the crystallization of the early and late assemblages amphibole plagioclase thermometry gives temperatures mainly of the order of 900 to 1000 c for both the early and late assemblages indicating nearly isothermal conditions feldspar thermometers yield lower temperatures relative abundances of minerals and their chemical compositions indicate that the late mineral assemblages tend to be richer in mgo na 2 o and cao than the early assemblages rapakivi texture is interpreted in this case mainly as a result of compositional changes related to the hybridization between granitic and more mafic magmas small release of pressure during crystallization of the magmas may have contributed to the origin of the mantled alkali feldspar megacrysts

the tynong pluton its mafic synplutonic sheets and igneous microgranular enclaves the nature of the mantle connection in i type granitic magmas in the lachlan orogen of south eastern australia the high level postorogenic 368 ma i type tynong pluton contains granitic to granodioritic rocks that crystallised from a variety of mainly crustally derived magmas emplaced in the shallow crust in an extensional regime the isotopic characteristics of the main plutonic rocks are relatively unevolved 87sr 86srt 0 705 0 706 and endt 0 4 to 0 6 suggesting source rocks not long separated from the mantle we infer that arc mafic to intermediate rocks and associated immature greywackes formed the main crustal source rocks and that these are located in the largely unexposed neoproterozoic cambrian selwyn block that forms the basement as exposed near its southern margin the pluton also contains minor pillowed sheet like intrusions of quartz dioritic rock that show mainly mingling structures with the enclosing granodiorites as well as some hybrid pods and fairly abundant igneous microgranular enclaves that we infer to have been derived from the quartz dioritic sheets despite this evidence of direct mantle input into the tynong magma system the main granodioritic series do not appear to have been formed by magma mixing processes of any i type granite in the region the tynong pluton has perhaps the most direct connection with mantle magmas nevertheless the main mantle connection here is probably in the mantle derived protolith for these crustal magmas and in the mantle thermal event that gave rise to melting of the deep crust in the selwyn block this degree of mantle connectedness seems typical for i type granitic rocks worldwide

relevance of mountain wave cooling for the formation of polar stratospheric clouds over scandinavia mesoscale dynamics and observations for january 1997 the effect of mesoscale mountain wave induced temperature anomalies on the formation potential of polar stratospheric clouds above northern scandinavia is analyzed with a one month mesoscale model integration the simulation results are contrasted with synoptic scale analyses and compared with remote sensing and in situ observations the mesoscale mass flux of air parcels with temperatures below the threshold for cloud formation through a control volume is compared with its synoptic scale counterpart a classification of the synoptic scale flow into periods of large and small mountain wave activity in the stratosphere is proposed the derived classification will be used for a climatology of stratospheric mountain wave activity above scandinavia

what is the source of the stratospheric gravity wave belt in austral winter abstractduring austral winter and away from orographic maxima or hot spots stratospheric gravity waves in both satellite observations and interim european centre for medium range weather forecasts ecmwf re analysis era interim data reveal enhanced amplitudes in a broad midlatitude belt extending across the southern ocean from east of the andes to south of new zealand the peak latitude of this feature slowly migrates poleward from 50 to 60 s wave amplitudes are much weaker across the midlatitude pacific ocean these features of the wave field are in striking agreement with diagnostics of baroclinic growth rates in the troposphere associated with midlatitude winter storm tracks and the climatology of the midlatitude jet this correlation suggests that these features of the stratospheric gravity wave field are controlled by geographical variations of tropospheric nonorographic gravity wave sources in winter storm tracks spontaneous adjustment emission from the midlatitude winter jet frontogenesi

cathodoluminescence and trace element zoning in quartz phenocrysts and xenocrysts quartz phenocrysts and xenocrysts are a common component of volcanic rocks but rarely contribute to our understanding of magmatic or eruptive processes due to an apparent internal chemical and structural homogeneity scanning electron microscopy cathodoluminescence imaging sem cl and secondary ion mass spectroscopy ion microprobe analysis sims are used here to demonstrate that quartz crystals in volcanic rocks show hitherto unrecognised internal structural and chemical zoning two contrasting crystal morphologies have been studied porphyritic euhedral bipyramidal quartz crystals in dacite from bonne nuit bay jersey uk show fine scale growth zoning in sem cl zones are narrow 1 40 m wide planar parallel to crystal faces and overgrow more broadly zoned rounded cores these crystals are interpreted to have formed at small degrees of undercooling by diffusion controlled growth quiescent magma conditions are indicated by the preservation of an al rich diffusive boundary layer which has not been removed by melt shearing during convection in contrast rounded and embayed porphyritic quartz grains in a quartz dacite from the esperanza mine e1 salvador northern chile show broad internal sem cl zones with irregular boundaries some of which are truncated by grain margins indicating dissolution crystal rounding may occur by dissolution or melting due to thermal or thermal chemical disequilibrium with surrounding melt and embayments by gas bubble enhanced convective dissolution are consistent with the development of incipient ocelli textures strings of amphibole inclusions adjacent to quartz rims several episodes of rounding can be recognised in some xenocrysts ion microprobe sims analysis of quartz from both samples shows that a1 contents are higher in areas of bright cl emission previous studies of cl in quartz have suggested that several factors control luminescence although a1 substitution for si in sio4 tetrahedra may be partly responsible for sem cl zoning recorded in volcanic quartz additional mechanisms including the effect of growth rate on defect density probably also play a major role

quasi lagrangian superpressure balloon measurements of gravity wave momentum fluxes in the polar stratosphere of both hemispheres 1 superpressure balloons were flown in 2002 and 2005 in the winter polar vortices of both hemispheres the balloons can drift for months in the stratosphere acting as quasi lagrangian tracers of air parcel motions the meteorological datasets acquired are used to retrieve small scale internal atmospheric gravity wave parameters using wavelet techniques for the first time gravity wave momentum fluxes are estimated over wide geographical areas and the results will help constrain gravity wave parameterization schemes used in general circulation climate models the importance of mountain waves is confirmed with largest fluxes observed in the lee of greenland and the antarctic peninsula however significant momentum fluxes are also observed over the oceans showing the importance of other wave generation mechanisms

observations and simulations of a large amplitude mountain wave breaking over the antarctic peninsula 1 a case study of a large amplitude orographic gravity wave occurring over the antarctic peninsula is presented based on observations from the vorcore balloon campaign and on mesoscale numerical simulations the vorcore campaign september 2005 to february 2006 consisted in the flight of 27 superpressure balloons in the core of the southern hemisphere stratospheric polar vortex at altitudes of 16 19 km from september 2005 to february 2006 on 7 october 2005 one of the balloons exploded as it was flying above the antarctic peninsula the observations collected by another balloon that was flying during the same time period above the peninsula suggest the presence of a very intense gravity wave peak to peak amplitude of the order of 25 30 m s 1 in zonal and meridional velocity disturbances the wave packet is likely undersampled in the balloon observations because of its high intrinsic frequency but the balloon data set is complemented with high resolution numerical simulations carried out with the weather research and forecast model the simulations are validated by comparison with the balloon measurements and show that the wave was breaking in the lower stratosphere at the time and height where the balloon exploded the simulations highlight several consequences of the mountain wave on the stratosphere forcing of the mean flow generation of secondary inertia gravity waves and turbulence and mixing in particular the momentum fluxes are calculated and are found to compare well with the estimates from balloon measurements the large values found are likely extreme values which raises the issue of their representativity to discuss this the balloon measurements are used in conjunction with operational analyses to estimate the frequency of such large amplitude gravity waves i e to provide an estimate of their intermittency

estimation of gravity wave momentum flux and phase speeds from quasi lagrangian stratospheric balloon flights part ii results from the vorcore campaign in antarctica the stratospheric gravity wave field in the southern hemisphere is investigated by analyzing observations collected by 27 long duration balloons that flew between september 2005 and february 2006 over antarctica and the southern ocean the analysis is based on the methods introduced by boccara et al in a companion paper special attention is given to deriving information useful to gravity wave drag parameterizations employed in atmospheric general circulation models the balloon dataset is used to map the geographic variability of gravity wave momentum fluxes in the lower stratosphere this flux distribution is found to be very heterogeneous with the largest time averaged value 28 mpa observed above the antarctic peninsula this value exceeds by a factor of 10 the overall mean momentum flux measured during the balloon campaign zonal momentum fluxes were predominantly westward whereas meridional momentum fluxes were equally northward and southward a local enhancement of southward flux is nevertheless observed above adelie land and is attributed to waves generated by katabatic winds for which the signature is otherwise rather small in the balloon observations when zonal averages are performed oceanic momentum fluxes are found to be of similar magnitude to continental values 2 5 3 mpa stressing the importance of nonorographic gravity waves over oceans last gravity wave intermittency is investigated mountain waves appear to be significantly more sporadic than waves observed above the ocean

textural variation in juvenile pyroclasts from an emergent surtseyan type volcanic eruption the capelas tuff cone sao miguel azores abstract here i present textural data i e vesicularity vesicle size distributions vsd plagioclase crystallinity crystal size distributions csd combined with fractal analyses of particle outlines from a natural succession of alternating fall and surge deposits in the emergent capelas tuff cone azores the textural variation in the capelas succession is surprisingly small considering the wide variety of fragmentation processes vent activity and emplacement mechanisms that are characteristic of emergent eruptions the plagioclase crystal content varies between 24 and 33 vol csd analyses of plagioclase show near linear trends with a slight increase in time for the smallest crystal sizes with surge deposits having more groundmass plagioclase when compared with fall deposits this is consistent with crystallization induced by degassing and decompression at lower eruption rates the vesicularities of the capelas pyroclasts are more variable 18 to 59 vol with vsds displaying kinked trends characteristic of coalescence this is especially evident in the fall deposits and consistent with being formed in continuous uprush jetting with an overall shallow fragmentation level within the conduit bubble coalescence can also be identified in the surge deposits although to a much lesser extent the amount of bubble coalescence is negatively correlated with the amount of groundmass crystallization i e plagioclase in the capelas deposits a relatively broad range of fractal dimensions with average dbox 1 744 and 0 032 for the outlines of pyroclastic fragments emplaced by fall or as surges indicate that there is little difference in the fragmentation process itself at capelas in addition to this the fact that the fractal dimensions for both the fall and surge end members completely overlap suggests that shape modification due to abrasion and chipping of grain edges was minor during emplacement of base surges these results are consistent with emergent eruptions building tuff cones to be a relatively low energy phreatomagmatic landform e g at least when compared with more energetic phreatomagmatic eruptions producing tuff rings and maar volcanoes

vhf radar measurements and model simulations of mountain waves over wales very high frequency vhf radar measurements of mountain waves over aberystwyth wales during 29 november 1997 are presented and compared with the predictions made by a three dimensional numerical model which is based on the linearized equations of motion the radar height time plot of vertical velocity reveals a wave field in the troposphere and lower stratosphere which changes significantly throughout the day four separate radiosonde soundings taken during the day are used to represent the steady background flow in the numerical model in this case the steady state model wave fields are shown to compare qualitatively well with the radar measurements and the three dimensional information provided by the model is used to help explain the changes in the wave field observed by the radar throughout the day the radiosonde profiles are interpolated in time to provide approximate basic state data at two hour intervals model steady state vertical velocity fields based on each of these 13 approximate basic state profiles are used to generate a model time height vertical velocity plot which is qualitatively similar to that obtained from the radar measurements indicating that to a reasonable approximation the evolving wave field can be regarded as a sequence of independent steady states this is generally true if the basic state flow remains steady over the time taken for wave packets to propagate over several wavelengths group velocity arguments are used to show that for typical mountain waves in the troposphere such time scales are generally less than one hour model simulations in which the basic state flow is allowed to vary in time continually based on either the interpolated radiosonde soundings or the radar horizontal wind measurements are conducted in this case the simulated wave fields are always unsteady the waves show a tendency to drift in response to changes in the basic state wind field for example during instances when the wind speed at a given level decreases whilst the wind direction remains the same the waves show an upwind phase propagation with a typical phase speed of the order of 1 m s 1 the consequence of this unsteadiness for the propagation of the waves is discussed copyright 2002 royal meteorological society

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

small scale wind disturbances observed by the mu radar during the passage of typhoon kelly abstract this paper describes small scale wind disturbances associated with typhoon kelly october 1987 that were observed by the mu radar one of the mst mesosphere stratosphere and troposphere radars continuously for about 60 hours with fine time and height resolution first in order to elucidate the background of small scale disturbances synoptic scale variation in atmospheric stability related to the typhoon structure during the observation is examined when the typhoon passed near the mu radar site the structure was no longer axisymmetric there is deep convection only in the front north northeast side of the typhoon while convection behind it is suppressed by a synoptic scale cold air mass moving eastward to the west of the typhoon a drastic change in atmospheric stability over the radar site as indicated by echo power profiles is likely due to the passage of the sharp transition zone of convection strong small scale wind disturbances were observed around the typhoon passage it is show

vhf profiler observations of winds and waves in the troposphere during the darwin area wave experiment dawex 1 a vhf atmospheric radar wind profiler was used to study tropospheric winds during the darwin area wave experiment dawex the profiler which operated at a frequency of 54 1 mhz was located at pirlangimpi garden point 11 4 s 130 5 e on the tiwi islands observations were made regularly up to heights near 8 km with maximum heights occurring when convective activity was strongest mean winds observed between october and december 2001 are in good agreement with conditions that prevailed across northern australia during this period during the first two intensive observation periods iop during october and november the zonal and meridional wind components were westward and northward respectively with stronger values in november by the time of iop3 in mid december the zonal flow was eastward a pattern that is typical of the australian monsoon fluctuations in the three wind components for periods less than 3 hours are analyzed for iop2 in november when strong convective storms hectors occurred on all afternoons over the tiwi islands the fluctuations which are ascribed to convectively generated gravity waves show a correspondingly strong diurnal cycle with horizontal wind variances peaking between 8 and 12 m2s 2 in the early afternoon in the lower troposphere variances are only 2 m2s 2 in the early morning hours a power spectral analysis shows that oscillations with ground based periods between 8 and 17 min are especially prominent during hector events the profiler observations are compared with a numerical model study of gravity wave generation by convection on 17 november 2001 there is a satisfactory degree of agreement between the behavior of the model and profiler oscillations both as a function of height and time

evidence for inertia gravity waves forming polar stratospheric clouds over scandinavia 1 at three successive days at the end of january 2000 the deutsches zentrum fur luft und raumfahrt dlr airborne lidar ozone lidar experiment explored mountain wave induced polar stratospheric clouds above the scandinavian mountain ridge global analyses and mesoscale modeling are applied to explain their complex internal structure and their day to day variability depending on the synoptical scale meteorological conditions stratospheric temperature anomalies of different amplitude and horizontal extent are generated by the upward propagating mountain waves short term excitation of about 6 hours resulted in localized stratospheric temperature anomalies directly above the mountain ridge as for 25 january 2000 in this case the elevation of the observed clouds differed not much from the synoptic scale clouds upstream above the norwegian sea on the other hand long lasting flow past the scandinavian mountain ridge formed huge 400 km horizontally extending stratospheric ice clouds in altitudes as much as 5 km above the elevation of the upstream clouds just 1 day later inertia gravity waves with horizontal wavelengths of about 350 km are responsible for their formation for the first time a predicted temperature minimum far downstream of the mountains could be proofed by the observation of an isolated stratospheric ice cloud above finland the observed particles are classified in terms of their measured optical properties such as backscatter ratio and depolarization in all cases mountain waves generated ice clouds in contrast to the nitric acid trihydrate tail of the ice cloud on 25 january the same classification results in a tail of liquid supercooled ternary solutions droplets 1 day later the particle structure downstream of the mountains is very complex and needs detailed microphyical modeling and interpretation

the rapakivi granites of south greenland stable isotope characteristics of their black and white facies and the nature of their protolith abstract the rapakivi granites of south greenland were emplaced into the ketilidian orogenic belt at about 1 74 ga during an episode of extensional tectonics petrographically they can be subdivided into a roughly subequal black facies and white facies distinguished by the colour turbidity of the alkali feldspars and by the associated mineralogy which is more hydrous i e amphibole and biotite compared to olivine and pyroxene in the white facies the oxygen isotope composition of these rocks is notably homogeneous from thirteen outcrops sampled over an area extending some 200 km 100 km all alkali feldspars have an average 18 o of 10 2 0 4 this lack of variation is consistent with the consensus petrogenetic model which invokes a very well mixed two component protolith the high abundance of 18 o mean whole rock 18 o 9 4 argues that the major contribution perhaps 90 although originally mantle derived had undergone 18 o enrichment in a low temperature sedimentary cycle there is no oxygen isotopic distinction between alkali feldspars in the black and white facies which is argued to be a consequence of the relatively anhydrous nature of the melt hydrogen isotope compositions vary widely by 30 but are coherent on a hand specimen scale as demonstrated by approximately equal d of biotite and alkali feldspar it is not clear at which stage the d h heterogeneity was introduced

large amplitude mountain wave breaking over greenland abstract a large amplitude mountain wave generated by strong southwesterly flow over southern greenland was observed during the fronts and atlantic storm track experiment fastex on 29 january 1997 by the noaa g iv research aircraft dropwindsondes deployed every 50 km and flight level data depict a vertically propagating large amplitude wave with deep convectively unstable layers potential temperature perturbations of 25 k that deformed the tropopause and lower stratosphere and a vertical velocity maximum of nearly 10 m s 1 in the stratosphere the wave breaking was associated with a large vertical flux of horizontal momentum and dominated by quasi isotropic turbulence the coupled ocean atmosphere mesoscale prediction system coamps nonhydrostatic model with four nested grid meshes with a minimum resolution of 1 7 km accurately simulates the amplitude location and timing of the mountain wave and turbulent breakdown finescale low velocity plumes that resemble wakelike structures emanate from highl

southern hemisphere extratropical gravity wave sources and intermittency revealed by a middle atmosphere general circulation model abstractsouthern hemisphere extratropical gravity wave activity is examined using simulations from a free running middle atmosphere general circulation model called kanto that contains no gravity wave parameterizations the total absolute gravity wave momentum flux mf and its intermittency diagnosed by the gini coefficient are examined during january and july the mf and intermittency results calculated from the kanto model agree well with results from satellite limb and superpressure balloon observations the analysis of the kanto model simulations indicates the following results nonorographic gravity waves are generated in kanto in the frontal regions of extratropical depressions and around tropopause level jets regions with lower higher intermittency in the july midstratosphere become more less intermittent by the mesosphere as a result of lower level wave removal the gravity wave intermittency is low and nearly homogeneous throughout the sh middle atmosphere during january this indicates t

triassic granitoids of the qinling orogen central china genetic relationship of enclaves and rapakivi textured rocks abstract granitoids varying in composition from biotite amphibole granodiorite to monzogranite with rapakivi textures have recently been recognized in the qinling orogen central china the granitoids are magnesian calc alkalic and metaluminous a cnk 0 71 0 95 they contain many mafic to intermediate microgranular enclaves the enclaves are quenched mafic melts in granitic host magma as evidenced by fine grained sinuous margins against or transitional contacts with the host granitoids as well as disequilibrium textures and mineral assemblages u pb zircon dating of the granitoids yields 209 2 ma and 212 2 ma and the enclaves 210 2 ma and 211 2 ma respectively the host granitoids and enclaves show obvious silica gap but similar ree and trace element patterns the whole rock 87sr 86sr t end t and zircon ehf t values for the granitoids vary from 0 70516 to 0 70634 2 3 to 4 4 and 0 7 to 7 6 and for the enclaves from 0 70467 to 0 70600 1 1 to 4 0 and 1 2 to 8 8 respectively showing overlapped end t and zircon ehf t values all these suggest that the two magmatic systems represented by the host rock and enclave are probably derived from distinct sources with sufficient interaction or common origin but underwent different degrees of crustal contamination mineralogical and geochemical data point to enclave dissolution in silicic magma as a major process accounting for the origin of the rapakivi texture the possible bimodal magmatism suggested by the coeval granitoids and lamprophyre dykes combined with the structural pattern geochemical features and regional tectonics suggest a post collision setting for the qinling rapakivi textured granitoid plutons

radiosonde observations of equatorial atmosphere dynamics over indonesia 2 characteristics of gravity waves this paper discusses the characteristics of gravity waves in the equatorial region revealed by analyzing radiosonde measurements of wind velocity and temperature fluctuations at 0 35 km with a height resolution of 150 m made every 5 7 hours between february 27 and march 22 1990 in east java indonesia we conducted hodograph analysis to delineate vertical and horizontal propagation characteristics and found that most gravity waves were generated in the middle of the troposphere and that they propagated upward into the stratosphere the amplitudes of wind velocity and temperature fluctuations due to gravity waves were larger in the stratosphere than in the troposphere the direction of horizontal propagation of gravity waves was rather uniformly distributed in the troposphere but it became eastward in the lower stratosphere being opposite to that of the mean winds because of quasi biennial oscillation the vertical wavenumber spectra of wind velocity were described fairly well by a saturated model spectrum although their amplitudes were smaller in the stratosphere a typical vertical wavelength was 2 2 5 km while the horizontal phase velocities were 5 7 and 12 m s in the troposphere and stratosphere respectively the amplitudes of small scale gravity waves were significantly larger in the equatorial stratosphere than at middle latitudes time height variation of the wind velocity variance due to gravity waves showed a clear correlation with that for high relative humidity which implies that cloud convection is an important mechanism of gravity wave generation in the equatorial region

observation and analysis of a large amplitude mountain wave event over the antarctic peninsula 1 we use measurements from the atmospheric infrared sounder airs on the aqua satellite to observe the 3 dimensional structure of a gravity wave event over the antarctic peninsula and determine the horizontal and vertical wavelengths propagation direction and temperature amplitude and from these we estimate wave momentum flux using theoretical knowledge of the weighting functions and radiative transfer for airs radiance measurements at temperature sensitive channels in the infrared we derive a method of estimating wave temperature amplitude directly from the radiance measurements comparison of the radiance based temperature amplitudes to the temperature amplitude in airs retrieved temperature fields shows close agreement because the radiances have 3 times better horizontal resolution than the retrievals our analysis suggests we can routinely observe important geophysical properties of waves with horizontal wavelengths as short as 80 km using airs radiances we further analyze a nearly identical wave event appearing in the european centre for medium range forecasts ecmwf temperature and wind fields from both assimilation and forecast data analysis of the ecmwf data and nearby radiosonde wind profiles allows the interpretation as a mountain wave event forced by flow over the topography of the antarctic peninsula

inertia gravity wave generation by the tropospheric midlatitude jet as given by the fronts and atlantic storm track experiment radio soundings 1 generation of inertia gravity waves by the midlatitude tropospheric jet is studied on the basis of the data obtained from the radio soundings over the north atlantic during the fronts and atlantic storm track experiment campaign a sample of 224 radio soundings is used to analyze the wave activity as a function of the distance to the jet it is shown that radio soundings displaying the most intense gravity wave activity both in the stratosphere and in the troposphere are the ones closest to the jet axis thus the jet region is the dominant source of gravity waves in this region far from orography further examination allows for identification of two specific regions of the flow that are associated with intense gravity wave activity the vicinity of the maximum of the jet velocity and the regions of strong curvature of the jet the detailed case studies we provide suggest that geostrophic adjustment is the dynamical mechanism responsible for the generation of large amplitude inertia gravity waves in the regions of the strong curvature of the wind the generation of waves in the vicinity of the regions where the wind veers in the deep troughs of the geopotential appears to be systematic

the effect of particle settling velocity on computed suspended sediment concentration profiles abstract a field study was performed at a site in san pablo bay california to evaluate how well suspended sediment distribution equations reproduce observed concentrations near bed measurements of current velocity suspended sediment concentrations and fluid and particle characteristics were made an in situ settling cylinder was used to determine settling velocity values of aggregated suspended sediments and photographs from a plankton camera provided size estimates in situ weighted average settling velocities were generally an order of magnitude greater than a weighted average for stokes calculations of settling velocity for the grain size distribution of the reference suspended sediment sample and two orders of magnitude greater than a stokes settling velocity for the median grain size of suspended sediment flocs were commonly 100 m in diameter and as large as 450 m with settling velocities as high as 0 2 cm s 1 calculated suspended sediment concentration profiles using in situ estimates of settling velocity yielded closer agreement with observed concentration profiles within 25 than using settling velocities calculated from the grain size distribution of suspended sediment samples within 40 50

met office unified model high resolution simulations of a strong wind event in antarctica during winter much of the antarctic coast is susceptible to severe and hazardous strong wind events swes associated with the enhancement of katabatic winds by synoptic weather systems in this study a swe that occurred at mawson east antarctica involving a hurricane force wind speed of 39 m s 1 is simulated by the met office unified model at high horizontal resolutions with grid lengths between 12 and 1 5 km it is shown that all the simulations capture the qualitative evolution of the swe but underestimate its peak wind speed the extent of the underestimate is dependent on horizontal resolution with the 4 and 1 5 km 12 km models underforecasting the peak wind speed by around 15 36 in addition to a strengthening of the katabatic flow the simulated low level cyclonic winds associated with the depression responsible for the swe caused the formation of a barrier type jet parallel to the coast resulting in strong wind convergence interaction at the coastline and suggesting a strong topographic influence on the dynamics responsible for swe formation moreover it suggests that mawson is influenced by small scale gravity waves that formed in response to the stronger winds and that representation of this was particularly sensitive to horizontal resolution additional experiments suggest that the met office unified model simulation of the swe is most sensitive to the representation of turbulent mixing under stable conditions this study is important to identify shortcomings in the performance of the met office unified model near antarctica s coastal regions as well as to improve understanding of the processes responsible for swes

formation of rapakivi feldspar in the deer isle granite complex coastal maine in situ lead isotope and trace element analysis rapakivi and alkali feldspar phenocrysts from the devonian deer isle granite complex maine were investigated to see if magma mixing or isothermal decompression was responsible for their formation pb isotope and trace element analyses of alkali feldspar ovoids and their plagioclase inclusions were obtained by la icp ms to determine the characteristics of the initial magma these were compared with the plagioclase mantles rapakivi grains show a decrease in pb isotopic values and an increase in ba la and ce concentrations from the ovoids and inclusions to the innermost plagioclase mantles adjacent to the ovoids these variations along with cl imagery of quartz phenocrysts indicate an open system with compositional changes in the magma chamber occurring during rapakivi feldspar growth repeated episodes of magma mixing replenishment by ba and lree enriched magmas with lower pb isotopic ratios along with hybridized variations with the host magma created localized dissolution of alkali feldspar and quartz alkali feldspar phenocrysts proximal to these zones of thermal perturbation were first resorbed and then mantled by plagioclase that records the more primitive signature of the more mafic melt pb isotopic values and ba la and ce concentrations trend back to the initial magma composition at the mantle rims as the effects of the mixing event dissipated for grains that were somewhat more distal to these zones of mixing resorption of the alkali feldspar crystals did not occur yet the fresh supply of ba resulted in ba rich alkali feldspar mantles over ba poor alkali feldspar cores other alkali feldspar crystals were too far from the site of mixing hence they lack any evidence of open system crystallization as crystallization of the chamber continued along solidification fronts batches of cooler crystal rich magmas settled en masse to the floor disaggregation of these batches during settling and subsequent accumulation on the reservoir floor brought grains with disparate crystallization histories together filter pressing of the cumulate pile flushed highly evolved melts fluids out from interstitial pores to the high silica upper portions of the chamber the crystallization transportation and juxtaposition of disparate types of feldspar phenocrysts suggest that a relatively large and active magma chamber periodically recharged by localized batches of melt must have existed in this case it is clear that rapakivi mantled feldspars are the result of magma mixing such interpretations may apply to many other occurrences as well

feldspar evolution in the roxby downs granite host to fe oxide cu au u mineralisation at olympic dam south australia abstract the textural relationships and geochemistry of feldspars from least altered to sericite hematite altered and mineralised 1 595 ga roxby downs granite rdg at olympic dam south australia were examined the sample suite is representative of rdg both distal 5 km and proximal 27 34 is recognised along with a more abundant less calcic plagioclase an 12 20 both displaying rapakivi and anti rapakivi textures with alkali feldspar alkali feldspars or 55 ab 43 an 2 record post magmatic evolution from cryptoperthite to patch perthite subsequent patch perthite is overprinted by highly porous near end member albite and k feldspar while plagioclase undergoes replacement by albite sericite ba rich k feldspar in sericite hematite altered and mineralised rdg along the margin of the odbc sericite replaces all plagioclase whereas red stained fe rich k feldspar persists sulphide uranium rare earth element mineralisation is observed in association with hydrothermal feldspars and increases in abundance with proximity to the orebody petrographic observations and whole rock geochemistry illustrate the transformation of plagioclase and alkali feldspar from igneous to hydrothermal processes and indicate that hydrothermal albite and k feldspar formed within the rdg without the need for an external source of alkalis feldspar geothermometry indicates a minimum crystallisation temperature of 765 c at 2 2 kbar for alkali feldspar pressure estimate obtained using plagioclase amphibole geobarometry followed by a range of lower temperature transformations late stage magma mixing contamination is postulated from supportive temperature and pressure estimates along with feldspar and mafic mineral relationships

rayleigh lidar observations of gravity wave activity in the winter upper stratosphere and lower mesosphere above davis antarctica 69 s 78 e 1 gravity wave activity in the upper stratosphere and lower mesosphere uslm is investigated using temperature data retrieved from a rayleigh lidar at davis antarctica 69 s 78 e during the 2007 and 2008 winters the temporal and height variabilities of waves with ground based periods greater than 2 h and vertical wavelengths between 4 km and 20 km are analyzed stratospheric gravity wave potential energy per unit mass shows a weaker correlation with stratospheric winds at davis than that reported in the arctic gravity waves dissipate above 40 km during winter while there is no dissipation in the autumn mesosphere a separate analysis of gravity waves with ground based periods of 2 6 h revealed lower dissipation in the winter mesosphere the seasonal cycle of gravity wave activity is evident throughout the uslm with peak activity observed during winter the gravity wave potential energy and vertical wavenumber power spectral density at davis are similar to that recorded at other high latitude sites

the surface windfield over the antarctic ice sheets the intense radiative cooling of air over the ice slopes of antarctica generates a surface wind regime that is strongly controlled by topography and plays a key role in determining the behaviour of the atmosphere and ocean in high southern latitudes1 7 resultant surface winds are intimately linked to the orientation of the ice terrain fig 1 and display the highest degree of persistence found on earth the close coupling between wind and topography allows estimation of the former if the latter is known with some precision here we report on time averaged near surface airflow over the antarctic continent during winter diagnosed from a recent accurate synthesis of terrain slopes and from estimates of the lower atmospheric temperature structure the simulated drainage pat tern exhibits strong spatial variability with the airflow concentrated into several zones near the coastal margin these confluence regions are responsible for strong persistent katabatic winds over downstream coastal stretches and are indicative of zones of greatest katabatic potential

crystallization of the shap granite evidence from zoned k feldspar megacrysts textural chemical and sr isotopic studies of feldspars from the subsolvus shap granite northern england demonstrate that a number of magma mixing events have dominated the evolution of this pluton k feldspar megacrysts are phenocrysts formed in the magma chamber they contain a number of ba rich zones that developed during periods of slight dissolution and regrowth linked to the hybridization of the granite by the intrusion of basic magmas diorite enclaves represent the relicts of these magmas and these also contain k feldspar megacrysts which show evidence of major dissolution they are xenocrysts picked up from the host granite and incorporated in the basic magma increasing h 2 o contents during fractional crystallization caused a late switch from growth of megacrysts to finer grained k feldspars in the matrix the chemically and isotopically zoned k feldspar megacrysts preserve an exceptional record of the evolution of the magma and the zones also had a significant influence on the development of exsolution microtextures during cooling