chronology of deformation within the turbidite dominated lachlan orogen implications for the tectonic evolution of eastern australia and gondwana ar ar data from fabric forming white mica in slates syntectonic quartz veins and granitic mylonites constrain the timing of metamorphism deformation and exhumation in the lachlan orogen australia these data also help define the tectonic evolution of the tasmanides during paleozoic time the lachlan orogen formed by the progressive accretion of a thick turbidite fan sequence and volcanic terrains to gondwana during the closing of a small marginal ocean or back arc basin this tectonic setting was similar to the present western and southwestern pacific region accretion of the lachlan orogen to gondwana occurred by closing of the basin system by subduction accretion processes and some translation the process is typified in the western lachlan orogen by a major eastward migrating deformation involving chevron folding and faulting over an eastward propagating decollement melange zone and is recorded by ar ar mica ages ranging from 455 ma in the western part to 390 ma in the eastern part in the central lachlan orogen deformation migrated southwestward from 440 430 to 405 ma away from the high temperature wagga omeo metamorphic complex where deformation metamorphism occurred between 440 and 400 ma in the north 400 ma mica ages record deformation and inversion of structures in the cobar basin in the eastern lachlan orogen ar ar mica dates range from 450 to 340 ma ages of 455 445 ma are yielded by the narooma accretionary complex 405 390 ma ages are found along the major thrust faults bounding high grade metamorphic complexes and 360 340 ma cooling ages are found in the inverted extensional basins e g hill end and related structural zones the ar ar results also document periods of reactivation on early formed structures during later deformation elsewhere in the orogen

the poleward motion of extratropical cyclones from a potential vorticity tendency analysis abstractthe poleward propagation of midlatitude storms is studied using a potential vorticity pv tendency analysis of cyclone tracking composites in an idealized zonally symmetric moist gcm a detailed pv budget reveals the important role of the upper level pv and diabatic heating associated with latent heat release during the growth stage the classic picture of baroclinic instability emerges with an upper level pv to the west of a low level pv associated with the cyclone this configuration not only promotes intensification but also a poleward tendency that results from the nonlinear advection of the low level anomaly by the upper level pv the separate contributions of the upper and lower level pv as well as the surface temperature anomaly are analyzed using a piecewise pv inversion which shows the importance of the upper level pv anomaly in advecting the cyclone poleward the pv analysis also emphasizes the crucial role played by latent heat release in the poleward motion of the cyclone the l

sensitivity of tropical cyclone forecasts as revealed by singular vectors abstract singular vector sv sensitivity calculated using the adjoint model of the u s navy operation global atmosphere prediction system nogaps is used to study the dynamics associated with tropical cyclone evolution for each model predicted tropical cyclone svs are constructed that optimize perturbation energy within a 20 by 20 latitude longitude box centered on the 48 h forecast position of the cyclone the initial svs indicate regions where the 2 day forecast of the storm is very sensitive to changes in the analysis composites of the svs for straight moving cyclones and non straight moving cyclones that occurred in the northern hemisphere during its summer season in 2003 are examined for both groups the initial time sv sensitivity exhibits a maximum within an annulus approximately 500 km from the center of the storms in the region where the potential vorticity gradient of the vortex first changes sign in the azimuthal direction the composite initial time sv maximum for the straight mov

an analysis of hurricane opal s forecast track errors using quasigeostrophic potential vorticity inversion abstract hurricane opal s landfall in october 1995 forms the basis of a serious hurricane forecast problem the potential for hurricane conditions over land with insufficient warning time official national hurricane center nhc a division of the tropical prediction center forecasts predicted landfall and passage inland over the eastern united states at a later time than observed because of underestimation of the northward component of the steering flow by the national centers for environmental prediction s ncep operational models and other hurricane track models the goal of this paper is to isolate the cause of the poor forecast of meridional storm motion in ncep s early eta model by using quasigeostrophic potential vorticity qgpv inversion qgpv inversion permits decomposition of the steering flow into contributions from different synoptic scale features the inversion procedure is applied to the eta analysis and 48 h eta forecast valid at 1200 utc 5 october 1995 analyses from the european centre

initiation of subduction zones along transform and accreting plate boundaries triple junction evolution and forearc spreading centres implications for ophiolitic geology and obduction

orographic influence on basic flow and cyclone circulation and their impacts on track deflection of an idealized tropical cyclone abstracta series of idealized numerical experiments and vorticity budget analyses is performed to examine several mechanisms proposed in previous studies to help understand the orographic influence on track deflection over a mesoscale mountain range when an idealized tropical cyclone tc is embedded in a uniform easterly flow and passes over a mountain with a moderate froude number it is deflected to the south upstream moves over the mountain anticyclonically and then resumes its westward movement the vorticity budget analysis indicates that the tc movement can be predicted by the maximum vorticity tendency vt the orographic effects on the above tc track deflection are explained by the following 1 upstream of the mountain the easterly basic flow is decelerated as a result of orographic blocking that causes the flow to become subgeostrophic which advects the tc to the southwest analogous to the advection of a point vortex embedded in a flow the vt is primarily dominated by the horizontal vo

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

genesis of tropical storm eugene 2005 from merging vortices associated with itcz breakdowns part i observational and modeling analyses abstract although tropical cyclogenesis occurs over all tropical warm ocean basins the eastern pacific appears to have the highest frequency of tropical cyclogenesis events per unit area in this study tropical cyclogenesis from merging mesoscale convective vortices mcvs associated with breakdowns of the intertropical convergence zone itcz is examined this is achieved through a case study of the processes leading to the genesis of tropical storm eugene 2005 over the eastern pacific using the national centers for environmental prediction reanalysis satellite data and 4 day multinested cloud resolving simulations with the weather research and forecast wrf model at the finest grid size of 1 33 km observational analyses reveal the initiations of two mcvs on the eastern ends of the itcz breakdowns that occurred more than 2 days and 1000 km apart the wrf model reproduces their different movements intensity and size changes and vortex vortex interaction at nearly the right timing and location at

the impact of extratropical transition on the downstream flow an idealized modelling study with a straight jet the interaction of a tropical cyclone undergoing extratropical transition et with the midlatitude synoptic scale flow is investigated using full physics numerical experiments with idealized initial conditions the emphasis is on the impact on the midlatitude flow downstream of the et event the midlatitude flow is represented by a balanced straight jet stream as the tropical cyclone approaches the jet a ridge trough couplet and a distinct jet streak form in the upper level flow a midlatitude cyclone develops rapidly downstream of the et system and the further evolution is characterized by downstream baroclinic development based on hovmoller diagrams the upper level development is interpreted as the excitation and subsequent dispersion of a rossby wave train on the potential vorticity gradient associated with the jet the characteristics of this wave train are sensitive to the structure of the jet and to moist processes in the midlatitudes the tropical cyclone undergoing et acts as a sustained forcing for the wave train and the structure of the et system impacts the development most significantly one to two wavelengths downstream of et piecewise inversion of potential vorticity complemented by the partitioning of the flow into its rotational and divergent parts is applied to assess the impact of the et system quantitatively both the cyclonic circulation and the outflow of the tropical cyclone are important contributors to the formation and amplification of the ridge trough couplet the outflow anomaly reduces the eastward motion of the ridge trough couplet significantly and thus promotes phase locking between the tropical cyclone and the upper level pattern copyright 2008 royal meteorological society

an idealized numerical study of shear relative low level mean flow on tropical cyclone intensity and size abstractgiven comparable background vertical wind shear vws magnitudes the initially imposed shear relative low level mean flow lmf is hypothesized to modify the structure and convective featu

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

mechanisms of poleward propagating intraseasonal convective anomalies in cloud system resolving models abstract an envelope of convection that propagates both poleward and eastward accounts for the largest fraction of intraseasonal variance of the tropical atmosphere during boreal summer here the mechanisms of poleward propagating convective anomalies are examined in a nonhydrostatic model with zonally symmetric boundary conditions integrated on a beta plane at resolutions high enough to explicitly represent moist convection when the domain has a narrow zonal dimension of 100 km or less the model produces a quasisteady intertropical convergence zone itcz meridionally propagating transients are produced for some prescribed sea surface temperature distributions but these transients are shallow vanish at finer resolutions and have a structure that bears little resemblance to that of observed poleward propagating anomalies this is in sharp contrast to previous studies that obtained robust poleward propagating anomalies in axisymmetric models using parameterized moist convection and it suggests that

structural style and kinematics of an underplated slate belt kodiak and adjacent islands alaska the kodiak formation composed of coherent maastrichtian turbidites is a slate belt whose dominant structures developed during underplating to an accretionary wedge in the latest cretaceous it consists of about 80 coherent landward dipping thrust packets zones of disrupted sandstone associated with a scaly argillite matrix constitute the remainder about half of these disrupted sandstone zones are related to pre accretion deformation and the rest formed along late stage strike slip faults that postdate development of slaty cleavage the formation is divided into three structural belts the landward and seaward belts include steeply dipping structures and the central belt contains shallowly dipping structures and rocks that have experienced the highest strain the central belt probably acted as a low angle southeast verging floor thrust zone beneath the landward belt the structural history of the kodiak formation includes 1 early soft sediment disruption 2 tectonic stratal disruption 3 thrust faulting slaty cleavage s 1 development and folding f 1 4 intrusion of granodioritic plutons dikes and sills and associated normal faulting 5 development of crenulations f 2 and crenulation cleavage s 2 6 thrust faulting and 7 development of right lateral strike slip faults event 3 produced the dominant northwest dipping structural grain and caused the greatest amount of shortening the timing of event 7 relative to events 5 and 6 is not certain the dominant structures of the kodiak formation are interpreted as developing during underthrusting underplating and intra wedge shortening during latest cretaceous time within an accretionary wedge the maximum time from deposition to emplacement was about 12 m y and the timing is constrained by the maximum depositional age 74 m y and the age of plutonic rocks 62 m y that crosscut the dominant fabric pre cleavage zones of stratal disruption reflect deformation on the lower plate during underthrusting slaty cleavage thrusts and f 1 folds developed during underplating that also resulted in the formation of duplexes crenulations are probably related to post underplating subhorizontal shortening of sediments within the accretionary wedge syn deformation dynamic recrystallization of quartz minimum syn accretion metamorphic temperatures between 205 and 250 c and pressures of at least 2 65 kb recorded during the earliest stages of deformation suggest underplating at 10 km

incipient subduction and deduction along the eastern margin of the japan sea the eastern margin of the japan sea has been under convergent tectonics since sometime after the pliocene the suture line is on the ocean continent boundary between the japan yamato basins and the tohoku northeast japan arc incipient subduction and obduction of the oceanic and sub oceanic crust are observed along the suture line with the occurrence of numerous n s trending fault bounded ridges and troughs focal mechanism solutions of several compressional type earthquakes with magnitudes of m 6 9 to 7 7 which have occurred along the zone are consistent with the observation of geological thrust faults the convergent stresses in the japan sea may be due to india eurasia collision and its associated intra plate or inter microplate movements in east asia the eastward movement of the amurian plate causes baikal extension along its western margin and the japan sea convergence along its eastern margin

large scale duplexes within the new britain accretionary wedge a possible example of accreted ophiolitic slivers a multichannel seismic line acquired in the western solomon sea images reflectors within the new britain accretionary wedge which we interpret as accreted duplexes of the downgoing oceanic plate the seaward edge of the largest duplex is located just 6 km from the toe of the accretionary wedge suggesting recent incorporation into the wedge these data therefore provide an excellent opportunity to determine the dynamics of oceanic basement accretion the oceanic basement is represented by a high amplitude low frequency reflector that can be traced up to 40 km arcward of the toe of the accretionary wedge on several seismic lines in this survey another prominent reflector similar in character to the basement reflector lies approximately one second higher in at least one seismic section this reflector is likely to be the top of a basement duplex structures imaged above the basement duplex define a preduplex accretionary wedge whereas those at the toe indicate a new episode of postduplex accretion we have tested this interpretation using both magnetic modeling and interval velocity analysis magnetic models of the wedge that include basement duplexes provide a good match to the observed magnetic data and provide limits on the size and interval velocities of the slivers interval velocities between the two strong reflectors calculated using stacking velocities and constrained through magnetic modeling exceed 5000 m s and are consistent with our interpretation of ophiolitic slivers within the accretionary wedge

the unexpected rapid intensification of tropical cyclones in moderate vertical wind shear part i overview and observations abstracta satellite based investigation is performed of a class of tropical cyclones tcs that unexpectedly undergo rapid intensification ri in moderate vertical wind shear between 5 and 10 m s

interaction of a baroclinic vortex with background shear application to hurricane movement abstract most extant studies of tropical cyclone movement consider a barotropic vortex on a plane however observations have shown that real tropical cyclones are strongly baroclinic with broad anticyclones aloft also the distribution of the large scale potential vorticity gradient in the tropical atmosphere is very nonuniform these properties may substantially influence the movement of such storms note that the anticyclone above a hurricane will interact with the lower hurricane vortex and induce storm motion such interaction can be caused by both the direct effect of ambient vertical shear and the effect of vertical variation of the background potential vorticity gradient in this paper an attempt to isolate the effect of background vertical shear is made the hurricane is represented in a two layer quasigeostrophic model as a point source of mass and zero potential vorticity air in the upper layer collocated with a point cyclone in the lower layer the model is integrated by the method of co

ophiolite accretion in the lachlan orogen southeastern australia slivers of dismembered cambrian ophiolites are preserved in major fault zones of the turbidite dominated western and central lachlan orogen of southeastern australia geometrical chronological and metamorphic constraints indicate that these slivers did not undergo classic tethyan style obduction but were incorporated into evolving turbidite wedges as offscraped slices imbricated fault slivers or duplexes and as blocks in melange the processes involved include decoupling of the oceanic crustal stratigraphy predominantly above the moho formation and metamorphism of serpentinite talc matrix melange up to blueschist conditions and accretion via underplating or offscraping during underthrusting these processes have produced major large scale fault zones within the chevron folded turbidites that show marked along strike variation in structural complexity that relate to magnitude of displacement the fault zones may have formed preferentially where topographic highs occurred in the oceanic crust promoting fold and fault nucleation within irregularities in the layering these fault zones have predominantly brittle character due to their formation under a low geothermal gradient duplex like structures in the fault zones and the inferred development through buckling of then faulting of the oceanic lithosphere have analogues in modern oceanic environments e g indian ocean and young subduction systems e g sulu sea southeast asia they are interpreted to have formed due to convergence in a non collisional intra oceanic setting during closure of a cambrian backarc basin

a submesoscale coherent eddy in the greenland sea in 2003 1 submesoscale coherent vortices scvs have been observed earlier in the greenland sea but their overall characteristics the formation and the dissolution mechanisms and the effects on the large scale hydrodynamics were not well understood in order to improve the understanding of these features a simultaneous investigation of hydrography chemical tracers and full depth velocity profiles in a scv was employed in september 2003 the observed eddy had a homogeneous cold core from 500 m to 2500 m depth with a radius of 8 15 km the velocity field of the eddy was higher than in the previous years and the eddy was in strong anticyclonic rotation in the intermediate layer 1000 2000 m the high velocity field led to the estimate of eddy vorticity twice as high as previous observations and this was accounted for the eddy migration while the earlier observed eddies were rather stationary around 75 n 0 e the eddy migrated northeast ward with a speed of 3 km day driven by the background mean flow under the strong effects of the background shear which tilted the rotation axis in the upper layer the concentrations of sulphur hexafluoride sf6 and chlorofluorocarbons cfcs in the eddy provided firm information about the source water end members the greenland sea arctic intermediate water and winter cold surface water were determined as the principal eddy source waters this differs from the earlier conception of eddies being sourced from intermediate waters at the periphery of the greenland basin

the effect of relative flow on the asymmetric structure in the interior of hurricanes abstract asymmetric structure of tropical cyclones simulated by the geophysical fluid dynamics laboratory high resolution triply nested movable mesh hurricane model was analyzed emphasis was placed on the quasi steady component of the asymmetric structure in the region of the eyewall it was found that the asymmetry was primarily caused by the relative wind that is the flow entering and leaving the storm region relative to the moving storm a set of idealized numerical experiments was first performed both with a constant and a variable coriolis parameter f and the addition of basic flows that were either constant or sheared with height analysis was then made for one case of hurricane gilbert 1988 to demonstrate that the quasi steady asymmetric structure analyzed in the idealized studies could be identified in this real data case vorticity analysis in the variable f experiment indicated that quasi steady asymmetries resulted in the eyewall region through the effect of vorticity advection due to

petrogenesis and implications for tectonic setting of cambrian suprasubduction zone ophiolitic rocks in the central beishan orogenic collage northwest china abstract the hongliuhe ophiolite is a fragment of the early paleozoic oceanic crust situated in a suture zone central to the beishan orogenic collage which is a subset to the central asian orogenic belt in northwest china it has lithologic geochemical and chronological similarities to the yueyashan xichangjing ophiolite 400 km east along strike allowing for correlative interpretations of marginal seafloor spreading processes the hongliuhe ophiolite is explored in this study with complete petrologic geochemical and structural descriptions the ultramafic body comprises cumulate layered lherzolite and gabbro plutonic lithologies tectonized with syn magmatic extension a u pb age of 520 3 5 8 ma was obtained by shrimp analysis of zircons from a pegmatitic gabbro the ultramafic rocks are variably depleted and some show refertilization of lile s consistent with slab dehydration in a supra subduction mantle wedge mineral chemistry shows high cr 36 82 populations of spinel and wide ranging lower mg 8 50 consistent with known forearc peridotite chemistry partially re equilibrated by tectonism or through staged magmatism olivine and pyroxene chemistries are consistent with this interpretation a thin volcanic cover is interlayered with red cherts and has a bimodal set of geochemical signatures both island arc tholeiite and calc alkaline they bear distinct nb ta anomalies consistent with slab derived fluid initiated melting in a supra subduction environment coarse volcaniclastic turbidites infilled paleo topography along the ophiolite and they are interbedded with quartzofeldspathic sandstones indicating an initial proximity to an arc the sandstones contain detrital spinel with analyses showing relation to both the ophiolite and possibly a secondary alkalic volcanic source the supracrustal sequence continues with a thick contiguous covering of margin related rocks including interlayered limestone pyroclastic and siliciclastic rocks and basalts as a constraint on emplacement we provide an u pb zircon shrimp date 413 6 3 5 ma from an undeformed granitoid body intruded within the overlying stratigraphy the entire analysis paints a picture of subduction rollback related extension affecting the margin of an emerging or mature arc just prior to a known magmatic cycle that ended with a collision in the devonian at the latest this suture is one of many in the beishan and our interpretation provides evidence in a long running debate supporting accretionary orogenesis in an island arc archipelago as the main system for growing sialic crust in the paleozoic central asia

a numerical study of the track deflection of supertyphoon haitang 2005 prior to its landfall in taiwan abstract a series of numerical simulations are conducted using the advanced research version of the weather research and forecasting model with a 4 km fine mesh to examine the physical processes responsible for the significant track deflection and looping motion before the landfall of supertyphoon haitang 2005 in taiwan which poses a unique scientific and forecasting issue in the control experiment a low level northerly jet induced by the channeling effect forms in the western quadrant of the approaching storm where the inner core circulation is constrained by the presence of taiwan s terrain because of the channeling effect the strongest winds of the storm are shifted to the western portion of the eyewall the northerly advection flow averaged asymmetric winds within 100 km radius results in a sharp southward turn of the westward moving storm the time series of the advection flow shows that the advection wind vectors rotate cyclonically in time and well match the motion of the simulated vortex

the relationship between storm motion vertical wind shear and convective asymmetries in tropical cyclones abstract the influence of the direction of storm motion on the azimuthal distribution of electrified convection in 35 atlantic basin tropical cyclones from 1985 to 1999 was examined using data from the national lightning detection network in the inner 100 km flashes most often occurred in the front half of storms with a preference for the right front quadrant in the outer rainbands r 100 300 km flashes occurred predominantly to the right of motion although the maximum remained in the right front quadrant the results are shown to be consistent with previous studies of asymmetries in rainfall radar reflectivity and vertical motion with respect to tropical cyclone motion the motion effect has been attributed to the influence of asymmetric friction in the tropical cyclone boundary layer the authors previously found a strong signature in the azimuthal distribution of lightning with respect to vertical wind shear because both effects show clearly vertical wind shear and storm motion must themse

at what stress level is the central indian ocean lithosphere buckling internal contrasts in strength are responsible for lithospheric buckling these are quantified by comparing the indian ocean data to two dimensional visco elasto plastic numerical models where the material properties depend on temperature and pressure the central indian basin is known for its intraplate seismicity and long wavelength undulations of the sea floor and associated gravity signatures to simulate the amplitudes of undulations that reach 1 km within about 11 ma of compression and 60 km of shortening the required mean yield strength of the lithosphere is 400 mpa if either a hydrostatic fluid pressure is considered in the crust or a mechanical decoupling at the depth of the moho small crustal wavelengths are superimposed on the long wavelength deformation in agreement with observations it is then possible to match the alternative indication that buckling commenced only 4 ma ago with a total amount of shortening of 30 km and with a required yield strength of 200 mpa about 10 of homogeneous thickening accompanies buckling taking into account variable thermal conductivity demonstrates that a change in the geotherm is sufficient to increase buckling amplitudes by 10 within 5 ma fl 2000 elsevier science b v all rights reserved

evolution of the upper tropospheric outflow in hurricanes iselle and julio 2014 in the navy global environmental model navgem analyses and in satellite and dropsonde observations upper tropospheric outflow was examined during the life cycles of two hurricanes in the eastern and central pacific ocean the outflow from hurricanes iselle and julio was evaluated using analyses from the navy global environmental model navgem which were very highly correlated with satellite atmospheric motion vector amv and noaa g iv dropsonde observations a synoptic overview provided the environmental context for the lifecycles of both tropical cyclones tcs then the outflow magnitude and direction within 6 radial degrees of each tc center were analyzed in relation to tc intensity the synoptic environment and inertial stability with the following results in both iselle and julio the azimuthally averaged outflow magnitude was maximized initially more than 4 radial degrees from the center and that maximum moved steadily inward during a 4 day intensification period and reached a position radially inward of 2 degrees within 6 h of the time of maximum surface winds furthermore the direction of the outflow in both tcs was related to the evolution of the large scale upper tropospheric flow pattern particularly the phasing of subtropical jet ridges and troughs moving eastward north of both tcs finally outflow channels were consistently bounded by regions of lowest highest values of inertial stability counterclockwise clockwise from the maximum outflow azimuth a pattern that persisted throughout the life cycles of both storms regardless of intensity environmental flow and the number and direction of outflow channels present

blueschist metamorphism during accretion in the lachlan orogen south eastern australia low t intermediate to high p assemblages indicative of the prehnite pumpellyite greenschist and blueschist facies are preserved in melange zones and slivers of oceanic crust within two major fault zones of the turbidite dominated lachlan orogen in one of these fault zones governor fault zone blueschists occur as franciscan like blocks in a serpentinite talc matrix that is interleaved with phyllites and slates and structurally overlain by a fault slice or duplex of predominantly pillow basalt chert and turbidite the blueschist metavolcanics are interpreted to have formed at 450 c and at a depth of approximately 21 27 km the presence of blue amphibole in the blocks rinds and matrix indicate that the metavolcanics were emplaced in the matrix prior to blueschist metamorphism blocks and matrix were partially exhumed interleaved with tectonic slices of phyllite and slate and subsequently folded at about 10 12 km depth inferred from bo values of the dominant mica fabric in the phyllites and slates metamorphic p t is highest in the structurally lowest slice melange zone and lowest in the overlying ophiolitic fault slice suggestive of an accretionary burial metamorphic pattern formed by underplating of the melange in the other fault zone heathcote fault zone blueschists transitional to greenschist facies are interpreted to have formed at 450 c and at a depth of approximately 15 21 km they occur as blocks in serpentinite talc matrix melange and are also associated with fault slices of oceanic crust textural and mineralogical evidence suggests that the protoliths for the blueschists in both fault zones were boninitic pillow lavas the metamorphic facies and patterns and the structural and lithological associations can be interpreted in terms of disruption of oceanic crust and overlying sediments during subduction and formation of serpentinite matrix melange overprinted by blueschist metamorphism either prior to or during underplating of the melange and duplex formation the presence of blueschist metavolcanics indicate that these processes occurred at considerable depth these interpretations have implications for the evolution of large scale fault zones in noncollisional convergent oceanic settings

cluster analysis of post landfall tracks of landfalling tropical cyclones over china in this paper we apply finite mixture model based clustering algorithms to cluster post landfall tracks of tropical cyclones tcs making landfall over china because existing studies find that landfall surfaces or elevations affect post landfall tc movements we also take account of elevations in addition to time orders in this model our study reveals three clusters with cluster 1 making landfall in hainan province and moving across the western coast of guangdong province most of the tc tracks in cluster 1 move over the ocean and make secondary landfalls over yunnan province of china and vietnam cluster 1 finally dissipates inland and moves westward as a result of the westward shift subtropical high westward steering flow easterly vertical wind shear and strong mountainous blocking cluster 2 makes landfall over guangdong and fujian provinces tcs in cluster 2 subsequently move inland and disappear due largely to westward shift subtropical high easterly steering flow easterly vertical wind shear and relatively strong mountainous blocking cluster 3 makes landfall along the fujian and zhejiang coast and sustains a long period of time recurving mostly to the mid latitude region owing to the surrounding eastward shift subtropical high westerly vertical wind shear weak mountainous blocking and westerly steering flow because cluster 2 is significantly associated with la nina events tcs more likely make landfall over southeastern china coast and move westward or northwestward without recurving cluster 3 sustains a longer time than clusters 1 and 2 in spite of its weak horizontal and vertical water vapor supply tcs in cluster 3 interact actively with westerlies during the post landfall period however we cannot observe any analogous interactions with the mid latitude westerlies in clusters 1 and 2 tcs of clusters 1 and 2 are influenced by summer monsoon flows moreover summer monsoon exerts a greater influence on cluster 1 than cluster 2 the composite 200 hpa divergence of cluster 3 is stronger than that of clusters 1 and 2 this explains to some degree why cluster 3 sustains longer than clusters 1 and 2 after making landfall

using tropopause maps to diagnose midlatitude weather systems the use of potential vorticity pv allows the efficient description of the dynamics of nearly balanced atmospheric flow phenomena but the distribution of pv must be simply represented for ease in interpretation representations of pv on isentropic or isobaric surfaces can be cumbersome as analyses of several surfaces spanning the troposphere must be constructed to fully apprehend the complete pv distribution following a brief review of the relationship between pv and nearly balanced flows it is demonstrated that the tropospheric pv has a simple distribution and as a consequence an analysis of potential temperature along the dynamic tropopause here defined as a surface of constant pv allows for a simple representation of the upper tropospheric and lower stratospheric pv the construction and interpretation of these tropopause maps which may be termed isertelic analyses of potential temperature are described in addition techniques to construct dynamical representations of the lower tropospheric pv and near surface potential temperature which complement these isertelic analyses are also suggested case studies are presented to illustrate the utility of these techniques in diagnosing phenomena such as cyclogenesis tropopause folds the formation of an upper trough and the effects of latent heat release on the upper and lower troposphere

origin and emplacement of ophiolites ever since their recognition ophiolites have been a source of controversy although all workers have agreed upon their importance a number of conflicting schools of thought have become unified in the interpretation of ophiolite complexes as fragments of oceanic crust and mantle formed at spreading centers an expanded version of the penrose ophiolite definition is proposed herein called the ophiolite association taking into account rocks which bear upon the origin and significance of ophiolite complexes an ideal ophiolite association includes the following units from bottom to top 1 a crystalline basement and shallow water sedimentary sequence 2 a tectonic unit of thrust slices of continental margin and rise and abyssal sediments and or melange 3 a metamorphic unit as much as a few hundred meters thick generally with higher grade rocks over lower grade ones 4 ultramafic tectonite unit composed dominantly of multiply deformed peridotite dunite and minor chromitite 5 a cumulate complex ultramafic at the base grading to mafic or intermediate at the top 6 a noncumulus unit of varitextured gabbro and minor trondhjemite 7 a sheeted dike complex 8 an extrusive section of massive and pillowed flows and intercalated sediments 9 an abyssal or bathyal sediment sequence which may include radiolarian chert red pelagic limestone metalliferous sediments breccias and or pyroclastic deposits and 10 postemplacement deposits of laterite reef limestone or shallow marine or subaerial sediments this expanded ophiolite association allows greater precision in inferring original origin and emplacement some ophiolite complexes particularly in the tethys herein designated tethyan type exhibit units 1 2 3 and 4 whereas others particularly in the cordilleran belt herein termed cordilleran type lack units 1 2 3 and in places 4 the emplacement of the former probably occurred during collision of a passive margin with a subduction zone or incipient subduction zone emplacement of the cordilleran type generally is not clear cut the nature of the spreading center which produced a given ophiolite is indicated more clearly by the presence or absence of units 5 9 than by chemistry or mineralogy some ophiolite complexes lack complete sections and may have formed along transform faults others contain volcanic pyroclastic deposits instead of pelagic sedimentary sequence and probably formed within or near an arc several ophiolite complexes may have originated by conversion of a transform fault into a subduction zone such conversion may result from normal plate evolution or from major plate reorganization major times of ophiolite emplacements appear to correspond with global plate reorganizations

attribution of projected future changes in tropical cyclone passage frequency over the western north pacific abstractthis paper performs an attribution analysis of future changes in the frequency of tropical cyclone tc passages over the western north pacific basin projected by seven general circulation models the models project increases in the passage frequency over the tropical central north pacific and decreases in regions to the west and northwest including east asian countries the attribution analysis reveals that while changes of the basinwide tc count would decrease the frequency of passages throughout the basin the gross horizontal contrast in the passage frequency changes is caused by a projected eastward shift of main tc development regions probably caused by el nino like sea surface temperature changes the change in the frequency of passages is also caused by changes of tc translation vectors and preferable tracks in particular the translation vector would rotate clockwise to point in a more easterly direction over oceanic regions south of japan decreasing the passage frequency over the kor

diagnosing forecast errors in tropical cyclone motion abstractthis paper reports on the development of a diagnostic approach that can be used to examine the sources of numerical model forecast error that contribute to degraded tropical cyclone tc motion forecasts tropical cyclone motion forecasts depend upon skillful prediction of the environment wind field and by extension the synoptic scale weather systems nearby the tc while previous research suggests that the deep layer mean dlm steering flow typically approximates the actual tc motion it is shown that the motion of even mature tcs can depart from the dlm steering flow an optimal environmental steering flow is defined which varies the vertical extent of the steering layer and the radius over which tc vorticity and divergence are removed errors in predicted tc motion are quantified using a diagnostic equation that accounts for not only differences in the synoptic scale flow but also differences in the depth and radius used to define the steering flow differences in the latter two parameters a

character and kinematics of faults within the turbidite dominated lachlan orogen implications for tectonic evolution of eastern australia reply fault zones within turbidite dominated orogenic systems typified by the lachlan orogen of eastern australia are characterised by higher than average strain and intense mica fabrics transposition foliation and isoclinal folds poly deformation with overprinting crenulation cleavages and steeply to moderately plunging meso and micro folds they have a different character compared to the brittle ductile fault zones of classic foreland fold and thrust belts such as the appalachians and the canadian rocky mountains multiple cleavages and transposition layering record a progressive shear related deformation history an intense mica fabric evolves initially during shortening of the overlying sedimentary wedge but is progressively modified during rotation and emplacement to higher structural levels along the steep parts of inferred listric faults the deformed wedge outside the fault zones generally undergoes one phase of deformation shown by a weak to moderately developed slaty cleavage which is parallel to the axial surface of upright subhorizontally plunging chevron folds other faults within the turbidites of the lachlan orogen include the steep zones of ductile strike slip deformation that bound a centrally located high t low p metamorphic complex characterised by s c mylonites these ductile shear zones indicate a southward passage of the metamorphic complex as a crustal wedge with emplacement to higher structural levels along a leading edge ductile thrust fault ar ar dating constrains the timing of regional deformation to be mostly late ordovician through silurian across the lachlan orogen faults in the low grade turbidite sequences record the kinematic evolution of the developing lachlan orogen and indicate progressive deformation associated with simultaneous eastward propagating and migrating deformation fronts in both the western and eastern parts of the fold belt these deformation fronts are related to accretionary style deformation at the leading edges of overriding plates in an inferred southwest pacific type subduction setting from the late ordovician to the mid devonian along the former gondwana margin the fault zones effectively accommodate and preserve movements within the structurally thickening migrating and prograding accretionary wedge

constraining the vandieland microcontinent at the edge of east gondwana australia abstract using airborne magnetic and marine gravity data the geological subdivisions of western tasmania have been interpreted north across bass strait into victoria the three westernmost tasmanian zones the king island rocky cape and burnie zones are inferred to form the largely concealed selwyn block in victoria the eastern tasmania zone correlates with the victorian tabberabbera zone thus the tasmanian tamar fracture zone corresponds with the victorian governor fault the victorian ceres gabbro is correlated with magnetic rocks west of king island that are tentatively considered to be neoproterozoic most of the cambrian felsic volcanic rocks of the tasmanian mount read volcanics lie above the burnie zone as do the similar rocks exposed in the jamieson licola and glen creek windows in central victoria reinterpretation of a victorian deep seismic reflection line indicates burnie zone equivalent rocks were thrust south west over rocky cape zone equivalents a link between western tasmania and central victoria is evident from upper devonian granites intruded into the selwyn block region the eastern end of the upper devonian cobaw complex and the warburton granodiorite contain calcsilicate enclaves interpreted to be derived from a northern equivalent to the smithton basin the mount disappointment granodiorite has high ni and cr contents and pseudomorphs after orthopyroxenes consistent with having been partly sourced from the underlying basaltic rocks like those on the eastern margin of the king island zone the magnetic responses under the strathbogie complex the cerberean caldera and the lysterfield granodiorite are attributed to metamorphism of part of an extension of the smithton basin probably equivalents to the 580 ma spinks creek volcanics quartzite cobbles in a devonian conglomerate in the south eastern melbourne zone may be derived from rocky cape group equivalents when integrated with the geological interpretation of tasmania we provide a stratotectonic map of the vandieland micro continent

well preserved underplating structure of the jadeitized franciscan complex pacheco pass california duplex structures several hundred metres thick bounded by marker beds exhibiting basalt chert association have been found in the franciscan complex near pacheco pass central diablo range california the terrane was regionally metamorphosed and deformed under blueschist facies conditions at 150 c and 7 8 kbar detailed mapping of the basalt chert sequence has clarified the change of environment from mid oceanic ridge to subduction zone eastward convergence of duplexing indicates eastward subduction of the oceanic plate during early cretaceous time the presence of duplexing and a reconstruction of oceanic plate stratigraphy recorded within the underthrust unit demonstrate the accretionary origin of protoliths of the franciscan coherent unit which has long been believed to have an in situ origin interpreted as either near trench volcanism or accreted terranes in which geosynclinal type volcanism occurred

a greenland sea perspective on the dynamics of postconvective eddies open ocean deep postconvection contributes to the formation of the dense waters that fill the global deep ocean the dynamics of postconvective vortices are key to understanding the role of convection in ocean circulation submesoscale coherent vortices scvs observed in convective regions are likely to be the anticyclonic components of hetons hetons are dipoles consisting of a surface cyclone and a weakly stratified subsurface anticyclone that can be formed by convection here key postconvective processes are investigated using numerical experiments of increasing sophistication with two primary goals 1 to understand how the ambient hydrography and topography influence the propagation of hetons and 2 to provide a theoretical context for recent observations of scvs in the greenland sea it is found that the alignment of hetons is controlled by ambient horizontal density gradients and that hetons self propagate into lighter waters as a result this provides a mechanism for transporting convected water out of a cyclonic gyre but the propagation is arrested if the heton meets large amplitude topography upon interaction with topography hetons usually separate and the surface cyclone returns toward denser water the anticyclone usually remains close to topography and may become trapped for several hundred days these findings may explain the observed accumulation and longevity of scvs at the greenland fracture zone on the rim of the greenland sea gyre the separation and sorting of cyclones from anticyclones have likely implications for the density and vorticity budgets of convective regions

the extratropical transitions of hurricanes felix and iris in 1995 abstract the extratropical transitions of hurricanes felix and iris in 1995 are examined and compared both systems affected northwest europe but only iris developed significantly as an extratropical system in both cases the hurricane interacts with a preexisting extratropical system over the western atlantic the remnants of the exhurricanes can be identified and tracked across the atlantic as separate low level potential vorticity pv anomalies the nature of the baroclinic wave involved in the extratropical transition is described from a pv perspective and shown to differ significantly between the two cases the role of vertical shear in modifying the hurricane structure during the early phase of the transition is investigated iris moved into a region of strong shear the high pv tower of iris developed a marked downshear tilt felix moved into a vertically sheared environment also but the shear was weaker than for iris and the pv tower of felix did not tilt much iris maintained its warm core struc

peeling oceanic crust in subduction zones thin slabs of oceanic pillow basalt formed at ridge axes with associated pelagic sediments are common features in ancient accretionary complexes estimates of the average thicknesses of scraped off basaltic sections of oceanic crust in accretionary prisms vary from a few tens of metres to 300 m with a mean thickness of 80 100 m in the complexes studied the permeability contrast within the uppermost part of the oceanic crust is an important factor governing the thickness of delaminated oceanic crust this mechanism is an effective means of separating oceanic crust altered at low temperatures from the remainder of the downgoing slab and thus controlling geochemical budgets in subduction zones

cloud microphysics impact on hurricane track as revealed in idealized experiments analyses of tropical cyclones created in an idealized environment reveal how and why cloud microphysical assumptions can influencestorm motion including speed and direction it is well known that in the absence of a mean flow a leading factor in storm propagation is the establishment of beta gyres owing to planetary vorticity advection by the storm s circulation previous research demonstrated that tangential winds well beyond the core influence storm motion by helping to determine the gyres orientation and intensity microphysical assumptions especially involving average particle fall speeds can strongly influence the winds at outer radius more specifically microphysics modulates the radial distribution of column average virtual temperature which largely determines the radial surface pressure gradient and therefore the winds because they tend to be in gradient balance beyond the core microphysics schemes can differ markedly with respect to average fall speed depending on the complexity of the scheme and how interactions among condensation types are handled average fall speed controls the outward movement of particles produced in the eyewall into the anvil where they can influence the environment through cloud radiative interactions and phase changes with the assistance of some special sensitivity tests the influence of microphysics and fall speed on radial temperature gradients leading to different outer wind strengths and tracks is shown among other things this work demonstrates that the treatment of outer rainbands in operational models can potentially influence how simulated storms move thus affecting position forecasts

observational relationship of climatologic beta drift with large scale environmental flows 1 while many numerical studies suggested that large scale environmental flows significantly affect beta drift this influence was not verified observationally and included in assessing changes of tropical cyclone tc tracks under the background of global warming this study investigates the influence of large scale environmental flow on climatologic beta drift in the northern west pacific using the best track dataset from joint typhoon warming center jtwc and the ncep monthly reanalysis over the period from 1965 to 2007 consistent with most previous numerical studies the meridional shear of zonal wind vertical shear of zonal wind and meridional gradient of relative vorticity which are mainly associated with the zonal environmental wind play an important role in affecting beta drift for the meridional shear of zonal flows the northward beta drift in an anticyclonic shear is faster than that in a cyclonic shear a poleward equatorward gradient of relative vorticity leads to faster slower westward beta drift than in a resting environment tcs tend to move to the left of the vector of vertical wind shear

petrology and geochemistry of cambrian boninites and low ti andesites from heathcote victoria in the heathcote greenstone belt of central victoria a sequence of boninites and low ti andesites is overlain and intruded by tholeiitic basalts with affinities to backarc basin basalts two suites of boninites have been identified one type a with ti zr ratios of 63 4 la yb n of 2 3 and hree 5 times chondritic levels the other suite type b overlies type a boninites and has ti zr ratios of 23 3 and lower tio2 and hree contents 2 3 chondrite but shows significantly greater lree enrichment with la yb n greater than 5 fractionation within both suites was largely controlled by the low ca pyroxenes protoenstatite and enstatite plagioclase phyric low ti high mg andesites occur in fault contact with the boninites and have ti zr and la yb n ratios very close to those of type b boninites but at higher absolute abundances of tio2 and hree they are not related to either boninite suite by any realistic fractionation scheme but originated from the same source as type b boninites by approximately half the degree of partial melting that generated the boninites

the motion and boundary between the capricorn and australian plates the motions between the somalian antarctic and australian plates the three plates believed to meet at the rodrigues triple junction in the indian ocean are inconsistent with the assumption that all three plates are rigid the discrepancy is best explained if the australian plate contains two component plates thus the traditionally defined indo australian plate consists of three component plates and multiple diffuse plate boundaries the pattern of present deformation indicates that the boundaries between the three component plates are two unconnected zones accommodating divergence and a larger zone which we interpret as three diffuse convergent plate boundaries and a diffuse triple junction

the dynamics of the enso atlantic hurricane teleconnection enso related changes to the north african asian jet affect atlantic basin tropical cyclogenesis abstract the nature of the teleconnection linking enso variability with atlantic basin tropical storm formation is investigated solutions of the linearized barotropic vorticity equation forced with august october el nino event divergence produce upper tropospheric vorticity anomalies over the sahel and at the mouth of the north african asian naa jet over the tropical atlantic these responses are similar in magnitude and orientation to observed enso vorticity variability for this region further investigation reveals that the vorticity anomalies over the subtropical atlantic develop primarily in response to very low wavenumber westward propagating stationary rossby waves excited by el nino related convective activity over the equatorial pacific ocean however the dynamics of this teleconnection change as the atlantic basin hurricane season progresses in august and september the response is dominated by the westward propagating stationary rossby waves that alter vorticity within the naa jet and to it

intracrustal detachments and implications for crustal evolution within the lachlan fold belt southeastern australia seismic reflection profiling in the southern lachlan fold belt australia indicates geometrically complex mid to lower crustal detachments possibly associated with crustal thickening by tectonic underplating of collided microplates and or oceanic plateaus low angle detachments either intersect or sole into the crust mantle boundary forming a crustal stacking wedge typical of lithospheric or a type subduction upper crustal reflections show that major moderately to steeply dipping reverse faults exposed at the surface flatten with depth and have listric form the chevron folded quartz rich turbidite sequence of the lachlan fold belt is therefore allochthonous with respect to the lower crust like the northern appalachian maritimes the lachlan fold belt has a composite crust with diverse lower crustal blocks overlain by allochthonous imbricated terranes of the surface rocks

numerical simulations of the genesis of hurricane diana 1984 part ii sensitivity of track and intensity prediction abstract the authors examine numerous simulations that probe the dynamics governing the intensification and track of tropical cyclone diana 1984 simulated in part i the development process is fundamentally dependent on a preexisting upper tropospheric trough ridge couplet this couplet focuses mesoscale vertical motion that in turn produces lower tropospheric potential vorticity pv anomalies which form the seed for the tropical storm removal of this trough ridge couplet from the initial conditions eliminates cyclogenesis the simulated rate of development of diana in the prehurricane phase depends principally on choices of cumulus parameterization boundary layer treatment sea surface temperature and grid spacing simulations with cumulus schemes that allow more grid scale precipitation on the 9 km grid exhibit unrealistic grid scale overturning and slower intensification primarily due to production of cyclonic vorticity anomalies at large radii use of an innermost nest with 3 km grid spacing

rapid emplacement of the oman ophiolite thermal and geochronologic constraints in understanding of ophiolite emplacement requires knowledge of the elapsed time between igneous crystallization and intraoceanic thrusting and the rate and duration of that thrusting hornblende 4oar 39ar ages demonstrate that the igneous oceanic crust in oman crystallized and cooled to 825 k in 1 2 m y hornblende ages from metamorphic rocks and from cross cutting dikes require that the basal metamorphic thrust fault beneath the ophiolite also cooled below 825 k in 1 2 m y motion along the sole thrust accounted for 200 km of displacement at a rate of 100 200 mm yr on the basis of age relationships and thermal considerations we favor a two stage model for the initial stages of samall ophiolite emplacement intraoceanic thrusting over 2 m y old lithosphere at 150 km m y parallel to a spreading ridge for 1 2 m y followed by equally rapid and brief thrusting over cold and old lithosphere preservation of the samail ophiolite is a direct result of its young age and positive buoyancy at the time of ocean closure and we propose that all ophiolites that originated near spreading centers and were emplaced onto continents were young at the time of intraoceanic thrusting

australian palaeozoic palaeomagnetism and tectonics ii a revised apparent polar wander path and palaeogeography abstract new palaeomagnetic data from mid to late palaeozoic rocks in australia have enabled us to revise the palaeozoic apparent polar wander path apwp this modified australian apwp is supported by data from other parts of gondwanaland the palaeomagnetic poles indicate that during the early and mid palaeozoic australia underwent rapid rotation first clockwise during the mid ordovician to the early silurian then counterclockwise from the mid silurian until the end of the devonian while it remained at low to equatorial latitudes this was succeeded by a rapid southward movement during mid carboniferous times the implications of the palaeomagnetic data for the tectonic relationship between the lachlan fold belt lfb and cratonic australia are consistent with the tectonic evidence that the lfb has been in place since the mid devonian

convergence and intraplate deformation in the lachlan fold belt of southeastern australia abstract the lachlan fold belt of southeastern australia is dominated by a widespread oceanic association including cambrian submarine mafic volcanics and an overlying widespread ordovician quartz rich turbidite and black shale succession with scattered mafic to andesitic volcanic centres these rocks are overlain by or in fault contact with deep marine to continental silurian to early carboniferous successions with mafic to silicic volcanics and abundant plutonic rocks major deformation achieved by thrusting and folding affected the fold belt during the silurian to middle devonian and the early carboniferous shortening estimates vary throughout the belt but the widespread ordovician quartz turbidite succession usually has at least 60 shortening which implies an original width of the fold belt of about 1700 km strike slip faulting was important on a local to regional scale but large scale strike slip displacements appear unlikely the large values of shortening are consistent with development of the belt in a convergent margin setting at least for the silurian to carboniferous the nature of the lower crust of the lachlan fold belt has always presented a problem of interpretation but we favour a late proterozoic quasi continental lower crustal layer that has deformed independently of the upper crust by either homogeneous flattening or crustal duplexing during silurian carboniferous convergence and provided a source for silurian devonian granites

potential vorticity analysis of tropical cyclone intensification the interaction of marginal tropical storm danny 1985 with an upper tropospheric positive potential vorticity anomaly was examined the intensification mechanism proposed earlier for mature hurricane elena appears to be valid for danny as well despite significant differences in the synoptic scale environment and in the stage of the tropical cyclone prior to the interaction both storms experienced rapid pressure falls as a relatively smallscale positive upper potential vorticity anomaly began to superpose with the low level tropical cyclone center the interaction is described in terms of a complex interplay between vertical wind shear diabatic heating and mutual advection among vortices at and below the level of the outflow anticyclone despite this complexity the superposition principle appears to be conceptually useful to describe the intensification of tropical cyclones during such interactions