spiral gravity waves radiating from tropical cyclones internal gravity waves are continuously generated by deep moist convection around the globe satellite images suggest that tropical cyclones produce short wavelength high frequency waves that radiate outward with the wave fronts wrapped into tight spirals by the large differential advection of the sheared tangential flow this letter presents new in situ observations of such waves from two sources flight level data from research aircraft that show radial wavelengths of 2 10 km and vertical velocity magnitudes from 0 1 to 1 0 ms 1 and surface observations from a research buoy in the pacific that indicate the passage of gravity waves overhead as tropical cyclones pass by at distances of 100 to 300 km numerical simulations are used to interpret these observations and to understand the broader horizontal and vertical structures of the radiating waves the simulations suggest a correlation between wave amplitude and cyclone intensity which could be used to make remote estimates of peak wind speeds

mineralogically mature sandstones in accretionary prisms abstract plate tectonic interpretations of sandstone composition are made in the hope that detrital framework modes of sandstone suites provide information about the tectonic setting of basins of deposition and associated provenances dickinson et al 1983 the underlying assumption that provenance tectonics are directly associated with tectonics of depositional and post depositional sedimentary settings is not however universally true as sandstones from two contemporary accretionary prism complexes nias island indonesia and barbados west indies illustrate mineralogically immature sandstones rich in feldspar and volcanic lithic fragments are expected in such tectonic settings but both nias island and barbadian sandstones are mineralogically very mature dominated by quartz in b th cases this discrepancy between inferred and actual tectonic setting has been explained by postulating that sands from a provenance petrogenetically unrelated to the arc trench system e g continental or recycled orogen sands have been introduced into the accretionary prism by sedimentary or tectonic processes sandstones which are transported sedimentologically or tectonically across the boundaries of sedimentary tectonic provinces and which therefore occur in tectonic settings petrogenetically unrelated to the tectonics of the sediment source area are important components of at least some active accretionary complexes the possibility of trans boundary sedimentary and or tectonic transport must be allowed for in making plate tectonic interpretations based on sandstone petrog aphy especially in reconstructions of ancient orogenic belts

rapid filamentation zones in intense tropical cyclones intense tropical cyclones often possess relatively little convection around their cores in radar composites this surrounding region is usually echo free or contains light stratiform precipitation while subsidence is typically quite pronounced in this region it is not the only mechanism suppressing convection another possible mechanism leading to weak echo moats is presented in this paper the basic idea is that the strain dominated flow surrounding an intense vortex core creates an unfavorable environment for sustained deep moist convection strain dominated regions of a tropical cyclone can be distinguished from rotationdominated regions by the sign of s 2 s 2 2 where s1 ux y and s2 x uy are the rates of strain and x uy is the relative vorticity within the radius of maximum tangential wind the flow tends to be rotation dominated 2 s 2 s 2 so that coherent structures such as mesovortices can survive for long periods of time outside the radius of maximum tangential wind the flow tends to be strain dominated s 2 s 2 2 resulting in filaments of anomalous vorticity in the regions of strain dominated flow the filamentation time is defined as fil 2 s 2 s 2 2 1 2 in a tropical cyclone an approximately 30 kmwide annular region can exist just outside the radius of maximum tangential wind where fil is less than 30 min and even as small as 5 min this region is defined as the rapid filamentation zone since the time scale for deep moist convective overturning is approximately 30 min deep convection can be significantly distorted and even suppressed in the rapid filamentation zone a nondivergent barotropic model illustrates the effects of rapid filamentation zones in category 1 5 hurricanes and demonstrates the evolution of such zones during binary vortex interaction and mesovortex formation from a thin annular ring of enhanced vorticity

numerical simulation of cyclone sidr using a cloud resolving model characteristics and formation process of an outer rainband abstractcyclone sidr one of the most devastating tropical cyclones that resulted in several thousand deaths and substantial damages developed in the north indian ocean and made landfall over the bangladesh coast on 15 november 2007 observation and simulation results show that sidr was embedded in a nonuniform environment and contained an intense outer rainband to the east of its center and a significant frontal band to the northwest a detailed study of the outer rainband is performed by numerical simulation the eastern band was a long quasi straight shape in the meridional direction that remained stationary relative to the cyclone center this band was composed of convective cells that developed southeast of the center within a synoptic scale convergence zone and propagated along the band toward the northeast quadrant the speed of the downwind propagating cells was greater than that of the cyclone which resulted in a convective cluster northeast of the center only the downwind portion of the band

provenance mixing in an intraoceanic subduction zone tonga trench louisville ridge collision zone southwest pacific abstract dredging on the lower slope of the tonga forearc at the intersection between the louisville ridge hotspot chain and the trench yielded both late tertiary volcaniclastic sediments and late cretaceous slightly tuffaceous pelagic sediments petrography and phase chemistry of volcanic debris of tertiary age samples indicates derivation from a low k tholeiitic arc volcanic glass has a low k2o content and shows an fe enrichment trend plagioclase grains are high in an and low in or components pyroxene grains calcic clinopyroxene orthopyroxene and pigeonite have low tio2 contents and show an fe enrichment trend alkali feldspar and biotite are absent the composition of the tertiary samples is similar to other tonga forearc sediments and is consistent with their derivation from the adjacent magmatic arc the character and composition of volcanogenic debris in cretaceous age samples indicates derivation from an intraplate alkali igneous source plagioclase compositions show an increasing or component with increasing ab alkali feldspar is a rare additional component of these samples calcic clinopyroxene has high tio2 contents and is titanaugite amphibole is also rich in tio2 and is kaersutite minor volcanic glass is rich in alkalis samples were dredged from the seaward slope of a small terrace on the lower trench slope a planar reflector located 2 6 km below the terrace is marked by an abrupt jump in seismic velocity and is interpreted as the top of an essentially undamaged late cretaceous guyot of the louisville chain that was subducted at the tonga trench about 0 5 ma this guyot is the likely source of the late cretaceous intraplate igneous detritus collected at the dredge site some dredge samples yielded a mixed volcanic arc intraplate provenance and or late tertiary late cretaceous ages this probably represents the mixing of the cretaceous seamount and tertiary magmatic arc sources during post collision slumping of the wedge of lower slope material as it re establishes its critical taper

modal composition and detrital clinopyroxene geochemistry of lithic sandstones from the new england fold belt east australia a paleozoic forearc terrane the new england fold belt of southeast australia is divided by the peel fault system into two time equivalent zones showing contrasting depositional structural and metamorphic histories these are inferred to represent a western magmatic arc frontal arc succession and an eastern subduction complex assemblage the composition of the early to middle paleozoic clastic rocks from both east and west of the peel fault system indicates derivation from an undissected volcanic arc detrital quartz is absent or present only in minor amounts and always as monocrystalline grains lithic fragments are almost exclusively volcanic and normally dominant over feldspar which is invariably plagioclase now largely albitized to the west of the fault the distribution of lathwork microlitic felsitic and vitric rock fragments as well as variation in the amount of detrital quartz indicates changes in provenance through time and two cycles of basaltic to silicic volcanic activity have been identified the composition of detrital calcic clinopyroxene grains particularly their low ti and al contents and their ti mn na ratios indicates that they crystallized mainly from subalkaline probably calc alkaline volcanic arc magmas the dominantly volcanogenic provenance of sandstone from east of the fault and the low ti content of most detrital clinopyroxene grains indicate that the volcanic chain that lay to the west of the peel fault was the most likely source for the major portion of the clastic debris in the eastern rocks however the presence of ti rich detrital clinopyroxenes identical in composition to those in the metabasalts of the subduction complex indicates that uplifted segments of the complex provided an additional sediment source

sediment provenance within subduction complexes an example from the aleutian forearc abstract the ultimate composition of any sandstone is affected by a host of primary and secondary factors including the lithologies present in source terranes climate depositional environment and diagenesis in the case of a subduction complex however unequivocal identification of detrital provenance may be impossible because of the cumulative effects of tectonic and sedimentary transport long distance sedimentary transport 1000 km is common within trenches and abyssal plain turbidites can be tectonically transported for long distances as the underlying oceanic basement drifts towards a subduction front post accretionary displacement can occur as a consequence of strike slip faulting and the total distance of tectonic dislocation may reach several thousand kilometers the present day aleutian forearc region north pacific ocean illustrates many of the problems which typify subduction zones several petrologic suites can be identified and there are significant variations in detrital modes in both time and space the aleutian region serves as a sobering modern analog for accreted rock units such as the franciscan complex of california where intercalations of discrete sandstone suites have been noted in the absence of paleomagnetic control interpretations of sediment provenance within ancient subduction complexes probably should be restricted to the generic level

an investigation of spiral gravity waves radiating from tropical cyclones using a linear nonhydrostatic model abstracta recent study showed observational and numerical evidence for small scale gravity waves that radiate outward from tropical cyclones these waves are wrapped into tight spirals by the radia

doppler radar analysis of the rapid intensification of typhoon goni 2015 after eyewall replacement abstracta ground based doppler radar observed the rapid intensification ri of typhoon goni 2015 for 24 h immediately after it completed an eyewall replacement cycle goni s ri processes were examined by using radar reflectivity and wind fields retrieved by the ground based velocity track display gbvtd technique the maximum wind at 2 km altitude increased by 30 m s 1 during the first 6 h of ri and it further increased by 20 m s 1 during the subsequent 12 h around the onset of ri relatively strong outflow 2 m s 1 was present both inside and outside the radius of maximum wind rmw above the boundary layer bl suggesting the existence of supergradient flow in and just above the bl despite this outflow angular momentum increased inside the rmw the low level rmw contracted rapidly from 50 to 33 km causing the rmw to slope greatly outward with height the radius of maximum reflectivity was a few kilometers inside the rmw a budget analysis of absolute angular momentum showed that the outflow

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

evolution of intra oceanic arc trench systems abstract intra oceanic island arc trench systems represent a locus of crustal thickening through the addition of mantle derived magmas which form the volcanoes and subjacent stratiform plutons the crust of immature island arcs and adjacent back arc basins is oceanic in chemistry in that it is dominated by mafic e g tholeiitic magmas a magma sequence is recognized in many arc systems which progress from boninite to arc tholeiite to calc alkaline and in some arcs to shoshonites the adjacent back arc basins are formed of morb like tholeiite arc systems may be dominated by extension rather than compression if the subducted and overriding plates are decoupled extension of the arc system may be associated with seaward retreat or roll back of the trench axis alternate cycles of extension and compression of the arc system can lead to both tectonic erosion of the fore arc and accretion of fragments from the incoming sea floor the izu bonin mariana tonga yap and palau trench arc systems are examples of different stages in a dynamic process which starts when subduction begins along old fracture zone traces crustal extension causes both fore arc subsidence and opening of back arc basins island arc volcanic chains and back arc basins are new crust formed largely of fractional melts of the mantle the evolution of an arc system may stop when blocking of the subduction zone or changes in relative plate motion causes overthrusting of back arc lithosphere on to former volcanic arcs many ophiolites preserve remnants of arc system crust and upper mantle

the dynamics of vortex rossby waves and secondary eyewall development in hurricane matthew 2016 new insights from radar measurements abstractthe structure of vortex rossby waves vrws and their role in the development of a secondary eyewall in hurricane matthew 2016 is examined from observations taken during the noaa sensing

compositional suites of terrigenous deep sea sands of the present continental margins the compositional variability shown by sands of present continental margins was determined through conventional microscopic techniques this allowed the establishment of a descriptive classification of deep sea terrigenous sands based on a restricted number of commonly used parameters the fundamental sand types include 1 qf suite sands in which quartzose and or feldspathic grains predominate carbonate l bearing sands on average richer in lithics occur within this suite 2 ql suite in which quartzose and or lithic grains predominate little compositional diversification is apparent within this suite 3 fl suite in which lithic and or feldspathic grains predominate two compositional members can be identified based on the k feldspar plagioclase ratio 4 lv suite consists of sands in which volcanic grains largely dominate the lithic types vitric and serpentine sands occur within this suite the suites are related to distinct source area types defined as follows 1 cratonic block 2 sedimentary orogenic belt 3 volcanic orogenic belt 4 volcanic arc some sands cannot be easily assigned to a single compositional suite because petrologic parameters overlap with an adjacent suite such critical compositions are commonly arkosic using roundness of the framework components it is possible to define a category identified as matured sands which are greatly enriched in resistates

rapid filamentation zone in a numerically simulated tropical cyclone abstract in a recent study rozoff et al proposed a possible mechanism to explain the formation and maintenance of the weak echo annulus or moat outside of the primary eyewall of a tropical cyclone observed in radar images by this mechanism the moat is determined to be a region of the strain dominated flow outside of the radius of maximum wind in which essentially all fields are filamented and deep convection is hypothesized to be highly distorted and even suppressed this strain dominated region is defined as the rapid filamentation zone wherein the filamentation time is shorter than the overturning time of deep convection an attempt has been made in this study to test the hypothesis in a full physics tropical cyclone model under idealized conditions and to extend the concept to the study of the inner core dynamics of tropical cyclones the foci of this paper are the evolution of the rapid filamentation zone during the storm intensification the potential roles of rapid filamentation in the organiz

low wavenumber structure and evolution of the hurricane inner core observed by airborne dual doppler radar abstract the asymmetric dynamics of the hurricane inner core region is examined through a novel analysis of high temporal resolution three dimensional wind fields derived from airborne dual doppler radar seven consecutive composites of hurricane olivia s 1994 wind field with 30 min time resolution depict a weakening storm undergoing substantial structural changes the symmetric and asymmetric mechanisms involved in this transformation are considered separately to zeroth order the weakening of the primary circulation is consistent with the axisymmetric vortex spindown theory of eliassen and lystad for a neutrally stratified atmosphere vertical shear however increased dramatically during the observation period leading to a strong projection of the convection onto an azimuthal wavenumber 1 pattern oriented along the maximum vertical shear vector recent theoretical ideas elucidating the dynamics of vortices in vertical shear are used to help explain this asymmetry the role of asymmetric vorticity d

convective scale downdrafts in the principal rainband of hurricane katrina 2005 abstract airborne doppler radar data collected during the hurricane rainband and intensity change experiment rainex document downdrafts in the principal rainband of hurricane katrina 2005 inner edge downdrafts ieds originating at 6 8 km altitude created a sharp reflectivity gradient along the inner boundary of the rainband low level downdrafts llds evidently driven by precipitation drag originated at 2 4 km within the heavy rain cells of each convective element the ied and lld were spatially separated by but closely associated with the updrafts within the rainband the ied was forced aloft by pressure perturbations formed in response to the adjacent buoyant updrafts once descending the air attained negative buoyancy via evaporative cooling from the rainband precipitation a convective scale tangential wind maximum tended to occur in the radial inflow at lower levels in association with the ied which enhanced the inward flux of angular momentum at lower levels convergence at the base of the

mechanisms for the generation of mesoscale vorticity features in tropical cyclone rainbands a high resolution tropical cyclone model with explicit cloud microphysics has been used to investigate the dynamics and energetics of tropical cyclone rainbands analysis of the vorticity interactions that occur within the simulated rainbands demonstrates that couplets of cyclonic anticyclonic mesovortices can be produced in outer bands the primary source of this vorticity is the upward tilting of system generated horizontal vorticity by diabatic heating gradients the vertical heating gradient in the stratiform cloud also creates a potential vorticity pv dipole that accelerates the tangential flow and develops a midlevel jet the strength of the jet is enhanced by the vortex pair that is oriented radially across the rainband the fourier decomposition of the absolute vorticity field shows two counterpropagating vortex rossby waves associated with the rainband the wave located on the inner side of the band transports energy toward the vortex center the outer wave is made up of high wavenumbers and uses the vorticity gradients generated by the rainband the results support the hypothesis that the heating profile in the stratiform regions of rainbands generates cyclonic pv across the freezing level which develops a midlevel jet this mechanism creates a vorticity gradient that enables the propagation of vortex rossby waves that could allow the rainbands to interact with the mean flow and potentially influence the evolution of the storm by contributing to the symmetric component of vorticity and the development of secondary eyewalls

structural relations in the subduction complex of the paleozoic new england fold belt eastern australia the new england fold belt of southeastern australia is divided by the peel fault system into a western magmatic arc frontal arc succession and an eastern subduction complex assemblage the western part of the subduction complex consists of repeated slices of a sequence which where most complete comprises dolerite overlain by basalt sometimes pillowed radiolarian chert siltstone and in the younger thicker slices sandstone the basal contact of this sequence is always faulted a planar veined surface separates overlying basic igneous rocks from a sheared mass composed mostly of sedimentary material in which are imbedded tectonically derived blocks of basic igneous rock this sheared zone passes gradationally down into less deformed sedimentary rocks of the underlying sequence slices each of which is usually a few hundred meters thick young constantly westward toward the magmatic arc forming a stacked steeplydipping sequence tens of kilometers thick the distribution and inter relationship of li

the boundary layer dynamics of tropical cyclone rainbands abstractspiral bands are ubiquitous features in tropical cyclones and significantly affect boundary layer thermodynamics yet knowledge of their boundary layer dynamics is lacking prompted by rece

the effect of vertical wind shear on radiative convective equilibrium states abstract using a three dimensional cloud ensemble model a systematic exploration is undertaken of radiative convective equilibrium states as a function of the structure and magnitude of an imposed background flow with vertical shear in such simulations mesoscale organization appears naturally independent of the particulars of the initial condition as the magnitude of an imposed low level shear increases the convection becomes increasingly organized in lines or arcs propagating broadly downshear as predicted by earlier work when the shear is very strong the convection tends to organize into lines at an angle to the shear such that the line normal component is not far from its theoretical optimal value midlevel shear favors shear parallel lines but if it occurs in conjunction with sufficiently strong low level shear the convection can become very strongly organized into lines or arcs generally orthogonal to the low level shear optimal organization occurs when the depth of the shear layer is c

vortex rossby waves in a numerically simulated tropical cyclone part i overall structure potential vorticity and kinetic energy budgets abstract the asymmetric structure in the inner core of a numerically simulated tropical cyclone is analyzed in this study the simulated tropical cyclone is found to be highly asymmetric in the inner core in the mid lower troposphere the asymmetry in the core is dominated by azimuthal wavenumber 1 and wavenumber 2 vortex rossby waves these waves propagate azimuthally upwind against the azimuthal mean cyclonic tangential flow around the eyewall and thus have a much longer cyclonic rotation period by a factor of 2 than the period of a parcel moving with the cyclonic mean tangential flow around the circumference they also propagate outward against the boundary layer inflow of the azimuthal mean cyclone the waves are only visible within a radius of about 60 km from the cyclone center beyond this distance the radial gradient of potential vorticity pv of the azimuthal mean cyclone is too weak to support the vortex rossby waves although the divergent motion remains strong the geopotential height an

a numerical study of convective scale structures in the outer cores of sheared tropical cyclones 1 updraft traits in different vertical wind shear magnitudes

quadrant distribution of tropical cyclone inner core kinematics in relation to environmental shear abstractairborne doppler radar data collected in tropical cyclones by national oceanic and atmospheric administration wp 3d aircraft over an 8 yr period 2003 10 are used to statistically analyze the vertical structure of tropical cyclone eyewalls with reference to the deep layer shear convective evolution within the inner core conforms to patterns shown by previous studies convection initiates downshear right intensifies downshear left and weakens upshear analysis of the vertical distribution of radar reflectivity and vertical air motion indicates the development of upper level downdrafts in conjunction with strong convection downshear left and a maximum in frequency upshear left intense updrafts and downdrafts both conform to the shear asymmetry pattern while strong updrafts occur in the eyewall intense downdrafts show far more radial variability particularly in the upshear left quadrant though they concentrate along the eyewall edges strong updrafts are collocated with low level inflow and

the structure and evolution of hurricane elena 1985 part ii convective asymmetries and evidence for vortex rossby waves a portable data recorder attached to the weather surveillance radar 1957 wsr 57 in apalachicola florida collected 313 radar scans of the reflectivity structure within 150 km of the center of hurricane elena in 1985 between 1310 and 2130 utc 1 september this high temporal and spatial 750 m resolution dataset was used to examine the evolution of the symmetric and asymmetric precipitation structure in elena as the storm rapidly strengthened and attained maximum intensity fourier decomposition of the reflectivity data into azimuthal wavenumbers revealed that the power in the symmetric wavenumber 0 component dominated the reflectivity pattern at all times and all radii by at least a factor of 2 the wavenumber 1 asymmetry accounted for less than 20 of the power in the reflectivity field on average and was found to be forced by the environmental vertical wind shear the small amplitude wavenumber 2 asymmetry in the core was associated with the appearance and rotation of an elliptical eyewall this structure was visible for nearly 2 h and was noted to rotate cyclonically at a speed equal to half of the local tangential wind outside of the eyewall individual peaks in the power in wavenumber 2 were associated with repeated instances of cyclonically rotating outward propagating inner spiral rainbands four separate convective bands were identified with an average azimuthal velocity of 25 m s 1 o r68 of the local tangential wind speed and an outward radial velocity of 5 2ms 1 the azimuthal propagation speeds of the elliptical eyewall and inner spiral rainbands were consistent with vortex rossby wave theory the elliptical eyewall and inner spiral rainbands were seen only in the 6 h period prior to peak intensity when rapid spinup of the vortex had produced an annular vorticity profile similar to those that have been shown to support barotropic instability the appearance of an elliptical eyewall was consistent with the breakdown of eyewall vorticity into mesovortices asymmetric mixing between the eye and eyewall and a slowing of the intensification rate the inner spiral rainbands might have arisen from high eyewall vorticity ejected from the core during the mixing process alternatively because the bands were noted to emanate from the vertical shear forced deep convection in the northern eyewall they could have formed through the axisymmetrization of the asymmetric diabatically generated eyewall vorticity

generation of moving spiral bands in tropical cyclones abstract a theory based on the shallow water equation is developed to explain the generation of moving spiral banded structures in tropical cyclones the theory proposes that fluctuation of the vorticity distribution in the compact core region can act as a source generating gravity waves that produce the banded structures this mechanism is usually called the lighthill radiation mechanism a numerical experiment using the fifth pennsylvania state university national center for atmospheric research mesoscale model mm5 code is used to test this theory the moving bands in the simulated tropical cyclone show good agreement with the theoretically calculated gravity waves that emerge from a core region with an elliptical distribution of vorticity results of the simulated cyclone also illustrate that spiral cloud bands are triggered by the propagating gravity waves

boundary layer structure and dynamics in outer hurricane rainbands part i mesoscale rainfall and kinematic structure abstract results of hurricane boundary layer experiments conducted in outer rainbands of hurricanes josephine 1984 and earl 1986 are presented comparisons of precipitation and kinematic structures in these storms and in hurricane floyd 1981 indicate that principal rainbands have common characteristic mesoscale and convective scale features in the boundary layer the two dimensional mesoscale structure suggests that these rainbands are made up of a linear aggregate of cellular reflectivity elements on the inner upshear side of the band and stratiform rain on the outer downshear side the bands are oriented perpendicular to the shear above the boundary layer and cells move downband at about 85 of the density weighted mean wind speed of the 0 2 6 km layer the boundary layer wind field is strongly influenced by the rainband with alongband and crossband wind maxima located on the outer side of the band axis and minima 4 8 km to the inner side maximum crossband convergence and cyclonic shear vor

a numerical study of outer rainband formation in a sheared tropical cyclone abstractthe dynamical process of outer rainband formation in a sheared tropical cyclone tc is examined in this study using the fully compressible nonhydrostatic tc model after the easterly vertical wind shear of 10 m s 1 was imposed upon an intensifying strong tc an outer rainband characterized by a wavenumber 1 structure formed as a typical principal rainband downshear further analysis indicates that the outer rainband formation was closely connected to the activity of the inner rainband previously formed downshear moving radially outward the inner rainband tended to be filamented owing to the strong radial gradient of angular velocity as the inner rainband approached the outer boundary of the inner core convection in its middle and upwind segments reinvigorated and nascent convective cells formed upwind of the rainband caused mainly by the decreased filamentation and stabilization subsequently the rainband reorganized into a typical outer rainband three different scenarios are found to be

coulomb wedge model applied to the subduction of seamounts in the japan trench results from the french japanese kaiko exploration program of the japan trench and complementary data are used to propose a model of subduction of seamounts examples in two seamount chains one at the junction between the japan and kuril trenches and the other in the southern part of the japan trench off inubo cape illustrate the stages of subduction the japan trench margin evolved as a homogeneous wedge of deformable noncohesive coulomb material during seamount subduction this is illustrated by the subduction of the daiichi kashima seamount in the southern japan trench our model predicts that the first consequence of seamount subduction is a compressive thickening of the toe of the wedge above the advancing flank of the seamount because of the oversteepening of the rigid base of the wedge this agrees with our observations in the daiichi kashima area this thickening shifts landward across the wedge with the advancing flank of the seamount erosion dominates the wedge above the trailing flank of the seamount because of the corresponding understeepening of the rigid base of the wedge a reentrant of the toe of the wedge is thus created it is largest when the oceanic flank of the seamount coincides with the base of the landward slope at this time the trench axis will probably have an abnormally large amount of sediments as illustrated at the junction between the japan and kuril trenches after the subduction of the seamount the edge of the wedge should progressively move back to its initial location frontal accretion is absent or very limited

tracking a long lasting outer tropical cyclone rainband origin and convective transformation abstractthis study used radar and surface observations to track a long lasting outer tropical cyclone rainband tcr of typhoon jangmi 2008 over a considerable period of time 10 h from its for

mesoscale and convective structure of a hurricane rainband abstract the mesoscale thermodynamic kinematic and radar structure of a hurricane floyd rainband observed on 7 september 1981 is presented data are from 26 aircraft passes through the rainband from 150 to 6400 m a composite technique which presents rainband structure as a function of distance from the storm circulation center reveals inflow from the outer edge of the band and a partial barrier to this flow below 3 km in the direction parallel to rainband orientation radar reveals cellular reflectivity structure on the upwind and central portions of the rainband the frequency of cellular precipitation decreases in favor of stratiform precipitation further downwind as the band spirals gradually towards the eyewall in the radial direction a decrease of 12 k in e is observed across the rainband in the subcloud layer convective scale up and downdrafts that are associated with cellular reflectivity structure are hypothesized to be responsible for the thermodynamic modification of the cloud and subc

clouds in tropical cyclones abstract clouds within the inner regions of tropical cyclones are unlike those anywhere else in the atmosphere convective clouds contributing to cyclogenesis have rotational and deep intense updrafts but tend to have relatively weak downdrafts within the eyes of mature tropical cyclones stratus clouds top a boundary layer capped by subsidence an outward sloping eyewall cloud is controlled by adjustment of the vortex toward gradient wind balance which is maintained by a slantwise current transporting boundary layer air upward in a nearly conditionally symmetric neutral state this balance is intermittently upset by buoyancy arising from high moist static energy air entering the base of the eyewall because of the radial influx of low level air from the far environment supergradient wind in the eyewall zone and or small scale intense subvortices the latter contain strong erect updrafts graupel particles and large raindrops produced in the eyewall fall out relatively quickly while ice splinters left

geography and history of the louisville hotspot chain in the southwest pacific the louisville ridge is a 4300 km long late cretaceous and cenozoic hotspot chain the south pacific equivalent of the hawaiian emperor chain its northwestern end is being consumed by the tonga kermadec subduction zone but seabeam and magnetic mapping shows that the chain still includes more than 60 major volcanoes of both normal and reversed polarity distributed along a 75 km wide band that can be fitted to small circles about three successive poles of pacific plate hotspot rotation this band obliquely crosses fracture zones of the eltanin system but there is little interaction and no evidence of any genetic connection between the two structures forty of the louisville volcanoes grew above sea level and are preserved as high latitude i e coral free guyots they are spaced less than 100 km apart along most of the chain but there are none within 750 km of the inferred present location of the hotspot beneath a swell at the southeast end of the chain the rate of volcano building by the louisville hotspot declined sharply about 20 m y ago after being remarkably constant at 3 4 103 km3 m y for the previous 50 m y and none of the louisville volcanoes built during the past 10 12 m y the time of most profuse hawaiian volcanism has reached sea level however a seamount from which pleistocene lavas were dredged rises to within 540 m of the sea surface from the crest of the hotspot swell at 50 5 s 139 2 w guyot heights demonstrate that a hotspot swell several hundred meters high has persisted throughout the known life of the chain and sometimes had an isostatic depression on its loaded crest the depths of guyot shelf breaks increase systematically to the northwest from 530 to 2100 m proportional to the square root of volcano age with some scatter and tilting caused by plate boundary tectonism and local isostatic subsidence and uplift

origin of convex accretionary wedges evidence from barbados the surface slopes of submarine accretionary wedges generally decrease away from the toe or defor mation front toward the arc this paper presents evidence that this characteristic convex cross sectional shape is a direct mechanical response to the lithification of sediments during accretion the recently accreted sediments near the toe which are typically unconsolidated and therefore very weak must deform until a critical taper is attained at which they are stable in the presence of the horizontal tectonic compression this critical wedge taper and thus the bathymetric slope of the accretionary prism is relatively high for the porous weak sediments near the toe in contrast the compacted sediments farther back in the wedge are stronger so they require a relatively modest critical taper and therefore a lower bathymetric slope to be stable under the same tectonic compression the result is a convex cross sectional wedge shape we investigate several possible causes of the increase in sediment strength within the wedge and conclude that the primary cause is an increase in cohesive strength with decreasing porosity a straightforward generalization of the exact critical taper model is combined with empirical cohesion porosity velocity relations to infer the distribution of porosity and p wave velocity within the barbados accretionary wedge we estimate that the porosity decreases from its near toe value of 70 to approximately 30 at a depth of 3 km below the seafloor and a distance of 60 km arcward from the front of the wedge

on the initial development of asymmetric vertical motion and horizontal relative flow in a mature tropical cyclone embedded in environmental vertical shear in this paper the authors focus on the initial development of asymmetric vertical motion and horizontal relative flow in a mature tropical cyclone tc embedded in an environmental vertical shear the fully compressible nonhydrostatic tc model was used to perform a series of numerical experiments with a mature tc with different intensities embedded in shear with different magnitudes and different vertical profiles results show that the development of both the wavenumber 1 asymmetric vertical motion and horizontal relative flow for a tc embedded in vertical shear is quite sensitive to both the magnitude and the vertical profile of wind shear as well as the intensity of the tc itself diagnostic analysis based on the quasi balanced potential vorticity inversion indicates that the balanced dynamics can only explain a small portion of the asymmetric vertical motion and relative flow the unbalanced processes contribute predominantly to the developmentoftheasymmetricflowinthesimulations itisshownthattheeyewallofamaturetcplaysarole somewhat like a material cylinder embedded in an environmental flow with vertical shear the interaction between the environmental shear and the eyewall produces vertical gradient of convergence divergence of horizontal wind around the lateral edge of the eyewall this forces much stronger asymmetric vertical motion than the balanced processes do and drives significant horizontal relative divergent flow over the storm core which opposes vertical shear and reduces the vertical tilt of the storm axis in addition the budget analysis for the axisymmetric tangential wind demonstrates that the asymmetric flow plays a dominant role in weakening the storm top down

the multiple vortex structure of the el reno oklahoma tornado on 31 may 2013 abstractthis study documents the formation and evolution of secondary vortices associated within a large violent tornado in oklahoma based on data from a close range mobile polarimetric rapid s

structural changes of an outer tropical cyclone rain band encountering the topography of northern taiwan this study utilized ground based doppler radar observations to document the detailed structures of an outer tropical cyclone rainband tcr of typhoon longwang 2005 as the rainband passed over the topography of northern taiwan on 1 october 2005 the tcr was oriented northeast southwest and was roughly parallel to the mountain barrier with a higher lower terrain height in its southern northern landfalling segment during the pre landfall stage the tcr was characterized by convective precipitation on its inner side where the front to rear flow met with the rear to front flow to lift air upward with overturning updraft like signatures significant relatively minor changes in the tcr s structures were evident in the southern northern landfalling segment during the landfalling stage in particular the southern landfalling segment exhibited a much stronger front to rear flow that passed through the region of the rainband resulting in the absence of low level organized convergence and a relatively disorganized nature of precipitation this structural change was shown to be closely related to a significant decrease in the cross barrier flow due to the orographic blocking that occurred as easterly ambient winds encountered local high mountains in the vicinity of the rainband segment as the tcr propagated over the western side of the major topography the low level rear to front flow reappeared due to the collapse of low level orographic blocking and the convergence between the front to rear flow and the rear to front flow tended to rebuild a well organized convective circulation along the rainband results from this case study provide insight into processes that contribute to rapid structural changes in a landfalling tcr over mountainous regions

dating of archean basement in northeastern wyoming and southern montana rb sr whole rock and u pb zircon ages of granite and gneiss cores from three deep drill holes extend known occurrences of archean rocks in the subsurface of northeastern wyoming and southern montana rb sr and k ar mineral ages are discordant and reflect early or middle proterozoic disturbance highly altered rocks occur in a thin zone immediately below the sub cambrian unconformity samples from a few metres deeper in the basement are much fresher but show the effects of this alteration in filled fractures and thin adjacent alteration haloes whole rock rb sr systems have retained a fair degree of integrity in spite of increased susceptibility to modification because of the disturbed mineral systems interaction of the rocks with water a few metres below the sub cambrian unconformity probably occurred for only a relatively short time fractures filled rapidly with secondary minerals such as chlorite anhydrite and carbonate to maintain a relatively impermeable crystalline basement in which the silicates and their contained isotopic systems were preserved ages of cores from two wells extend the archean basement to the nacp anomaly a possible suture related to early proterozoic tectonism these and published ages limit a possible ensimatic mobile belt to a zone 300 km wide beneath the williston basin however the possibility remains that archean crust was continuous between the wyoming age province and the superior province

a geochemical study of metabasalts from a subduction complex in eastern australia abstract east of the peel fault system in the new england fold belt of eastern australia a base faulted sequence of mafic igneous rocks conformably overlain by chert siltstone and minor sandstone occurs in repeated slices forming a stacked sequence tens of kilometres thick the mafic rocks show extensive mineralogical alteration but apart from the highly mobile alkali elements bulk whole rock compositions retain a strong igneous imprint two metabasalt groups are recognised group a shows a distinct tholeiitic fractionation trend with increasing feo tio 2 p 2 o 5 feo mgo zr and y relative to only a small increase in sio 2 the mean concentration of incompatible and immobile elements and the composition of relict endiopsidic and augitic pyroxenes is similar to mid ocean ridge tholeiites particularly the more evolved ferrobasalts group b metabasalts are alkalic in composition they tend to have higher al 2 o 3 mgo p 2 o 5 and zr and lower feo and sr than group a basalts relict pyroxenes have high ti and al concentrations and are salites these rocks were probably the product of oceanic within plate volcanism both groups represent fragments of oceanic crust incorporated into a subduction complex along the eastern margin of the australian continent

vortex rossby waves in a numerically simulated tropical cyclone part ii the role in tropical cyclone structure and intensity changes abstract in part i the author analyzed the asymmetric structure in the inner core of a numerically simulated tropical cyclone and found that the asymmetry near the eyewall in the mid lower troposphere is dominated by wavenumber 1 and 2 vortex rossby waves these waves are found to be well coupled with asymmetries in eyewall convection and thus may play an important role in the life cycle of a tropical cyclone in this paper analyses are extended to include the role of these vortex rossby waves in tropical cyclone structure and intensity changes the waves are found to transport angular momentum from the eyewall to the eye accelerating tangential winds in the eye at the expense of decelerating the tangential wind in the eyewall and thus they play an important role in the inner core dynamics of the tropical cyclone convection in the eyewall is enhanced between the downstream trough and upstream ridge in the vortex rossby waves but suppressed between the downstream ridge and upstream trough this close

late cretaceous pelagic sediments volcanic ash and biotas from near the louisville hotspot pacific plate paleolatitude 42 s abstract dredging on the deep inner slope of the tonga trench immediately north of the intersection between the louisville ridge hotspot chain and the trench recovered some late cretaceous maestrichtian slightly tuffaceous pelagic sediments they are inferred to have been scraped off a recently subducted late cretaceous guyot of the louisville chain in the vicinity of the louisville hotspot present location 50 26 s 139 09 w late cretaceous location 42 s longitude unknown late cretaceous rich diatom radiolarian silicoflagellate foraminiferal and coccolith biotas accumulated on the flanks of the guyot and are described in this paper rich sponge faunas are not described inoceramus prisms are present volcanic ash is of within plate alkalic character isotope ratios in bulk carbonate 18o 2 63 to 0 85 13c 2 98 to 3 83 are normal for pacific maestrichtian sediments the local ccd may have been shallower than the regional ccd because of high organic productivity in some samples late cretaceous materials have been mixed with neogene materials mixing may have taken place on the flanks of the guyot during transit across the western pacific or on the trench slope during or after subduction and offscraping about 0 5 ma

origin of the louisville ridge and its relationship to the eltanin fracture zone system we have combined shipboard and seasat altimeter derived data in an intergrated geological and geophysical study of the louisville ridge a 3500 km long seamount chain extending from the tonga trench to the eltanin fracture zone a break in the smooth trend of the ridge at latitude 37 5 s has been recognized in both bathymetric and altimetric data the 40ar 39ar dating of rocks dredged either side of the break suggest that it is analogous to the bend in the hawaiian emperor seamount chain although the general trend of the ridge can be fit by small circles about pacific absolute motion poles determined from other seamount chains the new bathymetric and age data allow us to refine pacific absolute motion poles the continuity in smooth trend of the ridge and the eltanin fracture zone suggests some relationship between them however a major offset developed on this transform between 60 and 80 ma prior to the oldest dated rocks from the ridge although magmatism was more or less continuous on the ridge during 28 60 ma it probably occurred on crust with little or no offset thus magmatism appears to have been little influenced by the developing fracture zone by 28 ma the distance between the magmatic source and the fracture zone had decreased sufficiently for a portion of the ridge to have been emplaced on crust with an offset after about 12 ma however volcanic activity on the louisville ridge apparently waned despite a possible influence on the magmatism of the fracture zone

spiral rainbands in a numerical simulation of hurricane bill 2009 part ii propagation of inner rainbands abstractthis is the second part of a study that examines spiral rainbands in a numerical simulation of hurricane bill 2009 this paper evaluates whether the propagation of inner rainbands in the hurricane bill simulation is consistent with previously proposed hypotheses results indicate that the propagation of inner rainbands is not consistent with gravity waves vortex rossby waves or squall lines an alternative hypothesis is offered arguing that inner rainbands are simply convective clouds that are advected by the rapidly rotating tropical cyclone wind field while being deformed into spiral shapes a summary and a discussion of the results of both parts i and ii are provided

subduction of a late cretaceous seamount of the louisville ridge at the tonga trench a model of normal and accelerated tectonic erosion the hotspot generated louisville ridge is a 4000 km chain of seamounts typically 2 2 5 km high and 10 40 km in diameter and an underlying crustal swell 1 5 km high and 100 km wide trending nnw across the southwestern pacific the northwest end of the ridge collides with the north trending tonga trench 26 s which just north of that point is exceptionally deep 10 8 km and lacks both a turbidite wedge and a bordering accretionary complex the collision zone is moving rapidly southward multichannel seismic reflection data in the collision zone show a west dipping subsurface platform 2 3 km beneath the lower western trench slope which is interpreted as the flat summit of a subducted guyot motuku of the louisville chain projected eastward the summit plain passes 1 2 km above the trench floor dredging of the nearby inner trench wall recovered uppermost cretaceous maestrichtian oceanic pelagic sediments interpreted to be fragments of the sedimentary mantle of a subducted louisville seamount the principal effects of hotspot ridge collision with a sediment starved trench are 1 the impacting seamounts are subducted rather than accreted and 2 although some seamount rocks are temporarily accreted the inner trench wall is tectonically eroded arcward at rates possibly as high as 50 km m y accelerated tectonic erosion is related to 1 fracturing shearing and general weakening of arc substrate rocks as they are lifted by the swell penetrated by impacting seamounts and left to collapse as the ridge moves away 2 a more effective removal of weakened rock in underthrusting grabens which are larger in the crustal swell 3 a possible elevation of the subduction decollement to account for the removal of as much as 30 000 km of material from a 400 km sector of the trench in 1 million years and 4 a reduction in supply of arc derived debris resulting from the gap in arc volcanism accompanying subduction of the ridge normal tectonic erosion in the tonga trench is apparently minor and we conclude that the bulk of the 37 000 km of material which fills subducting grabens each million years is arc derived volcanic and pelagic sediment

volcanic arc reconstruction using discriminant function analysis of detrital clinopyroxene and amphibole from the new england fold belt eastern australia discriminant function analysis dfa of ca rich clinopyroxene and amphibole from modern arc volcanics allows identification of the parent magma type basalt andesite or dacite rhyolite with a view to understanding the provenance of arc derived sandstones the dfa approach has been applied to a suite of well studied cambrian to devonian volcaniclastic sandstones of the new england fold belt of eastern australia which contain significant arc derived detrital clinopyroxene and occasionally amphibole previous provenance studies of these rocks have been based on petrography identifying two cycles of volcanism but the results of this study show this to be oversimplified instead dfa analysis shows that some units comprise both intermediate and acidic volcanic components with significant along strike or vertical variations in terms of arc derived detritus the dfa approach avoids the pitfalls of a component mixing that limits the usefulness of whole rock chemical analysis and b the qualitative as

hurricane spiral bands abstract the spiral bands that occur in tropical cyclones can be conveniently divided into two classes outer bands and inner bands evidence is presented here that the outer bands form as the result of nonlinear effects during the breakdown of the intertropical convergence zone itcz through barotropic instability in this process a zonal strip of high potential vorticity the itcz shear zone or monsoon trough begins to distort in a varicose fashion with the potential vorticity pv becoming pooled in local regions that are connected by filaments of high pv as the pooled regions become more axisymmetric the filaments become thinner and begin to wrap around the pv centers it is argued that inner bands form in a different manner as a tropical cyclone intensifies due to latent heat release the pv field becomes nearly circular with the highest values of pv in the cyclone center the radial gradient of pv provides a state on which pv waves the generalization of rossby waves can propagate the nonline