evolution of an axisymmetric tropical cyclone before reaching slantwise moist neutrality abstractin a previous study the authors showed that the intensification process of a numerically simulated axisymmetric tropical cyclone tc can be divided into two periods denoted by phase i a

on the height of the warm core in tropical cyclones abstractthe warm core structure of tropical cyclones is examined in idealized simulations using the weather research and forecasting wrf model the maximum perturbation temperature in a control simulation occurs in the midtroposphere 5 6 km in contrast to the upper tropospheric 10 km warm core that is widely believed to be typical this conventional view is reassessed and found to be largely based on three case studies and it is argued that the typical warm core structure is actually not well known in the control simulation the height of the warm core is nearly constant over a wide range of intensities from additional simulations in which either the size of the initial vortex or the microphysics parameterization is varied it is shown that the warm core is generally found at 4 8 km a secondary maximum often develops near 13 14 km but is almost always weaker than the primary warm core it is demonstrated that microwave remote sensing instruments are of insufficient resolution to detect this

rewriting the climatology of the tropical north atlantic and caribbean sea atmosphere abstract the jordan mean tropical sounding has provided a benchmark reference for representing the climatology of the tropical north atlantic and caribbean sea atmosphere for over 50 years however recent observations and studies have suggested that during the months of the north atlantic hurricane season this region of the world is affected by multiple air masses with very distinct thermodynamic and kinematic characteristics this study examined 6000 rawinsonde observations from the caribbean sea region taken during the core months july october of the 1995 2002 hurricane seasons it was found that single mean soundings created from this new dataset were very similar to c l jordan s 1958 sounding work however recently developed multispectral satellite imagery that can track low to midlevel dry air masses indicated that the 1995 2002 hurricane season dataset and likely jordan s dataset as well was dominated by three distinct air masses moist tropical mt saharan air layer sal and midlatit

evaluation of planetary boundary layer parameterizations in tropical cyclones by comparison of in situ observations and high resolution simulations of hurricane isabel 2003 part ii inner core boundary layer and eyewall structure this is the second of a two part study of the representation of the planetary boundary layer pbl in highresolutionweatherresearchandforecastmodel wrf simulationsofhurricaneisabel 2003 theyonsei university ysu pbl parameterization and the mellor yamada janjic myj pbl parameterization are evaluated by direct comparison to in situ data obtained by research aircraft the numerical model simulation design details of the pbl schemes and the representation of the boundary layer in the outer core were presented in part i this part presents a detailed study of the inner core pbl including its axisymmetric and asymmetric structures and comparisons to analyses of dropsonde data from previous studies although neither pbl scheme was designed specifically for hurricane conditions their simulated boundary layers are reasonably good representations of the observed boundary layer both schemes reproduce certain unique features of the hurricane boundary layer such as the separate depths of the well mixed layer and the inflow layer and the pronounced wind speed maxima near the top of the inflow layer modification of the original ysu and myj schemes to have ocean roughness lengths more in agreement with recent studies considerably improves the results of both schemes even with these improvements the myj consistently produces larger frictional tendencies in the boundary layer than the ysu scheme leading to a stronger lowlevel inflow and a stronger azimuthal wind maximum at the top of the boundary layer for both schemes differences in the low level asymmetries between the simulated and observed wind fields appear to be related to eyewall asymmetries forced by environmental wind shear the effects of varying horizontal and vertical resolutions are also considered increasing the vertical resolution in the pbl results in minor improvements in the inner core structures increasing the horizontal resolution around the eyewall also leads to improved boundary layers as well as an improvement of the vertical structure of the inner core wind field a summary and discussion of the results of both parts i and ii is provided

on the structure and dynamics of indian monsoon depressions abstractera interim reanalysis data from the past 35 years have been used with a newly developed feature tracking algorithm to identify indian monsoon depressions originating in or near the bay of bengal these were then rotated centralized and combined to give a fully three dimensional 106 depression composite structure a considerably larger sample than any previous detailed study on monsoon depressions and their structure many known features of depression structure are confirmed particularly the existence of a maximum to the southwest of the center in rainfall and other fields and a westward axial tilt in others additionally the depressions are found to have significant asymmetry owing to the presence of the himalayas a bimodal midtropospheric potential vorticity core a separation into thermally cold 1 5 k and neutral 0 k cores near the surface with distinct properties and the center has very large cape and very small cin variability as a function of background state has also been explo

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

the unexpected rapid intensification of tropical cyclones in moderate vertical wind shear part ii vortex tilt abstractwe investigate a class of tropical cyclones tcs that undergo rapid intensification ri in moderate vertical wind shear through analysis of a series of idealized model simulations two ke

warm cores eyewall slopes and intensities of tropical cyclones simulated by a 7 km mesh global nonhydrostatic model abstractbased on the data of a 1 yr simulation by a global nonhydrostatic model with 7 km horizontal grid spacing the relationships among warm core structures eyewall slopes and the intensities of tropical cyclones tcs were investigated the results showed that stronger tcs generally have warm core maxima at higher levels as their intensities increase it was also found that the height of a warm core maximum ascends descends as the tc intensifies decays to clarify how the height and amplitude of warm core maxima are related to tc intensity the vortex structures of tcs were investigated by gradually introducing simplifications of the thermal wind balance it was established that warm core structures can be reconstructed using only the tangential wind field within the inner core region and the ambient temperature profile a relationship between tc intensity and eyewall slope was investigated by introducing a parameter that characterizes the shape of eyewalls and can be evaluated from satellite m

the evolution of hurricane humberto 2001 abstractin 2001 the national oceanic and atmospheric administration and the national aeronautical and space administration marshaled their resources to sample hurricane humberto for 3 successive days during the fourth convection and moisture experiment camex 4 humberto developed from a tropical storm into a category 2 hurricane despite the deep layer vertical shear of the environmental horizontal wind vws increasing markedly on the second and third days of sampling as exhibited in earlier studies the eyewall convection developed an azimuthal wavenumber 1 n 1 asymmetry as the vws increased horizontal divergence and vertical stability within 100 km of the eye exhibited persistent relationships to the vws vector the warm core evolved in an unexpected way the warm anomaly was initially located in the lower troposphere and built upward as the storm intensified the maximum temperature anomaly remained in the lower troposphere on all 3 days while the development of the upper tropospheric warm anom

on the warm core of a tropical cyclone formed near the tropopause abstracton the basis of numerical results of a three dimensional model diagnosed using balance dynamics a mechanism by which the upper level warm core of tropical cyclones tcs forms is proposed the numerical results reveal that an upper level warm core develops when tcs intensify just prior to reaching the mature stage potential temperature budget analysis reveals that for the tendency of potential temperature the azimuthal mean component of advection is dominant at the upper level of the eye at the mature stage sawyer eliassen diagnosis shows that tendencies due to forced flow by diabatic heating and diffusion of tangential wind are dominant in the eye and are negatively correlated to each other the distributions of the diabatic heating in the simulated tc are not peculiar therefore it is unlikely that the heating distribution itself is the primary cause of the flow from the lower stratosphere the analyses of forced circulations of idealized vortices show that the upper level subsidence is enh

how does the eye warm part ii sensitivity to vertical wind shear and a trajectory analysis abstractin part ii of this study idealized simulations of tropical cyclones are used to investigate the influence of vertical wind shear on the structure of warming and descent in the eye results are compared with the no shear simulation that was analyzed in part i during intensification of a tropical cyclone in a quiescent environment time averaged eye descent is maximized at 12 13 km height warming is not generally maximized at these levels however because the static stability is at a minimum consequently the perturbation temperature is maximized at midlevels each of the above results remains valid for sheared tropical cyclones and therefore shear does not systematically alter the height of the warm core an analysis of over 90 000 parcel trajectories yields further insight into the mechanisms of eye warming and addresses several outstanding questions regarding the character of eye descent the rate at which parcels are stirred from the eye into the eyewall is a strong function of intensity w

rapid development of the tropical cyclone warm core this paper presents a simple theoretical argument to isolate the conditions under which a tropical cyclone can rapidly develop a warm core thermal structure and subsequently approach a steady state the theoretical argument is based on the balanced vortex model and in particular on the associated transverse circulation equation and the geopotential tendency equation these second order partial differential equations contain the diabatic forcing and three spatially varying coefficients the static stability a the baroclinity b and the inertial stability c thus the transverse circulation and the temperature tendency in a tropical vortex depend not only on the diabatic forcing but also on the spatial distributions of a b and c experience shows that the large radial variations of c are typically the most important effect under certain simplifying assumptions as to the vertical structure of the diabatic forcing and the spatial variability of a b and c the transverse circulation equation and the geopotential tendency equation can be solved via separation of variables the resultingradialstructureequationsretainthedynamicallyimportantradialvariationofcandcanbe solvedin terms of green s functions these analytical solutions show that the vortex response to a delta function in the diabatic heating depends critically on whether the heating occurs in the low inertial stability region outside the radius of maximum wind or in the high inertial stability region inside the radius of maximum wind this resultsuggeststhatrapidintensification isfavoredforstormsthathaveat leastsome oftheeyewallconvection inside the radius of maximum wind the development of an eye partially removes diabatic heating from the high inertial stability region of the storm center however rapid intensification may continue if the eyewall heating continues to become more efficient as the warm core matures and static stability increases over the inner core conditions there become less favorable for deep upright convection and the storm tends to approach a steady state

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

evolution of the warm core structure during the eyewall replacement cycle in a numerically simulated tropical cyclone abstractthis study examines the evolution of the warm core structure during the secondary eyewall formation sef and the subsequent eyewall replacement cycle erc in a numerically simulated tropi

phase equilibria of a low s and c lunar core implications for an early lunar dynamo and physical state of the current core abstract multiple lines of geochemical and geophysical evidence suggest the moon has a small metallic core yet the composition of the core is poorly constrained the physical state of the core now or in the past depends on detailed knowledge of its composition and unfortunately there is little available data on relevant multicomponent systems i e fe ni s c at lunar interior conditions in particular there is a dearth of phase equilibrium data to elucidate whether a specific core composition could help to explain an early lunar geodynamo and magnetic field intensities or current solid inner core liquid outer core states we utilize geochemical information to estimate the ni s and c contents of the lunar core and then carry out phase equilibria experiments on several possible core compositions at the pressure and temperature conditions relevant to the lunar interior the first composition is 0 5 wt s and 0 375 wt c based on s and c contents of apollo glasses a second composition contains 1 wt each of s and c and assumes that the lunar mantle experienced degassing of up to 50 of its s and c finally a third composition contains c as the dominant light element phase equilibrium experiments were completed at 1 3 and 5 gpa using piston cylinder and multi anvil techniques the first composition has a liquidus near 1550 c and solidus near 1250 c the second composition has a narrower liquidus and solidus temperatures of 1400 and 1270 c respectively while the third composition is molten down to 1150 c as the composition crystallizes the residual liquid becomes enriched in s and c but s enrichment is greater due to the incorporation of c but not s into solid metallic feni comparison of these results to thermal models for the moon allow an evaluation of which composition is consistent with the geophysical data of an early dynamo and a currently solid inner and liquid outer core composition 1 has a high enough liquidus to start crystallizing early in lunar history 4 3 ga consistent with the possible core dynamo initiated by crystallization of a solid inner core composition 1 also stays partially molten throughout lunar history and could easily explain the seismic data composition 2 on the other hand can satisfy one or the other set of geophysical data but not both and thus seems like a poor candidate for a lunar core composition composition 3 remains molten to temperatures that are lower than current estimates for the lunar core thus ruling out the possibility of a c rich and s poor lunar core the s and c poor core composition studied here composition 1 is consistent with all available geochemical and geophysical data and provides a simple heat source and mechanism for a lunar core dynamo core crystallization that would obviate the need for other primary mechanisms such as impacts core mantle coupling or unusual thermal histories

numerical simulation of hurricane bonnie 1998 part i eyewall evolution and intensity changes abstract in this study a 5 day explicit simulation of hurricane bonnie 1998 is performed using the fifth generation pennsylvania state university national center for atmospheric research mesoscale model mm5 with the finest grid length of 4 km the initial mass wind and moisture fields of the hurricane vortex are retrieved from the advanced microwave sounding unit a amsu a satellite measurements and the sea surface temperature sst is updated daily it is shown that the simulated track is within 3 latitude longitude of the best track at the end of the 5 day integration but with the landfalling point close to the observed the model also reproduces reasonably well the hurricane intensity and intensity changes asymmetries in cloud and precipitation as well as the vertical structures of dynamic and thermodynamic fields in the eye and eyewall it is shown that the storm deepens markedly in the first 2 days during which period its environmental vertical shear increases substantially it is found

evaluation of planetary boundary layer parameterizations in tropical cyclones by comparison of in situ observations and high resolution simulations of hurricane isabel 2003 part i initialization maximum winds and the outer core boundary layer in this study thefirst of two parts the planetary boundarylayer pbl depicted in high resolution weather research and forecast model wrf simulations of hurricane isabel 2003 is studied and evaluated by direct comparisons with in situ data obtained during the coupled boundary layer and air sea transfer experiment cblast in particular two boundary layer schemes are evaluated the yonsei university ysu parameterization and the mellor yamada janjic myj parameterization investigation of these schemes is useful since they are available for use with wrf are both widely used and are based on entirely different methods for simulating the pbl in this first part the model domains and initialization are described for additional realism of the low level thermodynamic environment a simple mixed layer ocean model is used to simulate ocean cooling the ysu and myj schemes are discussed along with some modifications standard measures of the accuracy of the hurricane simulations such as track maximum surface wind speed and minimum surface pressure are describedforavarietyofparameterchoicesandforthetwoparameterizations theeffectsontrackandintensity of increased horizontal and vertical resolutions are also shown a modification of the original ysu and myj schemes to have ocean roughness lengths more in agreement with recent studies considerably improves the results of both schemes instantaneous wind maximaon the innermost grid with 1 33 kmresolutionare shown to be an accurate representation of the simulated 1 min sustained winds thesimulatedboundarylayersareevaluatedby directcomparison ofthepblassimulatedandasobserved by in situ data from the cblast experiment in the outer core region of the storm the two pbl schemes and their modifiedcounterparts reproduce the observed pbl remarkably well comparisonsare also made to the observed vertical fluxes of momentum heat and moisture in part ii the detailed comparisons of the intensities and structures of the simulated and observed innercore boundary layers are presented and the reasons for the differences are discussed

reexamining the vertical structure of tangential winds in tropical cyclones observations and theory a few commonly held beliefs regarding the vertical structure of tropical cyclones drawn from prior studies bothobservationalandtheoretical areexaminedinthisstudy oneofthesebeliefsisthattheoutwardslopeof the radius of maximumwinds rmw is a function of the size of the rmw another belief is that the outward slope of the rmw is also a function of the intensity of the storm specifically shea and gray found that the rmw becomes increasingly vertical with increasing intensity and decreasing radius the third belief evaluated here is that the rmw is a surface of constant absolute angular momentum m these three conventional wisdoms of vertical structure are revisited with a dataset of three dimensional doppler wind analyses comprising seven hurricanes on 17 different days azimuthal mean tangential winds are calculated for each storm andtheslopesofthermwandmsurfacesareobjectivelydetermined theoutwardslopeofthermw is shown to increase with radius which supports prior studies in contrast to prior results no relationship is found between the slope of the rmw and intensity it is shown that the rmw is indeed closely approximated by an m surface for the majority of storms however there is a small but systematic tendency for m to decrease upward along the rmw utilizing emanuel s analytical hurricane model a new equation is derived for the slope of the rmw in radius pressure space this predicts a linear increase of slope with radius and essentiallyno dependence of slope on intensity an exactly analogous equationcan be derivedin log pressure height coordinates and a numerical solution yields the same conclusions in geometric height coordinates these conclusions are further supported by the results of simulations utilizing emanuel s simple timedependent axisymmetric hurricane model as both the model and the analytical theory are governed by the dual constraints of thermal wind balance and slantwise moist neutrality it is demonstrated that it is these two assumptionsthat requirethe slope of the rmw to be a functionof its size but not of the intensityof the storm finally it is shown that within the context of emanuel s theory the rmw must very closely approximate an m surface through most of the depth of the vortex

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

hurricane maximum intensity past and present hurricane intensity forecasting has lagged far behind the forecasting of hurricane track in an effort to improve the understanding of the hurricane intensity dilemma several attempts have been made to compute an upper bound on the intensity of tropical cyclones this paper investigates the strides made into determining the maximum intensity of hurricanes concentrating on the most recent attempts to understand the maximum intensity problem the theories of holland and emanuel are reviewed with the objective of assessing their validity in real tropical cyclones each theory is then tested using both observations and the axisymmetric hurricane numerical models of ooyama and emanuel it is found that ambient convective instability plays a minor role in the determination of the maximum intensity and that the emanuel model is the closest to providing a useful calculation of maximum intensity several shortcomings are revealed in emanuel s theory however showing the need for more basic research on the axisymmetric and asymmetric dynamics of hurricanes as an illustration of the importance of asymmetric vorticity dynamics in the determination of a hurricane s maximum intensity it is shown using ooyama s hurricane model that the maximum intensity of a tropical cyclone may be diminished by convectively generated vorticity anomolies excited outside the primary eyewall the vorticity anomolies are parameterized by adding a concentric ring of vorticity outside the primary eyewall that acts to cut off its supply of angular momentum and moist enthalpy it is suggested that the generation of vorticity rings or bands outside the primary eyewall is a major reason why tropical cyclones fail to attain their maximum intensity even in an otherwise favorable environment the upshot of this work points to the need for obtaining a more complete understanding of asymmetric vorticity processes in hurricanes and their coupling to the boundary layer and convection

gradient balance in tropical cyclones abstract analysis of a large inventory of in situ observations from research aircraft shows that the gradient wind approximates the axisymmetric swirling flow in the free atmosphere within 150 km of the centers of atlantic hurricanes and tropical storms in the middle and lower troposphere the rms difference between the azimuthal cream swirling and gradient winds is typically lt 1 5 m s 1 with zero bias this balance prevails only for the azimuthal mean not locally nor is balance to be expected in either the surface friction layer or the upper tropospheric outflow layer where the radial flow is comparable with the swirling flow it is theoretically possible that axisymmetric supergradient flow may occur in response to rapid radial acceleration where the radial flow slows in the friction layer beneath the eyewall or where it converges into intense diabatically forced updrafts nevertheless the observations in the free lower and midtroposphere show that systematic departures of the azimuthal mean vorte

an investigation of composite dropsonde profiles for developing and nondeveloping tropical waves during the 2010 predict field campaign abstractcomposite dropsonde profiles are analyzed for developing and nondeveloping tropical waves in an attempt to improve the understanding of tropical cyclogenesis these tropical waves were sampled by 25 reconnaissance missions during the 2010 pre depression investigation of cloud systems in the tropics predict field campaign comparisons are made between mean profiles of temperature mixing ratio relative humidity radial and tangential winds relative vorticity and virtual convective available potential energy cape for genesis and nongenesis cases genesis soundings are further analyzed in temporal progression to investigate whether significant changes in the thermodynamic or wind fields occur during the transition from tropical wave to tropical cyclone significant results include the development of positive temperature anomalies from 500 to 200 hpa 2 days prior to genesis in developing waves this is not observed in the nongenesis mean progressive mesoscale moistening of the column is observe

a multiscale numerical study of hurricane andrew 1992 part ii kinematics and inner core structures despite considerable research understanding of the temporal evolution of the inner core structures of hurricanes is very limited owing to the lack of continuous high resolution observational data of a storm in this study the results of a 72 h explicit simulation of hurricane andrew 1992 with a grid size of 6 km are examined to explore the inner core axisymmetric and asymmetric structures of the storm during its rapid deepening stage based on the simulation a conceptual model of the axisymmetric structures of the storm is proposed most of the proposed structures confirm previous observations the main ingredients include a main inflow outflow in the boundary layer upper troposphere with little radial flow in between a divergent slantwise ascent in the eyewall a penetrative dry downdraft at the inner edge of the eyewall and a general weak subsiding motion in the eye with typical warming drying above an inversion located near an altitude of about 2 3 km the storm deepens as the axes of these features contract it is found that the inversion divides the eye of the hurricane vertically into two parts with a deep layer of warm dry air above and a shallow pool of warm moist air below the air aloft descends at an average rate of 5c m s 21 and has a residency time of several days in contrast the warm moist pool consists of air from the main inflow and penetrative downdrafts offset somewhat by the air streaming in a returning outflow into the eyewall in the lowest 2 km it is subject to the influence of the upward heat and moisture fluxes over the underlying warm ocean the warm moist pool appears to play an important role in supplying high ue air for deep convective development in the eyewall the penetrative downdraft is dry and originates from the return inflow in the upper troposphere and it is driven by sublimative evaporative cooling under the influence of the asymmetric radial inflow of dry cold air in the midtroposphere it penetrates to the bottom of the eye azimuthally downshear with a width often greater than 100 km in a radially narrow zone along the slantwise inner edge of the eyewall it is further shown that all the meteorological fields are highly asymmetric whereas the storm scale flow features a source sink couplet in the boundary layer and dual gyres aloft the inner core structures exhibit alternative radial inflow and outflow and a series of inhomogeneous updrafts and downdrafts all the fields tilt more or less with height radially outward and azimuthally downshear furthermore pronounced fluctuations of air motion are found in both the eye and the eyewall sometimes a deep layer of upward motion appears at the center of the eye all these features contribute to the trochoidal oscillation of the storm track and movement the main steering appears to be located at the midtroposphere 4 5 km and the deep layer mean winds represent well the movement of the hurricane

kerguelen plateau crustal structure and basin formation from seismic and gravity data we use multichannel seismic data gravity and subsidence modeling in conjunction with plate reconstructions to evaluate the crustal origin and composition of the kerguelen plateau predominantly oceanic crust of the southern and parts of the central kerguelen plateau appears to include continental fragments related to the breakup of india and antarctica these fragments may have been metamorphosed during emplacement of the main plateau the upper crust is basaltic the middle crust is intrusive mafic rock and intruded continental crust and the lower crust is a plagioclase rich metamorphic rock the labuan basin crust is predominantly oceanic with stranded kerguelen plateau fault blocks high density lower crust in the labuan basin is probably composed of serpentinized peridotites formed during slow rifting and spreading plate reconstruction models indicate opening between eastern broken ridge and southern kerguelen plateau at 90 ma heralding the formation of the labuan basin and diamantina zone crustal attenuation and slow accretion of oceanic crust continued until the australian and antarctic plates separated at ci8 time 40 ma plate reconstructions of the free air gravity field indicate that the naturaliste plateau fits against antarctica and that elan bank and india were juxtaposed until 110 ma both naturaliste plateau and elan bank are probable microcontinents a 1 km positive residual depth anomaly in the oceanic basins adjacent to the plateau along with the positive geoid anomaly centered beneath the northern kerguelen plateau imply that the lithosphere is partially dynamically supported by an upwelling hot asthenosphere of the kerguelen hot spot

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

observed tropical cyclone eye thermal anomaly profiles extending above 300 hpa abstractas recently pointed out by stern and nolan much of our knowledge of the warm core structure of the tropical cyclone eye has come from composites of in situ data taken from multiple aircraft studies of three storms in the late 1950s and 1960s further observational confirmation of eye thermal structure has been lacking since much of the dropsonde data analyzed to date have been limited to pressure levels of 500 hpa or lower however there exist a number of dropsonde eye profiles extending to near 250 hpa these profiles were acquired from nasa aircraft during various field campaigns here the author uses these data to calculate eye temperature anomaly profiles these data are supplemented by several surface based radiosonde releases in tropical cyclone eyes over the period 1944 2003 the author finds that the pressure altitude of the maximum anomaly varies between 760 and 250 hpa the author also finds positive correlations between the maximum anomaly level and storm intensity size upper leve

assimilation of t trec retrieved winds from single doppler radar with an ensemble kalman filter for the forecast of typhoon jangmi 2008 abstracta tropical cyclone tc circulation tracking radar echo by correlation technique t trec developed recently is applied to derive horizontal winds from single doppler radar reflectivity z data combined with radial velocity vr data when available the typically much longer maximum range of z observations compared to vr data allows for much larger spatial coverage of the t trec retrieved winds vtrec when a tc first enters the maximum range of a coastal radar retrieved using data from more than one scan volume the t trec winds also contain valuable cross beam wind information the vtrec or vr data at 30 min intervals are assimilated into the advanced regional prediction system arps model at 3 km grid spacing using an ensemble kalman filter over a 2 h window shortly after typhoon jangmi 2008 entered the vr coverage area of an operational weather radar of taiwan the assimilation of vtrec data produces analyses of the typhoon structure and intensity that more closely match observations than

a multiscale numerical study of hurricane andrew 1992 part i explicit simulation and verification abstract in this study the inner core structures of hurricane andrew 1992 are explicitly simulated using an improved version of the penn state ncar nonhydrostatic two way interactive movable triply nested grid mesoscale model mm5 a modified betts miller cumulus parameterization scheme and an explicit microphysics scheme were used simultaneously to simulate the evolution of the larger scale flows over the coarser mesh domains the intense storm itself is explicitly resolved over the finest mesh domain using a grid size of 6 km and an explicit microphysics package containing prognostic equations for cloud water ice rainwater snow and graupel the model is initialized with the national centers for environmental prediction analysis enhanced by a modified moisture field a model generated tropical storm like vortex was also incorporated a 72 h integration was made which covers the stages from the storm s initial deepening to a near category 5 hurricane intensity and the landfall over florida as

structure and formation of an annular hurricane simulated in a fully compressible nonhydrostatic model tcm4 abstract the structure and formation of an annular hurricane simulated in a fully compressible nonhydrostatic tropical cyclone model tcm4 are analyzed the model is initialized with an axisymmetric vortex on an f plane in a quiescent environment and thus the transition from the nonannular hurricane to the annular hurricane is attributed to the internal dynamics the simulated annular hurricane has all characteristics of those recently documented by knaff et al from satellite observations quasi axisymmetric structure large eye and wide eyewall high intensity and suppressed major spiral rainbands a striking feature of the simulated annular hurricane is its large outward tilt of the wide eyewall which is critical to the quasi steady high intensity and is responsible for the maintenance of the large size of the eye and eyewall of the storm although the annular hurricane has a quasi axisymmetric structure marked low wavenumber asymmetries exist in the eyewall region the formation of the simulated a

on the distribution of subsidence in the hurricane eye two hurricane eye features that have yet to be adequately explained are the clear air moat that forms at the outer edge of the eye and the hub cloud that forms near the circulation centre to investigate whether these features can be explained by the spatial distribution of the subsidence field we have derived an analytical solution of the sawyer eliassen transverse circulation equation for a three region approximation with an unforced central eye region of intermediate or high inertial stability a diabatically forced eyewall region of high inertial stability and an unforced far field of low inertial stability this analytical solution isolates the conditions under which the subsidence is concentrated near the edge of the eye the crucial parameter is the dimensionless dynamical radius of the eye defined as the physical radius of the eye divided by the characteristic rossby length in the eye when this dimensionless dynamical radius is less than 0 6 there is less than 10 horizontal variation in the subsidence rate across the eye when it is greater than 1 8 the subsidence rate at the edge of the eye is more than twice as strong as at the centre of the eye when subsidence is concentrated at the edge of the eye the largest temperature anomalies occur near there rather than at the vortex centre this warm ring structure as opposed to a warm core structure is often observed in the lower troposphere of intense hurricanes copyright 2007 royal meteorological society

mesoscale and convective scale characteristics of mature hurricanes part ii inner core structure of hurricane allen 1980 abstract the eyewall structure of hurricane alien is examined from analyses of multiple aircraft data on two days 5 and 8 august 1980 these data sets are unique in that for the first time three instrumented aircraft executed coordinated radial penetrations of the eyewall at multiple levels the data collected on 5 august illustrate the persistence of various features on horizontal scales 10 km over several hours composite cross sections constructed from the 8 august data show similar structure although the eye diameter had decreased to less than half that of 5 august the convergence of air in the eyewall was highly two dimensional this convergence supported organized ascent that was along the inner edge of the high reflectivity region and displaced inward several kilometers from the radius of maximum wind rmw a mean eyewall updraft of 5 6 m s 1 is computed from integration of the two dimensional continuity equation embedded within the two dimensional eyewall were cores of high reflectivity t

dramatic inner core tropopause variability during the rapid intensification of hurricane patricia 2015 abstractdropsondes with horizontal spacing as small as 4 km were released from the stratosphere in rapidly intensifying hurricane patricia 2015 during the office of naval research tropical cyclone intensity experiment these observations provide cross sections of unprecedented resolution through the inner core of a hurricane on 21 october patricia exhibited a strong tropopause inversion layer til across its entire circulation with a maximum magnitude of 5 1 k 100 m 1 this inversion weakened between 21 and 22 october as potential temperature increased by up to 16 k just below the tropopause and decreased by up to 14 k in the lower stratosphere between 22 and 23 october the til over the eye weakened further allowing the tropopause to rise by 1 km meanwhile over patricia s secondary eyewall the til restrengthened and bulged upward by about 700 m into what was previously the lower stratosphere these observations support many aspects of recent modeling studies including eyewall penetration i

numerical study of convection observed during the winter monsoon experiment using a mesoscale two dimensional model abstract a two dimensional version of the pennsylvania state university mesoscale model has been applied to winter monsoon experiment data in order to simulate the diurnally occurring convection observed over the south china sea the domain includes a representation of part of borneo as well as the sea so that the model can simulate the initiation of convection also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle this allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck which typically occupies several hundred kilometers of the domain frank and cohen s cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area the major conclusions are ice phase processes are important in determining the level of maximum large scale heating and vertical motion because there is a strong anvil componen

an air sea interaction theory for tropical cyclones part ii evolutionary study using a nonhydrostatic axisymmetric numerical model abstract in part i of this study an analytical model for a steady state tropical cyclone is constructed on the assumption that boundary layer air parcels are conditionally neutral to displacements along the angular momentum surfaces of the hurricane vortex the reversible thermodynamics implied by this assumption allows the mature storm to be thought of as a simple carnot engine acquiring heat at the high temperature ocean surface and losing heat near the low temperature tropopause although the oceanic heat source is universally recognized as the sine qua non for the mature hurricane there is also wide acceptance of conditional instability of the second kind cisk which makes no specific reference to surface heat fluxes as the formative mechanism this ambivalence is seen in that all numerical simulation studies find it essential to have transfer from the ocean surface yet all start from a conditionally unstable atmosphere the hypothesis put forward in part i based on the steady state theory is t