rapidly intensifying hurricane guillermo 1997 part i low wavenumber structure and evolution abstract the structure and evolution of rapidly intensifying hurricane guillermo 1997 is examined using airborne doppler radar observations in this first part the low azimuthal wavenumber component of the vortex is presented guillermo s intensification occurred in an environmental flow with 7 8 m s 1 of deep layer vertical shear as a consequence of the persistent vertical shear forcing of the vortex convection was observed primarily in the downshear left quadrant of the storm the greatest intensification during the 6 h doppler observation period coincided with the formation and cyclonic rotation of several particularly strong convective bursts through the left of shear semicircle of the eyewall some of the strongest convective bursts were triggered by azimuthally propagating low wavenumber vorticity asymmetries mesoscale budget analyses of axisymmetric angular momentum and relative vorticity within the eyewall are presented to elucidate the mechanisms contributing to guillermo s structural evol

frost rings in trees as records of major volcanic eruptions new data about climatically effective volcanic eruptions during the past several thousand years may be contained in frost damage zones in the annual rings of trees there is good agreement in the timing of frost events and recent eruptions and the damage can be plausibly linked to climatic effects of stratospheric aerosol veils on hemispheric and global scales the cataclysmic proto historic eruption of santorini thera in the aegean is tentatively dated to 1628 26 bc from frost ring evidence

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

downdrafts and the evolution of boundary layer thermodynamics in hurricane earl 2010 before and during rapid intensification abstractusing a combination of noaa p 3 aircraft tail doppler radar noaa and nasa dropsondes and buoy and drifter based sea surface temperature data different types of downdrafts and their infl

multiscale structure and evolution of hurricane earl 2010 during rapid intensification abstractthe structure and evolution of hurricane earl 2010 during its rapid intensification as sampled by aircraft is studied here rapid intensification occurs in two stages during the early stage covering 24 h earl was a tropical storm experiencing moderate northeasterly shear with an asymmetric distribution of convection and the symmetric structure was shallow broad and diffuse the upper level circulation center was significantly displaced from the lower level circulation at the beginning of this stage deep vigorous convection termed convective bursts was located on the east side of the storm and appeared to play a role in positioning the upper level cyclonic circulation center above the low level center by the end of this stage the vortex was aligned and extended over a deep layer and rapid intensification began during the late stage rapid intensification continued as earl intensified 20 m s 1 during the next 24 h the vortex remained aligned in the presence of weaker vertical shear

distributions of shallow to very deep precipitation convection in rapidly intensifying tropical cyclones abstractshear relative distributions of four types of precipitation convection in tropical cyclones tcs are statistically analyzed using 14 years of tropical rainfall measuring mission trmm precipitation radar pr data the dataset of 1139 trmm pr overpasses of tropical storms through category 2 hurricanes over global tc prone basins is divided by future 24 h intensity change it is found that increased and widespread shallow precipitation defined as where the 20 dbz radar echo height 6 km around the storm center is a first sign of rapid intensification ri and could be used as a predictor of the onset of ri the contribution to total volumetric rain and latent heating from shallow and moderate precipitation 20 dbz echo height between 6 and 10 km in the inner core is greater in ri storms than in non ri storms while the opposite is true for moderately deep 20 dbz echo height between 10 and 14 km and very deep precipitation 20 dbz echo height 14 km the authors argue that ri is more likely

reintensification and eyewall formation in strong shear a case study of typhoon noul 2015 abstractstrong vertical wind shear produces asymmetries in the eyewall structure of a tropical cyclone tc and is generally a hostile environment for tc intensification typhoon noul 2015 howev

simulation of the downshear reformation of a tropical cyclone abstractthe downshear reformation of tropical storm gabrielle 2001 was simulated at 1 km horizontal resolution using the weather research and forecasting wrf model the environmental shear tilted the initial parent vortex downshear left and forced azimuthal wavenumber 1 kinematic thermodynamic and convective asymmetries the combination of surface enthalpy fluxes and a lack of penetrative downdrafts right of shear allowed boundary layer moist entropy to increase to a maximum downshear right this contributed to convective instability that fueled the downshear convection within this convection an intense mesovortex rapidly developed with maximum boundary layer relative vorticity reaching 2 2 10 2 s 1 extreme vortex stretching played a key role in the boundary layer spinup of the mesovortex cyclonic vorticity remained maximized in the boundary layer and intensified upward with the growth of the convective plume the circulation associated with the mesovortex and adjacent localized cyclonic vorti

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

intensity and inner core structure of typhoon haiyan 2013 near landfall doppler radar analysis abstractthe intensity and inner core structure of an extremely intense tropical cyclone typhoon haiyan 2013 were examined using real time ground based doppler radar products from the guiuan radar over the period of about 2 5 h immediately before the storm approached guiuan in eastern samar philippines haiyan s wind fields from 2 to 6 km altitude were retrieved by the ground based velocity track display gbvtd technique from the doppler velocity data the gbvtd retrieved maximum wind speed reached 101 m s 1 at 4 km altitude on the right side of the track the relatively fast forward speed of haiyan about 11 m s 1 increased maximum wind speed on the right hand side of the storm azimuthal mean tangential wind increased with height from 2 to 5 km and a local maximum of 86 m s 1 occurred at 5 km altitude the central pressure was estimated as 906 hpa with an uncertainty of 4 hpa by using the gbvtd retrieved tangential wind and by assuming gradient wind balance the radius of maximum radar reflecti

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

precipitation processes and vortex alignment during the intensification of a weak tropical cyclone in moderate vertical shear abstractthe mechanisms underlying the development of a deep aligned vortex and the role of convection and vertical shear in this process are explored by examining airborne doppler radar and deep

dual aircraft investigation of the inner core of hurricane norbert part i kinematic structure abstract on 24 25 september 1984 air motions and physical processes in the eyewall region of hurricane norbert were investigated with two national oceanic and atmospheric administration noaa aircraft operations center aoc wp 3d research aircraft one aircraft equipped with the airborne doppler radar flew repeated radial penetrations of the eyewall mapping the three dimensional wind field throughout a 40 km radius of the storm center these data provide the first complete documentation of the three dimensional wind field of the inner core of a hurricane on spatial scales of 10 25 km in the horizontal and 1 km in the vertical and temporal scales of 1 2 h the wind field was asymmetric and the asymmetry varied with altitude as altitude increased the location of the maximum tangential wind sloped upwind from left of the storm track at 1 km altitude to right of the storm track above 3 km the radial wind at 1 km altitude was inward in front of the storm and outward behind this pattern in the radial

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

heterogeneity in homogeneous brabantian loess during the late pleniglacial abstract the brabantian loess is often seen as a homogeneous sediment package deposited under cold and dry climatic conditions haesaerts et al 1981 however in 1981 two small tundra gleysols were discovered in the brabantian loess haesaerts et al 1981 to unravel other possible changes in the sedimentary system during deposition a more detailed look at the homogeneous brabantian loess is carried out the loess transporting process is reconstructed based on the combination of both grain size and grain shape parameters these parameters are defined with automated dynamic image analysis and statistically compared with the two dimensional kolmogorov smirnov test as suggested by vandenberghe et al 1998 our gleysols are generally correlated to a period of reduced grain size most likely the more subtle the gleysols the weaker the link between their formation and grain size reduction mazzullo et al 1992 already stated that aeolian transport was very selective regarding grain size and sorting capacities our research points toward an extremely selective aeolian transport regarding the shape of the grains therefore combining both particle size and particle shape can be very useful when reconstructing aeolian transport processes this combination can also discriminate samples with a different transport and sedimentation history

the effect of vertical shear on tropical cyclone intensity change abstract the effect of vertical shear on tropical cyclone intensity change is usually explained in terms of ventilation where heat and moisture at upper levels are advected away from the low level circulation which inhibits development a simple two layer diagnostic balance model is used to provide an alternate explanation of the effect of shear when the upper layer wind in the vortex environment differs from that in the lower layer the potential vorticity pv pattern associated with the vortex circulation becomes tilted in the vertical the balanced mass field associated with the tilted pv pattern requires an increased midlevel temperature perturbation near the vortex center it is hypothesized that this midlevel warming reduces the convective activity and inhibits the storm development previous studies have shown that diabatic heating near the storm center acts to reduce the vertical tilt of the vortex circulation these studies have also shown that there is an adiabatic process that acts to redu

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

effects of parameterized boundary layer structure on hurricane rapid intensification in shear abstractthis study investigates the role of the parameterized boundary layer structure in hurricane intensity change using two retrospective hwrf forecasts of hurricane earl 2010 in which the ver

asymmetric hurricane boundary layer structure from dropsonde composites in relation to the environmental vertical wind shear this study investigates the asymmetric structure of the hurricane boundary layer in relation to the environmentalverticalwind shearin theinner core region data from1878 gps dropsondesdeployed by research aircraft in 19 hurricanes are analyzed in a composite framework kinematic structure analyses based on doppler radar data from 75 flights are compared with the dropsonde composites shear relative quadrantmeancomposite analysesshow that boththekinematicandthermodynamic boundarylayerheight scalestend to decrease with decreasing radius consistent with previous axisymmetric analyses there is still a clear separation between the kinematic and thermodynamic boundary layer heights both the thermodynamic mixed layer and height of maximum tangential wind speed are within the inflow layer the inflow layer depth is found to be deeper in quadrants downshear with the downshear right dr quadrant being the deepest the mixed layer depth and height of maximum tangential wind speed are alike at the eyewall but are deeper outside in quadrants left of the shear the results also suggest that air parcels acquire equivalent potential temperature ue from surface fluxes as they rotate through the upshear right ur quadrant from the upshear left ul quadrant convection is triggered in the dr quadrant in the presence of asymmetric mesoscale lifting coincident with a maximum in ue energy is then released by latent heating in the downshear left dl quadrant convective downdrafts bring down cool and dry air to the surface and lower ue again in the dl and ul quadrants this cycling process may be directly tied to shear induced asymmetry of convection in hurricanes

the effects of wind transport on the shapes of quartz silt grains abstract wind blown terrigenous silt is a common component in marine sediment but it is often difficult to distinguish from fluvial silt a field experiment was conducted in the loess plateau of china to determine the effect of eolian transport on the shapes of detrital quartz silt grains and to define grain shape criteria for the recognition of eolian silt the results show that eolian transport results in a rapid downwind increase in the roundness of quartz silt grains and that this increase in roundness is apparently due to preferential transport or shape sorting of more rounded grains this capacity for shape sorting distinguishes eolian from fluvial transport which has no great effect upon the shapes of quartz silt grains and provides a petrographic criteria for the distinction of t e eolian and fluvial silt components in marine sediments

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

how does hurricane edouard 2014 evolve toward symmetry before rapid intensification a high resolution ensemble study abstracta 14 member high resolution ensemble of edouard 2014 a moderately sheared tropical storm that underwent rapid intensification ri is used to determine causes of vortex alignment and pr

concentric eyewall asymmetries in hurricane gonzalo 2014 observed by airborne radar abstracttwo eyewall replacement cycles were observed in hurricane gonzalo by the noaa p3 tail ta radar and the recently developed nasa high altitude imaging wind and rain airborne profiler hiwrap radar these observations captured detailed precipitation and kinematic features of gonzalo s concentric eyewalls both before and after the outer eyewall s winds became the vortex maximum winds the data were analyzed relative to the deep layer environmental wind shear vector during the beginning eyewall replacement cycle stages the inner and outer eyewalls exhibited different asymmetries the inner eyewall asymmetry exhibited significant low level inflow updrafts and positive tangential acceleration in the downshear quadrants consistent with observational and theoretical studies the outer eyewall asymmetry exhibited these features in the left of shear quadrants further downwind from those of the inner eyewall it is suggested that the low level inflow occurring at the outer but not at the inner eyewal

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

an improved real time global sea surface temperature analysis abstract the monthly global sea surface temperature sst analysis of reynolds using real time in situ and satellite sst data has now been improved by using sea ice data to simulate ssts in ice covered regions the simulated ssts now become the external boundary condition for the analysis solution this technique eliminates any high latitude satellite biases and extends the analysis to the ice edge the analysis with the ice data has been computed for the period january 1982 to present

numerical study on the extremely rapid intensification of an intense tropical cyclone typhoon ida 1958 abstractextremely rapid intensification eri of typhoon ida 1958 was examined with a 2 km mesh nonhydrostatic model initiated at three different times ida was an extremely intense tropical cyclone with a minimum central pressure of 877 hpa the maximum central pressure drop in 24 h exceeded 90 hpa eri was successfully simulated in two of the three experiments a factor crucial to simulating eri was a combination of shallow to moderate convection and tall upright convective bursts cbs under a strong environmental vertical wind shear 10 m s 1 shallow to moderate convection on the downshear side that occurred around the intense near surface inflow moistened the inner core area meanwhile dry subsiding flows on the upshear side helped intensification of midlevel 8 km inertial stability first a midlevel warm core appeared below 10 km in the shallow to moderate convection areas being followed by the development of the upper level warm core associated with tall convection when tall upright

observed hurricane wind speed asymmetries and relationships to motion and environmental shear abstractwavenumber 1 wind speed asymmetries in 35 hurricanes are quantified in terms of their amplitude and phase based on aircraft observations from 128 individual flights between 1998 and 2011 the impacts of motion and 850 200 mb environmental vertical shear are examined separately to estimate the resulting asymmetric structures at the sea surface and standard 700 mb reconnaissance flight level the surface asymmetry amplitude is on average around 50 smaller than found at flight level and while the asymmetry amplitude grows in proportion to storm translation speed at the flight level no significant growth at the surface is observed contrary to conventional assumption however a significant upwind storm motion relative phase rotation is found at the surface as translation speed increases while the flight level phase remains fairly constant after removing the estimated impact of storm motion on the asymmetry a significant residual shear direction relative asymmetry is found particularly at the

aeolian silt transport processes as fingerprinted by dynamic image analysis of the grain size and shape characteristics of chinese loess and red clay deposits abstract this study applied dynamic image analysis dia sympatec qicpic to characterize the grain size and shape of chinese aeolian sediments in order to fingerprint their transportation processes this is the first time this technique has been applied to late neogene and quaternary silt particles 2 63 m from the chinese loess plateau clp we selected four well studied quaternary loess palaeosol sequences along a north south transect across the clp and compared their grain size distribution obtained by dia with that yielded by laser diffraction particle size analysis ld fritsch analysette 22 and sympatec helos kr this comparison demonstrated that dia is successfully able to differentiate loess units from palaeosols and to characterize clearly spatiotemporal variations in the grain size records of loess palaeosol sequences formed during the last two glacial and interglacial periods this is consistent with grain size results obtained using ld dia is also able to characterize spatial variations in the more fine grained aeolian red clay deposits underlying the quaternary loess and allows the quantification of the fluvial contribution to red clay sequences dia of the characteristics of grain shapes in loess palaeosol sequences and red clay deposits revealed a systematic pattern whereby the aspect ratio decreased with increasing grain size indicating that systematic shape sorting occurred during the aeolian transportation of these dust particles it could be inferred from our study that particles in a certain grain size range correspond to a specific aspect ratio range and may in turn be aerodynamically distinguishable from each other and further correlated with the wind velocity strength also evident from analysis of our dia data was a subtle but systematic downwind decrease in the aspect ratio of the particles in the loess units this observation suggests that elongated and or flat particles with a low aspect ratio were transported further downwind than more symmetrically shaped particles with a high aspect ratio this study indicates that dia of grain size and shape characteristics can be an additional powerful tool for identifying grain size and shape sorting trends determining the dominant mode of transport and reconstructing transport pathways of silt sized aeolian sediments

reexamining the near core radial structure of the tropical cyclone primary circulation implications for vortex resiliency abstract recent theoretical studies based on vortex rossby wave vrw dynamics have established the importance of the radial structure of the primary circulation in the response of tropical cyclone tc like vortices to ambient vertical wind shear linear vrw theory suggests in particular that the degree of broadness of the primary circulation in the near core region beyond the radius of maximum wind strongly influences whether a tilted tc vortex will realign and resist vertical shear or tilt over and shear apart fully nonlinear numerical simulations have verified that the vortex resiliency is indeed sensitive to the initial radial structure of the idealized vortex this raises the question of how well the true nature of a tc s primary circulation is represented by idealized vortices that are commonly used in some theoretical studies in this paper the swirling wind structure of tcs is reexamined by utilizing flight level observations collected from atlantic and eastern pacific storms during 1977 2

the convective evolution and rapid intensification of hurricane earl 2010 abstractthe relationship between an inner core r 100 km lightning outbreak and the subsequent rapid intensification ri of hurricane earl 2010 is examined using lightning strikes recorded by the world wide lightning location network wwlln and in situ observations from various aircraft missions moderate 8 4 m s 1 northeasterly deep layer 850 200 hpa vertical wind shear caused by outflow from hurricane danielle existed over earl at the beginning of a prolonged period of ri over 70 of the lightning strikes within a 500 km radius occurred downshear with a preference toward downshear right in the outer rainbands in agreement with previous studies the location of inner core strikes in earl differed markedly from previous studies the inner core lightning activity precessed from left of shear to upshear an extremely rare event beginning just prior to the onset of ri diagnosis of the vortex tilt midway through the lightning precession showed this convection was occurring downtilt in the ups

distribution lithology and provenance of peridesert loess deposits in northeastern iran abstract silty deposits cover different landforms bordering the city of mashhad in ne iran despite the potential of these deposits to provide important information regarding landscape evolution as well as land use management little information has been published on their nature and origin the main objective of this study was to determine the nature and origin of silty deposits in this area based on particle size distribution abrupt particle size change between silty deposits and underlying materials the shape and microtexture of quartz grains chemical and geochemical data and geochemical homogeneity of silty deposits from different landforms and geomorphic positions the silty deposits appear to be wind blown in origin and are classified as loess they show a particle size distribution similar to that of typical loess deposits containing more than 70 silt mostly coarse silt 35 45 and low quantities of clay and sand bulbous edges and evidence of wind transportation on quartz grains confirm the aeolian nature of the quartz silt the amount of carbonates and gypsum in loess deposits are mostly in the range of 10 32 and 4 15 respectively silty deposits around the study area are geochemically homogenous similar geochemical signatures of gypsiferous marls and loess deposits the existence of gypsum enriched layers in the loess deposits and the geomorphic position show that gypsiferous marls are the main source of aeolian deposits this is further confirmed by the existence of detrital palygorskite in loess layers and the presence of a high amount of palygorskite in gypsiferous marls since the silt in loess deposits is not the result of weathering processes the loess deposits of the study area bordering the large deserts of the central iranian plateau are defined as peridesert loess

shear relative asymmetries in tropical cyclone eyewall slope abstractrecent studies have analyzed the azimuthal mean slope of the tropical cyclone tc eyewall this study looks at the shear relative azimuthal variability of different metrics of eyewall slope the 20 dbz surface the radius of maximum wind rmw and an angular momentum m surface passing through the rmw the data used are doppler radar composites from the noaa hurricane research division hrd this study examines 34 tcs with intensities ranging from 3 to 75 m s 1 and shear magnitudes ranging from 0 to 10 m s 1 calculation of the mean slope in each quadrant for all cases shows that rmw slope has the strongest asymmetry with downshear slope larger than upshear in 62 of cases slopes of momentum surfaces and dbz surfaces are also greater downshear in some cases 65 for m and 47 for dbz but there is more variance than in the rmw slope the azimuthal phase of maximum slope occurs most often downshear particularly downshear left consistent with the depiction of a mean vortex tilt approximate

the nature origin and accumulation of loess abstract loess can be defined simply as a terrestrial clastic sediment composed predominantly of silt size particles which is formed essentially by the accumulation of wind blown dust there are three fundamental requirements for its formation 1 a sustained source of dust 2 adequate wind energy to transport the dust and 3 a suitable accumulation site most loess has been modified to some degree by local reworking bioturbation and syn depositional weathering but a process of loessification is not necessary for a dust deposit to qualify as loess the terms primary loess and secondary loess have previously been used to described wind deposited loess and redeposited loess respectively but it is more accurate to describe material reworked and redeposited by non aeolian processes as loess derived colluvium or loess derived alluvium during the quaternary loess formed in three main situations 1 mid continental shield areas beyond the limits of ice sheets periglacial loess 2 on the margins of high mountain ranges perimontane loess and 3 on the semi arid margins of some lowland deserts peridesert loess peridesert loess is relatively poorly developed partly due to the limited efficiency of silt generating mechanisms in low land deserts compared with glaciation but also important is the tendency in arid areas for dust to be dispersed over a wide area and to be rapidly reworked after deposition particularly in areas which experience frequent climatic changes the remarkably thick loess of china and central asia results from an unusual combination of conditions which has persisted for much of the last 2 3 million years namely rapid uplift of the tibetan plateau and surrounding mountain ranges high rates of sediment production and supply to adjacent basins a strong northwesterly and westerly wind regime and the existence of effective dust traps downwind of the source regions

meltwater intensive glacial retreat in polar environments and investigation of associated sediments example from pine island bay west antarctica abstract modern pine island and thwaites glaciers which both drain into pine island bay are among the fastest changing portions of the cryosphere and the least stable ice streams in antarctica here we show that the uppermost sediment unit in pine island bay was deposited from a meltwater plume a plumite during the late stages of ice sheet retreat 7 8 6 k cal yr bp and argue that this deposit records episodes of meltwater intensive sedimentation the plumite is a hydraulically sorted glacially sourced draping deposit that overlies proximal glacimarine sediments and thickens towards the modern grounding line the uppermost sediment unit is interpreted as a product of non steady state processes in which low background sedimentation in large bedrock carved basins alternates with episodic purging of sediment laden water from these basins the inner part of pine island bay contains several basins that are linked by channels with a storage capacity on the order of 70 km 3 of stagnant water and significant sediment storage capacity purging of these basins is caused by changes in hydraulic potential and glacial reorganization the sediment mobilized by these processes is found here to total 120 km 3 this study demonstrates that episodes of meltwater intensive sedimentation in pine island bay occurred at least three times in the holocene the most recent episode coincides with rapid retreat of the grounding line in historical time and has an order of magnitude greater flux relative to the entire unit we note that the final phase of ice stream retreat in marguerite bay was marked by a similar sedimentary event and suggest that the modern thwaites glacier is poised for an analogous meltwater intensive phase of retreat

buoyancy of convective vertical motions in the inner core of intense hurricanes part ii case studies abstract this is the second of two papers on the buoyancy of convective vertical motions in the inner core of intense hurricanes this paper uses extensive airborne radar dropwindsonde and flight level observations in hurricanes guillermo 1997 and georges 1998 to illustrate typical azimuthal distribution of buoyant convection and demonstrate that the low level eye can be an important source region for buoyant eyewall convection in both hurricanes eyewall vertical velocity and radar reflectivity are asymmetric and exhibit persistent relationships with the direction of the environmental vertical wind shear mesoscale vertical motions exhibit a wavenumber 1 structure with maximum ascent downshear and weak descent upshear the mesoscale reflectivity maxima are located left of shear buoyant eyewall updraft cores and transient convective scale reflectivity cells are predominantly downshear and left of shear most eyewall downdraft cores that transport significant mass downward are located upshear nega

tropical cyclone motion and evolution in vertical shear abstract the motion and the evolution of tropical cyclone like vortices in an environmental flow with vertical shear are investigated using a baroclinic primitive equation model the study focuses on the fundamental dynamics of a baroclinic vortex in vertical shear the influence of vortex structure and the role of diabatic heating the results show that the initial response of the vortex to the vertical shear is to tilt downshear as soon as the tilt develops the upper level anticyclonic and lower level cyclonic circulations begin to interact with each other as a result of these interactions the tilted axis of the vortex reaches a stable state after an initial adjustment which varies with the structure of the vortex its environmental flow shear and the cumulus convective heating the motion of an adiabatic vortex in vertical shear is controlled by both the steering of the environmental flow and vertical coupling mechanisms most of the vortices move with the environmental flow at about 650 hpa or

interactions between simulated tropical cyclones and an environment with a variable coriolis parameter abstract numerical simulations of tropical cyclones are performed to examine the effects of a variable coriolis parameter on the structure and intensity of hurricanes the simulations are performed using the nonhydrostatic fifth generation pennsylvania state university national center for atmospheric research mesoscale model using a 5 km fine mesh and fully explicit representation of moist processes when a variable conolis parameter f environment is applied to a mature tropical cyclone a persistent north northwesterly shear develops over the storm center as a result of an interaction between the primary circulation of the storm and the gradient in absolute vorticity as a result the variable f storm quickly develops a persistent wavenumber 1 asymmetry in its inner core structure with upward motion and rainfall concentrated on the left side of the shear looking downshear in agreement with earlier studies in comparison the constant f storm develops weak transient asymmetries in structure that are

rapidly intensifying hurricane guillermo 1997 part ii resilience in shear this paper examines the structure and evolution of a mature tropical cyclone in vertical wind shear vws using airborne doppler radar observations of hurricane guillermo 1997 in part i the modulation of eyewall convection via the rotation of vorticity asymmetries through the downshear left quadrant was documented during rapid intensification here the focus is on the relationship between vws vortex tilt and associated asymmetry within the tropical cyclone core region during two separate observation periods a method for estimating local vws and vortex tilt from radar datasets is further developed and the resulting verticalstructureanditsevolutionaresubjectedtostatisticalconfidencetests guillermowasahighlyresilient vortex evidenced by its small tilt magnitude relative to the horizontal scale of the vortex core the deep layer tilt was statistically significant oriented on average 608 left of shear large scale vorticity and thermal asymmetries oriented along the tilt direction support a response of guillermo to shear forcing that is consistent with balanced dynamics the time averaged vertical motion asymmetry within the eyewall exhibited maximum ascent values 408 left of the deep layer shear or in this case right of the deep layer tilt the observation based analysis of guillermo s interaction with vws confirms findings of recent theoretical and numerical studies and serves as the basis for a more comprehensive investigation of vws and tropical cyclone intensity change using a recently constructed multistorm database of doppler radar analyses

rapid intensification of a sheared fast moving hurricane over the gulf stream abstracthurricane irene 1999 rapidly intensified from 65 to 95 kt 33 4 to 48 9 m s 1 in 18 h during the rapid intensification ri period the northeastward storm motion increased from 10 to 18 m s 1 the ambient southwesterly vertical wind shear increased from 6 7 to 10 13 m s 1 and the downshear tilt of the inner core vortex increased the azimuthal wavenumber 1 asymmetric convection that developed was consistent with a superposition of shear induced and storm motion induced forcing for vertical motion downshear and ahead of the center although the diabatic heating remained strongly asymmetric it was of sufficient intensity to dramatically increase the azimuthally averaged heating this heating occurred almost entirely inside the radius of maximum winds a region known to favor rapid warm core development and spinup of the vortex it is hypothesized that asymmetric forcing from the large vertical wind shear and rapid storm motion were responsible for ri an unanswered question is what determin

a lagrangian trajectory view on transport and mixing processes between the eye eyewall and environment using a high resolution simulation of hurricane bonnie 1998 the transport and mixing characteristics of a large sample of air parcels within a mature and vertically sheared hurricane vortex are examined data from a high resolution 2 km horizontal grid spacing numerical simulation of real case hurricane bonnie 1998 are used to calculate lagrangian trajectories of air parcels in various subdomains of the hurricane namely the eye eyewall and near environment to study the degree of interaction transport and mixing between these subdomains it is found that 1 there is transport and mixing from the low level eye to the eyewall that carries air possessing relatively high values of equivalent potential temperature e which can enhance the efficiency of the hurricane heat engine 2 a portion of the low level inflow of the hurricane bypasses the eyewall to enter the eye and this air both replaces the mass of the low level eye and lingers for a sufficient time order 1 h to acquire enhanced entropy characteristics through interaction with the ocean beneath the eye 3 air in the mid to upper level eye is exchanged with the eyewall such that more than half the air of the eye is exchanged i n5hi nthis case of a sheared hurricane and 4 that one fifth of the mass in the eyewall at a height of 5 km has an origin in the mid to upper level environment where e is much less than in the eyewall which ventilates the ensemble average eyewall e by about 1 k implications of these findings for the problem of hurricane intensity forecasting are briefly discussed

multiscale analysis of tropical cyclone kinematic structure from airborne doppler radar composites abstractthe multiscale inner core structure of mature tropical cyclones is presented via the use of composites of airborne doppler radar analyses the structure of the axisymmetric vortex and the convective and turbulent scale properties within this axisymmetric framework are shown to be consistent with many previous studies focusing on individual cases or using different airborne data sources on the vortex scale these structures include the primary and secondary circulations eyewall slope decay of the tangential wind with height low level inflow layer and region of enhanced outflow radial variation of convective and stratiform reflectivity eyewall vorticity and divergence fields and rainband signatures in the radial wind vertical velocity vorticity and divergence composite mean and variance fields statistics of convective scale fields and how they vary as a function of proximity to the radius of maximum wind show that the inner eyewall edge is associated with stronger updrafts and higher refl

examining polarimetric radar observations of bulk microphysical structures and their relation to vortex kinematics in hurricane arthur 2014 abstractdual polarization radar observations were taken of hurricane arthur prior to and during landfall providing needed insight into the microphysics of tropical cyclone precipitation a total of 30 h of data were composited and analyzed by annuli capturing storm features eyewall inner rainbands and outer rainbands and by azimuth relative to the deep layer environmental wind shear vector polarimetric radar variables displayed distinct signatures indicating a transition from convective to stratiform precipitation in the downshear right to downshear left quadrants which is an organization consistent with the expected kinematic asymmetry of a sheared tropical cyclone in the downshear right quadrant vertical profiles of differential reflectivity zdr and copolar correlation coefficient hv were more vertically stretched within and above the melting layer at all annuli which is attributed to convective processes an analysis of specific differential phase kdp indicated that nonspherical ice particle

observations of the structure and evolution of hurricane edouard 2014 during intensity change part ii kinematic structure and the distribution of deep convection abstractthe structural evolution of the inner core and near environment throughout the life cycle of hurricane edouard 2014 is examined using a synthesis of airborne and satellite measurements this study specifically focuses on differences in the distribution of deep convection during two periods when edouard intensified toward hurricane status and when edouard peaked in intensity and began to weaken while both periods saw precipitation maximized in the downshear left and upshear left quadrants deep convection was only seen from the aircraft during the intensifying period deep convection was located farther inside the radius of maximum winds rmw during the intensifying period than the weakening period this convection is traced to strong updrafts inside the rmw in the downshear right quadrant tied to strong low level convergence and high convective available potential energy cape as the storm remained over warm water in a moist environment strong updrafts persisted upshear left and were collo

hurricane vortex dynamics during atlantic extratropical transition abstract simulations of six atlantic hurricanes are diagnosed to understand the behavior of realistic vortices in varying environments during the process of extratropical transition et the simulations were performed in real time using the advanced research weather research and forecasting wrf model arw using a moving storm centered nest of either 4 or 1 33 km grid spacing the six simulations ranging from 45 to 96 h in length provide realistic evolution of asymmetric precipitation structures implying control by the synoptic scale primarily through the vertical wind shear the authors find that as expected the magnitude of the vortex tilt increases with increasing shear but it is not until the shear approaches 20 m s 1 that the total vortex circulation decreases furthermore the total vertical mass flux is proportional to the shear for shears less than about 20 25 m s 1 and therefore maximizes not in the tropical phase but rather during et this has important implications for predictin

a numerical study of hurricane erin 2001 part ii shear and the organization of eyewall vertical motion a high resolution numerical simulation of hurricane erin 2001 is used to examine the organization of vertical motion in the eyewall and how that organization responds to a large and rapid increase in the environmental vertical wind shear and subsequent decrease in shear during the early intensification period prior to the onset of significant shear the upward motion in the eyewall was concentrated in small scale convective updrafts that formed in association with regions of concentrated vorticity herein termed mesovortices with no preferred formation region around the eyewall asymmetric flow within the eye was weak as the shear increased an azimuthal wavenumber 1 asymmetry in storm structure developed with updrafts tending to occur on the downshear to downshear left side of the eyewall continued intensification of the shear led to increasing wavenumber 1 asymmetry large vortex tilt and a change in eyewall structure and vertical motion organization during this time the eyewall structure was dominated by a vortex couplet with a cyclonic anticyclonic vortex on the downtilt left downtilt right side of the eyewall and strong asymmetric flow across the eye that led to strong mixing of eyewall vorticity into the eye upward motion was concentrated over an azimuthally broader region on the downtilt side of the eyewall upstream of the cyclonic vortex where low level environmental inflow converged with the asymmetric outflow from the eye as the shear diminished the vortex tilt and wavenumber 1 asymmetry decreased while the organization of updrafts trended back toward that seen during the weak shear period based upon the results for the erin case as well as that for a similar simulation of hurricane bonnie 1998 a conceptual model is developed for the organization of vertical motion in the eyewall as a function of the strength of the vertical wind shear in weak to moderate shear higher wavenumber asymmetries associated with eyewall mesovortices dominate the wavenumber 1 asymmetry associated with the shear so that convective scale updrafts form when the mesovortices move into the downtilt side of the eyewall and dissipate on the uptilt side under strong shear conditions the wavenumber 1 asymmetry characterized by a prominent vortex couplet in the eyewall dominates the vertical motion organization so that mesoscale ascent with embedded convection occurs over an azimuthally broader region on the downtilt side of the eyewall further research is needed to determine if these results apply more generally

low level thermodynamic kinematic and reflectivity fields of hurricane guillermo 1997 during rapid intensification abstract from 0600 utc 2 august to 1200 utc 3 august hurricane guillermo 1997 deepened by 54 hpa over the eastern north pacific ocean easily exceeding the thresholds that define rapid intensification ri the noaa wp 3ds observed a portion of this ri with similar two aircraft missions on consecutive days the aircraft jettisoned 70 successful global positioning system gps dropwindsondes or gps sondes which reveal how conditions in the lower troposphere on the octant to quadrant scale evolved within 250 km of the eye reflectivity fields demonstrate that the deepening is correlated with a spiraling in of the northern eyewall that reduces the eye diameter by 10 km this behavior contrasts the more uniform contraction witnessed during eyewall replacement cycles mixing between the lower eye and eyewall as detailed by other investigators appears to have triggered the reduction in the eye diameter after ri the eyewall remains asymmetrical with the tallest echo tops and heaviest rain rates located o

granulometric characterization of paleosols in loess series by automated static image analysis abstract an automated image analysis method is proposed here to study the size and shape of siliciclastic sedimentary particles of paleosols of central european loess sequences several direct and indirect measurement techniques are available for grain size measurements of sedimentary mineral particles indirect techniques involve the use of some kind of physical laws however all requirements for calculations are in many cases not known even so the direct manual microscopic observation and measurement of large representative number of grains is time consuming and sometimes rather subjective therefore automated image analyses techniques provide a new and perspective way to analyse grain size and shape sedimentary particles here we test these indirect laser diffraction and direct automated static image analysis techniques and provide new granulometric size and shape data of paleosols our results demonstrate that grain size data of the mineral dust samples are strongly dependent on shape parameters of particles and shape heterogeneity was different between different size classes due to the irregular grain shape parameters uncertainties have arisen also for determination of grain sizes in this paper we present a possible correction procedure to reduce the differences among the results of the laser diffraction and image analysis methods by applying new correction factors results of the two approaches could become closer but the unknown thickness of particles remains a problem to solve the other presented correction procedure to assess the uncertain 3rd dimension of particles by their intensity size relationships makes us able to reduce further the deviations of the two sizing methods

two distinct regimes in the kinematic and thermodynamic structure of the hurricane eye and eyewall abstract using aircraft flight level data the present work demonstrates that the kinematic and thermodynamic distributions within the eye and eyewall of strong hurricanes are observed to evolve between two distinct regimes in the first regime angular velocity is greatest within the eyewall and relatively depressed within the eye in the second regime radial profiles of angular velocity are nearly monotonic with maxima found at the eye center considering sequential profiles within individual hurricanes the authors find that the evolution of the kinematic distribution is often marked by a transition from the first regime to the second the transition can occur in less than 1 h also noted during the transition are dramatic changes in the thermodynamic structure of the hurricane prior to the transition regime 1 the eye is typically very warm and dry and the equivalent potential temperature is often elevated within the eyewall and relatively depressed within the eye after the transition regime 2

tropical cyclone formation in a sheared environment a case study abstract the development of hurricane danny 1997 from depression to hurricane was examined using cloud to ground lightning data reconnaissance aircraft data and satellite imagery vertical wind shear between 850 and 200 hpa of 5 11 m s 1 produced persistent downshear convective outbreaks that became progressively more intense and closer to the center during the development early in the period the storm intensified steadily in the presence of this downshear convection during the last and most intense outbreak a second vortex appeared to develop within the convection evidence is presented that the new downshear vortex became the dominant vortex and absorbed the original based on these events it is hypothesized that the presence of moderate vertical wind shear accelerated the early development process equivalent potential temperature fields within 500 m of the surface were examined only well after the period of vortex interaction did the characteristic mature tropical cyclone radial profile of eq

environmental flow impacts on tropical cyclone structure diagnosed from airborne doppler radar composites abstractfollowing a recent demonstration of multicase compositing of axisymmetric tropical cyclone tc structure derived from airborne doppler radar measurements the authors extend the analysis to the asymmetric structure using an unprecedented database from 75 tc flights in particular they examine the precipitation and kinematic asymmetry forced by the tc s motion and interaction with vertical wind shear for the first time they quantify the average magnitude and phase of the three dimensional shear relative kinematic asymmetry of observed tcs through a composite approach the composite analysis confirms principal features of the shear relative tc asymmetry documented in prior numerical and observational studies e g downshear tilt downshear right convective initiation and a downshear left precipitation maximum the statistical significance of the composite shear relative structure is demonstrated through a stratification of cases by shear magnitude the impact of storm motion on eyewall convect

observations of the eyewall structure of typhoon sinlaku 2008 during the transformation stage of extratropical transition abstracta unique dataset observing the life cycle of typhoon sinlaku was collected during the observing system research and predictability experiment thorpex pacific asian regional campaign t parc in 2008 in this study observations of the transformation stage of the extratropical transition of sinlaku are analyzed research flights with the naval research laboratory p 3 and the u s air force wc 130 aircraft were conducted in the core region of sinlaku data from the electra doppler radar eldora dropsondes aircraft flight level and satellite atmospheric motion vectors were analyzed with the recently developed spline analysis at mesoscale utilizing radar and aircraft instrumentation samurai software with a 1 km horizontal and 0 5 km vertical node spacing the samurai analysis shows marked asymmetries in the structure of the core region in the radar reflectivity and three dimensional wind field the highest radar reflectivities were found in the left of shear semicircle and maximum ascent was

convective bursts downdraft cooling and boundary layer recovery in a sheared tropical storm abstracttropical storm edouard 2002 experienced episodic outbreaks of convection downshear within the storm core in the presence of 11 15 m s 1 of ambient vertical wind shear these outbreaks lasted 2 6 h and were followed by long periods with no deep convection flights from u s air force reconnaissance aircraft within the boundary layer were used to investigate the cause of one such oscillation low equivalent potential temperature e air filled the boundary layer as convection ceased creating a 4 6 k deficit in e within the convective region soundings within 110 km of the center were supportive of convective downdrafts with midlevel relative humidity below 15 and large downdraft cape deep convection ceased within 75 km of the center for more than 8 h tangential velocity reached hurricane force locally during the convective outbreak then became nearly symmetric after convection stopped arguably as a result of axisymmetrization and the storm weakened nevertheless the corresponding lack of

a numerical study on rapid intensification of typhoon vicente 2012 in the south china sea part ii roles of inner core processes abstractin part i of this study the role of environmental monsoon flow in the onset of rapid intensification ri of typhoon vicente 2012 was discussed in this part ii key inner core processes that effectively resist environmental vertical wind shear during ri onset are investigated the convective precipitation shield cps embedded in the downshear convergence zone plays a vital role in preconditioning the tropical cyclone tc vortex before ri the cps induces a mesoscale positive vorticity band pvb characterized by vortical hot tower structures upstream and shallower structures 4 km downstream multiple mesovortices form successively along the pvb and are detached from the pvb at its downstream end rotating cyclonically around the tc center the sufficient amount of vorticity anomalies in the pvb facilitates the upscale growth of a mesovortex into a reformed inner vortex which eventually replaces the parent tc vortex i e downshear reformation leading to ri onset the timing of downshe

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

mesoscale aspects of the downshear reformation of a tropical cyclone the downshear reformation of tropical storm gabrielle 2001 was investigated using radar reflectivity and lightning data that were nearly continuous in time as well as frequent aircraft reconnaissance flights initially the storm was a marginal tropical storm in an environment with strong 850 200 hpa vertical wind shear of 12 13 m s 1 and an approaching upper tropospheric trough both the observed outflow and an adiabatic balance model calculation showed that the radial vertical circulation increased with time as the trough approached convection was highly asymmetric with almost all radar return located in one quadrant left of downshear in the storm reconnaissance data show that an intense mesovortex formed downshear of the original center this vortex was located just south of rather than within a strong downshear left lightning outbreak consistent with tilting of the horizontal vorticity associated with the vertical wind shear the downshear mesovortex contained a 972 hpa minimum central pressure 20 hpa lower than minimum pressure in the original vortex just 3 h earlier the mesovortex became the new center of the storm but weakened somewhat prior to landfall it is argued that dry air carried around the storm from the region of upshear subsidence as well as the direct effects of the shear prevented the reformed vortex from continuing to intensify despite the subsequent weakening of the reformed center it reached land with greater intensity than the original center it is argued that this intensification process was set into motion by the vertical wind shear in the presence of an environment with upward motion forced by the upper tropospheric trough in addition the new center formed much closer to the coast and made landfall much earlier than predicted such vertical shear induced intensity and track fluctuations are important to understand especially in storms approaching the coast

evaluation of tropical cyclone center identification methods in numerical models abstractidentifying the center of a tropical cyclone in a high resolution model simulation has a number of operational and research applications including constructing a track calculating azimuthal means and perturbations and diagnosing vortex tilt this study evaluated several tropical cyclone center identification methods in a high resolution weather research and forecasting wrf model simulation of a sheared intensifying asymmetric tropical cyclone the simulated tropical cyclone tc contained downshear convective cells and a mesovortex embedded in a broader tc vortex complicating the identification of the tc vortex center it is shown that unlike other methods the pressure centroid method consistently 1 placed the tc center within the region of weak storm relative wind 2 produced a smooth track 3 yielded a vortex tilt that varied smoothly in magnitude and direction and 4 was insensitive to changes in horizontal grid resolution based on these results the authors recommend using the pr

an analysis of the observed low level structure of rapidly intensifying and mature hurricane earl 2010 abstract we examine dynamic and thermodynamic aspects of atlantic hurricane earl 2010 during its intensification and mature phases over four days of intensive measurements during this period earl underwent an episode of rapid intensification maturity secondary eyewall replacement re intensification and the early part of its decline the observations are used to appraise elements of a new model for tropical cyclone intensification the results affirm the conventional vortex interior and boundary layer spin up mechanisms that form dynamical elements of the azimuthally averaged view of the new intensification model the average maximum tangential winds beneath the eyewall are found to exceed the gradient wind by between 20 and 60 the results suggest also that the gradient wind balance approximation in the low level vortex interior above the strong inflow layer may not be as accurate in the inner core region of a tropical cyclone during its intensification as has been widely held an analysis of the low level thermodynamic structure affirms the radial increase of moist equivalent potential temperature e with decreasing radius during the intensification process a necessary ingredient of the new model for maintaining convective instability in the presence of a warming upper troposphere an unanticipated finding is the discovery of an unmixed boundary layer in terms of e within several hundred kilometres of the vortex centre in the inner core region this finding is not consistent with the axisymmetric eruption of the boundary layer into the eyewall unless there are non conservative eddy processes acting to modify the entropy of ascending air

airborne doppler observations of the inner core structural differences between intensifying and steady state tropical cyclones abstractdifferences in the inner core structure of intensifying in intensity increase of at least 20 kt 24 h 1 where 1 kt 0 51 m s 1 and steady state ss intensity remaining between 10 kt 24 h 1 tropical cyclones tcs are examined using composites of airborne doppler observations collected from noaa p 3 aircraft missions the in dataset contains 40 eyewall passes from 14 separate missions while the ss dataset contains 53 eyewall passes from 14 separate missions intensifying tcs have a ringlike vorticity structure inside the radius of maximum wind rmw lower vorticity in the outer core a deeper stronger inflow layer and stronger axisymmetric eyewall upward motion compared with steady state tcs there is little difference in the vortex tilt between 2 and 7 km and both in and ss tcs show an eyewall precipitation and updraft asymmetry whose maxima are located in the downshear and downshear left region the azimuthal coverage of eyewall and outer core precipitation is greater for in tcs

global composites of surface wind speeds in tropical cyclones based on a 12 year scatterometer database a 12 year global database of rain corrected satellite scatterometer surface winds for tropical cyclones tcs is used to produce composites of tc surface wind speed distributions relative to vertical wind shear and storm motion directions in each tc prone basin and various tc intensity stages these composites corroborate ideas presented in earlier studies where maxima are located right of motion in the earth relative framework the entire tc surface wind asymmetry is down motion left for all basins and for lower strength tcs after removing the motion vector relative to the shear direction the motion removed composites indicate that the surface wind asymmetry is located down shear left for the outer region of all tcs but for the inner core region it varies from left of shear to down shear right for different basin and tc intensity groups quantification of the surface wind asymmetric structure in further stratifications is a necessary next step for this scatterometer data set