composite titanomagnetite ferrian ilmenite grains and correlative magnetic components in a dacite with self reversed trm abstract electron microprobe and reflected light microscopic examinations confirm the presence of composite grains of ferrian ilmenite with x ilm 0 53 and titanomagnetite with x usp 0 13 in a dacite with self reversed trm a parallel trm component associated with titanomagnetite and a reversed component associated with self reversing ferrian ilmenite are the principal nrm components a subordinate parallel component is associated with ferrian ilmenite which is not magnetically coupled to an phase the natural self reversing properties are mainly a consequence of the dacite s high quenching temperature calculated at 862 864 c using the fe ti oxide geothermometer and are most consistent with the self reversal mechanism proposed by lawson et al 9 the conduction of thermal demagnetization and trm induction tests in air had a much greater effect on the fe ti oxides than did natural cooling and resulted in significant oxidation with the consequent modification of some magnetic properties and the formation of another reversed trm component the subdivision of titanomagnetite grains by oxidation along fractures decreased its effective grain size and caused an apparent increase in its magnetic intensity in addition to a slight increase in its resistance to alternating field demagnetization the phase associated with the reversed nrm component with 0 42 x ilm 0 31 became fe enriched during the earlier stages of heat treatment it is suggested that after heating at 600 c for two hours or more this phase exsolves as titanohematite with x ilm the ferrian ilmenite host is consequently enriched in ti and another phase much closer in composition to the host generates a reversed trm component with t b

cloud to ground lightning in hurricane andrew the spatial and temporal distribution of cloud to ground lightning was examined in hurricane andrew of 1992 lightning locations available from the national lightning detection network were superimposed on infrared satellite images to relate lightning activity to hurricane cloud structure a distinct radial variation occurred in time averaged flash density with a weak maximum in the eye wall a region of near zero flash density 40 to 100 km from the center and a steady increase to a large maximum in the outer rainbands 190 km from the center this radial distribution is consistent with the convective structure of mature hurricanes eye wall lightning tended to be episodic occurring almost exclusively prior to and during periods of intensification of the storm during these periods negative flashes occurred several kilometers inward from the highest eye wall cloud tops in the region of the largest radar reflectivity positive eye wall flashes while small in number tended to occur directly under the highest cloud tops the results are suggestive of a normal dipole in sign but outwardly tilted along the sloping eye wall in general hurricane flash characteristics resembled those for a background data set of nonhurricane flashes from the same area the exception occurred for negative flashes in the eye wall which had a much smaller mean peak current than the background 25 3 ka versus 44 9 ka

understanding atypical midlevel wind speed maxima in hurricane eyewalls abstractin tropical cyclones tcs the peak wind speed is typically found near the top of the boundary layer approximately 0 5 1 km recently it was shown that in a few observed tcs the wind s

a detailed magnetic and mineralogical study of self reversed dacitic pumices from the 1991 pinatubo eruption philippines 39 dacitic pumice and lithic samples from the 1991 eruption of mount pinatubo were investigated through both magnetic and mineralogical means as in a previous study natural remanent magnetization nrm is found to be reversed for most of the samples with respect to the direction of the actual geomagnetic field direction a few samples amongst them ancient lithics transported by pyroclastic flows show scattered nrm directions from thermal demagnetization of these particular samples it is concluded that their orientation changed after emplacement the emplacement temperature is estimated to be more than 460 c from thermal demagnetization of lithic samples two magnetic minerals with large grain sizes are observed under the optical microscope titanomagnetite tm and haemo ilmenite hem ilm microprobe analyses yield x 0 10 for tm and y 0 52 and y 0 54 for two hem ilm phases in agreement with the observed curie temperatures 480 c for tm and 250 c for hem ilm the hem ilm particles display chemical zonation which seems to be correlated with a change of the domain structure typically a ferrimagnetic fm phase with slightly higher titanium content is observed in the central part whilst the crystal margin which is weakly ferromagnetic wf due to spin canted antiferromagnetism is slightly poorer in titanium two different mechanisms for the origin and formation of the two observed phases are discussed 1 chemical zonation of hem ilm crystals due to a change in conditions in the magma chamber shortly before eruption 2 similar to the microstructures observed from synthetic samples this zonation in the large natural hem ilm could be the result of migration of the wf phase towards the grain boundary during residence below the order disorder transition temperature in the magmatic chamber the room temperature hysteresis loop which seems to be dominated by tm provides multidomain md like parameters jrs js 0 01 and hcr hc 20 the large coercivity of remanence 15 40 mt which is attributed to hem ilm may be intrinsic or due to interactions between wf and fm phases the field dependence of the magnitude of the thermoremanent magnetization trm is not linear it increases first reaches a maximum negative value for an applied field h close to 0 5 mt then decreases steadily by extrapolation it is estimated that the trm should be zero for a field of about 12 mt and become positive beyond this total trm is in fact the sum of several components af demagnetization of trms acquired in different fields shows the presence of at least three components a self reversed sr component that contains both hard and moderately hard components and a soft normal component independently of the value of h the median destructive field of the sr component is of the order of 70 mt which suggests that the fm phase is not entirely locked by exchange interaction with the wf phase and can experience noticeable wall movements however some 20 per cent of the sr trm component remains after af treatment of 220 mt although we believe that exchange interaction plays a key role in the process of sr trm acquisition torque curves in the high field of samples both with and without sr trm do not show clear evidence for unidirectional anisotropy similarly we do not observe any significant shift of major hysteresis loops or non vanishing hysteresis losses two characteristics generally considered as indicative of exchange anisotropy and usually observed for synthetic single domain pseudo single domain sd psd hem ilm indeed in addition to the exchange interaction the magnetostatic coupling must play some role here because of the large size of the hem ilm grains

a modeling study of typhoon nari 2001 at landfall 2 structural changes and terrain induced asymmetries 1 in this study a series of model output diagnoses using the cloud resolving simulations of typhoon nari 2001 with or without taiwan topography is performed to gain insight into the landfall characteristics of the storm as it moves across taiwan island various kinematic and precipitation features prior to and after landfall are examined with a focus on the dynamic effects of taiwan s high topography upon the generation of nari s asymmetric structures results show that tangential winds weaken whereas the low level inflows and midlevel outflows increase after landfall due to the increased friction and terrain blocking meanwhile the eye wall updrafts exhibit more cellular structures and tend to tilt more outward with height over the high topography however nari s primary and secondary circulations are stronger in the presence of terrain than those without terrain the radii of the maximum winds and the eye wall updrafts could contract further after landfall with more pronounced contraction occurring in the portion of the eye wall where more terrain retardation and blocking are present in particular the high topography allows the elevated low equivalent potential temperature e air over the rugged terrain to intrude into the inner core region causing the breakdown of the eye wall it is concluded that the interaction of nari s circulations with the elevated low e air combined with topographical effects accounts for most of the asymmetrical structures after landfall

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

development and application of a simplified coplane wind retrieval algorithm using dual beam airborne doppler radar observations for tropical cyclone prediction abstractbased on established coplane methodology a simplified three dimensional wind retrieval algorithm is proposed to derive two dimensional wind vectors from radial velocity observations by the tail doppler radars on board the noaa p3 hurricane reconnaissance aircraft validated against independent in situ flight level and dropsonde observations before and after genesis of hurricane karl 2010 each component of the retrieved wind vectors near the aircraft track has an average error of approximately 1 5 m s 1 which increases with the scanning angle and distance away from the aircraft track simulated radial velocities derived from a convection permitting simulation of karl are further used to systematically quantify errors of the simplified coplane algorithm the accuracy of the algorithm is strongly dependent on the time between forward and backward radar scans and to a lesser extent the zero vertical velocity assumption at large angles relative to a plane parallel with the aircraft wings a proof

structure of the eye and eyewall of hurricane hugo 1989 on 15 september 1989 one of noaa s wp 3d research aircraft n42rf lower aircraft la penetrated the eyewall of hurricane hugo the aircraft had an engine fail in severe turbulence while passing the radius of maximum wind and before entering the eye at 450 m altitude after the aircraft returned to controlled flight within the 7 km radius eye it gained altitude gradually as it orbited in the eye observations taken during this period provide an updated model of the inner core structure of an intense hurricane and suggest that la penetrated an intense cyclonic vorticity maximum adjacent to the strongest convection in the eyewall eyewall vorticity maximum evm this evm was distinct from the vortex scale cyclonic circulation observed to orbit within the eye three times during the 1 h that la circled in the eye at the time hugo had been deepening rapidly for 12 h the maximum flight level tangential wind was 89 m s 1 at a radius of 12 5 km however the primary vortex peak tangential wind derived from a 100 s filter of the flight level data was estimated to be 70 m s 1 also at 12 5 km radius the primary vortex tangential wind was in approximate gradient wind balance was characterized by a peak in angular velocity just inside the radius of maximum wind and had an annular vorticity structure slightly interior to the angular velocity maximum the evm along the aircraft s track was roughly 1 km in diameter with a peak cyclonic vorticity of 1 25 10 1 s 1 the larger circulation center with a diameter 15 km was observed within the eye and exhibited an average orbital period of 19 min this period is about the same as that of the angular velocity maximum of the axisymmetric mean vortex and is in reasonable agreement with recent theoretical and model predictions of a persistent trochoidal wobble of circulation centers in mature hurricane like vortices this study is the first with in situ documentation of these vortical entities which were recently hypothesized to be elements of a lower tropospheric eye eyewall mixing mechanism that supports strong storms

the structure and evolution of hurricane elena 1985 part i symmetric intensification one of the most complete aircraft reconnaissance and ground based radar datasets of a single tropical cyclone was recorded in hurricane elena 1985 as it made a slow 3 day anticyclonic loop in the gulf of mexico eighty eight radial legs and 47 vertical incidence scans were collected aboard noaa wp 3d aircraft and 1142 ground based radar scans were made of elena s eyewall and inner rainbands as the storm intensified from a disorganized category 2 to an intense category 3 hurricane this large amount of continuously collected data made it possible to examine changes that occurred in elena s inner core symmetric structure as the storm intensified on the first day of study elena was under the influence of vertical wind shear from an upper tropospheric trough to the west the storm was disorganized with no discernable eyewall and nearly steady values of tangential wind and relative vorticity early on the second day of study a near superposition and constructive interference occurred between the trough and elena coincident with upward vertical velocities and the radial gradient of reflectivity becoming concentrated around the 30 km radius once an inner wind maximum and eyewall developed the radius of maximum winds contracted and a sharp localized vorticity maximum emerged with much lower values on either side this potentially unstable vorticity profile was accompanied by a maximum in equivalent potential temperature in the eyewall deeper and stronger inflow out to 24 km from the eyewall and mean outflow toward the eyewall from the eye within 6 12 h intensification came to an end and elena began to slowly weaken vorticity and equivalent potential temperature at 850 hpa showed indications of prior mixing between the eye and eyewall during the weakening stage an outflow jet developed at the eyewall radius a strong 850 hpa updraft accompanied the outflow jet yet convection was less active aloft than before this feature appeared to represent a shallow outward sloping updraft channel associated with the spindown of the storm

the retrieval of asymmetric tropical cyclone structures using doppler radar simulations and observations with the extended gbvtd technique abstract the ground based velocity track display gbvtd technique is extended to two doppler radars to retrieve the structure of a tropical cyclone s tc s circulation with this extension it is found that the asymmetric part of the tc radial wind component can be derived up to its angular wavenumber 1 structure and the accuracy of the retrieved tc tangential wind component can be further improved although two radar systems are used a comparison with the traditional dual doppler synthesis indicates that this extended gbvtd egbvtd approach is able to estimate more of the tc circulation when there are missing data previous research along with this study reveals that the existence of strong asymmetric radial flows can degrade the quality of the gbvtd derived wind fields when a tc is observed by one radar it is suggested that the gbvtd method be applied to tcs over a flat surface e g the ocean where the assumption of relatively smaller asymmetric radial winds than asymmetric tangential winds is

inner core structure of hurricane alicia from airborne doppler radar observations abstract airborne doppler radar measurements are used to determine the horizontal winds vertical air motions radar reflectivity and hydrometer fallspeeds over much of the inner core region within 40 km of the eye of hurricane alicia 1983 the reconstructed flow field is more complete and detailed than any obtained previously the data show both the primary azimuthal and secondary radial height circulations the primary circulation was characterized by an outward sloping maximum of tangential wind the secondary circulation was characterized by a deep layer of radial inflow in the lower troposphere and a layer of intense outflow above 10 km altitude the rising branch of the secondary circulation was located in the eyewall and sloped radially outward discrete convective scale bubbles of more intense upward motion were superimposed on this mean rising current and convective scale downdrafts were located throughout and below the core of maximum precipitation in the eyewall precipitation particle

spatial and temporal patterns of benthic macrofaunal communities on the deep continental margin in the gulf of guinea abstract density taxonomic composition at higher taxon level and vertical distribution of benthic macrofaunal communities and sediment characteristics pore water nitrogen organic carbon sulfur c n ratio n alcohol biomarkers were examined at three deep sites on the congo gabon continental margin this study was part of the multidisciplinary biozaire project that aimed at studying the deep benthic ecosystems in the gulf of guinea sampling of macrofaunal communities and of sediment was conducted during three cruises january 2001 december 2001 and december 2003 at two downslope sites 4000 m depth one located near the congo submarine channel 15 km in the south and the other one far from the channel 150 km in the south the third area located 8 km north of the congo channel in the surroundings of a giant pockmark at 3160 m depth was sampled during one cruise in december 2003 at these three locations the macrofaunal communities presented relatively high densities 327 987 ind 0 25 m 2 compared with macrofaunal communities at similar depths that is due to high levels of food input related to the congo river and submarine system activities that affect the whole study area the communities were different from each other in terms of taxonomic composition at higher taxon level phylum class order for all the groups except for the polychaetes classified into families the polychaetes dominated the communities and were responsible for the increase in densities observed at both deep sites 4000 m between january 2001 and december 2003 whereas the tanaidaceans the isopods and the bivalves were the other most abundant taxa responsible for the spatial differences between these sites the community at 3150 m differed from the two deep communities by higher abundances in bivalves nemerteans and holothuroids the composition of the polychaete community also differed among sites in the vicinity of the congo channel the expected positive effect of the additional organic matter transported through the turbiditic currents on to the surrounding benthic communities was not observed as the increase in densities during the study period was higher at the site located away from the congo channel than near the channel 80 vs 30 that may be due to the low food value of the organic matter of terrestrial origin carried through the turbidites and or to the disturbance caused by these turbidites conversely far from the channel the macrofaunal communities benefit from organic matter of higher energetic value originating mainly from marine sources but also from continental sources carried by the congo plume or by near bed currents across or along the continental slope spatial and temporal variability in trophic and physical characteristics of the sediment habitat at both deep sites also affected the vertical distribution of the macrofaunal communities the activities of the very active congo system structure the deep macrofaunal communities on a large area in terms of densities composition and vertical distribution the food input is enhanced at regional scale as well as the heterogeneity of the sediment characteristics mainly in terms of organic matter quality marine vs terrigenous in turn the densities are enhanced as well as the regional diversity of the macrofaunal communities in terms of taxonomic composition and distribution

estimation and mapping of hurricane turbulent energy using airborne doppler measurements abstract hurricane turbulent kinetic energy tke was computed using airborne doppler measurements from the noaa wp 3d tail radars and tke data were retrieved for a variety of storms at different stages of their life cycle the geometry of the radar analysis coupled with the relatively small beam resolution at ranges 8 km allowed for the estimation of subkilometer turbulent processes two dimensional profiles of tke were constructed and revealed that the strongest turbulence was generally located in convective regions such as the eyewall with magnitudes often exceeding 15 m2 s 2 and in the boundary layer with values of 5 10 m2 s 2 in the lowest kilometer a correlation analysis showed that the strong turbulence was generally associated with strong horizontal shear of vertical and radial wind components in the eyewall and strong vertical shear of horizontal wind in the boundary layer mean vertical profiles of tke decrease sharply above the hurricane boundary layer and level off at low magnitude for al

observations of the structure and evolution of surface and flight level wind asymmetries in hurricane rita 2005 1 knowledge of the magnitude and distribution of surface winds including the structure of azimuthal asymmetries in the wind field are important factors for tropical cyclone forecasting with its ability to remotely measure surface wind speeds the stepped frequency microwave radiometer sfmr has assumed a prominent role for the operational tropical cyclone forecasting community an example of this instrument s utility is presented here where concurrent measurements of aircraft flight level and sfmr surface winds are used to document the wind field evolution over three days in hurricane rita 2005 the amplitude and azimuthal location phase of the wavenumber 1 asymmetry in the storm relative winds varied at both levels over time the peak was found to the right of storm track at both levels on the first day by the third day the peak in flight level storm relative winds remained to the right of storm track but it shifted to left of storm track at the surface resulting in a 60 degree shift between the surface and flight level and azimuthal variations in the ratio of surface to flight level winds the asymmetric differences between the surface and flight level maximum wind radii also varied indicating a vortex whose tilt was increasing

interaction between concentric eye walls in super typhoon winnie 1997 super typhoon winnie had one of the largest eye walls ever recorded in the western pacific ocean the diameter of the outer eye wall reached 370 km when winnie passed through okinawa on 16 august 1997 observations revealed a 24 hour intensity cycle of concentric eye walls after the large eye wall formed using the penn state university national center for atmospheric research mesoscale model mm5 with 3 km grid horizontal spacing on the finest nested mesh winnie was successfully simulated in terms of concentric eye walls spiral rain bands in the moat and the cycle of concentric eye walls the life cycle of concentric eye walls is found to be associated with vortex rossby wave propagation in the moat the propagation properties of the pv rainfall spiral bands are found to be consistent with predictions using vortex rossby theory the initial inward vorticity gradient at the inner edge of the outer eye wall and outward vorticity gradient at the outer edge of the inner eye wall support inward and outward pv rainfall spiral bands respectively in the moat at the lower level at the middle level only an outward vorticity gradient exists at the outer edge of the inner eye wall which permits the development of an outward pv band in the moat at initial time the inward spiral pv rain band moves faster than the outward pv rain band and both of them propagate cyclonically at 09 h when the fast inward pv band catches up to the slow outward pv band the slow outward rain band is replaced by the fast inward rain band resulting in a well developed and independent inner eye wall at 14 h after the vorticity gradient near the inner eye wall becomes stronger than that near the outer eye wall at lower level the whole convective core is attracted to the outer eye wall it finally merges with it at 37 h leaving a weak vortex in the centre the concentric eye walls of winnie interact with each other through vortex rossby waves copyright 2005 royal meteorological society

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

tropical cyclone environments over the northeastern and northwestern pacific based on era 15 analyses abstract this study uses a 1 1 lat long dataset extracted from ecmwf reanalyses for the 15 yr period 1979 93 era 15 to composite environmental characteristics and flow features in the vicinity of named tropical cyclones tcs in the eastern and western north pacific ocean basins tropical cyclones are partitioned into one of four classifications as they pass by selected locations along the axes of maximum frequency and tc tracks weak w strong s intensifying i or dissipating d results of this study show that peak values of rising motion within the same classification are greater for tc composites in the western pacific than for those in the eastern pacific the level of maximum rising motion was at or above the 500 hpa level for all locations and classifications except for the ss at our northernmost point 25 n 130 e in the western pacific their maximum upward motion occurred at 700 hpa it is also found that the latter systems contrary to all other points were located in a reg

structural and surface features of arc shaped radar echoes along an outer tropical cyclone rainband this study uses ground based dual doppler radar and surface observations to document the structural and surface features of the arc shaped radar echoes asres evident along an outer rainband of typhoon longwang as it approached northern taiwan on 1 october 2005 the particular aim of this study is to explore the possible distinction between the present case previously documented tropical cyclone rainbands tcrs and squall lines the dual doppler derived fields show that the leading precipitation of the studied asres exhibited a convective nature with a sharp horizontal gradient of reflectivity and a significant vertical extent theregionsbehindtheleadingconvectionwerecharacterizedbyband relativerear to frontflowatlowlevels and were associated with a broader area of stratiform precipitation the deep layer of front to rear flow extending from the surface to the upper troposphere was generally present ahead of the asres this flow appearstobeliftedupwardatandimmediatelyaheadoftheleadingedgeofthelow levelrear to frontflowto form rearward tilting updrafts these airflow patterns are similar to those of the convective region of squall lines but differ fundamentally from those of previously documented tcrs that were located closer to the inner core of cyclones the detailed analyses of surface fluctuations during the passage of one of the studied asresfurthershowanabruptpressurerise 2mb atemperaturedrop 48c andapronounceddeceleration of inflow air coincident with the leading heavy precipitation the evaluation presented suggests that the convectively generated cold pool may be important in influencing the structures and propagation of the studied asres

an integrated view of the 1987 australian monsoon and its mesoscale convective systems i horizontal structure this observational study is organized around three issues the forcing of the monsoon flow by embedded deep convection the thermodynamic conditions that support the convection and the structures of the mesoscale convective systems mcss that constitute much of the deep convection the monsoon convective cloudiness occurred predominantly offshore over the earth s warmest waters week long periods of widespread deep convection caused cycles of monsoon spin up culminating in tropical cyclone formation momentum transports by the convection also created smaller scale vortex pairs in the upper troposphere sounding data suggest that the convection was modulated by low level processes not by large scale deep forced ascent triggering by mesoscale boundary layer cold pool boundaries and coastlines determined specifically where convection occurred while several positive feedbacks acted to keep regional thermodynamic conditions favourable hence monsoon convection once initiated persisted as self exciting superclusters composed at any instant of many distinct mcss the observed mcss all contained areas of deep convection and stratiform precipitation areas stratiform precipitation usually evolved in place from convective cells although precipitation also occasionally fell from overhanging anvils created by upper level shear the mcss within similar synoptic wind environments tended to have similar mesoscale structures this fact reflects the effects illustrated herein of environmental winds upon the relative motions of cold pools which trigger new convective cells and stratiform precipitation areas which evolve from old convective cells

convective activity in an extratropical cyclone and its warm conveyor belt a case study combining observations and a convection permitting model simulation warm conveyor belts wcbs are important lagrangian features in extratropical cyclones for the evolution of clouds precipitation and flow dynamics according to the classical concept wcbs rise continuously from the boundary layer to the upper troposphere with ascent rates of less than 50 hpa hr recent studies identified embedded convection in wcbs with ascent rates exceeding 50 hpa hr however its significance and characteristics have not yet been analysed systematically this study presents a detailed analysis of a frontal wave cyclone that occurred during the north atlantic waveguide and downstream impact experiment nawdex and investigates the occurrence of convection with ascent rates exceeding 100 200 hpa hr embedded in the wcb a set of diagnostics based on the combination of meteosat products ecmwf data and a convection permitting simulation reveals consistently that convection occurs frequently in the warm sector of the investigated cyclone in particular in the region of the wcb these convective regions are characterized by increased surface precipitation low values of convective available potential energy and significant large scale forcing for ascent indicating that this type of convection embedded in wcbs differs from classical air mass convection with higher vertical velocities this is qualitatively confirmed by airborne radar observations of the considered cyclone with reflectivities hardly exceeding 30 dbz in the investigated wcb the ascent is not continuous but characterized by intermittent periods of very strong or even convective ascent and occasionally by short periods of descent together these results provide a refined view on the concept of wcbs and its embedded convection

convective structure of hurricanes as revealed by lightning locations cloud to ground lightning flash locations were examined for nine atlantic basin hurricanes using data from the national lightning detection network a common radial distribution in ground flash density was evident a weak maximum in the eyewall region a clear minimum 80 100 km outside the eyewall and a strong maximum in the vicinity of outer rainbands 210 290 km radius these results are consistent with the authors previous study of hurricane andrew none of the storms showed this characteristic radial structure during prehurricane stages the results support the division of precipitation in the hurricane into three distinct regimes the eyewall is a unique phenomenon but shares some attributes with deep weakly electrified oceanic monsoonal convection the region outside the eyewall and under the central dense overcast has characteristics of the trailing stratiform region of mesoscale convective systems including a relatively high fraction of positive polarity flashes the outer bands with mean maximum flash density at the 250 km radius contain the vast majority of ground flashes in the storms eyewall lightning defined as that within 40 km of the center was examined for four moderate to strong hurricanes such lightning occurred episodically during hurricane stage with 93 of hourly intervals containing no detected flashes eyewall lightning outbreaks over water always occurred at the beginning of or during times of intensification but often were indicative of the imminent end of deepening it is proposed that the existence of such inner core lightning might reveal the presence of an eyewall cycle for the one storm with available aircraft reconnaissance data eyewall cycles were reliably identified by the occurrence of inner core lightning and inner core lightning appeared only during such cycles suggestions are made as to how eyewall flashes in existing hurricanes might be used to help predict hurricane intensity change

low temperature partial magnetic self reversal in marine sediments by magnetostatic interaction of titanomagnetite and titanohematite intergrowths with various low temperature experiments performed on magnetic mineral extracts of marine sedimentary deposits from the argentine continental slope near the rio de la plata estuary a so far unreported style of partial magnetic self reversal has been detected in these sediments the sulphate methane transition smt zone is situated at depths between 4 and 8 m where reductive diagenesis severely alters the magnetic mineral assemblage throughout the sediment column magnetite and ilmenite are present together with titanomagnetite and titanohematite of varying compositions in the smt zone titano magnetite only occurs as inclusions in a siliceous matrix and as intergrowths with lamellar ilmenite and titanium rich titanohematite originating from high temperature deuteric oxidation within the volcanic host rocks these abundant structures were visualized by scanning electron microscopy and analysed by energy dispersive spectroscopy warming of field cooled and zero field cooled low temperature saturation remanence displays magnetic phase transitions of titanium rich titanohematite below 50 k and the verwey transition of magnetite a prominent irreversible decline characterizes zero field cooling of room temperature saturation remanence it typically sets out at 210 k and is most clearly developed in the lower part of the smt zone where low temperature hysteresis measurements identified 210 k as the blocking temperature range of a titanohematite phase with a curie temperature of around 240 k the mechanism responsible for the marked loss of remanence is therefore sought in partial magnetic self reversal by magnetostatic interaction of titano magnetite and titanohematite when titanohematite becomes ferrimagnetic upon cooling its spontaneous magnetic moments order antiparallel to the titano magnetite remanence causing an drastic initial decrease of global magnetization the loss of remanence during subsequent further cooling appears to result from two combined effects 1 magnetic interaction between the two phases by which the titano magnetite domain structure is substantially modified and 2 low temperature demagnetization of titano magnetite due to decreasing magnetocrystalline anisotropy the depletion of titanomagnetite and superior preservation of titanohematite is characteristic for strongly reducing sedimentary environments typical residuals of magnetic mineral assemblages derived from basaltic volcanics will be intergrowths of titanohematite lamellae with titanomagnetite relics low temperature remanence cycling is therefore proposed as a diagnostic method to magnetically characterize such alteration palaeo environments 2007 the authors journal compilation 2007 ras

importance of titanohematite in detrital remanent magnetizations of strata spanning the cretaceous paleogene boundary hell creek region montana intermediate composition titanohematite fe2 ytiyo3 with 0 5 y 0 7 is seldom the focus of paleomagnetic study and is commonly believed to be rare in nature while largely overlooked in magnetostratigraphic studies intermediate titanohematite has been identified as the dominant ferrimagnetic mineral in an array of late mesozoic and early cenozoic laramide clastic deposits throughout the central united states intermediate titanohematite is ferrimagnetic and has similar magnetic properties to titanomagnetite except its unique self reversing property due to these similarities and with detrital remanent magnetizations masking its self reversing nature intermediate titanohematite is often misidentified in sedimentary deposits past studies relied upon nonmagnetic techniques including x ray diffraction and electron microprobe analysis while these techniques can identify the presence of intermediate titanohematite they fail to test whether the mineral is the primary recorder to facilitate the identification of intermediate titanohematite in sedimentary deposits we characterize this mineral using low temperature magnetometry and high temperature susceptibility experiments and present a new identification technique based on titanohematite s self reversing property for sediments that span the cretaceous paleogene boundary hell creek region montana results from the self reversal test indicate that the majority of remanence is held by minerals that become magnetized parallel to an applied field but that intermediate self reversing titanohematite y 0 53 0 63 is an important ancillary carrier of remanence while earlier literature suggests that intermediate titanohematite is rare in nature reanalysis using specialized rock magnetic techniques may reveal that it is more abundant in the rock record particularly within depositional basins adjacent to calc alkaline volcanics than previously thought

polarimetric radar observations of the persistently asymmetric structure of tropical cyclone ingrid abstract tropical cyclone ingrid had a distinctly asymmetric reflectivity structure with an offshore maximum as it passed parallel to and over an extended coastline near a polarimetric weather radar located near darwin northern australia for the first time in a tropical cyclone polarimetric weather radar microphysical analyses are used to identify extensive graupel and rain hail mixtures in the eyewall the overall microphysical structure was similar to that seen in some other asymmetric storms that have been sampled by research aircraft both environmental shear and the land sea interface contributed significantly to the asymmetry but their relative contributions were not determined the storm also underwent very rapid changes in tangential wind speed as it moved over a narrow region of open ocean between a peninsula and the tiwi islands the time scale for changes of 10 m s 1 was of the order of 1 h there were also two distinct types of rainbands observed large scale principal bands with embedded d

a wintertime gulf coast squall line observed by edop airborne doppler radar abstract an extensive wintertime squall line on 13 january 1995 occurring along the u s gulf of mexico coastline is examined using airborne radar observations combined with conventional data analysis flight tracks with the er 2 doppler radar edop mounted on the high altitude 20 km er 2 aircraft provided a unique view of the vertical structure of this line in this paper the authors document the squall line structure and compare and contrast this structure with other published cases the squall line had several prominent features that differ from previous studies 1 the stratiform region was wide in comparison to more typical systems that are 50 100 km wide 2 the trailing stratiform region consisted of two to three separate embedded trailing bands rather than one continuous band 3 vertical motions in the trailing stratiform region were nearly twice as strong as previously reported values with mean values approaching 1 m s 1 between 7 and 9 km altitude and larger values 1 5 m s 1 in the em

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

convective contribution to the genesis of hurricane ophelia 2005 abstract the convection occurring in the tropical depression that became hurricane ophelia 2005 was investigated just prior to tropical storm formation doppler radar showed a deep wide intense convective cell of a type that has been previously thought to occur in intensifying tropical depressions but has not heretofore been documented in detail the updraft of the cell was 10 km wide 17 km deep had updrafts of 10 20 m s 1 throughout its mid to upper levels and contained a cyclonic vorticity maximum the massive convective updraft was maintained by strong positive buoyancy which was maximum at about the 10 km level probably aided by latent heat of freezing evaporative cooling and precipitation drag occurred in the rain shower of the cell but were insufficient to produce a strong downdraft or gust front outflow to force the updraft the convective updraft was fed by a layer of strong inflow that was several kilometers deep wind induced turbulence just above the ocean surface enriched the equi

finescale spiral band features within a numerical simulation of hurricane opal 1995 abstract one of the most recognizable features associated with a well organized tropical system are spiral rainbands these quasi stationary rainbands often extend hundreds of kilometers from the storm center and have been well described in the literature observational studies have since identified additional banding structures including outward propagating small scale spiral bands these rainbands may have considerable implications for core type tornadoes local wind maxima associated with downburst damage swaths as well as a role in overall hurricane dynamics as such here a numerical simulation of hurricane opal 1995 is examined with unprecedented resolution necessary to capture these small scale spiral bands opal was an intense landfalling hurricane that demonstrated small scale spiral banding features analogous to those observational studies the scale and characteristics of the simulated bands are consistent with observed small scale spiral banding of intense hurricanes a varietal of kelvi

an expanded dataset of hurricane eyewall sizes and slopes abstractusing airborne doppler radar data from 39 flights into hurricanes from 2004 to 2010 the authors examine the outward slope of the eyewall revisiting the recent studies of stern and nolan the slope of the radius of maximum winds rmw is found to increase nearly linearly with size and is uncorrelated with intensity the slope of the eyewall absolute angular momentum surface m increases with increasing size strong correlation and decreases with increasing intensity weak to moderate correlation two other measures of eyewall slope are also investigated the 20 dbz reflectivity isosurface dbz20 and the radius of maximum azimuthal mean updraft rwmax the slopes of both dbz20 and rwmax increase with their size the slope of dbz20 decreases with intensity though the correlation is weak while the slope of rwmax is uncorrelated with intensity the absolute angular momentum decreases on average along the rmw by 9 from 2 to 8 km heights with this larger dataset the previous results are genera

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

the kinematic structure of a hurricane with sea level pressure less than 900 mb abstract a national oceanic and atmospheric administration aircraft recorded the first doppler radar data in a tropical cyclone with a minimum sea level pressure mslp 50 m s 1 extended to 12 km higher than has been reported in previous hurricanes the inner eyewall contained weak

tropical cyclone kinematic structure retrieved from single doppler radar observations part iii evolution and structures of typhoon alex 1987 abstract this paper is the third of a series that focuses on the applications of the ground based velocity track display gbvtd technique and the gbvtd simplex center finding algorithm developed in the previous two papers to a real tropical cyclone tc the evolution and structure of typhoon alex 1987 including full tangential winds mean radial winds one component of the mean flow and their derived axisymmetric angular momentum and perturbation pressure fields are reconstructed from 16 volume scans 6 5 h of data with a 2 h gap from the civil aeronautic administration caa doppler radar while typhoon alex moved across the mountainous area in northern taiwan this analysis retrieves a plausible and physically consistent three dimensional primary circulation of a landfalling tc using a single ground based doppler radar highly asymmetric wind structures were resolved by the gbvtd technique where the maximum relative tangential wind at z 2 km evolved from 52 m s 1 before landfall to less than

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

a case study of severe storm development along a dryline within a synoptically active environment part i dryline motion and an eta model forecast through a case study approach the motion of a dryline on 16 may 1991 within a synoptically active environment in the southern plains along which severe storms ultimately developed is examined in detail observations from research aircraft surface mesonetwork stations mobile ballooning vehicles radar wind profilers and operational surface and upper air networks are examined and combined additionally output from the operational mesoscale eta model is examined to compare predictions of dryline motion with observations and to aid in interpretation of observations the dryline on this day advanced rapidly eastward and included formation of a bulge additionally in at least two instances it exhibited redevelopment loss of definition at one location and gain at another aircraft observations revealed that an eastward redevelopment occurred in the early afternoon and was characterized by a series of four steps along the western edge of the boundary layer moisture the westernmost and easternmost steps coincide with the locations of the dryline before and after redevelopment respectively the retreat of the dryline in the central and southern portion of the analysis domain in the late afternoon included both continuous motion and redevelopment toward the west northwest this dual mode retreat of the dryline was accompanied by gradual backing of the winds and moistening in low levels the eta model forecast initialized at 1200 utc produced dryline features that were qualitatively similar to observed fields the eastward motion of a broad area of enhanced moisture gradient agreed well with observations following an initial spinup period a north south moisture convergence axis preceded the rapid eastward motion of the dryline by several hours lack of subsidence in the air behind the modeled dryline leads to the conclusion that processes other than downward transfer of horizontal momentum by larger scale motions that would support eastward advection produced the rapid dryline motion and observed eastward dryline bulge results of diagnosing physical processes affecting model dryline motion point toward boundary layer vertical mixing coupled with advection of dry air aloft as vital components in rapid advance of the dryline eastward in this synoptically active case

probing hurricanes with stable isotopes of rain and water vapor abstract rain and water vapor were collected during flights in hurricanes olivia 1994 opal 1995 marilyn 1995 and hortense 1995 and analyzed for their stable isotopic concentrations or ratios h218o h2o and hdo h2o the spatial patterns and temporal changes of isotope ratios reflect details of a hurricane s structure evolution microphysics and water budget at all flight levels over the sea 850 475 hpa the lowest isotope ratios occur in or near regions of stratiform rains between about 50 and 250 km from the eye isotope ratios are higher in the eyewall and were particularly high in the crescent shaped eyewall of hurricane opal at a time when no rain was falling over a large area near the storm center in hurricane olivia isotope ratios decreased from 24 to 25 september after vertical and radial circulation weakened a two layer isotope model of a radially symmetric hurricane simulates these features the low isotope ratios are caused by fractionation in extensive thick precipitating cl

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

an observational and numerical study of a cold front interacting with the olympic mountains during coast iop5 abstract this paper documents the three dimensional flow and precipitation structures associated with a weak cold front interacting with the olympic mountains and the subsequent development of a puget sound convergence zone this study utilizes data collected during coast iop5 the fifth intensive observing period of the coastal observation and simulation with topography field experiment that took place on 11 12 december 1993 one of the most important data sources was a noaa p 3 aircraft which provided flight level data radar reflectivity and doppler winds as it circumnavigated the olympics initially frontal passage along the western foothills of the olympics was accompanied by a 2 3 c temperature drop a rapid wind shift to northwesterlies and an intense line of precipitation 35 45 dbz however the wind shift and associated precipitation structures attenuated when the front began to ascend the windward slopes of the olympics surface and p 3 observations document the deformation of the front

vertical structure of tropical cyclones with concentric eyewalls as seen by the trmm precipitation radar ten years of data from the tropical rainfall measurement mission satellite s precipitation radar are analyzed to determinethe typical vertical structure of the concentric eyewalls of tropical cyclones undergoing eyewall replacement the vertical structure of the secondary outer eyewall is different from the primary inner eyewall and also different from the eyewall of single eyewall storms the upper troposphere portions of the outer eyewalls are like the rainbands from which they evolve their lower tropospheric portions are more intense and more uniform than rainbands of single eyewall storms suggesting that these secondary eyewalls are forming from rainbands undergoing axisymmetrization and building from below the inner concentric eyewalls are more strongly affected by shear than are the eyewalls of single eyewall storms while the outer eyewalls are relativelyunaffectedby shear which suggeststhe outereyewall is amplifyingthe shearinduced asymmetry of the inner eyewall

the relationship between spatial variations in the structure of convective bursts and tropical cyclone intensification as determined by airborne doppler radar abstractthe relationship between radial and azimuthal variations in the composite characteristics of convective bursts cbs that is regions of the most intense upward motion in tropical cyclones

vertical structure of hurricane eyewalls as seen by the trmm precipitation radar abstractstatistical analysis of the vertical structure of radar echoes in the eyewalls of tropical cyclones shown by the tropical rainfall measurement mission trmm precipitation radar pr shows that the eyewall contains high reflectivities and high echo tops with deeper and more intense but highly intermittent echo perturbations superimposed on the basic structure the overall echo strength height of echo top and presence of intense echo perturbations all increase with vortex strength intense echo perturbations decrease in frequency with low sea surface temperatures when the pr data are normalized by the amount of radar echo in each sample and examined quadrant by quadrant relative to the direction of the environmental shear the nature of convective processes in different parts of the eyewall becomes apparent the normalized statistics of the echo intensity brightband structure and maximum echo top height show that processes generating convective precipitation are generally favored in the dow

reflectivity ice scattering and lightning characteristics of hurricane eyewalls and rainbands part ii intercomparison of observations abstract part i of this two part paper treats tropical rainfall measuring mission trmm radar passive microwave and lightning observations in hurricanes individually this paper part ii examines relationships between these parameters and implications of the relationships quantitative relationships between lightning occurrence and 85 ghz brightness temperature 37 ghz brightness temperature and radar reflectivity in the mixed phase region are established separately for hurricane eyewall regions inner rainband regions and outer rainband regions other tropical oceanic regions and tropical continental regions when any of the brightness temperature or radar parameters are held constant as controls lightning is more frequent in hurricane outer rainbands than elsewhere over tropical oceans and more frequent over continents than even in the outer rainbands reflectivity profiles associated with specific brightness temperatures are presented demonstrating a link between high altitude ice phase pre

an electrical and polarimetric analysis of the overland reintensification of tropical storm erin 2007 abstract while passing over central oklahoma on 18 19 august 2007 the remnants of tropical storm erin unexpectedly reintensified and developed an eyelike feature that was clearly discernable in weather surveillance radar 1988 doppler wsr 88d imagery during this brief reintensification period erin traversed a region of dense surface and remote sensing observation networks that provided abundant data of high spatial and temporal resolution this study analyzes data from the polarimetric koun s band radar total lightning data from the oklahoma lightning mapping array and ground flash lightning data from the national lightning detection network erin s reintensification was atypical since it occurred well inland and was accompanied by stronger maximum sustained winds and gusts 25 and 37 m s 1 respectively and lower minimum sea level pressure 1001 3 hpa than while over water radar observations reveal several similarities to those documented in mature tropical cyclones over open water including ou

self reversal explanation for the laschamp olby geomagnetic field excursion abstract the reversed natural remanent magnetisation nrm of the volcanic features at laschamp and olby chaine des puys auvergne france is commonly believed to document the youngest excursion of the geomagnetic field during the present brunhes epoch recent radiometric dating determines the age of these lavas to be 35000 45000 y continuous thermal demagnetisation indicates that under laboratory conditions the nrm of many olby samples undergoes complete or partial self reversal to a lesser extent this is also true for the laschamp material thus self reversal may be another possible explanation of the reversed nrm directions magnetic optical and microprobe analyses suggest that the self reversal mechanism is based upon magnetostatic interaction between differently oxidised titanomagnetite phases

analyzing simulated convective bursts in two atlantic hurricanes part i burst formation and development abstractunderstanding the structure and evolution of the tropical cyclone tc inner core remains an elusive challenge in tropical meteorology especially the role of transient asymmetric features such as localized strong updrafts known as convective bursts cbs this study investigates the formation of cbs and their role in tc structure and evolution using high resolution simulations of two atlantic hurricanes dean in 2007 and bill in 2009 with the weather research and forecasting wrf model several different aspects of the dynamics and thermodynamics of the tc inner core region are investigated with respect to their influence on tc convective burst development composites with cbs show stronger radial inflow in the lowest 2 km and stronger radial outflow from the eye to the eyewall around z 2 4 km than composites without cbs asymmetric vorticity associated with eyewall mesovortices appears to be a major factor in some of the radial flow anomalies that lead to cb development the anomalous outfl

observed structure of mesoscale convective systems and implications for large scale heating mesoscale convective cloud systems that produce large amounts of rain in mid latitudes and most of the rain in the tropics consist of a combination of convective and stratiform cloud the convective regions contain numerous deep cells that are often but not always arranged in lines the stratiform region is an outgrowth of the convective ensemble it lies adjacent to the convective region and is seeded by ice particles detrained from convective towers sometimes it lies to the rear of a propagating convective line while on other occasions it surrounds the convection the heating of the large scale environment by a mesoscale convective system is affected by both the convective and stratiform regions although processes such as melting and radiation are important the net heating by a system is dominated by condensation and evaporation associated with vertical air motions this paper reviews recent observational evidence regarding the mean vertical motion profiles in the convective and stratiform regions of mesoscale convective systems and the implications of these mean motions for the vertical distribution of heating of the large scale environment in both the convective and the stratiform regions vertical motions have been determined by various techniques including composites of rawinsonde and aircraft wind data single and dual doppler precipitation radar analyses and wind profiler observations in stratiform regions these data consistently show mean vertical velocity that is upward in the upper troposphere and downward in the lower troposphere the level separating upward from downward motion is located from 0 to 2 km above the 0 c level depending on location within the stratiform region diagnostic calculations show that these vertical motion profiles imply heating of the upper troposphere and cooling of lower levels by stratiform region processes data on vertical motions in the convective regions are less consistent from case to case these data sometimes indicate that the mean vertical velocity in convective regions is maximum in the lower troposphere in other cases the data indicate a maximum in the high troposphere diagnostic calculations show that heating profiles diagnosed from these two types of profile are quite different the first having a maximum of heating in the lower troposphere while the second has a maximum in the middle troposphere although it is difficult to determine whether or not the differences in estimates arise from different types of observations analysis methods or sampling strategies it seems likely that they stem from differences in the large scale environment of the different mesoscale systems the ubiquitous occurrence of stratiform regions in mesoscale convective systems and hurricanes together with their consistent heating profiles which systematically concentrate heating in upper levels while cooling lower levels are a major consideration in evaluating the interaction of mesoscale systems with the large scale environment however the consistency of the stratiform profiles from case to case indicates that the variability of net convective plus stratiform heating profiles from case to case lies primarily in the variation of the convective region profiles from one case to another it is suggested that future work should focus on the convective region vertical profiles of vertical motion and heating and on the large scale environmental factors that may control the variation of these profiles from case to case

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

surface pressure features of landfalling typhoon rainbands and their possible causes abstract this study uses temporally high resolution surface observations doppler radar and micro rain radar to document the finescale features of the two landfalling rainbands associated with typhoon longwang 2005 as they passed over northern taiwan the present case allows a unique opportunity to investigate well defined convectively active tropical cyclone rainbands over land in particular the surface pressure fluctuations observed during the passage of the two rainbands and their possible causes are explored the rainbands were predominantly convective in nature with embedded stratiform precipitation outside their inner outer edge analyses of surface observations show similar surface pressure fluctuations during the rainband s passage low high pressure with relatively strong weak cross band flow and warmer colder temperature was located inside the outer inner edge maximum minimum pressure perturbations were observed to be 1 5 1 mb with smaller magnitudes 0 4 mb outside th

kinematics of the secondary eyewall observed in hurricane rita 2005 abstractairborne doppler radar data collected from the concentric eyewalls of hurricane rita 2005 provide detailed three dimensional kinematic observations of the secondary eyewall feature the secondary eyewall radar echo shows a ring of heavy precipitation containing embedded convective cells which have no consistent orientation or radial location the axisymmetric mean structure has a tangential wind maximum within the reflectivity maximum at 2 km altitude and an elevated distribution of its strongest winds on the radially outer edge the corresponding vertical vorticity field contains a low level maximum on the inside edge which is part of a tube of increased vorticity that rises through the center of the reflectivity tower and into the midlevels the secondary circulation consists of boundary layer inflow that radially overshoots the secondary eyewall a portion of this inflowing air experiences convergence and supergradient forces that cause the air to rise and flow radially outward back into th

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

vertical structure of tropical cyclone rainbands as seen by the trmm precipitation radar abstractten years of data from the tropical rainfall measurement mission satellite s precipitation radar trmm pr show the vertical structure of tropical cyclone rainbands radar echo statistics show that rainbands have a two layered structure with distinct modes separated by the melting layer the ice layer is a combination of particles imported from the eyewall and ice left aloft as convective cells collapse this layering is most pronounced in the inner region of the storm and the layering is enhanced by storm strength the inner region rainbands are vertically confined by outflow from the eyewall but nevertheless are a combination of strong embedded convective cells and robust stratiform precipitation both of which become more pronounced in stronger cyclones changes in rainband coverage vertical structure and the amount of active convection indicate a change in the nature of rainbands between the regions inward and outward of a radius of approximately 200 km beyond this radius rainbands consis

a multiscale numerical study of hurricane andrew 1992 part vi small scale inner core structures and wind streaks abstract the objectives of part vi of this series of papers are to a simulate the finescale features of hurricane andrew 1992 using a cloud resolving grid length of 2 km b diagnose the formation of small scale wind streaks and c perform sensitivity experiments of varying surface fluxes on changes in storm inner core structures and intensity as compared to observations and a previous 6 km model run the results show that a higher resolution explicit simulation could produce significant improvements in the structures and evolution of the inner core eyewall and spiral rainbands and in the organization of convection the eyewall becomes much more compact and symmetric with its width decreased by half and the radius of maximum wind is reduced by 10 to 20 km a zone of deep and intense potential vorticity pv is formed at the edge of the eye a ring of maximum pv is collocated in regions of maximum upward motion in the eyewall and interacts strongly with the eyewall convection the convective cor

buoyancy of convective vertical motions in the inner core of intense hurricanes part i general statistics abstract the buoyancy of hurricane convective vertical motions is studied using aircraft data from 175 radial legs collected in 14 intense hurricanes at four altitudes ranging from 1 5 to 5 5 km the data of each leg are initially filtered to separate convective scale features from background mesoscale structure convective vertical motion events called cores are identified using the criteria that the convective scale vertical velocity must exceed 1 0 m s 1 for at least 0 5 km a total of 620 updraft cores and 570 downdraft cores are included in the dataset total buoyancy is calculated from convective scale virtual potential temperature pressure and liquid water content using the mesoscale structure as the reference state core properties are summarized for the eyewall and rainband regions at each altitude characteristics of core average convective vertical velocity maximum convective vertical velocity and diameter are consistent with previous studies of hurricane convection most cores are superi

the genesis of hurricane guillermo texmex analyses and a modeling study abstract the transformation of a mesoscale convective system into hurricane guillermo was captured by aircraft and doppler wind data during the tropical experiment in mexico the early phase of the system evolves in a way very similar to previously documented mesoscale convective systems with a midlevel mesocyclone developing in the stratiform precipitation region more unusually the cyclone extends to low altitudes a weak cyclone is discernable even in the 300 m altitude wind field after another day of evolution a small surface based warm core cyclone is observed to develop within the relatively cold air associated with the mesocyclone aloft this mesocyclone develops into a hurricane over the subsequent day a nonhydrostatic axisymmetric numerical model is used to explore the evolution of the initially cold core midlevel vortex into a tropical cyclone a mesoscale midlevel showerhead is switched on in an initially quiescent tropical atmosphere overlying a warm ocean surface evaporation of t

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

a modeling study of typhoon nari 2001 at landfall part i topographic effects abstract although there have been many observational and modeling studies of tropical cyclones understanding of their intensity and structural changes after landfall is rather limited in this study several 84 h cloud resolving simulations of typhoon nari 2001 a typhoon that produced torrential rainfall of more than 1400 mm over taiwan are carried out using a quadruply nested grid mesoscale model whose finest grid size was 2 km it is shown that the model reproduces reasonably well nari s kinematic and precipitation features as well as structural changes as verified against radar and rain gauge observations these include the storm track the contraction and sizes of the eye and eyewall the spiral rainbands the rapid pressure rise 1 67 hpa h 1 during landfall and the nearly constant intensity after landfall in addition the model captures the horizontal rainfall distribution and some local rainfall maxima associated with taiwan s orography a series of sensitivity experiments are performed i

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

reflectivity ice scattering and lightning characteristics of hurricane eyewalls and rainbands part i quantitative description abstract covering december 1997 through december 1998 261 overpasses of 45 hurricanes by the tropical rainfall measuring mission trmm satellite are used to document the observed radar reflectivity values passive microwave ice scattering magnitudes and total lightning cloud to ground plus in cloud these parameters are interpreted as describing convective vigor or intensity with greater reflectivities particularly aloft greater ice scattering lower 85 and 37 ghz brightness temperatures and increased lightning frequency indicating more intense convection for each parameter the full distribution of values observed during the trmm satellite s first year is presented for specific regions properties of three regions of the hurricane eyewall inner rainband and outer rainband are treated separately and compared to other tropical oceanic and tropical continental precipitation systems reflectivity profiles and ice scattering signatures are found to be fairly similar for both hurricane and non

the accuracy of vertical air velocities from doppler radar data abstract eight methods of calculating vertical air velocity in a column are compared each method requires some or all of the following data horizontal divergence vertical precipitation velocity hydrometeor terminal fall speed and vertical air velocity boundary conditions some or all of these quantities are commonly deduced or specified by a researcher during the analysis of doppler radar data the responses of the methods to different magnitudes and behaviors of errors in the input data are examined with a monte carlo method the experiments are conducted with both random and systematic errors two idealized kinds of systematic errors are considered bias error a constant error through the column and trend error an error of constant magnitude that changes sign at the midpoint of the mass of the column the performances of the methods are mapped over error space a researcher knowing approximately the characteristics of the errors of a particular set of doppler radar data can use the results of

palaeomagnetic investigations of the palaeozoic circum sowie gory mountains ophiolitic belt in the sudetes poland summary the investigated material comprises rocks of the palaeozoic ophiolitic assemblage exposed around the sowie gory mountains massif in the sudetes in the form of the three units lza z bkowice and nowa ruda the radiometric age u pb of the rocks stated as 420 20 ma places them in the silurian a palaeomagnetic study reveals the presence of four groups of palaeomagnetic poles one of these is derived from an isolated component representing permian overprinting the second remanence component fits with the silurian results from baltica and may therefore be regarded as being of silurian age according to this interpretation the ophiolitic complex would not have been involved in tectonic action after silurian times on the other hand this component does not agree with the results of the neighbouring bohemian massif but is consistent with late carboniferous data of the european variscans in this case the other two components should be interpreted as early to mid carboniferous overprints this interpretation implies important strike slip movements in order to exclude one of these hypotheses more data are still needed

airborne dual doppler observations of an intense frontal system approaching the pacific northwest coast airborne doppler radar data collected off the pacific northwest coast by a noaa wp 3d orion aircraft over an 8 h period on 8 december 1993 during the coastal observations and simulations with topography experiment reveal the mesoscale structure of an intense frontal system while it was well offshore and as it approached within 20 km of the oregon coastline during the offshore stage a portion of the narrow coldfrontal rainband was characterized by deep convective cores pseudo dual doppler analyses characterize the kinematic and precipitation structure of the deep convection pseudo dual doppler analyses describe the subsequent evolution of the narrow cold frontal rainband as it approached to within 20 km of the oregon coast deformation of the frontal zone appeared to cause the dissipation of one of three precipitation cores contained within the dual doppler area the precipitation cores and the strong convergence zone associated with the front conformed to some degree to the shape of the coastline near cape blanco oregon as the front neared the coast changes in the prefrontal flow that occurred as the front approached the coast were qualitatively consistent with theoretical and numerical studies of upstream orographic influence comparison of pseudo dual doppler derived velocity profiles with idealized numerical model calculations suggests that the nearshore evolution of the frontal rainband was significantly affected by an upstream influence of the coastal orography

characteristics of deep tropical and subtropical convection from nadir viewing high altitude airborne doppler radar abstract this paper presents observations of deep convection characteristics in the tropics and subtropics that have been classified into four categories tropical cyclone oceanic land and sea breeze vertical velocities in the convection were derived from doppler radar measurements collected during several nasa field experiments from the nadir viewing high altitude er 2 doppler radar edop emphasis is placed on the vertical structure of the convection from the surface to cloud top sometimes reaching 18 km altitude this unique look at convection is not possible from other approaches such as ground based or lower altitude airborne scanning radars the vertical motions from the radar measurements are derived using new relationships between radar reflectivity and hydrometeor fall speed various convective properties such as the peak updraft and downdraft velocities and their corresponding altitude heights of reflectivity levels and widths of reflectivity cores are estimated the most significant

the impact of horizontal grid spacing on the microphysical and kinematic structures of strong tropical cyclones simulated with the wrf arw model abstract using the advanced weather research and forecasting numerical model the impact of horizontal grid spacing on the microphysical and kinematic structure of a numerically simulated tropical cyclone tc and their relationship to storm intensity was investigated with a set of five numerical simulations using input data for the case of hurricane rita 2005 the horizontal grid spacing of the parent domain was systematically changed such that the horizontal grid spacing of the inner nest varied from 1 to 5 km by an increment of 1 km this while keeping geographical dimensions of the domains identical within this small range of horizontal grid spacing the morphology of the simulated storms and the evolution of the kinematic and microphysics field showed noteworthy differences as grid spacing increased the model produced a wider more tilted eyewall a larger radius of maximum winds and higher amplitude low wavenumber eyewall asymmetries the coarser resolution simulations also produced larger v

kinematics and microphysics of convection in the outer rainband of typhoon nida 2016 revealed by polarimetric radar abstractthis study analyzes the microphysics of convective cells in an outer rainband of typhoon nida 2016 using data collected by a newly upgraded operational polarimetric radar in china the li

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