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Robert A Houze - One of the best experts on this subject based on the ideXlab platform.
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dynamics of the stratiform sector of a tropical cyclone Rainband
AGU Fall Meeting Abstracts, 2013Co-Authors: Anthony C Didlake, Robert A HouzeAbstract:AbstractAirborne Doppler radar documented the stratiform sector of a Rainband within the stationary Rainband complex of Hurricane Rita. The stratiform Rainband sector is a mesoscale feature consisting of nearly uniform precipitation and weak vertical velocities from collapsing convective cells. Upward transport and associated latent heating occur within the stratiform cloud layer in the form of rising radial outflow. Beneath, downward transport is organized into descending radial inflow in response to two regions of latent cooling. In the outer, upper regions of the Rainband, sublimational cooling introduces horizontal buoyancy gradients, which produce horizontal vorticity and descending inflow similar to that of the trailing-stratiform region of a mesoscale convective system. Within the zone of heavier stratiform precipitation, melting cooling along the outer Rainband edge creates a midlevel horizontal buoyancy gradient across the Rainband that drives air farther inward beneath the brightband. The organi...
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Convective-Scale Downdrafts in the Principal Rainband of Hurricane Katrina (2005)
Monthly Weather Review, 2009Co-Authors: Anthony C Didlake, Robert A HouzeAbstract:Abstract Airborne Doppler radar data collected during the Hurricane Rainband and Intensity Change Experiment (RAINEX) document downdrafts in the principal Rainband of Hurricane Katrina (2005). Inner-edge downdrafts (IEDs) originating at 6–8-km altitude created a sharp reflectivity gradient along the inner boundary of the Rainband. Low-level downdrafts (LLDs) evidently driven by precipitation drag originated at 2–4 km within the heavy rain cells of each convective element. The IED and LLD were spatially separated by but closely associated with the updrafts within the Rainband. The IED was forced aloft by pressure perturbations formed in response to the adjacent buoyant updrafts. Once descending, the air attained negative buoyancy via evaporative cooling from the Rainband precipitation. A convective-scale tangential wind maximum tended to occur in the radial inflow at lower levels in association with the IED, which enhanced the inward flux of angular momentum at lower levels. Convergence at the base of the ...
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kinematic structure of convective scale elements in the Rainbands of hurricanes katrina and rita 2005
Journal of Geophysical Research, 2008Co-Authors: Deanna A Hence, Robert A HouzeAbstract:[1] Airborne Doppler radar data collected during the Hurricane Rainband and Intensity Change Experiment (RAINEX) show the convective-scale air motions embedded in the principal Rainbands of hurricanes Katrina and Rita. These embedded convective cells have overturning updrafts and low-level downdrafts (originating at 2–4 km) that enter the Rainband on its radially outward side and cross over each other within the Rainband as well as a strong downdraft emanating from upper levels (6+ km) on the radially inward side. These vertical motion structures repeat from one convective cell to another along each Rainband. The resulting net vertical mass transport is upward in the upwind portion of the band and greatest in the middle sector of the principal Rainband, where the updraft motions contribute generally to an increase of potential vorticity below the 3–4 km level. Because the convective cells in the middle sector are systematically located radially just inside the secondary horizontal wind maximum (SHWM), the local increase in vorticity implied by the convective mass transport is manifest locally as an increase in the strength of the SHWM at midlevels (� 4 km). The overturning updrafts of the convective cells tilt, stretch, and vertically transport vorticity such that the convergence of the vertical flux of vorticity strengthens the vorticity anomaly associated with the SHWM. This process could strengthen the SHWM by several meters per second per hour, and may explain how high wave number convective-scale features can influence a low wave number feature such as the principal Rainband, and subsequently influence the primary vortex.
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the hurricane Rainband and intensity change experiment observations and modeling of hurricanes katrina ophelia and rita
Bulletin of the American Meteorological Society, 2006Co-Authors: Robert A Houze, Shuyi S Chen, Michael M Bell, Wenchau Lee, Robert F Rogers, James A Moore, Greg Stossmeister, Jasmine Cetrone, Wei Zhao, Rita S BrodzikAbstract:The Hurricane Rainband and Intensity Change Experiment (RAINEX) used three P3 aircraft aided by high-resolution numerical modeling and satellite communications to investigate the 2005 Hurricanes Katrina, Ophelia, and Rita. The aim was to increase the understanding of tropical cyclone intensity change by interactions between a tropical cyclone's inner core and Rainbands. All three aircraft had dual-Doppler radars, with the Electra Doppler Radar (ELDORA) on board the Naval Research Laboratory's P3 aircraft, providing particularly detailed Doppler radar data. Numerical model forecasts helped plan the aircraft missions, and innovative communications and data transfer in real time allowed the flights to be coordinated from a ground-based operations center. The P3 aircraft released approximately 600 dropsondes in locations targeted for optimal coordination with the Doppler radar data, as guided by the operations center. The storms were observed in all stages of development, from tropical depression to category ...
Michael M Bell - One of the best experts on this subject based on the ideXlab platform.
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subRainband structure and dynamic characteristics in the principal Rainband of typhoon hagupit 2008
Monthly Weather Review, 2018Co-Authors: Xiaowen Tang, Wenchau Lee, Michael M BellAbstract:AbstractThe principal Rainband in tropical cyclones is currently depicted as a solitary and continuous precipitation region. However, the airborne radar observations of the principal Rainband in Typhoon Hagupit (2008) reveal multiple subRainband structures. These subbands possess many characteristics of the squall lines with trailing stratiform in the midlatitudes and are different from those documented in previous principal Rainband studies. The updraft and reflectivity cores are upright and elevated. The updraft is fed by a low-level radial outflow from the inner side. The tangential wind speed shows a clear midlevel jet on the inner side of the reflectivity core. Except for the structural similarities, the dynamics of the subbands is also similar to the squall lines. The local environment near the subbands shows little convective inhibition, modest instability, and vertical wind shear. The temperature retrieval shows a cold pool structure in the stratiform precipitation region. The estimated vertical w...
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a squall line like principal Rainband in typhoon hagupit 2008 observed by airborne doppler radar
Journal of the Atmospheric Sciences, 2014Co-Authors: Xiaowen Tang, Michael M BellAbstract:This study examines the structure and dynamics of Typhoon Hagupit’s (2008) principal Rainband using airborne radar and dropsonde observations. The convection in Hagupit’s principal Rainband was organized into a well-defined line with trailing stratiform precipitation on the inner side. Individual convective cells had intense updrafts and downdrafts and were aligned in a wavelike pattern along the line. The line-averaged vertical cross section possessed a slightly inward-tilting convective core and two branches of low-level inflow feeding the convection. The result of a thermodynamic retrieval showed a pronounced cold pool behind the convective line. The horizontal and vertical structures of this principal Rainband show characteristics that are different than the existing conceptual model and are more similar to squall lines and outer Rainbands. The unique convective structure of Hagupit’s principal Rainband was associated with veering low-level vertical wind shear and large convective instability in the environment. A quantitative assessment of the cold pool strength showed that it was quasi balanced with that of the low-level vertical wind shear. The balanced state and the structural characteristics of convection in Hagupit’s principal Rainband were dynamically consistentwith the theory ofcold pooldynamicswidely appliedtostrong andlong-livedsquall lines. Theanalyses suggest that cold pool dynamics played a role in determining the principal Rainband structure in addition to storm-scale vortex dynamics.
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the hurricane Rainband and intensity change experiment observations and modeling of hurricanes katrina ophelia and rita
Bulletin of the American Meteorological Society, 2006Co-Authors: Robert A Houze, Shuyi S Chen, Michael M Bell, Wenchau Lee, Robert F Rogers, James A Moore, Greg Stossmeister, Jasmine Cetrone, Wei Zhao, Rita S BrodzikAbstract:The Hurricane Rainband and Intensity Change Experiment (RAINEX) used three P3 aircraft aided by high-resolution numerical modeling and satellite communications to investigate the 2005 Hurricanes Katrina, Ophelia, and Rita. The aim was to increase the understanding of tropical cyclone intensity change by interactions between a tropical cyclone's inner core and Rainbands. All three aircraft had dual-Doppler radars, with the Electra Doppler Radar (ELDORA) on board the Naval Research Laboratory's P3 aircraft, providing particularly detailed Doppler radar data. Numerical model forecasts helped plan the aircraft missions, and innovative communications and data transfer in real time allowed the flights to be coordinated from a ground-based operations center. The P3 aircraft released approximately 600 dropsondes in locations targeted for optimal coordination with the Doppler radar data, as guided by the operations center. The storms were observed in all stages of development, from tropical depression to category ...
Yuqing Wang - One of the best experts on this subject based on the ideXlab platform.
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Effects of Vertical Wind Shear on Intensity and Rainfall Asymmetries of Strong Tropical Storm Bilis (2006)
2020Co-Authors: Yu Jinhua, Yuqing Wang, Tan Zhe-min, Zhe-min TanAbstract:Abstract The effects of environmental vertical wind shear (VWS) on the intensity and rainfall asymmetries in Tropical Storm (TS) Bilis (2006) have been analyzed based on the TRMM/TMI estimated surface rainfall data, the QuikSCAT wind fields, 850-hPa and 200-hPa winds of the NCEP/NCAR reanalysis, the precipitation data at 5-minute intervals from automatic weather stations over mainland China, and the best track data of TS Bilis. The results show that the simultaneous and 6h-lagged correlation coefficients between VWS and storm intensity (the minimum central sea level pressure) are 0.59145 and 0.57438 (P<0.01), respectively. The averaged VWS was found to be about 11 m s -1 and thus suppressed the intensification of Bilis. Distribution of precipitation in Bilis was highly asymmetric. The azimuthally averaged rainfall rate in the partial eyewall, however, was smaller than that in a major outer Rainband. As the storm intensified, the major Rainband showed an unusual outward propagation. The VWS had a great impact on the asymmetric distribution of precipitation. Consistent with previous modeling studies, heavy rainfall generally occurred downshear to downshear-left of the VWS vector both near and outside the eyewall, showing a strong wavenumber-one asymmetry, which was amplified as the VWS increased
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a numerical study of outer Rainband formation in a sheared tropical cyclone
Japan Geoscience Union, 2017Co-Authors: Yuqing Wang, Yihong DuanAbstract:AbstractThe dynamical process of outer Rainband formation in a sheared tropical cyclone (TC) is examined in this study using the fully compressible, nonhydrostatic TC model. After the easterly vertical wind shear of 10 m s−1 was imposed upon an intensifying strong TC, an outer Rainband characterized by a wavenumber-1 structure formed as a typical principal Rainband downshear. Further analysis indicates that the outer Rainband formation was closely connected to the activity of the inner Rainband previously formed downshear. Moving radially outward, the inner Rainband tended to be filamented owing to the strong radial gradient of angular velocity. As the inner Rainband approached the outer boundary of the inner core, convection in its middle and upwind segments reinvigorated and nascent convective cells formed upwind of the Rainband, caused mainly by the decreased filamentation and stabilization. Subsequently, the Rainband reorganized into a typical outer Rainband. Three different scenarios are found to be ...
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formation and quasi periodic behavior of outer spiral Rainbands in a numerically simulated tropical cyclone
EGUGA, 2012Co-Authors: Yuqing WangAbstract:AbstractThe formation and quasi-periodic behavior of outer spiral Rainbands in a tropical cyclone simulated in the cloud-resolving tropical cyclone model version 4 (TCM4) are analyzed. The outer spiral Rainbands in the simulation are preferably initiated near the 60-km radius, or roughly about 3 times the radius of maximum wind (RMW). After initiation, they generally propagate radially outward with a mean speed of about 5 m s−1. They are reinitiated quasi-periodically with a period between 22 and 26 h in the simulation. The inner spiral Rainbands, which form within a radius of about 3 times the RMW, are characterized by the convectively coupled vortex Rossby waves (VRWs), but the formation of outer spiral Rainbands (i.e., Rainbands formed outside a radius of about 3 times the RMW) is much more complicated. It is shown that outer spiral Rainbands are triggered by the inner-Rainband remnants immediately outside the rapid filamentation zone and inertial instability in the upper troposphere. The preferred rad...
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how do outer spiral Rainbands affect tropical cyclone structure and intensity
Journal of the Atmospheric Sciences, 2009Co-Authors: Yuqing WangAbstract:Abstract A long-standing issue on how outer spiral Rainbands affect the structure and intensity of tropical cyclones is studied through a series of numerical experiments using the cloud-resolving tropical cyclone model TCM4. Because diabatic heating due to phase changes is the main driving force of outer spiral Rainbands, their effect on the tropical cyclone structure and intensity is evaluated by artificially modifying the heating and cooling rate due to cloud microphysical processes in the model. The view proposed here is that the effect of diabatic heating in outer spiral Rainbands on the storm structure and intensity results mainly from hydrostatic adjustment; that is, heating (cooling) of an atmospheric column decreases (increases) the surface pressure underneath the column. The change in surface pressure due to heating in the outer spiral Rainbands is significant on the inward side of the Rainbands where the inertial stability is generally high. Outside the Rainbands in the far field, where the iner...
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tropical rainfall measuring mission observation and regional model study of precipitation diurnal cycle in the new guinean region
Journal of Geophysical Research, 2006Co-Authors: Li Zhou, Yuqing WangAbstract:[1] The diurnal cycle of precipitation in the New Guinean region is studied on the basis of satellite observations from Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) measurements and regional atmospheric model simulations. The study focuses on the effects of both the land-sea breeze and the orographic forcing on the diurnal evolution of precipitation during the rainy season (January–March) in the region. The 7-year TRMM PR data composite reveals several distinct features of the precipitation diurnal cycle in the region. Precipitation bands develop in the inland coastal region in the late morning to early afternoon and migrate inland from both northeast and southwest sides of the New Guinean Island following the inland penetration of the sea-breeze fronts. A separate convective Rainband develops over the central mountain ridge in the early afternoon as a result of the development of the upslope winds due to the elevated surface warming over the mountain in the morning hours. This mountain ridge Rainband intensifies and becomes the dominant Rainband as the coastal Rainbands associated with the sea-breeze fronts weaken during the late afternoon and the early evening. In the midnight to the early morning the Rainband over the mountaintop weakens as downslope winds develop and splits into two Rainbands, propagating away from the mountain ridge, one to the north and one to the south, and weakens over the lowland some distance away from the coasts. Meanwhile a coastal Rainband develops offshore on each side of the island in the late evening to midnight and remains strong through early morning before it migrates offshore. As a result, the rainfall rate peaks in the late afternoon to early evening in most land areas except for in the lowland regions between the coastlines and the mountain where the rainfall rate peaks during the midnight, while the rainfall rate peaks in the late evening to early morning in most coastal regions offshore. The distribution of the diurnal amplitude shows two maxima: one over the mountains and the other in the coastal regions offshore. Convective rainfall rate peaks in the late afternoon while stratiform rainfall rate peaks in the midnight to early morning. The latter dominates the large diurnal amplitude over the mountain areas in the early morning. The above broad features are simulated reasonably well in a control experiment with a high-resolution regional atmospheric model. A sensitivity experiment with the terrain removed is conducted to elucidate the role of orographic forcing in the diurnal evolution of both the local circulation and rainfall patterns. The results show that the orographic forcing affects the diurnal precipitation through three major processes. First, the orography increases the moisture convergence at low levels by blocking and deflecting the mean flow. Second, the upslope winds help initiate convection in the afternoon at the mountaintop. Finally, the deep convection over the mountain acts as a source of propagating gravity waves, which help initiate Rainbands in the coastal regions offshore in the late evening to early morning. Implication of the results is discussed.
Fuqing Zhang - One of the best experts on this subject based on the ideXlab platform.
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kinematics and microphysics of convection in the outer Rainband of typhoon nida 2016 revealed by polarimetric radar
Monthly Weather Review, 2018Co-Authors: Kun Zhao, Yihong Duan, Mingjun Wang, Anthony C Didlake, Matthew R Kumjian, Xiaomin Chen, Hao Huang, Fuqing ZhangAbstract: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...
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doppler radar analysis of a tornadic miniature supercell during the landfall of typhoon mujigae 2015 in south china
Bulletin of the American Meteorological Society, 2017Co-Authors: Kun Zhao, Fuqing Zhang, Mingjun Wang, Ming Xue, Wenchau Lee, Xiaomin Chen, Zhonglin Yang, Yi Zhang, Qing LinAbstract:AbstractOn 4 October 2015, a miniature supercell embedded in an outer Rainband of Typhoon Mujigae produced a major tornado in Guangdong province of China, leading to 4 deaths and up to 80 injuries. This study documents the structure and evolution of the tornadic miniature supercell using coastal Doppler radars, a sounding, videos, and a damage survey. This tornado is rated at least EF3 on the enhanced Fujita scale. It is by far the strongest typhoon Rainband tornado yet documented in China, and possessed double funnels near its peak intensity.Radar analysis indicates that this tornadic miniature supercell exhibited characteristics similar to those found in United States landfalling hurricanes, including a hook echo, low-level inf low notches, an echo top below 10 km, a small and shallow mesocyclone, and a long lifespan (3 h). The environmental conditions—which consisted of moderate convective available potential energy (CAPE), a low lifting condensation level, a small surface dewpoint depression, a large ...
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multiscale processes leading to supercells in the landfalling outer Rainbands of hurricane katrina 2005
Weather and Forecasting, 2011Co-Authors: Benjamin Green, Fuqing ZhangAbstract:AbstractShallow supercells are frequently observed within the outer Rainbands—both onshore and offshore—of landfalling tropical cyclones (TCs). Such supercells can produce tornadoes along the coast even when the center of the parent TC is hundreds of kilometers from land, as was the case with Hurricane Katrina (2005). A convection-permitting simulation with 1.5-km grid spacing in the innermost domain is used in conjunction with radar, radiosonde, and surface observations to investigate the multiscale conditions conducive to supercells in the landfalling outer Rainbands of Katrina. Several hours before the eye of the TC made landfall, a baroclinic zone developed along the coast; this front strongly influenced the horizontal distributions of cell-relative helicity and CAPE such that the largest values of these parameters were located over land and water, respectively. An example of a tornadic supercell in the outer Rainbands of Katrina is examined. This cell intensified just before landfall and spawned a to...
Peter V Hobbs - One of the best experts on this subject based on the ideXlab platform.
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a squall like narrow cold frontal Rainband diagnosed by combined thermodynamic and cloud microphysical retrieval
Atmospheric Research, 1995Co-Authors: Bart Geerts, Peter V HobbsAbstract:Abstract Doppler radar, airborne, and sounding data are used to describe the structure of an exceptionally vigorous narrow cold-frontal Rainband (NCFR). A combined thermodynamic and cloud microphysical retrieval technique is used to derive the pressure perturbations and buoyancy in balance with the flow field in the vicinity of the NCFR. The NCFR was triggered by a well-defined cold front that penetrated beneath a deep layer of conditionally unstable prefrontal air. The Rainband, which persisted for ∼ 6 h, was located over the Gulf Stream, just off the mid-Atlantic Coast of the U.S.A. It consisted of a series of short-lived cells with updraft maxima between 5 and 15 m s −1 and tops around 12 km. The updraft associated with the NCFR was driven primarily by buoyancy in the middle troposphere, which explains its convective nature. Trailing behind the NCFR was a broad region of stratiform precipitation. Pressure perturbations in the NCFR and the trailing stratiform region were produced mainly by a combination of frontal convergence and buoyancy opposition. The pressure perturbations surrounding the cells within the Rainband were due primarily to strong updrafts in the presence of wind shear parallel to the Rainband. The same dynamic and cloud microphysical processes that operate in stratiform regions behind some squall lines were present in this NCFR. However, in contrast to a squall line with a trailing stratiform region, the low-level cold pool that penetrated beneath the NCFR was maintained primarily by strong cold advection, rather than by evaporational cooling in a shallow rear-to-front flow. The preponderance of advective over diabatic cooling can be used as a criterion to diagnostically differentiate between NCFRs and squall lines.
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structure and evolution of winter cyclones in the central united states and their effects on the distribution of precipitation part i a synoptic scale Rainband associated with a dryline and lee trough
Monthly Weather Review, 1995Co-Authors: Jonathan E Martin, John D Locatelli, Peter V Hobbs, Pengyun Wang, Jeffrey A CastleAbstract:Abstract A convective Rainband, which was approximately 1500 km in length and affected large areas of the central United States for about 16 h, developed within an evolving winter cyclone. The Rainband, which will be referred to as the pre-drytrough Rainband, formed approximately 400 km ahead of a developing dryline and lee trough (drytrough, for short) that created an elevated, sloping layer of convective instability. The presence of a deep pool of high-potential-temperature air in the middle troposphere over the south-central United States, advected there from the elevated terrain to the southwest (i.e., an elevated mixed layer), produced a region of warm-air advection downstream of the high terrain. This enhanced the lifting associated with a migrating short wave aloft and generated the pre-drytrough Rainband. In previous studies the dryline, the lee trough, the elevated mixed layer, and the low-level jet in the central United States have generally been viewed as isolated features. Here the authors pre...
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a wide cold frontal Rainband and its relationship to frontal topography
Quarterly Journal of the Royal Meteorological Society, 1994Co-Authors: John D Locatelli, Jonathan E Martin, Peter V HobbsAbstract:A wide cold-frontal Rainband associated with a vigorous surface cold front was investigated using conventional meteorological data and the velocity and reflectivity data from high-resolution Doppler radar. It was found that the movement of the Rainband was closely related to the velocity of the frontal surface, and that the substructural features of the Rainband corresponded closely with the topographical features of that surface. The evolution of the topography of the frontal surface is described, and some processes that might affect frontal topography, and therefore the structure and movement of Rainbands, are examined.
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organization and structure of clouds and precipitation on the mid atlantic coast of the united states part iv retrieval of the thermodynamic and cloud microphysical structures of a frontal Rainband from doppler radar data
Journal of the Atmospheric Sciences, 1991Co-Authors: Bart Geerts, Peter V HobbsAbstract:Abstract The thermodynamic and cloud structure of a relatively weak wintertime frontal Rainband are derived from dual-Doppler radar measurements, soundings and high resolution surface observations, and with a cloud model. These derivations are simplified by the high degree of two-dimensionality and steadiness of the Rainband. Water vapor, cloud water, cloud ice, rain, and snow are parameterized in the cloud model, subject to a temperature distribution that is constrained to a dynamical balance. Air temperature is derived from buoyancy, which is retrieved from the airflow assuming momentum and heat balance. The results of the thermodynamic and cloud microphysical retrieval are compared with airborne measurements in the Rainband. The analysis indicates that the Rainband was driven by a weak cold front aloft (CFA), which made the prefrontal air conditionally symmetrically unstable. The CFA appeared as a midlevel intrusion of cold, dry air on the mesoγ scale. The CFA interacted dynamically with the planetary ...
