The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Ming Xue - One of the best experts on this subject based on the ideXlab platform.
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multiscale enkf assimilation of radar and conventional observations and ensemble forecasting for a tornadic mesoscale Convective System
Monthly Weather Review, 2015Co-Authors: Nathan Snook, Ming Xue, Youngsun JungAbstract:AbstractIn recent studies, the authors have successfully demonstrated the ability of an ensemble Kalman filter (EnKF), assimilating real radar observations, to produce skillful analyses and subsequent ensemble-based probabilistic forecasts for a tornadic mesoscale Convective System (MCS) that occurred over Oklahoma and Texas on 9 May 2007. The current study expands upon this prior work, performing experiments for this case on a larger domain using a nested-grid EnKF, which accounts for mesoscale uncertainties through the initial ensemble and lateral boundary condition perturbations. In these new experiments, conventional observations (including surface, wind profiler, and upper-air observations) are assimilated in addition to the WSR-88D and the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) radar data used in the previous studies, better representing meso- and Convective-scale features. The relative impacts of conventional and radar data on analyses and forecasts are examined, and bia...
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multiscale characteristics and evolution of perturbations for warm season convection allowing precipitation forecasts dependence on background flow and method of perturbation
Monthly Weather Review, 2014Co-Authors: Aaron Johnson, Xuguang Wang, Ming Xue, Fanyou Kong, Gang Zhao, Yunheng Wang, Kevin W Thomas, Keith Brewster, Jidong GaoAbstract:AbstractMultiscale convection-allowing precipitation forecast perturbations are examined for two forecasts and Systematically over 34 forecasts out to 30-h lead time using Haar Wavelet decomposition. Two small-scale initial condition (IC) perturbation methods are compared to the larger-scale IC and physics perturbations in an experimental convection-allowing ensemble. For a precipitation forecast driven primarily by a synoptic-scale baroclinic disturbance, small-scale IC perturbations resulted in little precipitation forecast perturbation energy on medium and large scales, compared to larger-scale IC and physics (LGPH) perturbations after the first few forecast hours. However, for a case where forecast convection at the initial time grew upscale into a mesoscale Convective System (MCS), small-scale IC and LGPH perturbations resulted in similar forecast perturbation energy on all scales after about 12 h. Small-scale IC perturbations added to LGPH increased total forecast perturbation energy for this case. ...
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the analysis and prediction of microphysical states and polarimetric radar variables in a mesoscale Convective System using double moment microphysics multinetwork radar data and the ensemble kalman filter
Monthly Weather Review, 2014Co-Authors: Bryan J Putnam, Ming Xue, Nathan Snook, Youngsun Jung, Guifu ZhangAbstract:AbstractDoppler radar data are assimilated with an ensemble Kalman Filter (EnKF) in combination with a double-moment (DM) microphysics scheme in order to improve the analysis and forecast of microphysical states and precipitation structures within a mesoscale Convective System (MCS) that passed over western Oklahoma on 8–9 May 2007. Reflectivity and radial velocity data from five operational Weather Surveillance Radar-1988 Doppler (WSR-88D) S-band radars as well as four experimental Collaborative and Adaptive Sensing of the Atmosphere (CASA) X-band radars are assimilated over a 1-h period using either single-moment (SM) or DM microphysics schemes within the forecast ensemble. Three-hour deterministic forecasts are initialized from the final ensemble mean analyses using a SM or DM scheme, respectively. Polarimetric radar variables are simulated from the analyses and compared with polarimetric WSR-88D observations for verification. EnKF assimilation of radar data using a multimoment microphysics scheme for ...
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tornadogenesis in a simulated mesovortex within a mesoscale Convective System
Journal of the Atmospheric Sciences, 2012Co-Authors: Alexander D Schenkman, Ming Xue, Alan ShapiroAbstract:AbstractThe Advanced Regional Prediction System (ARPS) is used to simulate a tornadic mesovortex with the aim of understanding the associated tornadogenesis processes. The mesovortex was one of two tornadic mesovortices spawned by a mesoscale Convective System (MCS) that traversed southwestern and central Oklahoma on 8–9 May 2007. The simulation used 100-m horizontal grid spacing, and is nested within two outer grids with 400-m and 2-km grid spacing, respectively. Both outer grids assimilate radar, upper-air, and surface observations via 5-min three-dimensional variational data assimilation (3DVAR) cycles. The 100-m grid is initialized from a 40-min forecast on the 400-m grid.Results from the 100-m simulation provide a detailed picture of the development of a mesovortex that produces a submesovortex-scale tornado-like vortex (TLV). Closer examination of the genesis of the TLV suggests that a strong low-level updraft is critical in converging and amplifying vertical vorticity associated with the mesovortex...
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ensemble probabilistic forecasts of a tornadic mesoscale Convective System from ensemble kalman filter analyses using wsr 88d and casa radar data
Monthly Weather Review, 2012Co-Authors: Nathan Snook, Ming Xue, Youngsun JungAbstract:AbstractThis study examines the ability of a storm-scale numerical weather prediction (NWP) model to predict precipitation and mesovortices within a tornadic mesoscale Convective System that occurred over Oklahoma on 8–9 May 2007, when the model is initialized from ensemble Kalman filter (EnKF) analyses including data from four Engineering Research Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) X-band and five Weather Surveillance Radar-1988 Doppler (WSR-88D) S-band radars. Ensemble forecasts are performed and probabilistic forecast products generated, focusing on prediction of radar reflectivity (a proxy of quantitative precipitation) and mesovortices (an indication of tornado potential).Assimilating data from both the CASA and WSR-88D radars for the ensemble and using a mixed-microphysics ensemble during data assimilation produces the best probabilistic mesovortex forecast. The use of multiple microphysics schemes within the ensemble aims to address at least partially the model physi...
Youngsun Jung - One of the best experts on this subject based on the ideXlab platform.
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multiscale enkf assimilation of radar and conventional observations and ensemble forecasting for a tornadic mesoscale Convective System
Monthly Weather Review, 2015Co-Authors: Nathan Snook, Ming Xue, Youngsun JungAbstract:AbstractIn recent studies, the authors have successfully demonstrated the ability of an ensemble Kalman filter (EnKF), assimilating real radar observations, to produce skillful analyses and subsequent ensemble-based probabilistic forecasts for a tornadic mesoscale Convective System (MCS) that occurred over Oklahoma and Texas on 9 May 2007. The current study expands upon this prior work, performing experiments for this case on a larger domain using a nested-grid EnKF, which accounts for mesoscale uncertainties through the initial ensemble and lateral boundary condition perturbations. In these new experiments, conventional observations (including surface, wind profiler, and upper-air observations) are assimilated in addition to the WSR-88D and the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) radar data used in the previous studies, better representing meso- and Convective-scale features. The relative impacts of conventional and radar data on analyses and forecasts are examined, and bia...
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the analysis and prediction of microphysical states and polarimetric radar variables in a mesoscale Convective System using double moment microphysics multinetwork radar data and the ensemble kalman filter
Monthly Weather Review, 2014Co-Authors: Bryan J Putnam, Ming Xue, Nathan Snook, Youngsun Jung, Guifu ZhangAbstract:AbstractDoppler radar data are assimilated with an ensemble Kalman Filter (EnKF) in combination with a double-moment (DM) microphysics scheme in order to improve the analysis and forecast of microphysical states and precipitation structures within a mesoscale Convective System (MCS) that passed over western Oklahoma on 8–9 May 2007. Reflectivity and radial velocity data from five operational Weather Surveillance Radar-1988 Doppler (WSR-88D) S-band radars as well as four experimental Collaborative and Adaptive Sensing of the Atmosphere (CASA) X-band radars are assimilated over a 1-h period using either single-moment (SM) or DM microphysics schemes within the forecast ensemble. Three-hour deterministic forecasts are initialized from the final ensemble mean analyses using a SM or DM scheme, respectively. Polarimetric radar variables are simulated from the analyses and compared with polarimetric WSR-88D observations for verification. EnKF assimilation of radar data using a multimoment microphysics scheme for ...
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ensemble probabilistic forecasts of a tornadic mesoscale Convective System from ensemble kalman filter analyses using wsr 88d and casa radar data
Monthly Weather Review, 2012Co-Authors: Nathan Snook, Ming Xue, Youngsun JungAbstract:AbstractThis study examines the ability of a storm-scale numerical weather prediction (NWP) model to predict precipitation and mesovortices within a tornadic mesoscale Convective System that occurred over Oklahoma on 8–9 May 2007, when the model is initialized from ensemble Kalman filter (EnKF) analyses including data from four Engineering Research Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) X-band and five Weather Surveillance Radar-1988 Doppler (WSR-88D) S-band radars. Ensemble forecasts are performed and probabilistic forecast products generated, focusing on prediction of radar reflectivity (a proxy of quantitative precipitation) and mesovortices (an indication of tornado potential).Assimilating data from both the CASA and WSR-88D radars for the ensemble and using a mixed-microphysics ensemble during data assimilation produces the best probabilistic mesovortex forecast. The use of multiple microphysics schemes within the ensemble aims to address at least partially the model physi...
Nathan Snook - One of the best experts on this subject based on the ideXlab platform.
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multiscale enkf assimilation of radar and conventional observations and ensemble forecasting for a tornadic mesoscale Convective System
Monthly Weather Review, 2015Co-Authors: Nathan Snook, Ming Xue, Youngsun JungAbstract:AbstractIn recent studies, the authors have successfully demonstrated the ability of an ensemble Kalman filter (EnKF), assimilating real radar observations, to produce skillful analyses and subsequent ensemble-based probabilistic forecasts for a tornadic mesoscale Convective System (MCS) that occurred over Oklahoma and Texas on 9 May 2007. The current study expands upon this prior work, performing experiments for this case on a larger domain using a nested-grid EnKF, which accounts for mesoscale uncertainties through the initial ensemble and lateral boundary condition perturbations. In these new experiments, conventional observations (including surface, wind profiler, and upper-air observations) are assimilated in addition to the WSR-88D and the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) radar data used in the previous studies, better representing meso- and Convective-scale features. The relative impacts of conventional and radar data on analyses and forecasts are examined, and bia...
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the analysis and prediction of microphysical states and polarimetric radar variables in a mesoscale Convective System using double moment microphysics multinetwork radar data and the ensemble kalman filter
Monthly Weather Review, 2014Co-Authors: Bryan J Putnam, Ming Xue, Nathan Snook, Youngsun Jung, Guifu ZhangAbstract:AbstractDoppler radar data are assimilated with an ensemble Kalman Filter (EnKF) in combination with a double-moment (DM) microphysics scheme in order to improve the analysis and forecast of microphysical states and precipitation structures within a mesoscale Convective System (MCS) that passed over western Oklahoma on 8–9 May 2007. Reflectivity and radial velocity data from five operational Weather Surveillance Radar-1988 Doppler (WSR-88D) S-band radars as well as four experimental Collaborative and Adaptive Sensing of the Atmosphere (CASA) X-band radars are assimilated over a 1-h period using either single-moment (SM) or DM microphysics schemes within the forecast ensemble. Three-hour deterministic forecasts are initialized from the final ensemble mean analyses using a SM or DM scheme, respectively. Polarimetric radar variables are simulated from the analyses and compared with polarimetric WSR-88D observations for verification. EnKF assimilation of radar data using a multimoment microphysics scheme for ...
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ensemble probabilistic forecasts of a tornadic mesoscale Convective System from ensemble kalman filter analyses using wsr 88d and casa radar data
Monthly Weather Review, 2012Co-Authors: Nathan Snook, Ming Xue, Youngsun JungAbstract:AbstractThis study examines the ability of a storm-scale numerical weather prediction (NWP) model to predict precipitation and mesovortices within a tornadic mesoscale Convective System that occurred over Oklahoma on 8–9 May 2007, when the model is initialized from ensemble Kalman filter (EnKF) analyses including data from four Engineering Research Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) X-band and five Weather Surveillance Radar-1988 Doppler (WSR-88D) S-band radars. Ensemble forecasts are performed and probabilistic forecast products generated, focusing on prediction of radar reflectivity (a proxy of quantitative precipitation) and mesovortices (an indication of tornado potential).Assimilating data from both the CASA and WSR-88D radars for the ensemble and using a mixed-microphysics ensemble during data assimilation produces the best probabilistic mesovortex forecast. The use of multiple microphysics schemes within the ensemble aims to address at least partially the model physi...
Edward J. Zipser - One of the best experts on this subject based on the ideXlab platform.
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Cloud-Resolving Modeling of Deep Convection during KWAJEX. Part I: Comparison to TRMM Satellite and Ground-Based Radar Observations
Monthly Weather Review, 2008Co-Authors: Yaping Li, Edward J. Zipser, Steven K Krueger, Mike A ZulaufAbstract:Abstract A global TRMM database of tropical cloud System precipitation features (PFs), which provides useful observational constraints on cloud System properties, is used to evaluate the bulk microphysics schemes in a cloud-resolving model (CRM). The simulation of the Mesoscale Convective System (MCS) of 11–12 August 1999 during the Kwajalein Experiment (KWAJEX) is executed using the 3D University of Utah CRM, which employs a one-moment bulk, three-ice category microphysical parameterization. The simulated precipitation features are compared with climatological “norms” for Kwajalein locations from the TRMM PF database to evaluate the precipitation microphysics of the cloud model simulation. The model-simulated reflectivities are also compared with vertical profiles of radar reflectivity obtained from a ground-based precipitation radar. Comparison of simulation results with the TRMM observation statistics indicates that the model tends to underestimate microwave brightness temperatures at ice-scattering fr...
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dynamical influence of microphysics in tropical squall lines a numerical study
Monthly Weather Review, 1997Co-Authors: Mitchell W. Moncrieff, Edward J. ZipserAbstract:Abstract Based on environmental conditions of the 22 and 23 June squall lines during the Convection Profonde Tropicale in 1981 (COPT81) experiment in West Africa, a series of numerical simulations are performed with a two-dimensional nonhydrostatic cloud model to examine the dynamical effect of microphysics in tropical squall lines. The role of ice-phase microphysics strongly depends on ambient conditions. For the environment of strong Convective instability, the ice phase is important regarding the System-scale structure but is not important to the Convective-scale dynamics. On the other hand, the ice influence is crucial to the squall-line Convective System if the environment has a weak Convective instability and is almost saturated at low levels.
Yuhlang Lin - One of the best experts on this subject based on the ideXlab platform.
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effects of unsaturated moist froude number and orographic aspect ratio on a conditionally unstable flow over a mesoscale mountain
Journal of the Meteorological Society of Japan, 2008Co-Authors: Shuhua Chen, Yuhlang Lin, Zhan ZhaoAbstract:Idealized numerical simulations of an unsaturated, conditionally unstable flow over a two-dimensional mountain ridge were used to study the effects of the moist Froude number (Fw) and the orographic aspect ratio of mountain height to width (h/a) on the propagation, cloud type, and pattern and amount of rainfall of orographically induced precipitation Systems. For low Fw, the flow belonged to an upstream propagating flow regime (i.e., Regime I) and was insensitive to h/a. For large Fw, both Fw and h/a dictated the precipitation pattern and the nature of the convection. When Fw was fixed, the flow shifted toward a downstream propagating regime as h/a increased. This dependence on h/a at higher wind speeds appears to be linked to the advection time and cloud growth time. A slightly larger Fw was required for the regime transition to occur when the fixed aspect ratio was small. We also found that although the local maximum rainfall was not directly controlled by Fw, the total domain rainfall was sensitive to Fw, in particular for Regimes I and II (i.e., flow with a long-lasting orographic Convective System over the mountain peak, upslope or lee slope) when the mountain half-width was fixed. On the other hand, for the unstable flow studied here, the total domain accumulated rainfall was not sensitive to h/a when Fw was fixed. It is suggested that flash floods may occur when quasi-stationary Convective precipitation Systems stay over the mountain area for flow Regime II or when abundant moisture is supplied for a significant period of time due to a low-level jet for flow Regimes III and IV, which are defined as flow with an orographic Convective precipitation System over the mountain and a downstream propagating Convective System and flow with an orographic stratiform precipitation System over the mountain and possibly a downstream propagating cloud System, respectively. In addition, local orographic rainfall from stratiform precipitation Systems (i.e., Regime IV) can be as heavy as that from Convective or mixed type precipitation Systems belonging to Regime III.
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the effects of a mountain on the propagation of a preexisting Convective System for blocked and unblocked flow regimes
Journal of the Atmospheric Sciences, 2007Co-Authors: Heather Dawn Reeves, Yuhlang LinAbstract:Abstract Observations and previous research of squall lines impinging on mountain ranges have revealed that the squall lines sometimes stall upstream of the mountains for several hours leading to copious accumulations of precipitation. It has been hypothesized that squall-line stagnation may be more prone to occur in flows where the Froude number (F = U/Nh, where U is the basic-state wind, N is the Brunt–Vaisala frequency, and h is the mountain height) is low. This hypothesis is tested herein through a series of idealized, two-dimensional experiments where a Convective System was triggered upstream of a mesoscale mountain in conditionally unstable flow. For simulations with relatively low Froude numbers, stagnation of the preexisting Convective System was not observed. In the simulations with high values of F, squall lines were noted to stagnate between 100 and 200 km upstream of the mountain. This result indicates that squall-line stagnation may be more favored for moderate to large values of F for condi...
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effects of moist froude number and cape on a conditionally unstable flow over a mesoscale mountain ridge
Journal of the Atmospheric Sciences, 2005Co-Authors: Shuhua Chen, Yuhlang LinAbstract:Abstract In this study, idealized simulations are performed for a conditionally unstable flow over a two-dimensional mountain ridge in order to investigate the propagation and types of cloud precipitation Systems controlled by the unsaturated moist Froude number (Fw) and the Convective available potential energy (CAPE). A two-dimensional moist flow regime diagram, based on Fw and CAPE, is proposed for a conditionally unstable flow passing over a two-dimensional mesoscale mountain ridge. The characteristics of these flow regimes are 1) regime I: flow with an upstream-propagating Convective System and an early, slowly moving Convective System over the mountain; 2) regime II: flow with a long-lasting orographic Convective System over the mountain peak, upslope, or lee slope; 3) regime III: flow with an orographic Convective or mixed Convective and stratiform precipitation System over the mountain and a downstream-propagating Convective System; and 4) regime IV: flow with an orographic stratiform precipitatio...