scholarly journals Comparison between Dual-Doppler and EnKF Storm-Scale Wind Analyses: The 29–30 May 2004 Geary, Oklahoma, Supercell Thunderstorm

2013 ◽  
Vol 141 (5) ◽  
pp. 1612-1628 ◽  
Author(s):  
Corey K. Potvin ◽  
Louis J. Wicker ◽  
Michael I. Biggerstaff ◽  
Daniel Betten ◽  
Alan Shapiro
Keyword(s):  
Doppler Radar ◽  
Three Dimensional ◽  
Radar Observations ◽  
Field Gradients ◽  
Single Moment ◽  
Supercell Thunderstorm ◽  
Model Initialization ◽  
Wind Retrievals ◽  
Microphysical Parameterization ◽  
Microphysical Parameterization Scheme

Abstract Kinematical analyses of storm-scale mobile radar observations are critical to advancing our understanding of supercell thunderstorms. Maximizing the accuracy of these analyses, and characterizing the uncertainty in ensuing conclusions about storm structure and processes, requires knowledge of the error characteristics of different retrieval techniques under different observational scenarios. Using storm-scale mobile radar observations of a tornadic supercell, this study examines the impacts on ensemble Kalman filter (EnKF) wind analyses of the number of available radars (one versus two), uncertainty in the model-initialization sounding, the sophistication of the microphysical parameterization scheme (double versus single moment), and assimilating reflectivity observations. The relative accuracy of three-dimensional variational data assimilation (3DVAR) dual-Doppler wind retrievals and single- and dual-radar EnKF wind analyses of the supercell is also explored. The results generally reinforce the findings of a previous study that used observing system simulation experiments to explore the same issues. Both studies suggest that single-radar EnKF wind analyses can be very useful once enough data have been assimilated, but that subsequent analyses that operate on the retrieved wind field gradients should be interpreted with caution. In the present study, severe errors appear to occur in computed Lagrangian circulation time series, imperiling interpretation of the underlying dynamics. This result strongly suggests that dual- and multiple-Doppler radar deployment strategies continue to be used in mobile field campaigns.

scholarly journals Comparison between Dual-Doppler and EnKF Storm-Scale Wind Analyses: Observing System Simulation Experiments with a Supercell Thunderstorm

2012 ◽  
Vol 140 (12) ◽  
pp. 3972-3991 ◽  
Author(s):  
Corey K. Potvin ◽  
Louis J. Wicker
Keyword(s):  
System Simulation ◽  
Radar Data ◽  
Model Errors ◽  
Radar Observations ◽  
Low Level ◽  
Flow Evolution ◽  
Supercell Thunderstorm ◽  
Wind Retrievals ◽  
Observing System Simulation Experiment ◽  
Microphysical Parameterization

Abstract Kinematical analyses of mobile radar observations are critical to advancing the understanding of supercell thunderstorms. Maximizing the accuracy of these and subsequent dynamical analyses, and appropriately characterizing the uncertainty in ensuing conclusions about storm structure and processes, requires thorough knowledge of the typical errors obtained using different retrieval techniques. This study adopts an observing system simulation experiment (OSSE) framework to explore the errors obtained from ensemble Kalman filter (EnKF) assimilation versus dual-Doppler analysis (DDA) of storm-scale mobile radar data. The radar characteristics and EnKF model errors are varied to explore a range of plausible scenarios. When dual-radar data are assimilated, the EnKF produces substantially better wind retrievals at higher altitudes, where DDAs are more sensitive to unaccounted flow evolution, and in data-sparse regions such as the storm inflow sector. Near the ground, however, the EnKF analyses are comparable to the DDAs when the radar cross-beam angles (CBAs) are poor, and slightly worse than the DDAs when the CBAs are optimal. In the single-radar case, the wind analyses benefit substantially from using finer grid spacing than in the dual-radar case for the objective analysis of radar observations. The analyses generally degrade when only single-radar data are assimilated, particularly when microphysical parameterization or low-level environmental wind errors are introduced. In some instances, this leads to large errors in low-level vorticity stretching and Lagrangian circulation calculations. Nevertheless, the results show that while multiradar observations of supercells are always preferable, judicious use of single-radar EnKF assimilation can yield useful analyses.

scholarly journals Simultaneous Assimilation of Radar and All-Sky Satellite Infrared Radiance Observations for Convection-Allowing Ensemble Analysis and Prediction of Severe Thunderstorms

2019 ◽  
Vol 147 (12) ◽  
pp. 4389-4409 ◽  
Author(s):  
Yunji Zhang ◽  
David J. Stensrud ◽  
Fuqing Zhang
Keyword(s):  
Doppler Radar ◽  
Three Dimensional ◽  
Lead Times ◽  
Probabilistic Prediction ◽  
Ensemble Forecasts ◽  
Radar Observations ◽  
Weather Radars ◽  
Infrared Radiance ◽  
Severe Thunderstorms ◽  
Ensemble Analysis

Abstract This study explores the benefits of assimilating infrared (IR) brightness temperature (BT) observations from geostationary satellites jointly with radial velocity (Vr) and reflectivity (Z) observations from Doppler weather radars within an ensemble Kalman filter (EnKF) data assimilation system to the convection-allowing ensemble analysis and prediction of a tornadic supercell thunderstorm event on 12 June 2017 across Wyoming and Nebraska. While radar observations sample the three-dimensional storm structures with high fidelity, BT observations provide information about clouds prior to the formation of precipitation particles when in-storm radar observations are not yet available and also provide information on the environment outside the thunderstorms. To better understand the strengths and limitations of each observation type, the satellite and Doppler radar observations are assimilated separately and jointly, and the ensemble analyses and forecasts are compared with available observations. Results show that assimilating BT observations has the potential to increase the forecast and warning lead times of severe weather events compared with radar observations and may also potentially complement the sparse surface observations in some regions as revealed by the probabilistic prediction of mesocyclone tracks initialized from EnKF analyses as various times. Additionally, the assimilation of both BT and Vr observations yields the best ensemble forecasts, providing higher confidence, improved accuracy, and longer lead times on the probabilistic prediction of midlevel mesocyclones.

scholarly journals Investigation of observational error sources in multi-Doppler-radar three-dimensional variational vertical air motion retrievals

2019 ◽  
Vol 12 (3) ◽  
pp. 1999-2018 ◽  
Author(s):  
Mariko Oue ◽  
Pavlos Kollias ◽  
Alan Shapiro ◽  
Aleksandra Tatarevic ◽  
Toshihisa Matsui
Keyword(s):  
Doppler Radar ◽  
Model Simulation ◽  
Three Dimensional ◽  
Wrf Model ◽  
Sampling Time ◽  
Added Value ◽  
Limiting Factors ◽  
Convective Systems ◽  
Air Motion ◽  
Wind Retrievals

Abstract. Multi-Doppler-radar network observations have been used in different configurations over the last several decades to conduct three-dimensional wind retrievals in mesoscale convective systems. Here, the impacts of the selected radar volume coverage pattern (VCP), the sampling time for the VCP, the number of radars used, and the added value of advection correction on the retrieval of the vertical air motion in the upper part of convective clouds are examined using the Weather Research and Forecasting (WRF) model simulation, the Cloud Resolving Model Radar SIMulator (CR-SIM), and a three-dimensional variational multi-Doppler-radar retrieval technique. Comparisons between the model truth (i.e., WRF kinematic fields) and updraft properties (updraft fraction, updraft magnitude, and mass flux) retrieved from the CR-SIM-generated multi-Doppler-radar field are used to investigate these impacts. The findings are that (1) the VCP elevation strategy and sampling time have a significant effect on the retrieved updraft properties above 6 km in altitude; (2) 2 min or shorter VCPs have small impacts on the retrievals, and the errors are comparable to retrievals using a snapshot cloud field; (3) increasing the density of elevation angles in the VCP appears to be more effective to reduce the uncertainty than an addition of data from one more radar, if the VCP is performed in 2 min; and (4) the use of dense elevation angles combined with an advection correction applied to the 2 min VCPs can effectively improve the updraft retrievals, but for longer VCP sampling periods (5 min) the value of advection correction is challenging. This study highlights several limiting factors in the retrieval of upper-level vertical velocity from multi-Doppler-radar networks and suggests that the use of rapid-scan radars can substantially improve the quality of wind retrievals if conducted in a limited spatial domain.

Polarimetric and Dual-Doppler Radar Observations of the Lipscomb County, Texas, Supercell Thunderstorm on 23 May 2002

2009 ◽  
Vol 137 (2) ◽  
pp. 544-561 ◽  
Author(s):  
Jeffrey Frame ◽  
Paul Markowski ◽  
Yvette Richardson ◽  
Jerry Straka ◽  
Joshua Wurman
Keyword(s):  
Doppler Radar ◽  
Polarimetric Radar ◽  
Vorticity Field ◽  
Radar Observations ◽  
Low Level ◽  
Mature Phase ◽  
Numerical Studies ◽  
Vorticity Generation ◽  
Supercell Thunderstorm ◽  
Dual Doppler Radar

Abstract Polarimetric and dual-Doppler observations of a supercell observed by the National Center for Atmospheric Research (NCAR) S-band Polarimetric (SPOL) radar, two Doppler-On-Wheels (DOW) radars, and the Greek XPOL radar on 23 May 2002 during the International H2O Project (IHOP) are presented. The polarimetric radar observations began as the storm organized into a supercell and continued for over an hour while the storm was in its mature phase. The hydrometeor distribution within the mature storm was retrieved using a fuzzy logic hydrometeor classification algorithm. The dual-Doppler radar observations began around the time that the polarimetric radar observations concluded, and they covered the end of the mature phase and much of the dissipation phase of the storm. The dual-Doppler wind syntheses are used to evaluate the importance of the forward-flank outflow in augmenting the horizontal vorticity field near the storm above 400 m. In this case, having a relatively weak low-level mesocyclone, the parcel trajectories and the horizontal vorticity field observed within the forward-flank outflow are not what one would likely expect based on prior numerical studies (having generally stronger low-level mesocyclones) that have emphasized an important dynamical role for forward-flank downdrafts in terms of their horizontal vorticity generation. Instead, the observed trajectories could not be traced from the forward-flank outflow toward the storm’s updraft and the horizontal vorticity vectors within the forward-flank outflow generally did not point (westward) toward the storm’s updraft.

scholarly journals Tornadogenesis in the 12 May 2010 Supercell Thunderstorm Intercepted by VORTEX2 near Clinton, Oklahoma

2018 ◽  
Vol 146 (11) ◽  
pp. 3623-3650 ◽  
Author(s):  
Paul M. Markowski ◽  
Timothy P. Hatlee ◽  
Yvette P. Richardson
Keyword(s):  
Doppler Radar ◽  
Radar Observations ◽  
Low Level ◽  
Time Period ◽  
Supercell Storms ◽  
Supercell Thunderstorm ◽  
Dual Doppler Radar

Abstract The 12 May 2010 supercell thunderstorm intercepted by the Second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) is analyzed during a time period of strong low-level rotation in which dual-Doppler radar observations were collected. Two different cyclonic vortices are documented. The first vortex was “marginally tornadic” before abruptly weakening, following the development of a descending reflectivity core (DRC) similar to those that have been documented in past studies of supercells. The second vortex rapidly developed immediately north of the DRC shortly after the DRC reached low altitudes, and was associated with a tornado that produced damage near Clinton, Oklahoma. The paper explores the possible roles of the first vortex in triggering the DRC, the DRC in the subsequent initiation of a new updraft pulse on its flank, and the updraft pulse on the development of the second, stronger vortex. The Clinton storm case is, unfortunately, a nice example of the challenges in predicting tornadogenesis within supercell storms even in environments understood to be favorable for tornadoes.

scholarly journals Comparison of single-Doppler and multiple-Doppler wind retrievals in Hurricane Matthew (2016)

2021 ◽  
Vol 14 (5) ◽  
pp. 3523-3539
Author(s):  
Ting-Yu Cha ◽  
Michael M. Bell
Keyword(s):  
Tropical Cyclone ◽  
Wind Field ◽  
Doppler Radar ◽  
Three Dimensional ◽  
Limited Information ◽  
Fourier Decomposition ◽  
Wind Retrieval ◽  
Retrieval Technique ◽  
Wind Retrievals ◽  
Doppler Analysis

Abstract. Hurricane Matthew (2016) was observed by the ground-based polarimetric Next Generation Weather Radar (NEXRAD) in Miami (KAMX) and the National Oceanic and Atmospheric Administration WP-3D (NOAA P-3) airborne tail Doppler radar near the coast of the southeastern United States for several hours, providing a novel opportunity to evaluate and compare single- and multiple-Doppler wind retrieval techniques for tropical cyclone flows. The generalized velocity track display (GVTD) technique can retrieve a subset of the wind field from a single ground-based Doppler radar under the assumption of nearly axisymmetric rotational wind, but it has been shown to have errors from the aliasing of unresolved wind components. An improved technique that mitigates errors due to storm motion is derived in this study, although some spatial aliasing remains due to limited information content from the single-Doppler measurements. A spline-based variational wind retrieval technique called SAMURAI can retrieve the full three-dimensional wind field from airborne radar fore–aft pseudo-dual-Doppler scanning, but it has been shown to have errors due to temporal aliasing from the nonsimultaneous Doppler measurements. A comparison between the two techniques shows that the axisymmetric tangential winds are generally comparable between the two techniques, and the improved GVTD technique improves the accuracy of the retrieval. Fourier decomposition of asymmetric kinematic and convective structure shows more discrepancies due to spatial and temporal aliasing in the retrievals. The strengths and weaknesses of each technique for studying tropical cyclone structure are discussed and suggest that complementary information can be retrieved from both single- and dual-Doppler retrievals. Future improvements to the asymmetric flow assumptions in single-Doppler analysis and steady-state assumptions in pseudo-dual-Doppler analysis are required to reconcile differences in retrieved tropical cyclone structure.

scholarly journals Investigation of observational error sources in multi Doppler radar vertical air motion retrievals: Impacts and possible solutions

2018 ◽  
Author(s):  
Mariko Oue ◽  
Pavlos Kollias ◽  
Alan Shapiro ◽  
Aleksandra Tatarevic ◽  
Toshihisa Matsui
Keyword(s):  
Doppler Radar ◽  
Three Dimensional ◽  
Sampling Time ◽  
Added Value ◽  
Limiting Factors ◽  
Convective System ◽  
Mesoscale Convective ◽  
Air Motion ◽  
Wind Retrievals ◽  
The Impact

Abstract. Multi-Doppler radar network observations have been used in different configurations over the last several decades to conduct three-dimensional wind retrievals in mesoscale convective systems. Here, the impact of the selected radar volume coverage pattern (VCP), the sampling time for the VCP, the number of radars used, and the added value of advection correction on the retrieval of the vertical air motion in the upper part of convective clouds is examined using the Weather Research and Forecasting (WRF) model simulation, the Cloud Resolving Model Radar SIMulator (CR-SIM) and a three-dimensional variational multi-Doppler radar retrieval technique. Comparisons between the model truth (i.e., WRF kinematic fields) and updraft properties (updraft fraction, updraft magnitude, and mass flux) retrieved from the CR-SIM-generated multi-Doppler radar field are used to investigate these impacts. In overall, the VCP elevation strategy and sampling time is found to have a significant effect on the retrieved updraft properties above 6 km altitude. Retrievals conducted using a 2-min or shorter VCPs show small impacts on the updraft retrievals, and the errors are comparable to retrievals using a snapshot cloud field. Increasing the density of elevations angles and/or an addition of data from one more radar can reduce this uncertainty. It is found that the VCP with dense elevation angles appears to be more effective than the addition of data from the fourth radar, if the VCP is performed in 2 minutes. The use of dense elevation angles combined with an advection correction applied to the 2-min VCPs can effectively improve the updraft retrievals. For longer VCP sampling periods (5 min) the errors are considerably larger, and the value of advection correction is challenging due to the rapid deformation of the dynamical structures in the simulated mesoscale convective system. This study highlights several limiting factors in the retrieval of upper-level vertical velocity from multi-Doppler radar networks and suggests that the use of rapid-scan radars can substantially improve the quality of wind retrievals if conducted in a limited spatial domain.

Preliminary Results of Weather Radar Observations of Sakurajima Volcanic Smoke

2016 ◽  
Vol 11 (1) ◽  
pp. 15-30 ◽  
Author(s):  
Masayuki Maki ◽  
◽  
Masato Iguchi ◽  
Takeshi Maesaka ◽  
Takahiro Miwa ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Doppler Radar ◽  
Three Dimensional ◽  
Weather Radar ◽  
Fall Velocity ◽  
Radar Observations ◽  
Preliminary Results ◽  
Ash Fall ◽  
X Band ◽  
Observation Instruments

Preliminary results of quantitative analysis of volcanic ash clouds observed over the Sakurajima volcano in Kagoshima, Japan, were obtained by using weather radar and surface instruments. The Ka-band Doppler radar observations showed the inner structure of a volcanic ash column every two minutes after an eruption. Operational X-band polarimetric radar provides information on three-dimensional ash fall amount distribution. The terminal fall velocity of ash particles was studied by using optical disdrometers, together with the main specifications of observation instruments.

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