scholarly journals Characteristic Analysis of the Downburst in Greely, Colorado on 30 July 2017 Using WPEA Method and X-Band Radar Observations

Atmosphere ◽  
2018 ◽  
Vol 9 (9) ◽  
pp. 348 ◽  
Author(s):  
Hao Wang ◽  
Venkatachalam Chandrasekar ◽  
Jianxin He ◽  
Zhao Shi ◽  
Lijuan Wang
Keyword(s):  
Phase Distribution ◽  
Potential Temperature ◽  
Ground Surface ◽  
Dual Polarization ◽  
Characteristic Analysis ◽  
Radar Observations ◽  
X Band ◽  
Future Events ◽  
Low Altitude ◽  
Differential Reflectivity

As a manifestation of low-altitude wind shear, a downburst is a localized, strong downdraft that can lead to disastrous wind on the ground surface. For effective pre-warning and forecasting of downbursts, it is particularly critical to understand relevant weather features that occur before and during a downburst process. It is important to identify the macroscopic features associated with the downburst weather process before considering fine-scale observations because this would greatly increase the accuracy and timeliness of forecasts. Therefore, we applied the wind-vector potential-temperature energy analysis (WPEA) method and CSU-CHILL X-band dual-polarization radar to explore the features of the downburst process. Here it was found that prior to the occurrence of the downburst of interest, the specific areas that should be monitored in future events could be determined by studying the atmospherically unstable areas using the WPEA method. Combining the WPEA method with dual-polarization radar observations, we can better distinguish the phase distribution of the hydrometeor in the process and greatly enhance the judgment of the possibility of the downburst. From exploration of the microphysical features of the downburst, we further found that ‘Zdr (differential reflectivity) column’ can be regarded as an important early warning indicator of the location of the downburst. Finally, a schematic of the formation process of the downburst according to the analyses was produced.

scholarly journals Rapid-Scan Radar Observations of an Oklahoma Tornadic Hailstorm Producing Giant Hail

2018 ◽  
Vol 33 (5) ◽  
pp. 1263-1282 ◽  
Author(s):  
Arthur Witt ◽  
Donald W. Burgess ◽  
Anton Seimon ◽  
John T. Allen ◽  
Jeffrey C. Snyder ◽  
...  
Keyword(s):  
Phased Array ◽  
Rotational Velocity ◽  
Weather Radar ◽  
Dual Polarization ◽  
Radar Observations ◽  
Rapid Scan ◽  
Phased Array Radar ◽  
X Band ◽  
Low Altitude ◽  
Rapid Scanning

Abstract Rapid-scan radar observations of a supercell that produced near-record size hail in Oklahoma are examined. Data from the National Weather Radar Testbed Phased Array Radar (PAR) in Norman, Oklahoma, are used to study the overall character and evolution of the storm. Data from the nearby polarimetric KOUN WSR-88D and rapid-scanning X-band polarimetric (RaXPol) mobile radar are used to study the evolution of low- to midaltitude dual-polarization parameters above two locations where giant hailstones up to 16 cm in diameter were observed. The PAR observation of the supercell’s maximum storm-top divergent outflow is similar to the strongest previously documented value. The storm’s mesocyclone rotational velocity at midaltitudes reached a maximum that is more than double the median value for similar observations from other storms producing giant hail. For the two storm-relative areas where giant hail was observed, noteworthy findings include 1) the giant hail occurred outside the main precipitation core, in areas with low-altitude reflectivities of 40–50 dBZ; 2) the giant hail was associated with dual-polarization signatures consistent with past observations of large hail at 10-cm wavelength, namely, low ZDR, low ρHV, and low KDP; 3) the giant hail fell along both the northeast and southwest edges of the primary updraft at ranges of 6–10 km from the updraft center; and 4) with the exception of one isolated report, the giant hail fell to the northeast and northwest of the large tornado and the parent mesocyclone.

scholarly journals Determination of ice water content (IWC) in tropical convective clouds from X-band dual-polarization airborne radar

2019 ◽  
Vol 12 (11) ◽  
pp. 5897-5911 ◽  
Author(s):  
Cuong M. Nguyen ◽  
Mengistu Wolde ◽  
Alexei Korolev
Keyword(s):  
Water Content ◽  
Ice Crystals ◽  
Airborne Radar ◽  
Dual Polarization ◽  
Differential Phase ◽  
Convective Clouds ◽  
X Band ◽  
Ice Water Content ◽  
Differential Reflectivity ◽  
Ice Water

Abstract. This paper presents a methodology for ice water content (IWC) retrieval from a dual-polarization side-looking X-band airborne radar. Measured IWC from aircraft in situ probes is weighted by a function of the radar differential reflectivity (Zdr) to reduce the effects of ice crystal shape and orientation on the variation in IWC – specific differential phase (Kdp) joint distribution. A theoretical study indicates that the proposed method, which does not require a knowledge of the particle size distribution (PSD) and number density of ice crystals, is suitable for high-ice-water-content (HIWC) regions in tropical convective clouds. Using datasets collected during the High Altitude Ice Crystals – High Ice Water Content (HAIC-HIWC) international field campaign in Cayenne, French Guiana (2015), it is shown that the proposed method improves the estimation bias by 35 % and increases the correlation by 4 % on average, compared to the method using specific differential phase (Kdp) alone.

scholarly journals A Comparison of X-Band Polarization Parameters with In Situ Microphysical Measurements in the Comma Head of Two Winter Cyclones

2016 ◽  
Vol 55 (12) ◽  
pp. 2549-2574 ◽  
Author(s):  
Joseph A. Finlon ◽  
Greg M. McFarquhar ◽  
Robert M. Rauber ◽  
David M. Plummer ◽  
Brian F. Jewett ◽  
...  
Keyword(s):  
Sample Volume ◽  
Dual Polarization ◽  
Axis Ratio ◽  
Winter Storms ◽  
Frequency Distributions ◽  
X Band ◽  
Data Points ◽  
Measured Polarization ◽  
Differential Reflectivity

AbstractSince the advent of dual-polarization radar, methods of classifying hydrometeors by type from measured polarization variables have been developed. The deterministic approach of existing hydrometeor classification algorithms of assigning only one dominant habit to each radar sample volume does not properly consider the distribution of habits present in that volume, however. During the Profiling of Winter Storms field campaign, the “NSF/NCAR C-130” aircraft, equipped with in situ microphysical probes, made multiple passes through the comma heads of two cyclones as the Mobile Alabama X-band dual-polarization radar performed range–height indicator scans in the same plane as the C-130 flight track. On 14–15 February and 21–22 February 2010, 579 and 202 coincident data points, respectively, were identified when the plane was within 10 s (~1 km) of a radar gate. For all particles that occurred for times within different binned intervals of radar reflectivity ZHH and of differential reflectivity ZDR, the reflectivity-weighted contribution of each habit and the frequency distributions of axis ratio and sphericity were determined. This permitted the determination of habits that dominate particular ZHH and ZDR intervals; only 40% of the ZHH–ZDR bins were found to have a habit that contributes over 50% to the reflectivity in that bin. Of these bins, only 12% had a habit that contributes over 75% to the reflectivity. These findings show the general lack of dominance of a given habit for a particular ZHH and ZDR and suggest that determining the probability of specific habits in radar volumes may be more suitable than the deterministic methods currently used.

scholarly journals Coupling X-band dual-polarized mini-radars and hydro-meteorological forecast models: the HYDRORAD project

2013 ◽  
Vol 13 (5) ◽  
pp. 1229-1241 ◽  
Author(s):  
E. Picciotti ◽  
F. S. Marzano ◽  
E. N. Anagnostou ◽  
J. Kalogiros ◽  
Y. Fessas ◽  
...  
Keyword(s):  
Decision Support ◽  
High Frequency ◽  
Weather Radar ◽  
Decision Support Tool ◽  
Dual Polarization ◽  
Radar Observations ◽  
Support Tool ◽  
Radar Network ◽  
X Band ◽  
Modelling System

Abstract. Hydro-meteorological hazards like convective outbreaks leading to torrential rain and floods are among the most critical environmental issues world-wide. In that context weather radar observations have proven to be very useful in providing information on the spatial distribution of rainfall that can support early warning of floods. However, quantitative precipitation estimation by radar is subjected to many limitations and uncertainties. The use of dual-polarization at high frequency (i.e. X-band) has proven particularly useful for mitigating some of the limitation of operational systems, by exploiting the benefit of easiness to transport and deploy and the high spatial and temporal resolution achievable at small antenna sizes. New developments on X-band dual-polarization technology in recent years have received the interest of scientific and operational communities in these systems. New enterprises are focusing on the advancement of cost-efficient mini-radar network technology, based on high-frequency (mainly X-band) and low-power weather radar systems for weather monitoring and hydro-meteorological forecasting. Within the above context, the main objective of the HYDRORAD project was the development of an innovative \\mbox{integrated} decision support tool for weather monitoring and hydro-meteorological applications. The integrated system tool is based on a polarimetric X-band mini-radar network which is the core of the decision support tool, a novel radar products generator and a hydro-meteorological forecast modelling system that ingests mini-radar rainfall products to forecast precipitation and floods. The radar products generator includes algorithms for attenuation correction, hydrometeor classification, a vertical profile reflectivity correction, a new polarimetric rainfall estimators developed for mini-radar observations, and short-term nowcasting of convective cells. The hydro-meteorological modelling system includes the Mesoscale Model 5 (MM5) and the Army Corps of Engineers Hydrologic Engineering Center hydrologic and hydraulic modelling chain. The characteristics of this tool make it ideal to support flood monitoring and forecasting within urban environment and small-scale basins. Preliminary results, carried out during a field campaign in Moldova, showed that the mini-radar based hydro-meteorological forecasting system can constitute a suitable solution for local flood warning and civil flood protection applications.

scholarly journals X-Band Dual-Polarization Radar Observations of Snow Growth Processes of a Severe Winter Storm: Case of 12 December 2013 in South Korea

2019 ◽  
Vol 36 (7) ◽  
pp. 1217-1235 ◽  
Author(s):  
S. Allabakash ◽  
S. Lim ◽  
V. Chandrasekar ◽  
K. H. Min ◽  
J. Choi ◽  
...  
Keyword(s):  
Polarimetric Radar ◽  
Atmospheric Conditions ◽  
Severe Winter ◽  
Dual Polarization ◽  
Winter Storm ◽  
Horizontal Polarization ◽  
Growth Processes ◽  
Radar Observations ◽  
X Band ◽  
Radar Signatures

AbstractThe characteristics of microphysical processes of a severe winter storm that occurred on the Korean Peninsula on 12 December 2013 was studied in this work for the first time via X-band dual-polarization weather radar observations. A new range–height indicator (RHI) scan-based quasi-vertical profile methodology, in which polarimetric radar variables were averaged at each height of the RHI scan, was introduced to investigate the snow microphysics, and the obtained polarimetric radar signatures served as fingerprints of the dendritic growth, aggregation, and riming processes. Enhanced differential reflectivity (Zdr) and specific differential phase shift (Kdp) bands were detected near the −15°C isotherm, which signified the growth of dendrites or platelike crystals. The observed correlation between the increases in the reflectivity factor at horizontal polarization Zh and copolar correlation coefficient ρhv and the decreases in Zdr and Kdp magnitudes at lower heights suggested the occurrence of the aggregation process. The combination of high Zh and low Zdr values with turbulent atmospheric conditions observed at the ground level indicated the occurrence of the riming process. In addition, the negative Kdp and Zdr values combined with high Zh and ρhv magnitudes (observed near the end of the snow event) indicated the formation of graupel particles. The polarimetric radar signatures obtained for the snow growth processes were evident from ground observations and agreed well with the results of the Weather Research and Forecasting Model and Modern-Era Retrospective Analysis for Research and Applications data. Furthermore, the spatial variability of Zh methodology was implemented to describe both aggregates and rimed ice particles.

Correction of X-Band Radar Observation for Propagation Effects Based on the Self-Consistency Principle

2006 ◽  
Vol 23 (12) ◽  
pp. 1668-1681 ◽  
Author(s):  
Eugenio Gorgucci ◽  
V. Chandrasekar ◽  
Luca Baldini
Keyword(s):  
Attenuation Correction ◽  
Rain Attenuation ◽  
The Self ◽  
Dual Polarization ◽  
Adaptive Sensing ◽  
Rain Medium ◽  
X Band ◽  
Differential Reflectivity ◽  
Self Consistency ◽  
New Algorithms

Abstract New algorithms for rain attenuation correction of reflectivity factor and differential reflectivity are presented. Following the methodology suggested for the first time by Gorgucci et al., the new algorithms are developed based on the self-consistency principle, describing the interrelation between polarimetric measurements along the rain medium. There is an increasing interest in X-band radar systems, owing to the early success of the attenuation-correction procedures as well as the initiative of the Center for Collaborative Adaptive Sensing of the Atmosphere to deploy X-band radars in a networked fashion. In this paper, self-consistent algorithms for correcting attenuation and differential attenuation are developed. The performance of the algorithms for application to X-band dual-polarization radars is evaluated extensively. The evaluation is conducted based on X-band dual-polarization observations generated from S-band radar measurements. Evaluation of the new self-consistency algorithms shows significant improvement in performance compared to the current class of algorithms. In the case that reflectivity and differential reflectivity are calibrated between ±1 and ±0.2 dB, respectively, the new algorithms can estimate both attenuation and differential attenuation with less than 10% bias and 15% random error. In addition, the attenuation-corrected reflectivity and differential reflectivity are within 1–0.2 dB 96% and 99% of the time, respectively, demonstrating the good performance.

scholarly journals Close-Range Observations of Tornadoes in Supercells Made with a Dual-Polarization, X-Band, Mobile Doppler Radar

2007 ◽  
Vol 135 (4) ◽  
pp. 1522-1543 ◽  
Author(s):  
Howard B. Bluestein ◽  
Michael M. French ◽  
Robin L. Tanamachi ◽  
Stephen Frasier ◽  
Kery Hardwick ◽  
...  
Keyword(s):  
Correlation Coefficient ◽  
Cross Correlation ◽  
Doppler Radar ◽  
Dual Polarization ◽  
Radar Beam ◽  
X Band ◽  
Close Range ◽  
Debris Cloud ◽  
The Cross ◽  
Differential Reflectivity

Abstract A mobile, dual-polarization, X-band, Doppler radar scanned tornadoes at close range in supercells on 12 and 29 May 2004 in Kansas and Oklahoma, respectively. In the former tornadoes, a visible circular debris ring detected as circular regions of low values of differential reflectivity and the cross-correlation coefficient was distinguished from surrounding spiral bands of precipitation of higher values of differential reflectivity and the cross-correlation coefficient. A curved band of debris was indicated on one side of the tornado in another. In a tornado and/or mesocyclone on 29 May 2004, which was hidden from the view of the storm-intercept team by precipitation, the vortex and its associated “weak-echo hole” were at times relatively wide; however, a debris ring was not evident in either the differential reflectivity field or in the cross-correlation coefficient field, most likely because the radar beam scanned too high above the ground. In this case, differential attenuation made identification of debris using differential reflectivity difficult and it was necessary to use the cross-correlation coefficient to determine that there was no debris cloud. The latter tornado’s parent storm was a high-precipitation (HP) supercell, which also spawned an anticyclonic tornado approximately 10 km away from the cyclonic tornado, along the rear-flank gust front. No debris cloud was detected in this tornado either, also because the radar beam was probably too high.

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