4:45 PM - 5:00 PM
[MTT38-05] Polarimetric radar analysis of a convective region that brought hail in the squall line on 3 June 2022 in the Kanto Region
Keywords:hail, X-band polarimetric radar
Hailfalls are usually brought by severe convective clouds and can cause extensive damage to agriculture, public infrastructures, vehicles and various ground objects. Hailstorms are also expected to change in response to a warming climate. In order to understand the microphysical properties of hail-producing clouds, it is important to improve our knowledge of hail formation and falling processes in the clouds.
Polarimetric radars are very effective instruments for observing the distribution of hail in the clouds. The typical radar hail signatures and their spatial distribution have been demonstrated in previous studies. However, the time evolution of the radar hail signatures is not well understood yet. In this study, we describe the time evolution of the polarimetric radar variables of a hail-producing cloud that occurred on 3 June 2022 using 4 X-band polarimetric radars in the Kanto region operated by the Ministry of Land, Infrastructure, Transport, and Tourism (MLIT). The polarimetric parameters used in the analysis are Zh (horizontal reflectivity), ZDR (differential reflectivity), KDP (specific differential phase), and ρHV (correlation coefficient between horizontal and vertical polarization signals). The hail distribution on the ground was verified using the weather report system called “Fururipo” operated by National Research Institute for Earth Science and Disaster Resilience (NIED), official hail reports from Saitama, Gunma and Chiba prefectures, and other citizens reports.
The convective region (CR) that brought hail (CR4) was part of a squall line with 5 CRs. Of the 5 CRs, only CR4 brought hail on the ground. CR4 showed two distinct hail peaks: the first hail peak from 1455 to 1535 Japan Standard Time (JST; UTC + 9 hours) and the second hail peak from 1555 to 1625 JST. During the first hail peak, CR4 showed that the representative polarimetric hail signatures of maximum Zh ≧ 55 dBZ, ZDR minima < 0 dB reaching the ground, KDP values between 3° km-1 and 7° km-1 below 2 km above sea level (ASL), and ρHV minima < 0.70 reaching the ground. These radar hail signatures were continuously observed during the first hail peak.
The evolution of polarimetric hail signatures reveals three distinct phases leading up to the first hail peak in CR4: 1) sporadic hail presence at the upper levels from 1320 to 1400 JST, 2) consistent hail presence at upper levels from 1400 to 1455 JST, and 3) ground-level hailfall from 1455 to 1535 JST. During the phase of the consistent hail presence at upper levels, the polarimetric signatures indicated sustained hail growth in the cloud. During the phase of ground-level hailfall, the polarimetric hail signatures indicated that both hail and rain, or water-coated hailstones, fell to the ground.
Polarimetric radars are very effective instruments for observing the distribution of hail in the clouds. The typical radar hail signatures and their spatial distribution have been demonstrated in previous studies. However, the time evolution of the radar hail signatures is not well understood yet. In this study, we describe the time evolution of the polarimetric radar variables of a hail-producing cloud that occurred on 3 June 2022 using 4 X-band polarimetric radars in the Kanto region operated by the Ministry of Land, Infrastructure, Transport, and Tourism (MLIT). The polarimetric parameters used in the analysis are Zh (horizontal reflectivity), ZDR (differential reflectivity), KDP (specific differential phase), and ρHV (correlation coefficient between horizontal and vertical polarization signals). The hail distribution on the ground was verified using the weather report system called “Fururipo” operated by National Research Institute for Earth Science and Disaster Resilience (NIED), official hail reports from Saitama, Gunma and Chiba prefectures, and other citizens reports.
The convective region (CR) that brought hail (CR4) was part of a squall line with 5 CRs. Of the 5 CRs, only CR4 brought hail on the ground. CR4 showed two distinct hail peaks: the first hail peak from 1455 to 1535 Japan Standard Time (JST; UTC + 9 hours) and the second hail peak from 1555 to 1625 JST. During the first hail peak, CR4 showed that the representative polarimetric hail signatures of maximum Zh ≧ 55 dBZ, ZDR minima < 0 dB reaching the ground, KDP values between 3° km-1 and 7° km-1 below 2 km above sea level (ASL), and ρHV minima < 0.70 reaching the ground. These radar hail signatures were continuously observed during the first hail peak.
The evolution of polarimetric hail signatures reveals three distinct phases leading up to the first hail peak in CR4: 1) sporadic hail presence at the upper levels from 1320 to 1400 JST, 2) consistent hail presence at upper levels from 1400 to 1455 JST, and 3) ground-level hailfall from 1455 to 1535 JST. During the phase of the consistent hail presence at upper levels, the polarimetric signatures indicated sustained hail growth in the cloud. During the phase of ground-level hailfall, the polarimetric hail signatures indicated that both hail and rain, or water-coated hailstones, fell to the ground.