暴雨灾害 (Apr 2023)
Dual-polarization radar echo characteristics of a hail supercell event in northeastern Hunan
Abstract
Using S-band dual-polarization radar data and other observation data, a supercell storm that caused a large hail in Changsha, Hunan Province on 10 May, 2021 was analyzed. The results show as below. (1) This process takes place under the synoptic condition of low-level warm advection, high energy, and convective instability. Besides, wet bulb 0 ℃ (WBZ) is obviously lower than the height of 0℃, which provided favorable conditions for the formation and maintenance of large hail supercell storms. (2) The area of strong center (horizontal reflectivity (Zh) ≥60 dBz) and the maximum horizontal reflectivity increase significantly. The vertical integrated liquid water content increases significantly, and the height of mass center develops to reach the effective growth layer of hail, which can be used as a criterion of major hail formation and development. (3) The evolution of differential reflectivity (Zdr) column, correlation coefficient (CC), and specific differential phase (Kdp) provides the important basis for distinguishing the changes in the cloud physical process of hail. In the early stage of storm development, the appearance of Zdr column corresponds to the updraft zone, which extends above WBZ. The supercooled raindrops in the Zdr column provide hail embryos for the development of hail. The Zdr-hole (< 0 dB) corresponds to the downdraft area and expands to near the ground. Small CC and Kdp-hole indicate the appearance of dry large hail. (4) The dual-polarization monitoring and identification model of hail supercell is constructed and which shows that due to the occlusion of precipitation echo, Zh does not show the characteristics of three body scatter spike (TBSS). The polarization TBSS characteristics of significantly negative Zdr and small CC and non-uniform beam filling can be used as an important criteria for identifying hail and hail scales.
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