2021年长兴四次冰雹过程对比分析

Comparative Analysis of Four Hail Events in Changxing in 2021

摘要: 用NCEP/NCAR 1˚ × 1˚再分析资料与湖州、杭州多普勒雷达回波资料对四次冰雹天气形成的天气学机制和雷达回波特征进行了分析，总结四次过程的相似点和不同点。结果表明，2021年长兴四次冰雹过程一次为冷涡槽后型，一次为副高边缘型，两次为副高控制型；四次冰雹过程当天均出现了30℃以上的较高气温，表明热力条件好，易形成不稳定层结；四次冰雹过程CAPE ≥ 1000 J/kg以上，K ≥ 32℃、LI ≤ −4℃、T (850~500) ≥ 26℃，WS ≥ 12 m/s，0℃及−20℃层高度适宜；极端大的K指数、整层大气可降水量、垂直风切变对大冰雹有预报意义；四次冰雹过程反射率 ≥ 60 dBz，回波顶高 ≥ 10 km，50 dBz回波伸展高度明显超过−20℃层高度，总体来看反射率依然是预报冰雹最直观最便捷的指标；VIL的大小和冰雹直径没有明确的关系，极端大的VIL对冰雹预报有意义；5月14日过程有明显中气旋、BWER、TBSS、“V”型缺口、负ZDR、低KDP等超级单体和冰雹特征。

Abstract: Using NCEP/NCAR 1˚ × 1˚ reanalysis data and Huzhou and Hangzhou Doppler radar echo data, the synoptic mechanism and radar echo characteristics of the four hail events were analyzed, and the similarities of the four processes were summarized and different points. The results show that one of the four hail events in Changxing in 2021 was the post-cold vortex type, one was the subtropical high edge type, and two were the subtropical high control type; the four hail events all had relatively high temperatures above 30˚C on the same day, indicating that the thermal under good conditions, unstable stratification is easy to form; CAPE ≥ 1000 J/kg or more in the four hail processes, K ≥ 32˚C, LI ≤ −4˚C, T (850~500) ≥ 26˚C, WS ≥ 12 m/s, 0˚C and −20˚C layer heights are suitable; the extremely large K index, the precipitable water in the whole layer of the atmosphere, and the vertical wind shear have forecast significance for large hail; the radar reflectivity of the four hail processes is ≥ 60 dBz, and the echo top height is ≥ 10 km, the extended height of the 50 dBz echo obviously exceeds the height of the −20˚C layer. Overall, the reflectivity is still the most intuitive and convenient indicator for hail forecasting; there is no clear relationship between the size of the VIL and the diameter of the hailstone, and an extremely large VIL is meaningful for hail forecasting; on May 14, there were obvious supercell and hail features such as mesocyclone, BWER, TBSS, V notch, negative ZDR, and low KDP.