Abstract:
The Yunnan-Kweichow Plateau is one of regions with high frequent hail events in China, however, the relevant studies on hail properties are few. On basis of 93 minus-level spectrum data collected from 60 hail events by 13 national meteorological stations in Honghe, southern Yunnan during 2018–2023, the annual, seasonal, daily and geographic distributions of the number of hail days, hail size and hailfall duration, as well as hail type and spectrum distribution are investigated in this study. Results show that the annual mean number of hail days was 10 d, with a maximum number of 24 d and minimum number of 3 d. The annual mean maximum hail size was 9–16 mm, and hailfall duration was 2–5 min. The number of hail days had apparent seasonal and diurnal variations. The number of hail days was 33 d in spring for six years, which accounted for more than 50 % in 60 d in total during this period, and least in autumn. The number of hail days mainly occurred in the afternoon and evening. The overall hail spectrum distribution was unimodal. There were higher hail number concentrations in spring and summer seasons with the maximum hail size of 19 mm in diameter, and was dominated by high-density hail. There was very low amount of low-density hail and graupel. Hail events had apparent geographic distribution properties. The western and southern subregions had the highest number of hail days, which was dominated by high-density hail and graupel and low-density hail were few. Therefore, hail events in the honghe region, Yunnan primarily occurred in spring and in the afternoon and evening. Hail events had short duration and were dominated by high-density small-sized hail. There was very low concentration in low-density hail and graupel.