Analyses and Calculation of Freezing Rain Falling Zone in Southern China
Based on the improved stratification analysis method, the freezing rain fall zones and the altitudes of five severe freezing rain processes that occurred in China during 2008-2019 are calculated, and the result is verified by using the glaze data observed at 2 〖KG-*5〗000 stations and the ice disaster data of power grid. The calculated freezing rain fall zones cover both the areas with glaze and the areas with severe freezing rain disaster. The calculated altitudes of freezing rain occurrence are also consistent with the altitudes of ice disasters. The calculated results can well explain the phenomenon that there is freezing rain disaster but no glaze records under complex terrain conditions. The five calculated freezing rain fall zones are superimposed, showing that there is a freezing rain belt from Guizhou, Hunan, Jiangxi to Zhejiang, with the day number of freezing rain from high to low. The freezing rain belt can develop northward to Sichuan, Chongqing, Hubei and southern Anhui， and southward to Yunnan, Guangxi, Guangdong and northern Fujian. There is a typical cold-warm-cold stratification above the freezing rain zone. However, there is a warm-cold-warm-cold stratification above the freezing rain zone in greatly undulate terrain, such as Zhejiang and the north of Guangxi, Guangdong and Fujian, that is, there is a shallow warm layer with temperature higher than 0℃ near the surface. Therefore, the freezing rain usually occurs in the mountainous areas with an altitude above 300-400 m in Zhejiang and northern Fujian. The northeast of Guangxi and the northwest of Guangdong are also affected by the deep warm layer, and the freezing rain mostly occurs in the hillside areas with an altitude of 300-1 〖KG-*5〗300 m.