Abstract:
In early and late February 2024, Hubei Province experienced two rare historical disasters of low temperature, rain, snow, and freezing, the disaster of freezing rain is especially serious, in order to analyze the causes of the freezing rain and snow weather, using the daily observation datas of 82 national meteorological stations in Hubei Province and the CRA40 reanalysis products, based on the improved composite index of continued low temperature rain and snow freezing, these two processes were compared with the strongest rain, snow and freezing weather in 2008. The influence of SST on circulation was analyzed by using the CRA40 data. The results show that: (1) In February 2024, the rain and snow phases were more complex, and the freezing rain range and extremity were stronger than those in 2008, but the duration and snow depth were not as good as those in 2008. (2) The 500 hPa geopotential height anomaly is a typical distribution of favorable precipitation, and the anomaly of the western Pacific subtropical high(WPSH) is enhanced, which cooperates with the cold air in the east to form a continuous low temperature rain, snow and ice freezing weather. The first process has deeper warm layer conditions and stronger southwest water vapor, mainly freezing rain; In the second process, the cold air was relatively stronger, but the southwest water vapor weakened, it is dominated by ice particles and graupel, mixed with freezing rain during the period, and the phase of rain and snow is more complex; (3) The two processes in February 2024 occurred under the background of a moderately strong El Niño event peaking and beginning to decay, the Indian Ocean is abnormally warming and exhibits a distribution characteristic of "warm in the west and cold in the east", in the later winter, it played an important role in the abnormal enhancement of the WPSH and the abnormal enhancement of water vapor in the south. (4) The abnormally warm sea surface temperature near the Yellow Sea to the Sea of Japan in China forces an anomalous anticyclonic circulation over the Sea of Japan, blocking the eastward movement of the westerly wind belt, the southward movement of cold air intersects with the enhanced WPSH transporting southern water vapor, resulting in sustained rain, snow, and freezing weather.