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2024年2月湖北省两次雨雪冰冻过程的天气特征及海温影响

Analysis of weather characteristics and sea surface temperature impact on rain and snow freezing process in Hubei Province in February 2024

  • 摘要: 2024年2月湖北省连续发生了两次雨雪冰冻天气,尤其冻雨的灾害严重,为深入分析这两次雨雪冰冻天气的发生原因,利用湖北省82个国家气象站1961年以来逐日观测资料,基于改进的持续低温雨雪冰冻强度综合指数,将此两次过程与2008年最强雨雪冰冻天气进行了对比,并利用中国第一代全球大气再分析产品CRA40资料分析了环流异常特征及海温对环流的影响,结果表明:(1) 2024年2月两次过程雨雪相态更复杂、冻雨范围和极端性均强于2008年,但持续时间和积雪深度不及2008年;(2) 500 hPa位势高度距平场为有利降水的典型 “西低东高”分布,西太平洋副热带高压(简称西太副高)异常增强,配合东路冷空气,形成持续低温雨雪冰冻天气过程;第一次过程具有更深厚的暖层条件和更强的西南水汽,以降冻雨为主;第二次过程冷空气相对更强,但西南水汽减弱,以冰粒和霰为主,期间夹杂冻雨,雨雪相态更为复杂;(3) 2024年2月两次过程发生于一次中等偏强厄尔尼诺事件达到峰值并开始衰减的海温背景下,印度洋异常增暖且呈“西暖东冷”分布,导致后冬西太副高异常增强、南方水汽充足;(4)我国黄海至日本海附近异常暖海温在日本海上空强迫出异常反气旋环流,阻挡西风带气流东移,冷空气南下与增强的西太副高输送的南方水汽交汇,形成持续雨雪冰冻天气。

     

    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.

     

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