2023年华南开汛偏早与大气环流和海温的关系

On the Relationship between Earlier-than-usual Onset of the 2023 Rainy Season in Southern China and General Circulation and Sea Surface Temperature

采用合成、相关分析及相关物理量诊断等方法,分析了华南地区三重La Ni1a背景下2023年华南开汛偏早的大气环流和海温特征并与2022年作对比,结果表明:(1)2022和2023年3月广东降水偏多与前冬北太平洋暖海温相关,2022、2023年华南开汛偏早分别与前冬中印度洋海岭海域海温、前冬东太平洋海丘的以东海域海温增暖有关。(2)2022和2023年3月850 hPa风场华南沿海均呈现反气旋式分布,华南处于西南到偏南气流中有利水汽输送。两年开汛偏早与冷空气南下有关。(3)2022和2023年3月华南地区局地哈德莱环流在赤道附近北支上升气流加强,北支下沉支减弱且南退,在0°N—20°N范围内为负距平,有利于2022和2023年3月广东降水偏多。

By using the methods of composite and correlation analysis and diagnosing relevant physical quantities,this paper analyzed the characteristics of the general circulation and sea surface temperature(SST)for the 2023 rainy season in southern China that started earlier than usual and against the background of triple La Niña episodes.They were then compared with the case of 2022.The results are shown as fol⁃lows.(1)In Marches 2022 and 2023,it rained relatively more in Guangdong province,which was correla⁃ted with relatively warm SST in North Pacific in the winters that just passed.Rainy seasons started earlier than usual in southern China in the two years of interest,as they were respectively related with high SST in waters of the central Indian Ocean ridges and off the east of the eastern Pacific dunes in the previous winters.(2)In Marches 2022 and 2023,850-hPa wind fields were anticyclonically distributed in the coastal waters of southern China where southwesterly and southerly air flows overland were favorable for the transport of wa⁃ter vapor.The earlier-than-usual onset of the rainy season in both of the years were related with the southward movement of cold air.(3)In Marches 2022 and 2023,the northern ascending branch of a local Hadley cell in southern China strengthened over the equatorial region while the northward descending branch weakened and retreated southward,showing negative anomalies in the range from 0°N to 20°N,being con⁃ducive for the precipitation to increase over Guangdong in Marches 2022 and 2023.