关键词: 重庆, 高温干旱, 拉尼娜, 环流成因, 下沉气流

Abstract:

The La Niña event was so related to China's climate that it had a significant impact on the high temperature and drought inChongqing. In recent years, the high temperature and drought in Chongqing had repeatedly reached new highs. Studying the characteris⁃tics of high temperature and drought in the region and its response to the La Niña event can improve the prediction and early warningcapabilities of high temperature and drought in Chongqing. Based on the MCI (meteorological drought composite index), high tempera⁃ture days, NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis of circu⁃lation field data and Hadley SST (sea surface temperature) data from 1981 to 2022, the temporal and spatial distribution characteristicsof meteorological drought stations and high temperature days during summer in Chongqing were analyzed. Furthermore, the impact ofLa Niña event on summer drought stations and high temperature days in Chongqing and its circulation anomaly characteristics were ex⁃plored. The results showed that summer was the season with the highest frequency and longest duration of drought in Chongqing.Drought and high temperatures were mainly distributed in the northeast and along the Yangtze River. High temperature and meteoro⁃logical drought promoted so each other that prolonged high temperature was conducive to the development of severe drought, while pro⁃longed drought was also conducive to the occurrence of extreme maximum temperatures. In the early winter and spring, the SST in theequatorial middle east Pacific was in La Niña state, which was conducive to the occurrence of high temperature and drought in Chongq⁃ing during summer. The weak La Niña event was conducive to the occurrence of summer high temperatures in Chongqing, while themoderate intensity La Niña event was conducive to the development of drought. Both the central and eastern types of La Niña eventwere conducive to the occurrence of summer high temperatures and drought in Chongqing. The reason was that, influenced by the LaNiña event, the south Asian high pressure was larger, stronger, and northward. Affected by this, the western Pacific subtropical highwas larger, stronger, and northward. Furthermore, high-altitude jets located in the northern region of China. These factors were impor⁃tant circulation reasons for high temperature and drought in Chongqing during summer. The middle and lower layers of the tropospherein Chongqing region were controlled by weak southwest winds. Combined with the two ridges and one trough pattern of the Eurasianmid high latitude circulation, forming a climate environment that was not conducive to the southward movement of cold air. As a result,Sichuan Basin, including Chongqing had been controlled by sinking airflow for a long time, which was the main reason for frequent hightemperatures and droughts in Chongqing.

Key words: Chongqing, high temperature and drought, La Ni?a event, cause of circulation, downdraft