State of the climate in the Three Gorges Region of the Yangtze River basin in 2020

In 2020, the average air temperature in the Three Gorges Region (TGR) of the Yangtze River basin was 17.2°C, which was close to normal, there were exceptionally fewer days than normal with high temperatures, and the high-temperature events mainly occurred in August. Meanwhile, the average precipitation was 1530.8 mm, which was a remarkable 29% more than usual, and the second-highest since 1961. The precipitation was obviously above-normal in summer, and the precipitation in both June and July was the second-highest of the same period in history. The average number of rainstorm days was higher than normal, and the second-highest since 1961. The average wind speed in the TGR was apparently higher than normal; the average relative humidity was slightly higher than normal; and there were no instances of acid rain, with the rain acidity showing a significant weakening trend over the previous 15 years. In the summer of 2020, the TGR experienced heavy rainstorms and flood disasters. Analysis shows that the frequent southward movement of cold air and abundant warm water vapor from the southwest were the direct causes of the abnormally high precipitation in the TGR from June to July. After the spring of 2020, the continuously high sea surface temperature in the Indian Ocean led to a continuously strong western Pacific subtropical high and its average location being situated more to the south than normal, which might have been an important cause for the abnormal climate conditions in the Yangtze River basin from June to July. 摘要 2020年, 长江三峡地区年平均气温17.2°C, 接近常年; 年平均降水量1530.8毫米, 偏多29%, 为1961年以来第二多, 仅次于1998年. 6月, 7月降水量及年平均暴雨日数均为1961年以来第二多. 平均风速较常年偏大; 相对湿度略偏高; 各月均无酸雨出现, 近十余年酸雨强度呈现明显减弱趋势. 2020年, 三峡地区夏季暴雨洪涝灾害重. 分析表明, 冷空气频繁南下与西南暖湿水汽丰沛是造成三峡地区6–7月降水异常偏多的直接原因. 2020年春季以来, 印度洋海温持续偏暖导致西北太平洋副热带高压持续偏强偏南可能是造成6–7月长江流域气候异常的重要原因.