Why is the rainy season so short this year?

Zhou Bing, chief climate service officer of the National Climate Center, said that according to the national standard of meiyu monitoring indicators, the meiyu area in the Jianghuai basin of China can be divided into three areas: Jiangnan area, the middle and lower reaches of the Yangtze River and Jianghuai area. The latest monitoring results of the National Climate Center show that the Jiangnan region entered Mei on June 19, which was later than normal (June 8). It can be seen that the plum rains in the middle and lower reaches of the Yangtze River and the Jianghuai area also entered Mei later than normal.

The main reason is that the intensity of the western Pacific subtropical high system is relatively strong, the area is relatively large, the ridge line is located to the north, and the ridge point extending to the west is located to the west. The process of transporting water vapor from the warm and humid air flow in the western Pacific to the south of China was blocked, and the precipitation in the south was less, which delayed the meiyu process.

Therefore, compared with the annual average, the meiyu period in the three monitoring areas started late, ended early, lasted short and had less meiyu. Compared with the past three years, this year's Meiyu period has become late-short-less, and the frequency of heavy rain and heavy precipitation in the Meiyu period in Jiangnan has decreased. It is predicted that there will be an obvious retreat of the subtropical high system in the western Pacific from south to east, which is conducive to the beginning and continuation of meiyu in the Jianghuai area and the middle and lower reaches of the Yangtze River. The key is whether the position of subtropical ridge line can be relatively stable. Meiyu is different in every region every year, which brings great challenges to the forecast and service of Meiyu.