Why is there so much rain in the north this year?

This is closely related to the anomaly of subtropical high.

In June, heavy precipitation mainly appeared in the south. In July, the subtropical high was earlier to the north than normal, and its intensity was stronger. The southeast warm and humid airflow guided by its periphery was transported to the north, which led to the early start of the rainy season in North China. Due to the strong subtropical high in the north, the eastward movement of the upper trough and the vortex system, there were two super-strong precipitation processes in the north.

The first time was an extremely heavy rainfall process in North China and Northeast China from July 1 1 to July 13. Heavy rains occurred in Beijing-Tianjin-Hebei, southeastern Shanxi, northern Henan, north-central Shandong and southern Liaoning. The daily rainfall of seven national meteorological observation stations in Hebei and Henan exceeded the maximum in July, and Jize, Hebei (206.4 mm) exceeded the historical maximum since meteorological records were recorded.

The second time was from July 17 to July 22. The heavy rainfall process in Henan, Hebei and Shanxi, in addition to the above mentioned situation, coupled with the water vapor transport support of the typhoon "Fireworks" and the blocking of the high-pressure dam on the east side, led to the slow movement of the precipitation system, and the accumulated rainfall in Henan, Shanxi and Hebei was extremely amazing.

Among them, the maximum accumulated rainfall occurred in qibin district, Hebi City (1 122.6 mm). During this rainfall period, the daily rainfall of 20 national weather stations such as Zhengzhou, Xinxiang, Hebi and Anyang * * * exceeded the historical extreme since the establishment of the station. The maximum hourly rainfall of Zhengzhou Meteorological Observatory reached 201.9mm (from 20th 16 to 17), which exceeded the historical maximum hourly rainfall of Chinese mainland (1.975, Zhuang Lin 1.98. 5mm).

In August, the subtropical high was strong to the west, and the circulation in the westerly belt in the middle and high latitudes fluctuated frequently, resulting in more continuous rainfall and convective weather, which led to more precipitation in northern China in August. By the end of August, the subtropical high was withdrawn southward, and the autumn rain in West China began ahead of schedule, which was very powerful. For example, Wanyuan in the northeast of Sichuan has a cumulative rainfall of 647mm from August 23rd to September 22nd, which is the highest since 195 1.

In big cities, the rainfall at many stations broke the extreme value. The data shows that from June/kloc-0 to September 22nd, the cumulative rainfall in Zhengzhou, Henan (1 318mm), Haidian, Beijing (1063.5mm) and Jinzhou, Liaoning (807.7mm) was June195/mm.