The rainstorm was formed when the middle and high latitude circulation situation is relatively straight, the Western Pacific subtropical high inclined to the west and north, the typhoon went to the north along the west of subtropical high and lots of warm moist air because of the typhoon convergence uplift at the Liaodong and met with the cold air.
There are always low pressure tank in the northeast of China because of the relatively flat western wind circulation in the 400- 500 N of Asian, the stable weak ridge in sea of Okhotsk and the movement of a trough to the east constantly from the cold low pressure in lake Baikal. The low pressure tank in the upper altitude combined with the cold front on the ground caused the rainstorm in the area of Hun River during the 1st and 2nd, August.
Besides, the Pacific subtropical high reached to the east coast of our country living in scattered areas, and the ridge of this high pressure was located in the north of 300 N. The 7th typhoon which landing at Fujian province caused a low-level jet stream with the airflow in the west of the Pacific subtropical high and keep going to the north quickly. The low-level jet stream brought a lot of warm moist air and unstably energy to the south of the northeast region.
The east region of Liaoning province and the south of Jilin province were located in the top of this low-level jet stream. The favorable circulation situation and the beneficial topography caused a strong convergence upward movement. Tonghua City in the south of Jilin province and the area between Grass Estuary and Gai County in the east of the Liaoning province belong to the sub-system of Changbai Mountains, and the mountains run from southwest to northeast. Among these mountains, the highest mountain is Laotuding Mountain, 1325 meters and the rainstorm mainly happened in the windward slope of this highest mountain, especially in the center of the rainstorm- Heigou of Kuandian County. The upward movement low-level jet stream became stronger than other areas because this area located in not only the windward slope but also the river valleys with the two sides are 200-500 meters high, and all of these caused the rainfall reached 503.6 millimeter from 14:00, 3rd to 14:00, 4th.
The information is provided by Disaster Risk Reduction Knowledge Service.
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