Causes of rainstorm in middle and south of northeast region in July and August in 1985

First flood season in 1985 , the west wind belt circulation system is relatively active , especially after July , the west of Asia was a low tension trough area , the frontal area was more southerly than formal years , intensity was strong , the activity of cold air was frequent , cold and warm air often maintained in the area of Liaodong peninsula , which was near the 40°N , Because it often influenced by high altitude trough , that caused four rainfall events occurred in the southern and central parts of the northeast region in July.

In early and middle August, three times of typhoon successively affected south-central of northeast region, this was extremely rare in history. Characteristics of its circulation were:

The position of the western Pacific subtropical high pressure was relatively east and north than normal years , stabled near Japan , the east flow on the southern of the sub-tropical high turned to be south-east on the Yellow Sea , brought abundant water vapor . Typhoon depression along the northeast side of the sub-tropical high always meet with cold air in the west wind trough that caused the rain , directly affected the south-central part of the northeast .

By the superposition of the West wind belt ridge on the north side of the Japanese sub-tropical high, a high pressure ridge was formed in east Asia, on the western side of the high pressure ridge, from Mongolia to Inner Mongolia and northern north China were the low pressure trough, that's the Mongolia low trough, cold air met with water from the south, caused heavy precipitation.

The tropical convergence zone on the south side of the Japanese sub-tropical high was far north, on the western Pacific Ocean, There were No. 8506, 8508 and 8509 typhoon had activities. It can be seen that the Japanese sub-tropical high , Mongolia low trough and the tropical convergence zone were the main circulation background of typhoon rainstorm in South-central of northeast China .

The information is provided by Disaster Risk Reduction Knowledge Service.