During flood happened in Heilongjiang Province , at 500hPa geopotential height circulation anormaly field prevail series ″+-+-″ quasi-stationary planetary wave and the circulation evolution tendency the fore of April-June . When flood happened , it prevail ″A″ rainfall type , or above normal in northern of China and below normal in south China . In June Prevail ″B″ rainfall type , or Huanghe River and the south of China above normal the other below normal,it is also divided by ″B1″ deputy type, or Changjiang River and Songhuajiang River above normal , the other below normal . In May and April prevail ″C″ and ″D″ rainfall type , or Huanghe River above normal and in the south and in the northern region below normal and the northern of Changjiang above normal and the south of Changjiang below normal . And indicate solicitation flood key area that is Huanghe River middle region and northern of Shanxi and Hebei Province above normal .