Abstract:

Based on the daily precipitation and NCEP/NCAR reanalysis data from 1961 to 2013, the forming reasons of flood and summer precipitation anomaly were analyzed in the three rivers valley and their tributaries of Heilongjiang province in 2013. The results show that the overmuch former precipitation is the main reason of flood and leads to high soil humidity and overfull water storage in the valley in 2013. At the same time, the rainstorm frequency is higher in 2013 than in the other years because of abundant and concentrative summer rainfall. The water storage capacity in many large and medium sizes reservoirs undertaking the flood control task exceeds the normal standard, so flood discharge increases in order to protect the safety of reservoir dam. The main reasons cause the more summer precipitation in Heilongjiang province are that the northeast cold vortex is active and its path is north-moving; water vapor transport is sufficient at 850 hPa; the location of the East Asian westerly jet is abnormal at 200 hPa and the East Asian summer monsoon is strong. At 500 hPa, the Eurasian zonal circulation is weak; the west Pacific subtropical high is abnormally north-moving in some stages; the Okhotsk blocking high is obvious; it is controlled by the negative anomaly in midsummer over the Heilongjiang region.

Key words: Precipitation, Three rivers valley, Flood disaster