Previous Signal Characteristics of Summer Anomaly Drought/flood in Shandong

By using monthly averaged NCEP/NCAR reanalysis data of the atmospheric circulation and the data of summer precipitation in 40 meteorological stations in Shandong province from 1960 to 2003,spatial and temporal characteristics of summer precipitation were analyzed.The atmospheric circulation characteristics and tropical convection were researched.The results showed the summer precipitation was downtrend from south to north of Shandong,and the spatial distribution was consistent.Before the flood year,wintertime polar vortex expanded eastward,and the East Asia major deep trough and the East Asian winter monsoon were stronger than normal years.And those were contrary to the drought year.The convection was enhancing from tropical Indian Ocean area,South China Sea to West Pacific Ocean area;the convection was weakening in tropical East Pacific Ocean area;the subtropical high pressure of West Pacific Ocean slanted to the north.The drought year and floor year were contrary results.The strength of winter monsoon and the activity of cold surge occurrence in low latitude enhanced convection and Hadely circulation,and they also enhanced energy water transportation.They are some previous signals for forecasting summer precipitation in Shandong.