Decadal Variations of Summer Precipitation in Northeast China and the Associated Circulation
Based on 91 stations monthly data,NCEP/NCAR reanalysis data and sea surface temperature data,the distribution characteristics,decadal variation of precipitation and circulation pattern were analyzed by empiri-cal orthogonal function (EOF) and significant test,and the annual variations in different decades are discussed.It is found that precipitation in Northeast China in summer has large decadal variability.Less precipitation in Northeast China in summer was observed in 1961-1983 (P1),more in 1984-1998(P2),and less in 1999-2012(P3).Compared with P1,cyclone anomaly in Northeast China,anticyclone anomaly in Mongolia,and cyclone anomaly in subtropical northwest Pacific were intensified in P2,and the contribution of easterly water vapor transport from Northwest Pacific was obvious.Compared with P2,Northeast cold vortex was weaker,and anomalous northerly wind on 850 hPa was over the east of Northeast China in P3.Furthermore,the southerly water vapor transport became weaker obviously.Pacific decadal oscillation (PDO) has a modulation effect on the decadal variation of precipitation in Northeast China and the associated circulation.Less precipitation is observed in P1 and P3.In these two periods,PDO are in negative phase,and anticyclone circulations in Northeast China are strong.For wet years in P1,the water vapor transport is mainly from the strong summer southerly wind,while in P3 may from the Northwest Pacific.
Northeast ChinaPrecipitation anomalyDecadal variationNortheast cold vortexWestern Pacific subtropical high