Variation in Principal Modes of Midsummer Precipitation over Northeast China and Its Associated Atmospheric Circulation

This study documents the first two principal modes of interannual variability of midsummer precipitation over Northeast China (NEC) and their associated atmospheric circulation anomalies. It is shown that the first principal mode exhibits the largest amount of variability in precipitation over the south of NEC (referred to as the south mode), whereas the second principal mode behaves with the greatest precipitation anomaly over the north of NEC (referred to as the north mode). Further findings reveal that, through modulating moisture transportation and upper- and lower-troposphere divergence circulation as well as vertical movement over NEC, the anomalous northwestern Pacific anticyclone and the anticyclone centered over northern NEC exert the dominant influence on the south and north modes, respectively. Additionally, it is quantitatively estimated that water vapor across the southern boundary of NEC dominates the moisture budget for the south mode, while the north mode has a close connection with moisture through NEC's northern and western boundaries. Furthermore, the north (south) mode is strongly related to the intensity (meridional shift) of the East Asian westerly jet.