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Recent changes in summer precipitation in Northeast China and the background circulation

This study documents recent changes in the characteristics of summer (July–August–September) precipitation in Northeast China (NEC). A significant shift to less precipitation occurred in 1999–2012 as compared with that in 1984–1998. The reduced precipitation in the later period is closely associated with the large‐scale anomalous high pressure over East Asia and anomalous descending motion over NEC. Furthermore, the significant reductions in the total cloud cover and moisture content also contribute to the reduced precipitation over NEC. To investigate the possible mechanism for the decadal shift of summer precipitation, a northeast Asian summer monsoon (NEASM) index is defined to describe the monsoon circulation over NEC. The results indicate that the NEASM has weakened since 1999 and is concurrent with the shift of the Pacific Decadal Oscillation (PDO) to the negative phase. Warming sea surface temperature (SST) in the North Pacific can zonally reduce the land‐sea thermal contrast and lead to a weak NEASM. Further investigation indicates that the negative phase of the PDO has significant impacts on the atmospheric circulation associated with the NEASM. Additionally, changes in synchronous Arctic sea ice cover (SIC) also likely induce an anomalous sinking movement and weaken water vapour transport; thus, the summer precipitation over NEC decreases.