资源环境科技发展态势分析平台

Using precipitation data from weather stations in China and reanalysis data from National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR), the inter-annual and inter-decadal variability of early-summer (May-June) and late-summer (July-August) precipitation (hereinafter referred to as MJP and JAP, respectively) over northeast China (NEC) and their background circulation during 1951-2016 were analysed. The following new findings have been highlighted: (a) There are significantly different inter-annual and inter-decadal variability characteristics between MJP and JAP over NEC. The inter-annual variability of MJP is independent from that of JAP, while the inter-decadal variability of the former is opposite to that of the latter. A significant shift to more MJP (less JAP) occurred in the early 2000s (late 1990s). (b) In terms of the inter-annual timescale, the large-scale atmospheric circulations-associated MJP is notably different from JAP over NEC. The variation in MJP is mainly dominated by the northeast China low (NECL) and the Okhotsk blocking high (OBH), while JAP is mainly influenced by the western Pacific subtropical high (WPSH), the NEC south wind (NESW), and the NECL. (c) On the inter-decadal timescale, MJP is associated with the inter-decadal variation of the East Asia/Pacific (EAP) teleconnection, while JAP is closely related to the inter-decadal variation of the NECL and NESW. When the EAP is in a positive phase, MJP is more than average. Furthermore in late summer, the strong NECL and NESW are both of benefit to the convergence of water vapour from the tropical southwest and East Asian subtropical westerlies over NEC, which contributes to the more JAP than average.