Modulation of sea surface temperature over the North Atlantic and Indian-Pacific warm pool on interdecadal change of summer precipitation over northwest China

Under the background of global warming, the summer precipitation over northwest China (NW) has experienced a significant interdecadal shift since the early 1990s, followed by a great increase in precipitation. This increase was mainly due to the anomalous water vapour input from the eastern boundary, whose transport has gradually become the main moisture transport belt affecting summer precipitation over NW in the past 30 years. Further research indicates that the anomalous easterly water vapour transport mainly originates from the Arctic and North Pacific Oceans. The interdecadal increase in precipitation and changes in water vapour transport pathways are related to the interdecadal warming of the North Atlantic (NA) and Indian-Pacific warm pool (IPWP) in the mid-1980s. The IPWP warming potentially weakens the land-sea thermal gradient, dampens the meridional circulation in East Asia, and thereby significantly reduces the southerly water vapour transport of the Asian summer monsoon, and generates anomalous northeasterly water vapour transport from high latitudes over East Asia. Moreover, the warmer sea surface temperature (SST) over the IPWP and NA can induce an anomalous teleconnection wave train, with anomalous anticyclones over Lake Baikal and the Aleutian Islands, and an anomalous cyclone over Japan. This type of teleconnection wave train contributes to anomalous northerly winds over eastern China and easterly winds over NW. The above-mentioned anomalous circulation favours moisture transport from both the Arctic and North Pacific toward the NW, resulting in an increase in summer precipitation associated with the anomalous regional ascending motion.