Interdecadal Change in the Interannual Relationship Between the Summer Precipitation in the Arid Region of Northwest China With North African Subtropical High and Western Pacific Subtropical High

ABSTRACT The zonal movement of both the western Pacific subtropical high (WPSH) and the North African subtropical high (NASH) correlates well with the summer precipitation in the arid region of Northwest China (ARNWC), but there is not enough understanding of the interdecadal change in the interannual relationship between the zonal position linkage of the two subtropical highs and summer precipitation in the ARNWC under different interdecadal backgrounds. Based on the observed precipitation data at 101 stations in the ARNWC, the NCEP–NCAR reanalysis data, and Hadley Centre surface sea temperature (SST) data for 1961–2022, the interdecadal change in the interannual relationship between the zonal position linkage of the two subtropical highs and summer precipitation in the ARNWC is investigated. Results show that the summer precipitation has experienced two distinct periods (dry period: 1961–1986; wet period: 1987–2022), and the zonal position linkage of the two subtropical highs correlates well with the summer precipitation in the eastern part of the ARNWC in the dry period and the Tarim Basin in the wet period, respectively. When the NASH and the WPSH move in opposite directions, the water vapour is directly (indirectly) transported from the eastern Asian monsoon region (tropical Indo‐Pacific Ocean) in the dry (wet) period. The Asian‐Pacific Oscillation (APO) and the sea surface temperature (SST) in the Indo‐Pacific warm pool both contribute to the zonal movement of the two subtropical highs in the dry period, but in the wet period, only the SST in the Indo‐Pacific warm pool plays an important role in modulating the zonal position linkage of the NASH and the WPSH.