Weakened Relationship Between Spring Asian‐Pacific Oscillation and Summer Precipitation in the Eastern Part of the Arid Region of Northwest China Since 2000

ABSTRACT Based on observational monthly precipitation data at 21 stations in the eastern part of the arid region of Northwest China (ARNWC), the NCEP/NCAR reanalysis atmospheric circulation data, and ERA5‐land reanalysis surface soil moisture and sensible heat flux data during 1961–2022, we examine the interdecadal change in the relationship between spring Asia‐Pacific Oscillation (APO) and summer precipitation in the eastern part of the ARNWC. Results show the relationship between spring APO and summer precipitation in the eastern part of the ARNWC has weakened significantly since 2000. The southward (northward) shift of the subtropical westerly jet over East Asia and anomalous anticyclone (cyclone) over the Mongolia Plateau play an important role in modulating the dynamical and water vapour conditions responsible for the summer precipitation in the eastern part of the ARNWC during 1961–1999 and 2000–2022. The soil moisture can “memorise” the anomalous signal of APO from spring to summer and feedback to the atmosphere via influencing the summer surface sensible heat in the Tibetan Plateau during 1961–1999. Therefore, the spring APO‐related atmospheric circulation can contribute to favourable dynamical and water vapour conditions responsible for the summer precipitation in the eastern part of the ARNWC. However, the land‐atmosphere interaction in the Tibetan Plateau cannot retain the signal of spring APO and release it in summer during 2000–2022. Therefore, the APO loses its close relationship with summer precipitation in the eastern part of the ARNWC in this period.