Interdecadal Pacific Variability dominated the decadal variation of cold season precipitation in arid West Asia

This study examines the interdecadal variation of cold season precipitation in arid West Asia (AWA) from 1960 to 2019 and identifies the underlying physical mechanisms. The results indicate that the precipitation in this region has exhibited significant interdecadal variation over the past 60 years, which is closely related to Interdecadal Pacific Variability (IPV). During the positive IPV phase, which was associated with a warming equatorial Middle East Pacific Ocean, an eastward-propagating Rossby wave induced a negative geopotential height anomaly over AWA, providing the dynamic conditions for precipitation. Additionally, IPV caused the westerly jet to move southward and strengthen, providing rich water vapor. Moreover, a positive geopotential height anomaly over the Indo-West Pacific, caused by cold sea surface temperature, led to the upward transport of water vapor from the Northern Indian Ocean to AWA, further enhancing the water vapor conditions. These factors together resulted in excess precipitation in AWA during the positive IPV phase, with a 17.6 mm increase compared to the negative phase, accounting for approximately 12% of the cold season precipitation. These findings were also confirmed by the piControl simulation of CESM2.