Interdecadal variability in the dominant synoptic patterns responsible for the summer daily extreme precipitation over the Tarim Basin, Northwest China

Abstract

Revealing the synoptic patterns associated with extreme precipitation is important in deepening our understanding of extreme precipitation formation. To examine whether the synoptic patterns responsible for the summer extreme precipitation (SEP) have experienced an interdecadal variability over the Tarim Basin (TB), we investigate and compare the synoptic patterns influencing regional SEP over the TB under different interdecadal backgrounds. Results show the SEP over the TB has experienced three distinct periods (1961–1987: dry period; 1988–2009: wet period I; 2010–2023: wet period II) and can be categorized into two dominant patterns, western pattern, and eastern pattern, respectively. The western and eastern patterns of SEP are dominated by the large-scale circulations characterized by directly influenced circulations: Subtropical Westerly Jet (SWJ), Central Asian Cyclone (CAC) and low-level easterly jet/cyclone, which affect the dynamics conditions, as well as indirectly influenced circulations: South Asian High (SAH), Iranian Subtropical High (ISH), Western Pacific Subtropical High (WPSH), Mongolian Anticyclone (MAC) and Siberian Ridge, which modulate water vapor transport. During the Dry Period to Wet Period II, with the increasing influence of the WPSH and MAC, the source and path of water vapor transport yielded an interdecadal adjustment from the Arabian Sea to the Bay of Bengal to the western Pacific Ocean. Regarding the SEP-dominant transition, the differences between the patterns are the location of the SWJ, CAC, and MAC, resulting in substantially different water vapor transport. In the western pattern, the change occurs mainly in the western water vapor path, whereas in the eastern pattern, it is the eastern water vapor that undergoes interdecadal changes. Moreover, discrepancies in the variations of ISH and WPSH in sub-periods not only contribute to the interdecadal variations, but also are responsible for variances between patterns.