Multiscale Interactions Driving Summer Extreme Precipitation in Central Asia

This study identified four patterns of regional extreme precipitation events (REPEs) in Central Asia (CA) and their crucial synoptic systems and multiscale interactions. Four patterns with distinct spatial distributions were identified in: northern Kazakhstan, southern Xinjiang, western CA, and the Tianshan Mountains. Focusing on the three most frequent REPEs, the kinetic energy (KE) cross-scale transfer from the basic-to synoptic-scale windows exhibited a zonal dipole, resulting in the development and enhancement of REPEs in northern Kazakhstan. The available potential energy (APE) cross-scale transfer exhibited opposing patterns between the upper and lower troposphere, indicating baroclinic instability in the lower troposphere and barotropic instability of the basic flow in the upper troposphere. Both mechanisms enhanced the Central Asian vortices (CAVs) in southern Xinjiang and induced REPEs. Conversely, the energy budgets exhibited baroclinic instability of the basic flow throughout the entire region when the Tianshan Mountains REPEs occurred, providing energy for prevalent CAVs. A self-organizing map was employed to classify the regional extreme precipitation events (REPEs) in Central Asia (CA) into four patterns with unique spatial distributions (northern Kazakhstan: P1, southern Xinjiang: P2, western CA: P3, and Tianshan Mountains: P4). This study further illuminated the multiscale interaction mechanisms for the development of key synoptic systems that generate REPEs for the three most frequent patterns (P1, P2, and P4). A zonal dipolar kinetic energy (KE) cross-scale transfer occurred throughout the region in P1, resulting in the development of a long-wave trough and the enhancement of REPEs. P2 is characterized by a negative eastward shift of the North Atlantic Oscillation-like in the original field and the reconstructed intraseasonal-scale field, which promotes the development of Central Asian vortices (CAVs) over southern Xinjiang. The available potential energy (APE) and KE cross-scale transfer from the basic-to synoptic-scale windows indicate that baroclinic and barotropic instability occur in the lower and upper troposphere, respectively. Thus, providing sufficient energy and dynamic conditions for CAVs enhances REPEs. Furthermore, the Silk Road pattern-like dominates over Eurasia, and CAVs occur over the northwestern Tianshan Mountains, as observed in P4. APE cross-scale transfer induces strong baroclinic instability throughout the troposphere and provides energy for more prevalent CAVs that intensify the REPEs. The long-wave trough and Central Asia (CA) vortex are the crucial synoptic systems of summer regional extreme precipitation in CA The crucial synoptic systems are powered by the basic- and intraseasonal-scale baroclinic instability The spatial inconsistency of local multiscale interactions affects the formation of the crucial synoptic systems and extreme precipitation