Decadal predictability of summer precipitation in Northwestern China originated from the North Atlantic Ocean

Abstract

Northwestern China (NWC) has a monsoon-like, arid and semi-arid climate with considerable decadal variability and long-term trends. Decadal prediction of summer precipitation remains challenging due to the mixed influence of external forcing and internal variability. This study shows that the decadal internal variability of domain-averaged summer precipitation over NWC (NWCP) primarily originates from the extratropical North Atlantic dipole (NAD) sea surface temperature anomalies (SSTA), which excite a Eurasian Rossby wave train by enhancing the transient eddy forcing. The resultant anomalous Mongolian cyclone increases the NWCP through the cyclonic vorticity-generated upward moisture transport. By combining this empirical relationship and dynamical models’ predicted NAD SSTA, we attempted a hybrid dynamic-empirical model to predict the decadal internal variability component. After adding the external forcing component, the model can predict the decadal NWCP 7–10 years in advance. Our result opens a pathway for decadal prediction of precipitation in central Eurasia’s dry regions.