Statistical downscaling model for late-winter rainfall over Southwest China

Abstract

A statistical downscaling model is built for the late-winter rainfall over Southwest China (SWC). A partial-correlation method is used for selecting factors. The results show that the selected factors for late-winter rainfall in SWC are sea level pressure in Western Europe (SNAO) and sea surface temperature in Western Pacific (WPT). SNAO is related to the southern pole of North Atlantic Oscillation (NAO) and excites Southern Eurasian teleconnection, which influences the development of the southern branch trough and the water vapor transport to SWC. WPT indicates the variability of ENSO in the tropical Western Pacific. WPT excites Pacific-East Asia teleconnection and an anticyclone (cyclone) is formed in the southern part of China and suppresses (enhances) rainfall over SWC. A regression statistical downscaling model using SNAO and WPT shows good performance in fitting the variability of late-winter rainfall in the whole SWC region and every observation station, and the model also shows strong robustness in the independent validation. The statistical model can be used for downscaling output from seasonal forecast numerical models and improve the SWC late winter rainfall prediction in the future.