Influence of different configurations of western North Pacific anticyclone and Siberian high on spring climate over China

Abstract

This study analyses the spring climate anomalies under different configurations of western North Pacific anticyclone (WNPA) and Siberian high (SH). Compared to the WNPA alone with increased precipitation over southern China, the out-of-phase configuration (strong-WNPA-weak-SH) can enhance the WNPA-related southwesterlies over eastern China, favouring increased precipitation with larger amplitude over southern China and southern Northeast China. Differently, the in-phase configuration (strong-WNPA-strong-SH) decreases and confines WNPA-related southwesterlies over southern China, causing decreased precipitation over eastern Southwest China; additionally, the WNPA-related southwesterlies converge with SH-related northwesterlies over the lower reaches of the Yangtze River, causing increased precipitation there. For surface air temperature, the WNPA alone induces warming over western Southwest China through changing heat flux, while the SH alone induces cooling over northern China through changing temperature advection, and over Northwest and southern China through changing heat flux. In the out-of-phase configuration, warming expands into Northern China due to the cooperation of weakening SH. In the in-phase configuration, SH-related cooling mainly occurs to the north of the Yangtze River because of the obstruction of WNPA. Further analysis indicates the eastern Pacific (EP) and central Pacific (CP) El Niño-Southern Oscillation (ENSO), European low and Ural high contribute to the different configurations of WNPA and SH. The EP ENSO-related zonal overturning circulation intensifies the WNPA and European low-induced warm advection weakens the SH, resulting in the outof-phase configuration. The CP ENSO-related zonal overturning circulation intensifies the WNPA with a northeast-southwest tilt and Ural high-induced cold advection intensifies SH, resulting in the in-phase configuration.