Onset of East Asian subtropical summer monsoon and rainy season in China

Here we use harmonic analyses to examine seasonal variations of China land rainfall, low-level winds, and atmospheric heating over East Asia during spring to summer and the associated subtropical summer monsoon activities. Our results indicate that the South China spring rainfall （SCSR） in March is the prophase of East Asian sub-tropical summer monsoon （EASSM）, and the onset of EASSM and China summer rainy season starts in early April, characterized by the enhanced rainfall in South China and the seasonal reverse of zonal land-sea thermal contrast in sub-tropical East Asia. The EASSM onset is earlier than that of South China Sea summer monsoon, and it is active in east of 100°E and north of 20°N. Our analyses suggest that the subsequent heating appears over India-China Peninsula in March and South China in April and causes the low-level atmospheric warming and the zonal land-sea thermal contrast seasonal reverse in East Asian subtropics. The atmospheric heating over South China is the main force to drive the southwesterly winds, updrafts and strengthen the summer precipitation in South China.