Precipitation variation characteristics and influencing factors in the subtropical monsoon marginal zone

We selected the monthly global gridded precipitation data from the climatic research unit of University of East Anglia to depict the subtropical monsoon domains for an investigation of the relationship between the monsoon marginal zone rainfall, monsoon intensity and monsoon area. We also analyzed the combined effect of Pacific decadal oscillation(PDO), El Ni?o-Southern Oscillation and atmospheric circulation on the subtropical monsoon marginal zone precipitation variation. The results showed that the precipitation in the area where the monsoon boundary line with small amplitude of oscillation had a significant an increasing trend, while the precipitation in the area where the boundary line swung to a large extent had a decreasing trend. Since the PDO was mainly in the warm phase in the past 50 years, the sea surface temperature in the western coast of North America was unusually warm, and the sea level pressure in the North Pacific was abnormally low, which weakened the monsoon circulation and suppressed the precipitation in the subtropical monsoon marginal region of the North Pacific Ocean. The East Asian summer monsoon marginal zone had an obvious drying tendency, of which the dryness trend was most obvious in the eastern Inner Mongolia Plateau and the Loess Plateau, while the wet conditions were obvious in the Qinghai-Tibet Plateau. The difference of boundary zone precipitation was significant, with precipitation decreasing in the southeast and northwest, while increasing in the central part.This study could help us understand the variability and regional differences of subtropical monsoon marginal zone precipitation, and to assess the sensitive response of monsoon marginal regions to global monsoon changes.