As an important factor of surface processes, soil moisture has great influence on atmospheric circulation and weather climate of local and adjacent areas. Because the observation sites of soil moisture in the Tibetan Plateau (TP) are sparse and the observation time is short, we use a set of satellite retrieval data which has validated by field observations, to study the relationship between earlier soil moisture of TP and later precipitation of eastern China and its mechanism. The results indicate that with the global warming, the general soil moisture of TP has an obvious trend to increase. After removing the linear trend, we define the Tibetan Plateau soil moisture index (TPSMI) to characterize the interannual variation of TP soil moisture. Such variations of soil moisture have great conformance in 0 similar to 10 cm, 10 similar to 40 cm and 40 similar to 100 cm, which makes soil moisture interannual signal from spring continue into summer. The correlation coefficient between spring and summer TPSMI is 0. 56. When the TPSMI is bigger, which means that the soil moisture of eastern TP is bigger, and when the soil moisture of western TP is smaller, there is a latent heat source (sensible heat source) in eastern (western) TP. The two heat sources together induce a cyclone-anticyclone-cyclone wave train from the west of TP through China mainland to northeast China, which presents a prominent quasi-barotropic structure through the middle and upper troposphere. This has great contribution to the enhancement of Northeast Cold Vortex, which leads to the outburst of cold air. At the same time, the South Asian anticyclone gets enhanced and eastward, while the Sub-tropical anticyclone gets enhanced and westward with the converge of warm moist airflow from south and cold dry airflow from north in the Yangtze River basin. In addition to the stronger rising movement, the summer precipitation of the Yangtze River basin is much more. On the contrary, when the TPSMI is smaller, the precipitation of the Yangtze River basin is much less.

It is known that aerosol and precursor gas emissions over East Asia may be underestimated by 50% due to the absence of data on regional rural and township industries. As the most important element of anthropogenic emissions, sulphur dioxide (SO2) can form sulfate aerosols through several chemical processes, thus affecting the regional and global climate. In this study, we use the Community Atmospheric Model 5.1 (CAM5.1) to investigate the effects of anthropogenic aerosols on radiative forcing and the climate over East Asia, taking into consideration various SO2 emission levels, including double the amount of SO2 emissions over East Asia. Numerical experiments are performed using high-resolution CAM5.1 with pre-industrial (PI) and present day (PD) aerosol emission levels, and with PD aerosol emission levels with double SO2 emissions over East Asia (PD2SO2). The simulated aerosol optical depth and surface sulfate concentrations over East Asia are significantly increased in PD2SO2, which is in better agreement with the observational results. The simulation results show extensive aerosol direct and indirect radiative forcing for PD PI (the difference between PI and PD), which significantly weakens the large-scale intensity of the East Asian summer monsoon (EASM) and reduces the summer precipitation. Compared to PD, the aerosol direct radiative forcing is significantly increased in PD2SO2, whereas the aerosol indirect radiative forcing is markedly decreased due to the inhibition of cloud formation, especially over North China. The increase in aerosol direct radiative forcing and decrease in aerosol indirect radiative forcing result in insignificant changes in the total amount of aerosol radiative forcing. These results also show that the large-scale intensity of the EASM and the associated summer precipitation are insensitive to the doubling of current SO2 emissions.