The relationship of the thermal contrast between the eastern Tibetan Plateau and its northern side with the plateau monsoon and the precipitation in the Yangtze river basin in summer

Using the NCEP/NCAR reanalysis data and observed daily rainfall from the 584 gauge stations from 1961-2011, the relationship between the atmospheric heat source (hereafter called 〈Q1〉) over the Tibetan Plateau and its surrounding areas and the plateau monsoon and the precipitation in China in the summer has been studied in this paper. The results show that there exists a distinct thermal contrast between the eastern Tibetan Plateau main area and the area north of it and the thermal contrast has significant influence over the plateau monsoon, so we defined an index to reflect the thermal contrast. When the index is high, the plateau monsoon is strong, and the precipitation is more in the Yangtze river basin, and vice versa. In the further study, when the index is high, the flows from the north and the south convergence over the Yangtze river basin, leading the warm vapor from the Pacific Ocean and the cold air from the high latitude to convergencing therein, and thus to increasing the water vapor content in this region. At the same time, the convergence and ascending motions strengthen, resulting in more rainfall in the Yangtze river basin; when the index is low, the southwesterly winds over the low-level in the Yangtze river basin strengthen, the more warm vapor from the India Ocean and the Pacific Ocean are transported to northern China, and the water vapor content over the Yangtze river basin is decreased, with the convergence and ascent weakened in this region, leading the precipitation in this region to becoming less.