干旱区生态环境知识资源中心

Monsoon rainfall has been the major precipitation source for many East Asian countries, particularly China. This rainfall typically forms as a band with a distinctive northwestward movement from early spring to midsummer and is known as the Meiyu front. Meiyu rainfall constitutes a part of the East Asian monsoon. As spring transitions into summer, the thermal contrast between the land and the ocean drives the monsoon’s circulation. The topography of western China’s highlands further intensifies this thermal contrast. The present study tries to analyze how Meiyu rainfall responds to the intensification of the monsoon’s driving force by China’s large-scale topography. In particular, the cascade of western China’s elevated lands toward the northeast seems to act as a "dynamic attractor’’ that causes the Meiyu rainband to move to the northwest. When this monsoonal rainfall is fully developed along the foot of China’s western highlands, the westerly downslope winds stop the convection, resulting in an abrupt cessation of the Meiyu rainband. The general topographic feature of China clearly defines the low-plain climate as wet versus the plateau climate as arid or semiarid. Analyses of precipitation, water vapor, Earth’s surface and near-surface air temperatures, and atmospheric circulation provide a clear picture of this land-ocean-atmosphere interaction.