Characteristics of Tropopause Height over China During East Asian Summer Monsoon

Tropopause, as a transition layer between the troposphere and stratosphere, plays an important role on the regional and global climate and weather. Influenced by the Tibetan Plateau and monsoon, tropopause over China can even affect the global weather and climate, especially by changing aerosol distribution. Focusing on characteristics of tropopause height, 3 different sub-regions are defined in China during the East Asian summer monsoon, using high vertical resolution sounding data from year 2008 to 2014 collected by the network of L-band sounder. Results are shown as follows. Tropopause height increases with decreasing latitudes. The region with high tropopause moves northward with the maximum locating over the south of the Tibetan Plateau and the region to the southeast of the Plateau after the summer monsoon breaking. The region with large southward and eastward gradient of tropopause height moves from 30°-40°N to 40°-50°N after the summer monsoon break. There is little latitudinal difference in tropopause height over all the three sub-regions, indicating that the topography has little influence. However, tropopause height changes greatly after summer monsoon breaking: In northeast China and central-east China, the tropopause increases and in south China it slightly decreases. Influenced by the surface heat and vertical velocity, the temperature increases in the troposphere and decreases in the troposphere-stratosphere transition layer, which results in an increasing vertical temperature gradient after the summer monsoon breaking over the northeast and central-east China, resulting in higher tropopause. For northeast China, the temperature profile shows double peaks before the monsoon breaking, which is easy to form double tropopauses with a low first tropopause. In south China the temperature increases through the whole atmosphere after the summer monsoon breaking, generating slightly decreased tropopause. Limited by the coarse temporal resolution, more temporal characteristics such as daily changes cannot be studied. Further research should combine various datasets such as satellite to get a comprehensive analysis on the tropopause behavior over the mainland China.