资源环境科技发展态势分析平台

The long-term trend in tropopause has profound implications for the expansion of tropical zone and the variation of large-scale circulation. However, the changes of tropopause in China have not been explicitly investigated as yet. In this study, the trend of lapse rate tropopause (LRT) height over China has been comprehensively revisited for the period of 1979-2016, using the newly released quality-controlled radiosonde data from China Meteorological Administration. Results show that the LRT height in most parts of China shows a significant upwards trend with a rate of 370m/decade, most likely due to global warming. The fastest increase occurs in northwest region, followed by the low-latitude regions (15 degrees-25 degrees N), while the slowest increase occurs in the high-latitude regions (45 degrees-55 degrees N). Overall, the LRT height varies with latitudes, exhibiting a south high and north low pattern. In particular, high LRT height over low latitudes is found to be expanding rapidly polewards in recent years, in contrast to almost constant LRT height over mid and high latitudes. In terms of the seasonality, tropopause height reaches the peak in summer and bottom in winter. The frequency distribution in the vertical direction exhibits a bimodal pattern with the major peak mostly occurring at around 15km and a secondary peak occurring between 8 and 12km. This bimodal distribution is similar to the findings revealed in previous studies. Our findings offer important circumstantial observational evidence for the polewards expansion of the Tropics under global warming.