Study Of Tropopause And Temperature Inversion In Boundary Layer And Possible Influential Factors Over East Asia

The tropopause has a profound impact on the polar expansion of the intertropical convergence zone(ITCZ)and changes in large-scale circulation.The temperature inversion of the atmospheric boundary layer can significantly change the near-surface pollution concentration and then affect the atmospheric pollution through complex feedback mechanism.Due to the lack of detailed atmospheric vertical structure observations,the understanding of the tropopause and boundary layer inversion climate characteristics and their influence mechanisms in China is very limited.Therefore,this paper mainly uses the latest radiosonde data released by the China Meteorological Administration to comprehensively study the variation of tropopause height in China from 1979 to 2016.In addition,with the help of 7-year sounding observation data from 2011 to 2017,the spatial and temporal distribution characteristics of the inversion frequency,intensity and thickness in the boundary layer were analyzed in depth and their main influencing factors were revealed.Results show that the LRT height in most parts of China shows a significant upwards trend with a rate of 370 m/decade.The fastest increase occurs in the northwest region,followed by the low-latitude regions(15o?25oN),while the slowest increase occurs in the high-latitude regions(45o?55oN).In terms of the seasonality,tropopause height reaches the peak in summer and descends to bottom in winter.The frequency distribution in the vertical direction exhibits a bimodal pattern with the major peak mostly occurring at around 15 km and a secondary peak occurring between 8 and 12 km.Overall,the TI exhibited large seasonal and geographic dependence.The frequency of surface-based inversion(SBI)exhibited a “West Low East High” pattern at 0800 Beijing time(BJT),whereas the pattern switched at 2000 BJT.The North China Plain(NCP)had the greatest SBI intensity,likely due to the strong interaction between aerosols and temperature inversions.The frequency of TI was found to be high in winter and low in summer.Both summertime SBI and EI reached a peak at 0800 BJT,but a trough at 1400 BJT.In the vertical,most EI episodes tended to occur at about 300 m in winter.The correlation analyses between local meteorology and TI indicated that larger lower tropospheric stability(LTS)corresponded to more frequent and stronger TI.The results of the tropopause spatiotemporal trend in this paper provide important observational evidence for the ITCZ expansion polewards under global warming.Furthermore,the findings regarding temperature inversions elucidate the temperature structure in the atmospheric boundary layer throughout China.These observational results will provide important scientific and technological supports for the Chinese governments in decisionmaking related to climate change policies and the governance of the atmospheric environment.