中文摘要：

利用基于光腔衰荡光谱（CRDS）技术自组装的大气CH4在线观测系统,于2010年7月—2011年10月在云南香格里拉大气本底站对大气CH4进行了在线观测.结果发现,该站春、夏、秋、冬季CH4平均本底值分别为（1850.7±6.9）×10^-9（体积分数,下同）、（1850.9±13.4）×10^-9、（1865.6±16.1）×10^-9和（1839.2±6.5）×10^-9.全年体积分数在9月最高,12月最低,月均值振幅约39.6×10^-9.4季日平均最低值均出现在14：00—16：00.日变化振幅在冬季最小,秋季最大,分别为4.4×10^-9和10.0×10^-9.西南来向的地面风会明显抬升CH4体积分数,而北偏东来向的地面风显著降低观测结果.通过4季每日整点后向轨迹聚类计算,结合观测资料分析发现,该站CH4主要受西南来向气团传输影响,尤其在春、夏、秋3季.

英文摘要：

Atmospheric CH4 concentration was continuously measured at Xianggelila background station by Cavity Ring Down Spectroscopy system from July 2010 to October 2011.The average CH4 background concentrations during spring,summer,autumn and winter were（1850.7±6.9）×10^-9,（1850.9±13.4）×10^-9,（1865.6±16.1）×10^-9 and（1839.2±6.5）×10^-9,respectively.The monthly average variation reached a maximum in September and a minimum in December with the amplitude about 39.6×10^-9.The hourly average CH4 concentration exhibited evident diurnal variation with minimal values around 14：00—16：00 for all seasons.The daily variation amplitude was the lowest in the winter（4.4×10^-9） and the highest in the autumn（10.0×10^-9）.Evident elevation of CH4 concentration was observed when the surface wind was from the southwest,whereas great decrease was associated with north to northeasterly wind.Combined with the observed CH4 concentrations,cluster analysis of 3 day backward trajectories suggested that the observed CH4 concentration during the four seasons at the station was mainly affected by the southwest air mass transport,especially in spring,summer and autumn.