中国5个大气本底站观测的CH4浓度变化规律

Changes of CH_4 Concentrations Obtained by Ground-based Observations at Five Atmospheric Background Stations in China

甲烷作为大气中仅次于二氧化碳的第二大温室气体,其浓度的增加会加速全球气候变暖。应用M-K突变检测等方法对2009年1月-2013年12月瓦里关(WLG)、临安(LAN)、龙凤山(LFS)、上甸子(SDZ)和2010年7月-2013年12月香格里拉(XGLL)本底站甲烷浓度的时间、空间变化特征及形成原因进行了分析。结果表明,研究时段内临安站点的甲烷体积浓度最高,平均值为1 965×10^(-9);龙凤山站次高,平均值是1 939×10^(-9);上甸子站居中,均值为1 914×10^(-9);瓦里关和香格里拉站的最低,平均值分别是1 864×10^(-9)和1 861×10^(-9)。瓦里关站甲烷浓度年均增长率为0.034%,临安、龙凤山、上甸子和香格里拉本底站的年均增长率分别为0.033%、0.025%、0.018%和0.01%。临安、龙凤山、上甸子均出现浓度突变点,突变点出现的时间与污染过程发生的时间相吻合。季节变化特征表现为:临安站甲烷浓度在7月份达到谷值;龙凤山为"W"型变化;上甸子站在7、8月份CH_4浓度最高,瓦里关季节变化与上甸子类似;而香格里拉站点夏季CH_4浓度受季风的影响较大,表现出明显的单峰。除了瓦里关站点,其它4个站点甲烷浓度的日变化均表现出同样的趋势:午后达到全天最低值,夜间和凌晨的浓度较高;而瓦里关正好相反,于正午达到全天甲烷浓度的峰值,这是由于牧区放牧造成的。

As the most important greenhouse gas next to carbon dioxide（CO2）, the enhancement of methane（CH4） concentrations will accelerate the global warming. M-K mutation detection and other methods were used to analyze temporal, spatial variation and its formative of CH4 concentrations in China＇s five major WMO/GAW background stations（Waliguan（WLG）,Lin＇an（LAN）, Longfengshan（LFS）, Shangdianzi（SDZ） and Shangri-La（XGLL））. The methane concentrations of WLG,LAN, LFS and SDZ sites are selected from January 2009 to December 2013, and the data of Shangri-La（XGLL） site is selected from July 2010 to December 2013. The results indicate that LAN station has the highest methane concentration, followed by LFS station, SDZ is in the middle, Shangri-La at least during the study period, with the mean value as 1 965×10^（-9）,1 939×10^（-9）, 1 914×10^（-9）, 1 864×10^（-9） and 1 861×10^（-9） respectively. The average annual growth rate of methane concentration in WLG is 0.034%, the average annual growth rate in LAN, LFS, SDZ is 0.033%, 0.025%, 0.018% and 0.01%, respectively.LAN, LFS, SDZ have mutation point. The time of occurrence of the mutation point coincides with the time of the pollution process. The seasonal variations of each site are as follows： methane concentration at LAN background station reaches the valley in July; LFS presents ＂W＂ type; SDZ has the highest CH4 concentration in July and August, WLG is similar to SDZ;XGLL site is affected by monsoon in summer, showing a distinct single peak. LAN, LFS, SDZ, XGLL stations show the same diurnal trend： the lowest value occurs in the afternoon, the concentration is higher in the night and early morning; there is a peak at midday at WLG station, which is due to grazing in pastoral areas.