甲烷(CH₄)作为仅次于二氧化碳(CO₂)的第二大温室气体,不仅在全球和区域尺度光化学反应中起着重要作用,而且在能量收支平衡及气候变化方面有着重要的影响.2013年,Auqa/EOS的大气红外探测仪(AIRS)热红外近地表CH₄产品在AIRS Version6.0产品中发布,其结果尚未在中国进行验证,利用热红外传感器分析中国近地表CH₄浓度的时空分布还处于初始阶段.本文利用中国青海瓦里关(WLG)、中国台湾鹿林山(LLN)及蒙古乌兰乌勒(UUM)地基观测资料对AIRS V6.0近地面CH₄浓度产品进行了验证,误差在2%以内,二者相关系数r分别为0.68、0.5、0.69,变化趋势一致,进而从地域、季节变化和年际变化3个方面探讨了2003年—2013年中国地区近地面CH₄浓度的时空分布特征.结果表明:CH₄浓度最低值位于西藏地区(1800 ppbv),高值区位于新疆维吾尔自治区北部、内蒙古自治区及黑龙江北部(1920 ppbv);夏季高,冬季低,季节性变化明显,年际变化基本上呈增长趋势.

As the second most important greenhouse gas after carbon dioxide (CO₂), methane (CH₄) plays a major role in photochemical reactions at global and regional scales and significantly affects energy balance and climate change. Although observations of near-surface CH₄ via the Atmospheric Infrared Sounder (AIRS version 6.0) of the EOS/Aqua platform have been published, they have yet to be documented in the context of China. Analysis of near-surface CH₄ concentration in China using thermal infrared sensor data is still in its initial phase. Ground-based observation data from Waliguan (WLG) in Qinghai, Taiwan Lulinshan (LLN), and Ulaan Uul in Mongolia (UUM) are employed to validate the near-surface CH₄ concentration obtained via AIRS V6.0. Results show a consistent trend for the WLG, LLN, and UUM data, with the error being less than 2% and the correlation coefficients being 0.68, 0.5, and 0.69, respectively. These data sets can be effectively applied in the analysis of the spatial and temporal distribution characteristics of near-surface CH₄ concentration. In this paper, the spatial and temporal distribution characteristics of the near-surface CH₄ concentration from 2003 to 2013 in China are discussed according to region, seasonal variation, and interannual variation. The following results are obtained. (1) The minimum near-surface CH₄ concentration is observed in Tibet (1800 ppbv), and the maximum is observed in northern Xinjiang, Inner Mongolia, and northern Heilongjiang (1920 ppbv). (2) Through the analysis of the 11-year AIRS data (2003—2013) on near-surface CH₄ concentration synthesis products, we find that the near-surface CH₄ concentration is low in the south and high in the north, a trend that is consistent with that in the middle and high latitude regions. (3) Regional statistics and the overall seasonal variation demonstrate that the seasonal change is significant, especially in the western region where the increase is observed from 1838 ppbv in April to 1882 ppbv in September. The lowest value is observed in April and May, and the highest value is observed in August and September. These results indicate high near-surface CH₄ concentrations in summer and autumn and low concentrations in winter and spring. In the northwest, high near-surface CH₄ concentrations are observed in December. (4) From 2003 to 2013, the national average CH₄ concentration near the ground showed a basic growing trend, except for the slight decrease in 2006 and 2010. The concentration values in the northwest and east regions vary consistently. A rapid increase is observed in northeast China, whereas the growth in the south is not obvious. Interannual fluctuations are bigger in the northwest than in the northeast. (4) In the south, the overestimated value of near-surface CH₄ concentration by AIRS is higher than the ground-based CH₄ products in LLN in summer.