青藏高原大气CH_(4)源汇及其浓度时空变化特征研究进展

The source and sink of atmospheric methane and spatial-temporal variation of its concentration on the Qinghai-Tibet Plateau

甲烷(CH_(4))是仅次于二氧化碳(CO_(2))的重要温室气体。随着青藏高原气候的暖湿化,整个高原将可能成为一个潜在的碳源,要实现《巴黎协定》的1.5℃和2℃温控目标,需要准确估算未来剩余的碳排放空间。因此,准确地认识青藏高原大气CH_(4)的源汇特征、时空变化过程及机理,对预测及应对变暖,帮助政府做出科学的节能减排决策具有重要的现实意义。本文从大气CH_(4)的观测方法、源和汇、CH_(4)浓度的时空分布特征3个方面总结了青藏高原已有大气CH_(4)的研究进展,结果表明:目前,青藏高原大气CH_(4)观测主要有地基观测和卫星遥感,缺少空基观测,在卫星产品中,AIRS的CH_(4)浓度数据质量最好;青藏高原大气CH_(4)以自然来源为主,可以确定的主要来源有湿地、湖泊和畜牧业,地质活动、植被和多年冻土是否是CH_(4)的主要源还存在争议;吸收汇主要是对流层的OH自由基和高山草甸;青藏高原CH_(4)浓度的季节分布呈单峰特征,夏季最高,CH_(4)浓度的增减与亚洲夏季风的进退同步;青藏高原CH_(4)浓度年均增长约为5~8 ng·g^(-1),大于周边地区;青藏高原近地面的CH_(4)高值出现在中部,从地面到对流层顶CH_(4)浓度逐渐减小,但高原东部和北部减小幅度大于西南部。未来应加强大气CH_(4)三维连续观测,改进卫星反演算法和源汇解析模型,准确量化青藏高原大气CH_(4)时空变化过程,揭示其变化机理,以期为未来高效减排政策提供科学依据。

Methane(CH_(4)) is regarded as the second most important greenhouse gas after carbon dioxide(CO_(2)).Under the warming and wetting of the climate, the Qinghai-Tibet Plateau may become a potential carbon source.To achieve the 1.5 ℃ and 2 ℃ temperature control targets of the Paris Agreement, it is necessary to accurately estimate the remaining carbon emission space in the future. Therefore, an accurate understanding of the source and sink functions, spatial-temporal changes and mechanisms of atmospheric CH_(4)in the Qinghai-Tibet Plateau is of great practical significance to predict and cope with warming and help the government make scientific decisions on energy conservation and emission reduction. This paper summarizes the existing research progress from the following three aspects: observation method of atmospheric methane, source and sink of methane, and the spatial-temporal variation of the atmospheric CH_(4). The results show that the observations of atmospheric CH_(4)on the Qinghai-Tibet Plateau are mainly ground-based observations and satellite remote sensing, lacking spacebased observations, and AIRS has the best data quality among satellite products;Methane of the Qinghai-Tibet Plateau is mainly from natural sources, the main sources are wetlands, lakes and animal livestock, geological activities, vegetation and permafrost are the uncertain CH_(4)sources. The sink of CH_(4)is mainly tropospheric hydroxyl radical and alpine meadow;The seasonal distribution of CH_(4)on the Qinghai-Tibet Plateau has a single-peak in summer, which is synchronized with the seasonal pattern of the Asian summer monsoon;The average rising rate of CH_(4)concentration on the Qinghai-Tibet Plateau is about 5~8 ng·g^(-1)·a^(-1), which is greater than that in the surrounding areas;The high value of CH_(4)concentration near the surface of Qinghai-Tibet Plateau appears in the middle part, and decreases gradually from the ground to the tropopause, but the decrease in the east and north of the plateau is greater than that in the southwest. In the future, three dimensional continuous observation of atmospheric CH_(4)should be strengthened, satellite inversion algorithm and source sink analytical model should also be improved. In addition, we need to accurately quantify the spatial-temporal change process of atmospheric CH_(4)in the Qinghai-Tibet Plateau and reveal its change mechanism to provide a scientific basis for the future efficient emission reduction policies.