大气甲烷探测进展与全球甲烷分布分析

甲烷（CH₄）是大气中具有化学活性和辐射活性的气体。随着人类文明的发展，CH₄的总量一直在增加。工业革命前全球CH₄浓度为700 ppbv，到20世纪90年代它的浓度达到1714 ppbv。研究阐述了CH₄地基探测、空基探测、星基探测及反演算法的发展现状。自1979~1983年Nimbus-7卫星上的SAMS探测仪首次实现对平流层CH₄浓度探测以来，国际上已有许多可探测CH₄的卫星探测仪。随着卫星探测技术的发展及反演算法的改进，卫星传感器反演的CH₄精度逐渐提高。其中天底模式下TROPOMI传感器反演的CH₄浓度与地面站点数据的偏差为14 ppbv（0.8%）；临边/掩星模式下ACE-FTS反演的对流层至平流层下部CH₄廓线精度在10%以内。而后，基于AIRS L3产品分析了300 hPa、150 hPa全球CH₄浓度变化趋势和分布特征， 2010~2020年全球CH₄浓度增长了约50 ppbv，年均增长率约为0.29%；全球CH₄浓度北高南低，高值区分布在大西洋中部、非洲北部、中东地区和中国西部。

Development of Atmospheric Methane Observation and Distribution of Global Methane

Methane （CH₄） is a chemically and radiologically active gas in the atmosphere. With the development of human civilization， the total amount of CH₄ has been increasing. Before the industrial revolution， the global CH₄ concentration was 700 ppbv， and it reached 1714 ppbv by the 1990s. This paper describes the development of CH₄ ground-based detection， space-based detection， satellite-based detection and inversion algorithms. During 1979~1983， the SAMS on Nimbus-7 satellite observated CH₄ concentration in the stratosphere for the first time. After that， many sensors have been launched to observe CH₄. The satellite-based instruments mainly observe CH₄ in the infrared band by nadir viewing， limb sounding or occulation observating. In recent years， the spatial resolution and spectral resolution of the sensors are greatly improved. The TROPOMI has a spatial resolution of 7 km×7 km； the spectral resolution of ACE-FTS、AIUS reach 0.02 cm^-1. In the near infrared band， WFM-DOAS is the main algorithm for inversion of CH₄ concentration， and OEM is mainly used in the mid and far-infrared band. With the development of satellite observation technology and the improvement of retrieval algorithms， the accuracy of CH₄ retrieved has gradually improved. The deviation between CH₄ concentration retrieved by TROPOMI in the nadir viewing and the CH₄ concentration provided by ground-based stations is 14 ppbv （0.8%）； The accuracy of CH₄ profile retrieved by ACE-FTS in the limb sounding/occultation observing is within 10% from troposphere to lower stratosphere.Then， the trends and distribution characteristics of global CH₄ concentration at 300 hPa and 150 hPa are described in this paper. The global CH₄ concentration increased by ~50 ppbv from 2010 to 2020， with an average annual growth rate of ~0.29%； At 300 hPa， the global CH₄ concentration was 1 767 ppbv in 2010 and increased by 55 ppbv in 2020； At 150 hPa， the global CH₄ concentration was less than 1 700 ppbv in 2010 and reached 1 745.6 ppbv in 2020； The global CH₄ concentration is higher in the north and lower in the south， the reason lies in that there are numerous methane emission sources （freshwater wetlands， rice cultivation， fossil fuel combustion and biomass combustion， etc） in the northern hemisphere； The high concentrations of CH₄ are distributed in the mid-Atlantic， northern Africa， the Middle East and western China.