Ground Methane Emission Monitoring In China Based On TROPOMI Satellite Observations

Methane（CH₄）is the second-largest greenhouse gas emitted by human activity and natural sources after carbon dioxide（CO₂）.Its relatively short lifetime in the atmosphere（about 12 years）means that we can mitigate the human impacts of climate change in a relatively short period of time by reducing CH₄ emissions.The creation of CH₄ emissions management policies can be based on the distribution maps of surface CH₄ concentration that are in large-scale and at high-resolution.The estimate of CH₄emissions with broad coverage are provided by currently extensively used satellite data supplemented with data from model simulations.However,it is at low spatial resolution.In this thesis,through the combination of atmospheric CH₄ observations from the TROPOMI sensor and wind data from the ECMWF global reanalysis,a straightforward divergence method is proposed to estimate the surface CH₄ emissions in China from March 2019 to September 2022 at a resolution of 7 km×7 km.This method was compared with the average annual CH₄ emissions of Emissions Database for Global Atmospheric Research（EDGARv7.0）,and the Root Mean Square Error（RMSE）is 2.53kg/km²/h and within error envelop（EE）is 72.93%,which represents the proportion of reliable values under certain uncertain conditions.The method in this thesis is used to monitor surface CH₄ emission in our country,and some results are given as follows:The areas with high concentrations of XCH₄ in China mainly include central China,East China,Beijing-Tianjin-Hebei region,Sichuan Basin and some northern parts of Xinjiang Uygur Autonomous Region,with an average concentration of 2064ppb（part per billion）,66ppb higher than the national average.In Tibet and Qinghai,the average concentration was 1934ppb,64ppb lower than the national average.The average annual CH₄emission in China during 2019-2022 was 81Tg（Terrogram）,and the emission in 2021 was the lowest（75Tg）due to the impact of COVID-19.In 2021,the largest anthropogenic emissions in China came from agriculture,energy activities and animal husbandry,accounting for 28%（20.8Tg）,25%（18.9Tg）and 19%（13.9Tg）of total emissions respectively,while wetlands,as the largest natural source,produced 14%（10.5Tg）of CH₄ emissions.The annual average CH₄ emission characteristics of Hebei Province and Jiangsu Province were compared and analyzed.The average CH₄ emission in 2019,2020,2021and 2022 was 5.60Tg,5.94Tg,6.03Tg and 6.11Tg,respectively,and the annual CH₄emission maintained a continuous growth.High CH₄ emissions areas include Shijiazhuang,Xingtai,Handan,Langfang,Tangshan and Hengshan.The average annual CH₄ emissions in Jiangsu Province increased year by year.From 2019 to 2022,the average CH₄ emission was 2.77Tg,3.63Tg,3.71Tg and 4.01Tg,respectively.The CH4 emission in Jiangsu Province showed a dependent distribution feature,mainly concentrated in the area around Hongze Lake and Taihu Lake.And the Beijing-Hangzhou Canal,Tongyu Canal,northern Jiangsu irrigation canal and other important rivers.