Spatio-temporal variations of atmospheric methane and its response to climate on the Tibetan Plateau from 2010 to 2022

The Tibetan Plateau (TP) is a pivotal region for investigating climate change and the emission of greenhouse gases in terrestrial ecosystems. In this study, atmospheric methane columnar concentration (XCH4) data obtained from GOSAT products were used from March 2010 to February 2022. The comparative study between GOSAT XCH4 and Waliguan (WLG) ground-based methane measurements in annual terms demonstrated a high consistency, with a correlation coefficient of 0.996, indicating similar trends and amplitudes. Subsequently, a comprehensive investigation was carried out to explore the long-term trends and spatial differences of XCH4 on the TP, along with its association with climate variables. The findings revealed an east-west gradient in the spatial distribution of XCH4, characterized by higher concentrations in the southeast and lower concentrations in the northwest. During the 12-year study period, a consistent upward trend of XCH4 was exhibited across the whole plateau, ranging from 7.53 to 10.15 ppb/yr, and the areas of exceeding 9 ppb/yr accounted for 80.4% of the study area. The seasonal variation of XCH4 displayed a typical unimodal distribution, with the highest XCH4 occurring in late August to early September. The interannual growth rate of XCH4 was the highest in summer, followed by autumn, winter, and the lowest in spring. To better understand the climate variables influencing XCH4 on the TP, a Principal Component Analysis (PCA) was performed with a biplot. The results indicated that temperature (TEM), precipitation (PER), soil temperature (Soil_TEM), and soil humidity (Soil_HUM) were positively correlated with XCH4. However, wind speed (WSPD) and wind direction (WDIR) demonstrated negative correlations with XCH4.