5:15 PM - 6:45 PM
[AAS09-P03] The influence of emission sources and atmospheric transport on regional methane vertical distributions over China
Keywords:GOSAT/TANSO-FTS, methane vertical distribution, MIROC4-ACTM
China is one of the world's largest methane source regions, with its anthropogenic emissions accounting for more than 10% of the global anthropogenic emissions [Peng et al., 2016]. We have analyzed vertical profiles and columnar amounts (XCH4) of methane over China obtained from the thermal infrared (TIR) band of TANSO (Thermal And Near-infrared Sensor for carbon Observation)-FTS (Fourier Transform Spectrometer) onboard GOSAT (Greenhouse Gases Observing Satellite) to clarify the characteristics of their seasonal variations and evaluate the influence of surface emissions and atmospheric transport on the methane vertical profiles.
We have first divided China into several regions by considering topography and methane emission sources and then calculated XCH4 and partial columnar amounts of methene (XpCH4) for each of the regions [Chandra et al., 2017]. In South China Sea, where there is no methane source, XCH4 and XpCH4 in all tropospheric layers showed minimum in summer, which reflects from the reaction with OH radicals in the troposphere. In Tibetan Plateau, in contrast, XCH4 and XpCH4 in all atmospheric layers were highest in summer, which could be explained both by methane emissions mainly from wetlands and atmospheric transports in the upper atmosphere. In North China, which is a high methane emission region, XCH4 and XpCH4 in atmospheric layers in the lower troposphere and above the upper troposphere were low in spring and high in summer and autumn; these seasonal variations could be caused by anthropogenic emissions and atmospheric transports in the upper atmosphere.
We have also compared XCH4 and XpCH4 based on the TANSO-FTS TIR data with those based on methane vertical profiles simulated by MIROC4-ACTM (Model for Interdisciplinary Research on Climate, version 4.0-based Atmospheric Chemistry-Transport Model) [Patra et al., 2018; Belikov et al., 2022]. In most regions over China, seasonal variations in XCH4 from the TIR and MIROC4-ACTM data were in general in good agreement to each other; however, MIROC4-ACTM XpCH4 were significantly higher than TIR XpCH4 in the lower troposphere.
We have first divided China into several regions by considering topography and methane emission sources and then calculated XCH4 and partial columnar amounts of methene (XpCH4) for each of the regions [Chandra et al., 2017]. In South China Sea, where there is no methane source, XCH4 and XpCH4 in all tropospheric layers showed minimum in summer, which reflects from the reaction with OH radicals in the troposphere. In Tibetan Plateau, in contrast, XCH4 and XpCH4 in all atmospheric layers were highest in summer, which could be explained both by methane emissions mainly from wetlands and atmospheric transports in the upper atmosphere. In North China, which is a high methane emission region, XCH4 and XpCH4 in atmospheric layers in the lower troposphere and above the upper troposphere were low in spring and high in summer and autumn; these seasonal variations could be caused by anthropogenic emissions and atmospheric transports in the upper atmosphere.
We have also compared XCH4 and XpCH4 based on the TANSO-FTS TIR data with those based on methane vertical profiles simulated by MIROC4-ACTM (Model for Interdisciplinary Research on Climate, version 4.0-based Atmospheric Chemistry-Transport Model) [Patra et al., 2018; Belikov et al., 2022]. In most regions over China, seasonal variations in XCH4 from the TIR and MIROC4-ACTM data were in general in good agreement to each other; however, MIROC4-ACTM XpCH4 were significantly higher than TIR XpCH4 in the lower troposphere.