Greenhouse gas measurement using a mobile FTS during ASIA-AQ

Monitoring greenhouse gases (GHGs) such as CO2 and CH4 is essential for understanding their role in climate change and informing mitigation strategies. The ASIA-AQ campaign, a multi-country field study on Asian air quality during winter, was jointly organized by research institutions from various countries and NASA. As part of the campaign, a mobile Fourier Transform Spectrometer (FTS) was deployed at Ewha Womans University (EW) in Seoul for targeted observations. The mobile FTS, while offering the advantage of mobility to assess regional GHG characteristics, has a lower spectral resolution of 0.5 cm-1, compared to the higher 0.02 cm-1 resolution of the stationary FTS at the Anmyeon-do (AMY) Global Atmosphere Watch (GAW) Regional Station in Korea. To validate the accuracy of the mobile FTS, its retrievals were compared with those from the stationary high-resolution FTS before and after the ASIA-AQ campaign through sideby- side observation. Pre-ASIA-AQ, both the IFS125HR and EM27/SUN showed consistent differences in XCO2 and XCH4 concentrations, with both instruments demonstrating high sensitivity, as evidenced by their ability to capture shortterm changes effectively. After the campaign, the difference increased, showing slightly different characteristics compared to before ASIA-AQ. During the ASIA-AQ campaign, XCO2 measurements at EW were slightly lower than those at AMY, though occasional higher concentrations were observed. For XCH4, concentrations were higher at EW. Additionally, the XCH4 to XCO2 ratio remained relatively stable at AMY, while it varied slightly at EW. TROPOMI measurements of XCH4, compared to EM27/SUN, showed similar trends but an underestimation.