[A-AS09] Atmospheric Chemistry

[AAS09-P07] Investigation of Altitude-Dependent variation on GHGs Ratios from aircraft measurements over the Yellow Sea in the western coast of the Korean Peninsula

*Jongbyeok Jun¹, Yongjoo Choi¹, Jeongwhan Kim¹, Chisung Yun¹, Jaegyu Kim¹, Shanlan Li², Sumin Kim², Daegeun Shin², Kyung-On Boo², Beom-Keun Seo^1,3 (1.Hnakuk University of Foreign Studies, Yongin, South Korea, 2.Climate Research Department, National Institute of Meteorological Sciences, Jeju, South Korea, 3.Environmental Research Center, Hanseo University, Seosan, South Korea)

Keywords:Aircraft, GHGs, Greenhouse gases, CH4, CO2

To attain Net Zero by 2050, it is crucial to accurately estimate the emissions of long-lived greenhouse gases (GHGs), such as CO₂ and CH₄. In general, GHGs monitoring has been conducted by long-term measurements at fixed locations and on global scale using satellite observations to capture trends. Recently, aircrafts have been employed to measure the vertical and spatial distribution of GHGs concentrations from the surface to the upper troposphere. Using GLA331-MCEA1 (OA-ICOS; ABB-LGR) which was equipped on a research aircraft (KingAir-C90GT, KingAir-350HW; NARA), we measured CO₂, and CH₄ concentrations over the Yellow Sea of Korea and nearby large coal-fired power plants in 2021 ~ 2024. To investigate the characteristics of regional emission sources, we calculated the ratios of ΔCH₄/ΔCO₂, where delta (Δ) indicates the subtraction of background concentrations (the 1st percentile of each flight), from the measured values. In this study, we utilize a time-centered 60-second rolling window, determined by timestamps for a maximum of 61 observations in each calculation, alongside a coefficient of determination cutoff of R² ≧ 0.5. Slope calculations with an R² below this threshold are regarded as effectively un-correlated and are thus excluded from the analysis. Moreover, the minimum number of points required for a valid slope is set at 3, and slopes with ΔCH₄ or ΔCO₂ less than 5 times the precision value are disregarded to prevent the inclusion of slopes potentially driven by noise rather than real covariance. Subsequently, based on back-trajectories from the HYSPLIT model, we analyzed the regional and altitude differences in ΔCH₄/ΔCO₂, which was divided into administrative districts. The estimated ΔCH₄/ΔCO₂ ratios obtained through airborne measurement will be compared with those from bottom-up GHGs emission inventories such as Emissions Database for Global Atmospheric Research (EDGAR v6.0) to validate the accuracy of emission inventories.