In Situ Aircraft Measurements of CO2 and CH4: Mapping Spatio-Temporal Variations over Western Korea in High-Resolutions

Abstract

A cavity ring-down spectroscopy (CRDS) G-2401m analyzer onboard a Beechcraft King Air 350, a new Korean Meteorological Administration (KMA) research aircraft measurement platform since 2018, has been used to measure in situ CO2, CH4, and CO. We analyzed the aircraft measurements obtained in two campaigns: a within-boundary layer survey over the western Republic of Korea (hereafter Korea) for analyzing the CO2 and CH4 emission characteristics for each season (the climate change monitoring (CM) CM mission), and a low altitude survey over the Yellow Sea for monitoring the pollutant plumes transported into Korea from China (the environment monitoring (EM) mission). This study analyzed CO2, CH4, and CO data from a total of 14 flights during 2019 season. To characterize the regional combustion sources signatures of CO2 and CH4, we calculated the short-term (1-min slope based on one second data) regression slope of CO to CO2 and CH4 to CO enhancements (subtracted with background level, present as ∆CO, ∆CO2, and ∆CH4); slope filtered with correlation coefficients (R2) (<0.4 were ignored). These short-term slope analyses seem to be sensitive to aircraft measurements in which the instrument samples short-time varying mixtures of different air masses. The EM missions all of which were affected by pollutants emitted in China, show the regression slope between ∆CO and ∆CO2 with of 1.8–6% and 0.3–0.7 between ∆CH4 and ∆CO. In particular, the regression slope between ∆CO and ∆CO2 increased to >4% when air flows from east-central China such as Hebei, Shandong, and Jiangsu provinces, etc., sustained for 1–3 days, suggesting pollutants from these regions were most likely characterized by incomplete fossil fuel combustions at the industries. Over 80% of the observations in the Western Korea missions were attributed to Korean emission sources with regression slope between ∆CO and ∆CO2 of 0.5–1.9%. The CO2 emissions hotspots were mainly located in the north-Western Korea of high population density and industrial activities. The higher CH4 were observed during summer season with the increasing concentration of approximately 6% over the background level, it seems to be attributed to biogenic sources such as rice paddies, landfill, livestock, and so on. It is also noted that occurrences of high pollution episodes in North-Western Korea are more closely related to the emissions in China than in Korea.

Interannual Variability of Atmospheric CH4 and Its Driver Over South Korea Captured by Integrated Data in 2019

“…We also computed the intercept of the Keeling plot to infer the isotopic signature of the source responsible for enhancements in CH 4 , and the intercept values for summer and autumn were found to be −53.3‰ and −52.9‰, respectively (Figure 5b), which is consistent with biogenic emissions. The aircraft data observed over western Korea in the summer season also revealed biogenic emissions signatures using CH 4 /CO ratio analysis [39]. As reported in [19], high-latitude CH 4 has distinct δ 13 C isotopic signatures, from −60 to −50‰ for CH 4 hydrates; ruminants-digesting C4 plants give off CH 4 at −55 to −50‰, whereas those eating C3 plants give off −65 to −60‰ CH 4 , since C3 and C4 plants have different photosynthetic pathways that result in a different signature.…”

Unexpected Urban Methane Hotspots Captured from Aircraft Observations

“…Therefore, in this study, we use aircraft measurements obtained during a greenhouse gas measurement campaign to detect and characterize urban emissions of CO 2 , CO, and CH 4 in Seoul. Previous studies have used aircraft measurements to observe greenhouse gases along the areas of the Korean Peninsula. , Nonetheless, contrary to earlier works using airborne observations in South Korea, this study is the first to perform aircraft measurements inside the city boundaries of Seoul. In addition, we carry out ratio analyses using the aircraft measurements to detect urban emission hotspots where ground-based observations are not available.…”

“…Moreover, aircraft fly over various locations of the urban area in 1 observation day and also provide information of the vertical distribution of gases in realtime. Therefore, many studies have utilized aircraft observations to understand the variability of atmospheric gases over urban areas as well as for point source detections. ,,− …”

Overview of the KMA/NIMS Atmospheric Research Aircraft (NARA) and its data archive: Annual airborne observations over the Korean peninsula

“…Although significant uncertainty can arise due to the inhomogeneity of the number of dropsondes released per month (Figure 10), the temperature variation tendency observed was consistent with the results of previous studies (Ahn et al, 1984; Peel et al, 2007). With an increase in datasets accumulated in the data archive, for example it can be possible to conduct long‐term studies of atmospheric characteristics for investigating on the trend analysis (Jung et al, 2019; Ku et al, 2020; Li et al, 2020).…”