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

• Main Authors: Shanlan Li, Youngmi Kim, Jinwon Kim, Samuel Takele Kenea, Tae-Young Goo, Lev D Labzovskii, Young-Hwa Byun
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: Remote Sensing
• Subjects: Aircraft; CO₂ and CH₄; regression slope between CO and CO₂; regression slope between CH₄ and CO; korea; spatio-temporal variations
• Online Access: https://www.mdpi.com/2072-4292/12/18/3093

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 △CO₂increased 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.