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.
Highlights
Observations of carbon dioxide (CO2) in the atmosphere to obtain its temporal and geographic distribution have been made since the 19th century [1]
Instruments were calibrated with auto-pressure controller (APC) by the following steps: first, the output pressure was roughly adjusted with a regulator installed in standard sample cylinders; second, each standard air sample was injected through the rotary valve automatically in 40 min based on the RS-232 communication method; third, the pressure was set in the electric panel of the pressure regulator approximately 0.5–0.7 bar above ambient pressure and the electronic pressure regulator automatically adjusted the pressure until the pressure was equivalent to that detected from the pressure sensor installed upstream of the cavity ring-down spectroscopy (CRDS)
We investigated the regression slope calculated for each change monitoring (CM) flight (Figure 4) to determine if the observations are associated with emissions in Korea by comparing the regression slope against that associated with a typical Chinese emission source in the environmental monitoring (EM) campaign
Summary
Observations of carbon dioxide (CO2) in the atmosphere to obtain its temporal and geographic distribution have been made since the 19th century [1]. Instruments were calibrated with APC by the following steps: first, the output pressure was roughly adjusted with a regulator installed in standard sample cylinders; second, each standard air sample was injected through the rotary valve automatically in 40 min based on the RS-232 communication method; third, the pressure was set in the electric panel of the pressure regulator approximately 0.5–0.7 bar above ambient pressure and the electronic pressure regulator automatically adjusted the pressure until the pressure was equivalent to that detected from the pressure sensor installed upstream of the CRDS. The Picarro CRDS was calibrated more regularly and frequently (two-month intervals) in our laboratory, with a series of three World Meteorological Organization (WMO) scale standard sample tanks for CO2 (374.06, 419.45, and 467.78 ppm) and CH4 (1756.7, 1901.4, and 2325.8 ppb), two for CO (311.1 and 89.7 ppb) from NOAA/ESRL, with full coverage of the observed range of ambient air. Instrument precision was calculated from the average 1-σ standard deviation during approximately 30 min of the standard sampling and was 0.03 ppm for CO2, 0.1 ppb for CH4, and 2.2 ppb for CO
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