Characteristics of Satellite-Based CO/CO2, CO/NO2 Ratio in South Korea and China

This study analyzed the ratio of carbon monoxide (CO) and carbon dioxide (CO2), CO and nitrogen dioxide (NO2) for cities and regions in Korea and China using column-averaged carbon dioxide dry-air mole fraction (XCO2) of the Orbiting Carbon Observatory-2/3, CO and NO2 vertical column density (named XCO, XNO2 in this study) of TROPOspheric monitoring instrument from April 2018 to April 2022, and presented the relationship between socioeconomic indicators (population, number of vehicles, Gross Regional Domestic Product) and ratio, and differences in characteristics between Korea and China. First, CO2 and CO were analyzed after calculating AXCO2 and AXCO removing the background value and trend line due to the difference in atmospheric residence time of three gaseous substances (CO2, CO, and NO2). Comparing the three values by regions, AXCO and AXCO2 were relatively higher in China and XNO2 were higher in Korea and the ratio of both values (AXCO/AXCO2, AXCO/XNO2) was higher in China than in Korea. AXCO/AXCO2, AXCO/XNO2 and socioeconomic indicators have a positive correlation suggesting that the concentration of air pollutants and greenhouse gases is higher as the city is large and the economic activity is active. Regarding the differences in the ratio characteristics of Korea and China, the relationship between AXCO and AXCO2 showed a negative correlation in Korea and a positive correlation in China. When the relationship between AXCO and XNO2 was examined for summer and winter, the change of AXCO by season was not significant in Korea, whereas the change of AXCO and XNO2 by season was large in China resulting in the relationship between two countries appeared differently. These results suggest that seasonal variability and national emission characteristics should be considered in the process of analyzing the ratio of greenhouse gases to air pollutants.