Identifying local anthropogenic CO2 emissions with satellite retrievals: a case study in South Korea

We used multiyear Greenhouse Gases Observing Satellite (GOSAT) dry air, column-integrated CO2 (XCO2) retrievals (2010-2013) to evaluate urban and local-scale CO2 emissions over East Asia and examined whether GOSAT XCO2 captures the impact of strong local CO2 emissions over South Korea, an East Asian downwind region with high atmospheric aerosol loading and strong summer monsoons. We chose a region in western Mongolia (upwind region) as the XCO2 background, and estimated XCO2 enhancements in South Korea to gauge local and regional emissions. We found that the cold season (November-February) was better suited for estimating XCO2 enhancements of local emissions due to the summer monsoon and stronger transboundary impacts in other seasons. In particular, we focused on three local GOSAT XCO2 footprints (about 10.5 km in diameter) in South Korea: the Seoul Metropolitan Area (SMA), the Gwangyang Steelworks and Hadong power plants (GYG), and the Samcheonpo power plants (SCH). The range of XCO2 enhancement was 7.3-10.7 ppm (14.1-21.3 mg m(-3) in standard temperature and pressure (STP)). By estimating other important contributions to XCO2 enhancements such as the XCO2 latitudinal gradients and Chinese fossil fuel combustions, we estimated the net enhancements caused mainly by local CO2 emissions in the range of 4.2-7.6 ppm (8.1-14.7 mg m(-3) in STP) These high enhancements imply that large point source contributions are an important factor in determining these enhancements, even if contributions are also made by broader-scale emissions. Additionally, differences in net XCO2 enhancements and trends between GYG (+ 4.2 ppm (+ 8.2 mg m(-3) in STP), - 0.2 ppm year(-1) (-0.4 mg m(-3) year(-1) in STP)) and SCH (+ 7.6 ppm (+ 14.9 mg m(-3) in STP), + 1.3 ppm year(-1) (+ 2.6 mg center dot m(-3) year(-1) in STP)) indicate that these closely located footprints (approximately 26 km apart) are separable. These results will be useful in evaluating and reducing uncertainties in regional and local anthropogenic greenhouse gas (GHG) emissions over East Asia.