Evaluation of the Potential Use of Satellite-Derived XCO2 in Detecting CO2 Enhancement in Megacities with Limited Ground Observations: A Case Study in Seoul Using Orbiting Carbon Observatory-2

Exact assessment of urban atmospheric CO2 enhancement, which is higher than background CO2 concentrations, is critical to mitigate carbon emissions in the city. However, ground-based atmospheric CO2 measurements covering the diverse landscape across the city are still limited. This study utilizes the column integrated CO2 concentration (XCO2) data obtained from the NASA Orbiting Carbon Observatory-2 (OCO-2) to evaluate urban CO2 enhancements over Seoul Capital Area (SCA) of South Korea for the period 2014–2018. In this study, Jirisan National Park (JNP), which is the cleanest area on the same orbit track with SCA, is defined as the background area considering its strong vegetation activity and low anthropogenic carbon emissions. By comparing XCO2 between SCA and JNP based on wind speed, we find an apparent increase in XCO2 by 1.71 to 2.21 ppm over SCA only on the days with wind speed less than 4 m s−1. Strong wind speed (e.g., over 4 m s−1) disrupts the identification of XCO2 enhancements over SCA due to atmospheric mixing between SCA and JNP. In addition, we compare estimated XCO2 differences between SCA and JNP from OCO-2 with other low-resolution data. This increase in XCO2 over SCA is only observed in OCO-2. Overall, our results suggest that high-resolution satellite remote sensing of XCO2 constrained by wind speed has strong potential to open up the possibility of identifying atmospheric CO2 enhancements in the city where ground-based observations are limited.