Direct measurement of urban CO2 emission in Gwangju, Korea

To quantify anthropogenic influenced on CO₂ exchanges between atmosphere-urban interface, direct flux measurements of CO₂ and H₂O as well as heat was taken place using eddy-covariance (EC) method at Gwangju (population density: 2,920 people/km²), Korea from November 2017 to this year. For the reliable measurement of fluxes in urban setting, the EC system has been installed on the helideck (86m, AGL) of city hall, since the mean building height was estimated as 12 m based on the Electronic Architectural administration Information System (EAIS) in Korea. To assess the building effects on the eddy break up, the Computational Fluid Dynamic (CFD) modeling was performed and only the results with building interference free data sets are used for further investigation. As a result, the observed CO₂ and sensible heat fluxes agree well with the magnitude of previously reported values in other urban settings, which range from -1700 μmol/m²s to 1129.1 μmol/m² s and from -200W/m² to 854.2W/m², respectively. Since our footprint analysis suggests that the EC measurements of this setting covered many diverse land uses such as commercial, residential and industrial area and provided possibilities of quantifying the emission strengths of whole variety of urban utilization activities. As a first effort, this work analyze the measurement to track the emission strength of CO₂ by urban traffic, since the flux measurements showed distinct day of week and diurnal patterns as expected; the CO₂ flux correlates well with traffic pattern. To estimate the CO₂ emission from traffic with minimizing the effect of seasonal and diurnal changes related with biogenic activities, fluxes and traffic difference between weekday and weekend within the time window of interest in a day were used. Our preliminary result shows that the CO₂ flux from the car was 0.0514 μmol/m²s/car as a mean value. More detailed analysis with deep interpretation on this value will be discussed during the meeting.