High-resolution simulation of wintertime fossil fuel CO₂ in Beijing, China: Characteristics, sources, and regional transport

In this study, a high-resolution simulation of fossil fuel CO₂ in Beijing and surrounding areas, China, during January 2014 is performed to investigate the characteristics and sources of Beijing fossil fuel CO₂ (FFCO₂) mixing ratios and the impact of regional transport. The model reasonably reproduces the observed meteorological fields in the study domain, including temperature, relative humidity, wind speed, and wind direction. The simulated CO₂ and CO mixing ratios in Beijing are in good agreement with the measurements. Elevated FFCO₂ levels are produced by the model in megacities, such as Beijing, Tianjin, Shijiazhuang, and Baoding. The model result shows that FFCO₂ mixing ratios are significantly correlated with observed total CO₂, CO, and PM_2.5 concentrations in Beijing. Sensitivity experiments show that Beijing FFCO₂ is mainly from industry and residential emissions (35% for each), followed by power plant (21%) and transportation (9%) emissions in January 2014. Spatially, the largest contributor for Beijing FFCO₂ is the local source, and regional transport also plays an important role in winter. The impact of regional transport is associated with wind direction, in which south/east (north/west) wind tends to accumulate (dilute) Beijing FFCO₂. In addition, the roles of regional transport during haze and clean episodes are significantly distinct in winter, and more contribution is found in haze episodes.