Downward and upward revisions of Chinese emissions of black carbon and CO in bottom-up inventories are still required: an integrated analysis of WRF/CMAQ model and EMeRGe observations in East Asia in spring 2018

Abstract. Accurate estimates of short-lived climate forcers (SLCFs) emissions are required to allow efficient strategies that mitigate climate change to be developed. However, there remain large uncertainties about emissions of SLCFs from Asia. We identified and improved the constraints of combustion-related emissions of black carbon (BC) and CO using the WRF/CMAQ model (v5.0.2) and the EMeRGe airborne observation data for East Asia in spring 2018. We performed case studies of air masses containing emissions from fires near Thailand and emissions from urban areas in the Philippines and China. Chinese emissions were analysed in depth. Unlike observations at ground-based stations, the observations from aircraft used here would not have been strongly influenced by local emissions and near-surface processes. We confirmed that the GFEDv4.1s inventory provided accurate data for emissions from fires near Thailand. However, anthropogenic BC and CO emissions from the Philippines (REASv2.1) were negatively biased. Marked positive and negative differences were found for BC (+1.62 µg m⁻³) and CO (−400 ppbv) from the HTAPv2.2z emission inventory for Chinese air masses, consistent with the results of previous ground-based studies. The Chinese BC/CO emission ratio, 3.5±0.1 ng m⁻³ ppb⁻¹, calculated using data from airborne observations in the altitude range ~0.3–1 km also agreed with the ground-based results. Linearly scaling BC emissions using an observation/model ratio (E(BC) = 0.48±0.13) gave our best estimate of 0.65±0.25 (Tg BC) yr^-1. The calculated BC/CO and CO/CO₂ ratios led us to estimate that emissions from China are 166±65 (Tg CO) yr^-1 and 12.4±4.8 (Pg CO₂) yr^-1. The results suggested that downward and upward revisions of Chinese emissions of BC (−50 %) and CO (+20 %), respectively, are required in HTAPv2.2z emission inventory.