Assessing BC and CO emissions from China using EMeRGe aircraft observations and WRF/CMAQ modelling

Abstract

Accurate estimates of short-lived climate forcer emissions are essential for effective climate change mitigation, yet large uncertainties remain across Asia. This study integrates the Weather Research and Forecasting/Community Multiscale Air Quality version 5.0.2 (WRF/CMAQv5.0.2) simulations with Effect of Megacities on the Transport and Transformation of Pollutants at Regional and Global Scales (EMeRGe) airborne observations from spring 2018 to refine combustion-related emissions of black carbon (BC) and CO over East Asia. Aircraft observations, which are less affected by near-surface processes, confirmed the accuracy of the Global Fire Emissions Database (GFEDv4.1s) inventory near Thailand. In contrast, anthropogenic BC and CO from the Regional Emission Inventory for Asia (REASv2.1) in the Philippines showed negative biases. For Chinese air masses, the Hemispheric Transport of Air Pollution with corrections (HTAPv2.2z) resulted in overestimation for BC and underestimation for CO, agreeing with our prior ground-based findings on Fukue Island. Scaling Chinese BC emissions using an observation/model ratio (0.48 ± 0.13) gave our best estimate of 0.65 ± 0.25 Tg BC yr−1. Chinese emissions were further estimated at 166 ± 65 Tg CO yr−1 and 12.4 ± 4.8 Pg CO2 yr−1 using the BC/CO and CO/CO2 ratios from observations. These results suggest HTAPv2.2z requires revisions of 50 % downward for BC and 20 % upward for CO, particularly over central East China during spring. Other inventories including Community Emissions Data System (CEDSv2021_02_05) remain notably biased, while Evaluating the Climate and Air Quality Impacts of Short-Lived Pollutants (ECLIPSEv6b) and Tropospheric Chemistry Reanalysis (TCR2) estimates fall within our identified uncertainty ranges.