Sector‐Based Top‐Down Estimates of NO( x ), SO(2), and CO Emissions in East Asia

Top‐down estimates using satellite data provide important information on the sources of air pollutants. We develop a sector‐based 4D‐Var framework based on the GEOS‐Chem adjoint model to address the impacts of co‐emissions and chemical interactions on top‐down emission estimates. We apply OMI NO(2), OMI SO(2), and MOPITT CO observations to estimate NO( x ), SO(2), and CO emissions in East Asia during 2005–2012. Posterior evaluations with surface measurements show reduced normalized mean bias (NMB) by 7% (NO(2))–15% (SO(2)) and normalized mean square error (NMSE) by 8% (SO(2))–9% (NO(2)) compared to a species‐based inversion. This new inversion captures the peak years of Chinese SO(2) (2007) and NO( x ) (2011) emissions and attributes their drivers to industry and energy activities. The CO peak in 2007 in China is driven by residential and industry emissions. In India, the inversion attributes NO( x ) and SO(2) trends mostly to energy and CO trend to residential emissions.