Top‐down analysis of the elemental carbon emissions inventory in the United States by inverse modeling using Community Multiscale Air Quality model with decoupled direct method (CMAQ‐DDM)

Abstract

A Community Multiscale Air Quality (CMAQ) model based inverse method is used for calibrating the 2004 elemental carbon (EC) emissions in the continental United States. We convert the Thermal Optical Transmittance (TOT) EC measurements to the Thermal Optical Reflectance (TOR) equivalents to fully utilize available observational networks. The reestimate of the total emissions is 0.40 Tg yr−1, about 13% higher than the a priori. The posterior CMAQ simulation driven by the adjusted emissions had an ∼10% reduction in annual average fractional error based on 24 h EC observations. Comparison of simulated EC concentrations to hourly aethalometer black carbon (BC) measurements improved as well. Also, using the EC scaling factors to adjust the primary particulate organic matter (OM) emissions improved performance for OM simulation. Results show that splitting sources further spatially and category‐wise increases the flexibility of adjusting emissions according to the spatial variability of the emissions strength and hence makes a better reestimate of emissions.