PNNL

Abstract

We applied a daily-assimilated inversion method to estimate NOx (NO+NO2) emissions for June-September 2007 and 2008 on the basis of the Aura Ozone Monitoring Instrument (OMI) observations of nitrogen dioxide (NO2) and model simulations using the Regional chEmistry and trAnsport Model (REAM). Over urban Beijing, rural Beijing, and the Huabei Plain, OMI column NO2 reductions are approximately 45%, 33%, and 14%, respectively, while the corresponding anthropogenic NOx emission reductions are only 28%, 24%, and 6%, during the full emission control period (July 20 – Sep 20, 2008). The emission reduction began in early July and was in full force by July 20, corresponding to the scheduled implementation of emission controls over Beijing. The emissions did not appear to recover after the emission control period. Meteorological change from summer 2007 to 2008 is the main factor contributing to the column NO2 decreases not accounted for by the emission reduction. Model simulations suggest that the effect of emission reduction on ozone concentrations over Beijing is relatively minor using a standard VOC emission inventory in China. With an adjustment of the model emissions to reflect in situ observations of VOCs in Beijing, the model simulation suggests a larger effect of the emission reduction.