Sensitivity analysis of photochemical ozone to its precursor emissions over East Asia by CMAQ-DDM

In the past three decades, anthropogenic emissions in East Asia have increased dramatically in parallel with the economic growth, and the trans-boundary air pollution arose as a concerning issue. For instance, high photochemical oxidant (over 120 ppbv) was observed at the remote clean island in Japan during 2007 springtime. In this event, many studies concluded that the high possibility of the impact of Asian-scale trans-boundary pollutants. To investigate the source-receptor relationships, modeling study is useful, however, if the chemical reaction involves the nonlinear response (e.g., ozone), to estimate its S-R relationships is quite difficult. The decoupled direct method (DDM) which was implemented in CMAQ ver. 4.7.1 is an efficient and accurate way of performing sensitivity analysis to model inputs. CMAQ-DDM has been extended to higher-order (HDDM) for gas-phase, and calculates first and second-order sensitivity coefficients representing the responsiveness of atmospheric chemical concentrations to perturbations in a model input or parameter (e.g., emission, reaction rate, initical condition, or boundary condition). This applications are well conducted in the U.S., whereas it is not fully examined in East Asia. In this study, we apply CMAQ-DDM technique for ozone and its precursor pollutants in East Asia. In the case of trans-boundary air pollution episode occurred on 7-9 May, 2007, the 1st order ozone sensitivity to the anthropogenic NOx emissions from China show the positive value in almost part over East Asia, namely represent the NOx-sensitive region, whereas in the large-point sources in China (e.g., Beijing and Shanghai), it shows the negative value due to the ozone titration by NO. We will also report more detailed region specified S-R analysis and cross-sensitivity analysis between NOx and VOC over China, Korea and Japan.