IN-SITU MEASUREMENT AND CMAQ SIMULATION OF SO 2 OVER CENTRAL CHINA

In spring 2008, in-situ measurements of tropospheric SO2 are conducted in central China. Vertical distribution of SO2 is obtained from the surface to 4000 m. And the flight routes are selected according to the NASA OMI SO2 products. The numerical simulation of this campaign is conducted using the CMAQ v4.6 model. We use the WRF v3.1 model to provide the meteorological field and the NASA INTEX-B (2006) emission inventory for emission inputs. Two nested domains with 30/10 km resolution are defined, and the simulation period is 45 days with the first 15 days as spin-up. Improvements of SO2 dry deposition and advection schemes have been done to modify the CMAQ systems, and 3 sensitivity runs are achieved. The comparison of in-situ and remotelysensed measurements with CMAQ simulation shows a reasonably consistent picture of tropospheric SO2. And the CMAQ model tends to underestimate the SO2 concentration within the PBL and overestimate it in the free troposphere (FT), probably caused by the parameterization of advections. With the update of SO2 dry deposition rate, CMAQ gives better evaluation of surface SO2. The change of advection scheme supports the calculation of horizontal advection, which leads to less than 3% error in the sulfur balance and SO2 lifetime as ~ 1.5 days.