A study on the ozone formation using CMAQ with PA and HDDM in the Seoul Metropolitan Area.

Abstract:

HDDM (High-order Decoupled Direct Method) is an efficient method to understand sensitivity of ozone peak concentration on the precursor emission of NOx and VOCs (Volatile Organic Compounds). PA (Process Analysis) in the CMAQ (Community Multiscale Air Quality Model) is a probing tool to identify the formation pathways of the ozone.

CMAQ with the HDDM and PA was used to simulate the high peak ozone concentrations in the Seoul Metropolitan Area (SMA) for 2009. The predicted ozone concentrations by CMAQ were compared with observations at air quality monitoring stations in the SMA. The results showed that the model could depict observed diurnal variations of ozone concentration but it had a tendency of underestimating the ozone peak concentration. One of the main reasons for such discrepancies is due to uncertainties of precursor emissions of NOx and VOCs. The main processes inducing peak ozone were the horizontal transport and gas phase chemistry according to the PA.

In order to improve capacity of prediction high peak ozone concentration, sensitivity test of the precursor emissions on ozone formation using HDDM was carried out to determine which emission of VOCs and NOx is a controlling one in the ozone formation. The results showed that the ozone concentrations increased with VOCs emissions and decreased with NOx emission, which implies the VOC-limited region. The further details of model comparisons with observations and results of HDDM and PA will be discussed in the presentation.