Abstract
A three-dimensional photochemical air pollution model was developed to simulate the regional scale summer time photochemical oxidants episodes. The numerical model includes transport, diffusion, dry deposition, emission and chemical reaction processes. Dry deposition processes were modeled using resistance theory that depends on land use data. Carbon-Bond Mechanism (CBM-IV) was used as chemical reaction scheme. The Colorado State University Mesoscale Model (CSUMM) with a dynamic initialization and a four-dimensional data assimilation based on observed wind data was used as meteorological driver to generate three-dimensional flow anddiffusion fields.
A model validation study was performed over the summer timeKanto area for 42 hours starting from 0400JST on July 16, 1981. NOx and NMHC emission intensities (including biogenic HC) estimated from 1 km2 data over the Kanto area. Numerical results were then quantitatively compared with the routine surface monitoring stations data and the three-dimensional airborne observation data.
The observed spatial and diurnal variations of 03, NOx and NO2 concentrations are well simulated by the present model. The predictive performance of thepresent model exceeds the model evaluation criteria recommended by the US-EPA. Furthermore, the present model qualitatively reproduces the three-dimensional behaviors of 03, NOx, NO2 and NMHC concentrations observed by the aircraft.
