Development of a One-way Nested Global-regional Air Quality Forecasting Model

Abstract

We evaluated the ozone distribution over the Kanto region in Japan, calculated by a one-way nested global-regional air quality forecasting (AQF) system. This AQF system consists of global and regional chemistry-transport models (CTMs). The global CTM is based on CHASER (Chemical Atmospheric General Circulation Model for the Study of Atmospheric Environment and Radiative Forcing) model, whereas the regional CTM is based on the WRF (Weather Research and Forecasting)/ Chem model. The lateral boundary of the regional CTM domain is updated every 3 hours from the global CTM output. An experimental phase for this model system began in July 2006 and has provided 15-hour forecasts of the distribution of ozone concentrations over the Kanto region four times daily. The time evolution and horizontal distribution of chemical species calculated by this AQF system were compared to ground-based observations. Values of statistical measures are within the range suggested by the U.S. Environmental Protection Agency (EPA). By changing the initial value of the meteorological field from 6-hour forecast values to an analysis meteorological field, the average value of the correlation coefficient increased from 0.763 to 0.773.