A new box model to forecast urban air quality: BOXURB

This paper presents a model to forecast concentrations of nitrogen dioxide NO2 in urban areas. A box model provides a simple and robust description of air quality in urban areas, especially where emissions data are only available on a fairly coarse grid. BOXURB is a box model with some novel features. It can use synoptic observations of the meteorology, or numerical forecasts of wind and cloud. Traffic emissions are adjusted by time and day of week, and space heating emissions by degree hours. The urban heat flux combines an urban heat store adjustment, a space heating term, and the rural heat flux. Pollutants accumulate with the onset of light winds. NO2 is forecast by subdividing the NOx into its constituents, NO (nitric oxide) and NO2. The subdivision is empirical for most of the year, but in ozone episodes the photostationary state is invoked. The forecasts are sent by the Met Office to NETCEN AEA Technology for use in the Department of Environment's Air Quality Bulletin System.