STUDYING HIGH OZONE CONCENTRATIONS BY USING THE DANISH EULERIAN MODEL

The long-range transport of air pollutants (LRTAP) over Europe is stud ied by a mathematical model based on a system of partial differential equations (PDEs). The number of PDEs is equal to the number of species studied and the model contains 35 species at present. Among the speci es are NO, NO2, NO3-, HNO3, NH3, NH4+, O3, PAN, SO2, SO42- and many hy drocarbons. Most of the 70 chemical reactions involved in the model ar e nonlinear (including here many photochemical reactions). The model r equires large sets of input data. Emissions of SO2, NO(x), NH3 and bot h natural and anthropogenic volatile organic compounds (VOC) are neede d in the model. The meteorological data consist of fields of wind velo cities, precipitation, surface temperatures, temperatures of the bound ary layer, relative humidities and cloud cover, which are read in the beginning of every 6-h interval. Both daytime and nighttime mixing hei ghts are used in the model. Many of the species in the model vary on a diurnal basis. An investigation of the main mechanisms that determine the diurnal variation of the ozone concentrations is performed. One o f the important conditions that is necessary if one wants to represent correctly the diurnal variations of the concentrations is to have acc ess to meteorological data that vary diurnally. This is especially tru e for the temperature and the mixing height. The use of modern numeric al algorithms (which are combined with vectorization of the most time- consuming numerical procedures) allows one to perform long-term runs w ith the model on several high-speed computers. Results obtained in run s with meteorological data for July 1985 and August-October 1989 are d iscussed. The computed concentrations and depositions are compared wit h measurements taken at stations located in different European countri es. The agreement between calculated concentrations and measurements i s reasonably good. Results obtained with several scenarios, in which t he NO(x) emissions and/or the anthropogenic VOC emissions are varied, are presented. Several main conclusions are drawn by studying the resu lts obtained during the comparisons. Some plans for future development of the models are discussed.