Essai de prevision synoptique de la pollution par l'acidite forte dans la region rouennaise

Abstract

Two simple synoptic criteria are defined for the prediction of high SO 2 concentration in the Rouen region: 1. (i) A period of 24 h during which the mean wind velocity was less than 3.0 m s −1. 2. (ii) A forecast of a similar situation for tomorrow. At the present time, the proposed method, which uses only information contained in the daily forecast of the Meteorological Office, is the only practicable forecast of air pollution. The mathematical diffusion models and the empirical diffusion formulas need numerical weather data which are not available today for tomorrow, thus they cannot be effectively used in a particular forecast. They may only be verified in retrospect. The proposed empirical method can allow to forecast pollution in calm periods. The mathematical diffusion models and the empirical correlation formulae have singularities when the wind velocity approaches zero and therefore cannot be used for calms. While a single year of observation seems too short for the assessment of a numerical forecast, the r.m.s. error of the present method is less than that of mathematical models, even when calculated for the days with the highest pollution of the winter. The principle of the proposed method of forecasting pollution is valid for other towns or regions, but the numerical data published herewith (quantitative relations between the length of the calm period and the pollutant level) are inseparable from the emissive complex in the given topography, namely the region of Rouen.