AN EXPERIMENTAL METHOD TO TEST THE EFFECTS OF LOCAL EMISSION REDUCTIONS DURING SUMMERSMOG

A method is presented that makes it possible to eliminate some of the meteorological influence on the change in air pollutant concentrations (mainly NO_χ and ozone) when considering the effects of local emission reductions. The relation of measurements outside the test area to values inside the area for normal conditions (i.e. defined weather type, no emission reduction in the test area) allows prediction of the values for the test area during emission reductions, but only if this relation shows a good correlation. This prediction includes the influence of meteorological factors that are distributed more or less homogeneously within an area of about 100 km × 100 km, which includes a large part of the meteorological influence. The comparison of predicted and measured values in the test area shows the effect of emission reduction, with the uncertainty of remaining meteorological effects, of course. The method is applied to the Heilbronn ozone experiment in summer 1994. Most precise results are obtained for ozone, while conclusions for nitrogen oxides are more uncertain.