THE UNCERTAINTY OF ATMOSPHERIC SOURCE-RECEPTOR RELATIONSHIPS IN EUROPE

This paper investigates the composite uncertainty of a long range transport model of sulfur in Europe. This composite uncertainty includes the effect on model output of uncertain transport wind, meteorological forcing functions, parameters, and spatial distribution of emissions. Other sources of uncertainty are omitted in the analysis. Stochastic simulation is used for computations. The combined effect of these uncertainties on total annual sulfur deposition at three receptors ranged from about 10 to 20% (coefficient of variation). In comparing the effects of different uncertainties on annual model output, meteorological forcing functions were found to be the least important because of their frequent temporal variation in the model. The stochastic procedure was also used to compute the uncertainty of transfer coefficients for 30 source-receptor combinations; their relative uncertainty ranged from about 10 to 30% and was not correlated with distance. However, their absolute uncertainty (standard deviation) was strongly correlated. with distance and was found to be proportional to the values of the transfer coefficients themselves. This insight was used to develop a simple method for estimating the uncertainty of sulfur deposition calculated with a transfer matrix. This method was then used to evaluated the "reliability" of emission reduction scenarios in reducing deposition. © 1990.