A Statistical Approach to Estimate Spatial Distributions of Wet Deposition in Germany

Abstract

The correct spatial interpolation from a few available point measurements of wet deposition - which contributes a major partto total deposition - is very important for the determination ofa possible exceeding of critical loads: A wide spatial variability is a property of both deposition and critical loads.For this purpose, the meteorological variables having relevant influence on wet deposition and being available from routine measurements were used as input data for a statistical model forthe estimation of wet deposition. Those variables are precipitation amount, preceding dry period, wind direction andseason. The results obtained from the developed model were validated using measurements from routine monitoring stations inGermany for daily wet deposition rates of the major anions andcations. After description of model development and verification,the application of the model is presented exemplarily for sulfate,chloride and nitrate. Therefore daily precipitation data from afew representative monitoring stations and additional informationabout wind direction from meteorological maps were used as modelinput. As a result, reliable point estimates for wet depositionwere available in addition to the measured data, thus allowingspatial interpolation with higher accuracy. The resulting wetdeposition maps reveal that the critical loads for theinvestigated substances are already exceeded in some areas ofGermany, particularly when the additional input from dry andoccult (fog and cloud) deposition is taken into account. Using allavailable daily precipitation data in an annual routine, depositionmaps could be available with high spatial resolution (<10 km).