| The EMEP MSC-W Eulerian chemical transport model, and its predictions of
deposition of acidifying and eutrophying pollutants over Europe, play a
key role in the development of emission control strategies for Europe.
It is important that this model is tested against observational data.
Here we compare the results of the EMEP model with measured data from 160
sites of the European Union/ICP Forest (Level II) monitoring network, for
the years 1997 and 2000. This comparison comprises: (a) Precipitation
amount, (b) Total deposition of SO2−4 to coniferous and
deciduous forests, (c) Wet deposition of SO2−4, NO3−
and NH4+ in open field sites, and (d) Concentrations of
SO2−4, NO3− and NH4+ in precipitation.
Concerning precipitation, the EMEP model and ICP network showed
very similar overall levels (within 4% for 1997 and 11% for 2000). The
correlation was, however, poor (r2=0.15–0.23). This can
be attributed largely to the influence of a few outliers,
combined with a small range of rainfall amounts for most points.
Correlations between modelled and observed deposition values in this study
were rather high (r2 values between 0.4–0.8 for most components
and years), with mean values across all sites being within 30%.
The EMEP model tends to give somewhat lower values for SO2−4,
NO3− and NH4+ wet deposition
to ICP, but differences in mean values were within 20% in 1997 and 30%
in 2000. Modelled and observed concentrations of SO2−4,
NO3− and NH4+ in precipitation are very similar
on average (differences of 0–14%), with good correlation between
modelled and observed data (r2=0.50–0.78). Differences between
the EMEP model and ICP measurements are thought to arise from a mixture
of problems with both the observations and model. However, the overall
conclusion is that the EMEP model performs rather well in reproducing
patterns of S and N deposition to European forests. |