Atmos. Chem. Phys. Discuss., 3, 3493-3523, 2003
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Operational mapping of atmospheric nitrogen deposition to the Baltic Sea
O. Hertel, C. Ambelas Skjøth, J. Brandt, J. H. Christensen, L. M. Frohn, and J. Frydendall
National Environmental Research Institute, Department of Atmospheric Environment, P.O. Box 358, Frederiksborgvej 399, 4000 Roskilde, Denmark

Abstract. A new model system for mapping and forecasting nitrogen deposition to the Baltic Sea has been developed. The system is based on the Lagrangian variable scale transport-chemistry model ACDEP (Atmospheric Chemistry and Deposition model), and aims at delivering deposition estimates to be used as input to marine ecosystem models. The system is tested by comparison of model results to measurements from monitoring stations around the Baltic Sea. The comparison shows that observed annual mean ambient air concentrations and wet depositions are well reproduced by the model. Diurnal mean concentrations of NHx (sum of  NH3 and NH4) and NO2 are fairly well reproduced, whereas concentrations of total nitrate (sum of HNO3 and NO3) are somewhat overestimated by the model. Wet depositions of nitrate and ammonia are fairly well described for annual mean values, whereas the discrepancy is high for the monthly mean values and the wet depositions are rather poorly described concerning the diurnal mean values. The model calculations show that the atmospheric nitrogen deposition has a pronounced south – north gradient with depositions in the range about 1.0 tonnes N km−2 in south and 0.2 tonnes N km−2 in north. The model results show that in 2000 the maximum deposition to the Danish waters appeared during the summer in the algae growth season. For the northern parts of the Baltic the highest depositions were distributed over most of the year.

Citation: Hertel, O., Ambelas Skjøth, C., Brandt, J., Christensen, J. H., Frohn, L. M., and Frydendall, J.: Operational mapping of atmospheric nitrogen deposition to the Baltic Sea, Atmos. Chem. Phys. Discuss., 3, 3493-3523, doi:10.5194/acpd-3-3493-2003, 2003.
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