On the dry deposition of ozone and reactive nitrogen species

Abstract

Dry deposition of ozone and reactive nitrogen species, such as NO, NO2, NO3, N2O5, HNO3, NH3 and NH4NO3, is examined in the context of numerical methods. These methods are based on the generally accepted micrometeorological ideas of the transfer of momentum, sensible heat, and matter near the Earth's surface, where chemical reactions among these trace species are considered. The fluxes in the turbulent region of the atmospheric surface layer are parameterized by first-order closure principles. The uptake processes by vegetation and the soil are described by a Deardorfl=type soil-vegetation-atmosphere transfer scheme. As in the case of HNO3 and NH3 the resistance of the system vegetation-soil against uptake of matter seems to be of minor importance, parameterization approaches for the more important transfer resistances of the interfacial sublayer adjacent to the surface are evaluated. The model results show that especially the dry deposition fluxes of reactive nitrogen species are not only influenced by micrometeorological and plant-physiological parameters, but also strongly affected by chemical reactions. In most cases, the fluxes of these trace constituents vary strongly with height and often show a change of direction. These flux results differ considerably from those derived with the constant flux approximation, sometimes up to several hundred percent. Thus, in such cases the most widely used "big leaf" multiple resistance approach which is based on the constant flux approximation seems to be inappropriate for deriving dry deposition fluxes and deposition velocities of reactive nitrogen species. © 1995.