Modelling and mapping ozone deposition in Europe

A new dry deposition module has been developed for European-scale mapping a nd modelling of ozone deposition fluxes (Emberson et al., 2000a,b). The mod ule is being implemented in the photochemical long-range transport model of EMEP that is currently used to estimate exceedance of the existing critica l levels for ozone within the UN ECE LRTAP programme. The deposition model evaluates the atmospheric, boundary layer and surface resistances to ozone transfer with the calculation of the dry deposition velocity performed acco rding to a standard resistance formulation. The approach differs from other existing methods through the use of a detailed stomatal uptake model that describes stomatal conductance as a function of plant species, phenology an d four environmental variables (air temperature, solar radiation, water vap our pressure deficit and soil moisture deficit). Comparison of preliminary model outputs for selected land-cover types indicate that the model is capa ble of predicting the seasonal and diurnal range in deposition velocities t hat have been reported previously in the literature. The application of thi s deposition scheme enables calculations of ambient ozone concentrations to be made using a biologically based method that can distinguish stomatal an d non-stomatal components of total ozone deposition. The ability to estimat e stomatal ozone fluxes (according to vegetation type, phenology and spatia l location) that are consistent with evaluations of atmospheric ozone conce ntrations will be helpful in future assessments of ozone impacts to vegetat ion.