engleski

Vertical diffusion verification in the EMEP model

Atmospheric boundary layer (ABL) turbulence is an important transport mechanism in the troposphere. All species emitted at the surface must pass through the ABL. Because turbulence acts on spatial scales that are much smaller than the typical size of the grid cells, turbulent diffusion must be parameterised in models. One of the objectives of EMEP4HR project is a implementation of a new scheme for vertical diffusion calculation. A new vertical structure of the EMEP4HR model will be defined and it needs to be tested with respect to the model’ s vertical diffusion parameterisation to secure a consistent description of vertical exchange. Presently in the EMEP model vertical diffusion coefficient, K(z), is calculated with Blackadar (1979) method in stable conditions and in unstable conditions K(z) is calculated due to O’ Brien (1970) formula. The new approach uses generalized form of O’ Brien’ s third-order polynomial K(z). It is an linear-exponential function with convenient analytic properties (Grisogono and Oerlemans, 2002). Here the new method for K(z) and the old one are tested and compared with measurements of surface NO2, SO2 and SO4 daily concentrations for January and July 2001 on EMEP model domain. First results of this study indicate improvements with the new method.

atmospheric boundary layer; vertical exchange; NO2; SO2

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