A Boundary Layer Parameterization for Global Dispersion Models

In this note we present the essentials of a simple algorithm which simulates the main features of a dry, horizontally homogeneous atmospheric boundary layer, a more comprehensive presentation of these ideas are found in Nappo and van Dop (1993). The algorithm or parameterization scheme is designed only for use in global-scale air chemistry and transport models. Details of dispersion in the convective and stable boundary layers are not addressed; instead, we specify the concentration profiles for these PBL conditions. It is this simplicity that makes this algorithm attractive for parameterizing subgrid-scale boundary-layer fluxes in numerical global-scale transport/chemistry models. The algorithm was developed for the Moguntia (Latin word for Mainz, FRG) global chemistry model (Zimmerman, 1987) which uses monthly-averaged meteorological input data. The algorithm can be used over land and sea surfaces provided grid-cell averaged convective mixing heights and stable PBL heights are given. Trace-gas removal and surface concentrations, including diurnal variations, are satisfactorily described. However, the effects of isolated thunderstorms and frontal systems are not parameterized.