Stable boundary layer: Parametrizations for local and larger scales

Stability functions f(Ri) for a very stable boundary layer were studied by experimenting in winter Antarctic conditions with a one-dimensional (1D) numerical model and comparing with the Plateau Site tower observations. The local representations for f(Ri) produced good simulations of the temperature profiles and wind hodographs, while the standard Monin-Obukhov formulation indicated too little, and the general-circulation model (GCM)-type formulations too much, vertical mixing. Next, idealised simulations were made for winter-night hilly northern Finland landscape with a high-resolution 2D model, using a local f(Ri) at each column. Realistic quasi-steady mesoscale katabatic flows resulted. These enhanced vertical mixing both locally and regionally. Area-averaged (i.e. regional) surface fluxes were compared with those obtained from simulations using GCM-type large-scale stability functions over flat land. New parametrizations for both local and larger scales are suggested based on the experiments. Copyright (C) 2009 Royal Meteorological Society