The influence of static stability on the effective roughness lengths for momentum and heat transfer

Abstract

AbstractThe area‐averaged properties of the planetary boundary layer over heterogeneous terrain are considered. Previous studies which dealt with the average momentum transfer properties in neutral static stability conditions are extended to include the influence of stratification and also area‐averaged properties for heat transfer. Results from numerical simulations demonstrate the utility of values of effective roughness length for both momentum and heat transfer. A heuristic model is found to show good agreement with the numerical simulations and to provide a simple method for estimating these roughness lengths for use in boundary‐layer parametrization.Significant anomalies in the surface heat fluxes, particularly those of sensible heat, accompanied the decrease in the sea ice concentration. Substantial atmospheric warming was simulated over and in the vicinity of areas in which leads were considered. In all but one experiment there were anomalous easterlies between about 40 and 60°S with westerly anomalies further to the south. The surface pressure at high latitudes appears to change in a consistent fashion with the fraction of open water, with the largest changes occurring in the Weddell and near the Ross Seas.Some of the feedbacks which may enhance the responses here, but which are not included in our model, are discussed.