A Simplified Boundary Layer Wind Model for Practical Application

Abstract

A parameterized boundary layer wind model, applicable not only in horizontally homogeneous conditions but also in the case of a discontinuity in roughness length, has been developed. The input data needed are wind speed and direction at standard anemometer level, the temperature difference between two levels near the ground, the roughness length at one site and a roughness length estimate for a neighboring area. The model consist of two parts: an Ekman-Taylor type model with a Monin-Obukhov surface layer for the basic, homogeneous case and a parameterized internal boundary layer model to handle the gradual modification of the wind profile after a discontinuity in surface roughness. The latter submodel is based on simulations with a two-dimensional higher order closure model. The basic, one-dimensional model has been tested against measurements over the Basic Sea, taken on an isolated rocky islet (surface layer measurements) and on a nearby island (pilot balloons up to 2000 m). The results are generally in good agreement, at least up to about 1000 m, but for greater heights, information on the thermal wind is needed as well. The two-dimensional model has been tested on a limited data set, including pilot balloon measurements at several sites from a coastline to 14 km inland, with the wind flow from the sea. The agreement between model prediction and measurements is very good.