Testing Various Morphometric Methods for Determining the Vertical Profile of Wind Speed Above Krakow, Poland

Abstract

Various morphometric methods used for wind-speed determination in urban areas inside the roughness sublayer have been tested in Krakow, Poland, using a hybrid modelling system. The hybrid modelling system combines the classic numerical meteorological modelling using ALADIN, MM5, and CALMET models with empirical, non-logarithmic relations determined on the basis of a wind-tunnel experiment. In the hybrid modelling system, the horizontally-averaged wind speed is determined using the displacement height d, roughness length z0, and an attenuation coefficient α. These parameters are determined using laser scanning data obtained in the MONIT-AIR project. The variability of the selected morphometric parameters in Krakow, the role of the size of the area from which they are determined and the consequences of replacing the frontal area index by the plan area index are analyzed. The different methods used to determine d, z0, and α are compared and the correctness of the procedures describing the wind profile are verified by comparisons with wind-speed data from road stations, with the wind speed measured between the traffic lanes or at the roadside at a height of 4 m, at standard meteorological stations, and from masts situated on buildings. It is shown that the use of a parametrization based on large-eddy simulations prepared for explicitly resolved buildings in Tokyo and Nagoya in Japan, and taking the maximum instead of the average height of building in empirical relations, significantly improves the modelling results, especially above the average height of buildings.