Surface-layer flow in complex terrain: Comparison of models and full-scale observations

Abstract

Four models of surface boundary-layer flow in complex terrain are compared with observations made at Blashaval Hill, North Uist, Scotland. The field experiment is described by Mason and King (1985). Three of the models are derived from the two-dimensional theory of Jackson and Hunt (1975) and are described in Mason and King (1985), Walmsley et al. (1986) and Troen and Petersen (1989). The fourth is a mass-consistent code based on Traci et al. (1979). The model results are in good agreement with each other and are generally within the observed range of variation ( -+ 16%) in normalized wind speed. For most wind direcions (7 of ll), model results of normalized wind speed at the summit were within 7% of the observed mean values. For some wind directions, calculations using the "Guidelines" of Walmsley et al. (1989) suggested that variations in surface roughness were important. This led us to apply one of our models incorporating nonuniform surface roughness. The lack of significant improvement for cases when water lay upstream of Blashaval Hill is attributed to compensating changes at summit and reference sites and to very local effects on the wind data. Sensitivity to topography lying to the west and northwest of Blashaval was also investigated. Results suggested an influence from those distant topographic features for some wind directions. When those features were incorporated, maximum errors in normalized wind speed at the summit were reduced from 18 to 13%.

Simulations of the influence of forest management on wind climate on a regional scale

“…It has also been found to give similar results to the airflow model MS-Micro/3 and the DAMS scoring system (Bell et al, 1995) when testing the three methods over the same short period (Walmsley et al, 1990). The largest expected errors in the results given by WAsP are related to calculation of the flow in complex terrain (Suárez et al, 1999), which was not the case here (altitude ranged between 85 and 190 m above sea level).…”

Influence of clear-cutting on the risk of wind damage at forest edges

“…The properties of the WAsP model, its parameters, inputs, and the validity of its outputs as assessed against other models and field measurements of wind speed have been discussed in detail earlier by Walmsley et al (1990), Mortensen and Petersen (1997), Suárez et al (1999), Mortensen et al (2000Mortensen et al ( , 2002, Achberger et al (2002).…”

The Bolund Experiment, Part II: Blind Comparison of Microscale Flow Models

“…Various model comparisons of atmospheric flows include linear models based on the theory of Jackson and Hunt (1975) and observations made at the Blashaval Hill (Mason and King 1985) by Walmsley et al (1990). Comparisons of flow over a triangular ridge made by several two-equation RANS models were made by Kim and Patel (2000), and a comparison of four LES codes simulating the neutrally-stratified atmospheric boundary layer is found in Andren et al (1994).…”