Representativeness of Wind Measurements in a Complex Terrain Region in Southern Virginia

Representative meteorological measurements are important in many applications, including air quality and dispersion modeling. The site selection for representative wind measurements in complex terrain is not always straightforward, and requires detailed investigations of the flows in the region around potential measurement sites. Topography has the potential to alter wind measurements over small spatial scales (< 1.5 km), especially during stable conditions when topographically induced flows are pronounced. A proposed mining and milling operation in Southern Virginia has motivated a study to investigate the representativeness of wind measurements at a single baseline site in this region that is characteristic of elevations differences of a few tens of meters over a horizontal scale of a few kilometers. The objective of this study is to determine the representativeness of wind measurements at this site. To address the objective, four 10-m meteorological towers were set up surrounding a 10-m meteorological tower at the baseline site. A variety of methods were used to determine the representativeness of the wind measurements from the baseline tower, including statistical and wind rose analyses, intensive field campaigns, and mesoscale model simulations using the Weather Research and Forecasting (WRF) model. The statistical and wind rose analyses showed that the representativeness of the baseline tower is significantly reduced during stable and synoptically quiescent conditions in the presence of topographically induced flows. Results from the field campaigns and WRF model simulations during these conditions show that topographically induced flows in the region can occur from different directions in the lowest few tens of meters above the ground. Based on our investigations, we recommend that for maximizing the representativeness of wind measurements at the baseline site, the measurements should be made at heights at or above 30 m. This study contributes to the development of better guidelines for collecting representative wind measurements at the study site in Chatham, Virginia and in other areas of moderately complex terrain.