On the representativeness of wind- and stability measurements in hilly terrain. A case study in southern Virginia

Many air quality models require the use of data from representative meteorological measurement sites. The selection of these representative sites can be a large challenge, especially in areas of complex terrain. In this presentation, we discuss the representativeness of wind and stability measurements at a proposed uranium mining and milling site located in southern Virginia using data from five 10-m towers for the first year of measurements from 1 July 2012 to 1 July 2013. Predominant wind directions at a temporary ‘baseline' site in the center are from the southwest and from the northwest. During nighttime, northwesterly flows are dominant and indicate the influence of drainage flows. A preliminary assessment is made of the representativeness of the location using a novel approach that involves the comparison of meteorological data from the central baseline tower with data from the four surrounding towers within a radius of about 1.5 kilometers. Preliminary analyses reveal that differences in wind speed and direction are smallest during the daytime and that the influence of shallow drainage flows at night may be more dominant at the baseline site than at the surrounding sites. The site is therefore most representative during the day and least representative during the night. A field experiment using two tethered balloon systems was conducted during several nights in the summer and fall of 2013 to investigate the extent to which the effect of drainage flows may be reduced by extending the height of the tower. Results of the field experiment and the approaches used to assess the representativeness of the meteorological measurements will be discussed.