Monday, 15 October 2001
Wind regime GOES cloud cover composites for the Wakefield, VA County Warning Area
A set of cloud cover composites for the Mid-Atlantic U.S have been derived from GOES-8 visible imagery for May through October, 1998-2000. Cloud cover is determined by comparing the radiance at each pixel with a cloud-cleared background image. The background image is determined by selecting the darkest pixel value from all images in a given month and hour. If the radiance for an individual image pixel exceeds the background by a specified threshold, it is assumed to be cloudy. The images over the three-year period (May-October) are divided into nine wind regimes by the mean boundary layer wind speed and direction over Wakefield, VA, as determined from the 12 UTC analysis of the ETA model. Then hourly cloud percentages for each pixel in the image are determined for each wind regime. From these composites, the effects of wind direction and surface characteristics on timing and preferred areas of cloudiness in the region are studied. Relevancy of this work for the Wakefield NWS Forecast Office operations will be presented along with selected results.
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