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Description:
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The VAD Wind Profile (VWP ) , a time -height display of winds computed by the National Weather Service's WSR -88D radar , is known on occasion to have errors at night during the fall and spring seasons . Several studies , such Haro and Gauthreaux (1998 ) , confirm that migrating birds often contaminate the VWP output . By means of telescopic observations of a full moon , birds were observed flying on two nights when VWP contamination was suspected . The nature of the VWP errors is consistent with migrating birds due to the seasonality , nocturnal nature , and the magnitude of the errors found (greater than 10 knots ) .
With careful selection of data , two clusters of points on the Velocity -Azimuth Display (VAD ) are found to exist at certain altitudes when birds begin migrating . One cluster of points is due to radar sample volumes containing birds , and the other cluster is from radar sample volumes without birds . Being able to determine which cluster represents the wind could allow the wind to be calculated by the VWP .
Present limitations with the Radar Product Generator's processor and memory prohibit a very advanced detection algorithm . Two simple objective techniques to determine the existence of the two clusters , and determine the wind , were tested . While they show some promise , these methods require further operational testing to determine their usefulness for real -time warning of bird contamination and the reporting of the true wind . |