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Embry-Riddle Aeronautical University


Birds represent a significant hazard to flying aircraft as illustrated by the “Miracle on the Hudson” encounter in 2009 between U.S. Airways Flight 1549 and a flock of Canada Geese, forcing the flight to ditch in the river. Birds are common in the skies over Florida during the spring migration season, and often appear in the National Weather Service’s (NWS) NEXRAD weather radar imagery as an easily recognizable signature known as a “roost ring.” This paper presents a NEXRAD roost ring case in central Florida in a rare instance where the signatures were confirmed by visual observations of the birds. In 2013 the NWS completed an upgrade of its NEXRAD systems to dual polarization, a technology designed to improve target classification. Use of new dual polarization weather radar variables to better discriminate birds from precipitation for the current case is demonstrated. It is shown that the dual polarization capability, and specifically, the correlation coefficient product, allows for greater confidence in identifying radar echoes due to birds, and therefore could lead to better situational awareness for aviation operations personnel able to recognize these signatures.