Polarimetric Prototype of the WSR-88D Radar Observations of Birds and Insect

Although the costliest birdstrikes to aviation occur during daytime, the number of birdstrikes is actually highest during nighttime. The reason is that large population of small birds migrates during the night and relatively small number of large birds migrates or hovers during daytime. Clear air observations with the KOUN polarimetric radar in 2004 contain detailed information of the spatial distribution and temporal variation of birds and insects in the planetary boundary layer during daytime and nighttime. These observations occurred mainly in spring and fall and reveal several important features of biological scatterers. On 8 September 2004 in 24 hours of continuous operations it is observed that differential reflectivity and differential phase abruptly changed at sunrise and sunset. Nocturnal birds migrate in spring and fall hence cause strong echoes with definite polarimetric signatures over very wide areas. Further, roosting birds over forests and hovering birds over urban areas also produce characteristic patterns in time and space. Such patterns will be seen in real time on the future operational polarimetric radars and therefore will be very useful to pilots for avoiding strikes on their aircraft.