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Moonwatch calibration of Radar

   Moonwatching is a direct visual method of verifying, quantifying, and determining the direction of bird migration. The "Migration Traffic Rate" can be measured by counting the numbers of birds crossing the disk of the full moon on a clear night.

Schematic of Moonwatching

   To correspond with base reflectivity, a measure of density, this rate must be adjusted for the velocity of the targets. Many sources of error exist in the correspondence between numbers of birds quantified by moonwatching and base reflectivity, including the size of the birds, numbers of other targets, such as insects or dust, co-occuring with birds, and differing bird aspects to the radar. Suitable nights for moonwatch calibration are rare, and the replication of nights corresponding to very heavy migration detection on NEXRAD (20-30 dBZ) is low.

Calibration curve for relationship between dBZ and bird densities

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