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Impact of birds on Doppler observations

Weather radars are used primarily to detect rain and other types of precipitation. But also non-meteorological targets are seen by the radar, such as airplanes, large ships, windmills, etc... Particularly, the radar is sensitive to the presence of birds in the atmosphere, at least when the number of birds per volume is high enough to produce a significant echo. Strong bird signals are seen in periods of heavy bird migration, especially in the Doppler scan of the radar. Information on bird migration is important to aviation for reducing the risk of collisions between birds and aircrafts.

The bird migration project at the RMI is financed by the European Space Agency (ESA) as part of the Flysafe / Avian Alert "Integrated Applications Program". The project is lead by the KNMI, and is a collaboration between KNMI, the Dutch and Belgian Airforces, the national meteorological services of Belgium and France, the University of Amsterdam and The Swiss Ornithological Institute.

In september 2007, the Swiss Ornithological Institute installed during four weeks its bird radar, the so-called superfledermaus, in the Belgian Ardennes region. The bird radar was installed a few kilometers away from the Wideumont weather radar, which allowed comparisons between the data collected by the two radars. Similar measurement campaigns were organised in the Netherlands and in France.



Bird radar (Superfledermaus) installed in Saint-Hubert in the Belgian Ardennes region.

Visual bird identification during daytime using a telescope mounted parallel to the radar antenna.

Very dense bird migrations have been observed during the measurement campaign in Belgium as illustrated by the two Doppler images below. On these images, particles or objects moving away from the radar are shown in blue, while particles or objects moving towards the radar are shown in yellow/red. The first image is a Doppler image taken with the Wideumont radar on Oct. 3, 2007, and shows the migration during fall, towards the southwest. Approximately six months later, during spring, a strong migration in the opposite direction is seen. Again, the radar was able to record this event of intense bird migration.


Doppler image of the Wideumont weather radar during the night of 3 October 2007

Doppler image of the Wideumont weather radar during the night of 19 April 2008.

The data collected during the measurement campaigns are analysed at KNMI. The objective is to develop a fully automated method for the detection and quantification of bird migration using operational weather radars.


Contact person for this topic: Laurent Delobbe