A Polarimetric Doppler Radar (POLDIRAD) has been operated since 1986 from the roof of DLR's Institute of Atmospheric Physics. It's a C-band weather radar designed for research. Although Doppler capability is now standard in modern operational weather service radars, there are only a few radars in Europe equipped with polarization ability. In Europe, selecting any polarization for transmitting and receiving is only possible with POLDIRAD.
The Doppler characteristics are utilized for wind investigations, and together with a bistatic radar it's possible to determine the entire three-dimensional flow field in an area with precipitation, such as a thunderstorm.
Variably polarized radar signals are used to determine and quantify the type of precipitation particles under investigation, whether raindrops, snow, sleet or hail. This can be done by exploiting the fact that the different particles have different shapes, and thus different backscatter behavior for different polarizations of electromagnetic waves. With a polarimetric radar the intensity of precipitation can be determined much better than with conventional radar. POLDIRAD has been used in a large number of projects and experiments, especially for thunderstorm research.