On the roof of the institute the polarimetric Doppler radar POLDIRAD has been operated since 1986. This radar operates in C-band and is designed for research purposes. Measurements of the Doppler velocity are meanwhile standard for operational radars. Only a few radars provide the capability of polarization diversity. In Europe only POLDIRAD is able to transmit and receive with any possible polarisation. The Doppler velocity is used to estimate the motion in the atmosphere. Together with the bistatic receivers it is now possible to estimate the full three dimensional wind field within a precipitation field, e.g. a thunderstorm.
Different polarised electromagnetic waves are used to identify and quantify the different types of precipitation particles (rain, snow, graupel, hail). This is based on the fact that the different precipitation particles have a different shape, resulting in different backscattered signals for various polarisations. With a polarimetric radar the estimation of the rainfall rate is more accurate than it is possible with a conventional radar. In the recent years POLDIRAD was used for various projects and field experiments. One major topic is the investigation of thunderstorms.