Different polarised electromagnetic waves are used to identify and quantify the different types of precipitation particles (rain, snow, graupel, hailThis is based on the fact that the different precipitation particles have a different shape, resulting in different backscattered signals for various polarisation's. With a polarimetric radar the estimation of the rain fall 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.