Dual polarisation and multifrequency measurements of rain rate and drop size distribution by ground-based radar and radiometers

Polarisation effects can be observed as well in radar as in radiometer data of stratiform and convective rain. These polarisation effects are due to different influences, e. g. the oblateness of large rain drops and path inhomogeneities. The dual polarisation technique is well known in radar meteorology. The emphasis in this contribution is therefore on the event based and statistical accuracy of the derived rain rate and on different sources of errors. In the passive remote sensing of rain the use of two polarisations is a new subject. By such measurements also drop size distributions can be derived, which improve the rain rate determination.