Abstract. Raindrops are one type of precipitation in stratiform and convective clouds. To get relationships for describing the raindrops two different methods were used. In the first way, the microphysical properties of the liquid hydrometeors were examined. For this the use of the Rayleigh approximation for small particles (raindrops at C-Band) and the drop size distribution by Ulbrich (Γ-DSD) lead to the calculation of the reflectivity at horizontal polarisation Z_HH, the reflectivity at vertical polarisation Z_VV and the differential reflectivity Z_DR. In the second way, rain signatures were separated from polarimetric measurements. The database of these measurements consists of datasets measured by the dual polarimetric C-Band weather radar POLDIRAD (DLR, Oberpfaffenhofen). The aim of this study was then to combine and to compare the results from the real radar measurements against the theoretical calculations in the Z_HH-Z_DR plane. Based on these observations and calculations, scientific results for future practical use will be presented in form of empirical equations including Z_HH-Z_DR. Finally in form of scientific discussion, the Z_HH-Z_DR plane will be critically assessed for outstanding problems or issues.