Rainfall is a key observable of the weather, of importance to society. Rain gauges only provide point measurements; for areal rainfall information a radar may be used. Radars measuring just reflectivity (Z) may suffer large errors in derived rainrates due to drop size distribution (DSD) variations. The introduction of dual-polarisation radars to operational networks should lead to improvements in rainfall estimation, although these radars suffer high noise levels in polarisation parameters (~ 0.7 dB in differential reflectivity [ZDR]).