A 3-cm pulsed Doppler radar constructed at the Royal Radar Establishment is described and the use of this equipment to increase knowledge of atmospheric precipitation processes is explained. With the aerial pointing vertically in widespread rain it is possible to deduce the drop size distribution in the free atmosphere and to study its variation with height. In showers it is possible to derive height-time sections of both vertical air motion and maximum particle velocity; examples of these sections are shown and discussed. A new mobile Doppler radar designed for investigation of thunderstorms is briefly mentioned. Finally, the application of Doppler radar operating at low angles of elevation to the measurement of horizontal convergence and vertical velocity of the air during widespread rain is described and initial results shown.