Extraction of breakpoints from radar-estimated rainfall fields

The breakpoint format for rainfall data, by recording the rainrate and the times when the rainrate changes, consists of variable length periods during which rain of constant intensity fell. It is compact and retains a level of detail equivalent to that found in high temporal resolution data. However, breakpoint data are available only at the relatively few locations where automatic raingauges produce pluviographs. On the other hand radar observations of rainfall provide precipitation data at a high spatial density but at poor time resolution. Advantage can be taken of this high spatial density to give more locations where breakpoints are available through interpolation between the radar images to provide precipitation data at sufficient temporal resolution for the extraction of breakpoints. The interpolation scheme, based on the PARAPLUIE method, detects the movement and evolution of precipitating echoes to provide additional interpolated radar images. Breakpoints, extracted at pixels of the images that contain raingauges, showed similar overall accumulations and characteristics when compared with those of the collocated raingauges. The similarity is particularly so for gauges within a 50 km radius of the radar where the spatial resolution of the radar and the temporal resolution of the raingauges are equivalent.