Assessment of quantitative precipitation estimates using weather radar and a distributed hydrologic model

Weather radar has been operating in Canada for several years as a method of measuring precipitation. The distributed data produced by radar systems provides better spatial resolution than the point data produced by rain gauges. This study is a survey of the suitability of C-band Doppler weather radar products produced by Environment Canada at King City, Ontario, Canada for hydrological applications. The University of Waterloo has archived conventional radar data from 1993 to 1999 and a composite conventional and Doppler radar product from 2000 to the present.

Radar data has only recently been able to provide adequate precipitation estimates for use in hydrologic models. Discrepancies between precipitation measured with radar and gauges are frequent. Severe convective storms are also more difficult to measure than frontal storms. To assess the impact of this disagreement, a comparison between radar data and gauge data is made at several locations within the radar's range. Doppler radar data and conventional non-Doppler radar data are both compared with gauge data. A trend is seen as the distance from the radar station increases. There is an initial increase until a distance of 100km after which the precipitation measured with radar decreases. A comparison will be made between gauge and radar data to account for these differences.

Streamflow is an alternate means to access radar data. A comparison between streamflow values calculated using the radar data in the distributed hydrologic model WATFLOOD and measured streamflows for several watersheds in Ontario, Canada will be presented. A closer examination will be made on the corrections made to severe local storms measured with radar. The goal is to accurately model the stream flows from these events using radar measurements in a hydrologic model. These comparisons will provide new insight into the value of radar for hydrology and in particular, will show if the new products and corrections are an improvement.