Effects Of Calibration Rain Gauge Densities On Radar Rainfall Estimates And Runoff Simulation And The Study Of A New Radar-Gauge Calibration Algorithm

Rainfall-runoff model named TOPMODEL is employed to simulate runoffs of Xianghongdian and Foziling sub-catchments located in the upper reaches of Pihe River. The input data for the model include evaporation and runoff data collected by the Huaihe River Commission of Ministry of Water Resource, P. R. C., and initial rain gauge data and Hefei CINRAD radar data obtained by the China heavy rainfall experiment under the frame of 973 Project and Project of Huaihe/Huanghe Basin Heavy Rainfall/Flooding Monitoring System. By employing the distance weighting algorithm, the effects of calibration rain gauge densities on radar rainfall and runoff simulations are studied, and a domain average calibration algorithm formed from average adjusting algorithm and distance weighting algorithm is depicted and studied. Following are main parts of this work:1)Data are firstly processed. By choosing and controlling calibration gauges manually, effects of adjusting gauge densities on radar rainfall estimates are studied;2)Rainfall series obtained from step 1) are input to the TOPMODEL model, runoffs are obtained, compared and analyzed;3)Based on the domain average calibration algorithm, areal rainfalls are computed and runoffs simulated. Results are compared with that obtained from average adjusting and distance weighting algorithms.Some conclusions based upon above investigations are given as follows:1)Two calibration gauges would be a good threshold while the error of precipitation estimation is less than 10% with the stable RMSE and correlation coefficients for cases studied over both sub-catchments; the corresponding gauge density is about 900km2 per gauge for Foziling sub-catchment, and 700km2 per gauge for Xianghongdian, respectively.2)Simulations show that runoffs are greatly affected by the accuracy of rainfall estimation. The threshold obtained from rainfall comparison still works in runoff simulations. All of the model efficiency criterion, RMSE and correlation coefficients keep steady on high levels with this threshold.3)Comparisons of rainfall series obtained from single gauges and over the whole catchment, also runoff simulations, show that the accuracy of rainfall estimation and runoff simulations can be obviously improved by the domain average calibration algorithm. Key words: radar-gauge calibration; runoff simulation; rain gauge densities; domain average calibration algorithm; TOPMODEL...