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floods and is a main effect of drought. Among common rainfalls-measuring facilities, GR shows suitable capabilities for measuring and forecasting rainfall. GR is an active sensor which is able to measure the power of microwave backscatter from hydrometeor particles due to the emission of electromagnetic energy. Of course, it cannot determine or recognize the quality and quantity of rainfall directly, but it can record the volume of electromagnetic waves back scattered (Z) from raindrop (R) that reaches to the radar receiver. In general, radar calibration follows two steps 1) mechanical calibration and 2) reflectivity calibration. when referring to ‘radar calibration’, we discuss, delegated adjustment of backscatter reflectivity from rainfall to the radar receiver.Many studies have been done about the radar-rainfall forecasting but, there is less attention to the accuracy of the forecasting output data. There are large differences between the amount of real rainfall and predicted amount. The fluctuations in the rainfall prediction amount may be not too important in light rainfall mode, but in the heavy precipitation irreparable damage happen, especially in mid-latitude regions. The main factor in forecasting errors is the multiplicity of uncertainty sources in the atmosphere. The best way to achieve an ideal prediction from radars, is calibration and adjustment them by effectiveness parameters. Radar calibration reduces the effect of uncertainty sources and eliminates some part of the errors. Much more of the radar uncertainty are related to reflectivity that backscatters from the radar. Assuming that most of the uncertainties are due to the height and distance from the radar, the discrepancy between relationship of real-rainfall amount and radar-reflectivity volume is dependent on range from the radar, and the discrepancy between relationship of real-rainfall amount and radar-reflectivity volume is correlated to the height above sea level.in brief, the main objective in this research is : to introduce a novel approach for ground-based radar calibration emphasizing of rainfall measurement. |
