Rainfall mesurements uisng weather radars have becoming very popular in these days. However, there are several problems in the procedure of transforming observed radar reflection factor into rinfall intensity. Especially, the identification of radar constants B and β, which represent the relationship between radar reflection factor and rainfall intensity (Z-R relation), is very important.
The radar constants B and β are generally determined using the correlation between radar reflection factor and observed surface rainfall. B and β are influenced by various factors such as weather condition, topographical effect, spatial scale of observation and so on.
In this paper, a new method to identify the optimum radar constants B and β based on the runoff analysis using discharge data, is proposed. The surface rainfall is mesured at only one site. But the discharge is a integration of all the rainfall in a basin. Therefore it is convenient to identify the radar constants taking account of runoff data.