The results show that the brightness temperature would be stronger when the raindrop size is bigger or the distribution of raindrop in space is wider (namely the reflection factor Z is larger) . In addition to the analysis of precipitation data measured by radiometer and disdrometer, precipitation echoes detected by VHF radar are also investigated . It is found that the parameter No in the expression of raindrop distribution N(D)=Noexp(-DD) isn’t a constant and the correlation between No, rain rate and rain accumulation is positive.
An empirical model describing the relation between terminal of velocity of raindrop and VHF backscatter Vt=αPβ proposed by Chu et al. (1999) is also investigated in this thesis. With the help of a and b, the coefficients of A and B in V(D)=ADB, where V(D) is terminal velocity of raindrop at radius of D.. The experiment results show that the regression coefficients of the model proposed by Chu et al. (1999) could be obtained analytically. We also found that the velocity of vertical wind field would affect the coefficient B.

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