A study on the relation between terminal velocity and VHF backscatter fromprecipitation particles using the Chung-Li VHF radar

The relationships between the mean Doppler terminal velocities V-r of the h ydrometeors with different phases and the range-corrected VHF backscatter P from the corresponding precipitation particles are investigated by using t he Chung-Li VHF radar. The radar precipitation data employed for the analys is were taken from four independent experiments conducted on different weat her conditions. They show that the observed alpha and beta values in the po wer-law approximation V-T = npp above the melting layer are generally small er than those below the layer, while in the bright band the values of beta (alpha) are enormously smaller (greater) than those above and below the bri ght band. Theoretical analysis shows that the mathematical relationship bet ween alpha and beta can be approximated very well by a simple exponential f unction, which is in excellent agreement with the observations. A new metho d for estimating the coefficient A and exponent B in the fall speed-diamete r relationship V(D) = AD(B) with respect to still air on the basis of the t heoretical relation between alpha and beta is also proposed. A comparison o f the estimations of A and B with those reported in the literature indicate s that the former are smaller than the latter. The authors believe that the difference in the two is due to the different types of the clouds producin g the precipitation. In addition, it is found that the value of A is propor tional to the height of the 0 degrees C isotherm, implying that the air tem perature plays a role in establishing the relationship between the fall spe ed and the diameter of the hydrometeors.