Estimation of raindrop size distribution using multiple wavelength radar systems


  • Julius Goldhirsh,

  • Isadore Katz


The possible use of multiple wavelength radar systems to determine raindrop size distributions is examined. Pairs of radars at 1, 3, and 10 cm, respectively, are considered; the method involves measurements of rain reflectivities at two wavelength and at two range intervals separated by about one km. Assuming a general exponential form for the drop distribution, equations are derived relating the distribution parameters to the measurements. From these analytical forms the sensitivities of these parameters to radar inaccuracies are examined. The results show that one needs combined 2-radar accuracies of 1 dB to get even marginal drop distribution accuracies. Such accuracies are considered impractical at present. Other impractical constraints implicit in the results are the assumed uniformity of reflectivity over distances of approximately 1 km, and the requirement to average as many as 104 independent power samples.