Correction of Drop Shape-Induced Errors on Rain Rates Derived from Radar-Measured Doppler Spectra at Vertical Incidence

Abstract

The shape of larger raindrops shows a deviation from spheres. This leads to a radar backscatter cross section different from the Rayleigh cross section. The drop shape-induced error for deducing rain rates is calculated. The resulting correction factor is applied to radar data measured during the CLEOPATRA field campaign in 1992. Depending on the drop size distribution, the correction led to reductions of the rain rate up to 10%. Furthermore. it is shown that the drop shape-induced error can be used as an indicator for drop size distribution.