Comparison of precipitation estimation using single- and dual-frequency wind profilers: Simulations and experimental results

The advantages and disadvantages of single-frequency (50 MHz) and dual-freq uency (50 and 915 MHz) wind profiler drop size distribution retrievals are discussed by comparing retrievals of median volume drop diameter and rain r ates. Simulated data, as well as observational data, show that the median v olume diameter estimated from the single-frequency technique is biased high er than what is retrieved using the dual-frequency technique. This result i s due to the strong 50-MHz Bragg scatter signal that masks the small drop ( low fall velocity) part of the precipitation spectrum. The error in the est imation of the median volume diameter increases markedly with increasing ve rtical air motion spectral width. The error in the estimation of the median volume diameter is minimum for median volume diameters ranging from 0.5 to about 2.5 mm for the dual-frequency technique and 1.2 to about 2.5 mm for the single-frequency technique. The comparison of retrieved rain rates with rain gauge data shows a very good agreement for both techniques, but it wa s not always possible to retrieve precipitation information using the singl e-frequency technique.