Profiler DSD retrievals: What is the impact of an additional profiler?

Radar profilers are excellent tools for validation of radar rainfall retrieval algorithms. The profiling DSD retrieval algorithms employ Doppler spectra measurements to estimate drops-size distributions. Often it is considered that retrievals using two different profilers operating at distinct frequencies are superior to single profiler ones. However, it is not always clear what is the added advantage of employing two profilers.

This study is dedicated to quantifying uncertainties in profiling DSD retrievals and to the development of an optimum DSD retrieval algorithm that uses spectral observations carried out by two profilers. As the basis for this study we assume that DSD retrieval algorithm is based on spectral observations by S-band profiler and the second profiler can be used to constrain the retrievals. It is also assumed that DSD can be approximated by a modeled distribution and therefore DSD retrieval algorithm is a non-linear least square solution for the parameters, sigma and v0, as well as that of the DSD model. For example for a Gamma model DSD parameters Nw, D0, mu are estimated.

As a starting point of this study we use sensitivity analysis to quantify uncertainties in the retrieval of the DSD parameters using an S-band profiler. From this study we determine which parameters contribute the most to the uncertainty in the retrieval. Than it is discussed how second frequency spectral observations can be incorporated to reduce errors in the DSD retrievals and what is an advantage of using two profiler DSD retrieval scheme.