Raindrop Size Distribution from a Slant Profiling Radar: Assessment Analysis

Knowledge of the raindrop size distribution versus height and time is important for several applications, among them, improved rainfall rate estimation and the understanding of microphysical and dynamical processes during rain. In cases where polarimetric measurements cannot be used (vertical profiling or light rain), the drop size distribution (DSD) can be estimated from Doppler power spectra, which implies that wind and turbulence have to be retrieved as well. An algorithm has been proposed for this purpose. This type of algorithm can also be applied for vertical profiling radars and elevation scanning radars (elevation range: 45^o-90^o). The outputs are the gamma DSD parameters, the radial wind and the Doppler spectrum width of turbulence.

This paper analyses first the raindrop size distribution retrievals in terms of differential reflectivity. The differential reflectivity is measured. However this radar variable is not used in the retrieval algorithm and acts as an independent assessment in cases of moderate and heavy precipitation. Further a self-consistency methodology based on the Doppler power spectrum width is discussed. The Analysis of the Composition of Clouds with Extended Polarization Techniques (ACCEPT) campaign data of the Transportable Atmospheric RAdar (TARA) are used for this study. The DSD parameters rely on calibrated Doppler power spectra. Therefore the reflectivity factors of the TARA radar (3 GHz) and cloud radar MIRA (35 GHz), which was next to TARA during ACCEPT, are compared.