Cloud Liquid Water and Ice Content Retrieval by Multiwavelength Radar

Abstract

Cloud liquid water and ice content retrieval in precipitating clouds by the differential attenuation method using a dual-wavelength radar, as a function of the wavelength pair, is first discussed. In the presence of non-Rayleigh scatterers, drizzle, or large ice crystals, an ambiguity appears between attenuation and non-Rayleigh scattering. The liquid water estimate is thus biased regardless of which pair is used. A new method using three wavelengths (long ?l, medium ?m, and short ?s) is then proposed in order to overcome this ambiguity. Two dual-wavelength pairs, (?l, ?m) and (?l, ?s), are considered. With the (?l, ?m) pair, ignoring the attenuation, a first estimate of the scattering term is computed. This scattering term is used with the (?l, ?s) pair to obtain an estimate of the attenuation term. With the attenuation term and the (?l, ?m) pair, a new estimate of the scattering term is computed, and so on until obtaining a stable result. The behavior of this method is analyzed through a numerical simulation and the processing of field data from 3-, 35-, and 94-GHz radars.