A DUAL-WAVELENGTH RADAR METHOD FOR ICE WATER CHARACTERIZATION IN MIXED-PHASE CLOUDS

A dual-wavelength method to differentiate supercooled water from ice and to measure mass content in each phase in cold stratiform clouds is proposed and discussed. The differential attenuation A(d), whose direct measurement is available with dual-wavelength radar, is a linear function of the liquid water content M(w) (the contribution from ice hydrometeors is negligible in comparison). Measuring both Ad and the radar reflectivity factor Z(e) leads to a system of two equations expressed as functions of M(w) and M(i) (ice water content); its solution provides the values of both M(w) and M(i) between any two ranges along the radar beam, and as a consequence the distribution pattern of those two parameters within the cloud. Simulations of the method on two idealized cloud structures with various spatial distributions of M(w) and M(i) are shown. From a comparative study, the wavelength couple of 3.2 cm and 0.86 cm has been selected as the most suitable one, either for ground-based midrange cloud observations or for an airborne radar.