Abstract
An algorithm has been developed to retrieve the vertical profiles of cloud microphysical properties from the surface observation based on three radars operated at three microwave bands (X-band, Ka-band, and W-band) and a microwave-radiometer. This algorithm has the advantage that it can be applied to any mixing condition of liquid and ice particles in clouds (i.e., pure-water clouds, pure-ice clouds, and mixed-phase clouds). To precisely treat the scattering processes of the radar waves in clouds, we pay attention to non-sphericity of ice-particles and radar wave attenuation by scattering, which are frequently neglected in the previous studies. The hexagonal ice-particles with various aspect ratios are considered. On the other hand, the observational data used in this algorithm need two assumptions: 1) the observed cloud does not contain precipitating and melting particles, and 2) the water vapor profiles are approximated by successive steady-state representations. The accuracy of the radar calibration required for this algorithm would be within ±0.1 dB, which is about the order of uncertainty of radar measurements. In the retrieval procedure, the mixing condition of water-droplets and ice-particles in the target cloud sub-layer can be identified by utilizing the wavelength-dependence of the scattering and attenuation properties. Once the mixing condition of the cloud sub-layer is determined, the microphysical properties of pure-water and pure-ice clouds are estimated by the algorithm, similar to the widely-used dual-wavelength technique, except for the fact that in the present algorithm, an equivalent aspect ratio of ice-particles can be estimated, in addition to ice-water-content and ice-particle size of pure-ice clouds. For mixed-phase clouds, the microphysical profiles, which satisfy the observed radar and microwave radiometer signals, can be estimated by iteratively changing aspect ratios of ice-particles in each sublayer. The retrieval algorithm is applied to the observational data obtained in the Vertically Pointing Measurements, Tsukuba, 2001 (VPM_TKB01). The retrieved microphysical profiles for the pure-ice clouds show reasonable performance of the present algorithm, although there are no in-situ measurements to validate the estimated values.
