Sensitivity of dual wavelength reflectivity ratio of 94/220 GHz space-borne radar to cloud parameters with non-spherical ice crystals

The dual wavelength reflectivity ratio (DWR) of 94/220 GHz radar to non-spherical ice clouds was obtained based on the scattering characteristics of ice crystals with different shapes, and the relationships between the DWR and the cloud parameters were analyzed. The vertical profiles of the unattenuated and attenuated radar reflectivity factors and DWR were studied. The results are as follows. (1) The DWR is sensitive to the size and shape of particles, the attenuation from clouds and the median maximum dimension of the particles size distribution (PSD) that can even be as small as 0.1 mm, but insensitive to the particle concentration and shape parameters of the PSD. (2) When the sensitivity of radar receiver is certain, the ability of space-borne radars to detect cloud thickness depends on the wavelengths of radars, the vertical profiles of the ice water content (IWC), the thickness of the cloud and the attenuation. In the condition of no attenuation correction, the DWR related to the attenuation and the maximum is determined by the detected cloud thickness, while higher IWC and shorter wavelength correspond to larger attenuation. As a result, the two radars can detect the ice clouds with IWC=0.001-0.1 g/m³ and thickness of 2 km. Furthermore, 94% of the cloud thickness can be explored for the ice clouds with IWC=0.001-0.2 g/m³ and the thickness of 5 km. (3) When the dielectric factors of water are using in the two radars' meteorological equations, the DWR can only be obtained after directly detected echo intensity is corrected.