The 94-GHz radar dim band: Relevance to ice cloud properties and CloudSat
Article first published online: 1 FEB 2008
Copyright 2008 by the American Geophysical Union.
Geophysical Research Letters
Volume 35, Issue 3, February 2008
How to Cite
2008), The 94-GHz radar dim band: Relevance to ice cloud properties and CloudSat, Geophys. Res. Lett., 35, L03802, doi:10.1029/2007GL031361., , , and (
- Issue published online: 1 FEB 2008
- Article first published online: 1 FEB 2008
- Manuscript Accepted: 23 NOV 2007
- Manuscript Revised: 23 OCT 2007
- Manuscript Received: 26 JUL 2007
- 94-GHz radar dim band;
 Details of the microphysics are shown to be responsible for a region of ice cloud which, when probed from above, has decreasing radar reflectivity (Ze) downwards at 94 GHz but increasing Ze at 9.7 GHz. This 94-GHz radar dim band is found to be due to the combination of ice particle aggregation and non-Rayleigh scattering effects. Observations and model calculations indicate that it occurs when the particle size distribution (PSD) broadens such that its slope, as derived from fitted PSD, decreases below about 15 cm−1, or equivalently, to a median volume diameter exceeding 0.25 cm. Dimming occurs at temperatures (T) primarily between −5 and 0°C but can occur at −30°C or below in convectively-generated ice clouds (anvils). The dimming effect may produce an appreciable low bias in the ice water content (IWC) retrieved from Ze measured by CloudSat's 94-GHz radar. Methods to estimate the IWC in the dim band are proposed.