TY - JOUR
T1 - The 94-GHz radar dim band
T2 - Relevance to ice cloud properties and CloudSat
AU - Heymsfield, Andrew J.
AU - Bansemer, Aaron
AU - Matrosov, Sergey
AU - Tian, Lin
PY - 2008/2/16
Y1 - 2008/2/16
N2 - 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.
AB - 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.
UR - https://www.scopus.com/pages/publications/41849089369
U2 - 10.1029/2007GL031361
DO - 10.1029/2007GL031361
M3 - Article
AN - SCOPUS:41849089369
SN - 0094-8276
VL - 35
JO - Geophysical Research Letters
JF - Geophysical Research Letters
IS - 3
M1 - L03802
ER -