The 94-GHz radar dim band: Relevance to ice cloud properties and CloudSat

Andrew J. Heymsfield; Aaron Bansemer; Sergey Matrosov; Lin Tian

doi:10.1029/2007GL031361

The 94-GHz radar dim band: Relevance to ice cloud properties and CloudSat

Andrew J. Heymsfield
, Aaron Bansemer
, Sergey Matrosov
, Lin Tian

Dynamical and Physical Meteorology

Research output: Contribution to journal › Article › peer-review

22 Scopus citations

Abstract

Details of the microphysics are shown to be responsible for a region of ice cloud which, when probed from above, has decreasing radar reflectivity (Z_e) downwards at 94 GHz but increasing Z_e 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 Z_e measured by CloudSat's 94-GHz radar. Methods to estimate the IWC in the dim band are proposed.

Original language	English
Article number	L03802
Journal	Geophysical Research Letters
Volume	35
Issue number	3
DOIs	https://doi.org/10.1029/2007GL031361
State	Published - Feb 16 2008

Access to Document

10.1029/2007GL031361

Cite this

@article{2cd0319ebbad45a692784c16a98e36ea,

title = "The 94-GHz radar dim band: Relevance to ice cloud properties and CloudSat",

abstract = "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.",

author = "Heymsfield, \{Andrew J.\} and Aaron Bansemer and Sergey Matrosov and Lin Tian",

year = "2008",

month = feb,

day = "16",

doi = "10.1029/2007GL031361",

language = "English",

volume = "35",

journal = "Geophysical Research Letters",

issn = "0094-8276",

publisher = "John Wiley and Sons Inc.",

number = "3",

}

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 -

The 94-GHz radar dim band: Relevance to ice cloud properties and CloudSat

Abstract

Access to Document

Other files and links

Fingerprint

Cite this