Ground-Based Cirrus Observation

[1] A novel parameterization is provided that relates the effective beam emissivity of a semitransparent atmospheric layer (emissivity between 0.05 and 0.95) to its optical depth, singlescattering albedo, and asymmetry factor and to the zenith viewing angle and estimates of the incoming radiation. It is derived from discrete ordinate radiative transfer calculations performed for optical properties representative for liquid water and ice clouds as well as aerosols. The formulation is kept simple and general and can be applied to any infrared window wavelength between 3 and 40 microns. It enables the efficient consideration of scattering of infrared radiation in fast radiative transfer models and remote-sensing algorithms. The greatest improvement over other straightforward approximations occurs when the single-scattering albedo is larger than 0.50. The parameterization also permits a better interpretation of the ratio of the effective optical depths at two wavelengths, which is highly correlated with cloud and aerosol microphysics. The possibilities are illustrated by a sample analysis of an advanced very high resolution radiometer image containing infrared signatures of contrails and stratocumulus clouds.

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Simultaneous Observations of Cirrus Clouds with a Millimeter-Wave Radar and the MU Radar

Wada

Hashiguchi

Yamamoto

et al. 2005

Journal of Applied Meteorology

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Observations of frontal cirrus clouds were conducted with the scanning millimeter-wave radar at the Shigaraki Middle and Upper Atmosphere (MU) Radar Observatory in Shiga, Japan, during 30 September–13 October 2000. The three-dimensional background winds were also observed with the very high frequency (VHF) band MU radar. Comparing the observational results of the two radars, it was found that the cirrus clouds appeared coincident with the layers of the strong vertical shear of the horizontal winds, and they developed and became thicker under the condition of the strong vertical shear of the horizontal wind and updraft. The result of the radiosonde observation indicated that Kelvin–Helmholtz instability (KHI) occurred at 8–9-km altitudes because of the strong vertical shear of the horizontal wind. The warm and moist air existed above the 8.5-km altitude, and the cold and dry air existed below the 8.5-km altitude. As a result of the airmass mixing of air above and below the 8.5-km altitudes, the cirrus clouds were formed. The updraft, which existed at 8.5–12-km altitude, caused the development of the cirrus clouds with the thickness of >2 km. By using the scanning millimeter-wave radar, the three-dimensional structure of cell echoes formed by KHI for the first time were successfully observed.

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Ground-Based Cirrus Observation

Cited by 4 publications

References 31 publications

Optical properties of terrestrial clouds

Optical properties of terrestrial clouds

Efficient parameterization of the infrared effective beam emissivity of semitransparent atmospheric layers

Simultaneous Observations of Cirrus Clouds with a Millimeter-Wave Radar and the MU Radar

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