Optical Scattering and Microphysical Properties of Subvisual Cirrus Clouds, and Climatic Implications
- 1 February 1989
- journal article
- Published by American Meteorological Society in Journal of Applied Meteorology and Climatology
- Vol. 28 (2) , 91-98
- https://doi.org/10.1175/1520-0450(1989)028<0091:osampo>2.0.co;2
Abstract
The optical and microphysical properties of subvisual cirrus clouds are derived from ground-based polarization lidar, shortwave radiation flux, and solar corona measurements of two ∼0.75 km deep cirrus located near the tropopause. The first cloud produced no visual manifestations under excellent viewing conditions, and the second appeared to be a persistent aircraft contrail that was generally visible except in the zenith direction. Average lidar linear depolarization ratios and volume backscatter coefficients for the two clouds were 0.19 and 0.35, and 0.6 × 10−3 and 1.4 × 10−3 (km sr)−1, respectively. It is estimated that the zenith-subvisual cirrus contained ice crystals of 25 μm effective diameter at a mean concentration of 25 L−1 and ice mass content of 0.2 mg m−3. The threshold cloud optical thickness for visual-versus-invisible cirrus derived from both broadband shortwave flux and 0.694 μm lidar data, is found to be τc ≈ 0.03. Such τ values are comparable to those of 5–10 km deep stratosphe... Abstract The optical and microphysical properties of subvisual cirrus clouds are derived from ground-based polarization lidar, shortwave radiation flux, and solar corona measurements of two ∼0.75 km deep cirrus located near the tropopause. The first cloud produced no visual manifestations under excellent viewing conditions, and the second appeared to be a persistent aircraft contrail that was generally visible except in the zenith direction. Average lidar linear depolarization ratios and volume backscatter coefficients for the two clouds were 0.19 and 0.35, and 0.6 × 10−3 and 1.4 × 10−3 (km sr)−1, respectively. It is estimated that the zenith-subvisual cirrus contained ice crystals of 25 μm effective diameter at a mean concentration of 25 L−1 and ice mass content of 0.2 mg m−3. The threshold cloud optical thickness for visual-versus-invisible cirrus derived from both broadband shortwave flux and 0.694 μm lidar data, is found to be τc ≈ 0.03. Such τ values are comparable to those of 5–10 km deep stratosphe...Keywords
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