Study of Planar Ice Crystal Orientations in Ice Clouds from Scanning Polarization Lidar Observations
By Vincent Noel, Kenneth Sassen. 2005
139 citations recorded by the source corpus.
This paper presents a study of the orientation of ice crystals in cirrus and midlevel clouds, based on the analysis of several cases of scanning polarization lidar observations. The maximum angle that crystals deviate from the horizontal plane is inferred at consecutive altitude levels by fitting angle-dependent measurements of the linear depolarization ratio and backscattered intensities to a theoretical model with a Gaussian distribution of tilt angles. The average deviation angle is linked to the angular variation of backscatter. A rare observation of so-called Parry-oriented columns is also given to highlight the different backscattering behavior with lidar angle. For planar crystals, two orientation modes are found that depend on cloud temperature. High-level cold (30°C) clouds show a maximum deviation angle of 1.0°, whereas for warmer (20°C) midlevel clouds this angle averages 2.0°. This difference is caused by variations in particle shape and fall attitude that depend on temperature, likely involving a transition from simple plates to more widely fluttering dendrites at the warmer temperatures. Polarization lidar scans are clearly uniquely suited for the study of ice crystal orientations in clouds.
Subfields: Atmospheric Science, Global and Planetary Change
View Paper: https://www.semanticscholar.org/paper/5532eda4a5aaed62a12b68cec03680e677a206d1
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Citations in the corpus
- Anisotropic Particles in Turbulence (2017, background): “For example, Noel & Sassen (2005) reviewed early work on ice crystals in clouds; Bernstein & Shapiro (1994) identified early laboratory experiments that measured particle orientations; and Zhang et al. (2001) reviewed work on the deposition of nonspherical particles.”
- A review of the light scattering properties of cirrus (2009, background): “common is ice crystal orientation in cirrus? There have been lidar observations of horizontally oriented hexagonal plates in cirrus [68] and in [69] it was reported that at least 40% of their space-based measurements of cirrus suggested that the ice crystals were horizontally oriented.”