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Icy wave-cloud lunar corona and cirrus iridescence
1Electrical and Computer Engineering Department, Montana State University, Bozeman, Montana 59717, USA. jshaw@montana.edu
Applied Optics
|October 22, 2011
Summary
Tiny ice crystals, not water droplets, caused cirrus iridescence and lunar coronas. Analysis of diffraction rings revealed a mean particle diameter of 14.6 μm, confirming ice formation in these atmospheric optical phenomena.
Area of Science:
- Atmospheric optics
- Cloud physics
- Remote sensing
Background:
- Atmospheric optical phenomena like iridescence and coronas are often observed in clouds.
- The precise composition and particle size responsible for these phenomena can be challenging to determine.
- Distinguishing between ice crystals and water droplets is crucial for understanding cloud properties.
Purpose of the Study:
- To identify the particle composition responsible for observed iridescence in cirrus clouds and a lunar corona in a wave cloud.
- To determine the size of the particles causing these optical effects.
- To validate findings using dual-polarization lidar and radiosonde data.
Main Methods:
- Utilized dual-polarization lidar and radiosonde data for atmospheric analysis.
- Analyzed photographic records of lunar corona diffraction rings to estimate particle size.
- Measured lidar cross-polarization ratios to differentiate between ice and water particles.
Main Results:
- Iridescence in cirrus and a lunar corona were attributed to tiny ice crystals, with a mean diameter of 14.6 μm.
- The iridescent cloud was situated at the tropopause (~11-13.6 km ASL) near -70 °C.
- The corona was observed at approximately 9.5 km ASL near -60 °C, with lidar data confirming ice formation in both cases (cross-polarization ratios of 0.5 and 0.4).
Conclusions:
- Tiny ice crystals, smaller than typical ones, are responsible for cirrus iridescence and lunar coronas.
- Dual-polarization lidar is effective in identifying ice particles in clouds causing optical phenomena.
- The study provides quantitative evidence for ice crystal composition in specific atmospheric optical events.
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