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Corona-producing ice clouds: a case study of a cold mid-latitude cirrus layer
Applied Optics
|February 13, 2008
Summary
Researchers studied a rare, cold cirrus cloud that generated a lunar corona. Analysis revealed ice particles around 22 micrometers, suggesting a new mode of acid-contaminated ice growth in these radiatively distinct clouds.
Area of Science:
- Atmospheric Science
- Cloud Physics
- Remote Sensing
Background:
- Cirrus clouds play a significant role in Earth's radiative balance.
- Previous studies often relied on indirect methods to infer particle size and composition.
- Rare optical phenomena like lunar coronas offer unique opportunities for in situ cloud studies.
Purpose of the Study:
- To investigate the microphysical properties of a high-altitude, cold cirrus cloud using multiple observational techniques.
- To analyze the composition and particle size of ice crystals within a cirrus cloud that produced a lunar corona.
- To explore the nucleation and growth processes of ice particles in cold cirrus clouds.
Main Methods:
- Ground-based polarization lidar and millimeter radar observations.
- In situ measurements using aircraft probes.
- Analysis of cirrus cloud lunar corona rings to determine effective particle diameter.
- Examination of impacted cloud samples for crystal structure.
Main Results:
- A rare lunar corona was observed, indicating specific cloud conditions.
- Corona ring analysis yielded an effective particle diameter of approximately 22 micrometers.
- In situ data, particularly near the cloud top, confirmed simple solid ice crystals.
- Homogeneous freezing of stratospheric sulfuric acid droplets is proposed as the dominant nucleation mode.
Conclusions:
- The study provides direct evidence of ice particle size in a corona-producing cirrus cloud.
- A potential new mode of acid-contaminated ice particle growth is identified.
- These small-particle, cold cirrus clouds may represent a radiatively distinct cloud type.
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