Backscatter by azimuthally oriented ice crystals of cirrus clouds

Area of Science:

• Atmospheric Optics
• Crystallography
• Remote Sensing

Background:

• Ice crystals in the atmosphere significantly influence light scattering.
• Understanding ice crystal orientation is crucial for climate and remote sensing applications.
• Mueller matrix measurements offer comprehensive polarization information.

Purpose of the Study:

• To compute the backscattering Mueller matrix for hexagonal ice crystals with defined orientations.
• To investigate the potential of polarization lidar for retrieving crystal orientation distributions.
• To identify specific Mueller matrix elements sensitive to crystal tilt angles.

Main Methods:

• First-time calculation of the backscattering Mueller matrix for hexagonal ice columns and plates.
• Consideration of crystals with preferential zenith and azimuth orientations.
• Analysis of polarization lidar measurement capabilities for full Mueller matrix retrieval.

Main Results:

• The m44 element (circular depolarization ratio) differentiates between low and high zenith tilts.
• Element m22 is suitable for retrieving azimuth tilts at low zenith tilts.
• Element m34 is suitable for retrieving azimuth tilts at high zenith tilts.

Conclusions:

• The full Mueller matrix measured by polarization lidar can determine ice crystal orientation distributions.
• Specific elements (m44, m22, m34) provide distinct information about zenith and azimuth tilts.
• This method offers a novel approach for characterizing atmospheric ice crystal properties.