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Investigating particle orientation in cirrus clouds by measuring backscattering phase matrices with lidar
Bruno V Kaul1, Ignatii V Samokhvalov, Sergei N Volkov
1Institute of Atmospheric Optics, Siberian Branch of the Academy of Sciences, Tomsk 634055, Russia.
Applied Optics
|January 14, 2005
Summary
Large ice crystals in clouds tend to align horizontally, but this orientation is often hidden by smaller particles. Lidar measurements reveal that wind pulsations may cause this particle alignment.
Area of Science:
- Atmospheric optics
- Cloud physics
- Remote sensing
Background:
- Particle orientation in ice-crystal clouds influences light scattering.
- Backscattering phase matrices (BSPMs) are crucial for understanding these optical properties.
Purpose of the Study:
- To investigate the relationship between particle orientation in ice-crystal clouds and their BSPMs.
- To develop and demonstrate a lidar-based technique for measuring BSPM elements related to particle orientation.
Main Methods:
- Utilized lidar to measure BSPM elements.
- Analyzed over 400 BSPM measurements for statistical generalization.
- Developed parameters to characterize particle orientation in azimuthal and horizontal directions.
Main Results:
- Coarse ice particles (large diameters) show a higher probability of non-random azimuthal and horizontal orientation.
- The orientation of large particles is frequently masked by smaller, randomly oriented particles.
- Overall cloud particle orientation, when averaged, indicates weak alignment.
Conclusions:
- Lidar measurements can quantify particle orientation in ice-crystal clouds.
- Wind-velocity pulsations are hypothesized as a cause for azimuthal particle orientation.
- The masking effect of small particles leads to an underestimation of overall cloud particle alignment.