Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5428880 | Journal of Quantitative Spectroscopy and Radiative Transfer | 2013 | 5 Pages |
The CALIPSO satellite mission consistently measures volume (including molecule and particulate) light depolarization ratio of â¼2% for smoke, compared to â¼1% for marine aerosols and â¼15% for dust. The observed â¼2% smoke depolarization ratio comes primarily from the nonspherical habits of particles in the smoke at certain particle sizes. In this study, the depolarization of linearly polarized light by small sphere aggregates and irregular Gaussian-shaped particles is studied, to reveal the physics between the depolarization of linearly polarized light and smoke aerosol shape and size. It is found that the depolarization ratio curves of Gaussian-deformed spheres are very similar to sphere aggregates in terms of scattering-angle dependence and particle size parameters when particle size parameter is smaller than 1.0Ï. This demonstrates that small randomly oriented nonspherical particles have some common depolarization properties as functions of scattering angle and size parameter. This may be very useful information for characterization and active remote sensing of smoke particles using polarized light. We also show that the depolarization ratio from the CALIPSO measurements could be used to derive smoke aerosol particle size. From the calculation results for light depolarization ratio by Gaussian-shaped smoke particles and the CALIPSO-measured light depolarization ratio of â¼2% for smoke, the mean particle size of South-African smoke is estimated to be about half of the 532Â nm wavelength of the CALIPSO lidar.
⺠CALIPSO measures light depolarization ratio of â¼2% for smoke. ⺠Depolarization of linearly polarized light by irregular particles is studied. ⺠Small irregular particles have common depolarization properties. ⺠Depolarization ratio could be used to derive smoke aerosol particle size. ⺠South-African smoke particle size is half of CALIPSO 532 nm wavelength.