Publication Abstracts

Coffeen and Hansen 1973

Coffeen, D.L., and J.E. Hansen, 1973: Airborne infrared polarimetry. In Proceedings of the 8th International Symposium on Remote Sensing of Environment, Ann Arbor, Mich., October 2-6, 1972, vol. 1. Environmental Research Institute of Michigan, pp. 515-522.

An infrared polarimeter (AEROPOL) was developed for an airborne remote sensing study of terrelltrial cloud particle sizes and shapes. The instrument is capable of ±0.1% accuracy for linear polarization, over the range 1.1-3.5μ, with a 1.5° field of view. It uses a rotating wire-grid polarization analyzer, PbS detector cooled with Freon-13, and operates under minicomputer control, giving a polarization leastsquares solution each 2.5 seconds. The AEROPOL instrument was flown on the NASA CV-990 aircraft, over a variety of continental anc1 maritime cloud forms.

Linear polarization was measured as a function of phase angle, for a given wavelength. Liquid water clouds exhibit considerable detail in their polarization curves, including a positive cloudbow near 40° phase angle, and negative polarization at phase angles less than 20° and greater than about 100°. Theoretical polarization computations have been made for single and multiple scattering by water spheres, as a function of wavelength, particle size, and cloud thickness. Many features are size-dependent; in particular the exact phase angle of the polarization inversion point is directly correlated with the mean size in the cloud tops. Cloud systems were found with mean particle radii as small as 5μ, and as large as 30μ.

A remarkable curve of polarization versus phase angle was obtained for thick tropical cirrus clouds. Polarization is negative at the large and small phase angles; it is positive from 20° to 145°. There is no indication of a cloudbow or other detniled structure. Theoretical calculations are not yet possible for these crystalline shapes. However it is very easy to differentiate between water and ice clouds based on the observeu polarizations.

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BibTeX Citation

@inproceedings{co08010e,
  author={Coffeen, D. L. and Hansen, J. E.},
  title={Airborne infrared polarimetry},
  booktitle={Proceedings of the 8th International Symposium on Remote Sensing of Environment, Ann Arbor, Mich., October 2-6, 1972},
  year={1973},
  volume={1},
  pages={515--522},
  publisher={Environmental Research Institute of Michigan},
  address={Ann Arbor, Mich.},
}

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RIS Citation

TY  - CPAPER
ID  - co08010e
AU  - Coffeen, D. L.
AU  - Hansen, J. E.
PY  - 1973
TI  - Airborne infrared polarimetry
BT  - Proceedings of the 8th International Symposium on Remote Sensing of Environment, Ann Arbor, Mich., October 2-6, 1972
VL  - 1
SP  - 515
EP  - 522
PB  - Environmental Research Institute of Michigan
CY  - Ann Arbor, Mich.
ER  -

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