Abstract

Photographs of clouds taken with a camera with a large aperture ratio must have a short depth of focus to resolve small droplets. Hence the sampling volume is small, which limits the number of droplets and gives rise to a large statistical error on the number counted. However, useful signals can be obtained with a small aperture ratio, which allows for a sample volume large enough for counting cloud droplets at aircraft speeds with useful spatial resolution. The signal is sufficient to discriminate against noise from a sunlit cloud as background, provided the bandwidth of the light source and camera are restricted, and against readout noise. Hence, in principle, an instrument to sample the size distribution of cloud droplets from aircraft in daylight can be constructed from a simple TV camera and an array of laser diodes, without any components or screens external to the aircraft window.

© 1999 Optical Society of America

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  1. R. G. Knollenberg, “The optical array: an alternative to scattering or extinction for airborne particle size determination,” J. Appl. Meteorol. 9, 86–103 (1970).
    [CrossRef]
  2. A. J. Heymsfield, J. L. Parrish, “A computational technique for increasing the effective volume of the PMS two-dimensional particle size spectrometer,” J. Appl. Meteorol. 17, 1566–1572 (1978).
    [CrossRef]
  3. P. D. Jonas, UMIST, Manchester, UK (personal communication, 1996).
  4. R. Greenler, Rainbows, Haloes, and Glories (Cambridge U. Press, Cambridge, UK, 1980), pp. 1–2.
  5. B. I. Bleaney, B. Bleaney, Electricity and Magnetism, 2nd ed. (Oxford U. Press, London, 1965), p. 275.
  6. H. C. van de Hulst, “Light Scattering by Small Particles” (Dover, New York, 1981).
  7. R. A. R. Tricker, Introduction to Meterological Optics (Elsevier, New York, 1970).
  8. H. K. Roscoe, W. H. Taylor, J. D. Evans, A. M. Tait, R. A. Freshwater, D. J. Fish, E. K. Strong, R. L. Jones, “Automated ground-based star-pointing UV–visible spectrometer for stratospheric measurements,” Appl. Opt. 36, 6069–6975 (1997).
    [CrossRef] [PubMed]
  9. C. D. Mackay, “Charge-coupled devices in astronomy,” Ann. Rev. Astron. Astrophys. 24, 255–283 (1986).
    [CrossRef]
  10. J. T. Houghton, The Physics of Atmospheres (Cambridge U. Press, Cambridge, UK, 1977), pp. 177–178.

1997 (1)

1986 (1)

C. D. Mackay, “Charge-coupled devices in astronomy,” Ann. Rev. Astron. Astrophys. 24, 255–283 (1986).
[CrossRef]

1978 (1)

A. J. Heymsfield, J. L. Parrish, “A computational technique for increasing the effective volume of the PMS two-dimensional particle size spectrometer,” J. Appl. Meteorol. 17, 1566–1572 (1978).
[CrossRef]

1970 (1)

R. G. Knollenberg, “The optical array: an alternative to scattering or extinction for airborne particle size determination,” J. Appl. Meteorol. 9, 86–103 (1970).
[CrossRef]

Bleaney, B.

B. I. Bleaney, B. Bleaney, Electricity and Magnetism, 2nd ed. (Oxford U. Press, London, 1965), p. 275.

Bleaney, B. I.

B. I. Bleaney, B. Bleaney, Electricity and Magnetism, 2nd ed. (Oxford U. Press, London, 1965), p. 275.

Evans, J. D.

Fish, D. J.

Freshwater, R. A.

Greenler, R.

R. Greenler, Rainbows, Haloes, and Glories (Cambridge U. Press, Cambridge, UK, 1980), pp. 1–2.

Heymsfield, A. J.

A. J. Heymsfield, J. L. Parrish, “A computational technique for increasing the effective volume of the PMS two-dimensional particle size spectrometer,” J. Appl. Meteorol. 17, 1566–1572 (1978).
[CrossRef]

Houghton, J. T.

J. T. Houghton, The Physics of Atmospheres (Cambridge U. Press, Cambridge, UK, 1977), pp. 177–178.

Jonas, P. D.

P. D. Jonas, UMIST, Manchester, UK (personal communication, 1996).

Jones, R. L.

Knollenberg, R. G.

R. G. Knollenberg, “The optical array: an alternative to scattering or extinction for airborne particle size determination,” J. Appl. Meteorol. 9, 86–103 (1970).
[CrossRef]

Mackay, C. D.

C. D. Mackay, “Charge-coupled devices in astronomy,” Ann. Rev. Astron. Astrophys. 24, 255–283 (1986).
[CrossRef]

Parrish, J. L.

A. J. Heymsfield, J. L. Parrish, “A computational technique for increasing the effective volume of the PMS two-dimensional particle size spectrometer,” J. Appl. Meteorol. 17, 1566–1572 (1978).
[CrossRef]

Roscoe, H. K.

Strong, E. K.

Tait, A. M.

Taylor, W. H.

Tricker, R. A. R.

R. A. R. Tricker, Introduction to Meterological Optics (Elsevier, New York, 1970).

van de Hulst, H. C.

H. C. van de Hulst, “Light Scattering by Small Particles” (Dover, New York, 1981).

Ann. Rev. Astron. Astrophys. (1)

C. D. Mackay, “Charge-coupled devices in astronomy,” Ann. Rev. Astron. Astrophys. 24, 255–283 (1986).
[CrossRef]

Appl. Opt. (1)

J. Appl. Meteorol. (2)

R. G. Knollenberg, “The optical array: an alternative to scattering or extinction for airborne particle size determination,” J. Appl. Meteorol. 9, 86–103 (1970).
[CrossRef]

A. J. Heymsfield, J. L. Parrish, “A computational technique for increasing the effective volume of the PMS two-dimensional particle size spectrometer,” J. Appl. Meteorol. 17, 1566–1572 (1978).
[CrossRef]

Other (6)

P. D. Jonas, UMIST, Manchester, UK (personal communication, 1996).

R. Greenler, Rainbows, Haloes, and Glories (Cambridge U. Press, Cambridge, UK, 1980), pp. 1–2.

B. I. Bleaney, B. Bleaney, Electricity and Magnetism, 2nd ed. (Oxford U. Press, London, 1965), p. 275.

H. C. van de Hulst, “Light Scattering by Small Particles” (Dover, New York, 1981).

R. A. R. Tricker, Introduction to Meterological Optics (Elsevier, New York, 1970).

J. T. Houghton, The Physics of Atmospheres (Cambridge U. Press, Cambridge, UK, 1977), pp. 177–178.

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