Abstract

Measurements of the angular scattering and extinction of IR (10.6-μm) laser radiation in laboratory water and ice clouds are reported and compared to theoretical predictions for spheres and visible (0.633-μm) light scattering data. Randomly oriented cloud particles with dimensions ranging from several times smaller to larger than the incident wavelength generated phase functions span the Rayleigh and Mie scattering domains and illustrate the effects caused by strong internal energy absorption. Dual-wavelength extinction measurements reveal information on the growth and dissipation of laboratory water clouds and the effects of cloud seeding. The remote sensing significance of the findings is discussed.

© 1981 Optical Society of America

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References

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  1. K. Sassen, K. N. Liou, J. Atmos. Sci. 36, 838 (1979).
    [CrossRef]
  2. A. Deepak, M. A. Box, Appl. Opt. 17, 2900 (1978).
    [CrossRef] [PubMed]
  3. K. Sassen, J. Appl. Meteorol. 17, 1319 (1978).
    [CrossRef]
  4. A. N. Rusk, D. Williams, M. R. Querry, J. Opt. Soc. Am. 61, 895 (1971).
    [CrossRef]
  5. M. Kerker, The Scattering of Light and Other Electromagnetic Radiation (Academic Press, New York, 1969).
  6. J. W. Schaaf, D. Williams, J. Opt. Soc. Am. 63, 726 (1973).
    [CrossRef]
  7. K. Sassen, K. N. Liou, J. Atmos. Sci. 36, 852 (1979).
    [CrossRef]
  8. P. Chylek, J. Atmos. Sci. 35, 296 (1978).
  9. R. G. Pinnick, S. G. Jennings, P. Chylek, H. J. Auvermann, J. Atmos. Sci. 36, 1577 (1979).
    [CrossRef]
  10. H. R. Byers, Elements of Cloud Physics (U. Chicago Press, Chicago, 1965).
  11. N. Fukuta, W. A. Schmeling, L. F. Evans, J. Appl. Meteorol. 10, 1174 (1971).
    [CrossRef]
  12. S. Asano, M. Sato, Appl. Opt. 19, 962 (1980).
    [CrossRef] [PubMed]
  13. J. B. Pollack, J. N. Cuzzi, J. Atmos. Sci. 37, 868 (1980).
    [CrossRef]

1980 (2)

S. Asano, M. Sato, Appl. Opt. 19, 962 (1980).
[CrossRef] [PubMed]

J. B. Pollack, J. N. Cuzzi, J. Atmos. Sci. 37, 868 (1980).
[CrossRef]

1979 (3)

K. Sassen, K. N. Liou, J. Atmos. Sci. 36, 838 (1979).
[CrossRef]

K. Sassen, K. N. Liou, J. Atmos. Sci. 36, 852 (1979).
[CrossRef]

R. G. Pinnick, S. G. Jennings, P. Chylek, H. J. Auvermann, J. Atmos. Sci. 36, 1577 (1979).
[CrossRef]

1978 (3)

P. Chylek, J. Atmos. Sci. 35, 296 (1978).

A. Deepak, M. A. Box, Appl. Opt. 17, 2900 (1978).
[CrossRef] [PubMed]

K. Sassen, J. Appl. Meteorol. 17, 1319 (1978).
[CrossRef]

1973 (1)

1971 (2)

A. N. Rusk, D. Williams, M. R. Querry, J. Opt. Soc. Am. 61, 895 (1971).
[CrossRef]

N. Fukuta, W. A. Schmeling, L. F. Evans, J. Appl. Meteorol. 10, 1174 (1971).
[CrossRef]

Asano, S.

Auvermann, H. J.

R. G. Pinnick, S. G. Jennings, P. Chylek, H. J. Auvermann, J. Atmos. Sci. 36, 1577 (1979).
[CrossRef]

Box, M. A.

Byers, H. R.

H. R. Byers, Elements of Cloud Physics (U. Chicago Press, Chicago, 1965).

Chylek, P.

R. G. Pinnick, S. G. Jennings, P. Chylek, H. J. Auvermann, J. Atmos. Sci. 36, 1577 (1979).
[CrossRef]

P. Chylek, J. Atmos. Sci. 35, 296 (1978).

Cuzzi, J. N.

J. B. Pollack, J. N. Cuzzi, J. Atmos. Sci. 37, 868 (1980).
[CrossRef]

Deepak, A.

Evans, L. F.

N. Fukuta, W. A. Schmeling, L. F. Evans, J. Appl. Meteorol. 10, 1174 (1971).
[CrossRef]

Fukuta, N.

N. Fukuta, W. A. Schmeling, L. F. Evans, J. Appl. Meteorol. 10, 1174 (1971).
[CrossRef]

Jennings, S. G.

R. G. Pinnick, S. G. Jennings, P. Chylek, H. J. Auvermann, J. Atmos. Sci. 36, 1577 (1979).
[CrossRef]

Kerker, M.

M. Kerker, The Scattering of Light and Other Electromagnetic Radiation (Academic Press, New York, 1969).

Liou, K. N.

K. Sassen, K. N. Liou, J. Atmos. Sci. 36, 852 (1979).
[CrossRef]

K. Sassen, K. N. Liou, J. Atmos. Sci. 36, 838 (1979).
[CrossRef]

Pinnick, R. G.

R. G. Pinnick, S. G. Jennings, P. Chylek, H. J. Auvermann, J. Atmos. Sci. 36, 1577 (1979).
[CrossRef]

Pollack, J. B.

J. B. Pollack, J. N. Cuzzi, J. Atmos. Sci. 37, 868 (1980).
[CrossRef]

Querry, M. R.

Rusk, A. N.

Sassen, K.

K. Sassen, K. N. Liou, J. Atmos. Sci. 36, 838 (1979).
[CrossRef]

K. Sassen, K. N. Liou, J. Atmos. Sci. 36, 852 (1979).
[CrossRef]

K. Sassen, J. Appl. Meteorol. 17, 1319 (1978).
[CrossRef]

Sato, M.

Schaaf, J. W.

Schmeling, W. A.

N. Fukuta, W. A. Schmeling, L. F. Evans, J. Appl. Meteorol. 10, 1174 (1971).
[CrossRef]

Williams, D.

Appl. Opt. (2)

J. Appl. Meteorol. (2)

N. Fukuta, W. A. Schmeling, L. F. Evans, J. Appl. Meteorol. 10, 1174 (1971).
[CrossRef]

K. Sassen, J. Appl. Meteorol. 17, 1319 (1978).
[CrossRef]

J. Atmos. Sci. (5)

K. Sassen, K. N. Liou, J. Atmos. Sci. 36, 852 (1979).
[CrossRef]

P. Chylek, J. Atmos. Sci. 35, 296 (1978).

R. G. Pinnick, S. G. Jennings, P. Chylek, H. J. Auvermann, J. Atmos. Sci. 36, 1577 (1979).
[CrossRef]

J. B. Pollack, J. N. Cuzzi, J. Atmos. Sci. 37, 868 (1980).
[CrossRef]

K. Sassen, K. N. Liou, J. Atmos. Sci. 36, 838 (1979).
[CrossRef]

J. Opt. Soc. Am. (2)

Other (2)

M. Kerker, The Scattering of Light and Other Electromagnetic Radiation (Academic Press, New York, 1969).

H. R. Byers, Elements of Cloud Physics (U. Chicago Press, Chicago, 1965).

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Figures (13)

Fig. 1
Fig. 1

Comparison of Mie theory predictions for incident vertically P22 and horizontally P11 polarized 10.6-μm radiation with experimental water cloud data (dashed line) with 1.0-μm modal droplet radius. Vertical bars show standard deviations of the four averaged nephelometer scans.

Fig. 2
Fig. 2

Variations in the single-particle extinction Qext and scattering Qscat cross sections at 0.633- and 10.6-μm wavelengths with water droplet radius and size parameter (for 10.6 μm). Qext = Qscat at the visible wavelength due to negligible energy absorption during scattering.

Fig. 3
Fig. 3

Typical photomicrographs of the ice crystals collected during the experiments described in the text. Each square is 30 μm on a side.

Fig. 4
Fig. 4

Comparison of Mie theory prediction for incident vertically polarized 10.6-μm radiation P22 with experiments for an ice cloud containing minute crystals (2.3-μm modal dimension). Theoretical results for ice spheres with the same size distribution as the ice crystal maximum dimensions. Vertical bars show standard deviations of the five averaged nephelometer scans.

Fig. 5
Fig. 5

Ice crystal size distributions for the data in Fig. 4 (dashed line) and Fig. 6 (solid and dash–dot lines), plotted as the percent of crystals per 1-μm maximum dimension interval.

Fig. 6
Fig. 6

Normalized phase functions from an ice cloud which maintained modal plate dimensions of 5 μm as the size distribution became increasingly skewed to larger sizes, showing the emergence of Mie scattering characteristics.

Fig. 7
Fig. 7

Comparison of phase functions from predominantly plate and column crystal clouds with similar size distributions (see Fig. 8).

Fig. 8
Fig. 8

Relative size distributions for the plate and column cloud data shown in Fig. 7.

Fig. 9
Fig. 9

Comparison of experimental data at 10.6- and 0.633-μm wavelengths for two ice clouds with similar particle size parameter distributions. P12 represents the depolarized component of scattered light with incident vertical polarization.

Fig. 10
Fig. 10

Relative size distributions for the ice cloud data shown in Fig. 9. Distributions in terms of size parameters at the two wavelengths used are rather similar.

Fig. 11
Fig. 11

Relation between 10.6- and 0.633-μm extinction coefficients in laboratory water clouds during two cycles of cloud formation and dissipation when large hydroscopic nuclei were present (dashed curves with arrows) and when little variability was observed on two other occasions with continental cloud condensation nuclei spectra (solid lines showing average relationships).

Fig. 12
Fig. 12

Variations in 10.6- and 0.633-μm extinction coefficients associated with the dry ice-seeding of a supercooled water cloud. The great difference in the two measurements just following seeding indicates the formation of numerous submicron sized particles.

Fig. 13
Fig. 13

Number size distributions (in particles/cm3 volume/1-μm dimension interval) from four cloud samples taken during the initial 20 sec following the cloud seeding in Fig. 12.

Equations (3)

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σ λ = - 1 R ln P r P i ,
β s ( θ ) = P s ( θ ) A b sin θ P r ω r V ( 90 ° ) ,
P ( θ ) / 4 π = β s ( θ ) / 2 π 0 2 π β s ( θ ) sin θ d θ .

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