Abstract

Lidar remote sensing of clouds provides direct measurement of the radar backscatter coefficient but not the extinction coefficient, which is needed for any calculations involving optical depth. The relationship between these quantities for single spheres is very complicated but becomes simpler for polydispersions or illumination by radiation with a broad spectrum. The accuracy of estimating the extinction coefficient from measured radar backscatter coefficients of thin clouds is examined for single- and multiple-wavelength lidar systems. The stability of the ratio of the coefficients is examined for radii between 1 and 100 μm for a polydispersion of 5-μm width. The results show that the extinction coefficients of a broad selection of thin clouds may be obtained from lidar measurements with errors of ∼15% by visible and near visible lidar systems. Multiple lidar wavelengths permit a reduction of the error to ∼9%.

© 1980 Optical Society of America

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References

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  1. H. C. van de Hulst, Light Scattering by Small Particles (Wiley, New York, 1957).
  2. S. Twomey, H. B. Howell, Appl. Opt. 4, 501 (1965).
    [CrossRef]
  3. J. V. Dave, Report 320-3237, IBM Scientific Center, Palo Alto, Calif. (1968).
  4. W. M. Irvine, I. B. Pollack, Icarus 8, 324 (1968).
    [CrossRef]
  5. D. Deirmendjian, Electromagnetic Scattering on Spherical Polydispersions (American Elsevier, New York, 1964).
  6. G. S. Kent, Appl. Opt. 17, 3763 (1978).
    [CrossRef] [PubMed]

1978

1968

W. M. Irvine, I. B. Pollack, Icarus 8, 324 (1968).
[CrossRef]

1965

Dave, J. V.

J. V. Dave, Report 320-3237, IBM Scientific Center, Palo Alto, Calif. (1968).

Deirmendjian, D.

D. Deirmendjian, Electromagnetic Scattering on Spherical Polydispersions (American Elsevier, New York, 1964).

Howell, H. B.

Irvine, W. M.

W. M. Irvine, I. B. Pollack, Icarus 8, 324 (1968).
[CrossRef]

Kent, G. S.

Pollack, I. B.

W. M. Irvine, I. B. Pollack, Icarus 8, 324 (1968).
[CrossRef]

Twomey, S.

van de Hulst, H. C.

H. C. van de Hulst, Light Scattering by Small Particles (Wiley, New York, 1957).

Appl. Opt.

Icarus

W. M. Irvine, I. B. Pollack, Icarus 8, 324 (1968).
[CrossRef]

Other

D. Deirmendjian, Electromagnetic Scattering on Spherical Polydispersions (American Elsevier, New York, 1964).

J. V. Dave, Report 320-3237, IBM Scientific Center, Palo Alto, Calif. (1968).

H. C. van de Hulst, Light Scattering by Small Particles (Wiley, New York, 1957).

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Figures (6)

Fig. 1
Fig. 1

Logarithm of the extinction coefficient βe vs radius for water spheres illuminated by light at 0.694-μm wavelength, refractive index 1.33−i(.35 × 10−7).

Fig. 2
Fig. 2

Logarithm of radar backscatter cross section β vs radius for water spheres, as in Fig. 1.

Fig. 3
Fig. 3

Logarithm of the ratio β/βe vs radius for water spheres, as in Fig. 1.

Fig. 4
Fig. 4

Logarithm of β/βe vs size parameter for index of refraction m = 1.33−i(0.35 × 10−7).

Fig. 5
Fig. 5

β/βe vs average radius for polydispersions of 5-μm width for water spheres, as in Fig. 1.

Fig. 6
Fig. 6

Logarithm of β/βe vs radius for water spheres for a wavelength of 10.6 βm and refractive index of m = 1.143−i(0.069).

Tables (4)

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Table I Refractive Indices of Ice and Water for Selected Laser Wavelengths

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Table II Characteristics of Selected Cloud Distributions

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Table III Means and Standard Deviations of the Ratio R at the Selected Laser Wavelengths for the Clouds Described in Table II

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Table IV Variation of β/β, for Simultaneous Illumination by Various Laser Wavelengths

Equations (1)

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β = 1 N i = 1 N β ( λ i ) ,

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