Abstract

The effects of changes in wavelength and ambient conditions on the atmospheric backscatter at CO2 wavelengths have been examined. It has been found that, with the exception of (NH4)2SO4-containing aerosols, whose size distributions have relatively large numbers of small particles, the variation of backscatter with CO2 wavelength is less than a factor of ~3. However, for such (NH4)2SO4 aerosol distributions, the variation of backscatter function with CO2 wavelengths between 9.1 and 11.1 μm may reach 1 order of magnitude. The effects of ambient humidity and temperature changes are negligibly small when the relative humidity is low (<75%). However, for a humid environment (>90%), a few percent change in humidity or a few degrees change in temperature may cause noticeable change in backscatter from aerosol particles of small sizes.

© 1983 Optical Society of America

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References

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  1. G. S. Kent, G. K. Yue, U. O. Farrukh, A. Deepak, Appl. Opt. 22, 1655 (1983).
    [CrossRef] [PubMed]
  2. G. S. Kent, G. K. Yue, U. O. Farrukh, A. Deepak, Appl. Opt. 22, 1666 (1983).
    [CrossRef] [PubMed]
  3. G. M. Hale, M. R. Querry, Appl. Opt. 12, 555 (1973).
    [CrossRef] [PubMed]
  4. E. P. Shettle, R. W. Fenn, “Models for the Aerosols of the Lower Atmosphere and the Effects of Humidity Variations on their Optical Properties,” Air Force Geophysical Laboratory, Hanscom Air Force Base, Mass., AFGL-TR-79-0214 (1979).
  5. E. M. Patterson, J. Geophys. Res. 86, 3236 (1981).
    [CrossRef]
  6. K. F. Palmer, D. Williams, Appl. Opt. 14, 208 (1975).
    [PubMed]
  7. O. B. Toon, J. B. Pollack, B. N. Khare, J. Geophys. Res. 23, 5733 (1976).
    [CrossRef]
  8. T. S. Cress, “Airborne Measurement of Aerosol Size Distributions Over Northern Europe, Vol. 1, Spring and Fall, 1976, Summer 1977,” Air Force Geophysical Laboratory, Hanscom Air Force Base, Mass., Environmental Research Paper 702 (1980).
  9. E. M. Patterson, C. S. Kiang, A. C. Delany, A. F. Wartburg, A. C. D. Leslie, B. J. Huebert, J. Geophys. Res. 85, 7361 (1980).
    [CrossRef]
  10. G. Hanel, Adv. Geophys. 19, 73 (1976).
    [CrossRef]
  11. P. Winkler, Aerosol Sci. 4, 373 (1973).
    [CrossRef]
  12. International Critical Tables, Vol. 3 (McGraw-Hill, New York, 1928).
  13. J. I. Gmitro, T. Vermeulen, “Vapor-Liquid Equilibria for Aqueous Sulfuric Acid,” Lawrence Radiation Laboratory UCRL-10886 (U. California, Berkeley, 1963).
  14. R. E. Newell, J. W. Kidson, D. G. Vincent, G. J. Boer, The General Circulation of the Tropical Atmosphere and Internations with Extratropical Latitudes, Vol. 1 (MIT Press, Cambridge, Mass., 1972).
  15. R. S. Longhurst, Geometrical and Physical Optics (Longmans, London, 1964), p. 423.

1983

1981

E. M. Patterson, J. Geophys. Res. 86, 3236 (1981).
[CrossRef]

1980

E. M. Patterson, C. S. Kiang, A. C. Delany, A. F. Wartburg, A. C. D. Leslie, B. J. Huebert, J. Geophys. Res. 85, 7361 (1980).
[CrossRef]

1976

G. Hanel, Adv. Geophys. 19, 73 (1976).
[CrossRef]

O. B. Toon, J. B. Pollack, B. N. Khare, J. Geophys. Res. 23, 5733 (1976).
[CrossRef]

1975

1973

Boer, G. J.

R. E. Newell, J. W. Kidson, D. G. Vincent, G. J. Boer, The General Circulation of the Tropical Atmosphere and Internations with Extratropical Latitudes, Vol. 1 (MIT Press, Cambridge, Mass., 1972).

Cress, T. S.

T. S. Cress, “Airborne Measurement of Aerosol Size Distributions Over Northern Europe, Vol. 1, Spring and Fall, 1976, Summer 1977,” Air Force Geophysical Laboratory, Hanscom Air Force Base, Mass., Environmental Research Paper 702 (1980).

Deepak, A.

Delany, A. C.

E. M. Patterson, C. S. Kiang, A. C. Delany, A. F. Wartburg, A. C. D. Leslie, B. J. Huebert, J. Geophys. Res. 85, 7361 (1980).
[CrossRef]

Farrukh, U. O.

Fenn, R. W.

E. P. Shettle, R. W. Fenn, “Models for the Aerosols of the Lower Atmosphere and the Effects of Humidity Variations on their Optical Properties,” Air Force Geophysical Laboratory, Hanscom Air Force Base, Mass., AFGL-TR-79-0214 (1979).

Gmitro, J. I.

J. I. Gmitro, T. Vermeulen, “Vapor-Liquid Equilibria for Aqueous Sulfuric Acid,” Lawrence Radiation Laboratory UCRL-10886 (U. California, Berkeley, 1963).

Hale, G. M.

Hanel, G.

G. Hanel, Adv. Geophys. 19, 73 (1976).
[CrossRef]

Huebert, B. J.

E. M. Patterson, C. S. Kiang, A. C. Delany, A. F. Wartburg, A. C. D. Leslie, B. J. Huebert, J. Geophys. Res. 85, 7361 (1980).
[CrossRef]

Kent, G. S.

Khare, B. N.

O. B. Toon, J. B. Pollack, B. N. Khare, J. Geophys. Res. 23, 5733 (1976).
[CrossRef]

Kiang, C. S.

E. M. Patterson, C. S. Kiang, A. C. Delany, A. F. Wartburg, A. C. D. Leslie, B. J. Huebert, J. Geophys. Res. 85, 7361 (1980).
[CrossRef]

Kidson, J. W.

R. E. Newell, J. W. Kidson, D. G. Vincent, G. J. Boer, The General Circulation of the Tropical Atmosphere and Internations with Extratropical Latitudes, Vol. 1 (MIT Press, Cambridge, Mass., 1972).

Leslie, A. C. D.

E. M. Patterson, C. S. Kiang, A. C. Delany, A. F. Wartburg, A. C. D. Leslie, B. J. Huebert, J. Geophys. Res. 85, 7361 (1980).
[CrossRef]

Longhurst, R. S.

R. S. Longhurst, Geometrical and Physical Optics (Longmans, London, 1964), p. 423.

Newell, R. E.

R. E. Newell, J. W. Kidson, D. G. Vincent, G. J. Boer, The General Circulation of the Tropical Atmosphere and Internations with Extratropical Latitudes, Vol. 1 (MIT Press, Cambridge, Mass., 1972).

Palmer, K. F.

Patterson, E. M.

E. M. Patterson, J. Geophys. Res. 86, 3236 (1981).
[CrossRef]

E. M. Patterson, C. S. Kiang, A. C. Delany, A. F. Wartburg, A. C. D. Leslie, B. J. Huebert, J. Geophys. Res. 85, 7361 (1980).
[CrossRef]

Pollack, J. B.

O. B. Toon, J. B. Pollack, B. N. Khare, J. Geophys. Res. 23, 5733 (1976).
[CrossRef]

Querry, M. R.

Shettle, E. P.

E. P. Shettle, R. W. Fenn, “Models for the Aerosols of the Lower Atmosphere and the Effects of Humidity Variations on their Optical Properties,” Air Force Geophysical Laboratory, Hanscom Air Force Base, Mass., AFGL-TR-79-0214 (1979).

Toon, O. B.

O. B. Toon, J. B. Pollack, B. N. Khare, J. Geophys. Res. 23, 5733 (1976).
[CrossRef]

Vermeulen, T.

J. I. Gmitro, T. Vermeulen, “Vapor-Liquid Equilibria for Aqueous Sulfuric Acid,” Lawrence Radiation Laboratory UCRL-10886 (U. California, Berkeley, 1963).

Vincent, D. G.

R. E. Newell, J. W. Kidson, D. G. Vincent, G. J. Boer, The General Circulation of the Tropical Atmosphere and Internations with Extratropical Latitudes, Vol. 1 (MIT Press, Cambridge, Mass., 1972).

Wartburg, A. F.

E. M. Patterson, C. S. Kiang, A. C. Delany, A. F. Wartburg, A. C. D. Leslie, B. J. Huebert, J. Geophys. Res. 85, 7361 (1980).
[CrossRef]

Williams, D.

Winkler, P.

P. Winkler, Aerosol Sci. 4, 373 (1973).
[CrossRef]

Yue, G. K.

Adv. Geophys.

G. Hanel, Adv. Geophys. 19, 73 (1976).
[CrossRef]

Aerosol Sci.

P. Winkler, Aerosol Sci. 4, 373 (1973).
[CrossRef]

Appl. Opt.

J. Geophys. Res.

O. B. Toon, J. B. Pollack, B. N. Khare, J. Geophys. Res. 23, 5733 (1976).
[CrossRef]

E. M. Patterson, C. S. Kiang, A. C. Delany, A. F. Wartburg, A. C. D. Leslie, B. J. Huebert, J. Geophys. Res. 85, 7361 (1980).
[CrossRef]

E. M. Patterson, J. Geophys. Res. 86, 3236 (1981).
[CrossRef]

Other

T. S. Cress, “Airborne Measurement of Aerosol Size Distributions Over Northern Europe, Vol. 1, Spring and Fall, 1976, Summer 1977,” Air Force Geophysical Laboratory, Hanscom Air Force Base, Mass., Environmental Research Paper 702 (1980).

International Critical Tables, Vol. 3 (McGraw-Hill, New York, 1928).

J. I. Gmitro, T. Vermeulen, “Vapor-Liquid Equilibria for Aqueous Sulfuric Acid,” Lawrence Radiation Laboratory UCRL-10886 (U. California, Berkeley, 1963).

R. E. Newell, J. W. Kidson, D. G. Vincent, G. J. Boer, The General Circulation of the Tropical Atmosphere and Internations with Extratropical Latitudes, Vol. 1 (MIT Press, Cambridge, Mass., 1972).

R. S. Longhurst, Geometrical and Physical Optics (Longmans, London, 1964), p. 423.

E. P. Shettle, R. W. Fenn, “Models for the Aerosols of the Lower Atmosphere and the Effects of Humidity Variations on their Optical Properties,” Air Force Geophysical Laboratory, Hanscom Air Force Base, Mass., AFGL-TR-79-0214 (1979).

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Figures (8)

Fig. 1
Fig. 1

βCO2 vs mode radius for different CO2 wavelengths and for different aerosol materials: (a) H2SO4; (b) dust; (c) (NH4)2SO4; (d) water soluble.

Fig. 2
Fig. 2

βCO2 vs CO2 wavelength for different aerosol materials and for different measured aerosol size distributions: (a) spring average aerosols reported by Cress8; (b) continental aerosols reported by Patterson et al.9; (c) marine aerosols reported by Patterson et al.9

Fig. 3
Fig. 3

Water vapor pressures of H2SO4, (NH4)2SO4, and NaCl at 25 and 15°C vs the weight percentage of the solute.

Fig. 4
Fig. 4

Variation of the real parts of the indices of refraction for H2SO4, (NH4)2SO4, and NaCl at λ = 10.6 μm as a function of the weight percentage of the solute.

Fig. 5
Fig. 5

Percentage βCO2 change vs relative humidity change for lognormal aerosol size distributions with mode radii equal to 0.05, 0.5, and 5.0 μm at temperatures 15 and 25°C: (a) H2SO4 aerosols at an initial relative humidity of 20%; (b) H2SO4 aerosols at an initial relative humidity of 60%; (c) NaCl aerosols at an initial relative humidity of 90%; (d) (NH4)2SO4 aerosols at an initial relative humidity of 90%.

Fig. 6
Fig. 6

Humidities at different heights as reported by Cress8 and Newell et al.14 Each dot represents an ambient condition reported by Cress, and the solid line is the median value for the data set. The short- and long-dashed lines are the 40°N Jan. and July values presented by Newell et al.,14 respectively.

Fig. 7
Fig. 7

Histogram of the percentage of cases of a given relative humidity at an altitude of 1 km reported by Cress. The curves represent the ratio of βCO2 at a given relative humidity to βCO2 at 0% relative humidity.

Fig. 8
Fig. 8

Percentage βCO2 change vs temperature change for lognormal aerosol size distributions with mode radii equal to 0.05, 0.5, and 5.0 μm at initial temperatures of 15 and 25°C: (a) H2SO4 aerosols at relative humidity 20%; (b) H2SO4 aerosols at relative humidity 60%; (c) NaCl aerosols at relative humidity 90%; (d) (NH4)2SO4 aerosols at relative humidity 90%.

Tables (1)

Tables Icon

Table I Refractive Indices of Common Aerosol Materials at CO2 Wavelengths

Equations (11)

Equations on this page are rendered with MathJax. Learn more.

β = r 1 r 2 Q ( n , α ) d N ( r ) d r d r ,
d N ( r ) d r = A r exp [ - ln 2 ( r / r m ) 2 ( ln σ g ) 2 ] ,
V ρ x = V ρ x ,
V V = ρ x ρ x ,
f = r r = ( ρ x ρ x ) 1 / 3 .
n ( r ) = A r exp { - ln 2 [ r / ( f r m ) ] 2 ( ln σ g ) 2 } .
n = n w + ( n 0 - n w ) × ( 1 + ρ 0 ρ w · m w m 0 ) - 1 ,
p = exp [ A ( x ) ln 298.15 T + B ( x ) T + C ( x ) + D ( x ) T ] ,
p = exp [ A ( x ) ln 298.15 T + B ( x ) T + C ( x ) + D ( x ) T ] ,
p = p ( T / T ) .
n 2 - 1 ( n 2 + 2 ) ρ = constant ,

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