Abstract

Ground based vertical path differential absorption measurements were obtained up to a height of 1.5 km with a CO2 lidar transmitting alternatively on the R(20) (10.247-μm) and R(18) (10.260-μm) lines during daylight in conditions of both strong and weak temperature inversions. The differential absorption between these lines for typical middle latitude lower atmosphere water vapor concentrations appears to be well suited to this type of measurement as the power loss on the more absorbed backscattered line [R(20)] is not too great as to unduly restrict the operating range, while the power differential is still sufficiently large to be readily measureable. In one set of measurements a strong temperature inversion at a height of 1 km resulted in a rapid vertical lapse in aerosol concentration with a consequent loss of SNR on the returns and severe distortion to the differential absorption profiles at this level. Water vapor profiles were derived from all measurements except in the region of the strong temperature inversion where the atmospheric backscattering cross section decayed rapidly. Reasonable results were obtained through the weak inversion region. The measurement capability of the lidar was found to be restricted by the length of the laser pulse tail and an inadequate signal-to-noise performance in regions of strong temperature inversions due to the associated decreases in aerosol concentration.

© 1983 Optical Society of America

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References

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  1. R. M. Schotland, “The Determination of the Vertical Profile of Atmospheric Gases by Means of a Ground Based Optical Radar,” in Proceedings, Third Symposium on Remote Sensing of the Environment (Environmental Research Institute of Michigan, Ann Arbor, 1964).
  2. E. V. Browell, T. D. Wilkerson, T. J. Mcllrath, Appl. Opt. 18, 3474 (1979).
    [CrossRef] [PubMed]
  3. E. R. Murray, R. D. Hake, J. E. Vander Laan, J. G. Hawley, Appl. Phys. Lett. 28, 542 (1976).
    [CrossRef]
  4. K. Asai, T. Itake, T. Igaraski, Appl. Phys. Lett. 35, 60 (1979).
    [CrossRef]
  5. M. S. Shumate, R. T. Menzies, J. S. Margolis, L.-G. Rosengren, Appl. Opt. 15, 2480 (1976).
    [CrossRef] [PubMed]
  6. It has been drawn to the author's attention by a reviewer that the absorption coefficient given in Ref. 5 for the R (20) line is now open to question.J. S. Ryan, M. H. Hubert, R. A. Crane in a recently reported measurement, Appl. Opt. 22, 711 (1983), have found a value nearly one half that of Ref. 5.
    [CrossRef] [PubMed]
  7. J. C. Peterson, M. E. Thomas, R. J. Nordstrom, E. K. Damon, R. K. Long, Appl. Opt. 18, 834 (1979).
    [CrossRef] [PubMed]

1983

1979

1976

M. S. Shumate, R. T. Menzies, J. S. Margolis, L.-G. Rosengren, Appl. Opt. 15, 2480 (1976).
[CrossRef] [PubMed]

E. R. Murray, R. D. Hake, J. E. Vander Laan, J. G. Hawley, Appl. Phys. Lett. 28, 542 (1976).
[CrossRef]

Asai, K.

K. Asai, T. Itake, T. Igaraski, Appl. Phys. Lett. 35, 60 (1979).
[CrossRef]

Browell, E. V.

Crane, R. A.

Damon, E. K.

Hake, R. D.

E. R. Murray, R. D. Hake, J. E. Vander Laan, J. G. Hawley, Appl. Phys. Lett. 28, 542 (1976).
[CrossRef]

Hawley, J. G.

E. R. Murray, R. D. Hake, J. E. Vander Laan, J. G. Hawley, Appl. Phys. Lett. 28, 542 (1976).
[CrossRef]

Hubert, M. H.

Igaraski, T.

K. Asai, T. Itake, T. Igaraski, Appl. Phys. Lett. 35, 60 (1979).
[CrossRef]

Itake, T.

K. Asai, T. Itake, T. Igaraski, Appl. Phys. Lett. 35, 60 (1979).
[CrossRef]

Long, R. K.

Margolis, J. S.

Mcllrath, T. J.

Menzies, R. T.

Murray, E. R.

E. R. Murray, R. D. Hake, J. E. Vander Laan, J. G. Hawley, Appl. Phys. Lett. 28, 542 (1976).
[CrossRef]

Nordstrom, R. J.

Peterson, J. C.

Rosengren, L.-G.

Ryan, J. S.

Schotland, R. M.

R. M. Schotland, “The Determination of the Vertical Profile of Atmospheric Gases by Means of a Ground Based Optical Radar,” in Proceedings, Third Symposium on Remote Sensing of the Environment (Environmental Research Institute of Michigan, Ann Arbor, 1964).

Shumate, M. S.

Thomas, M. E.

Vander Laan, J. E.

E. R. Murray, R. D. Hake, J. E. Vander Laan, J. G. Hawley, Appl. Phys. Lett. 28, 542 (1976).
[CrossRef]

Wilkerson, T. D.

Appl. Opt.

Appl. Phys. Lett.

E. R. Murray, R. D. Hake, J. E. Vander Laan, J. G. Hawley, Appl. Phys. Lett. 28, 542 (1976).
[CrossRef]

K. Asai, T. Itake, T. Igaraski, Appl. Phys. Lett. 35, 60 (1979).
[CrossRef]

Other

R. M. Schotland, “The Determination of the Vertical Profile of Atmospheric Gases by Means of a Ground Based Optical Radar,” in Proceedings, Third Symposium on Remote Sensing of the Environment (Environmental Research Institute of Michigan, Ann Arbor, 1964).

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Figures (13)

Fig. 1
Fig. 1

Schematic diagram of lidar and recording system.

Fig. 2
Fig. 2

Predicted differential absorption, R(18)–R(20), vs height for pulse lengths representative of CO2 laser output for a scale height HS of 500 m.

Fig. 3
Fig. 3

Temperature (a) and water vapor pressure (b) profiles from the radiosonde at 0950 CST 3–12–81.

Fig. 4
Fig. 4

Backscattered power from the long pulse sounding (65 pulse pairs) 0947-1017 CST 3–12–81.

Fig. 5
Fig. 5

Backscattered power from the short pulse sounding (63 pulse pairs) 1022-1054 CST 3–12–81.

Fig. 6
Fig. 6

Differential absorption vs height for the R(18)–R(20) line pair for the long pulse + and short pulse ○ soundings on 3–12–81.

Fig. 7
Fig. 7

Predicted long pulse differential absorption — together with replot of measured values + for 3–12–81.

Fig. 8
Fig. 8

Water vapor estimates for the long × and short pulse ○ lidar soundings for 3–12–81. Error bars show rms variations.

Fig. 9
Fig. 9

Temperature (a) and water vapor pressure (b) profiles from the radiosonde released at 1100 CST 24–11–81.

Fig. 10
Fig. 10

Backscattered power from the long pulse sounding (115 pulse pairs) 1002–1110 CST 24–11–81.

Fig. 11
Fig. 11

Backscattered power from the short pulse sounding (62 pulse pairs) 1112 CST 24–11–81.

Fig. 12
Fig. 12

Differential absorption vs height for the R(18)–R(20) line pair for the long pulse + and short pulse ○ soundings on 24–11–81.

Fig. 13
Fig. 13

Water vapor estimates for the long × and short pulse ○ lidar soundings for 24–11–81. Error bars show rms variations.

Tables (2)

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Table I CO2 Lidar Parameters

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Table II Water Vapor Absorption Coefficients at 300 K

Equations (5)

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e ( H + Δ H 2 ) = 1 2 Δ K Δ H { log [ P A ( H + Δ H ) P B ( H + Δ H ) ] log [ P A ( H ) P B ( H ) } ] ,
X = 0 H exp [ 2 ( H X ) TAU C ] exp ( X H S ) exp ( 2 K B Z = 0 X edZ ) / X 2 d X ,
X = 0 H exp [ 2 ( H X ) TAU C ] exp ( X H S ) exp ( 2 K B z = 0 X edZ ) / X 2 d X X = 0 H exp [ 2 ( H X ) TAU C ] exp ( X H S ) / X 2 d X .
D ̂ ( H j ) = i = j n i = j + n { k = 1 N [ log P 18 ( H i , t 2 k ) P 20 ( H i , t 2 k 1 ) ] } / ( n N ) ,
ê ( H j + Δ H 2 ) = 1 2 Δ K Δ H [ D ̂ ( H j + 1 ) D ̂ ( H j ) ] .

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