Abstract

The impact and potential of a polarization-selection technique to reduce the sky background signal for linearly polarized monostatic elastic backscatter lidar measurements are examined. Taking advantage of naturally occurring polarization properties in scattered skylight, we devised a polarization-discrimination technique in which both the lidar transmitter and the receiver track and minimize detected sky background noise while maintaining maximum lidar signal throughput. Lidar elastic backscatter measurements, carried out continuously during daylight hours at 532  nm, show as much as a factor of 10 improvement in the signal-to-noise ratio (SNR) over conventional unpolarized schemes. For vertically pointing lidars, the largest improvements are limited to the early morning and late afternoon hours, while for lidars scanning azimuthally and in elevation at angles other than vertical, significant improvements are achievable over more extended time periods with the specific times and improvement factors depending on the specific angle between the lidar and the solar axes. The resulting diurnal variations in SNR improvement sometimes show an asymmetry with the solar angle that analysis indicates can be attributed to changes in observed relative humidity that modifies the underlying aerosol microphysics and observed optical depth.

© 2006 Optical Society of America

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References

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  1. R. M. Schotland, K. Sassen, and R. J. Stone, "Observations by lidar of linear depolarization ratios by hydrometeors," J. Appl. Meteorol. 10, 1011-1017 (1971).
    [CrossRef]
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    [CrossRef]
  3. C. M. R. Platt, "Lidar observation of a mixed-phase altostratus cloud," J. Appl. Meteorol. 16, 339-345 (1977).
    [CrossRef]
  4. K. Sassen, "Scattering of polarized laser light by water droplet, mixed-phase and ice crystal clouds. 2. Angular depolarization and multiple scatter behavior," J. Atmos. Sci. 36, 852-861 (1979).
    [CrossRef]
  5. C. M. R. Platt, "Transmission and reflectivity of ice clouds by active probing," in Clouds, Their Formation, Optical Properties, and Effects, P. V. Hobbs, ed. (Academic, 1981), pp. 407-436.
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    [CrossRef]
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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]

2006 (1)

2005 (2)

Y. Y. Hassebo, B. Gross, F. Moshary, Y. Zhao, and S. Ahmed, "Polarization discrimination technique to maximize lidar signal-to-noise ratio," in Polarization Science and Remote Sensing II, J. A. Shaw and J. S. Tyo, eds., Proc. SPIE 5888, 93-101 (2005).

Y. Y. Hassebo, B. M. Gross, M. M. Oo, F. Moshary, and S. A. Ahmed, "Impact on lidar system parameters of polarization selection/tracking scheme to reduce daylight noise," in Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing, U. N. Singh, ed., Proc. SPIE 5984, 53-64 (2005).

2004 (1)

2002 (1)

1998 (1)

1981 (1)

G. Hanel and M. Lehmann, "Equilibrium size of aerosol particles and relative humidity: new experimental data from various aerosol types and their treatment for cloud physics application," Contrib. Atmos. Phys. 54, 57-71 (1981).

1979 (1)

K. Sassen, "Scattering of polarized laser light by water droplet, mixed-phase and ice crystal clouds. 2. Angular depolarization and multiple scatter behavior," J. Atmos. Sci. 36, 852-861 (1979).
[CrossRef]

1977 (1)

C. M. R. Platt, "Lidar observation of a mixed-phase altostratus cloud," J. Appl. Meteorol. 16, 339-345 (1977).
[CrossRef]

1975 (1)

P. V. N. Nair and K. G. Vohra, "Growth of aqueous sulfuric acid droplets as function of relative humidity," J. Aerosol Sci. 6, 265-271 (1975).
[CrossRef]

1974 (2)

J. Hansen and L. Travis, "Light scattering in planetery atmospheres," Space Sci. Rev. 16, 527-610 (1974).
[CrossRef]

K. Sassen, "Depolarization of laser light backscattered by artificial clouds," J. Appl. Meterol. 13, 923-933 (1974).
[CrossRef]

1971 (1)

R. M. Schotland, K. Sassen, and R. J. Stone, "Observations by lidar of linear depolarization ratios by hydrometeors," J. Appl. Meteorol. 10, 1011-1017 (1971).
[CrossRef]

Ahmed, S.

Y. Y. Hassebo, B. Gross, F. Moshary, Y. Zhao, and S. Ahmed, "Polarization discrimination technique to maximize lidar signal-to-noise ratio," in Polarization Science and Remote Sensing II, J. A. Shaw and J. S. Tyo, eds., Proc. SPIE 5888, 93-101 (2005).

Ahmed, S. A.

Y. Y. Hassebo, B. M. Gross, M. M. Oo, F. Moshary, and S. A. Ahmed, "Impact on lidar system parameters of polarization selection/tracking scheme to reduce daylight noise," in Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing, U. N. Singh, ed., Proc. SPIE 5984, 53-64 (2005).

D. S. Kokkinos and S. A. Ahmed, "Atmospheric depolarization of lidar backscatter signals," in Lasers '88: Proceedings of the International Conference, Lake Tahoe, Nevada, Paper No. A90-30956 12-36. (STS Press, McLean, Virginia, 1989), pp. 538-545.

Bissonnette, L. R.

Cairns, B.

Chen, B.

Chowdhary, J.

Fenn, R. W.

E. P. Shettle and R. W. Fenn, Models of the Aerosols of the Lower Atmosphere and the Effects of Humidity Variations on Their Optical Properties, Project 7670 (Air Force Geophysics Laboratory, Massachusetts, 1979).

Gobbi, G. P.

Gross, B.

Y. Y. Hassebo, B. Gross, F. Moshary, Y. Zhao, and S. Ahmed, "Polarization discrimination technique to maximize lidar signal-to-noise ratio," in Polarization Science and Remote Sensing II, J. A. Shaw and J. S. Tyo, eds., Proc. SPIE 5888, 93-101 (2005).

Gross, B. M.

Y. Y. Hassebo, B. M. Gross, M. M. Oo, F. Moshary, and S. A. Ahmed, "Impact on lidar system parameters of polarization selection/tracking scheme to reduce daylight noise," in Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing, U. N. Singh, ed., Proc. SPIE 5984, 53-64 (2005).

Hanel, G.

G. Hanel and M. Lehmann, "Equilibrium size of aerosol particles and relative humidity: new experimental data from various aerosol types and their treatment for cloud physics application," Contrib. Atmos. Phys. 54, 57-71 (1981).

G. Hanel, "The properties of atmospheric aerosol particles as functions of the relative humidity at thermodynamic equilibrium with the surrounding moist air," in Advances in Geophysics, H. E. Landsberg and J. Van Mieghem, eds. (Academic, 1976), Vol. 19, pp. 73-188.

Hansen, J.

J. Hansen and L. Travis, "Light scattering in planetery atmospheres," Space Sci. Rev. 16, 527-610 (1974).
[CrossRef]

Hassebo, Y. Y.

Y. Y. Hassebo, B. Gross, F. Moshary, Y. Zhao, and S. Ahmed, "Polarization discrimination technique to maximize lidar signal-to-noise ratio," in Polarization Science and Remote Sensing II, J. A. Shaw and J. S. Tyo, eds., Proc. SPIE 5888, 93-101 (2005).

Y. Y. Hassebo, B. M. Gross, M. M. Oo, F. Moshary, and S. A. Ahmed, "Impact on lidar system parameters of polarization selection/tracking scheme to reduce daylight noise," in Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing, U. N. Singh, ed., Proc. SPIE 5984, 53-64 (2005).

Klein, M. V.

M. V. Klein, Optics (Wiley, 1970).

Kokkinos, D. S.

D. S. Kokkinos and S. A. Ahmed, "Atmospheric depolarization of lidar backscatter signals," in Lasers '88: Proceedings of the International Conference, Lake Tahoe, Nevada, Paper No. A90-30956 12-36. (STS Press, McLean, Virginia, 1989), pp. 538-545.

Lehmann, M.

G. Hanel and M. Lehmann, "Equilibrium size of aerosol particles and relative humidity: new experimental data from various aerosol types and their treatment for cloud physics application," Contrib. Atmos. Phys. 54, 57-71 (1981).

Li, W.

Liou, K. N.

K. N. Liou, An Introduction to Atmospheric Radiation (Academic, 2002).

Measures, R. M.

R. M. Measures, Laser Remote Sensing (Wiley, 1984).

Moshary, F.

Y. Y. Hassebo, B. Gross, F. Moshary, Y. Zhao, and S. Ahmed, "Polarization discrimination technique to maximize lidar signal-to-noise ratio," in Polarization Science and Remote Sensing II, J. A. Shaw and J. S. Tyo, eds., Proc. SPIE 5888, 93-101 (2005).

Y. Y. Hassebo, B. M. Gross, M. M. Oo, F. Moshary, and S. A. Ahmed, "Impact on lidar system parameters of polarization selection/tracking scheme to reduce daylight noise," in Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing, U. N. Singh, ed., Proc. SPIE 5984, 53-64 (2005).

Nair, P. V. N.

P. V. N. Nair and K. G. Vohra, "Growth of aqueous sulfuric acid droplets as function of relative humidity," J. Aerosol Sci. 6, 265-271 (1975).
[CrossRef]

Oo, M. M.

Y. Y. Hassebo, B. M. Gross, M. M. Oo, F. Moshary, and S. A. Ahmed, "Impact on lidar system parameters of polarization selection/tracking scheme to reduce daylight noise," in Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing, U. N. Singh, ed., Proc. SPIE 5984, 53-64 (2005).

Platt, C. M. R.

C. M. R. Platt, "Lidar observation of a mixed-phase altostratus cloud," J. Appl. Meteorol. 16, 339-345 (1977).
[CrossRef]

C. M. R. Platt, "Transmission and reflectivity of ice clouds by active probing," in Clouds, Their Formation, Optical Properties, and Effects, P. V. Hobbs, ed. (Academic, 1981), pp. 407-436.

Roy, G.

Roy, N.

Sassen, K.

K. Sassen, "Scattering of polarized laser light by water droplet, mixed-phase and ice crystal clouds. 2. Angular depolarization and multiple scatter behavior," J. Atmos. Sci. 36, 852-861 (1979).
[CrossRef]

K. Sassen, "Depolarization of laser light backscattered by artificial clouds," J. Appl. Meterol. 13, 923-933 (1974).
[CrossRef]

R. M. Schotland, K. Sassen, and R. J. Stone, "Observations by lidar of linear depolarization ratios by hydrometeors," J. Appl. Meteorol. 10, 1011-1017 (1971).
[CrossRef]

Schotland, R. M.

R. M. Schotland, K. Sassen, and R. J. Stone, "Observations by lidar of linear depolarization ratios by hydrometeors," J. Appl. Meteorol. 10, 1011-1017 (1971).
[CrossRef]

Shettle, E. P.

E. P. Shettle and R. W. Fenn, Models of the Aerosols of the Lower Atmosphere and the Effects of Humidity Variations on Their Optical Properties, Project 7670 (Air Force Geophysics Laboratory, Massachusetts, 1979).

Simard, J.

Stamnes, J. J.

Stamnes, K.

Stone, R. J.

R. M. Schotland, K. Sassen, and R. J. Stone, "Observations by lidar of linear depolarization ratios by hydrometeors," J. Appl. Meteorol. 10, 1011-1017 (1971).
[CrossRef]

Travis, L.

J. Hansen and L. Travis, "Light scattering in planetery atmospheres," Space Sci. Rev. 16, 527-610 (1974).
[CrossRef]

Travis, L. D.

Tsay, S.-C.

Vohra, K. G.

P. V. N. Nair and K. G. Vohra, "Growth of aqueous sulfuric acid droplets as function of relative humidity," J. Aerosol Sci. 6, 265-271 (1975).
[CrossRef]

Yan, B.

Zhao, Y.

Y. Y. Hassebo, B. Gross, F. Moshary, Y. Zhao, and S. Ahmed, "Polarization discrimination technique to maximize lidar signal-to-noise ratio," in Polarization Science and Remote Sensing II, J. A. Shaw and J. S. Tyo, eds., Proc. SPIE 5888, 93-101 (2005).

Appl. Opt. (4)

Contrib. Atmos. Phys. (1)

G. Hanel and M. Lehmann, "Equilibrium size of aerosol particles and relative humidity: new experimental data from various aerosol types and their treatment for cloud physics application," Contrib. Atmos. Phys. 54, 57-71 (1981).

J. Aerosol Sci. (1)

P. V. N. Nair and K. G. Vohra, "Growth of aqueous sulfuric acid droplets as function of relative humidity," J. Aerosol Sci. 6, 265-271 (1975).
[CrossRef]

J. Appl. Meteorol. (2)

R. M. Schotland, K. Sassen, and R. J. Stone, "Observations by lidar of linear depolarization ratios by hydrometeors," J. Appl. Meteorol. 10, 1011-1017 (1971).
[CrossRef]

C. M. R. Platt, "Lidar observation of a mixed-phase altostratus cloud," J. Appl. Meteorol. 16, 339-345 (1977).
[CrossRef]

J. Appl. Meterol. (1)

K. Sassen, "Depolarization of laser light backscattered by artificial clouds," J. Appl. Meterol. 13, 923-933 (1974).
[CrossRef]

J. Atmos. Sci. (1)

K. Sassen, "Scattering of polarized laser light by water droplet, mixed-phase and ice crystal clouds. 2. Angular depolarization and multiple scatter behavior," J. Atmos. Sci. 36, 852-861 (1979).
[CrossRef]

Proc. SPIE (2)

Y. Y. Hassebo, B. Gross, F. Moshary, Y. Zhao, and S. Ahmed, "Polarization discrimination technique to maximize lidar signal-to-noise ratio," in Polarization Science and Remote Sensing II, J. A. Shaw and J. S. Tyo, eds., Proc. SPIE 5888, 93-101 (2005).

Y. Y. Hassebo, B. M. Gross, M. M. Oo, F. Moshary, and S. A. Ahmed, "Impact on lidar system parameters of polarization selection/tracking scheme to reduce daylight noise," in Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing, U. N. Singh, ed., Proc. SPIE 5984, 53-64 (2005).

Space Sci. Rev. (1)

J. Hansen and L. Travis, "Light scattering in planetery atmospheres," Space Sci. Rev. 16, 527-610 (1974).
[CrossRef]

Other (9)

C. M. R. Platt, "Transmission and reflectivity of ice clouds by active probing," in Clouds, Their Formation, Optical Properties, and Effects, P. V. Hobbs, ed. (Academic, 1981), pp. 407-436.

D. S. Kokkinos and S. A. Ahmed, "Atmospheric depolarization of lidar backscatter signals," in Lasers '88: Proceedings of the International Conference, Lake Tahoe, Nevada, Paper No. A90-30956 12-36. (STS Press, McLean, Virginia, 1989), pp. 538-545.

NOAA-CREST, http://www.fsl.noaa.gov.

M. V. Klein, Optics (Wiley, 1970).

R. M. Measures, Laser Remote Sensing (Wiley, 1984).

K. N. Liou, An Introduction to Atmospheric Radiation (Academic, 2002).

G. Hanel, "The properties of atmospheric aerosol particles as functions of the relative humidity at thermodynamic equilibrium with the surrounding moist air," in Advances in Geophysics, H. E. Landsberg and J. Van Mieghem, eds. (Academic, 1976), Vol. 19, pp. 73-188.

E. P. Shettle and R. W. Fenn, Models of the Aerosols of the Lower Atmosphere and the Effects of Humidity Variations on Their Optical Properties, Project 7670 (Air Force Geophysics Laboratory, Massachusetts, 1979).

U.S. Naval Observatory Astronomical Applications, http://aa.usno.navy.mil/data/docs/AltAz.html.

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Figures (16)

Fig. 1
Fig. 1

Sky background suppression geometry for a vertical pointing lidar: θ s is the solar zenith angle (equal to the scattering angle for this geometry), ϕ s is the solar azimuth angle and OAB is the solar scattering plane.

Fig. 2
Fig. 2

Schematic of the polarization experiment setup for elastic biaxial monostatic lidar (mobile lidar system).

Fig. 3
Fig. 3

Comparison of max P b versus min P b lidar signals at 6:29 p.m. on 7 October 2004.

Fig. 4
Fig. 4

Comparison of experimental return signals at 6:29 p.m., 3 p.m. and noon on 7 October 2004, range of 2 0 30 km both orthogonal cases are shown.

Fig. 5
Fig. 5

Experimental range-dependent SNR for maximum and minimum polarization orientations.

Fig. 6
Fig. 6

(a) G imp in detection wavelength of 532  nm versus local time on 19 February 2005. (b) G imp in detection wavelength of 532  nm versus solar zenith angle on 19 February 2005.

Fig. 7
Fig. 7

G imp in detection wavelength of 532   nm versus solar zenith angle on 23 February 2005.

Fig. 8
Fig. 8

PWV (cm) loading versus local time on 19 February 2005 and 23 February 2005.

Fig. 9
Fig. 9

Theoretical model agrees with experimental measurements, 19 February 2005. Rayleigh scattering alone is also shown.

Fig. 10
Fig. 10

RH versus local New York City time on 23 February 2005.

Fig. 11
Fig. 11

Particle equivalent radius ratio r / r o versus RH at different equivalent radius r o in the dry state (RH = 0) and for two aerosol models at 20 ° C temperature (Ref. 19).

Fig. 12
Fig. 12

Theoretical model, 23 February 2005.

Fig. 13
Fig. 13

Theoretical model agrees with experimental measurements, 23 February 2005.

Fig. 14
Fig. 14

Comparison of the solar azimuth angle and the angle of polarization rotation needed to achieve minimum P b , 14 April 2005.

Fig. 15
Fig. 15

Scattering angle θ sc between the solar and the lidar directions for the scanning lidar geometry as a function of the lidar zenith angle and the time of day showing periods where SNR improvement can be significant. The vertical lidar result is also plotted to contrast to the time periods.

Fig. 16
Fig. 16

Multiple-scattering model τ aer = 0.5 showing the minimum noise is parallel to the scattering plane irregardless of optical depth. Δ ϕ is the azimuth angle difference between the scattering and the polarization planes.

Tables (2)

Tables Icon

Table 1 Lidar System Specifications

Tables Icon

Table 2 Comparison of Experimental Results to Verify Shot-Noise Operation ( Δ R = R)

Equations (12)

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

G imp = SNR Max SNR Unpol = ( P b min + P b max P b min ) = 1 + ( P b max P b min ) .
T i ( μ ; μ o ) = ω ˜ 4 ( μ μ o ) P i eff ( e - τ / μ e τ / μ o ) ,
P i eff = τ mol P i mol + τ aer P i aer τ mol + τ aer ,
P Tot mol = 3 4 [ 1 + cos 2 ( θ sc ) ] .
τ mol = C o ( λ λ o ) 4 [ 1 + C 1 ( λ λ o ) 2 + C 2 ( λ λ o ) 4 ] ,
P i aer = S i ( θ sc ) ( 4 q 2 Q e ) ,
S i ( θ sc ) = S i norm ( r , θ sc ) n ¯ ( r ) d r .
P b max P b min ( θ sc ) = T ( μ ; μ o ) T ( μ ; μ o ) = P 2 eff P 1 eff ,
G imp Ray = 1 + s 2 ( θ sc ) ,
r ( a w ) = r o [ 1 + ρ m w ( a w ) m o ] 1 / 3 ,
a w = RH   exp [ 2 σ V w R w T 1 r ( a w ) ] ,
n eff = n w + ( n o n w ) [ r o r ( a w ) ] 3 .

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