Abstract

Our iterative inversion algorithm for retrieving absorption a(z) and backscattering b b(z) from profiles of upwelling and downwelling irradiance, on the basis of assuming a depth-independent phase function for the medium, was found to have unsatisfactory accuracy for b b(z) in clear waters. We modified the algorithm here by assuming a depth-independent phase function for the particles and then performing an additional iteration over the fraction of total scattering that is due to the water itself. The modified algorithm’s accuracy is considerably improved over the original in clear waters and reduces to the original in waters for which the particle contribution to b b(z) is dominant.

© 2002 Optical Society of America

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References

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  1. H. R. Gordon, G. C. Boynton, “Radiance-irradiance inversion algorithm for estimating the absorption and backscattering coefficients of natural waters: homogeneous waters,” Appl. Opt. 36, 2636–2641 (1997).
    [CrossRef] [PubMed]
  2. H. R. Gordon, G. C. Boynton, “Radiance-irradiance inversion algorithm for estimating the absorption and backscattering coefficients of natural waters: stratified water bodies,” Appl. Opt. 37, 3886–3896 (1998).
    [CrossRef]
  3. G. C. Boynton, H. R. Gordon, “Irradiance inversion algorithm for estimating the absorption and backscattering coefficients of natural waters: Raman scattering effects,” Appl. Opt. 39, 3012–3022 (2000).
    [CrossRef]
  4. T.J. Petzold, “Volume scattering functions for selected natural waters,” SIO Ref. 72–78 (Scripps Institution of Oceanography, Visibility Laboratory, San Diego, Calif., 1972).

2000 (1)

1998 (1)

1997 (1)

Boynton, G. C.

Gordon, H. R.

Petzold, T.J.

T.J. Petzold, “Volume scattering functions for selected natural waters,” SIO Ref. 72–78 (Scripps Institution of Oceanography, Visibility Laboratory, San Diego, Calif., 1972).

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Figures (5)

Fig. 1
Fig. 1

Error in a and b b as a function of the value of ρ w used in the inversion of the synthetic data set created for a homogeneous ocean with the IOPs in Table 1.

Fig. 2
Fig. 2

Schematic of the modified algorithm.

Fig. 3
Fig. 3

w >, the value of the column-averaged ρ w (z), as a function of the number of iterations for a homogeneous ocean with the IOPs given in Table 1. The horizontal dotted line gives the correct value of <ρ w > (0.228).

Fig. 4
Fig. 4

Absorption coefficient profile used to create the simulated irradiance data (filled circles), retrieved a(z) by use of the incorrect (Henyey-Greenstein) particle phase function (solid curve) in the retrieval algorithm, and contribution to a(z) by the water itself (vertical dotted line). The dashed curve is the retrieval obtained with the inversion algorithm in Ref. 2.

Fig. 5
Fig. 5

Backscattering coefficient profile used to create the simulated irradiance data (filled circles), retrieved b b (z) by use of the incorrect (Henyey-Greenstein) particle phase function (solid curve) in the retrieval algorithm, and contribution to b b (z) by the water itself (vertical dotted line). The dashed curve is the retrieval obtained with the inversion algorithm in Ref. 2.

Tables (1)

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Table 1 IOPs (in m-1) for the First Synthetic Data Set

Equations (3)

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bbi=2πbiπ/2π PiΘsin ΘdΘ,
bbz=b˜bwbw+b˜bpbpz, PΘ, z=bwPwΘ+bpzPpΘbw+bpz.
PΘ, z=ρwzPwΘ+1-ρwzPpΘ,

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