Algorithms to retrieve Inherent Optical Properties
GLOSSARY
Rrs(&lambda), &rhow(&lambda) &asymp bb(&lambda) / [a(&lambda) + bb(&lambda)], where
a(&lambda) = aw(&lambda) + adg(&lambda) + aph(&lambda), and
bb(&lambda) = bbw(&lambda) +bbp(&lambda)
coefficients often defined as product of dimensionless basis vector (spectral shape) and magnitude (M), e.g., adg(&lambda) = Mdg adg*(&lambda)
basis vectors used in the following algorithms are graphically presented below
reference | inversion | form | bbp | adg | aph |
---|
Maritorena et al. 2002 (GSM) | L-M | G88 | bbp(&lambdar) [&lambda/&lambdar]-n
n = 1.0337 | adg(&lambdar) exp(-S [&lambda - &lambdar])
S = 0.0206 | chl aph*
optimized aph* (SA) |
Hoge et al. 1996 (LMI) | matrix | G88 | bbp(&lambdar) [&lambda/&lambdar]-n
n = 0.8 Rrs(490)/Rrs(555) + 0.2 | adg(&lambdar) exp(-S [&lambda - &lambdar])
S = 0.018 | Gaussian @ 443
fwhm (&sigma) = 70 nm
aph(&lambda) = aph(&lambdar) exp(u)
u = [&lambdar2+886(&lambda - &lambdar)-&lambda2] / 2 &sigma2 |
Boss and Roesler 2006 Wang et al. 2005 | matrix | G88 | bbp(&lambdar) [&lambda/&lambdar]-n
0 < n < 2 | adg(&lambdar) exp(-S [&lambda - &lambdar])
0.01 < S < 0.02 | Ciotti et al. 2002
0 < Sf < 1 |
Lee et al. 2002 (QAA) | algebraic | G88 | bbp(&lambdar) [&lambda/&lambdar]-n
n = 2.2 (1 - 1.2 exp[-0.9 Rrs(443)/Rrs(555)]) | adg(&lambdar) exp(-S [&lambda - &lambdar])
S = 0.015 | a - adg - aw |
Smyth et al. 2006 (PML) | spectral slope
algebraic | &pi &real f/Q bb/a | bbp(&lambdar) [&lambda/&lambdar]-n
n = 0.5 | adg(&lambdar) exp(-S [&lambda - &lambdar])
S = 0.014 | a - adg - aw |
Pinkerton et al. 2006 (NIWA) | spectral slope
algebraic | &pi &real f/Q bb/a | bb~ b(490) n
n = 0.841 X2 - 2.806 X + 2.965
X = (&lambda / 490)
bb~ = 0.01756 | NA | NA |
Loisel and Stramski 2000 | algebraic | &pi &real f/Q bb/a | fcn[&rhow(&lambda), Kd(&lambda), solz, &eta(&lambda)] | NA | NA |
GSM
n, S, and a
ph* predefined; optimized (simulated annealing) to in situ data
solution via Levenberg-Marquardt nonlinear inversion
LMI
n, S, and a
ph* predefined
only 412, 490, and 555-nm considered
solution via 3 x 3 matrix inversion
Boss and Roesler 2006
n, S, and a
ph* (through S
f) ranges predefined
412 through 555-nm considered
solution via 3 x 5 matrix inversion
multiple solutions achieved using ranges of n, S, and a
ph*
median of viable solutions retained and uncertainties reported
QAA
a(555) from R
rs(443,490,555,640)
b
bp(555) from a(555) and R
rs(555)
n estimated using R
rs(443,555)
b
bp(&lambda) from n and b
bp(555)
a(&lambda) from b
bp(&lambda) and R
rs(&lambda)
a
ph(412) / a
ph(443) [ &zeta ] from R
rs(443,555)
a
dg(412) / a
dg(443) [ &xi ] from S
a
dg(443) from a(412,443), &zeta and &xi (algebraic)
a
dg(&lambda) from a
dg(443) and S
a
ph(&lambda) = a(&lambda) - a
dg(&lambda) - a
w(&lambda)
PML
n, S, and, &epsilon predefined
F (= &pi &real f/Q) defined via a, b, and viewing geometry in HydroLight LUT
F(&lambda) initialized using guess of a(&lambda) and b(&lambda)
b
b(510) from &epsilon
a(490,510), &epsilon
bb(490,510), F(490,510), and &rho
w(490,510)
b
b(&lambda) from b
b(510) and n
a(&lambda) from b
b(&lambda), F(&lambda), and &rho
w(&lambda)
updated F(&lambda) from a(&lambda) and b(&lambda) (= b
b(&lambda) / 0.01756)
iterate until F(&lambda) remains stable
a
dg(412) from &epsilon
dg(412,443), &epsilon
ph(412,443), and a(412,443)
a
dg(&lambda) from a
dg(412) and S
a
ph(&lambda) = a(&lambda) - a
dg(&lambda) - a
w(&lambda)
NIWA
a(&lambda) and b
b(&lambda) only (natively)
n and b
b~ (= 0.01756) predefined
F (= &real f/Q) defined via a, b, and viewing geometry in HydroLight LUT
iterate on F(&lambda) and b(&lambda) until F(&lambda) stabilizes, with initial guess for b(&lambda), b
b~, a
w(&lambda), and &rho
w(&lambda)
"lowest" b(490) defined as greatest of b(443) > b(490) > b(510)
define 15-element array of b(490) from "lowest" value to upper limit 60 ...
for each element: iterate on a(&lambda) and F(&lambda) until a(&lambda) stabilizes, with F(&lambda) initialized as 0.02, n, b
b~, and &rho
w(&lambda)
for each element: retain all b(490) that yield a(&lambda) that satisfy 1.32 < &epsilon
a(490,510) < 1.58
final b(490) is geometric mean of highest and lowest retained values
final b(&lambda) and b
b(&lambda) from n and b
b~
iterate on F(&lambda) and a(&lambda) until a(&lambda) stabilizes, with F(&lambda) initialized as last calculated value, final b
b(&lambda), and &rho
w(&lambda)
Loisel and Stramski 2000
a(&lambda) and b
b(&lambda) only (natively)
developed via radiative transfer simulation using infinitely deep ocean, optically homogeneous water column, and flat sea surface
does not assume spectral shapes for a(&lambda) or b
b(&lambda)
&rho(&lambda) from R
rs(&lambda,solz) LUT
K
d(&lambda) from R
rs(443,555,solz) LUT
b
b(&lambda) from K
d(&lambda), &eta (= b
w/b), and &mu
w (via solz)
&eta initialized as 0.05, then iterated upon using b(&lambda) = b
b(&lambda) / 0.0183
a(&lambda) from K
d(&lambda), &rho(&lambda), and solz
can adjust for Raman scattering
IOP spectral shapes
adg
aph
bbp