1. IOP inversion from shallow waters
Peng Wang

2. Rrs = f(a, bb) Lu(0-): upwelling radiance
Ed(0+): downwelling irradiance

3. PBR approach: • Basis vectors absorption
aφ(λ) = aφ(λ0) [Sf*amicro(λ0)+(1-Sf)apico(λ0)]
• adg(λ) = adg(λ0) exp(-S(λ-λ0))
backscattering
bbp(λ) = bbp(λ0) (λ/λ0)-Y
Radiance Reflectance equation [400:10:650]
Rrs = ( bb/(bb+a)) (bb/(bb+a))2
Linear regression method
Data set: simulated by hydrolight (Rrs, a and bb)

4. Some results: IOP comparison (a and bb)
Total Absorption Comparison
average of relative difference: 11.9%

5. total backscattering comparison
average of relative difference: 14.2%

6. Now story changed……

7. Rrs from shallow waters:
Strange rrs
Matlab complain
No solutions !!!

8. Ed Lu Ludp LuB Rrs = Lu/Ed = (Ludp + LuB)/Ed
= Ludp/Ed + LuB/Ed = Rrsdp + RrsB
downwelling irradiance, upwelling radiance from water column and bottom

9. simple idea, hard application; fortunately……
Semi-Analytical Hyperspectral Model of Lee, et al, 1998
basically:
rrs ≈ rrsdp[1-exp(-2KH)] + rrsBexp(-2KH) ≈
rrsdp(1-A0exp{-[(1/cosθw)+D0(1+D1u)0.5]αH}) +
A1ρexp{-[(1/cosθw)+D’0(1+D’1u)0.5] αH}.
rrs: subsurface remote-sensing reflectance, sr-1
rrsdp:subsurface remote-sensing reflectance for deep waters, sr-1
rrsB: subsurface remote-sensing reflectance for the bottom, sr-1
K: diffuse attenuation, m-1
H: bottom depth, m
θw:subsurface solar zenith angle, rad
u: bb/(a + bb)
α: attenuation coefficient (=a+bb), m-1
ρ: bottom albedo
A0,1 D0,1 D’0,1: from Lee et al, 1998

10. After subtracting the bottom influence, we get…
Now matlab smiled and we got solutions !!!

11. Coefficient of Variance: (express sample variability relative to the mean of the sample)
Total
absorption:
Backscattering:

12. IOP inversion results from shallow waters:
Total
Absorption:
Total
Backscattering:

13. Conclusions:
Bottom reflectance has a huge impact on the remote sensing reflectance;
Current semi-analytic algorithm can be successfully applied to invert IOPs after bottom correction;
PBR approach can find strange rrs which is caused by the environment or bad measurements?

14. Acknowledgements