1. Simulation for Case 1 Water
Deepak Mishra
Ocean Optics Course (2004)

2. Forward Technique Simulation started by creating a depth profile of
chlorophyll and assuming that the water body is
Case 1, i.e. chlorophyll bearing phytoplankton
and their covarying by-products are dominant in
determining the IOPs of the water.

3. Chlorophyll Profile

4. The total absorption coefficient a(z;λ) is obtained from
Prieur-Sathyendranath (1981) model upon substitution of
the assumed C(z) profile.
The model is given by:
where,
aw and ac*’ are absorption by pure sea water and
chlorophyll specific absorption coefficient respectively.
(Taken from Prieur and Sathyendranath, 1981)

5. a) a(z;λ) as a function of depth for selected wavelengthb)
b) a(z;λ) as a function of wavelength for selected depth

6. The total scattering coefficient b(z;λ) is obtained from
Gordon-Morel (1983) model upon substitution of
the assumed C(z) profile.
The model is given by:

7. a) b(z;λ) as a function of depth for selected wavelength
b) b(z;λ) as a function of wavelength for selected depth

8. Beam attenuation coefficient c(z;λ)
a) c(z;λ) as a function of depth for selected wavelength b)
b) c(z;λ) as a function of wavelength for selected depth

9. Albedo of single scattering ωo(z;λ)
a) w0(z;λ) as a function of depth for selected wavelength b)
b) w0(z;λ) as a function of wavelength for selected depth

10. Spectral downward and upward plane irradiances at selected depth

11. Irradiance Reflectance

12. Water leaving radiance and Remote sensing reflectance

13. PAR

14. Inversion Technique
IOPs (absorption and backscattering coefficients) from AOPs (Kd an d Rrs)
Gordon, et al. (1988) showed that for Case 1 waters, R/Q ratio can be useful to exploit the theoretical relationship between the Rrs and the inherent optical properties, specifically bb and a.
R = Irradiance reflectance
Q = Eu/Lu, provides information about the angular distribution of the upwelling light field

15. Gordon’s approximation
For Case 1 waters
Rrs≈ 0.54(R/Q)
R/Q ≈ (bb /(a+bb))
R/Q ≈ 0.11(bb/Kd)

16. IOP retrieval (absorption coefficient)

17. Absorption coefficient comparison

18. Backscattering coefficient

19. Chlorophyll retrieval
Chlorophyll was retrieved from Kd using a bio-optical model given by Morel (1988):
Where and are statistically derived functions that convert the chlorophyll concentration in mg m-3 to Kd values in m-1.

20. Chlorophyll retrieval

21. Comparison

22. Summary
There can be considerable error in Rrs from an improper removal of sea surface reflectance effect.
Based upon 1% of EPAR surface value depth of euphotic zone was found to be 19.8m.
Semi-analytical inversion algorithms, applied on Rrs spectra were able to retrieve chlorophyll concentration and IOPs such as absorption coefficient, backscattering coefficient.

23. Thank you!!