Simulation of AVIRIS Sensitivity for Detecting Chlorophyll over Coastal and Inland Waters

doi:10.1016/S0034-4257(98)00042-X

Remote Sensing of Environment

Volume 65, Issue 3, September 1998, Pages 333-340

https://doi.org/10.1016/S0034-4257(98)00042-X Get rights and content

Abstract

The availability of imaging spectrometers such as AVIRIS, CASI, ROSIS, and HYDICE has created a necessity for spectral methods and models that can predict the performance of these instruments for detecting and estimating water quality parameters in turbid inland and coastal waters as a water quality indicator. The aim of this study is to assess the performance of AVIRIS for estimating the sum of chlorophyll a and pheaophytin (CHL) by means of a sensitivity analysis. The irradiance reflectance R(0−) and, subsequently, the radiance at the sensor were simulated from the water constituent concentrations. These simulations enabled the quantification of the change in L_rs due to variations in CHL. Comparison of these changes with the noise equivalent radiance as specified for AVIRIS gives an indication of the accuracy for AVIRIS in estimating CHL. The biooptical model was calibrated for a coastal and an inland water in The Netherlands. From the simulation results for Lake IJsselmeer, it was concluded that AVIRIS can estimate chlorophyll a with an accuracy of 20% for relative low CHL values of 10 mg m⁻³ and 11–12% for CHL values of more than 30 mg m⁻³. A ratio of one of the AVIRIS bands around 713 nm to the band at 677 nm is most sensitive for detecting CHL. For the North Sea the most sensitive bands are found around 530 nm. The estimated accuracy for CHL retrieval ranges from 33% for CHL values of 2 mg m⁻³ to 10–12% for CHL of more than 12 mg m⁻³.

Section snippets

A Biooptical Model for Case II Waters

An analytical biooptical model is used to generate the subsurface irradiance reflectance, R(0−) from the constituent concentrations. Several models for ocean, coastal and inland waters were investigated by Gordon et al. (1975), Morel and Prieur (1977), Whitlock et al. (1981), Kirk (1991), Dekker (1993) and Dekker et al. (1994). In this study an analytical solution of the irradiance transfer equations (Aas, 1987) is used in Eq. (1): $R= 1 1+ μ_{d} μ_{u} b_{b} a+b_{b},$ where a is the total absorption coefficient, b_b

Lake IJsselmeer

In the first series of simulations we used Lake IJsselmeer as a case study representing shallow eutrophic waters. Figure 3 shows the results for R(0−) for CHL ranging from 10 mg m⁻³ to 190 mg m⁻³ with steps of 20 mg m⁻³. The dry weight of tripton remains constant at 20 g m⁻³ and the gilvin absorption is 1.8 m⁻¹ at 440 nm. The simulated R(0−) spectra indicate that near 400 nm the R(0−) does not change much: The increase in absorption by phytoplankton, tripton, and gilvin is balanced by the

Conclusions

In this exploratory study modeling was used to simulate a radiance at the sensor from the constituent concentrations. Different water types, eutrophic shallow inland waters and Case II coastal waters, were modeled for a range of CHL values. The simulations showed significant influence on the size and shape of the R(0−) spectra and the changes of R(0−) due to small variations in CHL. Hinge points in the R(0−) are identified that indicate spectral areas where increases in absorption are

Acknowledgements

The authors are indebted to Dr. J. de Haan for his clarifying reviews of the mathematical framework of the model and his help with the atmospheric modeling. Support by The Netherlands Remote Sensing Board and Rijkswaterstaat in the measurement campaigns is gratefully acknowledged.

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Simulation of AVIRIS Sensitivity for Detecting Chlorophyll over Coastal and Inland Waters

Abstract

Section snippets

A Biooptical Model for Case II Waters

Lake IJsselmeer

Conclusions

Acknowledgements

Remote Sens. Environ.

Two-stream irradiance model for deep waters

Appl. Opt.

A model for calculation of diffuse light attenuation (PAR) and secchi depth

Netherlands J. Aquat. Ecol.

Marine humic and fulvic acidstheir effects on remote sensing of ocean chlorophyll

Limnol. Oceanogr.

The remote sensing of inland water quality

The peak near 700 nm on radiance spectra of algae and waterrelationships of its magnitude and position with chlorophyll concentration

Int. J. Remote Sensing

Coupling of phytoplankton and detritus in a shallow, eutrophic lake (Lake Loosdrecht, The Netherlands)

Hydrobiologia

Remote assessment of ocean color for interpretation of satellite visible imagerya review

Computed relationships between the inherent and apparent optical properties of a flat homogeneous ocean

Appl. Opt.