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

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 Lrs 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.