Diffuse reflectance of oceanic waters. III. Implication of bidirectionality for the remote-sensing problem
Applied Optics
|November 25, 2010
Summary
Ocean color analysis requires understanding how light changes with chlorophyll and viewing angles. This study proposes a new method to derive chlorophyll concentration first, improving satellite data interpretation.
Area of Science:
- Ocean optics
- Remote sensing
- Bio-optical oceanography
Background:
- Oceanic radiance fields are anisotropic, influenced by illumination and water properties.
- Chlorophyll (Chl) concentration is a key indicator of water's optical properties in Case 1 waters.
- Satellite ocean color sensors interpret marine signals, which are affected by directional light variations.
Purpose of the Study:
- To systematically quantify spectral radiance variations with changing chlorophyll and geometric conditions (Sun angle, viewing angle, azimuth).
- To analyze the impact of these variations on satellite-derived marine signals and radiometric quantities.
- To develop a method for deriving chlorophyll concentration prior to other radiometric measurements.
Main Methods:
- Utilizing precomputed lookup tables for the f/Q ratio, which accounts for geometry, wavelength, and chlorophyll.
- Implementing a computationally fast, iterative process using two wavelengths to determine chlorophyll concentration.
- Reversing the conventional data-processing strategy to prioritize chlorophyll retrieval.
Main Results:
- The f/Q ratio is dependent on geometric configuration, wavelength, and chlorophyll concentration.
- Chlorophyll concentration can be accurately determined iteratively before calculating radiometric quantities.
- A practical method using lookup tables is proposed for handling bidirectional effects.
Conclusions:
- Deriving chlorophyll concentration first is crucial for accurate interpretation of satellite ocean color data.
- The proposed method effectively accounts for the bidirectional nature of oceanic radiance.
- This approach modifies data processing strategies for improved remote sensing of ocean properties.
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