Water Raman normalization of airborne laser fluorosensor measurements: a computer model study.

Area of Science:

• Ocean optics
• Remote sensing
• Environmental monitoring

Background:

• Airborne lidar measurements of chlorophyll fluorescence are crucial for assessing aquatic ecosystems.
• Normalizing fluorescence signals by water Raman scattering can improve data accuracy.
• Understanding the impact of excitation wavelength on signal integration depth is essential.

Purpose of the Study:

• To investigate the effectiveness of normalizing airborne lidar chlorophyll fluorescence measurements using water Raman scattering.
• To analyze the influence of different laser excitation wavelengths (480 nm and 532 nm) on this normalization technique.
• To determine the signal-integration depths for both fluorescence and Raman scattering.

Main Methods:

• Utilized a semianalytic Monte Carlo methodology (SALMON) for simulations.
• Investigated two laser-excitation wavelengths: 480 nm and 532 nm.
• Analyzed signal-integration depths for chlorophyll fluorescence (Z(90,F)) and Raman scattering (Z(90,R)).

Main Results:

• Signal-integration depth for chlorophyll fluorescence (Z(90,F)) is insensitive to excitation wavelength.
• For 532 nm excitation, Z(90,R) is comparable to Z(90,F).
• For 480 nm excitation, Z(90,R) is larger than Z(90,F) in clear waters but similar at higher chlorophyll concentrations.
• Raman normalization demonstrates a linear response to chlorophyll concentration for both wavelengths.

Conclusions:

• Raman normalization is a robust technique for airborne lidar chlorophyll fluorescence measurements.
• Excitation wavelength choice impacts signal-integration depths, potentially introducing ambiguities in clear waters.
• The method provides a reliable linear response for chlorophyll concentration estimation across tested wavelengths.