Global diffuse attenuation derived from vibrational Raman scattering detected in hyperspectral backscattered...

Area of Science:

• Oceanography
• Remote Sensing
• Climate Science

Background:

• Characterizing underwater light fields is vital for global ocean biogeochemical processes and heat budgets.
• These oceanographic factors significantly impact and respond to global climate change.

Purpose of the Study:

• To retrieve the diffuse attenuation coefficient (Kd) in the blue spectral range (390-426 nm) using satellite-based Vibrational Raman Scattering (VRS).
• To evaluate the performance of three hyperspectral satellite sensors (SCIAMACHY, GOME-2, OMI) for this application.

Main Methods:

• Vibrational Raman Scattering (VRS) was retrieved from backscattered radiances using Differential Optical Absorption Spectroscopy (DOAS).
• A look-up-table from ocean-atmosphere coupled radiative transfer modeling was used to derive Kd from the VRS signal.
• One year of overlapping sensor data was processed and compared with the Ocean Colour Climate Change Initiative (OC-CCI) Kd product.

Main Results:

• Good agreement was observed between the retrieved Kd and the OC-CCI Kd product when Kd values were below 0.15 m⁻¹.
• Differences among sensors and with OC-CCI were noted, attributed to instrumental effects and varying spatial/temporal resolutions.
• The study highlights potential biases in hyperspectral sensor data due to DOAS retrieval and instrumental factors.

Conclusions:

• The satellite-derived Kd product shows promise but requires further corrections for merging and long-term application.
• Instrumental effects and data resolution differences necessitate empirical corrections for a unified long-term Kd product.
• Accurate underwater light field characterization is essential for understanding climate change impacts on marine ecosystems.