Radiative transfer simulations of water-leaving radiance from the Skylight-Blocked Approach

Area of Science:

• Ocean optics
• Remote sensing
• Radiative transfer theory

Background:

• Accurate measurement of water-leaving radiance (Lw) is crucial for ocean color remote sensing.
• The Skylight-Blocked Approach (SBA) is used to measure Lw, but potential measurement biases are not fully understood.

Purpose of the Study:

• To quantify the impact of radiometer shield depth (z0) on SBA measurements of Lw.
• To evaluate an analytical correction scheme for SBA measurements.

Main Methods:

• Radiative transfer simulations were performed using diverse water optical properties.
• The impact of varying shield depth (z0) on Lw was analyzed.
• An analytical correction scheme using absorption and backscattering coefficients was tested.

Main Results:

• The shield-shaded water volume significantly lowers measured Lw, by several to tens of percent.
• This reduction is dependent on shield depth (z0), water attenuation, and wavelength.
• The analytical correction scheme showed potential but accuracy decreased with increasing z0 and turbidity.

Conclusions:

• Radiometer shield depth is a critical factor affecting SBA Lw measurements.
• An analytical correction can mitigate some bias, but its efficacy is limited by shield depth and water conditions.