A method to retrieve super-thin cloud optical depth over ocean background with polarized sunlight

In this work, an algorithm that uses the polarization angle of the backscattered solar
radiation to detect clouds with optical depth (OD) <∼ 0.3 is further developed. We find
that at viewing angles within ± ∼ 8◦ around the backscattering direction, the p-polarized
5 intensity that is parallel to the meridian plane of reflected light from surface is sensitive
to and nearly linearly related to the optical depth of super-thin clouds. Moreover, our
sensitivity study suggests that the p-polarized intensity at these viewing angles is not
sensitive to the ocean surface conditions. Using this property of p-polarized intensity,
super-thin clouds’ optical depth can be retrieved.