Articles | Volume 15, issue 20
Atmos. Chem. Phys., 15, 11909–11918, 2015
Atmos. Chem. Phys., 15, 11909–11918, 2015

Research article 27 Oct 2015

Research article | 27 Oct 2015

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

W. Sun1,6, R. R. Baize2, G. Videen3,4, Y. Hu2, and Q. Fu5 W. Sun et al.
  • 1Science Systems and Applications Inc., Hampton, VA 23666, USA
  • 2Science Division, NASA Langley Research Center, Hampton, VA 23681, USA
  • 3Space Science Institute, Boulder, CO 80301, USA
  • 4Army Research Laboratory, Adelphi, MD 20783, USA
  • 5Department of Atmospheric Sciences, University of Washington, Seattle, WA 98195, USA
  • 6Mail Stop 420, NASA Langley Research Center, Hampton, VA 23681, USA

Abstract. 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 intensity that is parallel to the meridian plane of reflected light from the 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.

Short summary
A method is reported for retrieving super-thin cloud optical depth with polarized light. It is found that near-backscatter p-polarized light is sensitive to clouds, but not to ocean conditions. Near-backscatter p-polarized intensity linearly relates to super-thin cloud optical depth. Based on these findings, super-thin cloud optical depth can be retrieved with little effect from surface reflection.
Final-revised paper