Polarimetric Detection of Super-thin Clouds and Dust Using CubeSats

Super-thin clouds with optical depths smaller than ~0.3 can seriously affect the remote sensing of aerosols, surface temperature, and the atmospheric composition gases. Without taking into account these clouds, the sea-surface temperature retrieved from satellite data could be ~5-10K lower than the actual values at tropical and midlatitude regions, where these clouds frequently exist [1, 2]. Super-thin clouds can consist of ice clouds at high altitudes and also water clouds at low altitudes. Detection of optically thin clouds at low altitudes from space is very difficult due to their partial transparency, land surface emission, and the fact that they are relatively warm [3]. Studies have shown that super-thin clouds can be detected by a polarimetric imager facing toward the backscattering direction of sunlight, exploiting a distinct, characterizing feature of the angle of linear polarization of the backscattered solar radiation [1, 2]. We are designing two CubeSats with polarimetric instrumentation to detect super-thin clouds, as well as dust aerosols that we anticipate will significantly improve environmental and climate modeling.

References:

1. Sun, W., G. Videen, and M. I. Mishchenko, 2014: Detecting super-thin clouds with polarized sunlight. Geophy. Res. Lett., 41, 688-693.
2. Sun, W., R. R. Baize, G. Videen, Y. Hu, and Q. Fu, 2015: A method to retrieve super-thin cloud optical depth over ocean background with polarized sunlight. Atmos. Chem. Phys., 15, 11909-11918.
3. Wu, Y., S. Chaw, B. Gross, F. Moshary, and S. Ahmed, 2009: Low and optically thin cloud measurements using a Raman–Mie lidar. Appl. Opt., 48, 1218-1227.