The impact of polarization on infrared sea-surface temperature sensing

One of the most strongly polarized natural infrared sources is the sea surface, yet polarization is rarely considered in infrared radiometric sea-surface temperature sensing. For an off-nadir incidence angle, sea-surface emission is vertically polarized, and reflected atmospheric radiance is horizontally polarized. The net degree of polarization is determined by the relative magnitudes of reflected and surface-emitted radiances, which actually tend to offset one another because of their orthogonal orientations. The significance of partially polarized radiances on radiometric sea-surface temperature measurements is determined primarily by the viewing angle and the inherent polarization sensitivity of the radiometer. This paper discusses several ways that polarization can affect infrared radiometric measurements of sea-surface temperature. A specific example is shown, wherein the polarization sensitivity of a Fourier transform infrared (FTIR) spectrometer results in small errors that are significant for high-accuracy radiometry