Polarimetric measurements of long-wave infrared spectral radiance from water.

Polarimetric measurements of the thermal infrared spectral radiance from water are reported and are compared with calculations from a recently published model over the spectral range of 600-1600 cm(-1) (6.25-16.67-mum wavelength). In this spectral range, warm water viewed under a dry, clear atmosphere appears vertically polarized by 6-12%. The measured spectral degree of polarization agrees with calculations within the measurement uncertainty (~0.5% polarization in spectral regions with high atmospheric transmittance and 1.5% polarization in spectral regions with low atmospheric transmittance). Uncertainty also arises from temporal changes in water and air temperatures between measurements at orthogonal polarization states, indicating the desirability of simultaneous measurements for both polarization states.