Latitude variations in light scattered from polar mesospheric clouds

Abstract

A middle ultraviolet imager over the northern and southern polar regions has measured the scattered intensities of polar mesospheric clouds (PMC) during the austral summer of 1997-98 and the arctic summer of 1999. The intensities, corrected for solar zenith angle, are those at the peak in the PMC radiance profiles for a waveband of 235-263 nm. The peak radiance averaged 12.0±11.0 mega-Rayleighs (MR) for 13 passes over the south polar region, where the scattering angle was ∼111°. The peak radiance averaged 11.4±7.6 MR for 12 passes over the north polar region, where the scattering angle was ∼48°. The PMC intensities increased with increasing latitude in both the north and the south, but the rate of increase was twice as fast in the south (0.60 MR/° latitude) as in the north (0.32 MR/° latitude).