Latitude variations in light scattered from polar mesospheric clouds

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 +/-1.0 mega-Rayleighs (MR) for 13 passes over the south polar region, where the scattering angle was similar to 111 degrees. The peak radiance averaged 11.4 +/-7.6 MR for 12 passes over the north polar region, where the scattering angle was similar to 48 degrees. 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/degrees latitude) as in the north (0.32 MR/degrees latitude).