Polar mesospheric cloud mass and the ice budget: 2. Application to satellite data sets

[ 1] We use satellite observations of mid-UV solar backscattered light from polar mesospheric clouds (PMCs) to constrain the water ice budget. We compare the PMC mass from observations by two instruments: the limb viewing Student Nitric Oxide Explorer (SNOE) and the nadir viewing Solar Backscattered UltraViolet (SBUV) experiments. At 70 +/- 2.5 degrees N we find that SNOE measures over three times more PMC mass than the less sensitive SBUV experiment. We directly compare the two data sets by selecting only the brightest 10% of SNOE clouds so that the SNOE and SBUV PMC occurrence frequencies are the same. This comparison shows that the PMC mass averaged over five northern seasons is the same to within uncertainties in the ice particle size distribution. We also find that near midday, the northern SBUV PMC mass is a factor of 2.4 times greater than the southern PMC mass. These results provide new constraints for global climate models of PMC formation.