AIM

The Cloud Imaging and Particle Size (CIPS) experiment on AIM has measured the frequency of occurrence of Polar Mesospheric Clouds for the entire Northern 2007 season. The figure shows the results for three latitude regions centered at 82.5N (top), 77.5N (center), and 72.5N (bottom). The +?s represent the daily averaged values of PMC occurrence frequency. The solid lines are a 7 day smooth of the daily values. The x-axis is in days from solstice (June 21, or day 172). The season begins near day -30 after which the cloud frequency increases. The maximum frequency occurs near day 20 at the highest latitude and is is larger than 80%. The highest frequency at 72.5N drops to 55% in the middle of the season. The season ends at about day 80, after which no clouds are observed by CIPS.

Credit: Cloud Imaging and Particle Size Experiment data processing team at the University of Colorado’s Laboratory for Atmospheric and Space Physics.