The Sensitivity of Polar Mesospheric Clouds to Mesospheric Temperature and Water Vapor

The polar mesospheric clouds (PMCs) obtained from Aeronomy of Ice in the Mesosphere (AIM)/Cloud Imaging and Particle Size (CIPS) and Himawari-8/Advanced Himawari Imager (AHI) observations are analyzed for the multi-year climatology and interannual variations. The PMCs dependence on mesospheric temperature and water vapor (H2O) are further investigated with data from Microwave Limb Sounder (MLS). Our analysis shows that PMCs onset date and occurrence rate are strongly dependent on the atmospheric environment, i.e. underlying seasonal behavior of temperature and water vapor. Upper-mesospheric dehydration by PMCs is evident in MLS water vapor observations, The spatial patterns of the depleted water vapor resemble the PMCs distribution over the Arctic and Antarctic region during the days after summer solstice. Year-to-year variabilities of the PMCs occurrence rate and onset date are highly correlated with the mesospheric temperature and H2O variations, particularly in the southern hemisphere (SH). The global increase of mesospheric H2O during the last decade may explain the increased PMCs occurrence in the northern hemisphere (NH). Although mesospheric temperature and H2O exhibits a strong 11-year variation, little solar cycle signature is found in the PMCs occurrence during 2005-2021.