Interannual Variability in PMCs from AIM/CIPS

Abstract:

The NASA Aeronomy of Ice in the Mesosphere (AIM) mission has measured polar mesospheric cloud (PMC) parameters since May of 2007, including eight PMC seasons in the northern hemisphere (NH) and seven in the southern hemisphere (SH). In this presentation we describe interannual variations in the clouds as measured by the AIM Cloud Imaging and Particle Size (CIPS) instrument, and relate these to measurements of temperature and water vapor from the NASA Microwave Limb Sounder (MLS) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instruments. Overall, interannual variability is larger in the SH than in the NH. In both hemispheres, there is significant variability from season to season in the season onset, with somewhat less variability in the season end. There is about a 20-day spread in the season onset dates in the NH; the NH 2013 season was the earliest, and began a week earlier than any other NH season. In mid-season the NH PMC frequencies were generally highest in 2011, 2013 and 2014, and lowest in 2007 and 2009, but with substantial day-to-day variations that increase with decreasing latitude. In the SH, the earliest season onsets occurred in 2009-2010, 2012-2013, and 2013-2014, which started about a month earlier than 2010-2011 and 2011-2012. The SH 2009-2010 season continued to show more PMCs than any other season throughout the summer, whereas PMC frequencies in the 2012-2013 and 2013-2014 seasons dropped to average values in mid-January. These results will be discussed in terms of teleconnections and solar cycle effects.