Persistent longitudinal variations in 8years of CIPS/AIM polar mesospheric clouds

The Cloud Imaging and Particle Size (CIPS) instrument on the Aeronomy of Ice in the Mesosphere (AIM) satellite provides an opportunity to study the longitudinal variation in polar mesospheric cloud (PMC). We examined the longitudinal variation in PMC albedo using 8years (2007-2014) of observations from the CIPS instrument. The results show that the PMC albedo in the Southern Hemisphere (SH), especially in the latitude band of 80 degree S-85 degree S, is persistently low (~65% relative to the rest of the hemisphere) within 60 degree W to 150 degree W longitude. In the Northern Hemisphere (NH), however, PMC albedo is found to be relatively zonally asymmetry. Harmonic analyses show that the persistent longitudinal variation in the SH PMC albedo is due to zonal wave numbers 1 through 4 (WN1-WN4) processes with minima in the longitude range of 60 degree W-150 degree W. The influence of temperature and H sub(2)O on the longitudinal variation of the PMC albedo is discussed based on results obtained using a simple 0-D PMC model and temperature from the Microwave Limb Sounder (MLS) and the Sounding of the Atmosphere with Broadband Emission Radiometry (SABER) and H sub(2)O from MLS. The modeled region of low ice mass in the SH is generally consistent with that of low PMC albedo seen in CIPS. Tidal analyses using the SABER temperatures indicate that the nonmigrating semidiurnal tides with modes of S0, W1, and E1 might be the main drivers of the persistent longitudinal variations of PMC albedo in the SH. Nonmigrating tides are much weaker in the NH and consistent with the observed lack of longitudinal variability in PMC albedo. Key Points * Persistent weak PMC albedo was found in 60 degree W-150 degree W of the SH but not in the NH * Weak PMC coincides with higher T from MLS and lower modeled ice density * Weak PMC coincides with warm phases of strong nonmigrating 12h tides from SABER