Northern PMC brightness zonal variability and its correlation with temperature and water vapor

Abstract

AbstractPolar mesospheric clouds (PMCs) measured by the Cloud Imaging and Particle Size instrument on the AIM satellite show strong zonal asymmetries, with prominent planetary‐scale variations. The correlations between zonal variations of cloud brightness and temperature or water vapor (H2O) are determined in different stages of the PMC season. Aura Microwave Limb Sounder measured temperature and water vapor are used in the analysis. A zero‐dimensional (0‐D) PMC model was used to interpret the observation. Analyses of all days of the five northern seasons from 2007 to 2011 indicate that temperature and albedo daily zonal variations are anticorrelated in the season start and end, whereas in the core of the season the correlation is relatively poor. The albedo and H2O correlation in the zonal direction is poor throughout the season. Zero‐dimensional model physics indicates that when clouds are weaker, or the environment is warmer and drier, temperature plays an increasingly important role in determining the cloud ice mass variation, which explains the stronger correlation of temperature and albedo at the start and end of the season. Water vapor takes a strong role in determining the ice mass variation in the core of the season when the clouds are stronger and the environment is colder and wetter. However, on a daily basis the H2O depletion associated with the ice production will lead to significant shift of the ice maxima and “post‐ice” H2O maxima in the zonal direction, which leads to the poor correlation between the observed H2O and albedo.