Dominant role of charged meteoric smoke particles in the polar mesospheric clouds

Abstract. Polar mesospheric clouds (PMCs), composed of ice particles, are sensitive to solar activity and atmospheric dynamics, and have been suggested as a potential indicator of climate change. However, the microphysical processes of PMCs, especially the mechanism of ice nucleation, remain poorly understood. This study presents an analysis of satellite PMC data, which reveals that the mean ice particle radius (r) and concentration (N) in PMCs are primarily influenced by the PMC height (h), rather than by the mean environment temperature (T). Additionally, the ice particle column concentration (N_c) exhibits a surprising decrease with latitude. These results support the hypothesis that charged meteoric smoke particles (MSPs) act as ice nuclei, based on which we propose the charged-MSPs nucleation (CMN) scheme for the PMC formation. In contrast to the conventional growth-sedimentation (GS) scheme, in the CMN scheme the nucleation occurs throughout the PMC altitude range, ice particles grow mainly in situ, and the ice particle radius is determined by the competition for the limited water vapor rather than by sedimentation. The CMN scheme provides new pathways for solar activity and atmospheric dynamics to affect PMCs, and can explain a number of puzzling phenomena in the GS scheme.