Morphology of polar mesospheric clouds as seen from space

Abstract

The Aeronomy of Ice in the Mesosphere (AIM) mission was launched in April 2007 and has completed observation of five northern hemisphere and four southern hemisphere seasons. One of the instruments aboard AIM, the Cloud Imaging and Particle Size (CIPS) Experiment produces high resolution images of Polar Mesospheric Clouds (PMCs) from space that reveal several interesting cloud structures in finer detail compared to previous space-based observations and on a larger scale than is commonly seen from ground based observations. We present the first classification of PMC structures as seen from space. Apart from Veils, Bands, and Whirls (Type I, II, and IV structures as identified in ground-based observations of noctilucent clouds (NLCs)) we also identify several structures that we denote as "Voids", "Ice Rings", "Fronts", and "Vortex-like structures". These structures are larger in scale compared to similar structures observed in ground-based NLC images. The structural similarity of several of the identified features in these space-based PMC images to those seen in tropospheric clouds and wintertime mesospheric airglow images suggests that similar processes (e.g., gravity waves, convective instability, Kelvin Helmholtz instability, turbulence etc.) influence the summer mesosphere. © 2012 Elsevier Ltd.