Case study of a mesospheric front observed in polar mesospheric clouds

Abstract:

Polar Mesospheric Clouds (PMCs) typically occur in the high-latitude summer mesosphere at ~83 km. PMCs are of scientific interest not only for their occurrence at the edge of space but also for the information they provide regarding the mesospheric environment. PMCs exhibit complex spatial structures with unique morphological forms that may be signatures of atmospheric waves. Here, we use PMC observations from CIPS/AIM instrument to focus on a ‘front’ like structure, which is a solitary wave or a sharp step-like boundary that separates a mesospheric cloud and no cloud region. Coincident temperature observations from SABER/TIMED indicate that a mesospheric inversion layer is responsible for the step-like boundary and the large temperature difference between the cloud and cloud-free region. This suggests that the mesospheric front may be similar to mesospheric bores observed in airglow images. We investigate the gravity wave (GW) activity between the two regions, and the lower atmospheric GW sources that may support the formation of PMC fronts. We will confirm possible lower atmospheric coupling to the mesosphere via GW ray-tracing simulations.