CSU Physics Colloquium

Ice, Smoke and Clusters in the Earth's Mesosphere

Jörg Gumbel

Stockholm University

Mon,  8/31

Despite the fact that the ambient density is a million times less than the air density near the Earth's surface, various aerosol layers can form in the mesosphere around 80 km altitude. Most prominently, Noctilucent Clouds (or Polar Mesospheric Clouds) occur during summer as the highest clouds in our atmosphere. Existing just at the edge of feasibility, these clouds are extremely sensitive to variations in atmospheric conditions. Consequently, they serve as important indicators for the state and long-term variability of their environment. Several decades of research have focused on the properties and interactions of these clouds, as currently highlighted by NASA's Aeronomy of Ice in the Mesosphere (AIM) satellite mission. However, in order to draw robust conclusions from global observations, we need a better understanding of the detailed physics behind the formation of ice in the mesosphere. Here other particle species like meteor smoke and cluster ions come into play as potential ice condensation nuclei. This talk reviews basic knowledge about particles in the mesosphere, highlights old and new open questions, and discusses current research perspectives.