Microphysics of ice particles at the polar summer mesopause (Microlce)

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Mesospheric ice particle may nucleate in the polar summer mesopause at heights between 80–90 km and temperatures below ~150 K on nanometer sized meteoric smoke particles. Under favorable conditions, they are visible from ground as noctilucent clouds. These ice particles modify the charge state of the surrounding plasma and are therefore accompanied by radar echoes, known as polar mesosphere summer echoes. Both phenomena can be observed straightforwardly by remote sensing methods from the ground and thus are valuable probes for the otherwise elusive physical and dynamical processes at the mesopause. Changes in these signals are often used to infer long term climatic trends in this height region. Despite of this importance, we are lacking fundamental knowledge about the nucleation and growth processes of ice in the thermodynamic, chemical and electrical environment of the mesopause. Progress in this understanding would significantly enhance the descriptive and predictive capabilities of mesospheric models and thus our understanding of the role of the mesopause region in the climate system. Comprehensive laboratory experiments on these processes have become possible only recently with the establishment of a new experimental setup at the Karlsruhe Institute of Technology (KIT), which allows to study ice nucleation on nanoparticles under realistic mesospheric conditions on well characterized mineral nanoparticles. In close collaboration between the experimental group in Karlsruhe (T. L.) and the modeling team in Kühlungsborn (M. R.) we propose to study the nucleation and growth rates of ice on realistic nanoparticles composed of typical minerals as olivine and to implement the findings into mesospheric modeling. All model results will be validated versus observational results available at the IAP Kühlungsborn. Furthermore we want to determine the optical properties of the growing mineral/ice systems to allow for a direct comparison with remote sensing signals. A parallel project (ELOMA) proposed by groups from the University of Rostock and the IAP in Kühlungsborn will complement the scheduled research with respect to the electronic and optical properties of the meteoric smoke particles.