Noctilucent clouds at the edge of space

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Ομιλητής :  
Δρ. Gerd Baumgarten (Leibniz Institute of Atmospheric Physics at the University of Rostock, Kühlungsborn, Γερμανία)
Αίθουσα :  
Αίθουσα Σεμιναρίων 2ou
Ημερομηνία :  

Ώρα : 

Περίληψη :

Noctilucent clouds are made of tiny ice crystals at an altitude of about 83 km near the edge of space. These clouds have been called the miner's canary of the middle atmosphere since their occurrence is governed by temperature and water vapour (created from methane in the middle atmosphere). On a century-scale, model studies have shown that their frequency, brightness, and height may be linked to increases in greenhouse gases like carbon dioxide and methane.

The noctilucent clouds provide unique information about a difficult-to-access region of the atmosphere (near the Kármán line) that is critical for understanding the Earth's interface with space.

The occurrence of the clouds was beleived to be limited to higher latitudes, however recent observations and modeling indicates that they spread to lower latitudes. Fundamental peculiaries of the mechanisms forming the thermal and dynamical structure of the middle atmosphere will presented. Recent Doppler-lidar, -radar and camera observations will be used to highlight the importance of atmospheric gravity waves and their transition to turbulence.