Heidelberg 2015 – wissenschaftliches Programm

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UP: Fachverband Umweltphysik

UP 2: Atmosphäre

UP 2.15: Vortrag

Mittwoch, 25. März 2015, 14:15–14:30, G/gHS

Lunar semi-diurnal tidal signatures in noctilucent clouds — •Christian von Savigny¹ and Matthew DeLand² — ¹Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, Greifswald, Germany — ²Science Systems and Applications, Inc., Lanham, MD, U.S.A.

Noctilucent clouds (NLCs) are optically thin water ice clouds occurring near the polar summer mesopause in the summer hemisphere. NLCs are a highly variable phenomenon subject to different sources of variability including planetary and gravity waves, solar variability and long-term changes of the middle atmosphere climate. In this contribution we report on another process affecting NLCs, i.e. the lunar semi-diurnal gravitational tide. While lunar ocean tides are a well known phenomenon, many aspects of lunar tidal signatures in the atmosphere are uncertain. To our best knowledge our results are the first robust identification of the lunar semi-diurnal tide in NLCs. Earlier studies on lunar semi-diurnal tidal signatures in NLCs reported unrealistically large amplitudes in NLC parameters or showed periods inconsistent with the lunar tide. In our study the lunar tidal signature is extracted from satellite observations of NLCs with the SBUV instruments using the superposed epoch analysis technique.