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First evidence of a 27-day signature in noctilucent cloud occurrence frequency

Charles Robert(1), Christian von Savigny(1), Heinrich Bovensmann(1), John Burrows(1) and Matthew DeLand(2)

(1) University of Bremen, Otto-Hahn-Allee 1, 28359, Bremen, Germany
(2) Science Systems and Applications, Inc. (SSAI), Otto-Hahn-Allee 1, 20706, Lanham (MD), United States


This paper presents for the first time evidence of a connection between the 27-day modulation of the solar activity and noctilucent clouds occurrence frequency as measured by SCIAMACHY and SBUV instruments.

Observations show a strong anti-correlation between the NLC occurrence rate anomaly and the Lyman-alpha irradiance variation throughout the summer season for several years. The anti-correlation is most pronounced for the northern hemisphere according to both instruments.

MLS mesospheric products suggest that the more likely driver for the variation in NLC occurrence is a change in temperature instead of water vapor, but the mechanisms responsible for the observed variation are not yet fully understood.


Workshop presentation