13:30 - 14:50
Room: Conference room
Oral presentations
Signatures of the semidiurnal lunar tide in noctilucent clouds in AIM/SOFIE data
Christoph Hoffmann1, Christian von Savigny1, Mark Hervig2, Esther Oberbremer1
1Universität Greifswald, Greifswald, Germany
2GATS Inc., Driggs, United States

Noctilucent clouds (NLCs) exhibit a pronounced temporal variability on various time scales. Not all the sources of this variability have been identified so far, which complicates particularly the discussed use of NLCs as an indicator for trends in the mesopause region. One possible natural source of variability are gravitational tides, which are caused by the moon.

The influence of lunar tides has been demonstrated for several mesospheric parameters like temperature, winds and airglow emissions. Also for some NLC parameters the lunar influence has already been shown, e.g., for the maximum NLC brightness. However, these studies were based on visual observations. Recently, lunar tides have been also identified in systematic satellite measurements of NLCs, particularly in the NLC occurrence rate, the NLC albedo and the ice water content measured with the SBUV instruments.

We extend this analysis here to the diverse dataset of the Solar Occultation for Ice Experiment (SOFIE) on the AIM satellite. As SOFIE is particularly designed for NLC research, it contains a variety of parameters including the background atmosphere (e.g., temperature and trace gases), NLC properties (e.g., ice water content, top and bottom altitude), microphysical properties (e.g., the particle size distribution), and mesopause properties. We find a signature of the semidiurnal lunar tide in all of these parameters and estimate amplitudes and phases of the response to the lunar forcing. The amplitudes and particularly the phases show for many parameters a complex altitude dependent structure. Although individual relationships between the signatures of different parameters can be attributed qualitatively to known NLC physics, the mechanisms behind other relationships cannot be easily explained.


Reference:
Dynamics 1-O-01
Session:
Long period waves in NLC
Presenter/s:
Christoph Hoffmann
Topic:
1) Mesospheric clouds and related sciences, including noctilucent clouds (NLCs), polar mesospheric clouds (PMCs), and polar mesospheric summer echoes (PMSEs).
Presentation type:
Oral communication 15 min
Room:
Conference room
Chair/s:
Gerd Baumgarten
Date:
Monday, 18 September
Time:
13:30 - 13:50