Temporal variability of tidal and gravity waves during a record long 10-day continuous lidar sounding
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Published:2018-01-12
Issue:1
Volume:18
Page:371-384
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ISSN:1680-7324
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Container-title:Atmospheric Chemistry and Physics
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language:en
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Short-container-title:Atmos. Chem. Phys.
Author:
Baumgarten KathrinORCID, Gerding MichaelORCID, Baumgarten GerdORCID, Lübken Franz-Josef
Abstract
Abstract. Gravity waves (GWs) as well as solar tides are a key driving mechanism for the
circulation in the Earth's atmosphere. The propagation of gravity waves is
strongly affected by tidal waves as they modulate the mean background wind
field and vice versa, which is not yet fully understood and not adequately
implemented in many circulation models. The daylight-capable
Rayleigh–Mie–Raman (RMR) lidar at Kühlungsborn (54∘ N,
12∘ E) typically provides temperature data to investigate both wave
phenomena during one full day or several consecutive days in the middle
atmosphere between 30 and 75 km altitude. Outstanding weather conditions in
May 2016 allowed for an unprecedented 10-day continuous lidar measurement,
which shows a large variability of gravity waves and tides on timescales of
days. Using a one-dimensional spectral filtering technique, gravity and tidal
waves are separated according to their specific periods or vertical
wavelengths, and their temporal evolution is studied. During the measurement
period a strong 24 h wave occurs only between 40 and 60 km and vanishes
after a few days. The disappearance is related to an enhancement of gravity
waves with periods of 4–8 h. Wind data provided by ECMWF are used to analyze
the meteorological situation at our site. The local wind structure changes
during the observation period, which leads to different propagation
conditions for gravity waves in the last days of the measurement period and
therefore a strong GW activity. The analysis indicates a further change in
wave–wave interaction resulting in a minimum of the 24 h tide. The observed
variability of tides and gravity waves on timescales of a few days clearly
demonstrates the importance of continuous measurements with high temporal and
spatial resolution to detect interaction phenomena, which can help to improve
parametrization schemes of GWs in general circulation models.
Funder
Deutsche Forschungsgemeinschaft Bundesministerium für Bildung und Forschung
Publisher
Copernicus GmbH
Subject
Atmospheric Science
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