Temporal variability of tidal and gravity waves during a record long 10-day continuous lidar sounding

• Published in: Atmospheric chemistry and physics Vol. 18; no. 1; pp. 371 - 384
• Main Authors: Baumgarten, Kathrin, Gerding, Michael, Baumgarten, Gerd, Lübken, Franz-Josef
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 12.01.2018; Copernicus Publications
• Subjects: Atmosphere; Atmospheric chemistry; Atmospheric circulation; Atmospheric models; Daylight; Earth; Earth atmosphere; Evolution; Forecasts and trends; General circulation models; Gravitational waves; Gravity waves; Gravity waves (Meteorology); Lidar; Lidar measurements; Local winds; Measurement; Meteorological research; Middle atmosphere; Observations; Optical radar; Parameterization; Remote sensing; Solar tides; Spatial discrimination; Spatial resolution; Temperature data; Temporal variability; Temporal variations; Tidal waves; Tides; Tsunamis; Variability; Wave interaction; Wave propagation; Wavelengths; Weather; Weather conditions; Wind data; Wind shear; Wind structure
• ISSN: 1680-7324; 1680-7316; 1680-7324
• DOI: 10.5194/acp-18-371-2018

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.