Radar observations of the quarterdiurnal tide at midlatitudes: Seasonal and long-term variations

• Published in: Journal of atmospheric and solar-terrestrial physics 2017-10, Vol.163, p.70-77
• Main Authors: Jacobi, Christoph, Krug, Amelie, Merzlyakov, Eugeny
• Format: Article
• Language: English
• Subjects: Atmospheric tides; Long-term trends; Mesosphere/lower thermosphere; Radar observations
• ISSN: 1364-6826; 1879-1824
• DOI: 10.1016/j.jastp.2017.05.014

The seasonal and interannual variability of the quarterdiurnal tide is analysed using meteor radar wind observations at the two midlatitude sites Collm and Obninsk. Generally tidal amplitudes increase with height. Maximum tidal amplitudes are found in winter. Meridional amplitudes are smaller than zonal ones on an average. Phases mainly differ between summer and winter. Zonal and meridional phases differ by slightly less than 90°. The vertical wavelengths are very long in winter, but shorter and on the order of 20 km in summer. Collm and Obninsk amplitudes and phases agree well, indicating that the migrating quarterdiurnal tide may be responsible for a major part of the observed waves. Observations since 1980 show that the tidal amplitudes have increased on a whole, although the increase is not linear but mainly happening during the late 1990s and the early 2000s. •Climatology of quarterdiurnal tidal amplitudes and phases based on radar observations at midlatitudes.•Seasonal amplitude and phase distribution observed at 2 sites agree with each other.•A long-term increase of quarterdiurnal amplitudes since the 1980s is found.