Observations of lunar tides in the mesosphere and lower thermosphere at Arctic and middle latitudes

Abstract

Abstract. Meteor radars have been used to measure the horizontal winds in the mesosphere and lower thermosphere over Castle Eaton (52 • N) in the UK and over Esrange (68 • N) in Arctic Sweden. We consider a 16-year data set covering the interval 1988-2004 for the UK and a 6-year data set covering the interval 1999-2005 for the Arctic. The signature of the 12.42-h (M 2 ) lunar tide has been identified at both locations. The lunar tide is observed to reach amplitudes as large as 11 ms −1 . The Arctic radar has an interferometer and so allows investigation of the vertical structure of the lunar tide. At both locations the tide has maximum amplitudes in winter with a second autumnal maximum. The amplitude is found to increase with height over the 80-100 km height range observed. Vertical wavelengths are very variable, ranging from about 15 km in summer to more than 60 km in winter. Comparisons with the Vial and Forbes (1994) model reveals generally good agreement, except in the case of the summer vertical wavelengths which are observed to be significantly shorter than predicted.

Where does Earth’s atmosphere get its energy?

“…These atmospheric tides are considerably smaller in amplitude than the dominant, atmospheric thermal tide of the Sun (Chapman & Lindzen 1970;Vial & Forbes 1994;Sandford et al 2006). The dominant component of the lunar atmospheric tide is the M 2 tide with a period of 12.42 h (Chapman & Lindzen 1970;Sandford et al 2006;Forbes et al 2013).…”

“…These atmospheric tides are considerably smaller in amplitude than the dominant, atmospheric thermal tide of the Sun (Chapman & Lindzen 1970;Vial & Forbes 1994;Sandford et al 2006). The dominant component of the lunar atmospheric tide is the M 2 tide with a period of 12.42 h (Chapman & Lindzen 1970;Sandford et al 2006;Forbes et al 2013). According to Chapman & Lindzen (1970), there are as many as 30 components comprising the lunar tide, most of which are much smaller in amplitude and, therefore, are often ignored due to the limited ability of measurements to detect their small signal (Sandford et al 2006).…”

“…The dominant component of the lunar atmospheric tide is the M 2 tide with a period of 12.42 h (Chapman & Lindzen 1970;Sandford et al 2006;Forbes et al 2013). According to Chapman & Lindzen (1970), there are as many as 30 components comprising the lunar tide, most of which are much smaller in amplitude and, therefore, are often ignored due to the limited ability of measurements to detect their small signal (Sandford et al 2006). Platzman (1991) performed an energy balance study of the lunar atmospheric tide by incorporating the three factors of the ocean, body, and load tides, characterized by barometric pressure data from Haurwitz & Cowley (1969) and satellite altimeter data of sea-tide dissipation and sea-tide elevation from NASA's Geodetic Satellite (Geosat) (Cartwright & Ray, 1990).…”

A measurement of the lunar semidiurnal tide at Wuhan (30°40′N, 114°30′E)

“…• N, 21.1 • E), Sandford et al (2006) found the lunar tide has maximum amplitudes in winter (January-February) with a second autumnal (September-October) maximum. At Wuhan there is a second northward amplitude peak in July and an eastward peak in August.…”

Lunar tides in the Mesosphere over Ascension Island (8° S, 14.4° W)

“…Lunar age is a measure of the phase of the Moon, where ν=0 signifies new moon (Stening et al, 1997(Stening et al, , 2003. This method has been used to successfully by Sandford et al (2006) and Stening et al (1997Stening et al ( , 2003. Because high spectral resolution is required to separate the Lunar M 2 and Published by Copernicus GmbH on behalf of the European Geosciences Union.…”