Abstract
Abstract Upper atmospheric winds have been measured at heights from 80 to 100 km overWuhan (30°40N, 114°30′E), China with a meteor radar from 2002 to 2005. The variations of lunar semidiurnal tidal amplitudes and phases with both seasons and heights are studied in detail to reveal the properties of the lunar semidiurnal tide. It is shown that the lunar semidiurnal tide is stronger in January than other months, and its second peak appears near August. For most months the eastward maximum is 3 ± 1 lunar hours later than the northward maximum, as classical theory predicts for a northern hemisphere tide. The observed seasonal and height variations are also compared with the Global Scale Wave Model (GSWM). The phases do not agree well with those of the GSWM model. The maximum amplitude occurs in a different month in the model. There are about 5 lunar hours phase difference between the observed and the model at 90 and 96 km in eastward and northward components. A comparison of the lunar and solar semidiurnal tides is also shown in this paper. The behavior of these two tides in season is different, especially for the month of appearance of maximum amplitude.
Highlights
The dynamics of the MLT region are dominated by waves and tides most of which propagate to this region from sources at lower heights
Using 6 years of data from Saskatoon, Stening et al (1987) found the largest amplitudes of the M2 lunar tide occur in January–February with a smaller maximum in summer
The second peak of the M2 lunar tide at Wuhan appears about one to two months earlier than that at Eaton and Esrange—both sites are at higher latitudes than Wuhan
Summary
The dynamics of the MLT region (mesosphere and lower thermosphere region) are dominated by waves and tides most of which propagate to this region from sources at lower heights. Understanding the tides and waves of the MLT region is crucial in understanding the entire circulation of this part of the atmosphere and how it couples to regions above and below In spite of their small amplitude, the lunar atmosphere tides are of considerable interest for many reasons. Speaking, the formulation of the atmospheric lunar tides is analogous to finding the atmospheric response to an oscillating lower boundary. They propagate upward to the upper atmosphere in the form of various tidal oscillation modes.
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