Variations in the phase of the semidiurnal tide over Davis,Antarctica |
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| Institution: | 1. Goddard Space Flight Center, Greenbelt, MD 20771, USA;2. Science Systems & Applications, Inc., Lanham, MD, USA;3. Applied Physic Laboratory, Johns Hopkins University, Laurel, MD, USA;4. Furman University, Greenville, SC, USA;5. Hong Kong University of Science and Technology, Hong Kong, China;1. Indian Institute of Tropical Meteorology, Pune, India;2. School of Chemistry, University of Leeds, Leeds, UK;3. National Centre for Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, UK;4. Centre for Research in Earth and Space Science, York University, Toronto, Canada |
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| Abstract: | The amplitude and time of maximum of the semidiurnal tide in the mesosphere and lower thermosphere above Davis varies through the summer months. In particular, the time of maximum can oscillate around a fixed value or, at some heights, shift by a whole cycle of local time. Recent studies of the semi-diurnal tide at the South Pole have suggested that an s=1 mode is common at high-southern latitudes. At mid-latitudes, the s=2 mode is thought to dominate suggesting that a region where these modes overlap is a possibility. Although it is not possible to discern which of these modes are present using single station data, the concept that more than one 12-h wave is present allows a new interpretation of the Davis semi-diurnal amplitudes and times of maximum. In this study, wind data obtained at Davis, Antarctica, during the summer of 1996/97 are used to show that the complex variations in time of maximum and amplitude can be explained by a sum of two waves. The simplest of models combines an invariant and a varying 12-h wave and yields characteristics for each component that are less complex than the original observation. There is also potential for changes to the interpretation of time of maximum vs. height profiles. |
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