Interannual variability of mesospheric mean winds observed with the MU radar |
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| Institution: | 1. National Institute of Geophysics, Geodesy and Geography (NIGGG), BAS, Sofia, Bulgaria;2. Space Science Division, Naval Research Laboratory, Washington, DC, USA;1. MNR Key Laboratory for Polar Science, Polar Research Institute of China, Shanghai, China;2. State Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing, China;3. National Institute of Polar Research, Tokyo, Japan;4. Department of Polar Science, The Graduate University for Advanced Studies, SOKENDAI, Hayama, Japan;1. Physics Department, Colorado State University, Fort Collins, USA;2. Center of Atmospheric and Space Sciences, Utah State University, Logan, USA;3. Department of Physics and Astronomy, Clemson University, Clemson, USA;1. Graduate School of Science and Technology, Hirosaki University, Japan;2. Faculty of Science and Technology, Hirosaki University, Japan;3. Institute for Space-Earth Environmental Research, Nagoya University, Japan;4. National Institute of Polar Research, Japan;5. Institute of Radiation Emergency Medicine, Hirosaki University, Japan;6. Micro Analysis Laboratory, Tandem Accelerator (MALT), The University of Tokyo, Japan |
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| Abstract: | In an effort to study the interannual variation of mesospheric (65–90 km altitude) mean winds, 10 years (1986–1995) of wind data collected with the MU radar at Shigaraki, Japan (34.9°N, 136.1°E) have been analysed. The analysis reveals that the mean zonal wind circulation in the mesosphere is dominated by an annual variation. The summer westward flow in the mesosphere shows a smooth variation with a peak value in the range 40–60 m/s in June/July. In contrast to the summer westward winds, the winter eastward winds exhibit much more variability. In some years it is found that the winds exceed even 60 m/s and the peak value may occur in any one of the winter months. Scrutiny of the duration of the summer westward winds reveals a two-year periodicity, which has been compared with the quasi-biennial oscillation (QBO) phases at the equator. The search for a dependence of the mean wind on solar activity does not reveal any indications of it. Ten-year averaged winds are compared with the model atmosphere, CIRA-86, values and certain agreements and disagreements are pointed out. |
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