Mean Motions and Tidal and Two-Day Structure and Variability in the Mesosphere and Lower Thermosphere over Hawaii

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Abstract
An overview of the motion field and an analysis of the tidal and 2-day wave motions observed in the mesosphere and lower thermosphere over the central Pacific from 1 October 1990 through 19 August 1992 is presented. Characteristics and interactions of motions at lower and higher frequencies will be addressed elsewhere. Wind measurements were obtained with an MF radar operating on Kauai, Hawaii (22°N, 160°W), using the partial reflection drift technique. Results presented in this paper reveal a zonal mean motion reflecting the mesopause semiannual oscillation (MSAO) observed at more equatorial latitudes from ∼ January to July, coinciding with the period during which the MSAO and the annual cycle of the zonal mean wind at higher latitudes are in phase. Eastward and westward maxima are 55 m s−1 below 80 km and 45 m s−1 near 85 km during the first year, with maxima of 57 and 53 m s−1 during the second year and evidence of substantial interannual variability. The second MSAO cycle is greatly suppresse... Abstract An overview of the motion field and an analysis of the tidal and 2-day wave motions observed in the mesosphere and lower thermosphere over the central Pacific from 1 October 1990 through 19 August 1992 is presented. Characteristics and interactions of motions at lower and higher frequencies will be addressed elsewhere. Wind measurements were obtained with an MF radar operating on Kauai, Hawaii (22°N, 160°W), using the partial reflection drift technique. Results presented in this paper reveal a zonal mean motion reflecting the mesopause semiannual oscillation (MSAO) observed at more equatorial latitudes from ∼ January to July, coinciding with the period during which the MSAO and the annual cycle of the zonal mean wind at higher latitudes are in phase. Eastward and westward maxima are 55 m s−1 below 80 km and 45 m s−1 near 85 km during the first year, with maxima of 57 and 53 m s−1 during the second year and evidence of substantial interannual variability. The second MSAO cycle is greatly suppresse...

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