Annual and Semi-Annual Oscillations of Zonal Mean Winds in the Mesopause Region
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Graphical Abstract
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Abstract
In this study the authors analyzed the global structures and inter-annual variations of the annual and semi-annual oscillations of the zonal mean winds in the mesopause region from 80 to 105 km, using nine years (2003-2011) of TIDI (TIMED Doppler Interferometer) observations. In the tropical regions, mean zonal winds dominate the semi-annual oscillation;peak amplitudes occur between 10°S and 20°S, with similar results for the semi-annual oscillation in the stratospheric zonal winds;the amplitudes of the TIDI observations are much smaller than previous results for the mesosphere using other measurement techniques. In the middle and high latitudes, zonal winds and meridional winds are dominated by annual oscillation. The annual oscillation of the zonal winds has two maximum centers in the middle and high latitudes below 100 km. The annual oscillation of the meridional winds is only found at the middle latitudes below 95 km, and the amplitude centers are distributed differently in the Northern and Southern Hemispheres. Results also show that the amplitudes of the annual and semi-annual oscillations in the zonal and meridional winds have significant inter-annual variations with nearly no change in phases. However a two-year period change, both in the amplitude and phase of the annual oscillation of the meridional winds, was found in the northern tropics.
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