Resonant Exitation-A Possible Forcing of the Middle Atmosphere from Above and Below

Tidal theory analysis, 2-D numerical modelling of a large-scale planetary transient waves excitation by external forcing and data analysis has revealed the possibility for resonant response of the middle atmosphere. Such reaction has a nature of a barotropic motions and looks like atmospheric Rossby waves. Two types of forcing has been realised in model runs: solar UV 27-day variability (from above) and tropospheric periodical disturbances (from below). The results of model calculations has shown that the middle atmosphere of the Earth has its own periods and may be excited by a weak signal. Some of these periods are near to solar rotation period and others to the meteorological periodicities (5-7 and 12-14 days). The amplitudes of the waves in terms of geopotential heights increase from below to the higher levels and reach the quantities of about 50-80 gpm in the lower mesosphere. A special 2-D statistical method for transient waves detecting has shown that the real waves with similar spatial structure and character periods are really exist in the troposphere and lower stratosphere.