Geographical Distribution of the Semidiurnal Pressure Oscillation at Different Seasons

Abstract

 From the investigations by Hann and Schou the amplitudes and phases of the 12-hourly pressure oscillation (S₂) were obtained for 136 stations for four months (January, March, July, and September). These data were grouped into latitude zones. It was then assumed that the observed oscillation is due to two component oscillations of the atmosphere: one (W₂) having the same phase in local time on each circle of latitude and the other (Z₂) having the same phase in Greenwich time on each circle of latitude. Because of lack of data from high latitudes only the amplitudes and the phase angles of W₂ could be determined with reasonable reliability. A strong asymmetry in the latitudinal distribution of the amplitudes of W₂ was found for January, resulting in larger amplitudes in the northern hemisphere than in the southern hemisphere. In March W₂ has likewise larger amplitudes in the northern hemisphere, while in July and September it has smaller amplitudes in the northern hemisphere. It is surmised that this asymmetry is due to the meridional temperature distribution of the atmosphere.
 The amplitude of W₂ shows at all latitudes a minimum in the summer, in agreement with earlier to season is small, and it is impossible to decide seasonal variation or is due to residual errors in the data.