Large-Scale Equatorial Waves Penetrating from the Upper Troposphere into the. Lower Stratosphere

Abstract

The three dimensional structure of large-scale disturbances found in the lower stratosphere and the upper troposphere in the equatorial Pacific is studied in detail by power spectral and synoptic analyses, using the special upper-air observations during the period April through July 1962. It is found that the sharp spectral peak of the meridional component of the wind near the 4.5-day period in the upper troposphere and the lower stratosphere is caused by the westward movement of large-scale eddies which are centered over the equator and penetrating through the tropopause with their axes tilting westward with height. A spectral method of estimating vertical and horizontal transports of energy is devised, by which energy flux is obtained from the correlation between horizontal wind and temperature or the tilt of phase lines. It is shown that the westward tilt of vertical phase lines or poleward transport of heat indicates the upward transport of wave energy. The large-scale waves in the upper troposphere provide the lower stratosphere with energy of the order of 6 ergs per cm2 sec and the vertical convergence of energy of the order of 1 erg per cm2 sec km occurs at the levels from 15 to 20 km. In the lower stratosphere horizontal convergence of wave energy occurs near the equator.