Some further results on the lower stratospheric winds and waves over Jicamarca

Abstract

The VHF radar at Jicamarca, Peru (12.0°S, 76.9°W) was used to probe the tropical lower stratosphere on 3–4 October and 6–8 December 1977. Velocity data obtained during these experiments exhibit features indicative of winds and waves in the stratosphere as follows: 1. (1) The amplitude and phase of a diurnal oscillation in the observed horizontal wind compare well with theoretically predicted values of the solar diurnal tide. An observed semidiurnal oscillation differs considerably from theoretical values, although minimal phase variation with height is a fundamental property of both theory and observation. The observed vertical wind oscillations are larger than theoretical values of vertical tidal components, although the data is consistent with recent rocket observations. 2. (2) Dominant velocity oscillations with periods near the Brunt-Väisälä period are frequently observed. 3. (3) Downward phase progression of the westerly regime of the quasi-biennial wind oscillation is observed during the course of the two observations. A long-period oscillation with a period exceeding two days also appears to be superposed on the quasi-biennial oscillation. 4. (4) Systematic differences are found between horizontal winds measured by the radar and those measured by rawinsondes launched from the Lima-Callao airport some 30 km west of Jicamarca.