Low frequency dynamics of the equatorial mesosphere

Abstract

Recent observations of the circulation of the equatorial mesosphere are summarized. Radar wind measurements made at Christmas Island (2°N, 157°W) in the central Pacific show a strong semiannual oscillation near the mesopause and a range of long-period wave activity. Comparisons with radar measurements made in Hawaii suggest that oscillations with periods near 2 and 5 days are manifestations of the (3, 0), and (1, 1) normal modes. The 2-day wave is especially prominent in the meridional wind component at Christmas Island. Significant, but transient, oscillations are also evident in the zonal wind component at periods near 3.5 and 7 days. These latter motions appear to be due to Kelvin waves. -Author