Dynamics of the equatorial mesosphere: First results with a new generation partial reflection radar

Abstract

The first observations of mesospheric winds made between January–August 1990 with an MF partial reflection radar located on Christmas Island (2°N, 157°W) in the central Pacific are described. The mean zonal winds are in general westward, but show clear evidence for a wave‐driven circulation. Power spectral studies indicate that waves are present over a wide range of periods. Ultra‐fast Kelvin waves are especially evident in January–March, with peak amplitudes ∼ 20 ms −1 , and intrinsic phase speeds of ∼ 150 ms −1 indicated. The Kelvin waves are estimated to contribute an eastward acceleration of up to 10 ms −1 day −1 . Gravity wave amplitudes are also found to be almost as large as those observed at mid‐latitude sites, which suggests that convection is a major source of gravity wave activity.