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



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.