Recent results with an MF radar at McMurdo, Antarctica: Characteristics and variability of motions near 12‐hour period in the mesosphere

We present an analysis of the first wind measurements obtained with an MF (medium frequency) radar installed at McMurdo Station, Antarctica in January 1996. The largest amplitude motions are the quasi‐12‐hr motions, with additional periodicities at 24 hr, ∼10 hr and 2 to 10 days. The quasi‐12‐hr motions occur at discrete periods distinct from 12 hr and exhibit pronounced amplitude and vertical wavenumber modulations at planetary wave periodicities. During the months analyzed in this report (mid‐January through April 1996) the 12‐hr wave is by far the dominant motion the mesosphere. The source of this wave is unknown, but our results provide additional support for the suggestion that such motions arise through nonlinear interactions involving the migrating semidiurnal tide and low‐frequency planetary wave motions.