Low latitude 2-day planetary wave impact on austral polar mesopause temperatures: revealed by a January diminution in PMSE above Davis, Antarctica

A new characteristic of the austral summer polar mesopause as revealed by ground‐based radar and satellite temperature measurements is reported, that is linked to inter‐annual variability of the low‐latitude easterly wind jet. Four consecutive seasons of polar mesosphere summer echoes (PMSE) and mesosphere temperature observations above Davis, Antarctica (68.6°S) show a mid‐January diminution in PMSE occurrence rate that coincides with a minor mesopause warming of several degrees. Spectral analyses of PMSE, Aura Microwave Limb Sounder (MLS) temperatures and radar meridional winds show the presence of ∼4–5‐day planetary waves (PWs) throughout the austral summer in the polar upper mesosphere together with enhanced ∼2‐day PW activity from mid‐January to mid‐February. Analysis of MLS temperatures show that the ∼2‐day PWs have zonal wavenumbers (S) with both westward (S = −2, −3) and eastward (S = +2, +3) components. Although displaying some inter‐annual variation in the peak onset time, the mid‐January mesopause warming coincides with a weakening of the equatorward meridional wind above Davis and enhancement of low‐latitude 2‐day PW activity.