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[1] Mesospheric temperatures derived from spectroscopic measurements of the hydroxyl (OH) nightglow have been observed from Rothera (67.6°S, 68.1°W) and Halley (75.6°S, 26.6°W) stations in Antarctica during the 2002 austral winter season. In addition to the normal seasonal changes, the temperatures at both sites, separated by 1658 km, showed several simultaneous shifts in temperature of between 10 and 20 K. These changes abruptly occurred in the space of 2–3 days and lasted for several days. These rapid variations in temperature were associated with large swings observed in the meridional component of the mesospheric wind measured by the Rothera MF radar. As there appeared to be no phase shift between the temperature variations at the two longitudinally separated stations indicating that planetary-waves caused the changes, these large-scale changes have been interpreted as variations in the inter-hemispheric meridional jet, and a corresponding modulation of the mesospheric descent and adiabatic heating rates over the polar region.