Mesospheric Temperature Enhancements over Antarctica During Wintertime Planetary Wave Surges in 2007

The southern hemisphere polar stratosphere-mesosphere and lower thermosphere exhibited large temperature enhancements during the 2007 austral winter. In this paper we present the 2007 temperature anomaly in hydroxyl (OH) rotational temperatures observed at South Pole and Davis station, Antarctica and in mesospheric and lower thermospheric temperatures from the NASA Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite. OH temperatures have been shown, in general, to follow the F10.7 solar flux cycle. However, both the airglow and satellite measurements show 2007 temperatures to be aberrantly higher than the average wintertime temperatures in 2006 and 2008. Since the OH rotational temperatures record began at South Pole in 1992, the 2007 temperature anomaly seen in the airglow data was the most remarkable, exhibiting mean wintertime temperatures which were about 6 K higher than the climatological mean. These temperature enhancements are not limited to the middle atmosphere as NCEP Reanalysis data also reveals the 2007 temperature anomaly at stratospheric heights. Analyses of NCEP and Navy Operational Global Atmospheric Prediction System - Advanced Level Physics High-Altitude (NOGAPS-ALPHA) data show that the 2007 temperature anomaly occurred during periods of large planetary wave activity. Eddy heat fluxes derived from NCEP show a correlation between temperature enhancements near 30 km and flux divergence which suggests that adiabatic warming might be responsible for the elevated temperatures presented in this paper.