Mesosphere and lower thermosphere temperature anomalies during the 2002 Antarctic stratospheric warming event

Abstract. We present kinetic temperatures at ~87 km and ~94 km altitudes inferred from OH (6,2) and O₂ At(0,1) airglow observations, respectively, at South Pole (90° S), Antarctica in the austral winter of 2002. These OH and O₂ rotational temperatures measurements show mesosphere and lower thermosphere (MLT) temperature anomalies prior to the 2002 Southern Hemisphere Sudden Stratospheric Warming (SSW) . In this paper we focus on the first of the three minor stratospheric warmings which preceded the major SSW event. Temperature anomalies observed in the MLT region show sudden cooling (ΔT=~30 K) in OH temperatures accompanied by warming (ΔT=~15 K) in O₂ temperatures preceding the onset of SSW event by about three to four weeks. This shallow vertical extent of mesospheric cooling is in agreement with the numerical simulation of Coy et al. (2005), however, the model cooling was centered well below the mesopause level. The other observed feature of the South Pole MLT temperature dataset is the intensification of planetary wave activity prior to the onset of SSW event. Fourier analyses of both OH and O₂ temperatures show amplification of planetary wave activity in the 5–10 day range prior to the onset of SSW. The timing of wave amplification seen in the wave spectra coincides with the peak in OH and O₂ temperature anomalies.