Summary
The existence of Polar Mesosphere Summer Echoes (PMSE) in the Southern Hemisphere (SH) has been confirmed using MST radar, HF radar and a Dynasonde. Studies spanned the geographic latitudes 62.1°S (Machu Picchu), 68.6°S (Davis), 69.0°S (Syowa), and 75.5°S (Halley Bay). An understanding of the occurrence and intensity of PMSE against latitude in the SH is needed to facilitate a comparison with the better spatial coverage of Northern Hemisphere (NH) PMSE observations. Such a comparison will contribute to the ongoing debate as to whether PMSE can provide a proxy for mesosphere temperature, and thus shed light on the existence of any interhemispheric asymmetry or otherwise in the polar mesosphere regions. The argument for different polar mesosphere environments spawned, in part, by the reported lack of SH PMSE observations. We report new MST radar bipolar results on PMSE characteristics and intensity from Davis (68.6°S) and Andenes (69.0°N) that reveal more prevalent occurrence rates with larger intensity at the northern polar station. Interestingly, height-occurrence and height-intensity distributions show that PMSE peak approximately 1 km higher in the south. The seasonal height-time intensity occurrence distribution of PMSE events above these two stations are considered in the context of the thermal and dynamical state of the mesosphere, as derived from satellite (i.e. AURA) and radar (i.e. MF) observations, respectively. The influence of atmospheric tides, gravity and planetary waves, and cosmic noise absorption on PMSE structure and intensity are considered. New SH observations of Polar Mesosphere Winter Echoes (PMWE) are also briefly presented.