Summary
Mesosphere Summer Echoes (MSE) have been observed with 50-MHz VHF radars at middle (MSE) and polar latitudes (PMSE) in the Northern Hemisphere for more than 20 years. However measurements in the Southern Hemisphere were in the past rare and limited to low southern latitudes. In 2003 the Australian Antarctic Division installed a 55-MHz VHF radar at Davis, Antarctica (68.6°S), located at a comparable southern geographical latitude to Andenes, Norway (69.3°N), where the Leibniz-Institute of Atmospheric Physics operates a 50-MHz radar for more than 10 years. The occurrence of PMSE is essentially determined by temperature, water vapour concentration and electron density, but their characteristics are additionally affected by system properties of the radar as well as the experiment configuration. Therefore the comparison of observations from different stations requires the absolute calibration of the respective radar systems, in order to determine system independent parameters like the radar volume reflectivity. VHF radars at Andenes/Norway (69°N, 16°E), Resolute Bay/Canada (75°N, 95°E), Kühlungsborn/Germany (54°N, 11°E) and Davis/Antarctica (69°S, 78°E) have undergone absolute calibration using two different methods and identical equipment. We discuss the sensitivity of these different radar systems and present the first seasonal comparison of PMSE observations from different VHF radars in the Northern and Southern Hemisphere on the basis of radar volume reflectivity.