Interannual variability of Antarctic snow melt events derived from scatterometer data

Microwave backscatter from the Antarctic snow cover depends on the surface roughness, properties and structure within the snow cover, and moisture content. Small increases in moisture content produce a significant reduction in backscatter. This acts as a sensitive indicator of the occurrence of snow melt conditions. The ERS wind scatterometers provide an almost continuous sequence of observations of microwave backscatter coefficients over Antarctica north of latitude 79/spl deg/S since August 1991. Normalised values of the backscatter coefficient are calculated by removing the anisotropic contributions, mainly from a dependence on incidence angle. Depression of these values below a long term dry snow average indicates occurrence of snow melt. The results show a large variability between summer seasons of melt extent and duration. There was very extensive and intense melting in 1991-92, with much less melt in following seasons probably in response to a cooling following the Pinatubo eruption. 1997-98 has extensive melt with a total area approaching that for 1991-92.