EFFECTS OF CLOUDS, ICE-SHEET, AND SEA-ICE ON THE EARTH RADIATION BUDGET IN THE ANTARCTIC

The effects of clouds, the continental ice sheet, and sea ice on the r adiation budget in the Antarctic are examined by using Earth Radiation Budget Experiment, International Satellite Cloud Climatology Project, and special sensor microwave/imager data in 1987/1988. The continenta l ice sheet affects not only the albedo but also the surface temperatu re because of elevation and hence the outgoing longwave radiation (OLR ). The high elevation of the Antarctic continent makes the radiation b udget in both polar regions asymmetric. At elevations below 2 km the O LR is reduced at the rate of 5-10 W/m(2)/km; above 2 km the rate is ab out 20 W/m(2)/km. Sea ice. which is a critical climate feedback factor , appears to have less impact on radiation than do clouds. Between 60 degrees and 65 degrees S in October, sea ice increases the top of the atmosphere albedo by about 0.2 and reduces the OLR by 7-10 W/m(2); thi s seems smaller than the formal cloud forcing, which increases the alb edo by 0.3 and reduces the OLR by 30-40 W/m(2). However, these numbers do not fully differentiate the independent effects of sea ice and clo udiness. A more detailed analysis shows that the independent effect of sea ice is as large as clouds, with clouds masking the radiative effe ct of sea ice by more than one half.