Cloud type and cloud cover effects on the surface radiative balance at several Polar sites

Summary ?The present work concerns measurements performed at five Polar sites in order to study the influence of cloud type and cloud cover on the surface radiative balance. Cloud cover index was retrieved with the Kasten and Czeplak formula (1980), and comparison with observed values showed the possibility of applying this formula in Polar regions. The Duchon and O’Malley (1999) methodology was adopted to estimate the cloud types present during the measurement period for each site. The results show that during the Antarctic summer clouds have a warming effect on the surface, while during a melting event recorded in the Arctic site clouds have a net cooling effect on the surface. This result allows us to conclude that, during a melting period a different cloud type formation, and a lower surface albedo, modify the effects of clouds on the surface radiation balance. Received April 5, 2002; revised August 1, 2002; accepted August 17, 2002