A new albedo parameterization for use in climate models over the Antarctic ice sheet

A parameterization for broadband snow surface albedo, based on snow grain size evolution, cloud optical thickness, and solar zenith angle, is implemented into a regional climate model for Antarctica and validated against field observations of albedo for the period 1995-2004. Over the Antarctic continent, modeled snow grain size exhibits expected behavior. The agreement between modeled and observed albedo at Neumayer, Dronning Maud Land, is very good, and subtle variability in albedo is well captured by the model. December-February mean differences in modeled and observed net shortwave radiation range from -8.7 to +3.8 W m(-2) between 1995 and 2004, with a mean value of -2.7 W m(-2). This is a considerable improvement compared to the previous albedo parameterization in the model, which led to overestimates of the net shortwave fluxes by +15.0 to +22.7 W m(-2), or 40-55% of the observed net shortwave flux, in the same period.