This award is for support for a two year study to deternine the surface area and effect on energy balance of lakes on the Greenland Ice Sheet. The objectives of the work are to determine the concentration of lakes, snow, and ice on parts of the Greenland ice sheet which experience vigorous summer melting, and to incorporate these concentrations into an energy balance calculation. The concentrations of lakes, snow, and ice will be determined by using satellite passive microwave data, with a method similar to that now routinely used for determining sea ice concentrations and types. Satellite synthetic aperture radar and AVHRR data will serve as auxiliary sources of information about the ice sheet, for location of general areas in which lakes form, and for use in determining microwave characteristics of the ground surface. The effect of lake formation on energy balance in the lake region of the ice sheet will be determined by extending and applying a surface energy balance model.