Top-of-atmosphere radiative cooling with white roofs: experimental verification and model-based evaluation

Abstract

We evaluate differences in clear-sky upwelling shortwave radiation reaching the top of the atmosphere in response to increasing the albedo of roof surfaces in an area of India with moderately high aerosol loading. Treated (painted white) and untreated (unpainted) roofs on two buildings in northeast India were analyzed on five cloudless days using radiometric imagery from the IKONOS satellite. Comparison of a radiative transfer model (RRTMG) and radiometric satellite observations shows good agreement ( R ^2 = 0.927). Results show a mean increase of ∼50 W m ^−2 outgoing at the top of the atmosphere for each 0.1 increase of the albedo at the time of the observations and a strong dependence on atmospheric transmissivity.

Keywords

• aerosol loading
• cool roof
• radiation balance
• satellite radiometry
• surface reflectance
• urban systems