SPECTRAL MEASUREMENTS OF INFRARED SKY RADIANCE.

Recent measurements of the thermal infrared radiance of the sky are presented, showing the spectral distribution of radiation from the zenith. Samples of the data are compared with computer calculations for similar meteorological conditions. The computer calculations are based on the computer program LOWTRAN 3B. In general, the data confirm expectations that Tucson, with clear skies and dry air, is a good location for infrared radiative cooling systems. For an idealized selective surface at 25 degree C. The average cooling rate would have been 89 w/m**2 in Tucson (8/14/78 to 10/5/78), and 65 w/m**2 in San Antonio (9/21/78 to 10/6/78). If this idealized selective surface were allowed to cool down, it would reach an average temperature of minus less than degree C in Tucson and minus 7 degree C in San Antonio.