VOLUMETRIC MEASUREMENT OF ULTRAVIOLET ENERGY IN AN URBAN ATMOSPHERE

This report describes a physical sensor developed to measure all of the UV (300 to 380 nm.) radiation incident on a volume in the atmosphere. Preliminary data is presented for Los Angeles during the smog season with the volumetric and the horizontal-plate sensors. For the smoggy atmosphere the volumetric values ranged from about 2.6 to 3.3 times those of the horizontal-plate sensor; for a clean atmosphere the range was from 2.0 to 3.2. The ratio of volumetric to the vertically incident radiation measurements showed an increasing value with increasing solar zenith angle, with a peak in the vicinity of 70 degrees. A linear line of regression is given for the volumetric radiation as a function of the vertically incident radiation for intensities below 30 w./m.2 The same relationship appears to be applicable for both polluted and unpolluted atmospheres. © 1969, American Chemical Society. All rights reserved.