Some Effects of the Yellowstone Fire Smoke Cloud on Incident Solar Irradiance

The influence of the 1988 Yellowstone National Park fire, smoke cloud on incident broadband and spectral solar irradiance was studied using measurements made at the Solar Energy Research Institute's Solar Radiation Research Laboratory, Golden, Colorado. Results indicate that the smoke cloud's optical depth (at 500 nm) on a smoke-affected day was a factor of 6.3 times greater than on a clear day. The daily total global-horizontal irradiance on the smoky day was 91 percent of that on the clear day. The daily total direct-normal irradiance on the smoky day was 63 percent of that on the clear day. The daily total diffuse sky irradiance on the smoky day was 340 percent of that on the clear day. Analysis of spectral solar irradiance data shows a much more severe attenuation of the shorter wavelengths (UV-visible) than the infrared region.