The Role of Atmospheric Conditions in Determining Intensity of Crepuscular and Anticrepuscular Rays

Abstract

During the summer of 2006, daily observations of crepuscular and anticrepuscular rays were made around sunset from central Oklahoma. A relative scale of ray intensity was developed and used to relate the rays to concurrent meteorological conditions. Evidence is presented suggesting that both topography and clouds can cast shadows leading to rays. Relationships are hypothesized between estimated ray intensity and atmospheric variables, and predictive equations are developed for ray intensity and assessed using data from the summer of 2008. Except for a few cases in which rays were traced back to topography east of the Rocky Mountains, the most intense rays were produced by towering cumulus (Cu) and cumulonimbus (Cb) clouds to the west after hot days with light winds.