Wildfires and Sunsets

February 03, 2011


: Stu Witmer
Summary Author: Stu Witmer

A few years ago, we happened to be in Central Idaho during a season of unusually large wildfires. The above photo, taken from our campsite at Craters of the Moon National Monument, clearly shows how the aerosols and smoke produced by the nearby fires can add color to a sunset. Smoke rises from behind a ridge until it is blown by high-level winds. Where the light from the setting Sun is filtered through the smoke we see red, orange and yellow colors. Otherwise, the cloud is smoke grey. The smoke particles are of the right size (slightly larger than molecules of air) to scatter the shorter wavelengths of light (blue and green colors) out of our view. At sunrise or sunset, this reddening is enhanced by the longer path length of the Sun’s rays. Away from the smoke, the sky is quite blue with a few high clouds. Photo taken August 29, 2007.

Photo Details: Camera Maker: NIKON; Camera Model: E5700; Focal Length: 8.9mm (35mm equivalent: 35mm); Aperture: f/2.8; Exposure Time: 0.0005 s (1/2000); ISO equiv: 100.