Searching for Rainbows

Image courtesy of Earth Science Picture of the Day. Credit: David Lien, Planetary Science Institute

Ubiquitous airborne particles called aerosols, which can have a big impact on the energy budget, are one the most poorly understood factors that influence our climate. Could searching for rainbows help scientists pinpoint the impact of the perplexing particles? Brain Cairns, the instrument scientist for the Aerosol Polarimetery Sensor (APS) on NASA’s Glory Mission, explains:

“The way that we diagnose whether we have small aerosol particles, big aerosols particles, non-spherical particles, ice particles, cloud droplets is primarily using polarization.

This is the most obvious and visually enticing example of polarization. On the left, is a picture that shows a rainbow. A polarizer was used, so you can actually see that rainbow. On the right, there’s no rainbow because there was no polarizer. The reflected light is so bright you simply can’t see the rainbow without a polarizer.

Why do we want to measure things like rainbows? It’s because the angular distribution and color of that light tells you exactly how big those close droplets are, and it tells you what the width of the size distribution is. This kind of information is what we use when we’re trying to diagnose how clouds form.”

–Adam Voiland, NASA’s Earth Science News Team