“The Color of Clouds”

by Caleb, KE0FOE

As we continue with our series covering JetStream, The National Weather Service’s new Online School for Weather, the topic this time is: Clouds.

Light from the Sun is considered to be white – meaning the Sun equally radiates all colors within the visible spectrum. However, down here on the Earth’s surface, we see anything but white in the sky – except when it comes to clouds. The reason for this is because of filtering and scattering by our atmosphere.

During sunrise and sunset, the sun appears orange and red because all other colors are filtered by the atmosphere. However, in the middle of the day, the sun looks yellow due to less filtering, and the sky appears blue because of scattering of blue light by air molecules. Because air molecules are similar in size to the wavelengths of blue light, the color blue scatters in our atmosphere making the sky appear blue during most of the day.

Clouds, on the other hand, are composed of water droplets which are much larger than air molecules. In fact, these droplets are so big that they tend to scatter all light from the sun equally during the middle of the day. Therefore, even though the Sun appears yellow on the Earth’s surface during midday, cloud tops look white and represent the true color of our Sun.

Of course, during sunrise and sunset, clouds will then appear to reflect the orange and red colors that are predominant at those times.

There are a lot of amazing facts and projects about earth’s atmosphere that you and your family can discover on the National Weather Service’s new Online School for Weather called JetStream. Visit their website: weather.gov/jetstream