A clear sky

Sky Color and Visibility

Learning Objectives:

  • Determine what factors affect sky color and visibility
  • Describe how these factors affect sky color and visibility

Supported NGSS Performance Expectations:

  • 5-ESS2-1: Develop a model using an example to describe ways the geosphere, biosphere, hydrosphere, and/or atmosphere interact.
  • MS-ESS2-1: Develop a model to describe the cycling of Earth's materials and the flow of energy that drives this process.
  • MS-ESS3-3: Apply scientific principles to design a method for monitoring and minimizing a human impact on the environment.

Sky Color

Shown on the panel are a series of sky color images. Click on each image on the bottom of the panel to enlarge it.

Observe the differences in sky color in the images and answer the following questions.

1- Describe the difference in color in each image.

2- What do you think could cause these differences in sky color?

Explain

What are aerosols?

Aerosols are small particles in the atmosphere. They can come from anthropogenic (man-made) sources such as smoke and fossil fuel emissions. They can also come from natural sources like ash, pollen, and dust.

NASA studies aerosols in multiple ways using satellites for total column measurements, ground and airborne missions for in situ measurements, and citizen science.

3- After learning about aerosols, make a prediction. How do you think aerosols affect sky visibility?

The diagram illustrates the difference in size between PM2.4, PM10, a strand of human hair, and a grain of sand. PM2.5 are generally 2.5 micrometers or smaller, while PM10 are 10 micrometers or smaller. Human hair is about 50-70 micrometers and a grain of sand is about 90 micrometers.

Visibility

In the panel, the images represent the sky with different levels of visibility. Select each of the images at the bottom of the panel to enlarge the image. When you are finished, answer the following questions.

4- Which image do you think would have the highest amounts of aerosols? Explain.

Aerosols Effect on Sky Color and Visibility

We can observe the effect of aerosols by looking at the sky. This is because aerosol concentration in the atmosphere changes how the sky looks.

Aerosols scatter light. When there are no aerosols in the sky the sky is deep blue and has high visibility. When there high levels of aerosols the sky becomes pale or milky and hazy. In the panel, view how sky color and visibility are affected by aerosols.

Summarize Findings:

5- What factors affect sky color and visibility?

6- How do they affect sky color and visibility?

Related Resources:

This virtual lesson is modified from the original Elementary GLOBE Learning Activity    Why (Not) So Blue?  created by the  UCAR Center for Science Education . There is an  activity mat (poster) for the original activity .