How does atmospheric pollution affect sky color?

Atmospheric pollution changes the sky's color by introducing different types of particles into the air, which scatter light differently than tiny gas molecules.

The key difference is particle size.

• Rayleigh Scattering (Clean Sky): Caused by tiny gas molecules (like nitrogen and oxygen) that are much smaller than the wavelength of light. This scatters blue light most.
• Mie Scattering (Polluted Sky): Caused by larger particles (like dust, smog, soot, wildfire smoke, or aerosols) that are closer in size to the wavelength of light.

Mie scattering is not as dependent on wavelength as Rayleigh scattering. It scatters all colors of light (red, green, blue, etc.) more or less equally. This effectively "adds" white light to the sky.

Effects of Pollution

1. Hazy or White Sky: On a polluted day, the blue light from Rayleigh scattering is mixed with the white light from Mie scattering. This dilutes the blue, making the sky appear a pale, washed-out blue, greyish, or even brownish-white.
2. More Vivid Sunsets: Pollution can sometimes make sunsets more dramatic. The extra particles in the air can scatter and absorb even more of the blue and green light, allowing only the most intense reds and oranges to pass through, creating a deep red sunset.