Behind the Forecast: The science of sunrises

LOUISVILLE, Ky. (WAVE) - Each morning and evening (when it’s not cloudy or raining) the sky puts on a show. Have you ever wondered why?

Sunlight hits a molecule in the atmosphere and scattering occurs, dispatching some of the light’s wavelengths in different directions. Oxygen and Nitrogen, two of the main components in our atmosphere, are small compared to the wavelengths of light, which causes them to scatter the shortest wavelengths best (blue and purple).

Our sky is blue due to Rayleigh scattering. Rayleigh scattering is dependent upon the wavelength of sunlight. When the sun is directly overhead, light scattering is at its maximum, and a bright blue is seen. At sunrise and sunset, the wavelength of visible light increases, causing us to see more red.

Large pollutions of particles in the lower atmosphere mute and muddy the colors of sunrise because they absorb more light and scatter all the wavelengths more or less equally.

We see brighter sunsets in the fall and winter particularly, especially in the Eastern half of the country, because the air along the path of the sun rays tends to be dryer and cleaner.

Clouds snag the last red-orange rays of sunset and the first lights of sunrise and reflect them to the ground. The best sunsets occur in skies with upper and mid-level clouds like altocumulus and cirrus clouds, NOAA reports.

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