What causes colorful sunsets and sunrises?

This week’s weather question comes from Dave Kerr of Columbus, Georgia. He wants to know what causes colorful sunsets and sunrises.

Typically a more vibrant sunset has more deep orange and red colors – and cloud cover plays a large role
in displaying those colors.

High and thin clouds (like wispy cirrus ones) are the best at scattering and reflecting the longer wavelengths of the electromagnetic spectrum – which are the deep oranges and red we see.

But when we have thick, low clouds it makes it hard for the same orange and red colors to be projected in the sky.

Pollutants also play a role in sunsets. The larger the particles of dust and pollution – the more they absorb
sunlight – which actually deters or mutes vibrant sunsets. That’s why areas like Los Angeles, where there is often heavy haze, has muted sunsets.

One of the reasons we see such beautiful and bright sunsets in the fall and winter, especially in the southeast, is because the air is cooler and drier . This ‘cleaner’ air is better at scattering and reflecting sunlight and creates such colorful sunsets.

If you’ve ever heard the phrase “Red sky at morning, sailors warning. Red sky at night, sailors delight” then that helps explain this. In the Northern Hemisphere a red, orange sunset often indicates clear air to the west since particles are smaller to create the vibrant sunset. We also know that storm systems (but not always and in the most general sense) travel west to east. When the sun sets in the west it is shining on clouds to the east (indicating that there is now clearing).

But in the the morning, it’s the complete opposite. A red sky could indicate an approaching storm. Since the sun rises in the east, sunlight is shining off of clouds to the west – where most of our cloud cover and storms track from.

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