Why the Catalinas glow pink at sunset

Amazing atmospheric optics in action.

Often times during the year, the peaks of the Santa Catalina Mountains glow during dusk and dawn. It’s a phenomenon known as “alpenglow”. Here’s how it works.

As the sun sits just below the horizon line, indirect sunlight is reflected by dust particles, water vapor and ice crystals in the atmosphere. This reflected light is then cast onto the mountains opposite the rising or setting sun.

The net result? A short-lived, but soft pink or purple glow on the mountain slopes surrounding Tucson.

It’s important to note that alpenglow is only visible just before the sun rises or sets. To see today’s sunrise and sunset times, click here.

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