© Amie Quirarte
SFGate reader Amie Quirarte of Tahoe Vista noticed what's known as a 22 degree halo at around 1 p.m. while sitting in her backyard with her husband, and shared the image above.
"I have not seen this before," Quirarte, who works as a real estate agent in Tahoe, wrote in a message to SFGate. "I looked up in gratitude and noticed a rainbow around the sun. I instantly told my husband to check it out. When he reassured me I wasn't crazy, I took a couple photos and posted them on social media. Within a few minutes, I had comments from friends saying they could see the same phenomenon in the sky.
She added: "I strongly believe in the power of the universe and today, I'm believing the rainbow in the sky is for all of our fallen soldiers."
These halos of light occur around the sun or moon when light is refracted by ice crystals associated with high-level clouds known as cirrostratus.
"When the light is bent by the ice crystal, it's like a prism," explained Christopher Johnston, a meteorologist with the National Weather Service office in Reno. "When the incoming sunlight hits the ice crystal, the light instead of going in a straight path is bent at a 22 degree angle. That's where you get the name 22 degree halo."
Johnston said the Tahoe sky was covered in a thick layer of cirrostratus clouds Monday, and these were at 25,000 to 30,000 feet where the temperatures would have been well below freezing. At these high elevations, the clouds are filled with tiny ice crystals.
Johnston says he has seen a 22 degree halo in the Tahoe area a couple times, but he observed this optical phenomenon often in the winter while growing up in Colorado and Illinois.
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