Bay Area residents were treated to an atmospheric spectacle on Saturday afternoon when a brilliant "22 degree halo" appeared around the sun. This optical phenomenon, as captured in a photo by Hoodline San Francisco, was visible across various locations, drawing the gaze of many towards the skies.
The halo was the work of cirrostratus clouds, dwelling at altitudes between 20,000 and 35,000 feet where temperatures plummet well below freezing. Ice crystals within these high-level clouds are the culprits behind the bending of sunlight at a precise 22 degree angle, giving rise to the halo that encircled the sun. While not a daily occurrence, the halo is certainly not unheard of, yet its appearance never ceases to be less than a delightful surprise for those lucky enough to witness it.
As per an explanation detailed on the National Weather Service website, the atmosphere is a stage for a variety of colorful displays, halos included. Light, when refracted by water drops or ice crystals acting as prisms, disperses into a spectrum of colors. This shattering of light into a rainbow is the foundation for these atmospheric optical phenomena. NWS elaborates that halos, sundogs, and sun pillars are all results of this prismatic action, depending on the position and nature of the ice crystals in the sky.
For those unaware, a halo is typically a luminous white ring, though it can sometimes exhibit hues, forming 22 degrees around the sun or moon when light refracts off ice crystals within cirrus clouds. Sundogs and sun pillars share a similar origin but manifest themselves differently due to the ice crystals' varying orientations relative to the viewer. While sundogs appear as colored spots beside the sun, pillars show as vertical shafts of light. Each painted by the same brush of refracted light; unique in its presence was the halo over Saturday's Bay Area, a reminder that the sky is more than just a backdrop for our weather - it is a canvas for nature's grand optics.
While the Bay Area is known for its iconic fog and rolling hills, the sky above often holds its own allure, providing us with transient artwork made up of sunlight and ice. Residents are encouraged to keep an eye on the heavens for such displays, as every so often, the conditions align to decorate the sky. Saturday's halo was just one instance of the atmosphere's capacity for beauty, a phenomena that requires no embellishment beyond its own natural splendor.
