An uncommon solar halo display for subtropical latitudes occurred over Maun, Botswana, last February. It’s called a circumscribed halo, and the sight of it brought to mind another type of halo that may adorn some hieroglyphs in ancient Egypt.
Searching for solar halo phenomena requires not only some knowledge of clouds (and sunglasses to cut down on glare) but also a habit of looking up more than down as the day progresses, as some phenomena can be fleeting. Here in Botswana, occurrences of the 22° solar halo and its associated ice-crystal phenomena — induced by interactions with rays of sunlight — are common during the country’s wet season. That’s when veils of ice-crystal-laden cirrostratus clouds (the type that usually produces the halo phenomenon) often precede or follow passing thunderstorms.
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