High cloud ice crystals cause: solar halo, corona, sundogs

San Diego's most colorful liquidambars

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Publish Date

Nov. 29, 2021

Solar corona

Atmospheric Ice-Crystal Effects are often observed, starting this time of year, because of the frequent appearance of high clouds made of tiny bits of ice. The most familiar of these optical effects is the 22˚-radius halo, or ring, around the sun or the moon. Less often seen is a “corona” (a colored disk around the sun or moon — not the same as the solar corona seen during total eclipse), “sundogs” (colored arcs left and right of the sun), the sun pillar (a vertical column of light above the rising or setting sun), and a host of other rare and inconspicuous optical phenomena. All of the optical effects mentioned are a consequence of sunlight or moonlight refracting through or reflecting from the tiny facets of ice crystals in cirrus and other types of high clouds.

Most liquidambars in our area regain their light green foliage by late February.

Liquidambar Trees, or sweet gums, the deciduous trees gracing front yards, parks, and campuses throughout the San Diego area, have been putting on an exceptionally colorful show. The leaves of some varieties turn to purple or red; the leaves of other varieties fade to golden yellow. Still other varieties hold on to their green leaves until sometime in December. Most liquidambars in our area regain their light green foliage by late February.