cirrus

Latin cirrus meant a curl, a ringlet, a tendril of hair. The word was domestic, intimate—a mother describing her child's curls, a poet describing a lover's hair. It had nothing to do with weather until Luke Howard, a London pharmacist and amateur meteorologist, published his Essay on the Modification of Clouds in 1802 and gave the clouds Latin names.

Howard chose cirrus for the high, wispy clouds that streak across the sky like strands of white hair. The name was immediately recognized as perfect. Cirrus clouds form above 20,000 feet, where temperatures are so cold that water vapor freezes directly into ice crystals. The crystals fall and are swept sideways by upper-atmosphere winds, producing the characteristic streaked, fibrous appearance that reminded Howard of curled hair.

Johann Wolfgang von Goethe was so moved by Howard's cloud classification that he wrote a series of poems in the meteorologist's honor. The cirrus poem described the clouds as aspirations rising toward heaven, the highest form, the closest to the divine. Howard's taxonomy transformed clouds from shapeless masses into named, knowable things.

Cirrus clouds are weather predictors. When cirrus thickens into cirrostratus, it often signals an approaching warm front and rain within 24 to 48 hours. Sailors and farmers have watched cirrus for centuries, even before they had a name for it. Howard gave the observation a word, and the word made the knowledge transmissible.