A Meteorological Rarity: Snow Across the Atacama Desert

The Atacama Desert, famed for its aridity and status as the driest non-polar desert on Earth, has experienced an extraordinary event: snowfall. Recent satellite imagery from NASA's Landsat 8, 9, and Terra satellites reveals the snow's source: two storms that occurred just days apart. This meteorological rarity led to the temporary shutdown of the Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope on the Chajnantor Plateau.

The snow spread across the Andes Mountains and reached the Pacific coast. While some locations received rain, the city of Taltal saw approximately 1.6 inches of precipitation over three days, ten times its usual annual rainfall. The Atacama typically only sees around 0.6 inches of precipitation per year. This desert is renowned for receiving moisture primarily through fog, as it is considered the driest non-polar desert globally.

Typically, the driest regions of the Sahara receive about 0.8 inches of precipitation annually. The unusual precipitation in the region is attributed to "cutoff lows," low-pressure systems that detach from the jet stream winds, bringing cold air onto warm air and resulting in rain and snow. In this instance, the cutoff low was driven by an exceptionally large atmospheric trough, contributing to the extended snowfall.

Climate change may be a contributing factor, as a stronger El Niño system in the Pacific has brought storm systems closer to Chile, leading to abnormal levels of rainfall and triggering destructive mudflows and flash floods. The same conditions caused snow to fall in the Atacama last year, a phenomenon not seen there since 2011.

Atmospheric scientist René Garreaud of the University of Chile noted that such events occur only a few times per decade in the region. The Atacama has become a winter wonderland, with weather patterns locked in the swirls of the Earth and the moon.