Last update: September 18th, 2019 at 6:00 pm
The skies over Portugal and Spain took on an unusually yellow hue this week. The culprit was a vast plume of sand and dust pushed northward from the Sahara desert by the calima, a warm southeasterly wind common in northern Africa in the winter. The calima often sends dust toward the Canary Islands, but a low pulled the winds north on February 21, 2016.
At 2 p.m. local time (14:00 UTC) on February 21, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired a natural-color image (lower) of dust sweeping over the Iberian peninsula. Other satellite sensors, including the Ozone Monitoring Instrument on Aura and the Ozone Monitoring Profile Suite on Suomi NPP, detected the plume as well. British astronaut Tim Peake also noticed the dust from the International Space Station; he shared his view of the dust (upper image) via Twitter on the same day.
The dust was transported north by an area of low pressure aloft in combination with a weak surface low-pressure system, according to a Weather Channel meteorologist. The transport of Saharan dust to the Iberian peninsula is fairly common, and research teams have analyzed similar dust plumes on several occasions. Researchers have shown, for instance, that most Saharan dust that arrives over the Iberian peninsula tend to be at an altitude of about 2.5 to 4.5 kilometers (1.6 to 2.8 miles).
Africa is the world’s largest source of dust to the atmosphere, contributing about 70 percent of the global total. Airborne mineral dust from the world’s deserts delivers nutrients to the land and ocean, and affects the atmosphere and climate.