Earlier this week, strong winds over the Saharan Desert blew westwards, pushing clouds of dust and sand over southern and central Morocco and out into the Atlantic Ocean.

This is part of a weather phenomenon known locally as ‘La Calima’, which blows airborne dust across Western Africa and the Canary Islands. In this case, the wall of dust stretched for 1300 km, reducing visibility and posing a health risk. Residents in the affected areas were advised to keep windows and doors closed and minimise exposure to the air.

This satellite image shows the Saharan dust storm over the Atlantic Ocean, with the islands of Fuerteventura and Lanzarote visible off the west coast of Morocco, as well as Gran Canaria, Tenerife and La Gomera further West. The image contains data from Copernicus Sentinel-3’s imaging spectrometer, the Ocean and Land Colour Instrument, known as OLCI.

The Sentinel-3 mission contributes images over both oceans and land to Copernicus, the European Commission’s unique satellite-based environmental monitoring programme. Over land, the Sentinel-3 satellites monitor wildfires, map land use, and provide data on vegetation health, as well as measuring the height of rivers and lakes. Over oceans, the mission measures temperature, colour and sea surface height, as well as sea ice thickness.