A thick plume of sand and dust from the Sahara Desert is seen in these images blowing from the west coast of Africa across the Atlantic Ocean.

Sandstorms, which are common over the Sahara, occur when large amounts of dust particles from the desert are swept up by strong winds. They can float for days or even weeks, depending on how dry, fast and turbulent the air masses become. Winds in the higher troposphere can then transport the dust across oceans and continents. This kind of Saharan dust storm is also known as the Saharan Air Layer, which typically forms between late spring and early autumn.

These images combine different observations from Copernicus Sentinel-3 and Copernicus Sentinel-5P on 7 May 2025. The Sentinel-3 optical image on the left shows a dense, orange plume of Saharan sand over approximately 150 000 sq km of the eastern Atlantic Ocean. The small islands of Cabo Verde peek out from beneath the clouds in the top left corner.

In the right image, a Sentinel-5P view has been overlaid on the Sentinel-3 image to show the concentration of aerosols in the dust plume: darker tones of orange denote denser aerosol concentrations. Sentinel-5P carries the state-of-the-art Tropomi instrument that maps a multitude of trace gases and can measure the aerosol index, which is an indicator of the presence and intensity of aerosols such as dust.

This combination of Sentinel-3 and -5P satellite imagery allows scientists to improve their understanding of these massive dust clouds, and forecasters to provide better air quality predictions.

These data are extremely important for air-quality models used by, for example, the Copernicus Atmosphere Monitoring Service to forecast air quality on a global scale by assessing the concentration of atmospheric particulate matter, as well as to monitor and predict how far the dust layer will travel and how it develops and therefore the effects it will have locally.

Sandstorms can be a major contributor to reduced air quality and can cause hazards to human health. The suspended particles, in fact, cause hazy skies, trigger air quality alerts and, when breathed, can lead to cardiovascular conditions and lung problems.

On the other hand, the travelling Saharan dust plays an important role in our ecosystem. It is a major source of minerals and nutrients for phytoplankton and for ecosystems on the other side of the world, including the Amazon rainforest.