Saharan dust launches off the Moroccan coast

Today’s Image of the Day from NASA Earth Observatory features a plume of Saharan dust pouring off the coast of southern Morocco.

The Sahara Desert is the world’s biggest source of airborne dust. Each year, it releases hundreds of millions of tons of mineral dust that are lifted into the atmosphere and transported across vast distances up to thousands of miles. 

Saharan Air Layer 

The transport of Saharan dust is primarily driven by the trade winds and atmospheric phenomena such as the Saharan Air Layer (SAL). This dry air mass often accompanies tropical storms across the Atlantic, sometimes even influencing the development and intensity of hurricanes. 

“From late spring to early fall, it is common for the dry, dusty Saharan Air Layer to carry the particles westward across the Atlantic Ocean high in the atmosphere. With different wind patterns in the winter and spring, dust emerging from North Africa can drift over the United Kingdom and western Europe at relatively low altitudes,” said NASA.

“Saharan Air Layer activity subsides after mid-August, according to NOAA, making it less likely that the plume shown here is bound for a transoceanic journey. Instead, it arcs to the north after blowing out over the ocean. Earlier in the summer, however, several clouds of fine dust from the Sahara reached the United States, creating hazy skies over Texas.”

Impacts of Saharan dust 

Saharan dust plays a crucial role in global climate and environmental systems. For example, Saharan dust can affect weather patterns by absorbing and scattering sunlight, influencing temperature and cloud formation. It also plays a role in fertilizing ecosystems, such as the Amazon rainforest, by providing essential nutrients like iron and phosphorus. 

However, Saharan dust also has more complex impacts. It can reduce air quality, leading to respiratory issues in people living downwind of the dust. In addition, the dust impacts ocean health by contributing to algae blooms, which can create dead zones in marine environments.

Dust clouds and human health

In a recent study from Texas A&M University, researchers explored the potential health impacts of bacteria and fungi that travel within dust plumes. 

The team found traces of several pathogens known to cause disease in humans, as listed by the World Health Organization (WHO).

Study co-author Dr. Daniel Spalink noted that while the DNA of several pathogenic bacteria and fungi were identified in African dust, it is not yet known if they can infect us and make us sick. 

Summertime dust events

“Scientists are interested in summertime Saharan dust events in part because of the influence they can have on large storm systems.

Dry, stable, dust-laden air can inhibit tropical cyclone formation in the North Atlantic. And in a new study, researchers found that dust can modulate the amount of rainfall brought by these storms,” noted NASA.

“Using a machine-learning model based on meteorological data, NASA’s IMERG (Integrated Multi-Satellite Retrievals for GPM) precipitation estimates, and other satellite measurements, the study’s authors found that dust optical depth – a measure of how much light filters through a dusty plume – was a key predictor of rainfall from tropical cyclones.”

The researchers concluded that smaller amounts of dust particles promote the formation of rain clouds, while the sunlight-blocking effects of large dust clouds ultimately suppress precipitation.

Saharan dust storms

Dust storms in the Sahara Desert are some of the most far-reaching in the world. These storms, also known as haboobs, occur when strong winds lift large quantities of sand and dust from the desert’s surface into the atmosphere. 

Saharan dust storms vary in intensity, with some being relatively mild while others are severe, reducing visibility to almost zero and creating hazardous conditions.

They often happen in the spring and early summer when the temperature difference between the desert and the surrounding regions creates strong pressure gradients, fueling powerful winds.

Ultimately, these dust storms are a natural part of life. They shape the landscape over time by eroding rock formations and redistributing sand dunes.

Despite their destructive potential, they are also a reminder of the dynamic and interconnected nature of Earth’s climate systems.

The image was captured on August 24, 2024 by the VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite.

Image Credit: NASA Earth Observatory 

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