Last week, a fascinating mass of air loaded with Sahara desert sand enveloped much of Italy, transforming the sky into a captivating display of milky and yellowish hues. This phenomenon sparked a wave of theories on social networks. Many users, abandoning the Sahara hypothesis, leaned towards alternative scenarios such as climate control through geoengineering. The duration and intensity of the event fueled debate, stimulating imagination and suspicion. Let’s explore this topic together to dispel any doubts and gain a clearer understanding of both the situation and our skies.

Is the substance in the sky really sand?

The answer is both yes and no. Yes, because it is Sahara sand, but not in the form we typically imagine. These are not the grains of sand found on our beaches. Sahara dust particles are extremely small, on the order of micrometres, ten times smaller than a human hair. These particles remain suspended in the atmosphere thanks to strong winds like the sirocco, which lift and carry them far away. It would therefore be more accurate to refer to it as Sahara dust.

How does the sand travel so far?

Although the Sahara seems distant from Italy, Sahara dust can travel much farther. For example, in March 2022, it reached as far as the United Kingdom (an event discussed in this blog). Once suspended in the atmosphere, these particles can linger there for a long time, moving with the winds and atmospheric currents. Consider the spread of particles emitted during the 2010 eruption of Iceland’s Eyjafjallajökull volcano, which caused serious air navigation problems across Europe.

How can we be sure it’s Sahara sand?

Data collected from the observatory “Ottavio Vittori” on Mount Cimone by ISAC (Institute of Atmospheric Sciences and Climate) of CNR show a significant increase in particles with diameters greater than one micron, consistent with the size of Sahara dust particles and above the threshold for identifying dust transport. Satellite images and air mass tracking programs from the US NOAA (National Oceanic and Atmospheric Administration) also confirm the Saharan origin of this dust cloud. Furthermore, atmospheric particulate monitoring stations equipped with chemically analyzable filters provide additional evidence.

Is Sahara dust transported only when there is wind?

Wind speed varies with altitude. Even when it seems calm at ground level, winds can be strong at higher altitudes. These upper-level winds are responsible for transporting sandy material, regardless of surface calm.

Why is this phenomenon more frequent and lasting longer nowdays?

In recent years, changes in atmospheric circulation have made this phenomenon more common. Italian summers traditionally featured the anticyclone of the Azores, which provided stable weather. Today, also due to increased Atlantic Ocean temperatures, the anticyclone of the Azores has been replaced by the subtropical anticyclone of the African. This extends from the Sahara, bringing not only dust but also high temperatures and humid heat.

In conclusion, understanding complex phenomena like Sahara dust transport requires informed curiosity and research based on reliable data. It’s crucial to avoid hasty conclusions or theories unsupported by concrete evidence. Everyone has the right to express doubts and curiosity, but the most fruitful approach remains deepening our understanding of the topics. This way, we can navigate environmental challenges with awareness and responsibility, preserving clarity both in our understanding and in our public discourse.