Saharan intrusions, more than just reddish snow

In February 2021, Saharan dust created spectacular images of snow-capped peaks tinged with a reddish color.

But beyond their viral nature on social media, these episodes also pose a risk to human health. Therefore, monitoring and tracking them should not be neglected. In this task, the air quality sensors offered by Arantec can play an important role.

What are Saharan intrusions?

Saharan intrusions, also known as African episodes or calimas, are air masses pushed by the wind and laden with sand and other particles from the desert that cross the Mediterranean or the Atlantic Ocean.

This particulate matter is primarily composed of minerals. Elements such as iron, phosphorus, calcium, and magnesium are abundant. In fact, as a curiosity, it should be noted that these contributions are essential for maintaining soil fertility. For example, 100% of the phosphorus found in the oak forests of the Montseny massif originates from locations such as the Bodele Depression in Chad, northern Sudan, or the Nubian Desert (1). In other words, Saharan intrusions also have positive effects that can be observed in the reduced intensity of hurricanes that hit the coasts of the Caribbean and the United States.

The occurrence of this phenomenon typically peaks during the spring season. However, it can also happen during winter when surface winds associated with low-pressure systems prevail, as noted by Nastos (2).

Factores meteorológicos de la irrupción de polvo sobre Canarias. Fuente: Meteored

Why is monitoring this Saharan dust important?

The transport of Sahara sand is a natural phenomenon, sometimes intensified by human activity. However, despite its origin, it has significant impacts on health, agriculture, and transportation. Therefore, monitoring and issuing alerts for Saharan dust is a crucial task.

Continuous monitoring is carried out by projects such as the Sand and Dust Storm Warning Advisory and Assessment System Project (SDS-WAS) by the World Meteorological Organization (WMO). This initiative has three regional nodes, with the one for the Middle East, North Africa, and Europe located in Barcelona. Its purpose (3), shared by the other centers (in China and the USA), is to:

  • Provide a basic surveillance and prediction system (up to 3 days in advance) validated for the research community and countries within the region.
  • Maintain an open web portal with information on dust and sand storms, where all observation systems, both satellite-based and ground-based, as well as prediction models, can contribute.
  • Implement an accessible web-based database with historical data from observations (satellites and ground-based remote sensing) and models to enable analysis.

These objectives indicate that two of the main sources of information are space satellites and ground-based remote sensing networks, which provide clear images like the one below, depicting the Saharan dust storm on February 6. By combining these sources of information, along with others, prediction models are developed to communicate alerts.

The role of sensor technology in monitoring Saharan intrusions

The advancement of sensor technology in recent years allows these instruments to complement the information collected by satellite systems and the mentioned ground networks.

However, their main strength lies in their potential for hyperlocal monitoring. They can provide firsthand data on aspects such as air quality resulting from a Saharan intrusion, enabling local authorities to take additional measures if deemed necessary.

One of the possibilities offered, for example, by our dust sensors. These devices, which can be implemented in the Smarty Air solution, allow real-time measurement of particle concentration, with the information being visualized through the Smartyplanet web platform.

The impact of Sahara sand on health: a matter of size

Saharan intrusions have a significant impact on air quality, which decreases drastically. In fact, these events can multiply particle concentrations by 3 (4).

The presence of Saharan dust in suspension also poses health problems for vulnerable population groups (children, pregnant women, elderly individuals, and people with respiratory and cardiovascular problems). In a way, its effects parallel those of forest fire smoke that we discussed some time ago.

This consequence is a direct result of the size of the particles carried by the wind. In this regard, three particle sizes are distinguished:

  • Coarse particles, with a diameter less than or equal to 10 microns (PM10)
  • Fine particles, less than or equal to 2.5 microns (PM2.5)
  • Ultrafine particles, not covered by current legislation, comprising materials with diameters smaller than 0.1 microns.

The air masses from the Sahara are abundant in coarse particles. Due to their size, these materials are trapped by the mucous membranes of the respiratory tract. However, a study published in 2021 has shown that their increase is also associated with higher mortality from cardiovascular problems, with a 2% increase for every 10 micrograms per cubic meter of air (5).

Greater concern is posed by fine particles (PM2.5), which sometimes originate from the segregation of PM10. Their small diameter allows them to reach the pulmonary alveoli, passing through them and entering the bloodstream. In these cases, a direct relationship with increased mortality has also been observed (6).


Although African dust has an undeniable positive aspect that contributes to the balance of the planet, the negative effects pose a problem resulting in economic and human losses.

Monitoring the concentration of suspended particles in the air using sensor technology, for example, can help make decisions to mitigate these consequences. After all, investing in advancements that improve quality of life has its rewards.

Sources consulted:

  • (1) Goudie, A., & Middleton, N. (2001). Saharan dust storms: nature and consequences. Earth-Science Reviews, 56(1-4), 179-204.
  • (2) Nastos, P. (2012). Meteorological patterns associated with intense Saharan dust outbreaks over Greece in winter. Advances In Meteorology, 2012, 1-17.
  • (3) Cuevas Agulló, E., Baldasano, J. M., Pérez, C., Querol, X., Martínez Rubio, M. Á., Nickovic, S., & Barrie, L. (2008). El sistema de alerta de tormentas de polvo y arena para Europa, África y Oriente Próximo de la Organización Meteorológica Mundial. Disponible en
  • (4) Querol, X., Pérez, N., Reche, C., Ealo, M., Ripoll, A., & Tur, J. et al. (2019). African dust and air quality over Spain: Is it only dust that matters?. Science Of The Total Environment, 686, 737-752.
  • (5) Domínguez-Rodríguez, A., Báez-Ferrer, N., Abreu-González, P., Rodríguez, S., Díaz, R., Avanzas, P., & Hernández-Vaquero, D. (2021). Impact of Desert Dust Events on the Cardiovascular Disease: A Systematic Review and Meta-Analysis. Journal Of Clinical Medicine, 10(4), 727.
  • (6) Mallone, S., Stafoggia, M., Faustini, A., Gobbi, G., Marconi, A., & Forastiere, F. (2011). Saharan Dust and Associations between Particulate Matter and Daily Mortality in Rome, Italy. Environmental Health Perspectives, 119(10), 1409-1414.

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