More Than Just a Haze in the Sky
Imagine standing on a beach in Portugal or on the volcanic islands of Cape Verde, watching as the sky gradually turns a milky orange. This isn't a weather phenomenon or a trick of the light—it's the arrival of mineral dust that has traveled thousands of kilometers from the Sahara Desert. While these atmospheric events create spectacular sunsets, they represent a far more significant story about how interconnected our planet's systems truly are.
of global atmospheric mineral dust originates from Northern Africa 1
Maximum PM10 concentrations recorded in Cape Verde during dust events 5
Contribution to aerosol optical depth over Portugal during intense episodes 2
Northern Africa accounts for more than 50% of the global atmospheric mineral dust 1 , creating an immense plume that regularly crosses continents and oceans. These dust particles are far from inert travelers—they influence everything from the air we breathe to the fundamental processes that regulate our climate 1 .
The Sahara Desert, Earth's most prolific dust source, generates dust through a process called soil ablation—where powerful winds lift fine mineral particles from dry lake beds and desert surfaces into the atmosphere 1 .
Sahara Source
Cape Verde
Portugal
Dust travels thousands of kilometers across the Atlantic
Located approximately 600 kilometers west of Senegal, this volcanic archipelago lies within the primary dust transport pathway over the tropical Atlantic 3 . The islands experience significant dust exposure throughout the year, with especially pronounced seasonal intrusions from October to March 5 .
Tropical Atlantic PathwaySituated further north, Portugal experiences dust transport primarily when specific weather patterns develop. These often involve cut-off lows located between the subtropical eastern North Atlantic and the western Mediterranean, combined with downstream high-pressure systems that funnel dust northward from Africa 7 .
Mediterranean InfluenceResearch conducted at the Cape Verde Atmospheric Observatory reveals that aerosol particles in the region can be categorized into four distinct types based on their size distribution and origin 5 :
For Portugal, the impact of Saharan dust is more directly felt in terms of air quality and human health. Studies have documented that dust intrusions can significantly increase particulate matter concentrations .
Recent research has highlighted that dust deposition on photovoltaic panels reduces solar power output by an average of 25-40% across Mediterranean countries, with losses exceeding 50% during extreme events 8 . In Portugal specifically, this decline ranges between 10.1-29.3% during high dust levels 8 .
To better understand the properties and impacts of Saharan dust over Portugal, scientists conducted the Desert Aerosols over Portugal (DARPO) campaign, which was linked to the larger Saharan Mineral Dust Experiment (SAMUM) .
The research team employed a comprehensive array of measurement techniques during dust outbreaks :
Measurements were conducted at a rural site in Évora, Portugal, to minimize the influence of local pollution sources and focus on the characteristics of the long-range transported dust .
The DARPO campaign yielded several important insights into the nature of Saharan dust over Portugal :
| Parameter | Measurement | Significance |
|---|---|---|
| Maximum dust mass concentration | ~150 μg/m⁻³ | Indicates substantial air quality impact |
| Scattering coefficient | 130 Mm⁻¹ | Quantifies visibility reduction and light interaction |
| Mass scattering efficiency | 0.87 m² g⁻¹ | Provides relationship between mass and optical effects |
| Aerosol optical depth | Up to 0.53 | Measures overall atmospheric haze from dust |
| Lidar ratio | 45-50 | Important for satellite remote sensing of dust |
Understanding the complex nature and effects of desert dust requires specialized instruments and methods. Researchers in both Cape Verde and Portugal rely on a sophisticated array of tools to detect, analyze, and track dust particles across their long-distance journeys.
Measure aerosol optical depth by looking at sunlight. Ground-based units in AERONET network at Cape Verde 3 .
Collect particles for chemical analysis. Identifying dust composition at Cape Verde 5 .
Determine light scattering by particles. Measuring dust scattering coefficients in Portugal .
Profile vertical distribution of dust layers. Tracking dust altitude during transport to Europe 1 .
Provide large-scale view of dust plumes. MODIS and CALIPSO tracking dust across Atlantic 1 .
Simulate dust emission, transport, and deposition. Forecasting dust events and their impacts 2 .
Recent years have seen notable changes in dust transport patterns, with increasing frequency and intensity of Saharan dust intrusions over Europe 7 . A preprint publication by Spanish researchers detected a sharp increase of Saharan dust intrusions over the Western Mediterranean and Euro-Atlantic region in February-March 2020-2022, noting that some events "displayed a duration never recorded before" 7 .
"Since 2020, we are monitoring increases on the temperature of the Mediterranean and a persistent drought in the Maghreb. These surface conditions are contributing to the occurrence of these exceptional winter Saharan events towards Europe in the last years" - Sara Basart, Scientific Officer at the World Meteorological Organization 7 .
This trend may be connected to changing climatic conditions, highlighting the importance of continued monitoring and research.
Understanding the past and present behavior of Saharan dust is essential to anticipating its future impacts on the environments and inhabitants of Cape Verde, Portugal, and the wider world connected by these remarkable atmospheric bridges.
The mineral dust that journeys from the Sahara to Cape Verde and Portugal represents far more than a meteorological curiosity—it is a dramatic manifestation of Earth's interconnected systems. These dust events link the world's largest desert to distant islands and continents, affecting everything from microscopic cloud-forming processes to macroscopic climate patterns.
As research continues at field stations in Cape Verde and across Portugal, scientists are gradually unraveling the complex roles that these dusty voyagers play in our environment. Their work highlights not only the incredible journey of mineral particles across thousands of kilometers but also the profound ways in which desert dust touches our lives—from the air we breathe to the energy we harvest from the sun.
Saharan dust creates atmospheric bridges connecting continents and influencing global systems