Large quantities of Saharan dust, which traveled thousands of kilometers from North Africa across the Atlantic to Europe, shaped this year’s Easter weather. The desert dust not only frequently led to very cloudy skies, but also to high levels of particulate matter pollution in Germany and other parts of Europe.
Saharan dust – a weather phenomenon
“Particularly over the Easter weekend, Saharan dust colored the sky in Germany and other European countries reddish, shrouding the sun and making it appear milky. When it rained, the reddish-brown dust particles of the Sahara dust rained down in the air as so-called “blood rain”. The pollution caused by Saharan dust was very high in many regions of Germany. In some cases, the measured fine dust values were two to three times higher than the limit values. The daily limit value for particulate matter (PM10) of particles with a diameter of less than 10 micrometres is 50 micrograms per cubic meter of air.
It is estimated that over 180,000 tons of Saharan sand were shipped into Switzerland on 30 March 2024. In Switzerland near Davos, the Federal Office for the Environment (FOEN) even measured up to 500 µg/m³. The high quantities of particulate matter from the Sahara were transported by the Alpine foehn. This developed from a pronounced low-pressure area and carried hot winds as far as Central Europe. Generally, particulate matter (PM10) is defined as dust with a particle size of less than ten micrometres.
Saharan dust in Europe
Saharan dust in European regions is generally not a rare occurrence. It occurs around five to fifteen times a year, mainly in spring and fall. It occurs when fine particles of mineral dust are stirred up and lifted thousands of meters in the world’s largest dry desert, the Sahara. The dust is then carried to Central Europe by the hot high-altitude wind. Around one billion tons of dust are blown out of the Sahara every year. Only the finest particles are transported towards Europe, while larger and heavier grains of sand cannot reach the higher air layers.
In most cases, desert dust goes unnoticed as its concentration is low. It only becomes more perceptible to humans when it has already reached high concentrations of fine mineral desert dust. Only hundreds of thousands of tons of sand floating in the air make the sky appear reddish. The sun is then barely perceptible. When it rains, the ferrous mineral dust falls down as so-called “blood rain” and can cover large areas with its reddish dust.
Composition of Saharan dust
The Saharan dust that reaches us in Central Europe is made up of around 60 percent quartz. Its other components are aluminum oxide of around 5 to 15 percent and smaller amounts of iron oxide as well as lime, magnesium oxide and potassium oxide.
Possible effects of desert dust
- The dust particles reflect in the air and scatter some of the sunlight. This causes the sky to turn yellowish to reddish in color.
- The many dust particles in the air mean that less sunlight reaches the ground, making it cooler.
- the dusts can form more condensation nuclei, which can lead to increased cloud formation.
- the development of hurricanes in the North Atlantic can be reduced by the particles, as Saharan dust can inhibit solar radiation and the underlying water is not sufficiently warmed.
- Sahara dust is a good mineral fertilizer for plant growth, as it consists of valuable substances such as calcium, magnesium, iron and phosphorus.
- For the South American rainforest, dusts are one of the best sources of minerals, carried there by the trade winds.
Health risks from desert dust
According to studies, Saharan dust is considered less harmful than traffic-related particulate matter. The risk of illness from large dust particles is rather low. However, finer dusts from Saharan sand can pose greater health risks, especially for children. Asthma can worsen and respiratory diseases can also develop. That there could be a possible link between the development of pollen allergies and the desert dust is only an assumption so far. According to the Federal Environment Agency, tests have shown that the fine particles of desert sand can lead to more allergies, inflammatory lung damage and cardiovascular diseases.
Sources:
Image source: 123rf.com © ferdel99, image no. 183314778
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