Why it rains Sahara sand more and more often and what it means in terms of pollution

If it rains sand from the Sahara on Europe it is due to a configuration of high and low pressures.This in itself is normal, but it is happening more and more often.

• Especially in spring and summer, but not only, sand from the Sahara desert rains on Europe.
• This is a normal phenomenon, due to a precise configuration of high and low pressures, but it is becoming more frequent.
• Dust suspended in the air can be inhaled and therefore pose a health risk.

When you notice dirt on your car or balcony after a short rain, or when you witness a spectacular sunset with the sky redder than usual, the explanation is often the same:it's there sand from the Sahara desert in the atmosphere.But it's just an impression, oh it's raining sand more and more often?How is this possible and, above all, are there any kind of consequences?

What happens when it rains Sahara sand

More than sand, it would be correct to talk about dust:in fact, grains of sand have a size between 0.06 and 2 millimeters and are therefore too heavy to be lifted, unlike dust particles which on average have a diameter of 0.02 millimetres.In any case, if these sediments reach Europe it is because of atmospheric circulation typical of the spring and summer period.

“There is a precise baric configuration of high and low pressures which position themselves in such a way as to lift this desert dust and bring it to us,” he explains Francesco Nucera, meteorologist from 3BMeteo.“On the one hand, in fact, there is the low pressure in the United Kingdom which acts as a 'heat pump' and drags the dust present above all in the Maghreb, on the other hand there is the anticyclone between North Africa and the Mediterranean.Europe is one of the areas affected especially in spring and summer.The waves of dust then mix with the rain and fall.It is a phenomenon that we know well, but which has become more frequent in recent years."

Because sand rains are increasingly frequent

Also the European Climate Change Monitoring Service, Copernicus, underlines how it is completely normal for sand from the Sahara to end up in the skies of Europe and Latin America.In recent years, however, these episodes have become increasingly intense and frequent and it is reasonable to assume that this is due to the changes in atmospheric circulation patterns.

A publication by Copernicus experts, for example, asks why sand was observed so often in the skies of the western Mediterranean and the Euro-Atlantic region between 2020 and 2022 between February and March, months in which it usually happens much more rarely.We also notice it in our Alps, when we notice that the snow takes on reddish shades.According to scholars, this is due on the one hand to the increase in temperature in the Mediterranean and the drought in the Maghreb;on the other hand, to the downstream high pressure systems.

Are we therefore witnessing yet another demonstration of the ongoing climate crisis?"THE climate changes they indirectly play a role, but we cannot say that they are a direct cause", clarifies meteorologist Francesco Nucera.

The consequences on air quality

This desert dust, through the trade winds, reaches the Amazon.And, once deposited on the ground, it contributes to soil fertility as it is rich in phosphorus and nutrients.Always Copernicus However, it clarifies how the impact on human health can be worrying, because it corresponds to an increase in fine dust in the air.

Copernicus scientists examined air quality at Canaries after calimas following one another in January 2022:these are episodes in which the sirocco wind brings with it dust and sand, causing a constant mist and a sudden increase in temperatures.PM10 concentrations even rose above 200 μg/m³;there daily threshold established by current Italian legislation is 50 μg/mc and is also more permissive compared to that recommended by the World Health Organization (WHO).

The so-called PM10 is inhaled, irritates the upper respiratory tract and worsens the symptoms of asthma, chronic rhinitis, allergies, chronic sinusitis and bronchitis in predisposed people.The phase in which it rains sand, which may seem the most annoying because it forces us to wash cars and balconies, is also the one in which atmospheric particulates are discharged to the ground:when it stops raining, therefore, it means that PM10 levels have significantly dropped.