Italy: Saharan dust brought by Scirocco winds clouds air
A cloud of cloud dust from the Sahara Desert was blown over Europe late last week which left skies and ski slopes brown in a number of countries. It is not uncommon for strong southerly winds to carry dust from the vast African desert during winter.
But last week, a notably thick cloud of dust turned the white ski slopes of Andorra brown.
Images of the weather event were shared on social media as skiers cut white tracks through the brown snow.
An image shared on Twitter, showed a helicopter on the brown snow with people observing the discoloured weather event.
In one video, a person was seen scraping a thin layer of dust away with a car key to reveal a white snowpack which lay beneath.
Matt Taylor, BBC meteorologist, tweeted: “At the start of the weekend #StormDarcy helped to drag Saharan dust northwards into SW Europe and did this to the snow cover in the Pyrenees.”
Former seismologist Baptiste Gombert tweeted: “Strong southern winds mean Toulouse is having a bit of a #SepiaDay, as sand from the Sahara Desert is blown away across the Mediterranean Sea.”
According to the site WeatherZone, dust can be problematic as the brown snow can turn people off skiing and snowboarding.
It also affects the albedo, which is a measure of how reflective a surface is.
Snow has a high albedo meaning it reflects a high proportion of the incoming solar radiation.
But for dust-covered snow, it has a lower albedo and absorbs more of the sun’s energy.
Studies found dirty snow can melt faster than clean white snow.
The Sahara Desert is one of the planet’s most well-known sources of intercontinental dust storms.
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However, Australia has also been known to turn snow brown in other countries.
During Australia’s Black Summer in 2019 and 2020, dust storms caused snow and glaciers in New Zealand to turn brown.
This was also accompanied at times by bushfire smoke, which created eerie scenes across the Tasman Sea.
In July last year, terrifying footage showed a huge wall of dust blanketing an entire city in Mexico.
This was caused by an unprecedented Saharan sand storm which wreaked havoc across the US.
The storm reached North America after travelling across the Atlantic and was one of the most significant Saharan dust storms in decades.
A recent Harvard study found long-term exposure to fine particles of pollution in the air, may be linked to higher rates of hospitalisation and death due to COVID-19.
The technical name for the dust storm is the Saharan Air Layer (SAL).
The SAL forms over the Sahara Desert and moves across the North Atlantic every three to five days from late spring to early fall, peaking in late June to mid-August, according to the National Oceanic and Atmospheric Administration.
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