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  • Writer's picture@ Cynthia Adina Kirkwood

Orange “Rain of Clay” Sky in Portugal Expected in Caribbean

Updated: Mar 17, 2022


Dust from the Sahara Desert in North Africa traveled first to Spain on March 14 and, then, to Portugal on the following day, painting the skies orange. The suspended particles affect air quality and can affect health, especially of the vulnerable.

While the Iberian Peninsula is at the forefront, northern Europe also is seeing the phenomenon. In Switzerland, the dust colored the skies over the Paverne Air Base near Lake Neuchatel, deposited itself on cars in Paris and reached as far north as London and southeast England on March 16 as dust on windows, reported ABC News (March 16).

“The general population should avoid prolonged exertion, limit physical activity outdoors and avoid exposure to risk factors such as tobacco smoke and contact with products that can cause irritation,” advised the Directorate-General of Health (DGS), according to Expresso (March 15).

This meteorological phenomenon is called “rain of clay”.

The Saharan dust is expected to cross the Atlantic to the Caribbean and South America, according to the European Centre for Medium-Range Forecasts (ECMWF) of the European Commission’s Copernicus Program (March 15).

In Portugal, it is expected to last until March 21, although in less intensity after March 17, according to SIC Noticias (March 17). The central and northern areas will be the most affected with the possibility of “dust deposition through precipitation”, mainly in the South.

“This is an intense event, but this type of event typically occurs once or twice a year, normally in February or March, when a low-pressure system over Algeria and Tunisia gathers up dust and carries it north to Europe. Dust can reach the U.K. or even Iceland as it did last year,” Carlos Perez Garcia, a researcher studying dust at the Barcelona Supercomputing Center, told The Associated Press, according to ABC News.

The Portuguese Institute of the Sea and Atmosphere (IPMA) explained that this type of event can reach the mainland and the Madeira archipelago a few times a year. It said that it happens after the “occurrence of storms”, according to Expresso.

“These storms give rise to strong winds that, when blowing over desert surfaces, lift the lightest particles from the ground. The dust/sands are then transported through the atmospheric circulation.”

The storm, in this instance, is Celia, which already has left seven districts in Portugal under an orange warning of alert due to the high sea wave and forced the cancellation of more than 40 flights in Madeira alone on March 15, reported Expresso.

“There is a situation of poor air quality on the mainland, especially, in the North and Central regions” due to “increasing concentrations of inhalable particles of natural origin in the air,” warned the DGS.

“This pollutant has effects on human health, especially on the most sensitive population, children and the elderly, whose health care must be redoubled during the occurrence of these situations,” read the DGS statement.

In the case of the most vulnerable group -- children, the elderly, and patients with chronic respiratory problems such as asthma and cardiovascular issues -- it is advisable to stay inside buildings and, preferably, with closed windows.

Until the passing of the phenomenon on March 17, the DGS recommends that the general population:

1. Avoid exertion

2. Limit physical activity outdoors;

3. Avoid exposure to risk factors, such as tobacco smoke and other products that cause irritation.

Chronic patients must maintain their ongoing medical treatments.

In the case of an aggravation of symptoms, please call Health Line 24 at (808 24 24 24) or a health service.

In the United States, the National Oceanic and Atmospheric Administration (NOAA) tracks the Saharan Air Layer (SAL):

“SAL outbreaks can form when ripples in the lower-to-middle atmosphere, called tropical waves, track along the southern edge of the Sahara Desert and loft vast amounts of dust into the atmosphere. As the SAL crosses the Atlantic, it usually occupies a 2- to 2.5-mile thick layer of the atmosphere with its base starting about 1 mile above the surface. The warmth, dryness and strong winds associated with SAL have been shown to suppress tropical cyclone formation and intensification.

“SAL activity typically ramps up in mid-June and peaks from late June to mid-August, with new outbreaks occurring every three to five days. During this peak period, it is common for individual SAL outbreaks to reach farther to the west – as far west as Florida, Central America and, even, Texas – and cover extensive areas of the Atlantic, sometimes as large as the lower 48 United States (every state but Hawaii and Alaska).”

In the summer of 2020, one of the largest recorded Saharan dust storms carried nearly 24 tons of dust to North and South America, hitting the Caribbean particularly hard, according to the National Aeronautics and Space Administration (NASA) (April 19, 2021).

With funding from NASA, an early warning system was developed and put in place just days before the event. With this tool, for the first time, people in Puerto Rico received advance notice of the dust storm.

“We were monitoring a couple of different NASA models and satellite images,” said Pablo Mendez-Lazaro, an associate professor at the University of Puerto Rico Medical Sciences Campus in San Juan, who led the development of the warning system.

“As soon as we saw the dust storm, we started communicating the news. We got in contact with corresponding government agencies and collaborating medical doctors.”

Saharan dust makes this journey every year, fertilizing soil with phosphorus and other nutrients, according to NASA. The right amount of dust feeds the coral of the Caribbean. However, too much dust can cause algae overgrowth.

The dust also can irritate people’s eyes, ears, noses and throats with fine particles of silica and other minerals that can infiltrate lung tissue, aggravate sensitivities and reduce visibility.

“During the summer of 2020, as in many other places, we were also struggling with COVID-19, and COVID-19 is a respiratory virus. We were very concerned with how the dust could exacerbate the symptoms,” said Mendez-Lazaro.

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