Some people in Europe parked their vehicles outside overnight, hoping a cleansing downpour would save them a trip to the carwash. But the rains had the opposite effect. The reason? Dust from the Sahara Desert.
A squeeze play between zones of high and low pressure has slingshotted a conveyor belt of airborne desert dust northward. Ordinarily, what happens in the Sahara stays in the Sahara — but recent strong winds have picked up dust by the ton, transporting a grimy layer of sand all the way to the Arctic Circle.
The dust has trekked as far poleward as Scandinavia, and could be swept back toward Greenland in the next 72 hours. In the meantime, concentrations are impressive. If you took a one-yard-by-one-yard column of dust out of the lower atmosphere over France on Tuesday afternoon, it would contain nearly 3,000 milligrams of dust. That’s the weight of more than a penny.
Much of it is clouding over the upper atmosphere. That could transform the light into a diffuse amber glow over the United Kingdom on Tuesday evening, and have a similar effect in Iceland on Wednesday night. Brilliant orange sunsets may be in the offing.
The United Kingdom Met Office writes that “Saharan dust is relatively common in the U.K.” They say it happens a few times a year when “big dust storms in the Sahara coincide with southerly wind patterns.” The dust can occasionally contribute to pollution levels.
The areas with the greatest amount of dust up high aren’t the same spots seeing the heftiest concentrations near the ground. Italy is in the crosshairs of the dust plume. Nearly 200 micrograms per cubic meter are present at the surface — equal to the weight of a fruit fly in every cubic meter. Imagine 200 fruit flies buzzing around inside a subway car — that’s the density of dust. It’s roughly half the mass density of last week’s pollen peak in Washington.
The dust doesn’t always stay in the sky. Thunderstorms can “scavenge” the aerosol from the atmosphere. That’s happening over the Adriatic Sea near the coast of Croatia, where a couple grams of dust are deposited every six hours. That would streak your windshield and could scratch your paint if you tried to scrub off the grime.
Not much has come down otherwise, and probably won’t outside of downpours — save for an infinitesimally small veil that could drop a few grains from Ukraine to Poland on Thursday.
Most of the dust should be swept away by Saturday as high pressure and northwesterly flow build into the weekend.