An Atmospheric River of Dust

Posted: March 19, 2022 by oldbrew in atmosphere, dust, ENSO, research, weather

At least a few times a year, strong and persistent winds from the south drive Saharan dust north toward Europe, as recent research explains. Two such events in 2021 ‘led to snow darkening by dust deposition over the Alps with 40% decrease in snow albedo’, among other effects. NASA says the dust plays a major role in Earth’s climate and biological systems, absorbing and reflecting solar energy and fertilizing ocean ecosystems with iron and other minerals that plants and phytoplankton need to grow. A slight positive trend in the frequency of such events since 1980 is suggested to be related to the El Niños in the period. The research paper hints at the need for climate models to take these events into account.
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On March 15, 2022, a plume of Saharan dust was blown out of North Africa and across the Mediterranean into Western Europe, says NASA’s Earth Observatory.

The dust turned skies orange, blanketed cities, impaired air quality, and stained ski slopes.

The plume was driven by an atmospheric river arising from Storm Celia, which brought strong winds, rain, and snow to the Canary Islands.

Atmospheric rivers, normally associated with extreme moisture, can also carry dust.

“You can think of them as the confluence of a dust river and a water vapor river within a single storm environment,” said Bin Guan, an atmospheric scientist at NASA’s Jet Propulsion Laboratory and the University of California, Los Angeles.

“The same atmospheric dynamics that give rise to a water vapor river—specifically strong winds—can act to pick up and transport dust as the storm moves across desert areas.”

Over the past four decades, 78 percent of atmospheric rivers over northwestern Africa have led to extreme dust events over Europe, according to research by Guan and colleagues.

Such “aerosol atmospheric rivers”—a term recently introduced in a NASA-led study that refers to narrow, elongated regions of extreme aerosol mass transport—can play an important role in climate and air quality around the world.

Continued here.
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NASA Earth Observatory — Aerosols: Tiny Particles, Big Impact

  1. Gamecock says:

    Trying to figure out what the news is here.

    ‘At least a few times a year, strong and persistent winds from the south drive Saharan dust north toward Europe, as recent research explains.’

    Well, yes, it is a weather condition that the Neanderthals probably observed.

  2. Bloke down the pub says:

    Question that struck me was, how many tonnes of dust does the Sahara lose evey year and, as there’s little vegetation to create new soil, is the cumulative loss appreciable?

  3. oldbrew says:

    From the cited study:

    At a weather station in the western Alps (the FluxAlps station), the effects of the rather moist and dusty atmosphere on the meteorological fields were quite remarkable. The snow albedo was reduced by up to 40%, the downward long-wave radiation flux increased up to 50 W m−2 above the 1980–2020 climatology. The combined effects of albedo reduction and increased LW led to a reduction of the snow depth by up to 50 cm (or 50% of the actual value). These figures are comparable to those reported by other authors such as Skiles and Painter (2017) over the Rocky Mountains in the United States.

  4. oldbrew says:

    Bloke – Wikipedia says:

    The Sahara is the largest source of aeolian dust in the world, with annual production rates of about 400-700 x 10^6 tons/year, which is almost half of all aeolian desert inputs to the ocean.[2] Saharan dust is often produced by natural process such as wind storms, and doesn’t appear to be heavily impacted by human activities.

    In another section: Dust and climate
    Saharan dust emissions and transports are sensitive to weather and climate conditions in the source regions. Dense dust clouds reduce the ocean surface exposure to sunlight, hence, reducing the ocean surface heating and therefore influencing the air-sea transfer of water vapor and latent heat, which are critical to climate. [bold added]

  5. Kip Hansen says:

    In the 2010s, my wife and I lived aboard our sailing cat in the northern Caribbean. One of the worst cleaning jobs was washing the orangey Africa dust off the cabin tops.

    Messy but terrific for life in the sea — the oceans are starving for IRON and even just a little bit boosts plankton productivity.

  6. oldmanK says:

    Re Saharan dust see this video here:

    Go to 33:23 where P DeMenocal indicates the abrupt drying of the Sahara. Change is abrupt, and this now is not it. This is bad but not abnormal.

  7. Gamecock says:

    The Cape Verde Season is a hurricane season within the hurricane season, running from mid-August to October. It is when tropical waves move into the Atlantic from Africa. Sometimes they develop into hurricanes – some of the fiercest.

    Every Cape Verde Season, the Weather Channel reports not just African tropical waves, but also Saharan sand storms moving into the Atlantic. These sand storms are known to impede hurricane development. Those with maritime interests are happy to see the sand storms.

    Again, this is old stuff.

  8. oldbrew says:

    Intense Saharan dust sandstorm hits Spain for the second time
    March 25, 2022

    Air quality in areas including the capital, Madrid, and cities Malaga and Seville was rated as “extremely unfavourable” – the worst rating by the national air quality index.

    People were encouraged to wear face masks and to avoid outdoor exercise.

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