Why Massive Saharan Dust Plumes Are Blowing Into the US The pandemic is still raging, the
Arctic is burning up, and microplastics are polluting every corner of the Earth, but do
try to take a deep breath. A plume of dust thousands of miles long has blown from the
Sahara across the Atlantic, suffocating Puerto Rico in a haze before continuing across
the Gulf of Mexico. And it has already arrived in Texas and Louisiana. How does Saharan
dust make it all the way across an ocean? It's a lesson in atmospheric science. Because
it's a desert, the Sahara is loaded whit particulate matter, from coarse sand down to the
tiniest of dirt specks, none of which is very well anchored to the ground. And it is
notoriously dry and hot. By contrast, the lush rainforests to the south of the Sahara
have trees that both block the wind and hold on to the soil with their roots, keeping
all the muck from being taken to the air. it's much cooler and wetter, on account of its
proximity to the equator. "The setup between those two - the hot to the north and the
cool, moist to the south - sets up a wind circulation that can become very strong, and it
can actually scour the surface of the desert," says Steven Misller, deputy director of
the Cooperative Institute for Research in the Atmosphere at Colorado State University,
which is monitoring the plumes. The process creates "pulses" of warm, dry dusty air
traveling along the Saharan Air Layer that cycle every three to five days, says Miller.
This happens reliably every summer, blowing east towards the Americas. The good news is,
the dust plumes can deflate newly forming hurricanes they might encounter on the way
over. But the bad news is tha tdust is a respiratory irritant, and we could use fewer of
those during the Covid-19 pandemic. As the weather cools in Africa starting in
mid-August, the temperature differential between the desert and the forests to the south
will weaken, zapping the SAL conveyor belt. The dust clouds will stop rolling across the
Atlantic. Then we can all go back to just worring about Covid-19 and microplastics and
a melting Arctic.