Saharan dust brings hazy skies to South Florida. Here's what it is and does

A plume of Saharan dust has moved into South Florida Thursday.

This is not the first time this season, but it is the thickest we’ve seen yet. This will continue to give us milky or cloudy-looking skies for the next few days. It will also help keep rain chances low.

We consistently talk about the Saharan dust during hurricane season, but do you really know what it is and what it does? You may be surprised at its many impacts.

What most do know is that as the thickest of plumes arrives in our sky, it can create apocalyptic horizons, like the one seen in South Florida in July 2023. And we've seen Saharan dust play a role in limiting tropical development.

But how?

What is Saharan dust and what is its role in hurricane season?

Saharan dust is exactly that--dust from the Sahara Desert, a particulate matter that moves across the Atlantic waters typically June through August. 

Just south of the desert, in the Sahel, is where the monsoon season begins and creates thunderstorms. Those storms either move into the Atlantic or fall apart. As they fall apart, outflow wind rushes out of the storms and into the desert, picking up the dust and sending it into the atmosphere. Once that happens, upper level trade winds can then pick it up and carry it all across the Atlantic basin.

"You can see that dust traveling very long distances. [It] makes it to the Caribbean, it makes it to the Amazon basin. That dust interacts with cloud formation,” Dr. Kirt Knobelspiesse, a NASA research oceanographer, said.

When there’s an abundance of dust, it makes it harder for tropical waves to strengthen. On the contrary, if a hurricane has already developed and moves into an environment with dust, the dust will start to weaken the storm as the dry air gets wrapped into the system.

Saharan dust can also affect any environment it moves into.

When the dust moves in, it creates a cap in the atmosphere, so the humid air that typically rises for daily afternoon storms in the summer can’t do that. The dust acts like a lid, and storms struggle to form.

The dust can also reflect sunlight and keep the air below it a few degrees cooler. If there is consistent and thick dust over the Atlantic waters, the surface temperature of the ocean can actually be impacted and cool.

Other impacts of Saharan dust

Saharan dust isn't just an important factor during hurricane season. It also impacts the ecosystem in a unique way.

“Once it settles down, it's also a fertilizer. It fertilizes growth of phytoplankton in the oceans. I believe it also fertilizes the Amazon basin and change the sort of things that are living there," Knobelspiesse said. "So these are sort of amazing kind of connections between what's happening in a desert in one part of the world to a very different environment in other parts of the world, and you can see it with satellites.”

And when it’s in our sky, it can create a picturesque landscape for sunrises and sunsets, while simultaneously triggering some discomfort for those with upper respiratory sensitivity.