Dust settles over Houston this weekend

HOUSTON – As we approach mid-July, not only are we actively monitoring the tropics, but we are also tracking the plumes of Saharan dust moving across the Atlantic from Africa.

This dust has traveled thousands of miles across the world to our Texas skies and is expected to hit the Texas area as early as this weekend and stay with us through next week.

But what is Saharan dust? Let’s decipher it.

In its simplest definition, Saharan dust is dust particles that originate from the Sahara Desert in Africa. These particles are made up of tiny particles of minerals, such as sand and soil.

The Saharan Air Layer (SAL) is a layer of warm, dry, dusty air that forms during the summer months. It extends vertically from the surface to about three miles into the atmosphere and can travel thousands of miles. It impacts weather, air quality, and even hurricane development. Let’s dive in!

Limits of tropical development: Hurricanes need moist, unstable air to form, like a thunderstorm. The Saharan air layer is dry and stable, which inhibits the development or intensification of tropical storms. I like to visualize Saharan dust as cedar shavings. If you throw cedar shavings on the ground, they will absorb moisture.

Saharan dust does the same thing, but in the air it creates a very dry atmosphere that is not conducive to thunderstorms. If the layer of Saharan dust is thick enough, it can also reflect some of the sunlight, which lowers the water temperature.

Beautiful sunrises and sunsets: As sunlight passes through Earth’s atmosphere, it interacts with particles in the air, such as dust, water droplets, and gases. The dust particles scatter the sunlight, resulting in vibrant, moving sunrises and sunsets, especially for red, orange, and pink hues (longer wavelength colors). This is the same phenomenon that explains why smoky skies bring more vibrant colors at dusk and dawn.

Help our marine ecosystem: As the Saharan dust moves over the Atlantic Ocean, some particles will be deposited on the ocean surface, including mineral nutrients, such as iron and phosphorus. These nutrients act as fertilizers, encouraging the growth of phytoplankton on the surface. Phytoplankton are tiny plant-like organisms that are the base of the marine food chain. More phytoplankton provides more food for all marine life, from zooplankton to small fish, then larger fish and whales.

Poor air quality: Saharan dust contains fine particles, called particulate matter (PM), that can be inhaled into the respiratory system. These particles can be small enough to penetrate deep into the lungs, causing breathing problems, especially in people with pre-existing respiratory conditions like asthma or bronchitis. When inhaled, the particles can cause irritation and inflammation in the respiratory system. This is why our air quality plummets with dust.

Reduced visibility: Saharan dust can reduce visibility by creating a haze in the air. This can be problematic for transportation such as airplanes, as reduced visibility increases the risk of accidents.

NOAA has a branch dedicated to studying the Saharan Air Layer. More and more satellites are contributing to a better understanding of how the Saharan Air Layer will impact us in the coming decades. To learn more about their research, visit this webpage.