You’ve probably heard meteorologists mention “Saharan dust” during hurricane season. But what exactly is it, and how does it affect tropical storms and hurricanes? Let’s break it down.
The Saharan Air Layer (SAL) is a warm, dry layer of air that forms over the Sahara Desert in North Africa during late spring, summer, and early fall. This layer carries large amounts of dust across the Atlantic Ocean, sometimes traveling for up to 7 days. The SAL typically starts around half a mile above the surface and can reach up to three miles.
Impact on tropical systems
The SAL’s impact on tropical systems is complex, depending on factors like the amount of dust, it’s altitude, and the specific characteristics of the storm. Generally, there is a negative influence on storm development and intensification:
- Stabilization: The dust absorbs radiation from the sun and thus warms the atmosphere resulting in less thunderstorm development.
- Cooler waters and Wind Shear: The SAL can cool the ocean water and strengthen wind shear (changes in wind speed and direction with height), which tears apart developing storms.
However, the SAL can occasionally have a positive effect by providing “seeds” (dust particles) for cloud formation, potentially enhancing rainfall within existing hurricanes.
Weaker vs. Stronger systems
The SAL a greater impact on weaker systems, such as tropical depressions. These weaker systems haven’t fully developed into mature storms and are more vulnerable to dry air, wind shear, and stabilization.
Stronger storms, like hurricanes, are better organized and can resist the negative influences most of the time. However, the dry air layer can still weaken or slow additional strengthening
Additional Factors
While the SAL plays a significant role in influencing tropical cyclone development and intensity, it’s not the only factor. Wind shear and sea surface temperatures can also be big players. In general, the SAL mostly has a negative impact on the tropical cyclones by dry air, wind shear, and stabilization.
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