HOUSTON – At KPRC 2, we’re dedicated to keeping Houstonians informed. As part of our Ask 2 series, the newsroom will answer your questions about all things Houston.
The question: Is there a correlation between Saharan dust storms and tropical activity in the Atlantic Ocean?
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The answer: Saharan dust, also known as the Saharan Air Layer (SAL), inhibits tropical activity in the Atlantic Ocean. The SAL is warm, dry, dusty air coming off the Saharan Desert in Africa. During the summer months, in particular, waves of these dust plumes move off the western coast of Africa, get caught up in the prevailing easterly wind, and migrate all the way to North America.
When these dust plumes are present, hurricanes are usually not. There are several reasons why:
Dry Air
The SAL is a very dry air mass. Hurricanes need deep tropical moisture to form.
Warm Air
The SAL is a warm air mass. It comes off the coast of Africa warm and stays that way. The dust absorbs some sunlight, reflects some sunlight back into outer space, and only allows a portion of the sun’s rays to penetrate all the way to the ocean surface. In effect, the SAL robs the ocean surface of warm sunshine, keeping the surface air and water cool and the dust layer warm.
The warm air aloft creates a temperature inversion, which stabilizes the atmosphere and prevents storm formation.
Cool Water
Hurricanes get their energy from the warmth of the ocean, so it stands to reason the warmer the water is, the greater the available energy is and the higher the chance is for hurricane formation. The slightly cooler water under Saharan dust plumes, then, means fewer hurricanes.
Strong Wind
The prevailing wind carrying the SAL across the Atlantic is relatively strong. That wind in the mid-levels of the atmosphere creates wind shear, which inhibits the development of tropical systems.
All of these factors make Saharan dust, or the Saharan Air Layer, a hurricane’s enemy. And, while these dust plumes happen every summer, sometimes they are more frequent than others. In years when they are most frequent, hurricane formation is suppressed.
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