Harmattan

The Harmattan is a dry, dusty northeasterly trade wind that carries Saharan air across West Africa, especially from November to March.

Northeast trade winds: Persistent easterly winds in the tropics, driven by air flowing toward the equator and deflected by Earth’s rotation. The Harmattan is a regional expression of these winds over West Africa.
Harmattan haze: Reduced visibility caused by dust and fine particles suspended in dry air during the Harmattan season. It is the wind’s most familiar atmospheric effect in many West African cities.
Harmattan etymology: The linguistic history of the word “Harmattan,” used for the dry-season wind of West Africa. The name entered European accounts through contact with West African coastal languages.
Dust deposition: The settling of airborne mineral particles onto land, water, vegetation, or built surfaces. Harmattan dust can coat crops and settlements after being carried through the air.
Saharan Air Layer: A warm, dry, dust-laden air mass that forms over the Sahara and travels over the tropical Atlantic. Harmattan air carries Saharan dust, though the layer’s strongest Atlantic expression is farther west.
Aviation meteorology: The study and forecasting of atmospheric conditions that affect aircraft operations. Dust haze can reduce visibility and disrupt flights during Harmattan episodes.
West African monsoon: A seasonal circulation that brings moist southwesterly winds and rainfall into West Africa. It is the moist seasonal counterpart to the Harmattan’s dry northeasterly flow.
African easterly jet: A mid-level atmospheric wind current over Africa that flows from east to west during the warm season. Its seasonal circulation interacts with dust transport and regional weather, though it is distinct from the surface Harmattan.
Intertropical Convergence Zone: A low-pressure belt near the equator where trade winds converge and rising air produces clouds and rainfall. Its seasonal movement helps govern when dry northeasterly air reaches West Africa.
Respiratory health: The condition of the airways and lungs and their ability to function without disease or impairment. Dry air and airborne dust can aggravate respiratory symptoms during the season.

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