The Harmattan is a season in West Africa that occurs between late November and mid-March. It is characterized by a dry and dusty northeasterly trade wind, also called Harmattan, which blows from the Sahara Desert across West Africa to the Gulf of Guinea. The term "Harmattan" is derived from the word haramata in the Twi language.
Climate Characteristics
The Harmattan wind typically blows during the dry season, which coincides with the months of the lowest solar intensity. During this period: - The subtropical ridge of high pressure remains over the central Sahara. - The Intertropical Convergence Zone (ITCZ) stays over the Gulf of Guinea.
As the wind travels over the Sahara, it picks up fine dust and sand particles (between 0.5 and 10 microns in size). It is sometimes referred to as the "doctor wind" due to its invigorating dryness compared with the typically humid tropical air.
Temperature and Humidity
- The season is marked by cold nights and early mornings, with daytime temperatures often rising significantly.
- Temperatures can drop to 9 °C (48 °F) and rise to 35 °C (95 °F) within the same day.
- Relative humidity can fall below 5%, contributing to dry atmospheric conditions.
Effects
Environmental Impact
The Harmattan creates desert-like weather conditions: - Lowered humidity - Dissipated cloud cover - Suppressed rainfall - Increased fire risk - Severe crop damage
The interaction between Harmattan and monsoon winds can also lead to the formation of tornadoes.
Harmattan Haze
In some parts of West Africa, dust accumulation during the Harmattan results in reduced visibility and can block sunlight for several days, creating a phenomenon known as Harmattan haze. This can: - Be as intense as heavy fog - Disrupt air travel, leading to cancelled or diverted flights - Dry out vegetation, causing branches of trees to wither
Health Impacts
A 2024 study revealed that dust from the Harmattan is associated with: - Increased infant and child mortality - Long-term adverse health outcomes for surviving children
Other health issues include: - Spontaneous nosebleeds - Chapped lips and skin - Dry eyes - Aggravation of asthma and other respiratory issues
Humidity levels can fall below 15%, exacerbating these conditions.
See Also
- Khamsin(https://en.wikipedia.org/wiki/Khamsin) – A similar dry wind in North Africa and the Middle East
References
- Chisholm, Hugh, ed. (1911). "Harmattan". Encyclopædia Britannica (11th ed.). Cambridge University Press.
External Links
(Links to academic studies, meteorological databases, and West African weather authorities can be listed here if needed.)