science

Harmattan

Harmattan is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Harmattan rather than just read about it. In short: The Harmattan is a season in West Africa that occurs between the end of November and the middle of March. It is characterized by a dry and dusty northeasterly trade wind, of the same name, which blows from the Sahara over West Africa into the Gulf of Guinea.

Key takeaways

Harmattan belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Harmattan to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Harmattan from memory before moving on to harder problems.

Reference excerpt

The Harmattan is a season in West Africa that occurs between the end of November and the middle of March. It is characterized by a dry and dusty northeasterly trade wind, of the same name, which blows from the Sahara over West Africa into the Gulf of Guinea. The name is related to the word haramata in the Twi language. The temperature is cold usually at night but can be very hot in certain places during the day. Generally, temperature differences can depend on local circumstances. The Harmattan blows during the dry season, which occurs during the months with the lowest sun. In this season, the subtropical ridge of high pressure stays over the central Sahara and the low-pressure Intertropical Convergence Zone (ITCZ) stays over the Gulf of Guinea. On its passage over the Sahara, the Harmattan picks up fine dust and sand particles (between 0.5 and 10 micrometres). It is also known as the "doctor wind", because of its invigorating dryness compared with oppressive humid tropical air.

Effects This season differs from winter because it is characterized by cold, dry, dust-laden wind, and also wide fluctuations in the ambient temperatures between the day and night. Temperatures can easily be as low as 9 °C (48 °F) early in the day, but in the afternoon the temperature can climb to as high as 35 °C (95 °F), while the relative humidity drops under 5%. It can also be hot in some regions, like in the Sahara.

The air is particularly dry and desiccating when the Harmattan blows over the region. The Harmattan brings desert-like weather conditions: it lowers the humidity, dissipates cloud cover, prevents rainfall formation and sometimes creates big clouds of dust which can result in dust storms or sandstorms. The wind can increase fire risk and cause severe crop damage. The interaction of the Harmattan with monsoon winds can cause tornadoes.

Harmattan haze In some countries in West Africa, the heavy amount of dust in the air can severely limit visibility and block the sun for several days, comparable to a heavy fog. This effect is known as the Harmattan haze. It costs airlines millions of dollars in cancelled and diverted flights each year. When the haze is weak, the skies are clear. The extreme dryness of the air may cause branches of trees to die.

Health A 2024 study found that dust carried by the Harmattan increases infant and child mortality, as well as persistent adverse health impacts on surviving children. Humidity can drop below 15%, which can result in spontaneous nosebleeds for some people. Other health effects on humans may include dryness of the skin, dried or chapped lips, eyes, and respiratory system, including aggravation of asthma.

Illustrations

Worked examples

Example 1 — a first encounter with Harmattan

Start with the simplest possible case. Write down what Harmattan claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Harmattan before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Harmattan ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Harmattan

In research: Harmattan appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Harmattan in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Harmattan is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cold, Geography of Ghana, Geography of Nigeria, so understanding it makes those chapters shorter.
In everyday life: Look for Harmattan outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Harmattan in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Harmattan means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Harmattan out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Harmattan in simple terms?

Why does Harmattan matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Harmattan?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Harmattan.