Harmattan

Geography glossary

Also called: Doctor wind · Topic: Atmospheric Pressure, Winds and General Circulation · NCERT: Beyond NCERT

Meaning

The Harmattan is a dry, dusty north-easterly wind. It blows from the Sahara over West Africa from about November to March. It is also called "the doctor", because its dry air brings relief from the hot, humid weather of the Guinea coast.

It matters because it shows how the seasonal shift of the ITCZ controls local weather. It is also a common UPSC trap: the Harmattan is dry, not moist, and it is a north-easterly, not a westerly.

Explanation

How it forms (cause → process → result)

  • Cause: the ITCZ moves south in winter
  • ITCZ (Inter Tropical Convergence Zone) is the low-pressure belt near the equator where the trade winds of the two hemispheres meet.

  • The ITCZ follows the overhead sun. In the northern winter it moves south, towards the Gulf of Guinea.

  • Process: the trade winds blow straight out of the desert

  • With the ITCZ further south, the north-east trade winds reach far into West Africa.
  • These winds start over the Sahara, so the air is hot by day, very dry and full of dust.

  • They do not cross any sea on the way, so they pick up almost no moisture.

  • Result: a dry, dusty season over West Africa

  • Humidity becomes very low.
  • A thick dust haze covers the region.

Its type

  • The Harmattan belongs to the group of hot, dry winds from deserts. Its nature comes from its source region, the hot, dry Sahara.
  • It is not a foehn-type wind. A foehn gets warm and dry because the air sinks down a mountain and gets squeezed. The Harmattan is dry because of where it starts.
  • It is a seasonal part of the trade wind system. It is not a short, one-day gust.

Its effects

  • Good effects: why it is called "the doctor"
  • The Guinea coast is normally hot and humid.

  • The dry Harmattan air lets sweat evaporate quickly, so people feel cooler.

  • Bad effects

  • Thick dust haze lowers visibility, so flights are disrupted.
  • Very dry air cracks the skin.
  • It dries out crops.

Where it occurs

  • Source: the Sahara Desert in North Africa.
  • Area affected: West Africa, including:
  • Nigeria
  • Ghana
  • Côte d'Ivoire

  • Senegal

  • Where its "doctor" effect is felt most: the humid Guinea coast along the Gulf of Guinea.

  • Season: about November to March (the northern winter).
  • India: India has no Harmattan. India's main hot, dry desert wind is the loo, which blows over the north-western plains (Punjab, Haryana, Delhi, Rajasthan, Uttar Pradesh, Bihar). It comes in a different season (May–June) and from a different direction (west).
  • Map tip: on a world outline map, mark the Harmattan in red (hot/warm) with "D" (dry) over West Africa.

Don't confuse with

  • Sirocco: also a Saharan wind, but it blows north, from the south or south-east, to Sicily and southern Italy. It picks up moisture over the Mediterranean and arrives humid, and can bring "blood rain". The Harmattan blows south-west over West Africa and stays dry.
  • Loo: a hot, dry westerly over the north-western plains of India in May–June (summer). The Harmattan is a north-easterly in November–March (winter), and it brings relief instead of heatstroke.
  • Foehn / Chinook: these are warm, dry winds that descend mountain slopes (the Alps and the Rockies) and warm up by being squeezed. The Harmattan is a desert wind. It is dry because of its Sahara source, not because it comes down a mountain.
  • Khamsin / Ghibli: hot, dry Saharan winds of Egypt and Libya in North Africa. The Harmattan is the Saharan wind of West Africa.

Prelims Hooks

  • Harmattan → West Africa (Nigeria, Ghana, Côte d'Ivoire, Senegal). Its source is the Sahara.
  • Direction: north-easterly. It is the north-east trade wind blowing out of the desert.
  • Season: about November to March. This is when the ITCZ moves south.
  • Nickname: "the doctor". Its dry air relieves the humid heat of the Guinea coast.
  • Trap: the Harmattan is dry, not moist. Among Saharan winds, only the sirocco turns moist (over the Mediterranean).
  • Wind → country matches: Harmattan–West Africa, Khamsin–Egypt, Ghibli–Libya, Leveche–Spain, Sirocco–Sicily and southern Italy.

Mains Points

  • Seasonal pressure shift as the cause (GS-I):
  • The ITCZ follows the sun. In the northern winter it moves south.
  • The north-east trades then blow straight out of the Sahara, so West Africa gets a dry, dusty season.

  • This shows how the planetary pressure belts and their seasonal movement shape a region's local weather.

  • Mixed effects on economy and livelihoods:

  • Helpful: dry air brings relief from the humid heat of the Guinea coast ("the doctor").
  • Harmful: dust haze disrupts flights, crops dry out and the skin cracks.

  • Planning needs both sides in view: aviation safety, crop protection and public health.

  • Climate change angle (GS-III):

  • When desert source regions get hotter and drier, desert winds become more dangerous. They bring more dust and more heat stress.
  • For West Africa, a stronger or dustier Harmattan would mean more health, farming and transport problems. Dust warnings should be part of disaster preparedness.

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