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Doldrums or equatorial belt of calm, a region around the planet located between the two belts of trade winds slightly north of the equator.
This belt extends from the equator to 10º N and 10º S latitudes.
Due to excessive heating horizontal movement of air is absent here and only convectional currents are there.
Therefore this belt is called doldrums (the zone of calm) due to the virtual absence of surface winds.
These are the regions of convergence because the winds flowing from sub tropical high-pressure belts converge here. This belt is also known as the Inter-Tropical Convergence Zone (ITCZ).

The force exerted by the rotation of the earth is known as the Coriolis force.
It deflects the wind to the right direction in the northern hemisphere and to the left in the southern hemisphere. The deflection is more when the wind velocity is high.
The Coriolis force is directly proportional to the angle of latitude. It is maximum at the poles and is absent at the equator.
The Coriolis force acts perpendicular to the pressure gradient force.
At the equator, the Coriolis force is zero and the wind blows perpendicular to the isobars. The low pressure gets filled instead of getting intensified. That is the reason why tropical cyclones are not formed near the equator.

Roaring Forties are strong westerly winds of the South Hemisphere.
It occurs between the latitudes of 40 and 50 degrees.
It plays a vital role where a major to the ships sailing the Brouwer Route from Europe to Australasia during the Age of sail.

Harmattan is a strong dry wind that blows over northwest Africa from the northeast.
Blowing directly from the Sahara desert, it is a hot, dry and dusty wind.
It provides a welcome relief from the moist heat and is beneficial to the health of people and hence known as ‘the doctor’.

Match List I with List II and select the correct answer List I A. Belt of Calm B. Deflecting Force C. Roaring Forties D. Harmattan List II 1. Coriolis 2. Doctor wind 3. Doldrums 4. Westerlies