Doldrums

The Doldrums, also called the "equatorial calms", is a nautical term for the equatorial trough, with special reference to the light and variable nature of the winds. It affects areas of the Atlantic Ocean, the Pacific Ocean and the Indian Ocean that are within the Intertropical Convergence Zone, a low-pressure area around the equator, where the prevailing winds are calm. The low pressure is caused by the heat at the equator, which makes the air rise and travel north and south high in the atmosphere, until it subsides again in the horse latitudes. Some of that air returns to the Doldrums through the trade winds. This process can lead to light or variable winds and more severe weather, in the form of heavy squalls, thunderstorms and hurricanes.