The Doldrums is an unstable weather zone, where winds are changeable and difficult to predict. This place is really difficult for sailors to apprehend, even if they can see it from very far away. At 100 miles (180 km), you can already see big clouds above the horizon. It is generally positioned between 8° N and 3° N from the African coast up to 35° West, sometimes narrowing.
Unpredictable, it changes shape regularly and can last from a few hours to a few days.
How is the Doldrums formed?
The Doldrums is formed by the confrontation between the trade winds of the Northern hemisphere, blowing from the NE and the trade winds of the Southern hemisphere, blowing from the SE. This meteorological area is also characterised by high humidity and heavy cloud cover. Indeed, the area is located near the Equator and temperatures are very high, both for the water (27 to 29°) and the air (35 to 40°). Evaporation is therefore significant and the humidity level is close to 100%, creating many clouds, which cover the area.
An unstable and variable area
Unstable and variable, the Doldrums change shape and bottom very frequently. As a result, it is very hard for sailors to plan their trajectory in advance. They can either take advantage of squalls and winds to make headway, or get stuck in the calms. Sailors find it difficult to predict its extent and density, but can rely on a few characteristics :
- It's always narrower towards 30° West
- It always takes longer to cross on the 20° West side..
It's therefore important to plan your entry into the Doldrums, at the risk of finding yourself too far to the west and being pushed towards the Brazilian coast by SE'ly winds. It would appear that the best trajectory for crossing the ITCZ is between 27° and 28° West.
The creation zone of tropical depressions
With strong trade winds and high water temperatures, the Doldrums is more active and extensive. When the water is very hot, evaporation is important and creates a large number of cumulonimbus clouds which can extend up to more than 12,000 metres in altitude. In terms of weather conditions, one can find lightning, thunder, reduced visibility, torrential rains or violent gusts of wind, and even waterspouts (a column that starts from the sea and mixes water and air in rotation to reach the sky) or Saint-Elme fires (a more or less continuous electrical discharge of moderate intensity).
It is often in the Doldrums that tropical depressions are born and can develop into cyclones as they move westward.
The origins of the Doldrums
The origins of the Doldrums are numerous. The first two have nothing to do with the marine world.
The word "pot au noir" was used to refer to a dangerous area in the 17th century, when the game of blind man's blind man's buff was played. The blindfolded person had to avoid the area or risk injury.
Another meaning would come from Cape Verde - located not far from this unstable zone. The Doldrums was a jar or pot that was used to receive rubbish in Cape Verdean homes.
Another hypothesis is to explain that during the time of slavery, slave traders would pass over sick men in this area. The ships sailed from Africa to North America and found themselves stuck in the calms of the Doldrums. Ships of the time, not having the capabilities of today's ships, could spend several days, or even weeks, stuck in this unstable area. However, to prevent diseases from spreading on board in this confined area, the slave traders preferred to throw the men overboard. A theory questioned by historians, but supported by the English, who did the same with animals.
Indeed, the British refer to this area as "Horse Latitude" because, stuck under a blazing sun for several days, they were forced to put the horses overboard because they consumed too much fresh water.
