Anticyclones and the Doldrums
Spindrift for Schools

 

 

By Dona Bertarelli

I want to thank all our partner schools, in France and Switzerland, and the 2,000 students who are following us. Whenever I can, I will be answering your many questions throughout this journey around the planet, a journey that we are taking together to discover the wonders of our world.
With all the crew of Spindrift 2, through our observations and our encounters, not only with marine life, but also with the islands and peninsulas that we pass, with the meteorological phenomena we experience, and with the birds and the stars that accompany us during our voyage, we will help you to live this adventure, like Phileas Fogg in Jules Verne’s famous book. We are calling our Spindrift for Schools series - Out of the Classroom.

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Anticyclones and the Doldrums

Questions from the pupils of the Vincent Van Gogh School in Baguer Morvan (France) - Teacher Karine Duprey
 
What is an anticyclone?
 
An anticyclone, or high, as it is often known, resembles a hill with a totally flat summit. Hills have sloping sides, which in meteorological terms means that there is wind. At the flat part on the summit, nothing very much happens: there is hardly any wind, just blue sky in the summer or persistent fog in the winter. At the seaside in the summer, beachgoers like anticyclonic weather, which brings warm temperatures, blue skies and sunshine. It is a great time to go to the beach, but is frustrating for us sailors, as there is not much wind for our sails.

We will see further on when we talk about the Intertropical Convergence Zone, known more familiarly to sailors as the doldrums. It is an area where masses of hot, damp anticyclonic air come together or converge, creating an unusual weather situation.  
 
What are the doldrums and where does the name come from?
 
The doldrums is the name given to a meteorological zone where the north-east winds of the northern hemisphere and the south-east winds of the southern hemisphere converge off the coast of Sierra Leone. They form a cone-shaped transitional zone towards South America, like a belt around the Earth’s equator.
 
The winds are light and there are lots of stormy squalls due to the large amount of evaporation just above the equator. As a rule, the doldrums lie between 3°N and 7°N and their activity is highly variable. They can change from light breezes and violent gusts with rain, to a large zone of calm weather, before a slow transition between two systems of trade winds of the northern and southern hemispheres.

Thanks to the many weather files and satellite images analysed by onshore router Jean-Yves Bernot and discussions on board with Erwan, our navigator, and Yann, our skipper, we were able to locate the best passage point through this tricky zone which would lose the least amount of speed before making headway towards the Southern Ocean.

The origin of the name ‘doldrums’ is shrouded in mystery. There is an old expression ‘to be in the doldrums’. Some say that this expression comes from the combination of two words. If you take the old word ‘dold’ or ‘dullard’, meaning ‘stupid’ or ‘dull or sluggish’, and add the ending of ‘tantrum’, meaning ‘a fit of petulance’, then you get ‘doldrums’. This is quite an accurate way to describe a changing nature. Others say that the expression came from reports from ships whose crews would say they were ‘in the doldrums’ when they passed through this zone. The name of the zone is thought to have resulted from a misapprehension, in that people would think the crew was describing where they were, when they were in fact using the expression to say how they felt. No-one knows for sure!  

In French, the Doldrums are called the Pot-au-Noir and the origin of the name is much less certain, inspired by many a legend and mariner’s tale.  

The seemingly most plausible story is as described by journalist and sailor Patrick Benoiton, in his inquiry when he took part in the Mini-Transat in 2005:
 
“From the start of the slave trade towards the Americas, the zone was so named by mariners, no doubt in order to purge their fear. As you approach from the north, you can tell that you are getting close to the zone as you start to see more and more cumulonimbus clouds. Torrential rain under each cloud meant that the barrels of fresh water could be refilled, replacing the often stagnant water that had been carried from Europe. Most importantly, it was an opportunity to take the cargo out to be washed, and to breathe air that was fresher and healthier than that in the holds. The cargo thus arrived in better shape and was easier to sell upon arrival. Hundreds of black slaves would end up on deck, which, understandably, would give them great pleasure. It was not long before the sailors considered this zone the friend of the black slaves, "le pote aux noirs". The term "pote" means friend or pal, and comes from local slang of the tiny port of Trentemoult, not far from Nantes, which supplied many a Cape Horner to the Royale, the French navy, and to commercial shipping. The zone thus became known as the "pote aux noirs". But very soon, the general staff opposed an expression that was so complimentary to the slaves and renamed the zone the “pot-au-noir", inventing a legend about barrels of tar used to make the hulls watertight (le pot au noir)."