Inter Tropical Convergence Zone


ITCZ, pronounced 'itch'. The Inter Tropical Convergence zone, also known as the Doldrums or the Calms, are the area on the world roughly around the equator where the Tradewinds of the northern hemisphere and southern hemisphere meet, and cancel each other out. Creating a windless area.

This area shifts north or sound with the changing of the seasons. The ITCZ moves away from the summer season area. So it shifts south during the summer in the Northern hemisphere and north during the summer in the southern hemisphere.

Due to the regular occurrence of thunderstorms on the edges of the ITCZ this area was in the past known as the Intertropical Front.

On land the ITCZ has a big effect on precipitation, creating dry and wet seasons.


If a sailing ship passes through the ITCZ it runs the risk of becoming becalmed. It gets stuck in an area with no wind. Where temperatures rise, and humidity reaches unpleasant levels. The sun will be straight above the ship, reducing the shadow areas to a minimum. Ever increasing the heat on and in the ship.

In addition there is also the fact that the seawater in those regions is significantly warmer than elsewhere on the planet due to there being less or no Ocean currents moving water from the poles to these regions. The only thing the crew can do is wait, and wait, for the ship to float into a windy area again, to continue their voyage, this waiting could last for weeks.

Even with modern meteorological tools ships occasionally get stuck in the Calms, as the ITCZ can be very difficult to predict and is irregular in its behaviour. But with engines it is possible to move to windy areas faster. That is a lot better then hoping the little currents there are push you in the right directions.


The Sunset Dawn gets stuck in the Doldrums during their voyage to Namibia. Read all about that here:

X Sperrgebiet
Prose | Nov 29, 2022

The 10th chapter. The Sunset Dawn travels south.

Cover image: by Johannes Plenio


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