Key Points

• The doldrums are confined to the area of time-mean convergence of the Atlantic Intertropical Convergence Zone (ITCZ)

• The frequency distribution of low wind speed events peaks between the edges of the ITCZ, which are characterized by increased convergence

• Low wind speed events within the ITCZ occur when precipitation is absent, suggesting they coincide with local low-level divergence

Plain Language Summary

The doldrums, an area between the trade winds formerly feared by mariners because of its low wind speeds and variable wind directions, have largely disappeared from mention in the scientific literature.

The most commonly given explanation for the existence of the doldrums, according to which the weaker surface winds result from the upward circulation of the trade winds, can only be true when averaged over timescales of days or weeks.

In this study, we re-examine this region and its relationship to the convergence of the trade winds.

We show that although low wind speed events occur in the region where the trade winds meet and precipitation rates are high on average, they occur precisely when there is no precipitation.

This leads us to the hypothesis that these regions of low wind speeds are characterized by sinking rather than rising air.

Introduction

“Day after day,

day after day,

We stuck, nor breath nor motion;

As idle as a painted ship

Upon a painted ocean”

is how S. T. Coleridge described the doldrums in the 1834 poem The Rime of the Ancient Mariner. Located between the trades, the doldrums were feared for their low wind speeds and variable wind directions by mariners when sailing ships were still the primary means of sea transportation.