| Abstrakt: |
The doldrums are regions of low wind speeds and variable wind directions in the deep tropics that have been known for centuries. Although the doldrums are often associated with the Intertropical Convergence Zone (ITCZ), the exact relationship remains unclear. This study re‐examines the relationship between low‐level convergence and the Atlantic doldrums. By analyzing the frequency distribution of low wind speed events in reanalysis and buoy data, we show that the doldrums are largely confined between the edges of the ITCZ marked by enhanced surface convergence. While the region between the edges is a region of high time‐mean precipitation, low wind speed events occur in the absence of precipitation. Based on these results, we hypothesize that low wind speed events occur in regions of low level divergence rather than convergence. 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. 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 convergenceLow wind speed events within the ITCZ occur when precipitation is absent, suggesting they coincide with local low‐level divergence [ABSTRACT FROM AUTHOR] |
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