The doldrums exist in a belt circling the globe, near the equator; this belt consistently features low atmospheric pressure, a lack of significant winds and weather that is often cloudy and rainy. Also called the intertropical convergence zone, or ITGZ, the doldrums lie between approximately five degrees north and five degrees south latitude. However, due to the Earth’s axial tilt, their extent shifts slightly south during the northern hemisphere's winter and slightly north during the northern hemisphere's summer.
Relationship to Global Wind Circulation
The doldrums fit into a global pattern of atmospheric wind circulation that involves three cells in each hemisphere. These cells entail zones of major wind belts, separated from each other by zones of relatively lighter winds in which air rises or sinks. The doldrums separate the trade winds in the northern hemisphere from the trade winds in the southern hemisphere. At the doldrums, warm air rises and flows away from the equator until about 30 degrees north and south latitude, respectively, where it descends. Some of the warm air then blows in a general westward direction in the form of trade winds, while the remaining portion blows toward the east, creating the prevailing westerlies. Air rises again around 60 degrees latitude, the boundary between the westerlies and the polar easterlies, and sinks once more at the poles.
About the Author
Based in western New York, Amy Harris began writing for Demand Media and Great Lakes Brewing News in 2010. Harris holds a Bachelor of Science in Mathematics from Penn State University; she taught high school math for several years and has also worked in the field of instructional design.