The “horse latitudes” refer to distinctive weather patterns. These areas are found approximately 30 to 35 degrees north and south of the equator. The unique atmospheric conditions in these latitudes have played a role in both historical navigation and global climate patterns.
Defining the Horse Latitudes
The horse latitudes are regions of subtropical high pressure, encircling Earth at roughly 30 to 35 degrees latitude in both the Northern and Southern Hemispheres. These atmospheric high-pressure belts are characterized by stability. Conditions commonly associated with these areas include light and variable winds. The air in these latitudes is typically dry, contributing to clear skies and minimal precipitation.
The Science Behind Their Formation
The formation of the horse latitudes is a result of large-scale atmospheric circulation patterns, particularly the Hadley Cells. Near the equator, solar heating causes warm, moist air to rise. As this air ascends, it cools, releases moisture, and then moves poleward in the upper atmosphere. Around 30 to 35 degrees latitude, this now cooler, drier air begins to descend back towards Earth’s surface.
This descending air compresses and warms, forming high atmospheric pressure. High pressure systems are associated with stable, sinking air, which suppresses clouds and precipitation. This explains the clear skies and arid conditions observed in the horse latitudes.
Historical Context and Characteristics
Historically, the calm and unpredictable winds of the horse latitudes posed significant challenges for sailing ships. Mariners often found themselves becalmed for days or even weeks, leading to prolonged voyages and dwindling supplies. One widely circulated explanation for the name “horse latitudes” suggests that during such prolonged periods of calm, ships transporting horses to the New World would sometimes throw the animals overboard. This drastic measure was reportedly taken to conserve precious drinking water or lighten the ship to catch any slight breeze.
Beyond their historical impact on maritime travel, the horse latitudes are climatically significant today. The persistent dry, stable air masses in these regions are directly linked to the presence of many of the world’s major deserts. Examples include the Sahara Desert in Africa, the Arabian deserts, and the southwestern United States deserts in the Northern Hemisphere, as well as the Atacama, Namib, Kalahari, and Australian deserts in the Southern Hemisphere. These arid zones are a direct consequence of the atmospheric conditions created by the descending air of the Hadley Cells.