Prevailing wind belts distribute heat and moisture across the globe. The Polar Easterlies are found in the highest latitudes of both the Northern and Southern Hemispheres. These winds are extremely cold and dry, maintaining the frigid conditions near the poles. They represent one of the three principal wind zones in the Earth’s atmospheric circulatory system.
Defining the Polar Easterlies
The Polar Easterlies are cold, dry surface winds originating from the high-pressure zones centered over the North and South Poles. These winds are located between the poles and approximately 60 degrees latitude in both hemispheres. They are named “Easterlies” because their flow is consistently from the east toward the west.
The winds are dense and carry very little moisture because cold air has a reduced capacity to hold water vapor. Their cold temperatures result from their origin over the polar caps. Compared to the Mid-latitude Westerlies, the Polar Easterlies are often weaker and more variable in speed and consistency.
They are considered a permanent wind system that forms the lower boundary of a major atmospheric circulation cell. These surface winds move outward and equatorward from the poles. Their movement is a fundamental component of high-latitude climate dynamics.
The Driving Mechanism: Polar High and the Coriolis Effect
The formation and direction of the Polar Easterlies are governed by thermal conditions and planetary rotation. Extreme cold temperatures at the poles cause the air to cool significantly, making it contract and become dense. This dense, cold air then sinks toward the surface, creating a persistent area of high atmospheric pressure known as the Polar High.
The pressure difference between the Polar High and the lower-pressure regions around the 60-degree latitude line creates a pressure gradient force. This force drives the cold, surface air outward toward the equator, seeking to equalize the pressure difference. This equatorward movement is the initial flow of the air mass.
The Earth’s rotation introduces a deflection known as the Coriolis effect. As the air moves across the rotating surface, the Coriolis effect causes the air mass to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This deflection turns the pole-to-equator flow into a consistent east-to-west wind.
The resulting surface wind circulation is a continuous outflow of cold, dense air, deflected by the Earth’s spin. This air moves from the Polar High toward the subpolar low-pressure belt near 60 degrees latitude.
Their Place in Global Circulation: The Polar Cell
The Polar Easterlies are the surface manifestation of the Polar Cell, the smallest and weakest of the three major atmospheric circulation cells in each hemisphere. This cell begins as cold air sinks at the pole, creating the Polar High. The sinking air then flows outward along the surface as the Polar Easterlies, moving toward the 60-degree latitude line.
The air mass eventually meets the warmer air masses of the mid-latitudes around 60 degrees, a boundary known as the Polar Front. This convergence causes the less dense, warmer air to rise, creating a low-pressure zone at the surface. This rising air then flows back toward the poles at high altitudes, completing the circulation loop of the Polar Cell.
The Polar Front is the boundary between the cold, dry air of the Polar Easterlies and the warmer, moist air carried by the Mid-latitude Westerlies. This collision of contrasting air masses results in a sharp temperature gradient and is a major zone for the formation of storms and mid-latitude cyclones.
The Polar Easterlies transport cold air away from the poles, contributing to the planet’s thermal balance. The Polar Cell is directly responsible for maintaining the cold and dry climates of the polar regions.