Polar easterlies are prevailing easterly winds found at high latitudes near the North and South Poles. They form the polar branch of Earths broad three cell atmospheric circulation and generally blow from polar high pressure regions towards lower pressure areas at subpolar latitudes. In the Northern Hemisphere, polar easterlies generally have a northeasterly component, while in the Southern Hemisphere they generally have a southeasterly component.
They are called easterlies because the wind generally has a westward component, meaning it comes from the east. The polar easterlies are typically cold and relatively dry near the surface because they originate in or near the polar regions. Their direction and strength vary with season, pressure patterns, sea ice, temperature contrasts and transient weather systems. They are therefore broad climatological circulation features rather than permanent winds blowing at a uniform speed.
The polar easterlies arise from the interaction between polar high pressure, subpolar lower pressure and Earths rotation. Intense radiative cooling near the poles makes surface air very cold and dense. Dense air tends to sink, contributing to relatively high surface pressure over the polar regions. Air then flows outward towards lower pressure at somewhat lower latitudes. The Coriolis effect deflects this equatorward moving air, producing an easterly component.
In the Northern Hemisphere the deflection is to the right, resulting in generally northeasterly flow, while in the Southern Hemisphere the deflection is to the left, producing generally southeasterly flow. This circulation forms part of the polar cell, in which air rises around subpolar latitudes, moves poleward aloft, descends over the polar region and returns towards lower latitudes near the surface.
Polar easterlies are generally cold because the air masses associated with them originate over high latitude surfaces where solar heating is weak, especially during polar winter. They can also be relatively dry because cold air has a low capacity to contain water vapour and because polar regions often receive little precipitation.
However, the actual moisture content and weather produced by polar easterly flow depend strongly on whether the air travels over ocean, sea ice or land before reaching a particular location. Air crossing open water can acquire moisture and become modified, potentially producing clouds or snow. Interaction with warmer ocean surfaces can also destabilise cold air and generate convective cloud formations. Therefore, describing polar easterlies simply as cold and dry is useful climatologically but does not mean that every individual polar easterly flow is cloudless or precipitation free.
The polar easterlies interact with the westerlies at the boundary between polar and middle latitude air masses. This region is associated broadly with the subpolar low pressure belt and the polar front, although the exact position and structure of the polar front vary considerably. Strong temperature contrasts between cold polar air and warmer middle latitude air can support cyclogenesis and frontal activity.
The upper atmosphere contains strong westerly winds and jet streams near these temperature gradients, while surface polar easterly flow can participate in the development and evolution of extratropical weather systems. The relationship between polar easterlies and the polar front is therefore dynamic rather than a simple fixed boundary. Weather systems can transport polar air far towards lower latitudes and relatively warm air towards the poles, temporarily disrupting the idealised circulation pattern.
The polar easterlies are influenced strongly by seasonal changes in solar radiation. During polar winter, prolonged darkness produces intense surface cooling and can strengthen polar high pressure and temperature gradients. During summer, continuous or prolonged daylight reduces the strength of radiative cooling, although the low solar elevation and reflective surfaces still limit heating compared with lower latitudes. Sea ice also modifies the surface energy balance by separating the atmosphere from relatively warm ocean water and reflecting incoming sunlight.
Seasonal changes in sea ice extent can therefore influence regional pressure patterns and atmospheric circulation. Land and ocean distribution differs greatly between the Arctic and Antarctic, so the two polar regions do not behave identically. Antarctica is a large high continental ice sheet surrounded by the Southern Ocean, whereas the Arctic is primarily an ocean surrounded by continents. These geographic differences produce important differences in polar atmospheric circulation.
Polar easterlies contribute to the transport of cold air away from polar regions and therefore participate in the global redistribution of heat. Although the global circulation does not simply transport air in a single continuous conveyor belt, the polar cells form part of a larger system through which energy is redistributed from regions of surplus heating towards regions of deficit.
Polar winds also influence sea ice movement, ocean surface conditions and the transfer of heat and moisture between the atmosphere and ocean. Strong winds over snow and ice can redistribute snow, expose or cover surfaces and affect surface energy balance. Near Antarctica, interactions between polar atmospheric circulation and the Southern Ocean contribute to broader climate processes. In the Arctic, winds influence sea ice drift and can affect the transport of heat and moisture into high latitudes.
The term polar easterlies refers primarily to the prevailing wind belt, not to every wind observed near the poles. Local pressure systems, katabatic winds, mountain effects, cyclones and other processes can produce winds from different directions. Antarctica in particular experiences strong katabatic winds, in which dense cold air flows downslope under gravity from the elevated interior towards the coast. These winds can have directions that differ from the idealised polar easterly circulation.
Similarly, Arctic coastal and continental environments experience local and regional wind systems that can temporarily dominate over the background circulation. The idealised three cell model is therefore a conceptual framework for understanding average global circulation, while actual polar wind fields are more complex and variable. Observations and numerical models reveal substantial regional and temporal variation.
Polar easterlies are important for understanding high latitude weather, climate and interactions between polar and middle latitude air. They help explain why cold air can move away from the polar regions and why strong temperature contrasts can develop near the polar front. They also form a useful counterpart to the tropical trade winds and middle latitude westerlies in the standard global circulation model. The three broad wind belts should not be interpreted as perfectly separated zones with sharp boundaries.
Their positions shift, overlap and interact with transient weather systems. The polar easterlies are therefore best understood as a large scale climatological tendency produced by polar cooling, pressure gradients and planetary rotation, with their real world behaviour modified by season, geography, sea ice, topography and atmospheric disturbances.
