An anticyclone is a large-scale area of high atmospheric pressure where air sinks and spirals outward, rotating clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. While the word sounds dramatic, anticyclones are behind some of the most familiar weather you experience: those stretches of clear, calm, sunny days that settle in and seem reluctant to leave. They are also behind some of the most dangerous weather events of recent decades, from record-shattering heat domes to prolonged droughts that devastate agriculture and strain power grids.
How Anticyclones Work
In a low-pressure system, air rises, cools, and condenses into clouds and rain. An anticyclone does the opposite. Air descends from higher altitudes, warming and drying as it compresses on the way down. That sinking motion suppresses cloud formation, which is why high-pressure systems are almost synonymous with fair weather. Winds around an anticyclone are typically light because the pressure gradient near the center is gentle, and the descending air discourages the kind of vertical mixing that generates strong gusts.
The direction of rotation follows from the Coriolis effect, the deflection of moving air caused by Earth’s spin. In the Northern Hemisphere, outward-flowing air curves to the right, producing a clockwise spiral. South of the equator, it curves left, giving the system a counterclockwise spin. This is the mirror image of what happens in cyclones, and the two types of system frequently sit side by side, with the anticyclone feeding dry, stable air into the space between storm tracks.
Anticyclones range widely in size and lifespan. Some are small, transient ridges that bring a pleasant weekend before the next front arrives. Others are semi-permanent features of global circulation: the Bermuda-Azores High in the North Atlantic, the North Pacific High off California, and the Siberian High that dominates central Asian winters are examples that influence weather patterns across entire continents for months at a time.
When Clear Skies Turn Dangerous
The same sinking air that keeps skies blue can become a liability when an anticyclone stalls. Without clouds, solar radiation pours in unimpeded. Without wind, hot air near the surface has no way to mix with cooler air aloft. Temperatures climb day after day, and nights fail to cool down because the dry air radiates heat poorly. This is the basic recipe for a heat wave, and research has shown that upper-level anticyclones act as a necessary precursor for their formation. In European heat waves, roughly a quarter to nearly half of air parcels arriving in these upper-tropospheric anticyclones were heated along the way, with remote heating helping to build the high-pressure system and nearby heating sustaining it once established.1Weather and Climate Dynamics. A Lagrangian analysis of upper-tropospheric anticyclones associated with heat waves in Europe
The term “heat dome” entered everyday language after the catastrophic June 2021 event in the Pacific Northwest, when temperatures in British Columbia reached nearly 50 °C. That event was driven by an interplay between a persistent, amplified atmospheric circulation pattern and drying soil. A resonant planetary wave configuration created a soil moisture deficit ahead of the event, and once the soils were dry they could no longer cool the surface through evaporation, amplifying warming through strong nonlinear feedbacks.2PubMed Central. Role of atmospheric resonance and land-atmosphere feedbacks as a precursor to the June 2021 Pacific Northwest Heat Dome event The anticyclone essentially locked the atmosphere in place while the ground beneath it superheated.
A climatological study of extreme heat events over North America found that those associated with closed anticyclones (true heat domes) are, on average, substantially larger than other extreme heat episodes. The mean spatial extent of a heat-dome event was about 560,000 square kilometers, compared with roughly 367,000 square kilometers for extreme heat events tied to other circulation features. The most spatially enormous events were almost always heat domes, meaning closed anticyclones carry outsized potential for widespread impact.3Weather and Climate Extremes. A climatology of heat domes over North America
Atmospheric Blocking and Why Weather Gets Stuck
Under normal conditions, weather systems move briskly from west to east in the mid-latitudes, pushed along by the jet stream. Occasionally, an anticyclone becomes large and strong enough to interrupt that flow entirely, forcing the jet stream to detour around it. Meteorologists call this a “block,” and it can keep the same weather parked over one region for days or even weeks.
Blocks come in recognizable shapes. A Rex or dipole block consists of an anticyclone sitting poleward of a cyclone, reversing the usual flow pattern. An omega block features a huge anticyclone flanked by a cyclone on each side, bending the jet stream into an Ω shape.4Weather and Climate Dynamics. Atmospheric blocking and weather extremes over the Euro-Atlantic sector – a review Both types are closely tied to breaking Rossby waves, the large meanders in the jet stream that normally propagate around the globe. When one of those waves breaks, it can deposit an anticyclone in a position where it resists displacement by incoming systems.
The consequences of blocking depend on which side of the block you are on. Under the anticyclone itself, you get clear skies and warmth that can escalate into drought or heat emergency. On the flanks, storm systems that would normally pass through are diverted, sometimes producing prolonged rainfall and flooding in regions that sit downstream of the block. The 1947 Central European drought, one of the worst of the twentieth century, has been linked to a persistent anticyclone over Central Europe combined with ridges of high pressure that extended over the region for weeks.5Inter-Research (Climate Research). The Central European drought of 1947: causes and consequences, with particular reference to the Czech Lands
Air Quality Under High Pressure
If you have ever noticed that smog or haze seems worse on hot, still days, you have experienced the air-quality side of anticyclones firsthand. The same descending air that suppresses clouds also creates a temperature inversion: a cap of warm air aloft that traps cooler, polluted air near the surface. With light winds, pollutants from traffic, industry, and wildfire smoke have nowhere to go.
Research tracking particulate pollution within anticyclonic systems has identified a distinctive pattern. The frontal edge of an approaching anticyclone can actually sweep pollutants away from a region. But once the central part of the high-pressure system settles overhead, with its weak pressure gradients and near-calm winds, pollutants accumulate. The trailing edge then draws in warm, moist air from the south, creating a stable channel that transports additional pollution into the area.6Atmospheric Environment. Impact of boundary-layer anticyclonic weather system on regional air quality This three-stage cycle means that the middle and late phases of a stalled anticyclone are often the worst for breathing, not the beginning.
Cities that already struggle with air quality, particularly those in basins or valleys where geography compounds the trapping effect, can see pollutant concentrations spike to hazardous levels during prolonged high-pressure episodes. For people with asthma or cardiovascular conditions, a persistent anticyclone is not just a forecast for sunshine; it is a health warning.
Anticyclones and the Ocean
High-pressure systems do not just affect what happens on land. In the extra-tropics, persistent atmospheric highs are a primary driver of marine heatwaves. When an anticyclone sits over the ocean for an extended period, the increased sunshine warms the sea surface while the reduced wind speeds suppress both evaporative cooling and the vertical mixing that normally brings cooler water from below.7Communications Earth & Environment. A global overview of marine heatwaves in a changing climate
This mechanism has been implicated in several of the most extreme marine heatwave events on record. A large proportion of the most intense extra-tropical marine heatwaves have been linked to persistent, large high-pressure systems. The connection is clearest in the Southern Hemisphere mid-latitudes, where many extreme ocean warming events formed on the equatorward flanks of high-pressure anomalies. In those locations, the anticyclone’s winds blow against the prevailing westerlies, slowing surface winds further and pushing warmer water poleward across the natural temperature gradient.8Scientific Reports. Drivers and impacts of the most extreme marine heatwave events The initial phase of the notorious “Blob,” the massive Pacific marine heatwave that began in late 2013 and disrupted ecosystems from Alaska to California, was triggered by exactly this kind of persistent high-pressure setup.
Marine heatwaves matter because they bleach coral, displace fish populations, fuel toxic algal blooms, and can alter weather patterns on nearby coasts for months after the atmospheric high has moved on. An anticyclone that hangs around for a week or two over open ocean can set in motion ecological consequences that last a year.
Polar Anticyclones and Arctic Implications
The polar regions have their own version. The Beaufort High is a semi-permanent anticyclone over the western Arctic Ocean whose clockwise winds drive the Beaufort Gyre, a major current that collects and stores freshwater from rivers and sea-ice melt. When the Beaufort High weakens or collapses, that gyre can release a pulse of fresh water into the North Atlantic, with potential consequences for ocean circulation.
In the winter of 2017, the normally anticyclonic surface winds and sea ice motion in the western Arctic reversed. The Beaufort High collapsed as low-pressure systems from the North Atlantic intruded into the Arctic Basin along the East Siberian coast, producing simultaneous anomalies in sea level pressure, surface wind, and sea ice circulation.9Geophysical Research Letters. Collapse of the 2017 Winter Beaufort High: A Response to Thinning Sea Ice? The question researchers raised is whether thinning sea ice itself made the high-pressure system more vulnerable to disruption, a feedback loop with uncomfortable implications for Arctic stability.
At the other pole, the Antarctic continent often sits beneath a strong wintertime high-pressure system fed by radiative cooling of the ice sheet. This polar anticyclone is one reason Antarctica’s interior is not just cold but extraordinarily dry, since the persistent sinking air prevents moisture from reaching the surface. Katabatic winds, the fierce gravity-driven flows that pour off the ice sheet, are partly shaped by the pressure distribution this anticyclone creates.
Impacts on Energy Systems
The collision between anticyclones and modern energy infrastructure became painfully visible during the European heatwaves of 2022. The anomalous high-pressure system that parked over Europe drove temperatures to records while simultaneously cutting renewable power generation. Wind turbines depend on wind, and the anticyclone weakened the low-tropospheric northwesterly winds that normally blow across southern Europe, reducing wind power output right when air conditioning demand was spiking.10Journal of Geophysical Research: Atmospheres. South European Heatwaves and Their Impacts on the Power System in 2022
That study highlighted a troubling double bind. Extreme heat increases electricity demand for cooling. At the same time, the very atmospheric pattern responsible for the heat suppresses wind power and can reduce river flows needed for hydropower and cooling thermal plants. As Europe leans more heavily on renewables, anticyclonic heatwaves represent a compound risk that grid planners need to account for. Battery storage, interconnectors between regions with different weather, and demand-response programs all become more critical when you recognize that anticyclones do not just bring heat but simultaneously take away a chunk of the tools for coping with it.
How Climate Change May Shift Anticyclone Behavior
One of the harder questions in climate science is whether blocking anticyclones will become more frequent, more persistent, or shift location as the planet warms. The research is not yet settled, but some patterns are emerging. Climate model projections suggest that during summer, blocking activity may shift poleward, leading to decreases in blocking frequency in the mid-latitudes but increases in high latitudes.11PubMed Central. Blocking and its Response to Climate Change
A poleward migration of summertime blocks could mean that traditional mid-latitude regions see fewer of these stalled events while the Arctic and sub-Arctic experience more. That matters for permafrost, wildfire risk in boreal forests, and the stability of polar ice sheets. Meanwhile, even if blocks do not become more common at lower latitudes, the heat waves they produce could become more severe simply because the baseline temperature is higher. A blocking anticyclone that would have produced a moderately hot week in 1990 can produce a deadly one in 2040 if it is stacking anomalous warmth on top of an already warmer climate.
The interaction with soil moisture adds another layer of concern. Drier soils amplify heat during anticyclonic events because there is less evaporative cooling to buffer rising temperatures. As droughts become more frequent in some regions, the soil is primed for more extreme heating the next time an anticyclone stalls. This kind of feedback was central to the 2021 Pacific Northwest event and is likely to become more common.
Jupiter’s Great Red Spot, the Solar System’s Most Famous Anticyclone
Anticyclones are not unique to Earth. Jupiter hosts the most spectacular example in the solar system: the Great Red Spot, a storm so large it could swallow Earth and still have room left over. It is the largest and longest-lived vortex observed in any planetary atmosphere, potentially first spotted in the seventeenth century.12Journal of Geophysical Research: Planets. Jupiter’s Great Red Spot: Strong Interactions With Incoming Anticyclones in 2019
The Great Red Spot has been shrinking. Its length has decreased from roughly 40,000 kilometers in 1879 to about 15,000 kilometers by 2020. At the same time, the maximum wind speed at its periphery has actually increased, from around 120 meters per second in 1979 to about 150 meters per second in 2020.13EGUsphere. Jupiter’s Great Red Spot Think of a figure skater pulling in their arms and spinning faster: as the vortex contracts, its rotation intensifies.
How the Great Red Spot formed has been debated for decades. Numerical simulations have ruled out two popular ideas: that it grew from the merger of smaller vortices or that it was born from a massive storm. The most likely origin appears to be a flow disturbance between the two opposed jet streams that bracket the spot to the north and south. If that is correct, the early Great Red Spot would have had relatively slow rotation that has accelerated over time as it contracted.14Geophysical Research Letters. The Origin of Jupiter’s Great Red Spot The storm’s longevity comes from its intense vorticity and its size advantage over anything that collides with it: smaller anticyclones that drift into it are absorbed rather than disrupting it.
Saturn, Neptune, and even Venus host their own anticyclonic features, though none approach the Red Spot’s scale or persistence. Studying these alien systems helps atmospheric scientists test theories about vortex dynamics in conditions impossible to replicate on Earth, where different rotation rates, atmospheric compositions, and energy sources produce strikingly different outcomes from the same basic physics.
Anticyclones in the Deep Past
Subtropical high-pressure belts, the semi-permanent anticyclones that ring the globe near 30° latitude, have not always sat where they do now. Geological evidence suggests they have shifted north and south over millions of years in response to changes in global temperature and continental configuration. Analysis of ancient sand dune orientations in northwest China, for example, traces the migration of the subtropical high-pressure belt during the Early Cretaceous period, roughly 140 to 100 million years ago. During that span, the high-pressure zone shifted substantially southward at least twice, with its position tracked by changes in prevailing surface wind direction recorded in the sedimentary rock.15GSA Bulletin. A westerly dominated Early Cretaceous eolian system in the Hami Basin, NW China
This matters for understanding our own future because the subtropical highs influence where deserts form, where rain falls, and where the major storm tracks run. Even modest shifts in the position or intensity of these anticyclonic belts can redraw the map of habitable and arable land. Evidence from the deep past suggests these shifts have happened repeatedly and sometimes rapidly on geological timescales, which is sobering when modern observations already show hints of poleward migration in some high-pressure features.