Antisykloner

Antisykloner, also known as anticyclones, are regions of high atmospheric pressure where the surface pressure is higher than in surrounding areas. They are associated with sinking air, which suppresses cloud formation and tends to produce clear skies and light winds. In the Northern Hemisphere the winds around a high rotate clockwise, while in the Southern Hemisphere they rotate counterclockwise.

The center features descending air that warms as it sinks (adiabatic heating). This stabilizes the column, reduces humidity, and limits convection. Weather is typically settled and dry; clouds are sparse and daytime temperatures can rise with warm air masses, while clear skies can lead to cool nights. In winter, inversion layers and fog can occur.

Antisykloner form when high pressure builds in the mid-latitudes, often upstream of a departing cyclone, or as upper-level ridges that create a surface high. They can be short-lived or persist for days or weeks, and blocking highs can slow or divert approaching storms.

They contrast with cyclones, which are low-pressure systems with rising air, cloud formation, and precipitation. Anticykloner move with prevailing winds and may become stationary, causing prolonged dry spells or temperature extremes, especially in continental climates. Weather maps depict them with widely spaced isobars indicating a weak surface pressure gradient.