anticyclonic

An anticyclone is a weather system characterized by high atmospheric pressure at its center, with air circulating outward from the center at the surface. In the Northern Hemisphere the circulation is clockwise; in the Southern Hemisphere it is counterclockwise. The air generally descends within an anticyclone, suppressing cloud formation and leading to clearer, drier conditions. As the air sinks, it warms adiabatically, which can produce a warm and dry spell in summer or contribute to temperature inversions in winter.

Anticyclones are associated with high-pressure ridges in the larger-scale atmospheric flow and can be persistent when they become blocking highs that disrupt the typical westerly flow. They form over land or sea and can cover large areas, sometimes lasting several days or weeks.

Weather effects vary by season and location. In the center of an anticyclone, winds are light, skies are usually clear, and temperatures may become extreme due to strong daytime heating or nighttime cooling. On the periphery, lighter winds and dry air can still produce gusty conditions. Moisture can stagnate under a strong center, increasing the risk of fog, frost, or haze.

Anticyclones contrast with cyclones, which are regions of low pressure with inward spiraling winds and associated clouds and precipitation. Anticyclonic conditions can occur at both surface and upper levels; an upper-level anticyclone corresponds to a ridge in the geopotential height field and often accompanies surface high pressure.

Notable examples include the Siberian High over Eurasia, the Azores High in the Atlantic, and the Pacific High. Anticyclones play a major role in regional climate patterns and short-term weather variability.