The Atmosphere
Movement in the Atmosphere
Atmospheric Stability
Localised Winds
Clouds
Fronts
Visibility and Fog
Aircraft Icing
Thunderstorms
Altimetry
Weather Reports and Forecasts
Practice Exam

Anticyclones

An area of high pressure at the surface is known as an anticyclone. Since it is a high pressure system, we know from the lessons on Air Pressure and Convergence & Divergence that the wind blows clockwise around an anticyclone and there is divergence at the surface.

Weather in an Anticyclone

The air is converging at high altitude and descending down the centre of the anticyclone, warming as it descends. So in an anticyclone we can expect:

A very stable atmosphere
Little cloud or clear skies
If the anticyclone persists, visibility will worsen as the descending air traps any dust, smoke, and other particles in the lower layers of the atmosphere
The isobars in an anticyclone are more widely spaced, so they have a weaker pressure gradient and lighter winds than a depression
Since the air is descending and warming, it can create an area of warmer air at altitude while the air close to the ground remains cooler – this is a subsidence inversion

The photo below was taken on a classic high pressure day. Subsidence has led to an inversion with haze trapped at low altitude, little cloud cover, and light winds.

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