Sunday, 10 February 2008


This image shows an anticyclone over Spain on 31st January 1999. Notice how the sky is clear - this is a defining feature of an anticyclone.

Anticyclones are areas of high pressure. They bring settled weather. If an anticyclone is sitting over the UK in the summer, it's an ideal opportunity to head for the beach!

In an anticyclone, air descends and pressure increases. This brings very light winds (which blow outwards from the centre in a clockwise motion), clear skies and dry conditions (because the air is descending and warming up, there are no clouds and no rain).

Summer Anticyclones
Summer anticyclones bring hot and sunny weather due to there being clear skies (because of the descending air). The days are long and the sun high in the sky, which gives plenty of opportunity for the land to be heated up. These conditions could therefore lead to convectional rainfall occurring.
Winter anticyclones
Winter anticyclones bring clear days too. However the sun is low in the sky and the days are short, meaning you get cool, crisp days. Clear skies on a winter’s night will allow frost to form. The land quickly loses heat during the night, as there is no cloud cover to act as insulation. The rapidly cooling ground cools and condenses any moisture in the air above it, forming droplets of ice when the temperature falls below freezing. This is frost.
Fogs are also caused by clear winter nights. The ground loses heat. This cools the air above it causing moisture to condensate around dust particles in the layer of air closest to the ground surface. This is fog.
Thanks to YouTube user BlackDollarBills for this video about the features of summer and winter anticyclones:

This video will help you to remember the key features of anticylcones.
You should now be able to complete the worksheet about the differences between depressions and anticyclones. Click on the image to be taken to the task.

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