Anticyclones are areas of high atmospheric pressure. Winds always blow clockwise in an anticyclone. Think of two ways in which you can tell that the pressure is high. Go to the forecasting tutorial for help!
High pressure at the surface of the earth results from air that is descending from high in the atmosphere and is stable air. Descending air discourages condensation so there will be little cloud cover and clear skies both in the winter and the summer. The weather that anticyclones bring has some similarities between the seasons.
Summer
Anticyclonic conditions in the summer bring clear skies, sunshine, low wind speeds, high temperatures and dry weather. Because anticyclones are stable areas of pressure they can stay over an area for many weeks. Prolonged periods of hot dry weather are sometimes called heat waves.Weather like this is good news for most people, we can enjoy the outdoors and it often coincides with school holidays. Sometimes though it gets just too hot and day after day can be very unpleasant and even dangerous when the heat index gets too high.
Winter
In the winter anticyclones again have stable air so there are clear skies and calm, dry conditions. The lack of cloud now tend to bring very cold weather. At night the lack of cloud cover means that any energy from the sun absorbed by the ground during the day is radiated back to space. Temperatures drop so low that frost can occur and even ice on surfaces like roads. During the day it can be sunny with clear blue skies and no rain but again it can feel cold.
Activities
- Outline four ways in which the weather map in the pdf version shows anticylonic conditions over the British Isles.
- Discuss with a partner or in small groups some ways in which people could be affected by anticyclonic weather in the summer and the winter.
- Summarize these ideas in the table available in the pdf version of this activity.
