- The Climate of a region is greatly affected by the characteristics of the bodies of air that the prevailing winds bring.
- In the UK the prevailing winds are south-westerly and come from over the Atlantic Ocean. So the air they bring is generally warm and moist.
- Rainfall tends to increase as you travel higher above sea level. As a result hilly areas have more rain than flat areas. This is especially true if they also have warm, wet prevailing winds.
- The temperature also falls by about 1'c for every 100m in height, so high land is often cooler than low lying land.
- The temperature fall with altitude also explains how convection rainfall works:
- Winds blow because air flows from areas of high pressure to areas of low pressure (called anticyclones or depressions)
- Lines that show the air pressure are called isobars.
- As the earth is a rotating globe, winds in the northern hemisphere blow clockwise around high pressure areas and anticlockwise round low pressure areas.
- High pressure systems are where air is descending towards the Earth's surface. These systems can bring clear weather which in summer can be very hot and in winter can be very cold.
- Low pressure systems usually occur when different air masses meet. The warmer air mass rises over the cooler air mass and is lifted cooling it and producing rain.