The Earth is surrounded by the atmosphere, which is made up of air. Air is a mixture of gas, solid and liquid particles. Energy from the sun heats up the atmosphere and the Earth unevenly.
Cold air contains more air particles than warm air. Cold air is therefore heavier and sinks down through the atmosphere, creating high pressure areas. Warm air rises through the atmosphere, creating low pressure areas. The air tries to balance out the low and high pressure areas – air particles move from areas of high pressure (cold air) to areas of low pressure (warm air). This movement of air is known as the wind.
The wind is also influenced by the movement of the earth. As it turns on its axis the air does not travel directly from areas of higher pressure to areas of lower pressure. Instead, the air is pushed to the west in the northern hemisphere and to the east in the southern hemisphere. This is known as the Coriolis force. Click to see a diagram of how the movement of the Earth affects wind. The Earth’s surface is marked with trees, buildings, lakes, sea, hills and valleys, all of which also influence the wind’s direction and speed. For example, where warm land and cool sea meet, the difference in temperature creates thermal effects, which causes local sea breezes.