You can't see it, you can't smell it, you can't always hear it, but you know it's there because of how everyday objects react to it. We know it as the wind, but where does the wind come from?

Have you ever noticed that when it's cold outside and someone opens the front door of your warm, cozy house, the precious warm air quickly disappears out the door to be replaced by the cold air that your house is designed to keep out in the first place! Well, wind is made a bit like that.

Put simply, when hot air from warmer countries such as Spain meets cool air from places like England two things will happen.

Firstly, warm air - which weighs less than cold air - will begin to rise above the heavier cold air. In this instance the cold air moves in and takes over the place originally occupied by the warm rising air.

Secondly, the warm air will contract at the point where it meets the cold air as the cold air will reduce the temperature of the warm air. This contraction creates a ‘partial vacuum ‘and has the effect of drawing more warm air in towards it.

These movements of the air are what we perceive as wind. The greater the differences in temperature are between two bodies of are – the greater the strength of wind is produced.

A more detailed and scientific answer follows:

The production of wind is caused by a variety of natural phenomenons. The ones that have the greatest effect are listed below:

1. It is the differing levels of heat on the surface of earth that is the main cause of wind. However, heat input from the sun will depend on the season, along with cloud cover, latitude, and surface conditions. There will also be differing effect depending on which part of the earth the sun is shining on. Ocean surfaces heat and cool slowly, while land heats and cools quickly.

2. This all combines to affect overall air pressure. When one area heats up the air pressure rises, and this higher pressure air will naturally expands and try to diffuse into areas of lower pressure and vice versa. however, the production of wind is also affected by the spin of the earth, and the orbiting pull of the moon.

3. As wind is the movement of air, anything moving on the earth can cause wind, albeit just on a very small scale.

4. Warmed air also rises, while cooling air sinks.

5. As air moves around the earth's surface it crosses areas that are moving either faster or slower than the air.

6. Close to the pole, the Earth - and the air flowing over it - are moving much slower than are the air and earth at the equator. Air moving outward from the axis or inward toward the axis has a different angular momentum that the area it is moving into. This is called the Coriolis Effect and it results in air moving in cyclonic patterns. The effect is relatively mild at the equator- but gains in strength as you move toward the poles and thus closer to the axis of rotation. This is why hurricanes become more forceful as they move away from the equatorial regions.

7. Air in a High pressure zone flows outward, dissipating its energy, resulting in calm weather. But air flowing into a low pressure zone is concentrating its energy into a smaller space. This is why low pressure zones cause generally higher winds and stronger cyclones.

8. Wind is caused by air flowing from high pressure to low pressure.

9. Winds form because air pressure varies from place to place and high air pressure will naturally move to a low air pressure area.

10. When the sun warms an air mass - over coastal land, for example - the warm air rises. Cooler air masses -over the ocean, for example - remain lower and will flow in under the warmer air mass creating an onshore breeze.

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