Mary Allen
The wind is moving air in the atmosphere. The wind is mainly caused by the fact that the air pressure is not the same everywhere. The greater the difference in air pressure, the stronger the wind blows. If the differences in air pressure are evened out, then the wind also stops.
The wind direction is given with the cardinal direction from which it comes – not in which direction the wind blows. The west wind comes from the west and blows to the east.
Wind also exists on planets other than Earth. This is wind from other gases that exist there, and not from the air as it is known on Earth. This is how we know about dust storms on Mars.
Not all air movement is wind: moving air in an enclosed space is a draft or draught. It arises when we open the windows for ventilation. But it also occurs when windows do not close tightly. Drafts can also occur in large or very high rooms if there are large temperature differences within the room. The wind is caused when a vehicle moves through the air.
How is wind created?
In an area with high air pressure, there are many air particles, that are close together. In an area with low air pressure, there are fewer air particles in the same space, so they have more space.
If one area is warmer or colder than another, then the air pressure is also different. The temperature plays a major role in the movement of air: If air is heated, for example by the sun, it becomes light and rises. This reduces the air pressure on the ground because there are fewer air particles there due to the air that has risen. Cold air, on the other hand, is heavy and sinks. The air particles then compress on the ground and the air pressure increases there.
But that doesn’t stay that way, because the particles in the air are distributed evenly: there should be the same number of air particles everywhere. The air therefore always flows from an area of high pressure to an area of low pressure. This creates an airflow. This is the wind. You can also say Colder air blows where warm air rises.
What kind of winds are there?
There are various zones on earth in which winds mainly come from a certain wind direction: For example, large parts of Central Europe are in the westerly wind zone. This means that there is often a wind that comes from the west and blows to the east.
Sometimes you can also tell the prevailing wind direction in an area from the trees: where moss or lichen grows on the bark of the tree, the wind also carries the rain to the tree, which then allows the moss and lichen to grow on the bark. It is therefore also said that the prevailing wind direction in an area is the “weather side”.
However, winds do not always flow evenly: there are many obstacles on Earth that can deflect the wind. On Earth, these are mainly mountains and valleys, but also built-up regions, even individual high-rise buildings. There are also winds that only arise in certain weather conditions. Sometimes such wind systems even have special names because they only appear in a certain area or at a certain time.
An example is the Alpenföhn: This is a dry and warm fall wind. It occurs on the north or south side of the Alps. Because it lost its rainwater while climbing, it then falls down into the valley as a dry and warm wind. It can become very violent and trigger foehn storms.
Another example is the land-sea wind system: the air over a lake on a warm summer day is cooler than the air over the ground, which warms up faster. At night, on the other hand, the ground cools down much faster and the lake stays warm longer. This also happens with the air above. Due to these temperature differences, it is often windy on a lake. During the day the wind blows from the cooler lake to the warmer land. It’s called sea wind. At night, on the other hand, the wind blows from the cooler land towards the warmer lake. This is the land wind.
A special type of wind is updrafts and downdrafts: an updraft can occur when the sun shines on the ground and warms the air. Warm air rises but often cools down again. As the air cools, it releases water because colder air cannot hold as much water. As a result, certain clouds form over these updrafts: the cumulus clouds, which are also called fleecy clouds. A glider pilot recognizes the updraft from these special clouds. The updraft is also called thermal. The thermal lifts a glider.
There are also downdrafts. You often hear on airplanes that you are flying through an “air hole”. But this is not a hole in the air, but an air parcel that falls down. The plane flies through it and is pulled down with it.