What is Air Pressure?
The air around us may not seem heavy but it really is, especially when it is moving as wind. Air movements can vary from light to strong and are caused by different air pressures.
Air pressure can be low or high depending on the temperature of the air. Low air pressure occurs when warm air rises. This air is lighter than cold air and is able to move upwards. This upwards movement results in low air pressure, as the general air pressure is lighter.
As the warm air moves cold air comes in to take its place. This movement of cooler air, which is denser, is called high air pressure. Cold air is always replacing the rising hot air.
High air pressure usually means fine weather. Low air pressure means there is a possibility of rain.
Air pressure can be low or high depending on the temperature of the air. Low air pressure occurs when warm air rises. This air is lighter than cold air and is able to move upwards. This upwards movement results in low air pressure, as the general air pressure is lighter.
As the warm air moves cold air comes in to take its place. This movement of cooler air, which is denser, is called high air pressure. Cold air is always replacing the rising hot air.
High air pressure usually means fine weather. Low air pressure means there is a possibility of rain.
Wind
Although we cannot see the air around us we can feel it when it moves. This movement is known as wind and can vary greatly in strength. Winds begin when the sun heats the ground. This heat then rises into the atmosphere causing low and high air pressure. This movement is felt as wind.
There are many different winds and they are often categorised by their strength and direction of flow.
The wind can also move in many different directions. Air tends to move from high pressure areas to low pressure areas in a spiral. The direction of the spiral depends on whether the wind is in the southern or northern hemisphere. In the southern hemisphere, which is where Australia is located, air that is in a high pressure system will spiral in an anti-clockwise direction and air in a low pressure system will spiral outwards in a clockwise direction. In the northern hemisphere it is the opposite.
Wind speeds can also vary greatly. Wind speed is determined by different air pressures. High pressure air (cold air) is always moving in to take the place of low pressure air (warm air). The greater the difference between the two pressures the stronger the wind will be, for example if there is a great amount of warm air rising (low pressure) then there will be a great amount of cold air (high pressure) moving in to take its place. Therefore the wind will be stronger.
Different winds are determined by their different strengths. Gentle winds are described as breezes and powerful winds are known as gales. The direction a wind is coming from can also be used in its description, for example weather reports will mention southerly winds.
There are many different winds and they are often categorised by their strength and direction of flow.
The wind can also move in many different directions. Air tends to move from high pressure areas to low pressure areas in a spiral. The direction of the spiral depends on whether the wind is in the southern or northern hemisphere. In the southern hemisphere, which is where Australia is located, air that is in a high pressure system will spiral in an anti-clockwise direction and air in a low pressure system will spiral outwards in a clockwise direction. In the northern hemisphere it is the opposite.
Wind speeds can also vary greatly. Wind speed is determined by different air pressures. High pressure air (cold air) is always moving in to take the place of low pressure air (warm air). The greater the difference between the two pressures the stronger the wind will be, for example if there is a great amount of warm air rising (low pressure) then there will be a great amount of cold air (high pressure) moving in to take its place. Therefore the wind will be stronger.
Different winds are determined by their different strengths. Gentle winds are described as breezes and powerful winds are known as gales. The direction a wind is coming from can also be used in its description, for example weather reports will mention southerly winds.
Experiment
Make a pinwheel wind collector
Australian Winds
Winds in AustraliaAustralia's wind patterns are as diverse as its landscape. Australia has coastal areas, mountain areas and dry open areas which all contribute to different types of winds.
Maatsuyker Island, of the south coast of Tasmania, is Australia's windiest place. The average wind speed, annually, is 32 kilometres per hour. See the image.
Australia's three most well-known winds are The Fremantle Doctor, The Southerly Buster and The Brickfielder.
The Fremantle Doctor winds hit areas around Perth and Fremantle, in Western Australia, every afternoon. These winds are sea breezes that come from the Indian Ocean and cool the area.
The Southerly Buster occurs in Sydney during hot days. This is a cool wind that comes from the Pacific Ocean and relieves Sydneysiders from the heat of summer. The Southerly Buster is similar to The Fremantle Doctor.
The Brickfielder winds are hot winds that hit South Australia. These winds develop in the centre of Australia (where there is mostly desert) and travel south. These winds are caused by extreme heat and can raise temperatures in South Australia to nearly 40 degrees Celsius. These winds can last for a few days.
Maatsuyker Island, of the south coast of Tasmania, is Australia's windiest place. The average wind speed, annually, is 32 kilometres per hour. See the image.
Australia's three most well-known winds are The Fremantle Doctor, The Southerly Buster and The Brickfielder.
The Fremantle Doctor winds hit areas around Perth and Fremantle, in Western Australia, every afternoon. These winds are sea breezes that come from the Indian Ocean and cool the area.
The Southerly Buster occurs in Sydney during hot days. This is a cool wind that comes from the Pacific Ocean and relieves Sydneysiders from the heat of summer. The Southerly Buster is similar to The Fremantle Doctor.
The Brickfielder winds are hot winds that hit South Australia. These winds develop in the centre of Australia (where there is mostly desert) and travel south. These winds are caused by extreme heat and can raise temperatures in South Australia to nearly 40 degrees Celsius. These winds can last for a few days.