How the gases in our atmosphere behave is affected by: zz
zz zz
Temperature Altitude Pressure
As a result, changes in atmospheric pressure have a big effect on our weather.
A scientist who studies the atmosphere is called a meteorologist. They can use changes in atmospheric pressure to predict the weather.
A barometer is used to measure atmospheric pressure.
Air moves from high to low pressure. This movement of air causes changes in our weather. z z
zz
Low atmospheric pressure usually brings wet and windy weather.
High atmospheric pressure usually brings calm and dry weather.
Weather Charts Lines on a weather chart that join areas of equal pressure are called isobars.
The closer the isobars are together on a weather chart, the stronger the wind will be.
The boundary between two different air masses is called a front. zz
zz
Warm fronts form where warm air rises over cold air. This causes cloudy weather. On a weather chart, a warm front is shown as a red line with red semicircles.
Cold fronts form where cold air replaces warmer air. This causes rain. On a weather chart, a cold front is shown as a blue line with blue triangles.
zz
Where a cold front overtakes a warm front, an occluded front forms. An occluded front causes changeable weather. On a weather chart, an occluded front is shown as a purple line with purple triangles and semicircles (a mix of the warm and cold front lines).
z Fig. 22.4.6
What weather conditions is Ireland experiencing in this picture?
z
Fig. 22.4.5 A barometer
22.4
Learn more about atmospheric pressure in Physical World 17.6
