Pressure systems refer to the air pressure pushing down at a particular spot on the surface of the Earth (air pressure is determined by heating or cooling of the air and it moves around).
A high pressure system coming into an area is related to good weather as the high pressure means that the gases in the air are being forced downwards and squished closer together. This causes them to heat up (warm weather) and prevents condensation (no clouds, more sun).
A low pressure system has a more complicated effect on the weather, but simply, low pressure means less compression of the molecules of gas which make up the air. This means that there is less of a heating effect and more chance of condensation and cloud formation.
It’s to do with moisture in the air also. Air that’s higher in the atmosphere tends to have no less moisture in it (because the water will have already been lost to clouds/rain, or will have evaporated elsewhere). So if air comes down from high up, it will contain less moisture and won’t bring rain as it comes down to earth. Contrast a low pressure system. There the air is near land and is rising. The moisture it carries with it (which has evaporated from rivers, lakes, oceans) will condense as the air rises and form clouds, bringing rain. Low pressure systems typically therefore involve rain.
I’m not 100% happy with this though. To me low pressure means “unsettled” and high pressure means “fine” so there is something else about airflow that I’m missing. To me lows are associated with more unsettled wind patterns. The difference in pressure between high and low means that air flow is towards the low pressure zone. Perhaps all the air flowing towards one low pressure means it’s a lot of unsettled activity. In high pressure zones, all the wind flows away, which is probably a more settled thing. Less chaotic mixing. There’s also the fact that lows have varied sunlight from the clouds, so the air is being heated and cooled by the sun more randomly, and that will also unsettle things.
Pressure systems refer to the air pressure pushing down at a particular spot on the surface of the Earth (air pressure is determined by heating or cooling of the air and it moves around).
A high pressure system coming into an area is related to good weather as the high pressure means that the gases in the air are being forced downwards and squished closer together. This causes them to heat up (warm weather) and prevents condensation (no clouds, more sun).
A low pressure system has a more complicated effect on the weather, but simply, low pressure means less compression of the molecules of gas which make up the air. This means that there is less of a heating effect and more chance of condensation and cloud formation.
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It’s to do with moisture in the air also. Air that’s higher in the atmosphere tends to have no less moisture in it (because the water will have already been lost to clouds/rain, or will have evaporated elsewhere). So if air comes down from high up, it will contain less moisture and won’t bring rain as it comes down to earth. Contrast a low pressure system. There the air is near land and is rising. The moisture it carries with it (which has evaporated from rivers, lakes, oceans) will condense as the air rises and form clouds, bringing rain. Low pressure systems typically therefore involve rain.
I’m not 100% happy with this though. To me low pressure means “unsettled” and high pressure means “fine” so there is something else about airflow that I’m missing. To me lows are associated with more unsettled wind patterns. The difference in pressure between high and low means that air flow is towards the low pressure zone. Perhaps all the air flowing towards one low pressure means it’s a lot of unsettled activity. In high pressure zones, all the wind flows away, which is probably a more settled thing. Less chaotic mixing. There’s also the fact that lows have varied sunlight from the clouds, so the air is being heated and cooled by the sun more randomly, and that will also unsettle things.
OK, I convinced myself.
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