# What Is Barometric Pressure?

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Barometric pressure refers to the pressure in the atmosphere that moves from high to low pressure areas. Learn about the factors that affect pressure in the air with help from a science teacher in this free video on physical science.

Part of the Video Series: Physical & Life Science
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## Video Transcript

Hi, I'm Steve Jones and I'm going to explain what barometric pressure is. When you look at a weather map, you will see these kind of lines and you'll see H's and L's on it and then you'll see numbers although you can't ever read the numbers and the numbers aren't really very important. But what they represent are the actual pressure. Now normal atmospheric pressure would be 1 bar represented by the line here. And pressure may be lower or may be higher and what you get are troughs of pressure and hills of pressure you might say, it's just like a contour diagram. So weather is a higher pressure, the pressure gets higher and higher until you reach peak pressure here or lower and lower until you reach the trough. Now obviously these differences in pressure which we call barometric pressure, these differences are produced by the way the earth's atmosphere moves and by the temperature of the surface and so forth. So there are various factors that affect the pressure of the air at any point. And of course as we know, if we've got a high pressure area and a low pressure area, we would expect movement of air from one to the other and it is this that produces wind current and so forth. Well it doesn't go straight like that, it tends to swirl and it tends to swirl in a particular direction and that is what produces the winds. Now if it's a low pressure area, we have to remember than low pressure area is quite small whereas the surrounding areas are quite large and therefore where you get a low pressure area you would expect the winds to be strongest at the weather to be worse. Where there is a high pressure area, it's bound to be fairly stable because the air moving from the high pressure area has a bigger area to move from, moving into the low pressure area. So that is basically what barometric pressure is and how it works on the surface of the earth.

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