These vertical movements of air are what cause high or low pressure. High pressure. High pressure is caused by downward moving air. As air is forced downward, its pressure increases as it gets closer and closer to the surface because pressure decreases as you go up in the atmosphere.
But why does that matter? Downward moving air causes significant changes in the weather. As air moves downward it will warm, and dry out significantly. High pressure continued. Typical horizontal air flow, at the surface, around high pressure is slightly outward, away from the center. As this air moves away from the high pressure at the surface, in order to keep balance, air above must sink in to take its place.
There are two classifications for high pressure systems: cold core and warm core. Cold core high. A cold core high pressure is one where the temperature will tend to decrease as you go closer to the center. Why is this important? Well cold core highs tend to lead to very little precipitation -- a little different from warm cold highs which you'll learn about next.
This image is looking at a vertical cross-section of the atmosphere. The lines are of constant pressure -- the closer the are, the colder the temperature. The further the lines are, the warmer the temperature. Warm core high. A warm core high pressure is one where the temperature will tend to increase as you go closer to the center. So what does this mean? Precipitation is still not very common with this type of high, but it is more likely than with a cold core high.
The warmer air is, the more moisture it can hold, and moisture acts like fuel to rain showers. This means the density of air is high inside the balloon. When the density of air is high, the air pressure is high. The pressure of the air pushes on the balloon from the inside, causing it to inflate. If you heat the balloon, the air pressure gets even higher.
Air pressure depends on the temperature of the air and the density of the air molecules. Atmospheric scientists use math equations to describe how pressure, temperature, density, and volume are related to each other. They call these equations the Ideal Gas Law. In these equations, temperature is measured in Kelvin. This equation helps us explain how weather works, such as what happens in the atmosphere to create warm and cold fronts and storms, such as thunderstorms.
For example, if air pressure increases, the temperature must increase. If air pressure decreases, the temperature decreases. It also explains why air gets colder at higher altitudes, where pressure is lower. Skip to main content. How Weather Works. Cold air is denser and heavier than warm air, so it tends to sink while warm air tends to rise.
In areas where winds converge at high altitude, cold air sinks and creates a temporary buildup of air near the Earth's surface and thus a zone of high pressure. Atmospheric pressure decreases with increasing altitude, so high pressure is actually a relative term; generally, weather forecasters use this to mean high relative to normal atmospheric pressure at that altitude. As moisture-laden warm air rises, it begins to cool. Eventually, it reaches the point where the temperature of the air is low enough to become saturated with moisture.
As long as there is dust available for the water to collect on, that moisture starts to condense to form clouds. Cool air sinking toward the ground, by contrast, is growing warmer as it becomes compressed, so cloud formation is inhibited. That's why high pressure weather systems tend to free of clouds. Without clouds, there is no rain and hence the weather tends to be clear and fair.
Air flows from regions of high pressure to regions of low pressure, so near the ground the air in a high-pressure system is flowing outward.
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