Air Pressure and Fronts: Understanding Atmospheric Processes, Study notes of Earth, Atmospheric, and Planetary Sciences

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Air Pressure and Fronts

Air Pressure

• Air has weight. Air is in constant motion and is pulled towards Earth’s center by gravity.
• Air pressure is greatest near Earth’s surface and decreases as altitude increases. Higher air pressure near the ground.

Fronts

Fronts occur where two large air masses collide at the earth’s surface. Each air mass has a different temperature associated with it. In the US, air masses usually travel west to east.

Four types of fronts

1. Cold Front
2. Warm Front
3. Stationary Front
4. Occluded Front

Why are there no fronts in the Tropics?

There are no cold air masses, just warm air.

Warm Front

Warm fronts occur when warm air replaces cold air by sliding over it. Altocumulus clouds form and may be associated with rain, snow, or sleet. Temperatures may warm slightly. Winds are usually gentle with this kind of front.

Stationary Front

Stationary fronts occur when neither warm nor cold air advances. Neither front is moving. These type of conditions can last for days, producing nothing but clouds. Temperatures remain the same and winds are gentle to none.

Occluded Front

Occluded fronts occur when a faster-moving cold air mass overtakes a slower-moving warm air mass and forces it up. The cold air mass continues until it catches up with a warmer cold air mass. Occluded fronts have cool temperatures and large amounts of precipitation.