Monday, January 19, 2009

The Coriolis Effect and the Pressure Gradient Force

How you ever wondered what enables weather on Earth? Well, it is the Coriolis effect. The Coriolis effect is a result of the Earth' rotation. To see it in action, draw a straight line on a spinning disc. The line you are drawing is straight, but it appears curved because the disc was moving. The same goes with the Earth. When a low-pressure system forms, the pressure-gradient force combines with the Coriolis effect. The pressure gradient force is the force that crates wind. Logically, air is pushed from the high-pressure to the low pressure area, just as air whooshes into a vacuum. This creates wind. The higher the difference in pressure and the shorter the distance, the stronger the wind is. Eventually, however, the Pressure Gradient Force is balanced off by the Coriolis effect, which sends the air in a spinning motion. In the northern hemisphere counterclockwise, in the Southern Hemisphere clockwise. For this reason, low-pressure systems cannot form over the Equator. If this spinning becomes associated with convection in tropical regions, the system becomes a tropical storm or hurricane.

This is a polar low-pressure system over Iceland. It is NOT a tropical system.

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