ch 6 GEOG 2050 - Chapter 6 FForces in the atmosphere 1...

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FForces in the atmosphere: 1. Pressure gradient force: the stronger the gradient, the stronger the pressure gradient force, and the stronger the wind Pressure gradient always pushes the air from a high spot to a low spot 2. Coriolis force: anytime you have air or anything in the atmosphere moving and it goes from one latitude from another, say something starts off at the equator and goes north, when it takes off, because it is sitting on the ground and rotating it takes off with a certain built in speed and as it flies north it goes through some areas with lower angular velocities so as it flies north it appears to run ahead of the areas its flying into so since it appears moving faster so it actually gets a little bit ahead. o So the coriolis force is kind of an “apparent” force it isn’t a “true” force, it is created by a difference in angular velocities and it affects the movements of air and other objects that is changing in its velocity. North defection goes to the right and the south to the left. At the equator the CF =0 that is the point were you are changing form one hemisphere to another so there is no CF. as you move toward the north pole the CF increases and the north pole it is its max. it is also max at the south pole. o They are the same strength and they point against each other. CF is zero at the equator and max at the poles and opposite and equal to PGF 3. Friction force: only near to the ground (about a mile). After the first mile of the atmosphere you don’t need to worry about friction a. Planetary boundary layer: first mile that we need to worry about atmosphere. Air moves more slowly to the ground because of the friction and balances the CF and wind actually crosses the isobars b. Free atmosphere: the level of atmosphere above that one-mile mark that you do not have to worry about friction. The wind stays parallel because of no friction. Winds in the upper atmosphere: Called the free atmosphere above about one mile PGF and CF are balanced by each other. Wind is perpendicular to the forces and flows parallel to the isobars. Geostrophic flow is the balance between the PGF and CF that creates wind that flows parallel to the isobars. Wind speeds up as it goes around the high pressure and slows down when it goes around the low pressure. o IF there is a large high-pressure cell the wind will accelerate around it. While this is happening, the CF goes up so the PGF and CF are temporarily out of balance. This is called the super-geostrophic (when the CF temporarily gets bigger. o When there is a low pressure cell, the CF gets smaller and this is called a sub-geostrophic o Gradient flow is the balance plus all of the temporary flows. Wind moves parallel to the isobars. In a high pressure cell the winds flow clockwise while the winds flow
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ch 6 GEOG 2050 - Chapter 6 FForces in the atmosphere 1...

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