5) It does not affect small scale wind motions (like a homerun hit in a baseball game). Airlines must make course corrections to compensate for the Coriolis Effect.
Curved Flow and the Gradient Wind Gradient Winds Winds which blow at a constant speed parallel to curved isobars. (This is especially true around cells of high or low pressure.) Cyclones These are centers of low pressure. The flow around them is considered to be cyclonic. Cyclonic Flow Has same direction of rotation as the Earth, that is it is counterclockwise in the Northern Hemisphere . Troughs elongated regions of low pressure flow around a trough is cyclonic
Anticyclones These are centers of high pressure. The flow around them is considered to be anticyclonic. Anticyclonic Flow Has the opposite direction of rotation as the Earth, that is it is clockwise in the Northern Hemisphere. Ridges Elongated regions of high pressure are called ridges. Flow around a ridge is anticyclonic.
Friction Winds do not become faster indefinitely. Friction acts to slow a moving object. Friction significantly influences air flow near Earth’s surface . Friction’s affect is negligible above about 2300 feet (700 meters). Friction force varies with : a) surface texture b) wind speed c) time of day or time of year d) atmospheric conditions Surface Friction : a) decreases wind speed b) decreases the Coriolis Effect c) causes convergence into an area of low pressure
Surface Winds Friction affects winds only within a few kilometers of Earth’s surface. (Friction has an appreciable effect only approximately within 2300 feet (700 meters) of the Earth’s surface.) Friction slows the movement of air and also reduces the Coriolis Effect which is proportional to wind speed . Because the pressure gradient force is not affected by wind speed, it wins the tug of war against the Coriolis Effect, and wind direction changes. The result is the movement of air at an angle across the isobars, toward the area of lower pressure.
Near the Surface Friction plays a major role in redistributing air within the atmosphere by changing the direction of airflow . By adding the effect of friction, the airflow crosses the isobars at varying angles , depending upon the roughness of the terrain, but always from higher to lower pressure . Above the Friction Layer (in the Northern Hemisphere) Winds blow counterclockwise around a cyclone and clockwise around an anticyclone, with winds nearly parallel to the isobars.
Cyclone With pressure decreasing inward, friction causes a net flow toward its center . Anticyclone With pressure decreasing outward, friction causes a net flow away from the center . Northern Hemisphere Resultant Winds Blow into and counterclockwise about a surface cyclone . Blow outward and clockwise about a surface anticyclone .
- Fall '16
- Mark Smith
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