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Global and Local Winds
Uneven heating of air in the atmosphere creates air temperature differences. Air that is warm expands and therefore is less dense and has lower pressure than colder air. WIND is the result of the air pressure and density differences caused by warm and cool air. Air flows from high-pressure areas to low-pressure areas, creating wind.
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Global Winds
Differing air temperatures around the world cause winds that loop across the planet. The sun's rays strike the Earth more directly near the equator than near the poles. So, the air heats up more near the equator equator than the poles. Therefore, warm air from the equator rises and moves toward the poles, while cold air from the poles moves toward the equator to replace it.
The Earth's rotation, combined with these differing air temperatures, causes the movement of air from the equator and the poles to curve in different directions. This is called the CORIOLIS EFFECT. The Coriolis effect causes winds to curve to either the east or west, creating predictable wind patterns in different parts of the world.
Jet Stream
Although some winds blow at the Earth's surface, there are also high-altitude winds, which are located in the upper troposphere. In North America, the global JET STREAM is formed at the boundary between cold and dry air from the North Pole, and warmer air from farther south.
The air temperature differences cause the jet stream to be very strong-up to a steady 250 miles per hour, which usually blows from west to east.
The air temperature differences cause the jet stream to be very strong-up to a steady 250 miles per hour, which usually blows from west to east.
Local Winds
There are daily breezes where the ocean meets the land because land cools and warms faster than water (water stays nearly the same temperature day and night). Land is heated during the day, which heats the air above it through condiction. This warm air rises, causing convection currents with cooler air from the ocean. During the day, cooler air moves ashore and is called a SEA BREEZE. At night, air above the ocean water is warmer than the air on land, so it rises. The resulting convection current forms a wind that moves out into the ocean from the land, called a LAND BREEZE. Local winds are also caused by topography, like the different temperatures in a valley or wind funneling through a mountain pass.