(WC) Winds Lesson

Winds

Air is a fluid that can move from place to place easily. We have already studied air pressure. Air pressure differences are the forces that will create winds. Areas of high pressure will move toward areas of low pressure. Wind is defined as the horizontal movement of air from high pressure areas to lower pressure areas.

All winds are caused by differences in air pressure.

What causes differences in air pressure?

Unequal heating of the atmosphere results in most of the differences in air pressure. Convection currents form by heating the Earth's surface by the sun's rays. The Earth's surface heats up causing the air over it to heat and begin to expand. As the air heats it becomes less dense and the heated air loses pressure. In the meantime if there is cooler air, that is more dense and has greater air pressure, nearby it will begin to flow under the heated air, less dense air. When the cooler air flows under the heated air, the heated air will push upward forcing the warm air to rise.

Measuring Wind

Winds are distinguished by their speed and their direction. Wind vanes can be used to determine wind direction. As the wind blows a wind vane will turn so that one end will point into the wind. Winds are named by the direction from which they are coming. For example if a north wind blows from the north to the south. Likewise, a south wind would blow from the south towards the north.

Think about it?

If a wind begins in the north and curves toward the east this wind would be called a answer.

To measure wind speed scientist use an anemometer.

Local Winds

Local winds blow over short distances. Local winds are caused by unequal heating of Earth's surface within a small area. Local winds form only when no winds are blowing from farther away.

Global Winds

Global winds blow over long distances. Global winds and local winds are caused by unequal heating of Earth's surface. Temperature at the equator is different from the temperature at the poles because of the amount of direct sunlight the areas receive. These temperature differences result in large convection currents in the atmosphere. The warm air will rise at the equator, and the cold, dense air will sink at the poles. Remember, warm air is less dense and has less air pressure; therefore, the air at the equator is less dense and has less pressure than the air at the poles. This causes winds from the poles to blow toward the equator, and to push the air from the equator toward the poles. The movement of air between the equator and the poles produces global winds.

Coriolis Effect

If you were holding a glass of water in your hand, and you wanted to stir the water, you could simply swirl the glass around in a circular motion to get the water in that glass to move. Our Earth rotates and the affect of that rotation is similar to the affect of swirling a glass. Winds curve in the direction of the Earth's spin. In the Northern Hemisphere, all global winds gradually turn toward the right. In the Southern Hemisphere, winds curve toward the left.

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