61 Clouds, Wind, and Storms-Low

Clouds. Wind. and Storms Written by Kira Freed

Introduction Somewhere on Earth almost every kind of weather is happening right now. Do you wonder what causes weather? Earth is surrounded by a layer of air. This layer is called the atmosphere. The air may be warm or cold. It may be dry or wet. Different kinds of air mix with each other all the time. This causes wind, clouds, precipitation, and storms.

The Sun's energy hits Earth and turns to heat. The warm ground heats the air above it. Warm and cool air mix to make weather. Some parts of Earth get more energy than others. The North and South Poles get less heat than Earth's middle. Dark parts get more heat than light parts. Parts of Earth also get more sunlight than others during different seasons.

Wind Wind is air that moves. We can't see it, but we can feel it. We can see how it moves plants, flags, and other things. Air moves because the ground warms air next to it. Warm air is lighter than cold air, so it rises. The cold air above sinks to the ground because it is heavier. As that cold air gets warmer, it starts to rise. Then other cold air takes its place. All this heating and cooling of air makes wind.

The city of Chicago is a good example of a place where mixing air of different temperatures makes wind. Chicago is on a lake. When the Sun shines, the air over land gets warmer than the air over water. Warm air over the city rises. Cool air over the lake moves toward the land and replaces the warm air that rose. This causes wind to blow from the lake to the land. The larger the temperature difference between the hot and cold air, the stronger the wind.

Changes in weather happen when air of different temperatures meets. Did you ever see the lines on a TV weather map? Those lines show where warm and cold air meet. The lines are called fronts. MEASURING THE WIND We measure the wind with an anemometer. Why do people measure the wind? Here are some reasons. Knowing wind speed helps scientists predict the weather. Airplane pilots cannot take off or land if the wind is blowing too hard. Ship captains need safe wind speeds to enter harbors. Machines called wind turbines turn strong wind into electricity. In some places, the wind is too calm to use wind turbines.