62 Clouds, Wind, and Storms-Mid

Clouds, Wind, and Storms Written by Kira Freed

《云、风和风暴》作者:基拉·弗里德

Introduction Somewhere on Earth, almost every kind of weather is happening right now. Did you ever wonder? what causes all these kinds of weather Around Earth is a layer of air called the atmosphere. The atmosphere is made of different kinds of air—warm, cold, dry, and wet. When different kinds of air move and mix with each other, it causes wind, clouds, precipitation, and storms.

在地球上的某个地方，几乎每一种天气都在发生。 你想过吗?地球周围有一层空气层，叫做大气。 大气是由不同种类的空气组成的——温暖的、寒冷的、干燥的和潮湿的。 当不同种类的空气移动并相互混合时，就会产生风、云、降水和风暴。

Weather happens in the part of the atmosphere closest to Earth's surface. The Sun's energy hits the ground and turns to heat. Then the air above the ground heats up. Some air becomes warmer than other air. When warm and cool air mix, the result is weather. Some parts of Earth get more energy than others. The air closer to the equator gets warmer than the air at the poles. Also, dark areas absorb more heat than light areas. Finally, different places get more sunlight than others during different seasons.

天气发生在大气中最接近地球表面的部分。 太阳的能量撞击地面并转化为热量。 然后地面上的空气变热。 有些空气比其他空气更热。 当暖空气和冷空气混合时，就形成了天气。 地球上的一些地方比其他地方获得更多的能量。 靠近赤道的空气比两极的空气更热。 而且，黑暗的区域比明亮的区域吸收更多的热量。 最后，不同的地方在不同的季节比其他地方得到更多的阳光。

Wind Wind is moving air. We can't see it, but we can feel it. And we can see how it moves plants, flags, and other things. Air moves because warm air. is lighter than cold air Air near the ground gets warmed up by the ground's heat. The warm air gets lighter, so it rises. Then colder, heavier air takes its place near the ground. The air that was warm starts to cool off higher in the atmosphere. Then as the cold air close to the ground becomes warmer, it rises. Now other cold air moves in to take its place. The cycle of heating and cooling of air makes wind.

风是流动的空气。我们看不见它，但我们能感觉到它。 我们可以看到它是如何移动植物、旗帜和其他东西的。 空气流动是因为暖空气。 比冷空气轻地面附近的空气被地面的热量加热。 暖空气变轻，所以上升。 然后更冷、更重的空气在靠近地面的地方取而代之。 温暖的空气在大气层的高处开始冷却。 然后，随着靠近地面的冷空气变暖，它上升。 现在其他冷空气进入取而代之。 空气的加热和冷却循环产生风。

Think about Chicago, which is on Lake Michigan. When the Sun shines, the air over land heats up more than the air over water. As warm air over the city rises, cooler air over the lake moves toward the land to take the place of the rising warm air. This causes a breeze from the lake to the land. Why is wind strong sometimes and just a light breeze at other times? Wind gets stronger as the difference in temperature between warm air and cool air becomes greater.

想想密歇根湖边的芝加哥。 当太阳照耀时，陆地上的空气比水面上的空气热得多。 当城市上空的暖空气上升时，湖上空的冷空气就会向陆地移动，取代上升的暖空气。 这就产生了从湖泊吹向陆地的微风。 为什么有的时候风很大，有的时候风很小? 暖空气和冷空气之间的温差越大，风就越强。

Changes in weather happen when air of different temperatures meets. The line where the warm and cold air meet is called a front. Fronts are where weather changes often start. Measuring the Wind We measure the wind with an anemometer. Why do people measure the wind? Here are some of the reasons. Wind speeds help scientists predict the weather. Pilots cannot take off or land if the wind is strong. Ship captains need safe winds to enter harbors. Machines called wind turbines change wind into electricity. In some places, the wind is too calm to use wind turbines.

当不同温度的空气相遇时，天气就会发生变化。 冷暖空气相遇的线叫做锋面。 锋面通常是天气变化开始的地方。 测量风我们用风速计测量风。 人们为什么要测量风? 以下是一些原因。 风速有助于科学家预测天气。 如果风力很大，飞行员就不能起降。 船长需要安全的风才能进港。 被称为风力涡轮机的机器将风能转化为电能。 在一些地方，风太平静，不能使用风力涡轮机。