42 Atmosphere and Climate-Mid

Atmosphere and Climate Written by Karen de Seve

《大气与气候》Karen de Seve著

Introduction Look up into the sky. There's a very thin, invisible shield surrounding Earth. It's called the atmosphere. This invisible shield makes life on Earth possible. It provides the air we breathe, the weather we experience, and the conditions needed for life on Earth. It protects us from the Sun's harmful rays. It controls the amount of Earth's heat that escapes into space. In this book you will learn about Earth's atmosphere, what it is made of, and how it makes life possible. You will learn the difference between weather over short and long periods of time. You'll also learn what makes up the atmosphere and how it is changing.

抬头看看天空。 地球周围有一层看不见的薄盾。 它叫做大气。 这个无形的盾牌使地球上的生命成为可能。 它提供了我们呼吸的空气，我们经历的天气，以及地球上生命所需的条件。 它保护我们免受太阳有害射线的伤害。 它控制着地球散发到太空中的热量。 在这本书中，你将了解地球的大气层，它是由什么组成的，以及它是如何使生命成为可能的。 你将了解短期和长期天气的区别。 你还将了解大气的组成以及它是如何变化的。

Earth's Invisible Shield The atmosphere is like a blanket. It protects and warms Earth's surface. The atmosphere rises more than 700 kilometers (430 mi.) above Earth's surface. It contains all the gases needed for life, such as nitrogen and oxygen. The atmosphere also contains small amounts of the gases argon, carbon dioxide (CO2), water vapor, and a few others. Oxygen is the gas that we need most. Without oxygen, life as we know it could not exist.

地球的隐形盾牌大气层就像一张毯子。 它保护和温暖地球表面。 大气层高出地球表面700多公里(430英里)。 它含有生命所需的所有气体，比如氮气和氧气。 大气中还含有少量的氩气、二氧化碳、水蒸气和其他一些气体。 氧气是我们最需要的气体。 没有氧气，我们所知道的生命就不可能存在。

Gases are like all matter. They are made up of small, invisible particles called molecules. Gravity pulls the molecules toward Earth, packing them together. This blanket of gas molecules creates air pressure on all things within the atmosphere. At the bottom of the atmosphere—at sea level—air pressure is fairly high. Far up in the atmosphere, the air pressure is much lower.

气体就像所有物质一样。 它们由一种叫做分子的看不见的小粒子组成。 重力将分子拉向地球，将它们聚集在一起。 这层气体分子毯对大气中的所有物体都产生了空气压力。 在大气的底部——海平面——气压相当高。 在大气层的高处，气压要低得多。

You do not usually feel air pressure. The reason is because the pressure inside your body is about the same as the pressure outside your body. But when you take off in an airplane or drive up a mountain, you go higher in the atmosphere, where the air pressure is lower. As the outside air pressure drops, the air pressure inside your ears stays the same. As air exits your ears, you might hear a popping sound. Do You Know? Air pressure drops the higher you go. If you go high enough, the air molecules are very spread out. You will need extra oxygen in order to breathe.

你通常感觉不到气压。 原因是你体内的压力和体外的压力差不多。 但当你乘飞机起飞或开车上山时，你会飞到大气层的高处，那里的气压较低。 当外界气压下降时，你耳朵里的气压保持不变。 当空气穿过耳朵时，你可能会听到爆裂的声音。 你知道吗?你走得越高，气压就越低。 如果高度足够高，空气分子就会非常分散。 你需要额外的氧气才能呼吸。

Layers of Atmosphere Scientists have divided Earth's atmosphere into five layers. Each layer gradually changes into the next one. We live in the first layer—the troposphere— where Earth's weather forms and changes. The stratosphere is above the troposphere. This layer protects Earth from the Sun's radiation. The lowest part of the stratosphere is the ozone layer. This lower part is important to living things because it absorbs harmful ultraviolet rays from the Sun. Certain chemical gases that people release at Earth's surface threaten the ozone layer. These chemicals can float up into the stratosphere and break down ozone. The ozone is then less able to absorb ultraviolet rays. The mesosphere is the middle layer, in which most meteors burn up. Spacecraft orbit in the thermosphere. The exosphere is the outermost layer.

科学家们把地球的大气层分为五层。 每一层逐渐变成下一层。 我们生活在第一层——对流层——地球天气形成和变化的地方。 平流层在对流层之上。 这一层保护地球免受太阳辐射。 平流层的最低部分是臭氧层。 下半部分对生物很重要，因为它吸收来自太阳的有害紫外线。 人类在地球表面释放的某些化学气体会威胁到臭氧层。 这些化学物质可以漂浮到平流层，破坏臭氧。 臭氧吸收紫外线的能力就会减弱。 中间层是中间的一层，大多数流星都在这里燃烧。 航天器在热层轨道上运行。 外层是最外层。