43 Atmosphere and Climate-High

Atmosphere and Climate Written by Karen de Seve

《大气与气候》Karen de Seve著

Introduction The next time you go outside, take a moment to look up into the sky. You won't see it, but there's a very thin, invisible shield surrounding and protecting 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. The atmosphere protects us from the Sun's harmful rays, and it controls the amount of Earth's heat that escapes into space. It even protects us from objects such as meteors falling from 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 and climate, as well as what makes up the atmosphere and how it is changing.

下次你出门的时候，花点时间抬头看看天空。 你看不见它，但有一个非常薄的无形的盾牌包围和保护着地球。 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。 大气层保护我们不受太阳有害射线的伤害，它还控制着地球散失到太空中的热量。 它甚至可以保护我们免受来自太空的流星等物体的伤害。 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。 你将了解天气和气候的区别，以及大气的组成和变化。

Earth's Invisible Shield The atmosphere acts like a blanket, protecting and warming Earth's surface. It rises more than 700 kilometers (430 mi.) above Earth's surface and contains all the gases needed for life. The atmosphere is a mixture of 78 percent nitrogen and 21 percent oxygen. There are also small amounts of argon, carbon dioxide (CO2) water vapor, and a few other gases, but it is oxygen that we need most. Without oxygen, life as we know it could not exist.

大气层就像毯子一样，保护着地球表面，使其变暖。 它高出地球表面700多公里(430英里)，含有生命所需的所有气体。 大气是78%的氮和21%的氧的混合物。 还有少量的氩气、二氧化碳水蒸气和其他一些气体，但我们最需要的是氧气。 没有氧气，我们所知道的生命就不可能存在。

Gases, like all matter, are made up of small, invisible particles called molecules. These molecules are pulled toward Earth by the force of gravity. Gravity pulls down on the air molecules, so air close to the ground is denser than air close to outer space. The blanket of gas molecules presses down, creating air pressure on all things within the atmosphere. Air at the top of the atmosphere is about a million times less dense than the air at sea level. This means the molecules are spread farther apart. As a result, the air pressure high in the atmosphere is much lower.

气体，像所有物质一样，是由一种叫做分子的看不见的小粒子组成的。 这些分子被地心引力拉向地球。 重力向下拉空气分子，所以靠近地面的空气比靠近外太空的空气密度大。 气体分子层向下挤压，对大气中的所有物体产生空气压力。 大气顶部的空气密度大约比海平面上的空气密度小一百万倍。 这意味着分子分散得更远。 因此，大气中的高压要低得多。

You do not normally feel the pressure of the atmosphere because the pressure inside your body is in balance with the outside pressure. But if you go higher in the atmosphere, the air pressure drops, while the pressure inside your body stays the same. That's why you feel your ears pop when you take off in an airplane or drive up a mountain. As the outside air pressure drops, the air pressure inside your ears stays the same. As air escapes, it makes 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, so you will need extra oxygen in order to breathe.

你通常感觉不到大气的压力，因为你体内的压力与外界的压力是平衡的。 但如果你在大气中走得更高，气压就会下降，而你体内的压力保持不变。 这就是为什么当你坐飞机起飞或开车上山时，你会感到耳朵胀胀的。 当外界气压下降时，你耳朵里的气压保持不变。 当空气逸出时，它会发出爆裂的声音。 你知道吗?你走得越高，气压就越低。 如果你走到足够高的地方，空气分子会非常分散，所以你需要额外的氧气才能呼吸。

Layers of Atmosphere Scientists have divided the atmosphere into five layers. Each layer is a sphere that surrounds Earth. One layer gradually changes into another. We live in the first layer of the atmosphere —the troposphere. Earth's weather forms and changes within the troposphere. The second layer— the stratosphere— acts like a filter. The lowest part of the stratosphere, called the ozone layer, 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. This leaves the living things on Earth's surface vulnerable. The mesosphere is the layer in which most meteors burn up. Spacecraft orbit in the thermosphere. The exosphere is the outermost layer.

科学家把大气层分为五层。 每一层都是一个围绕地球的球体。 一层逐渐变成另一层。 我们生活在大气的第一层——对流层。 地球的天气在对流层内形成和变化。 第二层——平流层——起着过滤器的作用。 平流层的最低部分被称为臭氧层，它对生物很重要，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。 这使得地球表面的生物变得脆弱。 中间层是大多数流星燃烧的地方。 航天器在热层轨道上运行。 外层是最外层。