As we get ready to get deeper into the study, let us first watch a short video so we can get a basic understanding of what really is the atmosphere and then we can touch on a few general points. Of course, we are going to expand on each one of these as we progress in this course.
As you understood from the video, the atmosphere is basically a thin envelope of air that surrounds our planet and it is a mixture of gases, each with its own physical properties. The main points to note here are:
- The earth’s atmosphere is a very thin layer wrapped around a very large planet.
- Two gases make up the bulk of the earth’s atmosphere: nitrogen (), which comprises 78% of the atmosphere, and oxygen (), which accounts for 21%. Various trace gases make up the remainder.
- Based on temperature, the atmosphere is divided into four layers: the troposphere, stratosphere, mesosphere, and thermosphere.
- Energy is transferred between the earth’s surface and the atmosphere via conduction, convection, and radiation.
The mixture is far from evenly divided. Two elements, nitrogen and oxygen, make up 99% of the volume of air. The other 1% is composed of “trace” gases, the most prevalent of which is the inert gaseous element argon. The rest of the trace gases, although present in only minute amounts, are very important to life on earth. Two in particular, carbon dioxide and ozone, can have a large impact on atmospheric processes.
Another gas, water vapor, also exists in small amounts. It varies in concentration from being almost non-existent over desert regions to about 4% over the oceans. Water vapor is important to weather production since it exists in gaseous, liquid, and solid phases and absorbs radiant energy from the earth.
Structure of the atmosphere
The atmosphere is divided vertically into four layers based on temperature: the troposphere, stratosphere, mesosphere, and thermosphere. Throughout this short course, we’ll focus primarily on the layer in which we live – the troposphere
The word troposphere comes from tropein, meaning to turn or change. All of the earth’s weather occurs in the troposphere.
The troposphere has the following characteristics.