Guided Notes about the Earth’s Atmosphere Chapter 11, Section 1 1. About 99 percent of the earth’s atmosphere is composed of nitrogen and oxygen. The percentages of these components are critical to life on earth. 2. The amount of atmospheric water vapor on Earth is constantly changing. It can range from as much as 4 percent to as little as zero. 3. The level of both carbon dioxide and water vapor are critical because they regulate the amount of energy that the atmosphere absorbs. 4. When water changes from one state to another, heat is either absorbed or released, and this greatly affects atmospheric motions that create weather and climate. 5. Ozone is a gas formed by the addition of a third oxygen atom to an oxygen molecule. It is important in the upper atmosphere because it absorbs ultraviolet radiation from the sun. Without an ozone layer, our skin could not tolerate exposure to the Sun. 6. The troposphere contains most of the mass of the atmosphere, including the water vapor. This is the layer in which most weather takes place, and it is characterized by a decrease in temperature from bottom to top. 7. The stratosphere is made up mainly of concentrated ozone, and it increases in temperature to the top of the layer. 8. The Sun is shining on and warming some portion of the Earth’s surface at all times through the method of energy transfer called radiation. 9. While the Earth is absorbing solar radiation, it is also continuously sending energy back into space. Only about 50% of incoming solar radiation is absorbed by the Earth’s surface. 10. Over the course of a year, Earth sends back into space just about as much energy as it receives from the Sun. If the Earth sent back too much, it would gradually cool off. If it sent back too little, it would warm up to potentially dangerous levels. 11.The energy radiated by Earth’s surface is absorbed by the atmosphere and warms air through the processes of conduction and convection. State how conduction affects the atmosphere: Energy is transferred from the particles of air near the earth’s surface to the particles of air in the lowest layer of the atmosphere Conduction only affects a very thin atmospheric layer near the earth’s surface 13.Convection is the transfer of energy by the flow of heated matter. As warm air rises, it expands and starts to cool. When it cools enough, it begins to sink because it increases in density.