Earth s Atmosphere. Composition & Structure

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1 Earth s Atmosphere Composition & Structure

2 Essential Questions 1. What is the Earth s atmosphere made of? 2. What are the different layers of the atmosphere? 3. What causes atmospheric pressure?

3 Historical Elements What were the four basic elements according to the Greeks?

4 Atmospheric Composition Permanent Gases Identify two gases that make up the overwhelming majority of the Earth s atmosphere. What is the proportion (percent) of each of these gases in Earth s atmosphere? What is meant by the term permanent gases?

5 Atmospheric Composition Variable Gases Identify three major variable gases. Explain the role of each of the variable gases within the atmosphere. A small component of the Earth s atmosphere consists of gases whose proportion can vary over time and location. These gases are known as variable gases. Variable gases such as water vapor (H 2 O), carbon dioxide (CO 2 ), and ozone (O 3 ), although small in quantity, can have a significant effect on weather and climate, and on the quality of life on Earth. Water Vapor: Water vapor is the most plentiful of the variable gases with an atmospheric proportion that can range from 0 to 4%. Water vapor is important because it: is the source for all precipitation on the Earth. warms the atmosphere by absorbing heat emitted by the Earth. absorbs and redistributes solar energy across the Earth. There have been large changes in the concentration of CO 2 in the atmosphere in the last century. Carbon Dioxide: Carbon dioxide currently makes up 0.039% of the atmosphere, although its concentration has changed dramatically over the last century. The amount of CO 2 in the atmosphere is very important because it has a significant role to play in the regulation of temperature in the atmosphere. Ozone: Ozone (O 3 ) makes up about % of the Earth s atmosphere. Ozone is extremely important, however, because it absorbs ultraviolet (UV) radiation from the sun. The Earth would be uninhabitable were it not for the protective presence of ozone.

6 Atmospheric Composition Aerosols Define the term aerosol. Identify some sources of aerosols in Earth s atmosphere. Describe a problem associated with aerosols. In addition to gases, the atmosphere also contains large numbers of suspended solid and liquid particles known as aerosols. These aerosols are so small that they can remain suspended in the air for long periods of time, and can travel great distances on wind currents before eventually falling back down to the Earth. Aerosols are produced both by natural and by human processes. Aerosol particles can come from many sources including ash and dust from volcanoes, windblown dust, smoke from fires, combustion, and industrial byproducts.

7 The Temperature Layers What is meant by the term environmental lapse rate? What physical property is used to divide the Earth s atmosphere into distinct layers?

8 The Temperature Layers What two layers contain 99.9% of the atmosphere s total mass? Why is the temperature in the stratosphere higher than in the underlying troposphere? The troposphere, the layer closest to the Earth s surface, is the layer in which we live. The Earth s weather occurs within the troposphere. Approximately 80% of the atmosphere s mass is contained in the troposphere. The stratosphere is a fairly stable atmosphere layer compared to the turbulent troposphere below it. This is the layer in which jet airplanes fly. The temperature in the stratosphere increases because it contains large quantities of ozone (O 3 ) molecules that trap ultraviolet light from the sun. The stratosphere contains 19.9% of the atmosphere s total mass. The mesosphere is the middle layer in the 5 identified atmospheric layers. The absence of ozone in this layer results in the atmospheric temperature again dropping in the mesosphere. The temperature drops as low as 90 C ( 130 F), the lowest temperature in the atmosphere. The thermosphere experiences a temperature rise because oxygen and nitrogen molecules absorb high energy solar radiation. There are so few particles in the thermosphere, however, that the actual heat content of the thermosphere is very, very low. Auroras and the International Space Station (ISS) can be found in this layer. The exosphere is where the already almost nonexistent atmosphere gradually merges into outer space.

9 The Electrical Layer What property is used to define the atmospheric layer known as the ionosphere? Why is the ionosphere important? Describe the cause of auroras. Although temperature properties are usually used to define atmosphere layers, an additional layer can also be identified on the basis of electrical properties. This layer, called the ionosphere contains large numbers of electrically charged particles called ions. These charged particles are caused primarily by atoms and electrons interacting with ultraviolet rays from the sun. The charged particles in the ionosphere are extremely useful since they serve to reflect AM radio signals back to the ground. This allows you to listen to AM radio stations often at great distances from their originating transmission towers. Auroras also take place within the ionosphere. An aurora is a shimmering light display by electrically charged particles emitted from the sun interacting with the Earth s magnetic field.

10 Atmospheric Pressure Describe the relationship between pressure and altitude. Describe the cause of atmospheric pressure. Explain why atmospheric pressure changes with altitude. Atmospheric pressure is due to the weight of the atmosphere (i.e. the force due to gravity acting downward on the air particles) pushing down on the surface of that object. Atmospheric pressure decreases as altitude increases simply because there are fewer and fewer air particles at higher elevations.