Most of the earth s weather occurs in the troposphere

Transcription

1 66 Atmosphere and Climate R E A D I N G Most of the earth s weather occurs in the troposphere (TROH-poh-sfeer). In Activity 58, The Causes of Climate, you learned that the ocean has currents that move warm and cold water from one place to another. The troposphere has currents as well. Air currents move air from one place to another. CHALLENGE What role does the atmosphere play in weather and climate? MATERIALS For each student 1 completed Student Sheet 64.1, Data from Air Samples 1 completed Mean Atmospheric Values data table from Activity 64, Earth s Atmosphere E-72

2 Activity 66 READING Earth s Atmosphere The atmosphere is the layer of gases that surrounds the earth. The main gases are nitrogen (78%) and oxygen (21%), with the remaining 1% made up of other gases including carbon dioxide, water vapor, and argon. Atmospheric scientists divide the atmosphere into five layers based on temperature differences (see the table below). Compared to the radius of the earth (6,370 km), the atmosphere is a very thin km. Earth s Atmospheric Layers Atmospheric Approximate height Layer above earth s surface What happens in this layer? Exosphere 120 km+ The earth s atmosphere merges into space. Thermosphere km The space shuttle orbits the earth. Mesosphere km Meteors usually burn up. Stratosphere km Ozone layer absorbs some pf the sun s harmful ultraviolet radiation before it strikes the earth s surface. Troposphere 0 12 km Most weather occurs. Cruising altitude of most commercial aircraft. Listen as your teacher reads aloud. Stop when you see this yellow pencil and close your book. Write down the main ideas you just heard. Atmosphere and Weather Weather occurs in the troposphere. Air in the troposphere is heated from the ground up. The surface of the earth absorbs the sun s energy and heats up. The heated earth then heats up the air above it. Since some parts of the earth s surface heat up faster than others, this causes differences in air temperature and pressure, resulting in wind. Wind is the horizontal movement of air. Air moves from areas of high pressure to areas of low pressure and can result in winds of different speeds. When there is very little or no difference between pressure in two neighboring regions, the air is calm and there is no wind. When there is a lot of difference in air pressure between two neighboring regions, strong winds can blow leaves off trees and push clouds across the sky. The fastest wind speed recorded to date is 513 km/hr (318 mi/hr) during a 1999 tornado in Oklahoma. In general, wind speeds tend to be higher in the daytime when there are greater differences in air temperature and pressure. E-73

3 Activity 66 Heat is spread through the troposphere because air is slightly unstable. Unstable air can cause the moisture in the atmosphere to condense and clouds to form. On average, clouds cover 40 50% of the earth at any given time. Clouds and storms form when pockets of air rise and cool. They are carried through the atmosphere by wind. The more unstable the atmosphere is, the more likely you are to see clouds and more severe weather, such as storms. 12 Cumulonimbus Cirrostratus 9 Cirrus Cirrocumulus Kilometers (km) 6 3 Stratus Altocumulus Stratocumulus Cumulus Altostratus Nimbostratus 0 Clouds are described by their height in the atmosphere and their shape. Atmosphere and Climate The way the earth s atmosphere interacts with the sun s energy and the oceans helps determine the earth s average temperatures and its different climate zones. Air heated at the equator eventually moves north or south to other climates. Some of the sun s energy reflects off the earth s surface and would be lost to space if there were no atmosphere. By trapping some of the sun s energy, the atmosphere helps maintain the different climates on earth. The constant movement of air in the earth s atmosphere also ensures a steady environment for living organisms. Almost all living organisms require gases found in the atmosphere for survival. The interaction between living organisms and the environment means that the earth s atmosphere supports life and that living organisms continue to produce gases that become part of the atmosphere. E-74

4 Activity 66 Atmosphere and Global Climate Change Substances in the earth s atmosphere help hold heat in the atmosphere, almost like a blanket around the earth. This is called the greenhouse effect. Respiration and volcanic eruptions add such greenhouse gases as water vapor and carbon dioxide (CO 2 ) to the atmosphere. The ability of these gases to hold heat near the earth is called the natural greenhouse effect. But human activities are changing the concentration of greenhouse gases, especially CO 2, in the atmosphere. The burning of fossil fuels, deforestation, agriculture, and industry have all added greenhouses gases. As a result of these human activities, CO 2 in the atmosphere has increased 33% since people started burning fossil fuels in the late 1700s. Evidence suggests that this increase will change climates around the world. Scientists predictions vary on how much the increased levels of greenhouse gases will change climates globally in the future. However, evidence suggests that certain effects are likely: cooler. receive more rain and snow, while others will receive less. temperature increases, ocean water will expand. These two changes will cause sea levels to rise. E-75

5 Activity 66 will kill some reefs and the fish that depend on them for survival. Other fish will find new habitats as ocean temperatures rise. plants will grow in some regions. become more severe. ANALYSIS 1. What is the relationship between the earth s atmosphere and its weather and climate? 2. As an atmospheric scientist, you are asked to write an encyclopedia entry about the atmosphere. Use your work from Activity 64, Earth s Atmosphere, and your knowledge about the atmosphere from Activities 65 and 66 to write a paragraph explaining the atmosphere and its layers. Be sure to describe significant similarities and differences among the different layers. 3. Write a paragraph predicting what you think will happen to the area you live in as a result of global climate change. As you write your prediction, you might want to consider the following: the effect be? rainfall or temperatures affect the crops grown now? mountains for their drinking water? What will happen if there is less snow due to global climate change? happen if there were more rain? 4. Reflection: In the past three activities, you have learned a lot about the earth s atmosphere. If you were an atmospheric scientist, what aspect of the earth s atmosphere would you most like to study? Why? EXTENSION Your teacher may post some of your predictions on the discussion board on the Issues and Earth Science page of the SEPUP website. Be sure to check that page of the SEPUP website to see what students in other parts of the country have predicted. E-76