BACKGROUND:

The atmosphere is the gaseous envelope which covers a planet or large satellite. Most planets in our solar system have some type of an atmosphere. The Earth's atmosphere is a mixture of gases. Heavier gases tend to settle to the lower layers and lighter gases like hydrogen and helium go toward the top of the atmosphere.

The atmosphere can be divided into the following layers: troposphere (0-8 to17.6 km depending on location on Earth, temperature decreases with height, major gas is nitrogen, water vapor is component); stratosphere (17.6-48 km, temperature constant, weather constant); ozone layer (32 km thick, ozone is formed by a photochemical process. Solar ultraviolet radiation causes oxygen O₂ to become O₃ or ozone); mesosphere (44-88 km, temperature falls); ionosphere (88-200 km; temperature rises, short wave radiation causes a large number of charged ions and free electrons, good conductor of electricity).

Clouds, in combination with wind and pressure differences, are useful indicators of weather changes. The amount of water vapor decreases the higher you go into the troposphere, the highest clouds are relatively thin. However, the lower levels of the atmosphere can form clouds that are both thicker and denser.

Precipitation is common among altostratus, nimbostratus, and cumulonimbus clouds. altocumulus, stratocumulus, stratus, or cumulus under special conditions can cause rain. Cirrus, cirrostratus, and cirrocumulus may produce snow. Stratus clouds may produce drizzle, whereas cumulus clouds usually produce showers. Cumulonimbus clouds are usually accompanied by showers or rain, snow or hail, often with thunderstorms or even tornadoes. Altostratus or nimbostratus usually produce a steady rain.

PROCEDURE:

1. Show students the many divisions of the atmosphere. Use the diagram below. Ask the students where most of the weather occurs? The troposphere, because the interaction of the water and land throughout the water cycle makes this layer a dynamic moving system

Click to enlarge

2.  In this lab the students will classify the clouds by using the enclosed pictures. Students may want to go outside first and classify the clouds that they see. Students should cut the photos out, label what they think each cloud is, and then put the clouds in some kind of collage that reflects the height of the clouds.
     
3. The following definitions can help you explain the characteristics of clouds. Stratus are layered, or blanket-like; cumulus are flat bottomed, globular, or heaped masses; cirrus are curl or streaks; nimbus means dark rain clouds; alto means high clouds.

FAMILY A. High clouds (mean lower level, 20,000 feet)

1. cirrus
2. Cirrocumulus
3. Cirrostratus

FAMILY B. Middle Clouds (mean upper level, 20,000 feet; mean lower level, 6,500 feet)

4. Altocumulus
5. Altostratus

FAMILY C. Low Clouds (Mean upper level, 6500 feet; mean lower level, close to surface)

6. Stratocumulus
7. Stratus
8. Nimbostratus

FAMILY D. Clouds with Vertical Development (mean upper level, that of cirrus; mean lower level, 1,600 feet)

9. Cumulus
10. Cumulonimbus

4. If you have internet access, visit the following site that can have students look at more cloud types. You can add clouds to this lab easily.
   http://www.australiansevereweather.com/
   Australian Severe Weather has a complete photography gallery of every cloud imaginable.
     
5. ANSWERS: