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NOVA scienceNOW: Hurricanes

Classroom Activity

Objective
To model how wetlands reduce the intensity of a hurricane

Hurricanes are intense, rotating, oceanic weather systems with winds exceeding 119 km (74 mph). Hurricanes are fueled by energy in the warm, moist air that rises above ocean water in tropical regions. Their impact on coastal land depends on several factors: the strength of the low pressure system, the amount of moisture a storm takes up, the tides, and land barriers, such as islands and wetlands. In the NOVA scienceNOW segment on hurricanes, Dr. Shea Penland of the University of New Orleans describes wetlands as a coastal area's first line of defense. "They're the 'speed bump' that slows a hurricane and reduces its intensity." Dense wetlands help weaken a hurricane by breaking the connection between the hurricane and warm ocean water. They also act as a physical barrier, slowing the waves that reach the shore and reducing their destructive force.

In this activity, students examine how wetlands can deprive a hurricane of some of the warm, moist air that supplies its energy. The steam represents the hurricane and different types of meshed materials represent dense and sparse wetlands. Students will record what happens to the plume of steam (hurricane) when different materials are placed in the steam's path.

Safety Note: This is a teacher demonstration only. Steam can cause burns.

• steam kettle with spout
• hot plate or equivalent heat source
• protective gloves, such as oven mitts or rubber gloves
• materials with different mesh size, such as coarse window screening, fine window screening, cheesecloth, facial tissue, paper towel, cotton cloth (e.g., T-shirt), flannel, and diaper
• solid barrier, such as a block of wood, sheet of cardboard, or spatula

• copy of the "Wetlands and Hurricanes" student handout (PDF or HTML)

Safety Note: Steam scalds! Wear protective gloves. When placing materials over the spout tip of the kettle, as instructed below, hold the materials so your hands are below the spout tip. Also, make the materials taut over the spout's opening so steam goes through the materials instead of being channeled out to the sides where it can scald your hands.

1. Boil water in the kettle. (You can make the steam more apparent by placing the kettle against a dark background.)

2. As the water heats, tell students that the water in the kettle represents the ocean, the hot plate represents the heat from Earth's tropical zone that warms ocean water, and the steam plume represents a hurricane. (Have students locate the tropical zone on a map.)

3. Remind the class that Dr. Penland said that dense wetlands weaken a hurricane by starving it of warm water, which is the "fuel" that drives a hurricane. Rising warm, moist air adds energy to a hurricane, which intensifies it.

4. Ask students to record their observations about the plume of steam on the "Wetlands and Hurricanes" student handout.

5. Ask students to predict how the different materials will affect the plume when you place them in its path. On the student handout, have them record their predictions and the thinking behind their predictions.

6. Put on the protective gloves and place one of the materials across the tip of the spout. Have the class observe and record the effects on the plume of steam. (See the table in Activity Answer for expected results.) Repeat the demonstration and prediction process using the remaining materials. Explore how students' predictions compare to what really happened.

7. Have each student answer the questions on the "Wetlands and Hurricanes" student handout. Try any promising ideas that model how to represent what happens when hurricanes make landfall. Review their answers to questions 4 and 5.

Just as wetlands interfere with a hurricane's supply of warm, moist air, the materials you put over the kettle spout disrupt the connection between the warm, moist air produced inside the kettle and the plume of steam at the spout. The class should see that the plume's strength diminishes as the mesh gets finer. The fine-meshed materials rob the plume of some of its warm, moist air. (See results for each material in the table below.)

Effect on a steam plume when placing different materials over the tip of a kettle spout

Answers to question 3 on the "Wetlands and Hurricanes" student handout include:

• What kind of wetlands does the coarse material represent? (Sparse wetlands)

• What kind of wetlands does the fine material represent? (Dense wetlands)

• Why did the fine material weaken the steam plume? (The fine material reduced the supply of warm, moist air from inside the kettle.)

• Why do dense wetlands help protect a coastal area from hurricanes? (Dense wetlands reduce the amount of warm, moist air going into a hurricane.)

Students' suggestions for ways to use the model to represent a hurricane that has traveled inland might include interrupting the flow of steam with a solid barrier, such as cardboard, or turning off the hot plate to eliminate the supply of warm, moist air.

Model Strengths: All the parts of the hurricane system are represented.

Model Weaknesses: The materials and their interactions are different than the actual situation.

Web Sites: Hurricanes

EXPLORES!
www.met.fsu.edu/explores/
Provides weather satellite interpretation and satellite imagery received at Florida State University, which implements the NOAA Direct Readout Program from three polar orbiting satellites.

Hurricanes: University of Illinois's On-Line Meteorology Guide
ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hurr/home.rxml
Offers resources for teaching meteorology and about the formation and behavior of hurricanes. The site has movies of hurricanes and over 20 years' worth of hurricane tracks.

National Oceanic and Atmospheric Administration's Defense Meteorological Satellite Program
www.ngdc.noaa.gov/dmsp/dmsp.html
Provides great satellite images of hurricanes and typhoons.

National Oceanic and Atmospheric Administration's Geostationary Satellite
www.goes.noaa.gov/
Provides satellite imagery of the continental U.S., Puerto Rico, Alaska, and Hawaii. It also provides sea surface temperatures. The information on tropical regions is particularly pertinent during the hurricane season.

National Weather Service's Climate Prediction Center
www.cpc.ncep.noaa.gov/products/outreach/education.shtml
Offers educational materials to help people understand how scientists make and use climate forecasts, and understand the role of the climate system and weather-related extreme events in their lives.

Web Sites: Wetlands

Coastal Wetlands Planning, Protection and Restoration Act
www.lacoast.gov/education/overview/Cwppra%20intro.htm
Provides an overview of the Coastal Wetlands Planning, Protection and Restoration Act, which discusses the importance of coastal restoration in Louisiana in terms of the future of coastal communities and protection from tropical storms and hurricanes.

Estuaries.Gov
estuaries.gov/
Provides information on National Estuaries Day activities and serves as a resource for information on the importance of estuaries and the need to protect them (joint NOAA and EPA site).

National Oceanic and Atmospheric Administration
www.nmfs.noaa.gov/habitat/habitatprotection/wetlands.htm
Provides an overview of NOAA's efforts to protect, conserve, enhance, and restore coastal wetlands.

U.S. Fish and Wildlife Service's National Wetlands Inventory
www.nwi.fws.gov
Provides information on the characteristics, extent, and status of the nation's wetlands, deepwater habitats, and other wildlife habitats.

Books: Hurricanes

Sean Smith and Brent A. Ford. Project Earth Science: Meteorology. Arlington, VA: National Science Teachers Association, 1994.
Contains integrated activities that introduce the atmosphere, weather, and variables that affect the movement of air masses. Includes a hurricane tracking activity. Provides lesson plans and student pages.

Jack Williams. The Weather Book: An Easy-to-Understand Guide to the USA's Weather. Arlington, VA: National Science Teachers Association, 1992.
Provides a reader-friendly introduction to weather and climate. Full-color graphics and photographs explain and illustrate weather concepts. Produced by the USA Today weather staff.

Books: Wetlands

William Niering. Wetlands. New York: Alfred A. Knopf, 1985.
Pubished by National Audubon Society. Comprehensive but accessible field guide includes descriptions of different kinds of wetlands and the plants and animals inhabiting them as well as a discussion of the dynamics of wetlands. Illustrated with maps, color plates, and photographs.

Laurence Pringle. Estuaries, Where Rivers Meet the Sea. New York: The MacMillan, 1993.
Combines simple, concise text with photographs. Describes bays and salt marshes and the plants and animals that live there. Examines the interrelationships between tides, grasses, crabs, fish, and birds.

John and Mildred Teal. Life and Death of the Salt Marsh. New York: Ballantine Books, 1969.
Describes the ecology of East Coast salt marshes, the plants and animals inhabiting them, their contributions to human welfare and the often-negative impact of human civilization on salt marshes. Authoritative, well illustrated, and easy to understand.

The "Wetlands and Hurricanes" activity aligns with the following National Science Education Standards:

Grades 5-8

	Science Standard B: Physical Science

Transfer of Energy:

• Heat moves in predictable ways, flowing from warmer objects to cooler ones, until both reach the same temperature.

	Science Standard D: Earth and Space Science

Structure of the Earth system:

• Global patterns of atmospheric movement influence local weather. Oceans have a major effect on climate because water in the oceans holds a large amount of heat.

• Living organisms have played many roles in the Earth system, including affecting the composition of the atmosphere, producing some types of rocks, and contributing to the weathering of rocks.

	Science Standard F: Science in Personal and Social Perspectives

Populations, resources, and environments:

• When an area becomes overpopulated, the environment will become degraded due to the increased use of resources.

• Causes of environmental degradation and resource depletion vary from region to region and from country to country.

Natural hazards:

• Internal and external processes of the Earth system cause natural hazards, events that change or destroy human and wildlife habitats, damage property, and harm or kill humans.

• Human activities also can induce hazards through resource acquisition, urban growth, land-use decisions, and waste disposal. Such activities can accelerate many natural changes.

• Natural hazards can present personal and societal challenges because misidentifying the change or incorrectly estimating the rate and scale of change may result in either too little attention and significant human costs or too much cost for unneeded preventive measures.

Risks and Benefits:

• Risk analysis considers the type of hazard and estimates the number of people that might be exposed and the number likely to suffer consequences. The results are used to determine the options for reducing or eliminating risks.

• Students should understand the risks associated with natural hazards (fires, floods, tornadoes, hurricanes, earthquakes, and volcanic eruptions).

• Individuals can use a systematic approach to thinking critically about risks and benefits. Examples include applying probability estimates to risks and comparing them to estimated personal and social benefits.

• Important personal and social decisions are made based on perceptions of benefits and risks.

Grades 9-12

	Science Standard B: Physical Science

Interactions of energy and matter:

• Waves, including sound and seismic waves, waves on water, and light waves, have energy and can transfer energy when they interact with matter.

	Science Standard D: Earth and Space Science

Energy in the Earth system:

• Heating of the Earth's surface and atmosphere by the sun drives convection within the atmosphere and oceans, producing winds and ocean currents.

	Science Standard F: Science in Personal and Social Perspectives

Personal and community health:

• Hazards and the potential for accidents exist. Regardless of the environment, the possibility of injury, illness, disability, or death may be present. Humans have a variety of mechanisms—sensory, motor, emotional, social, and technological—that can reduce and modify hazards

Natural resources:

• Humans use many natural systems as resources. Natural systems have the capacity to reuse waste, but that capacity is limited. Natural systems can change to an extent that exceeds the limits of organisms to adapt naturally or humans to adapt technologically.

Environmental quality:

• Natural ecosystems provide an array of basic processes that affect humans. Humans are changing many of these basic processes, and the changes may be detrimental to humans.

• Materials from human societies affect both physical and chemical cycles of the Earth.

• Many factors influence environmental quality.

Natural and human-induced hazards:

• Normal adjustments of Earth may be hazardous for humans. Humans live at the interface between the atmosphere driven by solar energy and the upper mantle where convection creates changes in the Earth's solid crust. As societies have grown, become stable, and come to value aspects of the environment, vulnerability to natural processes of change has increased.

• Human activities can enhance potential for hazards. Acquisition of resources, urban growth, and waste disposal can accelerate rates of natural change.

• Natural and human-induced hazards present the need for humans to assess potential danger and risk. Many changes in the environment designed by humans bring benefits to society as well as cause risks.

Classroom Activity Author

Developed by WGBH Educational Outreach staff.