SummaryGlobal wind patterns are dictated by the movement of the Earth on its axis and are significant factors in determining the climate for regions of the planet. Students learn how the Coriolis effect and Hadley convection cells determine the location of deserts on Earth. They manipulate inflated plastic globes to discover how the Coriolis effect drives wind clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. Then they incorporate latitudinal differences onto this modeling exercise to understand why deserts form at 30 degrees north and south of the equator. Once students understand the importance of global winds, they discuss hydropower in the desert. They compare and contrast two case studies: China’s Three Gorges Dam, and Chile’s proposed plant in the Atacama Desert that would creatively use solar power to move seawater up to the top of a mountain so that it can flow back down and generate power. Students note the economic, environmental, cultural and social impacts, issues and benefits of both power plants. Then they reflect, write, debate and discuss their ideas and opinions using evidence from the case studies and their own research.
As engineers improve infrastructure and ways to make available products and services to people, they consider the location, ease of access, and feasibility of projects from multiple points of view. In this activity, students practice analyzing important location facts in order to make decisions about hydropower placement. Engineers of all specialties routinely examine large amounts of data and consider how systems work together. This activity also asks students to consider factors from multiple points of view.
Helpful if students have some knowledge about the structure of the atmosphere and wind energy systems.
After this activity, students should be able to:
- Identify impacts on weather patterns and climate due to the Coriolis effect.
- Discuss potential benefits and drawbacks of hydropower plants and their placement.
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Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.
All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).
In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.
- Evaluate competing design solutions for developing, managing, and utilizing energy and mineral resources based on cost-benefit ratios. (Grades 9 - 12) Details... View more aligned curriculum... Do you agree with this alignment? Thanks for your feedback!
- Evaluate or refine a technological solution that reduces impacts of human activities on natural systems. (Grades 9 - 12) Details... View more aligned curriculum... Do you agree with this alignment? Thanks for your feedback!
Each group needs:
- map of the world with latitudes marked, such as available for download from Teacher Vision
- plastic inflatable globe
- dry erase marker
- (optional) string
- paper (or sticky notes) and pencils, for brainstorming
- notebooks or journals, for case study work
- Hydropower Journal Entry Grading Rubric
- computer with internet access for each pair, to conduct online research and post on discussion board
To share with the entire class:
- image of globe with wind patterns, latitude and Hadley cells
- case study articles: China’s Three Gorges Dam by the Numbers by Brian Handwerk for National Geographic News; and Huge Hydropower Plant to Harness Seawater and Solar Power in South America’s Driest Desert by Cole Mellino for EcoWatch
- student access to an online journal/discussion board
Today, we are going to learn how global wind patterns create deserts. We will investigate two important global wind patterns—the Coriolis effect and Hadley convection cells. Have you ever thought that wind and deserts might be related?
The Atacama Desert is located in South America, about 25-27 degrees south of the equator. This location is geographically important, because the climate has been impacted by global wind patterns.
Chile has secured approval to build a very large hydropower plant in the world’s driest region. But hydropower is power generated from falling water—how is that possible in a desert?! Let’s find out!
Coriolis effect: A phenomena that governs wind patterns in the Northern and Southern Hemispheres of the Earth.
desert: An area characterized by very low precipitation.
Hadley cells: An atmospheric circulation pattern located on either side of the Earth’s equator that creates the trade winds, tropical rain belts and hurricanes, subtropical deserts and the jet streams.
hydropower: Power derived from the energy of falling or fast-moving water by converting its kinetic energy into electricity. Also called water power.
In this activity, students learn how global wind patterns determine climate patterns and that hydropower plant placement is best chosen based on location in the context of global wind patterns. Global winds are driven by changes in density due to temperature. Convection currents drive these patterns worldwide. Warm air rises, while cool air sinks. These currents follow similar trends based on latitude. Around 30 degrees north and 30 degrees south, these wind patterns reduce precipitation values, which creates deserts.
The Coriolis effect occurs because of the rotation of the Earth on its axis. This phenomenon drives wind to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Latitude impacts redirect wind patterns towards the equator based on the circular nature of Coriolis winds. In addition to the Coriolis effect, Hadley cells operate in the 60-degree latitude range. In these unique convection cells, warm air is pulled away from the equator and creates arid conditions, driving the creation of deserts.
Hydropower is a renewable energy source that uses the power of moving water to generate electricity. When considering the placement of a new hydropower plant, it is important to consider water availability and many other considerations and impacts, especially in regions of arid climate conditions. This activity considers two case studies—hydropower generated from rivers and dams as well as from elevated seawater (!)—two different approaches that both use moving water to spin turbines to generate electricity.
Before the Activity
- Gather materials and make copies of the Hydropower Journal Entry Grading Rubric.
- Blow up the inflatable globes.
- Depending on the globes you procure, determine a mechanism for students to spin an inflated globe (perhaps from string) and make a removable mark on it (such as by using a dry erase marker). Refer to steps 3 and 4 below.
- Make available the case study articles in either digital or paper format; see the URLs in the Materials List. Within groups of four, one student pair looks at case study 1 (China) and the other student pair looks at case study 2 (Chile). To answer the activity’s question, student pairs start by looking for evidence by reading the articles; then they conduct independent research to fill in gaps.
- Arrange for student access to an online journal/discussion board for sharing and critiquing of findings and justifications.
With the Students
- Divide the class into groups of four students each. Have groups each brainstorm responses to the pre-activity assessment question: How does wind create deserts?
- Have groups write down all their thoughts, either on paper or sticky notes, and then compile them on the classroom board for the entire class to consider.
- Tell the students: Now that we have some ideas, let’s look at the science behind the relationships. Let’s first consider the Coriolis effect. Direct the groups to each take an inflated globe and spin it from west to east to model how the Earth moves on its axis.
- Let each student take a turn moving the marker from the North Pole region to the equator as the Earth continues spinning. Repeat again, moving up from the South Pole region. Once each team has several lines depicting wind patterns, expect them to be able to clearly visualize how the Earth’s movement determines the wind patterns seen in the Northern and Southern Hemispheres.
- Say to the students: Does that exercise answer our research question about wind patterns and deserts? No. So let’s consider another important pattern: Hadley convection cells. Who remembers what convection is? (Listen to student ideas.) That’s right, convection is when cool gas/fluid sinks and hot gas/fluid rises, which is a phenomenon seen many places, including in our atmosphere.
- Say to the students: Look at the map on your table. Where do you notice desert formations? Expect students to notice that deserts are common at 30 degrees north and 30 degrees south of the equator.
- Ask the class: Based on the geographical information, do you think it is a smart design decision to put a hydropower plant in Chile’s Atacama Desert? Expect students to have differing opinions about this question.
- Say to the students: Let’s compare two regions and two hydropower plants. Split your group into two pairs. One pair will read a case study on the Three Gorges Dam in China while the other pair reads a case study on Chile’s proposed plant.
- Tell the students: As you read, take note of important economic, social and environmental impacts of the hydropower plant on the local region. After you have finished your reading, you may need to conduct some independent research to fill in missing gaps in your understanding with additional evidence and information. Consider researching the weather patterns in both locations and nearby sources of available water. Once everyone is finished, we will compare our findings for both locations.
- Give students 10-15 minutes to research and confer with their partners about their findings.
- Direct the groups to each write down the benefits and drawbacks of their studied hydropower plants.
- Once all groups have written rough drafts, have each pair give a brief summary of their assigned case study. Then have each group debate which hydropower plant has fewer negative impacts on the region, citing evidence from their research.
Three Gorges Dam in China (built in 2003)
- Positive impacts: Dam promised to protect 5 million people and 1.5 million acres of farmland from future Yangtze River floods (has that happened in years since 2003?); expected to supply 3% of China’s electricity demand; expected to boost trade due to increased inland water cargo shipping and accommodating larger ships faster and farther in the water system; initially blocked ~10 million tons of trash from flowing to the ocean
- Negative impacts: Concrete rubble from blowing up (temporary) coffer dam; flooding three gorges (244 square miles) impacts those ecosystems (plant and animal life) and tourism; 100+ workers died during dam construction; costly to build at ~$24 billion; flooding displaced 1 million+ people in 1000+ towns and villages, who must be relocated and compensated (payments, homes, jobs, corruption, complaints); dozens of ancient architectural and cultural sites and relics flooded and covered by reservoir; concerns about dam’s ability to withstand earthquake (breach would be catastrophic); dam reducing downstream nutrient and sediment flow, which impacts river and seacoast ecosystems; flooding of factories, mines, dumps and human waste has contaminated the reservoir water; dam expected to “silt up” unless other dams are built up stream, which would shut down many currently free-flowing rivers
Tarapaca Mirror Power Plant in Chile (not built yet)
- Positive impacts: Unique combination of solar- and hydropower for 24-hour operation; uses solar power during the day to move seawater to mountain top; at night, water released to generate electricity as it falls; excellent location for solar energy; no dam needed since using ancient empty lake depressions to store seawater; cost is competitive with coal; uses seawater instead of freshwater; anticipate being able to supply power for all of South America
- Negative impacts: ecosystem destruction (plants/animals) in ancient lake depressions; myriad unforeseen impacts that accompany all innovative and large-scale projects like this
- Have each group use the information presented from the entire activity to draft a one-page essay reflecting on the drawbacks and implications, creating their own case study summaries. Require that students also reflect on how global wind patterns determine climate patterns and that hydropower plant placement is best if chosen based on location with consideration for the context of global wind patterns. Then have groups upload this information and their opinions into an online journal/discussion board where students can comment on, read and critique the work of their peers.
Class Discussion: Gauge students’ base knowledge in an open discussion by asking the class: How does wind create deserts? Example possible student responses: It moves dry wind in an area; it pushes moist wind away from certain regions.
Activity Embedded Assessment
Argumentation: As students complete each component of the case study assignment, they are required to provide justification. While students are learning about wind patterns and latitude, monitor group work and ask probing questions, such as:
- Do deserts occur at every latitude along 30 degrees north and/or 30 degrees south? (Answer: With few exceptions, deserts exist along the latitudes 30 degrees north and south of the equator.)
- How do we know that the Hadley cells are causing desert conditions? (Answer: Hadley cells operate in these regions, verifying that they play a part in the development of desert regions.)
- How might we prove that the Coriolis effect exists? (Answer: We could monitor the wind patterns in the Northern and Southern Hemispheres to prove the Coriolis effect.)
As students are working on the case study assignment, consider their discussions and notebook entries as formative assessments to determine if students understand the social, economic, cultural and environmental impacts of hydropower while weighing potential benefits from clean energy.
Journal Entries: Assess student groups on their understanding of the social, economic, cultural and environmental hydropower impacts compared to the benefits based on the reflective writing they produce using evidence from their case study work. Have them participate in an online journal/discussion board to share ideas and opinions from their hydropower case studies. Use the Hydropower Journal Entry Grading Rubric to assess their journal entries.
ContributorsHannah Brooks; Ashley Martin; Dale Gaddis; Shay Marceau; Lazar Trifunovic
Copyright© 2017 by Regents of the University of Colorado; original © 2016 North Carolina State University
Supporting ProgramRET Program, College of Engineering, North Carolina State University, and CORE Lab, University of North Carolina at Charlotte
This curricular unit was developed based upon work supported by the National Science Foundation under grant no. EEC 1542377—Grand Challenges for Engineering Focused RET with Stratified Teams, a collaboration of the College of Engineering at North Carolina State University, and the Control Optimization for Renewable Energies (CORE) Lab at the University of North Carolina at Charlotte. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.
Last modified: July 20, 2017