Earth's Emergency Heat Valve: The Hurricane

Vicki Cobb
The Master Chef of Kids' Hands-on Science

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     Earth has a problem. The sun creates hot spots over land, in the air and in the water.  That’s why there are winds, weather, and currents in the ocean as Earth tries to even out the heat, moving warmer masses of air and water to cooler areas.
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     During hurricane season ( from June 1-November 30), only 10 or 11 of the 80 tropical disturbances off the west coast of Africa (where most of our hurricanes originate) become large enough storms to be given a name.   Only two or three of them hit the United States.  They are not frequent but they are massive wind storms that can destroy life and property.

     Do they do anything good at all?    As far as the Earth is concerned, these largest of all storms are a safety valve to rapidly move heat that has been accumulating in the oceans up to the stratosphere (from 7 to 31 miles above the Earth’s surface).   From there it will be transported through the air to over the North Pole.  It’s the way Earth stops a fever.

     Once a hurricane forms, it must have an ocean surface that is at least 80°F to keep moving and to grow.  Under the storm, huge amounts of warm water become water vapor. Warm moist air rapidly rises through the spinning winds of the hurricane, up to the stratosphere.  When moist air reaches the frigid (-70°F) stratosphere the water vapor quickly condenses to liquid water (rain) releasing its heat.  This heat makes surrounding air molecules move faster forming winds.

     How do hurricanes cool off the oceans?  How do they move the heat?  Here’s a clue:  Wet your finger and wave it in the air.  How does it feel? Pretty cool, I bet!  That’s because the heat from your finger changes liquid water into water vapor (a gas) as your finger dries. Water vapor molecules store this extra heat.  They rise because they are lighter than other air molecules.

     So, a hurricane is a heat engine that moves water vapor from the ocean’s surface high enough to condense back into liquid water and release heat safely to the stratosphere forming rivers of wind that move it to the poles.

     Scientists predict that global warming will increase the number and the power of the hurricanes as the ocean surfaces become increasingly warmer during our summers.
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This diagram of the anatomy of a hurricane shows the direction of the winds. The blue represents cold air descending while the pink shows warm moist air rising. The outflow surface clouds form as water condenses into a "table-top" cloud, releasing heat that becomes wind. Kelvinsong via Wikimedia

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Hurricane Isabel (2003) as seen from orbit during Expedition 7 of the International Space Station. The  eye, eyewall, and surrounding rainbands, all characteristics of hurricanes, are clearly visible in this view from space.  Image courtesy of Mike Trenchard, Earth Sciences & Image Analysis Laboratory, NASA Johnson Space Center

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Vicki Cobb's  How Could We Harness a Hurricane?  offers questions and  provides new points of view that may just change peoples' thinking by showing young readers the work scientists and engineers are doing to avoid future disasters. The book includes hands-on experiments that make science fun, be it at home or in the classroom.  Here's a link to the book' s Trailer.

How Could We Harness a Hurricane was named a 2018 Best STEM Book K-12 by the National Science Teachers Association and the Children's Book Council.

Vicki is a member of iNK's Authors on Call so you can invite her to your classroom via iNK's videoconferening Zoom Room. Click here to find out more:

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MLA 8 Citation
Cobb, Vicki. "Earth's Emergency Heat Valve: The Hurricane." Nonfiction Minute,
     iNK Think Tank, 24 Apr. 2018, www.nonfictionminute.org/
     the-nonfiction-minute/Earths-Emergency-Heat-Valve-The-Hurricane.