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Urban Heat Island: Why it is hotter in the city than in the countryside?

Urban Heat Island: Why it is hotter in the city than in the countryside?. Los Angeles Model By Fernando Olmos 3/15/13. Lesson Outline. Day 1 Presentation of the Urban Heat Island Effect Hands-on activities at the stations Day 2 Worksheet

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Urban Heat Island: Why it is hotter in the city than in the countryside?

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  1. Urban Heat Island: Why it is hotter in the city than in the countryside? Los Angeles Model By Fernando Olmos 3/15/13

  2. Lesson Outline • Day 1 • Presentation of the Urban Heat Island Effect • Hands-on activities at the stations • Day 2 • Worksheet • Reflection on Solutions to the Urban Heat Island Effect

  3. Goal • Understand how the following phenomena contribute to the Urban Heat Island Effect: • Sun light • Black body properties of materials • 3 heat transfer mechanisms (conduction, convection, radiation) • Come up with solutions to mitigate the Urban Heat Island Effect

  4. Review of Heat Transfer Mechanisms • Conduction: heat is transferred by direct contact between objects • Convection: heat is transferred in a fluid (liquid or gas) • Radiation: heat is transferred in the form of electromagnetic waves • Remember: Heat is always transferred from HOT to COLD!!!

  5. Urban Heat Island (UHI) • A urban heat island is a metropolitan area that is at a warmer temperature than the surrounding countryside • Around 2 to 10 oF (2-6oC) • Not only air is hotter, but different surfaces are hotter.

  6. Causes of UHI • Presence of dark and dry surfaces • High heat (sunlight) absorption • Examples: pavement, asphalt, buildings • Absence of vegetation • Shade blocks solar radiation • Plants sweat water, and heat is removed (40 gallons a day)

  7. Consequences UHI • More air conditioning (1-1.5 gigawatts) • More electricity, more emission of GHG • More smog • More health problems • Eye irritation, lung damage, asthma • Vegetation issues

  8. Los Angeles UHI I • Increase of annual urban temperatures over the last decade in several UHIs

  9. Los Angeles UHI II • Increase in LA temperatures as a result of urbanization and industrialization

  10. Los Angeles UHI III • Increase in electricity use in LA. 2% increase for every 1oF increase in temperature

  11. Los Angeles UHI IV • Higher temperatures means more ozone or smog will be produce

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