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Heat Heat Transfer The Natural Greenhouse Effect.

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Presentation on theme: "Heat Heat Transfer The Natural Greenhouse Effect."— Presentation transcript:

1 Heat Heat Transfer The Natural Greenhouse Effect

2 Trapping Heat In an artificial greenhouse sunlight (solar radiation) passes through the glass Some of the solar radiation reflects off of the objects inside and escapes back through the window Some of the solar radiation is absorbed by the objects which become warm

3 Trapping Heat (continued) The heat in the objects heat the air in the greenhouse The hot air cannot escape so the greenhouse gets warmer and warmer Glass lets the sunlight in, but not the warm air out Greenhouses have devices to cool the air down if necessary

4 Insolation Insolation is the amount of solar radiation received by a region of the Earth’s surface Insolation depends on: latitude Specific characteristics of the lithosphere, atmosphere, and hydrosphere

5 The Natural Greenhouse Effect Some of the solar radiation that is absorbed by the Earth’s surface is re-emitted into the atmosphere as infrared radiation Most of this radiation is absorbed as thermal energy in the atmosphere by clouds and gases such as water vapour, CO 2, and CH 4 The absorption of thermal energy by the atmosphere is known as the natural greenhouse effect

6 Greenhouse Gases The Earth would be significantly cooler without the trapped thermal energy The natural greenhouse effect keeps our planet in the temperature range that supports life Water vapour, CO 2, NO and CH 4 are greenhouse gases Water vapour is the main contributor to the natural greenhouse effect

7 The Sun Emits Many Kinds of Energy

8 The Net Radiation Budget

9 The Net Radiation Budget (continued) The net radiation budget is the difference between the amount of incoming radiation and the amount of outgoing radiation The Earth receives 342W/m 2 per year of solar radiation (W = watts – units of energy per second) 31% is immediately reflected back into space by clouds,the atmosphere and land surfaces Approximately 30% is absorbed by the atmosphere The rest warms the Earth’s surface, which returns that heat to the atmosphere as infrared radiation, thermal energy and water vapour The atmosphere emits this radiation both up and down Less than 1% of incoming solar radiation is transformed (by photosynthesis) into chemical energy

10 Balancing the Radiation Budget Net Radiation Budget = Incoming Radiation – outgoing radiation = Zero On average the amount of incoming radiation is equal to the outgoing radiation for all planet Earth If this balance were to change, then the average global temperature would either increase or decrease Although the net radiation is balanced, some regions have an unbalanced net radiation budget (polar regions tend to have less incoming than outgoing and the reverse for the tropics)

11 Albedo Albedo is the percent of incoming solar radiation that is reflected from Earth’s surface. The albedo of Earth is about 30% Light-coloured, shiny surfaces reflect more solar radiation Darker, duller surfaces reflect less solar radiation Albedo varies with the seasons

12 Thermal Energy Transfer Thermal energy transfer from an area of high temperature to low temperature Thermal energy can occur by radiation, conduction or convection

13 Thermal Energy Transfer 2 Radiation Radiation is the emission of energy as waves When radiant energy encounters particles of matter it may be reflected or absorbed Absorbed energy increases the movement of the particles Any substance at a higher temperature than its surroundings will emit radiant energy usually as infrared radiation

14 Thermal Energy Transfer 3 Radiation Ex. the sun radiates solar radiation When it reaches Earth some is absorbed The warmer matter has molecules that are higher in energy The matter transfers some of its thermal energy to substances at a lower temperature or re- emits it as infrared radiation

15 Thermal Energy Transfer 4 Conduction Conduction is the transfer of thermal energy through direct contact This usually takes place between solids

16 Thermal Energy Transfer 5 Convection Convection is transfer of thermal energy through the movement of particles from one location to another This usually happens in fluids (liquids/gases) Water has a higher heat capacity than air has Water has a large effect on Earth’s climate

17 Thermal Energy Transfer 6 on Earth Although the Earth receives insolation from the sun, different parts receive different amounts Thermal energy is transferred throughout the atmosphere and hydrosphere

18 Thermal Energy Transfer in the Atmosphere & Hydrosphere Some Key Terms

19 Wind Heated atmospheric gases expand and rise (lower atmospheric pressure) Cooled atmospheric gases contract and fall (higher atmospheric pressure) Wind is the movement of air from areas of high to low pressure

20 The Coriolis Effect Air tends to move from the poles directly south or north Because the Earth is rotating on its axis the winds are deflected either left (southern hemisphere) or right (northern hemisphere) This is the coriolis effect

21 Global Wind Patterns The convection currents cause by rising and falling warm and cold air and the coriolis effect result in the global wind patterns

22 Jet Streams A jet stream is a band of fast-moving air in the stratosphere The Earth has several jet streams Jet streams affect the formation of severe weather

23 Thermal Energy Transfer in the Oceans

24 Vertical Transference Thermal energy is transferred vertically in water through convection currents Warm water tends to rise Cool water tends to sink

25 Currents As global winds blow on the ocean surface they push the water driving the surface currents in the ocean

26 The End Do learning checkpoint questions pg 278 Do key concept review pg 289 # 1 – 3, 5 – 8, 11 – 13 Do chapter 7 vocabulary


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