17 Chapter 17 The Atmosphere: Structure and Temperature

Energy Transfer as Heat 17.2 Heating the Atmosphere  Heat is the energy transferred from one object to another because of a difference in the objects’ temperature.  Temperature is a measure of the average movement of the individual atoms or molecules in a substance.

Temperature

Mr. Fetch’s Earth Science Classroom Heat Transfer in the AtmosphereRadiationConductionConvection

Conduction  Conduction is the transfer of heat through direct contact of matter.

Convection the transfer of heat through fluids (liquids & gases). –Warm air rising –Cold air sinking YouTube: Convection

Mr. Fetch’s Earth Science Classroom Convection Convection is the main way the atmosphere is heated.

Energy Transfer as Heat 17.2 Heating the Atmosphere  Radiation ©Radiation is the transfer of energy (heat) through space by electromagnetic waves that travel out in all directions. ©Unlike conduction and convection, which need material to travel through, radiant energy can travel through the vacuum of space. ©All objects, at any temperature, emit radiant energy. ©Objects that are good absorbers of radiation are good emitters as well.

Energy Transfer as Heat

17.2 Heating the Atmosphere  Electromagnetic Waves The sun emits light and heat as well as the ultraviolet rays that cause a suntan. These forms of energy emitted by the sun is called the electromagnetic spectrum.

Electromagnetic Spectrum

Visible Light Consists of an Array of Colors

What Happens to Solar Radiation? 17.2 Heating the Atmosphere  When radiation strikes an object, there usually are three different results. 1.Some energy is absorbed by an object. 2.Some energy is transmitted by an object. 3.Some energy is bounced off by an object.

Solar Radiation

What Happens to Solar Radiation? 17.2 Heating the Atmosphere  Absorption  Greenhouse gases, mainly water vapor and carbon dioxide, absorb or soak-in energy and send it back down to Earth.  This heating of the Earth’s atmosphere & surface by these gases is known as the greenhouse effect.  The greenhouse effect is GOOD!

Mr. Fetch’s Earth Science Classroom How our atmosphere is heated. 1. High-level energy from sun passes right through atmosphere without being absorbed. 2. This high-level energy is then absorbed by earth’s surface. 3. Energy is then re-emitted to the atmosphere as “low- level” energy, which is easily trapped and absorbed by the gasses in the atmosphere, thus, causing it to warm up.

17.2 Heating the Atmosphere  Reflection and Scattering both occur when light bounces off objects… Reflection has the same intensity of light out as it did in. Scattering produces a several weaker rays that travel in different directions. R S

Why Temperatures Vary 17.3 Temperature Controls  Temperature Control: any factor that causes temperature to vary from place to place and from time to time.  Examples: latitude heating of land and water altitude, geographic position cloud cover ocean currents.

Why Temperatures Vary 17.3 Temperature Controls  Latitude ©Variations in the angle of the sun’s rays & length of daylight depend on latitude. ©Different latitudes are responsible for warmer temperatures near the equator & colder temperatures near the poles.

Why Temperatures Vary 17.3 Temperature Controls  Land and Water ©Different surfaces absorb varying amounts of solar energy. ©Land heats more rapidly & to higher temp than water. ©Land cools more rapidly & cools to lower temp than water. ©This means that temperature variations are greater over land than over water. ©A city near the coast will have a milder climate than a city inland.

Mean Monthly Temperatures for Vancouver and Winnipeg

Why Temperatures Vary 17.3 Temperature Controls  Land and Water ©The Southern hemisphere has more water than the Northern hemisphere. ©Which hemisphere has milder climates? Southern!!

Why Temperatures Vary 17.3 Temperature Controls  Geographic Position ©Windward coast - A coastal city where prevailing winds blow from ocean onto the shore. ©experiences milder summers and winters. ©Leeward coast - A coastal city where prevailing winds blow from land toward the ocean. ©Experience more drastic summers and winters.

Mean Monthly Temperatures for Eureka and New York City

Why Temperatures Vary 17.3 Temperature Controls  Geographic Position ©Mountains – can act as barriers. ©Cities on opposite sides of mountains have different climates despite being at the same latitude and altitude.

Mean Monthly Temperatures for Seattle and Spokane

Why Temperatures Vary 17.3 Temperature Controls  Altitude ©The altitude can greatly influence temperatures experienced at a specific location. ©A city located at a higher altitude but at the same latitude as another city will experience a colder climate.

Mean Monthly Temperatures for Guayaquil and Quito

Why Temperatures Vary 17.3 Temperature Controls  Cloud Cover  During the day, clouds can reduce the amount of incoming solar radiation. This lowers the temperature.  At night, clouds have the opposite effect. They act as blankets trapping Earth’s out-going radiation & re- radiating it back down to Earth.  Therefore, the temperature on a cloudy night is HIGHER than on a clear night.

Clouds Reflect and Absorb Radiation

What is Albedo? 17.3 Temperature Controls  Albedo is the fraction of total radiation that is reflected by any surface.  Many clouds have a high albedo and therefore reflect as much as 20% of the sunlight that strikes them.

World Distribution of Temperature 17.3 Temperature Controls  Isotherms are lines on a weather map that connect points where the temperature is the same. ©Isotherms show the effects of the temperature control factors of latitude, distribution of land & water & ocean currents ©Isotherms generally trend east and west and show a decrease in temperatures from the tropics toward the poles.