Heat and the Atmosphere

What do we Remember… Temperature Thermal Energy Heat average of the kinetic energy of ALL the particles of a substance. Thermal Energy total kinetic energy of all the particles in a substance. Heat transfer of thermal energy

Heat Transfer: Conduction Conduction is the transfer of thermal energy by direct contact. Heat is transferred from high temperature, high kinetic energy particles to lower temperature, lower kinetic particles. For example, a cold spoon warms when placed in a cup of hot coffee. Thermal conductors transfer heat easily, while insulators do not. Metals are good conductors Good Insulators are: air, snow, wood and Styrofoam®

Heat Transfer: Convection “Lava” cools down - Molecules slow down, move closer together = INCREASE IN DENSITY Convection is the transfer of heat energy in fluids (liquids and gases) Convection is the movement of heat energy from hot to cold within a fluid, or the movement of hot liquid to an area of cool liquid. NB: GASES ARE FLUIDS! (because they move!) The “Lava” Falls The “Lava” Rises Heat from the light bulb warms the “lava” - Molecules speed up, move further apart = DECREASE IN DENSITY

Convection Currents in the Earth’s Core Huge chunks of land (called plates) float on top of these currents

Heat Transfer: Radiation Radiation is the transfer of radiant energy by waves. What we feel as heat is generally called infrared radiation. Earth’s interior thermal energy comes from the core, plus some radioactive element decay.

The Earth’s Atmosphere and Heat Transfer Earth’s atmosphere is a key factor in allowing life to survive here. This narrow band of air has the right ingredients, and maintains the correct temperature, to allow life to form and survive. Originally, Earth’s atmosphere was very different, and had no oxygen. Scientists think that oxygen first came from the breakdown of water by sunlight, then later by photosynthesis by plants.

The Earth’s Atmosphere and Heat Transfer Despite what most people think, the Earth’s atmosphere is NOT made mostly of oxygen! Air on Earth is 78% N2, 21% O2, 0.92% Ar, 0.04% CO2 and a variety of others. The density of the atmosphere decreases with altitude (as pressure decreases)

The Earth’s Atmosphere: Layers The Earth’s atmosphere is made of five layers: Troposphere Stratosphere Mesosphere Thermosphere Exosphere

A Closer Look: The Troposphere Closest to Earth’s surface, 8 km - 16 km thick Highest density layer because all other layers compressing it down. Almost all water vapour in the atmosphere is found here. Therefore, this is where most weather takes place. Solar energy and thermal energy from Earth keep air moving Temperatures range from average of +15ºC at the bottom to –55ºC at the top.

A Closer Look: The Stratosphere The second layer 10 km to 50 km above Earth, warming from –55ºC as altitude increases The transition from troposphere to stratosphere is called the tropopause. The air is cold, dry and clean in the stratosphere. Strong, steady winds, planes often fly here to avoid turbulent troposphere. The ozone layer is found here, which blocks harmful UV radiation. This is why the upper stratosphere warms more

A Closer Look: The Mesosphere The mesosphere: 50 km to 80 km above Earth This is the first layer in the “upper atmosphere” Temperatures are as low as –100ºC This layer is where space debris burns up when it begins to hit particles

A Closer Look: The Thermosphere The thermosphere: 80 km to 500 km above Earth Temperatures can reach +1500ºC to +3000ºC This is where the Northern Lights, aurora borealis, are found. Charged particles in Earth’s magnetic field collide with particles in the thermosphere

A Closer Look: The Exosphere 500 km to 700 km Where the atmosphere merges with outer space A Closer Look: The Exosphere

How Am I Supposed to Remember the Layers? use a mnemonic Exosphere = Excellent Thermosphere = Thermos Mesosphere = Makes Stratosphere = Soup Troposphere = Tasty

Your Turn! Make up your own mnemonic... Exosphere = E ______________ Thermosphere = Th _____________ Mesosphere = M ______________ Stratosphere = S ______________ Troposphere = T ______________

So… what does the atmosphere have to do with heat transfer???

The Atmosphere and Conduction: Putting it All Together! Almost all of the thermal energy on Earth comes from the Sun! This is only a small fraction of the solar radiation that reaches Earth! Most thermal energy is transferred near the equator, which receives a much more direct source of solar radiation (AKA. Insolation)

What is insolation? no not = insulation no not = insolent no not = isolation

… why isn’t it all transferred? Insolation = amount of solar radiation an area receives, measured in W/m2 Insolation decreases if there are particles of matter (dust, smoke) in the way, or if the angle of incidence of the solar radiation is too great. Angle of incidence

More clarification please!!! Angle of incidence = higher at the Earth’s poles = lower at the Equator Sun’s rays hit the Equator more directly = more solar radiation = more insolation

The Radiation Budget Earth’s incoming radiation = outgoing radiation if incoming radiation  outgoing radiation...Earth would heat up if incoming radiation  outgoing radiation ...Earth would cool down

Solar radiation does not heat the atmosphere directly. Earth’s surface absorbs solar radiation, heats up, then re-radiates the thermal energy into the atmosphere. This provides 70% of the air’s thermal energy! Convection in the air spreads the thermal energy around.

Albedo Albedo refers to the amount of energy reflected by a surface. Light-coloured surfaces have a high albedo, and reflect energy (snow, sand) Dark-coloured surfaces have a low albedo, and absorb energy (soil, water)

Use your notes to label the blanks on the “Important Figure” in your notes