Recap: Earth’s Main Climate Components
Earth’s Main Climate Components:
1. Land and water composition of the earth’s surface:
2. Composition of the atmosphere above the oceans and continents
3. Earth’s movement (rotation and revolution)
1. Land and water composition of the earth’s surface:
Climate role of water: higher heat capacity than land (absorbs and stores more heat); ocean currents transfer energy around the earth
2. Composition of the atmosphere above the oceans and continents:
Climate role of the atmosphere: Earth’s insulating blanket: reflects and traps energy; Winds transfer heat and moisture around the globe;
Revolution – one complete cycle around the sun every 365 days
The seasons are due to the Earth’s tilt and revolution, not distance from the Sun. How does this affect average summer and winter temperatures?
3. Earth’s movement (rotation and revolution)
Rotation – spins around on its own axis every 24 hours
Moderates temperature variations; affects direction of winds and ocean currents;
Earth’s Energy Balance and Energy Transfer
Where does almost all the energy used on Earth to sustain life and cause our changing weather systems come from?
The Sun
Without energy…
The average surface temperature is about 15 °C
The earth must maintain an energy balance.
If the energy absorbed > energy radiated,
the Earth heats up
If the energy absorbed < energy radiated,
the Earth cools down
About 30% of the sun’s incoming energy is immediately reflected by:
How do different characteristics of the Earth’s surface affect the absorption or reflection of energy?
Different surfaces have different albedos. Albedo is the ability to reflect radiation (light).
What surfaces on Earth do you think have high albedo? What surfaces on Earth do you think have low albedo?
Snow and ice have high albedo. Soil and deep ocean have low albedo.
How do different characteristics of the Earth’s surface affect the absorption or reflection of energy? (cont.)
Heat Sinks: materials which are very good at absorbing heat energy. What parts of the Earth’s surface are good heat sinks?
(The oceans)
Materials which have the ability to absorb a lot of energy without increasing in temperature very much have high heat capacity.
Methods of Transfer of Energy
Energy can be transferred from one place to another by 3 methods:
(1) Radiation
(2) Conduction
(3) Convection
How do you think each of these methods of energy transfer work?
Radiation:
Transfer of energy through electromagnetic waves (i.e. light waves)
Can travel through empty space!
Does not need a medium (solid, liquid or gas material) to transfer energy, unlike water and sound waves;
Why is this important for life on Earth?
If the transfer of energy from the Sun required a medium, life not have been possible on Earth!
Radiation can be absorbed, reflected or transmitted.
We can only see a very small part of the electromagnetic spectrum (visible light).
The shorter the wavelength, the higher the frequency, and the higher the energy.
Heat belongs to the Infrared (IR) part of the electromagnetic spectrum – long wavelength, low frequency radiation.
Ultraviolet light (UV) is short wavelength and high frequency radiation.
Conduction:
Transfer of energy through the collision of particles.
Transfers energy primarily through solids, and not as well through liquids and gases. Why?
When particles are heated, they vibrate quickly, collide with other particles, and transfer some energy to them. Liquid and gas particles are too far apart for this to happen quickly.
If the temperature of something is hot, it means that the particles vibrate quickly, and if something is cold, it means the particles vibrate slowly. Increasing an object’s temperature means the particles vibrate faster, and the number of particle collisions increases.
In conduction, heat is transferred from particles with a a lot of energy to particles with less energy (i.e. energy always travels from hot to cold).
Convection:
Transfer of energy by the movement of particles in a fluid (a liquid or a gas)
When particles in a liquid or gas are heated, they vibrate, move faster and move farther apart so that part of the fluid becomes less dense.
As a result, the fluid rises, and is replaced by cooler, denser fluid.
The continuous flow of fluid in this manner is known as a convection current.
In the daytime, the land is warmer than water, since water is a good heat sink.
The air above land is warmer, while the air above the water is cooler, so a convection current is created – wind is created!)
At night, the land cools faster than water so the air above the water is relatively warmer, changing the direction of the convection current.