Unit 1 Flashcards
What is radiation?
An energy transfer via electromagnetic waves
Where does radiation come from?
A source such as a fire or the sun
How, exactly, does radiation produce heat?
Energy (photons) hit molecules, then get absorbed, and finally add motion to these molecules. Think of heat from a fire
What is the process of heating the atmosphere?
Energy from the sun hits the Earth’s surface. Then, the ground begins to warm from radiation. Then, the ground molecules transfer heat directly above the ground via convection. Then, because of convection, the warm air rises vertically upward.
Latent heating/ cooling is also involved when water vapor is included.
What is convection?
VERTICAL air motions
What is advection?
HORIZONTAL air motions caused by the wind
How does advection warm/ cool a location?
By transporting air of different temperature at a location. It REQUIRES a temp gradient
What doesn’t emit radiation?
Nothing. Everything above 0°K emits radiation
Does radiation require some form of medium to travel (liquid, air, some solid)?
No. It is the only thing that can travel even inside of a vacuum
How fast does radiation travel?
The speed of light
What is considered a wavelength?
The distance between two successive crests on a wave
What are blackbodies?
Hypothetical bodies that absorb and emit the maximum radiation at every wavelength
What are some examples of a blackbody and what isn’t?
The Earth (the land specifically) and the Sun are blackbodies. The Earth’s atmosphere is not a blackbody
Why is the atmosphere not a blackbody?
It’s selective
What is the Stefan-Boltzmann Law?
It describes that energy is emitted based on its temperature
What radiates more energy: hot or cold bodies?
Hot bodies
What is Wien’s Law?
It details the wavelength of peak emission of a body based on its temperature
What is Earth’s peak wavelength, in micrometers?
10 micrometers
What is the Sun’s peak wavelength? Is it shorter or longer than the Earth’s?
It is shorter than the earth’s at 0.5 micrometers
If the Earth is radiating energy all the time, why is it not very cold?
The Earth is not only radiating energy, but absorbing energy as well. It is constantly in flux of radiating more energy that absorbing (cooling) and absorbing more energy than radiating (heating)
What is Radiative equilibrium as a concept, and what temperature is Earth’s Radiative equilibrium? What would the Earth’s average temperature be at this equilibrium?
Radiative equilibrium is when emission = absorption. If Earth were to be at equilibrium, its temperature would only be 255°K (mean temp is 290°K). The average temp on Earth would be 0°C
What are selective absorbers?
Objects such as gases in the atmosphere that selectively absorb and emit radiation. Aka “Kirchoff’s Law”
Are these selective absorbers good at emission too?
Yes, at a particular wavelength and vice versa. They allow solar in, but trap longwaves
What is the greenhouse effect?
When the atmosphere selectively absorbs infrared radiation from the Earth’s surface but acts as a window and transmits shortwave radiation
