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
What is an atmospheric window, and what does it allow Earth’s radiation to do?
It exists between 8-13 micrometers where very little infrared radiation is absorbed by the atmosphere. It allows for some of Earth’s emitted radiation to escape directly to space
What do clouds do to this atmospheric window?
It “closes” it
On cloudy nights, is it colder or warmer?
Warmer (radiation is trapped by the clouds)
On cloudy days, is it colder or warmer?
Colder (clouds are good reflectors of solar radiation)
Are clouds good at absorbing solar radiation?
No
“Based on how clouds impact radiation in the atmosphere, we can also consider liquid water to have a strong greenhouse effect.” T/F
False. Water is a good reflector
What is Rayleigh scattering?
Prefers short wavelengths (UV). Reflects off gas molecules in atmosphere. Scatters in all directions
What is Mie scattering?
Scatters all wavelengths (short and long). Scatters primarily forward. Involves aerosols
What is non-selective scattering?
Occurs when the particle size is bigger than the wavelength. Scatters in all directions
What is albedo?
The percent of solar radiation (outgoing/ incoming)
What has high albedo?
Snow and clouds
What has low albedo?
Dry, plowed field and forests
“Of the following, which is arguably the BEST method to keeping a car colder on a hot sunny summer day?”
Park in the shade
Why is the sky blue?
Rayleigh scatters incoming short solar radiation. This causes our eyes to see a blue sky due to this shortwave scattering
Why is the sky sometimes purple, light blue, and white?
When the sun is directly overhead, the time and ability to scatter wavelengths become shorter because of the shorter distance of the sun to the sky. This causes a deep, almost purple, hue to the sky. But at another angle, the sky will appear deep purple, but as it comes towards the ground, it becomes more blue. Further down the horizon, Mie scattering comes in and, because it allows all wavelengths, you will start to see whiter light which will turn the sky into more of a baby blue color.
Why are sunsets orange and red?
The sun is at the horizon, light from the sun has a longer distance to travel. Because of this, the shorter waves will dissipate which leave the longer waves (red and orange) to reach the Earth
Why are clouds white?
Solar ration enters the cloud, if it wasn’t already reflected, and scatter evenly no matter the size (because clouds are non-selective). Because white is the result of all of the colors of visible light combining, the particles will scatter evenly to produce a white cloud
Why are some clouds gray or black?
If a cloud is tall and deep, the white light would have depleted all of the white light.
What does it mean when an object has high specific heat capacity?
When an object requires a lot of energy to warm. Or when an object has high specific heat it equates to slow warming and slow cooling
What happens when water freezes into ice?
Releases energy in the form of heat called latent heating. This warms the air
