exam 1 EESC 105 Flashcards
heat
total energy of all molecular motion and bonds (thermal energy)
temperature
measure of thermal kinetic energy carried by a typical molecule
molecular motions that store heat
translational, rotational, vibrational
conduction
direct heat transfer from atom to atom
convection
parcels of fluid move and transfer heat through fluid
what is convection driven by?
temperature and pressure gradients within
latent heat transfer
heat uptake/release during phase changes (more/less disorganized bond structure)
what is the primary mechanism for heat movement around atmosphere?
convection
electromagnetic radiation
energy transfer through a vacuum due to electromagnetic oscillation
light
wave and streams of small particles carrying energy through space
how are wavelength and frequency related?
c = λ*v
photons
massless but carry discrete energy packets given by E = h*v
energy of a photon is directly propotional to what?
frequency
why do different substances absorb different wavelengths?
different substances absorb photons with stored energy that cause vibrations. these vibrations require a certain amount of energy so molecules will only absorb photons that will excite these vibrations
blackbody
theoretical substance capable of enough different vibrations that can interact with all wavelengths of radiation
what are qualities of blackbodies?
・absorb all EM radiation
・emit radiation at all wavelengths
・ λmax = b/T → higher temp, shorter λ
・ I = ⍷σT^4
bare-rock model
・energy in = energy out
・[(1-⍺)I]/4 = ⍷σ*T^4
・albedo times the amount of energy absorbed from sun (only absorbed by area of a circle not entire volume of sphere → Earth’s shadow) = earth acting as a blackbody emitting radiation upwards
what is the skin temperature of Earth?
255 K
albedo
fraction of light that is reflected back to space without ever being absorbed (⍺ = 0.3 for Earth)
greenhouse effect
visible light flows through atmosphere and is absorbed by Earth. infrared light is then emitted from Earth back towards space. the IR is absorbed by molecules in the atmosphere where these molecules re-emit radiation towards space and back towards the ground. now, there are multiple sources of incoming radiation with fewer outgoing and eventually temperature must increase to remain in an energy balance
skin temperature
outermost layer of a climate system
Tearth = 255K
major gases
nitrogen, oxygen, argon
minor gases
CO2, Ne, He, CH4, H2O
what makes a gas a greenhouse gas?
GHGs must experience a change in their dipole moment as a result of the vibration that occurs when IR radiation is absorbed
(must be able to absorb IR that cause vibrations that change that molecule’s polarity)
why aren’t oxygen and nitrogen GHGs?
they cannot absorb IR light and are symmetrical molecules with no dipole moment and no amount of vibrating/ stretching will ever create a dipole
wavenumber
1/λ
atmospheric window
part of Earth’s emission spectrum at which no radiation is absorbed by atmosphere
what does the total area on Earth’s radiation spectrum give you?
total outgoing IR radiation
on the emission spectrum, why does it look like radiation is coming from object’s of lower temperature?
molecules emit and absorb and then the molecules above do the same and the process continues until the highest layer emits it into space untouched so the satellite is absorbing IR from molecules further up in the atmosphere and the higher in the atmosphere, the colder it is
why is CO2 an important GHG?
it absorbs radiation at the peak of Earth’s emission spectrum
band saturation effect
nonlinear relationship of absorption of radiation per mole of a particular molecule in the atmosphere as concentration increases (each mole is less effective at absorbing heat as concentration increases)
climate sensitivity
equilibrium temperature resulting from doubling CO2
greenhouse warming timescale
adding CO2 means more radiation is absorbed so immediately energy of Earth is changed but temperature does not change immediately → takes time to reach a new equilibrium
why does the greenhouse effect work?
the greenhouse effect works because the energy balance keeps the ground warmer than the fixed skin temperature.