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.
troposphere
・lowest layer of atmosphere
・temperature decreases with height
stratosphere
・2nd layer of atmosphere
・temperature increases with height
tropopause
・boundary between troposphere and stratosphere
・temperature minimum
lapse rate
rate of temperature change with height
what part of the atmosphere radiates energy back to space?
troposphere (skin layer where GHGs live)
where is the pressure change the highest and why?
pressure change is the highest near the ground because most of the weight of the atmosphere is squeezed towards the bottom (high density of air particles at ground and decrease as you go up)
how do we reconcile lapse rate and convection?
adiabatic warming and cooling so temperature is not constant throughout atmosphere even with convection
adiabatic warming
when molecules are compressed together quickly, their mechanical energy is converted to heat
adiabatic cooling
when molecules are expanded quickly, heat is transferred to KE so they can expand
saturation vapor pressure
max amount of water vapor that air can hold at a given temperature
relative humidity
amount of water vapor as a percentage of saturation vapor pressure (“total” water vapor allowed)
what do convection and adiabatic cooling lead to?
supersaturation where vapor must condense out to droplets thus returning to saturation
moist adiabatic cooling rate
cooling results in condensation and latent heat release from water molecules and surrounding air is heated from latent heat so its warmer than expected from dry adiabatic lapse rate
how can the greenhouse effect and convection coexist?
convection maintains a temperature gradient of 6˚C per km due to the physics of moist convection
skin altitude
・average altitude from which IR escapes to space – last absorption and emission by a gas molecule
・adjustable and set by the amount of GHG in the atmosphere
Adding more greenhouse gases increases what?
increases the likelihood that photons are intercepted higher in the atmosphere which means Earth’s surface temp increases due to the equation Tground = Tskin + 6ºC/km(Hskin)
climate
long-term statistics of weather
weather
day-to-day
1st pattern of global climate
lower latitudes receive more direct sunlight →poles are colder than equator
what causes differences in temps across the year?
・Earth’s tilted axis means different parts are tilted more/less towards sun depending on the time of year
・duration of sunlight
latitude
angle between equator and point on Earth’s surface
・higher latitudes emit more than they absorb
・lower altitudes absorb more than they emit
thermal inertia
material’s tendency to resist changes in temperature especially when water’s present
・ΔQ = mcΔT
what is the 2nd pattern of global climate?
coastal regions undergo smaller temperature changes compared to inland regions due to the influence of the ocean (thermal inertia → takes a lot more energy to heat ocean)
what is the 3rd pattern of global climate?
difference in climates between coasts is caused by prevailing winds which carry weather
・ex: San Fran’s weather coming from ocean whereas Washington DC’s weather is coming from continental interior
in what direction do winds move?
・in tropics they move East → West
・in mid latitudes they move West → East
・in poles they move East → West
and all have vertical components
what forces control wind direction?
・Pressure gradient force
・coriolis effect
what does the pressure gradient force do?
pushes high pressure to low pressure (explains vertical wind patterns where convergence of wind along surfaces causes updrafts and divergence of wind along surfaces causes air to move down through atmosphere to fill gap)
what causes the Coriolis effect?
caused by Earth rotating quickly around us (relative motion)
what way does Coriolis effect work in northern and southern hemispheres?
・northern → to the right
・southern → to the left
what is the Coriolis effect responsible for?
responsible for east/west wind patterns
what is the fourth pattern of global climate?
・rainy tropics and mid latitudes (near equator bringing all the warm air upwards and raining down the moisture)
・dry subtropics and poles
what are the east/west components of wind responsible for?
weather
what are the north/south components of wind responsible for?
heat transfer
feedback
response of a system changes the magnitude of a stimulus or signal
positive feedback
amplifies effect of initial change
negative feedback
opposes effect of initial change and stabilizes system
ice/albedo feedback
melting of snow/ice leads to a lowered albedo which leads to an increase in absorbed sunlight which leads to more melting
water vapor feedback
warmer atmosphere can hold more water vapor and water vapor is a strong GHG so earth warms and cycle continues
cloud radiative effects
・warmer climate will have more clouds because warmer → more water vapor → more clouds
・clouds provide an albedo effect (cooling)
・clouds contribute to greenhouse effect (absorb and re-emit IR) (warming)
・low clouds reflect more sunlight
・high clouds trap more heat (IR that would’ve just escaped to space)
terrestrial biosphere feedback
・artic tree line is expanding
・shrubby tundra biome being replaced with thick, dark, low albedo forests (positive loop)
・expansion of forests and densification due to CO2 fertilization → store more carbon (negative loop)
what are Earth’s 4 carbon reservoirs?
land, atmosphere, ocean, geological
what is the smallest reservoir of carbon?
atmosphere (hub of cycle through which everything passes)
largest to smallest reservoirs
geological, ocean, land, atmosphere
residence time
average lifetime of a molecule
residence time of carbon in atmosphere
~3 years
biochemical cycle
ocean and land exchange with atmosphere (3 years and accounts for 3% of total carbon)
geological cycle
exchange between geological and atmosphere (>7000 years and accounts for 97% of total carbon)
geological and atmosphere carbon exchange
・ carbon source → volcanic outgassing (CO2 produced by metamorphism of carbonate rocks to silicates)
・carbon sink → chemical weathering (breakdown of silicate rocks by CO2 dissolved in rainwater)
feedback loop of volcanic outgassing and chemical weathering
more volcanism adds CO2 to atmosphere and warms Earth which leads to more rain with higher dissolved CO2 content which leads to more chemical weathering which leads to carbon being removed from atmosphere and Earth cools
atmosphere and biosphere carbon exchange
・CO2 sink → photosynthesis
・CO2 source → respiration/decay
ocean and atmosphere exchange
・chemical reactions occur between H2O and CO2 and cause more carbon to be absorbed by ocean to ensure equilibrium
・more dissolved carbon deeper in ocean because of the biological pump which can very much affect the levels of CO2 in atmosphere
carbon cycle feedback
change in temperature perturbs exchange between Earth’s natural carbon reservoirs resulting in more/less carbon in atmosphere
