Lectures 7&8: The Atmosphere and Global Heat Budget, The Greenhouse Effect Flashcards
How many Milankovitch Cycles are there?
Three: Eccentricity, Tilt, Precession
What is Eccentricity?
The change in Earth’s orbital path (from more circular to more oval-like/elongated vs. circular), when it is elongated it receives more variation in energy
How many periods does eccentricity have?
Three: 96k, 125k, 400k years
What are the driving forces for the ocean and atmospheric circulation?
-wind-driven ocean circulation, energy transfer (wind stress), albedo & thermal inertia, heat budget and transfer
-evaporation, conduction, radiation, precipitation
What is heat flux? What are the units?
amount of items per unit area per unit time, radiation: watts/m2
What is the solar heat flux?
342 watts/m2 (top of the atmosphere)
What is the geothermal heat flux?
0.075 watts/m2 (bottom of the atmosphere), almost negligible
What is black body radiation?
all objects emit electromagnetic energy proportional to temperature
-Sun emits way more than Earth & universal background radiation
-not all true ‘black bodies’
How is the troposphere only weakly density stratified?
heat from the bottom, colder/denser air is on the top, warmer/lighter air is on the bottom, lots of mixing occurs in the troposphere (high & low pressure systems)
How is the stratosphere strongly density stratified?
heated from above, colder/denser air below warmer/lighter air
What is the result when you combine the three Milankovitch Cycles?
glacial periods
What is the formula that equals the amount of heat absorbed by the Earth?
= S0 (solar constant) * (1-albedo) * πr2
What is the formula for heat radiated from Earth’s surface?
= (e * σ * k4)* 4πr2
Why is there a wet lapse rate?
Earth is not a true black body, wet lapse rate = 6.5℃/km
What is the Greenhouse Effect?
an atmosphere is able to trap warmth in, leading to a warmer planet than without it, trap IR radiation rather than transmit it
What is the Stephen-Boltzman relationship?
watts/m2 = E = e σ k4, little e is emissivity (1 in ideal cases)
What is the Stephen-Boltzman constant?
σ = 5.67 x 10^-8 Wm-2k-4
What is Wien’s Displacement Law?
the idea that as temperature increases the peak energy shifts to a more frequent wavelength
What are the three major EM bands we have to know?
ultraviolet (1-400 nm), visible (400-700 nm), infrared (700-100,000 nm)
What is axial tilt?
the tilt of Earth’s axis varies between 22.2-24.5, the greater the tile the more solar energy the poles receive
How many periods does axial tilt have?
1 period, 41k years
What is precession?
a gradual change or “wobble” in the orientation of Earth’s axis that affects the relationship between tilt and eccentricity
How many periods does precession have?
3 periods, 19k, 22k, 24k years
What is the relative albedo for ice?
20-70%
