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%
What is the relative albedo for ice?
20-70%
What is the relative albedo for the ocean?
2-10%
What is the relative albedo for the forest?
6-18%
What is the relative albedo for grasslands?
7-25%
What is the relative albedo for soils?
10-20%
What is the relative albedo for desert sand?
35-45%
What is the relative albedo for fresh snow?
70-80%
What type of radiation is inputted into the Earth?
short wave solar radiation
What type of radiation is output from the Earth?
long wave
Rank the major greenhouse gases
Water vapor (36-72%), carbon dioxide (9-26%), methane (4-9%), ozone (3-7%)
