Lecture 2 Flashcards
Earth's Energy Budget
weather
state of atmosphere at any given time and place
climate
average state of climate over some given time interval
typically 30 year weather “normals”
habitable zone
goldilock’s zone
- sweet spot that allows for evolution of complex life
- strongly controlled by distance from star
stars
astral body that emits different wavelengths of EMR
our sun emits…
mostly visible light (50%), some as infrared and longwave (40%), and the rest as UV or shortwave (10%)
wavelengths
peak to peak
frequency
how many waves in a given amount of time (waves/second)
light is measured in ____, and what are they
photons
- tiny balls of energy
- smallest amount of discrete energy transported by an EM wave
solar insolation
amount of energy passing through a given area over a given amount of time
flux
amount of energy (# of photons) in an EM wave passing through a ceratin area/time
solar flux is ____ at the poles because…
lower bc there is more area
flux is dependent on …
distance from sun and angle of incidence
inverse square law means distance plays even bigger role
eccentricity
elliptical orbit
- controls amount of solar insolation received
- 413000 years
precession
wobble
- 24000 years
obliquity
tilt
- 41000
blackbody
ideal absorber and emitter in all wavelengths
- 100% efficiency
- doesn’t actually exist
- but most objects behave similarly
energy in = energy out
Planck’s Law
relationship between intensity of radiation flux from a blackbody and its wavelength or frequency
Wiens law
states rad flux from a blackbody reaches its peak at a max wavelength inverse to its absolute temp
the hotter the object, the shorter the wavelength
what explains why the sun is yellow
Wien’s Law
stefan-boltzman law
energy flux emitted by a bb is proportional to abs temp ^4
the hotter it is, 4x more flux
first law of thermodynamics
law of conservation of energy
- when in equilibrium, earth is emitting to space the same amount it is absorbing from sun
emissivity
thermal radiation emitted from a body’s surface vs the radiation emitted from an ideal blackbody surface at the same temperature
0-1, 1 = perfect emission, perfect blackbody
Earth’s energy budget controlled by …
incoming/outgoing radiance
- temp of and distance from sun/
- radiated energy and earth’s albedo
energy emitted equation
stefan-boltzman law and area of a sphere
energy absorbed equation
energy intercepted - energy reflected
area of a circle and solar constant and 1-albedo
important difference between energy absorbed and emitted equations
one uses area of a circle one uses area of a sphere
all of earth emits at once, but only half receives sun at once
cause of discrepancy between what earth temp should be and what it is
greenhouse gases :)
the atmosphere
surface temp controlled by
○ Solar constant
○ Number of layers in the atmosphere
○ The albedo
One layer atmosphere
○ Transparent to incoming shortwave
○ Opaque to outgoing infrared
○ Behaves like a blackbody (emits what it absorbs)
○ Energy outwards goes to space and energy down is re-absorbed
- Calculation is too hot
N layer model
The more layers we have, the higher the temperature goes
- But each layer produces less warming than the last
high clouds emit ___ and reflect ___
less, less
warming effect, high and cold wispy clouds don’t emit or reflect well
low clouds emit ____ and reflect ____
more, more
cooling effect, big warm fluffly clouds emit and reflect well
