Transcript CH 24.3 Solar Radiation, Pressure, & Wind

CH 24.3 Solar Radiation, Pressure, & Wind
Earth’s Energy Balance
Input = Sun’s Energy = (Visible light + some
UV)
REFLECTED:
~ 25 % by clouds,
dust, & gases
~ 5 % by surfaces
ABSORBED:
~ 20 % by clouds,
dust, & gases
~50% by surfaces
Big Idea:
Most air is NOT
heated by the sun
directly.
Surfaces
Matter!
Albedo =
measure of
how much
solar energy a
surface
reflects. Ice
caps and
clouds have a
high albedo.
Positive
feedback
loops: More
ice caps -->
more solar
energy
reflected -->
cooler --> more
ice caps
Ch. 24.3: Albedo Values
Surfaces Matter to Earth’s Energy Balance
http://www.the-m-factory.com/portfolio/all_images/ill_maps-Albedo-Effect.jpg
Question: As icecaps melt, how will Earth’s albedo
change? How will this affect climate? Why?
Earth’s Energy Balance
Output = Energy Reflected from Earth back to space
Greenhouse
(Usually Infrared - longer wavelength)
Gases:
Surfaces
reradiate the
solar energy that
was absorbed by
releasing longer
wavelengths of
I.R. (heat)
Most of this I.R.
escapes into
outer space.
CO2, CH4, H2O
Allow Visible light &
UV to pass through,
but Reradiates I.R.
back to surface
instead of letting it
escape into space.
More GHG = more
I.R. = Warming
Temps.
Big Idea:
The amount of reflective surfaces and the amount of GHG can have a big impact on
TEMPS.
Feedback
Loops
Positive Feedback: a
change causes a process to
continue (amplify response)
Negative Feedback: a
change causes a process to
stop (supression)
A. Warming temperatures
cause ice caps to melt.
Discuss how this is a
“feedback loop”
B. Discuss how Snowball Earth
came about through positive
feedback
FEEDBACK = PROCESS THAT AMPLIFIES
OR SUPPRESSES SOME INITIAL CHANGE.
Examples:
Positive Feedback
Ice melts  Less energy reflected/more absorbed  E.
warms  ice melts
Ch. 24.3 Energy Transfer in the Atmosphere
1. Radiation: Energy travels as a wave on the EMS.
• UV & Vis. Light from sun absorbed by surfaces
• Infrared (IR) waves are radiated from surfaces &
heat air
2. Conduction: Heat energy is transferred by
molecule collisions w/in a few feet of E’s surface.
Requires contact b/w molecules.
3. Convection: Air masses transfer heat by
moving. Warm, less dense air masses rise; Cooler &
denser air masses sink ... Convection Current or Cells.
VERY IMPORTANT TO WEATHER & CLIMATE.
Heat Transfer