Transcript Solar Energy and the Atmosphere

Solar Energy and the
Atmosphere
Section 22.2
Radiation
 Movement of heat through space
 Includes all energy that travels in waves –
electromagnetic waves
 Travels about 300,000 km/s
 Radio, Microwaves, Infrared, Visible light,
UV, X-rays, Gamma rays
The Atmosphere and Solar
Radiation
 Upper atm absorbs almost all radiation with
wavelengths shorter than visible light
 N and O absorb X, gamma, and UV rays
– In which layers does this occur?
 UV rays are absorbed by ozone in the
stratosphere
 Longer wavelengths, visible light and IR, reach
surface
 IR waves are absorbed by carbon dioxide and
water vapor
Scattering
 Clouds, dust, water droplets, and gas
molecules
 Particles and gas molecules reflect and
bend solar rays.
 30% of sun’s radiation is reflected or
scattered
 Scattering makes the sky look blue and the
sun look red at sunrise and sunset.
Reflection
 Absorption or reflection
by the surface
depends on color,
texture, composition,
volume, mass,
transparency, state of
matter, and specific
heat of the material.
 Albedo – the fraction
of solar radiation that
is reflected off the
surface of an object
Fresh snow
80-85
Old snow
50-60
Grass
20-25
Forest
5-10
White paint
Black paint
80
5
Absorption and Infrared Energy
 Radiation not reflected or scattered is
absorbed.
 Absorption heats the lower atmosphere and
keeps Earth’s surface warm.
 Warm air can bend light rays to produce a
mirage.
Greenhouse Effect
 Burning more fossil
fuels has increased
carbon dioxide in
the atmosphere.
 This may intensify
the Greenhouse
Effect.
Variations in Temperature
 Lag time between absorption and warming
of the surface.
 Most intense sun’s rays at noon, but
warmest times mid to late afternoon
 Temperature of the atmosphere depends on
latitude, surface features, and time of year
and day.
Seasons
 Latitude and Earth’s tilt
 Energy at the equator is more intense than
at the poles.
Water and Temperature
 More water vapor and carbon dioxide, the
warmer the atmosphere.
 This is why desert temps vary.
 Water heats and cools slower than land, so
land near water will be cooler during the day
and warmer at night.
 Wind from the ocean will also moderate
temps.
Conduction
 Particles move faster when heated.
 Collisions cause the transfer of energy.
 Conduction – transfer of energy as heat
through a material
 Conduction heats only small amount of
atmosphere near surface.
Convection
 Gas rises and sinks due to temperature
change.
 Warm air rises, and cool air sinks.
 Warm air has less pressure.
 This is how winds are created.