Solar Radiation: The driving factorSolar Radiation: The driving factor• • Radiation (energy transmitted as waves, rays and particles)Radiation (energy transmitted as waves, rays and particles)

released, absorbed &released, absorbed &

reflected by all thingsreflected by all things

• • travels as both a particle andtravels as both a particle and

a wavea wave

• • is affected by is affected by

-- gravity, magnetism, andgravity, magnetism, and

atmosphere composition,atmosphere composition,distance, angle of incidencedistance, angle of incidence

• • provides Earth with anprovides Earth with an

external source of energyexternal source of energy

The sun produces most of its electromagnetic

energy in intermediate wavelengths / frequencies.

A. TrueB. False

Sources of radiation

• Sun and other stars are dominant source

- Sun is closest so it has a greater influence

• Earth emits some energy as well

- Solar radiation is absorbed by Earth andtransformed into longwave radiation

• Many other planets emit radiation as well

- e.g., Jupiter and Saturn- source is from the planet itself

not all is absorbed and re-emitted like Earth

The Sun• 93 million miles from Earth• It rotates once every 600 hrs (25 days)

• Has hot spots and "cool" spots- sunspots are relatively "cool"

• Produces electro-magnetic radiativeenergy

- concentrated inUV, Visible & IR spectral classes

Sunspots - cyclical magnetic “storms” that occur in 11 year cycles are lower in temperature, but increase solar output.

Sunspots - cyclical magnetic “storms” that occur in 11 year cycles are lower in temperature, but increase solar output.

Solar Max = lots of sunspots and increased energy output Solar Min = few to no sunspots and decreased energy output

Solar Max = lots of sunspots and increased energy output Solar Min = few to no sunspots and decreased energy output

Frequency (mHz) refers to vibration of particlesWavelength () = distance between wave crests

Electromagnetic SpectrumElectromagnetic Spectrum

Long Short

(

Position affects radiation• Far away=less radiation• Titled toward= more radiation• Far away=less radiation; Closer=more radiation• Titled away=less radiation; Tilted toward = more

The northern hemisphere experiences winter because the Earth is farther away from the Sun than it is during the summer months.

A. True

B. False

Summer Solstice Winter Solstice

• Sun's energy at 90°

at Tropic of Cancer

• Sun overhead at noon

• Sun's energy at 90°

at Tropic of Capricorn

• Sun overhead at noon

> ~June 21 ~December 21

Eccentricity100 kyr cycle

aphelion

Earth’s orbit

Obliquity41 kyr cycle

Perpendicular to the eclipticPerpendicular to the ecliptic

Axis 20 kyr agoAxis 20 kyr ago

Axis at presentAxis at present

Axis at 20 kyr in futureAxis at 20 kyr in future

Conditions now

Conditions 11 kyr ago

Precession of Equinox 22 kyr cycle

sun

sun

Earth at aphelion

Earth at perihelion

Path of Earth’s orbit around the sun

QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.

Precession 22 kyr cycle

Milankovitch cycles- pacemaker to the ice agesMilankovitch cycles- pacemaker to the ice ages

fromO18 ice and deep sea sediment cores

*

The atmosphere acts as a mirror, prism and a trap

• Scatters some of the radiation

- why the sky is blue

• Reflects some of the radiation

- clouds, snow, water etc.

• Absorbs some of the radiation

- ground, ozone, dust, etc.

Ozone & dust

Dust & clouds

Clouds & gases

mirror

prism

trap

Distribution of Radiation

• energy balance diagram

Albedo

･ A measure of the amount of reflected radiation

･ Some things reflect radiation better than others

- "dry" or "cold" Snow & Ice = high albedo- water = moderate for visible, low for infrared- plants= moderate for visible

･ Land absorbs and releases radiative energyquicker than water

Albedo = ________________incident radiationreflected radiation

Albedo of land surfaces on EarthAlbedo of land surfaces on Earth

Data collected by NASA’s MODIS satellite, April 2002Data collected by NASA’s MODIS satellite, April 2002

Warm colors are higher; cool are lower; white no data availableWarm colors are higher; cool are lower; white no data available

IR output from Earth

K

Effects of cloud type on radiation budget

• different types of interference havedifferent effects on Earth's energy budget