Radiation and Earth’s Atmosphere

Page
1

Slide 1

The earth’s global average surface temperature in present climate is 15C (59F). Without the atmosphere, it would be -18C (-0.4F),

About 33C or 59.4F colder! Atmosphere is the most important component of the earth’s climate.

Radiation vs. other heat sources:

Total energy enter the earth’s atmosphere: 174 petawatts or 174X1015 Watts

Solar: 99.978%, Geothermal: 0.013%, waste and fossil fuel: 0.007%, tidal: 0.002%

Slide 2

Earth’s Atmosphere

1. What is it?

A thin gaseous envelope around the planet.

2. Composition

Today’s atmosphere: nitrogen (78%), oxygen (21%), other (1%) – trace gases!

Nitrogen, oxygen, argon, water vapor, carbon dioxide, methane, and most other gases are invisible.

Clouds are not gas, but condensed vapor in the form of liquid droplets or ice particles.

Ground based smog, which is visible, contains reactants of nitrogen and ozone.

3. Structure

Four layers:

Troposphere

(overturning)

Stratosphere

(stratified)

From surface to 8-18 km

From troposphere top to 50 km

Mesosphere

Thermosphere

Blue sky!

Slide 3

The Structure of Earth’s Atmosphere

1. Four layers defined by

temperature

2. Importance to climate and climate change

Troposphere:

Troposphere:

Stratosphere:

Mesosphere:

Thermosphere:

T decreases with elevation

T increases with elevation

T decreases with elevation

T increases with elevation

80% of Earth’s gases

Most of Earth’s weather happens

Most of the measurements

Stratosphere:

19.9% of Earth’s gases

Ozone layer:

Blocking Sun’s ultraviolet radiation

Slide 4

Energy from the Sun

1. Characteristics

Travels through space (vacuum)

in a speed of light

3. Importance to climate and climate change

In the form of waves:

In stream of particles

Electromagnetic waves

(Photons)

Primary driving force of Earth’s climate engine

2. Electromagnetic spectrum

From short wavelength, high energy, gamma rays to long wavelength, low energy, radio waves

Releases heat when absorbed

Ultraviolet, Visible, Infrared

Slide 5

Sun’s Electromagnetic Spectrum

Solar radiation has peak intensities in the shorter wavelengths, dominant in the region we know as visible, thus shortwave radiation

Slide 6

Blackbody Radiation Curves

Any object above absolute zero radiates heat, as proportional to T4