Hand-outs

Fig. 4-17 Extras from Friday Graded Stuff

GARP 0102 Earth Radiation Balance (Part 1)

Class 8: Earth’s Radiation Balance I (Chapter 4)

1. Earth’s Radiation Balance: Sun, Atmosphere, and Earth’s Surface as a System

2. Electromagnetic Radiation: Shortwave vs. longwave radiation (Page 69-71)

3. Earth’s Radiation Balance: Shortwave vs. longwave radiation balance (Page 77-81)

4. A “typical” Radiation Day

GARP 0102 Earth Radiation Balance (Part 1)

Big Picture! Input (of energy) to the Earth = Output (of energy) from the Earth Balance!

Class 8: Earth’s Radiation Balance I (Chapter 4)

1. Earth’s Radiation Balance: Sun, Atmosphere, and Earth’s Surface as a System

2. Electromagnetic Radiation: Shortwave vs. longwave radiation (Page 69-71)

3. Earth’s Radiation Balance: Shortwave vs. longwave radiation balance (Page 77-81)

4. A “typical” Radiation Day

GARP 0102 Earth Radiation Balance (Part 1)

Solar Radiation hitting the Top of the Atmosphere

In the Atmosphere: 1. Reflection 2. Absorption 3. Transmission of solar radiation.

Solar Radiation received at the Earth’s surface

What’s the Role of the Atmosphere in all this?

GARP 0102 Earth Radiation Balance (Part 1)

Solar energy arriving at the Earth’s surface. (reflection and absorption)

Heating!

Solar energy arriving at the top of the atmosphere.

The Radiation Balance of the Earth (Fig. 4-17)

Solar energy transmitted through the atmosphere: transmission absorption reflection

Big Picture: The Role of the Atmosphere

GARP 0102 Earth Radiation Balance (Part 1)

Think: Cold Water on a Hot Stove!

The electricity does NOT heat the water directly…it heats the burner plate.

And the hot burner plate heats the cold water from the bottom!

Unstable Situation!

The Atmosphere is heated by the Earth’s Surface!

The solar energy does NOT heat the atmosphere directly.

Instead, the sun heats the surface of the Earth.

The (warm) surface of the Earth heats the overlying (cold) atmosphere from below.

GARP 0102 Earth Radiation Balance (Part 1)

“Colder” Atmosphere

“Hot” Earth Surface

“Colder” Water

“Hot” Stovetop

Not a Stable Situation! Imbalance!

Nature/Physics tries to create a Balance!

1) Atmosphere/Water heat up!

2) Convection (bubbles rise!)

3) Vertical Mixing

Weather!

GARP 0102 Earth Radiation Balance (Part 1)

GARP 0102 “Introduction to Physical Geography” Lecture 7 (Wednesday, 02/03/10)

Overall – there has to be a balance between:

1) The energy we receive from the sun!

2) The energy we send back into space!

Otherwise…we would melt!

Fig. 4-16

GARP 0102 Earth Radiation Balance (Part 1)

Big Picture! Electromagnetic radiation is your cell phone!

Class 8: Earth’s Radiation Balance I (Chapter 4)

1. Earth’s Radiation Balance: Sun, Atmosphere, and Earth’s Surface as a System

2. Electromagnetic Radiation: Shortwave vs. longwave radiation (Page 69-71)

3. Earth’s Radiation Balance: Shortwave vs. longwave radiation balance (Page 77-81)

4. A “typical” Radiation Day

GARP 0102 Earth Radiation Balance (Part 1)

Electromagnetic Radiation/Waves

= Radiation/waves that are able to transport energy without going through a solid medium (think radio waves, cell phone waves, etc.)

We characterize electromagnetic radiation based on its wavelength (= the distance from one wave crest to the next).

GARP 0102 Earth Radiation Balance (Part 1)

Visible Light = Sun Wavelength between 0.4 and 0.7 micrometers. “Visible” to Us! = Humans have build-in “sensors” that can “measure” or “receive” these particular wavelengths – our eyes!

The Electromagnetic Spectrum

Fig. 4-5

Visible Light = Sun Wavelength between 0.4 and 0.7 micrometers. “Visible” to Us! = Humans have build-in “sensors” that can “measure” or “receive” these particular wavelengths – our eyes!

Longer Wavelengths = Microwaves/radar/cell phone/radio/TV waves. “Invisible” to Us! = Humans have no “sensors” to “receive” them – but…your TV or radio or cell phone can “see” them!

413-575-2030

Fig. 4-5

The Electromagnetic Spectrum

Fig. 4-5

Visible Light = Sun Wavelength between 0.4 and 0.7 micrometers. “Visible” to Us! = Humans have build-in “sensors” that can “measure” or “receive” these particular wavelengths – our eyes!

Longer Wavelengths = Microwaves/radar/cell phone/radio/TV waves. “Invisible” to Us! = Humans have no “sensors” to “receive” them – but…your TV or radio or cell phone can “see” them!

Shorter Wavelengths = X-rays/UV rays. “Invisible” to Us”! = Visible on X-ray films, which can “receive” them.

Fig. 4-5

The Electromagnetic Spectrum

Fig. 4-5

Facts of Physics:

1. All bodies/objects emit electromagnetic radiation all the time.

2. The amount/intensity of the emitted electromagnetic radiation, and its wavelength, are determined by the temperature of the body/object.

(Now, we could derive these 2 facts using a whole bunch of scary differential equations…let’s not do that…)

Page 69-71

GARP 0102 Earth Radiation Balance (Part 1)

Facts of Physics:

1. All bodies/objects emit electromagnetic radiation all the time.

2. The amount/intensity of the emitted electromagnetic radiation, and its wavelength, are determined by the temperature of the body/object.

All bodies… You, me, your pencil, the cat, the table, the wall, the tree outside, the pond, the car, the ice cube, the freezer, the heater, the fan, the mountain, the shoe, the ground, the ice on the lake, etc.

Including… the clouds, the water vapor molecules, the dust in the air, the rain drop, the snow flake, the CO2 molecule, the fog in the morning, the haze, the smog, etc.

(doesn’t matter if liquid or solid)

(Now, we could derive these 2 facts using a whole bunch of scary differential equations…let’s not do that…)

GARP 0102 Earth Radiation Balance (Part 1)

Page 69-71

The hotter the object… (=Sun)

• The more energy it emits.

• The shorter the wavelength at which it emits this energy.

All bodies… You, me, your pencil, the cat, the table, the wall, the tree outside, the pond, the car, the ice cube, the freezer, the heater, the fan, the mountain, the shoe, the ground, the ice on the lake, etc.

Including… the clouds, the water vapor molecules, the dust in the air, the rain drop, the snow flake, the CO2 molecule, the fog in the morning, the haze, the smog, etc.

(doesn’t matter if liquid or solid)

(Now, we could derive these 2 facts using a whole bunch of scary differential equations…let’s not do that…)

Facts of Physics:

1. All bodies/objects emit electromagnetic radiation all the time.

2. The amount/intensity of the emitted electromagnetic radiation, and its wavelength, are determined by the temperature of the body/object.

GARP 0102 Earth Radiation Balance (Part 1)

Page 69-71

All bodies… You, me, your pencil, the cat, the table, the wall, the tree outside, the pond, the car, the ice cube, the freezer, the heater, the fan, the mountain, the shoe, the ground, the ice on the lake, etc.

Including… the clouds, the water vapor molecules, the dust in the air, the rain drop, the snow flake, the CO2 molecule, the fog in the morning, the haze, the smog, etc.

(doesn’t matter if liquid or solid)

The colder the object… (=Earth)

• The less energy it emits.

• The longer the wavelength at which it emits this energy.

The hotter the object… (=Sun)

• The more energy it emits.

• The shorter the wavelength at which it emits this energy.

(Now, we could derive these 2 facts using a whole bunch of scary differential equations…let’s not do that…)

Facts of Physics:

1. All bodies/objects emit electromagnetic radiation all the time.

2. The amount/intensity of the emitted electromagnetic radiation, and its wavelength, are determined by the temperature of the body/object.

GARP 0102 Earth Radiation Balance (Part 1)

Page 69-71

All bodies… You, me, your pencil, the cat, the table, the wall, the tree outside, the pond, the car, the ice cube, the freezer, the heater, the fan, the mountain, the shoe, the ground, the ice on the lake, etc.

Including… the clouds, the water vapor molecules, the dust in the air, the rain drop, the snow flake, the CO2 molecule, the fog in the morning, the haze, the smog, etc.

(doesn’t matter if liquid or solid)

The colder the object… (=Earth)

• The less energy it emits.

• The longer the wavelength at which it emits this energy.

The hotter the object… (=Sun)

• The more energy it emits.

• The shorter the wavelength at which it emits this energy.

Intensity = constants * T4 (Stefan-Boltzman Law)

Wavelength = constant / T (Wien’s Law)

(Now, we could derive these 2 facts using a whole bunch of scary differential equations…let’s not do that…)

Facts of Physics:

1. All bodies/objects emit electromagnetic radiation all the time.

2. The amount/intensity of the emitted electromagnetic radiation, and its wavelength, are determined by the temperature of the body/object.

GARP 0102 Earth Radiation Balance (Part 1)

Page 69-71

All objects radiate electromagnetic energy all the time (day and night). Hotter objects (i.e. the coffee cup) radiate with greater intensity than cooler objects (i.e. the soft drink).

GARP 0102 Earth Radiation Balance (Part 1)

The Sun and the Earth emit electromagnetic radiation all the time!

But the Sun is much hotter It emits more energy and at a shorter wavelength.

The Earth is much colder It emits less energy and at a longer wavelength.

GARP 0102 Earth Radiation Balance (Part 1)

Sun (temperature ~11,000°F)

Emits most of its electromagnetic waves (= energy) between 0.4 and 0.7 micrometer wavelength.

That…happens to be the wavelength that our eyes can “measure” (= see!).

Sun (temperature ~11,000°F)

Emits most of its electromagnetic waves (= energy) between 0.4 and 0.7 micrometer wavelength.

That…happens to be the wavelength that our eyes can “measure” (= see!).

Earth/Atmosphere (temperature ~55°F)

Emits most of their electromagnetic waves (= energy) between 5 and 30 micrometer wavelength.

And that…we can’t see with our eyes, but we can see it with special films!

GARP 0102 Earth Radiation Balance (Part 1)

Orange = Lot’s of Heat Loss

Purple = Much less Heat Loss

Earth/Atmosphere (temperature ~55°F)

Emits most of their electromagnetic waves (= energy) between 5 and 30 micrometer wavelength.

And that…we can’t see with our eyes, but we can see it with special films!

Big Picture! Now it gets complicated! But, overall, input has to equal output!

Fig. 4-16

Class 8: Earth’s Radiation Balance I (Chapter 4)

1. Earth’s Radiation Balance: Sun, Atmosphere, and Earth’s Surface as a System

2. Electromagnetic Radiation: Shortwave vs. longwave radiation (Page 69-71)

3. Earth’s Radiation Balance: Shortwave vs. longwave radiation balance (Page 77-81)

4. A “typical” Radiation Day

GARP 0102 Earth Radiation Balance (Part 1)

The Basics…

The Earth is constantly gaining energy from the Sun via shortwave solar radiation.

At the same time, the Earth is constantly loosing energy via its own longwave radiation.

In the long-term, there has to be a balance between our energy gains and losses, otherwise the Earth would be an Unstable System!

Analogy: Heating a House…

Fig. 4-16

GARP 0102 Earth Radiation Balance (Part 1)

Greenhouse Effect

The Simplified Radiation Balance

Following the main pathways of solar radiation and earth radiation.

GARP 0102 Earth Radiation Balance (Part 1)

Earth’s Radiation Balance includes two types of electromagnetic radiation.

1. Solar Radiation (also called “shortwave” radiation).

2. Earth Radiation (also called “terrestrial” or “longwave” or “infrared” radiation).

2a) Longwave radiation emitted by the earth’s surface upwards.

2b) Longwave radiation emitted by the atmosphere (e.g. clouds, water vapor, greenhouse gases, dust, etc.) upwards and downwards.

Solar Radiation and Earth Radiation are linked by the Greenhouse Effect.

Mean – Global – Still Simplified! (Fig. 4-17)

GARP 0102 Earth Radiation Balance (Part 1)

We will look at the details…

But – overall – the amount of energy we receive from the sun has to be balanced by the amount of energy we emit back into space from the atmosphere. Otherwise…it would get very hot down here very fast…

Incoming from Sun: 100 units (= 100 percent)

Outgoing from Earth: 31 + 61 + 8 = 100 units (= 100 percent)

Overall Balance!

Mean – Global – Still Simplified! (Fig. 4-17)

Confused? Page 77 - 79 (Fig. 4-17)

GARP 0102 Earth Radiation Balance (Part 1)

Shortwave Balance Longwave Balance

GARP 0102 Earth Radiation Balance (Part 1)

The Shortwave (Solar) Radiation Balance

100%/100 units of energy arrive from the Sun…

31% get reflected by the Earth’s surface or the atmosphere (without heating anything) back into space.

24% get absorbed in the atmosphere (by dust, ozone, clouds, water vapor, etc.) and heat up the atmosphere a bit.

45% finally arrive at the Earth’s surface…

Shortwave Balance

GARP 0102 Earth Radiation Balance (Part 1)

At the Earth’s Surface 1. The surface of the Earth absorbs this solar radiation! 2. The energy transported by the electromagnetic waves

from the sun is exchanged… 3. …and the surface of the Earth is heated up. The Earth’s surface, in turn, heats the overlying cool atmosphere from the bottom!

Shortwave Balance

The Shortwave (Solar) Radiation Balance

100%/100 units of energy arrive from the Sun…

31% get reflected by the Earth’s surface or the atmosphere (without heating anything) back into space.

24% get absorbed in the atmosphere (by dust, ozone, clouds, water vapor, etc.) and heat up the atmosphere a bit.

45% finally arrive at the Earth’s surface…

GARP 0102 Earth Radiation Balance (Part 1)

Solar Radiation enters the Atmosphere…

Some solar energy is reflected by the atmosphere or by clouds (i.e. it does not heat the atmosphere).

Some solar energy reaching the Earth’s surface is reflected back into space without any surface heating (think snow!).

A small amount of solar energy is absorbed and heats the atmosphere directly.

45% of solar energy reaches the Earth’s surface, warms the surface, and the surface in turn heats up the (cold) atmosphere from below! (Think stove top!)

Shortwave Balance

GARP 0102 Earth Radiation Balance (Part 1)

GARP 0102 Earth Radiation Balance (Part 1)

Shortwave Balance Longwave Balance

GARP 0102 Earth Radiation Balance (Part 1)

61 = 21 + 3 + 4 + 19 + 14

Shortwave Balance Longwave Balance

GARP 0102 Earth Radiation Balance (Part 1)

Confused? Page 77 - 79 (Fig. 4-17)

We will look at the details…

But – overall – the amount of energy we receive from the Sun has to be balanced by the amount of energy we emit back into Space from the Atmosphere. Otherwise…it would get very hot down here very fast…

Incoming from Sun: 100 units (= 100 percent)

Outgoing from Earth: 31 + 61 + 8 = 100 units (= 100 percent)

Overall Balance!

GARP 0102 Earth Radiation Balance (Part 1)

Radiation Balance – Cliff Notes…

• Sun heats up the Earth’s Surface (mostly) and the overlying Atmosphere (a bit).

• The Earth’s Surface heats the Atmosphere by emitting longwave radiation.

GARP 0102 Earth Radiation Balance (Part 1)

Radiation Balance – Cliff Notes…

• Sun heats up the Earth’s Surface (mostly) and the overlying Atmosphere (a bit).

• The Earth’s Surface heats the Atmosphere by emitting longwave radiation.

• The Atmosphere emits most of the energy back to us (= Greenhouse Effect) and into Space to balance the Radiation Balance = Recycling Loop.

The Atmosphere performs two critical functions

1. It traps much of the energy emitted by the Earth and sends it back down = Greenhouse Effect, which makes the Planet inhabitable.

2. It also sends this energy upwards into Space to balance the energy balance.

GARP 0102 Earth Radiation Balance (Part 1)

The atmosphere is heated from the bottom – by the Earth’s surface.

Radiation Balance – Cliff Notes…

• Sun heats up the Earth’s Surface (mostly) and the overlying Atmosphere (a bit).

• The Earth’s Surface heats the Atmosphere by emitting longwave radiation.

• The Atmosphere emits most of the energy back to us (= Greenhouse Effect) and into Space to balance the Radiation Balance = Recycling Loop.

The Atmosphere performs two critical functions

1. It traps much of the energy emitted by the Earth and sends it back down = Greenhouse Effect, which makes the Planet inhabitable.

2. It also sends this energy upwards into Space to balance the energy balance.

GARP 0102 Earth Radiation Balance (Part 1)

Class 8: Earth’s Radiation Balance I (Chapter 4)

1. Earth’s Radiation Balance: Sun, Atmosphere, and Earth’s Surface as a System

2. Electromagnetic Radiation: Shortwave vs. longwave radiation (Page 69-71)

3. Earth’s Radiation Balance: Shortwave vs. longwave radiation balance (Page 77-81)

4. A “typical” Radiation Day

GARP 0102 Earth Radiation Balance (Part 1)

Surface Radiation Balance 1 Day

NET R =

+SW (incoming solar radiation) –SW (reflected solar radiation) +LW (incoming longwave radiation from atmosphere, clouds, dust, etc.) –LW (emitted longwave radiation from Earth’s Surface) Night: Negative Balance (Earth is loosing Energy) Cooling! Day: Positive Balance (Earth is gaining Energy) Warming!

Typical summer/fall day in the mid-latitudes

GARP 0102 Earth Radiation Balance (Part 1)

The Warmest Time of the Day…

Does NOT occur at noon (= time of maximum solar radiation)

But (usually) in the late afternoon!

Why??

When a maximum amount of solar energy is absorbed by the earth’s surface and emitted back into the atmosphere as longwave radiation.

Maximum heating of the atmosphere!

GARP 0102 Earth Radiation Balance (Part 1)

GARP 0102 Earth Radiation Balance (Part 1)

Imagine…

A clear night (no clouds)

An overcast night (with clouds)

There’s no sun, so we’re not receiving any electromagnetic energy from the sun.

Imagine…

A clear night (no clouds)

An overcast night (with clouds)

There’s no sun, so we’re not receiving any electromagnetic energy from the sun.

Clear Skies The Earth still emits its electromagnetic radiation into space Most cooling! Overcast Skies Now, the radiation from the earth is trapped by the clouds. And the clouds also emit electromagnetic radiation – both into space and back to Earth Much warmer! ( = Greenhouse Effect)

GARP 0102 Earth Radiation Balance (Part 1)

GARP 0102 Earth Radiation Balance (Part 1)

Class 8: Earth’s Radiation Balance I (Chapter 4)

1. Earth’s Radiation Balance: Sun, Atmosphere, and Earth’s Surface as a System

2. Electromagnetic Radiation: Shortwave vs. longwave radiation (Page 69-71)

3. Earth’s Radiation Balance: Shortwave vs. longwave radiation balance (Page 77-81)

4. A “typical” Radiation Day

Hand-outs

Fig. 4-17 Extras from Friday Graded Stuff

GARP 0102 Earth Radiation Balance (Part 1)

3-2-1 Response That was a lot of material! • The 3 most interesting things you just learned. • The 2 most confusing things you just learned. • The 1 burning question you need to answer. Share with your neighbor.

That’s what happens when you attend a talk, lecture, or meeting. Some things will be interesting, others boring. Some things will be clear and well-explained, other not so much. Hopefully there will be at least 1 question you really need to find an answer to. Google, Wikipedia, Textbook, etc.