Climate and Global Change Notes 4-1 Energy and Radiation Energy Energy Types Temperature Driven Heat Transport Science Concepts Definition Potential Kinetic.

Climate and Global Change Notes

4-1

Energy and Radiation

Energy

Energy Types

Temperature Driven Heat Transport

Science Concepts

DefinitionPotentialKineticRadiant

RadiationWave EquationSpectrumStefan-Boltzmann LawWein’s Displacement Law

ConductionConvection

The Earth System (Kump, Kastin & Crane)

• Chap. 3 (pp. 34-41; pp. 45-46)


4-2

Energy

What happens when we drop an object?

What happens when water behind a dam spills to the river below?

What happens when wood burns?

What happens when we turn on a flashlight?


4-3

Energy

Definition

• Energy is the ability to do work

- Work = Force • Distance

- Units

> 1 calorie = energy required to heat 1 gm of water 1°C‡ Note: 1 Calorie (capital C) = 1000 calories = 1 kilocalorie

◊ Unit for food derived energy

Types of Energy

• Potential

- Chemical> Example: a fire

- Electrical> Voltage

‡ Example: a battery uses chemical potential energy to create a voltage and therefore electrical potential energy


4-4

Types of Energy (Con’t)

• Potential (Con’t)

- Gravitational

> Result of object's relative position‡ Example: a falling rock‡ Example: cold (dense) air (fluid) next to warm (less dense)

air (fluid)• Kinetic

- Result of an object's motion

- Large-scale motion

> Example: falling water (hydroelectric power generation)> Example: swinging hammer (drive nail)> Example: air motions, i.e., wind

- Micro-scale motion

> Example: molecular vibration or temperature. Also called thermal energy

Energy (Con’t)


4-5

Heat - Energy Transfer

Types of Energy (Con’t)

• Radiant

- Example: radiation from a fire in a fireplace

- Example: radiation from the Sun

Definition

• Heat - Energy in transit because of a temperature difference

“It is like the advent of thermodynamics … in about 1820. They knew there was something called ‘heat,’ but they were talking about it in terms that would later sound ridiculous.” In fact, he says, they weren’t even sure what heat was, much less how it worked. Most reputable scientists of the day were convinced that a red-hot poker, say, was densely laden with a weightless, invisible fluid known as caloric, which would flow out of the poker into cooler, less caloric-rich bodies at the slightest opportunity. Only a minority thought that heat might represent some kind of microscopic motion in the poker’s atoms. (The minority was right.)

Waldrop, M.M., 1992: Complexity-The Emerging Science at the Edge of Order and Chaos, Touchstone, pp. 297-298.


4-6

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.






How about this one ?

And this one ?

Would walk up and pick up this frying pan?


4-7


Three Mechanisms

• Conduction - Objects in contact; molecules bouncing off each other; solids

• Convection - Motion; hot air rises; gases and liquids

• Radiation - Transfer without requiring a medium; vacuum; Electromagnetic waves

ConductionRadiationConvection


4-8

Heat - Energy Transfer (Con’t)

Three Mechanisms (Con’t)

• Conduction - Objects in contact; molecules bouncing off each other; solids

- Caused by uneven temperature

> Examples: Heat conductivity

Material ( cal / s - cm - °C )Air (at 0°C) 0.000058Air (at 20°C) 0.0000614Dry soil 0.0006Dry sand 0.0013Water (at 10°C) 0.00143Concrete 0.0022Wet soil 0.0050Ice (at 0°C) 0.0054Steel 0.121Iron 0.161Aluminum 0.50Copper 0.918


4-9


• Conduction (Con’t)

- New fresh, light snow - Good insulator because of trapped air

- Older settled or wet snow - Not as good an insulator

0.001 0.002 0.003 0.004 0.005

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0

0

Conductivity in Snow ( cal / s - cm - °C)

Sno

w D

ensi

ty (

g /

cm

3 )


4-10



• Convection - Motion; hot air rises; gases and liquids

- Caused by uneven heating of fluids

- Thermal circulations; Many sizes

> Clouds

‡ Convective clouds - cumulus cell

> Sea breeze

> Monsoon - India and Arizona

> Global circulation

Effect of convection on flames - Left image (with gravity, i.e., convection)

Right image (low gravity in space, i.e., little convection)

http://microgravity.grc.nasa.gov/combustion/cfm/cfm_index.htm

Factoid -

An oil lamp with a hollow wick burns 10 times brighter than a lamp with a solid wick


4-11



• Radiation

- Transfer without requiring a medium; vacuum; Electromagnetic waves

- All objects with temperature above absolute zero emit radiation

- The analogy of waves is often used to describe radiation

Height

Crest

Trough

Wavelength

Amplitude


4-12



• Radiation (Con’t)

- The analogy of waves is often used to describe radiation

> Wave Equation

‡ Example: Boat dock

‡ Speed of wave = wavelength * frequency

or

frequency = Speed of wave / wavelength

where ( Speed of wave ) for radiation is the speed of light which equals 3 x 108 m / s

Frequency Units -

RPM - Revolutions / minute

Hertz - cycles / sec


4-13

“He recognized the model, and knew it was a state-of-the-art microwave protection system. Mounted on each sturdy pole beneath an aluminum hood was a dieletric transmitter and a receiver; a 15 GHz signal was set to one of several selectable AM signal patterns.”

Ludlum, Robert, 2002: The Janson Directive. p. 449.


Three Mechanisms (Con’t)• Radiation (Con’t)

- Radiation from materials is emitted with a range of wavelengths, i.e., a spectrum of wavelengths

10 -14

10 -10

1

10 6

10 23

10 18

10 14

10 10

10 6

10 2

1

10 2

Frequency (hertz)

Wavelength(m)

GammaRays

Ultraviolet

Infrared

Microwaves

Short-wave

10 -2

10 -6

X Rays

Visible

TV

Broadcast Band TV - FM

Long - WaveRadio

NOTE:

GHz = gigahertz = 109 Hz


4-14




- Visible range from 0.4 to 0.7 microns



http://observe.arc.nasa.gov/nasa/education/reference/reflect/ir.html

NOTE:

10-6 m = m= micron


4-15


Why is a red shirt red?

Why is a white shirt white?

Why is a black shirt black?

Why is a red flame red?

Why is a blue flame blue?


4-16



• Compare these two statements. Are they correct physics?

“The music was so loud, it was almost like no sound, like silence, in the same way that black is every color intensified into nothing.”

“K” is For Killer - Sue Grafton (p. 251)

“ ‘All colors taken together congeal to whiteness, the greatest part of space is black,’ say the journal notes.”

Golf in the Kingdom - Michael Murphy (p. 130)


4-17




- Ultraviolet (uv) C -Shortest wavelength; Most powerful; Filtered by the ozone layer

- uv B - Midrange uv; Less powerful; Produces both suntans and burns; Energy dissipated in outer layer of skin; Causes painful burns; Contributes to skin cancer; Do not penetrate glass

- uv A - Longer wavelength uv; Penetrates deeply into skin; causeslongterm damage; Causes premature aging; Adds to harmful effects of uv B; Can penetrate glass

Frequency (hertz)

Wavelength (m)

10-9

1018

1014

1013

Ultraviolet

10-5

10-6

Visible

0.20

0.320.29

uv C

uv B

uv A

ExpandedUltravioletWavelengths

Wavelength

(10 m)-6

0.40


4-18




- Radiation from materials is emitted with a range of wavelengths, i.e., a spectrum of wavelengths (Con’t)

10 20 30 40 50 60 70 80 90 1000

246

8

101214

16

1820

Exam Scores

Grades0N

um

be

r o

f S

tud

en

ts p

er

Gra

de

In

terv

al


4-19




- What is the Sun’s spectrum?> Below is the Sun’s emitted radiation spectrum; assumes the Sun’s

outer surface temperature is 6000 K

Note: The Sun emits much of it’s radiation in the visible range with its wavelength of maximum emission, (max), is about 0.48 m, i.e., in the blue-green range

17,500

15,000

12,500

10,000

7,500

5,000

2,500

0 0.5 1.0 1.5 2.00.0

max

Wavelength (m)

Em

itte

d R

ad

iati

on

Per

Wav

ele

ng

th I

nte

rva

l(C

al -

cm

-2 -

min

- m

m -1

)

Visible Note: 1 calorie = energy required to heat 1 gm of water 1°C

Note: 1 Calorie (capital C; Unit used for food derived energy) = 1000 calories (lower case c) = 1 kilocalorie

95% of the Sun’s emitted radiation is in the region between 0.25 and 2.5 m


4-20




- What is the Earth’s spectrum?> Below is the Earth’s emitted radiation spectrum; assumes the

Earth’s surface temperature is 288 K

Note: The Earth’s wavelength of maximum emission, (max), is about 9.8 m

95% of the Earth’s emitted radiation (gray area) is in the region between 2.5 and 25 m, i.e., at much longer wavelengths

0 10 20 300

0.025

0.050

Wavelength (m)

max

Em

itte

d R

ad

iati

on

Per

Wa

vele

ng

th I

nte

rval

(Cal

- c

m-2

- m

in -

mm

-1 )

Note: Energy amounts per wavelength interval much smaller than for the Sun


4-21


Stefan-Boltzmann Law

• The Total Radiation per unit area is directly proportional to the object’s absolute temperature to the fourth power, i.e.,

R = (Const) * T4 = (Const) * ( T * T * T * T )

where T is the temperature in Kelvin and the constant equals 5.67 x 10-8 watts / ( m2 K4 ).

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

Ludwig Boltzmann 1844-1906http://www-groups.dcs.st-and.ac.uk/

~history//Mathematicians/Boltzmann.html


Josef Stefan 1835-1893http://www-groups.dcs.st-and.ac.uk/~history//Mathematicians/Stefan_Josef.html


4-22


Stefan-Boltzmann Law

• Examples:

- For the Sun: T = 6000K

R(Sun) = 5.67 x 10-8 W / (m2 K4 ) * ( 6000K )4

= 7.35 x 107 W / m2

- For the Earth: T = 300K

R(Earth) = 5.67 x 10-8 W / (m2 K4 ) * ( 300K )4

= 4.6 x 102 W / m2


4-23


Wien's Displacement Law

• Wavelength of the maximum energy times the object’s temperature equals a constant

max* T = Const

where max is the wavelength of maximum energy, T is temperature in Kelvin and the constant equals 2.89 x 10-3 meter Kelvin.

Wilhelm Wien 1864-1928http://www-gap.dcs.st-and.ac.uk/~history/PictDisplay/Wien.html



4-24


Wien's Displacement Law

• Examples:

- For the Sun: T = 6000K max (Sun) = Wavelength of maximum energy (Sun)

= ( 2.89 x 10-3 m K ) / ( 6000K ) = 0.48 x 10-6 m= 0.48 microns

- For the Earth: T = 300K

max(Earth) = ( 2.89 x 10-3 m K ) / ( 300K )= 9.6 microns


4-25


Summary

• Sun emits 1.6 x 105 more energy per area than the Earth emits

• The Sun’s energy spectrum is centered in the visible region while the Earth’s energy spectrum is centered in the infrared range

• 95% of the Sun’s radiation is in the region between 0.25 and 2.5 microns while 95% of the Earth’s radiation is in the region between 2.5 and 25 microns

Climate and Global Change Notes 4-1 Energy and Radiation Energy Energy Types Temperature Driven Heat Transport Science Concepts Definition Potential Kinetic.

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