lecture 15. outline for rest of semester oct. 29 th chapter 9 (earth) nov 3 rd and 5 th chapter 9...

Lecture 15

Outline For Rest of Semester• Oct. 29th Chapter 9 (Earth)• Nov 3rd and 5th Chapter 9 and Chapter 10 (Earth and Moon)• Nov. 10th and 12th Chapter 11 (Mars, Venus, and Mercury)• Nov. 17th and 19th Chapter 12 (Jupiter and Saturn)• Nov 24th Chapter 13 (Uranus and Neptune)• Nov 26th Thanksgiving• Dec. 1st - Exam 3• Dec. 3rd – Chapter 14 (Pluto, and the Kuiper Belt)• Dec. 8th and 10th – Chapter 7 and 8 (Comparative Planetology I and II)• Tuesday December 15th (7:30 am – 10:15 am) Final Exam• No Reading days are scheduled this semester• Exam Period begins at 7:30 a.m. on Monday, December 14 and ends on

December 21

Outline For Today• Discuss Exam

• Earth’s Atmosphere (Reading: Chapter 9)– Energy conservation– Modes of energy transfer– The greenhouse effect– The ozone hole

A transition in approach

• Previously emphasis on how things worked• Starting now, emphasis on how things are• But will still make reference to things we learned

in past• Study prep: same as before but also know key

words + concepts they are associated with. Example: aurora – green light in atmosphere – caused by charged particles collide with atmosphere particles – create green light – color depends on molecule spectra.

Guiding Questions

1. What is the greenhouse effect? How does it affect the average temperature of the Earth?

2. What are global warming and the “ozone hole”? Why should they concern us?

3. How does our planet’s magnetic field protect life on Earth?

Key Words

• albedo• atmospheric pressure• global warming• greenhouse effect• greenhouse gas• ozone• ozone layer

Earth’s Protective Shields

• Atmosphere

• Magnetic field

Atmosphere

On Predictions

• If we know how atmospheric chemistry affects climate, why not engineer a solution?

Conservation of Energy

• Two usages:– To use less energy

– Energy of a closed system is not created or destroyed. It just changes form. (Radiation energy to chemical energy, chemical energy to electrical energy, etc.)

Energy

If “system” is our body, then chemical energy in must equal chemical energy out + heat energy out

Radiation energy in must equal heat energy + radiation energy out if temp. inside dotted line is not changing

Heat from wire

Heat from bulb

Radiation from bulb

Solar panel

Solar radiation

Energy Transfer

• Three modes of energy transfer–Convective – Bulk movement of

mass

–Conductive – jiggling material (atoms and molecules) but no bulk movement of mass

–Radiative – Electromagnetic

Energy Transfer

• Give examples of each type of energy transfer– Convective

– Conductive

– Radiative

Energy Balance

• Three modes of energy transfer– Convective – Bulk movement of mass

– Conductive – Jiggling material but no bulk movement of mass

– Radiative – why you feel colder when it is colder outside in a room that is always 70 degrees

Energy Balance

• Simple model: Sun inputs energy to big ball, Earth. What happens to temperature?

• Can’t convect energy to space

• Can’t conduct energy to space

• Need to radiate. And as something is heated up, it radiates more (remember blackbody curves?)

Energy Balance

Special Relationship

Wavelength

Sketch this curve for larger and smaller T

Ene

rgy

Flu

x In

tens

ity

T

1~max

4~ TF

110

A

B

= albedo

Radiation Energy in = Radiation Energy out

http://stephenschneider.stanford.edu/Graphics/EarthsEnergyBalance.png

• If Earth was covered with solar panels, what would happen to value A?

The Greenhouse effect

• Two usages:– An effect that occurs on a

planet with an Earth-like atmosphere

– An enhancement of the above effect due to human activity

The greenhouse effect simplified

Visible light passes through with ease

Greenhouse gasses (e.g., CO2)

Greenhouse gasses absorb energy that would have been otherwise sent back to space.



What must be happening to the temperature?


• Greenhouse gasses absorb energy that would have been otherwise sent back to space.

• If more energy comes in but less goes out, temperature must increase



Why won’t temperature continue to increase? Hint: use Stephan-Boltzman law


• Energy output of a body ~ T4. Earth is not a perfect blackbody, but the trend is the same. Higher energy input leads to higher temperature and hence higher energy output.



Greenhouse gasses absorb energy that would have been otherwise sent back to space. Thus temperature will increase.

?

solar visible and ultraviolet radiation infrared radiation




Why doesn’t radiation get absorbed by greenhouse gasses on the way down?

?

How is this connected to absorption spectra?

How is Global Warming Related to the Ozone Hole?

Ozone in Earth’s Atmosphere

Circulation in our atmosphere results from convection and the Earth’s rotation

Because of the Earth’s rapid rotation, the circulation in its atmosphere is complex.

Energy exchange is convective

Plate tectonics, or movement of the plates, is driven by convection within

the asthenosphere

Craters as seen on the Moon are not apparent on Earth at the present time because

A) the Moon protected Earth from impacts, and this resulted in the craters and maria on the Moon.

B) interplanetary objects have avoided Earth during its history.

C) plate tectonics has returned cratered surface layers into Earth's interior, and weathering has obliterated the more recent craters.

D) all the potentially damaging interplanetary bodies were stopped by Earth's atmosphere.

Conductive energy exchange?

• Give an example of conductive energy exchange on Earth (besides one on next slide)

Conductive energy exchange

Hot core conducts energy to the surface. There is no “bulk” movement of material between core and surface.

The heat that the core provides to atmosphere is much smaller than that provided by the Sun. How do we know?

lecture 15. outline for rest of semester oct. 29 th chapter 9 (earth) nov 3 rd and 5 th chapter 9...

Documents