Lecture 15

Outline For Rest of Semester Oct. 29 th Chapter 9 (Earth) Nov 3 rd and 5 th Chapter 9 and Chapter 10 (Earth and Moon) Nov. 10 th and 12 th Chapter 11 (Mars, Venus, and Mercury) Nov. 17 th and 19 th Chapter 12 (Jupiter and Saturn) Nov 24 th Chapter 13 (Uranus and Neptune) Nov 26 th Thanksgiving Dec. 1 st - Exam 3 Dec. 3 rd – Chapter 14 (Pluto, and the Kuiper Belt) Dec. 8 th and 10 th – Chapter 7 and 8 (Comparative Planetology I and II) Tuesday December 15 th (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 Energy Flux Intensity

110 A B = albedo

Radiation Energy in = Radiation Energy out

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., CO 2 ) Greenhouse gasses absorb energy that would have been otherwise sent back to space. Visible light passes through with ease

What must be happening to the temperature? Greenhouse gasses (e.g., CO 2 )

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

Visible light passes through with ease Greenhouse gasses absorb energy that would have been otherwise sent back to space. Why won’t temperature continue to increase? Hint: use Stephan- Boltzman law Greenhouse gasses (e.g., CO 2 )

Energy output of a body ~ T 4. Earth is not a perfect blackbody, but the trend is the same. Higher energy input leads to higher temperature and hence higher energy output.

Visible light passes through with ease Greenhouse gasses (e.g., CO 2 ) Greenhouse gasses absorb energy that would have been otherwise sent back to space. Thus temperature will increase. ? solar visible and ultraviolet radiation infrared radiation

Visible light passes through with ease Greenhouse gasses (e.g., CO 2 ) Greenhouse gasses absorb energy that would have been otherwise sent back to space. 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?