11 planetary atmospheres it’s a gas!. 11 goals what is an atmosphere? how does the atmosphere...
Post on 21-Dec-2015
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Planetary AtmospheresPlanetary Atmospheres
It’s a gas!
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GoalsGoals
• What is an atmosphere?• How does the atmosphere affect the
planet?
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Climate vs. Weather
• Climate is long term average of weather.
• “If the weather man can’t tell me if it is going to rain next Tuesday with any certainty, then why should I believe they can be certain of global warming?”
• Rolling dice.
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Coriolis Force
• We are all moving right now.• Release a ball from a car at 100mph.
How fast does ball hit bystander?• Same for planet.• We all go once around in 24 hours.
Person at equator has a lot more ground to cover than at poles.
• Rapidly fly from one latitude to another, see the difference.
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Jupiter’s Cells
• Single convection cells broken into convection bands.
• The faster the rotation, the greater the number of bands.
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Concept Test
• A ship fires a very long range canon at an enemy due north of him. In order to take the Coriolis effect into account, the gunner should aim the canon:a. Slightly to the west of the target.b. Slightly to the east of the target.c. Slightly to the north of the target.d. Slightly to the south of the target.e. Slightly above the target.
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The Terrestrial PlanetsWorld Atmos.
Compsn.Surface Pressure
Ave Surface Temp.
Winds, Weather
Clouds, Hazes
Mercury He, Na, O 10-14 bar Day: 800FNight: -280F
none none
Venus 96% CO23.5% N2
90 bars 880F Slow winds, acid rain
Sulfuric acid clouds
Earth 77% N221% O2H2O
1 bar 60F Winds, hurricanes, rain, snow
H2O clouds, pollution
Moon He, Na, Ar 10-14 bar Day:260FNight: -280F
none none
Mars 95% CO22.7% N2
0.007bar -60F Winds, dust storm
H2O and CO2 clouds, dust
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Atmospheres
• Outgassed from planet (billions of years).– Volcanoes, vents
• Envelope of gasses.• No clear boundary with space.
– At 14,000 ft, only half as much oxygen as at sea level.
– Artificial boundary at 60 km.
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Key Effects
1. Pressure determines if water can be a liquid.
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Key Effects
1. Pressure determines if water can be a liquid.
2. Scattering and absorption.– Blue skies– uv-, x-rays reach surface?
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Concept Test
• Suppose atmospheric molecules didn't scatter light at all. In that case, what color would the sky be?a. Blue, because the atmosphere still has the same
composition.b. Yellow, because the sun is yellow.c. White because the molecules don’t scatter light of
any color.d. Black, because the only place in the sky that would
be emitting light would be the sun.e. None of the above.
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Key Effects
1. Pressure determines if water can be a liquid.
2. Scattering and absorption.– Blue skies– uv-, x-rays reach surface?
3. Magnetosphere – solar particle protection.
4. Regulate Surface Temperature.
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Temperature• Recall thermal emission:
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Temperature
• Recall thermal radiation:– Hot things emit light.– Hot things have atoms that move around
quickly.– How do things get hot?– Things get hot by absorbing light.
• Absorption vs. reflection.– What isn’t reflected is absorbed.
• Why is a black street hotter than a white sidewalk?
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Albedo• Albedo is the
measure of how reflective a surface is (i.e., the percentage of incident light that is reflected).– High Albedo ~ 1 =
white– Low albedo ~ 0 =
blackMercury=0.11,Venus=0.65, Moon=0.12, Earth=0.37, Mars=0.15
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The Moon in eclipse.
Albedo and Moon
• In eclipse, there is no reflected light.
• Only thermal radiation.
Orion – by IRASR. Gendler
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Concept Test
• The sun gives off mostly ____ light. The Earth absorbs some and emits ___a. IR, UVb. UV, visiblec. UV, IRd. Visible, IRe. Visible, radio
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Opacity
• Different elements are opaque or transparent to different wavelengths of light.
m
KT
mKT
10
300
)()(
900,2
max
max
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Greenhouse Effect• Sunlight of all wavelengths hits the Earth.• Albedo. What’s not reflected is absorbed.• Absorbed light, heats surface.• Hot things (about 300K = 100F) radiate in
IR.• No atmosphere – IR radiated straight to
space.• With atmosphere, greenhouse gasses
absorb, reradiate IR.• Heats lower atmosphere.• Cooler in mountains because above much
of greenhouse gasses.
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Concept Test
• Light mainly at ____ wavelengths from the Sun passes through the atmosphere and strikes the surface, warming it. The surface _____ IR light, which is trapped by greenhouse gases such as _______, increasing the surface temperature.a. UV, absorbs, O2 & N2b. visible, reflects, CO2c. visible, emits, CO2 & H2Od. IR, transmits, H2Oe. visible, emits, O2 & N2
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Concept Test• Which of the following best describes how
the greenhouse effect works? a. The greenhouse effect is caused primarily by
ozone, which absorbs ultraviolet light and thereby makes the atmosphere much hotter than it would be otherwise.
b. A planet's surface absorbs visible sunlight and returns this absorbed energy to space as infrared light. Greenhouse gases slow the escape of this infrared radiation, which thereby heats the lower atmosphere.
c. Greenhouse gases absorb X-rays and ultraviolet light from the Sun, and this absorbed radiation then heats the atmosphere and the surface.
d. Greenhouse gases absorb infrared light coming from the Sun, and this absorbed sunlight heats the lower atmosphere and the surface.
e. None of the above.
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Key Effects
1. Pressure determines if water can be a liquid.
2. Scattering and absorption.– Blue skies– uv-, x-rays reach surface?
3. Regulate Surface Temperature.4. Magnetosphere – solar particle
protection.5. Climate and weather.
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Homework #17Homework #17
• Due Monday 6-Nov:• Read Bennett 10.4-10.5• Do 18, 19, 28, 38, 39