1. Atmosphere, Climate & Biomes

2. Origin of Modern Atmosphere
Original atmosphere: probably composed of H and He
Second atmosphere evolved from gases from molten Earth: H2O, CO2, SO2, CO, S2, Cl2, N2, H2, NH3, CH4
Modern Atmosphere
Evolved after Cyanobacteria started photosynthesizing
400 million years ago, oxygen started to be at present levels
2nd atmosphere: allowed formation of oceans and early life

3. Composition, Size and Layers of Atmosphere
78%
Oxygen 21%
Argon 0.9%
Other components including:
Water 0-4%
Ozone %
Carbon Dioxide %
Compared to the size of the earth (104km), the atmosphere is a thin shell (120km)
Exosphere
Thermosphere
(Ionosphere)
Mesosphere
Stratosphere
Troposphere
Water vapor depends on where you are and what time of day it it

4. Troposphere 8-14.5 km high (5- 9 miles) Most dense
Temperature drops from average of 17 to 52 degrees Celsius
Almost all weather

5. Stratosphere Extends to 50 km (31 miles) high Dry, less dense
Temperature gradually increases to -3 degrees Celsius
Every 1000 m = 11% less air pressure
Temp increase due to absorption of UV light
99% of air is located in first two layers

6. Mesosphere and Beyond Mesosphere: Thermosphere:
Contains ionosphere: site of Aurora lights
Temperature increases with height
Exosphere
Gases can escape from it into space
Mesosphere:
Temperature decreases from -5 degrees Celsius to -80 degrees Celsius
Cold enough to freeze water vapor
Thermosphere: temp due to temperature increases with height
Exosphere: molecular collisions are much reduced because of the low gas density

7. What Factors Influence Climate?
Key factors that determine an area’s climate
Incoming solar energy
The earth’s rotation
Global patterns of air and water movement
Gases in the atmosphere
The earth’s surface features
Part of Solar Insolation Lab!

8. Why is Solar Radiation so Important?
Without sun, all water would be frozen on Earth
Life would not exist as we know it
The sun’s energy powers ALL biogeochemical cycles
The Sun is the primary determinant of climate
It strikes our atmosphere as electromagnetic radiation in the form of:
Visible light
Infrared radiation
UV radiation

9. Incoming Solar Energy Albedo = reflectivity, reflectance of energy
30% of solar radiation that hits Earth is immediately reflected by Earth’s surface

10. Albedo

11. (sun aims directly at equator)
The Earth’s Rotation
Fall
(sun aims directly at equator)
Summer
(northern hemisphere
tilts toward sun)
Spring
(sun aims directly
at equator)
23.5º
Winter
tilts away from sun)
Solar
radiation

12. The Earth Has Many Different Climates
Weather
Temperature, precipitation, air pressure, wind speed, cloud cover
Hours to days
Climate
Area’s general pattern of atmospheric conditions over decades and longer

13. Weather Extremes include:
Short-term set of physical properties of the troposphere at a particular place and time.
Includes: temperature, pressure, humidity, precipitation, sunshine and cloud cover
Extremes include:
Tornadoes
Tropical cyclones
Atlantic = hurricanes
Pacific = typhoons

14. Air Temperature
Solar energy is more concentrated at the equator than at the poles = more heat
Warm air/water at the equator travel poleward while cold air/water travel equatorward in an attempt to equalize this contrast
It is the atmosphere's continual struggle for temperature balance that brings us our changing weather.
Demonstrate flashlight-poles indirect, equator directly on (10 vs 90 degrees)

15. Air Pressure
Caused by weight of air pressing down on the Earth, ocean & air below
Depends on the amount of air above measuring point
Falls as you go higher
Changes with weather

16. Let’s Talk About The Highs and Lows
Air in a high pressure area compresses and warms as it descends
Warming inhibits formation of clouds-sky is normally sunny in high pressure areas
Haze/fog might form
Opposite is true of low pressure
Moist surface warmed by sun
Flows toward low pressure,
picks up moisture and heat
Warm,
dry air
Hot, wet
air
Falls, is compressed, warms
Rises, expands, cools
Heat released
radiates to space
LOW
PRESSURE
HIGH
Cool, dry
Condensation
and
precipitation

17. Air Movement Air circulation in lower atmosphere due to
Uneven heating of the earth’s surface by sun
Rotation of the earth on its axis
Properties of air, water, and land
Animation

18. Three Types of Circulation Cells
Hadley:
Equatorial regions = high humidity, high clouds, heavy rains
Subtropical regions = low relative humidity, little clouds, high ocean evaporation
Ferrel:
Between 30⁰ and 60⁰ north/south latitudes
Defined seasons are the rule, strong cycles of temperature and precipitation

19. Three Types of Circulation Cells
Polar:
Icy-cold, dry, dense air that descends from the troposphere to the ground
Very little water exists- mostly ice
Low temps, severe winters, small amounts of precipitation

20. Winds Horizontal winds move from areas of high to low pressure
Speed is determined by differences in pressure
Coriolis Effect causes winds to spiral from high pressure zones into low pressure zones: clockwise out from high pressure, spiral counterclockwise in toward low pressure

21. Water Movement Ocean currents Prevailing winds Earth’s rotation
Redistribution of heat from the sun
Surface currents and deep currents

22. A shore upwelling
Cold Peruvian current flows toward equator along coasts of Ecuador and Peru
Upwelling of cold, nutrient filled waters - primary food source for millions of fish

23. The Earth Has Many Different Climates
Animations
El Niño-Southern Oscillation
Occurs every few years
Prevailing winds in tropical Pacific Ocean change direction
Affects much of earth’s weather for 1-2 years
La Nina: counterpart of El Nino: causes the opposite effect
Normal
El Nino:
Strong counter current

24. Case Study: El Nino this year
One of the strongest on record
The south will be cooler than average and the north will be warmer
More precipitation in the south
Other oscillations including the Arctic Oscillation and Madden- Julian Oscillation are playing a role
California could see some minor drought relief

25. Greenhouse Gases Warm the Lower Atmosphere
CO2
CH4
N2O
Natural greenhouse effect
Gases keep earth habitable
Human-enhanced global warming

26. Earth’s Surface Features Affect Local Climates
Mountains interrupt flow of prevailing winds
Rain shadow effect
Most precipitation falls on the windward side of mountain ranges
Deserts leeward
Cities create microclimates

27. Climate Helps Determine Where Organisms Can Live
Major biomes
Large land regions with certain types of climate and dominant plant life
Not uniform
Mosaic of patches
Change with latitude and elevation
Biomes are not fixed
They change as the climate changes
Human activities are likely to affect biome placement in the future