1. Ch 35- Weather
BIG IDEA: Weather has 6 elements: atmospheric pressure, temperature, wind, humidity, clouds, and precipitation

2. 35.1 The Atmosphere
Earth’s atmosphere= mix of gases (78% N. 21% O) and aerosols including dust, ash, pollen, pollution (~1%)
Atmosphere provides gases required by living things, and an insulating blanket to protect us

3. Climate= general weather pattern of an area
“Weather”= atmospheric pressure, temperature, wind, precipitation, cloudiness, and humidity
Climate= general weather pattern of an area
Air has weight, combined weight= atmospheric pressure
The reason we don’t feel the crushing weight of the atmosphere is our bodies are used to it, and the pressure inside our bodies is equal to that of the surrounding air

4. Air pressure and air density decrease w/ increasing altitude

5. 35.2 Structure of the Atmosphere
4 Atmospheric layers:
1. Troposphere: - lowest, where we live, where weather occurs.
- In troposphere temp decreases w/ increasing altitude
2. Stratosphere: Next layer, contains ozone (O3), which absorbs UV rays to protect us. Temp increases w/ increasing altitude

6. 3. Mesosphere: Gases don’t absorb much, cold layer
4. Thermosphere: Highest layer, absorbs lots of solar radiation, so very hot.
Ionosphere= upper mesosphere + lower thermosphere containing ions (charged electrons)
Ions+solar energy= aurora borealis (Northern lights)

7. Heating the Atmosphere
Solar radiation: electromagnetic heat energy, given off by Sun
On electromagnetic spectrum shorter wavelengths=higher frequency= more energy

8. Sun= ultimate source of energy
Terrestrial radiation: solar radiation absorbed by ground to heat Earth’s surface, much is reflected back into atmosphere
Greenhouse effect= Energy trapped in the atmosphere where greenhouse gases absorb and reemit solar energy many times before escaping into space. This build up causes increased temperatures
The re-radiated energy bounced off by the ground has less energy than when it was incoming. The greenhouse effect is named after a florist’s greenhouse. Without the greenhouse effect life on Earth would be frigid. However, when too many greenhouse gases build up in the atmosphere Earth’s temperature rapidly increases, causing global warming.

9. 35.3 Temperature Depends on Latitude
Latitude (runs East West) + Longitude (runs North  South) determine location
0° latitude= prime meridian, 0° longitude= equator
B/c of Earth’s shape the highest temps the equator, which gets the most direct sunlight.

10. 35.4 Why are there Seasons?
Earth’s axis tilting toward/ away from Sun through the course of a year causes seasons
* Whichever hemisphere is towards Sun =more direct sunlight, longer days, summer
Summer in N, winter in S
Summer in S, winter in N

11. 35.5 Flow of Atmosphere-Wind
Air moves from high pressure to low pressure
Wind is air that flows horizontally from high to low pressure
Bigger differences in air pressure= stronger, faster winds

12. 35.6 Some Winds are local-others are global
Local winds= pressure differences in small, short distances
Global winds= Huge pattern of air circulation around the globe that go in the same direction
* Global winds are produced by planet-scale pressure differences that occur b/c of unequal heating of Earth at the equator and poles

13. Unequal pressure of wind rising and sinking causes patterns called wind belts, which move air in predictable patterns
Jet streams are narrow belts of high-speed wind that blow in the upper troposphere and lower stratosphere.
* They don’t follow consistent paths, move fast, and their altitude and latitude vary

14. Coriolis effect
The Coriolis effect is the tendency of moving bodies (like air and water) to move to the right in the Northern hemisphere and to the left in the Southern hemisphere.
It is caused by Earth’s rotation on its axis

15. 35.7 Ocean currents distribute heat
Surface currents occur at the top of a body of water , and are created by global winds pushing water in certain directions
-The patterns created by surface currents along w/ the Coriolis effect cause circular flow patterns called gyres
Surface currents redistribute heat by taking water far from it’s source

17. Gulf stream warms the eastern coast of U. S
Gulf stream warms the eastern coast of U.S. by bringing water from Mexico up along in a Northeast pattern

18. 35.8 Water in the Atmosphere
Water vapor in the atmosphere produces humidity, clouds, and precipitation
Humidity- amount of water vapor in the air
Amount depends on temp. (more w/ hot weather, less w/ cold)

19. Water vapor:
High in atmosphere=clouds
Condenses near ground= fog
Condensing on surface when dew point is reached= dew
Dew point or below freezing= frost

20. Clouds are visible collections of billions of tiny water droplets or ice crystals
Solid particles like smoke or dust need to be present for the droplets/crystals to condense on

21. 3 types:
Cirrus- thin/wispy, high elevation, indicate rain or snow coming
Cumulus- “fair weather”, fluffy. Cumulonimbus are tall/dark, produce thunderstorms
Stratus- flat, low altitude, may produce drizzle of rain

22. Precipitation is water in liquid or solid phase that returns to Earth’s surface from the atmosphere
-Rain: most common, water above freezing temps
-Snow: water vapor goes to solid below freezing temps, produce 6 sided crystals called snowflakes!
-Hail: forms in cumulonimbus clouds, forms from frozen water droplets condensing for a long time, until large hailstones are produced. Can be very damaging

23. 35.9 Changing weather- Air masses, fronts, and cyclones
Air mass- a large pool of air w/ similar temp and characteristics throughout.
Have characteristics of where they were formed, but move by global winds
Tropical=warm, polar= cold, continental=land, maritime=water
Fronts- A boundary between air masses
- Dense, cool air sinks, warm air rises

24. Whichever air mass displaces the other determine what type of front (cold front vs. warm front)
Stationary front= neither air mass is moving

25. Cyclones: a low pressure weather system, associated w/ rough weather
Cyclones: a low pressure weather system, associated w/ rough weather. Wind moves counterclockwise
Anticyclone: high pressure, moves clockwise. Generally fair skies and no precipitation