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November 21, 2011
Happy Monday
http://www.youtube.com/watch?v=Fq-muLRSuAw
(Remind Students- Quiz on Wed on this PowerPoint and Intro to
Climate Drivers Reading)
Why are the tropics so wet?
 We know that the tropics are warm, but
why are they so wet???
-Sun’s rays heat up the air and water near the
equator
-Sunlight causes water to evaporate from plants
(transpiration), soils, and the bodies of water
-Water molecules rise with the warm air and
eventually bunch together and fall as rain over the
tropics
Challenge Questions
 It is a fact that WARM AIR RISES!
Why does warm air rise? (Think about the
movement of molecules)
-How do air molecules behave when they
are heated?
-Is the density of warm air molecules higher
or lower than the density of cold air
molecules?
What creates wind?
 http://www.vindselskab.dk/en/kids/intro/how.htm
As warm air moves upward,
colder air comes in to fill the
void left behind.

http://www.youtube.com/watch?v=uBqohRu2RRk
Global Air Circulation
 Warm air moves away from equator and
toward the poles. As it travels, it cools and
descends around the 30 degrees north or
south latitude. As the air cools, it loses
moisture and the air becomes very dry. This
is why deserts experience arid and dry
conditions.
 http://serc.carleton.edu/images/eslabs/weather/hadley_cells_semi_permanent.jpg
 http://serc.carleton.edu/images/eslabs/weather/climate_patterns_map.gif
 http://serc.carleton.edu/images/eslabs/weather/hadley_cells_semi_permanent.jpg
Ocean Circulation
 http://www.youtube.com/watch?v=w_8mw-
1HYFg&feature=related
 Thermohaline currents: Currents set up by warm and
 salty water that rises and sinks in the ocean are called
thermohaline currents.
 This makes huge masses of sea water flow in huge
currents all over the world!
Example of how ocean waters
move: Gulf Stream
 Water has the capacity to "absorb" heat and
transport it over great distances before
releasing it.
 Gulf Stream carries heat from locations near
the equator all the way to northern latitudes
that are usually associated with cold climates.


http://www.bing.com/images/search?q=map+of+gulf+stream&view=detail&id=DAA96B4F9B029242
CCD778FB0F2AE39ACD701278&first=0
http://www.macmillanmh.com/tlxnews/wp-content/uploads/2010/07/GulfStream_Map.jpg
Specifics of Gulf Stream
 Water in the north Atlantic is cooled by winds
from the Arctic.
 Cold water is more dense than warm water and
sinks to the ocean floor. Cold water then moves
towards the equator. To replace the cold equatorbound water, the Gulf Stream moves warm water
from the Gulf of Mexico north into the Atlantic.
 http://oceancurrents.rsmas.miami.edu/atlantic/gulf-stream.html
El Nino- Southern Oscillation
http://www.youtube.com/watch?v=7FVZrw7bk1w&fe
ature=related
***During an El Nino event: Warm water covers the
ocean surface in the tropics. This redistribution of
heat leads to evaporation and precipitation in eastern
Pacific and the Americas, but leads to drought
conditions in Australia and parts of Africa.
Coastal Areas vs. Continental
Interiors
 Coastal areas experience less extreme climate
compared to continental interiors (areas of land
that are not by the ocean).
 Coastal areas receive much more precipitation
Challenge Questions:
1. Why might coastal areas experience less extreme
climate?
2. How might the heat capacity of ocean water
affect climate?
Prep for Quiz!
 Why does warm air rise and why does cold air sink?
 Write a full explanation that includes:
 -movement of air molecules when air is heated and
cooled
 -mention the differences in densities of warm air and
cool air