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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