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Chapter 10.docx

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University of Calgary
GOPH 375

Chapter 10: Climate Change  Fig 10.2 Fig 10. 4  Weather is short term, climate is long term  Sun heats earth unequally, equator gets 2.4x more energy than poles (steeper ray angle). Earth’s spin and gravity (pull cold air) even out heat  Earth always has a band of cloud around the equator because it’s hotter there so hot air rises and condenses  Weather (atmospheric circulation) is the earth trying to distribute heat (clouds) around the equator to the poles. Through wind/water vapor (storms)  Poles snow increases albedo, increases reflection making it colder – greenhouse effect counters this, makes it warmer  Incoming sun rays are short wavelengths, outgoing is long wavelengths  100% energy coming in, variously reflected so only 45% is absorbed into atmosphere, land gets hot and heats air above it. Land reflects infrared rays, not UV?  Planet cools by radiating infrared radiations – some is trapped in the atmosphere: “Greenhouse effect” – most of GH is caused by water vapor in the air, without this the world would be 25 degrees cooler o Non-condensable gases, don’t rain out when in atmosphere o Glass (like atmosphere) is invisible so it absorbs heat but doesn’t release it  Water has a high heat capacity, oceans hold a lot of energy; released when water changes: o Evaporation (liquid to gas) Condensation (gas to liquid) Freezing (liquid to solid) Sublimation (solid to gas) Melting (solid to liquid)  Humidity: amount of water vapor in the air, holds a lot of energy as well o Saturation humidity: max amount of water air can hold (increases with temperature) o Dew-point temperature of air is when relative humidity = 100%. Relative is absolute : saturation humidity  Air is denser closer to earth because of gravity. Air flows up towards lower pressure, against gravity, by adding heat o Adiabatic process – when temperature changes without the loss of heat (air expanding, becoming cooler and sinking) o Altitude of 100% humidity is called lifting condensation level. Where clouds are made (condensation, releasing heat) o MONSOONS pg 272 fig 10.6  Earth layers Fig 10.7: structure of atmosphere. o Troposphere: lowest layer, most moisture. Warmer at the base, colder above. Where weather occurs; 8-10km in the winter, 15 km in summer  Connective part of atmosphere o Tropopause: higher layer of troposphere; cooling upward trend reverses and air begins to warm upward through stratosphere. Boundary, keeps weather in troposphere o Two places where atmosphere is heated; bottom and ozone layer (approx 50km) o Reverse thermal gradient – higher is warmer Redistribution of energy cannot be accomplished by two convection cell from the equator to the poles because the earth’s rotation complicates things. Three cells exist in each hemisphere:  Hadley cells: hot air from equator to tropics, lots of heat, from low to high altitudes, low latitude. Heavy rainfall. Hadley circulation is done when trade winds meet the intertropical convergence zone. This line shifts north and south Fig 10.8/10.9 o Winds going to poles are westerlies, winds going to equator are trade winds. Trade winds release heavy rainfall at the equator o Fig 10.9 –air is always going up near the equator (clouds/rain) lots of jungles, goes up to tropopause, can’t go any higher so as it goes off it cools off, water vapor evaporates, and you get dry air sinking down to the ground – band of descending dry air (no clouds because you got rid of water vapor) resulting in deserts. Sub tropical high pressure zones  Ferrel Cells: middle to high latitudes. Hadley, ferrel and polar cells create major convergent zones at the intertropical convergence zone  Polar cells: middle to high latitudes. polar front is where Hadley cells collide with westerlies Both hemispheres have subtropical high-pressure zones around 30 degrees Latitude were air descends to the surface via Hadley cells. Sub polar lows form around 60 degrees latitude, where polar air (polar cell) meets mid-latitude air (ferrel cell) and rises Coriolis Effect: A geometric effect caused by Earth’s rotation varying from the equator (approx 1670km/hr) to the pole (approx zero). This results in air masses (or water mass) deviating to the right in the northern hemisphere, and the left in the southern hemisphere  Since earth rotates, the cell doesn’t make it all the way to the pole, it comes down at 30 degrees; called the Coriolis Effect states that air gets bent sideways and doesn’t reach poles  Fig 10.8 Air rising heading North and bends right because the word is turning. As it starts heading N, the air goes eastward (right). If you start heading S, air will head to the west but it’ll turn to the right. Any direction air goes across latitude it will bend (world getting ahead of air)  Climate: long term variation; Approx 100 million years, 1 million, 100,000  Air dominantly moves from west to east under Earth’s rotation  Fronts: boundaries between different air masses. Lots of clouds/rain, vary in moisture content and temperature  Jet streams: narrow bands of high velocity winds from west to east at high altitudes (where circulation systems meet) speed accelerated by earth’s rotation. Main streams: o Polar jet – most powerful, west to east
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