First Quiz Study Guide
Topics and Concepts that may be on First Quiz
What is Climate? average weather over 30 year period
Five spheres of earth: atmosphere, hydrosphere, cryosphere, lithosphere, biosphere
Systems, open and closed. Includes boundaries around system.
Open system: energy and/or matter can cross boundaries in and out of system
Closed system: no energy or matter crosses boundaries into or out of system
What is an example of an open system?
Feedback, Positive and Negative
Positive: change occurring in system is enhanced by occurrence
example of positive feedback?
When sun shines on ice, part of it is reflected, but when sun begins to melt ice, then land is exposed. Exposed land absorbs more of the sunshine, heating more of the surface, melting more of the ice, which exposes more heat absorbing land, which melts more ice, etc. until all of the ice is gone.
Negative: change occurring in system is damped out, returning system to same conditions as in beginning
Example of negative feedback in nature?
When sun shines it warms the surface, which causes water to evaporate and air to rise; when rising air cools, clouds form and rain falls, cooling surface. When surface cools, air sinks, clouds evaporate, and sun comes out, warming the surface again. Then whole process begins again.
Albedo: Percentage of solar radiation reflected off of a surface
High albedo, examples -- snow, white clouds
Low albedo, examples -- dark forest, wet soil, asphalt
Earth's energy balance -- balance between incoming solar radiation (shortwave energy) and outgoing heat (longwave energy, infrared radiation)
Earth's albedo: ~30%
Greenhouse effect -- absorption of outgoing heat (longwave radiation) by greenhouse gases in the atmosphere, which keeps the earth warmer than it would otherwise be
How cold would the earth's surface be if there were no greenhouse gases in the atmosphere?
Greenhouses gases: carbon dioxide, methane, water vapor, nitrous oxide, ozone, CFCs
Major controls on Climate from place to place on earth:
(if not covered in lecture, included here for information purposes only)
Latitude -- high latitude (polar regions) are cold because of low sun angle, low solar radiation; low latitude (tropics) are warm because of high sun angle, intense solar radiation
Altitude -- warmest at sea level, colder with increasing elevation (because of thinner air)
Continentality -- difference between heat absorption of land versus water
Locations far from large water bodies have greater seasonal temperature variations -- warmer in summer and colder in winter; e.g. Siberia
Locations close to coast of oceans or large lakes tend to have lower differences between winter and summer, because water changes temperature slowly, heats slowly and cools slowly.
Large scale wind patterns, atmospheric circulation --
Tropics under high sun tend to have thunderstorms, frequent precipitation, and easterly trade winds;
Midlatitudes such as the U.S. receive precipitation in winter from the polar jet stream, dry west coast summers when the jet stream moves north, wet east coast summers from tropical storms coming onshore
Polar regions have very cold, drier conditions because there is less heat to evaporate and thus create clouds and snow
Ocean currents -- coastal locations influenced by warm or cold ocean currents;
e.g. Europe is warmed by the North Atlantic Drift, from the warm Gulf Stream
Vegetation cover -- generally creates lower albedo, warmer, more humid
Causes of Natural Climate Change, by time scale
Tectonic forces -- continental drift -- over tens to hundreds of millions of years
Orbital variations -- cyclic changes in earth's orbit around sun, tilt of the earth's axis, and wobble of the earth's axis that affects timing of Perihelion (closest to sun) and Aphelion (farthest from sun) -- on cycles of ~21,000, 41,000 and 100,000 years; causes of ice ages
Volcanic eruptions, asteroid impacts, sun spots, oscillations in ocean temperature pools, El Nino and La Nina -- all can cause climate change on time scale of centuries to decades; not all well understood by climatologists yet.
Last updated 7/11/07