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Unformatted text preview: EPS 201 – Lecture Notes 10 – March – 2009 Climate Atmosphere Composition and Structure Insolation Budget Unequal Heat Distribution Atmosphere Circulation In this next couple of weeks we’re going to be talking about the circulation of the atmosphere. We are going to look at how the atmosphere circulates today and how that drives weather patterns. What geologic evidence do we use to say that the climate is different from the past. Just to start us off, if I were to say that this is the range of climate that the earth has seen we are in an era that appears to be slightly cooler than mid-range overall. What is the composition of our atmosphere today. Dominant gas in atmosphere – 78% Nitrogen, 20% Oxygen, Argon < 1%, CO 2 << 1%, and H 2 O, and CH 4 . However, if we were to assume the Pre-Cambrian atmosphere, there was a lot of nitrogen, carbon dioxide, water, hydrogen sulfide, and silicon dioxide. The gases in the early atmosphere are results of mantle expulsions by means of volcanic activity. When we talk about the heat that is generated from the sun, we can talk about the incoming solar radiation. This is referred to by the word , meaning the heat that the atmosphere has received. About a third of the incoming insolation is reflected back to space. OF that that comes in, half is absorbed by the surface or by the clouds. (About two-thirds is absorbed, one-third reflected). That portion of incoming short-wave radiation that is absorbed by the earth, and the earth absorbs it, and radiates it out into long-wave heat wavelengths. Most of insolation the heat that is re-radiated from the earth stays in the system (bouncing off the clouds and earth and so forth) There are four main reasons why it is warmer on the low latitudes and cooler on the high latitudes. 1) Unequal Distribution of Energy of Insolation: The angle of insolation is increased at low latitudes near the equator over that received at high latitudes. This translates into a greater area of coverage by the same amount of energy at higher latitudes. 2) Angle of Insolation translates into a Thickness of Atmosphere: At high angles of insolation (low latitudes) there is a thinner layer of atmosphere than at lower angles of insolation (high latitudes). Since the atmosphere absorbs some of the solar radiation, this results in a greater absorption of solar radiation by the atmosphere at higher latitudes. 3) Angle of Incoming Radiation Has an Effect on Reflection: At higher angles, less of the incoming radiation is reflected back into space, at lower angles of insolation, more of the incoming radiation is reflected back out into space. 4) Albedo = Percentage of Reflectivity: Ice and snow reflect back about 60-90% of the insolation. Bare land reflects back 30-50% of the insolation, vegetated land reflects back 5 -20%. Water absorbs much of the insolation, reflecting back 5 – 10% of the insolation. Lower latitudes have a high amount of water and vegetated land, where much of the insolation is absorbed. Higher latitudes have greater amounts of bare land and ice, where insolation is likely to be reflected.likely to be reflected....
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- Spring '09
- Atmosphere, sea level, high latitudes, higher latitudes, Distribution Atmosphere Circulation