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GEO 103
radiation and seasons
34
Geology
Undergraduate 1
02/14/2010

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Term
radiation
Definition
travels at the speed of light and can travel thru a vacuum...doesn't need a solid to carry it

Term
wavelength
Definition
measured from one trough to the next trough, or from one crest to the next crest
Term
short wave radiation
Definition
emitted by the sun
Term
long wave radiation
Definition
emmited by objects on earth
Term
plane of the ecliptic
Definition
plane on which the earth orbits about the sun
Term
perihelion
Definition
the earth is closest to the sun january 3rd
Term
aphelion
Definition
the earth is farthest from the sun july 4th
Term
direct waves
Definition
provide more heating of the earth because: (1) Energy is spread over a larger surface area; and (2) incoming solar radiation (insolation) must pass through more atmosphere
Term
insolation
Definition
incoming solar radiation
Term
seasonality
Definition
seasonal variations in the Sun's rays above the horizon, & the changes in daylength throughout the year
Term
declination
Definition
the latitude that receives direct (at a 90 degree angle) rays from the sun (migrates between 23.50N & 23.50S)
Term
summer solstice
Definition
(June 20-21) - @Tropic of Cancer (23.5 N) - Sun's rays directly overhead
Term
winter solstice
Definition
(Dec 21-22) - @ Tropic of Capricorn (23.5 S) - Sun's rays directly overhead
Term
vernal equinox
Definition
( March 20-21) - Sun's rays directly overhead at the equator
Term
autumnal equinox
Definition
(Sept. 22-23) - Sun's rays directly overhead at the equator
Term
daylength (see diagram in notes)
Definition
varies throughout the year depending on latitude..
except at the equator and on the two equinoxes, all latitudes experience uneven daylength throughout the course of the year..
@ equator: 12 hrs of daylight & 12 hrs night
@ 40 N/S: ~6 hours difference in daylight
@ 50 N/S: ~8 hours difference in daylight
Term
altitude
Definition
sun angle above the horizon..also changes due to...
Term
What causes changes in daylength and altitude?
Definition
Earth's orientation to the Sun continually changes as it travels along its orbit..earth's curved surface the angle at which the Earth receives radiant energy from the sun varies with latitude..and the lower latitudes receive rays that are more direct (closer to the perpendicular) than do the higher latitudes
Term
Summary of what casuses Seasonality:
Definition
(1) Earth's revolution & rotation; (2) Earth's tilt on it's axis (23.50 from the vertical); and (3) its sphericity
Term
What leads to atmospheric and oceanic circulations?
Definition
an overall imbalance in radiant energy from the equator to poles
Term
conduction
Definition
the transfer of heat by molecular contact: molecule to molecule
Term
convection
Definition
the transfer of heat from one mass or sumbstance to another
Term
radiation
Definition
can be transferred thru a vacuum..ALL objects emit radiation
Term
blackbody
Definition
an object that is perfectly efficient at absorbing and radiating radiation (blackbodies do not exist in nature, but represent and ideal)
Term
3 things that happen to insolation
Definition
reflection, scattering, and absorbtion
Term
reflection
Definition
occurs at the interface between two different media (e.g. air & cloud) when some of the radiation striking the interface is thrown back
Term
scattering
Definition
similar to reflection, except insolation is dispersed in all directions
Term
absorbtion
Definition
radiation is converted to heat and emits that heat (radiation)..most absorption within the atmosphere is by oxygen, ozone, water vapor and various aersols (solid and liquid particles)
Term
direct insolation
Definition
insolation that is transmitted directly through the atmosphere to the earth's surface
Term
diffuse insolation
Definition
insolation that is scattered &/or reflected to the earth's surface
Term
insolation budget (see picture in notes)
Definition
-30 units reflected to space by clouds, the earth, and the atmosphere (thus, the albedo for the Earth as a whole (planetary albedo) is 30%
-20 units absorbed by clouds and the atmosphere
-50 units is absorbed at the earth's surface
Term
Greenhouse Effect
Definition
~direct and diffuse shortwave radiation from the sun is absorbed at the earth's surface
~the earth radiates longwave energy into the atmosphere where some of it is absorbed by the various greenhouse gases
~these gases gain kinetic energy and collide w/neighboring air molecules which increases the average KE of the air, which results in an increase of air temperature
~these same greenhouse gases also emit longwave radiation - some of which is transmitted to the earth's surface where it is absorbed and thus heats the ground
~the earth then reradiates longwave energy upward, where, once again, it is absorbed by the greenhouse gases and warms the lower atmosphere
thus, the greenhouse gases act as an "insulating layer" keeping some of the earth's radiant energy from escaping to space; and keeping the lower atmosphere considerably warmer than it would otherwise be
Term
greenhouse gases
Definition
water vapor, carbon dioxide, nitrous oxide, methane, Ozone
~These gases are poor absorbers of visible (shortwave) radiation, but good absorbers of infrared (longwave) radiation
Term
selective absorbers
Definition
(greenhouse gases are selective) only absorb certain wavelengths
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