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Canada (162,359)
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BIO205H5 (48)
Chapter 2

Chapter 2

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Christoph Richter

Chapter 2: Climate 2.1 Earth Intercepts Solar Radiation  solar radiation from sun travels as stream of photon/packets of energy (behave as either waves/particles)  All objects emit radiant energy (nature of energy emitted depends on temperature of object  hot Sun [5800C] emits shortwave radiation  cool Earth [15C] emits longwave radiation  Earth emits more longwave radiation than absorbs solar radiation b/c sun rad only recieved during day and Earth rad emitted day + night.  greenhouse effect =rad8n emitted by Earths surface trapped by CO2 in atmosphere and clouds and sent back to surface. o important for maintaining Earth's temperature  visible light =wavelengths 400 - 700nm o known as photosynthetically active radiation (PAR) 2.2 Intercepted Solar Radiation Varies Seasonally  Amount of solar radiation intercepted varies w/ latitude (two factors) 1. higher latitude = steepr angle of radiation hitting surface 2. Radiation travelling thru steep angle must go thru deeper layer of air  Process = radiation hits >particles in the air = >rad reflected back into space  Earth travels around the Sun in a plane called "ecliptic" o E rotates along its own axis at an angle 23.5 degrees to the ecliptic, not perpendicular o Tilt responsible for seasonal variations in temperature and day length o Only equator has exactly 12 hrs of daylight and dark every day of the year  Vernal + Autumnal equinox, sun directly overhead at equator (receives gr8test input of shortwave radiation) o Every place on earth receives same 12 hrs of daylight + night o Summer + winter solstice = longest + shortest days of the yr o Lowest annual input of solar radiation in high latitudes o annual temperatures higher in tropical regions and decline the closer to the poles u get 2.3 Air Temperature Decreases with Altitude  air gets cooler with increasing altitude  atmospheric/ air pressure = amt of force by air exerted over given surface area  gr8r pressure at Earth's surface = high density of air (#molecules/ unit volume)  air temperature decreases from Earth - altitude of 11 km (36000ft) o rate at which temp decreases called environmental lapse rate  decrease in air temperature cause by two factors: o air molecules moving slower at higher altitudes b/c decrease in pressure o decline in "warming effect" of Earths surface  adiabatic cooling = when decrease in air temperature is due to expansion (increased altitude, decreased pressure of molecules) not heat loss o rate of cooling depends on water content of air o cooling of dry air = 10 Celsius/100m elevation o adiabatic lapse rate = rate of temperature change with elevation 2.4 Air Masses Circulate Globally  atmosphere in a constant state of movement driven by rising + sinking air masses and Earth's rotation on its axis  equatorial regions = low pressure zone; polar regions = high pressure zone  Coriolis effect = air masses + moving objects in the North hemisphere deflected right (clockwise); left for Southern hemisphere (counter clockwise) o prevents direct simple flow of air from equator to poles o cr8s series of belts of prevailing winds (named for direction they come from) o six cells of air flow, 3 in each hemisphere  Equator o equatorial low = low pressure zone near surface o Hadley cells = descending air forms semipermanent high-pressure belt @ surface encircling Earth (subtropical high) o westerlies = prevailing wind that moves northward toward pole, pushed right (Coriolis effect) o trade winds = also known as northeast trades, move southward also deflected right o subpolar low = zone of low pressure air between westerlies and cold air from pole (polar front) where surface air converges and rises o Ferrel cell = second of three cells; surface air rises and falls (closes at) region
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