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Chapter 2

BIOL150 Chapter 2: Biol 150 Chap 2 Climate

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Rebecca Rooney

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Biology 150 Chapter 2 Climate
Organismal and Evolutionary Ecology Reading notes
Climate: Long-term average pattern of weather and may be described on a local, regional or
global scale
Different from weather which is the combination of temperature, humidity and other
atmospheric conditions occurring at a specific place and time
2.1 Solar Radiation (the electromagnetic energy emanating from the Sun)
- Sun (hot object) emits shortwave radiation; whereas Earth (cooler object) emits
longwave radiation.
- Only 51% of solar radiation reaches and makes it to Earth’s surface, the remaining
radiation may be reflected.
- Of the 51 units of the insolation (direct and indirect solar radiation reaches Earth’s
23 units
Evaporate water, driving the water cycle
7 units
Heat the air next to Earth’s surface, affecting thermal conditions for
21 units
Heat the landmasses and oceans, which in turn emit radiation back to
the atmosphere as thermal radiation
- Although Earth receives shortwave radiation only by day, it emits longwave radiation
both day and night. Most is absorbed by water vapour and carbon dioxide in the
atmosphere, and by clouds. This selective absorption of longwave radiation by
atmospheric gases, which then radiate the energy back to Earth as heat, is called the
greenhouse effect.
- Photosynthetically active radiation (PAR) is one portion of the electromagnetic
radiation emitted by the Sun, and it is important as it includes the wavelengths that
plants use in photosynthesis. (wavelength band from 380 to 740 nm)
2.2 Radiation and Temperature
- The amount of energy intercepted varies greatly with latitude:
(1) At higher latitudes, radiation hits the surface at steeper angle, spreading light
over more area
(2) Radiation penetrating the atmosphere at a steeper angle travelling through more
air and encounters more atmospheric particles, which reflect more of it back into
- Earth’s two distinct motions
(1) Orbits around the Sun and rotates on an axis passes through the North and South
Poles, giving rise to day and night (the diurnal cycle)
(2) Circumnavigates the Sun in a plane called the ecliptic. Earth’s axis is tilted at a
certain angle to the ecliptic, causing seasonal variations in temperature and day
2.3 Elevation and Temperature
- Altitude: distance above the Earth’s surface
- Elevation: distance above sea level
- Atmospheric/air pressure: the mass of air molecules exerts over a given area of
Earth’s surface
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