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Chapter 2

BIOL150 Chapter Notes - Chapter 2: Shortwave Radiation, Solar Constant, Water Cycle


Department
Biology
Course Code
BIOL150
Professor
Rebecca Rooney
Chapter
2

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Chapter 2
Weather: combination of temp, precipitation, wind, cloudiness, humidity and other atmospheric conditions occurring at a
specific place and time
Climate: long-term average pattern of weather and may be described on a local, regional, or global scale
2.1: solar radiation
-to describe a climate, 2 factors: temperature and precipitation are important climatic determinants of the kind of
ecosystem that occupies a particular region
-solar radiation: electromagnetic energy coming from the sun, travels relatively/almost freely through space until it reaches
the atmosphere
-there, molecular interactions create thermal patters that come together/pair with earth's rotation and revolution, creating
prevailing winds and ocean currents; these air and water movements effect weather, including the distribution of rainfall
-radiation- described as a stream of photon or packets of energy that behaves like waves or particles, depending on how
they are observed
-radiation varies in wavelength: distance from one crest to the other, and frequency: number of crests passing a given point
per second
-all objects radiate energy in a range of wavelengths depending on its temperature; hotter the object, more energetic
protons, shorter wavelength
-sun (hot object) emits mainly shortwave radiation, shorter wavelength; earth (cool object) emits mainly longwave
(thermal) radiation, longer wavelength
-solar constant: radiation that reaches the earth's atmosphere, 51% makes it to earth's surface; the rest is reflected,
scattered of absorbed the atmosphere
-Earth's albedo: reflectivity, is highly variable; 51% of radiation is insolation: direct or indirect solar radiation that reaches
earth's surface without being reflected
-From that 51% radiation that reaches the earth's surface, some evaporates water, driving water cycle, heat the air-
effecting thermal conditions for organisms, heat landmasses and oceans-which emit radiation back to atmosphere as
thermal radiation
-the amount of radiation emitted by earth is more than the solar radiation absorbed; earth's emits longwave radiation day
and night but only get shortwave radiation during the day; earth's emitted radiation absorbed by water vapours and carbon
dioxide and cloud, and some of it escapes to the space
-greenhouse effect: absorption of radiation by atmospheric gases that in return radiate the energy back to the earth as
heat, due to this earth gets more longwave radiation than shortwave radiation from the sun.
-energy lost at earth's surface equals energy gained at earth's surface including the longwave radiation and shortwave
radiation, 147 units
-photosynthetically active radiation: electromagnetic radiation that can be seen by naked eye, known as visible light which
includes the wavelengths that plants use in photosynthesis, 400 to 700nm
Ultraviolet radiation (UV): shorter wavelength than visible light, UV-A and UV-B, UV-B is dangerous to all life but plays a
roles in evolution creating mutations
Infrared radiation: wavelength longer than visible light, 2 types: near infrared, affects biological processes such as
flowering; far-infrared (thermal) radiation, thermal radiation greatly affects habitability by creating condition that affect life
2.2 Radiation and temperature:
-amount of energy gotten at any point on earth's surface varies with latitude. Two factors involved 1) higher latitudes,
radiation hits surface at steeper angle, spreading light over more area 2) radiation coming in at a steeper angle travels
through more air, comes in contact with more atmospheric particles, which reflect more of it back into space
-variation in intercepted radiation with latitude explains the decreasing temperature from equator to the poles, but doesn't
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