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CHAPTER 19: THE ATMOSPHERE (Atmosphere (Contains many particles…
CHAPTER 19: THE ATMOSPHERE
Atmosphere
Thin protective layer around the Earth.
Contains many particles originating both from natural processes and human activities.
Particulate matter: sea salts from wave action, soil blown by the wind, airborne pollen and microogranisms, smoke and soot from fires and volcanic eruptions.
Many of these particles absorb water and act as a nuclei for water condensation, influencing formation of clouds and fog. These particles intercept incoming solar radiations.
Atmospheric circulations, associated temperatures, wind and precipitation variations, determining our global climate patterns (the long term observes weather conditions affecting the Earth)
Structure of the atmosphere
Temperature varies with height above the Earth's surface; which helps divides the atmosphere into a number of layers of zones.
Troposphere
Where most of the mass of the atmosphere is found
Principle components: nitrogen, oxygen, argon, co2, water vapour
Stratosphere
Increase in Ozone conc (1-2ppm)
Protects the Earth's surface from harmful ultraviolet radiation.
Regions where the atmosphere warms up (where solar radiation in absorbed):
At ground level,
solar radiation
takes the form of visible light and
infrared radiation
. Infrared radiation is absorbed by the Earth, which heats up the nearby layer of air.
Warming occurs in the
stratosphere
because ozone absorbs
ultraviolet radiation
.
The atoms and molecules in the
thermosphere
heat up because they absorb very short ultraviolet radiation
STUDY DESIGN
Major factors that alter Earth’s atmosphere
• the structure of the atmosphere and the relative proportions of different gases, including greenhouse gases,
that regulate the natural and enhanced greenhouse effects
Greenhouse Effect
The process of retaining heat in the atmosphere.
Include water vapour, carbon dioxide, methane, nitrous oxide, chlorofluorocarbons and halons.
Water vapour is the most significant greenhouse gas, CO2 is the next significant and contributes the most to the enhanced greenhouse effect.
The surface temp of the sun is about 5800C, so the wavelength of solar radiation is in the short end of the electromagnetic spectrum. The wavelenght of solar radiation reaching the Earth's atmosphere is mainly in the range of 300 to 2500 nanometres. Much of the incoming radiation (38%) is visible to the human eye as light (wavelenghts of 390-700nm)...
As solar radiation passes through the atmosphere, some if it is absorbed by the components of the atmosphere, particularly water vapour, carbon dioxide, and other gases
On average, about 45% of the incoming solar radiation passes through the Earth's atmosphere and reached the Earth's surface (which varies greatly with location and time of the year)
Ozone in the stratosphere absorbs most of the ultraviolet radiation, so very little penetrated the atmosphere. The radiation reaching the Earth's surface is mainly in the visible and infrared part of the spectrum.
This solar energy is absorbed by the Earth and reradiated into the troposphere as infrarered radiation (heat) at a much longer wavelength. Some of the reradiated energy escapes into space and tthe rest is absorbed by the greenhouse gases in the troposphere and contributes to warming the troposphere and the Earth;s surface
The greenhouse gas molecules absorb these frequencies of radiation that match their characteristic resonant frequencies. They gain kinetic energy which cause the temperature to rise.
If the gases were not present, all the thermal radiation would be emitted out to space, resulting in an overall lower temperature of the Earth.