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Chapter 1&2

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Environmental Science
Sean Mc Master

Chapter 1: Atmosphere: mixture of as molecules, small suspended particles of solid and liquid and falling precipitation, very thin envelope of gases that surround the Earth and is most dense near the Earth’s surface Meteorology: study of the atmosphere and the processes (such as cloud formation, lightning and wind movements that cause weather Weacther: short term condtion of the climate  Elements of weather are ;  Current temperature  Humidity  Wind conditions  Amount and type of cloud cover  Presence or absence of precipitation Climate: long term Climatology: concerns itself with the same elements of the atmosphere that meteorology does, but on a Different time scale (averages taken over a number of years)  Relies on averages taken over a number of years in order to gauge typical atmospheric conditions for locations across Earth’s atmosphere  Concerned with changes in earth’s climate and factors responsible for those changes Aspects of Climate  Extreme heat, hail, or lightening Thickness of the Atmosphere:  Earth’s atmosphere becomes thinner at higher altitudes (don’t know where it stops though)  At 50 km it is only about 1 % of what it is at sea level  Most of the atmosphere is contained within a shallow envelope surrounding the oceans and continentsits motion over lager areas must be primarily horizontal  Horizontal wind speeds are typically 1000’s times greater than vertical wind speeds  Vertical winds speeds tend to determine most of atmospheric behaviour Composition of the Atmosphere  Atmosphere contains mixture of invisible gases and a large number of suspended microscopic solid particles and water droplets  Molecules of gasses can be exchanged between the atmosphere and earth through volcanic eruptions or by biological processes, such as plant and animal respiration  Steady state or dynamic equilibrium: when gas concentration in the reservoir remains constant as the gas that moves from surface to atmosphere is equal to gas that moves from atmosphere to surface  Residence time: average lengh of time that individual molecules of a given substance remain in the atmosphere  (Divide mass of substance in atmosphere kg/ by rate at which substances the substance enters and exits the atmosphere (kg/year)  Greater exchange rate (so more rapid) shorter residence time  Homosphere: region where vertical motions are more important than gravitational settling and thus processes other than settling under gravity explain its variations present  Reflects the homogenizing role of wind and other motions  Heterosphere: above the Homosphere, where gasses separate according to molecular weight  Heavier gasses are more abundant in the lower heterosphere , whereas lighter gasses such as hydrogen and helium are more abundant with increasing altitude  Permanent gasses: found everywhere in nearly the same proportion  Variable Gases: those whose distribution in the atmosphere is uneven in both time and space  Are rare so average values are hardly affected  20% by volume, 20% of the molecules are that gas The Permanent Gases:  the most abundant, is Nitrogen(N ,) oxygen, (inert gases; argon, neon..), Helium, Krypton, 2 Xenon, Hydrogen  nitrogen is a largely unreactive gas  Oxygen: (02) so diatomic  Nitrogen and oxygen make up about 99% of the atmosphere with argon taking on remainder Variable Gases:  Is only a small percent of the mass of the atmosphere  Has relative scarcity, and some of the gasses affect the behaviour of the atmosphere  Water Vapor:  Most abundant of variable gases  Individual gas molecules (can change to liquid, or solid)  Exhibits large changes over very short distances, more so than other variable gases  It is a very affective absorber of energy emitted by Earth’s surface  Its ability to absorb Earth’s thermal energy makes water vapour one of the ”greenhouse gases”  About ¼ of 1% o f the total volume of the atmosphere  Most atmospheric water vapour is found in the lowest 5 km of the atmosphere  Is not uniformly distributed with altitude  Hydrologic cycle: water is constantly exchanged between the planet and the atmosphere  Because of how quick global evaporation, condensation, and precipitation are , water vapour has a vary short residence time of only 10 days  At higher altitudes, water vapour is even rarer  Carbon Dioxide  Increase in CO2in the atmosphere may have some important climatic consequences which affect our societies  0.039% of the atmosphere’s volume= 390ppm  Supplied in the atmosphere by plant and animal respiration, the decay of organic material, volcanic eruptions, and natural and anthropogenic (human produced) combustion  The rate of carbon dioxide input is higher than rate of output so leading to a global increase in concentration  Absorbs radiation emitted by Earth’s Surface  Amount of CO2 is grater in the early spring (summer) and lowest in the late summer  During springtime there’s a lot of CO2 because during the winter, plant growth is slow , so plants take less Co2 from the air  Also, leaf litter has been decomposing all winter, which means carbon in the litter has been oxidized to CO2 , and has entered the air  During summer regrowth, carbon is removed from the atmosphere and so carbon dioxide levels fall  Ozone  O 3 ,ll amount exists in the upper atmosphere  Major component of air pollution causing irritation to lungs and eyes and damage to vegetation  Is part of the upper atmosphere called the stratosphere because it absorbs lethal uv radiation from the Sun than the Earth’s surface  Methane  CH4, increased due to rice cultivation, biomass burning, and fossil fuel extraction (coal and petroleum mining) Greenhouse Gases - water vapour -carbon dioxide -Methane -Nitrous oxide -ozone -chlorofluorocarbon Aerosols: small solid particles and liquid droplets in the air (excluding cloud droplets and precipitation) Vertical Structure of the Atmosphere: (Thermodynamic State of the Atmosphere)  The air becomes less dense with increasing altitude  Up to 80 km the composition remains constant Density:  Amount of mass of the substance contained in a unit of volume  Because of compression, the atmosphere is more dense near the bottom then at the top  Air density decreases gradually with increasing altitude Pressure  Units in America is (millibar (mb), and in Canada the kilopascal (kPa)  At sea level it is 1013mb or 101.3 kPa  Pressure decreases with increasing altitude  Pressure must decrease vertically but the rate of decrease is not constant (would be a curve not linear)  Pressure falls rapidly near the surface and more slowly away from the surface Temperature  air whose temperature decreases rapidly with height rises steadily , while air whoe temperature either decreases slowly or increases with height resists such motion  standard atmosphere: shows four layers :  troposphere: lowest of the 4 layers, and where most weather events occur, where most of weather events occur and temperature decreases with height  8-20 km  thicker over tropics than over the polar regions,  thicker during the summer than during the winter  tropopause: level at which temperature ceases to decrease with height  inversion: situations where temperature increases with height  the troposphere and stratosphere contain all atmospheric mass  Stratosphere: is above the stratosphere, little weather occurs in this region  At lowest part of the stratosphere, the temperature remains constant but when it reaches higher to 50 km above sea level, the temperature increases with altitude, until it reaches a mean  20-50 km  Has a part which is straight vertically because temperature doesn’t change with higher altitudes  Has an ozone layer which is responsible for absorbing the solar energy that warms the stratosphere , and protects life on Earth from UV radiation  a zone of increased ozone concentration at altitudes between 20 and 40 km  Mesosphere :80 km above sea level  Temperature decreases with altitude  Temperature falls rapidly with increasing altitude  Thermosphere: density is really low in the upper reaches of the thermosphere  Cannot measure temperature up there so cannot use  Main source of atomic oxygen needed for ozone  Photodissociation: is important for heating the thermosphere and most significantly shielding the surface from lethal doses of UV radiation A Layer Based on Electrical Properties: The lonesphere  Ionosphere: an additional layer, outer functional layer , which can be defined based on its electrical properties  Goes from the upper mesosphere into the thermosphere contains ions  Ionsphere is responsible for northern and southern lights  Absorbs cosmic, gamma, and X-rays and shorter wavelength ultraviolet radiation  Changes atoms to positively charged ions Earth’s First Atmosphere  2 possible explanations to how lightest
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