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ENV100Y5 (125)
Chapter 14

Chapter 14.docx

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University of Toronto Mississauga
Monika Havelka

Chapter 14: Atmosphere Science and Air Pollution • Atmosphere – thin layer of gas that surrounds the earth. o Consists of: nitrogen, gas, oxygen gas o Consists of both permanent (stable concentreation) and variable gases (change it from time to time) o Retained by gravity o most variable = water vapour! o 2nd most-variable = aerosols from a variety of sources! o affected by human activity • Ozone layer – 17-50km above sea level, reduces the amount of UV reaching the earth’s surface. • Atmosphere is layered: o Troposhere:  Bottommost layer  Blankets the earth’s surface and provides us with the air we need to live  Tropopasuse: acts like a cap, limiting mixing between the trosphere and atmosphereic later above it  80% of mass; 99% of water vapour & aerosols!  “tropos” = change → where weather occurs (well mixed!) o Stratosphere:  11-50km above sea level  more dry and dense than the troposphere temperature increases upward due to absorption of solar energy by ozone layer (17-30 km)!  O3 blocks UV radiation o Mesosphere:  above the stratosphere  air pressure is really low and temperature decreases  50km to80km above sea level o Thermosphere :  Top layer  altitude to 500 km!  warmed from above by solar radiation Earth’s atmosphere • Absorbs radiation and moderates climate! • Transports/recycles water, heat, pollutants, nutrients! • Vertical differences in temperature, density, and composition! • Human activity is changing the composition of the atmosphere • Layered: - thickest at equator; thin at poles Atmospheric properties include pressure, temperature, and humidity: • Atmospheric pressure: force per unit of area produced by a column of air o Decreases with altitude because higher the altitudes fewer molecules are pulled down by gravity • Property of air: relative humidity – ratio of water vapour is given colume of air contains to the maximum amount it could contain at a given temperature • Within troposphere, all three decline with increasing altitude • as altitude increases, there are fewer air molecules! • results in decreasing pressure, temperature, & humidity • 2 reasons for loss of temperature with altitude: o lower atmosphere is warmed by conductance from the Earth o as a parcel of air moves up it expands (lower pressure) and loses energy • humidity: o amount of vapour air can hold depends on temp! o saturated cold air has much less water than saturated warm air Solar energy heats the atmosphere: • heats and moves the air! • causes evaporation! • creates seasons! • influences weather and climate! • drives photosynthesis Unequal distribution of solar energy- fig.14.4 pg 410 Solar energy creates seasons – fig.14.5 Effect of axial tilt: changes in day length and altitude of the Sun at noon Air masses interact to produce weather: • Air mass = a large volume of air that is relatively homogeneous in temperature and humidity! • Front = boundary between air masses that differ in temperature, moisture, and density • front is named for the the of air mass that is arriving! • Warm front: warm, moist air moves in to replace colder, dry air that is moving away! • Cold front: where cold, dry air is pushing into warmer, moister What causes wind to blow: • Convection (hot air rises, cool air sinks)! • Pressure gradient force (variations in atmospheric pressure) • Coriolis force (influences the direction of movement of air) Rest look at slides! Indoor air pollution • Indoor air pollution contains higher concentrations of pollutants than outdoor air • Average person in North America indoors 90% of the time • This is problematic due to the attitude change in the 1970s •
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