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
• Atmosphere is layered:
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!)
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
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
• 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
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
• 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