Chapter 3
saturation mixing ratio
the maximum water vapor the air can hold at a given temperature before the water vapor condenses on the surfaces of aerosol particles as a liquid
water vapor
the most important spatially and temporally varying gas in the air; not considered a health-affecting air pollutant
nocturnal boundary layer
the portion of the daytime mixed layer that loses its buoyancy at night
convective mixed layer
the region of air just above the surface layer
greenhouse gas
water vapor is a natural greenhouse gas that readily absorbs thermal-IR radiation, but it also plays a vital role in the hydyrologic cycle on Earth; AS A GREENHOUSE GAS IT IS MUCH MORE IMPORTANT THAN CARBON DIOXIDE FOR MAINTAINING A CLIMATE SUITABLE FOR LIFE ON EARTH
temperature
at a given location and time is affected by energy transfer processes, including conduction, convection, advection, and radiation
mercury barometer; aneroid barometer (more advanced)
a barometer is a device for measuring atmospheric pressure
temperature
a measure of average kinetic energy of an air molecule (energy giving rise to the motion of air molecules)
partial pressure
a mixture is the pressure the gas exerts if it alone occupies the same volume as the mixture
free convection (thermal turbulence)
a predominantly vertical motion produced by buoyancy, which occurs when the sun heats different areas of the ground differently (clouds and hills)
well-mixed gases
gases can become well mixed in the bottom 100 km of the atmosphere only if they are (1) are long lived (have low chemical, physical and biological loss rates) and (2) are emitted uniformly over time. CO2 not well mixed
Standard sea level pressure
1,013 hPa
Avogadro's number
6.02252 x10 to the 23 molec mol; equal volumes of all gases at the same temp and pressure contained the same number of molecules
carbon dioxide domes
CO2 is not well mixed because its emission rate changes over short time scales due to human activity and because human emissions are concentrated in urban areas, giving rise to higher mixing ratios in urban areas than in surrounding rural areas
CO2
almost responsible for half of the higher global temperatures due to global warming; does not directly affect health, its anthropogenic emissions over cities produces domes that increase local temperatures and water vapor, both of which increase the concentrations of other pollutants that damage health; MIXING RATIOS HAVE INCREASED OVER TIME
forced convection
an upward or downward vertical movement of air caused by mechanical means.
Boyle's law
compressibility of gas
surface layer
comprises the bottom 10 percent of the boundary layer, is a region of strong change of wind speed with height
Pascal
confirmed Torricelli's theory
CO
criteria air pollutants; one of six
volume mixing ratio
defined as the number of gas molecules per molecule of dry air
equation of state
describes the relationship among pressure, volume and absolute temperature for a real gas
ideal gas law
describes the relationship for an ideal gas. an ideal gas is a gas for which the product of the pressure and volume is proportional to the absolute tmperature
thermal conductivity
determines the rate of a material's conduction; quantifies the rate of flow of thermal energy through a material in the presence of a temperature gradient
boundary layer
extends from the topographical surface up to between 500 and 3,000 m above the surface; all people live in the boundary layer; where air pollution is the biggest concern
air pressure decreases with increasing altitude
fact
vaiable gases
gases whose volume mixing ratios change in time and space; many organic gases degrade chemically before they reach the stratosphere, so their mixing ratios are low in the stratosphere
entrainment zone
inversion layer
stratosphere
large temperature inversion. The inversion is caused by ozone, which absorbs much of the sun's near-UV radiation and reemits thermal-IR radiation, heating the stratosphere.
volume mixing ratios
may be multiplied by 100 and expressed as a percentage of dry air volume, multiplied by 10 to the 6 and expressed in parts per million volume, multiplied by 10 to the 9 and expressed in parts per billion volume or multiplied by 10 to the 12 and expressed in parts per trillion volume
eddies
mix air vertically and horizontally
Pressure and density are controlled by by the concentrations of gases in the air
oxygen and nitrogen are responsible for much of the current pressure and density structure of the Earth's atmosphere
Torricelli
recorded a sustained vaccum
Charles's law
states that at constant pressure, the volume of a gas must decrease when its temperature decreases
zonally averaged
temperature is found by averaging temperatures over all longitudes at a given latitude and altitude
mesophere
temperatures decrease with increasing altitude; for the same reason they decrease in the background troposphere (the ground surface receives solar energy from the sun daily, heating the ground. The ground converts that solar energy to thermal infrared (heat) radiation, which is emitted back to the atmosphere))
thermosphere
temperatures increase with increasing altitude because O2 and N2 absorb very short, far-UV wavelengths in this region; but air in the thermosphere would not feel hot to the skin because the thermosphere contains so few gas molecules
homosphere
the bottom 100 km of the Earth's atmosphere; a region in which major gases are well mixed; divided to four layers, in which temperatures change with altitude; troposphere, stratosphere, mesosphere and thermosphere
chemical weathering
the breakdown and reformation of rocks and minerals at the atomic and molecular level by chemical reaction
turbulence
the effect of groups of eddies of different size
air pressure
the force of air exerted per unit area of underlying surface; calculated as the summed weight of all gas molecules between a horizontal plane and the top of the atmosphere, divided by the area of the plane (The more molecules present above a plane, the greater the air pressure)
advection
the horizontal movement of energy, gases and particles by the wind; like convection, advection results in the mass movement of molecules
sources and sinks
the main source is evaporation from the ocean, accounts for 85 percent of water vapor
air density
the mass of air per unit volume of air; decreases exponentially with increasing altitude
radiation
the transfer of energy by electromagnetic waves or photons, which do not require a medium, such as air, for their transmission (even without atmosphere)
conduction
the transfer of energy in a medium (the conductor) from one molecule to the next in the presence of a temperature gradient; experiences no molecular movement; occurs through soil, air and particles; affects air temperature by transferring energy between the soil surface and the bottom molecular layers of the air
convection
the transfer of energy, gases and particles by the mass movement of air, predominantly in the vertical direction; it differs from conduction in that during conduction, energy is transferred from one molecule to another, whereas during convection, energy is transferred as the molecules themselves move.
tropopause
the upper boundary of the troposphere
Gabriel Daniel Fahrenheit; Anders Celsius
thermometer scales
temperature inversion
top of the mixed layer is often bounded by this; an increase in temperature with increasing height.
John Dalton
total atmospheric pressure equals the sum of the partial pressures of the individual gases in the air
spatially and temporally varying gases
whose mixing ratios are small but vary in time and space, that are the most relevant to air pollution