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