Properties of the Atmosphere

Ø Temperature

̶        A measure of the average speed that molecules move in a substance (solid, liquid, gas)

̶        The average speed of the molecules will increase in the colder substances and decrease in the warmer substances.

̶        Temperature is related to the energy of motion of molecules

̶        Usually decreases rapidly upward away from the earth’s surface (about 12 km/7 miles)

̶        Above about 12 km the temp increases with height, then begin to decrease again about 50 km/31 miles

̶        Troposphere = layer of air in the lower atmosphere where temp decreases with height

̶        Stratosphere = layer above the troposphere where temp increase with height because of the absorption of the ultraviolet radiation by ozone in that layer

̶        Tropopause = boundary between troposphere and stratosphere

̶        Tropical storms grow to greater heights than storms that form in the middle of latitude and Polar Regions because the tropopause is higher in the tropics

Ø Pressure

̶        Force applied by air on a unit area of surface.

̶        Equivalent to the weight of a column of the air above a unit area

̶        Millibar (mb) = 1,000dynes/centimeter^2 or to a hectopascal (100 pascals)

̶        Average pressure at sea level is 1013.25 mb - pressure decreases rapidly while moving away from the earth’s atmosphere

̶        Measured with a Barometer–simplest to use is the mercury barometer

̶        Measurements are made worldwide every hour

Ø Moisture / Moisture Variables

̶        Clouds from water vapor (invisible gas composed of individual water molecules)

̶        Water vapor is mixed with other gases in the atmosphere (such as, nitrogen & oxygen)

̶        Vapor Pressure =  force per unit area applied by only the water vapor molecules (ranges from 0 in a cold atmosphere to 60mb in a humid tropical atmosphere)

̶        Atmosphere reaches saturation when the invisible vapor condenses into visible cloud droplets

̶        Saturation Vapor Pressure = vapor pressure at which the atmosphere becomes saturated

̶        The atmosphere's capacity for water vapor (and saturation vapor pressure) depends on temperature

Ø Phase Changes and Clouds

̶        Air contains water vapor and clouds in the air are composed of liquid and ice particles

·        Vapor to water = condensation

·        Water to ice = freezing

·        Vapor to ice = deposition

·        Ice to vapor = Sublimation

·        Water to vapor = evaporation

·        Solid to liquid = melting

·        Latent heat = hidden heat required for a phase change

Ø Wind

̶        The movement of air (direction and speed)

̶        Anemometer = device to measure wind speed

̶        Meteorologists depict wind speed and direction using wind barbs on a staff

Continually orbit around the earth in the general circulation, the large-scale pattern of prevailing winds and pressur