Unit 1Introduction to Atmospheric Science

1.1 CompositionOur atmosphere

Mix of gases surrounding entire planetHeld in place by gravityFilters out energy and materials from spaceRegulates temperature, allows for water in all 3

states

CompositionNitrogen – 78%Oxygen – 21%Argon – .9%All other gases and particulants – .1%

1.1 Composition

1.1 CompositionNitrogen and oxygen

Percentages are consistent to elevation of 50 miles (80 km)

Balance of destruction and production Nitrogen removed mostly by soil bacteria, plankton Returned by decay of plant and animal materials Oxygen removed through chemical reaction (oxidation),

organic decay, respiration Returned through photosynthesis

1.1 CompositionWater vapor

Invisible gas made of water moleculesSubstance follows the water cycleVaries greatly by locationTropical air may be up to 4% water, arctic air

may barely have anyActs as a “greenhouse” gas, trapping Earth’s

radiant energyLatent heat

Energy stored in water molecules, gained through evaporation

Released when water condenses to liquid

1.1 CompositionCarbon dioxide

Occupies .038%, but varies by locationEnters air through decay, volcanism, exhalation

of animals, burning of fossil fuelsRemoved through photosynthesis, dissolving into

oceans, absorption by phytoplankton Oceans may hold over 50X more CO2 than air

Past CO2 concentrations measured through Arctic and Antarctic ice cores

Evidence shows concentrations have increased 37% since the early 1800s.

Important greenhouse gas, contributes to climate change.

Stepped Art

Fig. 1-4, p. 7

1.1 CompositionOzone (O3)

Most forms naturally in stratosphereProvides protection from UV raysCan be formed at surface

Chemical reactions between pollutants and sunlight create ozone

Called photochemical smogIrritates eyes, lungs, damages plantsCommon near large cities

1.1 The Early AtmosphereThe Earth’s first atmosphere was composed mostly

of hydrogen and heliumEvolved due to outgassing of CO2, NH3, and H2O

from the cooling center of the Earth Caused heavy rain that would form an early ocean

Lakes and oceans acted as a sink, absorbing CO2 from atmosphere

Reactions with oxygen broke down ammonia, plus volcanic eruptions produced most N2

O2 was created almost completely through photosynthesis, first by cyanobacteria

Later, aquatic plants and algae, then terrestrial plants added O2 to today’s levels

1.2 Vertical Structure of the AtmosphereAir Pressure and Air Density

Weight = mass x gravityDensity = mass/volumePressure = force/areaAt the Earth’s surface the pressure of the

atmosphere is 14.7 lbs/in2 . Standard sea level pressure is 1013.25

millibars (mb) = 101,325 Pascals (Pa) = 29.92 in Hg

Atmospheric pressure decreases with height.

1.2 Vertical Structure of the AtmosphereLayers of the Atmosphere

Lapse rateChange in temperature with a change in

heightTypically inverse relationship, decrease in

temp with increase in heightIsothermal environment

No change in temperature with heightInversion layer

Reversal of standard lapse rateTemps increase with height

1.2 Vertical Structure of the AtmosphereLayers of the Atmosphere

TroposphereDecrease in temperature with heightDaily weather occurs here.Extends up about 12 miles

StratosphereOzone layer located here.Increase in temperature caused by

absorption of UV by O3 12 miles up to 50 miles

1.2 Vertical Structure of the Atmosphere

MesosphereDecrease in temperatureMost meteors burn up here50 to 85 miles

ThermosphereIncrease in temperatureSuns strongest radiation impact.Dramatic temperature swings day to night85 miles, up to the point where no gas

exists

Stepped Art

Fig. 1-11, p. 13

1.2 Vertical Structure of the AtmosphereIonosphere

Not a true layer but an electrified region Created when solar energy rips

electrons from gas atomsCreates ionized layers

Exists at the top of the atmosphere in the thermosphere

F,E,D layerSun light creates layers, D disappears at

night and less interference with AM radio transmissions.

1.3 Weather & ClimateWeather

Short term air temperature, air pressure, humidity, clouds, precipitation, visibility, and wind

ClimateLong term patterns and average

weather; not just magnitude but also frequency

1.3 Weather & ClimateMeteorology

Study of the atmosphere and its phenomena

Aristotle 340 B.C. Meterologica, meteoros: high in air

1843 telegraph1920s air masses1940s upper air1950s radar and computers1960s satellite

1.3 Weather & ClimateSatellite’s View

Geostationary satelliteMeridians measure longitude (W-E)Parallels measure latitude (N-S)Weather maps: pressure cells, fronts,

surface stations

1.3 Weather & ClimateWeather and Climate in Our Lives

Two general reasons for studying how weather and climate impacts our lives: economic efficiency and public safety.

ClothingCropsUtilitiesExtreme cold and heatTornados and hurricanes

1.3 Weather & ClimateMeteorologist

Any person with a college degree in meteorology or atmospheric science; not just the TV weather person

Half of 9000 meteorologists employed by the US National Weather Service

Researchers and operational meteorologists