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Unit 1. Introduction to Atmospheric Science. 1.1 Composition. Our atmosphere Mix of gases surrounding entire planet Held in place by gravity Filters out energy and materials from space Regulates temperature, allows for water in all 3 states Composition Nitrogen – 78% Oxygen – 21% - PowerPoint PPT Presentation
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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