critical

Introduction to the Atmosphere

Chapter 3 McKnight’s Text

Jason Scott

Size of Earth’s Atmosphere • Atmosphere completely

surrounds Earth’s landscape

• Held in place by gravity

• Density decreases with altitude, denser closer to surface

• Formed shortly after earth’s formation 4.6 billion years ago

• Transformed through phases; early stages of hydrogen & helium, to oxygen & nitrogen mostly now

Permanent Gases in Atmosphere

• Nitrogen (78%) & Oxygen

(21%) – two most abundant

gases

• Nitrogen added into

atmosphere by decay &

burning of organic matter

• Volcanic eruptions

• Chemical breakdown

rocks

• 1% remaining atmospheric

gas made up on inert gas

argon

Variable Gases • Water Vapor – water in

form of gas, invisible

• Carbon Dioxide –

abundant greenhouse gas,

absorbs thermal infrared

radiation & warms lower

atmosphere

• Ozone – molecule made

up of three oxygen atoms

(03), concentrated within

ozone layer

• 9-30 miles upward

Thermal Layers • Troposphere – lowest

layer of atmosphere,

closest to earth surface

• Stratosphere – Turbulent

& stagnant

• Mesosphere – beginning

50 miles above sea level

• Thermosphere – over 80

miles above sea level

• Exosphere – 210 miles

above, outermost layer

before space

Atmospheric Pressure • Atmospheric pressure equivalent

to weight of air, pushing downward towards surface

• Denser at sea levels

• Lesser away from sea level upward

• Altitude 3.5 miles upward from sea-level, decreases by 50%

• Less oxygen, difficult for humans to breath at elevation

• Think of climbers, Mt. Everest (29,000ft in the Nepalese Himalayas)

Human Induced Atmospheric Change • Rapidly increased effect since the

Industrial Revolution 1750s

• Further ramped up within the last century

• Anthropogenic (human-produced)

• Used evidence from weather balloons

• Satellite data & observation of altered ecosystem behavior

• Depletion of the Ozone Layer – 90% of ozone molecules (three O3) found in stratosphere

• Harmful UV radiation is absorbed from the Sun

Ozone Layer Depletion • “Hole” in the Ozone Layer

• First observed thinning 1970s

• Excess chlorofluorocarbons (CFCs) released into atmosphere

• Coolants, aerosol sprays, foams & various plastics

• Odorless, flameless

• Antarctic Polar Atmosphere – ozone depletion severe due to extreme cooling & whirling wind pattern causing a vortex from lower latitude air

Air Pollution • Highest concentration in cities

• Chemicals from industrial runoff,

cars, air conditioners, etc.

• Carbon Monoxide – a primary

pollutant released by carbon-based

fuels, especially by cars

• Odorless, colorless, hazard that

decreases oxygen to the human

brain

• Nitrogen Oxide – gas formed in water

& soil through biological processes

• Yellow, reddish-brown color

Air Pollution Cont. • Sulfur Compounds –

natural origin, released from volcanoes or hydrothermal vents (hot springs, Yellowstone, etc.)

• Hydrogen sulfide (rotten egg smell)

• Sulfur dioxide, lung irritant & corrosive

• Photochemical smog – secondary pollutants

• Chemical reactions from strong sunlight & UV radiation

Weather & Climate • Weather

Atmosphere energized by solar radiation

Weather refers to short-term atmospheric conditions at a given time, over a specific area

• Climate

Different because weather is subject to constant change

Weather conditions over a long period of time

Gaged over extended periods of time (three decades)

Coriolis Effect

• A result of earth’s rotation, all

things drifts sideways

• A deflection of free-moving

objects

• Move to the right in Northern

Hemisphere & to the left in the

Southern Hemisphere

• Deflection & drift is strongest at

the poles, lessens towards the

equator

• Sink & toilet water drain

clockwise in North Hem. &

Counterclockwise in South Hem.