Atmospheric Composition…

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  • Atmosphere
  • Atmospheric Basics

Atmospheric Composition…

  • Nitrogen – 78%
  • Oxygen – 21%
  • Argon - .93%
  • Carbon Dioxide - .03%
  • Water Vapor - .0 to 4%
  • Trace Gases

Key Atmospheric Components

  • Oxygen (O2)
    • Gas
    • Organisms need it to break down food for energy

Key Atmospheric Components

  • Carbon Dioxide (CO2)
    • Gas
    • Minor role in absorbing heat
    • plant fertilizer

Key Atmospheric Components

  • Ozone (O3)
    • Gas
    • Absorbs ultraviolet radiation from the sun

Key Atmospheric Components

  • Water Vapor(H2O)
    • Gas
    • Major role in absorbing heat
    • source of condensation for clouds

Key Atmospheric Components

  • Water
    • Liquid
    • source of rain
  • Singing in the Rain!

Key Atmospheric Components

  • Ice
    • Solid
    • Makes up snow, sleet, & hail
  • Legendary Vail Powder!

Key Atmospheric Components

  • Dust, Salt, Volcanic Ash
    • Solids
    • Provide solid surface for water vapor to condense (so that clouds can form)
    • Condensation nuclei
    • See next slide…
  • Salt Spray from Waves
  • Dust Storm

The Structure of the Atmosphere …


The Structure of the Atmosphere – The Troposphere

  • Description…
    • Tropo- (change)
    • 0-11 km
    • highest air pressure
    • Contains most gases of the atmosphere
  • Objects Found There
    • Weather
    • life forms
    • jets

The Structure of the Atmosphere – The Stratosphere

  • Description…
    • Strato- (layer)
    • 11-48 km
    • Molecular heat rises due to ozone layer absorbing UV radiation
  • Objects Found There
    • Ozone layer
    • Weather balloons

The Structure of the Atmosphere – The Mesosphere

  • Description…
    • Meso- (middle)
    • 48-95 km
    • Temperature falls b/c there’s not a whole lot here!
  • Objects Found There
    • Meteors (shooting stars) burn here

The Structure of the Atmosphere – The Thermosphere

  • Description…
    • Thermo- (heat)
    • 95-550 km
    • Molecular heat rises
  • Objects Found There
    • Ionosphere
    • Auroras

The Structure of the Atmosphere – The Exosphere

  • Description…
    • Exo- (outside)
    • Above 600 km
    • Outermost layer
    • Space!
  • Objects Found There
    • Some H and He
    • Satellites

Temperature Variations with Altitude

  • The layers are determined by temperature!

What Happens to the Sun’s Energy?

  • The State of the Atmosphere

The Temperature of the Atmosphere

  • The thermosphere is the hottest layer of the atmosphere but it feels so cold…
  • b/c even though molecules are moving very fast (which means they are very hot), they are so far apart that there is no heat transfer.
  • Astronaut Bruce McCandless II is feeling no heat!

The Temperature of the Atmosphere

  • Dew Point - temperature to which air must be cooled (at constant pressure) to reach saturation.
    • Dew point tells us how much water is in the air.
    • This is when dew is formed!
    • The higher the dew point, more humid and uncomfortable the air.

Vertical Temperature Changes

  • How is dew point determined?
    • … determine the temperature at which dew (condensation) forms by cooling the air.

Humidity Changes with Temperature…

  • What is humidity?
    • The amount of water air can hold at a given temperature. This is a constant!
  • What is relative humidity?
    • The amount of water the air is actually holding compared to how much it can hold
  • Relative humidity is determined by....using a wet/dry bulb thermometer & a relative humidity chart

Air Pressure and Density…

  • Density is mass (of air) per volume.
  • Air pressure is…
    • … force exerted by molecules of atmosphere as they are pulled toward Earth’s center by gravity.

Air Pressure and Density…

  • Air at the bottom of the atmosphere (troposphere) has higher density and pressure because...
    • … of the greater mass of the atmosphere above you (it contains the most gases)
    • … This is similar to being at the bottom of the ocean with tons of water above you!
    • … We are accustomed to the high air pressure so it doesn’t squash us.

Temperature-Density Relationship

  • Warm Air
    • a. As temperature increases… air becomes less dense.
    • b. Warm air is less dense and will rise.
    • c. The upward movement of warm air lowers pressure.
    • d. So, warm air rising causes low pressure.

Temperature-Density Relationship

  • Cold Air
    • As temperature decreases… air becomes more dense.
    • Cold air is more dense and will sink.
    • The downward movement of cold air raises pressure.
    • So, cold air sinking causes high pressure.

Creating Wind…

  • Cool air, which is denser, sinks.
  • This forces the warm air, which is less dense to move up.
  • Air moves from areas of high density to areas of low density.
  • In its simplest form, wind can be thought of as air moving from an area of high pressure to an area of low pressure.


  • The density imbalances that move air to produce wind are created by…
    • The unequal heating of Earth’s surface
  • Wind is measured by…
    • anemometers (mph or kph)
  • Wind speeds increase at high altitudes b/c…
  • Moisture in the Atmosphere

Three Ways Clouds Can Form…

  • a. from convection currents
  • b. from warm air rising over mountains (orographic lifting)
  • c. when air masses of different temperatures meet

Cloud Formation – Convection Currents


Cloud Formation – Orographic Lifting

  • Clouds form over a mountain.

Cloud Formation – Frontal


Cloud Types…Altitude

  • Cirro- high
    • Above 6000m
  • Alto - middle
    • Between 2000-6000m
  • Stratus - low
    • Below 2000m

More Clouds!

  • Meteorology
  • The Causes of Weather

Energy in the Atmosphere…

  • What two things are always in motion to distribute heat energy on and around the Earth?
    • ocean currents
    • global wind systems
  • What explains why the poles are never very warm?
    • The Sun’s rays don’t hit Earth as directly at the poles as at the tropics. (So the same amount of solar radiation is spread over a larger area.)

Air Masses…

  • Continental Tropical
    • Abbreviation - cT
    • Origin - land
    • Origin - tropical
    • Moisture Content - dry
    • Temperature - warm

Air Masses…

  • Maritime Tropical
    • Abbreviation - mT
    • Origin – ocean/water
    • Origin - tropical
    • Moisture Content - humid
    • Temperature - warm

Air Masses…

  • Continental Polar
    • Abbreviation - cP
    • Origin - land
    • Origin – high latitudes
    • Moisture Content - dry
    • Temperature – cool or cold

Air Masses…

  • Maritime Polar
    • Abbreviation - mP
    • Origin – ocean/water
    • Origin – high latitudes
    • Moisture Content - humid
    • Temperature – cool or cold

Air Masses…

  • Arctic (Continental)
    • Abbreviation - cA
    • Origin – land
    • Origin - Arctic
    • Moisture Content – dry
    • Temperature – very cold

Air Masses That Affect Our Weather…

Global Wind Systems


2. Chart:Global Wind Systems…

Global Wind Systems…

  • Prevailing Westerlies
    • Comes from the west
    • Located between 30 and 60 degrees latitude in both hemispheres
    • (30° - 60°)
    • This is the wind system that directs fronts across our country.

Global Wind Systems…

  • Trade Winds
    • Comes from the east
    • Located between the equator and 30 degrees latitude in both hemispheres
    • (0° - 30°)

The Intertropical Convergence Zone

  • What is the intertropical convergence zone (ITCZ)?
    • The area near the equator where the trade winds converge.
    • Air is forced up and creates an area of low pressure. (Remember – warm air rising!)
    • The ITCZ provides the moisture for many of the world’s tropical rain forests.
    • Picture on next slide…

The Doldrums…

  • What are the doldrums?
    • Another name for the ITCZ!
    • Sailing ships would often get stranded in this area because of the light (or no!) winds.
    • The phrase, “I’m stuck in the doldrums,” came from this phenomenon.
  • Looking for wind!

Horse Latitudes…

  • Why were the horse latitudes so named?
    • Around the 30 degrees latitude, sinking air creates a belt of high pressure which causes weak winds.
    • Sailors stranded here were said to throw their horses overboard when they couldn’t feed them!

Weather Systems in the USA

  • Which global wind system is responsible for much of the movement of weather across the USA and Canada?
    • The prevailing westerlies
  • The Causes of Weather

Pressure Systems – High Pressure

  • Cold air sinking
  • Fair weather
  • Rotates clockwise
  • Represented as a blue ‘H’
  • Good ‘H’air Day!

Pressure Systems – Low Pressure

  • Warm air rising
  • Clouds and precipitation
  • Rotates counter-clockwise
  • Represented as a red ‘L’
  • ‘L’ousy Weather Day!

Cold Front…

  • Definition – Cold, dense air displaces warm air and forces it up a steep front
  • Symbol – blue icicles!
  • Weather – clouds, showers, and thunder storms

Warm Front…

  • Definition – Advancing warm air displaces cold air and moves up slowly
  • Symbol – red lava rocks!
  • Weather – extensive cloudiness and precipitation

Stationary (Stalled) Front…

  • Definition – Two air masses meet and neither advances
  • Symbol – blue icicles alternate with red lava rocks
  • Weather – some clouds and precipitation

Occluded Front…

  • Definition – A cold air mass moves so rapidly that it overtakes a warm front and wedges the warm air up.
  • Symbol – purple alternating rocks/icicles
  • Weather – precipitation on both sides of the front
  • Gathering Weather Data


    • Measures temperature
    • Degrees Celsius or Fahrenheit
    • Thermometers contain liquids that expand when heated.


  • Measures air pressure
  • Millibars or inches of mercury
  • A barometer may contain mercury or a vacuum inside a metal chamber that contracts or expands with changes in air pressure.


    • Measures wind speed
    • … mph or km/h or knots
    • Has cupped arms that rotate as the wind blows.


    • Measures relative humidity
    • % age of water air is holding compared to how much it can hold.
    • Uses wet- and dry-bulb thermometers and determines how fast the water evaporates from the wet bulb.


    • Measures the height of cloud layers & estimates cloud cover
    • meters above ground level
    • Radar is beamed at the bottom of the clouds

Upper Level Data

  • To make accurate forecasts, meteorologist gather data up to 30,000 m.
  • A radiosonde is a balloon-borne package of weather sensors (upper level data)
    • Radiosondes take measurement on temperature, air pressure and humidity.
    • They can track how fast and in what direction it is moving to determine wind speed/direction.

Weather Radar and Satellites

  • Radar pinpoints where rain is falling at any given moment

The Doppler Effect…

  • … is the change in wave frequency of energy (sound or light) as it moves toward or away from an observer.
  • Meteorologists use Doppler Radar to plot the speed at which raindrops move toward or away from a radar station.
  • This allows them to detect severe weather events!

Weather Satellites…

  • a. Weather radar tracks rain.
  • b. Weather satellites track clouds.

Station Models…

  • What is a station model?
    • A record of weather data for a particular site at a particular time
  • What is the advantage of using a station model?
    • A large amount of data can be shown in a small space

Station Model Symbols…

  • Cloud/Sky Cover
  • Wind Speed

  • The Nature of Storms
  • Thunderstorms and Severe Weather

Average Number of Thunderstorm Days Annually… Florida is #1!!

Cause of Thunderstorms…

  • Warm air rises over a mountain
  • Temperature difference b/tw land & sea
  • Fronts

Types of Thunderstorms…

  • Air Mass - Mountain
    • Where… within one air mass over a mountain
    • Why… warm air rises over a mountain, forming storm clouds!
    • When… midafternoon

Types of Thunderstorms…

  • Air Mass - Sea-Breeze
    • Where… coastal areas, esp. tropics/subtropics
    • Why… temperature differences between land and sea create convection cells and updrafts
    • When… summer

Types of Thunderstorms…

  • Frontal - Cold
    • Where… at the leading edge of a cold front
    • Why… cold air pushes warm air rapidly up at the steep cold-front boundary
    • When… anytime a cold front moves in!

Types of Thunderstorms…

  • Frontal – Warm
    • Where… at the leading edge of a warm front
    • Why… warm air mass slides up over a cold air mass creating clouds
    • When… if a warm front moves in with enough moisture and instability


  • What is lightning?
    • A giant spark of static electricity
  • How does a lightning bolt form?
    • A ‘-’ channel of air from a cloud (stepped leader) connects with a ‘+’ channel on the ground (return stroke).


  • What causes thunder?
    • Super-heated air expanding and contracting
  • How hot is lightning?
    • 30,000 degrees Celsius

Lightning Damage…

  • The damage that lightning can do…
    • 7500 forest fires/year
    • 300 injuries/ 93 deaths/year
    • Property damage
  • Lightning-struck trees on the Blue Ridge Parkway

Lightning Safety…

  • “When lightning roars, go indoors!”

Tornadoes (Formation of…)

  • change in wind direction & speed creates horizontal rotation.
  • Strong updrafts tilt rotating air to vertical position.
  • Tornado forms within rotating winds.

Tornado Alley The Midwest!

  • A supercell is a giant, self-sustaining storm that can spawn tornados.
  • (A cP air mass from Canada meets a mT air mass from the Gulf of Mexico)
  • Tornado Alley is in the midwest.
  • Most tornadoes occur in May.

The Enhanced Fujita Scale…

  • This scale is used to classify a tornado AFTER the tornado has passed by looking at the damage and effects of the tornado.
  • EF0 to EF5

Tornado Safety…

  • Move to a pre-designated shelter – to a basement if possible.
  • Move to an interior room/hall, lowest floor, under sturdy furniture. (A bath tub is safest!)
  • Stay away from windows.
  • Get out of vehicles!
  • Don’t try to outrun a tornado.
  • If outside, lie flat in a ditch or depression.
  • Abandon a mobile home for a shelter.
  • Tropical Storms & Hurricanes

Tropical Cyclones…

  • A tropical cyclone can be described as a…
    • Large, rotating, low pressure storm
  • We call these storms…
    • hurricanes
  • Tropical cyclones derive energy from…
    • Warm, tropical oceans

Tropical Cyclones…

  • As a hurricane strengthens, what do the following components do?
    • Air pressure in eyewall– decreases
    • Surface wind speeds – increase

Tropical Cyclones…

  • Which direction do tropical cyclones turn in the northern hemisphere?
    • Counterclockwise
    • It is a low pressure system!
    • Remember the Coriolis effect?
  • Fran, 1996, Cape Fear, NC Name was retired!

Tropical Cyclones…

  • Tropical cyclones in the N. Hemisphere move steadily towards…
    • the west!
    • Which wind system moves across the USA and usually guides hurricanes out into the Atlantic Ocean?
    • the prevailing westerlies
  • Hurricane Rita – 2005, 3rd lowest pressure in Atlantic (897 mb), hit as cat. 3

Development of a Tropical Cyclone…

  • Tropical Disturbance – a weak, low-pressure system – group of thunderstorms collect

Development of a Tropical Cyclone…

  • Tropical Depression – a disturbance begins to rotate around the center of low pressure
  • Katrina as a tropical depression

Development of a Tropical Cyclone…

  • Tropical Storm – a depression is labeled a storm when the wind speeds reach 39 mph.
  • Tropical Storm Dalila, July 2007

Development of a Tropical Cyclone…

  • Tropical Hurricane – pressure drops and the wind speeds reach 74 mph
  • Ivan2006
  • Dean 2007
  • Katrina 2005

Classifying Hurricanes… The Saffir-Simpson Scale

  • 4 characteristics of a hurricane described…
    • Wind speed – how high?
    • Air pressure – how low?
    • Potential for damage – how much?!
    • Storm surge

Classifying Hurricanes…

  • The Saffir-Simpson Scale…
  • Categories 1 – 5
  • Category that does the most damage – 5
  • Wind speed of a cat 5? > 155 mph
  • Three most powerful storms to hit USA?
    • Florida Keys, 1935
    • Camille, 1969
    • Andrew, 1992

Classifying Hurricanes…

  • A hurricane runs out of energy
    • When it moves over land or cold water

Hurricane Hazards…

  • The strongest winds in a hurricane are in the…
    • eye wall

Hurricane Hazards…

  • What is a storm surge?
    • When hurricane force winds drive a mound of ocean water towards coastal areas

Storm Surge…

  • 9 of every 10 people who die in a hurricane are killed by the storm surge.
  • You should EVACUATE so you don’t get killed by the storm surge!

Hurricane Hazards…

  • What hurricane hazard is caused by great amounts of rain?
    • floods

Hurricane Hazards…

  • Which agency is responsible for tracking and forecasting hurricanes?
  • The National Hurricane Center in Miami, FL
  • (FIU Campus) (NOAA)

The World’s Best Hurricane Safety Tip…

  • Human Impact on Air Quality

Smog (Smokey Fog)…

  • Smog is a yellow-brown photochemical haze.
  • Smog is caused by solar radiation heating pollution (hydrocarbons & nitrogen oxides mostly from car exhaust).
  • Smog makes it difficult to breathe!
  • The major chemical in smog is ozone.
  • b/c Ozone irritates the eyes, nose, throat, & lungs.

Particulate Matter…

  • Four examples of particulate matter include…
    • ash, dust, pollen, & asbestos fibers.
    • These are forms of SOLID pollutants in the air.
  • Particulate matter is harmful to people because it can…
    • get in lung tissues & cause breathing difficulties & lung disease.
    • See next slide…

Review Only! The Greenhouse Effect

  • What is the greenhouse effect? It is heat from the sun being trapped by the gases in our atmosphere.
    • A greenhouse effect you may relate to is that of a closed car on a cold, sunny day in winter.
    • The greenhouse effect is a GOOD thing! It allows for life on our planet!

Global Warming…

  • Global warming is…
    • … an increase in Earth’s average surface temperature.
  • Some scientists believe that the cause of global warming is...
    • the burning of fossil fuels
    • Write examples in margin…
    • which releases carbon dioxide (CO2)
    • CO2 makes up only .04% of the atmosphere! (4 out of 10,000 molecules)
    • Coal for electricity
    • Gasoline for vehicles
    • Natural Gas for fireplaces and cooking

Fossil Fuel Use

  • Fossil Fuels Used…
    • Coal for electricity
    • Gasoline for vehicles
    • Natural Gas for fireplaces and cooking
  • There are many scientists who believe the Sun has the major role in global warming/cooling.
  • To reduce levels of CO2 in the atmosphere people can …
  • … reduce our use of fossil fuels! (And stop breathing!) How?

The Ozone Issue

  • Review! The ozone layer is found in the stratosphere.
  • Ozone absorbs ultraviolet radiation from the sun.

Add to Margin of Notes: 3 Effects of Ultraviolet Radiation…

      • Ultraviolet radiation from the sun can cause cataracts (a clouding of the lens of the eye) and skin cancer.
      • Ultraviolet radiation can kill the eggs of certain animals like amphibians because they lay their eggs in shallow water.

The Ozone Issue

  • Man-made chemicals called (CFCs) chlorofluorocarbons react with ozone and break it apart.
  • (The part of the CFC molecule that reacts with the ozone molecule is the chlorine atom.)

The Ozone Issue

  • CFCs are used as refrigerants, coolants, propellants in aerosol cans, and Styrofoam.

The Ozone Issue

  • We should eliminate sources of CFCs worldwide. (CFCs were banned in the late 1980’s in industrialized nations. They are still in use in some places in the world.)
  • “Under the 1987 Montreal Protocol, developing countries committed themselves to halving consumption and production of the CFCs by 2005 and to achieving an 85 percent cut by 2007.”

Acid Precipitation (Rain)…

  • 1. Acid precipitation (rain) is precipitation with a pH of less than 5.
  • The pH of natural precipitation is 5.0 to 5.6.
  • 2. Acid precipitation forms when sulfur dioxide (SO2) & nitrogen oxides (NO2) combine w/ atmospheric water to create sulfuric acid & nitric acid.
  • 3. Six types of acid precipitation are acidic rain, snow, fog, mist, gas, and dust.
  • Nitrous oxide and sulfur dioxide come from
  • volcanoes, marshes, and human activities

Coal-burning Power Plant – Jacksonville, FL

  • 5. The source of acid precipitation that receives the most attention is caused by coal-burning power plants in the midwestern USA.

Acid Rain…

  • 6. Three effects of acid precipitation are the damage it causes to…
    • … aquatic ecosystems
    • … plants & soil.
    • … stone buildings & statues.
  • Easy on the acid rain, guys!

Acid Rain…

Station Model…


Jet Streams…

  • Definition of Jet Stream…
    • Narrow bands of fast, high altitude westerly winds (which resemble jets of water)
    • Jet streams follow the boundaries between hot and cold air and are strongest in the winter.

A Jet Stream As It Appears on a Weather Map…

Jet Streams…

  • Location by Wind Systems…
    • A. Polar jet stream (separates polar easterlies from prevailing westerlies)
    • B. Subtropical jet stream (where the trade winds meet the prevailing westerlies)

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