Including...
Solar Energy and the Atmosphere
It's the water! a general review
Vaporization and Condensation: a Change of Phase
The Global Transfer of Thermal Energy
Energy Transfer in the Atmosphere : a separate summary
What is an atmosphere?
Ask for student input
Describe in general terms
Click here for information on the gasses of the atmosphere
What is the atmosphere?
Matter
Has mass, gravitational attraction, etc.
Source? Volcanic and/or cosmic
Current composition - see fig. 9-1, page 228; w/overhead
Gasses, solids, and liquids
Stratification of the atmosphere - See fig. 9-3, page 230; w/overhead
Primarily based on composition, density, and temperature differences
See fig. 9-5, page 232
Has evolved through time
Carbon dioxide out, nitrogen & oxygen in
Start with water pressure
Rock cod - a final trip to the surface
The Bends ("Without Remorse" by Tom Clancy pg. 333)
Submarines ("The Abyss" or "Crimson Tide")
Ammonites - nature's original submarine
Air has mass, gravity, weight
"Air pressure" is the weight of the matter at the surface
Decreases upward as atmosphere thins
14.7 lbs/in2 at the surface
Called "1 bar"
DEMO: meter stick and paper
All energy comes from the sun
But what type of energy is it?
Where are the ski resorts?
If heat comes directly from the sun, they should be in the valleys
Solar energy reflected or absorbed - see fig. 9-9, page 239
Reflected: lost to space
Albedo: increased by reflective materials (snow, ice, clouds)
Absorbed: added to earth's energy budget
Energy can be transmitted in 3 ways - see fig. 9-11, page 241
Radiation - direct electromagnetic waves from the source
The sun, heat register in a room, etc.
Conduction - direct contact with a heat source
Electric stove, hot sand
Convection - transfer of heat energy due to density differences
Causes currents from areas of high density to low density
Differential heating of surface by the sun (radiation)
Equator vs. polar regions: these are the extremes
Langley: basic unit of solar energy
Differential heating results in high vs. low pressure areas
High pressure
Cold air, molecules closer together, increased density
Low pressure
Warm air, molecules farther apart, decreased density
DEMO: metal can with small amount of water
Heat, drive out air, seal, cool, can will collapse
What happened?
Global wind patterns
Air currents always move from high to low pressure
In a perfect world...
All winds would blow from south to north, or the reverse
Due to convection - describe energy and flow patterns
Heating at equator
Air becomes less dense and rises
Sets up convection cells
But it's not a perfect world
Spinning on its axis
Causes the Coriolis Effect - Describe
Changes wind patterns
Refer to "Planet Earth: Atmosphere" Time/Life page 84/85 with overhead
What is water H2O
A "di-polar" molecule - explain
Universal solvent - HOH
Neutrality between acids and bases
Origin of water
Volcanic vs. cosmic sources
Water runs downhill due to gravity
Fills up the low elevations - ocean basins, lakes, stream channels, etc.
Hydro cycle
Recycles water between different temporary reservoirs
Oceans 1,300,000,000 km3 97.2% Ice 29,300,000 km3 2.15% Groundwater 8,400,000 km3 0.625% Lakes 230,000 km3 0.017% Atmosphere 13,000 km3 0.001% Streams 1,250 km3 0.0001%The ocean is clearly the largest of these temporary holding facilities
Holds a huge volume of water
We're going to concentrate on the 13,000 km3 held in the atmosphere
Moisture is the most variable constituent of the atmosphere
Varies from 0% to 4%
May not seem like much, but...
Leads to fundamental and profound differences in global climate and surface conditions
Click here for a general overview of Water in the Atmosphere and the Transfer of Thermal Energy
Very important aspects of the hydrologic cycle
Cleans and purifies the water
Transfers energy from the equator to the mid latitudes
Water in the ocean is held as a liquid
Somehow we have to get the liquid to change to a vapor
So it can enter the atmosphere as part of the hydro cycle
Water in the atmosphere is held as vapor - a gas
Somehow we have to get the vapor to change to a liquid
So it can fall as rain or snow
Talking change of phase here
Review the 3 states of matter - ice to water to steam
Heat energy is the driving force in all phase changes
Hot stuff is more 'excited' than cold stuff
Molecules move faster, therefore must require more energy
Reasonable to assume that any phase change results in the transfer of energy
Add energy to make vapor
Give up energy to condense back into a liquid
In the case of water, the change of phase requires 80 cal/cm3
This energy transfer works in both directions
Water to vapor - steals energy from environment and stores it in the vapor
Vapor to water - releases the stored energy back into the environment
Remember our global wind patterns?
The movement of large masses of air also results in the movement of large amounts of energy locked up in the vapor
More on this later when we discuss orographic lifting
Anyway, what causes the water to change phase so easily?
Let's make some moonshine
Anyone know how a still works?
Describe the process
Another important consideration
Warm air can hold more vapor than cold air
"Steamy Windows" by Tina Turner
Any ideas why this is true?
Probably related to the heat energy stored in the vapor
Greater thermal gradient when the air mass is cooler
Forces the vapor to give up the energy - causing condensation
Putting it all together...
Dew point - temperature where vapor condenses into liquid
Results in the formation of clouds
You can often "see" the dew point on a cloudy day
Look for groups of flat-bottomed clouds
The evaporation of water requires the addition of 80 calories of thermal energy per cubic centimeter.
This heat energy is robbed from the local environment
Is stored in the vapor
The energy remains locked up in the vapor until conditions change
The vapor condenses into the liquid phase
Releases the energy back into the environment
This addition and loss of energy directly affects our lives
Perspiration
When our bodies sweat, the water evaporates from our skin
Obtains the heat energy necessary for the phase change from the skin
Cools our bodies
In comparison, dogs have no sweat glands, so they have no cooling mechanism.
That's why they pant so much
All cooling comes from evaporation of water from their tongues.
Imagine no pores - we'd all pant like dogs
Wind chill factor
There is no actual drop in temperature - it only feels colder
Perception vs. reality
Global energy transfer and temperature moderation
Far more solar energy is received on earth at the equator than at the poles
Excess heat energy is used at the equator to evaporate seawater
Which is then transferred north and south to mid-latitudes
Cools, condenses, rains, and gives up the heat to areas which need it
This tends to moderate surface temperatures on earth
If you don't think this is important, try living on Mercury
Temperatures can vary up to 600 deg. C. from sunlight to shadow
And day to night
Review of the interaction between energy and air pressure
The earth is not uniformly heated
Areas of higher and lower temperature
Air masses take on the characteristics of the land they are in contact with
Cold, dry land = cold, dry air (high pressure)
Warm, moist land = warm, moist air (low pressure)
Hot air rises
Cools as it goes up
Condenses when it cools to the dew point
Causes formation of clouds
May lead to precipitation
Clearly, the equator has the most solar energy
And, thanks to current plate locations, very little land (mostly ocean)
Lots of langleys and lots of water
Rising, vapor-rich air masses
Cools and condenses
What land is at the equator gets pretty wet!
Show film "Clouds and Precipitation"
FK2345 (15 min) (grades 7-12)
With Video Study Guide
This will be on the test, so pay attention!
What causes air to rise?
Several processes are related to this
Orographic lifting - my personal favorite
Remember the energy stored in the vapor when it entered the atmosphere?
Let's do something with it
And at the same time answer the question:
"Why are arid lands common on the leeward side of mountain ranges?"
So common they even have a name: Rain shadow deserts
The basic process: (Draw profile on board)
Warm, moist air from the sea moves inland
Deflected upwards due to mountains, etc.
Air rises, expands, and cools
Cools at 5.5 deg. / 1000 feet (dry adiabatic rate)
Eventually reaches the dew point
Condensation begins
Releases energy at a rate of 80 cal/cm3 during condensation
This heat is liberated into the atmosphere
Offsets the cooling of the air as it rises
Wet adiabatic rate (3.5 deg. / 1000 feet)
Air mass continues to rise, cool, and precipitate to top of mountain
Descends other side
Warms back up AT THE DRY RATE
Results in warm, dry air on the lee slopes of mountains
This warm dry air is hungry for water - and is capable of holding quite a bit
Evaporates all it can find - adds to desert situation
Therefore, the simple loss of water vapor from the atmosphere results in an energy transfer to the atmosphere
Which results in heating of the air mass
Another process which causes air to rise (and cool to the dew point)
Review the interaction between energy and air pressure
The earth is not uniformly heated
Areas of higher and lower temperature
Air masses take on the characteristics of the land they are in contact with
Cold, dry land = cold, dry air (high pressure)
Warm, moist land = warm, moist air (low pressure)
Results in large areas of atmosphere with differing pressure and energy
There are 6 major air masses which affect the U.S. (refer to overhead)
Contacts between air masses are called fronts
Most "climate" occurs at fronts
Cold front vs. Warm front (see overhead)
Both result from the meeting of a cold air mass and a warm air mass
Both result in the warm air rising over top of the cold air
Main difference:
Cold front: the cold air is moving and "invades" the warm air
Forcing it up and over the cold air
Warm front: the warm air is moving and slide up and over the cold air
Both form low pressure areas due to rising air
Which may lead to condensation and precipitation
Results in some great frontal battles in the mid-west!
More on this later when we discuss thunderstorms and tornados
Been here over 20 years
Always worked hard and hoped for great time off
Noticed 2 things early on
Summer work - hot as blazes for 2 weeks (also very dry)
Then cool down 'til the next heat wave
Maybe even a bit of rain
DIGRESS TO: redwood roof of Selma house
Winter's off - lots of time but also lots of fog
Lived in Grants Pass
Either raining, or cold & foggy
Cold/foggy come in 2 week stretches
This 2 week pattern seems to hold - watch for it
Both summer (hot & dry) & winter (cold & foggy)
Associated with high pressure systems in both cases
Talked to National Weather Service meteorologist about this
Confirmed the 2 week pattern for the high pressure systems
Cause is very uncertain - it just happens?
Look what has happened in our area over Christmas / New Year (1997)
Storm after storm leading to an approx. 50 year flood
Then the high settles into the area
Cold and foggy indeed!
Consider this: It really wasn't that cold (it was January, after all)
Lows were in mid-high 20's
It could have been much colder
With the heavy rain and saturated ground (saturated everything!)
What would happen if we'd had a 50 year freeze following the flood?
Relate O'Brien cabin wet/freeze story
El Niño
El Niño: University of Illinois
Thunderstorms
Tornado
Tornado information index: USA Today
How tornadoes are classified: Fujita Scale
Index to information on tornadoes
Hurricane