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Midterm

Wind- Midterm Review.docx


Department
Environmental Science
Course Code
EESA09H3
Professor
Tanzina Mohsin
Study Guide
Midterm

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WIND EXAM REVIEW
LECTURE 1
Greeks (Euro-centric)-WIND MYTHOLOGY
Aeolus designated by Zeus to look after the four winds
Zephyrus gentle, west wind
Boreas chilly, north wind
Notos southern rain bringer
Eurus ill-tempered east breeze
Within greek mythology, Aeolus was designated by Zeus to look after four winds. Boreas is a
chilly north wind that originates in the NORTH and blows towards the SOUTH
Gaia Hypothesis
modifies the environment to best suit itself
21% oxygen is optimum for life
Mars and Venus are in a static equilibrium with high levels of carbon dioxide and methane
Why switch from anaerobic conditions to aerobic conditions 2.3 billion years ago?
Early sun produced 30% less energy (Archean)
arly earth with high levels of methane and carbon
dioxide had a strong greenhouse effect which lead to
conditions warm enough for life
year solar output increased and earth was becoming too warm, the switch to
aerobic life, reduced the greenhouse gases (CO2CH4) and cooled the planet
We now have considerably lower levels of CO2 in the atmosphere than the early earth
Gaia Hypothesis postulates that the atmospheric constituents have been controlled by life to
optimize conditions for life (BIOLOGIC CONTROL)
- Geologic control the atmosphere is static NOT dynamic
o 2.3 billiong years of methane and carbon dioxide and after than oxygen stabilized into
the environment at 21%
- BIOLOGIC CONTROL , the change from anaerobic to AEROBIC conditions
- ANTHROPOGENIC- Decaying plants are not fully oxidized , and coverted to COAL AND OIL due to
GEOLOGIC PRESSURE. This has lead ot many of today’s air quality problems, (smog, acid rain,
global warming)
- Coal IS THE FIRST anthropogenic modification of the atmosphere US (19th and 20th century)
and China- 11th century to present day
- Modern dumping ground fossil fuels, coal and other hydrocarbons acid rain, urban air
quality, urban heat island, global warming
- Air is made of GAS MAINLY, liquid (cloud) , and solid (particulate matter)
- Greenhouse gas atmospheric constituent that traps outgoing radiation
- What are examples of greenhouse gases water vapour, carbon dioxide, methane, nitrous
oxide, ozone and CFC’s

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- Greenhouse gas- gases that intercept radiation and reradiate back to the earth’s surface, which
causes the earth’s surface to be warmer than it would be otherwise
- Enhanced greenhouse gas effect- anthropogenic emissions of greenhouse gases traps excess
heat (GLOBAL WARMING)
- CLOUD NOMENCLATURE
o Stratus layer, cumulo-puffy, nimbo-rain, alto-mid , cirro-high
- FOUR DISTINCT LAYERS IN THE ATMOSPHERE (M SHAPE, temperature decreases with height in
alternating layers )
o Troposphere (decreases) (11 km) well mixed vertically, all weather conditions occur
here, 75% of the atmosphere, temperature decreases with height
o Stratosphere (Increases) (11-50) temperature increases with height , WHY ?
conversion of incoming solar radiation to energy via a layer of ozone
o Mesosphere (decreases) (50-85)
o Thermosphere (increases) (85incoming solar radiation is converted to KINETIC
ENERGY via a layer of ozone , its COLD , DENSE and a low transference of heat
- Temperature thermometer
- Pressure barometer
- Wind speed anemometer
- Wind direction weather vane
- Precipitation- rain/snow gauge
- Humidity hygrometer/psychrometer
o Hygrometer- measure of humidity due the expansion or contraction of a particular fluid
o Psychrometer which is based on wet and dry bulb temperature
o Dry bulb tempterature- ambient temperature
o Wet bulb temp- cooling of air due to evaporation until saturation occurs
- RISIING AIR COOLS AND SINKING AIR WARMS , the cooling air leads to condensation and later
cloud formation
- Wind movement of air in an ordered fashion , we cant see wind but we can feel it
- What causes wind to move? Differences in air pressure, vertical and horizontal (pressure
gradient)
o Pressure gradient force movement of wind from a HIGH TO LOW PRESSURE
- Coriolis Force- “ficticious force” – caused by the rotation of the earth’s surface
o Causes winds to deflect to the RIGHT in NORTHERN HEMISPHERE , and LEFT in the
SOUTHERN hemisphere
o Gaspard Gustave de Coriolis
o STEEP pressure GRADIENT (PG) or closely spaced isobars, indicate strong winds PGF and
high winds
o GEOSTROPHIC WINDS- BALANCE between pressure gradient force and coriolis force
Occurs 1 km above the surface (NO FRICTION)
- GLOBAL CIRCULATION- there is more energy released from the POLES than is absosrbed from
the sun and this works in REVERSE AS WELL, and this is due to ATMOSPHERIC CIRCULATION

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- ONE CELL THEORY- one , large overturning atmospheric cell air rises at the equator, expands
(convergence) moves towards the poles, cools , condenses and sinks AT THE POLES , at the
surface the winds move equator ward once again.
- ENERGY IS transported as SENSIBLE AND LATENT HEAT, and latent heat transport occurs when
warm air rises at the equator , cools , condenses and sinks at the poles and by doing so
RELEASES LATENT HEAT
- This theory is not realistic because it doesn’t take into consideration, coriolis force, and land
/sea contrasts , tilt etc.
- Named AFTER GEORGE HADLEY
- SENSIBLE HEAT- heat you can feel, LATENT HEAT- stored as water vapor, examined through
changes of state.
o CONDENSATION- HEAT IS RELEASED
o EVAPORATION- HEAT IS ABSORBED
- HADLEY CELL- air rises at the equator , moves poleward and sinks 30 degrees north and south
- FERRELL CELL- air rises at the equator moves poleward, and sinks 30-60 degrees north and south
- POLAR CELL- air rises at the equator moves poleward and sinks 60 degrees north and south
- Intertropical Convergence Zone- area of rising air at or near the equator and its located between
the two Hadley cells in the northern and southern hemisphere
o Occurs because of surface convergence on both sides of the equator
- TRADE WINDS: between the equator and 30 degrees north, the wind should flow to the SOUTH
but instead it flows to the SOUTH WEST, a surface component of THE HADLEY CELL
o NORTH AND SOUTHEAST TRADEWINDS
- SUBTROPICAL HIGH- subsiding air at 30 degree N and 30 degree S (HORSE LATITIUDES) ,
between the WESTERLIES AND TRADE WINDS , and corresponds to the descending branch of
Hadley and Ferrell cells
- Westerlies: winds from 30-60 degrees should flow NORTH but instead they flow NORTHEAST ,
the winds come from the west , surface component of the FERRELL CELL
- POLAR EASTERLIES- winds blowing from the EAST, should flow SOUTH , but go SOUTH WEST
INSTEAD (due to deflection of the winds) surface component of the POLAR CELL (60 degree
north and south)
- Doldrum: region of little wind between NORTH and SOUTH trade winds
- Polar front division between polar air and midlatitude air , occurs in the area between POLAR
AND FERRELL CELLS, where warm and cold air collide
- Land/sea contrasts occur because the land has a LOWER HEAT CAPACITY than the water and can
HEAT UP AND COOL DOWN MUCH MORE QUICKLY
o In NH high pressures form over land and then the opposite occurs in the summer
- UPPER LEVEL WINDS ARE GEOSTROPHIC and are not affected by friction or LAND/SEA
CONTRAST
- Jet Stream- swift flowing current of air , (10-15 km above the surface) thousands of km
long,hundred of km wide and a few km thick) , divisions between the three cells HADLEY ,
FERRELL AND POLAR
o Hadley and ferrell (subtropical jet) and Ferrell and polar (polar jet)
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