“I hear and I forget. I see and I remember. I do and I understand.”

THE ATMOSPHEREReview, prevailing winds, fronts, pollutions, greenhouse effect & ozone layer

September 27 2012

https://www.facebook.com/photo.php?fbid=474057782615238&set=a.456449604376056.98921.367116489976035&ty

Review: The Atmosphere

Concept map 1: Review

Factors Affecting Air Pressure

1. Number of air molecules (e.g. N2, O2): the higher the number of molecules, the more frequent the collisions, therefore the higher the pressure. Air pressure falls with increasing altitude.

2. Temperature of air: when temperature rises, air molecules move away from one another in order to restore a state of equilibrium, causing its density to drop, resulting in less collisions and thus, lower pressure.

Warm air is thus lighter than cold air and tends to rise.

• Air particles will move away from high-pressure areas to low-pressure areas, resulting in winds.

Anticyclones & Depressions

Fig. 11: http://www.atmos.umd.edu/~meto200/3_13_03_lecture_files/slide0030_image276.jpg

Prevailing Winds•Prevailing winds: major atmospheric

currents that blow in a given direction according to global patterns of movement.▫Polar easterlies: moving between the

poles and the 60th parallel▫* Westerlies: blow in the middle latitudes

between the 30th parallel and the 60th parallel

▫Trade winds: easterlies moving between the 30th parallel and the equator

Question 1 of the Day

Why do you think easterlies are called easterlies? Why are westerlies called

westerlies?

Prevailing Winds

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Polar Cell•Between 60o and the poles in either

hemisphere.Air at 60o is warmer than air from polar regions, therefore it rises at 60o air from both sides then rushes in to fill the bottom space left behind by the risen air mass warm air cools as it moves towards the poles and thus it sinks at the polar regions it then turns and moves towards the empty space left behind by the rising air at 60o creation of Polar cell.

(0o)

(30o)

(60o)

(Pole)

Ferrel Cell•Between 30o and 60o in either

hemisphere.

Fig. 7: http://www.geol.umd.edu/~jmerck/geol100/lectures/33.html

Cooled air from equator sinks at 30o, pulling down adjacent air space left behind by sunken air is replaced by air from both sides the relatively warmer air collides with the cooler air from the polar regions at 60o, forcing it to rise in either direction creation of Ferrel cell as well as a part of the polar cell.

(Pole)

(60o)

(30o)

(0o)

Hadley Cell•Between 0o and 30o in either hemisphere.

Warm moist air rises at (1) air cools, condenses and falls as rain at (2) cooled dry air moves towards 30o, sinks and warms up at (3) cooled dry air starts to heat up at (4) over the hot dry deserts as it moves towards 0o again at (1).

Fig. 6: http://andrewkfletchers.blogspot.ca/2012/03/operation-oasis-andrew-k-fletcher.html

Cold Front•Cold front: Advancing cold air meets

warm air warm air rises rapidly cools into thick cumulus clouds wind and heavy rain

Fig. 9: http://apollo.lsc.vsc.edu/classes/met130/notes/chapter11/cf_xsect.html

Warm Front•Warm front: Advancing warm air meets

cold air warm air rises gently thin, light nimbostratus clouds long-lasting cloudy weather and showers.

Fig. 10: http://earth.usc.edu/~stott/Catalina/WeatherPatterns.html

Pollutions• Contaminants:

1. Sulphur dioxide (SO2), nitrous oxides (NOX), dust and other airborne particles from factories and car exhausts.

2. Mercury (Hg), arsenic (As) and lead (Pb) from combustion of fossil fuels, waste incineration and glass-making.

3. Chlorofluorocarbons (CFCs) from refrigeration systems and aerosol cans.

Due to winds, the formation of acid rain can occur near or far from the point of emission.

Pollutions•Smog: a thick mixture of fog, smoke and

atmospheric pollutants that hangs over urban areas when a high pressure system prevents it from rising into the atmosphere. ▫intensity and composition varies with

weather and time

Climate change: the abnormal modification of climatic conditions on Earth, caused by human activity.

Question 2 of the Day

Is the greenhouse effect good or bad for the Earth?

Greenhouse Effect•Greenhouse effect: a natural process

that allows the Earth to retain some of the heat it receives from the sun

•Greenhouse gases (GHGs): mostly H2O, CO2, CH4 and NOX

Greenhouse Effect

Fig. 1: http://www.nps.gov/goga/naturescience/images/Greenhouse-effect.jpg

Ozone Layer•Ozone layer: the part of the atmosphere,

where a high concentration of ozone molecules (O3) absorbs some of the ultraviolet (UV) rays from the sun; thus protecting us.▫In 1987, 190 countries signed the Montreal

Protocol to gradually phase out the use of CFCs until 2010.

Question 3 of the Day

Is the damage of the ozone layer reversible or irreversible?