The Atmosphere

The atmosphere

• The atmosphere– Acts as a screen against harmful radiation– Retains heat allowing for life on Earth

– Includes O2 necessary for cellular respiration and CO2 necessary for photosynthesis

– Our atmosphere covers our planet because of the gravitational field of our planet

Composition of the air

• Atmosphere: layer of gas (especially nitrogen and oxygen) that surrounds our planet

• Air is made up of:– 78% Nitrogen (N)– 21% Oxygen (O2)– 1% of other gases

• Water Vapor• CO2• Argon• …

Atmospheric layers• Troposphere: (0-15km)

– Where meteorological phenomenon occur

• Stratosphere: (15-50 km)– Ozone layer– Temperature increases due to ozone layer

• Mesosphere: (50-80 km)– Coldest layer of the atmosphere (-80C)

• Thermosphere: (80-500 km)– Hottest layer of the atmosphere (1800C)

• Exosphere: (500 km and up)– Where satellites are placed

Atmospheric pressure

• Air is a fluid

• Atmospheric pressure– Is the weight per unit area (pressure) of the

column of air above that location.• the pressure of the air in the atmosphere• Varies with time and place

• To measure pressure we use a barometer• Units of measurement = Pascals• Average air pressure at sea level = 102.325 Pa

Factors affecting atmospheric pressure

• If the number of air particles – Increase : then pressure increases– Decrease: then pressure decreases

• There is a natural thinning of our atmosphere with altitude and therefore a natural decrease in pressure

• If temperature of the air– Increase: (the molecules are flying every which way)

the pressure will decrease– Decreases: the pressure will increase– **Warm air is therefore less dense than cold air

Another interesting factor

• Water vapor– If the amount of water vapor increases: the air

pressure will actually decrease, because humid air is actually less heavy than dry air.

Atmospheric Circulation

Coriolis Effect

• Definition:

• Winds deviate to the right in the Northern Hemisphere

• Winds deviate to the left in the Southern Hemisphere

Circulation cells

1. Hadley Cells• Between the equator and 30th latitude• Warm air rise at equator• Creates the trade wind

2. Ferrel cells– Between the 30th latitude and 60th latitude– Creates the westerlies (from west to east)

3. Polar Cells– Between the 60th latitude and the poles– Creates the polar easterlies (from east to west)

Weather Makers

Air Masses, anticyclones and cyclones

1. Air masses

• Definition:– Large expanse of the atmosphere with

relatively uniform temperature and humidity.

– Air mass characteristics:• Humidity (humid or dry)• Temperature (cold or warm)

1. Air masses

• When air masses collide they create fronts. They do not mix.

a) Cold Front

b) Warm Front

c) Stationary

d) Occluded

a) Cold front• Occurs when…

– A cold air mass overides a warm air mass

• Symbol

• Weather– The warm air rises abruptly, causing the water vapor

to rise and condense and produces storm clouds

a) Cold Front

b) Warm front• Occurs when…

– A warm air mass overides a cold air mass

• Symbol

• Weather– The warm air rises slowly, causing the water vapor to

rise and condense and produces clouds

b) Warm Front

c) Stationary Front

• Occurs when…– A warm air mass meets head on a cold air mass

• Symbol

• Weather– The masses collide, the warm air rises over the cold

denser air, causing the water vapor to rise and condense and produces clouds and rain on the cold front

d) Occluded Fronts

• Occurs when…– A cold front catches up with a warm front

• Symbol

• Weather– The cold front catches up with the warm front

and forces it from the ground

d) Occluded Front

2. Cyclones and anticyclones

• A cyclone:– Area of low atmospheric pressure. The air turns

counterclockwise in the Northern hemisphere and clockwise in the Southern Hemispheres.

• An anticyclone:– Area of high atmospheric pressure. The air turns

clockwise in the Northern hemisphere and counterclockwise in the Southern Hemispheres.

• Hurricanes:– A large cyclone characterized by violent winds

Atmospheric issues

• Smog– Thick layer of fog and smoke and atmospheric

pollutants

• Ozone layer thinning• Contaminants

– Acid Rain, smog, toxic chemicals, dust and ozone destruction

• Greenhouse gases– Climate change: abnormal modification of climatic

conditions on Earth, caused by human activity

Energy resources

• Solar energy

• Wind energy