Global Warming

Climate and Weather

Atmosphere and Weather• Earth is surrounded by a layer called the atmosphere. It

consists of a mix of gases, water vapour, dust and chemicals.

• The atmosphere provides the oxygen and carbon dioxide that all living things must have.

• Changes in the atmosphere provide the weather and affects the way you live.

• Weather is a day-to-day change in the atmosphere but a longer trend in atmospheric behaviour is called a climate.

• Climate varies with geographic location: lots of rain and snow, dry, hot and cold.

Atmosphere and Weather• Air is a mix of nitrogen (78%), oxygen (21%) and

other gases (argon, carbon dioxide, etc.). • There is also some water vapour but this varies with

atmospheric conditions.• In a given amount of air, up to 4% may be water

vapour.• The air usually contains dust, ash and chemicals. • The dust could be soil or pollen and salt spray from

the oceans. • The ash arrives from forest fires and volcanic

activity.

Atmosphere and Weather• Pollution adds unnatural chemicals into the air,

which mix with air making weak acids.• When pollutants get trapped near the Earth, a mix

of smoke and fog (SMOG) results.• Gravity pulls each air molecule down to create air

pressure. It is the highest at sea level.• Air pressure varies with altitude and air

temperature.• Meteorologists use air pressure to predict storm

movements.• Changes in air pressure make the winds.

Atmosphere and Weather• Temperature is the amount of heat energy in the

air. (Affects air pressure and water vapour content.)• Humidity is the amount of water vapour in the air.

(Affects clouds and rain.) • These three factors (air pressure, temperature and

humidity) are used to forecast the weather.

Wind• The air is heated more at the equator than at the

poles. • This heated air moves upwards to the poles and the

cooler air moves down to the equator.• The Earth’s rotation churns the air into wind belts,

stretching around the Earth. (Coriolis effect)• Wind blows primarily in one direction in a wind belt.• A region between two belts has wind that shifts

rapidly (between directions) or it won’t blow at all. • Wind is the movement of air from high to low

pressures.

Jet Streams• Jet Streams blow above the wind belts at the upper

edge of the troposphere. • These are narrow bands of high speed winds. (Often

faster than 300 km/h). • There are several jet streams around the Earth at

various latitudes. (2 or 3 in the North or South hemispheres)

• During cooler months, jet streams are closer to the equator and move faster.

• Jet stream changes cause squalls, storms and cyclones.

Jet Streams

Storms• Storms on the Earth’s surface are controlled by the

jet stream paths.• Storms are simply the way that nature moves

energy in the atmosphere.• There are 3 categories of Violent Storms:

Hurricanes, Tornados and Thunderstorms.

Hurricanes

• Hurricanes form over warm waters of the South Atlantic between two wind belts.

• The calm centre is called the eye of the hurricane.

• They may reach sizes of 640 km across and have winds up to 320 km/h.

• The US is hit about twice a year. • They can also create tornadoes and violent

thunderstorms.

Ocean Currents• Ocean currents also move thermal energy around

the Earth and are affected by the Coriolis effect.

Isabel

Tornados• Tornadoes are small but violent twisting storms.• These form ahead of strong cold fronts, travel on

land at about 30-60 km/h but winds in the funnel may reach 470 km/h.

• The centre of a tornado is at a very low pressure.• When objects like houses at normal air pressure

interact with the core, they explode into it.

Thunderstorms• Thunderstorms produce high winds, rain, hail and lightning. • Lightning strikes take place thousands of times every day. • These form when warm, moist air is thrust rapidly into the

atmosphere. • The cumulus clouds become cumulonimbus and may reach

heights of 27 km. • The rapidly moving winds generate friction, creating lightning. • If there is a strong updraft in a cloud, hail can result.• Thunderstorms are very common and several hundred of

them are occurring right now. • The average thunderstorm releases the same amount of

energy as an atomic bomb.

Weather Forecasting• Meteorologists study the atmosphere and how it works

to predict its behaviour.• Weather stations, barometers, satellite images and

weather balloons all help in this study.• Air masses, low and high-pressure areas, fronts and

violent weather are all shown on maps.• A forecast is a prediction on what might happen. • It includes information on the condition of the

atmosphere, a description of how it has behaved and a prediction on how it will behave.

• Forecasts pay close attention to violent weather for pilots and farmers.

Earth’s Biosphere• The biosphere is the thin layer of Earth that has

conditions to support life.• The atmosphere is the gas layer around the planet.• The lithosphere is the rock layer around the planet.• The hydrosphere is the water layer around the

planet.

Atmosphere Layers• The bottom layer of the atmosphere is

called the troposphere and is 0-10 km high and is 20 to -600C. This is where all weather occurs. Contains most of the CO2, water, (80% of whole atmospheric gas) and dust. Can support life.

• The second layer is called the stratosphere, is 40 km thick (10-50 km high) and is 0 to -600C. Very thin clouds exist here. Contains most of the ozone.

Atmosphere Layers• The 3rd layer is the mesosphere, is 50-

80 km high and is 0 to-1000C. It has very little gas, low pressure and few O2 molecules.

• The final layer is called the thermosphere at greater than 80 km high and ranges from -100 to 1000oC. Very little gas is here but gets very hot in the day and very cold at night.

Biomes• A biome is a large geographical region with defined

ranges of precipitation and temperature.• There are 6 biomes in Canada: Tundra, Boreal forest

(taiga), Temperate deciduous forest, Temperate grassland, Temperate Coniferous forests and Mountains.

• Mountains can show different types of biomes as you climb, with tundra at the top of the higher mountains.

• There is no distinct line between biomes, and some biomes may overlap characteristics.

Solar Energy and Weather• There are three methods of heat transfer:

conduction, convection and radiation.

Conduction: • The transfer of heat by contact when high-speed

molecules hit slow speed molecules, making them move faster.

• Heat always flows from hot to cold. (Molecules vibrate in solids and do not move)

Solar Energy and WeatherConvection: • When high-energy molecules move due to changes in

density. • Hot air will rise as it is less dense than cold air. • Cooler air will move into its place creating a

convection current. • Holding your hand above a candle is heating by

convection. • This occurs in liquids as well. • Some stoves use convection heating and heat things

quickly.

Solar Energy and WeatherConvection: • Convection also explains the wind patterns at the beach. • During the day, the beach is hotter so it has more hot air

rising. • The cooler air above the water rushes in to take its place

creating an onshore breeze. • At night, the heat stored by the high heat capacity of

water, rises up and the cooler air on the beach moves out to create an offshore breeze.

• Wind, in general is a result of convection and the Earth’s rotation.

Solar Energy and Weather

Radiation: • This is the emitted heat from hot objects. • Radiation is an electromagnetic wave. • Heat travels as an infrared wave. • These waves can travel through space.• The radiant energy from the sun is important for life

and drives all weather systems

Solar Energy and Weather

Radiation: • Solar radiation on the Earth’s surface is about 50%

of that emitted by the sun. (The amount at our atmosphere is 1367 J/m2s: the solar constant).

• The rest is lost as follows: 20% is absorbed by the many kilometres of atmosphere (air and clouds) and the remaining 30% is reflected off clouds, air and the ground itself.

• The Earth radiates energy into space as well such that the Earth does not cook from the constant solar energy. (lost as heat)

Solar Energy and Weather

Radiation: • The oceans maintain a fairly consistent temperature

because water has a special property called the specific heat capacity.

• It takes a lot of energy to heat water, which makes it good for car radiators.

• The energy goes into making the water molecules move faster.

Greenhouse Effect• Insolation is the amount of solar radiation received by a

region of the Earth’s surface.• The absorption of thermal energy by the atmosphere is called

the natural greenhouse effect.• Water vapour, carbon dioxide, nitrous oxide and methane are

called greenhouse gases.• Water is the main contributor of the natural greenhouse

effect.• The net radiation budget is the difference between the

amount of incoming radiation and the amount of outgoing radiation.

• Albedo measures the percent of incoming radiation the surface reflects. (Bright snow reflects a lot).