Chapter 7 -The Atmosphere

The Atmosphere (404)  The atmosphere is a layer that envelopes the Earth. - it acts as a screen, blocking dangerous UV rays - it ensures a stable climate by retaining heat - it includes O 2, necessary for cellular respiration & CO 2, necessary for photosynthesis

Atmospheric Pressure (404) Atmospheric pressure is the pressure of the air in the atmosphere. We measure the pressure in kilopascals (kPa) At sea level, the atmospheric pressure is kPa.

The Earth’s gravitational force pulls the atmospheric particles towards the planet. Therefore, air particles are closer together near the Earth’s surface than at high altitudes. Atmospheric Pressure (404)

Main Factors Affecting Atmospheric Pressure When the number of particles increases, they collide more frequently, and pressure rises. When the number of particles drops, the pressure falls. That is why pressure falls with increasing altitude. When the temperature rises, particles move more rapidly & collide more frequently. Pressure increases with temperature. However, in the atmosphere, air pressure approaches a state of equilibrium; when temperature rises, the particles move away from each other restoring the pressure to a value closer to normal. As a result air density drops. Warm air is therefore lighter than cold air.

The Composition of the Atmosphere Air is a mixture of gases 21% O2O2 78% N2N2 1% other gases including water vapour, argon, carbon dioxide, methane, ozone, CFCs - Water vapour is an important component of air. It is responsible for cloud formation and precipitation. - The measure of water vapour is ‘relative humidity’.

The Atmosphere’s Main Layers  Troposphere: 0-15 km  Stratosphere: km  Mesosphere: km  Thermosphere: km  Exosphere: 500 km & up

Air Masses (404) An air mass is a large expanse of the atmosphere with relatively uniform temperature and humidity. When two air masses meet, they do not combine. The denser, colder air mass slides underneath the lighter, warmer air. The line where the two meet is called a front. On weather maps: cold front: warm front:

Air Masses Cold Front: Cold air moves towards warm air. The warm air rises rapidly, then cools. The resulting condensation forms puffy clouds “cumulus” which produces wind and heavy rain. Warm Front: Warm air moves towards cold air. The warm air rises gently above the cold air and creates light clouds of many layers “nimbostratus” which bring cloudy weather and showers which are slow to disperse.

Anticyclones and Depressions (404) The area of high pressure is called an anticyclone ( H ). Due to the Coriolis Effect, the air turns clockwise in the Northern Hemisphere. The area of low pressure is called a depression ( L ). Due to The Coriolis Effect, the air turns counter clockwise in the Northern Hemisphere. DEPRESSION

Atmospheric Circulation Atmospheric circulation: Global scale movement of the layer of air surrounding the Earth. Air that has been warmed becomes lighter and less dense and moves towards the poles. It is replaced by denser, colder air coming from the poles. Coriolis Effect: Due to the rotation of the Earth, the Coriolis effect causes a deviation in wind direction. The Coriolis Effect is responsible for the formation of warm and cold fronts.

Anticyclones and Depressions Anticyclone: Areas of high pressure occur when cold air falls. The air turns clockwise around an anticyclone. Depression: Areas of low pressure occur when warm air rises. The air turns counter clockwise around a depression. H L - In an anticyclone, falling particles prevent cloud formation. The sky is clear. (Summer: dry & sunny, Winter: cold) - In a depression, rising air encourages cloud formation which results in precipitation.

Weather Map (404) A weather map usually indicates where high and low pressure systems are located as well as where warm and cold fronts exist. The location where the cold front meets the warm front will result in heavy precipitation.

Cyclones (404) Strong depressions may develop over warm waters which results in huge spiral formations and violent winds. These storms are called cyclones, hurricanes or typhoons. These storms bring a lot of torrential rain, can cause floods & landslides, rip roofs off of buildings, etc...

Cyclones Eye of the Storm: Hurricane Emilia (picture taken by Space Shuttle crew members with handheld camera) Images captured by NOAA inside a hurricane show the eye and the massive curving cloud wall. Hurricane Rita

Coriolis Effect (404) The Coriolis Effect deviates winds to the right in the Northern Hemisphere, to the left in the Southern Hemisphere

Prevailing Winds (466) A wind that blows more often from one direction that from any other direction is called a prevailing wind. (nice picture on p.228)

Prevailing Winds (466) Winds form great loops called circulation cells. The Hadley Cell: (equator – 30 th parallel) - Warm air over the equator rises into the atmosphere, it cools as it travels north/south towards the 30 th parallel, it descends & returns to the equator. The Ferrel Cell: (30 th – 60 th parallel) - Part of the falling air over the 30 th parallel moves towards the poles. Near the 60 th parallel, this air collides with winds form the polar cell and make it return to the 30 th parallel. The Polar Cell: (over the poles) - The temperature of the air drops over the poles which causes the air to sink back down to the Earth and return to the 60 th parallel where it collides with the Ferrel Cell. The air is forced to rise and return to the pole.

Prevailing Winds (466) Airplane pilots must be aware of the jet streams when they travel. They avoid the jet streams when travelling from east to west, against the wind. They use the jet streams to their advantage when travelling from west to east.

DID YOU KNOW! Your Big Mac is responsible for more global warming than your car. The international meat industry generates roughly 18% of the world’s greenhouse-gas emissions. Much of that comes from the methane in manure. Methane has a warming effect that is 23 times as great as that of carbon. There are 1.5 billion cattle and buffalo on the planet, along with 1.7 billion sheep and goats. Their populations are rising fast, especially in the developing world.

The Greenhouse Effect (404) p Greenhouse gases are water vapour, carbon dioxide, methane and nitrous oxide, they have always existed in our atmosphere. They are suspended in the atmosphere, they keep in some of the energy the Earth receives from the sun-like a greenhouse does. This is called the GREENHOUSE EFFECT.

i For many years, the amount of greenhouse gases have been constant but over the last 100 years the balance has changed. i CLIMATE CHANGE is the abnormal changing of the climate caused by human activity.  Global warming can lead to the melting of pack ice and glaciers.

Which Gases Cause Climate Change? Carbon dioxide is the largest single contributor to climate change. Methane and nitrous oxide are also gases that contribute to the increase in climate change.

Energy Resources (404) p 238

There are some forms of energy that comes from the atmosphere: Wind Energy : is energy that can be drawn from the wind (1 wind turbine can convert wind into electricity for houses) Solar Energy : is the energy that comes from the sun. (we use solar energy in our calculators) Some houses today have solar panels to heat their water.

Earth-Moon System p. 243 (404) The moon revolves around the Earth. The moon is the main cause of tides on Earth. Two high tides and two low tides occur every day. The water masses on the side closest to the moon are attracted to the moon. This causes high tides. Gravitational force is responsible for tides.

Gravitational Effect of the Moon (404) Two big bulges of water form on the Earth:  one directly under the moon  another on the exact opposite side As the Earth spins, the bulges follow the moon.

Tidal Range: The difference in water levels at low and high tides. The sun’s gravitational effect also influences the tides to a lesser degree. When the sun and moon are aligned with the Earth, the tidal range is maximum and this is called spring tides.