The Atmosphere. The atmosphere is a mixture of gases that surrounds a planet, such as Earth. Nitrogen, oxygen, carbon dioxide, and other gases are all.

The Atmosphere

The Atmosphere

• The atmosphere is a mixture of gases that surrounds a planet, such as Earth.

• Nitrogen, oxygen, carbon dioxide, and other gases are all parts of this mixture.

• Gases can be added to and removed from the atmosphere through living organisms. For example, animals remove oxygen when they breathe in and add carbon dioxide when they breathe out.

The Atmosphere

• The atmosphere insulates Earth’s surface.

• This insulation slows the rate at which the Earth’s surface loses heat and keeps Earth temperature at which living things can survive.

Composition of the Atmosphere

• Nitrogen makes up 78 percent of the Earth’s atmosphere, and enters the atmosphere when volcanoes erupt and when dead plants and animals decay.

• Oxygen is the second most abundant gas in the atmosphere and is primarily produced by plants.

• In addition to gases, the atmosphere contains many types of tiny, solid particles, or atmospheric dust.

Layers of The Atmosphere

• The atmosphere is divided into four layers based on temperature changes that occur at different distances above the Earth’s surface.

• The Troposphere• The Stratosphere• The Mesosphere• The Thermosphere

The Troposphere

• The troposphere is the lowest layer of the atmosphere in which temperature drops at a constant rate as altitude increases.

• This is the part of the atmosphere where weather conditions exist.

• The troposphere is Earth’s densest atmospheric layer and extends to 18 km above Earth’s surface.

The Stratosphere

• The stratosphere is the layer of the atmosphere that lies immediately above the troposphere and extends from about 10 to 50 km above the Earth’s surface increases.

• Temperature rises as altitude increases because ozone in the stratosphere absorbs the sun’s ultraviolet (UV) energy and warms the air.

Ozone• Ozone is a gas molecule that is made up

of three oxygen atoms.

• Almost all of the ozone in the atmosphere is concentrated in the stratosphere.

• Because ozone absorbs UV radiation, it reduces amount of UV radiation that reaches the Earth. UV radiation that does reach Earth can damage living cells.

The Mesosphere

• The layer above the stratosphere is the mesosphere.

• This layer extends to an altitude of about 80 km.

• This is the coldest layer of the atmosphere where temperatures have been measured as low as –93ºC.

The Thermosphere

• The atmospheric layer located farthest from Earth’s surface is the thermosphere.

• Here, nitrogen and oxygen absorb solar radiation resulting in temperatures measuring above 2,000 ºC.

• The air in the thermosphere is so thin that air particles rarely collide, so little heat is transferred, and would therefore not feel hot to us.

Heating of the Atmosphere• About half of the solar energy that enters the

atmosphere passes through it and reaches the Earth’s surface, while the rest of the energy is absorbed or reflected in the atmosphere by clouds, gases, and dust or it is reflected by Earth’s surface.

• The Earth does not continue to get warmer because the oceans and the land radiate the absorbed energy back into the atmosphere.

• Because the ocean both absorbs and releases heat slower than land, the temperature of the atmosphere changes more slowly.

Movement of Air in the Atmosphere

• As a current of air, warmed by Earth’s surface, rises into the atmosphere, it begins to cool, and eventually becomes more dense the air around it and sinks. This current then moves back toward the Earth until heated and less dense and then begins to rise again.

• The continual process of warm air rising and cool air sinking moves air in a circular motion is called a convection current.

WeatherWeather Temporary behavior of

atmosphere (what’s going on at any certain time)

Small geographic area

Can change rapidly

ClimateClimate Long-term behavior of

atmosphere (100+ years) LargeLarge geographic area Very slowslow to change

Air Masses• Body of air with a certain temperature

and moisture level• As it moves, the characteristics of an air

mass change and so does the weather.• Can be warm(T) or cold(P)• Can contain a lot of moisture(m) or not

a lot of moisture(c)• Named according to their source region.

Ex: cP, mT

Fronts• places where air masses meet• 4 Types: Warm, Cold, Occluded,

Stationary• Each kind can bring different kinds of

weather

Fronts• Cold Front – cold,

dense air moves into a region occupied by warmer air, leads to heavy downpours and gusty winds

• Warm Front – warm air moves into an area occupied by cooler air, Brings warmer temperatures and precipitation,

Fronts• Occluded Front –

an active cold front takes overtakes a warm front; complex weather pattern

• Stationary Front – flow of air is neither toward cold or warm air mass

Occluded Front

Stationary Front

How does Air Pressure How does Air Pressure affect weather?affect weather?

• Pressure exerted by weight of air above it. Exerted in ALL directions

• Measured with a BAROMETER• If it CHANGES, then new weather is

on the way:– Falling Air Pressure = stormy weather

coming– Rising Air Pressure = fair weather

coming– Steady Air Pressure = no change is

coming

WindsWinds = horizontal movement of air created from differences in air

pressure

• Moves from areas of HIGH to LOW pressure

• Greater the difference in pressure, the FASTER the wind blows

• Labeled from which direction they blow

Pressure Centers and Winds

• Cyclones – centers of low pressure; pressure decreases from outer isobars toward the center.

• Anticyclones – centers of high pressure; pressure increases from outside toward center

Severe Storms• Thunderstorms – form when warm, humid air

rises in an unstable environment; produce gusty winds and heavy precipitation

• Tornadoes – violent windstorms that take the form of a rotating column of air called a vortex. Vortex extends downward from a cumulonimbus cloud. – U.S. -770 per year; most form in

association with severe thunderstorms

• Hurricane – a whirling tropical cyclone that produces wind of at least 119 km/h; most powerful severe storm; develops when water temps. are warm enough to provide the necessary heat and moisture in the air

HumidityHumidity

Humidity – amount of water Humidity – amount of water vapor in the airvapor in the air

Controlled by temperatureControlled by temperature1. WarmWarm air holds more moisture than cool air (more space for water vapor between air molecules)2. As air warmswarms, relative humidity decreasesdecreases3. As air coolscools, relative humidity increasesincreases

Relative HumidityRelative Humidity Measure of the amount of

moisturemoisture in the air compared to what the air could hold

How “full” of water the air is Expressed as % 100% relative humidity =

saturatedsaturated air

Dew PointDew Point• Dew point is the

temperature the moisture in the air will condense to liquid water.

• Higher dew point= more humid.

Dew point and human comfortDew point F° Human Comfort

Over 80 Severely high. Even deadly

for asthma related illnesses

75-79 Extremely uncomfortable

70-74 Quite uncomfortable

65-69 Somewhat uncomfortable

60-64 Ok, but feels humid

55-59 Comfortable

50-54 Very comfortable

Less than 49 Dry

Human Impact on the Atmosphere

Air pollution Global warmingAcid rain Ozone Damage Smog

Air pollutionHuman activity produces two main types of air pollutant:

particulates – Tiny particles suspended in air (e.g. smoke) and are usually produced by the combustion of fossil fuels.

noxious gases – Include carbon dioxide (CO2), sulfur dioxide (SO2) and nitrogen oxides (NOx).

Air pollution has been a major problem since the Industrial Revolution of the late 18th Century, and has been made worse by humans’ reliance on burning fossil fuels for energy.Air pollution, global warming, acid rain, damage to the ozone layer and smog. Each of these has serious implications for the environment and human health.

Greenhouse Effect

• The greenhouse effect is the warming of the surface and lower atmosphere of Earth that occurs when carbon dioxide, water vapor, and other gases in the air absorb and reradiate infrared radiation.

• Without the greenhouse effect, the Earth would be too cold for life to exist.

Greenhouse Effect

• The gases in the atmosphere that trap and radiate heat are called greenhouse gases.

• The most abundant greenhouse gases are water vapor, carbon dioxide, methane, and nitrous oxide, although none exist in high concentrations.

• The quantities of carbon dioxide and methane in the atmosphere vary considerable as a result of natural and industrial processes.

Global warming and greenhouse gases

One of the greatest threats caused by air pollution is global warming. Global warming is caused by a build-up of greenhouses gases, which leads to an increase in the Earth’s temperature. Other effects include bizarre weather patterns, and melting of polar ice caps

Key greenhouses gases include: carbon dioxide methane water vapour nitrous oxide

Acid PrecipitationAcid Precipitation

• Caused by the release of sulfur

dioxide and nitrogen oxide from factories

• Effects include soil erosion, death of

animals and vegetation, erosion

of buildings

Ozone DepletionOzone Depletion

•Caused by the use of coolants and

aerosol cans

• Effects include increased UV radiation, skin cancer and eye

disorders

Smog

Smog is a mixture of air pollutants and particulates that is sometimes found in the lower levels of the atmosphere. It has a distinctive brownish haze.

Smog can reach dangerous levels in built-up areas, causing irritation to the eyes and lungs.