Topic 3: Introduction to Earth’s Atmosphere

Topic 3: Introduction to Earth’s Atmosphere
General Introduction: - Earth’s Atmosphere - Importance of the Atmosphere Composition of the Atmosphere: - Common Atmospheric Gases - Greenhouse Gases - Atmospheric Particulates

Topic 2: Introduction to Earth’s Atmosphere
Vertical Structure of the Atmosphere - Temperature Structure - Vertical Composition - Vertical Pressure Profile Weather and Climate - What is Weather? - What is Climate? - Weather and Climate Controls

The Earth’s Atmosphere
The atmosphere is a mixture of gases surrounding the earth Atmospheric gases originate from gases released from the interior of the earth by volcanism and subsequently modified by plants and animals Atmospheric gases are held in place by the force of gravity

Atmosphere may contain both solid and liquid impurities Atmosphere is densest at sea level and decreases with increasing altitude Hence, about 98% of atmospheric gases are found within 16 miles (or 26km) of the earth surface

Though earth atmospheric gases could be found as far away 6000 miles or 10,000 km What is the actual extent of earth’s atmosphere? Hint: What is the orbital altitude of the International Space Station (ISS)?

Average orbital altitude of ISS is 400 km More than 50% of the mass of the atmosphere lies below 3.6 miles (5.6 km) The three dominant gases are: - Nitrogen (78%) - Oxygen (21%) - Argon (0.93%)

Importance of the Atmosphere
It is the main source of oxygen and other gases needed by plants and animals It maintains water supply through the mechanism of the hydrological cycle It prevents temperature extremes and functions as a great insulator

Importance of the Atmosphere
It provides protection from cosmic or ultraviolet radiation It provides protection from the impacts of small-sized meteorites by causing them to be incinerated through friction

Principal Gases of Earth’s Atmosphere
Formula Percent By Volume Nitrogen N2 78.08 Oxygen O2 20.95 Argon Ar 0.934 Carbon Dioxide CO2 0.036 Neon Ne 0.0018 Helium He 0.0005 Methane CH4 0.0001 Krypton Kr Hydrogen H2

Principal Gases of Earth’s Atmosphere
Formula Percent By Volume Nitrous Oxide N2O Trace Xenon Xe Carbon Monoxide CO Ozone O3 Sulfur Dioxide SO2 Water Vapor H2O 0-4 (variable)

Greenhouse Gases in the Atmosphere
Greenhouse gases permit the passage of short-wave solar radiation They disallow the passage of long wave infrared radiant energy from the earth surface from going back to space Hence, radiant energy is allowed to accumulate to produce a warming effect or greenhouse effect

Common greenhouse gases in the atmosphere include: - CO2 (75% of global warming) - Chlorofluorocarbon (CFC) (20%) - Methane (15-20%) - Water Vapor - Ozone

Producers of >50% of greenhouse gases are: - European Union - Brazil - China - Russia Emission of greenhouses gases continues to rise with increasing growth in population

Effects of global warming include: - more rains and longer growing season in high latitudes (Scandinavia, Canada, Siberia) - hotter summers and severe droughts in American Midwest - rise in sea level and flooding of coastal areas like Louisiana

Loss of Coastal Land to Global Warming

The Ozone Layer and CFC Ozone (O3) is a triatomic oxygen It forms a complete layer between 9 and 35 miles (15 – 55 km) above the earth surface The ozone layer protects plants and animals from ultraviolet radiation in sun’s rays by absorbing the radiation

The Ozone Layer and CFC But ozone is a very fragile gas that can easily be destroyed naturally by: - sunspot cycle - oscillation of stratospheric wind - volcanic dust particles - effects of El Nino Or human use of CFC in: - refrigeration & air-conditioning - aerosol sprays - foam & plastic manufacturing

More rapid ozone depletion has been reported at the poles
The Ozone Layer and CFC Today, 5% more UV radiation gets to the earth surface than in 1969 Up to 5% of the ozone layer has been destroyed over much of the United States More rapid ozone depletion has been reported at the poles Since 1975, Antarctic ozone hole has been found and appears to be persistent

The Antarctic Ozone Hole
Lowest Ozone level

Causes CFC to set chlorine free
The Ozone Layer and CFC Within the ozone layer, CFC becomes unstable and easily broken down by UV radiation Causes CFC to set chlorine free Chlorine pulls off oxygen atom from ozone to change it to an oxygen molecule and a chlorine monoxide molecule

Destruction of Ozone By Chlorine from CFC

The Ozone Layer and CFC A free oxygen atom pulls an oxygen atom off chlorine monoxide molecule Freed chlorine atom attacks another ozone molecule One molecule of chlorine can destroy up to 100,000 molecules of ozone Increase of CFC in the ozone layer is causing the rapid loss of the ozone layer

The Ozone Layer and CFC Ozone depletion is more severe over the polar region because of: - extreme cooling of the poles in winter, especially the Antarctica, where whirling winter pattern (vortex wind) occur - the presence of stratospheric ice crystals forming polar stratospheric clouds increases the process

The Ozone Layer and CFC - the ice crystals form surfaces for the accumulation of chlorine-based molecules and allowing spring uv radiation to trigger ozone depletion process Ozone depletion is less over Arctic than the Antarctica Key ozone depletion areas: Antarctica, Australia, mountainous regions of Europe, Central Canada and New Zealand

The Ozone Layer and CFC Ozone depletion is highly correlated with increased levels of UV radiation Ground levels of UV radiation (or UV Index) are now established and useful for alerting on possible health risks

The Ozone Layer and CFC A number of efforts to protect the ozone layer include: - ban of the use of aerosol sprays in Canada and U.S. in the 1987 Montreal Protocol on Substances That Deplete Ozone Layer set a timetable to phase out all major ozone-depleting substances - ban of CFC use in 1996 & substitution with hydrochlorofluorocarbon (HCFC)

The Ozone Layer and CFC Since 2006, the loss of ozone is stabilizing
It is suggested in 2009 that the levels of ozone over the tropics would have become depleted to levels found in the poles by the year 2100

The Ozone Layer and CFC Some of the effects of exposure to ultraviolet radiation include: - causes skin cancer & damage to animal tissue - causes gene mutation - suppression of human immune system - causes eye problems including cataracts

- causes drop in crop yield worldwide
The Ozone Layer and CFC - causes marine deserts - causes drop in crop yield worldwide

Air Pollution Human activities have altered the composition of the atmosphere, especially in the cities Natural sources of pollution include: - smoke from wildfires - ash from volcanic eruptions - windblown dust storms - plant pollen & salt particles in waves

Air Pollution There are two general types of air pollution: - Primary pollution: (pollutants, such as particulates, sulfur or nitrogen compounds, carbon oxides and hydrocarbons, released directly into the air) - Secondary pollution: (caused by chemical reactions in the atmosphere like photochemical smog)

Primary Pollutants: Atmospheric Particulates
Sources of Atmospheric Particulates: - meteoric dusts - volcanic dusts and ash - wind blow surface materials - smoke from bush fires - salt crystals from sea sprays - particles of biological origin (pollen, spores, seeds & bacteria) - particles of human origins (factory smoke, automobile emissions, heating, etc)

Primary Pollutants: Effects of Particulates in the Atmosphere
The effects includes: - reduction of solar energy reaching earth’s surface due to absorption and reflection of sunlight - optical effects on low-angled rays to produce colorful sunrise and sunset

Primary Pollutants: Effects of Particulates in the Atmosphere
- absorption of water (hygroscopic) and may form condensation nuclei - hazy conditions & atmospheric smog

Primary Pollutants: Carbon Monoxide
Produced by the combustion of fossil fuels by automobile and industrial plants Could be fatal if CO enters the bloodstream

Primary Pollutants: Sulfur Compounds
May be natural in origin through releases by volcanoes or hydrothermal vents (Yellowstone National Park) May be of human origin through the burning of coal and petroleum SO2 may react in the atmosphere to form secondary pollutants like sulfur trioxide or sulfuric acid to form acid rain

Primary Pollutants: Sulfur Dioxide
Sulfur dioxide is corrosive and a major lung irritant

Primary Pollutants: Nitrogen Compound
Nitric oxide form through: - natural biological processes in water or soils - combustion in automobile engines Nitrogen dioxide gives polluted air its yellow or reddish-brown color Nitrogen dioxide may aid the production of smog by forming NO & leftover oxygen atom joins with O2 to form Ozone needed in photochemical smog

Primary Pollutants: Nitrogen Compound
Nitric oxide may react with VOC to form peroxy-acetyl nitrate (PAN) PAN may cause crop and forest damages

Primary Pollutants: Photochemical Smog
Nitrogen dioxide and hydrocarbons (or volatile organic compounds – VOC) contribute to the formation of photochemical smog Presence of ozone gives the smog its distinctive odor Causes damage to vegetation, corroding building materials, damaging sensitive human tissues (eyes, lungs and noses)

Vertical Composition of Atmosphere
The composition & percentage of gases in the lower 50 miles (80 km) of the atmosphere are homogenous & uniform This is the homosphere and includes: - Troposhere - Stratosphere - Mesosphere

Homosphere and Heterosphere of the Atmosphere

The composition and percentage of gases above 50 miles (80 km) are non-uniform due to little or no vertical mixing This is the heterosphere Gases in heterosphere are layered according to their molecular mass

The layered gases in the heterosphere: - Hydrogen (Top) - Helium - Oxygen - Nitrogen (Bottom) Ozonosphere is a continuous layer of maximum ozone concentration between 9 and 30 miles (15 and 48 km)

Ionosphere is a deep layer of high concentration of electrically charged gases (ions) between 40 & 250 miles (60 & 400 km) Ionosphere is important because: - it aids long distance communication by reflecting radio waves back to earth - it’s known for its auroral displays (northern lights – Aurora Borealis)

Vertical Distribution of Gases in the Atmosphere

Aurora Borealis, Fairbanks (Alaska)

Vertical Pressure of Atmosphere
Atmospheric pressure is highest at sea level Pressure decreases rapidly with altitude but not at a constant rate Rate of change is rapid in lower atmosphere and diminishes significantly at the upper atmosphere

Decrease of Atmospheric Density with Altitude

Decrease in Air Pressure with Increasing Altitude

Vertical Temperature Profile of the Atmosphere
The atmosphere consists of 5 thermal layers where temperature either increases or decreases with altitude The thermal layers are: - Troposphere - Stratosphere - Mesosphere - Thermosphere - Exosphere

Thermal Layers of Atmosphere

Vertical Temperature Profile of the Atmosphere: Troposphere
It’s the lowest thermal layer It’s about 11 miles (18 km) thick above the equator It’s progressively thinner towards the poles where it is only 5 miles (8 km) thick Thickness is related to temperature

Hence, troposphere is thickest at the equator where temperature is high and one mile thicker in summer due to higher temperature The upper limit of troposphere is called the tropopause

Temperature decreases with increasing altitude or the higher you go, the cooler it becomes Hence, temperature at the bottom of this layer (earth surface) is about 60o F (15o C) and temperature at the top of this layer (tropopause) is about - 60o F (-51o C)

It contains almost all the water vapor and clouds in the atmosphere Almost all weather phenomena and processes occur in this layer All precipitations originate in this layer Accounts for 80% of atmospheric mass

Vertical Temperature Profile of the Atmosphere: Stratosphere
Extends beyond the tropopause to about 30 miles (48 km) above sea level It’s the zone of maximum ozone concentration Temperature increases with increasing altitude or the higher you go, the hotter it becomes

Vertical Temperature Profile of the Atmosphere: Stratosphere
Temperature at stratopause (top of layer) is 32o F (0o C) Source of heat for this layer is at the stratopause where absorption of UV radiation by ozone occurs Little or no vertical mixing but strong horizontal winds called Jet Streams occur

Vertical Temperature Profile of the Atmosphere: Mesosphere
Extends beyond stratopause to about 50 miles (80 km) above sea level Temperature decreases with increasing altitude Temperature at the top of the layer (mesopause) is about -120o F (-84o C)

Vertical Temperature Profile of the Atmosphere: Thermosphere
Extends beyond mesopause and gradually merges with exosphere Temperature initially remains constant at about -120o F (-84o C) up to about 90 km above sea level then begins to increase with altitude

Vertical Temperature Profile of the Atmosphere: Thermosphere
At about 125 miles (200 km), temperature may be more than 2000o F Heat is obtained through absorption of UV radiation by ionized gases in this layer

What is weather? It is the short-term condition of the atmosphere of a place It is the sum of temperature, humidity, cloudiness, precipitation, winds, & storms of a place for a given short time period It refers to atmospheric conditions over short time periods like: few hours, a day, a week, a month, a year or a season

What is weather? Weather usually applies to a small area like a city Weather changes constantly because of changing atmospheric circulation Global warming is causing weather-related disasters like drought, floods, tornadoes, & ice storms to become more frequent and intense

What is Climate? Climate is the average weather condition of a place observed over a period of at least 30 years Climate also includes those extreme conditions or deviations from the average condition

What is Climate? It is said that “climate is what you expect; weather is what you get” Climatic elements are the same as weather elements except that the former is the average value Weather and climate have direct influence on agriculture, transportation and human life

What is Climate? Changes in weather and climatic elements are controlled by certain attributes of the earth surface called weather or climate controls

Weather and Climate Controls
Weather and climate elements like: - Temperature - Pressure - Wind - Humidity - Precipitation change over time and space Certain attributes of the earth surface called weather or climate controls cause these changes to occur

What is Climate? Weather and climate controls include: - Latitude - Land and Water - Atmospheric Circulation - General Circulation of Oceans - Altitude - Topographic Barrier - Storms - Earth’s Rotation

Major Weather & Climatic Elements and Their Controls
Temperature Latitude Pressure Distribution of land and water Wind General circulation of atmosphere, land & water Moisture Content General circulation Elevation Distance from the sea Storms Topographic barriers

Weather & Climate Control: Latitude
Latitude controls temperature because it determines the amount of solar energy received at a place Latitude does that through its direct influence on: - solar altitude - length of daylight

Solar Altitude and Solar Energy

Solar altitude or the angle of sun’s rays is closely related to latitude Low latitudes receive higher solar energy because of their relatively higher solar altitude Length of daylight is also closely related to latitude with more solar energy receipt on longer summer days (at the poles)

Lower latitudes (tropics) receive more solar energy because sun’s rays are more direct Higher latitudes receive less solar energy or more loss of energy because: - sun’s rays are more oblique - of atmospheric obstruction of oblique sun’s rays traveling longer distances through the atmosphere

Latitude, Angle of Incidence and Atmospheric Obstruction

Weather & Climate Control: Land and Water
Land and water tend to control the temperature and moisture content (humidity & precipitation) of a place Water bodies impose milder and a fairly uniform temperature regime on their surroundings (maritime influence) Water has higher specific heat (5x) than land

Continentality and Maritime Effects on Daily Temperature Patterns

Whereas, Land mass imposes a highly variable temperature regime on its surrounding (continentality effect) For example, land heats up more rapidly in summer to produce high summer temperatures and cools off very quickly in winter to produce low winter temperatures

Water bodies are major sources of moisture in the atmosphere Hence maritime areas are more humid, while continental land interiors tend to be drier

Weather & Climate Control: Atmospheric Circulation
Atmospheric circulation controls temperature and moisture content of a place The movement of air masses re-distribute atmospheric moisture and heat For example, cold Canadian air mass causes temperature to plummet in Edwardsville

Weather & Climate Control: Atmospheric Circulation
Whereas, warm tropical air mass from Gulf of Mexico raises the temperature Cold air mass is relatively drier & tends to bring dry conditions to an area Warm tropical air mass with plenty of moisture brings precipitation to an area

Weather & Climate Control: General Circulation of the Oceans
Ocean currents help in the meridonal transfer of heat Warm ocean currents transfer heat to the poles Cold currents transfer cool water towards the equator

Ocean Currents

Cold ocean currents are commonly found along the west coast of continents and tend to control the weather and climates of the adjoining coastal areas For example, Cold Humboldt is the cause of the adjoining Peruvian desert climate

and Cold Benguela current is the cause of the adjoining Kalahari desert Warm currents are common along the east coast of continents and they are often associated with moister conditions

Weather & Climate Control: Altitude
Temperature, Pressure and moisture conditions are partially controlled by elevation In general, temperature, pressure and moisture tend to decrease with altitude

Weather & Climate Control: Topographic Barrier
Topographic barriers like mountains have blocking and diverting effects on weather and climate Windward sides of mountains tend to receive more precipitation than expected due to their orographic effects (western slope California mountains)

Weather & Climate Control: Topographic Barrier
Whereas, The leeward side of the mountain receives little or no rain because of rain shadow effect (e.g. Nevada desert) In temperate regions, south facing slopes receive more sunlight than north facing slopes

Weather & Climate Control: Storms
Each type of storm imposes different weather conditions For example, hurricanes, tornadoes, thunderstorms, etc produce different weather conditions

Weather & Climate Control: Earth’s Rotation
Earth’s rotation imposes coriolis effect on the flow path of air and water For example, coriolis effects causes wind to: - flow from the east in the tropics - from the west in temperate latitudes

Weather & Climate Control: Earth’s Rotation
NE trade winds brings the harmattan dusty and dry conditions to most of West Africa in December through March

Review Questions for Topic 3

1) The main surface currents in the major ocean basins assist in the heat transfer around the world by moving warm water from the Northern Hemisphere to the Southern Hemisphere. cool water from the poles to the tropics. warm water from the poles to the tropics. cool water from the tropics to the poles. warm water from the Southern Hemisphere to the Northern Hemisphere. Figure 3-18

1) The main surface currents in the major ocean basins assist in the heat transfer around the world by moving warm water from the Northern Hemisphere to the Southern Hemisphere. cool water from the poles to the tropics. warm water from the poles to the tropics. cool water from the tropics to the poles. warm water from the Southern Hemisphere to the Northern Hemisphere. Level of Difficulty: 2 Text Reference: Weather and Climate Geography Standard: 7 Blooms Taxonomy: Skills Figure 3-18 Explanation: Northerly ocean currents from the poles to the tropics transport cooler water from higher latitudes to lower latitudes.

2) An example of climate (versus weather) for a given area is
the air temperature reached 78°F today. rain showers are predicted for next Saturday. the record high temperature is 122°F. the average rainfall in April is 15 inches. thunderstorms occurred last Mother’s day.

2) An example of climate (versus weather) for a given area is
the air temperature reached 78°F today. rain showers are predicted for next Saturday. the record high temperature is 122°F. the average rainfall in April is 15 inches. thunderstorms occurred last Mother’s day. Level of Difficulty: 2 Text Reference: Weather and Climate Geography Standard: 4 Blooms Taxonomy: Skills Explanation: Climate describes weather conditions over a long period. So, an average weather condition over a span of many months would be a climate condition

3) Temperature decreases with increasing elevation in which thermal atmospheric layers?
Troposphere and stratosphere Thermosphere and mesosphere Troposphere and mesosphere Troposphere only Stratosphere and thermosphere

3) Temperature decreases with increasing elevation in which thermal atmospheric layers?
Troposphere and stratosphere Thermosphere and mesosphere Troposphere and mesosphere Troposphere only Stratosphere and thermosphere Level of Difficulty: 3 Text Reference: Vertical Structure of the Atmosphere Geography Standard: Blooms Taxonomy: Identification Figure 3-5 Explanation: In Figure 3-5, we see that temperature values decrease as you ascend in the image. Through the remaining layers, temperature increases with height.

4) _______ is the most plentiful variable gas in the atmosphere
4) _______ is the most plentiful variable gas in the atmosphere However, it varies in location, not in time. Nitrogen Ozone Carbon dioxide Oxygen Water vapor

4) _______ is the most plentiful variable gas in the atmosphere
4) _______ is the most plentiful variable gas in the atmosphere However, it varies in location, not in time. Nitrogen Ozone Carbon dioxide Oxygen Water vapor Level of Difficulty: 2 Text Reference: Composition of the Atmosphere Geography Standard: 7 Blooms Taxonomy: Knowledge Explanation: Water vapor in the atmosphere is highly variable, falling out as precipitation and being replenished by water sources. Its composition can vary from 0-4% of the total atmosphere.

5) Oxygen accounts for what proportion of the of the volume of gases in the atmosphere?
21% 78% 0.037% 1-4% 0.9% Figure 3-1

5) Oxygen accounts for what proportion of the of the volume of gases in the atmosphere?
21% 78% 0.037% 1-4% 0.9% Level of Difficulty: 2 Text Reference: Composition of the Atmosphere Geography Standard: 7 Blooms Taxonomy: Knowledge Figure 3-1 Explanation: While oxygen is the most important element for life, it makes up a relatively small percentage of the atmosphere when compared to nitrogen.

6) If a wind of 55 mph were subjected to a Coriolis force that is double what exists on Earth, what would its new speed be? 110 mph 27.5 mph 45 mph 0 mph 55 mph Figure 3-22

6) If a wind of 55 mph were subjected to a Coriolis force that is double what exists on Earth, what would its new speed be? 110 mph 27.5 mph 45 mph 0 mph 55 mph Level of Difficulty: 4 Text Reference: Weather and Climate Geography Standard: 7 Blooms Taxonomy: Knowledge Figure 3-22 Explanation: The Coriolis force affects the direction of motion, but not the speed. Doubling the Coriolis force will not affect the speed of the wind.

7) The aurora borealis typically occurs in
the homosphere. the troposphere. the ionosphere. the stratosphere. the mesosphere. Figure 3-10

7) The aurora borealis typically occurs in
the homosphere. the troposphere. the ionosphere. the stratosphere. the mesosphere. Level of Difficulty: 2 Text Reference: Vertical Structure of the Atmosphere Geography Standard: 7 Blooms Taxonomy: Knowledge Figure 3-10 Explanation: In the ionosphere, charged particles interacting with ultraviolet solar Radiation cause these particles to glow, forming the aurora phenomena.

8) Which of the following is an example of a secondary pollutant?
Carbon monoxide Carbon dioxide Particulates Smog CFCs Figure 3-15

8) Which of the following is an example of a secondary pollutant?
Carbon monoxide Carbon dioxide Particulates Smog CFCs Level of Difficulty: 3 Text Reference: Human-Induced Atmospheric Change Geography Standard: 7 Blooms Taxonomy: Knowledge Figure 3-15 Explanation: Secondary pollutants form as a result of a process from a primary pollutant. Smog forms when smoke mixes with fog, so it is a secondary pollutant.

9) Ozone is depleted by CFCs
9) Ozone is depleted by CFCs. What is the primary atom in the CFC molecule that is responsible for ozone depletion? Oxygen Fluoride Fluorine Chloride Chlorine

9) Ozone is depleted by CFCs
9) Ozone is depleted by CFCs. What is the primary atom in the CFC molecule that is responsible for ozone depletion? Oxygen Fluoride Fluorine Cchloride Chlorine Level of Difficulty: 4 Text Reference: Human-Induced Atmospheric Change Geography Standard: 7 Blooms Taxonomy: Skills Figure 3-12 Explanation: The chlorine atom in a CFC molecule attracts oxygen atoms from ozone, causing the ozone molecule to break into a regular oxygen molecule, resulting in ozone depletion.

10) Los Angeles, California and Dallas, Texas have vastly different climates, despite existing at the same latitude. What causes the climate difference? Proximity to a desert Sun is more directly overhead in Dallas Los Angeles is near mountains Dallas is in the Plains Dallas is continental; Los Angeles is maritime.

10) Los Angeles, California and Dallas, Texas have vastly different climates, despite existing at the same latitude. What causes the climate difference? Proximity to a desert Sun is more directly overhead in Dallas Los Angeles is near mountains Dallas is in the Plains Dallas is continental; Los Angeles is maritime. Level of Difficulty: 2 Text Reference: Weather and Climate Geography Standard: 4 Blooms Taxonomy: Skills Explanation: LA’s proximity to water allows for a less variable climate in terms of temperature. In general, maritime regions have a less volatile climate than continental regions.

Topic 3: Introduction to Earth’s Atmosphere

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