class #1: introduction, energy

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Class #1: Introduction, Energy

Chapters 1 and 2

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The Earth and Its Atmosphere

Chapter 1

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Overview of the Earth’s Atmosphere

• The atmosphere is a delicate life giving blanket of air surrounding the Earth.

• Without the atmosphere the Earth would not have lakes or oceans.

• Radiant energy from the sun energizes the atmosphere driving day to day weather.

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Overview of the Earth’s Atmosphere

• Composition– 99% of the atmosphere is within 30km of the

Earth’s surface– N2 78% and O2 21%– The percentages represent a constant amount of

gas but cycles of destruction and production are constantly maintaining this amount.

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Overview of the Earth’s Atmosphere

• Composition– Water a variable gas following the hydrologic

cycle.– Carbon dioxide has risen in recent years and is an

important greenhouse gas.– Other greenhouse gases exist beyond carbon

dioxide.

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Overview of the Earth’s Atmosphere

• Special Topic: A Breath of Fresh Air– 1 breath of air = 1022 molecules– 1022 stars in the universe

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Overview of the Earth’s Atmosphere

• The Early Atmosphere– The Earth’s first atmosphere was composed mostly of

hydrogen and helium.– The atmosphere evolved due to outgassing of CO2 and

H2O from the cooling center of the Earth causing rain and eventually lakes and oceans.

– Lakes and oceans acted as a sink, absorbing CO2 from atmosphere.

– Plants evolved producing oxygen to form our current atmosphere several 100 million ybp.

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Vertical Structure of the Atmosphere

• Air Pressure and Air Density– Weight = mass x gravity– Density = mass/volume– Pressure = force/area– At the Earth’s surface the pressure of the atmosphere

is 14.7 lbs/in2 . – Standard sea level pressure is1013.25 mb = 1013.25

hPa = 29.92 in Hg– Atmospheric pressure decreases with an increase in

height.

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Vertical Structure of the Atmosphere

• Layers of the Atmosphere– Lapse rate = change in temperature with a change

in height– Isothermal environment = no change in

temperature with height– Inversion layer = change in the sign of the lapse

rate

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Vertical Structure of the Atmosphere

• Layers of the Atmosphere– Troposphere: decrease in temperature, day to day

weather, tropopause– Stratosphere: increase in temperature, ozone,

stratopause– Mesosphere: decrease in temperature,

mesopause– Thermosphere: increase in temperature, suns

strongest radiation

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Vertical Structure of the Atmosphere

• Special Topic: The Atmospheres of Other Planets– Each planet’s atmosphere is unique in terms of

temperature and composition.

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Vertical Structure of the Atmosphere

• Observation: Radiosonde– Weather balloon– Instrument and transmitter– Air temperature, humidity, pressure

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Vertical Structure of the Atmosphere

• The Ionosphere– Not a true layer but an electrified region – Ions = molecule with an additional or minus an

electron– Exists at the top of the atmosphere in the

thermosphere– F,E,D layer– Sun light creates layers, D disappears at night and

less interference with AM radio transmissions.

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Weather and Climate

• Weather: short term air temperature, air pressure, humidity, clouds, precipitation, visibility, and wind

• Climate: long term patterns and average weather; not just magnitude but also frequency

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Weather & Climate

• Meteorology– Study of the atmosphere and its phenomena– Aristotle 340 B.C. Meterologica, meteoros: high in

air– 1843 telegraph– 1920s air masses– 1940s upper air– 1950s radar and computers– 1960s satellite

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Weather & Climate

• Satellite’s View– Geostationary satellite– Meridians measure longitude (W-E)– Parallels measure latitude (N-S)– Weather maps: pressure cells, fronts, surface

stations

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Weather & Climate

• Weather and Climate in Our Lives– Two general reasons for studying how weather

and climate impacts our lives: economic efficiency and public safety.

– Clothing– Crops– Utilities– Extreme cold and heat– Tornados and hurricanes

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Weather & Climate

• Special Topic: Meteorologist– Any person with a college degree in meteorology

or atmospheric science; not just the TV weather person

– Half of 9000 meteorologists employed by the US National Weather Service

– Researchers and operational meteorologists

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Energy: Warming the earth and Atmosphere

Chapter 2

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Energy, Temperature, & Heat

• Energy is the ability to do work (push, pull, lift) on some form of matter.

• Potential energy is the potential for work (mass x gravity x height)

• Kinetic energy is energy of a moving object (half of mass x velocity squared)

• Temperature is the average speed of atoms and molecules

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Energy, Temperature, & Heat

• Which has more energy?– A lake or a cup of hot tea?

• Heat is the energy in the process of being transferred from one object to another because of a difference in temperature.

• Energy cannot be destroyed or created; First Law of Thermodynamics

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Temperature Scales

• Fahrenheit: 32 freeze, 212 boil• Celsius: 0 freeze, 100 boil• Kelvin: absolute; 0K = -273°C

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Specific Heat

• Heat capacity is the heat energy absorbed to raise a substance to a given temperature

• Specific hear is the heat capacity divided by mass or the amount of energy required to raise one gram of a substance 1°C

• High specific heat equates to slow warming and vice versa

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Latent Heat

Change of state or phase change represents change between solid, gas, and liquid.

Latent heat is the energy involved in the change of state.

Ice to vapor: absorb energy, cool environment (melt, evaporation, sublimation)

Vapor to ice: release energy, heat environment (freeze, condense, deposition)

Class #1 July 7, 2010 37Fig. 2-3, p. 33

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Heat Transfer in the Atmosphere

• Conduction: transfer heat from one molecule to another in a substance– Energy travels from hot to cold– Air a poor conductor, metal a good conductor

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Heat Transfer in the Atmosphere

• Special Topic: Sunbeam– Energy from sunlight on a lake can undergo many

transformations and help provide the moving force for many natural and human-made processes.

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Heat Transfer in the Atmosphere

• Convection: transfer of heat by the mass movement of a fluid (water or air)

• Convection circulation: warm air expands and rises then cools and sinks; thermal cell

Class #1 July 7, 2010 42Table 2-1, p. 32

Class #1 July 7, 2010 43Table 2-2, p. 34

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Heat Transfer in the Atmosphere

• Special Topic: Rising and Sinking– As air rises part of it s energy is lost as it expands

and cools and when the air sinks it is compressed and the energy of molecules increase causing temperature to increase.

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Radiation

• Energy from the sun travels through the space and the atmosphere in the form of a wave (electromagnetic waves) and is called radiation.

• Radiation and Temperature– All objects with a temperature greater than 0K

radiate energy.– As temperature of an object increases, the more

total radiation that is emitted by an object (Stefan Boltzmann Constant).

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Class #1 July 7, 2010 48Fig. 2-9, p. 39

Class #1 July 7, 2010 49Fig. 2-10, p. 39

Class #1 July 7, 2010 50Fig. 3, p. 40

Class #1 July 7, 2010 51Fig. 4, p. 41

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Radiation

• Radiation of the Sun and Earth– Sun 6000k emits radiation, electromagnetic

spectrum– Shortwave radiation (high energy) from the Sun– Longwave radiation (low energy) from the Earth

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Radiation

• Environmental Issue: Sunburn– UV index is a weather forecast product that

indicates the potential for sun burn due to high energy or short wavelengths emitted by the sun.

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Balancing Act

• If the Earth is radiating energy all the time, why is it not very cold?– Radiative equilibrium• Absorb > emit = warm• Emit > absorb = cool

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Selective Absorbers

• Good absorbers are good emitters at a particular wavelength and vice versa.

• Greenhouse effect: the atmosphere selectively absorbs infrared radiation from the Earth’s surface but acts as a window and transmits shortwave radiation

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Class #1 July 7, 2010 58Fig. 2-12, p. 43

Class #1 July 7, 2010 59Fig. 2-12, p. 43

Class #1 July 7, 2010 60Fig. 2-12, p. 43

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Greenhouse Enhancement

• Global warming is occurring due to an increase in greenhouse gases– Carbon dioxide– Methane– Nitrogen Oxide– Chlorofluorocarbons

• Positive feedbacks continue the warming trend.• Negative feedbacks decrease warming.

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Incoming Solar Radiation

• Conduction, convection, and infrared radiation warm the atmosphere from below, not sunlight or insolation from above.– Scattering – Reflection, albedo

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Incoming Solar Radiation

• Observation: Blue skies, red skies, and white clouds– Selective scattering of incoming solar radiation

causes reflectance in portion of the electromagnetic spectrum that correspond with the colors our eyes detect.

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Annual Energy Balance

• 50% of insolation reaches the Earth’s surface.• Earth absorbs 147 units, radiates 117 units, 30

unit surplus, warm.• Atmosphere absorbs 130 units, radiates 160

units, 30 unit deficit, cool.• Tropics have a surplus of energy .

Class #1 July 7, 2010 67Table 2-3, p. 48

Class #1 July 7, 2010 68Fig. 2-16, p. 48

Class #1 July 7, 2010 69Fig. 2-17, p. 49

Class #1 July 7, 2010 70Stepped Art

Fig. 2-17, p. 49