Download Class #1: Introduction, Energy

Class #1: Introduction, Energy
Chapters 1 and 2
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Chapter 1
The Earth and Its Atmosphere
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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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Chapter 2
Energy: Warming the earth and
Atmosphere
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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)
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Fig. 2-3, p. 33
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
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Table 2-1, p. 32
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Table 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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Fig. 2-9, p. 39
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Fig. 2-10, p. 39
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Fig. 3, p. 40
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Fig. 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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Fig. 2-12, p. 43
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Fig. 2-12, p. 43
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Fig. 2-12, p. 43
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 .
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Table 2-3, p. 48
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Fig. 2-16, p. 48
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Fig. 2-17, p. 49
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70 Art
Fig. 2-17, p. 49