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Weather and Climate


Introduction to the Atmosphere Dr. R. B. Schultz – PowerPoint PPT presentation

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Title: Weather and Climate

Introduction to the Atmosphere
Dr. R. B. Schultz
Weather and Climate
  • Weather refers to the state of the atmosphere at
    a given time and place. It is constantly
    changing, sometimes from hour to hour and other
    times from day to day.
  • Climate is an aggregate of weather conditions,
    the sum of all statistical weather information
    that helps describe a place or region.
  • The nature of both weather and climate is
    expressed in terms of the same basic elements,
    those quantities or properties measured

Elements of Weather
  • The most important elements are
  • (1) air temperature,
  • (2) humidity,
  • (3) type and amount of cloudiness,
  • (4) type and amount of precipitation,
  • (5) air pressure, and
  • (6) the speed and direction of the wind.

A Typical Weather Map
The Relevance of Weather Events
Catastrophic Events and Associated Deaths
Earths Spheres
  • Earth's four spheres include
  • the atmosphere (gaseous envelope),
  • the lithosphere (solid Earth),
  • the hydrosphere (water portion), and
  • the biosphere (life).
  • Each sphere is composed of many interrelated
    parts and is intertwined with all other spheres.
    The energy exchanges that continually occur
    between the atmosphere and Earth's surface, and
    between the atmosphere and space, produce the
    effects we call weather.

Earths Hydrosphere
  • A system is a group of interacting or
    interdependent parts that form a complex whole.
  • The Earth System involves the intricate and
    continuous interaction between the lithosphere,
    hydrosphere, atmosphere, and biosphere.
  • The two primary sources of the energy that power
    this system are
  • (1) solar energy that drives the external
    processes that occur at, or above, Earth's
    surface, and
  • (2) Earth's interior, heat remaining from when
    the planet formed and heat that is continuously
    generated by radioactive decay.

Our Air
  • Air is a mixture of many discrete gases and its
    composition varies from time to time and place to
  • After water vapor, dust, and other variable
    components are removed, two gases, nitrogen and
    oxygen, make up 99 percent of the volume of the
    remaining clean, dry air.
  • Carbon dioxide, although present in only minute
    amounts (0.036 percent), is thought to be an
    efficient absorber of energy emitted by Earth and
    thus, influences the heating of the atmosphere.
  • Because of the rising level of carbon dioxide in
    the atmosphere during the past century (since the
    Industrial Revolution) attributed to the burning
    of ever increasing quantities of fossil fuels,
    many scientists believe that a warming of the
    lower atmosphere will trigger global climate
  • However, we will explore new, more scientific
    conceptions of the Global Warming theory in
    this course.

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Variable Air Components
  • The variable components of air include
  • water vapor,
  • dust particles, and
  • ozone.
  • Like carbon dioxide, water vapor absorbs heat
    given off by Earth as well as some solar energy.
    When water vapor changes from one state to
    another, it absorbs or releases heat.

Latent Heat and Aerosols
  • In the atmosphere, water vapor transports this
    latent ("hidden") heat from one region to
    another, and it is the energy source that helps
    drive many storms.
  • Aerosols (tiny solid and liquid particles) are
    meteorologically important because these often
    invisible particles act as surfaces on which
    water can condense and are also absorbers and
    reflectors of incoming solar radiation.

  • Ozone, a form of oxygen that combines three
    oxygen atoms into each molecule (O3), is an
    important gas concentrated in the 10 to 50
    kilometer height in the atmosphere that absorbs
    the potentially harmful ultraviolet (UV)
    radiation from the Sun.
  • Over the past half century, people have placed
    Earth's ozone layer in jeopardy by polluting the
    atmosphere with chlorofluorocarbons (CFCs) which
    remove some of the gas.
  • Ozone concentrations take an especially sharp
    drop over Antarctica during the Southern
    Hemisphere spring (September and October).

Ozone (cont.)
  • Furthermore, scientists have also discovered a
    similar but smaller ozone thinning near the North
    Pole during spring and early summer.
  • Because ultraviolet radiation is known to produce
    skin cancer, ozone depletion seriously affects
    human health, especially among fair-skinned
    people and those who spend considerable time in
    the Sun.
  • In late 1987, the Montreal Protocol, which
    represents a positive international response to
    the ozone problem, was concluded under the
    auspices of the United Nations.

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Investigating the Atmosphere
  • Balloons play a significant role in the
    systematic investigation of the atmosphere by
    carrying radiosondes (lightweight packages of
    instruments that send back data on temperature,
    pressure, and relative humidity) into the lower
  • Rockets, airplanes, satellites, and weather radar
    are also among the methods used to study the

Atmospheric Boundary?
  • No sharp boundary to the upper atmosphere exists.
    The atmosphere simply thins as you travel away
    from Earth until there are too few gas molecules
    to detect.
  • The change that occurs in atmospheric pressure
    (the weight of the air above) helps understand
    the vertical extent of the atmosphere
  • One-half of the atmosphere lies below an
    altitude of 5.6 kilometers (3.5 miles), and
  • 90 percent lies below 16 kilometers (10 miles).
  • However, traces of the atmosphere extent for
    thousands of kilometers beyond Earth's surface.

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Layers of Our Atmosphere
  • Atmospheric temperature drops with increasing
    height above Earth's surface. Using temperature
    as the basis, the atmosphere is divided into four
  • The temperature decrease in the troposphere, the
    bottom layer in which we live, is called the
    environmental lapse rate.
  • Its average value is 6.5C per kilometer, a
    figure known as the normal lapse rate. The
    environmental lapse rate is not a constant and
    must be regularly measured using radiosondes.

Temperature Inversion
  • A temperature inversion, where temperatures
    increase with height, is sometimes observed in
    shallow layers in the troposphere.
  • The thickness of the troposphere is generally
    greater in the tropics than in polar regions.
  • Essentially all important weather phenomena occur
    in the troposphere.

The Stratosphere
  • Beyond the troposphere lies the stratosphere
  • The boundary between the troposphere and
    stratosphere is known as the tropopause.
  • In the stratosphere, the temperature at first
    remains constant to a height of about 20
    kilometers (12 miles) before it begins a sharp
    increase due to the absorption of ultraviolet
    radiation from the Sun by ozone.

Mesosphere and Thermosphere
  • The temperatures continue to increase until the
    stratopause is encountered at a height of about
    50 kilometers (30 miles).
  • In the mesosphere, the third layer, temperatures
    again decrease with height until the mesopause,
    some 80 kilometers (50 miles) above the surface.
  • The fourth layer, the thermosphere, with no
    well-defined upper limit, consists of extremely
    rarefied air that extends outward from the

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Key Terminology Climate Temperature
inversion Atmosphere Troposphere Hydrosphere
Stratosphere Biosphere Radiosondes Mesosphere A
ir Thermosphere Montreal
Protocol Homosphere Ozone Stratopause
Aerosols Mesopause Carbon
Cycle Tropopause System Heterosphere Weath
er Heterospheric gases Lithosphere Iono
sphere Environmental lapse rate Aurora
borealis Aurora australis