AOSC 200 Lesson 5

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AOSC 200Lesson 5
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Observing the Atmosphere

• There are several instruments that are used to
  measure the basic atmospheric variables/
• Temperature Thermometer
• Mercury
• Resistance
• Pressure Barometer
• Humidity psychrometer, dew point hygrometer
• Wind Speed - Anemometer
• Wind Direction Wind vane
• Precipitation Rain Gauge

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Max-min Thermometer
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Temperature Measurement

• Max-Min thermometer
• Resistance thermometer
• Remote measurement by observing thermal IR
  emissions.
• Clinical thermometer

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Fig. 5-3, p. 130
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Humidity Measurements

• Dew-point hygrometer.
• Uses a laser beam and a mirror. The mirror is
  cooled down, and when dew is formed on the
  mirror, the laser beam is scattered.
• Wet-bulb psychrometer. Two thermometers, one
  wrapped with a wet cloth. Air is passed over
  both, the wet bulb will show a lower temperature.
  Relative humidity obtained from pre-calculated
  tables.
• Remote measurements using Microwave wavelengths

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Mercury Barometer
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Fig. 5-4, p. 131
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Pressure Measurement

• Mercury barometer long tube sealed at one end
  and filled with mercury, with open end immersed
  in a bath of mercury. Closed end has vacuum above
  mercury column. Height of column measures the
  pressure.
• Aneroid barometer without liquid. Spiral thin
  wall cell which twists as the pressure changes.
  Not as accurate as the mercury barometer
• Electronic transistors whose resistance is
  sensitive to pressure.

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Fig. 5.4
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Wing Gauge
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Wind Measurement

• Anemometers measure wind speed
• Wind vanes measure wind direction
• Combination measures wind velocity
• Cup anemometers
• Propellers
• From space one can observe the speed with which
  clouds move

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Rain Gauge
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Tipping Rain Gauge
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Fig. 5-12, p. 139
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Radar Observations

• RAdio Detection And Ranging
• Pulse of radio waves is sent out from
  transmitter. Time it takes for the pulse to
  return gives the distance to the
  cloud/precipitation.
• The amount of the pulse that is scattered can be
  used to tell how much rain is falling.
• Doppler effect
• Doppler RADAR can detect wind speed
• Wind profiler

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Fig. 5.19
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Fig. 5.21a
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Fig. 5.21b
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Plot of boundary layer winds from the Fort Meade,
MD wind profiler during a high ozone episode
LLJ
LLJ
LLJ
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Geosynchronous Orbit
Fig. 5-13, p. 140
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Sun-synchronous (polar) orbit
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Satellite Observations

• Two principle orbits are used
• Sun-synchronous, aka polar orbiter, LEO
• Orbits in the sun-earth plane, crosses over the
  poles. NOAA LEO cross the equator at 2.00 pm and
  2.00 am each day. Each orbit takes about 90
  minutes
• Geosynchronous orbits around the earth always
  above the equator. Orbital period is 24 hours,
  i.e. it stays above the same point on the ground.

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Visible image from the GOES Satellite Aug 7, 2000
Fig. 5.14
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IR image from the GOES satellite, Aug 2, 2000
Fig. 5.15
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Water vapor image, August 7, 2000
Fig. 5.17
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Fig. 5.22