Atmospheric Variables

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Atmospheric Variables

• 11/16/2009

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Air Temperature

• Instrument used to measure
• Thermometer
• Units
• C, F, K
• How it is shown on a weather map
• Isotherms

• Important Information
• Solar radiation is the main source of heat energy
  for the atmosphere.
• The amount of solar radiation is affected by
• Hours of sunlight/day
• Reflection, refraction, and absorbtion

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Isotherms
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Air Pressure

• Instrument used to measure
• Barometer
• Units
• cm, inches, millibars
• How it is shown on a weather map
• Isobars, H and L pressure

• Important Information
• Affected by altitude, temperature, and moisture
  content.
• Warm air less dense low pressure
• Cold air more dense high pressure
• Dry air high pressure
• Moist air low pressure
• High altitude low pressure
• Pressure differences affects wind speed

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Moisture in the Air

• Instrument used to measure
• Hygrometer, psychrometer
• Units
• relative humidity
• C, F Dew point temperature
• How it is shown on a weather map
• Dew point temperature is shown on a station model

• Important Information
• Dew point temperature is the temperature at which
  air is saturated.
• Relative Humidity is the ratio of the amount of
  water vapor in the air to the maximum amount that
  it can hold at that temperature.
• Absolute humidity is the number of grams of water
  vapor in one cubic meter of air.

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Air Movement

• Instrument used to measure
• Anemometer (speed)
• Wind Vane (direction)
• Units
• Km/h, mi/h, knots
• N, E, S, W
• How it is shown on a weather map
• Isotachs or on a station model

• Important Information
• Wind ALWAYS blows from high pressure to low
  pressure and is influenced by the Coriolis
  Effect.
• In High pressure (anticyclone) winds blow out
  from the center and clockwise.
• In Low pressure (cyclone) winds blow toward the
  center and counterclockwise.

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Air Transparency

• How it is shown on a weather map
• a station model
• Visibility
• Horizontal distance the eye can see (mi)
• Cloud Cover
• Fraction/percentage of the sky that is obscured
  (covered) by clouds

• Cloud Ceiling
• The base height (bottom) of the cloud layers.
• Measure with a ceilometer which uses light pulses
  and photoelectric telescope.

Base height