Meteorology

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Meteorology

• Subject ADVANCED AERONAUTICS Subject
  Code AER 200
• Faculty Brian CARLICK Date January 11,
  2006

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• COMPOSITION AND STRUCTURE
• OF THE ATMOSPHERE
• PRESSURE
• STANDARD ATMOSPHERE
• TEMPERATURE
• MOISTURE
• STABILITY
• WINDS
• CLOUDS

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Atmosphere Compositionand Properties

• Atmosphere has weight
• 14.7 psi _at_ sea level or 1013.2 mb
• Half of it is below 18,000 feet
• No well defined upper surface but satellite drag
  data indicates
• some air at 1,000 miles
• Gases each contribute to
• atmospheric pressure
• Water vapour usually less than 1 but
  can be 3.5

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Properties / Structure of the Atmosphere

• Water Vapor is essential for weather
• found in lower levels
• responsible for clouds and precipitation
• H2O vapour (10) is lighter than O2 (16) or N2
  (14)
• H2O content varies hour to hour, day to day, by
  season and by latitude
• Water content changes depending on temp
  pressure

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Properties / Structure of the Atmosphere

• Air is a fluid
• Mobility, expansion compression
• Lifting agents can be Frontal, Thermal,
  Orographic, Mechanical
• Rising air is subjected to reducing pressure and
  expands and cools

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As air expands (rising) pressure decreases and
temperature decreases
15 oC
20 oC
As air compresses (sinks) pressure increases
andtemperature increases
25 oC
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Vertical Structure
THERMOSPHERE
3000 C _at_700km
IONOSPHERE
MESOPAUSE
MESOSPHERE
STRATOPAUSE
STRATOSPHERE
TROPOPAUSE
TROPOSPHERE
SEA LEVEL
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Vertical Structure
KM
-108 C
275,000 feet
Temperature distribution
-2.5 C
165,000 feet
-56.5 C
36,089 feet
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EXOSPHERE Starts 500 to 800 km up
IONOSPHERE 80km to 400km
Aurora
-108 C
MESOPAUSE
-2.5 C
STRATOPAUSE
6 to 30 miles
-56.5 C
TROPOPAUSE
C
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Humidity and Dew point

• Warm air can hold more moisture.
• The water vapor a volume of air can hold is
  governed by its temperature.
• Air is said to be saturated when it contains the
  maximum amount of water it can hold at that
  temperature.
• Dew point - the temperature to which unsaturated
  air must be cooled to become saturated.
• Relative Humidity - the ratio of actual water
  vapor present in the air to the amount which that
  volume of air would hold if saturated.
• When air is heated, without adding water, the
  relative humidity decreases.

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• The Thermosphere is important because it contains
  properties of mobility, and it has a capacity for
  expansion and contraction.
• Allows movement under it, ie. lows and highs
• The Thermosphere also contains the
• Ionosphere, which can affect radio waves.
• Jet Streams are found at the top of the
  troposphere, much lower than the thermosphere.
  They are higher at the equator and lower at the
  poles. They descend in winter and rise in summer.

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Pressure

• Is important for determining altitude
• Distribution determines winds (mobility).
• Is Force exerted by the air at that altitude
• Area
• Station pressure is the actual atmospheric
  pressure at the elevation of the observing
  station.
• MSL is used to compare the pressures of stations
  with different elevations.

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Pressure, Density Altimeter settings
14.90 29.92
Eg. Actual pressure Pressure setting
7.40 29.92
34000 feet
14.90 29.92
18000 feet
28.92 29.92
29.42 29.92
29.92 29.92
1000 feet
500 feet
Sea level
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Defining the Standard Atmosphere

• 29.92Hg (1013.2 mb) _at_ sea level
• 15 C _at_ sea level
• 1.98 C per 1,000 feet
• 1Hg 1,000 feet (varies with height)
• 1 mb 30 feet
• Air is presumed perfectly dry for standard

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Low Pressure

• Low or Cyclone is rising air
• Bad weather, poor visibility
• Stratus clouds, light winds
• Movement
• Summer 500 miles / day
• Winter 700 miles / day
• Winds
• Above 3000agl parallel to isobars
• Below 3000agl INTO the low
• Consistent day and night temperatures
• Low pressure is by comparison to surrounding
  areas
• Counterclockwise rotation in Northern hemisphere

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Buys Ballots Law

• Stand with the wind at your back.
• Stick out your left arm.
• Your fingers will point to the center of the low
  pressure area !!!

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High Pressure

• Anti-cyclone is descending air, compression
  occurs
• Clockwise circulation in Northern hemisphere
• Highs fill in Lows
• Surface winds blow outwards in a slow spiral
• Clear skies predominate
• Higher day temperatures, lower night temperatures
• Good visibility
• Cumulus type clouds
• Breezy

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Wind

• The heating of the earths surface is responsible
  for circulation. The sun heats the earth which
  then radiates the heat, heating the adjacent air
  at the surface.
• Upper winds flow parallel to isobars, with
• wind speed determined by the spacing.
• Surface winds are slower due to surface friction,
  and will blow in or out depending on the
  surrounding pressure.

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PRESSURE GRADIENT
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HIGHLOW2nd lowTROUGHCOLRIDGE1000
/-WIND
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Gusts and Squalls

• Gusts rapid, irregular fluctuation in velocity
  and direction. Peak 5 kt higher than 2 minute
  average
• Squalls longer in duration. 15 kt higher than
  mean speed and peak for 2 minutes

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Land Breeze
Wind
cooling land
water
Sea Breeze
Wind
warming land
water
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FUNNEL EFFECT
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Katabatic (night)
Chinooks
Anabatic (day)
Valley Breezes
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KATABATIC WIND
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ANABATIC WIND
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WIND vs TURBULENCE
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STRATUS
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CUMULUS
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Clouds

• Stable vs. Unstable (Horizontal/Vertical)
• 2 main types - Stratus vs. Cumulus
• Heights of clouds give 4 families
• - High
• - Middle
• - Low
• - Vertical development

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CLOUD CLASSIFICATIONS
GROUP TOPS 40,000 HIGH CLOUDS BASE 20,000 TOPS 20,000 MIDDLE CLOUDS BASE 6,500 TOPS 6,500 LOW CLOUDS BASE SURFACE CLOUDS OF VERTICAL DEVELOPMENT BASE 1,600 UP
TYPE CIRRUS CI CIRROSTRATUS CS CIRROCUMULUS CC ALTOSTRATUS AS ALTOCUMULUS AC ALTOCUMULUS CASTELLANUS ACC STRATUS ST NIMBO STRATUS NS STRATOCUMULUS SC STRATUS FRACTUS SF CUMULUS FRACTUS CF CUMULUS CU TOWERING CUMULUS TCU CUMULONIMBUS CB