Meteorology 2

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Meteorology 2
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five slide review first
Quiz Wednesday, 18th
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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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Vertical Structure
THERMOSPHERE
3000 C _at_700km
IONOSPHERE
MESOPAUSE
MESOSPHERE
STRATOPAUSE
STRATOSPHERE
TROPOPAUSE
TROPOSPHERE
SEA LEVEL
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Vertical Structure
KM
-108
275,000 feet
-2.5
165,000 feet
-56.5
36,089 feet
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HIGHLOW2nd lowTROUGHCOLRIDGE1000
/-WIND
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Pressure Areas

• Lows move at about 500 miles a day in the summer
  and faster, about 700 miles a day, in the winter.
• Flying from
• a HI to a LO
• LOOK
• OUT
• BELOW

L
H
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• LAPSE RATES
• RADIATION
• TEMPERATURE
• TURBULENCE
• AIR MASSES
• FRONTS
• WATER DROPLETS

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LAPSE RATES
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LAPSE RATES

• STANDARD LAPSE RATE 1.98OC
• DRY ADIABATIC LAPSE RATE 3OC
• SATURATED ADIABATIC LAPSE RATE 1.5OC
• SATURATED RANGE ACTUALLY 1.1OC TO 2.8OC
• STEEP LAPSE RATE
• SHALLOW LAPSE
• CONDITIONALLY UNSTABLE AIR DRY STABLE
• CONDITIONALLY UNSTABLE AIR WET - UNSTABLE
• POTENTIAL INSTABILITY AIR MASS ASCENT

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SHORT
Pg 2-5
RADIATED AS LONG WAVE
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Radiation Absorption Windows
Pg 2-4
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Radio Horizon

• Radio transmissions less than about 10 metres
  wavelength (VHF, UHF, RADAR) are refracted
  downward by the atmosphere, roughly a third
  beyond the distance to the visual horizon.
• A strong inversion and a significant humidity
  decrease with height can cause greater
  refraction. Such a layer is called a radio duct.
  It is typically 50 to 1,000 feet deep. The bend
  in the path is just enough for the wave to curve
  back to the surface, bounce off the earth, and
  continue on several further bounces. This is
  known as anomalous propagation. It is not
  related to the Ionosphere and its influence on
  radio waves.

Page 4-10 Air Command Weather Manual
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SUNS PARTICLES and UV RADIATION
THERMOSPHERE

Aurora
IONOSPHERE O2 H2 N2 fluoresce
- 108
MESOPAUSE
275000 feet
MESOSPHERE
- 2.5
STRATOPAUSE
165000
OZONOSPHERE ABSORBS UV HENCE TEMP INCREASE
HERE O3 CORROSIVE HARMFUL
STRATOSPHERE DEEP OVER POLES MAY BE THIN OVER
EQUATOR
65000
33000
- 56.5
SEA LEVEL
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SEASONAL HEATING
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HEAT ITS MOVEMENT

• The atmosphere is heated from below.
• Temperature increase decreases density.
• Advection horizontal movement of air. Cold air
  becomes warmed by the ground as it moves over it
• Convection sun heats ground, ground heats the
  air
• Turbulence vertical mixing of air due to winds
  and convection
• Compression air sinks, compresses and heats
  (Chinooks, highs)

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AIR IS A HUGE TRANSPORTER OF HEAT BY VIRTUE OF
THE MOISTURE EVAPORATED IN IT AS WATER VAPOUR.
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HEATING the TROPOSPHERE
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Advection horizontal movement of air. Cold air
becomes warmed (infrared) by the ground as it
moves over it
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CHANGES OF STATE
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Convection sun (short wave) heats ground,
ground (longer wave) heats the air
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Turbulence vertical mixing of air due to winds
and convection
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MECHANICAL TURBULENCE
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MECHANICAL TURBULENCE
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TURBULENCE

• Mechanical Friction between the air and ground
  causes eddies. Instability in the air aids in
  turbulence.
• Thermal Convection currents such as those found
  in storm clouds can be great enough to cause
  structural failure to some aircraft.
• Frontal Two opposing air masses produce
  turbulence in the frontal zone.
• Wind shear Any marked changes in wind with
  height produces local areas of turbulence.
• CAT Clear air turbulence (Jet streams)

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CLOUD CLASSIFICATION

• Turbulence related stable or unstable
• Rain - showers vs. steady
• Four families of cloud as below

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LOW CLOUD3,000 ASL
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MIDDLE CLOUD7,000 ASL
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MIDDLE CLOUD11,000 ASL
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HIGH CLOUD30,000 ASL
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Turbulence Levels

• Light slight changes in attitude, slight strain
  on seat belts.
• Moderate more intense, definite strain
• Severe large abrupt changes in altitude,
  attitude and airspeed. Occupants forced
  violently against seatbelts.

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Mountain Waves
L
C
L
R
Rapid pressure drop associated over crest of hill
Cap clouds, Rotor clouds and Lenticular Clouds
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Air Masses

• An air mass is a large section of the troposphere
  with uniform temperature and moisture in the
  horizontal.
• Weather in an air mass is determined by
• moisture content
• cooling process
• stability
• Formed over water Maritime
• Formed over land Continental

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Air Mass Stability

• Weather in an air mass is determined by
• moisture content saturated or unsaturated
  adiabatic lapse rate if cooled?
• cooling process various lift types
• stability
• Cold air mass usually unstable
• Warm air mass usually stable

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Air Masses of North America

• Continental Arctic Ca
• not in summer low water content warmed from
  below, strong winds produce turbulence heap
  clouds and snow showers rarely in B.C. except as
  a cold-air invasion
• (Continental Polar Cp)
• Maritime Arctic Ma
• starts as Ca that spends some time over the
  northern Pacific ocean moist and unstable at
  high altitudes stratocumulus and cumulus
  pe/sn/-shra Summer northern lakes affect air
  mass
• Maritime Polar Mp
• more time spent over Pacific ocean warmer in
  lower levels more stable than Ma orographic
  lifting makes rain west of mountains and dry east
  of mountains Summer Tsra/Cb
• Maritime Tropical Mt
• very warm and moist Gulf of Mexico, Caribbean
  south of 30N Winter rarely at surface N of
  Great lakes, but present at high altitudes
  unstable when Frontal lift sn/ra/zr/icing and
  turbulence FOG (east coast) Summer shra/tsra

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POLAR FRONT
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Fronts

• The transition zone between two air masses is
  called a front.
• Named by the movement of the cold air
• Cold Front that portion of the front where the
  cold air is advancing
• Warm Front that portion of the front where the
  cold air is retreating
• Stationary Front the cold air is neither
  advancing nor retreating.
• Occluded Fronts and Trowals trough of warm air
  aloft.

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The Cold Front

• Factors
• Moisture of the warm air mass
• stability of the warm air mass
• speed and steepness of the frontal surface
• Wind Veer, some gusts
• Temperature drops
• Visibility improves after passage
• Pressure approaching front, pressure will drop,
  then rise after passage
• Turbulence usually associated with Cbs
• Precipitation showery in character, usually a
  narrow band 50 n.m.

Cold
Warm
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Cold Front
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Cold Front
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The Warm Front

• Factors
• Moisture Degree of overrunning Stability
• Wind Veer
• Frontal Slope 1 in 150 to 1 in 200
• Temperature gradual rise
• Visibility low ceiling and low visibility fog
• Pressure drop, then rise
• Turbulence usually little
• Precipitation steady precipitation
• CI, CS, AS, NS

Warm
Cold
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The Warm Front
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WIND SHEAR _at_ WARM FRONT
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FRONTAL WAVE
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FRONTS
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FRONTS
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Warm
Colder
Cold
Warm
Colder
Cold
Warm
OCCLUSION or Occluded Front
Cold
Colder
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Precipitation

• Precipitation occurs when water droplets grow
  sufficiently in size and weight and then fall due
  to gravity.
• Showery precipitation Cumulus
• Steady precipitation Stratus
• Condensation Nuclei
• Smoke, sea salt, etc.

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Precipitation
.
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Precipitation
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MOISTURE CONTENT

_at_40OC one cubic metre of air can hold 50 grams of
water vapour. One M3 of air weighs about 1.35
kg. This represents about 3.5 by weight.