View
218
Download
0
Embed Size (px)
Citation preview
Meteorology 2Meteorology 2
five slide review firstfive slide review first
Quiz Wednesday, 18thQuiz Wednesday, 18th
Atmosphere CompositionAtmosphere Compositionand Propertiesand Properties
Atmosphere has weight– 14.7 psi @ 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% 0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Oxygen 21%
Water/Other 1%
Nitrogen 78%
TROPOSPHERE
TROPOPAUSE
STRATOSPHERESTRATOPAUSE
MESOSPHERE
MESOPAUSE
THERMOSPHERE 3000 ° C @700km
IONOSPHERE
Vertical StructureVertical Structure
SEA LEVEL
Vertical StructureVertical Structure
-110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 500
10
20
30
40
50
60
70
80
90
100
110
120
275,000 feet
36,089 feet-56.5
-2.5
-108
KM
165,000 feet
HIGHHIGH
LOWLOW
22ndnd low low
TROUGHTROUGH
COLCOL
RIDGERIDGE
1000 +/-1000 +/-
WINDWIND
Pressure AreasPressure 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”
H L
– LAPSE RATES– RADIATION – TEMPERATURE– TURBULENCE– AIR MASSES– FRONTS– WATER DROPLETS
LAPSE LAPSE RATESRATES
LAPSE RATESLAPSE 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
RADIATED AS LONG WAVE
SHORT Pg 2-5
Radiation Absorption & WindowsRadiation Absorption & Windows
Pg 2-4
Radio transmissions less than about 10 metres wavelength (VHF, Radio transmissions less than about 10 metres wavelength (VHF, UHF, RADAR) are refracted downward by the atmosphere, roughly a third UHF, RADAR) are refracted downward by the atmosphere, roughly a third beyond the distance to the visual horizon. beyond the distance to the visual horizon.
A strong inversion and a significant humidity decrease with height A strong inversion and a significant humidity decrease with height can cause greater refraction. Such a layer is called a radio duct. It is 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 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 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 several further bounces. This is known as anomalous propagation. It is not relatednot related to the Ionosphere and its influence on radio waves. to the Ionosphere and its influence on radio waves.
Radio HorizonRadio Horizon
Page 4-10 Air Command Weather Manual
STRATOSPHEREDEEP OVER POLES MAY BE THIN OVER EQUATOR
STRATOPAUSE
MESOSPHERE
MESOPAUSE
THERMOSPHERE
IONOSPHEREO2 H2 N2 fluoresce
SUN’S PARTICLESSUN’S PARTICLES and and UV RADIATIONUV RADIATION
SEA LEVEL
33000
165000 OZONOSPHERE ABSORBS UV
HENCE TEMP INCREASE HERE
O3 CORROSIVE & HARMFUL
275000 feet
65000
- 108
- 2.5
- 56.5
SEASONALSEASONAL HEATING HEATING
HEAT & IT’S MOVEMENTHEAT & IT’S 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)
AIR IS A HUGE AIR IS A HUGE TRANSPORTER TRANSPORTER OF HEAT BY OF HEAT BY VIRTUE OF THE VIRTUE OF THE MOISTURE MOISTURE EVAPORATED IN EVAPORATED IN IT AS WATER IT AS WATER VAPOUR. VAPOUR.
HEATING the TROPOSPHEREHEATING the TROPOSPHERE
AdvectionAdvection: : horizontal movement of horizontal movement of air. Cold air becomes warmed (infrared) air. Cold air becomes warmed (infrared)
by the ground as it moves over itby the ground as it moves over it
CHANGESCHANGES OF STATEOF STATE
ConvectionConvection: sun : sun (short (short
wave)wave) heats ground, heats ground, ground ground (longer wave)(longer wave)
heats the airheats the air
TurbulenceTurbulence: : vertical mixing of air vertical mixing of air
due to winds and due to winds and convectionconvection
MECHANICALMECHANICAL TURBULENCETURBULENCE
TURBULENCETURBULENCE
• 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)
CLOUD CLASSIFICATIONCLOUD CLASSIFICATION
• Turbulence related – stable or unstable• Rain - showers vs. steady• Four families of cloud as below
LOW CLOUDLOW CLOUD3,000 ASL3,000 ASL
MIDDLE CLOUDMIDDLE CLOUD7,000 ASL7,000 ASL
MIDDLE CLOUDMIDDLE CLOUD11,000 ASL11,000 ASL
HIGH CLOUDHIGH CLOUD30,000 ASL30,000 ASL
Turbulence LevelsTurbulence 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.
Mountain WavesMountain Waves
Cap clouds, Rotor clouds and Lenticular Clouds
Rapid pressure drop associated over crest of hill
L
L
R
C
Air MassesAir 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
Air Mass StabilityAir 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
Air Masses of North AmericaAir 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 30°N; 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
POLARPOLAR FRONTFRONT
FrontsFronts• 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.
The Cold FrontThe 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 Cb’s• Precipitation: showery in character, usually a narrow
band 50 n.m.
Cold Warm
Cold FrontCold Front
Cold FrontCold Front
The Warm FrontThe 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
ColdWarm
The Warm FrontThe Warm Front
WIND SHEAR @ WARM FRONTWIND SHEAR @ WARM FRONT
FRONTAL WAVEFRONTAL WAVE
FRONTSFRONTS
FRONTSFRONTS
Colder
Colder
Colder
Cold
Cold
Cold
Warm
Warm
Warm
OCCLUSION or Occluded Front
PrecipitationPrecipitation
• 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.
PrecipitationPrecipitation
.
PrecipitationPrecipitation
MOISTURE CONTENTMOISTURE CONTENT
@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.
+