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.

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