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

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

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%

Properties / Properties / Structure of the Structure of the

AtmosphereAtmosphere

• 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

Properties / Properties / Structure of the Structure of the

AtmosphereAtmosphere

• 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

As air compresses (sinks) pressure

increases andtemperature

increases

As air expands (rising) pressure decreases and temperature decreases

25 oC

20 oC

15 oC

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 °C

-2.5 °C

-108 °C

KM

165,000 feet

Temperature distribution

-108 °C

-56.5 °C

-2.5 °C

EXOSPHERE

Starts 500 to 800 km up

6 to 30 miles

MESOPAUSE

STRATOPAUSE

TROPOPAUSE

IONOSPHERE

80km to 400km

°C

Humidity and Dew pointHumidity 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.

• 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.

• 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.

Pressure:

Pressure, Pressure, Density & & Altimeter settings Altimeter settings

500 feet1000 feet

Sea level29.9229.92

29.4229.92

28.9229.92

18000 feet

34000 feet 7.4029.92

14.9029.92

14.9029.92

Eg. Actual pressure Pressure setting

Defining the Standard AtmosphereDefining the Standard Atmosphere

• 29.92”Hg (1013.2 mb) @ sea level

• 15° C @ sea level

• 1.98° C per 1,000 feet

• 1”Hg = 1,000 feet (varies with height)

• 1 mb = 30 feet

• Air is presumed perfectly dry for standard

Low PressureLow 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

Buys Ballot’s LawBuys Ballot’s 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 !!!

High PressureHigh 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

WindWind• The heating of the earth’s 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.

PRESSURE GRADIENTPRESSURE GRADIENT

HIGHHIGH

LOWLOW

22ndnd low low

TROUGHTROUGH

COLCOL

RIDGERIDGE

1000 +/-1000 +/-

WINDWIND

Gusts and SquallsGusts 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

cooling land water

Land Breeze

Wind

Sea Breeze

warming land

Wind

water

FUNNEL EFFECTFUNNEL EFFECT

Anabatic (day)

Katabatic (night)Chinooks

Valley Breezes

KATABATIC WINDKATABATIC WIND

ANABATIC WINDANABATIC WIND

WIND vs TURBULENCEWIND vs TURBULENCE

STRATUSSTRATUS

CUMULUSCUMULUS

• Stable vs. Unstable (Horizontal/Vertical)

• 2 main types - Stratus vs. Cumulus

• Heights of clouds give 4 families

- High

- Middle

- Low

- Vertical development

Clouds

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

CLOUD CLASSIFICATIONSCLOUD CLASSIFICATIONS