Meteorology Subject: ADVANCED AERONAUTICSSubject Code:AER 200 Faculty: Brian CARLICKDate:January 11, 2006

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

Atmosphere Composition and Properties Atmosphere has weight –14.7 sea level or 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%

Properties / Structure of the Atmosphere Water Vapor is essential for weather –found in lower levels –responsible for clouds and precipitation H 2 O vapour (10) is lighter than O 2 (16) or N 2 (14) H 2 O content varies hour to hour, day to day, by season and by latitude Water content changes depending on temp & pressure

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

As air compresses (sinks) pressure increases and temperature increases As air expands (rising) pressure decreases and temperature decreases 25 o C 20 o C 15 o C

TROPOSPHERE TROPOPAUSE STRATOSPHERE STRATOPAUSE MESOSPHERE MESOPAUSE THERMOSPHERE 3000 ° IONOSPHERE Vertical Structure SEA LEVEL

Vertical Structure ,000 feet 36,089 feet °C -2.5 °C -108 °C KM 165,000 feet Temperature distribution

-108 °C °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 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, & Altimeter settings Pressure, Density & Altimeter settings 500 feet 1000 feet Sea level feet feet Eg. Actual pressure Pressure setting

Defining the Standard Atmosphere 29.92”Hg ( sea level 15° 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 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 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 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

Wind 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 GRADIENT

HIGH LOW 2 nd low TROUGH COL RIDGE /- WIND

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

cooling land water Land Breeze Wind Sea Breeze warming land Wind water

FUNNEL EFFECT

Anabatic (day) Katabatic (night) Chinooks Valley Breezes

KATABATIC WIND

ANABATIC WIND

WIND vs TURBULENCE

STRATUS

CUMULUS

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

GROUPTOPS 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 CLASSIFICATIONS