Weather Theory - QT

Lesson Quicktakes cover the items that should be memorized from each of the wifiCFI Lessons. They do not cover all of the lesson details in-depth.


ATMOSPHERIC COMPOSITION

78% Nitrogen and 21% Oxygen.


TROPOSPHERE:

Where we live and fly (most of the time).

4-12 miles high over poles.

48,000 feet high over equator.

Temperature decreases 2C per 1,000’ of altitude gain.


TROPOPAUSE:

Thin layer above the troposphere.

Temperature remains fairly constant regardless of altitude.


GLOBAL CIRCULATION PATTERN:

Air at poles cools and sinks and then flows towards equator.

Air at equator heats and rises and then returns to poles.


CORIOLIS FORCE:

The spinning of the Earth deflects the airflow in the Circulation Pattern.

Northern Hemisphere = Air is deflected to the RIGHT.

Southern Hemisphere = Air is deflected to the LEFT.

Within 2,000’ of the ground = Friction slows speed of air movement and alters its direction.


STANDARD ATMOSPHERE:

Standard Pressure at Sea Level = 29.92.

Decreases 1 inch per 1,000’ of altitude gain.


Standard Temperature at Sea Level = 15c.

Decreases 2c per 1,000’ of altitude gain.


WIND AND CURRENTS:

Horizontally Moving Air = Wind.

Vertically Moving Air = Convection.

High Pressure Systems = Air flows clockwise, downward, and outward.

Low Pressure Systems = Air flows counterclockwise, inward, and upward.


WINDSHEAR:

A sudden and drastic change in wind direction or velocity over a short distance.

Low-Level Windshear = Windshear that occurs near the surface (very dangerous).


MICROBURSTS:

The most severe type of Windshear.

Lifespan = 5-15 minutes.

Downdrafts = Up to 6,000 FPM.

Headwind Losses = 30-90 knots.


ATMOSPHERIC STABILITY:

Stable Atmosphere = Resists vertical movement of air.

Poor visibility, little to no turbulence, showery precipitation.


Unstable Atmosphere = More vertical movement of air.

Better visibility, more turbulence, potential for hazardous storm weather.


INVERSIONS:

Occur when air temperature increases with an increase in altitude (up to a certain point, which is, the top of the inversion layer).


FOG TYPES:

Fog is just a cloud on the surface.

Radiation Fog = Clear nights with little to no wind present.

Advection Fog = Warm moist air moves over a cold surface. Winds up to 15 knots.

Upslope Fog = Moist air forced up sloping terrain. This moist air cools as it rises.

Steam Fog = Cold dry air moves over warmer water.

Ice Fog = Water vapor forms directly into ice crystals. Usually -25F or colder.


CLOUD FAMILIES:


FRONT TYPES:

Fronts are boundaries between 2 different air masses.

Warm Front = Warm air moves in and replaces cooler air.

Cold Front = Cold air moves in and replaces warmer air.

Stationary Front = Two fronts pushing against each other and not moving.

Occluded Front = Two fronts conjoining and moving together.


Front Symbols:


STAGES OF A THUNDERSTORM:

Cumulus Stage = Mostly updrafts. Storm is building.

Mature Stage = Updrafts and downdrafts. Precipitation begins to fall.

Dissipating Stage = Mostly downdrafts. Storm is dying out.


TYPES OF ICING:

Clear Ice = Clear in color. Mostly develops from large water droplets. Freezes as it runs back along the wing (like an icicle).


Rime Ice = Milky in color. Mostly develops from smaller water droplets. Freezes on impact with the wing.


Mixed Ice = Mixture of clear and rime ice.

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