~ Aviation Management ~

Ch. 6 Notes [Private Pilot]

- Variations in altimeter settings between weather reporting points are primarily caused by the unequal heating of the earth's surface.

- Friction causes wind to shift directions when near the earth's surface.

- Convective circulation patterns associated with sea breezes are caused by cool, dense air moving inland from over the water.

- Stability of an airmass is decreased by warming from below.

- The actual lapse rate can be used to determine the stability of the atmosphere.

- A smooth, stable layer of air and a temperature increase with altitude are features of a temperature inversion. Visibility in an inversion is usually poor due to trapped pollutants. In addition, high humidity beneath a low-level temperature inversion can contribute to the formation of fog, haze, or low clouds.

- A surface-based temperature inversion is often produced by terrestrial radiation of clear, cool nights when the air is relatively calm.

- Every physical process of weather is accompanied by a heat exchange.

- Water vapor is added to the atmosphere by evaporation and sublimation.

- The amount of moisture in the air depends on air temperature.

- Dewpoint is the temperature to which air must be cooled to become saturated. 

- You can calculate cloud based by using: Temperature (F) - Dewpoint (F) divided by 4.4 (degrees F) all multiplied by 1,000.

- Frost forms when the temperature of the collecting surface is at or below the dewpoint of the surrounding air and the dewpoint is below freezing.

- If frost is not removed from the wings before flight, it may spoil the smooth airflow over the wings, decrease lift, and increase drag, preventing the aircraft from becoming airborne at normal takeoff speed.

- Clouds, fog, or dew always form when water vapor condenses.

- A small and decreasing temperature/dewpoint spread indicates conditions are favorable for the formation of fog.

- Clouds are grouped by families according to their altitudes (height range).

- The term 'nimbus' describes clouds which produce rain.

- Stratus clouds form when moist, stable air flows upslope.

- Radiation fog forms in moist air over low, flat areas on clear, calm nights.

- Advection and upslope fog require wind for formation. Both types of fog commonly occur along coastlines where sea breezes transport air from warm water to the cooler land surfaces.

- Low-level turbulence and aircraft icing are associated with steam fog.

- Vertical cloud development and turbulence result from the lifting of unstable air.

- Ice pallets at the surface are an indication of a temperature inversion and rain at a higher altitude.

- Stable air is generally smooth with layered or stratiform clouds. Visibility is usually restricted, with widespread areas of clouds and steady rain or drizzle.

- Moist unstable air causes the formation of cumuliform clouds, showers, turbulence, and good surface visibility.

-  Fronts are boundaries between airmasses.

- One of the most easily recognized discontinuities across a front is the change in temperature.

- When you are flying across a front, you will notice a change in wind direction. Wind speed may also change.

- Steady precipitation with little turbulence usually precedes a warm front.

- Thunderstorm formation requires unstable conditions, a lifting force, and high moisture levels.

- A squall line is a non-frontal band of thunderstorms that often produces the most intense weather hazards for aircraft.

- The cumulus stage is characterized by continuous updrafts.

- Thunderstorms reach the greatest intensity during the mature stage which is signaled by the beginning of precipitation.

- A dissipating thunderstorm is characterized by downdrafts.

- Severe turbulence often exists in a cumulonimbus cloud, the most turbulent of all clouds.

- Lightning is always associated with thunderstorms.

- If you encounter turbulence during flight, establish maneuvering speed and try to maintain a level flight attitude.

- Wingtip vortices are created when an airplane generates lift.

- The greatest vortex strength occurs when the generating aircraft is heavy, slow, and in a clean configuration.

- Wingtip vortices tend to sink below the flight path of the aircraft which generated them. They are most hazardous during light, quartering tailwind conditions.

- Mountain wave turbulence can be anticipated when the winds across a ridge are 40 knots or more, and the air is stable.

- The crests of mountain waves may be marked by the lens-shaped, or lenticular, clouds.

- Although they may appear stationary, standing lenticular clouds may contain winds of 50 knots or more.

- Wind shear often exists near the surface when there is a frontal system, thunderstorm, or temperature inversion with strong upper-level winds in the area. Wind shear is also associated with clear air turbulence.

- Wind shear may occur during a low-level temperature inversion when cold, still surface air is covered by warmer air which contains winds of 25 knots or more at 2,000 to 4,000 ft. above the surface.

- Wind shear can exist at any altitude and may occur in all directions.

- Visible moisture is necessary for structural icing to form. Freezing rain usually produces the highest rate of ice accumulation.