Weather Flashcards
What is a trough?
Elongated area of low atmospheric pressure.
Can result in cloudiness and precipitation when in contact with high pressure system.
State the general characteristics of a low pressure and high pressure systems in the Northern Hemisphere.
Low Pressure - inward, upward, and counterclockwise
High Pressure - outward, downward, and clockwise
What is a ridge?
Elongated area of high atmospheric pressure.
Can result in clear skies and good weather.
What are the standard temperature and pressure values of sea level?
Atmospheric Pressure: 29.92
Temperature: 15C
What are isobars?
Lines on a weather chart which connects areas of equal or constant barometric pressure
If the isobars are relatively close together on a surface weather chart?
Steep pressure gradient and results in gusty winds.
What causes the winds aloft to float parallel to the isobars?
Coriolis force
Why do surface winds generally flow across the isobars at an angle?
Surface friction
At what rate does atmospheric pressure decrease with an increase of altitude?
1 inch per 1000ft
What does dew point mean?
Temperature a sample of must be to attain the state of saturation.
Could result in fog and lower visibility.
When temperature and dew point are within 5 degrees of each other what type of weather could occur?
Fog, low visibility, dew, carburetor ice
What factor primarily determines type and vertical extent of clouds?
Stability of the atmosphere
How do you determine the stability of the atmosphere?
“Rough” air is unstable
“Smooth”air is stable
During preflight planning what meteorological information should you be aware of with respect to icing?
Location of fronts Dew point Cloud layers Freezing levels - temperature Air pressure
What conditions are necessary for structural icing to occur?
Visible moisture
Freezing temperatures
Name the main types of icing an aircraft may encounter in-flight.
Structural
Induction system - carburetor and air filter
Instrument - static port and pitot tube
Name the three types of structural icing?
Clear ice - smooth sheet of ice
Rime ice - rough ice with milky white texture
Mixed ice - mixed with snow or ice particles
What action is recommended if you inadvertently encounter icing conditions?
Leave the area
Ascend above clouds
Descending below clouds
Changing course
Is frost considered hazardous to flight? Why?
Yes, the roughness of its surface spoils smooth air flow resulting in a loss of lift
What factors must be present for a thunderstorm to form?
Water vapor
Unstable air
A trigger - upward lifting such as a front
What are the three stages of a thunderstorm?
Cumulus
Mature
Dissipating
What is temperature inversion?
An increase of temperature with height instead of a decrease in temperature.
Air is stable with little to no turbulence
State two basic ways that fog may form.
Cooling the air to dew point
Adding moisture to air near surface.
Name several types of fog.
Radiation Advection Upslope Precipitation induced Ice
What causes radiation fog to form?
Ground cools adjacent air to the dew point on calm, clear nights
What is advection fog, and where is it most likely to form?
Results in transportation of warm humid air over a cold surface. Occurs around large bodies of water. Lakes, oceans, etc.