Fundamentals of Weather Flashcards
What is the standard temperature for sea level?
15°C / 32°F
At what rate does atmospheric pressure decrease with an increase in altitude?
Decreases approximately 2” Hg per 1,000 ft
What is the standard pressure value for sea level?
29.92”
What is the general characteristics in regards to flow of air around high-pressure systems in northern hemisphere?
Air flows inward, upward, and counterclockwise
What is the general characteristics in regards to flow of air around low-pressure systems in northern hemisphere?
Air flows outward, downward, and clockwise
What causes the winds aloft to flow parallel to the isobars?
Coriolis force
Why do you surface winds generally flow across the isobars at an angle?
Surface friction
What happens when temperature and dew point close together?
Visible moisture is likely, inform of clouds, dew, or fog
What factor primarily determines the type and vertical extent of clouds?
Stability of the atmosphere
What is the difference between stable and unstable atmosphere?
Stable atmosphere resist any upward or downward displacement.
Unstable atmosphere allows upward or downward displacement to grow into a vertical or convective current.
How do you determine the stability of the atmosphere?
When temperature decreases uniformly and rapidly as you climb, you have an indication of unstable air.
If temperature remains unchanged or decreases only slightly with altitude, air is stable.
What are the main types of icing an aircraft may encounter?
Structural, induction system, and instrument icing
What are the three types of structural icing?
Clear ice, Rime ice, mixed ice
Define clear ice:
Large drops and slowly freezes
Define Rime ice:
Small drops and freezes rapidly
Define mix ice:
Combination of clear and Rime ice
What is induction icing?
Carburetor engine ice.
Carb heat 10 to 15 minutes or until landing
What is instrument icing?
Pitot icing, nav antenna iced
What factors must be present for a thunderstorm to form?
A source of lift, heating, fast-moving front to lift/upslope.
Unstable air.
High moisture content.
What are the stages of a thunderstorm?
Cumulus stage: updrafts
Mature stage: first sign of rainfall begins
Dissipating stage: rain themselves out
What are squall line thunderstorms?
A non-frontal, narrow band of active thunderstorms.
Often develops ahead of cold front and moist, unstable air, but it may develop an unstable air far removed from any front.
How far do you circumnavigate a thunderstorm?
20 nautical miles around
How do you proceed if caught in a thunderstorm?
Wings level, maneuver speed
State two basic ways that a fog may form:
Cooling air it the dew point.
Adding moisture to the air.
Name the types of fog:
Ice fog
Radiation fog
Advection fog
Precipitation induced fog
Upslope fog
What causes radiation fog to form?
Clear sky, little/no wind, small dew point spread.
Forms during night/near daybreak.
What is advection fog and where is it most likely to form?
Moist air over colder ground or water.
Most common along costal areas.
But often develops deep in continental areas.
Define upslope fog:
Moist, stable air being cool adiabatically as it moves upsloping terrain.
Once upsloping winds cease, fog dissipates.
Rockies, Appalachian Mountains.
Define Ice fog:
Occurs in cold whether when temperature is much below freezing and water vapor sublimates directly as ice crystals.
Occurs mostly in Arctic regions.
What is precipitation induced fog?
When relatively warm air/drizzle falls thru cool air, evaporation from precipitation saturates cool air and forms fog.
Most commonly associated with warm fronts but also slow moving cold fronts and stationary fronts.
Industrial pollution also can cause this
Other than fog, what are several other examples of IFR weather producers?
Low clouds Haze Smoke Blowing obstructions to vision Precipitation Fog
What is a microburst?
Small scale down drafts.
Originate from low/mid layer convective clouds.
Can prove deadly to all planes.
What are the characteristics of a microburst?
Max life of 15min.
Against Microburst may encounter increased head winds.
In the middle of microburst may encounter strong down drafts.
With microburst may encounter improved performance.
Define freezing level:
Altitude where snow, frost & ice are likely to drop
