Ch 7 - Aviation Weather - Questions 631 - 701 Flashcards
Every physical process of weather is accompanied by, or is the result of, a
Heat exchange
What causes variations in altimeter settings between weather reporting points?
Unequal heating if the Earth’s surface
The wind at 5,000 feet AGL is southwesterly while the surface wind is southerly. This difference in direction is primarily due to
Friction between the wind and the surface
The development of thermals depends upon
Solar heating
Convective cirucaltion patterns associated with sea breezes are caused by
Cool, dense air moving inland from over the water
The boundary between two different air masses is referred to as a
Front
One weather phenomenon which will always occur when flying across a front is a change in the
Wind direction
One of the most easily recognized discontinuities across a front is
A change in temperature
If there is thunderstorm activity in the vicinity of an airport at which you plan to land, which hazardous atmospheric phenomenon might be expected on the landing approach?
Wind-shear turbulence
A nonfrontal, narrow band of active thunderstorms that often develop ahead of cold front is known as a
Squall line
What conditions are necessary for the formation of thunderstorms?
High humidity, lifting force, and unstable conditions
During the life cycle of a thunderstorm, which stage is characterized predominately by downdrafts?
Dissipating
Thunderstorms reach their greatest intensity during the
Mature stage
What feature is normally associated with the cumulus stage of a thunderstorm?
Continuous updraft
Which weather phenomenon signals the beginning of the mature stage of a thunderstorm?
Precipitation beginning to fall
Thunderstorms which generally produce the most intense hazard to aircraft are
Squall line thunderstorms
Which weather phenomenon is always associated with a thunderstorm?
Lightning
The mature stage of a thunderstorm begins with
The start of precipitation
The destination airport has one runway, 8-26, and the wind is calm. The normal approach in calm wind is a left-hand pattern to runway 8. There is no other traffic at the airport. A thunderstorm about 6 miles west is beginning its mature stage, and rain is starting to reach the ground. The pilot decides to
Delay departure until the thunderstorm has dissipated
You are avoiding a thunderstorm that is in your flightpath. You are over 20 miles from the cell; however, you are under the anvil of the cell. Is this a hazard?
Yes, hail can be discharged from the anvil
One in-flight condition necessary for structural icing to form is
Visible moisture
In which environment is aircraft structural ice most likely to have the highest accumulation rate?
Freezing rain
The presence of ice pellets at the surface is evidence that there
Is a temperature inversion with freezing rain at a higher altitude
How will frost on the wings of an airplane affect takeoff performance?
Frost will disrupt the smooth flow of air over the wing, adversely affecting its lifting capability.
Why is frost considered hazardous to flight?
Frost spoils the smooth flow of air over the wings, thereby decreasing litigant capability
How does frost affect the lifting surfaces of an airplane on takeoff?
Frost may prevent the airplane from becoming airborne at normal takeoff speed
Which conditions result in the formation of frost?
The temperature of the collecting surface is at or below the dew point of the adjacent air and the dew point is below freezing
An almond or lens-shaped cloud which appears stationary, but which may contain winds of 50 knots or more, is referred to as
A lenticular cloud
Crests of standing mountain eaves may be marked by stationary, lens-shaped clouds known as
Standing lenticular clouds
Possible mountain eaves turbulence could be anticipated when winds of 40 knots or greater blow
Across a mountain ridge, and the air is table.
Where does wind shear occur?
At all altitudes, in all directions
A pilot can expect a wind-shear zone in a temperature inversion whenever the wind speed at 2,000 to 4,000 feet above the surface is at least
25 Knots
When may hazardous wind shear be expected?
In areas of low-level temperature inversion, frontal zones and clean air turbulence
If the temperature/dewpoint spread is small and decreasing, and the temperature is 62 degrees F, what type weather is most likely to develop?
Fog or low clouds
What is meant by the term “dewpoint”?
The temperature at which condensation and evaporation are equal
The amount of water vapour which air can hold depends on the
Air temperature
What are the processes by which moisture is added to unsaturated air?
Evaporation and sublimation
Clouds, fog or dew will always form when
Water vapour condenses
Low-level turbulence can occur and icing can become hazardous in which type of fog?
Steam fog
In which situation is advection fog most likely to form?
An air mass moving in land from the coast in winter
What situation is most conductive to the formation of radiation fog?
Warm, moist air over low, flatland areas on clear, calm nights
What types of fog depend upon wind in order to exist?
Advection fog and upslope fog
Clouds are divided into four families according to their
Height range
The suffix “nimbus”, used naming clouds, means
A rain cloud
The conditions necessary for the formation of cumulonimbus clouds are a lifting action and
Unstable, moist air
What clouds have the greatest turbulence?
Cumulonimbus
What could types indicate convective turbulence?
Towering cumulus clouds
At approximately what altitude above the surface would the pilot expect the base of cumuliform clouds if the surface air temperature is 82 degrees F an the dewpoint is 38 degrees F?
10,000 feet AGL
What is the approximate base of the cumulus clouds if the surface air temperature at 1,000 feet MSL is 70 degrees F and the dewpoint is 48 degrees F?
6,000 feet MSL
Cumulus clouds often indicate
Possible turbulence
What is a characteristic of stable air?
Stratiform clouds
When warm, moist, stable air flows upslope, it
Produces stratus type clouds
If an unstable air mass if forced upward, what type of clouds can be expected?
Clouds with considerable vertical development and associated turbulence
What are the characteristics of unstable air?
Turbulence and good surface visibility
A stable air mass is most likely to have which characteristic?
Poor surface visibility
Steady precipitation preceding a front is an indication of
Stratiform clouds with little or no turbulence
What are the characteristics of a moist, unstable air mass?
Cumuliform clouds and showery precipitation
What measurement can be used to determine the stability of the atmosphere?
Actual lapse rate
What would decrease the stability of an air mass?
Warming from below
What are the characteristics of an unstable atmosphere?
A warm, humid air mass
Clouds with extensive vertical development over mountainous terrain are a sign of
An unstable air mass
