Aviation Weather Theory Flashcards
Standard Atmosphere was created by:
Averaging conditions to create an idealized atmosphere.
The standard temperature lapse rate in the lower layers of the atmosphere is:
A decrease of 2° C per 1,000’.
If the air temperature is +8°C at an elevation of 1,350 feet MSL and a standard (average) temperature lapse rate exists, what will be the approximate freezing level?
5,350 feet MSL.
Moving up in the atmosphere, unsaturated air gets cooler at approximately what rate (dry adiabatic lapse rate)?
3 °C per 1,000 feet.
A common type of ground or surface based temperature inversion is that which is produced by:
Ground radiation on clear, cool nights when the wind is light.
A temperature inversion will normally form only:
In stable air.
Which weather conditions should be expected beneath a low-level temperature inversion layer when the relative humidity is high?
Smooth air and poor visibility due to fog, haze, or low clouds.
The earth’s atmosphere is primarily composed of:
Nitrogen
Which of the following layers of the atmosphere extends from the surface to an altitude of about 20,000’ over the poles and 48,000’ over the equatorial regions?
Troposphere.
In the lower layers of the atmosphere, pressure decreases with an increase in altitude at a rate of approximately:
1 inch per 1,000 feet.
An increase in temperature with altitude is known as an:
Inverted lapse rate.
Which condition would cause the true altitude of the aircraft to be lower than the indicated altitude, even if the altimeter is accurate?
Temperature colder than standard.
Which combination would result in the lowest true altitude, assuming the altimeter setting remains constant?
Low pressure and low temperature.
Which of the following has the greatest effect in creating pressure differences?
Unequal heating of air.
Spacing between isobars on a weather chart can give the pilot a general indication of the:
Strength of the wind.
In the northern hemisphere, which of the following forces causes winds to apparently turn to the right?
Coriolis force.
Which of the following forces tends to slow the wind speed?
Friction.
The normal circulation around a high pressure area at the surface in the northern hemisphere is:
Clockwise and crossing the isobars at a 30° angle.
Although it is not a hard and fast rule, which of the following conditions would most likely produce the most favorable flying conditions?
High pressure.
Which of the following terms describes the amount of water vapor present compared to the total water vapor possible at a given temperature and is given as a percentage?
Relative humidity.
The temperature to which the air must be cooled to become saturated by the water vapor already present in the air is known as the:
Dew point.
Which of the following changes of state to moisture absorbs heat energy?
Evaporation and melting.
Microscopic particles of salt, dust, and combustion byproducts are necessary for water vapor molecules to change state from gas to liquid or solid. These are called:
Condensation nuclei.
Supercooled water droplets are abundant in clouds at temperatures from:
0° to -15° C
Most clouds are formed because the air:
Is cooled.
Which of the following are forms of precipitation?
All of the answers are correct.
Which is most related to the intensity of precipitation?
Cloud thickness.
Which condition would most likely produce fog?
Temperature-dew point spread is 5 °F (2.8 °C) and decreasing.
When air is lifted it expands and:
Cools due to decreasing pressure.
Compare the rate of cooling when saturated air is lifted to the rate of cooling when unsaturated air is lifted.
The rate of cooling in saturated air is slower.
Which condition would result in the air becoming unstable? The temperature of:
The air which was lifted is warmer than the surrounding air temperature.
Which type of clouds are most likely to form in moist stable air?
Stratiform.
Which type of clouds are most likely to form when there is a rapid decrease in temperature with an increase in altitude?
Cumuliform.
With a surface temperature of 28 °C and a surface dew point of 23 °C, what would you estimate the base of the clouds to be?
2,000 feet.
Restricted visibility at or near the surface over large areas usually indicates:
Stable air.
Moist air moving over a warm surface and heated from below will generally result in:
Rough flying conditions and increasing possibility of showers.
Which of the following clouds are part of the “high” cloud family?
All of the listed clouds.
Which of the following clouds are part of the “middle” cloud family?
Altocumulus.
Which of the following clouds are classified in the “low” family of clouds?
All of the listed clouds are in the low family of clouds.
Which of the following clouds would probably contain the worst turbulence?
Cumulonimbus.
Which cloud belongs to the family of “vertically developed” clouds?
Towering cumulus.
Which type of clouds are associated with a mountain wave?
Rotor clouds and altocumulus standing lenticular clouds.
Clouds, fog, or dew will always form when:
Water vapor condenses.
What type of clouds will be formed if very stable moist air is forced up slope?
Stratified clouds with little vertical development.
What type clouds can be expected when an unstable air mass is forced to ascend a mountain slope?
Clouds with extensive vertical development.
What determines the structure or type of clouds which form as a result of air being forced to ascend?
The stability of the air before lifting occurs.
Which of the following combinations of weather producing variables would likely result in cumuliform-type clouds, good visibility, rain showers, and possible clear-type icing in clouds?
Unstable, moist air, and orographic lifting.
Which family of clouds is least likely to contribute to structural icing on an aircraft?
High clouds.
What are the four families of clouds?
High, middle, low, and those with extensive vertical development.
During a hot summer afternoon along coastal areas, which will most likely form along the shoreline?
Cumuliform clouds.
The zone between two air masses of different properties is called:
A front.
Which of the following properties always changes across a front?
Wind.
Which of these best describes a cold front?
The leading edge of an advancing cold air mass.
A front is defined as stationary if:
Neither air mass is replacing the other.
When does an occluded front produce the most dangerous forms of weather?
With warm front occlusion that pushes unstable air aloft.
Which of the following is a factor regarding the type of weather found in a front?
All of the answers are correct.