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Aviation Weather Exam Study Guide
(IERW) Questions and Answers Rated A+
The lowest layer of the atmosphere is the ____ and is approximately ____ feet at the equator and ____ feet at the poles. ✔✔troposphere
60,000'
25,000'
What is the difference between dry air and natural air? ✔✔natural air contains water vapor and condensation nuclei
Name the two major conditions affecting atmospheric circulation: ✔✔uneven heating
rotation of the earth
Name one semi-permanent pressure (air mass) system that causes weather over the United States. ✔✔North American High (CP) or Bermuda High (MT) or Siberian High (MP)
One method of heat transfer is radiation. Define radiation: ✔✔transfer of heat by electromagnetic waves
What is the difference between convection and advection? ✔✔convection is the transfer of heat vertically via a gas; advection is the transfer of heat horizontally via the wind (gas).
What is the definition of an air mass? ✔✔a large body of air whose physical properties (temperature and moisture) are horizontally uniform
What does the air mass classification code "c" indicate? ✔✔the air mass was formed over land (continental)
What is the source region and temperature/moisture content of an mP air mass? ✔✔Maritime Polar (Atlantic or Pacific Oceans), cold/moist
Is an air mass designated cPk warmer or colder than the surface? ✔✔colder
Is a cPk air mass stable or unstable? ✔✔unstable
Define OLR: ✔✔observed lapse rate, the actual change in the air temperature with an increase in altitude
In what direction does the wind flow around a high pressure area in the northern hemisphere? ✔✔clockwise
How does the wind flow in relation to the isobars above the friction level (above 2,000' AGL) ✔✔parallel
What force modifies gradient force and causes the wind to flow parallel to the isobars above 2,000'? ✔✔coriolis
What force is evident at the surface that causes the wind to flow across the isobars? ✔✔friction
On the following diagrams draw the gradient and surface winds. ✔✔high pressure turns clockwise
low pressure turns counter-clockwise
Near the center of a high, the air tends to ____ and in a low it tends to ____. ✔✔sink, rise
State Buys Ballots Law: ✔✔in the northern hemisphere, with your back to the wind the are of lower pressure will be to your left
You are crabbing left to correct for a left crosswind, where is the area of lower pressure? ✔✔ahead of you
Water may exist in the atmosphere in three states; they are ____, ____, and ____. ✔✔vapor, liquid, solid
Define water vapor: ✔✔moisture in the form of an invisible gas
Water vapor in the atmosphere may begin to condense when the temperature/dew point spread is within ____ degrees. ✔✔2 degrees C
Define sublimination: ✔✔changing water vapor directly to ice or ice to water vapor
The dry adiabatic cooling rate is ____ degrees per thousand feet. ✔✔3 degrees C
Which of the clouds (of the 10 types) would have bases below 6,500'? ✔✔Cu, Cb, St, Ns, Sc
Define a front: ✔✔the boundary line between air masses of different densities
The four discontinuities across a frontal surface are: ✔✔temperature
dew point
pressure
wind direction
Which of the discontinuities would indicate to a pilot that the front has been penetrated while in flight? ✔✔temperature, wind shift
What is the primary cause of frontal weather? ✔✔lifting of warm moist air by cold air
Define a cold front and give its typical direction of movement: ✔✔the leading edge of an advancing mass of cold air; moves TO the southeast
If you take off in cold air behind a cold front and climb through the frontal sufrace, what will happen to the free air temperature? ✔✔FAT will decrease, increase, decrease
The typical width of the severe weather band with a cold front is ____ miles and it moves at an average speed of ____ knots. ✔✔50, 25
If a cold front is moving at a speed of 45 knots, what weather situation may form ahead of the front? ✔✔squall line
Define a warm front including its slope and direction of movement: ✔✔the trailing edge of a retreating cold air mass with an average slope of 1:200 and moves TO the northeast
Warm front weather occurs ____ the surface front and may extend for ____ miles. ✔✔ahead, 400 to 600
State the cloud sequence in order if you are approaching a stable warm front from the cold air side: ✔✔Ci, Cs, As, Ns, St
Name the three atmospheric conditions necessary for ALL fog formation: ✔✔high moisture content
condensation nuclei
a cooling action
For radiation fog, one additional factor is required, this is ____. ✔✔light wind (2-5 knots)
What weather condition may cause radiation fog not to form, yet this same condition may also delay its dissipation? ✔✔overcast sky (greenhouse effect)
What type of fog may form when warm moist air flows over a colder surface? ✔✔advection
____ fog is produced by adiabatic cooling. ✔✔upslope
In mountainous areas, what type of fog may form as a result of cold mountain air moving down slope? ✔✔valley fog
Name the three conditions necessary for a thunderstorm to form: ✔✔unstable air
lifting action
moisture
The two major categories of thunderstorms are ____ and ____. ✔✔air masses frontal
Convective and orographic thunderstorms are two examples of which type of thunderstorm? ✔✔air mass
Which of the two MAJOR types of thunderstorms (airmass or frontal) are the most dangerous to flying? ✔✔frontal
The three stages in the life cycle of a thunderstorm are: ✔✔cumulus mature dissipating
Which of the above stages is the most dangerous and when does its cycle begin? ✔✔mature; when precipitation begins to fall
The ____ stage of a thunderstorm has only updrafts and the ____ stage has only downdrafts. ✔✔cumulus, dissipating
The most hazardous icing conditions is known as ____ and would fe found under a warm front during the winter months. ✔✔freezing rain
What are the two most important conditions necessary in the formation of aircraft icing? ✔✔visible moisture
at or below-freezing temperatures
The three types of clouds that may form in a mountain wave condition are: ✔✔lenticular cap rotor
Of the three types of clouds, which would be the best visual indicator of a mountain wave? ✔✔lenticular
For helicopter flight, what is the most dangerous condition with a mountain wave? ✔✔clear air turbulence and downdrafts on the lee side of the mountain
What is the recommended flight procedure for crossing a mountain range if a wave condition is suspected? ✔✔cross at a 45 degree angle and as high as practical above mountain elevation. Remain clear of clouds
(84-116 done on practical exercise) ✔✔
