1. The earth's atmosphere is primarily composed of: Nitrogen.  Nitrogen comprises 78% of a dry atmosphere. Oxygen makes up about 21% and other gases comprise the remaining 1%. When water vapor is added, the percentages decrease proportionately.

2. Which of the following layers of the atmosphere extends from the surface to an altitude of about 30,000' at the poles and 60,000' at the equator? Troposphere.

3. At higher altitudes without oxygen, a person may be subject to which of the following conditions?
Hypoxia. In simple terms hypoxia is a lack of sufficient oxygen to keep the brain and other body tissues functioning properly. In addition to progressively insufficient oxygen at higher altitudes, anything interfering with the blood’s ability to carry oxygen can contribute to the brain’s tolerance to hypoxia.
 

4. In the lower layers of the atmosphere, pressure decreases with an increase in altitude at a rate of approximately: 1 inch per 1,000'

5. During a hot summer afternoon along coastal areas, which will most likely form along the shoreline?
Cumuliform clouds.

6. The standard temperature lapse rate in the lower layers of the atmosphere is:  A decrease of 2º C per 1,000'.

7. An increase in temperature with altitude is known as an: Inverted lapse rate.

8. 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.

9. Which combination would result in the lowest true altitude, assuming that the altimeter setting remains constant? Low pressure and low temperature.

10. Which of the following has the greatest effect in creating pressure differences? Unequal heating of the air.

11. Spacing between isobars on a weather chart can give the pilot a general indication of the: Strength of the wind.

12. In the northern hemisphere which of the following forces causes winds to apparently turn to the right?
Coriolis force.

13. Which of the following forces tends to slow the wind speed?  Friction.

14. The normal circulation around a high pressure area at the surface in the northern hemisphere is:  Clockwise and crossing the isobars at a 30º angle.

15. 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.

1. Which relates the actual water vapor content of the air to that which could be present and is expressed as a percentage?
Relative humidity.

2. 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.

3. Which changes of state of moisture absorb heat energy? Evaporation and melting.

4. 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.

5. Supercooled water droplets are abundant in clouds at temperatures from: 0º to -15º C.

6. Most clouds are formed because the air temperature: Is cooled

7. Which of the following contains forms of precipitation only? Ice pellets, freezing rain, snow grains, hail.

8. Which is most related to the intensity of precipitation? To produce significant precipitation, stratus clouds are usually 4,000 feet thick or more. The heavier the precipitation, the thicker the clouds are likely to be.

9. Which condition would most likely produce fog? Fog can form with a temperature-dew point spread of 5º F or less. It is most likely to form in areas with a high concentration of condensation nuclei.

10. When air is lifted it: Cools due to decreasing pressure.

11. Unsaturated air moving upward or downward cools or warms at what rate? 3º C per 1,000'

12. 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 faster. Condensation occurs when saturated air moves upward. Latent heat released through condensation partially offsets the expansional cooling. Therefore, the saturated adiabatic rate of cooling is slower than the dry adiabatic rate.

13. Which condition would result in the air becoming unstable? The temperature of the air which was lifted is warmer than the surrounding air temperature.

1. Which type of clouds are most likely to form in moist stable air? Stratiform.

2. Which type of clouds are most likely to form when there is a rapid decrease in temperature with an increase in altitude?
Cumuliform

3. With a surface temperature of 82º F and a surface dew point of 74º F, what would you estimate the base of the clouds to be?
2,000 feet.  When using Fahrenheit, DIVIDE the temperature DIFFERENCE by 4 and then multiply the result by 1000. 82-74=8 8/4=2 2X1000=2000.

4. Restricted visibility at or near the surface over large areas usually indicates: Stable air.

5. Moist air moving over a warm surface and heated from below will generally result in: When moist air is heated from below it becomes unstable. Unstable air normally produces cumuliform clouds with a greater probability of showers.

6. Which of the following clouds are part of the "high" cloud family? The high cloud family is cirriform and includes cirrus, cirrocumulus, and cirrostratus. They are composed almost entirely of ice crystals. The height of the bases of these clouds ranges from about 16,500 to 45,000 feet in middle latitudes.

7. Which of the following clouds are part of the "middle" cloud family? Altocumulus.


The middle cloud family includes altostratus, altocumulus, and nimbostratus clouds. These clouds are primarily water, much of which may be supercooled. The height of the bases of these clouds ranges from about 6500 to 23,000 feet in middle latitudes.

8. Which of the following clouds are classified in the "low" family of clouds?
The low family of clouds includes stratus, stratocumulus, and fair weather cumulus clouds. Low clouds are almost entirely water, but during cold seasons the droplets may be supercooled. Low clouds at sub-freezing temperatures can also contain snow and ice particles. The bases of these clouds range from near the surface to about 6500 feet in the middle latitudes.

9. Which of the following clouds would probably contain the worst turbulence?
Cumulonimbus clouds are the ultimate manifestation of instability. They are vertically developed clouds of large dimensions with dense boiling tops, often crowned with thick veils of dense cirrus (the anvil). Nearly the entire spectrum of flying hazards are contained in these clouds, including violent turbulence.

10. Which cloud belongs to the family of "vertically developed" clouds?
The vertically developed family of clouds includes towering cumulus and cumulonimbus. These clouds usually contain supercooled water above the freezing level.

1. What conditions are necessary for a thunderstorm to form?
The air must have sufficient water vapor, an unstable lapse rate, and an initial upward boost (lifting) to start the storm process in motion.

2. What are the three stages of a thunderstorm cell during its life cycle?
The three main stages of thunder storm development are the cumulus stage characterized by updrafts, the mature stage with both up and downdrafts, rain and lightning, and the dissipating stage where the predominate feature is an ending of rain and downdrafts.

4. What is an indication that a thunderstorm cell has reached the mature stage?
recipitation marks the BEGINNING of the MATURE stage of a thunderstorm cell. Raindrops in the cumulus stage grow larger and heavier. As they begin to fall the cold rain drags air with it creating a cold downdraft coexisting with the updraft.

5. Which of the following characterizes the dissipating stage of the thunderstorm cell?
Downdrafts characterize the dissipating stage of a thunderstorm cell and the storm dies rapidly. When rain has ended and downdrafts have abated, the dissipating stage is complete.

6. Which is the most likely time for on shore and off shore thunderstorms to form?
Since air mass thunderstorms generally result from surface heating, they reach maximum intensity and frequency over land during middle and late afternoon. Off shore, they reach a maximum during late hours of darkness when land temperature is coolest and cool air flows off the land over the relatively warm water.

7. Which type of thunderstorms tend to form with frontal weather systems?
Steady state thunderstorms are usually associated with weather systems. Fronts, converging winds, and troughs aloft force upward motion spawning these storms which often form into squall lines. Afternoon heating intensifies them. In a steady state storm, precipitation falls outside the updraft allowing the updraft to continue unabated. Thus, the mature stage updrafts become stronger and last much longer than in air mass storms. Hence the name "steady state".

8. A thunderstorm cloud which displays rounded, irregular pockets or festoons from its base is called "cumulonimbus mamma". This type of cloud is a signpost of: Violent turbulence and tornadoes.

9. A non-frontal narrow band of active thunderstorms which presents the single most intense weather hazard to aircraft is known as a:
Squall line. Squall lines often develop ahead of cold fronts in moist, unstable air but may develop in unstable air far removed from any front. The line may be too long to easily detour and too wide and severe to penetrate. It often contains severe steady state thunderstorms and presents the single most intense weather hazard to aircraft. It usually forms rapidly, generally reaching maximum intensity during the late afternoon and first few hours of darkness.

10. Which two hazards compete as the greatest thunderstorm hazards to aircraft? Hail and turbulence.
Hazardous turbulence is present in all thunderstorms and in a severe thunderstorm it can damage an airframe. Strongest turbulence within a cloud occurs with shear between updrafts and downdrafts. Outside the cloud shear turbulence has been encountered several thousand feet above and 20 miles laterally from a severe storm.

11. Which is prevalant with cold frontal or squall line thunderstorms and signifies an extremely turbulent zone?
A low level turbulent area is the shear zone between the plow wind and surrounding air. Often a "roll cloud" on the leading edge of a storm marks the eddies in the shear.

12. Which is the best indication as to the intensity of a thunderstorm? The more frequent the lightning, the more intense the storm.
Increasing frequency of lightning indicates a growing thunderstorm. Decreasing lightning indicates a storm nearing the dissipating stage.

3. You should avoid any thunderstorm identified as severe by at least:
20 miles. A severe thunderstorm can generate turbulence up to a distance of 20 miles horizontally from the storm itself.

14. If using airborne radar and flying in the vicinity of thunderstorms, what is a good procedure?
Tilting the antenna up may detect a hail shaft that will reach a point on your course by the time you do. Tilting it down may detect a growing thunderstorm cell that may reach your altitude.

15. Which is a good procedure if you are flying near thunderstorms?
Turn up your cockpit lights to highest intensity and wear sun glasses to lessen the possibility of temporary blindness from lightning.

1. The zone between two air masses of different properties is called:
The two air masses might have different temperatures, humidities, and wind. When you pass through a front the change from the properties of one air mass to those of the other is sometimes quite abrupt.

2. Which of the following properties always changes across a front?
Wind ALWAYS changes across a front. Wind discontinuity may be in direction, speed or both. Be alert for wind shifts when flying in the vicinity of a front.

3. Which of these best describes a cold front?
The leading edge of an advancing cold air mass is a cold front. At the surface cold air is replacing and overtaking the warmer air. Cold fronts move at an average speed of about 22 knots.

4. A front is defined as stationary if it is moving at a speed of less than:
5 knots. When neither air mass is replacing the other, the front is stationary. The opposing forces exerted by adjacent air masses of different densities are such that the frontal surface between them shows little or no movement.
 

5. In an occluded front, where is the most dangerous weather located?
The most dangerous weather is located 50 to 100 miles north of the point of occlusion along the upper front.

6. Which of the following is a factor regarding the type of weather found in a front?
Sufficient moisture must be available for clouds to form or there will be no clouds. Shallow frontal surfaces tend towards extensive cloudiness and large precipitation areas.

7. A narrow band of intense thunderstorms which may form in front of a fast moving cold front is called a:
Fast moving cold fronts can rapidly push warm moist air aloft where it is quickly cooled. The resulting condensation and release of massive amounts of energy can cause severe thunderstorm activity along a relatively narrow band referred to as a squall line.

8. Which type of clouds are associated with a mountain wave?
Rotor clouds and altocumulus standing lenticular clouds. The wave type action of air near mountains may cause the formation of rotor, standing lenticular, and altocumulus clouds.

9. Windshear may exist: at any level of the atmosphere in a horizontal or vertical direction.
Windshear may exist at any level and may be either horizontal or vertical. There are three areas of special interest:
Windshear with a low level temperature inversion.
Windshear in a frontal zone.
Clear air turbulence at high levels associated with a jet stream or strong circulation.

10. Why is windshear associated with a low level temperature inversion hazardous when on an approach to an airport?
Under certain conditions an airplane could encounter a stall. The wind near the surface in an inversion is usually calmer than the air above. The air above the inversion may be quite strong.

1. Which areas would be most conducive to the formation of fog?
Coastal areas and industrial areas.  When a stable air mass is associated with an industrial area and a narrow temperature dew point spread the result is predictable. The small particles of smoke combine with water vapor to produce an obscured ceiling. The fog will often lift later in the day but the improvement will generally be much slower than the clearing of fog alone.

2. Although fog may form during any season it occurs most frequently: During colder months. While fog forms most frequently during the colder months because of the narrow temperature dew point spread, it is wise to be alert for fog during all seasons

3. A clear sky, a light wind, and high relative humidity are conditions which aid the formation of: Radiation fog.
When the air temperature cools to the dew point, fog usually forms. Radiation fog is common in the morning after a rain storm which was followed by clearing skies.

4. Which wind tends to deepen a radiation fog formation? Wind up to 5 knots mixes the air and tends to deepen the fog by spreading the cooling through a deeper layer. Stronger wind tends to disperse the fog or mix the air through a still deeper layer which can cause low stratus clouds to form at the top of the layer.

5. Which type of fog usually forms along coastal areas in the winter? Advection fog.
The West Coast of the United States and the Gulf Coast areas are particularly vulnerable to advection fog.

6. Which types of fog must have a wind in order to form?
Advection and upslope fog. Upslope fog is formed when moist stable air is forced up rising terrain by a breeze. There must be a wind blowing for either upslope fog or advection fog to form.

7. Which type of fog is formed by the evaporation process? Precipitation induced fog . When relatively warm rain or drizzle falls through cool air, evaporation from the precipitation saturates the cool air and forms fog. Precipitation induced fog can become quite dense and continue for an extended period of time. It may cover large areas, completely suspending air operations.

8. Which type of fog is formed by the process of sublimation?

Ground fog.

Steam fog.

Ice fog.

Precipitation induced fog.
Ice fog occurs in cold weather when the temperature is much below freezing and water vapor sublimates directly as ice crystals.

Conditions favorable for its formation are the same as for radiation fog except for cold temperature, usually –25º F or colder.

It occurs mostly in the Arctic regions, but is not unknown in the mid latitudes during the cold season.

Ice fog can be quite blinding to someone flying into the sun

9. What is the primary difference between a ceiling caused by an obstruction to vision and one caused by clouds?
Obstructions to vision are based on the surface whereas clouds are based aloft. An obscured ceiling differs from a cloud ceiling. With a cloud ceiling you can normally see the ground and runway once you descend below the cloud base. However, with an obscured ceiling the obscuring phenomena restricts visibility between your altitude and the ground and you have restricted slant visibility. Thus, you cannot always clearly see the runway or approach lights even after penetrating the level of the obscuration ceiling.

10. Which of these conditions might produce fog? Clear sky, light wind, temperature dew point spread less than 15º F at dusk.
The following include conditions, which could result in the formation of fog: Moist air flowing over a cool surface. Narrow temperature/dew point spread.Clear skies, light wind, and a high relative humidity.

11. What type of fog tends to form when air is blowing from a cold surface over warmer water? Steam fog is formed by the evaporation of water into a stable air mass above. It is common near lakes, rivers, and streams

12. When a high pressure stagnates over an industrial area, during which time of the day would you expect the lowest visibility?
High pressures normally contain clear skies. Nighttime cooling produces inversions which become deepest at sunrise. Inversions invariably produce poor visibility, especially near industrial areas.

13. How long does it normally take radiation or ground fog to burn off? 1 to 3 hours. Since ground fog forms only with clear skies, as soon as the sun produces enough surface heating the ground fog burns off. This is normally 1 to 3 hours after sunrise.
 

1. What are the two conditions necessary for structural icing to form in flight? Temperatures freezing or below and visible liquid moisture.
The temperature at the point where the moisture strikes the aircraft must be 0º C or colder. The aircraft must be flying through visible water such as rain or cloud droplets. This combination normally results in structural icing.

2. Which type of icing is hard, heavy, tenacious, and most difficult to break off with deicing equipment? Clear. Clear ice forms when large supercooled water droplets strike the aircraft surface. After initial impact, some of the water freezes and a portion of the drop flows out over the airfoil surface. This type of ice forms when drops are large as in cumuliform clouds.

3. Which condition would be most likely for the formation of rime ice? Light drizzle or stratus clouds. Rime ice forms when small drops freeze on impact. Rime ice forms when drops are small, such as those in stratified clouds or freezing drizzle. The liquid portion remaining after initial impact freezes rapidly before the drop has time to spread over the aircraft surface. The small frozen droplets trap air between them, giving the ice a white appearance.

4. Ice forming on the static ports would cause which of the following instruments to be unreliable?
Airspeed indicator, altimeter, and VSI. Ice formation on the pitot tube will make airspeed indications unreliable. Icing on the STATIC PRESSURE PORT reduces the reliability of all instruments on the system. These include the AIRSPEED INDICATOR, ALTIMETER, and the VERTICAL SPEED INDICATOR.

5. Which of the following determines the severity of icing? Size of the water droplets and temperature. Large supercooled water drops are worse than smaller ones. The condition most favorable for very hazardous icing is the presence of many large supercooled water droplets.

6. Where would the heaviest icing most probably be found in a thick nimbostratus cloud? Temperatures at or slightly below freezing.


7. Which condition is most favorable for rapid accumulation of clear ice? Freezing rain below a frontal surface. Rain forms above the frontal surface at temperatures warmer than freezing. It falls through air at temperatures below freezing and becomes supercooled. The supercooled droplets freeze on impact with an aircraft surface. It may occur with either a warm front or a cold front. The icing can be critical because of the large amount of supercooled water.

8. If flying in IFR conditions and you encounter freezing rain beneath the frontal slope, what is the best procedure to avoid icing?
Climb to an altitude above the frontal slope where you will encounter above freezing temperatures

9. An accumulation of frost on the airfoil surface could cause which of the following?
A heavy coat of hard frost will cause a 5% to 10% increase in stall speed for fixed wing a/c. Even a small amount of frost on airfoils may prevent an aircraft from becoming airborne at normal takeoff speed

10. If you must climb through a layer of icing, which is the best procedure? Use an airspeed a little faster than normal climb speed.
When climbing through an icing layer, know what kind of ice to expect within the layer and climb at an airspeed a little faster than normal to avoid a stall.

11. At which temperature range would you expect to encounter the heaviest icing in cumuliform clouds?
0º to -15º C. When the temperature is below freezing, avoid all cumuliform clouds if it is possible. Clear ice may be encountered ANYWHERE above the freezing level. The MOST RAPID accumulations are usually found where the temperature is between 0 deg. and –15ºC

12. What is the best source of determining the location and intensity of actual icing conditions?
The man on the ground has no way of observing actual icing conditions. His only confirmation of the existence or absence of icing comes from pilots. Help your fellow pilot and the weather service by sending pilot reports when you encounter icing or when icing is forecast but not encountered.

14. Which two types of fog could form even though the skies are cloudy? Advection and upslope fog.
Both advection and upslope fog may form even though the skies are cloudy. Because of this they are less likely to burn off as long as the conditions which caused them persist.

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