What type of cloud would indicate convective turbulence?

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Every physical process of weather is accompanied by, or is the result of, a:

a) movement of air

b) pressure differential

c) heat exchange

c) Every physical process of weather is accompanied by, or is the result of, a heat exchange. A heat differential (difference between the temperatures of two air masses) causes a differential in pressure, which in turn causes movement of air.

What causes variations in altimeter settings between weather reporting points?

a) unequal heating of the Earth's surface

b) variation of terrain elevation

c) Coriolis force

a) Unequal heating of the Earth's surface causes differences in air pressure, which is reflected in differences in altimeter settings between weather reporting points

The wind at 5,000 ft AGL is southwesterly while the surface wind is southerly. This difference in direction is primarily due to:

a) stronger pressure gradient at higher altitudes

b) friction between the wind and the surface

c) stronger Coriolis force at the surface

b) Winds aloft at 5,000 ft are largely affected by Coriolis force, which deflects winds to the right, in the Northern hemisphere. But at the surface, the Coriolis force has less effect where the wind speed is slower. The wind speed is slower at the surface due to friction between the wind and the surface.

The development of thermals depends upon:

a) a counterclockwise circulation of air

b) temperature inversions

c) solar heating

c) Thermals are updrafts in small-scale convective currents. Convective currents are caused by uneven heating of the Earth's surface. Solar heating is the means of heating the Earth's surface.

Convective circulation patterns associated with sea breezes are caused by:

a) warm, dense air moving inland from over the water

b) water absorbing and radiating heat faster than the land

c) cool, dense air moving inland from over the water

c) Sea breezes are caused by cool and more dense air moving inland off the water. Once over the warmer land, the air heats up and rises. Thus, the cooler, more dense air from the sea forces the warmer air up. Currents push the hot air over the water where it cools and descends, starting the cycle over again. This process is caused by land heating faster than water.

The boundary between two different air masses is referred to as a:

a) frontolysis

b) frontogenesis

c) front

c) A front is a surface, interface, or transition zone of discontinuity between two adjacent air masses of different densities. It is the boundary between two different air masses.

One weather phenomenon which will always occur when flying across a front is a change in the:

a) wind direction

b) type of precipitation

c) stability of the air mass

a) The definition of a front is the zone of transition between two air masses of different air pressure or density. Due to the difference in changes in pressure systems, there will be a change in wind.

One of the most easily recognized discontinuities across a front is:

a) a change in temperature

b) an increase in cloud coverage

c) an increase in relative humidity

a) Of the many changes that take place across a front, the most easily recognized is the change in temperature. When flying through a front, you will notice a significant change in temperature, especially at low altitudes

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?

a) precipitation static

b) wind-shear turbulence

c) steady rain

b) The most hazardous atmospheric hazardous phenomenon near thunderstorms is wind shear turbulence.

A nonfrontal, narrow band of active thunderstorms that often develop ahead of a cold front is known as a:

a) prefontal system

b) squall line

c) dry line

b) A nonfrontal, narrow band of active thunderstorms that often develops ahead of a cold front is known as a squall line

What conditions are necessary for the formation of thunderstorms?

a) high humidity, lifting force, and unstable conditions

b) high humidity, high temperature, and cumulus clouds

c) lifting force, moist air, and extensive cloud cover

a) Thunderstorms form when there is sufficient water vapor, an unstable lapse rate, and an initial upward boost (lifting) to start the storm process

During the life cycle of a thunderstorm, which stage is characterized predominately by downdrafts?

a) cumulus

b) dissipating

c) mature

b) Thunderstorms have three life cycles: cumulus, mature, and dissipating. It is in the dissipating stage that the storm is characterized by downdrafts as the storm rains itself out

Thunderstorms reach their greatest intensity during the:

a) mature stage

b) downdraft stage

c) cumulus stage

a) Thunderstorms reach their greatest intensity during the mature stage, where updrafts and downdrafts cause a high level of wind shear

What feature is normally associated with the cumulus stage of a thunderstorm?

a) roll cloud

b) continuous updraft

c) frequent lightning

b) The cumulus stage of a thunderstorm has continuous updrafts that build the storm. The water droplets are carried up until they become too heavy. Once they begin falling and creating downdrafts, the storm changes from the cumulus to the mature stage

Which weather phenomenon signals the beginning of the mature stage of a thunderstorm?

a) the appearance of an anvil top

b) precipitation beginning to fall

c) maximum growth rate of the clouds

b) The mature stage of a thunderstorm begins when rain begins falling. This means that the downdrafts are occurring sufficiently to carry water all the way through the thunderstorm

Thunderstorms which generally produce the most intense hazard to aircraft are:

a) squall line thunderstorms

b) steady-state thunderstorms

c) warm front thunderstorms

a) A squall line is a nonfrontal, narrow band of active thunderstorms. It often contains severe, steady-state thunderstorms and presents the single most intense weather hazard to airplanes

Which weather phenomenon is always associated with a thunderstorm?

a) lighting

b) heavy rain

c) hail

a) A thunderstorm, by definition, has lightning, because lightning causes the thunder

The mature stage of a thunderstorm begins with:

a) formation of the anvil top

b) the start of precipitation

c) continuous downdrafts

b) The mature stage of a thunderstorm begins when rain begins falling. This means that the downdrafts are occurring sufficiently to carry water all the way through the thunderstorm

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:

a) depart expecting the thunderstorm to dissipate prior to arrival, then land on runway 8

b) delay departure until the thunderstorm has dissipated

c) fly an approach to runway 26 since any unexpected wind due to the storm will be westerly

b) During the mature stage of a thunderstorm, precipitation descends through the cloud and drags the adjacent air downward, creating a strong downdraft. The downdraft spreads out along the surface, well in advance of the parent thunderstorm cell, as a mass of cool, gusty air. Adverse winds always are found within thunderstorms and often many miles from the precipitation area.

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?

a) no, you are at a safe distance from the cell

b) yes, hail can be discharged from the anvil

c) yes, this is still in the area of dissipation

b) Pilots should anticipate possible hail with any thunderstorm but especially beneath the anvil of a large cumulonimbus

One in-flight condition necessary for structural icing to form is:

a) small temperature/dewpoint spread

b) statiform clouds

c) visible moisture

c) Two conditions are necessary for structural icing while in flight. First, the airplane must be flying through visible moisture, such as rain or cloud droplets. Second, the temperature at the point where the moisture strikes the airplane must be freezing or below

In which environment is aircraft structural ice most likely to have the highest accumulation rate?

a) cumulus clouds with below freezing temperatures

b) freezing drizzle

c) freezing rain

c) Freezing rain usually causes the highest accumulation rate of structural icing because of the nature of the supercooled water striking the airplane

The presence of ice pellets at the surface is evidence that there:

a) are thunderstorms in the area

b) has been cold frontal passage

c) is a temperature inversion with freezing rain at a higher altitude

c) Rain falling through colder air may freeze during its descent, falling as ice pellets. Ice pellets always indicate freezing rain at a higher altitude

An almond or lens-shaped cloud which appears stationary, but which may contain winds of 50 knots or more, is referred to as:

a) an inactive frontal cloud

b) a funnel cloud

c) a lenticular cloud

c) Lenticular clouds are lens-shaped clouds, which indicate the crests of standing mountain waves. They form in the updraft and dissipate in the downdraft, so they do not move as the wind blows through them. Lenticular clouds may contain winds of 50 kt, or more and are extremely dangerous

Crests of standing mountain waves may be marked by stationary, lens-shaped clouds known as:

a) mammatocumulus clouds

b) standing lenticular clouds

c) roll clouds

b) Lens-shaped clouds, which indicate crests of standing mountain waves, are called standing lenticular clouds. They form in the updraft and dissipate in the downdraft so that they do not move as the wind blows through them.

Possible mountain wave turbulence could be anticipated when winds of 40 knots or greater blow:

a) across a mountain ridge, and the air is stable

b) down a mountain valley, and the air is unstable

c) parallel to a mountain peak, and the air is stable

a) Always anticipate possible mountain wave turbulence when the air is stable and winds of 40 kt or greater blow across a mountain or ridge

Where does wind shear occur?

a) only at higher altitudes

b) only at lower altitudes

c) at all altitudes, in all directions

c) Wind shear is the eddies in between two wind currents of differing velocities, direction, or both. Wind shear may be associated with either a wind shift or a wind speed gradient at any level in the atmosphere

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:

a) 10 knots

b) 15 knots

c) 25 knots

c) When taking off or landing in calm wind under clear skies within a few hours before or after sunset, prepare for a temperature inversion near the ground. You can be relatively certain of a shear zone in the inversion if you know the wind is 25 kt or more at 2,000 to 4,000 ft. Allow a margin of airspeed above normal climb or approach speed to alleviate the danger of stall in the event of turbulence or sudden change in wind velocity

When may hazardous wind shear be expected?

a) when stable air crosses a mountain barrier where it tends to flow in layers forming lenticular clouds

b) in areas of low-level temperature inversion, frontal zones, and clear air turbulence

c) following frontal passage when stratocumulus clouds form indicating mechanical mixing

b) Wind shear is the abrupt rate of change of wind velocity (direction and/or speed) per unit of distance and is normally expressed as vertical or horizontal wind shear. Hazardous wind shear may be expected in areas of low-level temperature inversion, frontal zones, and clear air turbulence

If the temperature/dewpoint spread is small and decreasing, and the temperature is 62 F, what type weather is most likely to develop?

a) freezing precipitation

b) thunderstorms

c) fog or low clouds

c) The difference between the air temperature and dew point is the temperature / dew point spread. As the temperature / dew point spread decreases, fog or low clouds tend to develop

What is meant by the term "dewpoint"?

a) the temperature at which condensation and evaporation are equal

b) the temperature at which dew will always form

c) the temperature to which air must be cooled to become saturated

c) Dew point is the temperature to which air must be cooled to become saturated or have 100% humidity

The amount of water vapor which air can hold depends on the:

a) dewpoint

b) air temperature

c) stability of the air

b) Air temperature largely determines how much water vapor can be held by the air. Warm air can hold more water vapor than cool air

What are the processes by which moisture is added to unsaturated air?

a) evaporation and sublimation

b) heating and condensation

c) supersaturation and evaporation

a) Evaporation is the process of converting a liquid to water vapor, and sublimation is the process of converting ice to water vapor

Which conditions result in the formation of frost?

a) the temperature of the collecting surface is at or below freezing when small droplets of moisture fall on the surface

b) the temperature of the collecting surface is at or below the dewpoint of the adjacent air and the dewpoint is below freezing

c) the temperature of the surrounding air is at or below freezing when small drops of moisture fall on the collecting surface

b) Frost forms when both the collecting surface is below the dew point of the adjacent air and the dew point is below freezing. Frost is the deposition of water vapor to ice crystals

Clouds, fog, or dew will always form when:

a) water vapor condenses

b) water vapor is present

c) relative humidity reaches 100 percent

a) As water vapor condenses, it becomes visible as clouds, fog, or dew.

Low-level turbulence can occur and icing can become hazardous in which type of fog?

a) rain-induced fog

b) upslope fog

c) steam fog

c) Steam fog forms in winter when cold, dry air passes from land areas or over completely warm ocean waters and is composed entirely of water droplets that often freeze quickly. Low-level turbulence can occur, and icing can become hazardous.

In which situation is advancing fog most likely to form?

a) A warm, moist air mass on the windward side of mountains

b) An air mass moving inland from the coast in winter

c) A light breeze blowing colder air out to sea

b) Advection fog forms when moist air moves over colder ground or water. It is most common in coastal areas.

What situation is most conducive to the formation of radiation fog?

a) Warm, moist air over low, flatland areas on clear, calm nights

b) Moist, tropical air moving over cold, offshore water

c) The movement of cold air over much warmer water

a) Radiation fog is shallow fog of which ground fog is one form. It occurs under conditions of clear skies, little or no wind, and a small temperature/dew point spread. The fog forms almost exclusively at night or near dawn as a result of terrestrial radiation cooling the ground and the ground cooling the air on contact with it.

What types of fog depend upon wind in order to exist?

a) Radiation fog and ice fog

b) Steam fog and ground fog

c) Advection fog and upslope fog

c) Advection fog forms when moist air moves over colder ground or water. It is common in coastal areas. Upslope fog forms when wind blows moist air upward over rising terrain and the air cools below its dew point. Both advection fog and upslope fog require wind to move air masses.

Clouds are divided into four families according to their

a) outward shape

b) height range

c) composition

b) The four families of clouds are high clouds, middle clouds, low clouds, and clouds with extensive vertical development. Thus, they are based upon their height range.

The suffix "nimbus", used in naming clouds, means:

a) a cloud with extensive vertical development

b) a rain cloud

c) a middle cloud containing ice pellets

b) The suffix "nimbus" or the prefix "nimbo" means a rain cloud.

The conditions necessary for the formation of cumulonimbus clouds are a lifting action and:

a) unstable air containing an excess of condensation nuclei

b) unstable, moist air

c) either stable or unstable air

b) Unstable, moist air, in addition to a lifting action, ie convective activity, is needed to form cumulonimbus clouds.

What clouds have the greatest turbulence?

a) towering cumulus

b) cumulonimbus

c) nimbostratus

b) The greatest turbulence occurs in cumulonimbus clouds, which are thunderstorm clouds.

What cloud types would indicate convective turbulence?

a) cirrus clouds

b) nimbostratus clouds

c) towering cumulus clouds

c) Towering cumulus clouds are an early stage of cumulonimbus clouds, or thunderstorms, that are based on convective turbulence, ie an unstable lapse rate.

At approximately what altitude above the surface would the pilot expect the base of cumuliform clouds if the surface air temperature is 82 F and the dewpoint is 38 F?

a) 9,000 ft AGL

b) 10,000 ft AGL

c) 11,000 ft AGL

b) The height of cumuliform cloud bases can be estimated using surface temperature/dew point spread. Unsaturated air in a convective current cools at about 5.4F/1000ft, and dew point decreases about 1F/1000ft. In a convective current, temperature and dew point converge at about 4.4F/1000ft. Thus, if the temperature/dew point spread is 44F (82F-38F), divide 44 by 4.4 to obtain 10,000 ft AGL.

What is the approximate base of the cumulus clouds if the surface air temperature at 1,000 ft MSL is 70 F and the dewpoint is 48 F?

a) 4,000 ft MSL

b) 5,000 ft MSL

c) 6,000 ft MSL

c) The height of cumuliform cloud bases can be estimated using surface temperature/dew point spread. Unsaturated air in a convective current cools at about 5.4F/1000ft, and dew point decreases about 1F/1000ft. In a convective current, temperature and dew point converge at about 4.4F/1000ft. Thus, if the temperature and dew point are 70F and 48F, respectively, at 1,000 ft MSL, there would be a 22F spread that, divided by the lapse rate of 4.4, is approximately 5,000ft AGL, or 6,000 ft MSL (5,000 + 1,000).

What is characteristic of stable air?

a) stratiform clouds

b) unlimited visibility

c) cumulus clouds

a) Characteristics of a stable air mass include stratiform clouds, continuous precipitation, smooth air, and fair to poor visibility in haze and smoke

When warm, moist, stable air flows upslope, it:

a) produces stratus type clouds

b) causes showers and thunderstorms

c) develops convective turbulence

a) Moist, stable air flowing upslope can be expected to produce stratus type clouds as the air cools adiabatically as it moves up sloping terrain

If an unstable air mass is forced upward, what type clouds can be expected?

a) Stratus clouds with little vertical development

b) Stratus clouds with considerable associated turbulence

c) Clouds with considerable vertical development and associated turbulence

c) When unstable air is lifted, it usually results in considerable vertical development and associated turbulence, ie convective activity.

What are characteristics of unstable air?

a) Turbulence and good surface visibility

b) Turbulence and poor surface visibility

c) Nimbostratus clouds and good surface visibility

a) Characteristics of an unstable air mass include cumuliform clouds, showery precipitation, turbulence, and good visibility, except in blowing obstructions

A stable air mass is most likely to have which characteristic?

a) showery precipitation

b) turbulent air

c) poor surface visibility

c) Characteristics of a stable air mass include stratiform clouds and fog, continuous precipitation, smooth air, and fair to poor visibility in haze and smoke

Steady precipitation preceding a front is an indication of:

a) stratiform clouds with moderate turbulence

b) cumuliform clouds with little or no turbulence

c) stratiform clouds with little or no turbulence

c) Steady precipitation preceding a front is usually an indication of a warm front, which results from warm air being cooled from the bottom by colder air. This results in stratiform clouds with little or no turbulence.

What are characteristics of a moist, unstable air mass?

a) cumuliform clouds and shower precipitation

b) poor visibility and smooth air

c) stratiform clouds and showery precipitation

a) Characteristics of an unstable air mass include cumuliform clouds, showery precipitation, turbulence, and good visibility, except in blowing obstructions

What measurement can be used to determine the stability of the atmosphere?

a) atmospheric pressure

b) actual lapse rate

c) surface temperature

b) The stability of the atmosphere is determined by vertical movements of air. Warm air rises when the air above is cooler. The actual lapse rate, which is the decrease of temperature with altitude, is therefore a measure of stability.

What would decrease the stability of an air mass?

a) warming from below

b) cooling from below

c) decrease in water vapor

a) When air is warmed from below, even though cooling adiabatically, it remains warmer than the surrounding air. The colder, more dense surrounding air forces the warmer air upward, and an unstable condition develops.

What are the characteristics of an unstable atmosphere?

a) a cool, dry air mass

b) a warm, humid air mass

c) descending air in the northern hemisphere

b) The stability of the atmosphere depends on its ability to resist vertical motion. As air temperature and air moisture increase, the density of the air decreases, causing it to rise. This creatures an unable atmosphere in which small vertical air movements tend to become larger, resulting in turbulent airflow and convective activity.

What feature is associated with a temperature inversion?

a) a stable layer of air

b) an unstable layer of air

c) chinook winds on mountain slopes

a) A temperature inversion is associated with an increase in temperature with height, a reversal of normal decrease in temperature with height. Thus, any warm air rises to where it is the same temperature and forms a stable layer of air.

The most frequency type of ground or surface-based temperature inversion is that which is produced by:

a) terrestrial radiation on a clear, relatively still night

b) warm air being lifted rapidly aloft in the vicinity of mountainous terrain

c) the movement of colder air under warm air, or the movement of warm air over cold air

a) An inversion often develops near the ground on clear, cool nights when wind is light. The ground loses heat and cools the air near the ground while the temperature a few hundred feet above changes very little. Thus, temperature increases in height, which is an inversion.

When there is a temperature inversion, you would expect to experience:

a) clouds with extensive vertical development above an inversion aloft

b) good visibility in the lower levels of the atmosphere and poor visibility above an inversion aloft

c) an increase in temperature as altitude increases

c) By definition, a temperature inversion is a situation in which the temperature increases as altitude increases. The normal situation is that the temperature decreases as altitude increases.

Which weather conditions should be expected beneath a low-level temperature inversion layer when the relative humidity is high?

a) smooth air, poor visibility, fog, haze, or low clouds

b) light wind shear, poor visibility, haze, and light rain

c) turbulent air, poor visibility, fog, low stratus type clouds, and showery precipitation

a) Beneath temperature inversions, there is usually smooth air because there is little movement due to the inversion. There is also poor visibility due to fog, haze, and low clouds (when there is high relative humidity)

What cloud types would indicate convective turbulence quizlet?

What is convective turbulence?

What clouds are associated with turbulence?

Where is convective turbulence the strongest?