Weather

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? Group of answer choices 10,000 feet AGL. 11,000 feet AGL. 9,000 feet AGL.

10,000 feet AGL. When lifted, unsaturated air cools at approximately 5.4°F per 1,000 feet. The dew point cools at approximately 1°F per 1,000 feet. Therefore, the convergence of the temperature and dew point lapse rates is 4.4°F per 1,000 feet. The base of a cloud (AGL) that is formed by vertical currents can be roughly calculated by dividing the difference between the surface temperature and the dew point by 4.4 and multiplying the rounded result by 1,000. 1. 82°F surface temperature - 38°F dew point = 44°F 2. 44 ÷ 4.4 = 10 3. 10 x 1,000 = 10,000 feet AGL

A pilot can expect a wind-shear zone in a temperature inversion whenever the windspeed at 2,000 to 4,000 feet above the surface is at least Group of answer choices 10 knots. 15 knots. 25 knots.

25 knots. An increase in temperature with altitude is defined as a temperature inversion. A pilot can be relatively certain of a shear zone in the inversion if the pilot knows the wind at 2,000 to 4,000 feet is 25 knots or more.

What is the approximate base of the cumulus clouds if the surface air temperature at 1,000 feet MSL is 70°F and the dewpoint is 48°F? Group of answer choices 6,000 feet MSL. 5,000 feet MSL. 4,000 feet MSL.

6,000 feet MSL. When lifted, unsaturated air cools at approximately 5.4°F per 1,000 feet. The dew point cools at approximately 1°F per 1,000 feet. Therefore, the convergence of the temperature and dew point lapse rates is 4.4°F per 1,000 feet. The base of a cloud (AGL) that is formed by vertical currents can be roughly calculated by dividing the difference between the surface temperature and the dew point by 4.4 and multiplying the rounded result by 1,000. 1. 70°F surface temperature - 48°F dew point = 22°F 2. 22 ÷ 4.4 = 5 3. 5 x 1,000 = 5,000 feet AGL 4. 5,000 feet AGL + 1,000 feet field elevation = 6,000 feet MSL

What feature is associated with a temperature inversion? Group of answer choices Chinook winds on mountain slopes. An unstable layer of air. A stable layer of air.

A stable layer of air. If the temperature increases with altitude through a layer (an inversion), the layer is stable and convection is suppressed.

What measurement can be used to determine the stability of the atmosphere? Group of answer choices Actual lapse rate. Atmospheric pressure. Surface temperature.

Actual lapse rate. The difference between the existing lapse rate of a given mass of air and the adiabatic rates of cooling in upward moving air determines if the air is stable or unstable.

What types of fog depend upon wind in order to exist? Group of answer choices Steam fog and ground fog. Advection fog and upslope fog. Radiation fog and ice fog.

Advection fog and upslope fog. Advection fog forms when moist air moves over colder ground or water. It is most common along coastal areas, but often develops deep in continental areas. Advection fog deepens as wind speed increases up to about 15 knots. Wind much stronger than 15 knots lifts the fog into a layer of low stratus or stratocumulus. Upslope fog forms as a result of moist, stable air being cooled adiabatically as it moves up sloping terrain. Once upslope wind ceases, the fog dissipates.

In which situation is advection fog most likely to form? Group of answer choices A light breeze blowing colder air out to sea. A warm, moist air mass on the windward side of mountains. An air mass moving inland from the coast in winter.

An air mass moving inland from the coast in winter. Advection fog forms when moist air moves over colder ground or water. It is most common along coastal areas. This fog frequently forms offshore as a result of cold water, then is carried inland by the wind.

Where does wind shear occur? Group of answer choices Only at lower altitudes. At all altitudes, in all directions. Only at higher altitudes.

At all altitudes, in all directions. Wind shear may be associated with either a wind shift or a wind speed gradient at any level in the atmosphere.

If an unstable air mass is forced upward, what type clouds can be expected? Group of answer choices Clouds with considerable vertical development and associated turbulence. Stratus clouds with considerable associated turbulence. Stratus clouds with little vertical development.

Clouds with considerable vertical development and associated turbulence. When unstable air is forced upward, the disturbance grows. Any resulting cloudiness shows extensive vertical development.

What feature is normally associated with the cumulus stage of a thunderstorm? Group of answer choices Frequent lightning. Continuous updraft. Roll cloud.

Continuous updraft. The key feature of the cumulus stage is an updraft. Precipitation beginning to fall from the cloudbase is the signal that a downdraft has developed also and a cell has entered the mature stage.

What are characteristics of a moist, unstable air mass? Group of answer choices Poor visibility and smooth air. Stratiform clouds and showery precipitation. Cumuliform clouds and showery precipitation.

Cumuliform clouds and showery precipitation. Characteristics of a moist, unstable air mass include cumuliform clouds, showery precipitation, rough air (turbulence), and good visibility (except in blowing obstructions).

What clouds have the greatest turbulence? Group of answer choices Towering cumulus. Cumulonimbus. Nimbostratus.

Cumulonimbus. Cumulonimbus 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.

During the life cycle of a thunderstorm, which stage is characterized predominately by downdrafts? Group of answer choices Mature. Cumulus. Dissipating.

Dissipating. Downdrafts characterize the dissipating stage of the thunderstorm cell and the storm dies rapidly.

What are the processes by which moisture is added to unsaturated air? Group of answer choices Supersaturation and evaporation. Evaporation and sublimation. Heating and condensation.

Evaporation and sublimation. Evaporation is the changing of liquid water to invisible water vapor. Sublimation is the changing of solid water directly to the vapor phase or water vapor to ice, by passing the liquid state in each process.

If the temperature/dewpoint spread is small and decreasing, and the temperature is 62°F, what type weather is most likely to develop? Group of answer choices Freezing precipitation. Fog or low clouds. Thunderstorms.

Fog or low clouds. With a small temperature/dew point spread, the air is close to saturation. This will usually result in fog or low clouds. Anticipate fog when the temperature/dew point spread is 5°F or less and decreasing.

In which environment is aircraft structural ice most likely to have the highest accumulation rate? Group of answer choices Freezing drizzle. Freezing rain. Cumulus clouds with below freezing temperatures.

Freezing rain. A condition favorable for rapid accumulation of clear icing is freezing rain below a frontal surface.

How does frost affect the lifting surfaces of an airplane on takeoff? Group of answer choices Frost may prevent the airplane from becoming airborne at normal takeoff speed. Frost may cause the airplane to become airborne with a lower angle of attack at a lower indicated airspeed. Frost will change the camber of the wing, increasing lift during takeoff.

Frost may prevent the airplane from becoming airborne at normal takeoff speed. The roughness of the surface of frost spoils the smooth flow of air, thus causing a slowing of the airflow. This slowing of the air causes early air flow separation over the affected airfoil, resulting in a loss of lift. Even a small amount of frost on airfoils may prevent an aircraft from becoming airborne at normal takeoff speed.

Why is frost considered hazardous to flight? Group of answer choices Frost changes the basic aerodynamic shape of the airfoils, thereby increasing lift. Frost spoils the smooth flow of air over the wings, thereby decreasing lifting capability. Frost slows the airflow over the airfoils, thereby increasing control effectiveness.

Frost spoils the smooth flow of air over the wings, thereby decreasing lifting capability. The roughness of the surface of frost spoils the smooth flow of air, thus causing a slowing of the airflow. This slowing of the air causes early air flow separation over the affected airfoil, resulting in a loss of lift. Even a small amount of frost on airfoils may prevent an aircraft from becoming airborne at normal takeoff speed.

How will frost on the wings of an airplane affect takeoff performance? Group of answer choices Frost will change the camber of the wing, increasing its lifting capability. Frost will disrupt the smooth flow of air over the wing, adversely affecting its lifting capability. Frost will cause the airplane to become airborne with a higher angle of attack, decreasing the stall speed.

Frost will disrupt the smooth flow of air over the wing, adversely affecting its lifting capability. The roughness of the surface of frost spoils the smooth flow of air, thus causing a slowing of the airflow. This slowing of the air causes early air flow separation over the affected airfoil, resulting in a loss of lift. Even a small amount of frost on airfoils may prevent an aircraft from becoming airborne at normal takeoff speed.

What conditions are necessary for the formation of thunderstorms? Group of answer choices High humidity, lifting force, and unstable conditions. Lifting force, moist air, and extensive cloud cover. High humidity, high temperature, and cumulus clouds.

High humidity, lifting force, and unstable conditions. For a cumulonimbus cloud or thunderstorm to form, the air must have: 1. Sufficient water vapor, 2. An unstable lapse rate, and 3. An initial upward boost (lifting) to start the storm process in motion.

When may hazardous wind shear be expected? Group of answer choices When stable air crosses a mountain barrier where it tends to flow in layers forming lenticular clouds. Following frontal passage when stratocumulus clouds form indicating mechanical mixing. In areas of low-level temperature inversion, frontal zones, and clear air turbulence.

In areas of low-level temperature inversion, frontal zones, and clear air turbulence. Hazardous wind shear can occur near the ground with either thunderstorms or a strong temperature inversion.

Upon encountering severe turbulence, which flight condition should the pilot attempt to maintain? Group of answer choices Level flight attitude. Constant altitude and airspeed. Constant angle of attack.

Level flight attitude. The primary concern is to avoid undue stress on the airframe. This can best be done by attempting to maintain a constant attitude while keeping the airspeed below design maneuvering speed (V(A)).

Which weather phenomenon is always associated with a thunderstorm? Group of answer choices Lightning. Heavy rain. Hail.

Lightning. A thunderstorm is, in general, a local storm invariably produced by a cumulonimbus cloud, and is always accompanied by lightning and thunder.

A stable air mass is most likely to have which characteristic? Group of answer choices Showery precipitation. Turbulent air. Poor surface visibility.

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

Which weather phenomenon signals the beginning of the mature stage of a thunderstorm? Group of answer choices The appearance of an anvil top. Precipitation beginning to fall. Maximum growth rate of the clouds.

Precipitation beginning to fall. The key feature of the cumulus stage is an updraft. Precipitation beginning to fall from the cloudbase is the signal that a downdraft has developed also and the cell has entered the mature stage.

Which weather conditions should be expected beneath a low-level temperature inversion layer when the relative humidity is high? Group of answer choices Smooth air, poor visibility, fog, haze, or low clouds. Light wind shear, poor visibility, haze, and light rain. Turbulent air, poor visibility, fog, low stratus type clouds, and showery precipitation.

Smooth air, poor visibility, fog, haze, or low clouds. A ground-based inversion leads to poor visibility by trapping fog, smoke, and other restrictions into low levels of the atmosphere. The layer is stable and convection is suppressed.

Low-level turbulence can occur and icing can become hazardous in which type of fog? Group of answer choices Steam fog. Rain-induced fog. Upslope fog.

Steam fog. Steam fog forms in the winter when cold, dry air passes from land areas over comparatively warm ocean waters. Low-level turbulence can occur and icing can become hazardous in a steam fog.

What is a characteristic of stable air? Group of answer choices Stratiform clouds. Cumulus clouds. Unlimited visibility.

Stratiform clouds. Since stable air resists convection, clouds in stable air form in horizontal, sheet-like layers or 'strata.'

Which conditions result in the formation of frost? Group of answer choices The temperature of the collecting surface is at or below freezing when small droplets of moisture fall on the surface. The temperature of the collecting surface is at or below the dewpoint of the adjacent air and the dewpoint is below freezing. The temperature of the surrounding air is at or below freezing when small drops of moisture fall on the collecting surface.

The temperature of the collecting surface is at or below the dewpoint of the adjacent air and the dewpoint is below freezing. Frost forms in much the same way as dew. The difference is that the dew point of surrounding air must be colder than freezing.

What is meant by the term 'dewpoint'? Group of answer choices The temperature at which dew will always form. The temperature to which air must be cooled to become saturated. The temperature at which condensation and evaporation are equal.

The temperature to which air must be cooled to become saturated. Dew point is the temperature to which air must be cooled to become saturated by the water vapor already present in the air.

What cloud types would indicate convective turbulence? Group of answer choices Towering cumulus clouds. Nimbostratus clouds. Cirrus clouds.

Towering cumulus clouds. Towering cumulus signifies a relatively deep layer of unstable air. They show considerable vertical development and have billowing cauliflower tops. Showers can result from these clouds. Expect very strong turbulence, and perhaps some clear icing above the freezing level.

What are characteristics of unstable air? Group of answer choices Turbulence and poor surface visibility. Nimbostratus clouds and good surface visibility. Turbulence and good surface visibility.

Turbulence and good surface visibility. Characteristics of an unstable air mass include cumuliform clouds, showery precipitation, rough air (turbulence), and good visibility (except in blowing obstructions).

What causes variations in altimeter settings between weather reporting points? Group of answer choices Unequal heating of the Earth's surface. Coriolis force. Variation of terrain elevation.

Unequal heating of the Earth's surface. All altimeter settings are corrected to sea level. Unequal heating of the Earth's surface causes pressure differences.

What situation is most conducive to the formation of radiation fog? Group of answer choices Moist, tropical air moving over cold, offshore water. Warm, moist air over low, flatland areas on clear, calm nights. The movement of cold air over much warmer water.

Warm, moist air over low, flatland areas on clear, calm nights. Conditions favorable for radiation fog are clear sky, little or no wind, and small temperature/dew point spread (high relative humidity). Radiation fog is restricted to land because water surfaces cool little from nighttime radiation.

What would decrease the stability of an air mass? Group of answer choices Warming from below. Decrease in water vapor. Cooling from below.

Warming from below. When air near the surface is warm and moist, suspect instability. Surface heating, cooling aloft, converging or upslope winds, or an invading mass of colder air may lead to instability and cumuliform clouds.

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? Group of answer choices Wind-shear turbulence. Steady rain. Precipitation static.

Wind-shear turbulence. Wind shear is an invisible hazard associated with all thunderstorms. Shear turbulence has been encountered 20 miles laterally from a severe storm.

One of the most easily recognized discontinuities across a front is Group of answer choices an increase in cloud coverage. an increase in relative humidity. a change in temperature.

a change in temperature. Temperature is one of the most easily recognized discontinuities across a front.

An almond or lens-shaped cloud which appears stationary, but which may contain winds of 50 knots or more, is referred to as Group of answer choices a lenticular cloud. a funnel cloud. an inactive frontal cloud.

a lenticular cloud. Crests of standing waves may be marked by stationary, lens-shaped clouds known as standing lenticular clouds.

The suffix 'nimbus,' used in naming clouds, means Group of answer choices a middle cloud containing ice pellets. a rain cloud. a cloud with extensive vertical development.

a rain cloud. The prefix 'nimbo-' or suffix '-nimbus' means rain cloud.

Possible mountain wave turbulence could be anticipated when winds of 40 knots or greater blow Group of answer choices down a mountain valley, and the air is unstable. across a mountain ridge, and the air is stable. parallel to a mountain peak, and the air is stable.

across a mountain ridge, and the air is stable. Always anticipate possible mountain wave turbulence when strong winds of 40 knots or greater blow across a mountain or ridge and the air is stable.

The amount of water vapor which air can hold depends on the Group of answer choices dewpoint. stability of the air. air temperature.

air temperature. Temperature largely determines the maximum amount of water vapor air can hold.

When there is a temperature inversion, you would expect to experience Group of answer choices clouds with extensive vertical development above an inversion aloft. good visibility in the lower levels of the atmosphere and poor visibility above an inversion aloft. an increase in temperature as altitude increases.

an increase in temperature as altitude increases. An increase in temperature with altitude is defined as an inversion. An inversion often develops near the ground on clear, cool nights when wind is light. The ground radiates heat and cools much faster than the overlying air. Air in contact with the ground becomes cold while the temperature a few hundred feet above changes very little. Thus, the temperature increases with height. A ground-based inversion usually means poor visibility.

Convective circulation patterns associated with sea breezes are caused by Group of answer choices warm, dense air moving inland from over the water. cool, dense air moving inland from over the water. water absorbing and radiating heat faster than the land.

cool, dense air moving inland from over the water. Caused by the heating of land on warm, sunny days, the sea breeze usually begins during early forenoon, reaches a maximum during the afternoon, and subsides around dusk after the land has cooled. The leading edge of the cool sea breeze forces warmer air inland to rise. Rising air from over land returns seaward at higher altitude to complete the convective cell.

The wind at 5,000 feet AGL is southwesterly while the surface wind is southerly. This difference in direction is primarily due to Group of answer choices stronger Coriolis force at the surface. friction between the wind and the surface. stronger pressure gradient at higher altitudes.

friction between the wind and the surface. Friction between the wind and the surface slows the wind. The Coriolis force has less affect on slower winds, therefore there will be less deflection with surface winds than with winds at 5,000 feet AGL.

Every physical process of weather is accompanied by, or is the result of, a Group of answer choices movement of air. pressure differential. heat exchange.

heat exchange. Every physical process of weather is accompanied by, or is a result of, unequal heating of the Earth's surface.

Clouds are divided into four families according to their Group of answer choices height range. composition. outward shape.

height range. For identification purposes, clouds are divided into four families: high clouds, middle clouds, low clouds, and clouds with extensive vertical development.

The presence of ice pellets at the surface is evidence that there Group of answer choices are thunderstorms in the area. has been cold frontal passage. is a temperature inversion with freezing rain at a higher altitude.

is a temperature inversion with freezing rain at a higher altitude. Ice pellets always indicate freezing rain at higher altitude.

Thunderstorms reach their greatest intensity during the Group of answer choices cumulus stage. downdraft stage. mature stage.

mature stage. All thunderstorm hazards reach their greatest intensity during the mature stage.

When warm, moist, stable air flows upslope, it Group of answer choices develops convective turbulence. produces stratus type clouds. causes showers and thunderstorms.

produces stratus type clouds. When stable air is forced upward the air tends to retain horizontal flow and any cloudiness is flat and stratified.

Thunderstorms which generally produce the most intense hazard to aircraft are Group of answer choices warm front thunderstorms. steady-state thunderstorms. squall line thunderstorms.

squall line thunderstorms. A squall line is a non-frontal, narrow band of active thunderstorms. 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.

A nonfrontal, narrow band of active thunderstorms that often develop ahead of a cold front is known as a Group of answer choices prefrontal system. squall line. dry line.

squall line. A squall line is a nonfrontal, narrow band of active thunderstorms. 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.

Crests of standing mountain waves may be marked by stationary, lens-shaped clouds known as Group of answer choices mammatocumulus clouds. roll clouds. standing lenticular clouds.

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

Steady precipitation preceding a front is an indication of Group of answer choices cumuliform clouds with little or no turbulence. stratiform clouds with little or no turbulence. stratiform clouds with moderate turbulence.

stratiform clouds with little or no turbulence. Precipitation from stratiform clouds is usually steady and there is little or no turbulence.

The most frequent type of ground or surface-based temperature inversion is that which is produced by Group of answer choices terrestrial radiation on a clear, relatively still night. the movement of colder air under warm air, or the movement of warm air over cold air. warm air being lifted rapidly aloft in the vicinity of mountainous terrain.

terrestrial radiation on a clear, relatively still night. An inversion often develops near the ground on clear, cool nights when wind is light. The ground radiates heat and cools much faster than the overlying air. Air in contact with the ground becomes cold while the temperature a few hundred feet above changes very little. Thus, the temperature increases with height.

The mature stage of a thunderstorm begins with Group of answer choices formation of the anvil top. the start of precipitation. continuous downdrafts.

the start of precipitation. The mature stage of a thunderstorm is characterized by updrafts and downdrafts inside the cloud and the start of rain.

The conditions necessary for the formation of cumulonimbus clouds are a lifting action and Group of answer choices either stable or unstable air. unstable, moist air. unstable air containing an excess of condensation nuclei.

unstable, moist air. For a cumulonimbus cloud or thunderstorm to form, the air must have: 1. Sufficient water vapor, 2. An unstable lapse rate, and 3. An initial upward boost (lifting) to start the storm process in motion.

During a cross-country flight you picked up rime icing which you estimate is 1/2" thick on the leading edge of the wings. You are now below the clouds at 2000 feet AGL and are approaching your destination airport under VFR. Visibility under the clouds is more than 10 miles, winds at the destination airport are 8 knots right down the runway, and the surface temperature is 3 degrees Celsius. You decide to Group of answer choices approach and land at your normal speed since the ice is not thick enough to have any noticeable effect. use a faster than normal approach and landing speed. fly your approach slower than normal to lessen the 'wind chill' effect and break up the ice

use a faster than normal approach and landing speed. Ice will accumulate unevenly on the airplane. It will add weight and drag, and decrease thrust and lift. With ice accumulations, landing approaches should be made with a minimum wing flap setting and with an added margin of airspeed. Sudden and large configuration and airspeed changes should be avoided.

One in-flight condition necessary for structural icing to form is Group of answer choices visible moisture. stratiform clouds. small temperature/dewpoint spread.

visible moisture. Two conditions are necessary for structural icing in flight: 1. The aircraft must be flying through visible water such as rain or cloud droplets, and 2. The temperature at the point where the moisture strikes the aircraft must be 0°C (32°F) or colder.

Clouds, fog, or dew will always form when Group of answer choices relative humidity reaches 100 percent. water vapor condenses. water vapor is present.

water vapor condenses. As water vapor condenses or sublimates on condensation nuclei, liquid or ice particles begin to grow. Some condensation nuclei have an affinity for water and can induce condensation or sublimation even when air is almost, but not completely, saturated.

One weather phenomenon which will always occur when flying across a front is a change in the Group of answer choices stability of the air mass. type of precipitation. wind direction.

wind direction. Wind direction always changes across a front.