PTS Quiz #11

Smooth air, poor visibility, fog, haze, or low clouds. Explanation: Inversion layers are commonly shallow layers of smooth, stable air close to the ground with poor visibility and low clouds. B and C are incorrect because winds and turbulence are characteristics of unstable air.

The temperature to which air must be cooled to become saturated. Explanation: It is the definition of dewpoint.

air temperature. Explanation: Temperature largely determines the maximum amount of water vapor air can hold. Warm air can hold more water vapor than cool air. A is incorrect because air stability does not determine how much water vapor air can hold. B is incorrect because dewpoint can only determine relative humidity at a given temperature, and an increase in temperature would in effect raise the amount of water vapor that the air can hold.

Stratiform clouds. Explanation: Stable air masses are calm; stratiform clouds are smooth and they do not build vertically like cumulus clouds. B is incorrect because stable air usually contains dust or smoke, which will cause low visibility. C is incorrect because cumulus clouds are a sign of atmospheric instability.

produce upslope fog (a type of low cloud). Explanation: Upslope fog occurs when moist, stable air is forced up sloping land features like a mountain range. Fog is also classified as a type of low cloud formation. B is incorrect because a rain or snow is the characteristic of unstable air. C is incorrect because convective turbulence if the up and down air movement, which is obviously unstable.

10,000 feet AGL. Explanation: Temperature and dew points merge at a rate of 4.4 degrees F per 1000 feet. So (82-38)/4.4*1000=10,000 feet AGL.

Smooth air. Explanation: characteristics of stable air: stratiform clouds, continuous precipitation, smooth air, poor visibility. A and B are incorrect because of the following characteristics of unstable air: cumulus clouds, showery precipitation, turbulence, good visibility.

standing lenticular clouds. Explanation: It is easy to associate lens-shaped with "lenticular".

front. Explanation: The definition of a front is simply the boundary between two air masses.

across a mountain ridge, and the air is stable. Explanation: Mountain waves form when the wind blows perpendicular to a mountain range on the leeward (or downwind) side of the mountains after the wind passes up and over the mountain, creating turbulence and eddies that could "suck" an aircraft into the side of the mountain if flying too closely. A and B are both incorrect because the wind runs parallel to the mountain range in these circumstances, and mountain waves are less likely to occur.

squall line thunderstorms. Explanation: Squall line thunderstorms can produce heavy hail, destructive winds, or tornadoes.

An air mass moving inland from the coast in winter. Explanation: The advection fog is a result of moist air condensing as it moves over a cooler surface.

Troposphere Explanation: Most weather occurs in the troposphere, which extends from the surface to 20,000 feet over the poles and to 48,000 feet over the equator.

Both A and B Explanation: Both cabin pressurization and the use of supplemental oxygen are ways to mitigate the risk of hypoxia.

Variations in surface resulting in uneven heating Explanation: Different surfaces radiate heat in varying amounts. Plowed ground, rocks, sand, and barren land give off a large amount of heat; water, trees, and other areas of vegetation tend to absorb and retain heat. The resulting uneven heating of the air creates small areas of local circulation called convective currents. Convective currents cause the bumpy, turbulent air sometimes experienced when flying at lower altitudes during warmer weather.

heat exchange. Explanation: As water changes from one state to another, an exchange of heat takes place.

friction between the wind and the surface. Explanation: Differences between the surfaces of continents and oceans, and other factors such as frictional forces caused by the topography of the Earths surface modify the movement of the air in the atmosphere.

Warming from below. Explanation: Cooler air wants to stay near the ground and warmer air want to rise up. Warming up the air from below will always rise the bottom air up which makes the air less stable. B is incorrect because it will make the air more stable. C is incorrect because humid air is lighter than dry air, thus decreasing the water vapor will let the air heavier and more stable.

Turbulence and good surface visibility. Explanation: It is easy to associate turbulence with unstable air. B is incorrect because stable air usually contains dust or smoke, which will cause low visibility. So unstable air will have good visibility in contrast. C is incorrect because nimbostratus clouds are dark, low-level clouds with precipitation that exist in stable air.

unstable, moist air. Explanation: To form cumulonimbus clouds (thunderstorm), unstable air, high humidity, and lifting action are necessary.

High humidity, lifting force, and unstable conditions. Explanation: To form a thunderstorm (cumulonimbus clouds), unstable air, high humidity, and lifting action are necessary.

Warm, moist air over low, flatland areas on clear, calm nights. Explanation: Radiation fog can occur when clear sky, little or no wind, and a small temperature/dew point spread.

Fog or low clouds. Explanation: When the temperature and dew point are close, and the temperature is above freezing, it is more likely to form fog.

Down 2 degrees Celsius per 1,000 feet Explanation: The standard lapse rate is minus 2 degrees per 1,000 feet of altitude gain.

7.4 lb/sq in Explanation: At 18,000 feet, the weight of air is 7.4 lb/sq in, almost 50% than at sea level.

Unstable, clouds and precipitation Explanation: Air flows into a low pressure area to replace rising air. This air tends to be unstable, and usually brings increasing cloudiness and precipitation. Thus, bad weather is commonly associated with areas of low pressure.