What causes variations in altimeter settings between weather reporting points? |
Answer: Unequal heating of the earth's surface |
The wind at 5,000 feet AGL is southwesterly while the surface wind is southerly. This difference in direction is primarily due to |
Answer: friction between the wind and the surface |
Convective circulation patterns associated with sea breezes are caused by |
Answer: cool, dense air moving inland from over the water Explanation: During the day - land warmer than water - air flows from water to land. |
How will frost on the wings of an airplane affect takeoff performance? |
Answer: Frost will disrupt the smooth flow of air over the wing, adversely affecting its lifting capability |
Every physical process of weather is accompanied by, or is the result of, a |
Answer: heat exchange |
A temperature inversion would most likely result in which weather condition? |
Answer: Clouds with extensive vertical development above an inversion aloft Explanation: Normally, temperatures decrease with altitude. Inversion is opposite. |
the most frequent type of ground or surface-based temperature inversion is that which is produced by |
Answer: terrestrial radiation on a clear, relatively still night Explanation: Ground cools faster than overlying air |
Which weather conditions should be expected beneath a low-level temperature inversion layer when the relative humidity is high? |
Answer: Smooth air, poor visibility, fog, haze, or low clouds. |
What is meant by the term "dewpoint"? |
Answer: The temperature to which air must be cooled to become saturated |
The amount of water vapor which air can hold depends on the |
Answer: air temperature Explanation: Temperature is directly proportional to how much moisture can be in the air |
Clouds, fog, or dew will always form when |
Answer: water vapor condenses |
What are the processes by which moisture is added to unsaturated air? |
Answer: Evaporation and sublimation |
Which conditions result in the formation of frost? |
Answer: The temperature of the collecting surface is at or below the dewpoint of the adjacent air and the dewpoint is below freezing |
The presence of ice pellets at the surface is evidence that there |
Answer: is a temperature inversion with freezing rain at a higher altitude Explanation: Warm layer of air keeps rain in liquid form until it falls through a colder layer - inversion |
What measurement can be used to determine the stability of the atmosphere? |
Answer: Actual lapse rate Explanation: Stability - resistance to displacement up and down. Lapse rate - decrease in temperature with increase in altitude |
What would decrease the stability of an air mass? |
Answer: Warming from below |
What is a characteristic of stable air? |
Answer: Stratiform clouds Explanation: Cumulus clouds and good visibility - unstable air |
Moist, stable air flowing upslope can be expected to |
Answer: produce stratus type clouds |
If an unstable air mass is forced upward, what type clouds can be expected? |
Answer: Clouds with considerable vertical development and associated turbulence. |
What feature is associated with a temperature inversion? |
Answer: A stable layer of air |
What is the approximate base of the cumulus clouds if the surface air temperature at 1,000 feet MSL is 70 degrees F and the dewpoint is 48 degrees F? |
Answer: 6,000 feet MSL Explanation: Lapse rate - 4.5. Cloud base - Temp minus dewpoint divided by lapse rate times 1,000 plus elevation (70-48)/4.5)+1,000 |
At approximately what altitude above the surface would the pilot expect the base of cumuliform clouds if the surface air temperature is 82 degrees F and the dewpoint is 38 degrees F? |
Answer: 10,000 feet AGL Explanation: Lapse rate - 4.5. Cloud base - Temp minus dewpoint divided by lapse rate times 1,000 |
What are characteristics of a moist, unstable air mass? |
Answer: Cumuliform clouds and showery precipitation |
What are characteristics of unstable air? |
Answer: Turbulence and good surface visibility Explanation: Lifting motion produces turbulence and clears clouds and pollutants from sky |
A stable air mass is most likely to have which characteristic? |
Answer: Smooth air Explanation: Stable air resists the lifting motion |
The suffix "nimbus," used in naming clouds, means |
Answer: a rain cloud |
Clouds are divided into four families according to their |
Answer: height range |
The boundary between two different air masses is referred to as a |
Answer: front |
One of the most easily recognized discontinuities across a front is |
Answer: a change in temperature |
One weather phenomenon which will always occur when flying across a front is a change in the |
Answer: wind direction |
Steady precipitation preceding a front is an indication of |
Answer: stratiform clouds with little or no turbulence Explanation: These are indicative of stable air |
What situation is most conducive to the formation of radiation fog? |
Answer: Warm, moist air over low, flatland areas on clear, calm nights Explanation: Forms when moist air cools to the dewpoint. Ex. ground fog |
If the temperature/dewpoint spread is small and decreasing, and the temperature is 62 degrees F, what type weather is most likely to develop? |
Answer: Fog or low clouds Explanation: When temperature is close to dewpoint, you get condensation |
In which situation is advection fog most likely to form? |
Answer: An air mass moving inland from the coast in winter Explanation: When warmer air moves inland |
What types of fog depend upon wind in order to exist? |
Answer: Advection fog and upslope fog |
Low-level turbulence can occur and icing can become hazardous in which type of fog? |
Answer: Steam fog Explanation: formed by cold, dry air moving over warmer water |