Question 1

The environmental lapse rate decreases because of cold advection at higher altitudes and daytime solar heating.

Accepted Answer

The environmental lapse rate increases with cold advection at higher altitudes and daytime solar heating, as these processes make the upper atmosphere cooler and the surface warmer, respectively.

Question 2

Usually when a cumulonimbus cloud begins to dissipate, the bottom half of the cloud dissipates first.

Accepted Answer

The bottom half of a cumulonimbus cloud dissipates first because it is composed of water droplets, which are lighter than the ice crystals that make up the upper half of the cloud. As the cloud dissipates, the water droplets evaporate first, leaving behind the ice crystals.

Question 3

The up-and-down motions in layered clouds produce globular elements that give the clouds lumpy appearances.

Accepted Answer

The up-and-down motions within the atmosphere, particularly in stratiform or layered clouds, can lead to the formation of mammatus clouds, which are characterized by their globular, lumpy appearances. These formations are often associated with turbulent weather conditions and can appear on the underside of the cloud layer.

Question 4

Warm saturated air produces more liquid water than cold saturated air.

Accepted Answer

Warm saturated air can hold more water vapor than cold saturated air, so when it cools and condenses, it produces more liquid water.

Question 5

The environmental lapse rate is almost always the same as the adiabatic rate.

Accepted Answer

The environmental lapse rate, which is the rate at which the atmosphere's temperature decreases with an increase in altitude, varies depending on the specific conditions of the atmosphere at any given time and location. In contrast, the adiabatic rates (dry and moist) are theoretical rates at which the temperature of a parcel of air changes as it moves up or down in the atmosphere without exchanging heat with its surroundings. These rates are generally different from the actual environmental lapse rate.

Question 6

A layer of altostratus can change into one of altocumulus if the top of the original cloud deck cools while the bottom warms.

Accepted Answer

This transformation can occur because cooling at the top of the cloud layer increases stability, while warming at the bottom can lead to more convective activity, causing the cloud structure to break into smaller, cumulus-type clouds.

Question 7

If an air parcel is given a small push upward and it falls back to its original position, the atmosphere is said to be ____.

Accepted Answer

When an air parcel is given a small push upward and it falls back to its original position, the atmosphere is considered stable. This is because the parcel is returning to its equilibrium position, indicating that the surrounding atmospheric conditions are resisting its displacement.

Question 8

The temperature of rising air at a given level inside a cumulus cloud is normally warmer than the air around the cloud.

Accepted Answer

Rising air within a cumulus cloud is warmer than the surrounding air because it has been heated at the Earth's surface, causing it to rise due to its lower density compared to the cooler, denser air around it. This process is fundamental to the formation and sustenance of cumulus clouds.

Question 9

The combination of warming the surface and warming the air aloft creates the greatest atmospheric stability.

Accepted Answer

Warming the surface and cooling the air aloft increases atmospheric instability, leading to potential convection and turbulent weather. Stability is enhanced when the air aloft is warmer relative to the surface, reducing the tendency for air to rise.

Question 10

Subsidence inversions are just as common on Earth's surface as they are aloft.

Accepted Answer

Subsidence inversions are more common aloft because they typically form as air descends and warms adiabatically, which is a process more prevalent in the upper atmosphere than at Earth's surface.

Question 11

Cumulus clouds are a common phenomenon over cool water surfaces.

Accepted Answer

Cumulus clouds typically form over warm surfaces, as they are created by warm air rising due to convection. Cool water surfaces are less likely to produce the thermal updrafts needed for cumulus cloud formation.

Question 12

Environmental lapse rate and dry adiabatic rate are different expressions for the same phenomenon.

Accepted Answer

Environmental lapse rate refers to the actual rate at which atmospheric temperature decreases with altitude, while the dry adiabatic rate is the rate at which the temperature of a dry air parcel changes as it moves up or down in the atmosphere without exchanging heat with its surroundings.

Question 13

Convective instability associated with severe thunderstorms and tornadoes can be brought on by lifting a stable air layer whose surface is humid and whose top is dry.

Accepted Answer

Convective instability occurs when a layer of moist air at the surface is overlain by drier air aloft. When this moist surface air is lifted, it can cool at a rate slower than the dry air above it due to its moisture content. This differential cooling can lead to instability, promoting the development of severe thunderstorms and potentially tornadoes as the rising warm, moist air interacts with the cooler, drier air above.

Question 14

It is possible for a layer of air to be convectively unstable and absolutely stable at the same time.

Accepted Answer

Convective instability refers to the tendency of a fluid to overturn due to density differences, while absolute stability refers to the tendency of a fluid to resist overturning due to the presence of a stable density gradient. It is possible for a layer of air to be convectively unstable due to a lapse rate that is greater than the adiabatic lapse rate, but absolutely stable due to the presence of a stable density gradient caused by, for example, a temperature inversion.

Question 15

Subsidence has no effect on atmospheric stability.

Accepted Answer

Subsidence, or the sinking of air, typically leads to atmospheric stability because it warms the air adiabatically, making the lower atmosphere more stable and reducing the likelihood of convection and cloud formation.

Question 16

The atmosphere is normally most stable in the early morning and most unstable in the afternoon.

Accepted Answer

The atmosphere is typically most stable in the early morning due to the cooling of the surface overnight, which reduces vertical mixing. It becomes most unstable in the afternoon as the sun heats the surface, increasing vertical mixing and potential for convection.

Question 17

Sinking air sometimes cools adiabatically.

Accepted Answer

Sinking air typically warms adiabatically because as it descends, the pressure increases, causing the air to compress and increase in temperature.

Question 18

The safest place to build an airport in a mountainous region is along a deep valley.

Accepted Answer

A deep valley provides a relatively flat and stable surface for building an airport, and it is less likely to be affected by strong winds or other weather conditions that can make flying dangerous.

Question 19

A rising parcel of air expands and cools, whereas a sinking parcel is compressed and warms.

Accepted Answer

As a parcel of air rises, it expands due to lower atmospheric pressure at higher altitudes, which causes it to cool. Conversely, a sinking parcel of air is subjected to higher pressure, leading to compression and warming.

Question 20

Billow clouds form along the top of a cloud layer when changes in wind speed and direction reach a critical value, and an inversion caps the cloud-forming layers.

Accepted Answer

Billow clouds, also known as Kelvin-Helmholtz clouds, form due to wind shear and an inversion layer, which creates the necessary conditions for their distinctive wave-like appearance.

Quiz 6: Stability and Cloud Development