Science and Weather Quiz | Cloud Formation, Cloud Types and Fronts, Set 4

Relative humidity compares the current water-vapor content with the saturation amount at the current temperature. Even with the same water-vapor content, cooling reduces the amount needed to reach saturation, so relative humidity rises before condensation begins. Water-vapor content and relative humidity are not the same quantity.

The dew-point temperature is the temperature at which air cooled at constant water-vapor pressure reaches 100% relative humidity and condensation begins. The boiling point concerns a liquid boiling, and the freezing point concerns water freezing; neither describes the start of condensation in this situation.

As an air parcel rises, the surrounding pressure decreases, so the parcel expands and cools as it does work. Once it cools to its dew point and becomes saturated, water vapor condenses onto nuclei to form cloud droplets. The claim that rising air is compressed and warmed reverses the actual sequence.

Sea-salt particles provide surfaces on which water vapor can condense, acting as condensation nuclei, but they do not create the water. A cooled below its dew point and reached saturation, allowing condensation on the particles. B remained unsaturated, so nuclei alone were not enough to produce droplets.

Parcels of air with similar properties tend to reach their dew point and begin condensing at about the same altitude, producing the characteristically flat bases of cumulus clouds. Their tops can reach different heights as updraft strength and other conditions vary. Terrain does not physically trim the cloud bases.

White, delicate, fibrous clouds at high altitude are cirrus clouds, which are composed of ice crystals. Nimbostratus is a thick, dark layer that brings rain or snow, while cumulonimbus grows strongly in the vertical, so neither matches the described appearance.

Nimbostratus is a thick, dark-gray layered cloud that obscures the Sun and brings persistent rain or snow over a broad area. Cumulonimbus is more closely associated with intense, localized phenomena such as thunder and hail, which differs from the widespread, continuous precipitation in this case.

A cumulonimbus grows strongly upward in powerful updrafts, often develops an anvil-shaped top, and can produce thunder and hail. This does not mean every cumulonimbus produces every possible hazard, including hail or tornadoes. Stratus and altostratus do not have this strong vertical development as their defining feature.

A cold front advances toward a warm air mass, and temperature usually falls after it passes as colder air arrives. Temperature normally rises after a warm front passes, the opposite of this case. In practice, a weather chart and observations from multiple sites would also be used, but the typical changes given here fit a cold front.

An occluded front forms when the faster-moving cold front catches the warm front. A stationary front remains in nearly the same location and does not describe this catching-up process. Real occlusions can have cold-type and warm-type structures, but the basic formation process is the same.