Formation of Clouds Questions and Answers

Answer: C

Correct answer: 1 and 2 only

Statements 1 and 2 are correct: the air is cooled as it rises and precipitates on the windward slope, and it warms and dries as it descends the lee. Statement 3 is wrong and is the whole point of the foehn effect - the air ascended partly at the saturated rate but descends entirely at the dry rate, so it arrives at the original level warmer and much drier than it began. That asymmetry is what produces a rain shadow.

Answer: D

Both are true and the reason gives the asymmetry, and this is the physics of the foehn or chinook wind. The parcel ascends at the saturated rate but descends at the larger dry rate. The difference between the two rates is the whole of the warming observed.

Answer: A

Correct answer: True

If the environment cools with height faster than a rising dry parcel does, then any parcel displaced upward finds itself warmer than its surroundings and keeps rising, whether it is saturated or not. That is absolute instability, and it is why such lapse rates are found only in shallow layers near a strongly heated surface - convection removes them as fast as they form.

Answer: B

The word conditional means the instability appears only once the parcel is saturated. Most atmospheres capable of producing deep convection are conditionally unstable rather than absolutely so. The distinction turns entirely on whether the parcel has reached saturation.

Answer: C

An unsaturated parcel cools at the dry rate and is stable, but once it reaches its condensation level it cools more slowly and may become buoyant. The lifting needed to reach that level is what makes such a situation depend on a trigger.

Answer: D

Both are true and the reason gives what is missing, and the energy needed to reach that level is the convective inhibition. A capping inversion strong enough to prevent it can hold back a very unstable profile all afternoon.

Answer: A

An inversion caps the ascent and prevents parcels from reaching their level of free convection. The other three are the classic ingredients meteorologists look for when deep convection is expected. Any one of them missing is usually enough to keep the day quiet.

Answer: B

Drier and cooler surroundings mixed in evaporate some of the droplets, which cools the parcel further and reduces its buoyancy. It is the main reason observed updraught temperatures fall short of the undiluted adiabatic value.

Answer: C

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the mechanism. A real updraught is not sealed: turbulence mixes drier environmental air in through its edges, and evaporating cloud droplets to saturate that air takes latent heat out of the parcel. The result is an updraught cooler and less buoyant than the undiluted parcel calculation predicts, which is why simple parcel theory overestimates cloud tops.

Answer: D

Correct answer: 2 - 4 - 1 - 3

Surface heating makes a parcel buoyant, it rises and cools at the dry adiabatic rate, it reaches saturation at the lifting condensation level, and thereafter condensation releases latent heat so that it cools more slowly and remains buoyant for longer - which is what allows the cloud to deepen. Each stage follows from the one before, and the latent heat release at the end is why convective clouds grow so much taller than the initial buoyancy would suggest.