Precipitation reaches the ground only when hydrometeors
Answer: A
A cloud droplet falls too slowly to escape and evaporates on the way down. Growth by roughly a factor of a hundred in radius is required before a particle can leave the cloud and survive the descent. Everything in the subject turns on reaching that size.
Please log in or register to report this question.
Match each precipitation formation route with its defining feature.
List I
A. Warm rain
B. Cold rain
C. Seeder feeder
D. Orographic
List II
1. ice from above falling through low cloud
2. collision and coalescence only
3. forced ascent over rising terrain
4. ice phase followed by melting
Answer: B
The first two are microphysical routes and the last two describe how a cloud is supplied with condensate. A single event may combine several of them in the same column. The routes are not exclusive and often reinforce one another.
Please log in or register to report this question.
The seeder feeder mechanism enhances rainfall over hills by
Answer: C
Correct answer: ice or rain from an upper cloud sweeping out a lower orographic cloud
A shallow cap cloud over a hill contains liquid water but is too thin to grow drops large enough to fall. When precipitation from a deeper cloud above falls through it, those particles collect the small droplets on the way down and arrive at the surface much enlarged. The seeder supplies the particles and the feeder supplies the water, and neither alone would produce the rainfall that results.
Please log in or register to report this question.
Assertion (A): A shallow orographic cloud can produce heavy rain when an upper cloud lies above it.
Reason (R): Precipitation from above sweeps out the liquid water of the lower cloud efficiently.
Answer: D
Correct answer: Both A and R are true, and R is the correct explanation of A
Both are true and the reason is the mechanism. The shallow cloud cannot precipitate on its own, but it holds a high liquid water content that falling drops or crystals sweep out efficiently as they pass. That is why rainfall totals on windward slopes can far exceed what the local cloud depth would suggest, and why the enhancement disappears when the upper cloud does.
Please log in or register to report this question.
Consider the following statements about orographic precipitation.
1. Forced ascent over terrain generates condensate.
2. The seeder feeder process can multiply the rainfall considerably.
3. Orographic rainfall depends only on the height of the terrain.
Answer: A
The first two are correct. The third is far too simple, since wind speed, humidity and the presence of an upper cloud all matter as much as the height of the barrier itself. A modest hill in a moist strong flow can outrain a high dry one.
Please log in or register to report this question.
Stratiform precipitation is characterised by
Answer: B
Ascent of a few centimetres per second over a wide area produces long lasting moderate rain. The radar signature includes a bright band, which convective precipitation lacks. The two regimes are separated routinely from radar structure alone.
Please log in or register to report this question.
Match each precipitation type with its typical characteristics.
List I
A. Stratiform
B. Convective
C. Drizzle
D. Showers
List II
1. very small drops from shallow layer cloud
2. widespread, steady, with a bright band
3. brief and intermittent from cumuliform cloud
4. localised, intense, with strong vertical motion
Answer: C
The distinction is more than descriptive, since the two regimes differ in drop size distribution and in the coefficients used to convert radar reflectivity into a rainfall rate. Classifying the echo correctly is the first step in estimation.
Please log in or register to report this question.
Assertion (A): Radar rainfall estimates use different coefficients for convective and stratiform rain.
Reason (R): The two regimes have systematically different drop size distributions.
Answer: D
Correct answer: Both A and R are true, and R is the correct explanation of A
Both are true and the reason is why the practice is necessary. Radar measures reflectivity, which weights drop diameter to the sixth power, while rain rate weights it to roughly the third - so converting one to the other depends on the drop size distribution. Convective rain has fewer, larger drops and stratiform rain more numerous, smaller ones, so a single relationship applied to both introduces systematic error.
Please log in or register to report this question.
Drizzle is distinguished from rain principally by
Answer: A
Drizzle drops are typically a few hundred micrometres and fall at well under a metre per second. They originate in shallow layer cloud where collection has had little depth in which to operate. Shallow marine stratocumulus is the classic drizzle producer.
Please log in or register to report this question.
State whether the following is true or false.
Drizzle is more likely than rain to evaporate before reaching the ground.
Answer: B
Its small drops present far more surface area per unit mass and fall slowly. A dry sub-cloud layer of even modest depth is often enough to remove drizzle entirely. Drizzle observed aloft frequently fails to reach the surface.
Please log in or register to report this question.
