Global Precipitation Patterns Questions and Answers

Answer: A

Correct answer: 2 - 4 - 1 - 3

The pattern follows the general circulation. Rising air at the intertropical convergence zone gives the equatorial maximum; the descending branch of the Hadley cell gives the subtropical dry belt around 20 to 30 degrees; the mid-latitude storm track gives a second maximum around 40 to 60; and the cold, dry, subsiding air over the poles gives the polar desert.

Answer: B

Correct answer: True

Antarctic and high Arctic precipitation is a few tens to a couple of hundred millimetres a year - less than many hot deserts - because cold air can hold very little water vapour. The permanent snow cover reflects the fact that almost nothing melts or evaporates rather than that much falls, so the accumulation of thousands of years builds an ice sheet from a very small annual input.

Answer: C

The first two are correct. The third is wrong, since radar measures reflected power and must be calibrated against gauges to give a rainfall figure. Wind is the main source of gauge error. Snow is harder still to catch reliably.

Answer: D

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

Both are true and the reason gives the necessity. Radar measures reflectivity, which depends on the drop size distribution, and converting it to a rain rate requires a relationship that varies with the type of rain and with the height at which the beam samples. Gauges measure the rain reaching the ground at a point directly, so they anchor the radar’s excellent spatial coverage to a physical measurement - each supplying what the other lacks.

Answer: A

Cherrapunji and the Hawaiian mountains are the standard examples, where orographic uplift acts on very moist air. The combination of moisture supply and forced ascent is what produces the extremes. Both factors must be present at once.

Answer: B

Water is conserved, so what falls must have evaporated, and the atmosphere holds only a few days worth of it. Regional imbalances are made up by the transport of vapour and the return flow of rivers. The atmosphere stores only days of it.

Answer: B

The key's answer is that rainfall increases over the Ghats and then decreases westwards.

During the south-west monsoon, moist winds from the Arabian Sea strike the Western Ghats, are forced to rise, cool and drop heavy orographic rain on the windward slopes. Rainfall is therefore highest over the Ghats (Mahabaleshwar and Agumbe receive several metres) and lower on the coastal plain to the west of them, which lies further from the barrier, while east of the crest lies the rain shadow.

The other patterns ignore this mountain effect: rainfall does not rise uniformly westwards, nor fall over the Ghats, where it is in fact at its maximum, and a plain decrease westwards misses the peak over the Ghats.