MPSC 2021 Prelims Paper-I · Question 18 of 100

Correct — option (2), which reads (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i). Take the securest row first. Statement (d), the Alps, goes with item (i), the Foehn, and this pairing alone settles the entire question, because no other choice offers it. The Foehn is the type example of a warm, dry downslope wind on the lee side of a mountain range: moist air off the Mediterranean is forced up the southern flank of the Alps, cools, and drops its moisture as rain on the windward slope; the latent heat released in that condensation stays in the air, so when the now-dry air descends the northern side and is compressed it arrives warmer than it began, capable of lifting temperatures by as much as fourteen degrees in a matter of hours, melting snow and drying pasture. The name itself is Alpine, from a Latin word for a mild westerly, and the same mechanism carries other names elsewhere — Chinook in the Rockies, Santa Ana in California, Zonda in Argentina, Nor'wester in New Zealand, Halny in the Carpathians. Statement (c), Iran, goes with item (ii), Semun, the wind more usually spelt Simoom and known also as samiel, from words meaning poison wind; it is a strong, hot, dry, dust-laden wind of the deserts of western Asia and North Africa, blowing across the Sahara, Jordan, Iraq, Syria, the Arabian Peninsula and the Iranian deserts, where temperatures can exceed fifty-four degrees Celsius and relative humidity fall below ten per cent. Statements (a) and (b) are two names for one air stream, and understanding that is the key to the pair. A hot dry mass rises off the Sahara or the Arabian desert and is drawn north across the Mediterranean; on the Egyptian shore it is called the Khamsin, from the Arabic for fifty, after the season in which it blows, and that is item (iv) beside the Sahara. By the time the same stream reaches the northern shore it has crossed the sea and picked up moisture, and there it is called the sirocco, sirokos in Greece and scirocco in Italy and Malta, which is item (iii) beside Greece. The pairing therefore follows the convention that a local wind is named by the shore that experiences it, and the two rows are consistent rather than contradictory.

• (1)(a) - (i), (b) - (iii), (c) - (ii), (d) - (iv) — This choice gets the middle two rows right, giving the sirocco to Greece and the Semun to Iran, and then swaps the outer pair, putting the Foehn over the Sahara and the Khamsin over the Alps. Both halves of that swap are impossible. The Foehn requires a mountain barrier and a descending lee slope, and the Sahara is a low desert basin with no such range in the position needed; the Khamsin is by definition a wind of Egypt and the Saharan margin and has nothing to do with an Alpine valley. This is the choice that will catch a candidate who checks a couple of rows, finds them right and commits, and it is the reason the Alps row rather than the Greece row should be used as the anchor here.
• (3)(a) - (i), (b) - (ii), (c) - (iv), (d) - (iii) — Every row of this choice is displaced. It puts the Foehn on the Sahara, the Semun in Greece, the Khamsin in Iran and the sirocco over the Alps. The row that gives the sirocco to the Alps is the most instructive failure, because the sirocco is defined by its passage across the Mediterranean and by the humidity and the reddish dust it deposits on the northern shore — the blood rain of Italian folklore — which places it on a coast rather than on a mountain lee. Reading each local wind as a statement about a specific geography, rather than as a name to be remembered in isolation, makes a permutation like this one visibly wrong at every line.
• (4)(a) - (ii), (b) - (iv), (c) - (i), (d) - (iii) — This choice gives the Semun to the Sahara, the Khamsin to Greece, the Foehn to Iran and the sirocco to the Alps. The first row is the interesting one, because it is not absurd: the Simoom does blow across the Sahara as well as across the deserts of western Asia, so a candidate could defend it in isolation. That is precisely the danger of judging a matching question row by row instead of as a whole permutation. Once the other three rows are examined the choice collapses, since the Foehn cannot belong to Iran, which has no Alpine lee slope in the sense the wind requires, and the Khamsin is a wind of the African rather than the European shore.

Local winds are regional air movements produced by the interaction of pressure gradients with terrain and with the contrast between land and sea, and they are conventionally sorted into hot and cold. The hot group includes the Foehn of the Alps and its cousins the Chinook, the Santa Ana and the Zonda, all produced by adiabatic descent on a mountain's lee side; the Simoom, Khamsin, Sirocco, Harmattan and Loo, all produced by hot desert air moving outward; and the Brickfielder of Australia and the Norwester of New Zealand. The cold group includes the Mistral of the Rhone valley, the Bora of the Adriatic, the Blizzard, the Buran of central Asia, the Purga and the Pampero of Argentina. Two physical principles explain almost all of them. The first is adiabatic temperature change: air cools at about six and a half degrees per kilometre as it rises and warms at about ten degrees per kilometre as it descends dry, and the difference between those rates, caused by latent heat released during condensation, is why a Foehn arrives warmer than the air that started up the windward slope. The second is that air moving over a large water body gains moisture, which is why the same Saharan stream is dry as the Khamsin and humid as the sirocco.

Local winds are among the most reliably examined items in climatology because they can be tested as a pure matching exercise with no computation and no ambiguity, and because the list is finite. MPSC returns to them regularly, sometimes as a region-to-wind match as here, sometimes asking which of a list is a cold wind, and sometimes attaching the Indian members of the family — the Loo of the northern plains in May and June, the Kalbaisakhi of Bengal, the Mango showers of Kerala and Karnataka and the Norwesters of Assam. The habit the question rewards is learning each wind as a small package of facts rather than as a name: the region it blows in, whether it is hot or cold, whether it is wet or dry, and the mechanism that produces it. That package makes a permutation question answerable from any single row, and here the Alps and Foehn row is the one that carries the whole item, since it appears in only one of the four choices.

• The Foehn is a dry, relatively warm downslope wind on the lee of a mountain range, classically the Alps; latent heat released during condensation on the windward slope leaves the descending air warmer, and it can raise temperatures by up to fourteen degrees Celsius in a few hours.
• The Simoom, printed here as Semun and also called samiel or poison wind, is a strong, hot, dry, dust-laden wind of the Sahara, Jordan, Iraq, Syria, the Arabian Peninsula and the Iranian deserts; temperatures can exceed fifty-four degrees Celsius and humidity fall below ten per cent.
• The Khamsin, from the Arabic for fifty, is the Egyptian and Saharan name for the hot dry air stream drawn north from the desert; on the northern Mediterranean shore the same stream is the sirocco, called sirokos in Greece and scirocco in Italy and Malta.
• The sirocco starts as a dry tropical air mass but picks up moisture crossing the Mediterranean, bringing dust and dryness to the North African coast and rain, sometimes reddened by Saharan sand, to southern Europe.
• Regional cousins of the Foehn include the Chinook of the Rocky Mountains, the Santa Ana of California, the Zonda of Argentina, the Nor'wester of New Zealand and the Halny of the Carpathians.

• Judging a matching question row by row when a row can be defensible in isolation and still belong to a wrong permutation, as with Simoom and the Sahara here
• Treating the Khamsin and the sirocco as unrelated winds, when they are the same air stream under the names given by the two shores of the Mediterranean
• Assigning the Foehn to any hot region rather than to a mountain lee slope; the wind is defined by descent and adiabatic warming, not merely by warmth
• Confusing the Bora and Mistral, which are cold winds of the Mediterranean, with the sirocco and Khamsin, which are hot

Local winds appear in state services papers almost every year, usually as a region-to-wind match of exactly this construction, occasionally as a single-fact question about which country a named wind blows in or whether it is hot or cold, and sometimes embedded in a larger climatology question about the rain shadow or the general circulation. The commission varies difficulty mainly by choosing less familiar members of the family, such as the Semun, or by using regional spellings, so a candidate should recognise a wind under more than one transliteration. A one-page table with four columns — wind, region, hot or cold, and mechanism — covers the whole area, and once the Alpine Foehn, the Mediterranean pair and the desert winds are secure, most versions of the question resolve on a single row.

No directly related past PYQ was found.

• practice — not a real PYQ

  The warm dry wind that descends the lee slope of a mountain range and arrives warmer than the air that ascended the windward side is known in the Alps as the Foehn. What is the same type of wind called in the Rocky Mountains of North America ?

  • (a)Chinook
  • (b)Mistral
  • (c)Bora
  • (d)Harmattan

  Answer(a) Chinook — the North American counterpart of the Foehn, produced by the same adiabatic mechanism on the eastern slopes of the Rockies and known for melting snow rapidly. The Mistral and the Bora are cold winds of the Mediterranean region, and the Harmattan is a dry dusty wind blowing off the Sahara towards the Guinea coast of West Africa.

• practice — not a real PYQ

  The hot dry air stream drawn northward from the Sahara is called the Khamsin in Egypt. By what name is the same stream known when it reaches the northern shore of the Mediterranean ?

  • (a)Bora
  • (b)Sirocco
  • (c)Mistral
  • (d)Simoom

  Answer(b) Sirocco — sirokos in Greece and scirocco in Italy and Malta. Having crossed the sea the air has picked up moisture, so it brings humidity and rain to southern Europe, sometimes reddened by Saharan dust, where on the African shore it was dry and dust-laden. The Bora and the Mistral are cold winds of the same region, which is the usual source of confusion.