Identify the climate type based on the given below characteristics: 1. The annual precipitation is low and is around 15 cm. 2. The development of pronounced winter anticyclones and their weakening in summer sets in monsoon-like reversal of wind in this region. 3. Polewards, summer temperatures are low. Select the answer from the options given below:

Correct — C, Cold climate with dry winters. The three clues are lifted from one passage of the textbook, and each of them points at Koeppen's Dw. The first, an annual precipitation of about 15 centimetres, is startlingly low for a forested cold climate and matches the figure given for Dw, 12 to 15 centimetres, almost all of it falling in summer. The second clue is the signature of the type: a powerful anticyclone builds over north-eastern Asia in winter, chilled air sinking and spreading outwards, and it weakens in summer when the continent heats, so the winds reverse between the seasons in a way that resembles a monsoon. This is the Siberian high, the strongest and most persistent high-pressure cell on earth, and it is also why the winter is dry — sinking air does not produce precipitation. The third clue, that summer temperatures fall as you go poleward, tells you there is a real summer to speak of, and that latitude is what erodes it. Put together they describe eastern Siberia, Manchuria and northern Korea, the home of the cold climate with dry winters.

• (a)Subtropical steppe — Fits the first clue and nothing else. A subtropical steppe is dry, but it lies in the low latitudes under the subtropical high all year, has no seasonal anticyclone building and collapsing over it, and produces nothing resembling a monsoonal wind reversal.
• (b)Humid sub-tropical climate — Fails at the first clue. Humid subtropical is the no-dry-season climate of the eastern margins of continents, with rainfall running to well over a hundred centimetres a year. Fifteen centimetres rules it out immediately.
• (d)Tundra climate — The strongest wrong option, because the tundra is genuinely cold and genuinely dry. It fails on the second and third clues. The tundra lies poleward of about 70 degrees beyond the tree line, is not driven by a seasonal anticyclone reversal, and is defined by having no true summer at all — whereas the stem's third clue takes a summer for granted and only says it weakens poleward.

Koeppen's D group, the cold snow forest climates, occupies the large continental areas of the northern hemisphere between about 40 and 70 degrees. It splits in two: Df, cold with a humid winter, and Dw, cold with a dry winter. Dw is concentrated in north-eastern Asia, where an immense winter anticyclone over Siberia keeps the cold season almost rainless and reverses the wind direction between the seasons. Its precipitation is low and comes in summer, and its winters are among the most severe experienced anywhere outside the polar caps.

Identify-the-climate items reward you for finding the clue that only one climate can satisfy. Here that is the second one. Low precipitation on its own fits a steppe, a desert and a tundra as well as it fits Dw, and low poleward summer temperatures fit any high-latitude climate. Only Dw is characterised by a seasonal reversal of wind driven by a continental anticyclone, and the word 'anticyclone' is doing the discriminating work. It is also the clue that explains the other two: sinking air in a winter high suppresses precipitation, which is why the winter is dry and the annual total so small. There is a nice cross-connection to hold on to — the mechanism named here is the same one that drives India's monsoon, differential heating and cooling between a huge landmass and the ocean beside it, which is why the textbook calls the reversal monsoon-like rather than monsoonal.

• NCERT on Dw: 'Cold climate with dry winter occurs mainly over Northeastern Asia. The development of pronounced winter anti cyclone and its weakening in summer sets in monsoon like reversal of wind in this region.'
• Annual precipitation in the Dw region is 12 to 15 centimetres, and it falls in summer.
• In the standard table Dw is listed as the subarctic type with the characteristic 'winter dry and very severe'; Df is the cold climate with a humid winter.
• The Siberian high is the strongest and most persistent winter anticyclone on earth, and it is what dries and chills the Dw region.
• Verkhoyansk and Oymyakon, both in this climatic region, hold the lowest temperatures ever reliably recorded in the northern hemisphere, around minus 68 degrees Celsius.

• Choosing tundra because the clues say cold and dry. The reversal of wind is what separates the two, and the tundra has no such reversal.
• Assuming a cold climate must be wet. Cold air holds little moisture, and a winter anticyclone keeps what there is from falling.
• Reading 'monsoon-like reversal' as meaning the region has a monsoon climate. The mechanism is shared; the climate is not.

As an identify-the-climate item built from three or four described features, or as a straight code-to-region question — which region has a Dw climate, or which climate the letters describe.

• practice — not a real PYQ

  The seasonal reversal of wind in north-eastern Asia is caused mainly by

  • (a)the migration of the equatorial trough
  • (b)a pronounced winter anticyclone that weakens in summer
  • (c)the polar jet stream shifting southward
  • (d)the westward drift of the sub-tropical high

  Answer(b) a pronounced winter anticyclone that weakens in summer — the Siberian high spreads cold air outward in winter and collapses when the continent heats, reversing the wind direction between the seasons.

• practice — not a real PYQ

  In Koeppen's classification, the letter 'w' in the code Dw stands for

  • (a)warm summer
  • (b)windy conditions
  • (c)dry winter
  • (d)west coast location

  Answer(c) dry winter — Df is the cold climate with a humid winter and Dw the cold climate with a dry one.