CDS (I) 2024 General Knowledge · Question 86 of 120

Correct — B, desert climate. In Köppen's scheme the first capital letter names the broad group and B is the dry group, where evaporation exceeds precipitation. The second letter then splits that group by how dry it is: W stands for desert, from the German Wüste, and S stands for steppe or semi-arid. So BW is the true desert climate, and it is further divided by temperature into BWh, the hot desert, and BWk, the cold desert. Steppe belongs to BS, tundra to ET in the polar group E, and the mesothermal or mild temperate climates are group C — none of them is BW.

• (a)Steppe climate — Steppe is BS, the semi-arid half of the dry group. It is drier than a humid climate but wetter than a desert, and it usually fringes the deserts.
• (c)Tundra climate — Tundra is ET, in group E, the polar climates, where the warmest month averages between 0 and 10 degrees Celsius. It has nothing to do with the dry group.
• (d)Mesothermal climate — Mesothermal, or mild temperate, is group C, where the coldest month averages between 0 and 18 degrees Celsius. Its subtypes are written Cfa, Cwg, Csa and so on.

Wladimir Köppen classified world climates using temperature and precipitation, with a letter code. The five groups are A tropical, B dry, C mild temperate or mesothermal, D continental or microthermal, and E polar. Within group B, W marks a desert and S a steppe; a third letter, h or k, tells you whether it is hot or cold. Within group E, T marks tundra and F an ice cap.

The way to hold Köppen's code is to read it letter by letter rather than memorise whole strings. The first letter narrows you to a group, the second usually tells you about moisture, and the third about temperature. Here B alone already rules out tundra and mesothermal, both of which sit in other groups, so the real choice is only between desert and steppe. W for Wüste is the German word for desert, and S for steppe is its semi-arid neighbour — remember that pair and the item is done. India's own worked example is the western fringe of Rajasthan, classed BWhw, the hot desert of the Thar.

• BWh is the hot desert climate and BWk the cold desert climate; both belong to group B, the dry climates.
• BS is the semi-arid or steppe climate, split similarly into BSh and BSk.
• ET is tundra, where the warmest month averages between 0 and 10 degrees Celsius, and EF is the ice cap, with every month below 0 degrees Celsius.
• Group C, the mesothermal climates, has its coldest month averaging between 0 and 18 degrees Celsius with at least one month above 10 degrees Celsius.

• Swapping W and S — remembering only that both belong to the dry group and then guessing steppe.
• Reading B as a temperature group; the first letter for the polar and temperate groups is E and C, not B.
• Assuming the third letter is part of the desert or steppe distinction, when h and k only separate hot from cold.

Asked as a direct code-decoding item — one Köppen letter pair, four climate names, and only one match.

• practice — not a real PYQ

  In the Köppen classification, the code BS denotes which climate?

  • (a)Desert
  • (b)Steppe or semi-arid
  • (c)Ice cap
  • (d)Humid subtropical

  Answer(b) Steppe or semi-arid — S marks the semi-arid half of the dry group B, the fringe around the deserts.

• practice — not a real PYQ

  Which Köppen letter group covers the polar climates?

  • (a)A
  • (b)C
  • (c)D
  • (d)E

  Answer(d) E — the polar group, subdivided into ET, tundra, and EF, ice cap.