CDS (I) 2022 General Knowledge · Question 32 of 120

Correct — C, Bwhw. In Koeppen's grammar the first letter is the broad group and the rest are qualifiers. B is the arid group, in which evaporation exceeds precipitation. Within B, W means true desert and S means the drier steppe margin; h means hot and dry, and w means the dry season falls in winter. So BWhw reads as hot desert with a dry winter, and that is exactly what the western fringe of Rajasthan is — the Thar, where annual rainfall drops below about 150 mm while mean temperatures stay high. The NCERT table of Koeppen types for India assigns BWhw to extreme western Rajasthan and nothing else in the country; the adjacent semi-arid steppe belt of north-western Gujarat, the rest of western Rajasthan and Punjab is BShw, which is not among the options.

• (a)Amw — A is the tropical humid group, the opposite end of the moisture scale from the Thar. Amw is monsoon climate with a short dry season, and in India it belongs to the west coast south of Goa — one of the wettest strips in the country.
• (b)Aw — Aw is tropical savannah, still inside the humid A group. It covers most of the peninsular plateaus south of the Tropic of Cancer, where rainfall is far higher than in the Thar and the dry spell is seasonal rather than year-round.
• (d)Cwg — Cwg is the warm temperate monsoon type with a dry winter, and the small g marks the Gangetic plain. It applies to the Ganga plain, eastern Rajasthan, northern Madhya Pradesh and most of the North-East — the humid side of the Aravallis, not the arid side.

Koeppen's classification sorts climates by the temperature and rainfall thresholds that vegetation actually responds to. Five broad groups carry capital letters — A tropical, B dry, C warm temperate, D cold and E polar — and lower-case letters refine them. Koeppen used S for semi-arid and W for arid, and then f for sufficient precipitation, m for rain forest despite a dry monsoon season, w for a dry winter, h for dry and hot, c for fewer than four months above 10 degrees Celsius, and g for the Gangetic plain. On this scheme India falls into eight climatic regions.

The fastest way in is to fix the first letter and let the rest follow. Western Rajasthan is arid, so the answer must start with B, and only one option does. If you then want to check the sub-letters, W rather than S because the Thar is desert and not merely steppe, h because the mean annual temperature is high, and w because what little rain falls comes with the summer monsoon, leaving winter dry. The distractors are all humid types, so a candidate who remembers only that A is tropical and B is dry has already solved the question. Two notes on the printing. The paper renders the code in lower case as Bwhw, following the NCERT table's own typography; the standard form is BWhw. And the sub-letters used here belong to Koeppen's Indian application as taught in the NCERT chapter rather than to the modern Koeppen-Geiger tables, where the same desert would simply be written BWh.

• In Koeppen's scheme B is the dry group; W marks true desert and S the semi-arid steppe.
• The lower-case h stands for dry and hot, and w for a dry season in winter.
• NCERT's table of Indian climatic regions gives BWhw for extreme western Rajasthan and BShw for north-western Gujarat with parts of western Rajasthan and Punjab.
• Amw covers the west coast south of Goa, Aw most of the peninsular plateaus south of the Tropic of Cancer, and Cwg the Ganga plain, eastern Rajasthan, northern Madhya Pradesh and most of the North-East.
• India is divided into eight Koeppen climatic regions, from Amw on the wet west coast to E, the polar type, in Jammu and Kashmir, Himachal Pradesh and Uttarakhand.

• Reading the first letter as a temperature label — A, C and D are broadly thermal, but B is defined by dryness, so a hot desert is B and not A.
• Mixing up W and S: W is full desert, S the semi-arid steppe that fringes it.
• Assuming the letter g means anything general — in this scheme it specifically marks the Gangetic plain.

Usually by giving a code and asking for the region, or by naming a region and asking for the code; occasionally as a match-the-list item pairing four codes with four areas.

• practice — not a real PYQ

  In Koeppen's scheme, which lower-case letter is used to indicate a dry season occurring in winter?

  • (a)f
  • (b)m
  • (c)w
  • (d)h

  Answer(c) w — f marks sufficient precipitation through the year, m a rain forest despite a dry monsoon season, and h a hot and dry regime.

• practice — not a real PYQ

  According to the Koeppen classification as applied to India in the NCERT table, the climate of Arunachal Pradesh is designated as

  • (a)Aw
  • (b)Cwg
  • (c)Dfc
  • (d)BShw

  Answer(c) Dfc — cold humid winter with a short summer, the only D-type region shown for India.