According to Koppen’s climatic classifications of India, Great Northern Plains are represented by

Correct — A, Cwg Climate. In the Koppen scheme as applied to India, Cwg is read letter by letter: C is the warm temperate or mesothermal group, in which the coldest month averages between minus three and eighteen degrees Celsius; w means the dry season falls in winter; and g is Koppen's own sub-symbol for the Gangetic type, where the hottest month comes before the summer solstice and the rains. That combination — a hot, dry season ending in June, a wet south-west monsoon, and a cool dry winter — is exactly the Great Northern Plains. The NCERT table on India's climatic regions assigns Cwg to the Ganga plain, eastern Rajasthan, northern Madhya Pradesh and most of the North-East. Present-day Koppen maps built from station data give the same plain the label Cwa, since the modern scheme uses 'a' for a hot summer and no longer carries the 'g' sub-symbol; the classification of the region has not changed, only the notation.

• (b)Aw Climate — Aw is tropical savannah, and an A climate requires every month to average at least eighteen degrees. January on the northern plain runs well below that, so the plain cannot be an A climate at all. Aw covers most of the peninsular plateau south of the Tropic of Cancer.
• (c)Amw Climate — Amw is monsoon with a short dry season, assigned to the west coast south of Goa. That coast takes over two thousand millimetres from the Arabian Sea branch and has a dry spell of only a month or two, neither of which describes the plains.
• (d)As Climate — As is monsoon with a dry summer, and in India it is assigned to the Coromandel coast of Tamil Nadu, which gets its rain from the retreating north-east monsoon in October and November. Its dry season is in summer, the reverse of the plains.

Koppen's letters are a code, not a list to be memorised whole. The first capital gives the broad group — A tropical, B dry, C warm temperate, D cold, E polar. The second small letter gives the seasonality of rainfall — f for rain all year, m for a short dry season in an otherwise wet monsoon regime, w for a dry winter, s for a dry summer. The third letter refines temperature or, in Koppen's Indian usage, marks the Gangetic type. Read that way, Cwg unpacks into a plain-language description before any table is recalled.

The NCERT scheme divides India into eight Koppen regions: Amw on the west coast south of Goa, As on the Coromandel coast, Aw over most of the peninsular plateau, BShw as semi-arid steppe in north-western Gujarat and parts of western Rajasthan and Punjab, BWhw as hot desert in extreme western Rajasthan, Cwg over the Ganga plain and the North-East, Dfc in Arunachal Pradesh, and E as the polar type in the high Himalaya. Worth knowing that the rationalised NCERT edition has since dropped this section, so the table now has to be looked up in the older printing — the classification itself is unchanged.

• Cwg denotes monsoon with dry winter and covers the Ganga plain, eastern Rajasthan, northern Madhya Pradesh and most of the North-East.
• In Koppen's letter grammar w marks a dry winter, s a dry summer, m a rain forest despite a dry monsoon season, and f sufficient precipitation throughout.
• The sub-symbol g stands for the Gangetic plain type, where the hottest month falls before the summer solstice and the rains.
• Aw, tropical savannah, covers most of the peninsular plateaus south of the Tropic of Cancer.
• Amw is the west coast south of Goa and As the Coromandel coast, which takes its rain from the retreating monsoon.

• Choosing Aw for the plains because the region is hot for much of the year; the A group needs every month above eighteen degrees.
• Reading the third letter as a temperature marker in every case, when in Indian usage g marks the Gangetic type.
• Assigning As to the west coast; it belongs to the Coromandel coast, which rains in the retreating monsoon.

Asked as a straight code-to-region match. All four options are real Indian codes from the same table, so the answer turns on knowing the table rather than on eliminating nonsense.

• practice — not a real PYQ

  Under Koppen's classification as applied to India, the Coromandel coast of Tamil Nadu is designated

  • (a)Amw
  • (b)As
  • (c)Aw
  • (d)Cwg

  Answer(b) As — monsoon with a dry summer, since the coast takes its rain from the retreating north-east monsoon.

• practice — not a real PYQ

  In Koppen's scheme, the letter 'B' as the first symbol denotes which type of climate?

  • (a)Tropical
  • (b)Dry
  • (c)Warm temperate
  • (d)Polar

  Answer(b) Dry — with S for semi-arid steppe and W for arid desert as the second letter.