Identify the type of climate on the basis of the following characteristics relating to it: I. Temperature is high throughout the year. II. Rainfall is variable with a short wet season and a longer dry season. III. Climate of Sudan and Paraguay is an example of this climate type. Select the answer using the code given below:

Correct — D, Tropical wet and dry climate. This is the savanna climate, Koeppen's Aw, and each clue nails it. High temperature all year long is a mark of the tropical group as a whole, so clue I keeps you inside the tropics. Clue II then separates the three tropical types: the wet climate near the equator has rain in every month, the monsoon type has heavy summer rain and a dry winter, and only the wet and dry type has rainfall that is both distinctly variable and split into a short wet season against a longer, more severe dry one. Clue III settles it with two named examples that both belong to the standard Aw list — Sudan in Africa and Paraguay in South America, the latter lying in the belt south of the Amazon forest where this climate is most extensive. Deciduous forest and tree-scattered grassland, the savanna vegetation, grow in it.

• (a)Sub-tropical steppe climate — This is a dry climate, Koeppen's BSh, sitting in the transition zone between the humid and the truly arid. It receives only slightly more rain than the subtropical desert beside it — enough for sparse grassland — whereas the Aw climate is a humid tropical type with a genuine wet season.
• (b)Mid-latitude steppe — Fails on latitude and on temperature. The mid-latitude steppe, BSk, lies in the interiors of the mid-latitude continents and has cold winters, which is incompatible with clue I. Neither Sudan nor Paraguay lies in that belt.
• (c)Tropical monsoon climate — The nearest miss. Am also has high temperature all year and a dry winter, but its defining feature is heavy summer rainfall — the Indian subcontinent, north-eastern South America and northern Australia are the standard examples. Its rainfall is high, not the reduced and variable total described in clue II, and Sudan and Paraguay are not on its list.

The Koeppen scheme sorts world climates into five groups by temperature and rainfall, with the tropical humid group (A) lying between the Tropic of Cancer and the Tropic of Capricorn where the overhead Sun and the Inter Tropical Convergence Zone keep the air hot and humid. That group divides three ways: Af, tropical wet, near the equator with rain all year; Am, tropical monsoon, with heavy summer rain and a dry winter; and Aw, tropical wet and dry, which lies to the north and south of the Af belt and grades outward into the dry climates.

Identification items on climate are best solved by working from the clue that eliminates the most options. Here it is clue I. 'High throughout the year' removes every mid-latitude type at a stroke, including the mid-latitude steppe. The remaining three are all low-latitude, so clue II must separate them on rainfall regime, and clue III confirms with place names. It is worth learning two or three example regions for each Koeppen type precisely because UPSC-family papers use them as the deciding clue; Sudan is so strongly associated with this climate that the savanna belt is sometimes called the Sudan type.

• Tropical wet and dry climate (Aw) occurs to the north and south of the Af regions, bordering dry climate on the western side of a continent and Cf or Cw on the eastern side.
• Its most extensive stretches lie north and south of the Amazon forest in Brazil and adjoining parts of Bolivia and Paraguay, and in Sudan and south of Central Africa.
• Its annual rainfall is markedly less than in the Af and Am types and is variable; the wet season is shorter and the dry season longer, with more severe drought.
• Temperature stays high through the year, and the diurnal range of temperature is greatest in the dry season.
• Deciduous forest and tree-scattered grassland — savanna — are the characteristic vegetation.

• Confusing the savanna (Aw) with the steppe (BS) — one is a humid tropical climate with a wet season, the other a dry climate.
• Assuming that the mention of a dry season automatically means monsoon; the monsoon type is defined by heavy summer rain, not merely by a dry winter.
• Forgetting that Aw extends well into South America; Bolivia and Paraguay are as much part of its list as Sudan.

As a clue-based identification of a Koeppen type, as a description passage that must be matched to a region, or as a pairing of climate type with a named country.

• practice — not a real PYQ

  The savanna vegetation of tree-scattered grassland and deciduous forest is characteristic of which one of the following climate types?

  • (a)Tropical wet climate (Af)
  • (b)Tropical wet and dry climate (Aw)
  • (c)Mediterranean climate (Cs)
  • (d)Mid-latitude desert climate (BWk)

  Answer(b) Tropical wet and dry climate (Aw) — a short wet season and a long dry season favour grasses with scattered trees rather than closed forest.

• practice — not a real PYQ

  Which one among the following pairs of climate type and region is correctly matched?

  • (a)Tropical monsoon climate — Amazon Basin
  • (b)Tropical wet climate — Sudan
  • (c)Tropical monsoon climate — Indian subcontinent
  • (d)Mid-latitude steppe — Paraguay

  Answer(c) Tropical monsoon climate — Indian subcontinent; the Am type is found over the Indian subcontinent, north-eastern South America and northern Australia.