BharatNotes What is Köppen Climate Classification?
The Köppen Climate Classification is an empirical (not genetic) scheme that groups the world's climates on the basis of long-term monthly averages of temperature and precipitation, usually over 30 years or more. Its guiding assumption is that natural vegetation is the best single indicator of climate, so climate boundaries are drawn to coincide with major vegetation belts. It was first proposed by Wladimir Köppen in 1884, made quantitative around 1900, and revised by Köppen (1918, 1936) and Rudolf Geiger — hence the common name Köppen–Geiger system.
The Five Major Groups
Each climate is denoted by a code of two or three letters. The first (capital) letter marks the major group.
| Letter | Group | Defining criterion |
|---|---|---|
| A | Tropical | Every month averages above 18°C; no real winter |
| B | Dry (arid/semi-arid) | Precipitation below an evapotranspiration threshold |
| C | Temperate (mesothermal) | Coldest month between −3°C and 18°C; warmest above 10°C |
| D | Continental (microthermal) | Coldest month below −3°C; warmest above 10°C |
| E | Polar | Warmest month below 10°C |
(Some versions use a 0°C threshold for C/D; an "H" highland category is sometimes added.)
The Second and Third Letters
The second letter chiefly captures the precipitation pattern, and the third the temperature regime:
- f — no dry season (German feucht, moist)
- m — monsoon
- s — dry summer
- w — dry winter
- W / S — desert / steppe (used with group B)
- T / F — tundra / frost (used with group E)
- Third letter: h (hot), k (cold), and a/b/c for warm-to-cool summer gradients.
So Af is tropical rainforest, Aw is tropical savanna, BWh is hot desert, Cwg (in older Indian usage) is a monsoon-influenced temperate climate, and EF is perpetual frost.
Application to India
Köppen's scheme maps neatly onto India's monsoon-driven diversity. Broadly recognised types include tropical monsoon (Am) along the western coast and the north-east, tropical wet-and-dry/savanna (Aw) over much of the peninsular interior, hot desert (BWh) and semi-arid steppe (BSh) in Rajasthan and adjoining areas, and tundra/ice climates (ET/EF) in the high Himalaya, with temperate types in the Himalayan foothills.
Significance and Limitations
Its strengths are simplicity, objectivity, and a clear vegetation linkage, which is why it dominates textbooks and global climate maps. Limitations include sharp boundaries that mask gradual transitions, heavy reliance on temperature/precipitation alone (ignoring wind, sunshine and evaporation balance directly), and an over-broad treatment of mid-latitude climates — the gap Trewartha's 1966/1980 modification tried to close. For UPSC, contrast it with the genetic Thornthwaite scheme (based on precipitation effectiveness and moisture index) and remember it is empirical.
