Climate Classification
Notes
Climate classifications group regions with similar temperature and rainfall. Types: empirical (based on observed temperature and rainfall), genetic (based on causes, such as air masses) and applied.
Koppen's classification (1900; modified by Rudolf Geiger) Based on mean monthly temperature and precipitation, using natural vegetation as an indicator. Five main groups, with letters:
Group | Climate | Criterion | Example |
|---|---|---|---|
A | Tropical humid | Coldest month above 18°C | Equatorial (Af): Amazon, Congo; monsoon (Am); savanna (Aw) |
B | Dry | Evaporation exceeds precipitation | Desert (BW): Sahara, Thar; steppe (BS) |
C | Warm temperate (mesothermal) | Coldest month between -3°C and 18°C | Mediterranean (Cs); China type (Cw); west European (Cfb) |
D | Cold snow forest (microthermal) | Coldest month below -3°C, warmest above 10°C | Taiga (Dfc): Siberia, Canada |
E | Polar | Warmest month below 10°C | Tundra (ET), ice cap (EF) |
H | Highland | Altitude effect (added later) | Himalaya, Andes |
Sub-letters: f (no dry season), m (monsoon), w (dry winter), s (dry summer), W (desert), S (steppe), T (tundra), F (ice cap); a, b, c, d show summer heat and winter cold.
Koppen's types in India
- Amw: tropical monsoon with a short dry season (the Malabar coast, south of Goa).
- As: tropical with dry summer (the Coromandel coast).
- Aw: tropical savanna (most of peninsular India).
- BShw: semi-arid steppe (Rajasthan, Gujarat). BWhw: hot desert (the Thar).
- Cwg: monsoon type with dry winter (the Ganga plain; "g" for Gangetic).
- Dfc: cold humid winter with a short summer (Arunachal Pradesh).
- ET: tundra (the high Himalaya).
Other classifications
- Thornthwaite (1931, 1948): based on precipitation effectiveness and potential evapotranspiration.
- Trewartha: a modification of Koppen with a simpler, more realistic set of groups.
- Flohn: based on wind belts and precipitation; genetic schemes (Strahler, Bergeron) use air masses and fronts.
Major climate types (summary)
- Equatorial: hot and wet all year; daily convectional rain. Savanna (Aw): a wet and dry season. Monsoon: seasonal reversal of winds.
- Mediterranean: hot dry summers and mild wet winters. Humid subtropical (China type): hot, wet summers. Marine west coast: mild, rain all year.
- Taiga: long cold winters. Tundra and ice cap: very cold; permafrost.
Key Points
- Koppen: five groups, A (tropical), B (dry), C (warm temperate), D (cold), E (polar), plus H (highland).
- Letters show seasonal patterns; Koppen classified India into Amw, As, Aw, BShw, BWhw, Cwg, Dfc and ET types.
- Thornthwaite uses precipitation effectiveness and evapotranspiration.
- Empirical vs genetic classifications.
- Cwg is the climate of the Ganga plain.
MCQs
Q1. In Koppen's scheme, group "A" represents:
(a) Dry climates
(b) Tropical humid climates
(c) Cold climates
(d) Polar climates
Ans: (b). The coldest month is above 18°C.
Q2. The Ganga plain falls under which Koppen type?
(a) Aw
(b) Cwg
(c) BWhw
(d) Dfc
Ans: (b).
Q3. The climate classification based on precipitation effectiveness and potential evapotranspiration was given by:
(a) Koppen
(b) Thornthwaite
(c) Trewartha
(d) Flohn
Ans: (b).