Climate classification

Story hook

On a single day — 3 January 2024 — three thermometers in three parts of India read utterly different worlds. At Dras (Ladakh, 3,300 m), the mercury settled at -26°C under a sapphire-clear sky. 300 km southwest at Srinagar (1,585 m), it was -3°C with light snow on the Dal Lake houseboats. 2,800 km further south at Madurai (Tamil Nadu), it was 27°C under a low overcast — a warm winter morning, locals scarves on. And in Mawsynram (Meghalaya), 2,000 km east of Madurai, the day's accumulated rainfall — even in January, the dry season — was 186 mm.

India is not one climate. It is at least six. Wladimir Köppen, the Russian-German climatologist working at Hamburg, recognised this in his 1918 climate classification system — which is still the standard tool to map India's diversity. His five letters (A= Tropical, B=Arid, C=Temperate, D=Cold, E=Polar) capture rainfall + temperature; his second letter codes seasonality (f=continuously wet, m=monsoon, w=winter dry, s=summer dry); his third letter codes temperature extremes. By Köppen, India spans Aw (Maharashtra), Am (Western Ghats), As (Tamil Nadu), Bsh (Punjab), Bwh (Thar), Cwg (Hills), Cwa (Ganga Plain), Cfb (Coastal Mumbai), Dfa (Ladakh), ET (high Himalayas).

The Indian Council of Agricultural Research (ICAR) built its own classification — the 15 agro-climatic zones (1989) — specifically for farm planning. Planning Commission uses 14 zones; National Bureau of Soil Survey (NBSS-LUP) uses 20 agro-ecological zones. This file walks through all three systems — Köppen, ICAR, NBSS-LUP — that an UPSC candidate must know.

Why this matters for UPSC

UPSC Prelims has asked Köppen-classification questions in 2010, 2013, 2017, and 2022. Mains GS-I (Geography) has asked "Discuss India's climate using Köppen's classification" (2014), and "How relevant are agro-climatic zones to modern farm planning?" (2018). The topic also feeds into GS-III (Agriculture, food security) + Environment (climate change projections at agro-ecological scale).