Köppen climate classification

Developed by climatologist Wladimir Köppen and later revised by other researchers, the Köppen climate classification is an empirical scheme: it groups regions according to observed climatic conditions rather than attempting to classify them only by their causes. The system uses long-term temperature and precipitation patterns, including their seasonal distribution. Köppen also related climate types to characteristic natural vegetation, treating vegetation as an observable expression of climatic conditions.

The familiar Köppen-Geiger form has five major groups, represented by capital letters: A for tropical climates, B for dry or arid climates, C for temperate climates, D for continental climates and E for polar climates. Further letters encode distinctions such as rainfall seasonality, degree of dryness, or temperature characteristics. The resulting codes let readers summarize important climatic patterns in a compact form; the precise number and names of subtypes can vary among revisions of the scheme.

Researchers apply the classification to map climatic regions, compare places, and organize analyses of climate-related patterns. Global map projects calculate categories from station observations or gridded climate data; newer high-resolution maps can show more spatial detail, including variation associated with terrain. The system is also used in ecological studies and climate-impact assessments, where climate categories can help describe broad environmental patterns.

A Köppen-Geiger code is a useful summary, not a complete account of a place's climate. Boundaries are based on selected thresholds and climatological averages, so classifications can differ with the data source, reference period, map resolution or version used. Gradual climatic transitions do not necessarily follow the sharp lines shown on a map, and local conditions such as elevation and exposure may vary within a mapped class. Climate classifications describe patterns; they do not by themselves explain every process that produces them.

Köppen introduced his mathematical climate-classification system in 1900. The scheme was subsequently modified by Köppen, Rudolf Geiger and other researchers, giving rise to the commonly used name Köppen-Geiger. Later map studies have recalculated its categories with different station records, gridded observations and methods. The system remains widely used in teaching and research, while new datasets and versions continue to refine how its climate zones are mapped.