Köppen-Geiger Climate Classification

The Köppen-Geiger is a system of global climate classification created by Wladimir Peter Köppen and subsequently updated and revised by Köppen in collaboration with Rudolf Geiger. It is the best-known and most widely used global climate classification available.

Köppen was born in St. Petersburg, Russia, in 1846, and died 94 years later in Austria after making a prolific contribution to science. His early training in botany appears to have exerted considerable influence on the work for which he is best remembered—a global classification of climate. In an interesting twist of fate, his daughter married Alfred Wegener, the pioneer of continental drift, with whom Köppen collaborated on global paleoclimate reconstruction; this project presumably emphasized to him the importance of a global system of climate classification. In the 1930s, Köppen collaborated with Rudolf Geiger, his junior by 48 years, in writing the Handbuch der Klimatologie and in updating and revising his climate classification system, which Geiger continued to work on after Köppen's death in 1940. The classification is now widely referred to as the Köppen-Geiger classification in recognition of Geiger's contributions.

In this classification, climates are divided into five major categories, designated by the first five letters of the alphabet and always capitalized (see Table 1). Subsidiary properties of the classification are also denoted by letters of the alphabet, always in lowercase. The first major division in Köppen's system is the distinction between humid climates and dry climates. The climate zones A, C, D, and E are humid, and the arid B climates are divided into two groups using an uppercase letter—steppe (BS) or desert (BW). Within the humid climate group, distinction is made on the basis of temperature, progressing sequentially from tropical (A, mean temperature of the coldest month ≥18 °C), to temperate (C, mean temperature of the hottest month >10 °C and mean temperature of the coldest month between 0 °C and 18 °C), to cold (D, mean temperature of the hottest month >10 °C and mean temperature of the coldest month <10 °C), to polar (E, mean temperature of the warmest month <10 °C), with the E type climates also divided into two groups using an uppercase letter—ET indicating tundra and EF indicating frost climates.

The climate zones A, C, and D are further divided internally on the basis of the seasonality of rainfall using lowercase letters. No further subdivision is made in the case of the ET and EF climates. The tropical A climates are divided into f, rain forest climates, with high temperatures and rainfall all year; m, monsoon, with a dry season; and w, savanna, with the distinction between monsoon and savanna being based on the relative dryness of the dry season.

The arid (B) climates are separated from the humid climates using a dryness threshold and are then divided into steppe (BS) and desert (BW), also using the dryness threshold, which depends on the mean annual temperature and the seasonal distribution of rainfall. As in the subdivision of other climate types, an important principle is whether the most precipitation occurs during the warmer months of the year, when it will be more effective for plant growth. The dryness threshold varies depending on the seasonal distribution of rainfall. If 70% of the precipitation occurs in winter, then the dryness threshold is calculated as twice the mean annual temperature (in °C). Where 70% of the precipitation occurs in summer, the dryness threshold is calculated as 28 plus twice the mean annual temperature. Where the seasonal concentration of precipitation is below 70% in both seasons, the dryness threshold is calculated as 14 plus twice the mean annual temperature. Summer and winter are [Page 1666]defined as 6-month periods where summer (winter) is ONDJFM or AMJJAS.

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