The Köppen climate classification divides Earth's climates into five main climate groups, with each group being divided based on patterns of seasonal precipitation and temperature. The five main groups are A (tropical), B (arid), C (temperate), D (continental), and E (polar). Each group and subgroup is represented by a letter. All climates are assigned a main group (the first letter). All climates except for those in the E group are assigned a seasonal precipitation subgroup (the second letter). For example, Af indicates a tropical rainforest climate. The system assigns a temperature subgroup for all groups other than those in the A group, indicated by the third letter for climates in B, C, D, and the second letter for climates in E. Other examples include: Cfb indicating an oceanic climate with warm summers as indicated by the ending b, while Dwb indicates a semi-monsoonal continental climate, also with warm summers. Climates are classified based on specific criteria unique to each climate type.
The Köppen climate classification is the most widely used climate classification scheme. It was first published by German-Russian climatologist Wladimir Köppen (1846–1940) in 1884, with several later modifications by Köppen, notably in 1918 and 1936. Later, German climatologist Rudolf Geiger (1894–1981) introduced some changes to the classification system in 1954 and 1961, which is thus sometimes called the Köppen–Geiger climate classification. (Wandkarte 1:16 Mill.) – Klett-Perthes, Gotha.
As Köppen designed the system based on his experience as a botanist, his main climate groups represent a classification by vegetation type. In addition to identifying climates, the system can be used to analyze ecosystem conditions and identify the main types of vegetation within climates. Due to its association with the plant life of a given region, the system is useful in predicting future changes of plant life within that region.
The Köppen climate classification system was modified further within the Trewartha climate classification system in 1966 (revised in 1980). The Trewartha system sought to create a more refined middle latitude climate zone, which was one of the criticisms of the Köppen system (the climate group C was too general).
Overview
+ Köppen climate classification scheme symbols description table 1st 2nd 3rd A (Tropical)f (Rainforest) m (Monsoon) w (Savanna, dry winter) s (Savanna, dry summer) B (Dry)W (Arid desert) S (Semi-arid steppe)h (Hot) k (Cold) C (Temperate)w (Dry winter) f (No dry season) s (Dry summer)a (Hot summer) b (Warm summer) c (Cold summer) D (Continental)w (Dry winter) f (No dry season) s (Dry summer) a (Hot summer) b (Warm summer) c (Cold summer) d (Very cold winter) E (Polar)T (Tundra) F (Ice cap)
The Köppen climate classification scheme divides climates into five main climate groups: A (tropical), B (arid), C (temperate), D (continental), and E (polar). The second letter indicates the seasonal precipitation type, while the third letter indicates the level of heat. Summers are defined as the six-month period that is warmer either from April to September or October to March, while winter is the six-month period that is cooler.
Group A: Tropical climates
Tropical climates have an average temperature of or higher every month of the year, with significant precipitation. Af = Tropical rainforest climate; average precipitation of at least in every month. Am = Tropical monsoon climate; driest month (which nearly always occurs at or soon after the "winter" solstice for that side of the equator) with precipitation less than , but at least . Aw or As = Tropical wet and dry or savanna climate; with the driest month having precipitation less than and less than .
Group B: Desert and semi-arid climates
Desert and semi-arid climates are defined by low precipitation in regions that do not fit the polar (EF or ET) criterion of having no month with an average temperature greater than .
The precipitation threshold in millimeters is determined by multiplying the average annual temperature in Celsius by 20, then adding:
If the annual precipitation is less than 50% of this threshold, the classification is BW (arid: desert climate); if it is in the range of 50%–100% of the threshold, the classification is BS (semi-arid: steppe climate).
A third letter can be included to indicate temperature. Here, h signifies low-latitude climates (average annual temperature above ) while k signifies middle-latitude climates (average annual temperature less than 18 °C). In addition, n is used to denote a climate characterized by frequent fog and H for high altitudes. BWh = Hot desert climate BWk = Cold desert climate BSh = Hot semi-arid climate BSk = Cold semi-arid climate
Group C: Temperate climates
Temperate climates have the coldest month averaging between (or ) and and at least one month averaging above . For the distribution of precipitation in locations that both satisfy a dry summer (Cs) and a dry winter (Cw), a location is considered to have a wet summer (Cw) when more precipitation falls within the summer months than the winter months while a location is considered to have a dry summer (Cs) when more precipitation falls within the winter months. This additional criterion also applies to locations that satisfy both Ds and Dw. Cfa = Humid subtropical climate; coldest month averaging above (or ), at least one month's average temperature above , and at least four months averaging above . No significant precipitation difference between seasons (neither the abovementioned set of conditions fulfilled). Cfb = Temperate oceanic climate or subtropical highland climate; coldest month averaging above (or ), all months with average temperatures below , and at least four months averaging above . No significant precipitation difference between seasons (neither the abovementioned set of conditions fulfilled). Cfc = Subpolar oceanic climate; coldest month averaging above (or ) and 1–3 months averaging above . No significant precipitation difference between seasons (neither the abovementioned set of conditions fulfilled). Cwa = Monsoon-influenced humid subtropical climate; coldest month averaging above (or ), at least one month's average temperature above , and at least four months averaging above . At least ten times as much rain in the wettest month of summer as in the driest month of winter. Cwb = Subtropical highland climate or Monsoon-influenced temperate oceanic climate; coldest month averaging above (or ), all months with average temperatures below , and at least four months averaging above . At least ten times as much rain in the wettest month of summer as in the driest month of winter. Cwc = Cold subtropical highland climate or Monsoon-influenced subpolar oceanic climate; coldest month averaging above (or ) and 1–3 months averaging above . At least ten times as much rain in the wettest month of summer as in the driest month of winter. Csa = Hot-summer Mediterranean climate; coldest month averaging above (or ), at least one month's average temperature above , and at least four months averaging above . At least three times as much precipitation in the wettest month of winter as in the driest month of summer, and the driest month of summer receives less than . Csb = Warm-summer Mediterranean climate; coldest month averaging above (or ), all months with average temperatures below , and at least four months averaging above . At least three times as much precipitation in the wettest month of winter as in the driest month of summer, and the driest month of summer receives less than . Csc = Cold-summer Mediterranean climate; coldest month averaging above (or ) and 1–3 months averaging above . At least three times as much precipitation in the wettest month of winter as in the driest month of summer, and the driest month of summer receives less than .
Group D: Continental climates
Continental climates have at least one month averaging below (or ) and at least one month averaging above . Dfa = Hot-summer humid continental climate; coldest month averaging below (or ), at least one month's average temperature above , and at least four months averaging above . No significant precipitation difference between seasons (neither the abovementioned set of conditions fulfilled). Dfb = Warm-summer humid continental climate; coldest month averaging below (or ), all months with average temperatures below , and at least four months averaging above . No significant precipitation difference between seasons (neither the abovementioned set of conditions fulfilled). Dfc = Subarctic climate; coldest month averaging below (or ) and 1–3 months averaging above . No significant precipitation difference between seasons (neither the abovementioned set of conditions fulfilled). Dfd = Extremely cold subarctic climate; coldest month averaging below and 1–3 months averaging above . No significant precipitation difference between seasons (neither the abovementioned set of conditions fulfilled). Dwa = Monsoon-influenced hot-summer humid continental climate; coldest month averaging below (or ), at least one month's average temperature above , and at least four months averaging above . At least ten times as much rain in the wettest month of summer as in the driest month of winter. Dwb = Monsoon-influenced warm-summer humid continental climate; coldest month averaging below (or ), all months with average temperatures below , and at least four months averaging above . At least ten times as much rain in the wettest month of summer as in the driest month of winter. Dwc = Monsoon-influenced subarctic climate; coldest month averaging below (or ) and 1–3 months averaging above . At least ten times as much rain in the wettest month of summer as in the driest month of winter. Dwd = Monsoon-influenced extremely cold subarctic climate; coldest month averaging below and 1–3 months averaging above . At least ten times as much rain in the wettest month of summer as in the driest month of winter. Dsa = Mediterranean-influenced hot-summer humid continental climate; coldest month averaging below (or ), average temperature of the warmest month above and at least four months averaging above . At least three times as much precipitation in the wettest month of winter as in the driest month of summer, and the driest month of summer receives less than . Dsb = Mediterranean-influenced warm-summer humid continental climate; coldest month averaging below (or ), average temperature of the warmest month below and at least four months averaging above . At least three times as much precipitation in the wettest month of winter as in the driest month of summer, and the driest month of summer receives less than . Dsc = Mediterranean-influenced subarctic climate; coldest month averaging below (or ) and 1–3 months averaging above . At least three times as much precipitation in the wettest month of winter as in the driest month of summer, and the driest month of summer receives less than . Dsd = Mediterranean-influenced extremely cold subarctic climate; coldest month averaging below and 1–3 months averaging above . At least three times as much precipitation in the wettest month of winter as in the driest month of summer, and the driest month of summer receives less than .
Group E: Polar and alpine climates
Polar and alpine climates have average temperatures below in every month of the year. ET = Tundra climate; average temperature of warmest month between and . EF = Ice cap climate; eternal winter, with all 12 months of the year with average temperatures below .
Group A: Tropical/megathermal climates
Tropical climates are characterized by constant high temperatures (at sea level and low elevations); all 12 months of the year have average temperatures of 18 °C (64.4 °F) or higher; and generally high annual precipitation. They are subdivided as follows:
Af: Tropical rainforest climate