Köppen climate classification

The Köppen climate classification divides Earth 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.
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).
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 and/or October to March, while winter is the six-month period that is cooler.
Tropical climates have an average temperature of 18 °C (64.4 °F) or higher every month of the year, with significant precipitation.
Desert and semi-arid climates are defined by low precipitation in a region that does not fit the polar (EF or ET) criteria of no month with an average temperature greater than 10 °C (50 °F).
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 18 °C (64.4 °F)) 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.
Temperate climates have the coldest month averaging between 0 °C (32 °F) (or −3 °C (26.6 °F)) and 18 °C (64.4 °F) and at least one month averaging above 10 °C (50 °F). 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 applies to locations that satisfies both Ds and Dw as well.
Continental climates have at least one month averaging below 0 °C (32 °F) (or −3 °C (26.6 °F)) and at least one month averaging above 10 °C (50 °F).
Polar and alpine climates has every month of the year with an average temperature below 10 °C (50 °F).
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:
All 12 months have an average precipitation of at least 60 mm (2.4 in). These climates usually occur within 10° latitude of the equator. This climate has no natural seasons in terms of thermal and moisture changes. When it is dominated most of the year by the doldrums low-pressure system due to the presence of the Intertropical Convergence Zone (ITCZ) and when there are no cyclones then the climate is qualified as equatorial. When the trade winds dominate most of the year, the climate is a tropical trade-wind rainforest climate.
Some of the places with this climate are indeed uniformly and monotonously wet throughout the year (e.g., the northwest Pacific coast of South and Central America, from Ecuador to Costa Rica; see, for instance, Andagoya, Colombia), but in many cases, the period of higher sun and longer days is distinctly wettest (as at Palembang, Indonesia) or the time of lower sun and shorter days may have more rain (as at Sitiawan, Malaysia). Among these places, some have a pure equatorial climate (Balikpapan, Kuala Lumpur, Kuching, Lae, Medan, Paramaribo, Pontianak, and Singapore) with the dominant ITCZ aerological mechanism and no cyclones or a subequatorial climate with occasional hurricanes (Davao, Ratnapura, Victoria).
(The term aseasonal refers to the lack in the tropical zone of large differences in daylight hours and mean monthly (or daily) temperature throughout the year. Annual cyclic changes occur in the tropics, but not as predictably as those in the temperate zone, albeit unrelated to temperature, but to water availability whether as rain, mist, soil, or groundwater. Plant response (e.g., phenology), animal (feeding, migration, reproduction, etc.), and human activities (plant sowing, harvesting, hunting, fishing, etc.) are tuned to this 'seasonality'. Indeed, in tropical South America and Central America, the 'rainy season' (and the 'high water season') is called invierno (Spanish) or inverno (Portuguese), though it could occur in the Northern Hemisphere summer; likewise, the 'dry season (and 'low water season') is called verano or verão, and can occur in the Northern Hemisphere winter).
This type of climate results from the monsoon winds which change direction according to the seasons. This climate has a driest month (which nearly always occurs at or soon after the "winter" solstice for that side of the equator) with rainfall less than 60 mm (2.4 in), but at least 100 − ( t o t a l a n n u a l p r e c i p i t a t i o n ( m m ) 25 ) {\textstyle 100-\left({\frac {\mathrm {total\,annual\,precipitation\,(mm)} }{25}}\right)} of average monthly precipitation.
Aw climates have a pronounced dry season, with the driest month having precipitation less than 60 mm (2.4 in) and less than 100 − ( t o t a l a n n u a l p r e c i p i t a t i o n ( m m ) 25 ) {\textstyle 100-\left({\frac {\mathrm {total\,annual\,precipitation\,(mm)} }{25}}\right)} of average monthly precipitation.
Most places that have this climate are found at the outer margins of the tropical zone from the low teens to the mid-20s latitudes, but occasionally an inner-tropical location (e.g., San Marcos, Antioquia, Colombia) also qualifies. The Caribbean coast, eastward from the Gulf of Urabá on the Colombia–Panama border to the Orinoco River delta, on the Atlantic Ocean (about 4,000 km (2,500 mi)), have long dry periods (the extreme is the BWh climate (see below), characterized by very low, unreliable precipitation, present, for instance, in extensive areas in the Guajira, and Coro, western Venezuela, the northernmost peninsulas in South America, which receive <300 mm (12 in) total annual precipitation, practically all in two or three months).
This condition extends to the Lesser Antilles and Greater Antilles forming the circum-Caribbean dry belt. The length and severity of the dry season diminish inland (southward); at the latitude of the Amazon River—which flows eastward, just south of the equatorial line—the climate is Af. East from the Andes, between the dry, arid Caribbean and the ever-wet Amazon are the Orinoco River's Llanos or savannas, from where this climate takes its name.
Sometimes As is used in place of Aw if the dry season occurs during the time of higher sun and longer days (during summer). This is the case in parts of Hawaii, northwestern Dominican Republic, East Africa, southeast India and northeast Sri Lanka, and the Brazilian Northeastern Coast. In places that have this climate type, the dry season occurs during the time of lower sun and shorter days generally because of rain shadow effects during the 'high-sun' part of the year.
These climates are characterized by the amount of annual precipitation less than a threshold value that approximates the potential evapotranspiration. The threshold value (in millimeters) is calculated as follows:
Multiply the average annual temperature in °C by 20, then add
According to the modified Köppen classification system used by modern climatologists, total precipitation in the warmest six months of the year is taken as a reference instead of the total precipitation in the high-sun half of the year.
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 climate (average annual temperature above 18 °C) while k signified middle-latitude climate (average annual temperature below 18 °C).
Desert areas situated along the west coasts of continents at tropical or near-tropical locations characterized by frequent fog and low clouds, although these places rank among the driest on earth in terms of actual precipitation received, can be labeled BWn with the n denoting a climate characterized by frequent fog. An equivalent BSn category can be found in foggy coastal steppes.
In the Köppen climate system, temperate climates are defined as having an average temperature above 0 °C (32 °F) (or −3 °C (26.6 °F), as noted previously) in their coldest month but below 18 °C (64.4 °F). The average temperature of −3 °C (26.6 °F) roughly coincides with the equatorward limit of frozen ground and snow cover lasting for a month or more.
The second letter indicates the precipitation pattern—w indicates dry winters (driest winter month average precipitation less than one-tenth wettest summer month average precipitation). s indicates at least three times as much rain in the wettest month of winter as in the driest month of summer. f means significant precipitation in all seasons (neither above-mentioned set of conditions fulfilled).
The third letter indicates the degree of summer heat—a indicates warmest month average temperature above 22 °C (71.6 °F) while b indicates warmest month averaging below 22 °C but with at least four months averaging above 10 °C (50.0 °F), and c indicates one to three months averaging above 10 °C (50.0 °F).
These climates usually occur on the western sides of continents between the latitudes of 30° and 45°. These climates are in the polar front region in winter, and thus have moderate temperatures and changeable, rainy weather. Summers are hot and dry, due to the domination of the subtropical high-pressure systems, except in the immediate coastal areas, where summers are milder due to the nearby presence of cold ocean currents that may bring fog but prevent rain.
Dry-summer climates sometimes extend to additional areas where the warmest month average temperatures do not reach 22 °C (71.6 °F), most often in the 40s latitudes. These climates are classified as Csb.
Cold summer Mediterranean climates (Csc) exist in high-elevation areas adjacent to coastal Csb climate areas, where the strong maritime influence prevents the average winter monthly temperature from dropping below 0 °C (32 °F). This climate is rare and is predominantly found in climate fringes and isolated areas of the Cascades and Andes Mountains, as the dry-summer climate extends further poleward in the Americas than elsewhere. Rare instances of this climate can be found in some coastal locations in the North Atlantic and at high altitudes in Hawaii.
These climates usually occur on the eastern coasts and eastern sides of continents, usually in the high 20s and 30s latitudes. Unlike the dry summer Mediterranean climates, humid subtropical climates have a warm and wet flow from the tropics that creates warm and moist conditions in the summer months. As such, summer (not winter as is the case in Mediterranean climates) is often the wettest season.
The flow out of the subtropical highs and the summer monsoon creates a southerly flow from the tropics that brings warm and moist air to the lower east sides of continents. This flow is often what brings the frequent and strong but short-lived summer thundershowers so typical of the more southerly subtropical climates like the southeast United States, southern China, and Japan.
Cfb climates usually occur in the higher middle latitudes on the western sides of continents; they are typically situated immediately poleward of the Mediterranean climates in the 40s and 50s latitudes. However, in southeast Australia, southeast South America, and extreme southern Africa this climate is found immediately poleward of temperate climates, on places near the coast and at a somewhat lower latitude. In western Europe, this climate occurs in coastal areas up to 68°N in Norway.
These climates are dominated all year round by the polar front, leading to changeable, often overcast weather. Summers are mild due to cool ocean currents. Winters are milder than other climates in similar latitudes, but usually very cloudy, and frequently wet. Cfb climates are also encountered at high elevations in certain subtropical and tropical areas, where the climate would be that of a subtropical/tropical rainforest if not for the altitude. These climates are called "highlands".
Subtropical highland climates with uniform rainfall (Cfb) are a type of oceanic climate mainly found in the highlands of Australia, such as in or around the Great Dividing Range in the north of the state of New South Wales, and also sparsely in other continents, such as in South America, among others. Unlike a typical Cwb climate, they tend to have rainfall spread evenly throughout the year. They have characteristics of both the Cfb and Cfa climates, but unlike these climates, they have a high diurnal temperature variation and low humidity, owing to their inland location and relatively high elevation.
Subpolar oceanic climates (Cfc) occur poleward of or at higher elevations than the maritime temperate climates and are mostly confined either to narrow coastal strips on the western poleward margins of the continents, or, especially in the Northern Hemisphere, to islands off such coasts. They occur in both hemispheres, generally in the high 50s and 60s latitudes in the Northern Hemisphere and the 50s latitudes in the Southern Hemisphere.
Cwa is a monsoonal influenced version of the humid subtropical climate, having the classic dry winter–wet summer pattern associated with tropical monsoonal climates. They are found at similar latitudes as the Cfa climates, except in regions where monsoons are more prevalent. These regions are in the Southern Cone of South America, the Gangetic Plain of South Asia, southeastern Africa, parts of East Asia and Mexico, and Northern Vietnam of Southeast Asia.
Dry-winter subtropical highland climate (Cwb) is a type of climate mainly found in highlands inside the tropics of Central America, South America, Africa, and South and Southeast Asia or areas in the subtropics. Winters are noticeable and dry, and summers can be very rainy. In the tropics, the monsoon is provoked by the tropical air masses and the dry winters by subtropical high pressure.
Dry-winter cold subtropical highland climates (Cwc) exist in high-elevation areas adjacent to Cwb climates. This climate is rare and is found mainly in isolated locations mostly in the Andes in Bolivia and Peru, as well as in sparse mountain locations in Southeast Asia.
These climates have an average temperature above 10 °C (50 °F) in their warmest months, and the coldest month average below 0 °C (32 °F) (or −3 °C (26.6 °F), as noted previously). These usually occur in the interiors of continents and on their upper east coasts, normally north of 40°N. In the Southern Hemisphere, group D climates are extremely rare due to the smaller land masses in the middle latitudes and the almost complete absence of land at 40–60°S, existing only in some highland locations.
Dfa climates usually occur in the high 30s and low 40s latitudes, with a qualifying average temperature in the warmest month of greater than 22 °C (72 °F). In Europe, these climates tend to be much drier than in North America. Dsa exists at higher elevations adjacent to areas with hot summer Mediterranean (Csa) climates.
These climates exist only in the Northern Hemisphere because the Southern Hemisphere has no large landmasses isolated from the moderating effects of the sea within the middle latitudes.
In eastern Asia, Dwa climates extend further south into the mid-30s latitudes due to the influence of the Siberian high-pressure system, which also causes winters there to be dry, and summers can be very wet because of monsoon circulation.
Dsa exists only at higher elevations adjacent to areas with hot summer Mediterranean (Csa) climates.
Dfb climates are immediately poleward of hot summer continental climates, generally in the high 40s and low 50s latitudes in North America and Asia, and also extending to higher latitudes into the high 50s and low 60s latitudes in central and eastern Europe, between the maritime temperate and continental subarctic climates.
Like with all Group D climates, Dwb climates mostly only occur in the northern hemisphere.
Dsb arises from the same scenario as Dsa, but at even higher altitudes or latitudes, and chiefly in North America, since the Mediterranean climates extend further poleward than in Eurasia.
Dfc, Dsc and Dwc climates occur poleward of the other group D climates, or at higher altitudes, generally in the 50s and 60s latitudes.
Places with this climate have severe winters, with the temperature in their coldest month lower than −38 °C (−36 °F). These climates occur only in eastern Siberia, and are the second coldest, before EF. The coldest recorded temperatures in the Northern Hemisphere belonged to this climate. The names of some of the places with this climate have become veritable synonyms for the extreme, severe winter cold.
In the Köppen climate system, polar climates are defined as the warmest temperature of any month being below 10 °C (50 °F). Polar climates are further divided into two types, tundra climates and icecap climates:
Tundra climate (ET): warmest month has an average temperature between 0 °C (32 °F) and 10 °C (50 °F). These climates occur on the northern edges of the North American and Eurasian land masses (generally north of 70 °N although they may be found farther south depending on local conditions), and on nearby islands. ET climates are also found on some islands near the Antarctic Convergence, and at high elevations outside the polar regions, above the tree line.
Ice cap climate (EF): this climate is dominant in Antarctica, inner Greenland, and summits of many high mountains, even at lower latitudes. Monthly average temperatures never exceed 0 °C (32 °F).
The Köppen climate classification is based on the empirical relationship between climate and vegetation. This classification provides an efficient way to describe climatic conditions defined by temperature and precipitation and their seasonality with a single metric. Because climatic conditions identified by the Köppen classification are ecologically relevant, it has been widely used to map the geographic distribution of long-term climate and associated ecosystem conditions.
Over recent years, there has been an increasing interest in using the classification to identify changes in climate and potential changes in vegetation over time. The most important ecological significance of the Köppen climate classification is that it helps to predict the dominant vegetation type based on the climatic data and vice versa.
In 2015, a Nanjing University paper published in Scientific Reports analyzing climate classifications found that between 1950 and 2010, approximately 5.7% of all land area worldwide had moved from wetter and colder classifications to drier and hotter classifications. The authors also found that the change "cannot be explained as natural variations but are driven by anthropogenic factors".
A 2018 study provides detailed maps for present and future Köppen-Geiger climate classification maps at 1-km resolution.
All maps use the ≥0 °C (32 °F) definition for the temperate-continental border.