Köppen climate classification
The Köppen climate classification is one of the most widely used climate classification systems. It was first published by German-Russian climatologist Wladimir Köppen (1846–1940) in 1884,[2][3] with several later modifications by Köppen, notably in 1918 and 1936.[4][5] 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.[6][7]
The Köppen climate classification divides 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. For example, Cfb indicates an oceanic climate with warm summers as indicated by the ending b. Climates are classified based on specific criteria unique to each climate type.[8]
As Köppen designed the system based on his experience as a botanist, his main climate groups are based on the types of vegetation occurring in a given climate classification region. 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.[1]
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).[9]: 200–1
The Köppen climate classification scheme divides climates into five main climate groups: A (tropical), B (arid), C (temperate), D (continental), and E (polar).[11] The second letter indicates the seasonal precipitation type, while the third letter indicates the level of heat.[12] Summers are defined as the 6-month period that is warmer either from April–September and/or October–March while winter is the 6-month period that is cooler.[1][10]
Group A: Tropical climates
This type of climate has an average temperature of 18 °C (64.4 °F) or higher every month of the year, with significant precipitation.[1][10]
Group B: Arid climates
This type of climate is 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).[1][10]
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.[13][14][15]
Group C: Temperate climates
This type of climate has the coldest month averaging between 0 °C (32 °F)[10] (or −3 °C (27 °F))[8] and 18 °C (64.4 °F) and at least one month averaging above 10 °C (50 °F).[10][8] 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.[10] This additional criterion applies to locations that satisfies both Ds and Dw as well.[10]
Group D: Continental climates
This type of climate has at least one month averaging below 0 °C (32 °F) (or −3 °C (27 °F)) and at least one month averaging above 10 °C (50 °F).[10][8]
Group E: Polar and alpine climates
This type of climate has every month of the year with an average temperature below 10 °C (50 °F).[1][10]
Ecological significance
Biomass
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.[80]
Climate change
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.[12] 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.[81]
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".[82]
A 2018 study provides detailed maps for present and future Köppen-Geiger climate classification maps at 1-km resolution.[83]
North America
Europe
Russia
Central Asia
East Asia
South America
Africa
Western Asia
South Asia
Southeast Asia
Melanesia/Oceania
Australia
New Zealand
World (Present)
World (Future)
All maps use the ≥0 °C definition for the temperate-continental border.[1]