Köppen climate classification

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Updated Köppen–Geiger climate map[1]
  Af
  Am
  Aw
  BWh
  BWk
  BSh
  BSk
  Csa
  Csb
  Cwa
  Cwb
  Cwc
  Cfa
  Cfb
  Cfc
  Dsa
  Dsb
  Dsc
  Dsd
  Dwa
  Dwb
  Dwc
  Dwd
  Dfa
  Dfb
  Dfc
  Dfd
  ET
  EF

The Köppen climate classification is one of the most widely used climate classification systems. It was first published by Russian German climatologist Wladimir Köppen in 1884, with several later modifications by Köppen himself, notably in 1918 and 1936. Later, German climatologist Rudolf Geiger collaborated with Köppen on changes to the classification system, which is thus sometimes referred to as the Köppen–Geiger climate classification system. The system is based on the concept that native vegetation is the best expression of climate. Thus, climate zone boundaries have been selected with vegetation distribution in mind. It combines average annual and monthly temperatures and precipitation, and the seasonality of precipitation.[2]:200–1

Scheme[edit]

The Köppen climate classification scheme divides climates into five main groups, each having several types and subtypes. Each particular climate type is represented by a two- to four-letter symbol.

GROUP A: Tropical/megathermal climates[edit]

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 °F) or higher. They are subdivided as follows:

  • Tropical rainforest climate (Af):[2]:205–8 All 12 months have average precipitation of at least 60 mm (2.4 in). These climates usually occur within 5–10° latitude of the equator. In some eastern-coast areas, they may extend to as much as 25° away from the equator. This climate is dominated by the doldrums low pressure system all year round, so has no natural seasons.
    • Some of the places that have 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).
    • A few places with this climate are found at the outer edge of the tropics, almost exclusively in the Southern Hemisphere; one example is Santos, Brazil.
      Note. 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 predictable as those in the temperate zone, albeit unrelated to temperature but to water availability whether as rain, mist, soil, or ground water. 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 or inverno, 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.
  • Tropical monsoon climate (Am):[2]:208 This type of climate, most common in South America, 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, but more than 1/25 the total annual precipitation.
    • Examples:
    • Also, another scenario exists under which some places fit into this category; this is referred to as the 'trade-wind littoral' climate because easterly winds bring enough precipitation during the "winter" months to prevent the climate from becoming a tropical wet-and-dry climate. Nassau, Bahamas is included among these locations.
  • Tropical wet and dry or savanna climate (Aw):[2]:208–11 These climates have a pronounced dry season, with the driest month having precipitation less than 60 mm and also less than 1/25 the total annual precipitation.
    • Examples:
    • Most places that have this climate are found at the outer margins of the tropical zone, but occasionally an inner-tropical location (e.g., San Marcos, Antioquia, Colombia) also qualifies. Actually, the Caribbean coast, eastward from the Gulf of Urabá on the ColombiaPanamá border to the Orinoco River delta, on the Atlantic Ocean (about 4,000 km), have long dry periods (the extreme is the BSh climate (see below), characterised 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 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 diminishes 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. This is the case in parts of Hawaii, East Africa (Mombasa, Kenya), and Sri Lanka (Trincomalee), for instance. In most places that have tropical wet and dry climates, however, the dry season occurs during the time of lower sun and shorter days because of rainshadow effects during the 'high-sun' part of the year.

GROUP B: Dry (arid and semiarid) climates[edit]

These climates are characterized by actual precipitation less than a threshold value set equal to the potential evapotranspiration.[2]:212 The threshold value (in millimeters) is determined as:

  • Multiply the average annual temperature in °C by 20, then add (a) 280 if 70% or more of the total precipitation is in the high-sun half of the year (April through September in the Northern Hemisphere, or October through March in the Southern), or (b) 140 if 30%–70% of the total precipitation is received during the applicable period, or (c) 0 if less than 30% of the total precipitation is so received.
  • If the annual precipitation is less than 50% of this threshold, the classification is BW (desert climate); if it is in the range of 50%–100% of the threshold, the classification is BS (steppe climate).
  • A third letter can be included to indicate temperature. Originally, h signified low-latitude climate (average annual temperature above 18 °C) while k signified middle-latitude climate (average annual temperature below 18 °C, but the more common practice today (especially in the United States) is to use h to mean the coldest month has an average temperature above 0 °C (32 °F), with k denoting that at least one month averages below 0 °C.
    • Desert areas situated along the west coasts of continents at tropical or near-tropical locations are characterized by cooler temperatures than encountered elsewhere at comparable latitudes (due to the nearby presence of cold ocean currents) and frequent fog and low clouds, despite the fact that these places rank among the driest on earth in terms of actual precipitation received. This climate is sometimes labelled BWn.

The BSn category can be found in foggy coastal steppes.

  • Examples:
  • On occasion, a fourth letter is added to indicate if either the winter or summer is "wetter" than the other half of the year. To qualify, the wettest month must have at least 60 mm (2.4 in) of average precipitation if all 12 months are above 18 °C (64 °F), or 30 mm (1.2 in) if not; plus at least 70% of the total precipitation must be in the same half of the year as the wettest month — but the letter used indicates when the 'dry' season occurs, not the 'wet' one. This would result in Khartoum, Sudan, being reckoned as BWhw; Niamey, Niger, as BShw; Alexandria, Egypt, as BWhs; Asbi'ah, Libya, as BShs; Ömnögovi Province, Mongolia, as BWkw; and Xining, Qinghai, China, as BSkw (BWks and BSks do not exist if 0 °C in the coldest month is recognized as the h/k boundary). If the standards for neither w nor s are met, no fourth letter is added.

GROUP C: Temperate/mesothermal climates[edit]

These climates have an average temperature above 10 °C (50 °F) in their warmest months (April to September in northern hemisphere), and a coldest month average between −3 and 18 °C.

Some climatologists, particularly in the United States, however, prefer to observe 0 °C rather than −3 °C (27 °F) in the coldest month as the boundary between this group and the colder group D (humid continental). This is also done to prevent certain mild headland locations on the upper East Coast of the US and Japan from fitting into the C group.

When the boundary between C (temperate/mesothermal climates) and D (cold winter/microthermal climates) is increased to 0 °C (not the −3 °C suggested by Köppen), this creates a smaller C zone located further southward. In the USA, areas from the NYC metropolitan area (NYC/all but northwestern New Jersey/southern Connecticut) southward, as well as the lower Ohio Valley, lower Midwest and southern Plains, are located in the mild C group, while locations to the north of these regions – Northern Plains, Great Lakes, Midwest, upper Ohio Valley and upper East Coast (north of Boston) – are located in the cooler D group. Using 0 °C also pushes parts of northeast and northcentral Asia (northern Japan, northern China, and northern Korea) into the colder D/microthermal group (also known as humid continental).

  • 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; one variation also requires that the driest winter month have less than 30 mm average precipitation), s indicates dry summers (driest summer month less than 40 mm average precipitation and less than one-third wettest winter month precipitation) and f means significant precipitation in all seasons (neither above-mentioned set of conditions fulfilled).[1]
  • The third letter indicates the degree of summer heat — a indicates warmest month average temperature above 22 °C (72 °F) with at least four months averaging above 10 °C, b indicates warmest month averaging below 22 °C, but with at least four months averaging above 10 °C, while c means three or fewer months with mean temperatures above 10 °C.
  • The order of these two letters is sometimes reversed, especially by climatologists in the United States.
  • Dry-summer subtropical or Mediterranean climates (Csa/Csb):[2]:221–3 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.
  • Humid subtropical climates (Cfa, Cwa):[2]:223–6 These climates usually occur on the eastern coasts and eastern sides of continents, mainly in the high 20s and 30s latitude. Unlike the Mediterranean climates where summers are dry, humid subtropicals 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 southern 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 but short-lived summer thundershowers so typical of subtropical east-coast climates. East Asia has the world's best developed subtropical monsoons, and the classic dry winter/wet summer is characteristic of the region. In other eastern subtropical areas, like the USA and South America, mobile weather fronts/midlatitude storms tend to disrupt the normal dry winter/wet summer monsoon pattern.
  • Maritime temperate climates or Oceanic climates (Cfb, Cfc, Cwb, Cwc):[2]:226–9 Cfb climates usually occur on the western sides of continents between the latitudes of 45° and 55°; they are typically situated immediately poleward of the Mediterranean climates, although in Australia and extreme southern Africa this climate is found immediately poleward of the humid subtropical climate, and at a somewhat lower latitude. In western Europe, this climate occurs in coastal areas up to 63°N in Norway. These climates are dominated all year round by the polar front, leading to changeable, often overcast weather. Summers are cool due to cool ocean currents, but winters are milder than other climates in similar latitudes, but usually very cloudy.
  • Maritime subarctic climates or subpolar oceanic climates (Cfc):[2] These climates occur poleward of the maritime temperate climates, and are 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.
  • Dry-summer maritime subalpine climates (Csc):[2] This climate exists in high-elevation areas adjacent to coastal Csb climate areas, where the strong maritime influence prevent the average winter monthly temperature from dropping below −3 °C. This climate is extremely rare and is only found in isolated areas of the Cascades and Andes Mountains, as the dry-summer climate extends further poleward in the Americas than elsewhere.

GROUP D: Continental/microthermal climates[edit]

The snowy city of Sapporo

These climates have an average temperature above 10 °C (50 °F) in their warmest months, and a coldest month average below −3 °C (or 0 °C in some versions, 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.

  • The second and third letters are used as for group C climates, while a third letter of d indicates three or fewer months with mean temperatures above 10 °C and a coldest month temperature below −38 °C.

Group D climates are subdivided as:

Lettering

  • 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; one variation also requires that the driest winter month have less than 30 mm average precipitation), s indicates dry summers (driest summer month less than 30 mm average precipitation and less than one-third wettest winter month precipitation) and 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 (72 °F) with at least four months averaging above 10 °C, b indicates warmest month averaging below 22 °C, but with at least four months averaging above 10 °C, while c means three or fewer months with mean temperatures above 10 °C.

Scheme

  • Hot summer continental climates (Dfa, Dwa, Dsa):[2]:231–2 Dfa climates usually occur in the high 30s and low 40s latitudes, with a qualifying average temperature in the warmest month of >22 °C/72 °F. In Europe, these climates tend to be much drier than in North America. In eastern Asia, Dwa climates extend further south 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 at higher elevations adjacent to areas with hot summer Mediterranean (Csa) climates.
  • Warm summer continental or hemiboreal climates (Dfb, Dwb, Dsb):[2] Dfb and Dwb climates are immediately north of hot summer continental climates, generally in the high 40s and low 50s in latitude in North America and Asia, and also in central and eastern Europe and Russia, between the maritime temperate and continental subarctic climates, where it extends up to high 50s and even low 60 degrees latitude.
  • Continental subarctic or boreal (taiga) climates (Dfc, Dwc, Dsc):[2]:232–5 Dfc and Dwc climates occur poleward of the other group D climates, mostly in the 50s and low 60s north latitude, although it might occur as far north as 70°N.
  • Continental subarctic climates with extremely severe winters (Dfd, Dwd, Dsd):[2] Places with this climate have the temperature in their coldest month lower than −38 °C. These climates occur only in eastern Siberia. The names of some of the places with this climate — most notably Verkhoyansk (Dfd) and Oymyakon (Dwd)— have become veritable synonyms for extreme, severe winter cold.

GROUP E: Polar and alpine climates[edit]

Main articles: Polar climate and Alpine climate

These climates are characterized by average temperatures below 10 °C in all 12 months of the year:

  • Ice cap climate (EF):[2]:237 All twelve months have average temperatures below 0 °C (32 °F). This climate is dominant in Antarctica (e.g., Scott Base) and in inner Greenland (e.g., Eismitte or North Ice).
  • Occasionally, a third, lower-case letter is added to ET climates if either the summer or winter is clearly drier than the other half of the year; thus Herschel Island ('Qikiqtaruk', in Inuvialuit) off the coast of Canada's Yukon Territory, becomes ETw, with Pic du Midi de Bigorre in the French Pyrenees acquiring an ETs designation. If the precipitation is more or less evenly spread throughout the year, ETf may be used, such as for Hebron, Labrador. When the option to include this letter is exercised, the same standards that are used for Groups C and D apply, with the additional requirement that the wettest month must have an average of at least 30 mm precipitation (Group E climates can be as dry or even drier than Group B climates based on actual precipitation received, but their rate of evaporation is much lower). Seasonal precipitation letters are almost never attached to EF climates, mainly due to the difficulty in distinguishing between falling and blowing snow, as snow is the sole source of moisture in these climates.

Trewartha climate classification scheme[edit]

The Trewartha climate classification scheme (1966 and 1980 update) is a modified version of the Köppen system, and was an answer to some of the deficiencies of the 1899 Köppen system. The newer Trewartha theme attempts to redefine the middle latitudes in such a way as to be closer to vegetational zoning and genetic climate systems. This change was seen as most effective in Asia and North America, where many areas fell into a single zone (the C climate group). Under the standard Köppen system in the USA for example, western Washington and Oregon are classed into the same climate as southern California, even though the two regions have strikingly different weather and vegetation. The Köppen system also classes places in the Midwest like Iowa into the same climate zone as Louisiana or South Carolina.

Trewartha's modifications sought to reclass the middle latitudes into zones; 1) Subtropical – 8 or more months have a mean temperature of 50 F/10 C or higher. 2) Temperate – 4 to 7 months have a mean temperature of 10 C or higher. 3) Boreal (or subarctic) – 1 to 3 months have a mean temperature of 10 C or higher. This change from the older Köppen system was thought to reflect a more true or "real world" reflection of the global climate.[11]

  • Group A
This the tropical climate realm, defined the same as in Köppen's scheme (i.e., all 12 months average 18 °C or above). Climates with no more than two dry months (defined as having less than 60 mm average precipitation, same as per Köppen) are classified Ar (instead of Köppen's Af), while others are classified Aw if the dry season is at the time of low sun/short days or As if the dry season is at the time of high sun/long days. There was no specific monsoon climate identifier in the original scheme, but Am was added later, with the same parameters as Köppen's (except that at least three months, rather than one, must have less than 60 mm average precipitation).
  • Group B
BW and BS mean the same as in the Köppen scheme, with the Köppen BWn climate sometimes being designated BM (the M standing for "marine"). However, a different formula is used to quantify the aridity threshold: 10 X (T − 10) + 3P, with T equalling the mean annual temperature in degrees Celsius and P denoting the percentage of total precipitation received in the six high-sun months (April through September in the Northern Hemisphere and October through March in the Southern). If the precipitation for a given location is less than the above formula, its climate is said to be that of a desert (BW); if it is equal to or greater than the above formula but less than twice that amount, the climate is classified as steppe (BS); and if the precipitation is more than double the value of the formula the climate is not in Group B. Unlike in Köppen's scheme, no thermal subsets exist within this group in Trewartha's, unless the Universal Thermal Scale (see below) is used.
  • Group C
In the Trewartha scheme this category encompasses Subtropical climates (C) only (8 or more months above 10 °C). Cs and Cw have the same meanings as they do in Köppen's scheme, but the subtropical climate with no distinct dry season is designated Cr instead of Köppen's Cf (and for Cs the average annual precipitation must be less than 890 mm (35 in) in addition to the driest summer month having less than 30 mm precipitation and being less than one-third as wet as the wettest winter month).
  • Group D
This group represents Temperate climates (D) with (4 to 7 months above 10 °C). Temperate Oceanic maritime climates (most of Köppen's Cfb and Cwb climates, though some of these would fit into Trewartha's Cr and Cw respectively) are denoted DO in the Trewartha classification (although some places like Philadelphia near the east coasts of both North America and Asia actually qualify as DO climates in Trewartha's scheme when they fit into Cfa/Cwa rather than Cfb/Cwb in Köppen's), while Temperate Continental climates are represented as DCa (Köppen Dfa, Dwa, Dsa) and DCb (Köppen Dfb, Dwb, Dsb). For the continental climates, sometimes the third letter (a or b) is omitted and DC is simply used instead, and occasionally a precipitational seasonality letter is added to both the maritime and continental climates (r, w, or s, as applicable). The dividing point between the maritime and continental climates is −3 °C in the coldest month, however, some climatologists — particularly in the United States — now observe 0 °C in the coldest month as the equatorward limit of the continental climates in that scheme as well).
  • Group E
This represents Ice realms, defined the same as in Köppen's scheme (1 to 3 months with average temperatures of 10 °C or above; Köppen Cfc, Dfc, Dwc, Dsc, Dfd, Dwd). In the original scheme, this group was not further divided; later, the designations EO and EC were created, with EO (maritime subarctic) signifying that the coldest month averages above −10 °C, while EC (continental subarctic or "boreal") means that at least one month has an average temperature of −10 °C or below. As in Group D, a third letter can be added to indicate seasonality of precipitation. There is no separate counterpart to the Köppen Dfd/Dwd climate in Trewartha's scheme.
  • Group F
This is the polar climate group, split into FT (Köppen ET) and FI (Köppen EF).
  • Group H
Highland climates, in which altitude plays a role in determining climate classification.[2]:237–40 Specifically, this would apply if correcting the average temperature of each month to a sea-level value using the formula of adding 5.6 °C for each 1,000 meters of elevation would result in the climate fitting into a different thermal group than that into which the actual monthly temperatures place it. Sometimes G is used instead of H if the above is true and the altitude is 500 meters or higher but lower than 2,500 meters; but the G or H is placed in front of the applicable thermal letter rather than replacing it — and the second letter used reflects the corrected monthly temperatures, not the actual monthly temperatures.
  • Universal Thermal Scale
An option exists to include information on both the warmest and coldest months for every climate by adding a third and fourth letter, respectively. The letters used conform to the following scale:
i — severely hot: Mean monthly temperature ≥35 °C (95 °F) or higher
h — very hot: 28 to 34.9 °C (82.4 to 94.8 °F)
a — hot: 23 to 27.9 °C (73.4 to 82.2 °F)
b — warm: 18 to 22.9 °C (64.4 to 73.2 °F)
l — mild: 10 to 17.9 °C (50.0 to 64.2 °F)
k — cool: 0.1 to 9.9 °C (32.2 to 49.8 °F)
o — cold: −9.9 to 0 °C (14.2 to 32.0 °F)
c — very cold: −24.9 to −10 °C (−12.8 to 14.0 °F)
d — severely cold: −39.9 to −25 °C (−39.8 to −13.0 °F)
e — excessively cold: −40 °C (−40 °F) or below.
Examples of the resulting designations include Afaa for Surabaya, Indonesia, BWhl for Aswan, Egypt, Crhk for Dallas, Texas, U.S. DObk for London, EClc for Arkhangelsk, Russia, and FTkd for Barrow, Alaska, U.S..

World Map of the Köppen–Geiger climate classification for the period 1951–2000[edit]

Based on recent data sets from the Climatic Research Unit (CRU) of the University of East Anglia and the Global Precipitation Climatology Centre (GPCC) at the German Weather Service, a new digital Köppen–Geiger world map on climate classification for the second half of the 20th century has been compiled.[4]

Other maps[edit]

All maps use the ≥0 °C definition for temperate climates and the 18 °C annual mean temperature threshold to distinguish between hot and cold dry climates.[1]

See also[edit]

  • Holdridge life zones climate classification by three dimensions: precipitation, humidity, and potential evapotranspiration ratio

References[edit]

  1. ^ a b c d Peel, M. C. and Finlayson, B. L. and McMahon, T. A. (2007). "Updated world map of the Köppen–Geiger climate classification". Hydrol. Earth Syst. Sci. 11: 1633–1644. doi:10.5194/hess-11-1633-2007. ISSN 1027-5606.  (direct: Final Revised Paper)
  2. ^ a b c d e f g h i j k l m n o p q McKnight, Tom L; Hess, Darrel (2000). "Climate Zones and Types". Physical Geography: A Landscape Appreciation. Upper Saddle River, NJ: Prentice Hall. ISBN 0-13-020263-0. 
  3. ^ Linacre, Edward; Bart Geerts (1997). Climates and Weather Explained. London: Routledge. p. 379. ISBN 0-415-12519-7. 
  4. ^ a b c Kottek, M., J. Grieser, C. Beck, B. Rudolf, and F. Rubel (2006). "World Map of the Köppen–Geiger climate classification updated". Meteorol. Z. 15 (3): 259–263. Bibcode:2006MetZe..15..259K. doi:10.1127/0941-2948/2006/0130. Retrieved 2013-06-01. 
  5. ^ "CHAPTER 7: Introduction to the Atmosphere". physicalgeography.net. Retrieved 2008-07-15. 
  6. ^ Engineering Weather Data CD-ROM Station List, National Climate Data Center. Retrieved 2013-06-01
  7. ^ "Statistics for AUS WA.Perth.Airport RMY". EnergyPlus. U.S. Department of Energy. Retrieved 2009-01-19. 
  8. ^ "Climate classification of São Paulo state". Instituto Agronômico de Campinas. 
  9. ^ "Climatological Information for Juliaca, Peru". Hong Kong Observatory. 
  10. ^ "Iceland Met office: Monthly Averages for Reykjavík". Iceland Met Office. 2012.  Retrieved on January 4, 2013.
  11. ^ Akin, Wallace E. (1991). Global Patterns: Climate, Vegetation, and Soils. University of Oklahoma Press. p. 52. ISBN 0-8061-2309-5. 

External links[edit]

Climate records[edit]