Köppen climate classification

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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, notably in 1918 and 1936. Later, German climatologist Rudolf Geiger collaborated with Köppen on changes to the classification system, which is thus sometimes called the Köppen–Geiger climate classification system.

In the 1960s, the Trewartha climate classification system was considered a modified Köppen system that addressed some of the deficiencies (mostly that the middle latitude climate zone was too broad) of the Köppen 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.[1]:200–1

Scheme

Köppen climate classification scheme symbols description table.[2]
1st 2nd 3rd Description
A Tropical
f -Rainforest
m -Monsoon
w -Savanna
B Arid
W -Desert
S -Steppe
h --Hot
k --Cold
C Temperate
s -Dry Summer
w -Dry Winter
f -Without dry season
a --Hot Summer
b --Warm Summer
c --Cold Summer
D Cold (Continental)
s -Dry Summer
w -Dry Winter
f -Without dry season
a --Hot Summer
b --Warm Summer
c --Cold Summer
d --Very cold Winter
E Polar
T -Tundra
F -Frost (Ice cap)

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

Group A: Tropical/megathermal climates:

Group B: Dry (arid and semiarid) climates:

Group C: Temperate/mesothermal climates:

Group D: Continental/microthermal climates

Group E: Polar and alpine climates:

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. They are subdivided as follows:

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).

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, São Paulo, 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).

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.

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 Colombia–Panamá 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, northwestern Dominican Republic (Monte Cristi, Villa Vásquez, Luperón), 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 rain shadow effects during the 'high-sun' part of the year.

Group B: Dry (arid and semiarid) climates

These climates are characterized by actual precipitation less than a threshold value set equal to the potential evapotranspiration.[1]: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.

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

These climates have an average monthly temperature above 10 °C (50 °F) in their warmest months (April to September in northern hemisphere), and an average monthly temperature above −3 °C (27 °F) in their coldest months. Some climatologists prefer to observe 0 °C rather than −3 °C in the coldest month as the boundary between this group and the colder group D (continental).

In Asia, this includes areas from South Korea, to east- China from Beijing southward, to northern Japan. In Europe this includes areas from coastal Norway south to southern France, In the US, areas from near 40 latitude in the central and eastern states (a rough line from the NYC/NJ/CT area westward to the lower Ohio Valley, lower Midwest and southern Plains), are located in the Köppen C group.

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).[2]

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.

C climates (or mesothermal) are broken down into two types: 1) A dry-summer or Mediterranean climate and a temperate climate:

Under the Köppen–Geiger classification, dry-summer (Csb) extends to additional areas not typically associated with a typical Mediterranean climate, such as much of the Pacific Northwest, much of southern Chile, parts of west-central Argentina,areas of northern Spain and Portugal as well as areas in the Atlantic coast of Morocco.[2] Many of these areas would be oceanic (Cfb), except dry-summer patterns meet Köppen's Cs minimum thresholds. Additional highland areas in the subtropics also meet Cs requirements, although they, too, are not normally associated with Mediterranean climates.

New York City is on the borderline between this climate and that of the hot-summer humid continental Dfa climate, the line passing through the city.

Group D: Continental/microthermal climates

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.

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 and (for c and d) winter cold — 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, c indicates warmest month averaging below 22 °C and with three or fewer months with mean temperatures above 10 °C, but coldest month averaging above –38 °C, and d indicates warmest month averaging below 22 °C, three or fewer months averaging above 10 °C, and coldest month averaging below –38 °C.

Scheme

Group E: Polar and alpine climates

Main articles: Polar climate and Alpine climate

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

Ecological significance

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 geographic distribution of long term climate and associated ecosystem conditions.[13]

Over the recent years, there has been an increasing interest in using the classification to identify changes in climate and potential changes in vegetation over time.[14] 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.[15]

In 2015, a pair of Chinese scholars published analysis of climate classifications between 1950 and 2010, finding that more than 5% of all land area worldwide had moved from wetter and colder classifications to drier and hotter classifications.[16]

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

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.[12]

Trewartha climate classification scheme

The Trewartha climate classification is a climate classification system published by American geographer Glenn Thomas Trewartha in 1966, and updated in 1980. It is a modified version of the 1899 Köppen system, created to answer some of the deficiencies of the Köppen system. The Trewartha system attempts to redefine the middle latitudes to be closer to vegetation zoning and genetic climate systems. It was considered a more true or "real world" reflection of the global climate.

For example, under the standard Köppen system, western Washington and Oregon are classed into the same climate zone as southern California, even though the two regions have strikingly different weather and vegetation. Under the old Köppen system cool oceanic climates like that of London were classed in the same zone as hot subtropical cities like Savannah, GA or Brisbane, Australia. In the US, locations in the Midwest like Ohio and Iowa which have long, severe winter climates where plants are completely dormant, were classed into the same climate zone as Louisiana or northern Florida which have mild winters and a green winter landscape.

Other maps

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.[2]

See also

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 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.
  2. 1 2 3 4
  3. ↑ Linacre, Edward; Bart Geerts (1997). Climates and Weather Explained. London: Routledge. p. 379. ISBN 0-415-12519-7.
  4. ↑ "CHAPTER 7: Introduction to the Atmosphere". physicalgeography.net. Retrieved 2008-07-15.
  5. ↑ "Climatological Information for Athens Hellinikon, Greece", HNMS climatological table, web: .
  6. ↑ "Mediterranean Climate". California Rangelands. California Ragelands. Retrieved 2015-01-26.
  7. ↑ "Clima:Skagen". Climate.Date. Climate Date.org. Retrieved 2015-01-26.
  8. ↑ "Clima:Haus". Climate.Date. Climate Date.org. Retrieved 2015-01-26.
  9. ↑ "Climatological Information for Juliaca, Peru". Hong Kong Observatory.
  10. ↑
  11. ↑ "Iceland Met office: Monthly Averages for Reykjavík". Iceland Met Office. 2012. Retrieved on January 4, 2013.
  12. 1 2 Kottek, M., J. Grieser, C. Beck, B. Rudolf, and F. Rubel (2006). "World Map of the Köppen–Geiger climate classification updated" (PDF). Meteorol. Z. 15 (3): 259–263. Bibcode:2006MetZe..15..259K. doi:10.1127/0941-2948/2006/0130. Retrieved 2013-06-01. (direct- Kottek 2006 Paper)
  13. ↑ Chen, D. and H. W. Chen (2013). "Using the Köppen classification to quantify climate variation and change: An example for 1901–2010". Environmental Development 6: 69–79. doi:10.1016/j.envdev.2013.03.007. (direct: Final Revised Paper)
  14. ↑ http://hanschen.org/koppen/
  15. ↑ Critchfield, Howard J (1983). General Climatology (4th ed.). New Delhi: Prentice Hall. pp. 154–161. ISBN 978-81-203-0476-5.
  16. ↑ http://www.nature.com/articles/srep13487

External links

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Climate records

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