Trewartha climate classification world map

The Trewartha climate classification (TCC) or the Köppen–Trewartha climate classification (KTC) is a climate classification system first published by American geographer Glenn Thomas Trewartha in 1966. It is a modified version of the Köppen–Geiger system, created to answer some of its deficiencies. The Trewartha system attempts to redefine the middle latitudes to be closer to

vegetation Vegetation is an assemblage of plant species and the ground cover they provide. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic charact ...

zoning and genetic

climate Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologica ...

systems. It was considered a more true or "real world" reflection of the global climate. The changes were seen as most effective on the large landmasses in

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an ...

and North America, where many areas fall into a single group (''C'') in the Köppen–Geiger system. For example, under the standard Köppen system, Washington and

Oregon Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idah ...

are classed into the same climate zone (''Csb'') as parts of Southern California, even though the two regions have strikingly different weather and vegetation. Another example was classifying cities like

London London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...

Boston Boston (), officially the City of Boston, is the capital city, state capital and List of municipalities in Massachusetts, most populous city of the Commonwealth (U.S. state), Commonwealth of Massachusetts, as well as the cultural and financ ...

in the same climate group (''C'') as

Brisbane Brisbane ( ) is the capital and most populous city of the states and territories of Australia, Australian state of Queensland, and the list of cities in Australia by population, third-most populous city in Australia and Oceania, with a populati ...

New Orleans New Orleans ( , ,New Orleans

subtropical)—8 or more months have a mean temperature of or higher; ''D''

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...

—4 to 7 months have a mean temperature of 10 °C or higher; and ''E''

boreal climate The subarctic climate (also called subpolar climate, or boreal climate) is a climate with long, cold (often very cold) winters, and short, warm to cool summers. It is found on large landmasses, often away from the moderating effects of an ocean, g ...

—1 to 3 months have a mean temperature of 10 °C or higher. Otherwise, the tropical climates and polar climates remained the same as the original Köppen climate classification. The "highland" climate is ambiguously defined. Newer users of KTC generally omit this option.

Group A: Tropical climates

This is the tropical climate realm, defined the same as in Köppen's scheme (i.e., all 12 months average , or above). The "A" climates are the realm of the winterless frost-free zone. Climates with no more than two dry months (defined as having less than , average precipitation, same as per Köppen) are classified ''Ar'', 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: Dry (arid and semi-arid) climates

''BW'' and ''BS'' mean the same as in the Köppen scheme. However, a different formula is used to quantify the aridity threshold: 10(''T'' − 10) + 3''P'', with ''T'' equaling 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: Subtropical climates

In the Trewartha scheme the "C" climate group encompasses Subtropical climates that have 8 or more months with a mean temperature of or higher. There are only two types within the "C" or subtropical climate group, ''Cs'' which is a dry -summer or Mediterranean climate, and a ''Cf'' or humid Subtropical climate. ''Cw'' types occur within the ''Cf'' group and mean subtropical Monsoon climates (like much of east Asia).

Group D: Temperate and continental climates

In the Trewartha scheme the "D" climate group encompasses Temperate climates that have 4 to 7 months with a mean temperature of or higher. "D" climate groups have two types – an Oceanic type (Do), where the coldest month has a mean temperature or higher, and a Continental type (Dc), where the coldest monthly mean temperature reaches below 0 °C in some interior landmasses like North America and Asia. For the continental climates (Dc), sometimes the third letter (''a'' or ''b'') is used to denote a hot or cold summer. "Dca" is where the warmest month has a mean temperature of or higher, and "Dcb" is used for cool summer temperate climates, where the warmest month has a mean temperature below 22.2 °C. Most of Europe north of 44th parallel north exhibits ''Do'' or ''Dc'' climate types.

Group E: Boreal climates

This represents subarctic and subpolar oceanic climate realms, defined the same as in Köppen's scheme, where 1 to 3 months have an average temperature of or above. In this climate zone there is only a short period (normally 50 to 90 days) that is frost free. 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 , 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'', and ''Dsd'' climate types in Trewartha's scheme, but a letter can optionally be added to the end of the symbol to indicate the temperature of the coldest month ( see below).

Group F: Polar climates

This is the polar climate group, where all months must have a monthly mean air temperature of below . Polar climates have two subtypes ''Ft'' ( tundra) and ''Fi'' ( ice cap): In the "Ft" climate type, at least one month has an average temperature above (but not above ), so that there is a brief time when the surface might be free of snow or ice and a scrub or Tundra vegetation cover is possible. In the "Fi" climate type, all months have an average temperature below , this is the region of the vast deserts of perpetually frozen Ocean in the North Pole, and the permanent ice plateaus of Antarctica and Greenland.

Group H: Highland climates

Highland climates are those in which

altitude Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...

plays a role in determining climate classification.McKnight, 237–40 Specifically, this would apply if correcting the average temperature of each month to a sea-level value using the formula of adding for each 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 between , but the ''G'' or ''H'' is placed in front of the applicable thermal letter rather than replacing it. The second letter used reflects the ''corrected'' monthly temperatures, not the actual monthly temperatures. G stands for glacier for instances.

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 ≥ or higher *''h'' — very hot: *''a'' — hot: *''b'' — warm: *''l'' — mild: *''k'' — cool: *''o'' — cold: *''c'' — very cold: *''d'' — severely cold: *''e'' — excessively cold: or below.

Examples

;A: * ''Awha'' for Surabaya,

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

* ''Ambb'' for Mérida, Mérida,

Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in ...

* ''Arhb'' for

Miami Miami ( ), officially the City of Miami, known as "the 305", "The Magic City", and "Gateway to the Americas", is a coastal metropolis and the county seat of Miami-Dade County in South Florida, United States. With a population of 442,241 at th ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

;B: * ''BWil'' for

Riyadh Riyadh (, ar, الرياض, 'ar-Riyāḍ, Literal translation, lit.: 'The Gardens' Najdi Arabic, Najdi pronunciation: ), formerly known as Hajr al-Yamamah, is the capital and largest city of Saudi Arabia. It is also the capital of the Riyad ...

Saudi Arabia Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in Western Asia. It covers the bulk of the Arabian Peninsula, and has a land area of about , making it the List of Asian countries by area, fifth-largest country in Asia ...

* ''BWhl'' for

Aswan Aswan (, also ; ar, أسوان, ʾAswān ; cop, Ⲥⲟⲩⲁⲛ ) is a city in Southern Egypt, and is the capital of the Aswan Governorate. Aswan is a busy market and tourist centre located just north of the Aswan Dam on the east bank of ...

, Egypt * ''BSbc'' for

Ulaanbaatar Ulaanbaatar (; mn, Улаанбаатар, , "Red Hero"), previously anglicized as Ulan Bator, is the capital and most populous city of Mongolia. It is the coldest capital city in the world, on average. The municipality is located in north c ...

Mongolia Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 millio ...

* ''BSaa'' for Patos,

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

* ''BWho'' for Turpan, China * ''BWih'' for Dallol, Ethiopia * ''BSlk'' for Río Gallegos, Argentina ;C: * ''Cfak'' for

Tokyo Tokyo (; ja, 東京, , ), officially the Tokyo Metropolis ( ja, 東京都, label=none, ), is the capital and List of cities in Japan, largest city of Japan. Formerly known as Edo, its metropolitan area () is the most populous in the world, ...

* ''Csll'' for

San Francisco San Francisco (; Spanish language, Spanish for "Francis of Assisi, Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the List of Ca ...

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the ...

* ''Cfhk'' for

Dallas Dallas () is the List of municipalities in Texas, third largest city in Texas and the largest city in the Dallas–Fort Worth metroplex, the List of metropolitan statistical areas, fourth-largest metropolitan area in the United States at 7.5 ...

, U.S. * ''Cwhl'' for Hanoi,

Vietnam Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making it ...

* ''Cfbl'' for

Melbourne Melbourne ( ; Boonwurrung/ Woiwurrung: ''Narrm'' or ''Naarm'') is the capital and most populous city of the Australian state of Victoria, and the second-most populous city in both Australia and Oceania. Its name generally refers to a me ...

, Australia * ''Cfbk'' for Vigo,

Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = '' Plus ultra'' ( Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , ...

* ''Cflk'' for Nelson, New Zealand * ''Cfal'' for

Buenos Aires Buenos Aires ( or ; ), officially the Autonomous City of Buenos Aires ( es, link=no, Ciudad Autónoma de Buenos Aires), is the Capital city, capital and primate city of Argentina. The city is located on the western shore of the Río de la Plata ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, t ...

* ''Csal'' for Faro,

Portugal Portugal, officially the Portuguese Republic, In recognized minority languages of Portugal: :* mwl, República Pertuesa is a country located on the Iberian Peninsula, in Southwestern Europe, and whose territory also includes the Macaronesian ...

;D: * ''Dobk'' for

, U.K. * ''Dcao'' for

Seoul Seoul (; ; ), officially known as the Seoul Special City, is the Capital city, capital and largest metropolis of South Korea.Before 1972, Seoul was the ''de jure'' capital of the North Korea, Democratic People's Republic of Korea (North Korea ...

South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia, constituting the southern part of the Korea, Korean Peninsula and sharing a Korean Demilitarized Zone, land border with North Korea. Its western border is formed ...

* ''Dcbo'' for Klagenfurt,

Austria Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...

* ''Doak'' for

New York City New York, often called New York City or NYC, is the most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the most densely populated major city in the U ...

* ''Dclo'' for Cortina d'Ampezzo,

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical ...

;E: * ''Ecle'' for Oymyakon, Russia * ''Ecbd'' for Yakutsk, Russia * ''Eolo'' for Tromsø,

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

* ''Ecld'' for Norilsk,

Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eigh ...

* ''Eclc'' for Karasjok,

* ''Eolk'' for Punta Arenas,

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...

;F: * ''Ftkd'' for

Utqiagvik Utqiagvik ( ik, Utqiaġvik; , , formerly known as Barrow ()) is the borough seat and largest city of the North Slope Borough in the U.S. state of Alaska. Located north of the Arctic Circle, it is one of the northernmost cities and towns in th ...

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S ...

, U.S. * ''Ftkk'' for

Ushuaia Ushuaia ( , ) is the capital of Tierra del Fuego, Antártida e Islas del Atlántico Sur Province, Argentina. With a population of nearly 75,000 and a location below the 54th parallel south latitude, Ushuaia claims the title of world's souther ...

* ''Fide'' for Vostok Station in Antarctica.

References

{{reflist

External links

Use of the Köppen–Trewartha climate classification for the People’s Republic of China
Climate and weather classification systems