Oceanic_climate

World map showing the oceanic climate zones.

An oceanic climate (also called marine west coast climate, maritime climate, Cascadian climate and British climate for Cfb and subtropical highland for Cwb) is the climate typically found along the west coasts at the middle latitudes of some of the world's continents, and in southeastern Australia. Climates near the ocean have moderately cool summers and comparatively warm winters, they are generally characterized by a narrower annual range of temperatures than are encountered in other places at a comparable latitude, and generally do not have the extremely dry summers of Mediterranean climates.^[1]

Similar climates, at least in thermal range, are also found in tropical highlands even at considerable distance from any coastline. Generally, they fall into Köppen climate classification Cfb or Cwb. The narrow range of temperatures results not from proximity to a coastline but instead to the slight thermal range of temperatures between seasons characteristic of tropical lowlands; altitudes are high enough that somes places have at least one month cooler than 18 °C and do not qualify for grouping in the true tropical climates. Unlike the norm in true oceanic climates, these moist highland tropical climates may have a marked winter drought. Agricultural potential in both oceanic climates and moist tropical highland climates are practically identical. These climates are most dominant in Europe, where it spreads much farther inland than in other continents.

Precipitation

Precipitation is both adequate and reliable at all times of the year in oceanic climates, except in certain tropical highland areas, which would have tropical savanna or steppe climates (with a dry season in winter) if not for the high altitude making them cooler (Koppen Cwb). Under some variations of the Koeppen classification system, parts of the Pacific Northwest and south-central Chile are sometimes considered as having a Mediterranean climate (Koppen "Csb") due to a drying trend in the summer.

Temperature

Overall temperature characteristics vary among oceanic climates; those at the lowest latitudes are nearly subtropical from a thermal standpoint, but more commonly a mesothermal regime prevails, with cool, but not cold, winters and warm, but not hot, summers. Summers are also cooler (often much cooler) than in areas with a humid subtropical climate. Average temperature of warmest month must be less than 22 °C (72 °F) and that of the coldest month warmer than -3 °C (27 °F) although American scientists prefer 0 °C in the coldest month. Poleward of the latter is a zone of subpolar oceanic climate (Köppen Cfc), with long but relatively mild winters (coldest month warmer than -3 or 0) and cool summers and a short summer season (average temperature at least 10 °C or 50 °F) of less than four months; examples of this climate include parts of coastal Iceland in the Northern Hemisphere and extreme southern Chile and Argentina in the Southern Hemisphere (the fact that this form of climate exists in both hemispheres rules out the use of such terms as subarctic or boreal to denote it; even though these terms are used to refer to climates characterized by short summers, they are also synonyms for "northern" and therefore inappropriate).

Additional information

The British Isles experiences a typically maritime climate, with prevailing south-westerly winds from the Atlantic Ocean. The annual average temperature range in the British Isles is only about 14 °C (57 °F).^[2] Although the west coast of Alaska experiences a maritime climate, the absence of an equally significant warm Pacific current in the upper-mid latitudes means that these regions are generally colder in winter, with more precipitation falling as snow.

All mid-latitude oceanic climates are classified as humid. Some rainshadow climates with thermal régimes similar to those of oceanic climates but steppe-like (BSk) or even desert-like (BWk) scarcity of precipitation include lowland valleys of Washington and Oregon to the east of the Cascade Range, Patagonia in southern Argentina, and the Atacama Desert in northern Chile. Another example are coastal areas in southeast Western Australia.

Under Koeppen-Geiger, many areas generally considered to have Oceanic climates are classified as cool summer, dry-summer subtropical (Csb). These areas are not usually associated with a typical Mediterranean climate, and include much of the Pacific Northwest, southern Chile, parts of west-central Argentina, and northern Spain and Portugal.^[3] Many of these areas would be classified Oceanic (Cfb), except dry-summer patterns meet Koeppen's Cs thresholds, and cities such as Puerto Montt, Chile; Seattle, Washington; Portland, Oregon; and Victoria, British Columbia can be classified as Csb.

Regions/Cities with Oceanic Climates

Africa

The only noteworthy area of Maritime Climate at or near sea-level is in South Africa from Mossel Bay on the Western Cape coast to Plettenberg Bay, with additional pockets of this climate inland of the Eastern Cape and KwaZulu-Natal coast. It is usually hot all year.

Asia

The only significant area where this climate is found is in small pockets along or near the Tsugaru Strait in Japan.

Europe

Oceanic climate is prevalent in a good portion of Europe, particularly Western and Northern Europe. Its exists in northern and western France, the Netherlands, Belgium, western and northwestern Germany, western Switzerland (lowland areas), northern Spain (so-called "Green Spain": Galicia, Asturias, Cantabria...), northern extreme of Portugal, Azores, southwest Norway, parts of Denmark, Ireland, Sweden, Great Britain, and northern Turkey,

Oceania

Maritime Climates are prevalent in the more southerly locations of this region. A mild Maritime climate is in existence in New Zealand, the island of Tasmania, Australia, southern parts of Victoria and New South Wales, Australia. It can also be found along the western areas of the south coast of Western Australia.

South America

Oceanic Climates are found in isolated pockets in South America. It exists in Central Argentina, Southern Chile and parts of Brazil and Colombia.

North America

Oceanic Climate primarily exists along the coast of the Pacific Northwest in North America. It exists in the western parts of Oregon; Washington; the mildest coastal areas of the Alaskan panhandle in the (U.S.A.); the western portions of British Columbia (Canada). It also exists in extreme Northwest California (U.S.A.).

Notable Cities with Oceanic Climates

• • (Cfb/Cfa) Oceanic climate/Humid subtropical climate borderline.
  • (Cfb/Dfb) Oceanic climate/Humid continental climate borderline.

Subtropical Highland Climate

The Subtropical Highland variety of the oceanic climate exists in elevated portions of the world that are either within the tropics or subtropics though it is typically found in mountainous locations in some tropical countries. Despite the latitude, due to the higher altitudes of these regions, it tends to share characteristics with oceanic climates, though it also tends to experience noticeably drier weather during the “low-sun” season. In locations outside the tropics, Subtropical Highland climates tend to be essentially identical to an oceanic climate, complete with mild summers, noticeably cooler winters and in some instances, some snowfall. In the tropics, a Subtropical Highland climate tends to feature spring-like weather year-round. Temperatures here remain relatively constant throughout the year, with monthly averages for all 12 months below 22°C (72°F) but above -3°C (26.6°F) (or 0°C (32°F) using American standards). Also, at least one month's average temperature is below 18°C (64.4°F). Without the elevation, many of these regions would likely feature either tropical or humid subtropical climates. These regions usually carry a Cwb or Cfb designation.^{[citation needed]}. It exists in parts of east, south and south-eastern Africa, some mountainous areas across southern Europe, sections of mountainous Latin America, higher elevations of the southern Appalachians, and parts of the Himalayas.

Notable Cities with Subtropical Highland Climates

Subpolar Oceanic Climate

Map showing annual isotherms and precipitation isolines in Magallanes Region, Chile, which has a Subpolar Oceanic climate.

Areas with Subpolar Oceanic climates feature an oceanic climate but are usually located closer to Polar regions. As a result of its location, these regions tend to be somewhat cooler than other oceanic climates. Still, Subpolar Oceanic climates are less prone to temperature extremes than Subarctic climates or even Humid continental climates, featuring milder winters than these climates. Subpolar Oceanic climates feature only one to three months of average monthly temperatures that are at least 10°C (50°F). Like oceanic climates, none of its average monthly temperatures fall below -3°C (26.6°F). It typically carries a Cfc designation. This variant of an oceanic climate is found in parts of coastal Iceland, Faroe Islands, northwestern coastal areas of Norway reaching to 70°N on some islands, southern islands of Alaska and parts of the Alaskan Panhandle, the far south of Chile and Argentina and Mountainous areas of Europe, including the Scottish Highlands and uplands near the coast of southwestern Norway.

Notable cities with Subpolar Oceanic Climates

• Reykjavik, Iceland
• Vestmannaeyjar, Iceland
• Harstad, Norway
• Bodø, Norway
• Thorshavn, Faroe Islands
• Unalaska (AK), USA (formerly known as Dutch Harbor)
• Kodiak (AK), USA
• Ushuaia, Argentina (Cfc/Et)
• Puerto Williams, Chile
• Stanley, Falkland Islands

Marine West Coast Climate

The Marine West Coast climate is an oceanic climate that features a distinct Mediterranean-like drying trend during the summer months. Koeppen's minimum precipitation threshold limit of 30mm results in a Cfb designation for much of this zone. The climate is found on the west coast of most continents, particularly in the Pacific Northwest of North America, along sections of coastal Chile in South America and in sections of northern, coastal Spain and coastal Portugal in Europe.

For most of the year, the Marine West Coast climate is like all oceanic climates, generally experiencing damp, cloudy and cool conditions and, on occasion, outflows of colder arctic air from the interior of the continent during some winters. However, unlike most oceanic climates, summers in areas with the Marine West Coast climate are dry and sunny. In some instances, this drying trend is so pronounced that it technically can be classified as a Mediterranean climate under the Koppen-Geiger climate classification. However, a number of scientists and others usually classify these areas as a variation of an oceanic climate, due to the decidedly oceanic characteristics that these regions exhibit for the bulk of the year.

Notable Cities with a Marine West Coast Climate

• Seattle, USA, (Csb under Koeppen-Geiger)
• Portland, USA, (Csb under Koeppen-Geiger)
• Eugene, USA, (Csb under Koeppen-Gieger)
• Vancouver, Canada
• Victoria, Canada, (Csb under Koeppen-Geiger)
• Valdivia, Chile
• Puerto Montt, Chile, (Csb under Koeppen-Geiger)
• Vigo, Spain, (Csb under Koeppen-Geiger)
• A Coruña, Spain, (Csb under Koeppen-Geiger)
• Porto, Portugal, (Csb under Koeppen-Geiger)
• Viana do Castelo, Portugal (Csb under Koeppen-Geiger)

Isotherm boundary to Dfb climate

The 0 °C (32 °F) isotherm (freeze line) or the -3 °C (26.6 °F) isotherms (persistent snow line) are the possible lines dividing the oceanic and the warm summer humid continental (Dfb) climates, in between which are the following regions:

• Eastern Germany
• Luxembourg
• Liechtenstein
• Western and Southern Poland
• Eastern Switzerland and parts of Austria
• Western Alps between 700 and 1000 meters.
• Central and Eastern Alps between 500 and 800 meters.
• Southern Sweden
• Fjord areas inland from the coast of southwest Norway and parts of the southeast coast of Norway
• Much of Denmark
• Southern coastal areas of the Alaskan Panhandle
• Most of the Czech Republic
• Parts of western Slovakia
• West-Northwest Romania
• Most of Hungary
• Most of Slovenia
• Parts of Bosnia-Herzegovina
• Mountainous areas across southern Europe
• Himalayas
• Some southern coastal areas of New England
• Parts of the southern Appalachians at the higher elevations

Charts of Selected Cities with Oceanic Climates

Northern hemisphere

Southern hemisphere

Charts of Selected Cities with Subtropical Highland Climates

Charts of Selected Cities with Subpolar Oceanic Climates

Charts of Selected Cities with Marine West Coast Climates

See also

• Temperate climate
• Humid subtropical climate
• Mediterranean climate
• Subtropical climate
• Continental climate
• Polar climate

References

External links

• University of Wisconsin–Stevens Point: Marine (Humid) West Coast Climate
• EPIC Data Collection On-line ocean observational data collection
• NOAA In-situ Ocean Data Viewer Plot and download ocean observations
• http://www.ace.mmu.ac.uk/eae/Climate/Older/Maritime_Climate.html