Oceanic climate

World map showing oceanic climate zones, as defined by the Köppen climate types "Cfb", "Cfc", "Cwb" and "Cwc"

An oceanic climate (also known as marine, west coast and maritime) is the climate typical of west coasts in higher middle latitudes of continents, and generally features cool summers and cool (but not cold) winters, with a relatively narrow annual temperature range and few extremes of temperature.

It typically lacks a dry season, as precipitation is more evenly dispersed throughout the year. It is the predominant climate type across much of North Western Europe, the Pacific Northwest region of the USA and Canada, portions of southwestern South America and small areas of southeast Australia, and New Zealand as well as isolated locations elsewhere.

Properties

Oceanic climates generally have cool summers and cool (but not cold) winters. They are 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 or the hot summers of warm temperate climates. Oceanic climates are most dominant in Europe, where they spread much farther inland than in other continents.

Oceanic climates can have much storm activity as they are located in the belt of the stormy westerlies. Many oceanic climates have frequent cloudy or overcast conditions due to the near constant storms and lows tracking over or near them. The annual range of temperatures is smaller than typical climates at these latitudes due to the constant stable marine air masses that pass through oceanic climates, which lack both very warm and very cool fronts.

Precipitation

Seattle, a city with an oceanic climate

Precipitation is both adequate and reliable throughout the year in oceanic climates. Extended months of rain and cloudy conditions are common in oceanic climates. Seattle is an example of this. Between October and May, Seattle experiences high rainfall and is mostly or partly cloudy six out of every seven days.

In most areas with an oceanic climate, for the majority of the year precipitation comes in the form of rain. However, during the winter, some of areas with this climate see some snowfall annually. Outside of Australia and parts of New Zealand, most areas with an oceanic climate experience at least one snowstorm per year. In the poleward locations of the oceanic climate zone ("subpolar oceanic climates," described in greater detail below), snowfall is more frequent and commonplace.

Temperature

Overall temperature characteristics of oceanic climates feature cool temperatures and infrequent extremes of temperature. In the Köppen climate classification, Oceanic climates have a mean temperature of 0 °C (32 °F) or higher in the coldest month, compared to continental climates where the coldest month has a mean temperature of below 0 °C (32 °F). Summers are cool, with the warmest month having a mean temperature below 22 °C (72 °F). Poleward of the latter is a zone of the aforementioned subpolar oceanic climate (Köppen Cfc), with long but relatively mild winters and cool and short summers (average temperatures of at least 10 °C (50 °F) for one to three months). Examples of this climate include parts of coastal Iceland in the Northern Hemisphere and extreme southern Chile and Argentina in the Southern Hemisphere. Examples: Ushuaia and Punta Arenas.

Causation

Oceanic climates are not necessarily always found in coastal locations on the aforementioned parallels...however in most cases Oceanic climates parallel higher middle latitude oceans. The polar jet stream which moves in a west to east direction across the middle latitudes, advancing low pressure systems, storms, and fronts. In coastal areas of the higher middle latitudes (45 - 60 latitude), the prevailing onshore flow create the basic structure of most Oceanic climates. Oceanic climates are a product and reflection of the ocean adjacent to them. In the fall, winter, and early spring, when the Polar Jet is most active, the frequent passing of marine weather systems creates the frequent fogs, cloudy skies, and light drizzle often associated with oceanic climates. In summer, high pressure often pushes the prevailing westerlies north of many oceanic climates, often creating a drier summer climate (for example in the Pacific Northwest of the USA and Canada).

The North Atlantic Gulf Stream, a tropical oceanic current that passes north of the Caribbean and up the East Coast of the USA to North Carolina, then heads east-northeast to the Azores, is thought to greatly modify the climate of Northwest Europe. As a result of the Gulf Stream, West coast areas located in high latitudes like Ireland, the UK, and Norway, have much milder winters (for their latitude) than they would otherwise have. The lowland attributes of western Europe also helps driving marine air masses into continental areas, rendering cities such as Prague and Vienna to have marine climates in spite of being located well inland from the ocean.

Locations

London
Climate chart (explanation)
J F M A M J J A S O N D     55     8 2     41     8 2     42     11 4     44     14 6     49     18 9     45     21 12     45     24 14     50     23 14     49     20 11     69     16 8     59     10 5     55     8 3 Average max. and min. temperatures in °C Precipitation totals in mm Source: Met Office
Imperial conversion J F M A M J J A S O N D     2.2     47 36     1.6     47 36     1.6     52 39     1.7     58 42     1.9     64 48     1.8     70 53     1.8     74 57     1.9     74 57     1.9     68 53     2.7     60 47     2.3     50 41     2.2     47 37 Average max. and min. temperatures in °F Precipitation totals in inches

Europe

Oceanic climates in Europe occur mostly in Northwest Europe, from Ireland and Great Britain eastward to central Europe. Most of France (away from the Mediterranean), Germany, Norway, and southern portions of Sweden, also have oceanic climates. Examples of oceanic climates are found in London, Dublin, Berlin, Copenhagen, Paris, and Stockholm. With decreasing distance to the Mediterranean Sea, the oceanic climate of Northwest Europe gradually changes to the subtropical dry-summer (or Mediterranean climate) of southern Europe (Spain, southern France, Italy, Greece...etc.).

North America

The oceanic climate exists in an arc spreading across the north-western coast of North America from the Alaskan panhandle to northern California, in general the coastal areas of the Pacific Northwest. It includes the western parts of Washington and Oregon, the Alaskan panhandle, western portions of British Columbia, and north-western California. A significant portion of oceanic climate exhibited in North America features a drying trend in the summer, thus falling under the dry-summer subcategory explained below.

South America

The oceanic climate is found in isolated pockets in South America. It exists in southeast-central and southwest Colombia, Argentina and southern Chile.

Australia & New Zealand

The oceanic climate is prevalent in South Island, New Zealand. In Australia, the island of Tasmania, southeastern New South Wales (starting from the Illawarra region) and the southern parts of Victoria, also exhibit an Oceanic climate.

Varieties

Subpolar variety (Cfc)

Reykjavík
Climate chart (explanation)
J F M A M J J A S O N D     76     2 −3     72     3 −2     82     3 −2     58     6 0     44     9 4     50     12 7     52     13 8     62     13 8     67     10 5     86     7 2     73     3 −1     79     2 −3 Average max. and min. temperatures in °C Precipitation totals in mm Source: WMO
Imperial conversion J F M A M J J A S O N D     3     35 27     2.8     37 28     3.2     38 28     2.3     42 33     1.7     49 38     2     53 44     2     56 47     2.4     55 46     2.6     50 41     3.4     44 36     2.9     38 30     3.1     36 27 Average max. and min. temperatures in °F Precipitation totals in inches

Areas with subpolar oceanic climates feature an oceanic climate but are usually located closer to polar regions. As a result of their location, these regions tend to be on the cool end of oceanic climates. Snowfall tends to be more common here than in other oceanic climates. Subpolar oceanic climates are less prone to temperature extremes than subarctic climates or 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). As with oceanic climates, none of its average monthly temperatures fall below -3.0 °C (26.6 °F). Typically, these areas in the warmest month experience daytime maximum temperatures below 17 °C (68 °F), while the coldest month features highs near or slightly above freezing and lows just below freezing. It typically carries a Cfc designation. This variant of an oceanic climate is found in parts of coastal Iceland, the Faroe Islands, small sections of the Scottish Highlands, the Scottish archipelago of Shetland, northwestern coastal areas of Norway such as Lofoten and reaching to 70°N on some islands, uplands near the coast of southwestern Norway, southern islands of Alaska and northern parts of the Alaskan Panhandle, the far south of Chile and Argentina, and a few highland areas of Tasmania, and the Australian and Southern Alps. This type of climate is even found in the very remote parts of the Papuan Highlands in Indonesia. The classification used for this regime is Cfc. In the most marine of those areas affected by this regime, temperatures above 20 °C (68 °F) are extreme weather events, even in the midst of summer. Temperatures above 30 °C (86 °F) have been recorded on rare occasions in some areas of this climate, and in winter temperature down to −20 °C (−4 °F) have been recorded in some areas.

Dry summer variety (Csb)

Seattle
Climate chart (explanation)
J F M A M J J A S O N D     130     8 2     106     10 3     95     12 4     66     15 6     45     18 8     38     21 11     20     24 13     26     24 13     41     21 11     81     15 8     160     10 4     143     8 2 Average max. and min. temperatures in °C Precipitation totals in mm Source: [1]
Imperial conversion J F M A M J J A S O N D     5.1     46 36     4.2     49 37     3.8     53 39     2.6     58 42     1.8     64 47     1.5     70 52     0.8     75 55     1     76 56     1.6     70 52     3.2     60 46     6.3     51 40     5.6     46 36 Average max. and min. temperatures in °F Precipitation totals in inches

See also

• Climate classification
• Temperate climate
• Polar climate

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