An oceanic climate is the climate experienced in west coasts found in mid-latitude regions of the world. Other names for this climate include maritime climate, marine climate, highland climate, or west coast climate. It is predominant in most parts of Western Europe where it extends further inland as compared to other continents. It is also found in some regions of central Mexico, the southwestern portion of South America, the Northwest Coast which lies in the Pacific Northwest region, and the south-eastern portion of Australia which includes New Zealand and Tasmania.
Characteristics of the Oceanic Climate
Regions that experience oceanic climates have cool but not cold winters and warm summers. The annual temperature range of these areas is relatively narrow, except for regions where the climate transits to subarctic, highland or continental climates. According to Köppen climate classification, the mean temperature of marine climates during the coldest month is 0 °C or higher. During the warmest month, the average temperature is below 22 °C. Summers are therefore cooler in oceanic climates as compared to continental climates.
Precipitation in oceanic climates is sufficient, reliable, and evenly distributed throughout the year. Regions with this climate lack a dry season. The precipitation falls mainly in the form of rain, but some parts experience some snowfall every year during winter. Cloudy conditions and extended months of rain are predominant in marine climates. For example, in Seattle, the weather is cloudy six days in a week between October and May. During this period, the city also experiences high rainfall. In parts of Australia and New Zealand, most of the places with the oceanic climate suffer at least one snowstorm annually. As one move towards the poles, locations within the maritime climate zone experience snowfall more frequently.
Causes of the Oceanic Climate
Most areas that experience maritime climates are located next to large water bodies such as oceans or large lakes which play a crucial role in shaping their climates. Temperatures do not vary greatly in maritime climates, for example, because winds coming off the sea regulate temperatures in the adjacent onshore areas. In Northwest Europe, the North Atlantic Gulf stream is thought to be the cause of milder winters in west-coast areas found in the higher latitudes of the UK, Norway, and Ireland. Lowland attributes of this region also allow air masses from the sea to penetrate continental areas and reach inland cities like Vienna, Prague, and Dresden, causing them to experience maritime climates. The polar jet stream and prevailing winds like the westerlies also influence the oceanic climate in other parts of the world.
Variations of the Oceanic Climate
Subtropical Highland Variety
This variation of the oceanic climate is experienced in high altitude areas that lie within the tropics or subtropics. It is the prevailing climate in mountainous regions of some tropical countries. However, areas with the subtropical highland climate tend to receive less precipitation during winter or the lower-sun season as compared to other lower altitude regions at similar latitudes. Places that experience this climate within the tropics tend to have spring-like weather throughout the year, with relatively constant temperatures and no snowfall. Outside the tropics, the characteristics of this climate include mild summers, cooler and drier winters, and sometimes there is snowfall.
In the Köppen climate classification, places with this climate are designated as Cwb or Cfb. In Cwb regions, the average temperature of the coldest month is above 0 °C and the mean monthly temperature for all months is below 22 °C. In at least four months of the year, the average temperature must be above 10 °C. These areas receive the highest precipitation during the six warmest months of the year. Regions designated as Cfb have an identical climate, but precipitation tends to be uniformly distributed all year round. Some places such as Copacabana in Bolivia, however, exhibit a rare variation of the temperate oceanic climate denoted as Cwc. They have shorter summers and fewer than four months with an average temperature exceeding 10 °C. Other areas with this rare variation of the subtropical highland climate include Sichuan and Yunnan in China.
The subtropical highland climate dominates the higher elevation areas of south and south-eastern Africa, the eastern region of Africa up to Mozambique, and the western part of Africa as far as the southwestern highlands of Angola. It is also prevalent in parts of Sri Lanka and the Himalayas, some portions of the Grand Atlas Mountains, high altitude regions of southern Europe, and the mountainous regions of Central, North, and South America.
Places that experience the subpolar oceanic climate are located close to the Polar regions. This variety is denoted as Cfc in the Köppen classification. They get more snowfall as compared to places within the temperate oceanic climate, but their winters are milder than those of continental or subarctic climates. Mean monthly temperatures in the subpolar oceanic climate zones do not fall below 0 °C. These zones, however, have less than three months in which the mean temperature rises above 10 °C. During the warmest months, the maximum daytime temperatures are below 17 °C.
Regions that experience the subpolar variation of the oceanic climate include some portions of the Scottish Highlands, Shetland Islands, the Faroe Islands, Lofoten in Norway, the coastal regions of Iceland, and some highland portions of Tasmania. Other places include the southernmost regions of Argentina and Chile, and some regions of Alaska such as the Aleutian Islands and Southeast Alaska which is also called the Alaska Panhandle.
Other Places That Experience the Oceanic Climate
Other significant regions with the maritime climate include the Black Sea coast in Turkey, parts of Azerbaijan that are located near the Caspian Sea, and Tristan da Cunha, a remote archipelago found in the South Atlantic Ocean. In South Africa, the maritime climate dominates the coastal region of the Western Cape Province lying between Mossel Bay and Plettenberg Bay. It is also found in some inland portions of the Eastern Cape Province and along the coast of KwaZulu-Natal province.