Short essay on Temperate Oceanic Climate (Do)

This type of climate is found along the west coast of a continent in the west wind belt. That is why it is also known as marine west coast climate. Because of its proximity to sea and prevailing onshore westerly winds, this climate is the most equable or temperate in the real sense of the term. The multitude regions with this type of climate receive abundant precipitation throughout the year. The summers are moderate to cool.

Location:

Temperate oceanic climate occupies the windward (western) side of the middle- latitude continents between 40° and 65° N and S latitudes. It is noteworthy that the eastern sides of the middle-latitude land masses do not have temperate oceanic climate despite the proximity to the oceans. This is so because leeward location and the monsoon system of winds bring about large temperature contrasts between the warm and cool seasons.

In North America, the temperate oceanic climate is found along the west coast upto 60°N, where it borders the sub-arctic climate of Canada and Alaska. In Europe this type of climate extends along the west coast of Norway to 68°N. The pole-ward extension of this climate is made possible by the moderating influence of the North Atlantic Drift, a warm ocean current.

In the Southern Hemisphere, the southwest coast of Chile, southeast coast of Australia, the islands of Tasmania and New Zealand have this type of climate. The most extensive development of this climate is found in Western Europe including Great Britain, northwestern France, Germany, Denmark, Holland, Belgium and Norway.

Warm ocean currents found along the west coast of middle-latitude continents tend to further increase the moderating effect of the oceans. In fact, terrain features control the extension of the marine west coast climate into the interior of the continents. In the northwest United States, Chile, Canada and Scandinavia, the north-south highland barriers restrict the oceanic influence to narrow coastal regions.

Where such mountain barriers do not exist, the marine influence is carried far inland till the severe continental climate is reached. In Europe, where the westerlies blowing onshore have free access to the interior regions this marine west coast climate gradually becomes temperate continental climate.

In North America, where north-south Rockies present a formidable physical barrier, there is dry climate to the leeward east side of these mountains.

Temperature:

Temperatures in the marine west coast climate are influenced to a large extent by the oceanic influence and by the warm ocean currents. Therefore large seasonal extremes of temperature are absent. For their latitudes, the marine west coast climatic regions have relatively cool summers and mild winters so that the annual range of temperature is small.

Cool summers of this climatic type bring it closer to the coastal climate of the Mediterranean climate, even though summers lack the subtropical heat.

Average summer-month temperatures lie within the range of 15°C to 18°C. Mean July temperatures at certain stations in this type of climate in the Northern Hemisphere are as follows: Seattle in United States, 17°C, Paris, 19^HC, Bergen in Norway, 14.4°C and Dublin in Ireland, 15.6°C.

The climate being humid, night temperatures are not as low as in the Mediterranean climate. The average of the daily minima for the month of July at Bellingham and Seattle are 10.6°C and 12.8°C respectively, whereas the daily maxima at these two places are 21.7°C and 22.8°C respectively.

The annual range of temperature is nearly 11°. However, the daily maximum temperature, on rare occasions, may rise as high as 38°C. Occasional hot days in summer are uncomfortable.

Winters are exceptionally milder for the latitude. Most of the coastal locations in Western Europe have a positive anomaly of temperature ranging form 11° to 17°C. The marine influence is clearly perceptible when we find that winter temperatures decrease more rapidly from the coast towards the interior than they do pole-ward.

Mean January temperatures vary from 2″ to 10″C in Western Europe, while the continental interior of Eurasia records an average of -18°C to -40°C.

Average coldest month temperatures for various stations in this climate are as follows: Bordeaux 5°C, Melbourne 9.4°C, Portland 4°C and Reykjavik 0°C.

One of the most important factors contributing to the relatively high temperature averages for the coldest month is that the daily minimum temperatures are not very low because of cloud-cover and high moisture content of the air. The diurnal range of temperature is, therefore, low.

Frost occurs more frequently and it is more severe in the marine west coast climate. However, this climate has a long growing season of nearly 8 months.

Even during the cold months, frosts occur only less than 50 per cent nights. However, the frequency and intensity of frost increases inland, whereas it is relatively lower towards the polar margins.

Precipitation:

The marine west coast climate receives adequate precipitation in winter as well as summer. Depending on the terrain feature, the amount of precipitation is characterized by spatial variation.

In European lowlands the annual average precipitation varies from 50 cm to 85 cm. But on the windward side of the coastal ranges it may be between 250 cm and 375 cm, where the orographic uplift tends to increase the precipitation.

The Andes in Chile and the Rockies in North America get abundant precipitation on their windward sides by cyclonic as well as orographic uplift of maritime air masses in these latitudes.

Henderson Lake, British Columbia has a record precipitation of 655 cm a year. The leeward sides being deficient in precipitation have dry climates.

Most of the precipitation in this type of climate is cyclonic or frontal. However, orographic precipitation occurs at higher elevation. This type of climate has some of the cloudiest stations.

Although there is adequate precipitation all the year round, the winters tend to be foggier, cloudier, stormier and rainier than the summers. This is because in the cold season these regions are under the influence of the extra-tropical cyclones moving eastward with the westerlies.

The winter maximum of precipitation is the characteristic of the coastal areas, whereas far inland the continental stations have the summer maximum.

Snowfall occurs less frequently than it does in other climates in the comparable latitudes. This is because of marine influence and mild winter. Paris, London and Seattle-each of these lowland stations has, on an average 14, 13 and 10 snow-days respectively.

However, the incidence of snowfall increases pole-ward or towards the continental interiors. Snowfall on highlands is heavy and snow stays there for several months.

Natural vegetation:

Because of abundant precipitation the natural vegetation consists of forest. The more humid regions have more dense forest, and the rate of growth is also higher than that in the less wet regions.

The forest is composed of broad-leaf deciduous and needle-leaf conifers or a mixed forest of both. Pine, fir and spruce constitute the finest timber producing trees on a commercial scale.

The height of these coniferous trees generally exceeds 30 meters. Deciduous trees shed their leaves during winter. These forests are composed of oak, beech, birch, walnut, maple, elm and chestnut, etc.

In the cooler and more humid areas oak, ash and beech are the dominant species. Pine develops in such areas as the second-growth forests where original forests have been cleared.

However, most of these forests have been cleared in the British Isles and Europe because of the greater degree of urbanization. Some of the cleared areas have now been given to farming.

The coastal redwoods and Douglas firs of the northwestern coast of North America are examples of the finest coniferous forests, and these trees supply the best type of softwood lumber.

The temperate evergreen rainforest of the west coast of New Zealand are composed of the podearps which are fine examples of the evergreen forests of the Southern Hemisphere. These forests are dense, but the timber produced from them is of inferior quality.

Animal life:

The animal life of the marine west coast climate consists of animals that are found elsewhere. Typical animals that appear in the forest clearings are deer, foxes, rabbits, bears, wolves, otters and squirrels etc. Fish abound in the cold waters of the seas and oceans in these latitudes. Besides, whales and seals are the precious marine mammals.