Laurentian Climate – Cool Temperate Eastern Margin
- The cool temperate eastern margin climate is an intermediate type of climate between the British & Siberian type of climate
- Have features of both maritime & continental type of climate
- Laurentian type of climate is found only in two regions, that too in northern hemisphere only.
- One is N-E North America (Eastern Canada including Newfoundland and N-E USA including Maritime Provinces & New England States)
- Other is Eastern coastlands of Asia including Eastern Siberia, North China, Manchuria, Korea & northern Japan
- In the southern hemisphere, this climate is absent because only a small section of southern continents extends beyond 40* S & maritime influence is so high that neither continental nor eastern margin type of climate exist.
- The Laurentian type of climate has cold, dry winters & warm, wet simmers.
- Winter temp. may be well below freezing point & snow falls to quite a depth.
- Summers are warm as the tropics approx. 25* C & if were not for the cooling effects of the off shore cold currents from arctic, the summers may even be hotter.
- Though, rain falls throughout the year (except interiors of china), there is distinct summer maximum from the easterly winds from the oceans
- The annual precipitation is approx. 75 -150 cm with 2/3rd of it falling in summers.
- N-E American Region in Laurentian type of climate has remarkable characteristic of uniformity in precipitation with a slight late summer maximum i.e. July and August.
- This uniformity of precipitation is largely due to the Atlantic influence & that of the Great lakes.
- The warm Gulf Stream increases the moisture content of the easterly winds from the open Atlantic; & the prevailing westerlies which penetrate across the Rockies carry depressions over the Great lakes to the New England states, thus promotes wet conditions especially in winters, vital for the agricultural activities of this region.
- Meeting of warm Gulf Stream & cold Labrador Current on the coastal areas off Newfoundland produces dense mist & fog & give rise to much precipitation.
- In contrast, the rainfall distribution of the Asiatic region is far less uniform;
- Winters are cold & very dry while summers are very warm & exceptionally wet.
- Rainfall is mostly confined to five summer months with rest of the year dry, similar to the tropical monsoon conditions in India.
- The mountainous interior of China has such pronounced continental effects that the intense heating in summers creates a region of extreme low pressure, & moisture laiden winds from the Pacific & Sea of Japan blow in as S-E monsoon; also called as cool temperate monsoon climate.
- The climate of Japan is modified by its insularity, & also by the meeting of warm & cold ocean currents.
- It receives adequate rainfall from both the SE monsoon in summers & NE monsoon in winters.
- The latter is dry, cold wind from from mainland Asia, but after crossing the Sea of Japan, gathers sufficient moisture to give heavy relief rain or snow on western coast of Japan.
- The rainfall is more evenly distributed with two maxima, one in June, the plum rain & other in September, the Typhoon rain.
Natural Vegetation of Laurentian Climate
- Generally, the forest tend to be coniferous north of 50* N latitude
- In Asiatic region (eastern Siberia & Korea), the coniferous forests are infact a continuation of great coniferous belt of Taiga.
- South of 50* N latitude, the coniferous forests give way to deciduous forests with oak, beech, maple & birch, the principal trees.
- Lumbering & its associated timber, paper & pulp industries are the most important economic undertaking.
- Agriculture is less important in view of severity of winters & its long duration
- Fortunately the maritime influence & heavy rainfall enables some of the hardy crops to be raised for local needs such as potatoes, oats, rye & barley.
- Fishing is the most outstanding economic activity of Laurentian climatic region especially in Newfoundland & Japan mainly due to their geographical importance.
- Gently sloping continental shelves around the islands of Newfoundland & Japan are rich in planktons, mainly due to meeting of warm & cold ocean currents.
- Fish feeds on minute marine organisms – planktons, which are present in abundance only in shallow waters adjacent to land masses, where sunlight can penetrate through
- Japanese also make use of fish wastes, fish meals & seaweeds as fertilizers & is among one of the few countries involved in seaweed cultivation on submerged coastal farms.
- Another aspect of Japanese fishing is pearl culture obtained from the shale fish called pearl oyster found deep inside the sea.