The great plains of the northern continents.
Lands of hot summers, but cold winters. The bread baskets of the developed world,
they are also home to many great cities and are the heartlands for the two largest countries
on earth. In a band encircling the earth of the mid-latitudes…
Between the forbidding arctic cold to the north, and the deserts and humid plains to
the south… These are the lands of the Continental Climates. In our journey from equator to pole, we’ll
be leaving the southern hemisphere for a time as we set our focus on the great northern
continents. Being so far from the moderating influence of the oceans, these continents
produce a variety of climate types that have one thing in common – big temperature ranges
from summer to winter. There are two distinct biomes that occur within
North America and Eurasia. The colder and more northerly of these is the endless sub-arctic
pine forest – known as the Taiga. We’ll take this up in the next episode. In this
video, we’ll look at the warmer of these, which are the mixed woodlands and grasslands
that are home to hundreds of millions of people and countless cities stretching across Canada,
the United States, Northern and Eastern Europe, Russia and the northern Far East.
In the Koppen Climate Classification, there are, at first a seemingly bewildering number
of climates here, six in total. They are subdivided by rainfall pattern and temperature. Where
there is a hot summer, with the average day/night temperature being above 22°C, the designation
ends in “a”. Where there is a cooler, but still warm, summer below 22°C, the designation
ends in “b”. All continental climates by definition must
have the average day/night temperature in winter below -3°C, otherwise they fall under
the Oceanic, Mediterranean or Humid Subtropical climates.
Where there are wet winters and dry summers, this is an extension of the Mediterranean
climate into adjoining higher altitude areas, and is the least common of the Continental
climates, being limited to the interiors of the Pacific North-West and Turkey, along with
the western slopes of the Altai mountains in Central Asia.
When such a rainfall pattern is reversed, with dry winters and wet summers, we have
a form of monsoon. In fact the only places where this occur are in Eastern Asia, where
the Asian monsoon extends far into the north – Eastern Siberia, Northern China and Korea.
The most common continental climate is where the rainfall is distributed relatively evenly
throughout the year. Dfa is the continental humid hot summer, while Dfb is the continental
humid warm summer variant. These two make up the bulk of the population centres in the
mid-latitudes of the Northern Continents and so are especially important.
Now those of you paying attention in the last episode on Cool Deserts, might recall this
concept of “Continentality”, where land is so far from the ocean that it receives
little rain. So how is it that these continental interiors can support so much biosphere and
population? Well, firstly, they are, on the whole, further north than the cool deserts,
which reduces evaporation, due to a weaker sun, and so for a given amount of rain, more
plants can grow. This more northerly latitude also brings much
of western and central Eurasia under the sway of wet westerly winds blowing in from the
Atlantic, with no mountain ranges to stop them from the Baltic all the way to Siberia.
In this way, these areas, mostly of the Dfb warm humid summer variant, can be thought
of as a continental form of the Oceanic climate that we looked at in Episode 7.
In the case of North America, the moisture from the westerlies is all but blocked by
the Rocky Mountains, so much of the rain comes from the humid south. In this respect, this
climate can be viewed as simply a colder and drier form of the Humid Subtropical climate
that we looked at in Episode 5. As this warm southern air mixes with the very different
colder, drier arctic air over these areas, it often gives rise to extreme weather events
in the form of heavy thunderstorms, tornados and hailstorms.
Eastern Asia, like all climates in that region, is subject to the Asian monsoon, where due
to the enormity of this continent and the presence of the Tibetan plateau, the doldrums
of tropical wind convergence are pushed way to the north over Mongolia in summer, producing
low pressure that pulls in wet air from the nearby Pacific as far north as Eastern Siberia.
In winter, with high pressure over Mongolia, the wind direction is reversed, with dry air
now flowing over Northern China, Korea and Eastern Siberia. The result is wet summers
and dry winters. Compared to more southerly monsoon areas, though, the total rainfall
is much lower. And in general, all the continental climates are relatively dry compared to all
but the desert climates. The Continental Climate, with its wide temperature
range, has the most distinct of the traditional four season patterns found in the temperate
bands. Winters are always cold and snowy, and summers are marked by long days with plenty
of warm to hot sun, while Spring and Autumn are found between with their own well known
characters. So, where in the world are the continental
climate zones? Well, due to the lack of continental land mass below the equator, they all occur
in the North. Beginning just to the east of the Rockies
in Canada, the provinces of Alberta and Saskatchewan are dominated by the Cfb warm humid summer
variant. Moving east, and this band of Cfb gradually moves south to incorporate the Dakotas,
Minnesota, Wisconsin, Michigan, the whole of the Great Lakes region, upper New York
state, and all of New England, as well as all the main population centres of Ontario,
Quebec and the Maritime Provinces of Canada. Further south, and the heart of the Mid-West
comes under the sway of the hot summer continental Cfa variant, including the states of Nebraska,
Kansas, Iowa, Missouri and Illinois. As we head east, this band narrows between the Cfb
continental climate to the north and the Humid Subtropical climate to the south, with Indiana,
Ohio and Pennsylvania, sheltered from the warm Atlantic by the Appalachian mountains,
experiencing cold winters and hot summers. Skipping across the Atlantic, and past the
Oceanic climate zone of North-West Europe, we encounter again a huge area of the Cfb
variant of warm summers and cold winters, from Eastern Germany and Southern Scandinavia
in the West, moving through all of Eastern Europe, the Baltic States, Ukraine, Belarus
and encompassing much of European Russia. This band continues to extend for thousands
of miles deep into the heart of Asia and Siberia before finally being squeezed between the
sub-arctic forests of the north and the deserts to the south.
In Eastern Asia, the monsoon Dwa and Dwb variants dominate, with much of northern China and
Eastern Siberia and Korea experiencing hot or warm wet summers, and cold dry winters.
Due to its extreme altitude, we find the most southerly of all continental climates in Tibet,
where much of this plateau experiences cold, dry winters, and a mild to hot wet summer
in a similar way. Lastly, the north of Japan, including the
island of Hokkaido, being surrounded by water, has the year round rain of the Dfb variant,
while the northern half of Honshu island has the hotter summer Dfa variant. Because of
the bitterly cold winter wind blowing off from Siberia over the warm moist Sea of Japan,
this results in massive snowfalls over northern Japan – in fact Sapporo, Hokkaido’s capital,
is the snowiest city in the world. The natural vegetation of the continental
climate zones is a mixture of grasslands and forests of both deciduous and coniferous varieties,
depending on how much rain falls. On the fringes between this and the semi-arid climate, grasslands
dominate. On the border with the sub-arctic climates to the North, deciduous woodland
gradually gives way to uniform pine forest. Large scale mechanised agriculture dominates
these areas. In North America, the endless plains are covered by wheat and corn fields
as far as the eye can see. Soybeans and barley are also common. Ukraine and Southern Russia
is similarly dominated, while Eastern Europe and Southern Scandinavia, where the climate
is milder from bordering on the Oceanic climate, allows for a greater variety of crops and
livestock. Instead of rice which otherwise dominates
this country, Northern China sees much of the countryside, like the climatic counterparts
in Europe and North America, also given over to wheat, corn and barley production.
Between these endless plains, of course, lie many great and famous cities. And that’s the Continental Climate zones.
Please leave your comments, especially if you’re one of the many folks that live in
one of these climates, to share your experiences of them. And if you enjoyed the video, click
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you in the next episode, where we’ll be headed further north to view the endless pine
forests of the sub-arctic, and the most extreme temperature ranges to be found anywhere on