Microthermal
Encyclopedia
In climatology
, the term microthermal is used to denote the continental climate
s of Eurasia
and North America
.
The word microthermal is derived from two Greek
words meaning "having little heat." This is misleading, however, since the term is intended to describe only the temperature
conditions that prevail during the winter months, rather than those of the entire year.
The characteristic feature of the microthermal climate is cold winters — specifically, winters that are cold enough to ensure that snow
will remain on the ground continuously for a fixed period of time every year. Conceptually, an average temperature of 0°C or colder is assumed to be necessary to bring this about; thus the climate of a location where at least one full month is this cold is classified as microthermal (however, at least one month in the summer must average 10°C or higher; otherwise the climate would be reckoned as polar
). This definition places all of the world's microthermal climates in the Northern Hemisphere
, as the absence of broad land masses at upper-middle latitudes in the Southern Hemisphere
precludes the existence of such temperature conditions there.
Microthermal climates are typically subdivided into three categories based on the temperature characteristics of the summer season. The southernmost of the three is frequently referred to as the temperate continental climate, and has hot summers — that is to say, at least one month has an average temperature of 22°C (71.6°F) or above. The middle zone is often labelled hemiboreal
, and no summer month there has an average temperature as warm as 22°C, but at least four months will average 10°C (50°F) or higher. The northernmost of the three microthermal zones is the subarctic, or boreal
zone; there only one to three months will have average temperatures of at least 10°C.
In North America
, microthermal climates commence at roughly 40° North latitude along the Atlantic seaboard, this line drifting gradually southward further inland, reaching approximately 38° at the eastern edge of the Rocky Mountains
, then curving dramatically northward near the Pacific
coast, reaching the Pacific Ocean just south of Juneau, Alaska
. In Asia
, the latitude at which these climates begin is several degrees lower due to the pervasive influence of the vast Siberian anticyclone, or high-pressure system, and in continental Europe
the line actually runs longitudinally rather than latitudinally, cutting through central Poland
after beginning north of the Arctic Circle
along the Norwegian coast, thereafter moving diagonally across Scandinavia
.
The boundary between the microthermal and polar climate zones is farthest north in western Europe (actually within the Arctic Circle there), and farthest south along the east coast of North America (at about 56° North latitude on the central coast of Labrador
); it then trends northward across Canada
before dropping south again as it courses through Alaska
. Throughout most of Siberia
, the boundary tends to follow the Arctic Circle fairly closely.
In addition to having various summer temperature regimes, microthermal climates also differ from one another in how much precipitation
they receive — such climates may be humid, semiarid or arid
. Most of the Turkestan-Gobi
desert system has an arid microthermal climate, while the best-known example of the semiarid microthermal climate can be found in the "steppe
s of Central Asia
" immortalized by Russia
n classical music composer
Alexander Borodin
.
Climatology
Climatology is the study of climate, scientifically defined as weather conditions averaged over a period of time, and is a branch of the atmospheric sciences...
, the term microthermal is used to denote the continental climate
Continental climate
Continental climate is a climate characterized by important annual variation in temperature due to the lack of significant bodies of water nearby...
s of Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
.
The word microthermal is derived from two Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
words meaning "having little heat." This is misleading, however, since the term is intended to describe only the temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
conditions that prevail during the winter months, rather than those of the entire year.
The characteristic feature of the microthermal climate is cold winters — specifically, winters that are cold enough to ensure that snow
Snow
Snow is a form of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by...
will remain on the ground continuously for a fixed period of time every year. Conceptually, an average temperature of 0°C or colder is assumed to be necessary to bring this about; thus the climate of a location where at least one full month is this cold is classified as microthermal (however, at least one month in the summer must average 10°C or higher; otherwise the climate would be reckoned as polar
Polar climate
Regions with a polar climate are characterized by a lack of warm summers . Regions with polar climate cover over 20% of the Earth. The sun shines 24 hours in the summer, and barely ever shines at all in the winter...
). This definition places all of the world's microthermal climates in the Northern Hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...
, as the absence of broad land masses at upper-middle latitudes in the Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
precludes the existence of such temperature conditions there.
Microthermal climates are typically subdivided into three categories based on the temperature characteristics of the summer season. The southernmost of the three is frequently referred to as the temperate continental climate, and has hot summers — that is to say, at least one month has an average temperature of 22°C (71.6°F) or above. The middle zone is often labelled hemiboreal
Hemiboreal
Hemiboreal means halfway between the temperate and subarctic zones. The term is most frequently used in the context of ecosystems.-Botany:...
, and no summer month there has an average temperature as warm as 22°C, but at least four months will average 10°C (50°F) or higher. The northernmost of the three microthermal zones is the subarctic, or boreal
Boreal ecosystem
The term boreal is usually applied to ecosystems localized in subarctic and subantarctic zones, although Austral is also used for the latter....
zone; there only one to three months will have average temperatures of at least 10°C.
In North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, microthermal climates commence at roughly 40° North latitude along the Atlantic seaboard, this line drifting gradually southward further inland, reaching approximately 38° at the eastern edge of the Rocky Mountains
Rocky Mountains
The Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...
, then curving dramatically northward near the Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
coast, reaching the Pacific Ocean just south of Juneau, Alaska
Juneau, Alaska
The City and Borough of Juneau is a unified municipality located on the Gastineau Channel in the panhandle of the U.S. state of Alaska. It has been the capital of Alaska since 1906, when the government of the then-District of Alaska was moved from Sitka as dictated by the U.S. Congress in 1900...
. In Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
, the latitude at which these climates begin is several degrees lower due to the pervasive influence of the vast Siberian anticyclone, or high-pressure system, and in continental Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
the line actually runs longitudinally rather than latitudinally, cutting through central Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
after beginning north of the Arctic Circle
Arctic Circle
The Arctic Circle is one of the five major circles of latitude that mark maps of the Earth. For Epoch 2011, it is the parallel of latitude that runs north of the Equator....
along the Norwegian coast, thereafter moving diagonally across Scandinavia
Scandinavia
Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...
.
The boundary between the microthermal and polar climate zones is farthest north in western Europe (actually within the Arctic Circle there), and farthest south along the east coast of North America (at about 56° North latitude on the central coast of Labrador
Labrador
Labrador is the distinct, northerly region of the Canadian province of Newfoundland and Labrador. It comprises the mainland portion of the province, separated from the island of Newfoundland by the Strait of Belle Isle...
); it then trends northward across Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
before dropping south again as it courses through Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
. Throughout most of Siberia
Siberia
Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...
, the boundary tends to follow the Arctic Circle fairly closely.
In addition to having various summer temperature regimes, microthermal climates also differ from one another in how much precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...
they receive — such climates may be humid, semiarid or arid
Arid
A region is said to be arid when it is characterized by a severe lack of available water, to the extent of hindering or even preventing the growth and development of plant and animal life...
. Most of the Turkestan-Gobi
Gobi Desert
The Gobi is a large desert region in Asia. It covers parts of northern and northwestern China, and of southern Mongolia. The desert basins of the Gobi are bounded by the Altai Mountains and the grasslands and steppes of Mongolia on the north, by the Hexi Corridor and Tibetan Plateau to the...
desert system has an arid microthermal climate, while the best-known example of the semiarid microthermal climate can be found in the "steppe
Steppe
In physical geography, steppe is an ecoregion, in the montane grasslands and shrublands and temperate grasslands, savannas, and shrublands biomes, characterized by grassland plains without trees apart from those near rivers and lakes...
s of Central Asia
Central Asia
Central Asia is a core region of the Asian continent from the Caspian Sea in the west, China in the east, Afghanistan in the south, and Russia in the north...
" immortalized by Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
n classical music composer
Composer
A composer is a person who creates music, either by musical notation or oral tradition, for interpretation and performance, or through direct manipulation of sonic material through electronic media...
Alexander Borodin
Alexander Borodin
Alexander Porfiryevich Borodin was a Russian Romantic composer and chemist of Georgian–Russian parentage. He was a member of the group of composers called The Five , who were dedicated to producing a specifically Russian kind of art music...
.