Alpine climate is the typical
weather (
climate
Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...
) for elevations above the
tree line, where trees fail to grow due to cold. This climate is also referred to as a mountain climate or highland climate.
Definition
There are multiple definitions of alpine climate.
In the
Köppen climate classification
The Köppen climate classification is one of the most widely used climate classification systems. It was first published by German-Russian climatologist Wladimir Köppen (1846–1940) in 1884, with several later modifications by Köppen, nota ...
, the alpine and mountain climates are part of group ''E'', along with the
polar climate, where no month has a mean
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer.
Thermometers are calibrated in various temperature scales that historically have relied o ...
higher than .
According to the
Holdridge life zone system, there are two mountain climates which prevent tree growth :
a) the alpine climate,
which occurs when the mean
biotemperature
The Holdridge life zones system is a global bioclimatic scheme for the classification of land areas. It was first published by Leslie Holdridge in 1947, and updated in 1967. It is a relatively simple system based on few empirical data, giving ob ...
of a location is between . The alpine climate in Holdridge system is roughly equivalent to the warmest
tundra climates (ET) in the Köppen system.
b) the alvar climate, the coldest mountain climate since the biotemperature is between 0 °C and 1.5 °C (biotemperature can never be below 0 °C). It corresponds more or less to the coldest tundra climates and to the
ice cap climates (EF) as well.
Holdrige reasoned that plants net primary productivity ceases with plants becoming dormant at temperatures below and above . Therefore, he defined biotemperature as the mean of all temperatures but with all temperatures below freezing and above 30 °C adjusted to 0 °C; that is, the sum of temperatures not adjusted is divided by the number of all temperatures (including both adjusted and non-adjusted ones).
The variability of the alpine climate throughout the year depends on the latitude of the location. For tropical oceanic locations, such as the summit of
Mauna Loa, the temperature is roughly constant throughout the year. For mid-latitude locations, such as
Mount Washington
Mount Washington is the highest peak in the Northeastern United States at and the most topographically prominent mountain east of the Mississippi River.
The mountain is notorious for its erratic weather. On the afternoon of April 12, 1934 ...
in
New Hampshire
New Hampshire is a U.S. state, state in the New England region of the northeastern United States. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Gulf of Maine to the east, and the Canadian province of Quebec t ...
, the temperature varies seasonally, but never gets very warm.
Cause
The temperature profile of the atmosphere is a result of an interaction between
radiation and
convection
Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the c ...
. Sunlight in the
visible spectrum
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called '' visible light'' or simply light. A typical human eye will respond to ...
hits the ground and heats it. The ground then heats the air at the surface. If
radiation were the only way to transfer heat from the ground to space, the
greenhouse effect of gases in the atmosphere would keep the ground at roughly , and the temperature would decay exponentially with height.
However, when air is hot, it tends to expand, which lowers its density. Thus, hot air tends to rise and transfer heat upward. This is the process of
convection
Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the c ...
. Convection comes to equilibrium when a parcel of air at a given altitude has the same density as its surroundings. Air is a poor conductor of heat, so a parcel of air will rise and fall without exchanging heat. This is known as an
adiabatic process
In thermodynamics, an adiabatic process (Greek: ''adiábatos'', "impassable") is a type of thermodynamic process that occurs without transferring heat or mass between the thermodynamic system and its environment. Unlike an isothermal process, ...
, which has a characteristic pressure-temperature curve. As the pressure gets lower, the temperature decreases. The rate of decrease of temperature with elevation is known as the
adiabatic lapse rate, which is approximately 9.8 °C per kilometer (or 5.4 °F per 1000 feet) of altitude.
[
The presence of water in the atmosphere complicates the process of convection. Water vapor contains latent heat of vaporization. As air rises and cools, it eventually becomes saturated and cannot hold its quantity of water vapor. The water vapor condenses (forming clouds), and releases heat, which changes the lapse rate from the dry adiabatic lapse rate to the moist adiabatic lapse rate (5.5 °C per kilometre or 3 °F per 1000 feet). The actual lapse rate, called the environmental lapse rate, is not constant (it can fluctuate throughout the day or seasonally and also regionally), but a normal lapse rate is 5.5 °C per 1,000 m (3.57 °F per 1,000 ft). Therefore, moving up on a mountain is roughly equivalent to moving 80 kilometres (50 miles or 0.75° of ]latitude
In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north ...
) towards the pole. This relationship is only approximate, however, since local factors, such as proximity to ocean
The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wor ...
s, can drastically modify the climate. As the altitude increases, the main form of precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
becomes snow
Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes.
It consists of frozen crystalline water throughou ...
and the wind
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ...
s increase. The temperature continues to drop until the tropopause, at , where it does not decrease further. This is higher than the highest summit.
Distribution
Although this climate classification only covers a small portion of the Earth's surface, alpine climates are widely distributed. They are present in the Himalayas
The Himalayas, or Himalaya (; ; ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the planet's highest peaks, including the very highest, Mount Everest. Over 10 ...
, the Tibetan Plateau, Gansu, Qinghai, the Alps
The Alps () ; german: Alpen ; it, Alpi ; rm, Alps ; sl, Alpe . are the highest and most extensive mountain range system that lies entirely in Europe, stretching approximately across seven Alpine countries (from west to east): France, Sw ...
, the Pyrenees, the Cantabrian Mountains and the Sierra Nevada in Eurasia
Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelag ...
, the Andes
The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...
in South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...
, the Sierra Nevada, the Cascade Mountains, the Rocky Mountains
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico ...
, the northern Appalachian Mountains
The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. The ...
(Adirondacks and White Mountains), and the Trans-Mexican volcanic belt in North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...
, the Southern Alps in New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island coun ...
, the Snowy Mountains in Australia
Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
, high elevations in the Atlas Mountains and the Eastern Highlands of Africa
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
, and the central parts of Borneo
Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and e ...
and New Guinea
New Guinea (; Hiri Motu: ''Niu Gini''; id, Papua, or , historically ) is the world's second-largest island with an area of . Located in Oceania in the southwestern Pacific Ocean, the island is separated from Australia by the wide Torres ...
and the summits of Mount Pico in the Atlantic
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...
and Mauna Loa in the Pacific.
The lowest altitude of alpine climate varies dramatically by latitude. If alpine climate is defined by the tree line, then it occurs as low as at 68°N in Sweden, while on Mount Kilimanjaro in Africa, the tree line is at .[
]
See also
* Alpine plant
* Climate of the Alps
* List of alpine climate locations
References
{{DEFAULTSORT:Alpine Climate
*A
Köppen climate types
Mountain meteorology
Montane ecology
Climate by mountain range
Climate of the Alps