Typical weather for regions above the tree line
Alpine climate
is the typical
climate
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
[
edit
]
There are multiple definitions of alpine climate.
In the
Koppen climate classification
, the alpine and mountain climates are part of group
E
, along with the
polar climate
, where no month has a mean
temperature
higher than 10 °C (50 °F).
[1]
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
of a location is between 1.5 and 3 °C (34.7 and 37.4 °F). The alpine climate in Holdridge system is roughly equivalent to the warmest
tundra
climates (ET) in the Koppen 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 0 °C (32 °F) and above 30 °C (86 °F).
[2]
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.
[3]
For mid-latitude locations, such as
Mount Washington
in
New Hampshire
, the temperature varies seasonally, but never gets very warm.
[4]
[5]
Cause
[
edit
]
The temperature profile of the atmosphere is a result of an interaction between
radiation
and
convection
. Sunlight in the
visible spectrum
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 333 K (60 °C; 140 °F), and the temperature would decay exponentially with height.
[6]
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 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
, 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.
[6]
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).
[7]
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).
[8]
[9]
Therefore, moving up 100 metres (330 ft) on a mountain is roughly equivalent to moving 80 kilometres (50 miles or 0.75° of
latitude
) towards the pole.
[10]
This relationship is only approximate, however, since local factors, such as proximity to
oceans
, can drastically modify the climate.
[11]
As the altitude increases, the main form of
precipitation
becomes
snow
and the
winds
increase. The temperature continues to drop until the
tropopause
, at 11,000 metres (36,000 ft), where it does not decrease further. This is higher than the highest
summit
.
Distribution
[
edit
]
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
Tibetan Plateau
,
Gansu
,
Qinghai
and
Mount Lebanon
[12]
in
Asia
; the
Alps
, the
Urals
, the
Pyrenees
, the
Cantabrian Mountains
and the
Sierra Nevada
in
Europe
; the
Andes
in
South America
; the
Sierra Nevada
, the
Cascade Range
, the
Rocky Mountains
, the northern
Appalachian Mountains
(
Adirondacks
and
White Mountains
), and the
Trans-Mexican volcanic belt
in
North America
; the
Southern Alps
in
New Zealand
; the
Snowy Mountains
in
Australia
; high elevations in the
Atlas Mountains
,
Ethiopian Highlands
, and
Eastern Highlands
of
Africa
; the central parts of
Borneo
and
New Guinea
; and the summits of
Mount Pico
in the
Atlantic
[13]
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 650 metres (2,130 ft) at 68°N in Sweden,
[14]
while on
Mount Kilimanjaro
in Tanzania, the tree line is at 3,950 metres (12,960 ft).
[14]
See also
[
edit
]
References
[
edit
]
- ^
McKnight, Tom L; Hess, Darrel (2000).
"Climate Zones and Types: The Koppen System"
.
Physical Geography: A Landscape Appreciation
. Upper Saddle River, New Jersey: Prentice Hall. pp.
235?7
.
ISBN
978-0-13-020263-5
.
- ^
Lugo, A. E. (1999).
"The Holdridge life zones of the conterminous United States in relation to ecosystem mapping"
.
Journal of Biogeography
.
26
(5): 1025?1038.
Bibcode
:
1999JBiog..26.1025L
.
doi
:
10.1046/j.1365-2699.1999.00329.x
.
S2CID
11733879
. Retrieved
27 May
2015
.
- ^
"Period of Record Monthly Climate Summary"
.
MAUNA LOA SLOPE OBS, HAWAII
. NOAA
. Retrieved
2012-06-05
.
- ^
"Station Name: NH MT WASHINGTON"
. National Oceanic and Atmospheric Administration
. Retrieved
9 June
2014
.
- ^
"WMO Climate Normals for MOUNT WASHINGTON, NH 1961?1990"
. National Oceanic and Atmospheric Administration
. Retrieved
9 June
2014
.
- ^
a
b
Goody, Richard M.; Walker, James C.G. (1972).
"Atmospheric Temperatures"
(PDF)
.
Atmospheres
. Prentice-Hall. Archived from
the original
(PDF)
on 2016-07-29
. Retrieved
2016-05-02
.
- ^
"Dry Adiabatic Lapse Rate"
. tpub.com. Archived from
the original
on 2016-06-03
. Retrieved
2016-05-02
.
- ^
"Adiabatic Lapse Rate"
.
The IUPAC Compendium of Chemical Terminology
.
IUPAC
. 2009.
doi
:
10.1351/goldbook.A00144
.
ISBN
978-0-9678550-9-7
.
- ^
Dommasch, Daniel O. (1961).
Airplane Aerodynamics (3rd ed.)
. Pitman Publishing Co. p. 22.
- ^
"Mountain Environments"
(PDF)
. United Nations Environment Programme World Conservation Monitoring Centre. Archived from
the original
(PDF)
on 2011-08-25.
- ^
"Factors affecting climate"
. The United Kingdom Environmental Change Network. Archived from
the original
on 2011-07-16.
- ^
McColl, R. W. (May 14, 2014).
Encyclopedia of World Geography - Volume 1
. Facts On File, Incorporated. p. 537.
ISBN
9780816072293
.
- ^
"Climate atlas of the archipelagos of the Canary Islands, Madeira and the Azores"
(PDF)
.
IPMA
,
AEMET
. Retrieved
17 June
2021
.
- ^
a
b
Korner, Ch (1998).
"A re-assessment of high elevation treeline positions and their explanation"
(PDF)
.
Oecologia
.
115
(4): 445?459.
Bibcode
:
1998Oecol.115..445K
.
CiteSeerX
10.1.1.454.8501
.
doi
:
10.1007/s004420050540
.
PMID
28308263
.
S2CID
8647814
. Archived from
the original
(PDF)
on 2006-09-11
. Retrieved
2015-08-05
.
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Class A
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Class B
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Class C
| |
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Class D
|
- Humid continental
(Dfa, Dwa, Dsa, Dfb, Dwb, Dsb)
- Subarctic
(Dfc, Dwc, Dsc, Dfd, Dwd, Dsd)
|
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Class E
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