Climate pattern
Encyclopedia
A climate pattern is any recurring characteristic of the climate. Climate patterns can last tens of thousands of years, like the glacial
and interglacial
periods within ice age
s, or repeat each year, like monsoon
s.
A climate pattern may come in the form of a regular cycle
, like the diurnal cycle
or the seasonal cycle
; a quasi periodic event, like El Niño; or a highly irregular event, such as a volcanic winter
. The regular cycles are generally well understood and may be removed by normalization
. For example, graphs of trends of temperature change will usually have the effects of seasonal variation removed.
Measured via an empirical orthogonal function analysis, the mode of variability with the greatest effect on climates worldwide is the seasonal cycle, followed by El Niño-Southern Oscillation
, followed by thermohaline circulation
.
Other well-known modes of variability include:
Glacial period
A glacial period is an interval of time within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate within an ice age...
and interglacial
Interglacial
An Interglacial period is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age...
periods within ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
s, or repeat each year, like monsoon
Monsoon
Monsoon is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea...
s.
A climate pattern may come in the form of a regular cycle
Climate cycle
A climate cycle is a type of recurring climate pattern that involves natural cyclic variations in the Earth's surface temperature, as indicated by temperature proxies found in glacier ice, sea bed sediment, tree ring studies or otherwise....
, like the diurnal cycle
Diurnal cycle
A diurnal cycle is any pattern that recurs every 24 hours as a result of one full rotation of the Earth.In climatology, the diurnal cycle is one of the most basic forms of climate patterns. The most familiar such pattern is the diurnal temperature variation...
or the seasonal cycle
Season
A season is a division of the year, marked by changes in weather, ecology, and hours of daylight.Seasons result from the yearly revolution of the Earth around the Sun and the tilt of the Earth's axis relative to the plane of revolution...
; a quasi periodic event, like El Niño; or a highly irregular event, such as a volcanic winter
Volcanic winter
A volcanic winter is the reduction in temperature caused by volcanic ash and droplets of sulfuric acid obscuring the sun and raising Earth's albedo after a large particularly explosive type of volcanic eruption...
. The regular cycles are generally well understood and may be removed by normalization
Normalization
Normalization may refer to:- Mathematics and statistics:* Normalization property , term in mathematical logic and theoretical computer science* Noether normalization lemma, result of commutative algebra...
. For example, graphs of trends of temperature change will usually have the effects of seasonal variation removed.
Modes of variability
A mode of variability is a climate pattern with identifiable characteristics, specific regional effects, and often oscillatory behavior. Many modes of variability are used by climatologists as indices to represent the general climatic state of a region affected by a given climate pattern.Measured via an empirical orthogonal function analysis, the mode of variability with the greatest effect on climates worldwide is the seasonal cycle, followed by El Niño-Southern Oscillation
El Niño-Southern Oscillation
El Niño/La Niña-Southern Oscillation, or ENSO, is a quasiperiodic climate pattern that occurs across the tropical Pacific Ocean roughly every five years...
, followed by thermohaline circulation
Thermohaline circulation
The term thermohaline circulation refers to a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes....
.
Other well-known modes of variability include:
- The Antarctic oscillationAntarctic oscillationThe Antarctic oscillation is a low-frequency mode of atmospheric variability of the southern hemisphere...
- The Arctic oscillationArctic oscillationThe Arctic oscillation or Northern Annular Mode/Northern Hemisphere Annular Mode is an index of the dominant pattern of non-seasonal sea-level pressure variations north of 20N latitude, and it is characterized by pressure anomalies of one sign in the Arctic with the opposite anomalies centered...
- The Atlantic multidecadal oscillationAtlantic Multidecadal OscillationThe Atlantic multidecadal oscillation is a mode of variability occurring in the North Atlantic Ocean and which has its principal expression in the sea surface temperature field...
- The Indian Ocean DipoleIndian Ocean DipoleThe Indian Ocean Dipole is an irregular oscillation of sea-surface temperatures in which the western Indian Ocean becomes alternately warmer and then colder than the eastern part of the ocean.-The phenomenon:...
- The Madden–Julian oscillation
- The North Atlantic oscillationNorth Atlantic oscillationThe North Atlantic oscillation is a climatic phenomenon in the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level between the Icelandic low and the Azores high. Through east-west oscillation motions of the Icelandic low and the Azores high, it controls the...
- The Pacific decadal oscillationPacific decadal oscillationThe Pacific Decadal Oscillation is a pattern of Pacific climate variability that shifts phases on at least inter-decadal time scale, usually about 20 to 30 years. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 20° N...
- The Pacific-North American teleconnection patternPacific-North American teleconnection patternThe Pacific-North American teleconnection pattern is a climatological term for a large-scale weather pattern with two modes, denoted positive and negative, and which relates the atmospheric circulation pattern over the North Pacific Ocean with the one over the North American continent.The positive...
- The Quasi-biennial oscillationQuasi-biennial oscillationThe quasi-biennial oscillation is a quasi-periodic oscillation of the equatorial zonal wind between easterlies and westerlies in the tropical stratosphere with a mean period of 28 to 29 months. The alternating wind regimes develop at the top of the lower stratosphere and propagate downwards at...
Further reading
- Natural climate variability at the National Institute of Geophysics and Vulcanology (Bologna, Italy)