Teleconnection

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Teleconnection in atmospheric science refers to climate anomalies being related to each other at large distances (typically thousands of kilometers). The most emblematic teleconnection is that linking sea-level pressure at Tahiti and Darwin, Australia, which defines the Southern Oscillation. Another well-known teleconnection links the sea-level pressure over Iceland with the one over the Azores, traditionally defining the North Atlantic Oscillation (NAO). [1]

Contents

History

Teleconnections were first noted by the British meteorologist Sir Gilbert Walker in the late 19th century, through computation of the correlation between time series of atmospheric pressure, temperature and rainfall. They served as a building block for the understanding of climate variability, by showing that the latter was not purely random.

Indeed, the term El Niño–Southern Oscillation (ENSO) is an implicit acknowledgment that the phenomenon underlies variability in several locations at once. It was later noticed that associated teleconnections occurred all over North America, as embodied by the Pacific–North American teleconnection pattern.

In the 1980s, improved observations allowed detection of teleconnections at larger distances throughout the troposphere. [2] Concomitantly, the theory emerged that such patterns could be understood through the dispersion of Rossby waves due to the spherical geometry of the Earth. [3] This is sometimes called the "proto-model". [4]

Theory

Teleconnections within the tropical Pacific began to be understood thanks to the idealized calculations of A.E. Gill [5] and later through more complex models.

Building upon the "proto-model", much of the early theory of teleconnections dealt with barotropic, linearized model of atmospheric flow about a constant mean state. However, the model was soon invalidated when it was discovered that actual teleconnection patterns were nearly insensitive to the location of the forcing, in direct contradiction with the predictions offered by this simple picture. Simmons and collaborators [6] showed that if a more realistic background state was prescribed, it would become unstable, leading to a similar pattern regardless of the location of the forcing, in accordance to observations. This "modal" property turned out to be an artifact of the barotropicity of the model, though it has appeared for more subtle reasons in more realistic models.

More recent work has shown that most teleconnections from the tropics to the extratropics can be understood to surprising accuracy by the propagation of linear, planetary waves upon a 3-dimensional seasonally-varying basic state. [7] Because the patterns are persistent over time and somewhat "locked" to geographical features such as mountain ranges, these waves are called stationary .

Another mechanism of teleconnection between tropical oceans and midlatitude regions is symmetric along latitude circles (i.e. "zonal") and between hemispheres, unlike the stationary wave mechanism. It relies on interactions between transient eddies and the mean atmospheric flow that are mutually reinforcing (i.e. non-linear). It has been shown to explain some aspects of ENSO teleconnections in temperature [8] and rainfall. [9] Other authors suggested, as well, a correlation between many teleconnection patterns and local climate change factors. [10]

Applications

Since tropical sea surface temperatures are predictable up to two years ahead of time, [11] knowledge of teleconnection patterns gives some amount of predictability in remote locations with an outlook sometimes as long as a few seasons. [12] For instance, predicting El Niño enables prediction of North American rainfall, snowfall, droughts or temperature patterns with a few weeks to months lead time. In Sir Gilbert Walker's time, a strong El Niño usually meant a weaker Indian monsoon, but this anticorrelation has weakened in the 1980s and 1990s, for controversial reasons.[ citation needed ] For Western Europe, knowledge of the NAO can aid the predictability of patterns of temperature and precipitation. For instance, wintertime NAO+ is associated with stronger westerlies and increased precipitation over Northern Europe, whereas NAO- often corresponds to dry and cold periods over Northern Europe and increased storminess over Southern Europe. [13] [14]

See also

Related Research Articles

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El Niño is the warm phase of the El Niño–Southern Oscillation (ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific, including the area off the Pacific coast of South America. The ENSO is the cycle of warm and cold sea surface temperature (SST) of the tropical central and eastern Pacific Ocean.

<span class="mw-page-title-main">Jet stream</span> Fast-flowing atmospheric air current

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<span class="mw-page-title-main">La Niña</span> Coupled ocean-atmosphere phenomenon that is the counterpart of El Niño

La Niña is an oceanic and atmospheric phenomenon that is the colder counterpart of El Niño, as part of the broader El Niño–Southern Oscillation (ENSO) climate pattern. The name La Niña originates from Spanish for "the girl", by analogy to El Niño, meaning "the boy". In the past, it was also called an anti-El Niño and El Viejo, meaning "the old man."

<span class="mw-page-title-main">Climatology</span> Scientific study of climate, defined as weather conditions averaged over a period of time

Climatology or climate science is the scientific study of Earth's climate, typically defined as weather conditions averaged over a period of at least 30 years. This modern field of study is regarded as a branch of the atmospheric sciences and a subfield of physical geography, which is one of the Earth sciences. Climatology now includes aspects of oceanography and biogeochemistry.

<span class="mw-page-title-main">El Niño–Southern Oscillation</span> Physical oceanography

El Niño–Southern Oscillation (ENSO) is an irregular periodic variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean, affecting the climate of much of the tropics and subtropics. The warming phase of the sea temperature is known as El Niño and the cooling phase as La Niña. The Southern Oscillation is the accompanying atmospheric component, coupled with the sea temperature change: El Niño is accompanied by high air surface pressure in the tropical western Pacific and La Niña with low air surface pressure there. The two periods last several months each and typically occur every few years with varying intensity per period.

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Warren White is a professor emeritus, and a former Research Oceanographer at the Marine Biological Research Division at Scripps Institution of Oceanography at UC San Diego.

<span class="mw-page-title-main">Arctic oscillation</span> Climatic cycle over Earths North Pole

The Arctic oscillation (AO) or Northern Annular Mode/Northern Hemisphere Annular Mode (NAM) is a weather phenomenon at the Arctic pole north of 20 degrees latitude. It is an important mode of climate variability for the Northern Hemisphere. The southern hemisphere analogue is called the Antarctic oscillation or Southern Annular Mode (SAM). The index varies over time with no particular periodicity, and is characterized by non-seasonal sea-level pressure anomalies of one sign in the Arctic, balanced by anomalies of opposite sign centered at about 37–45° N.

<span class="mw-page-title-main">Pacific decadal oscillation</span> Recurring pattern of climate variability

The Pacific decadal oscillation (PDO) is a robust, recurring pattern of ocean-atmosphere climate variability centered over the mid-latitude Pacific basin. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 20°N. Over the past century, the amplitude of this climate pattern has varied irregularly at interannual-to-interdecadal time scales. There is evidence of reversals in the prevailing polarity of the oscillation occurring around 1925, 1947, and 1977; the last two reversals corresponded with dramatic shifts in salmon production regimes in the North Pacific Ocean. This climate pattern also affects coastal sea and continental surface air temperatures from Alaska to California.

<span class="mw-page-title-main">Madden–Julian oscillation</span> Tropical atmosphere element of variability

The Madden–Julian oscillation (MJO) is the largest element of the intraseasonal variability in the tropical atmosphere. It was discovered in 1971 by Roland Madden and Paul Julian of the American National Center for Atmospheric Research (NCAR). It is a large-scale coupling between atmospheric circulation and tropical deep atmospheric convection. Unlike a standing pattern like the El Niño–Southern Oscillation (ENSO), the Madden–Julian oscillation is a traveling pattern that propagates eastward, at approximately 4 to 8 m/s, through the atmosphere above the warm parts of the Indian and Pacific oceans. This overall circulation pattern manifests itself most clearly as anomalous rainfall.

<span class="mw-page-title-main">Tropical cyclogenesis</span> Development and strengthening of a tropical cyclone in the atmosphere

Tropical cyclogenesis is the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which temperate cyclogenesis occurs. Tropical cyclogenesis involves the development of a warm-core cyclone, due to significant convection in a favorable atmospheric environment.

<span class="mw-page-title-main">Azores High</span> High air pressure area in the Atlantic Ocean

The Azores High also known as North Atlantic (Subtropical) High/Anticyclone or the Bermuda-Azores High, is a large subtropical semi-permanent centre of high atmospheric pressure typically found south of the Azores in the Atlantic Ocean, at the Horse latitudes. It forms one pole of the North Atlantic oscillation, the other being the Icelandic Low. The system influences the weather and climatic patterns of vast areas of North Africa, Western Asia, Southern Europe, and to a lesser extent, eastern North America. The aridity of the Sahara Desert and the summer drought of the Mediterranean Basin is due to the large-scale subsidence and sinking motion of air in the system. In its summer position, the high is centered near Bermuda, and creates a southwest flow of warm tropical air toward the East Coast of the United States. In summer, the Azores-Bermuda High is strongest. The central pressure hovers around 1024 mbar (hPa).

<span class="mw-page-title-main">Atlantic multidecadal oscillation</span> Climate cycle that affects the surface temperature of the North Atlantic

The Atlantic Multidecadal Oscillation (AMO), also known as Atlantic Multidecadal Variability (AMV), is the theorized variability of the sea surface temperature (SST) of the North Atlantic Ocean on the timescale of several decades.

The Atlantic Equatorial Mode or Atlantic Niño is a quasiperiodic interannual climate pattern of the equatorial Atlantic Ocean. It is the dominant mode of year-to-year variability that results in alternating warming and cooling episodes of sea surface temperatures accompanied by changes in atmospheric circulation. The term Atlantic Niño comes from its close similarity with the El Niño-Southern Oscillation (ENSO) that dominates the tropical Pacific basin. For this reason, the Atlantic Niño is often called the little brother of El Niño. The Atlantic Niño usually appears in northern summer, and is not the same as the Atlantic Meridional (Interhemispheric) Mode that consists of a north-south dipole across the equator and operates more during northern spring. The equatorial warming and cooling events associated with the Atlantic Niño are known to be strongly related to rainfall variability over the surrounding continents, especially in West African countries bordering the Gulf of Guinea. Therefore, understanding of the Atlantic Niño has important implications for climate prediction in those regions. Although the Atlantic Niño is an intrinsic mode to the equatorial Atlantic, there may be a tenuous causal relationship between ENSO and the Atlantic Niño in some circumstances.

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The Tropical Atlantic Variability (TAV) is influenced by internal interaction and external effects. TAV can be discussed in different time scales: seasonal and interannual. tav can be discussed in different time scales:seasonal and interannual.and external effects.

<span class="mw-page-title-main">Pacific Meridional Mode</span> Climate mode in the North Pacific

Pacific Meridional Mode (PMM) is a climate mode in the North Pacific. In its positive state, it is characterized by the coupling of weaker trade winds in the northeast Pacific Ocean between Hawaii and Baja California with decreased evaporation over the ocean, thus increasing sea surface temperatures (SST); and the reverse during its negative state. This coupling develops during the winter months and spreads southwestward towards the equator and the central and western Pacific during spring, until it reaches the Intertropical Convergence Zone (ITCZ), which tends to shift north in response to a positive PMM.

Ocean dynamical thermostat is a physical mechanism through which changes in the mean radiative forcing influence the gradients of sea surface temperatures in the Pacific Ocean and the strength of the Walker circulation. Increased radiative forcing (warming) is more effective in the western Pacific than in the eastern where the upwelling of cold water masses damps the temperature change. This increases the east-west temperature gradient and strengthens the Walker circulation. Decreased radiative forcing (cooling) has the opposite effect.

Rodwell–Hoskins mechanism is a hypothesis about a climatic teleconnection between the Indian/Asian summer monsoon and the climate of the Mediterranean. It stipulates that ascending air in the monsoon region induces atmospheric circulation features named Rossby waves that expand westward and interact with the mean westerly winds of the midlatitudes, eventually inducing descent of the air. Descending air warms and its humidity decreases, thus resulting in a drier climate during the summer months. The interaction of this atmospheric flow with the topography such as the Atlas and Zagros mountains further modifies the effect.

References

  1. ↑ Lamb, Peter J.; Peppler, Randy A. (1987-10-01). "North Atlantic Oscillation: Concept and an Application". Bulletin of the American Meteorological Society. 68 (10): 1218–1225. doi:10.1175/1520-0477(1987)068<1218:NAOCAA>2.0.CO;2. ISSN   1520-0477.
  2. ↑ Wallace, John M.; Gutzler, David S. (1981). "Teleconnections in the Geopotential Height Field during the Northern Hemisphere Winter". Monthly Weather Review. 109 (4): 784. Bibcode:1981MWRv..109..784W. doi: 10.1175/1520-0493(1981)109<0784:TITGHF>2.0.CO;2 .
  3. ↑ Hoskins, Brian J.; Karoly, David J. (1981). "The Steady Linear Response of a Spherical Atmosphere to Thermal and Orographic Forcing". Journal of the Atmospheric Sciences. 38 (6): 1179. Bibcode:1981JAtS...38.1179H. doi: 10.1175/1520-0469(1981)038<1179:TSLROA>2.0.CO;2 .
  4. ↑ Trenberth, Kevin E.; Branstator, Grant W.; Karoly, David; Kumar, Arun; Lau, Ngar-Cheung; Ropelewski, Chester (1998). "Progress during TOGA in understanding and modeling global teleconnections associated with tropical sea surface temperatures". Journal of Geophysical Research. 103 (C7): 14291–14324. Bibcode:1998JGR...10314291T. doi: 10.1029/97JC01444 .
  5. ↑ Gill, A. E. (1980). "Some simple solutions for heat-induced tropical circulation". Quarterly Journal of the Royal Meteorological Society. 106 (449): 447–462. Bibcode:1980QJRMS.106..447G. doi:10.1002/qj.49710644905.
  6. ↑ Simmons, A. J.; Wallace, J. M.; Branstator, G. W. (1983). "Barotropic Wave Propagation and Instability, and Atmospheric Teleconnection Patterns". Journal of the Atmospheric Sciences. 40 (6): 1363. Bibcode:1983JAtS...40.1363S. doi: 10.1175/1520-0469(1983)040<1363:BWPAIA>2.0.CO;2 .
  7. ↑ Held, Isaac M.; Ting, Mingfang; Wang, Hailan (2002). "Northern Winter Stationary Waves: Theory and Modeling". Journal of Climate. 15 (16): 2125. Bibcode:2002JCli...15.2125H. CiteSeerX   10.1.1.140.5658 . doi:10.1175/1520-0442(2002)015<2125:NWSWTA>2.0.CO;2.
  8. ↑ Seager, Richard; Harnik, Nili; Kushnir, Yochanan; Robinson, Walter; Miller, Jennifer (2003). "Mechanisms of Hemispherically Symmetric Climate Variability*". Journal of Climate. 16 (18): 2960. Bibcode:2003JCli...16.2960S. doi:10.1175/1520-0442(2003)016<2960:MOHSCV>2.0.CO;2.
  9. ↑ Seager, R.; Harnik, N.; Robinson, W. A.; Kushnir, Y.; Ting, M.; Huang, H.-P.; Velez, J. (2005). "Mechanisms of ENSO-forcing of hemispherically symmetric precipitation variability". Quarterly Journal of the Royal Meteorological Society. 131 (608): 1501. Bibcode:2005QJRMS.131.1501S. doi:10.1256/qj.04.96.
  10. ↑ Ramadan, H. H.; Ramamurthy, A. S.; Beighley, R. E. (2011). "Inter-annual temperature and precipitation variations over the Litani Basin in response to atmospheric circulation patterns". Theoretical and Applied Climatology. 108 (3–4): 563. Bibcode:2012ThApC.108..563R. doi:10.1007/s00704-011-0554-1.
  11. ↑ Chen, Dake; Cane, Mark A.; Kaplan, Alexey; Zebiak, Stephen E.; Huang, Daji (2004). "Predictability of El Niño over the past 148 years". Nature. 428 (6984): 733–6. Bibcode:2004Natur.428..733C. doi:10.1038/nature02439. PMID   15085127.
  12. ↑ IRI Seasonal Climate Forecasts
  13. ↑ Wanner, Heinz; Brönnimann, Stefan; Casty, Carlo; Gyalistras, Dimitrios; Luterbacher, Jürg; Schmutz, Christoph; Stephenson, David B.; Xoplaki, Eleni (2001-07-01). "North Atlantic Oscillation – Concepts And Studies". Surveys in Geophysics. 22 (4): 321–381. doi:10.1023/A:1014217317898. ISSN   1573-0956.
  14. ↑ "North Atlantic Oscillation (NAO) | National Centers for Environmental Information (NCEI)". www.ncei.noaa.gov. Retrieved 2023-04-05.

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