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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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. Climate concerns the atmospheric condition during an extended to indefinite period of time; weather is the condition of the atmosphere during a relative brief period of time. The main topics of research are the study of climate variability, mechanisms of climate changes and modern climate change. This topic of study is regarded as part of the atmospheric sciences and a subdivision of physical geography, which is one of the Earth sciences. Climatology includes some aspects of oceanography and biogeochemistry.

<span class="mw-page-title-main">El Niño–Southern Oscillation</span> Climate phenomenon that periodically fluctuates between three phases

El Niño–Southern Oscillation (ENSO) is a global climate phenomenon that emerges from variations in winds and sea surface temperatures over the tropical Pacific Ocean. Those variations have an irregular pattern but do have some semblance of cycles. The occurrence of ENSO is not predictable. It affects the climate of much of the tropics and subtropics, and has links (teleconnections) to higher-latitude regions of the world. The warming phase of the sea surface temperature is known as El Niño and the cooling phase as La Niña. The Southern Oscillation is the accompanying atmospheric oscillation, which is coupled with the sea temperature change.

The North Atlantic Oscillation (NAO) is a weather phenomenon over the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level (SLP) between the Icelandic Low and the Azores High. Through fluctuations in the strength of the Icelandic Low and the Azores High, it controls the strength and direction of westerly winds and location of storm tracks across the North Atlantic.

<span class="mw-page-title-main">Intertropical Convergence Zone</span> Meteorological phenomenon

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<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.

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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

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<span class="mw-page-title-main">Indian Ocean Dipole</span> Climatic and oceanographic cycle affecting Southeast Asia, Australia and Africa

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<span class="mw-page-title-main">Pacific–North American teleconnection pattern</span> Large-scale weather pattern with two modes

The Pacific–North American teleconnection pattern (PNA) is 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. It is the second leading mode of natural climate variability in the higher latitudes of the Northern Hemisphere and can be diagnosed using the arrangement of anomalous geopotential heights or air pressures over the North Pacific and North America.

<span class="mw-page-title-main">North Pacific Oscillation</span> Climatic cycle affecting North America and East Asia

The North Pacific Oscillation (NPO) is a teleconnection pattern first described by Walker and Bliss and characterized by a north–south seesaw in sea-level pressure over the North Pacific Ocean.
Rogers, using surface atmospheric temperature from St. Paul, Alaska, and Edmonton, identified two phases of the NPO, an Aleutian below (AB) phase that correspond to a deepened and eastward shifted Aleutian Low and an Aleutian above (AA) phase that is the opposite.

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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.

The Rodwell–Hoskins mechanism is a hypothesis describing a climatic teleconnection between the Indian/Asian summer monsoon and the climate of the Mediterranean. It was formulated in 1996 by Brian Hoskins and Mark J. Rodwell [d]. The hypothesis 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 topography 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. S2CID   16702649.
  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. S2CID   122209745.
  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. S2CID   4372358.
  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. S2CID   17661504.
  14. ↑ "North Atlantic Oscillation (NAO) | National Centers for Environmental Information (NCEI)". www.ncei.noaa.gov. Retrieved 2023-04-05.

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