# Tropical Easterly Jet

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Tropical_Easterly_Jet
> Markdown URL: https://mediated.wiki/source/Tropical_Easterly_Jet.md
> Source: https://en.wikipedia.org/wiki/Tropical_Easterly_Jet
> Source revision: 1351822980
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

Jet stream

The **Tropical Easterly Jet** ([jet stream](/source/Jet_stream)) is the [meteorological](/source/Meteorological) term referring to an upper level easterly [wind](/source/Wind) that forms in late June and continues until early September. This strong flow of air that develops in the upper [atmosphere](/source/Atmosphere) during [the Asian monsoon](/source/Monsoon_of_South_Asia) is centred on 15°N, 50-80°E and extends from [South-East Asia](/source/South-East_Asia) to [Africa](/source/Africa).

A much weaker easterly jet exists in the northeast Pacific associated with the [North American Monsoon](/source/North_American_Monsoon).[1]

## Meteorology

The strongest development of the jet is at about 15 kilometres (9 mi) above the Earth's surface with wind speeds of up to 40 metres per second (140 km/h; 89 mph; 78 kn) over the [Indian Ocean](/source/Indian_Ocean).[2] This jet subsides at the [Somalia](/source/Somalia) coast with the Mascarene High,[3] and in the [Sahara Desert](/source/Sahara_Desert). It has been suggested that the subsidence in the northwestern quadrant of the Tropical Easterly Jet is an important factor producing the exceptional hyperaridity of the Sahara[4] – drier than any other desert outside of coastal [upwelling](/source/Upwelling) zones.[5][6]

The easterly jet induces significant vertical wind shear during the monsoonal months, especially from July to September, which suppresses any [tropical cyclone](/source/North_Indian_Ocean_tropical_cyclone) activity.[note 1]

## History of study

Although the upper-level easterly wind flow over India during the summer monsoon was established as early as the 1930s, the term "easterly jet" originated with Indian researcher P.R. Krishna Rao in 1952.[7] P. Koteswaram later in the 1950s demonstrated that the easterly flow is a jet stream in the strict sense of the term.[8] During the 1960s and 1970s it became recognised that the Tropical Easterly Jet arises due to the intense solar heating of the [Tibetan Plateau](/source/Tibetan_Plateau),[9] and that it was closely linked to the Asian monsoon in both day-to-day fluctuations and overall seasonal strength.

## Relationship with Asian monsoon

The Tropical Easterly Jet's outflow from the Tibetan Plateau is deeply connected to the low-level monsoonal flow over India. Studies have demonstrated that when the high-level easterly jet is weak, monsoonal rainfall over India[10] and seasonal rainfall as far east as [Micronesia](/source/Micronesia)[11] will be deficient.

It has been more recently suggested that variations in surface rainfall can actually drive variations in the strength of the jet,[12] contradicting earlier suggestions that the surface southwesterly monsoon flow is actually a return flow from the upper-level easterlies.

## Recent weakening

Since 1950, the Tropical Easterly Jet has weakened by as much as 25 percent, so that the contour of 30 metres per second (110 km/h; 67 mph; 58 kn) has disappeared.[13][14] This trend has been attributed to a combination of low-level [global warming](/source/Global_warming) with cooling near the [tropopause](/source/Tropopause) over continental Asia.[14] Other studies show that the greatest weakening has occurred in the highest-altitude parts of the jet, and in the westerly section over the [Arabian Sea](/source/Arabian_Sea).[15] The declining strength of the Tropical Easterly Jet has been tightly linked with declining rainfall over [Arunachal Pradesh](/source/Arunachal_Pradesh), [Jammu and Kashmir](/source/Jammu_and_Kashmir_(union_territory)) and certain parts of central India and the [Malabar Coast](/source/Malabar_Coast).[16] Further weakenings of the jet are expected under enhanced greenhouse gases – by at least 11 percent at the end of the twenty-first century.[1]

The northeastern Pacific easterly jet, however, is expected to weaken by as much as 77 percent under likely global warming scenarios,[1] which could reduce annual rainfall over [Central America](/source/Central_America) and [southern Mexico](/source/Administrative_divisions_of_Mexico#Regions_and_districts) by as much as 1,000 millimetres or 40 inches.

## See also

- [African easterly jet](/source/African_easterly_jet)

- [Somali Jet](/source/Somali_Jet)

## Notes

1. **[^](#cite_ref-7)** Monsoonal depressions, characteristic of the monsoon season in India, generally do not intensify into cyclones

## References

1. ^ [***a***](#cite_ref-Dramatic_1-0) [***b***](#cite_ref-Dramatic_1-1) [***c***](#cite_ref-Dramatic_1-2) Sihua Huang; Bin Wang; Zhiping Wen (October 2020). "Dramatic Weakening of the Tropical Easterly Jet Projected by CMIP6 Models". *Journal of Climate*. **33** (19): 8439–8455. [Bibcode](/source/Bibcode_(identifier)):[2020JCli...33.8439H](https://ui.adsabs.harvard.edu/abs/2020JCli...33.8439H). [doi](/source/Doi_(identifier)):[10.1175/JCLI-D-19-1002.1](https://doi.org/10.1175%2FJCLI-D-19-1002.1).

1. **[^](#cite_ref-2)** Hastenrath, Stefan (1985). *Climate and Circulation of the Tropics*. Kluwer Academic Publishers. p. 464. [ISBN](/source/ISBN_(identifier)) [90-277-2026-6](https://en.wikipedia.org/wiki/Special:BookSources/90-277-2026-6).

1. **[^](#cite_ref-3)** Krishnamurte, T.N.; Bhalme, H.N. (October 1976). "Oscillations of a Monsoon System. Part 1. Observational Aspects". *Journal of the Atmospheric Sciences*. **33** (10): 1937–1954. [Bibcode](/source/Bibcode_(identifier)):[1976JAtS...33.1937K](https://ui.adsabs.harvard.edu/abs/1976JAtS...33.1937K). [doi](/source/Doi_(identifier)):[10.1175/1520-0469(1976)033<1937:OOAMSP>2.0.CO;2](https://doi.org/10.1175%2F1520-0469%281976%29033%3C1937%3AOOAMSP%3E2.0.CO%3B2).

1. **[^](#cite_ref-4)** Webster, Peter J.; Fasullo, John (2003). "Monsoon: Dynamical Theory". In Holton, James R.; Curry, Judith A. (eds.). *Encyclopedia of Atmospheric Sciences*. London: Academic Press. pp. 1370–1385.

1. **[^](#cite_ref-5)** Nicholson, Sharon E. (27 October 2011). *Dryland Climatology*. Cambridge University Press. p. 303. [ISBN](/source/ISBN_(identifier)) [9781139500241](https://en.wikipedia.org/wiki/Special:BookSources/9781139500241).

1. **[^](#cite_ref-6)** Besla, Helga. "The Tropical Easterly Jet as a Cause for Intensified Aridity in the Sahara". In [Coetzee, Johanna Alida](/source/Johanna_Alida_Coetzee); van Zinderen-Bakker, Eduard Meine (eds.). *Palaeoecology of Africa, volume 16*. pp. 163–172. [ISBN](/source/ISBN_(identifier)) [9780203744512](https://en.wikipedia.org/wiki/Special:BookSources/9780203744512).

1. **[^](#cite_ref-8)** Krishna Rao, P.R. (1952). "Probable Regions of Jet Streams in the Upper Air over India". *Current Science*. **21**. [Bangalore](/source/Bangalore): Current Science Association.

1. **[^](#cite_ref-9)** Koteswaram, P. (19–21 February 1958). "The Indian Summer Monsoon and the General Circulation Over the Tropics". *Symposium on Monsoons of the World*. Meteorological Office, New Delhi.

1. **[^](#cite_ref-10)** Mason, Ralph B.; Anderson, Calvin E. (January 1963). "The Development and Decay of the 100 mb. Summertime Anticyclone over Southern Asia". *[Monthly Weather Review](/source/Monthly_Weather_Review)*. **91** (1): 3–12. [Bibcode](/source/Bibcode_(identifier)):[1963MWRv...91....3M](https://ui.adsabs.harvard.edu/abs/1963MWRv...91....3M). [doi](/source/Doi_(identifier)):[10.1175/1520-0493(1963)091<0003:TDADOT>2.3.CO;2](https://doi.org/10.1175%2F1520-0493%281963%29091%3C0003%3ATDADOT%3E2.3.CO%3B2).

1. **[^](#cite_ref-11)** Pattanaik, D. R.; Satyan, V. (2000). "Fluctuations of Tropical Easterly Jet during contrasting monsoons over India: A GCM study". *Meteorology and Atmospheric Physics*. **75** (1–2): 51–60. [Bibcode](/source/Bibcode_(identifier)):[2000MAP....75...51P](https://ui.adsabs.harvard.edu/abs/2000MAP....75...51P). [doi](/source/Doi_(identifier)):[10.1007/s007030070015](https://doi.org/10.1007%2Fs007030070015).

1. **[^](#cite_ref-12)** Minoru Tanaka (June 1982). "Internal Fluctuations of the Tropical Easterly Jet and the Summer Monsoon in the Asian Region". *Journal of the Meteorological Society of Japan*. **60** (3): 865–875.

1. **[^](#cite_ref-13)** Naidu, C.V.; Krishna, K. Muni; Ramalingeswara Rao, S.; Bhanu Kumar, O.S.R.U.; Durgalakshmi, K.; Ramakrishna, S.S.V.S. (January 2011). "Variations of Indian summer monsoon rainfall induce the weakening of easterly jet stream in the warming environment?". *Global and Planetary Change*. **75** (1–2): 21–30. [Bibcode](/source/Bibcode_(identifier)):[2011GPC....75...21N](https://ui.adsabs.harvard.edu/abs/2011GPC....75...21N). [doi](/source/Doi_(identifier)):[10.1016/j.gloplacha.2010.10.001](https://doi.org/10.1016%2Fj.gloplacha.2010.10.001).

1. **[^](#cite_ref-14)** Srinivasa Rao, B. R.; Bhaskar Rao, D. V.; Brahmananda Rao, V. (2004). "Decreasing trend in the strength of Tropical Easterly Jet during the Asian summer monsoon season and the number of tropical cyclonic systems over Bay of Bengal". *Geophysical Research Letters*. **31**. [Visakhapatnam](/source/Visakhapatnam): Department of Meteorology and Oceanography, [Andhra University](/source/Andhra_University).

1. ^ [***a***](#cite_ref-Weakening_15-0) [***b***](#cite_ref-Weakening_15-1) Abish, B.; Joseph, P.V.; Johannessen, Ola M. (1 December 2013). ["Weakening Trend of the Tropical Easterly Jet Stream of the Boreal Summer Monsoon Season 1950–2009"](https://doi.org/10.1175%2FJCLI-D-13-00440.1). *Journal of Climate*. **26** (23): 9409–9414. [Bibcode](/source/Bibcode_(identifier)):[2013JCli...26.9408A](https://ui.adsabs.harvard.edu/abs/2013JCli...26.9408A). [doi](/source/Doi_(identifier)):[10.1175/JCLI-D-13-00440.1](https://doi.org/10.1175%2FJCLI-D-13-00440.1).

1. **[^](#cite_ref-16)** Rai, P.; Dimri, A. P. (2017). "Effect of changing tropical easterly jet, low level jet and quasi-biennial oscillation phases on Indian summer monsoon". *Atmospheric Science Letters*. **18**: 52–59.

1. **[^](#cite_ref-17)** Sreekala, P. P.; Bhaskara Rao, S. V.; Arunachalam, M. S.; Harikiran, C. (November 2013). *A study on the decreasing trend in tropical easterly jet stream (TEJ) and its impact on Indian summer monsoon rainfall*. Theoretical and Applied Climatology.

---
Adapted from the Wikipedia article [Tropical Easterly Jet](https://en.wikipedia.org/wiki/Tropical_Easterly_Jet) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Tropical_Easterly_Jet?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.