Characteristics and Mechanisms of the Interannual Variability of the Northwest–Southeast Shift of the Tropical Easterly Jet’s Core in July

Shihua Liu aDepartment of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences, Fudan University, Shanghai, China

Search for other papers by Shihua Liu in
Current site
Google Scholar
PubMed
Close
https://orcid.org/0000-0003-3314-8397
,
Sihua Huang aDepartment of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences, Fudan University, Shanghai, China

Search for other papers by Sihua Huang in
Current site
Google Scholar
PubMed
Close
https://orcid.org/0000-0001-9008-6183
,
Yanke Tan aDepartment of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences, Fudan University, Shanghai, China

Search for other papers by Yanke Tan in
Current site
Google Scholar
PubMed
Close
,
Zhiping Wen aDepartment of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences, Fudan University, Shanghai, China
bInstitute of Eco-Chongming, Shanghai, China
cShanghai Key Laboratory of Ocean-Land-Atmosphere Boundary Dynamics and Climate Change, Fudan University, Shanghai, China
dJiangsu Collaborative Innovation Center for Climate Change, Nanjing, China

Search for other papers by Zhiping Wen in
Current site
Google Scholar
PubMed
Close
,
Xiaodan Chen aDepartment of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences, Fudan University, Shanghai, China

Search for other papers by Xiaodan Chen in
Current site
Google Scholar
PubMed
Close
, and
Yuanyuan Guo aDepartment of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences, Fudan University, Shanghai, China

Search for other papers by Yuanyuan Guo in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

Previous studies have pointed out that the tropical easterly jet (TEJ) core varies longitudinally or latitudinally. Whether there is a linkage between longitudinal and latitudinal variations of the TEJ core remains unclear. We found that, on the interannual time scale, the northward (southward) movement of the TEJ core is typically accompanied by a westward (eastward) shift, characterized by a noticeable northwest–southeast (NW–SE) displacement. This NW–SE shift is most evident in July. A locational index is defined to capture this shift by the difference of area-averaged 200-hPa zonal winds between the western Arabian Sea (AS) and the southern tip of the Indian Peninsula. Observations and numerical simulations demonstrated that the northwestward-shifted (southeastward-shifted) TEJ core is caused by the joint and individual influences from the enhanced (suppressed) convective activities over the eastern AS and suppressed (enhanced) convective activities over the northern Bay of Bengal–South China Sea (BOB–SCS). Enhanced (suppressed) convective activities over the eastern AS can induce upper-tropospheric divergence (convergence) and anticyclonic (cyclonic) circulations to the northwest of the convection, leading to anomalous easterly (westerly) over the western AS. The suppressed (enhanced) convective activities over the northern BOB–SCS can further facilitate the northwestward (southeastward) shift through inducing anomalous cyclonic (anticyclonic) circulation centering at the BOB and the associated anomalous westerly (easterly) over the southern tip of the Indian Peninsula. The NW–SE shift of the TEJ core may have an implication for the change in the area of the intense rainfall in South Asia.

Significance Statement

The purpose of this study is to explore the linkage between the zonal and meridional variations of the core of the tropical easterly jet (TEJ) and its underlying mechanisms. We found that the TEJ core features a pronounced northwest–southeast shift and this phenomenon only occurs in July. Thus, we defined a locational index to depict this unique characteristic and reveal its relationship with the anomalous convective activities over the eastern Arabian Sea and the northern Bay of Bengal–South China Sea. These results may help improve our understanding of the characteristics and mechanisms of the variations of the TEJ core.

© 2024 American Meteorological Society. This published article is licensed under the terms of the default AMS reuse license. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Sihua Huang, huangsh@fudan.edu.cn

Abstract

Previous studies have pointed out that the tropical easterly jet (TEJ) core varies longitudinally or latitudinally. Whether there is a linkage between longitudinal and latitudinal variations of the TEJ core remains unclear. We found that, on the interannual time scale, the northward (southward) movement of the TEJ core is typically accompanied by a westward (eastward) shift, characterized by a noticeable northwest–southeast (NW–SE) displacement. This NW–SE shift is most evident in July. A locational index is defined to capture this shift by the difference of area-averaged 200-hPa zonal winds between the western Arabian Sea (AS) and the southern tip of the Indian Peninsula. Observations and numerical simulations demonstrated that the northwestward-shifted (southeastward-shifted) TEJ core is caused by the joint and individual influences from the enhanced (suppressed) convective activities over the eastern AS and suppressed (enhanced) convective activities over the northern Bay of Bengal–South China Sea (BOB–SCS). Enhanced (suppressed) convective activities over the eastern AS can induce upper-tropospheric divergence (convergence) and anticyclonic (cyclonic) circulations to the northwest of the convection, leading to anomalous easterly (westerly) over the western AS. The suppressed (enhanced) convective activities over the northern BOB–SCS can further facilitate the northwestward (southeastward) shift through inducing anomalous cyclonic (anticyclonic) circulation centering at the BOB and the associated anomalous westerly (easterly) over the southern tip of the Indian Peninsula. The NW–SE shift of the TEJ core may have an implication for the change in the area of the intense rainfall in South Asia.

Significance Statement

The purpose of this study is to explore the linkage between the zonal and meridional variations of the core of the tropical easterly jet (TEJ) and its underlying mechanisms. We found that the TEJ core features a pronounced northwest–southeast shift and this phenomenon only occurs in July. Thus, we defined a locational index to depict this unique characteristic and reveal its relationship with the anomalous convective activities over the eastern Arabian Sea and the northern Bay of Bengal–South China Sea. These results may help improve our understanding of the characteristics and mechanisms of the variations of the TEJ core.

© 2024 American Meteorological Society. This published article is licensed under the terms of the default AMS reuse license. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Sihua Huang, huangsh@fudan.edu.cn

Supplementary Materials

    • Supplemental Materials (PDF 1.0626 MB)
Save
  • Abish, B., P. V. Joseph, and O. M. Johannessen, 2013: Weakening trend of the tropical easterly jet stream of the boreal summer monsoon season 1950–2009. J. Climate, 26, 94089414, https://doi.org/10.1175/JCLI-D-13-00440.1.

    • Search Google Scholar
    • Export Citation
  • Arkin, P. A., 1982: The relationship between interannual variability in the 200 mb tropical wind field and the southern oscillation. Mon. Wea. Rev., 110, 13931404, https://doi.org/10.1175/1520-0493(1982)110<1393:TRBIVI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Brown, T. J., and B. L. Hall, 1999: The use of t values in climatological composite analyses. J. Climate, 12, 29412944, https://doi.org/10.1175/1520-0442(1999)012<2941:TUOTVI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Cai, W., and Coauthors, 2014: Increasing frequency of extreme El Niño events due to greenhouse warming. Nat. Climate Change, 4, 111116, https://doi.org/10.1038/nclimate2100.

    • Search Google Scholar
    • Export Citation
  • Chen, H., Y. Ding, and J. He, 2007: The structure and variation of tropical easterly jet and its relationship with the monsoon rainfall in Asia and Africa (in Chinese). Chin. J. Atmos. Sci., 31, 926936, https://doi.org/10.3878/j.issn.1006-9895.2007.05.16.

    • Search Google Scholar
    • Export Citation
  • Chen, T.-C., and H. van Loon, 1987: Interannual variation of the tropical easterly jet. Mon. Wea. Rev., 115, 17391759, https://doi.org/10.1175/1520-0493(1987)115<1739:IVOTTE>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Chen, T.-C., and M.-C. Yen, 1991: Intraseasonal variations of the tropical easterly jet during the 1979 northern summer. Tellus, 43A, 213225, https://doi.org/10.3402/tellusa.v43i3.11928.

    • Search Google Scholar
    • Export Citation
  • Ding, Y., S. Zhao, and X. Fu, 1988: A study of the long-term mean circulation at 200 hPa over the global tropics and subtropics during northern summer-Part II: Planetary scale wind systems (in Chinese). Chin. J. Atmos. Sci., 12, 242249, https://doi.org/10.3878/j.issn.1006-9895.1988.03.03.

    • Search Google Scholar
    • Export Citation
  • Flohn, H., 1964: Investigations on the tropical easterly jet. Bonner Meteorology Abhandlungen, 83 pp., https://www2.meteo.unibonn.de/bibliothek/Flohn_Publikationen/K141-K190_1959-1965/K176.pdf.

  • Gill, A. E., 1980: Some simple solutions for heat-induced tropical circulation. Quart. J. Roy. Meteor. Soc., 106, 447462, https://doi.org/10.1002/qj.49710644905.

    • Search Google Scholar
    • Export Citation
  • Guo, Y., Z. Wen, R. Wu, R. Lu, and Z. Chen, 2015: Impact of tropical pacific precipitation anomaly on the East Asian upper-tropospheric westerly jet during the boreal winter. J. Climate, 28, 64576474, https://doi.org/10.1175/JCLI-D-14-00674.1.

    • Search Google Scholar
    • Export Citation
  • Haltiner, G. J., and R. T. Williams, 1984: Numerical Prediction and Dynamic Meteorology. 2nd ed. J. Wiley & Sons Ltd., 477 pp.

  • Hendon, H. H., 1986: Streamfunction and velocity potential representation of equatorially trapped waves. J. Atmos. Sci., 43, 30383042, https://doi.org/10.1175/1520-0469(1986)043<3038:SAVPRO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Hersbach, H., and Coauthors, 2018: Operational global reanalysis: Progress, future directions and synergies with NWP. ERA Rep. Series 27, 65 pp., https://doi.org/10.21957/tkic6g3wm.

  • Hersbach, H., and Coauthors, 2019: Global reanalysis: Goodbye ERA-interim, hello ERA5. ECMWF Newsletter, No. 159, ECMWF, Reading, United Kingdom, 17–24, https://www.ecmwf.int/sites/default/files/elibrary/2019/19027-global-reanalysis-goodbye-era-interim-hello-era5.pdf.

  • Hu, K., and S.-M. Long, 2020: Optimal heat source for the interannual variability of the western North Pacific summer monsoon. Atmos. Ocean. Sci. Lett., 13, 4147, https://doi.org/10.1080/16742834.2019.1680087.

    • Search Google Scholar
    • Export Citation
  • Huang, S., B. Wang, and Z. Wen, 2020: Dramatic weakening of the tropical easterly jet projected by CMIP6 models. J. Climate, 33, 84398455, https://doi.org/10.1175/JCLI-D-19-1002.1.

    • Search Google Scholar
    • Export Citation
  • Hulme, M., and N. Tosdevin, 1989: The tropical easterly jet and Sudan rainfall: A review. Theor. Appl. Climatol., 39, 179187, https://doi.org/10.1007/BF00867945.

    • Search Google Scholar
    • Export Citation
  • Izumo, T., J. Vialard, M. Lengaigne, and I. Suresh, 2020: Relevance of relative sea surface temperature for tropical rainfall interannual variability. Geophys. Res. Lett., 47, e2019GL086182, https://doi.org/10.1029/2019GL086182.

    • Search Google Scholar
    • Export Citation
  • Koteswaram, P., 1958: The easterly jet stream in the tropics. Tellus, 10A, 4357, https://doi.org/10.3402/tellusa.v10i1.9220.

  • Krishnamurti, T. N., and H. N. Bhalme, 1976: Oscillations of a monsoon system. Part I: Observational aspects. J. Atmos. Sci., 33, 19371954, https://doi.org/10.1175/1520-0469(1976)033<1937:OOAMSP>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Krishnamurti, T. N., and C. M. Kishtawal, 2000: A pronounced continental-scale diurnal mode of the Asian summer monsoon. Mon. Wea. Rev., 128, 462473, https://doi.org/10.1175/1520-0493(2000)128<0462:APCSDM>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Krishnamurti, T. N., N. Karmakar, V. Misra, B. Nag, D. Sahu, S. Dubey, and Z. Haddad, 2018: Association between upper level diffluence in the tropical easterly jet and the formation of the strongest Atlantic hurricanes in recent years. Proc. SPIE, 10782, 1078206, https://doi.org/10.1117/12.2500287.

    • Search Google Scholar
    • Export Citation
  • Lemburg, A., J. Bader, and M. Claussen, 2019: Sahel rainfall-tropical easterly jet relationship on synoptic to intraseasonal time scales. Mon. Wea. Rev., 147, 17331752, https://doi.org/10.1175/MWR-D-18-0254.1.

    • Search Google Scholar
    • Export Citation
  • Lu, J., and Y. Ding, 1989: Climatic study on the summer tropical easterly jet at 200 hPa. Adv. Atmos. Sci., 6, 215226, https://doi.org/10.1007/BF02658017.

    • Search Google Scholar
    • Export Citation
  • Matsuno, T., 1966: Quasi-geostrophic motions in the equatorial area. J. Meteor. Soc. Japan, 44, 2543, https://doi.org/10.2151/jmsj1965.44.1_25.

    • Search Google Scholar
    • Export Citation
  • Nicholson, S. E., 2008: The intensity, location and structure of the tropical rainbelt over West Africa as factors in interannual variability. Int. J. Climatol., 28, 17751785, https://doi.org/10.1002/joc.1507.

    • Search Google Scholar
    • Export Citation
  • Nicholson, S. E., A. I. Barcilon, M. Challa, and J. Baum, 2007: Wave activity on the tropical easterly jet. J. Atmos. Sci., 64, 27562763, https://doi.org/10.1175/JAS3946.1.

    • Search Google Scholar
    • Export Citation
  • Nithya, K., M. G. Manoj, and K. Mohankumar, 2017: Effect of El Niño/La Niña on tropical easterly jet stream during Asian summer monsoon season. Int. J. Climatol., 37, 49945004, https://doi.org/10.1002/joc.5137.

    • Search Google Scholar
    • Export Citation
  • Pattanaik, D. R., and V. Satyan, 2000: Fluctuations of tropical easterly jet during contrasting monsoons over India: AGCM study. Meteor. Atmos. Phys., 75, 5160, https://doi.org/10.1007/s007030070015.

    • Search Google Scholar
    • Export Citation
  • Rai, P., and A. P. Dimri, 2017: Effect of changing tropical easterly jet, low level jet and quasi-biennial oscillation phases on Indian summer. Atmos. Sci. Lett., 18, 5259, https://doi.org/10.1002/asl.723.

    • Search Google Scholar
    • Export Citation
  • Raman, M. R., V. V. M. J. Rao, M. V. Ratnam, M. Rajeevan, S. V. B. Rao, D. N. Rao, and N. P. Rao, 2009: Characteristics of the tropical easterly jet: Long-term trends and their features during active and break monsoon phases. J. Geophys. Res., 114, D19105, https://doi.org/10.1029/2009JD012065.

    • Search Google Scholar
    • Export Citation
  • Rao, B. R. S., D. V. B. Rao, and V. B. Rao, 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. Geophys. Res. Lett., 31, L14103, https://doi.org/10.1029/2004GL019817.

    • Search Google Scholar
    • Export Citation
  • Rao, S., 2016: Sensitivity of the tropical easterly jet to the distribution and magnitude of latent heating in an aqua-planet model. J. Meteor. Soc. Japan, 94, 371388, https://doi.org/10.2151/jmsj.2016-020.

    • Search Google Scholar
    • Export Citation
  • Rao, S., and J. Srinivasan, 2016: The impact of latent heating on the location and strength of the tropical easterly jet. Meteor. Atmos. Phys., 128, 247261, https://doi.org/10.1007/s00703-015-0407-z.

    • Search Google Scholar
    • Export Citation
  • Rao, V. B., C. C. Ferreira, S. H. Franchito, and S. S. V. S. Ramakrishna, 2008: In a changing climate weakening tropical easterly jet induces more violent tropical storms over the North Indian Ocean. Geophys. Res. Lett., 35, L15710, https://doi.org/10.1029/2008GL034729.

    • Search Google Scholar
    • Export Citation
  • Rayner, N. A., D. E. Parker, E. B. Horton, C. K. Folland, L. V. Alexander, D. P. Rowell, E. C. Kent, and A. Kaplan, 2003: Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J. Geophys. Res., 108, 4407, https://doi.org/10.1029/2002JD002670.

    • Search Google Scholar
    • Export Citation
  • Sathiyamoorthy, V., P. K. Pal, and P. C. Joshi, 2004: Influence of the upper-tropospheric wind shear upon cloud radiative forcing in the Asian monsoon region. J. Climate, 17, 27252735, https://doi.org/10.1175/1520-0442(2004)017<2725:IOTUWS>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Sathiyamoorthy, V., P. K. Pal, and P. C. Joshi, 2007: Intraseasonal variability of the tropical easterly jet. Meteor. Atmos. Phys., 96, 305316, https://doi.org/10.1007/s00703-006-0214-7.

    • Search Google Scholar
    • Export Citation
  • Sekizawa, S., H. Nakamura, and Y. Kosaka, 2018: Interannual variability of the Australian summer monsoon system internally sustained through wind-evaporation feedback. Geophys. Res. Lett., 45, 77487755, https://doi.org/10.1029/2018GL078536.

    • Search Google Scholar
    • Export Citation
  • Tanaka, M., 1982: Interannual fluctuations of the tropical easterly jet and the summer monsoon in the Asian region. J. Meteor. Soc. Japan, 60, 865875, https://doi.org/10.2151/jmsj1965.60.3_865.

    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., and D. J. Shea, 2005: Relationships between precipitation and surface temperature. Geophys. Res. Lett., 32, L14703, https://doi.org/10.1029/2005GL022760.

    • Search Google Scholar
    • Export Citation
  • Wang, B., X. Luo, Y.-M. Yang, W. Sun, M. A. Cane, W. Cai, S.-W. Yeh, and J. Liu, 2019: Historical change of El Niño properties sheds light on future changes of extreme El Niño. Proc. Natl. Acad. Sci. USA, 116, 22 51222 517, https://doi.org/10.1073/pnas.1911130116.

    • Search Google Scholar
    • Export Citation
  • Wang, B., C. Jin, and J. Liu, 2020: Understanding future change of global monsoons projected by CMIP6 models. J. Climate, 33, 64716489, https://doi.org/10.1175/JCLI-D-19-0993.1.

    • Search Google Scholar
    • Export Citation
  • Watanabe, M., and M. Kimoto, 2000: Atmosphere–ocean thermal coupling in the North Atlantic: A positive feedback. Quart. J. Roy. Meteor. Soc., 126, 33433369, https://doi.org/10.1002/qj.49712657017.

    • Search Google Scholar
    • Export Citation
  • Webster, P. J., and J. Fasullo, 2003: Monsoon: Dynamical theory. Encyclopedia of Atmospheric Sciences, Academic Press, 1370–1386, https://doi.org/10.1016/B0-12-227090-8/00236-0.

  • Wei, W., R. Zhang, M. Wen, B.-J. Kim, and J.-C. Nam, 2015: Interannual variation of the South Asian high and its relation with Indian and East Asian summer monsoon rainfall. J. Climate, 28, 26232634, https://doi.org/10.1175/JCLI-D-14-00454.1.

    • Search Google Scholar
    • Export Citation
  • Xie, S.-P., and S. G. H. Philander, 1994: A coupled ocean–atmosphere model of relevance to the ITCZ in the eastern Pacific. Tellus, 46A, 340350, https://doi.org/10.3402/tellusa.v46i4.15484.

    • Search Google Scholar
    • Export Citation
  • Yanai, M., S. Esbensen, and J.-H. Chu, 1973: Determination of bulk properties of tropical cloud clusters from large-scale heat and moisture budgets. J. Atmos. Sci., 30, 611627, https://doi.org/10.1175/1520-0469(1973)030<0611:DOBPOT>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Ye, J., Y. Guo, Z. Wen, P. Zhao, and S. Huang, 2023: Longitudinal oscillation mode of the tropical easterly jet in June: Role of precipitation anomalies in Asian monsoon region. Climate Dyn., 60, 15431558, https://doi.org/10.1007/s00382-022-06391-1.

    • Search Google Scholar
    • Export Citation
  • Zhan, R., Y. Wang, and Y. Ding, 2022: Impact of the western Pacific tropical easterly jet on tropical cyclone genesis frequency over the western North Pacific. Adv. Atmos. Sci., 39, 235248, https://doi.org/10.1007/s00376-021-1103-1.

    • Search Google Scholar
    • Export Citation
  • Zhan, X., Z. Wen, Y. Guo, and S. Huang, 2022: Interannual variability of the double easterly jets over the tropical western Pacific and their effects on tropical cyclone genesis. Int. J. Climatol., 43, 20502061, https://doi.org/10.1002/joc.7961.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 725 725 668
Full Text Views 57 57 46
PDF Downloads 74 74 67