Abstract
After the strong 2015/16 El Niño event, cold conditions prevailed in the tropical Pacific with the second-year cooling of the 2017/18 La Niña event. Many coupled models failed to predict the cold SST anomalies (SSTAs) in 2017. By using the ERA5 and GODAS (Global Ocean Data Assimilation System) products, atmospheric and oceanic factors were examined that could have been responsible for the second-year cooling, including surface wind and the subsurface thermal state. A time sequence is described to demonstrate how the cold SSTAs were produced in the central-eastern equatorial Pacific in late 2017. Since July 2017, easterly anomalies strengthened in the central Pacific; in the meantime, wind stress divergence anomalies emerged in the far eastern region, which strengthened during the following months and propagated westward, contributing to the development of the second-year cooling in 2017. At the subsurface, weak negative temperature anomalies were accompanied by upwelling in the eastern equatorial Pacific, which provided the cold water source for the sea surface. Thereafter, both the cold anomalies and upwelling were enhanced and extended westward in the centraleastern equatorial Pacific. These changes were associated with the seasonally weakened EUC (the Equatorial Undercurrent) and strengthened SEC (the South Equatorial Current), which favored more cold waters being accumulated in the central-equatorial Pacific. Then, the subsurface cold waters stretched upward with the convergence of the horizontal currents and eventually outcropped to the surface. The subsurface-induced SSTAs acted to induce local coupled air-sea interactions, which generated atmospheric-oceanic anomalies developing and evolving into the second-year cooling in the fall of 2017.
摘要
2015/16 年强厄尔尼诺事件之后, 热带太平洋海温呈冷异常状态, 并在2017/18年出现二次变冷过程. 许多耦合模型未能预测出2017年的海温冷异常. 本文利用ERA5和全球海洋数据同化系统(GODAS)数据, 研究了可能导致二次变冷的大气和海洋过程, 包括表层风和次表层热力状态.
文中给出了 2017 年后半年赤道中东部太平洋海温冷异常的完整演变过程. 自 2017 年 7 月以来, 太平洋中部的东风增强; 与此同时, 远东太平洋出现风应力辐散异常, 随后风应力辐散增强并向西传播, 促进了 2017 年二次变冷的发展. 在次表层, 弱的海温冷异常伴随着赤道东太平洋的上升流, 为海面源源不断地提供冷水. 随着时间推移, 赤道中东部太平洋海温冷异常和上升流增强并向西扩展. 这些变化与赤道潜流的季节性减弱和南赤道流的季节性增强有关, 有利于在赤道中太平洋聚集更多的冷水. 次表层冷水随着水平流场的辐合向上伸展, 最终露出海面. 次表层冷水上翻引起的海表温度冷异常激发局部的大气-海洋相互作用, 产生大气-海洋异常, 并进一步发展演化为 2017 年秋季的二次变冷.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Barnston, A. G., Tippett, M. K., L’Heureux, M. L., Li, S. & DeWitt, D. G, 2012: Skill of real-time seasonal ENSO model predictions during 2002–11: Is our capability increasing? Bull. Amer. Meteor. Soc., 93, 631–651.
Battisti, D. S., and A. C. Hirst, 1989: Interannual variability in the tropical atmosphere-ocean system: Influence of the basis state, ocean geometry and nonlinearity. J. Atmos. Sci., 46, 1687–1712, https://doi.org/10.1175/1520-0469(1989)046<1687:IVIATA>2.0.CO;2.
Behringer, D., and Y. Xue, 2004: Evaluation of the global ocean data assimilation system at NCEP: The Pacific Ocean. Preprints, Eighth Symp. on Integrated Observing and Assimilation Systems for Atmosphere, Oceans, and Land Surface, Seattle, WA, Amer. Meteor. Soc, 2. 3. [Available online at https://ams.confex.com/ams/84Annual/techprogram/paper_70720.htm
Cane, M. A., and S. E. Zebiak, 1985: A theory for El Niño and the southern Oscillation. Science, 228, 1085–1087, https://doi.org/10.1126/science.228.4703.1085.
Chen, H.-C., Z.-Z. Hu, B. H. Huang, and C.-H. Sui, 2016: The role of reversed equatorial zonal transport in terminating an ENSO event. J. Climate, 29(16), 5859–5877, https://doi.org/10.1175/JCLI-D-16-0047.1.
Chiodi, A. M., and D. E. Harrison, 2015: Equatorial pacific easterly wind surges and the onset of La Niña Events. J. Climate, 28(2), 776–792, https://doi.org/10.1175/JCLI-D-14-00227.1.
Copernicus Climate Change Service (C3S), 2017: ERA5: Fifth Generation of ECMWF Atmospheric Reanalyses of the Global Climate. Copernicus Climate Change Service Climate Data Store (CDS). [Available online from https://cds.climate.copernicus.eu/cdsapp#!/home]
Ding, R. Q., J. P. Li, Y.-H. Tseng, C. Sun, and F. Xie, 2017: Joint impact of North and South Pacific extratropical atmospheric variability on the onset of ENSO events. J. Geophys. Res., 122, 279–298, https://doi.org/10.1002/2016/D025502.
Feng, L. C., R.-H. Zhang, Z. G. Wang, and X. R. Chen, 2015: Processes leading to second-year cooling of the 2010–12 La Niña event, diagnosed using GODAS. Adv. Atmos. Sci., 32(3), 424–438, https://doi.org/10.1007/s00376-014-4012-8.
Gao, C., and R.-H. Zhang, 2017: The roles of atmospheric wind and entrained water temperature (Te) in the second-year cooling of the 2010–12 La Niña event. Climate Dyn., 48, 597–617, https://doi.org/10.1007/s00382-016-3097-4.
Hu, Z.-Z., A. Kumar, Y. Xue, and B. Jha, 2014: Why were some La Niñas followed by another La Niña? Climate Dyn, 42(3), 1029–1042, https://doi.org/10.1007/s00382-013-1917-3.
Huang, B. Y., Y. Xue, D. X. Zhang, A. Kumar, and M. J. McPhaden, 2010: The NCEP GODAS ocean analysis of the tropical Pacific mixed layer heat budget on seasonal to interannual time scales. J. Climate, 23, 4901–4925, https://doi.org/10.1175/2010/CLI3373.1.
Jin, F.-F., and J. D. Neelin, 1993: Modes of interannual tropical ocean-atmosphere inter-action—a unified view. Part I: Numerical results. J. Atmos. Sci., 50, 3477–3502.
Jin, F. F., 1997: An equatorial ocean recharge paradigm for ENSO. Part I: Conceptual model. J. Atmos. Sci., 54, 811–829, https://doi.org/10.1175/1520-0469(1997)054<0811:AEORPF>2.0.CO;2.
Kumar, A., and Z.-Z. Hu, 2012: Uncertainty in the ocean-atmosphere feedbacks associated with ENSO in the reanalysis products. Climate Dyn., 39(3–4), 575–588, https://doi.org/10.1007/s00382-011-1104-3.
Madden, R. A., and P. R. Julian, 1994: Observations of the 40–50-day tropical oscillation-A review. Mon. Wea. Rev., 122, 814–837, https://doi.org/10.1175/1520-0493(1994)122<0814:OOTDTO>2.0.CO;2.
Meinen, C. S., and M. J. McPhaden, 2000: Observations of warm water volume changes in the equatorial Pacific and their relationship to El Niño and La Niña. J. Climate, 13, 3551–3559, https://doi.org/10.1175/1520-0442(2000)013<3551:OOWWVC>2.0.CO;2.
Philander, S. G. H, 1992: Ocean-atmosphere interactions in the tropics: A review of recent theories and models. J. Appl. Meteorol., 31, 938–945, https://doi.org/10.1175/1520-0450(1992)031<0938:OAIITT>2.0.CO;2.
Ren, H.-L., F.-F. Jin, M. F. Stuecker, and R. H. Xie, 2013: ENSO regime change since the late 1970s as manifested by two types of ENSO. J. Meteorol. Soc. Japan, 91, 835–842, https://doi.org/10.2151/jmsj.2013-608.
Ren, H.-L., Y. Liu, F.-F. Jin, Y.-P. Yan, and X.-W. Liu, 2014: Application of the analogue-based correction of errors method in ENSO prediction. Atmos. Ocean. Sci. Lett., 7, 157–161, https://doi.org/10.3878/j.issn.1674-2834.13.0080.
Ren, H.-L., F.-F. Jin, B. Tian, and A. A. Scaife, 2016: Distinct persistence barriers in two types of ENSO. Geophys. Res. Lett., 43, 10973–10979, https://doi.org/10.1002/2016GL071015.
Suarez, M. J., and P. S. Schopf, 1988: A Delayed Action Oscillator for Enso. J Atmos Sci, 45, 3283–3287.
Stuecker, M. F., A. Timmermann, F.-F. Jin, S. McGregor, and H.-L. Ren, 2013: A combination mode of the annual cycle and the El Niño/Southern Oscillation. Nature Geoscience, 6, 540–544, https://doi.org/10.1038/ngeo1826.
Sun, C., F. Kucharski, J. P. Li, F.-F. Jin, I. S. Kang, and R. Q. Ding, 2017: Western tropical Pacific multidecadal variability forced by the Atlantic multidecadal oscillation. Nature Communications, 8(1), 15998, https://doi.org/10.1038/ncomms15998.
Terray, P., 2011: Southern Hemisphere extra-tropical forcing: A new paradigm for El Niño-southern Oscillation. Climate Dyn., 36, 2171–2199, https://doi.org/10.1007/s00382-010-0825-z.
Wang, X., C. Z. Wang, W. Zhou, L. Liu, and D. X. Wang, 2013: Remote influence of North Atlantic SST on the equatorial westerly wind anomalies in the western Pacific for initiating an El Niño Event: An atmospheric general circulation model study. Atmos. Sci. Lett., 14, 107–111, https://doi.org/10.1002/as12.425.
Weisberg, R. H., and C. Wang, 1997: Slow variability in the equatorial west-central Pacific in relation to ENSO. J. Climate, 10, 1998–2017, https://doi.org/10.1175/1520-0442(1997)010<1998:SVITEW>2.0.CO;2.
Wyrtki, K., 1985: Citation Classic — El-Niño — the Dynamic-Response of the Equatorial Pacific-Ocean to Atmospheric Forcing. Cc/Phys Chem Earth, 16–16.
Xue, Y., B. Y. Huang, Z.-Z. Hu, A. Kumar, C. H. Wen, D. Behringer, and S. Nadiga, 2011: An assessment of oceanic variability in the NCEP Climate Forecast System Reanalysis. Climate Dyn., 37(11–12), 2511–2539, https://doi.org/10.1007/s00382-010-0954-4.
Zebiak, S. E., and M. A. Cane, 1987: A model El Niño-southern oscillation. Mon. Wea. Rev., 115, 2262–2278, https://doi.org/10.1175/1520-0493(1987)115<2262:AMENO>2.0.CO;2.
Zhang, R.-H., and L. M. Rothstein, 2000: Role of off-equatorial subsurface anomalies in initiating the 1991–1992 El Niño as revealed by the national centers for environmental prediction ocean reanalysis data. J. Geophys. Res., 105(C3), 6327–6339.
Zhang, R.-H., F. Zheng, J. Zhu, and Z. G. Wang, 2013: A successful real-time forecast of the 2010–11 La Niña event. Scientific Reports, 3, https://doi.org/10.1038/srep01108.
Zhang, R.-H. and C. Gao, 2016: The IOCAS intermediate coupled model (IOCAS ICM) and its real-time predictions of the 2015–2016 El Niño event. Science Bulletin, 66(13), 1061–1070, https://doi.org/10.1007/s11434-016-1064-4.
Zhang, W. J., H. Y. Li, F. F. Jin, M. F. Stuecker, A. G. Turner, and N. P. Klingaman, 2015: The Annual-Cycle Modulation of Meridional Asymmetry in ENSO’s Atmospheric Response and Its Dependence on ENSO Zonal Structure. J Climate, 28, 5795–5812, https://doi.org/10.1175/JCLI-D-14-00724.1.
Zhang, X. B., and M. J. McPhaden, 2006: Wind stress variations and interannual sea surface temperature anomalies in the eastern equatorial Pacific. J. Climate, 19, 226–241, https://doi.org/10.1175/JCLI3618.1.
Zhang, X. B., and M. J. McPhaden, 2008: Eastern equatorial Pacific forcing of ENSO sea surface temperature anomalies. J. Climate, 21, 6070–6079, https://doi.org/10.1175/2008/CLI2422.1.
Zhang, X. B., and M. J. McPhaden, 2010: Surface layer heat balance in the eastern equatorial Pacific Ocean on interannual time scales: Influence of local versus remote wind forcing. J. Climate, 23, 4375–4394, https://doi.org/10.1175/2010JCLI3469.1.
Zheng, F., L. S. Feng, and J. Zhu, 2015: An incursion of off-equatorial subsurface cold water and its role in triggering the “double dip” La Niña event of 2011. Adv. Atmos. Sci., 32(6), 731–742, https://doi.org/10.1007/s00376-014-4080-9.
Acknowledgements
We thank the three anonymous reviewers for their valuable comments. This work was jointly supported by grants from the National Natural Science Foundation of China [Grant Nos. 41576029 and 41690122(41690120)], the National Program on Global Change and Air-Sea Interaction (Grant No. GASI-IPOVAI-03), the National Key Research and Development Program (Grant No. 2018YFC1505802), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant Nos. XDA19060102 and XDB 40000000). We thank the Climate Prediction Center Ocean Briefing group for providing the mixed-layer heat budget analyses in Fig. 8, which were downloaded from https://www.cpc.ncep.noaa.gov/products/GODAS.
Author information
Authors and Affiliations
Corresponding author
Additional information
Article Highlights
• The cooling of the 2017/18 La Niña event was of eastern equatorial Pacific origen, which is different from other second-year coolings.
• Both the wind stress anomalies and the subsurface cold anomalies played an important role in the second-year cooling of the 2017/18 La Niña event.
Rights and permissions
About this article
Cite this article
Feng, L., Zhang, RH., Yu, B. et al. Roles of Wind Stress and Subsurface Cold Water in the Second-Year Cooling of the 2017/18 La Niña Event. Adv. Atmos. Sci. 37, 847–860 (2020). https://doi.org/10.1007/s00376-020-0028-4
Received:
Revised:
Accepted:
Published:
Issue date:
DOI: https://doi.org/10.1007/s00376-020-0028-4