Advances in Atmospheric Sciences

, Volume 32, Issue 11, pp 1551–1564 | Cite as

Simulation of salinity variability and the related freshwater flux forcing in the tropical Pacific: An evaluation using the Beijing normal university earth system model (BNU-ESM)

  • Hai Zhi
  • Rong-Hua Zhang
  • Pengfei Lin
  • Lanning Wang


The climatology and interannual variability of sea surface salinity (SSS) and freshwater flux (FWF) in the equatorial Pacific are analyzed and evaluated using simulations from the Beijing Normal University Earth System Model (BNU-ESM). The simulated annual climatology and interannual variations of SSS, FWF, mixed layer depth (MLD), and buoyancy flux agree with those observed in the equatorial Pacific. The relationships among the interannual anomaly fields simulated by BNU-ESM are analyzed to illustrate the climate feedbacks induced by FWF in the tropical Pacific. The largest interannual variations of SSS and FWF are located in the western-central equatorial Pacific. A positive FWF feedback effect on sea surface temperature (SST) in the equatorial Pacific is identified. As a response to El Niño–Southern Oscillation (ENSO), the interannual variation of FWF induces ocean processes which, in turn, enhance ENSO. During El Niño, a positive FWF anomaly in the western-central Pacific (an indication of increased precipitation rates) acts to enhance a negative salinity anomaly and a negative surface ocean density anomaly, leading to stable stratification in the upper ocean. Hence, the vertical mixing and entrainment of subsurface water into the mixed layer are reduced, and the associated El Niño is enhanced. Related to this positive feedback, the simulated FWF bias is clearly reflected in SSS and SST simulations, with a positive FWF perturbation into the ocean corresponding to a low SSS and a small surface ocean density in the western-central equatorial Pacific warm pool.


freshwater flux salinity feedback tropical Pacific BNU-ESM 


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  1. Adler, R. F., and Coauthors, 2003: The version-2 global precipitation and climatology project (GPCP) monthly precipitation analysis (1979–present). Journal of Hydrometeorology, 4, 1147–1167.CrossRefGoogle Scholar
  2. Bellenger, H., E. Guilyardi, J. Leloup, M. Lengaigne, and J. Vialard, 2014: ENSO representation in climate models: From CMIP3 to CMIP5. Climate Dyn., 42, 1999–2018.CrossRefGoogle Scholar
  3. Cravatte, S., T. Delcroix, D. X. Zhang, M. McPhaden, and J. Leloup, 2009: Observed freshening and warming of the western Pacific Warm Pool. Climate Dyn., 33, 565–589.CrossRefGoogle Scholar
  4. Delcroix, T., and C. Henin, 1991: Seasonal and interannual variations of sea surface salinity in the tropical Pacific Ocean. J. Geophys. Res., 96, 22135–22150.CrossRefGoogle Scholar
  5. Delcroix, T., S. Cravatte, and M. J. McPhaden, 2007: Decadal variations and trends in tropical Pacific sea surface salinity since 1970. J. Geophys. Res., 112, C03012, doi: 10.1029/2006JC003801.Google Scholar
  6. Fedorov, A. V., R. C. Pacanowski, S. G. Philander, and G. Boccaletti, 2004: The effect of salinity on the wind-driven circulation and the thermal structure of the upper ocean. J. Phys. Oceanogr., 34, 1949–1966.CrossRefGoogle Scholar
  7. Fettweis, X., E. Hanna, C. Lang, A. Belleflamme, M. Erpicum, and H. Gallee, 2013: Brief communication “Important role of the mid-tropospheric atmospheric circulation in the recent surface melt increase over the Greenland ice sheet”. The Cryosphere, 7, 241–248.CrossRefGoogle Scholar
  8. Fujii, Y., M. Kamachi, S. Matsumoto, and S. Ishizaki, 2012: Barrier layer and relevant variability of the salinity field in the equatorial Pacific estimated in an ocean reanalysis experiment. Pure Appl. Geophys., 169, 579–594.CrossRefGoogle Scholar
  9. Guinehut, S., C. Coatanoan, A.-L. Dhomps, P.-Y. Le Traon, and G. Larnicol, 2009: On the use of satellite altimeter data in Argo quality control. J. Atmos. Oceanic Technol., 26, 395–402.CrossRefGoogle Scholar
  10. Hackert, E., J. Ballabrera-Poy, A. J. Busalacchi, R.-H. Zhang, and R. Murtugudde, 2011: Impact of sea surface salinity assimilation on coupled forecasts in the tropical Pacific. J. Geophys. Res., 116, C05009, doi: 10.1029/2010JC006708.Google Scholar
  11. Hackert, E., A. J. Busalacchi, and J. Ballabrera-Poy, 2014: Impact of Aquarius sea surface salinity observations on coupled forecasts for the tropical Indo-Pacific Ocean. J. Geophys. Res.: Oceans, 119(7), 4045–4067.CrossRefGoogle Scholar
  12. Ham, S., S.-Y. Hong, Y. Noh, S.-II An, Y.-H. Byun, H.-S. Kang, J. Lee, and W.-T. Kwon, 2012: Effects of freshwater runoff on a tropical Pacific climate in the HadGEM2. Asia-Pacific Journal of Atmospheric Sciences, 48(4), 457–463.CrossRefGoogle Scholar
  13. Han, W. Q., J. P. McCreary Jr., and K. E. Kohler, 2001: Influence of precipitation minus evaporation and Bay of Bengal rivers on dynamics, thermodynamics, and mixed layer physics in the upper Indian Ocean. J. Geophys. Res., 106, 6895–6916.CrossRefGoogle Scholar
  14. Howden, S. D., and R. Murtugudde, 2001: Effects of river inputs into the Bay of Bengal. J. Geophys. Res., 106, 19825–19843.CrossRefGoogle Scholar
  15. Huang, B. Y., and V. M. Mehta, 2005: Response of the Pacific and Atlantic oceans to interannual variations in net atmospheric freshwater. J. Geophys. Res., 110, C08008, doi: 10.1029/2004JC002830.Google Scholar
  16. Ji, D., and Coauthors, 2014: Description and basic evaluation of BNU-ESM version1. Geoscientific Model Development, 7, 1601–1647.CrossRefGoogle Scholar
  17. Kang, X. B., R. H. Huang, Z. G. Wang, and R.-H. Zhang, 2014: Sensitivity of ENSO variability to Pacific freshwater flux adjustment in the Community Earth System Model. Adv. Atmos. Sci., 31(5), 1009–1021, doi: 10.1007/s00376-014-3232-2.CrossRefGoogle Scholar
  18. Levitus, S., 1983: Climatological Atlas of the World Ocean. U.S. Government Printing Office, 173 pp.Google Scholar
  19. Lin, J.-L., 2007: The double-ITCZ problem in IPCC AR4 coupled GCMs: Ocean-atmosphere feedback analysis. J. Climate, 20, 4497–4525.CrossRefGoogle Scholar
  20. Lin, P. F., Y. Q. Yu and H. L. Liu, 2013a: Long-term stability and oceanic mean state simulated by the coupled model FGOALS-s2. Adv. Atmos. Sci., 30, 175–192, doi: 10.1007/s00376-012-2042-7.CrossRefGoogle Scholar
  21. Lin, P. F., Y. Q. Yu and H. L. Liu, 2013b: Oceanic climatology in the coupled model FGOALS-g2: Improvements and biases. Adv. Atmos. Sci., 30, 819–840, doi: 10.1007/s00376-012-2137-1.CrossRefGoogle Scholar
  22. Lukas, R., and E. Lindstrom, 1991: The mixed layer of the western equatorial Pacific Ocean. J. Geophys. Res., 96, 3343–3357.CrossRefGoogle Scholar
  23. Ma, H., L. X Wu, Z. Q. Li, 2013: Impact of freshening over the Southern Ocean on ENSO. Atmospheric Science Letters, 14(1), 28–33.CrossRefGoogle Scholar
  24. Maes, C., 2000: Salinity variability in the equatorial Pacific Ocean during the 1993–98 period. Geophys. Res. Lett., 27, 1659–1662.CrossRefGoogle Scholar
  25. Maes, C., J. Picaut, and S. Belamari, 2002: Salinity barrier layer and onset of El Nino in a Pacific coupled model. Geophys. Res. Lett., 29(24), 591–594, doi: 10.1029/2002GL016029.Google Scholar
  26. Mechoso, C. R., and Coauthors, 1995: The seasonal cycle over the tropical Pacific in coupled ocean-atmosphere general circulation models. Mon. Wea. Rev., 123, 2825–2838.CrossRefGoogle Scholar
  27. Murtugudde, R., and A. J. Busalacchi, 1998: Salinity effects in a tropical ocean model. J. Geophys. Res., 103, 3283–3300.CrossRefGoogle Scholar
  28. Rao, R. R., and K. V. Sanil Kumar, 1991: Evolution of salinity field in the upper layers of the east central Arabian Sea and northern Bay of Bengal during summer monsoon experiments. Proceedings of the Indian Academy of Sciences-Earth and Planetary Sciences, 100, 69–78.Google Scholar
  29. Rao, R. R., and R. Sivakumar, 1999: On the possible mechanisms of the evolution of a mini-warm pool during the pre-summer monsoon season and the genesis of onset vortex in the South-Eastern Arabian Sea. Quart. J. Roy. Meteor. Soc., 125, 787–809.CrossRefGoogle Scholar
  30. Schiffer, R. A., and W. B. Rossow, 1985: ISCCP global radiance data set: a new resource for climate research. Bull. Amer. Meteor. Soc., 66, 1498–1505.CrossRefGoogle Scholar
  31. S´evellec, F., and A. V. Fedorov, 2011: Stability of the Atlantic meridional overturning circulation and stratification in a zonally averaged ocean model: Effects of freshwater flux, Southern Ocean winds, and diapycnal diffusion. Deep Sea Research Part II: Topical Studies in Oceanography, 58, 1927–1943.CrossRefGoogle Scholar
  32. Sprintall, J., and M. Tomczak, 1992: Evidence of the barrier layer in the surface layer of the tropics. J. Geophys. Res., 97, 7305–7316.CrossRefGoogle Scholar
  33. Taylor, K. E., R. J. Stouffer, and G. A. Meehl, 2012: An overview of CMIP5 and the experiment design. Bull. Amer. Meteor. Soc., 93, 485–498.CrossRefGoogle Scholar
  34. Thompson, B., C. Gnanaseelan, and P. S. Salvekar, 2006: Variability in the Indian Ocean circulation and salinity and its impact on SST anomalies during dipole events. J. Mar. Res., 64, 853–880.CrossRefGoogle Scholar
  35. Webster, P. J., 1994: The role of hydrological processes in oceanatmosphere interactions. Rev. Geophys., 32, 427–476.CrossRefGoogle Scholar
  36. Wu, L. X., Y. Sun, J. X. Zhang, L. P. Zhang, and S. Minobe, 2010: Coupled ocean-atmosphere response to idealized freshwater forcing over the western tropical Pacific. J. Climate, 23(7), 1945–1954.CrossRefGoogle Scholar
  37. Wu, R. G., J. P. Chen, and Z. P. Wen, 2013: Precipitation-surface temperature relationship in the IPCC CMIP5 Models. Adv. Atmos. Sci., 30, 766–778, doi: 10.1007/s00376-012-2130-8.CrossRefGoogle Scholar
  38. Yang, S., K.-M. Lau, and P. S. Schopf, 1999: Sensitivity of the tropical Pacific Ocean to precipitation-induced freshwater flux. Climate Dyn., 15, 737–750.CrossRefGoogle Scholar
  39. Yu, L. S., 2011: A global relationship between the ocean water cycle and near-surface salinity. J. Geophys. Res., 116, C10025, doi: 10.1029/2010JC006937.CrossRefGoogle Scholar
  40. Yu, L. S., and R. A. Weller, 2007: Objectively analyzed air-sea heat fluxes for the global ice-free oceans (1981–2005). Bull. Amer. Meteor. Soc., 88, 527–539.CrossRefGoogle Scholar
  41. Zhang, L. P., C. Z Wang, and S.-K. Lee, 2014: Potential role of Atlantic Warm Pool-induced freshwater forcing in the Atlantic Meridional Overturning Circulation: Ocean-sea ice model simulations. Climate Dyn., 43, 553–574.CrossRefGoogle Scholar
  42. Zhang, R.-H., and A. J. Busalacchi, 2009: Freshwater flux (FWF)- induced oceanic feedback in a hybrid coupled model of the tropical Pacific. J. Climate, 22, 853–879.CrossRefGoogle Scholar
  43. Zhang, R.-H., A. J. Busalacchi, R. G. Murtugudde, P. A. Arkin, and J. Ballabrera-Poy, 2006: An empirical parameterization for the salinity of subsurface water entrained into the ocean mixed layer (Se) in the tropical Pacific. Geophys. Res. Lett., 33, L02605, doi: 10.1029/2005GL024218.Google Scholar
  44. Zhang, R.-H., G.H. Wang, D. K. Chen, A. J. Busalacchi, and E. C. Hackert, 2010: Interannual biases induced by freshwater flux and coupled feedback in the tropical Pacific. Mon. Wea. Rev., 138, 1715–1737.CrossRefGoogle Scholar
  45. Zhang, R.-H., F. Zheng, J. S. Zhu, Y. H. Pei, Q. A. Zheng, and Z. G. Wang, 2012: Modulation of El Nino-Southern Oscillation by freshwater flux and salinity variability in the tropical Pacific. Adv. Atmos. Sci., 29, 647–660, doi: 10.1007/s00376-012-1235-4.CrossRefGoogle Scholar
  46. Zhang, R.-H., F. Zheng, J. Zhu, and Z. G. Wang, 2013: A successful real-time forecast of the 2010–11 La Nina event. Sci. Rep. 3, 1108; DOI: 10.1038/srep01108.Google Scholar
  47. Zheng, F., and R.-H. Zhang, 2012: Effects of interannual salinity variability and freshwater flux forcing on the development of the 2007/08 La Nina event diagnosed from Argo and satellite data. Dyn. Atmos. (Oceans), 57, 45–57.CrossRefGoogle Scholar
  48. Zheng, F., R.-H. Zhang, and J. Zhu, 2014: Effects of interannual salinity variability on the barrier layer in the western-central equatorial Pacific: A diagnostic analysis from Argo. Adv. Atmos. Sci., 31, 532–542, doi: 10.1007/s00376-013-3061-8.CrossRefGoogle Scholar

Copyright information

© Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Hai Zhi
    • 1
  • Rong-Hua Zhang
    • 2
  • Pengfei Lin
    • 3
  • Lanning Wang
    • 4
  1. 1.The Earth System Modeling Center and College of Atmospheric SciencesNanjing University of Information Science and TechnologyNanjingChina
  2. 2.Key Laboratory of Ocean Circulation and Waves, Institute of OceanologyChinese Academy of SciencesQingdaoChina
  3. 3.State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina
  4. 4.College of Global Change and Earth System ScienceBeijing Normal UniversityBeijingChina

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