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Influence of anthropogenic aerosols and the Pacific Decadal Oscillation on tropical belt width

Nature Geoscience volume 7, pages 270–274 (2014)Cite this article

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Abstract

The tropical belt has widened by several degrees latitude since 1979, as evidenced by shifts in atmospheric circulation and climate zones1,2,3,4,5. Global climate models also simulate tropical belt widening, but less so than observed6,7. Reasons for this discrepancy and the mechanisms driving the expansion are uncertain. Here we analyse multidecadal variability in tropical belt width since 1950 using the Coupled Model Intercomparison Project Phase 5 climate model runs and find that simulated rates of tropical expansion over the past 30 years—particularly in the Northern Hemisphere—are in better agreement with observations than previous models. We find that models driven by observed sea surface temperatures over this interval yield the largest rate of tropical expansion. We link the tropical expansion in the Northern Hemisphere to the leading pattern of sea surface temperature variability in the North Pacific, the Pacific Decadal Oscillation. We also find, both from models and observations, that the tropical belt contracted in the Northern Hemisphere from 1950 to 1979, coincident with the reversal of the Pacific Decadal Oscillation trend. In both time periods, anthropogenic aerosols act to modify the Pacific Decadal Oscillation and therefore contribute to the width of the tropical belt. We conclude that tropical expansion and contraction are influenced by multidecadal sea surface temperature variability associated with both the Pacific Decadal Oscillation and anthropogenic aerosols.

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Figure 1: 1979–2009 annual mean tropical expansion in CMIP5 experiments and observations.
Figure 2: 1979–2009 Northern Hemisphere tropical expansion and the PDO.
Figure 3: 1979–2009 annual mean tropical expansion after removal of the PDO and ENSO.
Figure 4: 1950–2009 PDO time series in 20CEN/ALL and AER experiments.

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References

  1. Seidel, D. J., Fu, Q., Randel, W. J. & Reichler, T. J. Widening of the tropical belt in a changing climate. Nature Geosci. 1, 21–24 (2008).

    Article  Google Scholar 

  2. Hu, Y. & Fu, Q. Observed poleward expansion of the Hadley circulation since 1979. Atmos. Chem. Phys. 7, 5229–5236 (2007).

    Article  Google Scholar 

  3. Archer, C. L. & Caldeira, K. Historical trends in the jet streams. Geophys. Res. Lett. 35, L0880 (2008).

    Google Scholar 

  4. Zhou, Y. P., Xu, K-M., Sud, Y. C. & Betts, A. K. Recent trends of the tropical hydrological cycle inferred from global precipitation climatology project and international satellite cloud climatology project data. J. Geophys. Res. 116, D09101 (2011).

    Google Scholar 

  5. Bender, F., Ramanathan, V. & Tselioudis, G. Changes in extratropical storm track cloudiness 1983–2008: Observational support for a poleward shift. Clim. Dynam. 38, 2037–2053 (2012).

    Article  Google Scholar 

  6. Johanson, C. M. & Fu, Q. Hadley cell widening: Model simulations versus observations. J. Clim. 22, 2713–2725 (2009).

    Article  Google Scholar 

  7. Allen, R. J., Sherwood, S. C., Norris, J. R. & Zender, C. S. Recent Northern Hemisphere tropical expansion primarily driven by black carbon and tropospheric ozone. Nature 485, 350–354 (2012).

    Article  Google Scholar 

  8. Lu, J., Deser, C. & Reichler, T. Cause of the widening of the tropical belt since 1958. Geophys. Res. Lett. 36, L03803 (2009).

    Article  Google Scholar 

  9. Held, I. & Hou, A. Nonlinear axially symmetric circulations in a nearly inviscid atmosphere. J. Clim. 37, 515–533 (1980).

    Google Scholar 

  10. Lu, J., Vecchi, G. A. & Reichler, T. Expansion of the Hadley cell under global warming. Geophys. Res. Lett. 34, L06805 (2007).

    Google Scholar 

  11. Polvani, L. M., Waugh, D. W., Correa, G. J. P. & Son, S-W. Stratospheric ozone depletion: The main driver of twentieth-century atmospheric circulation changes in the Southern Hemisphere. J. Clim. 24, 795–812 (2011).

    Article  Google Scholar 

  12. Allen, R. J., Sherwood, S. C., Norris, J. R. & Zender, C. S. The equilibrium response to idealized thermal forcings in a comprehensive GCM: Implications for recent tropical expansion. Atmos. Chem. Phys. 12, 4795–4816 (2012).

    Article  Google Scholar 

  13. Taylor, K. E., Stouffer, R. J. & Meehl, G. A. An overview of CMIP5 and the experimental design. Bull. Amer. Meteorol. Soc. 93, 485–498 (2012).

    Article  Google Scholar 

  14. Mantua, N. J., Hare, S. R., Zhang, Y., Wallace, J. M. & Francis, R. C. A Pacific interdecadal climate oscillation with impacts on salmon production. Bull. Am. Meteorol. Soc. 78, 1069–1079 (1997).

    Article  Google Scholar 

  15. Deser, C., Alexander, M. A., Xie, S. P. & Phillips, A. S. Sea surface temperature variability: Patterns and mechanisms. Annu. Rev. Mar. Sci. 2, 114–143 (2010).

    Article  Google Scholar 

  16. Pierce, D. W. Distinguishing coupled ocean–atmosphere interactions from background noise in the North Pacific. Prog. Oceanogr. 49, 331–352 (2001).

    Article  Google Scholar 

  17. Newman, M., Compo, G. P. & Alexander, M. A. ENSO-forced variability of the Pacific decadal oscillation. J. Clim. 16, 3853–3857 (2003).

    Article  Google Scholar 

  18. Schneider, N. & Cornuelle, B. D. The forcing of the Pacific decadal oscillation. J. Clim. 18, 4355–4373 (2005).

    Article  Google Scholar 

  19. Lu, J., Chen, G. & Frierson, D. M. W. Response of the zonal mean atmospheric circulation to El Niño versus global warming. J. Clim. 21, 5835–5851 (2008).

    Article  Google Scholar 

  20. Grassi, B., Redaelli, G., Canziani, P. & Visconti, G. Effects of the PDO phase on the tropical belt width. J. Clim. 25, 3282–3290 (2012).

    Article  Google Scholar 

  21. Neale, R. B. et al. Description of the NCAR Community Atmosphere Model (CAM 5.0). Tech. Report NCAR/TN-486+STR (National Center for Atmospheric Research, 2012)

  22. Allen, R. J., Norris, J. R. & Wild, M. Evaluation of multidecadal variability in CMIP5 surface solar radiation and inferred underestimation of aerosol direct effects over Europe, China, Japan and India. J. Geophys. Res. 118, 6311–6336 (2013).

    Article  Google Scholar 

  23. Bond, T. C. et al. Bounding the role of black carbon in the climate system: A scientific assessment. J. Geophys. Res. 118, 5380–5552 (2013).

    Google Scholar 

  24. Adler, R. et al. The version-2 Global Precipitation Climatology Project (GPCP) monthly precipitation analysis (1979–present). J. Hydrometeor. 4, 1147–1167 (2003).

    Article  Google Scholar 

  25. Kalnay, E. et al. The NCEP/NCAR 40-year reanalysis project. Bull. Am. Meteorol. Soc. 77, 437–471 (1996).

    Article  Google Scholar 

  26. Kanamitsu, M. et al. NCEP-DOE AMIP-II Reanalysis (R-2). Bull. Am. Meteorol. Soc. 83, 1631–1643 (2002).

    Article  Google Scholar 

  27. Rienecker, M. M. et al. MERRA: NASA’s modern-era retrospective analysis for research and applications. J. Clim. 24, 3624–3648 (2011).

    Article  Google Scholar 

  28. Saha, S. et al. The NCEP climate forecast system reanalysis. Bull. Am. Meteorol. Soc. 91, 1015–1057 (2010).

    Article  Google Scholar 

  29. Compo, G. et al. The twentieth century reanalysis project. Q. J. R. Meteor. Soc. 137, 1–28 (2011).

    Article  Google Scholar 

  30. Yu, L. & Weller, R. A. Objectively analyzed air–sea heat fluxes for the global ice-free oceans (1981–2005). Bull. Am. Meteor. Soc. 88, 527–539 (2007).

    Article  Google Scholar 

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Acknowledgements

This study was financially supported by NASA grant number NNX13AC06G. We acknowledge the WCRP’s Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modelling groups for producing and making available their model output. For CMIP the U.S. DOE’s Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led development of software infrastructure in partnership with the Global Organization for Earth System Science Portals.

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Authors and Affiliations

  1. Department of Earth Sciences, University of California Riverside, Riverside, California 92521, USA

    Robert J. Allen & Mahesh Kovilakam

  2. Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093, USA

    Joel R. Norris

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  1. Robert J. Allen
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R.J.A. conceived the project, designed the study, carried out most of the data analysis and wrote the manuscript. J.R.N. advised on methods and interpretation, and assisted in the writing of the manuscript. M.K. assisted with data analysis.

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Correspondence to Robert J. Allen.

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Allen, R., Norris, J. & Kovilakam, M. Influence of anthropogenic aerosols and the Pacific Decadal Oscillation on tropical belt width. Nature Geosci 7, 270–274 (2014). https://doi.org/10.1038/ngeo2091

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