The Role of the Mean State in Meridional Mode Structure and Growth

Cristian Martinez-Villalobos Atmospheric and Oceanic Sciences Department, University of Wisconsin–Madison, Madison, Wisconsin

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Daniel J. Vimont Atmospheric and Oceanic Sciences Department, University of Wisconsin–Madison, Madison, Wisconsin

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Abstract

This study uses a simple linear coupled model to investigate the role of the WES feedback and ITCZ mean states in meridional mode variability. Optimal structures that maximize transient growth are calculated for mean states characteristic of boreal spring and boreal fall in the tropical Atlantic. During boreal spring the leading optimal structure is a zonal mode that propagates westward and does not resemble the observed meridional mode. In contrast, the leading optimal structure during fall is a sea surface temperature (SST) monopole over the Northern Hemisphere (NH) that propagates equatorward and westward and that closely matches meridional mode variability during this season. It is found that the boreal fall optimal growth greatly exceeds growth of the corresponding optimal during boreal spring, despite the observed boreal spring peak in Atlantic meridional mode variance.

Sensitivity studies are used to explore the role of Northern or Southern Hemisphere initial conditions, ITCZ width, and ITCZ location in meridional mode growth and structure. It is found that growth is favored (i) for optimal structures that originate in the Northern Hemisphere, especially for boreal fall mean states; (ii) for symmetric mean states, equatorially symmetric structures maximize growth under narrow ITCZ configurations, and antisymmetric structures maximize growth under wider ITCZ configurations; and (iii) for antisymmetric mean states (and realistic ITCZ width), growth is maximized when the ITCZ is located off of the equator. The implications of these findings are discussed.

Supplemental information related to this paper is available at the Journals Online website: http://dx.doi.org/10.1175/JCLI-D-15-0542.s1.

Corresponding author address: Cristian Martinez-Villalobos, 1225 W. Dayton St., Madison, WI 53706. E-mail: cmartinezvil@wisc.edu

Abstract

This study uses a simple linear coupled model to investigate the role of the WES feedback and ITCZ mean states in meridional mode variability. Optimal structures that maximize transient growth are calculated for mean states characteristic of boreal spring and boreal fall in the tropical Atlantic. During boreal spring the leading optimal structure is a zonal mode that propagates westward and does not resemble the observed meridional mode. In contrast, the leading optimal structure during fall is a sea surface temperature (SST) monopole over the Northern Hemisphere (NH) that propagates equatorward and westward and that closely matches meridional mode variability during this season. It is found that the boreal fall optimal growth greatly exceeds growth of the corresponding optimal during boreal spring, despite the observed boreal spring peak in Atlantic meridional mode variance.

Sensitivity studies are used to explore the role of Northern or Southern Hemisphere initial conditions, ITCZ width, and ITCZ location in meridional mode growth and structure. It is found that growth is favored (i) for optimal structures that originate in the Northern Hemisphere, especially for boreal fall mean states; (ii) for symmetric mean states, equatorially symmetric structures maximize growth under narrow ITCZ configurations, and antisymmetric structures maximize growth under wider ITCZ configurations; and (iii) for antisymmetric mean states (and realistic ITCZ width), growth is maximized when the ITCZ is located off of the equator. The implications of these findings are discussed.

Supplemental information related to this paper is available at the Journals Online website: http://dx.doi.org/10.1175/JCLI-D-15-0542.s1.

Corresponding author address: Cristian Martinez-Villalobos, 1225 W. Dayton St., Madison, WI 53706. E-mail: cmartinezvil@wisc.edu

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  • Battisti, D. S., E. S. Sarachik, and A. C. Hirst, 1999: A consistent model for the large-scale steady surface atmospheric circulation in the tropics. J. Climate, 12, 29562964, doi:10.1175/1520-0442(1999)012<2956:ACMFTL>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Bischoff, T., and T. Schneider, 2014: Energetic constraints on the position of the intertropical convergence zone. J. Climate, 27, 49374951, doi:10.1175/JCLI-D-13-00650.1.

    • Search Google Scholar
    • Export Citation
  • Chang, P., L. Ji, and H. Li, 1997: A decadal climate variation in the tropical Atlantic Ocean from thermodynamic air-sea interactions. Nature, 385, 516518, doi:10.1038/385516a0.

    • Search Google Scholar
    • Export Citation
  • Chang, P., L. Zhang, R. Saravanan, D. J. Vimont, J. C. H. Chiang, L. Ji, H. Seidel, and M. K. Tippett, 2007: Pacific meridional mode and El Niño–Southern Oscillation. Geophys. Res. Lett., 34, L16608, doi:10.1029/2007GL030302.

    • Search Google Scholar
    • Export Citation
  • Chiang, J. C. H., and D. J. Vimont, 2004: Analogous Pacific and Atlantic meridional modes of tropical atmosphere–ocean variability. J. Climate, 17, 41434158, doi:10.1175/JCLI4953.1.

    • Search Google Scholar
    • Export Citation
  • Chiang, J. C. H., S. E. Zebiak, and M. A. Cane, 2001: Relative roles of elevated heating and surface temperature gradients in driving anomalous surface winds over tropical oceans. J. Atmos. Sci., 58, 13711394, doi:10.1175/1520-0469(2001)058<1371:RROEHA>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Clement, A., P. DiNezio, and C. Deser, 2011: Rethinking the ocean’s role in the Southern Oscillation. J. Climate, 24, 40564072, doi:10.1175/2011JCLI3973.1.

    • Search Google Scholar
    • Export Citation
  • Czaja, A., 2004: Why is north tropical Atlantic SST variability stronger in boreal spring? J. Climate, 17, 30173025, doi:10.1175/1520-0442(2004)017<3017:WINTAS>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Czaja, A., P. van der Vaart, and J. Marshall, 2002: A diagnostic study of the role of remote forcing in tropical Atlantic variability. J. Climate, 15, 32803290, doi:10.1175/1520-0442(2002)015<3280:ADSOTR>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Dee, D. P., and Coauthors, 2011: The ERA-Interim reanalysis: Configuration and performance of the data assimilation system. Quart. J. Roy. Meteor. Soc., 137, 553597, doi:10.1002/qj.828.

    • Search Google Scholar
    • Export Citation
  • Enfield, D. B., A. M. Mestas-Nuñez, D. A. Mayer, and L. Cid-Serrano, 1999: How ubiquitous is the dipole relationship in tropical Atlantic sea surface temperatures? J. Geophys. Res., 104, 7841, doi:10.1029/1998JC900109.

    • Search Google Scholar
    • Export Citation
  • Evan, A. T., R. J. Allen, R. Bennartz, and D. J. Vimont, 2013: The modification of sea surface temperature anomaly linear damping time scales by stratocumulus clouds. J. Climate, 26, 36193630, doi:10.1175/JCLI-D-12-00370.1.

    • Search Google Scholar
    • Export Citation
  • Farrell, B. F., and P. J. Ioannou, 1996: Generalized stability theory. Part I: Autonomous operators. J. Atmos. Sci., 53, 2025–2040, doi:10.1175/1520-0469(1996)053<2025:GSTPIA>2.0.CO;2.

  • Frierson, D. M. W., and Coauthors, 2013: Contribution of ocean overturning circulation to tropical rainfall peak in the Northern Hemisphere. Nat. Geosci., 6, 940–944, doi:10.1038/ngeo1987.

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

    • Search Google Scholar
    • Export Citation
  • Hastenrath, S., and L. Heller, 1977: Dynamics of climatic hazards in Northeast Brazil. Quart. J. Roy. Meteor. Soc., 103, 7792, doi:10.1002/qj.49710343505.

    • Search Google Scholar
    • Export Citation
  • Hirst, A. C., 1986: Unstable and damped equatorial modes in simple coupled ocean–atmosphere models. J. Atmos. Sci., 43, 606632, doi:10.1175/1520-0469(1986)043<0606:UADEMI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Houghton, R. W., and Y. M. Tourre, 1992: Characteristics of low-frequency sea surface temperature fluctuations in the tropical Atlantic. J. Climate, 5, 765772, doi:10.1175/1520-0442(1992)005<0765:COLFSS>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Kossin, J. P., and D. J. Vimont, 2007: A more general framework for understanding Atlantic hurricane variability and trends. Bull. Amer. Meteor. Soc., 88, 17671781, doi:10.1175/BAMS-88-11-1767.

    • Search Google Scholar
    • Export Citation
  • Lindzen, R. S., and S. Nigam, 1987: On the role of sea surface temperature gradients in forcing low-level winds and convergence in the tropics. J. Atmos. Sci., 44, 24182436, doi:10.1175/1520-0469(1987)044<2418:OTROSS>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Linkin, M. E., and S. Nigam, 2008: The North Pacific Oscillation–west Pacific teleconnection pattern: Mature-phase structure and winter impacts. J. Climate, 21, 19791997, doi:10.1175/2007JCLI2048.1.

    • Search Google Scholar
    • Export Citation
  • Matsuno, T., 1966: Quasi-geostrophic motions in the equatorial area. J. Meteor. Soc. Japan, 44, 2543.

  • Moura, A. D., and J. Shukla, 1981: On the dynamics of droughts in Northeast Brazil: Observations, theory, and numerical experiments with a general circulation model. J. Atmos. Sci., 38, 26532675, doi:10.1175/1520-0469(1981)038<2653:OTDODI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Neelin, J. D., 1989: On the interpretation of the Gill model. J. Atmos. Sci., 46, 24662468, doi:10.1175/1520-0469(1989)046<2466:OTIOTG>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Nobre, P., and J. Shukla, 1996: Variations of sea surface temperature, wind stress, and rainfall over the tropical Atlantic and South America. J. Climate, 9, 24642479, doi:10.1175/1520-0442(1996)009<2464:VOSSTW>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Noguchi, H., 1998: Coupled ocean-atmospheric waves due to wind-evaporation-SST feedback (in Japanese). M.S. thesis, Graduate School of Environmental Science, Hokkaido University, 56 pp.

  • Okajima, H., S.-P. Xie, and A. Numaguti, 2003: Interhemispheric coherence of tropical climate variability: Effect of the climatological ITCZ. J. Meteor. Soc. Japan, 81, 13711386, doi:10.2151/jmsj.81.1371.

    • Search Google Scholar
    • Export Citation
  • Penland, C., and L. M. Hartten, 2014: Stochastic forcing of north tropical Atlantic sea surface temperatures by the North Atlantic Oscillation. Geophys. Res. Lett., 41, 21262132, doi:10.1002/2014GL059252.

    • Search Google Scholar
    • Export Citation
  • Rogers, J. C., 1981: The North Pacific Oscillation. J. Climatol., 1, 3957, doi:10.1002/joc.3370010106.

  • Schneider, T., T. Bischoff, and G. H. Haug, 2014: Migrations and dynamics of the intertropical convergence zone. Nature, 513, 45–53, doi:10.1038/nature13636.

  • Servain, J., I. Wainer, J. P. McCreary, and A. Dessier, 1999: Relationship between the equatorial and meridional modes of climatic variability in the tropical Atlantic. Geophys. Res. Lett., 26, 485488, doi:10.1029/1999GL900014.

    • Search Google Scholar
    • Export Citation
  • Smirnov, D., and D. J. Vimont, 2011: Variability of the Atlantic meridional mode during the Atlantic hurricane season. J. Climate, 24, 14091424, doi:10.1175/2010JCLI3549.1.

    • Search Google Scholar
    • Export Citation
  • Takahashi, K., and D. S. Battisti, 2007: Processes controlling the mean tropical Pacific precipitation pattern. Part I: The Andes and the eastern Pacific ITCZ. J. Climate, 20, 34343451, doi:10.1175/JCLI4198.1.

    • Search Google Scholar
    • Export Citation
  • Tanimoto, Y., and S.-P. Xie, 2002: Inter-hemispheric decadal variations in SST, surface wind, heat flux and cloud cover over the Atlantic Ocean. J. Meteor. Soc. Japan, 80, 11991219, doi:10.2151/jmsj.80.1199.

    • Search Google Scholar
    • Export Citation
  • Toma, V. E., and P. J. Webster, 2010a: Oscillations of the intertropical convergence zone and the genesis of easterly waves. Part I: Diagnostics and theory. Climate Dyn., 34, 587604, doi:10.1007/s00382-009-0584-x.

    • Search Google Scholar
    • Export Citation
  • Toma, V. E., and P. J. Webster, 2010b: Oscillations of the intertropical convergence zone and the genesis of easterly waves. Part II: Numerical verification. Climate Dyn., 34, 605613, doi:10.1007/s00382-009-0585-9.

    • Search Google Scholar
    • Export Citation
  • Tomas, R. A., and P. J. Webster, 1997: The role of inertial instability in determining the location and strength of near-equatorial convection. Quart. J. Roy. Meteor. Soc., 123, 14451482, doi:10.1002/qj.49712354202.

    • Search Google Scholar
    • Export Citation
  • Vimont, D. J., 2010: Transient growth of thermodynamically coupled variations in the tropics under an equatorially symmetric mean state. J. Climate, 23, 57715789, doi:10.1175/2010JCLI3532.1.

    • Search Google Scholar
    • Export Citation
  • Vimont, D. J., M. Alexander, and A. Fontaine, 2009: Midlatitude excitation of tropical variability in the Pacific: The role of thermodynamic coupling and seasonality. J. Climate, 22, 518534, doi:10.1175/2008JCLI2220.1.

    • Search Google Scholar
    • Export Citation
  • Wang, S. Y., M. L’Heureux, and H. H. Chia, 2012: ENSO prediction one year in advance using western North Pacific sea surface temperatures. Geophys. Res. Lett., 39, L05702, doi:10.1029/2012GL050909.

    • Search Google Scholar
    • Export Citation
  • Wu, R., B. P. Kirtman, and V. Krishnamurthy, 2008: An asymmetric mode of tropical Indian Ocean rainfall variability in boreal spring. J. Geophys. Res., 113, D05104, doi:10.1029/2007JD009316.

  • Xie, S.-P., 1996: Westward propagation of latitudinal asymmetry in a coupled ocean–atmosphere model. J. Atmos. Sci., 53, 32363250, doi:10.1175/1520-0469(1996)053<3236:WPOLAI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Xie, S.-P., 1999: A dynamic ocean–atmosphere model of the tropical Atlantic decadal variability. J. Climate, 12, 6470, doi:10.1175/1520-0442-12.1.64.

    • 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, doi:10.1034/j.1600-0870.1994.t01-1-00001.x.

    • Search Google Scholar
    • Export Citation
  • Xie, S.-P., and Y. Tanimoto, 1998: A pan-Atlantic decadal climate oscillation. Geophys. Res. Lett., 25, 21852188, doi:10.1029/98GL01525.

    • Search Google Scholar
    • Export Citation
  • Xie, S.-P., and K. Saito, 2001: Formation and variability of a northerly ITCZ in a hybrid coupled AGCM: Continental forcing and oceanic–atmospheric feedback. J. Climate, 14, 12621276, doi:10.1175/1520-0442(2001)014<1262:FAVOAN>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Xie, S.-P., Y. Tanimoto, H. Noguchi, and T. Matsuno, 1999: How and why climate variability differs between the tropical Atlantic and Pacific. Geophys. Res. Lett., 26, 16091612, doi:10.1029/1999GL900308.

    • Search Google Scholar
    • Export Citation
  • Zebiak, S. E., 1986: Atmospheric convergence feedback in a simple model for El Niño. Mon. Wea. Rev., 114, 12631271, doi:10.1175/1520-0493(1986)114<1263:ACFIAS>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Zhang, H., A. Clement, and P. D. Nezio, 2014a: The South Pacific meridional mode: A mechanism for ENSO-like variability. J. Climate, 27, 769783, doi:10.1175/JCLI-D-13-00082.1.

    • Search Google Scholar
    • Export Citation
  • Zhang, H., C. Deser, A. Clement, and R. A. Tomas, 2014b: Equatorial signatures of the Pacific meridional modes: Dependence on mean climate state. Geophys. Res. Lett., 41, 568574, doi:10.1002/2013GL058842.

    • Search Google Scholar
    • Export Citation
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