• Betts, A., 1997: The parameterization of deep convection. The Physics and Parameterization of Atmospheric Moist Convection, R. K. Smith, Ed., Kluwer, 255–279.

    • Search Google Scholar
    • Export Citation
  • Bretherton, C. S., , and A. H. Sobel, 2002: A simple model of a convectively coupled Walker circulation using the weak temperature gradient approximation. J. Climate, 15 , 29072920.

    • Search Google Scholar
    • Export Citation
  • Chiang, J. C. H., , and A. H. Sobel, 2002: Tropical tropospheric temperature variations caused by ENSO and their influence on the remote tropical climate. J. Climate, 15 , 26162631.

    • Search Google Scholar
    • Export Citation
  • Cubukcu, N., , and T. N. Krishnamurti, 2002: Low-frequency controls on the thresholds of sea surface temperature over the western tropical Pacific. J. Climate, 15 , 16261642.

    • Search Google Scholar
    • Export Citation
  • Doedel, E. J., , A. R. Champneys, , T. F. Fairgrieve, , Y. A. Kuznetsov, , B. Sandstede, , and X-J. Wang, 1997: AUTO97: Continuation and bifurcation software for ordinary differential equations. Tech. Rep., Department of Computer Science, Concordia University, Montreal, Canada, 157 pp. [Available online at http://indy.cs.concordia.ca/auto/bib/.].

    • Search Google Scholar
    • Export Citation
  • Ermentrout, B., 2002: Simulating, Analyzing, and Animating Dynamical Systems. A Guide to XPPAUT for Researchers and Students. SIAM, 290 pp.

    • Search Google Scholar
    • Export Citation
  • Fasullo, J., , and P. J. Webster, 1999: Warm pool SST variability in relation to the surface energy balance. J. Climate, 12 , 12921305.

  • Fasullo, J., , and P. J. Webster, 2000: Atmospheric and surface variations during westerly wind bursts in the tropical western Pacific. Quart. J. Roy. Meteor. Soc., 126 , 899924.

    • Search Google Scholar
    • Export Citation
  • Flatau, M., , P. J. Flatau, , P. Phoebus, , and P. P. Niller, 1997: The feedback between equatorial convection and local radiative and evaporative processes: The implications for intraseasonal oscillations. J. Atmos. Sci., 54 , 23732386.

    • Search Google Scholar
    • Export Citation
  • Fu, R., , A. D. Delgenio, , W. B. Rossow, , and W. T. Liu, 1992: Cirrus-cloud thermostat for tropical sea-surface temperatures tested using satellite data. Nature, 358 , 394397.

    • Search Google Scholar
    • Export Citation
  • Fuchs, Z., , and D. J. Raymond, 2002: Large-scale modes of a nonrotating atmosphere with water vapor and cloud–radiation feedbacks. J. Atmos. Sci., 59 , 16691679.

    • Search Google Scholar
    • Export Citation
  • Gent, P. R., 1991: The heat budget of the TOGA COARE domain in an ocean model. J. Geophys. Res., 96 , 33233330.

  • Gildor, H., , A. H. Sobel, , M. A. Cane, , and R. N. Sambrotto, 2003: A role for ocean biota in tropical intraseasonal atmospheric variability. Geophys. Res. Lett., 30 .1460, doi:10.1029/2002GL016759.

    • Search Google Scholar
    • Export Citation
  • Grabowski, W. W., , J. I. Yano, , and M. W. Moncrieff, 2000: Cloud resolving modeling of tropical circulations driven by large-scale SST gradients. J. Atmos. Sci., 57 , 20222039.

    • Search Google Scholar
    • Export Citation
  • Harrison, E. F., , P. Minnis, , B. R. Barkstrom, , V. Ramanathan, , R. D. Cess, , and G. G. Gibson, 1990: Seasonal-variation of cloud radiative forcing derived from the earth radiation budget experiment. J. Geophys. Res., 95 , 1868718703.

    • Search Google Scholar
    • Export Citation
  • Hartmann, D. L., , and M. L. Michelsen, 1993: Large-scale effects on the regulation of tropical sea surface temperature. J. Climate, 6 , 20492062.

    • Search Google Scholar
    • Export Citation
  • Hartmann, D. L., , and M. L. Michelsen, 2002a: Reply. Bull. Amer. Meteor. Soc., 83 , 13491352.

  • Hartmann, D. L., , and M. L. Michelsen, 2002b: No evidence for iris. Bull. Amer. Meteor. Soc., 83 , 249254.

  • Hartmann, D. L., , L. A. Moy, , and Q. Fu, 2001: Tropical convection and the energy balance at the top of the atmosphere. J. Climate, 14 , 44954511.

    • Search Google Scholar
    • Export Citation
  • Hendon, H. H., 2000: Impact of air–sea coupling on the Madden–Julian Oscillation in a general circulation model. J. Atmos. Sci., 57 , 39393952.

    • Search Google Scholar
    • Export Citation
  • Hendon, H. H., , and J. Glick, 1997: Intraseasonal air–sea interaction in the tropical Indian and Pacific Oceans. J. Climate, 10 , 647661.

    • Search Google Scholar
    • Export Citation
  • Hu, Q., , and D. Randall, 1994: Low-frequency oscillations in radiative convective systems. J. Atmos. Sci., 51 , 10891099.

  • Hu, Q., , and D. Randall, 1995: Low-frequency oscillations in radiative convective systems. Part II: An idealized model. J. Atmos. Sci., 52 , 478490.

    • Search Google Scholar
    • Export Citation
  • Inness, P. M., , and J. M. Slingo, 2003: Simulation of the Madden–Julian oscillation in a coupled general circulation model. Part I: Comparison with observations and an atmosphere-only GCM. J. Climate, 16 , 345364.

    • Search Google Scholar
    • Export Citation
  • Jones, C., , D. E. Waliser, , and C. Gautier, 1998: The influence of the Madden–Julian oscillation on ocean surface heat fluxes and sea surface temperature. J. Climate, 11 , 10571072.

    • Search Google Scholar
    • Export Citation
  • Kemball-Cook, S., , B. Wang, , and X. H. Fu, 2002: Simulation of the intraseasonal oscillation in the ECHAM-4 model: The impact of coupling with an ocean model. J. Atmos. Sci., 59 , 14331453.

    • Search Google Scholar
    • Export Citation
  • Krishnamurti, T. N., , D. K. Oosterhof, , and A. V. Mehta, 1988: Air–sea interaction on the timescale of 30 to 50 days. J. Atmos. Sci., 45 , 13041322.

    • Search Google Scholar
    • Export Citation
  • Lau, K. M., , and C. H. Sui, 1997: Mechanisms of short-term sea surface temperature regulation: Observations during TOGA COARE. J. Climate, 10 , 465472.

    • Search Google Scholar
    • Export Citation
  • Lee, M. I., , I. S. Kang, , J. K. Kim, , and B. E. Mapes, 2001: Influence of cloud–radiation interaction on simulating tropical intraseasonal oscillation with an atmospheric general circulation model. J. Geophys. Res., 106 , 1421914233.

    • Search Google Scholar
    • Export Citation
  • Lin, X., , and R. H. Johnson, 1996: Heating, moistening, and rainfall over the western Pacific warm pool during TOGA COARE. J. Atmos. Sci., 53 , 33673383.

    • Search Google Scholar
    • Export Citation
  • Lindzen, R. S., , M. D. Chou, , and A. Y. Hou, 2001: Does the earth have an adaptive infrared iris? Bull. Amer. Meteor. Soc., 82 , 417432.

    • Search Google Scholar
    • Export Citation
  • Lindzen, R. S., , M. D. Chou, , and A. Y. Hou, 2002: Comments on “No evidence for iris.”. Bull. Amer. Meteor. Soc., 83 , 13451349.

  • Lukas, R., , and E. Lindstrom, 1991: The mixed layer of the western equatorial Pacific Ocean. J. Geophys. Res., 96 , 33433357.

  • Madden, R. A., , and P. R. Julian, 1994: Observations of the 40–50-day tropical oscillation—A review. Mon. Wea. Rev., 122 , 814837.

  • Majda, A., , and R. Klein, 2003: Systematic multiscale models for the Tropics. J. Atmos. Sci., 60 , 393408.

  • Maloney, E. D., , and J. T. Kiehl, 2002: MJO-related SST variations over the tropical eastern Pacific during Northern Hemisphere summer. J. Climate, 15 , 675689.

    • Search Google Scholar
    • Export Citation
  • Neelin, J., 1997: Implications of convective quasi-equilibrium for the large-scale flow. The Physics and Parameterization of Moist Atmospheric Convection, R. K. Smith, Ed., Kluwer Academic, 413–446.

    • Search Google Scholar
    • Export Citation
  • Neelin, J., , and I. M. Held, 1987: Modeling tropical convergence based on the moist static energy budget. Mon. Wea. Rev., 115 , 312.

  • Neelin, J., , and N. Zeng, 2000: A quasi-equilibrium tropical circulation model: Formulation. J. Atmos. Sci., 57 , 17411766.

  • Newell, R. E., 1979: Climate and the ocean. Amer. Sci., 67 , 405416.

  • Ramanathan, V., , and W. Collins, 1991: Thermodynamic regulation of ocean warming by cirrus clouds deduced from observations of the 1987 El Niño. Nature, 351 , 2732.

    • Search Google Scholar
    • Export Citation
  • Ramanathan, V., , R. D. Cess, , E. F. Harrison, , P. Minnis, , B. R. Barkstrom, , E. Ahmad, , and D. Hartmann, 1989: Cloud-radiative forcing and climate: Results from the earth radiation budget experiment. Science, 243 , 5763.

    • Search Google Scholar
    • Export Citation
  • Raymond, D. J., 2000: Thermodynamic control of tropical rainfall. Quart. J. Roy. Meteor. Soc., 126 , 889898.

  • Seager, R., , S. E. Zebiak, , and M. A. Cane, 1988: A model of the tropical Pacific sea-surface temperature climatology. J. Geophys. Res., 93 , 12651280.

    • Search Google Scholar
    • Export Citation
  • Sobel, A. H., 2003: On the coexistence of an evaporation minimum and precipitation maximum over the warm pool. J. Climate, 16 , 10031009.

    • Search Google Scholar
    • Export Citation
  • Sobel, A. H., , and C. S. Bretherton, 2000: Modeling tropical precipitation in a single column. J. Climate, 13 , 43784392.

  • Sobel, A. H., , and C. S. Bretherton, 2003: Large-scale waves interacting with deep convection in idealized mesoscale model simulations. Tellus, 55 , 4560.

    • Search Google Scholar
    • Export Citation
  • Sobel, A. H., , J. Nilsson, , and L. M. Polvani, 2001: The weak temperature gradient approximation and balanced tropical moisture waves. J. Atmos. Sci., 58 , 36503665.

    • Search Google Scholar
    • Export Citation
  • Strogatz, S., 1994: Nonlinear Dynamics and Chaos: With Applications to Physics, Biology, Chemistry, and Engineering. Addison-Wesley, 498 pp.

    • Search Google Scholar
    • Export Citation
  • Su, H., , and J. D. Neelin, 2002: Teleconnection mechanisms for tropical Pacific descent anomalies during El Niño. J. Atmos. Sci., 59 , 26942712.

    • Search Google Scholar
    • Export Citation
  • Vecchi, G. A., , and D. E. Harrison, 2002: Monsoon breaks and subseasonal sea surface temperature variability in the Bay of Bengal. J. Climate, 15 , 14851493.

    • Search Google Scholar
    • Export Citation
  • Waliser, D. E., 1996: Formation and limiting mechanisms for very high sea surface temperature: Linking the dynamics and the thermodynamics. J. Climate, 9 , 161188.

    • Search Google Scholar
    • Export Citation
  • Waliser, D. E., , and N. E. Graham, 1993: Convective cloud systems and warm-pool sea-surface temperatures: Coupled interactions and self-regulation. J. Geophys. Res., 98 , 1288112893.

    • Search Google Scholar
    • Export Citation
  • Waliser, D. E., , K. M. Lau, , and J. H. Kim, 1999: The influence of coupled sea surface temperatures on the Madden–Julian oscillation: A model perturbation experiment. J. Atmos. Sci., 56 , 333358.

    • Search Google Scholar
    • Export Citation
  • Wallace, J. M., 1992: Effect of deep convection on the regulation of tropical sea-surface temperature. Nature, 357 , 230231.

  • Wang, B., , and X. Xie, 1998: Coupled modes of the warm pool climate system. Part I: The role of air–sea interactions in maintaining Madden Julian oscillation. J. Climate, 11 , 21162135.

    • Search Google Scholar
    • Export Citation
  • Watterson, I. G., 2002: The sensitivity of subannual and intraseasonal tropical variability to model ocean mixed layer depth. J. Geophys. Res., 107 .4020, doi:10.1029/2001JD000671.

    • Search Google Scholar
    • Export Citation
  • Woolnough, S. J., , J. M. Slingo, , and B. J. Hoskins, 2000: The relationship between convection and sea surface temperature on intraseasonal timescales. J. Climate, 13 , 20862104.

    • Search Google Scholar
    • Export Citation
  • Zeng, N., 1998: Understanding climate sensitivity to tropical deforestation in a mechanistic model. J. Climate, 11 , 19691975.

  • Zeng, N., , and J. D. Neelin, 1999: A land–atmosphere interaction theory for the tropical deforestation problem. J. Climate, 12 , 857872.

    • Search Google Scholar
    • Export Citation
  • Zeng, N., , J. D. Neelin, , and C. Chou, 2000: A quasi-equilibrium tropical circulation model: Implementation and simulation. J. Atmos. Sci., 57 , 17671796.

    • Search Google Scholar
    • Export Citation
  • Zhang, C. D., 1996: Atmospheric intraseasonal variability at the surface in the tropical western Pacific Ocean. J. Atmos. Sci., 53 , 739758.

    • Search Google Scholar
    • Export Citation
  • Zhang, C. D., , and H. H. Hendon, 1997: Propagating and standing components of the intraseasonal oscillation in tropical convection. J. Atmos. Sci., 54 , 741752.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 172 172 3
PDF Downloads 33 33 1

A Simple Time-Dependent Model of SST Hot Spots

View More View Less
  • 1 Department of Applied Physics and Applied Mathematics, and Department of Earth and Environmental Sciences, Columbia University, New York, New York
  • | 2 Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York
© Get Permissions Rent on DeepDyve
Restricted access

Abstract

The authors introduce a simple model for the time-dependent evolution of tropical “hot spots,” or localized regions where the sea surface temperature (SST) becomes unusually high for a limited period of time. The model consists of a simple zero-dimensional atmospheric model coupled to an ocean mixed layer. For plausible parameter values, steady solutions of this model can become unstable to time-dependent oscillations, which are studied both by linear stability analysis and explicit time-dependent nonlinear simulation. For reasonable parameter values, the oscillations have periods ranging from intraseasonal to subannual. For parameter values only slightly beyond the threshold for instability, the oscillations become strongly nonlinear, and have a recharge–discharge character.

The basic mechanism for the instability and oscillations comes from cloud-radiative and wind-evaporation feedbacks, which play the same role in the dynamics and are lumped together into a single parameterization. This is possible because, under the assumption that the shortwave and longwave radiative effects of high clouds cancel at the top of the atmosphere, their net effect is only to transfer energy from the ocean to the atmosphere exactly as a surface flux does, and because the two processes are observed to be approximately in phase on intraseasonal timescales. Both feedbacks move energy from the ocean to the atmosphere in convective regions, intensifying the convection and thus destabilizing the system. The same energy transfer cools the ocean, which eventually (but not instantaneously, because of the mixed layer’s heat capacity) reduces the SST enough to render the model stable to deep convection, shutting off the convection. At that point the SST begins warming again under the resulting clear skies, starting the cycle over.

The authors also examine the forced linear response of the model, in a weakly stable regime, to an imposed atmospheric oscillation. This is meant to crudely represent forcing by an atmospheric intraseasonal oscillation. The model’s response as a function of mixed layer depth is not monotonic, but has a maximum around 10–20 m, which happens to be close to the observed value in the western Pacific warm pool.

Corresponding author address: Dr. Adam H. Sobel, Department of Applied Physics and Applied Mathematics, Columbia University, 500 West 120th St., Rm. 217, New York, NY 10027. Email: ahs129@columbia.edu

Abstract

The authors introduce a simple model for the time-dependent evolution of tropical “hot spots,” or localized regions where the sea surface temperature (SST) becomes unusually high for a limited period of time. The model consists of a simple zero-dimensional atmospheric model coupled to an ocean mixed layer. For plausible parameter values, steady solutions of this model can become unstable to time-dependent oscillations, which are studied both by linear stability analysis and explicit time-dependent nonlinear simulation. For reasonable parameter values, the oscillations have periods ranging from intraseasonal to subannual. For parameter values only slightly beyond the threshold for instability, the oscillations become strongly nonlinear, and have a recharge–discharge character.

The basic mechanism for the instability and oscillations comes from cloud-radiative and wind-evaporation feedbacks, which play the same role in the dynamics and are lumped together into a single parameterization. This is possible because, under the assumption that the shortwave and longwave radiative effects of high clouds cancel at the top of the atmosphere, their net effect is only to transfer energy from the ocean to the atmosphere exactly as a surface flux does, and because the two processes are observed to be approximately in phase on intraseasonal timescales. Both feedbacks move energy from the ocean to the atmosphere in convective regions, intensifying the convection and thus destabilizing the system. The same energy transfer cools the ocean, which eventually (but not instantaneously, because of the mixed layer’s heat capacity) reduces the SST enough to render the model stable to deep convection, shutting off the convection. At that point the SST begins warming again under the resulting clear skies, starting the cycle over.

The authors also examine the forced linear response of the model, in a weakly stable regime, to an imposed atmospheric oscillation. This is meant to crudely represent forcing by an atmospheric intraseasonal oscillation. The model’s response as a function of mixed layer depth is not monotonic, but has a maximum around 10–20 m, which happens to be close to the observed value in the western Pacific warm pool.

Corresponding author address: Dr. Adam H. Sobel, Department of Applied Physics and Applied Mathematics, Columbia University, 500 West 120th St., Rm. 217, New York, NY 10027. Email: ahs129@columbia.edu

Save