Editorial Type:
Article
Article Type:
Research Article

Analysis of Atmospheric Energy Transport in ERA-40 and Implications for Simple Models of the Mean Tropical Circulation

Matthew E. Peters Department of Earth and Planetary Sciences, and School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts

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Zhiming Kuang Department of Earth and Planetary Sciences, and School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts

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Christopher C. Walker Department of Earth and Planetary Sciences, and School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts

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Print Publication:
15 Oct 2008
DOI:
https://doi.org/10.1175/2008JCLI2073.1
Page(s):
5229–5241
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Abstract

An analysis of atmospheric energy transport in 22 years (1980–2001) of the 40-yr ECMWF Re-Analysis (ERA-40) is presented. In the analyzed budgets, there is a large cancellation between divergences of dry static and latent energy such that the total energy divergence is positive over all tropical oceanic regions except for the east Pacific cold tongue, consistent with previous studies. The west Pacific and Indian Oceans are characterized by a balance between diabatic sources and mean advective energy export, with a small eddy contribution. However, in the central and eastern Pacific convergence zone, total energy convergence by the mean circulation is balanced by submonthly eddies, with a small diabatic source. Decomposing the mean advective tendency into terms due to horizontal and vertical advection shows that the spatial variation in the mean advection is due largely to variations in vertical advection; these variations are further attributed to variations in the vertical profile of the vertical velocity. The eddy energy export, due almost exclusively to eddy moisture export, does not exhibit any significant seasonal variation.

The relationship between the eddies and the mean circulation is examined. Large-scale moisture diffusion is correlated with eddy moisture export on (500 km)2 spatial scales, implying that eddy activity preferentially dries narrow convergence zones over wide ones. Eddy moisture export is further linked to the depth of mean convection in large-scale convergence zones with larger eddy export associated with shallower circulations. This suggests a mechanism that could contribute to the observed variation in mean divergence profiles across the northern tropical Pacific whereby sea surface temperature gradients set the width of convergence zones and eddy activity modulates the tropospheric relative humidity and divergence profile. The importance of variations in the vertical profile of the vertical velocity and eddies in closing the energy budget implies that simple models of the mean tropical circulation should include these effects.

Corresponding author address: Zhiming Kuang, Harvard University, Earth and Planetary Sciences Department, 20 Oxford St., Cambridge, MA 02138. Email: kuang@fas.harvard.edu

Abstract

An analysis of atmospheric energy transport in 22 years (1980–2001) of the 40-yr ECMWF Re-Analysis (ERA-40) is presented. In the analyzed budgets, there is a large cancellation between divergences of dry static and latent energy such that the total energy divergence is positive over all tropical oceanic regions except for the east Pacific cold tongue, consistent with previous studies. The west Pacific and Indian Oceans are characterized by a balance between diabatic sources and mean advective energy export, with a small eddy contribution. However, in the central and eastern Pacific convergence zone, total energy convergence by the mean circulation is balanced by submonthly eddies, with a small diabatic source. Decomposing the mean advective tendency into terms due to horizontal and vertical advection shows that the spatial variation in the mean advection is due largely to variations in vertical advection; these variations are further attributed to variations in the vertical profile of the vertical velocity. The eddy energy export, due almost exclusively to eddy moisture export, does not exhibit any significant seasonal variation.

The relationship between the eddies and the mean circulation is examined. Large-scale moisture diffusion is correlated with eddy moisture export on (500 km)2 spatial scales, implying that eddy activity preferentially dries narrow convergence zones over wide ones. Eddy moisture export is further linked to the depth of mean convection in large-scale convergence zones with larger eddy export associated with shallower circulations. This suggests a mechanism that could contribute to the observed variation in mean divergence profiles across the northern tropical Pacific whereby sea surface temperature gradients set the width of convergence zones and eddy activity modulates the tropospheric relative humidity and divergence profile. The importance of variations in the vertical profile of the vertical velocity and eddies in closing the energy budget implies that simple models of the mean tropical circulation should include these effects.

Corresponding author address: Zhiming Kuang, Harvard University, Earth and Planetary Sciences Department, 20 Oxford St., Cambridge, MA 02138. Email: kuang@fas.harvard.edu

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  • Allan, R. P., M. A. Pamment, and A. Slingo, 2004: Simulation of the Earth’s radiation budget by the European Centre for Medium-Range Weather Forecasts 40-year reanalysis (ERA40). J. Geophys. Res., 109 .D18107, doi:10.1029/2004JD004816.

    • Search Google Scholar
    • Export Citation

  • Back, L. E., and C. S. Bretherton, 2006: Geographic variability in the export of moist static energy and vertical motion profiles in the tropical Pacific. Geophys. Res. Lett., 33 .L17810, doi:10.1029/2006GL026672.

    • 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 , 2907–2920.

    • Search Google Scholar
    • Export Citation

  • Bretherton, C. S., M. E. Peters, and L. E. Back, 2004: Relationships between water vapor path and precipitation over the tropical oceans. J. Climate, 17 , 1517–1528.

    • Search Google Scholar
    • Export Citation

  • Bretherton, C. S., P. N. Blossey, and M. E. Peters, 2006: Interpretation of simple and cloud-resolving simulations of moist convection–radiation interaction with a mock-Walker circulation. Theor. Comp. Fluid Dyn., 20 , 421–442. doi:10.1007/s00162-006-0029-7.

    • Search Google Scholar
    • Export Citation

  • Cau, P., J. Methven, and B. Hoskins, 2005: Representation of dry tropical layers and their origins in ERA-40 data. J. Geophys. Res., 110 .D06110, doi:10.1029/2004JD004928.

    • Search Google Scholar
    • Export Citation

  • Emanuel, K. A., J. D. Neelin, and C. S. Bretherton, 1994: On large-scale circulations in converting atmospheres. Quart. J. Roy. Meteor. Soc., 120 , 1111–1143.

    • Search Google Scholar
    • Export Citation

  • Grell, A. G., 1993: Prognostic evaluation of assumptions used by cumulus parameterizations. Mon. Wea. Rev., 121 , 764–787.

  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77 , 437–471.

  • Mapes, B. E., and P. Zuidema, 1996: Radiative–dynamical consequences of dry tongues in the tropical troposphere. J. Atmos. Sci., 53 , 620–638.

    • Search Google Scholar
    • Export Citation

  • Neelin, J. D., 1997: Implications of convective quasi-equilibria for the large-scale flow. The Physics and Parameterization of Moist Convection, Kluwer Academic, 413–416.

    • Search Google Scholar
    • Export Citation

  • Neelin, J. D., and I. M. Held, 1987: Modeling tropical convergence based on the moist static energy budget. Mon. Wea. Rev., 115 , 3–12.

    • Search Google Scholar
    • Export Citation

  • Neelin, J. D., and N. Zeng, 2000: The first quasi-equilibrium tropical circulation model—Formulation. J. Atmos. Sci., 57 , 1741–1766.

    • Search Google Scholar
    • Export Citation

  • Nolan, D. S., C. Zhang, and S-h Chen, 2007: Dynamics of the shallow meridional circulation around intertropical convergence zones. J. Atmos. Sci., 64 , 2262–2285.

    • Search Google Scholar
    • Export Citation

  • Pan, H. L., and W. S. Wu, 1995: Implementing a mass flux convection parameterization package for the NMC medium-range forecast model. NMC Office Note 409, 40 pp. [Available from NCEP, 5200 Auth Road, Washington, DC 20233.].

  • Peters, M. E., and C. S. Bretherton, 2005: A simplified model of the Walker circulation with an interactive ocean mixed layer and cloud-radiative feedbacks. J. Climate, 18 , 4216–4234.

    • Search Google Scholar
    • Export Citation

  • Postel, G. A., and M. H. Hitchman, 1999: A climatology of Rossby wave breaking along the subtropical tropopause. J. Atmos. Sci., 56 , 359–373.

    • Search Google Scholar
    • Export Citation

  • Redelsperger, J-L., D. B. Parsons, and F. Guichard, 2002: Recovery processes and factors limiting cloud-top height following the arrival of a dry intrusion observed during TOGA-COARE. J. Atmos. Sci., 59 , 2438–2457.

    • Search Google Scholar
    • Export Citation

  • Sherwood, S. C., 1999: Convective precursors and predictability in the tropical west Pacific. Mon. Wea. Rev., 127 , 2977–2991.

  • Sobel, A. H., and D. J. Neelin, 2006: The boundary layer contribution to intertropical convergence zones in the quasi-equilibrium tropical circulation model framework. Theor. Comp. Fluid Dyn., 20 , 323–350.

    • Search Google Scholar
    • Export Citation

  • Sudradjat, A., R. R. Ferraro, and M. Fiorino, 2005: A comparison of total precipitable water between reanalyses and NVAP. J. Climate, 18 , 1790–1807.

    • Search Google Scholar
    • Export Citation

  • Tiedtke, M., 1989: A comprehensive mass flux scheme for cumulus parameterization in large-scale models. Mon. Wea. Rev., 117 , 1779–1800.

    • Search Google Scholar
    • Export Citation

  • Trenberth, K. E., and D. P. Stepaniak, 2003: Seamless poleward atmospheric energy transports and implications for the Hadley circulation. J. Climate, 16 , 3706–3722.

    • Search Google Scholar
    • Export Citation

  • Trenberth, K. E., J. M. Caron, and D. P. Stepaniak, 2001: The atmospheric energy budget and implications for surface fluxes and ocean heat transports. Climate Dyn., 17 , 259–276.

    • Search Google Scholar
    • Export Citation

  • Trenberth, K. E., D. P. Stepaniak, and J. M. Caron, 2002: Accuracy of atmospheric energy budgets from analyses. J. Climate, 15 , 3343–3360.

    • Search Google Scholar
    • Export Citation

  • Trenberth, K. E., J. Fasullo, and L. Smith, 2005: Trends and variability in column-integrated atmospheric water vapor. Climate Dyn., 24 , 741–758.

    • Search Google Scholar
    • Export Citation

  • Uppala, S. M., and Coauthors, 2005: The ERA-40 Re-Analysis. Quart. J. Roy. Meteor. Soc., 131 , 2961–3012.

  • Waugh, D. W., and L. M. Polvani, 2000: Climatology of intrusions into the tropical upper troposphere. Geophys. Res. Lett., 27 , 3857–3860.

    • Search Google Scholar
    • Export Citation

  • Yoneyama, K., 2003: Moisture variability over the tropical western Pacific ocean. J. Meteor. Soc. Japan, 81 , 317–337.

  • Yoneyama, K., and D. B. Parsons, 1999: A proposed mechanism for the intrusion of dry air into the tropical western Pacific region. J. Atmos. Sci., 56 , 1524–1546.

    • Search Google Scholar
    • Export Citation

  • Zhang, C., M. McGauley, and N. A. Bond, 2004: Shallow meridional circulation in the tropical eastern Pacific. J. Climate, 17 , 133–139.

    • Search Google Scholar
    • Export Citation

  • Zuidema, P., B. Mapes, J. Lin, and C. Fairall, 2006: The interaction of clouds and dry air in the eastern tropical Pacific. J. Climate, 19 , 4531–4544.

    • Search Google Scholar
    • Export Citation
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