Strengthening of the Walker circulation under globalwarming in an aqua-planet general circulation model simulation
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Most climate models project a weakening of theWalker circulation under global warming scenarios. It is argued, based on a global averaged moisture budget, that this weakening can be attributed to a slower rate of rainfall increase compared to that of moisture increase, which leads to a decrease in ascending motion. Through an idealized aqua-planet simulation in which a zonal wavenumber-1 SST distribution is prescribed along the equator, we find that the Walker circulation is strengthened under a uniform 2-K SST warming, even though the global mean rainfall–moisture relationship remains the same. Further diagnosis shows that the ascending branch of the Walker cell is enhanced in the upper troposphere but weakened in the lower troposphere. As a result, a “double-cell” circulation change pattern with a clockwise (anti-clockwise) circulation anomaly in the upper (lower) troposphere forms, and the upper tropospheric circulation change dominates. The mechanism for the formation of the “double cell” circulation pattern is attributed to a larger (smaller) rate of increase of diabatic heating than static stability in the upper (lower) troposphere. The result indicates that the future change of the Walker circulation cannot simply be interpreted based on a global mean moisture budget argument.
KeywordsWalker circulation global warming aqua-planet simulation
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- Endo, H., A. Kitoh, T. Ose, R. Mizuta, and S. Kusunoki, 2012: Future changes and uncertainties in Asian precipitation simulated by multiphysics and multi-sea surface temperature ensemble experiments with high-resolution Meteorological Research Institute atmospheric general circulation models (MRI-AGCMs). J. Geophys. Res., 117, D16118.CrossRefGoogle Scholar
- Holton, J. R., 2004: An Introduction to Dynamic Meteorology. 4th ed., Academic Press, 535 pp.Google Scholar
- Hsu, P.-C., and T. Li, 2012: Is “rich-get-richer” valid for Indian Ocean and Atlantic ITCZ? Geophys. Res. Lett., 39, L13705, doi: 10.1029/2012GL052399.Google Scholar
- IPCC, 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K. B. Averyt, M. Tignor, H. L. Miller, Eds., Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 996 pp.Google Scholar
- IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Stocker, T. F., and Coauthors, Eds. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 950 pp.Google Scholar
- Kain, J. S., and J. M. Fritsch, 1993: Convective parameterization for mesoscale models: The Kain-Fritsch scheme. The Representation of Cumulus Convection in Numerical Models, Emanuel and Raymond, Eds., Amer. Meteor. Soc., 165–170.Google Scholar
- Mizuta, R., and Coauthors, 2012: Climate simulations using the improved MRI-AGCM with 20-km grid. J. Meteor. Soc. Japan, 90A, 235–260.Google Scholar
- Shine, K. P., R. G. Derwent, D. J. Wuebbles, and J.-J. Morcrette, 1990: Radiative forcing of climate. Climate Change: The IPCC Scientific Assessment, Houghton et al., Eds. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 41–68.Google Scholar
- Stocker, T. F., 2001: Climate Change 2001: The Scientific Basis. Chapter 7, J. T. Houghton, Eds., Cambridge Univ. Press, Cambridge, 417–470.Google Scholar
- Yukimoto, S. H., and Coauthors, 2011: Meteorological research institute-earth system model Version 1 (MRI-ESM1)—Model description. Technical Reports of the Meteorological Research Institute, No. 64, 96 pp.Google Scholar