We thank Paul O’Gorman for performing the simulations without ocean heat transport and for helpful comments and discussions. We are grateful for support by the National Science Foundation (Grants ATM-0450059 and AGS-1019211), the Davidow Discovery Fund, and a David and Lucile Packard Fellowship. The simulations were performed on the Division of Geological and Planetary Sciences’s Dell cluster at the California Institute of Technology. The program code for the simulations described in this paper, and the simulation results themselves, are available from the authors upon request.
Archer, C. L., , and K. Caldeira, 2008: Historical trends in the jet streams. Geophys. Res. Lett., 35, L08803, doi:10.1029/2008GL033614.
Bordoni, S., , and T. Schneider, 2008: Monsoons as eddy-mediated regime transitions of the tropical overturning circulation. Nat. Geosci., 1, 515–519.
Caballero, R., 2007: Role of eddies in the interannual variability of Hadley cell strength. Geophys. Res. Lett., 34, L22705, doi:10.1029/2007GL030971.
Caballero, R., 2008: Hadley cell bias in climate models linked to extratropical eddy stress. Geophys. Res. Lett., 35, L18709, doi:10.1029/2008GL035084.
Caballero, R., , and M. Huber, 2010: Spontaneous transition to superrotation in warm climates simulated by CAM3. Geophys. Res. Lett., 37, L11701, doi:10.1029/2010GL043468.
Chen, J., , B. E. Carlson, , and A. D. Del Genio, 2002: Evidence for strengthening of the tropical general circulation in the 1990s. Science, 295, 838–841.
Dickinson, R. E., 1971: Analytic model for zonal winds in the tropics. II. Variation of the tropospheric mean structure with season and differences between hemispheres. Mon. Wea. Rev., 99, 511–523.
Frierson, D. M. W., 2007: The dynamics of idealized convection schemes and their effect on the zonally averaged tropical circulation. J. Atmos. Sci., 64, 1959–1976.
Frierson, D. M. W., , I. M. Held, , and P. Zurita-Gotor, 2006: A gray-radiation aquaplanet moist GCM. Part I: Static stability and eddy scale. J. Atmos. Sci., 63, 2548–2566.
Frierson, D. M. W., , J. Lu, , and G. Chen, 2007: The width of the Hadley cell in simple and comprehensive general circulation models. Geophys. Res. Lett., 34, L18804, doi:10.1029/2007GL031115.
Haynes, P. H., , M. E. McIntyre, , T. G. Shepherd, , C. J. Marks, , and K. P. Shine, 1991: On the “downward control” of extratropical diabatic circulations by eddy-induced mean zonal forces. J. Atmos. Sci., 48, 651–678.
Held, I. M., 2000: The partitioning of the poleward energy transport between the tropical ocean and atmosphere. J. Atmos. Sci., 58, 943–948.
Held, I. M., , and A. Y. Hou, 1980: Nonlinear axially symmetric circulations in a nearly inviscid atmosphere. J. Atmos. Sci., 37, 515–533.
Herweijer, C., , R. Seager, , M. Winton, , and A. Clement, 2005: Why ocean heat transport warms the global mean climate. Tellus, 57A, 662–675.
Hudson, R. D., , M. F. Andrade, , M. B. Follette, , and A. D. Frolov, 2006: The total ozone field separated into meteorological regimes. Part II: Northern Hemisphere mid-latitude total ozone trends. Atmos. Chem. Phys., 6, 5183–5191.
Lee, M. I., , M. J. Suarez, , I. S. Kang, , I. M. Held, , and D. Kim, 2008: A moist benchmark calculation for atmospheric general circulation models. J. Climate, 21, 4934–4954.
Lindzen, R. S., , and A. V. Hou, 1988: Hadley circulations for zonally averaged heating centered off the equator. J. Atmos. Sci., 45, 2416–2427.
Lu, J., , G. A. Vecchi, , and T. Reichler, 2007: Expansion of the Hadley cell under global warming. Geophys. Res. Lett., 34, L06805, doi:10.1029/2006GL028443.
Lu, P., , J. P. McCreary Jr., , and B. A. Klinger, 1998: Meridional circulation cells and the source waters of the Pacific Equatorial Undercurrent. J. Phys. Oceanogr., 28, 62–84.
McCreary, J. P., Jr., , and P. Lu, 1994: Interaction between the subtropical and equatorial ocean circulations: The subtropical cell. J. Phys. Oceanogr., 24, 466–497.
Mitas, C. M., , and A. Clement, 2005: Has the Hadley cell been strengthening in recent decades? Geophys. Res. Lett., 32, L03809, doi:10.1029/2004GL021765.
O’Gorman, P. A., , and T. Schneider, 2008a: Energy of midlatitude transient eddies in idealized simulations of changed climates. J. Climate, 21, 5797–5806.
O’Gorman, P. A., , and T. Schneider, 2008b: The hydrological cycle over a wide range of climates simulated with an idealized GCM. J. Climate, 21, 3815–3832.
O’Gorman, P. A., , and T. Schneider, 2008c: Weather-layer dynamics of baroclinic eddies and multiple jets in an idealized general circulation model. J. Atmos. Sci., 65, 524–535.
Quan, X.-W., , H. F. Diaz, , and M. P. Hoerling, 2004: Change in the tropical Hadley cell since 1950. The Hadley Circulation: Past, Present, and Future, H. F. Diaz and R. S. Bradley, Eds., Springer, 85–120.
Reichler, T., 2009: Changes in the atmospheric circulation as indicator of climate change. Climate Change: Observed Impacts on Planet Earth, T. M. Letcher, Ed., Elsevier, 145–164.
Rosenlof, K. H., 2002: Transport changes inferred from HALOE water and methane measurements. J. Meteor. Soc. Japan, 80, 831–848.
Santer, B. D., and Coauthors, 2005: Amplification of surface temperature trends and variability in the tropical atmosphere. Science, 309, 1551–1556.
Schneider, E. K., 1977: Axially symmetric steady-state models of the basic state for instability and climate studies. Part II. Nonlinear calculations. J. Atmos. Sci., 34, 280–296.
Schneider, T., , and S. Bordoni, 2008: Eddy-mediated regime transitions in the seasonal cycle of a Hadley circulation and implications for monsoon dynamics. J. Atmos. Sci., 65, 915–934.
Schneider, T., , and C. C. Walker, 2008: Scaling laws and regime transitions of macroturbulence in dry atmospheres. J. Atmos. Sci., 65, 2153–2173.
Seager, R., and Coauthors, 2007: Model projections of an imminent transition to a more arid climate in southwestern North America. Science, 316, 1181–1184.
Seidel, D. J., , and R. J. Randel, 2007: Recent widening of the tropical belt: Evidence from tropopause observations. J. Geophys. Res., 112, D20113, doi:10.1029/2007JD008861.
Seidel, D. J., , Q. Fu, , W. J. Randel, , and T. J. Reichler, 2008: Widening of the tropical belt in a changing climate. Nat. Geosci., 1, 21–24.
Sherwood, S. C., 2007: Simultaneous detection of climate change and observing biases in a network with incomplete sampling. J. Climate, 20, 4047–4062.
Simmons, A. J., , and D. M. Burridge, 1981: An energy and angular-momentum conserving vertical finite-difference scheme and hybrid vertical coordinates. Mon. Wea. Rev., 109, 758–766.
Tanaka, H. L., , N. Ishizaki, , and D. Nohara, 2005: Intercomparison of the intensities and trends of Hadley, Walker and monsoon circulations in the global warming projections. SOLA, 1, 77–80.
Trenberth, K. E., , and A. Solomon, 1994: The global heat balance: Heat transports in the atmosphere and ocean. Climate Dyn., 10, 107–134.
Trenberth, K. E., , and J. M. Caron, 2001: Estimates of meridional atmosphere and ocean heat transports. J. Climate, 14, 3433–3443.
Trenberth, K. E., , and D. P. Stepaniak, 2003: Seamless poleward atmospheric energy transports and implications for the Hadley circulation. J. Climate, 16, 3706–3722.
Walker, C. C., , and T. Schneider, 2005: Response of idealized Hadley circulations to seasonally varying heating. Geophys. Res. Lett., 32, L06813, doi:10.1029/2004GL022304.
Walker, C. C., , and T. Schneider, 2006: Eddy influences on Hadley circulations: Simulations with an idealized GCM. J. Atmos. Sci., 63, 3333–3350.
The values for α are 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.5, 3.0, 4.0, and 6.0.
These results contradict the hypothesis of Trenberth and Stepaniak (2003), according to which extratropical eddy heat fluxes were posited as a driver of the Hadley circulation. In our simulations, changes in the strength of the Hadley circulation between ocean simulations and slab simulations are not accompanied by changes in extratropical eddy heat fluxes that are nearly as large, and the total heat flux is not necessarily “seamless” in the subtropics.