Eddy Influences on Hadley Circulations: Simulations with an Idealized GCM

Walker, Christopher C.; Schneider, Tapio

doi:10.1175/jas3821.1

Cited by 247 publications

(314 citation statements)

References 33 publications

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“…Moreover, the results suggest that the scaling laws for dry Hadley circulations derived in dry theories and idealized atmosphere models that neglect vertical diffusion of momentum (e.g. Held and Hou, 1980;Walker and Schneider, 2006;Caballero et al, 2008) might not hold in Snowball Earth atmospheres. This should not be necessarily interpreted as a failure of these theories and idealized models, as they were often developed to capture the dynamics of present-day Earth Hadley circulations, for which surface sensible heat and dry buoyancy fluxes are comparably small and vertical diffusion does not play a dominant role.…”

Section: Discussionmentioning

confidence: 96%

The dynamics of the Snowball Earth Hadley circulation for off-equatorial and seasonally varying insolation

Voigt

2013

Earth Syst. Dynam.

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Abstract. I study the Hadley circulation of a completely icecovered Snowball Earth through simulations with a comprehensive atmosphere general circulation model. Because the Snowball Earth atmosphere is an example of a dry atmosphere, these simulations allow me to test to what extent dry theories and idealized models capture the dynamics of realistic dry Hadley circulations. Perpetual off-equatorial as well as seasonally varying insolation is used, extending a previous study for perpetual on-equatorial (equinox) insolation. Vertical diffusion of momentum, representing the momentum transport of dry convection, is fundamental to the momentum budgets of both the winter and summer cells. In the zonal budget, it is the primary process balancing the Coriolis force. In the meridional budget, it mixes meridional momentum between the upper and the lower branch and thereby decelerates the circulation. Because of the latter, the circulation intensifies by a factor of three when vertical diffusion of momentum is suppressed. For seasonally varying insolation, the circulation undergoes rapid transitions from the weak summer into the strong winter regime. Consistent with previous studies in idealized models, these transitions result from a mean-flow feedback, because of which they are insensitive to the treatment of vertical diffusion of momentum. Overall, the results corroborate previous findings for perpetual on-equatorial insolation. They demonstrate that descriptions of realistic dry Hadley circulations, in particular their strength, need to incorporate the vertical momentum transport by dry convection, a process that is neglected in most dry theories and idealized models. An improved estimate of the strength of the Snowball Earth Hadley circulation will also help to better constrain the climate of a possible Neoproterozoic Snowball Earth and its deglaciation threshold.

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Section: Discussionmentioning

confidence: 96%

The dynamics of the Snowball Earth Hadley circulation for off-equatorial and seasonally varying insolation

Voigt

2013

Earth Syst. Dynam.

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“…Very little poleward expansion of the winter Hadley cells is diagnosed in MS, which indicates that the changes of the meridional SST gradients and their effect on midlatitude eddy activity are not the main modulators of the Hadley cell poleward expansion. The major role of the SST gradient on the Hadley cell strength was largely expected from the idealized GCM study of Walker andSchneider (2006, 2005). These authors suggest that the Hadley cells are strongly dependent on extratropical climate as the eddy momentum flux strongly influences the strength of the Hadley cells in idealized GCM simulations.…”

Section: Discussionmentioning

confidence: 98%

The Hadley and Walker Circulation Changes in Global Warming Conditions Described by Idealized Atmospheric Simulations

Gastineau

Treut

2009

Journal of Climate

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Sea surface temperature (SST) changes constitute a major indicator and driver of climate changes induced by greenhouse gas increases. The objective of the present study is to investigate the role played by the detailed structure of the SST change on the large-scale atmospheric circulation and the distribution of precipitation. For that purpose, simulations from the Institut Pierre-Simon Laplace Coupled Model, version 4 (IPSL-CM4) are used where the carbon dioxide (CO 2 ) concentration is doubled. The response of IPSL-CM4 is characterized by the same robust mechanisms affecting the other coupled models in global warming simulations, that is, an increase of the hydrological cycle accompanied by a global weakening of the largescale circulation. First, purely atmospheric simulations are performed to mimic the results of the coupled model. Then, specific simulations are set up to further study the underlying atmospheric mechanisms. These simulations use different prescribed SST anomalies, which correspond to a linear decomposition of the IPSL-CM4 SST changes in global, longitudinal, and latitudinal components. The simulation using a globally uniform increase of the SST is able to reproduce the modifications in the intensity of the hydrological cycle or in the mean upward mass flux, which also characterize the double CO 2 simulation with the coupled model. But it is necessary (and largely sufficient) to also take into account the zonal-mean meridional structure of the SST changes to represent correctly the changes in the Hadley circulation strength or the zonal-mean precipitation changes simulated by the coupled model, even if these meridional changes by themselves do not change the mean thermodynamical state of the tropical atmosphere. The longitudinal SST anomalies of IPSL-CM4 also have an impact on the precipitation and large-scale tropical circulation and tend to introduce different changes over the Pacific and Atlantic Oceans. The longitudinal SST changes are demonstrated to have a smaller but opposite effect from that of the meridional anomalies on the Hadley cell circulations. Results indicate that the uncertainties in the simulated meridional patterns of the SST warming may have major consequences on the assessment of the changes of the Hadley circulation and zonal-mean precipitation in future climate projections.

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“…The potential temperature flux also does not exhibit the −3 -dependence on planetary rotation rate that nearly inviscid axisymmetric theory (Equation 2) would suggest [see Walker & Schneider (2006) for details and additional results]. One can rationalize some aspects of the parameter dependence of the meridional extent and strength of the simulated Hadley circulations by considering the influence of large-scale eddies.…”

Section: Figurementioning

confidence: 93%

“…Figure 4 shows series of simulations with convective lapse rates between 0.7 d and 0.9 d and with planetary rotation rates twice and four times that of Earth. For each series of simulations, the pole-to-equator surface temperature difference in radiative equilibrium h was varied from 15 K to 360 K [see Schneider & Walker (2006) [There are differences between the thermal driving in the GCM and in the model of Held & Hou (1980), such as the presence of a convection scheme and a radiative relaxation time that varies spatially near the surface; however, these differences are not what is primarily responsible for the different scaling behavior of the Hadley circulation in the simulations and in nearly inviscid axisymmetric theory (Walker & Schneider 2006). ] The Hadley circulation extent increases relatively rapidly for smaller H t h and is nearly constant for larger H t h .…”

Section: Influence Of Eddiesmentioning

confidence: 99%

The General Circulation of the Atmosphere

Schneider

2006

Annu. Rev. Earth Planet. Sci.

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324

212

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Theories of how Earth's surface climate may change in the future, of how it may have been in the past, and of how it is related to climates of other planets must build upon a theory of the general circulation of the atmosphere. The view of the atmospheric general circulation presented here focuses not on Earth's general circulation as such but on a continuum of idealized circulations with axisymmetric flow statistics. Analyses of observational data for Earth's atmosphere, simulations with idealized general circulation models, and theoretical considerations suggest how characteristics of the tropical Hadley circulation, of the extratropical circulation, and of atmospheric macroturbulence may depend on parameters such as the planet radius and rotation rate and the strength of the differential heating at the surface.

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Eddy Influences on Hadley Circulations: Simulations with an Idealized GCM

Cited by 247 publications

References 33 publications

The dynamics of the Snowball Earth Hadley circulation for off-equatorial and seasonally varying insolation

The dynamics of the Snowball Earth Hadley circulation for off-equatorial and seasonally varying insolation

The Hadley and Walker Circulation Changes in Global Warming Conditions Described by Idealized Atmospheric Simulations

The General Circulation of the Atmosphere

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