Radiative‐convective instability

By Kerry A. Emanuel, A. Wing, E. Vincent. 2014

172 citations recorded by the source corpus.

Radiative‐moist‐convective equilibrium (RCE) is a simple paradigm for the statistical equilibrium the earth's climate would exhibit in the absence of lateral energy transport. It has generally been assumed that for a given solar forcing and long‐lived greenhouse gas concentration, such a state would be unique, but recent work suggests that more than one stable equilibrium may be possible. Here we show that above a critical specified sea surface temperature, the ordinary RCE state becomes linearly unstable to large‐scale overturning circulations. The instability migrates the RCE state toward one of the two stable equilibria first found by Raymond and Zeng (2000). It occurs when the clear‐sky infrared opacity of the lower troposphere becomes so large, owing to high water vapor concentration, that variations of the radiative cooling of the lower troposphere are governed principally by variations in upper tropospheric water vapor. We show that the instability represents a subcritical bifurcation of the ordinary RCE state, leading to either a dry state with large‐scale descent, or to a moist state with mean ascent; these states may be accessed by finite amplitude perturbations to ordinary RCE in the subcritical state, or spontaneously in the supercritical state. As first suggested by Raymond (2000) and Sobel et al. (2007), the latter corresponds to the phenomenon of self‐aggregation of moist convection, taking the form of cloud clusters or tropical cyclones. We argue that the nonrobustness of self‐aggregation in cloud system resolving models may be an artifact of running such models close to the critical temperature for instability.

Subfields: Atmospheric Science, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/9414ff86b5bf5762287c19390b966fcb3e28a67c

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Citations in the corpus

Physical mechanisms controlling the initiation of convective self‐aggregation in a General Circulation Model (2015, background): “…thus shows that the phenomenon of self-aggregation pointed out in CRMs [Bretherton et al., 2005; Held et al., 2007; Muller and Held, 2012; Wing and Emanuel, 2014; Wing and Cronin, 2015; Muller and Bony, 2015] and a few other GCMs [Held and Zhao, 2008; Becker and Stevens, 2014; Shi and Bretherton,…”
The MJO as a Dispersive, Convectively Coupled Moisture Wave: Theory and Observations (2016, unknown): “This mechanism may, in turn, be related to the so-called radiative–convective instability discussed by Raymond (2000a), Wing and Emanuel (2014), and Emanuel et al. (2014).”
Self‐aggregation of convection in long channel geometry (2014, unknown): “Although the behaviour of the longwave radiation feedback term in our channel simulations appears to be consistent with the temperature dependence suggested by Emanuel et al. (2014), cloud effects rather than clear-sky radiative transfer lead to our negative longwave feedback at low TS (Figure 5).”
Organization of tropical convection in low vertical wind shears: Role of updraft entrainment (2017, background): “Both the long wave and short wave radiative impacts of the heterogeneous water vapor field can also drive convergence into moist regions [Wing and Emanuel , 2013; Emanuel et al., 2014; Sessions et al., 2016].”
What favors convective aggregation and why? (2015, background): “…that has received attention recently is the self-aggregation of convection [see, for instance, Held et al., 1993; Raymond and Zeng, 2000; Bretherton et al., 2005; Sobel et al., 2007; Muller and Held, 2012; Tobin et al., 2012; Craig and Mack, 2013; Jeevanjee and Romps, 2013; Emanuel et al., 2014].”
Convective Self-Aggregation in Numerical Simulations: A Review (2017, methodology): “Spontaneous symmetry breaking in two-dimensional and two-column models (Raymond 2000; Nilsson and Emanuel 1999) and multiple equilibria in weak temperature gradient simulations with single column (Sobel et al. 2007; Emanuel et al. 2014; Daleu et al. 2015) and two-dimensional cloud-resolving models (”
Global‐scale convective aggregation: Implications for the Madden‐Julian Oscillation (2015, background): “Previous work suggests that gustiness plays only a modest role in MJO dynamics [Araligidad and Maloney, 2008; Riley Dellaripa and Maloney, 2015], although it may contribute to mesoscale aggregation [Wing and Emanuel, 2014].”