Radiative-Convective Instability and Its Mean State Dependence (Invited Presentation)

David Raymond is among the first to investigate the possibility of a radiative-convective instability and its potential application to the tropical climate (Raymond 2000). Here we couple linear response functions constructed for a cloud-system-resolving model with parameterized large-scale dynamics to investigate radiative-convective instability over an oceanic surface and its dependence on the mean state. The results, while confirming the basic notion of radiative-convective instability put forward by Emanuel et al. (2014), also highlight the importance of the stabilizing effect due to convection’s tendency to remove free tropospheric moisture anomalies. This stabilizing effect is weaker in a drier mean state with weaker convection, which allows radiative convective instability to be stronger. This is offered as an explanation on why convective self-aggregation tends to be dominated by growth of dry patches. The dependence on the sea surface temperature will also be discussed.

Emanuel, K., A. A. Wing, and E. M. Vincent, 2014: Radiative-Convective Instability. J. Adv. Model. Earth Sys., 6, doi: 10.1002/2013MS000270.

Raymond, D. J., The Hadley circulation as a radiative-convective instability. J. Atmos. Sci., 57, 1286-1297 (2000).