title: Thermodynamic control of anvil cloud amount.
abstract: General circulation models show that as the surface temperature increases, the convective anvil clouds shrink. By analyzing radiative-convective equilibrium simulations, we show that this behavior is rooted in basic energetic and thermodynamic properties of the atmosphere: As the climate warms, the clouds rise and remain at nearly the same temperature, but find themselves in a more stable atmosphere; this enhanced stability reduces the convective outflow in the upper troposphere and decreases the anvil cloud fraction. By warming the troposphere and increasing the upper-tropospheric stability, the clustering of deep convection also reduces the convective outflow and the anvil cloud fraction. When clouds are radiatively active, this robust coupling between temperature, high clouds, and circulation exerts a positive feedback on convective aggregation and favors the maintenance of strongly aggregated atmospheric states at high temperatures. This stability iris mechanism likely contributes to the narrowing of rainy areas as the climate warms. Whether or not it influences climate sensitivity requires further investigation.
authors.affiliation: Laboratoire de Météorologie Dynamique/Institute Pierre-Simon Laplace (LMD/IPSL), CNRS, Sorbonne Universities, University Pierre and Marie Curie (UPMC) University of Paris 06, 75252 Paris, France; bony@lmd.jussieu.fr.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Bony
authors.affiliation: Max-Planck Institute for Meteorology, 20146 Hamburg, Germany;
authors.forename: Bjorn
authors.initials: B
authors.lastname: Stevens
authors.affiliation: Laboratoire de Météorologie Dynamique/Institute Pierre-Simon Laplace (LMD/IPSL), CNRS, Sorbonne Universities, University Pierre and Marie Curie (UPMC) University of Paris 06, 75252 Paris, France;
authors.forename: David
authors.initials: D
authors.lastname: Coppin
authors.affiliation: Max-Planck Institute for Meteorology, 20146 Hamburg, Germany;
authors.forename: Tobias
authors.initials: T
authors.lastname: Becker
authors.affiliation: School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000;
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Reed
authors.affiliation: Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964-1000;
authors.forename: Aiko
authors.initials: A
authors.lastname: Voigt
authors.affiliation: Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO 80307-3000.
authors.forename: Brian
authors.identifier: 0000-0003-2188-4784
authors.initials: B
authors.lastname: Medeiros
keywords: anvil cloud; climate sensitivity; cloud feedback; convective aggregation; large-scale circulation