Multiple equilibria of the vegetation-atmosphere system in radiative-convective equilibrium storm-resolving simulations with interactive leaf phenology

Storm-resolving simulations where deep convection can be explicitly resolved are performed in the idealized radiative-convective equilibrium framework to explore multiple equilibria in the vegetation-atmosphere system and the role of interactive leaf phenology. Firstly, by initializing the system with different initial soil moisture and leaf area index (LAI) conditions, we find three equilibrium states: a hot desert state without vegetation, an intermediate sparsely vegetated state, and a wet vegetated state. The existence of the three equilibrium states is subdued only to initial soil moisture conditions, not to initial LAI. The wet vegetated state is the most probable state among the multiple equilibria starting at different initial soil moisture and LAI. This indicates that a quite harsh environment, with soil moisture values very close to the permanent wilting point, is needed to kill leaves. It also implies that the vegetation-atmosphere system is more stable with interactive leaf phenology and can be interpreted as Amazon may be more resilient to the disturbances than we have thought. Secondly, interactive leaves allow an earlier transition between the intermediate to the wet vegetated state. These results imply that the vegetation-atmosphere system is more stable with interactive leaf phenology and can be interpreted as Amazon may be more resilient to the disturbances than we have thought. In our set-up, interactive leaves are only important for soil moisture larger than 54%, and their effect could be well approximated by prescribing the LAI to its maximum value. Finally, our sensitivity experiments reveal that leaves influence the climate equally through their controls on canopy conductance and vegetation cover, whereas albedo plays a negligible role.