Higher surface Bowen ratios ineffective at increasing updraft intensity

The sensitivity of various metrics of convective intensity to changes in boundary layer depth via changes in the surface Bowen ratio is explored with radiative-convective equilibrium (RCE) and initial condition simulations in the System for Atmospheric Modeling, a cloud-resolving model. In the RCE simulations, high-percentile updrafts showed little change in response to changes in the surface Bowen ratio. Initial condition simulations showed low surface Bowen ratios having stronger updrafts than high surface Bowen ratios. A parcel model was used to explore whether RCE results could be explained with an entrainment parameter independent of boundary layer depth. It was found that for every set of simulations in RCE, entrainment rates independent of boundary layer depth could explain the lack of change in updraft velocities with boundary layer depth. Given the indifference of high-percentile updraft velocities in our simulations to changes in the surface Bowen ratio, we conclude that convective intensity as measured by this quantity in the cloud-resolving model is not sensitive to this forcing.