资源环境科技发展态势分析平台

We derive an anvil cloud diagnostic from the continuity equation of cloud ice and apply it to the output of convection-permitting Energy Exascale Earth System Model (E3SM) simulations run in radiative-convective equilibrium mode. This diagnostic shows that anvil cloud fraction can be reliably diagnosed as a product of cloud detrainment and lifetime. Detrainment is found to be approximated well by a product of clear sky convergence and cloud ice mixing ratio, while cloud lifetime is dominated by sedimentation. Taken together, this diagnostic expresses anvil cloud fraction as a function of 5 physically-measurable quantities. Of these, clear-sky convergence changes drive the anvil cloud reduction with warming while an increase in cloud ice mixing ratio buffers the decrease. Accordingly, this study provides a theoretical foundation upon which the Stability-Iris hypothesis can be tested.