Addressing outstanding uncertainties associated with high clouds

Recent studies highlight remaining uncertainties in high cloud feedbacks, especially in optically thin high clouds and in the response of their albedo to warming. Along with these radiative implications, condensate formation in high clouds influences surface precipitation. We show that even the most recent generation of storm-resolving models have large variations in their predicted conversion efficiency of condensate to precipitation. We then highlight three factors that have limited our ability to more accurately simulate high clouds but also offer the possibility for progress going forward. First, ice microphysical processes are quite sensitive to variables for which our observations are limited or uncertain, including updraft velocity variability and ice-nucleating particle concentrations. Second, it remains unclear how many (and which) degrees of freedom are needed to reliably represent a given ice microphysical process. And lastly, ice-phase processes and variables are not always treated consistently across model components.