Evaluating assumed PDFs for continental moist convection in the 2-120 km resolution range

Assumed-probability density function (PDF) higher-order turbulence closures (assumed-PDF HOCs), such as CLUBB (Cloud Layers Unified By Binormals), are now widely used for parameterizing moist convection in climate models. With next-generation climate models adapting higher horizontal resolution on the order of several kilometers, it is essential to understand and quantify the performance of different PDF families that are assumed in these parameterizations across this extended range of model resolutions. In this study, we evaluated the PDF families of analytic double Gaussian using large-eddy simulations (LES) of a continental transition case from shallow to deep convection during Holistic Interactions of Shallow Clouds, Aerosols and Land-Ecosystems (HI-SCALE) field campaign. One of the PDF families is the double Gaussian form used in CLUBB; the other is based on CLUBB but assuming the prognosed skewnesses of thermodynamic scalars. The large horizontal domain size and high output frequency of the simulations allow us to examine the performance of the assumed PDFs for (1) horizontal grid spacings from 2 to 120 km; (2) different vertical portions of the cloud layer; and (3) shallow and deep periods of the continental convection diurnal cycle separately.