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Abstract
The atmospheric component of E3SM relies on probability density functions (PDFs) to represent subgrid-scale variability of prognostic variables. While PDFs characterize the horizontal variability, a separate treatment is needed to account for the vertical structure of clouds and precipitation. When sub-columns are drawn from these PDFs for microphysics or radiation parameterizations, as well as for instrument simulators, appropriate vertical correlations must be enforced via PDF overlap specifications. In this presentation, we evaluate the representation of PDF overlap currently employed in the Subgrid Importance Latin Hypercube Sampler (SILHS) as part of the turbulence and cloud scheme called the Cloud Layers Unified By Binormals (CLUBB) and propose an improved treatment, which takes into account a dependence on hydrometeor properties.
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