A stochastic parameter perturbation method to represent uncertainty in a microphysics scheme

With the convection parameterization no longer active, much uncertainty in the formulation of subgrid-scale processes moves to other areas such as the cloud microphysical, turbulence, and land surface parameterizations.

The goal of this study is to investigate experiments with stochastically perturbed parameters (SPP) within a microphysics parameterization and the model's horizontal diffusion coefficients. To estimate the "true" uncertainty due to parameter uncertainty, the magnitudes of the perturbations are chosen as realistically as possible and not with a purposeful intent of maximal forecast impact as some prior work has done. Spatial inhomogeneities and temporal persistence are represented using a random perturbation pattern with spatial and temporal correlations.