Development of a New Microphysics Scheme with In-Cloud Processes for Weather Forecasting

A new double-moment parameterization with in-cloud microphysical processes is developed for use in weather forecasting and climate studies. A main ingredient of the scheme utilizes a concept to represent the partial cloudiness effect on the microphysical processes, following the study of Kim and Hong (2018). The underlying assumption is that all the microphysical processes occur in a cloudy part of the grid box. Based on the long-term evaluation of the WRF Single-Moment (WSM) and WRF Double-Moment (WDM) schemes by WRF community, several revisions are made in microphysics terms, along with a newly introduced aerosol effect in ice processes. An aerosol-aware feature with prognostic aerosol emissions of sea salt, dust, anthropogenic and wildfire organic carbon for CCN is also designed. A mass-conserving Semi-Lagrangian sedimentation is re-configured for double-moment physics, which is superior to the conventional Eulerian algorithm in the context of the computational accuracy and numerical accuracy. The new scheme reproduces the storm structure in an idealized 2D testbed, accompanying better organized front-to-rear jets, cold pools, and convective updrafts, as compared to the results in the case of conventional microphysics. The wall-clock time is about a half in the US NOAA/GFS model, as compared to that of Thompson scheme.