A Pilot Study of Aerosol Dependency of the Community Convective Clouds (C3) Scheme in NOAA’s Unified Forecast System (UFS) Weather Model

A physics suite, which includes the aerosol-aware double moment Thompson-Eidhammer microphysics scheme (TH-E MP), the scale-aware and aerosol-aware Community Convective Cloud (C3) parameterization, and the MYNN-EDMF boundary layer and shallow cloud scheme, is under development at NOAA. We recently implemented a simple approach to improve the aerosol representation in these parameterizations, particularly TH-E and C3, in the UFS. Sea salt, dust, biomass burning, and anthropogenic aerosol emissions have been embedded as CCPP-compliant subroutines. The prognostic emissions of sea-salt, and organic carbon are combined to represent the “water friendly” aerosol emission, while the prognostic emissions of dust are used to represent “ice friendly” aerosol emission for TH-E MP. We previously examined how this aerosol representation modified the aerosol indirect feedback when using the TH-E scheme in the global UFS forecast with C768 (~13km) horizontal resolution and 127 vertical levels. There are significant cloud-radiation responses to the aerosol differences, and the severely positive precipitation bias over Europe and North America was significantly alleviated when applying this aerosol emission method for indirect feedback. In order to foster the collaboration across NOAA on convective parameterization, a new C3 parameterization, which adds several features from the currently operational SAS scheme to the Grell-Freitas parameterization, is under development. Here we further study the aerosol-awareness of the C3 convective parameterization through the cloudwater-rainwater conversion and precipitation efficiency processes. The aerosols are consistent between TH-E microphysics and C3 convection. This study indicates that aerosol-physics interactions using a very simple and computationally highly efficient approach have significant impacts on the numerical weather prediction in the UFS applications.