6.3 Introducing scale-aware microphysics and aerosol cloud interactions to the Weather Research and Forecasting Model (WRF-ACI)

Glotfelty, Timothy, Kiran Alapaty, United States Environmental Protection Agency, Patrick Hawbecker, North Carolina State University, Hugh Morrison, National Center for Atmospheric Research, Xiaoliang Song, and Guang Zhang, Scripps Institution of Oceanography

Aerosols interact with clouds by serving as cloud condensation nuclei or ice nuclei. Of the many challenges in simulating aerosol-cloud interactions (ACI), we endeavor to determine the factors controlling precipitation suppression and invigoration effects and how these interactions can be handled across spatial scales for grid-scale and subgrid-scale clouds. To accomplish these goals, WRF v3.8.1 has been developed to simulate ACI (WRF-ACI). In the WRF-ACI configuration: (1) the subgrid-scale cloud microphysics scheme of Song and Zhang (2011, SZ11) has been modified and updated for use in the Multi-scale Kain-Fritsch (MSKF) cumulus scheme; and (2) aerosol activation and ice nucleation parameterizations of SZ11 are also coupled to the Morrison double moment microphysics (MDM) scheme to ensure consistent aerosol cloud interactions in both the grid-scale and subgrid-scale cloud microphysics. Cloud effective radii are coupled from both schemes to the RRTMG radiation schemes. This allows WRF users to examine the impact of ACI on weather predictions across space-time scales, while minimizing computational expenses. Preliminary 5-day and seasonal simulations using CESM-derived aerosols indicate WRF-ACI produces similar results to the default WRF v3.8.1. These results indicate that WRF-ACI is appropriate for use in weather forecasting applications. Further, results from the scale-dependency simulations will also be presented.