. Advanced Physics Test for NOAA's Global Forecast System

Abstract
The NOAA Environmental Modeling Center (EMC) recently replaced the dynamic core in its flagship operational model, the Global Forecast System (GFS). Version 15 of the GFS (GFSv15), scheduled for implementation in 2019, will include the non-hydrostatic Finite-Volume Cubed-Sphere (FV3) dynamical core in place of the long-running spectral hydrostatic core. This modeling system serves as the foundation for the atmospheric component of the emerging Unified Forecast System (UFS), which is envisioned to be a full community-based Earth-System model. The next major upgrade of the GFS, scheduled for 2021, is expected to be in the area of model physics, with individual physical parameterizations upgraded or replaced to produce superior forecast performance. To address this challenge, two physics suites have been identified as possible replacements for the current GFS v15 suite. One of these was assembled and developed by NOAA's Global Systems Division (GSD) from years of community contributions for mesoscale applications through the Weather Research and Forecast (WRF) modeling system. The second candidate has components that were developed at multiple research centers and universities, including Colorado State University, University of Utah, the National Aeronautics and Space Administration (NASA), the National Center for Atmospheric Research (NCAR), and EMC. Its individual parameterizations have been applied primarily to medium- and long-range prediction scales. The performance of these two suites were compared to the suite tested by EMC in preparation for the operational implementation of GFS v15 and a very similar, but updated, GFS v15 suite. In addition to the differences in physics, it should be noted that the configurations differ in a few other aspects, including dynamics settings and computational platforms. Additionally, Suite 4 uses the Common Community Physics Package (CCPP; see poster by Heinzeller et al.) as a demonstration of the UFS' new paradigm for integrating physics and dynamics. Runs were conducted between December 2018 and February 2019. Each suite was applied in a total of 163 model initializations, and performance for 10-day forecasts was assessed objectively and subjectively. The initializations include 16 high-impact events selected by EMC's Model Evaluation Group (MEG) along with additional 147 dates from all seasons in 2016 and 2017. The Global Model Test Bed carried out the model runs, and EMC conducted comprehensive model verification. Additionally, GMTB produced verification using the Model Evaluation Tools (MET) and additional diagnostics focused on tropical cyclones, precipitation characteristics, spectral decomposition (see poster by Zhang et al.), energy budget, and boundary layer properties. In this poster, we will describe the methodology used for this test and provide highlights of the results.