GFDL SHiELD: A Unified System for Weather-to-Seasonal Prediction

Abstract

We present the System for High-resolution prediction on Earth-to-Local Domains (SHiELD), an atmosphere model developed by the Geophysical Fluid Dynamics Laboratory (GFDL) coupling the nonhydrostatic FV3 Dynamical Core to a physics suite originally taken from the Global Forecast System. SHiELD is designed to demonstrate new capabilities within its components, explore new model applications, and to answer scientific questions through these new functionalities. A variety of configurations are presented, including short-to-medium-range and subseasonal-to-seasonal prediction, global-to-regional convective-scale hurricane and contiguous U.S. precipitation forecasts, and global cloud-resolving modeling. Advances within SHiELD can be seamlessly transitioned into other Unified Forecast System or FV3-based models, including operational implementations of the Unified Forecast System. Continued development of SHiELD has shown improvement upon existing models. The flagship 13-km SHiELD demonstrates steadily improved large-scale prediction skill and precipitation prediction skill. SHiELD and the coarser-resolution S-SHiELD demonstrate a superior diurnal cycle compared to existing climate models; the latter also demonstrates 28 days of useful prediction skill for the Madden-Julian Oscillation. The global-to-regional nested configurations T-SHiELD (tropical Atlantic) and C-SHiELD (contiguous United States) show significant improvement in hurricane structure from a new tracer advection scheme and promise for medium-range prediction of convective storms.Plain Language Summary At many weather forecasting centers where computer weather models are run, different models are run for different applications. However, each separate model multiplies the effort needed to maintain and upgrade each model and makes it difficult to move improvements between models. We present a new "unified" weather modeling system, System for High-resolution prediction on Earth-to-Local Domains, able to be configured for a variety of applications. This system uses a powerful computer code, FV3, to compute the fluid motion of the atmosphere at any scale and also able to zoom in on areas of interest to better "see" severe storms or intense hurricanes. We show how we started from a quickly assembled model for testing FV3 and then gradually improved the representation of different atmospheric processes and expanded into new uses for the system, including short-range severe thunderstorm prediction, hurricane forecasting, and forecasts out to as long as 6 weeks. We address some of the challenges that we faced and discuss prospects for future model improvements. Since many of the parts of System for High-resolution prediction on Earth-to-Local Domains are used by models being developed by the National Weather Service for use by weather forecasters, the advances described here can be rapidly introduced into those models, eventually improving official forecasts. Unified Modeling at GFDLAs computing power increases, global atmosphere models are now capable of regular si...

AMIP Simulations of a Global Model for Unified Weather‐Climate Forecast: Understanding Precipitation Characteristics and Sensitivity Over East Asia

“…The Nonhydrostatic Icosahedral Atmosphere model (NICAM), which was originally developed as a kilometer‐scale global storm‐resolving model, has also been experimented for HighResMIP (Kodama et al., 2021). The GFDL shield system is developed for unified weather‐to‐seasonal prediction (Harris et al., 2020), serving as a research tool that maintains a tie with the FV 3 ‐based Global Forecast System. The Korean Integrated Model (Hong et al., 2018) has also been pushed toward global weather‐to‐seasonal prediction.…”

Improving Global Weather Prediction in GFDL SHiELD Through an Upgraded GFDL Cloud Microphysics Scheme

“…SHiELD uses the non‐hydrostatic solver of the Finite‐Volume Cubed‐Sphere Dynamical Core (FV3) developed at GFDL (Harris & Lin, 2013; Harris, Zhou, Chen, & Chen, 2020; Harris, Chen, et al., 2020; Putman & Lin, 2007; S. Lin, 2004). The physical parameterizations in SHiELD originated from that in GFS version 14 (Chen, Lin, Magnusson, et al., 2019), but contains substantial updates: In particular the simple microphysics scheme of Zhao and Carr (1997) and cloud fraction scheme of Xu and Randall (1996) are replaced by the inline GFDL cloud microphysics (Harris, Zhou, et al., 2020; Zhou et al., 2019). We have also redesigned cloud‐radiation interaction to combine the cloud microphysics processes and cloud radiative properties.…”

“…(2019)), was developed as a prototype of the Next‐Generation Global Prediction System of the National Weather Service and the broader Unified Forecast System (UFS) (Harris, Zhou, et al., 2020). SHiELD focuses on medium‐range weather (up to 10 days) prediction, but it can also be used for sub‐seasonal to seasonal (S2S; between 2 weeks and one season) (Harris, Zhou, et al., 2020) and convective‐scale (a few hours) (Harris et al., 2019) predictions as well. Notably, advances in SHiELD have migrated into UFS models slated for operational implementations at NCEP, including the GFS version 15 and version 16.…”

“…Liquid cloud fraction is also significantly under‐predicted over the global oceans. In addition, SHiELD tends to predict excessive light and extreme precipitation and under‐predict medium precipitation (Harris, Zhou, et al., 2020). Khain et al.…”

“…(2019) and Harris, Zhou, et al. (2020) have described key features of the GFDL MP, including thermodynamic consistency with the dynamical core, fast and stable sedimentation processes, and tight coupling between dynamics and physics. The GFDL MP is used in the operational GFS version 15 and 16 (Huang et al., 2021; Patel et al., 2021; Tong et al., 2020) and several other weather and climate models, including GFDL radiative‐convective equilibrium (RCE) simulations within a limited domain (Jeevanjee, 2017), the GFDL High‐resolution Atmosphere Model (HiRAM; Chen and Lin (2011), Chen and Lin (2013), Gao et al.…”