Global Modeling

BACKGROUND

A research to operations (R2O) initiative was established in 2014 by NOAA to upgrade the current operational Global Forecast System (GFS) to run as a unified and fully coupled Next Generation Global Prediction System (NGGPS). NOAA’s long-term plan seeks to integrate the capabilities of its short-term (GFS), ensemble (GEFS), and sub-seasonal (CFS) NWP applications under the infrastructure of NGGPS. A key challenge during this process is to develop a common physics infrastructure that works across all temporal and spatial scales as well as to accommodate an efficient R2O pipeline that effectively uses the expertise in both the research and operational communities. As part of this effort, the Global Model Testbed (GMTB) team was established within the Developmental Testbed Center (DTC) to facilitate community involvement in the development of NGGPS through several avenues: contributing to select aspects of code management and infrastructure for the community to interact with the system, supporting a hierarchical testing framework to NGGPS developers, and facilitating and performing testing and evaluation of innovations for the operational system. The GMTB consists of scientists and software engineers within RAL’s Joint Numerical Testbed (JNT) who take active roles in supporting R2O for global numerical weather prediction (NWP) by closely collaborating with NOAA’s Environmental Modeling Center (EMC) and the research community to develop a Common Community Physics Package (CCPP) and a physics testbed.

FY2018 ACCOMPLISHMENTS

Common Community Physics Package (CCPP)

A modular physics suite accessible both in-line as part of a prediction model, and off-line for isolated testing, will enable physics innovation and contribution from the broader community.  In support of this goal, the DTC and NGGPS put forth the concept of a Common Community Physics Package (CCPP) consisting of a library of physical parameterizations that are either currently operational or are candidates for an upcoming implementation and a generalized software framework for connecting a set of physical parameterizations with a host application (see, e.g. Figure 1). Over the past fiscal year, this concept has become reality, culminating in two software releases and significant progress toward transferring this technology to NOAA’s operational FV3GFS.

Figure 1. Representation of the CCPP embedded within FV3GFS as a host model. The gray box represents the CCPP library and the green “Physics Driver” box consists of a software cap for the host model and the CCPP software framework.
Figure 1. Representation of the CCPP embedded within FV3GFS as a host model. The gray box represents the CCPP library and the green “Physics Driver” box consists of a software cap for the host model and the CCPP software framework.

The CCPP physics library began with providing “CCPP-compliant” interfaces to the FY17 operational FV3GFS physics suite and was expanded to include evolutionary updates to that suite, the GFDL microphysics scheme, and a suite of advanced schemes put forward by EMC as a potential upgrade. In addition, the GMTB team provided support for third-party developers at NOAA Global Systems Division to transition the RAP/HRRR physics suite to the CCPP library. This collection of physical parameterizations will subsequently be assembled into candidate suites to be tested by staff at GMTB and evaluated by EMC and independent scientists as part of a physics selection exercise for the future Unified Forecast System (UFS) at NOAA.

The CCPP software framework has undergone significant development and reached a state of readiness suitable for two public releases. Both releases consisted of a software bundle that included the CCPP software framework, physics library, and a single-column model (SCM) that serves as a simple example for a host application. In addition, the second release was also made to function with the latest version of the FV3GFS, and the code required for integration was placed under version control within NOAA’s VLab repository-hosting service. The software framework allows for several modes of operation within FV3GFS: a temporary “hybrid” mode for running non-CCPP-compliant parameterizations with CCPP-compliant ones for R&D work at EMC, a dynamic mode that allows for flexible runtime configuration of physics suites, and a performance-oriented mode using static libraries designed to be used operationally. Comprehensive documentation in the form of a release website, a User’s/Technical Guide, a Developer’s Guide, a software design document, and scientific physics documentation were included with both releases.

Hierarchical Testing

To facilitate the development of an advanced physics suite for NGGPS, the JNT, working through the DTC, is developing a uniform ‘test harness’ to enable in-depth investigation of various physical parameterizations. The principal purpose of this physics testbed is to assist the research and operational communities in streamlining the testing process to accelerate the transfer of worthy improvements into operations. The testbed should see use as both a tool for physics developers to display merit and further improve upon their schemes and as an addition to EMC’s physics development decision-making arsenal. The test harness represents the logical progression for testing newly developed parameterizations that typically takes place within the scientific community. Components and complexity are gradually added and iterated upon as one moves through the hierarchy until the full forecast model complexity is reached. The hierarchy is designed to complement both the existing testing protocol at operational centers and independent testing typically performed by parameterization developers. The natural sequence of testing new physics schemes tends to follow tiers of progressively difficult and computationally intensive model runs as merit warrants, and the GMTB testbed mimics this progression (see, e.g. Figure 2).

Figure 2. Diagram illustrating the testing hierarchy plan.  LR indicates low resolution, MR medium resolution, and HR high resolution. Shading indicates where groups are anticipated to focus their efforts
Figure 2. Diagram illustrating the testing hierarchy plan.  LR indicates low resolution, MR medium resolution, and HR high resolution. Shading indicates where groups are anticipated to focus their efforts

Single Column Model (SCM)

A SCM that makes use of the CCPP was developed in FY17 to serve dual purposes: as an example host model to use with the CCPP and as a component of a physics testing harness. Given its connection to CCPP, it can serve as a continually up-to-date column version of the NOAA operational forecast model and as a tool to experiment with other candidate CCPP-compliant physics. Its current capability is limited to running individual case studies based on observational field campaigns, such as those created as part of the Global Atmospheric System Studies (GASS) project. The library of cases is relatively small but growing and users are encouraged to generate and share new ones. One set of case studies to highlight is based on the ongoing LES ARM Symbiotic Simulation and Observation (LASSO) project. This project provides both forcing and comparison data from observations and LES for SCMs. Although most of the cases focus on shallow continental cumulus conditions, the SCM is set up to run any of the potentially hundreds of experiments based on this dataset.

Workflow for Low-Resolution/Medium-Resolution Global Forecast Mode

To facilitate three-dimensional testing that provides information about the interaction between the physics packages and feedback on the large-scale flow, the GMTB maintained an end-to-end workflow for the atmospheric component of the FV3GFS in FY17 that includes post-processing, comprehensive verification, and production of graphics. In addition, GMTB also participated in planning for the next-generation workflow named Community, Research, and Operational Workflows (CROW) being developed at NOAA EMC. The DTC-contributed workflow components for creating Python-based forecast plots (e.g. temperature, moisture, convective vs. non-convective precipitation) and verification results (e.g., near-surface, upper-air, and precipitation verification) continued to be upgraded to include additional features and flexibility.

Work is also underway to expand the testbed capabilities to equip physics developers with a wide range of tools to assess strengths and deficiencies of physics. For example, an inventory of diagnostics has been started to identify and implement the highest priority diagnostic tools. Some of the tools that have been implemented include software to compare radiation output to SURFRAD and CERES data, code to produce bias information from GSI diagnostic files which provide “O-B” or (observation – background) information, and subseasonal to seasonal (S2S) oriented diagnostics developed by Drs. Zhuo Wang and Weiwei Li at University of Illinois Urbana-Champaign.

Model Evaluation for Research Innovation Transition (MERIT)

Another project within the DTC named MERIT dovetails nicely with the GMTB physics testing harness. Its purpose is to provide the research and operational communities with an end-to-end framework that will streamline the testing process, encourage community engagement, and provide an infrastructure that supports R2O and O2R. MERIT currently includes three cases of interest that were part of the initial FV3v0 public release. All cases were run through the testing framework previously discussed for both FV3-based and GSM-based configurations of the operational GFS to produce baseline results using the Model Evaluation Tools (MET) and python plotting tools (Fig. 3). Seven-day forecasts were run with both configurations with 6-hourly output. Objective verification was conducted for surface and upper-air temperature, specific (relative) humidity and wind speed as well as 6-hr precipitation accumulation.  Qualitative analysis and comparison of certain fields was also conducted, including 500-hPa geopotential height, mean sea-level pressure, and 24-hr precipitation accumulation. Select results of the verification evaluation are available for each forecast on the MERIT cases website (https://dtcenter.org/eval/meso_mod/merit/cases.php).

Figure 3. FV3 version 0 workflow included in MERIT.
Figure 3. FV3 version 0 workflow included in MERIT.

FY2019 PLANS

During FY19, work will continue toward making the CCPP software framework more robust and general to truly serve as a common framework amongst NOAA and NCAR earth system models. This year will also see a concerted effort to transition this framework to NOAA operations by conforming to agreed-upon acceptance criteria and by providing appropriate training to EMC scientists and engineers engaged in the physics effort. This work will culminate in a joint FV3GFS-CCPP release. GMTB staff will also participate in the physics testing and evaluation exercise geared toward guiding EMC’s decision about the future FV3GFS physics suite. In addition, work will continue toward expanding the capabilities in the physics testbed in order to equip physics developers with a wide spectrum of tools to assess strengths and deficiencies of physics parameterizations.