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.

FY2019 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, version 3 of this software was released to the public and was successfully transitioned to NOAA EMC’s UFS Atmosphere master repository.

Figure 1. Representation of the CCPP embedded within UFS Atmosphere 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 UFS Atmosphere 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.

This year witnessed significant growth in the CCPP physics library, corresponding to new schemes added by GMTB staff at NCAR RAL and NOAA GSD as well as schemes added by third parties with support from GMTB staff. An incomplete list of NOAA operational candidate schemes added includes the Chikira-Sugiyama and Grell-Freitas convection schemes, Simplified Higher-Order Closure (SHOC), Mellor-Yamada-Nakanishi-Niino, and scale-aware TKE eddy-diffusivity mass flux planetary boundary layer parameterizations, GFDL, Thompson, and Morrison-Gettelman microphysics schemes, the unified and RAP/HRRR gravity wave drag parameterizations, and the RUC and NoahMP land surface models. These parameterizations are assembled into four supported suites, each of which were subject to a large-scale multi-institutional testing and evaluation activity undertaken to inform the selection of physics for future UFS applications.

The CCPP software framework continues to evolve in order to improve its generality and its applicability to third-party models such that physics can be easily shared seamlessly across modeling platforms across the community. Through collaboration with NCAR CGD and MMM labs as well the Naval Research Laboratory, significant strides toward this goal have been met and continue into the current fiscal year. Improvements include the choice of build modes, with research-oriented dynamic libraries and runtime specification of physics suites or performance-oriented static libraries with compile-time specification of a set of possible physics suites, and an improved and extensible variable metadata format. 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 are included with the software and in-person trainings at NOAA EMC were conducted to familiarize the operational community with this community-oriented approach to calling physics.

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 FY19 that includes post-processing, comprehensive verification, and production of graphics. 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 completed during FY19 within the DTC named MERIT (Model Evaluation for Research Innovation Transition) 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 and used an early version of the FV3 public release. All cases were run through the testing framework previously discussed for the FV3-based configuration to produce baseline results using the Model Evaluation Tools (MET) and python plotting tools. Week-long forecasts were run 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 diagnostic investigations of select 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). 

FY2020 PLANS

During FY20, 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 complete the transition of this framework to NOAA operations by providing appropriate training to EMC scientists and engineers engaged in the physics effort. The CCPP physics and framework are currently slated to be included in the first UFS public release. 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.