Extending the NWMv3.0 Forcings Engine Capabilities into the NextGen Water Resource Modeling Framework

The National Center for Atmospheric Research (NCAR) has previously published a Python meteorological preprocessor package to support meteorological input data files for the National Water Model (NWM) operational domains. The NCAR Python tool, called the NWM Forcings Engine, uses a wide variety of meteorological data products which range from satellites, weather radar, numerical weather prediction (NWP) models, climate models, and various real-time or re-analysis datasets. The NWM Forcings Engine workflow includes Earth System Modeling Framework (ESMF) regridding capabilities, reformatting routines, and tools to standardize units from a variety of meteorological forcing products to support uniform forcing data over all NWM operational configurations (e.g. Short, Medium, Long range, etc.) currently utilized for water prediction. The NWM Forcings Engine also contains several important data processing routines for performing downscaling and statistical bias correction, which can significantly improve the quality of data for high-resolution hydrologic modeling applications. However, the existing NWM Forcings Engine requires modification in order to support formulations running in the Next Generation Water Resources Modeling Framework (NextGen). Here, we introduce the NextGen Forcings Engine, which is a universal forcings provider mimicking the existing NWM Forcings Engine workflow and can now be used as a model engine tool within the NextGen framework.

The NextGen Framework uses the Basic Model Interface (BMI) model coupling standard. A BMI is a list of “self-describing” functions used to standardize a model’s main program and exchange variable fields between model components across a variety of program languages. To enable the NextGen Forcings Engine to become BMI-complaint for NextGen, we had to translate then NWM Forcings Engine configuration file into a BMI configuration yml file and then modify the main program to allow the BMI to execute the forcings provider and extract meteorological data as needed based on a specified timestamp rather than an operational configuration time loop. As a BMI Python tool, the goal of the NextGen Forcings Engine is to directly advertise standard NWM meteorological forcing variables across any given hydrologic/hydraulic model domain as 1D array fields to be redistributed by the NextGen model engine spatial coupler. To enable regridding capabilities across any hydrologic domain, we expanded its regridding capabilities to include universal gridded and unstructured mesh options. This required us to modify all the supporting modules to include ESMF regridding techniques to support both grid types as well as creating preprocessing Python tools to translate coastal meshes and the NextGen hydrofabric into ESMF compliant meshes. Altogether, these modifications created the NextGen Forcings Engine BMI Python tool, which will directly provide meteorological forcings for all NWM operational configurations across any hydrologic model domain. Here, we present our work in transforming the original NWM Forcings Engine into a universal forcings provider using the BMI standard within the NextGen framework for research, development and testing, with the goal of operational use in the near future.