Restructuring of the NEMS Framework — to Adapt the Requirements for Independent Models Development

NOAA Environmental Modeling System (NEMS) has been established as a framework for serving a number of the operational multi-scale weather and climate prediction models based on the 1) existent NOAA Centers for Environmental Prediction (NCEP) models, 2) a set of the in-house developed scientific and domain specific shared libraries, tools and products, and 3) taking advantage of employing the Earth Science Modeling Framework (ESMF). As any of the framework design, the main requirements for NEMS were framed in the field of the justified common code reuse and reasonable polymorphism in data type and operations.

Therefore, initially, NEMS designers considered a componentization of NEMS into the NEMS super structure, shared post processing component, NEMSIO – a scalable I/O communication component; available common and model specific column of atmospheric physics collection, internal ensembles component, integrated several available models under development and a number of the placeholders.

Down the road, during multi-year intensive NEMS and NEMS-based models' development and integration of several more internal and external models, more and more of new requirements have derived. Periodic review of NEMS design different pros and cons have been addressed to question sufficiency of the initial NEMS design. For instance, extensive experience in NEMS development required verification of any trunk commits with a growing regression testing suite that required running not only developers model tests but all others as well. Another example is that in current NEMS software structure code dependencies lead to a necessity to rebuild meaningfully not targeted-for-change NEMS code components. Also, the latest active collaborative contribution to the NEMS of multi-agency National Unified Operational Predication Capability (NUOPC), with capability to couple within NEMS greatest classes independently developed Earth Science models (such as Ice, Ocean etc.) using similar mechanisms of model coupling.

This presentation will focus on NEMS restructuring solutions that can provide the model specific teams with opportunities to conduct more independent development while taking full advantage of renovated NEMS's framework features reuse.