MPAS-A spectral nudging v1.0

This repository contains a modified version of the Model for Prediction Across Scales – Atmosphere (MPAS-A, v8.2.2) that integrates: analysis nudging (FDDA) migrated from the implementation of Bullock Jr. et al. (2018) for MPAS-A v4.0, and a diffusion-based spatial filter inspired by Grooms et al. (2021) and implemented consistently with the GCM-Filters Python package. All original MPAS-A license terms are retained (BSD-style license).All modifications are clearly marked, and .original files are provided for comparison with the unmodified MPAS source. If you use this modified code, please cite all of the following: Bullock Jr., O. R., Foroutan, H., Gilliam, R. C., and Herwehe, J. A. (2018):Adding four-dimensional data assimilation by analysis nudging to the Model for Prediction Across Scales – Atmosphere (version 4.0),Geosci. Model Dev., 11, 2897–2922, https://doi.org/10.5194/gmd-11-2897-2018 Grooms, I. et al. (2021):Diffusion-Based Smoothers for Spatial Filtering of Gridded Geophysical Data,JAMES, 13, e2021MS002552, https://doi.org/10.1029/2021MS002552 Loose, N. et al. (2022):GCM-Filters: A Python Package for Diffusion-based Spatial Filtering of Gridded Data,JOSS, 7(70), 3947, https://doi.org/10.21105/joss.03947 MPAS-A model (https://mpas-dev.github.io)