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(1) Initial Conditions contain column of fill_values
Date of report: September 2025
Issue: When using NCL codes to create initial conditions from output from a previous CAM run, entire columns were being set to fill_values for large areas. It was discovered that the model top pressure altitude of the previous CAM run must be higher at all locations than the specified vertical levels when generating "real" file from the MPAS-Model directory.
Model response: MUSICAv1 fails to run
Model versions impacted: MUSICAv1: This issue arose when attempting to use a 32L CAM-Chem FV run with a 32L MPAS model grid with a top above 40 km. In the winter hemisphere, the top of the 32L CAM-Chem FV simulation was lower than 40 km, and entire columns for the dynamical field (e.g., rho, theta) were getting set to the fill_value (1e36).
Fix: To avoid this issue, the recommendation (from Bill Skamarock, MMM) is to use a simulation with a sufficiently high model top (e.g., 70L WACCM) for regridding initial conditions. This is advised in preference to reducing the model top of the MPAS model, which could have unintended consequences on a MUSICAv1 simulation. It is expected that there will be a forthcoming replacement to these NCL scripts with Python which will remove this issue.