Hello all, I’ve found an issue in RegCM5 when nesting a 10 km simulation (MOLOCH) within a 50 km (MM4 hydrostatic) where there is clearly a grid artifact superimposed on the wind curl field at all atmospheric levels. I am mainly interested in wind stress curl (tauu / tauv) at the surface, but I noticed the stipple pattern is present throughout the atmospheric column. It is a 50 to 10 km nest, so perhaps this is stemming from a SST or surface pressure interpolation in ICBC. I’ve done a 15 km nest previously and don’t recall seeing the pattern, so it is likely scale-dependent. I’ve masked out the land in the attached sample to remove noise from the terrain, but the grid pattern is visible in the U/V curl field at all levels and all times if you set the color scales correctly.

My current project focuses on wind stress changes, where this pattern is prominent throughout my figures, so I hope it can be solved before I submit our manuscript to a journal.

Thank you