The method was initially performed using the GCAS standard retrievals and the ERA5 wind reanalysis product . While this gave good results, we found that the level of noise was reduced and the known sources were better identified when we used the GCAS retrievals that were corrected using the CAMx air mass factors, and when we used the WRF-CAMx meteorology. These sensitivity tests revealed that CAMx simulations can be used to yield clear improvements in the flux divergence method.