Since there is no substantial preferential binding between the 1:1 conformers and Ar, we conclude that the global enrichment of cis-CH3ONO is a result of enhanced cis trapping in surface pockets due to its smaller van der Waals radius compared to the trans conformer. We also demonstrated that the cis abundance enhancement does not change with deposition angle, concluding that the surface morphology of the Ar matrix does not change significantly with deposition angle.