This study explores the influence of variable soil depths on simulated land?atmosphere exchanges from a currently operational land surface model over the North American Monsoon (NAM) region of southwestern North America. It is shown that the neglect of observed (actual) soil depths can limit land surface model performance at the sites studied. The main impact of accounting for shallower soil depths is to increase the dispersion, (i.e. the dynamic range) of sensible and latent heat fluxes when compared with simulations using a common fixed soil column depth of 2 meters. It is also shown that accounting for local soil depth variability can, moderately, improve land surface model flux estimation as compared with tower measurements. This [...]