NAMT is an acronym for North American Mountain Torque. As I'm sure you know, the mountain and frictional torques are exerted on/by the planetary surface on a particular axis and, long story short, disperse energy in such a way that the spatial distribution of atmospheric mass is affected. Here's a good paper on what I'm referring to over the Pacific domain: http://journals.ametsoc.org/doi/abs/10.1175/1520-0493(2003)131%3C2608:MTGFTA%3E2.0.CO%3B2