Using data sets generated by the Geophysical Fluid Dynamics Laboratory general circulation/transport model's U.S.-Canada combustion nitrogen source experiment, a detailed analysis of the simulated transport mechanisms producing the observed August NOy maximum at Hawaii is presented. Combustion nitrogen is not simply advected from the United States to Hawaii by the winds circulating around the climatological subtropical anticyclone. Rather, its transport results from a complicated three-way interaction of surface advection from source regions, enhanced vertical diffusion due to dry convection, and winds in the ''free troposphere.'' Backward trajectories from Hawaii using model pressure and isentropic surfaces were insufficient in explaining the transport. Model-consistent three-dimensional trajectories revealed that the transport originated in the ''free troposphere'' ''free troposphere'' along a path from northern Baja to the Texas Gulf coast. Combustion nitrogen from the source regions of southern California and as distant as the Texas Gulf area is advected along the surface toward the arid areas of Baja, the desert southwest, northern Mexico, and west Texas. Dry convection then vertically mixes the air to pressures of 800--650 mbar, where the subsiding wind flow from the east-northeast transports the NOy to Hawaii. Observed wind fields and heights of dry convection are compared to the model where data are available. ¿ American Geophysical Union 1990