THE RELATIONSHIP BETWEEN ATMOSPHERIC TRANSPORT AND THE PARTICLE SCATTERING COEFFICIENT AT THE GRAND-CANYON

Air trajectory and particle scattering data (b(sp)) for the period 198 4-1989 are used to determine the relationship between atmospheric tran sport and visual air quality at the Grand Canyon National Park. Using cluster analysis, 72-hour back-trajectories arriving four times per da y were grouped into distinct transport patterns. Northwesterly and sou therly/southwesterly flow dominate in the winter and summer seasons, r espectively. Comparisons of b(sp) values accompanying different transp ort patterns showed a clear relationship between air flow pathway and light scattering due to small particles during the non-summer months o nly. An index is defined which describes the percentage of annual traj ectories belonging to specific transport routes delivering predominant ly clear air to the GCNP.