Sensitivity of a Trajectory Model to the Spatial and Temporal Resolution of the Meteorological Data during CAPTEX

Abstract

Some recent analyses of long-range transport and dispersion indicated conflicting results regarding the improvement in trajectory calculations when either the spatial or temporal density of the meteorological data are enhanced. Tests conducted with a variety of combinations of meteorological data, collected during CAPTEX, showed that increased temporal resolution did increase trajectory accuracy; however, it was not significantly different from enhancing the spatial coverage. Trajectory error was assumed to equal the distance between the centroid locations of the measured and calculated air concentration patterns. The most accurate trajectories were calculated when both spatial and temporal resolution were enhanced, such that the rms trajectory error was decreased from 180 km to 154 km for travel times of 24 to 42 h. Although the inclusion of surface observations did not improve calculated trajectories, the addition of vertical motion in the trajectory calculation methodology resulted in a further reduction of trajectory error to an average of 144 km.