A Comparison of Two Types of Atmospheric Transport Models—Use of Observed Winds Versus Dynamically Predicted Winds

Abstract

Dynamic and kinematic trajectory Models were used to diagnose long-range transport during a 24-b period of the NEROS (1979) field study. The dynamic model consisted of a three-dimensional primitive equation model which predicted winds on a 25-km grid mesh for each model lime step (?60 s). Realistic terrain elevations were used as was a bulk formulation for the planetary boundary layer. The kinematic model determined the horizontal wind field by linearly interpolating between analyses of rawinsonde observations available at 12-h intervals. Even though only one tetroon trajectory was available for verification purposes, it was clear that the dynamic model was able to diagnose the transport more accurately than the kinematic model in this case because of its ability to provide for realistic, nonlinear variations or the windfield in space and time. The transport calculations performed using the kinematic model were shown to be quite sensitive to the type of operationally available wind data that were used. Significant differences in parcel trajectories resulted depending on whether a convenient but smooth hemispheric analysis was used or whether actual rawinsonde data were used to produce a more detailed analysis.