Simulation of atmospheric transport using observed and estimated winds

The spread of pollutants in the atmosphere is often mathematically simulated by the linear combination of transport by the mean wind and dispersion by parameterized turbulence. Several questions arise when trajectories are constructed in the plantary boundary layer. How accurately can trajectories simulate the observed positions of an air parcel along the air parcel's path. How accurate are trajectories constructed from surface winds compared with trajectories constructed from winds observed through the depth of the boundary layer. How does atmospheric stability effect the accuracy of trajectory calculations. One of the main objectivies of the Eastern Tennessee Trajectory Experiment (ETTEX) was to obtain a data base sufficient to answer these questions. In this study, the ETTEX pilot balloon wind observations are assumed to be a best realization of the real wind field. These data will be used to simulate the trajectories of tetroons released during stable, unstable and transition periods. For each class of stability, the error of the simulation will be determined at the end of each advection step of the trajectory calculation. The average and standard deviation of these errors form the overall accuracy of the trajectory simulation. These results will then be considered to be the best possible simulations. This procedure will then be repeated using estimated winds derived from vertically extrapolated surface winds. We can then judge the validity of atmospheric transport calculations using observed or estimated winds