Evaluation of Four Lagrangian Models Against the Cross-Appalachian and European Tracer Experiments

In this study, a comparison of model performance of four state-of-the practice Lagrangian dispersion models: CALPUFF, SCIPUFF, HYSPLIT, and FLEXPART is presented. These models were used to simulate the dispersion of the tracer cloud for the European Tracer Experiment (ETEX) and the Cross-Appalachian Tracer Experiment (CAPTEX). Dispersion simulations for each of the modeling systems were done using a common meteorological dataset derived from the NCAR/PSU MM5 model. Statistical evaluation procedures used for model verification follow a hybrid approach based upon the procedures used in the second Atmospheric Transport Model Evaluation Study (ATMES-II) and the NOAA Data Archive of Tracer Experiments and Meteorology (DATEM) project. Verification scores show that the NOAA HYSPLIT model performed best overall, followed by the SCIPUFF and FLEXPART models. CALPUFF performance was significantly poorer than the other three models in the ETEX experiment and improved in CAPTEX, but will require additional analysis to diagnose possible causes of predicted tracer advection errors noted in the ETEX experiment.