TRANSALP 1989 experimental campaign—II. Simulation of a tracer experiment with Lagrangian particle models

The capability of two 3D Lagrangian particle models (ARCO and SPRAY) in simulating the airborne dispersion in highly complex terrain is tested. The simulations are compared to the tracer experiment TRANSALP-I performed on the 19th of October 1989 in the Alpine region (Canton of Ticino, Switzerland). TRANSALP exercises were part of the EUROTRAC-TRACT Subproject. Tracer was released during one hour (11.00–12.00) near the ground at Iragna, a few kilometres upwind from the bifurcation of two valleys (Leventina and Blenio Valleys); about 40 samplers, located in the two valleys in the range of 40 km, measured 1/2 h average mean concentrations near the ground for five hours. The results of the simulations are presented and discussed. A statistical model evaluation aimed at quantifying the performance of the two models was carried out. The simulations reproduced with a reasonable degree of accuracy the general behaviour of the observed phenomena: the split of the plume between the two valleys, the space and time distribution of the concentration, the concentration maxima locations.