APOLLO2, a new long range Lagrangian particle dispersion model and its evaluation against the first ETEX tracer release

APOLLO2 is a new version of the long range Lagrangian particle dispersion model integrated into ARIES (Accidental Release Impact Evaluation System), the system that I.S.P.R.A. (Italian National Institute for Environmental Protection and Research) developed to provide prognosis about the dispersion of radioactive clouds in case of nuclear accidents. In this paper the theoretical aspects of the APOLLO2 formulation are briefly described. Moreover, the model performances have been evaluated qualitatively and quantitatively against the observations of the first release of the European Tracer Experiment (ETEX). The global analysis showed a FA2 = 56%, a FA5 = 78%, and a good agreement for intermediate values within the Q–Q plot. Considering a total of 126 stations, the number of locations where NMSE < 10, PCC > 0.7 and FMT > 20% is respectively 91, 65 and 86. The number of stations where the Chang and Hanna (2004) performance evaluation criteria are satisfied is 33. The capability of APOLLO2 to predict arrival time, cloud duration and time of peak is comparable to the one shown by similar models.Finally, the sensitivity of the model to some input variables has also been investigated.

► We present the APOLLO2 long range atmospheric Lagrangian particle model.
► Qualitative comparison of APOLLO2 predictions and ETEX1 observations is good.
► Quantitative comparison is also of good quality (e.g. FA2 = 56%, FA5 = 78%).
► Sensitivity analysis has given hints to improve the model performances.