Sensitivity study to select the wet deposition scheme in an operational atmospheric transport model

Arnaud Querel (1) , Denis Quelo (1) , Yelva Roustan (2) , Anne Mathieu (3)

1 IRSN/PSE-SANTE/SESUC/BMCA - Bureau de Modélisation des transferts dans l'environnement pour l'études des Conséquences des accidents
2 CEREA - Centre d'Enseignement et de Recherche en Environnement Atmosphérique
3 IRSN/PSE-ENV/SEREN/BERAP - Bureau d'expertise en radioprotection de la population

The response to a nuclear crisis is supported by the ability of operational atmospheric transport models to simulate the soil contamination caused by deposition processes. The Fukushima accident was characterised by wet deposits, which were difficult to simulate accurately based on observations. This may have been due to the scheme used in the models to represent the wet deposition flux. Is this scheme actually important? Can feedback from the Fukushima accident be used to make optimal decisions? A sensitivity study was used to investigate these questions based on seven wet deposition schemes integrated into operational and recognised atmospheric transport models and considering various sets of parameters, particularly those with an influence on wet deposition. The deposition maps produced from the multiple simulations are compared – with each other and with the deposits observed from the Fukushima accident – on the basis of criteria representing soil contamination crisis management needs. This study confirms the importance of the wet deposition scheme, particularly in some configurations, and quantifies the impact of this decision in a crisis management context. None of the schemes used in the study clearly appear as the best possible option to satisfy all of the criteria. Among them we identified similarities and discrepancies in average behaviour. Ultimately, the scheme used when modelling wet deposition in an operational atmospheric transport model must be carefully selected. In addition, uncertainty is too widespread with the Fukushima accident for this case to be used as a benchmark when selecting a wet deposition scheme. This study also highlights that crisis managers must not exclusively trust one single model for responses. At the current time, it is preferable to implement and use several wet deposition schemes as part of modelling tools of emergency responses.

Domaines: Physique [physics]

Arnaud Querel, Denis Quelo, Yelva Roustan, Anne Mathieu. Sensitivity study to select the wet deposition scheme in an operational atmospheric transport model. Journal of Environmental Radioactivity, 2021, 237, pp.106712. ⟨10.1016/j.jenvrad.2021.106712⟩. ⟨hal-03553596⟩