© 2018 Hungarian Meteorological Service. All Rights Reserved. Five years after the Fukushima accident, many estimates of the source term (ST) have been published. In this study, the relevance of several ST is examined by performing a sensitivity analysis using several meteorological fields. The simulations prove that the MRI meteorological fields with higher spatial and temporal resolution give better scores. However, the uncertainties on the meteorological fields and ST remain high since several contamination events remain difficult to reproduce. In addition, the inverse modeling method developed by IRSN is applied to evaluate new ST using MRI meteorological fields, Tsuruta137Cs air concentration and gamma dose rate measurements. Simulations forced by these new inverted ST improve the agreement between model and observations in comparison with previous simulations especially between March 20 and March 22. A better reconstruction of the most of contamination events is also obtained.