An atmospheric dispersion study was conducted for 2 different synoptical conditions for a hypotetical nuclear accident: the first is a pre-frontal condition with a typical Planetary Boundary Layer (PBL) and the second is a disturbed PBL due to a synoptic though. The site is a complex terrain area (Ipero - Brazil), where the topography modulates the circulation and the Low Level Jet (LLJ) is a common feature of the PBL. For one year a doppler lidar retrieved the wind vertical profile at Ipero, allowing to evaluate datasets that can be used as input data for the Atmospheric Transport and Dispersion Models (ATDM). Of the 3 datasets evaluated, only GDAS reproduced the LLJ and was chosen for running the HYSPLIT4 ATDM experiments.