Noise impact of road and railway infrastructures are more and more severely regulated by national laws: acceptable thresholds are decreasing. This implies noise prediction for longer distance of propagation. It becomes necessary to predict very finely meteorology and their connectivity with boundaries effects at the same time. Based on the Green's Function Parabolic Equation (GFPE), ATMOS (Advanced Theoretical Model for Outdoor Sound propagation) is a numerical code where new developments have been implemented to take complex topographies, sophisticated anti-noise protections with backscattering effects in the same way as relief, obstacle effects on wind speed profiles into account and to allow calculations of the temporal evolution of received signal. Comparisons with results given by different numerical methods used in outdoor sound propagation and for more sophisticated cases, by measurements accomplished on scale model, have been done to validate this new tool.