This document presents specific software architecture and numerical methods for environmental simulation codes, with application ranging from sea- weeds dispersion to lava flow but with a strong focus on wildfire behaviors and meteorology. ForeFire code is one of the main developments carried out, as well as the realization of coupled fire/atmosphere simulation of large fires, uncertainty quantification and estimation of fire danger using deep learning. For all these stud- ies there always have been a strong requirement to be able to deliver approaches that are or can be operational and of use with the development of a specific high resolution, computer intensive, fire weather forecasting system as a context to use such simulation. These approaches were developed at the frontiers between two research disciplines, software engineering and numerical simulation in geophysics and combustion with the collaboration of national and international laboratories.