 The Meso-NH atmospheric simulation system is a joint effort between the Center National de Recherche's Meteorologiques and Laboratoire de Rologie. It is designed as a research tool for small and mesoscale atmospheric processes and is freely accessible to the research community. The system comprises several elements, including a numerical model, a flexible file manager, an ensemble of facilities to prepare initial states, and a post-processing facility. Some distinctive features of this ensemble include the ability to simulate multiple scales of motion using interactive grid nesting, the transport and diffusion of passive scalars, and the use of Fortran 90 compiler. The present paper provides a general description of the adiabatic formulation and some basic validation simulations, as well as a list of available physical parameterizations and initialization methods. This article was authored by J. P. LaFour, J. Stein, Ana Sencio, and others. We are article.tv, links in the description below.