 In the present version of MEMO, a 3D second-order total-variation-diminishing (TVD) scheme is implemented which is based on the 1D scheme proposed by Harten (1986).It achieves a fair (but not any) reduction of numerical diffusion, the solution being independent of the magnitude of the scalar (preserving transportivity).Turbulence and radiative transfer are the most important physical processes that have to be parameterized in a prognostic mesoscale model.