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This paper presents the Meso-NH model version 5.4. Meso-NH is an atmospheric non hydrostatic research model that is applied to a broad range of resolutions, from synoptic to turbulent scales, and is designed for studies of physics and chemistry. It is a limited-area model employing advanced numerical techniques, including monotonic advection schemes for scalar transport and fourth-order centered or odd-order WENO advection schemes for momentum. The model includes state-of- the-art physics parameterization schemes that are important to represent convective-scale phenomena and turbulent eddies, as well as flows at larger scales. In addition, Meso-NH has been expanded to provide capabilities for a range of Earth system prediction applications such as chemistry and aerosols, electricity and lightning, hydrology, wildland fires, volcanic eruptions and cyclones with ocean coupling. Here, we present the main innovations to the dynamics and physics of the code since the pioneer paper of Lafore et al. (1998) and provide an overview of recent applications and couplings. [ABSTRACT FROM AUTHOR]

The paper describes a switchable parameterization of CIBU (Collisional Ice Break-Up), an ice multiplication process that fits in with the two-moment microphysical scheme LIMA (Liquid Ice Multiple Aerosols). The LIMA scheme with three ice types (pristine cloud ice crystals, snowaggregates and graupel-hail) was developed in the cloud-resolving mesoscale model Meso-NH. Here the CIBU process assumes that collisional break-up is mostly efficient for small snowaggregate class of particles with a fragile structure when hit by large and dense graupel particles. The increase of cloud ice number concentration depends on a prescribed number of fragments being produced per collision. This point is discussed and analytical expressions of the newly contributing CIBU terms in LIMA are given. The scheme is run in Meso-NH for the case of a three-dimension deep convective cloud with a heavy production of graupel. The consequence of dramatically changing the number of fragments produced per collision is explored in particular to estimate an upper bound of the CIBU effect. The case of a random number of fragments is also proposed to illustrate the consequence of the uncertainty of this parameter. Finally it is concluded that the assessment of CIBU certainly needs accurate laboratory experiments to check the conditions and to tune the efficiency of the process of ice crystal fragmentation. However the proposed parameterization which can be easily implemented in many two-moment microphysics schemes, could be used in this form to simulate the case of real deep tropical clouds where anomalously high concentrations of small ice crystals are suspected to occur. [ABSTRACT FROM AUTHOR]