Abstract. 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.

Large-eddy simulations (LES) of radiation fog were performed over an airport area to study the effect of urban canopy on fog. These LES were performed with the Meso-NH research model at very high resolution: 1.5 m in the horizontal and 1 m in the vertical and over a domain 4.5 km × 1.5 km.The blocking effect of the airport buildings led to strong wind shear and consequently to the production of turbulent kinetic energy (TKE). The airport buildings also had a strong effect on vertical velocity, with a subsidence region behind the buildings. The increase of both turbulence and vertical velocity strongly modified the fog formation. The fog layer took more time to form in the airport area, but the increase in turbulence facilitated the vertical development of the fog layer.The fog took 1.5 h to form over the whole simulated airport area. The fog height was heterogeneous during the formation phase, with the formation of very low clouds locally. The effect of airport buildings on vertical velocity could explain these heterogeneities of the fog height. During the mature phase of the fog, the buildings had little impact on the fog layer characteristics. The fog dynamics were mainly controlled by processes at its top.These results suggest that the inclusion of high levels of detail in the building representation remains important for the local forecasting of fog formation. Particularly, small-scale heterogeneities can explain the spatial variability of fog formation. It seems necessary to take small-scale variability of the urban canopy into account for local and accurate forecasts of fog formation over airport areas.

A large-eddy simulation (LES) was performed for a Hector thunderstorm observed on 30 November 2005 over the Tiwi Islands. On that day, ice particles reaching 19-km altitude were measured. The LES developed overshooting updrafts penetrating the stratosphere that compared well with observations. Much of the water injected in the form of ice particles sublimated in the lower stratosphere. Net hydration was found with a 16% increase in water vapour. While moistening appeared to be robust with respect to the grid spacing used, grid spacing on the order of 100 m may be necessary for a reliable estimate of hydration.