Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 13017-13035, 2017
https://doi.org/10.5194/acp-17-13017-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
06 Nov 2017
Large eddy simulation of radiation fog: impact of dynamics on the fog life cycle
Marie Mazoyer1, Christine Lac1, Odile Thouron2, Thierry Bergot1, Valery Masson1, and Luc Musson-Genon3 1CNRM (CNRS-Meteo-France), UMR3589, Toulouse, France
2CERFACS, Université de Toulouse, CNRS, CECI, Toulouse, France
3CEREA (Atmospheric Environment Teaching and Research Center, Joint Laboratory École des Ponts ParisTech-EDF R&D, Université Paris Est), EDF-R&D, Chatou, France
Abstract. Large eddy simulations (LESs) of a radiation fog event occurring during the ParisFog experiment are studied with a view to analyse the impact of the dynamics of the boundary layer on the fog life cycle. The LES, performed with the Meso-NH model at 5 m resolution horizontally and 1 m vertically, and with a 2-moment microphysical scheme, includes the drag effect of a tree barrier and the deposition of droplets on vegetation. The model shows good agreement with measurements of near-surface dynamic and thermodynamic parameters and liquid water path. The blocking effect of the trees induces elevated fog formation, as actually observed, and horizontal heterogeneities during the formation. It also limits cooling and cloud water production. Deposition is found to exert the most significant impact on fog prediction as it not only erodes the fog near the surface but also modifies the fog life cycle and induces vertical heterogeneities. A comparison with the 2 m horizontal resolution simulation reveals small differences, meaning that grid convergence is achieved. Conversely, increasing numerical diffusion through a wind advection operator of lower order leads to an increase in the liquid water path and has a very similar effect to removing the tree barrier. This study allows us to establish the major dynamical ingredients needed to accurately represent the fog life cycle at very high-resolution.

Citation: Mazoyer, M., Lac, C., Thouron, O., Bergot, T., Masson, V., and Musson-Genon, L.: Large eddy simulation of radiation fog: impact of dynamics on the fog life cycle, Atmos. Chem. Phys., 17, 13017-13035, https://doi.org/10.5194/acp-17-13017-2017, 2017.
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Short summary
Large eddy simulations of a radiation fog event occurring during the ParisFog experiment have been studied to analyze the impact of the dynamics on the fog life cycle. They included a sophisticated microphysical scheme, the drag effect of a trees barrier and deposition on vegetation. The blocking effect of the trees induces elevated fog formation and limits cooling and cloud water production. The deposition process was found to exert the most significant impact on the fog prediction.
Large eddy simulations of a radiation fog event occurring during the ParisFog experiment have...
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