Mesoscale Simulations of the Afternoon-Evening Transition for Two Contrasting Days during the BLLAST Campaign

In this work three mesoscale models (WRF, MesoNH, AROME) and one global model (ARPEGE) are used to simulate two contrasting days in terms of their convective boundary layers observed during the BLLAST campaign in southern France during June-July 2011 (Lothon et al., 2014). The main features responsible for the different evolution of the convective boundary layer during the two days are the magnitude of the surface fluxes and the synoptic- and mesoscale (mountain-valley winds) forcing.

All the models use their default configuration: operational one for AROME and ARPEGE and research one for WRF and MesoNH. Therefore, each model uses their own surface characteristics; WRF and MesoNH use ERA-Interim for the Lateral Boundary Conditions (LBCs) and initial conditions whereas AROME uses its own surface analysis and ARPEGE LBCs. The main objective is to analyze how those models perform in the representation of the boundary-layer variables during the afternoon-evening transition.

Additionally, we also analyze in detail the influence of the surface characteristics used by the different models on the surface flux heterogeneity and how they affect the results obtained by the models regarding the mesoscale circulations and the evolution of the boundary layer variables at the main site of the campaign.

Lothon, M., F. Lohou, D. Pino, F. Couvreux, E. R. Pardyjak, J. Reuder, J. Vilà-Guerau de Arellano, and coauthors The BLLAST field experiment: Boundary-Layer Late Afternoon and Sunset Turbulence. Atmos. Chem. Phys., 14, 10931-10960, 2014.