Assessment of WRF-LES Model Performance in Simulating Valley Breezes and Vertical Structure of the Planetary Boundary Layer in the Pyrenees.

A modeling study of a real case has been conducted to assess the performance of the large-eddy simulation version of the Weather Research and Forecasting Model (WRF-LES) in the Valle d'Aure region, situated on the northern side of the Pyrenees.This study aims to evaluate the model's ability to accurately simulate thermally-driven flows (TDF) and the vertical thermal and dynamic structure of the planetary boundary layer (PBL). This is essential because the characteristics of TDFs at mountain environments are influenced by factors such as the strength of the temperature gradient near the surface, interaction with winds of varying spatiotemporal scales, such as synoptic winds, and the vertical structure of the pre-existing PBL.The accurate simulation of turbulence in the PBL at sub-kilometer horizontal scales is a complex issue, but it offers advantages under stable conditions and over heterogeneous surfaces when local properties are required or when resolving small-scale surface features is desirable, as is the case of the valley here considered. To evaluate the performance of methods currently available in the WRF-LES model, different sensitivity experiments are conducted with different PBL treatments.To validate these simulations, data from the MOSAI1 field campaign, conducted in collaboration with the LATMOS-i2 and WINDABL3 projects, have been used. Throughout this campaign, meteorological radiosoundings were performed, and three meteorological stations were strategically installed in the valley, incorporating surface turbulence measurements.(1) MOSAI project (Model and Observation for Surface-Atmosphere Interactions, https://mosai.aeris-data.fr/).(2) LATMOS-i project (Land-ATMOSphere interactions in a changing environment: How do they impact on atmospheric-boundary-layer processes at the meso, sub-meso and local scales in mountainous and coastal areas?) (PID2020-115321RB-I00, funded by MCIN/AEI/ 10.13039/501100011033).(3) WINDABL project (PR2022-055). Project to impulse the career of young researchers funded by the University of Cdiz (Spain) (Plan Propio).