The WINDABL project: How are the surface thermally-driven WINDs influenced by the vertical structure and horizontal inhomogeneities of the Atmospheric Boundary Layer?

Thermally-driven breezes are diurnal wind circulations initiated by surface temperature gradients in coastal and mountainous areas when fair-weather synoptic conditions dominate. Understanding these breezes is crucial for many other physical processes or human applications: wind energy, human thermal comfort, transport and diffusion of pollutants/humidity, sea surface currents in coastal areas, convection initiation, or local weather differences, among others.

The characteristics of the mountain and coastal breezes depend on the strength of the surface temperature gradient, but also on the interaction with other winds of different spatio-temporal scales, such as synoptical winds. Besides, the thermodynamic vertical profile of the atmospheric boundary layer (ABL) can also impact the breeze characteristics. In this context, some recent modelling experiments have shown how the vertical structure of the pre-existing ABL is a key factor controlling the relative impact that specific surface changes have on the breeze evolution. This motivates further modelling and observational experiments, which is the main objective of the WINDABL project*.

Hence, we plan to characterise the vertical ABL structure and the horizontal heterogeneity of the terrain during favourable conditions for the breeze formation in coastal and mountainous areas. This will be carried out mainly with the launching of meteorological soundings and through the installation of meteorological stations at strategic locations, including surface turbulence measurements. The coastal area of interest corresponds to the northern part of the Gulf of Cádiz (southwestern Iberian Peninsula coast) while the mountain breezes will be investigated at the Vallée d’Aure, on the Northern side of the Pyrenees, taking advantage of the large amount of instrumentation that will be deployed close to this area in 2023 during the MOSAI field campaign**, and in collaboration with the LATMOS-i project***.

This joint observational effort will be complemented with high-resolution numerical simulations of selected cases with the Weather Research and Forecasting (WRF) model. In this sense, the observational data gathered with the new instrumentation will allow for a much more detailed model evaluation, for which a sensitivity study to the selected physical parameterizations will be performed.

In this work we will present the main observational and modelling strategy of WINDABL, as well as some preliminary results obtained from the observational data and numerical experiments.

 

* The WINDABL project (PR2022-055) is a project to impulse the career of young researchers funded by the University of Cádiz (Spain) (Plan Propio).

 ** MOSAI (Model and Observation for Surface-Atmosphere Interactions, https://mosai.aeris-data.fr/).

*** LATMOS-i (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).