Improving the understanding of the horizontal and vertical characteristics of sea breezes from mesoscale numerical simulations and observations

Sea breezes are mesoscale winds formed in coastal regions under weak synoptical surface-pressure gradients. The theoretical scheme of daytime sea breezes includes surface winds from the sea and a return flow at a certain height above. However, this canonical picture is rarely detected from observations due to the complexity, high variability and heterogeneity of the different factors affecting the final atmospheric boundary layer structure. This is the case in the Gulf of Cádiz (SW Spain), where sea breezes have important effects during summer, especially due to their capacity to mitigate warm temperatures and transport humidity. In this region, two main types of sea breezes typically form depending on the dominant background synoptic flow: the so-called “pure” and “non-pure” sea breezes. The former take their name due to their greater similarity to canonical ones, while the latter present different characteristics and are more influenced by the synoptic conditions.

This study outlines the research strategy followed to investigate these phenomena in the area using the Weather Research and Forecasting (WRF) mesoscale model, along with new observational data from recently deployed instrumentation, as well as from radiosoundings launched at strategic sites during sea breeze conditions. Among the instrumentation used, we highlight a sonic anemometer and an IRGASON system, installed at 10 m and 65 m above sea level, respectively. Positioned directly on the shoreline, these instruments allow the evaluation of turbulent fluxes “above the sea” with different objectives. First, we aim to analyse variations in turbulence under sea breeze conditions with a well-formed internal boundary layer. Secondly, we seek to monitor sea surface fluxes at the coast to investigate their influence on breeze formation and evaluate the flux values simulated by WRF.

The work has been developed within the framework of the following research projects:

 

* The LATMOS-i project (PID2020-115321RB-I00) (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?), funded by MCIN/AEI/ 10.13039/501100011033.

** The WINDABL project (PR2022-055) (How are the Surface Thermally Driven Winds influenced by the vertical structure and horizontal inhomogeneities of the Atmospheric Boundary Layer?), funded by Plan Propio de la Universidad de Cádiz, Convocatoria 2022 de Proyectos para investigadores nóveles.

*** The WIND4US project (CNS2023-144885) (Disentangling the complexity of the WIND systems in coastal areas FOR a better Understanding of their impacts on Society), funded by Convocatoria 2023 de Proyectos de Consolidación Investigadora.