How do the sea and the land conditions affect the coastal breezes? 20 days analysed from WRF simulations in the Gulf of Cádiz (Iberian Peninsula)

Sea breezes are common and recurrent thermally-driven winds formed in coastal areas under conditions of weak synoptic forcing, due to the differential heat capacity of the sea and the land. Their accurate forecast is key because of the impacts on maxima near-surface temperatures, humidity (and then thermal comfort), pollutants distribution, convective-systems formation, etc., being crucial for the wind energy sector and because they develop in areas that are normally densely populated.

Some studies have investigated the impacts of the surface conditions in coastal breezes in different regions around the world. Their findings are diverse, mostly attributed to differences in the marine boundary layer stability, which can favour or inhibit the vertical mixing. This is needed to vertically distribute thermal changes in the land or the sea surfaces to deeper atmospheric layers, and thus to modify the horizontal surface pressure gradients. In this work, we use the Weather Research and Forecasting (WRF) model to investigate how the coastal breezes are affected by changes in the surface representation in the Gulf of Cádiz, in the Atlantic coast of the Southwestern Iberian Peninsula. We focus on artificial and realistic changes in land use, soil moisture and sea surface temperature. The analysis is performed for a case study of 20 days in August 2020, characterised by many coastal-breeze events in the area analysed and by a gradual decrease in the sea surface temperature. The model is evaluated with observational data at different coast locations, inland and on the ocean, as well as using wind speed transects from satellite altimetry.