Observational study and numerical simulations of sea breezes on the coast of Malaga

Abstract

Sea breezes are thermally-driven flows that develop on the mesoscale as a result of differential surface heating between the land and ocean surface. These wind circulations appear on coastal areas, influencing their thermal regime and comfort, the characteristics of the Atmospheric Boundary Layer (ABL), the diffusion of pollutants, transport and circulation of relevant gasses, offshore wind power production and convection onset. Moreover, an important part of the worldwide population lives near the coast and is thus affected by sea breezes, highlighting the importance of their study and understanding of the associated processes. The sea breeze on the coast of Malaga (southern Spain) is analysed in this study, an area where the sea breeze has not been studied yet. This region features complex topography and shoreline orientation, high density of buildings as well as enhanced variability of sea-surface temperatures (SST) due to frequent coastal upwelling events. These factors interact with sea breezes, adding complexity and interest to the study. The first objective of this work is to characterize sea breezes in Malaga, for which observational data from three synoptic stations during the summer months of 2022 are analysed. Despite being relatively close to each other (a few kilometers), the sites exhibit differences in the evolution of temperature and humidity on sea breeze days. The arrival of the sea-breeze front is particularly visible closer to the shoreline, where it contributes to a temperature decrease, which is not apparent on sites 2-5 km inland. The sea breeze also causes an increase in the specific humidity and wind speed. The analysis of the breeze events and the SST suggest that this variable has an impact on temperature close to the shoreline on sea breeze days. The second objective is to perform and analyse a numerical simulation with the Weather Research and Forecasting (WRF) model of a sea breeze event of particular interest, in which important temperature differences existed between the observational sites. Results from the numerical simulation show that complex wind circulations appear in the study area and may explain the observed temperature differences, highlighting the contribution of high-resolution numerical simulations to the understanding of the underlying physical mechanisms.