A sea breeze convergence zone in the center of a complex terrain island

In the western Mediterranean island of Mallorca, sea breezes develop on roughly half of the days during the warm season. These wind circulations are characterized by low-level jets that penetrate the island from its two main basins and converge over its central area, a process strongly influenced by the synoptic environment and the island’s complex orography. This study characterizes the spatial and temporal structure of sea-breeze convergence under different synoptic conditions, with particular attention to the evolution, scales, variability, and governing physical processes of convergence events.

 

A six-day high-resolution numerical simulation was conducted with the Meso-NH 5.7 model, using three nested domains with horizontal resolutions of 5 km, 1 km, and 250 m. The simulation was validated against observations from automatic weather stations operated by the Spanish National Meteorological Agency (AEMET). In addition to reproducing the observed flow, the model provides access to budget terms for key variables, including turbulent kinetic energy, vertical and horizontal velocity, and potential temperature, enabling a process-based interpretation of their interactions. These diagnostics allow a precise assessment of the wind structure and the forcings that drive sea breeze initiation, inland propagation, convergence, and the associated updrafts.

 

The analysis identifies three types of sea breeze events, each associated with different synoptic conditions and associated patterns of convergence. Two dominant wind regimes emerge during these events: a coastal stationary regime, in which the front retains a nearly constant vertical structure at the shoreline; and an interior quasi-stationary phase associated with convergence and updraft development. This classification is reinforced by the behavior of the budget terms, which highlight the individual role of each physical process. Inland penetration is primarily driven by the pressure gradient forcing, while vertical turbulent mixing acts as the main opposing mechanism, weakening and disorganizing the sea breeze front. Together, these results clarify how mesoscale circulations evolve over complex terrain and highlight the interplay between local forcing and synoptic scale conditions in shaping sea breeze convergence over Mallorca.