Shelf Circulation Induced by an Orographic Wind Jet

Abstract

AbstractThe dynamical response to cross‐shelf wind‐jet episodes is investigated. The study area is located at the northern margin of the Ebro Shelf, in the Northwestern (NW) Mediterranean Sea, where episodes of strong northwesterly wind occur. In this case, the wind is channeled through the Ebro Valley and intensifies upon reaching the sea, resulting in a wind jet. The wind‐jet response in terms of water circulation and vertical density structure is investigated using a numerical model. The numerical outputs agree with water current observations from a high‐frequency radar. Additionally, temperature, sea level, and wind measurements are also used for the skill assessment of the model. For the wind‐jet episodes, the numerical results show a well‐defined two‐layer circulation in the cross‐shelf direction, with the surface currents in the direction of the wind. This pattern is consistent with sea level set‐down due to the wind effect. The comparison of the vertical structure response for different episodes revealed that the increase of stratification leads to an onshore displacement of the transition from inner shelf to mid‐shelf. In general, the cross‐shelf momentum balance during a wind‐jet episode exhibits a balance between the frictional terms and the pressure gradient in shallow waters, shifting to a balance between the Coriolis force and the wind stress terms in deeper waters.