Baroclinic modelling and analysis of tide- and wind-induced circulation in the Ría de Muros (NW Spain)

The circulation in the Ría de Muros, a large coastal embayment in the Rías Baixas region (NW Spain), is studied for the first time using a numerical model—a baroclinic model in two horizontal dimensions (2DH) driven by the tide, wind, and river inflows. The model grid covers the whole ría, including the alternately drying and flooding areas of the inner ría. In situ data of the current velocity and direction, temperature and salinity, river discharges, and wind velocity and direction are gathered for this purpose. The numerical results agree well with measurements from an Acoustic Doppler Current Profiler (ADCP); e.g. the correlation coefficient is 0.71 for the velocity component along the main axis of the ría. This indicates that the tide, wind, and river inflows are the most relevant factors driving ría circulation on a time scale of days to weeks. The model is then applied to an analysis of flood and ebb circulation patterns in two cases of interest: (1) a NNE wind, and (2) a WSW wind. The first is a typical summer condition in the Ría de Muros. The second, although characteristic of winter conditions, also occurred in July 2007, which is very atypical from a meteorological standpoint and was likely due to the Azores High not occupying its usual summer position to the NE of the eponymous islands. The strong similarities between the circulation patterns in both cases indicate that the tide is the main driving factor of ría hydrodynamics. Nonetheless, a more detailed analysis reveals that wind also plays a relevant role, especially in certain areas of the middle and outer ría.