The Role of Bottom Friction on theChanges of Salinity Front in the Persian Gulf

In this study, using the HYCOM, the role of bed friction in the salinity front was studied. A resolution of 0.05° horizontally and 29 hybrid layers were used for the simulation, and the simulation area includes the entire Persian Gulf and most parts of the Oman-Sea (up to 59.9°E). The model uses the initial conditions of the WOA13 data with a resolution of 0.25°, the sponge boundary condition in the east of the Oman Sea with an e-folding time of 78 day and a buffer zone of 50 km. The CFSV2 Atmospheric Forcing (0.2°) uses 1-hourly data with baro-tropic and baro-clinic time-steps of 15,120 seconds respectively. The model was integrated from 2011 to 2015, and the results of 2015 were selected for discussion. The results indicate that eddies are formed along the salinity front. The salinity front appears to be prone to baroclinic instability that mainly appears in the summer months in the form of cyclonic-eddies (more saline center) and anti-cyclonic eddies (less saline center), which peak in August. In this instability, in addition to seasonal changes and density stratification, the role of friction is important. Spectral analysis of water characteristics in the salinity front shows the time scales of eddies, which varies from several hours to about three-months. Once the drag coefficient is halved and then doubled. The results indicate that the advance of the salinity front into the Persian Gulf has an inverse relationship with the drag- coefficient. Also, in lower friction runs, anticyclone-eddies is not observed, but in higher friction mode, both cyclonic and anti-cyclonic eddies were observed.