Hindcast of eddy field in the Southeastern Baltic Sea and rotation of synthetic floating particles in submesoscale cyclonic and anticyclonic eddies

A very high resolution (0.125 NM grid) circulation model of the Southeastern Baltic Sea was compiled from the General Estuarine Transport Model (GETM) in order to simulate the submesoscale eddy field in the area. The model results were compared with optical and infrared satellite imagery. Most prominent eddies detected in the satellite images were reasonably well identified in the simulated patterns of the sea surface temperature, currents, and floating Lagrangian particles. In addition, a hypothesis of overwhelming dominance of cyclonic spirals on satellite images being caused by some sort of differences between rotary characteristics of the submesoscale cyclonic and anticyclonic eddies, was tested by the means of numerical experiments with synthetic floating Lagrangian particles. The experiments showed that the cyclonic spirals could be formed both from a horizontally uniform initial distribution and from the initially lined up particles during the advection time of the order of 1 day. Statistical analysis of the trajectories of the particles indicated that the submesoscale cyclonic eddies differ from the anticyclonic eddies in three ways favoring the formation of the spirals: larger angular velocity, more pronounced differential rotation and negative helicity.