This paper describes our experience in the application of Lagrangian mini-drifters in studies of coastal water circulation. As shown by our experiments in the Southeastern Baltic Sea, an application of Lagrangian mini-drifters makes it possible to detect the presence of complex sub-mesoscale vortex processes and inertial oscillations, i.e., processes that are difficult to numerically simulate. Moreover, the presence of vortex formations is able to keep passive objects drifts, oil anthropogenic pollution and so on floating in a strictly localized area for at least 1~week, even in changeable wind conditions. Special attention in the paper is paid to a performance comparison of the application of mini-drifters and an Acoustic Doppler Current Profiler ADCP. The advantages of drifters for determining flow parameters at low speeds are noted. The main advantages of the proposed drifters are taken into account: the low cost of manufacturing drifters $\sim 150$~USD per system along with the low cost of GSM communications, the ease of manufacturing and operation, with no special technical experience required, and the link to obtaining operational data in real-time for up to several weeks make these systems valuable supplementary tools for remote sensing studies of processes in coastal zones.
Lagrangian drifter, satellite remote sensing, coastal dynamics, Acoustic Doppler, Current Profiler ADCP, Seatrack Web HELCOM, submesoscale eddies, Black Sea, Baltic Sea
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