ИСТИНА

The natural hazards, associated with the marine environment, in the Azov Sea are storm surges. These extreme events lead to destroying consequences in the coastal zone of this sea. At present, due to the absent of observational data, numerical models are used for the study of surges and for their statistical estimation. When setting the boundary conditions for these models, data from different reanalyses are used. The ADCIRC (Advanced circulation model for oceanic, coastal and estuarine waters) model was chosen for calculating fluctuations in the sea surface and water circulation. This model uses a non-structural computational grid with a variable step and allows you to save small features of the coastline, channels in the delta regions of rivers, small islands and shallow banks. The model takes into account almost all the factors affecting the formation and height of surges, including wind waves (SWAN wave model integrated into ADCIRC). Another advantage of the model is the possibility of setting river flow and flooding of adjacent land. In this article used a two-dimensional version of the model. The step of the computational grid in the studied sea varies from 50 m to 5 km. The input data for the model were the wind and atmospheric pressure fields from the NCEP/CFCR/CFSv2 reanalysis for the period from 1980 to 2017. The Azov Sea is covered with ice in winter. To take into account the effect of ice on the formation of surge level fluctuations, the sea ice concentration was set with a daily interval and spatial resolution of ~ 0.2 ° × 0.2 ° from the OSI-450 database. To verify the calculated data at sea level, they were compared with field measurements, which showed their good agreement. During of numerical experiments, it was found that the ADCIRC model, adapted to the features of the Azov Sea, reliably reproduces the storm surges of the study area. After analyzing the model results, the seasonal and interannual distribution of storm surges in the Azov Sea are shown. The greatest number of surges is observed in the autumn-winter period. Actively storm surges develop from November to February. In the spring-summer period, the number of surges is significantly reduced (2.5-3 times). No interannual trend in the occurrence of surges in the Azov Sea for the study period was found. Nevertheless, years are distinguished for which the frequency of surges throughout the sea is the highest: 1981, 1993, 1998, 2003. The maximum number of surges is noted in the Taganrog Bay. The synoptic situations in which storm surges occur are determined. It is noted that the height and direction of the surge is determined mainly by the synoptic situation over the sea. A significant increase in the level during surge occurs when the wind speed is more than 10-15 m/s and duration from several hours to several days. Significant range in sea level fluctuations are confined to the east coast of the sea. This article was written with the financial support of the RFBR, grant No. 18-05-80088.