CYCLONIC ACTIVITY INFLUENCE ON THE ICE REGIME OF THE SEA OF OKHOTSK IN THE AUTUMN-WINTER PERIOD

Abstract

This paper presents the results of an analysis of the relationships between atmospheric circulation characteristics and ice cover in the Sea of Okhotsk, including the impact of cyclones, for the period from 2001 to 2020. The investigation is based on data from the ERA5 reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF), as well as on pentad ice concentration charts and surface weather analysis maps from the Japan Meteorological Agency (JMA). The analysis revealed that in >87 % of cases of cyclonic impacts on the Sea of Okhotsk, a decrease of ice area growth rate over 10 % is observed in at least one region of the sea (northwestern, northeastern, or southern), with >52 % of these cases occurring due to the central type of cyclonic impact and >35 % in the southern one. An assessment of the intensity of cyclone impacts on the ice cover during its autumn-winter development is provided, considering the typification of seasons according to the severity of ice conditions. Intraseasonal maximum values of ice extent slowdown during cyclonic passage were calculated. Relationships between the u-wind component and the standard deviation of surface pressure with the rate of ice extent change were identified for the whole Sea of Okhotsk and its individual regions. The largest deviations between the average values of atmospheric circulation parameters were identified with and without central or southern cyclonic influences on the sea area, specifically for the u- and v-wind components, wind speed, surface pressure and its standard deviation. Analysis of atmospheric circulation parameters and ice regime parameters allowed to quantify the contribution of various atmospheric processes to ice cover formation, facilitating the development of approaches to ice forecasting.