Influence of meteorological conditions on the formation of ice regime of the Lake Onega

The formation of the ice regime on large lakes is mostly determined by the complex meteorological processes occurring over the water area. Previous studies of the air temperature influence on the ice regime formation on the Lake Onega were based on observational data on the state of the ice cover in the Petrozavodsk Bay, as well as the materials of the rare missions of aerial reconnaissance performed in the second half of the XX century. So, it was necessary to revise the previously established dependencies using the present-day satellite data for 2000-2018, and to determine the nature of influence of other meteorological factors, among which a thickness of the snow cover on the Lake area. The authors obtained regularities of changes in the characteristic dates (complete freeze-up – ±5 days/°C and final clearing of ice – ±3 days/°C) of the ice regime on the Lake Onega, depending on changes in the average air temperature that preceded these dates (autumn and spring) for the period of two months. The regression equations to calculate these dates on the basis of the previous three and four-month periods from the data of 2000-2018 are also given. Relative to the above mentioned results for the previous period, a certain shift by a month ahead of twoand threeperiod exerting influence on the date of the complete freezeup is noted. Dependencies to calculate the cumulative daily temperatures for the period of the ice regime formation (the beginning of the formation of ice phenomena, complete freeze-up phase, the beginning of the breakup phase, clearing of the ice) were also deduced. Together with the data on the expected air temperature over the Lake these dates provide a potential possibility to estimate (predict) the characteristic dates of the ice regime. The significant influence of the average snow cover thickness on the process of destruction of the ice cover was shown, and the nature of the statistical relationship (along with the air temperature) was also determined.